Measuring thermal conductivity using H2-O2 flame on ceramic films prepared by atmospheric chemical vapor deposition.

Uneven micron-sized pores on the surface of the polycrystalline alumina (Al 2 O 3) substrates can affect their performance as electrical insulating plates. In this study, we investigated the sealing of these pores with amorphous Al 2 O 3 films deposited via atmospheric chemical vapor deposition. Furthermore, we conducted annealing treatments on the samples. The color change of the deposited Al 2 O 3 films was investigated using the Commission Internationale de I'Eclairage color space. Notably, the deposited films initially changed the sample color from white to orange or brown. However, increasing the annealing temperature and duration reversed this discoloration effectively and restored the original white (colorless) appearance of the sample. We measured thermal conductivity using the flame flash method with the H 2 -O 2 flame to assess the influence of sealing. While the unsealed substrate exhibited a thermal conductivity of 4.66 W/mK in the range of 400–500 °C, the annealed and flattened Al 2 O 3 film deposited on the substrate maintained a comparable thermal conductivity of 4.67 W/mK within the same temperature range. This finding demonstrates that our sealing method successfully filled the pores while having minimal influence on thermal conductivity, which is a crucial property for electrical insulation applications. [ABSTRACT FROM AUTHOR]