阅读说明：本技术 一种MXene电磁屏蔽织物及其制备方法和应用 (MXene electromagnetic shielding fabric and preparation method and application thereof ) 是由 侯成义 刘芮 吴钦鑫 王宏志 李耀刚 张青红 于 2020-12-03 设计创作，主要内容包括：本发明涉及一种MXene电磁屏蔽织物及其制备方法和应用。该方法包括：将柔性织物基底等离子体预处理,然后放入MXene分散液中浸渍,取出后干燥,在CO-2条件下低温退火处理。该电磁屏蔽织物具有良好的柔性、耐水洗性和电磁屏蔽特性。(The invention relates to an MXene electromagnetic shielding fabric and a preparation method and application thereof. The method comprises the following steps: pretreating a flexible fabric substrate by plasma, then soaking the flexible fabric substrate in MXene dispersion liquid, taking out the flexible fabric substrate, drying the flexible fabric substrate, and adding CO 2 And (5) annealing treatment at low temperature under the condition. The electromagnetic shielding fabric has good flexibility, water washing resistance and electromagnetic shielding property.)

1. An MXene electromagnetic shielding fabric is characterized in that a pretreated flexible fabric substrate is put into MXene dispersion liquid to be uniformly dip-coated, dried and then subjected to CO treatment₂Annealing under the condition, wherein the technological parameters of the annealing are as follows: placing the dried fabric in a rapid heating furnace in CO₂Heating to 60 ℃ at the speed of 10-20 ℃/s for preheating for 20-40min under the atmosphere, then heating to 60-80 ℃ at the same speed, treating for 24-36h, closing the rapid heating furnace, and then preserving heat for 2-4 h.

2. The MXene electromagnetic shielding fabric of claim 1, wherein the flexible fabric substrate is one of a non-woven fabric, a pure cotton fabric, a Ketone cloth, a pure linen fabric, and a bamboo fiber cloth.

3. The MXene electromagnetic shielding fabric of claim 1, wherein the MXene dispersion is prepared by passing MAX phase Ti₃AlC₂Adding into etching solution of lithium fluoride, hydrochloric acid and ultrapure water, stirring for reaction, centrifuging, dispersing the obtained precipitate in deionized water, centrifuging again, and collecting the dispersion solution.

4. According to claimThe MXene electromagnetic shielding fabric of claim 3, wherein the Ti is₃AlC₂The mass ratio of LiF to HCl to ultrapure water is 1: 1-2: 12.5-30: 5.5.

5. The MXene electromagnetic shielding fabric according to claim 3, wherein the stirring reaction temperature is 25-30 ℃ and the stirring reaction time is 22-26 h.

6. A preparation method of MXene electromagnetic shielding fabric comprises the following steps:

(1) plasma pre-treating a flexible fabric substrate;

(2) dipping the flexible fabric substrate pretreated in the step (1) in MXene dispersion liquid, taking out and drying;

(3) and (3) annealing the dried fabric to obtain the MXene electromagnetic shielding fabric, wherein the annealing process parameters are as follows: placing the dried fabric in a rapid heating furnace in CO₂Heating to 60 ℃ at the speed of 10-20 ℃/s for preheating for 20-40min under the atmosphere, then heating to 60-80 ℃ at the same speed, treating for 24-36h, closing the rapid heating furnace, and then preserving heat for 2-4 h.

7. The method of claim 6, wherein the plasma pretreatment in step (1) is: using a plasma processor in an atmosphere of O₂The power is 50-70W, and the processing time is 3-8 min.

8. The method according to claim 6, wherein the MXene dispersion liquid in the step (2) is prepared by: adding a MAX phase Ti₃AlC₂Adding into etching solution of lithium fluoride, hydrochloric acid and ultrapure water, stirring for reaction, centrifuging, dispersing the obtained precipitate in deionized water, centrifuging again, and collecting the dispersion solution to obtain Ti₃AlC₂The mass ratio of LiF to HCl to ultrapure water is 1: 1-2: 12.5-30: 5.5; the stirring reaction temperature is 25-30 ℃, and the stirring reaction time is 22-26 h.

9. The method according to claim 6, wherein the concentration of MXene dispersion in step (2) is 5-10 mg/mL.

10. Use of the fabric of claim 1 in a wearable garment.

Technical Field

The invention belongs to the field of electromagnetic shielding materials and preparation and application thereof, and particularly relates to an MXene electromagnetic shielding fabric and a preparation method and application thereof.

