Porous carbon aerogel with broadband negative dielectric response and preparation method thereof

Abstract

The invention discloses a porous carbon aerogel material with broadband negative dielectric response in a frequency band of 20MHz-1GHz and a preparation method thereof. Biomass material lignin is used as a carbon source, zinc chloride is used as a template pore-forming agent, the lignin and the zinc chloride are mixed in a formaldehyde solution, then the mixture is put into a high-pressure kettle with a polytetrafluoroethylene lining for heating reaction, and the porous carbon aerogel material with broadband negative dielectric response in the frequency band of 20MHz-1GHz is obtained. And carbonizing the product to prepare the porous carbon aerogel with different porosities and densities. The method is characterized in that the broadband negative dielectric response performance is obtained by controlling conditions such as the zinc chloride / lignin content ratio, the reaction temperature and the carbonization temperature. The preparation method is low in preparation cost, stable in process, simple in operation and treatment and large in performance regulation and control interval.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic metamaterials with negative dielectric response, and in particular to a porous carbon aerogel with broadband negative dielectric response and a preparation method thereof. Background Art

[0002] Intrinsic Electromagnetic Metamaterials mainly refer to new electromagnetic media that use the intrinsic properties of materials to construct percolation composite structures, thereby achieving negative dielectric constants (ε'<0), negative magnetic permeability (μ'<0) or near-zero dielectric constants (ε'~0) and other extraordinary electromagnetic parameters. Electromagnetic metamaterials can reshape the material construction paradigm and break through the traditional electromagnetic response architecture system through the fine design of microscopic structural units to customize the macroscopic physical field response. It is a structurally functional integrated artificial composite material with extraordinary electromagnetic properties.

[0003] Intrinsic electromagnetic metamaterials, as one of the important branches of electromagnetic metamaterials, achieve extraordinary electromagnetic response characteristics by designing percolation composite structures on a subwavelength physical scale to regulate the interaction between radio frequency (kHz-GHz) electromagnetic waves / fields and media. The radio frequency negative dielectric response (ε'<0) of intrinsic electromagnetic metamaterials usually has the characteristics of high magnitude, high loss, severe dispersion, and narrow response frequency band, which seriously limits its application in high performance, integration, and new electronic components. For example, a stacked capacitor constructed by introducing a negative dielectric material layer can significantly improve the energy storage density by means of positive-negative dielectric matching, and its negative dielectric response is urgently required to meet the characteristics of low dispersion and low loss. Intrinsic electromagnetic metamaterials with extremely weak negative dielectric constants (-10<ε'<0) have a refractive index of The negative dielectric response of the electromagnetic wave tends to zero, and the high-speed transmission of information in the circuit device can be realized by improving the transmittance of the electromagnetic wave and manipulating the directional propagation of the electromagnetic wave. Electronic components designed based on low-loss and broadband negative dielectric response are expected to solve the "Boltzmann tyranny" problem of chips and overcome the principle limitation of chip miniaturization. Realizing broadband negative dielectric response is not only a frontier hotspot in the current research of intrinsic electromagnetic metamaterials, but also a key difficulty it faces.

[0004] Chinese invention patent CN115305096B uses negative dielectric anisotropic liquid crystal composites to design a new display device, and Chinese invention patent CN116580965A uses a polymer layer with a negative dielectric constant to design a sandwich-type stacked capacitor, which can achieve an increase in energy storage density. The negative dielectric response of intrinsic electromagnetic metamaterials mainly includes two key factors: (i) the magnitude of the negative dielectric constant. Weak negative dielectric response (-1000<ε'<0) is usually accompanied by low dielectric loss, which can achieve good impedance matching and dielectric matching characteristics; (ii) the dispersion characteristics and response frequency window of the negative dielectric response. Low dispersion and broadband negative dielectrics are conducive to providing stable electromagnetic responses. Metals are the basic functional materials for constructing electromagnetic metamaterials. Their negative dielectric response usually comes from the plasma oscillation behavior of a large number of free electrons inside, which can be described by the classic Drude model. Metal materials have a high effective electron concentration inside, which leads to their cutoff frequency in the ultraviolet and other frequency bands, making the negative dielectric level of metal materials too high in the radio frequency band (ε'~-108), accompanied by strong losses. The key difficulty in the study of intrinsic electromagnetic metamaterials is to overcome the excessively high effective electron concentration of the functional phase and the resulting dispersion behavior, thereby achieving low dispersion, wide bandwidth, and weak negative dielectric response characteristics.

