Preparation method of silicon carbide

Abstract

The invention provides a preparation method of silicon carbide. The preparation method comprises the following steps: (1) uniformly mixing and stirring 2-methyl furan and oxalic acid to prepare a solution; (2) adding a degreased SiC biscuit for dipping; and (3) heating and curing the impregnated SiC biscuit, then placing the cured sample in a vacuum sintering furnace, and performing high-temperature Si infiltration in a vacuum environment to prepare the silicon carbide. The silicon carbide prepared by the preparation method disclosed by the invention is relatively high in density, bending strength and elastic modulus.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic non-metallic material preparation, and in particular to a method for preparing silicon carbide. Background Art

[0002] Optical remote sensing technology is an indispensable part of contemporary space science. With the increasing number of high-resolution observations and deep space exploration missions, the demand for large-aperture space observation equipment has increased dramatically, which in turn has driven the urgent need for large-size, lightweight, and high-strength reflector materials. Silicon carbide (SiC) has become an ideal material for manufacturing such reflector blanks due to its excellent physical and chemical properties, such as high hardness, high wear resistance, high thermal stability, and good radiation resistance.

[0003] Traditional silicon carbide preparation methods, such as hot pressing sintering and chemical vapor deposition (CVD), can produce silicon carbide materials with good performance, but they face many challenges when preparing large-sized and complex-shaped mirror blanks, such as high cost, complex process, and large material shrinkage that makes it difficult to control dimensional accuracy. Therefore, it is particularly important to develop a silicon carbide preparation technology that can both ensure material performance and simplify the preparation process and reduce costs.

[0004] As a new preparation process, gel casting reaction sintered silicon carbide (RB-SiC) technology achieves near-net-size molding of silicon carbide materials by mixing silicon carbide powder with a suitable binder to form a gel, followed by curing, drying and high-temperature sintering.

[0005] In addition, silicon carbide materials are not limited to the field of optical remote sensing, but also show wide application potential in many industries such as fine abrasives, advanced ceramics, refractory materials, and military absorbing materials. The performance indicators of silicon carbide, such as density, flexural strength, and elastic modulus, directly determine its applicability in different application scenarios. Therefore, continuously optimizing the preparation method of silicon carbide to improve these key performance indicators is the key to promoting the widespread application of silicon carbide materials. Based on this background, the present invention provides a method for preparing silicon carbide. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing silicon carbide, which improves the density, bending strength and elastic modulus of silicon carbide.

[0007] The present invention provides a method for preparing silicon carbide, the steps comprising:

[0008] (1) mixing 2-methylfuran and oxalic acid and stirring them to form a solution;

[0009] (2) adding degreased SiC blank for impregnation;

[0010] (3) The impregnated SiC blank is heated and solidified, and then the solidified sample is placed in a vacuum sintering furnace for high-temperature Si infiltration under a vacuum environment to prepare silicon carbide.

[0011] Furthermore, in the step (1), the mass ratio of 2-methylfuran to oxalic acid is 100:10-1.

[0012] Furthermore, in the step (1), the mass ratio of 2-methylfuran to oxalic acid is 100:5.

[0013] Furthermore, the immersion temperature in step (2) is 20-80°C.

[0014] Furthermore, the immersion temperature in step (2) is 20-50°C.

[0015] Furthermore, the immersion temperature in step (2) is 25-45°C.

[0016] Furthermore, the immersion time in step (2) is 2-12 hours.

[0017] Furthermore, the immersion time in step (2) is 3-5 hours.

[0018] Furthermore, the curing temperature in step (3) is 90-140°C.

[0019] Furthermore, the curing temperature in step (3) is 90-110°C.

[0020] Furthermore, in the step (3), the high temperature Si infiltration temperature is 1400-1700°C, and the high temperature Si infiltration time is 1-10h.

