A calcium feldspar-based ceramic rock plate with a wide firing temperature range and a preparation method thereof

Abstract

This invention provides a calcium feldspar-based ceramic slab with a wide firing temperature range and its preparation method. The preparation method first involves ball milling and blending calcium feldspar-based green body powder with a light absorber; then, through slurry preparation, spray granulation, and aging, a green body with reasonable gradation and uniform moisture content is obtained; next, through pressing and slow drying, a green body with uniform density and acceptable residual moisture content is obtained; then, through glazing and drying, a glaze layer with uniform thickness and strong adhesion is obtained; finally, the glazed green body is placed in a concentrated solar furnace and sintered by rotation within a wide window of 1000–1060℃ to obtain a calcium feldspar-based ceramic slab. The above preparation method further expands the sintering window of high-calcium slab from the existing 10–40℃ to 60℃, significantly reducing the difficulty of production control and the scrap rate; the performance of the obtained product meets the national standard GB / T 45817-2025 for ceramic slabs, and has the advantages of being green and low-carbon, having a high tolerance for errors, and low cost, making it suitable for industrial promotion.

Description

Technical Field

[0001] This invention relates to the field of green preparation technology of ceramic materials, and in particular to a calcium feldspar-based ceramic slab with a wide firing temperature range and its preparation method. Background Technology

[0002] High-temperature sintering in traditional electric or gas-fired kilns is the most energy-intensive and carbon-emission-intensive stage in the production of architectural ceramics, accounting for approximately 60% to 70% of total energy consumption. Carbon emissions per ton of ceramic product reach 0.92 tons of CO2, with a thermal efficiency generally only 35% to 42%. Traditional ceramic slab sintering requires prolonged holding at temperatures of 1080–1230℃, resulting in high energy consumption, significant emissions, and high production costs, making it difficult to meet the green and low-carbon transformation needs of the architectural ceramics industry under the "dual-carbon" strategy. With increasing global focus on energy security, climate change, and sustainable development, solar energy, as an inexhaustible zero-carbon renewable energy source, can provide a high-energy-density heat source through photothermal conversion, offering a feasible path for the low-carbon technological transformation of ceramic sintering. This allows for low-temperature, rapid firing while meeting product performance requirements, combining energy-saving and environmental benefits with green development value.

[0003] The firing temperature range of ceramics refers to the temperature interval within the kiln from the start of sintering to the formation of the target phase and properties. The lower limit is the initial firing temperature (the temperature at which the porosity of the green body decreases rapidly and the strength increases significantly), and the upper limit is the final firing temperature (the temperature at which the green body reaches its optimal density and properties, approaching over-firing deformation). Due to their high CaO content, calcium feldspar-based building ceramics possess strong fluxing properties and their phase evolution is highly sensitive to temperature fluctuations, inherently exhibiting a narrow firing temperature window. The firing temperature range of existing high-calcium ceramic slabs is generally only 10–40℃. During production, problems such as under-firing of green bodies and over-firing deformation easily occur due to temperature differences within the kiln. This places extremely high demands on the uniformity and precision of kiln temperature control, significantly increasing the difficulty of production management and the scrap rate.

[0004] Currently, publicly available calcium feldspar-based ceramic slab technologies still generally employ traditional kiln sintering, failing to effectively address the drawbacks of high firing temperatures and narrow firing windows. For example, Chinese invention patent CN115626774A discloses a soft-light, skin-like ceramic slab with a firing temperature of 1220–1230℃ and a firing window of only 10℃; CN119432162A discloses a metamorphic ceramic slab with a firing temperature of 1200–1220℃ and a firing window of only 20℃; CN114262218A discloses a high-performance calcium feldspar slab with a firing temperature of 1190–1230℃ and a firing window of only 40℃; and CN121021121A discloses a lithium slag-based ceramic slab with a wide firing range with a firing temperature of 1080–1120℃ and a firing window of only 40℃. None of the above technologies have been combined with concentrated solar energy sintering technology to achieve low-carbon sintering of calcium feldspar bedrock slabs over a wide temperature range, making it difficult to simultaneously meet the actual industrial needs of green production and a wide process window. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a calcium feldspar-based ceramic slab with a wide firing temperature range and its preparation method, thereby solving the technical problems of high firing temperature, narrow firing temperature range, high production energy consumption, and high production cost that are common in existing calcium feldspar-based ceramic slabs.

