Thin-wall low-resistance silicon carbide ceramic membrane and preparation process thereof

Abstract

The invention discloses a thin-wall low-resistance silicon carbide ceramic membrane and a preparation process thereof, the ceramic membrane is a tubular membrane which is prepared and formed by integral sintering and has one sealed end, and the ceramic membrane comprises an expansion end head, a connecting neck part, a tube body and a tube bottom from top to bottom. The wall thickness of the silicon carbide ceramic membrane is reduced and the running resistance is reduced while the strength and toughness of the ceramic membrane are ensured. According to the present invention, the toughening layer is added to the pipe body, the toughening material is adopted to increase the strength and the toughness of the ceramic membrane, the pipe body thickness of the silicon carbide ceramic membrane can be reduced to less than 10 mm, and compared with the common silicon carbide ceramic membrane, the thickness is reduced, the strength is improved, and the filtration resistance is reduced by more than 30%. The operation energy consumption is reduced, the strength of the ceramic membrane is improved, and the service life of the ceramic membrane is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of environmentally friendly new materials, and in particular relates to a thin-walled low-resistance silicon carbide ceramic membrane and a preparation process thereof. Background Art

[0002] Process industry plays an important role in the development of national economy. However, my country's process industry still has problems such as resource waste, high energy consumption and serious pollution. Its energy consumption accounts for 70% of the total national industrial energy consumption, smoke emissions exceed 50% of the total national emissions, and carbon emissions account for more than 80% of the total national emissions. With my country's increasing attention to the ecological environment, the problem of strengthening gas-solid separation in some harsh environments, especially in high temperature and high pressure environments and reaction systems, has become a bottleneck problem restricting the sustainable development of the industry, and urgently needs the support of new separation technologies. Silicon carbide ceramic membranes are known as efficient, energy-saving and environmentally friendly separation materials due to their excellent thermal stability and chemical stability. They have become one of the common technologies for solving major problems such as water resources, energy, and the environment, and have played an important supporting role in reducing pollution and carbon emissions in process industries. Silicon carbide ceramic membranes are rigid materials. In order to avoid breakage during use or installation, the thickness of the silicon carbide ceramic membranes will be increased to enhance the strength of the silicon carbide ceramic membranes. The wall thickness of the silicon carbide ceramic membranes currently used is generally more than 10 mm, resulting in large operating resistance and high operating energy consumption. Summary of the invention

[0003] In order to solve the problem of large wall thickness and high running resistance of existing silicon carbide ceramic membranes, the present invention discloses a thin-walled, low-resistance silicon carbide ceramic membrane and its preparation process, which reduces the wall thickness of the silicon carbide ceramic membrane and reduces the running resistance while ensuring the strength and toughness of the ceramic membrane.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solutions: A thin-walled, low-resistance silicon carbide ceramic membrane, which is a tubular membrane with one end sealed and formed by integral sintering, and comprises, from top to bottom, an expansion end, a connecting neck, a tube body, and a tube bottom; a bulge is formed inwardly around the inner side of the connecting neck to constitute an annular throat, the upper part of the bulge is located inside the expansion end, and the lower part is located inside the tube body, and penetrates into the expansion end and the tube body by 2-5 cm respectively; the tube wall of the end, connecting neck, tube body and tube bottom of the ceramic membrane is a multi-layer structure, and comprises, from the outside to the inside, a separation membrane layer, a transition layer, a toughening layer, and an inner support layer, the separation membrane layer is 50-100μm thick, the transition layer is 500-1000μm thick, the toughening layer is 3-4mm thick, the inner support layer is 2-3mm thick, and a toughening material is provided in the toughening layer, and the toughening material is one or more of a metal mesh, a porous foam metal or a foam ceramic; the bulge is thickened by the inner support layer material, and the thickness is 3-5mm.

[0005] Preferably, the thickness of the tube bottom is 30-50 mm, a positioning hole is recessed on the outer bottom surface at the center, the depth of the positioning hole is 8-15 mm, and the thickened part of the tube bottom is thicker than the tube body by a transition layer material.

[0006] Preferably, the expansion end is in the shape of a cone that is larger at the top and smaller at the bottom, and the diameter of the upper end is 1.3-1.5 times the diameter of the lower end.

[0007] Preferably, the separation membrane layer has a pore size of 2-30 μm and a porosity of 30-65%, the transition layer has a pore size of 10-50 μm and a porosity of 40-70%, the toughening layer has a pore size of 30-80 μm and a porosity of 50-80%, and the toughening material is prepared by infiltrating silicon carbide particles into the pores of the toughening material and sintering, the toughening material has a pore size of 800-2000 μm, and the inner support layer has a pore size of 50-100 μm and a porosity of 60-80%.

[0008] Preferably, the toughening material is in a cylindrical shape and placed in the entire tube body, or in a longitudinal strip shape and dispersed in the tube body. When the toughening material is in a strip shape, the spacing between them in the tube body is 0.5-1 cm.

