NL2033966A

NL2033966A - Multifunctional composite phase change material supported by nickel-plated foam and mxene collaboratively, and preparation method thereof

Info

Publication number: NL2033966A
Application number: NL2033966A
Authority: NL
Inventors: Cheng Ziling; Xue Bai
Original assignee: Univ Guizhou
Priority date: 2022-01-21
Filing date: 2023-01-16
Publication date: 2023-03-07
Also published as: NL2033966B1; CN114561192A; CN114561192B

Abstract

UITTREKSEL The present disclosure discloses a multifunctional composite phase change material supported by nickel—plated foam and MXene collaboratively, and a preparation method thereof. The multifunctional composite phase change material consists of a 5 regenerated cellulose/graphene—filled nickel—plated melamine sponge composite aerogel, a phase change material and, an. MXene film; the regenerated cellulose/graphene—coated nickel—plated melamine sponge composite aerogel is prepared by a vacuum freeze drying method, and a semi—finished product of the composite phase 10 change material is prepared by a vacuum impregnation method; and the MXene film is prepared by a vacuum—assisted suction filtration method, and, the multifunctional composite phase change material supported by the nickel—plated foam and the MXene collaboratively is prepared, by a physical binding method, or other preparation 15 methods. The Hmltifunctional composite phase change material has excellent comprehensive performance, the latent heat of phase change is up to 154.3 J/g, the thermal conductivity is increased to 0.47 WmﬁKﬁ, and the electromagnetic shielding effectiveness is 32.7 dB. 20 (+ Fig. 1)

Description

MULTIFUNCTIONAL COMPOSITE PHASE CHANGE MATERIAL SUPPORTED BY

NICKEL-PLATED FOAM AND MXENE COLLABORATIVELY, AND PREPARATION

METHOD THEREOF

TECHNICAL FIELD

The present disclosure relates to the technical field of mul- tifunctional composite materials, in particular to a multifunc- tional composite phase change material supported by nickel-plated foam and MXene collaboratively, and a preparation method thereof.

BACKGROUND ART

With the rapid development of science and technologies, high requirements are also put forward for preparation materials of electronic components to meet use requirements. There are lots of limitations to practical application of a single functional mate- rial, which may be solved by design of multifunctional materials.

For example, thermally conductive composite phase change materials have functions of thermal energy storage and release, which may effectively solve the problem of heat accumulation generated in operation of the electronic components. However, with the continu- ous improvement of the integration degree of the electronic compo- nents, the problem of electromagnetic radiation interference is inevitable. Thus, it is an effective solution to make the materi- als have high electromagnetic shielding effectiveness to reduce hazards and interference problems caused by electromagnetic waves.

At present, there are more and more researchers dedicated to de- velopment of multifunctional composite materials used in the field of electronic equipment, in which the thermally conductive compo- site phase change materials with high electromagnetic shielding effectiveness have high research value and broad application pro- spects.

Phase change materials may control latent heat stored or re- leased in a heating or cooling process by regulating temperature variation, which have the advantages of high energy storage densi- ty, low temperature fluctuation, good weatherability and the like.

However, the phase change materials also have the shortcomings of poor self-encapsulation, easy leakage and low thermal conductivi- ty. The shortcomings of a single phase change material may be ef- fectively overcome by introducing high-performance composite phase change materials. At present, the encapsulation types of the com- posite phase change materials include a microcapsule method, a po- rous framework encapsulating method, a melt blending method and the like, wherein the porous framework encapsulating method means that a matrix is constructed as a porous network structure to ad- sorb or encapsulate molten phase change materials to obtain the composite phase change materials with shape stability and good en- capsulating performance after solidification formation. At pre- sent, effective porous frameworks include metal foam, graphene aerogel, porous carbon, cellulose aerogel and the like.

Cellulose may be used for preparing porous aerogel due to its characteristics of wide sources, environmental friendliness, high strength, low density and the like. Nanofiber aerogels are common- ly used in composite phase change materials, while the application of regenerated cellulose aerogels is relatively rare. The struc- tural strength of the regenerated cellulose aerogels is higher than that of the nanocellulose aerogels, and the crosslinking den- sity is higher, which is more conducive to encapsulation of the phase change materials.

Therefore, the present disclosure discloses a multifunctional composite phase change material supported by nickel-plated foam and MXene collaboratively, and a preparation method thereof. The multifunctional composite phase change material consists of a re- generated cellulose/graphene-filled nickel-plated melamine sponge composite aerogel, a phase change material and an MXene film; the regenerated cellulose/graphene-coated nickel-plated melamine sponge composite aerogel is prepared by a vacuum freeze drying method, and a semi-finished product of the composite phase change material is prepared by a vacuum impregnation method; and the

MXene film is prepared by a vacuum assisted filtration method, and the multifunctional composite phase change material supported by the nickel-plated foam and the MXene collaboratively is prepared by a physical binding method or other preparation methods. The multifunctional composite phase change material has excellent com-

prehensive performance, the latent heat of phase change is up to 154.3 J/g, the thermal conductivity is increased to 0.47 Wm 'K™, and the electromagnetic shielding effectiveness is 32.7 dB. The composite material is capable of effectively encapsulating the phase change material due to its double-support network structure, and may be applied to thermal management materials and electromag- netic shielding materials in the electronic components.

