Nanowire Networks

Abstract

The present invention refers to a method for producing a network of nanowires, to a network of nanowires obtainable by said method, to a nonwoven material comprising the network, to an electrode comprising the network, to uses of the network of nanowires and to uses of the nonwoven material.

Description

[Technical field]

[0001] The present invention relates to the synthesis of nanowire networks, more particularly to a process for producing nanowire networks for use in areas such as wearable electronics, sensors, and flexible batteries. [Background technology]

[0002] Networks composed of nanowires have advantages over materials made of larger building blocks. Generally, nanowires are mechanically flexible due to their nanoscale dimensions and have a reduced amount of defects compared to bulk materials. They also exhibit various optoelectronic properties as a result of their small size and one-dimensional morphology. As a result, some of the properties of nanowire networks depend on the properties of the nanowires. Thus, a high degree of control over the crystalline quality, morphology, and size distribution of the nanowires is required.

[0003] WO2011156019(A2) describes the synthesis of group IV metal or semiconductor nanowires and their incorporation into macroscopic "fabrics" as-produced. These are free-standing nanowire networks that can be used in a variety of microelectronic devices that require large amounts of material, such as electrodes in lithium-ion batteries. The nanowires are produced under supercritical fluid conditions in an autoclave reactor, a process called supercritical fluid liquid solid (SFLS) growth.

[0004] A method has been reported to create "percolating networks" of nanowires, which involves the use of a spray nozzle to disperse nanowires aerotaxis-grown on a substrate (US9574286B). Notably, the fabrication of the percolating network is only carried out after the synthesis, as a subsequent and separate fabrication step. Moreover, it is not clear from US9574286B that such a method could lead to free-standing nanowire assemblies, a prerequisite for them to be considered as an integrated material in their own right.

[0005] Schaufele et al. (Mater. Horiz., 2020, 7, 2978-2984) describe a route to the continuous production of suspended silicon nanowires in the gas phase and their assembly into macroscopic sheets. The method is carried out by suspended catalytic chemical vapor deposition using an aerosol of gold particles. However, although the nanowires have a high aspect ratio and the resulting sheets combine good mechanical properties, this method produces not only nanowires but also (quasi-)spherical particles that can be detrimental to the bulk properties of the nanowire ensemble. The production of such nanoparticles rather than high aspect ratio nanowires is therefore often undesirable and should be avoided whenever possible.

[0006] In summary, there is a need to develop a one-step method for the synthesis of nanowire networks with good mechanical properties that overcomes the limitations of the prior art. Summary of the Invention

[0007] The inventors of the present invention have found a one-step method to produce free-standing networks of nanowires that have good mechanical properties, e.g., good flexibility when bending, and that allow the nanowires to have greater lengths, resulting in higher aspect ratios of said nanowires. The discovery of a free-standing network of nanowires that is also flexible is a breakthrough, since it allows the manipulation of the nanowire network after production, as an engineering material, rather than as a powder or filler, which typically degrades and / or shortens the nanowires during dispersion during processing. Furthermore, the inventors have observed that the method of the present invention allows the production of nanowire networks in large quantities and at high speeds, and advantageously, the method increases the proportion of nanowires in the nanowire network, thereby significantly reducing the presence of other structures, e.g., quasi-spherical particles.

[0008] This approach overcomes the current limitations of the prior art and is therefore of great importance for the wide variety of applications of nanowire networks in various technological fields. In addition, the method of the present invention is based on aerosol technology, which allows for a high level of process control and potentially allows for scalability to large quantities of product.

[0009] Thus, in a first aspect, the present invention provides a method for producing a network of nanowires, comprising the steps of: i. providing a gas flow mixture to a reaction vessel, the gas flow mixture comprising: at least one precursor compound, which comprises at least one element selected from Si, Ge, Cu, Zn, Cd, Ga, In, As, Ni, Se, Ta, Pt, Mo, W, N, O, Co, Mn, Li and Te, and which is a hydride or an organometallic compound; - metallic catalyst particles comprising one or more elements selected from Au, Ag, Cu, Fe, Ni, Ga, Co, Pt, In, and Al; at least one precursor compound is present in the gas stream mixture in a mole fraction (xi) of at least 0.005; The temperature in the reaction vessel is in the range of 1100°C to 1600°C; At least one precursor compound decomposes under the temperature in the reaction vessel and grows on the metallic catalyst particles, preferably by a vapor-liquid-solid (VLS) method, and / or a solid-liquid-solid (SLS) method, and / or a chemical vapor deposition (CVD) method; forming a network of nanowires; Methods are directed to wherein the network of nanowires comprises solid nanowires, hollow nanowires, or a mixture thereof.

[0010] In a second aspect, the present invention is directed to a network of nanowires obtainable by a method as defined above, wherein the aspect ratio (length / diameter) of the nanowires of the network of nanowires is at least 300, and the network of nanowires of the present invention comprises a volume of nanowires of at least 20% of the total volume of the network.

[0011] In a third aspect, the present invention is directed to a nonwoven material comprising at least two layers of the network of nanowires of the present invention.

[0012] Another aspect of the invention is directed to an electrode comprising the nanowire network of the invention in any of its detailed embodiments, or the nonwoven material of the invention in any of its detailed embodiments, and an electrical connection or current collector.

[0013] In a further aspect, the present invention is directed to the use of the network of nanowires of the present invention or the nonwoven material of the present invention in a battery, preferably a lithium battery.

[0014] In a further aspect, the present invention is directed to the use of the network of nanowires of the present invention or the nonwoven material of the present invention in an electronic device, preferably an optoelectronic device.

[0015] In further aspects, the present invention is directed to the use of the network of nanowires of the present invention or the nonwoven material of the present invention in heat transfer materials, biocompatible materials, or in radiation absorbing materials. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 shows a setup for producing SiC nanowires. [Diagram 2] FIG. 2 shows (a) an image of a free-standing network of SiC nanowires and (b) an electron microscope image of the nanowire network. [Diagram 3] FIG. 3 shows (a) a transmission electron microscope (TEM) micrograph of an individual SiC nanowire, (b) a crystalline SiC nanowire electron diffraction pattern, and (c) a statistical distribution of SiC nanowire diameters. [Figure 4] FIG. 4 shows Raman spectroscopy of the nanowire network. [Diagram 5] Figure 5 shows the powder X-ray diffraction (XRD) pattern of the SiC nanowires (right). [Figure 6] Figure 6 shows SEM micrographs of SiC nanowire networks obtained at different temperatures, namely (a) 1200 °C, (b) 1250 °C, and (c) 1300 °C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0018] The present invention is directed to a method for preparing a network of nanowires, a network of nanowires obtainable by said method, a nonwoven material comprising a network of nanowires, an electrode comprising a network of nanowires or a nonwoven material of the invention, and uses of the network of nanowires of the invention and the nonwoven material of the invention.

[0019] The nanowires of the nanowire network of the present invention are high aspect ratio structures that may be made of solid material or may be hollow (have a tubular shape). In one embodiment, the nanowires are continuous structures (not porous), preferably solid continuous structures. In another embodiment, the nanowires form a network by joining together during their synthesis.

