Low temperature facile sintering of silica-incorporated calcium hydroxyapatite for the immobilization of radioactive waste

Abstract

We have investigated the low temperature sintering behavior of pure hydroxyapatite (HA) and silica incorporated HA for the immobilizing radioactive nuclear waste. Solid state sintering conditions were optimized at 200 °C by applying a uniaxial pressure of 400 MPa for a short holding time (10 min). The results from high resolution x-ray diffraction, Fourier transform infra-red spectroscopy, micro hardness, and high resolution scanning electron microscopy confirmed the densification with enhanced mechanical properties. The increasing trend in relative sintered density has been observed with the loading amount of silica. No additional chemicals and binders were used during whole experimentation process. Therefore, this sintering route is totally environment benign, energy efficient and simplified. The ultra-low temperature can makes this sintering process widely useful for the immobilization of volatile radionuclides such as Cs-137 and I-129.