Dicalcium silicate/zirconia composite coating with 70 wt.% zirconia and 30 wt.% dicalcium silicate was prepared by plasma spraying. In vitro behaviors of human osteoblast cells on the coating were studied. As a result of rapid exchange of Ca and H in the culture media and dissolution of the dicalcium silicate component from the coatings, a large amount of Si-OH functional group was produced on the coating. These OH bonds were favorable to the adhesion of proteins and cells attachment and thus, the good cytocompatibility of the coatings. Honeycomb-like Ca-P minerals were formed on the coating surface after only 1 day incubation in the culture media. The deposition rate of the Ca-P minerals was greatly improved by the existence of proteins. It may be attributed to the increased Ca ion concentration in the culture media resulting from the dissolution of dicalcium silicate and the good protein adhesion properties of the coating.

Formation of bonelike apatite is an essential prerequisite for implants to make direct bond to living bone. The apatite formation can be assessed in vitro using a simulated body fluid (SBF) that has almost equal compositions of inorganic ions to human blood plasma. In this study, Ti coatings were prepared by vacuum plasma spraying, and then they were treated by NaOH aqueous solution, immersed in distilled water, heated at 600 °C in a furnace. Microstructure and bioactivity of the surface modified Ti coatings were examined by SEM observation and SBF test respectively. The results obtained revealed that a net-like structure comprising of many micropores was present on the surfaces of the treated Ti coatings. After immersed in SBF, apatite layer was formed on their surfaces, suggesting that the surface modification coatings have good bioactivity.

Titanium/dicalcium silicate composite coatings with different ratios (weight ratios as Ca 2 SiO 4 : Ti = 3:7, 5:5, 7:3) were prepared by plasma spraying. Effects of titanium addition on coating properties, such as bonding strength, Young’s modulus and dissolution in simulated physiological environment, were studied. Results showed that the bonding strength between coating and Ti-6Al-4V substrate increased with increase of titanium content in the composite coatings. It was explained by the narrowed dissimilarity of thermal expansion coefficients between the coatings and substrates. Degradation of mechanical properties after immersion in simulated body fluid was also studied. The dissolution of dicalcium silicate in the composite coatings resulted in the decrease of bend strength and Young’s modulus of the coatings in the simulated physiological environment. The higher titanium content in the composite coatings, the stabler are the composite coatings in the physiological environment.

Recent developments in the field of plasma sprayed ceramic coatings at Shanghai Institute of Ceramics (SIC) are presented. Nano-titania and nano-tungsten carbide coatings were prepared. Their structure and properties were detected. The super hard B 4 C coating was deposited by APS. The physical and mechanical and anti-irradiation properties of B 4 C were measured. Wollastonite coating was deposited and its bioactivity has been tested. The results obtained indicated that (1) nano-titania coating possessed porous structure and unique electric properties; (2) nano-WC-Co coating exhibited notable wear resistance; (3) B 4 C coating was excellent irradiation resistance and (4) the carbonate-containing hydroxyapatite was formed on the surface of wollastonite coating, which indicated that this coating has excellent bioactivity.

To improve the bonding strength of HA coating, several HA-based composite coatings (HA/Ti, HA/ZrO 2 HA/ZrO 2 SiO 2 and HA/NiCr composite coatings) have been fabricated via atmospheric plasma spraying. The bonding strengths of fabricated specimens were tested by ASTM C-633 method. The bioactivity of composite coatings was evaluated by examining carbonate-containing apatite formation on their surfaces in simulated body fluid (SBF). In vitro cell cultures were carried out to examine the biocompatibihty of composite coatings. The results obtained revealed that the addition of metal or ceramics in HA improved the bonding strength of coating significantly except HA/ZrO 2 -SiO 2 composite coating. In SBF test, all of these four coatings were covered by carbonate-containing apatite after immersed in SBF, indicating good bioactivity for composite coatings. The results of cell cultures produced the testimony of excellent biocompatibihty for the coatings except that HA/NiCr composite coating possessed cytotoxicity. By comprehensive survey of bonding strength, bioactivity and biocompatibihty, HA/Ti and HA/ZrO 2 composite coatings were candidates of prospective biocoatings.