Monoclinic strontium feldspar-SiC composite ceramic material and preparation method thereof

Abstract

The invention provides a monoclinic strontium feldspar-SiC composite ceramic material and a preparation method thereof, and belongs to the technical field of heat storage ceramic materials.The preparation method comprises the following steps that SiC, strontium carbonate, aluminum oxide, silicon dioxide and sodium carbonate are ball-milled and mixed to be uniform, and mixed powder is obtained; uniformly mixing the mixed powder with an adhesive, and performing compression molding to obtain a green body; and sintering the green body to obtain the hexagonal strontium feldspar-SiC composite ceramic. The sintering temperature is 1600-1650 DEG C, and the sintering time is 2-5 hours; the hexagonal strontium feldspar-SiC composite ceramic is subjected to heat preservation at the temperature of 1100-1300 DEG C for 6-12 h, and the monoclinic strontium feldspar-SiC composite ceramic is obtained. According to the present invention, the in-situ synthesized monoclinic strontium feldspar with characteristics of high melting point, high crystallization ability, good thermal stability and low thermal expansion coefficient is combined with SiC to develop the SiC heat storage composite ceramic, and the SiC heat storage composite ceramic has advantages of compact matrix, high heat storage density and good oxidation resistance, and can meet the energy storage requirement of the new generation heat storage system.

Description

Technical Field

[0001] The present invention relates to the technical field of heat storage ceramic materials, and in particular to a monoclinic strontium feldspar-SiC composite ceramic material and a preparation method thereof. Background Art

[0002] Solar high-temperature thermal power generation technology is a power generation technology that converts solar energy into high-temperature thermal energy and then converts it into electrical energy. This technology system covers multiple links such as concentrating and collecting solar energy, heat storage, and power generation. Among them, the heat storage system plays a core role. It can convert unstable solar energy into stably storable energy to cope with the volatility and intermittency of solar energy. To ensure that the heat storage system can operate long-term, efficiently and stably under high temperature conditions, the required heat storage materials must have a high heat storage density and exhibit excellent oxidation resistance. These properties together ensure that the heat storage material can maintain its performance in a continuous high-temperature environment and meet the strict requirements of solar thermal power generation systems for reliability and efficiency.

[0003] SiC ceramics, with their excellent high-temperature strength, wear resistance, low thermal expansion coefficient, high hardness, thermal shock resistance, chemical corrosion resistance, and high thermal conductivity, have become a research hotspot in the field of high-temperature solar thermal utilization. The Chinese invention patent, "High Thermal Conductivity Andalusite / SiC Composite Thermal Storage Ceramics and Preparation Methods Thereof" (CN106045486A), uses andalusite, bauxite, kaolin, talc, and SiC as raw materials. After ball milling, granulation, and aging, they are pressed into a blank. The blank is then wrapped with graphite powder and fired at 1540°C to produce the andalusite / SiC composite thermal storage ceramic. The volume density of this composite phase change thermal storage material is 2.47 g·cm -2 , thermal conductivity is 4.60W(m·K) -1 , flexural strength is 36.46MP, heat storage density is 900J·g -1 The Chinese invention patent "Solar Thermal Power Generation Heat Absorption / Storage Integrated Corundum / SiC Ceramic Material and Preparation Method thereof" (CN111253158A) uses SiC, corundum, kaolin, and borax as raw materials to prepare a solar thermal power generation heat absorption / storage integrated corundum / SiC ceramic material at 1400-1480°C. Tests show that the flexural strength of the integrated absorption and storage material is 76.03 MPa and the volume density is 2.35 g·cm -3 , the absorption rate is 91.47%, and the room temperature thermal conductivity is 3.39W(m·K) -1 ~7.65W(m·K) -1 After oxidation at 1000℃ for 100h, the oxidation weight gain rate is as high as 12.46mg·cm -3The Chinese invention patent "A densified mullite-corundum-SiC composite heat storage ceramic material for solar thermal power generation and its preparation method" (CN111269015B) uses a SiC mixed powder formed by mixing two particle sizes and adding highly active calcined bauxite. After calcination at 1520°C, mullite and corundum are introduced as the two binding phases. The bulk density of this heat storage material is 2.30g·cm -3 , flexural strength is 77.05MPa, heat storage density is 996J·g -1 .