SUMMARY

The present disclosure aims to overcome the shortcomings in the prior art, and provides a multifunctional composite phase change material supported by nickel-plated foam and MXene collabo- ratively, and a preparation method thereof. The multifunctional composite phase change material consists of a regenerated cellu- lose/graphene-filled nickel-plated melamine sponge composite aero- gel, a phase change material and an MXene film; the regenerated cellulose/graphene-coated nickel-plated melamine sponge composite aerogel is prepared by a vacuum freeze drying method, and a semi- finished product of the composite phase change material is pre- pared by a vacuum impregnation method; and the MXene film is pre- pared by a vacuum-assisted suction filtration method, and the mul- tifunctional composite phase change material supported by the nickel-plated foam and the MXene collaboratively is prepared by a physical binding method or other preparation methods. The multi- functional composite phase change material has excellent compre- hensive performance, the latent heat of phase change is up to 154.3 J/g, the thermal conductivity is increased to 0.47 WK’, and the electromagnetic shielding effectiveness is 32.7 dB. The composite material is capable of effectively encapsulating the phase change material due to its double-support network structure, and may be applied to thermal management materials and electromag- netic shielding materials in electronic components.

In order to fulfill the above technical objectives, the tech- nical solution is as follows:

A multifunctional composite phase change material supported by nickel-plated foam and MXene collaboratively is provided. The multifunctional phase change composite is prepared by compounding a regenerated cellulose/graphene-coated nickel-plated melamine sponge composite aerogel, a phase change material and an MXene film, and the regenerated cellulose/graphene-coated nickel-plated melamine sponge composite aerogel is of a three-dimensional dou- ble-support network structure; the MXene film is of a compact mul- tilayer structure, and the phase change material is effectively encapsulated in the multifunctional composite material; a thermal conductivity coefficient of the multifunctional composite phase change material supported by the nickel-plated foam and the MXene collaboratively ranges from 0.4 Wm 'K*® to 0.5 Wm 'K*'; and the electromagnetic shielding effectiveness ranges from 24 dB to 32 dB, and the latent heat of phase change ranges from 139.3 J/g to 154.3 J/g.

A preparation method of the multifunctional composite phase change material supported by the nickel-plated foam and the MXene collaboratively, includes the following steps: step S1: preparing the regenerated cellulose/graphene-coated nickel-plated melamine sponge composite aerogel from nickel-plated melamine sponge, regenerated cellulose and graphene by a vacuum freeze drying method; step S2: preparing a semi-finished product of the composite phase change material from the regenerated cellulose/graphene- coated nickel-plated melamine sponge composite aerogel obtained in step 81 and the phase change material by a vacuum impregnation method; step S3: preparing the few-layered MXene film through suction filtration of an MXene colloidal solution by a vacuum-assisted filtration method; and step S4: preparing the multifunctional composite phase change material supported by the nickel-plated foam and the MXene collab- oratively from the semi-finished product of the composite phase change material prepared in step S2 and the MXene film prepared in step S3 through physical binding.

Furthermore, the preparation method of the regenerated cellu- lose/graphene-coated nickel-plated melamine sponge composite aero- gel in step S1 includes the following steps: step S11: preparing the nickel-plated melamine sponge by a surface electroless nickel plating method, performing ultrasonic treatment on the washed melamine sponge in a sensitizing solution and an activation solution successively and respectively, placing the melamine sponge into an electroless plating solution after washing and drying, dropwise adding a reductant solution for ul-

5 trasonic reaction and electroless nickel plating, finally taking out the nickel-plated sponge for repeated washing, and drying it for later use; wherein the sensitizing solution is prepared from tin chloride hexa- hydrate and a hydrochloric acid solution, the activation solution is prepared from palladium chloride and a hydrochloric acid solu- tion, the electroless plating solution is a mixed solution pre- pared by mixing nickel chloride hexahydrate, sodium citrate dihy- drate and ammonium hydroxide in deionized water, and the reductant solution is prepared by dissolving sodium hypophosphite into de-

ionized water;

step S12: preparing the regenerated cellulose by dissolving cotton linters by a low-temperature alkali-urea-water dissolution system, adding graphene powder to the solution system in advance and performing low-temperature treatment to obtain a mixed solu-

