Preparation process of alumina fiber porous ceramic material

Abstract

The invention discloses a preparation process of an alumina fiber porous ceramic material, and relates to the field of functional ceramic materials. The invention relates to a preparation process of an alumina fiber porous ceramic material. The preparation process mainly comprises the following steps: preparing glue, pulping, preparing a blank, demolding, drying and sintering, on one hand, the porous ceramic material with uniform pore diameter can be obtained through high-temperature decomposition and moisture volatilization of the spinnable gel; and on the other hand, residual inorganic silicon-aluminum components are sintered and cured at a high temperature, and a crystalline cobweb skeleton structure is formed among alumina fibers, so that the binding force among the fibers can be improved, the toughness and strength of the material can be enhanced, the porosity of the material can be increased, and the adsorption loading effect of the ceramic material can be greatly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of functional ceramic materials, and particularly relates to a preparation process of alumina fiber porous ceramic material. BACKGROUND

[0002] The porous ceramic material is generally prepared from high-quality raw materials such as corundum sand, silicon carbide and cordierite, through forming and special high-temperature sintering process, and has the characteristics of open pore diameter and high open porosity, and also has the advantages of high temperature resistance, high pressure resistance, acid and alkali resistance and organic medium corrosion resistance, good biological inertness, controllable pore structure, high open porosity, long service life, good product regeneration performance and the like, and can be applied to precise filtration and separation of various media, high-pressure gas exhaust silencing, gas distribution and electrolytic diaphragm and the like scenes.

[0003] However, the existing production process often needs to add ceramic binders, dispersants, organic additives and the like to the ceramic slurry, and the products produced have the problems of poor pore distribution uniformity, low toughness strength and low porosity.

[0004] The high-porosity reticular structure ceramic material made of ceramic fibers has excellent heat insulation performance, thermal shock resistance, filtration performance and light weight, and is currently widely used as high-temperature insulation material, catalyst carrier and high-temperature filtration material. Therefore, it is an urgent problem in the field to prepare a porous ceramic material with high porosity, controllable pore diameter, excellent mechanical properties and not easy to collapse and crack. In view of this, the present application is proposed. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a preparation process of alumina fiber porous ceramic material which can overcome the above problems or at least partially solve the above problems.

[0006] To solve the above technical problems, the basic idea of the technical solution adopted by the present application is as follows: a preparation process of alumina fiber porous ceramic material mainly comprises the following steps: Step one, glue preparation: aluminum powder, crystalline aluminum chloride and distilled water are fully mixed and reacted, and then mixed and concentrated with a certain amount of polyvinyl alcohol and silica sol to prepare a spinnable gel; Step two, slurry preparation: the spinnable gel, water and alumina fibers are fully mixed in a certain proportion to obtain alumina fiber ceramic slurry; Step three, blank preparation: the uniformly mixed slurry is put into a forming tank, the porous model after surface treatment is immersed into the forming tank, and a vacuum filtration system is connected, so that the negative pressure formed by the vacuum pump makes the slurry adsorbed on the outer surface of the porous model to obtain a blank body with a certain thickness; Step four, demolding: after adsorption is completed, the porous model is taken out and demolding is performed to obtain a formed product; Step five, drying: the shaped product is placed in a drying furnace, and drying treatment is carried out at a temperature of 100 DEG C, most of the free water is discharged, and initial pore formation is achieved, and the drying time is determined by the thickness of the green body; Step six, sintering: the dried sample is sintered at high temperature to complete secondary pore formation and phase change, and a porous ceramic material with alumina fibers as the skeleton is obtained.

[0007] Further, in step one, the silica-alumina ratio of the spinnable gel can be adjusted as required, such as 5:95 or 28:72.

[0008] Further, in step two, the alumina fibers can be inert alumina fibers or active alumina fibers, and the viscosity of the alumina fiber ceramic slurry is 150-250 mPa・s.

[0009] Further, in step three, the thickness of the green body is controlled by the concentration, viscosity, filtration pressure and time of the ceramic fiber slurry, and the green body porosity is controlled by controlling the green body process formulation and filtration pressure.

