Alpha-Si3N4 phase generation rate control method in silicon powder nitriding process

Abstract

The invention belongs to the field of material forming, and particularly relates to a method for controlling the alpha-Si3N4 phase generation rate in a silicon powder nitriding process, which is characterized in that the time t for controlling the pressure in a sintering furnace to be reduced from a high point P2 to a low point P1 is taken as a target, and different working conditions are coped by coordinately controlling N2 gas flow, Ar gas flow, temperature and pressure parameters; finally, the silicon powder nitridation generation reaction rate is controlled. The adjustable range of coordinating and controlling the N2 gas flow, the Ar gas flow, the temperature, the pressure and other parameters is larger than that of controlling a single parameter, and the technical difficulties that the alpha-Si3N4 phase generation rate is difficult to measure and the alpha-Si3N4 phase generation rate is difficult to regulate and control through the single parameter are broken through. By controlling the generation rate of the alpha-Si3N4 phase in the sintering furnace, the content of the alpha-Si3N4 phase in the sintering reaction process is increased, and a basic raw material is provided for subsequent purification breakthrough of silicon nitride ceramic powder.

Description

TECHNICAL FIELD

[0001] The application relates to a method for controlling the generation rate of an alpha-Si3N4 phase in a silicon powder nitriding process and belongs to the field of material forming. BACKGROUND

[0002] In the preparation process of high-quality silicon nitride powder, the reaction rate of the generation of the alpha-Si3N4 phase needs to be controlled so that the silicon powder nitriding process can proceed smoothly. However, the generation reaction of the alpha-Si3N4 phase is affected by multiple factors, which makes it difficult to control the generation rate of the alpha-Si3N4 phase. Therefore, how to control the sintering process parameters in the silicon nitride powder sintering furnace, regulate the generation reaction process of the alpha-Si3N4 phase in the silicon powder nitriding process, and obtain high-quality silicon nitride powder without increasing the production cost, greatly reduces the material cost of high-quality silicon nitride powder.

[0003] The sintering control parameters of the silicon nitride powder sintering furnace include N2 gas flow, Ar gas flow, temperature, pressure and the like, and these sintering parameters will all affect the generation of the alpha-Si3N4 phase in the silicon powder nitriding process.

[0004] The silicon powder nitriding generation reaction belongs to a gas reduction reaction, and the adjustment of the N2 gas flow, Ar gas flow, temperature, pressure and the like is related to each other. For example, as the reaction proceeds, the consumption of N2 gas will cause the pressure to drop, at which time the N2 gas flow needs to be increased to ensure the continuous progress of the reaction.

[0005] Therefore, it is extremely necessary to develop a control method for coordinating the above parameters to accurately control the silicon powder nitriding generation reaction and thus ensure the quality of the sintered product.

[0006] However, no control method for coordinating the above parameters has been found, and there is currently a lack of a synergistic control technology that can effectively integrate and dynamically adjust the multi-dimensional parameters such as N2 gas flow, Ar gas flow, temperature and pressure, resulting in the difficulty in stabilizing the generation rate of the alpha-Si3N4 phase in the silicon powder nitriding process in the optimal range. The existing technology focuses on the static regulation of a single parameter or relies on empirical operation, and cannot realize real-time response and adaptive adjustment under the condition of multi-parameter coupling, thereby causing problems such as product quality fluctuation, production cycle extension and raw material waste. SUMMARY

[0007] The present application discloses a method for controlling the generation rate of an alpha-Si3N4 phase in a silicon powder nitriding process, which establishes a multi-parameter dynamic coupling model and combines a real-time feedback adjustment mechanism to realize accurate synergistic control of key reaction parameters in the sintering process of silicon nitride powder, and provides reliable technical support for industrial production of high-quality silicon nitride powder.

[0008] The scheme of the application is: a method for controlling the generation rate of alpha-Si3N4 phase in the silicon powder nitriding process is disclosed, taking the time t for the pressure in the sintering furnace to drop from a high point P2 to a low point P1 as the target, coordinating the control of N2 gas flow, Ar gas flow, temperature, and pressure parameters to cope with different working conditions, and finally realizing the control of the generation reaction rate of silicon powder nitriding.

