Method for preparing silicon carbide with high zirconium content from lignite

Abstract

The invention discloses a method for preparing high-zirconium-content silicon carbide from lignite, and relates to a preparation method of high-zirconium-content silicon carbide. The invention aims to solve the problems of non-uniform product distribution and poor performance improvement effect caused by the fact that zirconium compounds are introduced by adding the zirconium compounds into existing silicon carbide in the later period. The method comprises the following steps: 1, preparing a zirconic acid organic matter solution; 2, uniformly mixing a silicon source and lignite powder, adding the mixture into the zirconic acid organic matter solution, quickly adding deionized water, and stirring and reacting at room temperature; 3, high-temperature calcination; 4, removing carbon; and 5, grinding, sieving and carrying out ultrasonic treatment. The method is used for preparing the high-zirconium-content silicon carbide from the lignite.

Description

Technical Field

[0001] The present invention relates to a method for preparing silicon carbide with a high zirconium content. Background Art

[0002] Silicon carbide, as an important material, has a wide range of applications in many fields. Therefore, other elements can be doped into silicon carbide to enhance its performance. Zirconides are a class of compounds with a wide range of uses. In the field of ceramics, zirconides can be used to improve the performance of ceramics, such as enhancing hardness, improving wear resistance, etc., making ceramic products more high-quality and durable. And the addition of zirconides to silicon carbide brings many significant advantages to its performance. Among them, adding zircon can significantly improve the high-temperature stability of silicon carbide. In a high-temperature environment, the performance of materials is often affected, but the addition of zircon enables silicon carbide to maintain better structural integrity and mechanical properties, thus broadening its application range in high-temperature fields. However, in current research, most of them introduce zirconides by adding them later, but this method has problems such as uneven product distribution and poor performance improvement effect. Summary of the Invention

[0003] The present invention aims to solve the problem that the existing silicon carbide introduces zirconides by adding them later, resulting in uneven product distribution and poor performance improvement effect, and further provides a method for preparing silicon carbide with a high zirconium content using lignite.

[0004] A method for preparing silicon carbide with a high zirconium content using lignite is carried out according to the following steps:

[0005] I. Add zirconic acid organic matter to absolute ethanol, stir at a low speed to mix evenly, and then let it stand to obtain a zirconic acid organic matter solution;

[0006] II. Mix the silicon source and lignite powder evenly to obtain a mixed powder, add the mixed powder to the zirconic acid organic matter solution to obtain a mixed solution, quickly add deionized water to the mixed solution, and stir and react at room temperature. Finally, dry and grind to obtain a solid powder;

[0007] III. Under the conditions of an argon atmosphere and a temperature of 1400°C to 1550°C, calcine the solid powder at a high temperature for 1 h to 5 h, and then cool down to obtain a sintered sample;

[0008] IV. Under the conditions of an argon atmosphere and a temperature of 600°C to 800°C, remove carbon from the sintered sample for 2 h to 6 h, and then cool down to obtain a carbon-removed sample;

[0009] V. Grind, sieve, and ultrasonically treat the carbon-removed sample in sequence, and thus complete the method for preparing silicon carbide with a high zirconium content using lignite.

[0010] The beneficial effects of the present invention are as follows:

[0011] 1. The lignite selected in the present invention is from the lignite of Inner Mongolia Zhalainuoer Coal Industry. This lignite is rich in a large amount of carbon (up to 72%), with a rather rich carbon content, and the rest is water and ash impurities. The ash is composed of oxides of various metals and silicon dioxide, etc. Appropriate metal particles can promote the VLS reaction, which is beneficial to the formation of silicon carbide.

[0012] 2. By introducing a solid silicon source powder phase, it interacts with the carbon component in the lignite through a solid-phase reaction to achieve the formation of SiC. The preparation method of the present invention is simple, the process of one-step reaction is easy to control, suitable for large-scale industrial production, can reduce costs, maximize the resource utilization of lignite with high added value, and enhance the comprehensive utilization ability of lignite in China.

