A new process has been developed for the high rate plasma deposition of solid films from high molecular weight/low vapor pressure liquid, or even solid, monomer precursors. The gas resulting from the flash evaporation of a liquid monomer mixture, or from a suspension of liquid monomer and insoluble solid particles, is used as the support medium for a glow discharge in a Plasma Enhanced Chemical Vapor Deposition-like (PECVD) process. Due to the high molecular weight/low vapor pressure nature of the precursors, the plasma of the flash evaporated gas cryo-condenses at extremely high rate on substrates at ambient, and higher, temperatures. Upon condensation the liquefied plasma immediately begins to polymerize to form a solid film due to the high concentration of radicals and ions contained in the liquid film. The process has been successfully implemented in a vacuum roll coating system in a roll-to-roll deposition process. A variety of Polymer, and Polymer Composite, films have been deposited by this process ranging from 0.1 microns to 24 microns in thickness at webs speeds as high as 100 linear meters per minute. This new deposition process will be discussed along with some properties of the films fabricated with this new process.
Plasma polymerized organic layers have many advantageous properties, as e.g. good adhesion to most substrates, excellent uniformity and thickness control, no pin-hole formation. Their elemental composition and their physical and chemical properties (e.g. surface energy) can be varied in a wide range.
However, the limits are reached if a particular chemical structure or functional group (like primary amines or carboxylic groups) is targeted. In these cases, classical monomers (like allylamine or carboxylic acid) are often used as process gasses for plasma polymerization. The process is designed to retain the monomer structure, for example by pulsed plasma regimes. So, during the last few years a considerable body of experimental work was created in the field of pulsed plasma deposition from unsaturated monomers. In the paper the results of the authors regarding the deposition of anionic layers from a pulsed microwave ECR acrylic acid plasma will be compared with the results of other authors reported in the literature. It will be shown, that the results obtained at different laboratories are quite similar. Summarizing these results, a mechanism will be proposed, mainly based on the pre-formation of short oligomers (dimers, trimers) which than will be incorporated into the growing layer.
A complete understanding of the underlying chemistry that occurs during plasma polymerization will only be realized when gas-phase, surface, and gas-surface reactions are considered. This talk will focus on gas-surface reactions of radical plasma species during plasma polymerization. We have used our imaging of radicals interacting with surfaces (IRIS) technique to directly measure the steady-state surface reactivity of CFx (x = 1, 2) radicals, NHx, OH, and SiHx radicals during plasma polymerization of organic and inorganic materials. IRIS combines molecular beam and plasma technologies with laser-induced fluorescence (LIF) to provide spatially-resolved 2D images of species involved in film formation and allows for direct determination of radical-surface interactions during plasma processing. Results will be presented for CF and CF2 radicals on a variety of substrates under both etching and deposition conditions with different gas compositions including C2F6, C2F6/H2, CHF3, and hexafluoropropylene oxide (HFPO). We find that under many film deposition conditions, CF2 radicals are generated at the surface of a growing fluorocarbon polymer film. In contrast, CF radicals are consumed at the surface during film deposition. Ion bombardment effects as well as additional results for NH2 and OH radicals on polymer substrates will be presented. The implications of these results on the mechanisms for plasma polymerization will be discussed.
Cubic boron nitride (c-BN) has become the material of immense interest because of it's properties which could compete with diamond. Additional advantage of c-BN over diamond is that, it does not react with ferrous materials at higher temperature unlike diamond. Also c-BN can be doped to have both p and n type conductivity and hence p-n junction formation is possible. Cubic boron nitride thin films were synthesised by low pressure inductively coupled RF plasma chemical vapour deposition from B2H6+N2+Ar gas mixture. The substrate temperature was maintained at 800 K and deposition pressure was 30 mTorr. Intense ion bombardment is necessary for nucleating and sustaining the cubic phase. A window of ion energy was also observed below and above which only hexagonal phase formed.
