Preparation method of cordierite-spodumene glass ceramic combined aluminum silicate ceramic material and product thereof

Abstract

The invention discloses a preparation method of a cordierite-spodumene microcrystalline glass combined aluminum silicate ceramic material and a product thereof. The cordierite-spodumene microcrystalline glass combined aluminum silicate ceramic material is prepared from a base material and a binding agent, the base material is prepared from the following raw materials in percentage by weight: 10 to 25 percent of cordierite-spodumene microcrystalline glass powder, 10 to 30 percent of mullite aggregate, 30 to 60 percent of corundum aggregate and 10 to 20 percent of clay powder, and the cordierite-spodumene microcrystalline glass powder is prepared from the following raw materials in percentage by weight: 23 to 25 percent of MgO, 17 to 19 percent of Al2O3, 25 to 59 percent of SiO2 and 0.5 to 1 percent of Li2O. According to the invention, cordierite-spodumene microcrystalline glass is taken as a sintering aid, and cordierite and spodumene crystals are introduced into microcrystalline glass in an aluminum silicate ceramic matrix in an in-situ synthesis manner, so that not only is a low-temperature sintering aid provided, but also the performance of the aluminum silicate ceramic material is effectively improved; and the preparation method has important significance in overcoming the problems existing in application of microcrystalline glass in the prior art and improving the cost performance of the aluminum silicate ceramic material, so that the preparation method has wide market prospects and is beneficial to popularization and application and progress and development of industrial technologies.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and in particular to a preparation method of a cordierite-spodumene glass-ceramic combined with an aluminum silicate ceramic material and a product thereof. Background Art

[0002] Aluminosilicate ceramic materials are currently widely used in metallurgy, machinery manufacturing, petrochemical industry, power, and light industry. However, aluminosilicate ceramics have problems such as high thermal expansion coefficient and poor thermal shock resistance. In order to overcome these shortcomings, a combination of two different mineral phases is usually designed. The most common one is mullite-corundum. The difference in thermal expansion coefficients between the two is used to produce microcracks during thermal cycles to improve thermal shock resistance. However, its high thermal expansion coefficient is still a problem that needs to be solved. Introducing a low expansion phase is an effective way to solve this problem. Commonly used low expansion phases are cordierite and graphite. Among them, cordierite has good chemical compatibility with mullite and corundum, while graphite has poor wettability with mullite and corundum, so cordierite is often compounded with mullite and corundum to form two or three thermal expansion coefficient gradients.

[0003] Although the low thermal expansion coefficient of cordierite can optimize the performance of mullite and corundum, it is also difficult to sinter. Because the temperature of cordierite to form a liquid phase is usually above 1400°C, and its behavior of generating a liquid phase is a reaction of instantaneous large-scale generation at a certain temperature, which is reflected in the shrinkage curve as a nearly linear decline. This causes the problem of a narrow sintering temperature range and difficult sintering. In addition, the in-situ generated cordierite has a porous structure, which is not conducive to the structural density of the material.

[0004] The prior art also proposes to use cordierite-based microcrystalline glass as a sintering aid, and introduce cordierite by in-situ crystallization to obtain Al2O3-SiO2 system ceramics with high density and excellent thermal shock resistance. However, the problem of glass expansion during the crystallization process is not solved. This is a problem that must be faced in the process of transforming from high-density glass to low-density crystals. Therefore, a secondary sintering process at high temperature (1450-1500°C) is still required, and subsequent crystallization expansion is also difficult to avoid. At the same time, the lack of the addition of nucleating agents also requires the problem of insufficient number of crystals to be solved. Therefore, how to solve the problem of glass expansion during crystallization and the problem of improving glass crystallinity are of great significance for improving the quality of aluminum silicate ceramic materials and the application of microcrystalline glass sintering aids. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a cordierite-spodumene glass-ceramics combined with an aluminum silicate ceramic material, using cordierite-spodumene glass-ceramics as a sintering aid for aluminum silicate ceramics, introducing cordierite and spodumene by phase separation crystallization and in-situ synthesis, and by complementing the sintering properties of the glass and the ceramic matrix, thereby obtaining an aluminum silicate ceramic with high density and better thermal shock resistance. Another purpose of the present invention is to provide a product obtained by using the preparation method of the cordierite-spodumene glass-ceramics combined with an aluminum silicate ceramic material.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The invention provides a preparation method of a cordierite-spodumene glass-ceramics combined with an aluminum silicate ceramic material. The ceramic material is prepared from a base material and a binder. The base material comprises 10-25wt% of cordierite-spodumene glass-ceramics powder, 10-30wt% of mullite aggregate, 30-60wt% of corundum aggregate, and 10-20wt% of clay powder, wherein the cordierite-spodumene glass-ceramics powder comprises 23-25wt% of MgO, 17-19wt% of Al2O3, 57-59wt% of SiO2, and 0.5-1wt% of Li2O. The amount of the binder is 8-12wt% of the base material. The preparation method comprises the following steps:

[0008] (1) mixing the raw materials of the cordierite-spodumene glass-ceramics powder according to the composition ratio, melting them into glass liquid, then pouring the glass liquid into water to quench to obtain a frit, and obtaining the cordierite-spodumene glass-ceramics powder after ball milling;

[0009] (2) mixing the base materials according to the raw material composition ratio, adding a binder and mixing evenly, and then pressing and molding, and drying to obtain a green body;

[0010] (3) The green body is sintered in two stages, i.e., a low-temperature sintering is performed at 900-1000°C for a period of ≥10 hours, and then the temperature is raised to 1200-1300°C for a second high-temperature sintering for a period of 3-5 hours; and then naturally cooled to room temperature to obtain a cordierite-spodumene glass-ceramic combined with aluminum silicate ceramic material.

[0011] Furthermore, the particle size of the cordierite-spodumene microcrystalline glass powder of the present invention is 10-75 μm, the particle size of the mullite aggregate is 40-325 mesh, the particle size of the corundum aggregate is 40-500 mesh, and the particle size of the clay powder is 25-75 μm. The binder is a PVA solution with a concentration of 5wt%. The clay is a combination of two or more of kaolin, ball clay, and bauxite.

[0012] In the above scheme, the melting temperature in step (1) of the present invention is 1500-1600°C and the melting time is 2-3 hours. The moisture content of the green body after drying in step (2) is less than 1%.

[0013] The product obtained by the preparation method of the cordierite-spodumene microcrystalline glass combined with the aluminum silicate ceramic material has a water absorption rate of less than 7% and a thermal expansion coefficient of ≤3.95×10 -6 ℃ -1 , crystallinity ≥89%, flexural strength >65MPa, strength retention rate after thermal cycling (room temperature ~ 1100℃) ≥70%.

[0014] The present invention has the following beneficial effects:

[0015] (1) The present invention uses cordierite-spodumene glass-ceramics that can produce viscous flow at low temperature as a sintering aid, and low-temperature sintering and phase separation are carried out simultaneously. Through long-term heat preservation at low temperature, on the one hand, the low-temperature viscous flow of the glass frit and the wrapping of various aggregates and powders are utilized to promote the removal of pores inside the ceramic body, improve the density of the product, and achieve the purpose of reducing the sintering temperature of aluminum silicate ceramics; on the other hand, phase separation is promoted inside the glass frit, and the local component deviation caused by phase separation and the formed interface are utilized, combined with the surface defects of the frit powder, to jointly promote crystallization behavior and increase the number of crystals.

[0016] (2) The present invention only adds a small amount of Li2O to form low-expansion spodumene in situ in the microcrystalline glass, further reducing the thermal expansion coefficient, and forming a 4-level thermal expansion coefficient gradient with cordierite, mullite, and corundum, which can effectively improve the thermal shock resistance of the product. The introduction of Li2O can also enhance the low-temperature viscous flow of glass, increase the low-temperature sintering of glass, and promote phase separation.

