CN114574169A - Vanadium dioxide-boron nitride phase-change heat-conducting composite material and preparation method and application thereof - Google Patents

Abstract

The invention discloses a vanadium dioxide-boron nitride phase-change thermally conductive composite material and a preparation method and application thereof. The preparation method includes the following steps: hydrothermal reaction of vanadium salt, reducing agent, boron nitride and dopant in a solvent; wherein, the boron nitride is hexagonal boron nitride. The invention adopts the hydrothermal method to synthesize the vanadium dioxide-boron nitride phase-change thermally conductive composite material, and adsorbs the nanometer vanadium dioxide onto the hexagonal boron nitride nanosheets. On the one hand, the material is endowed with phase-change heat storage capacity through vanadium dioxide; on the other hand, through the electron-phonon coupling effect between vanadium dioxide and boron nitride, a higher loading of boron nitride can be obtained under the condition of lower loading. Thermal conductivity, reduce production costs, and at the same time boron nitride has a protective effect on vanadium dioxide and improves its thermal stability. Compared with the prior art, it has the advantages of no oil spill phenomenon, good thermal stability and high thermal conductivity.

Description

A kind of vanadium dioxide-boron nitride phase change thermally conductive composite material and its preparation method and application

technical field

The invention relates to the technical field of chemical engineering, in particular to a vanadium dioxide-boron nitride phase-change thermally conductive composite material and a preparation method and application thereof.

Background technique

Phase Change Material (PCM) can change the state of matter and provide latent heat under the condition of constant temperature. Among them, the traditional organic phase change materials have large phase change enthalpy, low cost, mild properties, no problems such as supercooling and corrosion, low price and easy acquisition, and have always been a research hotspot in the field of phase change materials. However, there are also two major difficulties in its application. First, most organic phase change materials belong to the category of solid-liquid phase change materials. After the material absorbs heat, it is in a liquid state, and the phase change volume changes greatly, which is prone to oil spills and is thermally stable. Second, the thermal conductivity of organic phase change materials is generally small, generally in the range of 0.15 to 0.3W/(m·K), which affects the rate of heat storage and release of the material and affects its use. Compared with organic phase change materials, inorganic phase change materials have the characteristics of reusability, generally no oil spillage, high reliability in long-term use, and environmental protection, and have broad application prospects in the field of thermal conductive materials. Among them, vanadium dioxide undergoes a first-order reversible phase transition at 68 °C, has a phase transition heat storage capacity, and has a small volume change during the phase transition process, and its intrinsic thermal conductivity is 4-6 W·m ^-1 · K ^-1 , has good thermal conductivity, but vanadium dioxide is easily oxidized when placed in the air for a long time, and its thermal stability is poor.

Hexagonal boron nitride has a layered crystal structure similar to graphite, so it is also called "white graphene". It has good electrical insulation, thermal conductivity and chemical stability, and is a good fire-resistant, high-temperature-resistant material and thermally conductive material. Therefore, the preparation of vanadium dioxide-boron nitride composite materials is expected to obtain phase change materials with good thermal conductivity and reliable stability.

SUMMARY OF THE INVENTION

In view of the above background technology, the present invention provides a vanadium dioxide-boron nitride phase-change thermally conductive composite material and a preparation method and application thereof, which utilize the phase-change heat storage capacity of vanadium dioxide and the good thermal stability and thermal stability of hexagonal boron nitride. Excellent thermal conductivity, innovatively assemble the two into a composite structure with both phase change heat storage and high thermal conductivity through hydrothermal treatment, providing a new phase change thermal conductivity material with good thermal stability.

To achieve the above object, the technical scheme adopted in the present invention is:

In one aspect, the present invention provides a method for preparing a vanadium dioxide-boron nitride phase-change thermally conductive composite material, comprising the following steps:

Hydrothermal reaction of vanadium salt, reducing agent, boron nitride and dopant in solvent;

Wherein, the boron nitride is hexagonal boron nitride.

