Heat-Conductivity Studies of Structural Ceramic Materials. Part VI. A Study of the Heat Conductivity of an Al2O3-Based Ceramic

Abstract

The heat conductivity of an Al₂O₃-based ceramic (KPF-5-grade refractory material) is studied. Two sets of specimens are tested: intact specimens, prepared from as-received material, and in-service specimens, subjected to high-temperature aging (at 1700°C for 1680 h). Temperature profiles and heat flows measured in the two sets of specimens are compared. Results for effective heat conductivity calculated by an explicit identification method show a standard deviation of about 10°C from experimental values. The use of a descriptive regularization method for data processing makes it possible to decrease the spread of curves by narrowing the domain of possible solutions, which was done by placing constraints (inequalities) on the X and Y-coordinate axes. The effective heat conductivity of the intact Al₂O₃ material at low temperatures (below 1000 K) is higher than that of the in-service (thermally aged) Al₂O₃ material, whereas the exact opposite is true at higher temperatures (more than 1200 K). For both materials, the effective heat conductivity is the same at a temperature of about 1100 K at which the curves intersect