Ceramic glaze-finished tile directly fired based on concentrated solar energy and preparation method thereof

Abstract

The application provides a kind of ceramic glaze throwing brick based on concentrated solar energy direct sintering and a preparation method thereof, the preparation method uses concentrated solar furnace as sintering device, uses clean renewable solar energy as heat source, fundamentally gets rid of the dependence on fossil energy, realizes zero carbon emission of ceramic sintering process;For the key problem of high efficient heat absorption of green glaze under solar heat source, the application introduces light absorber in ceramic green body and glaze pulp at the same time, forms the light-heat conversion system of green glaze cooperation, greatly improves the absorption and utilization efficiency of concentrated solar energy, so as to complete body burning and glaze firing in lower temperature and shorter time, significantly reduces energy consumption and shortens production cycle;On this basis, ZrO2 introduced in glaze pulp forms high hardness microcrystalline reinforcing phase in rapid sintering process, and cooperates with fine-grained microstructure formed by rapid sintering, so that the glaze hardness, wear resistance and gloss after polishing are improved synchronously, and finally realizes the organic unity of clean production and high performance product.

Description

Technical Field

[0001] This invention relates to the field of green preparation technology of ceramic materials, specifically to a ceramic polished glazed tile based on direct firing with concentrated solar energy and its preparation method, which is particularly suitable for preparing low-carbon building ceramic products with high strength, high fracture toughness and high flexural strength. Background Technology

[0002] Ceramic sintering, as a high-energy-consuming process in the building materials industry, is of significant practical importance in replacing traditional fossil fuels with renewable energy sources such as concentrated solar power to achieve zero carbon emissions. The mechanical properties of polished glazed ceramic tiles (such as flexural strength, hardness, and fracture toughness) are closely related to the sintering process. Currently, industrial production commonly uses traditional sintering processes powered by coal, natural gas, or electricity, optimizing product performance through precise control of parameters such as firing temperature, holding time, and heating rate. Polished glazed tiles are ceramic tiles with a decorative glaze and a transparent protective glaze applied to the surface of the tile body. After high-temperature firing, they possess high gloss, high hardness, and rich decorative effects, and are widely used in building floor and wall decoration. In existing technologies, typical polished glazed tile sintering processes usually control the maximum firing temperature at 1100℃~1250℃, with a holding time of 50~150min, resulting in polished glazed tiles with a flexural strength generally of 35~70MPa and a Mohs hardness of 5~8.

[0003] Chinese invention patent CN103739279A discloses a fully polished glazed brick. The brick body raw materials include clay, feldspar, quartz, talc, and sodium tripolyphosphate; the base glaze layer raw materials include sodium feldspar, kaolin, aluminum hydroxide, quartz, talc, zirconium silicate, sodium tripolyphosphate, and wollastonite; the top glaze layer raw materials include sodium feldspar, kaolin, aluminum hydroxide, talc, sodium tripolyphosphate, potassium feldspar, zinc oxide, wollastonite, and dolomite. This patent uses a fully automatic hydraulic brick press to press the powder into a brick body, pours glaze slurry onto the brick body to form a glaze layer, and fires it at 1200℃~1220℃ for 50~80 minutes to obtain the fully polished glazed brick. The product has an abrasion resistance level of 4 (equivalent to approximately Mohs hardness 5) and a flexural strength of 45~47MPa. Chinese invention patent CN119613084A discloses a lightweight polished glazed ceramic brick and its preparation method. The brick's body layer comprises kaolin, clay, cordierite, quartz, alumina, potassium feldspar, and a binder; the base glaze layer comprises potassium feldspar, calcined talc, frit, quartz, calcite, zirconium silicate, and calcined zinc oxide; and the surface glaze layer comprises frit, clay, sodium feldspar, zinc oxide, stone powder, and kaolin. The patent describes a process where the raw materials are pressed into a green body using a press. The green body is then sequentially glazed, dried for 12 hours, and then glazed. Finally, it undergoes three-stage sintering in a nitrogen atmosphere (950–1050℃) for 3–5 hours to obtain the sample. The sample exhibits a Vickers hardness (HV0.5) of 746.8–768.2 (equivalent to approximately Mohs hardness 6) and a flexural strength of 50–63 MPa. Chinese invention patent CN121591412A discloses a high-hardness, wear-resistant, fully polished glazed brick and its preparation method. The body layer comprises potassium sodium sand, stone powder, aluminum sand, high-temperature sand, talc, black mud, clay, and bentonite; the glaze layer comprises potassium feldspar, kaolin, calcined kaolin, quartz, and calcined alumina. The patent describes a process where a surface glaze is applied sequentially, followed by inkjet printing of a pattern and then a fully polished glaze, forming a surface glaze layer, a pattern layer, and a polished glaze layer. After drying, the brick is fired in a kiln at a temperature ranging from 1180 to 1220°C for 100 to 150 minutes to obtain the polished glazed brick. The product has a Mohs hardness of 7 to 7.5. Chinese invention patent CN120647155A discloses a high-hardness glaze, the preparation method of which is composed of medium-alumina frit, high-alumina frit, potassium feldspar, sodium feldspar, wollastonite, calcined talc, calcined zinc oxide, corundum powder, calcined alumina, dolomite, barium carbonate, calcined kaolin, kaolin, printing paste, printing oil, and water. The patent describes a process where the ceramic body is dried, a base glaze is applied, inkjet printing is used to print the high-hardness glaze, the firing temperature is 1200–1250℃, the firing cycle is 40–80 minutes, and after polishing, a high-hardness ceramic tile is obtained, with the product achieving a Mohs hardness of up to 8.

