Method for producing high-purity alpha-phase silicon nitride by using crystalline silicon slice silicon sludge

Abstract

The invention provides a method for producing high-purity alpha-phase silicon nitride by using crystalline silicon slice silicon sludge, which comprises the following steps: by taking the crystalline silicon slice silicon sludge as a raw material, firstly cleaning impurities on the surface of the silicon sludge through acid pickling to ensure the purity of the raw material, and then sequentially performing granulation, drying, nitridation reaction and crushing to obtain the high-purity alpha-phase silicon nitride. The particle diameter D50 of the granular silicon sludge obtained by granulation is controlled to be 5-12mm. The method provided by the invention not only can prepare the high-purity alpha-phase silicon nitride with the purity of more than or equal to 95% and the alpha-phase proportion of more than or equal to 99%, but also has the advantages of simplicity in operation, sufficient raw materials, low cost, reduction of waste discharge and the like, and is convenient to popularize and use.

Description

Technical Field

[0001] The invention relates to the technical field of silicon nitride powder preparation, and in particular to a method for producing high-purity alpha-phase silicon nitride by utilizing crystalline silicon slice silicon mud. Background Art

[0002] Silicon nitride (Si3N4), as an important inorganic non-metallic material, has excellent physical and chemical properties and is widely used in many fields. With the advancement of science and technology and changes in market demand, the application prospects of silicon nitride materials will be broader. Technological innovation and improvements in preparation processes will further reduce production costs and improve its market competitiveness. Especially in the fields of new energy vehicles, 5G communications and smart grids, the demand for silicon nitride ceramics will continue to grow, providing it with a broad market space. Therefore, silicon nitride will continue to play an important role in many industries in the future with its excellent performance and wide range of applications.

[0003] At present, there are two main methods for preparing silicon nitride powder: one is the self-diffusion method, and the other is the chemical silicon-ammonia decomposition method. The self-diffusion reaction method is to fully mix silicon powder and a part of metal, and then react in a high-temperature nitrogen environment to generate silicon nitride powder. The advantage of this method is that the process is simple, but the energy consumption is high, and the purity of the silicon nitride powder obtained is not high and the particle size is large. The chemical silicon-ammonia decomposition method is to generate silicon ammonia through chemical reaction first, and then thermally decompose it at high temperature. The advantage of this method is that the purity of the silicon nitride powder is high and the particle size is small, but the equipment is complex and the cost is high, and some emissions will pollute the environment.

[0004] In the process of preparing thin-sheet products such as solar cell substrates, integrated circuit substrates, electronic chips, and precision semiconductor chips, a large amount of silicon wafer sawdust is generated, including band sawdust, abrasive dust, diamond wire sawdust, etc. Taking silicon wafer wire cutting as an example, the thickness of silicon wafers is generally about 0.22mm, and the width of the wire saw seam is 0.18-0.30mm, which means that 40-60% of high-purity silicon materials become sawdust and enter the slurry. In general, the waste sawdust generated by the cutting process is mainly composed of silicon particles and a small amount of metal impurities. Some sawdust contains coolants such as polyethylene glycol. The silicon particles are only contaminated by metal impurities on the surface, and the interior is still high-purity silicon material. Impurities have not entered the silicon lattice, so high-purity silicon powder can be obtained through conventional acid washing and water washing processes.

[0005] Generally speaking, the waste fine silicon powder produced in the process of crystalline silicon slicing is called crystalline silicon slicing silicon mud. How to make full use of crystalline silicon slicing silicon mud is an urgent problem to be solved. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud, using crystalline silicon slice silicon mud as raw material, firstly cleaning the impurities on the surface of the silicon mud by pickling to ensure the purity of the raw material, and then sequentially performing granulation, drying, nitridation reaction, and crushing to obtain high-purity α-phase silicon nitride, and controlling the particle diameter D50 of the granular silicon mud obtained by granulation to be 5-12mm. The method of the present invention can not only prepare high-purity α-phase silicon nitride with a purity of ≥95% and an α-phase ratio of ≥99%, but also has the advantages of simple operation, sufficient raw materials, low cost, and reduced waste emissions, and is easy to promote and use.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The object of the present invention is to provide a method for producing high-purity α-phase silicon nitride by using crystalline silicon slice silicon mud, the method comprising the following steps:

[0009] The silicon mud of the crystalline silicon slices is acid-washed, and then washed with water until neutral to obtain high-purity silicon mud; the high-purity silicon mud is sequentially granulated, dried, nitrided, and crushed to obtain high-purity α-phase silicon nitride;

[0010] The particle diameter D50 of the granular silicon mud obtained by the granulation is 5-12 mm, for example, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm or 12 mm.

