Method for processing silicon nitride block

Silicon nitride is difficult to process as a granular material. It cannot be heated above its melting point of 1850°C, because silicon nitride will decompose into silicon and nitrogen above this temperature. Therefore, the traditional hot press sintering technology is not feasible. Silicon nitride powder can be sintered in a certain degree of liquid phase at a lower temperature by adding some other substances such as sintering aids or binders, and then combined into a bulk material. However, due to the need to add binders or sintering aids, this method introduces impurities in the bulk material produced. The use of spark plasma sintering is another way to prepare purer bulk materials. The compacted powder generates pulses in a short period of time (a few seconds). This method can be used at 1500-1700°C.

Silicon nitride can be produced by direct chemical reaction with elemental silicon and nitrogen at 1300-1400°C. The chemical formula is as follows:

 3Si(s) + 2N2(g) →Si3N4(s)

 It can also be synthesized with diimine:

 SiCl4(l) + 6NH3(g) →Si(NH)2(s) + 4NH4Cl(s) (0 °C)

3Si(NH)2(s) →Si3N4(s) +N2(g) + 3H2( g) (at 1000 °C)

 Or synthesized by carbothermal reduction reaction under a nitrogen atmosphere at 1400-1450°C:

 3SiO2(s) + 6 C(s) + 2N2(g) →Si3N4(s) + 6 CO(g)

 The method of synthesizing silicon nitride was developed with the rediscovery of silicon nitride in the 1950s. This is also the first method of mass production of silicon nitride powder. However, if the silicon raw material used is of low purity, the produced silicon nitride will contain impurities of silicate and iron.

The silicon nitride synthesized by the diamine decomposition method is amorphous and needs to be further annealed under nitrogen at 1400-1500°C to be transformed into crystalline powder. At present, the diamine decomposition method is only important in terms of the commercial production method of silicon nitride, followed by the nitridation method.

Carbothermal reduction reaction is the simplest method to manufacture silicon nitride, and it is also the most economical method to manufacture silicon nitride powder in industry.

Electronic grade silicon nitride film is manufactured by chemical vapor deposition or plasma enhanced chemical vapor deposition technology:

 3SiH4(g)+4NH3(g)→Si3N4(s)+12H2(g) 3SiCl4(g)+4NH3(g)→Si3N4( s) + 12 HCl(g) 3SiCl2H2(g) + 4NH3(g) →Si3N4 (s) + 6 HCl(g) + 6H2(g)

Overview of Silicon Nitride

Silicon nitride is an inorganic substance with the chemical formula Si3N4. It is an important structural ceramic material with high hardness, inherent lubricity, wear resistance, atomic crystals and high temperature oxidation resistance.

Application of silicon nitride

1) Manufacturing structural equipment: metallurgy, machinery, aviation, aerospace, etc.

2) Surface treatment of metals and other materials: such as molds, knives, turbine blades.

3) Composite materials: such as metal, ceramic and graphite composite materials, rubber, and plastics.

4) Colorless, transparent, self-lubricating and wear-resistant nano-particle film, used for high-level surface protection such as mobile phones and automobiles.

5) Ball bearings.

6) Ball valves and parts.

7) Corrosion resistant turbine.

Other applications of silicon nitride

Silicon nitride is used as an advanced refractory material. For example, SI3N4-SIC refractory materials and sic are used in blast furnace bodies and other parts, and SI3N4-BN materials and BN are used in horizontal continuous casting separation rings. The continuous casting separation ring is a fine-structure ceramic material with uniform structure, high mechanical strength, good thermal shock resistance, and will not be wetted by molten steel, which meets the requirements of continuous casting process

Silicon nitride ceramic materials have excellent properties such as high thermal stability, strong oxidation resistance, and high product dimensional accuracy. Since silicon nitride is a covalent compound with high bonding strength, it can form an oxide protective film in the air, so it also has good chemical stability and will not be oxidized below 1200°C. The protective film formed at 1200~1600°C can prevent further oxidation and will not be affected by aluminum, lead, tin, silver, brass, and nickel. Or corrosion, but can be corroded by molten magnesium, nickel-chromium alloy, stainless steel and other melts.

Silicon nitride ceramic materials can be used for high-temperature engineering parts, advanced refractories in the metallurgical industry, corrosion-resistant parts and seals in the chemical industry, tools and knives in the machining industry, etc. Carbide, aluminum oxide, thorium dioxide, boron nitride, etc. can form a firm bond, so it can be used as a bonding material to be modified in different proportions.

In addition, silicon nitride can also be applied to solar cells. After the silicon nitride film is coated by the PECVD method, it can not only be used as an anti-reflection film to reduce the reflection of incident light, but also in the deposition process of the silicon nitride film, the hydrogen atoms of the reaction product enter the silicon nitride film and the silicon wafer passivation Defects. The ratio of the number of silicon nitride to silicon atoms here is not strictly 4:3, but depends on the process conditions within a certain range. Internal fluctuations, different atomic ratios correspond to different physical properties of the film.

Used in ultra-high temperature gas turbines, aircraft engines, electric furnaces, etc.

Silicon nitride price

The price of silicon nitride will vary randomly with the production cost, transportation cost, international situation, exchange rate, and supply and demand in the silicon nitride market. Tanki New Materials Co., Ltd. aims to help various industries and chemical wholesalers find high-quality, low-cost nanomaterials and chemicals by providing a full set of customized services. If you are looking for silicon nitride, please feel free to send an inquiry to get the latest price of silicon nitride.

Silicon Nitride Supplier

As a global silicon nitride supplier, Tanki New Materials Co., Ltd. has extensive experience in the performance, application and cost-effective manufacturing of advanced engineering materials. The company has successfully developed a series of powder materials (titanium nitride, silicon nitride, titanium nitride, etc.) high-purity targets, functional ceramics and structural devices, and provides OEM services.