Cobalt Niobium Sulfide / Niobium Carbide Composite Absorbing Material and Its Preparation Method and Application

Abstract

The present invention discloses a cobalt niobium sulfide / niobium carbide composite microwave absorbing material, its preparation method and application, belonging to the technical field of microwave signal shielding materials. In the cobalt niobium sulfide / niobium carbide composite microwave absorbing material of the present invention, cobalt niobium sulfide is used as a load and attached to the interlayers and surfaces of accordion-shaped multi-layer Nb2C serving as a carrier, forming a surface-modified stable multi-layer and multi-porous material structure, which has high conductivity and chemical stability. Moreover, the preparation method is simple and effective, with few process steps, high repeatability and high product purity. The microwave signal shielding coating slurry prepared with the cobalt niobium sulfide / niobium carbide composite microwave absorbing material as the main material, dimethyl sulfoxide and hydroxyethyl cellulose as co-solvents and thickeners has the advantages of good chemical stability, high electromagnetic shielding efficiency and wide application scenarios.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave signal shielding materials, and particularly relates to a cobalt niobium sulfide / niobium carbide composite wave-absorbing material, a preparation method and an application thereof. Background Art

[0002] With the large-scale construction of satellite communication systems, the rapid popularization of mobile communication devices and the rapid development of near-field communication devices, more and more information will be transmitted in the form of electromagnetic waves. Therefore, the technology of microwave signal shielding materials has emerged as the times require, and is mainly applied to suppressing microwave signal interference between electronic devices and components, anti-radar signal detection of military targets, ensuring data security and privacy, and protecting the human body from electromagnetic radiation. Electromagnetic shielding materials are required to have good absorption performance for electromagnetic waves, good antioxidant ability and processability.

[0003] At present, the most widely used composite wave-absorbing materials are structural composite wave-absorbing materials, which are mainly composed of ferrite materials, ceramic materials, carbon materials or conductive polymer organic materials added to glass fiber or blended fabric matrix materials. These materials generally have the advantages of high mechanical strength, strong processability and good wave-absorbing effect. However, due to the low conductivity of glass fiber and organic fabric, the electromagnetic shielding efficiency of these materials shows obvious attenuation at a relatively thin thickness. Therefore, the coated composite wave-absorbing materials using conductive matrix materials have emerged as the times require. These materials are mainly composed of dispersing absorbents in a matrix with a special structure to form a composite material, so there is a significant improvement in conductivity. And because the composite material is adsorbed on the surface of the device that needs electromagnetic shielding protection in the form of coating, it has unique advantages in applicability and thinness.

[0004] Using transition metal carbides with multi-layer and multi-porous characteristics as the matrix of microwave absorption materials (such as titanium carbide) has been proven to produce good electromagnetic shielding effects. Compared with traditional structural composite microwave absorption materials, the improvement in their performance is attributed to the micro-nano structures conducive to reflection absorption and good chemical stability. However, due to the poor conductivity of transition metal carbide powders, the skin depth of this material is often too large when applied to coated composite microwave absorption materials. Therefore, it is urgent to improve the electromagnetic shielding efficiency by improving the conductivity of the material. Introducing highly conductive interlayer dispersants (such as nano-metals) into the multi-layer and porous structures is a method to increase the conductivity of the composite material and improve its microwave absorption performance. For example, Patent CN 113784606A discloses a titanium carbide and cobalt-nickel alloy composite microwave absorption material and its preparation method. The titanium carbide and cobalt-nickel alloy are compounded to prepare a multi-component composite material, and good electromagnetic absorption performance is obtained by changing the content of the cobalt-nickel alloy. Patent CN 110290691A discloses a composite microwave absorption material of lamellar MXene loaded with cobalt ferrite. The cobalt ferrite of the composite microwave absorption material is loaded between the layers of lamellar MXene, making the composite material more conducive to impedance matching with space and showing broadband and strong electromagnetic wave absorption characteristics. However, this method also has certain technical defects. First, the stability of the multi-layer titanium carbide matrix material in air is poor, and the lifespan of the coating will be affected under long-term operation. Second, the conductivity of the multi-layer titanium carbide matrix material is relatively low, which is likely to affect the electromagnetic absorption performance when applied to electromagnetic shielding coatings. Finally, nano-metal particles such as cobalt-nickel or cobalt-iron have obvious strong magnetic characteristics. Magnetic agglomeration is likely to occur between the nano-particles, and they will accumulate and adsorb charged dust in the air, and their adhesion ability to metal carbides is poor, which is also not conducive to maintaining the long-term working lifespan. In contrast, niobium carbide (Nb 2 C) not only has higher conductivity but also stronger chemical stability, and can still maintain the micro multi-layer structure morphology and high conductivity in an environment with high humidity and high oxygen content. In addition, the Co-Nb binary transition metal disulfide not only has better conductivity than nano-metal ions but also can avoid the adverse effects caused by magnetic agglomeration, improving the stability and electromagnetic absorption performance of the material.

