WO2023219168A1 - Wick and heat transport device - Google Patents

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

Wick and heat transport equipment

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.

Conventionally, heat transport devices such as heat pipes and vapor chambers that utilize phase change (more specifically, evaporation and condensation) of a working fluid are known. Such a heat transport device uses a wick that transports a working fluid in a liquid state by capillary force (suction force due to capillary action).

For example, Patent Document 1 describes that a sintered body of metal particles having an average particle diameter of 20 μm or more and 200 μm or less is used as a wick. For example, Patent Document 2 discloses a fiber-containing porous body in which at least a portion of a fibrous structure containing carbon fibers and/or oxidized fibers is filled with a carbonaceous porous body, the pore size distribution of the carbonaceous porous body being describes the use of a fiber-containing porous material having at least one peak in a region with a pore diameter of 10 μm or less as a wick.

JP2022-27310A Japanese Patent Application Publication No. 2020-112326

The heat transport device as described above uses a casing that at least partially has thermal conductivity, and has a configuration in which a wick is disposed within the casing and a working fluid is sealed therein. Inside the housing, the working fluid evaporates in relatively high-temperature areas where heat is supplied from the outside, and the working fluid in a gaseous state moves inside the housing and condenses in relatively low-temperature areas, transferring heat to the outside. The working fluid in a liquid state is transferred (returned) to a relatively high temperature area by the capillary force of the wick.

In recent years, due to the miniaturization of electronic devices into which heat transport devices can be incorporated, further improvements in heat transport performance have been required of heat transport devices. Conventionally, the speed at which a working fluid in a liquid state is transferred by the capillary force of a wick is generally smaller 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 is The speed at which the working fluid is transported by capillary forces in the wick may be limited. In order to improve the heat transport performance of the heat transport device, it is desirable that the transfer speed of the liquid working fluid in the wick be higher.

An object of the present disclosure is to provide a novel wick that has a high transfer rate of working fluid in a liquid state. A further object of the present disclosure is to provide a novel heat transport device using such a wick.

According to one aspect of the present disclosure, a wick used for heat transport, comprising:
The formula below:
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,
b is greater than 0 and less than or equal to 2)
A wick is provided that includes a material including nanofibers and/or two-dimensional materials represented by

According to another gist of the present disclosure, there is provided a heat transport device using phase change of a working fluid, comprising:
A housing having a space inside;
the wick disposed within the housing;
a working fluid sealed within the housing so as to be in contact with the wick;
A heat transport device is provided.

According to the present disclosure, a novel wick is provided that has a high transfer rate of working fluid in a liquid state. Furthermore, according to the present disclosure, a novel heat transport device using such a wick is provided.

FIG. 1 is a schematic cross-sectional view of a heat transport device in one embodiment of the present disclosure. 1 shows an XRD pattern of the material (TiCO) manufactured in Example 1. An FE-SEM image of the material (TiCO) produced in Example 1 is shown.

Hereinafter, the wick and the heat transport device in the embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to these embodiments.

(Embodiment 1: Wick)
This embodiment relates to a wick. In this disclosure, "wick" means 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.

In this embodiment, the wick includes a material containing nanofibers and/or a two-dimensional substance. In the present disclosure, the term "material" simply means "a material containing nanofibers and/or a two-dimensional substance" (in other words, a material containing at least one of nanofibers and a two-dimensional substance). In this embodiment, the material containing nanofibers and/or two-dimensional substances typically means a material that is solid and does not contain a binder or the like (for example, a polymer). A material containing nanofibers and/or a two-dimensional substance is, in a narrow sense, a material that essentially consists of at least one of nanofibers and a two-dimensional substance (including other objects or impurities that may be unavoidably mixed). good). However, materials including nanofibers and/or two-dimensional substances are not limited thereto.

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

The above-mentioned predetermined material is also simply referred to as "MQO" hereinafter. Examples of MQOs include materials represented by the formulas TiO ₂ , TiCO, TiCON, VO ₂ , VCO, VCON, CrO ₂ , CrCO, CrCON, MoO ₂ , MoCO, MoCON, MnO ₂ , MnCO, MnCON, etc. It will be done. For example, in formula (1), the M may be Ti and the Q may be C. Further, for example, in formula (1), a may be other than 0.

Typically, the above-mentioned predetermined material may have a peak in the diffraction angle 2θ in the range of 2° or more and 10° or less in an X-ray diffraction (XRD) pattern.

MQO has a crystal structure different from a hexagonal system. Although this embodiment is not bound by any theory, the crystal structure of MQO can be considered to be anatase type, lepidocrocite type, or a mixture thereof at present. For example, the crystal structure of MQO may be lepidocrocite type.

