Microwave absorbing and heating material and manufacturing method therefor

Abstract

The present invention relates to a microwave absorbing and heating material and a manufacturing method therefor and, more specifically, to a microwave absorbing and heating material capable of quickly absorbing electromagnetic waves and generating heat with respect to microwaves and having excellent high-temperature stability, and a manufacturing method therefor.

Description

Microwave absorbing and heating material and its manufacturing method

[0001] The present invention relates to a microwave absorbing and heating material and a method for manufacturing the same, and more particularly, to a microwave absorbing and heating material that can rapidly absorb electromagnetic waves and generate heat in response to microwaves and has excellent oxidation resistance and durability, and a method for manufacturing the same.

[0002] Microwave heating technology belongs to the electric heating technology family, which includes induction heating, radio frequency heating, direct resistance heating, and infrared heating. These heating methods all utilize specific electromagnetic spectrums. In certain fields, conventional heating methods and drying systems are already being completely replaced by microwave heating.

[0003] Conventional heating systems have the disadvantages of being bulky and difficult to operate. Furthermore, they emit pollutants that are harmful to the human body. Furthermore, from an energy consumption perspective, conventional heating systems use electricity, gas, and other sources for heating. These heating elements have a temperature rise rate of approximately 1 to 10 degrees Celsius per minute, requiring significant energy to reach the required high temperatures.

[0004] However, microwave heating offers many advantages, including rapid heat transfer, selective heating, compact equipment, rapid switching between heating and de-heating, and no combustion products, resulting in no environmental pollution. Conversely, as previously mentioned, conventional heating methods require a long time to reach high temperatures, consuming significant energy. Furthermore, even after heating is stopped, considerable time is required to cool to room temperature. However, microwave heating is characterized by reaching ultra-high temperatures in a very short time, within seconds, and immediately cooling to room temperature when heating is stopped.

[0005] Carbon fiber T-700 and T-1000 products from Toray of Japan have electrical resistance values ​​of 1.6 × 10 each. 3 Ω·cm and 1.4 × 10 3 Because it has a low resistance value of Ω·cm, it reacts violently with microwaves.

[0006] However, since carbon fiber is chemically composed of carbon layers, it undergoes an oxidation reaction in a short period of time when exposed to high temperatures above 480℃ in the air, eventually burning and being consumed, and because it reacts with H2, H2O, CO2, etc. at temperatures above 800℃, its use as a stable high-temperature microwave absorption and heating material is limited.

[0007] Another conventional microwave absorption technology involves plating carbon fibers with nickel, which has excellent conductivity. However, this technique, applied to fiber filaments, presents environmental concerns and increases weight due to plating. Furthermore, uniform fiber surface coating is difficult to achieve in preform-type products. Furthermore, when using these plated preforms to manufacture composites, the interfacial adhesion with the nickel coating layer is weak, making it impossible to achieve high-strength products.

[0008] Meanwhile, silicon carbide (SiC) is known as a stable microwave absorption and heat generation material even at high temperatures, but it has the problem that its heat generation performance is slower than that of carbon and a lot of energy is consumed to maintain high temperatures.

[0009] Therefore, it is necessary to develop a material for microwave absorption and heating that can quickly absorb electromagnetic waves and generate heat, and that is stable even at high temperatures.

[0010] [Prior Art Literature]

[0011] [Patent Document]

[0012] (Patent Document 1) Korean Patent No. 1745422 (Published: March 30, 2017)

[0013] (Patent Document 2) Korean Patent No. 2065524 (Published: June 21, 2019)

[0014] The purpose of the present invention is to provide a material for microwave absorption and heating that can rapidly absorb electromagnetic waves and generate heat in response to microwaves and is stable even at high temperatures, and a method for manufacturing the same.

[0015] In order to achieve the above purpose, one embodiment of the present invention provides a material for microwave absorption and heat generation characterized by reducing a metal oxide containing at least one metal element selected from the group consisting of titanium, cerium, and zirconium supported with molybdenum.

[0016] In a preferred embodiment of the present invention, the reduction treatment may be characterized in that it is performed at 300°C to 900°C in a reducing atmosphere.

[0017] In a preferred embodiment of the present invention, the reducing atmosphere may be characterized as being a reducing gas atmosphere containing at least one selected from the group consisting of hydrogen, carbon monoxide, ammonia, and methane.

[0018] In a preferred embodiment of the present invention, the molybdenum may be supported in an amount of 0.5 wt% to 20 wt% based on the total weight of the microwave absorbing and heating material.

