Electromagnetic shielding film and method for manufacturing the same

Abstract

The application discloses a preparation method of an electromagnetic shielding film, and comprises the following steps: preparing an MXenes dispersion liquid; dispersing a heat-conducting filler in anhydrous ethanol to prepare a heat-conducting filler dispersion liquid; adding the heat-conducting filler dispersion liquid into the MXenes dispersion liquid to obtain a mixed slurry; and shaping and drying the mixed slurry to obtain the electromagnetic shielding film, wherein the heat-conducting filler is one or a combination of silicon nitride, aluminum nitride, zirconium carbide, tantalum carbide and hafnium carbide. The application further discloses an electromagnetic shielding film. The electromagnetic shielding film prepared by the application has excellent electromagnetic shielding performance, heat-conducting performance, and good flexibility.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite films, and particularly relates to an electromagnetic shielding film and a preparation method thereof. BACKGROUND

[0002] With the rapid development of electronic equipment and wireless transmission technology, the harm of electromagnetic interference and electromagnetic radiation to portable electronics, aerospace, national defense security and human health is also becoming more and more serious. Traditional electromagnetic shielding materials represented by metals have the disadvantages of large density, poor flexibility, easy corrosion and the like, and are difficult to meet the development needs of lightweight portable electronic products.

[0003] In recent years, MXenes, as a new type of two-dimensional layered transition metal carbon / nitride, has excellent metal conductivity (electrical conductivity up to 65000 S / m) and ferromagnetism, and gradually becomes an ideal electromagnetic shielding material. However, at the same time, with the gradual approach of the 5G era, accompanied by the frequent updating and replacement of electronic products, the power consumption of equipment is increasing, and the heat generation is also rapidly rising. The bottleneck of the use of future high-frequency high-power electronic products is the electromagnetic radiation and heat generated thereby, and therefore the requirements for electromagnetic shielding materials are also higher and higher, and the materials with the functions of electromagnetic shielding, heat conduction and flexibility will become increasingly important.

[0004] Therefore, the prior art urgently needs an electromagnetic shielding film with better electromagnetic shielding and heat conduction performance and better flexibility. SUMMARY

[0005] To solve the drawbacks of the prior art, the application discloses a preparation method of an electromagnetic shielding film, comprising the following steps,

[0006] preparing an MXenes dispersion liquid;

[0007] dispersing a heat-conductive filler in anhydrous ethanol to prepare a heat-conductive filler dispersion liquid;

[0008] adding the heat-conductive filler dispersion liquid to the MXenes dispersion liquid to obtain a mixed slurry, and shaping and drying the mixed slurry to obtain the electromagnetic shielding film,

[0009] wherein the heat-conductive filler is one or a combination of silicon nitride, aluminum nitride, zirconium carbide, tantalum carbide and hafnium carbide.

[0010] Further, in the mixed slurry, the mass fraction of the MXenes dispersion liquid is 5-8 parts, and the mass fraction of the heat-conductive filler dispersion liquid is 3-5 parts.

[0011] Further, the heat-conductive filler is one or a combination of zirconium carbide, tantalum carbide and hafnium carbide.

[0012] Further, the purity of the zirconium carbide, the tantalum carbide and the hafnium carbide is 93%-97%.

[0013] Further, when preparing the thermally conductive filler dispersion liquid, the LDH nanosheet is dispersed in anhydrous ethanol together with the thermally conductive filler.

[0014] In the thermally conductive filler dispersion liquid, the mass fraction of the LDH nanosheet is 5-10 parts, and the mass fraction of the thermally conductive filler is 25-40 parts.

[0015] Further, the concentration of the MXenes dispersion liquid is 3-15 mg / mL.

[0016] Further, the specific method for preparing the MXenes dispersion liquid is as follows:

[0017] Dissolve 4-6 parts of lithium fluoride or sodium fluoride in 8-10 parts of hydrochloric acid to obtain an etching solution, slowly add 3-5 parts of MAX, centrifuge after water bath heating and stirring for 18-24 h, and wash the obtained precipitate with anhydrous ethanol until the pH of the supernatant is greater than or equal to 6.

