Method for preparing silicon carbide from monocrystalline silicon cutting waste and thermal field waste graphite

Abstract

The invention belongs to the technical field of clean and efficient utilization of secondary resources, and particularly relates to a method for preparing silicon carbide from monocrystalline silicon cutting waste and thermal field waste graphite. The silicon carbide is prepared by taking iron-containing monocrystalline silicon cutting waste and thermal field waste graphite as raw materials, uniformly mixing the raw materials according to a set molar ratio, then putting the mixture into an ultrahigh-temperature box-type resistance furnace, carrying out high-temperature roasting under the condition that protective gas is introduced, preparing loose and porous silicon carbide powder, grinding the loose and porous silicon carbide powder, putting the ground loose and porous silicon carbide powder into a tubular furnace, and carrying out oxidation so as to remove excess carbon, so that the silicon carbide is obtained. And finally, carrying out acid leaching and drying to obtain the high-quality silicon carbide powder. The method not only solves the problem of environmental pollution caused by monocrystalline silicon cutting waste and monocrystalline drawing thermal field waste graphite, but also improves the utilization efficiency, saves energy, and can reduce the production cost of monocrystalline silicon. Meanwhile, the prepared silicon carbide is high in quality and has high commercial application value, and high-value utilization of the silicon cutting waste and the waste graphite is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of clean and efficient utilization of secondary resources, and in particular relates to a method for preparing silicon carbide from single crystal silicon cutting waste and thermal field waste graphite. Background Art

[0002] The rapid development of the photovoltaic industry has led to an increasing demand for monocrystalline silicon. Monocrystalline silicon not only generates a large amount of waste during the cutting process, but also produces a large amount of waste graphite components during the crystal pulling process. Thermal field waste graphite contains the largest proportion of graphite, and monocrystalline silicon cutting waste contains a large amount of silicon powder. If these waste materials are not utilized, the accumulation of waste will not only pollute the environment but also lead to a waste of resources. Current patents related to the recycling and utilization of silicon cutting waste include: A method for producing high-quality silicon carbide from crystalline silicon cutting waste (CN107651691B); a method for producing high-quality silicon carbide from diamond wire cutting waste (CN107651690B); a method for producing nano-silicon carbide from crystalline silicon cutting waste (CN109734098A); a method for producing nano-silicon dioxide from crystalline silicon diamond wire cutting waste (CN110357115B); a method for producing micron-sized silicon dioxide from crystalline silicon diamond wire cutting waste (CN110282634B); and a method and system for producing sodium silicate using waste silicon sludge as a raw material (CN117735565A). These studies primarily focus on the recycling and utilization of silicon cutting waste alone, lacking systematic exploration of the synergistic utilization of thermal field waste graphite and silicon cutting waste.

[0003] Silicon carbide (SiC) has been widely used in various fields, including metallurgy, abrasives, functional ceramics, semiconductors, electronics, automotive, and environmental protection and energy conservation, due to its outstanding physical and chemical thermal stability, excellent radiation resistance and mechanical properties, high thermal conductivity and wide bandgap, high hardness, strong high-temperature load-bearing capacity, oxidation resistance, and wear resistance. Currently, patents related to the preparation of SiC include: a method for regenerating and recovering SiC from silicon melt refining slag (CN119858921A); a method for preparing high-quality SiC from crystalline silicon cutting waste (CN107651691B); a method for preparing high-quality SiC from diamond wire cutting waste (CN107651690B); a method for preparing β-SiC powder (CN115784232B); a method for preparing SiC (CN119100842A); and a method for producing high-purity SiC powder (CN118302384B). After searching, it was found that there are few reports on the technology of using thermal field waste graphite as carbon source and single crystal silicon cutting waste as silicon source in the patents for preparing silicon carbide, and there is still room for improvement in the comprehensive utilization rate of single crystal silicon cutting waste and waste graphite.

