Cordierite-based foam ceramic and preparation method and application thereof

Abstract

The application provides cordierite-based foam ceramic and a preparation method and application thereof. The preparation method of the cordierite-based foam ceramic comprises the following steps: mixing and milling fly ash, chrysotile tailings and auxiliary materials to obtain a green body powder; granulating, drying and aging the green body powder to obtain a green body powder particle; pressing and forming the green body powder particle to obtain a green body; drying and sintering the green body in stages to obtain the cordierite-based foam ceramic material. The cordierite-based foam ceramic is prepared by the preparation method of the cordierite-based foam ceramic, and the main crystal phase of the cordierite-based foam ceramic is alpha-cordierite. The cordierite-based foam ceramic can be applied to interior wall decoration, sound absorption material or waste liquid and water purification and filtration material. The raw materials adopted by the application are cheap and easy to obtain, the preparation process is simple, the cordierite synthesis temperature is low, and the energy consumption is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic material preparation, in particular to a cordierite-based foam ceramic and a preparation method and application thereof. BACKGROUND

[0002] In recent years, porous ceramics have been widely used in high-temperature waste gas filtration, corrosive gas filtration, external wall insulation, fabricated building materials, sound absorption and noise reduction, catalyst carriers, and wastewater treatment, etc. due to their many excellent properties, such as heat shock resistance, corrosion resistance, light weight, high strength, low thermal conductivity, high porosity, large specific surface area, and strong permeability. Cordierite-based foam ceramics with good thermal stability, low thermal expansion rate, strong heat shock resistance, and high-temperature resistance have attracted more and more attention in these applications.

[0003] Traditionally, the synthesis of cordierite is prepared by pure chemical reagents such as alumina, silica, and magnesia or mineral raw materials at a temperature range of 1350-1450℃. Although this preparation process is simple, it is not widely used due to the difficulty in obtaining raw materials and high energy consumption in the sintering process. In recent years, some new preparation methods have been developed, such as sol-gel, co-precipitation, and recrystallization. However, these methods require expensive raw materials or have very complex processing procedures, and even some methods require melting at a high temperature of 1600℃, which is not conducive to large-scale production and has not been effectively promoted. In summary, the existing mainstream production technology of foam microcrystalline ceramics has problems such as high production energy consumption, long process flow, and low solid waste utilization rate. Therefore, it is of great significance to use simple processes to prepare cordierite-based foam ceramics with excellent performance from easily accessible and low-cost raw materials, especially solid waste. SUMMARY

[0004] The present application aims to solve at least one of the above-mentioned deficiencies in the prior art. For example, one of the objectives of the present application is to provide a preparation method for cordierite-based foam ceramics with low production energy consumption, simple process flow, and high solid waste utilization rate. For another example, another objective of the present application is to provide a cordierite-based foam ceramic containing a high content of cordierite.

[0005] To achieve the above-mentioned objectives, the present application provides, in one aspect, a preparation method for cordierite-based foam ceramics, which can include the steps of: mixing and grinding fly ash, chrysotile asbestos tailings, and auxiliary materials to obtain a green body powder; granulating, drying, and aging the green body powder to obtain a green body powder particle; pressing the green body powder particle to obtain a green body; and drying and sintering the green body at a stage to obtain a cordierite-based foam ceramic material.

[0006] According to one or more exemplary embodiments of one aspect of the present application, the preparation method can further include: before the batching, performing a crushing treatment on the chrysotile asbestos tailings and the auxiliary materials to obtain -20 mesh raw material powder particles; and after the stage-wise temperature increasing sintering, performing a post-treatment on the sintered cordierite-based foam ceramic material, which can include: cooling the sintered cordierite-based foam ceramic material with furnace temperature reduction and forced air cooling, and then cutting and trimming the sintered cordierite-based foam ceramic material according to size requirements; the chrysotile asbestos tailings can be ultrabasic rock type chrysotile asbestos tailings; the auxiliary materials can include one or more of bauxite, kaolin and bentonite.