[0005] Niobium carbide (Nb 2 C) is a multi-layer transition metal carbide material. Its molecular structure is composed of two layers of Nb atoms and one layer of C atoms stacked in a staggered manner to form a typical hexagonal crystal system. It is widely used in fields such as electrocatalysis, lithium batteries, optical fibers, lasers, energy storage, and sensors, and there is no prior research precedent in the field of electromagnetic shielding. Usually, Nb 2 C is obtained from its ceramic precursor niobium aluminum carbide (Nb 2 AlC) through chemical treatment. Affected by the external oxygen-containing environment during the synthesis process, there are usually a large number of oxygen-containing functional groups on its surface. The existence of these functional groups endows Nb2 C excellent hydrophilicity. However, Nb 2 C Such multi-layer materials are prone to the collapse of the layered structure and the oxidation of the material during application. Using interlayer loading materials with appropriate size and performance is an effective method to improve the material stability. However, restricted by the interlayer spacing, traditional two-dimensional and three-dimensional materials such as nanosheets and nanotubes are difficult to effectively enter the interlayer to play a fixing role.

[0006] Transition metal disulfide materials are a type of novel nanomaterials with stable chemical properties and easy synthesis. In recent years, they have been widely used in a large number of composite materials such as semiconductors, and a large number of related technical applications have also been developed. However, when transition metal disulfides are applied to composite microwave absorption materials, there are generally two technical problems: First, affected by the semiconductor property, the intrinsic conductivity of transition metal disulfides is too small, so means such as doping or introducing crystal defects are needed to enhance the conductivity; Second, transition metal disulfides often exist in the form of nanosheets, and their radial size is too large, so it is difficult to introduce them into the interlayer of transition metal carbides with nanoscale pores.

[0007] In addition, the currently widely used electromagnetic shielding and microwave absorption materials are often in the form of plates, films, and fabrics, which are directly wrapped on the surfaces of equipment, wires, and devices, posing safety hazards such as heat dissipation and fire, and having a limited scope of application. In addition, there are also problems such as poor chemical stability of the materials and too high preparation costs, which all hinder the application of current electromagnetic shielding material technology in the military and civilian fields. Summary of the Invention

[0008] To solve the problems of poor adhesion ability, insufficient stability, and low loading amount in the application of transition metal carbide multi-layer materials as carriers in microwave absorption materials in the above-mentioned prior art, one of the purposes of the present invention is to provide a cobalt niobium sulfide / niobium carbide (Co 0.3 Nb 0.7 S 2 / Nb 2 C) composite microwave absorption material, and to provide a preparation method for designing cobalt niobium sulfide (Co 0.3 Nb 0.7 S 2 ) into a load with appropriate size and performance, and enabling the load to quickly, densely, and stably enter and distribute on the surface and interlayer of Nb 2 C. The prepared Co 0.3 Nb 0.7 S 2 / Nb 2 C composite microwave absorption material has high conductivity and excellent electromagnetic wave absorption ability; another purpose is to propose a preparation method of the above cobalt niobium sulfide / niobium carbide composite microwave absorption material for microwave signal shielding coating slurry.

[0009] To achieve the above object, the present invention provides a cobalt niobium sulfide / niobium carbide composite microwave absorbing material. The niobium carbide has an accordion-like layered structure, and the cobalt niobium sulfide is nano-particles with an amorphous crystal structure. The atomic ratio of sulfur, cobalt, and niobium in the cobalt niobium sulfide crystal is 2:0.3:0.7. The cobalt niobium sulfide as the loading substance is attached to the surface and between the layers of the niobium carbide as the carrier in a way of in-situ growth between the layers.

[0010] The grain diameter of the niobium carbide is 1000 - 1500 nm, and the number of layers is 50 - 100 layers; the particle size of the cobalt niobium sulfide is 30 - 50 nm.

