Wick and heat transport device

Abstract

Provided is a wick used to transport heat, the wick containing materials including nanofibers and / or a two-dimensional substance of a material represented by the formula MQaOb (wherein M is at least one element selected from the group consisting of Groups 3, 4, 5, 6, and 7, Q is at least one element (excluding O) selected from the group consisting of Groups 12, 13, 14, 15, and 16, a is 0 or more and 2 or less, and b is greater than 0 and 2 or less).

Description

Wicks and Heat Transport Devices

[0001] The present disclosure relates to a wick and a heat transport device, and more particularly to a wick used for heat transport and a heat transport device that utilizes a phase change of a working fluid.

[0002] Conventionally, heat transport devices that utilize the phase change (more specifically, evaporation and condensation) of a working fluid, such as heat pipes and vapor chambers, are known. These heat transport devices use a wick that transports the liquid working fluid by capillary force (the suction force caused by capillary action).

[0003] For example, Patent Document 1 describes the use of a sintered body of metal particles having an average particle size of 20 μm to 200 μm as a wick. Also, for example, Patent Document 2 describes the use of a fiber-containing porous body in which a carbonaceous porous body is filled in at least a portion of a fiber structure containing carbon fibers and / or oxidized fibers, and in which the pore size distribution of the carbonaceous porous body has at least one peak in a pore size range of 10 μm or less.

[0004] JP 2022-27310 A JP 2020-112326 A

[0005] Hussein O. Badr, et al., "Bottom-up, scalable synthesis of anatase nanofilament-based two-dimensional titanium carbo-oxide flakes", Materials Today (2021) https: / / doi.org / 10.1016 / j.mattod.2021.10.033

[0006] The heat transport device described above uses a housing that is at least partially thermally conductive, a wick disposed within the housing, and a working fluid sealed in. Inside the housing, the working fluid evaporates in a relatively high-temperature portion where heat is supplied from the outside, the gaseous working fluid moves within the housing, and condenses in a relatively low-temperature portion, thereby releasing heat to the outside, and the liquid working fluid is transported (returned) to the relatively high-temperature portion by the capillary force of the wick.

[0007] In recent years, due to the miniaturization of electronic devices into which heat transport devices can be incorporated, further improvements in the heat transport performance of heat transport devices are required. Conventionally, the speed at which a working fluid in a liquid state is transported by the capillary force of a wick is generally lower than the speed at which a working fluid in a gaseous state moves within a housing, and the heat transport performance of a heat transport device can be limited by the speed at which the working fluid in a liquid state is transported by the capillary force of the wick. To improve the heat transport performance of a heat transport device, it is desirable to have a faster transport speed of the working fluid in a liquid state in the wick.

[0008] An object of the present disclosure is to provide a novel wick that has a high transfer rate of a liquid working fluid. Another object of the present disclosure is to provide a novel heat transport device that uses such a wick.

[0009] According to one aspect of the present disclosure, there is provided a wick for use in heat transport, the wick having the following formula: MQ ａ O ｂ (wherein M is at least one element selected from the group consisting of Groups 3, 4, 5, 6, and 7; Q is at least one element selected from the group consisting of Groups 12, 13, 14, 15, and 16 (excluding O); a is 0 or more and 2 or less; and b is 0 or more and 2 or less.

[0010] According to another aspect of the present disclosure, there is provided a heat transport device that utilizes a phase change of a working fluid, the heat transport device including: a housing having an internal space; the wick disposed in the housing; and a working fluid sealed in the housing in a state capable of contacting the wick.

[0011] According to the present disclosure, a novel wick capable of transferring a liquid working fluid at a high speed is provided, and further, according to the present disclosure, a novel heat transport device using such a wick is provided.

[0012] 1 is a schematic cross-sectional view of a heat transport device according to one embodiment of the present disclosure, and shows an XRD pattern of the material (TiCO) produced in Example 1. 2 is a FE-SEM image of the material (TiCO) produced in Example 1.

[0013] The wick and the heat transport device according to the embodiments of the present disclosure will be described in detail below, but the present disclosure is not limited to these embodiments.

[0014] (Embodiment 1: Wick) This embodiment relates to a wick. In this disclosure, "wick" refers to a member used for heat transport. More specifically, "wick" refers to a member capable of transporting a working fluid in a liquid state by capillary force.

[0015] In this embodiment, the wick includes a material containing nanofibers and / or a two-dimensional material. In this disclosure, the mere mention of "material" refers to a "material containing nanofibers and / or a two-dimensional material" (in other words, a material containing at least one of nanofibers and a two-dimensional material). In this embodiment, a material containing nanofibers and / or a two-dimensional material typically refers to a material that is solid and does not contain a binder or the like (e.g., a polymer). In a narrower sense, a material containing nanofibers and / or a two-dimensional material can refer to a material that is substantially composed of at least one of nanofibers and a two-dimensional material (which may include other objects, impurities, etc. that may be unavoidably mixed in). However, materials containing nanofibers and / or a two-dimensional material are not limited to these.

[0016] The material contained in the wick of this embodiment is a nanofiber (or nanofilament, the same applies hereinafter) and / or two-dimensional material of a predetermined material (substance). The predetermined material that can be used in this embodiment is represented by the following formula (1): MQ ａ O ｂ ... (1) (In the formula, M is at least one element selected from the group consisting of Groups 3, 4, 5, 6 and 7, and may include at least one element selected from the group consisting of so-called early transition metals, for example, Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and Mn, and preferably at least one element selected from the group consisting of Ti, V, Cr, Mo and Mn; Q is at least one element selected from the group consisting of Groups 12, 13, 14, 15 and 16 (excluding O), and may include at least one element selected from the group consisting of B, C, N, Si, P and S; a is 0 or more and 2 or less; and b is 0 or more and 2 or less.)

