A talc porcelain of talc-clay system and its preparation method

Abstract

The present application relates to the technical field of daily ceramic, and particularly discloses a talc daily ceramic of a calcined talc-clay system and a preparation method thereof. The talc daily ceramic comprises the following preparation raw materials: calcined talc and clay. The calcined talc comprises the following preparation raw materials: potassium carbonate and raw talc. The present application carries out theoretical research on the mechanism of narrow sintering range of traditional talc ceramic. On the basis of the mechanism research, the calcined talc-clay system is first proposed, and the potassium carbonate is used as a flux. The flux is added in advance when the calcined talc is calcined. The clay and its decomposition products are dissolved before the SiO2-MS-M2A2S ternary eutectic reaction, so as to reduce the total liquid phase amount generated in the system, significantly improve the sintering temperature range and the clay amount of the talc ceramic, and ensure the forming performance. Compared with the talc daily ceramic of a certain factory, the light transmittance of the talc daily ceramic is improved by 21.5%, the whiteness is improved by 10.9%, and the bending strength is improved by 10%. The contradiction between the forming performance and the sintering performance in the production of the talc ceramic is fundamentally solved, and the green development of the talc daily ceramic is facilitated.

Description

Technical Field

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

[0002] Magnesia porcelain is a type of porcelain with MgO-containing aluminosilicate as its main crystalline phase. Classified according to the main crystalline phase, it can be divided into protoenstatite porcelain (talc porcelain), cordierite porcelain, spinel porcelain, and forsterite porcelain. Talc porcelain is a type of magnesium porcelain with talc as its main raw material. Talc porcelain was initially mainly used in high-frequency electrical porcelain. Zhu Aizhen et al. pointed out in their paper that the sintering temperature range of talc electrical porcelain is only about 20℃. However, in their solution, they indicated that adding about 6%-7% feldspar can broaden the sintering temperature range to a certain extent. However, the presence of alkali metal oxides in feldspar will significantly reduce its electrical properties and mechanical strength, so it should be strictly controlled and only used when manufacturing large porcelain pieces with low performance requirements. Compared with traditional feldspar porcelain, sericite porcelain, and bone china, talc porcelain has advantages such as high strength, good thermal stability, and good light transmittance, making it very popular with consumers. However, the production of talc-based daily-use porcelain has always faced problems such as difficulty in forming, narrow sintering temperature range, and easy deformation at high temperatures. Currently, the industry usually uses methods such as reducing the clay content and introducing bentonite to overcome the problems of difficult forming and narrow sintering temperature range. However, the whiteness and other properties of talc porcelain are significantly reduced as a result. The existing industrial production formulas for talc porcelain are all near the composition points initially determined by the Zibo Silicate Research Institute. After extensive experiments, the Zibo Silicate Research Institute has proven that the clay content should be selected at 15%, and insists that the amount of clay added to talc porcelain should not exceed 15%. If the forming requirements cannot be met, it is preferable 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 system for everyday 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 calcined talc-clay system.

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

[0008] A talc-clay system of calcined talc-based daily-use porcelain, comprising the following raw materials: calcined talc and clay; wherein the calcined talc comprises the following raw materials: potassium carbonate and raw talc.

[0009] In the above-mentioned talc-clay system of talc-based daily-use porcelain, the preferred raw materials include the following: 70-80 parts of calcined talc and 20-30 parts of clay; the calcined talc includes the following raw materials: potassium carbonate and raw talc, wherein the mass ratio of potassium carbonate to raw talc is 4-4.8:100.

[0010] In the above-mentioned talc-clay system of talc-based daily ceramics, preferably, it is made from the following raw materials in parts by weight: 75 parts talc and 25 parts clay; the talc includes the following raw materials: potassium carbonate and raw talc, wherein the mass ratio of potassium carbonate to raw talc is 4:100.

[0011] In the above-mentioned talc-clay system of talc-based daily ceramics, preferably, it is made from the following raw materials in parts by weight: 80 parts of calcined talc and 20 parts of clay; the calcined talc includes the following raw materials: potassium carbonate and raw talc, wherein the mass ratio of potassium carbonate to raw talc is 4.8:100.