[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 calcium feldspar-based ceramic slabs with a wide firing temperature range, comprising the following steps: S10, the calcium feldspar-based ceramic slab green body powder and light absorber are mixed evenly by ball milling to obtain a mixed powder; S20, water is added to the mixed powder to make a slurry, which is then spray-dried, granulated, and aged to obtain the raw material; S30 involves pressing the blank into shape and drying it to obtain a ceramic slab green body. S40 involves applying glaze to a ceramic slab green body using an immersion glazing method, followed by drying to obtain a glazed body. S50 involves placing the glaze blank in a concentrated solar furnace and sintering it by rotation within a wide firing temperature range of 1000–1060℃ to obtain calcium feldspar-based ceramic slabs.

[0007] Specifically, step S10, by adding a light absorber to the anorthite-based green body powder, can effectively enhance the photothermal conversion efficiency of the subsequent concentrated sintering process; step S20 can obtain a green body with reasonable particle size distribution and uniform moisture distribution, reducing the risk of uneven shrinkage during sintering from the raw material end; step S30 can obtain a ceramic slab green body with uniform density and acceptable residual moisture, reducing the risk of deformation and cracking during sintering; step S40 uses the dip-glazing method to apply and dry the glaze, which can ensure uniform glaze thickness and avoid appearance defects such as pinholes and glaze shrinkage; step S50... The process employs a concentrated solar furnace rotary sintering process, using zero-carbon solar energy as a heat source to replace traditional fossil fuels and electricity. By rotating the green body at a uniform speed, it ensures uniform light and heat distribution in all directions, expanding the effective firing window of calcium feldspar-based ceramic slabs to 60℃ (1000~1060℃), which is much wider than the existing firing range of 10~40℃ for high-calcium slabs. This significantly reduces the difficulty of temperature control and the scrap rate caused by over-firing and under-firing. At the same time, the sintering temperature is 20~170℃ lower than that of traditional kiln processes, achieving a balance between low carbon and energy saving and wide process adaptability.

[0008] Preferably, in step S10, the ball-to-material mass ratio is (1-3):1 (more preferably 2:1), and the ball milling time is 0.5-2 hours.

[0009] 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 the anorthite-based green body powder can be highly uniformly dispersed within the shortest ball milling cycle, and a mixed powder with suitable particle size distribution can be obtained.

[0010] Preferably, the chemical composition of the anorthite-based ceramic slab green powder, by mass percentage, comprises: 63.5 wt.%–64.5 wt.% SiO2, 17.0 wt.%–18.0 wt.% Al2O3, 0.9 wt.%–1.0 wt.% Fe2O3, 10.0 wt.%–11.0 wt.% CaO, 4.0 wt.%–5.0 wt.% MgO, 1.0 wt.%–1.5 wt.% K2O, 1.0 wt.%–1.5 wt.% Na2O, and 0.1 wt.%–0.2 wt.% TiO2, with the balance being unavoidable impurities, and the sum of the mass percentages of all components is 100 wt.%; the added mass percentage of the light absorber relative to the anorthite-based ceramic slab green powder is 5.0 wt.%–8.0 wt.%.

[0011] Specifically, the above-mentioned preferred calcium feldspar-based ceramic slab green powder and light absorber dosage are specially designed for sintering in a concentrating solar furnace. This ensures that the calcium feldspar main crystalline phase is stably generated within the temperature range of 1000–1060℃, forming a dense green body skeleton with high strength and low water absorption. Furthermore, the auxiliary light absorption and mild fluxing effect of a small amount of Fe2O3 and TiO2 reduces the sensitivity of the high-calcium system to temperature fluctuations, avoiding defects such as local overmelting deformation and under-burned core that are common in conventional high-calcium formulations. The addition of 5.0wt%–8.0wt% light absorber can precisely match the typical light power density of the concentrating solar furnace. This avoids both insufficient light absorber dosage leading to low photothermal conversion efficiency and slow green body heating rate, which makes it difficult to achieve densification, and excessive dosage leading to local photothermal enrichment, blistering on the green body surface, or over-burning deformation.

[0012] Preferably, the mixed powder is made from the following mineral raw materials in parts by weight: 35-40 parts diopside, 5-10 parts wollastonite, 20-25 parts quartz, 25-30 parts kaolinite, 2-6 parts flux and 1-5 parts light absorber; wherein the flux is an inorganic solid flux filler (preferably Guiguang talc powder) and the light absorber is a semiconductor oxide (preferably zinc oxide).

