CN114381129A

CN114381129A - Composite material and method for producing same

Info

Publication number: CN114381129A
Application number: CN202110113653.0A
Authority: CN
Inventors: 刘伟仁; 贺忻年; 谢怡廷
Original assignee: Chung Yuan Christian University
Current assignee: Chung Yuan Christian University
Priority date: 2020-10-19
Filing date: 2021-01-27
Publication date: 2022-04-22
Also published as: TW202216591A

Abstract

The invention provides a composite material for electromagnetic wave shielding or electromagnetic wave absorption and a manufacturing method thereof. The composite material includes an electromagnetic wave absorbing material containing two-dimensional graphene sheets, wherein the two-dimensional graphene sheets are prepared by crushing a carbon raw material by a principle of a cavity in a liquid phase exfoliation method, and drying the crushed material by an oven or freeze drying.

Description

Composite material and method for producing same

Technical Field

The present invention relates to a composite material and a method for manufacturing the same, and more particularly, to a composite material for electromagnetic wave shielding or electromagnetic wave absorption and a method for manufacturing the same.

Background

With the increasing operation speed of electronic devices such as smart phones, tablet computers, and notebook computers, the noise generated by the electronic components in the electronic devices is also increasing. For example, electronic components usually generate electromagnetic waves during operation, and the electromagnetic waves become noises that interfere with antennas in electronic devices, thereby reducing the signal transmitting/receiving capability of the antennas. Therefore, how to effectively improve the effect of shielding or absorbing electromagnetic waves is one of the problems that researchers in the field are demanding to solve.

Disclosure of Invention

The present invention is directed to a composite material and a method for manufacturing the same, which has a good electromagnetic wave shielding or electromagnetic wave absorbing effect.

An embodiment of the present invention provides a composite material for electromagnetic wave shielding or electromagnetic wave absorption including an electromagnetic wave absorbing material including a two-dimensional graphene sheet. The two-dimensional graphene sheet is prepared by crushing a carbon raw material by a cavitation principle in a liquid phase exfoliation method and drying the crushed material by an oven or freeze drying.

In an embodiment of the invention, the composite material further includes a conductive material containing a one-dimensional carbon material.

In one embodiment of the present invention, the content of the conductive material is 1 to 10 parts by weight based on 100 parts by weight of the electromagnetic wave absorbing material.

In an embodiment of the invention, the one-dimensional carbon material includes carbon nanotubes.

An embodiment of the present invention provides a method for manufacturing a composite material for electromagnetic wave shielding or electromagnetic wave absorption, including the steps of: crushing a carbon raw material by a cavity principle in a liquid phase stripping method to form a graphene suspension; and performing oven drying or freeze drying on the graphene suspension to form the electromagnetic wave absorbing material containing the two-dimensional graphene sheet.

In an embodiment of the invention, the method for manufacturing the composite material further includes mixing a conductive material containing a one-dimensional carbon material into the electromagnetic wave absorbing material.

In one embodiment of the present invention, the solvent used in the liquid phase stripping method is one or more selected from the following group: water, ethanol and N-methyl-2-pyrrolidone (NMP).

In one embodiment of the present invention, the carbon feedstock has a solids content of 1 wt% to 10 wt% in the solvent.

In an embodiment of the present invention, the number of crushing times in the liquid phase stripping method is greater than 1 and less than 100.

In one embodiment of the present invention, the temperature of oven drying is 40 ℃ to 100 ℃.

In one embodiment of the invention, the temperature of freeze-drying is from-110 ℃ to-30 ℃.

Based on the above, in the composite material and the method for manufacturing the same of the present invention, since the electromagnetic wave absorbing material including the two-dimensional graphene sheet can form a conductive chain or a conductive network inside the material, the electromagnetic wave entering the composite material can generate a current having the same direction as the electric field due to polarization, and the current forms a closed current loop inside the composite material to generate an eddy current (eddy current), so that the electricity can be further converted into heat energy to be consumed, and the composite material can have a good electromagnetic wave shielding or electromagnetic wave absorbing effect.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) image of preparative reference example 1, preparative example 1 and preparative example 2.

