Wide-temperature-range microwave heating method for strong-reflection material

Abstract

A wide-temperature-range microwave heating method for a strong-reflection material is characterized in that a stacked metamaterial film is placed on the surface of the strong-reflection material to form a stacked structure, the stacked structure containing the stacked metamaterial film is irradiated through microwaves, and wide-temperature-range microwave efficient heating is conducted on the strong-reflection material. The device has the advantages of wide applicable temperature range, high heating efficiency, high heating speed and the like.

Description

Technical Field

[0001] This invention relates to the field of microwave heating technology, and in particular to a microwave heating technology for highly reflective materials, specifically a wide-temperature-range microwave heating method for highly reflective materials. Background Technology

[0002] Microwaves cannot be fed into strongly reflective materials, therefore it is generally believed that these materials cannot be heated by microwaves. The inventors' team previously placed a dielectric layer and artificial microstructures on the surface of a strongly reflective material, forming an absorbing metasurface. By irradiating this metasurface with microwaves, they achieved efficient microwave heating of the strongly reflective material. However, due to the inherently temperature-sensitive electromagnetic properties of existing dielectric materials, the absorption peak of the metasurface is prone to shift over a wide temperature range, leading to a decrease in absorption performance. This poses a challenge to the stable microwave heating of strongly reflective materials over a wide temperature range. Summary of the Invention

[0003] The purpose of this invention is to address the problem that existing microwave absorbing metasurfaces are prone to degradation of microwave absorption performance over a wide temperature range and are difficult to stably microwave heat highly reflective materials. The invention provides a wide-temperature-range microwave heating method for highly reflective materials, which can achieve stable and efficient microwave heating of highly reflective materials over a wide temperature range.

[0004] The technical solution of this invention is:

[0005] A wide-temperature-range microwave heating method for highly reflective materials, characterized by: placing stacked metafilms on the surface of the highly reflective material to form a layered structure, and using microwave irradiation of the layered structure to perform wide-temperature-range efficient microwave heating of the highly reflective material; wherein the stacked metafilms are composed of... ( It consists of a dielectric layer and a patch, arranged in the order of dielectric layer 1, patch 1, dielectric layer 2, patch 2... dielectric layer patch The patches are arranged sequentially from the surface of the highly reflective material outwards; The area should be smaller than the patch. The area, and the patch The covered area should be on the patch Within the covered area.

[0006] The patch Area of ​​the circumcircle The following requirements should be met:

[0007] ,

[0008] And for any frequency The stacked structure at frequency Absorption rate at the location All conditions are met:

[0009] ,

[0010] in, The speed of light in a vacuum; temperature , and These represent the minimum and maximum values ​​of the heating temperature range for highly reflective materials, respectively. For the layered structure at temperature The lowest frequency in the absorption band with an absorption rate of 30%, For the layered structure at temperature The highest frequency in the absorption band with an absorption rate of 30%.

[0011] The absorption frequency band of the stacked structure is at any temperature point within the heating temperature range of the strong reflective material. It must meet the following requirements:

[0012] ,

[0013] in, and These are the minimum and maximum values ​​of the operating frequency band of the microwave heating equipment, respectively.

[0014] The highly reflective material refers to metals, alloys, and one or more reinforced composite materials selected from carbon fibers, carbon nanotube fibers, graphene fibers, metal meshes, and alloy meshes.

[0015] The patch is made of a conductive material, and the conductive material must have a conductivity higher than 10 in one direction. 4 S / m, such as metals like gold, aluminum, and nickel, alloys like stainless steel, carbon steel, and aluminum alloys, and conductive composite materials reinforced by one or more of carbon fibers, carbon nanotube fibers, graphene fibers, metal meshes, and alloy meshes.

[0016] The dielectric layer is made of one or more dielectric materials with a dielectric constant of less than 16 and a dielectric loss angle of less than 5, such as polymers, polymer composites, ceramics, ceramic composites, ferrite materials, ferroelectric materials, and ferromagnetic materials.