[0020] method In a first aspect, the present invention provides a method for producing a network of nanowires, comprising the steps of: i. providing a gas flow mixture to a reaction vessel, the gas flow mixture comprising: at least one precursor compound comprising at least one element selected from Si, Ge, Cu, Zn, Cd, Ga, In, As, Se, Ta, Pt, Mo, W, N, Ni, O, Co, Mn, Li and Te, and which is a hydride or an organometallic compound; - metallic catalyst particles comprising one or more elements selected from Au, Ag, Cu, Fe, Ni, Ga, Co, Pt, In, and Al; at least one precursor compound is present in the gas stream mixture in a mole fraction (xi) of at least 0.005; The temperature in the reaction vessel is in the range of 1100°C to 1600°C; At least one precursor compound decomposes under the temperature in the reaction vessel and grows on the metallic catalyst particles, preferably by a vapor-liquid-solid (VLS) method, and / or a solid-liquid-solid (SLS) method, and / or a chemical vapor deposition (CVD) method; forming a network of nanowires; Methods are directed to wherein the network of nanowires comprises solid nanowires, hollow nanowires, or a mixture thereof.

[0021] The method of preparing a network of nanowires may comprise the further step of converting the network of nanowires into a fiber, yarn or fabric. In one embodiment, the step of converting the network of nanowires into a fiber, yarn or fabric is optionally carried out simultaneously with step (i) of the method of the present invention.

[0022] In a particular embodiment, the method of preparing a network of nanowires comprises the further step (ii) of recovering the network of nanowires, in particular by spinning the network of nanowires (optionally as a yarn or fabric) and winding it onto a bobbin.

[0023] In one embodiment, the process of the present invention is a continuous aggregation process.

[0024] The method of producing a network of nanowires of the present invention comprises the step (i) of supplying a gas flow mixture to a reaction vessel containing at least one precursor compound comprising at least one element selected from Si, Ge, Cu, Zn, Cd, Ga, In, As, Se, Ta, Pt, Mo, W, N, Ni, O, Co, Mn, Li, and Te, wherein the at least one precursor compound is a hydride or an organometallic compound.

[0025] In a detailed embodiment, the gas stream mixture comprises H 2 In a particular embodiment, the gas flow mixture comprises an inert gas, particularly N 2 Includes.

[0026] Precursor Step (i) of the method of the present invention provides a gas flow mixture to a reaction vessel, said gas flow mixture comprising at least one precursor compound. In a detailed embodiment, the at least one precursor compound is a compound that participates in a reaction (i.e., a chemical reaction) that produces the nanowire network of the present invention. For example, hexamethyldisilane (HMDS) is a precursor compound that can result in a SiC nanowire network when used in the method of the present invention.

[0027] In a particular embodiment, the at least one precursor compound of the method of the invention comprises at least one element selected from Si, Ge, Cu, Zn, Cd, Ga, In, As, Se, Ta, Pt, Cu, Mo, W and Te, preferably from Si, Ge, Cu, Zn, Ga, In, Se, Ta, Pt, Mo, W and Te, particularly from Si, Ge, In, Ga, Se and Te, more particularly from Si, Ge, In and Ga, even more particularly from Si, Ge and In, even more particularly from Si and Ge, and even more particularly from Si.

[0028] In detailed embodiments, at least one element of the precursor compound is different from one or more elements of the metal catalyst particles.

[0029] In particular embodiments, the at least one precursor compound is a mixture of precursors.

[0030] In particular embodiments, the at least one precursor compound is one precursor compound.

[0031] The at least one precursor compound may be in solid, liquid form (i.e., aerosolized in the first gas stream of the method of the present invention), or gas form. In a detailed embodiment, the at least one precursor compound is in liquid or gas form, preferably in liquid form.

[0032] In a particular embodiment, at least one precursor compound of the method of the invention is a metal hydride or an organometallic compound. In a preferred embodiment, at least one precursor compound of the method of the invention is a metal hydride.

[0033] In another preferred embodiment, at least one precursor compound of the method of the present invention is an organometallic compound.

[0034] In the context of the present invention, organometallic compounds are chemical compounds known in the art that contain at least one bond between a metal or metalloid element (such as boron, silicon, germanium, arsenic, tellurium, or selenium) and a carbon atom belonging to an organic molecule or functional group.

[0035] Precursors of the present invention include (3-aminopropyl)triethoxysilane, N-sec-butyl(trimethylsilyl)amine, chloropentamethyldisilane, chloropentamethyldisilane, tetramethylsilane, silicon tetrabromide, silicon tetrachloride, tris(tert-butoxy)silanol, SiH 4 , tetramethylgermanium, triethylgermanium hydride, triphenylgermanium hydride, triphenylgermanium hydride, tetramethylgermanium, tributylgermanium hydride, triethylgermanium hydride, triphenylgermanium hydride, trimethylindium (TMin), trimethylindium (TEIN), trimethylgallium (TMG), triethylgallium (TEG), dimethylselenide, tellurium tetrachloride, trimethylaluminum (TMAl), triethylaluminum (TEAl), NH 3 , A.S.H. 3 , and P.H. 3 and more specifically, (3-aminopropyl)triethoxysilane, N-sec-butyl(trimethylsilyl)amine, chloropentamethyldisilane, hexamethyldisilane, tetramethylsilane, silicon tetrabromide, silicon tetrachloride, tris(tert-butoxy)silanol, SiH 4, tetramethylgermanium, triethylgermanium hydrolide, triphenylgermanium hydride, triphenylgermanium hydride, tetramethylgermanium, tributylgermanium hydride, triethylgermanium hydride, trimethylindium (TMin), trimethylindium (TEIN), trimethylgallium (TMG), triethylgallium (TEG), dimethylselenide, tellurium tetrachloride, more specifically (3-aminopropyl)triethoxysilane, N-sec-butyl(trimethylsilyl)amine, chloropentamethyldisilane, tetramethylsilane, silicon tetrabromide, silicon tetrachloride, tris(tert-butoxy)silanol, SiH 4 , tetramethylgermanium, triethylgermanium hydride, triphenylgermanium hydride, triphenylgermanium hydride, tetramethylgermanium, tributylgermanium hydride, triethylgermanium hydride, and triphenylgermanium hydride, more particularly SiH 4 , or hexamethyldisilane, but are not limited to these.

[0036] In one embodiment, the at least one precursor is a silane or a silane derivative, preferably a silane derivative, more preferably 3-aminopropyltriethoxysilane, N-sec-butyl(trimethylsilyl)amine, chloropentamethyldisilane, hexamethyldisilane, tetramethylsilane, or a mixture thereof, more preferably hexamethyldisilane.

[0037] In a detailed embodiment, the gas flow mixture includes two or more precursor compounds. In particular, the gas flow mixture includes a first precursor compound and an additional precursor compound. In a detailed embodiment, the additional precursor compound may be used as a dopant for the nanowire network (in a smaller amount than the main precursor compound). The suitable dopant depends on the nanowire material to be doped.

[0038] In a detailed embodiment, at least one precursor compound of the present invention is provided to the reaction vessel of the present invention at a flow rate of at least 0.0010 mol / h, preferably at a flow rate of at least 0.0015 mol / h, more preferably at least 0.0020 mol / h, and even more preferably at a flow rate of about 0.0025 mol / h.

[0039] In a detailed embodiment, the method comprises the step of: 2 The method includes adding or injecting an additional gas flow comprising:

[0040] In a more particular embodiment, the additional gas stream of the process of the present invention is H 2 Further includes:

[0041] In a detailed embodiment, a gas or gas mixture, preferably N 2 and / or H 2 Only these are used in the present invention.

