ICMCTF2004 Session TP: Symposium TS Poster Session

Thursday, April 22, 2004 5:00 PM in Room San Diego

Thursday Afternoon

Time Period ThP Sessions | Topic TS Sessions | Time Periods | Topics | ICMCTF2004 Schedule

TP-1 Biocompatibility of a Titanium-aluminum Nitride Film Coating on a Dental Alloy
K.H. Chung (National Yang-Ming University, Taiwan, R.O.C.); G.T. Liu, J.G. Duh (National Tsing Hua University, Taiwan, R.O.C.); J.H. Wang (Chunghwa Telecom Co. Ltd., Taiwan, R.O.C.)
The purpose of this investigation was to develop a titanium-aluminum nitride (Ti,Al)N film coating technique and study the characteristics of this novel film on a base-metal alloy (Wiron88) substrate. A thin layer of (Ti,Al)N film was deposited on the alloy surface using a reactive radio-frequency sputtering method. Electrochemical properties of three specimens with and without coating treatment were evaluated. The biocompatibility of three specimens was tested using a subcutaneous implantation test. Data were analyzed using the t-test with a significance level of p<0.05. Specimens coated with the (Ti,Al)N film demonstrated significantly improved corrosion resistance (p<0.05). Results from biocompatibility testing, base on tissue reactions at two and 12 weeks, revealed significantly improved biocompatibility for (Ti,Al)N coated samples when compared to uncoated samples. Results suggest that the (Ti,Al)N film can significantly improve electrochemical and biocompatibility properties of the base metal alloy.
TP-2 Auto-correlation Function Analysis of Phase Formation in the Initial Stage of Interfacial Reactions of Amorphous Titanium-silicon Multilayers Thin Films
T.H. Yang, S.L. Cheng (National Tsing Hua University, Taiwan, R.O.C.); L.J. Chen (National Tsing Hua University, Taiwan, ROC)
Auto-correlation function analysis has been applied to the high resolution transmission electron microscope images of amorphous interlayers formed in the interfacial reactions of ultrahigh vacuum deposited titanium thin films on (001)Si. No silicide phase was found to form in the as-deposited samples. On the other hand, Ti5Si3, TiSi, and Ti5Si4 were found to form simultaneously under certain annealing conditions. The intermediate silicide phases were found to form earlier than that of the previous study. Ti/amorphous-Si multilayers were observed to form by solid-state diffusion on silicon systems. The amorphous interlayers were generally formed first prior to the formation of crystalline silicides. The distribution of these silicide phases in the amorphous interlayers was also demonstrated.
TP-3 Adhesion of Clinically Relevant Microorganisms to Surfaces Modified with Molecular Films and Micropatterned Topography.
M.C. Cortizo, P.L. Schilardi, M. Fernandez Lorenzo de Mele, R.C. Salvarezza (Universidad Nacional de La Plata, INIFTA, Argentina)
Bacteria attach to surfaces and form biofilms. Biofilms are structured communities enclosed in a self-produced polymeric matrix. Sessile bacteria reveal different patterns of gene expression from their planktonic counter-parts in suspension. Biofilms are a common cause of persistent infections, included those associated with implantable devices, because they exhibit high resistance to antimicrobial agents such as antibiotics. In the case of dental implant materials biofilms are frequently associated to problems in the osseointegration process. Streptococci are one of the main microorganisms involved in dental problems. The degree of adherence depends on the substratum topography and wettability. However the changeable nature of the charge and hydrophobicity of bacterial surfaces makes the analysis difficult and deserves further investigations. The adsorbed molecules of self-assembled monolayers (SAMs) may be an alternative to modify the wettability of the surfaces to investigate the conditions that could yield to the inhibition of bacterial attachment. The aim of this work is to study the adhesion of Streptococci consortia to titanium and silice with different surface treatments. With this purpose the early stages of Streptococci biofilms development were studied. The surfaces of silice and titanium were modified with an octadecyltrichlorosilane (OTS) monolayer and micropatterned by using a mask and UV radiation in order to generate domains with different hydrophilic/hydrophobic characteristics. Substrates with micropatterned topography were also investigated. The attachment of bacteria on titanium and silice modified with the OTS SAM and with different topographies were compared with smooth and non-SAM-modified controls. Results showed that the influence of topography was more significant than that of wettability.
TP-4 Characterization and Bond Strength of HA/TiO2 Double Layers for Orthopaedic Applications
C.-M. Lin, S.-K. Yen (National Chung Hsing University, Taiwan, R.O.C.)
Insufficient bonding of juxtaposed bone to an orthopaedic/dental implant could be caused by material surface properties that do not support new bone growth. For this reason, fabrication of biomaterials surface properties which support osteointegration should be one of the key objectives in the design of the next generation of orthopaedic/dental implants. Titanium and titanium alloy have been widely used in several bioimplant application, but when implanted into the human body it still contained some disadvantages, such as poor osteoinductive properties, wear debris and ions release, which often lead to clinical failure. Electrolytic composite coatings of Titanium dioxide (TiO2) and Hydroxyapatite (HA) were successfully deposited on titanium substrates in TiCl4 solution and subsequently in the mixed solution of Ca(NO3)2 and NH4H2PO4, respectively. The coated specimens were evaluated by electrochemical polarization in 37 simulated body solution (SBF), bonding strength tests, surface morphology observations, immersion tests and XRD analyses. The biocompatibility of HA/TiO2 composite coatings were investigated by human G-292 osteoblast-like cells. Human G-292 osteoblast-like cells were found to be a valid experimental model for primary human osteoblast. The corrosion resistance, and bonding strength of the HA coated film were improved by the intermediate coating of TiO2 from 11.3 MPa to 46.7 MPa. The crystallization of the HA/TiO2 composite coating specimens were further identified in details. The crystallization and the surface morphology of the HA/TiO2 coated specimens annealed at 300 provide better support for the differentiation and adhesion of osteoblast-like G-292 cells. Furthermore, HA/TiO2 coated obtained in the present study exhibited in vitro apatite deposition ability.
TP-5 An Investigation of an Industrial Coating Environment with Planar Probe Technology
K.E. Cooke (Teer Coatings Limited, United Kingdom); A. Goodyear (The Open University, United Kingdom); J. Hampshire, D.G. Teer (Teer Coatings Limited, United Kingdom)