The films were characterised by glancing angle XRD, FTIR and XPS analysis. FTIR spectra showed cubic phase restrahlen band at 1060 - 1090 cm-1. At the optimum deposition conditions > 90% cubic phases were obtained in the film which is higher than reported by others using CVD method. Glancing angle XRD spectra showed reflections from all the planes of cubic phase upto (311). The crystallite sizes were calculated from the XRD spectra by Scherrer's equation and was found to be 45 A. XPS study indicated films are stoichiometric while some oxygen impurity was also observed.
Surface functionalization of inorganic and organic polymeric surfaces, including silica, polyethylene, polystyrene, polyester, etc., has been carried out under oxygen-, dichlorosilane- and hydrazine-RF-plasma environments. The influence of power, pressure, and the frequency of driving field on the plasma-mediated gas phase molecular fragmentation has been investigated. Kinetic modeling of the primary reactions of ammonia and hydrazine discharges has been performed. Immobilization of EMBED Equation.2 -chymotrypsin and nucleotides and the synthesis of oligonucleotides on plasma-functionalized surfaces have been investigated.
It has been found that the frequency has a significant effect on the plasma-mediated reaction mechanisms and that dichlorosilane can efficiently functionalize both inorganic and organic polymeric surfaces. It has been demonstrated that hydrazine discharges are more adequate for the implantation of primary amine functionalities in comparison to ammonia plasmas. EMBED Equation.2 -Chymotrypsin has been covalently immobilized on various polymeric substrates and it has been shown that by intercalating spacer molecules between the substrate and the biomolecules, enzyme activities comparable to the activity of the free enzyme can be achieved. It was demonstrated that high purity oligonucleotides (e.g.26 mer) can be synthesized and nucleotides can be immobilized on plasma- and in situ, second-stage-functionalized silica beads and glass surfaces.
Potential applications of plasma-functionalization reactions will be discussed.
Particle energies of cold plasmas are comparable with chemical bond energies and the particle densities and their energies can be controlled by external plasma parameters (e.g. power, pressure, frequency, etc.). Accordingly, surface functionalities and characteristics even of the most inert substrates can conveniently be tailored.
However, two major drawbacks limit considerably the technological applications of cold-plasma chemistry. Firstly, most of the processes require low pressure environments (which render costly vacuum facilities) and as a result plasma technologies are ab initio batch-type processes, and secondly complex-shaped, three-dimensional substrates cannot be easily plasma-processed owning to the complex antenna geometry which might be required for creating uniform plasma-exposure of the substrate surfaces. Atmospheric pressure plasma installations has already been designed and developed (e.g. corona and barrier discharges) however, these reactors operate mainly under non-reactive and non-toxic-gas atmosphere.
In this contribution three plasma reactors will be presented: Continuous-system, reactive-gas corona installation which allow the surface treatment of bi-dimensional substrates (films, fabrics, etc., in a wide pressure range (including atmospheric pressure) and reactive and toxic-gas environments; Rotating, capacitively coupled RF-plasma reactor which permit the surface modification of particulate matter (e.g. powders, beads) and small objects of irregular shape; Dense medium plasma reactor, designed to process liquid phase materials (e.g. liquids, solutions, suspensions, melts) at atmospheric pressure.
Specific plasma reaction processes developed using these reactors will be described and the feasibility of practical applications will be discussed.
Thin film technologies are evolving from single component structures to multi-component (nano composite) structures. Nano composites incorporate at least two structural and chemical groups and offer novel properties for today's marketplace. A new deposition source technology based on a hollow cathode can deposit Nanomatrixü thin films at high rates. Oxide and nitride structures can be doped with metallic or polymeric groups offering the properties of both components. For example, a stable low index silicon dioxide with metal dispersed through it can be conductive. Another example disperses a fluoropolymer into a silicon dioxide potentially offering the lubricity of Teflon« with the mechanical and thermal properties of SiO2. FTIR data and deposition rate information will be presented.