[0010] Further, in step six, when active alumina fibers are used, the sintering temperature is 800-900 DEG C, and the high-temperature sintering time is 30-60 min, and when inert alumina fibers are used, the sintering temperature is 1100-1200 DEG C, and the high-temperature sintering time is 30-60 min.

[0011] Further, the drying furnace comprises a furnace body, a door plate, an electric heating box provided with an electric heating assembly inside, a heat-resistant fan, an air inlet pipe and a connecting pipe, the door plate is symmetrically connected to the furnace opening of the furnace body, the electric heating boxes are symmetrically distributed on both sides of the furnace body, the heat-resistant fan is installed at the through opening of the lower end of the furnace body on both sides, the air inlet pipe is fixedly connected to the air inlet of the electric heating box, the connecting pipe is connected to the air outlet of the electric heating box and the through opening of the furnace body, respectively, and the upper end of the furnace body is provided with an exhaust port.

[0012] In order to facilitate the scraping of the condensed water droplets on the top, and to avoid the adverse effects of water droplets falling on the green body, further, a rotating column is rotatably connected to the upper end of the inside of the furnace body, a collecting box is fixedly connected to the rotating column through a support rod, a Y-shaped scraper is fixedly connected to the box opening of the collecting box, the two branch plates of the Y-shaped scraper are in sliding contact with the inner wall of the furnace body, the end of the rotating column away from the door plate extends out of the furnace body, a conical passage is formed in the inside of the rotating column, a plurality of conveying pipes are equidistantly connected between the collecting box and the conical passage of the rotating column, a transmission gear ring is fixedly connected to the end of the rotating column extending out of the furnace body, a driving motor is fixedly connected to the side of the furnace body close to the transmission gear ring through a mounting plate, and the output end of the driving motor is fixedly connected to a driving gear meshing with the transmission gear ring.

[0013] In order to facilitate the efficient recycling of the exhaust heat, the exhaust port of the furnace body is further fixedly connected with a first three-way pipe, both of the two gas outlets of the first three-way pipe are fixedly connected with gas conveying pipes, the gas outlets of the two gas conveying pipes are respectively connected with the gas inlets of the gas conveying pipes on the same side, a high-temperature-resistant gas-permeable water-impermeable film is installed in the exhaust port of the furnace body, and the lower surface of the gas-permeable water-impermeable film is on the same arc surface with the upper inner wall of the furnace body.

[0014] In order to facilitate the guarantee of the thermal efficiency of the drying stage and the process requirements of the cooling stage, the gas conveying pipe is further provided with a second three-way pipe, the gas outlet of the gas conveying pipe is connected with one of the gas inlets of the second three-way pipe, and the other gas inlet of the second three-way pipe is detachably connected with a sealing cover through screw threads.

[0015] In order to facilitate the provision of stable and self-adaptive limiting effect for the placing rack for placing the shaped products, the lower end of the inner part of the furnace body is further provided with two groups of limiting grooves, a plurality of gas bag strips filled with gas are fixedly connected in the limiting grooves at equal intervals, and the moving wheels at the bottom of the placing rack for placing the shaped products are limited.

[0016] Compared with the prior art, the present application has the following beneficial effects: the present application uses alumina fiber as the skeleton structure, the porosity of the material structure can reach more than 90%, and the pores are uniform.

[0017] The alumina fiber can be inert alumina fiber, which is used as a carrier; or can be active alumina fiber, which can play the role of a carrier and an active component.

[0018] The inorganic silicon-aluminum component forms a spider web-like skeleton structure among the alumina fibers, which is solidified through high-temperature sintering, thereby improving the bonding force among the fibers, enhancing the toughness and strength of the material, increasing the porosity of the material, and greatly improving the adsorption and loading effect of the ceramic material.

[0019] The silicon-aluminum gel can be used as a binder and a pore-forming agent, and a ceramic material with uniform pores can be obtained without adding other pore-forming agents.