[0009] The present invention also discloses a preparation process of a thin-walled low-resistance silicon carbide ceramic membrane, comprising the following steps: Step 1: prepare a toughening layer mixture and a toughening layer, add silicon carbide particles with a particle size of 20-200 μm, zirconium oxide particles with a particle size of 10-50 μm, and activated carbon powder with a particle size of 10-30 μm into a ball mill according to a proportion for ball milling and mixing, add polyvinyl alcohol and paraffin oil after mixing for a certain period of time and continue mixing, place the toughening material in a toughening layer rubber mold, add the mixed toughening layer mixture into the rubber mold, make the toughening layer mixture enter the pores of the toughening material by vibration, and obtain the toughening layer after extrusion molding and demolding; Step 2: Prepare a transition layer mixture, add silicon carbide particles with a particle size of 10-100 μm, zirconium oxide particles with a particle size of 5-30 μm, and activated carbon powder with a particle size of 8-20 μm into a ball mill according to a proportion, and mix them by ball milling. After mixing for a certain period of time, add polyvinyl alcohol and paraffin oil and continue mixing to obtain a transition layer mixture; Step 3: Prepare an inner support layer mixture, add silicon carbide particles with a particle size of 100-300 μm, zirconium oxide particles with a particle size of 30-60 μm, and activated carbon powder with a particle size of 20-35 μm into a ball mill according to a certain proportion, and then add polyvinyl alcohol and paraffin oil to continue mixing to obtain an inner support layer mixture after mixing for a certain period of time; Step 4: Pre-sintered embryo body preparation, the toughening layer prepared in step 1 is placed in the finished product mold, the transition layer mixture is filled on the outside, and the inner support layer mixture is filled on the inside. After filling, pre-extrusion is performed, and vibration mixing is performed after pre-extrusion to break the boundaries between the layers. Finally, the finished product is extruded, and after demoulding, it is placed in an atmosphere furnace for pre-sintering to obtain a pre-sintered embryo body; the inner side of the connecting neck is bulged inward for the inner support layer mixture; the thickened part of the bottom of the tube than the tube body is filled with the transition layer mixture; Step 5: Preparation of separation membrane layer: silicon carbide particles with a particle size of 5-15 μm, zirconium oxide particles with a particle size of 5-10 μm, mullite particles with a particle size of 1-5 μm, methyl cellulose solution, and ethanol are added to deionized water in proportion, vacuumed and stirred to prepare a coating liquid, and the prepared coating liquid is evenly sprayed on the pre-sintered embryo body prepared in step 4, and dried to obtain a pre-sintered embryo body with a separation membrane layer; Step 6: Place the pre-sintered blank with the separation membrane layer in an atmosphere furnace for programmed temperature sintering to obtain a thin-walled, low-resistance silicon carbide ceramic membrane.

[0010] Preferably, in the step one, the mass proportion of each component is 65-80% of silicon carbide particles, 2-4% of zirconium oxide particles, 8-15% of activated carbon powder, 5-10% of polyvinyl alcohol, and 3-6% of paraffin oil, and the extrusion molding pressure is 80-100 MPa; in the step two, the mass proportion of each component is 70-85% of silicon carbide particles, 3-6% of zirconium oxide particles, 5-10% of activated carbon powder, 7-15% of polyvinyl alcohol, and 3-6% of paraffin oil.

[0011] Preferably, in the step three, the mass proportion of each component is 65-75% of silicon carbide particles, 5-7% of zirconium oxide particles, 10-16% of activated carbon powder, 8-15% of polyvinyl alcohol, and 2-6% of paraffin oil; in step four, the pre-extrusion pressure is 50-90MPa, the finished product extrusion pressure is 160-200MPa, the finished product is maintained at pressure for 1-2h after extrusion, and the pre-sintering temperature is 600-900℃.

[0012] Preferably, in the step five, the mass proportion of each component is 20-40% for silicon carbide particles, 2-12% for zirconium oxide particles, 3-10% for mullite particles, 30-60% for methyl cellulose solution, and 1-5% for ethanol. The vacuum stirring time is 50-120 min, and the drying temperature is 60-90°C.

[0013] Preferably, in the step six, the temperature is first raised to 600-900°C, kept warm for 2-5h in an air atmosphere, then nitrogen is introduced, the temperature is raised to 1100-1800°C in a nitrogen atmosphere, kept warm for 2-4h, then the temperature is lowered to 500-600°C, and finally naturally cooled to room temperature, and the rate of programmed heating and programmed cooling is 5-15°C / min.

[0014] The present invention discloses a thin-walled low-resistance silicon carbide ceramic membrane and its preparation process. The toughening layer is added to the tube body, and the toughening material is used to increase the strength and toughness of the ceramic membrane. The tube body thickness of the silicon carbide ceramic membrane can be reduced to less than 10 mm. Compared with ordinary silicon carbide ceramic membranes, the thickness is reduced, the strength is improved, and the operating resistance is reduced by more than 30%, which reduces the operating energy consumption, increases the strength of the ceramic membrane, and prolongs the service life of the ceramic membrane. The thin-walled low-resistance silicon carbide ceramic membrane described in the present invention is provided with an expansion end at the top. When in use, it is directly suspended on the flower plate hole through the expansion end. In order to avoid the connection neck at the connection between the ceramic membrane and the flower plate hole from breaking, the inner side of the connection neck is thickened to form a protrusion. The protrusion can not only enhance the strength of the connection neck, but also form an inwardly contracted annular throat, so that the ceramic membrane connection neck forms a Venturi structure. During use, the reverse blowing into the ceramic membrane tube can be enhanced to enhance the airflow and the back-blowing effect. The toughening material set in the pipe body uses metal mesh, porous foam metal or foam ceramic porous toughness material. While enhancing the strength of the ceramic membrane, the silicon carbide mixed material can enter the pores of the toughening material, so that the silicon carbide material and the toughening material form a reinforced concrete structure, ensuring the overall performance of the silicon carbide ceramic membrane. The preparation process of the thin-walled low-resistance silicon carbide ceramic membrane adopts layered preparation, vibration breaks the boundaries of each layer and then high-temperature sintering to avoid incompatibility between the layers of the silicon carbide ceramic membrane, ensuring the overall performance of the thin-walled low-resistance silicon carbide ceramic membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the structure of the thin-walled, low-resistance silicon carbide ceramic membrane described in the present invention.

[0016] Figure 2 It is the longitudinal section structure diagram of the pipe body.

[0017] Figure 3 It is a cross-sectional structural diagram of the pipe body.

[0018] Figure 4 It is an electron microscope picture of the transverse and longitudinal sections of the tube body.

[0019] Figure 5 This is a data diagram of the pore size distribution of the pipe body toughening layer.

[0020] Figure 6 This is the pore size distribution diagram of the finished tube body.

[0021] Figure 7 This is a data chart of the air permeability of the thin-walled, low-resistance silicon carbide ceramic membrane.

