Nanometer composite dielectric material based on polyvinylidene fluoride and preparation method thereof

Abstract

The invention discloses a polyvinylidene fluoride-based nano composite dielectric material and a preparation method thereof, and relates to the field of nano composite material preparation. Comprising the following steps: carrying out surface modification on MXene powder by adopting polysilazane to obtain PSZ-coated MXene; the polysilazane on the surface of the PSZ (at) MXene is subjected to ceramization treatment, and ceramized PSZ (at) MXene powder is obtained; the ceramized PSZ (at) MXene powder is treated with a surface active agent, and surface active agent modified PSZ (at) MXene is obtained; and treating the ceramized PSZ (at) MXene powder by adopting a surfactant, so as to obtain the PSZ (at) MXene modified by the surfactant. The obtained nano composite dielectric material has high dielectric constant, low loss and stretchability, and is expected to be applied to the fields of flexible wearable electronics, energy and environment.

Description

Technical Field

[0001] The present invention relates to the field of nanocomposite material preparation, in particular to a polyvinylidene fluoride-based nanocomposite dielectric material and a preparation method thereof. Background Art

[0002] As electronic devices develop towards smaller sizes and higher performance, the demand for polymer films with high dielectric constant (ε) and low dielectric loss (tanδ) is increasing. Compared with ceramic dielectrics, polymer dielectrics have intrinsic advantages such as low cost, high breakdown field strength and excellent reliability. Among them, polyvinylidene fluoride (PVDF)-based ferroelectric polymers that produce high polarization based on carbon-fluorine bonds are a very promising class of high-energy-density dielectric materials. However, the dielectric constants of the above-mentioned ferroelectric polymer dielectrics are generally low (ε<10), which limits the energy storage density and makes it difficult to meet the requirements of modern electronic technology for fast charging and discharging capabilities. In order to overcome this defect, researchers have tried to composite ferroelectric polymers with conductive inorganic nanofillers in order to improve the dielectric properties of the material.

[0003] MXenes, or two-dimensional transition metal carbides, carbonitrides, or carbonitrides, are a general term for a new type of layered, two-dimensional crystalline material similar to graphene. Generally, MAX (where M = transition metal, A = aluminum or silicon, and X = C, N, or CN) can be obtained through chemical etching of the A phase and subsequent liquid-phase exfoliation to obtain a single or few-layer MXene. Due to the use of etching agents (such as hydrofluoric acid or its fluorinated alternatives), the MXene surface often has abundant polar functional groups such as -OH, -F, and -O, resulting in good dispersibility in water. Therefore, MXene not only possesses ultra-high metallic conductivity but also good hydrophilicity, and has broad application prospects in biomedicine, energy storage, catalysis, and flexible electronics. However, due to the metallic electronic structure and excessive surface polar groups of MXene, it exhibits high dielectric constant and high loss in dielectric polymer composites. Therefore, MXene requires surface modification to reduce dielectric loss while maintaining a high dielectric constant.

[0004] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a polyvinylidene fluoride-based nanocomposite dielectric material and a preparation method thereof, aiming to solve the problem of high dielectric loss of existing MXenes.

[0006] The technical solutions of the present invention are as follows:

[0007] The first aspect of the present invention provides a method for preparing a nanocomposite dielectric material based on polyvinylidene fluoride, comprising the following steps:

[0008] S1. MXene powder is surface-modified with polysilazane to obtain polysilazane-surface-modified MXene, denoted as PSZ@MXene.

[0009] S2, ceramicizing the polysilazane on the surface of the PSZ@MXene to obtain ceramicized PSZ@MXene powder;

[0010] S3, treating the ceramicized PSZ@MXene powder with a surfactant to obtain surfactant-modified PSZ@MXene;

[0011] S4. Melt or solvent blend the polyvinylidene fluoride and the surfactant-modified PSZ@MXene to obtain the polyvinylidene fluoride-based nanocomposite dielectric material.

[0012] Optionally, the MXene powder is prepared by a chemical exfoliation method.

[0013] Optionally, the MXene powder is prepared by the following preparation method:

[0014] The MXene raw material (preferably Ti3AlC2 powder) is added to a mixed solution of lithium fluoride and concentrated hydrochloric acid, and then reacted at a temperature of 25 to 50°C for 16 to 48 hours, and then centrifuged and washed to obtain a solid precipitate;

[0015] The solid precipitate is added to ethanol and stirred for 24-48 hours (for ethanol intercalation), followed by centrifugation to remove the ethanol, and then ultrasonicated in deionized water (for 60-120 minutes; at a power of 500-1500W); then centrifuged at a low speed (preferably 3000 rpm) to obtain a MXene colloidal solution; finally, centrifuged at a high speed (preferably 10000 rpm) and dried to obtain MXene powder.

