Method for preparing silicon carbide powder from biomass raw material

Abstract

The invention discloses a method for preparing silicon carbide powder by using a biomass raw material, which comprises the following steps: using a high-silicon biological material as a raw material, and carrying out dry distillation by using a dry distillation furnace to obtain a black carbonized high-silicon biological material; adding silica sol into the carbonized high-silicon biological material, and mixing to obtain black paste slurry; drying the black paste slurry; carrying out high-temperature calcination on the dried raw materials, and then carrying out furnace cooling to obtain carbon-containing silicon carbide; and carrying out low-temperature calcination on the carbon-containing silicon carbide to remove residual carbon, and then carrying out furnace cooling to obtain the final silicon carbide powder. According to the method for preparing the silicon carbide powder by utilizing the biomass raw material, the nano silica sol is introduced into the carbon high-silicon biological material, so that carbon in the raw material can participate in the reaction as much as possible to form silicon carbide, the loading capacity of a single furnace can be increased, the productivity can be improved, and finally, the production cost of the product is remarkably reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of material science, and in particular provides a method for preparing silicon carbide powder by utilizing biomass raw materials. Background Art

[0002] Silicon carbide has the characteristics of stable chemical properties, high thermal conductivity and high hardness. It is widely used in many fields such as semiconductors, aerospace, bulletproof, grinding and polishing. Among them, adding a small amount of silicon carbide powder to materials such as rubber and nylon can significantly improve the wear resistance of the material; in the sintering process of silicon carbide ceramics, adding a small amount of silicon carbide material can reduce the sintering temperature and increase the strength of the sintered ceramics; in the semiconductor field, silicon carbide powder is an excellent grinding and polishing material, and its performance is significantly better than that of alumina polishing materials. At present, the traditional preparation method of silicon carbide is to produce it by calcining quartz and coke. This method has the disadvantages of difficult to control product size and low purity. Further application generally requires crushing, screening and purification processes, and the preparation cost is high, which limits its application range.

[0003] Some cheap high-siliceous biological raw materials (rice husks, straw and other crop materials) have a high silicon dioxide content. The silicon dioxide therein can be reacted with biochar through high-temperature reaction to generate silicon carbide. The silicon carbide particles produced by this method are small and have a high purity. The usual preparation method of this technology is to carbonize fresh rice husks by anaerobic distillation to remove moisture, tar and other substances, and then calcine the carbonized rice husks at high temperature to obtain silicon carbide products. At this time, the silicon carbide product contains more residual carbon and is black. By low-temperature oxidation and carbon removal, a gray silicon carbide finished powder can be obtained. Using this method, about 42kg of carbonized rice husks can be obtained for every 100kg of fresh rice husks. 42kg of carbonized rice husks can be calcined to obtain about 20.5kg of carbon-containing silicon carbide, and then after low-temperature decarbonization, 7.9kg of the final silicon carbide product is finally obtained, and the product yield is only 7.9%. Through comprehensive calculations, the production cost of the product is still high. After analysis, there are two main reasons affecting the production cost of the product: 1. During the conversion of carbonized rice husk into silicon carbide, due to the high carbon content, a large amount of carbon elements cannot be utilized and can only be burned later, resulting in a low product yield; 2. The stacking density of carbonized rice husk is small, which makes it difficult to load more raw materials per unit volume, resulting in a reduction in the production capacity of a single furnace.

[0004] Therefore, it has become an urgent problem to propose a new method for preparing silicon carbide powder using biomass raw materials to reduce the production cost of the product from two aspects: improving the utilization rate of carbon elements and increasing the single furnace production capacity. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for preparing silicon carbide powder using biomass raw materials, so as to solve the problem of high production cost of preparing silicon carbide using high-silica biological raw materials.

[0006] The present invention provides a method for preparing silicon carbide powder using biomass raw materials, comprising:

[0007] Step 1: using high-silica biomaterial as raw material, and performing dry distillation in a dry distillation furnace to obtain black carbonized high-silica biomaterial;

[0008] Step 2: adding silica sol to the carbonized high-siliceous biomaterial, and mixing to obtain a black paste-like slurry;

[0009] Step 3: drying the black paste slurry;

[0010] Step 4: calcining the dried raw material at high temperature, and then cooling it in the furnace to obtain carbon-containing silicon carbide;

[0011] Step 5: calcining the carbon-containing silicon carbide at a low temperature to remove residual carbon, and then cooling it in the furnace to obtain the final silicon carbide powder.

[0012] Preferably, in step 1, the high-silica biomaterial is rice husk or rice straw.

[0013] More preferably, in step 2, the silica sol is an alkaline silica sol having a silicon dioxide content of 30%.

[0014] Further preferably, in step 2, the mass ratio of silicon dioxide to carbon in the black paste slurry is between 8:6 and 10:6.

[0015] Further preferably, in step 2, deionized water is added during the process of adding the silica sol.

[0016] More preferably, in step 2, the carbonized high-siliceous biomaterial and the silica sol are mixed by ball milling or stirring milling.

