A terahertz shield and its preparation method and application

Abstract

The present invention discloses a terahertz shield, its preparation method, and application, belonging to the field of terahertz wave shielding materials. The present invention comprises thoroughly mixing 100-105 parts by mass of hydroxy silicone oil (PDMS-OH) and 20-25 parts by mass of hydrogenated silicone oil (PDMS-H) to obtain a premix, then thoroughly mixing the premix with a Karstedt catalyst and 40-45 parts by mass of vinyl silicone oil (PDMS-Vi) to form a composite medium. Finally, the composite medium is placed in a mold for foaming and curing to obtain a terahertz shield. The terahertz shield has an absorptivity exceeding 99.9% for terahertz waves in the 0.4-1.4 THz terahertz band, an absorption shielding effectiveness exceeding 62.7 dB, and a reflection shielding effectiveness less than 0.01 dB. The present invention has broad application prospects in systems such as terahertz detection, terahertz communication, and terahertz sensing.

Description

Technical Field

[0001] The present invention belongs to the field of terahertz wave shielding materials, and in particular relates to a terahertz shield and a preparation method and application thereof. Background Art

[0002] Terahertz waves have shown significant application prospects in biosensing, security imaging, and wireless communications. In recent years, terahertz technology has garnered widespread attention worldwide. With the increasing popularity of terahertz electronic devices and the advancement of communications technology, the issue of electromagnetic radiation has become increasingly prominent. Electromagnetic interference not only affects the normal operation and service life of equipment but also poses a threat to human health. Consequently, research on electromagnetic shielding devices has garnered significant attention, with applications in areas such as electromagnetic radiation shielding and interference suppression. Metal materials, due to their high strength and conductivity, have long been the traditional choice for electromagnetic interference shielding. However, their high density, poor flexibility, and corrosion resistance have limited their widespread use, especially in extreme environments. It is worth noting that metal materials, primarily based on reflection as a shielding mechanism, cannot completely eliminate electronic interference. Reflected electromagnetic waves still have a certain impact on the environment, causing secondary pollution. With the rapid development of 6G communication technology, mobile terminals and base stations are generating significant incremental demand for electromagnetic shielding and thermal conductivity products. However, due to the short wavelength and high transmission loss of terahertz waves, these materials present both opportunities and challenges. With trends like automotive electrification and the large-scale antenna arrays of 6G communications, traditional electromagnetic shielding struggles to meet the demands of terahertz waves. Consequently, the development of shields capable of addressing high-frequency, high-speed electromagnetic interference is crucial. Terahertz waves have poor penetration and significant attenuation, significantly reducing their coverage. 6G communications place high demands on signal interference resistance, necessitating a large number of electromagnetic shields. Therefore, terahertz shields with high absorption, low reflection, low cost, and excellent flexibility play a crucial role in the application and development of terahertz technology. Summary of the Invention

[0003] The purpose of the present invention is to overcome the technical defects existing in the above-mentioned background technology and provide a terahertz shield and its preparation method and application.

[0004] In order to achieve the above object, the technical solution of the present invention is as follows:

[0005] In a first aspect, the present invention provides a method for preparing a terahertz shield, comprising thoroughly mixing 100 to 105 parts by mass of hydroxy silicone oil (PDMS-OH) and 20 to 25 parts by mass of hydrogenated silicone oil (PDMS-H) to obtain a premix, then thoroughly mixing the premix with a Karstedt catalyst and 40 to 45 parts by mass of vinyl silicone oil (PDMS-Vi) to form a composite medium, and finally placing the composite medium in a mold for foaming and curing to obtain a terahertz shield.

[0006] Based on the technical solution disclosed in the first aspect above, the present invention can further provide the following preferred solutions, and if there is no conflict, the preferred solutions can be combined with each other.

[0007] As a preferred embodiment of the first aspect, a graphene oxide aqueous solution is further added when preparing the premix, and the mass percentage of graphene oxide in the final composite medium is 0.05% to 0.1%.

[0008] As a preference for the first aspect above, the mass percentage of the graphene oxide in the final composite medium is 0.05%.

[0009] As a preferred embodiment of the first aspect, the concentration of the Karstedt catalyst in the composite medium is 10-100 ppm.

[0010] As a preferred embodiment of the first aspect, when preparing the premix, the materials are fully mixed by centrifugation, the centrifugal speed is 30π-50π rad / s, and the centrifugal mixing time is 5-20 min.

