Influence of modifying coatings on dielectric permittivity of ceramic materials with composite coatings

The results of research of features of modification of aluminosilicate ceramics by suspension of fluoroplastic, aluminophosphate binder (AFS), non-aqueous compositions of polyurethane components, are presented. Samples of aluminosilicate ceramics for research were obtained by technological methods, including batch preparation operations, sample pressing, pre-annealing and sintering at a temperature of 1200–1350 °C. Polydisperse powders of aluminosilicates obtained by grinding waste of porcelain production (porcelain ware, GOST 28390-89); low-melting clay raw materials were selected as initial components. Modification of surface of aluminosilicate materials was carried out by impregnation of aqueous compositions based on a suspension of fluoroplastic and aluminophosphate binder (AFS), non-aqueous compositions of polyurethane components used in the preparation of polyurethane foam and 5 % solution of polyethylene hydrosiloxane in toluene with the formation of composite coatings on the surface of ceramic materials. It is shown that the application of organic film coatings (based on polyurethane, aluminophosphate binder and a suspension of fluoroplastic-4D, polyethylene hydrosiloxane) leads to formation of a multilayer dielectric material in which there are interface surfaces separating areas with different dielectric properties. In the presence of an external electric field, conditions are created for migration polarization between the crystalline phase of the substrate and the amorphous phase of the coating, due to the redistribution of free charges in the volume of the composite. Moreover, the chemical interaction of AFS with ceramics leads to the smoothing of the surface relief of the aluminosilicate base and the overgrowth of deep pores. Composite “aluminosilicate – AFS-fluoroplastic coating” differs from other materials, primarily in that aluminophosphate binder coating chemically reacts with the ceramic base. The impurity ions introduced during coating application, its composite structure, as well as the heterogeneity of the interface determine the pronounced frequency dependence ε and tgδ, as well as large dielectric losses of the composite in comparison with the original aluminosilicate material.

Methodological Approaches in Assessing the Possibility of Using Waste Electrocorundum Materials in Concrete Compositions

Heat-resistant concretes have been successfully used in many heat units and building structures. Making concrete heat-resistant is possible through the development of a heat-resistant phosphate matrix, aluminophosphate binder. The compositions of high-refractory concretes on aluminophosphate binder with electrocorundum and chrome-aluminous slag have relatively high strength up to 70 MPa after heat treatment. Wastes generated as a result of technological activities of enterprises have several technical and economic advantages as industrial raw materials. After passing the production possibility frontier, the material not only has not lost its properties, but became more prepared with the position of the grain composition and growth of specific surface area, heat treatment for use in the technology of concrete and refractory concrete, in particular, as heat-resistant fillers. The methodological approach in the study of defective ceramic-bond abrasive wheels has been proposed herein. The chemical, grain and mineralogical analyses of the material after mechanical grinding allowed us to define it as an aggregate for concrete in order to give it heat-resistant properties. The obtained concrete composition has a tensile strength 2.5 times higher than conventional cement composition of concrete and thermal resistance (water, 800°C) of the composition with heat-resistant filler has increased in 5 times.