[0004] In the photovoltaic industry and semiconductor, silicon carbide (SiC) contained in the primary hot field material is the key impurity restricting the purification of waste hot field graphite. At the same time, in the silicon cutting waste, there are not only elemental silicon (Si), but also silicon-oxygen combination in the form of silicon oxide (SiO x , x = 1 ~ 2). The chemical inertness of SiO x is the core factor hindering the efficient purification of silicon. In view of the fact that the impurities in the two types of waste materials both form a significant restriction on the purification of the main materials (graphite, silicon), the present application proposes a "crystal seed oriented conversion" strategy: taking the SiC particles in the primary hot field graphite as the crystal seed, by regulating the directional reaction of the carbon-based components in the waste hot field graphite and the silicon main body (Si / SiO x ) in the silicon cutting waste at high temperature, the key impurities in the two types of waste materials are converted into high value-added silicon carbide products. This technology not only breaks through the limitations of traditional purification processes, but also is expected to achieve the dual goals of "impurity avoidance-resource value-added". SUMMARY

[0005] In view of the problem that the current single crystal silicon cutting waste and hot field waste graphite cannot be effectively utilized due to large accumulation, the present application provides a method for preparing silicon carbide from single crystal silicon cutting waste and hot field waste graphite. The method not only solves the environmental pollution problem caused by waste accumulation, but also improves the resource utilization rate and realizes the high value utilization of waste generated during the preparation of single crystal silicon, thereby having great economic benefits. At the same time, the obtained silicon carbide particles have a particle size span of less than or equal to 35 microns.

[0006] The method for preparing silicon carbide from single crystal silicon cutting waste and hot field waste graphite provided by the present application comprises the following steps:

[0007] Step one

[0008] According to the molar ratio, the single crystal silicon cutting waste particles: hot field waste graphite = 1:1-2.4, preferably 1:1.4-2. Dry single crystal silicon cutting waste particles and hot field waste graphite are taken and mixed uniformly to obtain standby material. The hot field waste graphite contains in-situ generated silicon carbide particles. The single crystal silicon cutting waste particles contain Fe, and according to the mass percentage, 1% ≥ Fe ≥ 0.0437%;

[0009] Step two

[0010] The standby material obtained in step one is placed in a sintering furnace and reacted under a protective atmosphere. After the reaction is completed, the product is obtained after grinding, excess carbon removal, acid immersion and drying. The reaction temperature is 1450-1575℃, preferably 1500-1550℃.

[0011] The application discloses a method for preparing silicon carbide from monocrystalline silicon cutting waste and hot field abandoned graphite.

[0012] The application discloses a method for preparing silicon carbide from monocrystalline silicon cutting waste and hot field abandoned graphite, and the monocrystalline silicon cutting waste contains Si ≥ 93.26% in percentage by mass.

[0013] The application discloses a method for preparing silicon carbide from monocrystalline silicon cutting waste and hot field abandoned graphite, and the hot field abandoned graphite contains C ≥ 89% in percentage by mass.

[0014] The application discloses a method for preparing silicon carbide from monocrystalline silicon cutting waste and hot field abandoned graphite, and the particle size of the monocrystalline silicon cutting waste and the hot field abandoned graphite is -200 mesh, and the particle size distribution is 50-150 microns.

[0015] The application discloses a method for preparing silicon carbide from monocrystalline silicon cutting waste and hot field abandoned graphite, and the reaction time is 1-4 hours, preferably 2-4 hours.

[0016] The protective atmosphere is preferably argon.

[0017] The excess carbon is treated by a tubular furnace, the temperature is 600-850 DEG C, and the time is 1-4 hours; further preferably, the temperature is 750-800 DEG C, and the time is 3-4 hours.

[0018] The acid source for the acid immersion is one or more mixed acids selected from sulfuric acid, nitric acid and hydrofluoric acid.

[0019] The acid immersion temperature is 30-70 DEG C, the acid immersion time is 30-90 minutes, and the acid source concentration is 0.5-3.5 mol / L.

[0020] The solid-liquid ratio of the acid immersion is 1:5-30, preferably 1:10-25, in gram / milliliter.

[0021] The monocrystalline silicon cutting waste contains a small amount of metal impurities Fe in addition to elemental silicon, and the content of Fe is 1% ≥ Fe ≥ 0.0437% in percentage by mass; in the process of preparing silicon carbide from the silicon cutting waste and the hot field abandoned graphite, Fe can be used as a high-efficiency catalyst to reduce the reaction activation energy and promote the generation of fine-particle silicon carbide. The catalytic mechanism is mainly as follows: Fe particles form liquid alloy droplets at high temperature, and these liquid droplets or alloy intermediate phases serve as active media, greatly promoting the diffusion and interface reaction of Si and C; when the concentrations of Si and C in the droplets reach a supersaturated state, silicon carbide nuclei are precipitated from the bottom of the droplets; with the continuous growth of the SiC crystals, the liquid droplets are continuously pushed upwards, and finally a unique one-dimensional nano-structure silicon carbide is formed.

