A microcrystalline ceramic composite far infrared heater

Abstract

The present application relates to a kind of far infrared heater of microcrystalline ceramic composite material, belong to far infrared heater technical field, including insulating substrate layer, electrode system, heat-conducting transition layer, microcrystalline ceramic radiation layer, the insulating substrate layer uses aluminum nitride ceramic plate, the electrode system uses embedded molybdenum metal grid electrode, the electrode system is set to insulating substrate layer, the heat-conducting transition layer uses silicon carbide nanowire reinforced alumina, the heat-conducting transition layer covers electrode system, the microcrystalline ceramic radiation layer is combined in heat-conducting transition layer.In the present application, compared with the radiation efficiency of only 0.6-0.8 of traditional metal heating body, emissivity ≥0.94 is adopted microcrystalline ceramic composite material radiation layer, with high radiation efficiency, laser microcrystallization surface layer forms nanoscale grain, can effectively shorten heat conduction path, to reduce heat consumption, more energy saving.

Description

Technical Field

[0001] This invention relates to the field of far-infrared heater technology, and in particular to a far-infrared heater made of microcrystalline ceramic composite material. Background Technology

[0002] A far-infrared heater is a device that uses far-infrared rays to transfer heat and heat objects. When an electric current is applied to the heating element inside the heater (such as a quartz tube, carbon fiber tube, ceramic plate / lamp, metal heating wire, etc.), it generates high temperature. The high temperature of the heating element will radiate electromagnetic waves, with the most energy concentrated in the far-infrared band. These far-infrared rays propagate out like light. When they shine on the surface of an object, the energy is absorbed by the object. After absorbing the far-infrared energy, the molecules inside the object will accelerate their vibration or rotation, thereby directly generating heat inside the object. This process is direct and does not require heating the air in between.

[0003] Traditional far-infrared heaters typically employ metal heating elements and ordinary ceramic heating elements. Metal heating elements, such as nickel-chromium alloys, suffer from low radiation efficiency and high energy consumption. Ordinary ceramic heating elements have slow thermal response, poor thermal shock resistance, and are prone to cracking. Carbon fiber materials are expensive, and their surface electrostatic charge poses a significant safety hazard. To address the problems of low radiation efficiency and poor structural reliability in traditional far-infrared heaters, a microcrystalline ceramic composite far-infrared heater is proposed. Compared to the radiation efficiency of only 0.6-0.8 for traditional metal heating elements, the microcrystalline ceramic composite material boasts an emissivity ≥0.94, exhibiting high radiation efficiency. Furthermore, the laser-microcrystallized surface layer forms nanoscale grains, enabling… It effectively shortens the heat conduction path, thereby reducing heat consumption and achieving greater energy efficiency. The gradient material design eliminates interfacial thermal stress and avoids delamination failure by conducting heat through the transition layer and radiation layer. The micropore array design expands the radiation area and improves the uniformity of heat distribution. The material is free of lead, chromium and other heavy metals, resulting in better environmental protection. The base layer provides electrical insulation and rapid heat conduction, preventing heat accumulation. The electrode layer distributes current evenly, reducing resistance heat loss. The transition layer buffers the difference in thermal expansion coefficients, enhancing the interlayer bonding strength. The radiation layer is the core heating element, efficiently emitting 6-14μm far-infrared rays. The functional layer expands the radiation area and regulates the spectral distribution. Summary of the Invention

[0004] This invention provides a far-infrared heater made of microcrystalline ceramic composite material, which solves the problems of low radiation efficiency and poor structural reliability of traditional far-infrared heaters. Through the three-in-one innovation of materials, structure and process, it realizes the high efficiency, long life and low cost of far-infrared heater manufacturing, and provides a reliable technical path for industrialization.

[0005] The present invention provides the following solution to the above-mentioned technical problems: a far-infrared heater made of microcrystalline ceramic composite material, comprising an insulating substrate layer, an electrode system, a thermally conductive transition layer, and a microcrystalline ceramic radiation layer. The insulating substrate layer is made of aluminum nitride ceramic plate, the electrode system is made of embedded molybdenum metal mesh electrode, the electrode system is disposed on the insulating substrate layer, the thermally conductive transition layer is made of silicon carbide nanowire reinforced alumina, the thermally conductive transition layer covers the electrode system, and the microcrystalline ceramic radiation layer is composite on the thermally conductive transition layer.

