A method for preparing a non-porous tourmaline ceramic glaze and its secondary firing process.

Abstract

This invention discloses a non-porous tourmaline ceramic glaze and its preparation method for secondary firing, belonging to the field of ceramic materials technology. The ceramic glaze is composed of a base glaze and ultrafine tourmaline powder (content 3-20 wt%, fineness ≥1000 mesh). During preparation, the unglazed body is first fired at 1150-1250℃ to stabilize its structure; after glazing, a secondary glaze firing is performed, uniquely divided into a "stabilization stage" (1180-1220℃ holding) and a "melting stage" (1280-1350℃ holding). This method, through the optimization of the ultrafine powder interface and the synergy of staged firing kinetics, completely eliminates pores on the glaze surface, making the glaze surface free of any visible holes under a 50x microscope. The resulting glaze surface possesses both a top-grade jade-like texture and gemstone luster, high hardness, easy cleaning, and can stably release beneficial trace elements and finely adjust the liquid pH value, achieving a revolutionary unity of ceramic aesthetics, physical properties, and health functions.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, and in particular to a non-porous tourmaline ceramic glaze and a method for preparing the ceramics therefrom after secondary firing. Specifically, it relates to a novel ceramic glaze composition, its preparation method and application, and especially to a tourmaline ceramic glaze that can achieve a glaze layer with no visible pores on the surface, excellent gloss, jade-like texture, gemstone luster and functionality, as well as a method for preparing ceramic products with the glaze layer using a specific secondary firing process. Background Technology

[0002] Ceramics, a treasure of Chinese civilization, derives its core value from the art and science of glaze. The glaze layer is the soul of ceramics, directly determining its aesthetic quality, tactile feel, and durability. For thousands of years, ceramic artisans and scientists have strived for the ultimate perfection of the glaze—an ideal state that is smooth as a mirror, warm as jade, and flawless. However, a long-standing and almost unavoidable technical problem has severely hampered the realization of this goal: glaze pores (also known as "pinholes" or "pores").

[0003] Glaze pores are tiny holes that form on the surface or inside the glaze layer during the high-temperature firing process of ceramics due to factors such as the decomposition of raw materials, the volatilization of organic matter, and poor venting of the glaze during melting. These pores microscopically disrupt the continuity and density of the glaze, and macroscopically lead to decreased gloss, a rough feel, and easy accumulation of dirt and grime, becoming a breeding ground for bacteria. This severely impacts the aesthetic appearance, hygiene, and lifespan of ceramic products. For high-end art porcelain and premium daily-use porcelain aiming for a "jade-like" effect, the presence of pores is a fatal quality defect. Historically, imperial kilns attempted to add precious minerals such as agate to improve the glaze quality, but due to insufficient understanding of the pore formation mechanism and limitations in technology, they were never able to fundamentally solve this problem.

[0004] The modern ceramics industry has conducted extensive research to reduce glaze porosity, and its technical approaches mainly revolve around the following aspects: Glaze formulation optimization: By adjusting the chemical composition of the glaze, such as introducing porcelain powder, wollastonite, or calcined talc, the high-temperature viscosity and surface tension can be optimized, or the Al2O3 / SiO2 content can be increased to delay the initial melting temperature, allowing time for gas to escape from the green body. Some studies have also added specially treated zinc oxide (such as RA95 type) to reduce glaze viscosity and expand the firing range. However, such adjustments often come at the cost of sacrificing certain processing properties of the glaze (such as flowability and color), and their effect on eliminating porosity is limited, making it difficult to achieve the top standard of "no visible porosity."

[0005] Glaze pretreatment processes: For example, complex pretreatment of the glaze before glazing, including multiple melting and quenching (such as in sodium nitrate solution) to pre-expel raw material gases and increase glaze stability. Such methods are cumbersome, energy-intensive, and mainly target the gases within the glaze itself, lacking sufficient control over gases generated during the glaze-body bonding process.

[0006] Firing regime control: Precise control of the firing curve, such as fully decomposing organic matter during the oxidation stage, accurately controlling the temperature transition to the reducing atmosphere, or using low-temperature slow firing to allow sufficient time for gas to escape. These methods place extremely high demands on kiln equipment and operating experience, have a narrow process window, and poor stability.

[0007] Introducing porous or functional materials: To endow ceramics with specific functions (such as releasing negative ions), existing technologies introduce functional minerals such as tourmaline into the ceramic system. However, conventional practices have significant drawbacks: they may be incorporated into porous ceramic bodies to utilize the large specific surface area to promote functionality, but this contradicts the pursuit of a dense, non-porous glaze; or they may be simply mixed into the glaze, but due to the mismatch in thermal expansion coefficients and melting behavior between tourmaline powder and the base glaze, as well as its easy decomposition and vaporization at high temperatures (>1300℃), new stress and pore sources are introduced, leading to problems such as cracking, crystallization, roughness, and increased bubbles in the glaze, creating a dilemma of "sacrificing aesthetics for functionality." Although existing patents record the addition of "modified tourmaline powder" to improve dispersibility and its use in easy-clean ceramics, its primary purpose is stain resistance and strength, and it does not address or solve the core aesthetic problem of "no visible pores" in the glaze.

[0008] In-depth analysis reveals that the core mechanism by which the introduction of tourmaline leads to increased porosity in the glaze lies in: 1) Physical mismatch: Tourmaline particles of ordinary size (e.g., 200-500 mesh) exist as solid inclusions in the glaze melt, and the physical interface between them and the melt is a weak area where gas easily accumulates and remains. 2) Chemical instability: If the decomposition and gasification behavior of tourmaline at high temperatures is not synchronized with the melting process of the glaze, the peak of gas generation may occur precisely at the stage when the glaze surface is about to close but the viscosity is already high, preventing gas from escaping. 3) Kinetic conflict: Traditional single-firing or simple two-firing processes produce continuous and monotonous temperature-time curves, which cannot provide a phased kinetic environment for the ideal process of "mild activation, smooth transition, and final integration" of tourmaline. Existing two-step calcination technologies are mostly applied to the synthesis of powder materials themselves. Their temperature range (the first stage is usually at a temperature far below the initial melting point of the glaze) and mechanism of action (such as removing bound water and preliminary crystallization) are fundamentally different from solving the problems of fusion of heterogeneous functional particles and porosity elimination in the glaze layer, and cannot be directly applied.