[0022] Because the prepared silicon carbide contains a small amount of Fe, in order to improve the purity of the silicon carbide, sulfuric acid, nitric acid and the like are selected to remove Fe; however, the sample contains a small amount of amorphous SiO2 oxide layer, and the continuous growth of the film layer induces the migration of metal impurities to the inside of the oxide layer. Specifically, the metal Fe element diffuses to the inside of the film layer through the defect channel of the oxide film, and is finally embedded in the intermediate transition region of the oxide film layer. Therefore, it is difficult to effectively destroy the structure of the oxide film layer using the conventional sulfuric acid, nitric acid and the like system, so that the embedded metal impurities cannot be fully leached out. In view of this problem, the application adopts a hydrofluoric acid cooperative leaching process: by utilizing the corrosion effect of HF on the silicon dioxide oxide layer, the thickness of the oxide film can be controllably thinned, so that the embedded metal impurities are exposed to the leaching system, thereby realizing the deep removal of metal elements.

[0023] The particle size of the silicon carbide product prepared by the application mainly concentrates on 1-10 mu m, and is positively skewed (right tail to 22.3 mu m). The secondary particle size peak between 10-20 mu m is mainly caused by insufficient dispersion or agglomeration of SiC particles. This is consistent with the scanning electron microscope analysis result of the silicon carbide product.

[0024] The application has the beneficial effects that:

[0025] (1) The single crystal silicon cutting waste contains a large amount of silicon powder, and the thermal field abandoned graphite not only contains a large amount of graphite, but also contains a small amount of in-situ generated silicon carbide particles, which is beneficial to the preparation of silicon carbide. The application uses single crystal silicon cutting waste and thermal field abandoned graphite as raw materials, not only solves the environmental pollution problem caused by waste accumulation, but also improves the resource utilization rate, turns waste into treasure, and has great economic benefits.

[0026] (2) The small amount of Fe element in the single crystal silicon cutting waste can be used as an efficient catalyst to reduce the reaction activation energy in the process of preparing silicon carbide from silicon cutting waste and thermal field abandoned graphite, and promote the generation of fine particle silicon carbide.

[0027] (3) The key impurities in the single crystal silicon cutting waste and the thermal field abandoned graphite are converted into high value-added silicon carbide products. The technology not only breaks through the limitations of traditional purification process, but also realizes the dual goals of "impurity avoidance-resource value increase".

[0028] (4) The purity of the silicon carbide prepared in the application is greater than 95%. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The process flow chart of the application.

[0030] Figure 2 The XRD pattern of high-quality silicon carbide generated by the reaction of single crystal silicon cutting waste and thermal field abandoned graphite;

[0031] Figure 3 Particle size distribution of the silicon carbide product in Example 4.

[0032] Figure 4 SEM image of the silicon carbide product in Example 4.

[0033] From Figure 1 The basic flow of the present application can be seen.

[0034] Figure 2 In the reaction, A is thermal field abandoned graphite, B is single crystal silicon cutting waste, and C is high-quality silicon carbide generated by the reaction. From Figure 2 It can be seen from the reaction that the purity of the product is extremely high.

[0035] From Figure 3 It can be seen that the particle size distribution of the product obtained by the present application is narrow.

[0036] From Figure 4 It can be seen that the silicon carbide particles obtained by the present application are secondary particles, and the particle size of the primary silicon carbide particles can reach nanometer level (less than or equal to 0.1 microns). DETAILED DESCRIPTION

[0037] The present application will be further described in detail below in conjunction with specific embodiments, but the scope of protection of the present application is not limited to the content described.