[0022] Among them, 1 is an expansion end, 2 is a connecting neck, 3 is a tube body, 4 is a tube bottom, 201 is a protrusion, 301 is a separation membrane layer, 302 is a transition layer, 303 is a toughening layer, 304 is an inner support layer, 3031 is a toughening material, and 401 is a positioning hole. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0024] A thin-walled low-resistance silicon carbide ceramic membrane, which is a tubular membrane with one end sealed and formed by integral sintering, and comprises, from top to bottom, an expansion end 1, a connecting neck 2, a tube body 3, and a tube bottom 4. A protrusion 201 is formed inwardly around the inner side of the connecting neck 2 to form an annular throat. The upper part of the protrusion 201 is located in the expansion end 1, and the lower part is located in the tube body 3, and penetrates into the expansion end 1 and the tube body 3 by 2 cm respectively. The tube wall of the end 1, the connecting neck 2, the tube body 3 and the tube bottom 4 of the ceramic membrane is a multi-layer structure, and comprises, from the outside to the inside, a separation membrane layer 301, a transition layer 302, a toughening layer 303, and an inner support layer 304. The separation membrane layer 301 is 50μm thick, the transition layer 302 is 500μm thick, the toughening layer 303 is 3mm thick, the inner support layer 304 is 2mm thick, and a toughening material 3031 is provided in the toughening layer 303, and the toughening material 3031 is a porous foam metal. The protrusion 201 is made of the inner support layer 304 material which is thickened to a thickness of 3 mm.

[0025] Furthermore, the thickness of the tube bottom 4 is 30 mm, and a positioning hole 401 is recessed on the outer bottom surface at the center, and the depth of the positioning hole 401 is 8 mm. The thickened portion of the tube bottom 4 compared to the tube body 3 is made of a transition layer 302 material.

[0026] Furthermore, the expansion end 1 is in the shape of a cone that is larger at the top and smaller at the bottom, and the diameter of the upper end is 1.3 times the diameter of the lower end.

[0027] Furthermore, the separation membrane layer 301 has a pore size of 2 μm and a porosity of 30%, the transition layer 302 has a pore size of 10 μm and a porosity of 40%, the toughening layer 303 has a pore size of 30 μm and a porosity of 50%, and the toughening material 3031 is made by infiltrating silicon carbide particles into the pores and sintering. The toughening material 3031 has a pore size of 800 μm, and the inner support layer 304 has a pore size of 50 μm and a porosity of 60%.

[0028] Furthermore, the toughening material 3031 is in a cylindrical shape and is placed inside the entire tube body 3 .

[0029] A process for preparing the above-mentioned thin-walled and low-resistance silicon carbide ceramic membrane comprises the following steps: Step 1: Prepare a toughening layer mixture and a toughening layer 303, add silicon carbide particles with a particle size of 20 μm, zirconium oxide particles with a particle size of 10 μm, and activated carbon powder with a particle size of 10 μm to a ball mill in proportion for ball milling and mixing, add polyvinyl alcohol and paraffin oil after mixing for a certain period of time, and continue to mix, place the toughening material 3031 in a toughening layer rubber mold, add the mixed toughening layer mixture to the rubber mold, make the toughening layer mixture enter the pores of the toughening material 3031 by vibration, and obtain the toughening layer 303 after extrusion molding and demolding; Step 2: Prepare a transition layer mixture, add silicon carbide particles with a particle size of 10 μm, zirconium oxide particles with a particle size of 5 μm, and activated carbon powder with a particle size of 8 μm into a ball mill according to a certain proportion, and then add polyvinyl alcohol and paraffin oil to continue mixing after mixing for a certain period of time to obtain a transition layer mixture; Step 3: Prepare an inner support layer mixture, add silicon carbide particles with a particle size of 100 μm, zirconium oxide particles with a particle size of 30 μm, and activated carbon powder with a particle size of 20 μm into a ball mill according to a certain proportion, and then add polyvinyl alcohol and paraffin oil after mixing for a certain period of time to obtain an inner support layer mixture; Step 4: Pre-sintered embryo body preparation, the toughening layer 303 prepared in step 1 is placed in the finished product mold, the transition layer mixture is filled on the outside, and the inner support layer mixture is filled on the inside. After filling, pre-extrusion is performed, and after pre-extrusion, the mixture is vibrated to break the boundaries between the layers, and finally the finished product is extruded. After demoulding, it is placed in an atmosphere furnace for pre-sintering to obtain a pre-sintered embryo body; the inner protrusion 201 around the inner side of the connecting neck 2 is filled with the inner support layer mixture; the thickened part at the bottom of the tube bottom 4 is filled with the transition layer mixture; Step 5: Preparation of separation membrane layer: silicon carbide particles with a particle size of 5 μm, zirconium oxide particles with a particle size of 5 μm, mullite particles with a particle size of 1 μm, methyl cellulose solution, and ethanol are added to deionized water in proportion, vacuumed and stirred to prepare a coating liquid, and the prepared coating liquid is evenly sprayed on the pre-sintered embryo body prepared in step 4, and dried to obtain a pre-sintered embryo body with a separation membrane layer; Step 6: Place the pre-sintered blank with the separation membrane layer in an atmosphere furnace for programmed temperature sintering to obtain a thin-walled, low-resistance silicon carbide ceramic membrane.

[0030] Furthermore, in the step one, the mass proportion of each component is 65% of silicon carbide particles, 4% of zirconium oxide particles, 15% of activated carbon powder, 10% of polyvinyl alcohol, and 6% of paraffin oil, and the extrusion molding pressure is 80 MPa. In the step two, the mass proportion of each component is 70% of silicon carbide particles, 6% of zirconium oxide particles, 10% of activated carbon powder, 10% of polyvinyl alcohol, and 4% of paraffin oil.

[0031] Furthermore, in the step three, the mass proportion of each component is 65% of silicon carbide particles, 7% of zirconium oxide particles, 16% of activated carbon powder, 8% of polyvinyl alcohol, and 4% of paraffin oil. In step four, the pre-extrusion pressure is 50MPa, the finished product extrusion pressure is 160MPa, the finished product is maintained at pressure for 1h after extrusion, and the pre-sintering temperature is 600°C.

[0032] Furthermore, in the step five, the mass proportion of each component is 20% of silicon carbide particles, 12% of zirconium oxide particles, 10% of mullite particles, 53% of methyl cellulose solution, and 5% of ethanol. The vacuum stirring time is 50 minutes, and the drying temperature is 60°C.

[0033] Furthermore, in the step six, the temperature is first raised to 600°C, kept at this temperature for 2 hours in an air atmosphere, and then nitrogen is introduced, and the temperature is raised to 1100°C in a nitrogen atmosphere, kept at this temperature for 2 hours, and then the temperature is lowered to 500°C, and finally naturally cooled to room temperature, and the rates of the programmed heating and cooling are both 5°C / min.

