An iron oxide-coated carbon microtube and its application in terahertz wave absorption

Abstract

The present invention relates to an iron oxide-coated carbon microtube and its application in terahertz wave absorption. The carbon microtube is a helical structure formed by continuous high-temperature carbonization and curling of biomass carbon fiber, and a layer of iron oxide nanosheets is coated on its surface by a hydrothermal method. The present invention constructs a unique heterostructure composite by combining the (110) plane of iron oxide with the carbon microtube. Due to the energy level matching between the Fermi level of the carbon microtube and the conduction band of iron oxide, the periodic injection and release of electrons on the carbon microtube to the iron oxide nanosheets are promoted under the radiation of periodic terahertz waves, realizing the inversion of Fe(III) and Fe(III<supgt;‑< / supgt;). The polarization relaxation induced by the valence inversion significantly enhances the terahertz wave absorption performance, and the highest absorption shielding efficiency at a frequency of 1.39 THz is up to 96.72 dB. This material has the advantages of light weight, ultrathin and strong absorption, and has important value in the fields of terahertz signal shielding of microelectronic devices, stealth coatings, etc.

Description

Technical Field

[0001] The present invention belongs to the field of terahertz wave absorption, and particularly relates to a composite material of iron oxide-coated carbon microtubes and its application in terahertz wave absorption. Background Art

[0002] Terahertz waves have frequencies between infrared and microwave. Due to their comprehensive advantages such as high bandwidth, material fingerprinting, and penetrability, they are important information media for moving towards the intelligent era and realizing visions such as intelligent interconnection, multi-dimensional perception, and human-computer interaction, and have important application values in fields such as communication, astronomy, and analytical science. However, with the rapid development of wireless communication technology and the wide application of electronic devices, terahertz wave radiation seriously threatens human health and damages the operation and lifespan of precision electrical equipment. Terahertz wave absorption materials can dissipate terahertz waves inside the material in the form of heat through various attenuation mechanisms, and have received increasing attention in preventing electromagnetic pollution. They need to meet the requirements of being lightweight, ultra-thin, and having strong absorption performance to match the miniaturization of electronic products and ultra-thin coating technology.

[0003] Carbon nanotubes are similar to rolled-up graphene sheets and have excellent electronic properties, mechanical strength, and light weight, etc., so they are widely used as electromagnetic wave absorption materials. However, the wavelength of terahertz waves ranges from 30 μm to 3 mm, which is much larger than the nanoscale, making it difficult to promote the resonance absorption and attenuation of terahertz waves through multiple scattering / reflection in carbon nanotubes. For iron oxide, although it has excellent electron migration efficiency and pseudocapacitance characteristics of high-speed redox, it is difficult for traditional bulk materials to achieve efficient electron transfer.

[0004] The significant advantages of heterointerfacial engineering and its unique electromagnetic properties provide support for designing efficient and fast-response electromagnetic absorption materials. However, there are still great challenges in utilizing and strengthening these interfacial effects from both microscopic and macroscopic perspectives.

[0005] Terahertz waves are composed of rapidly oscillating electric and magnetic fields. The key factors determining the terahertz wave dissipation performance of absorption materials are their dielectric or magnetic loss capabilities. Dielectric loss is one of the important loss mechanisms, and its diversity and complexity provide opportunities for seeking strong absorption. At present, it has been confirmed that although single-component absorbers have a certain terahertz wave absorption ability, due to their limited attenuation mechanisms and difficult control of electromagnetic parameters, they cannot meet the requirements of ideal terahertz wave absorption. Therefore, in order to improve the terahertz wave absorption performance, the commonly adopted strategies are: building a conduction network, dielectric-magnetic loss synergistic effect, component optimization, etc. The mechanism is mainly due to adjustable electromagnetic parameters, controllable impedance matching, and significant synergistic effects between different components.

[0006] So far, the research on terahertz absorption materials generally falls into two aspects: on the one hand, the research on artificial metamaterials. The essence of metamaterials is composed of several materials with narrow-band absorption through different design and assembly. However, most metamaterials are difficult to achieve broadband absorption performance and have problems such as complex design, expensive manufacturing, and time-consuming. On the other hand, the research on carbon-based materials, such as carbon nanotubes or graphene and other materials. However, these materials will cause strong surface reflection due to reasons such as interface mismatch, greatly reducing the terahertz absorption performance. Summary of the Invention

[0007] The object of the present invention is to provide a composite material of iron oxide-coated carbon microtubes and its application in terahertz wave absorption to solve the problem that existing terahertz wave absorption materials are difficult to provide efficient polarization relaxation loss and have limited wave absorption performance.