[0018] Take the precipitate and add anhydrous ethanol for ultrasonic dispersion, centrifuge to collect the upper suspension to obtain the MXenes dispersion liquid.

[0019] Further, the MXenes are one or a combination of nitrides, carbides and carbonitrides.

[0020] The nitride is one or a combination of boron nitride and carbon nitride.

[0021] The carbide is one or a combination of titanium carbide, vanadium carbide, niobium carbide and molybdenum carbide.

[0022] The carbonitride is one or a combination of titanium carbonitride, vanadium carbonitride and chromium carbonitride.

[0023] Further, the forming method is any one of vacuum suction filtration, casting, doctor blade coating, mold casting and pressure filtration.

[0024] The application further discloses an electromagnetic shielding film prepared by using the preparation method.

[0025] By using the above technical solution, the application has the following beneficial effects:

[0026] The application adds the thermally conductive filler, so that the prepared electromagnetic shielding film has better electromagnetic shielding performance and better thermal conductivity.

[0027] The application selects zirconium carbide, tantalum carbide and hafnium carbide as the heat-conducting filler, wherein, first, the zirconium carbide, tantalum carbide and hafnium carbide are super-high-temperature ceramic powders, and have excellent heat-conducting and heat-resistant properties; second, the free carbon contained in the zirconium carbide, tantalum carbide and hafnium carbide can be cross-linked and combined with the electronegative groups such as -OH on the surface of MXene, so as to give the electromagnetic shielding film better flexibility.

[0028] The application adds the LDH nanosheet, so that the electromagnetic shielding film has better flexibility at low temperature and better shielding performance at high temperature, and is better applicable to different use environments. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A photo of the electromagnetic shielding film prepared by the application;

[0030] Figure 2 A photo of the folded battery shielding film prepared by the application;

[0031] Figure 3 A photo of the folded battery shielding film prepared by the application; Figure 2 A photo of the unfolded battery shielding film. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the application will be clearly and completely described below, obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0033] The application discloses a preparation method of an electromagnetic shielding film, comprising the following steps,

[0034] Preparation of a MXenes dispersion liquid; preparation of a heat-conducting filler dispersion liquid by dispersing the heat-conducting filler in anhydrous ethanol; slow addition of the heat-conducting filler dispersion liquid into the MXenes dispersion liquid to obtain a mixed slurry; shaping and drying of the mixed slurry to obtain the electromagnetic shielding film.

[0035] The heat-conducting filler is one or a combination of silicon nitride, aluminum nitride, zirconium carbide, tantalum carbide and hafnium carbide; in the mixed slurry, the mass fraction of the MXenes dispersion liquid is 5-8 parts, and the mass fraction of the heat-conducting filler dispersion liquid is 3-5 parts.

[0036] The application adds the heat-conducting filler, so that the prepared electromagnetic shielding film has not only better electromagnetic shielding performance, but also better heat-conducting property, and is applicable to high-frequency and high-power electronic products with high heat generation.

[0037] The application preferably uses zirconium carbide, tantalum carbide and hafnium carbide as the heat-conducting filler. Compared with silicon nitride and aluminum nitride, the heat resistance, heat conductivity and flexibility of the electromagnetic shielding film prepared by using zirconium carbide, tantalum carbide and hafnium carbide are better. The reasons are as follows. First, zirconium carbide, tantalum carbide and hafnium carbide are super-high-temperature ceramic powders, and their heat resistance and heat conductivity are much better than those of silicon nitride and aluminum nitride. Second, zirconium carbide, tantalum carbide and hafnium carbide contain free carbon, and the free carbon can be cross-linked and combined with the electronegative groups such as -OH on the surface of MXene, thereby giving the electromagnetic shielding film better flexibility.

