Thermal Insulation Materials Based on Expanded Rocks of Uzbekistan

This study examines the production of thermal insulation materials using mineral raw materials sourced locally in Uzbekistan. Refractory, comprising a porous filler in the form of expanded rocks such as hydrobiotite and perlite, was developed by employing ceramic or ceramic-chemical binders based on clay raw materials characterized by varying refractoriness and plasticity. The structural transformations of the materials at elevated temperatures were analyzed using x-ray diffraction and electron microprobe analysis. The density of samples based on hydrobiotite and a clay-phosphate binder increased by 30 – 35% compared to samples based on a ceramic binder. In samples containing perlite filler, the introduction of a phosphate binder had no significant effect on apparent density. The incorporation of a pre-synthesized clay-phosphate binder based on red-firing clay into the initial perlite mixture resulted in a two-fold increase in strength without increasing density or thermal conductivity of the material. The testing of strength characteristics in perlite–ceramic samples with different phosphate binders over the temperature range of 300 – 950°C revealed strength stability up to 800°C, which indirectly reflects the structural transformation and operational temperature range of the material. Thermal insulation materials with enhanced thermal and mechanical properties were fabricated by semi-dry pressing using the following compositions: expanded hydrobiotite – secondary Samarkand kaolin and expanded perlite – secondary Samarkand kaolin – clay-phosphate binder based on red-firing clay. These materials are suitable for use at operating temperatures of 850 – 1100°C.