[0019] Another embodiment of the present invention provides a method for manufacturing a microwave absorbing and heating material, characterized by comprising the steps of: (a) supporting molybdenum on a metal oxide containing at least one metal element selected from the group consisting of titanium, cerium, and zirconium; (b) drying and calcining the support on which the molybdenum is supported; and (c) reducing the calcined product.

[0020] In another preferred embodiment of the present invention, step (a) may be characterized by supporting molybdenum in a metal oxide at 0.5 wt% to 20 wt% based on the total weight of the microwave absorbing and heating material.

[0021] In another preferred embodiment of the present invention, the calcination in step (b) may be performed at 300°C to 900°C.

[0022] In another preferred embodiment of the present invention, the reduction treatment in step (c) may be characterized by reducing at 300°C to 900°C in a reducing atmosphere.

[0023] In another preferred embodiment of the present invention, the reducing atmosphere may be characterized as being a reducing gas atmosphere comprising at least one selected from the group consisting of hydrogen, carbon monoxide, ammonia, and methane.

[0024] The microwave absorbing and generating heat material according to the present invention is manufactured by reducing a specific metal oxide containing molybdenum, so that the manufacturing process is simple, microwaves can be absorbed instantly and heat generated, and not only is oxidation resistance and durability very excellent even in a high-temperature environment, but since the microwave absorbing and generating heat material is formed in a powder form, it can be easily applied to heating elements of various shapes, so that it can be effectively applied to various fields.

[0025] In addition, the microwave absorption and heat generation material according to the present invention is in the form of a support in which molybdenum is supported, and a catalytically active component can be additionally supported on the support, so that it can be usefully utilized in a microwave-utilizing catalytic reaction.

[0026] Figure 1 is a graph measuring the amount of power according to the heat generation of microwave absorption and heat generation materials manufactured in examples and comparative examples of the present invention.

[0027] Figure 2 is a graph measuring the heating rate of a microwave absorbing and heating material manufactured in an example and comparative example of the present invention.

[0028] Unless defined otherwise, 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 belongs. In general, the nomenclature used herein is well known and commonly used in the art.

[0029] As used herein, singular expressions include plural expressions unless the context clearly indicates otherwise, and terms such as “comprise,” “include,” or “have” used herein should be interpreted to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, and should be understood to not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0030] Additionally, in this specification, when each layer or element is referred to as being formed “on” or “over” each layer or element, it means that each layer or element is formed directly on each layer or element, or that other layers or elements may be additionally formed between each layer, on the object, or on the substrate.

[0031] The present invention relates to a microwave absorbing and generating material capable of rapidly absorbing electromagnetic waves and generating heat in response to microwaves and being stable even at high temperatures, and a method for manufacturing the same. The microwave absorbing and generating material is characterized by being made by reducing a metal oxide containing at least one metal element selected from the group consisting of titanium, cerium, and zirconium supported with molybdenum.

[0032] To avoid duplication, the description of each of the above components is provided in the manufacturing method of the microwave absorption and heating material described below.

[0033] The method for manufacturing a microwave absorbing and heating material according to the present invention first includes supporting molybdenum (Mo) on a metal oxide containing at least one metal element selected from the group consisting of titanium (Ti), cerium (Ce), and zirconium (Zr) [step (a)].

[0034] The above molybdenum (Mo) plays a role in absorbing microwaves and can be supported on the metal oxide at 0.5 wt% to 20 wt%, preferably 1 wt% to 10 wt%, based on the total weight of the microwave absorbing and heating material.

[0035] If the above molybdenum is loaded in an amount of less than 0.5 wt% based on the total weight of the microwave absorbing and heating material, there may be a problem in that the temperature cannot reach a high temperature because there is little component capable of absorbing microwaves, and if it exceeds 20 wt%, the proportion of molybdenum existing alone without being combined with the support (metal oxide) increases, which may lower the microwave absorption performance and stability.

[0036] In addition, the metal oxide on which the molybdenum is supported may be a metal oxide containing one or more metal elements selected from the group consisting of titanium (Ti), cerium (Ce), and zirconium (Zr) in terms of having a strong interaction with the metal, which serves to stably maintain and support the molybdenum structure.

[0037] Meanwhile, any method capable of supporting molybdenum on the metal oxide can be used without limitation, and specifically, molybdenum can be supported on the metal oxide using a method known in the technical field to which the present invention pertains, such as an impregnation method, a co-precipitation method, a solid-phase supporting method, a vapor deposition method, a sol-gel method, or a hydrothermal synthesis method.