[0011] The method of the present invention uses silicon mud from crystalline silicon slices as raw material, firstly cleans the impurities on the surface of the silicon mud by pickling to ensure the purity of the raw material, then sequentially performs granulation, drying, nitridation reaction, and crushing to obtain high-purity α-phase silicon nitride, and controls the particle diameter D50 of the granular silicon mud obtained by granulation to be 5-12mm. The method of the present invention can not only prepare high-purity α-phase silicon nitride with a purity of ≥95% and an α-phase ratio of ≥99%, but also has the advantages of simple operation, sufficient raw materials, low cost, and reduced waste emissions, and is easy to promote and use.

[0012] It should be noted that the silicon powder particle size in the silicon mud for crystalline silicon slices is less than 1 μm. If the purified high-purity silicon powder is directly subjected to a subsequent nitridation reaction with nitrogen, the nitrogen gas flow will cause the high-purity silicon powder to disperse, causing pollution, waste, and even blocking the instrument pipeline. Therefore, the method of the present invention sequentially granulates, dries, and nitrides the high-purity silicon mud, and limits the particle diameter D50 of the granular silicon mud obtained by granulation to 5-12 mm, which makes the operation simple and easy while ensuring the purity of silicon nitride and the ratio of the α phase.

[0013] As a preferred technical solution of the present invention, the pickling comprises: uniformly mixing silicon mud of crystalline silicon slices with deionized water to form a silicon-water mixture, and adding inorganic acid to the silicon-water mixture for surface cleaning.

[0014] It should be noted that the pickling method described in the present invention is used to clean the surface of silicon mud of crystalline silicon slices, and the acid concentration, pickling time and pickling temperature are all directly proportional to the cleaning quality.

[0015] As a preferred technical solution of the present invention, the mass ratio of the crystalline silicon slice silicon mud to deionized water is 1:(4.5-5.5), for example, 1:4.5, 1:4.8, 1:5, 1:5.2 or 1:5.5.

[0016] Preferably, the inorganic acid comprises hydrochloric acid, hydrogen peroxide and hydrofluoric acid, and the concentration of hydrochloric acid is controlled to be 4-6wt%, for example, 4wt%, 4.5wt%, 5wt%, 5.5wt% or 6wt%, etc., the concentration of hydrogen peroxide is 0.8-2wt%, for example, 0.8wt%, 1wt%, 1.3wt%, 1.5wt%, 1.7wt% or 2wt%, etc., and the concentration of hydrofluoric acid is 1-3.5wt%, for example, 1wt%, 1.3wt%, 1.5wt%, 1.8wt%, 2wt%, 2.5wt%, 3wt% or 3.5wt%, etc.

[0017] It should be noted that the concentration of the aforementioned inorganic acid refers to the mass percentage of the inorganic acid in the entire system after the corresponding inorganic acid is added to the silicon-water mixture.

[0018] As a preferred technical solution of the present invention, the pickling temperature is 30-60°C, for example, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C.

[0019] Preferably, the pickling time is 4-8 h, for example, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h or 8 h.

[0020] As a preferred technical solution of the present invention, the granulation temperature is 40-80°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C.

[0021] Preferably, the granulation is carried out using a granulation equipment, and the rotation speed of the granulation equipment is 60-100r / min, for example, 60r / min, 65r / min, 70r / min, 75r / min, 80r / min, 85r / min, 90r / min, 95r / min or 100r / min, etc.

[0022] As a preferred technical solution of the present invention, the drying is carried out by drying, and nitrogen is used for protective drying during the drying process.

[0023] Preferably, the drying temperature is ≤150°C.

[0024] As a preferred technical solution of the present invention, the nitridation reaction includes: placing the dried granular silicon mud in a loading box, and then placing the whole in a vacuum heating furnace, and sequentially performing vacuuming, nitrogen flow, heating and temperature raising to perform a nitridation reaction.

[0025] As a preferred technical solution of the present invention, the material of the charging box is any one of graphite, alumina, silicon nitride or silicon carbide.

[0026] Preferably, the loading box is in the shape of a rectangular parallelepiped, is open, and has five walls evenly provided with ventilation holes.

[0027] Preferably, the diameter of the vent hole is ≥6 mm.

[0028] It should be noted that the material of the loading box of the present invention is non-metallic and high-temperature resistant. If a carbon-containing material is used, it will affect the carbon content of the final silicon nitride product. It is recommended to use a loading box made of silicon nitride.

[0029] It should be noted that the charging box in the method of the present invention is a structural design that is compatible with the previous granulation. On the one hand, the charging box is set to be a rectangular and open box, and vents are evenly arranged on the five walls, so that nitrogen can diffuse between the granular silicon mud balls and achieve the uniformity of the nitridation reaction. On the other hand, the charging box is designed to be easy to disassemble and easy to operate. Furthermore, through experimental research, the aperture of the vent is ≥6mm to ensure that nitrogen can fully diffuse into the charging box and fully react with the high-purity silicon powder in the box.