[0006] The microcrystalline ceramic radiant layer has the following composition by mass percentage: 65-75% α-Al2O3, 15-20% SiC, 5-8% rare earth oxides, and 3-5% ZrO2;

[0007] The microcrystalline ceramic radiation layer is laser microcrystallization treatment to form a surface functional layer with a microporous structure;

[0008] The preparation method of the far-infrared heater includes the following steps:

[0009] S1, substrate forming, using AIN powder, Y2O3 and PVA binder as raw materials, through casting film formation, lamination and cold isostatic pressing to process the insulating substrate layer;

[0010] S2, Electrode integration, the surface of the insulating substrate is laser-etched with trenches, then filled with molybdenum paste, sintered in a hydrogen atmosphere, and finally the surface is polished to complete the preparation of the electrode system.

[0011] S3, preparation of transition layer and radiation layer slurry, preparation of thermally conductive transition layer slurry, Al2O3 nanopowder, SiC nanowires and ethanol ball milling and mixing to complete the preparation;

[0012] The preparation of the slurry for the microcrystalline ceramic radiation layer involves high-energy ultrasonic dispersion of the component powders and the organic solvent xylene.

[0013] S4, gradient lay-up, the insulating substrate layer screen-printed transition layer, the cast microcrystalline ceramic radiation layer green body, and finally the lamination hot pressing;

[0014] S5, stepped sintering, stage 1, 1300℃ / 1h, for degreasing and pre-densification;

[0015] Stage 2, 1550℃ / 2h, complete densification;

[0016] S6, Surface functionalization treatment: The microcrystalline ceramic radiation layer is laser microcrystallized to form a surface functional layer with a microporous structure.

[0017] Chemical etching is performed on the surface functional layer to form a microporous structure;

[0018] S7, encapsulation and testing, edge coating with aluminum silicate insulating adhesive, emissivity testing using an integrating sphere spectrometer.

[0019] Based on the above technical solution, the present invention can be further improved as follows.

[0020] Furthermore, the insulating substrate layer is provided with a groove corresponding to the electrode system.

[0021] Furthermore, the rare earth oxide is a mixture of cerium oxide (CeO2) and yttrium oxide (Y2O3) in a mass ratio of 3:1.

[0022] Furthermore, the surface functional layer has a thickness of 50-100 μm, has a micropore array with a pore size of 10-50 μm, and nanocrystals are distributed on the inner wall of the micropores, wherein the nanocrystal size is ≤100 nm.

[0023] Furthermore, in step S2, the sintering temperature is 1450℃ and the sintering time is 2 hours.

[0024] Furthermore, in step S2, the mixing time is 12 hours and the ultrasonic dispersion time is 1 hour.

[0025] Furthermore, in step S6, laser microcrystallization is performed by scanning the surface of the radiation layer with a CO2 laser at a wavelength of 10.6 μm and scanning parameters: power density 10. 5 W / cm², scanning speed 50mm / s, spot diameter 0.2mm, surface layer instantaneously melts and forms a surface functional layer after ultra-fast cooling.

[0026] Furthermore, in step S6, the etching solution uses a volume ratio of 40%HF:65%HNO3 = 1:3, and the etching time is 30 min. It selectively dissolves the amorphous phase, taking advantage of the significant difference in dissolution rates between the amorphous and crystalline phases in specific chemical reagents. It directionally etches away the amorphous regions in the material, retains the crystalline phase structure, and forms a microporous structure. After etching, the residual HF is neutralized by using a saturated Na2CO3 solution as a stop solution. Finally, it is cleaned with deionized water and ethanol, and then dried by heating with nitrogen gas.

[0027] The beneficial effects of this invention are as follows: This invention provides a far-infrared heater made of microcrystalline ceramic composite material, which has the following advantages:

[0028] 1. Compared to the radiation efficiency of only 0.6-0.8 of traditional metal heating elements, the radiation layer of microcrystalline ceramic composite material has an emissivity of ≥0.94, which has high radiation efficiency. The laser microcrystallization surface layer forms nano-sized grains, which can effectively shorten the heat conduction path, thereby reducing heat consumption and making it more energy-efficient.

[0029] 2. The gradient material design eliminates interfacial thermal stress and avoids delamination failure by passing through the transition layer and radiation layer. The base layer provides electrical insulation and rapid heat conduction to prevent heat accumulation. The electrode layer distributes current evenly, reducing resistance heat loss. The transition layer buffers the difference in thermal expansion coefficients and enhances the interlayer bonding strength. The radiation layer is the core heating element, efficiently emitting 6-14μm far-infrared rays. The functional layer expands the radiation area and regulates the spectral distribution.

[0030] 3. The surface functional layer design with microporous array can expand the radiation area and improve the uniformity of heat distribution. The material is free of heavy metals such as lead and chromium, resulting in better environmental protection.

[0031] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0032] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0033] Figure 1 This is a schematic diagram of the structure of a far-infrared heater made of microcrystalline ceramic composite material according to an embodiment of the present invention;

[0034] Figure 2 This is a three-dimensional rendering of a far-infrared heater made of microcrystalline ceramic composite material, provided as an embodiment of the present invention.

