As the demand of thermal stability heightens for such products, porous silicon nitride and silicon carbide ceramics also have been developed. Cordierite is used as a raw material with the primary purpose of improving the heat fluctuation resistance of products, and alumina is used to increase a material’s strength and thermal stability. Moreover, the porosity, density, fluid resistance loss, and penetrability of these materials can be modulated by various processing techniques, and the commonly used material species includes alumina and cordierite. They can be used in many fields, including metallurgy, chemical engineering, environment protection, energy, and biology, for such applications as metal melt filtration, high-temperature gas purification, and catalyst support. In particular, these materials have many connective pores and capillary holes and have high specific surface energy on the inside, so they perform well in terms of filtration and adsorption under low fluid resistance loss conditions. Ĭeramic foam is an important part of porous ceramics, and the open-cell type of ceramic foam, which is a new type of highly porous ceramics, has a three-dimensional, reticulated structure with connective pores, resulting in great specific surface area, high fluid contact efficiency, and a small loss of fluid pressure.
![porus pot porus pot](https://manytutors.s3.ap-southeast-1.amazonaws.com/ask-mt/questions/1518100706-27291.jpg)
In light of the differences among their materials, there are several types of porous ceramics: silicate aluminosilicate diatomite carbon corundum silicon carbide and ocordierite.
![porus pot porus pot](http://www.insifindia.com/product/enlarge/porous-pot-empty-&-filled-1.gif)
This classification standard has not been adopted abroad because the rules about using porous materials vary widely from country to country. Macroporous material, for pore sizes over 50 nm Mesoporous material, for pore sizes of 2–50 nm Microporous material, for pore sizes of less than 2 nm Porous ceramics also can be classified according to the size of their pores, as follows : By properly matching the ceramic raw material to the preparation technique, porous ceramics may be created that have relatively high levels of mechanical strength, corrosion resistance, and stability under high temperatures that can satisfy the demands of severe conditions. These porous structures take on a relatively low level of bulk density and thermal conductivity, as well as varying levels of fluid penetrability which is high for the open-cell body. In addition, there are half open-cell ceramic foams.Īpparently, some ceramic foams have both open and closed pores. The distinction between the two types depends on whether the pore is enveloped by solid cell walls or not. Such differences can be clearly seen by comparing the fluid penetrability of these two sorts of foamed bodies. When pores are separated by solid cell walls, the closed-cell ceramic foam will be achieved. When the solid species constituting the foamed body is comprised only of pore struts, the connective pores will generate reticulated structures, resulting in open-cell ceramic foams. There are two sorts of ceramic foam: the open-cell, reticulated ceramic foam ( Figure 1.16a) and the closed-cell, bubblelike ceramic foam ( Figure 1.16b). Three-dimensional ceramic foams: (a) an open-cell reticulated ceramic foam, (b) a closed-cell bubblelike ceramic foam. When evaluated as supercapacitor electrode materials in two-electrode test systems, the as-prepared HPCs exhibit an excellent electrochemical performance: a specific capacitance of 253 F g −1, with almost no capacitance loss after 10 000 cycles.Figure 1.16. It is noteworthy that this “leavening” strategy is widely applicable to most of the biomass derivatives and biomass, including glucose, cellulose, chitin, starch, rice straw, bamboo, etc. Besides the well-defined hierarchical structure, the as-prepared HPCs also exhibit notably large specific areas (up to 1893 m 2 g −1). The “leavening method” is conducted simply by mixing the biomass with KHCO 3 followed by elevated temperature treatment. Inspired by leavening of bread, we design a strategy to fabricate HPCs with three-dimensional (3D) hierarchical pores consisting of macro, meso, and micropores. It still remains a big challenge to build HPCs from crude biomass, which is abundant on the earth, through a simple one-pot approach. However, most existing protocols highly rely on nanocasting and soft-templating, which usually make the use of specific raw materials and thus their industrial application unfeasible. Hierarchically porous carbons (HPCs) show great potential in energy storage due to their high surface area as well as short ion transport path derived from the interconnected porous framework.