As a preferred embodiment, the vanadium salt is a +5-valent vanadium salt, specifically ammonium metavanadate, ammonium pyrovanadate, ammonium orthovanadate, ammonium polyvanadate and ammonium decavanadate, etc., the above-mentioned vanadium salts It can be used singly or in any combination.

As a preferred embodiment, the reducing agent is selected from any one or more of oxalic acid, citric acid, formic acid and acetic acid.

As a preferred embodiment, the dopant is selected from any one of (1) tungsten, magnesium, molybdenum, niobium, tantalum, zinc, aluminum, copper salts, (2) transition metal tellurides, and (3) oxo telluride compounds or several;

Preferably, the dopant is selected from any one of ammonium tungstate and tellurium dioxide or used in combination; more preferably, ammonium tungstate and tellurium dioxide are used in combination.

In the technical solution of the present invention, the transition metal telluride can include vanadium telluride, titanium telluride, tungsten telluride, molybdenum telluride, copper telluride, zinc telluride and tin telluride, etc.; The group tellurium compound includes tellurium oxide, tellurium sulfide, tellurium selenide, and the like.

As a preferred embodiment, the solvent is an organic solvent, preferably any one or more of ethanol, N,N-dimethylformamide (DMF), isopropanol and N-methylpyrrolidone (NMP).

As a preferred embodiment, the temperature of the hydrothermal reaction is 180-260°C, such as 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C or any of them. temperature between any value;

Preferably, the time of the hydrothermal reaction is 12～24h;

Preferably, the hydrothermal reaction is carried out under stirring conditions, and the stirring speed is preferably 100-500 r/min.

In some specific embodiments, the preparation method further includes post-treatment; the post-treatment includes centrifugation, washing, drying and annealing; the washing is washing with ethanol and acetone respectively; the drying is drying at 40-80° C. 4~12h; the annealing is 600~800℃ annealing for 2~5h, such as 600℃ annealing, 620℃ annealing, 640℃ annealing, 660℃ annealing, 680℃ annealing, 700℃ annealing, 720℃ annealing, 740℃ annealing, Annealing at 760°C, annealing at 780°C, annealing at 800°C.

In the technical solution of the present invention, annealing can improve the purity of the VO ₂ phase with the phase transition function.

As a preferred embodiment, the preparation method specifically includes the following steps:

1) dissolving ammonium metavanadate, oxalic acid, hexagonal boron nitride, ammonium tungstate and/or tellurium dioxide in a solvent to obtain a dispersion;

2) heating the dispersion obtained in step 1) to 180-260°C under stirring at 100-500 r/min, and reacting for 12-24 h;

3) After centrifuging the product obtained in step 2), discard the supernatant, wash with ethanol and acetone to remove residual reactants, centrifuge, and dry in a vacuum drying box at 40-80° C. for 4-12 hours;

4) Annealing the product obtained in step 3) at 600-800° C. for 2-5 hours to obtain pure phase-change vanadium dioxide.

Preferably, in step 1), the dosage ratio of the ammonium metavanadate, oxalic acid, hexagonal boron nitride, ammonium tungstate and tellurium dioxide is (100～300mg): (200～700mg): (50～150mg) : (2.7-7.5 mg): (0.8-4.0 mg).

In another aspect, the present invention provides the vanadium dioxide-boron nitride phase change thermally conductive composite material obtained by the above preparation method.

In another aspect, the present invention provides the use of the above-mentioned vanadium dioxide-boron nitride phase-change thermally conductive composite material in preparing a thermal interface material.

