Silicon Carbide (SiC) is an outstanding non-oxide ceramic material with exceptional mechanical and thermal properties, including high hardness, low density, corrosion resistance and temperature strength. As such, SiC makes for an ideal material in harsh environments such as wear resistant applications as well as for use in refractories, ceramics and pumps.
– Preparation
Silicon carbide boasts a Mohs hardness rating of 9.5, making it one of the hardest materials available today. This hardness allows silicon carbide to be utilized in numerous industrial applications including metallurgical machinery and microelectronic devices. Furthermore, silicon carbide offers excellent chemical stability, oxidation resistance thermal shock resistance as well as high-temperature strength.
To create silicon carbide ceramic, the material is first ground into a fine powder. Next, this powder is combined with non-oxide sintering aid (binder) to form a paste before being compacted by extrusion or cold isostatic pressing into a shape and compressed further for shaping purposes. Finally, this finished product can then be used as raw material in further processing applications.
Silicon carbide ceramic can be modified using advanced preparation techniques to display better mechanical properties and higher performance in multiple applications, such as armour systems. Ballistic testing performed against 7.62 x 54 mm R B32 AP projectiles demonstrated its superior impact resistance compared to alumina ceramic materials.
For optimal silicon carbide ceramic manufacturing, selecting raw material that contains a large proportion of alpha silicon with an even microstructure is key. Furthermore, any intergranular phase that could potentially cause grain boundary sliding must also be absent in this material.
– Sintering
Sintering is a method used to bind ceramic particles together without the use of glass development as glue, instead relying on decreasing free energy to cause adjacent particles to migrate and rearrange themselves more closely together, so they pack tighter together. Sintering takes place at temperatures high enough for densification without dismantling its crystallinity structure.
The present invention provides a method of producing silicon carbide ceramics via liquid phase sintering. A ceramic slurry made up of silicon carbide powder combined with other ingredients such as boron, beryllium or aluminium based sintering aids as well as polystyrene plasticising additive is created. After injection molding into parts for liquid phase sintering, sintered parts are then produced via liquid phase sintering.
Liquid phase sintering offers several advantages over conventional hot pressing and isostatic pressing methods, including lower temperatures for sintering, inhibiting grain growth and eliminating costly press dies for graphite pressing dies. Furthermore, liquid phase sintering can achieve high theoretical density levels, improve fracture toughness/crack strength properties as well as provide homogenousness throughout its product.
Once the slurry is formed into its desired workpiece, air bubbles can be trapped by applying partial vacuum and/or initiating polymerisation with polymerisation initiators. Once air bubbles have been trapped in the liquid state of molten metal or wax, the green body produced may then be poured into molds composed of metal, glass, plastic or wax as is known in the art. Vibratory forces may be applied during mold filling by way of vibratory bath or through application of an intermittent electrical current pulse.
– Casting
Silicon carbide ceramic is an outstanding nonoxide ceramic with excellent toughness, heat resistance and corrosion resistance properties that make it suitable for applications requiring high temperature performance, such as mechanical seals and pump parts. Furthermore, its excellent refractory properties and extremely hard surface rival those found only in diamond, cubic boron nitride and tungsten carbide; additionally this ceramic can be cast into multiple shapes and sizes to meet specific industry applications such as brake pads for consumer automobiles.
Casting silicon carbide may include slip casting as described by Fredriksson U.S. Pat. No. 2,964,823. In this technique, ceramic material is cast into a plaster of paris mold with water miscible curable resin in order to cure. After curing is complete, heat treatment of the cast body carbonizes any remaining resin before being heated further to siliconize if necessary.
Gel injection molding is another near net size molding method that makes processing green bodies simpler, saving both time and money when preparing them for sintering. This involves infiltrating a compact composed of SiC powder mixed with organosilicon binder binders such as organosilicon binders into organosilicon molds before baking the paste resulting from this infiltration, before molding, baking again with additional additives such as boron, beryllium or aluminum being added as necessary, before sintered part is created resulting in finished ceramic part ready for production.
– Painting
IPS offers sintered silicon carbide (SSiC) ceramic rods, sheets, discs and custom parts made of Hexoloy SIX material with Mohs hardness of 9.5 and Knoop hardness between 2670 to 2815 kg/mm for numerous applications including refractory linings, ceramic fiber insulation thermal tubes in industrial furnaces wear parts for pumps and rocket engines as well as semiconductor substrates of light-emitting diodes (LED).
This material offers exceptional chemical stability, thermal shock resistance, mechanical strength and abrasion/erosion resistance at elevated temperatures. Furthermore, its low coefficient of thermal expansion and excellent radiation damage resistance make it an attractive alternative to metals and alloys in demanding environments like those found within petrochemical industries, metallurgical machinery production lines, microelectronic devices or aerospace applications.
Silicon carbide finds great application in ceramic glazes. Its carbon release helps reduce metallic oxides during oxidation firings and produces dramatic red hues easily (though fast firing may be required)! Silicon carbide glazes also work to produce hard surfaces with increased depth. Furthermore, glass may be coated with silicon carbide for scratch protection and thermal regulation – with various brands using various active chemical concentrations or resin formulas that serve the same function of protecting paint with some microns of silicon carbide coatings – all offering protection for paint!