Structure-Property Relationship in an Electroconductive Hydroxyapatite-Titanium Disilicide Composite

We elucidate here the structure-property relationship in a novel composite system consisting of hydroxyapatite (HA) and titanium disilicide that addresses the challenge of low electrical conductivity and fracture toughness of hydroxyapatite. Theoretical considerations indicated that the addition of 20 wt.% titanium disilicide (sigma similar to 10(6) S/m) favorably contributed to the increase in electrical conductivity (sigma similar to 10(5) S/m) of the HA-titanium disilicide system. As compared to theoretical value, a lower value of electrical conductivity of HA-20 wt.%TiSi2 composite (sigma similar to 67.117 +/- 3.57 S/m) was observed in experimental measurement using four probe method. However, this electrical conductivity of HA-20 wt.%TiSi2 composite was significantly higher than the HA, because no current was recorded in case of HA in the sensitivity range of the instrument. During spark plasma sintering, to raise per unit temperature, higher magnitude of current was utilized in case of HA-20TiSi(2) than HA. This resulted in higher densification of HA-20TiSi(2) during initial stage of sintering. Also, a significant improvement in fracture toughness was observed on the addition of TiSi2 to HA from 0.6 MPa.m(1/2) in HA to 1.2 MPa.m(1/2) in HA-20TiSi(2). The mechanism of increase in fracture toughness involved crack deflection, friction bridging, wake debonding, and elastic bridging.