[0016] Optionally, S1 includes the following steps:

[0017] The MXene powder was vacuum dried at 100-110°C for 24-48 hours, then added to a mixed solution of polysilazane and ethanol at room temperature, stirred for 12-48 hours, and then centrifuged, washed, and dried to obtain PSZ@MXene.

[0018] The mass ratio of MXene to polysilazane is 1 g:0.001-0.1, and the ratio of the mixed solution of MXene, polysilazane and ethanol is 1 g:50 ml; the centrifugal speed is 5000-10000 rpm, the time is 10-30 minutes, and the centrifugal temperature is 5-10°C; the washing solvent used is one of ethanol, cyclohexane, toluene or N,N-dimethylformamide; the drying temperature is 40-80°C, and the time is 120-600 minutes.

[0019] Optionally, S2 includes the following steps:

[0020] The PSZ@MXene is subjected to a low-temperature curing treatment to obtain a low-temperature cured PSZ@MXene powder; and the low-temperature cured PSZ@MXene powder is subjected to a high-temperature ceramicization under an inert atmosphere to obtain a ceramicized PSZ@MXene powder.

[0021] Optionally, the temperature of the low-temperature curing treatment is 100-400° C., and the time is 60-180 minutes; the temperature of the high-temperature ceramicization treatment is 600-1000° C., and the time is 60-180 minutes;

[0022] Preferably, the temperature of the low-temperature curing treatment is 200-300°C, and the time is 60-120 minutes; the temperature of the high-temperature ceramicization is 700-900°C, and the time is 60-120 minutes;

[0023] Preferably, the temperature of the low-temperature curing treatment is 250° C. and the time is 90 minutes; the temperature of the high-temperature ceramicization treatment is 750° C. and the time is 90 minutes.

[0024] Optionally, the inert atmosphere is argon or nitrogen.

[0025] Optionally, the surfactant in S3 is a nonionic or ionic surfactant. Preferably, it is a polyoxyethylene-polyoxypropylene triblock copolymer (F-127), an alkyl polyglycoside, sodium dodecylbenzenesulfonate, disodium lauryl sulfosuccinate, etc. More preferably, F-127 is used.

[0026] Optionally, S3 includes the following steps:

[0027] The ceramicized PSZ@MXene powder, surfactant and water are shear-mixed, and then vacuum-filtered, washed and dried.

[0028] Optionally, the mass ratio of the ceramicized PSZ@MXene powder, surfactant and water is 1 g: 0.001-0.5 g: 500 g; the shear rate is 1000-7000 rpm, and the time is 60-180 minutes;

[0029] Preferably, the mass ratio of the ceramicized PSZ@MXene powder, surfactant and water is 1 g:0.02 g:500 g; the shear rate is 3000-6000 rpm, and the time is 60-120 minutes;

[0030] Preferably, the shear rate is 5000 rpm and the time is 90 minutes.

[0031] Optionally, the filter membrane for vacuum filtration is a hydrophilic filter membrane with a pore size of 200 nm; the washing solvent is water; and the drying is performed at room temperature.

[0032] The melting in S4 includes the following steps:

[0033] Adding dried polyvinylidene fluoride and surfactant-modified PSZ@MXene into an internal mixer for melt blending, and then pressing into sheets at high temperature to obtain the polyvinylidene fluoride-based nanocomposite dielectric material;

[0034] The mass ratio of polyvinylidene fluoride and surfactant-modified PSZ@MXene is 1g:0.005-0.05g, the melt blending temperature is 180-210°C, and the time is 5-20 minutes; the tableting temperature is 180-210°C, the holding time is 5-10 minutes, and the cold pressing time is 5-10 minutes;

[0035] Preferably, the mass ratio of polyvinylidene fluoride and surfactant-modified PSZ@MXene is 1 g:0.02 g, the melt blending temperature is 190°C, and the time is 10 minutes; the tableting temperature is 200°C, the holding time is 8 minutes, and the cold pressing time is 8 minutes;

[0036] The solvent blending in S4 includes the following steps:

[0037] Adding dried polyvinylidene fluoride and surfactant-modified PSZ@MXene to an N,N-dimethylformamide solution and stirring, then casting the solution on a polytetrafluoroethylene mold, and obtaining the polyvinylidene fluoride-based nanocomposite dielectric material after the solvent evaporates and the material is dried;

[0038] The mass ratio of polyvinylidene fluoride to surfactant-modified PSZ@MXene is 1g:0.005-0.05g, the stirring speed is 500-2000rpm, the temperature is 80-200℃, and the time is 6-12h. The film-laying solvent evaporation time is 6-12h, the drying time is 6-12h, and the temperature is 80-110℃.