[0030] As a preferred technical solution of the present invention, the vacuum is evacuated to a furnace pressure below 1 Pa, and the nitrogen is passed to a furnace pressure of 3000-90000Pa, for example, 3000Pa, 5000Pa, 8000Pa, 10000Pa, 20000Pa, 40000Pa, 60000Pa, 80000Pa or 90000Pa.

[0031] It should be noted that the pressure in the furnace after nitrogen is passed through the furnace is 3000-90000Pa, which is lower than the atmospheric pressure, that is, the pressure in the furnace after nitrogen is passed through is negative pressure. Compared with the slightly positive pressure setting of nitrogen in the prior art, the temperature of the nitridation reaction will not be too high, and the formation of β-phase silicon nitride can be avoided.

[0032] Preferably, the heating temperature is increased in a step-by-step manner; starting from room temperature, the temperature is increased to 750-850°C, such as 750°C, 770°C, 790°C, 800°C, 810°C, 830°C or 850°C, at a rate of 3-8°C / min, such as 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min or 8°C / min, and the temperature is kept for 5-10h, such as 5h, 6h, 7h, 8h, 9h or 10h. etc., at a rate of 2-6°C / min, such as 2°C / min, 3°C / min, 4°C / min, 5°C / min or 6°C / min, etc., to 950-1050°C, such as 950°C, 970°C, 980°C, 1000°C, 1010°C, 1030°C or 1050°C, etc., and keep warm for 16-24h, such as 16h, 18h, 20h, 22h or 24h, etc., at a rate of 0.03-0.05°C / min, such as 0 .03℃ / min, 0.035℃ / min, 0.04℃ / min, 0.045℃ / min or 0.05℃ / min, etc., raise the temperature to 1150-1250℃, such as 1150℃, 1170℃, 1180℃, 1200℃, 1210℃, 1230℃ or 1250℃, etc., and keep warm for 5-7h, such as 5h, 5.5h, 6h, 6.5h or 7h, etc., at a rate of 0.01-0.03℃ / min, such as 0.01℃ / min, 0.015℃ / min, 0.02℃ / min, 0.025℃ / min or 0.03℃ / min, etc., raise the temperature to 1300-1360℃, for example, 1300℃, 1310℃, 1320℃, 1330℃, 1340℃, 1350℃ or 1360℃, etc., keep warm for 18-24h, for example, 18h, 19h, 20h, 21h, 22h, 23h or 24h, etc., and then cool naturally to room temperature.

[0033] It should be noted that in the heating process described in the present invention, the maximum temperature does not exceed 1360°C, and the heating process needs to be strictly controlled. When the temperature is raised to the range of 950-1050°C and the insulation is completed, the heating rate must be reduced during the heating to the maximum temperature to ensure the quality of silicon nitride.

[0034] As a preferred technical solution of the present invention, the method comprises the following steps:

[0035] Step S1: uniformly mixing crystalline silicon slice silicon mud and deionized water, wherein the mass ratio of the crystalline silicon slice silicon mud to the deionized water is 1:(4.5-5.5), to form a silicon-water mixture; adding hydrochloric acid, hydrogen peroxide and hydrofluoric acid to the silicon-water mixture, controlling the concentration of hydrochloric acid to be 4-6wt%, the concentration of hydrogen peroxide to be 0.8-2wt%, and the concentration of hydrofluoric acid to be 1-3.5wt%, acid washing at 30-60°C, stirring and washing for 4-8h; after filtering, repeatedly washing with deionized water until the pH value of the washing liquid is neutral, and finally filtering to obtain high-purity silicon mud;

[0036] Step S2: Put high-purity silicon mud into a granulation device, control the rotation speed to 60-100 r / min, and control the material temperature to 40-80° C. to obtain granular silicon mud balls with basically uniform diameters, and the particle diameter D50 is 5-12 mm;

[0037] Step S3: putting the granular silicon mud balls into an oven for drying, using nitrogen for protective drying during the drying process, controlling the drying temperature to be ≤150° C., and obtaining dry granular silicon mud balls with a moisture content of <0.3wt%;

[0038] Step S4: placing the dried granular silicon mud balls in a loading box, wherein the loading box is made of any one of graphite, alumina, silicon nitride or silicon carbide, and the loading box is in the shape of a rectangular parallelepiped, open, and has five walls evenly provided with vent holes with an aperture of ≥6 mm; and then placing the whole in a vacuum heating furnace;

[0039] Step S5: evacuate the vacuum heating furnace to a detected pressure of <1Pa; then introduce nitrogen to make the pressure in the furnace 3000-90000Pa; then heat and raise the temperature to carry out nitridation reaction;