[0017] Further preferably, in step 3, the ground black paste slurry is placed in a graphite sagger for drying at a drying temperature of 120-180°C.

[0018] Further preferably, in step 4, the high temperature calcination temperature is 1400-1950° C.; the calcination method is vacuum sintering or argon protective atmosphere sintering, and the sintering time is 1-4 hours.

[0019] More preferably, in step 5, the low-temperature calcination temperature is 500-1000° C., and the calcination time is 4-12 hours.

[0020] The method for preparing silicon carbide powder using biomass raw materials provided by the present invention introduces a nano-silica sol solution into a carbonized high-silica biomaterial, thereby providing an additional silicon source on the one hand, so that as much carbon as possible in the raw material participates in the reaction to form silicon carbide; on the other hand, after the carbonized high-silica biomaterial is mixed with the nano-silica sol, its volume is greatly reduced, which can increase the loading capacity of a single furnace, improve production capacity, and ultimately significantly reduce the production cost of the product. DETAILED DESCRIPTION

[0021] The present invention will be further explained below in conjunction with specific implementation schemes, but the present invention is not limited thereto.

[0022] The present invention provides a method for preparing silicon carbide powder using biomass raw materials, comprising:

[0023] Step 1: using high-silica biomaterial as raw material, and performing dry distillation in a dry distillation furnace to obtain black carbonized high-silica biomaterial;

[0024] Wherein, the high-silicon biomaterial can be a biomaterial with a high silicon content such as rice husk and rice straw;

[0025] Step 2: adding silica sol to the carbonized high-siliceous biomaterial, and mixing to obtain a black paste-like slurry;

[0026] Wherein, the silica sol is preferably an alkaline silica sol having a silicon dioxide content of 30%;

[0027] The mass ratio of silicon dioxide to carbon in the black paste slurry is between 8:6 and 10:6;

[0028] During the process of adding silica sol, deionized water is added to ensure that the silica sol solution can fully wet the carbonized high-siliceous biomaterial;

[0029] The carbonized high-silica biomaterial and the silica sol can be mixed by ball milling or stirring milling;

[0030] Step 3: drying the black paste slurry;

[0031] Preferably, the ground black paste slurry is placed in a graphite sagger for drying at a temperature of 120-180°C;

[0032] Step 4: calcining the dried raw material at high temperature, and then cooling it in the furnace to obtain carbon-containing silicon carbide;

[0033] Preferably, the high temperature calcination temperature is 1400-1950°C; the calcination method is vacuum sintering or argon protective atmosphere sintering, and the sintering time is 1-4 hours;

[0034] Step 5: calcining the carbon-containing silicon carbide at low temperature to remove residual carbon. Preferably, the low temperature calcination temperature is 500-1000° C. and the calcination time is 4-12 hours. Afterwards, the silicon carbide is cooled in the furnace to obtain the final silicon carbide powder.

[0035] The method for preparing silicon carbide powder using biomass raw materials introduces a nano-silica sol solution into the carbonized high-silica biomaterial, which, on the one hand, provides an additional silicon source so that as much carbon as possible in the raw material can participate in the reaction to form silicon carbide; on the other hand, after the carbonized high-silica biomaterial is mixed with the nano-silica sol, its volume is greatly reduced, which can increase the loading capacity of a single furnace, improve production capacity, and ultimately significantly reduce the production cost of the product.

[0036] Example 1

[0037] Preparation of silicon carbide powder using rice husk:

[0038] Step 1: 100 kg of fresh rice husks were used as raw materials, and were dry distilled at 800° C. in a dry distillation furnace to obtain 41.3 kg of black carbonized rice husks. The carbon content of the carbonized rice husks was found to be about 52% by testing;

[0039] Step 2: adding 53 kg of alkaline silica sol having a silica content of 30% to the carbonized rice husk, mixing, adding 2 kg of deionized water, and grinding with a ball mill to obtain a black paste slurry, wherein the mass ratio of silica to carbon in the black paste slurry is about 10:6;

[0040] Step 3: Place the ground black paste into a graphite sagger for drying at a temperature of 160°C;

[0041] Step 4: calcining the dried raw material at high temperature under vacuum conditions, wherein the high temperature calcination temperature is 1600° C., the sintering time is 1 hour, and a silicon carbide product containing residual carbon is obtained after cooling in the furnace;

[0042] Step 5: The carbon-containing silicon carbide is calcined at a low temperature in a wax removal furnace to remove residual carbon, wherein the low-temperature calcination temperature is 800° C. and the calcination time is 8 hours. Afterwards, the furnace is cooled to obtain 21 kg of final silicon carbide powder.

