ICMCTF2008 Session GP: Symposium G Poster Session
Thursday, May 1, 2008 5:00 PM in Room Town & Country
Thursday Afternoon
Time Period ThP Sessions | Topic G Sessions | Time Periods | Topics | ICMCTF2008 Schedule
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GP-1 Influence of Surfactants on Efficiency of Electroless Ni - P Coating Process
R. Elansezhian, B. Ramamoorthy, P. Kesavan Nair (Indian Institute of Technology Madras, India) The effect of surfactants on efficiency of electroless Nickel - Phosphorus surface protective coating obtained from an alkaline bath is presented in this paper. Electroless nickel (EN) coatings have gained widespread acceptance as it provides uniform deposit on irregular surfaces, direct deposition on surface activated non - conductors, high hardness and excellent resistance to wear, abrasion and corrosion. Besides all its distinct advantages, the major drawback of EN coating is its high cost of production due to various factors like cost of chemicals used, wastage in the form of metal bearing sludge, poor nickel recovery from the bath etc. Due to these reasons, the EN coating efficiency is reported to be poor and is of the order of only 35%. When nickel atoms are produced as a result of autocatalytic reaction, all of them are not forming a strong coherent metallic bond with the substrate instantaneously. Some portion of nickel particles leaves the substrate and reaches the locations other than substrate. Hence, the coating efficiency is affected. The above problem is addressed by altering the force balance between the adhesive forces (including the weight of the particles) and forces due to buoyancy (including forces due to turbulence). Anionic surfactant sodium dodecyl sulfate (SDS) and cationic surfactant cetyl trimethyl ammonium bromide (CTAB) are introduced to the aqueous electrolyte and they reduced the vertical surface tension forces which binds the nickel particles to the gas bubbles. Smaller the contact angle between the solid surface and liquid droplet, adhesion will be better and gas bubbles will not escape to the top surface. Smaller the surface tension force, quicker the wetting of the solid. The surfactants added in to the electrolyte reduced the contact angle from 81.6º to 6.9º. The rate of deposition is increased from 12.7 µm/hour to 32.2 µm/hour. The coating efficiency is increased from 35% to 95% . The study prevails that surfactant introduced greatly enhanced the rate of deposition on the substrate and coating efficiency. |
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GP-2 SiO2Like Thin Film Deposited by Atmospheric Pressure PECVD Using HMDS/Ar/O2
J.H. Lee, Y.S. Kim, S.J. Kyung, J.T. Lim, G.Y. Yeom (Sungkyunkwan University, Korea) Dielectric barrier discharges (DBDs) are one of the most promising sources for the generation of non-equilibrium plasmas used in atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD) processes. In this study, SiO2-like thin films were deposited at low temperature (< 50°C) by atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD) in a pin-to-plate-type dielectric barrier discharge (DBD) with a gas mixture of hexamethyldisilazane (HMDS)/Ar/O2 and the characteristics of those films with increasing HMDS and O2 were investigated. The increase of HMDS in the gas mixture increased the deposition rate, however, due to the enhanced homogeneous reaction with increasing HMDS. And having high roughness and low transmittance was obtained. The increase of O2 flow rate at a fixed HMDS flow rate increased the reaction of remaining HMDS on the substrate surface, therefore, the increase of deposition rate could be also obtained with increasing O2 flow rate until the remaining HMDS is completely reacted. However, the increase of oxygen flow rate also increased the surface roughness and decreased the optical transmittance slightly possibly. |
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GP-3 Internal Linear Inductively Coupled Plasma Source For Ultra Large Area Plasma Processing
J.H. Lim, J.G. Park, K.N. Kim, G.Y. Yeom (Sungkyunkwan University, Korea) Inductively coupled plasma (ICP) systems are widely studied because of their simple physics and scalability compared with other high density plasmas sources. However, when the ICP sources are applied to the processing of flat panel display having an extremely large substrate size, the ICP sources show many problems such as a large voltage on the antenna, and the increased thickness of dielectric window, etc. In this study, a larger size of double comb-type internal linear ICP source with the substrate area of 2,300mm × 2,000mm has been developed and the characteristics of the source such as voltage distribution, electrical properties, plasma uniformity, etc were studied to investigate the initial possibility of double comb-type internal linear antenna source for the application to the extremely large-area plasma processing. Using the ICP with the double comb-type internal linear antenna, a plasma density of 1.4 × 1011/cm3 could be obtained at about 10kW of rf power and with 15mTorr Ar. The plasma uniformity less than about 15% could be also obtained within the substrate area. |
