Technology for continuously preparing silicon nitride material by adopting direct nitriding method

Abstract

The invention relates to a technology for continuously preparing a silicon nitride material by adopting a direct nitriding method, which unifies the particle size distribution and polar distribution of silicon powder through a spray granulation technology, ensures the stability of nitrogen atmosphere by adopting a multi-temperature-zone continuous nitriding process, and avoids the self-propagating reaction of concentrated heat release and overheating through the design of subarea sinking cold zones. The problems of concentrated heat release, unstable product quality and the like in the silicon nitride preparation process in the prior art are solved, and continuous and stable production of silicon nitride is realized. The technology has a wide application prospect, especially in the fields of electronics, machinery, chemical engineering, new energy and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the preparation technology of silicon nitride material, in particular to a continuous preparation technology of silicon nitride material by direct nitriding method, aiming at solving the problems of concentrated heat release and unstable product quality in the preparation process of silicon nitride in the prior art. BACKGROUND

[0002] Silicon nitride (Si3N4) is an important ceramic material, widely used in electronic, mechanical, chemical and other fields. At present, the synthesis methods of silicon nitride mainly include the following:

[0003] 1. Direct combination reaction of elemental silicon and nitrogen: this method is carried out at 1000-1300℃, and a large amount of heat is released during the reaction process, which is easy to cause concentrated heat release, induce self-spreading combustion reaction, and further cause the conversion of silicon nitride to high temperature phase, and even the phenomenon of silicon flow.

[0004] 2. Imine synthesis method: this method is complex and high in cost, and is difficult to mass produce.

[0005] 3. Carbon thermal reduction reaction synthesis method: this method needs high temperature conditions, and by-products are produced during the reaction process, affecting the product quality.

[0006] In the prior art, the direct nitriding method has the following problems:

[0007] - concentrated heat release during the reaction process, leading to the conversion of silicon nitride to high temperature phase, and easy to cause self-spreading combustion reaction.

[0008] - intermittent production is adopted in the production process, which cannot guarantee the consistency of the product.

[0009] - the particle size distribution, bulk density and specific surface area of the silicon powder raw material are difficult to control uniformly, leading to unstable product quality. SUMMARY

[0010] The purpose of the present application is to provide a continuous preparation technology of silicon nitride material by direct nitriding method, which solves the problems of concentrated heat release and unstable product quality in the prior art by multi-temperature zone control process and continuous nitriding method.

[0011] TECHNICAL SCHEME

[0012] 1. Raw material consistency control: through spray granulation technology, the particle size distribution and packing of silicon powder are unified, the flowability and bulk density of silicon powder are consistent, and the phenomenon of silicon flow caused by over-temperature is avoided.

[0013] - particle size control of silicon powder: through fluidized bed crushing technology, the median particle size of elemental silicon powder is controlled at 0.44μm, and the particle size distribution of silicon powder is uniform.

[0014] - Spray granulation: Using spray granulation technology, 0.5% mass ratio of zinc stearate as binder, high flowability of silicon powder is obtained, ensuring the bulk density of silicon powder between 0.97-1.1 g / cm3. The silicon powder after spray granulation has good flowability and consistency, facilitating subsequent charging and nitriding reaction.

[0015] 2. Continuous nitriding process: Using push plate kiln or rotary kiln, through multi-temperature zone arrangement, continuous production of silicon nitride is realized. Nitrogen gas positive pressure and nitrogen gas curtain are used in the furnace to ensure the stability of nitrogen atmosphere.

[0016] - Multi-temperature zone control: Using 33 temperature zones of multi-temperature zone movable sintering method, the temperature of each temperature zone is accurately controlled between 1050-1150℃. Through distributed temperature zone control, the temperature zone section with concentrated heat release can be accurately positioned to avoid local overheating.

[0017] - Nitrogen atmosphere control: Nitrogen micro-positive pressure (0.1-0.3 MPa) is used in the furnace, and nitrogen curtain is set at the furnace mouth to ensure the purity and stability of the nitrogen atmosphere in the furnace, preventing external air from entering the furnace and affecting the reaction.

