Metallic interior fiber composite and method for producing a metallic fiber composite

Abstract

This invention relates to metal-inner-fiber composite materials comprising biopolymer-based fibers having fiber walls and void spaces, and metal microstructures that make the metal-inner-fiber composite material electrically conductive, wherein the fiber walls enclose the void spaces such that the void spaces form continuous void spaces within and along the fibers. The invention also relates to methods for producing metal-fiber composite materials, particularly metal-inner-fiber composite materials.

Description

[0001] This invention relates to the field of fiber-based functional composite materials and methods for producing the same. More specifically, this invention relates to metal-interior-fiber composite materials, wherein the fibers are based on biopolymers and include metal microstructures within the fibers. The invention also relates to methods for producing metal-fiber composite materials, wherein such methods can be used to produce metal-interior-fiber composite materials.

[0002] Many biopolymers, especially cellulose, are abundant, renewable, biodegradable, and natural polymers. Cellulose is obtained after the delignification of wood and exhibits biocompatibility and environmental compatibility. These characteristics make cellulose a particularly valuable material, especially considering concerns about environmental pollution from toxic, non-biodegradable materials and the commitment to sustainability.

[0003] In the following examples, examples 1 through 6 outline different areas, each including the specific problem it addresses. For all examples, fiber-based functional composites, which are based on biopolymers, can help solve each specific problem.

[0004] As a first example, using cellulose as a substrate in flexible electronic devices offers significant potential for reducing environmental impact, replacing plastic materials. Driven by a strong focus on wearable electronics and implantable medical devices, a significant increase in demand for flexible sensors, actuators, batteries, displays, and more is expected in the coming years. Since the typical lifespan of these devices will be shorter than that of their rigid counterparts, alternatives to non-degradable fossil fuel-based or difficult-to-recycle polymers such as polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PAN), and polyimide will be necessary to reduce the burden of electronic waste on our environment. Cellulose is an ideal alternative material for producing substrates for flexible electronic devices. In addition to its environmental friendliness, cellulose is also promising due to its low cost and lightweight nature. In fact, it has already attracted considerable attention from other areas of electronics.

[0005] As a second example: In fact, millions of people worldwide carry implantable medical devices that rely on onboard electronic equipment, including neurostimulators, cochlear implants, bowel and bladder control stimulation implants, cerebrospinal fluid shunt systems, visual prostheses, implantable drug infusion pumps, and of course, pacemakers and cardioverter defibrillators. All of these devices can be affected by electromagnetic radiation (EMR) emitted from any type of external electronic equipment, and malfunctioning devices can cause discomfort or even death. Electromagnetic interference (EMI) shielding and filtering are crucial to protecting implantable medical devices, and therefore, the host patient.

[0006] As a third example, electromagnetic hypersensitivity (EMH) is a controversial topic. People who claim to have EMH report sleep disturbances, fatigue, headaches, difficulty with memory and attention, dizziness, musculoskeletal pain, skin conditions, and mood disorders.

[0007] As a fourth example: Data security is of paramount importance today. Mobile phones, laptops, credit cards, and keyless entry systems for cars or data cables are all vulnerable to data theft.

[0008] As a fifth example: heated clothing products on the market include heating wires connected to batteries.

[0009] These products are typically quite rigid and bulky, and the embedded heating wires only heat the part of the clothing.

[0010] As a sixth example: thin electronic cables, such as those included in headphone cables, are prone to breakage under heavy use.

[0011] What is needed to solve the above problems is conductive fabric, especially fiber-based fabric, where the fiber is based on biopolymer.

[0012] Furthermore, a simple, rapid, and scalable method is needed for producing this conductive fabric.

[0013] Despite the many benefits of biopolymers such as cellulose or cellulose-based fibers, they lack a functional property that is crucial for addressing the aforementioned issues related to flexible electronics, electromagnetic shielding, resistance heating, etc. (i.e., conductivity).

[0014] Known methods for preparing conductive biopolymers (such as cellulose) involve combining them with conductive materials such as conductive polymers, carbon nanotubes, graphene oxide, conductive oxides, inorganic nanoparticles, or metals. To achieve high conductivity, metals, particularly copper, are the materials of choice as they are low-cost and highly conductive. Copper is biocompatible and antimicrobial; furthermore, it is attractive in terms of sustainability due to its abundance.

[0015] Besides copper, other metals may also be of interest depending on the specific application, such as gold, silver, palladium, platinum, and lead.

