Ceramic wafer, ceramic hearth, concentrating solar high-temperature furnace and preparation method of concentrating solar high-temperature furnace

Abstract

The invention relates to a ceramic chip, a ceramic hearth, a concentrating solar high-temperature furnace and a preparation method of the ceramic chip. The raw materials of the ceramic chip comprise basic components and additional components, the basic component comprises the following components in percentage by mass: 80-96% of aluminum oxide and 4-20% of kaolin; the additional components comprise titanium oxide accounting for 1-3% of the total mass of the basic components, zirconium oxide accounting for 1-6% of the total mass of the basic components, iron oxide accounting for 5-11% of the total mass of the basic components and The obtained ceramic chip has a good heat absorption and storage function, and when the ceramic chip is made into a ceramic hearth and assembled into a concentrating solar high-temperature furnace, continuous and stable sintering of a ceramic sample can be guaranteed when the ceramic chip is used for sintering the ceramic sample.

Description

Technical Field

[0001] The present invention relates to the field of ceramics, and in particular to a ceramic sheet, a ceramic furnace, a concentrating solar high-temperature furnace and a preparation method thereof. Background Art

[0002] In the field of architectural ceramic firing technology, traditional kilns (such as electric kilns, roller kilns, tunnel kilns, and shuttle kilns) rely primarily on non-renewable energy sources such as coal, oil, and natural gas. This results in high energy consumption, high carbon emissions, and serious environmental pollution. There is an urgent need to design and manufacture new high-temperature kilns that utilize renewable energy.

[0003] Solar sintering furnaces are gaining increasing attention in the field of ceramic firing technology as an environmentally friendly, energy-saving, and efficient sintering technology. The Chinese invention patent, "A Solar Ceramic Sintering Furnace and Temperature Control Method Thereof" (CN115247963A), achieves solar sintering of workpieces by irradiating the focused area of a solar concentrator or its divergent light onto the workpiece within the furnace body. The furnace body's light opening is located at the same level as the solar concentrator's focused area, and a movable device is used to adjust the furnace body's relative distance to the focused area to adjust the workpiece's heating temperature. The furnace body uses a refractory material with a low thermal conductivity as insulation, though the specific material is not disclosed. The Spanish paper "Solar sintering of aluminaceramics: Microstructural development" (Román R, Canadas I, Rodriguez J, et al. Solar sintering of alumina ceramics: Microstructural development[J]. Solar Energy, 2008, 82(10): 893-902) uses a PSA-CIEMAT solar furnace to prepare alumina ceramics. This solar furnace uses a concentrator to irradiate sunlight onto alumina ceramic samples, achieving concentrated sintering of the alumina ceramic samples. The furnace uses alumina ceramic fibers as the furnace insulation material, and porous zirconia ceramics as the furnace protection material. However, the solar sintering furnace designs in the above-mentioned literature mostly use conventional refractory materials, which lack heat storage capacity, making it difficult to maintain a stable temperature in the furnace. This defect is particularly prominent under conditions of insufficient or intermittent light (such as rainy days), making it impossible to ensure continuous and stable sintering of ceramic samples, limiting the practical application of solar sintering technology. To address the issue of continuous and stable sintering in solar furnaces, the Chinese invention patent, "A Solar Kiln for Firing Ceramics" (CN111521014A), uses a heat transfer conduit connected to the heat collector and heat exchanger of the solar concentrator to transfer heat to the kiln chamber. A fan is connected to one side of the kiln chamber via the heat transfer conduit, and the fan is connected to the heat collector and heat exchanger via a circulation pipe to achieve the firing of ceramic samples. The kiln uses ordinary refractory bricks as the furnace insulation material. While this heat exchange method solves the problem of continuous sample sintering to a certain extent, it significantly reduces the utilization rate of sunlight.

[0004] In addition, the furnace chamber of the solar furnace in existing literature mostly adopts a single sample fixed sintering mode, which makes the ceramics prone to cracking during the solar-driven sintering process due to the uneven temperature field distribution on the front and back of the sample irradiated by sunlight, thereby reducing the yield; at the same time, it is impossible to ensure the simultaneous sintering of multiple ceramic samples, which greatly reduces the production efficiency of the samples. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned technical deficiencies and provide a ceramic sheet, a ceramic furnace, a concentrating solar high-temperature furnace and a preparation method thereof, so as to solve the technical problem in the prior art that the temperature in the furnace of the solar sintering furnace body is difficult to maintain stably, resulting in the inability to ensure continuous and stable sintering of ceramic samples.

[0006] In order to achieve the above technical objectives, the technical solution provided by the present invention is: In a first aspect, the present invention provides a ceramic sheet, the raw materials of which include a basic component and an added component; in terms of mass percentage, the basic component includes 80-96% aluminum oxide and 4-20% kaolin; the added component includes 1-3% titanium oxide, 1-6% zirconium oxide, 5-11% iron oxide and 1-7% copper oxide, accounting for 1-3% of the total mass of the basic component.