[0012] In the above-mentioned talc-clay system of talc-based daily-use porcelain, preferably, it is made from the following raw materials in parts by weight: 70 parts talc and 30 parts clay; the talc includes the following raw materials: potassium carbonate and raw talc, wherein the mass ratio of potassium carbonate to raw talc is 4.4:100.

[0013] In the above-mentioned talc-clay system of talc-based daily-use porcelain, the preferred preparation method includes the following steps: taking raw talc and potassium carbonate, mixing them, and calcining them at 1300-1340℃ to form talc; taking calcined talc and clay, mixing them, shaping them, heating them to the sintering temperature, and cooling them.

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

[0015] Compared with the existing technology that adds 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 system of the present invention is enstatite, which significantly improves the whiteness of the product when the iron and titanium contents in the formula are similar.

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

[0017] The preparation method of talc-based daily-use porcelain in the talc-clay system described above includes the following steps:

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

[0019] Step (2): Take raw talc and potassium carbonate, mix them, and calcine them to make calcined talc;

[0020] Step (3): Take calcined talc and clay, mix them evenly, shape them, heat them to the sintering temperature, and then cool them.

[0021] In the above-described method for preparing talc-clay talc-based daily-use porcelain, preferably, the calcination temperature in step (2) is 1300-1340℃.

[0022] In the above-described method for preparing talc-clay talc-based daily-use porcelain, preferably, in step (3), the sintering temperature is reached and then held for 0-80 min; more preferably, in step (3), the sintering temperature is reached and then held for 20-60 min.

[0023] In the method for preparing talc-based daily-use porcelain in the talc-clay system described above, preferably, the following steps are included:

[0024] Step (1): Take the raw materials according to the proportions;

[0025] Step (2): Take raw talc and potassium carbonate, mix them, and calcine them at 1300-1340℃ to make calcined talc;

[0026] Step (3): Take calcined talc and clay, mix them evenly and shape them, then heat them to the sintering temperature at 4-6℃ / min. After reaching the sintering temperature, keep them at the temperature for 0-80 minutes and then cool them.

[0027] 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.

[0028] Based on this mechanism study, we attempted to prepare talc ceramics using a talc-clay-frit (small amount) system. The mechanism is as follows: using alkali metal or alkaline earth metal frit as a solvent, the frit dissolves the clay and its decomposition products before the SiO2-MS-M2A2S ternary eutectic reaction, thus avoiding the SiO2-MS-M2A2S ternary eutectic reaction, thereby reducing the total amount of liquid phase generated in the system, and increasing the sintering temperature range and clay usage of the talc ceramics. First, we explored solvent schemes using alkali metals potassium and sodium, as well as different alkaline earth metal frits, to investigate their effects on the sintering range of talc ceramics. When the alkali metal oxide was K₂O at a dosage of 40.8 g, the sintering temperature range was 50℃. Samples using Na₂O as the alkali metal oxide did not exhibit a wide sintering temperature range. When different alkaline earth metal oxides (basic magnesium carbonate, calcium carbonate, zinc oxide, strontium carbonate, and barium carbonate) were introduced into the flux, all samples deformed upon reaching the sintering temperature, and the shrinkage during sintering was inconsistent. We further investigated the effect of potassium frit as a solvent formulation on the properties of talc ceramics under different firing regimes. With potassium frit, samples with a heating rate of 10℃ / min exhibited a higher sintering temperature range, while samples with a heating rate of 5℃ / min deformed during the rapid shrinkage process, indicating overfiring just as they reached the sintering temperature, lacking a defined sintering temperature range. During the firing process, the furnace door was opened to observe the formation of defects in the samples. Samples using potassium frit as flux reached their maximum firing temperature at a heating rate of 10℃ / min. Upon natural cooling in the kiln, these samples exhibited a central depression defect. This indicates that the potassium frit solution offers a wide sintering temperature range at a heating rate of 10℃ / min, but under these conditions, the samples develop a central depression defect.

[0029] To improve the application performance of samples with K2O as the alkali metal oxide in the flux, a new calcined talc-clay system was explored. This system involves adding all potassium carbonate during the calcination of talc, eliminating the need for potassium frit preparation. Specifically, the added flux is first calcined together with raw talc to form calcined talc. The calcined talc is then mixed with clay, followed by ball milling, sieving, molding, and sintering.

