Thin-walled low-resistance silicon carbide ceramic membrane and its preparation process

Abstract

The application discloses a thin-wall low-resistance silicon carbide ceramic membrane and a preparation process thereof. The ceramic membrane is a tubular membrane with one end sealed and is integrally sintered and formed, and comprises an expansion end, a connecting neck, a tube body and a tube bottom from top to bottom. While the strength and toughness of the ceramic membrane are ensured, the wall thickness of the silicon carbide ceramic membrane is reduced, and the running resistance is reduced. The application adopts the mode of adding a toughening layer to the tube body, and the strength and toughness of the ceramic membrane are increased by using the toughening material. The thickness of the tube body of the silicon carbide ceramic membrane can be reduced to less than 10 mm. Compared with the ordinary silicon carbide ceramic membrane, the thickness is reduced, the strength is improved, and the filtering resistance is reduced by more than 30%. The running energy consumption is reduced, the strength of the ceramic membrane is increased, and the service life of the ceramic membrane is prolonged.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of new environmental protection materials, and particularly relates to a thin-wall low-resistance silicon carbide ceramic membrane and a preparation process thereof. BACKGROUND

[0002] The silicon carbide ceramic membrane is called a high-efficiency energy-saving and environment-friendly separation material due to its excellent thermal stability and chemical stability, and has become one of the common technologies for solving major problems such as water resources, energy and environment, and plays an important supporting role in reducing pollution and carbon in process industry. The silicon carbide ceramic membrane is a rigid material, in order to avoid breakage during use or installation, the thickness of the silicon carbide ceramic membrane is increased to enhance the strength of the silicon carbide ceramic membrane, and the wall thickness of the currently used silicon carbide ceramic membrane is generally more than 10 mm, which causes high running resistance and high energy consumption of the silicon carbide ceramic membrane. SUMMARY

[0003] In order to solve the problems of large wall thickness and high running resistance of the existing silicon carbide ceramic membrane, the present application discloses a thin-wall low-resistance silicon carbide ceramic membrane and a preparation process thereof, 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 purpose, the present application is realized by the following technical scheme:

[0005] A thin-wall low-resistance silicon carbide ceramic membrane, the ceramic membrane is a one-end sealed tubular membrane prepared by one-piece sintering, and comprises an expansion end head, a connecting neck, a tube body and a tube bottom from top to bottom; a protrusion is formed inwardly around the inner side of the connecting neck to form an annular throat, the upper part of the protrusion is located in the expansion end head, and the lower part is located in the tube body and respectively penetrates into the expansion end head and the tube body by 2-5 cm; the tube wall of the end head, the connecting neck, the tube body and the tube bottom of the ceramic membrane is a multi-layer structure, which comprises a separation membrane layer, a transition layer, a toughening layer and an inner support layer from outside to inside, the thickness of the separation membrane layer is 50-100 microns, the thickness of the transition layer is 500-1000 microns, the thickness of the toughening layer is 3-4 mm, and the thickness of the inner support layer is 2-3 mm, the toughening layer is provided with a toughening material, and the toughening material is one or more of a metal mesh, a porous foam metal or a foam ceramic; the protrusion is thickened with the inner support layer material, and the thickness is 3-5 mm.

[0006] Preferably, the thickness of the tube bottom is 30-50 mm, a positioning hole is provided in the concave outer bottom surface at the center position, the depth of the positioning hole is 8-15 mm, and the thickened part of the tube bottom compared with the tube body is thickened with the transition layer material.

[0007] Preferably, the expansion end head is a tapered shape with a large upper end and a small lower end, and the upper end diameter is 1.3-1.5 times the lower end diameter.

[0008] Preferably, the separation membrane layer has a pore size of 2-30 microns and a porosity of 30-65%, the transition layer has a pore size of 10-50 microns and a porosity of 40-70%, the toughening layer has a pore size of 30-80 microns and a porosity of 50-80%, the silicon carbide particles are sintered into the pores of the toughening material to form the toughening material, the toughening material has a pore size of 800-2000 microns, and the inner support layer has a pore size of 50-100 microns and a porosity of 60-80%.

[0009] Preferably, the toughening material is in the form of a cylinder arranged in the entire pipe body or in the form of a longitudinal strip arranged in the pipe body, and when the toughening material is in the form of a strip, the arrangement interval in the pipe body is 0.5-1 cm.

[0010] The application also discloses a preparation process of the thin-walled low-resistance silicon carbide ceramic membrane.

[0011] Step one: preparing the toughening layer mixture and the toughening layer, silicon carbide particles with a particle size of 20-200 microns, zirconium oxide particles with a particle size of 10-50 microns and activated carbon powder with a particle size of 10-30 microns are added into a ball mill in a certain proportion for ball milling and mixing, polyvinyl alcohol and paraffin oil are added for further mixing after a certain mixing time, the toughening material is arranged in a rubber mold of the toughening layer, the mixed toughening layer mixture is added into the rubber mold, the toughening layer mixture is made to enter the pores of the toughening material by vibration, and the toughening layer is obtained after extrusion forming and demolding.

[0012] Step two: preparing the transition layer mixture, silicon carbide particles with a particle size of 10-100 microns, zirconium oxide particles with a particle size of 5-30 microns and activated carbon powder with a particle size of 8-20 microns are added into a ball mill in a certain proportion for ball milling and mixing, polyvinyl alcohol and paraffin oil are added for further mixing after a certain mixing time, and the transition layer mixture is obtained.

