Talc-clay-frit system talc-based domestic porcelain and its preparation method

Abstract

This invention relates to the field of daily-use ceramics technology, specifically disclosing a talc-clay-fuse system for talc-based daily-use ceramics and its preparation method. The raw materials include: calcined talc, clay, and fuse; the fuse comprises: lithium carbonate, alumina, and quartz; the calcined talc comprises: fuse and raw talc. This invention addresses the narrow firing range of traditional talc ceramics through theoretical research. Based on this mechanistic study, a novel preparation process formula for a talc-clay-fuse (small quantity) system is proposed for the first time. Lithium fuse is used as a flux. The lithium fuse dissolves the clay and its decomposition products before the SiO2-MS-M2A2S ternary eutectic reaction, thereby avoiding the ternary eutectic reaction and reducing the total liquid phase generated in the system. This significantly improves the sintering temperature range and clay usage of the talc ceramic, ensuring its formability and fundamentally resolving the contradiction between formability and sintering performance in talc ceramic production.

Description

Technical Field

[0001] This invention relates to the field of daily-use ceramics technology, specifically to a talc-clay-fuse system talc-based daily-use ceramic and its preparation method. Background Technology

[0002] Magnesia ceramics are ceramics with MgO-containing aluminosilicates as the main crystalline phase. Classified according to the main crystalline phase, they can be divided into protoenstatite ceramics (talc ceramics), cordierite ceramics, spinel ceramics, and forsterite ceramics. Talc ceramics are magnesia ceramics with talc as the main raw material. Talc ceramics were initially mainly used in high-frequency electrical ceramics. Zhu Aizhen et al. pointed out in their paper that the sintering temperature range of talc-based electrical ceramics is only about 20℃. However, in their solution, they indicated that adding about 6%-7% feldspar could broaden the sintering temperature range to a certain extent. However, the presence of alkali metal oxides in feldspar would significantly reduce its electrical properties and mechanical strength, so it should be strictly controlled and only used when manufacturing large ceramic parts with low performance requirements. The talc ceramics developed by the Zibo Silicate Research Institute and others went into production in 1977, resulting in a "talc-feldspar-kaolin" system, pioneering a new compositional system in the field of daily-use ceramics. Compared to traditional feldspar porcelain, sericite porcelain, and bone china, talc porcelain boasts advantages such as high strength, good thermal stability, and excellent translucency, making it highly popular among consumers. However, the production of talc porcelain for daily use has consistently faced challenges, including difficulty in shaping, a narrow sintering temperature range, and susceptibility to deformation at high temperatures. Currently, industrial production typically employs methods such as reducing clay content and introducing bentonite to overcome these issues. However, this significantly reduces properties like whiteness in talc porcelain. The existing industrial production formulations for talc porcelain are all near the composition points initially determined by the Zibo Silicate Research Institute. Extensive experiments by the Zibo Silicate Research Institute have proven that a clay content of 15% is optimal, and they maintain that the clay addition in talc porcelain should not exceed 15%. If the shaping requirements are not met, they prefer to take other measures to improve the plasticity of the clay rather than increase the amount of clay. With a fixed clay content of 15% (alumina content in the formula is 7.06%), and varying the ratio of feldspar to calcined talc in the formula, the sintering temperature is 1280℃-1320℃ when calcined talc is 73% and feldspar is 12%. Because the clay content is limited to approximately 15 wt.%, bentonite and organic plasticizers are needed to increase plasticity. The use of bentonite reduces the whiteness of the product. Even with the use of bentonite and plasticizers, the process conditions for shaping talc-based daily-use porcelain remain demanding. The poor sintering performance of talc porcelain means that even slight errors during production can lead to a low yield rate and low tolerance for defects, resulting in a large amount of ceramic waste.

[0003] Most existing literature on talc-based daily-use porcelain suggests that increasing the amount of clay not only affects the whiteness of the porcelain body but also narrows the firing temperature range and reduces thermal stability. Li Xiaosheng et al., in their paper, proposed that the amorphous SiO2 released during talc calcination is the cause of talc porcelain slurry thickening. Their proposed solution is to pulverize raw talc and mix it with 2 wt.% feldspar and 0.1 wt.% barium carbonate before calcining. They also suggest reducing the amount of feldspar and increasing the amount of clay during batching to further improve the clay's forming properties. This process for talc porcelain can solve the slurry thickening problem without significantly increasing costs and allows for a slight increase in clay usage. However, the solvent used remains the traditional potassium feldspar. Potassium feldspar itself produces a large amount of liquid phase and has a strong dissolving ability for protoenstatite, so its addition should not be excessive; its primary purpose is to solve the slurry thickening problem. Currently, there is relatively little theoretical research on talc-based porcelain. Most studies attempt to broaden the sintering temperature range by adding feldspar, but the effect is limited, and the sintering temperature range is not determined using standard high-temperature microscopy. Jiang Weihui et al., in their "talc-feldspar-kaolin" system, increased the amount of kaolin to over 25% and added 2-5% alumina to ensure that the porcelain body contains both cordierite and protoenstatite crystal phases, with cordierite being more abundant than protoenstatite, resulting in a cordierite-protoenstatite porcelain. The patent publication number is CN101717248B, entitled "A Medium- and Low-Temperature Sintered Daily-Use Talc Porcelain and Its Production Method." The patent discloses a formula by weight ratio of talc 50-55%, kaolin 25-30%, feldspar 15-20%, and alumina 2-5%, with a predominantly talc:kaolin ratio of (1.9-2.6):1. Its firing temperature range is 1180℃-1230℃. The patent states that the narrow firing range of talc porcelain is due to its formula composition being close to the lowest eutectic point of the original enstatite-cordierite-tridymite ternary system. When the temperature is below the lowest eutectic point, no liquid phase is generated in the body; however, once the lowest eutectic point is reached, a large amount of liquid phase appears, and the amount of liquid phase increases rapidly with increasing temperature, leading to overfiring and deformation of the porcelain body. This manifests as a narrow firing range for talc porcelain, typically only around 20℃. This patent, by introducing sufficient feldspar raw materials, significantly reduces the sintering temperature of the body on the one hand; on the other hand, it allows the body to sinter earlier, much below the eutectic temperature, which is beneficial for expanding the sintering range of the body. Increasing the amount of feldspar can generate a large amount of liquid phase in the porcelain body at around 1200℃, promoting the sintering of the porcelain body. However, the porcelain body contains two crystalline phases: cordierite and protoenstatite, with cordierite being more abundant than protoenstatite, making it a cordierite-protoenstatite porcelain.

[0004] The high whiteness, high transparency, and high strength of talc porcelain are primarily due to its phase composition consisting of protoenzyme and a glassy phase. This is because fewer phase types reduce phase mismatch and interfacial scattering, thereby improving the flexural strength and light transmittance of the sample. Furthermore, the protoenzyme phase also possesses high whiteness. The initial formula determined by the Zibo Silicate Research Institute for industrial use, while producing products with a protoenzyme and glassy phase composition, suffers from problems such as difficulty in forming, a narrow sintering temperature range, easy deformation at high temperatures, and reduced whiteness. Therefore, developing a new method for manufacturing talc porcelain that maintains its high whiteness, high transparency, and high strength while increasing clay usage and the firing temperature range fundamentally resolves the contradiction between forming and sintering performance. Summary of the Invention

[0005] The first objective of this invention is to address the shortcomings of the prior art by providing a talc-clay-frit system for talc-based daily-use ceramics.

[0006] The second objective of this invention is to address the shortcomings of the prior art by providing a method for preparing talc-based daily-use porcelain based on a talc-clay-frit system.

[0007] To achieve the first objective mentioned above, the technical solution adopted by the present invention is as follows:

[0008] A talc-clay-fuse system for talc-based daily-use ceramics includes the following raw materials: calcined talc, clay, and fuse; the fuse includes the following raw materials: lithium carbonate, alumina, and quartz; the calcined talc includes the following raw materials: fuse and raw talc.

[0009] In the talc-clay-fuse system of talc-based daily-use ceramics as described above, preferably, the following raw materials are included: 70-74 parts of calcined talc, 24-28 parts of clay, and 2-4 parts of fuse; the fuse includes the following raw materials: 25-29 parts of lithium carbonate, 6-10 parts of alumina, and 60-70 parts of quartz; the calcined talc includes the following raw materials: fuse and raw talc, with a mass ratio of fuse to raw talc of 4-5.5:100.