[0039] Preferably, the mass ratio of polyvinylidene fluoride and surfactant-modified PSZ@MXene is 1 g:0.02 g, the stirring speed is 1000 rpm, the temperature is 110°C, and the time is 10 h; the film-laying solvent evaporation time is 10 h, the drying time is 9 h, and the temperature is 100°C.

[0040] It should be noted that the dried polyvinylidene fluoride is obtained by the following method: PVDF pellets are vacuum dried at 80-110° C. for 24-48 hours.

[0041] The second aspect of the present invention provides a polyvinylidene fluoride-based nanocomposite dielectric material prepared by the above method.

[0042] Beneficial effects:

[0043] 1) After PSZ@MXene is ceramicized, the polar groups on the MXene surface disappear, and PSZ is ceramicized into Si-NM bonds (M is the metal on the MXene), forming a dense protective film, which can increase the dielectric constant and reduce its dielectric loss;

[0044] 2) Due to the presence of the PSZ ceramic layer, MXene can maintain low macroscopic conductivity at high content, increase the percolation threshold, and reduce the high dielectric loss caused by the presence of the conductive network;

[0045] 3) Surfactant-modified PSZ@MXene has a strong interaction force with the CF chemical bond in polyvinylidene fluoride (fluorinated crystalline polymer) due to the presence of surfactant, which can significantly induce the formation of polar crystals of polyvinylidene fluoride; in addition, this strong interaction force can also improve the dispersibility of PSZ@MXene in the matrix.

[0046] In summary, the nanocomposite dielectric material obtained by the present invention not only has a high dielectric constant, but also has low loss and stretchability.

[0047] The high dielectric constant, low loss and stretchable polyvinylidene fluoride / PSZ@MXene nanocomposite material of the present invention is expected to be used in the fields of flexible wearable electronics, energy and environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a flowchart of the process of preparing a polyvinylidene fluoride-based nanocomposite dielectric material according to an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The present invention provides a polyvinylidene fluoride-based nanocomposite dielectric material and a preparation method thereof. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0050] This embodiment provides a method for preparing a nanocomposite dielectric material based on polyvinylidene fluoride. Figure 1 As shown, it includes the following steps:

[0051] S1. MXene powder is surface-modified with polysilazane to obtain polysilazane-surface-modified MXene, denoted as PSZ@MXene.

[0052] S2, ceramicizing the polysilazane on the surface of the PSZ@MXene to obtain ceramicized PSZ@MXene powder;

[0053] S3, treating the ceramicized PSZ@MXene powder with a surfactant to obtain surfactant-modified PSZ@MXene;

[0054] S4. Melt or solvent blend the polyvinylidene fluoride and the surfactant-modified PSZ@MXene to obtain the polyvinylidene fluoride-based nanocomposite dielectric material.

[0055] In this embodiment, PSZ@MXene is ceramicized to obtain ceramicized PSZ@MXene powder. This step eliminates the polar groups on the surface of MXene, and PSZ is ceramicized into Si-NM bonds (M is a metal on MXene), and a dense protective film is formed, which can increase the dielectric constant while reducing its dielectric loss. Due to the presence of surfactants, the surfactant-modified PSZ@MXene has a strong interaction force between the CF chemical bonds with polyvinylidene fluoride (the polyvinylidene fluoride can also be a copolymer of polyvinylidene fluoride), which can significantly induce the formation of polar crystals of polyvinylidene fluoride. In addition, this strong interaction force can also improve the dispersibility of PSZ@MXene in the matrix. Therefore, the nanocomposite dielectric material obtained in this embodiment not only has a high dielectric constant, but also has low loss and stretchability.

[0056] In one embodiment, the MXene powder is prepared by a chemical exfoliation method.

