TWI341854B - The microwave absorbing materials - Google Patents

Description

1341854 VII. Designated representative map: (1) The representative representative figure of this case is as follows: Figure 2: Sample electromagnetic wave attenuation and frequency relationship graph - (2) Simple description of the component symbol of this representative figure: 9 sample 1 graphite powder 25% thin film thickness lmm reflection Attenuation curve. 1 0 sample 2 graphite powder 27.5% sheet thickness 〇.97 mm reflection attenuation curve. 1 1 sample 3 graphite powder 30% sheet thickness 〇.97mm blood ‘reflection decay curve. 8. If there is a chemical formula in this case, please disclose the chemical formula that best shows the characteristics of the invention: IX. Description of the invention: [Technical field of the invention] The present invention relates to an electromagnetic wave material capable of attenuating microwaves, mainly of graphite having a micron size After the powder, the polymer and the dispersing aid are stirred, the sheet is applied to the metal surface to attenuate the electromagnetic wave.

[Prior Art] Absorbing materials are classified into two types according to the difference of the absorbent, the viscous material and the dielectric absorbing material. The magnetic absorbing wave obtains the high magnetic permeability of the material by controlling the nature, weight and thickness of the added magnetic material, and is designed by magnetic parameters to adjust the energy of the absorbing material to achieve the desired distribution within the designed thickness. 'To get the best absorbing performance. The dielectric type material is designed such that the surface impedance is close to the free ^' dielectric constant gradually along the thickness direction of the absorbing material, which contributes to the penetration and absorption of electromagnetic waves minus 4 1341854 reflection 'dielectric loss material 矽 or carbonization矽, etc., ink, acetylene carbon black, carbon

The electrical loss tangent angle depends on the high polarization, molecular polarization, boundary:::3 sub-polarization, and the ion dielectric material uses carbon black to reduce the absorption of electromagnetic waves. Light, good chemical stability and ancient characteristics 'Because of its specific gravity, the magnetic powder has characteristics such as electric constant from the 1950s. Wave material, the most widely used ferrite powder is used to absorb the powder. The powder is the most suitable for the electrical end of the powder = 'W in W... width and thickness, but: t ancient, the material has a better absorption frequency Ji stroke Ϊ has the disadvantage of being overweight. The improvement of the bandwidth and the absorption performance can be achieved by changing the shape. The US Patent Publication No. 6784419 and 6670546 ft are connected to the 丨 丨 & & 外 外 外 外 外 外 外 利用 利用 利用 利用 利用 利用 利用 利用 利用 利用 利用 利用 利用 利用 利用 利用 利用 利用 利用 利用 利用Multi-layer design to widen and absorb performance. Although the above inventions are both strong and characteristic, there are disadvantages such as thick thickness and heavy weight at x_Band = 2i έ '.

Dielectric materials are most widely used in carbon black, because of their low specific gravity, good chemical stability, high dielectric constant and high loss, but they have high dielectric constants due to their high loss properties. Can not match, so the amount of addition is limited to about 25~30% wt, causing the thickness to be too thick, which is a disadvantage; graphite is an allotrope of the element, which has the same light weight and good chemical stability. The value, after mixing with the polymer material, has a small loss term and is easy to match. It is very suitable for making a microwave absorbing material. The present invention is prepared by mixing micron-sized graphite powder with epoxy resin and adding a special dispersing aid. The sheet type absorber has an absorber having a good absorption effect, a small thickness, and a light weight. SUMMARY OF THE INVENTION The electromagnetic parameters of an ideal absorbing material should have the following characteristics: μ == ε in a wide frequency band, and the imaginary part is large, that is, the loss is large. Therefore, it is necessary to satisfy two basic conditions for absorbing electromagnetic waves: (1) When electromagnetic waves are incident on the surface of the material, the electromagnetic waves can enter the inside of the material to the maximum extent (matching characteristics). (2) The electromagnetic wave entering the inside of the material is rapidly and almost completely attenuated (attenuation characteristic). When electromagnetic waves advance into different media, the path may reflect, scatter, penetrate, or resonate within the medium. In general, the electromagnetic properties of a medium can be described by a dielectric constant (ε) and a magnetic permeability (μ). Both ε and μ are complex ' f = , a 〃. When a uniform absorbing material is applied to the metal surface, its thickness is d. When electromagnetic waves are incident on the absorbing material, electromagnetic waves may be in the medium according to the fundamental Maxwe丨丨, s Equations and Boundary Condition of the electromagnetic wave. Resonance occurs, that is, the incident electromagnetic wave energy is converted into a precession of spin in the medium by resonance, and finally the heat energy is dissipated, as if the incident electromagnetic wave energy is absorbed by the medium. According to the electromagnetic field electric field and magnetic field boundary conditions, the plane electromagnetic wave is incident on the sheet absorbing body with the metal plate attached as shown in Fig. 1. The reversible conductive magnetic wave reflection coefficient is 6 1341854