The above technical solution has the following advantages or beneficial effects:

The invention adopts the hydrothermal method to synthesize the vanadium dioxide-boron nitride phase-change heat-conducting composite material, and adsorbs the nanometer vanadium dioxide onto the hexagonal boron nitride nanosheets. During the hydrothermal reaction, the hexagonal boron nitride powder is hydrothermally exfoliated into hexagonal boron nitride nanosheets, while the pentavalent vanadium source is reduced to tetravalent vanadium, and in-situ growth of dioxide is formed on the hexagonal boron nitride nanosheets. vanadium. On the one hand, the present invention endows the composite material with phase-change heat storage capability through vanadium dioxide; Higher thermal conductivity can reduce production costs, while boron nitride plays a protective role on vanadium dioxide and improves its thermal stability. Compared with the prior art, it has the advantages of no oil spill phenomenon, good thermal stability and high thermal conductivity. In addition, the present invention also reduces the phase transition temperature of vanadium dioxide by doping metal ions, thereby expanding the application range of the phase change material.

Description of drawings

1 is a SEM image of the vanadium dioxide-boron nitride composite material prepared in Example 1.

2 is a graph showing the differential calorimetry test results of the vanadium dioxide-boron nitride composite materials prepared in Examples 1-4 and commercial vanadium dioxide.

FIG. 3 is the differential scanning calorimetry (DSC) curve of the vanadium dioxide-boron nitride composite material prepared in Example 1 and commercial vanadium dioxide and their heating at 300° C. for 3 h.

Detailed ways

The following embodiments are only some of the embodiments of the present invention, but not all of the embodiments. Accordingly, the detailed descriptions of the embodiments of the invention provided below are not intended to limit the scope of the invention as claimed, but are merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present invention.

In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or commonly used in the industry. The methods in the following examples, unless otherwise specified, are conventional methods in the art.

In the following examples, hexagonal boron nitride is in powder form, purchased from Sinopharm Chemical Reagent Co., Ltd.

Example 1:

(1) 200mg of ammonium metavanadate, 461.5mg of oxalic acid, 100mg of hexagonal boron nitride and 15mL of isopropanol were added to a glass beaker, and 4.36mg of ammonium tungstate and 1.36mg of tellurium dioxide were added, and stirred for 30min to obtain a dispersion;

(2) the above-mentioned dispersion liquid is transferred to the hydrothermal reaction kettle, and the polytetrafluoro stirring magnet is added to seal; under the magnetic stirring condition, the reaction kettle is gradually heated to 260 ° C, the stirring speed is set to 400 r/min, and the reaction is carried out for 24 hours. ;

(3) After the reaction is completed, it is cooled to room temperature, the reactor is opened, the product is transferred to a centrifuge tube, centrifuged at 8000 rpm for 10 minutes, the supernatant is discarded, washed once with ethanol and acetone respectively, and after centrifugation is carried out again under the same conditions , the product was dried in a vacuum drying oven at 40°C for 5 hours;

(4) The obtained product is placed in a tube furnace for annealing at 800° C. for 2 hours under a nitrogen atmosphere, and cooled to room temperature to obtain a vanadium dioxide-boron nitride phase-change thermally conductive composite material.

The vanadium dioxide-boron nitride phase change thermally conductive composite material prepared in this example is a nano-sheet material. As shown in FIG. 1 , vanadium dioxide is successfully attached to the boron nitride nano-sheet.

Example 2:

(1) 200mg of ammonium metavanadate, 461.5mg of oxalic acid, 100mg of hexagonal boron nitride, and 20mL of ethanol were added to a glass beaker, and 4.36mg of ammonium tungstate and 2.72mg of tellurium dioxide were added, and stirred for 30min to obtain a dispersion;

(2) the above-mentioned dispersion liquid is transferred to the hydrothermal reaction kettle, and the polytetrafluoro stirring magnet is added to seal; under the magnetic stirring condition, the reaction kettle is gradually heated to 260 ° C, the stirring speed is set to 400 r/min, and the reaction is carried out for 24 hours. ;

(3) After the reaction is completed, it is cooled to room temperature, the reactor is opened, the product is transferred to a centrifuge tube, centrifuged at 8000 rpm for 10 minutes, the supernatant is discarded, washed once with ethanol and acetone respectively, and after centrifugation is carried out again under the same conditions , the product was dried in a vacuum drying oven at 40°C for 5 hours;

(4) The obtained product is placed in a tube furnace for annealing at 800° C. for 2 hours under a nitrogen atmosphere, and cooled to room temperature to obtain a vanadium dioxide-boron nitride phase-change thermally conductive composite material.

