Structure of multicomponent SiO2-Al2O3-Fe2O3-CaO-MgO glasses for the preparation of fibrous insulating materials

Glasses used for the fabrication of fibrous insulating materials are made from natural raw materials, mainly basalts. Basalt alloys, however, show relatively high crystallization capability, which is disadvantageous for throwing and durability of the fibres prepared. In the work new raw materials, such as melaphyres and diabase from the Silesia region of Poland were applied for the preparation of aluminosilicate alloys. In order to study their crystallization ability the glasses were heated in an electric furnace at various temperatures for various time periods. Depending on the raw material used as well as the temperature of heat-treatment amorphous or crystalline materials were obtained. Crystalline phases were identified based on X-ray diffraction studies. It was found that magnetite/titanomagnetite crystallized in the first step. Then pyroxenes phases of diopsides or augite type appeared in the systems. Spectroscopic investigations in the mid IR region were carried out for all the glasses. This made it possible to determine the influence of thermal treatment on the structural changes of glasses (changes in the spectra shapes). Locations of the bands due to Al-O-Si and Si-O-Si bridges vibrations suggested that in most cases the augite-type phases were present in the systems (aluminium coordination number equal to 4 and 6). Appearance of aluminium in coordination 4 and 6 was confirmed by NMR investigations (two clear bands in the spectra). (c) 2004 Elsevier B.V. All rights reserved.