[0004] However, existing technologies have the following main shortcomings: First, the glaze surface hardness and wear resistance are insufficient, making it prone to staining and lacking durability. The Mohs hardness of existing polished glazed tiles is generally 5-8, and the Vickers hardness is mostly below 8 GPa. The microcrystalline phase of the glaze surface is not fully developed, resulting in poor gloss retention after polishing. Long-term use easily leads to scratches and wear, and the microporous structure of the glaze surface easily absorbs stains, making cleaning difficult and seriously affecting the decorative effect and service life. Second, the mechanical properties of the body are relatively low, making it difficult to meet the demand for large-format, thinner tiles. The flexural strength of polished glazed tiles prepared by existing technologies is generally below 70 MPa, and data on fracture toughness are rarely reported. This is insufficient for the development of thinner ceramic slabs. With the trend towards larger sizes, the strength and toughness of ceramics are no longer sufficient to meet the needs of high-end applications. At the same time, the bonding strength between the body and the glaze layer is insufficient, which easily leads to the peeling of the glaze in the later stage, restricting the overall durability and polishing effect of the product. Thirdly, it relies on fossil energy, with high sintering temperature and long cycle, which cannot be adapted to solar heat sources. Traditional processes have high sintering temperature (>1100℃) and long cycle (>50min), resulting in high energy consumption and carbon emissions. Moreover, existing technologies have not been formulated and designed for solar energy, a clean, high-throughput, and non-steady-state heat source, and cannot be directly applied to solar concentrated firing, thus restricting the green transformation of the ceramic industry.

[0005] In summary, developing a novel preparation technology that can fully utilize clean and renewable energy, achieve rapid sintering at lower temperatures, and simultaneously improve the hardness, wear resistance, stain resistance, and mechanical properties of glazed tiles has become an urgent need for the green manufacturing and high-performance development of the ceramic industry, and is also the core technical problem that this invention aims to solve. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a ceramic polished glaze tile based on direct firing by concentrated solar energy and its preparation method, so as to solve the technical problems of high energy consumption, large carbon emissions, low glaze hardness and easy contamination, poor mechanical properties of the body, high sintering temperature and long cycle of the existing ceramic polished glaze tile preparation process.

[0007] 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 ceramic glazed tiles directly fired using concentrated solar energy, comprising the following steps: S10, placing the ceramic green body containing the light absorber in a concentrating solar furnace and sintering it at 800-850°C to obtain a ceramic green body with a porous structure; the light absorber is selected from at least one of transition metal oxides and rare earth oxides. S20 involves applying a glaze slurry containing both light absorber and ZrO2 to the surface of a ceramic blank using either an immersion glaze method or a spray glaze method, followed by drying to obtain a glazed blank. S30 involves placing the glazed blank in a concentrated solar furnace and sintering it at 900–1000°C to obtain ceramic polished glazed tiles.

[0008] Specifically, step S10 utilizes concentrated solar energy as a heat source and enhances the absorption of sunlight through a light-absorbing agent to achieve low-temperature bisque firing, resulting in a ceramic bisque with a porous structure, which is beneficial for subsequent glaze adhesion. In step S20, a glaze slurry containing both a light-absorbing agent and ZrO2 is applied to the surface of the ceramic bisque using an immersion glaze method or a spray glaze method, so that the glaze layer has both light-absorbing function and ZrO2 reinforcing component, laying the foundation for subsequent low-temperature rapid firing. In step S30, the glazed bisque is placed in a concentrated solar furnace and sintered at 900-1000℃ using a rotary sintering process. The bisque and the light-absorbing agent in the glaze layer work together to absorb concentrated solar energy, completing the firing at a lower temperature. Rotary sintering ensures uniform heating, ultimately yielding polished glazed ceramic tiles.

[0009] Preferably, in step S10, the light absorber is selected from one or more of Co2O3, Fe2O3, Tm2O3, V2O5, NiO, ZnO, or SnO2; wherein, the absorption rates of the above light absorbers for sunlight are as follows: Co2O3 75%–85%, Fe2O3 70%–75%, Tm2O3 60%–70%, V2O5 75%–85%, NiO, ZnO, and SnO2 are all 60%–70%, and the preferred light absorber is a mixture of Tm2O3 and SnO2; in comparison, the absorption rate of sunlight for ceramic green bodies without added light absorbers is only 45%–55%.

