International Conference on Plasma Surface Engineering
Characterization of Nanostructured TiN and ZrN thin films elaborated by reactive magnetron sputtering
The present work deals with structural, mechanical and tribological charaterization of nanostructure of nitrides based films (ZrN, TiN) for cutting tool applications. Coatings are deposited by reactive magnetron sputtering from metallic targets (Ti, Zr and B) on static substrate holders with RF or DC bias. Thermo chemical treatments by plasma nitrided have been held on steel substrates for eventual duplex applications. The influence of plasma parameters (nitrogen partial pressure and substrate bias) on mechanical properties of ZrN an TiN is studied. In order to improve its mechanical properties, bore is then introduced to TiN and ZrN thin films. The fraction of bore into the coatings is then increased in order to achieve the formation of ZrBN and TiBN nanocomposite. Chemical, mechanical, tribological and structural properties are studied as a function of bore content using XPS, FTIR and nano indentation, Scratch tests, XRD, SEM and TEM techniques. C-BN and h-BN phases are detected from 1 at.% of bore by XPS measurements. An increase of the hardness is observed while adding bore to nitrides with two maximum at 5 and 10 at.% of bore. The resistance corrosion is also studied as function of deposition conditions.
The Improved Friction Properties of Bonded MoS2 Films by MAO Treating of Al Substrates
The bonded MoS2 films is widely used as solid lubricants in aerospace mechanisms due to their excellent tribological properties. Traditionally, the MoS2 was directly bonded on the Al substrate that was only treated by the technique named of sandblast. For improving the tribological properties of MoS2 films, micro arc oxidation (MAO) instead of sandblast was introduced as a new technique for treatment of Al substrate. In this article, the tribological properties of MoS2 films bonded on different surface of Al substrate as mentioned above was discussed, respectively. It is concluded from the test results that the MoS2 films bonded on substrate treated by MAO have better tribological properties than the ones treated by sandblast, and the endurance life against abrasion of the former is as high as twenty times than the latter by the stand test method of ball on disk using the UMT Multi-Specimen Test System. This test results can be illustrated by the following reasons. One point is the porous microstructures of MAO ceramic coatings on the Al substrate. The coatings have numerous pits to be good at increasing the binding force with the MoS2 films, and the pits can also provide a MoS2 lubricants reservoir during processes of friction. Both of them improved the MoS2 film’s ability of wear-protective. Otherwise, naturally the MAO coatings’ hardness is higher than the Al, and this ensures well wearing resistance, especially in practical application to big load-supporting moving parts, such as bearing, gear, etc…
Self-lubricating W-S-C-Cr tribological coatings deposited by r.f. magnetron sputtering
Tribological coatings composed of transition metal dichalcogenides (TMD) have long been studied for their excellent self-lubricant properties. However, they exhibit low load-bearing capacity, and their performance tends to deteriorate significantly in the presence of humidity. In previous works, doping disulfides and diselenides of tungsten and molybdenum has proven to be a way of greatly improving the tribological performance of this class of films in different environments. In this work, thin films were deposited by r.f. magnetron sputtering on silicon and steel samples, using two targets (carbon and chromium) and tungsten disulfide pellets. The final composition was controlled by the number of WS2 pellets and the ratio of the power applied to the targets. The carbon content was fixed at approximately 40 at.% in all depositions. The chromium content in the coatings was varied in the range 0 – 13.5 at.% and the S/W ratio was approximately 1.25 in all compositions in the series. The coatings were characterized in regard to their hardness, adhesion, chemical composition and bonding, microstructure and morphology, as well as their tribological behaviour.
Wear Properties of AISI 4140 Steels Modificated By Using Pulse Plasma Technique
In this study, the microstructure and wear properties of pulse plasma treated AISI 4140 steel was investigated. The surfaces of the samples were modified by using plasma pulse technique. The only one battery capacities (800mF) and two different sample plasma gun nozzle distances of 50mm, 60mm, 70mm, 80mm and different number of pulse were chosen for surface modification. XRD analyses were done for all samples. Wear test was done in CSM-linear wear test machine with 0.15 m/s constant sliding speed under 5N, 7N, and 9N loads for 200 m. It was observed that friction coefficient and wear value were changed in accordance with load. Friction coefficient values of modified specimens were lower than that of non-modified ones. Wear resistance was increased in modified samples. Worn surfaces of specimens were studied by SEM, EDS analyses techniques. Modification layer was formed on surface (in Fig.1a).
Oxidation behaviour of RuAl thin films: influence of diffusion barrier
Production and Characterization of Self-Healing Properties of B4C+SIC Added TBC
Thermal barrier coatings have significant interest for protecting of the effect of high temperature the materials used under high temperature. To coat the materials used under high temperature such as gas turbine liners, is considerably important. Yttria stabilized zirconia (YSZ) is the most common material used for that purposes in commercial applications. Thermal barrier coatings damage due to the thermal expansion and internal stress, formed by the temperature variation. The micro and macro cracks, which are formed under service life of the coating, causes the coating failures such as spallation by developing crack network. In this research SiC and B4C powders added into commercial YSZ powder to improve thermal shock resistance. Two different powder ratio were prepared as %25(%12,5 SiC +B4C) %75 YSZ and %50(%25 SiC +B4C) %50 YSZ. After preparing powders coatings were manufactured using F4 plasma gun. Coated samples were subjected to thermal shock test in burner rig testing equipment and as well oxidation tests were carried out as well for 10h, 20h and 50h at 1000°C. TG and XRD analysis were used to investigate self-healing products. Scanning Electron Microscope and Optical Microscope were used to examine microstructural properties of SiC and B4C added YSZ.
Effects of Production Method and Heat Treatment on the AdhesionStrength and Microstructural Behavior of MCrAlY Coatings
Thermal barrier coatings (TBCs) are widely-used as protective and insulative coatings on hot section components of gas turbines and their applications, like blades and combustion chambers, power generation. TBCs are used to allow higher service temperatures hot section of turbines and thus higher turbine efficiencies. TBCs generally consist of a metallic bond coating (BC) usually MCrAlY, a ceramic top coating (TC) usually ZrO2+Y2O3 and a thin oxide ceramic inter-layer (TGO) that forms under service condition within the bond coat / top coat interface. In this study, CoNiCrAlY powders were deposited on stainless steel substrate. High velocity oxy-fuel (HVOF) and Atmospheric plasma spraying (APS) techniques were used to produce two different types of bond coats. The ceramic top layers on both BC types were produced by APS. TBC specimens were subjected to heat treatment tests. Heat treatment tests was carried out in standard atmosphere at 550 °C, 650 °C and 750 °C for 1 and 2 hours. The microstructure and adhesion strength for top coat / bond coat interface of as sprayed and heat treated samples were investigated. Besides, the mechanical and microstructure behaviors of the produced layers in TBCs with heat treated and without heat treated samples were characterized and evaluated by SEM and optical microscope (OM). The results show the heat treatment of the coatings in different temperatures caused changes in microstructure and increase in adhesion strength properties of the coatings.
Oxidation Behavior of Thermal Barrier Coatings With Cold Gas Dynamic Sprayed CoNiCrAlY Bond Coats
The paper presents the results of investigation into the oxidation resistance and thermally grown oxide (TGO) of thermal barrier coatings (TBC). TGO occurred during in service affect the lifetime of the component by introducing several kinds of degradation mechanisms such as decreasing bonding strength, initiation of stress concentration and thermal stresses which lead to crack initiation and propagation associated with delamination or spallation failure. Therefore, TGO plays important role on TBC durability. In this study, TBCs that consist of a typical bond layer / top layer system (CoNiCrAlY bond layers and YSZ top layers) are deposited on Inconel 718 superalloy substrates. The metallic bond coatings are applied via Cold Gas Dynamic Spraying (CGDS); the ceramic top coatings via Atmospheric Plasma Spraying (APS). Investigations are done concerning the oxidation behavior of this TBC system at 1100 °C in normal atmosphere for 8h, 24h, 50 h and 100 hours. The oxidation behaviour and microstructural properties during the oxidation test were evaluated and compared, and TGO growth behavior was also investigated under high temperature oxidation. The microstructural features and oxidation behaviours were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. Phase stability of TBCs were evaluated by means of X-ray diffraction method.
Thermal stability of TiZrAlN films deposited by a reactive magnetron sputtering method
Quaternary TiZrAlN films are: • perspective for both oxidation and wear resistance applications and expectant substitution for TiN, (Ti,Al)N and (Ti,Zr)N hard films; • capable to possess by the unique properties due to possibility of nanocomposite structure formation during their synthesis. The aim of the present work is to study the thermal stability, under vacuum and air annealing, of quaternary transition metal nitride films, namely (Ti,Zr)1-xAlxN, with emphasis on the role of Al content on the structure and phase formation.
Lifetime Assessment and Shock Behavior of TBC in Gas Turbine Blades: Experimental and Numerical Investigations
In this study, the thermal shock behaviour of a thermal barrier coating system of a gas turbine engine’s turbine blade of the space and aircrafts are evaluated. The thermal shock behaviour of the thermal barrier coating system was investigated. Computer-assisted thermal (ANSYS) and crack growth (FCPAS) analyses were carried out with the help of the obtained information. Thermal barrier coating system consists of nickel based superalloy substrate, ytria stabilized zirconia (%8 YSZ) ceramic top coat and NiCrAlY bond coat. Plasma spray method was used for coatings. Damages that occurred in the specimens were assessed according to cycle numbers, thermal stress and heating time. With the aid of the experiments, stress analyses of the modelled TBC were performed. The crack profiles and crack progression rates were determined. Finally the coating life was determined.
Novel Nanometer Thin Films On Magnesium Alloy Prepared By Ultra-Shallow Nitrogen Implantation Using PECVD Method
The low density of magnesium alloys makes them especially attractive especially for the automotive, electronic and aeronautical industries. Unfortunately, magnesium alloys have a strong susceptibility to atmospheric, galvanic and pitting corrosion and need to be protected with anticorrosive coatings. Traditionally magnesium and magnesium alloys have been protected with chromium-based coatings with the consequent problem of pollution by Cr(IV) ions. The development of new corrosion resistant coatings, by using clean and environmentally friendly processes is very important and strategic for the European industry due to environmental, health and economic considerations. In this context plasma technology, including: Plasma Enhanced Chemical Vapor Deposition (PECVD) are becoming increasingly popular. In this paper, magnesium alloys AZ91 were treated using nitrogen plasma (N2 and NH3) generated in PECVD reactor. Then, some of magnesium alloys samples were oxidized in oxygen plasma, and for some magnesium alloys samples SiO2 layer was deposited (in PECVD reactor). The obtained coatings were investigated using various characterization methods. Electrochemical properties were based on analysis of the voltammetric curves and electrochemical impedance spectroscopy, the microscopic examination was performed by using the techniques of SEM / EDS.
Effect of nitrogen incorporated into oxide layer, formed on the magnesium alloys by using r.f. PECVD process, on their corrosion resistance.
This paper presents the changes in corrosion resistance of SiO2 coatings generated in the plasma process PECVD (Plasma Enhanced Chemical Vapour Deposition), using RF plasma (13.56 MHz), under the influence of the introduction of nitrogen to their volume. Two magnesium alloys AZ32 and AZ91 were put under the tests. On each of Mg alloys the coating of SiO2 was made with a thickness of 1000 nm, and the coatings of SiOxNy (oxynitride) with a thickness of 60 nm and 500 nm. The obtained results were compiled with the reference samples of these alloys. The corrosion properties of the tested coatings were determined based on the analysis of voltammetric curves. The obtained results show that the introduction of nitrogen to a volume of a thin layer of plasma produced SiO2, which is the formation of the layer of SiOxNy improves the corrosion resistance of both examined magnesium alloys. With a much smaller thickness of SiOxNy layer in relation to the thickness of SiO2 oxide layer the similar corrosion current density decreases were obtained.
Application of the dusty plasma technology for diamond ceramics production
Tribological Characterization and Wear Mechanisms of Novel Oxynitride PVD Coatings Designed for Applications at High Temperatures
In recent years, newly developed protective coatings for cutting tools have become more and more wear and abrasion resistant to the extreme environments associated with modern machining processes. On these new coatings the common pin on disk tribological tests have failed, resulting in practically no wear or strongly heterogeneous wear. For efficient tribological testing and determination of wear resistance of the new hard coatings it is therefore crucial to establish a valid set of room temperature and high-temperature wear test conditions. After a large number of preliminary tests performed on a state-of-the-art high-temperature pin on disc tester we identified optimized conditions for characterization of these new types of hard coatings. The investigated coatings comprised AlTiN-based reference, nanostructured Al-Cr-based nitride, oxynitride and oxide coatings deposited using an industrial rotating cathodes arc PVD process on cemented carbide. The nitrogen in the coating was progressively substituted by oxygen up to 100 at.% to create oxide structure in order to avoid oxidation of the coatings at high temperatures. These new oxide coatings are known to withstand extremely high temperatures in dry milling and turning of high-strength materials while exhibiting high wear resistance. However, characterization of their wear resistance by the common tribological tests had proven to be very difficult and new testing procedures had to be established.