MQO can be produced using the first raw material and the second raw material, for example, as follows. The first raw material contains at least the above M, the second raw material contains at least the above Q, and the first raw material and the second raw material can react in a protic solvent to generate MQO.

As the first raw material, a material represented by the following formula (2) may be used.
M _c A ¹ _d ...(2)
(In the formula, M is as above,
^A1 is at least one element selected from the group consisting of Groups 12, 13, 14, 15 and 16, for example selected from the group consisting of B, C, N, O, Si, P and S. may contain at least one element,
c and d are each independently from 1 to 5)
However, the material represented by formula (2) needs to be different from the MQO of the product. The material represented by formula (2) typically does not have a peak in the diffraction angle 2θ of 2° or more and 10° or less in an X-ray diffraction (XRD) pattern.

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 ₃ and the like. MnO ₂ that can be used as the first raw material has a peak in the vicinity of 2θ=13° in the XRD pattern, and does not have a peak in the range where 2θ is 2° or more and 10° or less.

Alternatively, or in addition to the above, a material represented by the following formula (3) (hereinafter also simply referred to as "MAX phase" or "MAX raw material") may be used as the first raw material.
M _m A ² X _n ...(3)
(In the formula, M is as 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 less than or equal to 5,
A ² is at least one element selected from the group consisting of Groups 12, 13, 14, 15 and 16, usually a Group A element, typically Group IIIA and Group IVA, and more details may contain at least one selected from the group consisting of Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, S and Cd, preferably Al)
The MAX phase has a layer composed of two A atoms located between two layers represented by M _m X _n (which may have a crystal lattice in which each X is located in an ^octahedral array of It has a crystal structure. Typically, in the MAX phase, when m=n+1, one layer of X atoms is arranged between each of the n+1 layers of M atoms (these are also collectively referred to as "M _m X _n layers"), It has a repeating unit in which a layer of A ² atoms (“A ² atomic layer”) is arranged as the next layer of the n+1-th layer of M atoms. However, the MAX phase is not limited to this.

Examples of the first raw material represented by formula (3) include Ti ₃ AlC ₂ , Ti ₃ GaC ₂ , Ti ₃ SiC ₂ and the like.

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).

An ion-binding substance having a carbon-containing group may be used as the second raw material. The ion-binding substance having a carbon-containing group contains C. Examples of the ion-binding substance include ammonium salts, phosphates, sulfates, and the like.

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, cetylpyridinium chloride (CPC), and the like. Among them, TMAH and TBAOH are preferred.

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

The protic solvent may be any solvent as long as it can at least partially dissolve the first raw material and the second raw material, and in particular may be an aqueous solvent. As the protic solvent, water, alcohol (eg, ethanol, 1-propanol, isopropanol), carboxylic acid (eg, acetic acid, formic acid), etc. are used. The aqueous solvent may be composed of water and optionally a liquid substance that is compatible with water (eg, a protic solvent other than water), and is preferably water.

The first raw material and the second raw material are reacted in a protic solvent. The second raw material may be added to the protic solvent in advance. The proportion 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, especially 20% by mass or more, and/or can be, for example, 80% by mass or less, especially 50% by mass or less. . The first raw material may be further added to the protic solvent to which the second raw material has been added and mixed. In such a mixture, the reaction that produces MQO proceeds. The temperature of the mixture (which may contain reaction products) (reaction temperature) may be, for example, 15° C. or higher, especially 40° C. or higher, and/or for example 100° C. or lower, especially 80° C. or lower. The mixing time (reaction time) may be, for example, one or more days, especially two or more days, and/or it may be, for example, no more than 10 days, especially no more than 7 days. Mixing can be carried out, for example, by rotating and stirring a magnetic stirrer placed in a container while maintaining the reaction temperature with a hot plate stirrer and a hot water bath. However, the treatment operations and conditions (temperature, time, etc.) that allow the reaction to proceed are not limited to those described above, and may be appropriately selected depending on the first raw material, second raw material, protic solvent, etc. to be used.

The above reaction produces MQO, which can eventually grow into MQO nanofibers and further into MQO nanoflakes. Without limiting the present disclosure, the resulting MQO nanofibers can be in the form of nanoribbons extending in nanoscale width. Further, a plurality of MQO nanofibers (for example, nanoribbons) may be bonded and/or integrated with each other to grow into two-dimensionally extending nanoflakes. Further, a plurality of MQO nanoflakes may overlap each other (eg, due to van der Waals forces) to form a laminate. Although the present disclosure is not bound by any theory, the generation and growth of such MQO may be considered to be due to a bottom-up synthetic reaction (see, for example, Non-Patent Document 1).