tion of dissolution system/graphene, controlling a mass concentra- tion of the graphene powder at 1 wt% to 5 wt%, then adding the cotton linters to the mixed solution of dissolution sys- tem/graphene, and quickly taking out and stirring the cotton lint- ers by an electric magnetic stirring rod to obtain a mixed solu-

tion of regenerated cellulose/graphene; wherein the dissolution system is a mixed solution of sodium hydrox- ide, urea and deionized water; and step S13: soaking the nickel-plated melamine sponge prepared in step S11 into the mixed solution of the regenerated cellu-

lose/graphene prepared in step S12 to absorb the mixed solution fully till there are no bubbles in the sponge, then, taking out the complex and quickly placing it into absolute ethyl alcohol for gelation, performing solvent displacement by the deionized water repeatedly, freezing a composite gel block in a liquid nitrogen atmosphere by an ice template method, and finally obtaining the blocky regenerated cellulose/graphene-coated nickel-plated mela- mine sponge composite aerogel through freeze drying.

Furthermore, the specific method for preparing the semi- finished product of the composite phase change material by the vacuum impregnation method in step S2 includes the following steps: melting the phase change material in advance, immersing the regenerated cellulose/graphene-coated nickel-plated melamine sponge composite aerogel in the molten phase change material for vacuum impregnation for 24 hours to 48 hours at a holding tempera- ture, taking it out and adsorbing phase change melts unadsorbed on a surface with oil absorbing paper, to obtain the semi-finished product of the composite phase change material after solidifica- tion at room temperature; wherein the phase change material in step S2 is at least one of poly- ethylene glycol, paraffin, fatty acid ester and polyol.

Furthermore, the specific method for preparing the few- layered MXene film in step S2 includes the following steps: generating HF through an in-situ reaction of lithium fluoride with a hydrochloric acid to etch a metal Al layer in Ti;AlC, pow- der, and hermetically storing the few-layered MXene colloidal so- lution prepared through reactive etching, centrifugal washing, ul- trasonic stripping and centrifugal collection in a refrigerator at 4°C to 6°C for later use; and conducting suction filtration on a certain amount of the MXene colloidal solution by the vacuum as- sisted filtration method, and vacuum drying it at 35°C to 40°C for 4 hours to 6 hours to obtain the MXene film.

Furthermore, the specific method for preparing the multifunc- tional composite phase change material supported by the nickel- plated foam and the MXene collaboratively through physical binding in step S4 includes the following steps: cutting the MXene film prepared in step S3 according to the same dimensions as the length and width of the semi-finished prod- uct of the composite phase change material prepared in step 382, and preparing the multifunctional composite phase change material from the MXene film and the semi-finished product of the composite phase change material through physical binding with molten poly- ethylene glycol.

Furthermore, the sensitizing solution is prepared from 2 g of tin chloride hexahydrate and 100 mL of hydrochloric acid solution (0.1 mol/L), the activation solution is prepared from 0.01 g of palladium chloride and 100 mL of hydrochloric acid solution (0.01 mol/L), the plating solution is a mixed solution prepared by mix- ing 2 g of nickel chloride hexahydrate, 3 g of sodium citrate di- hydrate and 12 mL of ammonium hydroxide in 90 mL of deionized wa- ter, and the reductant solution is prepared by dissolving 4 g of sodium hypophosphite into 10 mL of deionized water; reaction time for the electroless nickel plating ranges from 1 minute to 5 minutes, and is preferably 3 minutes; and the sponge needs to be washed with the deionized water for 4 to 6 times respectively after sensitization, activation and nickel plating, and vacuum dried at 35°C to 40°C for 24 hours to 48 hours after activation and nickel plating.

Furthermore, a mass ratio of the sodium hydroxide to the urea to the deionized water to the cotton linters in step S12 is (7- 14): (12-24): (81-162): (2-3); the cotton linters are prepared from a cotton pulp board by a pulverizer; an electric stirring speed ranges from 3500 rpm to 5000 rpm in the dissolution process; in the solvent displacement process in step $513, the compo- site gel is displaced with the deionized water for 2 to 4 times, wherein time of each displacement ranges from 8 hours to 12 hours; and the vacuum freeze drying is conducted in a freeze dryer under a vacuum degree less than 100 Pa at a cold trap temperature of - 60°C for 24 hours to 48 hours; furthermore, an amount of the lithium fluoride ranges from 1 g to 2 g, an amount of the hydrochloric acid ranges from 20 mL to 40 mL, and an amount of the Ti3A1C: powder ranges from 1 g to 2 g; the reaction is conducted at 35°C to 40°C and a rotational speed ranging from 1500 rpm to 2000 rpm for 36 hours to 48 hours; a rotational speed for the centrifugal washing is 3500 rpm, time is 10 minutes, and washing is conducted till a pH value of a supernatant is larger than 6; the ultrasonic stripping is conducted in an ice bath for 1 to

2 hours ultrasonically; and a rotational speed for the centrifugal collection is 3500 rpm, time ranges from 20 minutes to 60 minutes, and a supernatant dark green few-layered MXene colloidal solution is collected cy- clically.