[0016] Various techniques have been proposed for making biopolymer-based fibers conductive, such as through surface modification methods like atomic layer deposition, electrodeposition, magnetron sputtering, and electroless plating. For example, WO2016126212 discloses a method for plating metal onto textile fibers. Another example related to particulate coatings on fibrous materials is disclosed in WO2009129410. US20060068667 discloses metallized fibers and a method for producing them.

[0017] Of these techniques, atomic layer deposition is better suited for surface functionalization or for the generation of nucleation layers, while electrodeposition has always required a conductive substrate from the outset.

[0018] Recently, magnetron sputtering and electroless copper plating on cellulose fibers or paper have attracted much attention.

[0019] For example, magnetron sputtering can be used to deposit copper on the fibrous framework of cellulose paper. This simple and rapid method is used to produce flexible, self-supporting electrodes.

[0020] As a physical vapor deposition technique, magnetron sputtering provides uniform films. However, it is not ideal for coating high aspect ratio, porous, or 3D structures. Furthermore, the necessity of operating under vacuum increases costs. A cheaper and more widely studied alternative is electroless plating.

[0021] For example, hydrous, electroless copper plating of cellulose fibers in paper can be used to produce lightweight, flexible, and foldable current collectors for battery applications. It typically involves a multi-step synthesis requiring reduction and sintering steps to obtain the metallic copper coating.

[0022] Another approach involves depositing silver seeds onto a cellulose fabric, activating its surface. The silver seeds serve as a catalyst for subsequent electroless copper deposition.

[0023] Although electroless plating is a simple method in itself, the examples briefly outlined above show that coating biopolymer-based fibers or cellulose paper with copper still requires a catalyst or additional pretreatment or posttreatment of the original cellulose fibers or the copper-coated cellulose fibers, respectively.

[0024] Electrical conductivity exists only on the surface of the fiber, and if copper does not adhere well to the biopolymer or the coating is incomplete or broken, electrical conductivity can be completely suppressed.

[0025] What is needed is a biopolymer-based conductive material, especially a conductive material in the form of a starting material, which can be used to manufacture / produce conductive fabrics.

[0026] Therefore, biopolymer-based conductive materials should not suffer from problems related to delamination and / or cracking of the metal coating during mechanical deformation.

[0027] There is also a need for a simple, rapid, and scalable method for producing conductive fabrics and this biopolymer-based conductive material.

[0028] The purpose of this invention is to provide a biopolymer-based conductive material that does not suffer from the aforementioned drawbacks.

[0029] Another object of the present invention is to provide a method for producing conductive fabrics and biopolymer-based conductive materials.

[0030] The present invention relates to a metal-interior-fiber-composite material comprising a biopolymer-based fiber (2) having fiber walls and void spaces and a metal microstructure, wherein the fiber walls enclose the void spaces such that the void spaces are formed as continuous void spaces within the fiber and along the fiber.

[0031] The metal microstructure is a microstructure of an elemental metal that fills and extends through and along a continuous void space, such that fiber walls form a protective layer around the metal microstructure, comprising metal particles that are crystalline, have an average particle size of at least 80 nm, and are interconnected to form the metal microstructure. The metal particles are included in the metal-inner-fiber composite material, accounting for at least 60% by weight of the total weight of the metal-inner-fiber composite material, and the metal-inner-fiber composite material is made conductive based on the metal-inner-fiber composite material.

[0032] Therefore, metal-internal-fiber-composite materials refer to composite materials comprising non-metallic fibers having a metallic structure within the fibers.

[0033] The fiber wall can be microporous. In particular, the fiber wall has pores with an average pore size in the range of about 5 to 30 nm.

[0034] The void space may include a biopolymer-based pillar-like element that extends through a continuous void space without closing a first portion of the continuous void space from a second portion of the continuous void space.

[0035] The fiber, based on biopolymer, extends along the fiber direction, with void spaces forming a continuous void space inside the fiber and along the fiber direction.

[0036] Examples of biopolymer-based fibers include cellulose-based fibers, cotton fibers, silk, etc.

[0037] Fibers based on biopolymers are themselves non-conductive.

[0038] Metallic microstructures are microstructures of elemental metals, particularly those that do not include additional metallic phases, such as silver, palladium, and platinum, produced by production methods using metal catalysts. Therefore, the metallic microstructures according to the present invention do not include foreign metallic phases, which may adversely affect the physical properties of the metallic microstructures, such as electrical and / or thermal conductivity, thermal / chemical stability, etc.