General Regularities and Differences of Nanostructured Coatings Based on Nitrides of Zr, Ti, Hf, V, Nb Metals and Their Combinations
Using the vacuum-arc source with the HF discharge, nano-structured hard and super-hard coatings based on Ti-Hf-N(Fe), Ti-Hf-Si-N, Ti-Zr-Si-N, and (Ti, Zr, Hf, Nb, V)N of 1.2µm to 2.5µm thickness were manufactured. The coatings were studied using the proton micro-beam µ-PIXE, RBS, SIMS, SEM with EDS, XRD, and tested for adhesion resistance, wear, and nano-hardness. It was found that a concentration of Ti, Zr, Hf, V, and Nb metals as well as a bias potential applied to a substrate and residual pressure in a chamber (N or Ar/N) affected the formation regularities of solid solutions and quasi-amorphous phases based on a-Si3N4. Hardness of the resulting coatings reached 48GPa to 52GPa, their elastic modulus was 420GPa to 535GPa. The friction coefficient was 0.12 to 0.2, and temperature resistance was as high as 1300oC.[1] Coating structures varied from a columnar to a nanosized one. Grain sizes of the phases of the solid solutions were from 4nm to 10nm or 12nm. Those of a-Si3N4 inter-layer were from 0.8nm to 1.2nm.
Composition of plasmapolymeric coatings using O2/HMDSO gas mixtures and application on elastomers for tribological improvement
Synthesis and characterization of La2NiO4-d coatings deposited by reactive magnetron sputtering using plasma emission monitoring
It is well known that the short life time and the high cost of each component of nowadays Solid Oxide Fuel Cells (SOFC) are induced by their high operating temperature. Many researches focus on the decrease of this operating temperature without reduction of the fuel cell performances (IT-SOFC). Regarding the cathode, one solution is to increase the electrocatalytic properties. Purely electronic conductor perovskite materials (for example LSM: La1-xSrxMnO3) are used in standard SOFC devices. A2MO4+d compounds, with K2NiF4 structure have recently been investigated as substitutes to LSM. Indeed, these materials are mixed ionic and electronic conductors (MIECs) that moreover exhibit rather high electrocatalytic properties. It is then possible to synthesize them as dense materials for SOFC cathodes. Among these materials, lanthanum nickelates La2NiO4+d exhibits convenient electrochemical characteristics. Its thermal expansion coefficient (TEC) is very close to that of the most commonly used electrolyte materials (13 10-6 K-1, 11.9 10-6 K-1 and 11.6 10-6 K-1 for La2NiO4+d, CeO2-Gd2O3 (CGO) and ZrO2-Y2O3 (YSZ) respectively). Its oxygen ionic conductivity and surface exchange coefficient are interesting and seem much better than those of La1-xSrxMnO3 (LSM) and La1-xSrxCo1-yFeyO3 (LSCF), the most commonly used cathodes. The deposition of La2NiO4 coatings by reactive magnetron sputtering has already successfully been performed under so called stable conditions in a laboratory vessel. In this study, we investigate the feasibility of La2NiO4+d coatings deposited by reactive magnetron sputtering under unstable conditions using Plasma Emission Monitoring (PEM). The chemical composition of the coatings was measured by Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy. The influence of the La/Ni ratio on the structure was checked by X-Ray Diffraction analyses.
Chromium and Chromium nitride thin films deposited by HiPIMS using short pulses
The chromium nitride thin films are studied since several years and are widely use in mechanical applications as corrosion barrier. It has already been established that magnetron sputtering can improve by many ways the chromium nitride properties such as hardness, adhesion, oxidation resistance. A new development of this process, named HiPIMS (High Power Impulse Magnetron Sputtering), allows enhancing coating properties. In the first part, the objective of this study is to check the influence of the nitrogen content in the gas mixture on the CrN thin film (on the structure, the morphology). And next, the annealing treatment was investigated to study their behavior at high temperature.
Fatigue Behavior of Coated and Uncoated.Cemented Carbide Inserts Inverstigated by Impact test at the Cutting Edge Vicinity
Significant tool life improvements are attained by the application of harder and more wear-resistant materials and coating systems. In this context, the tools’ cutting edges affect directly the overall tool performance. In this paper, by impact tests at the cutting edge vicinity, a quick assessment of the cutting edge fatigue behavior of coated and uncoated cemented carbide inserts is enabled. Various substrate grades were examined and the effect of their surface treatment and coating on the fatigue endurance load was experimentally examined. The FEM simulation of the test procedure at various distances from the inserts’ cutting edge provides an insight in the developed stress fields and enables the fatigue endurance stress determination of the coating-insert system. The contribution of the substrate surface treatment and coating to the endurance of the cutting edge region was revealed. The developed method facilitates a rapid quality control of both coated and uncoated cutting inserts at loading conditions, close to those encountered during their standard operation.
Influence of Atmospheric Plasma Jet Pre-Treatments of TiO2 Electrodes on Dye Adhesion and DSSC Cell performance
Dye-sensitized solar cells (DSSC) based on nanocrystalline TiO2 were invented by O’Regan and Gratzel in 1991. DSSC are third generation, thin film solar cells. They are photoelectrochemical devices whose operating principle closely resembles the photosynthesis reaction of green plants. There is increasing interest in dye-sensitized solar cells (DSSCs) due to their relatively low cost and ease of manufacture. However, the performance of the DSSC solar cell in many cases is limited by the presence of oxygen vacancy (- Ti3+ defects site) along with surface contamination in the TiO2 electrode. To improve current density and the overall efficiency of the DSSCs surface contamination and surface defects need to be reduced. This study investigated the influence of plasma surface treatments of nanocrystalline TiO2 films on photovoltaic performance of the corresponding DSSCs. Two surface treatments, PlasmaTreat™ an atmospheric air plasma system and a Microwave (MW) plasma system were used for the first time to study the effect of plasma surface treatment of TiO2 on DSSC performance.
Composite layers “MgAl intermetalic layer / PVD coating” obtained by hybrid surface treatment method on the AZ91D magnesium alloy
AZ91D magnesium alloy intended for anticorrosion and anti-wear applications. The investigated composite layers were obtained with the use of the hybrid surface treatment technology, which consist of diffusion treatment in Al powder followed by electron beam deposition method. In order to present the technical realization of hybrid technology the authors designed an original technological process implemented in the hybrid multisource device (Fig.1), produced at the Institute for Sustainable Technologies – National Research Institute in Radom (Poland). The device has been equipped with two arc sources with the cathode diameter of ?=80 mm and with the 60kW electron gun with the dynamic electron beam deflection circuit and steering system. The device is equipped with modern, reliable power systems, substrate polarization system, multichannel process gases dosing system as well as the systems of monitoring and measuring substrate temperature and atmospheric gas pressure. The Al2O3 ceramic coatings was obtained on the AZ91D magnesium alloy with the intermetalic layer MgAl on the surface. The properties of the designed and created composite layers like as microstructure (optical microscopy technique), phase structure (X-ray diffraction), chemical composition (GDOES method) were investigated (Fig.2). The paper also demonstrates the results of adhesion (Scratch test), mechanical properties (Nano Hardness Tester), corrosion investigations (electrochemical corrosion test method) as well as tribology investigations (ball-on-disk method) carried out for AZ91D magnesium alloy covered by investigated composite layers. The obtained results proved that hybrid surface treatment technology – diffusion treatment in Al powder + electron beam deposition, which was developed by authors, enable to significant increase of corrosion and tribology resistance of AZ91D magnesium alloy.
DC Discharge Plasma Polymerization of 1-Naphthylamine
Polymerization of Acrylic Acid by a 4kJ plasma focus device
The most conventional way for polymerization of acrylic acid on different substrates is using RF devices and introducing of other devices is under way. In this work we have a new study on formation of polymer Acrylic Acid using APF plasma focus device. The formation of plasma polymer acrylic acid is discussed using results obtained from attenuated total reflectance infrared spectroscopy (ATR). The results show that after 15 shots, nitrogen pulses performed polymerization on the specimens and the main peaks of ATR spectra assured poly acrylic acid formation on SBR substrate
Thermal and electrical characterization of thin carbon nanotubes films
Carbon nanotubes (CNTs) are grown with a three steps process combining pulsed laser deposition and radio frequency plasma enhanced chemical vapor deposition techniques. The result is a dense thin film made of vertically aligned and multi-walled CNTs. To characterize the thermal properties of the film by pulsed photothermal method, it is necessary to deposit on the top a metallic thin layer of 600 nm acting as a photothermal transducer. The thermal conductivity and volumetric heat capacity of the CNTs film are identified. They are found to be respectively 180 Wm-1K-1 and 5x104 JK-1m-3. The thermal resistance between the CNTs film and the metallic transducer is identified as well: 1x10-7 Km2W-1.
Influence of the nano-structure and composition of titanium nitride based substrate on the carbon nanotubes grown by CVD
We present a study of the influence of the substrate nano-structure and composition on the morphological properties of the carbon nanotubes (CNTs) by sequentially growing in situ TiNx:Oy film, dispersed nickel catalyst particles, and CNTs obtained by CVD. The results show that the stoichiometry and the nanostructures of the substrate intervene in the growing process. Particular attention is pay to the influence of oxygen on the CNT growths. The results show that O prevents the coarsening of the catalyst nickel particles, avoiding the surface diffusion mobility of the precursor atoms involved in the nanotubes growth (Ostwald ripening)1. The dependence of the size and density of the CNTs on the amount of O present in the substrate are reported and discussed. The experimental findings show that, besides acting as diffusion barrier between the catalyst particles and the silicon, the substrate also influences the kinetics of growth of carbon nanotubes.
Fabrication of heterostructured M@M´Ox Nanorods by low temperature PECVD
In this communication we report on the fabrication of two different heterostructured core@shell 1D materials by low temperature (135 oC) plasma enhanced chemical deposition: Ag@TiO2 and Ag-NPs@ZnO nanorods (NRs). The controlled formation of these heterostructures on processable substrates such as Si wafers, fused silica and ITO is demonstrated. The NRs are studied by SEM, HAADF-STEM, TEM, XRD and in situ XPS in order to fully describe their microstructure and inner structure, eventually proposing a growth mechanism. The first type of nanostructures consists on a silver wire surrounded by a TiO2 shell that grows following the volcano-like mechanism. The Ag-NPs@ZnO nanostructures are formed by supported ZnO nanorods decorated with Ag nanoparticles (NPs). The 3D reconstruction by HAADF-STEM electron tomography reveals that the Ag NPs are distributed along the hollow interior of highly porous ZnO NRs. The aligned Ag-NPs@ZnO-NRs grow by a combination of different factors including geometrical distribution of precursor, plasma sheath and differences in the silver/silver oxide densities. Tuning the deposition angle, Ag-NPs@ZnO-NRs depicting different tilting angles can be homogeneously grown allowing the formation of zig-zag nanostructures. The as prepared surfaces are superhydrophobic with water contact angles higher than 150o. These surfaces turn into superhydrophilic with water contact angles lower than 10º after irradiation under UV light. In the case of the AgNPs@ZnO NRs such modification can be also provoked by irradiation with VIS light. The evolution rate of the wetting angle and its dependence on the light characteristics are related with the nanostructure and the presence of silver embedded within the NRs.
High Power Density Pulse Magnetron Sputtering - Process and Film Properties
In this paper specific advantages and disadvantages of different pulse magnetron sputtering processes (unipolar and bipolar pulse sputtering at high and very high power density including HIPIMS) as well as current and potential fields of application will be discussed.
Measurements of SiH4/H2 VHF Plasma Parameters with Heated Langmuir Probe
The parameters of SiH4/H2 VHF plasma were measured as a function of silane gas concentration with a heated Langmuir probe. When the sailane gas concentration was increased, the nagative ion density increased. The negative ion density was estimated from the reduction of the electron saturation current. In addition, the dependence of the sheath potential on the silane gas concentration agreed with the theoretical values derived from the Bohm sheath equation including negative ions.
High rate PECVD of a-C:H coatings in a hollow cathode arc plasma
Amorphous carbon films deposited by plasma-based processes are of increasing importance for tribologi-cal applications, e. g. as protective coatings on components or in order to reduce their friction. However, most plasma-activated CVD and PVD techniques suffer from their poor deposition rate and low economic efficiency. At Fraunhofer FEP, a hollow cathode-based plasma source has been established as a versatile, reliable, and highly efficient tool for plasma pretreatment, plasma-enhanced PVD processes, and reactive gas activation in large volumes. As a further application field, this plasma source has been evaluated for PECVD of amorphous hydrogenated carbon films (a-C:H). Acetylene has been introduced into the hollow cathode plasma as a precursor gas. The plasma composi-tion has been characterized by an energy-resolved ion mass spectrometer. Intense ionization, dissociation, and polymerization effects have been observed, which strongly increase when the argon gas flow rate through the hollow cathode tube is reduced. Moreover, the ion energy distributions show high energy tails up to 100 eV in dependence of the spatial distribution of ion generation. a-C:H films have been deposited on stainless steel and silicon substrates with growth rates up to 1000 nm/min. Nanoindentation measurement of the a-C:H coatings reveal hardness up to 18.2 GPa. In this paper, film properties and compositions will be discussed and related to the corresponding plasma condi-tions obtained by energy-resolved ion mass spectrometry.