[0013] Specifically, 35–40 parts diopside and 5–10 parts wollastonite serve as the main calcium-magnesium raw materials, exhibiting extremely low loss on ignition and mild firing aid properties. This allows for the stable release of structural stress during rapid heating under concentrated light, preventing exhaust cracking defects during fast firing. 20–25 parts quartz act as a high-temperature skeleton to support the green body structure, suppressing over-firing deformation caused by excessive glass phase formation at high temperatures. 25–30 parts kaolin provide the plasticity required for pressing and the aluminum source needed for anorthite formation, ensuring that large-format slab green bodies have sufficient transport and glazing strength. 2–6 parts flux can smoothly regulate the high-temperature viscosity of the system, promoting densification at low temperatures without causing a sharp drop in high-temperature viscosity. Combined with 1–5 parts light absorber, it can achieve uniform photothermal conversion during concentrated sintering, allowing the anorthite crystal phase development and green body densification process to proceed smoothly within a wide temperature range, further broadening the effective firing window.

[0014] Preferably, in step S20, the amount of water added is 5 wt.% to 20 wt.% of the mass of the mixed powder, and the aging time after granulation is 24 to 48 hours.

[0015] Specifically, in step S20, the amount of water added is controlled at 5wt.% to 20wt.% of the mass of the mixed powder, which can prepare a slurry with a viscosity suitable for the spray drying process. The granulated powder has a reasonable particle size distribution and good flowability, avoiding problems such as sticking to the tower and particle agglomeration caused by excessive water addition, or excessive fine powder and stratification caused by insufficient water addition. After granulation, aging for 24 to 48 hours can allow the moisture to fully diffuse and homogenize inside the particles, improve the plasticity of the powder, reduce the elastic aftereffect and delamination risk during the molding process, and avoid problems such as inconsistent shrinkage and deformation cracking caused by uneven moisture and density during sintering.

[0016] Preferably, in step S30, the molding pressure is 40-100 kN and the holding time is 30-70 s; the drying temperature after molding is 80-100℃ and the drying time is 24-48 h.

[0017] Specifically, a molding pressure of 40–100 kN combined with a holding pressure of 30–70 seconds ensures that the aged green body is fully compacted, resulting in uniform density and strength across all parts of the green body that meets the requirements for transport and glazing. This avoids both insufficient pressure leading to a loose green body and excessive sintering shrinkage, and excessive pressure or insufficient holding pressure leading to delamination and dark cracks in the green body. After molding, a low-temperature long-term drying process at 80–100℃ for 24–48 hours can gradually remove residual moisture from the green body, avoiding surface crusting and drying cracks caused by the inability to remove internal moisture during high-temperature rapid drying. This keeps the residual moisture of the green body entering the kiln within a reasonable range and eliminates the risk of the green body exploding during the rapid heating process.

[0018] Preferably, in step S40, the glaze is a matte frit glaze, the glazing time for a single ceramic slab green body is 5 to 20 seconds, the drying temperature after glazing is 80 to 100°C, and the drying time is 24 to 48 hours.

[0019] Specifically, using a matte frit glaze with a 5-20s immersion time can achieve a uniformly thick matte glaze layer. The high-temperature expansion coefficient of the glaze is highly matched with that of the calcium feldspar blank, avoiding both thin glaze and uneven gloss caused by too short an immersion time, and thick glaze with glaze flow and cracking caused by too long an immersion time. After glazing, drying at 80-100℃ for 24-48 hours can slowly remove moisture from the glaze layer, avoiding appearance defects such as pinholes, glaze shrinkage, and slag caused by rapid drying, ensuring a delicate and smooth glaze surface after firing, and achieving the decorative effect required for matte slabs.

[0020] Preferably, in step S50, the rotational speed of the rotary sintering is 10-15 r / min; the sintering in the concentrating solar furnace includes heating, holding and cooling stages in sequence: the heating stage raises the temperature from room temperature to 1000-1060°C at a rate of 30-40°C / min, the holding stage holds the temperature at 1000-1060°C for 20-40 min, and then cools to room temperature.

[0021] Specifically, a rotation speed of 10–15 r / min allows the glaze blank to rotate at a uniform speed under the concentrated light spot, ensuring that the amount of light and heat received by each part of the blank is highly uniform. This avoids local overheating, blistering, and deformation caused by excessively slow rotation speed, as well as displacement and falling of the blank caused by excessively fast rotation speed. A heating rate of 30–40 °C / min is adapted to the rapid heating characteristics of the concentrated solar furnace, achieving low-temperature rapid firing while ensuring that the thermal stress of the blank is controllable and cracking does not occur. Holding at 1000–1060 °C for 20–40 min ensures that the anorthite main crystal phase is fully developed and the blank is completely densified, without causing abnormal grain growth or excessive glass phase due to excessive holding time, which would lead to high-temperature deformation. After holding, cooling to room temperature with the furnace can fully release thermal stress and avoid cold cracking defects, ultimately achieving stable sintering over a wide temperature range.

