CN115942728A - Fusiform Co @ C-Mxene electromagnetic shielding material and preparation method thereof - Google Patents
Fusiform Co @ C-Mxene electromagnetic shielding material and preparation method thereof Download PDFInfo
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Abstract
The invention provides a spindle-shaped Co @ C-MXene electromagnetic shielding material and a preparation method thereof, and relates to the field of preparation of electromagnetic shielding materials, wherein the method comprises the following steps: preparing a Co @ C composite material by taking ZIF67 as a precursor; ultrasonically dispersing Co @ C pretreated by oxidized dodecyl dimethylamine into deionized water to obtain Co @ C suspension; then, the Co @ C suspension is dropped into Ti 3 C 2 T x Stirring in MXene aqueous solution in an ice bath for 1-2 h to obtain Co @ C-MXene composite material suspension; and freeze-drying the Co @ C-MXene composite material suspension to obtain the Co @ C-MXene electromagnetic shielding material. The electromagnetic shielding performance of the Co @ C-MXene electromagnetic shielding material prepared by the method is higher than 40dB and can reach 120dB at most in the 5-8.5GHz microwave frequency band.
Description
Technical Field
The invention belongs to the technical field of preparation of electromagnetic shielding materials, and particularly relates to a fusiform Co @ C-Mxene electromagnetic shielding material and a preparation method thereof.
Background
With the development of modern radio technology and the popularization of electronic equipment, electromagnetic radiation is increasingly serious, and the normal operation of electronic components is interfered, so that the electronic equipment is broken down, and potential harm is caused to human health. The development of high-performance electromagnetic shielding materials becomes an effective way for preventing and treating electromagnetic pollution. The traditional electromagnetic shielding material mostly uses metal materials such as copper, aluminum and the like, has high specific gravity and poor corrosion resistance, and limits the application of the traditional electromagnetic shielding material in the fields of movable equipment and the like. Therefore, the development of lightweight electromagnetic shielding materials is urgently needed. In recent years, the development of two-dimensional nano materials such as graphene, MXene, black phosphorus and the like promotes the development of electromagnetic protection technology.
However, the MXene-based composite electromagnetic shielding material is usually complex in preparation process, the electromagnetic shielding mechanism of the sample is single, and the performance needs to be further improved. Meanwhile, MXene materials are easy to stack and degrade by oxidation, and further development of the MXene materials is severely restricted. Therefore, it is urgently needed to develop a universal method for preparing the high-efficiency MXene-based electromagnetic shielding material so as to obtain a light-weight, high-efficiency and stable electromagnetic shielding material.
Disclosure of Invention
In order to solve the technical problems, the invention provides a fusiform Co @ C-Mxene electromagnetic shielding material and a preparation method thereof, wherein the Co @ C is used as an insert, and the-Mxene can be prevented from being stacked.
The invention discloses a preparation method of a spindle-shaped Co @ C-Mxene electromagnetic shielding material in a first aspect. The method comprises the following steps:
s1, preparing a Co @ C composite material by taking ZIF67 as a precursor through a thermal shock method;
s2, ultrasonically dispersing the Co @ C composite material pretreated by the oxidized dodecyl dimethylamine into deionized water to obtain the concentration of 2-3 mg/ml -1 Co @ C suspension of (1);
step S3, dripping a certain volume of the Co @ C suspension into the solution with the concentration of 1-2 mg/ml -1 Ti of (A) 3 C 2 T x Stirring in MXene aqueous solution in an ice bath for 1-2 h to obtain Co @ C-MXene composite material suspension;
and S4, freeze-drying the Co @ C-MXene composite material suspension in the step S3 to obtain the Co @ C-MXene electromagnetic shielding material.
According to the method of the first aspect of the present invention, in the step S1, the thermal shock method specifically includes the following steps:
the method comprises the following steps that a direct-current power supply is used as an energy supply power supply, two leads are led out from the positive electrode and the negative electrode of the direct-current power supply and are respectively connected with two pieces of carbon cloth aligned up and down to form a loop, then the ZIF67 is placed between the two pieces of carbon cloth, and thermal shock treatment is carried out on the ZIF67 under an inert gas atmosphere to obtain a Co @ C composite material;
the thermal shock treatment is carried out according to the processes of electrifying for 1-5 s, powering off for 2-5 s and electrifying for 1-5 s; the output temperature of the thermal shock is 800-900 ℃.
According to the method of the first aspect of the present invention, in the step S2, the preprocessing specifically includes the following steps:
ultrasonically dispersing 20mg of the Co @ C composite material into 30ml of the Co @ C composite material with the concentration of 8-20 mg/ml -1 Soaking the dodecyl dimethylamine oxide in the aqueous solution of the dodecyl dimethylamine oxide for 2 to 3 hours, and centrifuging the solution for later use.