[0007] In a second aspect, the present invention provides a method for preparing a ceramic sheet, comprising the following steps: mixing a basic component and an additional component with water and granulating the mixture to obtain a sheet-like green body; sintering the sheet-like green body at 1400-1500° C. and cooling the mixture to obtain a ceramic sheet.

[0008] In a third aspect, the present invention provides a ceramic furnace, which includes a furnace body and a furnace door installed on the furnace body; the furnace body is obtained by bonding the above-mentioned ceramic sheets with an adhesive; and the furnace door is made of the above-mentioned ceramic sheets.

[0009] In a fourth aspect, the present invention provides a concentrating solar high-temperature furnace, comprising a concentrating unit and a sintering unit, wherein the sintering unit comprises the above-mentioned ceramic furnace chamber; a light inlet is provided on the ceramic furnace chamber, and heat-resistant glass is installed on the light inlet; a loading platform is provided in the ceramic furnace chamber; the concentrating unit is used to concentrate sunlight and irradiate it onto the loading platform through the light inlet.

[0010] Compared with the prior art, the present invention has the following beneficial effects: The present invention controls the ratio of aluminum oxide and kaolin and adjusts the crystal phase composition to obtain high-strength ceramic sheets; by adding zirconium oxide, stress concentration at the crack tip is alleviated, thereby preventing crack propagation and improving the thermal shock resistance, density and toughness of the ceramic sheets; by adding titanium oxide and iron oxide, the light absorption effect of the ceramic sheets in the near-infrared band is improved; by adding copper oxide, the light absorption effect of the ceramic sheets in the ultraviolet and visible light bands is improved, so that the obtained ceramic sheets have good heat absorption and storage functions. When the ceramic sheets are made into a ceramic furnace and assembled into a concentrating solar high-temperature furnace and used for sintering ceramic samples, continuous and stable sintering of the ceramic samples can be guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a diagram of the concentrating solar high-temperature furnace system of the present invention; Figure 2 This is a schematic diagram of the partial structure of the concentrating solar high-temperature furnace of the present invention; Figure 3 It is a structural schematic diagram of the quadrangular pyramid rotating platform of the present invention; Among them, 1- focusing unit, 101- primary reflector, 102- focusing secondary reflector; 2- sintering unit, 201- ceramic furnace, 202- light inlet, 203- furnace door, 204- thermocouple, 205- stage, 2051- quadrangular pyramid rotating stage, 2052- rotating axis, 206- lifting platform, 207- track; 3- control unit; 4- ceramic sample; Figure 4 This is the ceramic firing curve of the high-temperature furnace for directly firing architectural ceramics using concentrated solar energy according to the present invention; Figure 5 It is the reflectivity spectrum of the black corundum furnace of the present invention; Figure 6 This is a cross-sectional SEM image of the black corundum furnace ceramic piece of the present invention; Figure 7 This is the XRD diagram of the black corundum furnace ceramic piece of the present invention. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0013] In existing technologies, most solar sintering furnace designs use conventional refractory materials, which lack heat storage capacity, making it difficult to maintain a stable temperature in the furnace. This defect is particularly prominent under conditions of insufficient or intermittent lighting (such as rainy days), making it impossible to ensure the continuous and stable sintering of ceramic samples, limiting the practical application of solar sintering technology. In addition, the furnaces of existing solar furnaces mostly use a single sample fixed sintering mode, which makes the ceramics prone to cracking during the solar-driven sintering process due to the uneven temperature field distribution on the front and back of the sample exposed to sunlight, thereby reducing the yield rate. At the same time, it is impossible to ensure the simultaneous sintering of multiple ceramic samples, which greatly reduces the production efficiency of the samples.

[0014] In view of this, the present invention provides a ceramic sheet, a ceramic furnace, a concentrating solar high-temperature furnace and a preparation method thereof. The special black corundum ceramic material is used to make the solar ceramic furnace have the heat absorption and storage function. After being assembled into a concentrating solar high-temperature furnace, it can be directly fired into building ceramics, and the continuous and stable sintering of ceramic samples is guaranteed.

[0015] In a first aspect, the present invention provides a ceramic sheet, the raw materials of which include a basic component and an added component; in terms of mass percentage, the basic component includes 80-96% aluminum oxide and 4-20% kaolin; the added component includes 1-3% titanium oxide, 1-6% zirconium oxide, 5-11% iron oxide and 1-7% copper oxide, accounting for 1-3% of the total mass of the basic component.

[0016] Preferably, the crystalline phase of the ceramic sheet includes 47.0 to 87.7 wt % of corundum, 4.6 to 32.0 wt % of mullite, 0.8 to 7.2 wt % of zirconium oxide, and 1.1 to 5.0 wt % of iron titanate.