[0013] 3. After adding zirconium, the performance of silicon carbide can be optimized. The zirconium content is greater than 50wt%. The present invention is mainly reflected in the improvement of surface morphology and thermal conductivity. The nano-particles generated by the present invention have regular shapes, with a diameter of about 50nm, belonging to β-SiC, and the crystal phase is 3C phase. It is a high-quality raw material powder for manufacturing high-performance silicon carbide ceramics, and can also be used as nano-materials, fireproof and heat-insulating materials, wave-absorbing materials, and heat storage materials, etc. Description of the Drawings

[0014] Figure 1 XRD spectrum of silicon carbide with high zirconium content prepared in Example 1;

[0015] Figure 2 Scanning electron micrograph of silicon carbide with high zirconium content prepared in Example 1;

[0016] Figure 3 Wave-absorbing performance diagram of silicon carbide with high zirconium content prepared in Example 1;

[0017] Figure 4 Compressive strength diagram of the carbon-removed sample prepared in Step 4 of Example 1. Detailed Embodiments

[0018] Detailed Embodiment 1: A method for preparing silicon carbide with high zirconium content using lignite in this embodiment is carried out according to the following steps:

[0019] 1. Add zirconic acid organic matter to absolute ethanol, stir at low speed to mix evenly and then let it stand to obtain a zirconic acid organic matter solution;

[0020] 2. Mix the silicon source and lignite powder evenly to obtain a mixed powder. Add the mixed powder to the zirconic acid organic matter solution to obtain a mixed solution. Quickly add deionized water to the mixed solution and stir and react at room temperature. Finally, dry and grind to obtain a solid powder;

[0021] III. Under the conditions of an argon atmosphere and a temperature of 1400°C to 1550°C, calcine the solid powder at a high temperature for 1 h to 5 h, and then cool it down to obtain a sintered specimen;

[0022] IV. Under the conditions of an argon atmosphere and a temperature of 600°C to 800°C, remove carbon from the sintered specimen for 2 h to 6 h, and then cool it down to obtain a carbon-removed specimen;

[0023] V. Grind, sieve, and ultrasonically treat the carbon-removed specimen in sequence to complete the method for preparing silicon carbide with a high zirconium content using lignite.

[0024] In the second step of this specific embodiment, a plastic film is covered to prevent impurities from entering, and continuous stirring is carried out at room temperature for a certain period of time to fully hydrolyze the zirconium organic acid and carry out a polycondensation reaction with the silicon source.

[0025] Principle: The main component of lignite is carbon. Using lignite as a raw material to introduce a carbon source as a reactant, a silicon source is subsequently introduced, and a zirconium organic acid is added simultaneously to achieve the addition of zirconium. The zirconium organic acid directly participates in the reaction, and high-zirconium SiC is generated under a high-temperature environment. In addition, Ar gas is introduced in the high-temperature reaction to act as an inert atmosphere; and a method of directly forming and then reacting is adopted to prepare high-zirconium SiC.

[0026] The beneficial effects of this embodiment are as follows:

[0027] 1. The lignite selected in this embodiment is from Inner Mongolia Zhalainuoer Coal Industry. This lignite is rich in a large amount of carbon (up to 72%), the carbon content is quite abundant, and the rest is water and ash impurities. The ash is composed of oxides of various metals and silicon dioxide, etc. Appropriate metal particles can promote the VLS reaction and are beneficial to the formation of silicon carbide.

[0028] 2. By introducing a solid silicon source powder phase, it interacts with the carbon component in lignite through a solid-phase reaction to achieve the formation of SiC. The preparation method of this embodiment is simple, the process of one-step reaction is easy to control, suitable for large-scale industrial production, can reduce costs, maximize the resource utilization of lignite with high added value, and enhance the comprehensive utilization ability of lignite in China.

