Preparation method of split-phase devitrified cordierite glass ceramic combined aluminum silicate ceramic material and product of split-phase devitrified cordierite glass ceramic combined aluminum silicate ceramic material

Abstract

The invention discloses a preparation method of a split-phase crystallization cordierite microcrystalline glass combined aluminum silicate ceramic material and a product thereof. The split-phase crystallization cordierite 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-based 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-based 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 and 25 to 59 percent of SiO2. According to the invention, split-phase devitrified cordierite microcrystalline glass is taken as a sintering aid, and cordierite crystals are introduced into microcrystalline glass in an aluminum silicate ceramic matrix in an in-situ synthesis manner, so that a low-temperature sintering aid is provided, and the performance of an 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 phase-separated crystallized cordierite glass-ceramic combined with an aluminum silicate ceramic material and a product thereof. Background Art

[0002] Cordierite glass-ceramics is an excellent binder with the advantages of low thermal expansion, high hardness, good dielectric properties, etc. It is widely used as an electronic packaging material and ceramic binder. The excellent properties of cordierite glass-ceramics mainly come from the cordierite crystals precipitated in the glass. In order to improve the crystallinity (number of crystals) of cordierite glass-ceramics, transition metal oxides such as TiO2 and Fe2O3 are often added to cordierite glass-ceramics as nucleating agents. However, the addition of these nucleating agents will obviously reduce the refractoriness of the glass and limit its application in the field of high-temperature structures. Therefore, how to improve the crystallinity of glass-ceramics without adding nucleating agents has been a problem that has plagued scientific researchers. Solving this problem will help promote the application of cordierite glass-ceramics as a high-temperature binder.

[0003] In addition to adding a nucleating agent to promote crystallization, using phase separation to promote crystallization is another way. Magnesium ions have a high ionic potential and are strong ions that promote phase separation. If phase separation can be used for crystallization, it is expected that the crystallinity of the glass can be improved without adding a nucleating agent.

[0004] In addition to the above problems, the volume expansion of glass during the crystallization process is also an important problem that limits its use as a binder. The expansion of glass during crystallization stretches the particles it bonds to, which can easily cause the structure to become loose. Only after crystallization can the glass have the performance required by the user, so how to overcome the contradiction between crystallization and bonding is also a problem that troubles scientific researchers. Correspondingly, if phase separation is added to promote crystallization, the anti-densification behavior will be further enhanced.

[0005] As a low-temperature sintering aid, cordierite glass-ceramics can make up for the disadvantage of high sintering temperature of aluminum silicate ceramics. It also has a low thermal expansion coefficient, which can reduce the thermal expansion coefficient of aluminum silicate ceramics, which is beneficial to its resistance to rapid cooling and heating. However, the crystallization expansion of the glass will cause anti-densification behavior and reduce its sintering properties. In addition, in order to improve its refractory properties, other nucleating agents are often not added to it. How to improve the crystallinity of the glass between particles is also very important. Therefore, how to effectively solve these two problems is of great significance to improving the quality of aluminum silicate ceramic materials and saving product costs. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing phase-separated crystallized cordierite glass-ceramics combined with aluminum silicate ceramic materials, using phase-separated crystallized cordierite glass-ceramics as a sintering aid for aluminum silicate ceramics, introducing cordierite by phase-separated crystallization and in-situ synthesis, and by complementing the sintering properties of glass and ceramic matrix, thereby obtaining aluminum silicate ceramics with high density and better thermal shock resistance. Another purpose of the present invention is to provide a product obtained by the above-mentioned preparation method of phase-separated crystallized cordierite glass-ceramics combined with aluminum silicate ceramic materials.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The present invention provides a preparation method of a phase-separated crystallized cordierite glass-ceramics combined with an aluminum silicate ceramic material. The ceramic material is prepared from a base material and a binder; the raw material composition of the base material is 10-25wt% of cordierite-based glass-ceramics powder, 10-30wt% of mullite aggregate, 30-60wt% of corundum aggregate, and 10-20wt% of clay powder, wherein the raw material composition of the cordierite-based glass-ceramics powder is 23-25wt% of MgO, 17-19wt% of Al2O3, and 57-59wt% of SiO2; the amount of the binder is 8-12wt% of the base material; the preparation method comprises the following steps:

[0009] (1) mixing the raw materials of the cordierite-based microcrystalline glass 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 then ball milling to obtain the cordierite-based microcrystalline glass powder;

[0010] (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;

[0011] (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 4-6 hours; and then naturally cooled to room temperature to obtain a cordierite glass-ceramic combined with aluminum silicate ceramic material.

