A high-temperature high-white lead-free cadmium-free ceramic glaze composition and a preparation method thereof

Abstract

This invention discloses a high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition and its preparation method, belonging to the field of ceramic glaze technology. The glaze composition contains the following components by weight percentage: SiO2 45-54%; Al2O3 7-12%; ZnO 9-17%; K2O 3-5%; Na2O 0.6-2.8%; B2O3 2-8%; nano-sodium zirconium phosphate 0.5-0.7%; and nano-yttrium aluminate 0.3-0.5%; and unavoidable impurities. The preparation method includes: surface modification and coating of nano-sodium zirconium phosphate and nano-yttrium aluminate using a coupling agent; mixing the oxide raw materials according to the stated weight percentages, and obtaining a frit after melting and quenching; mixing and grinding the surface-modified nanomaterials with the frit to obtain a glaze slurry. This invention uses 9-17% ZnO combined with K2O-Na2O-B2O3 to form a multi-component composite fluxing system. The glaze is fully melted at 1050-1120℃, with a whiteness ≥88.8 degrees and lead and cadmium leaching amounts both below 0.01 mg / L.

Description

Technical Field

[0001] This invention relates to the field of ceramic glaze technology, specifically to a high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition and its preparation method. Background Technology

[0002] Ceramic glazes are thin, vitreous layers applied to the surface of ceramic products, significantly influencing their appearance, mechanical properties, and chemical safety. Traditional ceramic glazes typically contain lead compounds. While lead effectively lowers the firing temperature and enhances gloss, it is neurotoxic, reproductively toxic, and developmentally toxic, cannot be metabolized in the human body, and long-term ingestion can lead to chronic poisoning. Furthermore, discarded lead-containing ceramic products become sources of soil and water pollution. With strict limits set on the migration of heavy metals such as lead and cadmium by regulations such as the EU RoHS Directive, US FDA standards, and China's GB4806.9-2016, the development of lead-free and cadmium-free ceramic glazes has become a crucial technological direction for the ceramic industry.

[0003] To achieve lead-free production and ensure the overall performance of the glaze, existing technologies have explored various approaches. Patent CN121202437B discloses a high-whiteness ceramic frit and its preparation method. This frit, by weight, consists of 46-48 parts quartz, 12-14 parts calcined alumina, 8-10 parts lithium kaolin ore, 4-5 parts magnesium slag, 6-8 parts cordierite powder, 3-4 parts lanthanum silicate, 1.8-2.0 parts strontium tetraborate, 0.9-1.1 parts sodium fluorosilicate, 0.5-0.7 parts nano-sodium zirconium phosphate, 0.3-0.5 parts nano-yttrium aluminate, and 0.1-0.2 parts nano-samarium oxide. Densification and fluxing are achieved through a chain-like synergistic mechanism among magnesium slag, strontium tetraborate, sodium fluorosilicate, and lithium kaolin ore. Nano-sodium zirconium phosphate and nano-yttrium aluminate are used as functional fillers to enhance whiteness and mechanical properties. The fluxing system of this patent relies entirely on a specific combination of magnesium slag, strontium tetraborate, sodium fluorosilicate, and lithium kaolin ore. The functions of each component are interdependent: magnesium slag and lithium kaolin ore jointly regulate the melt viscosity and fluidity, strontium tetraborate ensures sufficient reaction and wettability, and sodium fluorosilicate removes air bubbles to eliminate porosity. If any component is replaced, the overall densification and fluxing effect will be affected. At the same time, in this patent, the nanomaterials and all raw materials are sintered together at 1300-1320℃. The coupling agent coating layer on the surface of the nanomaterials may be damaged during the high-temperature preparation process.

[0004] Patent CN101759440A discloses a lead-free ceramic glaze and its preparation process. The glaze, by weight percentage, contains SiO2 50-65%, Al2O3 6-12%, ZnO 3-8%, K2O 1-6.5%, Na2O 1-5%, B2O3 1-8%, Li2O 0.5-5%, and La2O3 0.2-4%. This patent, through extensive research, found that a ZnO content of 3-8% has minimal impact on the color development of commonly used ceramic colors; in its embodiments, the upper limit of the ZnO content is 8%. The patent uses La2O3 to broaden the glaze's firing temperature range to 1020-1180℃, and its technical approach addresses firing process issues through rare earth oxides rather than increasing the ZnO content. However, this patent does not involve the introduction of nano-sodium zirconium phosphate or nano-yttrium aluminate, nor does it address surface modification treatment of nanomaterials.

[0005] Patent CN108017283B discloses a lead-free ceramic glaze and its preparation method. The glaze, by weight, contains 65-75 parts SiO2, 16-21 parts SnO2, 15-20 parts B2O3, 10-12 parts ZnO, 5-10 parts Al2O3, 4-10 parts K2O, and 3.5-4.5 parts Na2O. It uses a ZnO-K2O-Na2O-B2O3 fluxing system and SnO2 as an opacifying and whitening component. The firing temperature is 1350-1400℃. This patent also does not involve the introduction of nano-sodium zirconium phosphate or nano-yttrium aluminate, nor does it address surface modification treatment of nanomaterials.