[0007] According to one or more exemplary embodiments of one aspect of the present application, the chemical component mass percentage of the fly ash can be 38-55% SiO2, 25%-30% Al2O3, 5%-12% Fe2O3, 2%-7% CaO, 1-3% TiO2, 0.3%-3% MgO and 0.5-3% of the balance of trace components; the chemical component mass percentage of the chrysotile asbestos tailings can be 40-58% SiO2, 30-46% MgO, 6-12% Fe2O3, 2-7% Al2O3 and 0.5-3.5% of the balance of trace components; the chemical component mass percentage of the kaolin can be 48-62% SiO2, 37%-59% Al2O3, 0-3% Fe2O3, 0.5-3% K2O and 0.5-5% of the balance of trace components; the chemical component mass percentage of the bentonite can be 52-68% SiO2, 18-24% Al2O3, 6-12% Fe2O3, 4-9% MgO, 3-8% Na2O and 0.5-7% of the balance of trace components; and the chemical component mass percentage of the bauxite can be 51%-65% Al2O3, 41-52% SiO2, 2-8% Fe2O3, 2-7% TiO2 and 0.5-8% of the balance of trace components.

[0008] According to one or more exemplary embodiments of one aspect of the present application, the batching can include: batching the fly ash, the chrysotile asbestos tailings, the auxiliary materials and the foaming agent in a mass ratio of 45-55:30-40:15-25:0.1-0.6; and the mixing and grinding can include: performing dry grinding on the batched materials to obtain a green body powder with a particle size of -200 mesh.

[0009] According to one or more exemplary embodiments of one aspect of the present application, the foaming agent can be SiC.

[0010] According to one or more exemplary embodiments of one aspect of the present application, the granulating can include: spraying 0.5-2% binder aqueous solution into the green body powder at 6-10 parts by weight of the green body powder, spraying industrial water at 10-15 parts by weight into the green body powder after the granulation starts, and sieving the granules to obtain qualified granules of -20-+100 mesh size; the binder can include one or more of polyvinyl alcohol, carboxymethyl cellulose, and carboxymethyl cellulose salt; the drying can include drying the qualified granules to a moisture content of 7-10%; and the aging can include aging the dried qualified granules for more than 24 hours after being sealed.

[0011] According to one or more exemplary embodiments of one aspect of the present application, the press forming can include: placing the green body powder particles in a mold, and press forming under a pressure of 25-40 MPa, and holding the pressure for 1-5 seconds to obtain the green body.

[0012] According to one or more exemplary embodiments of one aspect of the present application, the drying of the green body can include drying to a moisture content of less than 2%, and the stage-wise temperature rising sintering of the dried green body can include three stages: from room temperature to 400-500°C at a temperature rising rate of 5-20°C / min and holding the temperature for 15-30 min; from 400-500°C to 900-1000°C at a temperature rising rate of 5-15°C / min and holding the temperature for 15-30 min; and from 900-1000°C to 1230-1300°C at a temperature rising rate of 5-30°C / min and holding the temperature for 30-60 min.

[0013] Another aspect of the present application provides a cordierite-based foam ceramic, which can be prepared by the method for preparing the cordierite-based foam ceramic described above, and the main crystal phase of the cordierite-based foam ceramic can be α-cordierite, the content of which can be 70-80%; the bulk density of the cordierite-based foam ceramic can be 0.7-0.9 g / cm 3 , the compressive strength can be 3.5-5 MPa, the open porosity can be 43-50%, the water absorption can be 50-70%, the water permeability coefficient can be 0.6-0.8 mm / s, and the specific surface area can be 0.5-0.7 m 2 / g.

[0014] Still another aspect of the present application provides an application of the cordierite-based foam ceramic, which can include applications in interior wall decoration, sound-absorbing materials, or waste liquid and water purification filtering materials.

[0015] Compared with the prior art, the present application has the following beneficial effects at least one of which is included:

[0016] (1) The preparation method of the cordierite-based foam ceramic has the advantages of convenient and cheap raw material source, simple preparation process, low cordierite synthesis temperature and low energy consumption.

[0017] (2) The cordierite-based foam ceramic has the characteristics of high strength and good water permeability, and has high cordierite content, good crystallinity and high porosity. BRIEF DESCRIPTION OF DRAWINGS

[0018] The above and other objects and features of the present application will become more apparent from the following description made with reference to the accompanying drawings, in which:

[0019] Figure 1 The XRD diagram of the cordierite-based foam ceramic of Example 1 of the present application is shown;

[0020] Figure 2 The Micro-CT diagram of the cordierite-based foam ceramic of Example 2 of the present application is shown;

[0021] Figure 3 The cross-sectional view of Figure 2 is shown;

[0022] Figure 4 The SEM diagram of the cordierite-based foam ceramic of Example 2 of the present application is shown. DETAILED DESCRIPTION

[0023] Hereinafter, a cordierite-based foam ceramic and a preparation method and application thereof will be described in detail with reference to the accompanying drawings and exemplary embodiments.

