Preparation method of low-expansion heat-resistant purple sand ceramic

Abstract

The invention relates to the technical field of ceramic preparation, in particular to a preparation method of low-expansion heat-resistant purple sand ceramic. Comprising the following steps: preparing lithium-doped pseudo-boehmite composite powder; preparing oxygen vacancy enhanced negative expansion powder; compounding the ceramic raw materials; and firing the ceramic. A (NH4) H2PO4 solution, an H42N10O42W12. XH2O solution, a C10H14NiO4 solution and a ZrOCl28H2O solution are prepared and subjected to a compound hydrothermal reaction, a product is ground and calcined to prepare a material which is rich in oxygen vacancies and has negative thermal expansion, the material is introduced into a ceramic material to be sintered, and the negative thermal expansion performance of the ceramic material is improved by utilizing the characteristics of thermal shrinkage and cold expansion of the material. The negative expansion material is doped with Ni and can offset the thermal expansion and cold contraction characteristics of other positive expansion materials in the ceramic material, so that the thermal expansion coefficient of the subsequently prepared purple sand ceramic is reduced, high-concentration oxygen vacancies can be formed in the negative expansion material through Ni doping, and the negative expansion capacity of the negative expansion material is further improved. The thermal expansion coefficient of the purple sand ceramic can be further reduced.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic preparation, in particular to a method for preparing low-expansion heat-resistant purple sand ceramics. Background Art

[0002] Zisha ceramics, as a treasure of traditional Chinese craftsmanship, are especially famous for their teapots. Their good adsorption and air permeability give the tea soup excellent fragrance and preservation capabilities. The teapots and tea sets made from them are also rich in trace elements and are deeply loved by people.

[0003] However, with the increasing performance requirements of modern tea ceremony utensils, especially the growing demand for thin walls (1.5-2mm) and resistance to sudden cooling and heating, the inherent defects of traditional purple clay ceramics have become increasingly prominent. Because purple clay is mainly composed of quartz and illite, its overall thermal expansion coefficient is relatively high. Under frequent alternations of hot and cold, the accumulation of internal thermal stress can easily lead to the expansion of microcracks and cause damage to the ceramic body.

[0004] Existing technologies often introduce low-expansion spodumene to reduce the thermal expansion coefficient of ceramic systems, but the addition amount often needs to be higher than 5wt% to effectively inhibit the expansion of ceramic materials. Moreover, a high content of spodumene can easily induce Li+ migration to form a glass phase, which not only masks the natural particle mechanism of the purple clay teapot, but also reacts with the iron color phase. At the same time, since spodumene relies on imports, resources are scarce, and costs are high, there is an urgent need to develop new low-expansion materials for ceramics to improve the low expansion coefficient of ceramics. Summary of the Invention

[0005] In order to solve the above technical defects, the present invention has developed a method for preparing low-expansion heat-resistant purple clay ceramics. By preparing a new type of negative expansion material and introducing it into the ceramic matrix, the positive expansion of the ceramic material can be effectively offset. The prepared purple clay ceramics have excellent low-expansion heat-resistant properties.

[0006] A method for preparing low-expansion heat-resistant purple sand ceramics comprises the following steps: S1: Preparation of lithium-doped pseudo-boehmite composite powders Spodumene, a KH-570 silane coupling agent, and an isopropyl alcohol aqueous solution are mixed and ultrasonically treated, and then ground using a sand mill to obtain a spodumene microparticle slurry. The spodumene microparticle slurry is mixed with high-purity water, and then aluminum isopropyl alcohol is added to perform hydrolysis and aging. The precipitate is collected, dispersed into an isopropyl alcohol aqueous solution, and spray-dried to obtain a lithium-doped pseudo-boehmite composite powder. S2: Preparation of oxygen vacancy enhanced negative expansion powder Prepare (NH4)H2PO4 solution, H 42 N 10 O 42 W 12 xH2O solution, C 10 H14 NiO4 solution and ZrOCl2•8H2O solution, then (NH4)H2PO4 solution and H 42 N 10 O 42 W 12 ·xH2O solution is mixed evenly, then C 10 H 14 The NiO4 solution was mixed evenly, and finally the ZrOCl2•8H2O solution was added dropwise. After adjusting the pH and stirring, the mixture was transferred to an autoclave for reaction. The reactants were collected, washed, centrifuged, and dried, and then calcined to obtain oxygen vacancy enhanced negative expansion powder. S3: Compounding of ceramic raw materials and firing of ceramics First, purple sand clay and cattail fluff are mixed and ball-milled, and then feldspar, mica iron oxide, Suzhou clay, lithium-doped pseudo-boehmite composite powder and oxygen vacancy enhanced negative expansion powder are added and ball-milled to obtain a mixed mud that is vacuum refined, aged, formed into blanks and calcined in stages. After cooling in the furnace, low-expansion heat-resistant purple sand ceramics are obtained.