[0006] In summary, while CN121202437B discloses the combined use of nano-sodium zirconium phosphate and nano-yttrium aluminate, its fluxing system relies on a specific magnesium slag-strontium tetraborate-sodium fluorosilicate-lithium kaolin ore chain synergistic mechanism, lacking guidance on alternative fluxing schemes. Although CN101759440A and CN108017283B disclose a ZnO-K2O-Na2O-B2O3 fluxing system, the ZnO content in the CN101759440A example does not exceed 8%, and neither of them involves the introduction of nano-sodium zirconium phosphate and nano-yttrium aluminate, nor the surface modification treatment of nanomaterials. Therefore, how to provide an alternative fluxing system for high-whiteness lead-free and cadmium-free ceramic glazes containing nano-sodium zirconium phosphate and nano-yttrium aluminate, so that the glaze can be fully melted at a lower temperature and obtain good glaze quality, is a technical problem that needs to be solved in this field. At the same time, how to effectively protect the surface modification layer of nanomaterials during the preparation process so that it can give full play to its function is another technical problem that needs to be solved in this field. Summary of the Invention

[0007] The technical problem this invention aims to solve is that existing lead-free ceramic glaze technologies, particularly high-whiteness glaze systems containing nano-sodium zirconium phosphate and nano-yttrium aluminate, typically rely on a specific magnesium-containing slag and boron-strontium-fluorine composite fluxing mechanism. The functions of each component are interdependent, and there is a lack of alternative fluxing solutions. Furthermore, existing technologies using zinc oxide as a flux generally have low zinc oxide content and do not involve the introduction of nano-sodium zirconium phosphate and nano-yttrium aluminate, nor their surface modification treatment. Therefore, the primary technical problem this invention aims to solve is how to provide an alternative high-content zinc oxide fluxing system for high-whiteness lead-free and cadmium-free ceramic glazes containing nano-sodium zirconium phosphate and nano-yttrium aluminate, enabling the glaze to fully melt at lower temperatures and achieve good glaze surface quality. Building upon this, another technical problem this invention aims to solve is how to effectively protect the surface modification layer of the nanomaterials during the preparation process, allowing it to fully function.

[0008] This invention provides a high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition, comprising the following components by weight percentage: SiO2 45-54%; Al2O3 7-12%; ZnO 9-17%; K2O 3-5%; Na2O 0.6-2.8%; B2O3 2-8%; nano-sodium zirconium phosphate 0.5-0.7%; and nano-yttrium aluminate 0.3-0.5%; and unavoidable impurities.

[0009] Furthermore, the weight ratio of K2O to Na2O is 1.5 to 2.5:1.

[0010] Furthermore, the nano-sized sodium zirconium phosphate has a particle size of 50–100 nm, and the nano-sized yttrium aluminate has a particle size of 50–70 nm.

[0011] Furthermore, the glaze composition also contains 0.8% to 1.5% ZrO2.

[0012] Furthermore, the glaze composition also contains at least one of the following components: CaO 7-12%, MgO 0.8-8%, and Li2O 0.5-1.5%.

[0013] Furthermore, the glaze composition also contains 0.1-0.2% nano-samarium oxide, and at least one of BaO 0-6% and SrO 0-4%.

[0014] More preferably, the glaze composition comprises the following components in weight percentage: 50-54% SiO2, 8-11% Al2O3, 12-16% ZnO, 3.8-4.5% K2O, 1.8-2.5% Na2O, 4-6% B2O3, 0.6-0.7% nano-sodium zirconium phosphate, 0.4-0.5% nano-yttrium aluminate, 1.0-1.4% ZrO2, 0.8-1.5% Li2O, 0.15-0.2% nano-samarium oxide, and unavoidable impurities.

[0015] This invention also provides a method for preparing a high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition, comprising the following steps: S1. Surface modification treatment of nano-sodium zirconium phosphate and nano-yttrium aluminate, wherein the surface modification treatment includes coating the nano-sodium zirconium phosphate and nano-yttrium aluminate with a coupling agent; S2. Mixing SiO2, Al2O3, ZnO, potassium-containing raw materials, sodium-containing raw materials, and boron-containing raw materials, and obtaining a frit by melting and quenching; wherein the potassium-containing raw material is selected from at least one of potassium carbonate, potassium oxide, potassium hydroxide, potassium nitrate, and potassium feldspar; the sodium-containing raw material is selected from at least one of sodium carbonate, sodium oxide, sodium hydroxide, sodium nitrate, and albite; and the boron-containing raw material is selected from at least one of boric acid, boron oxide, borax, and calcium borate; S3. Mixing and grinding the surface-modified nano-sodium zirconium phosphate and nano-yttrium aluminate from step S1 with the frit obtained in step S2 to obtain a glaze slurry.

[0016] Furthermore, the coupling agent in step S1 is a silane coupling agent, and the surface modification treatment further includes: mixing nano-sodium zirconium phosphate and nano-yttrium aluminate evenly, adding anhydrous ethanol for ultrasonic dispersion, and then coating with the coupling agent.

[0017] Furthermore, the process after ultrasonic dispersion and before coupling agent coating includes: calcining at 460–500°C for 25–35 min, and then pulverizing the calcined nanomaterials to a median particle size D50 of 0.3–0.5 μm.