[0011] As a preferred embodiment of the first aspect, when preparing the composite medium, the materials are fully mixed by centrifugation, the centrifugal speed is 300π~500π rad / s, and the centrifugal mixing time is 1~5 min.

[0012] As a preferred embodiment of the first aspect, during the foaming process, the mold containing the composite medium is placed in an environment of 20° C. to 28° C. for foaming, and the foaming time is 10 to 30 minutes.

[0013] As a preferred embodiment of the first aspect, during the curing process, the mold containing the composite medium is placed in a hot air circulation dryer for drying and curing, and the curing time is 2 to 4 hours.

[0014] In a second aspect, the present invention provides a terahertz shield prepared according to the preparation method described in any one of the solutions in the first aspect.

[0015] As a preferred embodiment of the second aspect, the thickness of the terahertz shield is 2-20 mm.

[0016] In a third aspect, the present invention provides an application of the terahertz shielding device described in the second aspect as a protective layer or protective shell to shield a device from terahertz waves.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1) The terahertz shielding device fabricated by this invention has excellent terahertz shielding properties. In the 0.4-1.4THz terahertz wave band, the absorption rate for terahertz waves reaches 99.9%, the reflectivity is less than 0.01%, the reflection shielding effectiveness is less than 0.01dB, and the maximum absorption shielding effectiveness is over 62.7dB.

[0019] 2) The terahertz shielding device fabricated with graphene oxide in this invention can enhance its terahertz shielding effectiveness. Due to graphene oxide's unique two-dimensional sheet structure, the van der Waals forces between the layers, and the π-π stacking effect, graphene oxide forms a conductive network within the composite material. Under terahertz electromagnetic radiation, this conductive network allows free electrons to migrate through the material, generating current or an electric dipole moment. This process effectively absorbs terahertz wave energy and converts it into heat, achieving strong terahertz wave absorption. Furthermore, the conductive electrons not only absorb terahertz wave energy but also scatter some of the electromagnetic wave through a scattering mechanism. Ultimately, the porous structure of the terahertz shield's dielectric causes the scattered electromagnetic wave to undergo multiple scatterings, resulting in energy loss and enhancing the material's absorption. Graphene oxide generates a thermal effect when absorbing electromagnetic waves, while the methyl foam structure formed by the remaining components effectively dissipates and disperses heat, preventing localized overheating and maintaining the material's stability.

[0020] 3) The material of the terahertz shield prepared by the present invention also has certain flame retardancy, which can effectively hinder the combustion rate of the composite medium under extreme conditions such as fire and ultra-high temperature.

[0021] 4) The terahertz shielding device prepared by the present invention has the advantages of simple manufacturing process, low manufacturing cost, high shielding effectiveness and excellent flame retardancy. At the same time, it can perform terahertz shielding operations in a wide temperature range of -100°C to 300°C, demonstrating its potential application value under extreme conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 These are optical photographs of three terahertz shield samples in the embodiments of the present invention, (a) is the terahertz shield sample prepared in Example 1, (b) is the terahertz shield sample prepared in Example 2, and (c) is the terahertz shield sample prepared in Example 3;

[0023] Figure 2 is the terahertz time domain spectrum of the terahertz shield prepared in Examples 1 to 3;

[0024] Figure 3 is the terahertz frequency domain spectrum of the terahertz shield prepared in Examples 1 to 3;

[0025] Figure 4is the terahertz absorption coefficient curve of the terahertz shield prepared in Examples 1 to 3;

[0026] Figure 5 is a diagram of the terahertz absorption and shielding effectiveness of the terahertz shields prepared in Examples 1 to 3;

[0027] Figure 6 is a diagram of the terahertz reflection shielding effectiveness of the terahertz shields prepared in Examples 1 to 3;

[0028] Figure 7 3 is a diagram of the total terahertz shielding effectiveness of the terahertz shields prepared in Examples 1 to 3. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in the various embodiments of the present invention can be combined accordingly without conflicting with each other.

[0030] This invention uses three silicone oils, graphene oxide (GO), and Karstedt catalyst to prepare a terahertz shield. Graphene oxide is an optional component. The three silicone oils are hydroxy silicone oil (PDMS-OH), hydrogen silicone oil (PDMS-H), and vinyl silicone oil (PDMS-Vi).

[0031] The molecular formula of hydroxy silicone oil (PDMS-OH) is as follows:

[0032]

[0033] The molecular formula of hydrogenated silicone oil (PDMS-H) is as follows:

[0034]

[0035] The molecular formula of vinyl silicone oil (PDMS-Vi) is as follows:

[0036]

[0037] The three silicone oils, graphene oxide (GO) and Karstedt catalyst are all existing commercially available materials, and commercial reagents can be used.

