A design method for composite electromagnetic shielding material based on quantum dot physical parameter regulation
By constructing exciton energy expressions and resonance condition expressions for quantum dots, and combining them with the Maxwell-Garnett effective medium theory, the problem of impedance matching and loss mechanism in the GHz band is solved, achieving high-efficiency shielding effect of composite electromagnetic shielding materials and avoiding the weight and pollution problems of traditional materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- EAST CHINA NORMAL UNIV
- Filing Date
- 2026-02-24
- Publication Date
- 2026-05-29
Smart Images
Figure CN122117170A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of new material design technology, and in particular to a design method for composite electromagnetic shielding materials based on the control of quantum dot physical parameters. Background Technology
[0002] Traditional composite electromagnetic shielding materials (such as metal foil, conductive polymers, and carbon-based composite electromagnetic shielding materials) mainly rely on high conductivity to achieve reflection-dominated shielding, but they suffer from problems such as heavy weight, susceptibility to corrosion, and secondary pollution. In recent years, absorbing composite shielding materials have attracted attention due to their low reflection and high absorption characteristics. However, the impedance matching and loss mechanism of existing absorbing materials in the GHz band (such as the operating frequency bands of 5G, radar, and quantum chips) are still difficult to precisely control.
[0003] Quantum dots (QDs), as artificial atomic structures, are functional fillers dispersed in matrix materials to form electromagnetic shielding materials. The electron exciton energy and dielectric function of quantum dots are strongly dependent on their size, composition, and surface states. Currently, there is no technical solution to directly embed the quantum physical parameters of quantum dots into electromagnetic shielding effectiveness (SE) calculation models. Summary of the Invention
[0004] This application provides a design method for composite electromagnetic shielding materials based on the control of quantum dot physical parameters. The quantum physical parameters of quantum dots can be directly embedded into the electromagnetic shielding effectiveness calculation model. By adjusting the physical parameters, the electromagnetic shielding effectiveness of the corresponding composite electromagnetic shielding material after parameter adjustment can be obtained, which can be used as a reference for the design of composite electromagnetic shielding materials.
[0005] This application provides a design method for composite electromagnetic shielding materials based on the control of quantum dot physical parameters. The composite electromagnetic shielding material is composed of a matrix material and quantum dots. The method includes: Based on the quantum confinement effect of quantum dots and the one-dimensional infinite potential well approximation principle, an expression for the exciton energy of quantum dots is constructed by combining the physical parameter variables of quantum dots. Based on the principle of matching the electromagnetic wave photon energy of the target shielding frequency with the exciton energy of the quantum dot, and combined with the exciton energy expression, a resonance condition expression between the quantum dot and the target shielding frequency is constructed. Using the Maxwell-Garnett effective medium theory, the complex permittivity expression of the composite electromagnetic shielding material is constructed based on the volume fraction of quantum dots in the composite electromagnetic shielding material, the complex permittivity of the quantum dots with the angular frequency corresponding to the target shielding frequency as the intrinsic resonance frequency, and the complex permittivity of the matrix material. By substituting the resonance condition expression into the complex permittivity expression of the composite electromagnetic shielding material, a mapping expression between the physical parameters of the quantum dot and the complex permittivity of the composite electromagnetic shielding material is constructed, so as to build an electromagnetic shielding effectiveness calculation model for the design of composite electromagnetic shielding materials.
[0006] In some embodiments, the method further includes: Obtain the physical parameters and volume fraction parameters of the electromagnetic shielding material, including the quantum dot parameters; input the electromagnetic shielding effectiveness calculation model; and output the electromagnetic shielding effectiveness of the electromagnetic shielding material. By changing the size of quantum dots in the volume fraction or physical parameters, the electromagnetic shielding effectiveness of the adjusted electromagnetic shielding material is obtained from the output of the electromagnetic shielding effectiveness calculation model.
