Nanoscale metal filtration membranes, methods of making and uses thereof

Abstract

The application belongs to the technical field of porous materials, and particularly relates to a nanoscale metal filter membrane, a preparation method and use thereof, and the preparation method comprises the following steps: S1, mixing metal powder, an aqueous solvent and a dispersing agent, and then adding the mixture into a high-speed grinding dispersing machine for dispersion to obtain a suspension slurry, wherein the average particle size of the metal powder is 100 nm to 5 microns; S2, spraying the suspension slurry on a porous support to form a metal powder coating on the porous support, and then performing drying treatment to obtain a nanoscale metal filter membrane precursor, wherein the material of the porous support is the same as that of the metal powder; and S3, sintering the nanoscale metal filter membrane precursor under vacuum conditions to obtain a nanoscale metal filter membrane. The nanoscale metal filter membrane prepared by the application has high filtering precision, can meet the requirement of high filtering precision in a separation and filtering process, and is widely applied in the fields of semiconductors and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of porous materials, and particularly relates to a nanoscale metal filter membrane and a preparation method and use thereof. BACKGROUND

[0002] The structure size of integrated circuit components in semiconductors is usually micron level or even nanometer level. If particles of similar size are deposited in the integrated circuit during the manufacturing process of the integrated circuit, the microstructure integrity of the integrated circuit will be damaged, and the device will fail. One of the current methods for eliminating particle contamination is to add a nanoscale high-precision gas filter at the front end of the process carrier gas inlet to intercept particles and prevent them from being deposited on the integrated circuit to form defects.

[0003] Currently, the research on filters mainly focuses on organic filter membranes and ceramic filter membranes. The organic filter membranes are low in strength and not resistant to high temperature, and the ceramic filter membranes are brittle and not resistant to thermal shock. Therefore, metal filter membranes are widely used in separation and filtration processes in various industries. However, most of the traditional metal filter membranes are micron level, and the filtration precision is low, which cannot meet the requirement of nanoscale filtration precision. There is little research on nanoscale metal filter membranes in the prior art. Therefore, it is of great significance to prepare a nanoscale metal filter membrane to meet the requirement of high filtration precision in the separation and filtration process. SUMMARY

[0004] In view of the above deficiencies in the prior art, the present application provides a nanoscale metal filter membrane and a preparation method and use thereof. The prepared nanoscale metal filter membrane has high filtration precision, can meet the requirement of high filtration precision in the separation and filtration process, and is widely used in the field of semiconductors and the like.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a preparation method of a nanoscale metal filter membrane, which comprises the following steps:

[0007] S1, preparation of a suspension slurry: mixing metal powder, an aqueous solvent and a dispersant, and then adding them into a high-speed grinding dispersing machine for dispersion to obtain a suspension slurry, wherein the average particle size of the metal powder is 100 nm to 5 μm (for example, it can be 100 nm, 300 nm, 500 nm, 700 nm, 1 μm, 3 μm or 5 μm, etc.), preferably 100 nm to 1 μm;

[0008] S2, preparation of the nanoscale metal filter membrane precursor: the suspension slurry is sprayed on a porous support to form a metal powder coating on the porous support, and then dried to obtain the nanoscale metal filter membrane precursor, wherein the material of the porous support is the same as that of the metal powder;

[0009] S3, preparation of the nanoscale metal filter membrane: the nanoscale metal filter membrane precursor is sintered under vacuum to obtain the nanoscale metal filter membrane.

[0010] The present application can ensure the filtering precision by adding the dispersant and using the high-speed grinding dispersion method to uniformly disperse the metal powder without agglomeration.

[0011] The present application can ensure the good matching of the membrane layer and the support, and the good bonding strength without peeling during the drying and sintering process by limiting the material of the porous support to be the same as that of the metal powder.

[0012] The nanoscale metal filter membrane prepared by the present application has high filtering precision, can meet the requirement of high filtering precision in the separation and filtering process, and is widely used in the field of semiconductors.

[0013] In the preparation method of the nanoscale metal filter membrane, as a preferred embodiment, the material of the metal powder is stainless steel, nickel or nickel-based alloy.

[0014] In the preparation method of the nanoscale metal filter membrane, as a preferred embodiment, the aqueous solvent is water or an alcohol solvent, preferably isopropyl alcohol.

[0015] In the preparation method of the nanoscale metal filter membrane, as a preferred embodiment, the dispersant includes at least one of polyvinyl alcohol, methyl cellulose and polyethylene glycol. The addition of the dispersant has an important adjusting effect on the dispersion of the superfine powder.

[0016] In the preparation method of the nanoscale metal filter membrane, as a preferred embodiment, the mass percentage of the metal powder in the suspension slurry is not less than 5% and not more than 20% based on 100% of the total mass of the suspension slurry, for example, can be 5%, 10%, 15% or 20%, and preferably is 10%. If the mass percentage of the metal powder in the suspension slurry is too large, the suspension concentration is too large to be ultrasonic sprayed, and if the mass percentage of the metal powder in the suspension slurry is too small, the suspension concentration is too low, the drying time is long, and the film forming efficiency is low.

[0017] In the method for preparing the nanoscale metal filter membrane, as a preferred embodiment, the mass ratio of the dispersant to the aqueous solvent is (0.01-1):100, for example, 0.01:100, 0.2:100, 0.4:100, 0.6:100, 0.8:100 or 1:100, etc. Too much dispersant will result in too high viscosity of the suspension, which cannot be ultrasonic sprayed, and too little dispersant will not have good dispersion effect.

