Preparation method of carbon aerogel microwave absorbing material derived from guar gum self-foaming

Abstract

This invention relates to the field of electromagnetic wave absorbing materials, specifically to a method for preparing carbon aerogel absorbing materials derived from guar gum self-foaming. It solves the technical problems of cumbersome procedures, high costs, thick pore walls, and impedance mismatch associated with commonly used carbon aerogel techniques. The method includes: Step 1: Dissolving Zn(NO3)2·6H2O in deionized water and adding guar gum to obtain a hydrogel; Step 2: Allowing the hydrogel to stand at room temperature and then freeze-drying it to obtain an aerogel precursor; Step 3: Calcining the precursor at high temperature to obtain the aerogel; Step 4: Allowing the aerogel to stand in a hydrochloric acid solution, followed by washing and drying to obtain the guar gum-derived carbon aerogel absorbing material. The raw materials used in this invention are economical and readily available, the preparation process is simple, and the resulting product has thin pore walls, is lightweight, and possesses a good dual-three-dimensional porous structure. It also enhances the multiple reflection losses of electromagnetic waves within the absorbing agent, resulting in excellent absorption performance.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic wave absorbing materials technology, specifically to a method for preparing carbon aerogel absorbing materials derived from guar gum self-foaming. Background Technology

[0002] In recent years, the rapid development of wireless electronic communication technology has led to the widespread application of high-frequency electronic and communication equipment, resulting in serious electromagnetic pollution problems. Studies have shown that excessive electromagnetic waves not only interfere with some high-precision instruments, severely affecting data reliability and hindering social progress, but also have varying degrees of impact on human health. For example, they can interfere with the normal physiological functions of cells and organs, stimulate the nervous system, and consequently affect the immune system—problems that cannot be ignored.

[0003] In recent years, carbon aerogel materials, especially polymer-derived carbon, have become highly competitive in microwave absorbing materials due to their light weight, tunable intrinsic conductivity, and scalability. However, a comprehensive analysis of related research reveals that existing mainstream carbon aerogel microwave absorbing materials still face several unresolved issues, including complex fabrication processes, high operating costs, and thick pore walls. These problems not only limit further improvements in the performance of carbon aerogel microwave absorbing materials but also hinder their widespread application. Therefore, obtaining carbon aerogel microwave absorbing materials with controllable microstructures through simple methods remains a key focus and challenge in this field. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems of cumbersome procedures, high cost, thick pore walls, and impedance mismatch in carbon aerogels formed by commonly used techniques. It aims to construct a three-dimensional honeycomb-like pore structure on the inner wall of existing aerogels, making their electromagnetic properties easily modulated and exhibiting good microwave absorption performance in the 2-18 GHz range. A brief overview of this invention is provided below to offer a basic understanding of certain aspects of the invention. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention.

[0005] The technical solution of this invention:

[0006] The preparation method of carbon aerogel microwave absorbing material based on guar gum self-foaming includes the following steps:

[0007] Step 1: Dissolve Zn(NO3)2·6H2O in deionized water and stir until homogeneous to obtain a transparent solution. Then add guar gum to the transparent solution and stir until homogeneous to obtain a hydrogel.

[0008] Step 2: Place the hydrogel at room temperature and let it stand. After standing, freeze dry to obtain the aerogel precursor.

[0009] Step 3: Place the aerogel precursor in a ceramic boat and calcine it at high temperature in a tube furnace under an argon atmosphere to obtain black aerogel.

[0010] Step 4: Place the aerogel in hydrochloric acid solution and let it stand. After standing, wash it with deionized water and anhydrous ethanol. After washing, place it in an oven to dry. After drying, you will get the guar gum-derived carbon aerogel microwave absorbing material.

[0011] Preferred: In step one, the amount of Zn(NO3)2·6H2O is 1.5g, the amount of deionized water is 100mL, and the amount of guar gum is 1g.

[0012] Preferably, the stirring temperature in step one is 35°C and the stirring time is 10 minutes.

[0013] Preferred method: The hydrogel in step two is allowed to stand for 48 hours. The freeze-drying process is to place the hydrogel after standing at -18°C for 12 hours, and then put it into a freeze dryer and vacuum dry it at -57°C for 72 hours.