[0039] Metallic microstructures are surrounded by fibrous walls, which form a protective layer around the microstructures. This protective layer can involve protecting the metallic microstructures from environmental corrosion / oxidation. Corrosion / oxidation of metallic microstructures typically leads to the degradation of at least some of their physical properties, such as electrical and / or thermal conductivity, thermal / chemical stability, etc. Therefore, the resistance of metallic microstructures to environmental impacts is increased.

[0040] The protective layer may involve a layer that protects the metallic microstructure from wear. Therefore, the protective layer protects the metallic microstructure from mechanical loads, causing the exposed metallic microstructure to exhibit improved wear resistance. This can be particularly advantageous when further processing the metal-inner-fiber composite to produce, for example, fabrics / textiles. During the relevant further processing, the metal-inner-fiber composite is typically subjected to mechanical loads.

[0041] Metal particles grown to an average size of at least 80 nm within the interstitial space are effectively retained within the fiber by the fiber wall, which may be microporous, particularly having pores with an average pore size in the range of about 5 to 30 nm.

[0042] Metal particles can interconnect by contacting and / or bonding together. Interconnection allows for the formation of self-supporting metal microstructures within fibers. In addition to interconnection, metal particles can also attach to the inner surface of the fiber. The combination of the size of the metal particles and the interconnected particles enables the metal microstructures to conduct electricity.

[0043] The metal-inner-fiber composite material comprises at least 60% by weight of a metal microstructure. This high metal load directly affects at least some physical properties of the metal microstructure, such as electrical conductivity / thermal conductivity.

[0044] According to an embodiment of the present invention, the biopolymer-based fiber is a cellulose-based fiber having a fiber wall and a fiber cavity, wherein the fiber wall encloses the fiber cavity such that the fiber cavity forms a continuous void space inside the fiber and along the fiber.

[0045] The fiber cavity may include a cellulose-based strut-like element that extends through a continuous void space without closing the first part of the fiber cavity from the second part of the fiber cavity.

[0046] Cellulose-based fibers extend along the fiber direction, wherein fiber cavities form continuous void spaces within the fiber and along the fiber direction.

[0047] According to an embodiment of the present invention, the elemental metal is one of copper, nickel, gold, silver, palladium, platinum and lead.

[0048] Copper is a low-cost, highly conductive material. Furthermore, it possesses favorable antimicrobial properties and exhibits high biocompatibility.

[0049] Therefore, the production of conductive composites of biopolymers and copper is very attractive in terms of conductivity, compatibility and cost.

[0050] According to an advantageous embodiment of the invention, the metal-inner-fiber composite material comprises at least 70% by weight, at least 80% by weight, at least 90% by weight, or at least 95% by weight of metal microstructures in the total weight of the metal-inner-fiber composite material.

[0051] According to another advantageous embodiment of the invention, the metal microstructure fills the void space to such an extent that the fiber wall is in close contact with the metal microstructure, the fiber wall is supported by the metal microstructure, and the fiber is expanded compared to the fiber in the void space being empty.

[0052] The fiber wall adheres tightly to the metal microstructure, and the fiber wall fits closely to the metal microstructure. Therefore, the fiber wall can have a large amount of contact with the exterior of the metal microstructure.

[0053] Metal microstructures can support the fiber wall by supporting the inner surface of the fiber wall.

[0054] Supports may involve stabilizing fiber walls to prevent collapse.

[0055] Support can be achieved by filling the void space with as many metal microstructures as possible, wherein points on the inner surface of the fiber wall of the metal microstructures are connected to radially opposite points on the inner surface via portions of the metal microstructures, which extend through the void space, particularly through the inner cavity, and generally in the radial direction.

[0056] If an impression occurs, the fiber expands, filling the edges. This can be evaluated, for example, by comparing biopolymer-based fibers, particularly cellulose-based fibers, with those having void spaces and / or cavities filled with metallic microstructures. Biopolymer-based fibers, particularly cellulose-based fibers, with void spaces and / or cavities typically exhibit collapsed fiber walls, whereas expanded fibers have fiber walls supported from the inside by metallic microstructures, causing the fiber walls to expand at least to a large extent.

[0057] Biopolymer-based fibers filled with this level of metallic microstructures exhibit improved functional properties related to, for example, the electrical / thermal conductivity or structural stability of the metallic microstructures.

[0058] According to another embodiment of the invention, the average particle size of the metal particles is 80 nm to 1000 nm, particularly at least 100 nm, 150 nm, 200 nm or 400 nm and at most 1000 nm, 800 nm or 600 nm.

[0059] According to another embodiment of the invention, the fiber is a plant-derived natural cellulose fiber.

[0060] According to another embodiment of the invention, the protective layer protects the metal microstructure from environmental corrosion and / or wear.