Fig. 2 is a tap density comparison image of production reference example 1, production example 1, and production example 2.

FIG. 3 is a Brayton's (BET) graph of production reference example 1 and production example 1.

FIG. 4 is a BET diagram of production reference example 1 and production example 2.

FIG. 5A shows the frequency and total Shielding Efficiency (SE) in the X-band of reference example 1 and examples 1 to 5_T) A graph of the relationship (c).

FIG. 5B is the reflection contribution (SE) of reference example 1 and examples 1 to 5_R) And absorption contribution (SE)_A) The shielding efficiency of (a) is compared.

FIG. 6A shows the frequency and the frequency of reference example 1 and example 1, and example 6 and example 7 in the X bandTotal Shield Efficiency (SE)_T) A graph of the relationship (c).

FIG. 6B is the reflection contribution (SE) of reference example 1, example 6 and example 7_R) And absorption contribution (SE)_A) The shielding efficiency of (a) is compared.

Fig. 7A to 7C are graphs showing the relationship between the frequency and the Reflection Loss (RL) in different thicknesses of reference example 2, example 8 and example 9, respectively.

Detailed Description

Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the description to refer to the same or like parts.

It will be understood that when an element such as it is referred to as being "on" or "connected to" another element, it can be directly on or connected to the other element or intervening elements may also be present. If an element is referred to as being "directly on" or "directly connected" to another element, there are no intervening elements present. As used herein, "connected" may refer to physical and/or electrical connection, while "electrically connected" or "coupled" may mean that there are other elements between the two. As used herein, "electrically connected" may include physically connected (e.g., wired) and physically disconnected (e.g., wireless).

As used herein, "approximate" or "substantially" includes the stated value and the average value over a range of acceptable deviations of the specified value as can be determined by one of ordinary skill in the art, taking into account the measurement in question and the specific amount of error associated with the measurement (i.e., limitations of the measurement system). For example, "about" can mean within one or more standard deviations of the stated values, or within ± 30%, ± 20%, ± 10%, ± 5%. Further, as used herein, "about", "approximately" or "substantially" may be selected based on optical properties, etching properties or other properties to select a more acceptable range of deviation or standard deviation, and not to apply one standard deviation to all properties.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. In this case, the singular form includes the plural form unless the context otherwise explains.

Fig. 1 is a Scanning Electron Microscope (SEM) image of preparative reference example 1, preparative example 1, and preparative example 2. Fig. 2 is a tap density comparison image of production reference example 1, production example 1, and production example 2. FIG. 3 is a Brayton's (BET) graph of production reference example 1 and production example 1. Fig. 4 is to charge the BET of the american ginseng 1 and examples 2.

The composite material for electromagnetic wave shielding or electromagnetic wave absorption may include an electromagnetic wave absorbing material including a two-dimensional graphene sheet, such that an electromagnetic wave entering the composite material can generate a current having the same direction as an electric field due to polarization by virtue of the characteristic that the two-dimensional graphene sheet can form a conductive chain or a conductive network therein, and the current forms a closed current loop inside the composite material to generate an eddy current (eddy current). That is, the electromagnetic wave entering the composite material can be converted into electric energy and further converted into heat energy to be consumed, so that the composite material can have a good electromagnetic wave shielding or electromagnetic wave absorbing effect. On the other hand, the high specific surface area and the structural characteristics of graphene can cause multiple scattering of electromagnetic waves incident to the composite material, thereby consuming the energy of the electromagnetic waves and achieving the purpose of absorbing the electromagnetic waves. The graphene sheets may include single-layer graphene, few-layer graphene (few layer graphene), multi-layer graphene (multi-layer graphene), or a combination thereof. The "few-layer graphene" indicates graphene having more than 1 layer and less than 10 layers. The "multilayer graphene" represents graphene having 10 or more layers. The thickness of the graphene sheet can be between 2nm and 10 nm.