[0030] In the new calcined talc-clay system, the effect of the calcination temperature of raw talc on the sintering temperature range was explored. A calcination temperature of 1200℃ was favorable for sintering. Further increasing the calcination temperature to 1320-1360℃ resulted in a wider sintering temperature range only at a calcination temperature of 1320℃.

[0031] In the new calcined talc-clay system, the effect of heat preservation time on sample properties was explored. As the heat preservation time increased, the light transmittance of the sample gradually increased, while the whiteness and flexural strength of the sample showed a trend of first increasing and then decreasing.

[0032] In the new calcined talc-clay system, after increasing the clay content to 30%, the light transmittance of the sample gradually increased with the increase of potassium carbonate content, while the whiteness and flexural strength both showed a decreasing trend. When the potassium carbonate content was 4.4 wt.%, the sample had better light transmittance, flexural strength and whiteness.

[0033] This invention innovatively applies a calcined talc-clay system for the first time. Compared to a sample of talc-based daily-use porcelain from a certain manufacturer, its performance is comprehensively improved. It also breaks through the initial assertion of the Zibo Silicate Research Institute during the research and development of talc-based daily-use porcelain: "If the clay content is around 15%, and this is insufficient to meet the forming requirements, it is better to take other measures to improve the plasticity of the clay than to increase the clay content." The clay content is increased to 25wt.%–30wt.%, thus eliminating the need for bentonite and solving the problem of low whiteness in existing malleable talc-based daily-use porcelain. Compared to the sample of 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, translucency is increased by 21.5%, whiteness by 10.9%, and flexural strength by 10%. This fundamentally resolves the contradiction between forming and sintering properties in the production of talc-based porcelain, which is conducive to the green development of talc-based daily-use porcelain.

[0034] The novel calcined talc-clay system of this invention cleverly utilizes the amorphous SiO2 produced by the decomposition of calcined talc. During calcination, K2CO3 is added to form a flux component, which allows for the dissolution of more alumina components with less flux. This not only improves the efficiency of flux utilization but also further reduces the process flow and lowers the production cost of talc porcelain compared to the frit system. Attached Figure Description

[0035] Appendix Figure 1 This refers to the composition range of talc-based porcelain.

[0036] Appendix Figure 2 This is a graph showing the change in flexural strength at different temperatures.

[0037] Appendix Figure 3 A diagram illustrating a method for broadening the sintering temperature range of talc porcelain by increasing the amount of clay used.

[0038] 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).

[0039] Appendix Figure 5 High-temperature microscopic images of sample 4-1#. (a) 25℃; (b) 1200℃; (c) 1310℃.

[0040] Appendix Figure 6 High-temperature microscopic images of sample 4-2#. (a) 1324℃; (b) 1370℃; (c) 1380℃.

[0041] Appendix Figure 7 High-temperature microscopic images of sample 4-3#. (a) 1340℃; (b) 1390℃; (c) 1400℃.

[0042] Appendix Figure 8 The curves showing the changes in the projected area of ​​samples 5-1# and 5-2# under a high-temperature microscope.

[0043] 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.

[0044] Appendix Figure 10a Flowchart of the preparation process for the calcined talc-clay system.

[0045] Appendix Figure 10b The curves showing the change in projected area of ​​samples 5-13# under a high-temperature microscope.

[0046] Appendix Figure 11 High-temperature microscopic images of samples 5-13#. (a) 24℃; (b) 1118℃; (c) 1348℃.

[0047] Appendix Figure 12 (a) shows the curves of the projected area changes of samples 5-14#, 5-15#, 5-16# and 5-13# under a high-temperature microscope. (b) is the region inside the rectangle in (a).

[0048] Appendix Figure 13 These are high-temperature microscopic images of samples 5-14#. (a) 1390℃; (b) 1400℃.

[0049] Appendix Figure 14 These are high-temperature microscopic images of samples 5-15#. (a) 1378℃; (b) 1388℃.

[0050] Appendix Figure 15 These are high-temperature microscopic images of samples 5-16#. (a) 1362℃; (b) 1372℃.