[0057] In some embodiments, the MXene powder is prepared by the following preparation method:

[0058] Add MXene raw material (preferably Ti3AlC2 powder) to a mixed solution of 2 g lithium fluoride and 40 mL concentrated hydrochloric acid (9 M), and then react at a temperature of 25-50 ° C for 16-48 hours, and then centrifuge and wash to obtain a solid precipitate;

[0059] The solid precipitate is added to ethanol and stirred for 24-48 hours (for ethanol intercalation), followed by centrifugation to remove the ethanol, and then ultrasonicated in deionized water (for 60-120 minutes; at a power of 500-1500W); then centrifuged at a low speed (preferably 3000 rpm) to obtain a MXene colloidal solution; finally, centrifuged at a high speed (preferably 10000 rpm) and dried to obtain MXene powder.

[0060] Polysilazane (PSZ) is a polymer with Si-N bonds as its backbone. Due to its unique structure, it is classified as either inorganic or organic. Si-N bonds are more easily converted into other types of bonds than Si-O and Si-Cl bonds because their bond energy is lower, approximately 355 kJ / mol. Polysilazane also contains Si-N, Si-H, and NH bonds, all of which readily react with other substances such as water, alcohols, silanols, phenols, and substances containing certain functional groups. These reactions primarily include hydrolysis / alcoholysis, condensation coupling, and hydrosilylation. Consequently, polysilazane possesses high chemical reactivity, making it suitable as a surface modifier for inorganic nanomaterials.

[0061] In some embodiments, S1 comprises the following steps:

[0062] The MXene powder was vacuum dried at 100-110°C for 24-48 hours, then added to a mixed solution of polysilazane and ethanol at room temperature, stirred for 12-48 hours, and then centrifuged, washed, and dried to obtain PSZ@MXene.

[0063] The mass ratio of MXene to polysilazane is 1 g:0.001 to 0.1 g, and the ratio of the mixed solution of MXene, polysilazane and ethanol is 1 g:50 ml. The centrifugal speed is 5000 to 10000 rpm, the time is 10 to 30 minutes, and the centrifugal temperature is 5 to 10°C. The washing solvent used is one or a mixture of ethanol, cyclohexane, toluene or N,N-dimethylformamide. The drying temperature is 40 to 80°C, and the time is 120 to 600 minutes.

[0064] In some embodiments, S2 comprises the following steps:

[0065] The PSZ@MXene powder is subjected to a low-temperature curing treatment at a temperature of 100 to 400° C. (preferably 200 to 300° C., more preferably 250° C.) for 60 to 180 minutes (preferably 60 to 120 minutes, more preferably 90 minutes) to obtain a low-temperature cured PSZ@MXene powder;

[0066] The low-temperature solidified PSZ@MXene powder is then subjected to high-temperature ceramicization under an inert atmosphere to obtain ceramicized PSZ@MXene powder; the high-temperature ceramicization temperature is 600-1000°C (preferably 700-900°C, more preferably 750°C), and the time is 60-180 minutes (preferably 60-120 minutes, more preferably 90 minutes).

[0067] In some embodiments, the inert atmosphere is argon or nitrogen.

[0068] In some embodiments, the surfactant in S3 is a nonionic or ionic surfactant, preferably a polyoxyethylene-polyoxypropylene triblock copolymer (F-127), an alkyl glycoside, sodium dodecylbenzenesulfonate, disodium lauryl sulfosuccinate, etc.; more preferably, F-127.

[0069] In some embodiments, S3 includes the following steps:

[0070] The ceramicized PSZ@MXene powder, a surfactant, and water in a mass ratio of 1 g:0.001-0.5 g:500 g (preferably 1 g:0.02 g:500 g) are shear mixed at a shear rate of 1000-7000 rpm (preferably 3000-6000 rpm, more preferably 5000 rpm) for 60-180 minutes (preferably 60-120 minutes, more preferably 90 minutes);

[0071] Then vacuum filtration, washing and drying are carried out.

[0072] In some embodiments, the filter membrane for vacuum filtration is a hydrophilic filter membrane with a pore size of 200 nm; the washing solvent is water; and the drying is performed at room temperature.

[0073] In some embodiments, the melting in S4 comprises the following steps:

[0074] Dried polyvinylidene fluoride and surfactant-modified PSZ@MXene are added to an internal mixer for melt blending, and then tabletted at high temperature to obtain the polyvinylidene fluoride-based nanocomposite dielectric material; wherein the melt blending temperature is 180-210°C (preferably 190°C) and the time is 5-20 minutes (preferably 10 minutes); the tableting temperature is 180-210°C (preferably 200°C), the holding time is 5-10 minutes (preferably 8 minutes), and the cold pressing time is 5-10 minutes (preferably 8 minutes).