Growth of Carbon Materials on Gold Substrate by Plasma Enhanced CVD
Carbon is a versatile building element of many interesting materials that have already find practical applications in the form of thin films (diamond, DLC) or potential applications in the form of nanostructures (fullerenes, carbon nanotubes, graphene). For electronics or sensors, it is important to provide a very good contact to the functional structures. Gold is the best choice taking into account its inertness, i. e. oxidation resistance. From this point of view the investigation of the growth of carbon materials on gold is important. The carbon-gold interaction plays an important role in different fields of electronics such as atomic force microscope lithography, bioelectronics or semiconductor industry. Research in this field is developing rapidly e. g. the modification of interface structure and contact resistance between a CNT and gold electrode was recently modified by Joule melting and amorphous C-Au nanocomposite thin films were deposited by dc magnetron co-sputtering. Herein we report on the preparation and characterization of the carbon nanocomposites which were synthesized on gold substrate from methane precursor using low pressure thermal chemical vapor deposition technique and two different plasma-enhanced chemical vapor deposition (PECVD) methods. The former one PECVD proceeded in microwave reactor at low pressure and the latter one was carried out using non-thermal atmospheric pressure plasma jet (ntAPPJ). Presented approach is based on the deposition of carbon material on gold instead of the deposition of gold on carbon material which is more common. Surprisingly, we didnt find similar studies dealing with the synthesis of carbon nanocomposites using direct deposition from hydrocarbon precursor on the gold thin _lm. The surface morphology was studied by high resolution scanning electron microscopy (HRSEM). Depth-structure profile including the film thickness was observed using the focused ion beam ablation. Energy-dispersive X-ray spectroscopy (EDX), infrared reflection absorption spectroscopy (IRRAS) and laser desorption-ionization time of flight mass spectrometry (LDI-TOF MS) were used to study the chemical properties. Gold and carbon related clusters were observed by means of mass spectrometric study.
Cr-DLC films deposited by dual pulsed laser ablation
Diamond-like carbon (DLC) and Cr doped diamond-like carbon (Cr-DLC) layers were studied for potential medical applications. DLC and Cr-DLC were deposited on silicon and titanium substrate by dual pulsed laser ablation using two KrF excimer lasers and two targets (graphite and chromium). The topology of layers was studied using scanning electron microscopy (SEM). The composition was analyzed using wavelength-dependent X-ray spectroscopy (WDS). Ethylene glycol, diodomethane and deionized water were used to measure their contact angles, which were used to evaluate the surface free energy.
Comparison of the wear particle size distribution of different a-C coatings deposited by vacuum arc
For biomedical application in the field of artificial hip joints diamond-like carbon (DLC) coatings have been widely studied due to their excellent mechanical, tribological and biological properties. The wear particles as the main factor limiting the life expectancy of hip joints have attracted more and more interest, not only the number of them, but also the distribution of their size. In this study we have deposited DLC coatings on stainless steel (P2000) by a vacuum arc adjustable from anodic to cathodic operation mode. To improve the adhesion of the DLC coating on P2000, titanium as a metallic interlayer was deposited by cathodic vacuum arc evaporation. The frequency distribution of wear particles generated using a disc-on-disc test was measured by a particle size analyzer. It was shown that the maximum of the frequency distribution e.g. at —1000 V bias can be shifted to below 1 µm with increasing anode/cathode diameter ratio da/dc.
On the deposition rate during High-Power Impulse Magnetron Sputtering.
ION Flux–Film Structure Realtionship During Reactive Magnetron Sputtering of Tungsten
Interpretation of optical emission in a strongly inhomogeneous PIAD environment
A variety of methods exists for the production of high quality optical coatings. These are for instance magnetron or ion beam sputtering, or thermal evaporation assisted by ion or plasma ion beam sources. The choice of a particular technique is due to the specific demands for tailoring the thin film properties such as homogeneity, refractive index, absorption, mechanical stress, porosity (optical shift), etc.. To allow for economic production of complex multilayer designs, the issue of reproducibility at the highest deposition rate possible has to be faced. The plasma ion assisted deposition (PIAD) has been invented to avoid contamination of the process environment present when gridded ion sources are employed. One example for this approach is the Advanced Plasma Source (APS) which holds a considerable market share in the field of optical coatings. The APS is a hot cathode (LaB6) DC glow discharge with an auxiliary magnetic field, typically operated with argon. A high density (ne ~ 1012 cm-3) and high temperature (Te ~ 20eV) plasma is generated in the source region (V ~ 0.7l) and expands to the chamber (V ~ 103 l) which is held at high vacuum (p ~ 2 • 10-2Pa). The expansion induces a strong drop of the plasma potential Vp which results in an acceleration of the ions towards the substrates. The setup is outlined in figure 1. By varying the discharge voltage (VD=50..150 V), the magnetic field (Bmax=10..40mT) and the gas flux (GAr=2..20 sccm) different characterstics of the plasma ion beam are obtained, where typical ion energies are Ei=50..150 eV. As is described in the references, various probe techniques were adopted to elucidate the mechanisms of plasma beam formation in this particular PIAD setup. In an earlier work the approach of optical emission spectroscopy (OES) has been pursued. This paper contains a description of the diagnostic installation allowing for tomographic reconstruction of the local optical emission near the source exit. With a simple corona model ne and Te could be estimated for an Ar/He mixture. The interpretation of emission close to the APS is hampered by the lack of detailed knowledge of neutral density and temperature in this region. In this extended abstract the preparation of a more elaborate approach using collisional radiative modelling is sketched. The new aspect is the consideration of a global electron energy probability function (EEPF) based on the nonlocal approximation. This concept is useful for reducing the complexity of electron kinetics by coordinate transformation from the 6D phase-space to a 1D total energy space. The analysis of OES data is not merely ment as a proof of principle. The final goal is to interpret the OES data in terms of electron parameters, as a foundation of a control scheme for the APS using non-invasive optical diagnostics. Although global parameters, such as voltages and currents can be maintained accurately, drifts in the plasma parameters which are not measured routinely in the industrial application, may lead to limitations in the reproducibility of the optical coatings. The main reason is suspected to be the alteration of the electrodes of the APS during the PIAD process.
Plasma polymers used for controlled interphase in polymer composites
The performance of fiber-reinforced composites is strongly influenced by the functionality of composite interphases. Sizing, i.e. functional coating (interlayer), is therefore tailored to improve the transfer of stress from the polymer matrix to the fiber reinforcement by enhancing fiber wettability, adhesion, compatibility, etc. The world market is dominated by glass reinforcement in unsaturated polyester. However, commercially produced sizing (wet chemical process) is heterogeneous with respect to the thickness and uniformity, and hydrolytically unstable. Companies search for new ways of solving the above problems. One of the alternative technologies is plasma polymerization. Plasma polymer films of hexamethyldisiloxane, vinyltriethoxysilane, and tetravinylsilane, pure and in a mixture with oxygen gas, were engineered as compatible interlayers for the glass fiber/polyester composite. The interlayers of controlled physicochemical properties were tailored using the deposition conditions with regard to the elemental composition, chemical structure, and Young’s modulus in order to improve adhesion bonding at the interlayer/glass and polyester/interlayer interfaces and tune the cross-linking of the plasma polymer. The optimized interlayer enabled a 6.5-fold increase of the short-beam strength compared to the untreated fibers. The short-beam strength of GF/polyester composite with the plasma polymer interlayer was 32% higher than that with commercial sizing developed for fiber-reinforced composites with a polyester matrix. The progress in plasmachemical processing of composite reinforcements enabled us to release a new conception of composites without interfaces.
Study of the transition between capacitive and inductive modes on propanethiol plasma polymer properties: correlation between plasma and film chemistry
Mechanical properties of plasma polymer films controlled by RF power
This study deals with plasma polymer films deposited on silicon substrates using tetravinylsilane monomer. The deposition technique was plasma-enhanced chemical vapour deposition. Nanoindentation was used as a method to investigate mechanical properties of samples prepared at different RF powers. The Young’s modulus and hardness of thin films were estimated from load-displacement curves. The nanoscratch test was employed to determine the critical normal load needed for film delamination, as a parameter describing adhesion to the substrate. AFM images of scratches were carried out to correlate the data with nature and shape of scratches.
Plasma deposition of hydrophobic coatings on structured surfaces for condensation and heat transfer applications
The control of vapor condensation processes by suitably prepared surfaces is a prominent research area with important applications in the industry. For example, it is well known that the efficiency of condensation heat exchangers can be significantly increased when the vapor condenses to form droplets on the surface, instead of a closed film which does not wet the surface. In the present work, hydrophobic thin films are deposited via plasma CVD processes on metallic surfaces to investigate the condensation of water vapor on these surfaces. The drop-wise condensation on the coated surfaces is analyzed by optical microscopy and the effect on the heat transfer is measured by heat flux measurements. In order to show the potential of the deposition process for industrial applications and to investigate the effect of drop-wise condensation on heat transfer, copper (Cu) substrates were coated with a plasma polymer film using an organosilicon monomer (Hexamethyldisiloxane, HMDSO) as a precursor. In addition, the effect of surface roughness on the drop-wise condensation is presented because the static contact angle of water on hydrophobic surfaces depends strongly on surface topography.
Silicon carbide surface micromachining using plasma ion etching of sacrificial layer
Rapid Stripping of Brass-plating on Fine Saw Wire by Triangle-type Multiple Magnetron Plasmas
To remove brass plating on fine saw wire, line-shaped magnetron plasma source has been newly developed. New type of multiple plasma sources has been developed by applying to multiple-triangle-type electrodes. The stripping effects were successfully established by using high density magnetron source with 20mm gap in an axially applied magnetic field. From the EDS analysis results of wire surface after plasma stripping during 30sec, it is clearly shown that Zn was removed after 10sec stripping and Cu after 30sec. (Fe:38.5%?97.7%, Cu:39.3%?2.43%, Zn:22.2%? 0.03%)
Scaling laws governing the NF3 cleaning plasma in a large area reactor
An important part of the thin film Silicon PECVD technology for photovoltaic industry is the Flourine based plasma cleaning of the reactor. Precursors like CxFy, SF6, NF3 or even F2 can be used. The present paper investigates scaling laws governing the processes in NF3 plasma in a large area reactor.
Cleaning of Organic Contamination from EUV Optics Surfaces Using Hydrogen-based Plasmas
The efficiency of optics used in extreme ultraviolet (EUV) range suffers from reflectivity degradation due to oxidation and carbon contamination of mirror surfaces. Therefore, an efficient cleaning procedure should be ascertained in order to facilitate applications of EUV lithography tools. Carbon contamination removal from the mirror surface has been reported in Hydrogen plasmas, and laser-induced Hydrogen plasmas in EUV tools. Here, we performed measurements in a helicon-type RF plasma reactor with hydrogen pressures similar to the ones used in laser-induced plasmas in EUV tools. The method of optical actinometry was used to determine hydrogen atom concentration and the degree of dissociation. The results are compared to those obtained by pressure-rise measurements. Preliminary results of plasma etching of thin organic films (PMMA) were also obtained to assess the cleaning efficiency.
Influences of surface-active substances on specific power inputs and on surface roughnesses of the metal product under plasma vacuum arc treatment
The use of the vacuum arc for cleaning of the material surfaces and for removal of various contaminations is an actual problem in view of essential advantages of this cleaning method in comparison with chemical, mechanical and other ones and, first of all, in view of absolute environmental safety of vacuum arc method [1-5]. However, in the case of vacuum arc cleaning of some kinds of the hot rolled metals covered with relative thick (6-12 microns) layers of oxide, the roughness of the surfaces after cleaning sometimes exceeds the necessary limit of 10-14 microns. Cleaning of such steels of thick layers and removal of the scale is accompanied by the large power inputs. It is a reason of necessity of improvement of plasma vacuum arc technology and of the study of the interaction mechanisms of cathode plasma of the vacuum arc with the material surfaces.
Plasma etching of aluminum nitride thin films prepared by magnetron sputtering method
Several properties of the AlN films as e.g., isomorphous crystallographic structure, high resistivity (~1013 O cm), high thermal stability (up to 2200 °C) and high thermal conductivity (~320 W/mK), make it excellent material for application in structure of HEMT, FET transistors, playing role of dielectric. However, reaching a level of considerable maturity by technology of any electronic material, requires not only adequate methods of its synthesis but also capabilities of material processing, among others availability of means of its selective etching.
Effect of Xe+ ion bombardment induced patterns in stainless steel on plasma nitriding processes
The texturing of surfaces is an important method applied in various technological areas of research. Much of the current interest on surface modifications stems from the possibility of obtaining special optical, magnetic, tribological, and mechanical properties in a variety of materials. The texturization of steel surface by ionic bombardment (atomic attrition) is an interesting route to modify plasma nitriding process. The observed changes in plasma nitriding are attributed to several causes such as increasing surface nitrogen retention, stress, and creation of lattice defects, altogether improving nitrogen diffusion.1 In this paper we report the effect of Xe+ ion bombardment on the surface of the steel (SS 316L and AISI 4140). The bombardment effect on plasma pulsed nitriding process is also reported.
Investigations on the active screen plasma nitriding process
This study presents the mechanism of nitrogen transfer in a large scale active screen plasma nitriding (ASPN) unit. The active screen provides a homogeneous temperature distribution within the workload as well as an arcing tendency is reduced, since the plasma is moved from the treated work pieces to the active screen. In order to study the mechanisms in detail, plasma diagnostics is necessary. The applied diagnostic methods for analyses of the excited process gas synthesised by the active screen include mass spectrometry and infrared diode laser spectroscopy (TDLAS). Together with a metallurgical characterisation of nitrided steels a better understanding of the chemical phenomena in the N2-H2 plasmas is achieved. Various N2/H2 gas mixtures and variable bias activation powers at the pressure of 200 Pa were investigated. It was found that even during heating up in nitrogen free process gas exited nitrogen (atomic or molecular) releases from the active screen. Infrared diode laser spectroscopy has been used as a diagnostic methode to measure the concentrations of the stable NH3 molecules downstream the plasma source. The ammonia production turns out to depend on the mixtures of N2-H2 and the current input of the bias activation. The results are discussed with the plasma parameters measured by the electrostatic probe. Thus, a contribution to the interpretation of the mass transfer in ASPN process has been realised.