[0018] In the method for preparing the nanoscale metal filter membrane, as a preferred embodiment, the rotating speed of the high-speed grinding disperser is 2000-3500 r / min (for example, 2000 r / min, 2500 r / min, 3000 r / min or 3500 r / min, etc.), preferably 3000 r / min.

[0019] In the method for preparing the nanoscale metal filter membrane, as a preferred embodiment, in step S1, the dispersion time is 2-4 h.

[0020] In the method for preparing the nanoscale metal filter membrane, as a preferred embodiment, the porous support includes a sheet-type support or a tube-type support, for example, the porous support can be one of a sintered metal powder porous material, a sintered metal fiber felt porous material and a filter tube.

[0021] In the method for preparing the nanoscale metal filter membrane, as a preferred embodiment, the average pore size of the porous support is 5-30 μm (for example, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm or 30 μm, etc.), preferably 5-15 μm.

[0022] In the method for preparing the nanoscale metal filter membrane, as a preferred embodiment, the thickness of the porous support is 0.3-6 mm, for example, 0.3 mm, 1 mm, 3 mm, 5 mm or 6 mm, etc.

[0023] In the method for preparing the nanoscale metal filter membrane, as a preferred embodiment, the material of the porous support is stainless steel, nickel or nickel-based alloy.

[0024] As a preferred embodiment in the preparation method of the nanoscale metal filter membrane, the spraying is ultrasonic spraying. Due to the particularity of superfine metal powder, the uniformity and thin film thickness of the film layer cannot be guaranteed by traditional flow casting or wet spraying. The ultrasonic spraying is selected for the preparation of the nanometer coating in the present application. The ultrasonic spraying is a spraying process using ultrasonic atomization technology. The spraying material is in a liquid state first, which can be a solution, a sol, a suspension, etc. The liquid coating is atomized into fine particles by an ultrasonic atomization device, and then uniformly coated on the surface of the substrate by a certain amount of carrier gas, so as to form a coating or a film. Compared with the traditional wet spraying, the present application has the advantages of high coating uniformity, high raw material utilization rate, high coating thickness control precision, thinner coating thickness, coating thickness can reach tens of nanometers, less spatter, no clogging of the spray head, low maintenance cost, etc.

[0025] As a preferred embodiment in the preparation method of the nanoscale metal filter membrane, the power of the ultrasonic spray head in the ultrasonic spraying is 1-15w (for example, it can be 1w, 3w, 5w, 7w, 10w, 13w or 15w, etc.), and the flow rate is 1mL / min-20mL / min (for example, it can be 1mL / min, 5mL / min, 8mL / min, 10mL / min, 12mL / min, 16mL / min or 20mL / min, etc.).

[0026] As a preferred embodiment in the preparation method of the nanoscale metal filter membrane, the thickness of the metal powder coating is 5-100μm (for example, it can be 5μm, 20μm, 30μm, 40μm, 50μm, 60μm, 80μm or 100μm, etc.), preferably 30-60μm. If the coating thickness is too thick, the filtration flux is small, and if the coating thickness is too thin, the filtration precision cannot be guaranteed.

[0027] As a preferred embodiment in the preparation method of the nanoscale metal filter membrane, in step S2, the drying temperature is 100-120℃ (for example, it can be 100℃, 110℃ or 120℃, etc.), and the drying time is 30min-60min (for example, it can be 30min, 40min, 50min or 60min, etc.).

[0028] As a preferred embodiment in the preparation method of the nanoscale metal filter membrane, in step S3, when sintering, the vacuum degree is <9×10 -3 Holding.

[0029] In the preparation method of the nanoscale metal filter membrane, as a preferred embodiment, in step S3, the sintering comprises: first, heating to 400-500°C (for example, 400°C, 420°C, 440°C, 460°C, 480°C or 500°C, etc.) at a heating rate of 2°C / min-10°C / min (for example, 2°C / min, 4°C / min, 6°C / min, 8°C / min or 10°C / min, etc.), and holding for 1-2h; then, heating to 600-900°C (for example, 600°C, 700°C, 800°C or 900°C, etc.) at a heating rate of 2°C / min-10°C / min (for example, 2°C / min, 4°C / min, 6°C / min, 8°C / min or 10°C / min, etc.), and holding for 2-4h; and finally, cooling with the furnace.

[0030] By limiting the stage-by-stage holding during sintering, the present application can ensure that the dispersant volatilizes as much as possible during sintering, and prevents the dispersant from remaining to affect the performance of the membrane layer.

[0031] In the preparation method of the nanoscale metal filter membrane, as a preferred embodiment, in step S2, the spraying is performed multiple times, wherein after each spraying is completed, the nanoscale metal filter membrane precursor is sintered under vacuum according to step S3, and then the next spraying is performed. The pore size and the permeability are a pair of contradictory properties. For a filter membrane, the smaller the pore size, the higher the permeability is better, but the two are contradictory. Compared with only one spraying and sintering, the present application embodiment uses multiple spraying and sintering, so that the pore sizes are similar (the filtering precision is close), but the permeability is improved.

[0032] In a second aspect, the present application provides a nanoscale metal filter membrane, which is prepared by the preparation method provided in the first aspect. The nanoscale metal filter membrane provided by the present application has high filtering precision, and the retention efficiency of impurity particles with a particle size of 80nm or more is greater than 99.9%.