[0042] catalyst The gas flow mixture provided in the method of preparing a network of nanowires of the present invention includes metallic catalyst particles.

[0043] In a detailed embodiment, the metallic catalyst particles used in the method of the present invention comprise one or more elements selected from Au, Ag, Cu, Fe, Ni, Ga, Co, Pt, In, and Al, in particular one or more elements selected from Au, Ag, Cu, Fe, Co, and Pt, preferably Fe. The metallic catalyst particles may consist of a single element or a combination (e.g., an alloy) of two or more elements. The metallic catalyst particles may be present in the gas stream as solid particles or as liquid particles, preferably as solid particles. In another detailed embodiment, the catalyst particles may be produced by decomposition of a metal precursor in the gas stream mixture, in particular an organometallic compound, more particularly ferrocene.

[0044] In another detailed embodiment, the metallic catalyst particles used in the method of the invention further comprise one or more additional elements selected from the group 16 elements for controlling and / or enhancing the growth of the nanowires, specifically selected from oxygen, sulfur, selenium, tellurium, and polonium, more specifically selected from S, Se, Te, and O.

[0045] In a particular embodiment, the metallic catalyst particles consist of one element selected from Au, Ag, Cu, Fe, Ni, Ga, Co, Pt, In and Al, in particular one element selected from Au, Ag, Cu, Fe, Co and Pt, preferably one element selected from Au, Ag, Cu, Co and Fe, preferably one element selected from Au, Co or Fe, preferably one element selected from Fe.

[0046] In a detailed embodiment, the metallic catalyst particles have an average diameter between 0.1 and 100 nm, preferably between 1 and 30 nm. The average diameter of the metallic catalyst particles of the present invention may be calculated from the average of values ​​obtained by measuring the diameter of more than 100 metallic catalyst particles using electron micrographs, or from size distributions obtained from different aerosol measurement techniques such as differential electrostatic classification (DMA).

[0047] Furthermore, the metallic catalyst particles may have an electric charge, or an electric charge may be imparted to the metallic catalyst particles.

[0048] The metallic catalyst particles may be provided to the reaction vessel in the form of an aerosol generated by an upstream aerosol generator, such as a plasma generator, a spark charge generator, and / or a thermal aerosol generator. Alternatively, the metallic catalyst particles may be formed in situ by providing a precursor compound, preferably a gaseous or liquid precursor compound. In a preferred embodiment, the metallic catalyst particles are provided as a metallic catalyst particle precursor compound, preferably an organometallic precursor compound, more preferably ferrocene.

[0049] In detailed embodiments, the metallic catalyst particle precursor compound comprises one or more elements selected from Au, Ag, Cu, Fe, Ni, Ga, Co, Pt, In, and Al, preferably one or more elements selected from Au, Ag, Cu, Fe, Co, and Pt, preferably Fe.

[0050] In a more detailed embodiment, the metallic catalyst particle precursor compound is mixed with at least one precursor compound of the present invention and injected into a reaction vessel.

[0051] In a more detailed embodiment, the gas stream mixture of step (i) comprises: (a) providing a mixture, the mixture comprising: a metallic catalyst particle precursor comprising one or more elements selected from Au, Ag, Cu, Fe, Ni, Ga, Co, Pt, In, and Al; at least one precursor compound comprising at least one element selected from Si, Ge, Cu, Zn, Cd, Ga, In, As, Se, Ta, Pt, Mo, W, N, Ni, O, Co, Mn, Li, and Te, and which is a hydride or an organometallic compound; (b) injecting the mixture into a reaction vessel to form the gas stream mixture of step (i), more preferably wherein the mixture is H 2 Injected with a gas; Generated by:

[0052] In a detailed embodiment, the mixture of step (a) is a liquid, and optionally, the injecting occurs by spraying said mixture into the reaction vessel. In a detailed embodiment, as the mixture of step (a) enters the reaction vessel, the metallic catalyst particle precursors are decomposed into metallic catalyst particles.

[0053] In a detailed embodiment, the metallic catalyst particles and / or metallic catalyst particle precursors have a molecular weight of at least 1×10 -5 g / h, preferably at least 1×10 -4 g / h, more preferably at least 1×10 -3g / h, more preferably 1×10 -3 g / h and 4×10 -3 g / h, and even more preferably between 1.5×10 -3 g / h and 3.5×10 -3 g / h, and even more preferably between 2.0×10 -3 g / h and 3.0×10 -3 The reaction vessel is fed with a flow rate of between 100 and 200 g / h.

[0054] A means for mixing may be used and, if necessary, pressure and flow rates may be adjusted to ensure proper mixing of the gas stream mixture.

[0055] In a detailed embodiment, the gas stream mixture flows through the reaction vessel at a flow rate of at least 60 l / h, preferably at least 120 l / h.

[0056] In another detailed embodiment, the gas flow mixture has a residence time in the reaction vessel of less than 500 seconds, particularly between 0.1 and 200 seconds, more particularly between 1 and 100 seconds, even more particularly between 2 and 90 seconds, preferably between 4 and 80 seconds.

[0057] In addition to the gas stream mixture, one or more sheath streams may be introduced into the reaction vessel of the present invention. The sheath stream may contain gases such as nitrogen, hydrogen, noble gases such as helium and argon, or mixtures thereof.

[0058] In the method of the present invention, the at least one precursor compound is present in the gas stream mixture in a mole fraction (xi) of at least 0.005.

[0059] In particular embodiments, the at least one precursor compound is present in the gas stream mixture in a mole fraction of at least 0.006, particularly at least 0.01, more particularly at least 0.015, and even more particularly between 0.01 and 0.5, preferably about 0.02. In the context of the present invention, mole fraction is expressed as the amount of a component (in moles) divided by the total amount of all components (also expressed in moles).

[0060] In a particular embodiment, at least one precursor compound of the present invention is at least 0.1×10 -4 Concentration in mol / l, specifically at least 1 × 10 -4 Concentration in mol / l, more precisely at least 1.5 × 10 -4 Concentration in mol / l, more precisely at least 2 × 10 -4 It is present in the gas stream mixture in a concentration of mol / l.

[0061] In a detailed embodiment, the gas stream mixture comprises H 2 Includes.

[0062] In one embodiment, the gas flow mixture comprises: at least one precursor mixture comprising at least one precursor compound consisting of at least one element selected from Si, Ge, Cu, Zn, Cd, Ga, In, As, Se, Ni, Ta, Pt, Mo, W, N, O, Co, Mn, Li, and Te, the precursor mixture being a hydride or an organometallic compound; - metallic catalyst particles consisting of one or more elements selected from Au, Ag, Cu, Fe, Ni, Ga, Co, Pt, In and Al; at least one sheath gas selected from nitrogen, hydrogen and a noble gas; Includes.

[0063] In one embodiment, the gas flow mixture comprises: at least one precursor compound which comprises at least one element selected from Si, Ge, Pt, Mo, W, Co, Mn, Li and Te and which is a hydride or an organometallic compound; - metallic catalyst particles consisting of one or more elements selected from Au, Ag, Cu, Fe, Ni, Pt, In and Al; at least one sheath gas selected from nitrogen, hydrogen and a noble gas; Includes.

