Titanium Textile

Abstract

A metal textile and method for its manufacture are provided, the metal textile comprising a titanium textile layer having an interconnected dendritic microstructure and a porosity of 20-95%. The titanium textile layer can be flexible enough to allow the titanium textile layer to be wrapped around itself. The metal textile can be incorporated into a wrapped product and / or used as a porous transport layer in an electrolysis cell.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 434,564, filed December 22, 2022, the entire contents of which are incorporated herein by reference.

[0002] FIELD OF THE DISCLOSURE This disclosure relates to the field of porous metal textiles, and more particularly to porous transport layers (PTLs) and titanium-containing PTLs, methods of making same, and methods of using same. [Background technology]

[0003] Porous metals and metal foams have unique properties and characteristics and have been used in a variety of applications. Thin metal porous layers have been successfully used in batteries, filtration, gas getters, spargers, aerators, electromagnetic shields, catalysts or catalyst supports, electrodes, and transport layers. One application of porous metals is as a metal porous transport layer (PTL), which is useful in electrochemistry to address the growing demand for renewable energy sources. One example of the use of PTLs in electrochemistry is proton exchange membrane water electrolyzers (PEMWEs). In such applications, the PTL conducts electrical charge, allowing the transport of water to the catalyst layer and the removal of gaseous oxygen. While various materials have been used as PTLs, titanium is preferred due to its unique corrosion resistance. Traditional titanium PTLs include meshes, expanded meshes, sintered fibers, and powders. Meshes and expanded meshes are flexible and can be fabricated into large areas. However, they are essentially composed of perforations that run through the layer, resulting in a small surface area. These characteristics affect their properties and limit their use in many applications. The structure and properties of sintered powders and fibers are limited by the particle or fiber packing used to produce the layer. Furthermore, PTLs made by sintering metal powders or fibers are limited by the size of the furnace in which they are produced. Typically, PTLs made from sintered powders have limited flexibility. Summary of the Invention

[0004] Therefore, improvements in the properties of titanium textiles are desirable, especially for use in electrolytic cells, batteries, filtration, catalysts, catalyst supports, and the like. A metal textile is provided that includes a titanium textile layer having an interlocking dendritic microstructure and a porosity of 20-95%.

[0005] In one embodiment, the titanium textile layer is sufficiently flexible to allow the titanium textile layer to be wrapped around itself. In one embodiment, the porosity is 40-95%, 50-90%, or more preferably 55-85%.

[0006] In another embodiment, the textile layer has a thickness of 50 μm to 3 mm, or preferably less than 500 μm. In a further embodiment, the textile layer further comprises a metallic or ceramic coating on its surface.

[0007] In another embodiment, the titanium textile layer comprises 0.05 to 2 wt. % oxygen, preferably 0.05 to 0.4 wt. % oxygen. In a further embodiment, a titanium textile layer is used as the metallic porous transport layer.

[0008] In a further embodiment, the metallic porous transport layer is flexible and can be wrapped as desired. In one embodiment, the metal textile is formed by depositing titanium powder onto a substrate.

[0009] In another embodiment, the porosity is characterized by pores having diameters between 5 and 250 μm. Also provided is a wrapped product comprising a metallic porous transport layer as described herein wrapped around itself.

[0010] A wrapped product is provided comprising a metallic porous transport layer as defined herein wrapped around itself. Additionally, a method for producing a titanium textile is provided, the method comprising consolidating titanium having a dendritic microstructure.

[0011] Additionally, a method for consolidating titanium having a dendritic microstructure using sintering is provided. Additionally, a method is provided in which pressure is used during sintering, which is carried out by heating the material to a temperature between 800°C and 80% of the melting point of titanium to obtain a titanium textile.

[0012] In one embodiment, the consolidation causes the dendritic microstructure to permanently interlock with one another. In one embodiment, sintering includes applying pressure onto the plates.

[0013] In a further embodiment, the applied pressure is to control the final thickness of the titanium textile during the sintering process with or without a spacer. In another embodiment, sintering causes the dendritic microstructures to permanently interlock with one another.

[0014] In a further embodiment, the temperature is between 1000 and 1400°C. In one embodiment, titanium having a dendritic microstructure is rolled prior to sintering (ie, direct powder rolling).

[0015] In a further embodiment, titanium having a dendritic microstructure is mixed with a liquid to facilitate shaping (e.g., by spreading, tape casting, or rolling into a thin layer, etc.) prior to sintering.