[0051] Appendix Figure 16 The graph shows the UV-Vis transmittance spectrum and transmittance variation of samples 5-17#, 5-18#, and 5-19#.

[0052] Appendix Figure 17 The graphs show the changes in whiteness and flexural strength for samples 5-17#, 5-18#, and 5-19#.

[0053] Appendix Figure 18 The XRD pattern of sample 5-19# after sintering.

[0054] Appendix Figure 19 This is a performance comparison chart of sample 5-19# and a talc-based daily-use porcelain sample from a certain factory.

[0055] Appendix Figure 20 (a) shows the curves of the projected area changes of samples 5-20#, 5-21#, 5-22#, 5-23# and 5-14# under a high-temperature microscope. (b) is a magnification of the region within the rectangle in (a).

[0056] Appendix Figure 21 This is a high-temperature microscopic image of sample 5-20#.

[0057] Appendix Figure 22 This is a high-temperature microscopic image of sample 5-21#.

[0058] Appendix Figure 23 This is a high-temperature microscopic image of sample 5-22#.

[0059] Appendix Figure 24 This is a high-temperature microscopic image of sample 5-23#.

[0060] Appendix Figure 25 The graph shows the UV-Vis transmittance spectrum and transmittance variation of samples 5-20#, 5-21#, and 5-22#.

[0061] Appendix Figure 26 The graphs show the changes in whiteness and flexural strength for samples 5-20#, 5-21#, and 5-22#.

[0062] Appendix Figure 27 The XRD pattern of sample 5-21# after sintering. Detailed Implementation

[0063] 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.

[0064] raw material

[0065] 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 exploratory experiments 1-2, examples 1-4, and comparative example 1 is as follows.

[0066] The chemical composition of the mineral raw materials is as follows.

[0067] Table 1 Chemical composition of mineral raw materials

[0068]

[0069] Testing and Characterization

[0070] (1) Determination of sintering temperature range

[0071] 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 .

[0072] 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.

[0073] 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.

[0074] (2) Determination of plasticity index

[0075] 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.

[0076] (3) X-ray diffraction analysis

[0077] 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.

[0078] (4) Thermal analysis (DTA / DSC)

[0079] 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.

[0080] (5) Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis

[0081] 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.

[0082] 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.

[0083] (6) Fourier Transform Infrared Spectroscopy (FT-IR) Analysis

[0084] 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 .

[0085] (7) Determination of flexural strength of materials

[0086] 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.

[0087] (8) Transmittance test

[0088] 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.

[0089] (9) Whiteness test

[0090] The whiteness of the talc porcelain samples was tested using a WSD-2A whiteness meter manufactured by Shanghai Xinrui Instrument Co., Ltd.

[0091] (10) Thermal stability test

[0092] 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.

[0093] Experiment 1: Exploring the Mechanism of the Narrow Firing Range of Traditional Talc Porcelain

[0094] 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 in economic operations. 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.

[0095] 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.

[0096] like Figure 1As 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.

[0097] Table 2. Composition of the formulation points

[0098]

[0099] 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.

[0100] Table 3 Test results for each sample

[0101]

[0102] "-" indicates that the sample does not have a detectable sintering temperature range, and therefore some properties of the sample cannot be tested.

[0103] 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 2b. 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.

[0104] 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.

[0105] 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.

[0106] Table 4. Chemical composition of the remaining solid phase and total liquid phase content in the system at 1355℃ for each formulation.

[0107]

[0108] 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.

[0109] In the K2O-Al2O3-SiO2 system at 985℃:

[0110]

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

[0112]

[0113] 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:

[0114] In the K2O-Al2O3-SiO2 system at around 1200℃:

[0115]

[0116] Interactions between the K2O-Al2O3-SiO2 system and the MgO-Al2O3-SiO2 system:

[0117] Around 1200℃: L1 + MgO·SiO2 (proto-enstatite) → L3

[0118] Around 1260℃: L3→L1+MgO·SiO2 (proto-enstatite)

[0119] In the MgO-Al₂O₃-SiO₂ system at 1355℃:

[0120]

[0121] 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.