[0010] Specifically, the aforementioned light absorbers can significantly improve the absorption rate of sunlight by ceramic green bodies. A mixture of Tm₂O₃ and SnO₂ is preferred as a composite light absorber. Compared to ceramic green bodies without added light absorbers (absorption rate of only 45%–55%), the absorption rate of sunlight by the green body is significantly increased, effectively enhancing the photothermal conversion efficiency and providing favorable conditions for sintering in a concentrating solar furnace. Simultaneously, the mixture of Tm₂O₃ and SnO₂ can also dope and modify the ceramic green bodies, optimizing their physical properties.

[0011] Preferably, the preparation process of the ceramic green body in step S10 is as follows: the green body raw material is mixed evenly with the light absorber, and then successively subjected to ball milling, sieving, granulation, aging, pressing and molding and drying to obtain the ceramic green body.

[0012] Specifically, through a complete process route of ball milling, sieving, granulation, aging, pressing and drying, the raw materials and light absorber are mixed evenly, the particle size distribution is reasonable, the molding performance is good, and the green body density is uniform.

[0013] Preferably, the ceramic green body comprises, by weight, 20-25 parts of potassium feldspar from Yingde, Guangdong; 5-10 parts of sodium feldspar from Yingde, Guangdong; 30-35 parts of quartz from Yingde, Guangdong; 30-35 parts of calcined bauxite from Xiaoyi, Shanxi; 1-5 parts of talc from Guangxi and Guangdong; and 1-5 parts of light absorber.

[0014] Specifically, the above-mentioned formulation system not only ensures the basic mechanical properties and sintering performance of the green body, but also achieves efficient absorption of solar energy through the introduction of light absorbers. At the same time, the amount of the light absorber added is moderate, which avoids the problems of insufficient addition leading to insignificant light absorption and low sintering efficiency, while also preventing the drawbacks of excessive addition interfering with the basic formulation system of the green body and affecting the mechanical properties and sintering behavior of the green body.

[0015] Preferably, the water absorption rate of the ceramic green body is 10% to 15%, the apparent porosity is 20% to 25%, and the flexural strength is not less than 30 MPa.

[0016] Specifically, the green body is controlled with a porous structure of 10% to 15% water absorption and 20% to 25% apparent porosity. This ensures a flexural strength of not less than 30 MPa to meet the requirements of subsequent glazing and handling. At the same time, the appropriate porosity provides favorable conditions for glaze penetration and physicochemical reactions during the firing process, which is conducive to improving the bonding strength between the body and the glaze.

[0017] Preferably, the preparation process of the glaze slurry in step S20 is as follows: The ZrO2-containing molten block was ball-milled and sieved separately to obtain a pretreated molten block; By weight, take 80-100 parts of pretreated frit, 5-10 parts of calcined Suzhou clay from Xiaoyi, Shanxi, and add the same weight of light absorber as the ceramic green body, and mix to obtain the glaze. The glaze and water are mixed at a material-to-water mass ratio of 1:(0.6-0.8) and placed in a ball mill. The mixture is then ball-milled at a material-to-ball mass ratio of 1:(1-2) (more preferably 1:2) for 1.5-2 hours until the glaze slurry has a fineness of 300-350 mesh (more preferably 325 mesh). After ball milling, the mixture is aged for 12-36 hours (more preferably 24 hours) to obtain a uniform and stable glaze slurry.

[0018] Specifically, step S20 pre-treats the ZrO2-containing frit by ball milling and sieving, effectively increasing the specific surface area of ​​the frit and promoting its melting and reaction during rapid firing in the solar furnace. An optimized formula of 80-100 parts pre-treated frit and 5-10 parts calcined Suzhou clay, along with the same mass fraction of light absorber as the ceramic green body, ensures the glaze slurry possesses both ZrO2 reinforcing phase and high-efficiency light absorption capacity, guaranteeing rapid firing of the glaze layer under concentrated solar energy. By controlling the material-to-water mass ratio to 1:(0.6-0.8), the material-to-ball mass ratio to 1:(1-2), ball milling for 1.5-2 hours to a fineness of 300-350 mesh, and then aging for 12-36 hours, a uniform and stable glaze slurry is finally obtained, providing quality assurance for subsequent glazing and firing.

[0019] Preferably, in step S20, the glaze thickness is 0.2–0.5 mm; the glazed ceramic blank is dried at 100–110°C for 4–6 hours.

[0020] Specifically, the above-mentioned glaze thickness ensures that the glaze layer has sufficient thickness to provide a good decorative effect and protective function, while avoiding defects such as firing cracking and peeling caused by excessive glaze thickness. After glazing, the glaze is dried at 100-110℃ for 4-6 hours to allow the moisture in the glaze layer to be slowly and evenly discharged, ensuring that the glaze layer is firmly bonded to the unglazed body and avoiding cracks or glaze peeling caused by excessively rapid drying.

