Porous ceramics is a kind of synthetic the body has a large number of the same or closed pores of ceramic materials, it not only has good chemical stability and thermal stability, but also has excellent permeability, developed surface, very low conductivity and thermal conductivity and other performance advantages, are widely used in chemical industry, environmental protection, energy, electronics, metallurgy, Bio-medicine and aerospace and other fields. Different use purposes, the material performance requirements vary. Therefore, the microstructure and physical and chemical properties of porous ceramic materials have become the key to the development and application.
The microstructure of building materials mainly includes crystal, vitreous and colloid. The microscopic structure of the crystals is characterized by the definite geometrical position of the microscopic particles that compose the matter in the arrangement of space. In general, the crystal structure of the material with high strength, hardness, a certain melting point, mechanical properties of the anisotropy of the common. The materials in the building materials (steel and aluminum alloy) and the gypsum in non-metallic materials and some minerals in the cement stone are typical crystalline structures.
The microscopic structure of the vitreous is characterized by the disordered and chaotic state of the micro-particles composing the material in space. The material of vitreous structure has the characteristics of high chemical activity, no definite melting point and isotropic mechanical properties. Fly ash, building with ordinary glass are typical of the vitreous structure.
Colloid is a common form of microstructure in building materials, usually formed by the distribution of very fine particles evenly in the liquid. The biggest difference between colloid and crystal and vitreous is that it can be divided into dispersed and reticular structures, which are called Sol and gel respectively. After the Sol is dehydrated, it becomes a gel structure with a certain strength, and the crystals or other solid particles in the material can be bonded as a whole. such as gas-hard cementitious materials water glass and Portland cement stone in the hydration of calcium silicate and hydrated ferric acid calcium are colloidal structure.
Application of porous Ceramics
The application of porous ceramic materials is mainly concentrated in the following aspects.
1 Building Materials
Porous ceramics have been widely used in the construction industry because of their characteristics such as light weight, non-flammable, sound insulation, processing performance and good decorative properties. With closed pores can be used as internal and external walls, floors and ceilings veneer, cold storage insulation layer, can also be used as water floating material;
2 Catalyst Carrier
Because porous ceramic materials have higher surface activity and adsorption performance, the catalyst is loaded on porous ceramic material, which can increase the contact area of chemical reaction effectively, improve the reaction rate and conversion rate, and thus improve the catalytic effect. According to statistics, at present, 90% of the world's vehicle catalytic carrier is porous ceramic carrier.
3 Filter Separator
Because porous ceramic materials have higher porosity, when filtrate passes, the pollutants such as suspended solids, colloid and microorganism are intercepted on the surface or inside of the filtration medium, and the purpose of separation and purification has never been achieved. Mainly include: molten metal filtration, removal of impurities and gases in liquid metal, precision filtration, such as sugar, brewing and water purification, gas separation and filtration, removal of radioactive contaminants, fluidization separators and cell separators and so on.
4 Biomedical Materials
Porous bioceramics have good biocompatibility, good bone induction, stable physical and chemical properties, non-toxic side effects and are used to make biomedical materials. Porous hydroxyapatite is used in the manufacture of artificial dental materials, artificial bones and so on.
5 Aerospace through-wave materials
Porous ceramics with closed-pore structure have the advantages of low dielectric loss, low density and lower absorption rate of radar on the unit thickness than other ceramic materials, which makes it have good potential in the application of aerospace materials which require high penetration wave.
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