Etanh(y Γ = 1_£_c_

Stanh(y^5) + 1 V ε c

Where € = 〆-/*£·", reed. Therefore, the reflection coefficient Γ is an equation of six parameters (f, d, 6*', 〆, 〆, ///quot;), and osrsl, here defines the attenuation value D in decibels (dB) Ζ) ξ 201 ( ^Γ|For the attenuation value exceeding 20dB, that is, |Γ|<0.1, the six parameters of the above reflection coefficient can be achieved by appropriate matching. The absorber made of micron graphite powder used in the present invention is subjected to free space measurement. The magnetic permeability coefficient is measured, the real part approaches 1 and the imaginary part approaches zero. The effect on the overall absorption performance is negligible, which is mainly determined by the value of the dielectric constant. Therefore, micron graphite can be regarded as pure media. Electrical absorbing material.

The invention adopts the particle size of 30; tzm graphite as the absorbing material, and adjusts the electromagnetic parameter matching of the absorbing body by adding an appropriate weight percentage of the high molecular polymer and the dispersing aid, and the absorption value in the X-Band band can be more than 20 dB. The absorbent body having a thickness of less than 1.0 mm and a weight of less than 1.3 kg/m2 is superior to the published dielectric absorbing material, having a thickness of 1.5 mm to 3.0 mm and a weight of 2.0 to 3.0 kg/m2. , magnetic absorbing materials, thickness of 1.5mm ~ 2.0mm, weight 3.0 ~ 6.0kg / m2 of the public information. [Embodiment] The present invention adopts Graphite Degu Company's 1341854 3 0 micron-sized graphite powder, which is designed to be 2 5~3 Ο % by weight, respectively, and is mixed with epoxy resin according to different weight percentages, and a suitable anion is added. The polymer interface activator is a dispersing aid, and is dispersed by a three-roller to a fineness of less than 5 ng. The milled slurry is placed in an aluminum mold of uniform thickness, and the mold is heated at an appropriate temperature and pressure. After being made into a sheet type, it is released from the mold. The material formula is detailed as shown in Table 1 ' 2 °

The comparative example uses CABOT company code XC-72 carbon black powder with particle size of 0·1 ym, respectively designed 25% by weight, mixed with epoxy resin according to different weight percentage, adding appropriate anionic polymer interface agent for dispersion Additives, and use three-roller grinding to disperse to less than 5 # m. The slurry is placed in a uniform thickness of aluminum mold, and the mold is heated at an appropriate temperature and pressure to form a sheet-shaped shape. The model is ready. The material formula is as shown in Table 1. Table of material formula ingredients

A material number and Wt% B polymer Wt% dispersing aid phr pair A+B number Wt°/〇FF33 2 5% 75% 10 phr FF33 2 7.5 % 72.5 10 phr FF33 3 0% 70% 10 phr VULCAN XC-72 2 5% 75% 10 phr 1341854 Table 2. Composition of polymer composition Table A Epoxy resin B Soft epoxy resin thinner C Hardened 剤 Pair A + BD Dispersant A + B 70% 3 0% 3 5p hr 50phr Epoxy: Shell Chemical EPON 828

Soft epoxy resin thinner: Dow Chemical DER 732

Hardening thorn: Jeffamine D-230 Dispersing agent: ED211 Example 1. Take FF33 graphite and Table 2 epoxy resin and dispersing aid according to the weight ratio of 25%: 75% and 10%, mix and stir evenly and then grind through three barrels. Disperse to 5/zm or less and pour into a 1mm mold to pressurize to 70kg/cm2, heat at 120°C, and release the mold for 30 minutes. Example 2: Take FF3 3 graphite and the epoxy resin and dispersing aid of Table 2 according to the weight ratio of 27.5%: 72.5% and 10%, mix and stir evenly and then disperse to 5 min. The mold was pressed to 70 kg/cm2, heated at 120 °C, and released for 30 minutes. Example 3: Take FF3 3 graphite and the epoxy resin and dispersing aid of Table 2 according to the weight ratio of 30%: 70% and 10%, mix and stir evenly and then disperse to 5 mins by three barrels and pour into 1mm of aluminum. The mold was pressed to 70 k g/cm2, heated at 120 ° C, and released for 30 minutes. The finished film was measured by the Damaskos free space material quality measurement system to measure the sample absorbing properties. 9 1341854

