Porous ceramic production, this article introduces several of the production methods.
1. Ion exchange method
Layered sodium silicate crystals and hexadecyltrimethylammonium bromide are thoroughly mixed in water, and the cations between the silicate layers will exchange with ammonium salt cations spontaneously. The lamellar structure of the crystalline material will be bent due to the introduction of ammonium salt, polycondensation occurs between the bent lamellae, the organic matter is surrounded by the lamellae, and the organic matter is removed by high-temperature sintering, that is, a porous sio2 circle is formed. Pennsylvania of the United States adopts the in-situ reduction method to reduce the Cu2 and Ni2 ions between the montmorillonite layers to Cu and Ni. These metals were originally aggregated into clusters, and the interlayer spacing was expanded to 0~50nm to form layered porous materials. Currently, the stability and specific surface area of this porous material are being studied, and it is expected to be applied in catalytic or adsorption systems.
2. PCVIPCⅤ [(pressure pulse chemical vapor infiltration) method
Generally used to prepare porous SiC, this method was first proposed by Sugiyama in Japan. He used porous carbon as a matrix, and under high-temperature conditions, SiCL4CH4-H2 was passed into the porous body in the form of pulses, SiCL4 reacted with CH4 to form SiC, and the product was attached to the porous carbon. After 2×104~4×104 times Pulsed, SiC-C porous ceramics production is formed
3. Pore gradient preparation method
Pore gradient ceramics refer to ceramic materials whose pore size decreases or increases regularly with thickness. According to the distribution of pores, they can be divided into continuous pore gradient ceramics and stepped pore gradient ceramics. The preparation methods of pore gradient porous ceramic production mainly include the porogen gradient arrangement method, organic precursor impregnation method, and precipitation generation method. The porogen gradient arrangement method is to lay the aggregates mixed with porogens of different particle sizes in the mold layer by layer in the order of the porogen particle size from large to small, and then press, dry, and sinter. And obtained pore gradient porous ceramic production the organic precursor impregnation method is to immerse organic precursors with different pore sizes into the ceramic slurry, then stack them together in order of pore size from large to small, and then dry and sinter to obtain pore gradient porous ceramic production. The precipitation generation method is to put the modified porogen powders of different particle sizes into the same ceramic slurry, and co-precipitation will occur. Porous ceramic production with pore gradients can be obtained after drying, shaping, and sintering the changed deposition layer. Recently, there have been reports on the preparation of pore gradient porous ceramics by centrifugal sintering technology, which uses centrifugal force to linearly change the pore gradient along the radial direction.