阅读说明：本技术 高α相氮化硅粉体的生产方法 (Production method of high alpha-phase silicon nitride powder ) 是由 夏静豪 夏凡 于 2020-12-11 设计创作，主要内容包括：高α相氮化硅粉体的生产方法,包括以下步骤：A：将硅粉研磨粉碎至D90为6μm；B：将研磨好的硅粉装入匣钵中,装料厚度在15-30mm之间；C：将多个装好硅粉的匣钵上下叠放成一摞,叠放后的一摞中的各匣钵中硅粉的厚度总和小于等于300mm；D：将多摞装好硅粉的匣钵放入真空加热炉,多摞装好硅粉的匣钵中的硅粉的总重量为70-100kg,多摞装好硅粉的匣钵呈阵列形式；E：将真空加热炉气压抽到100Pa以下；F：充入氮气至60kPa；G：升温反应。采用本方法规模化生产氮化硅,可以获得高α相含量。(The production method of the high alpha-phase silicon nitride powder comprises the following steps: a: grinding and crushing the silicon powder until D90 is 6 mu m; b: putting the ground silicon powder into a sagger, wherein the charging thickness is 15-30 mm; c: stacking a plurality of saggers filled with silicon powder into a stack up and down, wherein the sum of the thicknesses of the silicon powder in the saggers in the stacked stack is less than or equal to 300 mm; d: putting the stacked sagger with the stacked silicon powder into a vacuum heating furnace, wherein the total weight of the silicon powder in the sagger with the stacked silicon powder is 70-100kg, and the saggers with the stacked silicon powder are in an array form; e: pumping the air pressure of a vacuum heating furnace to be below 100 Pa; f: charging nitrogen to 60 kPa; g: and (5) heating for reaction. The method is adopted to produce silicon nitride in a large scale, and high alpha phase content can be obtained.)

1. The production method of the high alpha-phase silicon nitride powder is characterized by comprising the following steps: the method comprises the following steps:

a: grinding and crushing the silicon powder until D90 is 6 mu m;

b: putting the ground silicon powder into a sagger, wherein the charging thickness is 15-30 mm;

c: stacking a plurality of saggers filled with silicon powder into a stack up and down, wherein the sum of the thicknesses of the silicon powder in the saggers in the stacked stack is less than or equal to 300 mm;

d: putting the stacked sagger with the stacked silicon powder into a vacuum heating furnace, wherein the total weight of the silicon powder in the sagger with the stacked silicon powder is 70-100kg, and the saggers with the stacked silicon powder are in an array form;

e: pumping the air pressure of a vacuum heating furnace to be below 100 Pa;

f: charging nitrogen to 60 kPa;

g: the temperature rising reaction sequentially comprises the following substeps:

g1: firstly, the temperature is increased to 1120 ℃, and the temperature increase rate is 2-4 ℃/min; introducing nitrogen in the temperature rising process, wherein the flow of the nitrogen is as follows: kilogram number of silicon powder in the vacuum furnace is multiplied by 15L/h, and the pressure in the vacuum heating furnace is kept at 60 +/-2 kPa during the execution of the step;

g2: keeping the temperature for 15-20 hours at 1120 ℃, wherein the flow of nitrogen is unchanged during the heat preservation period; during the heat preservation period, the vacuum heating furnace is actively evacuated once within 3-5 hours until the pressure is below 10 kPa, and the pressure in the vacuum heating furnace is kept at 60 +/-2 kPa except before and after evacuation;

g3: heating to 1280 deg.C at a rate of 0.4-0.6 deg.C/min; when the temperature is higher than 1200 ℃, argon is introduced, the flow rate of the argon is 20 percent of the flow rate of the nitrogen, and the flow rate of the nitrogen is unchanged; during the period of introducing argon, the vacuum heating furnace is actively evacuated once every 30 minutes until the pressure is below 10 kPa, and the pressure in the step is kept at 60 +/-2 kPa before and after evacuation;

g4: reducing the temperature to 1230 ℃, wherein the temperature reduction rate is 0.3-0.4/min, the flow rates of nitrogen and argon are kept unchanged, the vacuum heating furnace is actively evacuated once every 30 minutes during the period of introducing argon until the pressure is below 10 kPa, and the pressure in the step is kept at 60 +/-2 kPa before and after evacuation;

g5: repeating the steps G3 and G4 for more than 10 times;

h: closing the system for heating, cooling the vacuum heating furnace, and cooling the system to the normal temperature within 15 to 20 hours;

i: taking out the reaction product, crushing and grinding into powder.

