Sintering and crystallization phenomena in Silceram glass

Abstract

An investigation has been carried out on the feasibility of employing a CaO-MgO-Al₂O₃-SiO₂ glass-ceramic (known as Silceram) as a matrix for a fibre composite produced by a powder route. Some important properties of the parent glass, e.g. surface energy, viscosity, have been measured as well as the kinetics and structural aspects of the sintering and crystallization processes. It was found that the crystallization of the main phase, diopside, occurred from the surface of individual particles and internally with activation energies of 392 to 452 kJ mol⁻¹ and 258 to 323 kJ mol⁻¹ respectively. However, the surface crystallization was only dominant when the glass powder was fine (<38μm). The work has demonstrated that this glass-ceramic shows promise as the matrix component of a composite because

• (i) both sintering and crystallization may be achieved by a single stage heat treatment at relatively low temperatures of 900° C to 1000° C, because the glass powder can be compressed and sintered by viscous flow before crystallization commences, and

• (ii) the resulting microstructure is fine, and in the case of the hot-pressed material there is negligible porosity.