[0022] Preferably, in step S50, the concentrating solar furnace sequentially includes a solar tracking plane heliostat, a parabolic concentrator, and a sintering furnace body along the optical path: Among them, the solar tracking plane heliostat is used to track the sun's position in real time and reflect sunlight in parallel to the parabolic concentrator; the parabolic concentrator is used to converge the received sunlight into a focal spot and project it onto the sintering position inside the sintering furnace; the sintering furnace is equipped with a rotating platform for placing the glaze blank to be sintered and driving the glaze blank to rotate at a uniform speed under the irradiation of the focal spot to complete the sintering.

[0023] Specifically, the solar tracking plane heliostat, arranged sequentially along the optical path, can track the sun's azimuth in real time and continuously reflect sunlight parallel to the parabolic concentrator, avoiding defocusing and power fluctuations caused by changes in the sun's azimuth. The parabolic concentrator can focus the received parallel sunlight into a high-energy-density focal spot with uniform energy, projecting it onto the sintering position inside the sintering furnace to provide a stable sintering temperature above 1000℃. The rotating platform inside the sintering furnace can drive the glaze blank to be sintered to rotate at a uniform speed, ensuring that the light irradiation intensity at all positions of the blank is consistent, eliminating local hot and cold spots from a hardware perspective, significantly reducing the temperature difference inside the furnace, and providing a uniform and stable temperature field for sintering with a wide temperature window.

[0024] Secondly, the present invention also provides a calcium feldspar-based ceramic slab with a wide firing temperature range, prepared by any of the methods described above; the calcium feldspar-based ceramic slab has a water absorption rate of 0.10–0.20% and a bulk density of 2.5–2.7 g / cm³. 3 Its performance meets the requirements of the national standard GB / T 45817-2025 for ceramic slabs.

[0025] Specifically, the calcium feldspar-based ceramic slabs prepared by this invention have excellent performance and are environmentally friendly and low-carbon, with a wide firing temperature range: the product's water absorption rate is stable at 0.10–0.20%, and its bulk density is 2.5–2.7 g / cm³. 3It has a high degree of densification, and its core properties such as mechanical strength, stain resistance, and thermal stability all meet the requirements of the national standard GB / T 45817-2025 "Ceramic Slabs". It can be directly used as a building decoration material. At the same time, the product uses zero-carbon solar energy as the sintering heat source, which combines performance advantages and environmental protection value, making it suitable for large-scale industrial promotion.

[0026] Furthermore, the present invention employs a concentrated solar furnace to sinter calcium feldspar-based ceramic slab, which can broaden the effective firing temperature window to 60°C. This wide-temperature sintering effect stems from the synergistic effect of composition control and process characteristics: on the one hand, the fluxing agent made of guiguang talc powder and the light absorber made of zinc oxide introduce Mg... 2+ Zn 2+ As intermediate ions in the glass network, they can increase the degree of polymerization of the high-temperature liquid phase, increase the viscosity of the liquid phase, and reduce its wettability to grain boundaries. Simultaneously, during sintering, they generate two high-melting-point crystalline phases, forsterite and zinc-aluminum spinel, which are uniformly distributed at the anorthite grain boundaries. Through physical pinning, they hinder grain boundary migration and slip at high temperatures, suppressing high-temperature softening and deformation of the green body and effectively raising the upper limit of the system's overheating temperature. On the other hand, the rapid heating mechanism of concentrated light sintering can suppress abnormal coarsening of anorthite grains, ensuring the stable performance of the fine-grain strengthening effect. This allows the green body's density and mechanical properties to remain stable over a wider temperature range. Ultimately, through the synergistic effect of phase pinning, viscosity control, and fine-grain strengthening, high-density sintering over a wide temperature range is achieved.

[0027] Furthermore, this invention employs a concentrated solar furnace for sintering calcium feldspar-based ceramic slabs, which significantly reduces the firing temperature by 100-200°C compared to traditional roller kilns. Its low-temperature rapid firing mechanism stems from the synergistic effect of the concentrated solar heating characteristics and the light absorber: under concentrated irradiation, the light absorber and mineral components in the green body excite lattice vibrations through photon absorption, directly converting light energy into heat energy, forming a gentle temperature gradient from the surface to the interior of the green body. This gradient drives the low-viscosity, high-temperature melt on the surface to penetrate directionally into the pores inside the green body, rapidly filling the pores and pushing the densification front inward, accelerating the densification process. Simultaneously, the light absorber, on the one hand, enhances the solar-to-thermal conversion efficiency through intrinsic absorption and the introduced defect energy levels; on the other hand, it synergistically reduces the liquid phase appearance temperature and high-temperature viscosity of the system with the fluxing components, promoting the low-temperature nucleation and growth of crystal phases such as calcium feldspar, quartz, forsterite, and zinc aluminum spinel, ultimately achieving complete densification of the green body at an even lower temperature.

