Sintering behaviour and properties of iron-rich glass-ceramics

Iron-rich glass-ceramics were obtained by the sintering of two glass powders, labeled G1 and G2, at heating rates of 5° and 20°C/min followed by an isothermal step in the 850°-1050°C temperature interval. The sintering process was evaluated by the linear shrinkage; the closed porosity was estimated by density measurements; the structure and the morphology of the glass ceramics were observed by scanning electron microscopy. The bending strength, the Young modulus, and Vickers hardness of the glass-ceramics materials were evaluated. The results showed that the sintering process and morphology of the glass-ceramics depends on the amount of magnetite and pyroxene formed. With a low percentage of crystal phase formed (25%-30% typical of G1) the structure is characterized by closed porosity; at higher crystallization (45%-50% typical of G2) open porosity is mainly formed. The properties of the glass-ceramics were not influenced by the heating rate but improved with an increase in the degree of crystallization