The multifunctional composite phase change material supported by the nickel-plated foam and the MXene collaboratively according to any one of the above, is characterized in that the multifunc- tional composite phase change material is applied to thermal man- agement materials and electromagnetic shielding materials in elec- tronic components.

The present disclosure provides the multifunctional composite phase change material supported by the nickel-plated foam and the

MXene collaboratively, and the preparation method thereof, which solve the problems of easy leakage, low thermal conductivity and single function of conventional phase change materials.

The present disclosure has the following beneficial effects:

The multifunctional composite material obtained by adopting the above technical solution is normally in a solid state, which may retain high shape stability even if being used at a tempera- ture higher than the melting temperature of the phase change mate- rial, and has the advantages of ideal thermal conductivity coeffi- cient, higher electromagnetic shielding effectiveness, higher la- tent heat of phase change and excellent thermal cycling stability.

The multifunctional composite phase change material prepared in the present disclosure has multiple complex structures. Where- in, the regenerated cellulose/graphene-coated nickel-plated mela- mine sponge composite aerogel has the double-support network structure; on the one hand, regenerated cellulose/graphene net- works make a major contribution to improvement of thermal conduc- tivity of the multifunctional composite phase change material, and on the other hand, a nickel-plated melamine sponge conductive framework in the aerogel plays a certain role in improving the electromagnetic shielding effectiveness of the multifunctional composite phase change material. In addition, the MXene conductive film is arranged at the bottom of the composite material, which is conducive to improvement of the thermal conductivity and electro-

magnetic shielding effectiveness of the composite material. The multifunctional composite phase change material stated in the pre- sent disclosure has excellent comprehensive performance, the ther- mal conductivity coefficient is 0.47 Wm K', the electromagnetic shielding effectiveness is 32.7 dB, and the latent heat of phase change is 154.3 J/g.

The composite aerogel stated in the present disclosure is higher in strength than most aerogels, is capable of effectively encapsulating the phase change material due to its double-support network structure, and is not prone to deform, which avoids the leakage problem of the molten phase change material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows scanning electron microscope (SEM) images of melamine sponge prepared in step 1 in Embodiment 1 of the present disclosure before and after nickel plating;

FIG. 2 shows an SEM image of a regenerated cellu- lose/graphene-coated nickel-plated melamine sponge composite aero- gel prepared in step 1 in Embodiment 1 of the present disclosure;

FIG. 3 shows sectional microscopic SEM images and energy dis- perse spectroscopy (EDS) images of a multifunctional composite phase change material prepared in Embodiment 1 of the present dis- closure;

FIG. 4 shows temperature rise and temperature drop curve graphs of multifunctional composite phase change materials pre- pared in Embodiments 1 to 3 of the present disclosure in differen- tial scanning calorimetry (DSC);

FIG. 5 shows a temperature rise-temperature drop curve graphs of a multifunctional composite phase change material prepared in

Embodiment 1 of the present disclosure after DSC is performed ini- tially and for 50 cycles;

FIG. 6 shows thermal conductivity of multifunctional compo- site phase change materials prepared in Embodiments 1 to 3 of the present disclosure;

FIG. 7 shows electromagnetic shielding effectiveness of mul- tifunctional composite phase change materials prepared in Embodi- ments 1 to 3 of the present disclosure and pure polyethylene gly- col (PEG);

FIG. 8 shows electromagnetic shielding effectiveness of a multifunctional composite phase change material prepared in Embod- iment 1 of the present disclosure; and

FIG.9 is a photograph showing leakage of a multifunctional composite phase change material prepared in Embodiment 1 of the present disclosure and pure PEG on a heating platform in a heating process.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure will be further described below with reference to drawings, but the protection scope of the present disclosure is not limited to the following description:

In order to better understand the technical solution of the present disclosure, a reaction process is described as follows:

Unless otherwise stated, all test materials used in the fol- lowing embodiments are conventional test materials in the art, and may be available commercially or prepared by the prior art.

Embodiment 1: 1. Firstly, washed melamine sponge is immersed into a sensi- tizing solution prepared from 2 g of tin chloride hexahydrate and 100 mL of hydrochloric acid solution (0.1 mol/L) for ultrasoni- cation for 30 minutes, then the melamine sponge is washed with de- ionized water for 5 times, and placed in an activation solution prepared from 0.01 g of palladium chloride and 100 mL of hydro- chloric acid solution (0.01 mol/L) for ultrasonication for 30 minutes, and then the activated melamine sponge is washed with the deionized water for 5 times, and vacuum dried at 35°C for 48 hours.

