Preparation of diatomite-based porous ceramics containing interlayer porous MgO by low-temperature sintering for integration of high strength and low thermal conductivity

In this work, hierarchical porous ceramics based on diatomite with both high strength and low thermal conductivity were prepared by low-temperature sintering using modified diatomite and dolomite as the main raw materials. In particular, dolomite served both as a pore-forming agent to produce CO₂ gas and as a ceramic component to produce porous MgO in situ. The prepared porous ceramics exhibited a hierarchical pore structure, retaining 2-300 nm nano-pores of the diatomite itself while using dolomite decomposition to produce 1-10μm macro-pores and porous MgO with inter-layer pore sizes of 50-300 nm. The main phases of porous ceramics were cristobalite phase, pyroxene phase, wollastonite phase and MgO phase with special structure. The effect of dolomite addition on the mechanical properties and thermal insulation of porous ceramics was investigated. It was found that the addition of 30% dolomite resulted in a porous ceramic with a porosity of 59.8% and the most favorable pore size distribution. At this time, the presence of wollastonite and pyroxene-like products in the porous ceramics contributed to the highest compressive and bending strengths of 29.66 MPa and 7.22 MPa, respectively. The lowest thermal conductivity of the porous ceramics reached 0.094 W·m^-1K^-1, which can be attributed to the synergistic effect of the hierarchical pores and the increasing interfacial thermal resistance. Overall, the prepared hierarchical porous ceramics exhibited great potential as an alternative material to ceramic fiber insulation in high-temperature kilns.