[0024] Exemplary Embodiment 1

[0025] The present exemplary embodiment provides a preparation method of a cordierite-based foam ceramic.

[0026] The preparation method of the cordierite-based foam ceramic mainly includes the following steps:

[0027] S1, warm asbestos tailings and auxiliary materials are crushed and broken.

[0028] S2, the fly ash and the raw and auxiliary material powder are dosed and mixed and ground to obtain a green body powder.

[0029] S3, the green body powder is granulated, dried and aged to obtain a green body powder particle.

[0030] S4, the green body powder particle is pressed and formed to obtain a green body.

[0031] S5, the green body is dried and sintered in stages at a rising temperature to obtain a cordierite-based foam ceramic body.

[0032] S6, the cordierite-based foam ceramic body is post-treated.

[0033] In the present exemplary embodiment, the main raw materials used in the preparation method of the cordierite-based foam ceramic include fly ash and chrysotile tailings. The chrysotile tailings can be chrysotile tailings of ultrabasic rock type. No additional fluxing agent is added in the raw materials of the preparation method of the present application, only a small amount of bentonite and kaolin is added to make up for the insufficient silicon and aluminum in the raw materials and to enhance the plasticity of the green body. At the same time, due to the presence of a certain amount of fluxing components such as CaO, Na2O and K2O in the mixture, these components can be provided in the raw materials used, only the content is different, for example, CaO can be provided by fly ash, Na2O can be provided by bentonite, and K2O can be provided by kaolin. The fluxing components can promote the generation of α-cordierite phase and reduce the sintering temperature, which is an effective way of synthesizing cordierite.

[0034] Further, the chemical composition of fly ash can include 38-55% SiO2, 25-30% Al2O3, 5-12% Fe2O3, 2-7% CaO, 1-3% TiO2, 0.3-3% MgO, and 0.5-3% of trace components. The chemical composition of chrysotile tailings can include 40-58% SiO2, 30-46% MgO, 6-12% Fe2O3, 2-7% Al2O3, and 0.5-3.5% of trace components.

[0035] In the present exemplary embodiment, the auxiliary materials can include one or more of bauxite, kaolin and bentonite. Kaolin, bentonite and bauxite all belong to high-Si and high-Al raw materials, the content of SiO2 and Al2O3 can reach more than 90%, which can make up for the lack of silicon and aluminum sources in the raw materials, so that the stoichiometric ratio of chemical components in the system meets the stoichiometry of cordierite phase. At the same time, bentonite has strong water absorption and can be used as a plastic raw material to improve the plasticity of the green body in subsequent pressing.

[0036] Further, the chemical composition of kaolin can include 48-62% SiO2, 37-59% Al2O3, 0-3% Fe2O3, 0.5-3% K2O, and 0.5-5% of trace components. The chemical composition of bentonite can include 52-68% SiO2, 18-24% Al2O3, 6-12% Fe2O3, 4-9% MgO, 3-8% Na2O, and 0.5-7% of trace components. The chemical composition of bauxite can include 51-65% Al2O3, 41-52% SiO2, 2-8% Fe2O3, 2-7% TiO2, and 0.5-8% of trace components.

[0037] In the present exemplary embodiment, in the S1 step, the chrysotile asbestos tailings and auxiliary materials are broken and crushed to obtain raw material powder particles of-20 mesh, which facilitates subsequent mixing and grinding.

[0038] In the present exemplary embodiment, in the S2 step, the ingredients can include: weighing and mixing the raw materials, and the ratio by weight is: fly ash 45-55 parts, chrysotile asbestos tailings powder 30-40 parts, auxiliary material powder 15-25 parts, and foaming agent 0.1-0.6 parts. For example, the mass ratio of fly ash: chrysotile asbestos tailings powder: auxiliary material powder: foaming agent can be 45:35:20:0.2, 50:32:18:0.3, 55:35:20:0.5, etc., and no additional flux is added.

[0039] Further, the foaming agent can be SiC. The present application uses SiC as a foaming agent, which has the advantage of being more conducive to foaming and uniform bubble formation.