[0029] 3. After adding zirconium, the performance of silicon carbide can be optimized. The zirconium content is greater than 50 wt%. This embodiment is mainly reflected in the improvement of surface morphology and thermal conductivity. The nano-particles generated in this embodiment have regular shapes, a diameter of about 50 nm, belong to β-SiC, and the crystal phase is the 3C phase. It is a high-quality raw material powder for manufacturing high-performance silicon carbide ceramics, and can also be used as nano-materials, fireproof and heat-insulating materials, wave-absorbing materials, and heat storage materials, etc.

[0030] Embodiment 2: The difference between this embodiment and Embodiment 1 is as follows: The zirconium organic acid in Step 1 is tetrabutyl zirconate, zirconium acetylacetonate or zirconium propionate; the mass percentage of the zirconium organic acid in the zirconium organic acid solution in Step 1 is 35% - 45%. Others are the same as in Embodiment 1.

[0031] Embodiment 3: The difference between this embodiment and either Embodiment 1 or Embodiment 2 is as follows: The low-speed stirring and mixing evenly in Step 1 specifically means stirring for 3 min - 10 min under the condition that the rotation speed is 100 r / min - 200 r / min. Others are the same as in Embodiment 1 or Embodiment 2.

[0032] Embodiment 4: The difference between this embodiment and any one of Embodiments 1 to 3 is as follows: The lignite powder in Step 2 is specifically prepared according to the following steps: Under the condition that the temperature is 60°C - 100°C, dry the large lignite for 1 h - 2 h, and then under the conditions that the rotation speed is 150 r / min - 500 r / min and the mass ratio of the balls to the material is (1 - 2):1, ball-mill for 0.5 h - 6 h to obtain the lignite powder, and use cemented carbide balls as the grinding balls during the ball-milling process. Others are the same as in Embodiment 3.

[0033] Embodiment 5: The difference between this embodiment and any one of Embodiments 1 to 4 is as follows: The silicon source in Step 2 is one or a combination of several of waste silicon powder, silicon dioxide, silica and silicone; the particle size of the silicon source in Step 2 is 1 μm - 10 μm. Others are the same as in Embodiments 1 to 4.

[0034] Embodiment 6: The difference between this embodiment and any one of Embodiments 1 to 5 is as follows: The mass ratio of the lignite powder to the silicon source in Step 2 is (1 - 3):3; the mass ratio of the mixed powder to the zirconium organic acid solution in Step 2 is (1 - 2):2; the addition amount of deionized water in Step 2 is 5% - 10% of the mass of the mixed solution. Others are the same as in Embodiments 1 to 5.

[0035] Embodiment 7: The difference between this embodiment and any one of Embodiments 1 to 6 is as follows: In Step 2, add deionized water to the mixed solution quickly at a rate of 1 mL / s - 5 mL / s, and under the conditions of room temperature and a stirring speed of 200 r / min - 500 r / min, stir and react for 2 h - 5 h, and finally under the condition that the temperature is 50°C - 80°C, dry for 12 h - 16 h and grind. Others are the same as in Embodiments 1 to 6.

[0036] Embodiment 8: The difference between this embodiment and any one of Embodiments 1 to 7 is as follows: In step three, under an argon atmosphere, first heat up at a rate of 2°C / min to 5°C / min to 400°C to 500°C, then heat up at a rate of 1°C / min to 10°C / min to 700°C to 800°C, then heat up at a rate of 2°C / min to 5°C / min to 900°C to 1000°C, and finally heat up at a rate of 2°C / min to 2.5°C / min to 1400°C to 1550°C; the cooling in step three is specifically carried out under an argon atmosphere, cooling at a rate of 2°C / min to 2.5°C / min to 900°C to 1000°C, then continuing to cool at a rate of 2°C / min to 5°C / min to 700°C to 800°C, then continuing to cool at a rate of 1°C / min to 10°C / min to 400°C to 500°C, and finally cooling at a rate of 2°C / min to 5°C / min to room temperature. Others are the same as those in Embodiments 1 to 7.