[0038] In a preferred embodiment of the present invention, a method for preparing a terahertz shield is provided. The method comprises: thoroughly mixing 100-105 parts by mass of hydroxy silicone oil (PDMS-OH) and 20-25 parts by mass of hydrogenated silicone oil (PDMS-H) to obtain a premix; then thoroughly mixing the premix with a Karstedt catalyst and 40-45 parts by mass of vinyl silicone oil (PDMS-Vi) to form a composite medium; and finally placing the composite medium in a mold for foaming and curing to obtain the terahertz shield.

[0039] In another embodiment of the present invention, another method for preparing a terahertz shield incorporating graphene oxide is provided, wherein the method comprises the following steps:

[0040] 100-105 parts by mass of hydroxy silicone oil (PDMS-OH), 20-25 parts by mass of hydrogenated silicone oil (PDMS-H) and a graphene oxide aqueous solution were fully mixed to obtain a premix. The premix was then fully mixed with a Karstedt catalyst and 40-45 parts by mass of vinyl silicone oil (PDMS-Vi) to form a composite medium. Finally, the composite medium was placed in a mold for foaming and curing to obtain a terahertz shield.

[0041] Both approaches, with and without the addition of graphene oxide, can produce terahertz shielding devices. In general, without the addition of graphene oxide, the resulting terahertz shield is composed of pure methyl foam; with the addition of graphene oxide, the resulting terahertz shield is a composite of methyl foam and graphene oxide, offering improved terahertz shielding performance.

[0042] In the above two solutions of the present invention, the specific materials and parameters in the preparation process are preferably as follows:

[0043] For the added Karstedt catalyst, the concentration of the Karstedt catalyst in the composite medium is 10 to 100 ppm. When preparing the above-mentioned premix, the materials can be thoroughly mixed by centrifugation, the centrifugal speed is 30π to 50π rad / s, and the centrifugal mixing time is 5 to 20 minutes. When preparing the composite medium, the materials can also be thoroughly mixed by centrifugation, the centrifugal speed is 300π to 500π rad / s, and the centrifugal mixing time is 1 to 5 minutes. During the foaming process, the mold containing the composite medium can be placed in an environment of 20°C to 28°C for foaming, and the foaming time is 10 to 30 minutes. During the curing process, the mold containing the composite medium can be placed in a hot air circulation dryer for drying and curing, and the curing time is 2 to 4 hours.

[0044] More preferably, the concentration of the Karstedt catalyst in the composite medium is 10-20 ppm. When preparing the premix, the mixture was stirred at 34πrad / s for 10 minutes in a centrifuge. When preparing the composite medium, the mixture was stirred at 400πrad / s for 1 minute in a centrifuge. During the foaming process, the mold containing the composite medium was placed in a 23°C environment for 20 minutes. During the curing process, the mold was placed in a hot air circulation dryer for 3.5 hours of drying and curing.

[0045] It should be noted that during the foaming and curing process, the terahertz shield can be manufactured into different shapes, such as a layer or shell, depending on the application scenario. This can be achieved by designing a corresponding mold. The terahertz shield prepared by the present invention can be used as a protective layer or protective shell to shield equipment from terahertz waves.

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the embodiments.

[0047] Example 1

[0048] A lightweight and efficient terahertz shield of pure methyl foam was prepared according to the following steps:

[0049] 500g of hydroxy silicone oil (PDMS-OH) and 100g of hydrogen silicone oil (PDMS-H) were preliminarily mixed and stirred in a centrifuge at 34πrad / s for 10 minutes to form a premix. 200g of vinyl silicone oil (PDMS-Vi) and 0.015g of Karstedt's catalyst were then preliminarily mixed with the premix and stirred in a centrifuge at 40πrad / s for 1 minute to thoroughly mix and form a composite medium. The composite medium was placed in a mold and foamed at room temperature (23°C) for 20 minutes. After foaming, it was transferred to a hot air circulating dryer and dried for 3.5 hours to complete the preparation of the terahertz shield.

[0050] In this example, the mass ratio of hydroxy silicone oil (PDMS-OH), hydrogen silicone oil (PDMS-H) and vinyl silicone oil (PDMS-Vi) is 100:20:40, and the Karstedt catalyst accounts for 10-20ppm of the total mass of the composite medium. The final terahertz shielding sample prepared is a layer with a thickness of 10mm. The optical photograph of the sample is shown in Figure 2. Figure 1 As shown in part (a) of .

