Strengthening of Al2O3 porous composites with a glass-ceramic binder doped with nanocopper

Glass ceramics are the result of controlled crystallisation of one or more crystalline phases embedded in the glass matrix, which usually results in better mechanical properties than conventional glasses. Crystalline phases precipitated in the vitrified bond improve mechanical strength and provide new functions that are not present in the original glass. The most widely encountered issue in standard composites is the presence of inclusions, generated during the process of thermal treatment, of finely dispersed crystalline phases, which are spread in the amorphous phase. Another way of increasing the mechanical properties of composites is via surface crystallisation of the binder. The mechanical strength can be significantly and permanently increased by inducing compressive stress at the glass surface. In the case of the binder designed here, the generated crystalline phase is willemite (Zn2SiO4), which is characterised by a low coefficient of thermal expansion (CTE). Zn2SiO4 usually crystallises at the glass surface, which results in the development of favourable compressive stresses in the glass-crystalline binder. Transition metal oxides significantly affect the crystallisation characteristics, thus influencing the thermal behaviour of glass ceramics. The majority of current publications focus on studies of the influence of copper on certain properties, and mainly the optical and photonic properties, and the influence of copper on the mechanical properties of silicate systems is still poorly recognised. This article investigates the mechanical and physical properties of porous Al2O3 composites with a glass-ceramic bond doped with nanocopper.