ICMCTF2005 Session GP: Symposium G Poster Session

Thursday, May 5, 2005 5:00 PM in Room Town & Country

Time Period ThP Sessions | Topic G Sessions | Time Periods | Topics | ICMCTF2005 Schedule

GP-1 Creation of C@sub 3@N@sub 4@ by Electron beam Processing
P.I. Petrov (Institute of Electronics, Bulgaria)
The industry is constantly looking for improvements of the optical, thermal, chemical, electrical and mechanical features of the materials. At the present time there is especially a demand for hard and super hard coatings. Liu A. Y. and Cohen M. L in 1989 was predicted theoretically that - C@sub 3@N@sub 4@ , a carbon nitride compound with the structure of - Si@sub 3@N@sub 4@ which does not exist in the nature, should have a hardiness close to that of the diamond and exceed those of c - BN. In our study carbon nitride thin films deposited on Si(100) by electron beam evaporation of graphite and simultaneously nitrogen ion bombardment. Electron beam with power 0.5-1 kW (at accelerating voltage 10 - 50 kV) and N + bombardment with low energies of 300-400 eV were used for deposition of the films. The substrate holder during the deposition was heated at range from 300@super o@C to 1000@super o@C. The layers were analyzed by X-ray photoelectron spectra, Fourier transforms infrared spectroscopy and Raman spectroscopy. C/N ratio has the value from 0.5 to 1.165. The C 1s XPS core level centered above 286 eV is about 67% of the entire peak. This peak together with the N1 s peak at 400 eV is a feature of the C-N bounds with sp@super 2@ coordination. The peak at 287.4 eV, of about 27% of the area, is considered to be due to sp@super 3@ coordination. N1 s XPS peak at 399 eV is attributed to C=N bonds with sp@super 3@ coordination. The results from XPS analysis were confirmed from Raman and FTIR analysis. Fourier transform IR spectroscopy shows typical Cï-N IR band centered at about 2150 cm-1.
GP-2 The Investigation of Structural, Mechanical and Tribological Properties of Plasma Nitrocarburized AISI 1020 Steel
A. Celik, M. Karakan, A. Alsaran, I. Efeoglu (Ataturk University, Turkey)
AISI 1020 steel was plasma nitrocarburized at different gas mixtures (N@sub 2@ and H@sub 2@), for different process times (1, 2, 4, 8 and 12 h) and at different temperatures (570 and 640@super o@C). The structural, mechanical and tribological properties of nitrocarburized steel were analyzed using X-Ray diffraction, microhardness tester, scanning electron microscopy, optical microscopy and pin-on-disk tribotester. The results have shown that the compound layer was composed of the ? - Fe@sub 2-3@(C, N) and ? - Fe4(C, N) iron carbonitrides and the thickness of this layer increased with increasing temperature and time. The nitrocarburizing process increases the surface hardness, roughness and the thickness of diffusion layer. It was seen that surface hardness increased about two times depending on process parameters, and the highest hardness was observed on austenite layer obtained at austenitic treatment (640@super o@C). The wear strength increased between 20 and 60% depending on process parameters. While the highest wear strength was obtained at austenitic nitrocarburizing for 4h, the lowest friction coefficient was also attained at austenitic treatment.
GP-3 Characteristics of Organic Light-Emitting Devices by the Surface Treatment of Indium Tin Oxide Surfaces using Atmospheric Pressure Plasmas and Low-Pressure Plasmas
C.H. Jeong, J.H. Lee, Y.H. Lee, G.Y. Yeom (Sungkyunkwan University, South Korea)
These days, organic light emitting diode (OLED) displays are widely investigated due to the superior properties such as faster response time, lower operating voltage, higher quantum efficiency, etc. in addition to the simpler deposition processing and the lower manufacturing cost compared to other flat panel displays such as liquid crystal displays and plasma display panels In fabrication of OLED, cleaning of the indium-tin-oxide (ITO) has crucial effects on the OLED performance, especially on the starting voltage of emission. Among the cleaning methods, a plasma treatment is most useful. Recent studies on the surface treatment of various materials are concentrated on the atmospheric pressure plasmas (APP) instead of low-pressure plasmas due to the various advantages of atmospheric pressure plasma. We investigated the effect of various plasma treatments of ITO surface for the performance of OLED using APP of different gases and low-pressure plasmas of different gases. The APP pre-cleaning treatment of the ITO surface lowered the operating voltage of the OLED and to the change in work function of ITO. These optimum gas compositions were selected after the measurements of contact angle by a contact angle measuring tool and carbon contents on the ITO surface by X-ray photoelectron spectroscopy after varying plasma pre-cleaning. The OLED structure used in this study was ITO glass/2-TNATA/NPD/Alq@sub3@/LiF/Al. The electrical characteristics of the fabricated OLED devices were measured using an electrometer and the luminescence characteristics were determined by measuring the photocurrent induced by light emission from the OLEDs using a picoammeter.
