ZnO modified CaO-Al2O3-SiO2 system ceramic rock plate and preparation method thereof

Abstract

This invention provides a ZnO-modified CaO-Al2O3-SiO2 system ceramic slab and its preparation method. The preparation method introduces ZnO as a light absorber into the green body powder, combined with the rapid heating characteristics of a concentrating solar furnace and a rotary sintering process, which significantly reduces the firing temperature while maintaining excellent flexural strength. The ZnO light absorber effectively improves the absorption efficiency of solar energy by the green body, making the sintering temperature much lower than that of traditional electric furnaces. The two-stage heat preservation process promotes the uniform precipitation and growth of anorthite and corundum crystal phases. The regulating effect of anorthite on the coefficient of thermal expansion and the pinning toughening effect of corundum particles work synergistically to fundamentally suppress the microcrack problem caused by the mismatch of the coefficient of thermal expansion, so that the room temperature flexural strength of the ceramic slab can reach 90-102 MPa, which is superior to the level of existing similar products.

Description

Technical Field

[0001] This invention relates to the field of green preparation technology of ceramic materials, and in particular to a ZnO-modified CaO-Al2O3-SiO2 system ceramic slab and its preparation method. Background Technology

[0002] With the increasing consumption of fossil fuels and the growing prominence of global warming, utilizing solar energy to fire ceramics holds significant strategic importance and environmental value under the strategic framework of "carbon peaking and carbon neutrality." CaO-Al2O3-SiO2 system ceramic slabs primarily utilize solid waste and low-grade raw materials, resulting in low raw material costs and broad application prospects. However, this system has a high calcium content and a large coefficient of thermal expansion, making its microstructure prone to cracking during firing, which restricts its large-scale application.

[0003] Extensive research has been conducted in this field to address the cracking problem of CaO-Al2O3-SiO2 system ceramic slabs. Patent document CN107352967B discloses a large ceramic slab and its manufacturing method, which suppresses cracking by controlling the mass ratios of CaO / MgO and SiO2 / CaO, and mitigates cracking caused by molding deformation by introducing wollastonite to obtain an elastic sintered body. Patent document CN114262218B discloses a method for preparing high-performance ceramic slabs, using talc, wollastonite, washed clay, lithium porcelain stone, and potassium feldspar as main raw materials. Addressing the technical challenge of cracking caused by mismatched thermal expansion coefficients, it reduces the difference in thermal expansion coefficients between the crystalline and glassy phases by increasing the calcium feldspar content, and solves the cracking problem by controlling the crystalline phase ratio. The firing temperature of this ceramic slab is 1190–1230℃, and its flexural strength is 85.23–88.93 MPa. Patent document CN115304352B discloses a green body formula for ceramic slabs, which uses coal gangue combustion ash as the main raw material and suppresses crack generation by improving the toughness and flexural strength of the green body.

[0004] In summary, existing technologies mainly enhance the toughened matrix by adjusting the raw material ratio, optimizing the crystal phase composition, or improving the matrix toughness, thereby suppressing crack formation. However, none of these methods fundamentally solve the problem of microcracks caused by the mismatch of thermal expansion coefficients, and the thermal shock resistance and mechanical properties of ceramic slabs still need further improvement. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a ZnO-modified CaO-Al2O3-SiO2 system ceramic slab and its preparation method, thereby solving the technical problems of existing CaO-Al2O3-SiO2 system ceramic slabs, such as slab cracking, high firing temperature, low flexural strength, and large environmental pollution.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a ZnO-modified CaO-Al2O3-SiO2 system ceramic slab, comprising the following steps: S10, the green powder and zinc oxide light absorber are mixed at a mass ratio of 100:(5~7), and then ball-milled to obtain a mixed powder; S20, add a binder to the mixed powder and granulate it to obtain a blank; S30 involves pressing the blank into shape and drying it to obtain a ceramic blank. S40, the ceramic blank is placed in a concentrating solar furnace and sintered by rotation in a wide firing temperature range of 1060 to 1100℃ for 30 to 50 minutes (preferably 40 minutes) to obtain ZnO modified CaO-Al2O3-SiO2 system ceramic slab.