The two-dimensional graphene sheet can be prepared by crushing a carbon raw material by a cavitation principle in a liquid phase exfoliation method and drying the crushed material by an oven or freeze drying. For example, a two-dimensional graphene sheet may be formed by the following steps.

First, a carbon raw material is crushed by a cavitation principle in a liquid phase exfoliation method to form a graphene suspension. For example, a continuous cell disruptor (continuous cell disruptor) may be used to homogeneously disrupt the carbon feedstock. The carbon raw material is instantaneously released at the outlet end of the continuous cell crusher under the high-pressure environment, so that the carbon raw material layers are instantaneously peeled, and the carbon between the middle layers of the carbon raw material can be delaminated to form the graphene sheet. The pressure used in the liquid phase stripping process may be from 0bar to 3000 bar. The number of crushing times in the liquid phase peeling method may be 1 to 100, wherein the pressure used for each crushing may be different, for example, two crushing times may be performed at different pressures. The temperature employed for the liquid phase stripping method may be, for example, greater than 4 ℃ and less than 50 ℃. The solvent used in the liquid phase stripping process may be one or more selected from the group consisting of: water, ethanol and N-methyl-2-pyrrolidone (NMP). The solid content of the carbon raw material in the can be 1 wt% to 10 wt%.

Next, the graphene suspension is oven-dried or freeze-dried to form an electromagnetic wave absorbing material containing two-dimensional graphene sheets. The temperature used for oven drying may be 40 ℃ to 100 ℃. The temperature of the dried cold can be from-110 ℃ to-30 ℃.

The graphene suspension is dried by adopting freeze drying, so that a gap between graphene and graphene can be maintained, the agglomeration phenomenon in the drying process is reduced, and the graphene formed by freeze drying has a good electromagnetic wave shielding or electromagnetic wave absorption effect. As shown in fig. 1, the tap density (about 0.0909g/ml) of the graphene formed by freeze-drying (e.g., preparation example 2) was less than the tap density (about 0.1961g/ml) of the graphene formed by oven-drying (e.g., preparation example 1), and as can be seen from fig. 2, the graphene formed by oven-drying had significant stacking lines between layers and the surface morphology was more regular, while the graphene formed by freeze-drying had no significant stacking lines between layers and the surface morphology was more irregular and had a larger aspect ratio. The tap density of graphene formed by either oven drying or freeze drying was less than that of graphite sheet (about 0.2778g/ml) as in preparative reference example 1.

Referring to FIGS. 3 and 4, the BET analysis results show that the formed product is oven-driedThe specific surface area of the resultant graphene (the specific surface area of preparation example 1 shown in FIG. 3 is 37.488 m)²Specific surface area of graphene formed by freeze-drying (specific surface area of preparation example 2 shown in FIG. 4 is 35.2 m)²(g)) was superior to the specific surface area of the graphite sheet (the specific surface areas of production reference example 1 shown in FIGS. 3 and 4 were 29.431m, respectively²G and 29.4m²/g)。

In some embodiments, the composite material may further include a conductive material containing a one-dimensional carbon material, so that gaps between the two-dimensional graphene sheets can be filled with the one-dimensional carbon material to form a denser conductive network, so that the electromagnetic wave shielding or absorbing effect of the composite material can be further improved. The content of the conductive material may be 1 to 10 parts by weight based on 100 parts by weight of the electromagnetic wave absorption material. The one-dimensional carbon material may be a carbon nanotube, but the invention is not limited thereto. In the present embodiment, the method for manufacturing a composite material for electromagnetic wave shielding or electromagnetic wave absorption includes the steps of: an electromagnetic wave absorbing material is mixed with a conductive material. A composite material including the electromagnetic wave absorbing material and the conductive material may be formed by mixing a conductive material containing a one-dimensional carbon material into the electromagnetic wave absorbing material.