[0021] Preferably, in step S30, the holding time for rotary sintering is 5 to 15 minutes, and the furnace is allowed to cool naturally after sintering, with a total firing time of 30 to 45 minutes.

[0022] Specifically, the rotary sintering in step S30 ensures uniform heating of the billet and good product consistency; the short holding time significantly shortens the sintering cycle, improves production efficiency, and reduces energy consumption; natural cooling in the furnace makes the billet cooling process gradual, effectively reducing the risk of cracking and deformation caused by thermal stress and ensuring product quality.

[0023] Secondly, the present invention also provides a ceramic glazed tile directly fired using concentrated solar energy, which is prepared by any of the methods described above.

[0024] Preferably, the bulk density of the glazed ceramic tile is 2.65–2.70 g·cm³. -3 The porosity is 0.01–0.10%, the water absorption rate is 0.01–0.20%, the flexural strength of the body is 100–120 MPa, the Vickers hardness of the glaze is 7.9–8.3 GPa, and the fracture toughness is 3.4–3.7 MPa·mm. 1 / 2 The glaze surface gloss at 60° incident angle is ≥90GU, whiteness is ≥50%, abrasion resistance is ≥4, and stain resistance is 5.

[0025] Specifically, the aforementioned ceramic glazed tiles have excellent comprehensive mechanical properties, long service life, and are easy to clean, thus meeting the needs of high-end architectural decoration.

[0026] Compared with existing technologies, the present invention has the following beneficial effects: The present invention provides a ceramic polished glaze tile based on direct firing with concentrated solar energy and its preparation method. The preparation method uses a concentrated solar furnace as a sintering device and clean and renewable solar energy as a heat source, fundamentally eliminating dependence on fossil energy and achieving zero carbon emissions in the ceramic sintering process. Addressing the key issue of efficient heat absorption of the body and glaze under solar heat source, the present invention simultaneously introduces a light absorber into the ceramic green body and glaze slurry, forming a synergistic photothermal conversion system between the body and glaze, significantly improving the absorption and utilization efficiency of concentrated solar energy. This allows for completion of bisque firing and glaze firing at lower temperatures and in a shorter time, significantly reducing energy consumption and shortening the production cycle. Furthermore, the ZrO2 introduced into the glaze slurry forms a high-hardness microcrystalline reinforcing phase during rapid firing, which works synergistically with the fine-grained microstructure formed by rapid firing, simultaneously improving the hardness, wear resistance, and gloss of the glaze surface, ultimately achieving an organic unity of clean production and high product performance. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the concentrating solar furnace in the method for preparing ceramic glazed bricks directly fired using concentrated solar energy, as provided in Example 1. Figure 2 The temperature rise curve during sintering of ceramic glazed bricks in the preparation method of ceramic glazed bricks based on direct firing by concentrated solar energy provided in this embodiment 1 is shown. Figure 3 This is a diagram illustrating the mechanism by which the light absorber enhances the solar light absorption rate and promotes sintering in the preparation method of ceramic glazed tiles directly fired based on concentrated solar energy provided in Example 1. Figure 4 The reflectance spectra of sunlight for different light-absorbing agents and the control group; Figure 5 This is a SEM image of the cross-section of the ceramic glazed brick sample prepared in Example 1. In the attached diagram: 101—Solar tracking plane heliostat; 102—Ultra-high precision flexible concentrator; 103—Sintering furnace body; 1031—Rotating stage. Detailed Implementation

[0028] 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.

[0029] The technical solution of the present invention will now be further described with reference to specific embodiments.

[0030] 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 this field: the microstructure of the sample cross-section is observed using a German Zeiss Sigma 300 field emission scanning electron microscope (SEM); water absorption and bulk density are tested according to GB / T 3810.3-2026; the flexural strength of the green body is determined using a universal testing machine according to GB / T 3810.4 Test Methods for Ceramic Tiles, Part 4; the Vickers hardness of the glaze is determined using a Vickers hardness tester according to GB / T 4340.1 Vickers Hardness Tests for Metallic Materials, Part 1; fracture toughness is determined according to GB / T 23806; the gloss of the glaze is determined using a 60° specular gloss meter according to GB / T 13891 was measured; whiteness was measured using a whiteness meter according to GB / T5950; abrasion resistance was measured using a ceramic tile abrasion tester according to GB / T 3810.7 Ceramic Tile Test Method Part 7; stain resistance was evaluated according to GB / T 3810.14.

[0031] Example 1: This embodiment 1 first provides a method for preparing ceramic glazed tiles directly fired using concentrated solar energy, the specific steps of which are as follows: (1) Raw material proportioning: Weigh 23 parts of potassium feldspar (KAlSi3O8) from Yingde, Guangdong, 8 parts of sodium feldspar (NaAlSi3O8) from Yingde, Guangdong, 30 parts of quartz (SiO2) from Yingde, Guangdong, 32 parts of calcined bauxite (mainly Al2O3) from Xiaoyi, Shanxi, and 5 parts of talc (Mg3Si4O3) from Guangxi and Guangdong according to the predetermined proportions. 10 (OH)2) to obtain the green body raw material.

