Patent Application
20240188191
The present invention relates to a heating material, and more specifically, to a heating film.
As existing heating materials, nichrome wires, copper wires, Kanthal (Fe—Cr—Al alloy), and the like have been used. In order to overcome the limitations of existing materials, such as low efficiency, opacity, a heavy weight, and a low rate of temperature increase, heating units using advanced materials have been developed, and there are those using graphene, carbon nanotubes, and reduced graphene oxide (rGO).
In the case of using graphene, there is an example in which a transparent heating unit is manufactured by applying graphene onto a substrate and used as a haze removal film, and when carbon nanotubes are used, there is an example in which a film is obtained from the “forest” in which single-walled carbon nanotubes grow and used as a transparent heating unit for automotive windows. However, the heating unit using graphene has disadvantages such as difficulty in mass production and a high cost.
In addition, in the case of using rGO, there are an example in which a transparent heating unit is manufactured by applying graphene oxide onto a substrate through spin coating and an example in which a heating woven fabric is manufactured by manufacturing it in the form of a fiber. However, the heating unit using rGO has a disadvantage such as excessive power consumption because heating efficiency is not high enough to be similar to that of CNTs.
The present invention is directed to providing a method of manufacturing a film which has high efficiency, a low operating voltage, and a light weight and does not need a substrate, and a heating unit using the same.
However, the technical objectives of the present invention are not limited to those described above, and other unmentioned technical objectives will be clearly understood by those skilled in the art from the following description.
One aspect of the present invention provides a composite heating film. The composite heating film includes conductive sheets stacked in a layered structure. Metal/metal oxide composite particles intercalated between neighboring conductive sheets among the conductive sheets are positioned.
The conductive sheet may be a two-dimensional material. The conductive sheet may be graphene, graphene oxide (GO), reduced graphene oxide (rGO), MXenes, transition metal dichalcogenides (TMDCs), or a combination thereof.
The metal/metal oxide composite particle may include a metal oxide particle and a metal part provided at a portion of the metal oxide particle. The metal part may be made by locally reducing a portion of the surface or inside of the metal oxide particle. The metal oxide particle may be an insulator, and the metal part may be a conductor. The metal part may be a conductive pathway electrically connecting the conductive sheets.
The metal/metal oxide composite particle may be a phase-separated mixture of a metal oxide and a metal reduced therefrom. The metal/metal oxide composite particle may have a higher atomic ratio of a metal ion compared to a metal (M0) having an oxidation number of 0.
Another aspect of the present invention provides a method of manufacturing the composite heating film according to one aspect. First, a conductive sheet dispersion solution in which a conductive sheet is dispersed in a dispersion medium is obtained. A metal oxide precursor is added to the conductive sheet dispersion solution. A film is formed using the conductive sheet dispersion solution to which the metal oxide precursor is added. The film is reduced through thermal treatment to manufacture the composite heating film.
The conductive sheet in the conductive sheet dispersion solution may have a liquid crystal phase. The conductive sheet may be a graphene oxide sheet. The metal oxide precursor may be a metal salt including a metal cation and anion. A temperature of the thermal treatment may be higher than a temperature at which the metal cation is reduced. The thermal treatment temperature may range from 700 to 900° C. The formation of a film may be performed by a filtration or coating method.
Still another aspect of the present invention provides a heating element. The heating element includes the composite heating film according to one aspect of the present invention and a pair of electrodes electrically connected to the composite heating film.
As described above, the present invention provides a composite heating film including metal/metal oxide composite particles intercalated between a plurality of conductive sheets stacked in a layered structure, and a method of manufacturing the same. The composite heating film can generate heat with high efficiency even at a low operating voltage and can be used as a portable heating unit due to having a light weight.
However, the effects of the present invention are not limited to the above-described effects, and other effects which are not described herein will be fully understood by those skilled in the art from the following descriptions.
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
While the present invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. However, it should be understood that there is no intent to limit the present invention to the particular forms disclosed, but on the contrary, the present invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention.
It will be understood that, when an element such as a layer, a region, or a substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present.
Referring to
A plurality of the conductive sheets 200 may be stacked in the composite heating film 100. Specifically, two to several hundreds of conductive sheets 200 may be stacked in the composite heating film 100. The conductive sheet 200 may be a carbon-based material such as graphene, graphene oxide (GO), reduced graphene oxide (rGO), carbon nanotubes, graphite, or the like, a non-carbon-based material such as MXenes, transition metal dichalcogenides (TMDCs), or the like, an organic material such as a conductive polymer or the like, or a combination thereof. In an example, the conductive sheets 200 may be a two-dimensional material and may be, for example, graphene, GO, rGO, MXenes, TMDCs, or a combination thereof.
