SiC-TiC composite ceramic for solar thermal power generation and normal-pressure sintering preparation method of SiC-TiC composite ceramic

Abstract

The invention discloses a normal-pressure sintering preparation method of SiC-TiC composite ceramic for solar thermal power generation, which is specifically implemented according to the following steps: step 1) firstly mixing SiC powder and TiC powder, and then adding Y2O3 powder into the mixed powder to obtain raw material powder; 2) mixing the raw material powder with ethanol to prepare slurry, performing ball milling on the slurry, and adding an ethanol solution containing PVA in the ball milling process; 3) drying the ball-milled slurry, sieving by using a sieve, then cold-pressing the sieved powder into a green body, and finally drying the green body; (4) embedding the green body dried in the step (3) by using graphite powder; 5) sintering the green body which is obtained in the step 4) and embedded with the graphite powder, and introducing argon in the sintering process for atmosphere protection.The method solves the problem that the preparation cost of an existing SiC composite ceramic high-temperature heat-absorbing material for solar thermal power generation is high, and further discloses the SiC-TiC composite ceramic for solar thermal power generation.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite ceramic preparation, and particularly relates to SiC-TiC composite ceramics for solar thermal power generation, and also relates to a method for preparing SiC-TiC composite ceramics by atmospheric pressure sintering for solar thermal power generation. Background Art

[0002] The increasing depletion of traditional fossil energy has prompted countries around the world to compete in developing renewable energy to replace traditional energy. Solar energy has received extensive attention due to its advantages such as wide distribution, rich reserves, and environmental friendliness. Solar thermal power generation technology is an effective method to solve the problem of energy shortage. Compared with other solar thermal power generation systems, the tower thermal power generation system has a higher concentration ratio and power generation efficiency, and has a broader research space. In the tower solar thermal power generation system, the absorber is a device that converts solar radiant energy into heat energy. The higher the outlet temperature and heat transfer efficiency of the absorber, the higher the "light-thermal-electric" conversion efficiency of the power generation system. The gradual increase in the outlet temperature of the absorber (>1000 °C) poses increasingly stringent requirements on the high-temperature resistance performance of the internal heat-absorbing material. Therefore, preparing a solar high-temperature heat-absorbing material with high thermal conductivity, good high-temperature mechanical properties, oxidation / thermal shock resistance, and light absorption performance is one of the key issues to improve the working efficiency of the tower solar thermal power generation system. Traditional metal materials are prone to material melting or softening damage under high-temperature hot air conditions, so their working temperature is limited. Oxide ceramics do not have a softening problem under high-temperature air conditions, but their thermal conductivity is low and their color is relatively white. When used as an absorber, a coating needs to be coated on its surface, and the coating is prone to cracking with the substrate during high-temperature use, so its use is also limited. Non-oxide ceramics such as carbides and borides have characteristics such as high melting point, high thermal conductivity, black color, good high-temperature stability, and inherent spectral selective absorption performance. As a very promising solar high-temperature heat-absorbing material, they have received more and more attention.

[0003] SiC ceramics have high melting points, high thermal conductivity, and excellent oxidation / thermal shock resistance, making them a highly promising high-temperature solar heat-absorbing material. Compared with other carbide and boride ceramics, the spectral absorptivity of SiC still has room for improvement. SiC belongs to a high-emissivity material, losing more heat when used at high temperatures, resulting in low photothermal conversion efficiency. To promote the application of SiC ceramics as high-temperature heat-absorbing ceramics, it is necessary to further improve their solar spectral absorptivity. Relevant literature studies have shown that by doping a second phase (such as TiC, ZrC, HfB2, etc.) into SiC ceramics to prepare SiC composite ceramics, the solar spectral absorptivity can be effectively increased and the emissivity can be reduced, thereby improving their solar photothermal conversion efficiency. Helene Arena et al. prepared SiC-TiC nanocomposite ceramics by plasma sintering in the article "Effect of TiC incorporation on the optical properties and oxidation resistance of SiC ceramics". By adjusting the ratio of SiC and TiC, the absorptivity of this composite ceramic in the solar spectral wavelength range of 0.25 - 25 μm can reach up to 84%, and the spectral selectivity is also higher than that of pure SiC samples, with good oxidation resistance and potential for application in solar absorbers. Sani et al. prepared carbon fiber-reinforced zirconium diboride (ZrB2) ultra-high temperature ceramic matrix composites by pressureless sintering in the article "Optical properties of ZrB2 porous architectures" and found that the solar spectral absorptivity of this composite material is as high as 85%, higher than that of pure ZrB2 and SiC, and has the potential to be used as a heat-absorbing material for high-temperature solar absorbers.

