Introdução

Silicon carbide is one of the most used advanced ceramic materials today. The impressive hardness and high thermal conductivity are some of the outstanding properties that have led to an increased demand and production of these SiC materials. With recent technology, you can produce silicon carbide industrially by pressureless sintering of SiC powder or a reaction bonded process. Today’s article will give you an overview of pressureless sintered silicon carbide materials, the properties, applications, and how they compare to silicon carbide and other materials. You will also learn how reaction sintering differs from pressureless sintering methods of SiC production. Lastly, you will see the current market trends of pressureless sintered silicon carbide.

Sintered Silicon Carbide

Sintered Silicon Carbide (SSIC) is a type of silicon carbide material that you can get from sintering highly purified fine silicon carbide powder together into a solid ceramic material. You can do this industrially under high heat, temperature, and pressure. SSIC materials have great compressive strength and hardness, high thermal conductivity, and strong resistance to chemicals and rusting. Applications that demand high-dimensional precision, high temperatures, and thermal stability benefit from the use of these SSIC materials. Pressureless sintered silicon carbide and reaction sintered silicon carbide are the major variations of SSIC materials.

What is Pressureless Sintered Silicon Carbide?

Pressureless sintered silicon carbide is a grade of Sintered SiC material produced from sintering ultra-fine, high purity silicon carbide powder in a vacuum atmosphere at atmospheric pressure and high temperatures ranging from 1980°C - 2200°C. As the name implies, no external pressure is needed to produce these materials. Sometimes, while pressing, you can use sintering additives like Alumina (Al2O3) and Boron Carbide (B4C) to fuse the SiC powder into solid ceramic materials with high thermal stability. Pressureless sintering makes the ceramic materials to have a very dense body because during production, the density is increased above 95% of the theoretical density.

Properties of Pressureless Sintered Silicon Carbide

Here are some of the unique properties of Pressureless Sintered SiC materials:

• It has high hardness

• A high melting point of 3103K

• Density of 3.21g/cm³

• High resistance to corrosion and chemical substances.

• High thermal conductivity of above 200 Wm-1k-1

• A large elastic modulus reaching 410 GPa

• The ability to withstand high temperatures reaching 1,600°C

• High compressive strength of about 3000 MPa

• SiC purity value of 99%

• A porosity of less than 0.2%

• Vickers Hardness of 2,500HVO.5

• Thermal expansion coefficient of 4×10-6i°C

Comparison Between Reaction Sintering and Pressureless Sintering of Silicon Carbide

There are two major ways you can produce Sintered Silicon Carbide materials industrially. They are: reaction sintering and pressureless sintering of silicon carbide materials.

Reaction Sintering of Silicon Carbide

You can produce this type of SSIC material by mixing graphite and fine particles of alpha-SiC in a predetermined amount. Then heat it to 1650°C, the high temperatures would make the alpha-SiC react with the carbon in the graphite body, forming beta SiC. Then silicon is infiltrated completely, and the remaining pores are filled to make a reaction sintered SSIC material. This process is faster and reduces cost compared to the pressureless SSIC materials. Low sintering temperatures are all that is needed to produce these reaction SSIC materials. Although the reaction sintering process is effective for making large-sized materials, the materials produced usually do not have an even density. Some of them even crack after final production. The reaction sintering process is also not environmentally friendly. Gas and liquid permeate it more compared to pressureless sintered SSIC due to the large porosity of this reaction sintered SSIC materials.

Pressureless Sintering of Silicon Carbide

You can manufacture SSIC materials through pressureless Sintering, which involves heating high-purity, ultra-fine SiC powders into solid materiais cerâmicos. This can be done in two ways: Solid Phase Sintering and Liquid Phase Sintering:

Solid Phase Sintering

In this type of sintering, you have two solid solutions, which we can refer to as additives, Boron and Carbon, for instance. You can use Boron to decrease the brain boundary energy of the SiC interface while carbon removes Silicon Dioxide (Silica Carbide) at the interface where you have SiC, which increases the surface energy. Solid phase Sintering uses other additives like Alumina (Al2O3), Boron Nitride (BN), or a combination of Boron Carbide and Alumina.