The electronic configuration of Group IV elements makes them particularly suitable for the formation of a covalent bond. Many unique as well as powerful properrties of the materials comprising these elements are due to the presence of covalent bonds, the best example being diamond with its hardness, high electrical resistivity and high thermal conductivity and silicon with its strong influence on today's life from dish washers to the space program. The interest concerning materials comprising Group IV elements is now more and more being shifted towards those of mixed composition, such as silicon carbide and silicon germanium. The present work is devoted to a group of materials of such a mixed conposition, namely to thin germanium/carbon films deposited in RF plasma from vaporized alkyl germanium derivatives such as tetramethylgermanium and tetraethylgermanium. In both cases films depsoited under high energy input are glassy and hard semiconductor materials (resistivity or the order 104 ohm m, density up to 3.6 gm/cc, optical gap 1.2 eV)> They enjoy the twin advantages of good thermal stability on the one hand and tunability of the optical gap on the other. A comparison of IR absorption reveals certain differences in the chemistry of film formation between both precursor compounds, however, the ultimate layers depositied under conditions of severe energy excess exhibit nearly identical IR absorption spectra.
SiOx film is an interesting material due to good oxygen gas barrier properties. The deposition of SiOx onto polymer film surfaces is expected to give us good packing materials for protection of foods and medicines from the deterioration of their quality by oxidation. In this study, we have investigated how to synthesize and deposit SiOx film on surfaces of polymer films such as PET and Nylon films. What starting material is suitable for SiOx formation by plasma polymerization, and how the plasma polymerization is controlled for SiOx deposition with good oxygen gas barrier properties are discussed from XPS spectra and oxygen permeation measurement.
The influence of the polymer film substrate on the barrier performance of plasma-deposited SiOx coatings has been investigated. It is well known that the barrier properties of a SiOx coating will vary depending on what substrate it is deposited on. SiOx-coated PET will have a typical oxygen transmission rate (OTR)<1, coated OPP<5 and coated LDPE<20 ml/m2, day, atm. The influence of various plasma parameters, such as discharge power, HMDSO:O2-ratio, pressure, coating thickness, plasma pretreatments was examined during deposition on a 12 µm polyethylene terphthalate (PET), an 20 µm oriented polypropylene (OPP) and a 40 µm low density polyethylene (LDPE) film. Most plasma parameters are critical for obtaining good barriers, but do not explain the varying results obtained on the different plastic substrates. These are rather explained by the surface properties of the substrates. (OPP) and a 40 µm low density polyethylene (LDPE) film. Most plasma parameters are critical for obtaining good barriers, but do not explain the varying results obtained on the different plastic substrates. These are rather explaine Gas Barrier Properties of Plasma - deposited Coatings and various plasma parameters coatings has been investigated plasma parameters comprise , and the coatings were deposited various Conventional plastic packaging Films , including polyethylene terphthalate ( P E T ) , and were found obtaining good barriers , but did both such as, and on natural polymer films (starch - based and polyltacetic acid - based films)
1) Thin Film Technology Research Center, Korea Institute of Science and Technology, P.O.Box 131, Cheongryang, Seoul 130-650, Korea
2) Plasma Tech Co. R&D Center, 506-10 Youlmi-Ri, Kyungki-Do, Korea
3) LG Electronics Inc., 76 Changwon Kyung Nam 641-711, Korea
Plasma polymerization on metal using DC glow discharge was carried out for the hydrophilic surface formation using hydrocarbon reactive monomer in various deposition time, voltage, current, and pressure. Strong adhesion of the polymerized film on metal and high surface energy(60-70dyne/cm) were obtained at certain optimum plasma discharge condition. The surface and interface of the polymer films were investigated by FT-IR and FT-Raman spectroscopy, ESCA and contact angle measurement. The FT-IR spectra of the polymer is similar to the spectra of the RF discharged polymer, but good adhesion of the polymer films on metal has been obtained by the DC discharge polymerization and permanent hydrophilic functional layer on metal was obtained at optimum combination of operation parameters. Hysterisis of dynamic contact angle was shown and influenced by the applied discharge conditions. Relationship between wettability and adhesion force has been discussed in terms of polymer damages, surface morphology, functional groups, and discharge conditions, and applications in heat exchanger, corrosion protection, paints, etc. will be presented.