[0011] The preparation method of the above-mentioned cobalt niobium sulfide / niobium carbide composite microwave absorbing material is characterized by including the following steps:

[0012] Step I: Soak aluminum niobium carbide in dilute hydrochloric acid, take out the precipitate, etch it with hydrofluoric acid aqueous solution, and vacuum dry to obtain niobium carbide powder.

[0013] Step II: Take octadecylamine, heat and stir it, add chloroform, stir and mix evenly, then add thioglucoside, and shake to obtain a semi-dissolved emulsion of octadecylamine.

[0014] Step III: Take the niobium carbide obtained in Step I and add it to the semi-dissolved emulsion of octadecylamine obtained in Step II. After stirring, successively add carbon tetrachloride solution and thiourea. After aging by electromagnetic stirring, add niobium pentachloride and cobalt dichloride, and heat up to 280 °C for heat preservation reaction.

[0015] Step IV: Wash, dissolve, and centrifuge the precipitate after the reaction is completed, collect the bottom precipitate, and vacuum dry to obtain the cobalt niobium sulfide / niobium carbide composite microwave absorbing material.

[0016] Furthermore, in Step I, the mass ratio of aluminum niobium carbide, dilute hydrochloric acid, and hydrofluoric acid aqueous solution is 1:(40 - 50):(50 - 60); the soaking time is 8 - 12 hours; the etching time is 20 - 30 hours; the vacuum drying temperature is 50 - 60 °C, and the vacuum drying time is 5 - 6 hours.

[0017] Furthermore, in Step II, the mass ratio of octadecylamine, chloroform, and thioglucoside is (4 - 5):(45 - 50):1, and the heating rate is controlled at 25 °C / min, and the temperature is raised to 55 - 60 °C.

[0018] Furthermore, in Step III, the mass ratio of niobium carbide, semi-dissolved emulsion of octadecylamine, carbon tetrachloride solution, and thiourea is 1:(45 - 50):(15 - 20):(3.5 - 4).

[0019] Application of the above cobalt niobium sulfide / niobium carbide composite microwave absorbing material in preparing a microwave signal shielding coating slurry.

[0020] The present invention also provides a microwave signal shielding coating slurry, which comprises the following steps: Step 1, mixing the cobalt niobium sulfide / niobium carbide composite microwave absorbing material with absolute ethanol, grinding, and vacuum freeze-drying to obtain a main powder material; Step 2, mixing and grinding the powder material obtained in Step 1 with hydroxyethyl cellulose, adding dimethyl sulfoxide to dissolve, and heating the uniformly mixed material to 120 °C; Step 3, performing three-roll rolling treatment on the slurry obtained in Step 2, and stirring and aging at room temperature for 3 hours.

[0021] Further, in Step 1, the mass ratio of the cobalt niobium sulfide / niobium carbide composite microwave absorbing material to absolute ethanol is 1:(5-5.5), the vacuum freeze-drying temperature is -45 to -40 °C, and the vacuum freeze-drying time is 32 to 36 hours.

[0022] Further, in Step 2, the mass ratio of the powder material, hydroxyethyl cellulose, and dimethyl sulfoxide is 1:(1.7-1.8):(18-20), and the heating time is 2 hours.

[0023] Inventive concept: Using the Co 0.3 Nb 0.7 S 2 / Nb 2 C composite microwave absorbing material as the active ingredient of the microwave signal shielding coating slurry, amorphous nano-particle-like Co 0.3 Nb 0.7 S 2 uniformly and in-situ grows on the surface of accordion-shaped Nb 2 C to form a stable nano-composite loading structure. The preparation method is to prepare accordion-shaped Nb 2 C by chemical room-temperature liquid-phase etching method, and then use the semi-dissolution emulsification method to adsorb Nb 5+ and Co 2+ on the inner surface of tiny emulsion droplets dispersed in an octadecylamine semi-dissolution emulsion; subsequently, use the organic solvent-assisted diffusion synthesis method to promote the diffusion of the tiny emulsion droplets into the interlayer of Nb 2 C and attach to the surface under the action of the non-polar solvent carbon tetrachloride; finally, add thiourea as a sulfur source, and an oxidation-reduction reaction occurs at high temperature to in-situ grow Co 2 Nb 0.3 S 0.7 particles in the interlayer of Nb 2 C.