[0004] Currently, the main preparation methods of SiC composite ceramics for solar thermal power generation include self-propagating high-temperature synthesis, plasma sintering, and hot pressing sintering. These preparation methods have the characteristics of high preparation temperature, high energy consumption, high cost, and high requirements for equipment. Summary of the Invention

[0005] The first object of the present invention is to provide an atmospheric pressure sintering preparation method for SiC-TiC composite ceramics for solar thermal power generation, which solves the problem of high preparation cost of high-temperature heat-absorbing materials of SiC composite ceramics for current solar thermal power generation.

[0006] The second object of the present invention is to provide SiC-TiC composite ceramics for solar thermal power generation.

[0007] The first technical solution adopted by the present invention is an atmospheric pressure sintering preparation method for SiC-TiC composite ceramics for solar thermal power generation, which is specifically implemented according to the following steps: Step 1) First, mix SiC powder and TiC powder, and then add Y2O3 powder to the mixed powder to obtain raw material powder; Step 2) Mix the raw material powder obtained in Step 1) with ethanol to form a slurry, and ball-mill the slurry. During the ball-milling process, an ethanol solution containing PVA needs to be added; Step 3) Dry the slurry after ball-milling in Step 2) in a blast drying oven to obtain uniformly mixed raw material powder, sieve it using a sieve mesh, then cold-press the sieved powder into a green body, and finally dry the green body in a blast drying oven; Step 4) Use graphite powder to place the green body dried in Step 3) into a crucible pre-lined with graphite paper, then embed it with graphite powder, and cover the lid; Step 5) Sinter the crucible containing the green body embedded with graphite powder obtained in Step 4). During the sintering process, argon is introduced for atmosphere protection. The features of the present invention also lie in: In Step 1, the mass ratio of SiC to TiC is 3 - 3.5:1, the addition amount of Y2O3 is 5% - 30% of their total mass, the particle size of SiC and TiC is 1μm - 2μm, and the particle size of Y2O3 is 50nm - 100nm.

[0008] The specific process of Step 2 is as follows: Mix the raw material powder obtained in Step 1) with ethanol to form a slurry with a mass percentage concentration of 25% - 30%, then pour the slurry into an alumina ball-milling tank, add alumina balls, where the ball-to-material ratio is 3 - 3.5:1, and the rotation speed is 500r / min - 550r / min; finally, place the ball-milling tank in a planetary ball mill for ball-milling and mixing for 8h - 10h; add an ethanol solution containing PVA 0.5h - 1h before the end of ball-milling.

[0009] In Step 2, the mass percentage concentration of PVA in the added ethanol solution containing PVA is 5% - 7%, and the addition amount is 15% - 20% of the total mass of the powder.

[0010] In Step 3, the aperture of the sieve mesh is 200 mesh - 270 mesh; the drying temperature of the slurry is 100°C - 120°C, and the time is 10h - 15h; the drying temperature of the green body is 100°C - 110°C, and the time is 12h - 15h; the pressure for cold-pressing into a green body is 50kN - 70kN.

[0011] In Step 4, the particle size of the graphite powder is 2μm - 3μm.

