EFFECTIVE THERMAL-CONDUCTIVITY OF BINARY DISPERSED COMPOSITES OVER WIDE RANGES OF VOLUME FRACTION, TEMPERATURE, AND PRESSURE

The effective thermal conductivity of binary dispersed composites prepared from mixed and compacted powders of AgCl and low-density polyethylene was measured over the entire range of volume fraction at temperatures in the range 100-330 K together with pressures up to 1.75 GPa. Measurements were made using the transient hot-wire method. The ratio of the thermal conductivities of AgCl and LDPE was an adjustable parameter in the range 2-8 at the temperatures and pressures employed. The rigorous effective medium approximation (EMA) provided a good description for most of our results although some limits to its applicability were also indicated. An empirical theory due to Nielsen provided a significantly less successful description. Suggestions are made for an improved theoretical approach going beyond the limits of the EMA.