2. The method for producing high α -phase silicon nitride powder according to claim 1, characterized in that: and B, after the silicon powder is filled into the sagger, dividing the powder in the sagger into a plurality of square grids, wherein the side length of each grid is 3-4cm, punching material holes at the intersection points of the grids, and the diameter of each material hole is 0.4-1cm and reaches the bottom of the sagger.

Technical Field

The invention relates to a production method of silicon nitride, in particular to an industrialized production method of high alpha-phase silicon nitride powder, belonging to the technical field of material production.

Background

Silicon nitride powder is a key core raw material for preparing silicon nitride ceramics, and the performance of the silicon nitride powder is the basis for influencing the performance of the ceramics. With the continuous expansion of silicon nitride ceramic market, the demand of silicon nitride powder, especially high-end silicon nitride powder, is increasing.

In order to obtain a silicon nitride ceramic having excellent physical and mechanical properties, it is necessary that the raw material silicon nitride powder has the following characteristics:

1. the silicon nitride powder has high alpha phase content to ensure high sintering activity of the powder, and compact silicon nitride ceramic is easy to obtain, so that the silicon nitride ceramic has high strength, high toughness and other properties. 2. Has reasonable grain diameter, grain size distribution and specific surface area, which are key factors for ensuring the sintering activity of the powder. 3. Has high purity. 4. Has reasonable nitrogen and oxygen content. At present, in the aspect of batch manufacturing of silicon nitride powder, three methods, namely a silicon powder nitriding method, a liquid phase method and an auto-ignition method, are mainly concentrated at home and abroad.

The basic principle of the silicon powder nitriding method is that silicon powder and nitrogen-containing gases such as nitrogen, ammonia and the like react at high temperature to generate silicon nitride, and the silicon nitride powder nitriding method has the advantages of good product performance stability, low cost and the like, and is a silicon nitride powder batch production method which is most widely applied and has the mature technology.

The silicon nitride powder synthesized by the liquid phase method does not need secondary crushing, and has uniform particle size distribution, but the technical threshold is high; self-propagating high-temperature synthesis is a new technology for preparing inorganic compound high-temperature materials which is emerging in recent years. The principle is that metal silicon powder is ignited by means of external energy, and because the reaction of silicon and nitrogen is exothermic, once the reactant is ignited, the reactant automatically propagates to an unreacted area until the reaction is completed. The method for synthesizing the silicon nitride powder has the advantages of high reaction speed, high powder purity and low cost. But the controllability of the preparation process is poor, and the alpha phase content of the silicon nitride powder is low. The Japanese UBE is the only enterprise for realizing industrialization of the liquid phase method at present, but the silicon nitride powder has high cost and high price, so the application is limited. The most mature and extensive mass production method of silicon nitride powder is that the germany ALZ, HC starck, Swedish, the international famous powder manufacturers of Vesta and most domestic manufacturers adopt a silicon powder nitriding method to produce silicon nitride powder in batches.

Although the principle of the powder nitriding process is simple, the actual reaction is very complex, and the core of obtaining the silicon nitride powder with high alpha phase content is the process control of temperature, pressure and gas in the process, because the silicon powder nitriding temperature is generally about 1350 ℃, which is very close to the melting point 1420 ℃ of metal silicon, and the silicon powder nitriding process is a heat-releasing process, the local temperature of the material can be increased along with the heat released greatly during the reaction, so that the metal silicon can be melted, namely, the silicon overflows, and further the gas inlet channel is blocked by the molten silicon, so that the reaction is not thorough, the content of residual free silicon is high, and how to control the reaction speed, and the silicon powder can be fully nitrided is the core problem in the process; secondly, the alpha phase in the silicon nitride powder is a high-temperature unstable phase, and the generated alpha silicon nitride powder is easily partially converted into a beta phase under the condition of local overheating, so that the sintering activity of the powder is influenced; finally, in addition to the reaction gas nitrogen in the gas in the silicon powder nitriding process, many technical schemes also comprise argon, hydrogen and the like for controlling the reaction process, and due to the complexity of the silicon powder nitriding process, the whole reaction cannot be carried out at a constant speed according to time, and how to design a reasonable process can obtain silicon nitride with high alpha phase content in production is the biggest problem in the production of domestic silicon nitride powder. The alpha phase content of domestic silicon nitride powder in the current industrialized production is generally not more than 90%, and the batch stability is difficult to ensure. Although the alpha phase content of silicon nitride powder obtained by the technical scheme stated in some documents can exceed 95 percent and even reach 98 percent (but the alpha phase is more likely not to be so high through the recognition of XRD patterns published by professionals), the occurrence of mass production products is not seen so far, which indicates that the process is unstable, unreliable and immature and is likely to stay at the laboratory level, because batch products can not be obtained according to the process of a laboratory in the actual production process, because the control difficulty and the influence factors are greatly increased in mass production, the development of relevant fields in China is seriously influenced since a large amount of silicon nitride with high alpha phase content urgently needed in China is basically dependent on foreign imports for many years. In the foreign technical list, China is limited, and the production of the silicon nitride powder with high alpha phase content is also one of the technical lists.