Control of nanoparticle formation in reactive plasmas and its application to fabrication of green energy devices
We are developing “plasma nano-factories” which are bottom-up guided assembly processes and miniature versions of macroscopic conventional factories. Here, we report plasma-based control of the size, size distribution, and structure of nanoparticles, their agglomeration and transport as well as sticking. We apply nano-particle films to green energy devices such as low energy consumption LSI’s, solar cells, and Li ion batteries. Our results show that core-shell nanoparticles are effective for improving performances of these devices.
Laminated Composite on the Basis of Plasma Modified PTFE Films and Thin Aluminum Layers
Copyright (c) 2023 International Conference on Plasma Surface Engineering
The formation of superhard coatings = 48 GPa in Ti-Hf-N (Fe) and analysis of their structure and properties.
Superhard nanostructured Ti–Hf–N(Fe) coatings are prepared. The formation of local regions of (Ti, Hf)N, FeN, and Hf is detected using µ-PIXE (ion microbeam). It is revealed that the synthesized coatings have a nanohardness of 48 ± 1 GPa and are composed of nanograins with a size of 4.8–10.6 nm, which are enveloped by finer entities of other phases (Ti, Fe)N and FeN. There is a good correlation between the results derived by XRD, TEM, AFM, and SEM and microanalysis, which in turn are complemented by the analysis results obtained using an ion microbeam and PIXE.
Electrochemical and mechanical properties of low friction nc-CrC/a-C:H and nc-WC/a-C:H coatings on construction materials deposited by magnetron sputtering.
The increased focus on the natural environment protection, the increasing fuel prices and the will to reduce the costs of machines’ maintenance - all that obliges us to search for innovative engineering solutions that would both limit the use of conventional lubricants and enhance the machines’ efficiency. To fulfil this challenging goal, the parts of machines are coated with special low friction and high wear resistant materials more and more often. The PVD methods play a great role in this field. As the examples of coatings deposited by a PVD method and assuring the above mentioned goals may serve the nc-CrC/a-C:H and nc-WC/a-C:H. This research focuses on the electrochemical and mechanical studies of low friction nc-CrC/a- C:H and nc-WC/a-C:H coatings deposited by magnetron sputtering on two kind of construction materials: Vanadis 23 steel and oxygen hardened Ti-6Al-4V alloy. The obtained coatings were investigated using various electrochemical and mechanical methods. The following parameters of coatings were determines: electrochemical (corrosion resistance), micro-mechanical (nanohardness, Young’s modulus) and tribological (wear resistance, friction coefficient). The results presented in this paper have been obtained within the project “KomCerMet” (contract no. POIG.01.03.01-00-013/08 with the Polish Ministry of Science and Higher Education) in the framework of the Innovative Economy Operational Programme 2007-2013.
Nanoparticle Synthesis in a Plasma Downstream Reactor – From Plasma Parameters to Nanoparticle Properties
In the presented study a tubular plasma reactor is investigated, which is normally used for the continuous plasma surface modification of fine-grained powders. The plasma reactor basically consists of a 1.5 m long glass tube with a gas and precursor feed unit at its top and a particle-gas separation unit at the lower end. The power is coupled inductively into the plasma via a coil which is wrapped around the reactor tube. Substrate powders normally pass the discharge tube with high velocity and are functionalized on their way through the plasma in approximately 0.1 s. Possible plasma surface functionalization processes for powders are illustrated in Figure 1.1. The wettability of powders is increased by the formation of polar groups on the surface. Films are deposited on particle surfaces to protect the substrate from harsh environments or for catalytic applications. In recent years, also a new plasma process, which increases the flowability of fine-grained powders, gained increasing attention. Nanostructured SiOx is formed in the plasma and directly deposited on the substrate particle surface. These nanoparticle structures increase the surface roughness of the substrate particles. Thus, the interparticle van der Waals forces are reduced, which leads to a major improvement of the powder flowability. This process shows promise for companies dealing with cohesive granular materials. The feasibility of this process was shown in the past, but at the same time the need for fundamental research in this field was recognized. Which ion density is required to yield in an effective surface modification? What is the thermal load of a substrate particle during the treatment? Which precursor should be used for a maximum improvement of the flowability? In order to answer such questions, we measured axial profiles of plasma parameters in this continuous reactor and studied the nanoparticle synthesis in detail. No substrate powder was fed during these investigations to facilitate probe measurements and to focus on the produced nanoparticles. Silica-like nanoparticles were produced from the four organosilicon monomers hexamethyldisiloxane (HMDSO), tetramethyldisiloxane (TMDSO), tetraethyl orthosilicate (TEOS), and tetramethyl orthosilicate (TMOS) in argon-oxygen gas mixtures. The chemical composition and morphology of the emerging particles and its production rate were studied as a function of process pressure (100 – 400 Pa), plasma power (200 – 350 W), gas velocity (5 – 16 m/s) and gas composition. Langmuir double probe and calorimetric probe measurements allowed determining the axial profiles of electron temperature, positive ion density, and energy influx along the vertical axis of this tubular reactor.
Silicon dioxide coating of titanium dioxide nano particles from dielectric barrier discharge in a gaseous mixture of silan and nitrogen
Titanium dioxide nanoparticles are used commonly in various applications due to their high catalytic activity. Many of these applications require subsequent treatments after the deposition of the TiO2 particles. Some of these include thermal processing at high temperatures, e.g. roof tiles. For all of these applications, the crystal structures as well as the microscopic properties are essential. Thus, sintering severely affects the catalytic activity in most of the cases. During thermal processing, the nanoparticles transform from the catalytical highly active anatas structure to the substantially less active rutil structure. This structural change has been found to be significantly retarded when coating the TiO2 nanoparticles with a closed film of SiO2. During the thermal treatment, these films break open, revealing the underlying TiO2 [i]. Thus, the film thickness has to be appropriate for the designated treatment subsequent to the nanoparticle deposition. In this study, we present an approach of SiO2 film deposition making use of silane gas. Pure silane gas is highly demanding on safety standards and technical installations, since it acts self-igniting and highly explosive when getting in contact with air or any oxygen containing gas. Thus, diluted process gases are used for most technical implementations, which contain just about 3% silane in 97% helium, neon, argon, hydrogen or nitrogen. While noble gases and hydrogen are used as dilution for a wide range of applications, the process gas consisting of nitrogen and silane is only implemented for silicon nitride deposition. Nevertheless, this gas should be the most suitable for many applications regarding economics and handling. Closed films produced by dielectric barrier discharges in such mixtures of gases consist of mainly non-stoichiometric silicon nitride, while the other diluted process gases produce metallic silicon films. The deposition of silicon dioxide films is rather complicated, since the silane reacts instantaneously with every oxygen-rich gas. Thus, both gases must not get in contact until they have arrived in front the surface that is to be coated. Most of the existing work found in the literature focuses on the implementation of this condition, to merge the silane and the oxygen right at the surface being coated. Taking a quite different approach, we divided the film deposition into two steps: In the first step, a silicon nitride film was deposited from the process gas with the silane diluted in nitrogen employing a dielectric barrier discharge plasma. As a second step, the silicon nitride film has been tried to convert into silicon dioxide by means of a second plasma discharge using either oxygen for a process gas or even environmental air. All studies have been carried out in an ultra high vacuum apparatus, while the plasma treatments have been carried out up to atmospheric pressure. During the investigations we employed Metastable Induced Electron Spectroscopy (MIES), Ultraviolet Photoelectron Spectroscopy (UPS) and X-ray Photoelectron Spectroscopy (XPS), as well as Atomic Force Microscopy (AFM). The microscopic measurements showed the deposited film to enclose the particles in a Frank van der Merwe – type growth mode. Film thicknesses determined by increased particle diameters in AFM were in good accordance to calculated film thicknesses from XPS peak intensity attenuation. Spectroscopic results show a formation of a silicon nitride film with substoichiometric nitrogen content, though free of oxynitrides. Surface impurities and adsorbates from the ex-situ preparation procedure were strongly removed and seemed to notably increase the growth rate. The second step gained a transformation of the film up to 98% silicon dioxide according to XPS. Remaining carbon impurities from the initially uncleaned surface were removed by both of the oxidizing plasmas. The transformation was found to be even more effective for the air plasma treatment than for the oxygen plasma treatment at a comparable oxygen partial pressure.
High Power Pulsed Hollow Cathode for Nanoparticle Synthesis
Copper nanoparticles were synthesized using a novel method based on sputtering material from a hollow cathode using high power pulses. The high power pulses provide a supersaturated vapor with a high degree of ionization from which the nanoparticles are formed in the gas phase. By adjusting the pulse parameters, the plasma environment and thus the nanoparticle growth can be affected. It was found that the nanoparticle size can be influenced by varying, e.g., the pulse frequency or the pulse power. The results using the high power pulsed hollow cathode are compared to nanoparticles synthesized with a dc discharge using the same setup.
Effect of low temperature air plasma treatment on physico-chemical properties of kaolinite
It was found in this study that air plasma treatment of particular kaolinite has led to the change of its wettability. This was reflected in the decreased values of water contact angles of wetting. There were determined yield locus and flow function dependencies at different stress levels for virgin and different time plasma treated samples (flow index - ffc, effective angle of internal friction - phie, unconfined yield strength - sigmac). It was found that by plasma treatment the character of the flow was shifting from region of very cohesive (ffc = 2.39) to the cohesive (ffc = 3.19). For untreated samples effective angle of internal friction was decreased with increasing applied consolidation stress, while for plasma treated kaolinite it was increased.
Study of the chemical etching of carbon surfaces facing argon/hydrogen plasmas in a helicon type reactor
The study of the chemical erosion by atomic hydrogen of graphite in the purpose of characterizing etching and re deposition growth kinetics is presented. Carbon samples undergo plasma treatment under different time-exposures and gas mixtures at 10 mTorr, determined as the optimal pressure. The etching outcomes are analyzed via mass loss and structure comparison (SEM, micro-Raman spectroscopy) in order to evaluate the impact of the different experimental conditions, i.e. pressure, gas mixture, RF power coupling mode and erosion duration.
Tribological properties of laser textured and DLC coated surfaces with solid lubricants
Hydrogen free diamond-like carbon coatings (DLC), i.e. tetrahedral amorphous carbon (ta-C) films, have high hardness and low coefficient of friction at ambient temperature and humid conditions. However, the coefficient of friction and wear rate in sliding contacts against steel surfaces increase severely at elevated temperatures. Adding solid lubricant into micro-reservoirs produced by Laser Surface Texturing (LST) has been reported to decrease the coefficient of friction of sliding surfaces. In this study, incorporation of MoS2 and WS2 solid lubricants onto laser textured and ta-C coated steel surface by burnishing was demonstrated to provide improved tribological properties such as low friction and high wear resistance at elevated temperature with an extended lifetime of the surfaces.
Zr-DLC coatings - analysis of the friction and wear mechanisms
In the last few decades, the amorphous or nanostructured carbon structures prepared by several deposition techniques are a subject of considerable research interest due to their excellent properties, such as high hardness and chemical inertness, wear resistance or low friction. There have been also attempts to improve the mechanical, chemical or tribological properties of carbon coatings by addition of other elements. Generally, specific chemical composition of the modified films strongly affects the surface energy, and may modify various physical properties and decrease compressive stress, making some metal-doped carbon films suitable for large variety of practical applications. Our work was focused on the structural, chemical and tribological properties of Zr-doped DLC coatings with controlled composition. The main attention was paid to the determination of the wear mechanisms, characterization of the worn surfaces and wear debris and formation of a tribolayer affecting the tribological process. The as-deposited coatings and worn surfaces were studied using 3D optical profilometry, Raman spectroscopy, X-Ray diffraction (XRD) and Scanning electron microscopy (SEM).
Control of Deposition Profile and Properties of Plasma CVD Carbon Films
We have succeeded to deposit anisotropic and top surface deposition profile on substrates with trenches using H-assisted plasma CVD of Ar + H2 + C7H8 at a low substrate temperature of 100 oC. For the anisotropic deposition profile, carbon is deposited without being deposited on side-wall of trenches. For the top surface deposition profile, carbon is deposited at only top surface. The optical emission measurements and evaluation of deposition rate have revealed that a high flux of H atmos is the key to the deposition profile control. The mass density of the films and their Raman spectrum have shown that their structure is a-C:H.
Plasma surface modification of diamond-like carbon films to graphene
Multifunctional coatings on fabrics by application of a low-pressure plasma process
Nowadays, there is an increased demand to produce highly-performant fabrics combining multiple properties such as flame retardancy, hydrophilicity/hydrophobicity, antibacterial, UV resistance, etc. In order to produce a wash-resistant-flame-retardant-water-repellent-dyed multifunctional coating on natural fabrics like cotton and silk, various protocols involving the Ar plasma-induced graft-polymerization (PIGP) process of suitable monomers were investigated. The burning behaviour of treated fabrics is discussed using LOI measurements. The water repellent behaviour is evaluated by means of Schmerber pressures (PSch.) and dyeing properties by spectrophotometric measurements. The wash-resistance of the coatings was tested by using an accelerated laundry method. The obtained results have shown that for each protocol, the flame retardant monomer is compatible with a water repellent or a dyeing treatment.
