Skyline:Six preparation methods of silicon nitride and aluminum nitride powder
Take silicon nitride as an example: silicon nitride is an inorganic substance with a chemical formula of Si3N4. It is an important structural ceramic material with high hardness, inherent lubricity, and wear resistance. It is an atomic crystal; it is resistant to oxidation at high temperatures. Moreover, it can resist the impact of cold and heat. It will not be broken if it is heated to above 1000°C in the air, cooled rapidly and then heated rapidly. Silicon nitride is often used to manufacture mechanical components such as bearings, turbine blades, and mechanical seal rings. If silicon nitride ceramics, which are resistant to high temperatures and difficult to transfer heat, are used to make the heating surfaces of engine components, not only can the quality of the diesel engine be improved, fuel savings, and thermal efficiency can be improved.
The ideal Si3N4 powder material should have high purity, fine particle size, and good dispersibility. In particular, the dispersibility of ultrafine powders has always been a key factor restricting product performance and downstream applications. Especially due to the large surface energy of Si3N4 powder, agglomeration can easily occur. How to improve the dispersibility of Si3N4 powder has become a problem that must be faced after preparing Si3N4 powder.
Currently, there are several methods for preparing silicon nitride powder:
（1）Silicon powder direct nitriding method
The direct nitridation of silicon powder is a traditional method, and its preparation process has gradually matured and has been used in industrial production. The method uses high-purity Si powder to react with N2 at high temperature to generate silicon nitride powder.
In this method, nitrogen is the source of nitrogen, so parameters such as the type and flow rate of the passed gas have an important influence on the silicon powder nitriding process and products. In addition, the size of silicon powder, nitriding heat treatment process and other parameters also affect the nitriding product of Si powder.
（2）Carbothermic reduction method
The carbothermal reduction method for preparing silicon nitride powder has the advantages of abundant raw materials, low price, simple process, large production scale, etc., and the Si3N4 powder prepared by this method has fine particles and high content of α-Si3N4.
The carbothermal reduction method for preparing silicon nitride powder has the advantages of abundant raw materials, low price, simple process, large production scale, etc., and the Si3N4 powder prepared by this method has fine particles and high content of α-Si3N4.
（3）Chemical vapor deposition
The chemical vapor deposition method is also an important method for preparing Si3N4. The chemical vapor deposition method has a fast reaction speed, high product purity and fine particles. At the same time, the product obtained by the reaction can be directly deposited on the specified substrate to form a silicon nitride coating, but it also exists The gas phase reaction is violent and difficult to control.
（4）Sol-gel method
The sol-gel method can be used to prepare high-purity, ultra-fine, low-cost silicon nitride powder, but the equipment is expensive and the process is complicated.
（5）Thermal decomposition method
The key of the pyrolysis method is to obtain high-purity imino silicon [Si(NH)2] and amino silicon [Si(NH)4]. The advantage of this method is that the product obtained is of high purity, fine and uniform particles.
（6）Self-propagating high-temperature synthesis
The principle of self-propagating high-temperature synthesis is that once the reactant is ignited, it will automatically propagate to the unreacted area until the reaction is complete. The synthetic product has the advantages of high purity, short reaction period, high production efficiency, relatively simple equipment, low investment, strong versatility, and no pollution.
At present, the plasma atomization preparation powder material production equipment developed by Hunan Tianji Smart Material Technology Co., Ltd. can be used to produce Si3N4/AlN and other nitrides, oxides, metals and their alloys.
Technical advantage and features
Innovation of equipment
1. Combined modular multifunctional raw material conveying device, including: uniform and precise feeding device for liquid, gas, and powder raw materials, uniform and precise feeding device for filamentous raw materials, and block vacuum melting precise flow limiting and diversion pouring device; it can meet different conditions Raw material production;
2. Plasma power supply and plasma generator are also key technological innovations of this technology. In order to improve the efficiency of atomization and the stable progress of the atomization process, this equipment technology proposes the ultra-high temperature plasma generator, the selection of plasma gas types, and the reasonable matching of gas flow and metal flow rate to produce a full range of high-performance metal simple substances and metal alloys. Micro/nano powder materials can also be used for the preparation of multiphase compound powder materials, including: chemically active metals Mg/Al/Ti/Zr and alloys, etc.; high temperature metals W/Mo/Nb/Ta and alloys, etc.; oxides , High-purity, spherical, micro/nano and powder materials of nitrides and carbides;
3. Its professionally designed chemical reaction chamber can react to produce a variety of high-combination, high-purity, multi-element powder materials;
4. The key technical points of precise and intelligent control of powder particle size, oxygen content and fluidity are put forward;
5. Rapid cooling technology to prepare nano-level powder materials.
Advanced equipment technology
1. The intelligent control of this equipment is highly integrated;
2. On-line measurement of powder particle size and feedback precision control technology, allowing industry technology to break away from the stage of dependence on personal experience and enter the era of intelligent manufacturing;
3. Comprehensive control technology of powder oxygen content process;
4. Key control technology of powder dispersion and fluidity index;
5. The key control technology to improve the yield of powder in the range of -50+15μm (applied to mainstream technology paths such as additive manufacturing SLM);
6. Continuous collection technology of ultra-fine micron, sub-micron, and nano-level powder materials;
7. Surface passivation technology of chemically active materials to ensure the safety of the product during use;
8. Equipment anti-static and explosion-proof design technology.
Hunan Tianji Smart Material Technology Co., Ltd. was established in 2018 (more than 20 years of industry experience). It is located in the Eastern Industrial Park of High-tech Zone, Yiyang City, Hunan Province. It is a high-tech company that specializes in R&D and manufacturing of intelligent new material production technology and equipment, and provides comprehensive solutions for the preparation of innovative materials. Technology companies, especially focusing on the research and development of various structural and functional ultra-fine, micro-nano powder new materials, and the manufacturing of production equipment. The product industry chain includes high-performance powder material preparation technology and equipment, powder material modification technology and equipment, powder rapid prototyping products sintering and heat treatment technology and equipment, etc. The industry technologies involved in chemistry, metallurgy, and materials science , Quantum mechanics, as well as mechanical design technology, thermal control technology, atmosphere control technology, vacuum control technology, intelligent control technology, Internet technology, etc. These intersecting sciences and technologies are integrated and integrated, which are comprehensive and professional, with a high degree of complexity. The company will continue to increase R&D investment, introduce innovative talents, develop several industry technologies and equipment with complete intellectual property rights, and apply for multiple patents; we will take professional technology as the guide, innovation-driven development, and integrate uniqueness and novelty. , Professional intelligent technology continuously upgrades our products and services, becoming the benchmark of product innovation in this industry, and making sparing efforts in innovation become our core competitiveness in the market.