Background

With the rapid development of modern electronic technology, electronic devices and wireless communication devices are widely used, and more electromagnetic radiation and interference are generated, so that the space electromagnetic environment is increasingly complicated. Electromagnetic radiation becomes a new type of pollution following noise, water and air pollution, which not only affects the information safety of communication equipment and the normal operation of electronic equipment, but also can harm human health. Therefore, research into a new electromagnetic shielding material has become an indispensable part for protecting electronic components and humans from electromagnetic interference.

The metal and metal oxide materials which are firstly applied to the electromagnetic shielding field have the defects of large density, poor chemical corrosion resistance, difficult processing and the like, so that the light and high-efficiency requirements of people on the electromagnetic shielding material are difficult to meet. And low-dimensional nano materials such as carbon nano tubes, graphene, MXene and the like are gradually an ideal choice for preparing the electromagnetic interference shielding material due to the characteristics of small density, high conductivity, easiness in processing and the like. Wherein, the novel two-dimensional nano material MXene has high conductivity (8000S/cm) and high electron mobility (5.03 multiplied by 103 cm) due to special structure and abundant surface functional groups²V · s), good biocompatibility, and diversified morphology, have great research prospects in functional materials. Meanwhile, MXene belongs to a normal-temperature photo-thermal conversion far-infrared high-radiation material, has high photo-thermal conversion rate, does not need a heat source, and has the characteristic of absorbing environmental heat and outputting the environmental heat in a far-infrared energy form. The single-layer MXene film can realize 20% of effective shielding of electromagnetic waves, the 24-layer (about 55nm in thickness) film has 99% of electromagnetic shielding performance (20dB), and the absolute shielding performance value reaches 3.89 x 106dB cm²The value is obviously superior to most of the electromagnetic shielding materials reported in the literature at present. However, most of the MXene-based flexible electromagnetic shielding composite materials are mainly prepared by filling MXene in a polymer material. Such as the patent: a preparation method of electrostatic spinning polyimide/MXene electromagnetic shielding film (publication number: CN111155239A), a waterborne polyurethane-MXene electromagnetic shielding bionic nano composite material film and a preparation method (publication number: CN110698847A) and the like are all used after monomers are polymerizedThe polymer stock solution is mixed with MXene dispersion liquid, and the composite material is prepared by simple suction filtration. The composite material can not be well applied to wearable and other directions needing electromagnetic shielding, and the conductive performance of the composite material is greatly reduced due to the coating of the high polymer material. The research of MXene-based high-performance electromagnetic shielding fabric is not complete.

Disclosure of Invention

The invention aims to solve the technical problem of providing an MXene electromagnetic shielding fabric, and a preparation method and application thereof, so as to overcome the defects of poor electromagnetic shielding effect and poor durability of the electromagnetic shielding fabric in the prior art.

The invention provides an MXene electromagnetic shielding fabric, which is prepared by uniformly dip-coating a pretreated flexible fabric substrate in MXene dispersion liquid, drying, and then adding the mixture into CO₂Calcining under the condition, wherein the annealing treatment process parameters are as follows: placing the dried fabric in a rapid heating furnace in CO₂Heating to 60 ℃ at the speed of 10-20 ℃/s for preheating for 20-40min under the atmosphere, then heating to 60-80 ℃ at the same speed, treating for 24-36h, closing the rapid heating furnace, and then preserving heat for 2-4 h.

The flexible fabric substrate is one of non-woven fabric, pure cotton cloth, ketone ammonia fiber cloth, pure linen cloth and bamboo fiber cloth.

The MXene dispersion is prepared by mixing MAX phase Ti₃AlC₂Adding into etching solution of lithium fluoride, hydrochloric acid and ultrapure water, stirring for reaction, centrifuging, dispersing the obtained precipitate in deionized water, centrifuging again, and collecting the dispersion solution.

The Ti₃AlC₂The mass ratio of LiF to HCl to ultrapure water is 1: 1-2: 12.5-30: 5.5.

The stirring reaction temperature is 25-30 ℃, and the stirring reaction time is 22-26 h.

The invention also provides a preparation method of the MXene electromagnetic shielding fabric, which comprises the following steps:

(1) plasma pre-treating a flexible fabric substrate;

(2) dipping the flexible fabric substrate pretreated in the step (1) in MXene dispersion liquid, taking out and drying;

(3) and (3) annealing the dried fabric to obtain the MXene electromagnetic shielding fabric, wherein the annealing process parameters are as follows:

placing the dried fabric in a rapid heating furnace in CO₂Heating to 60 ℃ at the speed of 10-20 ℃/s for preheating for 20-40min under the atmosphere, then heating to 60-80 ℃ at the same speed, treating for 24-36h, closing the rapid heating furnace, and then preserving heat for 2-4 h.

The plasma pretreatment in the step (1) comprises the following steps: using a plasma processor in an atmosphere of O₂The power is 50-70W, and the processing time is 3-8 min.

