A study of thermal conductivity of structural ceramic materials. Part I. State of research of thermal conductivity of structural materials

At the present time, experiment is a reliable method for studying the thermal conductivity of new ceramic materials and especially refractories. However, the range and possibilities of existing devices do not meet the requirements for measuring thermal conductivity, especially at a high temperature. At very high thermal loads under the conditions of formation of surface columnar crystal structures, thermoelastic stresses, disturbances in vibration of the elementary lattice, and other phenomena, the thermal conductivity can be a function of the temperature drop. The present paper concerns the physical fundamentals of heat conduction in current ceramic materials and refractories based on MgO, A1₂O₃, and Si₃N₄. The classical stationary and nonstationary methods for determining thermal conductivity are considered. Special attention is devoted high-temperature processes and the difficulties arising in this case. It is recommended to solve high-temperature problems by using methods based on solving inverse problems of heat conduction     

Some characteristics of heat-resisting concretes modified by SiO<Subscript>2</Subscript> and TiO<Subscript>2</Subscript> nanoparticles

Nanoparticles of SiO₂ or TiO₂ have been added in the preparation of heat-resisting concretes of two types. The major technical and chemical characteristics have been determined. Features have been found in some of the technological operations in making the concretes of both types, and also aspects of the physicomechanical properties. Higher chemical stability has been found for heat-resisting concrete containing TiO₂ nanoparticles in an NaOH solution.     

A study of heat conduction in structural ceramic materials. Part III. Mathematical model of measuring cell

The process of heat propagation in a specimen is considered in an approximation of a one-dimensional heat flow with side leakages of heat. They are modelled as a function of the heat sources (sinks). The chosen stationary heating and the temperature field in the specimen are described by a nonlinear one-dimensional differential equation. The boundary conditions and the source function are determined from experimental data. The nonlinear one-dimensional differential equation is used in an implicit identification method and solved numerically; a minimum of the quality criterion is determined at each iteration step in the search procedure. The identification procedure is performed by explicit and implicit methods of solution of inverse problems of heat conduction. A numerical simulation has shown that the method of component-wise minimization is the most efficient. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 4, pp. 39–42, April, 2000. Part I appeared in No. 8, 1999, and Part II in No. 2, 2000.