GP-4 A Comparative Study on Cutting Performance of TiN Coated Tungsten Carbide Cutting Tool with a Cobalt Interlayer
D.H. Kwon, M.C. Kang, S.Y. Yoon, J.H. Jeon, K.W. Kim (Pusan National University, South Korea)
In order to study effects of Co interlayer between TiN coatings and WC-Co substrate, interlayer Co was deposited on WC-Co substrates prior to TiN Coating. Effects of Co interlayer, Co content on adhesion strength were studied using a conventional scratch test. The high critical load was obtained at a WC particle size of 1ãZ> and Co content of 10 wt.%. Adhesion between the coating and substrate were considerably affected by the surface morphology and the interlayer. TiN coatings with and without Co interlayer were applied to end-mill tools made of WC-Co material by a arc ion plating. Cutting tests for the die material(SKD11) and their performances in various cutting conditions were studied. Also, In order to verify tool wear distribution, normal distribution and log normal distribution by Chi squared test was considered. As the result, tool life of coated tool with Co interlayer was improved over 25 % than TiN coated tools without interlayer.
GP-5 Cutting Performance using High Reliable Device of Ti-Si-N Coated Cutting Tool for High Speed Interrupted Machining
M.C. Kang, J.S. Kim, K.W. Kim (Pusan National University, South Korea)
Recently, high speed machining is strongly discussed in modern production engineering. The other hand, the serious problem of high speed machining is the short tool life due to a severe tool wear. So, superior coating materials have developed to improve the tool life and cutting force. In general, the cutting performance of coating tools have evaluated about cutting force using tool dynamometer and tool wear using microscope. In case of high speed interrupted machining with end-milling process, however, the evaluation system and actual performance with it were scarcely reported. In this work, an performance evaluation device of coating tool for high speed interrupted machining was designed. To measure cutting force, tool dynamometer which can monitor with high time resolution was newly developed using a piezo force sensor. Also, measuring system of tool wear using CCD camera and an exclusive jig considering run-out problem was newly designed. Cutting tests of the each coated tools were carried, and their performances in high speed cutting conditions were studied. Specially, this evaluation device can measure cutting force and tool wear on the table bed at the same time.
GP-6 The Study of Relationship between Morphology, Mechanical Properties and Gas Separation of Polyimide/Poly(silsesquioxane) Nanocomposite Thin Film
M.-H. Tsai, C.-J. Ko, Y.-L. Chen, S.-L. Huang (National Chin Yi Institute of Technology, Taiwan)
The synthesis of polyimide/poly(silsesquioxane) nanocomposite hybrid thin films for gas separation application are presented. The hybrid thin films are successfully prepared from the poly(amic acid) [3,3'-Oxydiphthalic anhydride (ODPA) and the 4,4'-Diaminodiphenyl ether (ODA)] with end-capped phenyltrialkoxysilane (PTS) and monoaryltrialkoxysilane via a self-catalyzed sol-gel process. p-aminophenyltrimethoxysilane was employed to provide bonding between the PTS and ODA-ODPA phase and controls the polyimide block chain length ranging from 5000 to 20000 g mole-1. The object here is to correlate the properties with the silica component and content, the polyimide block chain length, the crosslinking density and free volume. The effect of composition of the polyimide/poly (silsesquioxane) hybrid thin films on their morphology, thermal stability, thermal expansion coefficient, optical transparency in visible, dynamic mechanical properties, gas permeability and gas permselectivity were investigated. The more detail will be presented in the conference.