[0007] In some embodiments, based on the quantum confinement effect of quantum dots and the one-dimensional infinite potential well approximation principle, the exciton energy expression of quantum dots is constructed by combining the physical parameter variables of quantum dots, including: Based on the one-dimensional infinite potential well approximation principle, an expression for the initial exciton energy of quantum dots is constructed. Based on the quantum confinement effect of quantum dots, the Coulomb attraction energy term in the initial exciton energy expression is ignored, and the exciton energy expression is obtained by combining the physical parameter variables of quantum dots. In some embodiments, based on the principle of matching the electromagnetic wave photon energy of the target shielding frequency with the exciton energy of the quantum dot, and combined with the exciton energy expression, a resonance condition expression for the quantum dot and the target shielding frequency is constructed, including: Based on the principle that the electromagnetic wave photon energy at the target shielding frequency is equal to the quantum dot exciton energy minus the quantum dot bandgap energy, and combining the expressions for photon energy, exciton energy, and quantum dot bandgap energy, a resonance condition expression for the quantum dot and the target shielding frequency is constructed. In some embodiments, the exciton energy expression for a quantum dot is: ,in, Represents exciton energy, Planck's constant For R, for And the effective mass of holes is In some embodiments, the resonance condition expression between the quantum dot and the target shielding frequency is: ,in, The angular frequency corresponding to the target shielding frequency. Represents photon energy. This represents the exciton energy after neglecting the Coulomb attraction energy term and subtracting the quantum dot band gap energy.
[0008] 2. The method according to claim 6, characterized in that the complex permittivity expression of the composite electromagnetic shielding material is: ,in, The complex permittivity of the composite electromagnetic shielding material is... The complex permittivity of the matrix material is given by the volume fraction of quantum dots in the composite electromagnetic shielding material. , The complex permittivity of the quantum dot is such that the angular frequency corresponding to the target shielding frequency is taken as the intrinsic resonance frequency. , In the expression The imaginary unit, and the physical parameter variables of the quantum dot: high-frequency dielectric constant. , Damping coefficient Plasma angular frequency , carrier concentration Indicates the effective mass of charge carriers. Represents the vacuum permittivity. Represents elementary charge In some embodiments, the mapping expression is: ,in, = .
[0009] In some embodiments, after the mapping expression is constructed, the method further includes: The mapping expression is converted into an explicit expression of the complex permittivity of the composite electromagnetic shielding material. The explicit expression is: ,in, Indicates the real part, Indicates the imaginary part; Substituting the explicit real and imaginary parts into the shielding effectiveness formula, we construct an electromagnetic shielding effectiveness calculation model. The expression for the electromagnetic shielding effectiveness calculation model is as follows: ,in, The characteristic impedance of the composite electromagnetic shielding material, This represents the input impedance at the load end of the composite electromagnetic shielding material. Let be the distance the electromagnetic wave travels in the composite electromagnetic shielding material, and let c be the speed of light in a vacuum. This represents the real part of the effective permeability of the composite electromagnetic shielding material. For electromagnetic shielding effectiveness, For reflection loss, To absorb losses, This is a correction term for multiple reflections.
[0010] In some embodiments, the method further includes converting the resonance condition expression into a size expression for the quantum dot.
[0011] The design method for composite electromagnetic shielding materials based on the control of quantum dot physical parameters provided in this application involves constructing an exciton energy expression for the quantum dot using its physical parameters, thereby establishing a resonance condition expression between the quantum dot and the target shielding frequency. Next, based on the volume fraction of the quantum dot in the composite electromagnetic shielding material, the complex permittivity of the quantum dot with the angular frequency corresponding to the target shielding frequency as its intrinsic resonance frequency, and the complex permittivity of the matrix material, an expression for the complex permittivity of the composite electromagnetic shielding material is constructed. Finally, the resonance condition expression is substituted into the expression for the complex permittivity of the composite electromagnetic shielding material to establish a mapping expression between the physical parameters of the quantum dot and the complex permittivity of the composite electromagnetic shielding material. This establishes a mapping formula from the exciton energy of the quantum dot to the macroscopic complex permittivity, allowing the direct embedding of the physical parameters of the quantum dot into the electromagnetic shielding effectiveness calculation model. By adjusting the physical parameters, the electromagnetic shielding effectiveness of the composite electromagnetic shielding material after parameter adjustment can be obtained, providing a reference for the design of composite electromagnetic shielding materials. Attached Figure Description
[0012] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.