In the present disclosure, MQO is solid content. MQOs may typically be particles (or powders).

The mixture after the reaction (also referred to as reaction mixture) may be subjected to post-treatment as appropriate. Such post-treatments include, for example, washing, impact application (including application of shear force), drying (for example, freeze drying, heat drying), pulverization, and the like.

Washing may be performed using a protic solvent. Similar explanations as above may apply for protic solvents, which may be washed with water or alcohol, for example. After washing, separation operations (centrifugation and/or decantation) may be performed. The washing and separation operations can be repeated until the pH of the supernatant after centrifugation becomes, for example, 8 or less.

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

Shocks such as vibration and/or ultrasound may be applied during and/or after cleaning. This can promote the dispersion of MQO particles (for example, nanofibers/nanoflakes, hereinafter the same). If the MQO particles are aggregated, they can be disintegrated. Such an effect is significantly obtained when impact is applied during cleaning using an aqueous solution of a metal salt (it is thought that the metal cations derived from the metal salt can enter the gaps between the aggregates and disintegrate them). Shock 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, and the like.

Since the particles of MQO are solid, a separation operation can be performed at any appropriate timing to remove unnecessary liquid components if present. As a final separation operation, for example a drying operation, typically freeze-drying or thermal drying, may be carried out. Freeze-drying can be performed, for example, by freezing a mixture containing particles of MQO and a liquid component at any suitable temperature (eg, −40° C.) and then drying it under a reduced pressure atmosphere. Thermal drying can be carried out, for example, by drying a mixture containing MQO particles and a liquid component at a temperature of 25° C. or higher (for example, 200° C. or lower) under normal pressure or a reduced pressure atmosphere. The pulverization can be carried out using, for example, a mortar and pestle combination, an IKA mill, etc., but is not particularly limited. Grinding may be carried out after drying.

Through the above steps, particles of MQO can be obtained as a material containing MQO. As the MQO particles, for example, nanofibers (and in some cases, aggregates of MQO nanofibers, such as MQO nanoflakes, which are also collectively referred to as "MQO nanofibers, etc.") can be obtained.

Although MQO is represented by formula (1), the material containing MQO (typically, MQO particles) does not need to consist only of the constituent elements of formula (1). Without limiting this disclosure, the MQO-containing material may optionally include protons and/or metal cations. Additionally, without limiting the present disclosure, the MQO-containing material may optionally have a modification or termination T present on its surface selected from the group consisting of hydroxyl groups, chlorine atoms, oxygen atoms, and hydrogen and nitrogen atoms. It may have at least one kind. Additionally, a material containing MQO (typically, particles of MQO) may have two or more layers between which ammonium ions (e.g., quaternary ammonium cations) and metal cations ( For example, at least one selected from the group consisting of alkali metal ions and alkaline earth metal ions may be present.

Materials containing MQO, such as MQO nanofibers, may contain unreacted first raw materials and/or second raw materials as impurities, and may also contain substances derived from the first raw materials, second raw materials, and/or protic solvents. may include. For example, when a quaternary ammonium salt is used as the second raw material, N may exist (remain) in any form in the material containing MQO, such as MQO nanofibers. Although not limiting to this embodiment, the material containing MQO may include ammonium ions and tetramethylammonium ions. For example, when a MAX raw material is used as the first raw material, in the present disclosure, the material containing MQO contains a relatively small amount of residual A atoms, for example, 10% by mass or less with respect to the original A atoms. Good too. The residual amount of A atoms may be preferably 8% by mass or less, more preferably 6% by mass or less. However, even if the residual amount of A atoms exceeds 10% by mass, there may be no problem depending on the usage conditions.

In order to obtain MQO-containing materials such as MQO nanofibers with higher purity, it is preferable to repeat washing and centrifugation multiple times and collect the supernatant after the final centrifugation. Such a supernatant liquid can be made into a slurry containing MQO particles such as MQO nanofibers by directly diluting it with a liquid medium, or by mixing it with a liquid medium after drying.

The wick of this embodiment can be manufactured by shaping (molding, cutting, etc.) a material containing MQO, such as MQO nanofibers, into a desired shape and size using any appropriate method. Typically, the wick of this embodiment may be a fibrous structure formed using MQO nanofibers or the like. Such fibrous structures can be produced, for example, by applying a slurry containing nanofibers of MQO onto a substrate by any suitable method (e.g., filtration, spraying, bar coating, spin coating, dipping, etc.), drying, and then It can be manufactured by removing the base material. The liquid medium contained in the slurry can be selected as appropriate, and includes, for example, protic solvents (the same explanations as above apply), aprotic solvents (such as tetrahydrofuran, methylene chloride, acetonitrile, acetone, N, N- (dimethylformamide, dimethyl sulfoxide, etc.), nonpolar solvents (eg, hexane, benzene, toluene, diethyl ether, chloroform, ethyl acetate), and the like.