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GP-4 Inhibition of Streptococcus Mutans Biofilms Accumulation On Micro-Arc Oxide Films Containing Ca and P of Titanium
M.K. Kang (Yonsei University College of Dentistry, Korea); B.Y. Kim (University of Incheon); K.Y. Kim (MST Technology, Korea); K.N. Kim, Y.K. Lee (Yonsei University College of Dentistry, Korea) Titanium alloys have been proved to be very suitable materials for load bearing bioimplant application and have successfully been used in biomedical and dental implants for its minimal tissue reaction. Unfortunately, titanium exhibits poor osteoinductive properties like most metals. This drawback has recently been addressed by coating the metal with a layer of the hydroxyapatite(HA), which is the main component of bone as well as teeth and this a very good osteoinductor. Titanium oxide(TiO2) coatings on titanium alloys have demonstrated acting as a chemical barrier against release of metal ions from the implant. However, the chemical bond with the living bone in the body is not very strong, therefore a double layer of HA/TiO2 coatings on titanium alloys should possess a very good combination of biochemical stability and mechanical properties, particularly if the interfacial adhesion can be enhanced. Many techniques have been investigated for deposition of HA onto titanium alloys, including flame, plasma spraying, ion beam sputtering, chemical vapor deposition, dip coating, electrophoresis and electrochemical deposition. Among theses techniques, plasma spraying is the most popular method, but it is difficult to apply uniform coating on implants with complex geometries. Micro-arc oxidation represents a relatively new surface modification technique where thick, hard and anticorrosive oxide coatings can be easily and cost-effectively fabricated. In this study, a phosphate salt solution was used as the electrolyte for micro-arc oxidation. HA powder and ethylenediol were added to the distilled water for the preparation of the HA suspensions. pH value of the solution was adjusted in the range of 4-11 using ethylenediamine and malonic. For micro-arc oxidation, the specimens were immersed in a phosphate salt. A d.c. of 400 V was applied, giving a current density of 20-40 mA/cm2 and raising the bath temperature around 75°C. For electrophoretic deposition, the specimens were immersed in various HA suspensions and again provided with d.c. of 400 V for 10 min. After characterization of the coating film using XRD, SEM and EPMA, biofilms of Streptococcus mutans, which is the primary aetiological agent of dental caries, were formed on the hybrid coating film of titanium for 5 days. The dry weights of the biofilms onto the hybrid coating film were significant less than that of titanium alloys (p<0.05). This result indicates that a hybrid combination of micro-arc oxidation and electrophoretic deposition could be expected to prevent the biofilm accumulation on the dental implant. |
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GP-5 The Investigation on the Formation of Hydroxyl Radical in Optimal Thin Film Photocatalytic Process
K.S. Yao, C.Y. Chang, T.A. Cheng, C.Y. Cheng (Mingdao University, Taiwan) In recent years, advanced oxidation processes (AOPs) have been extensively utilized for the decomposition of hazardous or recalcitrant pollutants in the environment and many conclusions of studies reveal that AOPs are closely related to the applications of free radicals, such as the UV/TiO2 photocatalytic process in this study. Owing to their extremely high reaction rate and their exceptionally short presence in the environment, it is not easy to evidence the action of free radicals. In this study, titanium dioxide thin film was prepared by optimal parameters with the Taguchi method through chemical vapor deposition and salicylic acid was used as the free radical scavenger to investigate the formation of hydroxyl radical generated during photocatalysis. The results indicated that a higher conversion ratio of the organic substance could be achieved under catalytic oxidation temperature of 400°C, calcination temperature of 550°C, and spraying speed of 30 rpm. The effect of the carrier gas flow rate was rather insignificant. The other results showed that the optimal experimental conditions obtained in this study were irradiation with intensity of 2.9 mW cm-2 on salicylic acid at concentration of 250 mg L-1 by both agitation and aeration processes (dissolved oxygen level = 8.2mg O2 L-1) at pH 5, which could achieve optimal hydroxyl radical yield of 5.1 ×10-17 M. |
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GP-6 Nitriding of Titanium Films by Atmospheric Pressure Plasma
H.-Y. Chen, F.-C. Hsiao, W.-Y. Chang, C.-H. Tsai (National Kaohsiung University of Applied Sciences, Taiwan) A 2.45 GHz microwave plasma torch operated at atmospheric pressure is employed to the nitriding of titanium films. The metallic titanium films were prepared by magnetron sputtering. After that, the films were treated by nitrogen/hydrogen plasma at 800 W for 10 to 30 mins. The color changed from metallic luster to golden above 10 mins. The X-ray diffraction patterns show that as-deposited titanium films are (002) preferred orientation which were vanished after plasma nitriding. The titanium nitride (111) diffraction peak appeared above 10 mins, but the peak position lower than that value given by JCPDS database. The plasma constitutes correlate to the resultant films microstructure are also further investigated. |
