Sintering Behavior and Diametral Tensile Strength Properties of Hydroxyapatite-Zirconia Composites

. The aim of this study is to evaluate the sintering behavior and diametral tensile strength properties of hydroxyapatite-zirconia (HA-ZrO2) composites. HA powder were synthesized from gypsum waste with diammonium hydrogen phosphate (DHP) solution via microwave-precipitation treatment. HA mixed with various amounts of ZrO2 (0, 20, 30 and 40 wt.%) for six hours. HA-ZrO2 powder were molded in a metal die and pressed at 100 MPa. The green bodies were sintered for 2 hours at temperature 1450°C. Characterization of HA and HA-ZrO2 composites were conducted by XRD, XRF and SEM-EDX. The apparent porosity of HA-ZrO2 composites were measured using the Archimedes method. Diametral tensile strength testing of HA-ZrO2 composites were loaded at a crosshead speed of 5 mm/min. The results of the characterization of HA powder are the main (h k l) indices for HA are: (2 1 1), (2 0 2) and (0 0 2), Ca/P molar ratio is 1.71, level of purity is 88.68 %. The main (h k l) indices for HA-ZrO2 composites are: (2 2 0), (0 2 10) and (2 0 20). Porosity of HA-ZrO2 composites values in the range of 39.59-19.82%. Diametral tensile strength of HA-ZrO2 composites increased from 4.96 to 7.77 MPa when amounts of ZrO2 increased up to 40 wt%. This phenomenon is caused by porosity decrease and crack deflection.