A NiS / Ni 0.96 Carbon-based material composite wave-absorbing material and preparation method thereof

Abstract

The embodiment of the application discloses a kind of NiS / Ni 0.96 The application discloses a kind of carbon-based material composite wave-absorbing materials and its preparation method.The method comprises the following steps: carbon-based material is reacted with thioacetamide and nickel salt in the presence of a solvent in a stainless steel reactor by hydrothermal reaction.The application adopts a hydrothermal method to prepare nickel sulfide and a heterogeneous composite material of the heterogeneous phase of the nickel sulfide and a carbon-based material.The material has the advantages of wide bandwidth, thin thickness, light weight, strong absorption and simple preparation, and is a microwave absorbing material with broad application prospects.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of functional materials, in particular to a kind of NiS / Ni 0.96 S@ carbon-based material composite wave-absorbing material and preparation method thereof. BACKGROUND

[0002] In recent years, with the progress of science and technology, the popularity of electronic equipment and communication equipment makes electromagnetic pollution more and more serious. Electromagnetic pollution not only causes damage to electronic equipment, but also causes certain harm to human health. However, excellent wave-absorbing materials can solve the above problems as much as possible. Therefore, it is very important to find a material that can efficiently absorb electromagnetic waves.

[0003] Therefore, the present application is proposed. SUMMARY

[0004] Transition metal (Ni, Co, Mo, W, etc.) sulfides are widely used in semiconductor materials, catalysts, energy storage and other fields due to their excellent optical, thermal, electrical and magnetic properties. At the same time, transition metal sulfides have excellent electrical conductivity and high dielectric loss, and are widely used in microwave absorption field. However, transition metal sulfides are prone to high resistance and high dielectric loss, which leads to impedance mismatch. Carbon-based materials such as graphene, carbon nanotubes and carbon fibers have attracted more and more attention due to their low density, large specific surface area and good electrical conductivity. The present application combines transition metal sulfides and carbon-based materials to optimize the impedance matching of the composite material, so that it has excellent microwave absorption performance.

[0005] To achieve the above purpose, the embodiment of the present application provides the following technical scheme:

[0006] According to the first aspect of the embodiment of the present application, the present application provides a kind of NiS / Ni 0.96 Preparation method of S@ carbon-based material composite wave-absorbing material, the method comprises:

[0007] The carbon-based material, thioacetamide and nickel salt are subjected to hydrothermal reaction in a stainless steel reactor in the presence of a solvent.

[0008] Further, the carbon-based material is graphene or carbon nanotube. Carbon nanotubes have good chemical stability and high mechanical strength, and can maintain their structure unchanged during the reaction process, even at high temperature. Therefore, the carbon-based material of the present application is preferably carbon nanotube. Carbon nanotubes include single-walled carbon nanotubes and multi-walled carbon nanotubes. Compared with single-walled carbon nanotubes, multi-walled carbon nanotubes have more excellent toughness, strength, electrical conductivity and thermal stability. Therefore, the present application preferably uses multi-walled carbon nanotubes as carbon-based material.

[0009] Further, the nickel salt is nickel chloride and its hydrate, nickel sulfate, nickel nitrate, preferably nickel chloride and its hydrate.

[0010] Further, the molar ratio of the nickel salt to thioacetamide is 1:6-9.

[0011] Further, the mass ratio of the carbon-based material to the nickel salt is 1:8-20, preferably 1:13-14. Under the above preferred dosage relationship, the composite material has excellent electrical conductivity and impedance matching, and exhibits more excellent microwave absorption performance.

[0012] Further, the solvent is composed of deionized water and DMF in a volume ratio of 1:1-2.

[0013] Further, the hydrothermal reaction is carried out at 180-230℃ for 18-24 hours.

[0014] Further, when the carbon-based material is carbon nanotubes, the method further comprises, before the hydrothermal reaction, acidizing the carbon-based material. The acidized carbon-based material not only adjusts the electrical conductivity of the material but also optimizes the impedance matching of the material, making it possible for electromagnetic waves to attenuate into the material. At the same time, there are a large number of oxygen-containing functional groups, and carbon atom defects provide a large number of active sites for dipole polarization. In addition, the carbon nanotubes and nickel sulfide can form a conductive network to enhance the transmission of electrons, thereby enhancing the microwave conduction loss capability of the composite material.

[0015] Further, the acidizing treatment comprises: adding the carbon-based material into a mixed solvent of water and nitric acid for ultrasonic treatment, then placing it in a stainless steel reaction kettle at 100-140℃ for 8-12 hours, cooling to room temperature, washing with deionized water and ethanol several times, and freeze-drying.