[0017] (3) The present invention has designed a system for the complementary sintering properties of glass and ceramic blanks. Clay will expel structural water at low temperatures, forming pores, which is not conducive to the sintering of ceramic blanks. At this time, the low-temperature viscous flow of glass near its transition temperature point is used to offset this negative impact; when high-temperature crystallization occurs, the structure becomes loose due to the crystallization expansion effect, and the fine powder of clay is used to generate liquid phase flow to promote shrinkage, offsetting this expansion effect, thereby omitting the high-temperature (>1400°C) sintering process.

[0018] (4) The present invention avoids the crystallization temperature of the glass by keeping the temperature at a low temperature for a long time, thereby preventing crystallization from reducing the amount of viscous flow, thereby solving the problem that high sintering temperature causes crystallization to weaken the sinterability of the glass, thereby causing poor sintering effect.

[0019] (5) The present invention introduces Li2O into the microcrystalline glass to enhance the viscous flow of the glass, so that the glass and the ceramic body are partially wetted well, and the ion migration ability of the glass is enhanced. Combined with the high activity of clay and the effect of impurities, the glass is promoted to absorb part of the clay fine powder and corundum fine powder during the high-temperature crystallization process, and the missing Al2O3 and SiO2 in the glass are supplemented, so that its composition is closer to the chemical composition of cordierite and spodumene, thereby improving the crystallization ability of the glass.

[0020] (6) The present invention has a simple process and a low firing temperature, and is of great significance for improving the quality of aluminum silicate ceramic materials and overcoming various problems in the application of microcrystalline glass. Therefore, it has a broad market prospect and is conducive to the promotion and application and the progress and development of industry technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings:

[0022] Figure 1 This is the XRD spectrum of the cordierite-spodumene glass-ceramics combined with aluminum silicate ceramic material prepared in the embodiment of the present invention;

[0023] Figure 2 This is a microstructure diagram of the phase separation and crystallization of the glass-ceramics portion of the ceramic material of the present invention after acid corrosion (after HF acid corrosion for 60 seconds, scanning electron microscope secondary electron image). DETAILED DESCRIPTION

[0024] Embodiment 1:

[0025] A preparation method of a cordierite-spodumene glass-ceramic combined with an aluminum silicate ceramic material, which is prepared from a base material and a binder; the base material comprises 25 wt% of cordierite-spodumene glass-ceramic powder (particle size 75 μm), 30 wt% of mullite aggregate (including 15 wt% of 40 mesh particle size, 5 wt% of 80 mesh particle size, and 10 wt% of 325 mesh particle size), 30 wt% of corundum aggregate (including 15 wt% of 40 mesh particle size, 5 wt% of 120 mesh particle size, and 10 wt% of 400 mesh particle size), and 15 wt% of clay powder (particle size 25 μm) (including 7.5 wt% of kaolin and 7.5 wt% of bauxite); the raw material composition of the cordierite-spodumene glass-ceramic powder comprises 23 wt% of MgO, 19 wt% of Al2O3, 57 wt% of SiO2, and 10 wt% of Li2O3. 1wt%; the binder is a 5wt% PVA solution, and its amount is 12wt% of the base material; the preparation method has the following steps:

[0026] (1) mixing the raw materials of the cordierite-spodumene glass-ceramics powder according to the composition ratio, placing them in an electric furnace at a temperature of 1600° C. for 2 h to melt them into glass liquid, then pouring the glass liquid into water to quench and obtain a frit, and obtaining cordierite-spodumene glass-ceramics powder after ball milling;

[0027] (2) After mixing the above base materials according to the raw material composition ratio, adding a binder and mixing evenly, then pressing and molding, and drying at a temperature of 110° C. to obtain a green body with a moisture content of less than 1%;

[0028] (3) The green body is sintered in two stages, i.e., a low-temperature sintering is performed at 900°C for 11 hours, and then the temperature is raised to 1200°C for a second high-temperature sintering for 4 hours; and then naturally cooled to room temperature to obtain cordierite-spodumene glass-ceramics combined with aluminum silicate ceramic materials.

