A method for preparing a nano-porous stainless steel alloy hollow fiber membrane

Abstract

The present application relates to a kind of preparation methods of porous stainless steel alloy hollow fiber membrane, more particularly to a kind of preparation methods of nano-pore stainless steel alloy hollow fiber membrane.Step one: preparation spinning solution containing 316L stainless steel powder, copper powder, polymer binder and four components of organic solvent;Step two: using solution spinning method, through non-solvent induced phase separation (NIPS) process, spinning solution is made into hollow fiber, and air drying is obtained to obtain polymer hollow fiber precursor containing metal component;Step three: after drying, hollow fiber precursor is placed in tube furnace, and using programmed temperature method is calcined in gaseous atmosphere, and nano-porous stainless steel / copper alloy hollow fiber membrane is obtained.The present application solves the shortcomings that the apparent pore size of the existing porous stainless steel hollow fiber membrane is larger and the surface is rough.

Description

Technical Field

[0001] This invention relates to a method for preparing a porous stainless steel alloy hollow fiber membrane, and more specifically, a method for preparing a nanoporous stainless steel alloy hollow fiber membrane. Background Technology

[0002] Metallic materials possess characteristics such as high electrical conductivity, high mechanical strength, corrosion resistance, high temperature resistance, and high pressure resistance. Therefore, porous separation membranes based on metals have broad application prospects and significant commercial value in specialized separation fields under extreme environments. Currently, the apparent pore sizes of metal hollow fiber membranes reported in China are generally in the micrometer range, and their surface roughness is relatively high. For example, the stainless steel hollow fibers disclosed in patent documents CN103933866A and CN 108970417 B, and the nickel hollow fibers disclosed in patent document CN105126640 A, all have pore sizes in the micrometer range and a wide distribution, limiting their application to only a few areas such as filtration of larger particles and oil-water separation, severely restricting the development of metal hollow fiber membrane applications. Although current porous metal hollow fiber membranes all employ powder sintering methods, they all use single metal powders, lacking research on alloy system hollow fiber membranes. Patent document CN 112295414 A describes a method for preparing a layer of TiO2 on the surface of large-pore stainless steel hollow fibers to reduce the pore size, but research on in-situ preparation of nanoporous stainless steel hollow fiber membranes is still lacking. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing porous stainless steel hollow fiber membranes, such as large apparent pore size and rough surface, and to provide a method for preparing nanoporous stainless steel alloy hollow fiber membranes.

[0004] This invention discloses a method for preparing a nanoporous stainless steel alloy hollow fiber membrane, comprising the following steps:

[0005] Step 1: Prepare a spinning solution containing four components: 316L stainless steel powder, copper powder, polymer binder, and organic solvent.

[0006] The average particle size of the 316L stainless steel powder mentioned in step one is 0.5 to 3.0 μm, and the average particle size of the copper powder is 0.3 to 1.0 μm.

[0007] The polymer adhesive mentioned in step one is polyethersulfone (PES) or polyetherimide (PEI).

[0008] The organic solvent mentioned in step one is at least one of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), or a mixture of two solvents in any proportion. The organic solvent is a good solvent for both PES and PEI; only a good solvent can effectively dissolve PES and PEI to form a homogeneous polymer solution. The NIPS process can only occur because the solvent is miscible with water, and water is not a poor solvent for PEI and PES.

[0009] The mass proportions of the components in the spinning solution described in step one are as follows: 1) at least one stainless steel powder, 42%–54%; 2) at least one copper powder, 6%–18%; 3) at least one polymer binder, 6%–10%; 4) at least one organic solvent, 30%–34%. The sum of all components is 100%. This range of components ensures that the viscosity of the spinning solution is above 4000 cps, facilitating spinning, and that the final alloy fiber pore size is controlled to be around 100 nm.

[0010] Step 2: Solution spinning is used, followed by a non-solvent-induced phase separation (NIPS) process to produce hollow fibers from the spinning solution. These fibers are then air-dried to obtain a polymer hollow fiber precursor containing metal components. The non-solvent-induced phase separation (NIPS) process involves dissolving the polymer in a solvent to form a homogeneous solution. A reagent with stronger miscibility with the solvent (called an extractant, usually water) is then added to extract the solvent, forming a two-phase structure with the polymer as the continuous phase and the solvent as the dispersed phase. The solvent is then removed to obtain a polymer with a specific porous structure.