The flexible fabric substrate in the step (1) comprises but is not limited to one of non-woven fabric, pure cotton cloth, ketoamine fiber cloth, pure linen cloth and bamboo fiber cloth.

The preparation method of the MXene dispersion liquid in the step (2) comprises the following steps: adding a MAX phase Ti₃AlC₂Adding into etching solution of lithium fluoride, hydrochloric acid and ultrapure water, stirring for reaction, centrifuging, dispersing the obtained precipitate in deionized water, centrifuging again, and collecting the dispersion solution to obtain Ti₃AlC₂The mass ratio of LiF to HCl to ultrapure water is 1: 1-2: 12.5-30: 5.5.

The concentration of MXene dispersion liquid in the step (2) is 5-10 mg/mL.

The stirring reaction temperature is 25-30 ℃, the stirring reaction time is 22-26 h, and the stirring speed is 650-750 r/min.

The centrifugation is carried out for a plurality of times until the pH of the supernatant is close to 7.

The speed of the multiple centrifugation is 3000-4000 r/min, and the centrifugation time is 3-8min each time.

The speed of re-centrifugation is 3000-4000 r/min, and the time of re-centrifugation is 3-8 min.

The invention also provides application of the MXene electromagnetic shielding fabric in wearable clothes.

The fabric has higher strength, the MXene has good adhesion capacity on the surface of the fabric and high stability, the MXene and the fabric have the advantages of no toxicity, good biocompatibility and the like, the fabric has excellent skin-friendly property, is breathable and comfortable when contacting with a human body, and meets the requirements of the wearable field.

The fabric substrate is put into MXene dispersion liquid for impregnation, and after drying, the fabric substrate is put into CO₂And annealing at low temperature under the condition to obtain the MXene electromagnetic shielding fabric with the P-N junction microstructure on the surface. This is because of Ti₃C₂T_x-MXene in CO₂Evolution of the surface structure after atmospheric heat treatment. Ti prepared by chemical etching method₃C₂T_x-MXene, which contains a large number of-OH, -O and-F groups on the surface to ensure Ti₃C₂T_xThe structure is stable. In the heat treatment process, the exposed Ti layer on the outermost surface layer and the surface oxygen-containing group are subjected to oxidation reaction to generate anatase TiO₂While with increasing temperature anatase is partly converted to the more thermally stable rutile phase TiO₂. The oxidation reaction of the Ti atomic layer exposes the middle C layer, and forms an amorphous carbon phase of a two-dimensional lamellar layer. The reaction process causes TiO to be formed on the partial position of the outermost layer of the MXene conductive layer on the surface of the fabric₂The P-N junction microstructure of the-C is beneficial to improving the wave absorbing performance of the MXene electromagnetic shielding fabric.

MXene is not considered to be a very novel treatment, but in the prior art studies, high-temperature calcination is generally used, and Ar is used as a protective gas. Professor Yury Gogotsi, the father of MXene, published an article of International society of Electromagnetic Waves by 2D Transition Metal carbide Ti in the Science of the International Top-level journal₃CNT_x(MXene).[Aamir Iqbal,et al.Anomalous Absorption of Electromagnetic Waves by 2D Transition Metal Carbonitride Ti₃CNT_x(MXene),Science,2020.DOI:10.1126]. In this work the investigators used temperatures of 150 c, 250 c, and 350 c, respectively, to subject MXene to a thermal calcination treatment in an Ar atmosphere, although higher calcination temperatures would result in decreased interlayer spacing, but due to the increased degree of oxidation of the material, both pore size and pore volume increase. After calcination, the electromagnetic wave generated by the layered metamaterial-like structure is extremely high in absorption, and the electromagnetic shielding effect is respectively improved to 77dB, 99dB and 116 dB. Professor Wangdan of Chinese academy of sciences Process engineeringAn article named wall Synthesis of shredded Nitrogen-shredded MXene Nanosheets as A New sulphur Host for Lithium-sulphur Batteries [ Weizhai Bao, et al, wall Synthesis of shredded Nitrogen-shredded MXene Nanosheets as A New sulphur Host for Li thium-sulphur Batteries [ J].Advanced Energy Materials,2018,8(13).]. Using negatively charged Ti₃C₂T_xAfter the sheet and the melamine with positive charge are annealed, the wrinkled N-Ti is successfully prepared by electrostatic self-assembly₃C₂T_xNanosheet material, with N atoms successfully doped into Ti₃C₂T_xA material. The annealing method still uses high-temperature short-time calcination, but the annealing method and the reason for improving the electromagnetic shielding performance are different from other works. The annealing method used by the invention is low-temperature long-time annealing, so that MXene nanosheets loaded on the outermost layer of the MXene conductive layer on the surface of the fabric are fully and uniformly calcined, and CO is used₂The MXene nano-sheets on the outermost layer are completely oxidized by using the sacrificial gas as the calcining gas to form TiO on the partial position of the outermost layer₂-P-N junction microstructure of C. The surface of the composite fabric forms more heterogeneous interfaces, increases the electron concentration at the interfaces, and increases the transmission path of electromagnetic waves inside the material. And form a miniature capacitor-like circuit, these structural characteristics will enhance Ti₃C₂T_xThe electromagnetic wave absorbing ability of (1). In addition, Ti is not destroyed in the interior after the heat treatment process₃C₂T_xOn the premise of the two-dimensional structure, a large number of surface functional groups are reduced, an amorphous carbon phase is stripped, the conductivity of the material is improved, and the increase of the conductivity loss of electromagnetic waves in the material is facilitated. The formation of the low dielectric loss phase titanium dioxide is beneficial to optimizing the impedance matching of the material surface and the free space.