[0016] In another embodiment, the methods described herein further comprise adding a binder to the titanium prior to sintering. In a further embodiment, titanium having a dendritic microstructure is mixed with a binder and shaped (eg, extruded) prior to sintering.

[0017] In one embodiment, the method described herein further comprises hot rolling, cold rolling, or warm rolling the textile after sintering to reduce the thickness or to modify the density, structure, or surface finish of the titanium textile.

[0018] In one embodiment, the methods described herein further comprise coating the titanium textile with a metallic or ceramic coating. In one embodiment, the methods described herein further include interweaving or adhering the titanium textile with other pieces of titanium textile to increase its size.

[0019] In another embodiment, the titanium is in the form of wool or deaggregated dendrites produced by molten salt electrorefining. In another embodiment, the titanium is in the form of wool or deaggregated dendrites produced by the Armstrong process or any other method.

[0020] Many additional features and combinations thereof that improve the present invention will be apparent to those skilled in the art upon reading this disclosure. [Brief explanation of the drawings]

[0021] [Figure 1A] FIG. 1A is a scanning electron microscope (SEM) image of a sintered titanium powder according to the prior art. [Figure 1B] FIG. 1B is an SEM image of a titanium textile produced using fibers according to the prior art. [Figure 2A] Figure 2A is an SEM image of the titanium wool precursor at 50x magnification. [Figure 2B] Figure 2B is an SEM image of the deagglomerated titanium wool precursor at 50x magnification. [Figure 2C]Figure 2C is an SEM image of the titanium wool precursor at 200x magnification. [Figure 2D] Figure 2D is an SEM image of the titanium wool precursor at 500x magnification. [Figure 3A] FIG. 3A is a photograph of the device used to characterize the titanium textile. [Figure 3B] FIG. 3B is a schematic diagram showing the relationship between flow rate and pressure in radial flow. [Figure 3C] FIG. 3C is a photograph showing a close-up of the device of FIG. 3A. [Figure 3D] FIG. 3D is a photograph showing a close-up of the donut-shaped protector of the device of FIG. 3A. [Figure 4A] Figure 4A is a photograph of a titanium textile. [Figure 4B] Figure 4B is a photograph of the titanium textile being folded by hand. [Figure 5A] FIG. 5A is a microscope image of the titanium textile at 50× magnification. [Figure 5B] FIG. 5B is a microscope image of the titanium textile at 100x magnification. [Figure 5C] FIG. 5C is a microscope image of the titanium textile at 200x magnification. [Figure 5D] FIG. 5D is a microscope image of the titanium textile at 300x magnification. [Figure 6A] FIG. 6A is an SEM image of the titanium textile at 50x magnification. [Figure 6B] FIG. 6B is an SEM image of the titanium textile at 200x magnification. [Figure 7] Figure 7 is a graph comparing the thickness under compression of titanium textile, commercially available porous Ti powder sheet A, and commercially available porous Ti fiber sheet B. [Figure 8] FIG. 8 is a graph showing the resistance under compression of titanium textile, commercially available porous Ti powder sheet A, and commercially available porous Ti fiber sheet B. [Figure 9]FIG. 9 is a graph showing the resistivity under compression of titanium textile, commercially available porous Ti powder sheet A, and commercially available porous Ti fiber sheet B. [Figure 10] FIG. 10 is a graph showing the in-plane permeability under compression of titanium textile, commercially available porous Ti powder sheet A, and commercially available porous Ti fiber sheet B. [Figure 11] Figure 11 shows two photographs of an in-house designed electrolytic cell with an active area of ​​5 cm2 used for the in-situ characterization of the developed porous transport layer. [Figure 12] FIG. 12 is a graph showing the polarization curve of a PEMWE assembly. [Figure 13] FIG. 13 is a graph showing the polarization curve of a PEMWE assembly with ohmic loss compensation. [Figure 14A] FIG. 14A is a photograph of an example of two titanium textiles bonded together by cold rolling. [Figure 14B] FIG. 14B is a photograph of an example of two titanium textiles wrapped on a mandrel. [Figure 15A] Figure 15A is a 2D image of a cross section of a laminated felt, extracted from a 3D X-ray microtomography reconstructed volume, consisting of a denser surface with small pores (approximately 100 μm thick) and a more porous core with larger pores (approximately 200 μm). [Figure 15B] FIG. 15B is a magnified cross-sectional SEM image of the upper portion, showing a more detailed view of the denser surface above the more porous core. [Figure 16A] FIG. 16A is an SEM image showing a cross section of particulate-covered felt. [Figure 16B] FIG. 16B is an SEM image showing the top surface covered with fine powder, which has much less porosity and smaller pores compared to the opposite surface (FIG. 16C). [Figure 16C] FIG. 16C is an SEM image showing the opposite side, which is more porous than the particulate-covered side. DETAILED DESCRIPTION OF THE INVENTION

