Thermal Behavior of Spark Plasma Sintered Alumina-Based Nanocomposites

Al ₂O ₃/SiC and Al ₂O ₃–CNT nanocomposites have been fabricated by spark plasma sintering (SPS). Thermal properties (e.g., thermal diffusivity, specific heat capacity, and thermal conductivity) of the nanocomposites have been investigated at room temperature and at elevated temperatures for different nanophase contents and SPS temperatures. The field emission scanning electron microscopy with energy-dispersive spectroscopy, and transmission electron microscopy has been used to investigate the microstructure of nanocomposites. The thermal properties of the nanocomposites as well as those of pure alumina were investigated using direct measurement methods. The results showed that a maximum thermal conductivity of 34 W/m K was achieved on alumina after SPS at 1400∘C, while alumina containing 5 wt% SiC and 1 wt% MWCNTs nanocomposites have maximum thermal conductivities of 24.15 W/m K and 29.62 W/m K, respectively, at a SPS temperature of 1500∘C. The thermal properties of alumina decrease with the addition of the SiC and MWCNT nanophases, increasing its suitability for electro-discharge machining and fabrication of affordable products with intricate parts. The thermal behaviors of pure alumina and of the nanocomposites at elevated temperatures showed a decrease in the thermal diffusivity and thermal conductivity of alumina–SiC nanocomposites with increasing measurement temperature, while the specific heat capacity increased with increasing measuring temperature. The measurement properties correlated with the microstructure, and various transport phenomena were clearly explained.