[0013] Step three: preparing the inner support layer mixture, silicon carbide particles with a particle size of 100-300 microns, zirconium oxide particles with a particle size of 30-60 microns and activated carbon powder with a particle size of 20-35 microns are added into a ball mill in a certain proportion for ball milling and mixing, polyvinyl alcohol and paraffin oil are added for further mixing after a certain mixing time, and the inner support layer mixture is obtained.

[0014] Step four: preparing the pre-sintered body, the toughening layer prepared in step one is arranged in a finished product mold, the transition layer mixture is filled outside, and the inner support layer mixture is filled inside, pre-extrusion is performed after filling, vibration mixing is performed after pre-extrusion, the boundaries between the layers are broken, finished product extrusion is finally performed, and the pre-sintered body is obtained after demolding and pre-sintering in an atmosphere furnace; the inner side of the connecting neck is protruded inward to fill the inner support layer mixture; the bottom of the pipe bottom is thicker than the pipe body to fill the transition layer mixture.

[0015] Step 5: Preparation of the 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, methylcellulose solution, and ethanol are added to deionized water in a certain proportion. The coating solution is prepared by vacuum stirring. The prepared coating solution is uniformly sprayed onto the pre-sintered preform prepared in Step 4 and dried to obtain a pre-sintered preform with a separation membrane layer.

[0016] Step 6: Place the pre-sintered blank with the separation film layer in an atmosphere furnace for programmed temperature sintering to obtain a thin-walled, low-resistance silicon carbide ceramic film.

[0017] Preferably, in step one, the mass percentage of each component is 65-80% silicon carbide particles, 2-4% zirconium oxide particles, 8-15% activated carbon powder, 5-10% polyvinyl alcohol, and 3-6% paraffin oil, and the extrusion molding pressure is 80-100 MPa; in step two, the mass percentage of each component is 70-85% silicon carbide particles, 3-6% zirconium oxide particles, 5-10% activated carbon powder, 7-15% polyvinyl alcohol, and 3-6% paraffin oil.

[0018] Preferably, in step three, the mass percentages of each component are: silicon carbide particles 65-75%, zirconium oxide particles 5-7%, activated carbon powder 10-16%, polyvinyl alcohol 8-15%, and paraffin oil 2-6%; in step four, the pre-extrusion pressure is 50-90 MPa, the finished product extrusion pressure is 160-200 MPa, the finished product is held under pressure for 1-2 hours after extrusion, and the pre-sintering temperature is 600-900℃.

[0019] Preferably, in step five, the mass percentages of each component are as follows: silicon carbide particles 20-40%, zirconium oxide particles 2-12%, mullite particles 3-10%, methylcellulose solution 30-60%, ethanol 1-5%, the vacuum stirring time is 50-120 min, and the drying temperature is 60-90℃.

[0020] Preferably, in step six, the temperature is first programmed to 600-900℃ and held in air for 2-5 hours. Then, nitrogen is introduced, and the temperature is raised to 1100-1800℃ in nitrogen atmosphere and held for 2-4 hours. Then, the temperature is programmed to decrease to 500-600℃ and finally cooled naturally to room temperature. The programmed heating and cooling rates are both 5-15℃ / min.

[0021] The application discloses a thin-wall low-resistance silicon carbide ceramic membrane and a preparation process thereof. The thickness of the silicon carbide ceramic membrane is reduced to less than 10 mm by adding a toughening layer to the pipe body, and the strength and toughness of the ceramic membrane are increased by using the toughening material. Compared with the ordinary silicon carbide ceramic membrane, the thickness is reduced, the strength is improved, the running resistance is reduced by more than 30%, the running energy consumption is reduced, the ceramic membrane strength is increased, and the service life of the ceramic membrane is prolonged. The thin-wall low-resistance silicon carbide ceramic membrane has an expansion end head arranged at the upper portion, and the expansion end head is directly hung on a flower plate hole in use. In order to avoid breakage of the connecting neck portion at the connection position of the ceramic membrane and the flower plate hole, the connecting neck portion is thickened on the inner side to form a protrusion. The protrusion can not only enhance the strength of the connecting neck portion, but also form an inwardly retracting annular throat, so that a venturi structure is formed at the connecting neck portion of the ceramic membrane, the airflow in the ceramic membrane pipe is enhanced in the reverse blowing process, and the reverse blowing effect is enhanced. The toughening material arranged in the pipe body is made of a metal mesh, a porous foam metal or a porous ceramic foam toughness material, so that the strength of the ceramic membrane is enhanced, the silicon carbide mixed material can enter the pore channel of the toughening material, the silicon carbide material and the toughening material form a reinforced concrete structure, and the overall performance of the silicon carbide ceramic membrane is ensured. The thin-wall low-resistance silicon carbide ceramic membrane is prepared by layering, vibration and high-temperature sintering, so that the incompatibility between the layers of the silicon carbide ceramic membrane is avoided, and the overall performance of the thin-wall low-resistance silicon carbide ceramic membrane is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A structure schematic diagram of the thin-wall low-resistance silicon carbide ceramic membrane is shown.

[0023] Figure 2 A structure diagram of a longitudinal section of the pipe body is shown.

[0024] Figure 3 A structure diagram of a transverse section of the pipe body is shown.

[0025] Figure 4 A transverse and longitudinal section electron microscope diagram of the pipe body is shown.

[0026] Figure 5 A pore size distribution data diagram of the toughening layer of the pipe body is shown.