[0038] In order to give the electromagnetic shielding film flexibility without affecting the heat-conducting performance of the electromagnetic shielding film, the purity of zirconium carbide, tantalum carbide and hafnium carbide is preferably 93% to 97%. The application does not have high requirements for the purity of zirconium carbide, tantalum carbide and hafnium carbide, thereby reducing the production cost to a certain extent.

[0039] In a preferred embodiment of the application, the LDH nanosheet and the heat-conducting filler are dispersed in anhydrous ethanol to prepare a heat-conducting filler dispersion liquid. In the heat-conducting filler dispersion liquid, the mass fraction of the LDH nanosheet is 5 to 10 parts, and the mass fraction of the heat-conducting filler is 25 to 40 parts. The LDH nanosheet is a layered double hydroxide.

[0040] The hydroxyl ions in the LDH nanosheet can be cross-linked and combined with the free carbon in zirconium carbide, tantalum carbide and hafnium carbide, thereby further giving the electromagnetic shielding film better flexibility.

[0041] When the electromagnetic shielding film is used in the fields of mobile phones, watches and semiconductor heat dissipation, the flexibility of the electromagnetic shielding film is required to be high in addition to the electromagnetic shielding performance and heat-conducting performance. The application has better flexibility of the prepared electromagnetic shielding film by adding the LDH nanosheet, and is particularly suitable for the fields of mobile phones, watches and semiconductor heat dissipation.

[0042] The electromagnetic shielding film can also be applied to the field of base stations. When used in the field of base stations, the flexibility of the electromagnetic shielding film is not particularly strict, but if the electromagnetic shielding performance can be further improved, it will be more suitable for the field of base stations. The electromagnetic shielding film prepared by adding LDH nanosheets is particularly suitable for the field of base stations. Specifically, the LDH nanosheet is a layered double metal hydroxide, which can be converted into a layered double metal oxide at high temperature. When the hydroxide is converted into the oxide, the electromagnetic shielding performance can be further improved. The temperature at which the layered double metal hydroxide is converted into the layered double metal oxide is about 120 DEG C. Therefore, when the electromagnetic shielding film prepared by using the layered double metal hydroxide has better flexibility at low temperature (below 120 DEG C) and better electromagnetic shielding performance at high temperature (above 120 DEG C). When the electromagnetic shielding film is used in the fields of mobile phones, watches, semiconductor heat dissipation, etc., the temperature of the working environment is lower than 120 DEG C. When the electromagnetic shielding film is used in the field of base stations, the temperature of the working environment is higher than 120 DEG C. Therefore, the electromagnetic shielding film prepared by the present application can exhibit excellent flexibility when applied to the fields of mobile phones, watches, semiconductor heat dissipation, etc. which have higher requirements for flexibility, and can still exhibit excellent electromagnetic shielding performance when applied to the field of base stations which have higher requirements for shielding performance. This is not possessed by other electromagnetic shielding films in the prior art.

[0043] In an embodiment of the present application, the specific method for preparing the MXenes dispersion liquid is as follows: 4-6 parts of lithium fluoride or sodium fluoride is dissolved in 8-10 parts of hydrochloric acid (preferably 9M hydrochloric acid) to obtain an etching solution, 3-5 parts of MAX is slowly added, and after water bath heating and stirring reaction for 18-24h, centrifugation is performed, and the precipitate obtained by centrifugation is washed with anhydrous ethanol until the supernatant PH is greater than or equal to 6; the precipitate is treated by ultrasonic dispersion with anhydrous ethanol, and the upper suspension liquid is collected by centrifugation to obtain the MXenes dispersion liquid. The concentration of the MXenes dispersion liquid is 3-15mg / mL.

[0044] In the formula, MAX is a MAX phase material, wherein M represents a transition metal element; A represents a main group element; and X represents carbon or nitrogen, and the basic chemical formula can be represented as M(n+1)AXn.