[0009] In summary, existing technologies are fragmented and disjointed: techniques for improving glaze texture often do not address or may compromise the effectiveness of functional materials such as tourmaline; while techniques for introducing functional materials generally neglect or even worsen the aesthetic quality of the glaze. No disruptive technological solution has yet emerged in the industry that can systematically and fundamentally solve the problem of glaze porosity while perfectly integrating and maintaining the activity of functional minerals (such as tourmaline).

[0010] Two-step calcination, a sintering process using staged temperature control to optimize material structure, has been applied in lithium-ion battery electrode materials and cordierite ceramics. Its principle involves activating and initially reacting the raw materials through low-temperature pre-firing (e.g., 400-700℃) to eliminate internal stress, followed by high-temperature final firing (e.g., 800℃) to complete grain growth and structural densification. This process has been proven to increase material density, reduce porosity, and improve performance consistency. However, in the field of traditional ceramic glaze firing, especially in complex glaze systems involving heat-sensitive functional materials like tourmaline, the creative transformation of the core concept of two-step calcination into a specific glaze firing process that can synergistically resolve the contradiction between "densification" and "functional preservation" remains a gap.

[0011] Through long-term in-depth research and repeated practice, the inventors have come to a profound realization: to overcome the aforementioned technical difficulties, it is essential to abandon the traditional approach of "treating the symptoms rather than the root cause" and instead innovate from a systematic perspective encompassing "glaze composition design, powder interface control, and firing kinetics matching." This invention is the first to discover that by ultrafinely refining tourmaline powder to a specific range and combining it with a base glaze in precise proportions, coupled with a customized secondary firing process that includes clearly defined "stabilization" and "melting" stages, the dual goals of achieving highly dense glaze layers and enhancing the functional activity of tourmaline can be miraculously achieved. This is not merely a simple combination of process parameters, but a profound understanding and proactive utilization of the mechanisms of porosity formation and elimination in glazes, the phase transformation behavior of tourmaline, and the fusion laws of the glaze glass phase.

[0012] The inventors recognized that to overcome this long-standing technical bias and process bottleneck, it was necessary to move beyond simple modifications to existing methods and redesign the "functional phase-glaze matrix" composite system from a systems engineering perspective. This requires: 1) optimizing the physical morphology (particle size) of the functional phase (tourmaline) to a scale sufficient to alter its behavior in the high-temperature glaze melt; and 2) designing a firing regime capable of precisely controlling the interfacial reaction process and gas release / emission kinetics, so that the two originally conflicting processes (glaze densification and functional phase fusion) are decoupled in time and space and proceed in an orderly manner. This invention is based on this novel design concept. Summary of the Invention

[0013] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing a non-porous tourmaline ceramic glaze and its secondary firing process. This method, through the synergistic optimization of ultrafine powder interfaces and staged firing kinetics, completely eliminates pores on the glaze surface, resulting in a glaze surface without any visible holes under a 50x microscope. The resulting glaze surface possesses both a top-grade jade-like texture and gemstone luster, high hardness, easy cleaning, and the ability to stably release beneficial trace elements and finely adjust the liquid pH value, achieving a revolutionary unity of aesthetic quality, physical properties, and health functions in ceramics.

[0014] The primary objective of this invention is to overcome the technical biases and difficulties in the prior art, namely that ceramic glazes inevitably have visible pores, which limits their aesthetic quality, and that the introduction of functional minerals (such as tourmaline) will exacerbate glaze defects. The invention provides a tourmaline ceramic glaze that is highly dense at the microscopic level, has no visible pores on the surface, and has excellent jade-like texture, gem-like luster, and superior physical properties at the macroscopic level.

[0015] Another objective of this invention is to provide a method for preparing the aforementioned non-porous tourmaline ceramic glaze, and a matching, industrially scalable secondary firing process. The core of this process lies in achieving full vitrification of the body, optimization of the glaze-tourmaline interface reaction, orderly gas removal, and high homogenization of the final glaze glass phase through precise temperature control in stages. This ensures that the tourmaline component is perfectly integrated into the glaze and stably retains its functional properties.

[0016] Another object of the present invention is to provide ceramic products prepared by the above method. For the first time, this product simultaneously achieves top-level aesthetic value (no pores, jade-like texture, gemstone luster) and significant health function value (such as releasing trace elements, regulating liquid pH value, etc.) on a single carrier, representing a major breakthrough in the integration of ceramic technology in the three dimensions of "aesthetics-function-durability".

[0017] The above-mentioned objective of this invention is achieved through the following technical solutions: This invention provides a non-porous tourmaline ceramic glaze, which is composed of a base glaze and tourmaline powder; based on the total dry weight of the non-porous tourmaline ceramic glaze, the mass content of the tourmaline powder is 3wt% to 20wt%; the average particle size D50 of the tourmaline powder corresponds to a mesh number of not less than 1000 mesh.

[0018] According to one embodiment of the present invention, the mass content of the tourmaline powder is 5 wt% to 15 wt%, preferably 8 wt% to 12 wt%.

[0019] According to one embodiment of the present invention, the average particle size D50 of the tourmaline powder corresponds to a mesh size of 1500 to 3500 mesh, preferably 2000 to 3000 mesh.

[0020] According to one embodiment of the present invention, the base glaze further contains trace mineral element additives selected from at least one of selenium, strontium, and zinc.

[0021] According to one embodiment of the present invention, the tourmaline powder is selected from at least one of magnesium tourmaline, iron tourmaline, lithium tourmaline, and calcium magnesium tourmaline.

[0022] According to one embodiment of the present invention, the particle size distribution of the tourmaline powder satisfies D90≤15μm and D100≤30μm.

[0023] According to one embodiment of the present invention, the base glaze comprises the following components by dry weight percentage: SiO2 55-75%, Al2O3 8-18%, K2O 2-8%, Na2O 1-6%, CaO 3-10%, MgO 0.5-5%, and unavoidable impurities.

[0024] According to one embodiment of the present invention, the chemical composition of the base glaze satisfies the following molar ratio relationship: the molar ratio of alkali metal oxide (R2O) to alkaline earth metal oxide (RO) is (0.3-1.2):1; the molar ratio of SiO2 to Al2O3 is (5-12):1.

[0025] According to one embodiment of the present invention, the base glaze further includes 0.01-2 wt% of nano-sized fumed silica or nano-sized alumina in the total dry weight, which is used to adjust the rheology of the glaze slurry and the hardness of the fired glaze surface.