Each conductive sheet 200 may have a thickness of several angstroms to several nanometers and a width of several tens of nanometers to several micrometers. In an embodiment, the conductive sheets 200 may be rGO sheets. In this case, each rGO sheet may have a plate-shaped structure in which one to several tens of graphene atomic layers are stacked and have a thickness of several angstroms to several nanometers and a width of several tens of nanometers to several micrometers.
The metal/metal oxide composite particles 350 may be intercalated between neighboring conductive sheets 200 and electrically connected to the conductive sheets 200 adjacent to the upper and lower parts thereof. In this case, the metal/metal oxide composite particles 350 may be named bridging particles electrically connecting the conductive sheets 200 adjacent to the upper and lower parts thereof. When a plurality of the metal/metal oxide composite particles 350 are positioned in the same layer, they may be separately positioned. Accordingly, although it varies depending on the atmosphere in which the composite heating film 100 is located, when the composite heating film 100 is located in air, air may be filled between the metal/metal oxide composite particles 350.
The metal/metal oxide composite particle 350 may include a metal oxide particle 300 and a metal part 400 provided at a portion of the metal oxide particle 300. The metal part 400 may be made by locally reducing a portion of the surface or inside of the metal oxide particle 300 and may be composed of a metal (M0) having an oxidation number of 0. The metal/metal oxide composite particle 350 may be a phase-separated mixture of a metal oxide and a metal reduced therefrom.
In the metal/metal oxide composite particle 350, as the metal part 400 is formed by locally reducing only a portion of the surface and/or inside of the metal oxide particle 300, among metal elements in the metal/metal oxide composite particle 350, the atomic ratio of a metal (M0) which constitutes the metal part 400 and has an oxidation number of 0 may be 30 to 60 at %, and the remainder may be an oxidized metal ion (Mn+, n is 1 or more and 3 or less) which is present as a metal oxide and has an oxidation number of 1 or more. In an example, the metal/metal oxide composite particle 350 may have a higher atomic ratio of an oxidized metal ion (Mn+, n is 1 or more and 3 or less) which is present as a metal oxide and has an oxidation number of 1 or more compared to a metal (M0) which constitutes the metal part 400 and has an oxidation number of 0. In an embodiment, among metal elements in the metal/metal oxide composite particle 350, the atomic ratio of a metal (M0) which constitutes the metal part 400 and has an oxidation number of 0 may be 35 to 45 at %.
The metal oxide particle 300 may be an insulator, and the metal part 400 may be a conductor. Therefore, the metal part 400 may be a conductive pathway electrically connecting the conductive sheets 200. However, since the metal part 400 is made by locally reducing a portion of the surface or inside of the metal oxide particle 300, the conductive pathway is very narrow. Accordingly, when electrons move via the pathway, current crowding occurs, and thus efficient Joule heating may be performed. Therefore, the composite heating film 100 may exhibit a high heating temperature even at a low power density. In an example, the metal part 400 may appear in the form of a metal wire. One or several metal parts 400 may be present on the surface of the metal oxide particle 300 and may electrically connect the conductive sheets 200.
The metal oxide particle 300 may include Cu oxide, Sn oxide, Pb oxide, Ni oxide, Si oxide, Ti oxide, Al oxide, Mg oxide, Ca oxide, Fe oxide, Zn oxide, Cr oxide, or Mn oxide. In an example, the metal oxide particle 300 may be any one of SnO2, HgO, CuO, CO3O4, Fe2O3, PbO2, and NiO, but the present invention is not limited thereto, and any particle may be used as long as the reduction potential of a metal ion included in the particle is at a temperature of 700 to 900° C. Also, the metal part 400 may be a metal made by reducing the metal ion included in the metal oxide particle 300, that is, Sn, Hg, Cu, Co, Fe, Pb, or Ni.
In addition, the metal/metal oxide composite particle 350 may be a nano-sized particle and may be an approximately spherical particle having a diameter of several to several hundreds of nanometers, for example, 10 to 500 nm.
Referring to
Referring to
Referring to
The conductive sheet 201 may be the conductive sheet described with reference to
As a dispersion medium in the dispersion solution, any dispersion medium may be used as long as the conductive sheet 201 has a liquid crystal phase. When the conductive sheet 201 is a GO sheet, the dispersion medium may be a polar solvent, for example, a polar organic solvent such as dimethyl sulfoxide (DMSO), dimethylacetamide, dimethylformamide (DMF), N-methyl pyrrolidone, or the like, or water.