[0009] Firstly, the mutual relationship among the parameters such as N2 gas flow, Ar gas flow, temperature, and pressure and the influence on the generation reaction rate of alpha-Si3N4 phase in the silicon powder nitriding process are comprehensively considered. A real-time feedback adjustment mechanism is set, and during the operation of the sintering furnace, various sensors are used to collect the actual values of the parameters such as N2 gas flow, Ar gas flow, temperature, and pressure in real time, and these data are fed back to the control system.

[0010] Secondly, according to the real-time feedback data and the preset target value of the time t for the pressure in the sintering furnace to drop from a high point P2 to a low point P1, the control system uses a multi-parameter dynamic coupling model to calculate and analyze, and obtains the direction and amplitude of the adjustment of each parameter.

[0011] Finally, the parameters such as N2 gas flow, Ar gas flow, temperature, and pressure are coordinated and controlled to realize the precise control of the generation reaction rate of silicon powder nitriding, so that the generation rate of alpha-Si3N4 phase is stabilized in the optimal interval.

[0012] Further, the specific control process is as follows: in a static-dynamic cycle holding period, the time t for the pressure to drop from a high point P2 to a low point P1 is recorded, and it is judged whether t is within a given range t1

[0013] Further, the starting point T0 of the nitriding reaction is the set value of the furnace temperature, and the program is not started when the set value is lower than the set value; when the furnace temperature reaches the set value T0, the control program is automatically started, wherein T0 = 1150℃ ± 10℃.

[0014] Further, when the working condition is t1

[0015] Further, when the working condition is t > t2, that is, the reaction speed is low; the following adjustments are made, S1: reduce the Ar flow, and after a certain time, execute a judgment method once; S2: repeat S1 until the Ar flow is reduced to 0; S3: temperature is increased by X℃, and the inlet and outlet gas is dynamic during the temperature increasing process, and one-time judgment method is executed after the temperature increasing is completed; X is 20℃-30℃; S4: S3 is repeated until the temperature is increased to the highest temperature allowed by the process.

[0016] When the time t is greater than t2, it indicates that the pressure decreasing speed is too slow, which may be caused by insufficient N2 gas flow or too low temperature leading to insufficient reaction. In view of this situation, the control system will increase the N2 gas flow and increase the temperature to accelerate the reaction process, so that the pressure can be expected to decrease. Similarly, the adjustment of the Ar gas flow is also to optimize the furnace environment and promote the smooth progress of the reaction.

[0017] Further, the Ar flow of S1 is 1 / 4-1 / 2 of the total Ar flow, and the time is more than 30 minutes.

[0018] Further, when the working condition is t S5: increase the Ar flow, and after a certain time, one-time judgment method is executed; S6: S5 is repeated until the Ar flow is increased to the maximum flow allowed by the process. When the time t is less than t1, it indicates that the pressure decreasing speed is too fast, which may be caused by too large N2 gas flow or too high temperature leading to too violent reaction. At this time, the control system will automatically reduce the N2 gas flow and appropriately reduce the temperature to slow down the reaction rate, so that the pressure decreasing speed returns to the normal range. At the same time, the Ar gas flow can be finely adjusted according to the actual situation to maintain the stability of the furnace atmosphere.

[0019] Further, the Ar flow of S5 is 1 / 4-1 / 2 of the total Ar flow, and the time is more than 30 minutes.

[0020] Compared with the prior art, the beneficial effects of the present application are: The alpha-Si3N4 phase generation rate control method in the silicon powder nitriding process disclosed in the present application takes the time (t) for controlling the pressure in the sintering furnace from the high point (P2) to the low point (P1) as the target, and coordinates the control of the N2 gas flow, Ar gas flow, temperature, pressure and other parameters to realize the control of the silicon powder nitriding generation reaction rate, and the process is clear and the operation is simple.

[0021] The alpha-Si3N4 phase generation rate control method in the silicon powder nitriding process disclosed in the present application has a larger adjustable control range of the coordinated control of the N2 gas flow, Ar gas flow, temperature, pressure and other parameters than the control of a single parameter, and breaks through the technical difficulties that it is difficult to measure the alpha-Si3N4 phase generation rate and difficult to control the alpha-Si3N4 phase generation rate by a single parameter.

