Features and application of silicon powder

Silicon micropowder is made of natural quartz (SiO₂) or fused quartz (amorphous SiO₂ after high temperature melting and cooling of natural quartz) after crushing, ball milling (or vibration, jet milling), flotation, pickling purification, high-purity water treatment, etc. The micro powder processed by this technology. Silica powder is a non-toxic, odorless, non-polluting inorganic non-metallic material.

Physical and chemical properties

1.   The appearance of silica powder is gray or off-white powder, and its refractoriness is >1600°C. Bulk density: 200～250 kg/m³.

2.  The fineness of silica fume: more than 80% of the silica fume has a fineness of less than 1 micron, the average particle size is 0.1-0.3 microns, and the specific surface area is 20-28m²/g. Its fineness and specific surface area are about 80-100 times that of cement and 50-70 times that of fly ash. Common specifications for quartz powder are 400 mesh, 800 mesh, 1000 mesh, 1500 mesh and 2000 mesh.

3.  Particle morphology and mineral phase structure: During the formation process of silica fume, due to the effect of surface tension during the phase transition, amorphous spherical particles of amorphous phase are formed, and the surface is relatively smooth, and some have multiple circles. An agglomerate of spherical particles sticking together. It is a kind of volcanic ash material with large specific surface area and high activity. For materials mixed with silica fume, tiny spheres can play a lubricating effect.

Silica powder can fill the pores between cement particles, and at the same time form a gel with the hydration product, and react with the alkaline material magnesium oxide to form a gel. In cement-based concrete, mortar and refractory castables, mixing a proper amount of silica fume can play the following role:

1.   Significantly improve the compressive, flexural, impermeable, anti-corrosion, impact and wear resistance properties.

2.  It has the functions of retaining water, preventing segregation and bleeding, and greatly reducing the resistance of concrete pumping.

3.  Significantly prolong the service life of concrete. Especially in harsh environments such as chloride pollution erosion, sulfate erosion, and high humidity, the durability of concrete can be doubled or even several times higher.

4.  Significantly reduce the floor ash of sprayed concrete and castables, and increase the thickness of a single sprayed layer.

5.  It is a necessary component of high-strength concrete, and C150 concrete has been applied in engineering.

6.  It has about 5 times the effect of cement. It can reduce costs and improve durability when used in ordinary concrete and low-cement castables.

7.  Effectively prevent the occurrence of concrete alkali aggregate reaction.

8.  Improve the compactness of castable refractories. When coexisting with Al₂O₃, it is easier to form mullite phase, which increases its high-temperature strength and thermal shock resistance.

Application field

1.   Used in mortar and concrete: high-rise buildings, seaports, reservoirs and dams, water conservancy, culvert gates, railways, highways, bridges, subways, tunnels, airport runways, concrete pavements and coal mine tunnels, etc.

2.  In the material industry:

• High-grade, high-performance, low-cement refractory castables and prefabricated parts have a service life three times that of ordinary castables. The refractoriness is increased by about 100°C, and the high-temperature strength and thermal shock resistance are significantly improved. Has been widely used in: coke oven, ironmaking, steelmaking, steel rolling, non-ferrous metals, glass, ceramics and power generation industries.
• Large iron trenches and ladle materials, air-permeable bricks, smear repair materials, etc.
• Construction application of self-flowing refractory casting material and dry-wet spraying.
• Oxide-bonded silicon carbide products (ceramic kiln furniture, flame screens, etc.).
• High temperature type calcium silicate light-weight thermal insulation material.
• The corundum mullite push plate is used for the electric porcelain kiln.
• High temperature wear-resistant materials and products.
• Corundum and ceramic products.
• Sialon combined products.

At present, in addition to being widely used in castable refractories, it has also been widely used in fused and sintered refractories.

3.  New wall materials and facing materials:

• Polymer mortar, thermal insulation mortar and interface agent for wall insulation.
• Cement-based polymer waterproof material.
• Lightweight aggregate thermal insulation and energy-saving concrete and products.
• Putty powder processing for interior and exterior wall construction.

4.  Other uses:

• Silicate brick material.
• Production of water glass.
• Used as a reinforcing material for organic compounds. Because its composition is similar to that of white carbon black produced by gas phase method. It can be used as a filling and reinforcing material in polymer materials such as rubber, resin, paint, paint, unsaturated polyester, etc.
• Used as an anti-caking agent in the fertilizer industry.

Article source: China Powder Network