[0013] Figure 1 This is a flowchart illustrating a design method for composite electromagnetic shielding materials based on the control of quantum dot physical parameters, as provided in an embodiment of this application.
[0014] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation
[0015] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.
[0016] The terms “first”, “second”, etc. used in this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.
[0017] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems will be described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.
[0018] Please combine Figure 1 , Figure 1 A flowchart illustrating the design method for composite electromagnetic shielding materials based on the control of quantum dot physical parameters provided in this application, the design method may include the following steps: Step S110: Based on the quantum confinement effect of quantum dots and the one-dimensional infinite potential well approximation principle, construct the exciton energy expression of quantum dots by combining the physical parameter variables of quantum dots.
[0019] Specifically, firstly, based on the one-dimensional infinite potential well approximation principle, the initial exciton energy expression for the quantum dot is constructed: . Next, based on the quantum confinement effect of quantum dots, the Coulomb attraction energy term in the initial exciton energy expression is neglected (the Coulomb attraction energy term is...). Combining the physical parameter variables of quantum dots, we obtain the expression for the exciton energy: (1), where, Represents exciton energy, Planck's constant For R, for And the effective mass of holes is .
[0020] Understandably, based on the quantum confinement effect of semiconductor quantum dots, when the size of the quantum dot (size can refer to the radius) is smaller than the exciton Bohr radius, electrons and holes are confined in a finite space, and its exciton energy exhibits a discrete distribution. Therefore, when the design size is in the range of 1-5nm, such as when the quantum dot is a CdSe quantum dot, the quantum confinement effect is significant. At this time, the Coulomb interaction energy can be ignored (compared to the quantum confinement energy, the Coulomb term accounts for about 5%-10%, which can simplify the calculation). Therefore, the formula (1) can be converted from the initial exciton energy expression.
[0021] Step S120: Based on the principle of matching the electromagnetic wave photon energy of the target shielding frequency with the exciton energy of the quantum dot, and combined with the exciton energy expression, construct the resonance condition expression between the quantum dot and the target shielding frequency.
[0022] Specifically, based on the principle that the electromagnetic wave photon energy at the target shielding frequency is equal to the quantum dot exciton energy minus the quantum dot bandgap energy, and combining the expressions for photon energy, exciton energy, and quantum dot bandgap energy, a resonance condition expression for the quantum dot and the target shielding frequency is constructed.
[0023] It is understandable that the photon energy corresponding to the target shielding frequency... It needs to be matched with the exciton energy of the quantum dot to make the photon energy This equation shows that the exciton energy caused by quantum confinement must be equal to the photon energy of the electromagnetic wave in order to achieve resonant absorption.
[0024] The resonance condition expression between the quantum dot and the target shielding frequency is as follows: (2), where, The angular frequency corresponding to the target shielding frequency.
[0025] Step S130: Using the Maxwell-Garnett effective medium theory, the complex permittivity expression of the composite electromagnetic shielding material is constructed based on the volume fraction of quantum dots in the composite electromagnetic shielding material, the complex permittivity of the quantum dots with the angular frequency corresponding to the target shielding frequency as the intrinsic resonance frequency, and the complex permittivity of the matrix material.
[0026] Specifically, the Maxwell-Garnett effective medium theory is also known as the Maxwell–Garnett effective medium theory. The complex permittivity of quantum dots is constructed using the Lorenz-Lorentz model, which accurately describes the plasmon resonance and dielectric relaxation behavior of quantum dots. The expression for the complex permittivity of a quantum dot with the angular frequency corresponding to the target shielding frequency as the eigenre resonance frequency is: (3), among which, The angular frequency corresponding to the target shielding frequency. The imaginary unit, The volume fraction of quantum dots in the composite electromagnetic shielding material, and the physical parameter variables of the quantum dots: It is the high-frequency dielectric constant. The plasma angular frequency, It is the resonant angular frequency. The damping coefficient is the plasma angular frequency. , carrier concentration Indicates the effective mass of charge carriers. Represents the vacuum permittivity. It represents the elementary charge.