[0064] In one embodiment, the gas flow mixture comprises: at least one precursor compound which comprises at least one element selected from Si, Ge, Pt, W, Mn, Li and Te and which is a hydride or an organometallic compound; - metallic catalyst particles consisting of one or more elements selected from Au, Ag, Cu, Fe, Pt and In; at least one sheath gas selected from nitrogen, hydrogen and a noble gas; Includes.

[0065] In a preferred embodiment, the gas stream mixture comprises: at least one precursor compound which contains at least one element selected from Si and Ge and which is a hydride or an organometallic compound; - metallic catalyst particles made of Fe; at least one sheath gas selected from nitrogen, hydrogen and a noble gas; Includes.

[0066] In one embodiment, the gas stream mixture of the present invention comprises: at least one precursor compound which comprises at least one element selected from Si, Ge, Cu, Zn, Cd, Ga, In, As, Se, Ni, Ta, Pt, Mo, W, N, O, Co, Mn, Li and Te and which is a hydride or an organometallic compound; - metallic catalyst particles consisting of one or more elements selected from Au, Ag, Cu, Fe, Ni, Ga, Co, Pt, In and Al; at least one sheath gas selected from nitrogen, hydrogen and a noble gas; It consists of:

[0067] In one embodiment, the gas stream mixture of the present invention comprises: at least one precursor compound which comprises at least one element selected from Si, Ge, Pt, Mo, W, Co, Mn, Li and Te and which is a hydride or an organometallic compound; - metallic catalyst particles consisting of one or more elements selected from Au, Ag, Cu, Fe, Ni, Pt, In and Al; at least one sheath gas selected from nitrogen, hydrogen and a noble gas; It consists of:

[0068] In one embodiment, the gas stream mixture of the present invention comprises: at least one precursor compound which comprises at least one element selected from Si, Ge, Pt, W, Mn, Li and Te and which is a hydride or an organometallic compound; - metallic catalyst particles consisting of one or more elements selected from Au, Ag, Cu, Fe, Pt and In; at least one sheath gas selected from nitrogen, hydrogen and a noble gas; It consists of:

[0069] In a preferred embodiment, the gas stream mixture of the present invention comprises: - at least one precursor compound which contains at least one element selected from Si or Ge and which is a hydride or an organometallic compound; - metallic catalyst particles made of Fe; at least one sheath gas selected from nitrogen, hydrogen and a noble gas; It consists of:

[0070] Reaction vessel In a particular embodiment, the reaction vessel used in the process of the present invention is a gas reaction vessel, preferably a cylindrical reaction vessel, more preferably a ceramic or metallic cylindrical reaction vessel, even more preferably a ceramic cylindrical reaction vessel such as a tube.

[0071] In a detailed embodiment, the temperature inside the reactor vessel is uniform, specifically uniform within 50 degrees along the reactor tube, more specifically uniform over 80 cm from the hot zone, and specifically uniform between 30 cm and 50 cm of the hot zone.

[0072] In detailed embodiments, the temperature in the reaction vessel is in the range of 1100°C to 1600°C, preferably the temperature is in the range of 1150°C to 1550°C, more preferably in the range of 1200°C to 1500°C, more preferably in the range of 1250°C to 1450°C, more preferably in the range of 1260°C to 1400°C, and even more preferably about 1260, 1270, 1280, 1290, 1300, 1310, 1320, 1330, 1340, 1350, 1360, 1370, or 1380°C.

[0073] The authors of the present invention have observed that reaction temperatures of at least 1100°C and up to 1600°C significantly increase the proportion of nanowires in the nanowire network and their aspect ratio. In addition, it has been observed that the amount of quasi-spherical particles is significantly reduced by using said temperatures. As can be derived from the experimental data provided in the examples, the method of the present invention provides nanowires with a significantly higher average aspect ratio than those obtained by methods carried out at lower temperatures. Moreover, it can be observed that, especially at temperatures of at least 1300°C, the presence of quasi-spherical particles is almost negligible.

[0074] Furthermore, the nanowire networks obtained at said temperatures have been shown to have better mechanical properties and are more robust.

[0075] In a detailed embodiment, the pressure in the reaction vessel is between 500 mbar and 20000 mbar (50000 Pa and 2000000 Pa), preferably between 900 mbar and 3000 mbar (90000 Pa and 300000 Pa).

[0076] In a detailed embodiment, the temperature within the reaction vessel is achieved by any suitable heating means known in the art, preferably by plasma, arc discharge, resistive heating, hot wire heating, torch heating, or flame heating means, more preferably by resistive heating, hot wire heating, torch heating, or flame heating means.

[0077] Growth of nanowire networks In the method of the invention, at least one precursor compound decomposes under temperature conditions in a reaction vessel and is grown on the metallic catalyst particles by vapor-liquid-solid (VLS) and / or solid-liquid-solid (SLS) and / or chemical vapor deposition (CVD) to form a network of nanowires. In a detailed embodiment, the nanowires are grown while in the gas flow mixture (i.e., they are aerosolized). In a detailed embodiment, at least one precursor compound decomposes under temperature conditions in a reaction vessel and is grown on the metallic catalyst particles by floating catalyst chemical vapor deposition (CVD) to form a network of nanowires.

[0078] If necessary, one or more sheath flows may be introduced into the reaction vessel, in particular between the gas flow mixture and the wall of the reaction vessel.

[0079] By selecting appropriate precursor compounds, gas flows, temperatures, pressures, and metallic catalyst particles, nanowires can be grown axially about their longitudinal axis of symmetry, or radially, or a combination of these two growth modes; preferably, growth occurs in the axial direction, and more preferably, growth occurs in the 110 direction, particularly in the case of Si nanowires.

[0080] The growth of nanowires may be initiated by catalytic decomposition of at least one precursor compound on the surface of metallic catalyst particles and nucleation of nanowires on the surface of metallic catalyst particles. After nucleation, the nanowires may undergo directional growth to form elongated objects, i.e. nanowires. Growth may occur through vapor-liquid-solid (VLS) and / or solid-liquid-solid (SLS) and / or chemical vapor deposition (CVD) processes. At the same time, the nanowires reach a critical concentration and aggregate to form a network of nanowires in the reaction vessel. Thus, the method of the present invention is a continuous aggregation method. Preferably, a gas mixture flows through the reactor carrying metallic catalyst particles, and the nanowire network flows through the length of the reaction vessel.

[0081] In one embodiment, the network of nanowires includes hollow nanowires, such as nanotubes. In one embodiment, the network of nanowires includes hollow and non-hollow nanowires, such as solid nanowires. In another embodiment, the network of nanowires consists of hollow nanowires, such as nanotubes.

[0082] In the context of the present invention, the expression Chemical Vapor Deposition (CVD) is understood as a process in which one or more volatile precursor compounds react and / or decompose on a catalyst surface to produce one-dimensional structures, such as nanowires. The catalyst particles may be suspended in the gas phase and are generally referred to as suspended catalysts. The particles may be in a molten or solid state and may contain additional elements that control and / or promote the growth of nanowires, as described herein above. These additional elements include group 16 elements, such as S, Se, Te, or oxygen. The precursors may also partially decompose on the reactor surface.

