Silicon carbide ceramic composite material sintered at medium and low temperature and having high thermal shock resistance, preparation method and application

Abstract

The invention provides a medium-low temperature sintered silicon carbide ceramic composite material with high thermal shock resistance as well as a preparation method and application thereof, and belongs to the technical field of ceramic materials. The chemical composition of the composite material comprises CaObAlcSidCaeNaf, a, b, c, d, e and f are atomic contents of corresponding elements, a is larger than or equal to 8.68 and smaller than or equal to 23.81, b is larger than or equal to 45.30 and smaller than or equal to 57.79, c is larger than or equal to 9.83 and smaller than or equal to 17.85, d is larger than or equal to 13.20 and smaller than or equal to 20.29, e is larger than or equal to 0.77 and smaller than or equal to 2.03, and f is larger than or equal to 0 and smaller than or equal to 0.64. The composite material has a porous structure and contains nanoscale particles, and in an infrared spectrum, an acromion at 1166 cm <-1 > shows stretching vibration of Si-O, a strongest peak at 1091 cm <-1 > shows stretching vibration of a Si (Al)-O bond, a secondary strongest peak at 820-824 cm <-1 > shows Si-O-Si symmetric stretching vibration, and a secondary strongest peak at 781 cm <-1 > shows stretching vibration of a Si-Si bond. The composite material disclosed by the invention has high thermal shock resistance, high oxidation resistance and high wear resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and particularly relates to a silicon carbide ceramic composite material with high thermal shock resistance for medium and low temperature sintering, a preparation method and an application thereof. Background Art

[0002] The burner used in coal-fired thermal power generation is the key to the long-term and full-load safe production of the boiler. During the coal-fired power generation process, generally the pulverized coal wind speed is relatively high, usually greater than 20 m / s. The part where the pulverized coal flows through the burner and the nozzle part of the burner belong to the strong wear part of small particle materials and will undergo frequent thermal shocks. For example, the nozzle part will be subjected to a radiation temperature of up to 800°C to 1250°C from the furnace. In order to improve the wear resistance of the burner at high temperatures, heat-resistant alloy cast steel parts are usually used in the prior art, but it is not wear-resistant at small angles (0° to 30°), that is, the angle formed by the flow direction of the pulverized coal and the surface of the burner, resulting in serious wear of the metal components in the part where the pulverized coal of the burner flows through, and the combustion efficiency of the burner decreases. The nozzle at the hot end will generate thermal deformation, oxidation erosion and serious wear, which will further cause the flame at the nozzle to deflect, resulting in damage to the water wall and other accidents, and even forced boiler shutdown.

[0003] Chinese Patent Application (CN113446599A) discloses a composite ceramic burner and its preparation method. The composite ceramic burner is made of a composite ceramic material, which consists of the following components by mass percentage: 55 - 75% silicon carbide, 10 - 20% brown fused alumina, 5 - 15% aluminate cement, 2 - 5% high-temperature resistant stainless steel fiber, and 5 - 10% auxiliary materials. The composite ceramic burner is prepared by the following steps: 1) Raw material preparation: Prepare silicon carbide, brown fused alumina powder, aluminate cement, high-temperature resistant stainless steel fiber, and auxiliary materials in proportion. 2) Calculate the weight of the concentrator, weigh and mix silicon carbide, brown fused alumina, and aluminate cement in proportion, pour them into a mixer, add water accounting for 4 - 6% of the total raw materials, start the mixer for stirring for 12 - 18 minutes. After the material in the mixer becomes paste-like, add high-temperature stainless steel fiber and stir for another 3 - 8 minutes before discharging. 3) Pouring the outer frame of the pulverized coal concentrator: Line the inner cavity of the pre-prepared outer frame mold with 40g of release paper, place it on a vibrating table, fix the mold, turn on the vibrating table, and pour the stirred material into the mold gate until the mold gate is filled. 4) Pouring the guide plate: The guide plate is poured separately from the outer frame of the pulverized coal concentrator, and the method in step 3) is used to pour the guide plate. 5) Demolding: Perform demolding treatment after 12 hours at room temperature, and place it in the shade to dry for 2 days after demolding. 6) Drying: Place the demolded blank in a drying oven at 75 - 85°C for 2 days. 7) Low-temperature sintering treatment: Put the dried guide plate and outer frame blanks into a heat treatment furnace for sintering treatment. 8) Insert the deflector sintered in step 7) into the sintered outer frame for assembly, and use inorganic glue for gluing to form an integral concentrator. During its preparation process, the highest sintering temperature is 1380°C. However, when the sintering temperature exceeds 1350°C, the steel fiber may partially melt and oxidize, losing its strengthening effect. Moreover, the increased expansion coefficient of brown fused alumina is greater than that of silicon carbide, and its thermal conductivity is less than that of silicon carbide, which may generate large internal stresses during the use of the composite ceramic burner, resulting in the product being loose and cracked.

[0004] Currently, how to sinter at medium and low temperatures to improve the thermal shock resistance, oxidation resistance, and wear resistance of silicon carbide ceramic materials is a problem that needs to be further solved. The above information disclosed in the background art section is only used to enhance the understanding of the background of the present invention, so it may include information that does not constitute relevant technologies known to those of ordinary skill in the art. Summary of the Invention

[0005] Aiming at the problems in the prior art, the present invention first provides a silicon carbide ceramic composite material sintered at medium temperature with high thermal shock resistance, high oxidation resistance, and high wear resistance. Its chemical composition includes C a O b Al c Si d Ca e Naf , where a, b, c, d, e, and f are the atomic contents of the corresponding elements, 8.68 ≤ a ≤ 23.81, 45.30 ≤ b ≤ 57.79, 9.83 ≤ c ≤ 17.85, 13.20 ≤ d ≤ 20.29, 0.77 ≤ e ≤ 2.03, 0 ≤ f ≤ 0.64; the composite material has a porous structure and contains nanoscale particles. In the infrared spectrum, the shoulder peak at 1166 cm -1 shows the stretching vibration of Si-O, and the strongest peak at 1091 cm -1 shows the stretching vibration of the Si(Al)-O bond, and the second strongest peak at 820 cm -1 shows the symmetric stretching vibration of Si-O-Si, and the peak at 781 cm -1 shows the stretching vibration of the Si-Si bond.

[0006] Among them, the composite material has a porous structure, which can eliminate the stress generated when the composite material is used in a high-temperature environment and improve its thermal shock resistance.