GP-7 Preparation and Performance of Novel MEA with Multi Catalyst Layer Structure for PEFC by Magnetron Sputter Deposition Technique
C.-H. Wan, Q.-H. Zhuang, M.-T. Lin (Mingdao University, Taiwan)
Sputter deposition is widely used for integrated circuit manufacturing and has been investigated for the preparation of more effective fuel cell electrodes for more than a decade. The main problem encountered in this technique is that the required reaction area of fuel cell electrode has to be a three-dimensional reaction zone, given the sputter Pt catalyst layer is a two-dimensional thin film structure. This study proposes a novel catalyst layer structure composed of multi two-dimensional active layers. This structure is obtained by depositing a Pt layer by magnetron sputter deposition method on a nafion-carbon ink layer alternatively in order to attain the required three-dimensional reaction zone. SEM, X-ray, EDS and EPMA analysis were used to characterize microstructures, chemical composition and distributions for the obtained electrocatalyst layers. The correlation of microstructures and operation parameters, such as operating pressure and sputtering time, with respect to the electrode performance was investigated. The MEAs consists of a Nafion 117 membrane and a commercial electrocatalyst (20% Pt/C from E-TEK) on cathode side. Results showed that three layers of Pt sputter-deposited on the gas diffusion layer provided better performance (324.4mA/cm@super 2@ at 0.6V) than sputtering one Pt layer in the same loading, and providing an activity of 3244A/g at 0.6V for ultra-low loading (0.10mg/cm@super 2@). It demonstrated that the effective improvement of performance was due to the existences of the three-dimensional reaction zone. Keywords: Multi catalyst layer structures, Magnetron sputter deposition techniques, MEAs, three-dimensional reaction zone.
GP-8 In Vitro Investigation of Hemocompatibility of Hydrophilic SiN@sub x@:H Films Fabricated by Plasma-Enhanced Chemical Vapor Deposition (PECVD)
G.J. Wan (City University of Hong Kong and Southwest Jiaotong University, Hong Kong, China); P. Yang (Southwest Jiaotong University, China); X.J. Shi (Hong Kong University of Science & Technology, Hong Kong); M. Wong, H.F. Zhou, N. Huang (Southwest Jiaotong University, China); P.K. Chu (City University of Hong Kong)
The biocompatibility and bioactivity of silicon-based materials such as silicone rubber, SiO@sub 2@, and SiC have been investigated but silicon nitride has been relatively unexplored. Researchers have hitherto focused mainly on the dielectric, optical, and mechanical properties of silicon nitride instead of its potentially remarkable physicochemical characteristics in biomedical applications. Recently, some efforts have been made to study Si-N in biomedical micro-devices but the hemocompatibility of the materials has not been reported. A good understanding of the surface bioactivity is crucial to the introduction of Si-N to blood contacting biomedical devices. In this work, SiNx:H films with different N/Si ratios were synthesized by plasma enhanced chemical vapor deposition (PECVD). The objective is to obtain different hydrophilic properties, which is one of the important factors affecting thrombogenicity of blood contacting biomaterials. In vitro platelets adhesion was conducted to evaluate the hemocompatibility of the prepared films and the results are compared to low-temperature isotropic carbon (LTIC) which is the most common used materials in commercial blood contacting biomedical devices such as artificial heart valves. Our results indicate that films with higher N/Si ratios offer better hemocompatibility than LTIC. The improved haemocompatibility results from the Si-N bonding configuration. The proper chemical structure enhances the surface hydrophilicity consequently reducing thrombogenicity. Surface energy analysis is also performed to interpret the platelet adhesion behavior on the Si-N films.
GP-9 Surface Modification of Silicon Wafer for Biomedical Application
X.Y. Liu, J.P.Y. Ho, P.K. Chu (City University of Hong Kong); C.X. Ding (Shanghai Institute of Ceramics, Chinese Academy of Sciences)
Silicon wafers are the common substrate materials for fabrication of microchips including biochips and the package materials of biosensors. The surface bioactivity and biocompatibility of silicon are usually poor and the interaction between silicon-based biosensors or microelectromechanical systems (MEMS) and the human body may not be desirable. In this work, to obtain the special functional groups on silicon wafers, the surface was modified using wet chemical etching methods in order to improve the surface bioactivity and biocompatibility. The bioactivity and biocompatibility of the silicon wafer treated using wet chemical etching methods were investigated by simulated body fluid soaking test and cell culturing test. After treatment using wet chemical etching methods, the silicon wafer possessed a surface consisting of Si-OH and/or Si-H groups. Bone-like apatite could be precipitated on the surface of the treated silicon wafer after soaking in simulated body fluids for two weeks. The results indicate that the bioactivity of the silicon wafer can be improved by wet chemical methods.