[0122] Experiment 2: Preparation of Talc-Based Daily-Use Porcelain Using Alkali Metals Potassium and Sodium, and Different Alkali Earth Metal Fused Blocks as Solvents

[0123] 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 3 As shown.

[0124] (I) The Influence of Different Fuse Formulations on the Firing Range of Talc Porcelain

[0125] Table 5. Composition of different alkali metal flux formulations (wt.%)

[0126]

[0127] Table 6. Composition of formulations with different alkaline earth metal fluxes (wt.%)

[0128]

[0129]

[0130] 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: All 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.

[0131] Table 7. Composition of each sample formulation (wt.%)

[0132]

[0133] High-temperature microscopic testing and analysis were performed on each sample at a heating rate of 10℃ / min. For example... Figures 4 to 7As 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.

[0134] 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.

[0135] 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.

[0136] In samples with potassium-based flux, Al₂O₃ enters the liquid phase under charge balance conditions with alkali metal ions. Only a small portion of the Al₂O₃ in these samples enters the liquid phase between 600℃ and 1250℃; the majority of the Al₂O₃ remains 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℃.

[0137] 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.

[0138] (II) The effect of heating rate on performance

[0139] The F4-3# flux formulation was prepared into a frit (the preparation method of the frit remained unchanged), and then 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, the 3 wt.% 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.

[0140] Table 8. Experimental Effect of Heating Rate on Performance

[0141]

[0142] 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 9As 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.

[0143] By opening the furnace door during firing to observe the formation of defects in the samples, sample 5-1# developed defects during natural cooling in the kiln. For thin-plate samples, a central depression appeared. For samples using potassium 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 kiln. This is because the heating rate was too rapid, preventing the sample from fully reacting and homogenizing at high temperatures, leading to this defect due to differences in thermal expansion coefficients during cooling. Therefore, among the schemes for preparing talc ceramics using alkali metals potassium and sodium, as well as different alkaline earth metal frits, only the potassium frit scheme has a relatively wide sintering temperature range at a heating rate of 10℃ / min, but under this heating condition, the sample will exhibit a central depression defect.

[0144] Example 1: Preparation of talc porcelain using potassium carbonate as a flux in a calcined talc-clay system.

[0145] To ensure that samples with K₂O as the alkali metal oxide in the flux have better application performance, based on K... + To address this elemental characteristic, a new calcined talc-clay system is adopted, in which all potassium carbonate is added during the calcination of talc, eliminating the need for potassium frit preparation. This new calcined talc-clay system reduces the number of steps required. Furthermore, the original process introduced a certain amount of SiO2 and Al2O3 during frit preparation, limiting the upper limit of clay usage; the new system further reduces the amount of SiO2 and Al2O3 introduced. Specific preparation methods are as follows... Figure 10a As shown, the added flux is first calcined together with the raw talc to form calcined talc. The calcined talc is then mixed with clay to form a batch, followed by ball milling, sieving, molding, and sintering.

[0146] Table 9. Formulations of samples using potassium carbonate as flux under the new process conditions.

[0147]

[0148] Samples 5-13# were subjected to high-temperature microscopy at a heating rate of 5℃ / min to determine their sintering temperature range. The results are as follows: Figure 10b and Figure 11 As shown, the projected shrinkage of sample 5-13# reaches its maximum at temperature T1 (1350℃), at which temperature the sample has already sintered. From... Figure 11It can be seen that the morphology of sample 5-13# is irregular at 1350℃, indicating that the sample has already deformed during the intense shrinkage process. According to the change in the slope of the curve, adding the flux in advance during the calcination of talc is beneficial for the sintering of samples where the alkali metal oxide in the flux is K2O.

[0149] (I) The effect of calcination temperature on the sintering temperature range of samples with potassium carbonate as flux

[0150] High-temperature microscopy was performed on samples 5-14#, 5-15#, and 5-16# at a heating rate of 5℃ / min to determine the sintering temperature range for each sample. The experimental results are as follows: Figure 12-15 As shown. The sintering temperature of sample 5-14# was 1348℃~1394℃, with a sintering temperature of 46℃. The sintering temperature of sample 5-15# was 1351℃~1378℃, with a sintering temperature of 27℃. The sintering temperature of sample 5-16# was 1339℃~1362℃, with a sintering temperature of 23℃. As the temperature increased, the samples also exhibited a tendency to tilt to one side; therefore, the suitable calcination temperature is 1320℃.

