THE EFFECT OF THE PH VALUES AND SINTERING TEMPERATURES ON THE PHYSICAL, STRUCTURAL AND MECHANICAL PROPERTIES OF NANO HYDROXYAPATITE DERIVED FROM ARK CLAM SHELLS (ANADARA GRANOSA) PREPARED VIA THE WET CHEMICAL PRECIPITATE METHOD

The effect of three different initial alkaline pH values (pH = 8, 9 and 10) in synthesised hydroxyapatite (HA) via a wet chemical precipitation approach was investigated. Waste ark clam shells (ACS) were used in this work as a source of calcium oxide in order to utilise waste materials in the production of synthetic Hydroxyapatite (HA). The HA was treated at different sintering temperature from 200 to 1000 C to study the effect on the physical, the structural properties, the phase formation, the Vickers microhardness and the molar ratio of calcium to phosphate (Ca:P). From the results, the crystallite size and density of the HA obtained were increased as the sintering temperature increased. However, the appearance of biphasic HA and -tricalcium phosphate (-TCP) was detected at pH 9 with 1000 C, but did not occur at pH 8 and 10. In addition to the obtained results, it was clearly identified that the formation of -TCP in the HA phase is related to the initial pH value, sintering temperature and Ca:P ratio. The Vickers microhardness showed that the single-phase HA was the hardest one compared to the biphasic HA/-TCP. It shows the optimal value of the Vickers microhardness for the single-phase HA with a pH 10 at 1000 C is 4.15 MPa.