Through the above steps, the wick of this embodiment is obtained. The shape and dimensions of the wick of this embodiment can be appropriately selected depending on the desired use.

As described above, a material containing MQO typically has a peak in the diffraction angle 2θ of 2° or more and 10° or less in an X-ray diffraction (XRD) pattern. Although the present disclosure is not bound by any theory, the fact that the material containing MQO has a peak in the range of 2θ = 2° or more and 10° or less in the XRD pattern indicates that such MQO is a crystal that is different from known metal oxides. This is thought to mean that it has a structure.

Note that in this disclosure, the XRD pattern is a pattern obtained by scanning in the θ-axis direction with an XRD analyzer using CuKα rays (= about 1.54 Å) as characteristic X-rays (the vertical axis is the intensity, and the horizontal axis is the 2θ) and can also be referred to as an “XRD profile”. Peaks in the XRD pattern can be identified visually or using software used with an XRD analyzer. In order to measure the XRD pattern as accurately as possible in the low angle region of 2θ, a c-axis oriented MQO membrane is installed in the XRD analyzer (for example, as in the example described later, the filter is removed after suction filtration). It is preferable to measure the self-supporting membrane obtained by arranging the surface that was in contact with the filter on the lower side.

For example, the material of this embodiment (more specifically, MQO) has a Raman shift of at least 275 to 295 cm -1 , 435 to 295 cm ^-1 in a Raman spectrum using a laser with a wavelength of 514 nm, although this embodiment is not limited to It may have peaks at 455 cm ⁻¹ and 665 to 745 cm ⁻¹ .

Although this embodiment is not limited, for example, the material of this embodiment (more specifically, MQO) has a Raman shift of 140 to 160 cm ^-1 and 275 to 295 cm in a Raman spectrum using a laser with a wavelength of 514 nm. ^-1 , 435-455 cm ^-1 , and 665-745 cm ^-1 . Note that 140 to 160 cm ⁻¹ is an anatase type peak.

For example, the material of this embodiment (more specifically, MQO) has a crystal structure of anatase type, lepidocrocite type, or a mixture of these, although the present embodiment is not limited thereto. More preferably, it has a lepidocrocite crystal structure.

For example, the material of this embodiment (more specifically, MQO) has a Raman shift of at least 275 to 295 cm -1 , 435 to 295 cm ^-1 in a Raman spectrum using a laser with a wavelength of 514 nm, although this embodiment is not limited to It may have peaks at 455 cm ^-1 and 665 to 745 cm ^-1 , and when the intensity of each peak is X, Y, and Z, X is the largest.

Although this embodiment is not limited, more preferably, the material of this embodiment (more specifically, MQO) has a Raman shift of at least 180 to 200 cm ⁻¹ in a Raman spectrum using a laser with a wavelength of 514 nm, When there are peaks at the positions of 275 to 295 cm ^-1 , 375 to 395 cm ^-1 , 435 to 455 cm ^-1 , and 665 to 745 cm ^-1 and the intensities of each peak are V, X, Y, Z, and W. It may take the form that X is the largest.

Note that in the present disclosure, the Raman spectrum is measured with a Raman spectrometer using a laser beam with a wavelength of 514 nm as an excitation light source (the vertical axis is intensity and the horizontal axis is Raman shift). Peaks in a Raman spectrum can be identified visually or using software used with a Raman spectrometer.

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

The particle morphology of MQO is nanofibers and/or two-dimensional materials. The two-dimensional material includes one or more of nanoflakes and laminates of nanoflakes. In this embodiment, the two-dimensional material is not limited to only nanoflakes and a laminate of nanoflakes.

According to this embodiment, a material comprising MQO, typically particles (e.g. nanofibers/nanoflakes) of MQO, e.g. nanofibers of MQO (and optionally aggregates of nanofibers of MQO, e.g. nanoflakes of MQO) ) is provided. For example, MQO nanofibers have a hydrophilic surface and have nano-order cross-sectional dimensions. A wick containing such MQO nanofibers has a large ability to attract (e.g., suck up) a working fluid in a liquid state by capillary action, and therefore can transfer (e.g., suck up) a working fluid in a liquid state at a high speed. . The reason for this is that due to the nano-order cross-sectional dimensions, the volume density of the nanofibers in the wick is high, and the gaps between the nanofibers form a narrow space (flow path for the working fluid). The total surface area of the nanofibers obtained is large, and the hydrophilic surface makes it easier for a working fluid in a liquid state (typically, but not limited to, water) to wet and spread on the surface of the MQO nanofibers. This may be possible.

