A method for preparing a low-roughness microporous material, the microporous material and its applications

Abstract

This invention relates to a method for preparing a low-roughness microporous material, the microporous material itself, and its applications. The method includes: dissolving a binder in a single alcohol solvent to form a glue-water solution; mixing powder with the glue-water solution and vacuum degassing to form a cast slurry; casting, coating, and drying to obtain a cast green; rolling the cast green before sintering to rearrange and compact the powder particles before sintering; debinding and sintering to form a microporous material with interconnected micropores; and finally, post-sintering rolling to flatten surface protrusions to obtain a low-roughness microporous material. This invention utilizes cast forming to improve the uniformity of fine-particle-size powder forming, and through a two-stage rolling process before and after sintering, it synergistically reduces surface roughness while preserving the pore structure. This allows for the acquisition of a microporous material with small pore size, low roughness, and good permeability with minimal sacrifice of porosity, suitable for high-precision industrial filters and porous diffusion layers in PEM electrolytic water anodes.

Description

Technical Field

[0001] This invention relates to the field of porous material preparation technology, specifically to a method for preparing low-roughness microporous materials, the low-roughness microporous materials obtained by this method, and their applications. It is particularly suitable for applications with high requirements for pore structure, surface roughness, permeability, and interfacial contact performance, such as industrial high-precision filtration, key materials for hydrogen energy, and porous diffusion layers of PEM electrolytic water anodes. Background Technology

[0002] Microporous materials, due to their interconnected pore structure, adjustable pore size, certain porosity, and good permeability, are widely used in industrial filtration, electronic information, new energy, and precision manufacturing. With the development of high-end manufacturing and the hydrogen energy industry, traditional microporous materials are no longer merely required to provide gas-liquid flow channels; they are further demanded to possess smaller pore sizes, higher pore uniformity, lower surface roughness, good mechanical strength, and stable interfacial contact performance. Especially in applications such as the porous diffusion layer of the PEM water electrolysis anode, microporous materials need to provide channels for water, gas, and electron transport while also forming good contact with the anode catalyst layer. If the material surface roughness is high, it can easily lead to uneven interfacial contact, increased local contact impedance, and unstable mass transfer paths, thus affecting the stable operation and energy efficiency of the electrolyzer.

[0003] Titanium-based metals, with their advantages of being lightweight and high-strength, corrosion-resistant, having good electrical conductivity, and exhibiting good stability in strong acid and high-potential environments, have become important candidate materials in the fields of high-performance filtration and key materials for hydrogen energy. For example, in PEM water electrolysis systems, porous titanium plates, titanium felts, and other titanium-based microporous materials are often used as porous diffusion layers on the anode side. However, existing titanium-based microporous materials still face the challenge of simultaneously optimizing pore size, porosity, and surface roughness. Generally, reducing pore size and surface roughness often requires stronger compaction, rolling, or post-processing, but such treatments can easily lead to decreased porosity, pore collapse, or damage to the sintering neck. If the degree of compaction is reduced to maintain high porosity, it is difficult to fully eliminate surface protrusions, burrs, and particle edges, making it difficult to reduce surface roughness. Therefore, how to obtain low-roughness microporous materials without excessively sacrificing porosity and pore structure is a technical problem that urgently needs to be solved in this field.

[0004] Existing methods for preparing porous titanium materials or microporous metallic materials mainly include powder rolling, loose-pack sintering, tape casting, and chemical etching. Among these, powder rolling typically uses rolling as the primary forming method, which can obtain porous plates with controllable thickness to a certain extent, but it has high requirements for powder flowability and particle size. For powders with small particle sizes, especially those with D50 < 40 μm, the powder flowability is poor, making powder rolling difficult. On the other hand, to adapt to powder rolling, larger particle sizes are often required, which limits the space for further reduction of the final material's pore size and surface refinement. Although powder rolling can obtain initial plates with relatively low roughness, it essentially solves the forming problem rather than addressing the synergistic control of surface roughness, pore size, and porosity in microporous materials.

[0005] Loose-pack sintering relies primarily on the natural accumulation of powder in a mold and subsequent sintering to form porous materials. This process is relatively straightforward and can achieve high porosity under certain conditions. However, because loose-pack sintering depends on the natural accumulation of powder, the arrangement of powder particles, surface smoothness, and thickness uniformity are difficult to control precisely. Furthermore, the poor flowability of fine-particle-size powders is also evident in loose-pack sintering, making it unsuitable for preparing thin, small-pore-size, and low-surface-roughness microporous materials. For high-precision filtration or PEM water electrolysis anode porous diffusion layers, materials obtained through simple loose-pack sintering often suffer from high surface roughness, insufficient pore structure consistency, or subsequent pressing processes that easily sacrifice porosity.