[0075] In some embodiments, the solvent blending in S4 comprises the following steps:

[0076] Dried polyvinylidene fluoride and surfactant-modified PSZ@MXene are added to an N,N-dimethylformamide solution and stirred, and then the solution is cast on a polytetrafluoroethylene mold. After the solvent evaporates and dries, the polyvinylidene fluoride-based nanocomposite dielectric material is obtained; wherein the stirring speed is 500-2000 rpm (preferably 1000 rpm), the temperature is 80-200°C (preferably 110°C), and the time is 6-12h (preferably 10h); the casting solvent volatilization time is 6-12h (preferably 10h), the drying time is 6-12h (preferably 9h), and the temperature is 80-110°C (preferably 100°C).

[0077] The mass ratio of polyvinylidene fluoride to surfactant-modified PSZ@MXene is 1 g:0.005-0.05 g, preferably 1 g:0.02 g.

[0078] It should be noted that the dried polyvinylidene fluoride is obtained by the following method: PVDF pellets are vacuum dried at 80-110° C. for 24-48 hours.

[0079] This embodiment also provides a polyvinylidene fluoride-based nanocomposite dielectric material, which is prepared by the above method.

[0080] The present invention will be further analyzed below in conjunction with specific embodiments.

[0081] Example 1

[0082] A method for preparing a polyvinylidene fluoride-based nanocomposite dielectric material comprises the following steps:

[0083] S1. MXene powder is surface-modified with polysilazane to obtain polysilazane-surface-modified MXene, denoted as PSZ@MXene.

[0084] The specific steps are as follows:

[0085] The MXene powder was vacuum dried at 100 °C for 24 h, then added to a mixed solution of polysilazane and ethanol at room temperature, stirred for 20 h, and then centrifuged, washed, and dried to obtain PSZ@MXene.

[0086] Among them, the mass ratio of MXene to polysilazane is 1g:0.01g, and the ratio of the mixed solution of MXene, polysilazane and ethanol is 1g:50ml; the centrifugal speed is 7000rpm, the time is 25 minutes, and the centrifugal temperature is 5°C; the washing solvent used is ethanol; the drying temperature is 60°C, and the time is 150 minutes.

[0087] The preparation method of the MXene powder is as follows:

[0088] Slowly add 1g of Ti3AlC2 powder to a pre-prepared mixed solution of lithium fluoride and concentrated hydrochloric acid, and react for 20 hours at 45°C. After the reaction is completed, centrifuge and wash the mixed solution to obtain a solid precipitate until the centrifuge solution is neutral or nearly neutral.

[0089] The precipitate obtained in the previous step was intercalated with ethanol and then ultrasonically exfoliated in deionized water. A MXene colloidal solution was then obtained by low-speed centrifugation. A MXene solid powder was obtained by high-speed centrifugation and drying for later use.

[0090] S2. Ceramizing the polysilazane on the surface of the PSZ@MXene to obtain ceramic PSZ@MXene powder.

[0091] The PSZ@MXene was subjected to a low-temperature curing treatment at a temperature of 250° C. for 90 minutes to obtain a low-temperature cured PSZ@MXene powder;

[0092] The low-temperature-cured PSZ@MXene powder is then subjected to high-temperature ceramicization under an inert atmosphere at 750°C for 90 minutes to obtain ceramicized PSZ@MXene powder. The inert atmosphere is argon, but nitrogen can also be used.

[0093] S3. Treating the ceramicized PSZ@MXene powder with a surfactant to obtain surfactant-modified PSZ@MXene.

[0094] The ceramicized PSZ@MXene powder, surfactant (F-127), and water in a mass ratio of 1 g:0.02 g:500 g were shear mixed at a shear rate of 5000 rpm for 90 minutes;

[0095] Then vacuum filtration, washing and drying are carried out.

[0096] The filter membrane for vacuum filtration is a hydrophilic filter membrane with a pore size of 200 nm; the washing solvent is water; and the drying is performed at room temperature.

[0097] S4. Melt or solvent blend polyvinylidene fluoride (PVDF) and the surfactant-modified PSZ@MXene to obtain the polyvinylidene fluoride-based nanocomposite dielectric material.

[0098] PVDF was first dried in vacuum at 85°C for 30 h and then melted.

