Effect of Sealing on Thermal Conductivity of Aluminium Anodic Oxide Layer

Aluminum alloys have been regarded as a light structure material, but nowadays their thermal properties, such as thermal conductivity, enable them to utilize as a heat dissipation material. As the interest of thermal conductivity of aluminum alloys increases, it has become necessary to study for thermal properties of aluminum anodic oxide. The thermal conductivity of aluminum anodic oxide layer was measured by steady-state method. Before sealing the thermal conductivity of aluminum anodic oxide was 1.62 W/m · K, which is considerably lower value than Al2O3, because of its amorphous structure and hydrated alumina. As the empty tens of nano size pores were filled by sealing, the thermal conductivity were increased to 2.18 and 2.02 W/m · K after hydrothermal and cold NiF2 sealing, respectively. It is assumed that the crystalline boehmite formed by sealing is helpful to enhance the thermal conductivity of aluminum anodic oxide. The hydrothermal sealing leaded to form a more crystalline boehmite in the pores than cold NiF2 sealing.