Ceramics

Ceramics are usually made by pressing and firing powders, but silicon chemistry offers another route: shape or coat a part with a polymer, then heat it until the polymer turns into ceramic. It also helps the conventional route, by binding and treating powders, and at the end of it, by protecting finished ceramic surfaces.

Polymer-derived ceramics

Polysilazanes contain silicon, nitrogen and carbon in the backbone. Heated in a controlled atmosphere, they lose their organic groups and convert into amorphous SiCN or, in nitrogen, silicon nitride. Because the precursor is a liquid, it can coat a surface, infiltrate a fibre preform or be moulded before it becomes ceramic. The ceramic yield — the share of the polymer that remains as ceramic — decides how much the part shrinks; vinyl-functional grades reach 80–90%. Disilazanes are also used to prepare Si–C–N and Si–B–C–N precursors.

Silica sources and binders

Tetraethyl orthosilicate and ethyl silicate 40 hydrolyse to silica. They bind refractory powders in precision-casting shells, form silica coatings by sol-gel, and are added in ceramic processing to improve bonding and surface finish.

Treating ceramic powders

Long-chain alkyl silanes make ceramic, alumina, kaolin and silicon carbide powders hydrophobic, so they disperse in resins and polymers without clumping. Silicone resins are the binders of ceramic and cookware coatings, and fluorosilane treatments make fired ceramic surfaces stain-resistant.

What to check

• Ceramic yield and shrinkage for polymer-derived parts.
• Pyrolysis atmosphere — air, nitrogen or argon — which decides the ceramic phase.
• Silica content of silicate binders, which sets how much silica the binder leaves.

For a recommendation for your formulation, a COA, an SDS or a quotation, contact our technical sales team.