[0151] Table 10 Experiments on different calcination temperatures of raw talc.

[0152]

[0153] (II) Effect of holding time on the properties of samples with potassium carbonate as flux

[0154] Samples 5-17#, 5-18#, and 5-19# were incubated for different times, as shown in the table below, and were tested. The results are as follows. Figure 16-18 As shown, the light transmittance of the sample gradually increases with increasing holding time; however, the whiteness and flexural strength of the sample both initially increase and then decrease with increasing holding time. Considering the performance of light transmittance, and given that the whiteness and flexural strength of the sample do not decrease significantly when the holding time is 60 min, but the increase in light transmittance is more pronounced, a holding time of 60 min was selected for the sample with potassium carbonate clay as flux at 25 wt.%. From... Figure 18 As can be seen, the crystalline phase of sample 5-19# consists only of protoenstatite. This achieves the requirement, from both structural and performance perspectives, that the phase composition of talc-based fine porcelain for daily use be protoenstatite and a glassy phase.

[0155] Table 11 Effect of holding time on sample performance under the new process

[0156]

[0157] (III) Comparison of the best performance of the sample with potassium carbonate flux and the talc-based daily-use porcelain sample from a certain factory.

[0158] Next, the 5-19# sample, with potassium carbonate as the flux and exhibiting the best performance, was compared with a commercially available talc-based daily-use porcelain body sample from a certain manufacturer and exhibiting the best performance. The results are as follows: Figure 19 As shown, compared with a talc-based daily-use porcelain sample from a certain factory, the 5-19# sample with potassium carbonate flux showed a 21.5% increase in light transmittance, a 10.9% increase in whiteness, and a 10% increase in flexural strength.

[0159] (IV) Experiments on increasing the amount of talc porcelain clay

[0160] High-temperature microscopy tests were performed on samples 5-20#, 5-21#, 5-22#, and 5-23# at a heating rate of 5℃ / min to first determine the sintering temperature range for each formulation. The experimental results are as follows: Figure 20 and Figure 21 , Figure 22 , Figure 23 ,and Figure 24 The sintering temperature range for sample 5-20# is 1318℃~1363℃, with a minimum temperature of 45℃. The sintering temperature range for sample 5-21# is 1313℃~1370℃, with a minimum temperature of 57℃. The sintering temperature range for sample 5-22# is 1318℃~1364℃, with a minimum temperature of 46℃. Sample 5-23# reached its sintering temperature point at T1 of 1313℃. At this temperature, the sample morphology was irregular, indicating that deformation had occurred during the intense shrinkage process. Sample 5-23# does not have a wide sintering temperature range.

[0161] Table 12 Experimental study on the addition of potassium carbonate during calcination of talc when clay content is 30 wt.%.

[0162]

[0163] The performance of samples 5-20#, 5-21#, and 5-22# was examined. Figure 25 It can be seen that the transmittance of the sample gradually increases with the increase of potassium carbonate dosage. Figure 26 It can be seen that with the increase of potassium carbonate content, both the whiteness and flexural strength of the sample decrease. Considering all three properties, when the potassium carbonate content is 4.4 wt.%, the sample exhibits superior light transmittance, flexural strength, and whiteness. Figure 27 It can be seen that the crystal phase composition of sample 5-21# after firing is only protoenstatite, which meets the preset phase composition. Comparing sample 5-21#, which has the best performance with a clay content of 30wt.%, with sample 5-11#, which has the best performance with a talc-based daily-use porcelain body from a certain factory, the sintering temperature range is widened by 12℃, the plasticity index is improved by 35%, the whiteness is improved by 14%, and the flexural strength is improved by 6%.

[0164] Example 2

[0165] A talc-clay system of calcined talc-based daily-use porcelain comprises the following raw materials in parts by weight: 75 parts calcined talc and 25 parts clay. The calcined talc is prepared by mixing raw talc and potassium carbonate in a mass ratio of 100:4 and calcining at 1320°C.

