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- Author or Editor: L. Serban x
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Thermal analysis methods and X-ray diffractometry provided data on and permitted practical use of the eutectic mixture between Na2O·2SiO2 and SiO2, which melts at 790°C. Based on this, water glass was used as a binder to obtain artificial cluster granules, ceramically hardened by heating at 800°C. The process of water glass hardening in the presence of hardening reagents such as Na2SiF6, NH4Cl, silica gel and ultra-fine silica was studied by thermal analysis. In the first stage, gelification of the SiO2 sol takes place by neutralization of the NaOH deflocculant, while the second stage involves tridimensional cross-linking by polycondensation, promoted by powders rich in SiO2.
Thermal analysis coupled with the measurement of temperatures at which colour changes are observed in situ was used to test various inorganic pigments with the aim of introducing them into the compositions of thermo-indicating paints. Through a reversible or irreversible modification of the colour these can indicate an undesired increase in temperature of a fluid in a metallic enclosure. Three such pigments are described, which indicate temperatures of 110, 300 and 400°C. The paint contains the thermo-indicator pigment, soluble glass as binder and either ultrafine silica or silica gel, or a mixture of Na2SiF6 and finely-ground sand as hardener. Such paints are used for damage warning.