[0012] Furthermore, the particle size of the cordierite glass-ceramic 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.

[0013] 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%.

[0014] The product obtained by the preparation method of the phase separation crystallization cordierite glass-ceramics combined with the aluminum silicate ceramic material has a water absorption rate of ≤8.6% and a thermal expansion coefficient of ≤4.27×10 -6 ℃ -1 , glass crystallinity ≥85%, flexural strength >60MPa.

[0015] The present invention has the following beneficial effects:

[0016] (1) The present invention uses cordierite microcrystalline glass that can produce viscous flow at low temperature as a sintering aid, and low-temperature sintering and phase separation are carried out simultaneously. The present invention designs a glass composition with a high MgO content and a system of long-term heat preservation at low temperature. On the one hand, the high MgO content is used to enhance the low-temperature viscous flow of the glass frit (the higher the MgO content, the better the fluidity), and the long-term heat preservation at low temperature prolongs the flow time, so that the glass wraps various aggregates and powders, promotes the removal of pores inside the ceramic body, improves the density of the product, and achieves the purpose of reducing the sintering temperature of aluminum silicate ceramics; on the other hand, the high MgO content and long-term heat preservation at low temperature promote phase separation inside the glass frit, and the local component deviation and phase separation interface caused by phase separation are used, combined with the surface defects of the frit powder, to jointly promote crystallization behavior and increase the number of crystals.

[0017] (2) The present invention designs a sintering system that complements the sintering properties of microcrystalline glass and ceramic green bodies. Natural clay will expel structural water at low temperatures to form pores, which is an anti-densification behavior. Therefore, clay is often pre-calcined during production. At this time, the low-temperature viscous flow of glass near its transition temperature point is used to offset the pore-forming behavior; 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 part of the expansion effect, thereby avoiding the high-temperature (>1400°C) firing process and being more energy-efficient.

[0018] (3) 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, resulting in poor sintering effect.

[0019] (4) The present invention enhances the viscous flow of glass by designing a high MgO content, so that the glass and the ceramic body are partially wetted well, and the ion migration ability of the glass is enhanced. However, Al2O3 and SiO2 are lacking. At this time, the high activity of clay and a small amount of impurities are combined to promote the glass to absorb part of the clay fine powder and corundum fine powder during the high-temperature crystallization process, supplement the lack of Al2O3 and SiO2 in the glass, make its composition closer to the chemical composition of cordierite (2MgO 2Al2O35SiO2), and improve the crystallization ability of the glass.

[0020] (5) The process of the present invention is simple and the firing temperature is low. It 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 broad market prospects 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 phase-separated crystallized cordierite glass-ceramics combined with aluminosilicate ceramic material obtained 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] The present embodiment provides a method for preparing a phase-separated crystallized cordierite glass-ceramic combined with an aluminum silicate ceramic material, which is prepared from a base material and a binder; the raw material composition of the base material is 25wt% of cordierite-based glass-ceramic powder (particle size 75μm), 30wt% of mullite aggregate (including 15wt% of 40-mesh particle size, 5wt% of 80-mesh particle size, and 10wt% of 325-mesh particle size), 30wt% of corundum aggregate (including 15wt% of 40-mesh particle size, 5wt% of 120-mesh particle size, and 10wt% of 400-mesh particle size), and 15wt% of clay powder (particle size 25μm) (including 7.5wt% of kaolin and 7.5wt% of bauxite); the raw material composition of the cordierite-based glass-ceramic powder is 23wt% of MgO, 19wt% of Al2O3, and 58wt% of SiO2. wt%; the binder is a 5wt% PVA solution, which is used in an amount of 12wt% of the base material; the preparation method comprises the following steps:

[0026] (1) mixing the raw materials of the cordierite-based microcrystalline glass 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 then ball milling to obtain cordierite-based microcrystalline glass powder;

[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 glass-ceramics combined with aluminum silicate ceramic material.