[0020] The present application uses alumina fiber as the aggregate, and uses spinnable gel and water as the binder and the dispersing agent. On the one hand, the spinnable gel is decomposed at high temperature and the water is volatilized, thereby obtaining a porous ceramic material with uniform pore size; on the other hand, the residual inorganic silicon-aluminum component is solidified through high-temperature sintering, thereby forming a crystalline spider web-like skeleton structure among the alumina fibers, which can improve the bonding force among the fibers, enhance the toughness and strength of the material, increase the porosity of the material, and greatly improve the adsorption and loading effect of the ceramic material.

[0021] The specific embodiments of the present application will be further described in details below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0022] In the drawings: Figure 1 Process flow chart for the preparation of the present application; Figure 2 Structure diagram of the drying furnace of the present application Figure 1 ; Figure 3 Structure diagram of the drying furnace of the present application Figure 2 ; Figure 4 Structure diagram of the furnace body and the internal structure of the electric heating box of the present application; Figure 5 Structure diagram of the drying furnace of the present application Figure 6 Structure diagram of the drying furnace of the present application Figure 5 ; Figure 7 Structure diagram of the drying furnace of the present application Figure 1 ; Figure 8 Structure diagram of the drying furnace of the present application Figure 2 ; Figure 9 Structure diagram of the drying furnace of the present application Figure 10 Structure diagram of the drying furnace of the present application

[0023] In the drawings: 1, drying furnace; 101, furnace body; 102, door plate; 103, limiting groove; 104, air bag strip; 105, electric heating box; 106, heat-resistant fan; 107, air inlet pipe; 108, connecting pipe; 109, sealing cover; 1010, exhaust port; 1011, air-permeable water-impermeable membrane; 2, rotating column; 2001, conical channel; 201, driving motor; 202, driving gear; 203, transmission gear ring; 204, supporting rod; 205, collection box; 206, Y-shaped scraper; 207, conveying pipe; 3, first three-way pipe; 301, air conveying pipe. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments will be clearly and completely described below with reference to the drawings in the embodiments of the present application. The following embodiments are used to illustrate the present application, but not to limit the scope of the present application.

[0025] First embodiment: refer to Figure 1 , Figure 2 , Figure 3、 Figure 4 、 Figure 9 As shown in FIG. 1, a preparation process of a porous ceramic material based on active alumina fiber, comprising the following steps: Step one, glue preparation: mix aluminum powder, crystalline aluminum chloride and distilled water thoroughly, and then mix with a certain amount of polyvinyl alcohol and silica sol to concentrate, to prepare a spinnable gel with a silicon-aluminum ratio of 5:95. In this step, aluminum powder and crystalline aluminum chloride react in distilled water, laying a foundation for the formation of silicon-aluminum structure in the subsequent process, and the addition of polyvinyl alcohol and silica sol helps to adjust the performance of the gel to meet the requirements of the subsequent process; Step two, slurry preparation: mix the spinnable gel prepared in step one with water and active alumina fiber (γ-Al2O3) in a certain proportion to obtain alumina fiber ceramic slurry with a viscosity of 150-250 mPa・s. The active alumina fiber has a certain activity and can play a better role in the subsequent process. Controlling the slurry viscosity at 150-250 mPa・s is beneficial to the subsequent filtration process and can avoid alumina fiber sedimentation, ensuring uniform dispersion; Step three, blank preparation: put the mixed slurry into a forming tank, immerse the surface-treated porous model into the forming tank, and connect the vacuum filtration system. The negative pressure formed by the vacuum pump makes the slurry adsorb on the outer surface of the porous model to obtain a blank with a certain thickness. The blank thickness is controlled by the concentration, viscosity, filtration pressure and time of the ceramic fiber slurry, and the blank porosity is controlled by controlling the blank process formula and filtration pressure. By reasonably adjusting these parameters, a blank structure meeting the expected requirements can be obtained; Step four, demolding: after adsorption is completed, the porous model is taken out for demolding to obtain a shaped product. Careful operation is required during the demolding process to avoid damaging the structure of the shaped product; Step five, drying: the shaped product is placed in the drying furnace 1 through the rack, the drying furnace 1 comprises a furnace body 101, a door plate 102, an electric heating box 105 provided with an electric heating assembly inside, a heat-resistant fan 106, an air inlet pipe 107 and a connecting pipe 108, the door plate 102 is symmetrically connected to the furnace opening of the furnace body 101, the electric heating box 105 is symmetrically distributed on both sides of the furnace body 101, the heat-resistant fan 106 is installed at the through port of the lower end of the two sides of the furnace body 101, the air inlet pipe 107 is fixedly connected to the air inlet of the electric heating box 105, the connecting pipe 108 is connected to the air outlet of the electric heating box 105 and the through port of the furnace body 101 respectively, and the exhaust port 1010 is arranged at the upper end of the furnace body 101, when drying, the electric heating assembly in the electric heating box 105 is started to heat and warm the gas entering the electric heating box 105, then the heat-resistant fan 106 is started, the heat-resistant fan 106 will slowly send hot air from the bottom into the furnace body 101, and the heating power of the electric heating assembly is controlled, so that the temperature in the furnace body 101 can be kept at 100 DEG C, so that the shaped product is dried at 100 DEG C, most of the free water is discharged, the pore is preliminarily formed, the drying time is determined by the thickness of the blank, and the structure design of the drying furnace 1 can ensure that the temperature in the furnace is uniform, the heat is provided through the electric heating box 105, the air circulation is promoted through the heat-resistant fan 106, the shaped product is uniformly heated, and the stable discharge of water is beneficial; Step six, sintering: the sample dried in step five and cooled in the furnace is transferred to a muffle furnace, and slowly heated to 800 DEG C~900 DEG C, in this process, the water and gas are volatilized, the secondary pore forming is carried out, and the spidery framework structure is formed between the active alumina fibers, the high-temperature sintering time is 30 min~60 min, and finally the porous ceramic material with active alumina fibers as the framework is obtained as shown in Figure 9 Slowly heating can avoid the cracking of the sample due to sudden temperature change, and the sintering temperature of 800 DEG C~900 DEG C is suitable for the characteristics of the active alumina fibers, so that the spidery framework structure is formed.

