NL2033277B1

NL2033277B1 - Method for preparing porous ceramic

Info

Publication number: NL2033277B1
Application number: NL2033277A
Authority: NL
Inventors: Zhang Xizhi
Original assignee: Macao Univ Of Science And Technology
Priority date: 2022-10-11
Filing date: 2022-10-11
Publication date: 2023-06-16

Abstract

The present invention discloses a method for preparing a porous ceramic. A certain mass ratio of high white slurry and water are mixed to obtain ceramic slurry, wherein the high white slurry includes silica, alumina, potassium oxide, and sodium oxide. The ceramic slurry is added into a mixer, and kapok fiber after being air-dried under a natural air condition is added into the mixer, so that the ceramic slurry is impregnated with the air-dried kapok fiber. Alternatively, polymethyl methacrylate particles are added into the mixer to perform foaming processing on the ceramic slurry. In this way, a porous ceramic blank with better mechanical properties and not easy to collapse can be prepared. A porous ceramic with a high porosity, a controllable pore size, and excellent mechanical properties can be obtained after the porous ceramic blank is performed with sintering processing. (Fig. 1)

Description

METHOD FOR PREPARING POROUS CERAMIC

FIELD OF THE INVENTION

[0001] The present invention relates to the technical field of preparing porous ceramic materials, and in particular, to a method for preparing a porous ceramic.

BACKGROUND OF THE INVENTION

[0002] Porous ceramic is a ceramic material prepared through high-temperature sintering with a large number of internal pore structures that are connected with each other and are connected with the ceramic surface. According to pore sizes, porous ceramics can be classified into microporous ceramics (whose pore sizes are smaller than 2 nm), mesoporous ceramics (whose pore sizes are between 2 nm and 50 nm), and macroporous ceramics (whose pore sizes are greater than 50 nm). The porous ceramic has functions of filtration and separation, sound absorption and noise reduction, and reaction catalyzing due to advantages of high porosity, good surface activity, high temperature resistance, and corrosion resistance, and therefore is widely applied to the fields of sound-absorbing and noise-reducing materials, catalyst carriers, and biomedical. Meanwhile, the porous ceramic has advantages of excellent chemical stability, thermal stability, low density, low thermal conductivity, and high specific surface area, and therefore is widely applied to the fields of wastewater filtration and separation, catalyst carriers, thermal insulation materials, and electromagnetic wave absorbing materials.

[0003] Existing techniques for preparing the porous ceramic mainly include: the foaming method, the organic (polymer) foam impregnation technique, the pore-forming agent adding technique, and the solid-state sintering method. The porous ceramic material prepared by the foaming method has uniform pores and is mostly used for preparing closed- pore products, wherein closed pores are formed because the heating rate is so fast that the bubbles do not have enough time to diffuse to the surface of the ceramic material and remain within the ceramic material. However, conditions for the preparation technique of the closed-pore product are difficult to control, and the prepared porous ceramic has problems that the ceramic skeleton has low strength and has a lot of defects. The pore size of a porous ceramic prepared by the organic (polymer) foam impregnation technique mainly depends on a pore size of a selected organic (polymer) foam material, and the pore size and distribution of the prepared porous ceramic are limited. Moreover, strength of a porous ceramic blank prepared by the organic (polymer) foam impregnation technique is relatively weak, and has high requirements on fluidity of ceramic slurry. The porous ceramic material with a complex shape can be prepared by the pore-forming agent adding technique, but the ceramic material has poor uniformity of pore distribution, making it difficult to prepare a porous ceramic material with a high porosity. Factors such as density and sintering conditions (temperature, atmosphere, and pressure) of a porous ceramic blank obtained by the solid-state sintering method have great influence on the microstructure of the pore size of a porous ceramic obtained through sintering, and the pore size of the prepared porous ceramic is poorly controllable.

[0004] Therefore, how to prepare a porous ceramic material with a high porosity, good mechanical property, and a controllable pore size is a problem to be resolved urgently.