[0038] In one embodiment, the impregnation-based loading can be performed by dissolving a molybdenum precursor in a solvent, then dividing the solvent into several stages to evenly disperse the molybdenum precursor dissolved in the solvent into a metal oxide, and performing wet impregnation at 10°C to 200°C. The impregnation time can be applied without limitation as long as sufficient loading is possible depending on the situation, and can be performed for, for example, 1 to 12 hours.

[0039] At this time, the molybdenum precursor may be at least one selected from the group including organic compounds and inorganic compounds containing molybdenum ions, and specifically, ammonium molybdate [(NH4)2MoO4], ammonium molybdate tetrahydrate [(NH4)6Mo7O 24 ·4H2O], molybdic acid (H2MoO4), etc., and preferably ammonium molybdate tetrahydrate [(NH4)6Mo7O 24 ·4H2O] may be.

[0040] In addition, the solvent may be any known solvent capable of dissolving molybdenum, and specifically, may be a glycol solvent such as water, ethylene glycol, 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, diethylene glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, trimethylol propane, or an alcohol solvent such as methanol, ethanol, isopropyl alcohol (IPA), butanol, etc., and the solvent content may be used without limitation as long as it is an amount capable of uniformly dispersing the molybdenum precursor, and for example, may be 100 to 500 parts by weight with respect to 100 parts by weight of the molybdenum precursor.

[0041] Next, the support material in which molybdenum is supported on a metal oxide can be dried and calcined by controlling the time and temperature according to conditions such as the amount of molybdenum supported, the size and quantity of the metal oxide, etc. [step (b)].

[0042] For example, the drying can be controlled at 80°C to 150°C, preferably 90°C to 120°C, using a vacuum oven, hot air, constant temperature and humidity, microwave, etc., and the firing can be performed in various known furnace types such as a tube-type furnace, a convection-type furnace, and a grate-type furnace, and can be performed at 300°C to 900°C, preferably 400°C to 700°C, for a predetermined period of time in an oxidizing atmosphere to remove solvents, etc. while preventing changes in the crystal structure of the support. At this time, the firing time may vary depending on conditions such as the firing temperature, the size and amount of the support, but may be 1 hour to 15 hours.

[0043] If the above sintering temperature is less than 300°C, there is a problem that precursors remain due to the low temperature or molybdenum oxide is not formed, and if it exceeds 900°C, there may be a problem that molybdenum is sintered and the microwave absorption ability is reduced.

[0044] Afterwards, the calcined material can be reduced in a reducing atmosphere to activate it, thereby manufacturing a material for microwave absorption and heating [step (c)].

[0045] Specifically, the reduction treatment of the above-mentioned sintered product is to convert the structure of molybdenum into a form capable of absorbing microwaves. The reduction treatment is not limited to anything that can reduce molybdenum supported on a metal oxide, and the sintered product can be activated by reducing it to a temperature capable of reduction in a reducing atmosphere. Specifically, molybdenum in its fully oxidized form, MoO3, does not absorb microwaves, but its appropriately reduced form converts into a form capable of absorbing microwaves and generating heat, and the metal oxide supported with molybdenum can stably maintain the reduced molybdenum structure.

[0046] For example, methods include methods using reducing gases such as carbon monoxide, hydrocarbons, and hydrogen; methods adding reducing agents such as hydrazine, lithium aluminum hydride, and tetramethyl borohydride; and the like. In addition, when using a reducing gas, the reducing gas may be diluted with another inert gas (e.g., nitrogen, etc.) and used. Preferred reducing gases include hydrogen, carbon monoxide, ammonia, and methane, and more preferably hydrogen.

[0047] In addition, the above reduction treatment can be performed at 300°C to 900°C, preferably 300°C to 700°C, and the reduction treatment time may vary depending on the reduction treatment situation, but may be performed for, for example, 30 minutes to 24 hours, preferably 1 hour to 15 hours. If the reduction treatment temperature is less than 300°C, the molybdenum oxide may not be sufficiently reduced, which may cause a problem of not being activated, and if it exceeds 900°C, the molybdenum may be sintered, which may cause a problem of reduced microwave absorption capability.