[0061] The present invention further relates to a fabric comprising a metal-inner-fiber-composite material according to the present invention and as described above.

[0062] The fabric can be, for example, yarn, produced using the metal-inner-fiber-composite material according to the invention. Alternatively, the fabric can be, for example, a fabric made from yarn.

[0063] The present invention also relates to a method for producing metal-fiber composite materials. The method includes the following steps: providing a fiber material, particularly fibers; providing a first reactant mixture comprising a metal salt dissolved in a first alcohol; combining the first reactant mixture with the fiber material; heating the first reactant mixture combined with the fiber material to at least 140°C, particularly at least 160°C, wherein the first reactant mixture is combined with the fiber material at at least 140°C, particularly at least 160°C; adding a second reactant mixture to the first reactant mixture combined with the fiber material; and reacting the reactant mixture at at least 140°C, particularly at least 160°C, to metallize the fiber material. Thus, the second reaction mixture comprises a metal salt dissolved in the first alcohol, and the step of adding the second reactant mixture to the first reactant mixture combined with the fiber material is repeated at least once.

[0064] Therefore, metal-fiber composites involve composite materials comprising non-metallic fibers bonded to a metallic structure. Bonding may involve, for example, coating or impregnating / permeating the non-metallic fibers with a metallic structure.

[0065] The fibrous material can be, for example, fibers, or fabrics made from fibers, wherein the fibers and / or fabrics are non-metallic. Fibers that can be used to make fabrics can be biopolymers, particularly cellulose-based fibers. The fabric can be yarn or comprise yarns.

[0066] Combining the first reactant mixture with the fibrous material may involve adding the first reactant mixture to the fibrous material, or vice versa, adding the fibrous material to the first reactant mixture.

[0067] Heating to at least 140°C, particularly at least 160°C, can be done, for example, by using an oil bath or by using microwave radiation.

[0068] The second reactant mixture may be a portion of the first reactant mixture, for example, when the first reactant mixture is in the form of a stock solution.

[0069] Metallization involves forming metallic microstructures that make metal-fiber composites conductive.

[0070] The step of adding the second reaction mixture to the first reactant mixture combined with the fibrous material can be repeated, for example, at least two times, at least three times, at least four times, at least six times, etc.

[0071] According to embodiments of the present invention, the metal salt is one of copper, nickel, gold, silver, palladium, platinum and lead, particularly one of copper acetylacetonate, copper acetate, copper methoxide, nickel acetylacetonate, nickel acetate and nickel methoxide.

[0072] According to an advantageous embodiment of the invention, the first alcohol is benzyl alcohol or a derivative thereof. Derivatives of benzyl alcohol may be, for example, methylbenzyl alcohol, methoxybenzyl alcohol, etc.

[0073] According to another advantageous embodiment of the invention, the first and / or second reactant mixture includes a second alcohol, particularly one of methanol, ethanol and propanol.

[0074] According to another advantageous embodiment of the invention, the method comprises, when the first reactant mixture is combined with the fibrous material at at least 140°C, particularly at least 160°C, adding a third alcohol, particularly glycerol, to the first reactant mixture combined with the fibrous material, wherein the volume ratio of the first alcohol to the third alcohol is 3:1.

[0075] Alternatively, another polyol can be used instead of glycerol, such as one of ethylene glycol, diethylene glycol, triethylene glycol, etc.

[0076] According to another advantageous embodiment of the invention, the first reactant mixture has a metal salt dissolved in the first alcohol at a concentration in the range of 0.2 to 0.5 mol / L, particularly 0.22 or 0.44 mol / L.

[0077] According to another advantageous embodiment of the invention, the method comprises: the fiber material being a biopolymer-based fiber having fiber walls (3) and void spaces (4), wherein the fiber walls enclose the void spaces such that the void spaces are formed as continuous void spaces within and along the fiber; and reacting the reactant mixture at at least 140°C, particularly at at least 160°C, to form the metal-interior-fiber-composite material according to the invention and as described above.

[0078] The present invention also relates to metal-inner-fiber-composite materials produced according to the method of the present invention.

[0079] The metal-inner-fiber-composite material of the present invention and the method for producing the metal-fiber composite material of the present invention are described in more detail below by way of specific exemplary embodiments shown in the accompanying drawings. Other advantages of the invention are also explored. These are illustrated in detail below:

[0080] Figure 1 This is an optical micrograph of a metal-interior-fiber composite material according to an embodiment of the present invention, scale bar 50 micrometers;

[0081] Figure 2 This is an optical micrograph of a metal-interior-fiber composite material according to an embodiment of the present invention, scale bar 20 micrometers;

[0082] Figure 3 This is an electron micrograph of a metal-interior-fiber composite material according to an embodiment of the present invention, showing a view of a fiber having a fiber wall in close contact with a metal microstructure, having a supporting fiber wall and being expanded, with a scale bar of 10 micrometers.

