In-situ synthesis porous ZrB2-SiC composite ceramic for solar thermal power generation and normal-pressure sintering preparation method thereof

Abstract

The invention discloses a normal-pressure sintering preparation method of in-situ synthesis porous ZrB2-SiC composite ceramic for solar thermal power generation, which is specifically implemented according to the following steps: step 1) mixing silicon-zirconium alloy powder, boron carbide and phenolic resin to obtain raw material powder; (2) preparing the raw material powder and ethanol into slurry, and carrying out ball milling on the slurry; 3) drying the ball-milled slurry, sieving after drying, performing cold pressing on the sieved raw material powder to obtain a green body, and drying the obtained green body; 4, graphite powder is used for embedding the dried green body, the green body embedded with the graphite powder is sintered, and argon is introduced for atmosphere protection.By means of the method, the problems that an existing heat absorption material for solar thermal power generation is complex in preparation process and high in cost are solved. The invention further discloses the in-situ synthesis porous ZrB2-SiC composite ceramic for solar thermal power generation.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of composite ceramics, and particularly relates to an in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation, and also relates to a method for preparing an in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation by atmospheric pressure sintering. Background Art

[0002] Solar thermal power generation, relying on its unique "light-thermal-electricity" conversion path and molten salt energy storage technology, has become an effective way to solve the problems of power grid peak shaving and night power supply. Due to its advantages such as high concentration ratio (200 - 1000 kW / m²), high thermal cycle temperature, low heat loss, and system efficiency up to 22%, the tower solar thermal power generation system has become a key technology that various countries are competing to research and develop. In the tower solar thermal power generation system, the absorber plays an important role in converting solar radiant energy into heat energy, and its photo-thermal conversion efficiency determines the power generation efficiency of the tower solar thermal power generation system. At the same time, the absorber material needs to operate stably for a long time in a high-temperature (>1000°C), strong radiation, and oxidation environment, which poses strict requirements on the light absorption performance and high-temperature stability of the material. Although traditional metal-based absorbers perform well below 800°C, they are prone to problems such as creep deformation and surface oxidation and spalling under ultra-high temperature conditions, seriously restricting the system life and efficiency. In contrast, high-temperature ceramic materials, with their ultra-high melting points, low thermal expansion coefficients, and chemical inertness endowed by covalent bonds / ionic bonds, have become the preferred materials for high-temperature resistant absorbers.

[0003] According to the research results of researchers on ceramic materials for high-temperature solar absorbers in solar thermal power generation, the ceramic materials currently suitable for high-temperature solar absorbers mainly include carbides such as HfC, TaC, and SiC, borides such as HfB2, ZrB2, and TiB2, and MAX phases such as Ti3SiC2 and Zr3[Al(Si)]4C6, as well as composite ceramics composed of the above several ceramics. For example, Fang et al. prepared Ti3SiC2 and Zr3[Al(si)]4C6 layered ceramics by hot pressing sintering method in the article "Suitability oflayered Ti3SiC2and Zr3[Al(Si)]4C6ceramics as high temperature solar absorbersfor solar energy applications". The results showed that the solar spectral absorptivity of Ti3SiC2 ceramics at room temperature was 0.7. However, the equipment cost of the hot pressing sintering process is high. Simone Barbarossa et al. first synthesized ceramic powders by self-propagating high-temperature synthesis and then prepared two high-entropy boride ceramics, (Hf 0.2 Zr 0.2 Ta 0.2 Mo 0.2 Ti 0.2 )B2 and (Hf 0.2 Nb 0.2 Ta 0.2 Mo 0.2 Ti 0.2 )B2, in the article "Optical properties of bulk high-entropy diborides for solar energy applications". They have low thermal emissivity and high spectral selectivity at high temperatures, but the solar absorptivity is relatively low, about 0.4. The preparation process of this method is complex, costly, and has poor controllability of the microstructure. ElisaSani et al. prepared TaC and SiC ceramics by hot pressing method in the article "Hafnium and tantalum carbides for high temperature solarreceivers". The results showed that SiC had significantly higher absorptivity than TaC at high temperatures (TaC was 0.35 and SiC was 0.65 at 1100K), indicating that the absorptivity of SiC did not decay significantly in a high-temperature environment, but there was still room for improvement. SUMMARY OF THE INVENTION

[0004] The first object of the present invention is to provide an in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation, which solves the problem of insufficient solar spectral absorptivity of the current high-temperature absorber materials for solar thermal power generation.