According to the method of the first aspect of the present invention, in said step S3, the volume of said suspension of Co @ C is between 5 and 10ml.
According to the method of the first aspect of the invention, in the step S3, the Ti 3 C 2 T x The volume of MXene aqueous solution is 50-55 ml.
According to the method of the first aspect of the present invention, the step S4 includes:
s41, freezing the Co @ C-MXene composite material suspension by using liquid nitrogen to obtain a solid Co @ C-MXene composite material;
s42, freeze-drying the solid Co @ C-MXene composite material obtained in the step S41 for 20-24 h by using a freeze dryer, and sublimating liquid molecules to obtain the Co @ C-MXene electromagnetic shielding material;
wherein the freeze-drying temperature is lower than 70 ℃ below zero, and the pressure is less than 0.001Pa.
According to the method of the first aspect of the present invention, the ZIF67 is prepared as follows:
0.1 to 0.3g of Co (NO) 3 ) 2 ·6H 2 Fully dissolving O in 30-50 ml of methanol to obtain a solution A; fully dissolving 1-3 g of 2-methylimidazole in 30-50 ml of methanol to obtain a solution B; and then, quickly adding the solution B into the solution A, stirring at room temperature for 24 hours, and then carrying out centrifugal drying to obtain the ZIF67.
According to the method of the first aspect of the present invention, the inert gas is argon.
The invention discloses a spindle-shaped Co @ C-MXene electromagnetic shielding material prepared by the preparation method; the electromagnetic shielding performance of the fusiform Co @ C-MXene electromagnetic shielding material in a 5-8.5GHz microwave frequency band is higher than 40dB.
In summary, the solution proposed by the present invention has the following technical effects:
the invention creatively introduces the magnetic material and the dielectric material Co @ C into the MXene two-dimensional material, and effectively improves the electromagnetic shielding performance of the composite material. According to the invention, co @ C is firstly soaked in a dodecyl dimethylamine oxide solution with a certain concentration, and because C is a two-dimensional material with a large specific surface area, the surface of the Co @ C after pretreatment by the dodecyl dimethylamine oxide can adsorb the dodecyl dimethylamine oxide, so that the surface of the Co @ C has electropositivity. In addition, the pretreated Co @ C is dispersed in MXene aqueous solution at low temperature, and the MXene material surface is electronegative, so that the Co @ C is easily bonded by electrostatic adsorption. In addition, the MXene material has a large specific surface area and surface vacancies, so that the MXene material has strong surface adsorbability, and effective adsorption of Co @ C on MXene can be realized.
In addition, after the Co @ C-MXene composite material suspension is subjected to freeze drying treatment, two ends of the Co @ C particles are more sharp, the spindle shape is more obvious, and the Co @ C-MXene composite material suspension is beneficial to exciting electrons with higher density to incident electromagnetic waves, so that the Co @ C-MXene electromagnetic shielding material has a stronger shielding effect on the electromagnetic waves. The electromagnetic shielding performance of the Co @ C-MXene electromagnetic shielding material prepared by the method is higher than 40dB and can reach 120dB at most in a 5-8.5GHz microwave frequency band, and the Co @ C-MXene electromagnetic shielding material has the characteristics of light weight and good stability.
In addition, the Co @ C-MXene electromagnetic shielding material prepared by the freeze drying method is reliable in repeatability, capable of realizing batch production of materials and suitable for industrial production.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a flowchart illustrating a method for manufacturing a spindle-shaped Co @ C-MXene electromagnetic shielding material according to an embodiment of the present invention;
FIG. 2 (a) is a transmission electron micrograph of ZIF-67;
FIG. 2 (b) is a TEM photograph of Co @ C;
FIG. 2 (c) is a TEM photograph of the Co @ C-MXene EMI shielding material prepared in the embodiment 1 of the present invention;
FIG. 3 is an X-ray photoelectron spectrum of the electromagnetic shielding material of Co @ C-MXene according to embodiment 1 of the present invention;
FIG. 4 shows the results of testing the electromagnetic shielding performance of Co @ C and MXene and the Co @ C-MXene electromagnetic shielding material according to embodiment 1 of the present invention in the microwave frequency band of 5.5-8.5 GHz.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention discloses a preparation method of a spindle-shaped Co @ C-MXene electromagnetic shielding material. FIG. 1 is a flowchart of a method for preparing a fusiform Co @ C-MXene electromagnetic shielding material according to an embodiment of the present invention. As shown in fig. 1, the method includes:
and S1, preparing the Co @ C composite material by using ZIF67 as a precursor and adopting a thermal shock method.
S2, ultrasonically dispersing the Co @ C composite material pretreated by the oxidized dodecyl dimethylamine into deionized water to obtain the composite material with the concentration of 2-3 mg/ml -1 Suspension of Co @ C.