[0007] Furthermore, the nanoscale particles are lamellar particles, that is, they include flaky particles and stacked flaky particles, and their size is 200 nm - 500 nm. For example, the size can be 200 nm, 220 nm, 280 nm, 300 nm, 350 nm, 400 nm, 450 nm, 480 nm, 500 nm. The lamellar particles can increase the contact area between each other, making the composite material formed by the lamellar particles more dense and compact, and improving the strength and wear resistance of the composite material.

[0008] Furthermore, the radial size of the porous structure is 1 μm - 10 μm. For example, the radial size can be 2 μm, 4 μm, 5 μm, 6 μm, 8 nm, 9 μm, 10 μm.

[0009] Furthermore, the silicon carbide ceramic composite material includes a crystal structure, which can promote the sintering activity during the preparation process of the material and obtain a silicon carbide ceramic composite material with high strength and high wear resistance.

[0010] Furthermore, in the infrared spectrum, the peaks in the range of 480 - 650 cm -1 show the bending vibration mode of Si-O.

[0011] The present invention also provides a preparation method for the above-mentioned silicon carbide ceramic composite material with high thermal shock resistance by medium and low temperature sintering, including the following steps:

[0012] (1)Feeding the main materials: Obtain 55 - 75 parts by weight of pre - treated silicon carbide graded particles, 10 - 12 parts of silicon carbide fine powder with a mesh size of 200 - 300, 2 - 10 parts of aluminate cement, 2 - 10 parts of alumina micropowder, 2 - 10 parts of silica micropowder, and 0.5 - 5 parts of reinforcing material; wherein, the pre - treated silicon carbide graded particles include silicon carbide sand with different particle sizes.

[0013] (2)Feeding the auxiliary materials: Obtain 0.5 - 3 parts by weight of compound antioxidant sintering aids and 3 - 5 parts of water, and the compound antioxidant sintering aids include boron carbide powder.

[0014] (3)Mix the main materials and the auxiliary materials, and place them in a mold for molding to form a green body.

[0015] (4)Brush an anti - oxidation coating on the surface of the green body, and conduct medium - low temperature sintering, and the temperature of the medium - low temperature sintering is not higher than 750 °C.

[0016] Among them, the aluminate cement in the main materials can be calcium aluminate cement, which can improve the high - temperature performance of the silicon carbide ceramic composite material and make the material heat - resistant. The grade of calcium aluminate cement can be selected from any one of CA50, CA60, CA70, and CA80.

[0017] Among them, the pre - treated silicon carbide graded particles can be taken as 55 parts, 60 parts, 65 parts, 66 parts, 70 parts, 72 parts, 74 parts, 75 parts for example. The silicon carbide fine powder with a mesh size of 200 - 300 can be taken as 10 parts, 11 parts, 11.5 parts, 12 parts for example. The aluminate cement can be taken as 2 parts, 3 parts, 5 parts, 6 parts, 8 parts, 10 parts. The alumina micropowder can be taken as 2 parts, 3 parts, 5 parts, 6 parts, 8 parts, 10 parts. The silica micropowder can be taken as 2 parts, 3 parts, 5 parts, 6 parts, 8 parts, 9 parts, 10 parts. The reinforcing material can be taken as 0.5 parts, 1 part, 1.2 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 3.8 parts, 4 parts, 4.5 parts, 4.7 parts, 5 parts.

[0018] Among them, the compound antioxidant sintering aids in the auxiliary materials can be 0.5 parts, 1.2 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts. The water in the auxiliary materials can be 3 parts, 4 parts, 5 parts.

[0019] Further, before the main material is put in, the preparation method further includes preparing the pretreated silicon carbide graded particles, including: obtaining 12-15 parts by weight of silicon carbide sand with a diameter of 3.35 mm-4.75 mm, 27-35 parts by weight of silicon carbide sand with a diameter of 1.18 mm-2.8 mm, 15-22 parts by weight of silicon carbide sand with a diameter of 0.5 mm-0.7 mm, and 1-3 parts of modified sodium-type silica sol, mixing them, and then performing stirring and drying treatments to obtain the pretreated silicon carbide graded particles.

[0020] That is, in the embodiments of the present invention, the pretreated silicon carbide graded particles contain silicon carbide sand with different grades of particle sizes. According to the principle of similar compatibility, the silicon carbide sand with a smaller particle size can fill the gaps between the silicon carbide sand with a larger particle size, thereby improving the strength. And the silicon carbide sand with multiple particle sizes can reduce the bonding poles and correspond to wear particles of multiple sizes, thereby enhancing the wear resistance.

[0021] Among them, the silicon carbide sand with a diameter of 3.35 mm-4.75 mm can be 12 parts, 13 parts, 14 parts, 15 parts. The silicon carbide sand with a diameter of 1.18 mm-2.8 mm can be 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts. The silicon carbide sand with a diameter of 0.5 mm-0.7 mm is 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts. The modified sodium-type silica sol can be 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts.

[0022] Further, the modified sodium-type silica sol includes silicon dioxide and sodium silicate. For example, the sol obtained by uniformly mixing silica sol and sodium silicate. Among them, the silica sol is a dispersion of silicon dioxide particles in water or other solvents, and after adding a predetermined amount of sodium silicate and mixing, the modified sodium-type silica sol of the embodiments of the present invention is obtained. In some embodiments of the present invention, the weight content of SiO2 in the modified sodium-type silica sol can be 30%, and of course, it can also be other contents, such as 25%, 40%, etc. Those skilled in the art can prepare according to actual needs and no special limitation is made here. Using the modified sodium-type silica sol to treat the particles makes the surface of the particles have a layer of highly active SiO2, and the particles are more likely to be sintered at low temperature.

[0023] Further, the medium and low temperature sintering of the green body coated with the anti-oxidation coating in step (4) includes: heating the green body from room temperature to a first preset temperature, and keeping it at the first preset temperature for 4-6 h, then heating to a second preset temperature, and keeping it at the second preset temperature for 4-6 h, and naturally cooling to room temperature.

[0024] That is, after applying the anti-oxidation coating to the green body, medium and low temperature sintering is carried out. In the embodiments of the present invention, the first preset temperature is 130°C to 160°C. For example, the first preset temperature is 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, and the heating rate from room temperature to the first preset temperature is 30°C / h to 40°C / h. For example, the heating rate can be 30°C / h, 33°C / h, 35°C / h, 37°C / h, 38°C / h, 40°C / h. The second preset temperature is 650°C to 750°C, and the heating rate from the first preset temperature to the second preset temperature is 30°C / h to 40°C / h. For example, the second preset temperature is 650°C, 680°C, 700°C, 720°C, 730°C, 750°C, and the heating rate of the second preset temperature can be 30°C / h, 33°C / h, 35°C / h, 37°C / h, 38°C / h, 40°C / h. The heat preservation times of the first preset temperature and the second preset temperature can be 4h, 4.5h, 4.8h, 5h, 5.5h, 5.8h, 6h respectively.