[0022] A metal textile is provided that comprises a layer having an interconnected dendritic microstructure and a porosity of 20-95%, and therefore may be referred to as a porous metal textile.

[0023] Porous metal textiles are used in a variety of applications and are key components of electrolyzers, fuel cells, batteries, electrodes, gas getters, spargers, aerators, electromagnetic shields, catalysts and catalyst supports, as well as filtration media.

[0024] In one specific example, the porous metal textile is a porous transport layer (PTL), which is disposed between a bipolar plate (BP) and a catalyst-coated membrane (CCM). The PTL is one of the main components of a PEMWE and plays an important role in cell performance. In some embodiments, the PTL is disposed between the membrane electrode assembly (MEA) and the separator / bipolar plate (BP) on both electrode sides. The PTL may also be referred to as a gas diffusion layer (GDL), liquid / gas diffusion layer (LGDL), or current collector (CC). The PTL facilitates the transport of liquid and gas between the flow channels and the electrodes, electrical conduction, and heat conduction within the cell. The multiple functions that the PTL performs in the GDL on the anode or cathode of a PEMWE can be summarized as follows: transport of reactant water; removal of evolved gases (hydrogen and oxygen); promotion of good electrical conductivity between the BP and the catalyst layer; removal of heat from the reaction; and provision of mechanical support for the CCM, especially under compression. Additionally, the PTL must be corrosion-resistant and stable enough to withstand the acidic environment of the solid electrolyte and to withstand high overpotentials during operation. To facilitate fabrication and achieve optimal PTL performance within the PEMWE, it is important to balance PTL properties with respect to thickness, porosity, pore size, surface roughness, mechanical stability, flexibility, electrical and thermal conductivity, and surface passivation. This can be achieved with the titanium textiles described herein.

[0025] The disclosed metal PTL comprises a titanium textile layer having an interconnected dendritic microstructure. The PTL has a variable porosity between 20 and 95%. The porosity can be optimized depending on the specific application of the PTL. The titanium textile layer is flexible, and its flexibility is such that it can be rolled up on itself. This is advantageous because, when rolled up, it can facilitate the manufacturing, transportation, and storage of the titanium textile. This flexibility is achieved, in part, as a result of the interconnected dendritic microstructure achieved by solid-state sintering, as described in more detail herein below. The structure and properties of titanium textiles are unique (combination of porosity, pore size, flexibility, and high surface area) and are advantageous for the development of various devices (i.e., electrolytic cells, electrodes, catalysts, catalyst supports, filtration media, etc.).

[0026] As used herein, the term textile is intended to include, but is not limited to, for example, felt, mesh, foam, and wool or fibrous materials.

[0027] As will become apparent from this disclosure, the titanium textiles described herein offer many advantages. First, the unique structure (i.e., dendritic microstructure) of electrolytically refined products, combined with the manufacturing process, allows for the production of materials with unique structures, densities, and properties that are very different from existing products obtained by sintering powders, or fibers, meshes, or expanded meshes. Traditional fabrication of porous layers using fibers and powders does not offer high flexibility in controlling density and texture (i.e., texture and structure are largely dependent on stacking particles or fibers into the porous layer). Materials produced from powders are denser (porosity typically less than 50%), less permeable, not flexible, and cannot be manufactured as wound products (necessary for large-scale roll-to-roll manufacturing processes). Materials produced from sintered powders are difficult to produce in very thin layers and are usually very expensive, thus limiting their use in many applications. Materials produced from fibers or chips typically have low surface areas.