[0004] The above patent, as a SiC heat absorption / storage material, has difficulty in achieving densification and firing of SiC composite ceramics, resulting in problems such as low heat storage density and poor oxidation resistance, and cannot meet the demand for high-performance heat storage systems in practical applications. Summary of the Invention

[0005] In view of the technical problems existing in the background technology, the present application provides a monoclinic strontium feldspar-SiC composite ceramic material and a preparation method thereof, aiming to solve the technical problem that existing SiC heat absorption / storage materials are difficult to achieve densification sintering of SiC composite ceramics, resulting in low heat storage density and poor oxidation resistance.

[0006] In a first aspect, an embodiment of the present application provides a method for preparing a monoclinic strontium feldspar-SiC composite ceramic material, comprising the following steps: The SiC, strontium carbonate, aluminum oxide, silicon dioxide and sodium carbonate are mixed uniformly by ball milling to obtain a mixed powder; The mixed powder and the binder are mixed evenly, and pressed into shape to obtain a green body; The green body is sintered to obtain hexagonal strontium feldspar-SiC composite ceramics; the sintering temperature is 1600-1650°C and the sintering time is 2-5 hours; The hexagonal strontium feldspar-SiC composite ceramics are kept at a temperature of 1100-1300° C. for 6-12 hours to obtain monoclinic strontium feldspar-SiC composite ceramics.

[0007] In the technical solution of the embodiment of the present application, the present invention first sintered the raw materials at a high temperature of 1600~1650℃, and sodium carbonate can reduce the high-temperature liquid phase viscosity and promote densification; during the sintering process, strontium carbonate, aluminum oxide and silicon dioxide synthesize strontium feldspar through a liquid phase crystallization mechanism, and strontium feldspar melts into a liquid phase at high temperature, which can promote the rearrangement of SiC particles of different particle sizes, thereby promoting the densification of strontium feldspar-SiC composite ceramics; on the other hand, microcrystals are more easily precipitated in the SrO-Al2O3-SiO2 ternary system, and strontium feldspar is filled between the SiC particles in the form of liquid phase, and a large number of microcrystals are precipitated during the cooling process, and the microcrystals gradually grow, connect the SiC particles, and discharge pores to form dense strontium feldspar-SiC composite ceramics, thereby obtaining hexagonal strontium feldspar-SiC composite ceramics with higher heat storage density.

[0008] However, the expansion coefficient of hexagonal strontium feldspar does not match that of SiC. The present invention transforms the hexagonal strontium feldspar into monoclinic strontium feldspar by keeping it at 1100-1300°C for 6-12 hours, thereby obtaining a more stable monoclinic strontium feldspar-SiC composite ceramic.

[0009] The monoclinic strontium feldspar-SiC composite ceramic material prepared by the present invention exhibits good oxidation resistance in high-temperature environments. The main reasons are: first, monoclinic strontium feldspar has a high crystallization ability, and it is difficult for oxygen to diffuse further into the material through the intercrystalline phase of the crystallized strontium feldspar; second, the monoclinic strontium feldspar microcrystals promote the density of the monoclinic strontium feldspar-SiC composite ceramic, and the material has fewer pores, making it difficult for oxygen to diffuse further; third, monoclinic strontium feldspar has good high-temperature stability and a low thermal expansion coefficient (2.5×10 −6 / ℃), and its lower thermal expansion coefficient is comparable to SiC (4×10 −6 / °C), is less susceptible to volume expansion and cracking at high temperatures, making it difficult for oxygen to diffuse into the material. The oxidation resistance of this monoclinic strontium feldspar-SiC composite ceramic ensures long-term stability at high temperatures, meeting the demand for long-term usability of thermal storage materials in next-generation solar thermal power generation technology. This material ensures the efficient and stable operation of solar thermal power generation systems, making it an ideal material choice for thermal storage systems.

[0010] In some embodiments, the particle sizes of SiC include 150 μm, 45 μm, and 5 μm, and the mass ratio thereof is (1-3):(5-8):(1-2).