[0033] In the nanoscale metal filter membrane, as a preferred embodiment, the nanoscale metal filter membrane comprises a porous support body serving as a support and a metal membrane layer serving as a filter and arranged on the porous support body, the pore size of the metal membrane layer is smaller than the pore size of the porous support body, and the smaller the pore size of the metal membrane layer, the higher the filtering precision. The nanoscale metal filter membrane provided by the present application is a nanoscale metal filter membrane with a gradient structure, i.e., a porous material with a pore size that changes in a certain direction. This gradient property enables the gradient porous material to ensure a large filtering flux on the basis of a small pore size, and realizes the structure and performance that other uniform structure porous materials do not have, and greatly improves the filtering precision and filtering efficiency in the filtering and separation process.

[0034] In a third aspect, the present application provides a use of the nanoscale metal filtration membrane according to the second aspect in two-phase separation of any one of normal temperature gas / solid, normal temperature liquid / solid, high temperature gas / solid and high temperature liquid / solid.

[0035] Compared with the prior art, the present application has at least one of the following beneficial effects:

[0036] (1) The nanoscale metal filtration membrane prepared by the present application has high filtration precision, and the filtration efficiency of impurity particles with a particle size of 80 nm or more is greater than 99.9%, which can meet the requirements of high filtration precision in the separation and filtration process, and is widely used in the fields of semiconductors, LEDs, photovoltaics, etc.

[0037] (2) The present application uniformly disperses the metal powder by adding a dispersing agent and cooperating with a high-speed grinding and dispersing method, and the dispersion efficiency is high, and the particle size distribution on the metal film layer prepared is uniform; by limiting the material of the porous support to be the same as that of the metal powder, the good matching of the film layer and the support can be ensured, and the peeling and good bonding strength during drying and sintering can be ensured; by limiting the stage-by-stage heat preservation during sintering, the binder can be volatilized as much as possible during the sintering process, and the residual binder can be prevented from affecting the performance of the film layer.

[0038] (3) Compared with the traditional wet spraying method, the present application uses ultrasonic spraying, so that the coating uniformity is high, the raw material utilization rate is high, the coating thickness control precision is high, the coating thickness is thinner, the coating thickness can reach tens of nanometers, the splashing is less, the nozzle is not blocked, and the maintenance cost is low.

[0039] (4) Compared with only one-time spraying and sintering, the present application embodiment uses multiple spraying and sintering, so that the pore size is similar (the filtration precision is close), but the permeability is improved.

[0040] (5) The nanoscale metal filtration membrane provided by the present application is a nanoscale metal filtration membrane with a gradient structure, i.e. a porous material with varying pore size in a certain direction. This gradient property ensures that the gradient porous material can ensure a larger filtration flux on the basis of a smaller pore size, realizes structures and properties that other uniform structure porous materials do not have, and greatly improves the filtration precision and filtration efficiency in the process of filtration and separation. The nanoscale metal filtration membrane provided by the present application can be applied to ultra-high precision filtration in the semiconductor industry. Compared with the polymer membrane, it has better temperature resistance and higher strength. Compared with the ceramic membrane, it has higher toughness. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 TEM image of the surface of the metal film layer of the nanoscale metal filtration membrane prepared in Example 1. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions and advantages of the present application clearer, the following will be combined with the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. It should be appreciated by those skilled in the art that the embodiments are only used for understanding the present application and should not be regarded as specific limitations to the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present application.

[0043] The embodiments of the present application are implemented on the premise of the technical solutions of the present application, and detailed implementation manners and processes are given, but the protection scope of the present application is not limited to the following embodiments. The process parameters not specified in the following embodiments are usually according to the conventional conditions.

[0044] The endpoints of the ranges and any values described in this disclosure are not limited to the precise values stated. The ranges and values should be interpreted as approximations. Any numerical value, however, can typically include values up to and including the value stated, and values outside the stated range. For ranges, the endpoints and any values between the endpoints are included in the range. For any numerical range, the endpoints are included in the range.

[0045] In the present application, unless otherwise specified and / or described, all the numerical values related to the amount of components are "parts by weight". The process parameters not specified in the following embodiments are usually according to the conventional conditions. The experimental reagents used in the following embodiments are conventional biochemical reagents unless otherwise specified; the amount of the experimental reagents is the amount of reagents in conventional experimental operations unless otherwise specified, and the materials used are conventional materials purchased on the market unless otherwise specified.

[0046] In a first aspect, the present application provides a preparation method of a nanoscale metal filter membrane, the preparation method comprising the following steps:

[0047] S1, preparation of a suspension slurry: after mixing a metal powder, an aqueous solvent and a dispersant, the mixture is added into a high-speed grinding dispersing machine for dispersion for 2h-4h to obtain a suspension slurry, wherein the average particle size of the metal powder is 100nm-5μm, preferably 100nm-1μm, the material of the metal powder is stainless steel, nickel or nickel-based alloy, the aqueous solvent is water or an alcohol solvent, the dispersant comprises at least one of polyvinyl alcohol, methyl cellulose and polyethylene glycol, the mass percentage of the metal powder in the suspension slurry is not less than 5% and not more than 20%, the mass ratio of the dispersant to the aqueous solvent is (0.01-1):100, and the rotating speed of the high-speed grinding dispersing machine is 2000-3500r / min.

[0048] S2, preparation of the nanoscale metal filter membrane precursor: the suspension slurry is sprayed on a porous support by ultrasonic spraying to form a metal powder coating on the porous support, and then dried to obtain a nanoscale metal filter membrane precursor, wherein the material of the porous support is the same as that of the metal powder, the porous support includes a sheet support or a tubular support, the average pore size of the porous support is 5-30 μm, the thickness of the porous support is 0.3-6 mm, the material of the porous support is stainless steel, nickel or nickel-based alloy, the ultrasonic spraying head power of the ultrasonic spraying is 1-15 w, the flow rate is 1-20 mL / min, the thickness of the metal powder coating is 5-100 μm, the drying temperature is 100-120℃, and the drying time is 30-60 min.

