Production method of high alpha phase silicon nitride powder

Abstract

The production method of high α-phase silicon nitride powder includes the following steps: A: grinding and pulverizing silicon powder to a D90 of 6 μm; B: loading the ground silicon powder into a sagger, and the thickness of the charging is within 15-30mm time; C: stack multiple saggars filled with silicon powder up and down into a stack, and the total thickness of silicon powder in each saggar in the stacked stack is less than or equal to 300mm; D: stack multiple stacks of silicon powder Put the saggars into the vacuum heating furnace, the total weight of the silicon powder in the multiple stacks of saggars filled with silicon powder is 70-100kg, and the multiple stacks of saggars filled with silicon powder are in an array form; Pumped to below 100Pa; F: filled with nitrogen to 60kPa; G: heating reaction. By adopting the method for large-scale production of silicon nitride, a high content of α phase can be obtained.

Description

technical field [0001] The invention relates to a production method of silicon nitride, in particular to an industrialized production method of high alpha phase silicon nitride powder, and belongs to the technical field of material production. Background technique [0002] Silicon nitride powder is the core key raw material for the preparation of silicon nitride ceramics, and its performance is the basis for affecting the performance of ceramics. With the continuous expansion of the silicon nitride ceramic market, the demand for silicon nitride powder, especially high-end silicon nitride powder, is increasing. [0003] In order to obtain silicon nitride ceramics with excellent physical and mechanical properties, the raw silicon nitride powder needs to have the following characteristics: [0004] 1. Silicon nitride powder must have a high content of α phase to ensure that the powder has high sintering activity, and it is easy to obtain dense silicon nitride ceramics, so as t...

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Problems solved by technology

[0007] Although the principle of the powder nitriding process is simple, the actual reaction is very complicated. To obtain silicon nitride powder with high α-phase content, the core is to control the temperature, pressure and gas in the process. This is because, first of all, silicon powder The nitriding temperature is generally around 1350°C, which is very close to the melting point of metal silicon at 1420°C, while the nitriding process of silicon powder is an exothermic process, and a large amount of heat released as the reaction progresses will increase the local temperature of the material and cause metal Silicon melting, that is, the phenomenon of silicon overflow, and then the gas entering channel is blocked by molten silicon, resulting in incomplete reaction and high residual free silicon content, so how to control the reaction speed and fully nitriding silicon powder is the core problem in the process; secondly, silicon nitride The α phase in the powder is an unstable phase at high temperature, and the generated α silicon nitride powder is easily partially converted into the β phase under the condition of local overheating, thereby affecting the sintering activity of the powder; finally, the gas treatment during the silicon powder nitriding process In addition to the reaction gas nitrogen, many technical solutions also include argon, hydrogen, etc. to control the reaction process. Due to the complexity of the silicon powder nitriding process, the entire reaction cannot progress at a uniform speed according to time. How to design a reasonable process in production It is possible to obtain silicon nitride with high α-phase content, which is also the biggest problem in the production of domestic silicon nitride powder

At present, the α-phase content of silicon nitride powder produced in China in industrialized production generally does not exceed 90%, and the batch stability is difficult to guarantee

Although the α-phase content of the silicon nitride powder obtained by the technical solutions declared in some literatures can exceed 95%, or even 98% (but through the identification of XRD patterns published by professionals, many α-phases may not be so High), and no mass-produced products have been seen so far, indicating that its process is not stable, unreliable, and immature, and it is likely to stay at the laboratory level, because in the actual production process, it may be impossible to follow the laboratory process. It is impossible to obtain batch products, because the difficulty of control and influencing factors will greatly increase in large-scale production, which has caused a large number of urgently needed silicon nitride powders with high α-phase content in my country to rely on foreign imports for many years, which has seriously affected my country. developments in related fields

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