What is Silicon Carbide?

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1. Introduction to Silicon Carbide

1.1 What is Silicon Carbide?

The chemical formula of silicon carbide is SiC, it is an inorganic substance that is produced through a resistance furnace. By smelting three raw materials such as quartz sand, petroleum coke (or coal coke), and sawdust, silicon carbide can be obtained. 

silicon carbide

1.2 The Development History of Silicon Carbide

In 1891, American scientist Acheson serendipitously discovered a carbide while conducting experiments on electrically fused diamonds in the laboratory. 

In 1893, Acheson developed the industrial method for smelting silicon carbide, commonly known as the Acheson furnace, which has been in use ever since. This method involves using a resistance furnace with a carbon core to electrically heat a mixture of quartz (SiO2) and carbon, resulting in the production of silicon carbide. 

In 1905, silicon carbide was detected in meteorites for the first time. 

2. The Properties of Silicon Carbide

2.1 The Physical Properties of Silicon Carbide

Crystal Structure

Silicon carbide has a variety of crystal structures, including hexagonal (4H-SiC, 6H-SiC) and cubic (3C-SiC).

Hardness

Silicon carbide is known for its exceptional hardness, measuring 9.5 on the Mohs scale.

Melting Point

Silicon carbide has a very high melting point, approximately 2,730°C (4,946°F).

Thermal Conductivity

Silicon carbide has good thermal conductivity, making it an efficient conductor of heat.

2.2 The Chemical Properties of Silicon Carbide

Chemical Composition

The chemical formula of silicon carbide is SiC, with two basic elements of silicon (Si) and carbon (C).

Chemical Stability

Silicon carbide is highly chemically stable, especially in harsh environments and at high temperatures.

Antioxidant

Silicon carbide has excellent oxidation resistance.

3. The Manufacturing Process of Silicon Carbide

3.1 How is Silicon Carbide Made?

Acheson Process:

In 1891, Edward Acheson developed the Acheson process, which is regarded as the earliest method for making silicon carbide.

In this process, a mixture of high-purity silica (sand) and carbon (usually petroleum coke or anthracite) is heated in an electric resistance furnace at high temperatures (about 2000 to 2500 degrees Celsius).

The reaction results in the formation of silicon carbide crystals, which are then crushed and processed into the desired forms.

Carbothermal Reduction:

Carbothermal reduction involves heating a mixture of silica (SiO2) and carbon in an electric furnace.

The chemical reaction can be represented as SiO2 + 3C → SiC + 2CO.

This process is typically carried out at temperatures above 2000 degrees Celsius.

3.2 The Types of Silicon Carbide

There are two basic types of silicon carbide, black silicon carbide, and green silicon carbide, both of which belong to α- SiC.

①The SiC content of black silicon exceeds about 95%, and it has a better hardness than green silicon carbide. 

It is mostly used for processing materials with low tensile strength, such as glass, ceramics, stone, refractory materials, cast iron, and non-ferrous metals.

② Green silicon carbide contains over 97% SiC and has good self-sharpening properties. It is mostly used for processing hard alloys, titanium alloys, and optical glass, as well as for honing cylinder sleeves and precision grinding high-speed steel cutting tools.

3.3 The Advantages of Silicon Carbide

High Hardness * High Temperature Stability  * Wear Resistance * Chemical Inertness

High Thermal Conductivity * Electrical Conductivity * Abrasive Properties * High Cutting Efficiency

4. The Application of Silicon Carbide

The Application of Abrasive:

Silicon carbide is an artificially synthesized carbide with a molecular formula of SiC. It is only surpassed by diamonds in Mohs hardness.

Due to its high hardness, silicon carbide has high wear resistance and is widely used as an abrasive material in grinding wheels and other abrasive products.

The Application of Refractory:

SiC is widely used as a high-performance refractory material or as an additive to improve the performance of refractory materials, especially slag resistance and thermal shock stability, due to its advantages such as low thermal expansion coefficient, high thermal conductivity, high-temperature strength, good slag resistance, and the ability to form protective oxidation.

The Application of Functional Ceramic:

Silicon carbide ceramic materials have many excellent properties such as high-temperature resistance, good wear resistance, small thermal expansion coefficient, high hardness, thermal shock resistance, chemical corrosion resistance, etc., so they are widely used in automobiles, machinery, chemical industry, environmental protection, space technology, information electronics, energy, and other fields.

The Application of Metallurgical:

In the metallurgical industry, black silicon carbide is used in the production of iron and steel. It can be added to the molten metal to enhance its properties and improve the quality of the final product.

Silicon carbide is only surpassed by diamonds in Mohs hardness. It has great wear resistance and is an ideal material for wear-resistant pipelines, impellers, pump chambers, cyclones, and mining hopper linings. It has a wear resistance that is more than five times that of cast iron and rubber, and it is also one of the best materials for aviation flight runways.

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