[0007] Specifically, step S10 ensures uniform dispersion of ZnO in the green body powder, significantly improving the powder's absorption efficiency of sunlight. Step S20 improves the flowability and formability of the mixed powder, facilitating the acquisition of green bodies with uniform density. Step S30 presses and dries the granulated green body, yielding a ceramic green body with certain strength and density, ensuring the shape stability of the ceramic green body during subsequent sintering. Step S40 utilizes clean and renewable solar energy to replace traditional fossil energy, significantly reducing production energy consumption and carbon emissions. Simultaneously, rotary sintering ensures uniform heating of the ceramic green body, reducing internal temperature differences and thermal stress. Combined with the regulating effect of the relative thermal expansion coefficient of the pre-precipitated calcium feldspar crystals at low temperatures and the pinning and toughening effect of corundum, this effectively alleviates the microcrack problem caused by the mismatch in thermal expansion coefficients in the CaO-Al2O3-SiO2 system. Furthermore, the wide firing temperature window of 1060–1100℃ and the short sintering time of 30–50 min not only reduce production costs but also improve process stability, facilitating large-scale industrial production.

[0008] More specifically, the amount of light absorber is controlled at 5 wt.% to 7 wt.% of the green powder mass. If the amount of light absorber is too small, it cannot effectively absorb enough solar energy, resulting in the temperature not reaching the required sintering level. If the amount is too large, too much low-viscosity glass phase will be generated, which softens and encapsulates the grains at high temperatures, hindering direct grain contact, weakening grain boundary bonding, and causing a decline in the physical properties of the ceramic slab. In addition, this invention utilizes a concentrating solar furnace to prepare ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs. Through the rapid heating characteristics of the concentrating solar furnace, anorthite grains and corundum precipitate earlier at a lower temperature. Corundum, as a high-hardness second phase particle, disperses in the ceramic matrix and produces a pinning effect, hindering dislocation and grain boundary slip, improving the resistance to deformation, so that the ceramic slab can still have physical properties comparable to or even better than those sintered in an electric furnace at a lower sintering temperature.

[0009] Furthermore, the zinc oxide light absorber used in this invention has high absorption efficiency for ultraviolet light and good thermal conductivity, which can better transfer the absorbed heat to the sintering material and improve the reaction efficiency; at the same time, the light absorber has good chemical stability in high-temperature environments.

[0010] Preferably, the chemical composition of the green powder, by mass percentage, includes: 35.50 wt.%–40.50 wt.% SiO2, 35.22 wt.%–37.00 wt.% Al2O3, 1.55 wt.%–1.85 wt.% Fe2O3, 20.50 wt.%–25.50 wt.% CaO, 0.58 wt.%–0.99 wt.% MgO, 0.10 wt.%–0.30 wt.% K2O, 0–0.20 wt.% Na2O, 0.10 wt.%–0.30 wt.% TiO2, and 0.15 wt.%–0.35 wt.% MnO, with the balance being unavoidable impurities, and the sum of the mass percentages of all components is 100 wt.%.

[0011] Specifically, by rationally controlling the mass ratio of SiO2, Al2O3, and CaO, the green powder provides a material basis for the full precipitation of the anorthite and corundum crystalline phases, which is conducive to the formation of a microstructure that matches the crystalline phases and glass. The synergistic effect of various fluxing components such as Fe2O3, MgO, K2O, Na2O, and MnO can effectively reduce the firing temperature and promote low-temperature rapid firing. TiO2, as a nucleating agent, can promote crystallization and refine the grains.

[0012] Preferably, in step S10, the ball-to-material mass ratio is (1-3):1, and the ball milling time is 0.5-2 hours.

[0013] Specifically, the above-mentioned ball milling parameters can avoid the problems of uneven powder mixing and coarse particle size caused by too low a ball-to-material ratio and insufficient ball milling time, and prevent the effective firing window from narrowing due to component segregation and asynchronous local phase reactions in the subsequent sintering process. They can also avoid the defects of excessively high proportion of over-milled fine powder, molding stratification, excessive sintering shrinkage and easy deformation caused by too high a ball-to-material ratio and too long a ball milling time. In particular, when the ball-to-material ratio is further optimized to 2:1, the light absorber and green body powder can be highly uniformly dispersed in the shortest ball milling cycle, and a mixed powder with suitable particle size distribution can be obtained.

[0014] Preferably, in step S20, granulation is carried out using PVA granulation, and the amount of PVA added is 5 wt.% to 10 wt.% of the total weight of the mixed powder.