[0027] Figure 6 A pore size distribution diagram of the finished product of the pipe body is shown.

[0028] Figure 7 A data diagram of the air permeability of the thin-wall low-resistance silicon carbide ceramic membrane is shown.

[0029] The expansion end head, the connecting neck portion, the pipe body, the pipe bottom, the protrusion, the separation membrane layer, the transition layer, the toughening layer, the inner support layer, the toughening material and the positioning hole are shown. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example

[0031] A thin-walled, low-resistance silicon carbide ceramic membrane is a tubular membrane integrally sintered and sealed at one end. From top to bottom, it includes an expansion end 1, a connecting neck 2, a tube body 3, and a tube bottom 4. A protrusion 201 is formed around the inner side of the connecting neck 2, forming an annular throat. The upper part of the protrusion 201 is located inside the expansion end 1, and the lower part is located inside the tube body 3, penetrating 2 cm into both the expansion end 1 and the tube body 3. The tube walls of the ceramic membrane, including the end 1, connecting neck 2, tube body 3, and tube bottom 4, have a multi-layer structure, including 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 has a thickness of 50 μm, the transition layer 302 has a thickness of 500 μm, the toughening layer 303 has a thickness of 3 mm, and the inner support layer 304 has a thickness of 2 mm. The toughening layer 303 contains a toughening material 3031, which is a porous foam metal. The protrusion 201 is an inner support layer made of thickened 304 material, with a thickness of 3mm.

[0032] Furthermore, the tube bottom 4 has a thickness of 30mm, and a positioning hole 401 with a depth of 8mm is recessed on the outer bottom surface at the center. The thicker part of the tube bottom 4 compared to the tube body 3 is made of a thicker transition layer 302 material.

[0033] Furthermore, the expansion end 1 is a cone shape that is larger at the top and smaller at the bottom, with the diameter of the upper end being 1.3 times the diameter of the lower end.

[0034] 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 is obtained by sintering silicon carbide particles into the pores of the toughening material 3031. 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%.

[0035] Furthermore, the toughening material 3031 is cylindrical and placed inside the entire tube body 3.

[0036] A process for preparing a thin-walled, low-resistance silicon carbide ceramic film, as described above, includes the following steps:

[0037] Step one: preparation of the toughening layer mixture and the toughening layer 303, 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 are added to a ball mill in a certain proportion for ball milling mixing, after mixing for a certain time, polyvinyl alcohol and paraffin oil are added for continuous mixing, the toughening material 3031 is placed in the toughening layer rubber mold, the mixed toughening layer mixture is added to the rubber mold, the toughening layer mixture is made to enter the pores of the toughening material 3031 by vibration, and after extrusion forming and demolding, the toughening layer 303 is obtained;

[0038] Step two: preparation of the transition layer mixture, 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 are added to a ball mill in a certain proportion for ball milling mixing, after mixing for a certain time, polyvinyl alcohol and paraffin oil are added for continuous mixing, and the transition layer mixture is obtained;

[0039] Step three: preparation of the inner support layer mixture, 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 are added to a ball mill in a certain proportion for ball milling mixing, after mixing for a certain time, polyvinyl alcohol and paraffin oil are added for continuous mixing, and the inner support layer mixture is obtained;

[0040] Step four: preparation of the pre-sintered body, the toughening layer 303 prepared in step one 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 is completed, pre-extrusion is performed, after pre-extrusion is completed, vibration mixing is performed to break the boundaries between the layers, finally, finished product extrusion is performed, and after demolding, the pre-sintered body is placed in an atmosphere furnace for pre-sintering, and the pre-sintered body is obtained; the inner side of the one circumferential protrusion 201 in the connecting neck 2 is protruded inward, which is filled with the inner support layer mixture; the thickened part at the bottom of the pipe bottom 4 is filled with the transition layer mixture;

[0041] Step five: preparation of the 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 a certain proportion, vacuum stirring is performed to prepare a coating solution, the prepared coating solution is uniformly sprayed on the pre-sintered body prepared in step four, and drying is performed to obtain a pre-sintered body with a separation membrane layer;

[0042] Step six: the pre-sintered body with the separation membrane layer is placed in an atmosphere furnace for programmed temperature sintering, and a thin-walled low-resistance silicon carbide ceramic membrane is obtained.

[0043] Further, in the step one, the mass ratio 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, the extrusion forming pressure is 80 MPa, and in the step two, the mass ratio 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.

[0044] Further, in the step three, the mass ratio 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, the pre-extrusion pressure is 50 MPa, the finished product extrusion pressure is 160 MPa, the finished product extrusion pressure is maintained for 1 h, and the pre-sintering temperature is 600℃.

[0045] Further, in the step five, the mass ratio 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 min, and the drying temperature is 60℃.

[0046] Further, in the step six, the temperature is first programmed to 600℃, and then maintained for 2 h in an air atmosphere, then nitrogen is introduced, the temperature is programmed to 1100℃ in a nitrogen atmosphere, and then maintained for 2 h, then the temperature is programmed to 500℃, and finally naturally cooled to room temperature, the programming rates of temperature increase and decrease are both 5℃ / min.

[0047] The parameters of the thin-walled low-resistance silicon carbide ceramic membrane prepared in this embodiment and the parameters of the conventional silicon carbide ceramic membrane 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 lower than that of the conventional silicon carbide, the filtration resistance is reduced by more than 50%, but the mechanical strength is not significantly reduced.