[0017] The above-mentioned predetermined material will be hereinafter also referred to simply as "MQO." Examples of MQO include TiO ２ , TiCO, TiCON, VO ２ , VCO, VCON, CrO ２ , CrCO, CrCON, MoO ２ , MoCO, MoCON, MnO ２ , MnCO, MnCON, etc. For example, in formula (1), M may be Ti and Q may be C. Also, for example, in formula (1), a may not be 0.

[0018] The predetermined material may typically have a peak in an X-ray diffraction (XRD) pattern where the diffraction angle 2θ is in the range of 2° to 10°.

[0019] MQO has a crystal structure different from the hexagonal system. Although the present embodiment is not bound by any theory, the crystal structure of MQO is currently considered to be anatase type, lepidocrocite type, or a mixture of these. For example, the crystal structure of MQO may be lepidocrocite type.

[0020] MQO can be produced, for example, using a first raw material and a second raw material as follows: The first raw material contains at least M, and the second raw material contains at least Q, and the first raw material and the second raw material are capable of reacting in a protic solvent to produce MQO.

[0021] As the first raw material, a material represented by the following formula (2) can be used: M ｃ A １ ｄ ... (2) (wherein M is as defined above, A １ is at least one element selected from the group consisting of Groups 12, 13, 14, 15, and 16, and may include, for example, at least one element selected from the group consisting of B, C, N, O, Si, P, and S; and c and d are each independently 1 to 5. However, the material represented by formula (2) must be different from the product MQO. The material represented by formula (2) may typically have no peak in its X-ray diffraction (XRD) pattern in a diffraction angle 2θ range of 2° to 10°.

[0022] Examples of the first raw material represented by formula (2) include TiB ２ , TiB, TiC, TiN, TiO ２ , Ti ５ Si ３ , Ti ２ SbP, VO ２ , V ２ O ４ , NbC, Nb ２ O ５ , MoO ２ , MoO ３ , MoS ２ , MnO ２ , Mn ３ O ４ , MnCO ３MnO that can be used as the first raw material ２ In the XRD pattern, the material has a peak near 2θ=13° and no peak in the 2θ range of 2° or more and 10° or less.

[0023] Alternatively, or in addition to the above, a material represented by the following formula (3) (hereinafter also simply referred to as a "MAX phase" or "MAX raw material") may be used as the first raw material. ｍ A ２ X ｎ ...(3) (wherein M is as defined above, X is at least one element selected from the group consisting of C and N, n is 1 or more and 4 or less, m is greater than n and 5 or less, A ２ is at least one element selected from the group consisting of Groups 12, 13, 14, 15 and 16, and is usually a Group A element, typically Group IIIA and Group IVA, and more particularly may include at least one element selected from the group consisting of Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, S and Cd, preferably Al). The MAX phase is ｍ X ｎ (which may have a crystal lattice where each X is located in an octahedral array of M), ２ The MAX phase has a crystal structure in which layers composed of atoms are located. When m=n+1, typically, one layer of X atoms is located between each of n+1 layers of M atoms (collectively referred to as "M ｍ X ｎ layer), and the layer next to the n+1-th layer of M atoms is A ２ Atomic layer ("A ２ The MAX phase has repeating units arranged in "atomic layers." However, the MAX phase is not limited to this.

[0024] Examples of the first raw material represented by formula (3) include Ti ３ AlC ２ , Ti ３ GaC ２ , Ti ３ SiC ２ These include:

[0025] As the first raw material, the material represented by formula (2) and the material represented by formula (3) may be used together (for example, as a mixture).

[0026] As the second raw material, an ionically bondable substance having a carbon-containing group can be used. The ionically bondable substance having a carbon-containing group contains C. Examples of the ionically bondable substance include ammonium salts, phosphates, and sulfates.

[0027] More specifically, a quaternary ammonium salt may be used as the second raw material. Examples of quaternary ammonium salts include tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH or TBAOH), benzyltrimethylammonium hydroxide, tetrabutylammonium fluoride (TBAF), tetrabutylammonium chloride (TBACl), tetrabutylammonium bromide (TBAB), tetrabutylammonium iodide (TBAI), benzyltriethylammonium chloride (BTEAC), hexadecyltrimethylammonium bromide, cetyltrimethylammonium bromide (CTAB), benzethonium chloride, benzalkonium chloride, and cetylpyridinium chloride (CPC). Among these, TMAH and TBAOH are preferred.

[0028] Alternatively, or in addition to the above, other ion-binding substances containing P and / or S, etc. may be used as the second raw material.

[0029] The protic solvent may be any solvent capable of at least partially dissolving the first and second raw materials, and may be, in particular, an aqueous solvent. Examples of the protic solvent include water, alcohol (e.g., ethanol, 1-propanol, isopropanol), and carboxylic acids (e.g., acetic acid and formic acid). The aqueous solvent may be composed of water and, optionally, a liquid substance compatible with water (e.g., a protic solvent other than water), and is preferably water.