[0015] Specifically, PVA (Polyvinyl Alcohol), as an organic binder, can effectively improve the adhesion and flowability of the mixed powder, enhance the powder's molding performance, and facilitate uniform filling of the mold during pressing, resulting in a green body with uniform density. Simultaneously, PVA can significantly improve the strength of the green body, reducing breakage rates during handling and subsequent processes. Furthermore, PVA is completely burned off during sintering, leaving no residue in the finished product. The aforementioned amount of PVA added ensures sufficient bonding effect and green body strength while avoiding residual porosity or carbon defects after sintering due to excessive binder, thus ensuring the density and mechanical properties of the ceramic slab.

[0016] Preferably, in step S30, the molding pressure for pressing is 40-100 kN, and the holding time is 30-70 s.

[0017] Specifically, a molding pressure of 40–100 kN combined with a holding pressure of 30–70 seconds can ensure that the granulated green body is fully compacted, resulting in uniform density and strength in all parts of the green body that meets the requirements for transfer and glazing. This avoids both the looseness of the green body and the large shrinkage caused by insufficient pressure, as well as the delamination and dark cracks caused by excessive pressure and insufficient holding pressure.

[0018] Preferably, in step S30, the drying temperature after pressing and molding is 80-100°C, and the drying time is 24-48 hours.

[0019] Specifically, after molding, the green body is dried at a low temperature of 80-100℃ for 24-48 hours, which can slowly remove the residual moisture in the green body and avoid surface crusting and drying cracks caused by the inability to remove internal moisture due to high temperature and rapid drying. This keeps the residual moisture of the green body in the kiln within a reasonable range and eliminates the risk of the green body exploding during the process of rapid heating by concentrated light.

[0020] Preferably, in step S40, the rotational speed of the rotary sintering is 10-15 r / min.

[0021] Specifically, the aforementioned rotation speed can make the ceramic blank heat more evenly in the concentrating solar furnace, effectively reduce the temperature difference and thermal stress between different parts of the ceramic blank, and avoid microcracks and deformation defects caused by local overheating or uneven heating.

[0022] Preferably, in step S40, the sintering conditions include: heating from room temperature to 900°C, the temperature at which anorthite begins to precipitate, at a heating rate of 20–35°C / min, holding at that temperature for 10–20 min (preferably 10 min); continuing to heat to 1060–1100°C, holding at that temperature for 10–20 min, and then cooling to room temperature.

[0023] Specifically, the first stage of heat preservation at 900℃, the initial precipitation temperature of anorthite, promotes the uniform formation of anorthite crystal nuclei, laying the foundation for subsequent crystal phase growth. This also helps to control the thermal expansion coefficient of the system, reducing the difference in thermal expansion coefficients between the crystalline phase and the glassy phase, thus alleviating microcrack problems at the source. The second stage of heat preservation, continuing to raise the temperature to 1060–1100℃, promotes full densification of the green body, while allowing the anorthite and corundum crystal phases to grow fully and distribute evenly. Corundum, as the second phase particles, produces a pinning effect, improving the mechanical properties and deformation resistance of the ceramic slab. The above two-stage heat preservation process achieves stepwise control of crystallization and densification, which is conducive to obtaining ceramic slabs with reasonable crystal phase composition, uniform microstructure, and excellent performance. Moreover, the overall sintering temperature is low, the time is short, energy-saving and efficient, and easy for industrial production.

[0024] In a second aspect, the present invention also provides a ZnO-modified CaO-Al2O3-SiO2 system ceramic slab, which is prepared by any of the methods described above.

[0025] Preferably, the ZnO-modified CaO-Al2O3-SiO2 system ceramic slab has a room temperature flexural strength of 90–102 MPa, a water absorption rate of 0.10–0.50%, and a bulk density of 2.5–3.0 g / cm³. 3 Its performance meets the requirements of the national standard GB / T 45817-2025 for ceramic slabs.

[0026] Specifically, the ZnO-modified CaO-Al2O3-SiO2 system ceramic slab prepared by this invention exhibits a room temperature flexural strength of 90–102 MPa, which is superior to existing similar products. Its water absorption rate is as low as 0.10–0.50%, and its bulk density is 2.5–3.0 g / cm³. 3The results indicate that the product has high density and excellent mechanical properties. All of the above performance indicators meet the requirements of the national standard GB / T 45817-2025 for ceramic slabs. This shows that the technical solution of using a concentrated solar furnace for low-temperature rapid sintering combined with ZnO modification can not only achieve efficient and low-carbon preparation of ceramic slabs, but also obtain mechanical properties and densification levels that are comparable to or even better than those of traditional electric furnace sintering. The product quality is stable and has good prospects for industrial application and market competitiveness.