[0083] Figure 4 This is an electron micrograph of a metal-interior-fiber composite material according to an embodiment of the present invention, showing a view of a fiber having a fiber wall in close contact with a metal microstructure, having a supporting fiber wall and being expanded, with a scale bar of 10 micrometers.

[0084] Figure 5 This is an electron micrograph of a metal-interior-fiber composite material according to an embodiment of the present invention, showing a view of a fiber having a fiber wall in close contact with a metal microstructure, having a supporting fiber wall and being expanded, with a scale bar of 1 micrometer.

[0085] Figure 6 This is an electron micrograph of a metal-interior-fiber composite material according to an embodiment of the present invention, showing a view of a fiber having a fiber wall in close contact with a metal microstructure, having a supporting fiber wall and being expanded, with a scale bar of 1 micrometer.

[0086] Figure 7 This is an electron micrograph of a metal-interior-fiber-composite material according to an embodiment of the present invention, showing a view of the fiber cross-section caused by fiber breakage, scale bar 10 micrometers;

[0087] Figure 8 It is a fabric comprising a metal-inner layer-fiber-composite material according to an embodiment of the present invention;

[0088] Figure 9 These are optical micrographs of a fabric, specifically yarn, at a scale bar of 20 micrometers; and

[0089] Figure 10 Optical micrograph of a metal-internal-fiber composite material, with cellulose-based fibers being cotton fibers, scale bar 20 micrometers.

[0090] Figure 1 and 2 An optical micrograph of a metal-inner-fiber composite material 1 according to the present invention is shown. The metal element is copper. The fiber is a cellulose-based fiber 2. The metal-inner-fiber composite material is synthesized / produced by the method according to the present invention. The optical micrograph shows how bright and lustrous the metal-inner-fiber composite material is due to the metal microstructure 5.

[0091] Figures 3 to 7 Metal particles 6 are shown interconnected to form metal microstructures 5 within cellulose-based fibers 2. Figures 3 to 7 Also shown is a metallic microstructure 5 that fills and extends through and along the continuous void space of the fiber, such that the fiber wall 3 forms a protective layer around the metallic microstructure 5.

[0092] Figure 7 The fractured metal-interior-fiber composite material 1 is shown, along with a cross-section of the cellulose-based fiber 2 and a view of the continuous void space 4 / fiber cavity filled with metal particles 6.

[0093] The average particle size of the metal particles 6 in the metal microstructure 5 can be obtained from an electron micrograph by determining the extent of the metal particles 6 in several directions in the image plane, based on a reasonable number of measured metal particles 6. The size of the obtained metal particles is averaged by the number of measured metal particles 6. A reasonable number of metal particles 6 is, for example, 20, 50, or 100. The resulting average particle size of the metal-interior-fiber-composite material 1 is between 80 nm and 1000 nm.

[0094] Metal-inner-fiber composite material 1 has been prepared, comprising metal microstructures 5 comprising 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, or 98 wt% of the total weight of the metal-inner-fiber composite material.

[0095] Figures 3 to 7 The metal-internal-fiber-composite material 1 is shown, wherein the metal microstructure 5 fills the void space to the extent that the fiber wall 3 is tightly fitted to the metal microstructure 5.

[0096] Figures 3 to 7 It was also shown that the fiber wall 3 is supported by the metal microstructure 5, which prevents the fiber wall from collapsing.

[0097] Figures 3 to 7 It also showed that the fiber was expanded compared to the fiber in a state where the interstitial space was empty.

[0098] The metal-inner-fiber-composite material 1 according to the present invention forms a universal raw material for producing its fabric 7. Figure 8 Such a conductive fabric 7 is shown.

[0099] Fabric 7 is a paper-like structure comprising and produced from the metal-inner-fiber-composite material 1 according to the invention. Figure 8 Two alligator clips connecting the paper structure 7 to a 3V coin battery are shown, along with a red light-emitting diode (LED) 8 (2.5V, 25mA, 100W) on the experimental board.

[0100] Figure 9 An optical micrograph of a fibrous material, which is a yarn, is shown, wherein the fibrous material has been made conductive by the method according to the invention.

[0101] Figure 10 It shows a metal-internal-fiber-composite material, with the cellulose-based fiber being cotton fiber.