[0045] MXenes is a two-dimensional transition metal carbon / nitride, and its chemical formula can be represented as Mn+1XnTz, wherein M represents a transition metal element, X represents carbon or / and nitrogen, and T represents a surface group. The MXenes of the present application is one or a combination of nitride, carbide and carbonitride, wherein the nitride is one or a combination of boron nitride and carbon nitride; the carbide is one or a combination of titanium carbide, vanadium carbide, niobium carbide and molybdenum carbide; and the carbonitride is one or a combination of titanium carbonitride, vanadium carbonitride and chromium carbonitride.

[0046] In an embodiment of the present application, the specific method for preparing the thermally conductive filler dispersion liquid is to disperse the "thermally conductive filler" or "thermally conductive filler and LDH nanosheet" in anhydrous ethanol by stirring and ultrasonic treatment.

[0047] In an embodiment of the present application, the specific method for molding and drying the mixed slurry to obtain the electromagnetic shielding film is:

[0048] The mixed slurry is molded by any one of vacuum filtration, casting, knife coating, mold casting, and pressure filtration, and vacuum dried to obtain the electromagnetic shielding film, wherein the vacuum drying time is 6-24 h and the temperature is 40-80℃.

[0049] The present application also discloses an electromagnetic shielding film prepared by any of the above preparation methods. The electromagnetic shielding film prepared by the present application has an electromagnetic shielding effectiveness of ≥38 dB in the X-band of 8.2-12.4 GHz, which exceeds the commercial standard (20 dB); the thermal conductivity coefficient is ≥18.2 W / mK at 25℃, which exceeds that of pure MXene film (9.4 W / mK); and the electromagnetic shielding film prepared by the present application also exhibits good flexibility.

[0050] Example 1

[0051] Preparation of MXenes dispersion liquid: 4 parts of lithium fluoride were dissolved in 8 parts of 9M hydrochloric acid to obtain an etching solution, 3 parts of MAX (titanium aluminum carbide) were slowly added, and after water bath heating and stirring reaction for 18 h, centrifugation was performed, and the precipitate obtained by centrifugation was washed with anhydrous ethanol until the supernatant PH was ≥6; the precipitate was added with anhydrous ethanol for ultrasonic dispersion treatment, and the upper suspension was collected by centrifugation to obtain the MXenes dispersion liquid;

[0052] Preparation of thermally conductive filler dispersion liquid: 25 parts of zirconium carbide with a purity of 93% and 5 parts of LDH nanosheet were dispersed in anhydrous ethanol;

[0053] According to mass fraction, 3 parts of the above-mentioned thermally conductive filler dispersion liquid were added to 5 parts of the above-mentioned MXenes dispersion liquid to obtain a mixed slurry, the mixed slurry was vacuum filtered to form a film, and dried at 40℃ for 24 h to obtain an electromagnetic shielding film.

[0054] Example 2

[0055] Preparation of MXenes dispersion liquid: 6 parts of sodium fluoride were dissolved in 10 parts of 9M hydrochloric acid to obtain an etching solution, 5 parts of MAX (titanium niobium carbide) were slowly added, and after water bath heating and stirring reaction for 24 h, centrifugation was performed, and the precipitate obtained by centrifugation was washed with anhydrous ethanol until the supernatant PH was ≥6; the precipitate was added with anhydrous ethanol for ultrasonic dispersion treatment, and the upper suspension was collected by centrifugation to obtain the MXenes dispersion liquid;

[0056] Preparation of thermally conductive filler dispersion: 40 parts by mass of tantalum carbide with a purity of 97% and 10 parts by mass of LDH nanosheets were dispersed in anhydrous ethanol;

[0057] By weight, 5 parts of the above thermally conductive filler dispersion were added to 8 parts of the above MXenes dispersion to obtain a mixed slurry. The mixed slurry was vacuum filtered and shaped, and dried at 80°C for 6 hours to obtain an electromagnetic shielding film.