[0012] In Step 5, the sintering process is as follows: First, heat up at a rate of 8°C / min to 10°C / min to 800°C to 850°C, keep warm for 0.5 h to 1 h to remove binder, then heat up at a rate of 10°C / min to 12°C / min to 1380°C to 1420°C, heat up at a rate of 1°C / min to 2°C / min to 1580°C to 1620°C, and finally heat up at a rate of 0.5°C / min to 1°C / min to 1620°C to 1680°C and keep warm for 3 h to 5 h; subsequently, cool down at a rate of 3°C / min to 5°C / min to 480°C - 520°C, and then naturally cool down to room temperature.

[0013] In Step 5, during the sintering process, the furnace chamber pressure is maintained between 0.01 MPa and 0.02 MPa.

[0014] The second technical solution adopted in the present invention is that the SiC-TiC composite ceramic for solar thermal power generation is prepared by the above method.

[0015] The beneficial effects of the present invention are as follows: (1) In the method of the present invention, all the powder raw materials are mixed evenly, first cold-pressed into a green body, and then sintered by the embedding method to prevent the green body from deforming during the sintering process.

[0016] (2) The spectral absorptivity of the SiC-TiC composite ceramic prepared by the method of the present invention is related to the content of the sintering aid Y2O3; during the firing process, Y2O3 reacts with the oxide layer on the surface of the SiC raw material to generate Y x SiO y phase, bonding the SiC and TiC raw material particles to form a ceramic skeleton, thereby realizing the sintering behavior of the SiC-TiC composite ceramic at low temperature. If the content of Y2O3 is too small, it cannot effectively promote sintering, and if the content is too large, over-sintering is likely to occur, resulting in a decrease in the porosity of the composite ceramic. The porosity of the composite ceramic is beneficial to increasing the number and path of light reflection, thereby enhancing light trapping and improving spectral absorptivity.

[0017] (3) The method of the present invention uses atmospheric pressure sintering to prepare the SiC-TiC composite ceramic, which has the advantages of low cost, short cycle, low equipment requirements, and easy large-scale production. At the same time, the prepared SiC-TiC composite ceramic has a high spectral absorptivity. It is very necessary to study the atmospheric pressure sintering preparation method and its light absorption performance of the SiC-TiC composite ceramic to promote its application in the field of solar thermal power generation. Description of the Drawings

[0018] Figure 1 is the X-ray diffraction pattern of the SiC-TiC composite ceramic prepared in Example 3 of the present invention; Figure 2It is the low-magnification SEM photograph of the SiC-TiC composite ceramic prepared in Example 3 of the present invention; Figure 3 It is the high-magnification SEM photograph of the SiC-TiC composite ceramic prepared in Example 3 of the present invention; Figure 4 It is Figure 3 the distribution map of Si element in Figure 5 It is Figure 3 the distribution map of Ti element in Figure 6 It is Figure 3 the distribution map of Y element in Figure 7 It is the reflectance spectrum of the SiC-TiC composite ceramic prepared in Example 3 of the present invention in the wavelength range of 0.25 μm to 2.5 μm. Detailed implementation manners

[0019] The present invention will be described in detail below with reference to the accompanying drawings and specific implementation manners.

[0020] The present invention provides a method for preparing SiC-TiC composite ceramic by atmospheric pressure sintering for solar thermal power generation, which is specifically implemented according to the following steps: Step 1): First, mix SiC powder and TiC powder, and then add Y2O3 powder to the mixed powder to obtain raw material powder; In Step 1, the mass ratio of SiC to TiC is 3 to 3.5:1, the addition amount of Y2O3 is 5% to 30% of the total mass of the two, the particle sizes of SiC and TiC are both 1 μm to 2 μm, and the particle size of Y2O3 is 50 nm to 100 nm.

