ICMCTF2004 Session GP: Symposium G Poster Session
Thursday, April 22, 2004 5:00 PM in Room San Diego
Thursday Afternoon
Time Period ThP Sessions | Topic G Sessions | Time Periods | Topics | ICMCTF2004 Schedule
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GP-1 Application of TixN/Cr1-xN Coatings for Improvement of Die Performance in Aluminum Die-casting Industry
S.Y. Lee, S.D. Kim, Y.S. Hong (HanKuk Aviation University, South Korea) The effect of PVD coatings on the performance of high temperature mold steel, AISI H13 used for die steel in semi-solid forming, has been investigated. The mechanical properties enhanced by the variety of Cr content in the nanostructured TixN/Cr1-xN coating system were studied and the best coating conditions were applied to die inserts. The coatings were synthesized using a closed field unbalanced magnetron sputtering method with separate Ti and Cr targets and characterized in terms of chemical composition, crystal orientation, layer structure and mechanical properties by glow discharge optical emission spectroscopy (GDOES), X-ray diffractometry (XRD), transmission electron microscopy (TEM), nanoindentation and wear tests. The nanostructured TiN/CrN coatings synthesized in this work have a range of atomic concentration ratio of X=Cr/(Ti+Cr) from 0.15 to 0.59. The results from high-angle and low-angle XRD analysis show that the coating with X=0.15 is not a multi-layered film but a composite film mixed TiN and CrN with a grain size of approximately 16 nm. The hardness (H) of coatings was strongly dependent on the value of X and the maximum hardness and plastic deformation resistance (H3/E2) of approximately 41and 0.36 GPa respectively were measured in case of the coating with X=0.15. These values are 1.6 and 3 times higher than those of the single TiN coating (27 and 0.12 GPa), respectively. Also the wear resistance was largely increased than that of the single TiN coating. These enhancement of mechanical properties in the coating with X=0.15 could be attributed to the CrN doping effect, which has reduced the TiN grain size. Experimental results from the coated inserts in semi-solid processing of aluminium and copper alloys will be presented. |
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GP-2 An Atmospheric Pressure Chemical Vapor Deposition Process for Silicon Nitride Films for Solar Cell Applications - Equipment and Process Description
C. Blais, C. Amato-Wierda (University of New Hampshire) This paper will present our efforts to design and develop an atmospheric pressure plasma chemical vapor deposition technique for producing hydrogenated silicon nitride thin films for solar cell applications. Currently, the silicon nitride layer is deposited by various low pressure plasma techniques which are batch-type, require cumbersome vacuum equipment, and limit throughput. A simpler, continuous, large-volume, non-vacuum process would be more suitable for the solar cell industry. The key feature in our technique is a dielectric barrier discharge type of plasma sustained at atmospheric pressure with silane, ammonia, and hydrogen gases. Preliminary results indicate that the dielectric barrier discharge can deposit silicon nitride films at atmospheric pressure with no additional heating. The plasma behavior and film properties will be described as a result of varying equipment parameters, including: type of dielectric layer, thickness of the dielectric, gap distance between electrodes, relative amounts of silane and ammonia, and power. |
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GP-3 Characterization of a Hybrid PVD/PACVD System for the Deposition of TiC/CaO Nanocomposite Films by OES and Probe Measurements
W. Kulisch, P. Colpo, F. Rossi (Institute for Health and Consumer Protection, Italy); D.V. Shtansky, E.A. Levashov (Moscow State Institute of Steel and Alloys, Russia) TiC/CaO nanocomposite films have been deposited by a PVD/PACVD hybrid system with three different plasma sources: A dc magnetron to sputter a TiC0.5 + 10% CaO target in Ar atmosphere, an inductively coupled rf plasma (ICP) to provide a high plasma density, and a capacitively coupled substrate bias plasma to create a negative bias to the substrate holder. Besides the pressure, thus, the target current density, the ICP power and the bias voltage are the decisive parameters. The system was characterized by parametrical studies, optical emission spectroscopy (OES) and probe measurements. It was found that for low values of the three input parameters, the three plasma were fairly independent of each other. This situation changes drastically for high parameter values. The most striking effect is observed for high target currents: Owing to the high sputter rates and the resulting high concentration of target species in the gas phase, and owing to the much lower ionization energies of these species as compared to argon, the electron temperature decreases while the plasma density increases (plasma cooling). In the transition region, the plasma is spacially bisected which can be observed even optically. The results of these plasma diagnostical investigations were correlated with the growth rates and properties of TiC/CaO nanocomposite films obtained with this system. |
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GP-4 ZnCr Anticorrosion Coatings Optimised for Forming Applications
P. Choquet, C. Scott, C. Musik (IRSID-ARCELOR, France); L. Garrigues (RDCS-ARCELOR, France); A. Lamande (IRSID-ARCELOR, France) PVD techniques are currently being evaluated by steelmakers for developing new coatings on flat strip. Several authors have reported on the corrosion behavior of compounds of Zn alloyed with Ni, Co, Al, Cr, Mg and Ti produced by PVD technology. In these diverse studies, the highest corrosion resistance is very often achieved by the Zn-Cr alloy system. This paper will discuss the nature of three metastable ZnCr phases formed by co-evaporation of Zn and Cr onto steel substrates. Of particular interest for automobile applications are the ZnCr-d (hexagonal) phase and the ZnCr-z (monoclinic) phases. For coatings with Cr contents less than 20%wt. and substrate temperatures below 170°C the ZnCr-d phase is the dominant phase. Quantitative analysis of a series of interrupted tensile tests of coated steel substrates shows that the ZnCr-d phase is much more resistant to cracking and spalling than the ZnCr-z phase. This is attributed