[0048] Table 1 Comparison of parameters of the silicon carbide ceramic membrane prepared in this embodiment and the conventional silicon carbide ceramic membrane

[0049] Main index Unit Silicon carbide membrane of this example Conventional silicon carbide membrane Overall thickness mm 5.5 12 Resistance Pa 950 2000 Filtering accuracy μm 0.1 0.1 Mechanical strength MPa 23.5 25 Backflush pressure MPa 0.2 0.5 Backflush cycle h 3 1 Embodiment

[0050] A thin-walled low-resistance silicon carbide ceramic membrane, the ceramic membrane is integrally sintered into a sealed tubular membrane at one end, including an expansion head 1, a connecting neck 2, a tube body 3, and a tube bottom 4 from top to bottom, a convex 201 is formed on the inner side of the connecting neck 2, constituting an annular throat, the upper part of the convex 201 is located in the expansion head 1, and the lower part is located in the tube body 3, and respectively penetrates the expansion head 1 and the tube body 3 by 5 cm, the wall of the ceramic membrane of the expansion head 1, the connecting neck 2, the tube body 3 and the tube bottom 4 is a multi-layer structure, including a separation membrane layer 301, a transition layer 302, a toughening layer 303, and an inner support layer 304 from outside to inside, the thickness of the separation membrane layer 301 is 100 μm, the thickness of the transition layer 302 is 1000 μm, the thickness of the toughening layer 303 is 4 mm, and the thickness of the inner support layer 304 is 3 mm, the toughening material 3031 is arranged in the toughening layer 303, and the toughening material 3031 is a metal mesh. The convex 201 is thickened by the material of the inner support layer 304, and the thickness is 5 mm.

[0051] Further, the thickness of the tube bottom 4 is 50 mm, a positioning hole 401 is arranged in the center position of the outer bottom surface and recessed, and the depth of the positioning hole 401 is 15 mm. The thickened part of the tube bottom 4 compared with the tube body 3 is thickened by the material of the transition layer 302.

[0052] Further, the expansion head 1 is a taper with large upper end and small lower end, and the diameter of the upper end is 1.5 times that of the lower end.

[0053] Further, the pore size of the separation membrane layer 301 is 30 μm, the porosity is 65%, the pore size of the transition layer 302 is 50 μm, the porosity is 70%, the pore size of the toughening layer 303 is 80 μm, the porosity is 80%, the silicon carbide particles are sintered into the pore channel of the toughening material 3031, the pore size of the toughening material 3031 is 2000 μm, and the pore size of the inner support layer 304 is 100 μm, and the porosity is 80%.

[0054] Further, the toughening material 3031 is longitudinally arranged in the tube body 3 in a strip shape, and the arrangement interval in the tube body 3 is 0.5 cm.

[0055] A preparation process of the above-mentioned thin-walled low-resistance silicon carbide ceramic membrane, including the following steps:

[0056] Step one: preparing a toughening layer mixture and a toughening layer 303, 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 are added into a ball mill in a certain proportion for ball milling and mixing, polyvinyl alcohol and paraffin oil are added for continuous mixing after mixing for a certain time, the toughening material 3031 is arranged in the rubber mill of the toughening layer, the mixed toughening layer mixture is added into the rubber mill, the toughening layer mixture is made to enter the pores of the toughening material 3031 through vibration, and the toughening layer 303 is obtained after extrusion forming and demolding.

[0057] Step two: prepare the 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 in a certain proportion for ball milling mixing, add polyvinyl alcohol and paraffin oil after mixing for a certain time to continue mixing, and obtain the transition layer mixture;

[0058] Step three: prepare the 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 in a certain proportion for ball milling mixing, add polyvinyl alcohol and paraffin oil after mixing for a certain time to continue mixing to obtain the inner support layer mixture;

[0059] Step four: prepare the pre-sintered body, place the toughening layer 303 prepared in step one into a finished product mold, fill the transition layer mixture on the outside and the inner support layer mixture on the inside, complete the filling, then pre-extrude, perform vibration mixing after pre-extrusion to break the boundaries between the layers, finally perform finished product extrusion, and place it in an atmosphere furnace after demolding for pre-sintering to obtain a pre-sintered body; the inner side of the one circumferential protrusion 201 in the connecting neck 2 is inwardly protruding for the inner support layer mixture to fill; the thickened part at the bottom of the pipe bottom 4 is for the transition layer mixture to fill;

[0060] Step five: prepare the separation membrane layer, add 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 into deionized water in a certain proportion, stir to prepare a coating liquid after vacuumizing, uniformly spray the prepared coating liquid on the pre-sintered body prepared in step four, and perform drying to obtain a pre-sintered body with a separation membrane layer;

[0061] Step six: place the pre-sintered body with a separation membrane layer into an atmosphere furnace for programmed temperature sintering to obtain a thin-walled low-resistance silicon carbide ceramic membrane.

[0062] Further, in step one, the mass proportion of each component is 80% for silicon carbide particles, 4% for zirconium oxide particles, 8% for activated carbon powder, 5% for polyvinyl alcohol, and 3% for paraffin oil, the extrusion molding pressure is 100 MPa, in step two, the mass proportion of each component is 80% for silicon carbide particles, 3% for zirconium oxide particles, 5% for activated carbon powder, 7% for polyvinyl alcohol, and 5% for paraffin oil.