In the present disclosure, "nanofiber" of MQO is a solid substance extending in the longitudinal direction, and the external dimensions of a cross section perpendicular to the longitudinal direction (cross-sectional external dimensions) are nano-order (i.e., 1 nm or more and 1000 nm or more). (less than 1 nm) or smaller than that (less than 1 nm, for example, 0.1 nm or more and less than 1 nm). The length of the MQO nanofibers in the longitudinal direction is not particularly limited. That is, the length of the nanofiber in the longitudinal direction is not limited to nano-order (ie, 1 nm or more and less than 1000 nm), but may be micron-order (1 μm or more and less than 1000 μm). The cross-sectional dimensions of the nanofibers can be, for example, 0.1 nm or more, especially 1 nm or more, and for example 100 nm or less, especially 50 nm or less, preferably 15 nm or less. A wick including MQO nanofibers or the like having such a small cross-sectional dimension can transport a working fluid in a liquid state at a higher velocity. Although the present embodiment is not limited to this embodiment, according to the above-described manufacturing method, MQO nanofibers having such small cross-sectional dimensions can be realized.

In the present disclosure, the cross-sectional external dimensions of the MQO nanofibers mean the shortest distance passing through the center in a cross section that traverses the longitudinal direction of the MQO nanofibers. The shape of the cross section of the MQO nanofiber is not particularly limited, but may be approximated by, for example, a rectangle (rectangle, square, etc.) or an ellipse (oblate circle, perfect circle, etc.). When the MQO nanofiber is in the form of a nanoribbon, its cross-sectional shape can be approximated by a rectangle, and the cross-sectional external dimension can correspond to the short side length of the rectangle. When the MQO nanofiber is in the form of a nanofilament, its cross-sectional shape can be approximated by a flat circle, and the cross-sectional external dimensions can correspond to the short axis length of the flat circle.

The BET specific surface area of a material containing MQO such as MQO nanofibers is not particularly limited, but may be, for example, 10 m ² /g or more and 500 m ² /g or less. BET specific surface area is the isothermal adsorption curve of nitrogen gas or other gases mentioned above under liquid nitrogen temperature (77 K) by an adsorption method using nitrogen gas or other suitable gas (e.g. krypton (Kr) gas, etc.). It is calculated using the BET formula.

In the present disclosure, a "two-dimensional substance" has a two-dimensionally extending surface (also referred to as a plane or two-dimensional sheet surface), and the maximum dimension of the surface (which may correspond to the "in-plane dimension" of a particle) ), the thickness of which is nano-order (i.e., 1 nm or more and less than 1000 nm) or smaller sub-nano order (less than 1 nm, e.g. 0.1 nm or more and less than 1 nm). mean something The in-plane dimension is not limited to nano-order (ie, 1 nm or more and less than 1000 nm), but may be micron-order (1 μm or more and less than 1000 μm). The two-dimensional material includes one or more of nanoflakes and nanoflake stacks, as described above. Nanoflakes may also be referred to as nanosheets or two-dimensional (nano)sheets. The thickness of one layer of nanoflakes can be, for example, 0.01 nm or more, especially 0.8 nm or more, and eg 20 nm or less, especially 3 nm or less. The in-plane dimensions of the nanoflakes may be, for example, 0.1 μm or more, especially 1 μm or more, and for example 200 μm or less, especially 40 μm or less. Nanoflakes can be constructed by aggregating nanofibers.

A stack of nanoflakes may also be referred to as a multilayer MQO. The distance (interlayer distance or void size) between two adjacent nanoflakes (or two adjacent layers of MQO) is not particularly limited.

The above-mentioned dimensions are calculated using a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an atomic force microscope (processed by a method such as a focused ion beam (FIB), if necessary). In real space calculated from the number average dimension (number average of at least 40) based on photographs observed with AFM) or the position on the reciprocal lattice space of the (002) plane measured by X-ray diffraction (XRD) method. It can be determined as a distance. In the present disclosure, for example, the cross-sectional external dimensions of MQO nanofibers are determined by exposing the cross-section of a wick containing MQO nanofibers using a method such as a focused ion beam (FIB), and then using a scanning electron microscope (SEM) or a transmission electron microscope (SEM) to examine the exposed cross-section. Take an image using a TEM, extract at least 40 MQO nanofibers in which a cross section crossing the longitudinal direction appears, and calculate the number average of their cross-sectional external dimensions. is required.