[0038] Example 1

[0039] The method for preparing silicon carbide from the single crystal silicon cutting waste and the thermal field abandoned graphite, and the specific steps are as follows:

[0040] (1) The single crystal silicon cutting waste and the thermal field abandoned graphite are placed in a forced air drying oven and dried at 80°C for 72h;

[0041] (2) The single crystal silicon cutting waste and the thermal field abandoned graphite dried in step (1) are crushed, ground, and sieved to a powder with a particle size of 75μm; wherein the single crystal silicon cutting waste contains 0.0437wt% of Fe; the composition of the single crystal silicon cutting waste contains Si ≥ 93.26% by mass percentage;

[0042] (3) The sieved single crystal silicon cutting waste and the thermal field abandoned graphite in step (2) are mixed in a molar ratio of 1:1.4 using a agate mortar;

[0043] (4) The mixed raw materials in step (3) are dried and then loaded into a graphite crucible, and the graphite crucible is placed in an ultra-high temperature resistance furnace, and argon gas is introduced at 1500°C (argon gas flow rate is 0.3L / min) for 2h, and cooled to room temperature to obtain a loose and porous silicon carbide powder;

[0044] (5) The silicon carbide powder prepared in step (4) is ground to homogenize its composition;

[0045] (6) The ground silicon carbide powder in step (5) is loaded into a corundum crucible, and the corundum crucible is placed in a tube furnace, and the excess carbon is removed by passing air at 750°C for 3h;

[0046] (7) The silicon carbide powder after removing excess carbon in step (6) is subjected to acid immersion treatment, and the acid immersion conditions are as follows: the acid source is a mixed acid of 3 mol / L hydrofluoric acid and 3 mol / L nitric acid, the solid-liquid ratio is 1:20, the acid pickling time is 80 min, and the acid immersion temperature is 50°C. After filtration and drying, high-quality silicon carbide powder is obtained.

[0047] The silicon carbide prepared in this example is analyzed by XRD test and shows only the diffraction peak of silicon carbide, without other impurity peaks. The purity of the silicon carbide powder is 95.10%, the particle size distribution is positively skewed, D10 is about 0.62-0.64 μm, D50 is about 6.45-6.49 μm, and D90 is about 29.0-29.4 μm.

[0048] Example 2

[0049] The specific steps of the method for preparing silicon carbide from single crystal silicon cutting waste and hot field waste graphite are as follows:

[0050] (1) The single crystal silicon cutting waste and hot field waste graphite are dried in a forced air drying oven at 80°C for 72h;

[0051] (2) The dried single crystal silicon cutting waste and hot field waste graphite in step (1) are crushed, ground and sieved to a powder with a particle size of 75 μm. The single crystal silicon cutting waste contains 0.0437wt% of Fe, and the composition of the single crystal silicon cutting waste contains Si ≥ 93.26% by mass;

[0052] (3) The sieved single crystal silicon cutting waste and hot field waste graphite in step (2) are mixed in a 1:1.4 molar ratio using a agate mortar;

[0053] (4) The mixed raw materials in step (3) are dried and loaded into a graphite crucible, and the graphite crucible is placed in an ultra-high temperature resistance furnace, and the loose and porous silicon carbide powder is obtained by passing argon gas at 1550°C for 2h (argon gas flow rate is 0.3L / min) and cooling to room temperature;

[0054] (5) The silicon carbide powder prepared in step (4) is ground to homogenize its composition;

[0055] (6) the silicon carbide powder prepared in step (5) is put into a corundum crucible, and the corundum crucible is placed in a tube furnace, and excess carbon is removed by passing air at 750 DEG C for 3 h;

[0056] (7) the silicon carbide powder after removal of excess carbon in step (6) is subjected to acid immersion treatment, the acid immersion conditions are as follows: the acid source is a mixed acid of 3 mol / L hydrofluoric acid and 3 mol / L sulfuric acid, the solid-liquid ratio is 1:20, the acid pickling time is 60 min, and the acid immersion temperature is 50 DEG C, and high-quality silicon carbide powder is obtained after filtration and drying.

[0057] The silicon carbide prepared in this example is analyzed by XRD test, and only the diffraction peak of silicon carbide appears, and no other impurity peak appears, the purity of the silicon carbide powder is 95.60%, the particle size distribution is positively skewed, D10 is about 0.60-0.63 μm, D50 is about 4.70-54.75 μm, and D90 is about 27.25-27.30 μm.