[0063] Further, in step three, the mass proportion of each component is 75% for silicon carbide particles, 5% for zirconium oxide particles, 10% for activated carbon powder, 8% for polyvinyl alcohol, and 2% for paraffin oil, the pre-extrusion pressure in step four is 90 MPa, the finished product extrusion pressure is 200 MPa, the pressure holding time after finished product extrusion is 2 h, and the pre-sintering temperature is 900 ℃.

[0064] Further, in the step five, the mass percentage of each component is as follows: 40% of silicon carbide particles, 12% of zirconia particles, 10% of mullite particles, 35% of methyl cellulose solution, and 3% of ethanol. The vacuumizing and stirring time is 120 minutes, and the drying temperature is 90 DEG C.

[0065] Further, in the step six, the temperature is first programmed to 900 DEG C, and then the temperature is kept for 5 hours in air atmosphere. Then, nitrogen is introduced, and the temperature is programmed to 1800 DEG C in nitrogen atmosphere, and then the temperature is kept for 4 hours. Then, the temperature is programmed to 600 DEG C, and finally the temperature is naturally cooled to room temperature. The programming rates of temperature increase and decrease are both 15 DEG C / min.

[0066] The parameters of the thin-wall low-resistance silicon carbide ceramic membrane prepared in the embodiment and the parameters of conventional silicon carbide ceramic membrane are shown in Table 2. The thickness of the silicon carbide ceramic membrane prepared in the embodiment is only 8.1 mm, which is reduced by about 10% compared with conventional silicon carbide, the filtration resistance is reduced by 30%, and the mechanical strength is obviously increased.

[0067] Table 2 Comparison of parameters of silicon carbide ceramic membrane prepared in the embodiment and conventional silicon carbide ceramic membrane

[0068] Main index Unit Silicon carbide membrane of this example Conventional silicon carbide membrane Overall thickness mm 8.1 10 Resistance Pa 1200 1800 Filtering accuracy μm 0.1 0.1 Mechanical strength MPa 28 25 Backflush pressure MPa 0.3 0.4 Backflush cycle h 2 1.5 Embodiment

[0069] A thin-wall low-resistance silicon carbide ceramic membrane is integrally sintered and formed into a sealed tubular membrane at one end, which comprises, from top to bottom, an expansion end head 1, a connecting neck 2, a tube body 3, and a tube bottom 4. A convex 201 is formed inwardly around the inner side of the connecting neck 2, constituting an annular throat. The upper part of the convex 201 is located in the expansion end head 1, and the lower part is located in the tube body 3, and respectively extends into the expansion end head 1 and the tube body 3 by 3 cm. The walls of the end head 1, the connecting neck 2, the tube body 3, and the tube bottom 4 of the ceramic membrane are of a multi-layer structure, which comprises, from outside to inside, a separation membrane layer 301, a transition layer 302, a toughening layer 303, and an inner support layer 304. The thicknesses of the separation membrane layer 301, the transition layer 302, the toughening layer 303, and the inner support layer 304 are 80 μm, 700 μm, 3.5 mm, and 2.5 mm, respectively. The toughening layer 303 is provided with a toughening material 3031, which is a foamed ceramic. The convex 201 is thickened with the material of the inner support layer 304, and the thickness is 3 mm.

[0070] Further, the thickness of the tube bottom 4 is 40 mm, and a positioning hole 401 is formed in the center of the outer bottom surface, with a depth of 10 mm. The thickened part of the tube bottom 4 is thickened with the material of the transition layer 302.

[0071] Further, the expansion end head 1 is a taper with a large upper end and a small lower end, and the diameter of the upper end is 1.4 times that of the lower end.

[0072] Further, 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 the silicon carbide particles are sintered into the pores of the toughening material 3031, which has a pore size of 1200 μm, the inner support layer 304 has a pore size of 60 μm and a porosity of 70%.

[0073] Further, the toughening material 3031 is arranged in the form of longitudinal strips in the pipe body 3, and the arrangement interval of the toughening material in the pipe body 3 is 0.8 cm.

[0074] A preparation process of the above-mentioned thin-walled low-resistance silicon carbide ceramic membrane, comprising the following steps:

[0075] Step one: preparation of the toughening layer mixture and the toughening layer 303, the silicon carbide particles with a particle size of 100 μm, the zirconium oxide particles with a particle size of 40 μm, and the activated carbon powder with a particle size of 20 μm are added into a ball mill in a certain proportion for ball milling and mixing, and then polyvinyl alcohol and paraffin oil are added for further mixing, the toughening material 3031 is placed in a rubber mold for the toughening layer, the mixed toughening layer mixture is added into the rubber mold, and the toughening layer mixture is made to enter the pores of the toughening material 3031 through vibration, and then the toughening layer 303 is obtained after extrusion forming and demolding.

[0076] Step two: preparation of the transition layer mixture, the silicon carbide particles with a particle size of 60 μm, the zirconium oxide particles with a particle size of 20 μm, and the activated carbon powder with a particle size of 10 μm are added into a ball mill in a certain proportion for ball milling and mixing, and then polyvinyl alcohol and paraffin oil are added for further mixing to obtain the transition layer mixture.

[0077] Step three: preparation of the inner support layer mixture, the silicon carbide particles with a particle size of 200 μm, the zirconium oxide particles with a particle size of 40 μm, and the activated carbon powder with a particle size of 30 μm are added into a ball mill in a certain proportion for ball milling and mixing, and then polyvinyl alcohol and paraffin oil are added for further mixing to obtain the inner support layer mixture.

