Application of wollastonite to ceramic industry

 

 

 

(1) Lower firing temperature: Conventional ceramic raw materials mainly include kaoline which is a silicon-aluminum system that is fired under high temperatures (1250-1350°C) and the crystalline phases generated mainly include mullite. When wollastonite is incorporated to make up a silicon-aluminum-calcium low eutectic system, the main crystalline phase is anorthite. The temperature at which anorthite is generated from wollastonite and kaolinite is 900-1000°C, which is much lower than that at which mullite is generated from kaolinite。

 

(2) Shorter firing duration: As wollastonite powder particles are acicular, the acicular wollastonite crystals become passages for moisture to escape and thus allow the base material to be dried and fired more quickly. This shortens the firing duration as well as improves the work efficiency。

 

(3) Higher base material and product strength: The interwoven structure of acicular wollastonite crystals in the base material, small linear expandability of wollastonite, low volumetric contraction when being fired and interwoven structure of residual wollastonite improve the mechanical strength of both the base material and the product which is helpful for making high-strength ceramics.。

 

(4) Less moisture expansion: As less or no alkali metal compound flux is need in wollastonite-containing ceramics, the product fired contains less alkali and therefore lower moisture absorption. This increases the durability of the product。

 

(5) Production of low dielectric insulation ceramics: Wollastonite is an ideal material for producing high-strength electric insulation ceramics for its low dielectric consumption, acicular crystalline structure and low moisture absorption of ceramics fired 。

 

(6) Fewer base material and glaze defects: Wollastonite contains no volatile gases itself, which mitigates defects in the base material and prevents the glazed surface from pinholes and pockets. The low expansion and the fusibility of wollastonite are favorable for producing low expansion low temperature glazes。

 

(7) Production of high-temperature high-strength ceramic moulds: Asbestos moulds are no longer suitable for mass production due to its low strength and low applied temperature. In our trial, the powder bulk density is smaller than 1 while the bulk porosity is more than 60%. It is an ideal material for producing high temperature high strength ceramic moulds。