Advantageous effects

(1) The MXene electromagnetic shielding fabric has good flexibility and electromagnetic shielding characteristics, and has biocompatibility and environmental friendliness.

(2) The invention utilizes the characteristics of loose fabric fiber and rough surface structure, adopts MXene to modify the flexible fabric material, constructs and designs the MXene electromagnetic shielding fabric with the three-dimensional network structure, effectively improves the wave absorbing performance of the traditional electromagnetic shielding fabric, is applied to wearable clothing, and has great significance for protecting human health and reducing the harm of electromagnetic radiation.

(3) The method uses low-temperature long-time annealing to uniformly calcine the MXene nanosheets loaded on the outermost layer of the MXene conductive layer on the surface of the fabric, and uses CO₂The MXene nano-sheets at the outermost layer are completely oxidized by using the sacrificial gas as the calcining gas, and TiO is formed at the partial position of the outermost layer₂-P-N junction microstructure of C. The wave absorbing performance of the MXene electromagnetic shielding fabric is improved, and the washing durability of the fabric is improved.

(4) The method is simple and easy to implement, low in requirements on production equipment and low in cost.

Drawings

Fig. 1 is a flow chart of the preparation of the MXene electromagnetic shielding fabric of the invention.

Fig. 2 is an XRD pattern of MXene prepared in example 1.

Fig. 3 shows FESEM images of the MXene film prepared in example 1 before and after low temperature annealing treatment, wherein (a) shows the MXene film without low temperature annealing treatment, and (b) shows the MXene film with P-N junction microstructure after low temperature annealing treatment.

Fig. 4 shows FESEM images of the purified cotton fabric (a-c) prepared in example 1 and the MXene electromagnetic shielding purified cotton fabric (d-f) obtained in step (4) of example 1 at different magnifications.

Fig. 5 is electromagnetic shielding effectiveness of the MXene electromagnetic shielding pure cotton fabric subjected to low temperature annealing treatment prepared in example 1, the original pure cotton fabric and the MXene electromagnetic shielding pure cotton fabric not subjected to low temperature annealing treatment prepared in comparative example 1 at X band, wherein (a) the electromagnetic shielding effectiveness is absorbed; (b) reflecting electromagnetic shielding effectiveness; (c) the total electromagnetic shielding effectiveness; (d) electromagnetic interference shielding efficiency.

Fig. 6 shows MXene electromagnetic shielding cotton garment (c) and its applications (a, b) prepared in example 1, wherein a is unshielded and b is shielded.

Fig. 7 is a V-I curve before and after 30min water washing of the MXene electromagnetic shielding pure cotton fabric (a) without low temperature annealing treatment in comparative example 1 and the MXene electromagnetic shielding pure cotton fabric (b) with low temperature annealing treatment in example 1.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

The main reagent sources related to the embodiment of the invention are shown in table 1:

TABLE 1

Reagent	Chemical formula (II)	Specification of	Manufacturer of the product
				Lithium fluoride	LiF	Analytical purity	Chinese medicine
MAX phase	Ti3AlC2	Analytical purity	Chinese medicine
				36% concentrated hydrochloric acid	HCl	Analytical purity	Chinese medicine
Oxygen gas	O2	(High purity)	Shenzhong gas
				Carbon dioxide gas	CO2	(High purity)	Shenzhong gas

Example 1

(1) Preparation process of MXene:

an etching solution of 1.6g LiF, 19.25g HCl and 5.5mL ultrapure water was sufficiently stirred, and 1g MAX phase (Ti) was slowly added₃AlC₂) And (3) stirring the powder at the reaction temperature of 27 ℃ and the stirring speed of 700r/min for 24 hours till the etching is complete. The washing was performed by multiple centrifugations at 3500r/min until the supernatant pH was close to 7. And then fully dispersing the obtained precipitate in deionized water, centrifuging at 3500r/min for 5min, and collecting the upper black liquid, namely MXene dispersion liquid. Fig. 2 is an XRD pattern of MXene prepared in this example 1, which shows that MXene is completely etched.

