CN109705808B

CN109705808B - Cobalt-nickel alloy-porous carbon composite wave-absorbing material with MOF structure and preparation method thereof

Info

Publication number: CN109705808B
Application number: CN201910106896.4A
Authority: CN
Inventors: 姬广斌; 梁小会; 权斌; 陈家彬
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2019-02-02
Filing date: 2019-02-02
Publication date: 2021-09-24
Anticipated expiration: 2039-02-02
Also published as: CN109705808A

Abstract

The invention discloses a cobalt-nickel alloy-porous carbon composite wave-absorbing material with an MOF structure, which is in a porous nano sheet structure, wherein cobalt-nickel alloy particles are embedded in the porous structure, and a graphitized carbon layer is wrapped outside the cobalt-nickel alloy particles. The invention also discloses a preparation method of the cobalt-nickel alloy-porous carbon composite wave-absorbing material, which comprises the following steps: adding a large amount of cobalt nitrate, nickel nitrate and trimesic acid into DMF (dimethyl formamide), adding required amount of 4', 4-bipyridyl into the mixed solution after the reaction materials are completely dissolved, fully stirring and dissolving, and carrying out solvothermal reaction; washing and drying the product after reaction to obtain a precursor in an MOF structure; and calcining the precursor to obtain the cobalt-nickel alloy-porous carbon composite wave-absorbing material. The preparation method has the advantages of low preparation cost and simple process, and the prepared composite wave-absorbing material has excellent wave-absorbing performance and is suitable for large-scale industrial production.

Description

Cobalt-nickel alloy-porous carbon composite wave-absorbing material with MOF structure and preparation method thereof

Technical Field

The invention relates to a cobalt-nickel alloy-porous carbon composite wave-absorbing material with an MOF structure, and also relates to a preparation method of the cobalt-nickel alloy-porous carbon composite wave-absorbing material, belonging to the technical field of wave-absorbing materials.

Background

With the rapid development of electromagnetic wave technology in civil and military fields, such as new generation of miniaturized electronics, automobiles, radars, satellite communications, etc., many serious electromagnetic interference problems occur in daily life. Therefore, high-performance electromagnetic wave absorbing materials are attracting attention as effective means for solving these problems. The ideal and efficient electromagnetic wave absorption material has the characteristics of strong absorption characteristic, wide absorption frequency range, thin matching thickness, light density and the like. Traditional absorbents, such as metals, have strong electromagnetic wave absorption performance due to high conductivity and dielectric constant, but pure metals have the defects of poor corrosion resistance, high manufacturing cost, high density and the like in practical application. And an ideal electromagnetic wave absorber should have moderate dielectric properties and high magnetic permeability according to impedance matching conditions. In addition, the porous structure can effectively reflect the electromagnetic waves, and further more electromagnetic waves are lost. Therefore, it is necessary to design a new type of low density porous microwave absorbent.

In recent years, there have been a number of reports on the study of low density microwave absorbing materials. Beijing3D graphene-Fe was studied by the group of the subjects of the Quiang university₃O₄A composite exhibiting good microwave absorption properties. When the thickness is 3mm and the filling degree is 10 wt%, the maximum reflectivity reaches-23 dB and the frequency bandwidth is 9.2-15.0GHz under the frequency of 11.25 GHz. The Zhao Hai wave subject group of Chinese engineering and physics research institute researches nickel/carbon-based composite material, when the filling degree is 10 wt%, and the filling thickness is 2mm, the strongest reflection can reach-45 dB, and the frequency bandwidth can reach 4.6 GHz. However, the methods for preparing these materials require treatment in multiple steps, and are difficult to realize for large-scale industrial production.

Disclosure of Invention

The purpose of the invention is as follows: the technical problem to be solved by the invention is to provide a cobalt-nickel alloy-porous carbon composite wave-absorbing material with an MOF structure, and the composite wave-absorbing material still has strong reflection loss and a wide effective absorption frequency band under low filling degree and low thickness.

The technical problem to be solved by the invention is to provide the preparation method of the cobalt-nickel alloy-porous carbon composite wave-absorbing material, which does not need a highly toxic organic solvent, has low cost and simple process and can be used for large-scale industrial production.