[0021] Step 2): Mix the raw material powder obtained in Step 1) with ethanol to form a slurry, and ball-mill the slurry. During the ball-milling process, an ethanol solution containing PVA needs to be added; The specific process of Step 2 is as follows: Mix the raw material powder obtained in Step 1) with ethanol to form a slurry with a mass percentage concentration of 25% to 30%. Then pour the slurry into an alumina ball-milling tank, add alumina balls, and finally place the ball-milling tank in a planetary ball mill for ball-milling for 8 h to 10 h for mixing; add the ethanol solution containing PVA 0.5 h to 1 h before the end of ball-milling; wherein, the ball-to-material ratio is 3 to 3.5:1, and the rotation speed is 500 r / min - 550 r / min.

[0022] In Step 2, the mass percentage concentration of PVA in the added ethanol solution containing PVA is 5% to 7%, and the addition amount is 15% to 20% of the total mass of the powder.

[0023] Step 3) Dry the slurry after ball milling in step 2) in a forced-air drying oven to obtain a uniformly mixed raw material powder. Sieve it using a sieve mesh, then cold-press the sieved powder into a green body, and finally dry the green body in a forced-air drying oven. In step 3, the aperture of the sieve mesh is 200 mesh to 270 mesh; the drying temperature of the slurry is 100°C to 120°C, and the time is 10 h to 15 h; the drying temperature of the green body is 100°C to 110°C, and the time is 12 h to 15 h; the pressure for cold-pressing into a green body is 50 kN to 70 kN.

[0024] Step 4) Place the green body dried in step 3) into a crucible pre-lined with graphite paper, then embed it with graphite powder and cover the lid. In step 4, the particle size of the graphite powder is 2 μm - 3 μm.

[0025] Step 5) Place the crucible containing the green body obtained in step 4) into a tube furnace for sintering, and introduce argon during the sintering process for atmosphere protection.

[0026] In step 5, the sintering process is as follows: First, heat up at 8°C / min to 10°C / min to 800°C to 850°C, hold for 0.5 h to 1 h to remove the binder, then heat up at 10°C / min to 12°C / min to 1380°C to 1420°C, heat up at 1°C / min to 2°C / min to 1580°C to 1620°C, and finally heat up at 0.5°C / min to 1°C / min to 1620°C to 1680°C and hold for 3 h to 5 h; subsequently, cool down at 3°C / min to 5°C / min to 480°C - 520°C, and then naturally cool down to room temperature.

[0027] In step 5, during the sintering process, the furnace chamber pressure is maintained at 0.01 MPa to 0.02 MPa.

[0028] The present invention also provides a SiC-TiC composite ceramic for solar thermal power generation, which is prepared by the above method.

[0029] Example 1 The atmospheric pressure sintering preparation method of the SiC-TiC composite ceramic for solar thermal power generation is specifically implemented according to the following steps: Step 1) Mix 1 μm SiC powder and 1 μm TiC powder in a mass ratio of 3:1, and then add Y2O3 powder (particle size: 50 nm) accounting for 5% of the total mass of the two to obtain a raw material powder. Step 2) Prepare a slurry with a mass percentage concentration of 25% from the raw material powder obtained in Step 1) and ethanol. Place the slurry in a planetary ball mill and add alumina balls for ball milling and mixing. Among them, the ball-to-material ratio is 3:1, the rotation speed is 500 r / min, and the ball milling time is 8 h. Add an ethanol solution containing PVA with a mass percentage of 15% of the total mass of the raw material powder 0.5 h before the end of ball milling. The mass percentage concentration of PVA in the added ethanol solution containing PVA is 5%; Step 3) Dry the ball-milled slurry in a forced-air drying oven. Dry it at 110 °C for 12 h to obtain a uniformly mixed raw material powder. Sieve it through a 200-mesh sieve, then cold press the ball-milled mixed powder into a green body under a pressure of 50 kN, and finally place the green body in a forced-air drying oven and dry it at 110 °C for 12 h; Step 4) Place the green body sample in an alumina crucible pre-lined with graphite paper, embed it with 2-μm graphite powder, and cover the lid; Step 5) Place the crucible containing the green body in a tube furnace for sintering, and introduce argon for atmosphere protection. Sintering regime: Heat up to 850 °C at a rate of 10 °C / min and hold for 0.5 h to remove binder, then heat up to 1400 °C at a rate of 10 °C / min, heat up to 1600 °C at a rate of 2 °C / min, and finally heat up to 1650 °C at a rate of 1 °C / min and hold for 3 h. Subsequently, cool down to 500 °C at a rate of 5 °C / min and naturally cool to room temperature. During the sintering process, the furnace chamber pressure is maintained at 0.02 MPa.