[0030] The first and second raw materials are reacted in a protic solvent. The second raw material can be added to the protic solvent in advance. The ratio of the second raw material to the total of the protic solvent and the second raw material can be, for example, 5% by mass or more, particularly 20% by mass or more, and / or, for example, 80% by mass or less, particularly 50% by mass or less. The first raw material can be further added to the protic solvent to which the second raw material has been added, and mixed. In this mixture, a reaction to produce MQO proceeds. The temperature (reaction temperature) of the mixture (which may contain the reaction product) can be, for example, 15°C or more, particularly 40°C or more, and / or, for example, 100°C or less, particularly 80°C or less. The mixing time (reaction time) can be, for example, one day or more, particularly two days or more, and / or, for example, 10 days or less, particularly 7 days or less. Mixing can be performed, for example, by rotating a magnetic stirrer placed in a container while maintaining the reaction temperature using a hot plate stirrer and a warm water bath. However, the treatment operations and conditions (temperature, time, etc.) that can cause the reaction to proceed are not limited to those described above, and may be selected appropriately depending on the first raw material, second raw material, protic solvent, etc. that are used.

[0031] The above reaction produces MQO, which may eventually grow into MQO nanofibers and then MQO nanoflakes. While not limiting the present disclosure, the resulting MQO nanofibers may be in the form of nanoribbons extending in nanoscale widths. Alternatively, multiple MQO nanofibers (e.g., nanoribbons) may bond and / or integrate with each other to grow into two-dimensionally extending nanoflakes. Alternatively, multiple MQO nanoflakes may overlap each other (e.g., by van der Waals forces) to form stacks. While the present disclosure is not bound by any theory, the production and growth of MQO may be thought of as a bottom-up synthesis reaction (see, for example, Non-Patent Document 1).

[0032] In the present disclosure, MQO is a solid content. MQO may typically be in the form of particles (or powder).

[0033] The mixture after the reaction (also referred to as a reaction mixture) may be subjected to appropriate post-treatment, such as washing, impact (including shear force), drying (e.g., freeze-drying or heat drying), or pulverization.

[0034] The washing may be carried out using a protic solvent. The same explanation as above may be applied to the protic solvent, and the protic solvent may be washed with, for example, water or alcohol. After washing, a separation operation (centrifugation and / or decantation) may be carried out. The washing and separation operations may be repeated until the pH of the supernatant after centrifugation is, for example, 8 or less.

[0035] Optionally, instead of or in addition to the above washing, washing may be carried out using an aqueous solution of a metal salt. The metal salt may be, for example, a halide (fluoride, chloride, bromide, iodide) of an alkali metal (Li, Na, K, etc.), typically LiCl, NaCl, KCl, etc. Specifically, washing may be carried out using, for example, an aqueous solution of a metal salt having a molar concentration of 1 to 10. After washing, a separation operation (centrifugation and / or decantation) may be carried out. In this case, too, the washing and separation operations may be repeated as necessary until the pH of the supernatant after centrifugation becomes, for example, 8 or less.

[0036] Impact such as vibration and / or ultrasound may be applied during and / or after washing. This can promote the dispersion of MQO particles (e.g., nanofibers / nanoflakes, hereinafter the same). If the MQO particles are aggregated, they can be broken down. This effect is particularly pronounced when impact is applied during washing with an aqueous solution of a metal salt (it is believed that metal cations derived from the metal salt penetrate into the gaps between the aggregates and break them down). Impact can be applied using, for example, one or more of a handshake, an automatic shaker, a mechanical shaker, a vortex mixer, a homogenizer, an ultrasonic bath, etc.

[0037] Since the MQO particles are a solid component, a separation operation can be carried out at any appropriate time to remove unnecessary liquid components, if any. As a final separation operation, for example, a drying operation, typically freeze-drying or thermal drying, may be carried out. Freeze-drying can be carried out, for example, by freezing a mixture containing the MQO particles and a liquid component at any appropriate temperature (e.g., −40° C.) and then drying under reduced pressure. Thermal drying can be carried out, for example, by drying a mixture containing the MQO particles and a liquid component at a temperature of 25° C. or higher (e.g., 200° C. or lower) under atmospheric pressure or under reduced pressure. Pulverization can be carried out using, for example, a mortar and pestle combination, an IKA mill, or the like, without particular limitation. Pulverization may also be carried out after drying.

[0038] As a result, MQO particles can be obtained as a material containing MQO, such as nanofibers (and in some cases aggregates of MQO nanofibers, such as MQO nanoflakes; these are also collectively referred to as "MQO nanofibers, etc.").

[0039] Although MQO is represented by formula (1), a material containing MQO (typically, MQO particles) does not necessarily have to consist solely of the constituent elements of formula (1). While not limiting the present disclosure, a material containing MQO may optionally contain protons and / or metal cations. Furthermore, although not limiting the present disclosure, a material containing MQO may optionally have at least one type selected from the group consisting of hydroxyl groups, chlorine atoms, oxygen atoms, hydrogen atoms, and nitrogen atoms as a modification or terminal T present on its surface. Furthermore, a material containing MQO (typically, MQO particles) may have two or more layers, and at least one type selected from the group consisting of ammonium ions (e.g., quaternary ammonium cations) and metal cations (e.g., alkali metal ions, alkaline earth metal ions) may be present between these layers.

