SiC@MnO 2-x / Mn3O 4-x Nanocomposite absorbing materials

Abstract

The present invention discloses SiC@MnO 2‑x / Mn3O 4‑x Nanocomposite wave absorbing material and preparation method thereof. The present invention uses carbon cloth loaded with SiC nanowires as a substrate, uses a hydrothermal method to wrap a dense layer of MnO2 on the SiC nanowires, and then introduces oxygen vacancies by calcining in an argon atmosphere to induce the MnO2 wrapped on the SiC nanowires to form a dense layer of MnO2. 2‑x Phase transformation occurs to generate Mn3O 4‑x Finally, SiC@MnO 2‑x / Mn3O 4‑x Nanocomposite wave absorbing material. The experimental method adopted by the present invention is easy to operate, low in cost, easy to control, has many controllable variables, and can be repeated. 2‑x / Mn3O 4‑x The nanocomposite absorbing material has the advantages of good microwave absorption performance, thin matching thickness, wide effective absorption bandwidth and covering the entire Ku band. The present invention provides a good foundation for the development of composite material defect-induced polarization to promote electromagnetic wave absorption, and provides a good design idea for the multi-component composite of electromagnetic wave absorbing materials. Its good microwave absorption performance can play a good role in electromagnetic radiation and pollution of electronic equipment, and has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of nanocomposite materials and electromagnetic wave absorption technology, and specifically relates to SiC@MnO 2-x / Mn3O 4-x Nanocomposite absorbing materials. Background Art

[0002] With the vigorous development of electronic information technology, modern industries and many advanced technologies, such as the fifth generation communication technology (5G) and information long-distance transportation technology, are widely used in people's daily lives. Although these technologies have improved people's lives, they have also brought electromagnetic interference. The complex electromagnetic environment in life will affect the signal transmission efficiency of electronic equipment, and in severe cases it will even cause equipment failure, bringing immeasurable losses. In addition, long-term exposure to a complex electromagnetic environment is extremely harmful to the physiological system and may cause serious diseases. In order to reduce the harm of daily electromagnetic wave interference to production and people's lives, electromagnetic wave absorbing materials came into being.

[0003] Silicon carbide (SiC) has high temperature resistance, oxidation resistance and corrosion resistance as well as adjustable dielectric properties, and also shows great potential in electromagnetic wave absorption. Transition metal oxides have redox chemical properties. With the gradual advancement of research at home and abroad, transition metal oxides have great potential as active oxygen catalysts for energy storage and conversion. In recent years, the potential of transition metal oxides in the field of electromagnetic wave absorption has also been fully explored. Among them, MnO2 is widely regarded as an effective electromagnetic microwave absorption material due to its excellent dielectric loss. MnO2 has a wide range of crystal structures, and its low production cost makes it a promising research field. However, manganese dioxide as an absorbing material has a narrow effective absorption bandwidth (EAB) and poor electronic conductivity.

[0004] Defect engineering has brought new breakthrough ideas to some previous problems. Generally, dielectric loss consists of two parts: polarization loss and conductive loss, which are inseparable from the formation, transmission and aggregation of electrons in the material. It is now generally believed that oxygen vacancies in transition metal oxides can improve the conductivity of metal oxides. The generation of oxygen vacancies can optimize the electronic structure and increase the number of active sites. Through a more direct and effective treatment process, oxygen vacancy atomic-level defects can be directly generated within the intrinsic product. By adjusting the concentration of these vacancies and the resulting electronic structure, the correlation between microscopic defects, dipole polarization and electromagnetic wave absorption performance can be accurately elucidated.

[0005] The defect-induced dipole polarization can significantly improve the microwave absorption performance of the product, so the SiC@MnO 2-x / Mn3O 4-xNanocomposite absorbing materials are expected to achieve better polarization loss than a single or any two components alone, thereby achieving better impedance matching and electromagnetic wave absorption performance. Summary of the invention

[0006] The present invention aims to provide SiC@MnO 2-x / Mn3O 4-x The nanocomposite absorbing material has an easy-to-operate, efficient and time-saving preparation process. The SiC@MnO2 is prepared by introducing needle-shaped MnO2 into the existing SiC nanowires and then calcining them at high temperature in an argon atmosphere. 2-x / Mn3O 4-x Nanocomposite absorbing materials have excellent microwave absorption performance. As we all know, "thin, light, wide, and strong" are the main performance requirements of electromagnetic wave absorbing materials. Integrating the four major properties is a major difficulty in the current research field of absorbing materials. The SiC@MnO 2-x / Mn3O 4-x Nanocomposite absorbing materials can meet the above performance requirements to a certain extent. While having good electromagnetic wave absorption performance, they can also ensure the advantages of thin matching thickness and wide effective absorption bandwidth. The SiC@MnO prepared by the present invention is 2-x / Mn3O 4-x The effective absorption bandwidth of the nanocomposite absorbing material can cover the entire high-frequency Ku band.