[0005] In 2000, D.R. Smith and others from the University of California, USA, used artificially designed metal wires and open resonant ring array units to construct electromagnetic metamaterials with negative dielectric constant and negative permeability for the first time, triggering a wave of research on extraordinary electromagnetic properties in the physics and engineering communities. Intrinsic electromagnetic metamaterials are based on the theory of array electromagnetic metamaterials, and have expanded the use of random and disordered percolation structures to achieve structural and functional integrated composite materials with negative dielectric constant and negative permeability. The research group of Fan Runhua from Shandong University was the first in the world to propose an academic idea of ​​using metal / ceramic percolation composite structures to achieve negative dielectric response. This idea uses a template method to construct a metal network in a porous ceramic matrix, which greatly "dilutes" the effective free electron concentration of the metal composite material, and the negative dielectric constant achieved in the radio frequency band is 4-6 orders of magnitude lower than that of bulk metals. Subsequently, the team of T. Tsutaoka from Hiroshima University in Japan used a similar method to simultaneously obtain negative dielectric constants and permeabilities using metals and ferrites as electromagnetic functional phases. With the development of electronic information technology, the requirements for miniaturization, flexibility and integration of electromagnetic functional devices are becoming increasingly higher, and the requirements for the response characteristics and material properties of negative dielectric materials are becoming more stringent. Summary of the invention

[0006] The object of the present invention is to provide a porous carbon aerogel material having a broadband negative dielectric response in the frequency band of 20 MHz-1 GHz and a preparation method thereof, so as to solve the problems in the current market raised by the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for preparing a porous carbon aerogel having a broadband negative dielectric response, characterized in that it comprises the following method:

[0008] The porous carbon aerogel is prepared by using lignin as a carbon source and zinc chloride as a template pore-forming agent, and after heating reaction and carbonization reaction, by controlling the lignin / zinc chloride content ratio, reaction temperature and carbonization temperature to prepare a porous carbon aerogel with different porosities and densities, thereby achieving an adjustable broadband negative dielectric response. In the present invention, the lignin / zinc chloride mass ratio is between 1 / 1-4 / 1, the reaction temperature is between 150°C-180°C, and the carbonization temperature is between 700°C-900°C.

[0009] Compared with the prior art, the present invention has the following beneficial effects: the method has low preparation cost, stable process, simple operation and processing, and a wide performance control range. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A schematic diagram of the negative dielectric spectrum of the porous carbon aerogel with a density between 0.456-0.775 g / cm3 of the present invention;

[0011] Figure 2 Schematic diagrams of SEM and TEM of the porous carbon aerogel of the present invention; DETAILED DESCRIPTION

[0012] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0013] In the present invention, when the lignin / zinc chloride mass ratio is between 1 / 1-4 / 1, the reaction temperature is between 150°C-180°C, and the carbonization temperature is between 600°C-900°C, the porous carbon aerogel can form a three-dimensional network structure. As the lignin / zinc chloride mass ratio increases, the reaction temperature increases, the carbonization temperature increases, the density of the prepared carbon aerogel increases, and the negative dielectric constant value increases. The key technology of the present invention is to control the lignin / zinc chloride content ratio and reaction conditions to achieve broadband negative dielectric response. The negative dielectric response performance control process of the prepared carbon aerogel is changed by changing the lignin / zinc chloride mass ratio, reaction temperature and time, carbonization temperature and time and other conditions:

[0014] 1. Modulation of negative dielectric properties of porous carbon aerogels by changing the mass ratio of lignin to zinc chloride

[0015] In the present invention, the lignin used is soda lignin with a particle size of about 30-50 μm and a zinc chloride purity of 99.9%. According to a lignin / zinc chloride mass ratio of 1 / 1-4 / 1, four groups of samples are weighed, specifically 8 g / 2 g, 6 g / 2 g, 4 g / 2 g and 2 g / 2 g, and are fully mixed in a formaldehyde solution. The samples are then placed in a high-pressure reactor and reacted at 160° C. for 2 hours. The product is taken out and freeze-dried, and then carbonized at 900° C. for 2 hours under argon protection. The obtained samples are fully washed in a hydrochloric acid solution and dried.