[0005] The second object of the present invention is to provide a method for preparing an in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation by atmospheric pressure sintering, which solves the problems of complex preparation process and high cost of the current high-temperature absorber materials for solar thermal power generation.

[0006] The first technical solution adopted by the present invention is a method for preparing an in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation by atmospheric pressure sintering, which is specifically implemented according to the following steps: Step 1): Mix silicon-zirconium alloy powder, boron carbide (B4C) and phenolic resin to obtain raw material powder; Step 2): Prepare a slurry by mixing the raw material powder and ethanol, and ball-mill the slurry; Step 3): Dry the ball-milled slurry, sieve it after drying, cold-press the sieved raw material powder into a green body, and dry the obtained green body; Step 4): Embed the dried green body with graphite powder, sinter the graphite powder-embedded green body, and introduce argon for atmosphere protection.

[0007] The present invention is further characterized in that: In step 1, the mass ratio of silicon-zirconium alloy powder, boron carbide (B4C), and phenolic resin is 3-8:1-3:1-3; The molar ratio of silicon to zirconium in the silicon-zirconium alloy powder is 2:1.

[0008] Step 2 is specifically as follows: Prepare a slurry with a mass percentage concentration of 20% - 25% by mixing the raw material powder and ethanol, then pour the slurry into an alumina ball mill tank, add alumina balls, and finally place the ball mill tank in a planetary ball mill for mixing; add an ethanol solution containing PVA 0.5h - 1h before the end of ball milling; the added ethanol solution containing PVA accounts for 15% - 20% of the mass of the raw material powder; in the ethanol solution containing PVA, the mass percentage concentration of PVA is 4% - 7%.

[0009] In step 2, the ball-to-material ratio is 3:1 - 5:1, the rotational speed of the planetary ball mill is 500r / min - 550r / min, and the ball milling time is 8h - 10h.

[0010] Step 3 specifically includes: drying the ball-milled slurry at 105°C to 110°C for 12h to 15h to obtain a uniformly mixed raw material powder, sieving it through a 200-mesh to 270-mesh sieve, then cold-pressing the raw material powder into a green body under a pressure of 400MPa to 500MPa, and finally drying the green body at 105°C to 110°C for 12h to 15h.

[0011] In step 4, the particle size of the graphite powder is 2μm to 5μm.

[0012] In step 4, the sintering process is as follows: heating at 8°C / min to 10°C / min to 800°C to 850°C and holding for 0.5h to 1h to remove binder, then heating at 4°C / min to 5°C / min to 1350°C to 1450°C, heating at 1°C / min to 2°C / min to 1550°C to 1650°C, and finally heating at 0.5°C / min to 1°C / min to 1600°C to 1700°C and holding for 3h to 3.5h, and then cooling at 5°C / min to 8°C / min to 450°C to 550°C and naturally cooling to room temperature; In step 4, during the sintering process, the furnace chamber pressure is maintained at 0.01MPa to 0.02MPa.

[0013] The second technical solution adopted in the present invention is that the in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation is prepared by the above method.

[0014] The beneficial effects of the present invention are as follows: (1) The method of the present invention mixes all the powder raw materials uniformly, first cold-presses them into a green body, and then uses the embedding method for sintering to prevent the green body from deforming during the sintering process. The pores can increase the number and path of light reflection, thereby improving the spectral absorptivity of the composite ceramic.