[0026] The present invention also provides a method for preparing ceramic products with the above-mentioned non-porous tourmaline ceramic glaze, comprising the following steps: Step S1. Preparation of green body and first firing: The ceramic green body raw material is shaped into a green body, and then the first firing is carried out at 1150℃ to 1250℃ to obtain a green body; Step S2. Glazing: The non-porous tourmaline ceramic glaze is made into a glaze slurry and applied to the surface of the bisque-fired body; Step S3. Second firing: The glazed body is fired a second time. The second firing includes: first heating to 1180℃ to 1220℃ and holding for 0.5-2 hours as a stabilization stage, and then continuing to heat to 1280℃ to 1350℃ and holding for 1-3 hours as a melting stage.

[0027] According to one embodiment of the present invention, the highest temperature of the first firing in step S1 is 1180°C to 1220°C.

[0028] According to one embodiment of the present invention, the ceramic body raw material in step S1 is feldspar porcelain, high quartz porcelain or bone china body; the heating rate of the first firing is 80-150℃ / hour, and the temperature is held at the highest temperature for 0.5-3 hours, and the firing atmosphere is an oxidizing atmosphere.

[0029] According to one embodiment of the present invention, the specific gravity of the glaze slurry in step S2 is 1.40-1.55 g / cm³, and the dry glaze layer thickness is 0.15-0.6 mm.

[0030] According to one embodiment of the present invention, the stabilization stage of the second firing in step S3 is: heating to 1200℃±10℃ and holding for 0.5-2 hours; the melting stage is: continuing to heat to 1300℃ to 1320℃ and holding for 1-3 hours.

[0031] According to one embodiment of the present invention, in step S3, the heating rate from room temperature to the stable temperature is 80-120°C / hour; the heating rate from the stable temperature to the highest temperature of the melting zone is 40-70°C / hour.

[0032] According to one embodiment of the present invention, in step S3, the firing atmosphere of the stabilizing section is a neutral to weakly reducing atmosphere (CO content 0.5-3%); the firing atmosphere of the melting section is a weakly reducing atmosphere (CO content 1-5%).

[0033] According to one embodiment of the present invention, after the molten section is kept at a constant temperature in step S3, it is slowly cooled to 850-950°C at a rate of 60-100°C / hour, and then naturally cooled to room temperature with the furnace.

[0034] The present invention also provides a ceramic article whose glaze layer is formed by a non-porous tourmaline ceramic glaze of the above embodiments, and the surface of the glaze layer shows no visible pores when observed under a 50x optical microscope.

[0035] According to one embodiment of the present invention, the glaze has a jade-like texture and a gemstone luster, and its Mohs hardness is not less than 7.

[0036] According to one embodiment of the present invention, the ceramic product is a vessel for holding liquid, which is capable of releasing trace elements into the liquid and / or adjusting the pH of the liquid toward a slightly alkaline state.

[0037] According to one embodiment of the present invention, the 60° mirror gloss of the glaze layer is not less than 90 GU, preferably not less than 95 GU.

[0038] According to one embodiment of the present invention, the coefficient of thermal expansion of the glaze layer is (5.5-7.5)×10⁻¹⁰. -6 / K (room temperature - 400℃), the absolute value of the difference between the coefficient of thermal expansion and the coefficient of thermal expansion of the billet is ≤1.0×10 -6 / K.

[0039] According to one embodiment of the present invention, after deionized water (initial pH 6.5-7.0) is injected into the vessel at 25°C and allowed to stand for 24 hours, the pH value of the water sample increases by 0.3-1.0 units; and / or, the release of at least one of boron (B), magnesium (Mg), silicon (Si) elements derived from tourmaline and selenium (Se), strontium (Sr), zinc (Zn) elements derived from additives can be detected, with the release concentration in the range of 0.1 ppb to 10 ppb.

[0040] The technical principle of this invention lies in the following: by ultrafinely refining tourmaline powder to submicron or micron level (≥1000 mesh), the particle size is close to or smaller than the critical size of bubbles in the glaze melt, greatly increasing the particle surface area and reactivity, and lowering its surface softening temperature. After the first firing (bisque firing) completely removes the gases from the body, glaze is applied and a unique second firing is carried out. In the "stable zone" (1180-1220℃), the glaze begins to melt but the viscosity is high. At this time, the surface of the ultrafine tourmaline particles softens and begins to undergo ion exchange and interfacial reaction with the glaze melt, forming a preliminary chemical bonding layer. This temperature is lower than the temperature at which tourmaline decomposes violently, allowing its internal gases to be released slowly and discharged through the still somewhat permeable viscous melt layer. This process forms a gradually changing "buffer transition layer" around the tourmaline particles, effectively alleviating thermal mismatch stress. Subsequently, in the "melting zone" (1280-1350℃), the viscosity of the glaze decreases significantly, and its fluidity increases. After the tourmaline particles have undergone the "stabilization stage" pretreatment, the outer transition layer is completely melted, and the core functional ions (such as Mg) are released. 2+ Fe 2+ / 3+ B 3+ (etc.) diffuse into the glaze glass network, becoming a network modifier or intermediate. At the same time, the excellent fluidity and surface tension of the glaze melt can completely eliminate any minor defects that may remain from the early stage, and "pull" the very few microbubbles that have not been expelled to the surface to rupture, ultimately forming a glaze glass layer with no visible pores, high homogeneity, and functional ions dissolved in the network structure.

[0041] In summary, compared with the prior art, the present invention has at least one of the following beneficial technical effects: This invention represents a revolutionary breakthrough in achieving "no visible pores" in ceramic glazes: For the first time, it systematically and collaboratively utilizes three dimensions—ultra-fine raw material processing, optimized formulation, and firing kinetics—to successfully prepare ceramic glazes that show no pores under a 50x microscope. This fundamentally solves a millennia-old technological bottleneck that has hindered the improvement of high-end ceramic quality, pushing the density and perfection of ceramic glazes to new heights.

[0042] This invention creates a top-tier aesthetic effect that combines the "jade-like texture" and the "gemstone luster": a pore-free base is the prerequisite for this aesthetic expression. The glaze of this invention is not only smooth as a mirror, but also, due to the incorporation of tourmaline ions into the glass network, it alters the refractive index and internal scattering characteristics of the glaze layer, producing a warm, jade-like texture and a vibrant, dazzling gemstone luster that ordinary glazes cannot achieve, greatly enhancing the artistic and commercial value of the ceramics.

[0043] This invention successfully integrates and enhances functionality on the basis of ultimate aesthetics, breaking through the traditional dilemma that "adding functions damages aesthetics." Through process innovation, tourmaline is no longer a "foreign object" or source of defect in the glaze, but is transformed into an organic component of the glaze glass network. While achieving a perfect glaze surface, it miraculously preserves and optimizes the health functions of tourmaline, such as releasing trace elements and regulating the microenvironment, achieving a synergistic effect of "1+1>2".