[0021] Furthermore, in the step (3), the high temperature Si infiltration temperature is 1450-1550°C, and the high temperature Si infiltration time is 1-10h.

[0022] The beneficial effects of the present invention are:

[0023] The present invention improves the preparation efficiency and reduces energy consumption by optimizing process parameters such as impregnation temperature, curing temperature and high-temperature Si infiltration conditions. The prepared silicon carbide material has high density, flexural strength and elastic modulus and is suitable for a variety of application scenarios.

[0024] In the present invention, 2-methylfuran and oxalic acid are used as raw materials. After being uniformly mixed in a solution, a solution system that is conducive to the impregnation of SiC blank can be formed; 2-methylfuran may play the role of solvent and silicon carbide precursor, while oxalic acid may act as a catalyst or reaction accelerator to accelerate the formation of silicon carbide. The impregnation temperature has an important influence on the penetration speed and uniformity of the solution in the SiC blank. The appropriate temperature can ensure that the solution fully penetrates into the pores of the SiC blank and provides sufficient reactants for the subsequent silicon carbide generation; the impregnation time determines the penetration depth of the solution in the SiC blank. Too short a time may lead to incomplete penetration, while too long a time may increase production costs. The solidification process fixes the solution in the impregnated SiC blank to form a stable structure, which provides a basis for the subsequent high-temperature Si infiltration process; during the high-temperature Si infiltration process, silicon atoms penetrate into the SiC blank at high temperature and combine with carbon atoms to form silicon carbide. The temperature and time of this step have an important influence on the amount and quality of silicon carbide generated. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The method for preparing the SiC blank of the present invention comprises:

[0027] Add 2000 g of acrylamide (AM) and 30 g of N,N-methylenebisacrylamide (MBAM) into 2000 g of deionized water, then add 10 g of tetrabutylammonium bromide, and stir evenly to prepare a premixed solution.

[0028] 300 g of SiC ceramic powder was added to 1000 ml of premixed liquid, and after ball mixing for 4 hours, a high-solid content SiC slurry with good fluidity and uniform composition was obtained. After vacuum degassing, 3 g of ammonium persulfate and 8 g of N, N, N', N'-tetramethylethylenediamine (TEMED) were added and quickly injected into the mold; after standing for gelation, the mold was demolded, and then dried at 160°C for 4 hours, and degreased at 460-470°C for 1 hour to form a SiC blank with interconnected pores. After cooling to room temperature, it was cut into 40 mm × 40 mm × 5 mm specifications for use.

[0029] Example 1

[0030] This embodiment provides a method for preparing silicon carbide.

[0031] 2-Methylfuran and oxalic acid were prepared into a solution in a ratio of 100:10 (weight ratio), stirred evenly, and then a SiC blank of 40mm×40mm×5mm was put into the solution for immersion. The immersion temperature was 25°C and the immersion time was 4 hours.

[0032] The impregnated SiC blank was slowly heated to 100° C. and maintained at 100° C. for 3 hours for curing.

[0033] The solidified sample was subjected to high temperature Si infiltration at 1500° C. in a vacuum sintering furnace under vacuum conditions for 2 hours to prepare silicon carbide.

[0034] Example 2

[0035] 2-Methylfuran and oxalic acid were prepared into a solution in a ratio of 100:5 (weight ratio), stirred evenly, and then a SiC blank of 40mm×40mm×5mm was put into the solution for immersion. The immersion temperature was 25°C and the immersion time was 4 hours.

[0036] The impregnated SiC blank was slowly heated to 100° C. and maintained at 100° C. for 3 hours for curing.

[0037] The solidified sample was subjected to high temperature Si infiltration at 1500° C. in a vacuum sintering furnace under vacuum conditions for 2 hours to prepare silicon carbide.

[0038] Example 3

[0039] 2-Methylfuran and oxalic acid were prepared into a solution in a ratio of 100:5 (weight ratio), stirred evenly, and then a SiC blank of 40mm×40mm×5mm was put into the solution for immersion at a temperature of 35°C for 4 hours.