[0024] Beneficial effects

[0025] The present invention provides Co 0.3 Nb 0.7 S 2 / Nb2 Co-Nb-S / NbC composite wave-absorbing material, its preparation method, and its application in microwave communication signal shielding coating slurry, so as to solve the problems of limited application scope, poor chemical stability of materials, and too high preparation cost existing in the existing microwave communication signal shielding technology.

[0026] The Co 0.3 Nb 0.7 S 2 / Nb 2 C composite wave-absorbing material has the characteristics of high conductivity, high chemical stability, and low cost.

[0027] The present invention provides a preparation method of a mild octadecylamine semi-dissolved emulsion for surface pretreatment of multi-layer two-dimensional materials. The tiny emulsion droplets dispersed in the octadecylamine semi-dissolved emulsion can stably exist. In the environment of a polar solvent, glucosinolate can produce a strong electron pair shift with the amino group at the terminal of the octadecylamine molecule to form a hydrogen bond, and the electronegativity of several hydroxyl terminals in the glucosinolate molecule is significantly enhanced. The resulting electrostatic interaction can effectively complex the hydroxyl group with transition metal ions.

[0028] Compared with the existing multi-layer two-dimensional material filling technologies such as diffusion deposition, thermal injection, and intercalation, the surface pretreatment of multi-layer two-dimensional materials and the organic solvent-assisted diffusion synthesis method provided by the present invention can effectively improve the structure and properties of the composite material. Using a weakly polar solvent system as the chemical reaction environment can effectively avoid the collapse of layered materials caused by using water as the reaction system and the oxidation of materials caused by dissolved oxygen in the aqueous solution, and can effectively improve the purity and structural uniformity of the composite material. The tiny emulsion droplets of glucosinolate dispersed in the octadecylamine semi-dissolved emulsion can electrostatically adsorb Nb 5+ and Co 2+ on the inner surface layer, and under the action of the non-polar solvent carbon tetrachloride, carry and diffuse Nb 5+ and Co 2+ into the interlayers of Nb 2 C and adsorb them on the hydrophilic surface functional groups with electronegativity on the surface of Nb 2 C, laying the foundation for the redox reaction that occurs after subsequent heating.

[0029] Co 0.3 Nb 0.7 S 2 / Nb 2 The Co-Nb-S / NbC composite wave-absorbing material has a stable multi-porous structure, enabling the amorphous Co 0.3 Nb 0.7 S 2 particles to stably, massively, and tightly fill the interlayers of the accordion-shaped Nb 2 C. Co 0.3 Nb 0.7 S2 / Nb 2 The multi-porous three-dimensional structure of the Co 0.3 Nb 0.7 S 2 / Nb 2 C composite microwave absorbing material can achieve multi-stage absorption of electromagnetic waves of microwave communication signals, thus greatly improving the application effect of the composite microwave absorbing material in the microwave communication signal shielding coating slurry. The Co

[0030] Co 0.3 Nb 0.7 S 2 / Nb 2 C composite microwave absorbing material reported in this invention for the first time in the world has extremely excellent prospects in the field of microwave communication signal shielding coating slurry application technology. 0.3 Nb 0.7 S 2 / Nb 2 The preparation process of the microwave communication signal shielding coating slurry of the Co

[0031] In terms of the microwave communication signal shielding performance, compared with the single accordion-shaped transition metal carbide material of the prior art, the Co 0.3 Nb 0.7 S 2 / Nb 2 C composite microwave absorbing material of this invention has been significantly enhanced in the microwave communication signal shielding ability. After 10,000 hours of continuous operation test, the high-conductivity Co 0.3 Nb 0.7 S 2 / Nb 2 C composite microwave absorbing material of this invention can be significantly increased to more than 50 dB, and the performance has been improved by 80% compared with the single accordion-shaped Nb 2 C nanomaterial.

[0032] In terms of the conductivity of the composite microwave absorbing material, compared with the single accordion-shaped Nb 2 C nanomaterial of the prior art, the high-conductivity Co 0.3 Nb 0.7 S 2 / Nb 2The conductivity of the C composite absorbing material has been greatly improved. Compared with the single accordion-shaped Nb 2 C nanomaterial in terms of conductivity performance (1000 - 1500 S cm -1 ), the conductivity of the composite absorbing material of the present invention can be increased to 3000 S cm -1 or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the preparation process of the microwave communication signal shielding coating slurry of the Co 0.3 Nb 0.7 S 2 / Nb 2 C composite absorbing material for Example 1;

