Zinc oxide doped tubular cellulose-based wave-absorbing material and preparation method thereof

Abstract

The application relates to the field of wave-absorbing materials, and provides a zinc oxide-doped tubular cellulose-based wave-absorbing material and a preparation method thereof. The main purpose is to solve the problems of poor impedance matching and insufficient wave-absorbing performance caused by single loss mechanism of traditional single cellulose-derived carbon-based wave-absorbing materials, a heterojunction interface is constructed through zinc oxide doping to enhance interface polarization loss, and the wave-absorbing material with environmental protection and high performance is prepared by using waste cotton cloth, and the main scheme comprises the following steps. The material is a black fine powder composed of carbon tubes with a diameter of about 10 microns, and the surface of the carbon tube is covered with a layer of fine zinc oxide particles. The preparation method is that after the waste cotton cloth is cleaned, the waste cotton cloth is hydrothermally treated with a zinc chloride solution, and then high-temperature annealing is carried out, so that zinc oxide particles are grown on the surface of the carbon base, the dielectric properties and impedance matching of the carbon material are optimized, and excellent interface polarization loss is provided. The prepared wave-absorbing material has excellent absorbable bandwidth and maximum reflection loss.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials, and provides a zinc oxide-doped tubular cellulose-based microwave absorbing material and its preparation method. Background Technology

[0002] Electromagnetic wave technology, as a crucial technology in modern society, is inseparable from human civilization and has been applied in numerous fields, bringing immense convenience to society. This technology has achieved remarkable success, continuously meeting people's demands for high-speed data transmission and low-latency communication. However, the widespread application of electromagnetic waves has also caused many harms, such as electromagnetic interference and electromagnetic pollution, which can negatively impact human health and the operation of precision instruments. Therefore, electromagnetic wave absorbing materials, as a highly effective countermeasure, are becoming increasingly important. Among them, carbon-based absorbing materials have become a popular choice due to their excellent conductivity, low density, large specific surface area, and good thermal and mechanical properties.

[0003] Cellulose is the most abundant biomass polymer material in nature. Its renewable, biodegradable, and cost-effective characteristics give it unique advantages in the field of electromagnetic wave absorbing materials. This material can be assembled into a three-dimensional conductive network through simple high-temperature carbonization, creating materials with excellent electrical conductivity loss. However, absorbing materials prepared from single cellulose-derived carbon materials suffer from drawbacks such as a single loss mechanism, affecting their absorption performance. Cellulose itself is a high-molecular-weight polysaccharide composed of glucose units, and its surface is rich in hydroxyl groups, making it easy to chemically modify. Therefore, its performance can be improved by introducing specific components through doping. Currently, there is a significant waste of artificially used cellulose textiles. Recycling them to produce absorbing materials can reduce environmental pollution and bring economic benefits. Summary of the Invention

[0004] The technical problem solved by this invention is that traditional single cellulose-derived carbon-based microwave absorbing materials suffer from poor impedance matching and insufficient absorption performance due to their singular loss mechanism. This invention enhances interfacial polarization loss by constructing a heterogeneous interface through zinc oxide doping, and simultaneously utilizes waste cotton fabric to prepare a microwave absorbing material that is both environmentally friendly and high-performance.

[0005] Technical solution: The zinc oxide-doped carbon-based electromagnetic absorbing material described in this invention is a black, fine powder composed of carbon nanotubes covered with a layer of zinc oxide particles. The carbon nanotubes have a diameter of 10-12 μm, and the zinc oxide particles on the surface are spherical particles with a diameter of 500-600 nm. The zinc content is extremely low, accounting for only 0.36-0.5% of the total mass of the material.

[0006] The detailed steps of the preparation method of the zinc oxide-doped tubular cellulose-based microwave absorbing material are as follows:

[0007] Step 1: Wash and dry the collected waste cotton cloth with deionized water and ethanol respectively;

[0008] Step 2: Soak the cotton cloth prepared in Step 1 in zinc chloride solution, put it into the reaction vessel and perform hydrothermal treatment. After the reaction is completed, take out the solid material and dry it.

[0009] Step 3: The solid material obtained in Step 2 is subjected to high-temperature annealing, and the product is cooled and ground to obtain zinc oxide-doped tubular electromagnetic wave absorbing material.

[0010] In the above scheme, in steps 1 and 2, the temperature for drying the solid material is 70℃, and the drying time is 12 hours.

[0011] In the above scheme, in step 2, the hydrothermal reaction is set at 180℃ and the holding time is 8h.

[0012] In the above scheme, in step 3, the protective gas is argon. The temperature is first raised to 30°C at a heating rate of 5°C / min and held for 1 hour, and then raised to 600°C at a heating rate of 5°C / min and held for 2 hours.