[0044] It significantly improves the overall physical properties of ceramic products: the highly dense, non-porous glaze layer is like a sturdy "glass armor" for ceramics, greatly enhancing their hardness, strength, wear resistance, corrosion resistance, stain resistance, and ease of cleaning, thus extending the service life of the products and broadening their application scenarios.

[0045] The process is highly controllable and suitable for high-quality, large-scale production: The formulation range, powder requirements, and firing regime provided by this invention are clear and scientific, with a reasonable process window and good reproducibility. Compared with traditional methods that rely on craftsman experience, this invention is easier to standardize and scale up production through the digital control of modern kilns, providing a reliable technical solution for mass-producing high-value-added ceramic products that combine top aesthetics and functionality. Attached Figure Description

[0046] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0047] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to experimental data, performance test tables, and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Unless otherwise specified, the reagents, equipment, and methods used in this invention are commercially available products or conventional methods in this technical field.

[0049] The technical problem solved by this invention stems from the fundamental contradiction that arises when introducing functional minerals such as tourmaline into traditional ceramic glaze systems, where aesthetics and functionality are difficult to reconcile. Tourmaline, a boron-containing aluminosilicate mineral, undergoes thermal decomposition at high temperatures (typically exceeding 1250°C), releasing gases (such as B2O3 volatilization and structural water precipitation). If these gases cannot escape smoothly before the glaze layer is completely melted and sealed, permanent pores will form. Simultaneously, the difference in thermal expansion coefficients and poor wettability between tourmaline particles and the glassy phase of the base glaze can lead to microcracks and stress concentration points at the interface. These defects may evolve into sources of pores or cracks in the later stages of firing. Conventional single high-temperature firing processes involve intense and rapid glaze melting, causing gas escape channels to be prematurely sealed by the high-viscosity melt, resulting in trapped bubbles. While simple secondary firing (bisque firing + glaze firing) can expel gases from the body, it does not optimize the control of the complex gas release kinetics of the glaze itself and the body-glaze interface reaction. Therefore, existing technical solutions either sacrifice or reduce the addition of functional minerals in pursuit of aesthetic appeal, or tolerate numerous defects such as pores, dullness, and roughness in the glaze to preserve functionality. Consequently, they fail to achieve the ideal state where the glaze layer is highly dense in its microstructure and possesses both top-tier aesthetics and stable functional output in its macroscopic form. This invention, based on a profound understanding of this deep-seated contradiction, proposes a systematic solution integrating "raw material ultrafine processing, interface design, and staged kinetic firing."

[0050] In a first aspect, the present invention provides a non-porous tourmaline ceramic glaze, which is composed of a base glaze and tourmaline powder in a specific ratio.

[0051] Based on the total dry weight of the non-porous tourmaline ceramic glaze, the mass content of the tourmaline powder is 3wt% to 20wt%. Preferably, the content is 5wt% to 15wt%; more preferably, it is 8wt% to 12wt%. The inventors have found that when the tourmaline content is below 3wt%, its contribution to improving the glaze structure and functionality is negligible; while when the content exceeds 20wt%, excessive tourmaline is difficult to be completely melted and encapsulated by the glaze glass phase, easily leading to microcracks, crystallization, or residual particles on the glaze surface, thus damaging the integrity of the glaze surface. Within this preferred range, tourmaline can fully participate in the construction of the glaze glass network, effectively sealing pore channels, without negatively affecting the uniformity of the glaze surface.

[0052] The fineness of the tourmaline powder is one of the key factors in achieving the non-porous effect of this invention. Its average particle size D50 corresponds to a mesh size of not less than 1000 mesh. Preferably, it is 1500 to 3500 mesh; more preferably, it is 2000 to 3000 mesh. Traditional tourmaline-containing glazes often use coarse-grained powder (e.g., below 500 mesh), which does not react completely during glaze firing and exists as heterogeneous particles in the glaze. These particles not only act as stress concentration points but also easily become sites of bubble residue at their interface with the glaze. This invention, by ultra-finely refining the tourmaline powder, brings multiple synergistic effects: Significantly increases specific surface area and reactivity: The contact area between ultrafine powder and base glaze increases by orders of magnitude, enabling more rapid and uniform solid-phase reaction and melt diffusion during firing.

[0053] Promotes low-temperature eutectic melting and uniform dispersion: The ultrafine particles lower their own melting temperature, allowing them to begin softening and initially combining with the glaze at a relatively low "stable zone" temperature, thus avoiding the generation of gas through violent reactions at high temperatures.

[0054] Eliminating interface defects: The extremely fine particle size allows it to completely dissolve in the final glaze glass phase or be uniformly distributed as a network of modified ions, fundamentally eliminating interface pores and microcracks caused by the presence of coarse particles. This is the material basis for achieving a glaze surface that is "without visible pores" under a 50x microscope.

[0055] The preferred type of tourmaline powder is magnesium tourmaline or iron tourmaline, as its color (black or brown) can present a deep base color in the glaze, enhancing the visual effect of the gemstone's luster. Its chemical composition should be relatively pure, with impurity content (such as quartz, feldspar, etc.) below 5 wt%. It is recommended that the powder undergo iron removal and drying treatment (105℃ drying) before use to further reduce the introduction of impurities and color spots.

[0056] The base glaze is a ceramic glaze system known to those skilled in the art, suitable for high-temperature firing (1250℃-1350℃), such as, but not limited to, calcium-alkali glaze (feldspar glaze), lime glaze, magnesia glaze, or their composite glazes. Its specific composition (such as the proportion of oxides like SiO2, Al2O3, K2O, Na2O, CaO, MgO, etc.) can be conventionally designed and adjusted according to the final product's requirements for glaze gloss type (glossy, matte, or matte), color, and coefficient of thermal expansion (which needs to match the body).

[0057] As a preferred embodiment, the base glaze also contains trace amounts of special functional mineral element additives. These additives can be sources of trace elements beneficial to the human body, such as selenium (Se), strontium (Sr), and zinc (Zn). For example, specific mineral powders rich in selenium (such as purified purple clay) or chemical raw materials can be added. The amount added is typically 0.1 wt% to 5 wt% of the total weight of the glaze. The introduction of these trace elements, in synergy with tourmaline, can further optimize the glaze properties (such as color) and endow glazed products with richer health-promoting functions.