(2) Pretreatment of the fabric:

mixing 2.5X 2.5cm²Placing pure cotton cloth (thickness 2mm) in a plasma processor, setting the power at 60W, processing time at 5min, and processing at O₂Pretreating the pure cotton cloth under the atmosphere.

(3) And (3) putting the pure cotton cloth pretreated in the step (2) into a culture dish containing the MXene/water dispersion liquid with the concentration of 5mg/mL obtained in the step (1), soaking for 10 minutes, taking out after the soaking is sufficient, and drying by cold air. And repeating the impregnation step, and regulating and controlling the loading amount of MXene on the surface of the pure cotton fabric for 3 times.

(4) Low-temperature annealing treatment:

placing the dried MXene/pure cotton composite fabric in a rapid heating furnace in CO₂Heating to 60 ℃ at the speed of 10 ℃/s in the atmosphere, preheating for 20min, keeping the calcination temperature at 60 ℃ for 24h, closing the rapid heating furnace, keeping the temperature for 2h, and cooling along with the furnace to obtain the MXene electromagnetic shielding pure cotton fabric with the P-N junction microstructure on the surface. Fig. 1 is a flow chart of the preparation of the MXene electromagnetic shielding fabric in example 1. For the effect of the low-temperature annealing treatment on the MXene structure, the MXene obtained in the step (1) is subjected to suction filtration to form a film, and the same low-temperature annealing treatment operation is adopted on the MXene film, as shown in FIG. 3, FIG. 3 is an FESEM image of the MXene film prepared in the example 1 before and after the low-temperature annealing treatment, (a) is the MXene film without the low-temperature annealing treatment, and (b) is the MXene film with the P-N junction microstructure after the low-temperature annealing treatment. It is clearly observed that upon low temperature annealing the layer structure of MXene changes with an increase in monolayer thickness accompanied by a loose microporous structure. The method is beneficial to the increase of the electric conduction loss of electromagnetic waves in the material, and proves the effect of low-temperature annealing treatment on improving the wave absorption performance of the MXene electromagnetic shielding fabric. Fig. 4 shows FESEM images of the pure cotton fabric prepared in example 1 and the MXene electromagnetic shielding pure cotton fabric obtained in step (4) at different magnifications. (a-c) a pure cotton fabric; (d-f) MXene electromagnetic shielding pure cotton fabric. As can be seen, MXene is uniformly coated on the surface of the pure cotton fabric. Fig. 7 is a V-I graph of the MXene electromagnetic shielding pure cotton fabric subjected to the low-temperature annealing treatment prepared in example 1(a) and comparative example 1(b) before and after 30min water washing. After the MXene electromagnetic shielding fabric subjected to low-temperature annealing treatment is washed by water for 30min, the resistance is increased from 396 omega to 419 omega, and the resistance is only increased by 5%. After the MXene electromagnetic shielding fabric which is not subjected to low-temperature annealing treatment is washed for 30min, the resistance is increased from 408 omega to 890 omega, and the resistance is increased by 118%, which shows that the washing durability of the fabric is improved simultaneously by the low-temperature annealing treatment.

(5) And (4) carrying out electromagnetic shielding effectiveness test on the MXene electromagnetic shielding pure cotton fabric obtained in the step (4) by using a vector network analyzer. The test frequency is 8.2-12.4GHz, and the frequency step is 0.08 GHz. Meanwhile, in order to adapt to the size of the rectangular waveguide, MXene/fabric is made into the size of 22.9 multiplied by 10.2 multiplied by (2.0-6.0) mm, wherein 22.9 multiplied by 10.2mm is the size of the cross section of the rectangular waveguide, and the thickness of a sample is the thickness of the fabric. The results are shown in fig. 5, (fig. 5 shows the electromagnetic shielding effectiveness of the MXene electromagnetic shielding pure cotton fabric subjected to low-temperature annealing treatment prepared in example 1, the original pure cotton fabric and the MXene electromagnetic shielding pure cotton fabric not subjected to low-temperature annealing treatment prepared in comparative example 1 in the X band, wherein (a) the electromagnetic shielding effectiveness is absorbed, (b) the electromagnetic shielding effectiveness is reflected, (c) the total electromagnetic shielding effectiveness is reflected, (d) the electromagnetic interference shielding efficiency is increased, and when the frequency is 10GHz, the total electromagnetic shielding effectiveness, the absorption shielding effectiveness and the reflection shielding effectiveness of the pure cotton fabric are respectively 3.38dB, 2.22dB and 1.17dB, and the total shielding effectiveness is 39.96%; the total electromagnetic shielding effectiveness, the absorption shielding effectiveness and the reflection shielding effectiveness of the MXene electromagnetic shielding pure cotton fabric subjected to the low-temperature annealing treatment are 15.77dB, 8.31dB and 7.45dB respectively, and the total shielding effectiveness is 85.25%. The addition of MXene greatly improves the electromagnetic wave absorption capacity and the reflection capacity of the fabric, and the total shielding effectiveness of the MXene electromagnetic shielding pure cotton fabric in an X wave band is 84.5 percent and is enhanced by more than 1 time than that of the pure cotton fabric (41.6 percent) without the MXene coating.