[0027] The expression for the complex permittivity of the composite electromagnetic shielding material is: (4), of which, The complex permittivity of the composite electromagnetic shielding material is... is the complex permittivity of the matrix material.
[0028] Step S140: Substitute the resonance condition expression into the complex permittivity expression of the composite electromagnetic shielding material to construct a mapping expression between the physical parameters of the quantum dot and the complex permittivity of the composite electromagnetic shielding material, so as to construct an electromagnetic shielding effectiveness calculation model for the design of composite electromagnetic shielding materials.
[0029] Specifically, first, substituting formula (2) into formula (4), the mapping expression is as follows: , = (5) It is understandable that formula (5) introduces the quantum dot size R as a degree of freedom in the design of composite electromagnetic shielding materials, and controls its complex permittivity by adjusting R.
[0030] Next, the mapping expression is converted into an explicit expression for the complex permittivity of the composite electromagnetic shielding material, as follows: (6), among which, Indicates the real part, Indicates the imaginary part.
[0031] Finally, the explicit real and imaginary parts are substituted into the shielding effectiveness formula ( The electromagnetic shielding effectiveness calculation model was constructed. The expression for the electromagnetic shielding effectiveness calculation model is as follows: (7), among which, The characteristic impedance of the composite electromagnetic shielding material, This represents the input impedance at the load end of the composite electromagnetic shielding material. Let be the distance the electromagnetic wave travels in the composite electromagnetic shielding material, and let c be the speed of light in a vacuum. This represents the real part of the effective permeability of the composite electromagnetic shielding material. For electromagnetic shielding effectiveness, For reflection loss, To absorb losses, This is a correction term for multiple reflections.
[0032] In one implementation of the application stage, the electromagnetic shielding material parameters (including the parameters corresponding to the variables in the above formulas (1) to (7)) are obtained, including the physical parameters of the quantum dots and the volume fraction of the electromagnetic shielding material. The electromagnetic shielding material parameters are then input into the electromagnetic shielding effectiveness calculation model to output the electromagnetic shielding effectiveness of the electromagnetic shielding material. When the electromagnetic shielding effectiveness is within the preset effectiveness range, the electromagnetic shielding material parameters are determined as the design parameters of the electromagnetic shielding material.
[0033] Understandably, in the above technical solution, the exciton energy expression of the quantum dot is constructed using the physical parameters of the quantum dot, thereby establishing a resonance condition expression between the quantum dot and the target shielding frequency. Then, based on the volume fraction of the quantum dot in the composite electromagnetic shielding material, the complex permittivity of the quantum dot with the angular frequency corresponding to the target shielding frequency as the intrinsic resonance frequency, and the complex permittivity of the matrix material, an expression for the complex permittivity of the composite electromagnetic shielding material is constructed. Finally, the energy equation is substituted into the expression for the complex permittivity of the composite electromagnetic shielding material to establish a mapping expression between the physical parameters of the quantum dot and the complex permittivity of the composite electromagnetic shielding material. This establishes a mapping formula from the exciton energy of the quantum dot to the macroscopic complex permittivity, thereby directly embedding the physical parameters of the quantum dot into the electromagnetic shielding effectiveness calculation model. By adjusting the physical parameters, the electromagnetic shielding effectiveness of the composite electromagnetic shielding material after parameter adjustment can be obtained, providing a reference for the design of composite electromagnetic shielding materials.
[0034] In some embodiments, the design method further includes converting the resonance condition expression between the quantum dot and the target shielding frequency into a size expression for the quantum dot. The size expression is as follows: .
[0035] It is understandable that the size of the quantum dot can be intuitively obtained through its size expression, facilitating the study of its impact on electromagnetic shielding effectiveness. By controlling the size of the quantum dot, its plasma resonance frequency or exciton transition frequency can be matched with the frequency of electromagnetic waves, thereby enhancing dielectric loss.