[0025] Silicon carbide and the reinforcing material are prone to oxidation at high temperatures, for example, above 1300°C. However, in the embodiments of the present invention, the temperature of medium and low temperature sintering is not higher than 750°C, so the oxidation of silicon carbide and the reinforcing material can be avoided, further increasing the strength of the composite material and improving the oxidation resistance and thermal shock resistance of the silicon carbide composite material. In the embodiments of the present invention, the first preset temperature is 130°C to 160°C and the heat preservation is 4 to 6 hours, which can remove the moisture on the surface of the green body and the surface of the internal material (such as silicon carbide). During the slow heating process, when reaching 300°C to 500°C, the crystal water inside the green body material can be released, further drying the green body. When reaching the second preset temperature of 650°C to 750°C, a silicon carbide ceramic composite material with high strength, high wear resistance can be obtained.

[0026] In addition, the compound anti-oxidation sintering aid in the embodiments of the present invention includes boron carbide powder (B4C). Boron carbide powder can be oxidized to generate B2O3 at a lower temperature. B2O3 can react with silica in the green body material to form a glass phase, promoting the sintering of the materials in the green body at a lower temperature (650°C to 750°C). That is to say, it improves the sintering activity of the materials, and then enables the green body to obtain a silicon carbide ceramic material with high strength, high wear resistance and high thermal shock resistance even during medium and low temperature sintering, avoiding high temperature oxidation.

[0027] Furthermore, the compound antioxidant sintering aid further includes at least one of aluminum powder (Al), silicon powder (Si), alumina powder (Al2O3), silica fine powder (SiO2), and aluminum-silicon alloy powder (AlSi). The compound antioxidant sintering aid will undergo a process of melting and recrystallization during sintering, reducing the recrystallization temperature. Therefore, these materials can all promote the sintering activity of the green body at low temperatures and obtain a silicon carbide ceramic material with high strength and high wear resistance. Among them, the silica fine powder refers to the particle size of silica reaching the micron or nanometer level.

[0028] Furthermore, in the compound antioxidant sintering aid, the weight content of B4C powder is above 50%, such as 60%, 70%, 80%, etc., to ensure better low-temperature sintering performance. For example, the compound antioxidant sintering aid includes boron carbide powder and aluminum powder, and the weight ratio of boron carbide powder to aluminum powder is 1:1. Another example is that the compound antioxidant sintering aid includes boron carbide powder and aluminum-silicon alloy powder, and the weight ratio of boron carbide powder to aluminum-silicon alloy powder is 1:1.

[0029] Furthermore, the reinforcing materials in the main material include at least one of steel fibers (such as 310s stainless steel fibers), silicon nitride whiskers, silicon carbide whiskers, and alumina whiskers. These materials can further enhance the strength of the silicon carbide ceramic composite material. Since the temperature of the above low-temperature sintering is relatively low, these reinforcing materials (such as steel fibers) will not be oxidized and melted, which can significantly improve the strength of the silicon carbide ceramic composite material, increase toughness, and avoid cracking.

[0030] Furthermore, the above-mentioned reinforcing materials are all heat-resistant materials. For example, the steel fiber is a heat-resistant steel fiber. The steel fiber can be solution-treated and surface passivated, and its cross-sectional diameter is 0.2 mm to 0.5 mm. For example, the diameter can be 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, and the steel fiber is end-hooked or corrugated to increase the pull-out work of the steel fiber. The material of the steel fiber can be selected from any one of the following grades: 16Cr25N, 08Cr18Ni9, 20Cr23Ni13, 08Cr25Ni20, or 08Cr17Ni12Mo2.

[0031] Further, the anti-oxidation coating includes mullite fine powder, andalusite fine powder and modified sodium-type silica sol, and the weight ratio is 4:1:5. Among them, the modified sodium-type silica sol is the same as that in the pre-treated silicon carbide graded particles in the above embodiments, and will not be elaborated here. Mix and stir the above-mentioned fine powder and modified sodium-type silica sol, and water or other solvents can be added according to actual conditions to obtain the required viscosity to form an anti-oxidation coating. The thickness of the anti-oxidation coating brushed on the green body is 0.2 mm to 2 mm. In addition to the above two end values, the thickness can also be 0.5 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm. Those skilled in the art can select the thickness value according to actual conditions, and no special limitation is made here. The anti-oxidation coating can prevent the silicon carbide and reinforcing materials in the silicon carbide ceramic composite from being oxidized by oxygen in the working medium during sintering, further ensuring the strength of the silicon carbide ceramic composite and improving its antioxidant property.

[0032] Further, the auxiliary materials further include 0.1 to 0.3 parts of a rheology modifier, such as 0.1 part, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts. The rheology modifier includes at least one of sodium tripolyphosphate, sodium hexametaphosphate and polynaphthalene sulfonate. By adding the rheology modifier, the mixing between various components becomes smoother, the water consumption is reduced, the subsequent sintering time is further shortened, and the construction performance is improved.

[0033] Further, the auxiliary materials can further include 0.1 to 0.3 parts of a retarder, such as 0.1 part, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts. The retarder includes at least one of citric acid and oxalic acid.

[0034] In order to adjust the construction time and product performance of the silicon carbide ceramic composite at different temperatures (seasons), for example, when the ambient temperature is relatively high, the activities of various components are relatively high, and a retarder can be added to reasonably control the curing time of the material to make it reach the best performance.

[0035] Further, the auxiliary materials can further include 0.01 to 0.05 parts of an accelerator, such as 0.01 part, 0.02 parts, 0.03 parts, 0.04 parts, 0.05 parts. When the ambient temperature is relatively low, the activities of various components are relatively low. After adding the accelerator, the activities between various components can be increased, the curing time can be shortened, and the best performance can be achieved. Among them, the grade of the accelerator can be KAD-20 or CS-511. The accelerator can be anhydrous lithium chloride, lithium carbonate, etc.

[0036] Therefore, whether to add a retarder or an accelerator can be selected according to actual conditions to ensure that the silicon carbide ceramic composite has more excellent performance, and has a more sufficient construction time and a reasonable hydration time, thereby improving the product performance.

[0037] Further, the auxiliary materials further include 0.2 to 0.6 parts of an explosion-proof agent and 4.5 to 6.5 parts of water; wherein, the explosion-proof agent includes at least one of polypropylene fiber and polyethylene fiber.