[0028] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a calcium feldspar-based ceramic slab with a wide firing temperature range and its preparation method. The preparation method firstly involves ball milling and mixing calcium feldspar-based green powder with a light absorber to achieve high dispersion of the light absorber and avoid over-firing / under-firing caused by uneven local light absorption; secondly, through slurry preparation, spray granulation, and aging, a green material with reasonable gradation and uniform moisture content is obtained, eliminating shrinkage differences and stress risks in subsequent molding and sintering; finally, through pressing and slow drying, a uniform density and residual moisture content are obtained. The qualified green blanks are separated to avoid cracking caused by rapid evaporation of moisture during the fast firing process. Then, they are dipped in glaze and dried to obtain a uniform and firmly bonded glaze layer, reducing glaze defects such as pinholes, glaze shrinkage, and glaze runs. Finally, the glazed blanks are placed in a concentrated solar furnace and sintered in a wide window of 1000-1060℃. This not only uses zero-carbon solar energy to replace fossil energy to achieve low-temperature fast firing, but also expands the sintering window of high-calcium slabs from the existing 10-40℃ to 60℃, which greatly reduces the difficulty of production control and the scrap rate. The performance of the resulting products meets the national standard GB / T 45817-2025 for ceramic slabs, and has the advantages of being green and low-carbon, having a high fault tolerance rate, and low cost, making it suitable for industrial promotion. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the concentrating solar furnace in the method for preparing the calcium feldspar-based ceramic slab with a wide firing temperature range provided in Example 1. Figure 2 The heating regime curve of the concentrating solar furnace in the preparation method of the calcium feldspar-based ceramic rock plate with a wide firing temperature range provided in Example 1; Figure 3 The image shows the XRD pattern of the anorthite-based ceramic slab prepared in Example 1. Figure 4 This is a SEM image of the cross-section of the anorthite-based ceramic slab prepared in Example 1. Figure 5 This is a SEM image of the glaze-body bonding layer on the glaze of the calcium feldspar-based ceramic slab prepared in Example 1. In the attached diagram: 101—Solar tracking plane heliostat; 102—Solar tracking transmission mechanism; 103—Parabolic concentrator; 104—Sintering furnace body; 1041—Rotating platform. Detailed Implementation

[0030] 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.

[0031] To address the shortcomings of existing calcium feldspar-based ceramic slab sintering technologies, this invention employs concentrated solar energy as the sintering heat source, significantly reducing sintering energy consumption and slab production costs. Currently, no publicly available research has applied concentrated solar furnace sintering technology to the preparation of calcium feldspar-based architectural ceramic slabs. Filling this technological gap, this invention replaces traditional electric and gas-fired kilns with a concentrated solar energy system. By compounding light absorbers and fluxes into the slab raw materials, it simultaneously widens the firing temperature window and lowers the firing temperature of calcium feldspar-based ceramic slabs, verifying the technological advantages of concentrated solar furnace sintering for architectural ceramics and developing a new low-carbon sintering process that meets the performance requirements of next-generation architectural ceramics.

[0032] The technical solution of the present invention will now be further described with reference to specific embodiments.

[0033] 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 mineral composition of the sintered product is tested using a German Bruker D8 Advance X-ray diffractometer (XRD) and quantitatively analyzed using the Rietveld full-spectrum fitting method; the microstructure of the sample cross-section and the body-glaze bonding layer is observed using a German Zeiss Sigma 300 field emission scanning electron microscope (SEM); water absorption and bulk density are tested according to GB / T3810.3-2026 Ceramic Brick Test Method Part 3, and the product performance meets the requirements of GB / T 45817-2025 Ceramic Slabs; the diopside, wollastonite, quartz, kaolin, and talc powder used in the embodiments of this invention are all obtained from domestic ceramic raw material production enterprises, and the light absorber is commercially available industrial-grade semiconductor oxide zinc oxide.

