Method for preparing porous titanium-based material with low mass transfer resistance through magnetic field induction

Abstract

The invention discloses a method for preparing a porous titanium-based material with low mass transfer resistance by using magnetic field induction, and relates to the technical field of electrode manufacturing, and the method comprises the following steps: preparing titanium powder slurry containing magnetic components and titanium powder slurry without magnetic components, and preparing a double-layer or multi-layer composite structure from different slurries; directionally arranging the magnetic components by using a magnetic field; the sintering treatment enables the magnetic components to be decomposed or sintered to generate a directionally-arranged supporting structure, and the directionally-arranged supporting structure is obtained; and continuously sintering at the temperature higher than the first temperature interval, and pickling to remove the directionally arranged support structure to obtain the porous titanium-based material with the dual-scale pore structure, the problems that in the prior art, mass transfer efficiency is low, mass transfer resistance is large, a directional through pore structure is difficult to achieve, cooperative construction of pores with different pore diameters is difficult, the functionality of the pores is single, and the pores are prone to being polluted are solved.

Description

Technical Field

[0001] This invention relates to the field of electrode manufacturing technology, and in particular to a method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction. Background Technology

[0002] Porous titanium-based materials have important applications in many high-tech fields due to their excellent corrosion resistance, biocompatibility and electrical conductivity. In particular, they are key mass transfer components in electrochemical energy conversion equipment, where their pore structure directly affects mass transfer efficiency and electrochemical performance.

[0003] The main methods for preparing porous titanium-based materials currently include: Powder metallurgy: This method involves mixing titanium powder with a pore-forming agent and sintering the mixture. The pore-forming agent volatilizes during sintering to form pores. However, the main problem with this method is the random pore distribution, which makes it impossible to achieve a directional pore structure, resulting in high mass transfer resistance.

[0004] Titanium fiber sintering method: Titanium or titanium alloy fibers (short fibers or fiber mats) are laid up, pressed, and sintered to form a porous structure. The pore structure generated by this method is completely random, with high tortuosity (2.5~3.5), large mass transfer resistance, and it is difficult to achieve precise control of the pore size.

[0005] Template method: Organic foam or similar materials are used as templates. Titanium slurry is impregnated with the template and then sintered to remove it. The disadvantages of this method are high cost, potential template residue affecting material purity, and inability to precisely control pore direction.

[0006] Additive manufacturing (3D printing): This method uses lasers / electron beams to melt titanium powder layer by layer to precisely create pre-designed complex porous structures. However, this method involves expensive equipment, low production efficiency, and is difficult to scale up.

[0007] Currently, PTL (Potentially Transient Tolerancing) in PEM electrolyzers is mainly prepared using powder metallurgy or titanium fiber sintering. The main problems with these methods are the random pore distribution, making it impossible to achieve directional pore structures, resulting in high tortuosity (2.5~3.5), high mass transfer resistance, uneven surface pore size, and low catalyst utilization; and difficulty in precisely controlling pore parameters during the preparation process. Furthermore, the pores formed by titanium fiber sintering or powder sintering are randomly tortuous with high tortuosity. Traditional pore-forming agents (such as polystyrene microspheres) can only form isolated spherical pores, unable to create through-holes that facilitate mass transfer. While laser drilling and 3D printing can design through-holes, they are costly and inefficient.

[0008] In summary, existing technologies have many shortcomings in the preparation of porous titanium-based materials, such as random pore structure, high mass transfer resistance, complex processes, high costs, and difficulty in scaling up. There is an urgent need for a new preparation technology that can achieve directional pore structure, low mass transfer resistance, high-precision control, and is suitable for industrial production. Summary of the Invention

[0009] In view of the above analysis and in view of the shortcomings of the prior art, the present invention aims to provide a method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction, thereby solving at least one of the following problems in the prior art: low mass transfer efficiency, high mass transfer resistance, difficulty in achieving directional through-pore structure, difficulty in synergistic construction of pores with different pore sizes, single pore functionality, and susceptibility to contamination.

[0010] The objective of this invention is mainly achieved through the following technical solutions: This invention discloses a method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction, comprising: S1: Prepare titanium powder slurry containing magnetic components and titanium powder slurry without magnetic components; S2: Based on the coating method, titanium powder slurry containing magnetic components and titanium powder slurry without magnetic components are sequentially coated to prepare a double-layer or multi-layer composite structure; the magnetic components in the layered structure containing magnetic components are oriented and arranged by a magnetic field, and the first blank is obtained after the double-layer or multi-layer composite structure is completely cured. S3: Sintering the first blank in the first temperature range causes the magnetic components to decompose or sinter to produce a directional support structure, thereby obtaining a second blank with a directional support structure. S4: The second blank is sintered at a temperature higher than the first temperature range to obtain a third blank that has both a directional support structure and a first pore structure. S5: Pickling removes the oriented support structure in the third preform, obtaining a second oriented interconnected pore channel, and thus obtaining a porous titanium-based material with a dual-scale pore structure.