[0018] - Sinking hearth design: In the temperature zone of 1050-1150℃, sinking hearth lifting mechanism is used. When the temperature measurement shows abnormal rise, the reaction powder block is quickly lowered to leave the heating and insulation area, inhibiting the excessive nitriding reaction temperature and avoiding the occurrence of self-spreading combustion reaction.

[0019] 3. Energy saving and emission reduction design:

[0020] - Sinking design of inlet and outlet furnace mouth: Through sinking design of inlet and outlet furnace mouth, the uniformity of the atmosphere when the product enters and exits the furnace is ensured, and the heat loss is reduced, improving the energy utilization efficiency.

[0021] - Sub-area sinking cold zone design: In the temperature zone with concentrated heat release, sub-area sinking cold zone design is used to inhibit excessive reaction by rapid cooling, avoid high temperature phase transition of silicon nitride, and ensure the stability of product quality.

[0022] Advantages: Through spray granulation technology, multi-temperature zone control process and continuous nitriding method, the problems of concentrated heat release and unstable product quality in traditional direct nitriding method are solved, realizing continuous and stable production of silicon nitride. This technology has wide application prospect, especially in the fields of electronics, machinery, chemical industry and new energy. DETAILED DESCRIPTION

[0029] 1. Raw material processing: Elemental silicon is crushed in a fluidized bed to achieve a median particle size of 0.44 μm, and the bulk density of the resulting powder is 0.97-1.1 g / cm3. Subsequently, the silicon powder is obtained by spray granulation (using 0.5% by mass of zinc stearate as a binder) to achieve high flowability.

[0030] 2. Continuous nitriding process: A multi-zone movable sintering method with 33 temperature zones is used, and a slight positive pressure of nitrogen gas is provided in the furnace. A nitrogen gas curtain is used at the furnace opening to ensure the stability of the nitrogen atmosphere.

[0031] 3. Temperature zone control: In the temperature zone section of 1050-1150°C, a sinking furnace hearth lifting mechanism is used. When the temperature measurement shows an abnormal increase, the reaction powder block is quickly lowered to leave the heating and insulation area, and the excessive nitriding reaction temperature is inhibited.

Claims

1. A technique for continuously producing a silicon nitride material by a direct nitridation method, characterized by, The method comprises the following steps: -Uniform the particle size distribution and polarity of silicon powder by spray granulation technology, ensure the uniformity of flowability and bulk density of silicon powder; -Use push plate kiln or rotary kiln, realize the continuous production of silicon nitride by multi-temperature zone arrangement; -Use nitrogen positive pressure and nitrogen curtain protection in the furnace, ensure the stability of nitrogen atmosphere; -Through the sinking design of inlet and outlet furnace port, ensure the uniformity of product atmosphere and the thermal safety of inlet and outlet furnace; -Use zoning sinking cold zone design, accurately locate the heat release section by distributed temperature zone control, and use sinking cooling method to prevent self-spreading combustion reaction caused by concentrated heat release.

2. The technology according to claim 1, characterized in that, The median particle size of silicon powder is 0.44 μm, and the bulk density is 0.97-1.1 g / cm3.

3. The technology according to claim 1, characterized in that, The multi-temperature zone movable sintering method with 33 temperature zones is used, the nitrogen micro-positive pressure is used in the furnace, and the nitrogen curtain technology is used at the furnace port.

4. The technology according to claim 1, characterized in that, In the temperature zone of 1050-1150°C, the sinking furnace lifting mechanism is used, when the temperature measurement shows abnormal rise, the reaction powder block is quickly lowered to leave the heating and insulation area, and the excessive nitriding reaction temperature is inhibited.

5. The technology according to claim 1, characterized in that, The binder used in the spray granulation process is zinc stearate, and the mass ratio is 0.5%.

6. The technology according to claim 1, characterized in that, The nitrogen micro-positive pressure of the multi-temperature zone direct nitriding sintering furnace is 0.1-0.3 MPa.

7. The technology according to claim 1, characterized in that, The sinking furnace lifting mechanism works in the temperature zone of 1050-1150°C, when the temperature measurement shows abnormal rise, the reaction powder block can be lowered to the cold zone within 10 seconds to inhibit excessive reaction.

8. The technology according to claim 1, characterized in that, The number of temperature zones of the multi-temperature zone direct nitriding sintering furnace is 33, and the temperature of each temperature zone can be independently controlled.