In order to solve the technical problems, the technical means adopted by the invention is as follows:

the cobalt-nickel alloy-porous carbon composite wave-absorbing material with the MOF structure is of a porous nano sheet structure, cobalt-nickel alloy particles are embedded in the porous structure, and a graphitized carbon layer is wrapped outside the cobalt-nickel alloy particles.

Wherein the specific surface area of the wave-absorbing material is not less than 150m²(ii)/g, the average pore diameter of the pore structure is less than 20 nm.

The preparation method of the cobalt-nickel alloy-porous carbon composite wave-absorbing material specifically comprises the following steps:

step 1, sequentially adding reaction materials of cobalt nitrate, nickel nitrate and trimesic acid into DMF, adding required amount of 4', 4-bipyridyl into the mixed solution after the reaction materials are completely dissolved, fully stirring and dissolving, and carrying out solvothermal reaction; washing and drying the product after reaction to obtain a carbon skeleton precursor in an MOF structure;

and 2, calcining the precursor obtained in the step 1 to obtain the cobalt-nickel alloy-porous carbon composite wave-absorbing material.

Wherein, in the step 1, the solvothermal reaction temperature is 100-200 ℃.

Wherein in the step 1, the solvothermal reaction time is 4-8 h.

Wherein in the step 2, the temperature rise rate of the calcination treatment is 1-5 ℃/min.

In the step 2, the temperature of the calcination treatment is 700-900 ℃, and the time is 1-5 h.

The preparation principle of the composite wave-absorbing material of the invention is as follows: preparing CoNi/C two-dimensional nanosheets with MOF structures by using a solvothermal method, and preparing a bimetal alloy/porous carbon composite wave-absorbing material by using a high-temperature calcination thermal decomposition reaction of the CoNi/C two-dimensional nanosheets, wherein the electromagnetic property of the wave-absorbing material can be Co²⁺And Ni²⁺Regulating and controlling the molar ratio; finally, the flaky porous carbon composite wave-absorbing material is obtained by utilizing the catalytic action of metal cobalt, the density of the wave-absorbing material is effectively reduced by the porous structure, and the filling degree of the material in use is further reduced, so that the effect of light weight is achieved.

Compared with the prior art, the technical scheme of the invention has the beneficial effects that:

compared with the traditional microwave absorbent, the composite wave-absorbing material still has wide effective absorption frequency band and high microwave absorption strength under low thickness and extremely low filling degree, thereby having excellent microwave absorption performance; meanwhile, the invention does not need to use highly toxic chemical reagents for preparation, has simple process and low cost, and can be used for large-scale industrial production.

Drawings

FIG. 1 shows Co obtained in examples 1, 2 and 3 of the present invention_xNi_yAn X-ray diffraction pattern of/C;

FIG. 2 is a graph of the BET results of CoNi/C obtained in example 2 of the present invention;

FIG. 3 shows Co obtained in example 1 of the present invention₃Ni₇SEM picture of/C;

FIG. 4 is an SEM picture of CoNi/C prepared in example 2 of the present invention;

FIG. 5 shows Co obtained in example 3 of the present invention₇Ni₃SEM picture of/C;

FIG. 6 is a TEM image of CoNi/C obtained in example 2 of the present invention;

FIG. 7 shows Co obtained in example 1 of the present invention₃Ni₇A reflection loss plot of/C;

FIG. 8 is a graph of the reflection loss of CoNi/C prepared in example 2 of the present invention;

FIG. 9 shows Co obtained in example 3 of the present invention₇Ni₃Reflection loss plot of/C.

Detailed Description

Embodiments of the present invention are further described below with reference to the accompanying drawings.

The CoNi/C composite material prepared by the preparation method of the invention has a flaky structure with a loose surface, the size of the flaky structure can be controlled by the proportion of Co and Ni, and the preparation method mainly comprises the following two steps: solvothermal preparation of CoNi-MOF: dissolving cobalt salt and nickel salt in a certain proportion, adding a complexing agent, continuously stirring until the cobalt salt and the nickel salt are dissolved, then putting the mixture into a hydrothermal reaction kettle for hydrothermal reaction, centrifugally collecting and drying after the reaction is finished; and putting the dried CoNi-MOF precursor into a tube furnace for calcining to obtain the porous CoNi/C composite material.