Hierarchical, Plasma Nanotextured, Superamphiphobic Polymeric Surfaces
A facile, mass production amenable, rapid method for making superamphiphobic / amphiphobic surfaces by random plasma nanotexturing of polymers in plasmas is presented. Plasma etched and simultaneously randomly roughened (nanotextured) polymethylmethacrylate (PMMA) Polyether-ether-ketone (PEEK), Cyclic-olefin-copolymer (COC) and Polydimethylsiloxane (PDMS) substrates show hierarchical roughness and complex high-aspect-ratio morphology. Here, they are investigated as superamphiphilic surfaces after plasma etching or superamphiphobic surfaces, after plasma deposition of a thin fluorocarbon film following plasma etching. We show that polymer surfaces etched in oxygen (PMMA, PEEK, COC) or SF6 (PDMS) plasma for few minutes (with texture height< 600nm) exhibit excellent superamphiphobic behaviour, while surfaces treated for longer time show porous-like filamental morphology (filaments several microns height), which is coalesced and stabilized upon wetting, allowing their potential long-term use. Superamphiphobic / amphiphobic behaviour is observed in all cases.
Plasma processing of scaffolds: perspectives for Tissue Engineering
Formation of pH-responsive polymer composite membranes by plasma-induced graft polymerization method
The structure and the transport properties of polymer composite membranes consisting of a porous substrate and a polymer layer obtained by plasma-induced graft polymerization method were studied. It has shown that the presence of the polymer layer on the surface of porous substrate leads to changing its transport properties - the water permeability of the formed composite membranes substantially depends on the solution pH. These changes are caused by convertible conformational transitions of macromolecules of the grafted polymer layer from an expanded state into a compact one which is in turn caused by the degree of ionization of the functional groups on the surface of this layer.
Scuffing propagation of heavily-loaded, lubricated, coated friction joints
There is great interest in improving the wear and friction of a wide variety of machine components, e.g. gear systems, gears. In modern technology, due to the increase of the unit pressure, velocities, and hence temperatures in the tribosystems of machines, a risk of a very dangerous form of wear exists. This form is scuffing. The most effective way of to improve the mechanical properties of various engineering components is the modification of surface properties by the deposition of PVD/CVD coatings. In literature, the problem concerning whether it is the most beneficial to coat only one or both of the contacting surfaces and on when and how the coatings may improve the tribological situation in heavily loaded lubricated friction joints is not solved [2, 3]. The aim of this paper was to explore the mechanisms of scuffing propagation of heavily loaded friction pair elements coated with a low-friction WC/C coating for various material combinations.
Progress in Quantitative Adhesion Testing of Films and Coatings by means of Centrifuge Technology – Present State of the Art
Standardised conventional adhesion tests are time-consuming single-sample tests. Moreover, except for the pull-off test, all these tests provide only qualitative or semi-quantitative (ranking, respectively measurement of an adhesion-correlated quantity) information on adhesion. Sometimes, adhesion is evaluated even under compressive stress conditions (e.g. cross-cut and scratch test), which itself is a contradiction to adhesive strength as defined in terms of tensile force per area. For optical coatings it has been shown that the pull-off test in a centrifuge is definitely a promising alternative with respect to the reliable, fast and quantitative determination of adhesive strength in N/mm2. The force-controlled centrifuge test is the only multiple-sample test which provides reliable quantitative information on the adhesive strength in agreement with DIN EN 15870 and DIN EN ISO 4624 on a statistical basis for up to eight samples simultaneously tested under identical testing conditions.
Nano-Impact Tests on Micro-Blasted Coatings for Assessing Their Brittleness
Residual compressive stresses can be induced into a PVD film up to a certain depth from the coating surface via micro-blasting. Depending on the micro-blasting conditions, the deformed film depth varies, thus affecting the coatings performance in different applications. A method has been already introduced for determining mechanical strength properties gradation in coatings after micro-blasting.
Atmospheric pressure plasma treatments inside meander-like cavities
Optimization of APS Process Parameters Using a Designof Experiment for CSZ ( CeO2 Stabilized Zirconia) Coatings
Air Plasma Sprayed (APS) Ceria Stabilized Zirconia (CSZ) coatings have been extensively used as alternative material yo Yttria Stabilized Zirconia (YSZ) in the gas turbine industries due to the good mechanical properties and hot corrosion resistance at an elavated temperatures. Due to the high velocity and temperature gradients in the plasma jet, any changes in the process parameters can result in significant changes in the particle properties and consequently in the microstructure of the coating. For increasing coating quality, operational primer process parameters as plasma gas flow rates, plasma current, spray distance must be optimized. The statistically designed taguchi experiments and regression analysis are used to determine the effects of processing parameters on mechanical and microstructural properties of coatings. The effect of changing the processing parameters on properties such as density, thickness, deposition efficiency and the amount of porosity in the coatings has been investigated in this study. Results showed that the CSZ has a higher deposition efficiency and denser microstructure than the YSZ systems.
Microstructure and Mechanical Behaviour Relationship of Plasma Sprayed Mullit+YSZ Coatings
The YSZ/mullite composite coatings have been given an impression for improved high temperature resistance over YSZ coatings under severe service conditions and should be investigated further for its possible use in thermal barrier coating (TBC) systems. In this study, a composite thermal barrier coating made from a combination of YSZ and mullite (wt%25 to 50) was investigated. Powders of each powders were mechanically mixed together and then sprayed on superalloy substrates. Microstructure and mechanical behavior relationship of these composite coatings were investigated. Crystallinity and phase ratios were determined by XRD analysis. Results showed that mullite addition improved the mechanical behaviour of YSZ coating under high temperature conditions.
The effectiveness of prevailing plasma spray conditions in the synthesis of protective coatings
Protective and catalytic coatings of different composition are widely used in diverse fields of industry including a modification of surface layers of constructional materials. Mechanisms of film formation in plasma spray processes are not investigated thoroughly. It is not determined how the parameters of process influence the quality, specific surface area, thickness and adhesion of coatings. Therefore the investigation of the influence of formation technology on structure and properties of protective ceramic coatings is the main objective of present work.
A Comparative Study of Wear Effect on the Microstructures Behavior of CoNiCrAlY Coatings fabricated by APS, HVOF and CGDS Coatings
This work focuses on the micro-abrasion wear and microstructural properties of CoNiCrAlY coatings fabricated on nickel based super alloy substrates by using the atmospheric plasma spraying (APS), high-velocity oxygen fuel (HVOF), cold gas dynamic spraying (CGDS) methods. Tribological tests were performed on the samples in order to understand the wear mechanism of thermally sprayed coatings and influence of the coating microstructure on wear mechanism. The microstructures of as sprayed and weared coatings were investigated by scanning electron microscopy. Initial surface topography was examined by surface profilometer. Coating hardness measurements were performed with a micro-hardness tester. The micro-abrasion tests were carried out with some different durations. The lateral fracture was observed as wear mechanism on the specimens. The wear surface resistance have changed with coating process and surface features of specimens depending on the coating process.
Oxygen effect in Magnetron Sputtered Aluminum doped Zinc oxide films.
In this work, polycrystalline transparent conductive aluminum doped zinc oxide (ZnO:Al) films, have been successfully grown on glass and silicon substrates by rf magnetron sputtering technique at room temperature. The effect of oxygen content in plasma on the structural, optical and electrical properties of the films was systematically studied. The growth rate was fond to decrease with the increase in O2 content. The crystal structure of ZnO:Al films deposited on glass is hexagonal with C axis preferential orientation, while for film deposited on silicon substrate, the preferred orientation of crystallite shifts from (002) to (100) direction with the increase in O2 content. Intrinsic stress increases with an increase of oxygen content, and near stress-free film was obtained at 0 % O2 content. Low resistivity (?= 1.25x10-3 Ocm) associated to high transmittance (T>92 %) in the visible regions, were obtained for ZnO:Al film deposited at room temperature without oxygen content in the deposition chamber. From the optical characterization, we deduced that the band gap shifts towards lower energy with an increase of oxygen content.
Photocatalytic, hydrophilic titanium dioxide prepared by direct current magnetron sputtering
Photocatalytically Active Titania Produced by MOCVD Plasma Process
The deposition of photocatalytically active titania layers at ambient temperature was developed using the plasma enhanced metal organic chemical vapour deposition (PE-MOCVD) method at low and atmospheric pressure. An increase of the photo-activity in the near ultraviolet (UV) and blue light irradiation was achieved by doping the titania layers using the elements nitrogen and/or carbon. Investigation of the chemical and structural features of the titania layers was carried out by x-ray photoelectron spectroscopy, atomic force microscopy, and Raman. The optical energy bandgap and photocatalytic activity at 365/428 nm for various titania layers were analyzed using ellipsometry and the methylene blue dye bleaching according to ISO 10678:2010, respectively. The reduction of the aqueous methylene blue solution was similar for the two categories of titania layers. However, the photo-induced properties such as the mineralization of stearic acid for investigating anti-fingerprint effects evidenced a weaker interaction between the mostly hydrophobic PE-MOCVD titania surfaces than for the hydrophilic and rougher PVD produced titania layers when irradiated under UV light. The observed differences were related to the chemical and structural features since the hydrophobic PE-MOCVD produced titania layers were amorphous and nitrogen and carbon incorporation into TiO2 led to an enhanced photocatalytic ability by a factor of two regarding the dye tests, whereas the energy bandgap remained at about 3.2 eV. Substitutional and interstitial doping of nitrogen and/or carbon was evidenced by XPS. An additional benefit regarding the adhesion and abrasion resistance was observed for the tailored doping of titania layers.
Effect of the rapid thermal annealing on the structure and optical properties of TaOxNy thin films deposited by reactive magnetron sputtering
Tantalum oxynitride thin films are deposited by radio-frequency magnetron sputtering using a pure tantalum target under argon/oxygen/nitrogen gas mixture. The argon flow is kept constant while the oxygen and nitrogen flows are changed simultaneously in a way to keep constant the total flow of these reactive gases. We succeed to deposit TaOxNy films with stoichiometry ranging between those of TaN and Ta2O5. All films are deposited at room temperature without any biasing. A thermal annealing in a RTA furnace was applied to all the films in a nitrogen atmosphere. A phase transition was detected by XRD investigations and SEM scanning from as deposited to annealed films, noticing the crystallisation of all films which depends on the composition of each film.
The Structure-Phase Compositions of Ni - Cr and Co–Cr Based Powder Alloys Coatings Deposited by Plasma-Detonation on Steel Substrates
This paper presents new results of transmission electron microscopy (TEM), X-ray diffraction (XRD) and atomic force microscopy (AFM) investigation of the structure-phase compositions of thick (150 µm) coatings on the base of Ni–Cr and Co–Cr deposited by plasma-detonation on steel substrates. The phase structures and morphology of precipitation from solid solution are defined. The microstructure model of a thick plasma detonation coating on steel substrate is developed. The main aim of carrying out these investigations is developing science based recommendations for modification of plasma-detonation coatings by plasma-jet or e-beam.
Synthesis of intermetallic compounds in the surface layer of eutectic silumin by dense plasma impact
Evaluation of the PVD and CVD coatings’ structure using the modified method of spherical metallographic microsection (Baltest-M).
The Baltest-M testing method developed at the Institute of Precision Mechanics allows a precise metallographic analysis of the structures of the coating and substrate materials subject to a strong local plastic strain. The material structure of locally strained areological systems (coating: PVD, CVD – substrate: steel, carbides) is revealed on precise spherical polished sections. The essence of this new testing method is the fact that the spherical polished sections are made in the area of indentations formed during hardness testing (HB, HRC, HV, HK of the surface) of the areological system. Material structures of substrate and coating in the indenter strain area are analysed quantitatively and qualitatively. The Kulotester test rig with a high-quality optical system, a rotary x-y bench for a sample holder and a microprocessor controller allows a precise preparation of polished sections within the indentations formed during the hardness test.
Crystallinity control of sputtered ZnO films by utilizing buffer layers fabricated via nitrogen mediated crystallization: Effects of nitrogen flow rate
High quality ZnO:Al (AZO) films have been obtained by utilizing buffer layers fabricated via nitrogen mediated crystallization (NMC), where sputtering method is employed for preparation of both buffer layers and AZO films. Introduction of small amount of N2 (N2/(Ar+N2) = 16%) to the sputtering atmosphere of NMC-ZnO buffer layers drastically improves the crystallinity of buffer layers and thus AZO films. The most remarkable effect of the buffer layers is a significant reduction in the resistivity at high base pressure of background gases. The resistivity of conventional AZO films increases from 2.0 m O•cm to 70.0 O•cm with increasing the base pressure from 3×10-5 Pa to 1×10-3 Pa, while the resistivity of AZO films with NMC buffer layers increases from 0.5 mO•cm to 2.0 mO•cm, where the thickness of AZO film is 88 nm. Furthermore, AZO films with a sheet resistance of 10O/? and an optical transmittance higher than 80% in a wide wavelength range of 400–1100 nm have been obtained.
The Effect of Nitrogen Partial Pressure and Substrate Temperature on the Characteristics of Photocatalytic N:TiO2 Thin Films deposited by Filtered Vacuum Arc Deposition
Nitrogen doped Titanium Oxide (N:TiO2) thin films were deposited using filtered vacuum arc deposition, and their structure, composition and morphology were studied as functions of the total pressure, N2/O2 gas ratio and the substrate temperature. The film structure, surface morphology, and composition were determined by XRD, AFM and XPS. The optical characterization of the films was determined with spectrophotomery and ex-situ variable angle spectroscopic ellipsometry (VASE). In addition to the effects of other deposition conditions such as arc current, total deposition pressure, and post-deposition annealing on the film characteristics, photocatalytic activity was also determined as a function of deposition parameters and results were discussed.
