Investigating the Controlling Parameters Affecting Sintering and Densification of AlN/B4C Ceramics as a Promising Solar Absorber Material
摘要
In this work, the densification behavior of black AlN/B4C composites was examined with the aim of developing high-performance materials suitable for solar receiver applications. Hence, key processing parameters, including phase composition, sintering temperature, sintering time, and sintering additives were investigated. Black AlN/B4C ceramics with different B4C content (0-50 wt.%) were prepared by the pressureless sintering method at different temperatures (1600, 1700, and 1750 °C) and different times (2 and 4 hrs), with a controlled heating rate of 10 °C/min without/with using sintering additives of 5 wt.% graphite and 5 wt.% MgO + Al2O3. Moreover, thermal emissivity of the produced ceramics was evaluated to ensure their suitability as a highly efficient solar absorber material. The results indicated that increasing sintering temperature and time with using sintering additives have a crucial role on enhancing the sinterability of the proposed ceramics. The highest bulk density of 2.61 g/cm3 (nearly 81.3% of theoretical density) was achieved at the sintering temperature of 1750 °C for 2hrs with using 5 wt.% MgO + Al2O3. AlN/B4C composites recorded promising emissivity values in the range of 0.60-0.742. These values are similar to the ideal SiC receiver values. This confirms the suitability of the nitride/carbide composites as high-temperature solar receivers with high solar-to-thermal energy conversion efficiency.