[0034] Various parameters of the thin-walled, low-resistance silicon carbide ceramic membrane prepared in this embodiment and various parameters of conventional silicon carbide ceramic membranes are shown in Table 1. The thickness of the silicon carbide ceramic membrane prepared in this embodiment is only 5.5 mm, which is more than half the thickness of conventional silicon carbide, and the filtration resistance is reduced by more than 50%, but the mechanical strength is not significantly reduced.

[0035] Table 1 Comparison of various parameters of Example 1 and conventional silicon carbide film Main indicators unit The silicon carbide film of this embodiment Conventional silicon carbide film Overall thickness mm 5.5 12 resistance Pa 950 2000 Filtration accuracy μm 0.1 0.1 Mechanical strength MPa 23.5 25 Backflush pressure MPa 0.2 0.5 Backflush cycle h 3 1 Example 2

[0036] A thin-walled, low-resistance silicon carbide ceramic membrane, which is a tubular membrane with one end sealed and formed by integral sintering, and comprises, from top to bottom, an expansion end 1, a connecting neck 2, a tube body 3, and a tube bottom 4. A protrusion 201 is formed inwardly around the inner side of the connecting neck 2 to form an annular throat. The upper part of the protrusion 201 is located in the expansion end 1, and the lower part is located in the tube body 3, and penetrates 5 cm into the expansion end 1 and the tube body 3 respectively. The tube wall of the end 1, the connecting neck 2, the tube body 3 and the tube bottom 4 of the ceramic membrane is a multi-layer structure, and comprises, from the outside to the inside, a separation membrane layer 301, a transition layer 302, a toughening layer 303, and an inner support layer 304. The separation membrane layer 301 is 100 μm thick, the transition layer 302 is 1000 μm thick, the toughening layer 303 is 4 mm thick, the inner support layer 304 is 3 mm thick, and a toughening material 3031 is provided in the toughening layer 303, and the toughening material 3031 is a metal mesh. The protrusion 201 is made of the inner support layer 304 material which is thickened to a thickness of 5 mm.

[0037] Furthermore, the thickness of the tube bottom 4 is 50 mm, and a positioning hole 401 is recessed on the outer bottom surface at the center, and the depth of the positioning hole 401 is 15 mm. The thickened portion of the tube bottom 4 is thicker than the tube body 3 because the transition layer 302 material is thicker.

[0038] Furthermore, the expansion end 1 is in the shape of a cone that is larger at the top and smaller at the bottom, and the diameter of the upper end is 1.5 times the diameter of the lower end.

[0039] Furthermore, the separation membrane layer 301 has a pore size of 30 μm and a porosity of 65%, the transition layer 302 has a pore size of 50 μm and a porosity of 70%, the toughening layer 303 has a pore size of 80 μm and a porosity of 80%, and the toughening material 3031 is made by infiltrating silicon carbide particles into the pores and sintering. The toughening material 3031 has a pore size of 2000 μm, and the inner support layer 304 has a pore size of 100 μm and a porosity of 80%.

[0040] Furthermore, the toughening material 3031 is dispersed in the tube body 3 in the form of longitudinal strips, and the spacing between the strips in the tube body 3 is 0.5 cm.

[0041] A process for preparing the above-mentioned thin-walled and low-resistance silicon carbide ceramic membrane comprises the following steps: Step 1: prepare a toughening layer mixture and a toughening layer 303, add silicon carbide particles with a particle size of 200 μm, zirconium oxide particles with a particle size of 50 μm, and activated carbon powder with a particle size of 30 μm into a ball mill according to a proportion for ball milling and mixing, add polyvinyl alcohol and paraffin oil after mixing for a certain period of time, and continue to mix, place the toughening material 3031 in a toughening layer rubber mold, add the mixed toughening layer mixture into the rubber mold, make the toughening layer mixture enter the pores of the toughening material 3031 by vibration, and obtain the toughening layer 303 after extrusion molding and demolding; Step 2: Prepare a transition layer mixture, add silicon carbide particles with a particle size of 100 μm, zirconium oxide particles with a particle size of 30 μm, and activated carbon powder with a particle size of 20 μm into a ball mill according to a certain proportion, and then add polyvinyl alcohol and paraffin oil to continue mixing after mixing for a certain period of time to obtain a transition layer mixture; Step 3: Prepare an inner support layer mixture, add silicon carbide particles with a particle size of 300 μm, zirconium oxide particles with a particle size of 60 μm, and activated carbon powder with a particle size of 35 μm into a ball mill according to a certain proportion, and then add polyvinyl alcohol and paraffin oil after mixing for a certain period of time to obtain an inner support layer mixture; Step 4: Pre-sintered embryo body preparation, the toughening layer 303 prepared in step 1 is placed in the finished product mold, the transition layer mixture is filled on the outside, and the inner support layer mixture is filled on the inside. After filling, pre-extrusion is performed, and after pre-extrusion, the mixture is vibrated to break the boundaries between the layers, and finally the finished product is extruded. After demoulding, it is placed in an atmosphere furnace for pre-sintering to obtain a pre-sintered embryo body; the inner protrusion 201 around the inner side of the connecting neck 2 is filled with the inner support layer mixture; the thickened part at the bottom of the tube bottom 4 is filled with the transition layer mixture; Step 5: Preparation of separation membrane layer: silicon carbide particles with a particle size of 15 μm, zirconium oxide particles with a particle size of 10 μm, mullite particles with a particle size of 5 μm, methyl cellulose solution, and ethanol are added to deionized water in proportion, vacuumed and stirred to prepare a coating liquid, and the prepared coating liquid is evenly sprayed on the pre-sintered embryo body prepared in step 4, and dried to obtain a pre-sintered embryo body with a separation membrane layer; Step 6: Place the pre-sintered blank with the separation membrane layer in an atmosphere furnace for programmed temperature sintering to obtain a thin-walled, low-resistance silicon carbide ceramic membrane.

[0042] Furthermore, in the step one, the mass proportion of each component is 80% of silicon carbide particles, 4% of zirconium oxide particles, 8% of activated carbon powder, 5% of polyvinyl alcohol, and 3% of paraffin oil, and the extrusion molding pressure is 100 MPa. In the step two, the mass proportion of each component is 80% of silicon carbide particles, 3% of zirconium oxide particles, 5% of activated carbon powder, 7% of polyvinyl alcohol, and 5% of paraffin oil.