[0040] Materials containing MQO, such as MQO nanofibers, may contain unreacted first and / or second raw materials as impurities, and may also contain substances derived from the first, second, and / or protic solvents. For example, when a quaternary ammonium salt is used as the second raw material, N may be present (residual) in any form in materials containing MQO, such as MQO nanofibers. While not limiting this embodiment, materials containing MQO may contain ammonium ions or tetramethylammonium ions. Furthermore, for example, when a MAX raw material is used as the first raw material, materials containing MQO in this disclosure may contain a relatively small amount of residual A atoms, for example, 10% by mass or less relative to the original A atoms. The amount of residual A atoms may be preferably 8% by mass or less, more preferably 6% by mass or less. However, even if the amount of residual A atoms exceeds 10% by mass, this may not be a problem depending on the conditions of use, etc.

[0041] To obtain a material containing MQO, such as MQO nanofibers, with higher purity, it is preferable to repeat washing and centrifugation multiple times and recover the supernatant after the final centrifugation. Such a supernatant can be used as is, appropriately diluted with a liquid medium, or dried and then mixed with a liquid medium to form a slurry containing MQO particles, such as MQO nanofibers.

[0042] The wick of this embodiment can be manufactured by shaping (molding, cutting, etc.) a material containing MQO, such as MQO nanofibers, into the desired shape and dimensions by any appropriate method. Typically, the wick of this embodiment may be a fibrous structure formed using MQO nanofibers or the like. Such a fibrous structure can be manufactured, for example, by applying a slurry containing MQO nanofibers to a substrate by any appropriate method (e.g., filtration, spraying, bar coating, spin coating, immersion, etc.), drying, and then removing the substrate. The liquid medium contained in the slurry can be appropriately selected, and examples thereof include protic solvents (the same explanation as above may apply), aprotic solvents (e.g., tetrahydrofuran, methylene chloride, acetonitrile, acetone, N,N-dimethylformamide, dimethyl sulfoxide, etc.), and nonpolar solvents (e.g., hexane, benzene, toluene, diethyl ether, chloroform, ethyl acetate), etc.

[0043] The wick of this embodiment is obtained in this manner. The shape and dimensions of the wick of this embodiment can be appropriately selected depending on the desired application.

[0044] As described above, a material containing MQO may typically have a peak in an X-ray diffraction (XRD) pattern where the diffraction angle 2θ is in the range of 2° to 10° inclusive. Although the present disclosure is not bound by any theory, it is believed that the fact that a material containing MQO has a peak in an XRD pattern where 2θ is in the range of 2° to 10° inclusive means that such MQO has a crystal structure different from that of well-known metal oxides.

[0045] In the present disclosure, an XRD pattern is a pattern (vertical axis represents intensity, horizontal axis represents 2θ) obtained by scanning in the θ-axis direction with an XRD analyzer using CuKα radiation (approximately 1.54 Å) as characteristic X-rays, and may also be referred to as an "XRD profile." Peaks in the XRD pattern can be identified visually or using software used with the XRD analyzer. To measure the XRD pattern as accurately as possible in the low 2θ angle range, it is preferable to place a c-axis-oriented MQO film in the XRD analyzer (for example, as in the examples described below, a free-standing film obtained by removing the filter after suction filtration is placed with the surface that was in contact with the filter facing downward).

[0046] Although this embodiment is not limited to this embodiment, for example, the material of this embodiment (more specifically, MQO) has a Raman shift of at least 275 to 295 cm in a Raman spectrum using a laser with a wavelength of 514 nm. －１ , 435-455cm －１ , and 665-745 cm －１ It may have a peak at the position

[0047] Although this embodiment is not limited to this embodiment, for example, the material of this embodiment (more specifically, MQO) has a Raman shift of 140 to 160 cm in a Raman spectrum using a laser with a wavelength of 514 nm. －１ , 275-295cm －１ , 435-455cm －１ , and 665-745 cm －１ It may have a peak at a position of 140 to 160 cm －１ is the peak of the anatase type.

[0048] Although this embodiment is not limited thereto, for example, the material of this embodiment (more specifically, MQO) has a crystal structure of anatase type, lepidocrocite type, or a mixture of these. More preferably, it has a crystal structure of lepidocrocite type.

[0049] Although this embodiment is not limited to this embodiment, for example, the material of this embodiment (more specifically, MQO) has a Raman shift of at least 275 to 295 cm in a Raman spectrum using a laser with a wavelength of 514 nm. －１ , 435-455cm －１ , and 665-745 cm －１ and when the intensities of the respective peaks are X, Y, and Z, X is the largest.

[0050] Although this embodiment is not limited thereto, more preferably, the material of this embodiment (more specifically, MQO) has a Raman shift of at least 180 to 200 cm in a Raman spectrum using a laser with a wavelength of 514 nm. －１ , 275-295cm －１ , 375-395cm －１ , 435-455cm －１ , and 665-745 cm －１ and when the intensities of the respective peaks are V, X, Y, Z, and W, X is the largest.

[0051] In this disclosure, the Raman spectrum is measured with a Raman spectrometer using a 514 nm laser as an excitation light source (the vertical axis represents intensity, and the horizontal axis represents Raman shift). Peaks in the Raman spectrum can be identified visually or by using software used with the Raman spectrometer.

[0052] The particle size of the MQO particles may be, for example, 0.01 nm or more, in particular 0.1 nm or more, or even 1 nm or more, and / or may be, for example, less than 1000 nm, in particular 100 nm or less, or even 50 nm or less. Such particles may also be referred to as nanoparticles.

[0053] The particle form of MQO is nanofibers and / or two-dimensional materials. The two-dimensional materials include one or more of nanoflakes and stacks of nanoflakes. In this embodiment, the two-dimensional materials are not limited to only nanoflakes and stacks of nanoflakes.