[0058] To further optimize the performance of the glaze slurry and the hardness of the glaze surface, 0.01-2 wt% of nano-sized fumed silica or nano-alumina can be added to the base glaze. These nanoparticles can improve the suspension and thixotropy of the glaze slurry, making the glazing more uniform; during the firing process, they can act as crystal nuclei or network reinforcement points, which helps to improve the hardness and wear resistance of the glaze surface.

[0059] Secondly, referring to Figure 1 This invention provides a method for preparing ceramic products using the aforementioned non-porous tourmaline ceramic glaze, employing a meticulously designed two-stage firing process. This process is not a simple superposition of the traditional "bisque firing + glaze firing," but rather a revolutionary redefinition and synergistic design of the purpose, temperature range, and holding time of the two firing stages, specifically tailored to the characteristics of the "tourmaline-glaze" composite system.

[0060] Specifically, the following steps are included: Step S1. Preparation of green body and first firing (structural stabilization firing) Selected ceramic raw materials (such as kaolin, porcelain stone, quartz, feldspar, etc.) are kneaded, aged, and shaped into unglazed blanks according to conventional processes. Then, a first firing is carried out in a first temperature range. The highest temperature in the first temperature range is 1150℃ to 1250℃, preferably 1180℃ to 1220℃. The firing atmosphere is an oxidizing atmosphere.

[0061] The core purpose of this firing process is to achieve thorough oxidation and decomposition, and preliminary vitrification of the body. At this temperature, impurities such as organic matter, carbon, sulfides, and carbonates in the body are completely oxidized and decomposed, and a large amount of gas is released. Simultaneously, the body undergoes significant shrinkage, and crystals such as mullite begin to form, resulting in sufficient mechanical strength and a stable mineral phase composition. This step provides a clean, stable, and low-porosity substrate for subsequent glazing, avoiding the impact of secondary venting of the body during the glaze firing stage on the glaze surface. This stage can be considered a "complete purging" of the internal gases of the body and a "pre-stabilization" of its structure.

[0062] Step S2. Glazing The non-porous tourmaline ceramic glaze is mixed with deionized water and electrolytes (such as sodium carbonate and water glass) in a certain proportion, and then ball-milled for a long time (e.g., 6-12 hours) to prepare a glaze slurry with uniform particle size and suitable fluidity. The glaze slurry is then evenly applied to the surface of the completely cooled bisque-fired body obtained in step S1 by dipping, spraying, or pouring. The thickness of the dried glaze layer is controlled to be between 0.2 mm and 0.5 mm. Before glazing, the surface of the bisque-fired body must be clean and dry.

[0063] Step S3. Second firing (glaze functionalization and densification firing) The glazed body is placed in a kiln for a second firing. This is the most crucial and innovative step in the invention. The second firing employs a specific temperature-time curve, which is key to clearly dividing it into two functionally distinct stages: Phase 1: Stabilization Phase (Interfacial Reaction and Slow Gas Emission) The kiln temperature is increased from room temperature to 1180℃ to 1220℃ (preferably 1200℃±10℃) at a rate of 80-120℃ / hour, and held at this temperature for 0.5 hours to 2 hours. A weak reducing or neutral atmosphere is used during this stage.

[0064] The core function of this section: initial melting of the glaze and softening of tourmaline: Under this relatively "mild" high temperature, the base glaze begins to melt, forming a viscous glass melt. At the same time, the surface of the ultrafine tourmaline powder begins to soften, and elements such as boron and silicon in its crystal lattice begin to undergo ion exchange and interfacial reactions with the glaze melt, forming a strong chemical bond rather than a physical mixture.

[0065] Slow release of residual gases: The small amount of residual crystal water, structural water, and gases that may be adsorbed at the body-glaze interface in the glaze are released slowly and orderly at this stage when the viscosity is not yet extremely high. Due to proper temperature control, the tourmaline itself is prevented from decomposing and vaporizing violently due to overheating (>1250℃).

[0066] Formation of a transition layer: At this stage, tourmaline and glaze initially fuse together, forming a transition layer with a compositional gradient around the tourmaline particles. This greatly alleviates the later stress that may be caused by the difference in thermal expansion coefficients, laying the structural foundation for the next step of complete high-temperature melting.

[0067] Second stage: Melting section (complete homogenization and densification section) After the stabilization phase, the temperature is increased at a rate of 40-60℃ / hour to the final firing temperature of 1280℃ to 1350℃, preferably 1300℃ to 1320℃. After reaching the maximum temperature, the temperature is held for 1 to 3 hours. A weak reducing atmosphere can be used during this stage to facilitate glaze color development (if necessary) and to create a lustrous texture.

[0068] The core function of this section is: Complete melting and homogenization: At higher temperatures, the viscosity of the glaze further decreases, and its fluidity increases. The tourmaline-glaze interface reaction layer, which has already undergone the "stabilization stage" pretreatment, is completely melted, and the tourmaline components (such as Na, Mg, Fe, B, etc.) are completely integrated into the glaze glass network structure in ionic form, forming a highly homogeneous and uniform glass phase.

[0069] The gas eventually escapes and heals with the pores: the reduced viscosity of the glaze melt allows its surface tension to take effect, effectively "pulling" the tiny bubbles that failed to escape earlier to the surface and causing them to burst. At the same time, the excellent fluidity of the melt can completely smooth out any tiny pits (pinhole-like craters) left by the gas escape, achieving "self-healing" of the glaze surface.

[0070] Functional Phase Stabilization and Solidification: Although the characteristic structure of tourmaline is somewhat damaged at high temperatures, the permanent spontaneous polarization effect upon which its functions such as releasing negative ions and far-infrared radiation depend originates from its unique crystal structure. This invention protects the core structure of tourmaline particles through a pretreatment process called the "stabilization stage." In the "melting stage," its functional ions (such as iron and magnesium) are "frozen" in a rapidly cooling glass network, maintaining a certain electric field effect, thus ensuring continued functionality even after the product is finished.

[0071] After firing, a slow cooling process must be adopted (for example, slow cooling at 60-100℃ / hour above 800℃, and cooling with the kiln below 800℃) to prevent the glaze from cracking and to promote the precipitation of microcrystals in the glaze layer, thereby enhancing the jade-like texture.

[0072] This secondary firing process is fundamentally different from ordinary secondary firing or the secondary firing mentioned in the literature for specific artistic glazes (such as oil-spot Tenmoku glaze). The latter's secondary firing aims to change the kiln atmosphere by introducing an external "inoculant," inducing the precipitation and arrangement of specific crystals. Its focus is on crystal growth, not the extreme densification of the non-glaze glass phase. The process of this invention is a kinetic process specifically designed to eliminate porosity and integrate functional phases. The two stages are interlocking and indispensable.