[0049] S3, preparation of the nanoscale metal filter membrane: the nanoscale metal filter membrane precursor is sintered under vacuum conditions of <9×10 -3 to obtain a nanoscale metal filter membrane, wherein the sintering includes: first heating to 400-500℃ at a heating rate of 2-10℃ / min and holding for 1-2 h, then heating to 600-900℃ at a heating rate of 2-10℃ / min and holding for 2-4 h, and finally cooling with the furnace.

[0050] In the above preparation method of the nanoscale metal filter membrane, as a preferred embodiment, in step S2, the spraying is performed multiple times, wherein after each spraying, the nanoscale metal filter membrane precursor is sintered in sections under vacuum conditions according to step S3, and then the next spraying is performed.

[0051] The present application mainly aims at the need for high-precision filtration of carrier gas in the semiconductor industry, and develops nanoscale metal filter membranes with ultra-high precision and ultra-high filtration efficiency, thereby mastering the pretreatment technology of nanoscale raw materials, breaking through the matching design and preparation of nanoscale metal membrane pore size and permeability, and meeting the needs of ultra-high purity gas purification in the semiconductor industry. In fact, high-precision filtration products are needed in the production processes of LED, photovoltaic, MEMS equipment connection, etc.

[0052] At present, most of the traditional metal filter membranes are micron level, which cannot meet the requirement of nanometer level filtering precision, therefore, the present application mainly solves the technical problems of filtering precision and flux matching of ultra-high precision metal filter membrane and the technical problems of preparation process of nanometer powder coating. The difficulty of the present application lies in the preparation process of ultra-high precision membrane layer. In order to obtain higher filtering precision, nanometer powder is selected as the raw material of the surface membrane layer. However, the superfine metal powder has a large specific surface area and a high specific surface energy, and is in a thermodynamic unstable state. During the processing and treatment, the particles are prone to coagulation, agglomeration and formation of secondary particles, so that the particle size is increased. Therefore, the superfine metal powder cannot be directly used and needs to be dispersed. At present, the main dispersion methods of superfine powder particles are ball milling method, ultrasonic method and the like, but they cannot realize the sufficient dispersion of superfine metal particles. The impact, shearing, compression, abrasion and the like of the traditional ball milling method have obvious crushing and homogenization effects on micron level and coarser powder, but the effect on nanometer fine powder is limited. The ultrasonic oscillation dispersion has the problem that once the ultrasonic oscillation is stopped, the superfine powder may be re-agglomerated. After a period of ultrasonic treatment, the particle size cannot be further reduced, and the continued ultrasonic treatment may cause the re-agglomeration of the superfine powder. The present application adopts the way of high-speed grinding dispersion and dispersant regulation to disperse the superfine metal powder, the purpose is to uniformly disperse and stabilize the superfine metal powder, the dispersion effect is good, the dispersion efficiency is high, and the particle size distribution of the prepared filter membrane layer is uniform.

[0053] Similarly, due to the small particle size and high surface energy of the superfine metal powder, the superfine metal powder is easy to agglomerate, and it is difficult to prepare a uniform coating and control the precision of the coating thickness by using the traditional wet spraying and flow casting process. The present application adopts ultrasonic spraying to prepare the nanometer membrane layer. The coating uniformity is high by using this spraying method, the control precision of the coating thickness is high, and the coating thickness can reach several tens of nanometers.

[0054] In the second aspect, the present application provides a nanometer level metal filter membrane prepared by the preparation method provided in the first aspect. The nanometer level metal filter membrane comprises a porous support body for supporting and a metal membrane layer arranged on the porous support body for filtering.

[0055] In order to improve the filtering precision of the nanometer level metal filter membrane and maintain its high permeability, the nanometer level metal filter membrane prepared by the present application adopts an asymmetric structure, and superfine metal powder is selected as the membrane layer material. The thin surface membrane layer of the metal filter membrane mainly plays a filtering role, and the skeleton layer mainly plays a supporting role. The various micro-pore structures therein realize the filtering and purification of nanometer particles by the principles of interception, adsorption and the like.

[0056] In a third aspect, the present application provides a use of the nanoscale metal filtration membrane according to the second aspect in two-phase separation of any one of normal temperature gas / solid, normal temperature liquid / solid, high temperature gas / solid and high temperature liquid / solid.

[0057] In order to further understand the present application, the nanoscale metal filtration membrane, the preparation method and the use thereof provided by the present application are described in detail below in combination with examples, and the protection scope of the present application is not limited by the following examples.

[0058] Example 1

[0059] The preparation method of the nanoscale metal filtration membrane provided in this example includes the following steps:

[0060] S0, preparation of the porous support: the nickel powder is isostatic pressed and then high-temperature sintered to obtain the porous support, which is a nickel powder filter tube with an average pore size of 10 μm, a thickness of 3 mm and an outer diameter of 18 mm. The isostatic pressing includes: the nickel powder is filled in a mold and uniformly vibrated on a vibration platform, and then the mold is placed in a cold isostatic pressing machine for pressing forming, wherein the particle size range of the nickel powder is -150+250 mesh (can pass through a 150 mesh sieve but cannot pass through a 250 mesh sieve), the vibration powder filling time is 60 s, the forming pressure is 60 MPa, and the pressure holding time is 1 min; the high-temperature sintering includes: the green body (tube blank) formed by isostatic pressing is loaded into a sintering boat, in order to prevent longitudinal bending deformation of the tube blank, the tube blank is vertically placed in the sintering boat and surrounded by flexible constraints for vacuum high-temperature constraint sintering, wherein the vacuum degree is 10 -2 Pa, the sintering process is to first increase the temperature from room temperature to 450℃ at a rate of 7℃ / min and keep the temperature for 1 h, then increase the temperature to 900℃ at a rate of 15℃ / min and keep the temperature for 5 h, and then stop heating and cool down with the furnace.

[0061] S1, preparation of the suspension slurry: the metal powder, the aqueous solvent and the dispersant are weighed in proportion, uniformly stirred, and then poured into a high-speed grinding and dispersing machine for dispersion, to obtain the suspension slurry, the rotation speed of the grinding and dispersing machine is 2000 r / min, and the dispersion time is 3 h, the purpose is to uniformly disperse and stabilize the metal powder, wherein the material of the metal powder is nickel, and the average particle size of the metal powder is 0.5 μm; the aqueous solvent is ethanol; the addition of the dispersant plays an important adjusting role in the dispersion of the metal powder, and the dispersant is methyl cellulose; the mass ratio of the dispersant to the aqueous solvent is 0.05:100; the mass percentage of the metal powder in the suspension slurry is 18% based on the total mass of the suspension slurry, i.e. the mass ratio of the metal powder to the total mass of the dispersant and the aqueous solvent is 18:82.

[0062] S2, preparation of the nanoscale metal filter membrane precursor: pour the uniformly dispersed slurry prepared in step S1 into an ultrasonic dispersion sample injector of an ultrasonic spraying device, the ultrasonic dispersion sample injector can realize online dispersion stirring of the slurry to avoid powder sedimentation during spraying, and the slurry is uniformly sprayed on the porous support (nickel powder filter tube) prepared in step S0 by the ultrasonic spraying device to form a metal powder coating with a thickness of 100 pm on the outer surface of the porous support, and then dried at 100°C for 30 min to obtain the nanoscale metal filter membrane precursor. The coating thickness is adjusted by adjusting the ultrasonic nozzle power, spraying flow rate and spraying speed. The ultrasonic nozzle power is 2 W, and the spraying flow rate is 10 mL / min.

[0063] S3, preparation of the nanoscale metal filter membrane: the nanoscale metal filter membrane precursor prepared in step S2 is sintered in a vacuum furnace with a vacuum degree < 9*10 -3 at room temperature to 400°C at a heating rate of 6°C / min, and then cooled with the furnace to obtain the nanoscale metal filter membrane.

[0064] The nanoscale metal filter membrane prepared in this example includes a porous support serving as a support and a metal membrane layer serving as a filter on the outer surface of the porous support. The maximum pore size of the metal membrane layer is 0.7 pm, and the permeability of the nanoscale metal filter membrane is about 8*10 -5 L / (cm 2 ·pa·min).

[0065] Figure 1 TEM image of the surface of the metal membrane layer of the nanoscale metal filter membrane prepared in this example, which shows that the metal powder on the metal membrane layer is uniformly dispersed without agglomeration, and the pore size is small, which ensures the filtering precision. Figure 1

[0066] Example 2

[0067] The preparation method of the nanoscale metal filter membrane provided in this example includes the following steps:

[0068] ​S0, preparation of the porous support: 316L stainless steel powder was filled in a mold and uniformly vibrated on a vibration platform, and then the mold was placed in a cold isostatic pressing machine for pressing forming, wherein the particle size range of the 316L stainless steel powder was-50+150 mesh (capable of passing through a 50 mesh sieve but not capable of passing through a 150 mesh sieve), the vibration powder filling time was 30 s, the forming pressure was 150 MPa, and the pressure holding time was 2 min; the green compact, which was a pipe blank in this embodiment, was loaded into a boat, and in order to prevent longitudinal bending deformation of the pipe blank, the pipe blank was vertically erected in the boat and the surrounding was filled with flexible constraints for vacuum high-temperature constrained sintering, wherein the vacuum degree was 10 -2 Pa, the sintering process was first heated from room temperature to 500℃ at a heating rate of 8℃ / min, and held for 1h, then heated to 900℃ at a heating rate of 7℃ / min, held for 0.5h, then heated to 1250℃ at a heating rate of 3℃ / min, held for 4h, and finally stopped heating, and after the furnace cooled to 500℃, N2 was filled into the furnace to accelerate the cooling speed until it cooled to below 50℃, to obtain the porous support, which was a 316L stainless steel powder filter tube, the average pore size of the porous support was 13μm, the thickness of the porous support was 3mm, and the outer diameter of the porous support was 60mm.

[0069] S1, preparation of the suspension slurry: the metal powder, aqueous solvent and dispersant were weighed in proportion, and after being stirred relatively uniformly, they were poured into a high-speed grinding and dispersing machine for dispersion, to obtain the suspension slurry, the rotating speed of the grinding and dispersing machine was 3000r / min, and the dispersion time was 4h, the purpose being to uniformly disperse and stabilize the metal powder, wherein the material of the metal powder was 316L stainless steel powder with an average particle size of 1μm; the aqueous solvent was deionized water; the dispersant was polyethylene glycol; the mass ratio of the dispersant to the aqueous solvent was 0.5:100; and the mass percentage of the metal powder in the suspension slurry was 10% based on the total mass of the suspension slurry, i.e. the mass ratio of the metal powder to the total mass of the dispersant and the aqueous solvent was 10:90.

