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Silica

This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Silica is a new kind of clay discovered in the early 1980s in China Non-metallic minerals It is a mineral aggregate mainly composed of quartz and containing certain clay.^[1] Because it is similar to diatomite, it is easy to be mistaken as diatomite, but it is not biogenic. It does not contain the amorphous opal of diatomite remains, nor does it have the unique microporous structure unique to diatomite.

Chinese name: Silica
Foreign name: silica

Alias: Silica
Main components: silicon dioxide

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seven Development and utilization

essential information

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Silica is a new type Industrial minerals The raw material is mainly composed of quartz, containing a small amount of clay minerals. The rock structure is loose, with natural fine particles. After simple processing, micro powder products can be obtained. Because its main mineral composition is α－ Quartz is easy to be mixed with powdered quartz, but its particle size is finer, and it must contain clay minerals rather than pure α－ Quartz, so Al two O three The content is relatively high, with certain cohesiveness and plasticity. Some can be rolled into clay balls, and some plasticity indicators reach 3.48. These characteristics are not found in powdered quartz.^[2]

Physicochemical properties

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Chemical formula: SiO two

Mesh: 1000-3000

Molecular weight: 60.09

Density: 2.2 ～ 2.66 (g/cm three ）

Melting point: 1670 ℃

PH value: 5.5-7.5^[2]

Ore characteristics

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The appearance characteristics of silica are soft and hard. Among them, soft is the most common, some are powder, some are soil and adobe, and the texture is loose

It is soft, fragile, delicate, light, porous, and highly absorbent. After being sealed with wax, it can float on the water for a long time, and bubbles will appear when it is put into the water. The sedimentation is slow and gradually disintegrates into natural fineness. Hard silica, in relatively hard block shape, with porcelain fracture, looks like quicklime. Silica is generally grayish white, yellowish gray, yellow white, yellow brown and other colors, and light red when mixed with more impurities.

chemical composition

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The main component of silica is SiO 2， Next is AI two O 3、 Fe two O three And volatile matter 。 CaO、MgO、K two O、Na two The content of O is not high. SiO two And AI two O three There is obvious growth and decline relationship. Where SiO two Below 90%, AI two O three The content is higher; Where SiO two Over 90%, AI two O three The content is very low.

mineral composition

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The mineral composition of silica is relatively simple, and the main minerals are α－ Quartz, clay minerals and other impurity minerals are relatively few. α－ The quartz content is generally 60% - 80%, and some are higher. The mineral combination of silica is α－ Quartz+clay minerals. α－ Quartz>clay mineral 4.5-5.5 times. The clay mineral in the silica is mainly kaolinite, followed by illite and talc, and some montmorillonite and sepiolite. Ferrous mineral is the main factor of silica coloration.

Ore type

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As mentioned above, the main mineral composition of silica is α－ Quartz and clay minerals. Among them, α－ Quartz has many similarities and small differences, while clay minerals have both similarities and differences. Therefore, ore types are classified according to the types of clay minerals.

1. Kaolinite type silica

Mainly by α－ It is composed of quartz and kaolinite, α－ The content of quartz is generally 70% - 80%, and that of kaolinite is 13% - 16%, which is the main ore type of silica.

2. Illite type silica

Mainly by α－ Quartz and illite are two kinds of minerals with a certain amount of kaolinite.

3. Talc silica

Mainly by α－ Quartz and talc are two minerals.

4. High silica silica

The most prominent feature of this type of silica is that clay minerals are less than the three types mentioned above, so α－ The content of quartz is relatively high.

Development and utilization

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Silica as Industrial minerals Its development and utilization began in 1871 abroad. Although it was used to prepare porcelain clay and glaze in China in the 1950s, it was not successfully used because of unresolved technological problems. The real understanding of its industrial value and its development and utilization began in the 1980s. Its application fields are expanding and its consumption is increasing.

1. Make refractory materials;

2. Make investment coating;

3. Filling

(1) Make rubber filler;

(2) Make rubber imitation leather filler;

(3) Make plastic film filler;

(4) Make paint filler;

4. As cement admixture;

5. As raw material of calcium silicate;

6. Make electrical packing.

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