A novel electrostatic probe method has been applied to the plasma characterization of an industrial magnetron-based ion plating plasma system. The probe consists of a small, 7mm diameter, disk fitted with a guard ring, and mounted near the substrate position. A negative DC self-bias is achieved on the probe surface relative to the plasma by the application of a radio-frequency (RF) burst across an in-line capacitor. Following removal of the RF burst a current-voltage characteristic is obtained as the probe potential returns to a floating condition through the arrival of positive ions from the plasma. Use of capacitively coupled RF biasing permits operation of the probe in a deposition environment. The guard ring maintains sheath planarity at the probe surface and eliminates edge effects. Total positive ion flux and the energetic tail of the electron distribution function are determined from the probe's current-voltage characteristic. Results are reported for ion flux and electron energy distribution measurements in DC and pulsed DC plasmas in closed field unbalanced magnetron sputter ion plating (CFUBMSIP) industrial coating equipment. Argon and combined argon and reactive gas atmospheres, at below 0.5 Pa were used. Measurements are correlated with the deposition system's magnetic configuration and deposition parameters, including magnetron and substrate voltages, bias currents and pulsing conditions. Potential applications and limitations of the planar probe technique to for routine process control in an industrial coating environment are discussed.
TP-6 OES and FTIR Diagnostics of HMDSO/O2 Gas Mixtures for SiOx Deposition Assisted by RF Plasma
M. Goujon, T. Belmonte (INPL-Ecole des Mines, France); G. Henrion (Universite H. Poincare, France)
In this work, a capacitively coupled radio-frequency (CCRF) plasma is used to enhance SiOx deposition from a hexamethyldisiloxane-O2 gas mixture. The works carried out by Lamendola et al. [1] and Aumaille et al. [2] on similar deposition processes show comparable trends on the behavior of carbon- and oxygen-containing species observed by Optical Emission Spectroscopy (OES) when the HMDSO/O2 ratio in volume is varied. However, the behavior of SiO is rather different in the two studies. According to Lamendola et al., monitoring this species can be a efficient mean to describe the film growth. Results obtained from optical emission spectroscopy (OES) and Fourier Transformed Infra Red (FTIR) absorption spectroscopy analyses of a O2/HMDSO CCRF plasma for different dilution rates of HMDSO in oxygen are reported. An experimental study was carried out to determine the main reactive species in the discharge and to establish relationships between the density of various species (atoms, molecules, radicals...) and the nature and composition of the deposited films. We discuss the influence of the O2/HMDSO ratio on the composition of the deposited SiOx coatings and correlations are established between the characterization of the films and the plasma analyses with respect to the other published works. These results contribute to the proposal of a kinetic modeling to describe the behavior of the deposition plasma process. [1] R. Lamendola, R. d'Agostino, F. Fracassi, Plasmas and Polymers, 2-3 (1997) 147. [2] K. Aumaille, C. Vallee, A. Granier, A. Goullet, F. Gaboriau, G. Turban, Thin Solid Films, 359 (2000) 188.
TP-7 Characteristics of Zn-doped Hydroxiapatite Thin Films
A.I. Ide-Ektessabi, T.Y. Yamaguchi, K.S. Shirasawa, Y.T. Tanaka, Y.T. Tsukuda (Kyoto University, Japan)
Hydroxyapatite (HAp) coatings are popularly used for dental and orthopedic prostheses. The physicochemical bonds to bones (osseointegration) are necessary for dental/orthopedic implants, in order to minimize motion-induced damage to surrounding tissues. Zinc (Zn) is suggested to promote osteoblast (the bone-forming cell) and supports bone formation for osseointegration. In this study, HAp mixed with various concentrations of zinc were prepared. The mixtures were compressed and sintered into zinc-doped pellets at appropriate condition (compressing pressure, sintering temperature). The thin films of hydroxyapatite doped with zinc were fabricated using electron beam deposition (EBD). The ambient pressure and deposition rate were taken as the factors to control the deposition. The composition and crystallinity were measured using Rutherford backscattering spectroscopy (RBS) and X-ray diffraction (XRD), respectively.
TP-8 Photoluminescence Property of CdSe : Mn Nanocrystals and Undoped CdSe Via Alternative Method
H.J. Choi, S. Yoon, H.H. Park (Yonsei University, South Korea)
Recently there have been great interests on the alternative routes - greener approaches - for colloidal synthesis of semiconductor nanocrystals. As reported, the alternative routes are safe, simple, inexpensive, reproducible, and versatile and yield nanocrystals with well-controlled size and shape in comparison with the original organometallic approach. In our works, we have tried to make Mn doped CdSe nanocrystals via alternative routes and evaluate photoluminescence efficiency. Mn doped CdSe nanocrystals have been synthesized with alternative colloidal synthesis routes using CdO, TOPOSe, stearic acid, TOPO, TOP, and MnO. The photoluminescence property of nanocrystals has been observed with various ratio of Cd / Se and Cd / Mn. The size of nanocrystals was calculated by Debye formula using X-ray diffraction. The band gap changes of nanocrystals due to quantum confinement were observed by UV/vis spectrometer. The composition and chemical environment of nanocrystals could be analyzed with X-ray photoelectron spectroscopy.
TP-9 Development of Environmentally Friendly Non-chrome Conversion Coating for Electrogalvanized Steel
H.J. Kim (POSCO, South Korea)
Most metals are stable only under reducing conditions and corrode upon exposure to an oxidizing ambient. Metals producers combat this problem using various methods. Steel producers use various organic and inorganic coatings to protect electrogalvanized steel (EG) sheets from corrosion during shipment and storage. Traditionally, conversion coatings are produced by exposing electrogalvanized steel sheets to phosphoric acid (phosphating) or chromic acid (chromating) or both. The latter provides more effective corrosion protection. However, the toxicity of chromium salts created environmental and health-related concerns and, hence, generated a great deal of interest in developing chrome-free conversion coatings. Most of the new developments are based on organic coatings, which can also protect steel from fingerprints that act as seats for corrosion. Of the various organic conversion coatings being developed, the various silanes and fatty acids have surveyed. These reagents are capable of forming strong bonds to metal substrates and, at the same time, of forming cross-linking polymers on the surface, both of which contribute to producing strong conversion coatings. Furthermore, proper choice of the terminal groups of the silane coupling agents can improve the adhesion of organic topcoats. In this paper, studies were made to produce chrome-free conversion coatings on electrogalvanized steel sheets. Approaches taken here included coating the EG plates with silane coupling agents and/or appropriate surfactants. The results presented herewith included the work conducted on the EG plates. It has been found that the newly coated steel sheets to provide an impermeable conversion coating for corrosion prevention in this study have the same corrosion resistance as the conventionally chromated organic coated EG steel sheet.
TP-10 The Nanostructure of Nb Films Formation: Molecular Dynamic Simulation
I.G. Marchenko (Scientific Centre of Physical Technologies, Ukraine); I.I. Marchenko (Kharkov Politechnical University, Ukraine)