[0078] Step four: preparation of the pre-sintered blank, the toughening layer 303 prepared in step one is placed in a finished product mold, the transition layer mixture is filled outside, and the inner support layer mixture is filled inside, then pre-extrusion is performed, vibration mixing is performed after pre-extrusion, the boundaries between the layers are broken, and finally the finished product is extruded, demolded, and pre-sintered in an atmosphere furnace to obtain the pre-sintered blank; the inner support layer mixture is filled in the inward protrusion 201 around the inner side of the connecting neck 2; and the thickened part at the bottom of the pipe bottom 4 is filled with the transition layer mixture.

[0079] Step 5: Preparation of the 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, methylcellulose solution, and ethanol are added to deionized water in a certain proportion. The coating solution is prepared by vacuum stirring. The prepared coating solution is uniformly sprayed onto the pre-sintered preform prepared in Step 4 and dried to obtain a pre-sintered preform with a separation membrane layer.

[0080] Step 6: Place the pre-sintered blank with the separation film layer in an atmosphere furnace for programmed temperature sintering to obtain a thin-walled, low-resistance silicon carbide ceramic film.

[0081] Furthermore, in step one, the mass percentage of each component is 75% silicon carbide particles, 3% zirconium oxide particles, 10% activated carbon powder, 7% polyvinyl alcohol, and 5% paraffin oil, and the extrusion molding pressure is 90 MPa. In step two, the mass percentage of each component is 80% silicon carbide particles, 5% zirconium oxide particles, 5% activated carbon powder, 7% polyvinyl alcohol, and 3% paraffin oil.

[0082] Furthermore, in step three, the mass percentages of each component are as follows: silicon carbide particles 68%, zirconium oxide particles 6%, activated carbon powder 11%, polyvinyl alcohol 9%, and paraffin oil 4%. In step four, the pre-extrusion pressure is 80 MPa, the finished product extrusion pressure is 180 MPa, the finished product is held under pressure for 1.5 hours after extrusion, and the pre-sintering temperature is 800℃.

[0083] Furthermore, in step five, the mass percentages of each component are as follows: silicon carbide particles 30%, zirconium oxide particles 10%, mullite particles 10%, methylcellulose solution 45%, and ethanol 5%. The vacuum stirring time is 100 min, and the drying temperature is 80°C.

[0084] Furthermore, in step six, the temperature is first programmed to rise to 750°C and held at that temperature for 4 hours in an air atmosphere. Then, nitrogen gas is introduced, and the temperature is raised to 1500°C in a nitrogen atmosphere and held for 3 hours. Then, the temperature is programmed to drop to 550°C and finally cooled naturally to room temperature. The programmed heating and cooling rates are both 10°C / min.

[0085] The parameters of the thin-walled, low-resistance silicon carbide ceramic membrane prepared in this embodiment are shown in Table 3, and the parameters of the conventional silicon carbide ceramic membrane 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% less than that of conventional silicon carbide, and the filtration resistance is more than 30% less. The mechanical strength is comparable to that of conventional silicon carbide membranes.

[0086] Table 3 Comparison of various parameters between Example 3 and conventional silicon carbide films

[0087] Main index Unit Silicon carbide membrane of this example Conventional silicon carbide membrane Overall thickness mm 6.8 11 Resistance Pa 1000 1700 Filtering accuracy μm 0.1 0.1 Mechanical strength MPa 26 25 Backflush pressure MPa 0.25 0.4 Backflush cycle h 3 1.5 Embodiment

[0088] A thin-walled low-resistance silicon carbide ceramic membrane, which is integrally sintered and formed into a sealed tubular membrane, comprises an expansion head 1, a connecting neck 2, a tube body 3, and a tube bottom 4 from top to bottom. A convex 201 is formed on the inner side of the connecting neck 2, constituting an annular throat. The upper part of the convex 201 is located in the expansion head 1, and the lower part is located in the tube body 3, and respectively extends into the expansion head 1 and the tube body 3 by 4.5 cm. The walls of the expansion head 1, the connecting neck 2, the tube body 3, and the tube bottom 4 of the ceramic membrane are of a multi-layer structure, comprising a separation membrane layer 301, a transition layer 302, a toughening layer 303, and an inner support layer 304 from outside to inside. The thickness of the separation membrane layer 301 is 80 μm, the thickness of the transition layer 302 is 900 μm, the thickness of the toughening layer 303 is 3.8 mm, and the thickness of the inner support layer 304 is 2.3 mm. The toughening material 3031 is provided in the toughening layer 303, and the toughening material 3031 is a metal mesh and a foam ceramic. The convex 201 is thickened with the material of the inner support layer 304, and the thickness is 5 mm.

[0089] Further, the thickness of the tube bottom 4 is 33 mm, and a positioning hole 401 is provided in the outer bottom surface at the center position. The depth of the positioning hole 401 is 12 mm. The thickened part of the tube bottom 4 is thickened with the material of the transition layer 302.

[0090] Further, the expansion head 1 is tapered with the upper part larger and the lower part smaller. The diameter of the upper end is 1.4 times that of the lower end.

[0091] Further, the pore size of the separation membrane layer 301 is 20 μm, the porosity is 45%, the pore size of the transition layer 302 is 35 μm, the porosity is 65%, the pore size of the toughening layer 303 is 58 μm, the porosity is 75%, the silicon carbide particles are sintered into the pore channel of the toughening material 3031, the pore size of the toughening material 3031 is 1200 μm, and the pore size of the inner support layer 304 is 88 μm, and the porosity is 69%.