[0029] Embodiment 2:

[0030] The present embodiment provides a method for preparing a phase-separated crystallized cordierite glass-ceramic combined with an aluminum silicate ceramic material, which is prepared from a base material and a binder; the raw material composition of the base material is 10wt% of cordierite-based glass-ceramic powder (particle size 10μm), 20wt% of mullite aggregate (including 10wt% of 40-mesh particle size and 10wt% of 80-mesh particle size), 50wt% of corundum aggregate (including 30wt% of 40-mesh particle size, 10wt% of 250-mesh particle size and 10wt% of 500-mesh particle size), and 20wt% of clay powder (particle size 50μm) (including 10wt% of ball clay and 10wt% of bauxite); the raw material composition of the cordierite-based glass-ceramic powder is 24wt% of MgO, 17wt% of Al2O3 and 59wt% of SiO2; the binder is a PVA solution with a concentration of 5wt%, and its amount is 8wt% of the base material; the preparation method comprises the following steps:

[0031] (1) mixing the raw materials of the cordierite-based microcrystalline glass 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 fused block, and obtaining cordierite-based microcrystalline glass 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 5 hours; and then naturally cooled to room temperature to obtain cordierite glass-ceramics combined with aluminum silicate ceramic material.

[0034] Embodiment three:

[0035] The present embodiment provides a method for preparing a phase-separated crystallized cordierite glass-ceramics combined with an aluminum silicate ceramic material, which is prepared from a base material and a binder; the raw material composition of the base material is cordierite-based glass-ceramics powder (particle size 35 μm) 15wt%, mullite aggregate (particle size 80 mesh) 10wt%, corundum aggregate 60wt% (including 30wt% of 40 mesh, 10wt% of 325 mesh, and 20wt% of 500 mesh), and clay powder (particle size 68 μm) 15wt% (including 5wt% kaolin, 5wt% bauxite, and 5wt% ball clay); the raw material composition of the cordierite-based glass-ceramics powder is MgO 25wt%, Al2O3 18wt%, and SiO2 57wt%; the binder is a PVA solution with a concentration of 5wt%, and its amount is 10wt% of the base material; the preparation method comprises the following steps:

[0036] (1) mixing the raw materials of the cordierite-based microcrystalline glass 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 fused block, and obtaining cordierite-based microcrystalline glass 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 6 hours; and then naturally cooled to room temperature to obtain cordierite glass-ceramics combined with aluminum silicate ceramic material.

[0039] Embodiment 4:

[0040] The present embodiment provides a method for preparing a phase-separated crystallized cordierite glass-ceramics combined with an aluminum silicate ceramic material, which is prepared from a base material and a binder; the raw material composition of the base material is cordierite-based glass-ceramics powder (particle size 35 μm) 20wt%, mullite aggregate (particle size 80 mesh) 30wt%, corundum aggregate 40wt% (including 30wt% of 40 mesh particle size and 10wt% of 325 mesh particle size), and clay powder (particle size 75 μm) 10wt% (including 5wt% kaolin and 5wt% bauxite); the raw material composition of the cordierite-based glass-ceramics powder is MgO 24wt%, Al2O3 18wt%, and SiO2 58wt%; the binder is a PVA solution with a concentration of 5wt%, and its amount is 11wt% of the base material; the preparation method comprises the following steps:

[0041] (1) mixing the raw materials of the cordierite-based microcrystalline glass 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 then ball milling to obtain cordierite-based microcrystalline glass powder;

[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 5 hours; and then naturally cooled to room temperature to obtain cordierite glass-ceramics combined with aluminum silicate ceramic material.

[0044] Comparative Example 1, Comparative Example 2, and Comparative Example 3 are respectively prepared with no addition of clay powder (i.e., clay is replaced by mullite of the same particle size), no long-term low-temperature insulation (i.e., the insulation time of the first stage of low-temperature sintering is 3h), and no long-term high-temperature insulation (i.e., the insulation time of the second stage of high-temperature sintering is 3h) (other conditions are the same as those in Example 1).

[0045] Comparative Example 4 is a method in which clay powder is not introduced and the low-temperature heat preservation is not performed for a long time (ie, clay is replaced by mullite of the same particle size and the heat preservation time of a low-temperature sintering is 3 hours) (other conditions are the same as those of Example 2).

[0046] Comparative Example 5 is a method in which clay powder is not introduced and long-term low-temperature insulation and long-term high-temperature insulation are not performed (i.e., mullite with the same particle size is used to replace clay, the insulation time of the first low-temperature sintering is 3h, and the insulation time of the second high-temperature sintering is 3h) (other conditions are the same as those in Example 2).

[0047] 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.