to the hexagonal crystal structure, which provides more possible deformation modes, most notably basal slip. Upon heating to 170°C, the hexagonal ZnCr-d phase undergoes an allotropic transformation to the monoclinic ZnCr-z phase. This transformation is irreversible, and results in an untextured, fine grained equiaxed microstructure. The kinetics of the transformation depend upon the exact Cr concentration. The kinetics of Zn dissolution in a corrosive medium (NaCl 1M) were measured in the laboratory. Here the ZnCr-z phase clearly out-performs the ZnCr-d, due to a better adapted microstructure (absence of columnar grain boundaries linking the surface to the substrate) and a more efficient passivation behaviour. Thus it is possible to propose a tailored ZnCr coating, optimized for forming applications and consisting initially of the ZnCr-d phase. After forming, this coating can be transformed to the ZnCr-z phase, for example during the standard paint baking cycle for automobile panels, to improve the corrosion resistance. |
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GP-6 Structure and Ferroelectric Properties of PLZT Thin Films Formed by Photochemical Metal-organic Deposition with Various Zr/Ti Ratio
Hyeong-Ho Park, W.S. Kim, Hyung-Ho Park, R.H. Hill (Yonsei University, South Korea) Lanthanum-doped lead zirconate titanate (PLZT) thin films formed by photochemical metal-organic deposition (PMOD) using photosensitive starting precursors were characterized. The substitution of La for Pb was reported to induce the improved ferroelectric properties, especially fatigue property through the reduction of oxygen vacancies with excess e-. However some other properties such as remnant polarization and piezoelectric coefficient were reported to be decreased. This is because the doping of La modify the structural condition of PZT from the morphotropic phase boundary(MPB) composition, Zr / Ti = 52/48, showing the maximum ferroelectric properties. In this work, PLZT films were investigated to find the maximum remnant polarization and piezoelectric coefficient with various Zr/Ti ratios near MPB composition. Scanning electron microscopy was used to observe the image of self-patterned PLZT films. X-ray diffraction and ellipsometry were served to provide the information about the crystalline structure and thickness of the films after anneal. The doping effect of La and the influence of ion size on the microstructure and ferroelectric properties of PLZT films with various Zr/Ti ratios would be related. |
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GP-7 High Rate Deposition of Copper Thin Films using Newly Designed High Power Magnetron Sputtering Source
J.H. Boo, M.J. Jung, H.K. Park, K.H. Nam, J.G. Han (SungKyunKwan University, South Korea) We have deposited the copper (Cu) thin films on Si(100) and stainless steel substrates in the growth temperature between room temperature and 500°C using pulsed D. C. magnetron sputtering method. An unbalanced magnetron sputtering source with high current (20 - 120 mA/cm2) and low voltage (100 - 1000 eV) was designed and constructed for high rate deposition. Based upon the results of magnetic field simulation, we built-up the highest power (120 W/cm2) Cu magnetron sputtering source to enhance the sputtering yield and film growth rate. The maximum deposition rate and sputtering yield of the newly developed sputtering source are 2.8 µm/min. and 70%, respectively. When an ion extraction grid was adapted between the Cu target and substrate, however, the growth rate was increased over 3 µm/min. This is 10 times higher than that of conventional sputtering method, and the sputtering yield was also reached to 80% due to low voltage and high current Cu-accelerated ions. XRD and XPS showed that highly oriented polycrystalline Cu(111) thin films with no impurity were obtained on the stainless steel substrates. During film deposition, plasma diagnostics was also carried out in situ by optical emission spectroscopy analysis. Electrical conductivity was also measured with four-point probe method. |
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GP-8 New Approach for Thermal Spray Process Control with an Artificial Neural Network in Aero-engines
H. Abdullahi, M. Herter (MTU Aero Engines GmbH, Germany) Thermal spray coatings on basic materials of aero-engine components are indispensable for prolonging life and improving efficiency. Thermal spray processes are extremely complex; therefore it is impossible to represent them accurately enough in a traditional model thus simulating reliably. In this research work it will be shown how such processes can be represented with an artificial neural network that allows the thermal spray process to be controlled automatically. Data from plasma spray processes on turbo-compressor casings is used to train and verify the neural network. The results of the first prototype for a closed loop are very promising. |
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GP-9 Plasma Parameter Control Mechanisim in Plasma Sources
H.Y. Chang, Y.G. Daejeon (KAIST, South Korea) We have studied to control the plasma parameters such as electron temperature and electron density for next generation etching process. In this paper, three methods for controlling plasma parameters such as electron temperature and electron density have been suggested. And some etch results by these methods will be presented. The mechanism of controlling electron temperature with grid-biased voltage is studied experimentally and relevant physics is discussed in an inductively coupled plasma. With the grid method, etching selectivity of oxide to photo-resist is 74, which is ten times higher than that of without the grid. The electron energy distribution function and plasma parameters in various gas mixture (N2, O2, CF4 / He, Ar, Xe) discharges are measured. When He is mixed, the electron temperature increases but the electron density is almost constant. In He mixture discharge, the electron temperature is almost constant; the electron density increases rapidly near a mixing ratio of 1. Mixing Xe increases the electron density and decreases the electron temperature. Electron temperature decreases to 1.8 eV as driving frequency increases up to 100 MHz by using modified parallel resonance antenna and the plasma uniformity by controlling current of the outer antenna connected to the capacitor is achieved within 5%. |