Electric infrared heating film, its preparation method, electric infrared heating device

Abstract

The present invention provides an electric infrared heating film, a preparation method thereof, and an electric infrared heating device, and relates to the technical field of electric heating materials. The electric infrared heating film mainly comprises, by weight, 10-15 parts of low-defect graphene, 5-20 parts of inorganic filler, and 5-10 parts of amorphous carbon. In the electric infrared heating film, the low-defect graphene, inorganic filler, and amorphous carbon can reduce the volume expansion coefficient of the electric infrared heating film, reduce the difference in the volume expansion coefficient between the electric infrared heating film and substrates such as ceramic, quartz, and high-boron heat-resistant glass, prevent the electric infrared heating film from falling off from the surfaces of these materials, and extend the service life of the electric infrared heating device using the electric infrared heating film.

Description

[Technical field]

[0001] The present disclosure relates to an electric infrared heating film, its preparation method, and an electric infrared heating device, which belongs to the technical field of electric heating materials.

[0002] CROSS REFERENCE TO RELATED APPLICATIONS This disclosure claims priority to a Chinese application filed with the China Patent Office on February 26, 2021, bearing application number CN202110220155.6 and entitled "Electric infrared heating membrane, its preparation method, and electric infrared heating device," the entire contents of which are incorporated herein by reference. [Background technology]

[0003] At present, most high-temperature heating tube products that use air as a heat source adopt a tube body as a package (housing), in which a heater wire is placed. After heating by passing electricity, the heat is transferred through an inert gas, and radiated through a quartz / ceramic / metal tube to emit light and generate heat. After passing electricity, the heat generated by the heater wire heats the enclosed inert gas or vacuum (low-density air) through the surface of the electric heating wire, and the heat is transferred to the inner surface of the housing, and then transferred along the radial direction of the housing wall to the outer surface of the housing to heat the air. According to the first law of thermodynamics, the temperature of the outer surface of the housing is lower than the inner surface of the housing and lower than the heat transfer medium (enclosed gas) / the temperature of the inner wall interface is lower than the interface of the heat transfer medium / heater wire surface. This has disadvantages such as a reduced heat transfer rate and a reduced electrical energy utilization rate. To solve this problem, an electric heating material can be applied to the inner surface of the package housing to reduce the heat exchange in heat transfer and improve the heat transfer efficiency and electrical energy utilization rate.

[0004] However, current electric heating materials are mainly metal / alloy (heating wire) materials or carbon materials, and their thermal expansion coefficients are much larger than those of mainstream package housing materials (ceramics, quartz, high boron heat-resistant glass). After multiple heating and cooling cycles, especially in high-temperature applications, the relatively large difference in thermal expansion coefficients causes material stress changes, which makes the heating material easily fall off from the inner surface of the housing, shortening the service life of the heating equipment. Summary of the Invention

[0005] The present disclosure provides an electric infrared heating film, which mainly comprises, by weight, 10-15 parts of low defect graphene, 5-20 parts of inorganic filler, and 5-10 parts of amorphous carbon.

[0006] In some embodiments, in a Raman spectrum of the low-defect graphene, the ratio of D peak intensity to G peak intensity is 1 / 10 or less, and the molar ratio of carbon to oxygen in the low-defect graphene is 20:1 or more.

[0007] In some embodiments, the low defect graphene has a 2D peak in a Raman spectrum, and the interval between the 2D peak and a G peak is 5 cm or less relative to the interval between the 2D peak and the G peak of natural flake graphite. -1 It will decrease by more than this.

[0008] In some embodiments, the inorganic filler has a thermal expansion coefficient of 5×10 within the working temperature range of the electric infrared heating film or within the range of 0 to 600° C. -7 / K or less. In some embodiments, the particle size D50 of the inorganic filler is smaller than the particle size D50 of the low-defect graphene. In some embodiments, the particle size D50 of the inorganic filler is smaller than 1 / 150 of the particle size D50 of the low-defect graphene.

[0009] In some embodiments, the inorganic filler is any one or any combination of the following fillers: alumina ceramic powder, zirconia ceramic powder, silicon oxide powder, mica powder, silicon carbide powder, and the particle size D50 of the inorganic filler is 100 nm or less. In some embodiments, the electric infrared heating film has a thickness of 100 μm or less. In some embodiments, the electric infrared heating film has a thickness of 10 to 30 μm.

[0010] In some embodiments, the method includes applying a slurry mainly including low-defect graphene, an inorganic filler, a film-forming agent, and a solvent, forming a film, volatilizing the solvent, and then carbonizing the film to obtain the electric infrared heating film, wherein the film-forming agent is an organic polymer.

[0011] In some embodiments, the organic polymer is one or any combination of polyolefins, polystyrenes, polyacrylate-based polymers, polyethylene oxides, polyvinylidene fluorides, polyimides, polyurethanes, polyacrylonitriles, and phenolic resins.

[0012] In some embodiments, the slurry further comprises a graphene dispersant, the graphene dispersant comprising a slurry dispersant and a thin film dispersant, the slurry dispersant being one or any combination selected from diphenyl ether, C12-C16 alkyl benzene sulfonate, ethylene oxide, polyethylene glycol, dibasic acid ester, C12-C16 alkyl diphenyl ether monosulfonate, C12-C16 alkyl diphenyl ether disulfonate, C12-C16 alkyl sulfonate, p-C12-C16 alkyl benzene sulfonate, and the thin film dispersant being one or any combination selected from C12-C16 alkyl diphenyl ether monosulfonate, C12-C16 alkyl sulfonate, alkylated derivatives of polydextrose, propylene oxide, fatty alcohol alkoxylates, hydroxypropyl methylcellulose, and polyvinylpyrrolidone. In some embodiments, the carbonization temperature is 600 to 1200° C., and the carbonization time is 4 hours or longer. The present disclosure further provides an electric infrared heating device, comprising:

[0013] The present invention comprises an electric infrared heating element and an electric infrared heating film as described in any one of the above, the electric infrared heating film being installed on the inner wall of the electric infrared heating element and sealed inside the electric infrared heating element. In some embodiments, the electric infrared heating element comprises one of a lamp-type electric infrared heating element, a tube-type electric infrared heating element, or a plate-type electric infrared heating element.