[0015] (2) The method of the present invention uses phenolic resin as the carbon source. The resin carbon generated after the pyrolysis of phenolic resin during the sintering process is porous carbon, which increases the contact area between the resin carbon and other raw materials, thereby improving the reaction activity between the reactants and realizing the in-situ generation of porous ZrB2-SiC composite ceramic at low temperature and normal pressure.

[0016] (3) In the method of the present invention, atmospheric pressure sintering has the advantages of low cost, process flexibility and suitability for large-scale production, which highly coincides with the sustainability goal of solar application technology and provides important technical support for its application. This method solves the problems of complex preparation process and high cost of high-temperature heat absorber materials for current solar thermal power generation.

[0017] (4) The porous ZrB2-SiC composite ceramic prepared by the method of the present invention solves the problem of insufficient solar spectral absorptivity of the current high-temperature heat absorber material for solar thermal power generation. Description of the Drawings

[0018] Figure 1 is the XRD pattern of the porous ZrB2-SiC composite ceramic prepared in Example 1 of the present invention; Figure 2 is the low-magnification SEM photograph of the porous ZrB2-SiC composite ceramic prepared in Example 1 of the present invention; Figure 3 is Figure 2 the high-magnification SEM photograph of the position A in Figure 4 is Figure 3 the distribution map of Si element in Figure 5 is Figure 3 the distribution map of Zr element in Figure 6 is Figure 3 the distribution map of C element in Figure 7 is Figure 3 the distribution map of B element in Figure 8 is the absorptivity spectrum of the porous ZrB2-SiC composite ceramic prepared in Example 1 of the present invention in the wavelength range of 0.25 μm to 2.5 μm at room temperature and after oxidation in air at 1000 °C for 100 h. Specific Embodiments

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

[0020] The present invention provides a method for preparing in-situ porous ZrB2-SiC composite ceramic for solar thermal power generation by atmospheric pressure sintering, which is specifically implemented according to the following steps: Step 1) Mix silicon-zirconium alloy powder, boron carbide (B4C) and phenolic resin to obtain raw material powder; In Step 1, the mass ratio of silicon-zirconium alloy powder, boron carbide (B4C), and phenolic resin is 3-8:1-3:1-3; The molar ratio of silicon to zirconium in the silicon-zirconium alloy powder is 2:1.

[0021] Step 2) Prepare a slurry by mixing the raw material powder and ethanol, and ball-mill the slurry; Step 2 specifically includes: preparing a slurry with a mass percentage concentration of 20% - 25% from raw material powder and ethanol, then pouring the slurry into an alumina ball mill tank, adding alumina balls, and finally placing the ball mill tank in a planetary ball mill for mixing; adding an ethanol solution containing PVA 0.5 h - 1 h before the end of ball milling; the added ethanol solution containing PVA accounts for 15% - 20% of the mass of the raw material powder; in the ethanol solution containing PVA, the mass percentage concentration of PVA is 4% - 7%.

[0022] In Step 2, the ball-to-material ratio is 3:1 - 5:1, the rotational speed of the planetary ball mill is 500 r / min - 550 r / min, and the ball milling time is 8 h - 10 h.

[0023] Step 3) Dry the ball-milled slurry, sieve it after drying, cold-press the sieved raw material powder into a green body, and dry the obtained green body. Step 3 specifically includes: drying the ball-milled slurry in a forced-air drying oven at 105°C - 110°C for 12 h - 15 h to obtain a uniformly mixed raw material powder, sieving it with a 200 - 270 mesh sieve, then cold-pressing the raw material powder into a green body under a pressure of 400 MPa - 500 MPa, and finally placing the green body in a forced-air drying oven and drying it at 105°C - 110°C for 12 h - 15 h.

[0024] Step 4) Place the dried green body into a crucible pre-lined with graphite paper, then embed it with graphite powder, place the crucible with the green body in a tube furnace for sintering, and introduce argon for atmosphere protection.

[0025] In Step 4, the particle size of the graphite powder is 2 μm - 5 μm.