[0040] In the present exemplary embodiment, in the S2 step, the mixing and grinding can include: using dry grinding to obtain green body powder with a particle size of-200 mesh after mixing the ingredients. Here, the smaller the particle size of the green body powder, the better the performance indicators of the prepared foam ceramic. If the particle size is too large, for example, greater than 200 mesh, it will result in poor performance of the prepared foam ceramic, such as porosity, bulk density, water absorption, flexural strength, acid resistance, and alkali resistance. If the particle size is too large, the raw materials may not be uniformly mixed, or the contact reaction of the raw materials during sintering may not be sufficient, resulting in poor performance, and if the particle size of the raw materials is too small, it will also increase energy consumption.

[0041] Further, the mixed and ground materials can be placed in a ball mill, and balls are added at a ratio of material: ball = 1:0.8-1.2, under the condition of a rotation speed of 200-400 rpm for 30-90 min. For example, the rotation speed can be 224 rpm, 239 rpm, 289 rpm, 302 rpm, 338 rpm, 359 rpm, 379 rpm, etc. The ball milling time can be controlled at 39 min, 45 min, 55 min, 65 min, 75 min, 85 min, etc. The purpose is to enable the raw materials to be fully mixed and ground effectively. The amount of added balls should not be too low, as too low will result in poor flowability and ball milling effect. The amount of added balls should also not be too high, as too high will result in lower raw material quantity for one ball milling, thereby reducing efficiency. At the same time, the ball milling time should not be too short, as too short will result in insufficient ball milling, large particle size of the raw materials, and uneven mixing of the raw materials in the later stage, which can cause the foam ceramic to have layering or uneven foam, etc. The ball milling time should also not be too long, as too long will not significantly promote the preparation of the cordierite-based foam ceramic, and will increase energy consumption.

[0042] In the present exemplary embodiment, in the step S3, the granulation can include: spraying 6-10 parts, for example, 7 parts, 8 parts, 9 parts, etc., of the binder aqueous solution into the green body powder, taking the added amount of the green body powder as 100 parts. After the binder aqueous solution is sprayed uniformly, the granulation is started, and then 10-15 parts, for example, 11 parts, 12 parts, 13 parts, 14 parts, etc., of industrial water are sprayed. After the granules are formed into balls, the screening is performed. The granules can be screened by using a screen group composed of 20-mesh and 100-mesh standard screens. The uneven texture loose granular material obtained by molding is poured into the combined screen for screening, and the qualified powder particles are obtained by screening part of the screen, i.e., the qualified granules of the -20+100 mesh particle size, for example, 35 mesh, 45 mesh, 55 mesh, 65 mesh, 75 mesh, 85 mesh, 95 mesh, etc. The purpose is to make the granules uniformly dispersed in the mold during the compaction molding, so that the compacted body can be uniformly distributed, and the overall balance of the subsequent sintering sample is facilitated. Here, the +20 mesh particle size granules on the screen can be returned to the granulation starting step together with the -100 mesh particle size granules after being dispersed. Here, the granulation can use a disc granulator, and the frequency can be 40-50 Hz, for example, 42 Hz, 45 Hz, 48 Hz, etc. The present application adopts a two-stage granulation technology, which has the advantage of avoiding excessive use of binder aqueous solution and excessive viscosity, which can cause the particle size of the granules to be too large and affect the qualified rate of the qualified granules.

[0043] Further, the concentration of the binder aqueous solution used can be 0.5%-2%, for example, 0.55%, 0.65%, 0.75%, 0.85%, 0.95%, 1.25%, 1.55%, 1.75%, 1.85%, 1.95%, etc. The purpose of using this concentration is that a large amount of binder aqueous solution needs to be added for granulation. If the concentration used is too high, the viscosity of the granules will be too large, and after drying, hard particles will be formed, which is not conducive to the compaction. In terms of economy, the increase of the concentration of the binder aqueous solution will also increase the production cost.

[0044] Further, the binder can include one or more of polyvinyl alcohol, carboxymethyl cellulose, and carboxymethyl cellulose salt.

[0045] In the present exemplary embodiment, in the step S3, the drying can include: drying the qualified granules to a moisture content of 7-10%, for example, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, etc. The purpose is to prevent the particles from agglomerating due to excessive moisture, poor dispersibility, and poor molding effect due to low moisture, and to avoid leaving excess moisture in the mold during the subsequent compaction process, which can contaminate the mold.

[0046] In the present exemplary embodiment, in the step S3, the aging can include: aging the dried qualified granules in a sealed environment for more than 24 hours, so as to uniformly distribute the moisture in the granules, facilitate the subsequent compression molding and homogenization of the green body, and obtain qualified green powder particles after the aging is completed.