[0006] Casting, as a process for preparing thin materials, offers advantages such as easy thickness control, good molding uniformity, and strong adaptability to fine-particle-size powders. By dispersing powder in a slurry, casting can overcome the difficulties in direct molding caused by the poor flowability of fine powders to some extent, and is suitable for preparing relatively thin microporous preforms. However, traditional casting processes typically require the use of multiple organic solvents, plasticizers, dispersants, pore-forming agents, and other organic materials. Some of these organic materials are toxic and hazardous, adversely affecting equipment, the environment, and production personnel. Furthermore, if high levels of organic matter in the slurry are difficult to completely remove, it can lead to problems such as deformation, cracking, pore structure defects, or unstable sintering quality in subsequent processing. Therefore, there is still room for improvement in the environmental friendliness, process simplification, and synergistic control of pore structure and surface quality of microporous materials in traditional casting processes.

[0007] Furthermore, existing technologies also involve slight rolling or pressing of sintered porous materials, primarily for adjusting thickness, improving flatness, or shaping the finished product. However, if rolling is only performed after sintering, excessive rolling deformation can easily damage the sintering necks, collapse the pores, and significantly reduce porosity, since sintering necks have already formed between powder particles. If the rolling degree is too small, surface protrusions, burrs, and particle edges are difficult to eliminate sufficiently, resulting in limited improvement in roughness. In other words, simply rolling after sintering makes it difficult to achieve an ideal balance between low roughness and preservation of pore structure.

[0008] It is evident that existing powder rolling, loose-pack sintering, and traditional tape casting processes each have their limitations: powder rolling is limited by the ability to form fine-particle-size powders, loose-pack sintering is difficult to achieve both low roughness and thinness, traditional tape casting processes suffer from complex organic systems and insufficient control over subsequent pore structures, while single sintering followed by rolling is prone to sacrificing porosity and the integrity of the sintering neck in exchange for surface smoothness. Summary of the Invention

[0009] To address the challenge of achieving a balance between low surface roughness, small pore size, appropriate porosity, and environmental friendliness in existing microporous material preparation processes, this invention provides a method for preparing low-roughness microporous materials, the microporous materials obtained by this method, and their applications. This invention leverages the adaptability of tape casting to fine-particle-size powders and thin preforms, and combines pre-sintering and post-sintering rolling to synergistically control particle arrangement, sintering neck protection, and surface finishing. This significantly reduces the surface roughness of the microporous material without excessively sacrificing porosity and pore size structure, making the resulting microporous material suitable for applications requiring high-precision industrial filters, porous diffusion layers in PEM water electrolysis anodes, and other scenarios demanding high pore structure, permeability, and interfacial contact performance.

[0010] According to a first aspect of the present invention, a method for preparing a low-roughness microporous material is provided, comprising the following steps: The adhesive is dissolved in a single alcohol solvent to form an adhesive solution; The powder is mixed with the adhesive solution and then subjected to vacuum degassing to form a stable and uniform casting slurry. The casting slurry is cast, coated, and dried to obtain a cast green body; The cast green billet is rolled before sintering, so that the powder particles in the cast green billet are rearranged and compacted before sintering. The rolled green sheet before sintering is degreased and sintered to form sintering necks between powder particles and to form a microporous material with interconnected micropore structure. The microporous material is sintered and then rolled to flatten the protrusions on the surface of the microporous material, thereby obtaining a low-roughness microporous material.

[0011] In some technical solutions, the binder is one or more of methylcellulose, polyvinyl alcohol, and polyvinyl butyral, preferably polyvinyl butyral; the single alcohol solvent is ethanol and / or isopropanol, preferably ethanol; and the preparation method does not add pore-forming agents and / or plasticizers.

[0012] In some technical solutions, the mass ratio of the adhesive to the single alcohol solvent is 1-15:85-99, preferably 10:90; the mass ratio of the powder to the adhesive solution is 1-3:1, preferably 2:1.

[0013] In some technical solutions, the powder is one or more of metal powder, ceramic powder, and metal oxide powder; the metal powder includes one or more of titanium powder, nickel powder, and stainless steel powder, preferably dehydrogenated titanium powder; The particle size of the powder is 0–100 μm, preferably 10–20 μm or 60–80 μm.

[0014] In some technical solutions, during the casting coating process, the gap between the doctor blade and the base tape is 0.8–0.9 mm, and the base tape travel speed is 1–2 m / min; The drying process involves drying at room temperature for 1 to 3 hours, after which the cast green body is peeled off from the substrate.