[0070] S2, preparation of the nanoscale metal filter membrane precursor: the uniformly dispersed suspension slurry prepared in step S1 was poured into an ultrasonic dispersion sample injector of an ultrasonic spraying device, which could realize online dispersion and stirring of the suspension slurry to avoid powder sedimentation during the spraying process, and the suspension slurry was uniformly sprayed on the porous support prepared in step S0 through the ultrasonic spraying device to form a metal powder coating with a thickness of 30μm on the outer surface of the porous support, and then the coating was dried at 120℃ for 45min to obtain the nanoscale metal filter membrane precursor, and the coating thickness was adjusted by adjusting the ultrasonic nozzle power, spraying flow rate and spraying speed, the ultrasonic nozzle power was 3w, and the spraying flow rate was 12mL / min.

[0071] S3, preparation of the nanoscale metal filter membrane: the nanoscale metal filter membrane precursor prepared in step S2 is sintered in a vacuum furnace in several stages, the sintering process being as follows: first, the temperature is raised from room temperature to 450°C at a rate of 7°C / min, and then the temperature is raised to 900°C at a rate of 4°C / min, and then the furnace is cooled to room temperature; -3

[0072] The sintering process of step S2 and step S3 is repeated once to obtain the nanoscale metal filter membrane, and the thickness of the membrane layer is 60 μm.

[0073] The nanoscale metal filter membrane prepared in this embodiment comprises a porous support body for support and a metal membrane layer for filtration arranged on the outer surface of the porous support body, the maximum pore size of the metal membrane layer is 1.2 μm, and the permeability of the nanoscale metal filter membrane is about 6*10 -5 L / (cm 2 ·pa·min).

[0074] The microstructure of the metal membrane layer of the obtained nanoscale metal filter membrane is similar to that of Example 1, and the metal powder on the metal membrane layer is uniformly dispersed without agglomeration.

[0075] Example 3

[0076] The preparation method of the nanoscale metal filter membrane provided in this embodiment comprises the following steps:

[0077] S1, preparation of the suspension slurry: the metal powder (ultrafine metal powder), the aqueous solvent and the dispersant are weighed in proportion, and then they are stirred to be relatively uniform, and then they are poured into a high-speed grinding and dispersing machine for dispersion, so as to obtain the suspension slurry, the rotation speed of the grinding and dispersing machine is 3500 r / min, and the dispersion time is 2 h, the purpose being to uniformly disperse and stabilize the metal powder, wherein the material of the metal powder is 316L stainless steel, and the average particle size is 100 nm; the aqueous solvent is selected to be isopropyl alcohol; the addition of the dispersant has an important adjusting effect on the dispersion of the metal powder, and the dispersant is selected to be polyvinyl alcohol; the mass ratio of the dispersant to the aqueous solvent is 0.1:100; the mass percentage of the metal powder in the suspension slurry is 15% based on the total mass of the suspension slurry, that is, the mass ratio of the metal powder to the total mass of the dispersant and the aqueous solvent is 15:85.

[0078] ​S2, preparation of the nanoscale metal filter membrane precursor: pour the uniformly dispersed suspension slurry prepared in step S1 into an ultrasonic dispersion sample injector of an ultrasonic spraying device, which can realize online dispersion stirring of the suspension slurry to avoid powder sedimentation during the spraying process. Uniformly spray the suspension slurry on the porous support through the ultrasonic spraying device to form a metal powder coating layer with a thickness of 30 μm on one side of the porous support, and then dry at 120°C for 30 min to obtain the nanoscale metal filter membrane precursor. Adjust the coating thickness by adjusting the ultrasonic nozzle power, spraying flow rate and spraying speed (the spraying speed refers to the moving speed of the porous support relative to the ultrasonic spraying device). The ultrasonic nozzle power is 4 W, the spraying flow rate is 5 mL / min, the porous support is a 316L stainless steel metal fiber felt purchased from the market, the thickness of the porous support is 0.5 mm, and the average pore size of the porous support is 8 microns.

[0079] S3, preparation of the nanoscale metal filter membrane: segmentally sinter the nanoscale metal filter membrane precursor (filter material support coated with a surface filter membrane) prepared in step S2 in a vacuum furnace with a vacuum degree < 9 x 10 -3 at a temperature rising rate of 8°C / min from room temperature to 500°C, and then at a temperature rising rate of 3°C / min to 700°C, and then cooled with the furnace to obtain the nanoscale metal filter membrane.

[0080] The nanoscale metal filter membrane prepared in this example includes a porous support for supporting and a metal membrane layer for filtering arranged on one side of the porous support. The maximum pore size of the metal membrane layer is 0.3 μm, and the permeability of the nanoscale metal filter membrane is about 2 x 10 -5 L / (cm 2 ·pa·min).

[0081] The micro-morphology of the metal membrane layer on the obtained nanoscale metal filter membrane is similar to that of Example 1, and the metal powder on the metal membrane layer is uniformly dispersed without agglomeration.