[0054] According to this embodiment, there is provided a wick comprising a material containing MQO, typically MQO particles (e.g., nanofibers / nanoflakes), for example, MQO nanofibers (and optionally aggregates of MQO nanofibers, e.g., MQO nanoflakes). For example, the MQO nanofibers have a hydrophilic surface and a cross-sectional outer dimension on the nanometer order. Such a wick comprising MQO nanofibers has a high force for drawing (e.g., suction force) a liquid working fluid by capillary action, and is therefore capable of transporting (e.g., suctioning) the liquid working fluid at a high speed. This is thought to be because the cross-sectional outer dimension on the nanometer order increases the volume density of the nanofibers in the wick, forming narrow spaces (flow paths for the working fluid) due to gaps between the nanofibers and increasing the total surface area of ​​the nanofibers that can come into contact with the liquid working fluid, and the hydrophilic surface makes it easier for the liquid working fluid (typically, but not limited to, water) to wet and spread over the surface of the MQO nanofibers.

[0055] In the present disclosure, the term "nanofiber" of MQO refers to a solid object extending in the longitudinal direction, the cross-sectional dimensions of which (cross-sectional dimensions) perpendicular to the longitudinal direction are on the nano-order (i.e., 1 nm or more and less than 1000 nm) or even smaller, on the sub-nano-order (less than 1 nm, for example, 0.1 nm or more and less than 1 nm). The longitudinal length of the MQO nanofiber is not particularly limited. That is, the longitudinal length of the nanofiber is not limited to the nano-order (i.e., 1 nm or more and less than 1000 nm) and may be on the micron-order (1 μm or more and less than 1000 μm). The cross-sectional dimensions of the nanofiber may be, for example, 0.1 nm or more, particularly 1 nm or more, and may be, for example, 100 nm or less, particularly 50 nm or less, and preferably 15 nm or less. A wick including an MQO nanofiber or the like having such a small cross-sectional dimension can transport a liquid working fluid at a higher speed. Although not limiting the present embodiment, the above-described manufacturing method makes it possible to produce MQO nanofibers having such small cross-sectional dimensions.

[0056] In the present disclosure, the cross-sectional outer dimension of an MQO nanofiber refers to the shortest distance passing through the center of a cross section transverse to the longitudinal direction of the MQO nanofiber. The cross-sectional shape of an MQO nanofiber is not particularly limited, but can be approximated, for example, by a rectangle (rectangle, square, etc.) or an ellipse (flattened circle, perfect circle, etc.). When an MQO nanofiber is in the form of a nanoribbon, the cross-sectional shape can be approximated by a rectangle, and the cross-sectional outer dimension can correspond to the length of the short side of the rectangle. When an MQO nanofiber is in the form of a nanofilament, the cross-sectional shape can be approximated by a flattened circle, and the cross-sectional outer dimension can correspond to the length of the short diameter of the flattened circle.

[0057] The BET specific surface area of ​​a material containing MQO, such as MQO nanofibers, is not particularly limited, but is, for example, 10 m ２ / g or more 500m ２ The BET specific surface area is calculated using the BET equation from an isothermal adsorption curve of nitrogen gas or other suitable gas (e.g., krypton (Kr) gas, etc.) at liquid nitrogen temperature (77 K) by an adsorption method using nitrogen gas or other suitable gas.

[0058] In the present disclosure, the term "two-dimensional material" refers to a solid object having a two-dimensionally extending surface (also referred to as a plane or two-dimensional sheet surface) and a thickness that is relatively small compared to the maximum dimension of the surface (which may correspond to the "in-plane dimension" of a particle), with the thickness being on the nano-order (i.e., 1 nm or more but less than 1000 nm) or even smaller, on the sub-nano-order (less than 1 nm, for example, 0.1 nm or more but less than 1 nm). The in-plane dimension is not limited to the nano-order (i.e., 1 nm or more but less than 1000 nm) and may be on the micron-order (1 μm or more but less than 1000 μm). As described above, two-dimensional materials include one or more of nanoflakes and stacks of nanoflakes. Nanoflakes may also be referred to as nanosheets or two-dimensional (nano)sheets. The thickness of one layer of nanoflakes may be, for example, 0.01 nm or more, particularly 0.8 nm or more, and may be, for example, 20 nm or less, particularly 3 nm or less. The in-plane dimensions of the nanoflakes may be, for example, 0.1 μm or more, in particular 1 μm or more, and may be, for example, 200 μm or less, in particular 40 μm or less. The nanoflakes may be composed of an aggregate of nanofibers.

[0059] The stack of nanoflakes may also be referred to as a multi-layer MQO. The distance (interlayer distance or gap size) between two adjacent nanoflakes (or two adjacent layers of MQO) is not particularly limited.

[0060] The above-mentioned dimensions can be determined as a number-average dimension (number average of at least 40) based on a photograph observed with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an atomic force microscope (AFM) (processed by a method such as focused ion beam (FIB) if necessary), or as a distance in real space calculated from the position in reciprocal lattice space of the (002) plane measured by X-ray diffraction (XRD). In the present disclosure, for example, the cross-sectional outer dimensions of an MQO nanofiber can be determined by exposing a cross section of a wick containing an MQO nanofiber by a method such as focused ion beam (FIB), photographing the exposed cross section with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), extracting at least 40 cross sections that cross the longitudinal direction of the MQO nanofiber from the obtained image, and calculating the number-average outer dimensions of those cross-sectional outer dimensions.

[0061] However, it should be noted that in the present disclosure, the MQO is not limited to the above forms and may have any suitable form.

