Effect of starch on pore structure and thermal conductivity of diatomite-based porous ceramics

Considering the low-cost and environmental protection, the porous ceramics with high porosity using natural diatomite powder were successfully prepared by utilizing hot injection moulding and sacrificial fugitives. The impacts of different content of starch as a pore-forming agent on the phase composition, mechanical properties, thermal conductivity, and micro-structure of porous ceramics were investigated. The results demonstrate that starch content can significantly affect the mechanical properties and thermal conductivity of diatomite-based porous ceramics. When the starch content increased from 0 wt % to 50 wt %, the porosity increased from 61.2% to 80%, while the thermal conductivity decreases from 0.239 W/(m K) to 0.098 W/(m K). The low thermal conductivity of porous ceramics may be related to the macroporous–mesoporous composite structure. With the starch content increased, a greater chance of starch granule contact, higher internal pore sizes and a wider pore size distribution in the prepared samples, which resulting in lower mechanical strength, such as the three-point bending strength from 2.83 MPa to 0.46 MPa.