Example 1

step 1, weighing 263mg of cobalt nitrate and 610mg of nickel nitrate, dissolving the cobalt nitrate and the nickel nitrate into 60mL of N, N-dimethylformamide together, and stirring until the cobalt nitrate and the nickel nitrate are completely dissolved; weighing 3mmol of trimesic acid and 3mmol of 4', 4-bipyridine, adding into the mixed solution, continuously stirring for 30min, transferring the mixed solution into a high-pressure reaction kettle, placing in a forced air drying oven, heating to 120 ℃, and preserving heat for 4 h; naturally cooling to room temperature, then centrifugally separating the obtained precipitate, washing and drying to obtain a precursor in an MOF structure;

step 2, putting the precursor obtained in the step 1 into a tube furnace to calcine at 800 ℃ under the nitrogen atmosphere2h, the heating rate is 2 ℃/min; calcining and naturally cooling to obtain a product Co₃Ni₇the/C composite wave-absorbing material is a loose and porous carbon material, cobalt-nickel alloy particles are embedded in a pore structure, and a graphitized carbon layer is wrapped outside the cobalt-nickel alloy particles.

Example 2

step 1, weighing 438mg of cobalt nitrate and 316.5mg of nickel nitrate, dissolving the cobalt nitrate and the 316.5mg of nickel nitrate into 60mL of N, N-dimethylformamide, and stirring until the cobalt nitrate and the nickel nitrate are completely dissolved; weighing 3mmol of trimesic acid and 3mmol of 4', 4-bipyridine, adding into the mixed solution, continuously stirring for 30min, transferring the mixed solution into a high-pressure reaction kettle, placing in a forced air drying oven, heating to 120 ℃, and preserving heat for 4 h; naturally cooling to room temperature, then centrifugally separating the obtained precipitate, washing and drying to obtain a precursor in an MOF structure;

step 2, putting the precursor obtained in the step 1 into a tube furnace, calcining for 2h at 800 ℃ under the nitrogen atmosphere, wherein the heating rate is 2 ℃/min; and naturally cooling after calcining to obtain a product CoNi/C composite wave-absorbing material, wherein the composite wave-absorbing material is a loose and porous carbon material, cobalt-nickel alloy particles are embedded in a pore structure, and a graphitized carbon layer is wrapped outside the cobalt-nickel alloy particles.

Example 3

step 1, weighing 613mg of cobalt nitrate and 261mg of nickel nitrate, dissolving the cobalt nitrate and the 261mg of nickel nitrate together in 60mL of N, N-dimethylformamide, and stirring until the cobalt nitrate and the nickel nitrate are completely dissolved; weighing 3mmol of trimesic acid and 3mmol of 4', 4-bipyridine, adding into the mixed solution, continuously stirring for 30min, transferring the mixed solution into a high-pressure reaction kettle, placing in a forced air drying oven, heating to 120 ℃, and preserving heat for 4 h; naturally cooling to room temperature, then centrifugally separating the obtained precipitate, washing and drying to obtain a precursor in an MOF structure;

step 2, putting the precursor obtained in the step 1 into a tube furnace to calcine at 800 ℃ under the nitrogen atmosphere2h, the heating rate is 2 ℃/min; calcining and naturally cooling to obtain a product Co₇Ni₃the/C composite wave-absorbing material is a loose and porous carbon material, cobalt-nickel alloy particles are embedded in a pore structure, and a graphitized carbon layer is wrapped outside the cobalt-nickel alloy particles.

FIG. 1 shows Co obtained in examples 1, 2 and 3₃Ni₇/C, CoNi/C and Co₇Ni₃X-ray diffraction pattern of/C, as can be seen from fig. 1, examples 1, 2, 3 have similar diffraction peaks, with three distinct diffraction peaks within the measured range, being the (111), (200) and (220) crystal planes of the CoNi alloy, respectively.

FIG. 2 is the BET test result of CoNi/C obtained in example 2, and FIG. 2 can show that CoNi/C is mesoporous material, and the curve shows that CoNi/C has mesoporous material characteristic and specific area 178m²G, with an average pore diameter of 16nm, mainly thanks to the microporous structure of CoNi-MOF and the catalytic action of the metal particles on the carbon layer.