[0038] Adding the above explosion-proof agent to the auxiliary materials can prevent the green body (preform) from bursting during use and extend the service life of the silicon carbide ceramic composite material. Among them, the explosion-proof agent can be at least one of polypropylene fiber and polyethylene fiber, with a length of 2 mm to 10 mm (for example, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm) and a diameter of 10 to 50 μm (for example, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm).

[0039] Among them, the explosion-proof agent can be 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, and the water can be 4.5 parts, 4.8 parts, 5 parts, 5.5 parts, 5.8 parts, 6 parts, 6.2 parts, 6.5 parts.

[0040] The present invention also provides an application of the silicon carbide ceramic composite material with high thermal shock resistance sintered at medium and low temperature described in any one of the above embodiments in a burner.

[0041] Further, the silicon carbide ceramic composite material can be used to form a burner, or at least used to form the part through which high-temperature pulverized coal in the burner flows and the nozzle.

[0042] It can be seen from the above technical solutions that the silicon carbide ceramic composite material and its preparation method according to the embodiments of the present invention have at least one of the following beneficial effects:

[0043] Due to the porous structure of the silicon carbide ceramic composite material, it can eliminate the stress generated during the use of the composite material in a high-temperature environment and improve its thermal shock resistance. During the preparation process, the pre-treated silicon carbide graded particles contain silicon carbide sand with different particle sizes and reinforcing materials, which can enhance the wear resistance of the silicon carbide ceramic composite material. During the sintering process, the compound antioxidant sintering aid includes boron carbide powder. Boron carbide powder can be oxidized to generate B2O3 at a relatively low temperature. B2O3 can react with silicon oxide in the green body material to form a glass phase, improving the sintering activity of the material, enabling the materials in the green body to reach the required performance by sintering at a relatively low temperature (650°C - 750°C), avoiding high-temperature oxidation, eliminating internal stress in the product, improving the thermal shock resistance of the silicon carbide ceramic composite material, and increasing toughness. By brushing an anti-oxidation coating on the surface of the green body, it can further prevent the silicon carbide and reinforcing materials in the silicon carbide ceramic composite material from being oxidized by oxygen in the working medium during sintering, further ensuring the strength of the silicon carbide ceramic composite material. Therefore, the silicon carbide ceramic composite material prepared by the above method has higher oxidation resistance, higher strength and wear resistance, and extends the service life. Description of the Drawings

[0044] By referring to the drawings and describing its exemplary embodiments in detail, the above and other features and advantages of the present invention will become more apparent.

[0045] Figure 1 XRD test diagram of the silicon carbide ceramic composite material of Example 1.

[0046] Figure 2 Infrared test diagram of the silicon carbide ceramic composite material of Example 1.

[0047] Figure 3 EDS test diagram of the silicon carbide ceramic composite material of Example 1.

[0048] Figure 4 SEM test of the silicon carbide ceramic composite material of Example 1 Figure 1 .

[0049] Figure 5 SEM test of the silicon carbide ceramic composite material of Example 1 Figure 2 .

[0050] Figure 6 TEM test diagram of the silicon carbide ceramic composite material of Example 1.

[0051] Figure 7 XRD test diagram of the silicon carbide ceramic composite material of Example 2.

[0052] Figure 8 Infrared test diagram of the silicon carbide ceramic composite material of Example 2.

[0053] Figure 9 EDS test diagram of the silicon carbide ceramic composite material of Example 2.

[0054] Figure 10 SEM test diagram of the silicon carbide ceramic composite material of Example 2.

[0055] Figure 11 TEM test diagram of the silicon carbide ceramic composite material of Example 2.

[0056] Figure 12 EDS test diagram of the silicon carbide ceramic composite material of Example 3.

[0057] Figure 13 SEM test diagram of the silicon carbide ceramic composite material of Example 3.

[0058] Figure 14 EDS test diagram of the silicon carbide ceramic composite material of Example 4.

[0059] Figure 15 SEM test diagram of the silicon carbide ceramic composite material of Example 4.

[0060] Figure 16 EDS test diagram of the silicon carbide ceramic composite material of Example 5.

[0061] Figure 17 EDS test diagram of the silicon carbide ceramic composite material of Example 6. Detailed implementation manners

[0062] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. Like reference numerals in the figures denote like or similar structures and thus their detailed description will be omitted.

[0063] The operations / steps in the embodiments are not necessarily executed in the order described in the figures. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may be changed according to the actual situation.

[0064] Performance testing 1. XRD (X-ray diffraction) testing Instrument name: X-ray diffractometer Model: D8 ADVANCE (Bruker Corporation, Germany) Test conditions: Cu-Kα radiation (0.15406 nm).

[0065] 2. Fourier transform infrared spectroscopy (FTIR) test Instrument name: Fourier transform infrared spectrometer Model: VERTEX70 type made by Bruker, Germany Test conditions: Wavenumber range: 4000 - 400 cm -1 ; Resolution: 2 cm -1 ; Number of scans: 32 times.

[0066] 3. EDS (Energy Dispersive Spectrometer) analysis Instrument name: Field emission transmission electron microscope & Energy Dispersive Spectrometer Model: ZEISS Sigma 300 & OXFORD Ultim® Max100 Test conditions: Accelerating voltage is 200 kV.

[0067] 4. SEM (Scanning Electron Microscope) test Instrument name: Scanning Electron Microscope Model: ZEISS Sigma 300 Test conditions: Accelerating voltage is 10 kV.

[0068] 5. TEM (Transmission Electron Microscope) test Instrument name: Transmission Electron Microscope Model: Tecnai G 2 F20 S-TWIN Test conditions: The sample is ultrasonically treated and dispersed in water; Accelerating voltage is 200 kV.

[0069] 6. Thermal shock resistance test

[0070] Based on GB / T30873 - 2014, the thermal shock resistance of the silicon carbide ceramic composite material in the examples of this application is tested by the water quenching method, as follows.

[0071] Equipment: (1) Test furnace, which can be an electric heating furnace with uniform furnace temperature distribution in the sample loading area, ensuring that the temperature difference between any two points at the heated end of the sample is not greater than 15°C, and the isothermal zone should be sufficient to accommodate more than 3 samples for testing simultaneously. The temperature measuring end of the thermocouple is 10 mm - 20 mm away from the heated end face of the sample. (2) Flow water tank, which can accommodate multiple samples for rapid cooling simultaneously, and ensure that the temperature rise of the water flowing into and out of the water tank is not greater than 10°C. There is a bracket for placing samples in the water tank, and the surface of the bracket is not less than 20 mm away from the bottom of the water tank to ensure the normal flow of cooling water. The depth of the water in the water tank should ensure that the samples are completely immersed in the water. (3) Manipulator or fixture. (4) Sample cooling rack, which should be a steel frame paved with parallel refractory bricks and can place 50 mm × 50 mm cylindrical samples. (5) Electrothermal blast drying oven, room temperature - 300°C. (6) Thermometer, accurate to 1°C. (7) Steel ruler, accurate to 1 mm.