[0102] Figures 1 to 10 This indicates that the metal-interior-fiber-composite material 1 according to the invention increases the elasticity of the composite material because the metal microstructures and metal particles 6 are protected inside the cellulose-based fibers 2 and cannot be detached from them during further processing, since there may be a metal coating on the surface of the cellulose-based fibers.

[0103] A drawback associated with biopolymer-based fibers having a metallic coating on their surface is that the coating may be incomplete or conductivity may be suppressed by cracks in the coating. The metal-inner-fiber-composite material 1 according to the invention does not have this drawback.

[0104] The following outlines a method for producing the metal-fiber composite material according to the present invention.

[0105] In an exemplary embodiment of this method, the following chemicals are used:

[0106] Benzyl alcohol (especially anhydrous, 99.8% purity) is used as the primary alcohol, copper(II) acetylacetonate as the metal salt (Cu(acac)2, especially 99.99% purity), and glycerol as the tertiary alcohol (especially ≥99% purity), methanol as the secondary alcohol (especially anhydrous, 99.9% purity), and acetone (especially ultra-dry, ≥99.8%). All chemicals are used without further purification.

[0107] Alternatively, its derivatives can be used instead of benzyl alcohol. For example, one of methylbenzyl alcohol, methoxybenzyl alcohol, etc.

[0108] Alternatively, another polyol can be used instead of glycerol, such as one of ethylene glycol, diethylene glycol, triethylene glycol, etc.

[0109] Alternatively, one of ethanol and propanol can be used instead of methanol.

[0110] In addition, lignin-free cellulose in pulp form is used as a fibrous material.

[0111] Delignified cellulose can be obtained, for example, in the form of a mixture of 33% by weight of cellulose in water, wherein water can be removed by drying the cellulose at 60°C in an oven with an ambient atmosphere.

[0112] In this exemplary embodiment, Cu(acac)2 is used as a metal salt; however, one of copper acetate, copper methoxide, nickel acetylacetonate, nickel acetate and nickel methoxide, or gold, silver, palladium, platinum and lead metal salts may also be used as a metal salt in combination with the chemicals listed above, and in the exemplary embodiments of the methods outlined below.

[0113] In this exemplary embodiment, delignified cellulose is used as a fibrous material; however, biopolymer-based fibers, cellulose-based fibers and fibrous fabrics, especially polymer fiber fabrics, can be used as fibrous materials in combination with the chemicals listed above, and in exemplary embodiments of the methods outlined below.

[0114] For production, according to an embodiment of the method for producing metal-fiber composite materials, the metal-inner-fiber composite material according to the invention is produced by dissolving 600 mg Cu(acac)₂ in 5.2 mL of anhydrous benzyl alcohol (resulting in a concentration of 0.44 mol Cu(acac)₂ / L), particularly in a glove box under an argon atmosphere. Alternatively, the concentration can be in the range of 0.2 to 0.5 mol / L, particularly 0.22 mol / L.

[0115] Add 5 drops of methanol and stir the mixture, especially for several hours. Transfer the reactant mixture / solution to a glass container containing 30 mg of loose cellulose fibers, especially in a glove box.

[0116] Seal the reaction vessel with a Teflon cap, especially after removing it from the glove box, and transfer it to a preheated oil bath set at 160°C. Do not stir the solution and maintain it at 160°C for 3 hours. However, stirring is optional, meaning the solution may be stirred.

[0117] Add 1.8 ml of glycerol (vol% of total benzyl alcohol: volume% of glycerol = 3:1) to the top of the solution.

[0118] During the next hour, while still at 160°C, the liquid around the now slightly reddish cellulose fibers turned orange and transparent.

[0119] Following the color change, add 2.6 ml of a pre-prepared 0.44 mol / L anhydrous benzyl alcohol solution containing methanol (the concentration can be in the range of 0.2-0.5 mol / L, especially 0.22 mol / L Cu(acac)2). This addition of the reactant solution should be performed more than twice, and between each addition step, the reaction should be maintained at 160°C for 1.5 hours until the liquid turns orange and clear again.

[0120] After the final color change, drop 2.7 mL of glycerol onto the top of the supernatant. This step is optional and can be omitted.

[0121] The reaction was maintained at 160°C for a total of less than 24 hours, particularly less than 12 hours or less than 8 hours. If the addition of glycerol is omitted (see above), the reaction can be maintained at 160°C for a total of less than 12 hours. Afterward, the reaction mixture was cooled to room temperature.