[0028] In contrast, the titanium textiles of the present disclosure are produced using titanium materials with dendritic microstructures in wool or deaggregated form. In some embodiments, titanium textiles are included in the form of wool or deaggregated dendrites produced by molten salt electrorefining, the Armstrong process (reduction of titanium tetrachloride with metallic sodium), or any other known method. The dendritic microstructure of powder produced from titanium wool connects to each other after solid-state sintering to produce titanium textiles. The dendritic microstructure can be described as having irregular, branched projections. The dendrites or branched structures physically connect to each other, improving interparticle bonding and thereby improving the mechanical properties of the textile.

[0029] Porosities between 20 and 95% can be achieved in the PTL of the present disclosure. Porosity can have a direct impact on charge and mass transport within the PTL. Porosities between 50 and 95% are typically preferred. It is recognized that high porosity facilitates gas removal but increases ohmic resistance. Pore gradients can play a role in achieving an optimal compromise between the efficiency of the PTL in PEMWE (i.e., reactant and gas diffusion and contact resistance).

[0030] The pore size of titanium textiles (typically 10-500 μm) can be modified by adjusting the precursor structure, particle size, and felt manufacturing process. High porosity reduces the number of contact points at the PTL-catalyst layer (CL) interface, increasing contact resistance. Large pore sizes (typically greater than 150 μm) can increase ohmic losses due to insufficient contact between the PTL and CL. Generally, larger pores promote water and gas transport at the expense of electrical and thermal conductivity, while smaller pores do the opposite. Furthermore, large pore sizes can compromise the mechanical integrity and stability of titanium textiles. Therefore, pore sizes should not exceed 500 μm.

[0031] The thickness of the titanium textile is an important parameter when considering its use in a PTL. The thickness and quality of the interface between the PTL and the catalyst layer (CL) affect the performance of the PTL and PEMWE. Therefore, smaller thicknesses are usually preferred, typically less than 500 μm, less than 450 μm, less than 400 μm, less than 375 μm, less than 350 μm, less than 300 μm, less than 250 μm, or less than 200 μm. Thicker products for other applications can be obtained by stacking or assembling layers of titanium textile.

[0032] The significant flexibility of titanium textiles is an advantage of the textile material of the present invention. Generally, flexibility refers to the amount that a textile can bend without breaking, as well as its ability to return to its original shape after bending. Flexibility is influenced not only by the intrinsic properties of the material, but also by its shape; i.e., the thinner the textile, the more flexible it is.

[0033] The titanium textiles of the present disclosure are characterized by a high surface area, which varies depending on the precursor shape (i.e., dendritic), its thickness, and processing conditions. The increased surface contact between the PTL and CL reduces the contact resistance, which depends on the density of the PTL surface, the surface roughness of the PTL, and the applied pressure.

[0034] Titanium usually inevitably contains a small amount of oxygen in the form of a solid solution or surface oxide. As a result, titanium textile layers usually contain a small amount of oxygen. In one example, there may be 0.05 to 2 wt. % of oxygen, preferably 0.05 to 1 wt. % of oxygen, or 0.1 to 0.4 wt. % of oxygen. Solid solution oxygen reduces the ductility of titanium and may also affect the flexibility of the felt. Surface oxidation may affect the surface conductivity.

[0035] The flexible and permeable titanium textiles provided herein are produced at low cost compared to other commercially available materials. The precursor material is electrolytically refined titanium, such as titanium wool, which has a network of dendritic filaments. The dendritic structure is important because it provides a precursor with a very low apparent density. The low apparent density of the textile allows for tailoring of the textile's density. The dendritic structure aids in interconnection and flexibility compared to sintered powders. As encompassed herein, prior to sintering, compaction methods such as loose powder distribution, direct powder rolling, or compaction may be used. After sintering, the interconnections become permanent. The density of the textile can be tailored by controlling the amount of precursor, the pressure (before, during, and after sintering), and the temperature of the sintering process. This allows for the production of materials with controlled porosity and porosity levels. Because the density of the precursor is much lower than the powders typically used to produce sintered powders, much lower densities can be achieved, providing greater flexibility in controlling the density of the textile. The flexibility limitations found with sintered powders are overcome with flexible titanium textiles. Because of their flexibility, these products can be wound and used in roll-to-roll processes. Furthermore, the size and stiffness of PTLs pose significant constraints when manufacturing PEMWEs. This size limitation of conventional materials is also overcome herein because multiple sheets of titanium textile can be bonded together to increase the total surface area. Thus, the size of the titanium textile is not limited by the size of the plate.

