Silicon specialties for advanced technical ceramics

Advanced materials to meet very specific needs

Silicon is used by manufacturers of advanced technical ceramics to produce materials for applications with specific features, in particular resistance to abrasion and extreme heat. These are mainly based on combinations of silicon carbide or silicon nitride in different formats.

These applications include ceramic materials and coatings for harsh environments. The features of these advanced technical ceramics include:

• Thermal stability
• Thermal expansion
• Resistance to thermal shock
• Thermal conductivity

In this article, we look at a few of the most representative silicon carbide or silicon nitride solutions. This overview is not intended to cover all applications of silicon in advanced ceramics and so, if you require more information for your specific applications or if you need more detailed information about the products we offer, please contact us.

Key features of bonded silicon carbides

Silicon and carbon are combined at elevated temperatures to create a reaction that forms the bonding of the structure to produce silicon carbide which, is very hard and enables the production of high-strength ceramic materials.

Silicon carbide structures can also be produced by mixing silicon carbide powder, silicon powder and a carbon containing compounds to achieve the required features for a wide range of applications. In this application it is typical to use smaller silicon particles.

Elkem Silicon provides several different silicon grades, including:

• Silgrain® HQ MC
• Silgrain® CG MC
• Silgrain® XC MC

The silicon infiltration process to produce silicon carbide

Carbon structures and shapes can also be produced by silicon infiltration, causing a reaction to take place between the liquid silicon and the solid carbon to produce silicon carbide. The infiltration process is carried out by melting the silicon in a vacuum furnace, which means that it is important to make sure the silicon melts easily and contains a low amount of fine particles. The requirements for the silicon to be used depend strongly on the process equipment and the required properties of the final product. Elkem provides several qualities or grades that have been specially developed for this application.

Products typically used for this application include:

• Silgrain® HQ 0,2-0,8
• Silgrain® CG 0,2-0,8
• Si-Tec®

The production of silicon nitride-bonded silicon carbide

Silicon carbide structures can also be produced by mixing silicon carbide powder and silicon powder in a water-based slurry.

The slurry is shaped using a slip casting method and dried to remove water. The silicon particles react with nitrogen at elevated temperatures and the formed silicon nitride bonds the structure. Elkem produces different grades for this application.

Products used for this application include:

• Silgrain® XO MC
• Silgrain® CG MC

Key features of silicon nitride

Pure silicon nitride is produced by a reaction between silicon powder with nitrogen at elevated temperatures. Due to the large range of purity requirements, Elkem Silicon has developed several products suited for these applications, supplying both ready-sized silicon powders and silicon that can be resized for the silicon nitride to be produced.

Product used for this application include:

• Silgrain® HQ 0,2-0,8
• Silgrain® CG 0,2-0,8
• Silgrain® HQ MC
• Silgrain® MC

Sustainability: the key to the future

As we develop new applications and continue to supply high-purity silicons for a great diversity of applications, we are also increasingly focused on an added dimension: achieving responsible and sustainable development. This begins with our own in-house environmental policies, based on using a maximum of renewable and low-carbon energies in our processes. It continues with the work we do with all our stakeholders, in implementing environmentally and socially responsible policies.

As demonstrated in this article, we offer a great variety of purities and sizes and so we invite you to please contact us! Our experts are always available to support you, discuss technical information and processing issues and provide samples and quotes.