[0017] The beneficial effects of this invention are:

[0018] 1. By adjusting the shape and size parameters of each component in the stacked metafilm, the electromagnetic absorption performance of the stacked structure can be easily designed.

[0019] 2. The stacked structure containing stacked metafilms has stable electromagnetic absorption performance over a wide temperature range, enabling stable and efficient microwave heating of highly reflective materials over a wide temperature range. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the stacked metafilm of the present invention.

[0021] Figure 2 This is an electromagnetic simulation model for designing stacked metafilms, as described in this invention.

[0022] Figure 3 This invention relates to the stacked structure containing a double-layered stacked metafilm and its electromagnetic absorption characteristics.

[0023] Figure 4 The temperature-dependent electromagnetic properties of the stacked structure containing a double-layer stacked metafilm of the present invention are as follows: (a) absorption curve of the stacked structure in the temperature range from room temperature to 400 °C; (b) temperature-dependent absorption rate curve at a frequency of 2.45 GHz.

[0024] Figure 5 The microwave heating effect of the stacked structure containing double-layer stacked metafilm of the present invention is shown in the following figures: (a) Schematic diagram of thermocouple temperature measurement; (b) Temperature curve of the stacked structure under different microwave power density inputs; (c) Temperature curve under cyclic heating-cooling; (d) Electromagnetic absorption curve of the stacked structure after 6 cycles of heating-cooling.

[0025] Figure 6 This is a typical application case for the consolidation of CF / PEEK composites. (a) Schematic diagram of vacuum bag arrangement; (b) Real-time temperature curve of the laminated structure containing double-layer stacked metamaterial films during the consolidation process. Detailed Implementation

[0026] The method solution of the present invention will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0027] like Figure 1 As shown.

[0028] A wide-temperature-range microwave heating method for highly reflective materials involves placing stacked metafilms on the surface of the highly reflective material to form a layered structure, and then using microwave irradiation of the layered structure to efficiently heat the highly reflective material over a wide temperature range. The stacked metafilms are composed of... ( It consists of a dielectric layer and a patch, arranged in the order of dielectric layer 1, patch 1, dielectric layer 2, patch 2... dielectric layer patch The patches are arranged sequentially from the surface of the highly reflective material outwards; The area should be smaller than the patch. The area, and the patch The covered area should be on the patch Within the covered area.

[0029] In this invention, the patch Area of ​​the circumcircle The following requirements should be met:

[0030] ,

[0031] And for any frequency The stacked structure at frequency Absorption rate at the location All conditions are met:

[0032] ,

[0033] in, The speed of light in a vacuum; temperature , and These represent the minimum and maximum values ​​of the heating temperature range for highly reflective materials, respectively. For the layered structure at temperature The lowest frequency in the absorption band with an absorption rate of 30%, For the layered structure at temperature The highest frequency in the absorption band with an absorption rate of 30%.

[0034] In this invention, to ensure that the highly reflective material can be stably heated by microwaves over a wide temperature range, the absorption frequency band of the stacked metafilm structure is within any temperature range of the heating temperature of the highly reflective material. It must meet the following requirements:

[0035] ,

[0036] in, and These are the minimum and maximum values ​​of the operating frequency band of the microwave heating equipment, respectively.

[0037] In this invention, the patch is made of a conductive material, and the conductive material must have a conductivity higher than 10 in a certain direction. 4S / m, such as metals like gold, aluminum, and nickel; alloys like stainless steel, carbon steel, and aluminum alloys; and conductive composite materials reinforced with one or more of carbon fibers, carbon nanotube fibers, graphene fibers, metal meshes, and alloy meshes. As a specific embodiment, the patch is made of stainless steel, but is by no means limited to stainless steel. The aforementioned conductive materials that meet the conductivity requirements can all achieve good heating effects after optimizing the shape, size, and material of the stacked metamaterial.

