High Temperature Resistant Polycrystalline Zirconia Ceramic Fiber

Zirconia ceramic fiber is a type of polycrystalline ceramic fiber. In addition to the common properties of ceramic fiber, it has the other excellent properties such as high melting point (2600℃), good high temperature resistance (2200℃), oxidization resistance, corrosion resistance  and low thermal conductivity. It plays a special role in the world of inorganic fibrous materials. It is a high performance insulation and corrosion resistant material. It has an important position in the thermal insulation field. 

Due to the low viscosity and high melting point of zirconia, it cannot be made by the melting method like ceramic fiber and high alumina ceramic fiber, but the precursor approach such as the carrier method, inorganic salt method and sol-gel method. 

 

Zirconia has excellent high temperature properties and can maintain the fibrous state even at 2480℃. It still has reelability at 1400℃. Zirconia fiber can be use above the melting point of alumina, up to 2200℃. It can not only be used in the oxidizing atmosphere but also the reducing atmosphere and vacuum. Zirconia fiber has a small vapor pressure at high temperature, 1.064×10-9Pa at 1370℃. It is the ideal insulation material in the vacuum. Zirconia has low thermal conductivity. The thermal conductivity of zirconia fiber is up to the density, like other most ceramic fiber. Its low density provides it the most effective insulation properties. 

 

Zirconia ceramic fiber has excellent corrosion resistance and does not react with corrosive chemicals. It has special corrosion resistance to 700℃ molten alkali metal chlorides and 230℃ alkali metal hydride solution. So, it seldom reacts with or pollutes the metals in a long-term use. Besides, zirconia fiber will not react in a short time when exposed to inorganic acids at the boiling point. 

 

Zirconia fiber products include zirconia fiber felt and rigid zirconia fiber products. According to the form, they can be used under different conditions. 

 

Zirconia fiber felt is a felt made of needled organic fiber felt as the precursor by impregnating in zirconium salt solution and heating. Its processing method is the same to that of zirconia fiber. It is mainly used in the insulation of crystal growth furnaces. It can maintain its form at the working temperature of the crystal growth furnaces, 1920℃. 

 

In the laser single crystal growth furnace, using zirconia fiber felts as insulation materials can reduce energy consumption, recover precious metal iridium, guarantee the stability of the temperature field in the crystal growth furnace and improve the optical quality and the finished product rate of the crystals.

 

Rigid zirconia ceramic fiber products are made of zirconia fiber which is cut into short fiber, then added into aqueous suspensions made of low temperature and high temperature binders and finally firing into finished products. The products include zirconia fiber board, cover, and other shaped products, which can be machined. The key for the production of zirconia fiber products is the preparation of zirconia fiber suspension solution and the design of the mold. In order to make the molded products have certain strength for self-supporting, low temperature binders are added. Water-soluble binders are better, such as polyvinyl alcohol and methyl cellulose. The products made of silica binder as the high temperature binder have a low working temperature, generally 1650 ℃.The working temperature of products made with zirconium sol  as the binder can reach up to 2000℃.Dispersants are added to the suspension solution to help the molding operation. The mold should be designed to have microporous structure which has small resistance. The thermal heat treatment temperature of zirconia fiber products is up to the working temperature of the products, with the linear shrinkage on reheating at the working temperature as the standard. 

 

Zirconia fiber has excellent high temperature resistance, corrosion resistance and oxidization resistance. It can be used in aviation industry, aerospace industry, chemical industry and metallurgy industry.