[0058] Example 3

[0059] The method for preparing silicon carbide from single crystal silicon cutting waste and thermal field waste graphite comprises the following specific steps:

[0060] (1) the single crystal silicon cutting waste and the thermal field waste graphite are placed in a forced air drying oven and dried at 80 DEG C for 72 h;

[0061] (2) the single crystal silicon cutting waste and the thermal field waste graphite dried in step (1) are crushed, ground and sieved to a powder with a particle size of 75 μm; the single crystal silicon cutting waste contains 0.0440wt% of Fe; the composition of the single crystal silicon cutting waste contains Si ≥ 93.26% by mass percentage;

[0062] (3) the sieved single crystal silicon cutting waste and thermal field waste graphite in step (2) are mixed in a ratio of 1:2 using a agate mortar;

[0063] (4) the mixed raw materials in step (3) are dried and then put into a graphite crucible, and the graphite crucible is placed in a super-high temperature resistance furnace, and the furnace is fired in an argon atmosphere (argon flow rate is 0.3 L / min) at 1500 DEG C for 2 h, and loose and porous silicon carbide powder is obtained after cooling to room temperature;

[0064] (5) the silicon carbide powder prepared in step (4) is ground to make its composition uniform;

[0065] (6) the ground silicon carbide powder in step (5) is put into a corundum crucible, and the corundum crucible is placed in a tube furnace, and excess carbon is removed by passing air at 750 DEG C for 3 h;

[0066] (7) The silicon carbide powder after excess carbon in step (6) is subjected to acid immersion treatment, and the acid immersion conditions are as follows: the acid source is a mixed acid of hydrofluoric acid with a concentration of 3 mol / L and nitric acid with a concentration of 3 mol / L, the solid-liquid ratio is 1:20, the acid pickling time is 80 min, and the acid immersion temperature is 50 DEG C. After filtration and drying, high-quality silicon carbide powder is obtained.

[0067] The silicon carbide prepared in the embodiment is subjected to XRD test analysis, and only the diffraction peak of silicon carbide appears, and no other impurity peak appears. The purity of the silicon carbide powder is 97.52%, the particle size distribution is positively skewed, D10 is about 0.68-0.70 microns, D50 is about 3.70-3.75 microns, and D90 is about 24.15-24.20 microns.

[0068] Example 4

[0069] The method for preparing silicon carbide from the single crystal silicon cutting waste and the thermal field abandoned graphite, and the specific steps are as follows:

[0070] (1) The single crystal silicon cutting waste and the thermal field abandoned graphite are placed in a forced air drying oven and dried at 80 DEG C for 72 hours;

[0071] (2) The single crystal silicon cutting waste and the thermal field abandoned graphite dried in step (1) are crushed, ground, and sieved to a powder with a particle size of 75 microns. The single crystal silicon cutting waste contains 0.0440wt% of Fe, and the composition of the single crystal silicon cutting waste contains Si ≥ 93.26% by mass percentage;

[0072] (3) The single crystal silicon cutting waste and the thermal field abandoned graphite sieved in step (2) are mixed in a ratio of 1:2 using a agate mortar;

[0073] (4) The mixed raw materials in step (3) are dried and then loaded into a graphite crucible. The graphite crucible is placed in an ultra-high temperature resistance furnace, and argon gas is introduced at a flow rate of 0.3 L / min at 1550 DEG C for 2 hours. After cooling to room temperature, a loose and porous silicon carbide powder is obtained;

[0074] (5) The silicon carbide powder prepared in step (4) is ground to homogenize the composition;

[0075] (6) The ground silicon carbide powder in step (5) is loaded into a corundum crucible, and the corundum crucible is placed in a tube furnace. Excess carbon is removed by introducing air at 750 DEG C for 3 hours;

[0076] (7) The silicon carbide powder after excess carbon removal in step (6) is subjected to acid immersion treatment, and the acid immersion conditions are as follows: the acid source is a mixed acid of 3 mol / L hydrofluoric acid and 3 mol / L sulfuric acid, the solid-liquid ratio is 1:20, the acid pickling time is 60 min, and the acid immersion temperature is 40°C. After filtration and drying, high-quality silicon carbide powder is obtained.

[0077] The silicon carbide prepared in this example is analyzed by XRD test and only the diffraction peak of silicon carbide appears without other impurity peaks. The purity of the silicon carbide powder is 98.65%, the particle size distribution is positively skewed, D10 is about 0.85 μm, D50 is about 3.20 μm, and D90 is about 22.40 μm.