[0010] In the talc-clay-fuse system of talc-based daily-use ceramics as described above, preferably, it is made from the following raw materials in parts by weight: 72 parts calcined talc, 25 parts clay, and 3 parts fuse; the fuse is made from the following raw materials in parts by weight: 27 parts lithium carbonate, 7.5 parts alumina, and 65.6 parts quartz; the calcined talc is made from the following raw materials in the following mass ratio: fuse: raw talc = 5:100.

[0011] In the talc-clay-fuse system of talc-based daily ceramics as described above, preferably, it is made from the following raw materials in parts by weight: 70 parts calcined talc, 28 parts clay, and 4 parts fuse; the fuse is made from the following raw materials in parts by weight: 25 parts lithium carbonate, 6 parts alumina, and 70 parts quartz; the calcined talc is made from the following raw materials in the following mass ratio: fuse: raw talc = 4:100.

[0012] In the talc-clay-fuse system of talc-based daily-use ceramics as described above, preferably, it is made from the following raw materials in parts by weight: 74 parts calcined talc, 24 parts clay, and 2 parts fuse; the fuse is made from the following raw materials in parts by weight: 29 parts lithium carbonate, 10 parts alumina, and 60 parts quartz; the calcined talc is made from the following raw materials in the following mass ratio: fuse: raw talc = 5.5: 100.

[0013] In the talc-clay-fuse system of talc-based daily-use ceramics as described above, preferably, the preparation method includes the following steps: mixing lithium carbonate, alumina, and quartz to prepare a fuse; mixing the fuse with raw talc evenly and calcining it to form calcined talc; taking the calcined talc, clay, and fuse, molding them, heating them to the sintering temperature, and then cooling them.

[0014] In the talc-clay-fuse system of talc-based daily-use porcelain as described above, the main crystalline phase in the porcelain body is protoenstatite.

[0015] Compared with the existing technology that uses feldspar to broaden the sintering temperature range and prepares talc ceramics with cordierite and enstatite as the main crystalline phases, the main crystalline phase of the talc-clay-fuse system of the present invention is enstatite, which significantly improves the whiteness of the product, while keeping the iron and titanium content in the formula at a similar level.

[0016] To achieve the second objective mentioned above, the technical solution adopted by the present invention is as follows:

[0017] The method for preparing talc-based daily-use porcelain in the talc-clay-frit system as described in any of the preceding claims includes the following steps:

[0018] Step (1): Take the raw materials according to the proportions;

[0019] Step (2): Mix lithium carbonate, alumina, and quartz to prepare a frit;

[0020] Step (3): Mix the molten material with raw talc evenly and calcine it to make calcined talc;

[0021] Step (4): Take calcined talc, clay, and frit, shape them, heat them to the sintering temperature, keep them warm, and then cool them.

[0022] In the preparation method of talc-clay-fuse system talc-based daily porcelain as described above, preferably, the heating rate in step (4) is 4-6℃ / min.

[0023] In the preparation method of talc-clay-fuse system talc daily ceramics as described above, preferably, after reaching the maximum firing temperature in step (4), the temperature is held for 0-60 min; more preferably, after reaching the maximum firing temperature in step (4), the temperature is held for 20-60 min; and then the ceramics are cooled naturally in the furnace or removed from the furnace for cooling.

[0024] In the method for preparing talc-based daily-use porcelain in the talc-clay-fuse system described above, preferably, the following steps are included:

[0025] Step (1): Take the raw materials according to the proportions;

[0026] Step (2): Mix lithium carbonate, alumina and quartz, ball mill, calcine at 1250-1300 degrees Celsius, quench in water, collect the fragments, ball mill, and prepare frit;

[0027] Step (3): Mix the frit and raw talc evenly, and calcine at 1180-1220℃ to produce calcined talc;

[0028] Step (4): Take calcined talc, clay and frit, mix them evenly, sieve, age and shape them, raise the temperature at 4-6℃ / min, hold the temperature for 0-60 minutes after reaching the firing temperature, and let them cool naturally in the furnace or take them out of the furnace to cool.

[0029] The advantages of this invention are:

[0030] This invention addresses the narrow sintering range of traditional talc ceramics based on the calcined talc-clay-feldspar system. Through extensive experiments, testing, analysis, and multiple revisions, and combined with phase diagram theory, a theoretical explanation was provided. The main mechanism can be divided into three stages: The first stage occurs at approximately 1200℃, where quartz, mullite, and potassium feldspar undergo a eutectic reaction, resulting in a liquid phase that dissolves some of the protoenstatite. The second stage occurs at approximately 1260℃, where protoenstatite re-precipitates, maintaining the liquid phase within a certain range. As the temperature increases, cordierite begins to appear, and the cordierite content at this stage determines the liquid phase content in the third stage. Finally, at 1355℃, a quartz-protoenstatite-cordierite (SiO2-MS-M2A2S5) eutectic reaction occurs, forming a large amount of liquid phase.

[0031] Based on this mechanistic study, this invention proposes for the first time a new preparation process formula for a talc-clay-fuse (small amount) system. Its mechanism of action is to use alkali metal or alkaline earth metal fuse as a solvent. By dissolving the clay and its decomposition products before the SiO2-MS-M2A2S ternary eutectic reaction, the SiO2-MS-M2A2S ternary eutectic reaction is avoided, thereby reducing the total amount of liquid phase generated in the system, increasing the sintering temperature range and clay usage of talc ceramics, ensuring formability, and resolving the contradiction between formability and sintering performance in the production of talc ceramics.

[0032] This invention compares the effects of different types and amounts of alkali metal oxides and alkaline earth metal oxides in the frit system on the sintering range of talc ceramics. When the alkali metal oxide is K2O and the amount is 40.8g, the sintering temperature range is 50℃; samples with Na2O as the alkali metal oxide do not have a wide sintering temperature range; when the alkali metal oxide is Li2O and the amount is 13g, the sintering temperature range is 57℃. However, when different alkaline earth metal oxides (basic magnesium carbonate, calcium carbonate, zinc oxide, strontium carbonate, and barium carbonate) are introduced into the flux, all samples deform before reaching the sintering temperature, and the shrinkage of the samples is inconsistent during sintering.

[0033] This invention investigated the effects of different firing regimes on the properties of talc ceramics using alkali metal oxides (Li₂O and K₂O) in a frit system. In potassium frit, samples with a heating rate of 10℃ / min exhibited a high sintering temperature range, while samples with a heating rate of 5℃ / min deformed during the rapid shrinkage process, meaning they were overfired just as they reached the sintering temperature and lacked a defined sintering temperature range. In lithium frit, samples with heating rates of 5-10℃ / min all exhibited a high sintering temperature range. Observation of defects in the cooled samples revealed that potassium frit samples developed defects during cooling, while lithium frit samples, after reaching the maximum firing temperature at a heating rate of 10℃ / min, showed a central depression defect upon natural cooling. Therefore, only a scheme using lithium frit as a solvent in the frit system, with lithium frit samples at a heating rate of around 5℃ / min, is suitable for preparing talc ceramics with a wide sintering temperature range.

[0034] In the lithium fused mass system, this invention studied the effect of different holding times after reaching the highest sintering temperature on the sample performance. It was found that as the holding time increased, the light transmittance of the sample gradually increased, while the whiteness and flexural strength first increased and then decreased. When the holding time was 20 min, the sample structure was uniform, and the whiteness and flexural strength reached their maximum values.

[0035] In the lithium fused mass system, this invention compared the effects of different cooling regimes on the performance of lithium fused mass samples. The primary crystalline phase of the samples cooled naturally in the furnace was protoenstatite, and the secondary crystalline phase was MgO·Al₂O₃·4SiO₂. In contrast, the samples cooled externally in the furnace contained not only the primary crystalline phase protoenstatite but also a very small amount of MgO·Al₂O₃·4SiO₂. Compared to the samples cooled naturally in the furnace, external cooling reduced the number of phases, decreased the mismatch between phases, and improved the flexural strength.