[0022] By controlling the formation rate of the α-Si3N4 phase in the sintering furnace, the content of the α-Si3N4 phase during the sintering reaction can be increased, providing a basic raw material for the subsequent breakthrough in the purification of silicon nitride ceramic powder. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the method for controlling the formation rate of the α-Si3N4 phase during the silicon powder nitriding process described in this invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings. The drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. Example 1

[0025] The method for controlling the α-Si3N4 phase formation rate during silicon powder nitriding in this embodiment aims to control the time t it takes for the pressure inside the sintering furnace to drop from a high point P2 to a low point P1. This is achieved by coordinating and controlling N2 gas flow rate, Ar gas flow rate, temperature, and pressure parameters to address different operating conditions, ultimately controlling the silicon powder nitriding reaction rate. The method uses temperature data to determine whether the α-Si3N4 phase formation reaction has occurred. If the temperature has not reached the initial reaction temperature, the α-Si3N4 phase production reaction rate control program will not be initiated regardless of changes in pressure parameters, N2 gas flow rate, or Ar gas flow rate. When the temperature is within the control range of the reaction, the speed at which the N2 gas flow rate reaches the program-set flow rate is determined based on the temperature. For example, at a temperature of 1150℃, the flow control process can be completed within 1 minute, while at a temperature of 1400℃, the flow control process can be completed within 30 seconds. To achieve flow rate adjustment within 30 seconds to 1 minute, the N2 gas flow valve is adjusted every 3 seconds by controlling the Ar flow rate and total pressure data (the partial pressure of the gas can reflect the content of the gas inside, which is equivalent to a sensor for detecting the actual content of N2 gas).

[0026] The specific steps are as follows: Before starting the nitriding reaction, first set the target time t for the pressure inside the sintering furnace to drop from the high point P2 to the low point P1, and at the same time set the starting temperature T0 of the nitriding reaction, T0=1150℃±10℃. The program will not start if the temperature is lower than this set value.

[0027] When the furnace temperature reaches the set value T0, the control program is automatically started. During the operation of the sintering furnace, various sensors are used to collect the actual values ​​of parameters such as N2 gas flow rate, Ar gas flow rate, temperature, and pressure in real time, and these data are fed back to the control system. Within a static-dynamic cyclic holding period, the actual time t for the pressure to drop from the high point P2 to the low point P1 is recorded, and it is determined whether t is within the given range t1 < t < t2, where P1 = 0.01MPa~0.02MPa, P2 = 0.1MPa~0.5MPa, t1 = 0.2h~0.5h, and t2 = 1h~2h. In this embodiment, P1 is... The pressure is 0.01 MPa, P2 is 0.3 MPa, t1 is 0.5 h, and t2 is 2 h. For times t within the set range, the gas flow rate and temperature are controlled and adjusted in a coordinated manner to regulate the formation rate of the α-Si3N4 phase.

[0028] Different adjustment methods are applied to different working conditions: If time t is within the set range t1 < t < t2, that is, the reaction rate is normal, the intake and exhaust remain unchanged, the temperature remains unchanged, and the N2 gas flow rate is kept within a suitable range. The gas flow rate and temperature are adjusted in a coordinated manner to regulate the formation rate of the α-Si3N4 phase.

[0029] If time t > t2, i.e. the reaction rate is too low, the following adjustments are made: S1: Reduce the Ar flow rate by 1 / 4 to 1 / 2 of the total Ar flow rate in a single operation. In this embodiment, the Ar flow rate is reduced by 1 / 2 of the total Ar flow rate in a single operation over a period of 30 minutes. Perform one judgment method. S2: Repeat S1 until the Ar flow rate is reduced to 0. S3: Increase the temperature by X °C, where X = 20~30 °C. In this embodiment, the temperature is 20 °C. The time taken for heating is set according to the actual situation. During the heating process, the intake and exhaust are dynamic. After the heating is completed, perform one judgment method. S4: Repeat S3 until the temperature rises to the maximum allowable temperature of the process.

[0030] like Figure 1As shown, if time t is less than t1, it indicates that the current reaction rate is too high, and corresponding adjustment measures need to be taken. The specific steps are as follows: S5: First, the flow rate of argon (Ar) needs to be increased. The increase should be controlled between 1 / 4 and 1 / 2 of the total Ar flow rate, and the duration after adjustment should be no less than 30 minutes. In this embodiment, the total Ar flow rate is reduced by 1 / 2 at a time and maintained for 30 minutes. Then, a judgment method is performed to evaluate the adjustment effect. S6: If the reaction rate is still too high after step S5, step S5 needs to be repeated until the argon (Ar) flow rate is increased to the maximum flow rate allowed by the process. Through the above series of steps, key parameters such as nitrogen (N2) flow rate, argon (Ar) flow rate, reaction temperature, and system pressure can be coordinated and controlled according to different operating conditions, thereby achieving precise control of the silicon powder nitridation reaction rate and ensuring that the formation rate of the α-Si3N4 phase is stable within the optimal range to achieve the best process effect.