Sinterização em fase líquida

In this phase, you can use different eutectic oxides like Y2O3-Al2O3 as an additive or one element. This phase works better with low temperatures. The densification of SiC is obtained through the movement of the SiC particles, the diffusion and transfer of mass, which is generated by the low eutectic point.

Some manufacturers prefer the liquid phase sintering method to the solid phase sintering because it has good thermal stability, requires fewer raw materials, and lower cost of production.

Overall, pressureless sintering of silicon carbide gives superior SSIC materials with higher purity and better density. This means it can be utilized by industries that produce high-temperature electronic devices, or even in applications that demand high precision and thermal stability. However, if you want to save time and reduce your cost of production, you can opt for the reaction sintering process of producing sintered SiC. So your choice of these two depends on what you intend to do, and how you want your application to be done.

Comparison Between Sintered Silicon Carbide and Silicon Carbide

Sintered silicon carbide (SSIC) is a type of SiC ceramic material produced from sintering ultra-fine and high-purity SiC particles into hard and super-solid ceramic materials. Silicon Carbide (SiC), on the other hand, is an advanced ceramic material made of Silicon and Carbide. SiC exists in the artificial form, carborundum, or the natural form, moissanite. Now, these two elements (Silicon and carbon) are chemically combined in high-tech industries under intense heat to produce ceramic materials with high compressive strength, hardness, thermal stability, and resistance to corrosion and chemicals. You can use SiC materials mostly for the production of abrasives, tough, hard-faced materials like ceramic heat sinks, machine spare parts, aerospace and automobile engine parts, etc.

SSIC materials are generally superior to silicon carbide materials because these materials have become more strengthened by intense heat, their porosity has been reduced, while their electrical and thermal conductivity has been greatly enhanced compared to that of silicon carbide components.

Applications of Pressureless Sintered Silicon Carbide

Pressureless sintered silicon carbide has so many applications in various sectors today. Some of them are:

Manufacturing Industry

You can use these high-performance pressureless SSIC materials to produce seal rings, slide bearings, and tough wear-resistant parts in heavy industrial machines.

Indústria Elétrica

In today’s electrical industry, you can use these SSIC ceramic materials to make semiconductors, weapons and artillery, high temperature power electronics and equipment due to their excellent compressive strength and ability to stand tough in unfavourable conditions.

Metallurgy Industry

You can use pressureless sintered silicon carbide in the production of metallic instruments and equipment that require quick transfer of heat or electrical conductivity. Materials such as ceramic heat sinks, combustion nozzles, kiln lining components, etc.

Glass industry

Materials made of glass, like windows, car windshields, side mirrors, and optical instruments, can all be made from pressureless sintered SiC material.

Current Market Trends and Market Value of Pressureless Sintered Silicon Carbide

The Pressureless sintered silicon carbide market is growing at an astonishing rate if you check world economics. Wondering why?, It’s simply because currently the market doesn’t have any better substitutes for silicon carbide ceramics and its various grade types, which include the pressureless SSIC materials.

In 2023, the global pressureless sintered SiC market was valued at $2.3 billion, with a large market size of over $3 billion. So if you want to invest, know that the Compound Annual Growth Rate (CAGR) is at 8.5% within the set period of 2024-2030, so expect the market value to hit $3.8 billion by 2030.

Aqui em GGSCerâmica, we offer the best blend of pressureless sintered silicon carbide ceramics materials at affordable prices, just to meet your ceramics needs.

Perguntas frequentes

At what temperature does silicon carbide sinter?

Silicon Carbide sinters at temperatures ranging between 1950°C - 2200°C.

Do silicon carbide materials have any limitations?

Yes, because of their high strength, they tend to be very brittle and react poorly to high impact or mechanical shock.

What is the stiffness of SiC?

The stiffness of silicon carbide materials is about 440 GPa - 490 GPa. Indicating that it can maintain its original shape while under any form of mechanical stress.

Conclusão

Pressureless sintered silicon carbide is a low-cost yet effective grade of silicon carbide ceramic material. With these improved mechanical properties, ultra-high purity, great density, and diverse applications in various sectors, it’s definitely hitting greater heights with innovations in the near future. Watch out for these  silicon carbide materials and product.