[0026] In Step 4, the sintering process is as follows: heating at 8°C / min - 10°C / min to 800°C - 850°C and holding for 0.5 h - 1 h to remove binder, then heating at 4°C / min - 5°C / min to 1350°C - 1450°C, heating at 1°C / min - 2°C / min to 1550°C - 1650°C, and finally heating at 0.5°C / min - 1°C / min to 1600°C - 1700°C and holding for 3 h - 3.5 h, then cooling at 5°C / min - 8°C / min to 450°C - 550°C and naturally cooling to room temperature; During the sintering process, the furnace chamber pressure is maintained at 0.01 MPa - 0.02 MPa.

[0027] The present invention also provides an in-situ self-generated porous ZrB2 - SiC composite ceramic for solar thermal power generation, which is prepared by the above method.

[0028] Introduction to the manufacturers and specifications of the main raw materials in Examples 1-6: The zirconium silicide alloy powder used in the present invention is provided by Beijing Huawei Ruike Chemical Technology Co., Ltd., with an average particle size of 10 microns, a purity of 94%, a Si mass percentage content of 38.46%, and a Zr mass percentage content of 55.42%. The B4C powder is provided by Beijing Huawei Ruike Chemical Technology Co., Ltd., with an average particle size of 1 micron. The phenolic resin is a commercially available phenolic resin powder with a residual carbon content of 58%.

[0029] Example 1 An atmospheric pressure sintering preparation method of in-situ self-generated porous ZrB2-SiC composite ceramics for solar thermal power generation is specifically implemented according to the following steps: Step 1) Mix the zirconium silicide alloy powder (ZrSi2), boron carbide (B4C), and phenolic resin in a mass ratio of 5:1:1 to obtain raw material powder; the molar ratio of silicon to zirconium in the zirconium silicide alloy powder is 2:1.

[0030] Step 2) Prepare a slurry with a mass percentage concentration of 23% by mixing the raw material powder and ethanol, then pour the slurry into an alumina ball milling tank, add alumina balls, with a ball-to-material ratio of 3:1, and finally place the ball milling tank in a planetary ball mill for mixing. The rotational speed of the planetary ball mill is 500 r / min, the ball milling time is 8 h, and an ethanol solution containing PVA is added 0.5 h before the end of ball milling; the added ethanol solution containing PVA accounts for 15% of the mass of the raw material powder; in the ethanol solution containing PVA, the mass percentage concentration of 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 raw material powder into a green body under a pressure of 400 MPa, 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 in an alumina crucible pre-lined with graphite paper, then embed the green body with 2-μm graphite powder, place the crucible containing the green body in a tube furnace for sintering, and introduce argon for atmosphere protection. The sintering regime is as follows: heat up to 800 °C at a rate of 10 °C / min and hold for 1 h for debinding, then heat up to 1400 °C at a rate of 5 °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, and then 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 0.01 MPa.

[0031] In the present invention, the proportions between raw materials are formulated according to the reaction formula 2ZrSi2 + B4C + 3C = 2ZrB2 + 4SiC. According to the XRD results of Example 1, the main phases of the fired sample are ZrB2 and SiC, indicating that the C formed by the pyrolysis of phenolic resin at high temperature reacts in-situ with Si in the ZrSi2 alloy to generate SiC, while the B decomposed from B4C at high temperature reacts in-situ with Zr in ZrSi2 to generate ZrB2.