[0016] Further, the concentration of the nitric acid is 65-68%, and the volume ratio of water to nitric acid is 1:1-3.

[0017] The mass-to-volume ratio of the carbon-based material to the mixed solvent is 1:75-150.

[0018] The ultrasonic treatment is carried out at room temperature with a frequency of 80-120 kHz.

[0019] The freeze-drying is carried out at a cold trap temperature of ≤-60℃, a vacuum degree of ≤50 Pa, and a time of 12-24 h.

[0020] According to a second aspect of the embodiments of the present application, the present application provides a NiS / Ni 0.96 S@carbon-based material composite wave-absorbing material, which is prepared by the method according to any one of the above.

[0021] The embodiments of the present invention have the following advantages:

[0022] This invention employs a simple hydrothermal method to prepare nickel sulfide and its heterogeneous composite material with a carbon-based material. The introduction of the carbon-based material enhances the dielectric loss of the composite material. Simultaneously, the particle size of the heterogeneous nickel sulfide decreases, and its specific surface area increases, which is beneficial for improving the microwave absorption capacity of the sample. The NiS / Ni composite material provided by this invention... 0.96 S@carbon-based composite materials have advantages such as wide absorption bandwidth, thin thickness, light weight, strong absorption and simple preparation, making them a microwave absorbing material with broad application prospects. Attached Figure Description

[0023] 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 introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0024] Figure 1 The NiS / Ni provided by the present invention 0.96 S and NiS / Ni 0.96 XRD patterns of S@MWCNTs;

[0025] Figure 2 The NiS / Ni provided by the present invention 0.96 S and NiS / Ni 0.96 Scanning electron microscope images and EDS spectra of S@MWCNTs;

[0026] Figure 3 The NiS / Ni prepared for Comparative Example 1 of this invention 0.96 The reflection loss spectrum of S;

[0027] Figure 4 The NiS / Ni prepared in Example 1 of this invention 0.96 Reflection loss spectrum of S@MWCNTs;

[0028] Figure 5 The NiS / Ni prepared in Example 2 of this invention 0.96 Reflection loss spectrum of S@MWCNTs;

[0029] Figure 6 The NiS / Ni prepared in Example 3 of this invention 0.96 Reflection loss spectrum of S@MWCNTs;

[0030] Figure 7 The NiS / Ni prepared in Example 4 of this invention0.96 Reflection loss spectrum of S@MWCNTs;

[0031] Figure 8 NiS / Ni 0.96 Schematic diagram of microwave absorption mechanism of S@MWCNTs; DETAILED DESCRIPTION

[0032] The present application will be described in greater detail by the following specific examples, and a person with ordinary skill in the art can easily understand other advantages and effects of the present application from the contents disclosed in the specification. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person with ordinary skill in the art without creative labor fall within the scope of protection of the present application. The test methods used in the examples are considered to be conventional methods if not otherwise specified; the materials, reagents, etc. used are commercially available if not otherwise specified.

[0033] Multi-walled carbon nanotubes (MWCNTs): Mcllvin, ≥95%, ID: 5-12 nm, OD: 30-50 nm, Length: 10-20 μm.

[0034] Example 1

[0035] The present embodiment provides a kind of NiS / Ni 0.96 Preparation method of S@MWCNTs composite wave-absorbing material:

[0036] Step 1: acid treatment of multi-walled carbon nanotubes

[0037] 0.2 g of multi-walled carbon nanotubes was added to 15 mL of water and 15 mL of nitric acid and ultrasonically treated (temperature 25°C, frequency 100 kHz) for 60 minutes, and the resulting uniform solution was transferred to a 50 mL Teflon stainless steel reactor, which was kept at 120°C for 10 hours, and then cooled to room temperature. The acid-treated multi-walled carbon nanotubes were repeatedly washed with deionized water and ethanol several times, and then freeze-dried (-70°C, 5 Pa) overnight to obtain fluffy multi-walled carbon nanotube powder (acidified MWCNTs).