[0051] Example 2

[0052] A lightweight and efficient terahertz shielding device made of methyl foam and 0.05% graphene oxide was prepared according to the following steps:

[0053] 500g of hydroxy silicone oil (PDMS-OH), 100g of hydrogenated silicone oil (PDMS-H), and 22g of a 1.9wt% graphene oxide aqueous solution were initially mixed and stirred in a centrifuge at 34πrad / s for 10 minutes to form a premix. 200g of vinyl silicone oil (PDMS-Vi) and 0.015g of Karstedt's catalyst were then added to the premix and stirred in a centrifuge at 40πrad / s for 1 minute to form a composite medium. The composite medium was placed in a mold and foamed at room temperature (23°C) for 20 minutes. After foaming, it was transferred to a hot air circulating dryer and dried for 3.5 hours to complete the preparation of the terahertz shield.

[0054] In this example, the mass ratio of hydroxy silicone oil (PDMS-OH), hydrogen silicone oil (PDMS-H) and vinyl silicone oil (PDMS-Vi) is 100:20:40, graphene oxide accounts for 0.05% of the total mass of the composite medium, and Karstedt catalyst accounts for 10-20ppm of the total mass of the composite medium. The final terahertz shielding sample prepared is a layer with a thickness of 10mm. The optical photograph of the sample is shown below. Figure 1 As shown in part (b) of .

[0055] Example 3

[0056] A lightweight and efficient terahertz shielding device made of methyl foam and 0.1% graphene oxide was prepared according to the following steps:

[0057] 500g of hydroxy silicone oil (PDMS-OH), 100g of hydrogenated silicone oil (PDMS-H), and 45g of a 1.9wt% aqueous solution of graphene oxide were initially mixed and stirred in a centrifuge at 34πrad / s for 10 minutes to form a premix. 200g of vinyl silicone oil (PDMS-Vi) and 0.015g of Karstedt's catalyst were then initially mixed with the premix and stirred in a centrifuge at 40πrad / s for 1 minute to thoroughly mix and form a composite medium. The composite medium was placed in a mold and foamed at room temperature (23°C) for 20 minutes. After foaming, it was transferred to a hot air circulating dryer and dried for 3.5 hours to complete the preparation of the terahertz shield.

[0058] In this example, the mass ratio of hydroxy silicone oil (PDMS-OH), hydrogen silicone oil (PDMS-H) and vinyl silicone oil (PDMS-Vi) is 100:20:40, graphene oxide accounts for 0.1% of the total mass of the composite medium, and Karstedt catalyst accounts for 10-20ppm of the total mass of the composite medium. The final terahertz shielding sample prepared is a layer with a thickness of 10mm. The optical photograph of the sample is shown below. Figure 1 As shown in part (c) of the figure.

[0059] Based on the lightweight and efficient terahertz shield of pure methyl foam prepared in Example 1, the lightweight and efficient terahertz shield of methyl foam plus 0.05% graphene oxide prepared in Example 2, and the lightweight and efficient terahertz shield of methyl foam plus 0.1% graphene oxide prepared in Example 3, terahertz wave reflection and transmission spectrum experimental tests were performed on the three lightweight and efficient terahertz shield samples using a terahertz time-domain spectroscopy detection system. The terahertz time-domain spectroscopy system operates as follows: a titanium-sapphire femtosecond mode-locked pulse laser generates 960mW of excitation power, with a central wavelength of 800nm, a repetition rate of 80MHz, and a pulse width of 100. The beam is split by a beamsplitter into a stronger pump beam and a weaker probe beam. The pump beam is modulated by a chopper and focused by a lens onto a gallium arsenide (GaAs) crystal photoconductive antenna to excite a terahertz pulse. The terahertz pulse is collimated by two off-axis metal parabolic mirrors and incident on the sample. It is then focused by two more metal parabolic mirrors onto a 2mm-thick zinc telluride (ZnTe) crystal, where it merges with the probe beam after passing through a delay line. The electric field of the terahertz electromagnetic radiation pulse modulates the refractive index ellipsoid of the ZnTe crystal through the linear electro-optic effect, causing the polarization state of the probe beam to change. This polarization state is detected by a balanced diode and then fed into a lock-in amplifier for amplification. The entire time-domain waveform of the terahertz signal is detected by varying the length of the delay line. In order to avoid the influence of water vapor in the air on the experimental results, the terahertz transmitter, receiver and measured sample were placed in a sealed cover filled with nitrogen. The temperature inside the cover was 21 °C and the air humidity was about 5%.