[0014] Preferably, the mass of the aerogel precursor in step three is 0.6g.

[0015] Preferred method: In step three, the high-temperature calcination process involves controlling the tube furnace to heat up at a rate of 5°C / min to 800°C for 2 hours.

[0016] Preferred method: In step four, the concentration of hydrochloric acid solution is 4 mol / L, the volume of hydrochloric acid solution is 30 mL, and the standing time is 12 hours.

[0017] The present invention has the following beneficial effects:

[0018] The guar gum-derived carbon aerogel microwave absorbing material prepared by this invention uses economical and readily available raw materials, has a simple preparation process, thin pore walls, and a complete and uniform three-dimensional structure.

[0019] The guar gum-derived carbon aerogel microwave absorbing material prepared by this invention has a good dual three-dimensional porous structure, which enhances the multiple reflection loss of electromagnetic waves inside the microwave absorbing agent.

[0020] The guar gum-derived carbon aerogel microwave absorbing material prepared by this invention is thin, lightweight, and has excellent microwave absorption performance. Attached Figure Description

[0021] Figure 1 This is a scanning electron microscope image of a carbon aerogel absorbing material derived from guar gum and a sample.

[0022] Figure 2 XRD patterns of carbon aerogel microwave absorbing material derived from guar gum and a control sample;

[0023] Figure 3 These are the Raman spectra of guar gum-derived carbon aerogel absorbing materials and comparative samples;

[0024] Figure 4 The graph shows the real part of the dielectric constant of the guar gum-derived carbon aerogel microwave absorbing material and the comparison sample.

[0025] Figure 5 The graph shows the imaginary part of the dielectric constant of the guar gum-derived carbon aerogel microwave absorbing material and the comparative sample.

[0026] Figure 6 The waveform impedance curves are of guar gum-derived carbon aerogel absorbing material and a comparative sample.

[0027] Figure 7 The graph shows the loss factor curves of guar gum-derived carbon aerogel absorbing material and a comparative sample.

[0028] Figure 8 This is a diagram showing the electromagnetic wave absorption performance of carbon aerogel absorbing materials derived from guar gum.

[0029] Figure 1 Image a shows a scanning electron microscope (SEM) image of the control sample, and image b shows a scanning electron microscope (SEM) image of the guar gum-derived carbon aerogel absorbing material. After the introduction of Zn(NO3)2·6H2O, a three-dimensional honeycomb-like pore structure appears on the layered inner wall of the aerogel, and the pore walls become thinner and the pore size becomes larger. Figure 2 Curve a represents the XRD pattern of the control sample, and curve b represents the XRD pattern of the guar gum-derived carbon aerogel microwave absorbing material. Comparison with the X-ray diffraction standard card shows that both the carbon aerogel prepared in Example 1 and the control sample are predominantly composed of amorphous carbon. Figure 3 Curve a is the Raman spectrum of the comparison sample; curve b is the Raman spectrum of the guar gum-derived carbon aerogel absorbing material. Their Ig... D / I G The values ​​are the same, mainly because their carbonization temperatures and carbonization times are the same. Figure 4 Curve a represents the real part of the dielectric constant of the control sample; curve b represents the real part of the dielectric constant of the guar gum-derived carbon aerogel absorbing material. The real part of the dielectric constant of the guar gum-derived carbon aerogel absorbing material is higher than that of the control sample. This is because the introduction of zinc nitrate increases the pore volume, porosity, and reduces the bulk density. This makes it easier for the sample per unit mass to construct a conductive network within the paraffin matrix under the influence of an external electromagnetic field, thereby effectively improving electron transport efficiency. Figure 5Midline a represents the imaginary part curve of the dielectric constant of the control sample; curve b represents the imaginary part curve of the dielectric constant of the graphitized gradient hollow carbon / cobalt microsphere microwave absorbing material. The imaginary part value of the dielectric constant of the guar gum-derived carbon aerogel microwave absorbing material is higher than that of the control sample. This is because the introduction of zinc nitrate increases the pore volume, porosity, and reduces the bulk density. Under the influence of an external electromagnetic field, the sample per unit mass can easily construct a conductive network in the paraffin matrix, thereby improving the conductivity of the material. Figure 6 In Figure a, the wave impedance curve of the control sample is shown; in Figure b, the wave impedance curve of the guar gum-derived carbon aerogel absorbing material is shown. The wave impedance value of the guar gum-derived carbon aerogel absorbing material is lower than that of the control sample, indicating that the impedance matching characteristics of the material are improved by constructing a three-dimensional honeycomb pore structure on the inner wall. Figure 7 Curve a represents the loss factor curve of the control sample; curve b represents the loss factor curve of the guar gum-derived carbon aerogel absorbing material. The loss capability of the control sample is not as strong as that of the guar gum-derived carbon aerogel absorbing material, indicating that the loss capability of the material can be controlled by constructing a three-dimensional honeycomb pore structure on the inner wall. Figure 8 Figure a shows the three-dimensional reflection loss diagram, and Figure b shows the two-dimensional reflection loss diagram. The minimum reflection loss of the guar gum-derived carbon aerogel prepared in Example 1 reaches -25.5dB at 18.0GHz, with an effective absorption bandwidth of 5.8GHz and a thickness of 1.8mm. The frequency range with a reflection loss of less than -10dB is approximately 4.0 to 18.0GHz (about 14GHz), which can achieve C-band, X-band, and Ku-band coverage, indicating that the guar gum-derived carbon aerogel absorbing material has excellent electromagnetic wave absorption capability. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0031] Specific implementation method one: Combining Figures 1-8 This embodiment describes a method for preparing a carbon aerogel microwave absorbing material based on guar gum self-foaming, which includes the following steps:

[0032] Step 1: Dissolve Zn(NO3)2·6H2O in deionized water and stir until homogeneous to obtain a transparent solution. Then add guar gum to the transparent solution and stir until homogeneous to obtain a hydrogel.

[0033] Step 2: Place the hydrogel at room temperature and let it stand. After standing, freeze dry to obtain the aerogel precursor.

[0034] Step 3: Place the aerogel precursor in a ceramic boat and calcine it at high temperature in a tube furnace under an argon atmosphere to obtain the aerogel.

[0035] Step 4: Place the aerogel in hydrochloric acid solution and let it stand. After standing, wash it with deionized water and anhydrous ethanol. After washing, place it in an oven to dry. After drying, you will get the guar gum-derived carbon aerogel microwave absorbing material.

[0036] Specific Implementation Method Two: Combining Figures 1-8 This embodiment describes the preparation method of carbon aerogel microwave absorbing material based on guar gum self-foaming, in step one, the amount of Zn(NO3)2·6H2O is 1.5g, the amount of deionized water is 100mL, and the amount of guar gum is 1g.

[0037] Specific implementation method three: Combining Figures 1-8 This embodiment describes the preparation method of carbon aerogel microwave absorbing material based on guar gum self-foaming. In step one, the stirring temperature is 35°C and the stirring time is 10 minutes, which helps to promote full cross-linking and make the material more uniformly dispersed.

[0038] Specific implementation method four: Combination Figures 1-8 This embodiment describes the preparation method of carbon aerogel microwave absorbing material based on guar gum self-foaming. In step two, the hydrogel is allowed to stand for 48 hours. The freeze-drying process involves placing the hydrogel at -18°C for 12 hours, then placing it in a freeze dryer and vacuum drying at -57°C for 72 hours.

[0039] Specific Implementation Method Five: Combining Figures 1-8 This embodiment describes the preparation method of carbon aerogel microwave absorbing material based on guar gum self-foaming, wherein the mass of the aerogel precursor in step three is 0.6g.

[0040] Specific Implementation Method Six: Combination Figures 1-8 This embodiment describes the preparation method of carbon aerogel microwave absorbing material based on guar gum self-foaming. In step three, the high-temperature calcination process involves controlling the tube furnace to heat up at a rate of 5°C / min to 800°C for 2 hours to ensure that it has the expected porous and carbonized characteristics.

[0041] Specific implementation method seven: Combination Figures 1-8 This embodiment describes the preparation method of carbon aerogel microwave absorbing material based on guar gum self-foaming. In step four, the hydrochloric acid solution is 4 mol / L, the volume of the hydrochloric acid solution is 30 mL, and the standing time is 12 hours to ensure complete removal of metallic zinc.