[0018] Furthermore, after step S3, the following steps are also included: S4. The ceramic body is bisque-fired at 800-850°C; S5. The glaze slurry obtained in step S3 is applied to the surface of the bisque-fired ceramic body in step S4, and the glaze layer thickness is 0.2-0.3 mm; S6. Glaze firing is carried out at a temperature of 1050-1120°C to obtain a high-temperature, high-whiteness, lead-free, and cadmium-free ceramic material.

[0019] Furthermore, the glaze firing in step S6 is carried out according to the following firing regime: from room temperature to 400°C, heating rate 2-3°C / min; from 400°C to 600°C, heating rate 3-4°C / min; from 600°C to 900°C, heating rate 4-5°C / min; from 900°C to the maximum firing temperature, heating rate 5-6°C / min; holding at the maximum firing temperature for 30-40 min; cooling stage: from the maximum firing temperature to 800°C, cooling rate 3-4°C / min; from 800°C to 600°C, cooling rate 4-5°C / min, and holding at 700°C for 8-12 min; from 600°C to room temperature, natural cooling.

[0020] The high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition and its preparation method provided by this invention have the following advantages compared with the prior art: 1. The glaze composition uses zinc oxide as the core flux, combined with potassium oxide, sodium oxide, and boron oxide to form a multi-component composite flux system. This system can achieve full melting of the glaze and form a uniform and dense glass phase at a relatively low temperature of 1050-1120℃. The firing temperature is 250-300℃ lower than that of conventional high-temperature lead-free glazes. At the same time, zinc oxide, as an environmentally friendly metal oxide, works together with potassium oxide and sodium oxide to reduce the lead and cadmium leaching amounts to less than 0.01mg / L, fully complying with the EU RoHS directive, US FDA standards, and Chinese GB4806.9-2016 and other environmental regulations.

[0021] 2. The nano-sized opacifying droplets formed by nano-sodium zirconium phosphate in the glaze composition have a size comparable to the wavelength of visible light, which can produce a strong scattering effect on visible light, making the whiteness of the glaze reach 88.8 degrees or higher, and up to 96 degrees, with a gloss of not less than 85.0 GU. The whiteness is 15% to 30% higher than that of existing lead-free ceramics. When the glaze composition further includes zirconium oxide, the microcrystalline phase precipitated by zirconium oxide at high temperature can form a dual opacifying mechanism with the nano-sized opacifying droplets of nano-sodium zirconium phosphate, further enhancing the opacifying and whitening effect.

[0022] 3. The nano-yttrium aluminate in the glaze composition significantly improves the thermal stability and crack resistance of the glaze at high temperatures by refining grains, pinning grain boundaries, and inhibiting abnormal grain growth. This allows the product to withstand more than three rapid cooling and heating cycles from 200℃ to 20℃ without cracking, and the coefficient of thermal expansion matches well with the body. Simultaneously, the dispersed distribution of nano-sodium zirconium phosphate and nano-yttrium aluminate in the glaze matrix forms a nano-second phase toughening effect, increasing the flexural strength of the glaze surface to over 78MPa, approximately 40% higher than the standard for ordinary daily-use porcelain, and achieving a Mohs hardness of 6.5–7. When the glaze composition further includes nano-samarium oxide, the Sm in the nano-samarium oxide… 3+ By competitively absorbing 280–380 nm ultraviolet light through 4f electron transitions, the effects of Fe can be mitigated. 3+The yellow-brown coloring caused by stimulation makes the glaze base color purer and the visual whiteness more authentic.

[0023] 4. The preparation method adopts a two-step process of first preparing a frit and then mixing and grinding the surface-modified nanomaterials with the frit. This process avoids the damage to the coupling agent coating layer on the surface of the nanomaterials during the high-temperature preparation process of the frit. The complete coupling agent coating layer ensures the uniform dispersion of nano-sodium zirconium phosphate and nano-yttrium aluminate in the glaze slurry, giving full play to their nano-effects of opacification, whitening and grain refinement.

[0024] 5. The preparation method adopts a two-stage firing process that combines bisque firing and glaze firing. Bisque firing allows the body to complete the main shrinkage in advance, and the difference in shrinkage between the body and glaze is greatly reduced after glazing. This fundamentally solves the cracking and deformation problems caused by the mismatch between body and glaze shrinkage in a single firing, and significantly improves the product qualification rate. Attached Figure Description

[0025] Figure 1 This is a flowchart of the preparation method of the high-temperature, high-whiteness, lead-free and cadmium-free ceramic glaze composition and ceramic materials of the present invention; Figure 2 yes Figure 1 Firing temperature curve for the glaze firing process. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be obtained commercially.

[0027] The nano-sodium zirconium phosphate (chemical formula NaZr2(PO4)3, NASICON-type crystal structure) and nano-yttrium aluminate (chemical formula Y3Al5O) used in this invention 12 Yttrium aluminum garnet (YAG) crystals are commercially available products and can be purchased through commercial channels. Nano-samarium oxide is a commercially available nano-rare earth oxide powder. Typical technical indicators for the above nanomaterials are: purity ≥ 99.5%, specific surface area ≥ 15 m². 2 / g.