[0036] Electrorefined titanium is consolidated by sintering at high temperatures (at least 800°C), optionally under pressure, to produce a thin, porous layer (i.e., textile). Consolidation occurs below the melting point of titanium. In some embodiments, the temperature is 1000°C to 1400°C. The titanium wool may be spread and uniformly distributed on a substrate and sintered under a plate that provides pressure to even out and control the thickness of the thin, flat textile. In some embodiments, sintering occurs in a non-oxidizing atmosphere, such as under vacuum or in an inert gas such as Ar or He. Another method that can improve the uniformity of the textile begins with deagglomerating the wool, followed by distributing and sintering as described above. This deagglomeration can be achieved by various shearing methods, such as milling, carding, or blade cutting in various gas or liquid media. Following this deagglomeration process, the powder can be further sieved, filtered, or separated, if desired, to obtain a given particle size distribution that is favorable for PTL performance (i.e., removal of ultrafine or oversized particles). The amount of wool or titanium powder dispensed onto the substrate, the temperature, and the pressure (weight of the plates on the precursor during sintering), as well as the thickness of the spacers between the plates, determine the thickness of the titanium textile.

[0037] The wool or titanium powder can be spread into a thin layer using a liquid, a binder, or a combination thereof. Shaping can occur when the binder is molten. The material may also be compacted using pressure before sintering, for example, using direct powder rolling. In some embodiments, a slurry of titanium particles in a liquid suspension is formed and subsequently deposited on a substrate surface to form a textile. In other embodiments, cold spraying can be used as well, using dry particles.

[0038] Coatings can be used to prevent adhesion of the textile to the plates during sintering or to minimize contamination of the textile during processing. The density and properties of the resulting textile can be adjusted by varying the structure of the electrorefined precursor, the amount of material, the pressure (i.e., the weight of the plates), the thickness of the spacer between the plates, the sintering temperature, and the time.

[0039] By assembling the materials (e.g., by gluing or welding multiple textile sheets together), rolls of textiles can be produced. Precursors and methods allow for the production of textiles with porosities ranging from 20 to 95%, allowing for tailored textile and PTL properties. These attributes are important for the mass production of porous transport layers, but also for the production of many other devices, including electrodes, catalyst supports, filtration media, and more.

[0040] The density and properties of the resulting textile can be adjusted by varying the structure of the electrorefined precursor, the method of depositing the material on the plates, the amount of electrorefined precursor, the method of compacting the material, the pressure (i.e., the weight of the plates), the spacing between the plates, the sintering temperature, and the time. The density, structure, properties, thickness, and surface finish can be modified by cold-, warm-, or hot-rolling the textile to the desired thickness. The structure and properties of PTL can be adjusted by stacking layers to produce laminates with different structures or properties (e.g., denser layers on the outer surface and more porous layers in the core). Sintered textiles can also be coated to modify their structure (e.g., applying powder to the surface of the textile and sintering). The surface of titanium can be treated or coated to modify the surface composition, surface properties, and its corrosion resistance.

[0041] Ti-based PTL materials preferably have a coating (typically a noble metal such as Pt, Ir, Au, or Ta, which acts as a protective layer, prevents the formation of an oxide layer, and minimizes interfacial contact resistance). Titanium coated with platinum, tantalum, or iridium is possible. Alternatively, due to the cost of noble metals, surface treatment may instead be performed by etching the Ti with an acid such as HCl. During acid etching, a Ti hydride underlayer, which has very high thermal and chemical strength, can form and acts as a protective layer against passivation. The formation of Ti hydride occurs when the hydrogen content in the metal exceeds its solubility limit. Other possible surface treatments to improve conductivity have also been used, such as the incorporation of a microporous layer, gas nitriding, and antimony-doped TiO coating.

[0042] The PTLs described herein have many applications, including hydrogen production, which represents a large market. With rising global energy consumption and increasing interest in developing sustainable energy production methods, hydrogen production and consumption are expected to grow significantly over the next few years. Commercially viable green hydrogen production using PEMWE technology requires cost reduction of PTLs. Water electrolysis is currently the most environmentally friendly method for producing high-purity hydrogen, and this production method is expected to expand. Porous transport layers (PTLs) are essential components in the production of PEMWEs and represent a significant portion of the cost of these devices (typically 15–25%; Doan et al., International Journal of Energy Research, 2021, 45, 14207). Reducing the cost of PTLs should help reduce the cost of electrolyzers, making this manufacturing method more attractive. Access to rolled PTLs, as achieved herein, would enable the development of roll-to-roll manufacturing processes (currently batch processes) and help reduce the cost of electrolyzers. Better PTLs would also help improve device efficiency and lifetime, making this manufacturing method more attractive. Currently, water electrolysis accounts for only 4% of global hydrogen production, but the market share of PEMWE is expected to expand, especially as electrolyzers become cheaper, more efficient, and more reliable (Yu et al., Applied Catalysis B: Environmental, 2018, 239, 133).