[0026] The active alumina fibers are used as the framework structure, the porosity of the material structure can reach more than 90%, and the pores are uniform, so that the material has good filtering and adsorbing performance, and can efficiently separate and adsorb substances.

[0027] The inorganic silicon aluminum component forms a spidery framework structure between the active alumina fibers, which is solidified through high-temperature sintering, not only improves the bonding force between the fibers, enhances the toughness and strength of the material, but also increases the porosity of the material, greatly improves the adsorption and loading effect of the ceramic material, and the structure makes the material not easy to be damaged when bearing certain external force, and can better load various substances, thereby expanding the application range.

[0028] The silica-alumina gel serves as both a binder and a pore-forming agent, and a ceramic material with uniform pores is obtained without adding other pore-forming agents, thereby simplifying the preparation process and reducing production costs.

[0029] The second embodiment is described below with reference to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 10 A preparation process of a porous ceramic material based on inert alumina fibers is shown in the drawings, and includes the following steps: Step 1: gel preparation: aluminum powder, crystalline aluminum chloride, and distilled water are fully mixed and reacted, and then mixed with a certain amount of polyvinyl alcohol and silica sol to concentrate, to prepare a spinnable gel with a silica-alumina ratio of 28:72. Compared with the gel preparation step of the active alumina fiber preparation process, the silica-alumina ratio is adjusted here to adapt to the characteristics of the inert alumina fiber and the subsequent process requirements. Step 2: slurry preparation: the spinnable gel obtained in step 1 is fully mixed with water and inert alumina fibers (α-Al2O3) in a certain proportion to obtain alumina fiber ceramic slurry with a viscosity of 150-250 mPa・s. The inert alumina fiber has relatively stable chemical properties, and the slurry viscosity is also controlled at 150-250 mPa・s to ensure good performance of the slurry. Step 3: green body preparation: the uniformly mixed slurry is placed in a forming tank, a porous model subjected to surface treatment is immersed in the forming tank, and a vacuum filtration system is connected, so that the negative pressure formed by the vacuum pump causes the slurry to be adsorbed on the outer surface of the porous model to obtain a green body with a certain thickness. The thickness of the green body is controlled by the concentration, viscosity, filtration pressure, and time of the ceramic fiber slurry. The porosity of the green body is controlled by controlling the green body process formulation and filtration pressure. This step has the same principle as the green body preparation step of the active alumina fiber preparation process, and the required green body is obtained by adjusting the relevant parameters. Step 4: demolding: after the adsorption is completed, the porous model is taken out for demolding to obtain a shaped product. Attention should be paid to protecting the structural integrity of the shaped product during operation. Step 5: drying: the shaped product is placed in the same structure of the drying furnace 1, and the shaped product is dried at a temperature of 100℃ to remove most of the free water and initially form pores. The drying time is determined by the thickness of the green body. The excellent structure of the drying furnace 1 ensures uniform drying of the shaped product, which prepares for subsequent sintering. Step 6: sintering: the sample cooled with the furnace after step 5 is transferred to a muffle furnace and slowly heated to 1100℃-1200℃. In this process, water and gas are volatilized, secondary pore formation is performed, the spinnable gel is transformed from amorphous to crystalline, and a spider web-like skeleton structure is formed between the inert alumina fibers. The high-temperature sintering time is 30-60 min, and finally a porous ceramic material based on inert alumina fibers is obtained as shown in Figure 10The porous ceramic material shown with inert alumina fiber as the skeleton has higher sintering temperature than that of active alumina fiber due to the higher high-temperature resistance of the inert alumina fiber, and the high temperature of 1100-1200°C can ensure that the gel can be fully converted to form a stable structure.