[0015] In some technical solutions, during the pre-sintering rolling, the gap between the two rolls of the rolling mill is 0.28–0.32 mm, preferably 0.30–0.32 mm, and the rolling speed is 0.5–2 m / min, preferably 1 m / min; and / or, In the post-sintering rolling process, the gap between the two rolls of the rolling mill is 0.24–0.26 mm, preferably 0.25–0.26 mm, and the rolling speed is 0.5–2 m / min, preferably 1 m / min.

[0016] In some technical solutions, the degreasing sintering is carried out in a vacuum sintering furnace with an internal gas pressure of 1×10⁻⁶. -2 Below Pa; The degreasing sintering includes a first stage, a second stage, and a third stage. In the first stage, the temperature is increased to 250–350°C at a heating rate and held for 30–90 min. In the second stage, the temperature is increased to 450–550°C at a heating rate and held for 30–60 min. In the third stage, the temperature is increased to 800–2000°C at a heating rate and held for 60–180 min. The heating rate is preferably 5°C / min, and the temperature of the third stage is preferably 800–1100°C.

[0017] In some technical solutions, the thickness of the low-roughness microporous material is 0.2–0.4 mm, the surface roughness is ≤3 μm, the average pore diameter is 5–15 μm, and the porosity is 35%–55%. Preferably, the thickness of the low-roughness microporous material is 0.24–0.26 mm, the surface roughness is 0.5–1.5 μm, the average pore diameter is 6–10 μm, and the porosity is 40%–50%.

[0018] According to a second aspect of the present invention, a low-roughness microporous material is further provided, the low-roughness microporous material being prepared by the above-described preparation method, the low-roughness microporous material having a connected microporous structure formed by sintering powder particles, and the low-roughness microporous material having a surface roughness ≤3μm, an average pore diameter of 5~15μm, a porosity of 35%~55%, and a thickness of 0.2~0.4mm.

[0019] According to a third aspect of the invention, the application of the above-described low-roughness microporous material in industrial high-precision filters or porous diffusion layers of PEM water electrolysis anodes is further provided.

[0020] The present invention, by employing the above technical solution, has at least the following beneficial effects: 1. This invention employs tape casting as the initial forming method for microporous materials, allowing the powder to be dispersed in a slurry system before forming the green body. Compared to powder rolling and loose-pack sintering, this method is less dependent on powder flowability and can broaden the range of powder particle size selection, especially beneficial for the uniform forming of fine-particle-size powders. Because fine-particle-size powders can participate more stably in tape casting, the resulting green body has advantages in thickness uniformity, powder dispersion uniformity, and thinness, providing a forming basis for subsequently obtaining microporous materials with small average pore size, low surface roughness, and stable interconnected pore structures.

[0021] 2. This invention sets the rolling process in two stages: before and after sintering, with each rolling stage playing a different regulatory role. Pre-sintering rolling is applied to the cast green billet before the formation of the sintering neck. At this stage, the powder particles are not yet firmly bonded. Rolling promotes the rearrangement and moderate compaction of the powder particles, reducing the gaps between them and reducing particle edges and surface protrusions, thereby improving the surface condition after sintering. Because partial compaction and leveling are completed before sintering, the deformation required for subsequent post-sintering rolling is correspondingly reduced, minimizing the damage to the sintering neck and connecting hole structure caused by simple post-sintering rolling.

[0022] 3. This invention further involves rolling after sintering to refine the surface of the microporous material with the formed sintered neck. This process flattens burrs, protrusions, and localized unevenness on the material surface, resulting in a lower surface roughness for the microporous material. Compared to rolling only after sintering, this invention improves powder arrangement and the foundation for surface protrusions through pre-sintering rolling. Therefore, post-sintering rolling does not require a significant sacrifice in porosity or severe pore collapse to achieve surface smoothness. Consequently, it can better preserve the interconnected micropore structure, average pore size, and porosity of the microporous material while reducing roughness.

[0023] 4. This invention achieves a synergistic balance between low roughness, small pore size, and appropriate porosity through the continuous coordination of casting, pre-sintering rolling, debinding sintering, and post-sintering rolling. Traditional microporous materials typically require increased compaction or post-treatment intensity to reduce roughness and pore size, but this can easily lead to decreased porosity, pore collapse, or damage to the sintering neck. This invention, however, controls the arrangement of green powder and the surface morphology after sintering at different stages, resulting in a microporous material that maintains a connected pore structure and permeability while possessing low surface roughness, thereby improving filtration accuracy, pore structure uniformity, and material surface smoothness.