[0030] Example 2 A method for preparing SiC-TiC composite ceramics for solar thermal power generation by atmospheric pressure sintering is specifically implemented according to the following steps: Step 1) Mix 2-μm SiC powder and 1-μm TiC powder in a mass ratio of 3.2:1, and then add Y2O3 powder (particle size: 80 nm) with a total mass ratio of 10% of the two to obtain a raw material powder; Step 2) Prepare a slurry with a mass percentage concentration of 28% from the raw material powder obtained in Step 1) and ethanol. Place the slurry in a planetary ball mill and add alumina balls for ball milling and mixing. The ball-to-material ratio is 3:1, the rotation speed is 520 r / min, and the ball milling time is 9 h. Add an ethanol solution containing PVA with a mass percentage of 17% of the total mass of the raw material powder 1 h after the end of ball milling. The mass percentage concentration of PVA in the added ethanol solution containing PVA is 6%; Step 3) Dry the ball-milled slurry in a forced-air drying oven. Dry it at 100 °C for 10 h to obtain a uniformly mixed raw material powder. Sieve it through a 250-mesh sieve, then cold press the ball-milled mixed powder into a green body under a pressure of 55 kN, and finally place the green body in a forced-air drying oven and dry it at 105 °C for 13 h; Step 4) Place the green body sample into an alumina crucible pre-lined with graphite paper, embed it with 3μm graphite powder, and cover the lid. Step 5) Place the crucible containing the green body into a tube furnace for sintering, and introduce argon for atmosphere protection. Sintering regime: Heat up to 840 °C at 9 °C / min and hold for 0.6 h for debinding, then heat up to 1380 °C at 11 °C / min, then heat up to 1580 °C at 1 °C / min, and finally heat up to 1620 °C at 0.5 °C / min and hold for 4 h. Subsequently, cool down to 480 °C at 4 °C / min and then naturally cool to room temperature. During the sintering process, the furnace chamber pressure is maintained at 0.01 MPa.

[0031] Example 3 A method for preparing SiC-TiC composite ceramics for solar thermal power generation by atmospheric pressure sintering, which is specifically implemented according to the following steps: Step 1) Mix 1μm SiC powder and 1μm TiC powder in a mass ratio of 3:1, and then add Y2O3 powder (particle size: 50 nm) accounting for 20% of the total mass of the two to obtain raw material powder. Step 2) Prepare a slurry with a mass percentage concentration of 25% by mixing the raw material powder obtained in Step 1) with ethanol. Place the slurry in a planetary ball mill and add alumina balls for ball milling and mixing. The ball-to-material ratio is 3:1, the rotation speed is 500 r / min, and the ball milling time is 8 h. Add an ethanol solution containing 15% of the total mass of the raw material powder with PVA in the last half hour before the end of ball milling. The mass percentage concentration of PVA in the added ethanol solution containing PVA is 5%. Step 3) Dry the ball-milled slurry in a blast drying oven at 110 °C for 12 h to obtain uniformly mixed raw material powder. Sieve it through a 200-mesh sieve, then cold press the ball-milled mixed powder into a green body under a pressure of 60 kN, and finally place the green body in a blast drying oven and dry it at 110 °C for 12 h. Step 4) Place the green body sample into an alumina crucible pre-lined with graphite paper, embed it with 2μm graphite powder, and cover the lid. Step 5) Place the crucible containing the green body into a tube furnace for sintering, and introduce argon for atmosphere protection. Sintering regime: Heat up to 850 °C at 10 °C / min and hold for half an hour for debinding, then heat up to 1400 °C at 10 °C / min, then heat up to 1600 °C at 2 °C / min, and finally heat up to 1650 °C at 1 °C / min and hold for 3 h. Subsequently, cool down to 500 °C at 5 °C / min and then naturally cool to room temperature. During the sintering process, the furnace chamber pressure is maintained at 0.02 MPa.