[0038] Step 2: preparation of NiS / Ni 0.96 S@MWCNTs composite material

[0039] Step 1: The same as example 1; Step 2: Preparation of NiS / Ni@MWCNTs composite material

[0040] Example 2

[0041] The present example provides a method for preparing a NiS / Ni 0.96 S@MWCNTs composite wave-absorbing material

[0042] Step 1: The same as example 1; Step 2: Preparation of NiS / Ni@MWCNTs composite material

[0043] Step 2: Preparation of NiS / Ni 0.96 S@MWCNTs composite material

[0044] Step 1: The same as example 1; Step 2: Preparation of NiS / Ni@MWCNTs composite material

[0045] Example 3

[0046] The present example provides a method for preparing a NiS / Ni 0.96 S@MWCNTs composite wave-absorbing material

[0047] Step 1: The same as example 1; Step 2: Preparation of NiS / Ni@MWCNTs composite material

[0048] Step 2: Preparation of NiS / Ni 0.96 S@MWCNTs composite material

[0049] Step 1: The same as example 1; Step 2: Preparation of NiS / Ni@MWCNTs composite material

[0050] Example 4

[0051] The present example provides a method for preparing a NiS / Ni0.96 A method for preparing S@MWCNTs composite wave-absorbing material

[0052] Step 1: same as Example 1;

[0053] Step 2: preparation of NiS / Ni 0.96 S@MWCNTs composite material

[0054] 0.8 g of thioacetamide and 0.3438 g of nickel chloride hexahydrate were dispersed in deionized water and DMF in a volume ratio of 1:1, then 0.0310 g of acidified MWCNTs of step 1 was added, and the resulting mixed solution was stirred at room temperature for 2 hours to obtain a uniform solution of the mixture. The above uniform solution was transferred into a 50 mL Teflon stainless steel reaction kettle, and kept at 200°C for 24 hours. The precipitate was obtained by washing with deionized water and anhydrous ethanol for several times.

[0055] Comparative Example 1

[0056] This comparative example provides NiS / Ni 0.96 A method for preparing S material

[0057] 0.8 g of thioacetamide and 0.3438 g of nickel chloride hexahydrate were dispersed in deionized water and DMF in a volume ratio of 1:1. The above uniform solution was transferred into a 50 mL Teflon stainless steel reaction kettle, and kept at 200°C for 24 hours. The precipitate was obtained by washing with deionized water and anhydrous ethanol for several times.

[0058] Test Example 1

[0059] 1. Material characterization

[0060] The materials prepared in Examples 1-4 and Comparative Example 1 were subjected to X-ray diffraction analysis, and were compared with NiS, Ni 0.96 S and C, and the results are shown in Figure 1 (S0-S4 correspond to Comparative Example 1, Examples 1-4 samples in turn), it can be seen from the figure that the materials prepared in Examples 1-4 have diffraction peaks of NiS, Ni 0.96 S and C.

[0061] The materials prepared in Examples 1-4 and Comparative Example 1 were subjected to scanning electron microscopy analysis, and the results are shown in Figure 2 (a-e, wherein a, b-e correspond to Comparative Example 1, Examples 1-4 samples in turn), it can be found from the SEM figure that with the increase of the content of carbon nanotubes, the particle size of the heterogeneous nickel sulfide gradually decreases. The material prepared in Example 3 was subjected to EDS energy spectrum analysis, and the results are shown in Figure 2 f, it can be seen from the figure that Ni, S and C elements exist.

[0062] 2. Performance test

[0063] The materials prepared in Examples 1-4 and Comparative Example 1 were uniformly mixed with a paraffin base to obtain test samples, wherein the mass ratio of the material to paraffin was 3:7.

[0064] The electromagnetic parameters of each sample were measured using a vector network analyzer. Based on transmission line theory, the reflection loss of the material was tested using the following equation:

[0065]

[0066]

[0067] In the formula, RL is the reflection loss, and Z is the reflection loss. in Z0 is the input wave impedance of the absorber, and Z0 is the free space impedance (377Ω). r and ε r RL represents the relative complex permeability and relative complex permittivity of the absorbing medium, respectively; f is the frequency of the incident electromagnetic wave; d is the thickness of the absorber; and c is the speed of light in vacuum. The value of RL is usually negative; a larger absolute value indicates greater electromagnetic wave attenuation loss and better absorption performance. Generally, when the RL value is below -10dB, it indicates that the material's electromagnetic wave attenuation loss reaches 90%, and the corresponding electromagnetic wave frequency range is called the effective absorption bandwidth.

[0068] NiS / Ni prepared in Comparative Example 1 were compared within a simulated thickness range of 1.0 mm to 5.0 mm. 0.96 The reflection loss of S was tested. See the results below. Figure 3 As can be seen from the figure, all RL values ​​are above -10dB across the entire frequency range. This indicates that NiS / Ni 0.96 The microwave absorption performance of S material is not ideal.