The activated sponge is placed in a plating solution prepared from 2 g of nickel chloride hexahydrate, 3 g of sodium citrate dihy- drate, 12 mL of ammonium hydroxide and 90 mL of deionized water, a reductant solution (prepared by dissolving 4 g of sodium hypophos- phite into 10 mL of deionized water) is dropwise added to the plating solution for ultrasonic reaction at 50°C for 3 minutes, the sponge with a surface having metallic nickel gloss is taken out, and washed with the deionized water for 5 times, the washed sponge is vacuum dried at 35°C for 48 hours to obtain nickel-plated mela- mine sponge, and the nickel-plated melamine sponge is hermetically stored at room temperature for later use; then, a dissolving solu- tion is prepared from 7 g of sodium hydroxide, 12 g of urea and 81 g of deionized water, 5 wt% of graphene is added to the dissolving solution, the dissolving solution is placed in a refrigerator for precooling at -12°C for 4 hours, and then 3 g of cotton linters are added to the dissolving solution, and quickly stirred by an elec- tric stirring rod (5000 rpm, 8 minutes) to obtain a mixed solution of regenerated cellulose/graphene after dissolution; the nickel- plated sponge is immersed into the mixed solution of the regener-

ated cellulose/graphene to fully absorb the mixed solution, till there are no bubbles in the sponge, the sponge filled with the re- generated cellulose/graphene is transferred into absolute ethyl alcohol for standing for 10 minutes, a gelated regenerated cellu- lose/graphene-coated nickel-plated melamine sponge gel block is immersed into the deionized water for solvent displacement for 48 hours, the deionized water is replaced once every 10 hours, and obtained regenerated cellulose/graphene-coated nickel-plated mela- mine sponge hydrogel is dried by a vacuum freeze dryer for 48 hours after being frozen in a liquid nitrogen atmosphere by an ice template method, to obtain a blocky regenerated cellu- lose/graphene-coated nickel-plated melamine sponge composite aero- gel.

2. Polyethylene glycol is molten in a vacuum oven at 80°C in advance, the composite aerogel is immersed into the molten poly-

ethylene glycol for vacuum impregnation at 80°C for 48 hours, and taken out, polyethylene glycol melts unadsorbed on a surface are adsorbed with oil absorbing paper, and the composite aerogel is solidified at room temperature to obtain a semi-finished product of the composite phase change material.

3. 2 g of lithium fluoride and 40 mL of 9M hydrochloric acid react in situ for 30 minutes to form an HF etching solution, 2 g of MAX powder is slowly added to the HF etching solution for stir- ring at 40°C for 36 hours, and the mixture is washed with the de- ionized water for 5 times cyclically and centrifugally (3500 rpm,

10 minutes), till a pH value of a supernatant is 6 or so; a pre- cipitate at a bottom of a centrifugal tube is collected, 20 mL of deionized water is added, and the mixed solution is shaken up vio- lently by hand for ultrasonication under an ice bath condition for 1.5 hours; the above mixed solution is centrifuged at 3500 rpm for 30 minutes, and a supernatant dark green liquid is collected, which is a few-layered MXene colloidal solution; and 10 mg/mL of few-layered MXene colloidal solution is prepared, 10 mL of MXene colloidal solution is subjected to suction filtration by a vacuum- assisted filtration method to form a film, and the film is vacuum dried at 35°C for 4 hours to obtain an MXene film. 4. The prepared MXene film is cut according to the same di- mensions as the length and width of the above semi-finished prod- uct of the composite phase change material, and a multifunctional composite phase change material is prepared from the MXene film and the semi-finished product of the composite phase change mate- rial through physical binding with the molten polyethylene glycol.

Embodiment 2:

This embodiment differs from Embodiment 1 in that a content of graphene in step 1 is 3 wt%. Other steps and parameters are the same as those in Embodiment 1.

Embodiment 3

This embodiment differs from Embodiments 1 and 2 in that a content of graphene in step 1 is 1 wt%. Other steps and parameters are the same as those in Embodiment 1.

As shown in FIG. 1, after a melamine sponge framework is sub- jected to surface electroless nickel plating, a compact metal nickel coating is attached to the smooth surface, and therefore the melamine sponge framework has electrical conductivity.

As shown in FIG. 2, the regenerated cellulose/graphene-coated nickel-plated melamine sponge composite aerogel has a double- support network structure, and a regenerated cellulose/graphene network is of a three-dimensional cross-linked network structure, by which the nickel-plated melamine sponge framework is tightly coated to provide a high support strength for the composite aero- gel.