[0036] This invention innovatively applies a talc-clay-fuse (small quantity) system to prepare talc-based daily-use porcelain. Compared to samples from a certain manufacturer, the performance is comprehensively improved. Furthermore, it breaks through the initial assertion of the Zibo Silicate Research Institute that "if the clay content of around 15% is insufficient to meet the forming requirements, other measures should be taken to improve the plasticity of the clay rather than increasing the clay content." The clay content is increased to 25wt.%–28wt.%, thus eliminating the need for bentonite and solving the problem of low whiteness in existing malleable talc-based daily-use porcelain. Compared to samples from a certain manufacturer, whiteness is increased by 14%, and forming and sintering properties, which are related to the current demanding production process, are further improved. The sintering temperature range is further widened by 12℃, and the plasticity index is improved by 35%. This fundamentally resolves the contradiction between forming and sintering properties in talc porcelain production, promoting the green development of talc-based daily-use porcelain. Attached Figure Description

[0037] Appendix Figure 1 This refers to the composition range of talc-based porcelain.

[0038] Appendix Figure 2 This is a graph showing the change in flexural strength at different temperatures.

[0039] Appendix Figure 3a A diagram illustrating a method for broadening the sintering temperature range of talc porcelain by increasing the amount of clay used.

[0040] Appendix Figure 3b A process flow diagram for the preparation of the talc-clay-fuse system.

[0041] Appendix Figure 4 (a) shows the curves of the projected area change of samples 4-1#, 4-2# and 4-3# in a high-temperature microscope. (b) is a magnification of the region within the rectangle in (a).

[0042] Appendix Figure 5 High-temperature microscopic images of sample 4-1#. (a) 25℃; (b) 1200℃; (c) 1310℃.

[0043] Appendix Figure 6 High-temperature microscopic images of sample 4-2#. (a) 1324℃; (b) 1370℃; (c) 1380℃.

[0044] Appendix Figure 7 High-temperature microscopic images of sample 4-3#. (a) 1340℃; (b) 1390℃; (c) 1400℃.

[0045] Appendix Figure 8 The curves showing the change in projected area of ​​samples 5-1# and 5-2# under a high-temperature microscope.

[0046] Appendix Figure 9 These are high-temperature microscope images of samples 5-1# and 5-2# when they reached their sintering temperature. (a) 10℃ / min; (b) 5℃ / min.

[0047] Appendix Figure 10 (a) shows the curves of the projected area change of samples 5-3# and 5-4# under a high-temperature microscope. (b) is a magnification of the area within the rectangle in (a).

[0048] Appendix Figure 11 High-temperature microscopic images of sample 5-4#. (a) 1362℃; (b) 1371℃.

[0049] Appendix Figure 12 The UV-Vis transmittance spectra and transmittance variations of samples 5-4#, 5-5#, 5-6#, and 5-7# are shown.

[0050] Appendix Figure 13 The graphs show the changes in whiteness and flexural strength for samples 5-4#, 5-5#, 5-6#, and 5-7#.

[0051] Appendix Figure 14 The test results are for samples #5-6. The left figure shows the XRD pattern of the samples after firing, and the right figure shows the DSC curve of the samples during the cooling process.

[0052] Appendix Figure 15 This is a comparison chart of the performance of samples under different cooling regimes.

[0053] Appendix Figure 16 The XRD patterns of samples 5-8# after sintering are shown.

[0054] Appendix Figure 17 The image shows a performance comparison between samples 5-8# and a talc-based daily-use porcelain body from a certain factory. Detailed Implementation

[0055] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the description of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0056] raw material

[0057] The raw materials mainly consist of minerals such as raw talc powder, washed kaolin, and potassium feldspar, as well as chemical raw materials such as potassium carbonate, sodium carbonate, lithium carbonate, basic magnesium carbonate, calcium carbonate, zinc oxide, strontium carbonate, and barium carbonate. All chemical raw materials are of analytical grade. Potassium carbonate, sodium carbonate, and lithium carbonate were purchased from Sinopharm Chemical Reagent Co., Ltd. The chemical composition of the mineral raw materials used in the exploratory experiments, Examples 1-5, and Comparative Example 1 is as follows.

[0058] Table 1 Chemical composition of mineral raw materials

[0059]

[0060] Testing and Characterization

[0061] (1) Determination of sintering temperature range

[0062] The test is mainly based on the high-temperature microscopy method in QB / T 1547-2016 "Test Method for Sintering Temperature Range of Ceramic Materials". The experimental principle is to determine the sintering temperature range based on the change in the projected area of ​​the sample during the heating process. The lower limit T is the temperature at which the projected shrinkage of the sample reaches its maximum value. L The upper limit is the temperature at which the sample expands due to overheating or shrinks due to softening. h The sintering temperature range of the sample is T. L ~T h .

[0063] To determine the sintering temperature range of talc porcelain, it is necessary to distinguish between the volume expansion phenomenon caused by the precipitation of the original sinter during talc porcelain firing and the over-firing expansion phenomenon. The sintering temperature is defined as the temperature at which refractory materials or ceramic green bodies reach the state of minimum porosity, maximum shrinkage, highest product density, best performance, or become a solid aggregate through sintering. Based on this definition, three conditions are summarized for determining the sintering temperature range of a sample: (1) The sample must reach a densified state. For daily-use porcelain, the criterion is that the water absorption rate of the sample is less than 0.5%; (2) The sample will not have defects within the sintering temperature range, mainly referring to the deformation or irregular morphology of the sample; (3) The performance of the sample, such as flexural strength and thermal stability, will not decrease significantly within the sintering temperature range.

[0064] The sintering temperature range of the samples was tested using an EM301 high-temperature microscope manufactured by Hesse GmbH, Germany, with an upper limit of 1550℃. Sample preparation: After grinding, the samples were passed through a 200-mesh sieve to form cylindrical samples with a diameter of 2mm × 2mm.

[0065] (2) Determination of plasticity index

[0066] The plasticity index was determined by the ball pressing method, and the instrument used was the SKY-45 plasticity meter produced by Jingdezhen Electric Porcelain Company.

[0067] (3) X-ray diffraction analysis

[0068] Phase analysis of the samples was performed using a Bruker D8 X-ray powder diffractometer (Germany). The test conditions were: Cu-Kα radiation, and the X-ray wavelength was... The tube voltage is 40KV, the tube current is 40mA, the scanning range is 2θ=10~70°, the scanning step width is 0.02°, and the test rate is 5 steps / s.

[0069] (4) Thermal analysis (DTA / DSC)

[0070] Differential thermal-thermogravimetric analysis (DTA-TGA) of the samples was performed using a Netzsch GmbH STA449C simultaneous thermal analyzer to test the effects of the samples during the heating process. The test temperature range was room temperature to 1450℃, the test atmosphere was argon, and the reference material was high-purity alumina.

[0071] (5) Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis

[0072] The microstructure and morphology of the samples were analyzed using a SU-8010 field emission scanning electron microscope (SEM) from HITACHI Corporation, Japan. X-ray micro-area analysis was performed using the SU-8010 SEM. The test conditions were as follows: accelerating voltage: 5 kV, resolution: 1.0–1.3 nm, equipped with an IXRF Model 550i electrically cooled energy dispersive spectrometer.

[0073] Sample preparation: Take a flat section from the sample, etch it with 5v% HF for 30 seconds, and then ultrasonically clean it with deionized water for 10 minutes.

[0074] (6) Fourier Transform Infrared Spectroscopy (FT-IR) Analysis

[0075] Infrared spectroscopy of the sample was performed using a Nicolet 5700 Fourier transform infrared spectrometer from Thermo Fisher Scientific. 1 mg of powdered sample was weighed and mixed with pure KBr (sample:KBr = 1:150, mass ratio), then pressed into a pellet for infrared spectroscopy analysis. The wavenumber range was 4000–400 cm⁻¹. -1 The resolution is 0.4cm. -1 .

[0076] (7) Determination of flexural strength of materials

[0077] The test was conducted using a WDW-20 microcomputer-controlled universal testing machine with a span of 20 mm. The flexural strength tester employed the three-point bending method. Samples were processed into 35 mm × 6 mm × 6 mm strips, and the surface was polished. Simultaneously, the long edges of the strips were chamfered at 45° to eliminate stress defects on the sample surface and edges caused by processing. The sample was placed on the universal testing machine's sample stage, with the center aligned with the indenter. The indenter was slowly lowered at a loading rate of 0.2 mm / min until the sample fractured, and the maximum loading load value P was recorded. Then, the width b and thickness h of the wet oxygen were measured, and the flexural strength was calculated using the formula.