[0122] If stirring is applied (see above) and the addition of glycerol is omitted (see above), the reaction can be maintained at 160°C for a total of less than 6 hours.

[0123] The metal-inner-fiber-composite material containing copper as its elemental metal was washed several times with acetone until the supernatant was clear and colorless, and then dried under vacuum.

[0124] The use of a glove box is optional, as all steps of the method can be performed outside the glove box under ambient atmospheric conditions.

[0125] Instead of 160℃, temperatures of 140℃ or 180℃ can also be used.

[0126] Heating can also be achieved by using microwave irradiation.

[0127] The formation of cellulose-based intrafiber metallic microstructures occurs via the conversion of metal ions from metal salts into metals. It has been observed that the addition of methanol to the first and / or second reactant mixture supports the reduction process, making it proceed more rapidly and completely.

[0128] The primary alcohol, particularly benzyl alcohol, acts as both a solvent and a reducing agent. It has been further observed that glycerol, in addition to the primary and / or secondary alcohols, can further support the reduction process. After a 3-hour reaction time, adding glycerol to the reactant mixture / solution may allow sufficient time for the metal salt to permeate into the biopolymer-based fibers. It is assumed that adding glycerol at the start of synthesis may excessively accelerate the reaction mechanism, and that the metal may form in solution rather than preferentially within the biopolymer-based fibers.

[0129] It has been observed that, without repeating the step of adding the second reactant mixture to the first reactant mixture combined with the fiber material, the amount of metal microstructures formed inside the biopolymer-based fiber is insufficient to make the metal-interior-fiber-composite material conductive.

[0130] Without repeating the step of adding the second reactant mixture to the first reactant mixture combined with the fiber material, the metal-inner-fiber composite typically contains approximately 35% by weight of metallic microstructures as the total weight of the metal-inner-fiber composite. The amount of metallic microstructures contained within the metal-inner-fiber composite can be determined, for example, based on weighing the fiber material before and after the production of the metal-inner-fiber composite. It can also be determined based on weighing the metal-inner-fiber composite and weighing it after selectively removing the fiber material.

[0131] A metal-interior-fiber composite material containing a desired amount of metallic microstructures can be prepared by repeatedly adding a second reactant mixture to a first reactant mixture combined with the fiber material. For example, the included metallic microstructures may constitute 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, or at least 95% by weight of the total weight of the metal-interior-fiber composite material.

[0132] Analysis of the prepared metal-interior-fiber composite and fiber materials by X-ray diffraction (not shown) showed that the metal microstructures consisted of crystalline metal particles.

[0133] Other advantages of the method for producing the metal-fiber composite material according to the present invention are briefly described below:

[0134] - No expensive high-vacuum processes such as magnetron sputtering are required.

[0135] -Using relatively inexpensive heating sources, especially oil baths, and simple synthesis of microwave radiation.

[0136] - No catalyst is needed, only solvent and metal salt are required.

[0137] - No pretreatment or post-treatment is required for metal-fiber composites to make them conductive.

[0138] - Compared to other electroless liquid phase methods, this method is rapid (<24h).

[0139] - This method also enables the growth of large metallic microstructures within the fibrous material, particularly within the pore space of the fiber, wherein pathways to the interior are provided through pores that are significantly smaller than the particles of the formed metallic microstructures.

[0140] - This method can also be used to prepare conductive biopolymer-based fibers or three-dimensional fiber structures, such as cellulose-based fibers or three-dimensional fiber structures, rather than just 2D-like structures.

[0141] This method is easily scalable, requiring no changes to process parameters other than using more chemicals and longer reaction times.

[0142] - Metal-fiber composites can be blended or spun with other natural or synthetic fibers.

Claims

1. Metal-internal-fiber-composite material (1), comprising ○ A biopolymer-based fiber (2) having a fiber wall (3) and a void space (4), wherein the fiber wall encloses the void space such that the void space is formed as a continuous void space within the fiber and along the fiber. ○ Metal microstructures (5), Its features The metal microstructure ○ represents the microstructure of metallic elements. ○ The fiber walls fill and extend through and along the continuous void space, such that they form a protective layer around the metallic microstructure. ○ Includes metal particles (6), said metal particles ○ It is crystalline. ○ Has an average particle size of at least 80 nm. Interconnected to form the metal microstructure, ○ Included in the metal-inner-fiber-composite material, comprising at least 60% by weight of the total weight of the metal-inner-fiber-composite material, and Make the metal-interior-fiber-composite material conductive.

2. The composite material of claim 1, wherein, The biopolymer-based fiber is a cellulose-based fiber (2) having a fiber wall (3) and a fiber cavity, wherein the fiber wall encloses the fiber cavity such that the fiber cavity is inside the fiber and forms the continuous void space along the fiber.