In the present embodiment, the thickness of the graphene sheet prepared by crushing the carbon raw material by the principle of cavitation in the liquid phase exfoliation method is in the order of nanometers, but the sheet diameter thereof is only slightly smaller than that of the carbon raw material. For example, the sheet diameter (d)₅₀) Graphite sheet of about 11.15 μm can be prepared to have a sheet diameter (d) by the above-mentioned liquid phase exfoliation method₅₀) Graphene sheets of about 8-9 μm and about 2nm to 10nm in thickness, wherein the graphene formed by oven drying has a larger sheet size (e.g., about 8.59 μm) and the graphene formed by freeze drying has a smaller sheet size (e.g., about 8.11 μm).

In some embodiments, the composite material may further include other additives as desired. For example, the composite material may include carbon black, iron oxide, or a combination thereof.

In some embodiments, the composite material may further include a covering or support material, such as paraffin, silicone rubber, or epoxy, to make a composite block for electromagnetic wave shielding or electromagnetic wave absorption. In the present embodiment, the magnetic wave absorbing material and the conductive material may be added to the covering material or the supporting material in a ratio of 1 wt% to 80 wt% based on the weight of the covering material or the supporting material.

The features of the present invention will be described more specifically below with reference to reference examples 1 and 2 and examples 1 to 9. Although the following examples are described, the materials used, the amounts and ratios thereof, the details of the treatment, the flow of the treatment, and the like may be appropriately changed without departing from the scope of the present invention. Therefore, the present invention should not be construed as being limited by the examples described below.

Reference example 1

First, 7.5g of paraffin wax was weighed out and heated at 70 ℃ until completely melted. Next, 1.875g of graphite sheet was added to paraffin wax and stirred with a homogenizer for 2 hours (3000 rpm) until dispersed uniformly in the liquid paraffin wax solution. Then, the solution was poured into a square mold of 3cm × 3cm, and after it was solidified, it was pressure-molded at a pressure of 17000 lbf.

Example 1

First, 7.5g of paraffin wax was weighed out and heated at 70 ℃ until completely melted. Next, 1.875g of oven dried graphene sheets were added to the paraffin wax and stirred with a homogenizer for 2 hours (3000 rpm) until the graphene sheets were dispersed in the liquid paraffin wax solution. Then, the solution was poured into a square mold of 3cm × 3cm, and after it was solidified, it was pressure-molded at a pressure of 17000 lbf.

Example 2

First, 7.5g of paraffin wax was weighed out and heated at 70 ℃ until completely melted. Next, 1.85625g of oven-dried graphene sheets and 0.01875g of carbon nanotubes were added to paraffin and stirred with a homogenizer for 2 hours (4000 rpm) until the graphene sheets and carbon nanotubes were uniformly dispersed in the liquid paraffin solution. Then, the solution was poured into a square mold of 3cm × 3cm, and after it was solidified, it was pressure-molded at a pressure of 17000 lbf.

Example 3

First, 7.5g of paraffin wax was weighed out and heated at 70 ℃ until completely melted. Next, 1.81875g of the oven-dried graphene sheets and 0.05625g of the carbon nanotubes were added to paraffin wax, and stirred with a homogenizer for 2 hours (rotation speed: 4000rpm) until the graphene sheets and the carbon nanotubes were uniformly dispersed in the liquid paraffin wax solution. Then, the solution was poured into a square mold of 3cm × 3cm, and after it was solidified, it was pressure-molded at a pressure of 17000 lbf.

Example 4

First, 7.5g of paraffin wax was weighed out and heated at 70 ℃ until completely melted. Next, 1.78125g of the oven-dried graphene sheet and 0.09375g of the carbon nanotubes were added to paraffin, and stirred with a homogenizer for 2 hours (rotation speed 4000rpm) until the graphene sheet and the carbon nanotubes were uniformly dispersed in the liquid paraffin solution. Then, the solution was poured into a square mold of 3cm × 3cm, and after it was solidified, it was pressure-molded at a pressure of 17000 lbf.