[0024] 5. This invention uses a single alcohol solvent and binder to prepare the adhesive solution, eliminating the need for pore-forming agents and plasticizers. This reduces the use of multiple toxic organic solvents, plasticizers, and high-content organic additives in traditional casting processes. This method not only helps reduce raw material costs and environmental burden, and improves the impact of the production process on equipment, the environment, and operators, but also helps reduce the adverse effects of organic residues on the drying, degreasing, and sintering processes of the green body, reducing deformation, cracking, and pore structure defects, and improving the simplification and stability of the preparation process.

[0025] 6. This invention utilizes a staged debinding and sintering process to gradually remove organic components from the cast green body. During the high-temperature stage, it promotes the formation of strong sintering necks between powder particles, ultimately resulting in a monolithic material with an interconnected microporous structure. The staged heating and holding processes help reduce cracking, deformation, or uneven pore structure caused by rapid volatilization of organic matter. Furthermore, it allows for the selection of appropriate sintering temperatures based on different powder materials and particle sizes. This makes the invention applicable not only to titanium-based microporous materials but also to microporous materials prepared from other metal powders, ceramic powders, or metal oxide powders.

[0026] 7. The low-roughness microporous material obtained by this invention is particularly suitable for the porous diffusion layer of the anode in PEM water electrolysis. Due to its low surface roughness, a more uniform and sufficient interfacial contact can be formed between the material and the anode catalyst layer, thereby reducing the problems of poor local contact and increased interfacial impedance. At the same time, the material retains an interconnected microporous structure and appropriate porosity, which can meet the functional requirements of water transport, gas discharge, and electron conduction. Therefore, this invention can improve the interfacial contact state between the porous diffusion layer and the catalyst layer in the PEM water electrolysis system, reduce the mass transfer overpotential affected by interfacial contact, and improve the operating efficiency and stability of the electrolyzer. Attached Figure Description

[0027] Figure 1 This is a microscopic morphology image of the microporous material obtained in Example 1 of the present invention; Figure 2 This is a macroscopic morphology image of the microporous material obtained in Example 1 of the present invention; Figure 3 This is a microscopic morphology image of the microporous material obtained in Example 2 of the present invention; Figure 4 This is a macroscopic morphology image of the microporous material obtained in Example 2 of the present invention; Figure 5 The microstructure of the microporous material obtained by sintering without rolling in the rolling control experiment of this invention is shown in the image. Figure 6 This is a microscopic morphology image of the microporous material obtained from the rolling experiment before sintering in the rolling control experiment of this invention; Figure 7 The microstructure of the microporous material obtained by rolling only after sintering in the rolling control experiment of this invention is shown in the microstructure diagram of the microporous material obtained by rolling only after sintering. Figure 8 This is a mass transfer polarization curve obtained in an application example of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are only used to illustrate the technical concept and implementation process of the present invention, and are not intended to limit the scope of protection of the present invention. Without departing from the core concept of the present invention, those skilled in the art can make adaptive adjustments to the raw material type, proportion, casting parameters, rolling parameters and sintering temperature according to the powder type, powder particle size, target thickness, target pore size, target porosity and target application scenario.

[0029] The method for preparing low-roughness microporous materials provided by this invention mainly includes steps such as preparing a glue solution, preparing a casting slurry, casting molding, pre-sintering rolling, debinding and sintering, and post-sintering rolling. This method differs from powder rolling processes, which use rolling as the main forming method, and also from loose-pack sintering processes that rely on the natural accumulation of powder. This invention uses casting molding as the initial forming method, allowing the powder to be uniformly dispersed in the slurry system first, and then forming a casting green body with uniform thickness through casting, thereby improving the adaptability to fine-particle-size powders; subsequently, rolling is used as a means to control the roughness and pore structure of the microporous material, and is performed before and after sintering. Pre-sintering rolling is used to rearrange and compact powder particles that have not yet formed sintering necks, reducing the gaps between powder particles and reducing particle edges and surface protrusions; post-sintering rolling is used to refine the surface of the material that has already formed a microporous structure, flattening burrs and protrusions on the material surface, thereby reducing the surface roughness of the material while preserving the microporous structure and porosity as much as possible.