[0092] Further, the toughening material 3031 is in a cylindrical shape and is placed in the entire tube body 3, and the metal mesh is placed inside the foam ceramic.

[0093] A preparation process of the above-mentioned thin-walled low-resistance silicon carbide ceramic membrane, comprising the following steps:

[0094] Step one: preparing the toughening layer mixture and the toughening layer 303, the silicon carbide particles with a particle size of 180 μm, the zirconium oxide particles with a particle size of 45 μm, and the activated carbon powder with a particle size of 28 μm are added to a ball mill in a certain proportion for ball milling mixing, and after mixing for a certain time, polyvinyl alcohol and paraffin oil are added for further mixing, the toughening material 3031 is placed in the toughening layer rubber mold, the mixed toughening layer mixture is added to the rubber mold, and the toughening layer mixture is made to enter the pores of the toughening material 3031 by vibration, and after extrusion forming and demolding, the toughening layer 303 is obtained;

[0095] Step two: preparing the transition layer mixture, the silicon carbide particles with a particle size of 86 μm, the zirconium oxide particles with a particle size of 19 μm, and the activated carbon powder with a particle size of 18 μm are added to a ball mill in a certain proportion for ball milling mixing, and after mixing for a certain time, polyvinyl alcohol and paraffin oil are added for further mixing to obtain the transition layer mixture;

[0096] Step three: preparing the inner support layer mixture, the silicon carbide particles with a particle size of 240 μm, the zirconium oxide particles with a particle size of 35 μm, and the activated carbon powder with a particle size of 32 μm are added to a ball mill in a certain proportion for ball milling mixing, and after mixing for a certain time, polyvinyl alcohol and paraffin oil are added for further mixing to obtain the inner support layer mixture;

[0097] Step four: preparing a pre-sintered body, the toughening layer 303 prepared in step one is placed in a finished product mold, the transition layer mixture is filled on the outside, and the inner support layer mixture is filled on the inside, then pre-extrusion is performed, vibration mixing is performed after pre-extrusion, the boundaries between the layers are broken, and finally finished product extrusion is performed, and after demolding, the pre-sintered body is placed in an atmosphere furnace for pre-sintering to obtain a pre-sintered body; the inner support layer mixture is filled in the one-week inward protrusion 201 on the inner side of the connecting neck 2; and the thickened part at the bottom of the pipe bottom 4 is filled with the transition layer mixture;

[0098] Step five: preparing a separation membrane layer, the silicon carbide particles with a particle size of 12 μm, the zirconium oxide particles with a particle size of 9 μm, the mullite particles with a particle size of 2 μm, the methyl cellulose solution, and the ethanol are added to deionized water in a certain proportion, vacuum stirring is performed to prepare a coating solution, the prepared coating solution is uniformly sprayed on the pre-sintered body prepared in step four, and drying is performed to obtain a pre-sintered body with a separation membrane layer;

[0099] Step six: placing the pre-sintered body with the separation membrane layer in an atmosphere furnace for programmed temperature sintering to obtain a thin-walled low-resistance silicon carbide ceramic membrane.

[0100] Further, in the step one, the mass ratio 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, the extrusion forming pressure is 95 MPa, in the step two, the mass ratio 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.

[0101] Further, in the step three, the mass ratio of each component is 72% of silicon carbide particles, 6% of zirconium oxide particles, 12% of activated carbon powder, 8% of polyvinyl alcohol, and 2% of paraffin oil, the pre-extrusion pressure is 75 MPa, the finished product extrusion pressure is 190 MPa, the holding time after extrusion is 1.8 h, and the pre-sintering temperature is 850℃.

[0102] Further, in the step five, the mass ratio 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 min, and the drying temperature is 80℃.

[0103] Further, in the step six, the temperature is first programmed to 870℃, and then held for 4 h in air atmosphere, then nitrogen is introduced, the temperature is programmed to 1750℃ in nitrogen atmosphere, and then held for 3 h, then the temperature is programmed to 560℃, and finally naturally cooled to room temperature, the programming rate of temperature rising and temperature falling is 9℃ / min.

[0104] The parameters of the thin-walled low-resistance silicon carbide ceramic membrane prepared in this embodiment and the parameters of the conventional silicon carbide ceramic membrane are shown in Table 4, the thickness of the silicon carbide ceramic membrane prepared in this embodiment is only 7.1 mm, which is reduced by 29% compared with the conventional silicon carbide, the filtration resistance is reduced by more than 30%, and the mechanical strength is slightly increased compared with the conventional silicon carbide membrane.

[0105] Table 4 Comparison of parameters of the silicon carbide ceramic membrane prepared in this embodiment and the conventional silicon carbide ceramic membrane

