Development and Evaluation of Characteristics of Nanoporous Materials

It has been well-known that nanoporous materials show extremely low thermal conductivity, however, they do not retain stiffness enough to be processed into arbitrary shapes. Therefore, it is crucial to realize high thermal insulations as well as high strength. To cope with the problem, we have developed a high performance thermal insulation, which has enough strength to be processed into arbitrary shapes. First, nanoporous composites are prepared by direct bonding of ceramic fibers and nanoparticles. Then, the nanoporous materials are formed simply by dry pressing of the nanoporous composites with SiC particles. In this study, we evaluated the strength and thermal conductivity of the nanoporous materials in detail, and proposed the estimation equation for the thermal conductivity. The nanoporous material had the bending strength over 0.8MPa. The thermal conductivity was from about 0.023 to 0.04W/(m·K) in the temperature range from 400 to 600°C. Furthermore, the thermal conductivity obtained by the proposed estimation equation agreed with the measurement result within an error of ±15%.