[0032] From Figure 1It can be seen that the composition of the composite ceramic consists of SiC, TiC, Y2O3, Y2SiO5, Y2Si2O7 and SiO2, where the main phases are SiC and TiC, indicating that the SiC-TiC composite ceramic has been successfully prepared by firing. From Figure 2 It can be seen that the morphology of the composite ceramic is uniform and has a certain porosity (39 - 43%). The pores can increase the number and path of light reflection, thereby improving the spectral absorption rate of the composite ceramic. From Figure 3 It can be seen that the composite ceramic contains three phases: gray, light gray and white. From Figures 4 to 6 It can be seen that red represents Si element, purple represents Ti element, and green represents Y element. The darker the color, the higher the aggregation concentration of the element at this location. Combining Figures 4 to 6 it can be inferred that Figure 3 the medium gray phase is SiC, the light gray phase is TiC, and the white phase is the bonding phase composed of Y2O3, Y2SiO5, Y2Si2O7 and SiO2 (abbreviated as Y-Si-O), indicating that the Y2O3 additive forms a liquid phase at high temperature and forms a Y-Si-O bonding phase between the SiC and TiC grains by dissolving the oxide layer on the surface of the raw materials, promoting the sintering of the composite ceramic. From Figure 7 Based on the reflectivity diagram of the composite ceramic, the spectral absorption rate of the composite ceramic in the wavelength range of 0.2 μm - 2.5 μm is 84%.

[0033] Example 4 A method for preparing SiC-TiC composite ceramic by atmospheric pressure sintering for solar thermal power generation is specifically implemented according to the following steps: Step 1) Mix SiC powder and TiC powder with a particle size of 2 μm in a mass ratio of 3:1, and then add Y2O3 powder (particle size: 50 nm) accounting for 30% of the total mass of the two to obtain raw material powder; Step 2) Prepare a slurry with a mass percentage concentration of 25% by mixing the raw material powder obtained in Step 1) with ethanol. Place the slurry in a planetary ball mill and add alumina balls for ball milling and mixing. The ball-to-material ratio is 3:1, the rotation speed is 500 r / min, and the ball milling time is 8 h. Add an ethanol solution containing 15% of PVA based on the total mass of the raw material powder half an hour before the end of ball milling. The mass percentage concentration of PVA in the added ethanol solution containing PVA is 5%; Step 3) Dry the ball-milled slurry in a blast drying oven at 110 °C for 12 h to obtain uniformly mixed raw material powder. Sieve it through a 270-mesh sieve, then cold press the ball-milled mixed powder into a green body under a pressure of 70 kN, and finally place the green body in a blast drying oven and dry it at 110 °C for 12 h; Step 4) Place the green body sample in an alumina crucible pre-lined with graphite paper, embed it with 2 μm graphite powder, and cover the lid; Step 5) Place the crucible with the green body into a tube furnace for sintering, and introduce argon for atmosphere protection. Sintering regime: Heat up to 850 °C at a rate of 10 °C / min and hold for half an hour to remove binder, then heat up to 1400 °C at a rate of 10 °C / min, heat up to 1600 °C at a rate of 2 °C / min, and finally heat up to 1650 °C at a rate of 1 °C / min and hold for 3 h. Subsequently, cool down to 500 °C at a rate of 5 °C / min and then naturally cool to room temperature. During the sintering process, the furnace chamber pressure is maintained at 0.02 MPa.