[0036] In another implementation method during the application phase, the electromagnetic shielding material parameters are obtained, and the electromagnetic shielding effectiveness calculation model is input to output the electromagnetic shielding effectiveness of the electromagnetic shielding material. Then, the size of the quantum dots in the volume fraction or physical parameters is changed to obtain the adjusted electromagnetic shielding effectiveness output by the electromagnetic shielding effectiveness calculation model, which can be used as a reference for the design of composite electromagnetic shielding materials.
[0037] The advantages of the electromagnetic shielding effectiveness calculation model constructed by the design method provided in this application will be further illustrated below through examples and comparative examples.
[0038] Example 1: Target Shielding Frequency f 0 =8GHz, using CdSe quantum dots. Obtain the electromagnetic shielding material parameters and input them into the electromagnetic shielding effectiveness calculation model, then perform the following calculations: Step S1: The angular frequency corresponding to the target shielding frequency is ， Planck constant And the physical parameters of quantum dots: E g=1.74 eV, effective electron mass is The rest mass of free electrons Approximately 9.11 × 10 −31 Substitute kg into formula (2).
[0039] according to Formula (2) can be obtained. = And then calculate .
[0040] Considering the influence of the Coulomb term on the exciton energy, the actual size needs to be corrected. The Coulomb term leads to a decrease in exciton energy; to maintain the matching of exciton energy and photon energy, the quantum dot size needs to be appropriately reduced. After correction, the optimal size of the CdSe quantum dot was finally determined to be R = 3.5 nm. This size is smaller than the CdSe exciton Bohr radius (5.6 nm), exhibiting a significant quantum confinement effect and enabling efficient resonant absorption in the 8 GHz band.
[0041] Step S2: First calculate the plasma angular frequency. The carrier concentration of CdSe quantum dots with a size of 3.5 nm Effective carrier mass (the combined effective mass of electrons and holes) Vacuum permittivity 8.854×10 −12 F / m, elementary charge 1.602×10 −19 Substituting C Obtain the plasma angular frequency .
[0042] Next, the high-frequency dielectric constant Approximately 10.2, damping coefficient 1.2×10 10 rad / s and plasma angular frequency Approximately Substitute the formula obtained by rationalizing complex numbers using formula (3) In the middle, we obtained Calculate the real part: Calculate the imaginary part: For quantum dots of the above size, the following can be fitted around 8 GHz: Step S3: Calculate the volume fraction , The complex permittivity of the matrix material was obtained from the literature. , Substituting into formula (6), the complex permittivity of the composite electromagnetic shielding material is obtained. .
[0043] It is understandable that volume fraction directly affects the dielectric and mechanical properties of composite electromagnetic shielding materials. If the volume fraction is too low, the contribution of quantum dots to dielectric loss is insufficient; if the volume fraction is too high, it easily leads to quantum dot aggregation, reducing the uniformity and mechanical properties of the composite electromagnetic shielding material. Based on existing experimental experience, this embodiment selects the optimal volume fraction of quantum dots. The aforementioned quantum dots are dispersed in the matrix middle.
[0044] The volume fraction is calculated based on the density of the quantum dots and the matrix: in, The density of CdSe quantum dots ( ), The density of the matrix material ( ), The diameter of the quantum dot. For the number of quantum dots, Let be the volume of the matrix material. When The mass fraction can be calculated using the above formula. This ratio is easy to achieve in experiments and ensures that the quantum dots are uniformly dispersed in the matrix.
[0045] Step S4: The complex permittivity Input impedance at the load end of the composite electromagnetic shielding material The distance electromagnetic waves travel in the composite electromagnetic shielding material is t = 2 mm; the speed of light in a vacuum is c = 3 × 10⁻⁶. 8 m / s, real part of effective permeability of composite electromagnetic shielding material Substituting into formula (7), we obtain the electromagnetic shielding effectiveness. .