[0014] The present disclosure further provides an electric infrared heating device, comprising a tube, the electric infrared heating film according to any one of the above, and two electrodes, the electric infrared heating film being installed on the inner wall of the tube and sealed inside the tube, and both of the two electrodes being electrically connected to the electric infrared heating device, configured to heat the electric infrared heating film when energized. In some embodiments, the tube is a quartz tube, a ceramic tube, or a glass tube.

[0015] The present disclosure further provides an electric infrared heating device, comprising a plate-type electric infrared heating element and the electric infrared heating film according to any one of the above claims, the plate-type electric infrared heating element includes a plate body and an electrode, the electric infrared heating film is installed on an inner wall of the plate body, the electrode is electrically connected to the electric infrared heating device, and configured to heat the electric infrared heating film when electricity is applied. [Brief description of the drawings]

[0016] [Figure 1] FIG. 13 is a schematic diagram of an electric infrared heating device according to a thirteenth embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an electric infrared heating device according to Examples 13, 19, and 20. [Diagram 3] 1 is a graph showing temperature rise curves when the electric infrared heating devices according to the embodiment and the comparative example are heated to 300° C. in Experimental Example 2. [Figure 4] FIG. 1 is a schematic diagram of an electric infrared heating device according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present invention will be described using embodiments and examples, but the terminology used in this specification is intended to describe the purpose of the particular embodiments and examples only and is not intended to limit the scope of the present invention.

[0018] The term "defective graphene" as used herein means that various defects are introduced or left in the raw material during the preparation of graphene. The defects in graphene are classified into three types. The first type of defect is a carbon atom missing at the substitutional position of the sp2 hybridized carbon atom of graphene, i.e., a carbon vacancy, and a carbon atom in the gap between the carbon atoms, i.e., an interstitial carbon. The second type of defect is an "intrinsic defect", which is due to a carbon atom with non-sp2 orbital hybridization, and the change in the orbital hybridization mode of these carbon atoms is due to a shortage or excess of carbon atoms in the carbon hexagon in which it is located or in the surrounding carbon hexagon. Typically, an intrinsic defect is due to a carbon atom with non-sp2 orbital hybridization in graphene, which has a limited graphene flake size and has non-bonding electrons at the edge. The third type of defect is an impurity defect, also called "impurity defect", which is due to impurities that form bonds at substitutional positions, interstitial positions, or carbon atoms on the (001) plane, and these defects are due to non-carbon atoms that form covalent bonds with graphene carbon atoms. For example, in the graphite oxide reduction method by chemical method, a large amount of oxygen-containing functional groups are introduced into graphene oxide during the preparation process, so that the sp2 carbon lattice structure is severely destroyed, and the graphene prepared thereby has a large amount of carbon sp2 lattice disorder defects (typically has no 2D peak in Raman spectrum). In this specification, "low defect graphene" generally refers to a graphene material that has almost no first type defects and third type defects (impurity defects), or a graphene material that has relatively low first type defects and third type defects. Typically, the graphene material is a graphene material whose defects are mainly second type defects (intrinsic defects), and has almost no or relatively low first type defects and third type defects. Typically, the intrinsic defects of "low defect graphene" are mainly due to carbon atoms at the edges of graphene sheet layers. Typically, "low defect graphene" generally has a crystal structure mainly composed of sp2 carbon and has a high carbon to oxygen ratio. Typically, in the Raman spectrum of low defect graphene, the ratio of D peak intensity to G peak intensity (D peak intensity / G peak intensity) is 1 / 10 or less.Typically, the molar ratio (carbon atom / non-carbon atom) of carbon atoms to non-carbon atoms (e.g., heteroatoms such as N and O) in low defect graphene is 20: 1 or more. For example, the molar ratio (carbon / oxygen) of carbon to oxygen in low defect graphene is 20: 1 or more. For example, the low defect graphene may be graphene prepared by a physical expansion method. As used herein, the term "amorphous carbon" refers to a carbon material having an extremely low degree of crystallinity and in an amorphous state (i.e., the arrangement of carbon atoms has no long-range order, also referred to as a glassy aggregate state), such as carbon black, and is one of the allotropes of carbon.

[0019] The term "natural flake graphite" as used herein refers to natural crystalline graphite, which has a scaly shape, belongs to a hexagonal crystal system, and has a layered structure. Natural flake graphite usually has good high temperature resistance, electrical conductivity, thermal conductivity, lubricity, plasticity, acid resistance, alkali resistance, etc. The term "D peak" as used herein refers to a Raman characteristic peak of a C-atom crystal, and the D-peak represents a defect in the C-atom crystal. The term "G peak" as used herein belongs to the Raman characteristic peaks of C-atom crystals, and the G-peak represents the in-plane stretching vibration of the sp2 hybridization of C atoms.

[0020] The term "2D peak" as used herein is also called the G* peak and is due to double-resonance Raman scattering by two phonons, and the basic condition for the appearance of the "2D peak" is that it has a crystal structure characteristic of a hexagonal mesh formed by long-range ordered sp2 carbon bonds. The present disclosure provides an electric infrared heating film that has a relatively small difference in thermal expansion coefficient with the packaging housing material, which can significantly extend the service life of the heating equipment. The present disclosure further provides a method for preparing the above electric infrared heating film, and an electric infrared heating device using the above electric infrared heating film. An embodiment of the present disclosure provides an electric infrared heating film, which adopts the following technical solution:

[0021] The electric infrared heating film mainly comprises, by weight, 10 to 15 parts of low defect graphene, 5 to 20 parts of inorganic filler, and 5 to 10 parts of amorphous carbon. In some embodiments, the electric infrared heating film mainly comprises, by weight, the following components. The low defect graphene is, for example, 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts, or 15 parts, the inorganic filler is, for example, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, or 20 parts, and the amorphous carbon is, for example, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, or 10 parts.

