Preparation of low thermal conductivity hierarchically porous diatomite ceramics by doped with ZrSiO opacifier-based foam-gelcasting method

Hierarchically porous diatomite ceramics (HPDCs) doped with ZrSiO as the opacifier were successfully prepared by means of foam-gelcasting with diatomite powder as original material. The effects of the opacifier, ZrSiO, on the microstructure, mechanical properties, and thermal conductivity of the HPDCs were studied. The HPDCs doped with ZrSiO showed a typical porous structure with excellent properties such as high porosity (84.5–89.1%) and high compressive strength (0.66–1.99 MPa). The added ZrSiO hardly influenced the porosity, bulk density, and compressive strength, but decreased the thermal conductivity, especially at high temperatures. When 5 wt% ZrSiO was added to HPDC, its thermal conductivity at 298 and 1073 K decreased to 0.068 and 0.132 W/(m K), respectively. This decrease in the thermal conductivity could be attributed to the outstanding scattering and absorption of the infrared electromagnetic waves by the added opacifier. The results indicated that the addition of ZrSiO as an opacifier is a promising approach for enhancing the properties of porous ceramics at high temperatures.