Systematic evaluation of thin electrically insulating layers on common engineering materials
Thin insulating layers are often required for typical engineering materials, e.g. steel, alumina, titanium and the respective alloys. A very dense insulating layer for subsequent conducting layers acting as electrical paths is crucial. Experiments have shown, however, that the electrical insulation of such substrates is often not sufficient or fails completely and is seldom repeatable. To determine the most important influences regarding the insulation, a systematic evaluation based on a screening design of experiments for the variation of ten parameters is introduced. The films were deposited using a radiofrequency magnetron sputter system and a non-reactive process as well as a SiO2 target for the deposition of the insulation. A thin layer of a Cu-Ni-alloy was successively deposited through a mask on top of the insulating layer. The resistance between the substrate material and the conducting layer was investigated to determine the major influencing parameters with respect to the quality of the insulation layer. Based on the results, further experiments on film thickness variations with less parameters were carried out and Al2O3 layers were compared to those utilizing SiO2.
Ultra-shallow fluorine implantation from r.f. plasma as a method for improvement of electro-physical properties of MIS structures with PECVD gate dielectric layers
In this work a comprehensive analysis of changes in electrical and reliability parameters, which are introduced by the presence of a fluorine-rich layer in the gate structure based on MOS (Al/SiO2/Si) and MIS (Al/SiOxNy/Si) system, has been carried out. The surface of silicon substrates prior to the test structure execution was subjected to the processes of ultra-shallow ion implantation from CF4 plasma, different, than those usually found in the literature. To this end, the conventional plasma reactors were utilized to carry out a plasma enhanced chemical vapour deposition process PECVD and reactive ion etching RIE. To perform gate dielectric layers the PECVD method was used. The conducted analysis of the electrical properties was complemented by spectroscopic measurements (SIMS), which allowed the identification of causes and effects of observed changes in electro-physical parameters.
Towards deeper understanding of a HiPIMS discharge by time-resolved optical plasma diagnostics
Study of the ionisation in a nickel plasma by Inductively Coupled Impulse Sputtering (ICIS)
Inductively coupled impulse sputtering (ICIS) removes the need for a magnetron, while delivering equal or higher ion to neutral ratios compared to other ionised PVD technologies such as high power impulse magnetron sputtering (HIPIMS). This is especially advantageous for the sputtering of magnetic materials, as these would shunt the magnetic field of the magnetron, thus reducing the efficiency of the sputtering and ionisation process. ICIS produces highly ionised metal-dominated plasmas inside a high power pulsed RF coil with a magnet free high voltage pulsed DC powered cathode. ICIS processing with Ti and Cu has been attempted before; however operation with magnetic target materials has not been attempted so far. The paper aims to clarify the effects of power and pressure on the deposition flux and structure of deposited Ni films. The setup comprises of a 13.56 MHz pulsed RF coil operating at a frequency of 500 Hz and a pulse width of 150 µs, which results in a duty cycle of 7.5 % . A pulsed DC voltage of 1900 V was applied to the cathode to attract Argon ions and initiate sputtering. Optical emission spectra (OES) for argon and nickel species sputtered at a constant pressure of 14 Pa, show a linear intensity increase for peak RF powers of 1000 W - 4800 W. Ni neutral line intensity increased linearly exhibiting two different slopes for powers below 2000 W and those above 2000 W RF - power. The influence of pressure on the process was studied at a constant peak RF power of 3000 W for pressures of 3.2 – 26 Pa. The intensity of nickel neutrals rises linearly for pressures of 3.2- 26 Pa and saturates for pressures from 12 – 21.4 Pa. Argon neutrals rise linearly with increasing pressure. Ni ions have not been visible in the OES spectra and analysis into the ion to neutral ratios will be conducted by other techniques. From the Ti process we know, that the intensity of neutrals and ions increases linearly with power and pressure. Intensity modelling is also conducted for the Ni process. The deposition rate for Ni is 50 nmh-1 for a RF-power of 3000 W and a pressure of 14 Pa. The microstructure of the Ni coatings shows columnar dendritic growth. Bottom coverage of unbiased vias with width 0.300 µm and aspect ratio of 3.3:1 was 15 % and for an aspect ratio of 1.5:1 was 47.5 %. Parameters for this coating are mean values from a power and pressure matrix. To investigate ionisation influence, coatings have also been deposited at higher power and pressure. The current work has shown that the concept of combining a RF powered coil with a magnet-free pulsed DC powered cathode works very well for the sputtering of hard magnetic material in very stable plasma.
Effect of time in plasma electrolytic oxidation process on titanium substrate with addition nano alpha alumina powder in electrolyte and investigate wear behavior of coating
Titanium and its alloys have wide applications in industry and recently researches have been expanded in this area. The main reasons are unique features of titanium such as biological behavior, corrosion resistance and high strength to weight ratio. The fundamental problem of titanium is low wear resistance that leads to be worn in industrial applications. Plasma electrolytic oxidation (PEO) is a novel method to create ceramic coatings on metals and improve wear resistance. Base of this method is similar to electrochemical coating methods with difference the high voltage discharge phenomenon. In this research hard nano alpha-alumina particles (hardness of 9 Mohs) were added to the electrolyte for improving wear properties of titanium.
Performance of atmospheric plasma sprayed HA coatings under dry and wet fatigue conditions
Hydroxyapatite (HA) is widely used as a bio-medical coating on press-fit (cementless) orthopaedic implants to enhance the biological response of the device. Presently atmospheric plasma spray (APS) is the most widely applied technology for the deposition of such bio-medical coatings. There have been concerns however, regarding the high deposition temperatures to which the HA precursor powder is exposed during APS processing, as this can result in changes to the HA powder’s crystallinity. Furthermore, concerns have been raised regarding the affect these crystalline alterations may have on the solubility of the deposited HA coating, and thus, the affect they may have on the integrity of the coating at the metal interface. The aim of this study is to evaluate the fatigue performance of APS HA coatings, carried out under both dry and wet fatigue conditions. The wet fatigue conditions were facilitated using a Simulated Body Fluid (SBF) solution, which enabled the in vitro simulation of the HA coating response in a typical in vivo environment. SEM and XRD examination of both the reference (as received) and dry samples demonstrated the coating properties were almost identical after 10 million cycles, while the evaluation of the wet samples suggested complete failure of the HA coating had occurred during testing. In conclusion, HA coating delamination during the wet fatigue testing was attributed to significant weakening of the coating, due to material loss from dissolution as a result of exposure to the SBF solution. Significantly the dissolution was found to occur both at the interface and within the coating.
Comparison of microbiological effects in long fine-lumen tubes by low and atmospheric pressure plasmas
Minimal invasive treatment using tubes such as catheters and endoscopes is well-established. Since the introduction of flexible endoscopy into medical practice, many cases of infectious complications involving bacteria, fungi and viruses have been linked to endoscopic procedures. Inadequate cleaning and disinfection during the reprocessing of the instruments have been reasonable factors as well as insufficient final rinsing and incomplete drying of the endoscope or contaminated flushing equipment for the air/ water-channel. Flexible endoscopes are thermo-labile and cannot withstand heat sterilization processes. Common disinfection processes like ethylene oxide or hydrogen peroxide vapour as well as formaldehyde are more or less effective, but require long contact and aeration times. Furthermore, these processes use toxic and explosive substances. Therefore, the development of new methods for the sterilization of thermo sensitive devices especially with long fine lumen is very important. A promising possibility is the decontamination by plasma discharge treatment. Various plasma setups have been developed. However, due to the complexity of plasma techniques and technologies, setups and parameters, it is impossible to compare their antimicrobial efficacy by single experiments. A standardization of microbiological parameters is necessary to attribute the observed effects solely to the plasma efficacy. This work is based on round robin tests with and without plasma treatment by three institution (the Fraunhofer IGB Stuttgart, Germany; the HygCen GmbH Schwerin, Germany and the INP Greifswald, Germany) and the publications by Maucher et al. (2011) and Schnabel et al. (2012).
Surface Interaction and Processing Using Polyatomic Cluster Ions
We developed two types of polyatomic cluster ion sources, one of which was a liquid cluster ion source using organic materials with a high-vapor pressure. Vapors of liquid material such as ethanol and water were ejected through a nozzle into a vacuum region, and liquid clusters were produced by an adiabatic expansion phenomenon. Another type was a cluster ion source using ionic liquids with a relatively low-vapor pressure. Positive and negative cluster ions were produced by a high-electric field emission. In addition, the interaction of polyatomic cluster ions with solid surfaces such as Si(100), SiO2, glass, and PMMA surfaces was investigated, and chemical sputtering was predominant for the Si(100) surfaces irradiated by ethanol cluster ion beams. Also, the irradiation damage of the Si(100) surfaces by ethanol and water cluster ion beams was smaller than that by Ar monomer ion irradiation at the same acceleration voltage. With regard to surface modification, PMMA surfaces were chemically modified by water cluster irradiation. Also, glass surfaces changed to electrically conductive surfaces by ionic liquid cluster ion irradiation. Furthermore, to demonstrate engineering applications of high-rate sputtering and low-damage irradiation by ethanol cluster ion beams, micro-patterning was performed on the Si surfaces.
Hierarchical simulation of microcrystalline PECVD silicon film growth and structure
We have designed and implemented a hierarchical simulation methodology capable of addressing the growth rate and microstructural features of thin silicon films deposited through PECVD (Plasma Enhanced Chemical Vapor Deposition). Our main objective is to elucidate the microscopic mechanisms as well as the interplay between atomic level and macroscopic design parameters associated with the development of nano- or micro-scale crystalline regions in the grown film. The ultimate goal is to use multi-scale modeling as a design tool for tackling the issue of local crystallization and its dependence on operating variables. At the heart of our simulation approach is a very efficient, large-scale kinetic Monte Carlo (kMC) algorithm which allows generating samples of representative Si films based on a validated chemistry model. In a second step, the generated film is subjected to an atomistic simulation study which restores the molecular details lost or ignored in the kMC model. The atomistic simulations are computationally very demanding; they are, however, an important ingredient of our work: we use it to back-map the coarse grained model employed in the kMC simulations to an all-atom model which is further relaxed through detailed NPT molecular dynamics (MD) or Monte Carlo simulations. This tunes local structure thus also important morphological details associated with the presence of crystalline and amorphous regions (and the intervening interfacial domains) in the grown film. The kMC algorithm is based on a carefully chosen set of reacting or active radicals (species) in the gas phase impinging the film and a detailed set of surface reactions. Inputs for species fluxes are taken from a well-tuned plasma fluid model that includes a detailed gas phase chemistry reaction scheme. The growth mechanism consists of various surface kinetic events including radical-surface and adsorbed radical-radical interactions, radical-surface diffusion, and surface dissociation reactions. The very fast surface diffusion is decoupled from the rest of the kMC events and is treated deterministically in our work. For a three-dimensional Si(001)-(2x1):H crystalline lattice, our kMC algorithm allows us to simulate film growth over several seconds, resulting in thickness on the order of tens of nanometers. In the following pages we provide more details about the implementation of our kMC algorithm along with validation results.
Plasma Directed Assembly: Process Issues, Materials and Applications
The Study about Surface Modification of Steel by Water Plasma
Recently, a lot of research has been carried out to improve the properties of steel surface such as ion-nitriding, gas nitriding. However, they need high vacuum rate or very expensive equipment and longer treatment time. In this study, new nitriding process proposed which have extremely shorter treatment time and very simple equipment by using water plasma. For the water plasma, JIS-SCM420 specimen was used as cathode, and rolled punching stainless steel plate (SUS304) was used as anode. Voltage was applied between electrodes by DC pulsed power supply. Pulsed power supply was used to prevent discharge from concentrating on one point. Urea (H2N)2C=O used as supply source of nitrogen and potassium hydrate (KOH) for adjusting electric conductivity. And it was put into distilled water as electrolyte. Treatment voltage was 600 V, and experiments were conducted by varying conditions such as treatment time and concentration of electrolyte. After water plasma treatment, a lot of fine discharge pores can be seen on the treated steel surface. And also, a few µm modified layer is formed on the steel surface after water plasma treatment within 5min. At the results of XRD analysis, iron nitrides are detected with Fe peaks and the hardness of nitride layer shows about 800HV.
Study of the growth kinetics, microhardness and morphology of PEO coatings formed on Al 2024 alloy in alkaline-silicate electrolytes using different current waveforms
Optical Layer Systems for Product Authentication:Interference, Scattering, Light Diffusion and Ellipsometric Encoding as Public, Hidden and Forensic Security Features
Embedding of information on surfaces is state of the art for identification testing in which public, hidden and forensic features are used. In many instances, the legal authentication of a product, a material or a document is required. Among the surface-based encoded labels, bar codes and data matrices are most frequently applied. They are publicly visible. The material itself is irrelevant, only a sufficient optical contrast is required. However, a strong material dependence of the label can be achieved by means of Fabry-Perot layer stacks. Stack designs are described with regard to all three security levels: public features (e.g. color and tilt effect) perceptible by the human eye, hidden features (e.g. optical response in a given spectral range) detectable by commonly available instruments and forensic features (ellipsometric quantities ? and ? as a function of wavelength ? and angle of incidence AOI) only detectable by sophisticated instruments. Regarding material-correlated authentication, ellipsometric quantities ? and ? are used as encoded forensic features for the first time. Hence, Fabry-Perot layer stacks as information carriers in combination with imaging ellipsometry as optical read-out system provide all-in-one anti-counterfeiting capabilities.