[0043] Example 2

[0044] Preparation of silicon carbide powder using rice husk:

[0045] Step 1: 100 kg of fresh rice husks were used as raw materials, and were dry distilled at 800° C. in a dry distillation furnace to obtain 46 kg of black carbonized rice husks. The carbon content of the carbonized rice husks was found to be about 47% by testing;

[0046] Step 2: adding 14.5 kg of alkaline silica sol having a silica content of 30% to the carbonized rice husk, adding 20 kg of deionized water after mixing, and grinding with a ball mill to obtain a black paste slurry, wherein the mass ratio of silica to carbon in the black paste slurry is about 8:6;

[0047] Step 3: Place the ground black paste into a graphite sagger for drying at a temperature of 180°C;

[0048] Step 4: calcining the dried raw material at high temperature under an argon protective atmosphere, wherein the high temperature calcination temperature is 1400° C., the sintering time is 2 hours, and a silicon carbide product containing residual carbon is obtained after cooling in the furnace;

[0049] Step 5: The carbon-containing silicon carbide is calcined at low temperature in a wax removal furnace to remove residual carbon, wherein the low temperature calcination temperature is 1000°C and the calcination time is 4 hours. Afterwards, the furnace is cooled to obtain 18 kg of final silicon carbide powder.

[0050] Example 3

[0051] Preparation of silicon carbide powder using rice straw:

[0052] Step 1: 100 kg of fresh rice straw is used as raw material, and is dry distilled at 800° C. in a dry distillation furnace to obtain 36 kg of black carbonized rice straw. The carbon content of the carbonized rice straw is about 51% after testing;

[0053] Step 2: adding 33 kg of alkaline silica sol having a silica content of 30% to the carbonized rice straw, adding 1 kg of deionized water after mixing, stirring and grinding, and obtaining a black paste slurry after grinding, wherein the mass ratio of silica to carbon in the black paste slurry is about 9:6;

[0054] Step 3: Place the ground black paste into a graphite sagger for drying at a temperature of 120°C;

[0055] Step 4: calcining the dried raw material at high temperature under vacuum conditions, wherein the high temperature calcination temperature is 1950° C., the sintering time is 4 hours, and a silicon carbide product containing residual carbon is obtained after cooling in the furnace;

[0056] Step 5: The carbon-containing silicon carbide is calcined at a low temperature in a dewaxing furnace to remove residual carbon, wherein the low-temperature calcination temperature is 500° C. and the calcination time is 12 hours. Afterwards, the furnace is cooled to obtain 14.8 kg of final silicon carbide powder.

[0057] The final silicon carbide powder obtained in Examples 1-3 was tested and found to have a purity of more than 98%, a particle size of about 5 μm, and a small amount of whisker structure.

[0058] In summary, compared with the prior art, the present invention can obtain the finished silicon carbide powder only by carbonizing the high-siliceous biomaterial, high-temperature calcining, and low-temperature oxidation decarbonization. Examples 1-3 significantly improve the single-furnace product yield of the unit weight of rice husk raw materials. In addition, since the bulk density of the raw materials is significantly improved during the treatment process, more raw materials can be sintered in a single furnace, thereby greatly improving the single furnace capacity. Combining the above two advantages, the production cost of production is ultimately reduced.

[0059] The embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for preparing silicon carbide powder using biomass raw materials, characterized in that: include: Step 1: using high-silica biomaterial as raw material, and performing dry distillation in a dry distillation furnace to obtain black carbonized high-silica biomaterial; Step 2: adding silica sol to the carbonized high-siliceous biomaterial, and mixing to obtain a black paste-like slurry; Step 3: drying the black paste slurry; Step 4: calcining the dried raw material at high temperature, and then cooling it in the furnace to obtain carbon-containing silicon carbide; Step 5: calcining the carbon-containing silicon carbide at a low temperature to remove residual carbon, and then cooling it in the furnace to obtain the final silicon carbide powder.

2. The method for preparing silicon carbide powder using biomass raw materials according to claim 1, characterized in that: In step 1, the high-silica biomaterial is rice husk or rice straw.

3. The method for preparing silicon carbide powder using biomass raw materials according to claim 1, characterized in that: In step 2, the silica sol is an alkaline silica sol with a silicon dioxide content of 30%.

4. The method for preparing silicon carbide powder using biomass raw materials according to claim 1, characterized in that: In step 2, the mass ratio of silicon dioxide to carbon in the black paste slurry is between 8:6 and 10:

6.

5. The method for preparing silicon carbide powder using biomass raw materials according to claim 1, characterized in that: In step 2, deionized water is added during the addition of silica sol.

6. The method for preparing silicon carbide powder using biomass raw materials according to claim 1, characterized in that: In step 2, the carbonized high-siliceous biomaterial and the silica sol are mixed by ball milling or stirring milling.

7. The method for preparing silicon carbide powder using biomass raw materials according to claim 1, characterized in that: In step 3, the ground black paste slurry is placed in a graphite sagger for drying at a temperature of 120-180°C.

8. The method for preparing silicon carbide powder using biomass raw materials according to claim 1, characterized in that: In step 4, the high temperature calcination temperature is 1400-1950° C.; the calcination method is vacuum sintering or argon protective atmosphere sintering, and the sintering time is 1-4 hours.

9. The method for preparing silicon carbide powder using biomass raw materials according to claim 1, characterized in that: In step 5, the low-temperature calcination temperature is 500-1000° C., and the calcination time is 4-12 hours.