[0016] 2. Regulating the negative dielectric properties of porous carbon aerogels by changing the reaction temperature

[0017] In the present invention, the lignin used is soda lignin, the particle size is about 30-50 μm, the zinc chloride purity is 99.9%, and according to the lignin / zinc chloride mass ratio of 1 / 1-4 / 1, 4 groups of samples are weighed, specifically 8g / 2g, 6g / 2g, 4g / 2g and 2g / 2g, fully mixed in formaldehyde solution, and then placed in a high-pressure reactor, respectively reacted at 150° C., 160° C., 170° C., 180° C. for 2 hours, the product is taken out and freeze-dried, and then carbonized at 900° C. for 2 hours under argon protection. The obtained sample is fully washed in a hydrochloric acid solution and dried.

[0018] 3. Regulating the negative dielectric properties of porous carbon aerogels by changing the reaction time

[0019] In the present invention, the lignin used is soda lignin with a particle size of about 30-50 μm and a zinc chloride purity of 99.9%. According to a lignin / zinc chloride mass ratio of 1 / 1, 4 groups of samples are weighed, fully mixed in a formaldehyde solution, and then placed in a high-pressure reactor, reacted at 160° C. for 1 hour, 2 hours, 3 hours, and 4 hours, respectively, the product is taken out and freeze-dried, and then carbonized at 900° C. for 2 hours under argon protection, and the obtained sample is fully washed in a hydrochloric acid solution and dried.

[0020] 4. Regulating the negative dielectric properties of porous carbon aerogels by changing the carbonization temperature

[0021] In the present invention, the lignin used is soda lignin with a particle size of about 30-50 μm and a zinc chloride purity of 99.9%. According to a lignin / zinc chloride mass ratio of 1 / 1, 4 groups of samples are weighed, fully mixed in a formaldehyde solution, and then placed in a high-pressure reactor to react at 160° C. for 2 hours. The product is taken out and freeze-dried, and then carbonized at 600° C., 700° C., 800° C., and 900° C. for 2 hours under argon protection. The obtained samples are fully washed in a hydrochloric acid solution and dried.

[0022] 5. Regulating the negative dielectric properties of porous carbon aerogels by changing the carbonization time

[0023] In the present invention, the lignin used is soda lignin with a particle size of about 30-50 μm and a zinc chloride purity of 99.9%. According to a lignin / zinc chloride mass ratio of 1 / 1, 4 groups of samples are weighed, fully mixed in a formaldehyde solution, and then placed in a high-pressure reactor to react at 160° C. for 2 hours. The product is taken out and freeze-dried, and then carbonized at 900° C. for 1 hour, 2 hours, 3 hours, and 4 hours under argon protection, respectively. The obtained samples are fully washed in a hydrochloric acid solution and dried.

[0024] The successfully prepared porous carbon aerogels are Figure 2 As shown, the pore size and density of the aerogel are controlled, thereby regulating its negative dielectric response properties, such as Figure 1 As shown in Figure 2, all porous carbon aerogel samples achieved broadband negative dielectric constants in the 20MHz-1GHz frequency band. As the density of the carbon aerogel changes, the value of the negative dielectric constant is regulated, and its magnitude is in the range of 10 0 -10 4 Changes between.

[0025] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A porous carbon aerogel with broadband negative dielectric response and a method for preparing the same, characterized in that: The following methods are included: The porous carbon aerogel is prepared by using lignin as a carbon source and zinc chloride as a template pore-forming agent, and after heating reaction and carbonization reaction, by controlling the lignin / zinc chloride content ratio, reaction temperature and carbonization temperature.

2. The method for preparing a porous carbon aerogel having a broadband negative dielectric response according to claim 1, characterized in that: The mass ratio of lignin to zinc chloride is between 1 / 1 and 4 / 1.

3. The method for preparing the porous carbon aerogel having broadband negative dielectric response according to claim 1, characterized in that: The reaction temperature is between 150°C and 180°C.

4. The method for preparing the porous carbon aerogel having broadband negative dielectric response according to claim 1, characterized in that: The carbonization temperature is between 700°C and 900°C.

5. A porous carbon aerogel with broadband negative dielectric response, characterized in that: The porous carbon aerogel with broadband negative dielectric response is prepared by the method for preparing the porous carbon aerogel with broadband negative dielectric response according to any one of claims 1 to 4.

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