[0011] In some embodiments, the particle size of strontium carbonate is 0.3-0.5 μm.

[0012] In some embodiments, the raw materials include, by mass, 52-57 parts of SiC, 17-19 parts of strontium carbonate, 12-13 parts of aluminum oxide, 14-16 parts of silicon dioxide, and 0.8-1.5 parts of sodium carbonate.

[0013] In some embodiments, the aluminum oxide particle size is 0.5 to 5 μm; And / or, the silica particle size is 0.5 to 5 μm.

[0014] In some embodiments, before sintering, the green body is buried in a sagger filled with graphite powder and coke powder, and then placed in a muffle furnace for sintering.

[0015] In some embodiments, the sintering process includes the following steps: Heat from room temperature to 1000℃ at a rate of 5~8℃ / min, and keep warm for 30min every time the temperature rises by 200℃; Heat from 1000℃ to 1600~1650℃ at a rate of 3~5℃ / min, and keep warm for 60min every time the temperature rises by 100℃; Keep at 1600~1650℃ for 3h; The temperature was cooled from 1600~1650℃ to 1100~1300℃ at a cooling rate of 5~8℃ / min.

[0016] In some embodiments, the binder is 5 wt % polyvinyl alcohol, and the binder accounts for 3-5 wt % of the mixed powder.

[0017] In some embodiments, during the press molding process, single-press pressing is used, and the single-press pressure is 50-80 MPa.

[0018] In a second aspect, an embodiment of the present application provides a monoclinic strontium feldspar-SiC composite ceramic material, which is prepared using the above method.

[0019] Different from the existing technical solutions, the beneficial effects of this application include: 1. The present invention provides a preparation method for synthesizing monoclinic strontium feldspar-SiC composite ceramics using strontium feldspar as a sintering aid. By in-situ synthesizing monoclinic strontium feldspar with a high melting point, high crystallization ability, good thermal stability, and low thermal expansion coefficient and combining it with SiC, a SiC thermal storage composite ceramic is developed. Its matrix is denser, the thermal storage density is higher, and the oxidation resistance is better, which can meet the energy storage requirements of the new generation of thermal storage systems.

[0020] 2. The strontium feldspar-SiC composite ceramics prepared by the present invention have a heat storage density of 1075-1114 kJ / kg in the temperature range of 0-1000°C, and the oxidation weight gain rate after oxidation at 1100°C for 100h is less than 4.85 mg·cm -2 In addition, the bulk density is 2.9 to 3.05 g / cm 3 , porosity is 0.9% to 2.1%, water absorption is 0.3% to 0.7%, flexural strength is 125 to 155 MPa, thermal conductivity is 13.75% to 15.87 W·(m·K) -1 , there is no cracking after 30 thermal shock cycles from 1100℃ to room temperature.

[0021] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To more clearly illustrate the technical solution of this application, the following is a brief introduction to the drawings used in this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0023] Figure 1 This is the SEM image of the monoclinic strontium feldspar-SiC composite ceramic material prepared in Example 1 of the present application, wherein Figure 1 (a) is the cross-sectional SEM image of monoclinic strontium feldspar-SiC composite ceramic material; Figure 1 (b) is the SEM image of the cross section of the monoclinic strontium feldspar-SiC composite ceramic material after HF corrosion.

[0024] Figure 2 This is the XRD spectrum of the monoclinic strontium feldspar-SiC composite ceramic material prepared in Example 1 of the present application.

[0025] Figure 3 This is the XRD spectrum of the monoclinic strontium feldspar-SiC composite ceramic material prepared in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0026] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0028] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0029] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0030] 1. Preparation method Example 1 A method for preparing a monoclinic strontium feldspar-SiC thermal storage ceramic material, the preparation comprising the following steps: (1) Raw material preparation: 57 wt% SiC of different particle sizes, where the particle size ratio is 150 μm:45 μm:5 μm (1:8:1), 12 wt% alumina, 17 wt% strontium carbonate, 14 wt% silicon dioxide, and 0.8 wt% sodium carbonate, are mixed by ball milling for 1 h, where the ball-to-material mass ratio is 2:1, to obtain a mixed powder; (2) Granulation and aging: 5% by weight of PVA was added to the mixed powder by spray drying method for granulation, and then aged for more than 12 hours to obtain the blank; (3) Green body forming: The aged green body is pressed with a pressure of 50 kN using a tablet press to obtain a strontium feldspar-SiC green body; (4) Burying powder: bury the green body in a mixture of graphite and coke powder, with the mass ratio of graphite to coke being 1:1.