[0011] The solution spinning method described in step two is a well-known solution spinning process. Using mechanical power or compressed gas as the driving force, the spinning solution is extruded from a hollow spinneret at a certain speed. After passing through a 0-15cm air bath, it enters a water or aqueous solution coagulation bath. The core solution is water or an aqueous solution. After 24-48 hours of solvent exchange (NIPS), a solidified polymer hollow fiber precursor is obtained. The size of the spinneret is not limited, but a corrosion-resistant metal spinneret with an inner diameter of 1.0-1.5mm, an outer diameter of 2.0-3.0mm, and an inner core diameter of 0.5-0.9mm is preferred.

[0012] Step 3: Place the dried hollow fiber precursor in a tube furnace. The dried hollow fiber precursor needs to be placed in a corundum tube with a diameter of 10 mm and then placed in the tube furnace. Sintering is carried out in a gas atmosphere using a programmed temperature rise method to obtain a nanoporous stainless steel alloy hollow fiber membrane.

[0013] The programmed temperature range described in step three is 25℃ to 1100℃, with a heating rate of 5℃ to 15℃ / min, and a sintering time of 10min to 120min at the highest temperature. 15℃ is the upper limit of the heating rate for a typical tube furnace; rates below 5℃ are too slow, wasting time and not beneficial to the final result. A sintering time of 10min or more ensures the basic strength of the fibers, while a time above 120min results in excessively low fiber porosity.

[0014] The gas atmosphere described in step three is a reducing gas at a flow rate of 50–200 mL / min, which can be carbon monoxide or hydrogen with a purity of 99.999%. Reducing gases are more effective at removing polymers than ordinary inert gases.

[0015] Compared with the prior art, the positive effects of the present invention are:

[0016] This invention can be used to prepare a nanoporous stainless steel alloy hollow fiber membrane. A hollow fiber precursor containing 316L stainless steel and copper is sintered in pure hydrogen gas, successfully reducing the pore size of the metal hollow fiber surface to within 100 nm, while significantly reducing the surface roughness. The resulting porous hollow fiber membrane has excellent gas-liquid permeability, broadening the application range of porous metal membranes, and has significant application prospects in energy, environment, biomedicine, electronics and other fields. Attached Figure Description

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific implementation methods.

[0018] Figure 1 This is a SEM image of the surface of the alloy hollow fiber prepared in Example 1;

[0019] Figure 2 The image shows the pore size distribution of the hollow fibers in the alloy prepared in Example 1. Detailed Implementation

[0020] This invention discloses a method for preparing a nanoporous stainless steel alloy hollow fiber membrane, comprising the following steps:

[0021] Step 1: Prepare a spinning solution containing four components: 316L stainless steel powder, copper powder, polymer binder, and organic solvent.

[0022] The average particle size of the 316L stainless steel powder mentioned in step one is 0.5 to 3.0 μm, and the average particle size of the copper powder is 0.3 to 1.0 μm.

[0023] The polymer adhesive mentioned in step one is polyethersulfone (PES) or polyetherimide (PEI).

[0024] The organic solvent mentioned in step one is at least one or a mixture of two solvents in any proportion, such as N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO).

[0025] The mass proportions of the components in the spinning solution described in step one are as follows: 1) at least one stainless steel powder, 42%–54%; 2) at least one copper powder, 6%–18%; 3) at least one polymer binder, 6%–10%; 4) at least one organic solvent, 30%–34%. The sum of all components is 100%.

[0026] Step 2: Using solution spinning, the spinning solution is made into hollow fibers through a non-solvent induced phase separation (NIPS) process, and then dried in the air to obtain a polymer hollow fiber precursor containing metal components.

[0027] The solution spinning method described in step two is a well-known solution spinning process. Using mechanical power or compressed gas as the driving force, the spinning solution is extruded from a hollow spinneret at a certain speed. After passing through a 0-15cm air bath, it enters a water or aqueous solution coagulation bath. The core solution is water or an aqueous solution. After 24-48 hours of solvent exchange (NIPS), a solidified polymer hollow fiber precursor is obtained. The size of the spinneret is not limited, but a corrosion-resistant metal spinneret with an inner diameter of 1.0-1.5mm, an outer diameter of 2.0-3.0mm, and an inner core diameter of 0.5-0.9mm is preferred. The resulting fibers have a diameter of 1mm or more and a thickness of 0.2mm or more, ensuring strength.