[0008] The technical solution of the present invention is: a composite material of iron oxide-coated carbon microtubes, which is a composite with a unique heterostructure constructed by coating carbon microtubes with iron oxide nanosheets, and the (110) plane of the iron oxide nanosheets is combined with the carbon microtubes.

[0009] Preferably, the carbon microtubes are helical structures formed by continuous high-temperature carbonization and curling of biomass carbon fibers, with a diameter of 4-12 μm, a pitch of 5-45 μm, and a wall thickness of 0.8±0.1 μm.

[0010] Preferably, the iron oxide nanosheets are oxidized from two-dimensional iron sulfide as a precursor, with a planar size of 200-300 nm and a thickness of 40.7±0.1 nm.

[0011] Preferably, the mass fraction of iron oxide nanosheets in the composite material of iron oxide-coated carbon microtubes is 40-70%, preferably 60%.

[0012] The preparation method of the above-mentioned composite material of iron oxide-coated carbon microtubes is as follows:

[0013] Step 1: Wash and dry natural cotton pads, and carbonize them at 600±20 °C for 4-6 h at a certain heating rate in an inert atmosphere to obtain helical carbon microtubes;

[0014] Step 2: Dissolve anhydrous ferrous chloride powder and thiourea in an ethylene glycol solution, dropwise add an aqueous solution of sodium citrate, add the helical carbon microtubes described in Step 1, stir evenly under a protective gas, and then transfer them to a high-pressure reaction kettle and react at 210±10 °C for 12-14 h;

[0015] Step 3: After the reaction, wash the sample and oxidize it at 90±10 °C for 24-36 h under an oxygen flow of 50 sccm to obtain the composite material of iron oxide-coated carbon microtubes.

[0016] Preferably, in step 1, the inert atmosphere is Ar gas; the heating rate is 10 °C / min.

[0017] Preferably, in step 2, the mass ratio of the helical carbon microtubes to anhydrous ferrous chloride depends on the mass fraction of the iron oxide nanosheets in the obtained iron oxide-coated carbon microtube composite material. The mass ratio of thiourea to anhydrous ferrous chloride is 1:1; the concentration of the sodium citrate aqueous solution added is 0.1 wt%, and the mass ratio of sodium citrate to anhydrous ferrous chloride is 1:1; high-purity argon gas with a purity of 99.999% is used as the protective gas.

[0018] The present invention provides the application of the above iron oxide-coated carbon microtube composite material in terahertz wave absorption.

[0019] The present invention also provides a terahertz wave absorption material, which is the above iron oxide-coated carbon microtube composite material. The absorption material has an effective shielding efficiency (shielding efficiency ≥ 10 dB) within 0.2 - 1.8 THz.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention relates to an iron oxide-coated carbon microtube and its application in terahertz wave absorption. The advantage of carbon microtubes compared to carbon nanotubes is that the size of carbon microtubes better matches terahertz waves. Through the continuous medium dynamics equation, its intrinsic vibration frequency is calculated to be in the range of 0.2 - 1.8 THz, so it can promote resonance loss. At the same time, its high electron mobility is beneficial to the transfer of electrons to other heterostructure materials, which can enhance the conduction loss of terahertz waves; Fe(III) of iron oxide has a stable d-shell (5 electrons in the d layer) configuration, and its electron cloud is inversion symmetric; due to the matching of the Fermi level of carbon microtubes with the energy level of the conduction band of iron oxide, under the radiation of periodic terahertz waves, electrons on the carbon microtubes will be injected into and released from the iron oxide nanosheets. The injection / release of electrons causes the valence of Fe atoms to change between Fe(III) and Fe(III-), and the excess electrons destroy the symmetrically distributed electron cloud, promoting terahertz wave absorption in the form of polarization relaxation. The results show that when the thickness of the pressed sample is 2 mm, the material with the best ratio exhibits effective shielding efficiency (shielding efficiency ≥ 10 dB) throughout the test range of 0.2 - 1.8 THz. The shielding efficiency can reach 97.72 dB at 1.39 THz, and the average terahertz shielding efficiency reaches 71.8 dB. And most of the shielding efficiency comes from the absorption of the material, and the reflection shielding efficiency accounts for a very small proportion in the total shielding efficiency. Description of the Drawings

[0021] Figure 1 It is the total shielding efficiency diagram of the helical carbon microtubes within the range of 0.2 - 1.8 THz.