FIGS. 3, 4 and 5 show Co obtained in examples 1, 2 and 3, respectively₃Ni₇/C, CoNi/C and Co₇Ni₃The SEM pictures of/C can be seen from figures 3-5, the sheet structure of the obtained CoNi and carbon composite becomes more and more obvious with the increase of the addition of cobalt nitrate, and the shrinkage of the carbon MOF framework during heat treatment and calcination is increased, so that the pore density and the specific surface area of the finally obtained material are increased, and the performance of the product is further improved.

FIG. 6 is a TEM image of CoNi/C obtained in example 2. As can be seen from FIG. 6, the alloy particles are embedded in the porous carbon layer, and only a small portion of CoNi alloy particles are agglomerated.

FIG. 7 shows Co obtained in example 1₃Ni₇Reflection loss plot of/C, Co, as can be seen in FIG. 7₃Ni₇the/C composite material has good microwave absorption performance, the matching thickness is 1.8mm, the maximum reflection loss can reach-13 dB when the frequency is 16GHz, and the effective absorption frequency band is 14.5-17.5 GHz.

FIG. 8 is a reflection loss graph of CoNi/C prepared in example 2, and it can be seen from FIG. 8 that the CoNi/C composite material shows excellent microwave absorption performance, when the frequency is 14.9GHz and the matching thickness is 1.7mm, the maximum reflection loss can be as high as-42.5 dB, and the effective absorption frequency band is 13-18 GHz.

FIG. 9 shows Co obtained in example 3₇Ni₃Reflection loss plot of/C, Co, as can be seen in FIG. 9₇Ni₃The microwave absorption performance of the/C composite material is-11.2 dB when the matching thickness is 1.5mm and the frequency is 17.6 GHz.

The CoNi/C composite wave-absorbing material is prepared by calcining a CoNi-MOF precursor to obtain a CoNi alloy and porous carbon composite material. In the CoNi/C composite wave-absorbing material, the CoNi alloy improves the graphitization degree of the surrounding carbon layer, and the alloy has high conductivity, so that the CoNi/C composite wave-absorbing material has high dielectric loss capability; and a large number of holes appear due to the shrinkage of the carbon skeleton in the heat treatment calcination process, the density of the composite wave-absorbing material is greatly reduced by the holes, and the filling degree of the material is further reduced, so that the invention can still achieve stronger reflection loss and wider effective absorption frequency band under lower filling degree.

The excellent performance of the CoNi-MOF composite wave-absorbing material mainly comes from the interface polarization between a graphitized carbon layer and alloy particles, and simultaneously, the larger specific surface area causes more surface defects, and the two simultaneously cause incident electromagnetic waves to be consumed; the strong conductivity and low density ensure that the material has high dielectric constant under low filling degree and low thickness, so the existence of various loss mechanisms ensures the strong absorption of the composite wave-absorbing material to incident electromagnetic waves.

Claims

1. A cobalt-nickel alloy-porous carbon composite wave-absorbing material with an MOF structure is characterized in that: the wave-absorbing material is in a porous nano sheet structure, cobalt-nickel alloy particles are embedded in the porous structure, and a graphitized carbon layer is wrapped outside the cobalt-nickel alloy particles; the specific surface area of the wave-absorbing material is not less than 150m²(ii)/g, the average pore diameter of the pore structure is less than 20 nm;

the preparation method of the cobalt-nickel alloy-porous carbon composite wave-absorbing material with the MOF structure specifically comprises the following steps:

step 1, adding a large amount of cobalt nitrate, nickel nitrate and trimesic acid into DMF (dimethyl formamide), adding a required amount of 4' 4-bipyridyl into the mixed solution after the reaction materials are completely dissolved, fully stirring and dissolving, and carrying out solvothermal reaction; washing and drying the product after reaction to obtain a precursor in an MOF structure; the reaction temperature of the solvothermal reaction is 100-200 ℃, and the reaction time of the solvothermal reaction is 4-8 h;

step 2, calcining the precursor in the step 1 to obtain a cobalt-nickel alloy-porous carbon composite wave-absorbing material; the calcination treatment is to heat the mixture to 700-900 ℃ for calcination for 1-5 h in a nitrogen atmosphere at a heating rate of 1-5 ℃/min.