[0034] Example 5 A method for preparing SiC-TiC composite ceramics for solar thermal power generation by atmospheric pressure sintering, which is specifically implemented according to the following steps: Step 1) Mix SiC powder with a particle size of 1 μm and TiC powder with a particle size of 1 μm in a mass ratio of 3.5:1, and then add Y2O3 powder (particle size: 100 nm) accounting for 30% of the total mass of the two to obtain raw material powder. Step 2) Prepare a slurry with a mass percentage concentration of 30% by mixing the raw material powder obtained in Step 1 and ethanol, and place the slurry in a planetary ball mill and add alumina balls for ball milling and mixing. Among them, the ball-to-material ratio is 3:1, the rotation speed is 500 r / min, and the ball milling time is 10 h. Add an ethanol solution containing PVA accounting for 20% of the total mass of the raw material powder 1 h before the end of ball milling, and the mass percentage concentration of PVA in the added ethanol solution containing PVA is 7%. Step 3) Dry the ball-milled slurry in a blast drying oven, dry at 120 °C for 15 h to obtain uniformly mixed raw material powder, sieve it through a 270-mesh sieve, then cold press the ball-milled mixed powder into a green body under a pressure of 70 kN, and finally place the green body in a blast drying oven and dry at 100 °C for 15 h. Step 4) Place the green body sample into an alumina crucible pre-lined with graphite paper, embed it with 2-μm graphite powder, and cover the lid. Step 5) Place the crucible with the green body into a tube furnace for sintering, and introduce argon for atmosphere protection. Sintering regime: Heat up to 800 °C at a rate of 8 °C / min and hold for 1 h to remove binder, then heat up to 1420 °C at a rate of 12 °C / min, heat up to 1620 °C at a rate of 2 °C / min, and finally heat up to 1680 °C at a rate of 1 °C / min and hold for 5 h. Subsequently, cool down to 520 °C at a rate of 3 °C / min and then naturally cool to room temperature. During the sintering process, the furnace chamber pressure is maintained at 0.02 MPa.

[0035] Example 6 A method for preparing SiC-TiC composite ceramics for solar thermal power generation by atmospheric pressure sintering, which is specifically implemented according to the following steps: Step 1) Mix 1 μm SiC powder and 1 μm TiC powder in a mass ratio of 3.5:1, and then add Y2O3 powder (particle size: 100 nm) accounting for 30% of the total mass of the two to obtain raw material powder; Step 2) Prepare a slurry with a mass percentage concentration of 30% from the raw material powder obtained in Step 1 and ethanol. Place the slurry in a planetary ball mill and add alumina balls for ball milling and mixing. Among them, the ball-to-material ratio is 3:1, the rotation speed is 550 r / min, and the ball milling time is 10 h. Add an ethanol solution containing PVA accounting for 20% of the total mass of the raw material powder 1 h before the end of ball milling. The mass percentage concentration of PVA in the added ethanol solution containing PVA is 7%; Step 3) Dry the ball-milled slurry in a blast drying oven, dry at 120 °C for 15 h to obtain uniformly mixed raw material powder, sieve it through a 270-mesh sieve, then cold press the ball-milled mixed powder into a green body under a pressure of 50 kN, and finally place the green body in a blast drying oven and dry at 100 °C for 15 h; Step 4) Place the green body sample in an alumina crucible pre-lined with graphite paper, embed it with 2 μm graphite powder, and cover the lid; Step 5) Place the crucible containing the green body in a tube furnace for sintering, and introduce argon for atmosphere protection. Sintering regime: Heat up to 800 °C at a rate of 10 °C / min and hold for 1 h to remove binder, then heat up to 1420 °C at a rate of 12 °C / min, heat up to 1600 °C at a rate of 2 °C / min, and finally heat up to 1680 °C at a rate of 1 °C / min and hold for 5 h. Subsequently, cool down to 520 °C at a rate of 3 °C / min and cool naturally to room temperature. During the sintering process, the furnace chamber pressure is maintained at 0.02 MPa.

