The Study of Plasma-Sprayed Porcelain/Hydroxyapatite Composite Coatings on Alumina Substrate

• Main Authors: Chun Shen Choun, 邱俊憲
• Other Authors: Edward Chang
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/17241397702038077749

碩士 === 國立成功大學 === 材料科學及工程學系 === 87 === Abstract Hydroxyapatite（HA）has recently been used as a bone substitute in orthopedic and dental surgery applications, owing to its excellent biocompatibility. However, the poor mechanical properties of HA limit the material's application in the loading condition. In this study, HA was coated onto the surface of alumina substrate, with a view to overcome the poor mechanical properties of HA and the biocompatibility of alumina. Improvement of the bonding strength of HA coatings to alumina substrate was attempted by adding a bond coat of porcelain via plasma-spraying and by post heat-treatment. HA-50wt﹪porcelain and pure porcelain were used to manufacture two kinds of bond coat before HA coating, and then all the specimens were heat-treated at 750℃, 800℃, 850℃, 900℃for 0.5 hours. The results showed that the bonding strength of as-sprayed P0, P50 and P100 samples were all nearly 13 MPa. The bonding strength of post-heat-treated P0 at 900℃ was found to increase by 5 MPa as compared to that of pure HA coatings. And, the bonding strength of post-heat-treated P50 and P100 at 850℃ increased by 8 MPa as compared to that of P50 and P100 coatings in as-sprayed condition. Besides, post-heat-treatment at 850℃ achieved the maximum bonding strength for P50 and P100 samples. By XRD analysis of the HA coatings, impurity phases, such as Ca3(PO4)2, Ca4P2O9, and CaO phase, were identified in as-sparyed and post-heat- treatment states. Investigating the coating morphologies showed that the surface roughness of HA coatings with bond coat increased as compared with coating without bond coat, and the surface roughness of former HA coatings decreased after heat-treatment. By EPMA element analysis, it was found that at interface of HA and porcelain, calcium diffused from HA into porcelain, which apparently enchance the bonding of the interface. The fracture mechanism of the tensile test was observed by the SEM analysis. It was found that P0 sample in as-sprayed and post-heat-treatment at 750℃ and 800℃ fractured along lamellar splats of HA and at interface of HA and Al2O3 substrate. And, the post-heat-treated P0 at 850℃ and 900℃ primarily fractured along the interface of HA and Al2O3 substrate. However, P50 and P100 samples in as-sprayed and post-heat-treatment at 750℃ were fractured along lamellar splats of HA and at interface of bond coat and Al2O3 substrate. After heat treatment of P50 and P100 at 800℃, 850℃ and 900℃, fracture of the tensile test occurred primarily along the lamellar splats of HA and the inside of bond coat.