[0042] The guar gum-derived carbon aerogel absorbing material prepared by this invention can achieve a maximum reflection loss of -25.5 dB. With an absorber thickness of 1.8 mm, the bandwidth with a reflection loss of less than -10 dB can reach approximately 5.8 GHz, ranging from 12.2 to 18.0 GHz.

[0043] Example 1

[0044] Dissolve 1.5g Zn(NO3)2·6H2O in 100mL of deionized water and stir until homogeneous to obtain a transparent solution. Then add 1g of guar gum and stir thoroughly until a hydrogel is formed.

[0045] The hydrogel was left to stand at room temperature for 48 hours, then frozen at -18°C for 12 hours, and then placed in a freeze dryer and vacuum dried at -57°C for 72 hours to obtain the aerogel precursor.

[0046] The aerogel precursor was placed in a ceramic boat and calcined at high temperature in an argon atmosphere in a tube furnace. The heating rate of the tube furnace was 5℃ / min, the calcination temperature was 800℃, and the calcination time was 2 hours. After calcination, black aerogel was obtained.

[0047] The black aerogel was placed in a 30 mL solution of 4 mol / L hydrochloric acid and allowed to stand for 24 hours. After standing, it was washed with deionized water and anhydrous ethanol. After washing, it was placed in a drying oven to dry. After drying, the guar gum-derived carbon aerogel microwave absorbing material was obtained.

[0048] The control sample was prepared without adding Zn(NO3)2·6H2O in step one, and other conditions were the same as in Example 1.

[0049] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutation and combination. Therefore, the present invention will not describe the technical solutions after permutation and combination one by one, but it should be understood that the technical solutions after permutation and combination have been disclosed by the present invention.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing carbon aerogel microwave absorbing materials derived from guar gum self-foaming, characterized in that, Includes the following steps: Step 1: Dissolve Zn(NO3)2·6H2O in deionized water and stir until homogeneous to obtain a transparent solution. Then add guar gum to the transparent solution and stir until homogeneous to obtain a hydrogel. Step 2: Place the hydrogel at room temperature and let it stand. After standing, freeze dry to obtain the aerogel precursor. Step 3: Place the aerogel precursor in a ceramic boat and calcine it at high temperature in a tube furnace under an argon atmosphere to obtain black aerogel. Step 4: Place the aerogel in hydrochloric acid solution and let it stand. After standing, wash it with deionized water and anhydrous ethanol. After washing, place it in an oven to dry. After drying, you will get the guar gum-derived carbon aerogel microwave absorbing material.

2. The method for preparing carbon aerogel microwave absorbing material based on guar gum self-foaming according to claim 1, characterized in that: In step one, the amount of Zn(NO3)2·6H2O used is 1.5g, the amount of deionized water is 100mL, and the amount of guar gum is 1g.

3. The method for preparing carbon aerogel microwave absorbing material based on guar gum self-foaming derivative according to claim 1, characterized in that: In step one, the stirring temperature is 35℃ and the stirring time is 10 minutes.

4. The method for preparing carbon aerogel microwave absorbing material based on guar gum self-foaming according to claim 1, characterized in that: In step two, the hydrogel is allowed to stand for 48 hours. The freeze-drying process involves placing the hydrogel at -18°C for 12 hours, then placing it in a freeze dryer and vacuum drying at -57°C for 72 hours.

5. The method for preparing carbon aerogel microwave absorbing material based on guar gum self-foaming according to claim 1, characterized in that: The mass of the aerogel precursor in step three is 0.6g.

6. The method for preparing carbon aerogel microwave absorbing material based on guar gum self-foaming derivative according to claim 1, characterized in that: In step three, the high-temperature calcination process involves controlling the tubular furnace to heat up at a rate of 5°C / min until it reaches 800°C, with a calcination time of 2 hours.

7. The method for preparing carbon aerogel microwave absorbing material based on guar gum self-foaming derivative according to claim 1, characterized in that: In step four, the concentration of the hydrochloric acid solution is 4 mol / L, the volume of the hydrochloric acid solution is 30 mL, and the standing time is 12 hours.

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