**4.2. Thermal properties**

Fine-grained W-based composites produced by doping with rare-earth oxides such as Y2O3 and La2O3 and carbides such as TiC and ZrC were subjected to transient heat flux tests. It was observed that a high heat flux of 200 MW/m2 can be sustained by these materials, which is nearly 100% higher than conventionally sintered pure W. This promising behavior may be the result of the processing route, i.e., a sol–gel method, heterogeneous precipitation, spray drying, hydrogen reduction and ordinary sintering in sequence [5].

However, oxide- and carbide-doped W composite samples, when subjected to a thermal shock, showed cracks. However, pure W sintered at 2400°C withstands thermal shocks well [20].

The responses of W composites consisting of 20%-80% porous W and infiltrated by Cu, Al or Si and then exposed to a high-temperature environment have been thoroughly studied. These composites exhibit good strength, conductivity and good melt layer stability at high temper‐ atures. In contrast with pure W, some W-based composites can withstand plasma edge temperatures in excess of 200 eV [82].

The thermal conductivity of TiC/W composites and pure W produced by chemical reduction followed by SPS at 1800°C decreases when the temperature is increased from ambient to 827°C. However, the conductivity remains above 120 W/m-K at RT [13]. The effect of the temperature on the thermal conductivity of ODS-W composites prepared by adding 1wt% Pr2O3 was examined, and the behavior of pure W was compared with that of pure W. The conductivity of both materials decreased when the temperature was increased from 25 to 800°C, but the conductivity of these materials exceeds 150 W/m-K at room temperature [26].