Step S3, dripping a certain volume of the Co @ C suspension into the solution with the concentration of 1-2 mg/ml -1 Ti of (A) 3 C 2 T x And stirring the MXene aqueous solution in an ice bath for 1 to 2 hours to obtain a Co @ C-MXene composite material suspension.
And S4, freeze-drying the Co @ C-MXene composite material suspension in the step S2 to obtain the Co @ C-MXene electromagnetic shielding material.
The electromagnetic shielding principle of the Co @ C-MXene electromagnetic shielding material prepared by the invention is that MXene reflects and scatters electromagnetic waves and Co @ C absorbs the electromagnetic waves. MXene can enhance the reflection and scattering of Co @ C-MXene to electromagnetic waves and prevent the electromagnetic waves from transmitting through the material; the Co @ C can also absorb the reflected and scattered electromagnetic waves, and the electromagnetic shielding performance of the Co @ C-MXene composite material is further improved.
According to the invention, co @ C is firstly soaked in a dodecyl dimethylamine oxide solution with a certain concentration, and because C is a two-dimensional material with a larger specific surface area, the surface of the Co @ C after pretreatment by the dodecyl dimethylamine oxide can adsorb the dodecyl dimethylamine oxide, so that the surface of the Co @ C is combined with oxygen-containing groups (such as O and OH). In addition, the pretreated Co @ C is dispersed in MXene aqueous solution at low temperature, and the MXene material surface is electronegative, so that the Co @ C is easily bonded by electrostatic adsorption. In addition, the MXene material has a large specific surface area and surface vacancies, so that the MXene material has strong surface adsorbability, and effective adsorption of Co @ C on MXene can be realized.
In step S1, the Co @ C composite material is prepared by taking ZIF67 as a precursor and adopting a thermal shock method.
In some embodiments, the ZIF67 is prepared as follows:
0.1 to 0.3g of Co (NO) 3 ) 2 ·6H 2 Fully dissolving O in 30-50 ml of methanol to obtain a solution A; fully dissolving 1-3 g of 2-methylimidazole in 30-50 ml of methanol to obtain a solution B; and then, quickly adding the solution B into the solution A, stirring at room temperature for 24 hours, and then centrifugally drying to obtain the ZIF67.
The treatment process of the thermal shock method is as follows:
utilize DC power supply as energy supply, follow two wires are drawn forth to DC power supply's positive negative pole, are connected with the carbon cloth of aligning about two respectively and constitute the return circuit, later will ZIF67 is arranged in between two carbon cloths, and is right under the inert gas atmosphere ZIF67 carries out thermal shock processing and obtains Co @ C combined material.
The thermal shock treatment is carried out according to the processes of electrifying for 1-5 s, powering off for 2-5 s and electrifying for 1-5 s; the output temperature of the thermal shock is 800-900 ℃.
The invention selects the thermal shock temperature not less than 800 ℃, and can ensure that Co is not dissolved in the gas 2+ Is completely reduced into simple substance Co. Meanwhile, the simple substance Co can be prevented from being oxidized into CoO under the inert gas atmosphere.
According to the invention, the thermal shock preparation of Co @ C is carried out on the ZIF67 by innovatively adopting an intermittent heating mode, and compared with a continuous heating thermal shock process, the intermittent heating can ensure a rapid heating-cooling process. In this process, co is maintained in a nanocrystalline state. If the continuous heating is carried out without a cooling process, the cluster of the Co nanocrystals grows up, and the Co nanocrystals with the size of 50-80 nm cannot be obtained. Meanwhile, the intermittent heating mode is safer, and the fire is easily caused by continuous power-on operation at high temperature.
Specifically, the energization time may be 1s, 2s, 3s, 4s, 5s. Preferably, the energization time is 2 to 4 seconds. Further preferably, the energization time is 3s.
Specifically, the output temperature of the thermal shock may be 800 ℃, 820 ℃, 840 ℃, 850 ℃, 860 ℃, 880 ℃, 900 ℃. Preferably, the output temperature of the thermal shock is 820 to 880 ℃. Further preferably, the output temperature of the thermal shock is 840 to 860 ℃.
In some embodiments, the inert gas is argon.
In step S2, the Co @ C composite material pretreated by the oxidized dodecyl dimethylamine is ultrasonically dispersed in deionized water to obtain the concentration of 2-3 mg/ml -1 Suspension of Co @ C.
According to the invention, the Co @ C composite material is pretreated by the oxidized dodecyl dimethylamine, so that on one hand, the suspended chemical bonds on the surface of the Co @ C can be improved abundantly, the surface of the Co @ C particle has electropositivity, and the Co @ C can be strongly combined with the MXene material and is not easy to fall off. On the other hand, co @ C particles are prevented from agglomerating and remain in a nano state of high dispersion.