[0062] (Embodiment 2: Heat Transport Device) This embodiment relates to a heat transport device. In this disclosure, the term "heat transport device" refers to a device that transports heat by utilizing a phase change of a working fluid. The phase change of the working fluid refers to evaporation and condensation.

[0063] 1 , a heat transport device 20 of this embodiment includes a housing 1 having an internal space, a wick 3 disposed within the housing 1, and a working fluid (not shown) sealed within the housing 1 in a state in which the working fluid can come into contact with the wick 3. The wick 3 used is the same as that described in the first embodiment.

[0064] 1 exemplarily illustrates a case in which the heat transport device 20 is a loop heat pipe, although this is not intended to limit the present embodiment. In the illustrated example, the housing 1 includes an evaporator 11, a condenser 13, and a gas flow path 15 and a liquid flow path 17 connecting these components, respectively. The evaporator 11, the condenser 13, the gas flow path 15, and the liquid flow path 17 integrally form the internal space of the housing 1. The wick 3 is disposed within the evaporator 11. A working fluid (not shown) is sealed within the internal space of the housing 1. At least the evaporator 11 and the condenser 13 of the housing 1 are made of a thermally conductive material (e.g., metal).

[0065] Within the housing 1, the working fluid evaporates in the evaporator 11 (a relatively high-temperature portion) to which heat is supplied from the outside (heat source). The gaseous working fluid moves through the gas flow path 15 and condenses in the condenser 13 (a relatively low-temperature portion), thereby releasing heat to the outside. The liquid working fluid is transported (returned) to the evaporator 11 through the liquid flow path 17 by the capillary force of the wick 3. As a result, the working fluid circulates within the housing 1 while undergoing a phase change. In FIG. 1, the flow of the working fluid is schematically indicated by dotted arrows, and the supply of heat from the outside (heat input) and the heat dissipation to the outside (heat output) are schematically indicated by dashed arrows.

[0066] According to this embodiment, the heat transport device 20 uses the wick 3 described above in embodiment 1, so that the working fluid in a liquid state can be transported at a high speed, resulting in high heat transport performance and improving the maximum heat transport amount of the heat transport device 20.

[0067] In the example shown in Figure 1, the heat transport device 20 is a loop-type heat pipe, but the heat transport device of this embodiment may be one that applies the configuration of a known heat transport device equipped with a wick (e.g., a tubular heat pipe, a vapor chamber, etc.), except that it uses the wick 3 described above in embodiment 1.

[0068] Although the wick and the heat transport device according to an embodiment of the present disclosure have been described in detail above, various modifications of the present disclosure are possible. Note that the wick of the present disclosure may be manufactured by a method different from the manufacturing method of the above-described embodiment.

[0069] Example 1 Example 1 relates to the wick of embodiment 1, which uses TiCO nanofibers.

[0070] Preparation of a slurry containing TiCO nanofibers First, titanium diboride (TiB ２ 1 g of ethanol (Alfa Aesar) and 30 mL of 25% by weight tetramethylammonium hydroxide (TMAH) aqueous solution (Tokyo Chemical Industry Co., Ltd.) were added to the container. A stirrer tip with a length (35 mm) approximately equal to the inner diameter of the circular bottom of the container was placed therein. The container was maintained at 50 °C in a water bath, and the mixture in the container was stirred with the stirrer tip for 120 hours, allowing the reaction to proceed. Next, the reaction mixture in the container was transferred to a 50 mL centrifuge tube using a stainless steel spatula (without adding a liquid medium such as ethanol or water). The solids were sedimented by centrifugation at 3500 G for 5 minutes. (i) After centrifugation, the supernatant was discarded, (ii) 40 mL of ethanol (Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the remaining sediment in the centrifuge tube, and the mixture was shaken for 5 minutes (reslurry), and (iii) the centrifugation was repeated under the same conditions as above. These steps (i) to (iii) were repeated until the pH of the supernatant became 8 or less. After three repetitions, the pH of the supernatant became 8 or less, so the supernatant was discarded and the repetition process was terminated. 40 mL of pure water was added to the remaining sediment in the centrifuge tube, and the mixture was shaken and stirred for 15 minutes using an automatic shaker. Then, the mixture was centrifuged at 3500 G for 30 minutes using a centrifuge, and the supernatant was collected as a sample slurry. The resulting sample slurry corresponds to a slurry containing TiCO nanofibers (see the analysis results below).

[0071] - Preparation of wick The sample slurry prepared above was suction filtered overnight using a Nutsche filter. A membrane filter (Durapore, pore size 0.45 μm, manufactured by Merck Ltd.) was used as the suction filtration filter. After suction filtration, the precursor film on the filter was dried overnight at 80 ° C in a vacuum oven, and the filter was removed to obtain a free-standing film. The obtained free-standing film was cut into a rectangle to obtain a wick sample with a width (W) of 1 cm, a length (L) of 2 cm, and a thickness (T) of 100 μm.

[0072] Wick evaluation The wick sample prepared above was placed vertically in a petri dish containing water with the WT surface (1 cm x 100 μm) at the top and bottom. When the sample was immersed in water to a depth of about 1 mm, the sample absorbed water to the top at a rate of 4 mm / s. From this result, it was found that the volume of water absorbed by the wick sample per unit time and per unit area was 4 x 10 －３ m ３ / (m ２ s), so the mass of water absorbed per unit time and unit area is 4 kg / (m ２ s) (specific gravity of water: 1000 kg / m ３ Since the heat of evaporation of water per unit mass at 25°C is 2442 kJ / kg, the amount of heat that this wick sample can remove by evaporation of water at 25°C is 9768 kW / m ２ That is, the wick sample of Example 1 has a water transport speed of 4 mm / s and a water heat transport performance of about 10 at 25°C. ４ kW / m ２ It was.