[0099] Melting includes the following steps:

[0100] Dried polyvinylidene fluoride and surfactant-modified PSZ@MXene are added to an internal mixer for melt blending, and then tableting is performed at high temperature to obtain the polyvinylidene fluoride-based nanocomposite dielectric material; wherein the melt blending temperature is 190°C and the time is 10 minutes; the tableting temperature is 200°C, the holding time is 8 minutes, and the cold pressing time is 8 minutes.

[0101] Among them, the mass ratio of polyvinylidene fluoride and surfactant-modified PSZ@MXene is 1g:0.02g.

[0102] Example 2

[0103] The other preparation methods were the same as those in Example 1, except that the mass ratio of MXene to polysilazane in S1 was 1 g:0.005 g.

[0104] Example 3

[0105] The preparation method was the same as that in Example 1, except that the mass ratio of MXene to polysilazane in S1 was 1 g:0.03 g.

[0106] Example 4

[0107] The preparation method was the same as that in Example 1, except that the mass ratio of ceramicized PSZ@MXene powder, surfactant (F-127) and water in S3 was 1 g:0.05 g:500 g.

[0108] Example 5

[0109] The preparation method was the same as that in Example 1, except that the mass ratio of ceramicized PSZ@MXene powder, surfactant (F-127) and water in S3 was 1 g:0.1:500 g.

[0110] Example 6

[0111] The preparation method was the same as that in Example 1, except that the mass ratio of PVDF and surfactant-modified PSZ@MXene in S4 was 1 g:0.008 g.

[0112] Example 7

[0113] The preparation method was the same as that in Example 1, except that the mass ratio of PVDF and surfactant-modified PSZ@MXene in S4 was 1 g:0.01 g.

[0114] Example 8

[0115] The preparation method was the same as that in Example 1, except that the mass ratio of PVDF and surfactant-modified PSZ@MXene in S4 was 1 g:0.04 g.

[0116] Example 9

[0117] The preparation method is the same as that of Example 1, except that the low-temperature curing treatment temperature in S2 is 200°C.

[0118] Example 10

[0119] The preparation method is the same as that of Example 1, except that the low-temperature curing treatment temperature in S2 is 300°C.

[0120] Example 11

[0121] The preparation method is the same as that of Example 1, except that the high-temperature ceramicization temperature in S2 is 700°C.

[0122] Example 12

[0123] The preparation method is the same as that of Example 1, except that the high-temperature ceramicization temperature in S2 is 800°C.

[0124] Example 13

[0125] The other preparation methods are the same as those in Example 1, except that S4 uses solvent blending, including the following steps:

[0126] Dried polyvinylidene fluoride and surfactant-modified PSZ@MXene are added to an N,N-dimethylformamide solution and stirred, and then the solution is cast on a polytetrafluoroethylene mold. After the solvent evaporates and dries, the polyvinylidene fluoride-based nanocomposite dielectric material is obtained; wherein the stirring speed is 1000 rpm, the temperature is 110°C, and the time is 10 hours; the film casting solvent volatilization time is 10 hours, the drying time is 9 hours, and the temperature is 100°C.

[0127] Comparative Example 1

[0128] Polyvinylidene fluoride (PVDF), MXene and surfactant (F-127) are added into an internal mixer for melt blending, and then pressed into sheets at high temperature to obtain the polyvinylidene fluoride-based nanocomposite dielectric material; wherein the melt blending temperature is 190°C and the time is 10 minutes; the sheeting temperature is 200°C, the holding time is 8 minutes, and the cold pressing time is 8 minutes.

[0129] Among them, the mass ratio of polyvinylidene fluoride and surfactant-modified PSZ@MXene is 1g:0.02g.

[0130] The difference between this comparative example and Example 1 is that the MXene in this comparative example is modified by S1, S2, and S3.

[0131] Comparative Example 2

[0132] This comparative example differs from Example 1 in that polysilazane is not used to modify the MXene surface in S1, and the other steps remain unchanged, including the subsequent ceramic treatment in S2, the surfactant treatment in S3, and the melting in S4.

[0133] Comparative Example 3

[0134] The difference between this comparative example and comparative example 1 is that the mass ratio of PVDF and surfactant-modified PSZ@MXene in S4 is 1 g:0.008 g.

[0135] Comparative Example 4

[0136] The difference between this comparative example and comparative example 1 is that the mass ratio of PVDF and surfactant-modified PSZ@MXene in S4 is 1 g:0.01 g.

[0137] Comparative Example 5

[0138] The difference between this comparative example and comparative example 1 is that the mass ratio of PVDF and surfactant-modified PSZ@MXene in S4 is 1 g:0.04 g.