[0047] In the present exemplary embodiment, in the step S4, the compression molding can include: uniformly laying the green powder particles in a mold, and compressing under a pressure of 25-40 MPa, and keeping the pressure for 1-5 seconds, to obtain a green body after demolding. For example, keeping the pressure for 2 seconds under 30 MPa, keeping the pressure for 3 seconds under 35 MPa, or keeping the pressure for 4 seconds under 38 MPa. Here, if the molding pressure is low and the pressure keeping time is short during the compression molding, the molding is not easy. If the molding pressure and the pressure keeping time are increased, the performance of the product will be improved, but the improvement is not obvious. For example, after the pressure exceeds 40 MPa and the pressure keeping time reaches 5 seconds, the performance of the product will not be obviously improved, and the high pressure will increase the energy consumption, and the long pressure keeping time will reduce the production efficiency, thus, it is appropriate to keep the pressure for 1-5 seconds under a pressure of 25-40 MPa.

[0048] In the present exemplary embodiment, in the step S5, the drying of the green body can include: drying to a water content of less than 2%. The purpose is to remove the free water between the particles, and at the same time, to enhance the strength of the green body, prevent the green body from being damaged due to shaking or collision in the furnace, and avoid the evaporation of water in the green body due to the high water content in the subsequent heating process, so as to prevent the green body from being damaged and affect the final product.

[0049] In the present exemplary embodiment, in the step S5, the dried green body can be placed in a roller kiln, and the staged heating and sintering can include three stages.

[0050] The first stage: from room temperature to 400-500°C, the heating rate is 5-20°C / min, and the holding time is 15-30 min, so as to remove the binder and prevent the green body from cracking. For example, from room temperature to 460°C, the heating rate is 15°C / min, and the holding time is 25 min. Greater than 500°C is easy to crack, and less than 400°C is time-consuming. The heating is too fast, the heat is not uniform, and the heating is too slow, the time is long. The first stage can prevent the green body from cracking. If the green body cracks, the appearance and the pores of the final product prepared will be uneven, and the performance will be poor.

[0051] The second stage: from 400-500℃ to 900-1000℃, the heating rate is 5-15℃ / min, and the holding time is 15-30min. For example, the temperature is raised from 480℃ to 970℃ at a rate of 13℃ / min, and the holding time is 25min. In this way, the carbon and organic matter in the original material can be removed, and the structure of the chrysotile tailings can be changed. The chrysotile tailings belong to dangerous solid waste, and during the second stage of heat treatment, the carcinogenic clinochrysotile can be converted into a safe mineral phase. If the carbon and organic matter are not completely removed, it will affect the uniform foaming in the subsequent high-temperature process, and affect the performance. If the structure of the tailings cannot be completely destroyed at this temperature, it will also affect the physical and chemical reactions in the high-temperature reaction process, which is not conducive to the pore formation. If the heating is too fast, the heat transfer is uneven, and if it is too slow, the time is long, and the temperature range provided in the present application is beneficial to the volatilization of carbon.

[0052] The third stage: from 900-1000℃ to 1230-1300℃, the heating rate is 5-30℃ / min, and the holding time is 30-60min. For example, the temperature is raised from 960℃ to 1260℃ at a rate of 25℃ / min, and the holding time is 40min. The purpose is to promote the generation of liquid phase in the body, promote the foaming in the body, control the crystallization, control the pore size and connectivity (here, the opening, not the closed pore). When the temperature is less than 1230℃, the content of cordierite will be less, the foaming effect will not be obvious, and all the pores will be small and closed, with poor permeability, which is not suitable for use as a filter material. When the temperature is greater than 1300℃, the pores are prone to collapse, and qualified products cannot be obtained. The holding time should not be too long, otherwise the pores will collapse when the liquid phase flows excessively, and it is also not conducive to energy saving.

[0053] In the present exemplary embodiment, in the step S6, the post-processing can include: cooling the sintered cordierite-based foam ceramic body to room temperature with the furnace temperature decreasing and forced air cooling, so as to facilitate the subsequent processing. This process mainly utilizes the temperature difference between the inside and outside of the furnace to cool the sample, and when the temperature difference between the sample and the room temperature is small, the cooling speed of the sample with the furnace is slowed down, and at this time, the sample needs to be cooled by air cooling to quickly cool down.