[0017] Preferably, the basic components include 81.03-95.92% of α-Al2O3 and 4.08-18.97% of Longyan kaolin, calculated by mass percentage.

[0018] In order to save costs, industrial grade α-Al2O3 can be used.

[0019] In the present invention, the ratio of α-Al2O3 to Longyan kaolin is designed to be related to the ratio of corundum / mullite crystal phases. By controlling the ratio of corundum / mullite crystal phases, the strength of the sample matrix is optimized. In order to improve the thermal shock resistance of the corundum-mullite composite ceramic, 1-6wt% of zirconium oxide is added to the sample. When zirconium oxide undergoes a martensitic phase transformation in the ceramic, it will produce volume expansion and microcracks. These microcracks can absorb energy, reduce stress concentration at the crack tip, and thus prevent crack propagation. At the same time, their diffuse distribution can also improve the density and toughness of the ceramic. The addition of 1-3wt% of titanium oxide and 5-11wt% of iron oxide can produce lattice distortion in the corundum-based ceramic, thereby causing vibration absorption and improving the light absorption effect of the sample in the near-infrared band (750 to 2500nm). The addition of 1-7wt% of copper oxide can improve the light absorption effect of the sample in the ultraviolet and visible light bands (300 to 750nm). Finally, a composite ceramic is formed in black corundum with corundum as the main crystal phase and mullite, zirconia and iron titanate as the secondary crystal phases.

[0020] In a second aspect, the present invention provides a method for preparing a ceramic sheet, comprising the following steps: mixing a basic component and an additional component with water and granulating the mixture to obtain a sheet-like green body; sintering the sheet-like green body at 1400-1500° C. and cooling the mixture to obtain a ceramic sheet.

[0021] The amount of water added to the basic components and the additional components is based on the ability to successfully granulate.

[0022] Preferably, the sintering time is 3 to 5 hours.

[0023] Preferably, the heating rate of the sheet green body from room temperature to 1000°C is 5-8°C / min, and the heating rate from 1000°C to 1400-1500°C is 3-5°C / min; the cooling rate from 1400-1500°C to 1200°C is 5-8°C / min, and it is furnace cooled from 1200°C to room temperature; wherein, when the temperature is less than 1000°C, the heat preservation time is 20-30 minutes for each 100°C, and when the temperature is ≥1000°C, the heat preservation time is 30-60 minutes for each 100°C. When preparing the furnace body (ceramic sheet) of the ceramic furnace of the present invention, the heating process (raising the temperature from room temperature to 1400-1500°C), the insulation process (insulating at 1400-1500°C for 3-5 hours) and the cooling process (maximum temperature to 1200°C, and then from 1200°C to room temperature) are controlled in stages to control the heating and cooling rates, and to control the insulation temperature and insulation time to ensure the structural stability and performance optimization of the ceramics in different temperature ranges, effectively reduce thermal stress and defects, and improve the quality of the ceramics.

[0024] In a third aspect, the present invention provides a ceramic furnace, which includes a furnace body and a furnace door installed on the furnace body; the furnace body is obtained by bonding the above-mentioned ceramic sheets with an adhesive; and the furnace door is made of the above-mentioned ceramic sheets.

[0025] Preferably, the binder is a composite high-temperature binder of aluminum dihydrogen phosphate-alumina-silicon powder; the ceramic sheets are bonded with the binder to obtain a ceramic furnace, specifically comprising: applying the binder on the edges of the ceramic sheets and splicing and fixing them into a furnace main frame, and sintering them directly or with the sample to obtain the furnace main body.

[0026] In the present invention, the ceramic sheets are bonded with an adhesive to avoid the defect of stress concentration caused by direct one-time molding of the ceramic furnace. It can be understood that the amount of adhesive used is relatively small, and it can be sintered conventionally or directly sintered together with the ceramic sample to be sintered.

[0027] Further preferably, the binder comprises 20-30 wt% aluminum dihydrogen phosphate, 15-20 wt% β-Al2O3, 16-20 wt% silicon powder, and 30-44 wt% deionized water. In the present invention, square black corundum ceramic sheets are bonded with a high-temperature adhesive to form a furnace material. The size of the resulting ceramic furnace can be adjusted as needed, for example, with a side length of 120-150 mm and a wall thickness of 10-15 mm.

[0028] In a fourth aspect, the present invention provides a concentrating solar high-temperature furnace, comprising a concentrating unit and a sintering unit, wherein the sintering unit comprises the above-mentioned ceramic furnace chamber; a light inlet and a sample inlet are provided on the ceramic furnace chamber, heat-resistant glass is installed on the light inlet, and a furnace door is installed on the sample inlet; a loading platform is provided in the ceramic furnace chamber; the concentrating unit is used to concentrate sunlight and irradiate it onto the loading platform through the light inlet.

[0029] Preferably, the heat-resistant glass is double-layer quartz glass.