A metal oxide precursor may be added to the conductive sheet dispersion solution (S20). As the metal oxide precursor, any metal oxide precursor that is able to form any one metal oxide selected from the group consisting of SnO2, HgO, CuO, CO3O4, Fe2O3, PbO2, and NiO may be used without limitation, and specifically, the metal oxide precursor may be a metal salt or a C1 to C4 metal alkoxide. The metal salt may be metal halides (here, a halide may be F−, Cl−, Br−, or I−), metal sulfides, metal nitrides, metal phosphates, metal hydrogen phosphates, metal dihydrogen phosphates, metal sulfates, metal nitrates, metal hydrogen sulfates, metal nitrites, metal sulfites, metal perchlorates, metal iodates, metal chlorates, metal bromates, metal chlorites, metal hypochlorites, metal hypobromites, metal carbonates, metal chromates, metal hydrogen carbonates, metal dichromates, metal acetates, metal formates, metal cyanide, metal amides, metal cyanates, metal peroxides, metal thiocyanates, metal oxalates, metal hydroxides, or metal permanganates. In an embodiment, the metal oxide precursor may be a nickel oxide precursor, and the nickel oxide precursor may be nickel chloride (NiCl2).
The metal oxide precursor may be added in the form of a solution to the conductive sheet dispersion solution. In this case, a solvent in the metal oxide precursor solution may be an alcohol such as methanol, ethanol, propanol, or the like, water, or a mixture thereof.
The metal oxide precursor added to the conductive sheet dispersion solution dissociates into a metal cation 301, and then the metal cation 301 may be bonded to the surface of the conductive sheet 201. In an example, when the conductive sheet 201 is a GO sheet, the oxygen-containing functional group of the GO sheet and the metal cation may be bonded by electrostatic interaction.
A film may be formed using the conductive sheet dispersion solution to which the metal oxide precursor is added (S30). The formation of a film may be performed by filtration or coating. The filtration may be filtration under reduced pressure such as vacuum filtration or the like, and the coating may be spin coating, bar coating, spray coating, or dip coating. Also, the metal cation 301 in the film may be in the form in which it is bonded to the surface of the conductive sheet 201.
Afterward, the film may be reduced through thermal treatment (S40). A temperature of the thermal treatment may be higher than a temperature at which the metal cation is reduced. In an example, when the metal cation is a nickel ion, the thermal treatment temperature may be 700 to 900° C., specifically 750 to 850° C., and more specifically 780 to 820° C. An atmosphere for thermally treating the film may be a nitrogen atmosphere or an inert gas atmosphere, for example, an argon atmosphere.
When the film is thermally treated, the metal cation 301 bonded to the conductive sheet 201 is changed into a metal oxide seed, and neighboring metal oxide seeds are merged to form a metal oxide particle 300. Afterward, when the temperature further increases, a portion of the surface or inside of the metal oxide particle 300 is locally reduced to form a metal part 400, and thus metal/metal oxide composite particles 350 may be produced.
In an example, when the conductive sheet 201 is a GO sheet, the GO sheet is reduced to form reduced graphene oxide (rGO) when the metal cation 301 is changed into a metal oxide seed. Afterward, when the temperature further increases, for example, when the temperature reaches about 700° C., and specifically, 710° C. or more in the case of nickel, rGO is decomposed to generate CO gas, and the CO gas locally reduces the metal oxide particles 300 to form the metal part 400 and is converted into CO2 gas.
Hereinafter, exemplary examples will be described for aiding understanding of the present invention. However, the following examples should be considered in a descriptive sense only, and the scope of the present invention is not limited to the examples.
An aqueous graphene oxide dispersion solution was prepared by chemical exfoliation using a modified Hummer's method and then diluted to 0.1 wt %. Nickel chloride (NiCl2) as a metal oxide precursor was added to an aqueous methanol solution in which water and methanol were mixed in a ratio of 1:9 to obtain a 3.3 wt % metal oxide precursor solution. 4 ml of the 3.3 wt % metal oxide precursor solution was added dropwise to 18 ml of the 0.1 wt % aqueous graphene oxide dispersion solution and mixed. In the resulting mixture, nickel was contained at a ratio of 4 mg per 20 mg of graphene oxide. At this time, vigorous stirring was performed to prevent agglomeration at the point where the aqueous graphene oxide dispersion solution and the metal oxide precursor solution come into contact with each other. After stirring was performed for about 30 minutes, the resultant was filtered under reduced pressure through a PVDF filter having a pore size of 0.45 μm to form a film. The manufactured film was heated to 800° C. at a temperature increase rate of 10° C./min under an Ar atmosphere and then thermally treated for 2 hours to obtain a heating film.