[0022] The electric infrared heating film according to the present disclosure employs low-defect graphene, so that when electricity is applied to the electric infrared heating film, the temperature can be quickly raised to 300°C or higher (including 300°C) and the expansion coefficient of the electric infrared heating film can be suppressed; the inorganic filler has a smaller expansion coefficient than the low-defect graphene, suppressing the volumetric expansion coefficient of the electric infrared heating film and reducing the thermal stress generated when the temperature is quickly raised; and the amorphous carbon has elasticity and can buffer the volumetric expansion of the low-defect graphene and the inorganic filler, thereby further reducing the volumetric expansion of the electric infrared heating film, thereby reducing the difference in the volumetric expansion coefficient between the electric infrared heating film and base materials such as ceramic, quartz, and high-boron heat-resistant glass, preventing the electric infrared heating film from falling off from the surfaces of these materials, and extending the service life of the electric infrared heating device employing the electric infrared heating film.

[0023] In addition, the low thermal expansion property of the inorganic filler in the electric infrared heating film according to the present disclosure can improve the integrity of the film during the heat generation process, and the low-defect graphene can improve the thermal conductivity of the electric infrared heating film, thus improving the heat exchange efficiency between the electric infrared heating film and the substrate, and the unique semiconductor electronic structure of low-defect graphene has the ability to emit photons with wavelengths in the infrared-far infrared region through electronic relaxation to radiate heat to the target object, and the pz orbital and sp2-σ orbital of the carbon atom in low-defect graphene are highly bonded, so that low-defect graphene can provide good high-temperature resistance and good structural stability at high temperatures compared to other conductive materials, thereby improving the safety and extending the service life of devices using the electric infrared heating film. Compared with conventional high-temperature electric heating materials, the electric infrared heating film according to the present disclosure has the advantages of a small thermal expansion coefficient and fast heat conduction.

[0024] The disclosed electric infrared heating film has a thermal expansion coefficient that matches well with that of a quartz tube, and at a heating rate of 50°C / s, the stress due to the difference in thermal volume expansion with quartz at a temperature of 800°C is smaller than the peel strength of the electric infrared heating film, thereby significantly increasing the upper heat generation temperature limit of the electric infrared heating film. The electric infrared heating film according to the present disclosure may further contain a certain amount of impurity components in addition to defective graphene, amorphous carbon and inorganic fillers.

[0025] In order to further improve the thermal conduction performance of the electric infrared heating film, the ratio of D peak intensity to G peak intensity in the Raman spectrum of the low defect graphene is 1 / 10 or less. For example, the ratio of D peak intensity to G peak intensity is 1 / 10, 1 / 20, 1 / 30, 1 / 40, 1 / 50, 1 / 60 or 1 / 70. Generally, the ratio of D peak intensity to G peak intensity in the Raman spectrum represents the defect density of graphene. In the present disclosure, the thermal conduction performance of the low defect graphene heat exchange film can be further improved by reducing the defect density of the low defect graphene. The molar ratio of oxygen to carbon in the low defect graphene is 1 / 20 or less (i.e., the molar ratio of carbon to oxygen in the low defect graphene is 20:1 or more). For example, the molar ratio of oxygen to carbon in the low defect graphene is 1 / 20, 1 / 30, 1 / 40, 1 / 50, 1 / 60 or 1 / 70. In the present disclosure, by keeping the molar ratio of oxygen to carbon in the low defect graphene within the above range, it is possible to ensure good thermal conductivity and electrical conductivity of the material and prevent changes in power and heat exchange performance caused by atomic rearrangement of graphene as a main conductive material at high temperatures. In the present disclosure, by lowering the defect concentration of the low defect graphene used, the infrared heating film has a thermal conductivity coefficient of more than 200 W / (K·m) when the thickness is less than 30 μm. In order to further ensure the stability and thermodynamic properties such as thermal conductivity of the low defect graphene, in some representative embodiments, the low defect graphene has a 2D peak in the Raman spectrum, and the interval between the 2D peak and the G peak of the low defect graphene is 5 cm shorter than the interval between the 2D peak and the G peak of natural flake graphite. -1 A decrease of more than 5 cm, for example -1 , 8cm -1 , 10cm -1 , 12cm -1 , 14cm -1 , 16cm -1 Decreases.

[0026] In some embodiments, the particle size D50 of the low defect graphene is 10 to 20 μm, for example, 10 to 15 μm, 15 to 20 μm, or 12 to 18 μm, for example, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm.

[0027] The inorganic filler used in the present disclosure has good chemical and structural stability within the working temperature range of the electric infrared heating film. In some exemplary embodiments, the inorganic filler has a thermal expansion coefficient of 5×10 within the working temperature range of the electric infrared heating film. -7 / K or less (5×10 -7 / K included).

[0028] Considering the cost, the slurry dispersibility, and the structural stability of the electric infrared heating film, the inorganic filler is any one or any combination of fillers selected from the group consisting of alumina ceramic powder, zirconia ceramic powder, silicon oxide powder (i.e., silicon dioxide powder), mica powder, and silicon carbide powder. The inorganic fillers listed above have a thermal expansion coefficient of 5×10 at 0 to 600° C. -7 / K or less (5×10 -7 / K included).

[0029] In some exemplary embodiments, the particle size D50 of the inorganic filler is smaller than the particle size D50 of the low defect graphene, and in some exemplary embodiments, the particle size D50 of the inorganic filler is smaller than 1 / 150 of the particle size D50 of the low defect graphene.

[0030] In order to further reduce the expansion coefficient of the electric infrared heating film, in some representative embodiments, the particle size D50 of the inorganic filler is 100 nm or less. In some embodiments, the particle size D50 of the inorganic filler is 20 nm or more. Since the diameter of the graphene flakes as a two-dimensional structural material is much larger than the particle size of the inorganic filler, the gaps between the graphene flakes are filled with the inorganic filler and amorphous carbon after film formation, which suppresses the increase in the overall stress of the thin film caused by the vibration of graphene at high temperatures, thereby maintaining the integrity of the graphene composite thin film at high temperatures.

[0031] In some embodiments, the amorphous carbon is formed in part or in whole by carbonization of an organic polymer. In some embodiments, the organic polymer includes, but is not limited to, one or any combination of polyolefins, polystyrene, polyacrylate-based polymers, polyimides, polyurethanes, polyacrylonitrile and modified derivatives thereof, and phenolic resins. In some embodiments, the polyolefin includes, but is not limited to, one or any combination of polyethylene and polypropylene. The polyacrylate-based polymer can be, for example, polymethyl methacrylate.