(6) Combining the area of the ordinary clothes needing shielding with the MXene electromagnetic shielding fabric obtained by the low-temperature annealing treatment in the step (4), and making the MXene electromagnetic shielding pure cotton fabric into a pocket at the position of the heart opening, wherein as shown in FIG. 6, when the MXene electromagnetic shielding pure cotton fabric is not shielded, the radiation detector displays that the electric field radiation intensity is 309.76V/m when the mobile phone dials; the mobile phone is placed in an MXene electromagnetic shielding fabric pocket, and the radiation detector displays that the radiation intensity of an electric field is 0V/m when the mobile phone is dialed. The preparation method of the MXene electromagnetic shielding fabric provided by the invention is applied to wearable clothes, and has great significance in protecting human health and reducing harm of electromagnetic radiation.

Example 2

(1) Preparation process of MXene:

an etching solution of 1g LiF, 12.5g HCl and 5.5mL ultrapure water was sufficiently stirred, and 1g MAX phase (Ti) was slowly added₃AlC₂) And (3) stirring the powder at the reaction temperature of 25 ℃ and the stirring speed of 650r/min for 22 hours till the etching is complete. Centrifuging for many times at 3000r/minWashing was carried out until the supernatant pH was close to 7. And then fully dispersing the obtained precipitate in deionized water, centrifuging for 3min at 3000r/min, and collecting the upper layer black liquid, namely MXene dispersion liquid.

(2) Pretreatment of the fabric:

mixing 2.5X 2.5cm²The pure linen (thickness 3mm) is put into a plasma processor, the power is set to be 50W, the processing time is 3min, and the process is carried out at O₂And (4) pretreating the pure linen in the atmosphere.

(3) And (3) putting the pure linen pretreated in the step (2) into a culture dish containing the MXene/water dispersion liquid with the concentration of 7.5mg/mL obtained in the step (1), soaking for 15 minutes, taking out after full soaking, drying by cold air, repeating the step of soaking, and regulating and controlling the loading capacity of the MXene on the surface of the pure linen fabric for 4 times.

(4) Low-temperature annealing treatment:

placing the dried MXene/pure cotton composite fabric in a rapid heating furnace in CO₂Heating to 60 ℃ at the rate of 15 ℃/s for preheating for 30min under the atmosphere, heating to 70 ℃ at the same heating rate, calcining for 30h, closing the rapid heating furnace, preserving heat for 3h, and cooling along with the furnace to obtain the MXene electromagnetic shielding pure hemp fabric with the P-N junction microstructure on the surface. Fig. 1 is a flow chart of the preparation of the MXene electromagnetic shielding fabric in example 1.

(5) And (4) carrying out electromagnetic shielding effectiveness test on the MXene electromagnetic shielding pure linen fabric obtained in the step (4) by using a vector network analyzer. The test frequency is 8.2-12.4GHz, and the frequency step is 0.08 GHz. Meanwhile, in order to adapt to the size of the rectangular waveguide, MXene/fabric is made into the size of 22.9 multiplied by 10.2 multiplied by (2.0-6.0) mm, wherein 22.9 multiplied by 10.2mm is the size of the cross section of the rectangular waveguide, and the thickness of a sample is the thickness of the fabric. When the frequency is 10GHz, the total electromagnetic shielding effectiveness, the absorption shielding effectiveness and the reflection shielding effectiveness of the pure linen fabric are 1.52dB, 1.15dB and 0.37dB respectively; the total electromagnetic shielding effectiveness, the absorption shielding effectiveness and the reflection shielding effectiveness of the MXene electromagnetic shielding fabric are 10.66dB, 6.05dB and 4.61dB respectively, and the total shielding effectiveness is 61.8%. The addition of MXene greatly improves the electromagnetic wave absorption capacity and the reflection capacity of the fabric, and the total shielding effectiveness of the MXene electromagnetic shielding pure hemp fabric in an X wave band is 64 percent and is enhanced by nearly 1 time compared with that of the pure hemp fabric (33.6 percent) without the MXene coating.