[0032] It can be seen from Figure 1 that the composition of this multiphase ceramic includes ZrB2, SiC, and a small amount of B and C that are not completely reacted after the high-temperature decomposition of the raw materials, indicating that the following reaction occurred among ZrSi2, B4C, and the resin carbon formed by the pyrolysis of phenolic resin: 2ZrSi2 + B4C + 3C = 2ZrB2 + 4SiC, and two main phases, ZrB2 and SiC, were formed in-situ, and porous ZrB2-SiC multiphase ceramic was formed in-situ under low-temperature and normal-pressure conditions; It can be seen from Figure 2 that the morphology of this multiphase ceramic is uniform. After firing at 1650 °C under normal pressure in a tube furnace, there are also a certain number of pores distributed, and a porous ZrB2-SiC multiphase ceramic with a porosity of 43% is obtained. The pores can increase the number and path of light reflection, thereby improving the spectral absorptivity of the multiphase ceramic. From Figure 3 it can be seen that the white grains and gray grains in the multiphase ceramic are closely combined with each other. It can be seen from Figures 4 - 7 that Figure 4 in Figure 5 blue represents Si element, Figure 6 red represents Zr element, Figure 7 yellow represents C element, Figures 4 - 7 and cyan represents B element. The darker the color, the higher the aggregation concentration of this element at this place. Combining Figures 4 - 7 it can be inferred that the white particles in the multiphase ceramic are ZrB2 grains, and the gray ones are SiC grains.

[0033] ZrB2 has excellent spectral absorption characteristics, and its absorptivity in the visible to near-infrared band can reach more than 85%. Combining ZrB2 with SiC can improve the spectral absorptivity of pure SiC ceramic, making the ZrB2-SiC multiphase ceramic exhibit excellent antioxidant performance and light absorption performance. According to Figure 8 the reflectance spectrum of the multiphase ceramic, it is calculated that the solar spectral absorptivity of the prepared porous ZrB2-SiC multiphase ceramic in the 0.25μm - 2.5μm band is 0.86; after oxidation in air at 1000 °C for 100h, the solar spectral absorptivity of the multiphase ceramic in the 0.25μm - 2.5μm band is 0.84, and the decline is not obvious, indicating that its light absorption performance has good high-temperature stability.

[0034] Example 2 A method for preparing an in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation by atmospheric pressure sintering, which is specifically implemented according to the following steps: Step 1) Mix silicon zirconium alloy powder (ZrSi2), boron carbide (B4C), and phenolic resin in a mass ratio of 8:1:1 to obtain raw material powder; the molar ratio of silicon to zirconium in the silicon zirconium alloy powder is 2:1.

[0035] Step 2) Prepare a slurry with a mass percentage concentration of 20% by mixing the raw material powder and ethanol, then pour the slurry into an alumina ball mill tank, add alumina balls, with a ball-to-material ratio of 3:1, and finally place the ball mill tank in a planetary ball mill for mixing. The rotational speed of the planetary ball mill is 520 r / min, the ball milling time is 9 h, and an ethanol solution containing PVA is added 0.6 h before the end of ball milling; the added ethanol solution containing PVA accounts for 16% of the mass of the raw material powder; in the ethanol solution containing PVA, the mass percentage concentration of PVA is 5%.

[0036] Step 3) Dry the ball-milled slurry in a forced-air drying oven at 105 °C for 13 h to obtain a uniformly mixed raw material powder, sieve it through a 200-mesh sieve, then cold-press the raw material powder into a green body under a pressure of 450 MPa, 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 in an alumina crucible pre-lined with graphite paper, then embed the green body with 3-μm graphite powder, place the crucible with the green body in a tube furnace for sintering, and introduce argon for atmosphere protection. The sintering regime is as follows: heat up to 800 °C at a rate of 8 °C / min and hold for 0.5 h to remove the binder, then heat up to 1350 °C at a rate of 4 °C / min, heat up to 1550 °C at a rate of 1 °C / min, and finally heat up to 1600 °C at a rate of 0.5 °C / min and hold for 3 h, and then cool down to 450 °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.

[0037] Example 3 A method for preparing an in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation by atmospheric pressure sintering, which is specifically implemented according to the following steps: Step 1) Mix silicon zirconium alloy powder (ZrSi2), boron carbide (B4C), and phenolic resin in a mass ratio of 3:1:1 to obtain raw material powder; the molar ratio of silicon to zirconium in the silicon zirconium alloy powder is 2:1.