[0083] In a detailed embodiment, the method for preparing a network of nanowires of the present invention comprises the step of: -7 Specifically, under the aerogelation parameters of at least 1 × 10 -6 More specifically, under the aerogelation parameters of at least 2 × 10 -6The aerogelation is carried out under the following aerogelation parameters:

[0084] In the context of the present invention, the expression "aerogelation parameter" is understood as the product of the average aspect ratio (length / diameter) of the nanowires and the volume concentration (vc (volume of nanowires / volume of reactor)).

[0085] In the context of the present invention, the expression "vapor-liquid-solid" (VLS) method is a mechanism for growing one-dimensional structures, e.g. nanowires, from chemical vapor deposition by direct adsorption of a gas (i.e. at least one precursor compound in the vapor phase) onto liquid catalyst particles that can rapidly adsorb the vapor to supersaturation levels, from which crystal growth can occur from nucleation seeds at the gas-liquid-solid interface.

[0086] In a particular embodiment, the nanowire network of the present invention is formed while present in the gas flow mixture (in the reaction vessel), and in particular a network of nanowires in which the nanowires are aggregated (i.e., the nanowires are joined, entangled, connected or fused together with each other) is obtained at the outlet of the reaction vessel of the present invention.

[0087] In particular embodiments, the nanowire networks of the present invention are produced as a continuous process. Alternatively, the nanowire networks may be produced individually. In preferred embodiments, the nanowire networks of the present invention are produced continuously.

[0088] In a detailed embodiment, the method of the invention further comprises a step (ii) of recovering the network of nanowires. In one embodiment, the recovering step is performed on a substrate, preferably the substrate is a filter, more preferably a vacuum filter. In a more detailed embodiment, the method of the invention further comprises a step of densifying the network of nanowires, preferably by using a solvent or a mixture of solvents, more preferably an organic solvent or a mixture of organic solvents, even more preferably a solvent or a mixture of solvents containing alcoholic or aromatic groups, even more preferably by using alcohols and / or benzene derivatives, even more preferably isopropanol and / or xylene.

[0089] In particular embodiments, the nanowire networks of the present invention are produced at a rate of at least 0.01 g / h, preferably at a rate of at least 0.02 g / h, more preferably at a rate of at least 0.05 g / h, and even more preferably at a rate of about 0.1 g / h.

[0090] In another detailed embodiment, the nanowire network of the present invention is produced at a rate between 0.01 g / h and 10 g / h, preferably between 0.02 g / h and 5 g / h, more preferably between 0.05 g / h and 1 g / h, and even more preferably between 0.09 g / h and 1 g / h.

[0091] Nanowire Networks One aspect of the present invention is directed to a network of nanowires obtainable by the method of the present invention in any of its detailed embodiments, wherein the average aspect ratio (length / diameter) of the nanowires of the network of nanowires is at least 300, and the network of nanowires of the present invention comprises a volume of nanowires that is at least 20% of the total volume of the network. In a detailed embodiment, the total volume of the network refers to the total volume of the components of the network, such as nanowires, nanoparticles, amorphous materials, etc.

[0092] In a detailed embodiment, the nanowire network of the present invention comprises nanowires with a volume of at least 22%, preferably at least 25%, more preferably at least 30%, and even more preferably at least 40% of the total volume of the nanowire network.

[0093] In a detailed embodiment, the nanowire volume percentage relative to the total volume of the nanowire network is between 20% and 99%, preferably between 22% and 98%.

[0094] More particularly, the nanowire network of the present invention comprises nanowires in a volume of at least 50% of the total volume of the network, preferably at least 60% by volume, more preferably at least 70% by volume, significantly preferably at least 80% by volume, and most preferably at least 90% by volume.

[0095] In a detailed embodiment, the nanowire network of the present invention comprises at least 22 wt% nanowires based on the total weight of the network, preferably at least 25%, more preferably at least 30%, and even more preferably at least 40% nanowires.

[0096] In a detailed embodiment, the weight percentage of the nanowires relative to the total weight of the nanowire network is between 20% and 99%, preferably between 22% and 98%.

[0097] More particularly, the nanowire networks of the present invention comprise at least 50 wt% nanowires based on the total weight of the network, preferably at least 60 wt%, more preferably at least 70 wt%, significantly preferably at least 80 wt%, and most preferably at least 90 wt% nanowires based on the total volume of the network.

[0098] In another preferred embodiment, the nanowires of the nanowire network of the present invention are crystalline nanowires.

[0099] The volume percentage of the crystalline nanowires relative to the total volume of the network may be calculated from image analysis of electron micrographs using methods known in the art where the contribution of the nanowires may be separated from other materials. For example, the volume fraction of the crystalline nanowires relative to the total effective volume of the network may be calculated from the projected area (A) occupied by the nanowires obtained from a number of electron micrographs. NW ) and the projected area (A OM ) The volume fraction may then be converted to volume %. Additionally, the weight % of the crystalline nanowires relative to the total weight of the network may be calculated from the volume % value using the density of the material, as known in the art.

[0100] In the context of the present invention, a crystalline nanowire is understood as a nanowire having an organized crystalline structure. In a detailed embodiment, a crystalline nanowire comprises at least 80 wt% of the total weight of the nanowire as a crystalline structure, preferably more than 90 wt%, more preferably more than 95 wt%, even more preferably more than 97 wt%, even more preferably more than 99, 99.5 or 99.9 wt%.

[0101] In a detailed embodiment, the crystalline nanowires are - between 80 wt% and 99.9 wt% of the total weight of the nanowires is crystalline material; - between 0.01 wt% and 20 wt% of the total weight of the nanowires is amorphous material, the total weight of the nanowires being 100 wt%.

[0102] In a detailed embodiment, the crystalline nanowires are - between 90 wt% and 99.9 wt% of the total weight of the nanowires is crystalline material; - between 0.01 wt% and 10 wt% of the total weight of the nanowires is amorphous material, the total weight of the nanowires being 100 wt%.

[0103] In a detailed embodiment, the nanowires of the nanowire network of the present invention form a network, preferably the nanowires of the nanowire network are mechanically joined, entangled, connected or interlocked between each other, preferably entangled, connected, more preferably entangled between each other. In one embodiment, the nanowire network comprises an aggregate of nanowires.

[0104] In a detailed embodiment, the network of nanowires is free-standing. In the context of the present invention, the term "free-standing" refers to a structure that is not supported by another body or structure, such as a substrate. In one embodiment, the network of nanowires does not include an additional phase, such as an additional matrix or binder.

[0105] In particular embodiments, the nanowires of the inventive network are agglomerated, in particular strongly agglomerated, in particular they are strongly agglomerated by secondary forces such as van der Waals forces, permanent dipoles, hydrogen bonds, and / or covalent bonds, entanglements, and other forms of mechanical interlocking. By strongly agglomerated, in the context of the present invention, it is implied that the material forms a solid object, and that the nanowires comprising the network cannot be easily dispersed without resorting to sonication, stirring, cutting, or similar methods.

[0106] In a particular embodiment, the network of nanowires of the present invention is a continuous network, which in the context of the present invention is understood as a percolated network.

[0107] In a particular embodiment, the nanowire network of the present invention is an aerogel, i.e., a low density, preferably 10 -2 g / cm 3 Less than 10 -3 g / cm 3 less than 10 -4 g / cm 3 less than 10 -5g / cm 3 In a detailed embodiment, the nanowire network of the present invention has a mass of at least 0.001 g / cm. 3 , specifically at least 0.01 g / cm 3 has a density of

[0108] In more particular embodiments, the nanowire networks of the present invention are densified, particularly by mechanical, solvent addition, electromagnetic, or similar methods.