[0031] (5) Firing of green bodies: Place the powder-filled sagger in a muffle furnace for calcination, raising the temperature from room temperature to 1650°C at a rate of 5°C / min; maintain the highest temperature for 3 hours; and then cool down to 1200°C at a rate of 5°C / min. When the temperature is less than 1000°C, maintain the temperature for 30 minutes at each 200°C interval; when the temperature is ≥1000°C, maintain the temperature for 60 minutes at each 100°C interval.

[0032] (6) Secondary insulation process: insulation time at 1200℃ is 6h.

[0033] Example 2 A method for preparing a monoclinic strontium feldspar-SiC thermal storage ceramic material, the preparation comprising the following steps: (1) Raw material preparation: 52 wt% SiC of different particle sizes, where the particle size ratio is 3:5:2 (150 μm:45 μm:5 μm), 13 wt% alumina, 19 wt% strontium carbonate, 16 wt% silicon dioxide, and 0.8 wt% sodium carbonate, are mixed by ball milling for 1 h, where the ball-to-material mass ratio is 2:1, to obtain a mixed powder; (2) Granulation and aging: 5% by weight of PVA was added to the mixed powder by spray drying method for granulation, and then aged for more than 12 hours to obtain the blank; (3) Green body forming: The aged green body is pressed with a pressure of 50 kN using a tablet press to obtain a strontium feldspar-SiC green body; (4) Burying powder: bury the green body in a mixture of graphite and coke powder, with the mass ratio of graphite to coke being 1:1.

[0034] (5) Firing of green bodies: Place the powder-filled sagger in a muffle furnace for calcination, raising the temperature from room temperature to 1650°C at a rate of 5°C / min; maintain the highest temperature for 3 hours; and then cool down to 1200°C at a rate of 5°C / min. When the temperature is less than 1000°C, maintain the temperature for 30 minutes at each 200°C interval; when the temperature is ≥1000°C, maintain the temperature for 60 minutes at each 100°C interval.

[0035] (6) Secondary insulation process: insulation time at 1200℃ is 6h.

[0036] Example 3 A method for preparing a monoclinic strontium feldspar-SiC thermal storage ceramic material, the preparation comprising the following steps: (1) Raw material preparation: 57 wt% SiC of different particle sizes, where the particle size ratio is 150 μm: 45 μm: 5 μm (2:7:1), 12 wt% alumina, 17 wt% strontium carbonate, 14 wt% silicon dioxide, and 0.8 wt% sodium carbonate, are mixed by ball milling for 1 h, where the ball-to-material mass ratio is 2:1, to obtain a mixed powder; (2) Granulation and aging: 5% by weight of PVA was added to the mixed powder by spray drying method for granulation, and then aged for more than 12 hours to obtain the blank; (3) Green body forming: The aged green body is pressed with a pressure of 50 kN using a tablet press to obtain a strontium feldspar-SiC green body; (4) Burying powder: bury the green body in a mixture of graphite and coke powder, with the mass ratio of graphite to coke being 1:1.

[0037] (5) Firing of green bodies: Place the powder-filled sagger in a muffle furnace for calcination, raising the temperature from room temperature to 1600°C at a rate of 5°C / min; maintain the highest temperature for 3 hours; and then cool down to 1200°C at a rate of 5°C / min. When the temperature is less than 1000°C, maintain the temperature for 30 minutes at each 200°C interval; when the temperature is ≥1000°C, maintain the temperature for 60 minutes at each 100°C interval.

[0038] (6) Secondary insulation process: insulation time at 1200℃ is 6h.