[0030] The inert alumina fiber is used as the skeleton structure, and the porosity of the material can also reach more than 90%, and the pores are uniformly distributed. The high porosity ensures that the material has good air permeability and filtration performance, and the uniform pore distribution is conducive to improving the stability of the material performance.

[0031] The spider web-like skeleton structure formed by the inorganic silicon aluminum component between the inert alumina fibers is effectively improved after high-temperature sintering and solidification, which effectively improves the bonding force between the fibers, so that the material has high toughness and strength, and can be used in harsh environments. At the same time, the increased porosity also improves the adsorption capacity of the material.

[0032] Similarly, without the need for additional pore-forming agents, the silicon-aluminum gel plays the role of both a binder and a pore-forming agent, simplifying the process and reducing costs, and the prepared ceramic material has excellent performance and can be applied to various scenarios such as high-temperature insulation and gas filtration.

[0033] In summary, the two preparation processes based on different types of alumina fibers can both prepare high-performance alumina fiber porous ceramic materials, and each has its own application scenarios, providing an effective preparation scheme for the field of functional ceramic materials.

[0034] Referring to Figure 3 , Figure 4 , Figure 5 , Figure 7 , Figure 8 As shown: the inner upper end of the furnace body 101 is rotatably connected with a rotating column 2, the rotating column 2 is fixedly connected with a collecting box 205 through a support rod 204, the box opening of the collecting box 205 is fixedly connected with a Y-shaped scraper 206, the two branch plates on the Y-shaped scraper 206 are in sliding contact with the inner wall of the furnace body 101, the end of the rotating column 2 away from the door plate 102 extends out of the furnace body 101, a conical passage 2001 is formed in the interior of the rotating column 2, a plurality of conveying pipes 207 are equidistantly connected between the collecting box 205 and the conical passage 2001 of the rotating column 2, a transmission gear ring 203 is fixedly connected to the end of the rotating column 2 extending out of the furnace body 101, a driving motor 201 is fixedly connected to the side of the furnace body 101 close to the transmission gear ring 203 through a mounting plate, and the output end of the driving motor 201 is fixedly connected with a driving gear 202 which is in meshing with the transmission gear ring 203.

[0035] During the drying process, the free water discharged from the shaped product will form a large amount of steam under the dry environment of 100℃. When part of the steam contacts the top of the furnace body 101 which has a relatively low temperature, it is easy to condense into water droplets. If these water droplets fall randomly, they may wet the shaped product below, causing the local humidity to rise, affecting the drying uniformity, and even causing the green body to crack due to uneven moisture distribution.