Example 5

First, 7.5g of paraffin wax was weighed out and heated at 70 ℃ until completely melted. Next, 1.74375g of the oven-dried graphene sheets and 0.13125g of the carbon nanotubes were added to paraffin wax, and stirred with a homogenizer for 2 hours (rotation speed: 4000rpm) until the graphene sheets and the carbon nanotubes were uniformly dispersed in the liquid paraffin wax solution. Then, the solution was poured into a square mold of 3cm × 3cm, and after it was solidified, it was pressure-molded at a pressure of 17000 lbf.

Example 6

First, 7.5g of paraffin wax was weighed out and heated at 70 ℃ until completely melted. Next, 1.875g of the freeze-dried graphene sheet was added to paraffin and stirred with a homogenizer for 2 hours (3000 rpm) until the graphene sheet and the carbon nanotubes were uniformly dispersed in the liquid paraffin solution. Then, the solution was poured into a square mold of 3cm × 3cm, and after it was solidified, it was pressure-molded at a pressure of 17000 lbf.

Example 7

First, 7.5g of paraffin wax was weighed out and heated at 70 ℃ until completely melted. Next, 1.78125g of the freeze-dried graphene sheet and 0.09375g of the carbon nanotubes were added to paraffin, and stirred with a homogenizer for 2 hours (rotation speed 4000rpm) until the graphene sheet and the carbon nanotubes were uniformly dispersed in the liquid paraffin solution. Then, the solution was poured into a square mold of 3cm × 3cm, and after it was solidified, it was pressure-molded at a pressure of 17000 lbf.

Reference example 2

First, 25g of silicone rubber was weighed out and 2.5g of graphite sheet was added to the silicone rubber, dispersed for 15 minutes with a planetary stirring device and then dispersed with three rollers. 2.5g of crosslinker were then added and dispersed for 15 minutes with a planetary stirring apparatus. Then, the mixture was poured into a square mold of 15cm × 15cm, and hot press molded.

Example 8

First, 25g of silicone rubber was weighed out and 2.5g of oven-dried graphene sheets were added to the silicone rubber, dispersed for 15 minutes with a planetary stirring device and then dispersed with three rollers. 2.5g of crosslinker were then added and dispersed for 15 minutes with a planetary stirring apparatus. Then, the mixture was poured into a square mold of 15cm × 15cm, and hot press molded.

Example 9

First, 25g of silicone rubber was weighed out, and 2.5g of the freeze-dried graphene sheet was added to the silicone rubber, dispersed for 15 minutes with a planetary stirring apparatus, and then dispersed with three rollers. 2.5g of crosslinker were then added and dispersed for 15 minutes with a planetary stirring apparatus. Then, the mixture was poured into a square mold of 15cm × 15cm, and hot press molded.

The above reference examples 1 and 2 and examples 1 to 9 are collated in the following table 1.

[ Table 1]

Experiment 1

The test of the electromagnetic wave shielding efficiency in the X band was conducted for reference example 1 and examples 1 to 7. The experimental data for reference example 1 and examples 1-7 are shown in fig. 5A, 5B, 6A and 6B and table 2 below. Reference example 1 and examples 1 to 5Total Shielding Efficiency (SE) in X band_T) Can be seen in FIG. 5A, and the total Shielding Efficiency (SE) of reference example 1, examples 1, 6, 7 in the X-band_T) Can be seen in fig. 6A. Reflection contribution (SE) in the X band of reference example 1 and examples 1, 6 and 7_R) And absorption contribution (SE)_A) The comparison of the shielding efficiencies of (1) and (6) and (7) can be seen in FIG. 5B, while the reflection contribution (SE) of reference example 1 and examples 1, 6 and 7_R) And absorption contribution (SE)_A) A comparison of the shielding efficiencies of (a) can be seen in fig. 6B.

[ Table 2]

As can be seen from the results shown in table 1, the electromagnetic wave shielding efficiencies of examples 1 to 7 are superior to the electromagnetic wave shielding efficiency of reference example 1. In addition, as can be seen from the results of the shielding efficiency tests in examples 1 and 6 and examples 4 and 7, the two-dimensional graphene sheets obtained by the freeze-drying process have better shielding efficiency because the graphene layers are prevented from being stacked during the drying process. In addition, as can be seen from the results of the shielding efficiency tests of examples 2 to 4, the shielding efficiency is better as the proportion of the conductive material in the composite material is higher. However, referring to the results shown in example 5, when the ratio of the conductive material in the composite material is too high, the shielding efficiency is rather decreased due to the occurrence of the agglomeration phenomenon.