[0032] The thickness of the electric infrared heating film according to the present disclosure can be freely set according to the application scene, for example, 100 μm or less. In some embodiments, the thickness of the electric infrared heating film is 10-30 μm. When used in a scene requiring heat exchange efficiency when heating a product, such as a rapid heating device, an electric infrared heating film having a thickness of 10-30 μm has an advantage in use compared to a thicker electric infrared heating film. One embodiment of the present disclosure provides a method for preparing an electric infrared heating film, which adopts the following technical solution:

[0033] The method for preparing the electric infrared heating film described above involves applying a film-forming slurry that mainly contains low-defect graphene, an inorganic filler, a film-forming agent which is an organic polymer, a graphene dispersant, and a solvent, forming a film, volatilizing the solvent, and then carbonizing the film to obtain the electric infrared heating film.

[0034] The method for preparing an electric infrared heating film according to the present disclosure involves applying a film-forming slurry, volatilizing the solvent to form (solidify) the applied thin film, and then firing the entire thin film under a protective atmosphere to promote the film-forming agent in the thin film to carbonize and form amorphous carbon, thereby forming an electric infrared heating film. This method can easily control the uniformity of the electric infrared heating film, release the stress in the thin film and the stress between the thin film and the substrate, extend the material life, improve the heat exchange efficiency of the electric infrared heating film, and be suitable for a series of different high-temperature heating products, while reducing production costs.

[0035] In some representative embodiments, the mass ratio of the inorganic filler to the low-defect graphene is 5-20:10-15, for example, 5-15:10-15, 10-20:11-15, or 15-20:11-14.

[0036] The organic polymer is a polymer that can be formed into amorphous carbon by carbonization, for example, a resin. In order to improve the film-forming performance of the film-forming slurry and reduce production costs, in some embodiments, the organic polymer film-forming agent is one or any combination of polyolefin, polystyrene, polyacrylate-based polymer, polyethylene oxide, polyvinylidene fluoride, polyimide, polyurethane, polyacrylonitrile and its modified derivatives, and phenolic resin. The organic polymers listed above are all commercially available general polymer resins that can be used for high-temperature carbonization and have excellent film-forming performance. In some embodiments, the polyolefin is one or any combination of polyethylene and polypropylene. The polyacrylate-based polymer is one or any combination of polymethyl methacrylate and polyethyl acrylate.

[0037] In some representative embodiments, the mass ratio of the film-forming agent to low-defect graphene is 2.6-9.8:4.9-10.4, such as 3.0-9.8:5.0-10.4, 2.6-8.0:5.0-9.0, or 3.5-8.5:5.5-7.5.

[0038] The graphene dispersant may be any dispersant capable of promoting the dispersion of graphene in a system so that the low-defect graphene component is well dispersed during the low-temperature solidification film formation process of the above-mentioned film-forming slurry, and the low-defect graphene and film-forming agent are uniformly distributed after film formation. In order to improve the dispersion performance of the low-defect graphene in the above-mentioned film-forming slurry and ensure the uniformity of the material after the slurry is applied, the graphene dispersant may include a slurry dispersant. The slurry dispersant may be, for example, any one or a combination of a plurality of types selected from diphenyl ether, C12-C16 alkylbenzene sulfonate, ethylene oxide, polyethylene glycol, dibasic acid ester, C12-C16 alkyldiphenyl ether monosulfonate, C12-C16 alkyldiphenyl ether disulfonate, C12-C16 alkyl sulfonate, and p-C12-C16 alkylbenzene sulfonate. In some representative embodiments, the molecular weight (M w ) is less than 400. The slurry dispersants listed above are all commercially available common compounds that are effectively volatilized during the solvent volatilization process, or that have very little residue in the formed thin film and can be completely volatilized during carbonization. In some embodiments, the mass ratio of the slurry dispersant to the low-defect graphene is 1.1:1 or more, for example, 1.1 to 2.1:1, so as to ensure that low-defect graphene powder is insoluble in any neutral solvent, has a low degree of solvation with most solvents, and can be sufficiently uniformly dispersed in the film-forming slurry.

[0039] In order to improve the stability of dispersion (infiltration) of low-defect graphene in thin film formation, the dispersant includes a thin film dispersant. In some representative embodiments, the thin film dispersant is one or any combination of C12-C16 alkyl diphenyl ether monosulfonate, C12-C16 alkyl sulfonate, alkylated derivative of polydextrose, propylene oxide, fatty alcohol alkoxylate, hydroxypropyl methylcellulose, and polyvinylpyrrolidone. Thin film dispersants with a large amount of polar functional groups may release gas during the carbonization process, which may damage the integrity and denseness of the electric infrared heating film. In some representative embodiments, the mass ratio of the thin film dispersant in the film-forming slurry is 1% or less. The mass ratio of the thin film dispersant after carbonization is negligibly small compared to the mass ratio of the film-forming agent after carbonization. All of the organic polymers listed above are commercially available common dispersants.

[0040] In some exemplary embodiments, the C12-C16 alkyl diphenyl ether monosulfonate is, for example, sodium hexadecane diphenyl ether monosulfonate. The C12-C16 alkyl diphenyl ether disulfonate is, for example, sodium hexadecane diphenyl ether disulfonate. The p-C12-C16 alkyl benzene sulfonate is, for example, p-propyl toluene sulfonate. The C12-C16 alkyl sulfonate is, for example, sodium hexadecane sulfonate.

[0041] In order to further optimize the processability of the conductive layer, the slurry further comprises an additive, which is any one or a combination of a leveling agent, a thickening agent, a thixotropic agent, and a conductive agent, and the mass ratio of the additive to the low-defect graphene is 1:20 or less.

[0042] In some embodiments, the film-forming slurry has a viscosity of more than 3000 Pa·s and a solid content of more than 10 wt%. In some embodiments, the film-forming slurry has a solid content of 18.9 to 25.5%, e.g., 19%, 20%, 21%, 22%, 23%, 24%, or 25%, and a viscosity of 3800 to 7300 Pa·s, e.g., 4000 to 7300 Pa·s, 3800 to 7000 Pa·s, or 4500 to 6500 Pa·s, e.g., 4000 Pa·s, 4500 Pa·s, 5000 Pa·s, 5500 Pa·s, 6000 Pa·s, 6500 Pa·s, 7000 Pa·s, or 7200 Pa·s. In some embodiments, the particle size D50 of the low-defect graphene in the film-forming slurry is 10 to 20 μm.

