Yang Yunzhi, Ran Junguo and Zheng Changqiong

Department of Inorganic Materials, Sichuan University, Chengdu, 6100665, China
suucust@rose.cnc.ac.cn

Because the difference of chemical and physical properties between coating and substrate, which lead to the sudden change of structure and properties, make the boundary zone the weakest zone of the whole composite system, study on improving the adhesion of coating to substrate is always an attractive and active field. Especially, the poor adhesion of coating to substrate is ratherly most made by thermal stress. The train of thought of this paper is first, the gradient interlayers is used to reduce the thermal stress and improve the adhesion by mans of gradually regulating and varying the composition from coating to substrate in the boundary zone. Second, the idea of functionally gradient materials is introduced into biomedical engineering filed and used to improve the adhesion of coating of biomaterials such as artificial hart valve. In this paper diamond like carbon (DLC) / stainless steel biofunctionally gradient films have been prepared with two target magnetron cosputtering to solve the poor adhesion of DLC with excellent haemocompatibility to implant stainless steel with high strength and toughness. The research work is classified in three parts. The first is the preparation of DLC film and stainless steel films had been studied by means of SEM, X-ray diffraction, ZPS and Laman. The second is the preparation of DLC / stainless steel gradient films with two target magnetron cosputtering. The third is evaluation of composition, structure, and properties of gradient films, in which the composition and structure of gradient films have been studied with XPS, SEM and X-ray diffraction. The adhesion and microhardness of gradient films have been measured with scratch test an d hardness test. Haemocompatability of gradient films had been preliminarily evaluated with kinetic clotting time in vitro and haemolysis tests. The experimental results show the adhesion of DLC coating to stainless steel implants have been significantly improved with the gradient interlayers and biofunctionally gradient materials with excellent haemocompatability, strength, hardness and toughness have been prepared successively.

* The Project is supported by the National Science Foundation and PhD Degree Program of the National Education Committee of China