[0043] Furthermore, in the step three, the mass proportion of each component is 75% of silicon carbide particles, 5% of zirconium oxide particles, 10% of activated carbon powder, 8% of polyvinyl alcohol, and 2% of paraffin oil. In step four, the pre-extrusion pressure is 90MPa, the finished product extrusion pressure is 200MPa, the finished product is kept at pressure for 2h after extrusion, and the pre-sintering temperature is 900°C.

[0044] Furthermore, in the step five, the mass proportion of each component is 40% of silicon carbide particles, 12% of zirconium oxide particles, 10% of mullite particles, 35% of methyl cellulose solution, and 3% of ethanol. The vacuum stirring time is 120 minutes, and the drying temperature is 90°C.

[0045] Furthermore, in the step six, the temperature is first raised to 900°C, kept at this temperature for 5 hours in an air atmosphere, and then nitrogen is introduced, and the temperature is raised to 1800°C in a nitrogen atmosphere, kept at this temperature for 4 hours, and then the temperature is lowered to 600°C, and finally naturally cooled to room temperature, and the rates of the programmed heating and programmed cooling are both 15°C / min.

[0046] The parameters of the thin-walled, low-resistance silicon carbide ceramic membrane prepared in this embodiment and the parameters of conventional silicon carbide ceramic membranes are shown in Table 2. The thickness of the silicon carbide ceramic membrane prepared in this embodiment is only 8.1 mm, which is about 10% thinner than conventional silicon carbide, the filtration resistance is reduced by 30%, and the mechanical strength is significantly increased.

[0047] Table 2 Comparison of various parameters of Example 2 and conventional silicon carbide film Main indicators unit The silicon carbide film of this embodiment Conventional silicon carbide film Overall thickness mm 8.1 10 resistance Pa 1200 1800 Filtration accuracy μm 0.1 0.1 Mechanical strength MPa 28 25 Backflush pressure MPa 0.3 0.4 Backflush cycle h 2 1.5 Example 3

[0048] A thin-walled low-resistance silicon carbide ceramic membrane, the ceramic membrane is a tubular membrane with one end sealed and formed by integral sintering, comprising from top to bottom an expansion end 1, a connecting neck 2, a tube body 3, and a tube bottom 4, a bulge 201 is formed inwardly around the inner side of the connecting neck 2 to form an annular throat, the upper part of the bulge 201 is located in the expansion end 1, and the lower part is located in the tube body 3, and penetrates into the expansion end 1 and the tube body 3 by 3 cm respectively, the tube wall of the end 1, the connecting neck 2, the tube body 3 and the tube bottom 4 of the ceramic membrane is a multi-layer structure, comprising from the outside to the inside a separation membrane layer 301, a transition layer 302, a toughening layer 303, and an inner support layer 304, the separation membrane layer 301 is 80μm thick, the transition layer 302 is 700μm thick, the toughening layer 303 is 3.5mm thick, the inner support layer 304 is 2.5mm thick, and a toughening material 3031 is provided in the toughening layer 303, and the toughening material 3031 is foam ceramic. The protrusion 201 is made of the inner support layer 304 material which is thickened to a thickness of 3 mm.

[0049] Furthermore, the thickness of the tube bottom 4 is 40 mm, and a positioning hole 401 is recessed on the outer bottom surface at the center, and the depth of the positioning hole 401 is 10 mm. The thickened portion of the tube bottom 4 is thicker than the tube body 3 because the transition layer 302 material is thicker.

[0050] Furthermore, the expansion end 1 is in the shape of a cone that is larger at the top and smaller at the bottom, and the diameter of the upper end is 1.4 times the diameter of the lower end.

[0051] Furthermore, the separation membrane layer 301 has a pore size of 10 μm and a porosity of 50%, the transition layer 302 has a pore size of 30 μm and a porosity of 50%, the toughening layer 303 has a pore size of 50 μm and a porosity of 60%, and is made by infiltrating silicon carbide particles into the pores of the toughening material 3031 and sintering. The toughening material 3031 has a pore size of 1200 μm, and the inner support layer 304 has a pore size of 60 μm and a porosity of 70%.

[0052] Furthermore, the toughening material 3031 is dispersed in the tube body 3 in the form of longitudinal strips, and the toughening material is arranged in the tube body 3 at a spacing of 0.8 cm.

[0053] A process for preparing the above-mentioned thin-walled and low-resistance silicon carbide ceramic membrane comprises the following steps: Step 1: prepare a toughening layer mixture and a toughening layer 303, add silicon carbide particles with a particle size of 100 μm, zirconium oxide particles with a particle size of 40 μm, and activated carbon powder with a particle size of 20 μm into a ball mill according to a proportion for ball milling and mixing, add polyvinyl alcohol and paraffin oil after mixing for a certain period of time, and continue to mix, place the toughening material 3031 in a toughening layer rubber mold, add the mixed toughening layer mixture into the rubber mold, make the toughening layer mixture enter the pores of the toughening material 3031 by vibration, and obtain the toughening layer 303 after extrusion molding and demolding; Step 2: Prepare a transition layer mixture, add silicon carbide particles with a particle size of 60 μm, zirconium oxide particles with a particle size of 20 μm, and activated carbon powder with a particle size of 10 μm into a ball mill according to a certain proportion, and then add polyvinyl alcohol and paraffin oil to continue mixing after mixing for a certain period of time to obtain a transition layer mixture; Step 3: Prepare an inner support layer mixture, add silicon carbide particles with a particle size of 200 μm, zirconium oxide particles with a particle size of 40 μm, and activated carbon powder with a particle size of 30 μm into a ball mill according to a certain proportion, and then add polyvinyl alcohol and paraffin oil after mixing for a certain period of time to continue mixing to obtain an inner support layer mixture; Step 4: Pre-sintered embryo body preparation, the toughening layer 303 prepared in step 1 is placed in the finished product mold, the transition layer mixture is filled on the outside, and the inner support layer mixture is filled on the inside. After filling, pre-extrusion is performed, and after pre-extrusion, the mixture is vibrated to break the boundaries between the layers, and finally the finished product is extruded. After demoulding, it is placed in an atmosphere furnace for pre-sintering to obtain a pre-sintered embryo body; the inner protrusion 201 around the inner side of the connecting neck 2 is filled with the inner support layer mixture; the thickened part at the bottom of the tube bottom 4 is filled with the transition layer mixture; Step 5: Preparation of separation membrane layer: silicon carbide particles with a particle size of 10 μm, zirconium oxide particles with a particle size of 8 μm, mullite particles with a particle size of 3 μm, methyl cellulose solution, and ethanol are added to deionized water in proportion, vacuumed and stirred to prepare a coating liquid, and the prepared coating liquid is evenly sprayed on the pre-sintered embryo body prepared in step 4, and dried to obtain a pre-sintered embryo body with a separation membrane layer; Step 6: Place the pre-sintered blank with the separation membrane layer in an atmosphere furnace for programmed temperature sintering to obtain a thin-walled, low-resistance silicon carbide ceramic membrane.