[0078] (8) Transmittance test

[0079] The talc porcelain sample was processed into a Φ40mm circular thin sheet. Both sides of the sample were then ground sequentially using 150-grit, 600-grit, and 2000-grit wet sandpaper. Finally, MgO powder was used to polish the sample to a 1mm mirror finish. The transmittance of the polished sample was measured using a Lambda 850 UV-Vis spectrophotometer from Platinum Elmer, USA, with a light source wavelength range of 175–900nm.

[0080] (9) Whiteness test

[0081] The whiteness of the talc porcelain samples was tested using a WSD-2A whiteness meter manufactured by Shanghai Xinrui Instrument Co., Ltd.

[0082] (10) Thermal stability test

[0083] According to GB / T3298-2009 "Test Method for Thermal Shock Resistance of Daily-Use Ceramic Ware", the test samples should be five products of the same batch, specifications, and type, without any damage or cracks. The heating furnace is set to the test temperature. Once the furnace reaches the set temperature, the samples are placed inside. After the furnace temperature returns to the set temperature, it is held for 30 minutes. After the holding period, the samples are immersed in water at (20±2)℃ within 15 seconds and kept submerged for 10 minutes. The water level should be 2 cm above the sample, and the temperature increase should not exceed 4℃. After the holding period, the samples are removed and observed for cracks using a staining solution. The samples are then left to stand for 24 hours before being re-examined.

[0084] Exploration Experiment

[0085] Currently, industrially, reducing clay content is commonly used to improve sintering performance. However, reducing clay content worsens formability, and the use of bentonite to achieve plasticity requirements severely impacts the whiteness of the finished product. This firstly leads to a low yield of talc porcelain, resulting in a significant waste of resources and energy. Secondly, using bentonite to improve plasticity drastically reduces the whiteness of the product, failing to meet the performance requirements of high-grade daily-use porcelain. This clearly contradicts the concept of green development. The sintering of talc porcelain is a liquid-phase sintering process, and the amount of liquid phase plays a decisive role in its sintering performance.

[0086] Phase diagram analysis is an ideal method for quantitatively characterizing the physicochemical reactions during firing. However, the current ternary formulation of talc porcelain belongs to the quaternary system of K2O-MgO-Al2O3-SiO2, and there are no relevant phase diagram research results in the existing literature. The inventors designed different formulation compositions by utilizing the main crystalline phase formed by talc porcelain in the indicative mineral composition, and explored the physicochemical reactions of talc porcelain during firing by using phase diagrams combined with different hypothetical methods. Based on the established method of using phase diagrams, the liquid phase content at different temperature points of each sample was calculated to analyze the changes in sintering performance. Further corrections to the physicochemical reactions during the firing process of traditional talc-based daily-use porcelain were made through DTA and XRD tests at different temperatures. Based on this, the mechanism of the narrow sintering temperature range of traditional talc-based daily-use porcelain when the clay content is high was analyzed.

[0087] like Figure 1 As shown, points a and b were selected within the composition range of the original enstatite porcelain, and points f and g were selected within the composition range of the original enstatite-cordierite porcelain. To study the effect of clay content in the formula on sample performance, discretely distributed ingredient composition points c and e were selected from top to bottom in the middle region of their composition ranges, with increasing clay content. In existing literature, the feldspar content in talc-based daily-use porcelain formulas is greater than 10 wt.%. To study the role of feldspar in sintering, point d, with a feldspar content less than 10 wt.%, was selected. The formula composition of the composition points is shown in Table 2.

[0088] Table 2. Composition of the formulation points

[0089]

[0090] The test results are shown in Table 3. The plasticity index of the samples gradually increases with the increase of clay content. Only sample 3-1#, with a clay content of 13 wt.%, has a relatively wide sintering temperature range. The flexural strength of sample 3-6#, whose main crystalline phase composition contains cordierite, is lower than that of the sample whose main crystalline phase is only protoenstatite. The whiteness of sample 3-6#, with a clay content of 30 wt.%, is 73%, and the whiteness of sample 3-7#, with a clay content of 35 wt.%, is 72%. This means that simply increasing the clay content cannot solve the problem of low whiteness in existing malleable talc-based daily-use porcelain. Protoenstatite-cordierite porcelain also exhibits a phenomenon of flexural strength decreasing with temperature. During the experiment, it was also found that samples 3-7#, whose main crystal phases were protoencite and cordierite, showed obvious volume expansion due to overheating. However, the samples did not change in temperature within the range of 1220℃ to 1280℃ at a heating rate of 5℃ / min.

[0091] Table 3 Test results for each sample

[0092]

[0093]

[0094] "-" indicates that the sample does not have a detectable sintering temperature range, and therefore some properties of the sample cannot be tested.

[0095] The flexural strength of samples 3-7# and 3-1# was tested within the range of regular morphology. The experimental results are as follows: Figure 2 As shown in the figure, the flexural strength of sample 3-7# gradually decreases with increasing firing temperature, indicating that the significant volume expansion during firing has a substantial impact on the flexural strength of sample 3-7#. The effect of firing temperature on the flexural strength of sample 3-1#, whose main crystalline phase is protoencite, within the sintering temperature range is compared with that of sample 3-1#. The experimental results are shown in the figure. Figure 2 b. From Figure 2 b. As can be seen, the firing temperature has little effect on the flexural strength of sample 3-1#. This further illustrates that the flexural strength of sample 3-7# decreases with increasing firing temperature because the sample undergoes significant volume expansion with increasing temperature.

[0096] The above analysis shows that simply increasing the amount of clay in the ternary formula of clay-calcined talc-potassium feldspar cannot solve the problem of low whiteness in existing malleable talc-based everyday porcelain, and also leads to a decrease in flexural strength. When the amount of clay is high, none of the samples exhibit a wide sintering temperature range.

[0097] Subsequently, the composition points of each formulation were represented using chemical composition representation. The calcium oxide, potassium oxide, sodium oxide, and iron oxide components were converted into magnesium oxide and aluminum oxide according to the conversion factor. The liquid phase amount of each sample was calculated using the MgO-Al2O3-SiO2 ternary system phase diagram. It was found that, assuming that the chemical composition of the formulations all participated in the phase transformation reaction in the MgO-Al2O3-SiO2 ternary system phase diagram, when the composition points of each sample were placed in the MgO-Al2O3-SiO2 ternary system phase diagram, the primary crystallization region of some samples conflicted with the actual primary crystallization region. The method of representing the chemical composition of the formulation was further revised. Assuming that potassium feldspar does not participate in the phase transformation reaction in the MgO-Al2O3-SiO2 ternary system phase diagram, potassium feldspar was listed separately. Only the contents of Al2O3, SiO2 and MgO in the calcined talc and clay in the formulation were calculated. After converting the chemical composition of each sample and putting it into the MgO-Al2O3-SiO2 ternary system phase diagram, it was found that the calculated composition point was on the boundary between the original enstatite and the primary crystal region of quartz, indicating that the theoretical assumption was correct. Subsequently, it was considered that potassium feldspar did not melt alone but instead underwent a ternary eutectic reaction with quartz and clay in the K₂O-Al₂O₃-SiO₂ system to produce a liquid phase. Further, it was assumed that each batching point first underwent a phase transition reaction in the K₂O-Al₂O₃-SiO₂ ternary system phase diagram, and the remaining solid phase then underwent a phase transition reaction in the MgO-Al₂O₃-SiO₂ ternary system phase diagram. This decomposed the K₂O-MgO-Al₂O₃-SiO₂ quaternary system into a K₂O-Al₂O₃-SiO₂ ternary system (denoted as system A) and a MgO-Al₂O₃-SiO₂ ternary system (denoted as system B), along with their interactions. System A underwent a solid-liquid phase transition reaction at a lower temperature, and the remaining solid phase then underwent a solid-liquid phase transition reaction in system B at a higher temperature. Therefore, in the ternary formulation of potassium feldspar-calcined talc-clay, the amount of liquid phase generated by the eutectic reaction of potassium feldspar-quartz-mullite at 985℃ can be calculated first according to the K2O-Al2O3-SiO2 phase diagram. The remaining solid phase is then calculated according to the MgO-Al2O3-SiO2 ternary system phase diagram to generate the amount of liquid phase generated by the ternary eutectic reaction of SiO2-MS-M2A2S5 at 1355℃. After converting the composition of each formulation, the amount of liquid phase L1 generated at 985℃ is calculated according to the A system phase diagram, and the amount of liquid phase L2 generated at 1355℃ is calculated according to the B system phase diagram. The total amount of liquid phase TL is then calculated as TL = L1 + L2. The results are shown in the table below.

