Monetite- and Nanodispersed Silica-Based Ceramics: Structure and Properties

Abstract

Calcium–phosphate ceramics based on monetite and nanosized silica are produced at 500 °C. It is established that phase changes and solid-phase reactions occur during sintering to form ceramics that contain β-calcium pyrophosphate (Са₂Р₂О₇), calcium silicate (wollastonite, CaSiO₃), and insignificant content of β-tricalcium phosphate (Са₃(РО₄)₂). It is shown that the addition of silica inhibits recrystallization of calcium pyrophosphate into tricalcium phosphate, if compared with ceramics prepared from monetite without silica addition. It is established that increasing of silica content in the starting composition leads to decreasing of minimum pore size from 0.83 to 0.21 μm. Only high pure nanosized silica (content of SiO₂  > 99%) prepared by heat-treating of silicon carbide waste in solar furnace was researched. The porosity of ceramics produced reached 43.5–46.8% and the compressive strength was 16–24 MPa.