how to make nitride bonded silicon carbide

nitride bonded silicon carbide is an advanced refractory material with superior thermal shock resistance and strong strength at higher temperatures, excellent creep resistance, and wear resistance properties. Furthermore, this advanced refractory has superior creep resistance as well as excellent creep resistance properties and provides outstanding creep resistance and creep resistance. In addition, this wear resistant material also features superior creep resistance properties.

This invention concerns an improved silicon nitride-bonded silicon carbide refractory. This improvement can be obtained by coating silicon carbide grains with zirconium oxide-generating compounds prior to shaping them into green refractory shapes.

Process

nitride bonded silicon carbide, commonly referred to as NBSiC, is a ceramic composite material created through bonding silicon carbide grains together with a nitride phase through nitridation - a process in which commercial silicon powder containing iron oxide or other impurities is heated in an atmosphere rich with nitrogen gas in order to nitride the silicon carbide grains and form an extremely durable and strong ceramic material.

NBSiC stands out among other materials due to its exceptional resistance against erosion and corrosion as well as thermal shock and oxidation, along with being easily formed into intricate shapes for use in various applications. Furthermore, its strength and creep resistance make it suitable for high temperature use.

NBSiC stands out amongst competing materials due to its ability to withstand heavy loads caused by vibration or impact, making it ideal for construction and mining applications. Unfortunately, its only limitation lies within its resistance to brittle cracking.

NBSiC can be produced in several ways, including gelcasting and sintering. Sintering involves firing a mixture of silicon carbide with other materials at very high temperatures in a furnace - generally 1600 degC - in order to produce a solid ceramic with a crystalline structure at relatively low production costs.

Composition

nitride bonded silicon carbide is an advanced refractory with wide industrial applications. This material exhibits excellent thermal shock resistance, alkali corrosion resistance, resistance to slag formation and oxidation resistance - key attributes in blast furnace environments for iron production. NbSC is commonly found on lower parts of stack, bellies, boshes and tuyeres of iron-making blast furnaces as well as copper incinerators and kiln furniture applications.

The nitride ceramic phase is created through the reaction of silicon atoms with nitrogen gas at high temperatures in an exothermic reaction that favors high nitrogen concentration in nitriding atmosphere. Additionally, this protection also shields SiC grains from chemical attacks while increasing thermal shock resistance.

Crystalline silicon carbide exists in various polymorphic forms that can be classified as either a-SiC or b-SiC. While a-SiC typically possesses a cubic structure, b-SiC contains hexagonal and rhombohedral noncubic structures.

Nitride-bonded silicon carbide displays excellent wear resistance in light soil conditions and excellent impact resistance, but its wear resistance diminishes considerably when used on heavy soil despite its hardness due to an increase in frictional forces that contribute to intensified wear. Furthermore, loose particles from heavy soil layers accelerating wear acceleration as well as increased abrasion wear on its top layer accelerates this wear process.

Characteristics

nitride bonded silicon carbide offers exceptional strength and toughness as well as exceptional creep resistance, thermal stability, oxidation resistance, corrosion protection, making it the perfect material to use in harsh environments with high temperatures. Silcarb offers this material in various shapes, sizes, profiles and applications including kiln furniture which supports green refractory ware during firing.

NBSiC boasts high load carrying capacities at elevated temperatures, far surpassing those of oxide-bonded silicon carbide. Furthermore, it is highly resistant to chemical attack by acids, molten salts and halogens - making it the ideal material choice as a secondary thermocouple protection tube, protecting mullite or alumina primary thermocouples from direct flame impingement.

Material for this material is created through reaction sintered from coarse and medium grained silica powders containing 5-15% alumina-silica binder in air. This binder acts as an intermediate phase between silica particles and silicon carbide particles and boasts higher fracture toughness than silicate-bonded silicon carbide.

Nitride layer provides a protective slag coating which improves wear resistance of products coated in this way, such as silicon carbide with an embedded nitride coating. Friction tests demonstrated lower mean wear rates for these bonded silicon carbides compared to special steels and padding weld in similar soil conditions, due to them tending to recut upon impact rather than swell when hit, with further wear rate reduction in heavy soils.

Applications

nitride bonded silicon carbide is an extremely hard, wear-resistant material with one of the highest load-carrying capacities among engineering materials, capable of withstanding very high temperatures without losing strength, as well as resisting creep and oxidation while offering exceptional fracture toughness.

Tetrahedral structures with tight packing can increase its strength by several orders of magnitude, making this material highly tough and durable. This material is an ideal choice for applications requiring high performance such as cutting tools, bearings and nozzles requiring maximum performance; additionally it's resistant to acid and alkalis environments which makes it suitable for harsh conditions such as corrosion. NB SiC can be various shapes, sizes and profiles for use in a wide variety of applications. These include crucibles, combustion boats, mortars and laboratory ware. Kiln batts used to carry green refractory during firing are also made out of this material as are pipe linings, control flow chokes and mining operations.