[0039] Example 4 A method for preparing a monoclinic strontium feldspar-SiC thermal storage ceramic material, the preparation comprising the following steps: (1) Raw material preparation: 57 wt% SiC of different particle sizes, where the particle size ratio is 150 μm:45 μm:5 μm (2:7:1), 12 wt% alumina, 17 wt% strontium carbonate, 14 wt% silicon dioxide, and 1.5 wt% sodium carbonate, are mixed by ball milling for 1 h, where the ball-to-material mass ratio is 2:1, to obtain a mixed powder; (2) Granulation and aging: 5% by weight of PVA was added to the mixed powder by spray drying method for granulation, and then aged for more than 12 hours to obtain the blank; (3) Green body forming: The aged green body is pressed with a pressure of 50 kN using a tablet press to obtain a strontium feldspar-SiC green body; (4) Burying powder: bury the green body in a mixture of graphite and coke powder, with the mass ratio of graphite to coke being 1:1.

[0040] (5) Firing of green bodies: Place the powder-filled sagger in a muffle furnace for calcination, raising the temperature from room temperature to 1650°C at a rate of 5°C / min; maintain the highest temperature for 3 hours; and then cool down to 1200°C at a rate of 5°C / min. When the temperature is less than 1000°C, maintain the temperature for 30 minutes at each 200°C interval; when the temperature is ≥1000°C, maintain the temperature for 60 minutes at each 100°C interval.

[0041] (6) Secondary insulation process: insulation time at 1200℃ is 6h.

[0042] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the secondary insulation process in step (6) is not performed, and the other steps are the same as those in Example 1.

[0043] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the temperature of sintering the strontium feldspar-SiC composite ceramic in step (5) is lower, and the other steps are the same as those in Example 1. The sintering process includes the following steps: (5) Green body firing: Place the powder-filled sagger in a muffle furnace for calcination, raising the temperature from room temperature to 1550°C at a rate of 5°C / min; maintain the highest temperature for 3 hours; and then cool down to 1200°C at a rate of 5°C / min. When the temperature is less than 1000°C, maintain the temperature for 30 minutes at each 200°C interval; when the temperature is ≥1000°C, maintain the temperature for 60 minutes at each 100°C interval.

[0044] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the amount of sodium carbonate added is higher, and the other steps are the same as Example 1. The raw materials include 57wt% SiC of different particle sizes, wherein the particle size ratio is 150μm:45μm:5μm, which is 2:7:1, 12wt% alumina, 17wt% strontium carbonate, 14wt% silicon dioxide, and 2.0wt% sodium carbonate.

[0045] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the amount of sodium carbonate added is lower, and the other steps are the same as Example 1. The raw materials include 57wt% SiC of different particle sizes, wherein the particle size ratio is 150μm:45μm:5μm, which is 2:7:1, 12wt% alumina, 17wt% strontium carbonate, 14wt% silicon dioxide, and 0.5wt% sodium carbonate.

[0046] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the amount of strontium feldspar added is lower, and the other steps are the same as Example 1. The raw materials include 62wt% SiC of different particle sizes, wherein the particle size ratio is 150μm:45μm:5μm, which is 2:7:1, 11wt% alumina, 15wt% strontium carbonate, 12wt% silica, and 0.8wt% sodium carbonate.

[0047] Comparative Example 6 The difference between Comparative Example 5 and Example 1 is that the amount of strontium feldspar added is higher, and the other steps are the same as Example 1. The raw materials include 45wt% SiC of different particle sizes, wherein the particle size ratio is 150μm:45μm:5μm, which is 2:7:1, 15.6wt% alumina, 22wt% strontium carbonate, 17.4wt% silica, and 0.8wt% sodium carbonate.

[0048] 2. Test Method 1. Heat storage density test method: The thermophysical properties and specific heat capacity of the samples were tested using a differential scanning calorimeter (Q20) manufactured by TA Corporation of the United States. For solid sensible heat storage materials, the heat storage density per unit mass is calculated as shown in the equation; ; where T0 and Ts are the starting heating temperature and the final specified temperature, respectively, and Css is the specific heat capacity of the solid heat storage material.