[0038] In this invention, the dielectric layer is made of one or more dielectric materials with a dielectric constant less than 16 and a dielectric loss angle less than 5, such as polymers, polymer composites, ceramics, ceramic composites, ferrite materials, ferroelectric materials, and ferromagnetic materials. Preferably, materials with good dielectric properties, such as polyimide and polytetrafluoroethylene, are selected. As a specific embodiment, the dielectric layer in the stacked metafilm is made of polyimide film with a high temperature resistance range and good mechanical flexibility. However, the dielectric layer material is not limited to polyimide. After optimization of the stacked metafilm, the dielectric layers of the above materials can all achieve good heating effects.

[0039] In this invention, the patches of the stacked metafilm are formed into corresponding geometric shapes by chemical etching, electroplating, laser etching, and other methods.

[0040] The material, thickness, and shape and size of the dielectric layer within the aforementioned stacked metafilm were all determined using finite element simulation. A single-port electromagnetic analysis model of the "stacked metafilm + highly reflective material" with periodic boundaries was established in electromagnetic simulation software (e.g., Figure 2 The structural parameters mentioned above are iteratively optimized using parametric scanning, and the structural form and size requirements that can meet the heating needs at commonly used microwave heating frequencies (such as 2.40-2.50 GHz, 915 MHz, etc.) are selected. While the above process appears complex, it is actually all performed by a computer, and the above work lacks creativity.

[0041] Below is one specific example based on the above principles:

[0042] A bilayer stacked metamaterial for consolidating carbon fiber reinforced high-temperature resin-based composites. For example... Figure 3 As shown, this stacked metamaterial film consists of two patches and a dielectric layer stacked in the thickness direction, from bottom to top as dielectric layer 1, patch 1, dielectric layer 2, and patch 2. The patches are all made of stainless steel film, which is both high-temperature resistant and flexible, while the dielectric layer is made of polyimide film, which is also both high-temperature resistant and flexible. Here, the high-reflectivity material uses a substrate made of stainless steel film.

[0043] A single-port electromagnetic simulation model was established using the Floquet port in the HFSS frequency domain simulation software. Under the condition of a fixed dielectric layer thickness, the influence of the length difference between patch 1 and patch 2 on the electromagnetic absorption rate of the "double-layer metafilm + strong reflective material" was investigated (e.g., Figure 3 This demonstrates the ease of design of double-layer stacked metafilms. Since the absorbing center frequency used is 2.45 GHz, the circumcircle of the patch needs to meet the following requirements. After parametric scanning and dimensional iteration, the final dimensions of the structure are: , , , .

[0044] Based on this, a double-layer stacked metafilm was prepared using a laser etching machine, and the electromagnetic properties of the double-layer stacked metafilm + stainless steel substrate were tested in the temperature range from room temperature to 400 °C. The test results are as follows: Figure 4 As shown in the figure, when the temperature rises from room temperature to 180 ℃, the electromagnetic absorption performance curve of the "double-layer stacked metafilm + stainless steel substrate" hardly changes. With further temperature increases, the low-frequency absorption peak gradually broadens, and the entire electromagnetic absorption peak shows a trend towards lower frequencies. When the temperature exceeds 300 ℃, the two absorption peaks gradually merge into a single broad absorption peak. Since the commonly used microwave heating frequency is 2.45 GHz, the absorptivity of the "double-layer stacked metafilm + stainless steel substrate" at 2.45 GHz was statistically analyzed. The results show that although the electromagnetic absorption rate fluctuates throughout the heating process, the minimum absorptivity still exceeds 75%, meeting the requirements.