[0139] The dielectric properties and mechanical tensile properties (elongation at break) of the polyvinylidene fluoride-based nanocomposite dielectric material (a blended film) prepared in the above examples and comparative examples were tested; wherein the frequency range of the dielectric properties is 10 0 to 10 6 Hz, the working voltage is 1V; the dumbbell-shaped spline is used to test the tensile properties, and its thickness is 0.3mm.

[0140] The obtained dielectric properties and mechanical tensile properties are shown in Table 1.

[0141] As shown in Table 1, the dielectric constant of pure PVDF (Comparative Example 1) is 12 at 100Hz, and the corresponding dielectric loss is 0.1, but it has good flexibility and an elongation at break of about 250%. Due to its high electrical conductivity, MXene is introduced into the PVDF system to significantly improve its dielectric properties. For example, when the MXene content is 2% (Comparative Example 2), the dielectric constant of the system is 400 at 100Hz, but its corresponding dielectric loss increases to 1.1. Although excessive MXene content can further improve the dielectric constant of PVDF, its dielectric loss also increases accordingly (Comparative Example 5). It can be seen that the modification of the dielectric properties of PVDF by unmodified MXene has certain limitations. When MXene is modified by polysilazane ceramics, it increases the dielectric constant of the PVDF system while maintaining the dielectric loss at a low level. For example, compared with Comparative Example 2, when the MXene content is the same, in Example 1, the dielectric constant of the system is increased to 600, while the dielectric loss is only 0.08. In addition, further increasing the content of polysilazane (Example 3) further increases the corresponding dielectric constant, while the dielectric loss does not increase much. This indicates that the ceramicization of polysilazane on the MXene surface can synergistically improve the dielectric properties of PVDF. The possible reason is the formation of Si-N-Ti chemical bonds, which changes the electronic structure of MXene. The study further shows that the temperature of the low-temperature curing and high-temperature ceramicization process can also slightly change the dielectric properties of the system, which may be due to the degree of ceramicization of polysilazane.

[0142] Table 1 Parameters and performance measurement results of the preparation methods of each embodiment and comparative example

[0143]

[0144]

[0145] In summary, the present invention provides a nanocomposite material having the following advantages:

[0146] 1) After PSZ@MXene is ceramicized, the polar groups on the MXene surface disappear, and PSZ is ceramicized into Si-NM bonds (M is the metal on the MXene), forming a dense protective film, which can increase the dielectric constant and reduce its dielectric loss;

[0147] 2) Due to the presence of the PSZ ceramic layer, MXene can maintain low macroscopic conductivity at high content, increase the percolation threshold, and reduce the high dielectric loss caused by the presence of the conductive network;

[0148] 3) Surfactant-modified PSZ@MXene has a strong interaction force with the CF chemical bond in polyvinylidene fluoride (fluorinated crystalline polymer) due to the presence of surfactant, which can significantly induce the formation of polar crystals of polyvinylidene fluoride; in addition, this strong interaction force can also improve the dispersion of PSZ@MXene in the matrix.

[0149] The polyvinylidene fluoride-based nanocomposite dielectric material of the present invention has high dielectric constant, low loss and stretchability, and is expected to be used in flexible wearable electronics, energy and environmental fields.

[0150] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a nanocomposite dielectric material based on polyvinylidene fluoride, characterized in that: The steps include: S1. MXene powder is surface-modified with polysilazane to obtain polysilazane-surface-modified MXene, denoted as PSZ@MXene. S2, ceramicizing the polysilazane on the surface of the PSZ@MXene to obtain ceramicized PSZ@MXene powder; S3, treating the ceramicized PSZ@MXene powder with a surfactant to obtain surfactant-modified PSZ@MXene; S4. Melt or solvent blend the polyvinylidene fluoride and the surfactant-modified PSZ@MXene to obtain the polyvinylidene fluoride-based nanocomposite dielectric material.

2. The method for preparing a polyvinylidene fluoride-based nanocomposite dielectric material according to claim 1, characterized in that: S1 includes the following steps: The MXene powder was vacuum dried at 100-110°C for 24-48 hours, then added to a mixed solution of polysilazane and ethanol at room temperature, stirred for 12-48 hours, and then centrifuged, washed and dried to obtain PSZ@MXene.