[0022] Figure 2 It is a schematic diagram of the energy levels of carbon microtubes and iron oxide obtained by first-principles calculations.

[0023] Figure 3 In (a) is the scanning electron microscope image of the iron oxide-coated carbon microtube composite; (b) is the scanning electron microscope image of the local iron oxide nanosheets; (c) is the selected area diffraction of the iron oxide-coated carbon microtube composite; (d) is the X-ray diffraction pattern of the carbon microtubes and the iron oxide-coated carbon microtube composite.

[0024] Figure 4 It is the total shielding effectiveness diagram of the iron oxide-coated carbon microtubes with a thickness of 2 mm in the range of 0.2 - 1.8 THz.

[0025] Figure 5 In (a) are the absorption shielding effectiveness diagrams of the iron oxide-coated carbon microtube films with thicknesses of 1 mm and 2 mm respectively, and (b) is the reflection shielding effectiveness diagram.

[0026] Figure 6 In (a) are the total shielding effectiveness diagrams of the iron oxide-coated carbon microtubes with iron oxide mass fractions of 40%, 50% and 70% respectively in the range of 0.2 - 1.8 THz, and (b) is the average shielding effectiveness diagram in the range of 0.2 - 1.8 THz. Specific implementation manners

[0027] The natural cotton pads of the present invention are washed, dried, and carbonized at 600 °C for 4 h at a certain heating rate in an inert atmosphere to obtain spiral carbon microtubes. There are reports in the literature that the stress generated by continuous heating of carbon nanotubes will form a spiral structure, but no literature has been found reporting the preparation of spiral carbon microtubes similar to those in the present invention. The spiral shape of the present invention is formed by the stress generated by continuous heating of natural cotton pads at high temperature. The present invention constructs a unique heterostructure composite by combining the (110) plane of iron oxide with carbon microtubes. Due to the energy level matching between the Fermi level of carbon microtubes and the conduction band of iron oxide, the periodic injection and release of electrons on carbon microtubes to iron oxide nanosheets are promoted under the radiation of periodic terahertz waves, realizing the inversion of Fe(III) and Fe(III-), and the polarization relaxation induced by valence inversion significantly enhances the terahertz wave absorption performance. The present invention prepares high-performance absorption materials based on the physical properties of the materials themselves. The carbon microtubes coated with iron oxide prepared by the present invention exhibit excellent terahertz wave absorption performance in the range of 0.2 - 1.8 THz due to the change of their inherent dipole moment. The filler used for the terahertz wave absorption in the range of 0.2 - 1.8 THz is high-density polyethylene, and the corresponding filling ratio of the composite material is 20 - 80 wt% (preferably 60 wt%). The terahertz wave absorption performance in the range of 0.2 - 1.8 THz is obtained by terahertz time-domain spectroscopy. Through the terahertz time-domain spectroscopy system, the electrical and magnetic properties of the material itself can be obtained, and the shielding and absorption performance of terahertz waves can be obtained through the refractive index and extinction coefficient of the material.

[0028] There are no specific restrictions on the sources of the raw materials and instruments used in the examples. They can be purchased on the market or prepared by conventional methods well-known to those skilled in the art. Based on the examples in the present invention, all other examples obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0029] It should be noted that for the natural cotton pads involved in the present invention, there are no special regulations on the sources and purchase channels. That is, the inventor has tried several manufacturers, and the natural cotton pads produced by them can all be used to prepare the spiral carbon microtubes described in the present invention. The natural cotton pads used in the following examples are purchased from Suzhou Linglan Medical Supplies Co., Ltd.