[0034] Example 1: This embodiment 1 first provides a method for preparing calcium feldspar-based ceramic slabs with a wide firing temperature range, the specific steps of which are as follows: (1) Raw material preparation: Diopside, wollastonite, quartz, kaolin, and talc powder were weighed according to the preset mass ratio and mixed evenly to obtain anorthosite bedrock green powder; using zinc oxide as a light absorber, ZnO and anorthosite bedrock green powder were added to a ball mill according to the preset mass ratio, controlling the ball-to-material mass ratio to be 2:1, and ball milling was performed for 1 hour until the light absorber was evenly dispersed in the anorthosite bedrock to obtain a mixed powder; wherein, the chemical composition of the obtained anorthosite bedrock green powder, by mass percentage, includes: The composition consists of 64 wt.% SiO2, 18.0 wt.% Al2O3, 1.0 wt.% Fe2O3, 10.8 wt.% CaO, 4.0 wt.% MgO, 1.0 wt.% K2O, 1.0 wt.% Na2O, and 0.1 wt.% TiO2, with the balance being unavoidable impurities. The total mass percentage of each component is 100 wt.%. The added mass percentage of ZnO relative to the anorthite-based ceramic slab green body powder is 5.0 wt.%.

[0035] (2) Granulation and aging: Add 10wt% water to the mixed powder to prepare a slurry that meets the spraying requirements. After granulation in a pressure spray drying tower, it is sent to a closed silo for aging for 36 hours to obtain a molding blank with reasonable particle size distribution and uniform moisture content.

[0036] (3) Blank forming: The aged blank is filled into a steel mold and pressed under 80kN pressure for 50s to obtain ceramic slab blank; the ceramic slab blank is placed in an electric heating drying oven and dried at 90℃ for 24h until the residual moisture of the ceramic slab is ≤0.5%.

[0037] (4) Glazing: After drying, the surface of the green body is cleaned by blowing away the floating dust. Commercial matte frit glaze is applied by dipping. The dipping time for a single body is controlled at 10s. The thickness of the glaze layer after firing is 0.5mm. After glazing, the body is put back into the drying oven and dried at 90℃ for 24h until the residual moisture of the glaze layer is qualified.

[0038] (5) Sintering of body and glaze: Place the dried glaze body in Figure 1 Sintering is carried out on the rotating platform of the sintering furnace body of the medium-concentration solar furnace to obtain calcium feldspar-based ceramic slabs.

[0039] Please see Figure 1 , Figure 1 The concentrating solar furnace used for preparing calcium feldspar-based ceramic slabs with a wide firing temperature range provided in this embodiment 1 includes a solar tracking plane heliostat 101 with a high reflectivity plane mirror structure, a gear and rack solar tracking transmission mechanism 102 connected to the solar tracking plane heliostat 101, a parabolic concentrator 103 with a concave parabolic reflection structure, a sintering furnace body 104 with a closed metal cavity structure, and a rotating platform 1041 set at the scorch spot position inside the sintering furnace body; Among them, the sun-tracking transmission mechanism 102 can drive the sun-tracking plane heliostat 101 to adjust the pitch angle and azimuth angle in real time, track the changes in the sun's position and altitude, and ensure that the sunlight is always reflected parallel to the parabolic concentrator 103. The concentrator focuses the sunlight into a high-energy-density focal spot and projects it into the sintering furnace body 104. The rotating platform 1041 drives the glaze blank to be sintered to rotate at a uniform speed to ensure uniform heating.

[0040] Please see Figure 2 In Example 1, the entire sintering process of the concentrating solar furnace is divided into three stages: heating, holding, and cooling. In the initial stage of sintering, the temperature is rapidly increased from room temperature at a constant rate of 35°C / min, reaching the target sintering temperature of 1050°C in about 29 minutes. Then, the constant temperature holding stage is entered, and the temperature is maintained at 1050°C for 30 minutes to ensure that the anorthite, magnesium olivine, and zinc aluminum spinel crystal phases in the green body are fully developed, and the green body is densified. After the holding stage, the furnace cooling stage is entered, and the green body naturally cools down to room temperature with the furnace temperature, completing the entire sintering process. This heating regime matches the rapid photothermal conversion characteristics of the concentrating solar furnace, which greatly improves the heating rate compared with traditional kilns. The total sintering cycle is only about 160 minutes. At the same time, the gentle heating and cooling rates can avoid cracking of the green body caused by thermal stress, making it suitable for the rapid sintering of large-size slabs.

[0041] Please see Figure 3 The main crystalline phase of the anorthite-based ceramic slab sample prepared in Example 1 is anorthite (CaAl2Si2O8), with a small amount of residual quartz (SiO2) and high-melting-point crystalline phases of zinc aluminum spinel (ZnAl2O4) and forsterite (Mg2SiO4) generated in situ during sintering. Among them, the high-melting-point zinc aluminum spinel and forsterite are uniformly distributed at the anorthite grain boundaries, which can inhibit grain boundary migration and glass phase flow at high temperatures through grain boundary pinning, thereby raising the over-firing temperature of the system. This is an important phase basis for achieving a wide sintering window of 60℃. The XRD detection results of Example 1 are completely consistent with the wide-temperature sintering mechanism of the present invention.