[0054] In the present exemplary embodiment, in the step S6, the post-processing can further include: after cooling, cutting and trimming according to the size requirements, so that the prepared foam ceramic body is suitable for the required application.

[0055] Exemplary Embodiment 2

[0056] The present exemplary embodiment provides a cordierite-based foam ceramic.

[0057] The cordierite-based foam ceramic can be prepared by the preparation method of the cordierite-based foam ceramic described in the above exemplary embodiment 1.

[0058] In the present exemplary embodiment, the main crystal phase of the cordierite-based foam ceramic can be alpha-cordierite, and the content thereof can be 70-80%. The secondary crystal phase can be at least one of aluminum magnesium spinel phase and enstatite phase.

[0059] In the present exemplary embodiment, the bulk density of the cordierite-based foam ceramic can be 0.7-0.9 g / cm 3 , the compressive strength can be 3.5-5 MPa, the open porosity can be 43-50%, the water absorption can be 50-70%, the water permeability coefficient can be 0.6-0.8 mm / s, and the specific surface area can be 0.5-0.7 m 2 / g.

[0060] In order to better understand the above-mentioned exemplary embodiment 2 of the present application, it is further described below in combination with specific examples.

[0061] Figure 1 The XRD pattern of the cordierite-based foam ceramic of Example 1 of the present application is shown; Figure 2 The Micro-CT pattern of the cordierite-based foam ceramic of Example 2 of the present application is shown; Figure 3 The cross-sectional view of Figure 2 is shown; Figure 4 The SEM pattern of the cordierite-based foam ceramic of Example 2 of the present application is shown.

[0062] Example 1

[0063] (1) Taking warm asbestos tailings and fly ash as main raw materials, bentonite and kaolin as auxiliary materials, the warm asbestos tailings are broken and crushed to obtain warm asbestos tailings powder of -20 mesh.

[0064] (2) The warm asbestos tailings powder, bentonite and kaolin are weighed according to the mass ratio of fly ash: warm asbestos tailings powder: bentonite: kaolin: SiC = 53.5: 36: 8: 8: 0.3, and then placed in a ball mill jar. Balls are added according to the ratio of raw materials: balls = 1:1. Ball milling is carried out at a speed of 400 rpm for 60 minutes, and the sample is sieved with a standard sieve (200 mesh). The undersize sample is taken to obtain the green body powder, and the oversize sample is reused for secondary ball milling.

[0065] (3) The green body powder is placed in a round pan granulator. First, 8% of the binder aqueous solution with a concentration of 1% is sprayed under the condition of 50 Hz, and then 12% of industrial water is sprayed. The green body powder is formed into balls. The granules are sieved with a sieve group composed of 20 mesh and 100 mesh standard sieves. The middle part of the sieve is taken, and the undersize and oversize are reused. Then, the qualified granules in the middle part of the sieve are placed in a 90℃ oven for drying for 4h, so that the water content is about 8%. The granules are taken out and sealed in a sealed tank for aging for 24h to obtain the green body powder particles.

[0066] (4) Place the aged green powder into a pressing mold, hold it under pressure of 30 MPa for 2 seconds, and obtain the green body after demolding.

[0067] (5) Before sintering, the obtained green body is placed in an oven at 105℃ and dried for 8 hours to make its moisture content less than 2%. Then, the green body is heated to 450℃ in a high-temperature furnace at a heating rate of 20℃ / min and held for 20 minutes. Then, it is heated to 950℃ at a heating rate of 10℃ / min and held for 20 minutes. Finally, it is heated to 1240℃ at a heating rate of 20℃ / min and held for 30 minutes. After cooling with the furnace temperature, cordierite-based foam ceramics are obtained.

[0068] The XRD pattern of the cordierite-based foam ceramic prepared in this example is as follows: Figure 1 As shown, from Figure 1 It can be seen that the main crystalline phase of the prepared cordierite-based foam ceramic is α-cordierite. The content of this crystalline phase is 76%. It should be noted that XRD is X-ray diffraction. Figure 1 In this context, intensity represents the relative intensity, and 2theta represents the diffraction angle.

[0069] Example 2

[0070] (1) Take chrysotile asbestos tailings and fly ash as the main raw materials, and bentonite, kaolin and bauxite as auxiliary materials. Crush and pulverize the chrysotile asbestos tailings and bauxite to obtain -20 mesh chrysotile asbestos tailings powder and bauxite powder.