[0073] Analysis: The freestanding film obtained in the same manner as above was analyzed by X-ray photoelectron spectroscopy (XPS). Peaks corresponding to Ti 2p, C 1s, O 1s, and N 1s were observed in the obtained XPS spectrum, and therefore Ti, C, O, and N were detected. Since N is thought to be a residual component of the raw material TMAH, the material of the freestanding film is thought to be composed of Ti, C, and O. Furthermore, the XRD profile of the freestanding film obtained in the same manner as above was measured using an XRD device (MiniFlex, manufactured by Rigaku Corporation) (characteristic X-rays: CuKα = 1.54 Å). The obtained XRD pattern is shown in Figure 2. As can be seen from Figure 2, this material had a peak at 2θ = 7.26°.

[0074] Furthermore, 0.01 g of a slurry containing TiCO nanofibers obtained in the same manner as above and 1 g of pure water were added to a centrifuge tube and the mixture was shaken and stirred for 5 minutes using an automatic shaker. The resulting slurry was then dropped onto an alumina porous substrate (manufactured by Cytiva), and the TiCO nanofibers were observed using an FE-SEM (S-4800, manufactured by Hitachi High-Technologies Corporation). An FE-SEM image is shown in Figure 3. As can be seen from Figure 3, this material had a cross-sectional outer dimension of approximately 5 nm.

[0075] Comparative Example 1 Comparative Example 1 relates to a wick using particles of MXene, a type of two-dimensional material.

[0076] Preparation of MAX particles (precursor of MXene particles) TiC powder, Ti powder, and Al powder (all manufactured by Kojundo Chemical Laboratory Co., Ltd.) were mixed in a molar ratio of 2:1:1 in a ball mill containing zirconia balls for 24 hours. The resulting mixed powder was fired at 1350°C for 2 hours in an Ar atmosphere. The fired body (block) thus obtained was pulverized with an end mill to a maximum size of 40 μm or less. As a result, TiC powder was obtained as MAX particles. ３ AlC ２ particles were obtained.

[0077] Precursor etching (ACID method) Ti prepared by the above method ３ AlC ２ Using particles (powder), etching was performed under the following etching conditions to remove Ti３ AlC ２ A solid-liquid mixture (slurry) containing solid components derived from the powder was obtained. (Etching conditions) Precursor: Ti ３ AlC ２ (Sieved through a 45 μm mesh) Etching solution composition: 49% HF 6 mL H ２ O 18 mL HCl (12 M) 36 mL Precursor input amount: 3.0 g Etching container: 100 mL Eye Boy Etching temperature: 35°C Etching time: 24 h Stirrer rotation speed: 400 rpm

[0078] Washing after etching The above slurry was divided into two parts and placed in two 50 mL centrifuge tubes, respectively. After centrifuging at 3500 G using a centrifuge, the supernatant was discarded. 40 mL of pure water was added to the remaining precipitate in each centrifuge tube, and the tubes were centrifuged again at 3500 G to separate and remove the supernatant. This operation was repeated 11 times. After the final centrifugation, the supernatant was discarded, and Ti ３ C ２ T ｘ - Water medium clay was obtained.

[0079] Li intercalation Ti prepared by the above method ３ C ２ T ｘ The clay was stirred for 12 hours at 20°C to 25°C under the following conditions using LiCl as the Li-containing compound, and the mixture was subjected to Li intercalation. (Li intercalation conditions) ３ C ２ T ｘ - Water medium clay (MXene after washing): solid content 0.75 g LiCl: 0.75 g Intercalation container: 100 mL Eye Boy Temperature: 20 ° C or higher and 25 ° C or lower (room temperature) Time: 10 h Stirrer rotation speed: 800 rpm

[0080] Delamination The above Ti ３ C ２ T ｘ(i) 40 mL of pure water was added to the water medium clay, followed by stirring for 15 minutes on a shaker. (ii) The mixture was centrifuged at 3,500 G, and (iii) the supernatant was collected as a single-layer MXene-containing solution. These steps (i) to (iii) were repeated a total of four times to obtain a single-layer MXene-containing supernatant. This supernatant was then centrifuged at 4,300 G for two hours using a centrifuge, after which the supernatant was discarded, yielding a single-layer / few-layer MXene-containing clay as a single-layer / few-layer MXene-containing sample.

[0081] Preparation of a slurry containing MXene particles: This MXene-containing clay and pure water were mixed in appropriate amounts to prepare a sample slurry with a solids concentration (MXene particle concentration) of 34 mg / mL. The resulting sample slurry corresponds to a slurry containing MXene particles (MXene-water dispersion).

[0082] - Preparation of wick A wick sample having a width (W) of 1 cm, a length (L) of 2 cm, and a thickness (T) of 100 μm was obtained in the same manner as in Example 1, except that the sample slurry prepared above was used.

[0083] Wick Evaluation The wick sample prepared above was placed vertically in a petri dish containing water with the WT surface (1 cm × 100 μm) at the top and bottom ends, and immersed in water to a depth of about 1 mm. However, it was not able to absorb any water at all (absorption height: 0 mm).

[0084] Comparative Example 2 Comparative Example 2 relates to a wick using a sintered body (porous metal sintered body) of metal powder (copper powder).