[0038] Step 2) Prepare a slurry with a mass percentage concentration of 25% by mixing the raw material powder and ethanol. Then pour the slurry into an alumina ball mill tank, add alumina balls with a ball-to-material ratio of 5:1. Finally, place the ball mill tank in a planetary ball mill for mixing. The rotational speed of the planetary ball mill is 500 r / min, the ball milling time is 10 h, and an ethanol solution containing PVA is added 1 h before the end of ball milling; the added ethanol solution containing PVA accounts for 20% of the mass of the raw material powder; in the ethanol solution containing PVA, the mass percentage concentration of PVA is 7%.

[0039] Step 3) Dry the ball-milled slurry in a forced-air drying oven at 108 °C for 14 h to obtain a uniformly mixed raw material powder. Sieve it through a 200-mesh sieve, and then cold-press the raw material powder into a green body under a pressure of 500 MPa. Finally, place the green body in a forced-air drying oven and dry it at 108 °C for 14 h; Step 4) Place the green body in an alumina crucible pre-lined with graphite paper, then embed the green body with 4-μm graphite powder. Put the crucible containing the green body into a tube furnace for sintering, and introduce argon for atmosphere protection. The sintering regime is as follows: heat up to 850 °C at a rate of 10 °C / min and hold for 1 h to remove binder, then heat up to 1450 °C at a rate of 5 °C / min, heat up to 1650 °C at a rate of 2 °C / min, and finally heat up to 1700 °C at a rate of 1 °C / min and hold for 3 h. Subsequently, cool down to 550 °C at a rate of 8 °C / min and then naturally cool to room temperature. During the sintering process, the furnace chamber pressure is maintained at 0.01 MPa.

[0040] Example 4 A method for preparing an in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation by atmospheric pressure sintering, which is specifically implemented according to the following steps: Step 1) Mix silicon zirconium alloy powder (ZrSi2), boron carbide (B4C), and phenolic resin in a mass ratio of 5:1:3 to obtain a raw material powder; the molar ratio of silicon to zirconium in the silicon zirconium alloy powder is 2:1.

[0041] Step 2) Prepare a slurry with a mass percentage concentration of 22% by mixing the raw material powder and ethanol. Then pour the slurry into an alumina ball mill tank, add alumina balls with a ball-to-material ratio of 4:1. Finally, place the ball mill tank in a planetary ball mill for mixing. The rotational speed of the planetary ball mill is 500 r / min, the ball milling time is 10 h, and an ethanol solution containing PVA is added 0.5 h before the end of ball milling; the added ethanol solution containing PVA accounts for 15% of the mass of the raw material powder; in the ethanol solution containing PVA, the mass percentage concentration of PVA is 6%.

[0042] Step 3) Dry the ball-milled slurry in a forced-air drying oven at 109 °C for 15 h to obtain a uniformly mixed raw material powder. Sieve the powder through a 200-mesh sieve, then cold-press the raw material powder into a green body under a pressure of 400 MPa, and finally dry the green body in a forced-air drying oven at 109 °C for 15 h; Step 4) Place the green body in an alumina crucible pre-lined with graphite paper, then embed the green body with 5-μm graphite powder. Place the crucible containing the green body in a tube furnace for sintering, and introduce argon for atmosphere protection. The sintering process is as follows: Heat up to 820 °C at a rate of 9 °C / min and hold for 1 h to remove binder, then heat up to 1400 °C at a rate of 4 °C / min, then heat up to 1600 °C at a rate of 2 °C / min, and finally heat up to 1650 °C at a rate of 0.5 °C / min and hold for 3.5 h. Subsequently, cool down to 520 °C at a rate of 7 °C / min and then naturally cool to room temperature. During the sintering process, the furnace chamber pressure is maintained at 0.02 MPa.