[0098] Table 4. Chemical composition of the remaining solid phase and total liquid phase content in the system at 1355℃ for each formulation.

[0099]

[0100] By placing the chemical compositions of each sample in Table 4 into the MgO-Al2O3-SiO2 ternary phase diagram, it was found that the primary crystallization regions where each composition point falls are basically consistent with the actual primary crystallization regions. Thus, according to the phase diagram analysis results, phase transformation reactions occurred in two systems at two temperatures in the ternary formulation of calcined talc-clay-potassium feldspar.

[0101] In the K2O-Al2O3-SiO2 system at 985℃:

[0102] SiO2 (quartz) + 3Al2O3·2SiO2 (mullite) + K2O·Al2O3·6SiO2

[0103] In the MgO-Al₂O₃-SiO₂ system at 1355℃:

[0104] SiO2 (quartz) + MgO·SiO2 (proto-enstatite) + 2MgO·2Al2O3·5SiO2

[0105] According to theory, talc-based ceramic bodies can be fully sintered when the liquid phase content is 35%, but deformed when it reaches 45% (Hu Zhiqiang et al., Fundamentals of Inorganic Materials Science, 2004: 197). Based on the phase diagram calculations, the liquid phase content L1 generated by the eutectic reaction at 985℃ did not exceed 35% for any of the samples, meaning none of the samples could be sintered at lower temperatures. At 1355℃, the total liquid phase content TL after the eutectic reaction was close to the upper limit of 45% for sample 3-1# with a clay content of 13%, while sample 3-2# ​​with a clay content of 15% exceeded 45%. When the clay content in the samples was ≥15%, all samples softened and collapsed after reaching 1355℃. Next, the phase diagram analysis results were verified using the experimentally measured sintering temperatures. A high-temperature microscope was used with a heating rate of 10℃ / min to obtain the projection area change curve and analytical photographs of the samples under the microscope. It was found that the projection shrinkage of sample 3-1# reached its maximum at T1 temperature of 1343℃, with a lower limit temperature of 1343℃. The curve began to decline at T2 temperature of 1389℃. Combined with the analytical photographs showing that the sample was over-sintered at 1400℃, it was determined that the sintering temperature range for sample 3-1# was 46℃, from 1343℃ to 1389℃. The test results for all samples are listed in Table 3. XRD analysis of the samples at different temperature points revealed that system A undergoes a solid-liquid phase transition reaction at a lower temperature, dissolving some of the protoenstatite from system B. However, the protoenstatite precipitates back from the liquid phase before the solid-liquid phase transition reaction occurs in system B. Furthermore, the temperature at which the protoenstatite, quartz, and cristobalite phases begin to decrease significantly was found to be around 1200℃. DTA analysis of the samples indicates that this temperature corresponds to the decomposition of Al-Si spinel into mullite. Therefore, the eutectic reaction temperature in the K₂O-Al₂O₃-SiO₂ system is around 1200℃. Based on further analysis using DTA and XRD at different temperatures, the corrected physicochemical reactions during the firing process of traditional talc-based daily-use ceramics are as follows:

[0106] In the K2O-Al2O3-SiO2 system at around 1200℃:

[0107] SiO2 (quartz) + 3Al2O3·2SiO2 (mullite) + K2O·Al2O3·6SiO2

[0108] Interactions between the K2O-Al2O3-SiO2 system and the MgO-Al2O3-SiO2 system:

[0109] Around 1200℃: L1 + MgO·SiO2 (proto-enstatite) → L3

[0110] Around 1260℃: L3→L1+MgO·SiO2 (proto-enstatite)

[0111] In the MgO-Al₂O₃-SiO₂ system at 1355℃:

[0112] SiO2 (quartz) + MgO·SiO2 (proto-enstatite) + 2MgO·2Al2O3·5SiO2

[0113] The mechanism of the narrow firing range of traditional talc porcelain is mainly divided into three stages: In the first stage, at around 1200℃, quartz, mullite, and potassium feldspar undergo a eutectic reaction, and the resulting liquid phase dissolves some of the protoenstatite; In the second stage, at around 1260℃, protoenstatite re-precipitates, keeping the amount of liquid phase within a certain range. As the temperature rises, cordierite begins to appear, and the amount of cordierite at this point determines the amount of liquid phase in the third stage; Finally, as the temperature rises to 1355℃, quartz, protoenstatite, and cordierite undergo a eutectic reaction, forming a large amount of liquid phase.

[0114] Example 1: Effect of using alkali metal and alkaline earth metal frits as solvents on the firing temperature range of talc-based daily-use ceramics

[0115] Based on the results of exploratory experiments, when the clay content is high, the softening and collapse of the sample is caused by the large amount of liquid phase generated by the ternary eutectic reaction of cordierite, protoencite, and quartz in the SiO2-MS-M2A2S5 system at 1355℃. Therefore, to achieve a good sintering temperature range for talc porcelain while increasing the clay content, it is necessary to strictly control the amount of liquid phase generated in the body during the firing process. Once a phase changes from solid to liquid, it does not participate in the eutectic reaction of the solid phase of another system. Based on this, a hypothesis is proposed: if the aluminum-containing solid phase enters the liquid phase before the SiO2-MS-M2A2S5 ternary eutectic reaction, that is, before cordierite is formed, the cordierite that determines the amount of liquid phase generated by the SiO2-MS-M2A2S5 ternary eutectic reaction will disappear. This would prevent the SiO2-MS-M2A2S5 ternary eutectic reaction from occurring, and thus significantly reduce the total amount of liquid at the eutectic temperature. When the amount of liquid phase generated during the eutectic reaction corresponds to the ingredient composition, it was found that 25g came from clay and 26.2g from MgSiO3. To reduce the SiO2-MS-M2A2S5 ternary eutectic reaction and allow clay to enter the liquid phase alone, the total amount of liquid phase in the system can be significantly reduced. Exploratory experiments revealed that the amount of clay and its decomposition products dissolved by potassium feldspar through the K2O-A12O3-SiO2 system is very limited. Therefore, it is necessary to find a solvent with stronger dissolving power to replace potassium feldspar, thereby further expanding the firing range of talc porcelain. Based on the above theory, the solvent needs to simultaneously meet the following conditions: ① able to dissolve clay before the SiO2-MS-M2A2S5 ternary eutectic reaction; ② reduce the SiO2-MS-M2A2S5 ternary eutectic reaction and control the amount of liquid phase between 35% and 45%; ③ dissolve as much clay and its decomposition products as possible, while minimizing the dissolution of MgSiO3; ④ use a small amount of the solvent itself. Methods for widening the sintering temperature range of talc porcelain by increasing clay content, such as... Figure 3a As shown.

[0116] Table 5. Composition of different alkali metal flux formulations (wt.%)

[0117]

[0118] Table 6. Composition of formulations with different alkaline earth metal fluxes (wt.%)

[0119]

[0120] The sintering temperature range of the samples was tested using alkali metals and alkaline earth metals. F4-1# to F4-15# frits were prepared using the following method: The raw materials in the formula were mixed and ball-milled in a high-speed ball mill for 15-25 minutes, then calcined in a frit furnace at 1250-1300 degrees Celsius, quenched in water, and the fragments were collected. Finally, the fragments were ball-milled into 200-mesh powder using a high-speed sample preparation machine. 5 wt.% (compared to the amount of raw talc) of frit was added during the calcination of the raw talc. This 5 wt.% frit was present in the calcined talc during the batching process, and its equivalent in the total formula was 3.4 wt.%. The remaining 3 wt.% frit was then mixed with the calcined talc and clay according to the table below. The specific preparation process is as follows: Figure 3b As shown.