[0035] The attached diagram lists the components represented by each number as follows:

[0036] 1. Insulating base layer; 2. Electrode system; 3. Thermally conductive transition layer; 4. Microcrystalline ceramic radiation layer; 5. Surface functional layer. Detailed Implementation

[0037] The following is in conjunction with the appendix Figure 1-2 The principles and features of the present invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description and claims. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0039] like Figure 1-2 As shown, this invention provides a far-infrared heater made of microcrystalline ceramic composite material, comprising an insulating substrate layer 1, an electrode system 2, a thermally conductive transition layer 3, and a microcrystalline ceramic radiating layer 4. The insulating substrate layer 1 is made of aluminum nitride ceramic plate, the electrode system 2 is made of embedded molybdenum metal mesh electrode, and the electrode system 2 is disposed on the insulating substrate layer 1. The thermally conductive transition layer 3 is made of silicon carbide nanowire reinforced alumina and covers the electrode system 2. The microcrystalline ceramic radiating layer 4 is composited on the thermally conductive transition layer 3. The composition of the microcrystalline ceramic radiating layer 4 by mass percentage is: 65-75% α-Al2O3, 15-20% SiC, 5-8% rare earth oxides, and 3-5% ZrO2. The microcrystalline ceramic radiating layer 4 is laser microcrystallized to form a surface functional layer 5 with a microporous structure.

[0040] Preferably, the insulating substrate layer 1 is provided with a groove corresponding to the electrode system 2.

[0041] Preferably, the rare earth oxide is a mixture of cerium oxide (CeO2) and yttrium oxide (Y2O3) in a mass ratio of 3:1.

[0042] Preferably, the surface functional layer 5 has a thickness of 50-100 μm, has a micropore array with a pore size of 10-50 μm, and the inner wall of the micropore is distributed with nanocrystals with a particle size of ≤100 nm.

[0043] The specific working principle and usage method of this invention are as follows:

[0044] S1, substrate forming: using AlN powder, Y2O3 and PVA binder as raw materials, the substrate is formed by casting and laminating through a casting machine. The laminated preform is then subjected to uniform pressure by a cold isostatic press to prepare the insulating substrate 1.

[0045] S2, Electrode integration: The electrode system 2 is prepared by laser etching grooves on the surface of the insulating substrate 1 using a laser etching machine, followed by filling with molybdenum paste, and then sintering in a hydrogen atmosphere using a hydrogen sintering furnace at a temperature of 1450℃ for 2 hours. Finally, the surface is polished to complete the preparation of the electrode system 2.

[0046] S3, Preparation of transition layer and radiation layer slurry. The transition layer slurry was prepared by mixing Al2O3 nanopowder, SiC nanowires and ethanol by ball milling in a high-energy ball mill for 12 hours.

[0047] Radiation layer slurry preparation: The powder components and the organic solvent xylene were dispersed by high-energy ultrasonication for 1 hour.

[0048] S4, gradient lay-up, insulating substrate 1 screen-printed transition layer, cast radiation layer greening through casting-lamination machine, and finally lamination hot pressing;

[0049] S5, stepped sintering, is carried out by stepped sintering in a hot press sintering furnace;

[0050] Stage 1: Argon gas at 1300℃ for 1h, heating rate 5℃ / min, for degreasing and pre-densification;

[0051] Stage 2: Argon gas at 1550℃ for 2 hours, hot-pressed at 20MPa, to achieve full densification with a relative density >99.2%;

[0052] S6, surface functionalization treatment, laser microcrystallization, using a CO2 laser to scan the surface of the radiation layer at a wavelength of 10.6 μm, scanning parameters: power density 10 5 W / cm², scanning speed 50mm / s, spot diameter 0.2mm, surface instantaneous melting followed by ultra-fast cooling to form a nanocrystalline amorphous composite layer;

[0053] Chemical etching is performed in an ultrasonic-assisted etching tank. The etching solution uses a volume ratio of 40%HF:65%HNO3=1:3 and the etching time is 30 min. It selectively dissolves the amorphous phase by taking advantage of the significant difference in dissolution rates between the amorphous and crystalline phases in specific chemical reagents. This allows for the directional etching removal of amorphous regions from the material while preserving the crystalline structure, thus forming a microporous structure. After etching, the residual HF is neutralized by using a saturated Na2CO3 solution as a stop solution. Finally, the material is cleaned with deionized water and ethanol, and then dried with nitrogen in a vacuum drying oven.

[0054] S7, Encapsulation and Testing: Aluminum silicate insulating adhesive is applied to the edges using an automatic dispensing machine. The aluminum silicate insulating adhesive is temperature resistant to 800℃. Standard AC power is applied, and an integrating sphere spectrometer is used to test the emissivity.