[0043] In some embodiments, the method for preparing the film-forming slurry includes bead milling a mixed material mainly consisting of low-defect graphene powder material, inorganic filler, slurry dispersant, and some solvent, and then adding a film-forming agent, a thin film dispersant, and the remaining solvent, and uniformly mixing to obtain the film-forming slurry. The bead milling process can better disperse the low-defect graphene and prevent the graphene sheets from re-stacking. In particular, the low-defect graphene used lacks defects and oxidized functional groups, and has a relatively poor polarization effect with the solvent. The crushing of the low-defect graphene raw material, the bead milling process of the mixed material, and the use of the dispersant all promote the uniform dispersion of the low-defect graphene in the slurry and prevent the graphene sheets from re-stacking, ensuring that the low-defect graphene exists in the electric infrared heating film in the form of a few sheet layers and a complete structure, thereby improving the infrared radiation performance of the film.

[0044] In order to reduce costs and improve dispersion efficiency, in some embodiments, the solvent is one or any combination of methanol, ethanol, n-butanol, propylene glycol, ethyl acetate, toluene, xylene, N-methylpyrrolidone (NMP), acetone, N,N-dimethylformamide, tetrahydrofuran, epoxy reactive diluents, and 1,4-butanediol diglycidyl ether.

[0045] In order to balance the effect of bead milling dispersion, in some representative embodiments, the mass ratio of the low defect graphene slurry to the slurry dispersant in the slurry is 8-15:1-5, for example, 10-15:1-5, 11-15:1-4, or 12-15:1-3, for example, 2.9-9.5:1. When preparing the low defect graphene slurry, a part of the solvent is used as a main solvent, and the remaining solvent is used as a dilution solvent in the prepared low defect graphene slurry. In some representative embodiments, the main solvent is one or any combination selected from N-methylpyrrolidone and ethyl acetate. The dilution solvent is N-methylpyrrolidone. The mass ratio of the dilution solvent to the main solvent is 39-54.8:11.4-22.1, for example, 40-54:11.5-22.0, 39-54:12-20, or 40-52:15-20.

[0046] In some embodiments, the carbonization temperature is 600 to 1200°C, and the carbonization time is 4 hours or more. In some embodiments, before the carbonization, the temperature is first raised to 400°C and kept at that temperature for 1 hour, and then raised to the carbonization temperature for carbonization. The temperature rise rate is 5°C / min. After the carbonization, the temperature is first lowered from the carbonization temperature to 500°C and kept at that temperature for 1 hour, and then further lowered. The carbonization is performed under a protective atmosphere.

[0047] An embodiment of the present disclosure provides an electric infrared heating device, comprising: an electric infrared heating element; and any one of the electric infrared heating films described above, wherein the electric infrared heating film is installed on the inner wall of the electric infrared heating element and sealed inside the electric infrared heating element. In some embodiments, the electric infrared heating element comprises one of a lamp-type electric infrared heating element, a tube-type electric infrared heating element, or a plate-type electric infrared heating element. In some embodiments, the electric infrared heating element is a tubular electric infrared heating element. In some embodiments, the tubular electric infrared heating element comprises a tube.

[0048] In some embodiments, the electric infrared heating device comprises a tubular electric infrared heating element and any one of the electric infrared heating films described above, the tubular electric infrared heating element including a tube and electrodes, the electric infrared heating film being installed on the inner wall of the tube, the electrodes being electrically connected to the electric infrared heating device, and configured to cause the electric infrared heating film to generate heat when electricity is applied. An embodiment of the present disclosure provides an electric infrared heating device, which adopts the following technical solution:

[0049] The electric infrared heating device comprises a tube, any one of the above-mentioned electric infrared heating films, and two electrodes, the electric infrared heating film being installed on the inner wall of the tube and sealed inside the tube, and both of the two electrodes being electrically connected to the electric infrared heating device so as to cause the electric infrared heating film to generate heat when electricity is applied.

[0050] The electric infrared heating device according to the present disclosure uses the above-mentioned electric infrared heating film, which has a relatively small expansion coefficient, so that the expansion coefficients of the electric infrared heating film and the base are well matched when electricity is passed between them, preventing the electric infrared heating film from falling off the base and providing a relatively long service life.

[0051] The electric infrared heating device according to the present disclosure can realize rapid heating to high temperatures (>300°C) by installing the electric infrared heating film according to the present disclosure on the inner wall of the tube body (or electric infrared heating element), and the electric infrared heating film is mainly composed of low-defect graphene, inorganic filler, and amorphous carbon, which can ensure the work performance and structural stability of the electric infrared heating device in a working state of repeated heating and cooling and in a working state at high temperatures. The electric infrared heating film fully retains the sheet structural characteristics of low-defect graphene, so that the electric infrared heating device can fully exert the inherent advantages of low-defect graphene material, such as high infrared emissivity and high thermal conductivity.

[0052] In order to further extend the service life of the electric infrared heating film, the inside of the tube (or electric infrared heating element) is evacuated or an inert gas is introduced. By evacuating the inside of the tube-type (or electric infrared heating element) substrate or introducing an inert gas into the tube-type substrate, oxidation of low-defect graphene and amorphous carbon at high temperatures can be prevented.

[0053] In some embodiments, the tube is one of quartz tube, ceramic tube, and glass tube, for example, quartz tube. In some embodiments, the tube is selected as quartz tube, and the difference in the expansion coefficient between the electric infrared heating film of the present disclosure and quartz is relatively small, so that the service life of the electric infrared heating device can be further extended by using the quartz tube as the substrate.

[0054] In some embodiments, the inner diameter of the tube is 8 to 13 mm, e.g., 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm, 12 mm, or 13 mm, and the wall thickness of the tube is 0.1 to 2 mm, e.g., 0.2 mm, 0.5 mm, 0.7 mm, 1 mm, 1.5 mm, 1.8 mm, or 2 mm.

