What is the application prospect of porous Ceramic Filter Materials

Porous Ceramic Filter Materials are a kind of ceramic matrix composite material rich in pores. In addition to having the properties of high temperature resistance, corrosion resistance and non-aging of ceramic materials, porous ceramic filter materials also have excellent properties that other dense materials do not have, such as light weight, sound absorption, heat insulation, energy absorption and high specific surface area. These properties make porous ceramics have good applications in filtration and purification, catalyst loading, sound absorption, shock absorption, fire prevention and heat preservation. In terms of its thermal insulation performance, due to the low thermal conductivity of the ceramic itself, the gas filled in the porous structure greatly enhances the thermal insulation performance of the material, so that the porous ceramics can be used as high temperature insulation materials in construction, aerospace, storage, machinery and other fields, in a variety of buildings, engines, refrigerators, industrial kilns and other engineering applications are very suitable, It is an important functional material for heat preservation, heat insulation and cold preservation. So the study of porous ceramic insulation material has very important practical significance.

Porous ceramic materials

Insulation materials can be divided into high temperature insulation and low temperature insulation according to their specific purposes. High temperature insulation is to prevent the internal heat of the object from spreading out, improve the utilization of heat energy, or to keep the temperature of the object or container from falling. Low temperature insulation is designed to block the incoming heat from the outside world, thereby preventing the internal temperature of the object from rising. Porous ceramics have high melting point and are usually used as high temperature heat insulation materials. At present, porous ceramics have been widely used as heat insulation materials in traditional gas furnace and high temperature electric furnace at 1600℃. In Shenzhou spacecraft and Long March rockets, multi-layer insulation materials consisting of porous ceramic and metal insulation materials have been well applied. The space shuttle's insulated shell is made of vacuumized porous ceramics, the best insulation material in the world. The following Xiaobian will make a brief introduction to the important porous thermal insulation ceramic materials and their application fields.

Fiber porous ceramics

Ceramic fiber is a kind of traditional insulation materials, refractory excellent performance in one of the fiber light refractory material, the main chemical composition is aluminum silicate, structure has high porosity, porosity and specific surface area, etc.. The internal structure of ceramic fiber products is a porous structure composed of ceramic fiber and air. The characteristics of the microstructure are that both solid and gas phases exist in the form of continuous phases, solid substances exist in the form of fibers, and constitute a continuous phase skeleton, while the gas phase exists continuously in the framework gap of the fiber material. It is because of this structure that ceramic fiber has higher porosity, larger pore size and specific surface area, so that ceramic fiber has excellent heat insulation performance and small volume density.

SEM photos of porous Mullite fiber frame structure holes

Ceramic fiber insulation materials have been the first choice for missile and aerospace thermal protection systems due to their advantages of low density, low thermal conductivity and high thermal capacity. For example, the thermal insulation tile used for high speed spacecraft outer surface insulation is one of them.

Large particle sintered ceramics

With the development of modern industry, the ceramic industry and metallurgical industry produced more and more slag and ceramic waste, researchers to polishing waste slag, high temperature sand, low temperature sand, clay as raw materials to prepare environmental protection porous ceramic materials with heat insulation function, realize the real sense of waste into treasure. The porous ceramics prepared by this method have lower thermal insulation and strength than other ceramics, but the process is simple, the raw materials are abundant and the price is low, and some industrial wastes can be disposed of environmentally friendly.

An environmentally friendly porous ceramic material prepared with polishing slag, Hunan stone powder, b5 sand and intermediate spherical clay

Due to the rapid consumption of natural resources, people are also trying to convert waste materials into industrial production, such as the use of quartz sand and other preparation of non-clay hollow brick, which can not only achieve the purpose of saving raw materials, but also energy saving and emission reduction. At present, 70~80% of the wall materials in Europe and the United States have become porous bricks. The application of porous insulation materials can make the house warm in winter and cool in summer, which can reduce the use of heating and air conditioning and other electrical appliances to a great extent, and indirectly save energy.

Porous thermal barrier ceramic coating

Thermal barrier ceramic coating is the most effective thermal insulation material for aircraft engine at present. The most mature technology is yttrium oxide stabilized zirconia coating (PYSZ) TBCs. Thermal barrier coating has been widely used in spacecraft and turbine hot end parts, which protect the hot end parts by reducing the temperature of metal matrix. In order to further improve the thermal insulation performance of thermal barrier coating, the thermal barrier coating is prepared into porous form. Some researchers studied the effect of temperature and porosity on thermal conductivity and confirmed that the introduction of porosity can improve the thermal insulation performance of thermal barrier coating.

Porous ceramics have excellent heat insulation performance, high temperature bearing capacity, has incomparable advantages in the field of high temperature heat insulation, especially in the field of aerospace thermal protection with harsh environment and harsh quality requirements, so porous ceramics used as heat insulation materials has a very good development prospect. At present, researchers have developed a variety of porous ceramic insulation materials and put them into use in production practice, but there are still some limitations and deficiencies in the development of porous ceramic insulation materials, such as the mechanism and control conditions of various thermal conductivity processes of materials have not been fully mastered, and the control factors of porous ceramic insulation performance can not be completely mastered. Therefore, it restricts the wider application of porous ceramics. In the future, relevant researchers should further explore the thermal conductivity mechanism of porous materials, and industrialization of the preparation of porous materials is the development direction of porous ceramics.