[0030] In practice, the binder is first added to a single alcohol solvent and stirred thoroughly to dissolve or uniformly disperse the binder in the solvent, forming a stable adhesive solution. The binder can be one or more of methylcellulose, polyvinyl alcohol, and polyvinyl butyral, preferably polyvinyl butyral; the single alcohol solvent can be ethanol, isopropanol, or other alcohol solvents, preferably ethanol or anhydrous ethanol. The mass ratio of binder to single alcohol solvent can be 1–15:85–99, preferably 10:90. Compared to the multi-component organic solvents such as toluene, methanol, acetone, and chloroform commonly used in traditional casting processes, as well as plasticizers such as dibutyl phthalate, dioctyl phthalate, and glycerin, this invention preferably uses a single alcohol solvent with a small amount of binder to form an adhesive solution, eliminating the need for additional pore-forming agents and plasticizers. This reduces the use of toxic or environmentally unfriendly organic substances, lowers material costs and environmental burden, and reduces the risk of deformation, cracking, or pore structure defects in the green body due to the difficulty in completely removing high levels of organic matter.

[0031] Subsequently, the powder is added to the adhesive solution and stirred to ensure thorough mixing and the formation of a uniform slurry. The powder can be metal powder, ceramic powder, or metal oxide powder; alternatively, nickel powder, stainless steel powder, titanium powder, or other powders suitable for sintering to form microporous structures can be selected depending on the specific application. In the application of the porous diffusion layer of the PEM water electrolysis anode, dehydrogenated titanium powder is preferred. The mass ratio of powder to the adhesive solution is 1–3:1, preferably 2:1. The particle size of the powder can be 0–100 μm, preferably 10–20 μm or 60–80 μm dehydrogenated titanium powder. Because this invention uses a slurry casting method for initial forming, the powder does not require the good natural flowability of powder rolling or loose-pack sintering. Even with relatively fine powder, a uniform slurry casting green body can be formed through dispersion, thus providing a basis for preparing thin microporous materials with small pore size and low roughness.

[0032] In practice, after the powder and adhesive solution are mixed to form a slurry, the slurry is transferred to a vacuum degassing and mixing equipment for vacuum degassing and mixing to remove air bubbles and improve the uniformity of the slurry, forming a bubble-free, stable, and uniform cast slurry. Vacuum degassing treatment helps reduce pore defects, air bubble defects, and local thickness unevenness in the cast green body, thereby improving the stability of the green body during subsequent debinding, sintering, and rolling processes. The vacuum-degassed cast slurry is then cast and coated using a casting machine. The gap between the doctor blade and the substrate is controlled according to the required thickness, preferably 0.8–0.9 mm, and the substrate travel speed is controlled at 1–2 m / min, thus forming a cast green body with uniform thickness on the substrate. Subsequently, the substrate carrying the cast green body is dried at room temperature for 1–3 hours to form a cast green body with certain strength and peelability. The dried cast green body is then peeled off from the substrate.

[0033] The key to this invention is that, after the cast green body is peeled off, it is not directly sent to the sintering furnace for sintering, but is first rolled before sintering. Pre-sintering rolling is applied to the cast green body before a sintering neck has formed; at this stage, the powder particles are not yet firmly bonded together, and the particles still have a certain degree of rearrangement. Through pre-sintering rolling, the powder particles in the green body can be rearranged and moderately compacted before sintering, reducing the gaps between powder particles, reducing particle sharpness and surface protrusions, and further homogenizing the thickness of the cast green body. Preferably, in pre-sintering rolling, the gap between the two rolls of the mill can be set to 0.28–0.32 mm, preferably 0.30–0.32 mm, and the rolling speed can be 0.5–2 m / min, preferably 1 m / min. Through this pre-sintering rolling step, the surface state of the microporous material obtained by subsequent sintering is pre-optimized, thereby reducing the reduction required for post-sintering rolling and minimizing damage to the sintering neck and interconnected microporous structures caused by post-sintering rolling.

[0034] The rolled green sheet, after pre-sintering, is fed into a vacuum sintering furnace for debinding and sintering. Preferably, the debinding and sintering is performed by evacuating the furnace pressure to 1×10⁻⁶. -2 The process is carried out under vacuum conditions below Pa. Debinding and sintering can be divided into three stages. The first and second stages are mainly used to gradually remove organic binders from the cast green body, while the third stage is used for sintering and bonding between powder particles and shaping the microporous structure. Specifically, the first stage can be heated to 250–350°C at a certain heating rate and held for 30–90 min, preferably to about 300°C and held for about 60 min; the second stage can be heated to 450–550°C at a certain heating rate and held for 30–60 min, preferably to about 500°C and held for about 30 min; the third stage, depending on the type and particle size of the powder material, can be heated to 800–2000°C at a certain heating rate and held for 60–180 min, preferably within the range of 800–1100°C and held for about 120 min. The preferred heating rate is 5°C / min. Through staged degreasing and sintering, organic matter can be removed relatively smoothly, reducing the risk of cracking, deformation or uneven pore structure caused by rapid volatilization of organic matter; during the high-temperature sintering stage, a strong sintering neck is formed between powder particles, thereby forming an integral microporous material with a certain strength and a connected microporous structure.