[0029] Embodiment 2:

[0030] A preparation method of a cordierite-spodumene glass-ceramic combined with an aluminum silicate ceramic material, which is prepared from a base material and a binder; the base material comprises 10 wt% of cordierite-spodumene glass-ceramic powder (particle size 10 μm), 20 wt% of mullite aggregate (including 10 wt% of particles with a particle size of 40 mesh and 10 wt% of particles with a particle size of 80 mesh), 50 wt% of corundum aggregate (including 30 wt% of particles with a particle size of 40 mesh, 10 wt% of particles with a particle size of 250 mesh and 10 wt% of particles with a particle size of 500 mesh), and 20 wt% of clay powder (particle size 50 μm) (including 10 wt% of ball clay and 10 wt% of bauxite); the raw material composition of the cordierite-spodumene glass-ceramic powder comprises 23.5 wt% of MgO, 17 wt% of Al2O3 and 59 wt% of SiO2. wt%, Li2O0.5wt%; the binder is a 5wt% PVA solution, and its amount is 8wt% of the base material; the preparation method has the following steps:

[0031] (1) mixing the raw materials of the cordierite-spodumene glass-ceramics powder according to the composition ratio, placing them in an electric furnace at a temperature of 1500° C. for 3 hours to melt them into glass liquid, then pouring the glass liquid into water to quench and obtain a frit, and obtaining cordierite-spodumene glass-ceramics powder after ball milling;

[0032] (2) After mixing the above base materials according to the raw material composition ratio, adding a binder and mixing evenly, then pressing and molding, and drying at 100° C. to obtain a green body with a moisture content of less than 1%;

[0033] (3) The green body is sintered in two stages, i.e., a low-temperature sintering is performed at 950°C for 11 hours, and then the temperature is raised to 1250°C for a second high-temperature sintering for 4 hours; and then naturally cooled to room temperature to obtain cordierite-spodumene glass-ceramics combined with aluminum silicate ceramic materials.

[0034] Embodiment three:

[0035] A preparation method of a cordierite-spodumene glass-ceramic combined with an aluminum silicate ceramic material, which is prepared from a base material and a binder; the base material comprises 15wt% of cordierite-spodumene glass-ceramic powder (particle size 35μm), 10wt% of mullite aggregate (particle size 80 mesh), 60wt% of corundum aggregate (including 30wt% of particles with a particle size of 40 mesh, 10wt% of particles with a particle size of 325 mesh, and 20wt% of particles with a particle size of 500 mesh), and 15wt% of clay powder (particle size 68μm) (including 5wt% of kaolin, 5wt% of bauxite, and 5wt% of ball clay); the cordierite-spodumene glass-ceramic powder comprises 25wt% of MgO, 17wt% of Al2O3, 57wt% of SiO2, and 10wt% of Li2O3. 1wt%; the binder is a 5wt% PVA solution, and its amount is 10wt% of the base material; the preparation method has the following steps:

[0036] (1) mixing the raw materials of the cordierite-spodumene glass-ceramics powder according to the composition ratio, placing them in an electric furnace at a temperature of 1550° C. for 2.5 hours to melt them into glass liquid, then pouring the glass liquid into water to quench and obtain a frit, and obtaining the cordierite-spodumene glass-ceramics powder after ball milling;

[0037] (2) After mixing the above base materials according to the raw material composition ratio, adding a binder and mixing evenly, then pressing and molding, and drying at a temperature of 110° C. to obtain a green body with a moisture content of less than 1%;

[0038] (3) The green body is sintered in two stages, i.e., a low-temperature sintering is performed at 1000°C for 10 hours, and then the temperature is raised to 1300°C for a second high-temperature sintering for 3 hours; thus, cordierite-spodumene glass-ceramics combined with aluminum silicate ceramic material are obtained.