[0007] The present invention adopts the following technical solutions to achieve the above-mentioned purpose:

[0008] (1) SiC pretreatment and preparation of hydrothermal solution

[0009] Select carbon cloth loaded with SiC nanowires, prepare 2.5 mol / L NaOH aqueous solution to soak the carbon cloth loaded with SiC nanowires to remove the surface SiO2 amorphous layer and activate the surface, then soak and rinse with deionized water for multiple times to remove alkalinity, and prepare a hydrothermal solution of KMnO4 and H2SO4 with a concentration of 98%;

[0010] (2) Preparation of SiC@MnO2 nanocomposites

[0011] After the prepared hydrothermal solution is fully stirred until uniform, it is poured into the reactor, and the pretreated SiC is placed vertically into the reactor so that both sides can contact the hydrothermal solution and fully react. The oven temperature is set to 140-180°C for 3.5 hours, and the reactor is placed in the reactor. After it is completely cooled, the product is taken out, which is the SiC@MnO2 nanocomposite material;

[0012] (3)SiC@MnO 2-x / Mn3O 4-xPreparation of Nanocomposite Microwave Absorbing Materials

[0013] The hydrothermal product SiC@MnO2 nanocomposite material is placed in a tubular furnace and calcined with argon gas. The calcination temperature is 350-500°C, the temperature is kept for 2 hours, and the heating rate is 5°C / min. The obtained product is SiC@MnO 2-x / Mn3O 4-x Nanocomposite absorbing materials.

[0014] The present invention successfully prepared a SiC@MnO by hydrothermal method and high temperature calcination under argon atmosphere. 2-x / Mn3O 4-x Nanocomposite wave absorbing material. The preparation process of the present invention is simple, time-saving and low-cost. The prepared SiC@MnO 2-x / Mn3O 4-x Nanocomposite absorbing materials have the advantages of thin matching thickness, low material density, wide effective absorption band range, and high absorption intensity. In addition, the dielectric absorbing material SiC has a low dielectric constant, good stability, and can optimize impedance matching. In addition, SiC has a network structure, which makes its dielectric properties even better. However, SiC has insufficient multiple reflection loss capacity, so the introduction of needle-shaped MnO2 enhances its multiple reflection loss capacity and improves its electromagnetic wave absorption capacity. Then, by introducing defects into MnO2, SiC@MnO 2-x / Mn3O 4-x Nanocomposite absorbing material. Defect-induced dipole polarization further enhances electromagnetic wave absorption efficiency. The present invention provides a good foundation for the development of multi-component composite materials and a good design idea for the application of defect engineering in the field of electromagnetic wave absorbing materials.

[0015] The advantages of the present invention over other absorbing materials are mainly reflected in the following points:

[0016] (1) Through the vapor deposition method, we obtained SiC nanowire-based composite absorbers that combine the advantages of multi-level and multi-loss mechanism coordination. We mastered the key preparation technology of the selected products, providing technical support and guidance for the research and development of other nanocomposite absorbers.

[0017] (2) Taking defect engineering as the starting point, the oxygen vacancy concentration of the product is effectively controlled by high-temperature argon calcination, and its induced dipole polarization mechanism, phase transition and heterostructure generation process are explained.

[0018] (3) Clarify the structure-function relationship between the product microstructure / state and its electromagnetic parameters, explore effective ways to improve the product's microwave absorption performance, and establish the microwave attenuation mechanism under the synergistic effect of multiple factors such as impedance matching, dielectric loss, and polarization loss, so as to provide multi-faceted theoretical support for the structural design innovation of nanocomposite absorbing materials, the induced dipole polarization of defect engineering, and the improvement of microwave absorption performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The SiC@MnO prepared in Example 1 2-x / Mn3O 4-x XRD pattern of nanocomposite absorbing material.

[0020] Figure 2 The SiC@MnO prepared in Example 1 2-x / Mn3O 4-x SEM image of nanocomposite absorbing material.

[0021] Figure 3 The SiC@MnO prepared in Example 1 2-x / Mn3O 4-x Raman graph of nanocomposite absorber.

[0022] Figure 4 The SiC@MnO prepared in Example 1 2-x / Mn3O 4-x XPS spectra of nanocomposite absorbers.

[0023] Figure 5 The SiC@MnO prepared in Example 1 2-x / Mn3O 4-x EPR graph of nanocomposite absorbing material.