[0040] The impregnated SiC blank was slowly heated to 100° C. and maintained at 100° C. for 3 hours for curing.

[0041] The solidified sample was subjected to high temperature Si infiltration at 1500° C. in a vacuum sintering furnace under vacuum conditions for 2 hours to prepare silicon carbide.

[0042] Example 4

[0043] 2-Methylfuran and oxalic acid were prepared into a solution in a ratio of 100:5 (weight ratio), stirred evenly, and then a SiC blank of 40mm×40mm×5mm was put into the solution for immersion. The immersion temperature was 45°C and the immersion time was 4 hours.

[0044] The impregnated SiC blank was slowly heated to 100° C. and maintained at 100° C. for 3 hours for curing.

[0045] The solidified sample was subjected to high temperature Si infiltration at 1500° C. in a vacuum sintering furnace under vacuum conditions for 2 hours to prepare silicon carbide.

[0046] Example 5

[0047] 2-Methylfuran and oxalic acid were prepared into a solution in a ratio of 100:5 (weight ratio), stirred evenly, and then a SiC blank of 40mm×40mm×5mm was put into the solution for immersion at a temperature of 35°C for 4 hours.

[0048] The impregnated SiC blank was slowly heated to 120° C. and maintained at 100° C. for 3 hours for curing.

[0049] The solidified sample was subjected to high temperature Si infiltration at 1500° C. in a vacuum sintering furnace under vacuum conditions for 2 hours to prepare silicon carbide.

[0050] Example 6

[0051] 2-Methylfuran and oxalic acid were prepared into a solution in a ratio of 100:5 (weight ratio), stirred evenly, and then a SiC blank of 40mm×40mm×5mm was put into the solution for immersion at a temperature of 35°C for 4 hours.

[0052] The impregnated SiC blank was slowly heated to 140° C. and maintained at 100° C. for 3 hours for curing.

[0053] The solidified sample was subjected to high temperature Si infiltration at 1500° C. in a vacuum sintering furnace under vacuum conditions for 2 hours to prepare silicon carbide.

[0054] Example 7

[0055] 2-Methylfuran and oxalic acid were prepared into a solution in a ratio of 100:5 (weight ratio), stirred evenly, and then a SiC blank of 40mm×40mm×5mm was put into the solution for immersion at a temperature of 35°C for 4 hours.

[0056] The impregnated SiC blank was slowly heated to 120° C. and maintained at 100° C. for 3 hours for curing.

[0057] The solidified sample was subjected to high temperature Si infiltration at 1550° C. in a vacuum sintering furnace under vacuum conditions for 2 hours to prepare silicon carbide.

[0058] Example 8

[0059] 2-Methylfuran and oxalic acid were prepared into a solution in a ratio of 100:5 (weight ratio), stirred evenly, and then a SiC blank of 40mm×40mm×5mm was put into the solution for immersion at a temperature of 35°C for 4 hours.

[0060] The impregnated SiC blank was slowly heated to 120° C. and maintained at 100° C. for 3 hours for curing.

[0061] The solidified sample was subjected to high temperature Si infiltration at 1650° C. in a vacuum sintering furnace under vacuum conditions for 2 hours to prepare silicon carbide.

[0062] Comparative Example 1

[0063] 2-Hydroxymethylfuran and oxalic acid were prepared into a solution in a ratio of 100:10 (weight ratio), stirred evenly, and then a SiC blank of 40mm×40mm×5mm was put into the solution for immersion. The immersion temperature was 25°C and the immersion time was 4 hours.

[0064] The impregnated SiC blank was slowly heated to 100° C. and maintained at 100° C. for 3 hours for curing.

[0065] The solidified sample was subjected to high temperature Si infiltration at 1500° C. in a vacuum sintering furnace under vacuum conditions for 2 hours to prepare silicon carbide.