[0078] Example 5

[0079] The method for preparing silicon carbide from single crystal silicon cutting waste and thermal field abandoned graphite includes the following specific steps:

[0080] (1) The single crystal silicon cutting waste and the thermal field abandoned graphite are dried in a forced air drying oven at 80°C for 72 h;

[0081] (2) The dried single crystal silicon cutting waste and the thermal field abandoned graphite in step (1) are crushed, ground, and sieved to a powder with a particle size of 75 μm. The single crystal silicon cutting waste contains 0.0442 wt% of Fe, and the composition of the single crystal silicon cutting waste contains Si ≥ 93.26% by mass percentage;

[0082] (3) The sieved single crystal silicon cutting waste and the thermal field abandoned graphite in step (2) are mixed in a ratio of 1:2.4 by mole using a agate mortar;

[0083] (4) The mixed raw materials in step (3) are dried and then loaded into a graphite crucible. The graphite crucible is placed in an ultra-high temperature resistance furnace and calcined at 1500°C under an argon atmosphere (argon flow rate is 0.3 L / min) for 2 h. After cooling to room temperature, a loose and porous silicon carbide powder is obtained;

[0084] (5) The silicon carbide powder prepared in step (4) is ground to make its composition uniform;

[0085] (6) The ground silicon carbide powder in step (5) is loaded into a corundum crucible, and the corundum crucible is placed in a tube furnace and subjected to excess carbon removal under an air atmosphere at 750°C for 3 h;

[0086] (7) The silicon carbide powder after carbon removal in step (6) is subjected to acid immersion treatment, and the acid immersion conditions are as follows: the acid source is a mixed acid of 3 mol / L hydrofluoric acid and 3 mol / L nitric acid, the solid-liquid ratio is 1:20, the acid pickling time is 80 min, and the acid immersion temperature is 50°C. After filtration and drying, high-quality silicon carbide powder is obtained.

[0087] The silicon carbide prepared in the embodiment is analyzed by XRD test, only diffraction peaks of silicon carbide appear, no other impurity peaks appear, the purity of the silicon carbide powder is 96.85%, the particle size distribution is positively skewed, D10 is about 0.65-0.70 μm, D50 is about 4.20-4.25 μm, and D90 is about 24.65-24.70 μm.

[0088] Example 6

[0089] The method for preparing silicon carbide from the single crystal silicon cutting waste and the thermal field abandoned graphite, and the specific steps are as follows:

[0090] (1) The single crystal silicon cutting waste and the thermal field abandoned graphite are placed in a blast drying oven and dried at 80°C for 72h;

[0091] (2) The single crystal silicon cutting waste and the thermal field abandoned graphite dried in step (1) are crushed, ground, and sieved into a powder with a particle size of 75 μm; the single crystal silicon cutting waste contains 0.0442wt% of Fe; the composition of the single crystal silicon cutting waste contains Si ≥ 93.26% by mass percentage;

[0092] (3) The single crystal silicon cutting waste and the thermal field abandoned graphite sieved in step (2) are mixed in a molar ratio of 1:2.4 using a agate mortar;

[0093] (4) The mixed raw materials in step (3) are dried and then loaded into a graphite crucible, and the graphite crucible is placed in an ultra-high temperature resistance furnace, and calcined at 1550°C under an argon atmosphere (argon flow rate is 0.3L / min) for 2h, and then cooled to room temperature to obtain a loose and porous silicon carbide powder;

[0094] (5) The silicon carbide powder prepared in step (4) is ground to make its composition uniform;

[0095] (6) The ground silicon carbide powder in step (5) is loaded into a corundum crucible, and the corundum crucible is placed in a tube furnace, and an air atmosphere is introduced at 750°C for 3h to remove excess carbon;

[0096] (7) The silicon carbide powder after carbon removal in step (6) is subjected to acid immersion treatment, the acid immersion conditions are: the acid source is a mixed acid of 3mol / L hydrofluoric acid and 3mol / L sulfuric acid, the solid-liquid ratio is 1:20, the acid pickling time is 60min, and the acid immersion temperature is 40°C, and after filtration and drying, high-quality silicon carbide powder is obtained.