[0055] In some embodiments, the electric infrared heating element is a plate-type electric infrared heating element, which includes ceramic plate-type electric infrared heating elements, mica plate-type electric infrared heating elements, quartz plate-type electric infrared heating elements, and ceramic masked metal plate-type electric infrared heating elements.

[0056] In some embodiments, the electric infrared heating device includes a plate-type electric infrared heating element and any one of the electric infrared heating films described above, the plate-type electric infrared heating element includes a plate body and an electrode, the electric infrared heating film is installed on the inner wall of the plate body, the electrode is electrically connected to the electric infrared heating device, and is configured to heat the electric infrared heating film when electricity is applied. In some embodiments, the plate body includes a first base plate and a second base plate. In some embodiments, the first base plate and the second base plate are configured to be bonded to each other by a method such as thermocompression bonding to form a sealed body, and the electric infrared heating film is located on the first base plate or the second base plate on the bonding side of the first base plate and the second base, or on both the first base plate and the second base plate. In some embodiments, the material of the plate body includes quartz, borosilicate, mica, a carbon steel plate with an insulating ceramic layer, and an aluminum alloy plate with an insulating ceramic layer.

[0057] The manufacturing method of the electric infrared heating device according to the present disclosure includes the steps of applying a slurry containing mainly low-defect graphene, an inorganic filler, a film-forming agent and a solvent to the inner wall of a tube to form a film, volatilizing the solvent and then carbonizing the tube, lowering the temperature, and attaching electrodes to seal the tube. Low defect graphene for use in the present disclosure may be purchased or prepared by the methods disclosed in the Chinese application having publication number CN108622887A. The technical solution of the present disclosure will be further described below with reference to specific embodiments. Working Example 1. Example of electric infrared heating film according to the present disclosure

[0058] Example 1 The electric infrared heating film according to this embodiment is composed of 5 parts by weight of amorphous carbon, 10 parts by weight of low defect graphene, and 10 parts by weight of inorganic filler. The inorganic filler is nano-silica, and has a particle size D50 of 20 nm. The low defect graphene has a particle size D50 of 15 μm, and has a 2D peak in the Raman spectrum of low defect graphite, and the interval between the 2D peak and the G peak is 5 cm longer than the interval between the 2D peak and the G peak of natural flake graphite. -1 or more (5cm -1 The intensity of the D peak and the intensity of the G peak were decreased, the ratio of the D peak intensity to the G peak intensity was 1 / 20, and the molar ratio of carbon to oxygen in the low defect graphene was 30:1. The thickness of the electric infrared heating film was 15 μm.

[0059] Examples 2 to 6 The electric infrared heating membranes according to Examples 2 to 6 each consist of amorphous carbon, low defect graphene, and an inorganic filler. The low defect graphene according to each Example has a 2D peak in the Raman spectrum, and the interval between the 2D peak and the G peak is 5 cm longer than the interval between the 2D peak and the G peak of natural flake graphite. -1 or more (5cm -1 The ratio of the D peak intensity to the G peak intensity was 1 / 20, and the molar ratio of carbon to oxygen in the low defect graphene was 30: 1. The weight parts of the amorphous carbon, low defect graphene, and inorganic filler in the electric infrared heating film according to each of the examples, the particle size of the low defect graphene, the type and particle size D50 of the inorganic filler, and the thickness of the electric infrared heating film are shown in Table 1.

[0060] [Table 1]

[0061] The low-defect graphene raw material used in each of Examples 7 to 12 was obtained from Zhengzhou New Materials Technology Co., Ltd. (CP1002 low-defect graphene fine powder series product), and was graphene prepared by physical expansion method. When the low-defect graphene raw material was subjected to Raman spectrum detection, it was found that the Raman spectrum of low-defect graphene had a 2D peak, and the distance between the 2D peak and the G peak was 5 cm longer than the distance between the 2D peak and the G peak of natural flake graphite. -1 or more (5cm -1 The ratio of D peak intensity to G peak intensity was 1 / 20, and the molar ratio of carbon to oxygen was 30:1. 2. Example of the preparation method of the electric infrared heating film according to the present disclosure

[0062] Example 7 The preparation method of the electric infrared heating film according to this embodiment takes the preparation method of the electric infrared heating film according to Example 1 (component blending ratio, specifications and parameters) as an example, and includes the following steps: (1) Low-defect graphene raw material was subjected to airflow pulverization to obtain low-defect graphene powder material. (2) A membrane-forming slurry was prepared.

[0063] The slurry dispersant and the main solvent were uniformly mixed to obtain a composite base liquid, and then the main carbon material and the inorganic filler were added into the composite base liquid and stirred until the main carbon material and the inorganic filler were uniformly dispersed in the composite base liquid. At a temperature of 20°C, the mixture was subjected to bead milling treatment at a linear speed of 15 m / s using 0.3 mm zirconium balls as polishing media to obtain a low-defect graphene dispersion. The membrane-forming agent, dilution solvent and thin film dispersant were added into the low-defect graphene dispersion, and the mixture was stirred at a temperature of 40°C at a speed of 500 rpm for 2 hours to obtain a membrane-forming slurry.

[0064] The slurry dispersant used was a combination of ethylene oxide and dibasic acid ester (DBE), with a mass ratio of ethylene oxide to DBE of 1:2, the main solvent was N-methylpyrrolidone (NMP), the inorganic filler was nanosilica, the film-forming agent was polyacrylonitrile (PAN), the dilution solvent was N-methylpyrrolidone, and the thin film dispersant was polyvinylpyrrolidone (PVP K30).

[0065] The main carbon material used was low-defect graphene, and in the low-defect graphene dispersion, the particle size D50 of the low-defect graphene was 15 μm, and the particle size D50 of the inorganic filler was 20 nm.

[0066] The slurry dispersant used accounted for 15% of the mass of the film-forming slurry, the main solvent used accounted for 44.1% of the mass of the film-forming slurry, the low-defect graphene powder material and inorganic filler used each accounted for 7.4% of the mass of the film-forming slurry, the film-forming agent used accounted for 3.7% of the mass of the film-forming slurry, the thin film dispersant used accounted for 0.7% of the mass of the film-forming slurry, and the dilution solvent used accounted for 29.1% of the mass of the film-forming slurry. The obtained film-forming slurry had a solid content of 19.1 wt% and a viscosity of 6000 Pa·s.