[0048] Table 1 Performance and glass crystallinity of ceramic materials obtained in the embodiments of the present invention and the comparative examples

[0049]

[0050] 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 in the blank, which was then divided by the amount of glass added.

[0051] It can be seen from Table 1 that the cordierite 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.

[0052] By comparing the data of Example 1 with 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 the microcrystalline glass and also increases the thermal expansion coefficient.

[0053] By comparing the data of Example 1 with Comparative Example 2, it can be seen that the lack of long-term low-temperature insulation increases the water absorption rate of the product, increases the thermal expansion coefficient, and decreases the crystallinity. This is because, on the one hand, the lack of low-temperature viscous flow of glass increases the number of pores, and on the other hand, the lack of a long-term low-temperature insulation step results in a small number of phase separations, and the lack of glass phase separations and interfaces is not conducive to crystallization.

[0054] By comparing the data of Example 1 with Comparative Example 3, it can be seen that without long-term heat preservation at high temperature, the water absorption rate of the product is relatively high, the thermal expansion coefficient increases, and the crystallinity decreases. This is because high-temperature heat preservation promotes the precipitation of clay liquid phase to promote densification, and at the same time, highly active clay dissolves into the glass, which can supplement the lack of SiO2 and Al2O3 in the glass, making the glass composition close to the chemical composition of cordierite, which is conducive to increasing the crystal content;

[0055] By comparing the data of Example 2 with Comparative Example 4, it can be seen that without the simultaneous introduction of clay and long-term low-temperature insulation, the water absorption rate and thermal expansion coefficient of the product are higher, and the crystallinity is further reduced, because there is a lack of high-activity clay dissolved in the glass, and there is a lack of a complementary design of sintering properties, which reduces the density, reduces the number of phase separation and crystallization, reduces the crystallinity of the microcrystalline glass, and also increases the thermal expansion coefficient;

[0056] By comparing the data of Example 2 with Comparative Example 5, it can be seen that if clay and long-term low-temperature and high-temperature insulation are not introduced at the same time, the performance of the product will be greatly reduced. This is because there is a lack of a complementary design for sintering properties and a lack of high-temperature absorption of clay to promote crystallization.

[0057] The phase separation crystallization cordierite glass-ceramics prepared in the embodiment of the present invention is combined with an aluminum silicate ceramic material, such as Figure 1 As shown, it contains the crystal phases of corundum, mullite and cordierite; 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 phase-separated crystallized cordierite glass-ceramics combined with aluminum silicate ceramic material, characterized in that: The ceramic material is prepared from a base material and a binder; the raw material composition of the base material is 10-25wt% of cordierite-based microcrystalline glass powder, 10-30wt% of mullite aggregate, 30-60wt% of corundum aggregate, and 10-20wt% of clay powder, wherein the raw material composition of the cordierite-based microcrystalline glass powder is 23-25wt% of MgO, 17-19wt% of Al2O3, and 57-59wt% of SiO2; the amount of the binder is 8-12wt% of the base material; the preparation method comprises the following steps: (1) mixing the raw materials of the cordierite-based microcrystalline glass 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 then ball milling to obtain the cordierite-based microcrystalline glass powder; (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 4-6 hours; and then naturally cooled to room temperature to obtain a cordierite glass-ceramic combined with aluminum silicate ceramic material.

2. The method for preparing phase-separated crystallized cordierite glass-ceramics combined with aluminosilicate ceramic material according to claim 1, characterized in that: The particle size of the cordierite 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 phase-separated crystallized cordierite glass-ceramics combined with aluminosilicate 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 phase-separated crystallized cordierite glass-ceramics combined with aluminosilicate ceramic material according to claim 1, characterized in that: The clay is two or more of kaolin, ball clay and bauxite.

5. The method for preparing phase-separated crystallized cordierite glass-ceramics combined with aluminosilicate 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 phase-separated crystallized cordierite glass-ceramics combined with aluminosilicate 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. Products obtained by the preparation method of phase-separated crystallized cordierite glass-ceramics combined with aluminum silicate ceramic material as described in any one of claims 1 to 6.

8. The product according to claim 7, characterized in that: The cordierite glass-ceramics combined with the aluminum silicate ceramic material has a water absorption rate of ≤8.6% and a thermal expansion coefficient of ≤4.27×10 -6 ℃ -1 , glass crystallinity ≥85%, flexural strength>60MPa.

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