[0048] The microwave absorbing and heating material manufactured by the manufacturing method according to the present invention can absorb microwaves instantly and generate heat, and not only has excellent high-temperature stability, but also has high heat radiation efficiency to the outside because it is formed in a powder form, so that energy efficiency can be significantly improved, and can be easily applied to heating elements of various shapes.

[0049] Hereinafter, the present invention will be described in more detail by way of preferred embodiments to aid understanding; however, the following embodiments are merely illustrative of the present invention, and the scope of the present invention is not limited to the following embodiments.

[0050] <Example 1>

[0051] Ammonium molybdate tetrahydrate [(NH4)6Mo7O 24·4H2O] 2.209 g was dissolved in 100 ml of deionized water, and 10 g of TiO2 was added to the molybdenum precursor solution, and then the water was removed using a reduced pressure distiller, dried in an oven at 110°C for 6 hours, and then heated to 600°C at a rate of 5°C / min and calcined in a kiln for 6 hours to obtain a calcined product. The obtained calcined product was reduced at 450°C for 2 hours in a 10 vol% H2 / N2 atmosphere to produce a microwave absorbing and heating material in which molybdenum was loaded at 10 wt% based on the total weight of the microwave absorbing and heating material.

[0052] <Example 2>

[0053] A microwave absorbing and heating material was manufactured in the same manner as Example 1, but as shown in Table 1, 10 g of CeO2 was dispersed in 100 ml of deionized water instead of TiO2 to prepare a CeO2 slurry, and using this, a microwave absorbing and heating material was manufactured in which 10 wt% of molybdenum was loaded based on the total weight of the microwave absorbing and heating material.

[0054] <Example 3>

[0055] A microwave absorbing and heating material was manufactured in the same manner as Example 1, but as shown in Table 1, 10 g of ZrO2 was dispersed in 100 ml of deionized water instead of TiO2 to prepare a ZrO2 slurry, and using this, a microwave absorbing and heating material was manufactured in which 10 wt% of molybdenum was loaded based on the total weight of the microwave absorbing and heating material.

[0056] <Example 4>

[0057] A microwave absorbing and heating material was manufactured in the same manner as in Example 1, but as shown in Table 1, a microwave absorbing and heating material was manufactured in which 10 wt% of molybdenum was loaded based on the total weight of the microwave absorbing and heating material by reduction at 300°C.

[0058] <Example 5>

[0059] A microwave absorbing and heating material was manufactured in the same manner as in Example 1, but as shown in Table 1, a microwave absorbing and heating material was manufactured in which molybdenum was loaded at 10 wt% based on the total weight of the microwave absorbing and heating material by reduction at 600°C.

[0060] <Example 6>

[0061] A microwave absorbing and heating material was manufactured in the same manner as in Example 1, but as shown in Table 1, a microwave absorbing and heating material was manufactured in which molybdenum was loaded at 10 wt% based on the total weight of the microwave absorbing and heating material by reduction at 800°C.

[0062] <Comparative Example 1>

[0063] A microwave absorbing and heating material was manufactured in the same manner as in Example 1, but as shown in Table 1, 10 g of Al2O3 was dispersed in 100 ml of deionized water instead of TiO2 to prepare an Al2O3 slurry, and a microwave absorbing and heating material was manufactured using this.

[0064] <Comparative Example 2>

[0065] A microwave absorption and heat generation material was manufactured in the same manner as in Example 1, but as shown in Table 1, instead of TiO2, 10 g of MgO was dispersed in 100 ml of deionized water to prepare an MgO slurry, and a microwave absorption and heat generation material was manufactured using this.

[0066] <Comparative Example 3>

[0067] A microwave absorbing and heating material was manufactured in the same manner as in Example 1, but as shown in Table 1, instead of TiO2, 10 g of ZSM-5 was dispersed in 100 ml of deionized water to prepare a ZSM-5 slurry, and a microwave absorbing and heating material was manufactured using this.

[0068] <Comparative Example 4>

[0069] A microwave absorbing and heating material was manufactured using the same method as Example 1, but was reduced at 200°C as shown in Table 1.

[0070] Comparative Example 5

[0071] TiO2 used in Example 1 was used.

[0072] <Comparative Example 6>

[0073] The TiO2 used in Example 1 was reduced in the same manner as in Example 1 to produce reduced TiO2.

[0074] Comparative Example 7

[0075] Ammonium molybdate tetrahydrate [(NH4)6Mo7O 24 ·4H2O] was calcined at 500°C for 4 hours to produce MoO3.