A heating film was obtained in the same manner as in Preparation Example 1, except that the film filtered under reduced pressure was heated to 500° C. at a temperature increase rate of 10° C./min under an Ar atmosphere and then thermally treated for 2 hours.
A heating film was obtained in the same manner as in Preparation Example 1, except that the film filtered under reduced pressure was heated to 600° C. at a temperature increase rate of 10° C./min under an Ar atmosphere and then thermally treated for 2 hours.
A heating film was obtained in the same manner as in Preparation Example 1, except that the film filtered under reduced pressure was heated to 700° C. at a temperature increase rate of 10° C./min under an Ar atmosphere and then thermally treated for 2 hours.
A heating film was obtained in the same manner as in Preparation Example 1, except that the film filtered under reduced pressure was heated to 900° C. at a temperature increase rate of 10° C./min under an Ar atmosphere and then thermally treated for 2 hours.
A heating film was obtained in the same manner as in Preparation Example 1, except that the film filtered under reduced pressure was heated to 1000° C. at a temperature increase rate of 10° C./min under an Ar atmosphere and then thermally treated for 2 hours.
A heating film was obtained in the same manner as in Preparation Example 1, except that, as 1 ml of the 3.3 wt % metal oxide precursor solution was used, nickel was contained at a ratio of 1 mg per 20 mg of graphene oxide in a mixture of the aqueous graphene oxide dispersion solution and the metal oxide precursor solution.
A heating film was obtained in the same manner as in Preparation Example 1, except that, as 2 ml of the 3.3 wt % metal oxide precursor solution was used, nickel was contained at a ratio of 2 mg per 20 mg of graphene oxide in a mixture of the aqueous graphene oxide dispersion solution and the metal oxide precursor solution.
A heating film was obtained in the same manner as in Preparation Example 1, except that, as 3 ml of the 3.3 wt % metal oxide precursor solution was used, nickel was contained at a ratio of 3 mg per 20 mg of graphene oxide in a mixture of the aqueous graphene oxide dispersion solution and the metal oxide precursor solution.
A heating film was obtained in the same manner as in Preparation Example 1, except that, as 6 ml of the 3.3 wt % metal oxide precursor solution was used, nickel was contained at a ratio of 6 mg per 20 mg of graphene oxide in a mixture of the aqueous graphene oxide dispersion solution and the metal oxide precursor solution.
An aqueous graphene oxide dispersion solution was prepared by chemical exfoliation using a modified Hummer's method and then diluted to 0.1 wt %. The 0.1 wt % aqueous graphene oxide dispersion solution was filtered under reduced pressure through a PVDF filter having a pore size of 0.45 μm to form a film. The manufactured film was heated to 800° C. at a temperature increase rate of 10° C./min under an Ar atmosphere and then thermally treated for 2 hours to obtain a heating film.
In the following Table 1, the main process factors in the manufacture of heating films according to Preparation Examples 1 to 10 and Comparative Example are summarized.
Referring
As described above, in the case of Preparation Example 2 in which reductive thermal treatment was performed at 500° C., it can be confirmed that NiO particles were generated on the rGO sheet (a and g of
In addition, referring to the C-AFM current mapping images (b) of
Referring to
Referring to
Referring to
From these results, in the case of Preparation Examples 1 and 3 to 5, particularly, Preparation Example 1, it can be seen that particles in which a portion of the NiO particle was reduced to Ni were positioned between the reduced graphene sheets, and thus high Joule heating efficiency was exhibited, as compared to Preparation Example 2 in which NiO particles were positioned between the reduced graphene sheets or Preparation Example 6 in which Ni particles were positioned between the reduced graphene sheets. Accordingly, it can be seen that, when a reductive thermal treatment temperature is 700 to 900° C., specifically, 800° C., only a portion of the NiO particle is reduced to Ni, and thus Joule heating efficiency is improved.
Referring to
The present invention has been described in detail with reference to the exemplary examples but is not limited to the examples. Also, it will be understood by those skilled in the art that various changes and modifications may be made within a range without departing from the technical spirit and the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2021-0046292 | Apr 2021 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2022/005132 | 4/8/2022 | WO |