[0028] Example 1 This embodiment provides a high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition and its preparation method. The chemical composition of the glaze composition, by weight percentage, is as follows: SiO2 49.8%, Al2O3 9.5%, ZnO 14.6%, K2O 3.8%, Na2O 1.9%, B2O3 4.5%, ZrO2 0.8%, nano-sodium zirconium phosphate 0.6%, nano-yttrium aluminate 0.4%, nano-samarium oxide 0.15%, CaO 7.8%, MgO 2.0%, Li2O 0.8%, with the remainder being unavoidable mineral raw material impurities.

[0029] The average particle size of the nano-sodium zirconium phosphate is 80 nm, the average particle size of the nano-yttrium aluminate is 60 nm, the average particle size of the nano-samarium oxide is 50 nm, and the weight ratio of K2O to Na2O is 2.0:1.

[0030] The preparation method of this glaze composition includes the following steps, the preparation process as follows: Figure 1 As shown.

[0031] S1. Surface modification treatment of nanomaterials 0.6 kg of nano-sodium zirconium phosphate, 0.4 kg of nano-yttrium aluminate, and 0.15 kg of nano-samarium oxide were mixed evenly, and 5% anhydrous ethanol (by mass of the three) was added. The mixture was then ultrasonically dispersed for 12 minutes. The purpose of ultrasonic dispersion was to utilize the cavitation effect of ultrasound to initially deagglomerate the soft aggregates between nanoparticles, thereby achieving pre-dispersion of the three nanomaterials in the liquid medium.

[0032] The ultrasonically dispersed nanomaterials were placed in a muffle furnace and heated to 480°C at a rate of 5°C / min, and held at that temperature for 30 minutes for calcination. The purpose of calcination is to remove adsorbed moisture and residual organic matter from the surface of the nanomaterials, activate the surface of the nanoparticles, expose their surface hydroxyl groups, and provide active sites for subsequent coupling agent coating.

[0033] The calcined nanomaterials were pulverized using an air jet mill to a median particle size (D50) of 0.4 μm to eliminate any hard agglomerates that might form during calcination. Subsequently, a KH550 silane coupling agent-ethanol solution was added to the pulverized nanoparticle mixture for coating. The mass of KH550 silane coupling agent (γ-aminopropyltriethoxysilane) in this solution accounted for 0.3% of the combined mass of the ethanol solution and KH550 silane coupling agent, while the mass of the KH550 silane coupling agent-ethanol solution accounted for 5% of the mass of the nanoparticle mixture. The mixture was stirred at 400 rpm for 20 minutes at room temperature, and then dried in a 60°C forced-air drying oven for 1 hour to obtain the surface-modified nanomaterials.

[0034] The mechanism of coupling agent coating is as follows: the ethoxy group (-OC2H5) at one end of the KH550 silane coupling agent molecule hydrolyzes in the presence of moisture to generate silanol groups (-Si-OH), which undergo a condensation reaction with the hydroxyl groups on the surface of nanoparticles to form stable Si-O-nanoparticle chemical bonds; the amino group (-NH2) at the other end points outward and has good compatibility with the silicon-oxygen network in the glaze matrix. Thus, the coupling agent forms an organic-inorganic interface transition layer on the surface of the nanoparticles. On the one hand, this reduces the surface energy of the nanoparticles, preventing them from re-aggregating during subsequent grinding and storage; on the other hand, it improves the interfacial bonding force between the nanoparticles and the glass phase matrix of the glaze, ensuring that the nanoparticles can be firmly embedded in the glaze layer after glaze firing.

[0035] S2. Fused Ingot Preparation The following ingredients are prepared: 48 kg of quartz powder (SiO2 content ≥ 99.5%), 13 kg of calcined alumina (Al2O3 content ≥ 99%), 15 kg of zinc oxide (ZnO content ≥ 99.5%), 4 kg of potassium carbonate (K2CO3 content ≥ 98%, with K2O introduced as K2O), 2 kg of sodium carbonate (Na2CO3 content ≥ 98%, with Na2O introduced as Na2O), and 5 kg of boric acid (H3BO3 content ≥ 99.5%, with B2O3 introduced as B2O3). 10 kg of calcium carbonate (CaCO3 content ≥ 98.5%, with CaO introduced as CaO) , 4 kg of magnesium carbonate (MgCO3 content ≥ 98%, with MgO introduced as MgO) , 1.5 kg of lithium carbonate (Li2CO3 content ≥ 98%, with Li2O introduced as Li2O) , and 1 kg of zirconium oxide (ZrO2 content ≥ 99%) are mixed evenly and placed in a high-temperature furnace. The mixture is heated to 1310℃ at a heating rate of 5℃ / min and held at this temperature for 38 minutes to ensure complete melting of the raw materials. At high temperatures, the raw materials decompose and melt: carbonates decompose, releasing CO2 gas and transforming into corresponding oxides; boric acid dehydrates and transforms into B2O3; and the oxides melt at high temperatures to form a silicate melt. The purpose of the holding stage is to fully homogenize the melt, remove residual bubbles, and ensure uniform composition of the molten mass.

[0036] The molten material is poured into cold water at 30°C for quenching. During quenching, the high-temperature melt cools rapidly, its viscosity increases sharply, and the atoms are "frozen" before they can arrange themselves in an orderly manner, forming an amorphous glassy frit. The glassy frit has higher chemical activity than the crystalline material and can be remelted and leveled at a lower temperature during subsequent glazing. The quenched frit is dehydrated using a vibrating screen and dried at 102°C for 1 hour to obtain the final frit.

