Count The Functional Applications Of Carbon Fiber

 

The biggest feature of carbon fiber is its high specific strength and high specific modulus. Most carbon fiber composite materials use this property of carbon fiber. In composite materials, carbon fiber is compounded with plastic, ceramic, metal and even carbon matrix. The matrix material plays the role of transferring load in composite materials, and it transfers external force to carbon fiber. Carbon fiber plays the role of bearing load in composite materials, so the destruction of composite materials must first break the carbon fiber.

 

This is our common carbon fiber composite material. In addition to high specific strength, carbon fiber also has high temperature resistance, corrosion resistance, soft and easy to weave, small thermal expansion coefficient, and easy conductivity. Although the application of these properties of carbon fiber is not as good as structural materials, it has also formed certain special products. This article is a brief introduction to this type of application.

 

As A Thermal Insulation Material

Isn’t carbon fiber high in thermal conductivity? How can it be used as a thermal insulation material? This starts with the way heat is transferred. There are three ways of heat transfer: heat transfer, convection, and thermal radiation. Heat transfer is the contact between objects of different temperatures, and heat is transferred from the high temperature object to the low temperature object. Convection is the transfer of heat through fluid flow. Thermal radiation is the transfer of heat to another object in the form of radiation waves.

 

The carbon fiber is needled into felt, which becomes a loose and porous carbon fiber aggregate. The friction between the fibers maintains the shape of the felt body. The fibers are overlapped together, which is a point contact, which greatly reduces the heat transferred through the solid heat transfer path. When the temperature is above 800℃, as the radiation intensity increases, thermal radiation becomes the main form of heat transfer. The radiation wave is constantly reflected between the fibers and dissipated inside the felt body, thereby achieving the effect of heat insulation.

 

At present, the carbon fiber used as insulation material is also divided into three types: viscose-based, polyacrylonitrile-based, and asphalt-based. Polyacrylonitrile-based raw materials are cheap and the production process is simple. Many domestic companies are using this type of carbon felt, but after high-temperature treatment, this type of carbon felt is brittle and prone to broken fiber scraps, which is harmful to the furnace environment and human health. Therefore, foreign companies rarely use polyacrylonitrile-based carbon felt.

 

Viscose-based carbon fiber is not easy to graphitize during high-temperature treatment, so the heat transferred through the solid is very small. Under the same conditions, the thermal insulation effect is also the best of the three materials. However, the carbon yield in the production process of viscose-based carbon fiber is relatively low, and even 10 kg of raw silk can produce 1 kg of viscose-based carbon fiber, so additives are needed to increase the carbon yield, which will produce other elements. Residue, but now many companies can also make it very pure. Asphalt-based carbon fiber is easy to graphitize, so the purity can be improved very well.

 

Activated Carbon Fiber

Write down the title, careful friends may see a “typo”, in fact, it is mainly distinguished from the difference between carbon and charcoal, which will be discussed later. As we all know, activated carbon mainly uses the principle of solid surface adsorption.

 

Why does the solid surface have an adsorption effect? ​​This is because there are other atoms around the atoms inside the solid, so it is in a state of equilibrium, but there are no atoms on the surface atoms, so the surface atoms are in a non-equilibrium state, so it has a tendency to adsorb other atoms to reach a state of equilibrium.

 

The larger the specific surface area of ​​activated carbon, the more atoms on the surface, and the higher the adsorption rate. However, there is also an adsorption efficiency issue. If impurities are to be adsorbed on the surface of solid activated carbon, they need to diffuse, and the micropores on the surface of activated carbon can promote the migration of adsorbed atoms.

 

Activated carbon fiber is a fibrous activated carbon. Its characteristic is that there are many micropores on the fiber surface, which can drive the adsorbed atoms to diffuse to the solid surface of activated carbon. The pore structure of traditional activated carbon is mainly composed of macropores, mesopores, and micropores. Most of the micropores are in mesopores and macropores, which increases the adsorption path, making the adsorption efficiency not as good as that of activated carbon fiber.

 

Activated carbon fiber has been widely used, such as air purifier filters, mask filters, gas masks, medical accessories, etc., in precious metal extraction, organic solvent recovery, water pollution treatment, air pollution treatment and many other aspects. With the further implementation of national environmental protection policies, this type of carbon fiber application will become more and more common.

 

Carbon Fiber Sealing Material

The packing is usually woven from softer linear objects, and the cross-sectional area is usually square or rectangular, and the round strips are filled in the sealing cavity to achieve sealing. In some corrosive or high-temperature environments, carbon fiber packing has its own advantages.

 

Mainly use carbon fiber for no creep, good fatigue resistance, small thermal expansion coefficient, good corrosion resistance, and good thermal conductivity. Mainly used in high temperature, high pressure and wear-resistant working conditions.

 

Carbon Fiber Heating Material

I remember when I first arrived at the Carbon Fiber Center, both air conditioners broke down in winter. The instructor temporarily took a few carbon fiber heating tubes and connected them online. The room suddenly became much warmer and very comfortable. Carbon fiber heating materials use the electrical conductivity and thermal radiation properties of carbon fiber.

 

At present, the floor heating and bathroom heaters with the concept of carbon fiber are very popular, and it is also a hot spot for the use of carbon fiber. Carbon fiber heating materials have the advantages of long life, high thermal efficiency, and good radiation waves for the body. The most important thing is that the thermal radiation waves emitted by carbon fiber will not cause the skin to lose moisture while heating the body, and there is no dry feeling of skin after using traditional bathroom heaters.

 

Carbon Fiber Powder Conductive Material

This type of material is widely used, but the characteristics are all based on the easy conductivity of carbon fiber. The carbon fiber is cut and ground to obtain cylindrical particles of equal length. It retains many excellent properties of carbon fiber, and has a small shape, a pure surface, a large specific surface area, and is easily wetted and dispersed by resin. It has been widely used in conductive additives for positive and negative electrode materials of nickel-hydrogen and nickel-cadmium batteries, electronic chips, conductive plates, conductive floors, electronic machinery, anti-static industry (coatings, floors, paints, inks), anti-static filter elements, national defense and military industry, building insulation, chemical food coarse-effect filtration, motorcycle mufflers, paint drying room air filtration, polytetrafluoroethylene and other fields.