[0071] (2) Weigh the fly ash: chrysotile tailings powder: bentonite: kaolin: bauxite powder: SiC = 50: 32: 8: 6: 4: 0.2 by mass ratio, then place it in a ball mill jar, add balls at a ratio of raw material: ball = 1: 1, ball mill at 400 rpm for 60 min, and sieve the sample with a standard sieve (200 mesh), take the undersize sample to obtain the raw powder, and re-ball mill the oversize sample.

[0072] (3) Place the raw powder in a round pot granulator and spray 6% of a 1.2% binder aqueous solution at 50Hz, followed by 13% industrial water to make the raw powder spherical. Use a sieve group consisting of 20 mesh and 100 mesh standard sieves to screen the granules. Take the middle part of the sieve and reuse the underside and overside. Then place the qualified granules in the sieve in a 105℃ oven to dry for 4 hours to make the moisture content about 8%. After cooling to room temperature, put them in a sealed container and age for 24 hours to obtain raw powder granules.

[0073] (4) Place the aged green powder into a pressing mold, hold it under pressure of 30 MPa for 2 seconds, and obtain the green body after demolding.

[0074] (5) Before sintering, the green body is placed in an oven at 105℃ and dried for 8 hours to make its moisture content less than 2%. Then, the green body is heated to 450℃ in a high-temperature furnace at a heating rate of 20℃ / min and held for 20 minutes. Then, it is heated to 950℃ at a heating rate of 10℃ / min and held for 20 minutes. Finally, it is heated to 1240℃ at a heating rate of 20℃ / min and held for 30 minutes. After cooling with the furnace temperature, cordierite-based foam ceramics are obtained.

[0075] Performance tests were conducted on the product, and the bulk density of the microcrystalline ceramic product in Example 2 was 0.74 g / cm³. 3 It has a compressive strength of 4.8 MPa, an open porosity of 45.38%, a water absorption rate of 52.31%, a permeability coefficient of 0.66 mm / s, and a specific surface area of ​​0.67 m². 2 / g.

[0076] Figure 2 This is a Micro-CT image of cordierite-based foam ceramics, showing the cross-sectional view. Figure 3 The cordierite-based foam ceramic clearly shows an open-cell structure, which is advantageous for its application in building and filtration materials. Examples include interior wall decoration, sound-absorbing materials, and wastewater and water purification filtration materials. It should be noted that Micro-CT stands for micro computed tomography.

[0077] Figure 4 This is a SEM image of cordierite-based foam ceramics. The image shows that cordierite and the liquid phase intertwine to form an aggregate on the inner wall structure of the foam ceramic. This intertwined structure helps improve the strength of the foam ceramic. Furthermore, due to the high-temperature resistance of cordierite, this foam ceramic material can be used in high-temperature environments. It should be noted that SEM refers to scanning electron microscopy.

[0078] Exemplary Example 3

[0079] This exemplary embodiment provides an application of cordierite-based foam ceramics.

[0080] Applications of cordierite-based foam ceramics may include interior wall decoration, sound-absorbing materials, or waste liquid and water purification filtration materials.

[0081] In summary, the advantages proposed by this invention include at least one of the following:

[0082] (1) The preparation method of the present invention uses chrysotile asbestos tailings and fly ash as the main raw materials, and the comprehensive utilization rate of solid waste can reach more than 75%, which puts forward a new idea for the resource utilization of hazardous solid waste chrysotile asbestos tailings.

[0083] (2) The preparation method of the present application utilizes the alkali metal oxides contained in the yellow sand, and the cordierite-based foam ceramic can be prepared at a lower temperature without adding additional fluxing agent in the foam ceramic batch.

[0084] (3) The cordierite-based foam ceramic provided by the present application can be applied to interior wall decoration, sound-absorbing material or waste liquid and water purification filtering material.

[0085] Although the cordierite-based foam ceramic, its preparation method and application have been described above by combining the exemplary embodiments, it should be clear for those skilled in the art that various modifications and changes can be made to the exemplary embodiments of the present application without departing from the spirit and scope defined by the claims.

