Comparison of Microstructures of Bovine Hydroxyapatite and Sol-Gel Derived Porous Alumina-Hydroxyapatite Biocomposite Powders

Abstract:

Alumina (α-Al₂O₃) and hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) are biocompatible ceramic materials. Alumina is described as “bioinert” while hydroxyapatite as “bioactive”. These ceramics can be used in production of orthopedic prostheses, dental implants and bone filling materials either separately or in composite form. Especially porous materials attract attention due to their supportive structure for cell and tissue growth/development.Alumina was derived via sol-gel method. Firstly, boehmite (AlOOH) sol was produced by hydrolyzing the starting material, aluminium iso-propoxide (AIP, Al(OC₃H₇)₃). Then this sol was mixed with hydroxyapatite powders (Bovine Hydroxyapatite, BHA) obtained from bovine bones. Subsequently, the mixture was gelated at 110 °C for 3 hours and the resulting gel mixture was heat treated at 1300 °C for 2 hours. BHA powders were not synthetic and added as 10 and 30 wt.% of AIP to the boehmite sol. Irregular shape of the powders produced after the heat treatment was interpreted as a sign of porosity.SEM-EDS and XRD characterization studies were performed on heat treated powders. XRD results showed that powders were composed of α-alumina and apatite based phases such as tricalcium phosphate and hydroxyapatite. SEM images of the composite powders indicated that neck bonds were not formed between α-alumina and apatite based phases. Comparison of SEM images and EDS results of pure BHA and composite powders revealed that pure BHA powders possess granular particle shape. Furthermore, needle shaped alumina particles were observed in the composite sample with 10 wt.% BHA. Finally, it has been found out that alumina particles were placed layer by layer in the composite powders with 30 wt.% BHA.

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