[0035] After sintering, the microporous material is slowly cooled to room temperature and then fed into a rolling mill for post-sintering rolling. The purpose of post-sintering rolling differs from pre-sintering rolling; its main function is to refine the surface of the microporous material, which has already formed sintered necks and interconnected micropore structures, flattening burrs, protrusions, and localized unevenness, thereby further reducing the surface roughness of the material. Preferably, during post-sintering rolling, the gap between the two rolls of the rolling mill can be set to 0.24–0.26 mm, more preferably 0.25–0.26 mm, and the rolling speed can be 0.5–2 m / min, more preferably 1 m / min. Since the present invention has already completed powder reorganization and preliminary compaction through rolling before sintering, post-sintering rolling does not require excessive reduction to achieve surface finishing. Therefore, it can avoid or reduce sintered neck damage, pore collapse, and excessive porosity reduction caused by simple post-sintering rolling.

[0036] The low-roughness microporous material obtained by this invention has a thickness of 0.2–0.4 mm, a surface roughness ≤3 μm, an average pore size of 5–15 μm, and a porosity of 35%–55%. In a preferred embodiment, the obtained low-roughness microporous material has a thickness of 0.24–0.26 mm, a surface roughness of 0.5–1.5 μm, an average pore size of 6–10 μm, and a porosity of 40%–50%. These performance ranges indicate that this invention does not simply reduce roughness through strong compaction, but rather achieves a comprehensive balance between low surface roughness, small average pore size, and good pore structure uniformity while maintaining a connected microporous structure and appropriate porosity.

[0037] Example 1 The specific method for preparing low-roughness porous titanium plates is as follows: 10 g of polyvinyl butyral and 90 g of ethanol are mixed and stirred evenly to form a stable adhesive; 200 g of dehydrogenated titanium powder with a particle size of 10-20 μm is added to the adhesive and stirred until a uniform slurry is formed; the slurry is transferred to a vacuum degassing and stirring device for vacuum degassing and stirring to form a bubble-free stable casting slurry; the casting slurry is cast and coated through a casting machine, with the gap between the doctor blade and the substrate controlled at 0.8-0.9 mm and the substrate travel speed controlled at 1-2 m / min, to obtain a casting blank with uniform thickness; the substrate carrying the casting blank is placed in a room temperature environment and dried for 1-3 h; the dried blank is peeled off from the substrate and sent to a rolling mill for pre-sintering rolling, with the gap between the two rolls of the rolling mill set at 0.3-0.32 mm and the rolling speed at 1 m / min, to obtain a blank with uniform thickness after one rolling.

[0038] Subsequently, the pre-rolled billets are fed into a vacuum sintering furnace for degreasing and sintering. The furnace pressure is then reduced to 1×10⁻⁶. -2 Below Pa, a three-stage heating sintering process was then performed: the first stage involved heating at 5℃ / min to 280–320℃ and holding for 1 hour; the second stage involved heating at 5℃ / min to 500℃ and holding for 0.5 hours; and the third stage involved heating at 5℃ / min to 900℃ and holding for 2 hours. This process allowed for the formation of strong sintering necks between the titanium powder particles in the film, and after slow cooling to room temperature, a uniform microporous material was obtained. The sintered microporous material was then fed into a rolling mill for post-sintering rolling. The gap between the two rolls of the rolling mill was set to 0.25–0.26 mm, and the rolling speed was 1 m / min. After one rolling pass, a low-roughness microporous material with uniform thickness and a smooth surface was obtained. The micropore morphology under an electron microscope is shown in the image below. Figure 1-2 The results of some physical property characterizations are shown in Table 1.

[0039]

[0040] Example 2 The specific method for preparing low-roughness porous titanium plates is as follows: 10 g of polyvinyl butyral and 90 g of anhydrous ethanol are mixed and stirred evenly to form a stable adhesive; 200 g of dehydrogenated titanium powder with a particle size of 60-80 μm is added to the adhesive and stirred until a uniform slurry is formed; the slurry is transferred to a vacuum degassing and stirring device for vacuum degassing and stirring to form a bubble-free stable casting slurry; the casting slurry is cast and coated through a casting machine, with the gap between the doctor blade and the substrate controlled at 0.8-0.9 mm and the substrate travel speed controlled at 1-2 m / min, to obtain a casting blank with uniform thickness; the substrate carrying the casting blank is placed in a room temperature environment and dried for 1-3 hours; the dried blank is peeled off from the substrate and sent to a rolling mill for pre-sintering rolling, with the gap between the two rolls of the rolling mill set at 0.3-0.32 mm and the rolling speed at 1 m / min, to obtain a blank with uniform thickness after one rolling.