3. The composite material of claim 1 or 2, wherein, The element is one of copper, nickel, gold, silver, palladium, platinum, and lead.

4. The composite material according to claim 1 or 2, wherein, The metal-inner-fiber composite material comprises at least 70% by weight of metal microstructures.

5. The composite material according to claim 4, wherein, The metal-interior-fiber composite material comprises at least 80% by weight of metal microstructures.

6. The composite material according to claim 5, wherein, The metal-inner-fiber composite material comprises at least 90% by weight of metal microstructures.

7. The composite material according to claim 6, wherein, The metal-inner-fiber composite material comprises at least 95% by weight of metal microstructures.

8. The composite material according to claim 1 or 2, wherein, The metallic microstructure fills the void space to such an extent that: ○ The fiber wall is in close contact with the metal microstructure. ○ The fiber wall is supported by the metal microstructure, and ○ The fiber is expanded compared to a fiber in a state where the void space is empty.

9. The composite material according to claim 1 or 2, wherein, The average particle size of the metal particles (6) is 80 nm to 1000 nm.

10. The composite material according to claim 9, wherein, The average particle size of the metal particles (6) is at least 100 nm and at most 1000 nm.

11. The composite material according to claim 10, wherein, The average particle size of the metal particles (6) is at least 150 nm and at most 800 nm.

12. The composite material according to claim 11, wherein, The average particle size of the metal particles (6) is at least 200 nm and at most 600 nm.

13. The composite material according to claim 12, wherein, The average particle size of the metal particles (6) is at least 400 nm and at most 600 nm.

14. Fabrics (7), of which, The fabric comprises a metal-inner-fiber-composite material as described in any one of claims 1 to 13.

15. A method for producing the metal-inner-fiber-composite material according to any one of claims 1 to 13, comprising the following steps: ○ Provide a fibrous material, wherein the fibrous material is a biopolymer-based fiber (2) having fiber walls (3) and void spaces (4), wherein the fiber walls enclose the void spaces such that the void spaces are formed as continuous void spaces within the fiber and along the fiber. ○ Provide a first reactant mixture containing a metal salt dissolved in a first alcohol. ○ Combine the first reactant mixture with the fiber material. ○ The first reactant mixture combined with the fiber material is heated to at least 140°C. ○ While the first reactant mixture in combination with the fiber material is heated to at least 140°C, a second reactant mixture is added to the first reactant mixture in combination with the fiber material. ○ The reactant mixture is reacted at at least 140°C to metallize the fiber material. in ○ The second reaction mixture contains a metal salt dissolved in the first alcohol, and The step of adding the second reactant mixture to the first reactant mixture combined with the fiber material is repeated at least once.

16. The method according to claim 15, wherein, The metal salt is one of copper, nickel, gold, silver, palladium, platinum, and lead.

17. The method according to claim 16, wherein, The metal salt is one of copper acetylacetonate, copper acetate, copper methoxide, nickel acetylacetonate, nickel acetate, and nickel methoxide.

18. The method according to any one of claims 15 to 16, wherein, The first alcohol is benzyl alcohol or a derivative thereof.

19. The method according to any one of claims 15 to 16, wherein, The first reactant mixture and / or the second reactant mixture comprises a second alcohol.

20. The method according to claim 19, wherein, The second alcohol is one of methanol, ethanol, and propanol.

21. The method according to any one of claims 15 to 16, comprising adding a third alcohol to the first reactant mixture combined with the fiber material at the first reactant mixture in combination with the fiber material at the first reactant mixture at at least 140°C.

22. The method according to claim 21, wherein, The third alcohol is glycerol.

23. The method according to claim 21, wherein, The volume ratio of the first alcohol to the third alcohol is 3:

1.

24. The method according to any one of claims 15 to 16, wherein, The first reactant mixture contains the metal salt dissolved in the first alcohol at a concentration of 0.2 to 0.5 mol / L.

25. The method according to claim 24, wherein, The first reactant mixture contains the metal salt dissolved in the first alcohol at a concentration of 0.22 or 0.44 mol / L.

26. The method according to any one of claims 15 to 16, wherein, The first reactant mixture and the second reactant mixture have the metal salt dissolved in the first alcohol at a concentration of 0.2 to 0.5 mol / L.

27. The method according to claim 26, wherein, The first reactant mixture and the second reactant mixture have the metal salt dissolved in the first alcohol at a concentration of 0.22 or 0.44 mol / L.

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