[0027] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a ZnO-modified CaO-Al2O3-SiO2 system ceramic slab and its preparation method. The above preparation method introduces ZnO as a light absorber into the green body powder, combined with the rapid heating characteristics of a concentrating solar furnace and a rotary sintering process, which significantly reduces the firing temperature while maintaining excellent flexural strength; the ZnO light absorber effectively improves the absorption efficiency of solar energy by the green body, reducing the sintering temperature to 1060-1100℃, which is significantly lower. Compared to the traditional electric furnace sintering temperature, the two-stage heat preservation process promotes the uniform precipitation and growth of calcium feldspar and corundum crystal phases. The regulating effect of calcium feldspar on the coefficient of thermal expansion and the pinning and toughening effect of corundum particles work synergistically to fundamentally suppress the microcrack problem caused by the mismatch of the coefficient of thermal expansion. This allows the room temperature flexural strength of the ceramic slab to reach 90-102 MPa, which is superior to the level of existing similar products and comparable to or even better than products sintered in traditional electric furnaces. At the same time, it significantly reduces production energy consumption and carbon emissions, which is in line with the green and low-carbon development direction. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the concentrating solar furnace in the preparation method of the ZnO-modified CaO-Al2O3-SiO2 system ceramic rock plate provided in Example 1. Figure 2 The heating curve of the concentrating solar furnace at a sintering temperature of 1080℃ in the preparation method of the ZnO modified CaO-Al2O3-SiO2 system ceramic rock plate provided in Example 1; Figure 3 The XRD patterns of ZnO-modified CaO-Al2O3-SiO2 ceramic slabs prepared at different sintering temperatures in Example 1 are shown below. Figure 4 This is a SEM image of the cross section of the ZnO-modified CaO-Al2O3-SiO2 ceramic slab prepared at a sintering temperature of 1080℃ in Example 1 of this invention. Figure 5 This is a diagram showing the energy flux density distribution during the firing of ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs in a concentrating solar furnace provided in Example 1. Figure 6This is a heat flow data fitting curve for firing ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs in a concentrating solar furnace provided in Example 1; In the attached diagram: 101—Solar tracking plane heliostat; 102—Parabolic concentrator; 103—Sintering furnace body; 1031—Rotating platform. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] To address the shortcomings of existing sintering technologies for CaO-Al2O3-SiO2 system ceramic slabs, this invention provides a ZnO-modified CaO-Al2O3-SiO2 system ceramic slab and its preparation method. By adding ZnO to the CaO-Al2O3-SiO2 system ceramic slab, it can effectively solve technical problems such as cracking, high firing temperature, low flexural strength, and significant environmental pollution in ceramic slabs.

[0031] The technical solution of the present invention will now be further described with reference to specific embodiments.

[0032] Unless otherwise specified, all raw materials and reagents used in the embodiments of this invention are commercially available conventional industrial-grade raw materials; all grinding, granulation, molding, drying, and sintering equipment used are conventional experimental / industrial equipment in the field of ceramic preparation; performance testing, unless otherwise specified, adopts standard methods in the field: the mineral composition of the sintered product is tested using a Bruker D8 Advance X-ray diffractometer (XRD) and quantitatively analyzed using the Rietveld full-spectrum fitting method; the microstructure of the sample cross-section is observed using a Zeiss Sigma 300 field emission scanning electron microscope (SEM); the energy flux density distribution during the sintering process is characterized by an energy flux density distribution diagram, and the heat flux data is analyzed through fitting curves; water absorption and bulk density are tested according to GB / T 3810.3-2026 Test Methods for Ceramic Bricks, Part 3; room temperature flexural strength is tested according to the methods specified in GB / T 45817-2025 Ceramic Slab Standard.