[0030] More preferably, the long-term use temperature of the double-layer quartz glass is 1100-1300°C, and the short-term use temperature is 1500-1550°C; the average light transmittance is greater than 90%, and the thermal expansion coefficient is 5.1-5.4×10 -7 / ℃, thermal conductivity is 1.4~2.1W·(m·K) -1 , the softening point is 1683 ~ 1754 ° C. Among them, long-term means that the quartz glass can maintain stable performance after working for more than 500 hours, and short-term means the working time is less than 500h.

[0031] Further preferably, the interlayer distance of the double-layer quartz glass is 2 to 10 mm, and a filter is installed in the interlayer.

[0032] More preferably, the filters include a red light filter (622-760 nm), a green light filter (492-577 nm), a blue light filter (450-492 nm), a full spectrum filter (350-2500 nm), and the like.

[0033] Preferably, the focusing unit includes a primary reflector and a focusing secondary reflector, the primary reflector is a plane mirror and is used to reflect sunlight to the focusing secondary reflector; the focusing secondary reflector is a concave mirror, which is used to focus sunlight and then irradiate it onto the stage through the light inlet.

[0034] Preferably, the stage includes a rotating shaft and a pyramidal rotating platform for placing the sample to be sintered. The lower end of the rotating shaft passes through the bottom of the ceramic furnace and is connected to the power device. The pyramidal rotating platform is made of four equilateral triangular silicon carbide ceramic sheets bonded to a square silicon carbide ceramic sheet via a binder. The side lengths and rotational speed of the pyramidal rotating platform can be selected as needed, for example, with each side length being 90 to 100 mm to form a regular square pyramid. The rotational speed can be 0 to 30 rpm. The binder used here is also a composite high-temperature binder of aluminum dihydrogen phosphate, aluminum oxide, and silicon powder.

[0035] During the process of using solar energy to sinter ceramics, multiple ceramic samples are tightly attached to the four sides of a tetrahedral turntable, which rotates at a constant speed to achieve uniform and synchronous sintering of multiple samples. Thanks to the high thermal conductivity of silicon carbide, the temperature difference between the front and back of the ceramic samples is significantly reduced, effectively avoiding the delamination and cracking caused by uneven thermal stress between the sunlight-irradiated side and the back, ensuring a uniform and efficient sintering process for the ceramic samples.

[0036] More preferably, the thermal conductivity of the silicon carbide ceramic sheet is 71 to 95 W·(m·K) -1 .

[0037] Preferably, a temperature measuring device for measuring the temperature inside the ceramic furnace is also installed on the ceramic furnace. The temperature measuring device is connected to a control unit, and the control unit is used to regulate the position of the ceramic furnace, the temperature inside the ceramic furnace, and the rotation rate of the carrier.

[0038] It is understandable that the temperature measuring device can use a thermocouple; in order to better focus and regulate the temperature, a necessary lifting platform can be set at the bottom of the ceramic furnace, and by adjusting the reflector in the focusing unit or adjusting the height of the ceramic furnace, the focused sunlight can be irradiated onto the stage through the light inlet.

[0039] Specifically, see Figure 1 and Figure 2 The concentrating solar high-temperature furnace of the present invention includes a concentrating unit 1, a sintering unit 2 and a control unit 3; the concentrating unit 1 includes a primary reflector 101 and a concentrating secondary reflector 102; the sintering unit 2 includes a ceramic furnace 201, and a light inlet 202 and a sample inlet are provided on the ceramic furnace 201, heat-resistant glass is installed on the light inlet 202, and a furnace door 203 is installed at the sample inlet.

[0040] A thermocouple 204 is also installed on the ceramic furnace 201 for measuring the internal temperature thereof to facilitate real-time temperature control.

[0041] See also Figure 2 and Figure 3 A loading platform 205 is installed inside the ceramic furnace 201. The loading platform 205 includes a connected quadrangular pyramid rotating platform 2051 and a rotating shaft 2052. The conical surface of the quadrangular pyramid rotating platform 2051 is used to place the ceramic sample 4 to be sintered; the lower end of the rotating shaft 2052 passes through the bottom of the ceramic furnace 201 and is connected to the rotating motor.

[0042] The ceramic furnace 201 is installed on a lifting platform 206, and the lifting platform 206 is installed on a horizontal track 207. The ceramic furnace 201 can be translated and raised and lowered by the lifting platform 206 and the track 207.

[0043] The control unit 3 includes the necessary control electrical box; the control unit 3 is mainly used to regulate the position of the ceramic furnace 201, the temperature inside the ceramic furnace 201 and the rotation rate of the tetrahedral rotating platform 2051. There are many specific implementation methods and they are relatively conventional, so no specific limitations are given here.