[0121] Table 7. Composition of each sample formulation (wt.%)

[0122]

[0123] High-temperature microscopic testing and analysis were performed on each sample at a heating rate of 10℃ / min. For example... Figures 4 to 7 As shown, sample 4-1# reached its maximum projected shrinkage at temperature T1 (1310℃), indicating that it had sintered at this temperature, but its shape was irregular. Comparing this with the high-temperature microscope image of the sample at 1200℃, it is evident that sample 4-1# underwent deformation during the drastic shrinkage process from 1200℃ to 1310℃, meaning it was over-sintered just as it reached its sintering temperature. The sintering temperature range for sample 4-2# was 1324℃~1370℃, with a value of 46℃. The sintering temperature range for sample 4-3# was 1340℃~1390℃, with a value of 50℃. Only samples 4-2# and 4-3# had relatively wide sintering temperature ranges. As the amount of K2O in the flux increased, the sintering temperature range of the samples gradually increased, and the initial sintering temperature also gradually increased. As the amount of K2O in the flux increases, the less Al2O3-containing crystalline phase is present in the SiO2-MS-M2A2S5 ternary eutectic reaction, the less liquid phase is generated. This prevents the amount of liquid phase generated from exceeding the upper limit allowed for sintering of talc ceramics as the temperature increases, thus gradually increasing the sintering temperature range of the sample. Since the total amount of liquid phase in the sample is also less, the sample needs to reach the required amount of liquid phase for sintering talc ceramics at a higher temperature. Therefore, as the K2O content in the flux increases, the initial sintering temperature of the sample gradually increases.

[0124] High-temperature microscopic analysis was performed on samples 4-4# to 4-6#. The sintering temperature range of sample 4-4# was 1319℃~1340℃, with a value of 21℃. The sintering temperature range of sample 4-5# was 1337℃~1342℃, with a value of 5℃. The sintering temperature range of sample 4-6# was 1308℃~1312℃, with a value of 4℃. Based on the XRD patterns and DTA curves of the samples, it was found that the flux in sample 4-6# nearly completely dissolved the clay and its decomposition products at 1000℃, and as the temperature continued to rise, the alumina-containing crystalline phase in the liquid phase re-precipitated. Samples in this group with Na₂O as the alkali metal oxide in the flux did not have a wide sintering temperature range.

[0125] High-temperature microscopic analysis was performed on samples 4-7# to 4-9#. The sintering temperature range of sample 4-7# was 1291℃~1348℃, with a value of 57℃. The sintering temperature range of sample 4-8# was 1260℃~1266℃, with a value of 6℃. The sintering temperature range of sample 4-9# was 1259℃~1264℃, with a value of 5℃. Among these samples, only sample 4-7# had a relatively wide sintering temperature range.

[0126] XRD analysis was performed on samples 4-7# to 4-9# after quenching at different temperatures. No cordierite phase was found in the XRD patterns of all three samples after quenching at different temperatures, but the MgO·Al2O3·3SiO2 phase was observed. Furthermore, the content of the MgO·Al2O3·3SiO2 phase increased with increasing Li2O content in the flux (using corundum as a reference). DTA analysis of the three samples showed no exothermic peaks around 1000℃ and 1200℃, indicating that the lithium frit has a stronger dissolving ability for clay. However, an exothermic peak appeared around 900℃, with sample 4-7# exhibiting the smallest peak amplitude at this temperature. As the Li2O content in the solvent continued to increase, the peak amplitude gradually increased, indicating that increasing the Li2O content in this solvent formulation caused the dissolved clay to precipitate in the form of other aluminum-containing crystalline phases. This is consistent with the result that increasing the Li2O content increased the content of the MgO·Al2O3·3SiO2 phase.

[0127] High-temperature microscopic analysis of sample 4-10# revealed deformation during the shrinkage process from 1078℃ to 1325℃, indicating that sample 4-10# was over-burned upon reaching its sintering temperature. The reason for this is that the mixed alkali effect weakens the flux's ability to dissolve clay at the sintering temperature, causing Al2O3 and SiO2 to enter the liquid phase in large quantities only near the sintering temperature.

[0128] Samples 4-3# with potassium flux and 4-7# with lithium flux both exhibited good sintering temperature ranges. However, the sintering processes of the two samples differed significantly. In the potassium flux sample, Al2O3 entered the liquid phase as alkali metal ions to achieve charge balance. Only a small portion of the Al2O3 in this sample entered the liquid phase between 600℃ and 1250℃, with the majority remaining in the Mg phase. 2+ It enters the liquid phase under the influence of [something]. However, when it reaches the sintering state at 1350℃, Mg [something]... 2+ Al₂O₃ precipitates as protoencite, maintaining equilibrium with K⁺ in the liquid phase. Thus, Mg… 2+ It acted as an intermediate medium, with a liquid phase content of 37.4 wt.% at 1350℃. The Al2O3 in the sample with lithium frit flux was in the form of Mg. 2+ Under the condition of charge balance, the lithium molten metal enters the liquid phase. During the firing process, the lithium molten metal can completely dissolve the clay and its fractionated products at around 1200℃. When the sintering temperature reaches 1330℃, the amount of liquid phase in the sample is 45wt.%, and the main phase composition of the sample is also protoencite and glass phase.

[0129] High-temperature microscopy tests were performed on samples 4-11#, 4-12#, 4-13#, 4-14#, and 4-15# at a heating rate of 10℃ / min. Sample 4-11# deformed during the drastic shrinkage from 1099℃ to the sintering temperature; sample 4-12# deformed from 1223℃ to the sintering temperature; sample 4-13# deformed from 1171℃ to the sintering temperature; sample 4-14# deformed from 1172℃ to the sintering temperature; and sample 4-15# deformed from 1086℃ to the sintering temperature. When 18.3 wt.% of different alkaline earth metal oxides were introduced into the flux, all samples deformed at the sintering temperature, and the shrinkage during sintering was inconsistent. The addition of alkaline earth metal oxides weakened the flux's ability to dissolve clay in all samples, which is attributed to the alkali-pressure effect of the melt. When alkaline earth metal oxides are added to alkali-containing melts, the migration ability of ions in the melt is weakened. This is because the higher charge and larger radius of alkaline earth metal oxides hinder the migration of alkali metal ions.

[0130] Example 2: Optimization Experiment of Firing Conditions for Fused System

[0131] (I) The effect of heating rate on performance

[0132] The F4-3# and F4-7# flux formulations were prepared into frits (the preparation method of the frits is the same as in Example 1), and ball-milled into 200-mesh powder using a rapid sample preparation machine. 5 wt.% (compared to the amount of raw talc) of frit was added during the calcination of raw talc, and it was present in the calcined talc during the batching process. The amount of the added 5 wt.% frit in the total formulation was calculated to be 3.4 wt.%. Then, 3 wt.% of the frit was further batched with the calcined talc and clay according to the table below, and the effect of different heating rates on performance was compared.

[0133] Table 8. Experimental Effect of Heating Rate on Performance

[0134]

[0135] As previously known, the sintering temperature range of sample 5-1# (potassium carbonate 4-3#) is 1340℃~1390℃, with a value of 50℃. High-temperature microscopy was performed on sample 5-2# to determine its sintering temperature range. The results are as follows... Figure 8 and Figure 9 As shown, the projection shrinkage of sample 5-2# in high-temperature microscopy reaches its maximum at temperature T1 of 1340℃. However, the morphology is irregular at this temperature, indicating that sample 5-2# has already deformed during the violent shrinkage process. That is, the sample was over-burned when it just reached the sintering temperature, and sample 5-2# has no sintering temperature range.

[0136] As previously known, the sintering temperature range of sample 5-3# (lithium carbonate 4-7#) is 1291℃~1348℃, with a value of 57℃. High-temperature microscopy was performed on sample 5-4# to determine its sintering temperature range. The results are as follows... Figure 10 and 11 As shown, the projected area curve of sample 5-4# in high-temperature microscopy reaches its maximum value at temperature T1 (1302℃), and the lower limit temperature for sample 5-4# is 1302℃. The projected area curve begins to decrease at temperature T2 (1362℃). To determine whether this is softening shrinkage, combined with... Figure 11 It can be seen that the sample began to soften and collapse after 1370℃. T2 temperature of 1362℃ is the temperature before the sample softens and shrinks, and the upper limit temperature of sample 5-4# is 1362℃. Therefore, the sintering temperature range of sample 5-4# is 1302℃~1362℃, which is 60℃.

