THE NATURE AND CONDITIONS OF FORMATION OF THERMOELECTRIC PROPERTIES IN NATURAL AND ARTIFICIAL LAYERED ALUMOSILICATES

Abstract

The review analyzes the physical and che­mi­cal properties of modified natural and artificial layered aluminosilicates, which form the basis for the emergence of thermoelectric properties in materials based on them. It represented the main methods of modification and analysis of structural and thermoelectric properties of these materials. Chemical modi­fication of layered aluminosilicates is carried out by the reaction of solid aluminosilicate with concentrated aqueous solutions of metal hydroxides of groups I and II, their silicates, or phosphoric acid. The products of such interaction are called geopolymer. This name used to describe the reaction of the transformation of amorphous aluminosilicate into crystalline products during the interaction the solid pro­duct with concentrated alkali solutions of me­tals from the groups I and II, or the formation of composites and gel systems. The change in particle size, acidity of the media and impurity exchangeable cations in layered aluminosilicates significantly affects its acid-base and catalytic properties in aqueous solutions. The use of aqueous solutions increases the effect of hydrolytic processes on the number of hydroxide groups in the composition of the mineral, which are responsible for the adsorption pro­perties and create the possibility of oxidative-destructive catalysis with the participation of the mineral. The ion-exchange capacity of layered aluminosilicates depends on the degree of their dispersion. The increasing degree of the Perdispersion level increases the ion-exchange capacity of the material. It is also possible to modify layered aluminosilicates with phosphoric acid, which can form polymers. Using phosphoric acid allows high temperatures over 900 C to change the electrical properties of minerals. The priority directions for strengthening the properties of heat-to-electricity conversion through the development of composite materials based on layered aluminosilicates using metal nanoparticles, silicon carbide, carbon, graphene, graphene-like materials, and metal oxides embedded in the aluminosilicate matrix have been established.