[0076] Comparative Example 8

[0077] Ammonium molybdate tetrahydrate [(NH4)6Mo7O 24 ·4H2O] was calcined at 500°C for 4 hours to obtain MoO3, which was then reduced in the same manner as in Example 1 to produce reduced MoO3.

[0078] <Comparative Example 9>

[0079] SiC sold by Aldrich was used.

[0080] <Experimental Example 1: Measurement of Microwave Absorption and Heat Generation Characteristics>

[0081] In order to measure the microwave (MW) absorption and heat generation characteristics of the materials manufactured in the examples and comparative examples, 1 cc of the materials manufactured in the examples and comparative examples were filled into a quartz tube equipped with a microwave generator, and then microwaves were generated and the temperature of the stabilized materials was measured 10 minutes later. At this time, the power of the microwave equipment was fixed at 50 W, and the frequency was 2.45 GHz.

[0082] [Table 1]

[0083]

[0084] As shown in Table 1, the materials manufactured in Examples 1 to 5 were able to quickly absorb microwaves and generate heat up to a maximum of 884°C, whereas the materials manufactured in Comparative Examples 1 to 8 were not able to absorb microwaves and even if they did, they generated heat at less than 50°C.

[0085] Experimental Example 2: Microwave Power Measurement

[0086] In order to measure the microwave (MW) power of the materials manufactured in the examples and comparative examples, 1 cc of the materials of examples 1 and 2 and comparative example 9 was filled into a quartz tube equipped with a microwave generator, and then microwaves were generated and the power when the heating temperature of the materials was maintained at 800°C was measured, and the results are shown in Fig. 1.

[0087] As shown in Fig. 1, it was confirmed that the materials of Examples 1 and 2 consumed less power to maintain a temperature of 800°C compared to the SiC of Comparative Example 9.

[0088] <Experimental Example 3: Measurement of Heat Generation Rate>

[0089] In order to measure the heat generation rate of the materials manufactured in the examples and comparative examples, 1 cc of the materials of examples 1 and 2 and comparative example 9 was filled into a quartz tube equipped with a microwave generator, and then the heat generation rate according to microwave generation was measured using an IR temperature sensor, and is shown in Fig. 2.

[0090] As shown in Fig. 2, it was confirmed that the material of Example 1 was heated at a faster rate than the SiC of Comparative Example 9.

[0091] While the present invention has been described with reference to the above-described embodiments, various embodiments may be constructed within the spirit and scope of the present invention. Accordingly, the scope of the present invention is defined by the appended claims and their equivalents, and is not limited to the specific embodiments described herein.

Claims

1. A material for microwave absorption and heat generation characterized by reducing a metal oxide containing at least one metal element selected from the group consisting of titanium, cerium, and zirconium supported with molybdenum.

2. In paragraph 1, A material for microwave absorption and heating, characterized in that the above reduction treatment is performed at 300°C to 900°C in a reducing atmosphere.

3. In paragraph 2, A material for microwave absorption and heat generation, characterized in that the above reducing atmosphere is a reducing gas atmosphere containing at least one selected from the group consisting of hydrogen, carbon monoxide, ammonia, and methane.

4. In paragraph 1, A microwave absorbing and heating material characterized in that the above molybdenum is supported at 0.5 wt% to 20 wt% based on the total weight of the microwave absorbing and heating material. 5.(a) A step of supporting molybdenum on a metal oxide containing at least one metal element selected from the group consisting of titanium, cerium, and zirconium; (b) a step of drying and calcining the support material containing the molybdenum; and (c) A method for manufacturing a microwave absorbing and heating material, characterized by including a step of reducing the above-mentioned material.

6. In paragraph 5, A method for manufacturing a microwave absorbing and heating material, characterized in that the step (a) above comprises supporting molybdenum on a metal oxide in an amount of 0.5 wt% to 20 wt% based on the total weight of the microwave absorbing and heating material.

7. In paragraph 5, A method for manufacturing a microwave absorbing and heating material, characterized in that the sintering in step (b) is performed at 300°C to 900°C.

8. In paragraph 5, A method for manufacturing a microwave absorbing and heating material, characterized in that the reduction treatment of the above step (c) is performed at 300°C to 900°C in a reducing atmosphere.

9. In paragraph 8, A method for manufacturing a microwave absorbing and heating material, characterized in that the above reducing atmosphere is a reducing gas atmosphere containing at least one selected from the group consisting of hydrogen, carbon monoxide, ammonia, and methane.

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