However, it should be noted in this disclosure that the MQO is not limited to the above forms, but may have any suitable form.

(Embodiment 2: Heat transport device)
This embodiment relates to a heat transport device. In the present disclosure, a "heat transport device" refers to a device that transports heat using a phase change of a working fluid. Phase change of the working fluid refers to evaporation and condensation.

Referring to FIG. 1, the heat transport device 20 of the present embodiment includes:
A housing 1 having a space inside;
A wick 3 disposed within the housing 1;
A working fluid (not shown) sealed in the housing 1 in a state where it can come into contact with the wick 3;
including. As the wick 3, the one described above in the first embodiment is used.

Although not limiting the present embodiment, FIG. 1 exemplarily shows a case where the heat transport device 20 is a loop-type heat pipe. 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 that connect these, respectively. The passage 15 and the liquid flow passage 17 integrally constitute the internal space of the housing 1 . The wick 3 is placed within the evaporator 11. A working fluid (not shown) is sealed in the internal space of the housing 1 . The housing 1 is made of a thermally conductive material (for example, metal) at least in the evaporator 11 and the condenser 13.

Inside the housing 1, the working fluid is evaporated in the evaporator 11 (relatively high temperature part) to which heat is supplied from the outside (heat source), and the working fluid in a gaseous state moves in the gas flow path 15, By condensing in the condenser 13 (a relatively low-temperature part), heat is released to the outside, and the working fluid, which has become a liquid, passes through the liquid flow path 17 to the evaporator 11 due to the capillary force of the wick 3. be transported (returned). Thereby, the working fluid circulates within the housing 1 while changing its phase. In FIG. 1, the flow of the working fluid is schematically shown by dotted line arrows, and the supply of heat from the outside (heat input) and the radiation of heat to the outside (thermal output) are schematically shown by dotted line arrows.

According to this embodiment, since the wick 3 described in Embodiment 1 is used in the heat transport device 20, the working fluid in the liquid state can be transported at a high speed, and high heat transport performance can be obtained. , the maximum heat transport amount of the heat transport device 20 is improved.

The example shown in FIG. 1 shows a case where the heat transport device 20 is a loop-type heat pipe, but the heat transport device of this embodiment uses no wick except for using the wick 3 described above in Embodiment 1. The structure of a known heat transport device (for example, a tubular heat pipe, a vapor chamber, etc.) may be applied.

Although the wick and the heat transport device in an embodiment of the present disclosure have been described above in detail, the present disclosure can be modified in various ways. Note that the wick of the present disclosure may be manufactured by a method different from the manufacturing method in the embodiments described above.

(Example 1)
Example 1 relates to the wick of Embodiment 1, which uses TiCO nanofibers.

・Preparation of slurry containing TiCO nanofibers First, in a container (100 mL Eyeboy), 1 g of titanium diboride (TiB ₂ , manufactured by Alfa Aesar) and 30 mL of a 25% by mass tetramethylammonium hydroxide (TMAH) aqueous solution (Tokyo (manufactured by Kasei Kogyo Co., Ltd.). A stirrer tip with a length approximately the same size (35 mm) as the inner diameter of the circular bottom of the container was placed there. While keeping the container at 50° C. in a water bath, the mixture in the container was stirred with a stirrer tip and maintained for 120 hours, thereby allowing the reaction to proceed. The reaction mixture in the container was then transferred to a 50 mL centrifuge tube with a stainless steel spatula (without adding any liquid medium such as ethanol or water). Centrifugation was performed using a centrifuge at 3500 G for 5 minutes to sediment the solid content. (i) After centrifugation, discard the supernatant, (ii) add 40 mL of ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to the remaining sediment in the centrifuge tube, and handshake for 5 minutes (reslurry). (iii) Centrifugation was performed under the same conditions as above. These operations (i) to (iii) were repeated until the pH of the supernatant liquid became 8 or less. After repeating the procedure three times, the pH of the supernatant liquid became 8 or less, so the supernatant liquid was discarded and the repeating operation was completed. 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. Thereafter, centrifugation was performed using a centrifuge at 3500 G for 30 minutes, and the supernatant was collected as a sample slurry. The sample slurry obtained corresponds to a slurry containing TiCO nanofibers (see analysis results below).

- 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 Co., Ltd.) was used as a filter for suction filtration. After suction filtration, the precursor film on the filter was dried in a vacuum oven at 80° C. overnight, and the filter was removed to obtain a self-supporting film. The obtained self-supporting membrane was cut into a rectangular shape to obtain a wick sample having a width (W) of 1 cm, a length (L) of 2 cm, and a thickness (T) of 100 μm.

