Journal of the American Ceramic Society, Vol.89, No.8, 2466-2472, 2006
Processing and performance of hydroxyapatite/fluorapatite double layer coating on zirconia by the powder slurry method
A hydroxyapatite/fluorapatite (HA/FA) double layer was coated on ZrO2 by a powder slurry method. The FA layer between the HA layer and the ZrO2 substrate was effective in suppressing the reaction between HA and ZrO2. The rheological properties of the slurry and the thermal treatment conditions were optimized. Addition of small amounts of tri-ethyl phosphate dispersant and polyvinylbutyral binder (up to 5 wt%) was effective in reducing the slurry viscosity, even at high loadings of HA powder. Each layer (HA, FA) was deposited on ZrO2 repeatedly to induce a uniform layer, and the final heat treatment was carried out above 1200 degrees C to consolidate the coating layer. During this process, without the FA-intermediate layer, a severe reaction between HA and ZrO2 occurred to form tri-calcium phosphate and CaZrO3 products. However, the presence of the FA layer between HA and ZrO2 effectively suppressed the reaction up to 1300 degrees C. The obtained HA/FA double coating layer was micro-porous and relatively rough, but was firmly adhered to the ZrO2 substrate, having a bonding strength of approximately 25 MPa after heat treatment above 1200 degrees C. The osteoblast-like cells cultured on the HA/FA coating layer spread and proliferated favorably, having a cell proliferation rate comparable to that of a plastic control and HA bulk ceramic.