[0036] By driving the motor 201 to rotate the drive gear 202, the meshing transmission gear ring 203 will drive the rotating column 2 to rotate, and then the collecting box 205 and the Y-shaped scraper 206 connected by the supporting rod 204 will move back and forth on the top of the furnace body 101. The two branch plates of the Y-shaped scraper 206 slide and adhere to the inner wall of the furnace body 101, which can efficiently scrape off the condensed water droplets on the top, avoiding the adverse effects of water droplet falling on the green body.

[0037] The scraped water droplets will gather along the arc surface of the Y-shaped scraper 206 under the action of centrifugal force, and then flow into the collecting box 205, and then enter the conical passage 2001 inside the rotating column 2 through the multiple conveying pipes 207, and finally be discharged outside the furnace through the opening of the conical passage 2001. This process can timely remove the condensed water in the furnace, ensure the stability of the dry environment, ensure that the shaped product is heated uniformly and the moisture is discharged smoothly during the entire drying process, thereby ensuring the uniformity of the initial pore formation and providing a green body with stable quality for the subsequent sintering step.

[0038] Referring to Figure 3 , Figure 4 , Figure 5 , the body 6 shows that the first three-way pipe 3 is fixedly connected at the exhaust port 1010 of the furnace body 101, and the two gas outlets of the first three-way pipe 3 are fixedly connected with the gas conveying pipes 301. The gas outlets of the two gas conveying pipes 301 are respectively connected with the gas inlets of the same side gas inlet pipe 107. A high-temperature resistant gas-permeable water-impermeable membrane 1011 is installed in the exhaust port 1010 of the furnace body 101, and the lower surface of the gas-permeable water-impermeable membrane 1011 is on the same arc surface as the upper inner wall of the furnace body 101.

[0039] During the drying process, the combination of the first three-way pipe 3, the gas conveying pipe 301 and the high-temperature resistant gas-permeable water-impermeable membrane 1011 at the exhaust port 1010 of the furnace body 101 can realize efficient recycling of the discharged heat. During drying, the heat generated by the electric heating assembly in the furnace body 101 causes the free water in the shaped product to evaporate into steam. The steam carrying heat will be discharged through the exhaust port 1010. The high-temperature resistant gas-permeable water-impermeable membrane 1011 installed at the exhaust port 1010 allows the gas components (containing heat) in the high-temperature steam to pass through, while preventing liquid water from passing through, ensuring that only dry gas carrying heat is discharged. These heat-containing gases are divided by the first three-way pipe 3 and then introduced into the gas inlet pipe 107 of the same side electric heating box 105 through the two gas conveying pipes 301, re-entering the heating circulation system.

[0040] This design recovers the heat that would otherwise be directly lost, reduces the additional energy consumption required by the electric heating box 105 to maintain the 100℃ drying temperature in the furnace 100, improves energy utilization efficiency, and at the same time, the structure that the lower surface of the air-permeable water-impermeable film 1011 and the inner wall of the furnace body 101 are on the same arc surface reduces the gas flow resistance, ensures smooth heat recovery, and avoids the leakage of condensed water in the furnace through the exhaust port 1010, which affects the heat recovery effect, thereby achieving energy saving and consumption reduction on the basis of ensuring drying efficiency, and at the same time, it is also convenient for the Y-shaped scraper 206 to scrape off the moisture on the lower surface of the air-permeable water-impermeable film 1011 when rotating.

[0041] Referring to Figure 2 , Figure 3 , the air inlet pipe 107 is a second three-way pipe, the gas outlet of the gas conveying pipe 301 is connected to one of the air inlets of the second three-way pipe, and the other air inlet of the second three-way pipe is detachably connected with a sealing cover 109 through threads.

[0042] The design of the air inlet pipe 107 as a second three-way pipe and the structure of the sealing cover 109 can flexibly adapt to the different needs of the drying and cooling stages. During the drying process, by tightening the sealing cover 109 to block the other air inlet of the second three-way pipe, a closed loop of the gas circulation path can be formed. At this time, the hot gas discharged from the furnace body 101 enters the electric heating box 105 through one air inlet of the second three-way pipe after passing through the first three-way pipe 3 and the gas conveying pipe 301, and then is sent back into the furnace body 101 after being heated. This design can minimize heat loss, ensure efficient recycling of hot gas, and maintain a stable drying temperature of 100℃ in the furnace, which meets the requirement of uniform temperature during the drying process.