[0033] Example 1: This embodiment 1 first provides a method for preparing ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs, the specific steps of which are as follows: (1) Raw material preparation: The green powder and ZnO light absorber were mixed at a mass ratio of 100:5 and then added to a ball mill. The ball-to-material mass ratio was controlled at 2:1. The mixture was ball-milled for 1 hour until the light absorber was evenly dispersed in the green powder to obtain a mixed powder. The green powder was derived from calcined bauxite from Xiaoyi, Shanxi and wollastonite from Kete, Jiangxi. Its chemical composition, by mass percentage, included: 40.50 wt.% SiO2, 36.00 wt.% Al2O3, 1.75 wt.% Fe2O3, 23.80 wt.% CaO, 0.78 wt.% MgO, 0.23 wt.% K2O, 0.15 wt.% Na2O, 0.18 wt.% TiO2 and 0.21 wt.% MnO, with the remainder being unavoidable impurities.

[0034] (2) PVA granulation and aging: Add 8wt% PVA powder to the mixed powder and granulate for 1 hour to obtain a molding blank with reasonable particle size distribution and uniform moisture content.

[0035] (3) Green body forming: The granulated green body is filled into a steel mold and pressed under 80kN pressure for 50s to obtain a ceramic green body; the ceramic green body is placed in an electric heating drying oven and dried at 90℃ for 24h until the residual moisture of the ceramic green body is ≤0.5%.

[0036] (5) Sintering of the green body: The dried ceramic green body is placed in Figure 1 The sintering process of the sintering furnace body of the medium-concentration solar furnace is carried out on a rotating platform at a sintering temperature range of 1060-1100℃ for 50 minutes to obtain ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs.

[0037] Please see Figure 1 , Figure 1 This is a schematic diagram of the concentrating solar furnace in the preparation method of ZnO modified CaO-Al2O3-SiO2 system ceramic rock plate provided in this embodiment 1; the concentrating solar furnace includes: a solar tracking plane heliostat 101 with a high reflectivity plane mirror structure, a parabolic concentrator 102 with a concave parabolic reflection structure, a sintering furnace body 103 with a closed metal cavity structure, and a rotating stage 1031 set at the scorch spot position inside the sintering furnace body 103; Among them, the solar tracking plane heliostat 101 tracks the changes in the sun's position and altitude by adjusting the pitch and azimuth angles in real time, ensuring that sunlight is always reflected parallel to the parabolic concentrator 102; the parabolic concentrator 102 focuses the parallel sunlight into a high-energy-density focal spot and projects it into the sintering furnace body 103; the rotating platform 1031 of the sintering furnace body 103 drives the ceramic blank to be sintered to rotate at a uniform speed to ensure uniform heating.

[0038] Please see Figure 2The sintering process of the concentrated solar furnace in Example 1 is as follows: The temperature is rapidly increased from room temperature, with an average heating rate of approximately 30–35 °C / min, consistent with the designed range of 20–35 °C / min. When the temperature reaches approximately 900 °C (the temperature at which anorthite begins to precipitate), the first stage of heat preservation is initiated to promote uniform precipitation of anorthite nuclei. The temperature is then further increased to approximately 1080 °C, entering a high-temperature heat preservation stage. This temperature falls within the firing temperature range of 1060–1100 °C, ensuring sufficient densification of the green body and full growth of the crystal phase. After heat preservation, the temperature is rapidly reduced, taking approximately 15 minutes to drop from the highest temperature to room temperature. The entire sintering cycle (including heating, heat preservation, and cooling) is approximately 50 minutes, significantly shorter than the traditional electric furnace sintering process, demonstrating the high efficiency and energy-saving advantages of the concentrated solar furnace.

[0039] Please see Figure 3 In Example 1, at sintering temperatures of 1060℃, 1080℃, and 1100℃, the main crystalline phases of the ZnO-modified CaO-Al2O3-SiO2 ceramic slabs were anorthite, corundum, Gahnite (ZnAl2O4), and Hardystonite (Ca2ZnSi2O7). Anorthite exhibited the highest diffraction peak intensity, indicating it was the dominant crystalline phase, followed by corundum. This demonstrates that under the rapid sintering conditions of a concentrated solar furnace, anorthite and corundum can fully mature. The precipitation of zinc aluminum spinel and zinc silicon calcium stone indicates that ZnO not only acts as a light absorber to improve light absorption efficiency, but also participates in solid-state reactions, reacting with components such as Al2O3, CaO, and SiO2 in the system to generate zinc-containing crystalline phases, thus achieving crystalline phase modification of the ceramic system. As the sintering temperature increases from 1060℃ to 1100℃, the diffraction peak intensity of each crystalline phase generally shows an increasing trend, indicating more complete crystalline phase development. Furthermore, a stable crystalline phase composition mainly composed of anorthite and corundum can be formed within a wide temperature range of 1060~1100℃, verifying that the system has a wide sintering temperature window and good process adaptability.

