Mullite-Corundum-Al2TiO5 Foamed Ceramics with Extremely Low Thermal Conductivity Induced by Multiple Thermal Resistance

Abstract

In the context of the global implementation of the dual carbon strategy, enhancing the thermal insulation performance of kiln insulation layers to reduce energy consumption is a highly effective route to achieving energy conservation and emission reduction. In this work, mullite foamed ceramics were fabricated via a direct-foaming method using industrial alumina and white clay as raw materials, and the thermal conductivity was decreased by introducing a secondary phase and increasing the interfacial thermal resistance. The influence of the TiO₂ addition on the phase composition, pore characteristics, and properties was systematically investigated by means of XRD, SEM, and EDS. The results indicate that the foamed ceramics are mainly composed of mullite, with minor phases including corundum and aluminum titanate. It has been demonstrated that increasing the TiO₂ addition decreased the ceramic’s thermal conductivity, due to the formation of low-thermal-conductivity Al₂TiO₅ phases and the elevation of the interfacial thermal resistance. The specimen exhibiting the optimal properties is characterized by a porosity of 77.8%, a strength of 1.86 MPa, and a thermal conductivity of 0.216 W/(m·K) (1000 °C), achieved with a TiO₂ addition of 6 wt%.

Keywords

Mullite foamed ceramics / Al2TiO5 phase / Low thermal conductivity / Thermal insulation

Author Contributions

Methodology, W.Z.; Investigation, W.Z., L.Z. and Z.Z.; Writing—Original Draft Preparation, W.Z.; Data Curation, W.Z., X.J., J.K. and P.D.; Writing—Review & Editing, W.Z. and C.L; Supervision, D.Z.; Project Administration, W.Z., D.Z. and X.L.; Funding Acquisition, D.Z.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data are available from the corresponding author on reasonable request.

Funding

This research was funded by the Natural Science Foundation of Shandong Province (Nos. ZR2025QC605 and ZR2024QE044), Opening Fund of State Key Laboratory of Advanced Refractory Materials (NO. SKLAR202411), Shandong Provincial Key Research and Development Program (No. 2025CXGC020107), the Innovation Capacity Improvement Project for Technology-based Small and Medium Enterprises in Shandong Province (No. 2024TSGC0788), and Jinan City-School Integration Development Strategy Project (Nos. JNSX2023015 and JNSX2023018).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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