[0137] By opening the furnace door during firing, the formation of defects in the samples was observed. Samples 5-1# and 5-3# developed defects during natural cooling in the furnace. For thin-plate samples, a central depression appeared. For samples using potassium and lithium frit as flux, after reaching the maximum firing temperature at a heating rate of 10℃ / min, a central depression defect appeared during natural cooling in the furnace. This was because the heating rate was too rapid, preventing the samples from fully reacting and homogenizing at high temperatures, leading to this defect due to differences in thermal expansion coefficients during cooling. Therefore, a suitable heating rate for the samples is 5℃ / min. Only sample 5-4#, using lithium frit as flux, exhibited a good sintering temperature range.

[0138] (II) The effect of heat preservation time on performance

[0139] The F4-7# solvent formulation was prepared into a frit (the preparation method of the frit is the same as in Example 1), and ball-milled into 200-mesh powder using a rapid sample preparation machine. 5 wt.% (compared to the amount of raw talc) of frit was added during the calcination of raw talc, and it was present in the calcined talc during the batching process. The amount of the added 5 wt.% frit in the total formulation was calculated to be 3.4 wt.%. Then, 3 wt.% of the frit was further batched with the calcined talc and clay according to the table below, and the effect of different holding times on performance was compared.

[0140] Table 9. Experimental Effect of Insulation Time on Performance

[0141]

[0142] like Figure 12 As shown in the ultraviolet-visible light transmission spectrum of the sample, it can be seen that as the heat treatment time increases, the sample at 400 cm⁻¹... -1 ~780cm -1 Within the visible light wavenumber range, the curve gradually shifts upward, indicating that the transmittance of visible light in the sample gradually increases with the increase of heat preservation time. Plotting the maximum transmittance of the sample in the visible light range as a line graph shows that although the transmittance of the sample gradually increases with the increase of heat preservation time, the rate of increase gradually decreases.

[0143] like Figure 13As shown, the whiteness and flexural strength of the samples initially increase and then decrease with increasing holding time. This is because when the holding time is 20 minutes, the sample structure reaches a relatively homogeneous state, and both the whiteness and flexural strength reach their maximum values. As the holding time continues to increase, the glass phase in the sample gradually increases, so both the whiteness and flexural strength begin to decrease. For high-grade daily-use fine porcelain, light transmittance is more important. When the holding time is 40 minutes, the whiteness and flexural strength of the sample do not decrease significantly, but the light transmittance increases considerably. Therefore, the optimal holding time for samples with lithium frit flux is 40 minutes.

[0144] (III) The impact of cooling system on performance

[0145] The F4-7# solvent formulation was prepared into a frit (the preparation method of the frit is the same as in Example 1), and ball-milled into 200-mesh powder using a rapid sample preparation machine. 3.4g of the frit was added during the calcination of raw talc, and then 3g of the frit was mixed with calcined talc and clay according to the table below. The effects of different cooling regimes on performance were compared. "Removed from the furnace" in the table refers to the process where, after the sample reaches the firing temperature range and is held at that temperature for a period of time, it is first allowed to cool naturally in the furnace to 1200℃, and then removed from the furnace for further cooling.

[0146] Table 10 Experimental Effects of Cooling Regime on Performance

[0147]

[0148] like Figure 14 As shown, the main crystalline phase of samples 5-6# is protoenstatite, and the secondary crystalline phase is MgO·Al2O3·4SiO2. In the study of samples using lithium frit as flux during the heating process, the XRD patterns of these samples at higher temperatures only showed the protoenstatite phase, suggesting that MgO·Al2O3·4SiO2 precipitated during the cooling process. Therefore, differential thermal analysis (DTA) was performed on samples 5-6# during the cooling process. The results show a large exothermic peak around 1150℃, confirming the hypothesis that MgO·Al2O3·4SiO2 precipitated during cooling. The transmittance, whiteness, flexural strength, and thermal stability of sample 5-8# were tested and compared with those of sample 5-6#. The results are as follows. Figure 15 As shown, the flexural strength of sample 5-8# is significantly improved compared to sample 5-6#; for example... Figure 16 XRD results showed that the main crystalline phase of samples 5-8# after sintering was protoenstatite, with a very small amount of MgO·Al2O3·4SiO2. The reduction in the content of MgO·Al2O3·4SiO2 resulted in the sample's phase composition being mainly protoenstatite and glassy phase. The reduction in the number of phase types would reduce the mismatch between phases, thereby improving the flexural strength of the sample.

[0149] (iv) Performance comparison between a sample with lithium flux and a sample of talc-based daily-use porcelain from a certain factory.

[0150] The performance of samples 5-8# was compared with that of a certain manufacturer's talc-based daily-use porcelain body. First, the effect of heat preservation time on the performance of the talc-based daily-use porcelain body from the certain manufacturer was studied to ensure that the performance of the comparison samples represented its superior performance. Commercially available talc-based daily-use porcelain bodies from the manufacturer were taken and tested according to the table below.

[0151] Table 11 Experimental Design of the Effect of Heat Insulation Time on the Properties of Talc-Based Daily-Use Porcelain Body in a Certain Factory

[0152]

[0153] Based on the UV-Vis transmittance spectra, transmittance variation diagrams, flexural strength variation diagrams, and whiteness variation diagrams of samples 5-9# to 5-12#, it was found that the sample performance was optimal when the holding time was 40 min. Sample 5-8# was compared with the optimal-performing sample 5-11#. The results are as follows... Figure 17 As shown, samples 5-8# with lithium flux have improved all properties compared with talc-based daily-use porcelain samples from a certain factory. The sintering temperature range has been widened by 15℃, the light transmittance has increased by 20%, the whiteness has increased by 11%, the flexural strength has increased by 5%, and the thermal stability has increased by 10℃.

[0154] Example 3

[0155] A talc-clay-fuse system for talc-based daily-use ceramics comprises the following raw materials: calcined talc, clay, and fuse, wherein the fuse is made of 27 parts lithium carbonate, 7.5 parts alumina, and 65.6 parts quartz; the fuse and raw talc are mixed at a mass ratio of 5:100 and calcined at 1200℃ to form calcined talc; then the fuse, calcined talc, and clay are mixed in the following weight proportions: 72 parts calcined talc, 25 parts clay, and 3 parts fuse.

[0156] The preparation method of the frit is as follows: after mixing the raw materials in the frit formula, the mixture is ball-milled in a high-speed ball mill for 15-25 minutes, then placed in a frit furnace and calcined at 1250-1300 degrees Celsius, quenched in water, the fragments are collected, and finally ball-milled into 200-mesh powder using a high-speed sample preparation machine.

[0157] The raw materials, after being batched, were passed through a 200-mesh sieve. After aging and shaping, they were placed in an electric furnace and heated at 5℃ / min until the maximum firing temperature was reached. The temperature was then held for 40 minutes, and the samples were removed from the furnace and cooled to room temperature. The resulting samples underwent performance testing: sintering temperature range of 1302-1362℃, light transmittance of 16.5%, whiteness of 77.1, flexural strength of 122.79 MPa, and thermal stability: no cracking after a single heat exchange from 210℃ to room temperature. The samples showed no defects. XRD results indicated that the main crystalline phase of the samples was protoenstatite.

[0158] Example 4

[0159] A talc-clay-fuse system for talc-based daily-use ceramics includes the following raw materials: calcined talc, clay, and fuse, wherein the fuse is made of 25 parts lithium carbonate, 6 parts alumina, and 70 parts quartz; the fuse and raw talc are mixed at a mass ratio of 4:100 and calcined at 1220℃ to form calcined talc; then the fuse, calcined talc, and clay are mixed in the following weight proportions: 70 parts calcined talc, 28 parts clay, and 4 parts fuse.

[0160] The preparation method of the frit is as follows: after mixing the raw materials in the frit formula, the mixture is ball-milled in a high-speed ball mill for 15-25 minutes, then placed in a frit furnace and calcined at 1250-1300 degrees Celsius, quenched in water, the fragments are collected, and finally ball-milled into 200-mesh powder using a high-speed sample preparation machine.

[0161] The raw materials, after being batched, were passed through a 200-mesh sieve. After aging and shaping, they were placed in an electric furnace and heated at 4℃ / min until the maximum firing temperature was reached. The temperature was then held for 20 minutes, and the samples were removed from the furnace and cooled to room temperature. The resulting samples underwent performance testing: sintering temperature range of 1311-1370℃, light transmittance of 15.3%, whiteness of 82.3, flexural strength of 125.24 MPa, and thermal stability: no cracking after a single heat exchange from 210℃ to room temperature. The samples showed no defects. XRD results indicated that the main crystalline phase of the samples was protoenstatite.

