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Recently, the practical use of high performance insulation materials such as nanoparticles insulation material or the vacuum insulation material has been spreading to various kinds of industrial fields including industrial furnaces, buildings, home electric appliances, thermal or cold insulation boxes. However, it is very difficult to measure the thermal conductivity. For this purpose, uniform temperature gradient for applying Fourier's low must be achieved in the test specimen. To solve this issue, we have proposed a new method to measure the thermal conductivity of specimens which includes ununiformed temperature gradient areas, and have developed the cheaper apparatus with simple structure. This method had been already applied for the GHP method to achieve its high accuracy. In this paper, we have applied it for the simple structure apparatus, which heated one board with a pair of heaters. As the result, the thermal conductivity of ceramics fiber insulation and the nanoparticles insulation material agreed within ±10% for the previous studies.

The particle's surface property plays an important role on controlling the thermal insulation performance of fibrous silica compacts. In the present study, the effect of addition of hydrophobic silica on the thermal conductivity of the fibrous silica compacts is investigated. The measurement was conducted using laser flash method and differential scanning calorimeter (DSC) method. The thermal conductivity of fibrous silica compacts is only 0.042 W/m K. The addition of 5% hydrophobic silica further reduces the thermal conductivity of fibrous silica compacts to 0.033 W/m K. The thermal conductivity reaches a constant value with higher hydrophobic silica content. The flexural strength decreases with the increase of hydrophobic silica content. A compromise between the thermal insulation and strength is needed. The performance of fibrous silica compacts shows strong dependence on the surface structure of glass fibers.

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