[0106] Main index Unit Silicon carbide membrane of this example Conventional silicon carbide membrane Overall thickness mm 7.1 10 Resistance Pa 1100 1600 Filtering accuracy μm 0.1 0.1 Mechanical strength MPa 27.5 26 Backflush pressure MPa 0.2 0.4 Backflush cycle Main index Unit Silicon carbide membrane of this example Conventional silicon carbide membrane Overall thickness mm Resistance Pa Filtering accuracy μm Mechanical strength MPa Backflush pressure MPa Backflush cycle Main index Unit Silicon carbide membrane of this example Conventional silicon carbide membrane Overall thickness mm Resistance Pa Filtering accuracy μm Mechanical strength MPa Backflush pressure MPa 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 one-end sealed tubular membrane prepared by integral sintering, which comprises an expansion end (1), a connecting neck (2), a tube body (3), and a tube bottom (4) from top to bottom; a convex (201) is formed on the inner side of the connecting neck (2) in a circumferential direction, constituting a ring-shaped throat, the upper part of the convex (201) is located in the expansion end (1), and the lower part is located in the tube body (3), and respectively penetrates into the expansion end (1) and the tube body (3) by 2-5 cm; the tube wall of the expansion end (1), the connecting neck (2), the tube body (3), and the tube bottom (4) is a multi-layer structure, which comprises a separation membrane layer (301), a transition layer (302), a toughening layer (303), and an inner support layer (304) from outside to inside, the thickness of the separation membrane layer (301) is 50-100 μm, the thickness of the transition layer (302) is 500-1000 μm, the thickness of the toughening layer (303) is 3-4 mm, the thickness of the inner support layer (304) is 2-3 mm, the toughening material (3031) is arranged in the toughening layer (303), the toughening material (3031) is one or more of a metal mesh, a porous foam metal, or a foam ceramic, and the convex (201) is thickened with the material of the inner support layer (304) and has a thickness of 3-5 mm.

2. The thin-walled, low-drag, silicon carbide membrane of claim 1, wherein, The tube bottom (4) has a thickness of 30-50 mm, a positioning hole (401) is arranged on the outer bottom surface at the center position, the depth of the positioning hole (401) is 8-15 mm, and the thickened part of the tube bottom (4) is thickened with the material of the transition layer (302) compared with the tube body (3).

3. The thin-walled, low-drag silicon carbide membrane of claim 1, wherein, The expansion end (1) is a tapered shape with a large upper end and a small lower end, and the diameter of the upper end is 1.3-1.5 times that of the lower end.

4. The thin-walled, low-drag, silicon carbide membrane of claim 1 wherein, 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 silicon carbide particles are sintered into the pore channel of the toughening material (3031), the toughening material (3031) has a pore size of 800-2000 μm, and the inner support layer (304) has a pore size of 50-100 μm and a porosity of 60-80%.

5. The thin-walled, low-drag, silicon carbide membrane of claim 1 wherein, The toughening material (3031) is in a cylindrical shape arranged in the entire tube body (3), or is in a longitudinal strip shape dispersedly arranged in the tube body (3), and when the toughening material (3031) is in a strip shape, the arrangement spacing in the tube body (3) is 0.5-1 cm.

6. The process for preparing thin-walled low-resistance silicon carbide membrane according to any one of claims 1-5, characterized in that, The method comprises the following steps: Step one: 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 into a ball mill in a certain proportion for ball milling and mixing, adding polyvinyl alcohol and paraffin oil for continuous mixing after mixing for a certain time, placing the toughening material (3031) in a rubber mill for the toughening layer, adding the mixed toughening layer mixture into the rubber mill, making the toughening layer mixture enter the pores of the toughening material (3031) through vibration, and obtaining the toughening layer (303) after extrusion molding and demolding; Step two: preparation of transition layer mixture, silicon carbide particles with a particle size of 10-100 μm, zirconia particles with a particle size of 5-30 μm, activated carbon powder with a particle size of 8-20 μm are added to the ball mill in proportion for ball milling mixing, after mixing for a certain time, polyvinyl alcohol and paraffin oil are added for continuous mixing to obtain the transition layer mixture; Step three: preparation of inner support layer mixture, silicon carbide particles with a particle size of 100-300 μm, zirconia particles with a particle size of 30-60 μm, activated carbon powder with a particle size of 20-35 μm are added to the ball mill in proportion for ball milling mixing, after mixing for a certain time, polyvinyl alcohol and paraffin oil are added for continuous mixing to obtain the inner support layer mixture; Step four: preparation of pre-sintered body, the toughening layer (303) prepared in step one is placed in the finished product mold, the outer side is filled with the transition layer mixture, and the inner side is filled with the inner support layer mixture, after filling, pre-extrusion is performed, after pre-extrusion, vibration mixing is performed to break the boundaries between the layers, and finally finished product extrusion is performed, after demolding, it is placed in an atmosphere furnace for pre-sintering to obtain a pre-sintered 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 pipe bottom (4) is filled with the transition layer mixture; Step five: preparation of separation membrane layer, silicon carbide particles with a particle size of 5-15 μm, zirconia 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, vacuum stirring is performed to prepare a coating solution, the prepared coating solution is uniformly sprayed on the pre-sintered body prepared in step four, and drying is performed to obtain a pre-sintered body with a separation membrane layer; Step six: the pre-sintered body with the separation membrane layer is placed in an atmosphere furnace for programmed temperature sintering to obtain a thin-walled low-resistance silicon carbide ceramic membrane.

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

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

9. The process for producing thin-walled low-resistance silicon carbide membrane according to claim 6, wherein In step five, the mass proportion of each component is 20-40% for silicon carbide particles, 2-12% for zirconia 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 ℃.

10. The process for producing thin-walled low-resistance silicon carbide membrane according to claim 6, wherein In the step six, the temperature is first programmed to 600-900 DEG C, and then the temperature is kept for 2-5 hours in air atmosphere, then nitrogen is introduced, the temperature is programmed to 1100-1800 DEG C in nitrogen atmosphere, and then the temperature is kept for 2-4 hours, then the temperature is programmed to 500-600 DEG C at a rate of 5-15 DEG C / min, and finally the temperature is naturally cooled to room temperature.

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