CN-115568199-B - Preparation method of double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material

CN115568199BCN 115568199 BCN115568199 BCN 115568199BCN-115568199-B

Abstract

The invention discloses a preparation method of a double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material, which comprises the steps of preparation of a molybdenum glycerate nanosphere, preparation of a polydopamine precursor nanosphere, preparation of a double-shell Mo 2 C/C nanosphere with a hollow structure, wave-absorbing performance detection and the like. The carbon skeleton thermal reduction method has the advantages that in the carbon thermal reduction process, polydopamine is converted into a carbon skeleton and simultaneously undergoes a reduction reaction with the molybdenum glycerate nanospheres, a layered structure is formed while the reaction is converted into molybdenum carbide and the carbon skeleton, the higher carbon thermal reduction temperature improves the graphitization degree of the carbon skeleton, is beneficial to enhancing the dielectric loss energy capacity of the composite material, the air sealed inside the double-shell hollow structure improves the inherent impedance of the material, the double-shell hollow structure forms a network structure for confining incident electromagnetic waves, the multiple reflection attenuation of the incident electromagnetic waves is enhanced, the electromagnetic energy main consumption area is formed inside the carbon shell, the electromagnetic energy loss is improved, and the wave absorbing performance is enhanced.

Inventors

WANG YAHUI
DENG XUESONG
LI ZHIGANG
CHEN ZONGSHENG
SHI JIAMING
ZHAO DAPENG
Lv Xiangyin

Assignees

中国人民解放军国防科技大学

Dates

Publication Date: 20260508
Application Date: 20221020

Claims (10)

1. The preparation method of the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material is characterized by comprising the following steps of: 1. preparation of molybdenum glycerate nanospheres (1) Mixing deionized water and isopropanol solution, stirring uniformly, then adding glycerol, stirring and mixing to form a uniform mixed solution; (2) Adding molybdenum acetylacetonate into the mixed solution obtained in the step (1), and performing ultrasonic treatment until the mixed solution is colorless and transparent; (3) Transferring the transparent mixed solution obtained in the step (2) into a high-temperature high-pressure reaction kettle, putting the transparent mixed solution into a baking oven for reaction, cooling the reaction product along with the baking oven, taking out the reaction product, centrifugally collecting the obtained powder, washing the powder with ethanol for a plurality of times, and drying the powder at room temperature; 2. preparation of polydopamine precursor nanospheres (4) Mixing and stirring absolute ethyl alcohol and deionized water, adding the powder obtained in the step (3) into a mixed solution, then adding dopamine hydrochloride, and carrying out ultrasonic treatment; (5) Stirring the solution subjected to ultrasonic treatment in the step (4) in a magnetic stirrer, adding ammonia water solution in the stirring process, and continuously stirring; (6) After the mixed solution in the step (5) is stirred, transferring the mixed solution into a high-temperature high-pressure reaction kettle for reaction for 2 hours, cooling the mixed solution with a baking oven, taking out the mixed solution, centrifugally collecting obtained powder, washing the powder with deionized water and absolute ethyl alcohol for a plurality of times, and then putting the powder into the baking oven for baking; 3. Preparation of Mo 2 C/C nanospheres with double-shell hollow structure (7) Placing the sample in the step (6) into a porcelain boat, introducing argon into a tube furnace, respectively increasing the temperature to 700-900 ℃ at a heating rate of 2 ℃ per minute, performing carbothermic reaction, preserving the heat for 3 hours at a preset temperature, cooling to room temperature after the reaction is completed, and collecting the sample, namely the target product Mo 2 C/C composite wave-absorbing material; 4. Detection of wave absorbing performance of Mo 2 C/C nanospheres with double-shell hollow structure (8) Adding 40mg of the composite wave-absorbing material in the step (7) and 60mg of sliced paraffin into an agate mortar, putting the mortar into a 70 ℃ oven, heating for 20min, taking out the mortar after the paraffin is completely melted, quickly grinding, fully mixing the melted paraffin with a powder sample until the paraffin is re-solidified, and then transferring the mixed sample into a sample preparation mold for tabletting to obtain a concentric ring-shaped test sample; (9) And (3) putting the concentric ring prepared in the step (8) into a concentric shaft transmission line clamp of the vector network analyzer, connecting the clamp with the vector network analyzer, setting electromagnetic parameters of a parameter test material, and taking out a sample after the test is completed.
2. The preparation method of the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material according to claim 1, wherein in the first step, the volume ratio of isopropanol to water to glycerin in the mixed solution is (3.5-5): (0.8-1.2): 1, and the volume mass ratio of the mixed solution to molybdenum acetylacetonate is (2-3).
3. The preparation method of the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material according to claim 2, wherein the molar ratio of glycerin to molybdenum acetylacetonate in the step (2) is 0.25-0.40.
4. The method for preparing the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material according to claim 1, wherein the reaction condition of (3) is that the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material is prepared by placing the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material in a 150mL high-temperature high-pressure reaction kettle, placing the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material in a baking oven at 160 ℃ for reaction for 5 hours, and cooling the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material in the baking oven.
5. The method for preparing the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material according to claim 1 is characterized in that in the second step, the volume ratio of absolute ethyl alcohol to deionized water in the mixed solution is (1.5-1): 1, the weight ratio of the molybdenum glycerate nanosphere powder to dopamine hydrochloride is (0.95-1.05): 1, and the molar ratio of dopamine hydrochloride to ammonia in an aqueous ammonia solution is (9.5-10.5): 1.
6. The preparation method of the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material according to claim 1, wherein the specific step of the thermal reaction in the step (6) is that after the mixed solution in the step (5) is stirred for 10min, the mixed solution is transferred into a 100mL high-temperature high-pressure reaction kettle, reacted for 2h at 140 ℃, taken out along with cooling of a drying oven after the reaction, the obtained powder is collected through centrifugation, washed with deionized water and absolute ethyl alcohol for several times, and then put into the drying oven at 60 ℃ for 10h.
7. The method for preparing the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material according to claim 1, wherein the temperature of the thermal reduction reaction in the step (7) is 700 ℃, the temperature is kept at 700 ℃ for 3 hours, the temperature is reduced to room temperature after the reaction is completed, a sample is collected to obtain a target product Mo 2 C/C composite wave-absorbing material, which is denoted as DS-Mo 2 C/C-700, and electromagnetic absorption performance test is carried out.
8. The method for preparing the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material according to claim 1, wherein the temperature of the thermal reduction reaction in the step (7) is 800 ℃, the temperature is kept at 800 ℃ for 3 hours, the temperature is reduced to room temperature after the reaction is completed, a sample is collected to obtain a target product Mo 2 C/C composite wave-absorbing material, which is denoted as DS-Mo 2 C/C-800, and electromagnetic absorption performance test is carried out.
9. The method for preparing the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material according to claim 1, wherein the temperature of the thermal reduction reaction in the step (7) is 900 ℃, the temperature is kept at 900 ℃ for 3 hours, the temperature is reduced to room temperature after the reaction is completed, a sample is collected to obtain a target product Mo 2 C/C composite wave-absorbing material, which is denoted as DS-Mo 2 C/C-900, and electromagnetic absorption performance test is carried out.
10. The method for preparing the double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material according to claim 1, wherein in the step (9), the circular specifications of the concentric circular ring test sample are 3mm in inner diameter, 7mm in outer diameter and 2mm in thickness.