[0054] Furthermore, in the step one, the mass proportion of each component is 75% of silicon carbide particles, 3% of zirconium oxide particles, 10% of activated carbon powder, 7% of polyvinyl alcohol, and 5% of paraffin oil, and the extrusion molding pressure is 90 MPa. In the step two, the mass proportion of each component is 80% of silicon carbide particles, 5% of zirconium oxide particles, 5% of activated carbon powder, 7% of polyvinyl alcohol, and 3% of paraffin oil.

[0055] Furthermore, in the step three, the mass proportion of each component is 68% of silicon carbide particles, 6% of zirconium oxide particles, 11% of activated carbon powder, 9% of polyvinyl alcohol, and 4% of paraffin oil. In step four, the pre-extrusion pressure is 80MPa, the finished product extrusion pressure is 180MPa, the finished product is maintained at pressure for 1.5 hours after extrusion, and the pre-sintering temperature is 800°C.

[0056] Furthermore, in the step five, the mass proportion of each component is 30% of silicon carbide particles, 10% of zirconium oxide particles, 10% of mullite particles, 45% of methyl cellulose solution, and 5% of ethanol. The vacuum stirring time is 100 minutes, and the drying temperature is 80°C.

[0057] Furthermore, in the step six, the temperature is first raised to 750°C, kept at this temperature for 4 hours in an air atmosphere, and then nitrogen is introduced, and the temperature is raised to 1500°C in a nitrogen atmosphere, kept at this temperature for 3 hours, and then the temperature is lowered to 550°C, and finally naturally cooled to room temperature, and the rates of the programmed heating and programmed cooling are both 10°C / min.

[0058] Various parameters of the thin-walled, low-resistance silicon carbide ceramic membrane prepared in this embodiment and various parameters of conventional silicon carbide ceramic membranes are shown in Table 3. The thickness of the silicon carbide ceramic membrane prepared in this embodiment is only 6.8 mm, which is more than 20% thinner than conventional silicon carbide, and the filtration resistance is reduced by more than 30%, and the mechanical strength is equivalent to that of conventional silicon carbide membranes.

[0059] Table 3 Comparison of various parameters of Example 3 and conventional silicon carbide film Main indicators unit The silicon carbide film of this embodiment Conventional silicon carbide film Overall thickness mm 6.8 11 resistance Pa 1000 1700 Filtration accuracy μm 0.1 0.1 Mechanical strength MPa 26 25 Backflush pressure MPa 0.25 0.4 Backflush cycle h 3 1.5 Example 4

[0060] A thin-walled low-resistance silicon carbide ceramic membrane, the ceramic membrane is a tubular membrane with one end sealed by integral sintering, and includes an expansion end 1, a connecting neck 2, a tube body 3, and a tube bottom 4 from top to bottom. A bulge 201 is formed inwardly around the inner side of the connecting neck 2 to form an annular throat. The upper part of the bulge 201 is located in the expansion end 1, and the lower part is located in the tube body 3, and penetrates into the expansion end 1 and the tube body 3 by 4.5 cm respectively. The end 1 and the connecting neck of the ceramic membrane are 2. The tube wall of the tube body 3 and the tube bottom 4 is a multi-layer structure, which includes a separation membrane layer 301, a transition layer 302, a toughening layer 303, and an inner support layer 304 from the outside to the inside. The separation membrane layer 301 is 80 μm thick, the transition layer 302 is 900 μm thick, the toughening layer 303 is 3.8 mm thick, and the inner support layer 304 is 2.3 mm thick. The toughening layer 303 is provided with a toughening material 3031, which is a metal mesh and foam ceramic. The protrusion 201 is a thickening material of the inner support layer 304, and the thickness is 5 mm.

[0061] Furthermore, the thickness of the tube bottom 4 is 33 mm, and a positioning hole 401 is recessed on the outer bottom surface at the center, and the depth of the positioning hole 401 is 12 mm. The thickened portion of the tube bottom 4 is thicker than the tube body 3 because the transition layer 302 material is thicker.

[0062] Furthermore, the expansion end 1 is in the shape of a cone that is larger at the top and smaller at the bottom, and the diameter of the upper end is 1.4 times the diameter of the lower end.

[0063] Furthermore, the separation membrane layer 301 has a pore size of 20 μm and a porosity of 45%, the transition layer 302 has a pore size of 35 μm and a porosity of 65%, the toughening layer 303 has a pore size of 58 μm and a porosity of 75%, and the toughening material 3031 is made by infiltrating silicon carbide particles into the pores and sintering. The toughening material 3031 has a pore size of 1200 μm, and the inner support layer 304 has a pore size of 88 μm and a porosity of 69%.

[0064] Furthermore, the toughening material 3031 is in a cylindrical shape and is placed inside the entire tube body 3, and the metal mesh is placed inside the foam ceramic.