Specifically, the concentration of the Co @ C composite may be 2 mg-ml -1 、2.1mg·ml -1 、2.2mg·ml -1 、2.3mg·ml -1 、2.4mg·ml -1 、2.5mg·ml -1 、2.6mg·ml -1 、2.7mg·ml -1 、2.8mg·ml -1 、2.9mg·ml -1 、3.0mg·ml -1 . Preferably, the concentration of the Co @ C composite material is 2.2-2.8 mg/ml -1 . More preferably, the concentration of the Co @ C composite material is 2.4-2.6 mg/ml -1 。
In some embodiments, the pre-treatment process is specifically as follows:
ultrasonically dispersing 20mg of the Co @ C composite material in 30ml of the composite material with the concentration of 8-20 mg/ml -1 Soaking the dodecyl dimethylamine oxide in the aqueous solution of the dodecyl dimethylamine oxide for 2 to 3 hours, and centrifuging the solution for later use.
The principle of shielding electromagnetic waves by Co @ C is absorption of incident electromagnetic waves. When the concentration of the dodecyl dimethylamine oxide is more than 20 mg/ml -1 When the Co @ C particles are completely wrapped by the oxidized dodecyl dimethylamine, the conductive ability of the Co @ C is reduced, which is unfavorable for the absorption of the Co @ C to the electromagnetic waveAnd further reduces the electromagnetic shielding capability of the Co @ C-MXene composite material. Meanwhile, when the concentration of the dodecyl dimethylamine oxide is less than 8 mg/ml -1 When the binding agent is used, the surface dangling bonds of Co @ C are few, and the binding agent is not enough to be effectively combined with MXene.
Specifically, the concentration of the dodecyl dimethylamine oxide can be 8 mg/ml -1 、10mg·ml -1 、12mg·ml -1 、14mg·ml -1 、15mg·ml -1 、16mg·ml -1 、18mg·ml -1 、20mg·ml -1 . Preferably, the concentration of the dodecyl dimethylamine oxide is 12-16 mg-ml -1 . Further preferably, the concentration of the dodecyldimethylamine oxide is 14-15 mg-ml -1 。
Specifically, the soaking time may be 120min, 130min, 140min, 150min, 160min, 170min, 180min. Preferably, the soaking time is 130-170 min. Further preferably, the soaking time is 140-160 min.
In step S3, a certain volume of the suspension of Co @ C is dropped into the suspension of 1-2 mg/ml -1 Ti of (A) 3 C 2 T x And stirring the MXene aqueous solution in an ice bath for 1 to 2 hours to obtain Co @ C-MXene composite material suspension.
MXene can be prevented from decomposing and being oxidized by adopting ice bath stirring.
Specifically, the Ti 3 C 2 T x MXene concentration may be 1 mg/ml -1 、1.1mg·ml -1 、1.2mg·ml -1 、1.3mg·ml -1 、1.4mg·ml -1 、1.5mg·ml -1 、1.6mg·ml -1 、1.7mg·ml -1 、1.8mg·ml -1 、1.9mg·ml -1 、2.0mg·ml -1 . Preferably, the Ti 3 C 2 T x The concentration of MXene is 1.2-1.8 mg/ml -1 . Further preferably, the Ti 3 C 2 T x The concentration of MXene is 1.4-1.6 mg/ml -1 。
Specifically, the time of ice-bath stirring may be 60min, 70min, 80min, 90min, 95min, 100min, 110min, 120min. Preferably, the stirring time of the ice bath is 80-110 min. Further preferably, the stirring time in the ice bath is 90 to 100min.
In some embodiments, the volume of the Co @ C suspension is 5 to 10ml.
In particular, the volume of the Co @ C suspension may be 5ml, 6ml, 7ml, 8ml, 9ml, 10ml. Preferably, the volume of the Co @ C suspension is 7-8 ml.
In some embodiments, the Ti 3 C 2 T x The volume of MXene aqueous solution is 50-55 ml.
And S4, freeze-drying the Co @ C-MXene composite material suspension in the step S3 to obtain the Co @ C-MXene electromagnetic shielding material.
Compared with other drying means, the freeze drying can better retain the integral two-dimensional structure of the Co @ C-MXene composite material. Meanwhile, the Co @ C-MXene composite material can be prevented from being oxidized due to exposure under the condition of a little water and air.
In some embodiments, the step S4 comprises:
and S41, freezing the Co @ C-MXene composite material suspension by using liquid nitrogen to obtain the solid Co @ C-MXene composite material.
And S42, freeze-drying the solid Co @ C-MXene composite material obtained in the step S41 for 20-24 hours by using a freeze dryer, and sublimating liquid molecules to obtain the Co @ C-MXene electromagnetic shielding material.