[0046] Specifically, The magnitude of the reflection coefficient is determined as follows: For non-magnetic materials, the intrinsic impedance of the material is according to Its model: Phase: Then the square root: then: Calculate the real and imaginary parts: Real part: Virtual part: so Calculate the reflection coefficient: Calculate the square of the modulus: Molecular model: Denominator: then: The calculation of the multiple reflection correction term is as follows: Calculations show that the electromagnetic shielding effectiveness is... .
[0047] Example 2: Calculation of the effect of quantum dot size on the shielding effectiveness of composite electromagnetic shielding materials. Similar to Example 1, the difference is that, keeping other parameters constant (volume fraction 15%, target frequency band 8GHz), the electromagnetic shielding effectiveness corresponding to CdSe quantum dots of different sizes was calculated. The results are shown in Table 2. Table 2: This example 2 illustrates that as the size of the quantum dot decreases, the exciton energy increases, that is, the exciton level spacing increases, and the dielectric constant of the quantum dot increases. An increase in the imaginary part (dielectric loss) significantly improves electromagnetic shielding effectiveness. When the size is 2.0 nm, the electromagnetic shielding effectiveness reaches 36.7 dB, but at this size, the quantum dots are more difficult to fabricate and are prone to aggregation.
[0048] Example 3 In Example 3, the quantum dot size is kept at 3.5 nm, and other parameters remain unchanged. The difference from Example 1 is that the electromagnetic shielding effectiveness corresponding to different volume fractions is calculated, and the results are shown in Table 3: Table 3: In Example 3, as the volume fraction of quantum dots increases, the absorption loss of the composite electromagnetic shielding material decreases. Enhanced electromagnetic shielding effectiveness (SE) T The volume fraction should be gradually increased. When the volume fraction exceeds 20%, the improvement in shielding effectiveness slows down, and quantum dots tend to aggregate, leading to a decrease in the mechanical properties of the composite electromagnetic shielding material. Therefore, 15%-20% is the optimal volume fraction range that balances shielding effectiveness and mechanical properties.
[0049] Comparative Example 1 Traditional electromagnetic shielding methods use the same material parameters as in Example 1, do not consider quantum confinement effects, and the calculation steps are as follows: The absorption loss is: SE A =8.686 α t =8.686×6.94×0.002≈0.121dB The loss is: The overall electromagnetic shielding effectiveness is: The calculation of the shielding effectiveness of the nano-quantum dot composite system using the bulk material dielectric constant in Comparative Example 1, which completely ignores size-dependent interfacial polarization and relaxation mechanisms, results in predicted values that are two orders of magnitude lower than the actual performance. This method not only contains numerical errors but also misleads the direction of material design.
[0050] Compared to existing technologies, this invention proposes a "design method for composite electromagnetic shielding materials based on the control of quantum dot physical parameters." Specifically, by controlling the size of quantum dots, the design of composite electromagnetic shielding materials can be accurately captured to capture the unique electromagnetic behavior of nanomaterials and achieve the rational design of high-performance shielding materials.
[0051] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.
[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A design method for composite electromagnetic shielding materials based on the control of quantum dot physical parameters, characterized in that, The composite electromagnetic shielding material is composed of a matrix material and quantum dots, and the method includes: Based on the quantum confinement effect of quantum dots and the one-dimensional infinite potential well approximation principle, an expression for the exciton energy of quantum dots is constructed by combining the physical parameter variables of quantum dots. Based on the principle of matching the electromagnetic wave photon energy of the target shielding frequency with the exciton energy of the quantum dot, and combined with the exciton energy expression, a resonance condition expression for the quantum dot and the target shielding frequency is constructed. Using the Maxwell-Garnett effective medium theory, the complex permittivity expression of the composite electromagnetic shielding material is constructed based on the volume fraction of quantum dots in the composite electromagnetic shielding material, the complex permittivity of the quantum dots with the angular frequency corresponding to the target shielding frequency as the intrinsic resonance frequency, and the complex permittivity of the matrix material. By substituting the resonance condition expression into the complex permittivity expression of the composite electromagnetic shielding material, a mapping expression between the physical parameters of the quantum dot and the complex permittivity of the composite electromagnetic shielding material is constructed, thereby building an electromagnetic shielding effectiveness calculation model for the design of composite electromagnetic shielding materials.