[0011] Preferably, in step S1, the magnetic component can be one or more of the following: magnetic particles or oxide-coated materials of MnO2, Mn2O3, Mn3O4, BaTiO3, and SrTiO3.

[0012] Preferably, the oxide coating material is at least one of MnO2, Mn2O3, Mn3O4, BaTiO3, and SrTiO3 as a coating for the fibers, and the fibers can be short fibers of PMMA, PAN, PS, PET, PI, or carbon fiber.

[0013] Preferably, the diameter of the fiber coating is 40μm~60μm and the length is 200μm±50μm.

[0014] Preferably, the particle size of the magnetic particles is 300nm~500nm.

[0015] Preferably, step S2 includes: S201: A first layered structure containing magnetic components is formed using a titanium powder slurry containing magnetic components; S202: Apply a magnetic field perpendicular to the surface of the first layered structure; S203: Obtained by coating a slurry containing magnetic components with a titanium powder slurry that does not contain magnetic components on its surface after surface drying, and then curing the second layered structure.

[0016] Preferably, the magnetic field strength in step S202 is 0.50T~0.80T.

[0017] Preferably, the first temperature range in step S3 is 250℃~650℃.

[0018] Preferably, the sintering temperature in step S4 is 650℃~1080℃.

[0019] A porous titanium-based material with low mass transfer resistance is prepared by the above-mentioned method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction, comprising: a bilayer or multilayer composite structure composed of odd-numbered functional layers and even-numbered functional layers stacked alternately. In the composite structure, the odd-numbered functional layers are provided with a second pore channel that is oriented and connected through the thickness direction of the odd-numbered functional layers, and the even-numbered functional layers are provided with a first pore structure with a smaller gap than the second pore channel.

[0020] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: (1) This invention uses a magnetic field to orient the magnetic components and sinter them in the first temperature range, so that the magnetic components decompose to form a stable support structure, ensuring that the pore channels remain stable in the subsequent sintering process. The support structure is removed by acid washing, and finally a directional connected pore channel with low mass transfer resistance is formed, realizing efficient gas and liquid transport, significantly reducing mass transfer resistance, reducing the overall tortuosity to 1.2~1.4, and the gas permeability to 8.8×10-11m2~1.28×10-10m2 (N2, 0.1MPa pressure difference), solving the problems of low mass transfer efficiency and high mass transfer resistance in the prior art.

[0021] (2) In this invention, small and medium pores (10~30μm) are naturally formed by sintering titanium powder particles. At the same time, the magnetic components are oriented and aligned by a magnetic field. Sintering at the first temperature causes the magnetic components to decompose and form a stable support structure, ensuring that the pore channels remain stable during subsequent sintering. The support structure is removed by acid washing, and finally a dual-scale pore structure is formed. The overall tortuosity is reduced to 1.25~1.40, and the pore connectivity is significantly improved. Isolated dead-end pores are avoided, and the problems of existing technologies that make it difficult to achieve oriented through pore structures and the difficulty of synergistic construction of pores with different pore sizes are solved.

[0022] (3) The first layered structure prepared by the present invention uses magnetic field to induce the formation of high-density large-diameter through-holes / semi-through-holes, which reduces mass transfer resistance; the second layered structure forms micropores (5~15μm) by titanium powder sintering, realizing differentiated pore design and differentiated pore control and functional gradient design between the first layered structure and the second layered structure, meeting the needs of different application scenarios. The low tortuosity through-holes of the first layered structure significantly improve the mass transfer efficiency, while the second layered structure improves the catalyst utilization rate, solving the problem of single pore functionality in the prior art.

[0023] (4) The present invention uses magnetic materials (such as MnO2, BaTiO3, etc.) that do not contain Fe, Ni, or Co as magnetic field induction materials, and removes the magnetic materials by acid washing after sintering to ensure material purity; avoids irreversible contamination of the proton exchange membrane, and ensures that the material is suitable for applications with high purity requirements such as PEM electrolysis cells. MnO2 is converted into Mn3O4 during sintering and is completely removed by acid washing. The residual Mn content is less than 5ppm, which has no effect on the PEM membrane and solves the problem of easy contamination of PEM membrane in the prior art.

[0024] (5) The present invention achieves integrated molding of materials through magnetic field induction and sintering process, avoiding interface problems caused by multi-step assembly; through step-by-step sintering (S2 and S3), the stability of materials and the formation of pore structure at different stages are ensured; by removing the support structure through acid washing, the pore structure is further optimized, and the post-processing steps are simplified, achieving integrated molding, reducing the complexity of multi-step assembly, significantly simplifying the preparation process, reducing costs, and improving production efficiency. Attached Figure Description

[0025] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0026] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention.