Plasmachemical processing combined with classic chemical synthesis allows to enhance significantly the selectivity of surface modifications for polymers. One approach to practise it is to apply a plasma gas specific surface functionalisation immediately followed by a chemical unification of the coexisting plasma functional groups. The ideal result is a surface which shows only one type of functional groups. This process was introduced by Smolinsky who used diborane to reduce O functional groups to OH functionalities in 1984 [1]. Other reaction pathways, e.g. the reduction with vitride (sodium bis (2-methoxyethoxy)aluminium hydride) and LiAlH4, broadened the scope. The optimization of these reduction processes gives the possibility to reach a yield in up to 14 OH groups per 100 carbon atoms. This result was measured by means of XPS at the surface of PP. In maximum 60 % of all plasma O-functionalized species could be reduced to OH groups. In contrast to this only 3 OH groups were measured applying standard O2 plasma treatment without a post-plasma reduction. The same procedure was applied to ammonia plasma surface modified polymer surfaces. First attempts were made to reduce plasma N-functionalized groups to NH2 in supercritical ammonia. The method was again upgraded by introducing molecular spacers in order to give a better availability of the OH or NH2 groups for a linkage with oligomers, nucleotides or DNA molecules. Silanes, diisocyanates and glycolates were used as spacers. The OH end groups at the spacers were modified by amino acids. A remarkable increase in the selectivity of the plasma process was reached by plasma surface bromination and chlorination with HCBr3 or CCl4. The resulting selectivity was 65 %. Subsequent to bromination a simple Williamsson ether synthesis was applied. In that case a reduction of plasma functional groups by diborane or other chemicals can be avoided. A further increase in the selectivity of plasma functionalization was obtained by applying a pulsed plasma. In the case of plasma surface bromination using bromoform more than 85% of all plasma-introduced functional groups originate from covalent bound C-Br. The surface concentration of Br groups could be increased to more than 30 Br per 100 carbon atoms. The stability of Br groups which were fixed to PP by a pulsed R.F. plasma with 10% "plasma on" pulses and 90% "plasma off" duration (duty cycle = 0.1) was high. By THF extraction 10 to 30% of C-Br species were removed. Comparing the bromine attachment by pulsed R.F. plasma to that by a continuously operating R.F. plasma it indicates that the majority of bromine atoms should be attached onto the PP surface during the "plasma off" time.
R.F. pulse plasma was also applied to plasma polymerization which was described first by Yasuda in 1977 [2]. Timmons was able to show that plasma pulse deposited polymer layers predominantly consist of chemically well-defined building blocks in contrast to irregularly composed plasma polymers deposited by a continuously working R.F. discharge [3]. In the "plasma off" phase regular radical graft polymerisation occurs without any disturbance by plasma particle bombardment and vacuum UV irradiation. Plasma polymerisation is the relevant process in the "plasma on" period whereas a recombination polymerization of fragmented monomer molecule radicals occurs when the plasma is switched off. Here, unsaturated conjugated polymer layers were deposited from ethylene, acetylene, butadiene and styrene. The number of C=C double bonds was measured by NEXAFS spectroscopy. Afterwards a co-deposition of metals as dopants was accomplished. Furthermore, polymer layers with functional groups from acrylonitrile, allyl amine, allyl alcohol and acrylic acid were deposited.