Example 1 Microwave Measurement Results Example 1 Thickness (mm) 1mm Weight (kg/m2) 1.27kg/m2 Absorption characteristic diagram Curve 9 in Figure 2 Maximum attenuation intensity (dB) 21.32dB Maximum attenuation frequency (GHz) 11.82GHz Example Two microwave absorption characteristics measurement results: Item Example 2 Thickness (mm) 0.97mm Weight (kg/m2) 1.26kg/m2 Absorption characteristic diagram Curve in Figure 2 Maximum attenuation intensity (dB) 22.95dB Maximum attenuation frequency (GHz) 10.62GHz Example 3 Microwave Absorption Characteristics Measurement Results: Item Example 3 Thickness (mm) 0.97mm Weight (kg/m2) 1.29kg/m2 Absorption characteristic diagram Curve in Figure 2 Maximum attenuation intensity (dB) 20.02dB Maximum attenuation frequency (GHz) 9.62GHz

Comparative example Microwave absorption characteristics measurement results: Item Comparative example Thickness (mm) 2.10mm Weight (kg/m2) 2.29kg/m2 Maximum attenuation intensity (dB) 22.02dB 10 1341854

Maximum attenuation frequency (GHz) 9.60 GHz Comprehensive analysis of experimental results: Project example 1 Example 2 Example 3 Comparative example Powder particle size 3 0 /zm 3 0 // m 3 0 kernel m 0 . 1 // m Powder to resin weight ratio % 25:75 27.5 : 72.5 30 : 70 25:75 Thickness (mm) 1.00 0.97 0.97 2.10 Weight (kg/ m2) 1.27 1.26 1.29 2.29 Maximum attenuation strength (dB) 21.32 22.95 20.22 -20.02 Maximum attenuation frequency (GHz) 11.82 10.62 9.62 9.60 10dB Attenuation bandwidth (GHz) 1.77 1.68 1.53 1.50 Attenuation 10dB Starting frequency (GHz) 10.89~ 12.66 9.81 ~ 11.49 8.88 ~ 10.41 8.80- 14.30 20dB Bandwidth (GHz) 0.27 0.15 0.09 0.08 Attenuation 20dB Starting frequency (GHz) 11.70~ 11.97 10.47 ~ 10.62 9.57 ~ 9.66 9.56 ~ 9.65 From the above comparison table, it can be clearly seen that the present invention is made of a micron-sized graphite powder of 25 to 30% wt and an epoxy resin of 70 to 75 % wt to a thickness of less than or equal to 1mm, the sheet-type absorbing material with a weight less than 1.30kg/m2 has an absorption performance of 20dB or more at the main peak of 8~12GHz, and the 1341854 10dB bandwidth is about 2GHz, and the present invention effectively reduces the weight. Thickness, to enhance absorption performance X-Band frequency band. Therefore, the invention has the advantages of light weight in the X-Band frequency band, better absorption effect, thinner thickness and lighter weight, and is suitable for the absorbing material of the X-Band frequency band. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view of a sheet absorption body in which a positive wave of electromagnetic waves is incident on a back side of a metal plate. Figure 2 shows the relationship between sample electromagnetic wave attenuation greater than 20 dB and frequency.

[Main component symbol description] 1 Dielectric graphite powder absorption sheet. 2 back cover metal plate. 3 free space incident electromagnetic waves. 4 electromagnetic and dielectric parameters of the absorber. 5 The absorber is reflected back to the free-space electromagnetic wave. 6 absorbs the z-axis position where the sheet thickness is zero. 7 absorbs the z-axis position of the sheet thickness d. 8 electromagnetic wave propagation travels +z axis direction.

9 sample 1 sheet thickness lmm graphite powder content is 25% of the reflection attenuation curve. 10 sample 2 sheet thickness 0. 9 7mm graphite powder content is 27.5% of the reflection attenuation curve. 1 1 sample 3 sheet thickness 0.97mm graphite powder content is 30% of the reflection attenuation curve.

Claims (1)

1341854 i-----l X. Patent application scope: :----------- 1. A micro-graphite powder X-frequency absorbing material composition, comprising: (a) a particle size of 25 〜35// m finely disintegrated graphite powder containing Dong to 25~30wt%; (b) a high molecular polymer content of 70~75wt%; (c) a dispersing aid The content is 总>x2 10wt% of the sum of (a) and (b); (a) is added to (b) and (c) and stirred uniformly, and then dispersed by three-roller grinding, poured into a mold and heated under pressure. In the form of a sheet, the composition of the first aspect of the patent application, wherein (a) the purity of the graphite is 95.0 to 97.0%. 3. For example, the composition of the first paragraph of the patent application garden, wherein (b) means epoxy resin, epoxy soft diluent and hardener. 4. The composition of claim 1 wherein (c) means that the anionic polymeric surfactant has a graphite powder dispersed.