[0031] This solution reduces the difficulty of controlling the silicon powder nitridation reaction while ensuring the sintering quality of high-performance silicon nitride ceramic materials. In practical applications, this control method demonstrates significant stability and reliability. By enabling real-time monitoring and adjustment of key parameters within the sintering furnace, the reaction rate during silicon powder nitridation can be precisely controlled, thus ensuring the consistency of silicon nitride powder quality. Furthermore, this method offers high flexibility, allowing for rapid adjustments to the control strategy based on varying production needs and operating conditions to adapt to diverse production environments. Implementing this control method not only improves the production efficiency of silicon nitride powder but also effectively reduces production costs, providing strong technical support for the industrial production of silicon nitride ceramic materials.

[0032] The above embodiments are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions should also fall within the protection scope of the invention, which should be defined by the claims.

Claims

1. A method for controlling the formation rate of α-Si3N4 phase during silicon powder nitriding, characterized in that, With the goal of controlling the time t for the pressure inside the sintering furnace to drop from the high point P2 to the low point P1, the gas flow rate, temperature, and pressure parameters are coordinated and controlled to cope with different working conditions, ultimately achieving control of the silicon powder nitridation reaction rate.

2. The method for controlling the formation rate of α-Si3N4 phase during silicon powder nitriding according to claim 1, characterized in that, The specific control process is as follows: During a static-dynamic cyclic heat preservation cycle, the time t for the pressure to drop from the high point P2 to the low point P1 is recorded. It is determined whether t is within the given range t1 < t < t2, where P1 = 0.01 MPa ~ 0.02 MPa, P2 = 0.1 MPa ~ 0.5 MPa, t1 = 0.2 h ~ 0.5 h, and t2 = 1 h ~ 2 h. If the time t is within the set range, the gas flow rate and temperature are adjusted in a coordinated manner to regulate the formation rate of the α-Si3N4 phase.

3. The method for controlling the formation rate of α-Si3N4 phase during silicon powder nitriding according to claim 2, characterized in that, The starting point of the nitriding reaction, T0, is the set value of the furnace temperature. If the temperature is lower than the set value, the program will not start. When the furnace temperature reaches the set value T0, the control program will start automatically, where T0 = 1150℃ ± 10℃.

4. The method for controlling the formation rate of α-Si3N4 phase during silicon powder nitriding according to claim 3, characterized in that, The gas flow rates are N2 gas flow rate and Ar gas flow rate.

5. The method for controlling the formation rate of α-Si3N4 phase during silicon powder nitriding according to claim 4, characterized in that, Under the operating condition t1 < t < t2, the reaction rate is normal, the intake and exhaust remain constant, and the temperature remains constant.

6. The method for controlling the formation rate of α-Si3N4 phase during silicon powder nitriding according to claim 4, characterized in that, The operating condition is t>t2, meaning the reaction rate is too low; the following adjustments are made: S1: Reduce Ar flow, and after a certain period of time, execute a judgment method once; S2: Repeat S1 until the Ar flow is reduced to 0; S3: Temperature increases by X℃. During the heating process, the intake and exhaust are dynamic. After the heating is completed, a judgment method is executed once. X is 20℃~30℃. S4: Repeat S3 until the temperature rises to the maximum temperature allowed by the process.

7. The method for controlling the formation rate of α-Si3N4 phase during silicon powder nitriding according to claim 6, characterized in that, The Ar flow rate in step S1 is 1 / 4 to 1 / 2 of the single-time reduced overall Ar flow rate, and the time is more than 30 minutes.

8. The method for controlling the formation rate of α-Si3N4 phase during silicon powder nitriding according to claim 4, characterized in that, The operating condition is t < t1, meaning the reaction rate is too high; the following adjustments are made. S5: Increase the Ar flow rate, and execute the judgment method once after a certain period of time; S6: Repeat S5 until the Ar flow rate increases to the maximum allowed flow rate of the process.

9. The method for controlling the formation rate of α-Si3N4 phase during silicon powder nitriding according to claim 8, characterized in that, The Ar flow rate of S5 is 1 / 4 to 1 / 2 of the total Ar flow rate in a single increase, and the time is more than 30 minutes.

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