[0007] Furthermore, step S1 of preparing lithium-doped pseudo-boehmite composite powder comprises the following steps: S1.1: 8-10 parts by weight of spodumene and 0.3-0.5 parts by weight of KH-570 silane coupling agent are mixed in a container, followed by the addition of 20-25 parts by weight of an 85-90% aqueous isopropyl alcohol solution. The mixture is ultrasonically dispersed in an apparatus at a frequency of 35-40 kHz for 10-15 minutes, then transferred to a sand mill, steel balls are added, and the mixture is ground at a speed of 2500-3000 rpm for 2-2.5 hours. The steel balls are separated to obtain a spodumene particle slurry. S1.2: 30-35 parts by weight of spodumene microparticle slurry and 25-30 parts by weight of high-purity water are mixed and placed in a reactor. After stirring evenly, 45-50 parts by weight of aluminum isopropoxide are added, and then hydrolyzed at 60-80°C for 4-5 hours. After adding 1-2 parts by weight of polyethylene glycol and stirring for 10-15 minutes, the mixture is aged at 85-90°C for 2-3 hours. After natural cooling, it is filtered, the precipitate is collected and added to 30-35 parts by weight of an isopropanol aqueous solution with a concentration of 50-60%, stirred at a stirring speed of 80-100 rpm for 25-30 minutes, and then spray-dried to obtain a lithium-doped pseudo-boehmite composite powder.

[0008] Furthermore, step S2 of preparing oxygen vacancy enhanced negative expansion powder comprises the following steps: S2.1: Dissolve (NH4)H2PO4 in deionized water to prepare a (NH4)H2PO4 solution with a concentration of 0.02-0.03 mol / L. 42 N 10 O 42 W12 Dissolve xH2O in deionized water to prepare a H solution with a concentration of 0.001-0.0015 mol / L. 42 N 10 O 42 W 12 xH2O solution, C 10 H 14 NiO4 was dissolved in anhydrous ethanol to prepare a C 10 H 14 NiO4 solution, dissolve ZrOCl2•8H2O in deionized water to prepare a ZrOCl2•8H2O solution with a concentration of 0.3-0.4 mol / L; S2.2: Mix 12-15 parts by volume of (NH4)H2PO4 solution and 12-15 parts by volume of H 42 N 10 O 42 W 12 · xH2O solution was mixed in a container and stirred evenly, then 4-6 parts by volume of C 10 H 14 Stir the NiO4 solution evenly, then add 1.5-2 parts by volume of ZrOCl2•8H2O solution dropwise. After the addition is complete, adjust the pH to 8.5-9, and continue stirring for 1-2 hours to obtain a milky white mixed solution. S2.3: Transfer the milky white mixed solution to a polytetrafluoroethylene autoclave and react at 30-32°C for 24-30 hours. Take out the reactants and wash them first using a centrifuge, then centrifuge them again, collect the precipitates and dry them in a forced air drying oven to obtain a block precursor, grind the block precursor into powder and place it in a muffle furnace, calcinate it at 800-900°C for 3-4 hours to obtain oxygen vacancy enhanced negative expansion powder.

[0009] Furthermore, step S3 of compounding ceramic raw materials and firing the ceramics includes the following steps: S3.1: 50-60 parts by weight of purple sand clay and 2-3 parts by weight of cattail wool are added to a ball mill and mixed and ball-milled. Then, 8-10 parts by weight of feldspar, 3-5 parts by weight of micaceous iron oxide, 1-3 parts by weight of Suzhou clay, 0.3-0.5 parts by weight of lithium-doped pseudo-boehmite composite powder, and 4-6 parts by weight of oxygen vacancy enhanced negative expansion powder are added and ball-milled again to obtain a mixed clay; S3.2: Transfer the mixed mud to a vacuum mud refiner for vacuum mud refining, and then age it. Repeat the vacuum mud refining and ageing and then make a blank to obtain a blank. Place the blank in a muffle furnace and heat it to 250-300℃ within 60 minutes under air atmosphere, then heat it to 600-650℃ within 90 minutes, and then heat it to 900-920℃ within 120 minutes, and finally heat it to 1250-1300℃ within 180 minutes for calcination. Keep it warm for 20 minutes, cool it with the furnace and take it out to obtain low-expansion heat-resistant purple clay ceramics.

[0010] Furthermore, the steel balls added to the sand mill in step S1.1 account for 50-55% of the volume of the cylinder, and the diameter of the steel balls is 0.2-0.3 mm.

[0011] Furthermore, in step S2.2, the pH is adjusted by adding ammonia water.

[0012] Furthermore, in step S2.3, the rotation speed of the centrifugal washing is 200-300 rpm, which lasts for 15-20 minutes, and the rotation speed of the centrifugal separation is 8000-10000 rpm, which lasts for 10-15 minutes.

[0013] Furthermore, the main chemical components of the purple clay in step S3.1 are 50-56% SiO2, 22-28% Al2O3, 12-16% Fe2O3, 0.1-0.5% CaO, 5-10% MgO, 1.5-2.5% K2O and 0.1-0.3% Na2O.

[0014] The beneficial effects are: 1. The present invention prepares (NH4)H2PO4 solution, H 42 N 10 O 42 W 12 xH2O solution, C 10 H 14 NiO4 solution and ZrOCl2•8H2O solution are subjected to a composite hydrothermal reaction, and the block precursor obtained by the hydrothermal reaction is ground and calcined to obtain a material rich in oxygen vacancies and having negative thermal expansion, which is introduced into ceramic material for sintering. By utilizing its thermal contraction and cold expansion characteristics, it can "offset" the thermal expansion and cold contraction characteristics of other positive expansion materials in the ceramic material, thereby reducing the thermal expansion coefficient of the subsequently prepared purple clay ceramics. Ni doping can promote the formation of high concentration oxygen vacancies in the negative expansion material, further improving the negative expansion capacity of the negative expansion material, further reducing the thermal expansion coefficient of the purple clay ceramics, and improving the thermal stability of the ceramics.

[0015] 2. The present invention adds spodumene microparticle slurry during the hydrolysis process of preparing pseudo-boehmite, so that the spodumene nanoparticles are evenly wrapped by the nano-sheet structure of the pseudo-boehmite. The obtained lithium-doped pseudo-boehmite composite powder is added to the ceramic material, which can effectively reduce the expansion coefficient of the system with a small addition amount, greatly reduce the use of spodumene, and jointly reduce the thermal expansion coefficient of purple clay ceramics with the oxygen vacancy enhanced negative expansion powder, thereby improving the thermal stability of the ceramics.

[0016] 3. The present invention adds cattail fluff to the mixed mud of ceramic precursor materials, and then prepares a blank together with the mixed mud for sintering. During the sintering process, the carbon skeleton formed by the cattail fluff can combine with the matrix to form a network structure inside the ceramic, thereby enhancing the stability of the ceramic structure and forming fine pores inside the ceramic, thereby improving the thermal insulation ability of the obtained purple clay ceramic. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of the preparation method of low-expansion heat-resistant purple sand ceramics used in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] Example 1 A method for preparing low-expansion heat-resistant purple sand ceramics, such as Figure 1 As shown, the following steps are included: S1: Preparation of lithium-doped pseudo-boehmite composite powders S1.1: 8 parts by weight of spodumene and 0.3 parts by weight of KH-570 silane coupling agent were mixed in a container, followed by the addition of 20 parts by weight of an 85% aqueous isopropyl alcohol solution. The mixture was then treated in an ultrasonic dispersion apparatus at a frequency of 35 kHz for 10 minutes. The mixture was then transferred to a sand mill and steel balls were added, with the steel balls accounting for 50% of the volume of the sand mill and having a diameter of 0.2 mm. The mixture was ground at a speed of 2500 rpm for 2 hours, and the steel balls were separated to obtain a spodumene particle slurry. S1.2: Mix 30 parts by weight of spodumene microparticle slurry and 25 parts by weight of high-purity water and place them in a reactor. After stirring evenly, add 45 parts by weight of aluminum isopropoxide, and then place it at 60°C for hydrolysis for 4 hours. After adding 1 part by weight of polyethylene glycol and stirring for 10 minutes, continue to age at 85°C for 2 hours. After natural cooling, filter, collect the precipitate and add it to 30 parts by weight of a 50% isopropanol aqueous solution. Stir at a stirring speed of 80 rpm for 25 minutes, and then spray dry to obtain lithium-doped pseudo-boehmite composite powder.

[0020] S2: Preparation of oxygen vacancy enhanced negative expansion powder S2.1: Dissolve (NH4)H2PO4 in deionized water to prepare a (NH4)H2PO4 solution with a concentration of 0.02 mol / L. 42 N 10 O 42 W 12 xH2O was dissolved in deionized water to prepare a H solution with a concentration of 0.001 mol / L. 42 N 10 O 42 W 12 xH2O solution, C 10 H 14 NiO4 was dissolved in anhydrous ethanol to prepare a C 10 H 14 NiO4 solution, dissolve ZrOCl2•8H2O in deionized water to prepare a ZrOCl2•8H2O solution with a concentration of 0.3 mol / L; S2.2: Mix 12 parts by volume of (NH4)H2PO4 solution and 12 parts by volume of H 42 N 10 O 42 W 12 ·xH2O solution was mixed in a container and stirred evenly, then 4 parts by volume of C 10 H 14 The NiO4 solution was stirred evenly, and then 1.5 parts by volume of ZrOCl2•8H2O solution was added dropwise. After the addition was complete, ammonia water was added to adjust the pH to 8.5, and then stirring was continued for 1 hour to obtain a milky white mixed solution. S2.3: Transfer the milky white mixed solution to a polytetrafluoroethylene autoclave and react at 30°C for 24 hours. Take out the reactants and wash them first using a centrifuge, and then centrifuge them. The speed of centrifugal washing is 200 rpm, and the duration is 15 minutes. The speed of centrifugal separation is 8000 rpm, and the duration is 10 minutes. Collect the precipitate and place it in a blast drying oven to dry it to obtain a block precursor. Grind the block precursor into powder and place it in a muffle furnace. Calcinate it at 800°C for 3 hours to obtain oxygen vacancy enhanced negative expansion powder.

[0021] S3: Compounding of ceramic raw materials and firing of ceramics S3.1: 50 parts by weight of purple sand clay and 2 parts by weight of cattail were added to a ball mill and mixed and ball-milled. Then, 8 parts by weight of feldspar, 3 parts by weight of micaceous iron oxide, 1 part by weight of Suzhou clay, 0.3 parts by weight of lithium-doped pseudo-boehmite composite powder, and 4 parts by weight of oxygen vacancy enhanced negative expansion powder were added and ball-milled again to obtain a mixed clay. S3.2: Transfer the mixed mud to a vacuum mud refiner for vacuum mud refining, and then age it. Repeat the vacuum mud refining and ageing and then make a blank to obtain a blank. Place the blank in a muffle furnace and heat it to 250°C within 60 minutes under an air atmosphere, then heat it to 600°C within 90 minutes, and then heat it to 900°C within 120 minutes. Finally, heat it to 1250°C within 180 minutes for calcination. Keep it warm for 20 minutes, cool it in the furnace and take it out to obtain low-expansion heat-resistant purple clay ceramics.

[0022] Example 2 A method for preparing low-expansion heat-resistant purple sand ceramics, such as Figure 1 As shown, the following steps are included: S1: Preparation of lithium-doped pseudo-boehmite composite powders S1.1: 10 parts by weight of spodumene and 0.5 parts by weight of KH-570 silane coupling agent were mixed in a container, followed by the addition of 25 parts by weight of an 85% aqueous isopropyl alcohol solution. The mixture was ultrasonically dispersed in an apparatus at 35 kHz for 10 minutes. The mixture was then transferred to a sand mill and filled with steel balls, which accounted for 50% of the volume of the sand mill and had a diameter of 0.2 mm. The mixture was ground at 2500 rpm for 2 hours, and the steel balls were separated to obtain a spodumene particle slurry. S1.2: Mix 35 parts by weight of spodumene microparticle slurry and 30 parts by weight of high-purity water and place them in a reactor. After stirring evenly, add 50 parts by weight of aluminum isopropoxide, and then place it at 60°C for hydrolysis for 4 hours. After adding 2 parts by weight of polyethylene glycol and stirring for 10 minutes, continue to age at 85°C for 2 hours. After natural cooling, filter, collect the precipitate and add it to 35 parts by weight of 50% isopropanol aqueous solution. Stir at a stirring speed of 80 rpm for 25 minutes, and then spray dry to obtain lithium-doped pseudo-boehmite composite powder.

[0023] S2: Preparation of oxygen vacancy enhanced negative expansion powder S2.1: Dissolve (NH4)H2PO4 in deionized water to prepare a (NH4)H2PO4 solution with a concentration of 0.02 mol / L. 42 N 10 O 42 W 12xH2O was dissolved in deionized water to prepare a H solution with a concentration of 0.001 mol / L. 42 N 10 O 42 W 12 xH2O solution, C 10 H 14 NiO4 was dissolved in anhydrous ethanol to prepare a C 10 H 14 NiO4 solution, dissolve ZrOCl2•8H2O in deionized water to prepare a ZrOCl2•8H2O solution with a concentration of 0.3 mol / L; S2.2: Mix 15 parts by volume of (NH4)H2PO4 solution and 15 parts by volume of H 42 N 10 O 42 W 12 ·xH2O solution was mixed in a container and stirred evenly, then 6 parts by volume of C 10 H 14 The NiO4 solution was stirred evenly, and then 2 parts by volume of ZrOCl2•8H2O solution was added dropwise. After the addition was complete, ammonia water was added to adjust the pH to 8.5, and then stirring was continued for 1 hour to obtain a milky white mixed solution. S2.3: Transfer the milky white mixed solution to a polytetrafluoroethylene autoclave and react at 30°C for 24 hours. Take out the reactants and wash them first using a centrifuge, and then centrifuge them. The speed of centrifugal washing is 200 rpm, and the duration is 15 minutes. The speed of centrifugal separation is 8000 rpm, and the duration is 10 minutes. Collect the precipitate and place it in a blast drying oven to dry it to obtain a block precursor. Grind the block precursor into powder and place it in a muffle furnace. Calcinate it at 800°C for 3 hours to obtain oxygen vacancy enhanced negative expansion powder.

[0024] S3: Compounding of ceramic raw materials and firing of ceramics S3.1: 60 parts by weight of purple sand clay and 3 parts by weight of cattail were added to a ball mill and mixed and ball-milled. Then, 10 parts by weight of feldspar, 5 parts by weight of micaceous iron oxide, 3 parts by weight of Suzhou clay, 0.5 parts by weight of lithium-doped pseudo-boehmite composite powder, and 6 parts by weight of oxygen vacancy enhanced negative expansion powder were added and ball-milled again to obtain a mixed clay; S3.2: Transfer the mixed mud to a vacuum mud refiner for vacuum mud refining, and then age it. Repeat the vacuum mud refining and ageing and then make a blank to obtain a blank. Place the blank in a muffle furnace and heat it to 250°C within 60 minutes under an air atmosphere, then heat it to 600°C within 90 minutes, and then heat it to 900°C within 120 minutes. Finally, heat it to 1250°C within 180 minutes for calcination. Keep it warm for 20 minutes, cool it in the furnace and take it out to obtain low-expansion heat-resistant purple clay ceramics.

[0025] Example 3 A method for preparing low-expansion heat-resistant purple sand ceramics, such as Figure 1 As shown, the following steps are included: S1: Preparation of lithium-doped pseudo-boehmite composite powders S1.1: 8 parts by weight of spodumene and 0.3 parts by weight of KH-570 silane coupling agent were mixed in a container, followed by the addition of 20 parts by weight of a 90% aqueous isopropyl alcohol solution. The mixture was treated in an ultrasonic dispersion apparatus at a frequency of 40 kHz for 15 minutes. The mixture was then transferred to a sand mill and steel balls were added, with the steel balls accounting for 55% of the volume of the sand mill and having a diameter of 0.3 mm. The mixture was ground at a speed of 3000 rpm for 2.5 hours, and the steel balls were separated to obtain a spodumene particle slurry. S1.2: Mix 30 parts by weight of spodumene microparticle slurry and 25 parts by weight of high-purity water and place them in a reactor. After stirring evenly, add 45 parts by weight of aluminum isopropoxide, and then place it at 80°C for hydrolysis for 5 hours. After adding 1 part by weight of polyethylene glycol and stirring for 15 minutes, continue aging at 90°C for 3 hours. After natural cooling, filter, collect the precipitate and add it to 30 parts by weight of a 60% isopropanol aqueous solution. Stir at a stirring speed of 100 rpm for 30 minutes, and then spray dry to obtain lithium-doped pseudo-boehmite composite powder.

[0026] S2: Preparation of oxygen vacancy enhanced negative expansion powder S2.1: Dissolve (NH4)H2PO4 in deionized water to prepare a (NH4)H2PO4 solution with a concentration of 0.03 mol / L. 42 N 10 O 42 W 12 xH2O was dissolved in deionized water to prepare a H solution with a concentration of 0.0015 mol / L. 42 N 10 O 42 W 12 xH2O solution, C 10 H 14 NiO4 was dissolved in anhydrous ethanol to prepare a C 10 H 14 NiO4 solution, dissolve ZrOCl2•8H2O in deionized water to prepare a ZrOCl2•8H2O solution with a concentration of 0.4 mol / L; S2.2: Mix 12 parts by volume of (NH4)H2PO4 solution and 12 parts by volume of H 42 N 10 O 42 W 12·xH2O solution was mixed in a container and stirred evenly, then 4 parts by volume of C 10 H 14 The NiO4 solution was stirred evenly, and then 1.5 parts by volume of ZrOCl2•8H2O solution was added dropwise. After the addition was complete, ammonia water was added to adjust the pH to 9, and then stirring was continued for 2 hours to obtain a milky white mixed solution. S2.3: Transfer the milky white mixed solution to a polytetrafluoroethylene autoclave and react at 32°C for 30 hours. Take out the reactant and wash it with a centrifuge first, and then centrifuge it. The speed of centrifugal washing is 300 rpm, and it lasts for 20 minutes. The speed of centrifugal separation is 10,000 rpm, and it lasts for 15 minutes. Collect the precipitate and put it into a blast drying oven to dry it to obtain a block precursor. Grind the block precursor into powder and place it in a muffle furnace. Calcine it at 900°C for 4 hours to obtain oxygen vacancy enhanced negative expansion powder.

[0027] S3: Compounding of ceramic raw materials and firing of ceramics S3.1: 50 parts by weight of purple sand clay and 2 parts by weight of cattail were added to a ball mill and mixed and ball-milled. Then, 8 parts by weight of feldspar, 3 parts by weight of micaceous iron oxide, 1 part by weight of Suzhou clay, 0.3 parts by weight of lithium-doped pseudo-boehmite composite powder, and 4 parts by weight of oxygen vacancy enhanced negative expansion powder were added and ball-milled again to obtain a mixed clay. S3.2: Transfer the mixed mud to a vacuum mud refiner for vacuum mud refining, and then age it. Repeat the vacuum mud refining and ageing and then make a blank to obtain a blank. Place the blank in a muffle furnace, heat it to 300°C within 60 minutes under an air atmosphere, then heat it to 650°C within 90 minutes, and then heat it to 920°C within 120 minutes, and finally heat it to 1300°C within 180 minutes for calcination. Keep it warm for 20 minutes, cool it with the furnace and take it out to obtain low-expansion heat-resistant purple clay ceramics.

[0028] Comparative Example 1 The difference from Example 1 is that, in Comparative Example 1, step S1 is removed, and the subsequent lithium-doped pseudo-boehmite composite powder is replaced with spodumene of equal mass. The remaining steps are the same as in Example 1 to produce purple clay ceramics.

[0029] Comparative Example 2 The difference from Example 1 is that, in Comparative Example 2, step S2 is removed, and oxygen vacancy enhanced negative expansion powder is not added in step S3.1. The remaining steps are the same as in Example 1 to produce purple sand ceramics.

[0030] Comparative Example 3 The difference from Example 1 is that in Comparative Example 3, cattail wool is not added in step S3.1, and the remaining steps are the same as those in Example 1 to produce purple clay ceramics.

[0031] Experiment 1: The low-expansion heat-resistant purple clay ceramics prepared in Examples 1-3 and the purple clay ceramics prepared in Comparative Examples 1-2 were taken as test samples, and three test samples of each were taken for testing of the thermal expansion coefficient and thermal stability. The thermal expansion coefficient was measured in accordance with the standard QB / T1321-2012 "Method for Determination of Average Linear Thermal Expansion Coefficient of Ceramic Materials", and the measuring temperature was 0-700°C. The thermal stability was measured in accordance with the method in the standard QB / T2580-2018 "Fine Ceramic Cooker". The test sample was dry-heated to 660°C, and then poured with 20°C water. The operation was repeated, and the number of times it was not cracked was recorded. The test results were averaged, as shown in Table 1.

[0032] Table 1: Thermal expansion coefficient and number of unbroken times of the test samples

[0033] It can be seen from the data of Examples 1-3 in Table 1 that the products prepared in the examples of the present application all have excellent low expansion performance and heat-resistant thermal stability. From the data of Comparative Example 1, it can be seen that when the lithium-doped pseudo-boehmite composite powder replaces spodumene, the thermal expansion coefficient increases and the thermal stability decreases. It can be seen that the use of pseudo-boehmite-coated spodumene added to ceramic materials can reduce the thermal expansion coefficient of purple clay ceramics and improve the thermal stability of ceramics. From the data of Comparative Example 2, it can be seen that the oxygen vacancy enhanced negative expansion powder prepared in the present application can also reduce the thermal expansion coefficient of purple clay ceramics and improve the thermal stability of ceramics.

[0034] Experiment 2: The low-expansion heat-resistant purple clay ceramics prepared in Examples 1-3 and the purple clay ceramics prepared in Comparative Example 3 were taken as test samples, and three test samples of each were taken to test the thermal conductivity. The test results are shown in Table 2.

[0035] Table 2: Thermal conductivity of test samples

[0036] It can be seen from the data of Examples 1-3 and Comparative Example 3 in Table 2 that the products prepared in the examples all have a low thermal conductivity coefficient. When cattail wool is not added, the thermal conductivity coefficient increases sharply. It can be proved that adding cattail wool together with the mixed mud to prepare the embryo body and sintering it can improve the insulation capacity of purple clay ceramics.

[0037] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for preparing low-expansion heat-resistant purple sand ceramics, characterized in that: The following steps are involved: S1: Preparation of lithium-doped pseudo-boehmite composite powders Spodumene, a KH-570 silane coupling agent, and an isopropyl alcohol aqueous solution are mixed and ultrasonically treated, and then ground using a sand mill to obtain a spodumene microparticle slurry. The spodumene microparticle slurry is mixed with high-purity water, and then aluminum isopropyl alcohol is added to perform hydrolysis and aging. The precipitate is collected, dispersed into an isopropyl alcohol aqueous solution, and spray-dried to obtain a lithium-doped pseudo-boehmite composite powder. S2: Preparation of oxygen vacancy enhanced negative expansion powder Prepare (NH4)H2PO4 solution, H 42 N 10 O 42 W 12 xH2O solution, C 10 H 14 NiO4 solution and ZrOCl2•8H2O solution, then (NH4)H2PO4 solution and H 42 N 10 O 42 W 12 ·xH2O solution is mixed evenly, then C 10 H 14 The NiO4 solution was mixed evenly, and finally the ZrOCl2•8H2O solution was added dropwise. After adjusting the pH and stirring, the mixture was transferred to an autoclave for reaction. The reactants were collected, washed, centrifuged, and dried, and then calcined to obtain oxygen vacancy enhanced negative expansion powder. S3: Compounding of ceramic raw materials and firing of ceramics First, purple sand clay and cattail fluff are mixed and ball-milled, and then feldspar, mica iron oxide, Suzhou clay, lithium-doped pseudo-boehmite composite powder and oxygen vacancy enhanced negative expansion powder are added and ball-milled to obtain a mixed mud that is vacuum refined, aged, formed into blanks and calcined in stages. After cooling in the furnace, low-expansion heat-resistant purple sand ceramics are obtained.

2. The method for preparing low-expansion heat-resistant purple sand ceramics according to claim 1, characterized in that: Step S1: Preparation of lithium-doped pseudo-boehmite composite powder, comprising the following steps: S1.1: 8-10 parts by weight of spodumene and 0.3-0.5 parts by weight of KH-570 silane coupling agent are mixed in a container, followed by the addition of 20-25 parts by weight of an 85-90% aqueous isopropyl alcohol solution. The mixture is ultrasonically dispersed in an apparatus at a frequency of 35-40 kHz for 10-15 minutes, then transferred to a sand mill, steel balls are added, and the mixture is ground at a speed of 2500-3000 rpm for 2-2.5 hours. The steel balls are separated to obtain a spodumene particle slurry. S1.2: 30-35 parts by weight of spodumene microparticle slurry and 25-30 parts by weight of high-purity water are mixed and placed in a reactor. After stirring evenly, 45-50 parts by weight of aluminum isopropoxide are added, and then hydrolyzed at 60-80°C for 4-5 hours. After adding 1-2 parts by weight of polyethylene glycol and stirring for 10-15 minutes, the mixture is aged at 85-90°C for 2-3 hours. After natural cooling, it is filtered, the precipitate is collected and added to 30-35 parts by weight of an isopropanol aqueous solution with a concentration of 50-60%, stirred at a stirring speed of 80-100 rpm for 25-30 minutes, and then spray-dried to obtain a lithium-doped pseudo-boehmite composite powder.