[0037] Embodiment 9: The difference between this embodiment and any one of Embodiments 1 to 8 is as follows: In step four, under an argon atmosphere, first heat up at a rate of 5°C / min to 10°C / min to 400°C to 500°C, then heat up at a rate of 3°C / min to 5°C / min to 600°C to 800°C; the cooling in step four is specifically carried out under an argon atmosphere, first cooling at a rate of 3°C / min to 5°C / min to 400°C to 500°C, then cooling at a rate of 5°C / min to 10°C / min to room temperature. Others are the same as those in Embodiments 1 to 8.

[0038] Embodiment 10: The difference between this embodiment and any one of Embodiments 1 to 9 is as follows: The flow rate of the argon atmosphere in step three and step four is 20 mL / min to 100 mL / min, and the purity ≥ 99.99%; the sieving in step five is through a 60-mesh to 120-mesh sieve; the ultrasonic treatment in step five is specifically carried out under the condition of an ultrasonic power of 100 W to 300 W for 0.5 h to 1 h. Others are the same as those in Embodiments 1 to 9.

[0039] The following examples are used to verify the beneficial effects of the present invention:

[0040] Example 1:

[0041] A method for preparing silicon carbide with a high zirconium content from lignite is carried out according to the following steps:

[0042] 1. Add zirconic acid organic matter to absolute ethanol, stir for 5 min under the condition of a rotation speed of 150 r / min, and then let it stand to obtain a zirconic acid organic matter solution;

[0043] The zirconium organic acid mentioned is tetrabutyl zirconate; the mass percentage of the zirconium organic acid in the zirconium organic acid solution is 40%;

[0044] II. Mix the silicon source and lignite powder evenly to obtain a mixed powder. Add the mixed powder to the zirconium organic acid solution to obtain a mixed solution. Add deionized water to the mixed solution quickly at a rate of 2 mL / s, and stir and react for 2 h at room temperature and a stirring speed of 300 r / min. Finally, dry for 12 h and grind at a temperature of 60 °C to obtain a solid powder;

[0045] The lignite powder mentioned is specifically prepared according to the following steps: Dry the large lignite at a temperature of 80 °C for 2 h, and then ball-mill for 2 h at a rotation speed of 300 r / min and a ball-to-material mass ratio of 1:1 to obtain the lignite powder. During the ball-milling process, zirconia balls with a diameter of 20 mm are used as grinding balls; the large lignite comes from the lignite of Inner Mongolia Zhalainuoer Coal Industry, in which the moisture accounts for 8.12% of the mass of the lignite, the fixed carbon accounts for 66.46% of the mass of the lignite, the volatile matter accounts for 12.98% of the mass of the lignite, the ash accounts for 12.44% of the mass of the lignite, and the particle size is mainly concentrated in the range of 0.75 μm to 2.75 μm, with an average particle size of 1.75 μm;

[0046] The silicon source is a combination of waste silicon powder and silicon dioxide with a mass ratio of 1:1; the waste silicon powder comes from Inner Mongolia Haitai Huacai Co., Ltd., and the silicon content is greater than 80 wt%; the average particle size of the silicon source is 6 μm;

[0047] The mass ratio of the lignite powder to the silicon source is 1:1; the mass ratio of the mixed powder to the zirconium organic acid solution is 1:1; the addition amount of deionized water is 10% of the mass of the mixed solution;

[0048] III. Under the conditions of an argon atmosphere and a temperature of 1500 °C, calcine the solid powder at high temperature for 2 h, and then cool down to obtain a sintered specimen;

[0049] IV. Under the conditions of an argon atmosphere and a temperature of 700 °C, remove carbon from the sintered specimen for 2 h, and then cool down to obtain a carbon-removed specimen;

[0050] V. Grind the carbon-removed specimen and pass it through a 60-mesh sieve, and then ultrasonicate for 0.5 h under the condition of an ultrasonic power of 200 W to obtain silicon carbide with a high zirconium content.