As shown in FIG. 3, the multifunctional composite phase change material is of an asymmetric structure consisting of a blocky regenerated cellulose/graphene-coated nickel-plated mela-

mine sponge/polyethylene glycol composite phase change material and an MXene film. It can be known from a Ti element map that the

MXene is tightly fit to the bottom of the composite material; and it can be known from a Ni element map that the melamine sponge framework is distributed in the blocky composite material.

It can be known from FIG. 4 that melting temperatures of the multifunctional composite phase change materials in Embodiments 1 to 3 are all higher than that of the polyethylene glycol, and crystallization temperatures are all lower than that of the poly- ethylene glycol, wherein the melting temperature and the crystal- lization temperature of the multifunctional composite phase change material in Embodiment 1 are 63°C and 38.9°C respectively; and in addition, the latent heat of phase change of the polyethylene gly- col is 157.3 J-g™*, and the latent heat of phase change of the mul- tifunctional composite phase change materials in Embodiments 1 to 3 is 154.3 Jrg, 150.0 Jrg, and 139.3 Jg respectively.

It can be known from FIG. 5 that the multifunctional compo- site phase change material in Embodiment 1 is small in change of latent heat of phase change and phase change temperature after 50 cycles of heating-cooling, which proves that the multifunctional composite phase change material provided by the present disclosure has high phase change stability.

As shown in FIG. 6, a thermal conductivity coefficient of the polyethylene glycol is 0.27 WmóK*, and thermal conductivity coef- ficients in Embodiments 1 to 3 are 0.47, 0.43 and 0.4 respective- ly, which are increased by 48% to 74% compared with the thermal conductivity coefficient of the polyethylene glycol, proving that the multifunctional composite phase change material provided by the present disclosure has high thermal conductivity.

As shown in FIG. 7, at X wavebands (8.2 GHz to 12.4 GHz), an electromagnetic shielding effectiveness value of the polyethylene glycol ranges from 1.30 dB to 1.35 dB; an electromagnetic shield- ing effectiveness value of the multifunctional composite phase change material in Embodiment 1 ranges from 31.0 dB to 35.7 dB; an electromagnetic shielding effectiveness value of the multifunc- tional composite phase change material in Embodiment 2 ranges from 24.3 dB to 25.4 dB; and an electromagnetic shielding effectiveness value of the multifunctional composite phase change material in

Embodiment 3 ranges from 22.8 dB to 26.2 dB. The electromagnetic shielding effectiveness values in Embodiments 1 to 3 are all larg- er than 20 dB, and meet the requirements for commercial use, which prove that the multifunctional composite phase change material provided by the present disclosure has excellent electromagnetic shielding effectiveness. Additionally, as shown in FIG. 8, the to- tal electromagnetic shielding effectiveness value of the multi- functional composite phase change material in Embodiment 1 is a sum of a reflection effectiveness value and an absorption effec- tiveness value, an average electromagnetic shielding effectiveness value thereof is 32.7 dB, an average reflection effectiveness val- ue is 25.9 dB, and an average absorption effectiveness value is 6.8 dB.

As shown in FIG. 9, after a polyethylene glycol block and the block of the multifunctional composite phase change material in

Embodiment 1 are heated to 80°C on a heating platform, the polyeth- ylene glycol is molten completely, while a sample in Embodiment 1 still remains a complete shape, and is free of obvious leakage, which proves that the multifunctional composite phase change mate- rial provided by the present disclosure has excellent leak-proof performance and shape stability.

In conclusion, the present disclosure discloses the multi- functional composite phase change material supported by nickel- plated foam and MXene collaboratively, and a preparation method thereof. The multifunctional composite phase change material con- sists of a regenerated cellulose/graphene-filled nickel-plated melamine sponge composite aerogel, a phase change material and an

Mxene film; the regenerated cellulose/graphene-coated nickel- plated melamine sponge composite aerogel is prepared by a vacuum freeze drying method, and a semi-finished product of the composite phase change material is prepared by a vacuum impregnation method; and the MXene film is prepared by a vacuum-assisted suction fil- tration method, and the multifunctional composite phase change ma- terial supported by the nickel-plated foam and the MXene collabo- ratively is prepared by a physical binding method or other prepa- ration methods. The multifunctional composite phase change materi-

al has excellent comprehensive performance, the latent heat of phase change is up to 154.3 J/g, the thermal conductivity is in- creased to 0.47 Wm 'K', and the electromagnetic shielding effec- tiveness is 32.7 dB. The composite phase change material is capa- ble of effectively encapsulating the phase change material due to its double-support network structure, and may be applied to the thermal management materials and the electromagnetic shielding ma- terials in the electronic components.