[0030] Example 1

[0031] The natural cotton pads were washed with absolute ethanol and deionized water and then placed in a vacuum drying oven to be dried for 12 h. After drying, they were placed in a quartz tube with a diameter of 2 cm at intervals of 10 cm (the main component of the natural cotton pads is biomass carbon, and its internal organic components will be released during the high-temperature carbonization process. An interval of 10 cm is to allow the organic substances therein to volatilize fully. If they are stacked too densely, it may cause blockage, resulting in the failure to release the internal organic components or their attachment to the surface of the carbon microtubes), and the quartz tube was placed at the center of the upstream and downstream temperature zones of the tube furnace. Argon was introduced at 50 sccm, and carbonization was carried out at 600 °C for 4 h at a heating rate of 10 °C / min. The carbon microtubes were continuously heated at 600 °C to generate stress, and spiral carbon microtubes were obtained. The spiral carbon microtubes have a spiral structure formed by the continuous high-temperature carbonization and curling of natural cotton pads, with a diameter of 4 - 12 μm, a pitch of 5 - 45 μm, and a wall thickness of 0.8 ± 0.1 μm.

[0032] The spiral carbon microtubes obtained in Example 1 were analyzed for their terahertz wave absorption performance in the range of 0.2 - 1.8 THz using a scanning electron microscope, X-ray diffraction.

[0033] As Figure 1 shown in (a) and (b) therein, the spiral carbon microtubes have a spiral structure formed by the continuous high-temperature carbonization and curling of biomass carbon fibers, with a diameter of 4 - 12 μm, a pitch of 5 - 45 μm, and a wall thickness of 0.8 ± 0.1 μm; as Figure 1 shown in (c) therein, the two XRD diffraction peaks are located at 2θ = 25.6° and 43.2°, corresponding to the (002) and (103) planes of the carbon microtubes respectively. As Figure 1 shown in (d) therein, when the coating thickness is 2 mm, the effective shielding efficiency range of the spiral carbon microtubes in the 0.2 - 1.8 THz band can reach 90.62% (shielding efficiency ≥ 10 dB), the highest shielding efficiency can reach 48.87 dB at 1.80 THz, and the average shielding efficiency in the entire test range reaches 27.42 dB.

[0034] Example 2

[0035] 100 mg of anhydrous ferrous chloride powder and 100 mg of thiourea were dissolved in 40 ml of ethylene glycol solution, 2 ml of sodium citrate aqueous solution (with a concentration of 0.1 wt%) was added dropwise, 30 mg of the carbon microtubes prepared in Example 1 was added, and after magnetic stirring for 30 min under an Ar gas flow, it was transferred to a 50 mL autoclave and reacted at 210 °C for 12 h to obtain an iron oxide-coated carbon microtube composite with an iron oxide mass fraction of 60%; the reacted sample was washed 3 times each with deionized water and ethanol, and oxidized at 80 °C for 24 h under an oxygen flow of 50 sccm to obtain an iron oxide nanosheet-coated carbon microtube composite. The sodium citrate aqueous solution and metal cations (Fe 2+) It has good complexing ability and can prevent the aggregation of Fe in the experiment to obtain bulk materials. Thus, two-dimensional FeS nanosheets are first obtained by hydrothermal reaction, and then iron oxide nanosheets are obtained by oxidizing them. 2+ To study the electron transfer driving force on the iron oxide-coated carbon microtube composite material, the energy level structure of this absorption material was studied.

[0036] The composite material is a unique heterostructure composite formed by coating carbon microtubes with iron oxide nanosheets. The so-called "unique" heterostructure lies in that the conduction band of the (110) plane of the iron oxide nanosheets is well matched with the Fermi level of the carbon tubes (as

[0037] ) After the heterojunction interface between the two is established, the electrons on the carbon tubes can easily transfer to the (110) plane of the iron oxide nanosheets. The energy level schematic diagram of the carbon microtube absorption material coated with iron oxide nanosheets is as Figure 2 shown: The work function of the carbon microtube obtained by first-principles calculation is 4.66 eV; the work function of the (110) plane of iron oxide is 5.66 eV, and the bandwidth is 2.05 eV. Since iron oxide is an n-type semiconductor, its Fermi level is closer to the conduction band. Therefore, the Fermi level of the heterojunction interface formed by the carbon microtube and the (110) plane of iron oxide can transfer electrons with the conduction band of iron oxide, realizing the injection and release of electrons from the carbon microtube to the (110) plane of iron oxide in a periodic electromagnetic field, making the valence of Fe atoms change between Fe(III) and Fe(III-), and the excess electrons destroy the symmetrically distributed electron cloud. Figure 2 The composite material obtained in Example 2 was analyzed using a scanning electron microscope, a transmission electron microscope, and X-ray diffraction.