Experiment 2

The reflection loss test was performed for reference example 2 and examples 8 and 9, and the experimental results are shown in fig. 7A to 7C, respectively. Fig. 7A to 7C are graphs showing the relationship between the frequency and the Reflection Loss (RL) in different thicknesses of reference example 2, example 8 and example 9, respectively. The higher the reflection loss and the wider the covering frequency, the better the electromagnetic wave shielding efficiency, and it can be seen from the results shown in fig. 7A to 7C that example 8 and example 9 have reflection loss superior to reference example 2, and example 9 has reflection loss superior to example 8.

As described above, in the composite material and the method for manufacturing the same according to an embodiment of the present invention, since the electromagnetic wave absorbing material including the two-dimensional graphene sheet can form a conductive chain or a conductive network inside the material, the electromagnetic wave entering the composite material can generate a current having the same direction as the electric field due to polarization, and the current forms a closed current loop inside the composite material to generate an eddy current, so that the electricity can be further converted into heat energy to be consumed, and the composite material can have a good electromagnetic wave shielding or electromagnetic wave absorbing effect. On the other hand, when the composite material further comprises a conductive material containing a one-dimensional carbon material, the gaps between the two-dimensional graphene sheets can be filled with the one-dimensional carbon material to form a more compact conductive network, so that the electromagnetic wave shielding or absorbing effect of the composite material can be further improved.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite material for electromagnetic wave shielding or electromagnetic wave absorption, comprising:

an electromagnetic wave absorbing material comprising a two-dimensional graphene sheet,

the two-dimensional graphene sheet is prepared by crushing a carbon raw material by a cavity principle in a liquid phase stripping method and drying the crushed carbon raw material in an oven or freeze drying.

2. The composite of claim 1, further comprising:

the conductive material contains a one-dimensional carbon material.

3. The composite material according to claim 2, wherein the content of the conductive material is 1 to 10 parts by weight based on 100 parts by weight of the electromagnetic wave absorbing material.

4. The composite material of claim 2, wherein the one-dimensional carbon material comprises carbon nanotubes.

5. A method of manufacturing a composite material for electromagnetic wave shielding or electromagnetic wave absorption, the method comprising:

crushing a carbon raw material by a cavity principle in a liquid phase stripping method to form a graphene suspension; and

and carrying out oven drying or freeze drying on the graphene suspension to form the electromagnetic wave absorption material containing the two-dimensional graphene sheet.

6. The method of manufacturing a composite material of claim 5, further comprising:

mixing a conductive material containing a one-dimensional carbon material into the electromagnetic wave absorbing material.

7. The method of manufacturing a composite material according to claim 6, wherein the content of the conductive material is 1 to 10 parts by weight based on 100 parts by weight of the electromagnetic wave absorbing material.

8. The method of manufacturing a composite material according to claim 6, wherein the one-dimensional carbon material comprises carbon nanotubes.

9. The method of manufacturing a composite material according to claim 5, wherein the solvent used in the liquid phase stripping method is one or more selected from the group consisting of: water, ethanol and N-methyl-2-pyrrolidone.

10. The method of manufacturing a composite material according to claim 9, wherein the solid content of the carbon raw material in the solvent is 1 wt% to 10 wt%.

11. The method of manufacturing a composite material according to claim 5, wherein the liquid phase exfoliation method is broken more than 1 time and less than 100 times.

12. The method of manufacturing a composite material according to claim 5, wherein the temperature of the oven drying is 40 ℃ to 100 ℃.

13. The method of manufacturing a composite material according to claim 5, wherein the temperature of the freeze-drying is from-110 ℃ to-30 ℃.