SUMMARY OF THE INVENTION

[C003] To resolve a problem in the prior art that a prepared porous ceramic has a low porosity, poor mechanical properties, and poor controllability of a pore size, the present invention discloses a method for preparing a porous ceramic, including the following steps:

[00086] step 1, adding high white slurry and water into a mixer, and starting the mixer to stir to obtain ceramic slurry;

[0007] step 2, adding pretreated kapok fiber into the mixer to perform impregnation processing on the ceramic slurry, drying, and then preparing a porous ceramic blank, or

[0008] adding polymethyl methacrylate particles into the mixer to perform foaming processing on the ceramic slurry to obtain mixed slurry, and pouring the mixed slurry into a mold and drying, to prepare a porous ceramic blank; and

[0009] step 3, sintering of the porous ceramic blank in a high-temperature furnace to prepare the porous ceramic.

[0010] In some implementations of the present invention, in step 2, the step of adding pretreated kapok fiber into the mixer to perform impregnation processing on the ceramic slurry, drying, and then preparing a porous ceramic blank specifically includes:

[0011] adding the pretreated kapok fiber into the mixer to completely impregnate the ceramic slurry; taking out the kapok fiber and then discharging excess ceramic slurry in the kapok fiber through extrusion or centrifugal rotation; drying the kapok fiber after the foregoing steps are repeated for 3-5 times; and adjusting temperature for drying and time for drying, to prepare the porous ceramic blank.

[0012] In some implementations of the present invention, the pretreated kapok fiber instep 2 is kapok fiber with a water content less than 20% after being air-dried under natural arr.

[0013] In some implementations of the present invention, the mass ratio of the ceramic slurry to the kapok fiber is 5-10:1.

[0014] In some implementations of the present invention, the mass ratio of the high white slurry to water is 17.18:1-1.5.

[0015] The applicant finds that, when the ceramic slurry includes the high white slurry and water, the mass ratio of the high white slurry to water is 17.18:1-1.5, the kapok fiber is placed in a natural air condition for air-drying, the water content of the air-dried kapok fiber is less than 20%, and the mass ratio of the ceramic slurry to the kapok fiber is 5-10:1, adding the kapok fiber with a water content less than 20% into the mixer can fully impregnate the ceramic slurry with the kapok fiber. The ceramic slurry with excellent thixotropy has better fluidity under external force, and viscosity of the ceramic slurry is reduced. In this case, the kapok fiber can be fully impregnated, which facilitates extrusion of the ceramic slurry in the kapok fiber performed with the impregnation processing. After the ceramic slurry in the kapok fiber is extruded, the external force disappears, and the ceramic slurry remains in a gel state because the viscosity of the ceramic slurry increases and the fluidity thereof decreases. Subsequently, the kapok fiber is dried, so that the ceramic slurry on the kapok fiber can be easily solidified and shaped, thereby avoiding a problem that holes are plugged because the ceramic slurry flows and falls off.

[00186] Meanwhile, the kapok fiber is placed in a natural air condition for air-drying, and the water content of the air-dried kapok fiber is less than 20%. The naturally air-dried kapok fiber is not deformed, and has relatively low decomposition temperature. After the ceramic slurry is fully impregnated with the kapok fiber with a water content less than 20% and the excess ceramic slurry is extruded, the porous ceramic blank prepared by drying the kapok fiber has better mechanical properties. In this case, damages to the porous ceramic blank caused by thermal stress can be effectively avoided during the drying process, and collapse of the porous ceramic blank can be avoided. Moreover, the pore size of the porous ceramic mainly depends on the pore size of the kapok fiber. The porous ceramic blank obtained by impregnating the ceramic slurry with the kapok fiber has good mechanical properties and is not easy to collapse. Therefore, the porous ceramic prepared by performing sintering processing on the porous ceramic blank has a high porosity, a controllable pore size, and excellent mechanical properties, and thus a honeycombed porous ceramic with high strength, interconnected pores, and a high porosity can be prepared.