[0040] Please see Figure 4 In Example 1, the ZnO-modified CaO-Al2O3-SiO2 ceramic slab prepared at a sintering temperature of 1080℃ exhibited a good microstructure: the grains were mainly short columnar and near-spherical, with relatively uniform grain size and clearly distinguishable grain boundaries, indicating that grain boundary migration and grain growth were still relatively sufficient under the rapid sintering conditions of a concentrated solar furnace; the overall density was high, with only a small number of small closed pores, indicating a good degree of compaction of the green body; the cross-section was mainly characterized by intergranular fracture, with complete and clear grain outlines, reflecting high grain boundary bonding strength, which is beneficial to improving the flexural strength and thermal shock resistance of the ceramic slab.

[0041] Please see Figure 5 and Figure 6In Example 1, the heat flux density distribution of ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs fired in a concentrated solar furnace exhibits a typical Gaussian distribution: the heat flux density is highest in the central region of the scorch spot, with a peak value of approximately 1100, and gradually decreases towards the two sides and edges, with an overall symmetrical distribution curve. This non-uniform heat flux distribution, with a high center and low edges, is an important reason for adopting the rotary sintering process—by rotating the green body at a uniform speed, each part is uniformly irradiated with heat flux of different intensities, thereby achieving uniform heating of the whole, effectively reducing the temperature difference and thermal stress inside the green body, which is beneficial for suppressing the generation of microcracks and improving the consistency of product performance.

[0042] The properties and microstructure of the ZnO-modified CaO-Al2O3-SiO2 ceramic slab prepared in Example 1 were characterized: Gradient sintering verification showed that the effective firing temperature range of the sample in Example 1 was 1060–1100℃, with a firing window of 40℃; the room temperature flexural strength reached 98.00 MPa; the product water absorption rate was 0.20%; and the bulk density was 2.70 g / cm³. 3 All performance characteristics meet the requirements of GB / T45817-2025 ceramic slab standard.

[0043] Comparative Example 1 (without light absorber): The preparation method of the CaO-Al2O3-SiO2 system ceramic slab provided in Comparative Example 1 is basically the same as that in Example 1, except that the raw material formula is adjusted: no light absorber zinc oxide is added, and the reduced component mass is made up with an equal mass of kaolin to ensure that the total mass of the formula remains unchanged. The other process parameters such as ball milling, granulation, and molding, as well as the sintering regime of the concentrating solar furnace, are completely consistent with those in Example 1.

[0044] The properties and microstructure of the ZnO-modified CaO-Al2O3-SiO2 ceramic slab prepared in Comparative Example 1 were characterized: After gradient sintering verification, the sample in Comparative Example 1 was not fired; its room temperature flexural strength reached 12.00 MPa; the product water absorption rate was 24.91%; and the bulk density was 1.76 g / cm³. 3 .

[0045] Comparative Example 2 (Sintering in a conventional resistance furnace): The preparation method of the ZnO-modified CaO-Al2O3-SiO2 system ceramic slab provided in Comparative Example 2 is basically the same as that in Example 1, except for the adjustment of the sintering method: instead of using a concentrated solar furnace, a traditional resistance furnace in the ceramic industry is used for sintering. All other raw material formulations, ball milling, granulation, and molding process parameters are completely consistent with those in Example 1. The sintering process adopts the slow firing regime commonly used in the ceramic industry: the dried ceramic green body is placed in the resistance furnace and heated from room temperature to the maximum firing temperature at a conventional heating rate of 5℃ / min. After holding at this temperature for 120 minutes, the sample is naturally cooled with the furnace to obtain the sample.

[0046] Performance testing revealed that Comparative Example 2, due to its use of a traditional resistance furnace external heating mode, lacked the surface-to-interior temperature gradient mass transfer effect of concentrated light sintering. Even with the addition of ZnO light absorber, it still required heating to 1170℃ to complete the densification of the green body.

[0047] The properties and microstructure of the ZnO-modified CaO-Al2O3-SiO2 ceramic slab prepared in Comparative Example 2 were characterized: Through gradient sintering verification, the effective firing temperature range of the sample in Comparative Example 2 was 1170–1190℃, with a firing window of 20℃; the room temperature flexural strength reached 85.00 MPa, the water absorption rate was 0.34%, and the bulk density was 2.62 g / cm³. 3 .