[0051] In Step 3, under an argon atmosphere, the temperature is first raised to 500 °C at a rate of 5 °C / min, then raised to 800 °C at a rate of 10 °C / min, then raised to 1000 °C at a rate of 5 °C / min, and finally raised to 1500 °C at a rate of 2.5 °C / min; the cooling in Step 3 is specifically carried out under an argon atmosphere, cooling to 1000 °C at a rate of 2.5 °C / min, then continuing to cool to 800 °C at a rate of 5 °C / min, then continuing to cool to 500 °C at a rate of 10 °C / min, and finally cooling to room temperature at a rate of 5 °C / min.

[0052] In Step 4, under an argon atmosphere, the temperature is first raised to 500 °C at a rate of 10 °C / min, then raised to 700 °C at a rate of 5 °C / min; the cooling in Step 4 is specifically carried out under an argon atmosphere, first cooling to 500 °C at a rate of 5 °C / min, then cooling to room temperature at a rate of 10 °C / min.

[0053] The flow rate of the argon atmosphere described in Step 3 and Step 4 is 40 mL / min, and the purity is ≥99.99%.

[0054] In this embodiment, a tube furnace is used. In actual production for large-scale sintering, it is possible to first evacuate the vacuum and then introduce a protective gas before sintering.

[0055] Figure 1 It is the XRD pattern of the high-zirconium-content silicon carbide prepared in Example 1; as can be seen from the figure, the main components in the product are silicon carbide and zirconia, belonging to β-SiC, and the crystal phase is the 3C phase; through calculation, the content of zirconia can reach 50 wt%, indicating that the method of this embodiment realizes the introduction of silicon carbide components and zirconides, and it shows that the high-zirconium SiC is successfully prepared by the method in this embodiment.

[0056] Figure 2 It is the scanning electron micrograph of the high-zirconium-content silicon carbide prepared in Example 1; as can be seen from the figure, most of the products are nanoparticles with regular shapes and a diameter of about 50 nm.

[0057] The microwave absorption performance of the high-zirconium-content silicon carbide prepared in Example 1 is tested. The high-zirconium-content silicon carbide is mixed with paraffin to prepare a hollow cylindrical ring with an outer diameter of 7 mm, an inner diameter of 3 mm, and a height of about 3 mm. Figure 3 It is the microwave absorption performance diagram of the high-zirconium-content silicon carbide prepared in Example 1; in the field of electromagnetic wave absorption, the range of < -10 dB means that within this waveband, 90% of the incident waves can be absorbed. As can be seen from the figure, it has good absorption performance in the range of 16 GHz to 26 GHz, and 90% of the incident waves can be absorbed within this frequency band.

[0058] The carbon-removed specimen prepared in Step 4 of Example 1 was subjected to a compressive property test. The sample was directly cut into cubes of 1 mm×1 mm×1 mm for testing. The carbon-removed specimen prepared in Step 4 of Example 1 was subjected to a compressive property test. Figure 4 It is the compressive property diagram of the carbon-removed specimen prepared in Step 4 of Example 1; as can be seen from the figure, the specimen will undergo obvious fracture only when a pressure of 15 N is applied, indicating that it has certain compressive properties.

Claims

1. A method for preparing high zirconium content silicon carbide using lignite, characterized in that It is carried out in the following steps:

1. Add zirconate organic matter into anhydrous ethanol, stir at a low speed until mixed evenly, and then let stand to obtain a zirconate organic matter solution; 2. Evenly mix the silicon source and lignite powder to obtain a mixed powder, add the mixed powder to a zirconate organic solution to obtain a mixed solution, quickly add deionized water to the mixed solution, stir and react at room temperature, and finally dry and grind to obtain a solid powder; 3. In an argon atmosphere at a temperature of 1400°C to 1550°C, the solid powder is calcined at high temperature for 1h to 5h, and then the temperature is lowered to obtain a sintered sample; 4. In an argon atmosphere at a temperature of 600°C to 800°C, the sintered sample is decarbonized for 2h to 6h, and then cooled to obtain a decarbonized sample; 5. The decarbonized sample is ground, sieved and ultrasonicated in sequence, thereby completing the method for preparing silicon carbide with high zirconium content using lignite.