(6) Combining the area of the common garment needing shielding with the MXene electromagnetic shielding fabric obtained after the low-temperature annealing treatment in the step (4), and making the MXene electromagnetic shielding pure hemp fabric into a pocket at the position of the heart opening. When the mobile phone is not shielded, the radiation detector displays that the radiation intensity of an electric field is 312.65V/m when the mobile phone dials; the mobile phone is placed in an MXene electromagnetic shielding fabric pocket, and the radiation detector displays that the radiation intensity of an electric field is 13V/m when the mobile phone is dialed. The preparation method of the MXene electromagnetic shielding fabric provided by the invention is applied to wearable clothes, and has great significance in protecting human health and reducing harm of electromagnetic radiation.

Example 3

(1) Preparation process of MXene:

an etching solution of 2g LiF, 30g HCl and 5.5mL of ultrapure water was sufficiently stirred, and 1g of MAX phase (Ti) was slowly added₃AlC₂) And (3) stirring the powder at the reaction temperature of 30 ℃ and the stirring speed of 750r/min for 26 hours till the etching is complete. The washing was carried out by multiple centrifugations at 4000r/min until the pH of the supernatant was close to 7. And then fully dispersing the obtained precipitate in deionized water, centrifuging for 8min at 4000r/min, and collecting the upper layer black liquid, namely MXene dispersion liquid.

(2) Pretreatment of the fabric:

mixing 2.5X 2.5cm²The bamboo fiber cloth (thickness 4mm) was placed in a plasma processor, the power was set at 70W, the processing time was set at 8min, and the surface treatment was carried out at O₂Pretreating the bamboo fiber cloth under the atmosphere.

(3) And (3) putting the bamboo fiber cloth pretreated in the step (2) into a culture dish containing the MXene/water dispersion liquid with the concentration of 10mg/mL obtained in the step (1), soaking for 20 minutes, taking out after full soaking, drying by cold air, repeating the step of soaking, and regulating and controlling the loading amount of MXene on the surface of the bamboo fiber fabric for 5 times.

(4) Low-temperature annealing treatment:

placing the dried MXene/bamboo fiber composite fabric in a rapid heating furnace in CO₂Heating to 60 deg.C at 20 deg.C/s under atmosphere for 40min, and heating at the same temperatureAnd (3) raising the temperature to 80 ℃, keeping the calcination time at 36h, closing the rapid heating furnace, keeping the temperature for 4h, and cooling along with the furnace to obtain the MXene electromagnetic shielding bamboo fiber fabric with the P-N structure on the surface. Fig. 1 is a flow chart of the preparation of the MXene electromagnetic shielding fabric in example 1.

(5) And (4) carrying out electromagnetic shielding effectiveness test on the MXene electromagnetic shielding bamboo fiber fabric obtained in the step (4) by using a vector network analyzer. The test frequency is 8.2-12.4GHz, and the frequency step is 0.08 GHz. Meanwhile, in order to adapt to the size of the rectangular waveguide, MXene/fabric is made into the size of 22.9 multiplied by 10.2 multiplied by (2.0-6.0) mm, wherein 22.9 multiplied by 10.2mm is the size of the cross section of the rectangular waveguide, and the thickness of a sample is the thickness of the fabric. When the frequency is 10GHz, the total electromagnetic shielding effectiveness, the absorption shielding effectiveness and the reflection shielding effectiveness of the bamboo fiber fabric are 1.98dB, 1.65dB and 0.33dB respectively; the total electromagnetic shielding effectiveness, the absorption shielding effectiveness and the reflection shielding effectiveness of the MXene electromagnetic shielding fabric are 12.2dB, 6.87dB and 5.33dB respectively, and the total shielding effectiveness is 75.2%. The addition of MXene greatly improves the electromagnetic wave absorption capacity and reflection capacity of the fabric, and the total shielding effectiveness of the MXene electromagnetic shielding bamboo fiber fabric in an X wave band is 75.2%, which is nearly 1 time enhanced compared with that of the bamboo fiber fabric (38.1%) without the MXene coating.