[0109] In a detailed embodiment, the nanowires of the networks of the invention have an average aspect ratio (length / diameter) of at least 300, more preferably 350, and even more preferably 400.

[0110] In more particular embodiments, the nanowires of the networks of the invention have an average aspect ratio (length / diameter) of between 300 and 2000, preferably between 350 and 2000, more preferably between 400 and 1800, even more preferably between 500 and 1800, and even more preferably between 1000 and 1800.

[0111] A method for determining the aspect ratio uses image analysis of electron micrographs taken with an electron microscope. From these micrographs it is possible to determine the diameter (φ) and length (L) of the nanowires, and therefore the aspect ratio of the nanowires is given by:

number

[0112] The average aspect ratio of the nanowires of the networks of the invention may be calculated from the average of values ​​obtained by measuring the dimensions of a significant number (greater than 100) of nanowires. Thus, the average aspect ratio can be determined by the following formula:

number

[0113] In a particular embodiment, the average length of the nanowires of the inventive network is at least 1 micron, in particular at least 2 microns, preferably at least 3, 4, 5, 6, 7, 8, or 9 microns, more preferably at least 10 microns. In a particular embodiment, the average length of the nanowires of the inventive network is between 1 micron and 40 microns, more particularly between 1 micron and 30 microns, preferably between 2 microns and 20 microns, more preferably between 3 microns and 15 microns. In another preferred embodiment, the average length of the nanowires of the inventive network is between 10 microns and 40 microns. The average length of the nanowires of the inventive network may be calculated from the average of values ​​obtained by measuring the length of more than 100 nanowires using electron microscopy.

[0114] In particular embodiments, the nanowire networks of the present invention have a porosity of less than 99.9%, particularly less than 99%, more particularly less than 97%, and even more particularly about 96%.

[0115] In another detailed embodiment, the nanowire network of the present invention has a porosity of less than 90.0%.

[0116] In alternative embodiments, the nanowire networks of the present invention have a porosity of between 99.9% and 30%, particularly between 50% and 98%, more particularly between 60% and 97%, and even more particularly about 96%.

[0117] The porosity of the nanowire networks has been measured using methods known in the art, for example by optical and / or electron microscopy, typically by determining the volume of a sample and gravimetrically measuring its weight, and the porosity is then calculated by comparison with the theoretical density of a monolithic crystal of the same material as the nanowires, as known in the art.

[0118] In particular embodiments, the nanowires of the nanowire network of the present invention are selected from the group consisting of GaAs, InP, GaP, Ga x In 1-x As y P 1-y , Al x Ga 1-x As y P 1-y , GaSb, Ga x In 1-x As y Sb 1-y , GaN, InN, AlN, Al z Ga x In 1-x-z N, Si, SiC, Ge or Si x Ge 1-x , SiO x , TiO x , ZnO x , CdS, Ta x , MoS y , W.S. y , MoTe y ,TaSe y , NbSe y , NiTe y , BN, Bi z Te y , Bp, Cu, Pt, CoO x , MnO x , CuO x , Li x Mn y O, Li x Ni y Mn z O, and Ni x wherein 0≦x≧1, 0≦y≧1, and 0≦z≧1, and preferably, Si, SiC, Ge, or Si x Ge 1-x , and SiO x and 0≦x≧1, and more preferably Si, Ge or Si x Ge 1-x , and SiO xwhere 0≦x≧1, more preferably comprises Si or Ge, and even more preferably comprises Si. In a detailed embodiment, the nanowires of the nanowire network of the present invention further comprise a coating, preferably an inorganic coating or a carbon coating.

[0119] In another detailed embodiment, the nanowires of the nanowire network of the present invention are selected from the group consisting of GaAs, InP, GaP, Ga x In 1-x As y P 1-y , Al x Ga 1-x As y P 1-y , GaSb, Ga x In 1-x As y Sb 1-y , GaN, InN, AlN, Al z Ga x In 1-x-z N, Si, SiC, Ge or Si x Ge 1-x , SiO x , TiO x , ZnO x , CdS, Ta x , MoS y , W.S. y , MoTe y ,TaSe y , NbSe y , NiTe y , BN, Bi z Te y , Bp, Cu, Pt, CoO x , MnO x , CuO x , Li x Mn y O, Li x Ni y Mn z O, and Ni x wherein 0≦x≧1, 0≦y≧1, and 0≦z≧1, and preferably, Si, SiC, Ge, or Si x Ge 1-x , and SiO xwhere 0≦x≧1, more preferably at least one material selected from Si, SiC, and Ge, even more preferably Si or SiC. In another detailed embodiment, the nanowires of the nanowire network of the invention comprise at least one material selected from Si, SiC, and Ge, and a coating, preferably an inorganic coating or a carbon coating.

[0120] In a detailed embodiment, the nanowire network of the present invention has a density of at least 0.01 g / cm 3 , specifically at least 0.05 g / cm 3 of at least 0.075 g / cm 3 of at least 0.080 g / cm 3 Preferably at least 0.150 g / cm 3 of at least 0.200 g / cm 3 , more preferably about 0.128 g / cm 3 It has a volume density of

[0121] In a detailed embodiment, the nanowire network of the present invention has a density of 0.01 g / cm 3 and 0.20g / cm 3 Between, specifically 0.07g / cm 3 and 0.30 g / cm 3 The volume density of the nanowire networks of the present invention may be calculated from any experimental technique known in the art, in particular it is determined from the area density and thickness of a sample of the nanowire network.

[0122] In particular embodiments, the nanowires of the nanowire networks of the present invention are entangled, preferably physically entangled.

[0123] In a detailed embodiment, the nanowire network of the present invention is a network that includes nanowires. In a detailed embodiment, the nanowires forming the network can have the same or different properties. In a more detailed embodiment, the nanowires included in the network have different compositions and / or aspect ratios.

[0124] In particular embodiments, the nanowires of the network of nanowires are hollow (i.e., they are nanotubes), and preferably they are nanotubes. In more particular embodiments, the hollow nanowires are made of Si, SiC, Ge or Si. x Ge 1-x , and SiO x wherein 0≦x≧1, and more preferably Si, SiC, Ge or Si x Ge 1-x , and SiO x , preferably made of at least one material selected from Si and SiC, and more preferably made of SiC.

[0125] In a detailed embodiment, the nanowire networks of the present invention further comprise metallic catalyst particles for use in the methods of the present invention.

[0126] In particular embodiments, the nanowires of the network of nanowires of the present invention further comprise a coating, in particular an inorganic coating or a carbon coating, more preferably a carbon coating.

[0127] In another detailed embodiment, the nanowire networks of the present invention can be chemically functionalized by a gas phase process, a liquid phase process, an annealing process, or an irradiation process. In a detailed embodiment, the chemical functionalization of the nanowires is performed during the synthesis process or in an additional step.

[0128] In a detailed embodiment, the nanowires of the nanowire network of the invention further comprise a labeling or marking element or compound, said labeling element or compound providing traceability of the nanowires, in a detailed embodiment, the labeling or marking of the nanowires is carried out during the synthesis process or in an additional step after said synthesis.

[0129] In particular embodiments, the nanowires of the nanowire networks of the present invention are predominantly aligned.