The vanadium dioxide-boron nitride phase-change thermally conductive composite material prepared in this example is a nano-sheet material.

Example 3:

(1) 200mg of ammonium metavanadate, 461.5mg of oxalic acid, 100mg of hexagonal boron nitride and 20mg of DMF were added to a glass beaker, and 4.36mg of ammonium tungstate was added, and stirred for 30min to obtain a dispersion;

(2) above-mentioned dispersion liquid is transferred in the hydrothermal reaction kettle, and polytetrafluoro stirring magnet is added to seal; Under the magnetic stirring condition, the reaction kettle is gradually heated to 260 ℃, and the stirring speed is set to 400rpm, and the reaction is 24 hours;

(3) After the reaction is completed, it is cooled to room temperature, the reactor is opened, the product is transferred to a centrifuge tube, centrifuged at 8000 rpm for 10 minutes, the supernatant is discarded, washed once with ethanol and acetone respectively, and after centrifugation is carried out again under the same conditions , the product was dried in a vacuum drying oven at 40°C for 5 hours;

(4) The obtained product is placed in a tube furnace for annealing at 800° C. for 2 hours under a nitrogen atmosphere, and cooled to room temperature to obtain a vanadium dioxide-boron nitride phase-change thermally conductive composite material.

The vanadium dioxide-boron nitride phase-change thermally conductive composite material prepared in this example is a nano-sheet material with a multi-level structure.

Example 4:

(1) 200mg of ammonium metavanadate, 461.5mg of oxalic acid, 100mg of hexagonal boron nitride and 20mg of NMP were added to a glass beaker, and 2.72mg of tellurium dioxide was added, and stirred for 0.5 hours to obtain a dispersion;

(2) the above-mentioned dispersion liquid is transferred to the hydrothermal reaction kettle, and the polytetrafluoro stirring magnet is added to seal; under the magnetic stirring condition, the reaction kettle is gradually heated to 260 ° C, the stirring speed is set to 400 r/min, and the reaction is carried out for 24 hours. ;

(3) After the reaction is completed, it is cooled to room temperature, the reactor is opened, the product is transferred to a centrifuge tube, centrifuged at 8000/min for 10 minutes, the supernatant is discarded, washed once with ethanol and acetone respectively, and after centrifugation is carried out again under the same conditions , the product was dried in a vacuum drying oven at 40°C for 5 hours;

(4) The obtained product is placed in a tube furnace for annealing at 800° C. for 2 hours under a nitrogen atmosphere, and cooled to room temperature to obtain a vanadium dioxide-boron nitride phase-change thermally conductive composite material.

The vanadium dioxide-boron nitride phase-change thermally conductive composite material prepared in this example is a nano-sheet material.

Effect Example

(1) Thermal conductivity test:

The vanadium dioxide-boron nitride phase-change thermally conductive composite material prepared in Examples 1-4 was added to bisphenol A epoxy resin (containing 40 wt% of curing agent) at 40 wt %, and the mixture was heated in a vacuum mixer at 2000 r /min stirring and defoaming for 30min, poured into the mold, cured at 165 ℃ for 2h to obtain the test sample block, and tested the thermal conductivity on the hot wire method transient thermal conductivity instrument. The test results are shown in Table 1.

Table 1

It can be seen from Table 1 that the composite material prepared by the present invention has good thermal conductivity, and when tungsten and tellurium are doped at the same time, it has better thermal conductivity.

(2) Differential scanning calorimetry test:

Figure 2 shows the differential calorimetry test results of the composite materials in Examples 1-4 of the present invention and commercial pure vanadium dioxide. It can be seen from the figure that the composite materials provided in Examples 1-4 of the present invention maintained Vanadium dioxide has the characteristics of first-order phase transition, and the phase transition temperature is lower than that of commercial pure vanadium dioxide.

(3) Thermal stability:

Figure 3 shows the difference between the commercial pure vanadium dioxide (VO ₂ ) and the vanadium dioxide-boron nitride (VO ₂ -BN) composite material prepared in Example 1 of the present invention and its heating at 300°C for 3h Scanning calorimetry (DSC) curve. It can be seen from the figure that the DSC peak of pure VO ₂ after heating and oxidation treatment is obviously weakened, that is, the thermal stability is poor; while the DSC peak of VO ₂ -BN composite has no obvious change before and after heating and oxidation treatment, indicating its thermal stability. Sex was significantly improved.

The above is only the preferred embodiment of the present invention, it should be pointed out: for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.

Claims (10)

1. a preparation method of vanadium dioxide-boron nitride phase change thermally conductive composite material, is characterized in that, comprises the following steps: Hydrothermal reaction of vanadium salt, reducing agent, boron nitride and dopant in solvent; Wherein, the boron nitride is hexagonal boron nitride. 2. preparation method according to claim 1 is characterized in that, described vanadium salt is +5 valence vanadium salt. 3. The preparation method according to claim 1, wherein the reducing agent is selected from any one or more of oxalic acid, citric acid, formic acid and acetic acid. 4. preparation method according to claim 1 is characterized in that, described dopant is selected from ① salt of tungsten, magnesium, molybdenum, niobium, tantalum, zinc, aluminum, copper, ② transition state metal telluride, ③ Any one or more of the oxytellurium compounds; Preferably, the dopant is selected from any one of ammonium tungstate and tellurium dioxide or used in combination; more preferably, ammonium tungstate and tellurium dioxide are used in combination. 5. preparation method according to claim 1 is characterized in that, as preferred embodiment, described solvent is organic solvent, preferably ethanol, N,N-dimethylformamide, isopropanol and N-methyl Any one or more of pyrrolidones. 6. The preparation method according to claim 1, wherein the temperature of the hydrothermal reaction is 180-260 °C; Preferably, the time of the hydrothermal reaction is 12～24h; Preferably, the hydrothermal reaction is carried out under stirring conditions, and the stirring speed is preferably 100-500 r/min. 7. The preparation method according to claim 1, wherein the preparation method further comprises post-processing; the post-processing comprises centrifugation, washing, drying and annealing; the washing is ethanol and acetone washing respectively; the The drying is 40-80 ℃ for 4-12 hours; the annealing is 600-800 ℃ for 2-5 hours. 8. preparation method according to claim 1, is characterized in that, described preparation method specifically comprises the following steps: 1) dissolving ammonium metavanadate, oxalic acid, hexagonal boron nitride, ammonium tungstate and/or tellurium dioxide in a solvent to obtain a dispersion; 2) heating the dispersion obtained in step 1) to 180-260°C under stirring at 100-500 r/min, and reacting for 12-24 h; 3) After centrifuging the product obtained in step 2), discard the supernatant, wash with ethanol and acetone to remove residual reactants, centrifuge, and dry in a vacuum drying box at 40-80° C. for 4-12 hours; 4) annealing the product obtained in step 3) at 600 to 800° C. for 2 to 5 hours to obtain pure phase-change vanadium dioxide; Preferably, in step 1), the dosage ratio of the ammonium metavanadate, oxalic acid, hexagonal boron nitride, ammonium tungstate and tellurium dioxide is (100～300mg): (200～700mg): (50～150mg) : (2.7-7.5 mg): (0.8-4.0 mg). 9. The vanadium dioxide-boron nitride phase-change thermally conductive composite material obtained by the preparation method of any one of claims 1-8. 10. Use of the vanadium dioxide-boron nitride phase-change thermally conductive composite material according to claim 9 in the preparation of thermal interface materials.

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