[0040] The heating temperature is increased in stages; starting from room temperature, the temperature is increased to 750-850°C at a rate of 3-8°C / min, and the temperature is kept for 5-10 hours; the temperature is increased to 950-1050°C at a rate of 2-6°C / min, and the temperature is kept for 16-24 hours; the temperature is increased to 1150-1250°C at a rate of 0.03-0.05°C / min, and the temperature is kept for 5-7 hours; the temperature is increased to 1300-1360°C at a rate of 0.01-0.03°C / min, and the temperature is kept for 18-24 hours; then the temperature is naturally lowered to room temperature along with the furnace to obtain high-purity α-phase silicon nitride granular spheres;

[0041] Step S6: crushing and grinding the high-purity silicon nitride granules to obtain high-purity α-phase silicon nitride powder.

[0042] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0043] (1) The present invention provides a method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud. The crystalline silicon slice silicon mud is used as a raw material. The impurities on the surface of the silicon mud are first cleaned by acid washing to ensure the purity of the raw material. Then, granulation, drying, nitridation reaction, and crushing are performed in sequence to obtain high-purity α-phase silicon nitride. The particle diameter D50 of the granular silicon mud obtained by granulation is controlled to be 5-12 mm. The method of the present invention can prepare high-purity α-phase silicon nitride with a purity of ≥95% and an α phase ratio of ≥99%;

[0044] (2) The method of the present invention mainly uses waste silicon mud generated by crystalline silicon slicing as raw material, and the price of these raw materials is relatively low, thereby effectively reducing the preparation cost of silicon nitride powder. Compared with the existing silicon nitride preparation method, the method of the present invention is more economical;

[0045] (3) The method of the present invention is simple and easy to implement, avoiding the complex steps of high-temperature solid-phase reaction or chemical synthesis followed by thermal decomposition required in the existing silicon nitride preparation method, thereby greatly simplifying the preparation process, improving production efficiency, and reducing production costs; the preparation method of the present invention can obtain silicon nitride powder with high purity and good quality, because the process of the present invention is pollution-free, simple and controllable;

[0046] (4) The raw material of the method described in the present invention is crystalline silicon slice silicon mud, which has a particle size of less than 1 micron, thereby saving the step of raw material grinding. The larger the scale of photovoltaic development, the more silicon mud will be produced. The method described in the present invention can reduce the cost of waste treatment and effectively utilize waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a flow chart of the method for producing high-purity α-phase silicon nitride by using crystalline silicon slice silicon mud according to the present invention;

[0048] Figure 2 is a front view of the charging box described in Example 1 of the present invention;

[0049] Figure 3 is a side view of the charging box described in Example 1 of the present invention;

[0050] Figure 4 It is a bottom view of the loading box described in Example 1 of the present invention. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0052] The present invention provides a method for producing high-purity α-phase silicon nitride by using crystalline silicon slice silicon mud. Figure 1 As shown, the method comprises the following steps:

[0053] The silicon mud of crystalline silicon slices is pickled and then washed with water until neutral to obtain high-purity silicon mud; the high-purity silicon mud is successively granulated, dried, nitrided and crushed to obtain high-purity α-phase silicon nitride; wherein the particle diameter D50 of the granular silicon mud obtained by granulation is 5-12mm.

[0054] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0055] The material models of the embodiments of the present invention are: crystalline silicon slice silicon mud, purity 92%; hydrochloric acid, concentration 36%, analytical grade; hydrogen peroxide, concentration 33%, analytical grade; hydrofluoric acid, concentration 50%, analytical grade; the three inorganic acids are all from domestic chemical plants; nitrogen, purity 99.99%, from a domestic gas company.

[0056] Example 1

[0057] This embodiment provides a method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud, the method comprising the following steps:

[0058] Step S1: uniformly mix crystalline silicon slice silicon mud and deionized water, wherein the mass ratio of crystalline silicon slice silicon mud to deionized water is 1:5, to form a silicon-water mixture; add hydrochloric acid, hydrogen peroxide and hydrofluoric acid to the silicon-water mixture, wherein the concentration of hydrochloric acid is controlled to be 4wt%, the concentration of hydrogen peroxide is controlled to be 0.8wt%, the concentration of hydrofluoric acid is controlled to be 1wt%, the temperature is controlled to be 45°C for pickling, stirring and washing for 6 hours, filtering, repeatedly washing with deionized water until the pH value of the washing liquid is neutral, and finally filtering to obtain high-purity silicon mud;

[0059] Step S2: Put high-purity silicon mud into a granulation device, control the device speed to 65r / min, and the material temperature to 45°C to obtain granular silicon mud balls with basically uniform diameters, and the particle diameter D50 is 12mm;

[0060] Step S3: putting the granular silicon mud balls into an oven for drying, using nitrogen for protective drying during the drying process, controlling the drying temperature to be 150° C., and obtaining dry granular silicon mud balls with a moisture content of less than 0.3 wt %;