Disclosure of Invention

The invention aims to overcome the problems in the industrial production of silicon nitride with high alpha phase content at present and provide a production method of high alpha phase silicon nitride powder.

In order to realize the purpose of the invention, the following technical scheme is adopted: the production method of the high alpha-phase silicon nitride powder comprises the following steps:

a: grinding and crushing the silicon powder until D90 is 6 mu m;

b: putting the ground silicon powder into a sagger, wherein the charging thickness is 15-30 mm;

c: stacking a plurality of saggers filled with silicon powder into a stack up and down, wherein the sum of the thicknesses of the silicon powder in the saggers in the stacked stack is less than or equal to 300 mm;

d: putting the stacked sagger with the stacked silicon powder into a vacuum heating furnace, wherein the total weight of the silicon powder in the sagger with the stacked silicon powder is 70-100kg, and the saggers with the stacked silicon powder are in an array form;

e: pumping the air pressure of a vacuum heating furnace to be below 100 Pa;

f: charging nitrogen to 60 kPa;

g: the temperature rising reaction sequentially comprises the following substeps:

g1: firstly, the temperature is increased to 1120 ℃, and the temperature increase rate is 2-4 ℃/min; introducing nitrogen in the temperature rising process, wherein the flow of the nitrogen is as follows: kilogram number of silicon powder in the vacuum furnace is multiplied by 15L/h, and the pressure in the vacuum heating furnace is kept at 60 +/-2 kPa during the execution of the step;

g2: keeping the temperature for 15-20 hours at 1120 ℃, wherein the flow of nitrogen is unchanged during the heat preservation period; during the heat preservation period, the vacuum heating furnace is actively evacuated once within 3-5 hours until the pressure is below 10 kPa, and the pressure in the vacuum heating furnace is kept at 60 +/-2 kPa except before and after evacuation;

g3: heating to 1280 deg.C at a rate of 0.4-0.6 deg.C/min; when the temperature is higher than 1200 ℃, argon is introduced, the flow rate of the argon is 20 percent of the flow rate of the nitrogen, and the flow rate of the nitrogen is unchanged; during the period of introducing argon, the vacuum heating furnace is actively evacuated once every 30 minutes until the pressure is below 10 kPa, and the pressure in the step is kept at 60 +/-2 kPa before and after evacuation;

g4: reducing the temperature to 1230 ℃, wherein the temperature reduction rate is 0.3-0.4/min, the flow rates of nitrogen and argon are kept unchanged, the vacuum heating furnace is actively evacuated once every 30 minutes during the period of introducing argon until the pressure is below 10 kPa, and the pressure in the step is kept at 60 +/-2 kPa before and after evacuation;

g5: repeating the steps G3 and G4 for more than 10 times (including 10 times);

h: closing the system for heating, cooling the vacuum heating furnace, and cooling the system to the normal temperature within 15 to 20 hours;

i: taking out the reaction product, crushing and grinding into powder.

Further, the method comprises the following steps of; and B, after the silicon powder is filled into the sagger, dividing the powder in the sagger into a plurality of square grids, wherein the side length of each grid is 3-4cm, punching material holes at the intersection points of the grids, and the diameter of each material hole is 0.4-1cm and reaches the bottom of the sagger.