[0085] Wick Preparation: Copper powder with an average particle size D50 of 50 μm was used as the metal powder, and acrylic resin (binder) and copper powder were mixed at a volume ratio of 1:1. The resulting mixture was heat-treated at 400°C for 1 hour to burn off the acrylic resin, resulting in a porous metal sintered body. The resulting porous metal sintered body was cut to obtain a wick sample with a width (W) of 1 cm, a length (L) of 2 cm, and a thickness (T) of 100 μm.

[0086] Wick evaluation: The wick sample prepared above was placed vertically in a petri dish filled with water, with the WT surface (1 cm x 100 μm) at the top and bottom. When the sample was immersed in water to a depth of about 1 mm, the water was absorbed to the top at a speed of 0.5 mm / s. From this result, it was found that the wick sample of Comparative Example 2 had a water transport speed of 0.5 mm / s, and by calculation similar to that of Example 1, the heat transport performance of water at 25°C was about 10 ３ kW / m ２ It was.

[0087] Comparative Example 3 Comparative Example 3 relates to a wick using a sintered body (porous metal sintered body) of metal powder (titanium powder).

[0088] - Preparation of wick A wick sample having a width (W) of 1 cm, a length (L) of 2 cm, and a thickness (T) of 100 μm was obtained in the same manner as in Comparative Example 2, except that titanium powder having an average particle size D50 of 50 μm was used as the metal powder.

[0089] The wick samples prepared above were evaluated in the same manner as in Comparative Example 2. Water was absorbed to the upper end surface at a speed of 0.5 mm / s. From these results, it was found that the wick sample of Comparative Example 3 had a water transport speed of 0.5 mm / s and a water heat transport performance of approximately 10 at 25°C. ３ kW / m ２ It was.

[0090] The wick of the present disclosure can be used to transport a working fluid by capillary force in a heat transport device that utilizes a phase change of the working fluid. The heat transport device of the present disclosure can be incorporated into an electronic device and used to release (remove) heat from a heat source of the electronic device. However, the wick and heat transport device of the present disclosure can be used for any suitable application other than these.

[0091] <1> A wick used for heat transport, having the following formula: MQ ａ O ｂ(wherein M is at least one element selected from the group consisting of Groups 3, 4, 5, 6, and 7; Q is at least one element selected from the group consisting of Groups 12, 13, 14, 15, and 16 (excluding O); a is 0 to 2 inclusive; and b is 0 to 2 inclusive). <2> The wick according to <1>, wherein the material of the nanofiber has a peak in an X-ray diffraction pattern at a diffraction angle 2θ in the range of 2° to 10° inclusive. <3> The wick according to <1> or <2>, wherein the nanofiber has a cross-sectional outer dimension of 1 nm to 15 nm inclusive. <4> A heat transport device that utilizes a phase change of a working fluid, comprising: a housing having an internal space; the wick according to any one of <1> to <3>, disposed in the housing; and a working fluid sealed in the housing in a state capable of contacting the wick.

[0092] This application claims priority from Japanese Patent Application No. 2022-079566, which is incorporated herein by reference.

[0093] REFERENCE SIGNS LIST 1 Housing 3 Wick 11 Evaporator 13 Condenser 15 Gas flow path 17 Liquid flow path 20 Heat transport device

Claims

1. A wick used for heat transport, comprising: The formula: MQ ａ O ｂ (wherein M is at least one element selected from the group consisting of Groups 3, 4, 5, 6 and 7; Q is at least one element selected from the group consisting of Groups 12, 13, 14, 15, and 16 (excluding O); a is greater than 0 and less than or equal to 2; b is greater than 0 and less than or equal to 2; A material comprising nanofibers and / or two-dimensional materials represented by Including, Wick.

2. The wick of claim 1 , wherein the material comprising the nanofibers and / or two-dimensional substances has a peak in an X-ray diffraction pattern with a diffraction angle 2θ in the range of 2° to 10°.

3. The nanofiber and / or the material containing the two-dimensional substance has a Raman shift of 140 to 160 cm in a Raman spectrum using a laser with a wavelength of 514 nm. －１ , 275-295cm －１ , 435-455cm －１ , and 665-745 cm －１ The wick of claim 1 having a peak at a position

4. The wick of claim 1 , wherein the material comprising the nanofibers and / or two-dimensional material has an anatase or lepidocrocite crystal structure, or a mixture thereof.

5. The wick of claim 1 , wherein the material comprising the nanofibers and / or two-dimensional material has a lepidocrocite type crystal structure.

6. The nanofiber and / or material comprising the two-dimensional substance has a Raman shift of at least 180 to 200 cm in a Raman spectrum using a laser with a wavelength of 514 nm. －１ , 275-295cm －１ , 375-395cm －１ , 435-455cm －１ , and 665-745 cm －１ The wick of claim 1, wherein the intensities of the peaks are V, X, Y, Z, and W, respectively, and X is the largest.

7. The wick of claim 1 , wherein the nanofibers have a cross-sectional dimension of greater than or equal to 1 nm and less than or equal to 15 nm.

8. A wick as described in claim 1, which is a wick composed of a material substantially consisting of the nanofibers and / or two-dimensional material.

9. A heat transport device utilizing a phase change of a working fluid, A housing having a space therein; A wick according to any one of claims 1 to 8 disposed within the housing; A working fluid sealed in the housing in a state in which the working fluid can come into contact with the wick; A heat transport device comprising: