CN112473579B - A kind of metal phase change microcapsule with thermal expansion cavity and preparation method thereof - Google Patents

Abstract

The invention discloses a metal phase change microcapsule with a thermal expansion cavity, which takes metal particles as a core material, wherein a porous inorganic wall material layer is coated outside the core material, and a thermal expansion cavity is arranged between the core material and the porous inorganic wall material layer; the heat expansion cavity and the porous inorganic wall material layer are obtained by carrying out heat treatment on an organic layer and an inorganic layer which are coated outside the core material, and decomposing organic matters in the organic layer into gas which escapes from the inorganic layer. The metal phase change microcapsule provides a thermal expansion space for metal, solves the microcapsule rupture problem caused by metal thermal expansion from the source, greatly improves the thermal cycle stability, breaks through the technical bottleneck of metal microcapsule preparation, has good functions of heat conduction, energy storage, temperature regulation and the like, and can be widely applied to the fields of heat storage, electronic equipment heat dissipation and the like.

Description

A kind of metal phase change microcapsule with thermal expansion cavity and preparation method thereof

technical field

The invention relates to the technical field of phase change microcapsule materials, in particular to a metal phase change microcapsule with thermal expansion cavity and a preparation method thereof.

Background technique

There is a lot of waste heat in the exhaust gas of steel, chemical industry and marine diesel engines. Due to the unstable working conditions, this part of the heat is difficult to be directly utilized and discharged directly. Therefore, the use of high-efficiency heat storage medium to recover this part of the heat has a good application prospect. The demand for high-energy-density lithium-ion batteries is increasing as electric vehicles, laptops, and smartphones become more commonplace. However, batteries generate a lot of heat during charging and discharging, and the performance of batteries is largely dependent on temperature, so developing advanced thermal management techniques for Li-ion batteries is critical to ensuring the safe use of these batteries and maintaining battery performance . In addition, there are also shortcomings in solar thermal utilization, and the use of high-efficiency heat storage media can effectively solve such problems. As an energy storage carrier, phase change materials (PCM) can store/release a large amount of heat during the melting/solidification process, and have broad application prospects in waste heat utilization, solar thermal utilization, and heat dissipation of electronic equipment.

The direct use of phase change materials will cause leakage during the phase change process, and microencapsulation of phase change materials is an effective method to solve this problem. Phase change microcapsules (MEPCM) are energy storage media that coat a layer of film (wall material) on the surface of phase change particles (core material) to form a core-shell structure. In recent years, it has received extensive attention from scholars at home and abroad.

At present, most studies on microcapsules at home and abroad choose organic phase change materials such as paraffin as the core material, and there are very few reports on metals or metal alloys as the core material of phase change microcapsules. There are many kinds of metals or metal alloys, and they have a large optional phase transition temperature range. For example, the phase transition temperature of liquid metal Ga is 29.8°C, and the phase transition temperature of alloy SnBi58 is 138°C, etc., and the unit volume of metal or metal alloy is The latent heat value is relatively large. In recent years, there have been a few reports on metal microcapsules, but the performance is not ideal, and there is still a considerable gap from industrial application. In addition to the problems of low-temperature organic phase change microcapsules, the main problems are: poor thermal cycle performance, large thermal expansion of metals at medium and high temperature, and further increase in volume after solid-liquid phase change, direct coating will be due to heat swelling and rupture of the microcapsules.

SUMMARY OF THE INVENTION

In view of the above deficiencies of the prior art, the object of the present invention is to provide a metal phase change microcapsule with thermal expansion cavity and a preparation method thereof, so as to solve the problem that the thermal cycle performance of the existing metal microcapsule is poor, and the metal microcapsule is easy to cracks, etc. Based on this, the inventor conceived and conducted in-depth research, and proposed the "double-layer coating, sacrificing the inner layer" method to prepare metal phase change microcapsules with thermal expansion cavities, which can solve the microcapsule rupture caused by metal thermal expansion from the source. question.

For achieving the above purpose, the technical scheme adopted in the present invention is:

A metal phase change microcapsule with a thermal expansion cavity, the microcapsule uses metal particles as a core material, the core material is covered with a porous inorganic wall material layer, and the core material and the porous inorganic wall material layer are between the core material and the porous inorganic wall material layer. There is a layer of thermal expansion cavity in between; wherein, the thermal expansion cavity and the porous inorganic wall material layer are thermally treated by the organic layer and the inorganic layer wrapped outside the core material, and the organic matter in the organic layer is decomposed into gas from Obtained after the inorganic layer escapes.

Further, the porous inorganic wall material layer is further coated with a dense inorganic wall material layer.

Further, the metal particles are at least one of tin, bismuth metal and metal alloy materials including tin and bismuth elements.

Further, the organic matter in the organic layer is at least one of polymethyl methacrylate, zein, urea-formaldehyde resin, melamine-formaldehyde resin, and chitosan.

Further, the inorganic material in the dense inorganic wall material layer and the porous inorganic wall material layer is at least one of silicon dioxide, titanium dioxide and calcium carbonate.

In another aspect of the present invention, there is provided a method for preparing a metal phase change microcapsule with thermal expansion cavity as above, the preparation method comprising the following steps:

S1: Weigh a certain amount of metal particles, and uniformly disperse them in a solvent to obtain a dispersion; then add easily decomposable volatile organic compounds, and coat the organic matter on the surface of the metal particles by ultrasonic immersion to obtain an organic layer coating The coated metal phase change microcapsules; or by adding a certain amount of organic monomers to the dispersion liquid, and then adding a certain amount of initiator, after the dropping is completed, the interfacial polymerization reaction is carried out under the assistance of ultrasound, and the reaction is completed. Then obtain organic layer-coated metal phase change microcapsules containing easily decomposable volatile organic compounds;

S2: Weigh a certain amount of inorganic sources, add surfactants with a mass-to-volume ratio of 4-6g:130-150ml and deionized water and stir to prepare a sol, or add ethanol with a volume-to-volume ratio of 8-10:0.5-1.5 After stirring with ammonia water, a sol is prepared; the organic layer-coated metal phase change microcapsules obtained in step S1 are added to the sol, and a gel is formed on the surface of the sol to obtain a metal double-coated organic layer and an inorganic layer. Phase change microcapsules;

S3: heat-treating the double-coated metal phase change microcapsules obtained in step S2 in a furnace, the organic matter in the organic layer is decomposed to form gas, which escapes through the inorganic layer under thermal expansion, and simultaneously forms a thermal expansion cavity layer and porous inorganic wall material layer to obtain the metal phase change microcapsule with thermal expansion cavity.

Further, in the step S2, a certain amount of easily decomposable volatile organic compounds are mixed into the inorganic source, and the organic compounds decompose and escape at the heat treatment temperature.

Further, a dense inorganic wall material layer is coated on the heat-treated metal phase change microcapsules through a sol-gel reaction to obtain metal phase change microcapsules with thermal expansion cavities.

Further, in step S1, the weight-to-volume ratio of the metal particles to the solvent is 2-6 g: 80-100 ml, the mass percentage of the organic matter in the dispersion liquid is 0.4-0.8%; the organic matter monomer, initiator The mass ratio to the dispersion liquid is 0.5 to 2.0:0.01 to 0.03:100.

Further, in step S2, the mass percentage of the inorganic source in the sol is 1-8%, and the mass ratio of the organic layer-coated metal phase change microcapsules to the inorganic source is 1:0.75-2.5.

Further, in step S3, the heat treatment adopts nitrogen atmosphere for protection, and the treatment temperature is 350-450°C.

Beneficial effects of the present invention:

The metal phase change microcapsule of the invention provides a thermal expansion space for metal, solves the microcapsule rupture problem caused by metal thermal expansion from the source, greatly improves its thermal cycle stability, and breaks through the technical bottleneck of metal microcapsule preparation.

The metal phase change microcapsule of the invention improves the technical level of phase change energy storage, has better functions of heat conduction, energy storage and temperature regulation, and can be applied to the fields of heat storage, heat dissipation of electronic equipment and the like.

Description of drawings

FIG. 1 is a scanning electron microscope (SEM) photograph of the metal phase change microcapsule with thermal expansion cavity in Example 1 of the present invention.

FIG. 2 is a scanning electron microscope (SEM) photograph of the metal phase change microcapsule with thermal expansion cavity in Example 1 of the present invention for 500 thermal cycles.

3 is a differential scanning calorimeter (DSC) photograph of the metal phase change microcapsule with thermal expansion cavity in Example 1 of the present invention after thermal cycling.

4 is an energy dispersive spectrometer (EDS) photograph of the metal phase change microcapsule with thermal expansion cavity in Example 2 of the present invention.

FIG. 5 is the X-ray photoelectron spectroscopy (XPS) analysis of the metal phase change microcapsule with thermal expansion cavity in Example 3 of the present invention.

6 is a scanning electron microscope (SEM) photograph of the cavity of the metal phase change microcapsule with thermal expansion cavity in Example 4 of the present invention.

7 is a differential scanning calorimeter (DSC) photograph of the metal phase change microcapsule with thermal expansion cavity in Example 5 of the present invention.

Detailed ways

The following description serves to disclose the invention to enable those skilled in the art to practice the invention. The preferred embodiments described below are given by way of example only, and other obvious modifications will occur to those skilled in the art.

Example 1

The preparation method of the metal phase change microcapsule with thermal expansion cavity of the present embodiment includes the following steps:

S1: Weigh 6g of spherical metal alloy powder (SnBi58), uniformly disperse it in 100ml of deionized water to obtain a dispersion; then add 0.55g of methacrylic acid (MAA) monomer, and then add 0.02g of ammonium persulfate as an initiator , under the power of 200w, ultrasonic-assisted interfacial polymerization on the surface of alloy particles, and the reaction was carried out for 30min to obtain pre-microcapsules. The pre-microcapsules were washed three times with deionized water and then suction filtered, and dried at 80 °C for 5h to obtain PMMA/ SnBi58 phase change microcapsules;

S2: prepare an aqueous solution of ammonium fluorotitanate with a concentration of 100 g/L and an aqueous solution of boric acid with a concentration of 100 g/L; take 5 g of the PMMA/SnBi58 phase change microcapsules obtained in step S1, add 0.5 g of surfactant CTAB and 30 ml of deionized water , and then added 30 ml of ammonium fluorotitanate aqueous solution and 90 ml of aqueous boric acid solution, reacted at 50 °C for 5 h under magnetic stirring, washed with deionized water three times, filtered with suction, and dried at 80 °C for 5 h to obtain TiO ₂ /PMMA/SnBi58 phase transition Microcapsules;

S3: Put the obtained microcapsules in a box-type atmosphere furnace, heat to 400°C at a heating rate of 1°C/min in a nitrogen atmosphere, and keep at 400°C for 1 h to decompose the PMMA layer to obtain a thermal expansion cavity. Alloy Microcapsules.

The test results show that, as shown in Figures 1 and 2, the obtained metal phase change microcapsules with thermal expansion cavities maintain a good spherical shape, have a smooth surface, and have a complete "core-shell" structure. The particle size is between 30 and 50 μm. The differential scanning calorimeter test of the metal phase change microcapsules with thermal expansion cavity shows that the latent heat value is 43.03 J/g, the melting peak temperature is 141.4 °C, and the solidification peak temperature It is 129.3℃, and the supercooling degree is 7.4℃. As shown in Fig. 3, the number of thermal cycles of the metal phase change microcapsules reaches 500 times, and still maintains good thermal stability.

Example 2

The preparation method of the metal phase change microcapsule with thermal expansion cavity of the present embodiment includes the following steps:

S1: Weigh 6g of spherical metal alloy powder (SnBi58), uniformly disperse it in 100ml of deionized water to obtain a dispersion; add 1g of methacrylic acid (MAA) monomer, and then add 0.02g of benzoyl peroxide as an initiator , under the power of 200w, ultrasonic-assisted interfacial polymerization on the surface of alloy particles, and the reaction was carried out for 30min to obtain pre-microcapsules. The pre-microcapsules were washed three times with deionized water and then suction filtered, and dried at 80 °C for 5h to obtain PMMA/ SnBi58 phase change microcapsules;

S2: prepare an aqueous solution of ammonium fluorotitanate with a concentration of 100 g/L and an aqueous solution of boric acid with a concentration of 100 g/L; take 5 g of the PMMA/SnBi58 phase change microcapsules obtained in step S1, add 0.5 g of surfactant CTAB and 30 ml of deionized water , and then added 30 ml of ammonium fluorotitanate aqueous solution and 90 ml of aqueous boric acid solution, reacted at 50 °C for 5 h under magnetic stirring, washed with deionized water three times, filtered with suction, and dried at 80 °C for 5 h to obtain TiO ₂ /PMMA/SnBi58 phase transition Microcapsules;

S3: Put the obtained microcapsules in a box-type atmosphere furnace, heat to 400°C at a heating rate of 1°C/min in a nitrogen atmosphere, and keep at 400°C for 1 h to decompose the PMMA layer to obtain a thermal expansion cavity. Alloy Microcapsules.

The test results show that, as shown in Figure 4, the obtained metal phase change microcapsules with thermal expansion cavity maintain a good spherical shape, and the surface is smooth and has a complete "core-shell" structure. Between 30 and 50 μm; the differential scanning calorimeter test of the metal phase change microcapsules with thermal expansion cavity shows that the latent heat value is 42.83 J/g, the melting peak temperature is 140.8 °C, and the solidification peak temperature is 128.0 °C , the supercooling degree is 6.7 ℃. The number of thermal cycles reaches 500 times, and it still maintains good thermal stability.

Example 3

The preparation method of the metal phase change microcapsule with thermal expansion cavity of the present embodiment includes the following steps:

S1: Weigh 6g of spherical metal alloy powder (SnBi58), uniformly disperse it in 100ml of deionized water to obtain a dispersion; add 2g of methacrylic acid (MAA) monomer, and then add 0.02g of benzoyl peroxide as an initiator , under the power of 200w, ultrasonic-assisted interfacial polymerization on the surface of alloy particles, and the reaction was carried out for 30min to obtain pre-microcapsules. The pre-microcapsules were washed three times with deionized water and then suction filtered, and dried at 80 °C for 5h to obtain PMMA/ SnBi58 phase change microcapsules;

S2: prepare an aqueous solution of ammonium fluorotitanate with a concentration of 100 g/L and an aqueous solution of boric acid with a concentration of 100 g/L; take 5 g of the PMMA/SnBi58 phase change microcapsules obtained in step S1, add 0.5 g of surfactant CTAB and 30 ml of deionized water , and then added 30 ml of ammonium fluorotitanate aqueous solution and 90 ml of aqueous boric acid solution, reacted at 50 °C for 5 h under magnetic stirring, washed with deionized water three times, filtered with suction, and dried at 80 °C for 5 h to obtain TiO ₂ /PMMA/SnBi58 phase transition Microcapsules;

S3: Put the obtained microcapsules in a box-type atmosphere furnace, heat to 400°C at a heating rate of 1°C/min in a nitrogen atmosphere, and keep at 400°C for 1 h to decompose the PMMA layer to obtain a thermal expansion cavity. Alloy Microcapsules.

The test results show that, as shown in Fig. 5, the prepared metal phase change microcapsules are the metal phase change microcapsules with thermal expansion cavity obtained after heat treatment of TiO ₂ /PMMA/SnBi58 phase change microcapsules, which maintains good performance. It has a spherical shape with smooth surface and a complete "core-shell" structure. The particle size of the microcapsules is between 30 and 50 μm. , the latent heat value is 48.46J/g, the melting peak temperature is 141.1℃, the solidification peak temperature is 128.1℃, and the supercooling degree is 6.4℃. The number of thermal cycles reaches 500 times, and it still maintains good thermal stability.

Example 4

The preparation method of the metal phase change microcapsule with thermal expansion cavity of the present embodiment includes the following steps:

S1: uniformly disperse 2g tin powder (Sn) in 80ml deionized water to obtain a dispersion; add 0.5g polymethyl methacrylate (PMMA), and coat the PMMA on the surface of the tin powder particles by ultrasonic immersion, After filtering and drying, PMMA/Sn phase change microcapsules were obtained;

S2: Under the ultrasonic stirring speed of 50 °C and 800 rpm, take 2 g of the PMMA/Sn phase change microcapsules obtained in step S1, add 0.5 g of the surfactant SDBS and 125 mL of deionized water, and stir in the conical flask for 0.5 to 1 h ; Use a constant pressure funnel to add 25ml of CaCl ₂ solution at a rate of 1 drop/second, the mass ratio of CaCl ₂ to deionized water is 1:25, and react for 0.5 to 1h; finally, add 25ml of Na at a rate of 1 drop/2 seconds ₂ CO ₃ solution, the mass ratio of Na ₂ CO ₃ and deionized water is 1:25, react for 1 h to 2 h; stop stirring, wash with deionized water and ethanol for 2 to 3 times respectively, and dry to obtain CaCO ₃ /PMMA/Sn Phase change microcapsules;

S3: heat-treating the CaCO ₃ /PMMA/Sn phase change microcapsules obtained in step S2 at a temperature of 400° C. to obtain metal microcapsules with thermal expansion cavities.

The test results show that, as shown in Figure 6, the obtained metal phase change microcapsules with thermal expansion cavity maintain a good spherical shape, have a smooth surface, and have a complete "core-shell" structure. Between 30 and 50 μm, the differential scanning calorimeter test of the metal phase change microcapsules with thermal expansion cavity shows that the latent heat value is 56.05 J/g, the melting peak temperature is 235.1 °C, and the solidification peak temperature is 144.0 °C , the supercooling degree is 76.7 ℃. The number of thermal cycles reaches 200 times, and it still maintains good thermal stability.

Example 5

The preparation method of the metal phase change microcapsule with thermal expansion cavity of the present embodiment includes the following steps:

S1: uniformly disperse 2g tin powder (Sn) in 80ml ethyl acetate to obtain a dispersion; add 0.5g polymethyl methacrylate (PMMA), and coat the PMMA on the surface of the tin powder particles by ultrasonic immersion , after filtration and drying, PMMA/Sn phase change microcapsules were obtained;

S2: Stir 80 mL of ethanol and 10 mL of ammonia water respectively to form a mixed solution, then add 1.5 g of tetraethyl orthosilicate and 0.5 g of cetyl trimethyl ammonium bromide while stirring, and continue to stir at room temperature for a certain amount of time. After the sol was formed, 2 g of the PMMA/Sn phase-change microcapsules obtained in step S1 were weighed and added to the sol, and the reaction was stopped after ultrasonic stirring at 70° C. for 1 h. The surface of the sol formed a gel, which was washed with ethanol. After several times, filter and dry to obtain cetyltrimethylammonium bromide@SiO ₂ /PMMA/Sn phase change microcapsules;

S3: Place the cetyltrimethylammonium bromide@SiO ₂ /PMMA/Sn phase-change microcapsules obtained in step S2 in a box-type atmosphere furnace, N ₂ atmosphere, and heat treatment at 400 °C for 1 h to make the inorganic wall material in the The hexadecyl trimethyl ammonium bromide and PMMA in the organic layer decompose into gas and escape from the interior of the phase change microcapsules, forming a porous inorganic wall material and a corresponding thermal expansion cavity layer simultaneously; it will have a thermal expansion cavity. The phase change microcapsules and 3-aminopropyltrimethoxysilane were placed at 80 ° C and the ethanol solution with a pH of 4.5 was re-coated, and the 3-aminopropyltrimethoxysilane was hydrolyzed on the surface of the capsule to form dioxide The silicon coating is used to seal the pores on the surface of the capsule, and finally a metal phase change microcapsule with thermal expansion cavity is formed.

The test results show that the obtained metal phase change microcapsules with thermal expansion cavity maintain a good spherical shape, have a smooth surface, and have a complete "core-shell" structure, and the microcapsule particle size is between 30 and 50 μm; As shown in Figure 7, the differential scanning calorimeter test of the metal phase change microcapsules with thermal expansion cavity shows that the latent heat value is 58.01 J/g, the melting peak temperature is 235.0 °C, and the solidification peak temperature is 141.7 °C , the supercooling degree is 74.8 ℃. The number of thermal cycles reaches 200 times, and it still maintains good thermal stability.

The foregoing has shown and described the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions describe only the principles of the present invention. Without departing from the spirit and scope of the present invention, there are various Variations and improvements are intended to fall within the scope of the claimed invention.

Claims (9)

1. The metal phase change microcapsule with the thermal expansion cavity is characterized in that metal particles are taken as a core material, a porous inorganic wall material layer is coated outside the core material, and a thermal expansion cavity is arranged between the core material and the porous inorganic wall material layer; the thermal expansion cavity and the porous inorganic wall material layer are obtained by carrying out heat treatment on an organic layer and an inorganic layer which are coated outside the core material, and decomposing organic matters in the organic layer into gas which escapes from the inorganic layer; the organic matter in the organic layer is polymethyl methacrylate; the preparation method of the microcapsule comprises the following steps:

s1: weighing a certain amount of metal particles, and uniformly dispersing the metal particles in a solvent to obtain a dispersion liquid; then adding easily decomposed and volatile organic matters, and coating the organic matters on the surfaces of the metal particles in an ultrasonic impregnation mode to obtain metal phase change microcapsules coated by an organic layer; or dropping a certain amount of organic monomers into the dispersion liquid, then adding a certain amount of initiator, carrying out interfacial polymerization reaction under the assistance of ultrasound after dropping is finished, and obtaining the metal phase change microcapsule coated with the organic layer containing the volatile organic compounds which are easy to decompose after the reaction is finished;

s2: weighing a certain amount of inorganic source, and adding the inorganic source into the mixture according to the mass-volume ratio of 4-6 g: stirring 130-150 ml of surfactant and deionized water to prepare sol, or adding the surfactant and the deionized water in a volume ratio of (8-10): stirring 0.5-1.5 of ethanol and ammonia water to prepare sol; adding the organic layer coated metal phase change microcapsule obtained in the step S1 into the sol to form gel on the surface of the sol, so as to obtain the organic layer and inorganic layer double-layer coated metal phase change microcapsule;

s3: and (4) carrying out heat treatment on the double-layer coated metal phase change microcapsule obtained in the step (S2) in a furnace, decomposing organic matters in the organic layer to form gas, allowing the gas to escape through the inorganic layer under thermal expansion, and synchronously forming a thermal expansion cavity layer and a porous inorganic wall material layer to obtain the metal phase change microcapsule with the thermal expansion cavity.

2. The metal phase change microcapsule with a thermally expansive cavity according to claim 1, wherein the porous inorganic wall material layer is further coated with a dense inorganic wall material layer.

3. The metallic phase change microcapsule with a thermally expansive cavity according to claim 1, wherein the metallic microparticles are at least one of tin, bismuth metal and a metallic alloy material comprising tin and bismuth elements.

4. The metallic phase change microcapsule having a thermally expansive cavity according to claim 2, wherein the inorganic material in the dense inorganic wall material layer and the porous inorganic wall material layer is at least one of silica, titanium dioxide, and calcium carbonate.

5. The metallic phase-change microcapsule according to claim 1 having a thermally expandable cavity, wherein a predetermined amount of easily decomposable organic substances is further mixed into the inorganic source in step S2, and the organic substances are decomposed and released at the heat treatment temperature.

6. The metal phase-change microcapsule with a thermal expansion cavity according to claim 1, wherein the metal phase-change microcapsule with a thermal expansion cavity is obtained by coating a dense inorganic wall material layer outside the metal phase-change microcapsule after heat treatment through sol-gel reaction.

7. The metal phase change microcapsule with a thermally expansive cavity according to claim 1, wherein in step S1, the weight to volume ratio of the metal microparticles to the solvent is 2-6 g: 80-100 ml of the dispersion liquid, wherein the organic matter accounts for 0.4-0.8% of the dispersion liquid by mass percent; the mass ratio of the organic monomer to the initiator to the dispersion liquid is 0.5-2.0: 0.01-0.03: 100.

8. the metal phase change microcapsule with the thermally expansive cavity according to claim 1, wherein in step S2, the inorganic source accounts for 1-8% of the sol by mass, and the organic layer covers the metal phase change microcapsule and the inorganic source at a mass ratio of 1: 0.75 to 2.5.

9. The metal phase change microcapsule with the thermally expandable cavity according to claim 1, wherein in step S3, the heat treatment is performed under a nitrogen atmosphere, and the treatment temperature is 350 to 450 ℃.

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