[0061] Step S4: Place the dried granular silicon mud balls in a loading box made of graphite. Figure 2-4 As shown, the charging box is a rectangular parallelepiped, open, and five walls are evenly provided with ventilation holes with a diameter of 10 mm; then the whole is placed in a vacuum heating furnace;

[0062] Step S5: evacuate the vacuum heating furnace until the detected pressure is less than 1Pa; then pass nitrogen to make the pressure in the furnace 3000Pa; then heat and increase the temperature to carry out nitridation reaction; wherein, the heating and temperature increase adopts a step-by-step heating method; starting from room temperature, heat to 800°C at a heating rate of 3°C / min, and keep warm for 5h; heat to 1000°C at a heating rate of 2°C / min, and keep warm for 16h; heat to 1200°C at a rate of 0.03°C / min, and keep warm for 6h; heat to 1320°C at a rate of 0.01°C / min, and keep warm for 18h; then naturally cool to room temperature with the furnace to obtain high-purity α-phase silicon nitride granular spheres;

[0063] Step S6: crushing and grinding the high-purity silicon nitride granules to obtain high-purity α-phase silicon nitride powder.

[0064] Example 2

[0065] This embodiment provides a method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud, the method comprising the following steps:

[0066] Step S1: evenly mix crystalline silicon slice silicon mud and deionized water, the mass ratio of crystalline silicon slice silicon mud to deionized water is 1:5, to form a silicon-water mixture; add hydrochloric acid, hydrogen peroxide and hydrofluoric acid to the silicon-water mixture, control the concentration of hydrochloric acid to be 5wt%, the concentration of hydrogen peroxide to be 1wt%, the concentration of hydrofluoric acid to be 1.6wt%, the temperature is controlled at 50°C for pickling, stir and wash for 7h, filter, repeatedly wash with deionized water until the pH value of the washing liquid is neutral, and finally filter to obtain high-purity silicon mud;

[0067] Step S2: Put high-purity silicon mud into a granulation device, control the device speed to 70r / min, and the material temperature to 50°C to obtain granular silicon mud balls with basically uniform diameters, and the particle diameter D50 is 10mm;

[0068] Step S3: putting the granular silicon mud balls into an oven for drying, using nitrogen for protective drying during the drying process, controlling the drying temperature to be 150° C., and obtaining dry granular silicon mud balls with a moisture content of less than 0.3 wt %;

[0069] Step S4: placing the dried granular silicon mud balls in a loading box made of alumina, wherein the loading box is a rectangular parallelepiped, open, and has five walls evenly provided with vent holes with a diameter of 10 mm; and then placing the whole into a vacuum heating furnace;

[0070] Step S5: evacuate the vacuum heating furnace until the detected pressure is less than 1Pa; then pass nitrogen to make the pressure in the furnace 8000Pa; then heat and increase the temperature to carry out nitridation reaction; wherein, the heating and temperature increase adopts a step-by-step heating method; starting from room temperature, heat to 800°C at a heating rate of 4°C / min, and keep warm for 6 hours; heat to 1000°C at a heating rate of 3°C / min, and keep warm for 18 hours; heat to 1200°C at a rate of 0.04°C / min, and keep warm for 6 hours; heat to 1320°C at a rate of 0.02°C / min, and keep warm for 20 hours; then naturally cool to room temperature with the furnace to obtain high-purity α-phase silicon nitride granular spheres;

[0071] Step S6: crushing and grinding the high-purity silicon nitride granules to obtain high-purity α-phase silicon nitride powder.

[0072] Example 3

[0073] This embodiment provides a method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud, the method comprising the following steps:

[0074] Step S1: uniformly mix crystalline silicon slice silicon mud and deionized water, wherein the mass ratio of crystalline silicon slice silicon mud to deionized water is 1:5, to form a silicon-water mixture; add hydrochloric acid, hydrogen peroxide and hydrofluoric acid to the silicon-water mixture, wherein the concentration of hydrochloric acid is controlled to be 5wt%, the concentration of hydrogen peroxide is controlled to be 1wt%, the concentration of hydrofluoric acid is controlled to be 1.8wt%, the temperature is controlled to be 60°C for pickling, stirring and washing for 8h, filtering, repeatedly washing with deionized water until the pH value of the washing liquid is neutral, and finally filtering to obtain high-purity silicon mud;

[0075] Step S2: Put high-purity silicon mud into a granulation device, control the device speed to 90r / min, and control the material temperature to 60°C to obtain granular silicon mud balls with basically uniform diameters, and the particle diameter D50 is 6mm;

[0076] Step S3: putting the granular silicon mud balls into an oven for drying, using nitrogen for protective drying during the drying process, controlling the drying temperature to be 150° C., and obtaining dry granular silicon mud balls with a moisture content of less than 0.3 wt %;

[0077] Step S4: placing the dried granular silicon mud balls in a loading box made of graphite, wherein the loading box is a rectangular parallelepiped, open, and has five walls evenly provided with vent holes with a diameter of 7 mm; and then placing the whole into a vacuum heating furnace;

[0078] Step S5: evacuate the vacuum heating furnace until the detected pressure is less than 1Pa; then pass nitrogen to make the pressure in the furnace 20000Pa; then heat and increase the temperature to carry out nitridation reaction; wherein, the heating and temperature increase adopts a step-by-step heating method; starting from room temperature, heat to 800°C at a heating rate of 4°C / min, and keep it warm for 8h; heat to 1000°C at a heating rate of 4°C / min, and keep it warm for 20h; heat to 1200°C at a rate of 0.05°C / min, and keep it warm for 6h; heat to 1320°C at a rate of 0.02°C / min, and keep it warm for 22h; then naturally cool to room temperature with the furnace to obtain high-purity α-phase silicon nitride granular spheres;

[0079] Step S6: crushing and grinding the high-purity silicon nitride granules to obtain high-purity α-phase silicon nitride powder.

[0080] Example 4

[0081] This embodiment provides a method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud, the method comprising the following steps:

[0082] Step S1: evenly mix crystalline silicon slice silicon mud and deionized water, the mass ratio of crystalline silicon slice silicon mud to deionized water is 1:5, to form a silicon-water mixture; add hydrochloric acid, hydrogen peroxide and hydrofluoric acid to the silicon-water mixture, control the concentration of hydrochloric acid to 6wt%, the concentration of hydrogen peroxide to 1.3wt%, the concentration of hydrofluoric acid to 2.3wt%, control the temperature at 60°C for pickling, stir and wash for 8h, repeatedly wash with deionized water until the pH value of the washing liquid is neutral, and finally filter to obtain high-purity silicon mud;

[0083] Step S2: putting high-purity silicon mud into a granulating device, controlling the device speed to 100 r / min, and the material temperature to 60° C., to obtain granular silicon mud balls with substantially uniform diameters, and the particle diameter D50 is 5 mm;

[0084] Step S3: putting the granular silicon mud balls into an oven for drying, using nitrogen for protective drying during the drying process, controlling the drying temperature to be 150° C., and obtaining dry granular silicon mud balls with a moisture content of less than 0.3 wt %;

[0085] Step S4: placing the dried granular silicon mud balls in a loading box made of silicon nitride, wherein the loading box is a rectangular parallelepiped, open, and has five walls evenly provided with vent holes with a diameter of 6 mm; and then placing the whole into a vacuum heating furnace;

[0086] Step S5: evacuate the vacuum heating furnace to a detected pressure of <1Pa; then pass nitrogen to make the pressure in the furnace 40000Pa; then heat and raise the temperature to carry out nitridation reaction; wherein, the heating and raising the temperature adopts a step-by-step heating method; starting from room temperature, heating to 800°C at a heating rate of 6°C / min, and keeping it warm for 8h; heating to 1000°C at a heating rate of 5°C / min, and keeping it warm for 24h; heating to 1200°C at a rate of 0.03°C / min, and keeping it warm for 6h; heating to 1320°C at a rate of 0.03°C / min, and keeping it warm for 24h; then naturally cooling down to room temperature with the furnace to obtain high-purity α-phase silicon nitride granular spheres;

[0087] Step S6: crushing and grinding the high-purity silicon nitride granules to obtain high-purity α-phase silicon nitride powder.

[0088] Example 5

[0089] This embodiment provides a method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud, the method comprising the following steps:

[0090] Step S1: uniformly mix crystalline silicon slice silicon mud and deionized water, wherein the mass ratio of crystalline silicon slice silicon mud to deionized water is 1:5, to form a silicon-water mixture; add hydrochloric acid, hydrogen peroxide and hydrofluoric acid to the silicon-water mixture, wherein the concentration of hydrochloric acid is controlled to be 6wt%, the concentration of hydrogen peroxide is controlled to be 2wt%, the concentration of hydrofluoric acid is controlled to be 3wt%, the temperature is controlled to be 60°C for pickling, stirring and cleaning for 7h, repeatedly washing with deionized water until the pH value of the washing liquid is neutral, and finally filtering to obtain high-purity silicon mud;

[0091] Step S2: putting high-purity silicon mud into a granulating device, controlling the device speed to 100 r / min, and the material temperature to 80° C., to obtain granular silicon mud balls with substantially uniform diameters, and the particle diameter D50 is 5 mm;

[0092] Step S3: putting the granular silicon mud balls into an oven for drying, using nitrogen for protective drying during the drying process, controlling the drying temperature to be 150° C., and obtaining dry granular silicon mud balls with a moisture content of less than 0.3 wt %;