[0065] A process for preparing the above-mentioned thin-walled and low-resistance silicon carbide ceramic membrane comprises the following steps: Step 1: Prepare a toughening layer mixture and a toughening layer 303, add silicon carbide particles with a particle size of 180 μm, zirconium oxide particles with a particle size of 45 μm, and activated carbon powder with a particle size of 28 μm to a ball mill in proportion for ball milling and mixing, add polyvinyl alcohol and paraffin oil after mixing for a certain period of time, and continue to mix, place the toughening material 3031 in a toughening layer rubber mold, add the mixed toughening layer mixture to the rubber mold, make the toughening layer mixture enter the pores of the toughening material 3031 by vibration, and obtain the toughening layer 303 after extrusion molding and demolding; Step 2: Prepare a transition layer mixture, add silicon carbide particles with a particle size of 86 μm, zirconium oxide particles with a particle size of 19 μm, and activated carbon powder with a particle size of 18 μm into a ball mill according to a certain proportion, and then add polyvinyl alcohol and paraffin oil to continue mixing after mixing for a certain period of time to obtain a transition layer mixture; Step 3: Prepare the inner support layer mixture, add silicon carbide particles with a particle size of 240 μm, zirconium oxide particles with a particle size of 35 μm, and activated carbon powder with a particle size of 32 μm into a ball mill according to a certain proportion, and then add polyvinyl alcohol and paraffin oil to continue mixing to obtain the inner support layer mixture after mixing for a certain period of time; Step 4: Pre-sintered embryo body preparation, the toughening layer 303 prepared in step 1 is placed in the finished product mold, the transition layer mixture is filled on the outside, and the inner support layer mixture is filled on the inside. After filling, pre-extrusion is performed, and after pre-extrusion, the mixture is vibrated to break the boundaries between the layers, and finally the finished product is extruded. After demoulding, it is placed in an atmosphere furnace for pre-sintering to obtain a pre-sintered embryo body; the inner protrusion 201 around the inner side of the connecting neck 2 is filled with the inner support layer mixture; the thickened part at the bottom of the tube bottom 4 is filled with the transition layer mixture; Step 5: Preparation of separation membrane layer: silicon carbide particles with a particle size of 12 μm, zirconium oxide particles with a particle size of 9 μm, mullite particles with a particle size of 2 μm, methyl cellulose solution, and ethanol are added to deionized water in proportion, vacuumed and stirred to prepare a coating liquid, and the prepared coating liquid is evenly sprayed on the pre-sintered embryo body prepared in step 4, and dried to obtain a pre-sintered embryo body with a separation membrane layer; Step 6: Place the pre-sintered blank with the separation membrane layer in an atmosphere furnace for programmed temperature sintering to obtain a thin-walled, low-resistance silicon carbide ceramic membrane.

[0066] Furthermore, in the step one, the mass proportion of each component is 78% of silicon carbide particles, 3% of zirconium oxide particles, 9% of activated carbon powder, 6% of polyvinyl alcohol, and 4% of paraffin oil, and the extrusion molding pressure is 95 MPa. In the step two, the mass proportion of each component is 79% of silicon carbide particles, 4% of zirconium oxide particles, 7% of activated carbon powder, 7% of polyvinyl alcohol, and 3% of paraffin oil.

[0067] Furthermore, in the step three, the mass proportion of each component is 72% for silicon carbide particles, 6% for zirconium oxide particles, 12% for activated carbon powder, 8% for polyvinyl alcohol, and 2% for paraffin oil. In step four, the pre-extrusion pressure is 75 MPa, the finished product extrusion pressure is 190 MPa, the finished product is maintained at pressure for 1.8 hours after extrusion, and the pre-sintering temperature is 850°C.

[0068] Furthermore, in the step five, the mass proportion of each component is 36% of silicon carbide particles, 11% of zirconium oxide particles, 6% of mullite particles, 44% of methyl cellulose solution, and 3% of ethanol. The vacuum stirring time is 110 minutes, and the drying temperature is 80°C.

[0069] Furthermore, in the step six, the temperature is first raised to 870°C, kept at this temperature for 4 hours in an air atmosphere, and then nitrogen is introduced, and the temperature is raised to 1750°C in a nitrogen atmosphere, kept at this temperature for 3 hours, and then the temperature is lowered to 560°C, and finally naturally cooled to room temperature, and the rates of the programmed heating and cooling are both 9°C / min.

[0070] The parameters of the thin-walled, low-resistance silicon carbide ceramic membrane prepared in this embodiment and the parameters of conventional silicon carbide ceramic membranes are shown in Table 4. The thickness of the silicon carbide ceramic membrane prepared in this embodiment is only 7.1 mm, which is 29% thinner than conventional silicon carbide, and the filtration resistance is reduced by more than 30%. The mechanical strength is slightly increased compared with conventional silicon carbide membranes.

[0071] Table 4 Comparison of various parameters of Example 4 and conventional silicon carbide film Main indicators unit The silicon carbide film of this embodiment Conventional silicon carbide film Overall thickness mm 7.1 10 resistance Pa 1100 1600 Filtration accuracy μm 0.1 0.1 Mechanical strength MPa 27.5 26 Backflush pressure MPa 0.2 0.4 Backflush cycle h 3 1.5

Claims

1. A thin-walled, low-resistance silicon carbide ceramic membrane, characterized in that: The ceramic membrane is a tubular membrane with one end sealed and formed by integral sintering, and comprises, from top to bottom, an expansion end (1), a connecting neck (2), a tube body (3), and a tube bottom (4); a bulge (201) is formed inwardly around the inner side of the connecting neck (2) to form an annular throat, the upper part of the bulge (201) is located inside the expansion end (1), and the lower part is located inside the tube body (3), and penetrates into the expansion end (1) and the tube body (3) by 2-5 cm respectively; the tube wall of the end (1), the connecting neck (2), the tube body (3) and the tube bottom (4) of the ceramic membrane is a multi-layer structure, and comprises, from the outside to the inside, a separation membrane layer (3 01), transition layer (302), toughening layer (303), inner support layer (304), the separation membrane layer (301) has a thickness of 50-100 μm, the transition layer (302) has a thickness of 500-1000 μm, the toughening layer (303) has a thickness of 3-4 mm, the inner support layer (304) has a thickness of 2-3 mm, a toughening material (3031) is provided in the toughening layer (303), and the toughening material (3031) is one or more of a metal mesh, a porous foam metal or a foam ceramic; the protrusion (201) is a thickened material of the inner support layer (304), and has a thickness of 3-5 mm.