[0072] Specimen: The sample preparation is carried out according to the provisions of YB / T5116, and specimens of 40 mm × 40 mm × 160 mm are used.

[0073] Test procedure: (1) Dry the specimen in the electrothermal drying oven at 110°C ± 5°C until constant weight. (2) Preheat the heating furnace to 1100°C ± 10°C, and after holding for 15 min, quickly move the specimen into the isothermal zone in the furnace cavity. The specimens shall not be stacked and shall be separated from each other, and the distance between specimens shall be not less than 10 mm, and the distance between the specimen and the surface of the heating element shall be not less than 30 mm. (3) After the specimen is put into the furnace, the furnace temperature drop shall not be greater than 50°C, and it shall recover to the test temperature within 5 min. The specimen is held at the test temperature for 20 min. (4) Quickly immerse the specimen into the flowing water at 5°C - 35°C, and adjust the water flow rate to ensure that the temperature rise of the water flowing into and out of the water tank is not greater than 10°C. (5) After the specimen is rapidly cooled in the water tank for 3 min, immediately take it out and place it on the cooling rack, and place it in the air for not less than 5 min. When the specimen is rapidly cooled, the furnace door shall be closed in time to keep the furnace temperature within ±10°C of the test temperature. (6) When the specimen has been held in the air for 5 min and the furnace temperature has recovered to the test temperature, the specimen can be quickly moved into the furnace, and the above rapid cooling and heating process shall be repeated until the test is completed. (7) During the thermal alternation process, no mechanical loss shall occur to the specimen. (8) The test stops when visible cracks appear on the specimen or when the agreed number of times is reached.

[0074] Example 1

[0075] The preparation method of the silicon carbide ceramic composite material in this example includes the following steps (1) - (4).

[0076] (1) Feeding the main materials

[0077] Weigh the following components by weight parts: 66 parts of pre-treated silicon carbide graded particles, 11 parts of silicon carbide fine powder with 200 meshes, 8 parts of calcium aluminate cement, 8 parts of alumina fine powder, 7 parts of silica fine powder and 4 parts of steel fibers.

[0078] Among them, the pre-treated silicon carbide graded particles include:

[0079] 12 parts of silicon carbide sand with a diameter of 3.35 mm to 4.75 mm, 32 parts of silicon carbide sand with a diameter of 1.18 mm to 2.8 mm, 20 parts of silicon carbide sand with a diameter of 0.5 mm to 0.7 mm and 2 parts of modified sodium-type silica sol. Among them, the silicon carbide sand with different diameters and the modified sodium-type silica sol are dried after being stirred and mixed evenly to obtain the pre-treated silicon carbide graded particles.

[0080] (2) Add auxiliary materials

[0081] Weigh the following components by weight parts: 2 parts of compound antioxidant sintering aid (B4C and Al powder, mass ratio 1:1), 0.2 parts of rheological modifier (sodium tripolyphosphate), 0.2 parts of retarder (citric acid), 0.5 parts of explosion-proof agent (polypropylene fiber) and 5 parts of water.

[0082] (3) Mix the main materials and auxiliary materials and place them in a mold for molding to form a green body.

[0083] (4) Brush an anti-oxidation coating with a thickness of approximately 1 mm on the green body. The anti-oxidation coating includes mullite fine powder, andalusite fine powder and modified sodium-type silica sol, with a weight ratio of 4:1:5. After brushing the anti-oxidation coating, perform medium and low-temperature sintering. Heat from room temperature to 150 °C at a heating rate of 30 °C / h to 40 °C / h. After reaching 150 °C, keep it warm for 5 h, then continue to heat to 700 °C at a heating rate of 30 °C / h to 40 °C / h, keep it warm for 5 h, and cool naturally to room temperature to obtain a silicon carbide ceramic composite material doped with steel fibers.

[0084] Perform XRD testing on the silicon carbide ceramic composite material of this example. As Figure 1 shown, it contains a large number of inorganic compound crystals. The XRD peaks are similar to the characteristics of olivine and kaolinite, and there is a strong peak at 35.5 degrees, further proving that the silicon carbide ceramic composite material of this example is a highly wear-resistant refractory material.

[0085] As Figure 2 shown, the infrared test shows that the shoulder peak at 1166 cm -1 of the composite material of this example shows the stretching vibration of Si-O, and the strongest peak at 1091 cm -1 shows the stretching vibration of Si(Al)-O bond. The second strongest peak at 820 cm -1 shows the symmetric stretching vibration of Si-O-Si, 781 cm-1 It is shown as the stretching vibration of Si-Si bonds, 480 - 650 cm -1 The peaks in the range show the bending vibration mode of Si-O.

[0086] Figure 3 The EDS spectrum of the composite material of this embodiment is shown, combined with the EDS spectrum analysis results below:

[0087] The chemical composition of the composite material of this embodiment is C 16.89 O 52.22 Al 12.39 Si 17.19 Ca 1.31 Of course, in fact, the composite material of the present invention may also include other trace elements or impurities, such as B, P, etc. Within the allowable error of EDS measurement, due to their extremely small amount, they are not shown.

[0088] Figure 4 The SEM photograph of... shows that the composite material of this embodiment has a porous structure, and the radial dimension (diameter) of the porous structure is about 1μm - 10μm. Figure 5 The SEM photograph of... shows that there is a porous structure in the composite material, indicating that the composite material includes lamellar materials.

[0089] Figure 6 The TEM photograph of... further proves that the composite material includes lamellar particles.

[0090] The thermal shock resistance test was carried out on the composite material of this embodiment, and the results are shown in Table 1.

[0091] Table 1 Test Results

[0092] Example 2

[0093] The preparation method of the silicon carbide ceramic composite material of this embodiment includes the following steps (1) - (4).

[0094] (1) Feeding the main materials

[0095] Weigh the following components by weight: 64 parts of pre-treated silicon carbide graded particles, 11 parts of 250-mesh silicon carbide fine powder, 8 parts of calcium aluminate cement, 10 parts of alumina fine powder, 7 parts of silica fine powder, and 4 parts of steel fibers.