3. The method for preparing a polyvinylidene fluoride-based nanocomposite dielectric material according to claim 2, characterized in that: The mass ratio of the MXene powder to polysilazane is 1:0.001-0.1, and the ratio of the MXene powder to the mixed solution of polysilazane and ethanol is 1g:50ml; the centrifugal speed is 5000-10000rpm, the time is 10-30 minutes, the centrifugal temperature is 5-10°C; the drying temperature is 40-80°C, and the time is 120-600 minutes.

4. The method for preparing a polyvinylidene fluoride-based nanocomposite dielectric material according to claim 1, characterized in that: S2 includes the following steps: The PSZ@MXene is subjected to a low-temperature curing treatment to obtain a low-temperature cured PSZ@MXene powder; and the low-temperature cured PSZ@MXene powder is subjected to a high-temperature ceramicization under an inert atmosphere to obtain a ceramicized PSZ@MXene powder.

5. The method for preparing a polyvinylidene fluoride-based nanocomposite dielectric material according to claim 4, characterized in that: The temperature of low-temperature curing treatment is 100-400°C, and the time is 60-180 minutes; the temperature of high-temperature ceramicization is 600-1000°C, and the time is 60-180 minutes; Preferably, the temperature of the low-temperature curing treatment is 200-300°C, and the time is 60-120 minutes; the temperature of the high-temperature ceramicization is 700-900°C, and the time is 60-120 minutes; Preferably, the temperature of the low-temperature curing treatment is 250° C. and the time is 90 minutes; the temperature of the high-temperature ceramicization treatment is 750° C. and the time is 90 minutes.

6. The method for preparing a polyvinylidene fluoride-based nanocomposite dielectric material according to claim 1, characterized in that: The surfactant in S3 is a nonionic or ionic surfactant.

7. The method for preparing a polyvinylidene fluoride-based nanocomposite dielectric material according to claim 6, characterized in that: S3 includes the following steps: The ceramicized PSZ@MXene powder, surfactant and water are shear-mixed, and then vacuum-filtered, washed and dried.

8. The method for preparing a polyvinylidene fluoride-based nanocomposite dielectric material according to claim 7, characterized in that: The mass ratio of the ceramicized PSZ@MXene powder, surfactant, and water is 1 g: 0.001-0.5 g: 500 g; the shear rate is 1000-7000 rpm, and the time is 60-180 minutes; Preferably, the mass ratio of the ceramicized PSZ@MXene powder, surfactant and water is 1 g:0.02 g:500 g; the shear rate is 3000-6000 rpm, and the time is 60-120 minutes; Preferably, the shear rate is 5000 rpm and the time is 90 minutes.

9. The method for preparing a polyvinylidene fluoride-based nanocomposite dielectric material according to claim 1, characterized in that: The melting in S4 includes the following steps: Adding dried polyvinylidene fluoride and surfactant-modified PSZ@MXene into an internal mixer for melt blending, and then pressing into sheets at high temperature to obtain the polyvinylidene fluoride-based nanocomposite dielectric material; The mass ratio of polyvinylidene fluoride and surfactant-modified PSZ@MXene is 1g:0.005-0.05g, the melt blending temperature is 180-210°C, and the time is 5-20 minutes; the tableting temperature is 180-210°C, the holding time is 5-10 minutes, and the cold pressing time is 5-10 minutes; Preferably, the mass ratio of polyvinylidene fluoride and surfactant-modified PSZ@MXene is 1 g:0.02 g, the melt blending temperature is 190°C, and the time is 10 minutes; the tableting temperature is 200°C, the holding time is 8 minutes, and the cold pressing time is 8 minutes; The solvent blending in S4 includes the following steps: Adding dried polyvinylidene fluoride and surfactant-modified PSZ@MXene to an N,N-dimethylformamide solution and stirring, then casting the solution on a polytetrafluoroethylene mold, and obtaining the polyvinylidene fluoride-based nanocomposite dielectric material after the solvent evaporates and the material is dried; The mass ratio of polyvinylidene fluoride to surfactant-modified PSZ@MXene is 1g:0.005-0.05g, the stirring speed is 500-2000rpm, the temperature is 80-200℃, and the time is 6-12h. The film-laying solvent evaporation time is 6-12h, the drying time is 6-12h, and the temperature is 80-110℃. Preferably, the mass ratio of polyvinylidene fluoride and surfactant-modified PSZ@MXene is 1 g:0.02 g, the stirring speed is 1000 rpm, the temperature is 110°C, and the time is 10 h; the film-laying solvent evaporation time is 10 h, the drying time is 9 h, and the temperature is 100°C.

10. A nanocomposite dielectric material based on polyvinylidene fluoride, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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