[0037] S3. Preparation of glaze slurry The frit obtained in step S2 is mixed with the surface-modified nanomaterial obtained in step S1, and an appropriate amount of water is added. The mixture is then ground in a ball mill until the fineness is 0.4% residue on a 325-mesh sieve to obtain a glaze slurry. An appropriate amount of sodium carboxymethyl cellulose (CMC) is added to the glaze slurry as a thickener to adjust the viscosity to 35s (Ford-4 cup, 25°C). The slurry is then passed through a 200-mesh sieve to remove impurities and large particles, resulting in a glaze slurry that can be directly used for glazing.

[0038] This process employs a two-step method: first, preparing the frit, then mixing and grinding it with pretreated nanomaterials. Compared to a one-step process where nanomaterials are sintered together with all raw materials, this two-step method has significant technical advantages: frit preparation requires a high temperature of 1300–1320°C, while the coupling agent coating layer on the surface of the nanomaterials is an organosilane, whose thermal decomposition temperature is approximately 300–400°C. If the nanomaterials are added to all raw materials before sintering using a one-step method, the coupling agent coating layer will be completely ablated and decomposed during the high-temperature frit preparation process, losing its function of improving nanoparticle dispersion and interfacial bonding. This invention separates frit preparation from nanomaterial incorporation, allowing the coupling agent coating layer to be completely preserved. The nanoparticles are then uniformly dispersed in the glaze slurry during the subsequent ball milling stage, and during glaze firing, they form a strong bond with the glaze glass phase matrix through the interfacial transition layer of the coupling agent.

[0039] The glaze composition (glaze slurry form) prepared by steps S1 to S3 above is the glaze composition of the present invention. Steps S4 to S6 further describe the complete process of manufacturing ceramic products using this glaze composition.

[0040] S4. Plain roast The ceramic blank is placed in the kiln and heated to 830°C at a rate of 4°C / min, held at that temperature for 30 minutes, and then allowed to cool naturally to room temperature. The purpose of bisque firing is to allow the blank to undergo drying shrinkage and partial sintering shrinkage in advance, thereby increasing the strength of the blank and providing sufficient mechanical strength for subsequent glazing operations, while also reducing further shrinkage of the blank during the glaze firing stage.

[0041] S5. Glazing The glaze slurry obtained in step S3 is applied to the surface of the bisque-fired ceramic body after step S4 using an impregnation method, with the glaze layer thickness controlled at 0.25 mm. The glazed body is then allowed to dry naturally at room temperature for 2 hours, and then dried in a drying oven at 60°C for 4 hours to reduce the moisture content of the glaze layer to below 0.5%, thus avoiding defects such as pinholes and bubbles caused by rapid evaporation of moisture during the glaze firing stage.

[0042] S6. Glaze firing The glazed and dried clay body is placed in the kiln, and then... Figure 2 The glaze is fired using the firing temperature curve shown, and the specific firing regime is as follows: From room temperature to 400℃, the heating rate is 2.5℃ / min. This stage mainly involves the slow removal of residual moisture from the glaze and the decomposition of organic additives. The low heating rate can prevent glaze cracking caused by rapid evaporation of water vapor.

[0043] The temperature is increased from 400℃ to 600℃ at a rate of 3.5℃ / min. This stage removes the water of crystallization from the mineral raw material and further decomposes the carbonates.

[0044] The temperature ranges from 600℃ to 900℃, with a heating rate of 4.5℃ / min. During this stage, the green body begins to show a liquid phase, and the glaze particles begin to soften. Appropriately increasing the heating rate is beneficial to production efficiency.

[0045] The temperature range is 900℃ to 1080℃, with a heating rate of 5.5℃ / min. During this stage, the glaze enters a rapid melting phase, and the synergistic melting point reduction effect of the ZnO-K2O-Na2O-B2O3 multi-component fluxing system plays a concentrated role in this temperature range.

[0046] Hold at 1080℃ for 35 minutes. During the holding stage, the glaze is fully melted and leveled to form a uniform and dense glassy phase. At the same time, nano-sodium zirconium phosphate and nano-yttrium aluminate particles are convected and diffused in the melt, and are evenly distributed in the glaze layer.

[0047] Cooling stage: 1080℃ to 800℃, cooling rate 3.5℃ / min; 800℃ to 600℃, cooling rate 4.5℃ / min, and holding at 700℃ for 10 minutes. The purpose of the 700℃ holding platform is to allow the glaze layer to relax stress near its glass transition temperature, releasing the thermal stress caused by the difference in thermal expansion coefficients between the glaze layer and the body, and reducing the risk of cooling cracking. Cooling from 600℃ to room temperature naturally yields a high-temperature, high-whiteness, lead-free, and cadmium-free ceramic material.

[0048] The ceramic material prepared in this embodiment was subjected to performance tests, and the results are as follows: the whiteness of the glaze is 89.2 degrees (determined according to QB / T 1503-2011 "Method for Determination of Whiteness of Daily-use Ceramics", with 100% standard whiteness of magnesium oxide as the benchmark), and the gloss is 86.5 GU (determined according to GB / T 3295-2025 "Test Method for Specular Gloss of Ceramic Products"); the lead leaching and cadmium leaching are both less than 0.01 mg / L (determined according to GB / T 3534 "Method for Determination of Lead and Cadmium Leaching in Daily-use Ceramics"); the product showed no cracks after being rapidly cooled from 200℃ to 20℃ three times (tested according to GB / T 3298 "Method for Determination of Thermal Shock Resistance of Daily-use Ceramics"); the flexural strength is 79 MPa (determined according to GB / T 4741 "Test Method for Flexural Strength of Ceramic Materials"); the Mohs hardness is 6.7; and there are no corrosion marks after immersion in 10% hydrochloric acid solution for 24 hours.