・Wick evaluation The wick sample prepared above was placed in a petri dish filled with water with the WT surface (1 cm x 100 μm) vertically placed on the top and bottom surfaces, and placed at a depth of about 1 mm. When it was soaked in water, water was sucked up to the top surface at a speed of 4 mm/s. From this result, the volume of water sucked up by the wick sample per unit area per unit time is 4×10 ^-3 m ³ /(m ² s), and therefore the mass of water sucked up per unit area per unit time 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 take away by evaporating water at 25° C. is calculated to be 9768 kW/m ² . That is, in the wick sample of Example 1, the water transport speed was 4 mm/s, and the water heat transport performance at 25° C. was about 10 ⁴ kW/m ² .

・Analysis When the free-standing 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. Therefore, Ti, C, O, and N were detected. Since N is considered to be a residual component of the raw material TMAH, the material of the self-supporting film is considered to be composed of Ti, C, and O.
Furthermore, the XRD profile of the self-supporting film obtained in the same manner as above was measured using an XRD device (MiniFlex, manufactured by Rigaku Corporation) (characteristic X-ray: CuKα = 1.54 Å). The obtained XRD pattern is shown in FIG. As understood from FIG. 2, this material had a peak at 2θ=7.26°.

In addition, 0.01 g of the 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. (manufactured by Cytiva), and the TiCO nanofibers were observed using FE-SEM (S-4800, manufactured by Hitachi High-Tech Corporation). FIG. 3 shows an FE-SEM image. As can be seen from Figure 3, this material had a cross-sectional profile of approximately 5 nm.

(Comparative example 1)
Comparative Example 1 relates to a wick using particles of MXene, which is a type of two-dimensional material.

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

・Precursor etching (ACID method)
Using the Ti ₃ AlC ₂ particles (powder) prepared by the above method, etching was performed under the following etching conditions to obtain a solid-liquid mixture (slurry) containing a solid component derived from the Ti ₃ AlC ₂ powder.
(Etching conditions)
・Precursor: Ti ₃ AlC ₂ (passed through a 45 μm sieve)
・Etching solution composition: 49%HF 6mL
18 mL _H2O
HCl (12M) 36mL
・Precursor input amount: 3.0g
・Etching container: 100mL Eye Boy ・Etching temperature: 35℃
・Etching time: 24h
・Stirrer rotation speed: 400 rpm

- Washing after etching The slurry was divided into two parts, inserted into two 50 mL centrifuge tubes, centrifuged at 3500 G using a centrifuge, and then the supernatant liquid was discarded. The operation of adding 40 mL of pure water to the remaining precipitate in each centrifuge tube, performing centrifugation again at 3500 G, and separating and removing the supernatant liquid was repeated 11 times. After the final centrifugation, the supernatant was discarded and the Ti ₃ C ₂ T _x -water medium clay was obtained.

・Li intercalation The Ti ₃ C _{2 T} Intercalation was performed.
(Li intercalation conditions)
・Ti ₃ C ₂ T _x - Water medium clay (MXene after washing): Solid content 0.75 g
・LiCl: 0.75g
・Intercalation container: 100mL Eyeboy ・Temperature: 20℃ or higher and 25℃ or lower (room temperature)
・Time: 10h
・Stirrer rotation speed: 800 rpm

・Delamination: (i) Add 40 mL of pure water to the above Ti ₃ C ₂ T _x -water medium clay, stir for 15 minutes in a shaker, (ii) centrifuge at 3500G, and (iii) convert the supernatant into a single layer. It was recovered as a liquid containing MXene. These operations (i) to (iii) were repeated a total of four times to obtain a supernatant containing monolayer MXene. Furthermore, this supernatant liquid was centrifuged using a centrifuge at 4300G for 2 hours, the supernatant liquid was discarded, and a single-layer/poor-layer MXene-containing clay was prepared as a mono-layer/poor-layer MXene-containing sample. I got it.

- Preparation of slurry containing MXene particles This MXene-containing clay and pure water were mixed in appropriate amounts to prepare a sample slurry having a solid content concentration (MXene particle concentration) of 34 mg/mL. The obtained sample slurry corresponds to a slurry containing MXene particles (MXene-water dispersion).

- Production of wick A wick sample with 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. .

・Wick evaluation The wick sample prepared above was placed in a petri dish filled with water with the WT surface (1 cm x 100 μm) vertically placed on the top and bottom surfaces, and placed at a depth of about 1 mm. When it was soaked in water, it was unable to absorb water at all (the suction height was 0 mm).