3. The method for preparing low-expansion heat-resistant purple sand ceramics according to claim 2, wherein: Step S2: Preparation of oxygen vacancy enhanced negative expansion powder, comprising the following steps: S2.1: Dissolve (NH4)H2PO4 in deionized water to prepare a (NH4)H2PO4 solution with a concentration of 0.02-0.03 mol / L. 42 N 10 O 42 W 12 Dissolve xH2O in deionized water to prepare a H solution with a concentration of 0.001-0.0015 mol / L. 42 N 10 O 42 W 12 xH2O solution, C 10 H 14 NiO4 was dissolved in anhydrous ethanol to prepare a C 10 H 14 NiO4 solution, dissolve ZrOCl2•8H2O in deionized water to prepare a ZrOCl2•8H2O solution with a concentration of 0.3-0.4 mol / L; S2.2: Mix 12-15 parts by volume of (NH4)H2PO4 solution and 12-15 parts by volume of H 42 N 10 O 42 W 12 · xH2O solution was mixed in a container and stirred evenly, then 4-6 parts by volume of C 10 H 14 Stir the NiO4 solution evenly, then add 1.5-2 parts by volume of ZrOCl2•8H2O solution dropwise. After the addition is complete, adjust the pH to 8.5-9, and continue stirring for 1-2 hours to obtain a milky white mixed solution. S2.3: Transfer the milky white mixed solution to a polytetrafluoroethylene autoclave and react at 30-32°C for 24-30 hours. Take out the reactants and wash them first using a centrifuge, then centrifuge them again, collect the precipitates and dry them in a forced air drying oven to obtain a block precursor, grind the block precursor into powder and place it in a muffle furnace, calcinate it at 800-900°C for 3-4 hours to obtain oxygen vacancy enhanced negative expansion powder.

4. The method for preparing low-expansion heat-resistant purple sand ceramics according to claim 3, characterized in that: Step S3, compounding ceramic raw materials and firing the ceramic, includes the following steps: S3.1: 50-60 parts by weight of purple sand clay and 2-3 parts by weight of cattail wool are added to a ball mill and mixed and ball-milled. Then, 8-10 parts by weight of feldspar, 3-5 parts by weight of micaceous iron oxide, 1-3 parts by weight of Suzhou clay, 0.3-0.5 parts by weight of lithium-doped pseudo-boehmite composite powder, and 4-6 parts by weight of oxygen vacancy enhanced negative expansion powder are added and ball-milled again to obtain a mixed clay; S3.2: Transfer the mixed mud to a vacuum mud refiner for vacuum mud refining, and then age it. Repeat the vacuum mud refining and ageing and then make a blank to obtain a blank. Place the blank in a muffle furnace and heat it to 250-300℃ within 60 minutes under air atmosphere, then heat it to 600-650℃ within 90 minutes, and then heat it to 900-920℃ within 120 minutes, and finally heat it to 1250-1300℃ within 180 minutes for calcination. Keep it warm for 20 minutes, cool it with the furnace and take it out to obtain low-expansion heat-resistant purple clay ceramics.

5. The method for preparing low-expansion heat-resistant purple sand ceramics according to claim 2, characterized in that: The steel balls added to the sand mill in step S1.1 account for 50-55% of the volume of the cylinder, and the diameter of the steel balls is 0.2-0.3 mm.

6. The method for preparing low-expansion heat-resistant purple sand ceramics according to claim 3, characterized in that: In step S2.2, the pH is adjusted by adding ammonia water.

7. The method for preparing low-expansion heat-resistant purple sand ceramics according to claim 3, characterized in that: In step S2.3, the rotation speed of the centrifugal washing is 200-300 rpm, which lasts for 15-20 minutes, and the rotation speed of the centrifugal separation is 8000-10000 rpm, which lasts for 10-15 minutes.

8. The method for preparing low-expansion heat-resistant purple sand ceramics according to claim 4, characterized in that: The main chemical components of the purple clay in step S3.1 are 50-56% SiO2, 22-28% Al2O3, 12-16% Fe2O3, 0.1-0.5% CaO, 5-10% MgO, 1.5-2.5% K2O and 0.1-0.3% Na2O.

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