The multifunctional composite phase change material prepared in the present disclosure has multiple complex structures. Where- in, the regenerated cellulose/graphene-coated nickel-plated mela- mine sponge composite aerogel has the double-support network structure; on the one hand, regenerated cellulose/graphene net- works make a major contribution to improvement of thermal conduc- tivity of the multifunctional composite phase change material, and on the other hand, a nickel-plated melamine sponge conductive framework in the aerogel plays a certain role in improving elec- tromagnetic shielding effectiveness of the multifunctional compo- site phase change material. In addition, the MXene conductive film is arranged at the bottom of the composite material, which is con- ducive to improvement of the thermal conductivity and electromag- netic shielding effectiveness of the composite material. The mul- tifunctional composite phase change material stated in the present disclosure has excellent comprehensive performance, the thermal conductivity coefficient is 0.47 Wm 'K*, the electromagnetic shielding effectiveness is 32.7 dB, and the latent heat of phase change is 154.3 J/g.

The composite aerogel stated in the present disclosure is higher in strength than most aerogels, capable of effectively en- capsulating the phase change material due to its double-support network structure, and is not prone to deform, to avoid the leak- age problem of the molten phase change material.

So far, those skilled in the art know that, although the em- bodiments of the present disclosure have been shown and described in detail herein, many other variations or modifications meeting the principle of the present disclosure may still be directly de- termined or deduced according to the content disclosed by the pre- sent disclosure without departing from the spirit and range of the present disclosure. Therefore, the scope of the present disclosure should be appreciated and designated to cover all these other var- iations or modifications.

Claims

CONCLUSIONS

A multifunctional phase change composite material supported by nickel-plated foam and MXene, characterized in that the multifunctional phase change composite material is formed by joining together regenerated cellulose/graphene coated nickel-melamine sponge composite airgel, phase change material and MXene film, and the regenerated cellulose/graphene coated nickel-melamine sponge composite airgel has a three-dimensional double supporting network structure; the MXene film has a dense multi-layer structure, the phase change material is effectively encapsulated in the multifunctional composite material, and the thermal conductivity of the multifunctional phase change composite material supported by nickel-plated foam and MXene is 0.2-0.5W target ; the electromagnetic shielding effectiveness is 24-32 dB, and the latent heat of the phase transition is 139.3-154.3 J/g; wherein the preparation method of the multifunctional phase change composite material supported by nickel-plated foam and MXene comprises the following steps: Step S1: Using nickel-plated melamine sponge, regenerated cellulose and graphene, the regenerated cellulose/graphene coated nickel-laminated melamine was sponge compound airgel prepared by vacuum freeze-drying method; Step S2: The regenerated cellulose/graphene coated nickel-plated melamine sponge composite airgel and the phase change material prepared in Step S1 are prepared by a vacuum impregnation method to prepare a phase change composite semi-finished product; Step S3: MXene colloidal solution was pumped and filtered by vacuum-assisted filtration method to prepare low-layer MXene thin films; Step S4: The multifunctional phase change composite material supported by nickel-plated foam and MXene is synergistically prepared by mixing the semi-finished product of the phase change composite material prepared in Step S2 and the phase change composite material prepared in Step S3.

MXene film to physically bond together.

A multifunctional phase change composite material supported by nickel-plated foam and MXene according to claim 1, characterized in that the preparation method of regenerated cellulose/graphene coated nickel foam composite airgel in step S1 comprises the following steps: S11: the nickel-plated melamine sponge is prepared by surface electroless nickel plating method; the washed melamine sponge is treated by ultrasonic wave in a sensitizing solution and an activating solution respectively; after washing and drying, the melamine sponge is placed in an electroless plating solution; a reducing agent solution is added dropwise; the nickel plated sponge is electroless plated by ultrasonic wave reaction; finally, the nickel-plated sponge is fished out for repeated washing and drying for standby; the sensitizing solution is prepared by stannic chloride hexahydrate and hydrochloric acid solution, the activating solution is prepared by palladium chloride and hydrochloric acid solution, the electrofusion solution is a mixed solution prepared by mixing nickel chloride hexahydrate, sodium citrate dihydrate and ammonia water in deionized water, and the reducing agent solution is prepared by dissolving sodium hypophosphite in deionized water; Step S12: Regenerated cellulose was prepared by dissolving cotton linters in a low-temperature alkali-urea-water solution system, adding graphene powder to the solution system in advance, and treating it at low temperature to obtain the solution system/graphene mixture, the checking the mass concentration of graphene powder to be 1 wt%-5 wt%, then adding cotton short fiber into the dissolving system/graphene mixed solution, quickly taking and stirring with electric magnetic stirring bar to obtain the regenerated cellulose/graphene mixed solution; the dissolution system is a mixed solution of sodium hydroxide, urea and deionized water; Step S13: The nickel-plated melamine sponge prepared in the step S11 is soaked in the regenerated cellulose/graphene mixed solution prepared in the step S12, completely absorbing the mixed solution, then the compound body is quickly put into anhydrous ethanol for gel formation, the solvent is replaced by de-ionized water for many times, the compound gel block is frozen by ice template method in liquid nitrogen atmosphere, and finally the bulk regenerated cellulose/graphene coated nickel-plated melamine sponge compound airgel is obtained by vacuum freeze-drying.