GP-10 Improvement of Bioactivity and Corrosion Resistance of Titanium Metal via Electrolytic Deposition Anatase TiO@sub 2@ Coatings
C-.M. Lin (National ChungHsing University, Taiwan)
Titanium and titanium alloys for implants have been widely applied to the orthopaedic and dental fields, due to their excellent corrosion resistance, good mechanical properties and biocompatibility. However, the near bioinert and metallic ions release are still the major problems in the clinical failure. For these reasons, fabrication and modification of biomaterials surface properties, which support bioactivity and corrosion resistance, should be one of the key objectives in the design of the next generation of orthopaedic/dental implants. Cathodic electrolytic deposition of nanocrystalline anatase TiO@sub 2@ coating has been successfully deposited on pure titanium substrate. After annealed at 300°C for 1 hr, the coating were further condensed into anatase TiO@sub 2@, and gradually transformed into rutile TiO@sub 2@ at 500°C. The dynamic cyclic polarization tests appeared that dense and nanocrystalline of anatase TiO@sub 2@ coated effectively improved corrosion resistance to avoid aggression of fluoride ion. For immersion tests, the matching structure of anatase TiO@sub 2@ and apatite may play an important role in the apatite formation ability. Moreover, the cell culture results also indicated that nanocrystalline of anatase TiO@sub 2@ promoted not only cells differentiation, but also appeared more bioactive while maintaining non-toxicity. Obviously, the materials characteristics such as crystal structure, surface morphology and corrosion resistance may play an important role in the osteointegration.
GP-11 Effects of Fluorine Doping of Amorphous Diamond-Like Carbon Films on Platelet Adhesion and Activation
S. Yohena (Keio University School of Science and Technology, Japan); T. Hasebe (Tachikawa Hospital/Keio University School of Science and Technology, Japan); T. Saito, Y. Matsuoka (Keio University School of Science and Technology, Japan); A. Kamijo, K. Takahashi (The University of Tokyo Hospital, Japan); T. Suzuki (Keio University School of Science and Technology, Japan)
Thrombogenic complications remain as one of the main problems for blood-contacting implants and can trigger life-threatening device failure. Recently, diamond-like carbon (DLC) films have received much attention because of their antithrombogenicity of inhibiting platelet adhesion and activation. With regard to surface energy, it is well known that fluorocarbon polymers exhibit significantly lower surface energy compared with other polymer materials, and that is, incorporation of fluorinate into DLC films improve the haemocompatibility of materials.@paragraph@ The purpose of this study is to evaluate the effects of fluorine doping of DLC films (F-DLC) on platelet adhesion and activation at various fluorine contents. The static evaluation of F-DLC films incubated with platelet rich plasma (PRP) showed dramatic reductions in platelet adhesion and activation on the surface as increasing the amount of doped fluorine into the films, which was clearly shown by SEM. F-DLC films thus have great potential for developing antithrombogenic surfaces in blood-contacting materials.
GP-13 Bioactive Titanium-Particle-Containing Dicalcium Silicate Coating
Y.T. Xie, P.K. Chu (City University of Hong Kong)
Titanium and its alloys are considered to be one of the best metallic materials for orthopedic and dental implants. A macro-porous layer of titanium coating fabricated by plasma spraying is widely used. The morphological fixation of an implant to bone through the porous titanium surface layer is, however, essentially a mechanical fixation which requires a long immobilization time and may cause mechanical loosening at the bone-implant interface. The fabrication of a bioactive hydroxyapatite coating on the implant is a good way to improve the physiological chemical bond between the implant and bone. However, the dissolution of the hydroxyapatite often causes failure in long-term in vivo conditions. In this paper, titanium particles with typical size ranging from 80-140 µmm were used as scaffolds and bioactive dicalcium silicate (finer than 20 µmm) was synthesized by atmospheric plasma spraying to improve the physiological chemical bonding between the coating and bone. In vitro bioactivity evaluation in simulated body fluids (SBF) shows that dense layers of apatite precipitate on the coating surfaces after 7 days of immersion. In the biocompatibility experiments, human osteogenetic cells are observed to spread and differentiate directly on the coating surface. The dissolution rate of the coatings in the tris-HCl solution decreases because of the abundant nearly insoluble titanium. The durability of the coatings is monitored by the mechanical properties changes of the coating in the SBF solution. Our experimental results show that the micro-hardness, bend toughness and Young's modulus change very little during the 28 days of immersion in SBF. The results show that a bioactive coating with good durability is obtained.