2. The method for preparing high zirconium content silicon carbide using lignite according to claim 1, characterized in that The zirconate organic matter described in step one is tetrabutyl zirconate, zirconium acetylacetonate or zirconium propionate; the mass percentage of the zirconate organic matter in the zirconate organic matter solution described in step one is 35% to 45%.

3. The method for preparing silicon carbide with high zirconium content using lignite according to claim 1, characterized in that The low-speed stirring and uniform mixing described in step 1 specifically comprises stirring for 3 minutes to 10 minutes at a rotation speed of 100 r / min to 200 r / min.

4. The method for preparing silicon carbide with high zirconium content using lignite according to claim 1, characterized in that The lignite powder described in step 2 is specifically prepared according to the following steps: drying the large piece of lignite at a temperature of 60°C to 100°C for 1h to 2h, and then ball milling for 0.5h to 6h at a rotation speed of 150r / min to 500r / min and a ball-to-material mass ratio of (1 to 2):1 to obtain lignite powder, and cemented carbide balls are used as grinding balls during the ball milling process.

5. The method for preparing silicon carbide with high zirconium content by using lignite according to claim 1, characterized in that The silicon source described in step 2 is one or a combination of waste silicon powder, silicon dioxide, silica and organosilicon; the particle size of the silicon source described in step 2 is 1 μm to 10 μm.

6. The method for preparing high zirconium content silicon carbide using lignite according to claim 1, characterized in that The mass ratio of the lignite powder to the silicon source in step 2 is (1-3):3; the mass ratio of the mixed powder to the zirconate organic solution in step 2 is (1-2):2; the amount of deionized water added in step 2 is 5% to 10% of the mass of the mixed solution.

7. The method for preparing high zirconium content silicon carbide using lignite according to claim 1, characterized in that In step 2, deionized water is quickly added to the mixed solution at a rate of 1 mL / s to 5 mL / s, and the mixture is stirred for 2 h to 5 h at room temperature and a stirring rate of 200 r / min to 500 r / min. Finally, the mixture is dried for 12 h to 16 h and ground at a temperature of 50° C. to 80° C.

8. The method for preparing high zirconium content silicon carbide using lignite according to claim 1, characterized in that In step 3, under an argon atmosphere, the temperature is first increased to 400°C to 500°C at a rate of 2°C / min to 5°C / min, then increased to 700°C to 800°C at a rate of 1°C / min to 10°C / min, then increased to 900°C to 1000°C at a rate of 2°C / min to 5°C / min, and finally increased to 1400°C to 1550°C at a rate of 2°C / min to 2.5°C / min; the cooling described in step 3 is specifically in an argon atmosphere, cooled to 900°C to 1000°C at a rate of 2°C / min to 2.5°C / min, then continued to cool to 700°C to 800°C at a rate of 2°C / min to 5°C / min, then continued to cool to 400°C to 500°C at a rate of 1°C / min to 10°C / min, and finally cooled to room temperature at a rate of 2°C / min to 5°C / min.

9. The method for preparing high zirconium content silicon carbide using lignite according to claim 1, characterized in that In step 4, under an argon atmosphere, the temperature is first increased to 400°C~500°C at a rate of 5°C / min~10°C / min, and then increased to 600°C~800°C at a rate of 3°C / min~5°C / min; the cooling described in step 4 is specifically in an argon atmosphere, first cooled to 400°C~500°C at a rate of 3°C / min~5°C / min, and then cooled to room temperature at a rate of 5°C / min~10°C / min.

10. The method for preparing silicon carbide with high zirconium content by using lignite according to claim 1, characterized in that The flow rate of the argon atmosphere described in step 3 and step 4 is 20mL / min~100mL / min, and the purity is ≥99.99%; the screening described in step 5 is through a 60-mesh to 120-mesh sieve; the ultrasound described in step 5 is specifically for 0.5h~1h at an ultrasound power of 100W~300W.

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