Claims

1. A method for preparing a cordierite-based foam ceramic, characterized by, The preparation method comprises the steps of: The fly ash, chrysotile tailings and auxiliary materials are proportioned and mixed and ground to obtain a green body powder; The proportioning comprises: the fly ash, chrysotile tailings, auxiliary materials and foaming agent are proportioned at a mass ratio of 45-55:30-40:15-25:0.1-0.6; The green body powder is granulated, dried and aged to obtain a green body powder particle; The green body powder particle is pressed to form a green body; The green body is dried and sintered in a stage-by-stage temperature rising mode to obtain a cordierite-based foam ceramic material; The stage-by-stage temperature rising sintering of the dried green body comprises three stages: from room temperature to 400-500 DEG C, the temperature rising rate is 5-20 DEG C / min, the holding time is 15-30 min; from 400-500 DEG C to 900-1000 DEG C, the temperature rising rate is 5-15 DEG C / min, the holding time is 15-30 min; from 900-1000 DEG C to 1230-1300 DEG C, the temperature rising rate is 5-30 DEG C / min, the holding time is 30-60 min; The main crystal phase of the cordierite-based foam ceramic material is alpha-cordierite, the content of which is 70-80%, and the open porosity is 43-50%.

2. The method of claim 1, wherein the method further comprises the step of: Before the proportioning, the chrysotile tailings and auxiliary materials are broken and crushed to obtain a -20 mesh raw material powder particle; After the stage-by-stage temperature rising sintering, the sintered cordierite-based foam ceramic material is post-treated, which comprises: the sintered cordierite-based foam ceramic material is cooled with the furnace temperature and forced air cooling, and then is cut and trimmed according to the size requirements after cooling; The chrysotile tailings are ultrabasic rock type chrysotile tailings; The auxiliary materials comprise one or more of bauxite, kaolin and bentonite.

3. The method of claim 2, wherein the method further comprises the step of: The fly ash has a chemical component mass percentage of 38-55% SiO2, 25%-30% Al2O3, 5%-12% Fe2O3, 2%-7% CaO, 1-3% TiO2, 0.3%-3% MgO and 0.5-3% of the balance of trace components; The chrysotile tailings have a chemical component mass percentage of 40-58% SiO2, 30-46% MgO, 6-12% Fe2O3, 2-7% Al2O3 and 0.5-3.5% of the balance of trace components; The kaolin has a chemical component mass percentage of 48-62% SiO2, 37%-59% Al2O3, 0-3% Fe2O3, 0.5-3% K2O and 0.5-5% of the balance of trace components; The bentonite has a chemical component mass percentage of 52-68% SiO2, 18-24% Al2O3, 6-12% Fe2O3, 4-9% MgO, 3-8% Na2O and 0.5-7% of the balance of trace components; The bauxite has a chemical component mass percentage of 51%-65% Al2O3, 41-52% SiO2, 2-8% Fe2O3, 2-7% TiO2 and 0.5-8% of the balance of trace components.

4. The method of claim 1, wherein the method further comprises the step of: The mixed grinding comprises: using dry grinding to obtain the green body powder with particle size of-200 mesh.

5. The method of claim 4, wherein the method further comprises the step of: The foaming agent is SiC.

6. The method of claim 1, wherein the method further comprises the step of: The granulation comprises: spraying 0.5-2% adhesive aqueous solution 6-10 parts into the green body powder, taking the added amount of the green body powder as 100 parts, spraying industrial water 10-15 parts into the green body powder when starting granulation, and screening the granules to obtain qualified granules with particle size of-20-+100 mesh; The adhesive comprises one or more of polyvinyl alcohol, carboxymethyl cellulose and carboxymethyl cellulose salt. The drying comprises: drying the qualified granules to have water content of 7-10%. The aging comprises: sealing the dried qualified granules and aging for more than 24 hours.

7. The method of claim 1, wherein the method further comprises the step of: The press forming comprises: placing the green body powder granules in a mold, pressing under a pressure of 25-40 MPa, keeping pressure for 1-5 seconds, and demolding to obtain the green body. ​ 8. The method of claim 1, wherein the method further comprises the step of: The drying of the green body comprises: drying to have water content of less than 2%. ​ 9. A cordierite-based foam ceramic, characterized by, The cordierite-based foam ceramic is prepared by the method of claim 1-8, and has a bulk density of 0.7-0.9 g / cm 3 , a compressive strength of 3.5-5 MPa, a water absorption of 50-70%, a water permeability coefficient of 0.6-0.8 mm / s, and a specific surface area of 0.5-0.7 m 2 / g.

10. The cordierite-based foam ceramic in claim 9, applied in interior wall decoration, sound absorption material or waste liquid and water purification filter material.

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