[0043] Example 5 A method for preparing in-situ self-generated porous ZrB2-SiC composite ceramics for solar thermal power generation by atmospheric pressure sintering, which is specifically implemented according to the following steps: Step 1) Mix silicon-zirconium alloy powder (ZrSi2), boron carbide (B4C), and phenolic resin in a mass ratio of 5:3:1 to obtain a raw material powder; the molar ratio of silicon to zirconium in the silicon-zirconium alloy powder is 2:1.

[0044] Step 2) Prepare a slurry with a mass percentage concentration of 21% by mixing the raw material powder and ethanol, then pour the slurry into an alumina ball mill tank, add alumina balls, and the ball-to-material ratio is 3:1. Finally, place the ball mill tank in a planetary ball mill for mixing. The rotational speed of the planetary ball mill is 500 r / min, and the ball milling time is 8 h. Add an ethanol solution containing PVA 0.5 h before the end of ball milling; the added ethanol solution containing PVA accounts for 15% of the mass of the raw material powder; in the ethanol solution containing PVA, the mass percentage concentration of PVA is 5%.

[0045] Step 3) Dry the ball-milled slurry in a forced-air drying oven at 110 °C for 13 h to obtain a uniformly mixed raw material powder. Sieve the powder through a 200-mesh sieve, then cold-press the raw material powder into a green body under a pressure of 450 MPa, and finally dry the green body in a forced-air drying oven at 110 °C for 13 h; Step 4) Place the green body into an alumina crucible pre-lined with graphite paper, then embed the green body with 5 μm graphite powder. Put the crucible containing the green body into a tube furnace for sintering, and introduce argon for atmosphere protection. The sintering regime is as follows: heat up to 840 °C at a rate of 9 °C / min and hold for 1 h for debinding, then heat up to 1400 °C at a rate of 4 °C / min, then heat up to 1600 °C at a rate of 1 °C / min, and finally heat up to 1650 °C at a rate of 1 °C / min and hold for 3.5 h. Subsequently, cool down to 500 °C at a rate of 8 °C / min and then naturally cool to room temperature. During the sintering process, the furnace chamber pressure is maintained at 0.01 MPa.

[0046] Example 6 In-situ self-generated porous ZrB2-SiC composite ceramics for solar thermal power generation and its atmospheric pressure sintering preparation method are specifically implemented according to the following steps: Step 1) Mix zirconium silicide powder (ZrSi2), boron carbide (B4C), and phenolic resin in a mass ratio of 5:2:2 to obtain raw material powder; the molar ratio of silicon to zirconium in the zirconium silicide powder is 2:1.

[0047] Step 2) Prepare a slurry with a mass percentage concentration of 24% by mixing the raw material powder and ethanol. Then pour the slurry into an alumina ball milling tank, add alumina balls, and the ball-to-material ratio is 3:1 to 5:1. Finally, place the ball milling tank in a planetary ball mill for mixing. The rotational speed of the planetary ball mill is 500 r / min, the ball milling time is 9 h, and an ethanol solution containing PVA is added 0.5 h to 1 h before the end of ball milling; the added ethanol solution containing PVA accounts for 20% of the mass of the raw material powder; in the ethanol solution containing PVA, the mass percentage concentration of PVA is 6%.

[0048] Step 3) Dry the ball-milled slurry in a blast drying oven at 109 °C for 15 h to obtain uniformly mixed raw material powder. Sieve it through a 200-mesh sieve, then cold press the raw material powder into a green body under a pressure of 500 MPa, and finally place the green body in a blast drying oven and dry it at 109 °C for 15 h; Step 4) Place the green body into an alumina crucible pre-lined with graphite paper, then embed the green body with 2 μm graphite powder. Put the crucible containing the green body into a tube furnace for sintering, and introduce argon for atmosphere protection. The sintering regime is as follows: heat up to 850 °C at a rate of 10 °C / min and hold for 1 h for debinding, then heat up to 1400 °C at a rate of 5 °C / min, then heat up to 1600 °C at a rate of 1 °C / min, and finally heat up to 1650 °C at a rate of 0.8 °C / min and hold for 3.4 h. Subsequently, cool down to 500 °C at a rate of 7 °C / min and then naturally cool to room temperature. During the sintering process, the furnace chamber pressure is maintained at 0.02 MPa.