[0073] Thirdly, the present invention provides ceramic articles prepared by the above method.

[0074] The most striking feature of this ceramic product lies in the quality of its glaze: under a 50x optical microscope, the glaze surface is continuous and smooth, completely free of visible pores, pinholes, or bubbles. Its glaze gloss (60° specular gloss) can reach over 95%, possessing a strong jade-like warmth and exhibiting a unique "gemstone brilliance" under specific lighting angles—a shimmering visual effect similar to the internal refraction of crystal or gemstones. This is an optical phenomenon produced by the combined action of a highly pure, uniform, and dense glaze glass phase and molten tourmaline components.

[0075] The physical and chemical properties of the glaze are significantly improved: the Mohs hardness can reach level 7 or above, and the wear resistance is excellent; the glaze is hydrophilic and easy to clean, and has strong stain resistance; due to the absence of open pores, its acid and alkali resistance and corrosion resistance are also far superior to ordinary ceramic glazes.

[0076] More importantly, this product achieves a unity of functionality and aesthetics. Testing has shown that vessels (such as cups, bottles, and bowls) made from this glaze, after being filled with water or weakly acidic liquids and left to stand for a period of time, can stably release detectable trace elements beneficial to the human body (such as selenium), and can cause a small but stable positive adjustment of the liquid's pH value towards a slightly alkaline direction. This proves that the activity of tourmaline and other functional components is effectively preserved after high-temperature firing and can continue to function during use.

[0077] Example and comparative data table: Table 1: Effect of different tourmaline contents on glaze properties (fixed tourmaline fineness: 2500 mesh, firing regime: 1210℃ / 1.5h + 1315℃ / 2h)

[0078] Table 2: Effect of different tourmaline powder fineness on glaze properties (fixed tourmaline content: 10wt%, firing regime: 1210℃ / 1.5h + 1315℃ / 2h)

[0079] Table 3: Effect of different secondary firing regimes on glaze properties (fixed glaze: 10wt% 2500 mesh tourmaline) Example 1: Preparation of Poreless Tourmaline Ceramic Glaze and its Ceramic Plate

[0080] Glaze preparation: Basic glaze: 900g of standard high-temperature transparent feldspar glaze powder from Jingdezhen (chemical composition wt%: SiO2 68, Al2O3 12, K2O 4, Na2O 3, CaO 6, MgO 2, others 5).

[0081] Tourmaline powder: Take 100g of black magnesium tourmaline powder with an average particle size D50 of approximately 2500 mesh (approximately 6 micrometers). Confirm its particle size distribution using a laser particle size analyzer; D90 < 10 micrometers.

[0082] Mixing process: Both materials were placed in an alumina ceramic jar, and an equal weight of deionized water and 0.5 wt% (dry weight) of sodium metasilicate were added as a dispersant. Zirconia balls were used as the grinding medium at a ball-to-material ratio of 3:1, and the mixture was ball-milled for 8 hours. After milling, the glaze was passed through a 325-mesh (45-micron) sieve to remove iron. The specific gravity of the glaze was adjusted to 1.45 g / cm³, and the glaze was aged for 24 hours before use. The resulting glaze contained 10 wt% tourmaline powder.

[0083] Green body preparation and first firing: Raw material: Standard white porcelain clay made from high-quality kaolin and porcelain stone from Jingdezhen.

[0084] Molding: A disc-shaped blank with a diameter of 15cm is made by slip casting and dried until the moisture content is <2%.

[0085] Single firing (bisque firing): The bisque is placed in an electric kiln and heated to 1200℃ at a rate of 100℃ / hour, and held at this temperature in an oxidizing atmosphere for 1 hour. It is then cooled in the kiln to below 80℃ before being removed from the kiln. The resulting bisque has a water absorption rate of about 15%, moderate strength, and a crisp sound when tapped.

[0086] Glazing: Immerse the bisque-fired ceramic body in the above glaze slurry for 3 seconds, lift it out at a uniform speed, and air dry it in an environment with constant humidity. The average thickness of the dry glaze layer was measured to be approximately 0.3 mm.

[0087] Secondary firing (glaze firing): Place the glazed body in the gas kiln. The firing curve is strictly followed as follows: heat to 1210°C at a rate of 100°C / hour, then transfer to a weak reducing atmosphere (CO content 1-2%), and hold at this temperature for 1.5 hours (stabilization phase).

[0088] Then, continue heating at a rate of 50°C / hour to 1315°C, maintaining a weak reducing atmosphere, and hold at that temperature for 2 hours (melting section).

[0089] After the heat preservation period, the furnace is slowly cooled to 850°C at a rate of 80°C / hour, then the power is cut off, and the furnace is allowed to cool naturally to room temperature. The total firing cycle is approximately 24 hours.

[0090] Product testing and characterization: Macroscopic appearance: The resulting ceramic plate has a smooth, mirror-like glaze that shines brightly. The color is a deep blue-black, refracting a distinct, crystalline "gemstone-like" sheen under different angles of light. It has an extremely smooth, warm, and weighty feel.

[0091] Microscopic morphology: Multiple fields of view at the center and edges of the glaze were observed using a 50x optical microscope (KEYENCE VHX-7000). The results showed that the glaze surface was completely continuous, and no pores, pinholes, or unmelted matter larger than 5 micrometers in diameter were observed. In contrast, the glaze of Comparative Example 1 (using 500-mesh tourmaline, 10% content, and conventionally rapid firing at 1315℃ for 3 hours) showed a large number of dense pores and unmelted tourmaline particles ranging in size from 20 to 100 micrometers under the same conditions.

[0092] Physical properties: The hardness of the enamel is >7 when tested with a Mohs hardness pen. The average gloss level is 98 GU when tested with a gloss meter (60° angle).

[0093] Preliminary functional testing: 200 ml of deionized water (initial pH = 6.8, conductivity < 5 μS / cm) was poured into the ceramic dish and left to stand at room temperature (25℃) for 24 hours. Subsequently, a precision pH meter and inductively coupled plasma mass spectrometry (ICP-MS) were used for analysis. The results showed that the pH of the water sample rose to 7.4; trace amounts of magnesium (Mg), silicon (Si), and boron (B) ions were also detected, with a significant detection of boron derived from tourmaline. Example 2: Preparation of tourmaline glaze containing selenium-rich minerals and its ceramic cups

[0094] This embodiment aims to demonstrate the application of the present invention in introducing composite functional elements.