2. A thin-walled low-resistance silicon carbide ceramic membrane according to claim 1, characterized in that: The thickness of the tube bottom (4) is 30-50 mm, a positioning hole (401) is provided in a recessed manner on the outer bottom surface at the center, and the depth of the positioning hole (401) is 8-15 mm. The thickened portion of the tube bottom (4) is thicker than the tube body (3) and is made of a transition layer (302) material.

3. A thin-walled low-resistance silicon carbide ceramic membrane according to claim 1, characterized in that: The expansion end (1) is in the shape of a cone that is larger at the top and smaller at the bottom, and the diameter of the upper end is 1.3-1.5 times the diameter of the lower end.

4. A thin-walled low-resistance silicon carbide ceramic membrane according to claim 1, characterized in that: The separation membrane layer (301) has a pore size of 2-30 μm and a porosity of 30-65%. The transition layer (302) has a pore size of 10-50 μm and a porosity of 40-70%. The toughening layer (303) has a pore size of 30-80 μm and a porosity of 50-80%. The toughening material (3031) is made by infiltrating silicon carbide particles into the pores and sintering. The toughening material (3031) has a pore size of 800-2000 μm. The inner support layer (304) has a pore size of 50-100 μm and a porosity of 60-80%.

5. A thin-walled low-resistance silicon carbide ceramic membrane according to claim 1, characterized in that: The toughening material (3031) is in a cylindrical shape and is placed in the entire tube body (3), or is in a longitudinal strip shape and is dispersed in the tube body (3). When the toughening material (3031) is in a strip shape, the spacing between them in the tube body (3) is 0.5-1 cm.

6. A process for preparing a thin-walled low-resistance silicon carbide ceramic membrane according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: preparing a toughening layer mixture and a toughening layer (303), adding silicon carbide particles with a particle size of 20-200 μm, zirconium oxide particles with a particle size of 10-50 μm, and activated carbon powder with a particle size of 10-30 μm to a ball mill in proportion for ball milling and mixing, adding polyvinyl alcohol and paraffin oil after mixing for a certain period of time and continuing to mix, placing the toughening material (3031) in a toughening layer rubber mold, adding the mixed toughening layer mixture to the rubber mold, vibrating the toughening layer mixture to allow it to enter the pores of the toughening material (3031), extruding and demolding, and obtaining the toughening layer (303); Step 2: Prepare a transition layer mixture, add silicon carbide particles with a particle size of 10-100 μm, zirconium oxide particles with a particle size of 5-30 μm, and activated carbon powder with a particle size of 8-20 μm into a ball mill according to a proportion, and mix them by ball milling. After mixing for a certain period of time, add polyvinyl alcohol and paraffin oil and continue mixing to obtain a transition layer mixture; Step 3: Prepare an inner support layer mixture, add silicon carbide particles with a particle size of 100-300 μm, zirconium oxide particles with a particle size of 30-60 μm, and activated carbon powder with a particle size of 20-35 μm into a ball mill according to a certain proportion, and then add polyvinyl alcohol and paraffin oil to continue mixing to obtain an inner support layer mixture after mixing for a certain period of time; Step 4: Pre-sintering embryo body preparation, placing the toughening layer (303) prepared in step 1 in the finished product mold, filling the transition layer mixture on the outside, and filling the inner support layer mixture on the inside, pre-extruding after filling, vibrating the mixture after pre-extrusion to break the boundaries between the layers, and finally extruding the finished product, demoulding, placing it in an atmosphere furnace for pre-sintering to obtain a pre-sintered embryo body; the inner side of the connecting neck (2) is filled with the inner support layer mixture; the thickened part at the bottom of the tube bottom (4) is filled with the transition layer mixture; Step 5: Preparation of separation membrane layer: silicon carbide particles with a particle size of 5-15 μm, zirconium oxide particles with a particle size of 5-10 μm, mullite particles with a particle size of 1-5 μm, methyl cellulose solution, and ethanol are added to deionized water in proportion, vacuumed and stirred to prepare a coating liquid, and the prepared coating liquid is evenly sprayed on the pre-sintered embryo body prepared in step 4, and dried to obtain a pre-sintered embryo body with a separation membrane layer; Step 6: Place the pre-sintered blank with the separation membrane layer in an atmosphere furnace for programmed temperature sintering to obtain a thin-walled, low-resistance silicon carbide ceramic membrane.

7. The process for preparing a thin-walled low-resistance silicon carbide ceramic membrane according to claim 6, characterized in that: In the step one, the mass proportion of each component is 65-80% of silicon carbide particles, 2-4% of zirconium oxide particles, 8-15% of activated carbon powder, 5-10% of polyvinyl alcohol, and 3-6% of paraffin oil, and the extrusion molding pressure is 80-100MPa; in the step two, the mass proportion of each component is 70-85% of silicon carbide particles, 3-6% of zirconium oxide particles, 5-10% of activated carbon powder, 7-15% of polyvinyl alcohol, and 3-6% of paraffin oil.

8. The process for preparing a thin-walled low-resistance silicon carbide ceramic membrane according to claim 6, characterized in that: In the step three, the mass proportion of each component is 65-75% of silicon carbide particles, 5-7% of zirconium oxide particles, 10-16% of activated carbon powder, 8-15% of polyvinyl alcohol, and 2-6% of paraffin oil; in step four, the pre-extrusion pressure is 50-90MPa, the finished product extrusion pressure is 160-200MPa, the finished product is kept at pressure for 1-2h after extrusion, and the pre-sintering temperature is 600-900℃.

9. The process for preparing a thin-walled low-resistance silicon carbide ceramic membrane according to claim 6, characterized in that: In the step 5, the mass proportion of each component is 20-40% of silicon carbide particles, 2-12% of zirconium oxide particles, 3-10% of mullite particles, 30-60% of methyl cellulose solution, and 1-5% of ethanol. The vacuum stirring time is 50-120 minutes, and the drying temperature is 60-90°C.

10. The process for preparing a thin-walled low-resistance silicon carbide ceramic membrane according to claim 6, characterized in that: In the step six, the temperature is first raised to 600-900°C, kept warm for 2-5 hours in an air atmosphere, and then nitrogen is introduced, and the temperature is raised to 1100-1800°C in a nitrogen atmosphere, kept warm for 2-4 hours, and then the temperature is lowered to 500-600°C, and finally naturally cooled to room temperature. The rate of programmed heating and programmed cooling is 5-15°C / min.

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