The method for producing silicon nitride in scale can obtain high alpha phase content, the alpha phase content of the silicon nitride produced by the method exceeds 92 percent, even can reach more than 95 percent, a technical scheme which is equivalent to the method is not found in the related technology for producing the silicon nitride in a modeling mode by adopting a silicon powder nitriding method at present, although the mechanism of the method is not clear, the method firstly effectively controls the reaction speed and the temperature distribution in the reaction system under the condition of selecting proper raw material granularity, so that the temperature distribution in the reaction system can realize nitriding and can not be converted into beta phase, the formation of the alpha phase silicon nitride can be promoted in the temperature rising and reducing process of about 1230-1280 ℃, the overhigh local temperature can be strictly avoided, the addition of argon can effectively influence and control the reaction speed, the temperature of the system is controlled within a controlled interval, the material holes can play the roles of heat dissipation, gas flow promotion, contact area increase and the like, the system is more balanced in the reaction process, and the method can realize the mass production of the high alpha-phase silicon nitride.

Drawings

Figure 1 is one of the XRD patterns of a batch of product produced by the present method.

Figure 2 is a second XRD pattern of another batch of product produced by the present method.

FIG. 3 is a schematic view of silicon powder loaded into a sagger.

Detailed Description

In order to more fully explain the implementation of the present invention, the implementation examples of the present invention are provided, which are merely illustrative of the present invention and do not limit the scope of the present invention.

The various references in the drawings are: 1: silicon powder; 2: a sagger; 3: and (7) material holes.

The temperature monitoring in this application adopts the thermocouple, has arranged 6 thermocouples at the different positions of vacuum heating furnace, and the average value of 6 thermocouples is taken to the temperature.

Example 1:

the production method of the high alpha-phase silicon nitride powder comprises the following steps:

a: grinding and crushing the silicon powder until D90 is 6 mu m;

b: putting the ground silicon powder into a sagger, wherein the charging thickness is 15-30 mm; after silicon powder is filled into a sagger, dividing powder in the sagger into a plurality of square grids, wherein the side length of each grid is 3-4cm, punching material holes on materials at the intersection points of the grids, and the diameter of each material hole is 0.8cm and reaches the bottom of the sagger; FIG. 3 is a schematic view of the sagger loaded with silicon powder.

C: stacking a plurality of saggers filled with silicon powder into a stack up and down, wherein the sum of the thicknesses of the silicon powder in the saggers in the stacked stack is less than or equal to 300 mm;

d: putting the stacked sagger with the stacked silicon powder into a vacuum heating furnace, wherein the total weight of the silicon powder in the sagger with the stacked silicon powder is 70-100kg, and the saggers with the stacked silicon powder are in an array form;

e: pumping the air pressure of a vacuum heating furnace to be below 100 Pa;

f: charging nitrogen to 60 kPa;

g: the temperature rising reaction sequentially comprises the following substeps:

g1: firstly, the temperature is increased to 1120 ℃, and the heating rate is 2.8 ℃/min; introducing nitrogen in the temperature rising process, wherein the flow of the nitrogen is as follows: kilogram number of silicon powder in the vacuum furnace is multiplied by 15L/h, and the pressure in the vacuum heating furnace is kept at 60 +/-2 kPa during the execution of the step;

g2: keeping the temperature at 1120 ℃ for 18 hours, wherein the flow of nitrogen is unchanged during the heat preservation; the vacuum heating furnace is actively evacuated once in 4.5 hours during the heat preservation period, and except before and after evacuation, the pressure in the vacuum heating furnace is kept at 60 +/-2 kPa;

g3: the temperature is increased to 1280 ℃, and the heating rate is 0.6 ℃/min; when the temperature is raised to 1200 ℃, argon is introduced, the flow rate of the argon is 20 percent of the flow rate of the nitrogen, and the flow rate of the nitrogen is unchanged; during the period of introducing argon, the vacuum heating furnace is actively evacuated once every 30 minutes until the pressure is below 10 kPa, and the pressure in the step is kept at 60 +/-2 kPa before and after evacuation;

g4: reducing the temperature to 1230 ℃, wherein the temperature reduction rate is 0.35/min, the flow rates of nitrogen and argon are kept unchanged, the vacuum heating furnace is actively evacuated once every 30 minutes during the period of introducing the argon until the pressure is below 10 kPa, and the pressure in the step is kept at 60 +/-2 kPa before and after evacuation;

g5: repeating the steps G3 and G4 for 10 times;

h: closing the system for heating, cooling the vacuum heating furnace, and cooling the system to the normal temperature within 15 to 20 hours;

i: taking out the reaction product, crushing and grinding into powder.

