Role of Wollastonite in the Ceramic Industry

I. Lowering the firing temperature

The wollastonite powder has a significant effect of reducing the firing temperature in ceramic glaze materials. This is mainly due to its unique chemical composition and crystal structure. The main component of wollastonite is CaSiO₃. During the ceramic firing process, it can react with other components in the ceramic body to form a low-melting-point eutectic. For example, wollastonite and kaolin can react at temperatures ranging from 900 to 1000°C to form calcium feldspar, while the reaction temperature for kaolin to form mullite itself is usually between 1250 and 1350°C. The reduction of this reaction temperature enables the ceramics to achieve a good sintering state at a lower temperature.

In actual production, taking a certain ceramic factory as an example, before using wollastonite powder, the firing temperature of its traditional ceramic bodies was usually above 1200°C. However, after adding an appropriate amount (generally 5% - 20%, depending on the type of ceramics and the formula) of wollastonite powder to the raw materials, the firing temperature could be reduced to 1000 - 1100°C. The reduction of the firing temperature brings many benefits. On the one hand, it significantly shortens the firing time. The original firing cycle that might take 10 - 12 hours can now be shortened to 6 - 8 hours, improving production efficiency. On the other hand, fuel consumption is significantly reduced. According to statistics, fuel costs can be reduced by 20% - 30%, which means a significant cost saving for ceramic production enterprises.

II. Improving product performance

a. Enhancing mechanical properties: The needle-like or fibrous crystal structure of wollastonite powder can form an interwoven network structure in the ceramic body, just like the reinforcing effect of steel bars in concrete. This effectively improves the mechanical properties of ceramics. When ceramics are subjected to external forces, these interwoven crystal structures can disperse stress and prevent the expansion of cracks, thereby enhancing the flexural strength and impact resistance of ceramics. Studies have shown that adding an appropriate amount of silicon dioxide powder to the ceramic body can increase the flexural strength by 10% - 30%, and the impact resistance also shows a significant improvement, making ceramic products more durable and less prone to damage in daily use.

b. Reducing cracks and warping: The low thermal expansion coefficient of wollastonite powder is 6.5×10⁻⁶mm/(mm・℃) at 25 - 800°C. During the firing and cooling process of ceramics, this low expansion characteristic helps reduce the internal stress of the body caused by temperature changes, effectively reducing the probability of cracks and warping in ceramic products. For example, in the production of building ceramic tiles, the bodies with wollastonite powder added have better flatness after firing and higher dimensional stability, significantly improving the qualification rate of products and reducing the defective rate.

c. Increasing glaze surface gloss: Adding wollastonite powder to the glaze can significantly improve the gloss of the glaze surface. Wollastonite powder can improve the melting performance of the glaze, allowing the glaze to spread more uniformly on the surface of the ceramic body during firing, forming a smooth and flat glaze layer. At the same time, it can promote the growth and development of crystals in the glaze, optimizing the microstructure of the glaze layer, thereby enhancing the reflection and refraction ability of the glaze surface, making the glaze surface appear brighter and more lustrous. Some high-end ceramic tableware and art ceramics, by reasonably using wollastonite powder in the glaze, can increase the gloss of the glaze surface by 15% - 25%, enhancing the aesthetic appeal and added value of the products.

d. Increasing body strength: wollastonite powder in the ceramic body can also promote the densification of the body. During the firing process, the minerals such as calcium feldspar formed by the reaction of wollastonite with other components fill the pores in the body, making the body structure more compact, thereby increasing the strength of the body. This increase in strength is not only reflected in the physical properties of the ceramics, but also has a positive impact on their subsequent processing and use. For example, during the cutting and polishing processes of ceramics, a high-strength core is easier to process and is less prone to damage and other problems.