[0041] Subsequently, the pre-rolled billets are fed into a vacuum sintering furnace for degreasing and sintering. The furnace pressure is then reduced to 1×10⁻⁶. -2 Below Pa, a three-stage heating sintering process was then performed: the first stage involved heating at 5℃ / min to 280–320℃ and holding for 1 hour; the second stage involved heating at 5℃ / min to 500℃ and holding for 0.5 hours; and the third stage involved heating at 5℃ / min to 1050℃ and holding for 2 hours. This process allowed for the formation of strong sintering necks between the titanium powder particles in the film, followed by slow cooling to room temperature to obtain a uniform microporous material. The sintered microporous material was then fed into a rolling mill for post-sintering rolling. The gap between the two rolls of the rolling mill was set to 0.25–0.26 mm, and the rolling speed was 1 m / min. After one rolling pass, a low-roughness microporous material with uniform thickness and a smooth surface was obtained. The micropore morphology under an electron microscope is shown in the image below. Figure 3-4 The results of some physical property characterizations are shown in Table 2.

[0042]

[0043] As can be seen from the two embodiments above, when using 10-20 μm dehydrogenated titanium powder with a finer particle size, the resulting microporous material has a lower average pore size and surface roughness, making it suitable for scenarios with higher requirements for filtration accuracy and interfacial contact. When using 60-80 μm dehydrogenated titanium powder, the resulting microporous material still maintains a low surface roughness and high porosity, indicating that the present invention is not limited to powders of a single particle size, but can select powders of different particle sizes according to the target pore size, porosity, and application requirements. Since different powder materials and different particle sizes correspond to different sintering temperatures, the sintering temperature in the third stage can be adjusted within a wide range according to the powder material and particle size to ensure the formation of stable sintering necks between powder particles and the construction of interconnected microporous structures.

[0044] To illustrate the synergistic effect of the two-stage rolling process of this invention, the following comparative experiments were conducted. See Table 3 for details.

[0045]

[0046] The above results show that pre-sintering rolling alone leaves no obvious traces of damage to the sintering neck and improves surface smoothness compared to no rolling, indirectly increasing surface roughness while preserving the original porosity to a greater extent. Post-sintering rolling alone leaves obvious traces of damage to the sintering neck, and the surface is rolled to a smooth finish, indicating that the improved roughness is achieved at the expense of the porosity and strength of the porous material. The combination of pre- and post-sintering rolling processes... Figure 1 and Figure 5-7 The SEM images clearly show that the porosity of the porous material is well preserved without severely damaging the sintering neck. This is an effective way to control surface roughness without excessively sacrificing the porosity of the porous material.

[0047] Under the condition of the same initial green blank thickness of 0.35 mm, the effects of different rolling distributions on the porosity and surface roughness of the finished product can be compared by adjusting the rolling gap before sintering and the rolling gap after sintering. See Table 4 for details.

[0048]

[0049] Therefore, pre-sintering rolling is not a routine step that can be ignored, but an important control step used to reduce the rolling load after sintering and protect the sintering neck and pore structure.

[0050] The low-roughness microporous materials obtained in Examples 1 and 2 of this invention are further compared with similar products on the market, as detailed in Table 5.

[0051]

[0052] This demonstrates that the microporous material obtained by the present invention has significant improvements in both surface roughness and average pore size, while still maintaining a porosity range suitable for PEM water electrolysis applications.

[0053] In PEM water electrolysis applications, the low-roughness porous titanium plate obtained by this invention can be used as an anode porous diffusion layer. Due to its low surface roughness, it can improve the interfacial contact state between itself and the anode catalyst layer, increase the effective contact area, and reduce the local impedance increase caused by poor interfacial contact. Simultaneously, its internal interconnected microporous structure and appropriate porosity are beneficial for water transport, gas expulsion, and electron conduction. When the low-roughness porous titanium plate and conventional commercial titanium felt are tested for water electrolysis under the same operating conditions, such as… Figure 8The low-roughness porous titanium plate exhibits superior interfacial contact performance and significantly reduces the mass transfer overpotential affected by interfacial contact, with a reduction of nearly 50%. Therefore, the low-roughness microporous material obtained in this invention can improve the mass transfer and interfacial contact performance of PEM electrolyzers, which is beneficial to improving the operating efficiency and stability of the electrolyzers.