(6) Combining the area of the common garment needing shielding with the MXene electromagnetic shielding fabric obtained after the low-temperature annealing treatment in the step (4), and making the MXene electromagnetic shielding bamboo fiber fabric into a pocket at the position of the heart opening. When the mobile phone is not shielded, the radiation detector displays that the radiation intensity of an electric field is 310.36V/m when the mobile phone dials; the mobile phone is placed in an MXene electromagnetic shielding fabric pocket, and the radiation detector displays that the radiation intensity of an electric field is 15V/m when the mobile phone is dialed. The preparation method of the MXene electromagnetic shielding fabric provided by the invention is applied to wearable clothes, and has great significance in protecting human health and reducing harm of electromagnetic radiation.

Comparative example 1

(1) Preparation process of MXene:

mixing the components in a mass ratio of 1.6 g: 19.25 g: 5.5mL of LiF, HCl and ultrapure water etching solution were fully stirred, and 1g of MAX phase (Ti) was slowly added₃AlC₂) Powder, the reaction temperature is 27 ℃,the stirring speed is 700r/min, and the stirring is continued for 24 hours until the etching is complete. The washing was performed by multiple centrifugations at 3500r/min until the supernatant pH was close to 7. And then fully dispersing the obtained precipitate in deionized water, centrifuging at 3500r/min for 5min, and collecting the upper black liquid, namely MXene dispersion liquid. Fig. 2 is an XRD pattern of MXene prepared in this example 1, which shows that MXene is completely etched.

(2) Pretreatment of the fabric:

mixing 2.5X 2.5cm²Placing pure cotton cloth (thickness 2mm) in a plasma processor, setting the power at 60W, processing time at 5min, and processing at O₂Pretreating the pure cotton cloth under the atmosphere.

(3) And (3) putting the pure cotton cloth pretreated in the step (2) into a culture dish containing the MXene/water dispersion liquid with the concentration of 5mg/mL obtained in the step (1), soaking for 10 minutes, taking out after the soaking is sufficient, and drying by cold air. And repeating the step of dipping, and regulating and controlling the loading capacity of MXene on the surface of the pure cotton fabric for 3 times to obtain the MXene electromagnetic shielding pure cotton fabric. Fig. 7 is a V-I curve before and after 30min water washing of the MXene electromagnetic shielding pure cotton fabric (a) without low temperature annealing treatment in comparative example 1 and the MXene electromagnetic shielding pure cotton fabric (b) with low temperature annealing treatment in example 1. After the MXene electromagnetic shielding fabric subjected to low-temperature annealing treatment is washed by water for 30min, the resistance is increased from 396 omega to 419 omega, and the resistance is only increased by 5%. After the MXene electromagnetic shielding fabric which is not subjected to low-temperature annealing treatment is washed for 30min, the resistance is increased from 408 omega to 890 omega, and the resistance is increased by 118%.

(4) And (4) carrying out electromagnetic shielding effectiveness test on the MXene electromagnetic shielding pure cotton fabric obtained in the step (3) by using a vector network analyzer. The test frequency is 8.2-12.4GHz, and the frequency step is 0.08 GHz. Meanwhile, in order to adapt to the size of the rectangular waveguide, MXene/fabric is made into the size of 22.9 multiplied by 10.2 multiplied by (2.0-6.0) mm, wherein 22.9 multiplied by 10.2mm is the size of the cross section of the rectangular waveguide, and the thickness of a sample is the thickness of the fabric. As shown in fig. 5, the total electromagnetic shielding effectiveness, the absorption shielding effectiveness and the reflection shielding effectiveness of the MXene electromagnetic shielding fabric subjected to the low-temperature annealing treatment are 15.77dB, 8.31dB and 7.45dB, respectively, and the total shielding effectiveness is 85.25% at a frequency of 10 GHz; the MXene electromagnetic shielding fabric without low-temperature annealing treatment has the total electromagnetic shielding effectiveness, the absorption shielding effectiveness and the reflection shielding effectiveness of 14.28dB, 7.75dB and 6.54dB respectively, and the total shielding effectiveness is 83.2 percent. The electromagnetic wave absorption capacity and reflection capacity of the loaded MXene/pure cotton composite fabric are improved by the low-temperature annealing treatment, and the total shielding efficiency of the MXene electromagnetic shielding pure cotton fabric in an X waveband is enhanced.

(5) Combining the area of the ordinary clothes needing shielding with the MXene electromagnetic shielding fabric obtained in the step (3) without low-temperature annealing treatment, making the MXene electromagnetic shielding pure cotton fabric into a pocket at the position of the heart opening, and when the MXene electromagnetic shielding pure cotton fabric is not shielded, displaying that the electric field radiation intensity is 286.23V/m when the mobile phone dials; the mobile phone is placed in an MXene electromagnetic shielding fabric pocket, and the radiation detector displays that the radiation intensity of an electric field is 1.2V/m when the mobile phone is dialed.