[0096] Among them, the pre-treated silicon carbide graded particles include:

[0097] 12 parts of silicon carbide sand with a diameter of 3.35 mm to 4.75 mm, 30 parts of silicon carbide sand with a diameter of 1.18 mm to 2.8 mm, 20 parts of silicon carbide sand with a diameter of 0.5 mm to 0.7 mm, and 2 parts of modified sodium-type silica sol. Among them, the silicon carbide sands with different diameters and the modified sodium-type silica sol are uniformly mixed by stirring and then dried to obtain pretreated silicon carbide graded particles.

[0098] (2)Put in auxiliary materials

[0099] Weigh the following components by weight: 2 parts of compound antioxidant sintering aid (B4C and AlSi powder, mass ratio 1:1), 0.2 part of rheological modifier (sodium hexametaphosphate), 0.2 part of retarder (citric acid), 0.5 part of explosion-proof agent (polyethylene fiber), and 5 parts of water.

[0100] (3)Mix the main materials and auxiliary materials and place them in a mold for molding to form a green body.

[0101] (4)Brush an anti-oxidation coating with a thickness of approximately 1 mm on the green body. The anti-oxidation coating includes mullite micropowder, andalusite micropowder, and modified sodium-type silica sol, with a weight ratio of 4:1:5. After brushing the anti-oxidation coating, perform medium and low-temperature sintering. Heat from room temperature to 150 °C at a heating rate of 30 °C / h to 40 °C / h. After reaching 150 °C, hold for 5 h, then continue to heat to 700 °C at a heating rate of 30 °C / h to 40 °C / h, hold for 5 h, and cool naturally to room temperature to obtain a silicon carbide ceramic composite material doped with steel fibers.

[0102] Perform XRD testing on the silicon carbide ceramic composite material of this example, as Figure 7 shown. It contains a large number of inorganic compound crystals. The XRD peaks are similar to the characteristics of olivine and kaolinite, with a strong peak at 35.5 degrees, further proving that the silicon carbide ceramic of this example is a highly wear-resistant refractory material.

[0103] As Figure 8 shown, infrared testing shows that the shoulder peak at 1166 cm -1 of the composite material of this example shows the stretching vibration of Si-O, and the strongest peak at 1091 cm -1 shows the stretching vibration of Si(Al)-O bond. The second-strongest peak at 824 cm -1 shows the symmetric stretching vibration of Si-O-Si, and the peaks in the range of 480 - 650 cm -1 show the bending vibration mode of Si-O.

[0104] Figure 9 Shows the EDS spectrum of the composite material of this example, combined with the EDS spectrum analysis results below:

[0105] The chemical composition of the composite material in this embodiment is C 13.90 O 54.44 Al 13.30 Si 16.34 Ca 2.03 .

[0106] Figure 10 SEM photos of Figure 10 show that the composite material in this embodiment has a porous structure, and the radial dimension (diameter) of the porous structure is about 1 μm to 10 μm.

[0107] Figure 11 TEM photos of Figure 11 further prove that the composite material includes lamellar materials.

[0108] Example 3

[0109] The preparation method of the silicon carbide ceramic composite material in this embodiment includes the following steps (1) to (4).

[0110] (1) Feeding the main materials

[0111] Weigh the following components by weight: 66 parts of pretreated silicon carbide graded particles, 11 parts of 300-mesh silicon carbide fine powder, 3 parts of calcium aluminate cement, 8 parts of alumina fine powder, 7 parts of silica fine powder, and 4 parts of steel fiber.

[0112] Among them, the pretreated silicon carbide graded particles include:

[0113] 12 parts of silicon carbide sand with a diameter of 3.35 mm to 4.75 mm, 32 parts of silicon carbide sand with a diameter of 1.18 mm to 2.8 mm, 20 parts of silicon carbide sand with a diameter of 0.5 mm to 0.7 mm, and 2 parts of modified sodium-type silica sol. Among them, the silicon carbide sand with different diameters and the modified sodium-type silica sol are uniformly mixed by stirring and then dried to obtain the pretreated silicon carbide graded particles.

[0114] (2) Feeding the auxiliary materials

[0115] Weigh the following components by weight: 2 parts of compound antioxidant sintering aid (B4C), 0.2 part of rheological modifier (sodium tripolyphosphate), 0.2 part of retarder (citric acid), 0.5 part of explosion-proof agent (polypropylene fiber), and 5 parts of water.

[0116] (3) Mix the main materials and the auxiliary materials and place them in a mold for molding to form a green body.

[0117] (4)Brush an anti-oxidation coating with a thickness of approximately 2 mm on the green body. The anti-oxidation coating includes mullite micropowder, andalusite micropowder, and modified sodium-type silica sol, with a weight ratio of 4:1:5. After brushing the anti-oxidation coating, perform medium and low-temperature sintering. Heat from room temperature to 160 °C at a heating rate of 30 °C / h to 40 °C / h. After reaching 160 °C, hold for 4 h, then continue to heat to 750 °C at a heating rate of 30 °C / h to 40 °C / h, hold for 4 h, and naturally cool to room temperature to obtain the silicon carbide ceramic composite material doped with steel fibers.

[0118] Figure 12 The EDS spectrum of the composite material of this example is shown, combined with the following EDS spectrum analysis results:

[0119] The chemical composition of the composite material of this example is C 23.81 O 45.30 Al 9.83 Si 20.29 Ca 0.77 。

[0120] Figure 13 The SEM photograph of shows that the composite material of this example has a porous structure, and the radial dimension (diameter) of the porous structure is about 1 μm to 10 μm.

[0121] Example 4

[0122] The preparation method of the silicon carbide ceramic composite material of this example includes the following steps (1) to (4).

[0123] (1)Put in the main materials

[0124] Weigh the following components by weight: 75 parts of pre-treated silicon carbide graded particles, 10 parts of silicon carbide fine powder with a mesh size of 200, 10 parts of calcium aluminate cement, 10 parts of alumina micropowder, 10 parts of silica micropowder, and 5 parts of steel fibers.

[0125] Among them, the pre-treated silicon carbide graded particles include:

[0126] 15 parts of silicon carbide sand with a diameter of 3.35 mm to 4.75 mm, 35 parts of silicon carbide sand with a diameter of 1.18 mm to 2.8 mm, 22 parts of silicon carbide sand with a diameter of 0.5 mm to 0.7 mm, and 3 parts of modified sodium-type silica sol. Among them, the silicon carbide sand with different diameters and the modified sodium-type silica sol are stirred and mixed evenly and then dried to obtain the pre-treated silicon carbide graded particles.

[0127] (2)Put in the auxiliary materials

[0128] Weigh the following components by weight parts: 3 parts of compound antioxidant sintering aid (B4C and Al powder, mass ratio is 1:1), 0.3 part of rheological modifier (sodium tripolyphosphate), 0.3 part of retarder (citric acid), 0.6 part of explosion-proof agent (polypropylene fiber) and 6.5 parts of water.