[0027] Figure Labels 01-Second layered structure; 011-First pore structure; 02-First layered structure; 022-Second pore channel. Detailed Implementation

[0028] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0029] On one hand, this invention discloses a method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction, comprising: S1: Prepare titanium powder slurry containing magnetic components and titanium powder slurry without magnetic components; S2: Based on the coating method, titanium powder slurry containing magnetic components and titanium powder slurry without magnetic components are sequentially coated to prepare a double-layer or multi-layer composite structure; the magnetic components in the first layer structure are oriented using a magnetic field, and the first blank is obtained after the double-layer or multi-layer composite structure is completely cured. S3: Sintering the first blank in the first temperature range causes the magnetic components to decompose or sinter to produce a directional support structure, thereby obtaining a second blank with a directional support structure. S4: The second blank is sintered at a temperature higher than the first temperature range to obtain a third blank that has both a directional support structure and a first pore structure. S5: Pickling removes the oriented support structure in the third preform, obtaining a second oriented interconnected pore channel, and thus obtaining a porous titanium-based material with a dual-scale pore structure.

[0030] Compared with existing technologies, this invention uses a magnetic field to orient magnetic components, followed by sintering at a first temperature range. This causes the magnetic components to decompose and form a stable support structure, ensuring the stability of the pore channels during subsequent sintering. The support structure is then removed by acid washing, ultimately forming oriented, interconnected pore channels with low mass transfer resistance. This achieves highly efficient gas and liquid transport, significantly reducing mass transfer resistance. The overall tortuosity is reduced to 1.2~1.4, and the gas permeability is 8.8×10⁻⁶. - ¹¹m²~1.28×10 - ¹ 0 m²(N2, 0.1MPa pressure difference) solves the problems of low mass transfer efficiency and high mass transfer resistance in existing technologies.

[0031] Compared with existing technologies, this invention naturally forms small to medium pores (10~30μm) through the sintering of titanium powder particles. At the same time, a magnetic field is used to orient the magnetic components. Sintering at a first temperature causes the magnetic components to decompose and form a stable support structure, ensuring that the pore channels remain stable during subsequent sintering. The support structure is removed by acid washing, ultimately forming a dual-scale pore structure. The overall tortuosity is reduced to 1.25~1.40, and the pore connectivity is significantly improved. Isolated dead-end pores are avoided, solving the problems of existing technologies that are difficult to achieve directional through-pore structures and the difficulty of synergistic construction of pores with different pore sizes.

[0032] Compared with existing technologies, this invention achieves integrated molding of materials through magnetic field induction and sintering processes, avoiding interface problems caused by multi-step assembly; through stepwise sintering (S2 and S3), it ensures the stability of materials and the formation of pore structures at different stages; by removing the support structure through acid washing, the pore structure is further optimized, while simplifying the post-processing steps, achieving integrated molding, reducing the complexity of multi-step assembly, significantly simplifying the preparation process, reducing costs, and improving production efficiency.

[0033] Specifically, step S1 involves preparing a titanium powder slurry containing magnetic components, including: S101. Mix the slow-evaporating solvent, binder and dispersant at a speed of 100 rpm to 200 rpm for 10 min to 20 min. S102. Add titanium powder and continue stirring at 100 rpm to 200 rpm for 20 min to 30 min. S103. Add magnetic particles and ball mill at 100 rpm to 300 rpm for 1 to 1.5 hours to ensure uniform dispersion of magnetic particles.

[0034] It should be noted that slow-evaporating solvents (such as NMP) provide sufficient fluidity, ensuring good workability of the slurry during subsequent coating processes. Their slow evaporation also extends the workability of the slurry, preventing premature drying. Binders (such as PVA solutions) enhance the adhesion between titanium powder particles, ensuring structural stability of the slurry during coating and drying, and preventing particle dispersion. Low-speed stirring avoids excessive shearing that could lead to particle breakage, while ensuring uniform distribution of titanium powder in the base solution. Ball milling creates a good interaction between magnetic particles and titanium powder particles, enhancing the overall stability of the slurry and ensuring a uniform structure during coating and sintering. The ball milling process further refines the particles, reduces agglomeration, and improves the uniformity and stability of the slurry.

[0035] Specifically, the mass fractions of titanium powder, magnetic particles, binder, and dispersant are as follows: titanium powder 60%~72%, magnetic particles 12%~25%, binder 1%~4%, dispersant 0.1%~0.5%, and the remainder is made up with slow-evaporating solvents.

[0036] Specifically, the titanium powder has a particle size of 15μm to 50μm.

[0037] Specifically, the magnetic component can be one or more of the following: magnetic particles or oxide-coated materials of MnO2, Mn2O3, Mn3O4, BaTiO3, and SrTiO3.