[0038] The electron microscope image of the iron oxide-coated carbon microtube composite material is as shown in (a) of

[0039] Figure 3 Figure 3 and presents a helical structure; Figure 3 (b) in Figure 3 shows that the iron oxide nanosheets on the composite material have regular shapes and nanoscale thicknesses; by selecting the diffraction Figure 3 (c) in

[0040] diffraction spots corresponding to the (002) plane of the carbon microtube and the (110) plane of iron oxide were found;

[0041] X-ray diffraction in (d) shows that the carbon microtube and iron oxide have good crystallinity, and the (110) plane of iron oxide is dominant, and there are no other impurity components.

[0040] The terahertz wave absorption performance of the iron oxide-coated carbon microtube composite material obtained in Example 2 was analyzed in the range of 0.2 - 1.8 THz.

[0041] The test of the terahertz wave absorption performance of the iron oxide-coated carbon microtube composite material in the range of 0.2 - 1.8 THz was carried out through a terahertz time-domain spectroscopy system. The filler used was high-density polyethylene, and the filling ratio of the composite material (mass ratio of the composite material) was 60 wt%. Weigh 100 mg in total of the composite material (60 mg) and high-density polyethylene (40 mg), grind and mix them thoroughly in a mortar, and then transfer them to a tablet mold and press them into a 2-mm-thick sample under a pressure of 10 MPa. Through the terahertz time-domain spectroscopy signal, the refractive index, extinction coefficient, complex dielectric constant, etc. of the material itself can be obtained. And the shielding effectiveness of materials with different thicknesses can be calculated through the refractive index and extinction coefficient.

[0042] For the iron oxide-coated carbon microtube composite material, under the radiation of terahertz waves, the electron transfer between the carbon microtubes and the iron oxide nanosheets causes the electrons on the carbon microtubes to be periodically injected and released to the (110) plane of the iron oxide nanosheets. Since the polarization induced by the atomic valence inversion cannot follow the transformation of the high-frequency terahertz waves, this will enhance the absorption and shielding of terahertz waves through polarization relaxation.

[0043] For the iron oxide-coated carbon microtube composite material, the total shielding effectiveness of the obtained iron oxide-coated carbon microtube composite material in the range of 0.2 - 1.8 THz and as Figure 4 shown in: when the coating thickness is 2 mm, the material with the optimal ratio shows effective shielding effectiveness (shielding effectiveness ≥ 10 dB) throughout the entire test range of 0.2 - 1.8 THz, and the shielding effectiveness can reach 96.12 dB at 1.39 THz. The terahertz shielding effectiveness of the iron oxide-coated carbon microtube composite material is divided into absorption shielding effectiveness and reflection shielding effectiveness. Figure 5 In (a) of [], it is the absorption shielding effectiveness diagram of the material with the optimal ratio at thicknesses of 1 mm and 2 mm, and the highest can reach 47.14 dB and 96.72 dB at 1.39 THz. Figure 5 In diagram (b) of [], it is the reflection shielding effectiveness diagram at coating thicknesses of 1 mm and 2 mm, and the highest only reaches 0.395 dB, proving that the shielding effectiveness in the terahertz band mainly comes from the absorption of the material.

[0044] Example 3

[0045] Example 3 presents carbon microtube composites coated with iron oxide in different proportions. Specifically, 44.6 mg, 66.7 mg, and 155.4 mg of anhydrous ferric chloride and thiourea (the mass ratio of anhydrous ferric chloride to thiourea is 1:1) were dissolved in 40 ml of ethylene glycol solution, and an aqueous solution of sodium citrate with a concentration of 0.1 wt% (the mass ratio of anhydrous ferric chloride to sodium citrate is 1:1) was added. Then, 30 mg of the carbon microtubes prepared in Example 1 were added. After magnetic stirring for 30 min under an Ar flow, the mixture was transferred to a 50 mL autoclave and reacted at 210 °C for 12 h to obtain carbon microtube composites coated with iron oxide with mass fractions of iron oxide of 40%, 50%, and 70% respectively. The terahertz wave absorption performance was analyzed in the range of 0.2 - 1.8 THz (marked as 40%, 50%, and 70%-Fe2O3@CMT respectively in (a) of Figure 6 ). When the coating thickness is 2 mm, the shielding effectiveness of the 40%-Fe2O3@CMT composite can reach up to 57.65 dB at most, the effective shielding effectiveness range can reach 88.12%, and the average shielding effectiveness is 30.66 dB. The effective shielding effectiveness of 50%-Fe2O3@CM and 70%-Fe2O3@CMT can reach 100% in the test band, the maximum shielding effectiveness can reach 59.46 dB and 72.15 dB respectively, and the average absorption effectiveness can reach 39.67 dB and 53.91 dB respectively. Figure 6 Figure (b) in shows the average shielding effectiveness of carbon microtube composites coated with iron oxide in different proportions at 1 mm and 2 mm in the range of 0.2 - 1.8 THz. The average shielding effectiveness of the composite with the best proportion can reach 35.91 dB when the thickness is 1 mm and 71.8 dB when the thickness is 2 mm. It can be found from the experimental data that the composite with an iron oxide mass fraction of 60% in the example has the best performance and excellent terahertz shielding effectiveness.