[0058] Example 3

[0059] Preparation of MXenes dispersion: Dissolve 5 parts sodium fluoride in 9 parts 9M hydrochloric acid by weight to obtain etching solution, slowly add 4 parts MAX (molybdenum titanium carbide), heat and stir in a water bath for 20 h, then centrifuge. Wash the precipitate obtained by centrifugation with anhydrous ethanol until the pH of the supernatant is ≥6. Take the precipitate, add anhydrous ethanol and perform ultrasonic dispersion treatment, centrifuge and collect the upper suspension to obtain MXenes dispersion.

[0060] Preparation of thermally conductive filler dispersion: 30 parts by mass of hafnium carbide with a purity of 97% and 8 parts by mass of LDH nanosheets were dispersed in anhydrous ethanol;

[0061] By weight, 4 parts of the above thermally conductive filler dispersion were added to 6 parts of the above MXenes dispersion to obtain a mixed slurry. The mixed slurry was vacuum filtered and shaped, and dried at 60°C for 15 hours to obtain an electromagnetic shielding film.

[0062] Figure 1 This is a photograph of the battery shielding film prepared according to the present invention. Figure 2 This is a photograph of the battery shielding film of the present invention after it has been folded. Figure 2 It showed that it did not break after being folded. Figure 3 To be Figure 2 A photo of the battery shielding film after it has been unfolded. Figure 3 The screen showed that it was undamaged when unfolded. Figure 2 , Figure 3 This indicates that the battery shielding film prepared by the present invention has good flexibility.

[0063] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing an electromagnetic shielding film, characterized in that: Includes the following steps, Preparation of MXenes dispersion; A thermally conductive filler dispersion was prepared by dispersing the thermally conductive filler in anhydrous ethanol. A thermally conductive filler dispersion was added to an MXenes dispersion to obtain a mixed slurry. The mixed slurry was then shaped and dried to obtain an electromagnetic shielding film. The thermally conductive filler is one or a combination of zirconium carbide, tantalum carbide, and hafnium carbide; When preparing the thermally conductive filler dispersion, LDH nanosheets and thermally conductive fillers are dispersed together in anhydrous ethanol; In the thermally conductive filler dispersion, the mass fraction of LDH nanosheets is 5-10 parts, and the mass fraction of thermally conductive filler is 25-40 parts.

2. The preparation method according to claim 1, characterized in that: In the mixed slurry, the mass fraction of MXenes dispersion is 5-8 parts, and the mass fraction of thermally conductive filler dispersion is 3-5 parts.

3. The preparation method according to claim 1 or 2, characterized in that: The purity of zirconium carbide, tantalum carbide, and hafnium carbide is 93%-97%.

4. The preparation method according to claim 1, characterized in that: The concentration of the MXenes dispersion is 3-15 mg / mL.

5. The preparation method according to claim 1, characterized in that: The specific method for preparing MXenes dispersion is as follows: By weight, dissolve 4-6 parts of lithium fluoride or sodium fluoride in 8-10 parts of hydrochloric acid to obtain an etching solution. Slowly add 3-5 parts of MAX, heat and stir in a water bath for 18-24 hours, then centrifuge. Wash the precipitate with anhydrous ethanol until the pH of the supernatant is ≥6. The precipitate was dispersed by ultrasonication with anhydrous ethanol, and the upper suspension was collected by centrifugation to obtain the MXenes dispersion.

6. The preparation method according to claim 1, characterized in that: The MXenes are one or a combination of nitrides, carbides, and carbonitrides. The nitride is one or a combination of boron nitride and carbon nitride; The carbide is one or a combination of titanium carbide, vanadium carbide, niobium carbide, and molybdenum carbide; The carbonitride is one or a combination of titanium carbonitride, vanadium carbonitride, and chromium carbonitride.

7. The preparation method according to claim 1, characterized in that: The forming method is any one of vacuum filtration, casting, doctor blade coating, mold casting, and pressure filtration.

8. An electromagnetic shielding film, characterized in that: Prepared using the preparation method described in any one of claims 1-7.

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