Description

Preparation method of double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material Technical Field The invention relates to the technical field of wave-absorbing materials, in particular to a preparation method of a double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material. Background The use of advanced electronics, particularly the use of high power electromagnetic equipment, creates excessive electromagnetic contamination that not only interferes with industrial production, but may also jeopardize the health of the biological system. Electromagnetic absorption is an ideal method for alleviating electromagnetic pollution through energy conversion. Over the past few decades, much research has been devoted to achieving efficient electromagnetic absorption performance by constructing composites, such as magnetic metal composites, conductive polymer composites, and carbon-based composites. Among the various composite materials, carbon-based magnetic composite materials have been leading to the development of electromagnetic absorbing materials, not only because of the low density, good chemical stability, and variety of types of carbon-based materials, but also because of the optimized combination of magnetic and dielectric losses, which is beneficial for attenuation of electromagnetic energy. However, these composite materials still have the disadvantages of high density and poor corrosion resistance, and at the same time, the magnetic coupling interaction between the magnetic particles is significantly weakened due to the presence of the carbon matrix in the carbon-based magnetic composite material, and the attenuation of electromagnetic energy in the composite material is mainly based on dielectric loss. Based on this, researchers have proposed the preparation of carbon-based composites with dielectric components instead of magnetic components. In recent years, carbon-based carbide composite materials are used as potential dielectric materials, and have attracted wide attention in the aspect of electromagnetic energy attenuation due to the advantages of adjustable dielectric properties, good oxidation resistance, good chemical stability and the like. In particular, the advent of Mo 2 C has further promoted the potential use of carbon-based carbides in the field of electromagnetic wave absorption. Mo 2 C nanoparticles can be obtained at relatively low pyrolysis temperatures compared to other carbides (e.g., siC or Ti 3C2 mxnes), which is beneficial for inhibiting crystal growth and promoting uniform distribution. However, application research of the Mo 2 C composite material in electromagnetic wave absorption has been recently reported, and only a small amount of Mo 2 C/C composite wave absorbing material is mainly concentrated on a simple composite or single core-shell structure in structural design, so that a relatively narrow qualified response bandwidth and poor impedance matching are caused. The invention aims to solve the problems of single structural design, poor controllability, poor impedance matching, effective absorption bandwidth, and the like of a Mo 2 C composite material by designing a special double-shell hollow micro-nano structure. Double shell nanostructures serve as an interesting nanostructure, with unique advantages in terms of electromagnetic energy attenuation by virtue of their hollow structure, relatively low density and rich heterogeneous interfaces. The double-shell hollow structure is beneficial to optimizing impedance matching, because the packaging air between the double shells can play a role of an intermediate medium, and the inherent impedance is promoted to be as close to the impedance of the external air as possible. In addition, the double-shell hollow structure can enhance reflection loss by expanding the propagation path of the incident electromagnetic wave to promote multiple reflection and refraction thereof. Mo 2 C nano particles are uniformly dispersed in the multi-shell carbon skeleton, so that the dielectric constant of the carbon skeleton is regulated to a certain extent, and the tiny Mo 2 C nano particles also provide abundant polarization loss for electromagnetic energy attenuation, and the synergistic effect between material loss and structural loss improves the wave absorbing performance. Therefore, the double-shell hollow Mo 2 C/C nanosphere composite wave-absorbing material decorated by Mo 2 C nano particles is constructed through two steps of hydrothermal and pyrolysis processes, and the preparation method of the double-shell hollow micro-nano structured Mo 2 C/C composite wave-absorbing material is obtained. Disclosure of Invention The invention aims to solve the defects in the prior art, and provides a preparation method of a double-shell molybdenum carbide/carbon nanosphere composite wave-absorbing material. In order to achieve the above purpose, the present invention adopts the following technical schem