[0129] (3) Mix the main materials and auxiliary materials and place them in a mold for molding to form a green body.

[0130] (4) Brush an anti-oxidation coating with a thickness of approximately 1 mm on the green body. The anti-oxidation coating includes mullite fine powder, andalusite fine powder and modified sodium-type silica sol, and the weight ratio is 4:1:5. After brushing the anti-oxidation coating, carry out medium and low temperature sintering. Heat from room temperature to 150 °C at a heating rate of 30 °C / h to 40 °C / h. After reaching 150 °C, keep it warm for 5 h, and then continue to heat to 700 °C at a heating rate of 30 °C / h to 40 °C / h, keep it warm for 5 h, and naturally cool down to room temperature to obtain the silicon carbide ceramic composite material doped with steel fibers.

[0131] Figure 14 Show the EDS spectrum of the composite material in this embodiment, combined with the following EDS spectrum analysis results:

[0132] The chemical composition of the composite material in this embodiment is C 15.11 O 53.92 Al 15.36 Si 13.20 Ca 1.88 Na 0.53 .

[0133] Figure 15 The SEM photograph of shows that the composite material in this embodiment has a porous structure and includes lamellar particles.

[0134] Example 5

[0135] The preparation method of the silicon carbide ceramic composite material in this embodiment includes the following steps (1) to (4).

[0136] (1) Put in the main materials

[0137] Weigh the following components by weight parts: 70 parts of pretreated silicon carbide graded particles, 10 parts of silicon carbide fine powder with 200 meshes, 8 parts of calcium aluminate cement, 2 parts of alumina fine powder, 2 parts of silica fine powder and 0.5 part of steel fiber.

[0138] Among them, the pretreated silicon carbide graded particles include:

[0139] 14 parts of silicon carbide sand with a diameter of 3.35 mm to 4.75 mm, 35 parts of silicon carbide sand with a diameter of 1.18 mm to 2.8 mm, 18 parts of silicon carbide sand with a diameter of 0.5 mm to 0.7 mm, and 3 parts of modified sodium-type silica sol. Among them, the silicon carbide sands with different diameters and the modified sodium-type silica sol are uniformly mixed by stirring and then dried to obtain pretreated silicon carbide graded particles.

[0140] (2)Putting in auxiliary materials

[0141] Weigh the following components by weight: 0.5 parts of a compound antioxidant sintering aid (B4C and Al powder, mass ratio 1:1), 0.1 part of a rheological modifier (sodium tripolyphosphate), 0.01 part of a coagulant (lithium carbonate), 0.2 part of an explosion-proof agent (polypropylene fiber), and 4.5 parts of water.

[0142] (3)Mix the main material and the auxiliary materials and place them in a mold for molding to form a green body.

[0143] (4)Brush an anti-oxidation coating with a thickness of approximately 1 mm on the green body. The anti-oxidation coating includes mullite micropowder, andalusite micropowder, and modified sodium-type silica sol, with a weight ratio of 4:1:5. After brushing the anti-oxidation coating, perform medium and low-temperature sintering. Heat from room temperature to 150 °C at a heating rate of 30 °C / h to 40 °C / h. After reaching 150 °C, hold for 5 h, then continue to heat to 650 °C at a heating rate of 30 °C / h to 40 °C / h, hold for 5 h, and naturally cool to room temperature to obtain a silicon carbide ceramic composite material doped with steel fibers.

[0144] Figure 16 Show the EDS spectrum of the composite material of this example, combined with the following EDS spectrum analysis results:

[0145] The chemical composition of the composite material of this example is C 17.62 O 53.06 Al 15.37 Si 11.77 Ca 1.54 Na 0.64 。

[0146] Example 6

[0147] The preparation method of the silicon carbide ceramic composite material of this example includes the following steps (1) to (4).

[0148] (1)Putting in the main material

[0149] Weigh the following components by weight: 57 parts of pretreated silicon carbide graded particles, 10 parts of silicon carbide fine powder with a mesh size of 200, 9 parts of calcium aluminate cement, 8 parts of alumina micropowder, 7 parts of silica micropowder, and 4 parts of steel fibers.

[0150] Among them, the pretreated silicon carbide graded particles include:

[0151] 12 parts of silicon carbide sand with a diameter of 3.35 mm to 4.75 mm, 27 parts of silicon carbide sand with a diameter of 1.18 mm to 2.8 mm, 15 parts of silicon carbide sand with a diameter of 0.5 mm to 0.7 mm, and 3 parts of modified sodium-type silica sol. Among them, the silicon carbide sands with different diameters and the modified sodium-type silica sol are stirred and mixed evenly and then dried to obtain the pretreated silicon carbide graded particles.

[0152] (2) Adding auxiliary materials

[0153] Weigh the following components by weight: 3 parts of compound antioxidant sintering aid (B4C and Al powder, mass ratio 1:1), 0.2 part of rheological modifier (sodium tripolyphosphate), 0.2 part of retarder (citric acid), 0.5 part of explosion-proof agent (polypropylene fiber), and 5 parts of water.

[0154] (3) Mix the main material and the auxiliary materials and place them in a mold for molding to form a green body.

[0155] (4) Brush an anti-oxidation coating with a thickness of approximately 1 mm on the green body. The anti-oxidation coating includes mullite micropowder, andalusite micropowder, and modified sodium-type silica sol, with a weight ratio of 4:1:5. After brushing the anti-oxidation coating, carry out medium and low-temperature sintering. Start heating from room temperature to 150 °C at a heating rate of 30 °C / h to 40 °C / h. After reaching 150 °C, keep it warm for 5 h, then continue to heat to 600 °C at a heating rate of 30 °C / h to 40 °C / h, keep it warm for 5 h, and naturally cool to room temperature to obtain the silicon carbide ceramic composite material doped with steel fibers.

[0156] Figure 17 Show the EDS spectrum of the composite material in this example, combined with the following EDS spectrum analysis results:

[0157] The chemical composition of the composite material in this example is C 8.68 O 57.79 Al 17.85 Si 13.59 Ca 1.60 Na 0.50 .

[0158] Comparative Example 1

[0159] A preparation method of a silicon carbide ceramic composite material, which is different from Example 1 in that: the main material does not contain pretreated silicon carbide graded particles, but only contains silicon carbide particles with a diameter of 1.18 to 2.8 mm in the pretreated silicon carbide graded particles.

[0160] Comparative Example 2

[0161] A preparation method of a silicon carbide ceramic composite material, which is different from Example 1 in that: the compound antioxidant sintering aid does not contain boron carbide, and only contains silicon powder and aluminum oxide, and the mass ratio is 1:1.