Wherein the temperature of the freeze drying is lower than 70 ℃ below zero, and the pressure is lower than 0.001Pa.
Specifically, the freeze-drying time may be 20h, 21h, 22h, 23h, 24h. Preferably, the freeze-drying time is 22h.
The invention discloses a spindle-shaped Co @ C-MXene electromagnetic shielding material in a second aspect. The electromagnetic shielding performance of the fusiform Co @ C-MXene electromagnetic shielding material in a 5-8.5GHz microwave frequency band is higher than 40dB.
Detailed description of the preferred embodiment 1
Preparation of Co @ C-MXene electromagnetic shielding material
(1) 0.2g ofCo (NO) of 3 ) 2 .6H 2 O was sufficiently dissolved in 40ml of methanol as a solution A; 2g of 2-methylimidazole was sufficiently dissolved in 40ml of methanol to prepare a solution B; and then, quickly adding the solution B into the solution A, stirring at room temperature for 24 hours, and then carrying out centrifugal drying to obtain ZIF67.
(2) The method comprises the following steps that a direct-current power supply is used as an energy supply power supply, two leads are led out from the positive electrode and the negative electrode of the direct-current power supply and are respectively connected with two pieces of carbon cloth aligned up and down to form a loop, then ZIF67 is placed between the two pieces of carbon cloth, and thermal shock treatment is carried out on the ZIF67 under an argon atmosphere to obtain a Co @ C composite material;
wherein the thermal shock treatment is carried out according to the processes of electrifying for 3s, powering off for 3s and electrifying for 3 s; the output temperature of the thermal shock was 850 ℃.
(3) Ultrasonic dispersing 20mg Co @ C composite material in 30ml of 14 mg/ml -1 The dodecyl dimethylamine oxide is soaked in the aqueous solution for 2.5 hours and then is centrifugally treated for standby. The Co @ C composite material pretreated by the oxidized dodecyl dimethylamine is ultrasonically dispersed in deionized water to obtain the concentration of 2.5 mg/ml -1 Suspension of Co @ C. 8ml of Co @ C suspension is dropped into 50ml of 1-2 mg/ml -1 Ti of (A) 3 C 2 T x MXene aqueous solution was stirred in ice bath for 1.5h to obtain Co @ C-MXene composite suspension.
(4) And (3) freezing the Co @ C-MXene composite material suspension obtained in the step by using liquid nitrogen to obtain the solid Co @ C-MXene composite material. And then, freeze-drying the solid Co @ C-MXene composite material for 22h by using a freeze dryer to obtain the Co @ C-MXene electromagnetic shielding material.
Wherein the temperature of the freeze drying is lower than 70 ℃ below zero, and the pressure is lower than 0.001Pa.
FIG. 2 (a) is a TEM photograph of ZIF-67, showing that ZIF-67 has a regular polyhedron shape before thermal shock is applied. FIG. 2 (b) is a TEM photograph of Co @ C, showing that the Co @ C particles formed by thermal decomposition of ZIF67 are spindle-shaped with two tips, and Co nanocrystals embedded in the C film are about 50-80 nm. FIG. 2 (c) is a TEM image of the Co @ C-MXene EMI shielding material prepared in the embodiment 1 of the present invention. As can be seen from fig. 2 (c), the spindle-shaped co @ c and MXene substrate are well combined, and after freeze-drying treatment, two ends of the co @ c particles are more sharp, the spindle shape is more obvious, and the co @ c-MXene electromagnetic shielding material is helpful for exciting electrons with higher density to incident electromagnetic waves, so that the co @ c-MXene electromagnetic shielding material has a stronger shielding effect on the electromagnetic waves.
FIG. 3 is an X-ray photoelectron spectrum of the electromagnetic shielding material of Co @ C-MXene according to embodiment 1 of the present invention. FIG. 3 further demonstrates the presence of Co, C, ti, O, F elements. Wherein the Co element is derived from Co @ C, ti, O and F are derived from MXene, and C is derived from Co @ C and MXene.
FIG. 4 shows the results of testing the electromagnetic shielding performance of Co @ C and MXene and the Co @ C-MXene electromagnetic shielding material according to embodiment 1 of the present invention in the microwave frequency band of 5.5-8.5 GHz. As can be seen from FIG. 4, compared with single Co/C nanocrystalline particles and MXene films, the electromagnetic shielding performance of Co/C @ MXene at 5.5-8GHz is significantly improved, and can reach 120dB at most.
Specific example 2
Preparation of Co @ C-MXene electromagnetic shielding material
(1) 0.3g of Co (NO) 3 ) 2 .6H 2 O is fully dissolved in 50ml of methanol to be used as a solution A; 3g of 2-methylimidazole was sufficiently dissolved in 50ml of methanol to prepare a solution B; and then, quickly adding the solution B into the solution A, stirring at room temperature for 24 hours, and then carrying out centrifugal drying to obtain ZIF67.