The multifunctional phase change composite material supported by nickel-plated foam and MXene according to claim 1, characterized in that the specific method for preparing the semi-finished product of the phase change composite material by a vacuum impregnation method in step S2 is as follows: the phase change material is pre-melted, the regenerated cellulose/graphene-coated nickel-coated melamine sponge composite airgel is immersed in the molten phase change material, vacuum impregnation at constant temperature for 24-48 hours, and the phase change melt not sticking to the surface is adsorbed is taken out by oil absorption paper, then the semi-finished product of the phase change composite material is obtained after solidification at room temperature; the phase change material in step S2 is at least one of polyethylene glycol, paraffin, fatty acid ester or polyol.

A multifunctional phase change composite material supported by nickel-plated foam and MXene according to claim 1, characterized in that the specific method for preparing a small layer of MXene film in step S3 is as follows: Ti3AlC- is etched with HF, generated by in-situ reaction of lithium fluoride and hydrochloric acid, and the metal-Al layer in the powder is etched by reaction, centrifugal washing, ultrasonic stripping, and centrifugal collection to prepare a few layers of MXene colloidal solution, which is sealed and stored in a refrigerator at 4-6°C for later use; a certain amount of MXene colloidal solution was filtered through vacuum

assisted filtration method, and then dried in vacuum at 35-40°C for 4-6 hours to prepare MXene membrane.

The multifunctional phase change composite material supported by nickel plated foam and MXene according to claim 1, characterized in that the specific method for preparing the multifunctional phase change composite material supported by nickel plated foam and MXene synergistically by means of physical adhesion in step S4 is as follows: the MXene film prepared in step S3 is cut into a format having the same length and width as the semi-finished product of the phase change composite material prepared in step S2, and the multifunctional phase change composite material is prepared by physical bonding of the MXene film and the semi-finished phase change composite material by means of molten polyethylene glycol.

A multifunctional phase change composite material supported by nickel-plated foam and MXene according to claim 1, characterized in that the sensitizing solution consists of 2g stannous chloride hexahydrate and 100mL hydrochloric acid solution having a concentration of 0.1 mol/L, the activating solution consists of 0.01g palladium chloride and 100mL hydrochloric acid solution with a concentration of 0.01 mol/L, the plating solution is a mixed solution consisting of 2g nickel chloride hexahydrate, 3g sodium citrate dihydrate and 12mL ammonia water mixed in 90mL deionized water, and the reduction solution consists of 4g sodium hypophosphite dissolved in 10mL deionized water; the reaction time of electroless nickel plating is 1-5 min; after the sensitization, activation and nickel plating are completed, the sponge should be washed with deionized water for 4-6 times, and after the activation and nickel plating are completed, the sponge should be vacuum dried at a temperature of 35-40°C for 24 -48 hours.

A multifunctional phase change composite material supported by nickel-plated foam and MXene according to claim 2, characterized

notes that the sodium hydroxide in step S12 is: the mass ratio of urea: deionized water: cotton short fiber {7-14): (12-24): (81-162): (2-3); the short cotton fiber is obtained from a cotton pulp board through a crushing mechanism; when dissolving, the electric stirring speed is 3500-5000rpm; in the solvent replacement process in step S13, the compound gel is replaced by deionized water for 2-4 times, the replacement time being 8-12 hours each time; the vacuum freeze-drying method is drying in a freeze dryer for 24-48 hours under the condition that the vacuum degree is less than 100 Pa and the cold fall temperature is 60°C, it is dried in a freeze dryer for 24-48 hours.

A multifunctional phase change composite material supported by nickel-plated foam and MXene according to claim 4, characterized in that the dosage of lithium fluoride is 1-2 g, hydrochloric acid is 20-40 mL, powdery Ti3AlC is: 1-2 g; the reaction conditions: the temperature is 35-40°C, the rotational speed is 1500-2000rpm, the reaction time is 36-48 hours; the rotating speed of the centrifugal washing is 3500 rpm, the time is 10 minutes, and the pH of the washing supernatant is greater than 6; the ultrasonic stripping condition is ultrasonic for 1-2 hours under ice bath; the centrifugal collection speed is 3500 rpm, the time is 20-60 min, and the top layer of deep dark green and several layers of MXene colloidal solution are collected circularly.

A multifunctional phase change composite material supported by nickel-plated foam and MXene according to any one of claims 2 to 8, characterized in that the multifunctional phase change composite material is applied to thermal management and electromagnetic shielding materials in electronic components.