[0028] Step 3: Place the dried hollow fiber precursor in a tube furnace and sinter it in a gas atmosphere using a programmed temperature rise method to obtain a nanoporous stainless steel / copper alloy hollow fiber membrane.

[0029] The temperature range described in step three is 25℃~1100℃, the heating rate is 5~15℃ / min, and the sintering time at the highest temperature is 10min~120min.

[0030] The gas atmosphere described in step three is a reducing gas with a flow rate of 50-200 mL / min, which can be carbon monoxide or hydrogen with a purity of 99.999%.

[0031] This invention can be used to prepare a nanoporous stainless steel alloy hollow fiber membrane. A hollow fiber precursor containing 316L stainless steel and copper is sintered in pure hydrogen gas, successfully reducing the pore size of the metal hollow fiber surface to within 100 nm, while significantly reducing the surface roughness. The resulting porous hollow fiber membrane has excellent gas-liquid permeability, broadening the application range of porous metal membranes, and has significant application prospects in energy, environment, biomedicine, electronics and other fields.

[0032] Any aspects not covered in this invention are applicable to existing technologies.

[0033] The following are specific embodiments of the present invention. These embodiments are merely illustrative of the present invention and do not limit the scope of protection of the claims of the present invention.

[0034] Example 1:

[0035] Step 1: Preparation of spinning solution. Add 6g of PES to 34g of N-methylpyrrolidone (NMP) and stir at room temperature for 3 hours. Then add 54g of 316L stainless steel powder and 6g of copper powder, and continue mechanical stirring for 3 hours to obtain a spinning solution with a total mass of 100g. The mass ratio of the four components—316L stainless steel powder, copper powder, PES, and N-methylpyrrolidone (NMP)—is 54:6:6:34, and the total amount of the four components is always 100%.

[0036] Step 2: Prepare polymer hollow fiber precursor from spinning solution. Place the spinning solution in a ball mill and continuously ball mill for 10 hours to further disperse the metal powder uniformly and ensure the homogeneity of the spinning solution. Then transfer it to a stainless steel syringe and degas under a vacuum of 0.005 MPa for 10 hours. Using solution spinning, the spinning solution is ejected from the syringe through a spinneret using a syringe pump. After a non-solvent (water) induced phase separation (NIPS) process, the spinning solution is formed into hollow fibers. The obtained hollow fibers are soaked in water at room temperature for 24 hours and then air-dried to obtain a polymer hollow fiber precursor containing two metal powders.

[0037] Step 3: Place the dried hollow fiber precursor in a tube furnace and calcine it in a pure hydrogen atmosphere using a programmed temperature rise method. The heating rate is 10℃ / min, the final sintering temperature is 1100℃, the sintering time is 30min, and the hydrogen supply is 50mL / min. After natural cooling, a nanoporous stainless steel / copper alloy hollow fiber membrane is obtained.

[0038] The average pore size was measured to be 70 nm using a pore size analyzer, and the N2 flux at 1 atm pressure was 12700 GPU. The pore size on the surface of the metal hollow fiber was successfully reduced to within 100 nm, while significantly reducing surface roughness. Membranes with pore sizes smaller than 100 nm have a wider range of applications compared to membranes with pore sizes in the micrometer range. They can filter smaller substances due to their smaller size cutoff. They can also serve as carrier membranes, loading nanomaterials ranging from tens to hundreds of nanometers. The N2 gas flux demonstrates that the mass transfer capacity of the hollow fiber is positively correlated to some extent with its pore size and porosity.

[0039] Example 2: This example differs from Example 1 in that the sintering time in step 3 is 10 minutes, while the remaining steps are the same as in Example 1. The average pore size was measured to be 102 nm, and the N2 flux at 1 atm pressure was 43950 GPU.

[0040] Example 3: This example differs from Example 2 in that the sintering time in step 3 is 60 minutes, while the remaining steps are the same as in Example 1. The average pore size was measured to be 62 nm, and the N2 flux at 1 atm pressure was 2050 GPU.