(2) The method comprises the following steps that a direct-current power supply is used as an energy supply power supply, two leads are led out from the positive electrode and the negative electrode of the direct-current power supply and are respectively connected with two pieces of carbon cloth aligned up and down to form a loop, then ZIF67 is placed between the two pieces of carbon cloth, and thermal shock treatment is carried out on the ZIF67 under an argon atmosphere to obtain a Co @ C composite material;
wherein the thermal shock treatment is carried out according to the processes of 5s of electrification, 4s of outage and 5s of electrification; the output temperature of the thermal shock was 800 ℃.
(3) Ultrasonic dispersing 20mg Co @ C composite material in 30ml of 20 mg/ml -1 Soaking in the aqueous solution of dodecyl dimethylamine oxide for 2h, and centrifuging for later use. Will be oxidized byThe Co @ C composite material pretreated by the alkyl dimethylamine is dispersed in deionized water by ultrasound to obtain the concentration of 3mg.ml -1 Suspension of Co @ C. 10ml of Co @ C suspension was dropped into 50ml of 2 mg/ml solution -1 Ti of (A) 3 C 2 T x MXene aqueous solution is stirred for 2h in an ice bath to obtain Co @ C-MXene composite material suspension.
(4) And (3) freezing the Co @ C-MXene composite material suspension obtained in the step by using liquid nitrogen to obtain the solid Co @ C-MXene composite material. And then, freeze-drying the solid Co @ C-MXene composite material for 24 hours by using a freeze dryer to obtain the Co @ C-MXene electromagnetic shielding material.
Wherein the temperature of the freeze drying is lower than 70 ℃ below zero, and the pressure is lower than 0.001Pa.
Specific example 3
Preparation of Co @ C-MXene electromagnetic shielding material
(1) 0.1g of Co (NO) 3 ) 2 .6H 2 O is fully dissolved in 30ml of methanol to be used as a solution A; 1g of 2-methylimidazole was sufficiently dissolved in 30ml of methanol to prepare a solution B; and then, quickly adding the solution B into the solution A, stirring at room temperature for 24 hours, and then carrying out centrifugal drying to obtain ZIF67.
(2) The method comprises the following steps that a direct-current power supply is used as an energy supply power supply, two leads are led out from the positive electrode and the negative electrode of the direct-current power supply and are respectively connected with two pieces of carbon cloth aligned up and down to form a loop, then ZIF67 is placed between the two pieces of carbon cloth, and thermal shock treatment is carried out on the ZIF67 under an argon atmosphere to obtain a Co @ C composite material;
wherein the thermal shock treatment is carried out according to the processes of electrifying for 2s, powering off for 2s and electrifying for 2 s; the output temperature of the thermal shock was 880 ℃.
(3) Ultrasonic dispersing 20mg Co @ C composite material in 30ml of 8 mg/ml -1 Soaking in aqueous solution of dodecyl dimethylamine oxide for 3h, and centrifuging for later use. Ultrasonically dispersing Co @ C composite material pretreated by dodecyl dimethylamine oxide in deionized water to obtain the concentration of 2mg.ml -1 Suspension of Co @ C. 10ml of Co @ C suspension was added dropwise to 55ml of 1 mg/ml solution -1 Ti of (A) 3 C 2 T x MXene aqueous solution, stirring for 1h in ice bath to obtain Co @ C-MXene composite material suspension.
(4) And (3) freezing the Co @ C-MXene composite material suspension obtained in the step by using liquid nitrogen to obtain the solid Co @ C-MXene composite material. And then, freeze-drying the solid Co @ C-MXene composite material for 20h by using a freeze dryer to obtain the Co @ C-MXene electromagnetic shielding material.
Wherein the temperature of the freeze drying is lower than 70 ℃ below zero, and the pressure is lower than 0.001Pa.
Specific example 4
Preparation of Co @ C-MXene electromagnetic shielding material
(1) 0.15g of Co (NO) 3 ) 2 .6H 2 O was dissolved in 35ml of methanol sufficiently as a solution A; 1.5g of 2-methylimidazole was sufficiently dissolved in 35ml of methanol to prepare a solution B; and then, quickly adding the solution B into the solution A, stirring at room temperature for 24 hours, and then carrying out centrifugal drying to obtain ZIF67.
(2) The method comprises the following steps of (1) utilizing a direct-current power supply as an energy supply, leading out two leads from the positive electrode and the negative electrode of the direct-current power supply, respectively connecting the leads with two pieces of carbon cloth aligned up and down to form a loop, then placing ZIF67 between the two pieces of carbon cloth, and carrying out thermal shock treatment on the ZIF67 in an argon atmosphere to obtain a Co @ C composite material;
wherein the thermal shock treatment is carried out according to the processes of electrifying for 1s, powering off for 2s and electrifying for 1 s; the output temperature of the thermal shock was 900 ℃.