Molecular dynamic computer simulation was used to study vacuum deposition of Nb films on Nb (110) substrate. The atomic structure, surface roughness, temperature changes through films were investigated.

The thickness of deposited films was about 15 nm. Substrate temperature was 300K. The Johnson-Oh potential developed by the embedded atom method was used for atomic interaction simulation.

It was found that films density changes from zero at the front of growing film to its stationary value in the film depth. The thickness of transition layer is about 2 nm. The stationary density is 93% by volume. This reduction of atomic density is caused by void formation. Voids are situated along <100> direction in {110} plane. It appears to be due to the development of ripples on films surface. It was found that these ripples can relax with edge dislocation formation.

Others proposed the model for explanation of nano-grain appearance by dislocation walls formation from relaxed ripples.

TP-11 Determination of Soldering Reaction Mechanisms between Aluminum and Selected Die Coatings used in Aluminum Pressure Die Casting
E.K. Tentardini (Universidade Federal do Rio Grande do Sul, Brazil); M.C. Castro (Universidade Federal de Minas Gerais, Brazil); A.O. Kunrath, J.J. Moore (Colorado School of Mines)
Soldering of aluminum alloys to die-casting dies in aluminum pressure die casting is a common problem that results in substantial losses of time, energy and production costs. The mechanisms that lead to this phenomenon are based on a series of events comprising reactions between aluminum and the die material or coating. Most of the published work currently available is based on ‘post mortem’ examination of dies that have exhibited soldering, i.e., after the phenomenon has occurred. In this work the reactions between aluminum and the die material (H13 tool steel) and selected coatings, e.g., TiN and CrN, are investigated using a novel in-situ laboratory technique that employs differential thermal analysis (DTA) and subsequent x-ray diffraction (XRD) and chemical analysis of the reaction products.
Time Period ThP Sessions | Topic TS Sessions | Time Periods | Topics | ICMCTF2004 Schedule