[0095] Glaze preparation: Base glaze: Same as in Example 1, take 850g.

[0096] Tourmaline powder: 120g of tourmaline powder with a fineness of 3000 mesh.

[0097] Functional additive: Take 30g of selenium-rich mineral powder (containing approximately 100 ppm selenium) obtained by purifying, calcining, and ultra-fine grinding natural selenium-rich purple clay to 3000 mesh.

[0098] Mixing process: The three components are mixed in the above proportions, and the ball milling process is the same as in Example 1. The final glaze slurry contains approximately 12 wt% tourmaline and approximately 3 wt% selenium-rich mineral powder.

[0099] Shaping and firing: The blank is a machine-made ceramic cup. It is fired once at a maximum temperature of 1220℃ and held for 1 hour.

[0100] The glaze thickness is 0.25 mm. During the second firing, the stabilization zone is held at 1190℃ for 1 hour, and the melting zone is held at 1300℃ for 2.5 hours. The remaining processes are the same as in Example 1.

[0101] Product effects: The glaze also meets the standard of having no visible pores, and the color is warm gray with a strong jade-like feel.

[0102] Functional testing (method as in Example 1): After standing for 24 hours, in addition to Mg, Si, and B ions, selenium (Se) was specifically detected in the water sample, with a concentration of 0.5 ppb (far exceeding the detection limit). Simultaneously, the pH value increased slightly from 7.0 to 7.5. This demonstrates that the process of this invention can effectively and stably dissolve trace elements such as selenium in the glaze layer and allow for slow release under mild conditions. Example 3: Tourmaline Content Gradient Experiment

[0103] This experiment was conducted to verify the influence boundary of tourmaline content on glaze performance.

[0104] Experimental Design: The tourmaline powder fineness was fixed at 2000 mesh, and the base glaze was the same as in Example 1. Four groups of glazes with tourmaline mass contents of 3%, 8%, 15%, and 20% were prepared respectively. Using the same standard porcelain bisque (fired once at 1200℃), after glazing, they were fired in the same kiln using the same two-firing regime (1210℃ / 1.5h + 1315℃ / 2h).

[0105] Results and Analysis: 3% content group: The pores of the glaze are significantly reduced, but under a microscope (50x), there are still scattered tiny pores (<10 per field of view). The glaze has good gloss, but the "gemstone light" effect is weak.

[0106] The 8% and 15% content groups: The glaze is completely free of visible pores under a microscope, and the surface is perfect. The "gemstone-like" visual effect of the glaze in the 15% group is more obvious and deeper than that in the 8% group.

[0107] 20% content group: The glaze surface is still relatively smooth overall, but under a microscope, a very small number of slight glaze flow marks and individual micro-cracks can be observed at the edges or where the glaze layer is thicker. There are no pores, but the uniformity of appearance is slightly inferior.

[0108] Conclusion: The preferred range for the tourmaline content in this invention is 5%-15%, which ensures a pore-free glaze and a perfect appearance. 8%-12% is the optimal range, balancing aesthetics and process stability.

[0109] Comparative Example 1: Coarse-grained tourmaline and one-time firing process This comparative example is used to contrast the shortcomings of traditional methods.

[0110] Glaze preparation: Ordinary tourmaline powder with an average particle size of about 500 mesh, with a content of 10%, was simply mixed with the same base glaze as in Example 1 and ball-milled for 4 hours to form a slurry.

[0111] Firing process: The glaze slurry is applied directly to the unfired green body and a conventional one-time firing system is adopted: the temperature is directly raised to 1315℃ at 150℃ / hour, held in an oxidizing atmosphere for 3 hours, and then cooled naturally.

[0112] Results: The product's glaze is rough and dull (60° gloss level only 65 GU). Under a 50x microscope, numerous dense pores (20-100 μm in diameter) and a large number of unmelted white tourmaline particles are visible. The glaze lacks any jade-like or gem-like luster. Functional testing showed extremely slight changes in water quality.

[0113] Comparative Example 2: Second firing, but the "stabilization stage" was omitted. This comparative example is used to verify the necessity of the "stable section" in the process of this invention.

[0114] Glaze preparation: Same as in Example 1 (10% content, 2500 mesh).

[0115] Firing process: Biscuit firing is the same as in Example 1. During glaze firing, the specific "stabilization period" of heat preservation is eliminated, and the temperature is directly increased from room temperature to 1315°C at a rate of 80°C / hour, and then held for 2.5 hours.

[0116] Results: The glaze quality was significantly better than Comparative Example 1, but inferior to Example 1. A small number of scattered micropores (approximately 5-15 μm in diameter) were visible under a microscope. The glaze gloss was approximately 90 GU, with a less pronounced "gemstone shine" effect. This indicates a lack of a smooth transition in the "stable section," insufficient interfacial reaction between the glaze and tourmaline, and the failure of some gases to escape before the glaze completely melted. Furthermore, the insufficient integration of the tourmaline affected the final glaze density and optical properties. Example 4: Effect of different firing temperature regimes on glaze properties

[0117] This embodiment explores the effect of the "melting section" temperature on the fine-tuning of glaze properties.

[0118] Using the glaze and bisque from Example 1, the "stabilization zone" was fixed at 1210℃ / 1.5h, and the final temperature of the "melting zone" was varied: 1#: 1290℃, 2#: 1315℃ (standard), 3#: 1330℃.

[0119] Sample #1 (1290℃): The glaze is fully vitrified and free of pores, but the luster is slightly softer (matte-like), and the "gemstone shine" effect is weaker. The glaze hardness is slightly low (approximately 6.5).

[0120] Sample #2 (1315℃): The glaze effect is as described in Example 1, and is the best.

[0121] Sample #3 (1330℃): The glaze is bright and dazzling (strong vitreous luster), the jade-like texture is weakened, and there is a slight tendency for "wavy lines" caused by overfiring at the edges, but no pores are found under the microscope. Functional tests show that excessively high temperatures may cause some functional ions to volatilize, and the water quality regulation ability is slightly reduced.

[0122] Conclusion: A "melting zone" temperature of 1300-1320℃ best balances the glaze gloss type, jade-like texture, functionality, and process safety window. Example 5: Effects of different base glaze compositions and nano-additives

[0123] This embodiment aims to illustrate the range of possible compositions and effects of nano-additives in the basic glaze.

[0124] Experimental design: The tourmaline content was fixed at 10 wt% and the fineness was 2500 mesh. Three groups of different base glazes (G1, G2, G3) and one group of glazes with added nano-alumina (G4) were designed. The dry composition of the materials is shown in Table 4. The same green body (single firing at 1200℃) and two firing regime (1210℃ / 1.5h + 1315℃ / 2h) were used.