[0017] In some implementations of the present invention, in step 2, the step of adding polymethyl methacrylate particles into the mixer to perform foaming processing on the ceramic slurry, to obtain mixed slurry, and preparing a porous ceramic blank after the mixed slurry is poured into a mold for drying specifically includes:

[0018] adding the polymethyl methacrylate particles into the mixer; starting the mixer to stir the ceramic slurry and the polymethyl methacrylate particles, so that the polymethyl methacrylate particles perform foaming processing on the ceramic slurry to obtain the mixed slurry; pouring the mixed slurry into the mold; drying the mixed slurry; and adjusting temperature for drying and time for drying, to prepare the porous ceramic blank.

[0019] In some implementations of the present invention, the mass ratio of the ceramic slurry to the polymethyl methacrylate particles is 15:1-2.

[0020] In some implementations of the present invention, the diameter of the polymethyl methacrylate particle is 5 mm.

[0021] In some implementations of the present invention, the high white slurry includes silica, alumina, potassium oxide, and sodium oxide; and the mass ratio of the silica, the alumina, the potassium oxide, and the sodium oxide is 34.5-35.5:9.5-10.5:1:1-1.25.

[0022] In some implementations of the present invention, the temperature for drying is 25-30°C, and the time for drying is 24-48 h. 5 [0023] In some implementations of the present invention, in step 1, stirring time is 5-10 min, and a stirring rate is 800-1200 r/min.

[0024] The applicant finds that when the ceramic slurry includes the high white slurry and water, the mass ratio of the high white slurry to water is 17.18:1-1.5, and the mass ratio of the ceramic slurry to the polymethyl methacrylate particles is 15:1-2, the ceramic slurry with excellent thixotropy has better fluidity under external force, and viscosity of the ceramic slurry is reduced. In this case, the ceramic slurry can be fully immersed into pores of the polymethyl methacrylate particle and fully wrap the polymethyl methacrylate particle. When stirring of the ceramic slurry and the polymethyl methacrylate particles is stopped, the external force disappears, and the ceramic slurry remains in a gel state because the viscosity of the ceramic slurry increases and the fluidity thereof decreases. In this way, the ceramic slurry on the polymethyl methacrylate particles can be easily solidified and shaped, thereby avoiding a problem that holes are plugged because the ceramic slurry flows and falls off.

[0025] In addition, the polymethyl methacrylate particle has a diameter of 5 mm, has certain hardness, is not easy to deform, and has relatively low decomposition temperature. The porous ceramic blank prepared from the polymethyl methacrylate particles and the ceramic slurry through stirring, mold forming, and drying has better mechanical properties. In this case, damage to the porous ceramic blank caused by thermal stress is effectively avoided during the drying process, and collapse of the porous ceramic blank is avoided. Therefore, the porous ceramic prepared by performing sintering processing on the porous ceramic blank has a high porosity, a controllable pore size, and excellent mechanical properties, and thus a porous ceramic with high strength, uniform pore size distribution, and a high porosity can be prepared.

[0026] In some implementations of the present invention, in step 3, the sintering of the porous ceramic blank in a high-temperature furnace specifically includes:

[0027] putting the porous ceramic blank into the high-temperature furnace; heating the high-temperature furnace from 25-30°C to 380-420°C at a heating rate of 2°C/min, and keeping the temperature for 3.8-4.5 h; subsequently, heating the high-temperature furnace to 1200-1250°C at a heating rate of 5°C/min, and keeping the temperature for 3.8-4.5 h; and finally, cooling for 7.5-8.5 h to complete sintering, to prepare the porous ceramic.

[0028] The porous ceramic blank is placed in the high-temperature furnace, and the sintering process is divided into a low-temperature sintering stage (during which the high- temperature furnace is heated from 25-30°C to 400-450°C at a heating rate of 2°C/min; and the temperature is kept for 4-4.5 h) and a high-temperature sintering stage (during which the high-temperature furnace is heated from 400-450°C to 1200-1250°C at a heating rate of 5°C/min; the temperature is kept for 4-4.5 h; and finally, cooling is performed for 8-8.5 h).