[0043] The PTLs used in the production of PEMWEs were initially developed for other applications (e.g., filtration) and are not fully adapted to the production of electrolyzers. The cost of these materials is currently more than two orders of magnitude higher than the cost of high-density titanium. Optimization of novel PTLs adapted to the specific needs of PEMWEs could reduce the cost of PEMWEs, which could contribute to the expansion of this alternative method of producing and transporting clean energy. Here, this is realized with titanium textiles.

[0044] In addition to PTLs used in PEMWEs, the materials produced herein are valuable for many other applications (e.g., filtration, catalyst supports, medical applications) due to their unique structure. The size and stiffness of titanium PTLs are characteristics that determine their limitations in various applications. However, titanium textiles overcome these traditional limitations. For example, as explained above, access to rolled titanium felt allows for the continuous manufacturing of devices such as cells. [Example]

[0045] Example 1 For comparison purposes, scanning electron microscope images are provided showing the microstructures of a commercially available sintered titanium powder (FIG. 1A) and a commercially available titanium fiber (FIG. 1B). These two materials have traditionally been used as PTLs. Neither of these materials possesses the dendritic microstructure of the titanium textiles realized herein. Additionally, the properties of the resulting titanium textiles also differ from those of the materials shown in FIGS. 1A-1B.

[0046] In this example, all scanning electron microscopy images were performed using scanning electron microscopy (SEM) and secondary electron imaging (SEI) mode to assess the morphology of the powders and textiles at various magnifications.

[0047] Titanium textiles encompassed herein were produced using titanium wool produced by electrorefining in molten salt. Scanning electron microscope images of the titanium wool precursor were taken and are shown in Figures 2A-2D. As can be seen in Figures 2A-2D, the titanium wool has a dendritic microstructure characterized by non-uniform tree-like grain protrusions visible at all magnifications shown.

[0048] Titanium textiles were produced by solid-state sintering of titanium wool. The titanium wool was consolidated under pressure at a temperature of 1000°C to produce a thin porous layer (i.e., titanium textile). Pressure was applied by placing the titanium wool under a plate, which provided pressure to level and control the thickness of the thin, flat sheet. The applied pressure and resulting density of the material could be adjusted by varying the weight on the plate.

[0049] A three-in-one device was used to simultaneously measure thickness under compression (TUC), resistivity under compression (RUC), and in-plane permeability (IPP) (Figure 3A). This was achieved by measuring the flow-pressure relationship in radial flow using an annular gas diffusion layer (GDL) sample (Figure 3B). The device provided air compression with varying loads up to 10 MPa. A two-piece transverse permeability (TPP) adapter was designed for TPP measurements. The lower plate used a donut-shaped protector, and the upper plate used a disk-shaped protector (Figure 3C-D). The GDL of the sample was 24 mm in diameter, and the effective TPP area was 12 mm in diameter.

[0050] A photograph of the resulting titanium textile is shown in Figure 4A. The resulting flexibility allowed the titanium textile to bend without fracture, as shown in Figure 4B. The microstructure was observed by optical microscope imaging (Figures 5A-5D) and scanning electron microscope imaging (Figures 6A-6B). As can be seen from the microscope imaging, the dendritic microstructures are interconnected to form the titanium textile. None of the prior art microstructures (Figures 1A-1B) resemble the titanium textile obtained in the present invention, as they all lack the interconnected dendritic microstructure of the titanium textile.

[0051] The properties of titanium textiles obtained as provided herein were compared using two materials (commercially available porous Ti sheet A made from Ti powder and commercially available porous Ti sheet B made from Ti fibers) (Table 1). The average thickness of the titanium textiles produced using the method described herein was 344 μm, with a standard deviation of 9 μm. The average porosity was 75%, with a standard deviation of 2%.