References: 1 R. G. Nuzzo, G. Smolinsky, Macromolecules, 17 (1984) 1013 2 H. Yasuda, T. Hsu, J. Polym. Sci.: Polym. Chem. Edit., 15 (1977) 81 3 Ch. Savage, R. B. Timmons, J. W. Lin, Chem. Mater., 3 (1991) 575
Hyunuk Lee, Joong-Hwan Yang and Samchul Ha; 2LG Electronics Inc., Changwon 641-711, Korea
When synthesized by plasma polymerization employing DC glow discharge under rigorous conditions, high-quality polymer films have been deposited on metallic substrate with improved properties in wettability and adhesion. However, rigid binding of the polymer film with substrate limits proper characterization for the quality of the deposited films. In this work, we report optical reflectance measurements of the polymer films coated on the aluminum substrate, over a wide spectral range from 80 to 5 104 cm-1 (0.01 - 6 eV). While the reflectance spectra, R( ) , remain almost unc hanged in the infrared (I R) range as compared with the bare aluminum, R (f ) starts to decrease significantly in the higher frequency above 20000 c m - 1 . This decrease in R (f ) arises from electronic absorptions characteristic of the polymer film, as clearly demonstrated in the following Kramers - Kronig analysis of the R (f ) . Moreover, the details of R (f ) in the UV range above 3000 cm- 1 exhibit corresponding fabrication conditions of the polymer films, thereby reflecting the quality of the polmer films. Our results demonstrate that this optical measurement can be used as an excellent method to characterize and monitor the quality of the polymer films deposited by plasma polymerization process.
It was established that the surface energy of the carbon films could be varied over a wide range by adjusting the deposition conditions and the atomic surface structure. The surface energy of the carbon films can have an influence on the orientation of the epitropic liquid crystal molecules.
This paper descrives the correlation between the structure and properties of Diamond Like Carbon (DLC) films and the orientation of epitropic liquid crystals. The optical dichroism technique eas used to determine the type of orientation on the epitropic liquid crystals. The orientation order parameter "s" was calculated for DLC films with different degrees of lyophilicity. The crystal surface tension was calculated from the angles of contact of epitropic liquid crystals on SiO2 substrates covered by DLC films. The experimental results have shown that varying the lyophilic nature of DLC films one can obtain the optimized conditions for orientation of thin liquid crystal layers. The results obtained show that the DLC films investigated are characterized not only by the ability to control the liquid crystal orientation but also have the ability to create liquid crystal layers with a controlled thickness.
In conclusion the possibilities of applying DLC as an orientation layer in microelectronic devices will be discussed.
Advanced Refractory Technology has developed a conductive, low surface energy Diamond-Like Nanocomposite (DYLYN() thin film coating. The coatings inhibit eschar formation during use in a surgical procedure. In both cutting and cauterizing, the best results were achieved when the electrical impedance and surface energy was in the range of 1 -1000 ohm and 22 -25 mN/m, respectively. The coatings were deposited with a proprietary plasma-assisted chemical vapor deposition process. The general features of the coating process will be described. The following properties of the films were measured: micro-hardness, elastic modulus, residual stress, electrical impedance, Raman spectra , ESCA, and FTIR. These results will be presented and the relationship between deposition conditions on selected film properties.
Plasma copolymerisation of a "functionalised" monomer with a hydrocarbon "diluent" comonomer may be used to fabricate surfaces of controlled surface chemistry. By employing low plasma power , fragmentation can be kept to a minimum and the functional group preserved from the functionalised monomer to the plasma polymer deposit. This has been demonstrated for acrylic acid,1 allyl alcohol2 and allyl amine.1 Changing the ratio of functionalised monomer to hydrocarbon monomer allows films of varying functional group concentration (functional groups per 100 carbons) to be prepared. The solubility and surface energetics of these plasma copolymers have been investigated.
