Hierarchically porous diatomite ceramics were fabricated by the freeze-drying method using Xanthan Gum as a gelling agent. They showed high porosity of 84.8–92.7% and a low thermal conductivity value of 0.061–0.123 W m−1 K−1 (tested at 473–1073 K). Their compressive strength increased with increasing the preparation temperature and/or the solid loading level. The porous sample with 15 wt-% solid loading, after 2 h firing at 1373 K, showed a porosity level of 92.7%, a compressive strength of 0.11 ± 0.01 MPa and a thermal conductivity value as low as 0.061 ± 0.001 W m−1 K−1. The above data indicated that hierarchically porous diatomite ceramics prepared by the present freeze-drying method possessed reasonable mechanical strength but superior thermal insulation properties.
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