[0130] In particular embodiments, the nanowires of the nanowire networks of the present invention are drawn, stretched, or subjected to electromagnetic or electrochemical methods to align the nanowires.

[0131] In particular embodiments, the nanowire networks of the present invention further comprise particles, preferably amorphous particles, more preferably amorphous spherical particles.

[0132] In a detailed embodiment, the nanowires of the nanowire network of the present invention are crystalline, preferably the nanowires are formed by a single crystal, more preferably the nanowires of the nanowire network are single crystalline and continuous, more preferably of SiC, even more preferably of the cubic and / or hexagonal phase of SiC.

[0133] In one embodiment, the nanowire network of the present invention comprises a crystalline phase and an amorphous phase, preferably the crystalline phase is present at least 25 wt% or 40 wt%, more preferably at least 50 wt%, and even more preferably at least 60 wt%, based on the total weight of the network, and even more preferably the crystalline phase comprises crystalline nanowires and the amorphous phase comprises amorphous particles, preferably amorphous spherical particles.

[0134] In one embodiment, the nanowire network of the present invention comprises at least 25 wt%, preferably at least 30 wt%, and more preferably at least 40 wt% crystalline nanowires based on the total weight of the network.

[0135] The crystallinity of the nanowires can be determined by X-ray diffraction analysis (XRD) and Raman spectroscopy.

[0136] In another detailed embodiment, the nanowire network of the present invention consists of nanowires.

[0137] In one embodiment, the nanowire networks of the present invention have an energy-to-break value of at least 0.05 J / g, preferably between 0.1 and 0.5 J / g, as measured by mechanical tensile testing of nanowire network samples using conventional mechanical testing equipment as known in the art.

[0138] In one embodiment, the nanowire network of the present invention has a specific tensile strength greater than 0.5 MPa / SG, preferably greater than 0.8 MPa / SG, more preferably greater than 1 MPa / SG. In particular, specific tensile strength values ​​are in units of MPa / SG, where SG is g / cm. 3 By specific tensile strength is meant the specific gravity, numerically equivalent to the density of the nanowire network, in units of tensile strength. Specific tensile strength may be measured by any tensile testing technique known in the art, for example by mechanical tensile measurement of a sample of the nanowire network using a Textechno Favimat tensile tester at a strain rate of 10% / min and preferably with a gauge length of 5 mm.

[0139] Non-woven materials In another aspect, the invention is directed to a nonwoven material comprising at least two layers of the network of nanowires of the invention, in a detailed embodiment, each of the two layers has a thickness of at least 0.1 microns, preferably 0.5 microns, more preferably at least 1 micron.

[0140] In another detailed embodiment, the nonwoven material of the present invention is a nonwoven fabric, preferably a unidirectional nonwoven fabric.

[0141] In another detailed embodiment, the nanowires of the network of nanowires in the nonwoven material of the present invention are oriented in a single direction, preferably in a single parallel direction.

[0142] In another detailed embodiment, the nonwoven material of the present invention is a nonwoven fabric in which the nanowires of the network of nanowires are oriented in a single direction, preferably in a single parallel direction.

[0143] In another detailed embodiment, the nonwoven material of the present invention is a yarn.

[0144] In another detailed embodiment, the nonwoven materials of the present invention can be chemically functionalized by gas phase, liquid phase, annealing, or irradiation processes that modify the surface chemistry of the nanowires.

[0145] In a detailed embodiment, the nonwoven material of the present invention further comprises additives such as binders or pigments.

[0146] use Another aspect of the invention is directed to the use of the network of nanowires of the invention or the nonwoven material of the invention in an electronic device, preferably an optoelectronic device.

[0147] Another aspect of the invention is directed to the use of the nanowire networks or nonwoven materials of the invention in, and preferably as, heat transfer materials.

[0148] Another aspect of the invention is directed to the use of the nanowire networks or nonwoven materials of the invention in, and preferably as, radiation absorbing materials.

[0149] Another aspect of the invention is directed to the use of the nanowire networks or nonwoven materials of the invention in, and preferably as, biocompatible materials.

[0150] Another aspect of the invention is directed to the use of the inventive nanowire network or the inventive nonwoven material in a battery, preferably in a lithium battery. In one embodiment, the invention is directed to the use of the inventive nanowire network or the inventive nonwoven material in a battery, preferably in a lithium battery, particularly in a battery electrode, separator, and / or current collector, preferably in an electrode.

[0151] electrode Another aspect of the present invention is a method for producing a (a) a network of nanowires of the present invention in any of its detailed embodiments, or a nonwoven material of the present invention in any of its detailed embodiments; (b) an electrical connection or current collector, preferably comprising a conductive wire or conductive current collector, in particular an electrical connection between the wire or current collector and the network of nanowires; The present invention relates to an electrode comprising:

[0152] In a detailed embodiment, the nanowire network of the invention in any of its detailed embodiments, or the nonwoven material of the invention in any of its detailed embodiments, is coated with at least a conductive compound, preferably at least a carbon-based conductive compound, more preferably a conductive carbon such as carbon black.

[0153] In one embodiment, the electrode comprises: (a) a network of nanowires of the invention in any of its detailed embodiments, or a nonwoven material of the invention in any of its detailed embodiments, optionally coated, more preferably coated with at least a conductive compound, preferably coated with a carbon-based conductive compound, more preferably coated with conductive carbon such as carbon black; (b) an electrical connection or current collector, preferably a conductive wire or conductive current collector, in particular an electrical connection or current collector in which the wire or current collector and the network of nanowires are electrically connected.

[0154] In a more particular embodiment, the electrode is a cathode.

[0155] The present authors have realized that the mechanical properties imparted by the nanowire network obviate the use of reinforcing additives (e.g., polymeric binders) in the electrodes and enable methods of processing or integrating such electrodes without the need for previously used solvents or other forms of dispersion. In addition, the present authors have observed that the electrodes of the present invention exhibit improved performance. EXAMPLES

[0156] The present invention is illustrated by the following examples, which are not intended to limit the scope of the invention in any way.

[0157] Working Example Example 1. Synthesis and characterization of SiC nanowire networks SiC nanowire networks were synthesized in a vertical floating catalytic chemical vapor deposition (FCCVD) reactor through a vapor-liquid-solid (VLS) mechanism at different temperatures (1200°C, 1250°C, and 1300°C) using Fe as the metal catalyst and hexamethyldisilane (HMDS) as the SiC precursor.

[0158] First, ferrocene was added to liquid HMDS until it reached saturation (≈16 mg / ml). The mixture of ferrocene and HMDS was introduced at a flow rate of 0.5 ml / h through an injector located at the top of a vertical floating catalytic chemical vapor (FCCV) reactor. The injection system was in a capillary tube and was heated with ambient H 2 The flow was 60 ml / min.

[0159] The reactor tube (Mullite 660, φ=7 cm) was heated in an inert atmosphere with H 2 Atmosphere 3lpm H 2 The reaction temperature was maintained at the desired temperature (1200° C., 1250° C., or 1300° C.) while maintaining a constant flow rate of 1000 mL (see FIG. 1).

[0160] When the mixture of ferrocene and HMDS entered the reaction zone, an aerosol was formed, generating iron particles, which then agglomerated to form an aerosol of catalytic nanoparticles, which were responsible for the decomposition of the precursors and the growth of 1D nanowires via supersaturation from the precursor vapor and subsequent extrusion of 1D nanowires.