Example 2:

the production method of the high alpha-phase silicon nitride powder comprises the following steps:

a: grinding and crushing the silicon powder until D90 is 6 mu m;

b: putting the ground silicon powder into a sagger, wherein the charging thickness is 15-30 mm; after silicon powder is loaded into the sagger, dividing powder in the sagger into a plurality of square grids, wherein the side length of each grid is 3-4cm, punching material holes on materials at the intersection points of the grids, and the diameter of each material hole is 0.6cm and reaches the bottom of the sagger;

c: stacking a plurality of saggers filled with silicon powder into a stack up and down, wherein the sum of the thicknesses of the silicon powder in the saggers in the stacked stack is less than or equal to 300 mm;

d: putting the stacked sagger with the stacked silicon powder into a vacuum heating furnace, wherein the total weight of the silicon powder in the sagger with the stacked silicon powder is 70-100kg, and the saggers with the stacked silicon powder are in an array form;

e: pumping the air pressure of a vacuum heating furnace to be below 100 Pa;

f: charging nitrogen to 60 kPa;

g: the temperature rising reaction sequentially comprises the following substeps:

g1: firstly, the temperature is increased to 1120 ℃, and the heating rate is 3 ℃/min; introducing nitrogen in the temperature rising process, wherein the flow of the nitrogen is as follows: kilogram number of silicon powder in the vacuum furnace is multiplied by 15L/h, and the pressure in the vacuum heating furnace is kept at 60 +/-2 kPa during the execution of the step;

g2: keeping the temperature at 1120 ℃ for 20 hours, wherein the flow of nitrogen is unchanged during the heat preservation; the vacuum heating furnace is actively evacuated once within 5 hours during the heat preservation period, and the pressure in the vacuum heating furnace is kept at 60 +/-2 kPa except before and after evacuation;

g3: the temperature is increased to 1280 ℃, and the heating rate is 0.5 ℃/min; when the temperature is raised to 1200 ℃, argon is introduced, the flow rate of the argon is 20 percent of the flow rate of the nitrogen, and the flow rate of the nitrogen is unchanged; during the period of introducing argon, the vacuum heating furnace is actively evacuated once every 30 minutes until the pressure is below 10 kPa, and the pressure in the step is kept at 60 +/-2 kPa before and after evacuation;

g4: reducing the temperature to 1230 ℃, wherein the temperature reduction rate is 0.4/min, the flow rates of nitrogen and argon are kept unchanged, the vacuum heating furnace is actively evacuated once every 30 minutes during the period of introducing the argon until the pressure is below 10 kPa, and the pressure in the step is kept at 60 +/-2 kPa before and after evacuation;

g5: repeating the steps G3 and G4 for 10 times;

h: closing the system for heating, cooling the vacuum heating furnace, and cooling the system to the normal temperature within 15 to 20 hours;

i: taking out the reaction product, crushing and grinding into powder.

The grinding into powder is a known technique for those skilled in the art, and will not be described herein.

The silicon nitride with high alpha phase content can be obtained by repeating the process for many times.

Fig. 1 and 2 are XRD patterns of silicon nitride obtained by the present production process, and from the peak heights of the two side β phases corresponding to the horizontal coordinate 35 of the patterns, the peak tops of the two side β phases are significantly lower than the bottom of the middle peak valley, which proves that the content of the α phase therein is high (almost all the patterns prove that the content of the α phase is not more than 90% if the peak tops of the two side β phases are higher than the bottom of the middle peak valley). The silicon nitride alpha phase content shown in fig. 1 exceeds 95%, and the silicon nitride alpha phase content in fig. 1 exceeds 93%. Shows that the silicon nitride with high alpha phase content can be obtained by the method in large-scale production.

After the embodiments of the present invention have been described in detail, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention, and it is intended that all simple modifications, equivalent changes and modifications made to the above embodiments based on the technical spirit of the present invention shall fall within the technical scope of the present invention, and the present invention shall not be limited to the embodiments illustrated in the description.