Claims

1. An atmospheric pressure sintering preparation method of in-situ self-generated porous ZrB2-SiC composite ceramics for solar thermal power generation, characterized in that, The implementation is specifically carried out according to the following steps: Step 1) Mix silicon-zirconium alloy powder, boron carbide and phenolic resin to obtain raw material powder; Step 2) Prepare a slurry from the raw material powder and ethanol, and ball-mill the slurry; Step 3) Dry the ball-milled slurry, sieve it after drying, cold-press the sieved raw material powder into a green body, and dry the obtained green body; Step 4) Embed the dried green body with graphite powder, sinter the graphite powder-embedded green body, and introduce argon for atmosphere protection.

2. The atmospheric pressure sintering preparation method of the in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation according to claim 1, characterized in that, In Step 1, the mass ratio of silicon-zirconium alloy powder, boron carbide and phenolic resin is 3-8:1-3:1-3; The molar ratio of silicon to zirconium in the silicon-zirconium alloy powder is 2:

1.

3. The atmospheric pressure sintering preparation method of the in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation according to claim 1, characterized in that, Step 2 is specifically: Prepare a slurry with a mass percentage concentration of 20% - 25% from the raw material powder and ethanol, 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 mixing; Add an ethanol solution containing PVA 0.5h - 1h before the end of ball milling; The added ethanol solution containing PVA accounts for 15% - 20% of the mass of the raw material powder; In the ethanol solution containing PVA, the mass percentage concentration of PVA is 4% - 7%.

4. The atmospheric pressure sintering preparation method of in-situ self-generated porous ZrB2-SiC composite ceramics for solar thermal power generation according to claim 3, characterized in that, In Step 2, the ball-to-material ratio is 3:1 - 5:1, the rotational speed of the planetary ball mill is 500r / min - 550r / min, and the ball-milling time is 8h - 10h.

5. The atmospheric pressure sintering preparation method of in-situ self-generated porous ZrB2-SiC multiphase ceramics for solar thermal power generation according to claim 1, characterized in that, Step 3 is specifically: Dry the ball-milled slurry at 105°C - 110 °C for 12h - 15h to obtain uniformly mixed raw material powder, sieve it with a 200-mesh - 270-mesh sieve, then cold-press the raw material powder into a green body under a pressure of 400MPa - 500 MPa, and finally dry the green body at 105°C - 110 °C for 12h - 15h.

6. The atmospheric pressure sintering preparation method of in-situ self-generated porous ZrB2-SiC multiphase ceramics for solar thermal power generation according to claim 1, characterized in that, In Step 4, the particle size of the graphite powder is 2μm - 5μm.

7. The atmospheric pressure sintering preparation method of the in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation according to claim 1, characterized in that, In Step 4, the sintering process is: Heat up to 800°C - 850 °C at a rate of 8°C / min - 10°C / min and hold for 0.5h - 1h to remove binder, then heat up to 1350°C - 1450 °C at a rate of 4°C / min - 5°C / min, heat up to 1550°C - 1650 °C at a rate of 1°C / min - 2°C / min, and finally heat up to 1600°C - 1700 °C at a rate of 0.5°C / min - 1°C / min and hold for 3h - 3.5h, then cool down at a rate of 5°C / min - 8°C / min to 450°C - 550 °C, and naturally cool to room temperature.

8. The atmospheric pressure sintering preparation method of the in-situ self-generated porous ZrB2-SiC composite ceramic for solar thermal power generation according to claim 1, characterized in that, In Step 4, during the sintering process, the furnace chamber pressure is maintained at 0.01MPa - 0.02MPa.

9. In-situ self-generated porous ZrB2-SiC composite ceramics for solar thermal power generation, characterized in that, Prepared by the method described in any one of claims 1 - 8.

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