[0161] A bluish aerogel of nanowires was then formed. The aerogel was recovered in the reactor as a free-standing SiC nanowire network (see Fig. 2 and Fig. 3). The crystallinity of the nanowires of the resulting nanowire network was characterized by X-ray diffraction analysis (XRD) and Raman spectroscopy (Fig. 4 and Fig. 5). In particular, the Raman spectrum of the nanowire network analyzed in Fig. 4 shows the Raman modes of SiC, indicating that the sample is mainly made of SiC and not other Si- or C-containing materials. Furthermore, the XRD pattern in Fig. 5 indicates that the resulting nanowire network is highly crystalline and mainly formed of cubic and / or hexagonal phases of SiC. In addition, the nanowire dimensions (length and diameter) and network properties were statistically examined by multiple measurements (more than 50) from the data collected from scanning electron microscope (SEM) and transmission electron microscope (TEM).

[0162] Synthesizing SiC nanowire networks at high temperatures (above 1100°C) has two advantages simultaneously: increasing the selective conversion ratio of nanowires in the network and increasing the aspect ratio. The selective conversion ratio refers to the conversion ratio of precursors to nanowires (quasi-spherical particles, amorphous particles, and other materials different from nanowires).

[0163] Figure 6 shows SEM micrographs of SiC nanowire networks obtained at different temperatures: (a) 1200° C., (b) 1250° C., and (c) 1300° C. From these images, the average aspect ratio of the nanowires was calculated from the average of the values ​​obtained by measuring the dimensions of more than 50 nanowires, which includes the following:

number

[0164] As explained above, the aspect ratio of each nanowire is given by the following formula:

number

[0165] Additionally, we determined the average aspect ratio considering both the nanowire and nanoparticle products of the reaction, which gives an indication of the amount of undesirable low aspect ratio quasi-spherical particles. This effective aspect ratio is termed the population-average aspect ratio, which is:

number

[0166] In addition, the volume percentage of crystalline nanowires relative to the total volume of the nanowire network was also determined for each synthesis temperature used.

[0167] The volume percentage of crystalline nanowires relative to the total volume of the nanowire network components was calculated from image analysis of a statistically significant number of electron micrographs (taken with microscopy techniques) in which the nanowires were distinguishable from quasi-spherical particles and other amorphous materials.

[0168] For comparison, Si nanowires were also prepared at 650 °C and 720 °C according to the method described by Schaufele et al. (Mater. Horiz., 2020, 7, 2978-2984). Table I below shows the length, average aspect ratio (S), determined as explained above, of the nanowires obtained by the method of the present invention and by the method described by Schaufele et al. NW ), and S TOTAL values, as well as the crystalline nanowire volume fraction are shown. [Table 1]

[0169] The results show that at reaction temperatures of at least 1100 °C, the proportion and length of nanowires in the samples increased significantly, thus resulting in nanowires with higher aspect ratios. Furthermore, the amount of undesirable low aspect ratio quasi-spherical particles, as derived from the total number-average aspect ratio, was significantly reduced. In addition, the nanowire networks obtained at high temperatures had better mechanical properties and were more robust.

[0170] Example 2 An electrode and battery are developed that includes the nanowire network of the present invention. The nanowire network of Example 1 is coated with a conductive layer of carbon. The carbon-coated nanowire network is then affixed to a metal current collector to form an electrode. This electrode is then assembled into a housing along with a separator, cathode, and electrolyte to form a complete cell.

[0171] The performance of the electrolyte is evaluated by conventional electrochemical measurements under constant current charge-discharge cycles in a half cell (i.e., using lithium as the electrode). When measured at the same current density, the electrodes of the present invention show a higher areal capacity (mAh / cm) compared to a commercial graphite electrode. 2 ) is observed.

Claims

1. 1. A method for producing a network of nanowires, comprising: i. providing a gas flow mixture to a reaction vessel, said gas flow mixture comprising: at least one precursor compound comprising at least one element selected from Si, Ge, Cu, Zn, Cd, Ga, In, As, Se, Ni, Ta, Pt, Mo, W, N, O, Co, Mn, Li and Te, and which is a hydride or an organometallic compound; metallic catalyst particles comprising one or more elements selected from Au, Ag, Cu, Fe, Ni, Ga, Co, Pt, In and Al, the at least one precursor compound is present in the gas stream mixture in a mole fraction (xi) of at least 0.005; The temperature in the reaction vessel is in the range of 1250° C. to 1450° C. The at least one precursor compound decomposes under the temperature in the reaction vessel and grows on the metallic catalyst particles, forming a network of nanowires; The method, wherein the network of nanowires comprises solid nanowires, hollow nanowires, or a mixture thereof.

2. The method of claim 1, wherein the at least one precursor compound decomposes under the temperature in the reaction vessel and grows on the metallic catalyst particles by a vapor-liquid-solid (VLS) method, and / or a solid-liquid-solid (SLS) method, and / or a chemical vapor deposition (CVD) method.

3. The gas stream mixture of step (i) (a) providing a mixture, said mixture comprising: at least one precursor compound comprising at least one element selected from Si, Ge, Cu, Zn, Cd, Ga, In, As, Se, Ni, Ta, Pt, Mo, W, N, Ni, O, Co, Mn, Li, and Te, and which is a hydride or an organometallic compound; a metallic catalyst particle precursor comprising one or more elements selected from Au, Ag, Cu, Fe, Ni, Ga, Co, Pt, In and Al; (b) injecting said mixture into said reaction vessel to form said gas stream mixture of step (i); The method of claim 1 or 2, wherein the compound is produced by

4. said at least one precursor compound comprises at least one element selected from Si, Ge, Pt, Mo, W, Co, Mn, Li and Te; The method of claim 1, wherein said metallic catalyst particles consist of one or more elements selected from Au, Ag, Cu, Fe, Co, and Pt.

5. The method of claim 1 , wherein the at least one precursor compound is a silane or a silane derivative.

6. The gas stream mixture is H ２ The method of claim 1 , comprising:

7. 10. The method of claim 1, wherein the temperature in the reaction vessel ranges from 1260°C to 1400°C.

8. The method of claim 1 , comprising the further step (ii) of recovering the network of nanowires.

9. The method of claim 8, wherein the further step (ii) of recovering the nanowire network is accomplished by spinning and winding the nanowire network onto a bobbin.

10. A nanowire network obtained by the method of claim 1, wherein the nanowire aspect ratio of the nanowire network is at least 300, the nanowire network of the present invention comprises nanowires with a volume of at least 80% of the total volume of the network, the nanowires are entangled, and the nanowire network is free-standing.

11. 11. The nanowire network of claim 10, wherein the aspect ratio of the nanowires is at least 400, the length of the nanowires is at least 10 microns, the nanowires of the nanowire network are solid continuous crystalline nanowires, and the nanowire network of the present invention comprises crystalline nanowires by volume that is at least 80% of the total volume of the network.

12. The nanowire network of claim 10 having a porosity between 60% and 97%.

13. The nanowires are made of Si, SiC, Ge or Si ｘ Ge １－ｘ , and SiO ｘ 11. The nanowire network of claim 10, wherein:

14. A nonwoven material comprising at least two layers of the nanowire network defined in claim 10.

15. A network of nanowires according to claim 10 or a nonwoven material according to claim 14; an electrical connection or current collector; An electrode comprising:

Images