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GP-7 Effects of Electroless Nickel Interlayer on Surface Properties of Cr-N-O Arc-Coated ADI
C.-H. Hsu, K.-L. Chen, J.-H. Lu (Tatung University, Taiwan) Because of its low cost, high tensile strength, fatigue resistance, and wear resistance, austempered ductile iron (ADI) has been widely applied in the automotive industry. However, in opposition to the above-mentioned mechanical properties, the shortcomings of ADI are its surface hardness (Hv: 396) and corrosion resistance. And, because its relatively low austempered temperature falls in the range of Ms-450°C (Ms: the martensite start temperature), ADI cannot be case hardened using traditional high temperature heat treatment. This study utilized electroless nickel (EN) and cathodic arc deposition (CAD) technologies with lower processing temperature to treat ADI substrate and then evaluated the availability of applying the EN and Cr-N-O duplex coatings on ADI. Coating properties such as roughness, hardness, and adhesion were analyzed and microstructures of ADI before and after surface treatment were observed. Also, polarization tests were carried out for further understanding the effect of the coatings on the corrosion resistance of ADI. The results showed that the unique microstructure of ADI did not deteriorate after EN and CAD treatments. Though the use of EN interlayer resulted in the increase of surface roughness, it could evidently improve adhesion and hardness for these Cr-N-O coatings. In the performance of corrosion resistance, all coated specimens were better than that of uncoated one in 3.5 wt% NaCl aqueous solution. Moreover, the coatings with EN interlayer were superior to that without EN interlayer. |
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GP-8 Investigation on Junction Between Ordered Mesoporous Silica Film and Copper Metal Electrode
T.J. Ha, S.G. Choi (Yonsei University, Korea); B.G. Yu (Electronics and Telecommunication Research Institute, Korea); H.-H. Park (Yonsei University, Korea) Due to the rapid decrease in physical dimension of devices, lower resistive metal and/or lower dielectric constant material have to be applied. Recently, ordered mesoporous silica film has been drawn an attention for low-k material due to its ordered pore structure. The ordered pore structure allows silica film a low dielectric constant and superior mechanical strength. When ordered mesoporous silica film is applied to real device as a low-k material, junction problem including pore filling of metal and rough interface may be occurred between ordered mesoporous silica film and metal electrode due to porous surface. This may induce an signal delay. In this study, ordered mesoporous silica film was synthesized using Brij-76 block copolymer by sol-gel reaction and copper metal electrode was deposited by e-beam evaporation. The interface between ordered mesoporous silica film and copper metal was investigated to find out the junction problem. To prevent the problem, an almost pore less silica ultrathin film was deposited between ordered mesoporous silica film and copper metal electrode. The effect of buffer film was investigated in aspects on flatness of interface, change of pore structure and electrical properties. The electrical properties including dielectric constant were monitored and compared for the junction system with or without a introduction of pore free buffer ultrathin film layer. |
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GP-9 Structure and Properties of p-ZnO Evaluated by Rietveld Method at Various Substrate Temperatures
H.-H. Huang (Cheng Shiu University, Taiwan); C.-C. Huang, F.-H. Wang (National Chung Hsing University, Taiwan); C.-F. Yang (National University of Kaohsiung, Taiwan) The p-type zinc oxide films were prepared by Spray Pyrolysis at various substrate temperatures onto glass substrates. The effects of substrate temperature on crystal structure, resistivity, and Photo Luminescence of thin films were investigated by way of Rietveld evaluation. Results show that the ZnO films in Wurtzite phase with diffraction peaks of (100), (002), and (101) are found, and the ZnO thin films with (002) preferred orientation were enhanced at higher substrate temperature. The temperature dependence of lattice constant, atomic position and Zn-O bond length of ZnO thin film were investigated by Rietveld method. The resistivity and PL spectra of thin film were also investigated. |
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GP-10 Influence of Time Domain Parameters on Unipolar Pulse Plasma System Transition State
