4 Sintering Processes for Silicon Carbide

Making silicon carbide ceramic biscuits using selective laser sintering

Silicon carbide ceramic can be made by selective laser sintering method. The manufacturing process includes:

  1. Ceramic powder is mixed with a dispersing agent, silicon carbide ceramic grinding balls, and deionized water to obtain a slurry.
  2. A water-based thermosetting resin or thermosetting resin emulsion, a curing agent, and a defoaming agent is added to the slurry to obtain a ceramic slurry.
  3. Spray drying granulation on the ceramic slurry is carried out by a spray granulation tower.
  4. The obtained powder is screened, graded and placed in a selective laser sintering (SLS) equipment to produce a silicon carbide ceramic biscuit.

Refer to this patent for more information.

Avoiding corrosive buildups in sintering of silicon carbide

To avoid corrosive buildups in the sintering of silicon carbide, a process with the following steps is carried out:

  1. The first step is to wash silicon carbide powder with a solution of hydrofluoric acid, followed by rinsing in distilled water. This removes granules which have silicon dioxide shell.
  2. After that, the prepared silicon carbide powder undergoes gel-casting process. In this process the silicon carbide powder is mixed with water or a non-aqueous solvent, a dispersant, and gel-forming organic monomers to obtain a ceramic slurry.
  3. The ceramic slurry is then exposed to a partial vacuum to remove air from it.
  4. Next, a polymerization initiator is added to the ceramic slurry commencing a gel-forming reaction. It follows the step of pouring the ceramic slurry into a mold and casting the ceramic slurry into a desired workpiece shape. After that, heating the mold in a curing oven or setting the mold with a catalyst.
  5. Finally, removing a gel-cast part from the mold, drying the gel-cast part to remove the water or the non-aqueous solvent and obtain a dried cast ceramic part, firing the dried cast ceramic part in an oven at temperatures ranging from about 100°C to about 1600°C and sintering the dried cast ceramic part at temperatures ranging from about 1600°C to less than about 2200°C. These steps are carried out while maintaining pressure in the crucible by capping it and applying virbatory forces to the molten liquid.

Refer to this patent for more information.

Sinter silicon carbide coated carbon composites

A silicon carbide-coated carbon composite can be made by sintering a carbon base material followed by a chemical vapor deposition (CVD) process.

The surface of the sintered carbon base undergoes reaction with SiO gas in an atmosphere at a temperature of 1400°C to 1600°C and a pressure of 1 to 150 Pa to form silicon carbide. Thus, a silicon carbide-coated carbon base material is produced.

The total content of sintering aid is kept below 0.1% by weight.

Sintered silicon carbide has high relative density of 90% to 100%.

Refer to this patent for more information.

Manufacture of SiC-based anode for Li-ion batteries by sintering

SiC-based anode can be made by sintering silicon carbide with an interstitial material in conjunction with a graphene coating process.

The interstitial material can include silicon derived from milled silicon particulates.

Very fine graphite is co-milled in ethanol with the silicon carbide and silicon and form a nano size carbon coating on the silicon carbide and silicon. When sintered in a 10-5 or 10-6 torr vacuum at 1,400°C, to form a graphene coating on the silicon and silicon carbide.

The graphene coating precludes oxidation on the surface of the particle, which increases the electrical conductivity.

The graphene coating also enhances the Schottky effect and increases both the rate and total amount of lithiation.

Refer to this patent for more information.

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