[0166] The mixed raw materials were ground and 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 60 minutes, and the furnace was allowed to cool to room temperature. The resulting samples were subjected to performance tests: sintering temperature range of 1348-1394℃, light transmittance of 16.4%, whiteness of 77.3%, flexural strength of 128MPa, and thermal stability of 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.

[0167] Example 3

[0168] A talc-clay system of calcined talc-based daily-use porcelain comprises the following raw materials in parts by weight: 80 parts calcined talc and 20 parts clay. The calcined talc is prepared by mixing raw talc and potassium carbonate in a mass ratio of 100:4.8 and calcining at 1300℃.

[0169] The mixed raw materials were ground and 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 40 minutes, and the furnace was allowed to cool to room temperature. The resulting samples were subjected to performance tests: sintering temperature range of 1351-1395℃, light transmittance of 15.3%, whiteness of 78.2, flexural strength of 122.3 MPa, and thermal stability of 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.

[0170] Example 4

[0171] A talc-clay system of calcined talc-based daily-use porcelain comprises the following raw materials in parts by weight: 70 parts calcined talc and 30 parts clay. The calcined talc is prepared by mixing raw talc and potassium carbonate in a mass ratio of 100:4.4 and calcining at 1340°C.

[0172] The mixed raw materials were ground and 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 80 minutes, and the furnace was allowed to cool to room temperature. The resulting samples were subjected to performance tests: sintering temperature range of 1313-1370℃, light transmittance of 13.5%, whiteness of 79.7, flexural strength of 123.1 MPa, and thermal stability of 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.

[0173] Comparative Example 1

[0174] A talc-clay system of calcined talc-based daily-use porcelain comprises the following raw materials in parts by weight: 75 parts calcined talc and 25 parts clay. The calcined talc is prepared by mixing raw talc and potassium carbonate in a mass ratio of 100:2 and calcining at 1320°C.

[0175] The mixed raw materials were ground and 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 60 minutes, and the furnace was cooled to room temperature. The resulting samples were subjected to performance tests: the sintering temperature range was 1372-1393℃.

[0176] Example 5

[0177] The chemical composition of the mineral raw materials used in this embodiment is as follows.

[0178] Table 13 Chemical Composition of Mineral Raw Materials

[0179]

[0180] A talc-clay system of calcined talc-based daily-use porcelain comprises the following raw materials in parts by weight: 75 parts calcined talc and 25 parts clay. The calcined talc is prepared by mixing raw talc and potassium carbonate in a mass ratio of 100:4 and calcining at 1320°C.

[0181] The mixed raw materials were ground and 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 60 minutes, and the furnace was allowed to cool to room temperature. The resulting samples were subjected to performance tests: sintering temperature range of 1349-1396℃, light transmittance of 16.2%, whiteness of 86.1%, flexural strength of 128.23 MPa, and thermal stability of 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.

[0182] 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 type of talc-based daily-use porcelain based on a talc-clay system, characterized in that, It is made from the following raw materials in parts by weight: 70-80 parts calcined talc and 20-30 parts clay; the calcined talc includes the following raw materials: potassium carbonate and raw talc, wherein the mass ratio of potassium carbonate to raw talc is 4-4.8:100; the preparation method includes the following steps: take raw talc and potassium carbonate, mix them, and calcine them at 1300-1340℃ to form calcined talc; take calcined talc and clay, mix them, shape them, heat them to the sintering temperature, and cool them; the main crystalline phase in the ceramic body is protoenstatite.

2. The method for preparing talc-based daily-use porcelain in the talc-clay system according to claim 1, characterized in that, Includes the following steps: Step (1): Take the raw materials according to the proportion; Step (2): Take raw talc and potassium carbonate, mix them, and calcine them to make calcined talc; Step (3): Take calcined talc and clay, mix them evenly, shape them, heat them to the sintering temperature, and then cool them.

3. The method for preparing talc-based daily-use porcelain in a calcined talc-clay system according to claim 2, characterized in that, After reaching the sintering temperature in step (3), hold the temperature for 0-80 minutes, and then allow it to cool naturally inside the furnace or remove it from the furnace for cooling outside.

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