Wide-angle broadband AR coating by combining interference layers with a plasma-etched gradient layer
Sensitization of Er3+ Emission in Er- and Yb-doped Si Thin Films by Laser Ablation
Erbium (Er)- and ytterbium (Yb)-doped Si (Si:Er,Yb) thin films have been controllably synthesized over the Er and Yb concentrations ranging from 1018 to 1020 cm-3 by laser ablation technique. From the PL spectra and the concentration dependence of the intensity of Er3+ emission at 1.54 µm, Yb3+ acts as an efficient sensitizer of the Er3+-related PL. Enhancement by a factor of 1.5 due to Yb codoping is observed from the Si:Er,Yb films.
Plasma Nitriding Performed under Atmospheric Pressure using Pulsed-Arc Plasma Jet
Plasma nitriding is achieved by spraying the nitrogen pulsed-arc plasma jet under atmospheric-pressure N2/H2 mixture. The quality of nitriding is found to depend on the H2 flow rate, which has an optimal value. We propose a simple mechanism of this dependence. Moreover, the amount of H2 necessary for best nitriding can be decreased to 1/20 by changing the way of H2 addition.
Effect of Plasma Nitriding and Nitrocarburising Process on the Corrosion Resistance of Grade 2205 Duplex Stainless Steel
Grade 2205 duplex stainless steel is a type of stainless steel possessing a nearly equal amount of the ferrite (a-Fe) and austenite (?-Fe) phases as a matrix. Since this steel has a relatively low hardness of 256 HV0.1, an attempt has been made to improve its hardness and wear properties without compromising the corrosion resistance by plasma nitriding and nitrocarburising process. Plasma nitriding and plasma nitrocarburising process was performed with 80% nitrogen and 20% hydrogen gas and 78% nitrogen, 20% hydrogen and 2% acetylene gas respectively at 350, 400, 450 and 500 oC for 4 hours. The temperature played an important role in the distribution of nitrogen and carbon in the original austenite and ferrite phases present in the bulk material. As a result there was an improvement in microhardness and corrosion properties after these treatments. It was observed that plasma nitrocarburising process performed better than plasma nitriding process in improving the corrosion properties due to the presence of carbon.
Wear Properties of Plasma Nitrided Inconel 718 Superalloy
Inconel 718 is a nickel-based superalloy that is extensively used in a broad range of applications such as turbine blades, power generation, petroleum and nuclear reactor technology due to its good mechanical properties at intermediate and high temperatures. Contrast to its wide range of usage, high plasticity and good corrosion resistance, poor wear resistance of Inconel 718 limits its usage in some applications. In order to improve the wear resistance of Inconel 718 several surface treatment methods are used. One of the most important methods, that is used to prevent the metal from wear is to modify the surface with a nitride layer by plasma nitriding. In this study Inconel 718 super-alloy was plasma nitrided in different parameters and the wear mechanism of plasma nitrided Inconel 718 was investigated using a pin-on-disk wear tribotester. Microstructure and phase components of Inconel 718 were investigated using SEM and XRD before and after plasma nitriding process.
Effects of ion-beam bombardment and nitridation on physical/mechanical properties of 100Cr6 TiN coated steels
The effect of ion-beam bombardment on the physical properties of 100Cr6 steel is reported. The energy dependence of the in-depth stress and the pattern formation are presented. The modified region by the relative low energy (< 1keV) ions extend orders of magnitude deeper than the stopping region of the projectiles. The formation of peculiar patterns on the treated surface is explained by the current model of surface instability created by preferential sputtering and surface diffusion in metals.
Mechanism of Ti99.2 titanium unconventional ion nitriding
Evaluation of the Mechanical Behaviour of a DLC Film on Plasma Nitrided AISI 420 with Different Surface Finishing
Diamond-like-carbon films (DLC) are hard coatings with a very low friction coefficient, a high wear resistance and chemically inert. However, these coatings have adhesion problems on metallic substrates, because the high residual stresses in the DLC films cause failure of the interface between the film and the substrate. Different methods have been tested to improve the adhesion: deposition of interlayers, multilayer coatings between the substrate and the DLC film have been used as interface, chemical and physical modifications of the carbon coating or diffusion treatments of substrate surface. Plasma nitriding is a well-established method to harden stainless steels and can act as a pretreatment to increase adhesion and improve tribological behaviour of the DLC coating. Hopwever, the characteristics and phases of the nitrided layer can influence on the adhesion and the mechanical behaviour of the system. In this work, the mechanical behaviour of a DLC film deposited over non-nitrided and nitride martensitic stainless steel with two different surface finishing is studied.
Nanocomposite Nitrid Thin films for hard coatings : Applications in wear and corrosion resistance
New simple and duplex coatings were elaborated by triode sputtering and ionic nitriding, imposed to low alloy steel and characterized by the mean of various experimental techniques (EDS, XPS, XRD, SEM, TEM, FTIR, …). Their ability to protect substrate against corrosion and wear has been evaluated. These deposits are either CrN or ZrN monolayer, or nanocomposite deposits formed by the dispersion of BN into ZrN matrix. The experiments show the good physical, chemical and mechanical properties of the films. The tribological analysis permitted us to define the optimal conditions of triode sputtering and the ionic nitriding ones used in the duplex treatments. A great amelioration in the tribological properties was observed and was explained by the good stress repartition into the layers. Simples and duplex treatments were imposed to low alloy steel cutting tools. Their application in peeling of wood and corrosion shows their efficiency.
Wear behaviour of PN+CrN, PN+CrAlN and PN+TiCrAlN layer composite during ball-on-disk tests in higher temperature
On the Injected Gas/Electric Power Relation for Deposition Efficiency Control During the Gims Deposition
During the last AEPSE2011 conference there were presented the concept as well as the first results of the use of working gas injection to control the generation of pulsed plasma. The problem was discussed on the basis of two methods: Impulse Plasma Deposition (IPD) and Magnetron Sputtering (MS) e.g. The first results indicated the desirability of a deeper interest in such a way of plasma process control. The idea of using the working gas injection instead of stationary gas flow mode assumes in the first approximation that the lack of cold gas in the chamber space prior to gas injection could next avoid the kinetic energy dissipation on collision between the plasma particles and the cold gas. Previously presented studies have shown the initial experimental results proving the positives of proposed modification of the well known methods of plasma surface deposition (in the case of IPD - possibility of exceptionally effective producing of antiabrasive layers on unheated substrates and from the other hand - the positive change in the morphology of layers as well as a different way of target erosion during the layer deposition by MS). Lately carried out experiments have showed that during the GIMS deposition of AlN coatings (GIMS - Gas Injection Magnetron Sputtering) higher amounts of Al-Al bonds have occurred in comparison with the case of continuous gas flow mode. It seems to us that the reason of that metallic “tail” could be both the diminishing of the portion of reactive gas and/or self sputtering effect of the aluminum target arising during the last phase of working gas injection. The studies describes below concerns the very last our studies on the possibilities of control the gas/electric power relation during the GIMS process.
Influence of the Ion Beam Current on Microstructures and Optical Properties of Al2O3 Thin Films by Oxygen Ion Beam Assisted Pulse Reactive Magnetron Sputtering
Formation of plasma technological influence of vacuum arc on the internal surfaces of metal pipes and putting of the protecting coatings
In many cases of industrial applications it is economically profitable or technically necessary to combine bulk features of one material with surface features of another one in a single material. Vacuum-arc treatment of products from inexpensive materials to form new required features of surface layers is more perspective owing to its unlimited feasibility in process efficiency. Pipes are in great demand in oil-gas industries and power engineering. But there are no effective methods for pipe inner surface treatment and pipe coating deposition, which makes it impossible to use inexpensive steel pipes under conditions of aggressive liquids, high temperature, high pressure and other parameters leading to oxidation, erosion and pipe life. Therefore, development of plasma-arc technologies of pipe inner surface treatment and pipe coating deposition is very topical and actual. A specific effect of vacuum-arc discharge on material surface is due to high concentration of energy in a chaotically rapidly moving cathode spot, short-term local heating of surface and its rapid cooling. The technological effect of cathode plasma on surface is based on cathode spot movement. The effect of a plasma flow of cathode spots formed on the outer surface of a pipe cathode and controlled by a system of vacuum-arc cathode spot fixation with magnets placed inside an electrode has been considered. A great number of studies have been devoted to explaining and investigating “anomalous” movement of the cathode spots. It has been shown that the cathode spot moves in the direction of the greatest action of discharge’s own magnetic field and outer magnetic field. The magnets initiate an arc magnetic field that confines the cathode spots and makes it possible to scan (control) them on the electrode-cathode surface and act with a plasma flow and deposit coats on inner surface of a coaxially placed pipe-product. The high efficiency of the plasma vacuum-arc method for pipe inner surface treatment and coat deposition has been found.
Features of DC magnetron sputtering of mosaic copper-graphite targets
Sn Thin Film Deposition using a Hot Refractory Anode Vacuum Arc
A Hot Refractory Anode Vacuum Arc (HRAVA) starts as cathodic arc, heating the anode and depositing on it cathode material. When the anode is hot, all deposited cathode material is reevaporated from the anode forming cleaner radially expanding plasma. It was shown that the rate of deposition reached 2-3 µm/min with significantly reduced macroparticle contamination in Sn films produced by HRAVA with current I=60–175 A and duration up to 180 s.
Hydrophilization treatment of polyimide using Ar-O2 mixture gas surface wave plasma – Oxygen radical density and plasma parameter dependence
The hydrophilization treatment of polyimide is important in various applications. This paper has described the experimental research findings which explore what the parameter with large effect in the plasma treatment of polyimide is. The low pressure surface wave plasma of the argon oxygen mixed gas which can expect large homogeneity spatially was used for the experiment. The plasma state was measured by the electrostatic probe. The oxygen radical expected to be active species important for surface treatment was measured by the catalyst probe. It turned out that it depends for the water contact angle on the surface of polyimide by which plasma treatment was carried out in an oxygen radical density strongly.
In-situ FTIR-ATR spectroscopic investigations of atmospheric-pressure plasma modification of polyolefin thin films
Surface treatment of polyolefines by atmospheric-pressure dielectric barrier discharges (DBDs) in virtually oxygen-free nitrogen-containing gases was studied in situ byFourier transform infrared spectroscopy in the attenuated total reflection mode (FTIR-ATR)in order to follow the plasma-chemical generation of chemical functional groups and their further temporal development in the presence of inert or reactive atmospheres. Polyolefin thin films of thicknesses between 50 and 200 nm were prepared directly on ZnS ATR crystals by spin-coating from hot solutions of linear low-density polyethylene (LLDPE), low density polyethylene (LDPE), or polypropylene (PP) in hydrocarbons solvents like xylene or decalin. After the exposure to the afterglows of DBDs in N2 or in mixtures of N2 with H2 or NH3, infrared spectra were taken in situ under inert conditions and after controlled exposure to various reagents, resp., such as water vapor or oxygen. In order to unravel the complex spectra which are generally due to several functional groups with overlapping vibrational bands, exchange reactions with vapor of heavy water (D2O) was applied in order to identify groups which are known to exhibit a rapid H/D exchange like >N=H (imine), -NH2(prim. amine), >NH (sec. amine), -CO-NRH(prim. or sec. amide), using characteristic ratios of wavenumber ratios for corresponding vibrational bands in the deuterated and the protonated moiety. In addition, reactions of the plasma-treated surface with vapors of4-(trifluoromethyl)-benzaldehyde (TFBA) or4-(trifluoromethyl) phenyl isothiocyanate (TPI) were studied by FTIR-ATR in situ. Based on these experiments, tentative assignments of the observed vibration bands to imino, amino, and amido groups are made and interpreted in terms of feasible or probable chemical mechanisms.
Functional coatings for polymer composites
The development of high-performance polymer composites is tightly bound with the functional surface modification of reinforcements. A new method, based on the principle of the fiber-bundle pull-out test, was used to analyze the interfacial properties between the long fibers in the form of a bundle and the polymer matrix. The pull-out test can be used for a relative comparison of different surface modifications if the bundle geometry is unknown. Glass fibers coated by plasma polymer films of tetravinylsilane were tested to determine the interfacial shear strength as a function of RF power and film thickness that was varied from 50 nm to 10 µm. SEM micrographs of pulled-out (debonded) fiber bundle were used to characterize adhesion at the interlayer/fiber and polymer/interlayer interfaces.