[0093] Step S4: placing the dried granular silicon mud balls in a loading box made of silicon carbide, wherein the loading box is a rectangular parallelepiped, open, and has five walls evenly provided with vent holes with a diameter of 6 mm; and then placing the whole into a vacuum heating furnace;

[0094] Step S5: evacuate the vacuum heating furnace until the detected pressure is less than 1Pa; then pass nitrogen to make the pressure in the furnace 40000Pa; then heat and increase the temperature to carry out nitridation reaction; wherein, the heating and temperature increase adopts a step-by-step heating method; starting from room temperature, heat to 800°C at a heating rate of 6°C / min, and keep warm for 8h; heat to 1000°C at a heating rate of 5°C / min, and keep warm for 22h; heat to 1200°C at a rate of 0.03°C / min, and keep warm for 6h; heat to 1320°C at a rate of 0.02°C / min, and keep warm for 24h; then naturally cool to room temperature with the furnace to obtain high-purity α-phase silicon nitride granular spheres;

[0095] Step S6: crushing and grinding the high-purity silicon nitride granules to obtain high-purity α-phase silicon nitride powder.

[0096] Example 6

[0097] This embodiment provides a method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud. Compared with Example 5, the only difference is that in step S5, a mixed gas of nitrogen and argon is passed through, and the pressure in the furnace is made 400,000 Pa by the introduction of argon.

[0098] Example 7

[0099] This embodiment provides a method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud. Compared with Example 5, the only difference is: in step S5, after keeping the temperature at 1000°C for 22 hours, the temperature is increased to 1200°C at a rate of 0.1°C / min and kept for 6 hours; the temperature is increased to 1320°C at a rate of 0.05°C / min and kept for 24 hours.

[0100] Example 8

[0101] This embodiment provides a method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud. Compared with Example 5, the only difference is that in step S4, the loading box made of silicon carbide is omitted, and the dried granular silicon mud balls are placed in an ordinary cylindrical corundum crucible.

[0102] Example 9

[0103] This embodiment provides a method for producing high-purity α-phase silicon nitride by using crystalline silicon slice silicon mud. Compared with Embodiment 5, the only difference is that in step S4, the aperture of the vent hole of the charging box is reduced to 4 mm.

[0104] It should be noted that, although in the above embodiment, the particle diameter D50 in step S2 is smaller than the vent hole diameter in step S4, due to the stacking effect of the particles, there will be no problem of particles leaking from the vent holes.

[0105] The high-purity α-phase silicon nitride prepared in the above embodiment was subjected to purity test and α-phase ratio test. The specific test results are shown in Table 1.

[0106] Table 1

[0107]

[0108] In summary, the present invention provides a method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud. Crystalline silicon slice silicon mud is used as raw material. Impurities on the surface of the silicon mud are first cleaned by acid washing to ensure the purity of the raw material. Then, granulation, drying, nitridation reaction, and crushing are carried out in sequence to obtain high-purity α-phase silicon nitride. The particle diameter D50 of the granular silicon mud obtained by granulation is controlled to be 5-12mm. The method of the present invention can prepare high-purity α-phase silicon nitride with a purity of ≥95% and an α phase ratio of ≥99%.

[0109] The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0110] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0111] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0112] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud, characterized in that: The method comprises the following steps: The silicon mud of the crystalline silicon slices is acid-washed, and then washed with water until neutral to obtain high-purity silicon mud; the high-purity silicon mud is sequentially granulated, dried, nitrided, and crushed to obtain high-purity α-phase silicon nitride; The particle diameter D50 of the granular silicon mud obtained by granulation is 5-12 mm.

2. The method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud according to claim 1, characterized in that: The pickling comprises: uniformly mixing silicon mud of crystalline silicon slices with deionized water to form a silicon-water mixed liquid, and adding inorganic acid to the silicon-water mixed liquid to perform surface cleaning.

3. The method for producing high-purity α-phase silicon nitride using crystalline silicon slice silicon mud according to claim 2, characterized in that: The mass ratio of the crystalline silicon slice silicon mud to the deionized water is 1:(4.5-5.5); Preferably, the inorganic acid comprises hydrochloric acid, hydrogen peroxide and hydrofluoric acid, and the concentration of hydrochloric acid is controlled to be 4-6wt%, the concentration of hydrogen peroxide is controlled to be 0.8-2wt%, and the concentration of hydrofluoric acid is controlled to be 1-3.5wt%.

4. The method for producing high-purity α-phase silicon nitride by using crystalline silicon slice silicon mud according to any one of claims 1 to 3, characterized in that: The pickling temperature is 30-60°C; Preferably, the pickling time is 4-8 hours.