[0013] By implementing the above scheme, the beneficial effects of the present invention are:

[0014] I. The reagents used in the synthesis of this invention are all commercially available chemical reagents, which can be used directly in the reaction without purification, simplifying the raw material pretreatment process. The synthesis steps can be completed under conventional experimental conditions, without the need for precision instruments or special environments, and modular operation ensures the stability and reproducibility of the process. This method is cost-effective and industrially adaptable, suitable for large-scale production.

[0015] II. This invention utilizes waste cotton fabric as a carbon source to prepare a carbon fiber electromagnetic absorbing material with a surface covered by zinc oxide particles. The zinc element is distributed on the surface of the carbon nanotubes in the form of zinc oxide particles, forming numerous heterogeneous interfaces and enhancing interfacial polarization loss. Simultaneously, the cellulose material exhibits excellent electrical conductivity loss after high-temperature annealing. Therefore, this material, as an electromagnetic wave absorber, possesses good reflection loss and an effective absorption bandwidth. Furthermore, the carbon source of this material is waste cotton fabric, which not only reduces costs but also emphasizes environmental protection. The preparation process does not use highly toxic organic solvents, is simple, suitable for industrial production, and has broad prospects for practical application. Attached Figure Description

[0016] Figure 1 This is a SEM image of composite material A prepared in Example 1 of the present invention.

[0017] Figure 2 The elemental characteristic spectrum is shown for composite material A prepared in Example 1 of the present invention.

[0018] Figure 3 X-ray diffraction patterns of samples prepared in Examples 1-3 of the present invention.

[0019] Figure 4 Raman spectra of samples prepared in Examples 1-3 of this invention.

[0020] Figure 5 This is a waveform absorption performance diagram of composite material A (annealing temperature of 600℃) prepared in Example 1 of the present invention.

[0021] Figure 6 This is a waveform absorption performance diagram of composite material B (annealing temperature of 700℃) prepared in Example 2 of the present invention.

[0022] Figure 7 This is a waveform absorption performance diagram of composite material C (annealing temperature of 500℃) prepared in Example 3 of the present invention. Detailed Implementation

[0023] The principle of this invention is as follows: Zinc oxide-doped tubular carbon fiber materials are prepared by hydrothermal treatment of cellulose materials with zinc chloride solution, followed by high-temperature annealing. This method optimizes the poor impedance matching caused by the single loss mechanism of traditional carbon materials. The introduced zinc oxide particles improve the loss mechanism of carbon materials by constructing a ZnO / C heterogeneous interface, giving them excellent electromagnetic wave absorption performance.

[0024] Example 1

[0025] Step 1: Wash the collected waste cotton cloth with deionized water and ethanol by vigorous stirring, and then dry it at 70°C.

[0026] Step 2: Take 2g of washed cotton cloth, soak it in 50ml of 1mol / L zinc chloride solution, then transfer it to a hydrothermal reactor, heat it to 180℃ and keep it at that temperature for 8 hours. After it cools naturally to room temperature, take it out and dry it.

[0027] Step 3: The solid material obtained in Step 2 is heated to 30°C at a heating rate of 5°C / min under an argon atmosphere, held for 1 hour, then heated to 600°C at a heating rate of 5°C / min, held for 2 hours, cooled to room temperature and then ground to obtain composite material A.

[0028] Example 2

[0029] Step 1: Wash the collected waste cotton cloth with deionized water and ethanol by vigorous stirring, and then dry it at 70°C.

[0030] Step 2: Take 2g of washed cotton cloth, soak it in 50ml of 1mol / L zinc chloride solution, then transfer it to a hydrothermal reactor, heat it to 180℃ and keep it at that temperature for 8 hours. After it cools naturally to room temperature, take it out and dry it.

[0031] Step 3: The solid material obtained in Step 2 is heated to 30°C at a heating rate of 5°C / min under an argon atmosphere, held for 1 hour, then heated to 700°C at a heating rate of 5°C / min, held for 2 hours, cooled to room temperature and then ground to obtain composite material B.

[0032] Example 3

[0033] Step 1: Wash the collected waste cotton cloth with deionized water and ethanol by vigorous stirring, and then dry it at 70°C.

[0034] Step 2: Take 2g of washed cotton cloth, soak it in 50ml of 1mol / L zinc chloride solution, then transfer it to a hydrothermal reactor, heat it to 180℃ and keep it at that temperature for 8 hours. After it cools naturally to room temperature, take it out and dry it.