[0032] (2) Preparation of ceramic green body: The above green body raw materials and 5 parts of light absorber (a mixture of Tm2O3 and SnO2, and Tm2O3:SnO2=1:1) are mixed evenly and put into a ball mill for wet ball milling. The mass ratio of material to ball to water is controlled at 1:2 and the ball milling time is 2h. After ball milling, the slurry is passed through a 200-mesh sieve to remove coarse particles and impurities that have not been ground finely, so as to ensure that the slurry is uniform and pure. The slurry after sieving is prepared into granular powder by spray granulation process to improve the flowability and molding performance of the powder. The granulated powder is aged in a sealed environment for 24 hours to allow moisture to diffuse evenly between the particles, eliminate internal stress, and improve the molding performance of the powder. The aged powder is then dry-pressed into green bodies with a certain shape and size. The molding pressure is 40 MPa and the holding time is 10 seconds to ensure uniform density of the green body. Finally, the green body is dried at 90℃ for 24 hours to remove free moisture. After drying, the moisture content of the green body is controlled below 0.5%, resulting in a ceramic green body that meets the requirements of subsequent processes.

[0033] Step (3) Preparation of ceramic green body: Place the dried ceramic green body in... Figure 1 The sintering process of the sintering furnace body of the medium-concentration solar furnace is carried out at 800℃ on the rotating platform to obtain a ceramic blank with a porous structure (water absorption rate of 12% and apparent porosity of 25%) and moderate strength (flexural strength of 31MPa).

[0034] Step (4) Preparation of glaze: First, select zircon white frit or transparent frit containing ZrO2, ball mill the frit separately and sieve it, and increase its specific surface area by refining the frit particles to promote its melting and reaction in the rapid firing process of the solar furnace, and obtain pretreated frit for later use; then carry out glaze batching, weigh 90 parts of pretreated frit, 8 parts of calcined Suzhou clay from Xiaoyi, Shanxi, and add 5 parts of light absorber (a mixture of Tm2O3 and SnO2, and Tm2O3:SnO2=1:1), mix evenly to obtain glaze; among them, the introduction of light absorber enables the glaze layer to also have efficient light absorption capacity, ensuring the rapid firing of the glaze layer under the action of concentrated solar energy.

[0035] Step (5) Preparation of glaze slurry: Mix the prepared glaze material with water at a material-to-water mass ratio of 1:0.7, place it in a planetary ball mill, and ball mill for 2 hours at a material-to-ball mass ratio of 1:2 until the fineness of the glaze slurry reaches 325 mesh; after ball milling, let it stand for 24 hours to allow the glaze slurry to have uniform and stable properties.

[0036] Step (6) Glazing and drying: Apply the glaze evenly to the surface of the ceramic blank prepared in step (3) using the glazing dipping method or the glazing spraying method. The glaze thickness is 0.5 mm. After glazing, dry the ceramic blank at 100℃ for 6 hours to allow the glaze layer to dry fully and bond firmly with the ceramic blank, thus obtaining the glazed blank.

[0037] Step (7) Sintering of glaze blank: Place the dried glaze blank in... Figure 1 Sintering is carried out on the rotating platform of the sintering furnace body of the central concentrating solar furnace to obtain ceramic polished glazed bricks.

[0038] Please see Figure 1 , Figure 1 The concentrating solar furnace used in the method for preparing ceramic glazed bricks based on direct firing of concentrated solar energy provided in this embodiment 1 includes a solar tracking plane heliostat 101 with a high reflectivity plane mirror structure, an ultra-high precision flexible 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 can adjust the pitch angle and azimuth angle in real time to track the changes in the sun's position and altitude, ensuring that the sunlight is always reflected parallel to the ultra-high precision flexible concentrator 102; after receiving the parallel sunlight, the ultra-high precision flexible concentrator 102 focuses it into a high energy density focal spot and projects it into the sintering furnace body 103. The rotating platform 1031 inside the sintering furnace body 103 drives the glaze blank to be sintered to rotate at a uniform speed to ensure uniform heating.

[0039] Specifically, the concentrating solar furnace is equipped with an ultra-high precision flexible concentrator 102 and a real-time temperature control system, enabling rapid sintering of the glaze blank under uniform heating and high-precision temperature control. The entire sintering process includes three stages: heating, holding, and cooling. The specific heating regime is as follows: Figure 2 As shown. By Figure 2 It can be seen that the heating system in step (7) exhibits a stepped rapid heating characteristic: the initial temperature is about 300℃, and it gradually rises to the highest firing temperature of about 950℃ through multiple heating steps, with a heating stage of about 30 minutes; then it is held at the highest temperature for about 5 minutes to ensure that the glaze layer is fully melted and reacted; finally, it is rapidly cooled down, dropping from the highest temperature to about 350℃ in about 5 minutes, with a total sintering cycle of about 40 minutes, which is much shorter than the firing cycle of several hours in traditional kilns, reflecting the advantages of concentrated solar energy rapid firing; the stepped heating is conducive to the gradual discharge of gas in the body and the orderly progress of physical and chemical reactions, avoiding defects such as cracking and deformation caused by rapid heating, and ensuring stable product quality.