[0034] Figure 2 X-ray diffraction pattern of the Co 0.3 Nb 0.7 S 2 / Nb 2 C composite absorbing material for Example 1;

[0035] Figure 3 SEM image of the Co 0.3 Nb 0.7 S 2 / Nb 2 C composite absorbing material for Example 1;

[0036] Figure 4 Local structure SEM image of the Co 0.3 Nb 0.7 S 2 / Nb 2 C composite absorbing material for Example 1;

[0037] Figure 5 Comparison chart of the electromagnetic shielding effectiveness of the microwave communication signal shielding coating slurry of the Co 0.3 Nb 0.7 S 2 / Nb 2 C composite absorbing material for Example 1;

[0038] Figure 6 Test chart of the long-term stability performance of the microwave communication signal shielding coating slurry of the Co 0.3 Nb 0.7 S 2 / Nb 2 C composite absorbing material for Example 1;

[0039] Figure 7 For the Co of Example 1 0.3 Nb 0.7 S 2 / Nb 2 Conductivity performance diagram of microwave communication signal shielding coating slurry of C composite absorbing material. DETAILED DESCRIPTION

[0040] In the present invention, all the raw materials used for preparation are analytically pure and can be used directly. Glucosinolate was purchased from Shanghai Fantai Biotechnology Co., Ltd., metal salts and octadecylamine were purchased from Aladdin Chemical Reagent Platform, chloroform and thiourea were purchased from Shanghai Bailingwei Chemical Technology Co., Ltd., and ceramic precursor materials were purchased from Qingdao Laiyin Intelligent New Materials Co., Ltd.

[0041] Example 1

[0042] The invention relates to a cobalt niobium sulfide / niobium carbide composite absorbing material, wherein the niobium carbide has an accordion-shaped layered structure, the cobalt niobium sulfide is a nanoparticle with an amorphous crystal structure, the atomic number ratio of sulfur, cobalt and niobium in the cobalt niobium sulfide crystal is 2:0.3:0.7, the cobalt niobium sulfide as a load is attached to the surface and interlayers of the niobium carbide as a carrier in an interlayer in-situ growth manner, the niobium carbide grain diameter is 1000-1500nm, and the number of layers is 50-100; the particle size of the cobalt niobium sulfide is 30-50nm.

[0043] The cobalt niobium sulfide / niobium carbide composite absorbing material is prepared by the following method:

[0044] Step I: 1.0 g 300 mesh Nb 2 AlC powder was fully ground, and 50 mL of 1 mol / L dilute hydrochloric acid was added and soaked for 10 hours to remove impurities. After the soaking was completed, the precipitate was taken out and washed with sufficient deionized water and anhydrous ethanol, and then placed in a vacuum drying oven at 55 °C for 6 hours. 1 g of accordion-shaped Nb 2 C was slowly added into 50 ml of 20% volume fraction hydrofluoric acid aqueous solution and stirred thoroughly with a magnetic stirrer. The mixed solution was then added into a 75 ml polytetrafluoroethylene reaction container. After reacting for 24 hours, the precipitate at the bottom of the reaction container was collected. After filtering, the sample was placed in a vacuum drying oven at 55°C and dried for 6 hours. A dark black powder was obtained, which was the accordion-shaped multilayer Nb 2 C;

[0045] Step II: using semi-solution emulsion method to prepare multilayer Nb 2 C surface-modified emulsion. First, 5 g of octadecylamine was placed in a quartz glass reactor and heated to 58°C, then 50 g of chloroform was slowly added while stirring, and after the two components were completely miscible, 1 g of glucosinolate was added, and the mixed solution was shaken on a vortex oscillator for 1 hour and then taken out to prepare a turbid octadecylamine semi-dissolved emulsion;

[0046] Step III, using organic solvent assisted diffusion synthesis method to grow and prepare the composite material. Take 1g of Nb 2 C black powder, add 50g of the semi-dissolved emulsion of octadecylamine described in step (2), stir evenly, and then add 20g of carbon tetrachloride solution and thiourea to the mixed solution; then heat the mixed solution to 58°C, age it under electromagnetic stirring for 12 hours, and after the aging is completed, add 2.4g NbCl 5 and 0.5 g CoCl 2 The mixed solution was then sealed and heated to 280°C, kept at this temperature for 24 hours, and then naturally cooled to room temperature, and filtered to obtain the light grey precipitate at the bottom;

[0047] Step IV: The light grey precipitate described in step III is washed with sufficient toluene, then transferred to a sufficient methanol solution for dissolution, centrifuged in a high-speed centrifuge, and the bottom precipitate is collected and vacuum dried at 50°C to prepare Co 0.3 Nb 0.7 S 2 / Nb 2 C composite absorbing material.