[0162] Example 5

[0163] A talc-clay-fuse system for talc-based daily-use ceramics includes the following raw materials: calcined talc, clay, and fuse, wherein the fuse is made of 29 parts lithium carbonate, 10 parts alumina, and 60 parts quartz; the fuse and raw talc are mixed at a mass ratio of 5.5:100 and calcined at 1180℃ to form calcined talc; then the fuse, calcined talc, and clay are mixed in the following weight proportions: 74 parts calcined talc, 24 parts clay, and 2 parts fuse.

[0164] The preparation method of the frit is as follows: after mixing the raw materials in the frit formula, the mixture is ball-milled in a high-speed ball mill for 15-25 minutes, then placed in a frit furnace and calcined at 1250-1300 degrees Celsius, quenched in water, the fragments are collected, and finally ball-milled into 200-mesh powder using a high-speed sample preparation machine.

[0165] The raw materials, after being batched, were passed through a 200-mesh sieve. After aging and shaping, they were placed in an electric furnace and heated at 6℃ / min until the maximum firing temperature was reached. The temperature was then held for 60 minutes, and the samples were removed from the furnace and cooled to room temperature. The resulting samples underwent performance testing: sintering temperature range of 1298-1352℃, light transmittance of 17.1%, whiteness of 76.3, flexural strength of 121.23 MPa, and thermal stability: no cracking after a single heat exchange from 200℃ to room temperature. The samples showed no defects. XRD results indicated that the main crystalline phase of the samples was protoenstatite.

[0166] Comparative Example 1

[0167] A talc-clay-fuse system for talc-based daily-use ceramics comprises the following raw materials: calcined talc, clay, and fuse, wherein the fuse is made of 13 parts lithium carbonate, 7.5 parts alumina, and 65.6 parts quartz; the fuse and raw talc are mixed at a mass ratio of 5:100 and calcined at 1200℃ to form calcined talc; then the fuse, calcined talc, and clay are mixed in the following weight proportions: 72 parts calcined talc, 25 parts clay, and 3 parts fuse.

[0168] The preparation method of the frit is as follows: after mixing the raw materials in the frit formula, the mixture is ball-milled in a high-speed ball mill for 15-25 minutes, then placed in a frit furnace and calcined at 1250-1300 degrees Celsius, quenched in water, the fragments are collected, and finally ball-milled into 200-mesh powder using a high-speed sample preparation machine.

[0169] The raw materials, after being mixed, were passed through a 200-mesh sieve. After aging and shaping, they were placed in an electric furnace and heated at 5℃ / min until the maximum firing temperature was reached. The temperature was then held for 40 minutes, and the samples were removed from the furnace and cooled to room temperature. The resulting samples were then subjected to performance tests: the sintering temperature range was 1342~1351℃.

[0170] Example 6

[0171] The chemical composition of the mineral raw materials used in this embodiment is as follows.

[0172] Table 12 Chemical Composition of Mineral Raw Materials

[0173]

[0174] A talc-clay-fuse system for talc-based daily-use ceramics comprises the following raw materials: calcined talc, clay, and fuse, wherein the fuse is made of 27 parts lithium carbonate, 7.5 parts alumina, and 65.6 parts quartz; the fuse and raw talc are mixed at a mass ratio of 5:100 and calcined at 1200℃ to form calcined talc; then the fuse, calcined talc, and clay are mixed in the following weight proportions: 72 parts calcined talc, 25 parts clay, and 3 parts fuse.

[0175] The preparation method of the frit is as follows: after mixing the raw materials in the frit formula, the mixture is ball-milled in a high-speed ball mill for 15-25 minutes, then placed in a frit furnace and calcined at 1250-1300 degrees Celsius, quenched in water, the fragments are collected, and finally ball-milled into 200-mesh powder using a high-speed sample preparation machine.

[0176] The raw materials, after being batched, were passed through a 200-mesh sieve. After aging and shaping, they were placed in an electric furnace and heated at 5℃ / min until the maximum firing temperature was reached. The temperature was then held for 40 minutes, and the samples were removed from the furnace and cooled to room temperature. The resulting samples underwent performance testing: sintering temperature range of 1302-1360℃, light transmittance of 16.3%, whiteness of 86.2, flexural strength of 124.23 MPa, and thermal stability: no cracking after a single heat exchange from 220℃ to room temperature. The samples showed no defects. XRD results indicated that the main crystalline phase of the samples was protoenstatite.

[0177] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A talc-clay-fractor system for talc-based daily-use porcelain, characterized in that, The preparation materials include: 70-74 parts calcined talc, 24-28 parts clay, and 2-4 parts frit; the frit includes: 25-29 parts lithium carbonate, 6-10 parts alumina, and 60-70 parts quartz; the calcined talc includes: frit and raw talc, wherein the mass ratio of frit to raw talc is 4-5.5:100; the preparation method includes the following steps: mixing lithium carbonate, alumina, and quartz to prepare frit; mixing frit and raw talc evenly and calcining to obtain calcined talc; taking calcined talc, clay, and frit, molding, heating to the sintering temperature, and cooling; the main crystalline phase of the ceramic body is protoenstatite.

2. The talc-clay-felted system talc-based daily-use porcelain according to claim 1, characterized in that, It is made from the following raw materials in parts by weight: 72 parts calcined talc, 25 parts clay, and 3 parts frit; the frit is made from the following raw materials in parts by weight: 27 parts lithium carbonate, 7.5 parts alumina, and 65.6 parts quartz; the calcined talc is made from the following raw materials in the following mass ratio: frit: raw talc = 5:

100.

3. The talc-clay-felted system talc-based daily-use porcelain according to claim 1, characterized in that, It is made from the following raw materials in parts by weight: 70 parts calcined talc, 28 parts clay, and 4 parts frit; the frit is made from the following raw materials in parts by weight: 25 parts lithium carbonate, 6 parts alumina, and 70 parts quartz; the calcined talc is made from the following raw materials in the following mass ratio: frit: raw talc = 4:

100.

4. The talc-clay-felted system talc-based daily-use porcelain according to claim 1, characterized in that, It is made from the following raw materials in parts by weight: 74 parts calcined talc, 24 parts clay, and 2 parts frit; the frit is made from the following raw materials in parts by weight: 29 parts lithium carbonate, 10 parts alumina, and 60 parts quartz; the calcined talc is made from the following raw materials in the following mass ratio: frit: raw talc = 5.5:

100.

5. The method for preparing talc-based daily-use porcelain based on the talc-clay-fuse system according to any one of claims 1-4, characterized in that, Includes the following steps: Step (1): Take the raw materials according to the proportion; Step (2): Mix lithium carbonate, alumina, and quartz to prepare a frit; Step (3): Mix the molten material with raw talc evenly and calcine it to make calcined talc; Step (4): Take calcined talc, clay, and frit, shape them, heat them to the sintering temperature, keep them warm, and then cool them.

6. The method for preparing talc-based daily-use porcelain in the talc-clay-fuse system according to claim 5, characterized in that, The heating rate in step (4) is 4-6℃ / min.

7. The method for preparing talc-based daily-use porcelain in the talc-clay-fuse system according to claim 6, characterized in that, After reaching the highest firing temperature in step (4), hold the temperature for 0-60 minutes, and then allow it to cool naturally inside the furnace or remove it from the furnace for cooling outside.

8. The method for preparing talc-based daily-use porcelain in the talc-clay-fuse system according to claim 7, characterized in that, Includes the following steps: Step (1): Take the raw materials according to the proportion; Step (2): Mix lithium carbonate, alumina and quartz, ball mill, calcine at 1250-1300 degrees Celsius, quench in water, collect the fragments, ball mill, and prepare frit; Step (3): Mix the frit and raw talc evenly, and calcine at 1180-1220℃ to produce calcined talc; Step (4): Take calcined talc, clay and frit, mix them evenly, sieve, age and shape them, raise the temperature at 4-6℃ / min, hold the temperature for 0-60 minutes after reaching the firing temperature, and let them cool naturally in the furnace or take them out of the furnace to cool.

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