[0045] The microwave heating performance of the "double-layer stacked metamaterial film + stainless steel substrate" in this example is as follows: Figure 5 As shown in (a), an electromagnetically shielded thermocouple was attached to the central region of the back side of the stainless steel substrate to monitor temperature changes in real time. Experimental results show that when the microwave power density reaches 1.728 W / dm², 3 At that time, the "double-layer stacked metamaterial film + stainless steel substrate" can be heated from room temperature to 400 ℃ in just 7.7 minutes (e.g., Figure 5 (b)). For example Figure 5 As shown in (c) and (d), after six cycles of heating and cooling, the electromagnetic absorption peak of the “double-layer stacked metafilm + stainless steel substrate” only showed very slight peak broadening and intensity reduction, which demonstrates the good reusability of the double-layer stacked metafilm.

[0046] Finally, this double-layer stacked metamaterial was used for the consolidation of CF / PEEK composites. For example... Figure 6As shown in (a), a double-layer stacked metafilm is placed on a stainless steel equalizing plate on the surface of a CF / PEEK composite preform. Then, a vacuum bag is used to tightly bond the double-layer stacked metafilm, the stainless steel equalizing plate, and the CF / PEEK composite preform together. Although the CF / PEEK composite and its surface stainless steel equalizing plate are strongly reflective of microwaves and cannot be heated by microwaves, the double-layer stacked metafilm + stainless steel equalizing plate has better electromagnetic absorption performance. High-power microwave heating of the double-layer stacked metafilm + stainless steel equalizing plate can heat the CF / PEEK composite preform through heat conduction. Figure 6 (b) shows the real-time temperature curve of the stainless steel equalizing plate surface. It can be seen that under microwave irradiation, the stainless steel equalizing plate can steadily rise at a heating rate of approximately 3 °C / min, and after reaching a minimum temperature of 380 °C and a maximum temperature not exceeding 400 °C, it enters a 20-minute holding period, followed by a slow cooling rate of less than 2 °C / min, achieving the consolidation of the CF / PEEK composite. During the wide temperature range of room temperature to 400 °C consolidation, the temperature curve shows no significant fluctuations, demonstrating the stable microwave heating performance of this method.

[0047] The parts not covered in this invention are the same as or can be implemented using existing technologies.

Claims

1. A wide-temperature-range microwave heating method for a highly reflective material, characterized in that: A stacked metafilm is placed on the surface of a highly reflective material to form a layered structure. The layered structure is then irradiated with microwaves to achieve wide-temperature-range, high-efficiency microwave heating of the highly reflective material. The stacked metafilm is composed of… ( It consists of a dielectric layer and a patch, arranged in the order of dielectric layer 1, patch 1, dielectric layer 2, patch 2... dielectric layer patch The patches are arranged sequentially from the surface of the highly reflective material outwards; The area should be smaller than the patch. The area, and the patch The covered area should be on the patch Within the covered area.

2. The method according to claim 1, characterized in that: The patch Area of ​​the circumcircle The following requirements should be met: ， And for any frequency The stacked structure at frequency Absorption rate at the location All conditions are met: ， in, The speed of light in a vacuum; temperature , and These represent the minimum and maximum values ​​of the heating temperature range for highly reflective materials, respectively. For the layered structure at temperature The lowest frequency in the absorption band with an absorption rate of 30%, For the layered structure at temperature The highest frequency in the absorption band with an absorption rate of 30%.

3. The method according to claim 1, characterized in that: The absorption frequency band of the stacked structure is at any temperature point within the heating temperature range of the strong reflective material. It meets the following requirements: ， in, and These are the minimum and maximum values ​​of the operating frequency band of the microwave heating equipment, respectively.

4. The method according to claim 1, characterized in that: The highly reflective material refers to metals, alloys, and one or more reinforced composite materials selected from carbon fibers, carbon nanotube fibers, graphene fibers, metal meshes, and alloy meshes.

5. The method according to claim 1, characterized in that: The patch is made of a conductive material, and the conductive material must have a conductivity higher than 10 in a certain direction. 4 S / m.

6. The method according to claim 1, characterized in that: The dielectric layer is made of one or more dielectric materials with a dielectric constant of less than 16 and a dielectric loss angle of less than 5.

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