The Secret Of How The Light Of Ceramic Grinding Balls Can Identify People
Mar 18, 2024
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Many surfaces of ceramic grinding balls are shiny, and some can even be used to identify people. What's the little secret inside?
In fact, the factor that determines whether the surface of a ceramic grinding ball is shiny is the flatness of the sphere; the smoother the sphere, the better the mirror effect; the rougher the sphere, the worse the mirror effect. The main factors that affect the flatness of the spherical surface are: the internal structure of the material and the degree of external processing of the spherical surface. Among them, spherical surface processing is easier to understand. For example, the spherical surface of a grinding ball just after sintering is matte, and the spherical surface may have a mirror effect only after polishing. The internal structure of the material includes: pores, grain size, liquid phase, etc. Their effects on the flatness of the spherical surface are as follows:
1. Stomata
Since the sintered ceramic grinding balls now generally have a high density and there are very few pores caused by sintering, the pores we talk about here usually refer to large defects caused by molding and other reasons.
For example, the powder materials used for rolling balls include airflow powder, spray dry powder, granulating powder, etc. They are essentially fake particles composed of countless single crystal grains. However, due to the different powder making processes and the different particle strengths of the powder, some false particles may not be completely crushed during use, resulting in the crystal grains not being completely close during the sintering process, resulting in defects such as large pores.
2. Grain size
When the types of raw materials are different, the degree of grinding of the raw materials by each manufacturer is different, and the formula and firing process are different, it will lead to different internal grain sizes of the sintered grinding balls. The finer the grains, the smoother the spherical surface; the coarser the grains, the more uneven the spherical surface, just like paving with stones and paving with sand.
The grains of zirconia grinding balls are mostly in the range of 0.3um-0.5um, and the grains of alumina grinding balls are mostly in the range of 1um-5um. The grains of zirconia are finer and the spherical surface has higher flatness, so the zirconia spherical surface is brighter than the alumina spherical surface.
3. Liquid phase
Taking alumina ceramics as an example, in general production, in order to reduce the sintering temperature of ceramics, some additives are added. Some of them are additives that can generate a liquid phase in high-alumina porcelain, such as kaolin, boronite, silica powder, etc., which can work with other additives to generate binary, ternary or more complex low-melting point eutectics. After adding an appropriate amount of additives, on the one hand, the sintering temperature of the ceramic can be reduced and the crystal grains can be made finer; on the other hand, the liquid phase formed will be like the asphalt paving the road, making the spherical surface smoother and naturally brighter.
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