[0049] 2. Oxidation weight gain rate test method: The main steps of the antioxidant test are as follows: (a) weigh the sample before oxidation and measure its surface area; (b) place the sample in a silicon carbon rod furnace at 5 ℃·min -1 The temperature was raised to 1000 °C at a rate of 10 °C·min -1(c) Remove the sample, cool it to room temperature, and weigh it. (d) Repeat the above steps until the oxidation time reaches 100 h. The oxidation weight gain rate is calculated according to the following formula: ∆W = (m-m0) / S; Where: ΔW-oxidation weight gain rate, mg·cm -2 ; m-mass of sample after oxidation experiment, mg; m0-mass of sample before oxidation, mg; S-surface area of sample, cm 2 .

[0050] 3. Bulk density test method: Based on the Archimedes principle and static weighing method, the bulk density (D / g·cm -3 ).

[0051] 4. Porosity detection method: According to the Archimedes principle and the static weighing method, the apparent porosity (Pa / %) of the fired sample was measured using a TXT digital ceramic water absorption meter produced by Xiangtan Xiangyi Instrument Co., Ltd.

[0052] 5. Water absorption test method: Based on the Archimedes principle and the static weighing method, the water absorption (Wa / %) of the fired sample was measured using a TXT digital display ceramic water absorption tester produced by Xiangtan Xiangyi Instrument Co., Ltd.

[0053] 6. Flexural strength test method: The flexural strength of the fired samples was measured using an RGM-4100 microcomputer-controlled electronic universal testing machine manufactured by Shenzhen Ruige Company.

[0054] 7. Thermal conductivity testing method: The thermal conductivity of the sample was tested using a laser thermal conductivity meter manufactured by NETZSCH, Germany.

[0055] 8. Thermal shock cycle test method: The SX-2-5-12 box-type energy-saving resistance furnace produced by Hubei Yingshan Jianli Electric Furnace Manufacturing Co., Ltd. is used to conduct thermal shock resistance test on the samples. The thermal shock test process is as follows: the fired samples are placed in the thermal shock furnace and heated at 5℃·min -1 The temperature was raised to 1000°C at a rate of 1000°C, kept at that temperature for 15 minutes, and then cooled to room temperature. This was considered one thermal shock process. After multiple cycles of thermal shock, the flexural strength of the sample was tested, and the strength loss rate was used to characterize the thermal shock resistance of the sample.

[0056] 3. Analysis of test results of various embodiments and comparative examples (1) Take the samples sintered in Example 1 and perform XRD test (see Figure 1 ), SEM test of composite ceramic cross section (see Figure 2XRD testing revealed that the strontium feldspar in the strontium feldspar-SiC composite ceramics obtained using the secondary heat preservation process is a monoclinic phase, and cross-sectional SEM analysis clearly shows that the composite ceramics have become densified. Densified SiC composite ceramics have a high heat storage density, and the dense sample can prevent oxygen from entering the matrix, giving the strontium feldspar-SiC ceramics a high antioxidant capacity.

[0057] Take the sample sintered in Comparative Example 1 and carry out XRD test (see Figure 3 ), XRD testing revealed that the strontium feldspar in the strontium feldspar-SiC composite ceramics obtained without the secondary thermal insulation process was a hexagonal phase. The thermal expansion coefficient of hexagonal strontium feldspar was large, and its matching degree with the thermal expansion coefficient of SiC was low, which was not conducive to the thermal shock resistance of the sample as a whole.

[0058] (2) The performance of the strontium feldspar-SiC composite ceramic materials prepared in each embodiment and comparative example was tested. The test results are shown in Table 1 below.