[0048] The above-mentioned cobalt niobium sulfide / niobium carbide composite absorbing material is used as an active component to prepare a microwave communication signal shielding coating slurry. The specific steps of the preparation are as follows:

[0049] Step 1, take 10g Co 0.3 Nb 0.7 S 2 / Nb 2 Mix C with 50g of anhydrous ethanol and grind thoroughly until the powder has a uniform texture;

[0050] Step 2, then placing the black mud obtained in step 1 in an open glass container, placing it in a manifold vacuum freeze dryer, setting the freezing temperature to -45°C, and freeze drying for 36 hours;

[0051] Step 3, 10 g of the powder obtained in step 2 is mixed with 18 g of hydroxyethyl cellulose and ground, then 200 g of dimethyl sulfoxide is added to dissolve, and then the mixed material is heated to 120° C.;

[0052] Step 4, subjecting the slurry obtained in step 3 to a three-roll rolling process, and then stirring and aging at room temperature for 3 hours to prepare a microwave communication signal shielding coating slurry.

[0053] Co 0.3 Nb 0.7 S 2 / Nb 2 Schematic diagram of the preparation process of C composite absorbing material as an active ingredient for microwave communication signal shielding coating slurry, such as Figure 1 shown.

[0054] The present invention conducts XRD diffraction and scanning electron microscopy analysis on the Co 0.3 Nb 0.7 S 2 / Nb 2 C composite microwave absorbing material prepared in Example 1, and the results are as Figures 2 - 4 shown.

[0055] The present invention also prepares test samples and testing methods for the electromagnetic shielding effectiveness, stability, and conductivity of the microwave communication signal shielding coating slurry of the Co 0.3 Nb 0.7 S 2 / Nb 2 C composite microwave absorbing material prepared in Example 1 as follows:

[0056] Preparation of test samples: (1) Take 1 g of the microwave communication signal shielding coating slurry prepared as described in Example 1 and place it in a mortar, and grind for 5 minutes; (2) Pour the above black slurry onto a polyvinylidene fluoride filter membrane with a thickness of 0.25 mm, and place it on a vacuum coating machine. With the assistance of vacuum filtration, scrape the slurry on the surface of the polyvinylidene fluoride filter membrane to form a thin film sample to be tested, so that the thickness of the microwave communication signal shielding coating is 50 μm; (3) Place the thin film sample to be tested described in step (2) in a vacuum drying oven and dry it at 60 °C for 24 hours, and then take it out; (4) Cut the dried thin film sample described in step (3) into a thin slice sample of 4×4 cm.

[0057] Testing method: Use a material electromagnetic shielding effectiveness tester to test the electromagnetic shielding effectiveness of the thin slice sample, and the frequency range of the microwave communication signal is 8.2 - 12.4 GH z ; Use a material electromagnetic shielding effectiveness tester to test the stability of the electromagnetic shielding effectiveness of the thin slice sample, and the frequency of the microwave communication signal is 10.0 GH z , and the total test duration is 10,000 hours, and the electromagnetic shielding effectiveness test is carried out every 500 hours; Use a four-probe film sheet resistance meter to test the conductivity of the thin slice sample, and the total test duration is 10,000 hours, and the conductivity test is carried out every 500 hours. The test results are as Figure 5 , Figure 6 and Figure 7 .

[0058] As Figure 1 shown, the Co 0.3 Nb 0.7 S 2 / Nb 2Schematic diagram of the preparation process of the CoNbS / NbC composite microwave absorbing material and its application as an active ingredient in the preparation of a microwave communication signal shielding coating slurry. The preparation process includes pickling, chemical etching, vacuum drying, semi-dissolution emulsification method, organic solvent-assisted diffusion synthesis method, annealing, grinding, pulping, and rolling, etc.

