THE EFFECT OF RAW MATERIALS CONCENTRATION ON HYDROXYAPATITE POWDER CHARACTERISTICS AND SINTERING BEHAVLOR

Ultrafine hydroxyapatite (HAp) powders with crystallite size in the range of ۱۰-۹۰ nm were synthesized by chemical precipitation process using Ca(OH)۲ and H۳PO۴ solutions as starting materials. Molar ratio of Ca/P=۱.۶۸ was kept constant throughout the process and alkaline condition for the reaction was maintained using ammonium hydroxide. The role of raw material concentration on HAp crystallite size and morphology were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The results revealed that variations in crystallite size and morphology of synthesized HAp are strongly affected by the concentration of acid solution. To study the sintering behavior of HAp particles, the powders were pressed at ۲۰۰ MPa using a uniaxial press. Sintering experiments were carried out at temperatures of ۱۱۰۰, ۱۲۵۰ and ۱۳۰۰°C with various soaking times at maximum temperatures. XRD was also used in determining thephases present after sintering process. The results indicated the decomposition of HAp into a-tricalcium phosphate (TCP) and b-TCP phases at ۱۳۰۰°C. The microstructure of the sintered HAp ceramics was characterized by SEM.

Keywords:

HYDROXYAPATITE , CHEMICAL PRECIPITATION , NANOCRYSTALLITES , MORPHOLOGY , SINTERING , MICROSTRUCTURE