[0043] When the drying is completed and the blank needs to be cooled, the sealing cover 109 is simply unscrewed to open the other air inlet, and then the natural wind from outside can enter the electric heating box 105 through this channel and enter the furnace body 101 under the action of the heat-resistant fan 106. Since the temperature of the natural wind is close to the room temperature, and the conveying method through the pipeline and the fan is relatively gentle, slow cooling of the blank can be achieved, which avoids the cracking of the blank caused by rapid cooling due to thermal stress, and matches the process logic of slow cooling after drying.

[0044] This structure does not require additional equipment or complex operations, but only needs to switch the sealing cover 109 to switch the working mode, which not only ensures the thermal efficiency during the drying stage, but also meets the process requirements during the cooling stage, simplifies the operation process, and improves the practicality of the equipment.

[0045] Referring to Figure 4 , Figure 5As shown: the lower end of the furnace body 101 is provided with two groups of limiting grooves 103, a plurality of gas bag strips 104 filled with gas are fixedly connected in the limiting grooves 103 at equal intervals, which are used for limiting the moving wheels at the bottom of the placing rack for placing the shaped products.

[0046] The limiting grooves 103 and the gas bag strips 104 at the lower end of the furnace body 101 can provide stable and self-adaptive limiting effect for the placing rack for placing the shaped products. When the placing rack is pushed into the furnace body 101, the moving wheels at the bottom thereof will accurately fall into the limiting grooves 103 and be naturally clamped between two adjacent gas bag strips 104, so that preliminary positioning is realized, displacement of the placing rack in the drying process due to slight vibration of the equipment or air flow disturbance is avoided, the shaped products are ensured to be in the preset drying position, and uniform heating is ensured.

[0047] With the advancement of the drying process, the temperature in the furnace body 101 gradually rises to 100℃, the gas filled in the gas bag strips 104 expands due to heating, so that the gas bag strips 104 are inflated and closely fit on both sides of the moving wheels. The automatic expansion characteristic based on the temperature rise can dynamically enhance the clamping force of the moving wheels with the temperature rise, further limit the moving space of the placing rack, and prevent accidental sliding of the placing rack in the high-temperature environment due to factors such as thermal expansion and cold shrinkage of materials.

[0048] The design does not need additional power driving, and the self-adaptive improvement of the limiting strength is realized by using the temperature change in the drying process. The structure is simplified, and reliable fixation of the placing rack is provided in the key high-temperature drying stage, so that the shaped products are stably placed in the ideal drying environment, and the uniformity and consistency of the drying effect are indirectly promoted.

[0049] The contents not described in detail in the specification belong to the prior art known to those skilled in the art.

[0050] The above only describes the preferred embodiments of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiments, it is not intended to limit the present application.

Claims

1. A preparation process for alumina fiber porous ceramic material, characterized in that, The main steps include: Step 1: Preparing the adhesive: Aluminum powder, crystalline aluminum chloride, and distilled water are thoroughly mixed and reacted, and then mixed and concentrated with a certain amount of polyvinyl alcohol and silica sol to make a spinnable gel. Step 2, Pulping: A spinnable gel, water, and alumina fibers are thoroughly mixed in a certain proportion to obtain alumina fiber ceramic slurry. Step 3: Preparing the blank: The uniformly mixed slurry is placed into the forming tank, and the surface-treated porous model is immersed in the forming tank. The system is connected to a vacuum filtration system, and the negative pressure generated by the vacuum pump is used to adsorb the slurry onto the outer surface of the porous model to obtain a green body with a certain thickness. Step 4: Demolding After adsorption is complete, the porous mold is removed and demolded to obtain the molded product; Step 5: Drying: The molded product is placed in a drying oven (1) and dried at 100°C to remove most of the free water and form initial pores. The drying time is determined by the thickness of the blank. Step Six: Sintering The dried sample was fired at high temperature to complete the secondary pore formation and phase change, resulting in a porous ceramic material with alumina fiber as the skeleton.