The applicant finds that, heating slowly at the low-temperature sintering stage can not only make the polymethyl methacrylate particle or the kapok fiber fully decomposed and volatilized during the sintering process, but also avoid a problem of cracking or collapse of the porous ceramic blank caused by violent decomposition of the polymethyl methacrylate particle or the kapok fiber due to a too fast heating rate. At the high-temperature sintering stage, the heating rate can be appropriately increased, so as to save sintering time.

[0029] In view of the above, according to the present invention, the kapok fiber with a water content less than 20% after being air-dried under a natural air condition is added into the mixer, so that the ceramic slurry is impregnated with the air-dried kapok fiber with a water content less than 20%. Alternatively, the polymethyl methacrylate particles are added into the mixer to perform foaming processing on the ceramic slurry. In this way, a porous ceramic blank with better mechanical properties and not easy to collapse can be prepared. A porous ceramic with a high porosity, a controllable pore size, and excellent mechanical properties can be obtained after the porous ceramic blank is performed with sintering processing. Compared with the prior art, the method for preparing a porous ceramic disclosed in the present invention has the following advantages.

[0030] (1) The kapok fiber used for performing impregnation processing on the ceramic slurry is the kapok fiber with a water content less than 20% after being air-dried under a natural air condition, which can improve roughness and hydrophilicity of a kapok fiber skeleton, so that the ceramic slurry can be fully impregnated with the kapok fiber.

Moreover, the naturally air-dried kapok fiber is not deformed. During the drying process, the ceramic slurry on the kapok fiber can be easily solidified and shaped, thereby avoiding a problem that holes are plugged because the ceramic slurry flows and falls off.

[0031] (2) The naturally air-dried kapok fiber with a water content less than 20% is not deformed. After the ceramic slurry is fully impregnated with the air-dried kapok fiber with a water content less than 20% and the excess ceramic slurry is extruded, the porous ceramic blank prepared by drying the kapok fiber has better mechanical properties.

Moreover, the pore size of the porous ceramic mainly depends on the pore size of the kapok fiber. By adjusting temperature during the sintering process, heating slowly at the low- temperature sintering stage can not only make the polymethyl methacrylate particle or the kapok fiber fully decomposed and volatilized during the sintering process, but also avoid a problem of cracking or collapse of the porous ceramic blank caused by violent decomposition of the polymethyl methacrylate particle due to a too fast heating rate. After the porous ceramic blank is performed with sintering processing, a honeycombed porous ceramic with high strength, interconnected pores, and a high porosity can be prepared.

[0032] (3) The ceramic slurry includes high white slurry and water. A surface modification step for natural kapok fiber is saved by impregnating the ceramic slurry with the kapok fiber. Therefore, the preparation technique is simple, and the ceramic slurry can be more firmly bonded to the kapok fiber skeleton. According to the present invention, preparing the ceramic slurry by mixing the high white slurry with water can significantly improve dispersibility and stability of the ceramic slurry.

[0033] (4) A pore-making step for the porous ceramic is saved by performing foaming processing on the ceramic slurry with the polymethyl methacrylate particles. The pore size of the porous ceramic is determined by the size of the polymethyl methacrylate particle, wherein a larger particle size indicates a lower porosity of the porous ceramic. If a guantity of pores with small pore sizes increases, the pore size distribution is more uniform.

Moreover, the polymethyl methacrylate particle has certain hardness and is not easy to deform, and thus a closed-pore porous ceramic with relatively high strength, uniform pore size distribution, and a high porosity can be prepared.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a surface morphology diagram of kapok fiber with a water content of 17% after being air-dried under a natural air condition according to Embodiment 1 of the present invention;

[0035] FIG. 2 is a surface morphology diagram of a honeycombed porous ceramic prepared according to Embodiment 1 of the present invention;

[0036] FIG. 3 is a surface morphology diagram of polymethyl methacrylate particles according to Embodiment 3 of the present invention; and

[0037] FIG. 4 is a surface morphology diagram of a closed-pore porous ceramic prepared according to Embodiment 3 of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] To make the foregoing objectives, features, and advantages of this application more obvious and easier to be understood, this application is further described in detail below with reference to specific implementations.