[0162] Comparative Example 3

[0163] A preparation method of a silicon carbide ceramic composite material, which is different from Example 1 in that: after the green body is formed, it is directly subjected to medium and low temperature sintering without coating an antioxidant coating on the green body.

[0164] Comparative Example 4

[0165] A preparation method of a silicon carbide ceramic composite material, which is different from Example 1 in that: the green body is first subjected to medium and low temperature sintering, and then an antioxidant coating is brushed and baked at 200°C to 300°C until dry.

[0166] The physical and chemical performance indexes of the silicon carbide ceramic composite materials in Examples 1-6 of the present invention were tested, and the results are shown in Table 2.

[0167] Table 2 Physical and Chemical Performance Indexes

[0168] In Table 2, the tests of various performances simulate their usual use environments. For example, the ceramic material will be subjected to a radiation temperature of 800°C to 1250°C. The detection standard of the wear amount is GB / T18301. When testing the wear amount, the sample starts to be tested for wear after being kept at 900°C for 3 hours. The room temperature flexural strength is tested after the specimen is kept at different temperatures (110°C to 1350°C) for a certain time. For example, 110°C × 24h means that the specimen is kept at 110°C for 24h.

[0169] It can be seen from Table 2 that the physical and chemical performance indexes of the silicon carbide ceramic composite materials in the examples of the present invention meet the requirements of the industry standard. Among them, the wear amount of the silicon carbide ceramic composite material is increased from the original ≤8 cm 3 to ≤5 cm 3 ; the flexural strength is increased from the original ≥8 MPa to ≥25 MPa; at 20°C - 750°C, its average thermal expansion coefficient is increased from the original 0.47% to 0.4%. And the above physical and chemical performance indexes of the composite materials in Comparative Examples 1-4 are all inferior to those of the examples. Thus, it can be seen that the above performances of the silicon carbide ceramic composite material sintered at medium and low temperatures in the present invention have been greatly and comprehensively improved.

[0170] It should be understood that the present invention is not limited in its application to the detailed construction and arrangement of components set forth in this specification. The present invention is capable of other embodiments and of being practiced and carried out in various ways. The foregoing variations and modifications fall within the scope of the present invention. It should be understood that the invention as disclosed and defined in this specification extends to all alternative combinations of two or more separate features mentioned or evident in the text and / or drawings. All such different combinations constitute various alternative aspects of the present invention. The embodiments described in this specification illustrate the best mode known for practicing the invention and will enable those skilled in the art to utilize the invention.

Claims

1. A silicon carbide ceramic composite material with high thermal shock resistance for medium and low temperature sintering, characterized in that, Its chemical composition includes C a O b Al c Si d Ca e Na f , where a, b, c, d, e, f are the atomic contents of the corresponding elements, 8.68 ≤ a ≤ 23.81, 45.30 ≤ b ≤ 57.79, 9.83 ≤ c ≤ 17.85, 13.20 ≤ d ≤ 20.29, 0.77 ≤ e ≤ 2.03, 0 ≤ f ≤ 0.64; the composite material has a porous structure and contains nanoscale particles. In the infrared spectrum, the shoulder peak at 1166 cm -1 shows the stretching vibration of Si-O, and the strongest peak at 1091 cm -1 shows the stretching vibration of the Si(Al)-O bond. The second-strongest peak at 820 - 824 cm -1 shows the symmetric stretching vibration of Si-O-Si, and the peak at 781 cm -1 shows the stretching vibration of the Si-Si bond.

2. The composite material according to claim 1, wherein, The nanoscale particles are lamellar particles with a size of 200 nm to 500 nm.

3. The composite material according to claim 1 or 2, characterized in that, The radial size of the pore structure is 1 μm to 10 μm.

4. The composite material according to claim 1 or 2, characterized in that, The composite material has a crystal structure.

5. The composite material according to claim 1 or 2, characterized in that, In the infrared spectrum, the peaks in the range of 480 - 650 cm -1 show the bending vibration mode of Si - O.

6. A method for preparing a silicon carbide ceramic composite material with high thermal shock resistance by medium and low temperature sintering as described in any one of claims 1 to 5, characterized in that, Including: Feeding the main materials: obtaining 55 - 75 parts by weight of pre-treated silicon carbide graded particles, 10 - 12 parts by weight of silicon carbide fine powder with a mesh size of 200 - 300, 2 - 10 parts by weight of calcium aluminate cement, 2 - 10 parts by weight of alumina fine powder, 2 - 10 parts by weight of silica fine powder, and 0.5 - 5 parts by weight of reinforcing material; wherein, the pre-treated silicon carbide graded particles contain silicon carbide sands with different particle sizes. Feeding the auxiliary materials: obtaining 0.5 - 3 parts by weight of a compound antioxidant sintering aid and 3 - 5 parts by weight of water, and the compound antioxidant sintering aid includes boron carbide powder. Mix the main materials and the auxiliary materials, and pour them into a mold to form a green body. Brush an anti-oxidation coating on the surface of the green body, and perform medium and low-temperature sintering, and the temperature of the medium and low-temperature sintering is not higher than 750 °C.

7. The method according to claim 6, characterized in that, Before feeding the main materials, the method further includes preparing the pre-treated silicon carbide graded particles, including: Obtaining 12 - 15 parts by weight of silicon carbide sand with a diameter of 3.35 mm - 4.75 mm, 27 - 35 parts by weight of silicon carbide sand with a diameter of 1.18 mm - 2.8 mm, 15 - 22 parts by weight of silicon carbide sand with a diameter of 0.5 mm - 0.7 mm, and 1 - 3 parts by weight of modified sodium-type silica sol, and mixing them, then stirring and drying to obtain the pre-treated silicon carbide graded particles.

8. The method according to claim 6 or 7, characterized in that Performing medium and low-temperature sintering on the green body brushed with the anti-oxidation coating, including: Heating the green body from room temperature to a first preset temperature, and holding for 4 - 6 h at the first preset temperature, then heating to a second preset temperature, and holding for 4 - 6 h at the second preset temperature, and naturally cooling to room temperature.

9. According to the method described in claim 8, wherein The first preset temperature is 130 °C - 160 °C, and the heating rate from room temperature to the first preset temperature is 30 °C / h - 40 °C / h; The second preset temperature is 650 °C - 750 °C, and the heating rate from the first preset temperature to the second preset temperature is 30 °C / h - 40 °C / h.

10. Application of the silicon carbide ceramic composite material according to any one of claims 1 to 5 and the silicon carbide ceramic composite material prepared by the method according to any one of claims 6 to 9 in a burner.

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