ICMCTF2004 Session TS4-1: Coatings and Thin Films for Biomedical Applications

Monday, April 19, 2004 10:30 AM in Room Royal Palm 1-3

Monday Morning

Start	Invited?	Item
10:30 AM		TS4-1-1 Mechanical Characteristics and Corrosion Behavior of the (Ti,Al)N Coating on Dental Alloys G.T. Liu, J.G. Duh (National Tsing Hua University, Taiwan, R.O.C.); K.H. Chung (National Yang-Ming University, Taiwan, R.O.C.); J.H. Wang (Chunghwa Telecom Co. Ltd., Taiwan, R.O.C.) Titanium aluminum nitride films were deposited on special dental alloys by reactive RF sputtering to modify characteristics of nickel-base and chromium-base dental material. Surface hardness of (Ti_1-x,Al_x)N films was measured by nanoindentation technique. It was revealed that hardness of the (Ti,Al)N was enhanced by the introduction of aluminum as compared to pure TiN films. The scratch behavior and the adhesion strength were evaluated by the scratch tester. The effect of the internal stress on failure mode and acoustic emission signal were also evaluated. The morphology and microstructure of the coating were analyzed by X-ray diffractometry and scanning electron microscopy. For simulating the environment in the oral cavity for practical application, the physiological saline (0.9% sodium chloride) was used as electrolyte in the study of corrosion test. In addition, the biocompatibility of the (Ti,Al)N coatings were investigated by the in vitro cell culture of 3T3 fibroblasts.
10:50 AM		TS4-1-2 Corrosion-Fatigue Performance of an AISI 316L Stainless Steel Coated with Different PVD ZrN_x Films J. Berríos-Ortiz (Universidad Central de Venezuela); G. Mesmacque (IUT A, France); E.S. Puchi-Cabrera (Universidad Central de Venezuela) The corrosion-fatigue performance of an AISI 316L stainless steel coated with three different under stoichiometric ZrN_x films, deposited by PVD magnetron sputtering, tested in a 3 wt. % NaCl solution has been investigated and compared with the performance shown by uncoated substrate when tested in similar conditions. It has been determined that such a steel can be safely coated with these ZrN_x films in order to improve some of its surface properties, without compromising its corrosion-fatigue behavior. It is believed that the elevated compressive residual stresses and mechanical strength of the films, together with their excellent adherence to the substrate, give rise to a significant improvement of the corrosion-fatigue performance of the base steel. Previous fractographic analysis conducted on coated samples tested in tension revealed that the ZrN_x coatings remain well adhered to the substrate even after severe plastic deformation of the coating-substrate system. Corrosion-fatigue tests were carried out under rotation bending conditions at maximum alternating stresses in the range of 485-480 MPa. The stress life curves obtained from the results of such tests allowed the computation of the constants involved in the simple parametric relationship usually employed for the description of these kinds of data. This information was subsequently employed in the evaluation of the percentage of increase in fatigue life due to the presence of the coatings, which was found to be always above 100%. Several fracture surfaces of selected samples tested at different maximum alternating stresses were evaluated by means of SEM techniques. In general, it has been found that the corrosion-fatigue process of the coated samples involves the participation of several cracks and that the coatings are able to endure severe damage on the plane of fracture.
11:10 AM	Invited	TS4-1-3 Biomedical Applications of Diaomond-Like Carbon (DLC) Coatings G. Dearnaley, J.H. Arps (Southwest Research Institute) With a hardness that can exceed that of alumina and exceptional chemical inertness, diamond-like carbon (DLC) is a very attractive coating material for a variety of biomedical application, particularly in orthopedic and cardiovascular components such as stents and heart valves. Coating adhesion is very high, given good surface preparation and control of compressive stress. DLC comprises a broad family of materials containing variable amounts of hydrogen and possible additives such as nitrogen, silicon, titanium or chromium. Many methods are available for deposition of such coatings, the most common being by plasma decomposition of methane, or by use of a filtered carbon cathodic arc, in this case, producing hydrogen-free DLC. This paper will review the wide literature on DLC coatings and draw certain conclusions. One is that in orthopedic application it is important to achieve a very smooth surface in order to minimize wear of a UHMWPE or other counterface. All texts reported have shown excellent biocompatibility and good haemocompatibility. There is a need for more hip joint simulator trials leading to in vivo testing, but the prospects for well-engineered DLC coatings are very good.
11:50 AM		TS4-1-5 Wear and Corrosion Protection of Femoral Implants by Deposition of AgZrN Nanocomposite Thin Films M. Debessai, S.M. Aouadi (Southern Illinois University); Z. Marcano, M. Suaréz, M.H. Staia (Universidad Central de Venezuela) Wear and corrosion mechanisms on mobile components of surgical implants, like femoral prosthesis, are responsible for the reduced lifetime of these devices. Ceramic binary films such as TiN, ZrN, NbN, VN and HfN are commonly used as protective coatings because of their high hardness, electrochemical immunity, and biocompatibility. Nanocomposite films of AgZrN and multilayers of Ag/ZrN and Ta/ZrN were deposited on titanium alloys and silicon using reactive magnetron sputtering. The structural and chemical properties of these coatings were investigated using X-ray diffraction and X-ray Photoelectron Spectroscopy. The mechanical properties were tested using nanohardness and the abrasive wear resistance using a mechanical simulator for hip prosthesis developed in our laboratory. The abraded surfaces were investigated with scanning electron microscopy as a function of the number of cycles in the simulator. The corrosion resistance of the coated titanium alloy was investigated using a potentiodynamic polarization in an aqueous solution environment.
12:10 PM		TS4-1-6 Structure and Properties of Phosphorus Plasma Implanted Titanium X.Y. Liu, R.W.Y. Poon, S.C.H. Kwok, P.K. Chu (City University of Hong Kong); C.X. Ding (Shanghai Institute of Ceramics, PR China) Titanium and its alloys are widely applied in the biomedical field. In order to meet clinical needs, their biological properties must be improved using various technologies. Phosphorus is an important element in the human body, especially in bone tissues. In this work, phosphorus was implanted into titanium using plasma immersion ion implantation to improve its biological properties. The phosphorus elemental depth profile of the implanted titanium was acquired by X-ray photoelectron spectroscopy (XPS). The results show that phosphorus was successfully implanted into titanium using a specially designed plasma ion source. To examine the bioactivity, both the phosphorus implanted and control (un-implanted) samples were ultrasonically washed in acetone and rinsed in deionized water. They were then soaked in a simulated body fluid to investigate the formation of bone-like apatite on their surfaces. After the P-implanted titanium sample has been soaked in the simulated body fluid for 28 days, no distinctive changes can be observed and so implantation of phosphorus into titanium has not obviously improve the bioactivity of titanium in this work. The biocompatibility of phosphorus-implanted titanium was also evaluated by cell tests and osteoblasts were found to grow and proliferate on the surface of the P-ion implanted titanium, thereby indicating that the materials do possess good biocompatibility. The details of the structure as well as biological properties of the materials will be presented in this paper.