[0060] The terahertz time domain waveforms of three lightweight and efficient terahertz shields are as follows: Figure 2 As shown in the figure, the terahertz wave time domain spectra of different graphene oxide contents have different performances, and the time domain peak heights have certain differences. The corresponding terahertz wave frequency domain spectrum can be obtained by Fourier transforming the time domain spectrum, as shown in the figure. Figure 3 shown. Figure 4 The terahertz wave absorption coefficients of three lightweight and efficient terahertz shields are shown in Figure 4. The graphene oxide content has a certain influence on the terahertz wave absorption coefficients. Figure 5 The terahertz absorption and shielding effectiveness of three lightweight and efficient terahertz shields can be seen. The higher the graphene oxide content, the stronger the absorption and shielding effectiveness of the terahertz shield. When the graphene oxide content is 0.1%, the terahertz absorption and shielding effectiveness of the terahertz shield can reach 62.7dB. Figure 6 The terahertz reflection shielding effectiveness of three lightweight and efficient terahertz shields. It can be seen from the figure that the reflection shielding effectiveness of the three composite media is less than 0.01dB. Figure 7The total terahertz shielding effectiveness of three lightweight and efficient terahertz shields is shown in Figure 2, where the absorption shielding effectiveness accounts for more than 99.9% of the total shielding effectiveness.

[0061] In summary, the lightweight, highly efficient terahertz shielding device fabricated by the present invention utilizes terahertz wave absorption as its primary shielding mechanism, exhibiting low terahertz wave reflectivity. This device acts as a protective layer or shell to shield equipment from terahertz waves, preventing them from re-entering the environment and causing secondary contamination. This device has broad application prospects. The terahertz shielding devices fabricated in the three aforementioned embodiments can substantially eliminate terahertz waves and maintain their terahertz shielding effectiveness over a wide temperature range of -100°C to 300°C, demonstrating potential application value in extreme conditions.

[0062] However, the detailed description of the embodiments of the present invention above is not intended to limit the scope of the claimed invention, but rather merely represents some of the preferred embodiments of the present invention. Based on the embodiments of the present invention, the various parameter ranges can be adjusted accordingly. Through relevant gradient experiments, theoretically, a premix of 100-105 parts by mass of hydroxy silicone oil (PDMS-OH), 20-25 parts by mass of hydrogenated silicone oil (PDMS-H), and a graphene oxide aqueous solution (accounting for 0.05 wt.% to 0.1 wt.% of the composite medium) is thoroughly mixed to form a premix. This premix is ​​then thoroughly mixed with a Karstedt catalyst (at a concentration of 10-100 ppm in the composite medium) and 40-45 parts by mass of vinyl silicone oil (PDMS-Vi) to form a composite medium. Finally, the composite medium is placed in a mold for foaming and curing. Both methods can produce terahertz shields, with only differences in shielding performance.

[0063] Therefore, those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A method for preparing a terahertz shield, characterized in that: 100-105 parts by mass of hydroxy silicone oil and 20-25 parts by mass of hydrogenated silicone oil are fully mixed to obtain a premix, and then the premix is ​​fully mixed with Karstedt catalyst and 40-45 parts by mass of vinyl silicone oil to form a composite medium. Finally, the composite medium is placed in a mold for foaming at 20°C-28°C for 10-30 minutes. The mold containing the composite medium is then placed in a hot air circulation dryer for drying and curing for 2-4 hours to obtain a terahertz shield with a thickness of 2-20 mm.

2. The method for preparing the terahertz shield according to claim 1, wherein: When preparing the premix, a graphene oxide aqueous solution is also added, and the mass percentage of graphene oxide in the final composite medium is 0.05% to 0.1%.

3. The method for preparing the terahertz shield according to claim 1 or 2, characterized in that: The concentration of the Karstedt catalyst in the composite medium is 10-100 ppm.

4. The method for preparing the terahertz shield according to claim 1 or 2, characterized in that: When preparing the premix, the materials are fully mixed by centrifugation, the centrifugal speed is 30π~50π rad / s, and the centrifugal mixing time is 5~20 min.

5. The method for preparing the terahertz shield according to claim 1 or 2, characterized in that: When preparing the composite medium, the materials are fully mixed by centrifugation, the centrifugal speed is 300π~500π rad / s, and the centrifugal mixing time is 1~5 min.

6. A terahertz shield prepared according to the preparation method according to claim 1 or 2.

7. Use of the terahertz shield as claimed in claim 6 as a protective layer or protective shell to shield a device from terahertz waves.

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