(3) Ultrasonic dispersing 20mg Co @ C composite material in 30ml of 12 mg/ml -1 Soaking in aqueous solution of dodecyl dimethylamine oxide for 130min, and centrifuging for use. The Co @ C composite material pretreated by dodecyl dimethylamine oxide is ultrasonically dispersed in deionized water to obtain the concentration of 2.2 mg/ml -1 Suspension of Co @ C. 7ml of Co @ C suspension was added dropwise to 50ml of a 1.2 mg/ml concentration -1 Ti of 3 C 2 T x MXene aqueous solution, stirring in ice bath for 80min to obtain Co @ C-MXene composite material suspension.
(4) And (3) freezing the Co @ C-MXene composite material suspension obtained in the step by using liquid nitrogen to obtain the solid Co @ C-MXene composite material. And then, freeze-drying the solid Co @ C-MXene composite material for 21h by using a freeze dryer to obtain the Co @ C-MXene electromagnetic shielding material.
Wherein the temperature of the freeze drying is lower than 70 ℃ below zero, and the pressure is lower than 0.001Pa.
Specific example 5
Preparation of Co @ C-MXene electromagnetic shielding material
(1) 0.25g of Co (NO) 3 ) 2 .6H 2 O was dissolved in 45ml of methanol sufficiently as a solution A; 2.5g of 2-methylimidazole was sufficiently dissolved in 45ml of methanol to prepare a solution B; and then, quickly adding the solution B into the solution A, stirring at room temperature for 24 hours, and then carrying out centrifugal drying to obtain ZIF67.
(2) The method comprises the following steps that a direct-current power supply is used as an energy supply power supply, two leads are led out from the positive electrode and the negative electrode of the direct-current power supply and are respectively connected with two pieces of carbon cloth aligned up and down to form a loop, then ZIF67 is placed between the two pieces of carbon cloth, and thermal shock treatment is carried out on the ZIF67 under an argon atmosphere to obtain a Co @ C composite material;
wherein the thermal shock treatment is carried out according to the processes of electrifying for 4s, powering off for 5s and electrifying for 4 s; the output temperature of the thermal shock was 820 ℃.
(3) Ultrasonic dispersing 20mg Co @ C composite material in 30ml of 16 mg/ml -1 Soaking in the aqueous solution of dodecyl dimethylamine oxide for 160min, and centrifuging for later use. The Co @ C composite material pretreated by the oxidized dodecyl dimethylamine is ultrasonically dispersed in deionized water to obtain the concentration of 2.8 mg/ml -1 Co @ C suspension. 6ml of Co @ C suspension was added dropwise to 53ml of a 1.8 mg/ml concentration -1 Ti of (A) 3 C 2 T x MXene aqueous solution, stirring in ice bath for 110min to obtain Co @ C-MXene composite material suspension.
(4) And (3) freezing the Co @ C-MXene composite material suspension obtained in the step by using liquid nitrogen to obtain the solid Co @ C-MXene composite material. And then, freeze-drying the solid Co @ C-MXene composite material for 23 hours by using a freeze dryer to obtain the Co @ C-MXene electromagnetic shielding material.
Wherein the temperature of the freeze drying is lower than 70 ℃ below zero, and the pressure is lower than 0.001Pa.
In summary, the scheme provided by the invention has the following technical effects:
the invention creatively introduces the magnetic material and the dielectric material Co @ C into the MXene two-dimensional material, and effectively improves the electromagnetic shielding performance of the composite material. According to the invention, co @ C is firstly soaked in a dodecyl dimethylamine oxide solution with a certain concentration, and because C is a two-dimensional material with a large specific surface area, the surface of the Co @ C after pretreatment by the dodecyl dimethylamine oxide can adsorb the dodecyl dimethylamine oxide, so that the surface of the Co @ C has electropositivity. In addition, the pretreated Co @ C is dispersed in MXene aqueous solution at low temperature, and the MXene material surface is electronegative, so that the Co @ C is easily bonded by electrostatic adsorption. In addition, the MXene material has a large specific surface area and surface vacancies, so that the MXene material has strong surface adsorbability, and effective adsorption of Co @ C on MXene can be realized.
In addition, after the Co @ C-MXene composite material suspension is subjected to freeze drying treatment, two ends of the Co @ C particles are more sharp, the spindle shape is more obvious, and the Co @ C-MXene composite material suspension is beneficial to exciting electrons with higher density to incident electromagnetic waves, so that the Co @ C-MXene electromagnetic shielding material has a stronger shielding effect on the electromagnetic waves. The electromagnetic shielding performance of the Co @ C-MXene electromagnetic shielding material prepared by the method is higher than 40dB and can reach 120dB at most in a 5-8.5GHz microwave frequency band, and the Co @ C-MXene electromagnetic shielding material has the characteristics of light weight and good stability.