[0049] Example 2 This embodiment optimizes the glaze formulation based on Example 1, providing a preferred implementation method. The optimized glaze composition, by weight percentage, is as follows: SiO2 52.0%, Al2O3 10.0%, ZnO 14.0%, K2O 4.2%, Na2O 2.1%, B2O3 5.5%, ZrO2 1.2%, nano-sodium zirconium phosphate 0.65%, nano-yttrium aluminate 0.45%, nano-samarium oxide 0.18%, CaO 6.5%, MgO 1.5%, Li2O 1.2%, with the remainder being unavoidable mineral impurities. The weight ratio of K2O to Na2O is 2.0:1.

[0050] The preparation method is the same as steps S1 to S6 of Example 1, except that: the maximum glazing temperature is adjusted to 1060℃ and the holding time is extended to 40 minutes; the calcination temperature of the nanomaterial in step S1 is increased to 500℃ and the calcination time is extended to 35 minutes; the amount of KH550 silane coupling agent is 0.4% of the total mass of ethanol solution and KH550 silane coupling agent.

[0051] The ceramic material prepared in this embodiment was subjected to performance tests, and the results are as follows: the whiteness of the glaze is 91.5 degrees, the gloss is 88.7 GU; the lead leaching and cadmium leaching are both less than 0.01 mg / L; no cracks were found after four cycles of rapid cooling and heating from 200℃ to 20℃; the flexural strength is 83 MPa; and the fracture toughness is 1.68 MPa·m^(1 / 2).

[0052] Example 3 This embodiment provides a basic formulation implementation that does not contain ZrO2 or nano-samarium oxide, to verify that the glaze composition of the present invention can still achieve the basic technical effect without the above-mentioned optional components.

[0053] The chemical composition of this glaze composition, by weight percentage, is as follows: SiO2 51.5%, Al2O3 11.5%, ZnO 12.5%, K2O 4.0%, Na2O 2.0%, B2O3 4.2%, nano-sodium zirconium phosphate 0.6%, nano-yttrium aluminate 0.4%, CaO 10.5%, MgO 2.0%, Li2O 0.8%, with the remainder being unavoidable mineral impurities. The weight ratio of K2O to Na2O is 2.0:1, the average particle size of nano-sodium zirconium phosphate is 80 nm, and the average particle size of nano-yttrium aluminate is 60 nm.

[0054] The preparation method is the same as steps S1 to S6 of Example 1, except that: no zirconium oxide and nano samarium oxide are added in the preparation of the frit, and only nano sodium zirconium phosphate and nano yttrium aluminate are surface modified in the pretreatment of nanomaterials.

[0055] The ceramic material prepared in this embodiment was subjected to performance tests, and the results are as follows: the glaze whiteness is 85.3 degrees, the gloss is 82.0 GU; the lead and cadmium leaching amounts are both less than 0.01 mg / L; no cracks were observed after two rapid cooling and heating cycles from 200℃ to 20℃; and the flexural strength is 72 MPa. Compared with Example 1, the whiteness and thermal stability of this embodiment are slightly reduced, but they still meet the basic performance requirements of daily-use ceramics, indicating that the basic technical solution defined by this invention can still achieve the expected technical effects without ZrO2 and nano-samarium oxide.

[0056] Example 4 This embodiment provides an implementation containing only nano-sodium zirconium phosphate and nano-yttrium aluminate, without nano-samarium oxide, to further demonstrate the non-essentiality of nano-samarium oxide.

[0057] The chemical composition of the glaze composition by weight percentage is as follows: SiO2 50.5%, Al2O3 10.5%, ZnO 13.5%, K2O 4.0%, Na2O 2.0%, B2O3 5.0%, ZrO2 1.0%, nano-sodium zirconium phosphate 0.6%, nano-yttrium aluminate 0.4%, CaO 9.5%, MgO 2.0%, Li2O 1.0%, with the remainder being unavoidable mineral raw material impurities.

[0058] The preparation method is the same as steps S1 to S6 of Example 1, except that: only nano-sodium zirconium phosphate and nano-yttrium aluminate are surface modified in the nanomaterial pretreatment, and nano-samarium oxide is not added.

[0059] The ceramic material prepared in this embodiment was subjected to performance tests, and the results are as follows: the whiteness of the glaze is 88.5 degrees, and the gloss is 85.5 GU; the lead and cadmium leaching amounts are both less than 0.01 mg / L; no cracks were observed after three cycles of rapid cooling and heating from 200℃ to 20℃; and the flexural strength is 77 MPa. Compared with Example 1, the whiteness of this embodiment is slightly lower, but still reaches 88.5 degrees, indicating that nano-samarium oxide is not a necessary component for achieving high whiteness. Its main function in the glaze composition is to improve the whiteness of the glaze through the process of Sm... 3+ The 4f electron transition further optimizes the optical properties of the glaze, making the whiteness more pure.