[0048] In summary, the technical solution provided by this invention has the following advantages compared to existing technologies: (1) Effectively suppress microcracks: In this invention, ZnO is selected as a highly efficient light absorber. On the one hand, it increases the ultraviolet-visible light absorption rate of the ceramic body by 15.4%, significantly enhancing the photothermal conversion effect. On the other hand, it participates in the solid-phase reaction to generate new phases such as zinc aluminum spinel, which improves the strength and density of the sample. At the same time, it harmonizes the thermal expansion coefficient of the system and suppresses the formation of microcracks.

[0049] (2) Low firing temperature and high strength: This invention uses a concentrated solar furnace instead of a traditional roller kiln as a heat source. By adding ZnO light absorber, ceramic slabs are sintered. The firing temperature is only 1060-1100℃, which is about 100-200℃ lower than that of a traditional roller kiln. While significantly reducing the firing temperature, it still maintains excellent flexural strength. The resulting ceramic slabs have a flexural strength of 90-102MPa, low water absorption, and high bulk density. All properties meet the requirements of the national standard GB / T45817-2025 for ceramic slabs.

[0050] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0051] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs, characterized in that, Includes the following steps: S10, the green powder and zinc oxide light absorber are mixed at a mass ratio of 100:(5~7), and then ball-milled to obtain a mixed powder; S20, add a binder to the mixed powder and granulate it to obtain a blank; S30, the blank is pressed into shape and dried to obtain a ceramic blank; S40, the ceramic blank is placed in a concentrating solar furnace and sintered by rotation in a wide firing temperature range of 1060 to 1100°C for 30 to 50 minutes to obtain a ZnO-modified CaO-Al2O3-SiO2 system ceramic slab.

2. The method for preparing ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs according to claim 1, characterized in that, The chemical composition of the green powder, by mass percentage, includes: 35.50 wt.%–40.50 wt.% SiO2, 35.22 wt.%–37.00 wt.% Al2O3, 1.55 wt.%–1.85 wt.% Fe2O3, 20.50 wt.%–25.50 wt.% CaO, 0.58 wt.%–0.99 wt.% MgO, 0.10 wt.%–0.30 wt.% K2O, 0–0.20 wt.% Na2O, 0.10 wt.%–0.30 wt.% TiO2, and 0.15 wt.%–0.35 wt.% MnO, with the balance being unavoidable impurities. The sum of the mass percentages of all components is 100 wt.%.

3. The method for preparing ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs according to claim 1, characterized in that, In step S10, the ball-to-material mass ratio is (1-3):1, and the ball milling time is 0.5-2 hours.

4. The method for preparing ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs according to claim 1, characterized in that, In step S20, granulation is performed using PVA granulation, and the amount of PVA added is 5 wt.% to 10 wt.% of the total weight of the mixed powder.

5. The method for preparing ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs according to claim 1, characterized in that, In step S30, the molding pressure is 40-100kN and the holding time is 30-70s.

6. The method for preparing ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs according to claim 1, characterized in that, In step S30, the drying temperature after pressing and molding is 80-100℃, and the drying time is 24-48h.

7. The method for preparing ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs according to claim 1, characterized in that, In step S40, the rotational sintering speed is 10-15 r / min.

8. The method for preparing ZnO-modified CaO-Al2O3-SiO2 system ceramic slabs according to claim 1, characterized in that, In step S40, the sintering conditions include: heating from room temperature to 900°C, the temperature at which anorthite begins to precipitate, at a heating rate of 20–35°C / min, holding at that temperature for 10–20 min; continuing to heat to 1060–1100°C, holding at that temperature for 10–20 min, and then cooling to room temperature.

9. A ZnO-modified CaO-Al2O3-SiO2 system ceramic slab, characterized in that, It is prepared by the method according to any one of claims 1 to 8.

10. The ZnO-modified CaO-Al2O3-SiO2 system ceramic slab according to claim 9, characterized in that, The ZnO-modified CaO-Al2O3-SiO2 system ceramic slab has a room temperature flexural strength of 90–102 MPa, a water absorption rate of 0.10–0.50%, and a bulk density of 2.5–3.0 g / cm³. 3 Its performance meets the requirements of the national standard GB / T 45817-2025 for ceramic slabs.

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