I. Popovic, M. Zlatanovic (Faculty of Electrical Engineering, Serbia) Plasma surface treatment of large components like windturbine parts requires large vacuum vessels and high power supplies. Pulse plasma provides reliable operation but a new type of unhomogeneity due to periodic transition to the stationary state exists resulting in non homogenous surface properties of treated materials. The analysis of unipolar pulse plasma system electrical response has shown that the transition of the gas discharge to the stationary state is related not only to the gas discharge properties but also to switching circuit and interconnection line properties. The detailed analysis of different parameter influence on the gas discharge electrical signal waveforms was conducted based on the pulse plasma system equivalent circuit. Switching IGBT transistor, gate drive circuit and interconnection lines are the integral parts of the system equivalent circuit. Gas discharge transition state depends on the IGBT turn on characteristic, gate drive circuit properties, gas mixture, operating pressure, cathode temperature, cathode physical properties and other parameters. The value of the IGBT gate drive current determines the transistor turn on delay time. After the turn on the switching IGBT transistor, the shape of gas discharge current and cathode voltage corresponds to the second order underdamped system response whose time domain parameters are in relation with the gas discharge equivalent dynamic resistance, equivalent capacitance, parasitic interconnection inductance, etc. The design of pulse power supply and its connection to the process chamber are of importance for homogeneous plasma surface treatment techniques like plasma nitriding. |
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GP-12 Ignition Characteristics of Multilayer Foils of Aluminum and Nickel
I.E. Gunduz, K. Fadenberger, M. Kokonou, C. Rebholz (University of Cyprus); C. Doumanidis (University of Cyprus and National Science Foundation) Self-propagating exothermic reactions in multilayer films/foils (MF) are receiving attention as novel heat sources due to their high energy density. Typically consisting of hundreds of alternating metallic layers in the nanometer range, MF structures can be produced by plasma-assisted physical vapor deposition (PVD) techniques, such as magnetron sputtering, and have recently been reported in the Al-Ni and Al-Ti systems. However, the application of MF’s as heat sources is limited. After ignition using an electrical spark with an unspecified width, the flame propagates at speeds up to 10 m/s, which can be tuned by thicknesses of individual layers. There are no known means to stop and restart the reaction after ignition so all the heat is generated in one quick burst. In this study we investigated the effect of spark size on the ignitability of MF's. We employed numerical methods using the authors previous work to simulate the effect. Numerical results indicate that there is a critical spark size around 15 µm, below which the reaction does not self propagate. Experimentally, the effect can be demonstrated using the dielectric breakdown of nanoscale aluminum oxide layers obtained by anodization of the top and bottom of the foils, under different electric potentials. This method can be used to start the reaction and extract a certain amount of heat from the foils and can be repeated as desired. |
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GP-13 Designing Coated Maraging Steels Systems for Tools in Forming Process
S. Molas (CTM Centre Tecnològic, Spain); L. Llanes (Universitat Politècnica de Catalunya, Spain); D. Casellas, M.R. Cruz (CTM Centre Tecnològic, Spain); F. Montalá (TTC Recubrimientos Avanzados, Spain); J. Caro (CTM Centre Tecnològic, Spain) The aim of this work have been establish an overview of various PVD-CVD plasma assisted system coatings over maraging steels. A completed tribological characterization have been carried out to determinate the more adequate industrial process to obtain forming tools coated that improve the wear performance under real conditions. The coatings used were: TiN and TiC, mono-layered and multi-layered with PVD and CVD proceses carriet out at diferents temperatures and post thermic treatment to obtain one coated system whiteout softened maraging steel. |
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GP-15 Evaluation of the Effects of the Electrodeposition Parameters on Corrosion Resistance of Sn-Ni Coatings
H. Jiménez (Fundacite Bolívar, Venezuela); L. Gil (Unexpo Vicerectorado Puerto Ordaz, Venezuela); E.S. Puchi, M.H. Staia (Universidad Central de Venezuela) The present research was performed with the aim of evaluating the influence of both the chemical composition and the current density of the bath on the corrosion resistance of the tin-nickel coatings deposited on steel plate substrate. The corrosion performance of the Sn-Ni coating-substrate systems was evaluated using open circuit potential and polarization resistance (Rp) measurements using a Gamry PC4/750 Potentiostat/Galvanostat Model DHC2. The tests were realized on circular samples with an area exposed of 0,005 in2 in an acidic solution, containing 15 g/l of NaCl and 15 g/l of citric acid; to a scan rate of 0,5 mVs-1. The microstructure and morphological characteristics of the coatings before and after the corrosion test was studied using scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDX). The electrodepostion process, carried out in chloride-fluoride and pyrophosphate baths, produces a stoichiometric intermetallic compound Sn-Ni coating, which has approximately 65 wt.% Sn and 35 wt.% Ni. The results show that the Sn-Ni coatings obtained using the chloride-fluoride bath exhibit the best corrosion resistance, irrespective to the current density value employed during deposition. |