[0060] Explanation of component substitution and changes In the above embodiments of the present invention, SiO2 is introduced in the form of quartz powder, and Al2O3 is introduced in the form of calcined alumina. In other specific embodiments of the present invention, SiO2 and Al2O3 can also be introduced in the form of natural mineral raw materials, such as potassium feldspar and sodium feldspar simultaneously introducing SiO2, Al2O3, and a portion of K2O and Na2O, or kaolin simultaneously introducing SiO2 and Al2O3. Introducing them in the form of natural mineral raw materials helps to reduce raw material costs. In another specific embodiment of the present invention, potassium feldspar (chemical composition approximately 65% ​​SiO2, 18% Al2O3, 12% K2O, and 3% Na2O) and sodium feldspar (chemical composition approximately 68% SiO2, 20% Al2O3, 10% Na2O, and 1% CaO) can be used as partial sources of SiO2, Al2O3, K2O, and Na2O. After formula calculation, they are used in combination with quartz, alumina, and other raw materials. The fired glaze has a whiteness of 87.6 degrees and a gloss of 84.0 GU. It can withstand three cycles of rapid cooling and heating from 200°C to 20°C without cracking.

[0061] In the above embodiments of the present invention, K2O is introduced in the form of potassium carbonate, and Na2O is introduced in the form of sodium carbonate. In another specific embodiment of the present invention, K2O and Na2O can be introduced simultaneously in the form of potassium feldspar and sodium feldspar, simplifying the batching process. In yet another specific embodiment of the present invention, K2O is introduced in the form of potassium hydroxide or potassium nitrate, and Na2O is introduced in the form of sodium hydroxide or sodium nitrate. These alternative raw materials can all decompose or be converted into corresponding oxides at high temperatures without affecting the final chemical composition and properties of the glaze.

[0062] In the above embodiments of the present invention, B2O3 is introduced in the form of boric acid. In another specific embodiment of the present invention, B2O3 is introduced in the form of boron oxide or borax. Borax may also introduce a portion of Na2O, which needs to be taken into account when calculating the formulation.

[0063] In the above embodiments of the present invention, the coupling agent used in step S1 is KH550 silane coupling agent. In another specific embodiment of the present invention, KH560 silane coupling agent can be used to coat the nanomaterials, as its epoxy groups have good reactivity with the hydroxyl groups in the glaze matrix. In yet another specific embodiment of the present invention, KH570 silane coupling agent can be used for coating. In yet another specific embodiment of the present invention, titanate coupling agents or aluminate coupling agents can be used instead of silane coupling agents.

[0064] In the above embodiments of the present invention, the glazing method in step S5 is immersion glazing. In other specific embodiments of the present invention, depending on the shape and size of the ceramic product, the glazing method can be spray glazing or brush glazing: spray glazing is suitable for large-area flat products, which can ensure uniform glaze thickness and high production efficiency; brush glazing is suitable for small-batch products with complex shapes, and is flexible in operation.

[0065] Variation Example The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, within the scope of the present invention's concept, several modifications can be made according to actual application scenarios and process conditions.

[0066] For example, regarding the content of each component in the glaze composition, SiO2 can be adjusted within the range of 45% to 54%, and Al2O3 can be adjusted within the range of 7% to 12% to meet the matching requirements of the thermal expansion coefficients of different green bodies. The ZnO content can be selected within the range of 9% to 17% according to the target firing temperature: when the target firing temperature is lower, the ZnO content is preferably 13% to 17% to obtain a stronger fluxing effect; when the target firing temperature is higher, the ZnO content can be 9% to 13% to balance cost and glaze performance.

[0067] Regarding the particle size of nano-sodium zirconium phosphate and nano-yttrium aluminate, within the range defined in the claims, it can be selected according to the dispersion process conditions and target performance. Example 3 has demonstrated that 80 nm nano-sodium zirconium phosphate and 60 nm nano-yttrium aluminate can achieve the technical effects of the present invention. When a smaller particle size, such as 50–70 nm, is selected, the nanoparticles have stronger light scattering ability and grain refinement effect, but the dispersion process requirements are higher; when a larger particle size, such as 80–100 nm, is selected, the nanoparticles are easier to disperse uniformly, which is suitable for large-scale production with relatively relaxed process control requirements. Those skilled in the art can make reasonable selections within this range according to actual production conditions.

[0068] Regarding the nanomaterial pretreatment process in step S1, the ultrasonic dispersion medium is not limited to anhydrous ethanol; isopropanol, acetone, or other low surface tension organic solvents can also be used. The calcination temperature can be adjusted within the range of 460–500℃, and the calcination time can be adjusted within the range of 25–35 minutes. The target particle size for air jet milling can be selected within the range of D50 of 0.3–0.5 μm.

[0069] Regarding the frit preparation in step S2, the melting temperature can be selected within the range of 1300–1320℃, and the holding time can be selected within the range of 35–40 minutes; the temperature of the cooling water used for quenching can fluctuate within the range of 25–35℃, as long as it can achieve rapid cooling of the melt to form a glassy state. In step S3, the grinding fineness can be adjusted to below 0.5% sieve residue.