[0042] Please see Figure 4 The ceramic slab prepared in Example 1 has a dense overall cross-sectional structure with fine and uniform grain size. It has only a very small number of isolated closed pores and no interconnected pores or obvious microcracks. This indicates that the green body has been fully densified at the sintering temperature of 1050℃ and the concentrated rapid heating process effectively suppressed abnormal grain growth.

[0043] Please see Figure 5The calcium feldspar-based ceramic slab prepared in Example 1 has no obvious layering interface or through cracks in the glaze-body bonding layer, forming a continuous and natural transition layer. There are only a few isolated spherical closed bubbles in the glaze layer, and no glaze defects such as pinholes or glaze peeling. This indicates that the matte frit glaze used in Example 1 has a good match with the calcium feldspar body in terms of thermal expansion coefficient and strong bonding force. No glaze cracking or glaze peeling occurred during the rapid light-concentrating sintering process, and the glaze quality was stable after firing.

[0044] The properties and microstructure of the anorthite-based 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 1000–1060℃, with a firing window of 60℃, achieving wide-range densification sintering under concentrated light conditions; the product had a water absorption rate of 0.15% and a bulk density of 2.6 g / cm³. 3 All performance characteristics meet the requirements of GB / T45817-2025 ceramic slab standard.

[0045] Comparative Example 1 (no light absorber, no flux): 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: the light absorber zinc oxide and the flux Guiguang talc powder are not 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 ball milling, granulation, molding, glazing process parameters, as well as the sintering regime of the concentrating solar furnace, are completely consistent with those in Example 1.

[0046] Performance testing revealed that, due to the lack of a light absorber to enhance photothermal conversion and the lack of a flux to lower the liquid phase formation temperature, the water absorption rate of Comparative Example 1 after sintering at 1050℃ was 13.82%, and the bulk density was 1.95 g / cm³. 3 Gradient sintering verification showed that the formula required a temperature of 1190℃ to achieve the ceramic standard of water absorption ≤0.5%, and the effective sintering window was only 30℃ (1190~1220℃). If the temperature exceeded 1190℃, over-firing defects such as edge deformation and glass phase overflow would occur, and the wide window low-temperature sintering effect of 1000~1060℃ described in this invention could not be achieved.

[0047] 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 for the adjustment of the sintering method: instead of using a concentrated solar furnace, a traditional resistance furnace used in the ceramic industry is used for sintering. All other process parameters, including raw material formulation, ball milling, granulation, molding, and glazing, are completely consistent with those in Example 1. The sintering process adopts the slow firing regime commonly used in the ceramic industry: the dried glaze blank is placed in the resistance furnace and heated from room temperature to 1200℃ at a conventional heating rate of 5℃ / min. After holding at this temperature for 60 minutes, the sample is naturally cooled with the furnace to obtain the sample.

[0048] Performance testing revealed that Comparative Example 2, employing 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 light absorbers and fluxes, a temperature of 1200℃ was still required to achieve compaction of the green body. The sample sintered at the optimal temperature exhibited a water absorption rate of 0.36% and a bulk density of 2.43 g / cm³. 3 Gradient sintering verification showed that the effective sintering window of the sample under this process was only 20℃ (1200~1220℃), which could not achieve low-temperature wide-window sintering of 1000~1060℃, and the sintering energy consumption per unit product was much greater than that of Example 1, with no zero carbon emission reduction advantage.

[0049] In summary, the technical solution provided by this invention has the following advantages compared to existing technologies: (1) Wide sintering temperature range of 1000~1060℃: This invention, through the formulation design of light absorber and flux and the synergistic effect of light-concentrating rotary sintering process, expands the effective sintering window of calcium feldspar-based ceramic slabs from 10~40℃ in the traditional process to 60℃, greatly reducing the requirements for kiln temperature control accuracy, reducing defects such as over-firing, under-firing, and deformation, and significantly improving the yield of large-size slabs.

[0050] (2) Low sintering temperature: The present invention reduces the sintering temperature by about 100-200℃ compared with the traditional roller kiln. It uses zero-carbon solar energy as the only sintering heat source, which greatly reduces the sintering energy consumption per unit product and further reduces carbon emissions. It does not require supporting flue gas treatment equipment, which meets the dual-carbon transformation requirements of the building materials industry.

[0051] (3) Stable product performance: The calcium feldspar-based ceramic rock slab prepared by this invention has a water absorption rate of 0.12% to 0.15% and a bulk density of 2.6 to 2.65 g / cm³. 3 All performance characteristics meet the GB / T 45817-2025 ceramic slab standard. The raw materials are common bulk raw materials used in the industry, which are low in cost, highly replicable, and have the potential for large-scale promotion.