[0044] The present invention has the following advantages: (1) The present invention designs and manufactures a ceramic furnace: the ceramic furnace is mainly composed of ceramic sheets, the main crystal phase of the ceramic sheets is black corundum (i.e., black corundum ceramic material), and the black corundum ceramic has a high solar light absorption rate and a high surface roughness, ensuring that the furnace can effectively absorb the light source energy during the solar sintering process; at the same time, the black corundum ceramic furnace has excellent heat storage capacity and can effectively store the absorbed light source energy; thereby ensuring that the furnace can efficiently absorb and store the light source energy during the solar sintering process, thereby maintaining the temperature in the furnace stable under insufficient light or intermittent light conditions (such as rainy days), reducing the impact of temperature fluctuations on the quality of ceramics, and ensuring a continuous and stable sintering process for ceramic samples.

[0045] (2) The present invention designs and manufactures a silicon carbide tetrahedral pyramid turntable: a tetrahedral pyramid turntable is provided inside the ceramic furnace of the concentrating solar high-temperature furnace for placing ceramic samples to be sintered. The tetrahedral pyramid turntable is made of silicon carbide with high thermal conductivity. At the same time, a rotating motor is connected to the lower part of the turntable. The rotating motor can adjust the speed according to user needs to ensure the synchronous sintering of multiple ceramic samples. By the uniform rotation of the tetrahedral pyramid turntable, each ceramic sample is ensured to be heated evenly during the sintering process, effectively avoiding the problem of sample cracking caused by uneven temperature field distribution. In addition, the silicon carbide tetrahedral pyramid turntable can sinter the back of the ceramic sample during the solar sintering process, and the uniform temperature distribution avoids the delamination and cracking of the sample caused by thermal stress between the side facing the sun and the side facing away from the sun during the sintering process.

[0046] (3) The light inlet adopts a double-layer quartz glass: the double-layer quartz glass has a certain heat preservation effect, which prevents the ceramic sample from cracking due to rapid cooling during sintering and cooling; at the same time, the middle layer in the double-layer quartz glass can be set with high-temperature resistant filters of different wavelengths to realize the preparation of different types of building ceramic samples with different wavelengths of sunlight such as ultraviolet, visible light, and near-infrared. Users can choose different wavelengths of light spots such as ultraviolet, visible light, and near-infrared to burn different types of building ceramic samples according to their needs.

[0047] Therefore, the present invention adopts a special black corundum with heat absorption and storage function as the furnace; in the process of solar sintering ceramics, sunlight enters the furnace through the light inlet, and the black corundum furnace can effectively absorb the energy of the light source. Part of the energy is released as heat energy, and the other part is stored as the internal energy of the furnace, so as to ensure that the temperature in the furnace can be kept stable under insufficient light or intermittent light conditions (such as rainy days), ensuring a continuous and stable sintering process of the ceramic sample. The mechanism is that the ceramic furnace converts solar energy into lattice vibration energy storage when absorbing heat through the high specific heat capacity and heat storage density of the black corundum composite ceramic. When the ambient temperature drops, the stored heat energy is slowly released through lattice heat conduction and infrared radiation to maintain the furnace temperature stable; thus, the high-temperature furnace has outstanding heat storage performance, which can ensure the continuous and stable sintering of ceramic samples; through the design of the silicon carbide tetrahedral turntable, multiple ceramic samples are close to the side of the turntable, and uniform rotation is used to achieve uniform and synchronous sintering of multiple samples, so that the high-temperature furnace has the characteristics of better uniform sintering of ceramic samples, which can avoid the occurrence of cracking of ceramic samples during the sintering process; and a double-layer quartz glass with a filter is set at the light inlet of the furnace body to achieve the regulation of sunlight of different wavelengths. The present invention solves the problems of sintering interruption caused by insufficient heat storage, sample cracking caused by uneven temperature field distribution, and difficulty in synchronous sintering of multiple samples in the prior art, thereby providing a new type of solar ceramic high-temperature furnace.

[0048] The solar light absorption rate of the black corundum ceramic hearth obtained by the present invention was 90-95% as measured by an ultraviolet-visible spectrophotometer, and the roughness was 51-85 μm as measured by an optical profilometer. The flexural strength of the black corundum ceramic hearth (measured by an electronic universal testing machine) was 164.77-238.54 MPa, and the room temperature thermal conductivity (measured by a laser thermal conductivity meter) was 10.87-16.78 W·(m·K). -1 Specific heat capacity (measured by microcalorimetry) is 1.26~1.45J·(g·K) -1 (1000℃), heat storage density is 1233.49~1481.12kJ·kg -1 After 30 thermal shock tests (1000°C), the flexural strength of the black corundum ceramic furnace samples was 173.43-267.63 MPa (an increase of 0.55-1.56% compared to before the thermal shock), and the absorption rate was 91.9-92.1% (a decrease of 1.9-2.9% compared to before the thermal shock).

