A NiCu alloy paper-type film and its preparation method

Abstract

The present invention provides a NiCu alloy paper-type film and a preparation method thereof. The material composition includes nickel, copper, and silver. The mass ratio of copper to nickel is (5-10):3, and the doped silver content ion in the NiCuAg alloy paper-type film is 5-30 PPMppm. The preparation process of the NiCu alloy paper-type film uses a nickel foil as the substrate, obtains a composite layer by electro-depositing copper and silver, and further forms pores through the Kirkendall effect during the high-temperature diffusion reaction process to obtain a uniform, fine, and rich pore structure. The overall thickness of the nickel-copper alloy paper-type film provided by the present invention is about 100-200 μm, and the pore diameter is about 0.5-5 μm. It has excellent permeation performance and filtration accuracy, and at the same time has good flexibility and can be applied to a gas purifier for endoscopic surgery.

Description

Technical Field

[0001] The invention belongs to the technical field of filter materials, and in particular relates to a NiCu alloy paper-type membrane and a preparation method thereof. Background Art

[0002] At present, the main filter elements of air filters on the market, such as masks and air purifiers, are non-woven fabrics made of organic fibers. Organic porous membrane materials are widely used because of their low air resistance, large air flow, and high filtration efficiency, especially because of their flexibility and good chemical resistance. However, organic porous membrane materials have a short lifespan, are not resistant to high temperatures, and are prone to breeding bacteria. They need to be replaced regularly, which also limits their application areas and increases their cost of use. In contrast, porous metal membranes have a unique combination of ideal properties, with high strength, high toughness, and excellent antibacterial properties, thermal stability, and mechanical properties. At the same time, the filtration method of porous metal membrane materials is physical interception, with high filtration accuracy. Compared with the electrostatic adsorption filtration mechanism that is susceptible to organic porous membranes, their filtration accuracy will not change before the membrane layer is mechanically damaged.

[0003] At present, porous metal membranes are mostly coated with a layer of fine powder slurry on a macroporous metal support by spraying, scraping, etc., and after degreasing and sintering, a composite membrane with a macroporous support layer and a small pore separation layer is formed. The porous metal membranes prepared by these methods have many disadvantages. First, spraying, scraping, etc. cannot evenly cover the fine powder slurry on the macroporous substrate, resulting in an uneven fine powder layer, and there may be uncovered macropores, resulting in macropore defects in the final porous membrane layer, and low filtration accuracy. In addition, due to the difference in the thermal expansion coefficient of the support and the membrane layer, the metal membrane is prone to peeling, cracking and other defects during the sintering preparation process, and the overall thickness is thicker, the overall rigidity, the air permeability is low, and the filtration efficiency is low.

[0004] Patent publication number CN111359451A discloses "A Fe~Al metal porous membrane and its preparation method", which introduces a method of forming a slurry from FeAl metal powder and metal fiber as raw materials with a water-based adhesive, followed by film casting, degreasing, sintering and other processes to obtain a porous metal membrane with high porosity. However, the porous membrane prepared by this method often has a large pore size, a wide pore distribution, and is prone to macropore defects.

[0005] Patent publication number CN111672331A discloses "a method for preparing porous metal membrane by sol-gel method", which introduces the use of two metal powders, alloy powders, etc. with different particle sizes as raw materials through sol-gel method, with the gaps between powder particles as pore sources, where the large particle size metal powder is sintered as a macroporous support layer, and the small particle size powder is sintered as a separation layer, and finally a porous membrane material is formed. However, its double-layer structure often has a large overall thickness of the membrane layer, and the membrane layer is not flexible. Summary of the invention

[0006] In view of the defects of traditional asymmetric membranes, such as poor filtration accuracy, low filtration efficiency, large thickness and difficulty in folding, the object of the present invention is to provide a flexible NiCu alloy paper-type membrane with good filtration effect and a preparation method thereof.

[0007] The present invention provides a NiCu alloy paper-type membrane, the material of which includes nickel, copper and silver. The mass ratio of copper to nickel is (5-10):3, and the silver ions doped in the NiCu alloy paper-type membrane are 5-30 PPM. The nickel-copper alloy has good corrosion resistance and antibacterial properties. In addition, doping silver ions is mainly to further enhance the antibacterial and bactericidal effects of the nickel-copper alloy.

[0008] The overall thickness of the membrane is about 100-200 μm, the porosity is greater than 50%, the pore diameter is 0.5-5 µm, and it has a fine and rich pore structure, which can ensure good permeability and filtration accuracy.

[0009] The present invention also provides a preparation method of the NiCu alloy paper-type membrane, which includes the following steps:

[0010] S1. Select a nickel foil with a thickness of 30-70 µm, and perform pretreatment on the surface of the nickel foil in sequence;

[0011] S2. Use an electrochemical method to cathodically deposit copper on the surface of the nickel substrate to obtain a NiCu metal composite membrane. The anode is a Cu plate, the cathode is a Ni foil, and the electrolyte includes a solution system composed of nitric acid, copper nitrate and silver nitrate; the current density is 100-300 A / m 2 , the temperature of the electrolyte is 30-80 °C, and the thickness of the deposited copper layer is about 50-80 µm;

[0012] S3. Wash the NiCu metal membrane with water, and then dry it.

[0013] S4. Transfer the dried NiCu metal membrane into a furnace for high-temperature sintering reaction to form pores, and the nickel-copper alloy paper-type membrane can be obtained after furnace cooling.

[0014] Preferably, the nickel substrate is a nickel foil, and the thickness of the nickel substrate is 20-100 µm. Selecting a nickel foil as the substrate has a higher melting point than a copper foil, has good support during subsequent sintering, and can ensure the continuity and integrity of the paper-type membrane after sintering.

[0015] Preferably, the pretreatment in step S1 is a step of sequentially performing ultrasonic degreasing and cleaning, deionized water washing, pickling with dilute acid to remove oxide scale, and again deionized water washing on the surface of the nickel foil. Degreasing and removing oxide scale should be sufficient, otherwise the uniformity and adhesion of the coating will be affected. Pretreatment can enhance the bonding between Cu and Ni foil during subsequent electrodeposition and ensure that subsequent diffusion will not be affected by other factors.

[0016] Preferably, the copper layer is electro-deposited on the surface of the nickel substrate by electro-chemical deposition. Compared with the nitric acid system, the nitric acid system can better control the concentration of silver ions and achieve a better co-deposition effect of copper and silver.

[0017] Preferably, the NiCu alloy paper-type film precursor includes a nickel substrate and a copper layer on its surface. The silver ions doped in the copper layer are 5-30 PPM. If the silver doping amount is too high, the cost will be too high; if it is too low, it is difficult to significantly improve the antibacterial and bactericidal performance. Therefore, to ensure the composition ratio of the nickel-copper alloy, the thickness of the electro-deposited copper layer is 50-80 µm. The thickness of the electroplated layer should match the thickness of the nickel substrate to ensure that the alloy formed after sintering and diffusion is within the above composition range.

[0018] Preferably, in the step S2, the steps of adding gelatin, thiourea and a complexing agent to the electrolyte are further included. Adding additives such as gelatin and thiourea can significantly regulate the electro-deposition stress and achieve thickness and uniform plating.

[0019] The main function of gelatin: it can promote the formation of electroplated copper with fine crystals and a smooth surface, and can inhibit the generation of lumps. Due to its surface adsorption effect, it can reduce the growth rate of microcrystals, which is beneficial to the generation of new crystal nuclei, thereby obtaining dense, flat and extremely fine-grained deposited copper.

[0020] The main function of thiourea is to facilitate the refinement of the cathode crystal and the densification of the plate surface, playing a role in refining the crystal. The complexing agent 5,5-dimethylhydantoin has a strong coordination with Ag + ions, while having a weak coordination with Cu 2+ ions or not undergoing a coordination reaction, making the deposition potentials of Cu 2+ ions and Ag + ions close to each other to achieve Cu-Ag co-deposition.

[0021] Preferably, the concentration of nitric acid in the electrolyte is 30-80 g / L, the concentration of copper nitrate is 100-300 g / L, the concentration of silver ions is 50-100 mg / L, the concentration of gelatin is 5-10 mg / L, the concentration of thiourea is 5-10 mg / L, and the concentration of the complexing agent is 10-16 g / L.

[0022] The NiCu alloy paper-type film provided by the present invention uses an electro-chemical deposition method to prepare a composite film precursor, and performs preferential diffusion and pore formation through the Kirkendall effect during the sintering process. Finally, a NiCu alloy porous film with high air permeability, small pore diameter, high porosity, antibacterial ability, high strength and flexibility is prepared.

[0023] Preferably, in step S4, sintering is carried out in a segmented manner. The annealed material is transferred into a vacuum sintering furnace for gradient temperature rise sintering, which specifically includes the following steps:

[0024] (1) The composite film precursor obtained by electrodeposition is first transferred into an annealing furnace and heat-preserved for 0.5 - 2 h at 300 °C - 500 °C in a hydrogen atmosphere for stress relief annealing. This process can prevent the deformation of the metal film and the peeling of the coating during the subsequent sintering diffusion process, and at the same time improve the activity of Ni and Cu components, promoting subsequent high-temperature diffusion.

[0025] (2) Subsequently, it is placed in a vacuum furnace for sintering. First, it is heated to 100 °C - 150 °C within 30 - 50 min, and then heat-preserved for 0.5 - 3 hours to remove the moisture remaining on the surface of the metal film.

[0026] (3) It is heated to 700 °C - 900 °C within 100 - 160 min and heat-preserved for 2 - 6 hours; at this temperature, the diffusion rate of Ni in Cu is much lower than that of Cu in Ni, and the Kirkendall effect is obvious, which is beneficial to the formation of pores in the film layer. And at this temperature, the saturated vapor pressure of Cu is relatively low and it is not easy to volatilize under high vacuum. If it is directly heated to a high temperature, the pure copper that is not alloyed on the surface of the film layer will directly volatilize.

[0027] (4) It is heated to 800 °C - 1000 °C within 20 - 50 min and heat-preserved for 1 - 3 hours. Sintering at this temperature can promote the uniform diffusion of nickel, copper, and silver elements in the porous film, forming a paper-like film with a well-developed pore structure, well-developed sintering necks, and uniform composition. After sintering, it is cooled in the furnace to obtain a nickel-copper alloy paper-like film.

[0028] The NiCu alloy paper-like film provided by the present invention is flexible and bendable, has a high filtration accuracy, has antibacterial and bacteriostatic capabilities, and has a good air permeability, and can be used as a laparoscopic purification material. Since the gas composition in laparoscopic surgery is complex and the filtration working environment is the surgical scenario, there are relatively high technical difficulties in harmful gas filtration. The special working environment poses higher requirements for the filtration equipment and materials: the filtration equipment needs to be small in size and easy to use without affecting the normal operation of medical staff; therefore, the filtration material requires higher filtration accuracy and better filtration effect, and maintains a long effective filtration time. At the same time, the filtration material must also have antibacterial and disinfectable characteristics during use to ensure surgical safety.

[0029] The paper-like film material provided by the present invention can be used as a laparoscopic purification material, which can ensure excellent filtration effect of the gas in laparoscopic surgery, improve the stability of laparoscopic surgery, and protect the physical health of patients and medical staff. And the NiCu alloy paper-like film can be repeatedly cleaned and used, which is more environmentally friendly and cost-saving. Description of the Drawings

[0030] The above and other objects, features and advantages of the present invention will become more apparent from the preferred embodiments of the present invention shown in the accompanying drawings. In all the drawings, the same reference numerals indicate the same parts, and the drawings are not deliberately drawn to scale in actual size, and the emphasis is on showing the gist of the present invention.

[0031] Figure 1 Product photo of the NiCu alloy paper-type film provided for the invention. Detailed Description of the Invention

[0032] The technical solution of the present invention will be further described in detail below in conjunction with specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments cited are not intended to limit the present invention.

[0033] In order to have a further understanding and recognition of the technical solution of the present invention, several preferred embodiments are now cited to further describe it in detail.

[0034] Embodiment 1

[0035] Select a nickel foil with a thickness of 50 µm for pretreatment, including ultrasonic degreasing and cleaning in ethanol, washing with deionized water, pickling with dilute acid to remove oxide scale, and washing with deionized water again to obtain a Ni foil without oxide scale and other impurities as the nickel substrate.

[0036] Copper is deposited on the nickel substrate by an electrochemical method. The anode is a Cu plate, the cathode is a Ni foil, the electrolyte is a nitric acid / copper nitrate solution system, the additives are gelatin 8 mg / L and thiourea 7 mg / L, the complexing agent is 5,5-dimethylhydantoin 13 g / L, the current density is 220 A / m2, the electrolyte temperature is 50 °C, and the thickness of the deposited layer is about 50 µm. The concentration of nitric acid in the electrolyte is 30 - 80 g / L, the concentration of copper nitrate is 100 - 300 g / L, the concentration of silver ions is 50 - 100 mg / L, the concentration of gelatin is 5 - 10 mg / L, the concentration of thiourea is 5 - 10 mg / L, and the concentration of the complexing agent is 10 - 16 g / L. Wash the electrodeposited NiCu metal film with water to remove impurities on the film surface, and then transfer it to a vacuum drying oven for drying.

[0037] Transfer the dried NiCu metal film to an annealing furnace and perform stress relief annealing at 400 °C for 1 h in a hydrogen atmosphere to prevent the metal film from deforming during the subsequent sintering and diffusion process.

[0038] After the sample is cooled, transfer it to a vacuum sintering furnace for partial diffusion pore formation. The sintering is carried out in a segmented heating sintering mode. The sintering process is as follows:

[0039] First, heat up to 120 °C in 40 min and hold for 1 h;

[0040] Then, it is heated to 800 °C within 140 min and held for 4 h.

[0041] Finally, it is heated to 900 °C within 30 min and held for 2 h to fully alloy the film layer and homogenize the composition; finally, it is cooled to room temperature in the furnace. A NiCu alloy paper-type film is obtained.

[0042] The mass ratio of nickel to copper in the NiCu alloy paper-type film prepared in this example is 7:3, the average film thickness is less than 100 µm, the porosity reaches 60%, and the average pore diameter is 0.3 - 1 µm. Refer to the appendix Figure 1 It can be seen that the NiCu alloy paper-type film prepared in this example has good flexibility.

[0043] The NiCu alloy paper-type film prepared in Example 1 is subjected to PM2.5 filtration effect test, air permeability effect test, and killing rate effect test on Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa.

[0044] Among them, the test method for the PM2.5 filtration effect test is: cut the NiCu alloy porous membrane into appropriate sizes and shapes, and place it on an automatic filter material tester for testing.

[0045] The test method for the air permeability effect test is: cut the NiCu alloy porous membrane into appropriate sizes and shapes, and place it on a bubble pressure method filter membrane pore size analyzer for testing.

[0046] The test method for the killing rate effect test on Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa is: quantitatively inoculate bacteria on the porous membrane prepared in Example 1 and the clear water control sample according to the national standard GB 21551.2 - 2010. After 24 h of cultivation, the number of surviving bacteria in the two groups of samples is measured, and the antibacterial rate of the porous membrane in Example 1 is compared and calculated.

[0047] The specific test results are shown in Table 1.

[0048] Table 1

[0049]

[0050] In summary, it can be seen that the NiCu alloy paper-type film provided by the present invention has high strength and flexibility, has the advantages of large air permeability, small pore diameter, and high porosity, and also has very good antibacterial ability. After the tested NiCu alloy paper-type film is removed and cleaned, and then tested again, the test results are basically the same as those in Table 1. It can be known that the NiCu alloy paper-type film provided by the present invention can be repeatedly cleaned and used.

[0051] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A NiCu alloy paper-type film, characterized in that, its material includes nickel, copper and silver, the mass ratio of copper to nickel is (5~10):3, and the silver ions doped in the NiCu alloy paper-type film are 5~30 PPM; The preparation method of the NiCu alloy paper-type film includes the following steps: S1. Select a nickel foil with a thickness of 30~70 µm, and perform pretreatment on the surface of the nickel foil in sequence to obtain a nickel substrate; S2. Use an electrochemical method to deposit copper on the surface of the nickel substrate to obtain a NiCu metal film, where the anode is a Cu plate, the cathode is the nickel substrate, and the electrolyte includes a solution system composed of nitric acid, copper nitrate and silver nitrate; the current density is 100~300 A / m2, the electrolyte temperature is 30~80 °C, and the thickness of the deposited copper layer is 50~80 µm; gelatin, thiourea and a complexing agent are added to the electrolyte; the concentration of the gelatin is 5~10 mg / L, the concentration of the thiourea is 5~10 mg / L, and the concentration of the complexing agent is 10~16 g / L; the complexing agent is 5,5~dimethylhydantoin; S3. Wash the NiCu metal film with water, and then dry it; S4. Transfer the dried NiCu metal film into a furnace for high-temperature sintering reaction, and perform partial diffusion to form pores through the Kirkendall effect during the sintering process. After furnace cooling, a nickel-copper alloy paper-type film is obtained; In the step S4, sintering is carried out in a segmented heating and sintering manner, which specifically includes the following steps: (1) Place the electrodeposition precursor in an annealing furnace, and perform stress relief annealing at 300 °C~500 °C for 0.5~2 h in a hydrogen atmosphere; (2) Then place it in a vacuum furnace for sintering. First, heat it up to 100~150 °C within 30~50 min, and then keep it warm for 0.5~3 hours; (3) Heat it up to 700~900 °C within 100~160 min and keep it warm for 2~6 hours; (4) Heat it up to 800~1000 °C within 20~50 min and keep it warm for 1~3 hours.

2. The NiCu alloy paper-type film according to claim 1, characterized in that, the average thickness of the NiCu alloy paper-type film is 100~200 µm, the porosity is greater than 50%, and the pore diameter is 0.5~5 µm.

3. The NiCu alloy paper-type film according to claim 1, characterized in that, in the step S1, the pretreatment is a step of sequentially performing ultrasonic degreasing cleaning, deionized water washing, pickling with dilute acid, and again deionized water washing on the surface of the nickel foil to obtain a nickel substrate.

4. The NiCu alloy paper-type film according to claim 1, characterized in that, the concentration of nitric acid in the electrolyte is 30~80 g / L, the concentration of copper nitrate is 100~300 g / L, and the concentration of silver ions is 50~100 mg / L.

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