Claims

1. A method for preparing SiC-TiC composite ceramics for solar thermal power generation by atmospheric pressure sintering, characterized in that, The implementation is specifically carried out according to the following steps: Step 1) First, mix SiC powder and TiC powder, and then add Y2O3 powder to the mixed powder to obtain raw material powder; Step 2) Mix the raw material powder obtained in Step 1) with ethanol to form a slurry, and ball-mill the slurry. During the ball-milling process, an ethanol solution containing PVA needs to be added; Step 3) Dry the slurry ball-milled in Step 2) to obtain uniformly mixed raw material powder, sieve it using a sieve mesh, then cold-press the sieved powder into a green body, and finally dry the green body; Step 4) Embed the green body dried in Step 3) with graphite powder; Step 5) Sinter the green body embedded with graphite powder obtained in Step 4). During the sintering process, argon is introduced for atmosphere protection.

2. The atmospheric pressure sintering preparation method of the SiC-TiC composite ceramic for solar thermal power generation according to claim 1, characterized in that, In Step 1, the mass ratio of SiC to TiC is 3 - 3.5:1, the addition amount of Y2O3 is 5% - 30% of the total mass of the two, the particle size of SiC and TiC is 1μm - 2μm, and the particle size of Y2O3 is 50nm - 100nm.

3. The atmospheric pressure sintering preparation method of the SiC-TiC multiphase ceramic for solar thermal power generation according to claim 1, characterized in that, The specific process of Step 2 is as follows: Mix the raw material powder obtained in Step 1) with ethanol to form a slurry with a mass percentage concentration of 25% - 30%, then pour the slurry into an alumina ball-milling tank, add alumina balls, where the ball-to-material ratio is 3 - 3.5:1 and the rotation speed is 500r / min - 550r / min; finally, place the ball-milling tank in a planetary ball mill for ball-milling and mixing for 8h - 10h; add an ethanol solution containing PVA 0.5h - 1h before the end of ball-milling.

4. The atmospheric pressure sintering preparation method of the SiC-TiC composite ceramic for solar thermal power generation according to claim 3, characterized in that In Step 2, the mass percentage concentration of PVA in the added ethanol solution containing PVA is 5% - 7%, and the addition amount is 15% - 20% of the total mass of the powder.

5. The atmospheric pressure sintering preparation method of the SiC-TiC composite ceramic for solar thermal power generation according to claim 1, wherein, In Step 3, the pore size of the sieve mesh is 200 mesh - 270 mesh; the drying temperature of the slurry is 100°C - 120°C and the time is 10h - 15h; the drying temperature of the green body is 100°C - 110°C and the time is 12h - 15h; the pressure for cold-pressing into the green body is 50kN - 70kN.

6. The atmospheric pressure sintering preparation method of the SiC-TiC composite ceramic for solar thermal power generation according to claim 1, characterized in that, In Step 4, the particle size of the graphite powder is 2μm - 3μm.

7. The atmospheric pressure sintering preparation method of the SiC-TiC composite ceramic for solar thermal power generation according to claim 1, characterized in that In Step 5, the sintering process is as follows: First, heat up at 8°C / min - 10°C / min to 800°C - 850°C, keep warm for 0.5h - 1h to remove binder, then heat up at 10°C / min - 12°C / min to 1380°C - 1420°C, heat up at 1°C / min - 2°C / min to 1580°C - 1620°C, and finally heat up at 0.5°C / min - 1°C / min to 1620°C - 1680°C and keep warm for 3h - 5h; then cool down at 3°C / min - 5°C / min to 480°C - 520°C, and then naturally cool down to room temperature.

8. The atmospheric pressure sintering preparation method of the SiC-TiC composite ceramic for solar thermal power generation according to claim 1, characterized in that, In Step 5, during the sintering process, the furnace chamber pressure is maintained between 0.01MPa and 0.02MPa.

9. SiC-TiC composite ceramics for solar thermal power generation, characterized in that, Prepared by the method according to any one of claims 1 - 8.

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