The characteristics and applications of several new thermal insulation materials that have emerged in recent years.
1. Aerogel thermal insulation materials
Aerogel super thermal insulation material has nano-level pores and framework particles, and its thermal insulation performance is very superior, and its thermal conductivity generally does not exceed 0.1W/(m·K), which has caused extensive research by refractories. Aerogel is a gel material whose dispersion medium is gas. Because of its translucent color and ultra-light weight, it is also called "solid smoke". Because aerogel has nano-level pores, this structure can be significant Reduce the heat conduction and heat convection of gas molecules in the material. At the same time, the nano-scale framework particles can significantly reduce the solid heat conduction. Therefore, the thermal conductivity of the prepared insulation material is usually lower than that of air, and it also has a relatively small density and elastic modulus. , Is an ideal light-weight insulation material. So far, many kinds of aerogels have been developed, including single-phase aerogels, multi-phase aerogels, organic aerogels and carbon aerogels. American Cabot Company used the supercritical drying method to successfully prepare nano-scale SiO2 aerogels by retaining the arrangement structure of SiO2 particles in their gel state. The prepared SiO2 aerogel has a sponge-like porous network structure, the size of its pores and framework particles is mostly below 100nm, the thermal conductivity is only 0.05W/(m·K), and the heat insulation effect is excellent.
2. Vacuum insulation materials
Vacuum insulation materials were first proposed by the British scholar Dewar in 1893. At that time, they were mainly used as insulation materials for storing liquid air containers. Later, vacuum insulation technology was used in aerospace, special alloy smelting, electronic industry and other scientific and technological fields. Obtained rapid development. Vacuum insulation materials, also called high-temperature multilayer insulation materials, are mainly composed of low emissivity metal foils and low thermal conductivity interlayer materials. Since the heat transfer can be effectively prevented under vacuum conditions, the thermal conductivity of this material is much lower than that of ordinary insulating materials. Wen Shulin and others have successfully developed a high-efficiency heat insulation material for high-temperature vacuum, which is composed of aluminum foil or nickel foil and quartz fiber mats. With the further research on vacuum insulation materials, the preparation of closed vacuum pore structure materials has become one of the important research directions of the majority of workers.
3. Carbon thermal insulation materials
The new carbon thermal insulation material has excellent properties such as low thermal conductivity, low heat capacity, low bulk density, low linear expansion coefficient, high temperature resistance, good thermal shock resistance, strong chemical resistance, high purity and no pollution, etc., and is widely used Used in high-temperature places such as vacuum resistance furnaces, induction furnaces, sintering furnaces, and heat treatment furnaces. Its good heat insulation effect can save 30~70% of energy. In 2010, Japan Carbon Corporation developed a carbon fiber thermal insulation material with high thermal insulation performance, which not only has a good thermal insulation effect, but also has high strength and precise dimensions. Carbon heat insulation materials have excellent performance and are suitable for various production equipment such as ceramic sintering, metal heat treatment, rare earth magnetic materials manufacturing, and solar cell silicon casting furnaces.
4. Composite thermal insulation materials
Composite thermal insulation materials have the excellent performance of each single material, so they are widely used in various fields. After fully understanding the respective characteristics of the materials, the composite thermal insulation materials can be organically combined according to the needs. The purpose is to make full use of the advantages of each material to make the overall product perform best in all aspects. Composite thermal insulation materials are divided into two categories: inorganic and inorganic composite (also called composite silicate) and foam and silicate composite. The main types of inorganic and inorganic composite thermal insulation materials include magnesium silicate, silicon-magnesium-aluminum, rare earth composite thermal insulation materials, etc., and their thermal insulation performance and strength are significantly better than single aluminum, magnesium, and silicon thermal insulation materials. Sepiolite insulation material, as an outstanding one among inorganic and inorganic composite insulation materials, has excellent thermal insulation performance and application effect, and has attracted people's attention. Foamed plastic and silicate composite thermal insulation materials not only have good thermal insulation performance, but are also cheap and simple in production technology. They are widely used in chemical production, housing construction, food industry, energy transmission and other fields. Long Zhiqin and others used polystyrene foam, ordinary Portland cement, and fly ash to prepare foam and silicate composite thermal insulation boards, which not only have excellent thermal insulation performance, but also have waterproof functions.