[0039] Embodiment 1

[0040] Step 1. High white slurry and water were added into a mixer, and the mixer was started to stir, wherein stirring time was 5 min and a stirring rate was 800 r/min. In this way, ceramic slurry was prepared.

[0041] Step 2. Kapok fiber with a water content of 17% after being air-dried under a natural air condition was added into the mixer, so that the kapok fiber was completely immersed in the ceramic slurry; the kapok fiber was taken out and then excess ceramic slurry in the kapok fiber was discharged through centrifugal rotation; and the kapok fiber was dried at a temperature condition of 25°C for 30 h after the foregoing steps were repeated for 4 times. In this way, a porous ceramic blank was prepared.

[0042] Step 3. The porous ceramic blank was put in a high-temperature furnace; the high-temperature furnace was heated from 25°C to 400°C at a heating rate of 2°C/min, and the temperature was kept for 4 h; subsequently, the high-temperature furnace was heated to 1230°C at a heating rate of 5°C/min, and the temperature was kept for 4 h; and finally, cooling was performed for 8 h to complete sintering. In this way, a honeycombed porous ceramic was prepared.

[0043] The mass ratio of the high white slurry to water is 17.18:1.

[0044] The high white slurry includes silica, alumina, potassium oxide, and sodium oxide. The mass ratio of the silica, the alumina, the potassium oxide, and the sodium oxide is 34.5:10.5:1:1.25.

[0045] The mass ratio of the ceramic slurry to the kapok fiber is 10:1.

[0046] Embodiment 2

[0047] Step 1. High white slurry and water were added into a mixer, and the mixer was started to stir, wherein stirring time was 8 min and a stirring rate was 1000 r/min. In this way, ceramic slurry was prepared.

[0048] Step 2. Kapok fiber with a water content of 15% after being air-dried under a natural air condition was added into the mixer, so that the kapok fiber was completely immersed in the ceramic slurry; the kapok fiber was taken out and then excess ceramic slurry in the kapok fiber was discharged through extrusion; and the kapok fiber was dried at atemperature condition of 28°C for 40 h after the foregoing steps were repeated for 5 times.

In this way, a porous ceramic blank was prepared.

[0049] Step 3. The porous ceramic blank was put in a high-temperature furnace; the high-temperature furnace was heated from 27°C to 410°C at a heating rate of 2°C/min, and the temperature was kept for 4.3 h; subsequently, the high-temperature furnace was heated to 1240°C at a heating rate of 5°C/min, and the temperature was kept for 4.3 h; and finally, cooling was performed for 8.3 h to complete sintering. In this way, a honeycombed porous ceramic was prepared.

[0050] The mass ratio of the high white slurry to water is 17.18:1.3.

[0051] The high white slurry includes silica, alumina, potassium oxide, and sodium oxide. The mass ratio of the silica, the alumina, the potassium oxide, and the sodium oxide is 35.5:9.5:1:1.

[0052] The mass ratio of the ceramic slurry to the kapok fiber is 7:1.

[0053] Embodiment 3

[0054] Step 1. High white slurry and water were added into a mixer, and the mixer was started to stir, wherein stirring time was 10 min and a stirring rate was 1200 r/min. In this way, ceramic slurry was prepared.

[0055] Step 2. Polymethyl methacrylate particles with a diameter of 5 mm were added into the mixer; the mixer was started to stir the ceramic slurry and the polymethyl methacrylate particles, so that the polymethyl methacrylate particles perform foaming processing on the ceramic slurry to obtain mixed slurry; the mixed slurry was poured into a mold; and the kapok fiber was dried at a temperature condition of 30°C for 24 h. In this way, a porous ceramic blank was prepared.

[0056] Step 3. The porous ceramic blank was put in a high-temperature furnace; the high-temperature furnace was heated from 28°C to 380°C at a heating rate of 2°C/min, and the temperature was kept for 4 h; subsequently, the high-temperature furnace was heated to 1200°C at a heating rate of 5°C/min, and the temperature was kept for 4 h; and finally, cooling was performed for 7.5 h to complete sintering. In this way, a closed-pore porous ceramic was prepared.

[0057] The mass ratio of the high white slurry to water is 17.18:1.