[0066] Comparative Example 2

[0067] 2,5-dimethylfuran and oxalic acid were prepared into a solution in a ratio of 100:10 (weight ratio), stirred evenly, and then a SiC blank of 40mm×40mm×5mm was put into the solution for immersion. The immersion temperature was 25°C and the immersion time was 4 hours.

[0068] The impregnated SiC blank was slowly heated to 100° C. and maintained at 100° C. for 3 hours for curing.

[0069] The solidified sample was subjected to high temperature Si infiltration at 1500° C. in a vacuum sintering furnace under vacuum conditions for 2 hours to prepare silicon carbide.

[0070] The silicon carbide prepared in the above examples 1-8 and comparative examples 1-2 was ground and polished, and the density was measured according to GB / T7962.20-2010 "Colorless optical glass test method density". The room temperature flexural strength and elastic modulus were measured by a three-point bending test method, with a sample size of 4mm×3mm×40mm and a span of 30mm. The experimental data are shown in the following table:

[0071] Group <![CDATA[Density g / cm 3 > Bending strength MPa Elastic modulus from GPa Example 1 3.33 402 397 Example 2 3.52 404 389 Example 3 3.66 412 400 Example 4 3.68 400 402 Example 5 3.66 426 418 Example 6 3.42 398 399 Example 7 3.69 428 433 Example 8 3.69 428 433 Comparative Example 1 3.11 391 366 Comparative Example 2 3.01 362 371

[0072] According to the above data, by comparing Example 1 with Example 2, it can be seen that when the ratio of 2-methylfuran to oxalic acid is 100:5, the density is high. By comparing Example 2 with Examples 3 and 4, it can be seen that when the impregnation temperature is 35°C, the performance is further improved, and when the impregnation temperature is 45°C, the density and elastic modulus are improved, but the flexural strength is reduced. By comparing Example 3 with Examples 5 and 6, it can be seen that when the curing temperature is 120 degrees Celsius, the flexural strength and elastic modulus are further improved. When the curing temperature is 160 degrees Celsius, the performance is poor. By comparing Example 5 with Examples 7 and 8, the high-temperature Si infiltration temperature is preferably 1550-1650°C.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing silicon carbide, characterized in that the steps include: (1) mixing 2-methylfuran and oxalic acid and stirring them to form a solution; (2) adding degreased SiC blank for impregnation; (3) The impregnated SiC blank is heated and solidified, and then the solidified sample is placed in a vacuum sintering furnace for high-temperature Si infiltration under a vacuum environment to prepare silicon carbide.

2. A method for preparing silicon carbide according to claim 1, characterized in that: In the step (1), the mass ratio of 2-methylfuran to oxalic acid is 100:10-1.

3. A method for preparing silicon carbide according to claim 1, characterized in that: In the step (1), the mass ratio of 2-methylfuran to oxalic acid is 100:

5.

4. A method for preparing silicon carbide according to claim 1, characterized in that: The immersion temperature in step (2) is 20-80°C.

5. The method for preparing silicon carbide according to claim 1, characterized in that: The immersion temperature in step (2) is 20-50°C.

6. A method for preparing silicon carbide according to claim 1, characterized in that: The immersion time in step (2) is 2-12 hours.

7. The method for preparing silicon carbide according to claim 1, characterized in that: The curing temperature in step (3) is 90-140°C.

8. The method for preparing silicon carbide according to claim 1, characterized in that: The curing temperature in step (3) is 90-110°C.

9. The method for preparing silicon carbide according to claim 1, characterized in that: In the step (3), the high temperature Si infiltration temperature is 1400-1700°C, and the high temperature Si infiltration time is 1-10h.

10. The method for preparing silicon carbide according to claim 1, characterized in that: In the step (3), the high temperature Si infiltration temperature is 1450-1550°C, and the high temperature Si infiltration time is 1-10h.