[0097] The silicon carbide prepared in the example is analyzed by XRD test, and only diffraction peaks of silicon carbide appear, without other impurity peaks, the purity of the silicon carbide powder is 96.55%, the particle size distribution is positively skewed, D10 is about 0.61-0.64 μm, D50 is about 4.10-4.13 μm, and D90 is about 24.50-24.55 μm.

[0098] Comparative Example 1

[0099] The other conditions are consistent with those in Example 4, except that:

[0100] (4) The mixed raw materials in step (3) are dried and then loaded into a graphite crucible, and the graphite crucible is placed in an ultra-high temperature resistance furnace, heated to 1550°C under an argon atmosphere (the argon flow rate is 0 L / min), and kept for 2 h;

[0101] The obtained product is silicon carbide powder with a purity of 92.0%, a particle size distribution that is positively skewed, D10 of about 3.25 μm, D50 of about 16.55 μm, and D90 of about 53.60 μm.

[0102] Comparative Example 2

[0103] The other conditions are consistent with those in Example 1, except that the broken single crystal silicon cutting waste in step 2 is first cleaned to remove iron by using sulfuric acid;

[0104] The obtained product is silicon carbide powder with a purity of 89.0%, a particle size distribution that is positively skewed, D10 of about 3.65 μm, D50 of about 17.31 μm, and D90 of about 54.25 μm.

[0105] The specific examples of the application are described in detail above, but the application is not limited to the above examples, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the application.

Claims

1. A method for preparing silicon carbide from single crystal silicon cutting waste and thermal field waste graphite, characterized in that: The steps include: Step 1 The molar ratio of single crystal silicon cutting waste particles to thermal field waste graphite is 1:1-2.4, preferably 1:1.4-2. Dry single crystal silicon cutting waste particles and thermal field waste graphite are mixed uniformly to obtain a reserve material, wherein the thermal field waste graphite contains in-situ generated silicon carbide particles; and the single crystal silicon cutting waste particles contain Fe, and by mass percentage, 1% ≥ Fe ≥ 0.0437%; Step 2 The prepared material obtained in step 1 is placed in a sintering furnace and reacted under a protective atmosphere. After the reaction is completed, the product is obtained by grinding, removing excess carbon, acid leaching, and drying. The reaction temperature is 1450-1575°C, preferably 1500-1550°C.

2. The method for preparing silicon carbide from single crystal silicon cutting waste and thermal field waste graphite according to claim 1, characterized in that: Place the single crystal silicon cutting waste and thermal field waste graphite in a drying oven and dry them at 60~85℃ for 48~96h.

3. The method for preparing silicon carbide from single crystal silicon cutting waste and thermal field waste graphite according to claim 1, characterized in that: The composition of the single crystal silicon cutting waste contains Si ≥ 93.26% by mass.

4. The method for preparing silicon carbide from single crystal silicon cutting waste and thermal field waste graphite according to claim 1, characterized in that: The composition of thermal field waste graphite contains C ≥ 89% by mass.

5. The method for preparing silicon carbide from single crystal silicon cutting waste and thermal field waste graphite according to claim 1, characterized in that: The particle size of the single crystal silicon cutting waste particles and the thermal field waste graphite is -200 mesh, and the particle size distribution is 50-150 μm.

6. The method for preparing silicon carbide from single crystal silicon cutting waste and thermal field waste graphite according to claim 1, characterized in that: The reaction time is 1-4 h, preferably 2-4 h.

7. The method for preparing silicon carbide from single crystal silicon cutting waste and thermal field waste graphite according to claim 1, characterized in that: In step 2, the protective atmosphere is preferably argon.

8. The method for preparing silicon carbide from single crystal silicon cutting waste and thermal field waste graphite according to claim 1, characterized in that: Excess carbon is removed in a tubular furnace at a temperature of 600-850° C. for 1-4 hours; more preferably, the temperature is 750-800° C. for 3-4 hours.

9. The method for preparing silicon carbide from single crystal silicon cutting waste and thermal field waste graphite according to claim 1, characterized in that: The acid source for acid leaching is one or more mixed acids of sulfuric acid, nitric acid, and hydrofluoric acid.

10. The method for preparing silicon carbide from single crystal silicon cutting waste and thermal field waste graphite according to claim 1, characterized in that: The acid leaching temperature is 30-70°C, the acid leaching time is 30-90 minutes, and the acid source concentration is 0.5-3.5 mol / L.

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