[0059] As Figure 2 shown, the X-ray diffraction pattern of the CoNbS / NbC composite microwave absorbing material shows that in the diffraction peaks of the composite microwave absorbing material described in Example 1 of the present invention, there are simultaneously hexagonal NbS 0.3 Nb 0.7 S 2 / Nb 2 C (JCPDS 89-3042), hexagonal CoS 2 (JCPDS 89-3042), and the characteristic main peak of Nb 2 C, and no other obvious impurities appear, indicating that there are no other impurities in the material described in the present invention. 2

[0060] As Figure 3 and Figure 4 shown, the SEM image of the CoNbS / NbC composite microwave absorbing material shows that it includes accordion-shaped Nb 0.3 Co 0.7 Nb 2 S 2 / Nb C and amorphous granular Co 2 Nb 0.3 C 0.7 S 2 crystals; among them, the amorphous nanoparticle-like Co 0.3 Nb 0.7 S 2 crystals are uniformly attached to the inner surface of Nb 2 C, and the morphological structure of the composite microwave absorbing material has the characteristics of multi-porosity.

[0061] As Figure 5 shown, the electromagnetic shielding effectiveness comparison diagram of the microwave communication signal shielding coating slurry based on the CoNbS / NbC composite microwave absorbing material shows that the microwave communication signal shielding coating slurry based on the CoNbS / NbC composite microwave absorbing material prepared in the embodiment of the present invention achieves an electromagnetic shielding effectiveness of up to 50 dB under the microwave signal noise of 8.2 - 12.4 GHz. Compared with the single accordion structure of Nb 0.3 Co 0.7 Nb 2 S 2 / Nb 0.3 C 0.7 S 2 / Nb 2 C composite microwave absorbing material, 2With an electromagnetic shielding effectiveness of less than 30 dB of C, the coating slurry of the present invention has achieved a huge performance improvement in the shielding of microwave communication signals.

[0062] As Figure 6 shown in the long-term stability performance test chart of the microwave communication signal shielding coating slurry based on Co 0.3 Nb 0.7 S 2 / Nb 2 C composite microwave absorbing material, it can be seen that the slurry of the present invention also has good chemical stability. Even under changing temperature and environmental humidity conditions, the test results show that after 10,000 hours, the microwave communication signal shielding coating slurry can still maintain a high level of electromagnetic shielding effectiveness (50 - 52 dB). In contrast, the single accordion structure Nb 2 C shows a significant performance decay from 32 dB to 22 dB.

[0063] Figure 7 As shown in the conductivity performance chart of the microwave communication signal shielding coating slurry based on highly conductive Co 0.3 Nb 0.7 S 2 / Nb 2 C composite microwave absorbing material, it can be seen that the improvement of the electromagnetic shielding effectiveness of the slurry of the present invention is attributed to the increase in the conductivity of the material. Due to the high conductivity characteristics of the loaded material NbS 2 , compared with the single accordion-shaped Nb 2 C (1000 - 1500 S cm -1 ), the slurry of the present invention has a more superior conductivity (3000 - 3200 S cm -1 ).

[0064] The Co 0.3 Nb 0.7 S 2 / Nb 2 C composite microwave absorbing material prepared by the organic solvent-assisted diffusion synthesis method has self-supporting stability and maintains the structural characteristics of multi-porosity; in the composite microwave absorbing material, Co 0.3 Nb 0.7 S 2 nano-particles can build a bridge for the conductivity of Nb 2 C, which helps to improve the overall conductivity of the composite material. The structural layer spacing of the single accordion-shaped Nb 2 C is at the nanoscale, and the layers are in contact with each other by van der Waals bonds, resulting in the conductivity of the material being mainly the two-dimensional conductivity within each sheet layer, and the overall conductivity of the material is low. The amorphous nano-particle-shaped Co 0.3 Nb 0.7 S 2It has good electrical conductivity and is filled as a support material between the layers of Nb 2 C, which can change the conductance mode of each layer of Nb 2 C from within the sheet layer to between the sheet layers, significantly enhancing the electrical conductivity of the bulk material; in addition, due to Nb 2 C and Co 0.3 Nb 0.7 S 2 have different band gaps, and there is an electron energy level transition at the composite interface of the two materials. This radiative transition process can trigger strong coupled absorption of microwave signals by the composite material. The interlayer spacing and pore size of the composite material can provide a localized space for the multi-stage reflection absorption of incident electromagnetic waves and resonance absorption. The interlayer nanoparticles with high electrical conductivity can also generate a high-frequency resonance effect with the microwave signal noise near the 10 GHz frequency band. The electromagnetic shielding effectiveness of the composite material under the superposition of the structural gain and material characteristics has been increased from 30 dB to 50 dB.