[0058] The high white slurry includes silica, alumina, potassium oxide, and sodium oxide. The mass ratio of the silica, the alumina, the potassium oxide, and the sodium oxide is 34.5:10.5:1:1.25.

[0059] The mass ratio of the ceramic slurry to the polymethyl methacrylate particles is 15:1.

[0060] Embodiment 4

[0061] Step 1. High white slurry and water were added into a mixer, and the mixer was started to stir, wherein stirring time was 7 min and a stirring rate was 900 r/min. In this way, ceramic slurry was prepared.

[0062] Step 2. Polymethyl methacrylate particles with a diameter of 5 mm were added into the mixer; the mixer was started to stir the ceramic slurry and the polymethyl methacrylate particles, so that the polymethyl methacrylate particles perform foaming processing on the ceramic slurry to obtain mixed slurry; the mixed slurry was poured into a mold; and the kapok fiber was dried at a temperature condition of 27°C for 48 h. In this way, a porous ceramic blank was prepared.

[9063] Step 3. The porous ceramic blank was put in a high-temperature furnace; the high-temperature furnace was heated from 30°C to 420°C at a heating rate of 2°C/min, and the temperature was kept for 4.5 h; subsequently, the high-temperature furnace was heated to 1250°C at a heating rate of 5°C/min, and the temperature was kept for 4.5 h; and finally, cooling was performed for 8.5 h to complete sintering. In this way, a closed-pore porous ceramic was prepared.

[0064] The mass ratio of the high white slurry to water is 17.18:1.5.

[0065] The high white slurry includes silica, alumina, potassium oxide, and sodium oxide. The mass ratio of the silica, the alumina, the potassium oxide, and the sodium oxide is 35.5:9.5:1:1.25.

[0066] The mass ratio of the ceramic slurry to the polymethyl methacrylate particles is 15:1.7.

[0067] Performance test:

[0068] The porosities of the porous ceramics obtained in Embodiment 1,

Embodiment 2, Embodiment 3, and Embodiment 4 were tested by a ceramic porosity tester, and the porosities were respectively 70-90%, 70-90%, 40-90%, and 40-90%.

[0069] Surface morphology diagrams of the porous ceramics prepared in

Embodiment 1 and Embodiment 3 were respectively tested by an SEM scanning electron microscope. The surface morphology diagrams of the porous ceramics prepared in

Embodiment 1 and Embodiment 3 were shown in FIG. 2 and FIG. 4, respectively.

[0070] In view of the above, according to Embodiment 1, the kapok fiber is placed in a natural air condition for air-drying, and the water content of the air-dried kapok fiber is 17%. The ceramic slurry can be fully impregnated by adding the air-dried kapok fiber with a water content of 17% into the mixer. The naturally air-dried kapok fiber with a water content of 17% is not deformed. Subsequently, the porous ceramic blank is prepared by drying the kapok fiber. The prepared porous ceramic blank has better mechanical properties, and thus a problem of collapse of the porous ceramic blank can be effectively avoided, wherein such problem is caused by the damage to the porous ceramic blank due to thermal stress during the drying process. On this basis, after sintering processing is performed on the porous ceramic blank, a honeycombed porous ceramic with relatively high strength, interconnected pores, and a porosity up to 70-90% can be prepared. The preparation technique is simple with low costs, and the prepared honeycombed porous ceramic with a porosity of 70-90% can be applied to sound-absorbing and noise-reducing materials.

[0071] According to Embodiment 3, the polymethyl methacrylate particle with a diameter of 5 mm, which has certain hardness and is not easy to deform and has relatively low decomposition temperature, is mixed with the ceramic slurry. Subsequently, the porous ceramic blank prepared through mold forming and drying has better mechanical properties, and thus a problem of collapse of the porous ceramic blank can be effectively avoided, wherein such problem is caused by the damage to the porous ceramic blank due to thermal stress during the drying process. On this basis, after sintering processing is performed on the porous ceramic blank, a closed-pore porous ceramic with relatively high strength, uniform pore size distribution, and a porosity of 40-90% can be prepared. The prepared closed-pore porous ceramic can be applied to sound-absorbing and noise-reducing materials.