[0052] 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.

[0053] 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 of producing a calcium-feldspar-based ceramic rock plate having a wide firing temperature range, characterized by, Includes the following steps: S10, the calcium feldspar-based ceramic slab green body powder and light absorber are mixed evenly by ball milling to obtain a mixed powder; S20, water is added to the mixed powder to make a slurry, which is then spray-dried, granulated, and aged to obtain a raw material; S30, the blank is pressed into shape and dried to obtain a ceramic slab green blank; S40, the ceramic slab green body is glazed by glazing method, and the glazed body is obtained after drying; S50, the glaze blank is placed in a concentrating solar furnace and sintered by rotation in a wide firing temperature range of 1000 to 1060°C to obtain calcium feldspar-based ceramic slabs.

2. The method for preparing calcium feldspar-based ceramic slabs with a wide firing temperature range 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.

3. The method for preparing calcium feldspar-based ceramic slabs with a wide firing temperature range according to claim 1, characterized in that, The chemical composition of the anorthite-based ceramic slab green powder, by mass percentage, comprises: 63.5 wt.%–64.5 wt.% SiO2, 17.0 wt.%–18.0 wt.% Al2O3, 0.9 wt.%–1.0 wt.% Fe2O3, 10.0 wt.%–11.0 wt.% CaO, 4.0 wt.%–5.0 wt.% MgO, 1.0 wt.%–1.5 wt.% K2O, 1.0 wt.%–1.5 wt.% Na2O, and 0.1 wt.%–0.2 wt.% TiO2, with the balance being unavoidable impurities. The sum of the mass percentages of all components is 100 wt.%. The light absorber, relative to the anorthite-based ceramic slab green powder, has an added mass percentage of 5.0 wt.%–8.0 wt.%.

4. The method for preparing calcium feldspar-based ceramic slabs with a wide firing temperature range according to claim 1, characterized in that, The mixed powder is made from the following mineral raw materials in parts by weight: 35-40 parts diopside, 5-10 parts wollastonite, 20-25 parts quartz, 25-30 parts kaolinite, 2-6 parts flux and 1-5 parts light absorber; wherein the flux is an inorganic solid flux filler and the light absorber is a semiconductor oxide.

5. The method for preparing calcium feldspar-based ceramic slabs with a wide firing temperature range according to claim 1, characterized in that, In step S20, the amount of water added is 5 wt.% to 20 wt.% of the mass of the mixed powder, and the aging time after granulation is 24 to 48 hours.

6. The method for preparing calcium feldspar-based ceramic slabs with a wide firing temperature range according to claim 1, characterized in that, In step S30, the molding pressure is 40-100kN and the holding time is 30-70s; the drying temperature after molding is 80-100℃ and the drying time is 24-48h.

7. The method for preparing calcium feldspar-based ceramic slabs with a wide firing temperature range according to claim 1, characterized in that, In step S40, the glaze is a matte frit glaze, and the glazing time for a single ceramic slab green body is 5 to 20 seconds; the drying temperature after glazing is 80 to 100°C, and the drying time is 24 to 48 hours.

8. The method for preparing calcium feldspar-based ceramic slabs with a wide firing temperature range according to claim 1, characterized in that, In step S50, the rotational speed of the rotary sintering is 10-15 r / min; the sintering in the concentrating solar furnace includes heating, holding and cooling stages in sequence: the heating stage raises the temperature from room temperature to 1000-1060℃ at a rate of 30-40℃ / min, the holding stage holds the temperature at 1000-1060℃ for 20-40 min, and then cools to room temperature.

9. The method for preparing calcium feldspar-based ceramic slabs with a wide firing temperature range according to claim 1, characterized in that, In step S50, the concentrating solar furnace includes, in sequence along the optical path, a solar tracking plane heliostat, a parabolic concentrator, and a sintering furnace body: The solar tracking plane heliostat is used to track the sun's position in real time and reflect sunlight in parallel to the parabolic concentrator. The parabolic concentrator is used to focus the received sunlight into a focal spot and project it onto the sintering position inside the sintering furnace. The sintering furnace is equipped with a rotating platform for placing the glaze blank to be sintered and driving the glaze blank to rotate at a uniform speed under the irradiation of the focal spot to complete the sintering.

10. A calcium feldspar-based ceramic slab with a wide firing temperature range, characterized in that, The method is prepared by any one of claims 1 to 9; the water absorption of the anorthite-based ceramic rock plate is 0.10-0.20%, the bulk density is 2.5-2.7g / cm 3 , and the performance meets the requirements of GB / T 45817-2025 national standard for ceramic rock plate.

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