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GP-16 Influence of Post-Hydrogen Plasma Treatment on Resistivity of Al-Doped ZnO Thin Films
H.-P. Chang, F.-H. Wang, Y.-C. Chen (National Chung Hsing University, Taiwan); H.-H. Huang (Cheng Shiu University, Taiwan) Aluminum-doped ZnO (AZO) thin films were prepared by RF sputtering working distance, substrate temperature, working power and depositional duration were, respectively, 100 mm, 25°C - 300°C, 100 W and 20 min. The structure, morphology and resistivity of AZO thin films were analyzed by X-ray diffraction, scanning electronic microscopy, and four-point probe. In the present study, the effects of post hydrogen plasma treatment on resistivity of AZO films were studied. Results shows that the resistivity of the AZO film significantly decreased after post-hydrogen plasma treatment, meanwhile, it decreased because of the longer post hydrogen plasma treatment duration. It should be deduced that the oxygen located at grain boundary reacted with the hydrohen after post-hydrogen treatment, consequently, the resistivity of thin film decreases. |
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GP-17 Effect of Modified Layer on Fretting Fatigue Properties of Plasma Nitrided 316L Steel
F. Yildiz, A.F. Yetim, A. Alsaran, A. Celik (Ataturk University, Turkey) 316L stainless steel was plasma nitrided under various processing conditions. Fretting fatigue tests were carried out with a tension comprehension fatigue machine, using S-N curve to evaluate the fretting fatigue properties of nitrided steel. The effect of thickness, hardness and composition of modified layer on the fretting fatigue of nitrided 316L steel was investigated. It has been showed that decrement of fretting fatigue life decreased with an increase in the modified layer thickness and hardness. The best fretting fatigue life obtained in sample with the modified layer including S-phase. Fractographic investigations showed that while crack initiation was localized under the modified layer for the plain fatigue specimens, the cracks originated at the contact surface for the fretting fatigue specimens. |
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GP-18 Plasma Surface Treatment With An Atmospheric Pressure Dielectric Barrier Discharge
V. Rohani (Maizieres les Metz, France); G. Bauville, B. Lacour, V. Puech (Université Paris-Sud, France); D. Duminica, E. Silberberg (Liege, Belgium) Dielectric Barrier Discharge (DBD) appears to be a very promising technology to make surface treatments at atmospheric pressure, particularly for the development of treatments of large-dimension flat objects for on-line industrial applications. Besides the fact of allowing short tims of treatment (a few seconds up to a few minutes according to the appication), the advantage of the treatment at atmospheric pressure is the strong reduction of the constraints correlated to the implmentation of the vacuum devices necessary for low pressure treatments. But at the present time, if this technology showed its ability for the surface cleaning it is not still the case as for thin film deposition over large surfaces. The main problem which limits considerably its use for surface coating is an insufficient homogeneity. The study of the layer's uniformity leads us to search links between the internal physical phenomena in the reactor and the on-surface chemistry. This presentation will be focused mainly on the study of the internal physical and chemical phenomena conditioning the thin film deposition by an atmospheric pressure dielectric barrier discharge with gas mixtures including a chemical precursor. In this study, we have chosen to work with a precursor already widely used in the PACVD (Plasma Assisted Chemical Vapour Deposition): HMDSO. This last one allows the elaboration of thin films of silicon-oxide (SiOx), materials, for which the chemical and physical properties can be easily determined and correlated to the properties of the plasma produced by the DBD. By using various approaches of study, it will be shown that the internal thermohydrodynamics is strongly correlated to the chemistry of thin layers deposited. It will also be demonstrated that it is possible to control the homogeneity and the chemistry of thin layers by optimizing the thermo-hydrodynamics regime of the discharge. In addition, it will be shown that the excitation mode of the DBD (sinusoidal or pulsed) induces different results for the same mean electric power deposition. In the pulsed mode, the influence, on the thin films properties, of the energy per pulse and of the pulsed repetition frequency will be discussed. |