Effect of Grain Thermal Expansion Mismatch on Thermal Conductivity of Porous Ceramics

摘要: Many ceramics contain microcracks, which are often situated between sintered grains. These microcracks constitute thermal resistances, may affect heat transfer through the material and its effective thermophysical properties. The thicknesses contact areas of change with temperature as a result expansion mismatch grains on opposite sides microcracks. This physical mechanism affects changes material's conductivity, k, temperature. above usually plays minor role at atmospheric pressure, where flow via gas filling cracks. Hence, temperature-induced crack geometry have little effect transfer. However, low pressures, occurs mainly areas, grains' causes unusual behavior conductivity observed for several industrial refractories. In this paper, influence is discussed relative to other mechanisms described in literature. A simple model bonded by an agent, having different coefficients, developed. allows calculation area average microcrack opening functions temperature, characteristic sizes their permanent area. parameters evaluated used calculate ceramic materials containing that appear contraction calculated satisfactorily correlates experimental data collected chrome-magnesite refractories over wide range temperatures pressures.