[0039] Embodiment 4:

[0040] A preparation method of a cordierite-spodumene glass-ceramic combined with an aluminum silicate ceramic material, which is prepared from a base material and a binder; the base material comprises 20 wt% of cordierite-spodumene glass-ceramic powder (particle size 35 μm), 30 wt% of mullite aggregate (particle size 80 mesh), 40 wt% of corundum aggregate (including 30 wt% of 40 mesh particle size and 10 wt% of 325 mesh particle size), and 10 wt% of clay powder (particle size 75 μm) (including 5 wt% of kaolin and 5 wt% of bauxite); the cordierite-spodumene glass-ceramic powder comprises 24 wt% of MgO, 18 wt% of Al2O3, 57.25 wt% of SiO2, and 0.75 wt% of Li2O; the binder is a PVA solution with a concentration of 5 wt%, and its dosage is 11 wt% of the base material; the preparation method has the following steps:

[0041] (1) mixing the raw materials of the cordierite-spodumene glass-ceramics powder according to the composition ratio, placing them in an electric furnace at a temperature of 1575° C. for 3 hours to melt them into glass liquid, then pouring the glass liquid into water to quench and obtain a frit, and obtaining the cordierite-spodumene glass-ceramics powder after ball milling;

[0042] (2) After mixing the above base materials according to the raw material composition ratio, adding a binder and mixing evenly, then pressing and molding, and drying at a temperature of 110° C. to obtain a green body with a moisture content of less than 1%;

[0043] (3) The green body is sintered in two stages, i.e., a low-temperature sintering is performed at 975°C for 12 hours, and then the temperature is raised to 1300°C for a second high-temperature sintering for 4 hours; and then naturally cooled to room temperature to obtain cordierite-spodumene glass-ceramics combined with aluminum silicate ceramic materials.

[0044] Comparative Example 1, Comparative Example 2, and Comparative Example 3 are respectively prepared without adding clay powder (i.e., replacing clay with mullite of the same particle size), with a low-temperature sintering holding time of 3 h, and without adding Li2O to the microcrystalline glass powder (the remaining MAS oxide composition is based on the original ratio) (other conditions are the same as those in Example 1).

[0045] Comparative Example 4 is a case where clay powder and Li2O are not introduced simultaneously (the clay powder is replaced by mullite of the same particle size, and the MAS composition of the microcrystalline glass powder is the original ratio) (other conditions are the same as those of Example 2).

[0046] The various properties and glass crystallinity of the ceramic materials prepared in the examples of the present invention and the comparative examples are shown in Table 1.

[0047] Table 1 Performance and glass crystallinity of ceramic materials obtained in the embodiments of the present invention and the comparative examples

[0048]

[0049] The glass crystallinity was calculated by the internal standard method (with corundum as reference) and the MDI Jade 6.5 software to calculate the amount of cordierite and spodumene in the blank, and then divided by the amount of added glass.

[0050] It can be seen from Table 1 that the cordierite-spodumene glass-ceramics combined with the aluminum silicate ceramic material prepared in the embodiments of the present invention have low water absorption, low thermal expansion coefficient, high crystallinity and high strength.

[0051] From the data of Example 1 and Comparative Example 1, it can be seen that without adding clay as part of the ceramic body, the water absorption rate of the product increases, the thermal expansion coefficient increases, and the crystallinity decreases. Because the high-temperature sintering effect of clay is lacking, the effect of glass crystallization expansion is not offset. At the same time, the lack of high-activity clay integrated into the glass reduces the crystallinity of cordierite and spodumene, and also increases the thermal expansion coefficient. From the data of Example 1 and Comparative Example 2, it can be seen that without long-term insulation at low temperature, the water absorption rate of the product increases, the thermal expansion coefficient increases, and the crystallinity decreases. This is because, on the one hand, the low-temperature viscous flow of the glass is lacking, which increases the number of pores. On the other hand, the lack of a long-term low-temperature insulation step results in a small number of phase separations and a lack of glass separation. Phase quantity and interface are not conducive to crystallization; comparing the data of Example 1 and Comparative Example 3, it can be seen that Li2O is not added to the microcrystalline glass, the sintering effect of the microcrystalline glass is reduced, and the crystallinity is reduced. Due to the lack of Li2O, the fluidity of the glass is reduced, spodumene cannot be precipitated, and it is not easy to absorb clay fine powder, resulting in a decrease in crystallinity. At the same time, there is a lack of a 4-level gradient of the thermal expansion coefficient, which is not conducive to thermal shock resistance; comparing the data of Example 2 and Comparative Example 4, it can be seen that if clay and Li2O are not introduced at the same time, the water absorption rate of the product increases, the thermal expansion coefficient increases, the crystallinity decreases, and the strength decreases. This is because there is a lack of a design that complements the sintering properties, and there is a lack of high-temperature absorption of clay to promote crystallization, which shows that clay + Li2O is very necessary.