Claims

1. A composite material of iron oxide-coated carbon microtubes, characterized in that, The composite material is a composite with a unique heterostructure constructed by carbon microtubes coated with iron oxide nanosheets, and the (110) plane of the iron oxide nanosheets is combined with the carbon microtubes; It is prepared by the following steps: Step 1: Wash and dry natural cotton pads, and carbonize them in an inert atmosphere at 600±20 °C for 4-6 h to obtain helical carbon microtubes; Step 2: Dissolve anhydrous ferrous chloride powder and thiourea in an ethylene glycol solution, add an aqueous sodium citrate solution dropwise, add the helical carbon microtubes described in Step 1, stir evenly under a protective gas, and then transfer them to a high-pressure reactor, and react at 210±10 °C for 12-14 h; Step 3: After the reaction is completed, wash the sample, and oxidize it at 90±10 °C under an oxygen flow for 24-36 h to obtain an iron oxide-coated carbon microtube composite material.

2. The iron oxide-coated carbon microtube composite material according to claim 1, wherein The carbon microtubes are helical structures formed by continuous high-temperature carbonization and curling of biomass carbon fibers, with a diameter of 4-12 μm, a pitch of 5-45 μm, and a wall thickness of 0.8±0.1 μm.

3. The iron oxide-coated carbon nanotube composite material according to claim 1, characterized in that, The iron oxide nanosheets are oxidized from two-dimensional iron sulfide as a precursor, with a planar size of 200-300 nm and a thickness of 40.7±0.1 nm.

4. The iron oxide-coated carbon microtube composite material according to claim 1, characterized in that In the iron oxide nanosheet-coated carbon microtube composite material, the mass fraction of the iron oxide nanosheets is 40-70%, preferably 60%.

5. The preparation method of the iron oxide-coated carbon nanotube composite material according to any one of claims 1-4, characterized in that, The steps are as follows: Step 1: Wash and dry natural cotton pads, and carbonize them in an inert atmosphere at 600±20 °C for 4-6 h to obtain helical carbon microtubes; Step 2: Dissolve anhydrous ferrous chloride powder and thiourea in an ethylene glycol solution, add an aqueous sodium citrate solution dropwise, add the helical carbon microtubes described in Step 1, stir evenly under a protective gas, and then transfer them to a high-pressure reactor, and react at 210±10 °C for 12-14 h; Step 3: After the reaction is completed, wash the sample, and oxidize it at 90±10 °C under an oxygen flow for 24-36 h to obtain an iron oxide-coated carbon microtube composite material.

6. The method according to claim 5, wherein In Step 2, the mass ratio of thiourea to anhydrous ferrous chloride is 1:1; the concentration of the aqueous sodium citrate solution added dropwise is 0.1 wt%, and the mass ratio of sodium citrate to anhydrous ferrous chloride is 1:1; high-purity argon with a purity of 99.999% is used as the protective gas.

7. Application of the iron oxide-coated carbon microtube composite material according to any one of claims 1-4 in terahertz wave absorption.

8. A terahertz wave absorbing material, characterized in that, The absorbing material is the iron oxide-coated carbon microtube composite material according to any one of claims 1-4.

9. The terahertz wave absorbing material according to claim 8, characterized in that, The absorbing material has effective shielding efficiency within 0.2-1.8 THz.

10. The terahertz wave absorbing material according to claim 8, characterized in that, The average terahertz shielding efficiency of the absorbing material within 0.2-1.8 THz is greater than 70 dB.

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