[0082] Comparative Example 1

[0083] The preparation method of the nanoscale metal filter membrane provided in this comparative example is basically the same as that of Example 3, except that the ball milling method is used for dispersion in step S1, which specifically includes the following steps:

[0084] S1, preparation of the suspension slurry: the metal powder, aqueous solvent and dispersant were weighed in proportion, stirred relatively uniformly, then poured into a ball mill for dispersion, the ball-to-material ratio was controlled to be 10:1, the rotation speed of the ball mill was 120 rpm, and the mixing time was 8 h, so that the three components were uniformly mixed to obtain the suspension slurry, wherein the metal powder was 316L stainless steel with an average particle size of 100 nm; the aqueous solvent was isopropyl alcohol; the dispersant played an important role in the dispersion of the metal powder, and the dispersant was polyvinyl alcohol; the mass ratio of the dispersant to the aqueous solvent was 0.1:100; the mass percentage of the metal powder in the suspension slurry was 15% based on the total mass of the suspension slurry, i.e., the mass ratio of the metal powder to the total mass of the dispersant and the aqueous solvent was 15:85.

[0085] S2, preparation of the nanoscale metal filter membrane precursor: after the preparation of the suspension, because of the non-uniform dispersion and fast settling speed, the suspension could not be sprayed by ultrasonic spraying, and was sprayed by a traditional spraying method. The suspension slurry prepared in step S1 was sprayed on a porous support by a spray gun to form a metal powder coating with a thickness of 50-100 μm on one side of the porous support (the coating thickness control precision of the traditional wet spraying method is low, and it is difficult to form a thin coating with poor thickness uniformity), and then the coating was dried at 120 °C for 30 min to obtain the nanoscale metal filter membrane precursor. The coating thickness was adjusted by adjusting the spraying pressure, spraying flow rate and spraying speed, and the spraying pressure was controlled to be 0.5 MPa, the spraying flow rate was 72 mL / min, the porous support was a 316L stainless steel metal fiber felt purchased from the market, the thickness of the porous support was 0.5 mm, and the average pore size of the porous support was 8 microns.

[0086] S3 is the same as step S3 of Example 3.

[0087] The nanoscale metal filter membrane prepared in this comparative example includes a porous support serving as a support and a metal film layer serving as a filter layer arranged on one side of the porous support. It can be seen from observation that the metal film layer has poor surface uniformity and particle agglomeration, the maximum pore size of the metal film layer is 8 μm, and the nanoscale metal filter membrane has low filtration precision.

[0088] Comparative Example 2

[0089] The preparation method of the nanoscale metal filter membrane provided in this comparative example is basically the same as that of Example 3, except that the traditional spraying method is used in step S2, which specifically includes the following steps:

[0090] S1 is the same as step S1 of Example 3.

[0091] S2, preparation of the nanoscale metal filtration membrane precursor: the slurry prepared in step S1 is sprayed on the porous support by using a spray gun to form a metal powder coating with a thickness of 50-100 pm on one side of the porous support, and then dried at 120°C for 30 min to obtain the nanoscale metal filtration membrane precursor. The coating thickness is adjusted by adjusting the spraying pressure, spraying flow rate and spraying speed. The spraying pressure is controlled to be 0.5 MPa, the spraying flow rate is 72 mL / min, the porous support is a 316L stainless steel metal fiber felt purchased from the market, the thickness of the porous support is 0.5 mm, and the average pore size of the porous support is 8 microns.

[0092] S3, same as step S3 of Example 3.

[0093] The nanoscale metal filtration membrane prepared in the present comparative example comprises a porous support serving as a support and a metal membrane layer serving as a filter arranged on one side of the porous support. The maximum pore size of the metal membrane layer is 2 pm, the permeability of the nanoscale metal filtration membrane is about 1*10 -5 L / (cm 2 ·pa·min), the nanoscale metal filtration membrane layer has a large thickness, the thickness is uneven, and the permeability is low.

[0094] Comparative Example 3

[0095] The preparation method of the nanoscale metal filtration membrane provided in the present comparative example is basically the same as that of Example 2, except that only one spraying is performed. Specifically, the method comprises the following steps:

[0096] S0-S1, same as steps S0-S1 of Example 2.

[0097] S2, preparation of the nanoscale metal filtration membrane precursor: the slurry prepared in step S1 is sprayed on the porous support by using a spray gun to form a metal powder coating with a thickness of 50-100 pm on one side of the porous support, and then dried at 120°C for 30 min to obtain the nanoscale metal filtration membrane precursor. The coating thickness is adjusted by adjusting the spraying pressure, spraying flow rate and spraying speed. The spraying pressure is controlled to be 0.5 MPa, the spraying flow rate is 72 mL / min, the porous support is a 316L stainless steel metal fiber felt purchased from the market, the thickness of the porous support is 0.5 mm, and the average pore size of the porous support is 8 microns.

[0098] S3, preparation of the nanoscale metal filtration membrane: the nanoscale metal filtration membrane precursor prepared in step S2 is placed in a vacuum degree < 9*10 -3The nanoscale metal filter membrane is obtained by sintering in a vacuum furnace in sections, and the sintering process is as follows: first, the temperature is raised from room temperature to 450 DEG C at a rate of 7 DEG C / min, and then the temperature is raised to 900 DEG C at a rate of 4 DEG C / min, and then the furnace is cooled to obtain the nanoscale metal filter membrane.

[0099] The nanoscale metal filter membrane prepared in the present comparative example comprises a porous support body for supporting and a metal film layer arranged on the outer surface of the porous support body for filtering, the maximum pore size of the metal film layer is 1.2 μm, and the permeability of the nanoscale metal filter membrane is about 4*10 -5 L / (cm 2 ·pa·min).