Applications of Low Pressure Plasma in High-tech Textiles
The textile and clothing industries especially in developed countries are facing now-a-days some big challenges largely because of the globalization process. Therefore, the market of a high-functional, added value and technical textiles is deemed to be essential for their sustainable growth. The growing environmental and energy-saving concerns will also lead to the gradual replacement of many traditional wet chemical-based textile processing by various forms of low liquor and dry-finishing processes. The main reason for the increasing interest is that industrially well-established surface finishing processes suffer considerably from environmental demands such as large amount of water, energy and effluents. Plasma technology, when developed at a commercially viable level, has strong potential to offer in an attractive way to obtain new functionalities in textiles. The synthetic fibres such as polypropylene (PP), polyester (PES), Aramid (AR) etc. are widely used in apparel and home furnishings due to their good physical and chemical properties. The demand of these fibres increases greatly for high performance applications such as smart textiles, technical textiles, operation clothing etc. and more recently, for their potential applications in electronic textiles. But these fibres often reveal hydrophobic nature due to the lack of polar functional groups. The hydrophobic nature of such fabrics limits their application to the above mentioned areas. In addition, adhesion is fundamentally a surface property, often governed by a layer of molecular dimensions, which necessarily required for coating, bonding and printing of synthetic textiles. The low surface energy of hydrophobic polymeric materials results in intrinsically poor adhesion. On the other hand, some natural fibres (e.g. cotton, wool, linen) and synthetic fibres (e.g. rayon, viscose, acetate, spun nylon) exhibit to be hydrophilic in nature due to their polar functionalities. Hydrophilicity of such fibres may act as a barrier for their applications in many areas where liquids repellent is necessary. It is a wide-reaching technical effect that is sought after in several industry sectors, from biosciences, healthcare and electronics to industrial filtration, sports and active wear. In addition to water repellency, other liquids such as oils, inks and alcohols repellency often required. Liquids are constantly in use around us, in the majority of cases in the form of rain water and food and beverages. Arguably, the most noticeable, unfavorable interactions of these liquids are with textile products such as clothing, carpets and upholstery, so added value can be provided by protecting these items from interacting with the liquids, enabling the liquids to roll off or be dabbed away, leaving the underlying material unchanged. Furthermore, hydrophobicity of textiles is frequently associated with self-cleaning properties. When a water droplet rolls off the surface, the surface impurities such as dust get carried away by the droplet resulting in a self-cleaning effect. Using plasma technology to modify textile surfaces with precision cleaning, etching, chemical priming for lowering or raising surface energy can be used to obtain a desirable property of an end product. The plasma technology, a dry and eco-friendly technique, avoids waste water production which is a unique advantage over the wet-chemical processes. This benefit extends into all market areas, where the end product can undergo the plasma enhancement process to provide properties such as adhesion, hydrophilic, liquid-repellent etc. However, to transfer this technology from laboratory into industry, both the scale-up and economic aspects have to be regarded. Main objective of this work is to study the possibility of substituting plasma processes for the traditional wet chemical methods using an industrial plasma reactor aiming to produce wash permanent super-hydrophilic, super hydrophobic textile surfaces.
Poly(acrylic) nanocoatings deposited by AP-PECVD processes on paper substrates for packaging applications
Poly(acrylic acid) coatings on paper substrates have been prepared by atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD). The structure/properties relationships of the samples were studied in dependence of the plasma experimental conditions. Acrylic acid monomer/helium ratio and treatment speed clearly influences the wettability properties of the paper substrate: advancing contact angle values were reduced to the half (around 60 º) if compare to non-treated paper (120 º approximately). The surface morphology of the films did not greatly vary with the plasma polymerization treatment.
Atmospheric Plasma surface treatment of Styrene-Butadiene Rubber
Thermoplastic rubbers are widely used in a large number of applications (e.g. footwear, adhesives manufacturing, molded or extruded goods). Due to the non-polar nature of these rubbers, poor adhesion is achieved with polar polyurethane (PU) adhesive thus, a surface treatment is required to chemically modify the rubber surface and produce suitable joints. Surface treatments have been demonstrated to be suitable for the improvement of adhesion and wettability properties of non-polar synthetic rubbers. Over the last two decades progresses in adhesion of rubber were achieved by changing of the ingredients in rubber composition or by modifying surfaces by the use of a chemical agent (halogenation, cyclization, etc.) or using high energy irradiation such as bombarding the surface by electron beam or gamma irradiation. Actually, wet-chemical treatments are not well acceptable because of environmental and safety considerations and question on uniformity and reproducibility. Plasma surface treatment process was been proposed as an environmentally friendly and have gained large acceptance because it can be easily integrated into existing production lines and because their effectiveness in the treatment of several materials with different shapes and sizes. The effectiveness of plasma treatment on enhancement of adhesion depends on the gas used to generate the plasma and also on the formulation of the rubber. Vulcanized rubbers like, styrene-butadiene rubber (SBR), are especially difficult to bond due to low molecular weight ingredients in their formulation that may migrate to the rubber surface limiting its interaction with the adhesive. This study attempts to find an alternative treatment to improve the adhesion of SBR surface and PU adhesive. Plasma treatments were performed in an air plasma system from Acxys and were selected three types of SBR rubbers with different percentages of styrene-butadiene which were provided by Procalçado. The effect of experimental variables such as distance, speed and scan number on the adhesion of PU adhesive was evaluated and compared with halogenated SBR rubbers.
Formation of plasma-generated nanostructures on polymer surfaces for various polymer types
To produce functional elements for optical applications, the components often have to be coated or joined together. Low adhesion is usually caused by different polarity or surface chemistry of the individual components. Therefore, measures have to be taken to modify the respective interfaces to improve the adhesion. In the case of highly transparent polymers (e.g. PC, PMMA, COC, PA) this turns out to be problematic due to the demands on the optical properties. Many methods for adhesion promotion, as etching with chemicals or mechanical roughening, lead to a significant deterioration in the transparency of such components. In many cases a plasma treatment alone has no sufficient effect on improving the adhesion. The Fraunhofer Institute in Jena (IOF) is working several years now on the nano-structuring of polymer surfaces by plasma etching. Except for antireflection purposes, such a structure can also be used to promote adhesion. However, large structure depths and high aspect ratios are necessary therefore. In the experiments carried out here the self-organizing formation of such nanostructures on various polymer types was studied.
Biocompatible thin films obtained from Heparim-methane plasma process
Heparin is an appropriate molecule to suppress the thrombus formation in the initial stages of blood contact with an artificial material. Therefore the covering of a synthetic material with heparin-like molecules is a great importance issue in biomaterial science and engineering. In order to reach this goal this paper deals with the plasma deposition of thin heparin-like films on microscope slides from RF-excited heparin/methane low pressure plasmas. Plasma were excited by a RF-power supply operating on 13.56 MHz at a fixed power of 50 W. Heparin was diluted in ethanol and fed into the plasma chamber in mixtures of 50% of CH4 (in pressure) at 10 Pa. Films molecular structure was characterized by Fourier transform infrared spectroscopy (FTIR here in). Molecular spectra presented absorption bands due C-H, O-H and C-O stretching and bending modes. Films surface wettability was investigated by contact angle measurements. The experimental results show values varying from 650 to 200. Surfaces optical microscopy showed the occurrence of heparin islands distributed almost uniformly over the _lm. The bloods coagulation time placed in contact with glass substrate covered by plasma deposited heparin/methane films was measured by thrombosis time and activated thromboplastin.
Analysis of the aging of cell-adhesive plasma-polymer coatings on titanium surfaces
Plasma polymer deposition is the method of choice for the finishing of metallic implant materials like titanium with nitrogen-containing bioactive coatings. The deposited cell-adhesive plasma polymer films have to possess special properties such as homogeneity, film stability on air as well as in different media, sufficient density of functional groups and the appropriate surface charge. But also the knowledge of long-term stability is essential for the application as implant surface. Therefore, aging studies of plasma polymer coatings on titanium surfaces are important to detect the changes of surface chemistry over a longer time period. For this purpose, results of physicochemical surface diagnostics were combined with adequate tissue culture experiments. The objective of this paper was to measure surface chemical characteristics of thin plasma polymerized allylamine (PPAAm) coatings on polished titanium with the main focus on FT-IR studies over a time period of one year and to correlate these data with the adhesion of human MG-63 osteoblastic cells.
Comparison of surface properties of DLC and ultrananocrystalline diamond films with respect to their bio-applications
DLC layers are entirely amorphous or contain micro- or nanocrystalline diamond or graphite and possess a disordered structure with a mixture of carbon bonding configurations. Furthermore, DLC can be hydrogen free (a-C) or containing hydrogen (hydrogenated amorphous carbon (a-C:H)). DLC films exhibit excellent physical and chemical properties, as well as high level of biocompatibility [1]. The films are dense, mechanically hard, smooth, abrasion resistant, IR transparent, chemically inert, resistant to attack by both acids and bases, have a low coefficient of friction, low wear rate, and are biocompatible and thromboresistant [2-3]. DLC coatings can be adherent on various biomaterials; neither toxicity toward certain living cells nor inflammatory response or loss of cell integrity were reported [4]. DLC shows an excellent hemocompatibility, a decreased tendency of thrombus formation and coated heart valves and stents are already commercially available [5]. The properties of the DLC coatings depend strongly on the hydrogen content and sp3/sp2 ratio which, in turn, depend on the deposition process and its parameters. The range of the properties of the DLC produced by different methods and under different process parameters is considerable. Diamond is a material with quite a number of excellent properties [6], like extreme hardness, high elastic modulus, high wear resistance, optical transparency in a broad spectral range, resistivity controllable by the level of dopants, etc. which make it a promising candidate for diverse applications. Due to its outstanding electrochemical properties, superior chemical inertness and biocompatibility, artificially grown diamond has been recognised as an extremely attractive material for both (bio-)chemical sensing and as an interface to biological systems. This holds for all forms of diamond: monocrystalline (natural or artificial) and poly- (PCD), nano- (NCD) and ultrananocrystalline (UNCD) films. In the current work the surface and antibacterial properties of DLC and UNCD films including the nature of the surface bonding and termination, wettability, surface energy and tests with Gram-positive and Gram-negative bacteria were studied and discussed.
New methods for reprocessing of medical devices based on plasma treatment
The rapid progress in the development of new devices for minimal invasive surgery leads to more complex and fragile instruments including a mixture of different materials most of them thermo labile. In consequence these instruments become more and more expensive which increases the demand for reuse. By now, the manufacturers are obligated to specify the reprocessing procedure which may be a restriction in the development of new products. Therefore, there is a real need for new reprocessing procedures. Especially, plasma processes are commonly discussed as a promising alternative although only few plasma based techniques are currently commercial available. Three examples for plasma based reprocessing are discussed in detail: 1. Classical gas sterilization device: Based on commercial steam sterilizers of low temperature and formaldehyde (LTSF). The formaldehyde unit is replaced by plasma gas generator based on the PLexc® technology developed at INP. This plasma based decontamination technique was tested on long tubes similar to biopsy channels of endoscopes. 2. Atmospheric pressure plasma coating with nanoparticles in order to generate antimicrobial acting surfaces. With a special treatment unit based on the principle of a dielectric barrier discharge the inner surfaces of tubes are coated with nanoparticles. 3. “Plasmoscope”: using special plastic tubes, which include a helical electrode structure it is possible to manufacture endoscopes which allow plasma operation in their biopsy channel. This plasma can either used for decontamination, a reprocessing or under modified operation condition also for therapeutically applications. To simulate the complete reprocessing procedure the “plasmoscope” can be integrated in a reprocessing demonstrator allowing the combination of cleaning and decontamination steps.
Fabrication and plasma modification of polymer scaffolds for regenerative and replacement medicine
Materials that serve as analogues for the native extra-cellular matrix (ECM) can be used in medicine to aid in either the reconstruction or regeneration of damaged tissue and organs. Polymer matrices have been used for regeneration of bone, liver, pancreas, skin and other tissues. Macroporous. biodegradable polymer scaffolds have been prepared by numerous techniques including solvent casting/salt leaching, phase separation, solvent evaporation, and fiber bonding to form a polymer mesh. The main goal of this research was to apply novel physical processing techniques to fabricate and modify highly porous implantable biodegradable scaffolds. More specifically, this involves fabricating scaffolds using electrospinning, piezoelectric printing, gel sublimation techniques and finally modification of matrixes by plasma treatment in order to control chemical structure and morphology of scaffolds.
The Corrosion Properties of Zirconium and Titatium Loadbearing Implant Materials with Protective Oxide Coatings
At present study the comparative analysis of parameters for oxide Al2O3 and ZrO2 films deposited by reactive magnetron sputtering (RMS) method on the load-bearing implant materials such as titanium-based (Ti4Al6V) and Zr has been made. The corrosion examinations of anodic polarization by potentiodynamic method, Tafel and Stern curves and also impedance method at SBF solution were presented.
Development and Application of New Multicomponent Electrode Materials for Deposition Technologies
Spotless arc activated high-rate deposition using novel dual crucible technology for titanium dioxide coatings
For deposition of thin oxide coatings there are a lot of qualified PVD processes today. If high productivity or large-area coating is necessary for economic reasons processes with high deposition rate are reasonable. Using electron beam (EB) evaporation all inorganic materials can be evaporated with high rates. Microstructure of coatings deposited by EB-evaporation depends on substrate temperature during layer growth and melting temperature of coating material. Particularly in case of high melting materials columnar and porous microstructure is obtained. For large area coating several plasma sources have been developed in order to enhance energy of condensing particles and to get denser layer microstructure. Spotless arc Activated Deposition (SAD) combines electron beam high-rate evaporation using axial gun and a spotless arc discharge burning in metal vapor on hot evaporating cathode [2]. The SAD process is suitable for evaporation of high-melting metals like titanium, zirconium or tantalum providing high deposition rate up to 2000 nm/s. Moreover plasma-activation enables reactive mode of operation and deposition of oxides, nitrides or other compounds with a high rate in the range of 20 to 100 nm/s. A Spotless arc is an arc discharge burning in metal vapor which is obtained if the cathode temperature is high enough to enable high thermionic electron emission current density. Spotless mode results in relatively low cathodic arc current density and droplets known from arc evaporators with cold cathode are completely avoided [3]. Nevertheless high DC arc current up to 2000 A is possible. Recent work has shown that SAD process is well suited for deposition of titanium dioxide coatings based on evaporation of titanium and reactive processing in oxygen atmosphere [4]. TiO2 layers were deposited at very high deposition rates between 40 and 70 nm/s. Depending on process conditions amorphous coatings or crystalline phases were obtained. Coatings consisting of anatase phase show very good properties concerning photoinduced superhydrophilicity and photocatalysis. Transparent layers with high refractive indexes in the range of 2.30 and 2.58 could be reached.