[0040] Depend on Figure 3 It is understood that the mechanism by which light absorbers improve solar light absorption and promote sintering is a photothermal synergistic effect: when sunlight shines on the surface of a green body containing a light absorber, the light absorber induces electrons to jump from the valence band (VB) to the conduction band (CB) through photoexcitation, simultaneously forming oxygen vacancy energy levels in the band gap, achieving band gap reconstruction and effectively broadening the absorption range of sunlight; the excited high-energy electrons convert light energy into lattice vibrational heat energy through photon-phonon coupling, and transmit it to the surroundings through lattice vibration, forming a local high-temperature region inside the material, thereby promoting the low-temperature rapid sintering of ceramics. This photothermal synergistic mechanism enables the light absorber to efficiently capture sunlight in a broad spectrum range of 300–2500 nm, significantly improving solar energy utilization efficiency and providing an intrinsic physical basis for the rapid sintering of concentrating solar furnaces.

[0041] Depend on Figure 4It can be seen that, compared with the control group without added light absorbers, the solar reflectance of ceramic green bodies with different added light absorbers was significantly reduced across the entire spectral range of 300–2500 nm, indicating that the introduction of light absorbers effectively improved the absorption capacity of the green body for sunlight. Among them, Co2O3 and V2O5 had the most significant anti-reflection effect and the lowest full-spectrum reflectance, followed by Fe2O3. Tm2O3, NiO, ZnO, and SnO2 also had significant anti-reflection effects. The reflectance of all samples increased with increasing wavelength, with lower reflectance and stronger absorption in the visible light region, and gradually increasing reflectance in the near-infrared region. These results demonstrate that light absorbers can effectively broaden the light absorption range of the green body and improve the solar energy utilization efficiency, providing a light absorption basis for the low-temperature rapid sintering of concentrating solar furnaces.

[0042] Depend on Figure 5 It can be seen that the ceramic glazed brick prepared by sintering in the solar furnace in Example 1 has a dense microstructure in its cross section: a large number of short rod-shaped and needle-shaped grains grow intertwined and are evenly distributed in the glass phase matrix together with block grains to form a "crystal phase-glass phase" composite structure; the grains are fully developed, evenly distributed and have few pores, indicating that the green body can still achieve full sintering and densification under the conditions of rapid firing by concentrated solar energy.

[0043] The ceramic glazed tile prepared in Example 1 was characterized for its properties and microstructure: the bulk density was 2.70 g·cm³. -3 The porosity is 0.05%, the water absorption rate is 0.05%, the flexural strength of the body is 110 MPa, the Vickers hardness of the glaze is 8.3 GPa, and the fracture toughness is 3.6 MPa·mm. 1 / 2 The glaze gloss (60° incident light) is 90 GU, whiteness is 82%, abrasion resistance is level 4, and stain resistance is level 5. The concentrated solar sintering temperature is 150-200℃ lower than that of a traditional electric furnace, and the sintering time is reduced by more than 70%. The ceramic polished glazed tile sample prepared in Example 1 showed no cracking, and all physical properties significantly exceeded the requirements of the ceramic slab industry standard T / CBCSA 40-2021.

[0044] Comparative Example 1 (without light absorber): The preparation method of the calcium feldspar-based 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 is added to the ceramic green body and glaze, and the reduced component mass is made up with an equal mass of calcined clay from Xiaoyi, Shanxi to ensure that the total mass of the formula remains unchanged. The other process parameters of ball milling, granulation, molding, glazing, and sintering in the concentrating solar furnace are completely consistent with those in Example 1.

[0045] The ceramic glazed tile prepared in Comparative Example 1 was characterized in terms of performance and microstructure: its bulk density was 2.59 g·cm³. -3The porosity is 0.14%, the water absorption rate is 0.05%, the flexural strength of the body is 94.86 MPa, the Vickers hardness of the glaze is 7.6 GPa, and the fracture toughness is 3.4 MPa·mm. 1 / 2 The glaze gloss (60° incident light) is 86 GU, the whiteness is 75%, the abrasion resistance is level 4, and the stain resistance is level 5.

[0046] Comparative Example 2 (Sintering in a conventional resistance furnace): The preparation method of the calcium feldspar-based ceramic slab provided in Comparative Example 2 is basically the same as that in Example 1, except that the sintering method is adjusted: in steps (3) and (7), a concentrating solar furnace is not used, but a traditional resistance furnace in the ceramic industry is used for sintering. All other process parameters, such as raw material formulation, ball milling, granulation, molding, and glazing, are completely consistent with those in Example 1. The sintering process in step (7) adopts the common slow firing regime in the ceramic industry: the dried glaze blank is placed in the resistance furnace and heated from room temperature to 1150°C at a conventional heating rate of 5°C / min. After holding at this temperature for 120 minutes, the sample is obtained by natural cooling with the furnace.

