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Excessive sintering shrinkage leads to severe deformation and cracking, affecting the microstructure and properties of porous ceramics. Therefore, reducing sintering shrinkage and achieving near‐net‐size forming is one of the effective ways to prepare high‐performance porous ceramics. Herein, low‐shrinkage porous mullite ceramics were prepared by foam‐gelcasting using kyanite as raw material and aluminum fluoride (AlF3) as additive, through volume expansion from phase transition and gas generated from the reaction. The effects of AlF3 content on the shrinkage, porosity, compressive strength, and thermal conductivity of mullite‐based porous ceramics were investigated. The results showed that with the increase of content, the sintering shrinkage decreased, the porosity increased, and mullite whiskers were produced. Porous mullite ceramics with 30 wt% AlF3 content exhibited a whisker structure with the lowest shrinkage of 3.5%, porosity of 85.2%, compressive strength of 3.06 ± 0.51 MPa, and thermal conductivity of 0.23 W/(m·K) at room temperature. The temperature difference between the front and back sides of the sample reached 710°C under high temperature fire resistance test. The low sintering shrinkage preparation process effectively reduces the subsequent processing cost, which is significant for the preparation of high‐performance porous ceramics. [ABSTRACT FROM AUTHOR]

Abstract: Blue-and-white porcelain is a kind of famous underglaze color porcelain in Chinese ceramic history. In this paper, 13 pieces of blue-and-white porcelain shards collected in Beijing were adopted as samples. Microstructure characteristics and distributions of chemical elements were investigated. Quartz and mullite were the main crystalline phases in blue-and-white porcelain bodies. The column-like crystals in the glaze were anorthite crystals. Microstructures of interaction layers in the blue decorations could be divided into two categories with morphologically distinctive microstructures: column-like and flower-like structures. The coloring elements surrounded by dense anorthite crystals mainly concentrated in the center of interaction layers, and the cobalt blue pigments were identified as cobalt aluminate (CoAl2O4). [Copyright &y& Elsevier]

Honeycomb-like structured porous Si 3 N 4 ceramics with exceptionally high number of cells per square inch were prepared by the self-organization method of alginate. The obtained samples have highly ordered channels, high porosity and well mechanical strength. It is found that the microstructure and properties of obtained porous Si 3 N 4 ceramics can be effectively controlled by choosing different kinds of alginates. And it is worth to note that the obtained ceramics possess interesting hierarchical pore structure, including the unidirectionally aligned channels with pore size of 50–120 µm (first pore structure) and the interlocked microstructure of fibrous β-Si 3 N 4 grains within channel walls with pore size of 0.8–2.6 µm (secondary pore structure), making it desirable for filter applications. [ABSTRACT FROM AUTHOR]