[0052] [Table 1]

[0053] Using the three-in-one device, the TUC of the titanium textile was measured under compression up to 4 MPa. The TUC of the titanium textile was also compared to the TUC of commercial porous Ti sheet A and commercial porous Ti sheet B under the same compression conditions (Figure 7). Similar resistance to thickness loss under compression was observed for the Ti textile and commercial porous Ti sheets A and B. Using the three-in-one device, the resistance and resistivity were also measured as a function of compression (Figures 8 and 9). The titanium textile achieved similar decreases in resistance and resistivity when compared to commercial porous Ti sheet A and commercial porous Ti sheet B. The in-plane permeability was also measured (Figure 10). The titanium textile achieved very similar permeability under compression to commercial porous Ti sheet A but different from commercial porous Ti sheet B.

[0054] Example 2 To further characterize the developed titanium textile and compare it with commercially available PTLs, this material was tested as a porous transport layer (PTL) in a proton exchange membrane water electrolyzer (PEMWE). To do this, Ti Sheet A and the titanium textile described herein were incorporated into a self-designed PEM water electrolyzer cell with an active area of ​​5 cm² (Figure 11). The test station was operated at a maximum power of 150 W, a maximum current of 36 A, and a voltage of 5 V, with operating temperatures ranging from ambient to 90 °C, and an air bladder compression of 50-100 psi. On the anode side, uncoated PTL material was inserted into a fixture equipped with a cathode gas diffusion layer (GDL) made of commercially available Toray carbon paper TGP-H-120 with 5% PTFE. A catalyst-coated membrane (CCM) was inserted between the anode PTL and the cathode GDL. The CCM contained 2.0 mg IrOx / cm on the anode side. 2 The catalyst was applied to the cathode side at 1.0 mg Pt / cm 2 It was made from Nafion 117 incorporating a catalyst (as Pt / C).

[0055] The cell stack detailed above was first tested using commercially available Ti Sheet A to generate polarization curves under various current densities, twice in the as-conditioned state (repeated) and again with a new sheet of the same material (repeated) to assess measurement variability. The Ti textile described herein was then measured under similar conditions, and Ti Sheet A was retested. Figure 12 confirms that the Ti textile performs similarly to Ti Sheet A, as the measurements are within the variability achieved with the Ti Sheet A material. When the cell voltage is corrected for ohmic losses in the assembly, similar behavior can be observed, although the CCM may have been adversely affected by the multiple assembly / disassembly cycles performed in this test, resulting in a noticeable increase in the cell's charge transfer resistance (Figure 13).

[0056] Example 3 A roll-to-roll process may be interesting for the industrialization, automation, and mass production of some products. In such applications, it is interesting to have long pieces of felt that can be wound onto a mandrel. If the size of the felt is limited by the size of the equipment and the process used (e.g., sintering), it may be interesting to bond different felt pieces together to produce a longer piece of material and then wind the resulting product onto a mandrel. Various techniques for bonding may be considered, such as welding, brazing, adhesive bonding, and cold forming. This example shows the bonding of felt pieces using cold rolling.

[0057] Felt strips were produced using a process similar to that described in Example 1. Felt strips (300 μm thick) were glued together by rolling consecutive felt ends together (i.e., the end of one felt over the start of the next felt) with an overlap (3 cm overlap). The felt was rolled to a thickness of 300 μm. By thinning the overlap (2 × 300 μm = 600 μm) to 300 μm, the two layers of felt intertwined and the two felts were glued together. The resulting felt strip was longer ( FIG. 14A ), more flexible, and could be handled and wound on a mandrel ( FIG. 14B ).

[0058] Example 4 In some applications, varying porosity across the cross-section of the felt can be advantageous. Different methods could be used to achieve different porosity levels in the core and surface of the felt. In this example, two methods are presented for producing felts with gradient porosity. The first method involved stacking felts of different porosities. A precursor was fabricated using titanium metal particles of similar commercial purity, ranging in size from 63 to 212 μm, pre-sintered into a 1 mm-thick felt. One of the felts was cold-rolled to 200 μm. Next, two 200 μm-thick sheets of felt were sandwiched between the as-sintered felt (i.e., unrolled). The resulting stack was rolled to 400 μm. Cold rolling allowed the different layers of felt to bond together, resulting in a sandwich structure with high density and small pore size on the top and bottom surfaces of the felt (Figure 15B).