2. The method according to claim 1, characterized in that, The method further includes: Obtain the physical parameters of the quantum dots and the electromagnetic shielding material parameters of the volume fraction, input them into the electromagnetic shielding effectiveness calculation model, and output the electromagnetic shielding effectiveness of the electromagnetic shielding material. By changing the size of the quantum dots in the volume fraction or physical parameters, the adjusted electromagnetic shielding effectiveness of the electromagnetic shielding material is obtained from the output of the electromagnetic shielding effectiveness calculation model.
3. The method according to claim 1, characterized in that, The exciton energy expression for quantum dots, based on the quantum confinement effect and the one-dimensional infinite potential well approximation principle, combined with the physical parameter variables of quantum dots, is constructed, including: Based on the one-dimensional infinite potential well approximation principle, an expression for the initial exciton energy of quantum dots is constructed. Based on the quantum confinement effect of quantum dots, the Coulomb attraction energy term of the initial exciton energy expression is ignored, and the exciton energy expression is obtained by combining the physical parameter variables of quantum dots.
4. The method according to claim 1, characterized in that, The principle of matching the electromagnetic wave photon energy based on the target shielding frequency with the quantum dot exciton energy, combined with the exciton energy expression, constructs a resonance condition expression for the quantum dot and the target shielding frequency, including: Based on the principle that the electromagnetic wave photon energy at the target shielding frequency is equal to the quantum dot exciton energy minus the quantum dot bandgap energy, and combining the expressions for photon energy, exciton energy, and quantum dot bandgap energy, a resonance condition expression for the quantum dot and the target shielding frequency is constructed.
5. The method according to claim 1, characterized in that, The expression for the exciton energy of the quantum dot is: ,in, Represents exciton energy, Let R be Planck's constant, and let R be the physical parameters of the quantum dot: the size of the quantum dot is R, and the effective electron mass is R. And the effective mass of holes is .
6. The method according to claim 5, characterized in that, The resonance condition expression between the quantum dot and the target shielding frequency is: ,in, The angular frequency corresponding to the target shielding frequency. Represents photon energy. This represents the exciton energy after neglecting the Coulomb attraction energy term and subtracting the quantum dot band gap energy.
7. The method according to claim 6, characterized in that, The complex permittivity of the composite electromagnetic shielding material is expressed as follows: ,in, The complex permittivity of the composite electromagnetic shielding material is... The complex permittivity of the matrix material is given by the volume fraction of quantum dots in the composite electromagnetic shielding material. , The complex permittivity of the quantum dot is used to take the angular frequency corresponding to the target shielding frequency as the intrinsic resonance frequency. , In the expression The imaginary unit, and the physical parameter variables of the quantum dot: high-frequency dielectric constant. resonant angular frequency Damping coefficient Plasma angular frequency , carrier concentration Indicates the effective mass of charge carriers. Represents the vacuum permittivity. It represents the elementary charge.
8. The method according to claim 7, characterized in that, The mapping expression is: ,in, = .
9. The method according to claim 8, characterized in that, After the mapping expression is constructed, the method further includes: The mapping expression is then converted into an explicit expression for the complex permittivity of the composite electromagnetic shielding material. The explicit expression is: ,in, Indicates the real part, Indicates the imaginary part; By substituting the explicit real and imaginary parts into the shielding effectiveness formula, an electromagnetic shielding effectiveness calculation model is constructed. The expression of the electromagnetic shielding effectiveness calculation model is as follows: ,in, The characteristic impedance of the composite electromagnetic shielding material, This represents the input impedance at the load end of the composite electromagnetic shielding material. Let be the distance the electromagnetic wave travels in the composite electromagnetic shielding material, and let c be the speed of light in a vacuum. This represents the real part of the effective permeability of the composite electromagnetic shielding material. For electromagnetic shielding effectiveness, For reflection loss, To absorb losses, This is a correction term for multiple reflections.
10. The method according to claim 1, characterized in that, The method further includes converting the resonance condition expression into a size expression for the quantum dot.