[0035] Step 3: The solid material obtained in Step 2 is heated to 30°C at a heating rate of 5°C / min under an argon atmosphere, held for 1 hour, then heated to 500°C at a heating rate of 5°C / min, held for 2 hours, cooled to room temperature and then ground to obtain composite material C.

[0036] The SEM image of sample A obtained in Example 1 is shown below. Figure 1 As shown, the carbon fiber has a diameter of about 10 μm and a dense layer of zinc oxide particles on its surface, with a particle diameter of about 500 nm.

[0037] The elemental characteristic spectrum of sample A obtained in Example 1 is as follows: Figure 2 As shown in the curve, the material contains C, O, and Zn. The characteristic peak for zinc is extremely weak because it accounts for only 0.36% of the total mass of the material.

[0038] The zinc oxide-doped cellulose-based microwave absorbing materials prepared by high-temperature annealing in Examples 1-3 were analyzed by X-ray diffraction. The results showed that the zinc oxide-doped carbon fibers synthesized at different annealing temperatures had diffraction peaks at similar positions, with obvious diffraction peaks appearing at positions such as 31.8° (100), 34.4° (002), 37.3° (101), 47.5° (102), 56.6° (110), and 62.9° (103), which perfectly matched the standard card (JCPDS 36-1451) for hexagonal wurtzite structure zinc oxide. The measurement results are as follows. Figure 3 As shown.

[0039] Figure 4 Raman spectra of zinc oxide-doped cellulose-based absorbing materials, from Figure 2 It can be seen that the I of sample A D / I GThe value is 0.8106, and the I of sample B is... D / I G The value is 0.8895, and the I of sample C is... D / I G The value of 0.7265 proves that the carbon element in the cellulose-based material after high-temperature annealing is converted into graphitized carbon, and the degree of graphitization increases with increasing temperature.

[0040] like Figure 5 , Figure 6 , Figure 7 As shown in the reflection loss spectra, sample A, with a fill ratio of 30 wt%, exhibits an effective absorption bandwidth of 7.14 GHz and a minimum reflection loss of -40.06 dB. Sample B, with a fill ratio of 30 wt%, exhibits an effective absorption bandwidth of 5.44 GHz and a minimum reflection loss of -44.96 dB. Sample C, with a fill ratio of 30 wt%, has an effective absorption bandwidth of 0, which is due to the low annealing temperature, low graphitization of the carbon material, and insufficient growth of zinc oxide particles.

[0041] The zinc oxide-doped cellulose-based microwave absorbing material of the present invention produced the best-performing sample in the experimental group by adjusting the annealing temperature. The sample with an annealing temperature of 600°C and a filling ratio of 30wt% had an effective absorption bandwidth of 7.14GHz with a matching thickness of 2.6mm; and a minimum reflection loss of -40.06dB with a matching thickness of 3.0mm.

[0042] The above description is merely a preferred embodiment of the present invention and is not the only limitation thereof. Those skilled in the art can make changes or modifications based on the above technical solutions to obtain equivalent embodiments. Any simple modifications, equivalent substitutions, and alterations based on the technical essence of the present invention are included within the protection scope of the present invention.

Claims

1. A zinc oxide-doped tubular cellulose-based microwave absorbing material, characterized in that: The material is a fine black powder composed of carbon nanotubes with zinc oxide particles covering the surface. The carbon nanotubes have a diameter of 10–12 μm, and the zinc oxide particles on the surface are spherical particles with a diameter of 500–600 nm. Zinc accounts for 0.36–0.5% of the total mass of the material.

2. The method for preparing a zinc oxide-doped tubular cellulose-based microwave absorbing material according to claim 1, characterized in that: Includes the following steps: Step 1: Wash and dry the collected waste cotton cloth with deionized water and ethanol respectively; Step 2: Soak the cotton cloth prepared in Step 1 in zinc chloride solution, put it into the reaction vessel and perform hydrothermal treatment. After the reaction is completed, take out the solid material and dry it. Step 3: The solid material obtained in Step 2 is subjected to high-temperature annealing, and the product is cooled, ground and annealed to obtain zinc oxide-doped tubular electromagnetic wave absorbing material.

3. The preparation method according to claim 2, characterized in that: In both steps 1 and 2, the solid material is dried at 70°C for 12 hours.

4. The preparation method according to claim 2, characterized in that: In step 2, the hydrothermal reaction is set at 180℃ and the holding time is 8 hours.

5. The preparation method according to claim 2, characterized in that: In step 3, the protective gas is argon. The temperature is first raised to 30°C at a heating rate of 5°C / min and held for 1 hour. Then, the temperature is raised to 500-700°C at a heating rate of 5°C / min and held for 2 hours. The material is then cooled and ground to obtain the microwave absorbing material.

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