[0049] The firing temperature range of the concentrating solar high-temperature furnace obtained by the present invention is 1000-1400°C, preferably 1000-1300°C, and the continuous stable sintering time can be up to 5 hours. A stepped heat preservation firing curve is used for segmented temperature control and precise heat preservation to ensure that the ceramic samples are fully sintered and have a uniform structure. The furnace temperature uniformity index (TUI) detected by an infrared thermal imager is ≤18°C, which is better than the 40-60°C of traditional kilns; due to the presence of a high thermal conductivity silicon carbide tetrahedral rotating table, the temperature difference between the ceramic sample facing the sunlight and the back facing the sunlight during the sintering process is ≤30°C, which greatly reduces the phenomenon of ceramic sample delamination and cracking; the prepared architectural ceramic samples do not crack and have excellent physical properties, with a volume density of 3.0-3.5g / cm 3 The porosity is 0.1-0.2%, the water absorption is 0.09-0.16%, and the flexural strength is 98-121 MPa; the test results show that the performance of the architectural ceramic samples prepared using the concentrating solar high-temperature furnace of the present invention meets the industry standard of "Ceramic Rock Plate" (T / CBCSA 40-2021).

[0050] The present invention will be further described in detail below through specific embodiments. To avoid redundancy, some of the same components used are described here: the silicon carbide quadrangular pyramid turntable: It is made of four equilateral triangles (side length: 100 mm) and one square (side length: 100 mm) silicon carbide ceramic sheets bonded together with a high-temperature adhesive; the thermal conductivity of silicon carbide is 95W·(m·K). -1 The rotating table speed is 15 rpm. Characteristics of double-layer quartz glass: Long-term operating temperature is 1300°C, and short-term operating temperature is up to 1550°C. The interlayer distance of the double-layer quartz glass is 5 mm. The average light transmittance of the double-layer quartz glass is 95%, and the thermal expansion coefficient is 5.1×10 -7 / °C, thermal conductivity is 1.4W·(m·K) -1 , the softening point is 1754°C.

[0051] Example 1 A concentrating solar high-temperature furnace comprises the following steps: S1, black corundum ceramic sheet: S101, using 85.77 wt% industrial-grade α-Al2O3 and 14.23 wt% Longyan kaolin as raw materials, and adding 2 wt% titanium oxide, 5 wt% zirconium oxide, 7 wt% iron oxide, and 5 wt% copper oxide, and uniformly mixing to obtain a mixture; adding water to the mixture to granulate (to form balls), and then forming a sheet-like green body; a light inlet and a sample inlet are reserved on the sheet-like green body; S102, the sheet-like green body is sintered and cooled to obtain a ceramic sheet, wherein the sintering and cooling include: Heating process: from room temperature to 1450°C; holding process: holding at 1450°C for 2 hours; cooling process: from maximum temperature to 1200°C and then from 1200°C to room temperature; from 1200°C to room temperature, furnace cooling is used. Heating and cooling rates are 5°C / min (room temperature - 1000°C), 3°C / min (1000 - maximum temperature), and 5°C / min (maximum temperature - 1200°C), respectively. When the temperature is less than 1000°C, the holding time is 30 minutes per 100°C; when the temperature is ≥1000°C, the holding time is 60 minutes per 100°C.

[0052] The black corundum ceramic furnace is constructed from square black corundum ceramic sheets of the same size (150 mm side length, 13 mm thickness) bonded together with a high-temperature adhesive. The adhesive is a composite high-temperature adhesive of aluminum dihydrogen phosphate, alumina, and silicon fume, comprising 20 wt% aluminum dihydrogen phosphate, 20 wt% β-Al₂O₃, 20 wt% silicon fume, and 40 wt% deionized water.

[0053] S2, apply the adhesive on the edge of the ceramic sheet and splice and fix it into the main frame of the furnace, assemble the remaining components into a concentrating solar high-temperature furnace, and place the building ceramic sample to be sintered (the building ceramic sample is composed of 45% quartz sand, 25% potassium feldspar, 20% kaolin, 8% calcium carbonate, 2% iron oxide and 1.5% zinc oxide, and forms a quartz-mullite main crystal phase structure after sintering) on the four cone surfaces of the tetrahedral turntable. The rotation speed of the tetrahedral turntable is 15 r / min, and the sintering is carried out at 1250°C for 1 hour to obtain the building ceramic sample.

[0054] The concentrating solar high temperature furnace of the present invention is Figure 4 The sintering curve shown in the figure is heated, and the actual test value of the temperature in the furnace is basically the same as the set value. This shows that the concentrating solar high-temperature furnace of the present invention can control the temperature in sections and accurately keep the temperature, ensuring that the ceramic samples are fully sintered and have a uniform structure.

