The role of preactivation of SiO2, CaCO3 and CaSiO3 minerals and a scale factor in the process of SH-synthesis of heat insulators, structure-phase transformations and properties of materials

Abstract

The role of a scale factor in the development of the combustion process, formation of the phase composition of SH-synthesis products and properties of the obtained composition materials is shown on the example of multicomponent charge mixtures containing SiO₂, CaCO₃ and CaSiO₃ after mechanochemical treatment and modification of powder mixtures. The combustion temperature and total time of synthesis are shown to increase with the increase in the volume of experimental samples. The presence of wollastonite in the charge mixture enhances the development of a scale factor (in the process) of quartz combustion. Modification of a charge mixture with organic compounds stabilizes synthesis of samples of a large volume at higher combus-tion temperature. Mechanochemical treatment of the charge contributes to the increase in the strength of SHS-products. The increase in the strength correlates with the increase in the products of helenite synthesis, with formation of aluminium nitride and FeAl₃Si₂. The values of thermal conductivity for the studied systems get stabilized with the increase in the size of the samples being synthesized. Thermal conductivity of SHS-samples changes within 0.31-0.06 W/m·K depending on the ratio of the charge mixture components (quartz + calcite + wollastonite), conditions of modifications at MCT and a scale factor. It is shown that under the conditions of SHS it is possible to obtain a product with high thermal-physical properties by varying the composition of the charge from the natural minerals being used, conditions of its mechanochemical treatment with modifiers as well as the sizes of the product being synthesized.