[0054] This invention utilizes a coordinated process of tape casting, pre-sintering rolling, debinding sintering, and post-sintering rolling. Tape casting ensures uniform blank formation and adaptability to fine-particle sizes; pre-sintering rolling facilitates powder repositioning and reduces particle spacing; debinding sintering forms sintering necks and interconnected microporous structures; and post-sintering rolling refines the surface and reduces roughness. This process route achieves a balance of low roughness, small average pore size, appropriate porosity, and good application adaptability using environmentally friendly and simplified raw material systems. It is suitable for the preparation of titanium-based microporous materials and other metal, ceramic, or metal oxide microporous materials.

[0055] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a low-roughness microporous material, characterized in that, Includes the following steps: The adhesive is dissolved in a single alcohol solvent to form an adhesive solution; The powder is mixed with the adhesive solution and then subjected to vacuum degassing to form a stable and uniform casting slurry. The casting slurry is cast, coated, and dried to obtain a cast green body; The cast green billet is rolled before sintering, so that the powder particles in the cast green billet are rearranged and compacted before sintering. The rolled green sheet before sintering is degreased and sintered to form sintering necks between powder particles and to form a microporous material with interconnected micropore structure. The microporous material is sintered and then rolled to flatten the protrusions on the surface of the microporous material, thereby obtaining a low-roughness microporous material.

2. The preparation method according to claim 1, characterized in that, The binder is one or more of methylcellulose, polyvinyl alcohol, and polyvinyl butyral, preferably polyvinyl butyral; the single alcohol solvent is ethanol and / or isopropanol, preferably ethanol; the preparation method does not add pore-forming agents and / or plasticizers.

3. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of the binder to the single alcohol solvent is 1-15:85-99, preferably 10:90; the mass ratio of the powder to the adhesive solution is 1-3:1, preferably 2:

1.

4. The preparation method according to claim 1, characterized in that, The powder is one or more of metal powder, ceramic powder, and metal oxide powder; the metal powder includes one or more of titanium powder, nickel powder, and stainless steel powder, preferably dehydrogenated titanium powder; The particle size of the powder is 0–100 μm, preferably 10–20 μm or 60–80 μm.

5. The preparation method according to claim 1, characterized in that, In the casting coating process, the gap between the doctor blade and the base tape is 0.8–0.9 mm, and the base tape travel speed is 1–2 m / min; The drying process involves drying at room temperature for 1 to 3 hours, after which the cast green body is peeled off from the substrate.

6. The preparation method according to claim 1, characterized in that, In the pre-sintering rolling process, the gap between the two rolls of the rolling mill is 0.28–0.32 mm, preferably 0.30–0.32 mm, and the rolling speed is 0.5–2 m / min, preferably 1 m / min; and / or, In the post-sintering rolling process, the gap between the two rolls of the rolling mill is 0.24–0.26 mm, preferably 0.25–0.26 mm, and the rolling speed is 0.5–2 m / min, preferably 1 m / min.

7. The preparation method according to claim 1, characterized in that, The debinding sintering is performed in a vacuum sintering furnace at an internal gas pressure of 1 x 10 -2 Pa or less; The degreasing sintering includes a first stage, a second stage, and a third stage. In the first stage, the temperature is increased to 250–350°C at a heating rate and held for 30–90 min. In the second stage, the temperature is increased to 450–550°C at a heating rate and held for 30–60 min. In the third stage, the temperature is increased to 800–2000°C at a heating rate and held for 60–180 min. The heating rate is preferably 5°C / min, and the temperature of the third stage is preferably 800–1100°C.

8. The preparation method according to claim 7, characterized in that, The low-roughness microporous material has a thickness of 0.2–0.4 mm, a surface roughness of ≤3 μm, an average pore size of 5–15 μm, and a porosity of 35%–55%. Preferably, the low-roughness microporous material has a thickness of 0.24–0.26 mm, a surface roughness of 0.5–1.5 μm, an average pore size of 6–10 μm, and a porosity of 40%–50%.

9. A low-roughness microporous material, characterized in that, The low-roughness microporous material is prepared by the preparation method according to any one of claims 1-8. The low-roughness microporous material has a connected microporous structure formed by sintering and connecting powder particles, and the surface roughness of the low-roughness microporous material is ≤3μm, the average pore diameter is 5-15μm, the porosity is 35%-55%, and the thickness is 0.2-0.4mm.

10. The application of the low-roughness microporous material according to claim 9 in the porous diffusion layer of industrial high-precision filters or PEM water electrolysis anodes.

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