GP-14 Effect of Additives on the Durability and Bioactivity of Plasma-Sprayed Dicalcium Silicate Coatings
Y.T. Xie (City University of Hong Kong); C.X. Ding (Shanghai Institute of Ceramics, Chinese Academy of Scienc); X.Y. Liu, P.K. Chu (City University of Hong Kong)
Ca@sub 2@SiO@sub 4@ is a useful medical material in artificial bones and dental roots because of its good bioactivity and biocompatibility. There is, however, concern on its long-term stability. Dissolution of calcium ions from the coatings is beneficial to the bioactivity but at the same time deteriorates the long-term stability. Yttria stabilized zirconia (YSZ) and titanium or its alloys are often used as reinforcement in bioactive ceramics and coatings because of their high strength and enhanced toughening characteristics and corrosion resistance. It has been shown that the strength and toughness of bulk bioglass consisting of zirconia powders can be enhanced and strength degradation of the bioglass in the physiological environment is mitigated. In this work, composite coatings with 70 wt% titanium or zirconia with typical size ranging from 40-110 µmm and 30 wt% dicalcium silicate were fabricated by atmospheric plasma spraying. Titanium and zirconia were used as scaffolds and dicalcium silicate acted as a reservoir of calcium ions to enhance bone formation and bonding. The in vitro bioactivity and durability of the coatings were evaluated by immersion in SBF solution and tris-HCl buffer solution. Dense layers of apatite were found to precipitate on the surface of the composite coatings after 7 days of immersion, demonstrating that the composite coatings have good bioactivity even for that comprising 70 wt% of the bio-inert component. The large difference in the thermal expansion coefficient between the coatings and substrates is one of the reasons for the rapid deterioration of the coatings properties. The addition of titanium or zirconia helps to reduce the thermal expansion coefficient difference and effectively diminish the residual stresses at the interface between the coating and substrate. Consequently, the bonding strength and durability of the composite coatings are improved significantly.
GP-15 Plasma Nitriding of Various Substrates using D.C. Glow Discharges Under a Triode Configuration
J.C. Avelar-Batista, E. Spain, J. Housden (Tecvac Ltd., United Kingdom); A. Matthews (Sheffield University, United Kingdom); F. Montala (Tratamientos Termicos Carreras (TTC), Spain)
The benefits of plasma nitriding in terms of superior hardness and enhanced fatigue resistance have already been exploited by industries worldwide. In order to ally the favourable properties of nitrided layers to the superior wear and corrosion resistance of PAPVD coatings, combined treatments consisting of plasma nitriding followed by PAPVD deposition were developed. Such treatments often improve the load-bearing capacity of PAPVD films, as elastic and plastic deformation of the substrate is significantly reduced. Using a D.C. glow discharge under a triode configuration, as usually found in PAPVD coaters, to perform plasma nitriding, has several advantages over conventional D.C. diode plasma nitriding. These include improved kinetics of the low pressure triode process in terms of dissociation and ionisation of species, lower gas flow rates, better control of the nitrided layer structure, lower energy and consumables costs and shorter delivery time for customers. In this paper, plasma nitriding of different substrates such as Ti6Al4V, AISI 316 stainless and AISI M2 steels was achieved by means of D.C. glow discharges assisted by thermionic emission (triode configuration). Deep nitrided cases were obtained for all substrates in significantly shorter treatment times in comparison to conventional (D.C. diode) plasma nitriding. The technological relevance of plasma nitriding soft substrates (e.g., Ti6Al4V and stainless steel) as a pre-treatment for subsequent PAPVD coating is also discussed.
Time Period ThP Sessions | Topic G Sessions | Time Periods | Topics | ICMCTF2005 Schedule