[0067] (3) The film-forming slurry was poured into a quartz tube with an inner diameter of 8 mm, and the slurry was repeatedly inverted inside the quartz tube in a temperature environment of 50°C. The slurry was then discharged from both ends of the quartz tube until no more slurry flowed out from either end within 1 min (the slurry was discharged by turning the quartz tube upside down or tilting it).

[0068] (4) The quartz tube from which the slurry was discharged in step (3) was placed in a 90° C. air-blowing oven and rotated coaxially in one direction at a speed of 4 rpm for 30 minutes, whereby the slurry on the inner wall of the tube was solidified. (5) After solidification, the quartz tube was placed in a blast oven at 200° C. and dried for 30 minutes to obtain a uniform coating layer on the inner wall of the tube with a thickness of 20 μm.

[0069] (6) The quartz tube was placed in a tube furnace, argon gas was introduced at a flow rate of 0.25 L / min, the temperature was increased at a rate of 5°C / min, the temperature was maintained at 400°C for 1 hour, the temperature was further increased to 800°C and maintained at that temperature for 4 hours, the temperature was then decreased to 500°C and maintained at that temperature for 1 hour, and the temperature was then naturally decreased, thereby forming an electric infrared heating film with a thickness of 15 μm on the inner wall of the quartz tube.

[0070] Examples 8 to 12 Examples 8 to 12 correspond to the electric infrared heating film preparation method (component blending ratio, specifications and parameters) of Examples 2 to 6, respectively, and the electric infrared heating film preparation method of Examples 8 to 12 refers to the electric infrared heating film preparation method of Example 7. The components of the film-forming slurry of each Example are shown in Tables 2 and 3, and the solid content and viscosity of the prepared film-forming slurry, the tube used, the inner diameter and wall thickness of the tube, and the thickness of the prepared electric infrared heating film are shown in Table 4. The contents not shown in Tables 2 to 4 were the same as the electric infrared heating film preparation method of Example 7.

[0071] [Table 2]

[0072] [Table 3]

[0073] [Table 4]

[0074] As another example of the method for preparing an electric infrared heating film according to the present disclosure, a ceramic tube may be used instead of the quartz tube in the methods for preparing an electric infrared heating film according to Examples 9 and 12, and a glass tube may be used instead of the quartz tube in the method for preparing an electric infrared heating film according to Example 11. 3. Examples of electric infrared heating devices according to the present disclosure

[0075] Example 13 The electric infrared heating device of Example 13 is shown in Figures 1 and 2, and comprises a quartz tube 1, an electric infrared heating film 2, two extraction electrodes 3, and two sealing heads 4. The electric infrared heating film 2 is formed by applying the electric infrared heating film prepared by the preparation method of Example 7 to the inner wall of the quartz tube 1. The two extraction electrodes 3 are respectively installed so as to fit into the quartz tube 1 from both ends of the quartz tube 1 and are electrically connected to the electric infrared heating film 2 at both ends of the quartz tube 1. The two sealing heads 4 are respectively located at both ends of the quartz tube 1 and seal the quartz tube 1. The two extraction electrodes 3 and the electric infrared heating film 2 are located within the sealed space of the quartz tube 1. Each of the two sealing heads 4 is provided with a wire-passing hole for passing a lead wire that is electrically connected to the extraction electrode at the corresponding end.

[0076] Example 14 The electric infrared heating device according to this embodiment differs from the electric infrared heating device according to Example 13 only in that the electric infrared heating film on the inner wall of the quartz tube was an electric infrared heating film prepared by the preparation method according to Example 8.

[0077] Example 15 The electric infrared heating device according to this embodiment differs from the electric infrared heating device according to Example 13 only in that the electric infrared heating film on the inner wall of the quartz tube was an electric infrared heating film prepared by the preparation method according to Example 9.

[0078] Example 16 The electric infrared heating device according to this embodiment differs from the electric infrared heating device according to Example 13 only in that the electric infrared heating film on the inner wall of the quartz tube was an electric infrared heating film prepared by the preparation method according to Example 10.

[0079] Example 17 The electric infrared heating device according to this embodiment differs from the electric infrared heating device according to Example 13 only in that the electric infrared heating film on the inner wall of the quartz tube was an electric infrared heating film prepared by the preparation method according to Example 11.

[0080] Example 18 The electric infrared heating device according to this embodiment differs from the electric infrared heating device according to Example 13 only in that the electric infrared heating film on the inner wall of the quartz tube was an electric infrared heating film prepared by the preparation method according to Example 12.

[0081] In each of the electric infrared heating devices according to Examples 13 to 18, an electric infrared heating film is formed in a quartz tube by the electric infrared heating film preparation method adopted therefor, then a lead wire is welded to an extraction electrode, and silver nanopaste is applied to the electric infrared heating film at both ends of the quartz tube. Two extraction electrodes are placed in the quartz tube at both ends of the quartz tube, and fixed so as to be bonded to the electric infrared heating film at the position where the silver nanopaste is applied to the electric infrared heating film. A sealing head is attached to both ends of the quartz tube in a high-purity argon gas environment. A lead wire is pulled out from the wire-passing hole provided in the sealing head at the corresponding end, and then the gap between the lead wire and the wire-passing hole and the gap between the sealing head and the quartz tube are sealed with a heat-resistant sealing adhesive.

[0082] Example 19 The electric infrared heating device of this embodiment uses a ceramic tube instead of the quartz tube in the electric infrared device of Example 13, and has a wire passing hole in the sealing head at only one end of the high-temperature glass tube, with the number of wire passing holes being two, for passing lead wires electrically connected to the two extraction electrodes.

[0083] Example 20 The electric infrared heating device of this embodiment differs from the electric infrared heating device of embodiment 18 only in that a high temperature glass tube is used instead of the quartz tube and a hot laminate is used instead of the sealing head, so a detailed description is omitted here.