[0072] This application is described above in detail with reference to specific implementations and exemplary examples. However, these descriptions should not be construed as limitation to this application. A person skilled in the art should understand that, without departing from the spirit and the scope of this application, various equivalent replacements, modifications, or improvements can be made to the technical solutions and implementations of this application, which shall all fall within the scope of this application.

The protection scope of this application shall be subject to the appended claims.

Claims

CONCLUSIONS

A method for manufacturing a porous ceramic, comprising the following steps: step 1, adding a high-white slurry and water to a mixer, and starting the mixer to obtain a ceramic slurry by stirring ; step 2, adding pre-treated kapok fibers to the mixer to perform an impregnating action on the ceramic slurry, drying and then manufacturing a porous ceramic substrate ('blank'), or adding polymethyl methacrylate particles to the mixer to performing a foaming action on the ceramic slurry to obtain a mixed slurry, and preparing a porous ceramic substrate after the mixed slurry is poured into a mold to dry; and step 3, sintering the porous ceramic substrate in a high temperature furnace to produce the porous ceramic.

The method for manufacturing a porous ceramic according to claim 1, wherein in step 2, the step of adding pretreated kapok fiber to the mixer to perform an impregnating action on the ceramic slurry, drying and then preparing a porous ceramic substrate specifically includes: adding the pretreated kapok fiber to the mixer to fully impregnate the ceramic slurry; removing the kapok fiber and then discharging excess ceramic slurry in the kapok fiber by extrusion or by centrifugal rotation; drying the kapok fiber after repeating the previous steps 3-5 times; and adjusting the drying temperature and drying time to produce the porous ceramic substrate.

The method for manufacturing a porous ceramic according to claim 2, wherein the pre-treated kapok fiber in step 2 is kapok fiber having a water content of less than 20% after being air-dried under a natural air condition.

The method for manufacturing a porous ceramic according to claim 2, wherein a mass ratio between the ceramic slurry and the kapok fiber is 5-10:1.

The method for manufacturing a porous ceramic according to claim 1, wherein in step 2, the step of adding polymethyl methacrylate particles to the mixer to perform the foaming action on the ceramic slurry to obtain the mixed slurry, and preparing a porous ceramic substrate after the mixed slurry is poured into a mold for drying, specifically comprising: adding the polymethyl methacrylate particles to the mixer; starting the mixer to stir the ceramic slurry and the polymethyl methacrylate particles so that the polymethyl methacrylate particles perform a foaming action on the ceramic slurry to obtain the mixed slurry; pouring the mixed slurry into the mould; drying the mixed slurry; and adjusting the drying temperature and drying time to prepare the porous ceramic substrate.

The method for manufacturing a porous ceramic according to claim 5, wherein a mass ratio between the ceramic slurry and the polymethyl methacrylate particles is 15:1-2.

The method for manufacturing a porous ceramic according to claim 3 or 6, wherein a mass ratio between the high white slurry and water is 17.18:1-1.5.

The method for manufacturing a porous ceramic according to claim 7, wherein the high white slurry comprises silica, alumina, potassium oxide and sodium oxide; and wherein a mass ratio of the silica, alumina, potassium oxide and sodium oxide is 34.5-35.5:9.5-10.5:1:1-1.25.

The method for manufacturing a porous ceramic according to claim 2 or 5, wherein the drying temperature is 25-30°C and the drying time is 24-48 hours.

The method for manufacturing a porous ceramic according to claim 1, wherein in step 3, sintering the porous ceramic substrate in a high temperature furnace specifically comprises the steps of:

placing the porous ceramic substrate in the high temperature furnace; heating the high temperature oven from 25-30°C to 380-420°C at a heating rate of 2°C/min, and maintaining the temperature for 3.8-4.5 hours; then heating the high temperature furnace to 1200-1250°C at a heating rate of 5°C/min, and maintaining the temperature for 3.8-4.5 hours; and finally cooling for 7.5-8.5 hours to complete sintering, to prepare the porous ceramic.