[0055] The solar light absorption rate of the black corundum ceramic furnace obtained in this embodiment was 94% as measured by UV-visible spectrophotometer (see Figure 5 The surface roughness of the sample measured by an optical profilometer is 55μm. The flexural strength (tested by an electronic universal testing machine), room temperature thermal conductivity (tested by a laser thermal conductivity meter), specific heat capacity (tested by a microcalorimeter), and heat storage density of the black corundum ceramic furnace are 238.54MPa and 16.78W·(m·K), respectively. -1 , 1.26 J·(g·K) -1 (1000℃), and 1233.49 kJ·kg -1After 30 thermal shock tests (1000°C), the flexural strength of the black corundum ceramic sample was 242.26 MPa (an increase of 1.56% compared to before the thermal shock), and the absorption rate was 92.1% (a decrease of 2.9% compared to before the thermal shock).

[0056] The cross-sectional SEM image of the ceramic piece of the black corundum ceramic furnace obtained in this embodiment is as follows: Figure 6 As shown, the XRD pattern is Figure 7 As shown by Figure 6 and Figure 7 It can be seen that the ceramic sheet of the black corundum ceramic furnace of the present invention is a composite ceramic with corundum as the main crystal phase and mullite, zirconia and iron titanate as the secondary crystal phases, including 70.1wt% corundum, 22.1wt% mullite, 5.0wt% zirconia and 2.8wt% iron titanate.

[0057] After testing, the concentrating solar high temperature furnace of this embodiment (see Figure 1-Figure 3 ) The temperature range in which it can stably operate is 1000-1400℃, and the continuous stable sintering time can be up to 5h. The temperature uniformity index (TUI) of the furnace detected by infrared thermal imager is 11℃, which is better than the 40-60℃ of traditional kilns. Due to the presence of high thermal conductivity silicon carbide quadrangular pyramid turntable, the temperature difference between the ceramic samples facing the sunlight and facing away from the sunlight during the sintering process is ≤30℃, which greatly reduces the delamination and cracking of the ceramic samples.

[0058] The four architectural ceramic samples prepared in this example did not crack and had excellent physical properties. The architectural ceramic sample with the best performance had a volume density of 3.5 g / cm 3 The porosity is 0.16%, the water absorption is 0.09%, and the flexural strength is 121 MPa; the test results show that the performance of the architectural ceramic samples prepared using the concentrating solar high-temperature furnace of the present invention meets the industry standard of "Ceramic Rock Plate" (T / CBCSA 40-2021).

[0059] Comparative Example 1 Compared with Example 1, the only difference is that the additives of the black corundum ceramic furnace are adjusted to 2wt% titanium oxide and 5wt% zirconium oxide, and iron oxide and copper oxide are removed. Other steps and conditions are the same as those in Example 1.

[0060] Compared with Example 1, in the case where other steps and conditions are the same as those in Example 1, the additives of the black corundum ceramic hearth in Comparative Example 1 are set to 2wt% titanium oxide and 5wt% zirconium oxide. The solar absorption rate of the prepared black corundum ceramic hearth is only 32% (see Figure 5), which greatly reduces the light absorption rate of the high-temperature furnace hearth, resulting in a narrower firing temperature range of the concentrated solar high-temperature furnace, a shorter continuous and stable sintering time, and an increased uniformity index of the hearth; which in turn causes the volume density and flexural strength of the prepared architectural ceramic samples to decrease, and the porosity and water absorption to increase.

[0061] The test results show that the firing temperature range of the high-temperature furnace obtained in this comparative example is 700-800°C, the continuous stable sintering time is less than 0.5h, and the furnace uniformity index (TUI) is 127°C; the best performance sample among the four architectural ceramic samples prepared has a bulk density of 2.1g / cm 3 , porosity of 6.54%, water absorption of 4.67%, and flexural strength of 42.1 MPa. The test results show that the performance of the architectural ceramic samples prepared using the concentrating solar high-temperature furnace designed and manufactured in Comparative Example 1 cannot meet the industry standard for "Ceramic Rock Plate" (T / CBCSA 40-2021).

[0062] Comparative Example 2 Compared with Example 1, the only difference is that the silicon carbide quadrangular pyramid rotating platform is removed, and the other steps and conditions are the same as those in Example 1.

[0063] Compared to Example 1, Comparative Example 2, with the other steps and conditions remaining the same as Example 1, removed the silicon carbide quadrangular pyramid turntable. The resulting high-temperature furnace, lacking a high-thermal-conductivity turntable, significantly reduced the efficiency of producing architectural ceramic samples. Furthermore, the resulting architectural ceramic samples exhibited significant delamination and cracking due to the significant temperature difference between the front and back surfaces relative to the light source, significantly reducing the sample yield.

[0064] After testing, the architectural ceramic samples prepared by the high-temperature furnace in this comparative example had obvious cracking phenomenon, among which the architectural ceramic sample with the best performance had a volume density of 2.0g / cm 3 , the porosity is 5.74%, the water absorption rate is 3.72%, and the flexural strength is 48.7MPa; the test results show that the performance of the building ceramic samples prepared by using the concentrated solar energy direct firing building ceramic high-temperature furnace designed and manufactured in Comparative Example 2 cannot meet the industry standard of "Ceramic Rock Plate" (T / CBCSA 40-2021).

