In industrial production, two materials, silica fume and wollastonite, are often used, especially in the preparation of refractory materials, silica fume and wollastonite powder may be used, but except for their almost identical names, they are Even the appearance is very similar, so what is the difference between silica fume and wollastonite? How to distinguish them?
The difference between silica fume and wollastonite
1. Different production methods
- Silica fume: Silica fume, also known as microsilica fume, is a by-product of industrial ferrosilicon smelting. Ferrosilicon smelting will release a large amount of flue gas, which is mixed with a large amount of free silica and other elements. After industrial After the dust is captured by the dust removal equipment, it is condensed together to form silica fume.
- Wollastonite: Wollastonite is actually a calcium silicate mineral, which is mainly used in industrial production in the form of powder after mining.
2. Different physical and chemical properties
- Silica fume: The chemical composition of silica fume is mainly SiO2, the content is 85% to 96%, and the rest is a small amount of iron oxide, aluminum oxide, calcium oxide, sulfur oxide, sodium oxide (potassium) and the content of which does not exceed 2%. carbon. Particles with a fineness of less than 1 μm account for more than 80% of silica fume, the average particle size is 0.1-0.3 μm, and the specific surface area is 20-28m²/g.
- Wollastonite: The chemical composition of wollastonite is mainly CaO and SiO2, the contents are 48.3% and 51.7% respectively, and Ca is often replaced by Fe, Mg, Mn, Ti, Sr ions to form isomorphs. The fineness of powder particles varies according to the equipment used in the grinding process. The product fineness is between 4 μm and 50 μm. The main reference is the needle-shaped ultrafine powder of wollastonite, and the particle length-diameter ratio is better between 8 and 12.
3. Different effects
- Silica fume: The main function of silica fume is to fill the pores between other material particles. The dosage is small. It is mainly used as an admixture to form a gel with hydration products, thereby improving the compression resistance, flexural resistance, impermeability, and Impact resistance, corrosion resistance and wear resistance.
- Wollastonite: Wollastonite powder itself has a hardness of 4.5~5.0. It is mainly used as a raw material or filler for cement, rubber, plastic, etc., as a gas filter material, heat insulation material, or as a co-solvent for metallurgy.
How to distinguish between silica fume and wollastonite
The way to distinguish silica fume and wollastonite is mainly to observe their appearance. Although they are all white or off-white powders, the specific states are still different.
- There are many colors of silica fume, but it is difficult to distinguish white and off-white from wollastonite, but the fineness of silica fume is very fine, which can be distinguished directly by the naked eye and the touch of fingers.
- The particles of silica fume are mainly round particles, which are relatively smooth, while the particles of wollastonite powder are relatively coarse, mainly long needle-shaped, fiber crystal-like particles, and the touch is rough.
- The color of silica fume is dark, while the surface of wollastonite powder has glass luster and high whiteness.
It can be seen from the above content that the difference between silica fume and wollastonite is still quite large. The point that is difficult to distinguish lies in the color and name of the appearance. Although it may be used in a certain material at the same time, its role is also obvious. It’s different, I hope you don’t get confused when using it.