[0070] Regarding the secondary firing process in steps S4 to S6, the bisque firing temperature can be selected within the range of 800–850℃; the glaze firing temperature can be selected within the range of 1050–1120℃. The heating rate of the glaze firing in step S6 can be reasonably adjusted within the range defined in the claims, based on the kiln characteristics, product size, and production cycle.

[0071] The application of the glaze composition of the present invention in ceramic products is not limited to the tableware daily-use ceramics described in the examples, but can also be extended to the fields of art ceramics, building ceramics and sanitary ceramics.

[0072] The above-mentioned modifications are all conventional adjustments in the field. Those skilled in the art can implement them without creative effort after reading this specification and can obtain the same or similar technical effects as the present invention. Therefore, they should all be included within the protection scope of the present invention.

[0073] The above-described specific embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition, characterized in that, It contains the following components by weight percentage: SiO2 45-54%; Al2O3 7-12%; ZnO 9-17%; K2O 3-5%; Na₂O 0.6–2.8%; B2O3 2-8%; Nano-sized sodium zirconium phosphate 0.5-0.7%; Nano-yttrium aluminate 0.3-0.5%; as well as Unavoidable impurities.

2. The high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition according to claim 1, characterized in that, The weight ratio of K2O to Na2O is 1.5 to 2.5:

1.

3. The high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition according to claim 1, characterized in that, The nano-sized sodium zirconium phosphate has a particle size of 50–100 nm, and the nano-sized yttrium aluminate has a particle size of 50–70 nm.

4. The high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition according to claim 1, characterized in that, It also contains ZrO2 0.8–1.5%.

5. The high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition according to claim 1, characterized in that, It also contains at least one of the following components: CaO 7-12%, MgO 0.8-8%, and Li2O 0.5-1.5%.

6. The high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition according to claim 1, characterized in that, It also contains 0.1-0.2% nano-samarium oxide, and at least one of BaO 0-6% and SrO 0-4%.

7. The high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition according to claim 1, characterized in that, It contains the following components by weight percentage: SiO2 50-54%, Al2O3 8-11%, ZnO 12-16%, K2O 3.8-4.5%, Na2O 1.8-2.5%, B2O3 4-6%, nano-sodium zirconium phosphate 0.6-0.7%, nano-yttrium aluminate 0.4-0.5%, ZrO2 1.0-1.4%, Li2O 0.8-1.5%, nano-samarium oxide 0.15-0.2%, and unavoidable impurities.

8. A method for preparing a high-temperature, high-whiteness, lead-free, and cadmium-free ceramic glaze composition according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Surface modification treatment of nano-sodium zirconium phosphate and nano-yttrium aluminate, wherein the surface modification treatment includes coating the nano-sodium zirconium phosphate and nano-yttrium aluminate with a coupling agent; S2. SiO2, Al2O3, ZnO, potassium-containing raw material, sodium-containing raw material, and boron-containing raw material are mixed in the weight percentages of any one of claims 1 to 7, and then melted and quenched to obtain a frit; wherein the potassium-containing raw material is selected from at least one of potassium carbonate, potassium oxide, potassium hydroxide, potassium nitrate, and potassium feldspar; the sodium-containing raw material is selected from at least one of sodium carbonate, sodium oxide, sodium hydroxide, sodium nitrate, and albite; and the boron-containing raw material is selected from at least one of boric acid, boron oxide, borax, and calcite. S3. The nano-sodium zirconium phosphate and nano-yttrium aluminate obtained in step S1 are mixed and ground with the frit obtained in step S2 to obtain a glaze slurry.

9. The preparation method according to claim 8, characterized in that, The coupling agent mentioned in step S1 is a silane coupling agent, and the surface modification treatment further includes: mixing nano-sodium zirconium phosphate and nano-yttrium aluminate evenly, adding anhydrous ethanol for ultrasonic dispersion, and then coating with the coupling agent.

10. The preparation method according to claim 8, characterized in that, The following steps are included after step S3: S4. The ceramic green body is bisque fired at 800-850℃; S5. Apply the glaze slurry obtained in step S3 to the surface of the ceramic body after bisque firing in step S4, with a glaze layer thickness of 0.2 to 0.3 mm; S6. Firing the glaze at a temperature of 1050–1120℃ yields a high-temperature, high-whiteness, lead-free, and cadmium-free ceramic material.

11. The preparation method according to claim 9, characterized in that, The process after ultrasonic dispersion and before coupling agent coating includes: calcining at 460–500°C for 25–35 min, and then pulverizing the calcined nanomaterials to a median particle size D50 of 0.3–0.5 μm.

12. The preparation method according to claim 10, characterized in that, The glaze firing in step S6 is carried out according to the following firing regime: From room temperature to 400℃, the heating rate is 2-3℃ / min; 400℃ to 600℃, heating rate 3~4℃ / min; 600℃ to 900℃, heating rate 4~5℃ / min; From 900℃ to the maximum firing temperature, the heating rate is 5-6℃ / min; Hold at the highest firing temperature for 30–40 minutes; Cooling stage: The maximum firing temperature is 800℃, and the cooling rate is 3-4℃ / min; The temperature was reduced from 800℃ to 600℃ at a rate of 4-5℃ / min, and then held at 700℃ for 8-12 minutes. Bring from 600℃ to room temperature and allow to cool naturally.

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