5. The method for producing high-purity α-phase silicon nitride by using crystalline silicon slice silicon mud according to any one of claims 1 to 4, characterized in that: The granulation temperature is 40-80°C; Preferably, the granulation is carried out using a granulation equipment, and the rotation speed of the granulation equipment is 60-100r / min.

6. The method for producing high-purity α-phase silicon nitride by using crystalline silicon slice silicon mud according to any one of claims 1 to 5, characterized in that: The drying is carried out by drying, and nitrogen is used for protective drying during the drying process; Preferably, the drying temperature is ≤150°C.

7. The method for producing high-purity α-phase silicon nitride by using crystalline silicon slice silicon mud according to any one of claims 1 to 6, characterized in that: The nitriding reaction comprises: placing the dried granular silicon mud in a loading box, and then placing the whole in a vacuum heating furnace, and sequentially performing vacuuming, nitrogen flow, heating and temperature raising to perform a nitriding reaction.

8. The method for producing high-purity α-phase silicon nitride by using crystalline silicon slice silicon mud according to claim 7, characterized in that: The material of the charging box is any one of graphite, alumina, silicon nitride or silicon carbide; Preferably, the loading box is in the shape of a rectangular parallelepiped, open, and has five walls evenly provided with ventilation holes; Preferably, the diameter of the vent hole is ≥6 mm.

9. The method for producing high-purity α-phase silicon nitride by using crystalline silicon slice silicon mud according to claim 7, characterized in that: The vacuuming is performed until the pressure in the furnace is below 1Pa, and the nitrogen is passed until the pressure in the furnace is 3000-90000Pa; Preferably, the heating temperature is increased in a step-by-step manner; starting from room temperature, the temperature is increased to 750-850°C at a rate of 3-8°C / min, and kept warm for 5-10 hours; the temperature is increased to 950-1050°C at a rate of 2-6°C / min, and kept warm for 16-24 hours; the temperature is increased to 1150-1250°C at a rate of 0.03-0.05°C / min, and kept warm for 5-7 hours; the temperature is increased to 1300-1360°C at a rate of 0.01-0.03°C / min, and kept warm for 18-24 hours; and then the temperature is naturally cooled to room temperature.

10. The method for producing high-purity α-phase silicon nitride by using crystalline silicon slice silicon mud according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: Step S1: uniformly mixing crystalline silicon slice silicon mud and deionized water, wherein the mass ratio of the crystalline silicon slice silicon mud to the deionized water is 1:(4.5-5.5), to form a silicon-water mixture; adding hydrochloric acid, hydrogen peroxide and hydrofluoric acid to the silicon-water mixture, controlling the concentration of hydrochloric acid to be 4-6wt%, the concentration of hydrogen peroxide to be 0.8-2wt%, and the concentration of hydrofluoric acid to be 1-3.5wt%, acid washing at 30-60°C, stirring and washing for 4-8h; after filtering, repeatedly washing with deionized water until the pH value of the washing liquid is neutral, and finally filtering to obtain high-purity silicon mud; Step S2: Put high-purity silicon mud into a granulation device, control the rotation speed to 60-100 r / min, and control the material temperature to 40-80° C. to obtain granular silicon mud balls with basically uniform diameters, and the particle diameter D50 is 5-12 mm; Step S3: putting the granular silicon mud balls into an oven for drying, using nitrogen for protective drying during the drying process, controlling the drying temperature to be ≤150° C., and obtaining dry granular silicon mud balls with a moisture content of <0.3wt%; Step S4: placing the dried granular silicon mud balls in a loading box, wherein the loading box is made of any one of graphite, alumina, silicon nitride or silicon carbide, and the loading box is in the shape of a rectangular parallelepiped, open, and has five walls evenly provided with vent holes with an aperture of ≥6 mm; and then placing the whole in a vacuum heating furnace; Step S5: evacuate the vacuum heating furnace to a detected pressure of <1Pa; then introduce nitrogen to make the pressure in the furnace 3000-90000Pa; then heat and raise the temperature to carry out nitridation reaction; The heating temperature is increased in stages; starting from room temperature, the temperature is increased to 750-850°C at a rate of 3-8°C / min, and the temperature is kept for 5-10 hours; the temperature is increased to 950-1050°C at a rate of 2-6°C / min, and the temperature is kept for 16-24 hours; the temperature is increased to 1150-1250°C at a rate of 0.03-0.05°C / min, and the temperature is kept for 5-7 hours; the temperature is increased to 1300-1360°C at a rate of 0.01-0.03°C / min, and the temperature is kept for 18-24 hours; then the temperature is naturally lowered to room temperature along with the furnace to obtain high-purity α-phase silicon nitride granular spheres; Step S6: crushing and grinding the high-purity silicon nitride granules to obtain high-purity α-phase silicon nitride powder.

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