[0069] Similarly, within a simulated thickness range of 1.0 mm to 5.0 mm, the NiS / Ni prepared in Examples 1-4 were tested respectively. 0.96 The reflection loss of S@CNTs was tested. The results are shown below. Figures 4-7 As can be seen from the figure, the NiS / Ni prepared in Example 1 0.96 At a thickness of 4.5 mm, the S@MWCNTs composite material exhibits high RL efficiency. min The impedance is -21.6 dB, and the effective absorption bandwidth is 1.92 GHz. Figure 4 Example 2: NiS / Ni 0.96 S@CNTs composite material at a thickness of 5 mm, RL min The impedance is -19.4dB, and the effective absorption bandwidth is 1.28GHz. Figure 5 Example 3: NiS / Ni 0.96The effective absorption bandwidth of the S@MWCNTs composite material at a thickness of 1.3 mm is 3.76 GHz, and in addition, at a frequency of 10.0 GHz, the RL min of the S@MWCNTs composite material at a thickness of 2.0 mm is -35.5 dB. Figure 6 ). The NiS / Ni 0.96 S@MWCNTs composite material at a thickness of 4.5 mm has an RL min of -17.65 dB, and the effective absorption bandwidth is only 1.28 GHz Figure 7 ). The above results show that the NiS / Ni 0.96 S@MWCNTs composite material prepared in the embodiments of the present application has the advantages of thin thickness, light weight and strong absorption, and the embodiment 3 has the most excellent microwave absorption performance.

[0070] Referring to Figure 8 , the microwave absorption mechanism of the NiS / Ni 0.96 S@MWCNTs wave-absorbing agent is mainly determined by interface polarization, conduction loss, and multiple reflection and scattering. First, there are a large number of oxygen-containing functional groups on the acidified carbon nanotubes, which provide multiple active sites for microwave reflection and scattering, and increase the dielectric loss ability of the material to electromagnetic waves. Second, the NiS / Ni 0.96 S@MWCNTs has good electrical conductivity, and the carbon nanotubes are intertwined with each other to form a conductive network, resulting in strong conduction loss. Finally, the heterogeneous nickel sulfide and carbon nanotube composite material constructs a multi-level structure and has a large number of interfaces, including the interfaces between NiS / Ni 0.96 S, NiS / MWCNTs and Ni 0.96 S / MWCNTs, thereby producing different interface polarizations and enhancing dielectric relaxation. Therefore, the synergistic effect of various electromagnetic loss mechanisms results in the NiS / Ni 0.96 S@MWCNTs wave-absorbing agent having excellent microwave absorption performance.

[0071] Although the present application has been described in detail in the foregoing description with general principles and specific embodiments, some modifications or improvements can be made on the basis of the present application, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the present application, all belong to the scope of protection claimed by the present application.

Claims

1. A NiS / Ni 0.96 The method for preparing S@carbon-based composite microwave absorbing material is characterized by... The method includes: Carbon-based materials are subjected to a hydrothermal reaction with thioacetamide and nickel salt in the presence of a solvent in a stainless steel reactor. The carbon-based material is a multi-walled carbon nanotube. Before the hydrothermal reaction, the carbon-based material is acidified. The acidification process includes: adding the multi-walled carbon nanotube to a mixed solvent of water and nitric acid for ultrasonic treatment, then placing it in a stainless steel reactor and maintaining it at 100~140ºC for 8~12 hours, cooling it to room temperature, washing it repeatedly with deionized water and ethanol several times, and freeze-drying it. The nickel salt is nickel chloride; The molar ratio of the nickel salt to thioacetamide is 1:6~9; The mass ratio of the carbon-based material to the nickel salt is 1:13~14; The solvent is composed of deionized water and DMF in a volume ratio of 1:1~2; The conditions for the hydrothermal reaction are: maintaining at 180~200ºC for 18~24 hours; The concentration of the nitric acid is 65-68%, and the volume ratio of water to nitric acid is 1:1-3. The mass-to-volume ratio of the carbon nanotubes to the mixed solvent is 1:75~150; The conditions for the ultrasonic treatment are: room temperature, frequency 80~120 kHz; The freeze-drying conditions are: cold trap temperature ≤ -60ºC, vacuum degree ≤ 50 Pa, and time 12~24 h.

2. A NiS / Ni 0.96 S@carbon-based composite microwave absorbing material, characterized in that... It is made by the method described in claim 1.

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