ABSTRACT
A new specimen cell, used in conjunction with a previously described dual heat-flux metered system, has been fabricated to allow measurement at different densities of the thermal conductivity of powders used as the components of ceramic materials. The design and fabrication of the cell is discussed in this paper. Thermal conductivity values as a function of density for two different sizes of aluminium powders (18 micron and 5 micron) at room temperature are presented. Values of about 0.2 W/(m-K) were found at approximately 1000 Kg/m3, increasing 5- to 10-fold for the powder compressed to 1500 Kg/m3. Theories of thermal resistance of multiple materials are discussed. Luikov et al’s model can be made to fit the data at the low densities by adjusting parameters. At higher densities, metal-to-metal contact resistance is an important component of the thermal conductivity. The results show that the thermal conductivity of the powder is relatively insensitive to density until the density increases beyond a critical point when the thermal conductivity notably increases with increasing density. This is of significant importance in the design of the ceramic combustion synthesis when control of the conversion zone determines the quality of the produced material.