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

- Preparation of wick 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 and obtain a porous metal sintered body. The obtained porous metal sintered body was cut to obtain a wick sample having a width (W) of 1 cm, a length (L) of 2 cm, and a thickness (T) of 100 μm.

・Wick evaluation The wick sample prepared above was placed in a petri dish filled with water with the WT surface (1 cm x 100 μm) vertically placed on the top and bottom surfaces, and placed at a depth of about 1 mm. When it was soaked in water, water was sucked up to the top surface at a speed of 0.5 mm/s. From this result, the wick sample of Comparative Example 2 has a water transfer rate of 0.5 mm/s, and according to the same calculation as Example 1, the water heat transfer performance at 25°C is approximately 10 ³ kW/m. It was ² .

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

・Production of wick Width (W) 1 cm, length (L) 2 cm, thickness (T) in the same manner as Comparative Example 2 except that titanium powder with an average particle size D50 of 50 μm was used as the metal powder. A 100 μm wick sample was obtained.

-Evaluation of Wick The wick sample prepared above was evaluated in the same manner as Comparative Example 2, and water was sucked up to the upper end surface at a speed of 0.5 mm/s. From these results, the wick sample of Comparative Example 3 had a water transfer rate of 0.5 mm/s and a water heat transfer performance of about 10 ³ kW/m ² at 25°C.

The wick of the present disclosure can be used in a heat transport device that utilizes phase change of a working fluid to transport the working fluid by capillary force. 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 not only in these applications but also in any suitable application.

<1>
A wick used for heat transport,
The formula below:
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,
b is greater than 0 and less than or equal to 2)
Wick containing nanofibers of material represented by.
<2>
The wick according to <1>, wherein the material of the nanofiber has a peak in a diffraction angle 2θ in a range of 2° or more and 10° or less in an X-ray diffraction pattern.
<3>
The wick according to <1> or <2>, wherein the nanofiber has a cross-sectional external dimension of 1 nm or more and 15 nm or less.
<4>
A heat transport device that utilizes phase change of a working fluid,
A housing having a space inside;
The wick according to any one of <1> to <3>, disposed within the housing;
a working fluid sealed within the housing so as to be in contact with the wick;
heat transport equipment, including

This application claims priority to Japanese Patent Application No. 2022-079566, which is a Japanese patent application, as the basic application. Japanese Patent Application No. 2022-079566 is incorporated herein by reference.

1 Housing 3 Wick 11 Evaporator 13 Condenser 15 Gas flow path 17 Liquid flow path 20 Heat transport device

Claims (8)

1. A wick used for heat transport,
   The formula below:
   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,
   b is greater than 0 and less than or equal to 2)
   A wick comprising a material containing nanofibers and/or a two-dimensional substance represented by:
2. The wick according to claim 1, wherein the material containing the nanofibers and/or the two-dimensional substance has a peak in a diffraction angle 2θ in a range of 2° or more and 10° or less in an X-ray diffraction pattern.
3. The material containing nanofibers and/or two-dimensional substances has Raman shifts of 140 to 160 cm ^-1 , 275 to 295 cm ^-1 , 435 to 455 cm ^-1 , and 665 to 745 cm in a Raman spectrum using a laser with a wavelength of 514 nm. The wick according to claim 1 or 2, having a peak at the ^-1 position.
4. The wick according to any one of claims 1 to 3, wherein the material containing the nanofibers and/or the two-dimensional substance has a crystal structure of anatase type, lepidocrocite type, or a mixture thereof.
5. The wick according to any one of claims 1 to 4, wherein the material containing the nanofibers and/or the two-dimensional substance has a lepidocrocite crystal structure.
6. The material containing nanofibers and/or two-dimensional substances has a Raman shift of at least 180 to 200 cm ^-1 , 275 to 295 cm ^-1 , 375 to 395 cm ^-1 , 435 to 455 cm in a Raman spectrum using a laser with a wavelength of 514 nm. ^-1 , and has a peak at a position of 665 to 745 cm ^-1 , and when the intensity of each peak is V, X, Y, Z, W, X is the largest, according to any one of claims 1 to 5. Wick as described.
7. The wick according to any one of claims 1 to 6, wherein the nanofiber has a cross-sectional external dimension of 1 nm or more and 15 nm or less.
8. A heat transport device that utilizes phase change of a working fluid,
   A housing having a space inside;
   The wick according to any one of claims 1 to 7, disposed within the housing;
   a working fluid sealed within the housing so as to be in contact with the wick;
   heat transport equipment, including.

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