[0038] During implementation, magnetic particles can decompose to form new oxides (e.g., MnO2→Mn3O4→Mn3O4) or sinter and recrystallize to generate a stable support structure (e.g., Mn3O4). The support structure can remain stable when titanium powder is sintered at higher temperatures, avoiding titanium powder erosion and ensuring the integrity of the subsequent second pore channel structure.

[0039] Compared with existing technologies, this invention uses magnetic materials free of Fe, Ni, and Co (such as MnO2, BaTiO3, etc.) as magnetic field induction materials, and removes the magnetic materials by acid washing after sintering to ensure material purity. It avoids irreversible contamination of the proton exchange membrane and ensures that the material is suitable for applications with high purity requirements, such as PEM electrolysis cells. MnO2 is converted into Mn3O4 during sintering and is completely removed by acid washing. The residual Mn content is less than 5ppm, which has no effect on the PEM membrane. This solves the problem of easy contamination of PEM membranes in existing technologies.

[0040] Specifically, the oxide coating material can be at least one of MnO2, Mn2O3, Mn3O4, BaTiO3, and SrTiO3 as a coating for fibers, and the fibers can be short fibers of PMMA, PAN, PS, PET, PI, or carbon fiber.

[0041] Preferably, the oxide coating material can be MnO2, Mn2O3 or Mn3O4, with less residual metal ions after acid washing, ≤4.2ppm.

[0042] Specifically, the diameter of the fiber coating is 40μm~60μm and the length is 200μm±50μm.

[0043] Specifically, the magnetic particles have a diameter of 300 nm to 500 nm.

[0044] It should be noted that the above mass ratio and the particle size of titanium powder and magnetic particles help maintain good flowability and keep the viscosity of the slurry at 150 cP to 280 cP.

[0045] Specifically, the adhesive may be one or more of polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, polyacrylamide, gelatin, starch, and polyvinylpyrrolidone.

[0046] It should be noted that the above-mentioned adhesive should be able to exist stably during the sintering process and should not react adversely with titanium powder or other components; the adhesive should be able to completely decompose or volatilize during the sintering process and leave no impurities that affect the material properties.

[0047] Specifically, the dispersant can be one or more of sodium polyacrylate, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), carboxymethyl cellulose (CMC), gelatin, polyphosphate (such as sodium hexametaphosphate), polyacrylic acid, and polymaleic acid.

[0048] Specifically, the slow-evaporating solvent can be NMP.

[0049] Preferably, step S102 may involve adding PMMA microspheres as an auxiliary pore-forming agent with a particle size of 20-40 μm, which can create mesopores between the second pore and the first pore.

[0050] Specifically, step S1, which involves preparing a titanium powder slurry without magnetic components, includes: S111: Mix the fast-evaporating solvent, slow-evaporating solvent and adhesive thoroughly; S112: Add ultrafine titanium powder and stir at 400 rpm to 600 rpm for 30 min to 60 min to ensure uniform dispersion of titanium powder.

[0051] Specifically, the ultrafine titanium powder has a particle size of 1μm~5μm, which can be used to prepare dense micropores with high specific surface area.

[0052] Specifically, in step S111, the slow-evaporating solvent and binder are the same as those in the titanium powder slurry containing magnetic components; the fast-evaporating solvent can be ethanol.

[0053] Specifically, step S2 includes: S201: A first layered structure containing magnetic components is formed using a titanium powder slurry containing magnetic components; S202: Apply a magnetic field perpendicular to the direction of the first layered structure; S203: After the slurry containing magnetic components is dried on the surface, a titanium powder slurry without magnetic components is coated on its surface, and after curing, a double-layer composite structure is obtained.

[0054] Specifically, the coating process in step S201 includes: Scraper gap: 250μm~350μm; Coating speed: 0.8m / min~1.5m / min; Coating environment: Temperature 25℃~30℃, humidity 50%~60%.

[0055] Specifically, the magnetic field strength in step S202 is 0.50T~0.80T.

[0056] Preferably, step S202 employs a multi-stage heating and holding process until surface dryness, including: Phase 1: 30℃~40℃, relative humidity 50%~70%, maintain the temperature for 5~6 hours in a windless environment. Second stage: rapidly raise the temperature to 50℃~60℃ and keep it at a wind speed of 0.3m / s~0.4m / s for 6h~12h; Third stage: Maintain the same temperature as the second stage and continue to keep warm for 12h to 24h.

[0057] It should be noted that the lower temperature and appropriate humidity in the first stage help maintain the low viscosity of the slurry, making it easier for the magnetic particles to move and orient themselves under the influence of the magnetic field; the higher temperature and appropriate wind speed in the second stage can accelerate the evaporation of the solvent, allowing the slurry to solidify quickly, thereby locking the oriented structure of the magnetic particles; the longer heat preservation time in the third stage can ensure that the solvent in the slurry evaporates completely, allowing the material to reach a completely surface-dry state.

[0058] Compared with the prior art, the first layered structure of the present invention uses magnetic field induction to form high-density large-diameter through-pores / semi-through-pores, reducing mass transfer resistance; the second layered structure forms micropores (5~15μm) through titanium powder sintering, realizing differentiated pore design and differentiated pore control and functional gradient design between the first and second layered structures, meeting the needs of different application scenarios. The low tortuosity through-pores of the first layered structure significantly improve mass transfer efficiency, while the second layered structure improves catalyst utilization, solving the problem of single pore functionality in the prior art.

[0059] Specifically, the coating process in step S203 includes: Scraper gap: 30μm~60μm (to form a thinner second layer); Coating speed: 0.5m / min~1.2m / min.

[0060] Specifically, the curing process in step S203 includes: S2031: Curing at room temperature in natural environment for 24-30 hours; S2032: Continue drying at 85℃±10℃, vacuum degree≤5Pa, for 3h~5h.

[0061] Specifically, in step S3, the lower limit of the first temperature range needs to be higher than the decomposition temperature of the magnetic components or the temperature at which a stable support structure can be formed; the upper limit of the first temperature range needs to be lower than the sintering start temperature of the titanium powder itself.

[0062] Specifically, the first temperature range is 250℃~650℃.

[0063] Specifically, step S3 requires a high-purity argon atmosphere (99.999%) with a flow rate of 150 L / h to 200 L / h.

[0064] For example, the heating process in step S3 could be: From room temperature to 400°C: slowly increase the temperature at a rate of 1.5°C / min to 3°C / min to ensure the decomposition of organic matter in the adhesive and the coating fibers; 400°C to 550°C: at a rate of 1.5°C / min to 3°C / min, the magnetic components begin to decompose or sinter in this temperature range; 550°C to 600°C: After heating to 600°C at a rate of 2°C / min to 4°C / min, hold for 3 to 4 hours. During this temperature range, the magnetic components are completely decomposed or sintered, and a supporting structure has been formed.

[0065] Specifically, in step S4, the sintering zone needs to ensure that the titanium powder can be fully sintered while ensuring the stability of the support structure.

[0066] Specifically, step S4 requires a high-purity argon atmosphere (99.999%) with a flow rate of 150 L / h to 200 L / h.

[0067] Preferably, the sintering temperature in step S4 can be 650℃~1080℃.

[0068] For example, the temperature control program in step S4 could be: 600°C to 700°C: Heating rate 4°C / min ~ 8°C / min; 700°C to 950°C: Heating rate 4°C / min ~ 8°C / min; 950°C to 1050~1080°C: heating rate 2°C / min~4°C / min, after heating to 1050°C~1080°C, hold for 3~4 hours. During this temperature range, the titanium powder is completely sintered and the support structure remains stable. 1050°C~1080°C to 200°C and below: cooling rate 2°C / min~4°C / min.

[0069] Specifically, step S5 includes: S501, First pickling: Select 10% H2SO4, and pickle at a temperature of 60°C~70°C and an ultrasonic power of 150W~200W for 1h~1.5h. Then, use X-ray diffraction (XRD) or scanning electron microscopy (SEM) to detect the removal of magnetic oxides. S502, Second pickling: Select 12%~15% HCl + 3%~5% H2O2, pickle at 60°C~70°C and ultrasonic power 150W~200W for 1h~1.5h, and then use X-ray diffraction (XRD) or scanning electron microscopy (SEM) to detect the removal of magnetic oxides. S503, Cleaning and Drying: Ultrasonic cleaning with deionized water 2-4 times, each time for more than 20 minutes; neutralize with dilute alkali (e.g., 0.1% NaOH) for more than 5 minutes; rinse with deionized water again 2-4 times and then dry.

[0070] In practice, through steps S501-S503, the oriented support structure in the third preform is removed by acid washing, resulting in oriented and interconnected second pore channels, thereby obtaining a porous titanium-based material with a dual-scale pore structure. This process ensures the purity of the material and the integrity of the pore structure, providing a high-quality material for final applications.

[0071] On the other hand, the present invention also discloses a porous titanium-based material with low mass transfer resistance, which is prepared by the above method and includes: a double-layer or multi-layer composite structure composed of odd-numbered functional layers and even-numbered functional layers stacked alternately. In the composite structure, the odd-numbered functional layers are provided with a second pore channel that is oriented and connected through the thickness direction of the odd-numbered functional layers, and the even-numbered functional layers are provided with a first pore structure with a smaller gap than the second pore channel.

[0072] Preferably, in the porous titanium-based material with low mass transfer resistance, the pore size of the second pore channel ranges from 30 to 60 μm, and the pore size of the first pore structure ranges from 10 to 30 μm.

[0073] The following embodiments and comparative examples are provided to better illustrate the present invention: Example 1 This embodiment discloses a method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction, including: S1: Preparation of titanium powder slurry containing magnetic components and titanium powder slurry without magnetic components, including: S101: Mix the slow-evaporating solvent (NMP), binder (polyvinyl alcohol), and dispersant (sodium polyacrylate) at 150 rpm for 15 minutes.

[0074] S102: Add titanium powder (particle size 30μm) and continue stirring at 150rpm for 25 minutes.

[0075] S103: Add magnetic particles (MnO2, particle size 400nm) and ball mill at 200rpm for 1.2 hours to ensure uniform dispersion of magnetic particles.

[0076] Mass fraction: 66wt% titanium powder, 18.5wt% magnetic particles, 2.5wt% binder, 0.3wt% dispersant, with the remainder made up with slow-evaporating solvents.

[0077] S111: Mix the fast-evaporating solvent (ethanol), the slow-evaporating solvent (NMP), and the binder (polyvinyl alcohol) until homogeneous.

[0078] S112: Add ultrafine titanium powder (particle size 3μm), stir at 500rpm for 45 minutes to ensure uniform dispersion of titanium powder.

[0079] S2: Based on a coating method, titanium powder slurry containing magnetic components and titanium powder slurry without magnetic components are sequentially coated to prepare a double-layer or multi-layer composite structure, including: S201: Forming a first layered structure containing magnetic components using a titanium powder slurry containing magnetic components, including: Scraper gap: 300μm; Coating speed: 1.2 m / min; Coating environment: Temperature 28℃, humidity 55%.

[0080] S202: Apply a magnetic field perpendicular to the surface of the first layered structure.

[0081] Magnetic field strength: 0.65T; Phase 1: 35℃, 60% relative humidity, heat preservation for 5.5 hours in a windless environment; Second stage: rapidly raise the temperature to 55℃ and keep it at that temperature for 9 hours with a wind speed of 0.35m / s; Phase 3: Maintain 55℃ and continue to keep warm for 18 hours.

[0082] S203: After the slurry containing magnetic components is dried on the surface, a titanium powder slurry without magnetic components is coated on its surface, and after curing, a double-layer composite structure is obtained.

[0083] Scraper gap: 45μm; Coating speed: 0.85 m / min.

[0084] S2031: Cured at room temperature in natural environment for 27 hours.

[0085] S2032: Continue drying at 85℃ with a vacuum degree ≤5Pa for 4 hours.

[0086] S3: Sintering the first blank in the first temperature range causes the magnetic components to decompose or sinter to produce a directional support structure, thereby obtaining a second blank with a directional support structure. Under a high-purity argon atmosphere (99.999%), the flow rate is 175 L / h.

[0087] Heating program: From room temperature to 400°C: increase the temperature slowly at a rate of 2°C / min; 400°C to 550°C: Increase temperature at a rate of 2°C / min; 550°C to 600°C: Increase the temperature to 600°C at a rate of 3°C / min, and then hold for 3.5 hours.

[0088] S4: The second green body is sintered at a temperature higher than the first temperature range to obtain a third green body that simultaneously possesses a directional support structure and a first pore structure, including: Under a high-purity argon atmosphere (99.999%), the flow rate is 175 L / h.

[0089] Temperature control program: 600°C to 700°C: heating rate 6°C / min; 700°C to 950°C: heating rate 6°C / min; 950°C to 1065°C: heating rate 3°C / min, after heating to 1065°C, hold for 3.5 hours; 1065°C to 200°C and below: cooling rate 3°C / min.

[0090] S5: Acid pickling removes the oriented support structure in the third preform, obtaining oriented and interconnected second pore channels, thereby obtaining a porous titanium-based material with a dual-scale pore structure, including: S501, First pickling: The removal of magnetic oxides was detected by X-ray diffraction (XRD) or scanning electron microscopy (SEM) after 1.2 hours of pickling with 10% H2SO4 at 65°C and ultrasonic power of 175W.

[0091] S502, Second pickling: The removal of magnetic oxides was detected by X-ray diffraction (XRD) or scanning electron microscopy (SEM) after 1.2 hours of pickling with 13.5% HCl + 4% H2O2 at 65°C and ultrasonic power of 175W.

[0092] S503, Cleaning and Drying: Ultrasonic cleaning with deionized water 3 times, 25 minutes each time; neutralization with dilute alkali (0.1% NaOH) for 6 minutes; rinsing with deionized water 3 times again and then drying.

[0093] This embodiment also discloses a porous titanium-based material with low mass transfer resistance, which is prepared by the above method and includes: a double-layer or multi-layer composite structure composed of odd-numbered functional layers and even-numbered functional layers stacked alternately. In the composite structure, the odd-numbered functional layers are provided with a second pore channel that is oriented and connected through the thickness direction of the odd-numbered functional layers, and the even-numbered functional layers are provided with a first pore structure with a smaller gap than the second pore channel.

[0094] Test results: ICP-MS analysis showed that the residual Mn content in the porous titanium-based material with low mass transfer resistance was 4.2 ppm, which had no effect on the PEM membrane.

[0095] Geometric dimensions: Total thickness: 245±8μm; Second layered structure: 40μm; First layer structure: 205 μm.

[0096] Pore ​​structure (μ-CT and SEM analysis): First layered structure: Large-diameter through-hole (MnO2 chain removal hole): Pore ​​size: 32~56μm; Average pore size: 42 μm; Pore ​​density: 210 pores / mm²; Average spacing: 69μm; Throughness: 97% of the channels vertically penetrate the entire thickness; Torque (through hole itself): 1.06.

[0097] Small to medium pore size (sintered pores in titanium powder): Aperture: 12~28μm; Average pore size: 18 μm; Distribution: Filling the spaces between through holes; Twistability: Approximately 2.0.

[0098] Overall performance of the first layered structure: Total porosity: 81%; Overall tortuosity: 1.33; Calculation: Through holes account for 60% of the hole volume (τ=1.06), and small and medium-sized holes account for 40% (τ=2.0). 1 / τ=0.6 / 1.06+0.4 / 2.0=0.566+0.200=0.766; τ = 1.31 ≈ 1.33 (actual measurement).

[0099] Second layer structure: Pore ​​size: 6~14μm (titanium powder deposited pores); Average pore size: 9 μm; Porosity: 52%; Tortuosity: 1.82.

[0100] Overall tortuosity: (40×1.82+205×1.33) / 245=1.37≈1.38.

[0101] Electrical properties: Contact resistance: 0.32 mΩ·cm²; Total resistance: 45 mΩ·cm².

[0102] Mass transfer performance: Gas permeability: 8.8 × 10⁻⁶ - ¹¹m² (N2, 0.1MPa pressure difference).

[0103] It is 192% better than traditional titanium felt.

[0104] The above test results were all obtained using existing testing standards or methods.

[0105] Example 2 The method in this embodiment has been adjusted compared to Embodiment 1 as follows: First-layer slurry adjustment: Titanium powder (20~50μm): 64wt% (reduced).

[0106] Large particle MnO2 (400nm): 20wt% (increased).

[0107] NMP: 14wt%.

[0108] PVA + dispersant: 2wt%.

[0109] Magnetic field strength increased by 0.75T.

[0110] Induction time: extended to 30 hours.

[0111] Preparation of through hole dimensions: Pore ​​size: 42~62μm.

[0112] Average: 52 μm (10 μm larger than in Example 1).

[0113] Pore ​​density: 240 pores / mm² (higher).

[0114] Optimized performance: Twistability: 1.28 (lower); Gas permeability: 1.05 × 10⁻⁶ - ¹ 0 m².

[0115] Example 3 The method in this embodiment is adjusted from that in Example 1 as follows: MnO2-coated fibers are used instead of magnetic particles. The preparation of MnO2-coated fibers includes: Step 1, Matrix fiber preparation: PAN fiber: 45μm in diameter, continuous in length.

[0116] Plasma treatment (O2, 5 minutes): Introduces -OH and -COOH groups.

[0117] Step 2, MnO2 coating: Immerse in a mixture of MnSO4 solution (0.2M) and KMnO4 (0.1M).

[0118] Temperature: 70°C.

[0119] Time: 5 hours.

[0120] Chemical reaction: 3Mn² + +2MnO4 - +2H₂O→5MnO₂↓+4H + .

[0121] Coating thickness: 8μm.

[0122] Wash with water and dry at 120°C.

[0123] Step 3, Cutting and Sieving: Cut to length: 220μm; Screening: Removing fibers that are too long or too short; Final product: Diameter 61±2μm (45+8×2), length 220μm.

[0124] Through hole dimensions (extremely high precision): Pore ​​size: 59~63μm; Average: 61μm (precisely corresponding to fiber diameter); Standard deviation: 2 μm (extremely low, excellent uniformity).

[0125] Pore ​​density: 200 pores / mm².

[0126] performance: First layer tortuosity: 1.18 (lowest).

[0127] Overall tortuosity: 1.32.

[0128] Gas permeability: 1.28 × 10⁻⁶ - ¹ 0 m² (highest).

[0129] Current density @2V: 5.4A / cm² (maximum).

[0130] Contact resistance: 0.30 mΩ·cm² (minimum).

[0131] Example 4 The method in this embodiment is adjusted from that in Embodiment 1 as follows: a single-layer large-aperture through-hole porous transport layer with only a first layered structure is prepared, therefore step S203, which uses titanium powder slurry without magnetic components to coat and prepare the first layered structure, is omitted. The formulation of the titanium powder slurry containing magnetic components is adjusted as follows: Titanium powder (15~50μm): 68wt% Large particle MnO2 (400nm): 18wt% NMP: 12wt% PVA: 2wt%.

[0132] The results of the first layered structure test show: Through holes: 45μm diameter, 230 holes / mm² density; Small to medium pore size: 12~26μm; Total porosity: 83%; Tortiness: 1.28 (single layer, lowest).

[0133] Example 5 The method in this embodiment was adjusted from that in Example 1 as follows: barium titanate (BaTiO3, thermal decomposition temperature >1300°C) with the same particle size range and dosage was used to replace MnO2; the magnetic field strength in step S202 was adjusted to 0.85T; and the second pickling was performed using 5%HF + 10%HNO3 at 40°C for 180 minutes. The rest was the same as in Example 1.

[0134] The partial test results of the porous titanium-based materials with low mass transfer resistance prepared in Examples 1 and 5 are shown in Table 1 below: Table 1. Partial Detection Results of Examples 1 and 5

[0135] As can be seen from the above, the porous titanium-based material prepared by this invention has the following properties: Large-diameter through-hole (second pore channel): Aperture range: 30~60μm; Pore ​​density: 150~300 pores / mm²; Throughput rate: 92%~97%; Tortuosity: 1.05~1.10.

[0136] Small and medium pores (first pore structure): Aperture range: 10~30μm; Porosity: 30%~50%; Tortuosity: 1.8~2.2; Total porosity: 75%~85%; Overall tortuosity: 1.25~1.40.

[0137] Contact resistance: 0.30 mΩ·cm² ~ 0.35 mΩ·cm²; Overall resistance: 35~50mΩ·cm²; Gas permeability: 8.8 × 10⁻⁶ - ¹¹m²~1.28×10 - ¹ 0 m² (N2, 0.1MPa pressure difference).

[0138] The residual amount of magnetic material is <5ppm.

[0139] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction, characterized in that, include: S1: Prepare titanium powder slurry containing magnetic components and titanium powder slurry without magnetic components; S2: Based on the coating method, titanium powder slurry containing magnetic components and titanium powder slurry without magnetic components are sequentially coated to prepare a double-layer or multi-layer composite structure; the magnetic components in the layered structure containing magnetic components are oriented and arranged by a magnetic field, and the first blank is obtained after the double-layer or multi-layer composite structure is completely cured. S3: Sintering the first blank in the first temperature range causes the magnetic components to decompose or sinter to produce a directional support structure, thereby obtaining a second blank with a directional support structure. S4: The second blank is sintered at a temperature higher than the first temperature range to obtain a third blank that has both a directional support structure and a first pore structure. S5: Pickling removes the oriented support structure in the third preform, obtaining a second oriented interconnected pore channel, and thus obtaining a porous titanium-based material with a dual-scale pore structure.

2. The method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction according to claim 1, characterized in that, In step S1, the magnetic component is one or more of the following: magnetic particles or oxide-coated materials of MnO2, Mn2O3, Mn3O4, BaTiO3, and SrTiO3.

3. The method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction according to claim 2, characterized in that, The oxide coating material is at least one of MnO2, Mn2O3, Mn3O4, BaTiO3, and SrTiO3 used to coat the fibers, and the fibers are short fibers of PMMA, PAN, PS, PET, PI, or carbon fiber.

4. The method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction according to claim 3, characterized in that, The diameter of the fiber coating is 40μm~60μm and the length is 200μm±50μm.

5. The method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction according to claim 2, characterized in that, The magnetic particles have a diameter of 300nm~500nm.

6. The method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction according to claim 1, characterized in that, Step S2 includes: S201: A first layered structure containing magnetic components is formed using a titanium powder slurry containing magnetic components; S202: Apply a magnetic field perpendicular to the surface of the first layered structure; S203: After the slurry containing magnetic components is dried on the surface, a titanium powder slurry without magnetic components is coated on its surface, and after curing, a double-layer composite structure is obtained.

7. The method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction according to claim 6, characterized in that, In step S202, the magnetic field strength is 0.50T~0.80T.

8. The method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction according to claim 1, characterized in that, In step S3, the first temperature range is 250℃~650℃.

9. The method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction according to any one of claims 1-8, characterized in that, The sintering temperature in step S4 is 650℃~1080℃.

10. A porous titanium-based material with low mass transfer resistance, characterized in that, The method for preparing porous titanium-based materials with low mass transfer resistance using magnetic field induction as described in any one of claims 1-9 includes: a bilayer or multilayer composite structure composed of odd-numbered functional layers and even-numbered functional layers stacked alternately; In the composite structure, the odd-numbered functional layers are provided with a second pore channel that is oriented and connected through the thickness direction of the odd-numbered functional layers, and the even-numbered functional layers are provided with a first pore structure with a smaller gap than the second pore channel.

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