[0047] The ceramic glazed tile prepared in Comparative Example 2 was characterized in terms of performance and microstructure: its bulk density was 2.58 g·cm³. -3 The porosity is 0.28%, the water absorption rate is 0.11%, the flexural strength of the body is 87.11 MPa, the Vickers hardness of the glaze is 7.3 GPa, and the fracture toughness is 3.3 MPa·mm. 1 / 2 The glaze gloss (60° incident light) is 81 GU, the whiteness is 72%, the abrasion resistance is level 4, and the stain resistance is level 5.

[0048] In summary, the technical solution provided by this invention has the following advantages compared to existing technologies: (1) Wide sintering temperature range of 900~1000℃: This invention significantly reduces the requirements for kiln temperature control accuracy by combining the formulation design of light absorber and flux with the concentrated rotation sintering process, thereby reducing defects such as over-firing, under-firing, and deformation, and significantly improving the yield of large-size slab production.

[0049] (2) The comprehensive mechanical properties of the ceramic glazed tiles of the present invention are significantly improved, and the smoothness of the glaze surface is significantly improved after polishing: the flexural strength of the ceramic glazed tiles prepared by the present invention reaches 100-120 MPa, which is 20%-40% higher than that of the traditional sintering method; the Vickers hardness reaches 7.9-8.3 GPa, and the fracture toughness reaches 3.4-3.7 MPa·mm 1 / 2 Its comprehensive mechanical properties far exceed industry standards.

[0050] Specifically, the mechanism by which the mechanical properties of the ceramic glazed tile surface are improved according to the present invention includes four aspects: Firstly, the glaze formulation was innovatively designed. By introducing the same Tm2O3-SnO2 composite light absorber as the body into the glaze, SnO2 partially precipitates in the form of microcrystals during firing and is uniformly dispersed in the glaze glass phase. This generates a dispersion strengthening effect by pinning dislocations and deflecting cracks, significantly improving hardness and toughness. At the same time, the introduction of Tm2O3 optimizes the network structure of the glass phase, enhances the grain boundary bonding strength, and improves the chemical stability and density of the glaze layer, thereby enhancing its anti-fouling ability.

[0051] Secondly, there is the microcrystalline reinforcement mechanism of the glaze layer. The ZrO2 introduced into the glaze reacts with the SiO2 in the glaze layer during the sintering process to generate ZrSiO4 microcrystals. The unreacted ZrO2 exists in the form of tetragonal or monoclinic phase (Mohs hardness 8.5), while SnO2 also exists in the form of microcrystals. These high-hardness microcrystals are evenly distributed in the glaze glass phase, forming a "microcrystalline-glass phase" structure, which greatly improves the wear resistance and scratch resistance of the glaze surface, thus ensuring the long-lasting gloss after polishing.

[0052] Third, the rapid firing in the solar furnace promotes grain refinement and uniform distribution. The high energy flux density of the solar furnace heats the glaze rapidly, allowing it to reach the melting temperature in a very short time. This inhibits the abnormal growth of microcrystals, forming fine and uniformly distributed ZrSiO4 and SnO2 microcrystals. At the same time, it reduces bubbles and defects inside the glaze layer, improves the smoothness of the polished glaze surface, and thus achieves high gloss and low staining.

[0053] Fourthly, microstructure control: solar furnace concentrated sintering promotes significant coarsening of mullite grains in the body, resulting in alternating growth of "short rod-shaped" and "needle-shaped" grains, which interweave with corundum grains to form a "three-dimensional interlocking structure". This structure can effectively prevent crack propagation. At the same time, the coarsened mullite and corundum grains provide a harder microscopic support for polishing, making the glaze surface smoother and brighter, and less prone to microcracks.

[0054] (3) The sintering temperature and sintering time of the glaze blank of the present invention are reduced, and the photothermal conversion efficiency is high: The present invention significantly improves the absorption efficiency and photothermal conversion efficiency of the blank to sunlight through the design of the Tm2O3-SnO2 composite light absorber. Comparative Example 1, under the same sintering regime in a concentrating solar furnace, showed significantly lower performance than Example 1 with added light absorber due to the absence of added light absorber, directly demonstrating the key role of the composite light absorber in promoting sintering through efficient photothermal conversion. Under concentrating conditions, the Tm2O3-SnO2 in the light absorber... 3+The 4f electron transition and the oxygen vacancy defect level of SnO2 efficiently capture photons, and rapidly convert light energy into lattice thermal energy through photon-phonon coupling, forming a local high-temperature region inside the material and significantly reducing the ion diffusion activation energy. Therefore, this invention can complete glazing at an extremely low temperature of 900-1000℃ and an extremely short holding time of 5-15 minutes, which is 150-250℃ lower than the sintering temperature of traditional electric furnaces, shortens the sintering time by more than 70%, and reduces energy consumption by more than 80%.