2. The preparation process of an alumina fiber porous ceramic material according to claim 1, characterized in that, In step one, the silica-alumina ratio of the spinnable gel can be adjusted as needed, such as 5:95 or 28:

72.

3. The preparation process of an alumina fiber porous ceramic material according to claim 1, characterized in that, In step two, the alumina fiber can be either inert alumina fiber or activated alumina fiber, and the viscosity of the alumina fiber ceramic slurry is 150~250 mPa·s.

4. The preparation process of an alumina fiber porous ceramic material according to claim 1, characterized in that, In step three, the thickness of the green body is controlled by the concentration, viscosity, filtration pressure and time of the ceramic fiber slurry, and the porosity of the green body is controlled by controlling the green body process formula and filtration pressure.

5. The preparation process of an alumina fiber porous ceramic material according to claim 3, characterized in that, In step six, when active alumina fibers are used, the sintering temperature is 800℃~900℃ and the high-temperature sintering time is 30min~60min; when inert alumina fibers are used, the sintering temperature is 1100℃~1200℃ and the high-temperature sintering time is 30min~60min.

6. The preparation process of an alumina fiber porous ceramic material according to claim 1, characterized in that, The drying oven (1) includes an oven body (101), a door panel (102), an electric heating box (105) with an electric heating component inside, a heat-resistant fan (106), an air inlet pipe (107), and a connecting pipe (108). The door panel (102) is symmetrically rotated and connected to the oven opening of the oven body (101). The electric heating box (105) is symmetrically distributed on both sides of the oven body (101). The heat-resistant fan (106) is installed at the opening at the lower end of both sides of the oven body (101). The air inlet pipe (107) is fixedly connected to the air inlet of the electric heating box (105). The two ends of the connecting pipe (108) are respectively connected to the air outlet of the electric heating box (105) and the opening of the oven body (101). An exhaust port (1010) is opened at the upper end of the oven body (101).

7. The preparation process of an alumina fiber porous ceramic material according to claim 6, characterized in that, A rotating column (2) is rotatably connected to the upper part of the furnace body (101). A collection box (205) is fixedly connected to the rotating column (2) via a support rod (204). A Y-shaped scraper (206) is fixedly connected to the opening of the collection box (205). The two branch plates on the Y-shaped scraper (206) slide against the inner wall of the furnace body (101). The end of the rotating column (2) away from the door panel (102) extends out of the furnace body (101). A conical channel (204) is opened inside the rotating column (2). 01), the collection box (205) and the conical channel (2001) of the rotating column (2) are connected by multiple conveying pipes (207) at equal intervals. A transmission gear ring (203) is fixedly connected to one end of the rotating column (2) extending out of the furnace body (101). A drive motor (201) is fixedly connected to the side of the furnace body (101) near the transmission gear ring (203) through a mounting plate. A drive gear (202) that meshes with the transmission gear ring (203) is fixedly connected to the output end of the drive motor (201).

8. The preparation process of an alumina fiber porous ceramic material according to claim 7, characterized in that, A first three-way pipe (3) is fixedly connected to the exhaust port (1010) of the furnace body (101). Both outlets of the first three-way pipe (3) are fixedly connected to gas supply pipes (301). The outlets of the two gas supply pipes (301) are respectively connected to the inlet of the gas inlet pipe (107) on the same side. A high-temperature resistant, breathable, and waterproof membrane (1011) is installed inside the exhaust port (1010) of the furnace body (101). The lower surface of the breathable and waterproof membrane (1011) is on the same arc surface as the upper inner wall of the furnace body (101).

9. The preparation process of an alumina fiber porous ceramic material according to claim 8, characterized in that, The air inlet pipe (107) is a second three-way pipe. The air outlet of the air supply pipe (301) is connected to one of the air inlets of the second three-way pipe. The other air inlet of the second three-way pipe is detachably connected to a sealing cap (109) by a thread.

10. The preparation process of an alumina fiber porous ceramic material according to claim 6, characterized in that, The furnace body (101) has two sets of limiting grooves (103) at the lower end of its interior. Multiple gas-filled airbag strips (104) are fixedly connected at equal intervals in the limiting grooves (103) to limit the movement of the wheels at the bottom of the placement rack for placing the molded products.

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