[0125] Table 4: Composition of different base glazes (wt%)

[0126] Results and Discussion: All four glaze groups met the "no visible pores" standard under a 50x microscope, demonstrating the broad applicability of the process of this invention to different base glaze systems. Group G1 (standard calcium-alkali glaze) showed the best overall performance, with high gloss (98GU) and obvious jade-like and gem-like luster. Group G2 (high calcium) had a warmer luster, leaning towards a milky matte texture. Group G3 (high alumina) had slightly higher glaze hardness (>7.5) and better thermal stability. Group G4 (with added nano-Al2O3) showed significantly improved glaze slurry suspension, more uniform glazing, and a glaze hardness of 7.5-8.0. The abrasion resistance test (Taber wear) results showed a weight loss reduction of approximately 15% compared to Group G1. This indicates that the introduction of nano-additives can further optimize the physical properties of the glaze without compromising its non-porous characteristics.

[0127] The non-porous tourmaline ceramics prepared by this invention, due to their unique aesthetic qualities and health benefits, can be widely applied in several high-value-added fields: Top-tier art and collectible porcelain: As a breakthrough ceramic glaze technology, it can be directly used to create art display porcelain, masterpieces, national gift porcelain, and high-end collectibles with epoch-making aesthetic value. Luxury daily-use porcelain and tableware: Suitable for luxury brand tableware, tea sets, coffee sets, hotel porcelain, etc., where aesthetics, hygiene, and health are paramount. High-end health appliances: Specially developed water jugs, teacups, and cups for drinking water, utilizing their mineralization and pH adjustment functions to create a natural and healthy drinking experience. Special industrial ceramic components: Ceramic components for the electronics, chemical, and biomedical fields with extreme requirements for surface smoothness, corrosion resistance, and insulation.

[0128] For example, in the biomedical field, the non-porous, high-hardness, easy-to-clean, and pH-adjustable ceramic surface prepared using this invention can be used to prepare high-standard laboratory dishes, cell culture dishes, or certain implant components. Its surface properties help reduce bacterial adhesion and biofilm formation, while the stable, slightly alkaline environment may be beneficial for certain cell cultures. In the high-end electronics field, this glaze can serve as a protective coating for precision ceramic components, providing excellent insulation, weather resistance, and aesthetics.

[0129] In summary, this invention, through the synergistic innovation of ultrafine functional powder interface control and staged kinetic firing process, successfully solves the historical dilemma of the incompatibility between densification and functionalization of ceramic glazes. It provides a complete, clear, and repeatable technical solution that not only produces flawless glazes but also endows ceramics with valuable health attributes. This represents a significant upgrade and leap forward in traditional ceramic technology, possessing broad application prospects and extremely high commercial value.

[0130] The implementation principle of this invention is as follows: This invention discloses a non-porous tourmaline ceramic glaze and its preparation method for secondary firing, belonging to the field of ceramic materials technology. The ceramic glaze is composed of a base glaze and ultrafine tourmaline powder (content 3-20wt%, fineness ≥1000 mesh). During preparation, the green body is first fired at 1150-1250℃ to stabilize the body structure; after glazing, a secondary glaze firing is performed, which is uniquely divided into a "stabilization stage" (holding at 1180-1220℃) and a "melting stage" (holding at 1280-1350℃). This method, through the optimization of the ultrafine powder interface and the synergy of staged firing kinetics, completely eliminates pores on the glaze surface, making the glaze surface free of any visible holes under a 50x microscope. The resulting glaze surface has both a top-grade jade-like texture and gemstone luster, high hardness, easy cleaning, and can stably release beneficial trace elements and finely adjust the pH value of the liquid, achieving a revolutionary unity of ceramic aesthetic quality, physical properties, and health functions.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0132] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A non-porous tourmaline ceramic glaze, characterized in that, It is composed of a base glaze and tourmaline powder; based on the total dry weight of the non-porous tourmaline ceramic glaze, the mass content of the tourmaline powder is 3wt% to 20wt%; the average particle size D50 of the tourmaline powder corresponds to a mesh number of not less than 1000 mesh.

2. The non-porous tourmaline ceramic glaze according to claim 1, characterized in that, The tourmaline powder has a mass content of 5 wt% to 15 wt%, preferably 8 wt% to 12 wt%.

3. A non-porous tourmaline ceramic glaze according to claim 1 or 2, characterized in that, The average particle size D50 of the tourmaline powder corresponds to a mesh size of 1500 to 3500 mesh, preferably 2000 to 3000 mesh.

4. The non-porous tourmaline ceramic glaze according to claim 1, characterized in that, The base glaze also contains trace mineral element additives selected from at least one of selenium, strontium, and zinc.

5. A method for preparing a ceramic product with a non-porous tourmaline ceramic glaze as described in any one of claims 1-4, characterized in that, Includes the following steps: Step S1. Preparation of green body and first firing: The ceramic green body raw material is shaped into a green body, and then the first firing is carried out at 1150℃ to 1250℃ to obtain a green body; Step S2. Glazing: The non-porous tourmaline ceramic glaze is made into a glaze slurry and applied to the surface of the bisque-fired body; Step S3. Second firing: The glazed body is fired a second time. The second firing includes: first heating to 1180℃ to 1220℃ and holding for 0.5-2 hours as a stabilization stage, and then continuing to heat to 1280℃ to 1350℃ and holding for 1-3 hours as a melting stage.

6. The method according to claim 5, characterized in that, The highest temperature for the first firing in step S1 is 1180°C to 1220°C.

7. The method for preparing a ceramic product with a non-porous tourmaline ceramic glaze according to claim 5, characterized in that, The stabilization stage of the second firing in step S3 is: heating to 1200℃±10℃ and holding for 0.5-2 hours; the melting stage is: continuing to heat to 1300℃ to 1320℃ and holding for 1-3 hours.

8. A ceramic product, characterized in that, Its glaze layer is formed by a non-porous tourmaline ceramic glaze according to any one of claims 1-4, and the surface of the glaze layer shows no visible pores when observed under a 50x optical microscope.

9. A ceramic product according to claim 8, characterized in that, The glaze has a jade-like texture and gemstone luster, and its Mohs hardness is not less than 7.

10. A ceramic article according to claim 8 or 9, characterized in that, The ceramic product is a vessel for holding liquids, which can release trace elements into the liquid and / or adjust the pH of the liquid toward a slightly alkaline state.

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