[0055] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Content not described in detail in this specification is prior art known to those skilled in the art.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A far-infrared heater made of microcrystalline ceramic composite material, comprising an insulating substrate layer (1), an electrode system (2), a thermally conductive transition layer (3), and a microcrystalline ceramic radiating layer (4), characterized in that: The insulating substrate (1) is made of aluminum nitride ceramic plate, the electrode system (2) is made of embedded molybdenum metal mesh electrode, the electrode system (2) is disposed on the insulating substrate (1), the thermally conductive transition layer (3) is made of silicon carbide nanowire reinforced alumina, the thermally conductive transition layer (3) covers the electrode system (2), and the microcrystalline ceramic radiation layer (4) is composited on the thermally conductive transition layer (3). The microcrystalline ceramic radiation layer (4) has the following composition by mass percentage: 65-75% α-Al2O3, 15-20% SiC, 5-8% rare earth oxides, and 3-5% ZrO2; The microcrystalline ceramic radiation layer (4) is laser microcrystallization treatment to form a surface functional layer (5) with a microporous structure. The preparation method of the far-infrared heater includes the following steps: S1, substrate forming, using AIN powder, Y2O3 and PVA binder as raw materials, through casting, lamination and cold isostatic pressing to process the insulating substrate layer (1). S2, Electrode integration, the surface of the insulating substrate (1) is laser-etched with trenches, then filled with molybdenum paste, sintered in a hydrogen atmosphere, and finally the surface is ground to complete the preparation of the electrode system (2); S3, preparation of slurry for transition layer and radiation layer, preparation of slurry for thermally conductive transition layer (3), Al2O3 nanopowder, SiC nanowires and ethanol ball milling and mixing to complete the preparation; The preparation of the slurry for the microcrystalline ceramic radiation layer (4) was completed by high-energy ultrasonic dispersion of the powder components and the organic solvent xylene. S4, gradient lay-up, the insulating substrate layer (1) screen-printed transition layer, the cast microcrystalline ceramic radiation layer (4) green body, and finally the lamination hot pressing; S5, stepped sintering, stage 1, 1300℃ / 1h, for degreasing and pre-densification; Stage 2, 1550℃ / 2h, complete densification; S6, surface functionalization treatment, the microcrystalline ceramic radiation layer (4) is laser microcrystallization treatment to form a surface functional layer (5) with a microporous structure. Chemical etching is performed on the surface functional layer (5) to form a microporous structure; S7, encapsulation and testing, edge coating with aluminum silicate insulating adhesive, emissivity testing using an integrating sphere spectrometer.

2. The far-infrared heater made of microcrystalline ceramic composite material according to claim 1, characterized in that, The insulating substrate layer (1) is provided with a groove for the corresponding electrode system (2).

3. The far-infrared heater made of microcrystalline ceramic composite material according to claim 1, characterized in that, The rare earth oxide is a mixture of cerium oxide (CeO2) and yttrium oxide (Y2O3) in a mass ratio of 3:

1.

4. The far-infrared heater made of microcrystalline ceramic composite material according to claim 1, characterized in that, The surface functional layer (5) has a thickness of 50-100 μm, has a micropore array with a pore size of 10-50 μm, and has nanocrystals distributed on the inner wall of the micropores, wherein the nanocrystals have a particle size ≤100 nm.

5. The far-infrared heater made of microcrystalline ceramic composite material according to claim 1, characterized in that, In step S2, the sintering temperature is 1450℃ and the sintering time is 2 hours.

6. The far-infrared heater made of microcrystalline ceramic composite material according to claim 1, characterized in that, In step S2, the mixing time is 12 hours and the ultrasonic dispersion time is 1 hour.

7. The far-infrared heater made of microcrystalline ceramic composite material according to claim 1, characterized in that, In step S6, laser microcrystallization is performed by scanning the surface of the radiation layer with a CO2 laser at a wavelength of 10.6 μm and scanning parameters: power density 10. 5 W / cm², scanning speed 50mm / s, spot diameter 0.2mm, surface layer instantaneously melts, and forms surface functional layer after ultra-fast cooling (5).

8. The far-infrared heater made of microcrystalline ceramic composite material according to claim 1, characterized in that, In step S6, the etching solution uses a volume ratio of 40%HF:65%HNO3 = 1:3, and the etching time is 30 min. It selectively dissolves the amorphous phase, taking advantage of the huge difference in the dissolution rate between the amorphous phase and the crystalline phase in specific chemical reagents. It directionally etches to remove the amorphous regions in the material, retains the crystalline phase structure, and forms a microporous structure. After etching, the residual HF is neutralized by saturated Na2CO3 solution as a stop solution. Finally, it is cleaned with deionized water and ethanol, and then dried by heating with nitrogen.

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