[0100] Performance test

[0101] Filtering precision test: the filtering efficiency of the metal filter membranes prepared in each example and comparative example is tested, the test is based on GB / T 6165-2021 "High efficiency air filter performance test method efficiency and resistance", the test instrument and device are H47-2 hot type gas mass flow meter, T-H120 condensation nucleus particle counter and T-H27 filter material detection device, the dust source for detection is sodium chloride sol with a particle size of 80 nm (the particle that is most easily penetrated by the filter membrane); the particle counters are used to test the particle numbers in the upstream and downstream, and the filtering efficiency = (1-C1 / C2) * 100%, wherein C1 represents the particle number in the downstream, and C2 represents the particle number in the upstream. The test results are shown in Table 1.

[0102] Table 1

[0103]

[0104] At least the following points can be seen from the examples 1-3 and comparative examples 1-3 of the present application and Table 1:

[0105] (1) The filtering efficiency of the nanoscale metal filter membranes prepared in examples 1-3 for sodium chloride sol with a particle size of 80 nm can reach 99.99999%, which indicates that the nanoscale metal filter membranes prepared by the present application have high filtering precision.

[0106] (2) The filtering efficiency of the nanoscale metal filter membrane prepared in comparative example 1 is 90% by using the ball milling method for dispersion in step S1, which is significantly lower than that of example 3, and the surface uniformity of the metal film layer is poor and there is particle agglomeration, which indicates that the present application can make the metal powder uniformly dispersed without agglomeration by adding a dispersing agent and cooperating with a high-speed grinding dispersion method, so as to improve the filtering precision and filtering efficiency of the filter membrane.

[0107] (3) The comparative example 2 uses the traditional wet spraying to prepare the coating, compared with the example 3, the filtering efficiency is lower, and the film layer thickness is uneven, the film layer thickness is thicker, the permeability of the filter membrane is low, which shows that the present application has higher filtering efficiency, higher uniformity of the coating thickness, higher control precision of the coating thickness, and thinner coating thickness by using the ultrasonic spraying.

[0108] (4) It can be known from the comparative example 3 and the example 2 that when the one-time spraying and sintering is used, the filtering precision is not reduced, but the permeability of the filter membrane is reduced, which shows that compared with the one-time spraying and sintering, the present application uses the multiple spraying and sintering, so that the pore size is similar (the filtering precision is close), but the permeability is improved.

[0109] Obviously, the above examples are only examples for clearly illustrating, but not limit the embodiments. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for preparing a nanoscale metal filter membrane, characterized in that, The preparation method includes the following steps: S1. Preparation of suspension slurry: After mixing metal powder, aqueous solvent and dispersant, the mixture is added to a high-speed grinding and dispersing machine to obtain suspension slurry, wherein the average particle size of the metal powder is 100nm~5μm; S2. Preparation of nanoscale metal filter membrane precursor: The suspension slurry is sprayed onto a porous support to form a metal powder coating on the porous support, and then dried to obtain a nanoscale metal filter membrane precursor, wherein the material of the porous support is the same as the material of the metal powder. S3. Preparation of nanoscale metal filter membrane: The nanoscale metal filter membrane precursor is sintered under vacuum conditions to obtain a nanoscale metal filter membrane. The spraying is ultrasonic spraying; In step S2, the spraying is performed multiple times. After each spraying, the nanoscale metal filter membrane precursor is sintered under vacuum conditions according to step S3 before the next spraying is performed.

2. The method for preparing the nanoscale metal filter membrane according to claim 1, characterized in that, The metal powder is made of stainless steel, nickel, or a nickel-based alloy. And / or, the aqueous solvent is water or an alcohol solvent; And / or, the dispersant includes at least one of polyvinyl alcohol, methylcellulose, and polyethylene glycol; And / or, based on the total mass of the suspension slurry being 100%, the mass percentage of metal powder in the suspension slurry is not less than 5% and not more than 20%; And / or, the mass ratio of the dispersant to the aqueous solvent is (0.01-1):

100.

3. The method for preparing the nanoscale metal filter membrane according to claim 1, characterized in that, The rotational speed of the high-speed grinding and dispersing machine is 2000-3500 r / min; And / or, in step S1, the dispersion time is 2h-4h.

4. The method for preparing the nanoscale metal filter membrane according to claim 1, characterized in that, The porous support includes a sheet support or a tubular support; And / or, the average pore size of the porous support is 5-30 μm; And / or, the thickness of the porous support is 0.3mm-6mm; And / or, the porous support is made of stainless steel, nickel, or a nickel-based alloy.

5. The method for preparing a nanoscale metal filter membrane according to claim 1, characterized in that, The ultrasonic spraying head has a power of 1-15W and a flow rate of 1mL / min-20mL / min.

6. The method for preparing the nanoscale metal filter membrane according to claim 1, characterized in that, The thickness of the metal powder coating is 5-100 μm; And / or, in step S2, the drying temperature is 100-120℃ and the drying time is 30min-60min; And / or, in step S3, during the sintering, the vacuum degree is <9×10⁻⁶. -3 Entrust; And / or, in step S3, the sintering includes: first heating to 400~500℃ at a heating rate of 2℃ / min-10℃ / min and holding at that temperature for 1~2h, then heating to 600~900℃ at a heating rate of 2℃ / min-10℃ / min and holding at that temperature for 2~4h, and finally cooling with the furnace.

7. A nanoscale metal filter membrane, characterized in that, The nanoscale metal filter membrane is prepared by the method described in any one of claims 1-6.

8. The use of the nanoscale metal filter membrane as described in claim 7, characterized in that, The nanoscale metal filter membrane is used for two-phase separation of any of the following: room temperature gas / solid, room temperature liquid / solid, high temperature gas / solid, and high temperature liquid / solid.

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