[0065] The above is for the convenience of those of ordinary skill in the art to understand and apply the present invention. Obviously, those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the embodiments herein, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A cobalt niobium sulfide / niobium carbide composite microwave absorption material, characterized in that, the niobium carbide has an accordion-like layered structure, and the cobalt niobium sulfide is nano-particles with an amorphous crystal structure. The atomic ratio of sulfur, cobalt, and niobium in the cobalt niobium sulfide crystal is 2:0.3:0.

7. The cobalt niobium sulfide as the loading substance is attached to the surface and between the layers of the niobium carbide as the carrier in a way of in-situ growth between layers.

2. The cobalt niobium sulfide / niobium carbide composite microwave absorption material according to claim 1, characterized in that, the grain diameter of the niobium carbide is 1000 - 1500 nm, and the number of layers is 50 - 100 layers; the particle size of the cobalt niobium sulfide is 30 - 50 nm.

3. The preparation method of the cobalt niobium sulfide / niobium carbide composite microwave absorption material according to any one of claims 1 or 2, characterized in that, it includes the following steps: Step I, soak aluminum niobium carbide in dilute hydrochloric acid, take out the precipitate and etch it with hydrofluoric acid aqueous solution, and vacuum dry to obtain niobium carbide powder; Step II, take octadecylamine, heat and stir, add chloroform, stir and dissolve, then add thioglucoside, and shake to obtain a semi-dissolved emulsion of octadecylamine; Step III, take the niobium carbide obtained in Step I and add it to the semi-dissolved emulsion of octadecylamine in Step II. After stirring, successively add carbon tetrachloride solution and thiourea. After aging by electromagnetic stirring, add niobium pentachloride and cobalt dichloride, and raise the temperature to 280 °C for heat preservation reaction; Step IV, wash, dissolve, and centrifuge the precipitate after the reaction is completed, collect the bottom precipitate and vacuum dry to obtain the cobalt niobium sulfide / niobium carbide composite microwave absorption material.

4. The preparation method of the cobalt niobium sulfide / niobium carbide composite microwave absorption material according to claim 3, characterized in that, in Step I, the mass ratio of aluminum niobium carbide, dilute hydrochloric acid, and hydrofluoric acid aqueous solution is 1:(40 - 50):(50 - 60); the soaking time is 8 - 12 hours; the etching time is 20 - 30 hours; the vacuum drying temperature is 50 - 60 °C, and the vacuum drying time is 5 - 6 hours.

5. The preparation method of the cobalt niobium sulfide / niobium carbide composite microwave absorption material according to claim 3, characterized in that, in Step II, the mass ratio of octadecylamine, chloroform, and thioglucoside is (4 - 5):(45 - 50):1, and the heating rate is controlled at 25 °C / min, and the temperature is raised to 55 - 60 °C.

6. The preparation method of the cobalt niobium sulfide / niobium carbide composite microwave absorption material according to claim 3, characterized in that, in Step III, the mass ratio of niobium carbide, semi-dissolved emulsion of octadecylamine, carbon tetrachloride solution, and thiourea is 1:(45 - 50):(15 - 20):(3.5 - 4).

7. The application of the cobalt niobium sulfide / niobium carbide composite microwave absorption material according to claim 1 or 2 in the preparation of a microwave signal shielding coating slurry.

8. A microwave signal shielding coating slurry, characterized in that: it is prepared by the following steps: Step 1, mix the cobalt niobium sulfide / niobium carbide composite microwave absorption material according to claim 1 or 2 with absolute ethanol and grind, and vacuum freeze-dry to obtain the main powder material; Step 2: Mix and grind the powder material in Step 1 with hydroxyethyl cellulose, add dimethyl sulfoxide for dissolution, and heat the uniformly mixed material to 120 °C; Step 3: Perform three-roll rolling treatment on the slurry in Step 2, and stir and age at room temperature for 3 hours.

9. The microwave signal shielding coating slurry according to claim 8, characterized in that, in Step 1, the mass ratio of cobalt niobium sulfide / niobium carbide composite wave-absorbing material to absolute ethanol is 1:(5 - 5.5), the vacuum freeze-drying temperature is -45 to -40 °C, and the vacuum freeze-drying time is 32 to 36 hours.

10. The microwave signal shielding coating slurry according to claim 8, characterized in that, in Step 2, the mass ratio of the powder material, hydroxyethyl cellulose, and dimethyl sulfoxide is 1:(1.7 - 1.8):(18 - 20), and the heating time is 2 hours.

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