[0059] The second method involves coating the felt with a suspension of fine titanium particles (less than 20 μm) followed by sintering at 1000°C under vacuum for 1 hour. Felts were produced using the method described in Example 1. A precursor (made from commercially pure titanium metal particles with a particle size of 63-212 μm) was pre-sintered into a 1 mm thick felt and then cold-rolled to 450 μm. One side was coated with a suspension of titanium particles less than 20 μm. The felt was dried and heat-treated under vacuum at 1000°C for 1 hour. The resulting felt had finer porosity on one side than the core of the felt. Figure 16A shows a cross-section of the felt. The top side (Figure 16B) is covered with fine powder and has very low porosity compared to the other side (Figure 16C). Using this technique, the core and surface porosity can be tailored to optimize the felt properties (e.g., optimizing surface contact and reducing contact resistance while maintaining high core permeability).

[0060] While the present disclosure has been described in relation to specific embodiments thereof, it will be understood that the disclosure is capable of further modifications, and this application is intended to cover any such changes, uses, or adaptations including departures from the present disclosure as come within known or customary practice in the art and as may be applied to the essential features described hereinabove and as set forth in the following appended claims.

Claims

1. a titanium textile layer having an interconnected dendritic microstructure; and 20-95% porosity, Including, metallic textiles.

2. 10. The metal textile of claim 1, wherein the titanium textile layer is sufficiently flexible to allow the titanium textile layer to be wrapped around itself.

3. 3. The metal textile layer according to claim 1 or 2, wherein the porosity is 40 to 95%, 50 to 90%, or 55 to 85%.

4. 4. The metal textile according to claim 1, wherein the textile layer has a thickness of from 50 μm to 3 mm, or less than 500 μm.

5. A metal textile layer according to any one of claims 1 to 4, further comprising a metal or ceramic coating on the surface.

6. 6. The metal textile layer according to any one of claims 1 to 5, comprising 0.05 to 2 wt. % oxygen, or 0.05 to 0.4 wt. % oxygen.

7. The metal textile according to any one of claims 1 to 6, used as a metal porous transport layer.

8. 8. The metal textile of claim 7, wherein the metallic porous transport layer is flexible and can be wrapped as desired.

9. A metal textile according to any one of claims 1 to 8, formed by deposition of titanium powder on a substrate.

10. 10. A metal textile according to any one of the preceding claims, wherein the porosity is characterized by pores with a diameter of 5 to 250 μm.

11. 10. A wound product comprising the metallic porous transport layer of claim 7 wrapped around itself.

12. A method for producing a titanium textile comprising consolidating titanium having a dendritic microstructure to obtain a titanium textile.

13. The consolidation providing titanium having a dendritic microstructure on a plate; and sintering the titanium by heating it to a temperature of from 800°C to 80% of the melting point of titanium to obtain the titanium textile; 13. The method of claim 12, comprising:

14. The method of claim 13 , wherein the sintering comprises applying pressure on the plates.

15. 15. The method of claim 14, wherein the applied pressure is to control the final thickness of the titanium textile during the sintering process with or without a spacer.

16. 16. The method of any one of claims 12 to 15, wherein the sintering causes the dendritic microstructures to permanently interconnect with each other.

17. The method according to any one of claims 12 to 16, wherein the temperature is from 1000 to 1400°C.

18. The method of any one of claims 12 to 17, further comprising rolling the titanium prior to sintering.

19. 20. The method of claim 18, wherein the titanium is rolled using powder rolling.

20. A method according to any one of claims 12 to 19, wherein the titanium is provided mixed with a liquid to facilitate shaping prior to sintering.

21. The method of any one of claims 12 to 20, further comprising adding a binder to the titanium prior to sintering.

22. 22. The method of any one of claims 12-21, further comprising hot rolling, cold rolling, or warm rolling the textile after sintering to reduce the thickness and modify the density, structure, or surface finish of the titanium textile.

23. 23. The method of any one of claims 12 to 22, further comprising coating the titanium textile with a metallic or ceramic coating.

24. 24. The method of any one of claims 12 to 23, further comprising interweaving or adhering the titanium textile with other pieces of titanium textile to increase its size.

25. A method according to any one of claims 12 to 24, wherein the titanium is in the form of wool or deaggregated dendrites produced by molten salt electrorefining.

26. A method according to any one of claims 12 to 24, wherein the titanium is in the form of wool or deaggregated dendrites produced by the Armstrong process or any other method.

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