[0055] (4) This invention has the effects of energy saving, emission reduction and environmental protection, and has good energy economy: This invention uses a solar furnace as a sintering device and clean and renewable sunlight as a heat source to realize low-carbon emission sintering of ceramic glazed tiles, effectively alleviating the environmental pollution problems caused by the reliance on fossil energy in traditional processes. This technology meets the requirements of green manufacturing, and at the same time, solar energy resources are abundant and low-cost, with good economic efficiency and sustainability, which meets the requirements of green manufacturing and sustainable development.

[0056] 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.

[0057] 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 ceramic glazed tiles directly fired using concentrated solar energy, characterized in that, Includes the following steps: S10, placing the ceramic green body containing the light absorber in a concentrating solar furnace and sintering it at 800-850°C to obtain a ceramic green body with a porous structure; the light absorber is selected from at least one of transition metal oxides and rare earth oxides. S20, using an immersion glaze method or a spray glaze method, a glaze slurry containing both the light absorber and ZrO2 is applied to the surface of the ceramic blank, and after drying, a glaze blank is obtained; S30, the glaze blank is placed in the concentrating solar furnace and sintered by rotation at 900-1000°C to obtain ceramic polished glaze bricks.

2. The method for preparing ceramic glazed tiles based on direct firing using concentrated solar energy according to claim 1, characterized in that, In step S10, the light absorber is selected from one or more of Co2O3, Fe2O3, Tm2O3, V2O5, NiO, ZnO or SnO2.

3. The method for preparing ceramic glazed tiles directly fired using concentrated solar energy according to claim 1, characterized in that, The preparation process of the ceramic green body in step S10 is as follows: the green body raw material is mixed evenly with the light absorber, and then successively subjected to ball milling, sieving, granulation, aging, pressing and molding and drying to obtain the ceramic green body.

4. The method for preparing ceramic glazed tiles directly fired using concentrated solar energy according to claim 3, characterized in that, The ceramic green body comprises, by weight, 20-25 parts of potassium feldspar from Yingde, Guangdong; 5-10 parts of sodium feldspar from Yingde, Guangdong; 30-35 parts of quartz from Yingde, Guangdong; 30-35 parts of calcined bauxite from Xiaoyi, Shanxi; 1-5 parts of talc from Guangxi and Guangdong; and 1-5 parts of the light absorber.

5. The method for preparing ceramic glazed tiles directly fired using concentrated solar energy according to claim 4, characterized in that, The ceramic green body has a water absorption rate of 10% to 15%, an apparent porosity of 20% to 25%, and a flexural strength of not less than 30 MPa.

6. The method for preparing ceramic glazed tiles based on direct firing using concentrated solar energy according to claim 3, characterized in that, The preparation process of the glaze slurry in step S20 is as follows: The ZrO2-containing molten ingot was ball-milled and sieved separately to obtain a pretreated molten ingot; By weight, take 80-100 parts of pretreated frit, 5-10 parts of the calcined Suzhou clay from Xiaoyi, Shanxi, and add the light absorber in the same weight proportion as the ceramic green body, and mix to obtain the glaze; The glaze and water are mixed at a material-to-water mass ratio of 1:(0.6-0.8) and placed in a ball mill. The mixture is then ball-milled at a material-to-ball mass ratio of 1:(1-2) for 1.5-2 hours until the glaze slurry has a fineness of 300-350 mesh. After ball milling, the mixture is aged for 12-36 hours to obtain the glaze slurry.

7. The method for preparing ceramic glazed tiles based on direct firing using concentrated solar energy according to claim 6, characterized in that, In step S20, the glaze thickness is 0.2–0.5 mm; the glazed ceramic blank is dried at 100–110°C for 4–6 hours.

8. The method for preparing ceramic glazed tiles directly fired using concentrated solar energy according to claim 1, characterized in that, In step S30, the holding time for rotary sintering is 5 to 15 minutes, and the furnace is allowed to cool naturally after sintering. The total firing time is 30 to 45 minutes.

9. A type of ceramic glazed tile fired directly using concentrated solar energy, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

10. The ceramic glazed tile directly fired using concentrated solar energy according to claim 9, characterized in that, The bulk density of the ceramic glazed tile is 2.65–2.70 g·cm³. -3 The porosity is 0.01–0.10%, the water absorption rate is 0.01–0.20%, the flexural strength of the body is 100–120 MPa, the Vickers hardness of the glaze is 7.9–8.3 GPa, and the fracture toughness is 3.4–3.7 MPa·mm. 1 / 2 The glaze surface gloss at 60° incident angle is ≥90GU, whiteness is ≥50%, abrasion resistance is ≥4, and stain resistance is 5.

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