Substratum surface chemistry is known to play a critical role in the attachment, spreading and proliferation and differentiation of cells in tissue culture. The culturing of keratinoctyes and osteoblasts on plasma polymer films containing carboxylic acid, alcohol and amine-type environments has been investigated, as a function of functional group and concentration. It was found that for both cell-types, optimum attachment, spreading and proliferation were obtained on surfaces containing carboxylic acid groups, but that only 3 carboxylic acid groups per 100 carbons were required.
The role that serum proteins play was demonstrated with osteoblasts, in a simple experiment with and without fetal calf serum, FCS, added to the tissue culture medium. In this experiment three surfaces (a carboxylic acid-containing plasma polymer surface, tissue culture polystyrene, TCPS, and a hydrocarbon plasma-deposited surface) were compared. With serum, good attachment was seen on the acid plasma polymer surface and TCPS, but not the hydrocarbon surface. Proliferation was significantly greater on the acid surface than on TCPS. No proliferation was seen on the hydrocarbon surface. Without serum, good attachment was seen on all three surfaces, but, proliferation was only seen on the acid surface.
A comparative study of the attachment and spreading of osteoblasts and fibroblasts was made on the acid plasma polymer surface and on acid- and methyl-terminated self assembled monolayers (SAMs).3 Again, the importance of the acid group for attachment was demonstrated. Comparable cells numbers attached to both the acid plasma polymer and to the acid-terminated alkyl thiol SAMs. This result is (perhaps) surprising given the differences between these surfaces is marked. The plasma polymer contained only 3 carboxylic acids (per 100 carbons) and it is not clear if these were presented at the liquid interface (the water contact angle of 80° suggests a hydrophobic surface). The acid-terminated SAMs comprised of well packed "rod-like" molecules, where the functional group is known to be presented at the liquid interface. This result suggests that cell response is controlled by more than simple surface hydrophilicity/hydrophobicity, and that even comparatively small numbers of carboxylic acid groups are sufficient to control protein adsorption and conformation to enhance cell attachment and spreading.
1. R M France, R D Short, R A Dawson and S MacNeil, J. Mater. Chem., 1998, 8, 1, 37-42
2. R M France, R D Short, E Duval, F R Jones, R A Dawson and S MacNeil, Chem. Mater. 1998, 10 (4) 1176-1183
3. R Daw, I M Brook, A J Devlin, R D Short, E Cooper and G J Leggett, submitted J. Mater. Chem.
Depsoition of plasma-polymerized organic films on metals or polymer films is a well-known process. Deposition of such polymer films onto particulate matter, i.e. fine powders, has not been described much. We have developed two types of reactors for modifying powder properties by the plasma-polymerization process, viz., a vacuum fluidized bed reactor and a tumbler-type reactor. The designed specific advantage of these two types of reactors will be discussed.
Several applications of powder particle surface modification will be highlighted in this paper. They will include: 1) modification of organic pigment properties; 2) using the plasma polymer film as a membrane, resulting in slow release properties of water-soluble powders; 3) temporary or permanent protection of air or water-sensitive powders or flakes.
Aramid cords and fibers and polyester tire cords were treated in a pulsed DC plasma containing organic monomers such as pyrrole or acetylene in a custom built reactor. Of the treated cords the rubber adhesion was measured in a standard pull-out test. It was found that the plasma polymer coating can significantly increase pull-out forces, even higher than that obtained by commercial dip coatings. The effect of pulsing the DC power and the power-to-pressure ratio on the performance of the treated cords or fibers was investigated. It was found that, in general, low power and high pressure conditions gave better results than high power/low pressure conditions. Coatings obtained under these conditions were thoroughly characterized by a range of analytical tools. Based on these data and on failure interface analysis, models were developed to accomodate the experimental findings.