In addition, the Co @ C-MXene electromagnetic shielding material prepared by the freeze drying method is reliable in repeatability, capable of realizing batch production of materials and suitable for industrial production.
It should be noted that the technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, however, as long as there is no contradiction between the combinations of the technical features, the scope of the present description should be considered. The above examples only express several embodiments of the present application, and the description thereof is more specific and detailed, but not to be construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (9)
1. A preparation method of a spindle-shaped Co @ C-MXene electromagnetic shielding material is characterized by comprising the following steps:
s1, preparing a Co @ C composite material by taking ZIF67 as a precursor through a thermal shock method;
s2, ultrasonically dispersing the Co @ C composite material pretreated by the oxidized dodecyl dimethylamine into deionized water to obtain the Co @ C composite material with the concentration of 2-3mg.ml -1 Co @ C suspension of (1);
step S3, dripping a certain volume of the Co @ C suspension into the solution with the concentration of 1-2mg -1 Ti of (A) 3 C 2 T x Stirring in MXene aqueous solution in an ice bath for 1-2 h to obtain Co @ C-MXene composite material suspension;
and S4, freeze-drying the Co @ C-MXene composite material suspension in the step S3 to obtain the Co @ C-MXene electromagnetic shielding material.
2. The method for preparing a fusiform Co @ C-MXene electromagnetic shielding material according to claim 1, wherein in the step S1, the thermal shock method comprises the following specific treatment processes:
the method comprises the following steps that a direct-current power supply is used as an energy supply power supply, two leads are led out from the positive electrode and the negative electrode of the direct-current power supply and are respectively connected with two pieces of carbon cloth aligned up and down to form a loop, then the ZIF67 is placed between the two pieces of carbon cloth, and thermal shock treatment is carried out on the ZIF67 under an inert gas atmosphere to obtain a Co @ C composite material;
the thermal shock treatment is carried out according to the processes of electrifying for 1-5 s, powering off for 2-5 s and electrifying for 1-5 s; the output temperature of the thermal shock is 800-900 ℃.
3. The method for preparing the spindle-shaped Co @ C-MXene electromagnetic shielding material according to claim 1, wherein in the step S2, the pretreatment process specifically comprises:
ultrasonically dispersing 20mg of Co @ C composite material into 30ml of Co @ C composite material with the concentration of 8-20mg -1 The dodecyl dimethylamine oxide is soaked in the aqueous solution for 2 to 3 hours and then is centrifugally treated for standby.
4. The method for preparing the spindle-shaped Co @ C-MXene electromagnetic shielding material according to claim 1, wherein in the step S3, the volume of the Co @ C suspension is 5-10 ml.
5. The method as claimed in claim 1, wherein in step S3, the Ti is added 3 C 2 T x The volume of MXene aqueous solution is 50-55 ml.
6. The method for preparing a fusiform Co @ C-MXene electromagnetic shielding material according to claim 1, wherein the step S4 comprises:
s41, freezing the Co @ C-MXene composite material suspension by using liquid nitrogen to obtain a solid Co @ C-MXene composite material;
s42, freeze-drying the solid Co @ C-MXene composite material obtained in the step S41 for 20-24 h by using a freeze dryer, and sublimating liquid molecules to obtain the Co @ C-MXene electromagnetic shielding material;
wherein the temperature of the freeze drying is lower than 70 ℃ below zero, and the pressure is lower than 0.001Pa.
7. The preparation method of the fusiform Co @ C-MXene electromagnetic shielding material according to claim 1, wherein the ZIF67 is prepared by the following steps:
0.1 to 0.3g of Co (NO) 3 ) 2 .6H 2 Fully dissolving O in 30-50 ml of methanol to obtain a solution A; 1 to 3g of 2-methylimidazole is fully dissolved in 30 to 50ml of methanolSolution B; and then, quickly adding the solution B into the solution A, stirring at room temperature for 24 hours, and then carrying out centrifugal drying to obtain the ZIF67.
8. The method for preparing a fusiform Co @ C-MXene electromagnetic shielding material as claimed in claim 2, wherein the inert gas is argon gas.
9. The fusiform Co @ C-MXene electromagnetic shielding material prepared by the method for preparing the fusiform Co @ C-MXene electromagnetic shielding material according to any one of claims 1-8, wherein the electromagnetic shielding performance of the fusiform Co @ C-MXene electromagnetic shielding material in a 5-8.5GHz microwave frequency band is higher than 40dB.
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