[0024] Figure 6 The SiC@MnO prepared in Example 1 2-x / Mn3O 4-x Reflection loss (RL) plot of nanocomposite absorbers. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to specific examples, but these examples do not limit the scope of the present invention in any way.

[0026] Example 1

[0027] SiC@MnO 2-x / Mn3O 4-x Nanocomposite absorbing material, including the following operations:

[0028] Cut the carbon cloth loaded with SiC nanowires into 3*4cm2 The rectangular shape was soaked in a 3 mol / L NaOH aqueous solution for 2 hours and then rinsed with deionized water until it was neutral. Subsequently, KMnO4 was dissolved in 70 ml of deionized water and magnetically stirred for 1 hour, while H2SO4 was added dropwise, and the molar ratio of KMnO4 to H2SO4 was 1:1. The resulting solution was then transferred to a 100 mL polytetrafluoroethylene-lined container and kept at 160 ° C for 3.5 hours. Finally, the obtained sample was rinsed several times with deionized water and anhydrous ethanol and dried. The obtained product was labeled as SiC@MnO2 nanocomposite absorber. The SiC@MnO2 nanocomposite absorber was calcined in a tubular furnace with argon for 120 minutes at a calcination temperature of 450 ° C, and the product SiC@MnO was obtained after natural cooling. 2-x / Mn3O 4-x Nanocomposite absorbing material. The XRD, SEM, Raman, XPS and EPR spectra of the product are Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 . And from the known results, it can be known that SiC@MnO 2-x / Mn3O 4-x The nanocomposite absorber was successfully prepared, and the introduction of vacancies did not change the original needle-like structure of MnO2, nor did it destroy the multiple reflection loss mechanism. The XPS spectrum shows that the product contains Si, C, Mn and O elements, among which the presence of Mn and O elements indicates that MnO2 has been successfully coated on the SiC nanowires, and the EPR signal indicates the generation of oxygen vacancies, indicating that SiC@MnO 2-x / Mn3O 4-x Nanocomposite absorbing materials have been successfully prepared.

[0029] SiC@MnO 2-x / Mn3O 4-x Nanocomposite absorbing materials for microwave absorption testing. Figure 6 As can be seen from the reflection loss (RL) of SiC@MnO 2-x / Mn3O 4-x The nanocomposite absorbing material has achieved excellent absorbing performance at a relatively thin matching thickness, and at the same time has a wide effective absorption band, which has completely covered the entire high frequency band (Ku band). This illustrates the effective method of improving the absorbing performance of materials by inducing defect engineering.

Claims

1. SiC@MnO 2-x / Mn3O 4-x The nanocomposite wave absorbing material is characterized by: SiC@MnO was obtained by hydrothermal method and argon high temperature calcination method. 2-x / Mn3O 4-x The main steps of nanocomposite absorbers are as follows: (1) SiC pretreatment and preparation of hydrothermal solution Select carbon cloth loaded with SiC nanowires, prepare 2.5 mol / L NaOH aqueous solution to soak the carbon cloth loaded with SiC nanowires to remove the surface SiO2 amorphous layer and activate the surface, then soak and rinse with deionized water for multiple times to remove alkalinity, and prepare a hydrothermal solution of KMnO4 and H2SO4 with a concentration of 98%; (2) Preparation of SiC@MnO2 nanocomposites After the prepared hydrothermal solution is fully stirred until uniform, it is poured into the reactor, and the pretreated SiC is placed vertically into the reactor so that both sides can contact the hydrothermal solution and fully react. The oven temperature is set to 140-180°C for 3.5 hours, and the reactor is placed in the reactor. After it is completely cooled, the product is taken out, which is the SiC@MnO2 nanocomposite material; (3)SiC@MnO 2-x / Mn3O 4-x Preparation of Nanocomposite Microwave Absorbing Materials The hydrothermal product SiC@MnO2 nanocomposite material is placed in a tubular furnace and calcined with argon gas. The calcination temperature is 350-500°C, the temperature is kept for 2 hours, and the heating rate is 5°C / min. The obtained product is SiC@MnO 2-x / Mn3O 4-x Nanocomposite absorbing materials.

2. SiC@MnO according to claim 1 2-x / Mn3O 4-x Nanocomposite wave absorbing material, characterized by: The molar ratio of KMnO4 and H2SO4 with a concentration of 98% is 1:

1.

3. SiC@MnO according to claim 1 2-x / Mn3O 4-x Nanocomposite wave absorbing material, characterized by: Calcination was carried out under argon atmosphere.

4. SiC@MnO according to claim 1 2-x / Mn3O 4-x Nanocomposite wave absorbing material, characterized by: The heating rate during calcination was 5°C / min.

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