[0052] The cordierite-spodumene glass-ceramics prepared in the embodiment of the present invention are combined with aluminum silicate ceramic materials, such as Figure 1 As shown in Figure 1, it contains the crystal phases of corundum, mullite, cordierite, and spodumene. Figure 2 As shown in the figure, after HF acid corrosion, the protrusions are not easily corroded and separated, while the crystals mainly grow on a large scale at the interface or edge of the separated phases, which illustrates the importance of separation to crystallization.

Claims

1. A method for preparing cordierite-spodumene glass-ceramics combined with aluminum silicate ceramic material, characterized in that: The ceramic material is prepared from a base material and a binder; the base material comprises 10-25wt% of cordierite-spodumene glass-ceramics powder, 10-30wt% of mullite aggregate, 30-60wt% of corundum aggregate, and 10-20wt% of clay powder, wherein the cordierite-spodumene glass-ceramics powder comprises 23-25wt% of MgO, 17-19wt% of Al2O3, 57-59wt% of SiO2, and 0.5-1wt% of Li2O; the amount of the binder is 8-12wt% of the base material; and the preparation method comprises the following steps: (1) mixing the raw materials of the cordierite-spodumene glass-ceramics powder according to the composition ratio, melting them into glass liquid, then pouring the glass liquid into water to quench to obtain a frit, and obtaining the cordierite-spodumene glass-ceramics powder after ball milling; (2) mixing the base materials according to the raw material composition ratio, adding a binder and mixing evenly, and then pressing and molding, and drying to obtain a green body; (3) The green body is sintered in two stages, i.e., a low-temperature sintering is performed at 900-1000°C for a period of ≥10 hours, and then the temperature is raised to 1200-1300°C for a second high-temperature sintering for a period of 3-5 hours; and then naturally cooled to room temperature to obtain a cordierite-spodumene glass-ceramic combined with aluminum silicate ceramic material.

2. The method for preparing the cordierite-spodumene glass-ceramics combined with an aluminum silicate ceramic material according to claim 1, characterized in that: The particle size of the cordierite-spodumene microcrystalline glass powder is 10-75 μm, the particle size of the mullite aggregate is 40-325 meshes, the particle size of the corundum aggregate is 40-500 meshes, and the particle size of the clay powder is 25-75 μm.

3. The method for preparing the cordierite-spodumene glass-ceramics combined with an aluminum silicate ceramic material according to claim 1, characterized in that: The binder is a PVA solution with a concentration of 5 wt%.

4. The method for preparing the cordierite-spodumene glass-ceramics combined with an aluminum silicate ceramic material according to claim 1, characterized in that: The clay is a combination of two or more of kaolin, ball clay and bauxite.

5. The method for preparing the cordierite-spodumene glass-ceramics combined with an aluminum silicate ceramic material according to claim 1, characterized in that: In the step (1), the melting temperature is 1500-1600° C. and the melting time is 2-3 hours.

6. The method for preparing the cordierite-spodumene glass-ceramics combined with an aluminum silicate ceramic material according to claim 1, characterized in that: The moisture content of the green body after drying in step (2) is less than 1%.

7. A product obtained by the preparation method of cordierite-spodumene glass-ceramics combined with aluminum silicate ceramic material according to any one of claims 1 to 6.

8. The product according to claim 7, characterized in that: The cordierite-spodumene glass-ceramics combined with the aluminum silicate ceramic material has a water absorption rate of less than 7% and a thermal expansion coefficient of ≤3.95×10 -6 ℃ -1 , crystallinity ≥89%, flexural strength >65MPa, strength retention rate after thermal cycling (room temperature ~ 1100℃) ≥70%.

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