[0041] Example 4: This example differs from Example 2 in that the hydrogen supply in step 3 is 25 mL, while the remaining steps are the same as in Example 1. The average pore size was measured to be 116 nm, and the N2 flux at 1 atm pressure was 34610 GPU.

[0042] Example 5: This example differs from Example 2 in that the hydrogen supply in step 3 is 75 mL, while the remaining steps are the same as in Example 1. The average pore size was measured to be 61 nm, and the N2 flux at 1 atm pressure was 5785 GPU.

[0043] Example 6: This example differs from Example 2 in that the hydrogen supply in step 3 is 100 mL, while the remaining steps are the same as in Example 1. The average pore size was measured to be 57 nm, and the N2 flux at 1 atm pressure was 1832 GPU.

Claims

1. A method for preparing a nanoporous stainless steel alloy hollow fiber membrane, characterized in that, Includes the following steps: Step 1: Prepare a spinning solution containing four components: stainless steel powder, copper powder, polymer binder, and organic solvent; Step 2: Using solution spinning, through a non-solvent induced phase separation (NIPS) process, the spinning solution is made into hollow fibers, which are then dried in the air to obtain a polymer hollow fiber precursor containing metal components; Step 3: Place the dried hollow fiber precursor in a tube furnace and calcine it in a gas atmosphere using a programmed temperature rise method to obtain a nanoporous stainless steel alloy hollow fiber membrane. The mass proportions of each component in the spinning solution described in step one are as follows: 1) at least one stainless steel powder, 42%–54%; 2) at least one copper powder, 6%–18%; 3) at least one polymer binder, 6%–10%; 4) at least one organic solvent, 30%–34%; the sum of all components is 100%. The temperature range described in step three is 25 ℃~1100 ℃, the heating rate is 5~15 ℃ / min; the sintering time at the highest temperature is 10 min~120 min; This preparation method is used to prepare a nanoporous stainless steel alloy hollow fiber membrane. The hollow fiber precursor containing 316L stainless steel and copper is sintered in pure hydrogen gas to reduce the pore size of the metal hollow fiber surface to less than 100 nm.

2. The method for preparing a nanoporous stainless steel alloy hollow fiber membrane according to claim 1, characterized in that: The stainless steel powder mentioned in step one is 316L stainless steel powder, and the average particle size of 316L stainless steel powder is 0.1 to 10.0 μm.

3. The method for preparing a nanoporous stainless steel alloy hollow fiber membrane according to claim 1, characterized in that: The average particle size of the copper powder mentioned in step one is 0.05–3.0 μm.

4. The method for preparing a nanoporous stainless steel alloy hollow fiber membrane according to claim 1, characterized in that: The polymer adhesive mentioned in step one is polyethersulfone (PES) or polyetherimide (PEI).

5. The method for preparing a nanoporous stainless steel alloy hollow fiber membrane according to claim 4, characterized in that: The organic solvent mentioned in step one is a good solvent for PES and PEI and is miscible with water, including at least one or a mixture of two solvents in any proportion, such as N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO).

6. The method for preparing a nanoporous stainless steel alloy hollow fiber membrane according to claim 1, characterized in that: In the solution spinning method described in step two, the spinning solution is placed in a ball mill for continuous ball milling, then transferred to a stainless steel syringe for degassing under vacuum. The spinning solution is then quantitatively extruded from the hollow spinneret using mechanical power or compressed gas as the driving force. After passing through a 0-15 cm air bath, it enters a water or aqueous solution coagulation bath. The core liquid is water or an aqueous solution. After 24-48 hours of solvent exchange (NIPS), a solidified polymer hollow fiber precursor is obtained.

7. The method for preparing a nanoporous stainless steel alloy hollow fiber membrane according to claim 1, characterized in that: The gas atmosphere described in step three is a 99.999% reducing gas at a flow rate of 50–200 mL / min.

8. The method for preparing a nanoporous stainless steel alloy hollow fiber membrane according to claim 6, characterized in that: The spinneret is a corrosion-resistant metal spinneret with an inner diameter of 1.0–1.5 mm, an outer diameter of 2.0–3.0 mm, and an inner core diameter of 0.5–0.9 mm.

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