Yoshinori Hatanaka; Research Institute of Electronics, Shizuoka University, Hamamatsu 432, Japan
Remote oxygen plasma chemical vapor deposition (ROP-CVD), using tetraethoxysilane (TEOS) as single-source compound was investigated to get insight into the mechanism of silica film growth. In particular, an effort was made to elucidate the chemical nature of silica film-forming precursors. ROP-CVD selected as a model process suitable for mechanistic study, has been examined in terms of the effects of atomic oxygen concentration, of the contents of the ground - and excited-state oxygen atoms in atomic oxygen fraction, and of thermal activation. The growth rate of silica film does not depend on the composition of the atomic oxygen fraction but is proportional to total concentration of atomic oxygen fed into the CVD reactor. In the light of the apparent activation energy Ea values calculated from the Arrhenius plots of the substrate temperature dependencies of film growth rate, the mechanism of ROP-CVD is related to the concentration of atomic oxygen. The Ea 0 found at low concentration of atomic oxygen (1.5 x 1014 cm-3) implies that ROP-CVD is a non-thermally activated process; diffusion of the precursors from the gas-phase to the substrate seems to be the ROP-CVD's rate limiting factor under these condition. The Ea<0 observed for high concentrations of atomic oxygen ( 9.7 x 1014 cm-3) indicates that the adsorption of the precursors onto the substrate is a main factor controlling the ROP-CVD's rate. Products of the gas-phase conversion of TEOS investigated by a high-resolution gas chromatography/mass spectrometry, revealed the presence of linear and cyclic siloxane oligomers containing the -(EtO)2SiO- repeating unit. The structure of identified oligomers, results of the study of TEOS reactions with atomic oxygen, structure of the film deposited, chemiluminescence spectra of the gas-phase products in the CVD reactor, as well as the results of step coverage tests account for diethoxysilanone (high-reactivity intermediate) and hexaethoxydisiloxane (high-surface-mobility and low-reactivity intermediate) as the major precursors of silica film growth.
Glow discharge plasma is an effective method of treating surfaces, sputtering, etching, plasma-assisted deposition, ashing, and a range of other processes. Sigma Technologies Int'l, Inc., has developed a novel plasma system which can be operated at atmospheric pressure thereby eliminating the need for vacuum chambers and pumps. This atmospheric plasma system can be effectively used for surface treatment and for plasma-assisted deposition. This plasma system has been tested successfully for the functionalization of various polymer films. The surface energies of the films treated by the newly developed atmospheric plasma system have been shown to increase substantially, thereby enhancing the wettability and adhesion properties of these films. Details of the atmospheric pressure plasma system, and the results from treatment tests will be presented
1) Electrical Discharge and Plasma Laboratory, Tel-Aviv University, POB 39040, Tel-Aviv 69978, Israel
2) Department of Materials Engineering, Technion - Israel Institute of Technology, Haifa 3200, Israel
3) Research Centre in Surface Engineering, University of Hull, Cottingham Road, Hull HU6 7RX, UK
Thin metal/ceramic coatings were deposited onto polysulfone S2010 substrates using a triple-cathode vacuum arc plasma source connected to a magnetized plasma duct in order to improve the tribological properties of the polymer surface. Various combinations of multi-layer coatings having metal sub-layers, and nitrides of Ti, Zr, Nb, and ternary (Ti,Zr)N as wear-resistant layers were deposited and evaluated. The structure and composition of the coatings were studied using XRD, AES, and SEM. Scratch tests were used to evaluate the adhesive strength between the substrate and the coating, and reciprocating wear tests against a steel ball were used to study the friction and wear rates of the coated samples It was shown that the nitride coatings possessed a nanocrystalline structure or a mixture of an amorphous and a nanocrystalline structure with random orientation. . It was observed that carbide formed at the interface of the Ti intermediate layer and the substrate. The results suggest that the formation of a carbide interface improves the coating adhesion, and provides better wear performance of the bi-layer metal/nitride coating, and, vice versa, the coatings where carbide was not formed at the interface, failed completely during wear tests because of poor adhesion to the substrate.
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