[0065] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A ceramic sheet, characterized in that: The raw materials of the ceramic sheet include a basic component and an additional component; in terms of mass percentage, the basic component includes 80-96% alumina and 4-20% kaolin; The added components include 1-3% of titanium oxide, 1-6% of zirconium oxide, 5-11% of iron oxide and 1-7% of copper oxide, accounting for 1-3% of the total mass of the basic components.

2. The ceramic sheet according to claim 1, wherein The crystal phase of the ceramic sheet includes 47.0-87.7 wt % of corundum, 4.6-32.0 wt % of mullite, 0.8-7.2 wt % of zirconium oxide, and 1.1-5.0 wt % of iron titanate.

3. The ceramic sheet according to claim 1, wherein Calculated by mass percentage, the basic components include 81.03-95.92% of α-Al2O3 and 4.08-18.97% of Longyan kaolin.

4. The method for preparing a ceramic sheet according to any one of claims 1 to 3, wherein: The following steps are involved: The basic component and the additional component are mixed with water and then granulated to obtain a sheet-like green body; The sheet-like green body is sintered at 1400-1500° C. and then cooled to obtain a ceramic sheet.

5. The method for preparing a ceramic sheet according to claim 4, wherein: The sintering time is 3 to 5 hours; and / or, The sintering conditions also include: the heating rate of the sheet green body from room temperature to 1000°C is 5-8°C / min, and the heating rate from 1000°C to 1400-1500°C is 3-5°C / min; the cooling rate from 1400-1500°C to 1200°C is 5-8°C / min, and the sheet green body is cooled from 1200°C to room temperature with the furnace; wherein, when the temperature is less than 1000°C, the temperature is kept for 20-30 minutes for each 100°C, and when the temperature is 1000≤°C and less than 1400°C, the temperature is kept for 30-60 minutes for each 100°C.

6. A ceramic furnace, characterized in that: The ceramic furnace comprises a furnace body and a furnace door mounted on the furnace body; The furnace body is obtained by bonding the ceramic sheets according to any one of claims 1 to 3 with a binder; The furnace door is made of the ceramic sheet according to any one of claims 1 to 3.

7. The ceramic furnace according to claim 6, characterized in that: Calculated by mass percentage, the components of the binder include 20-30% aluminum dihydrogen phosphate, 15-20% β-Al2O3, 16-20% silicon powder, and 30-44% deionized water.

8. A concentrating solar high temperature furnace, characterized in that: It includes a focusing unit and a sintering unit, wherein, The sintering unit comprises the ceramic furnace according to any one of claims 6 to 7; A light inlet is provided on the ceramic furnace, and heat-resistant glass is installed on the light inlet; A loading platform is provided in the ceramic furnace; The focusing unit is used to focus sunlight and irradiate the sunlight onto the stage through the light inlet.

9. The concentrated solar high temperature furnace according to claim 8, characterized in that: The heat-resistant glass is double-layer quartz glass; The double-layer quartz glass has a long-term operating temperature of 1100-1300°C when the working time is ≥500h, and a short-term operating temperature of 1500-1550°C when the working time is <500h; the average light transmittance is >90%, and the thermal expansion coefficient is 5.1-5.4×10 -7 / ℃, thermal conductivity is 1.4~2.1W·(m·K) -1 , softening point is 1683~1754℃; The interlayer distance of the double-layer quartz glass is 2 to 10 mm, and a filter is installed in the interlayer. The filter includes one or more of a red light filter, a green light filter, a blue light filter and a full-spectrum filter.

10. The concentrated solar high temperature furnace according to claim 8, characterized in that: The focusing unit includes a primary reflector and a secondary focusing reflector, wherein the primary reflector is a plane mirror and is used to reflect sunlight to the secondary focusing reflector; the secondary focusing reflector is a concave mirror and is used to focus sunlight and then irradiate the sunlight onto the stage through the light inlet; and / or, The stage includes a connected rotating shaft and a quadrangular pyramid rotating platform for placing the sample to be sintered. The lower end of the rotating shaft passes through the bottom of the ceramic furnace and is connected to the power device. The quadrangular pyramid rotating platform is made of four equilateral triangular silicon carbide ceramic pieces and a square silicon carbide ceramic piece bonded by a binder. The thermal conductivity of the silicon carbide ceramic sheet is 71 to 95 W·(m·K) -1 ; The ceramic furnace is also equipped with a temperature measuring device for measuring the temperature inside the furnace. The temperature measuring device is connected to a control unit, which is used to regulate the position of the ceramic furnace, the temperature inside the ceramic furnace, and the rotation rate of the carrier.

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