[0059] Table 1 Performance test results of strontium feldspar-SiC composite ceramic materials prepared in various examples and comparative examples

[0060] As can be seen from Table 1, the monoclinic strontium feldspar-SiC composite ceramic materials prepared in Examples 1-4 have a dense matrix, high thermal storage density, and excellent oxidation resistance. Comparative Example 1 lacks secondary heat preservation, resulting in a high thermal expansion coefficient of the hexagonal strontium feldspar in the resulting ceramic material, poorly matching the thermal expansion coefficient of the SiC, which is detrimental to the overall thermal shock resistance of the sample. In Comparative Example 2, the sintering temperature is low, resulting in a high porosity in the resulting ceramic material, which reduces the thermal storage density. In Comparative Example 3, the excessive addition of sodium carbonate results in an excessively low liquid phase viscosity, resulting in a large number of closed pores within the sample. This reduces the bulk density, thermal storage density, and thermal conductivity. In Comparative Example 4, the low sodium carbonate content results in a high high-temperature liquid phase viscosity, making it difficult to completely fill the pores, resulting in difficulty in densification. This also reduces the thermal storage density and thermal conductivity. In Comparative Example 5, the low addition of strontium feldspar results in a small amount of high-temperature liquid phase, making it difficult to completely fill the pores. This makes densification difficult, resulting in a decrease in both the thermal storage density and thermal conductivity. In Comparative Example 6, when the addition amount of strontium feldspar is high, densification can be achieved, but the thermal conductivity of strontium feldspar itself is low, so the overall thermal conductivity of the composite ceramic decreases.

[0061] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a monoclinic strontium feldspar-SiC composite ceramic material, characterized in that: The steps include: The SiC, strontium carbonate, aluminum oxide, silicon dioxide and sodium carbonate are mixed uniformly by ball milling to obtain a mixed powder; The mixed powder and the binder are mixed evenly, and pressed into shape to obtain a green compact; Sintering the green body to obtain hexagonal strontium feldspar-SiC composite ceramics; the sintering temperature is 1600-1650° C., and the sintering time is 2-5 hours; The hexagonal strontium feldspar-SiC composite ceramic is kept at a temperature of 1100-1300° C. for 6-12 hours to obtain the monoclinic strontium feldspar-SiC composite ceramic.

2. The method for preparing a monoclinic strontium feldspar-SiC composite ceramic material according to claim 1, wherein: The particle sizes of the SiC include 150 μm, 45 μm and 5 μm, and the mass ratio thereof is (1-3):(5-8):(1-2).

3. The method for preparing a monoclinic strontium feldspar-SiC composite ceramic material according to claim 1, wherein: Calculated by mass, the raw materials include 52-57 parts of SiC, 17-19 parts of strontium carbonate, 12-13 parts of aluminum oxide, 14-16 parts of silicon dioxide and 0.8-1.5 parts of sodium carbonate.

4. The method for preparing a monoclinic strontium feldspar-SiC composite ceramic material according to claim 1, wherein: The particle size of the strontium carbonate is 0.3-0.5 μm.

5. The method for preparing a monoclinic strontium feldspar-SiC composite ceramic material according to claim 1, wherein: The alumina particle size is 0.5-5 μm; And / or, the silica particle size is 0.5-5 μm.

6. The method for preparing a monoclinic strontium feldspar-SiC composite ceramic material according to claim 1, wherein: Before sintering, the green compact is buried in a sagger filled with graphite powder and coke powder, and then placed in a muffle furnace for sintering.

7. The method for preparing a monoclinic strontium feldspar-SiC composite ceramic material according to claim 1, wherein: The sintering process comprises the following steps: Heat from room temperature to 1000℃ at a rate of 5~8℃ / min, and keep warm for 30min every time the temperature rises by 200℃; Heat from 1000℃ to 1600~1650℃ at a rate of 3~5℃ / min, and keep warm for 60min every time the temperature rises by 100℃; Keep at 1600~1650℃ for 3h; The temperature was cooled from 1600~1650℃ to 1100~1300℃ at a cooling rate of 5~8℃ / min.

8. The method for preparing a monoclinic strontium feldspar-SiC composite ceramic material according to claim 1, wherein: The adhesive is 5 wt% polyvinyl alcohol, and the adhesive accounts for 3-5 wt% of the mass of the mixed powder.

9. The method for preparing a monoclinic strontium feldspar-SiC composite ceramic material according to claim 1, wherein: During the compression molding process, single-press compression molding is adopted, and the single-press pressure is 50-80 MPa.

10. A monoclinic strontium feldspar-SiC composite ceramic material, characterized in that: The method is as described in any one of claims 1 to 9.

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