[0084] Example 21 As shown in Fig. 4, the electric infrared heating device according to this embodiment includes a plate body 5, an electric infrared heating film 2, and a concave metal electrode 6, and the plate body 5 includes a first base plate 51 and a second base plate 52, and the first base plate 51 and the second base plate 52 are made of the same material, both of which are quartz. The electric infrared heating film 2 is formed by applying the film-forming slurry prepared by the preparation method of steps (1) to (2) of Example 7 to the surface of the second base plate 52, leaving it to stand in an environment of 50 ° C until the slurry does not flow out within 1 minute when the second base plate 52 is vertically placed, and then placing the second base plate 52 coated with the electric infrared heating film 2 in a ventilated oven at 90 ° C for 30 minutes, so that the slurry on the wall of the second base plate 52 solidifies, and the operation is performed according to steps (5) to (6) of Example 7 to form an electric infrared heating film having a thickness of 25 μm on the second base plate 52.

[0085] Two concave metal electrodes 6 are fixed to both ends of the electric infrared heating film 2, respectively, and connected to the electric infrared heating film 2. They are fitted between the first base plate 51 and the second base plate 52, and the two arms of the concave metal electrodes 6 are exposed to the outside of the plate as electrodes so as to be connected to wires. Then, the surface of the second base plate 52 on which the electric infrared heating film 2 is applied is covered with the first base plate 51, and they are sealed together by a method of sealing with heat and pressure to form a sealed space (the concave metal electrodes 6 were selected to reduce stress and gas leakage points caused by sealing with pressure).

[0086] Example 22 The electric infrared heating device according to this embodiment differs from that of the embodiment 21 only in that the plate body 5 is made of borosilicate material. Sealing was performed by thermocompression bonding.

[0087] Example 23 The electric infrared heating device of this embodiment differs from that of Example 21 only in that the plate 5 is made of mica material and sealed with a high-temperature resistant adhesive.

[0088] Example 24 The electric infrared heating device of this embodiment differs from that of embodiment 21 only in that the plate body 5 is a carbon steel plate with an insulating ceramic layer, the insulating layer is installed on the inner side, and the carbon steel plate material part faces outward. It is sealed with a high temperature resistant adhesive.

[0089] Example 25 The electric infrared heating device of this embodiment differs from that of embodiment 21 only in that the plate body 5 is an aluminum alloy plate with an insulating ceramic layer, the insulating layer is placed on the inner side, and the aluminum alloy material part faces outward. It is sealed with high temperature resistant adhesive. The reduced and oxidized graphene used in the comparative example was prepared by the HUMMER method and has a large number of defects.

[0090] Comparative Examples 1 to 6 The electric infrared heating devices according to Comparative Examples 1 to 6 differ from the electric infrared heating device according to Example 13 only in that the electric infrared heating film in the quartz tube is different.

[0091] When preparing the electric infrared heating film on the inner wall of the quartz tube according to each of Comparative Examples 1 to 6, the preparation method of the electric infrared heating film according to Example 7 was referred to. In Comparative Examples 2 to 6, the addition ratio (solid content) of the dilution solvent was adjusted so that the electric infrared heating film with a thickness of 15 μm could be uniformly applied inside the quartz tube. In addition, the main carbon material, solid content, linear speed of the bead milling process, circulation number, thickness of the prepared electric infrared heating film, and mass ratio of the main carbon material, filler, and amorphous carbon in the electric infrared heating film in the film formation slurry prepared in each Comparative Example are shown in Table 5, and the contents not shown were the same as those in Example 7.

[0092] [Table 5]

[0093] Experimental Example 1 In the process of forming an electric infrared heating film on a quartz tube, the film forming performance of the film forming slurry was compared between Examples 13, 16, and 18 and Comparative Examples 1 to 6. The comparison results are shown in Table 6.

[0094] [Table 6]

[0095] As can be seen from Table 6, low-defect graphene is used in the electric infrared heating film according to the present disclosure (taking Examples 13, 16, and 18 as examples), and the solvation performance of low-defect graphene is low. Mechanical mixing can be used to increase the solid content of the low-defect graphene electric infrared heating film material.

[0096] The defect concentration of the commercially available redox graphene used in the comparative example is relatively high, and the graphene prepared by the redox method generally has a relatively small piece size and a high degree of solvation in the slurry. When the components of the graphene dispersion and the contents of each component are the same, the use of commercially available redox graphene significantly increases the consistency of the slurry and significantly decreases the fluidity, and uniform application in the tube cannot be achieved by the method of step (4) (step (4) of Example 7) and other methods. When a graphene material with a large piece size is used, the concentration (density) of the redox graphene edges decreases, the degree of solvation decreases, and the defects in the (110) plane of the repaired graphene oxide material decrease, so the degree of solvation can be further reduced, and therefore the slurry solid content can be significantly increased. Similarly, carbon nanotubes and carbon nanoballs have a relatively large specific surface area and a high degree of solvation, and cannot increase the solid content. For this reason, in Comparative Examples 2 to 6, the slurry was prepared by a method to reduce the solid content. However, the method of improving the fluidity of the slurry by reducing the slurry solid content reduces the viscosity (not the consistency) of the slurry, which is disadvantageous for smooth and stable adhesion of the slurry inside the pipe wall (Comparative Example 2). In addition, during the drying process, a large amount of the solvent in the applied slurry evaporates, making the internal structure of the film loose and prone to pinholes, which is disadvantageous for the film-forming performance of the material after drying.

[0097] In Experimental Examples 2 to 4, all parallel comparative tests were conducted in an open, convection-free environment, and unless otherwise noted, the environmental temperature for all tests was 25±0.5° C. The electric infrared heating devices according to Examples 13, 16, and 18 and Comparative Examples 4 to 6 had an outer diameter of 10 mm and an effective heat generation length of 285 mm, i.e., an effective heat generation area of ​​89.5 cm 2 The temperature was measured using an infrared imager with an accuracy of ±0.1°C and an error of ±2°C. The experimental power supply was a constant voltage variable AC power supply with a frequency of 50Hz, an accuracy of ±0.1V and an error of ±1V.

[0098] Experimental Example 2 Repeated heating tests were conducted on the electric infrared heating devices of Examples 13, 16, and 18 and Comparative Examples 4 to 6 at a constant power of 180W. After the temperature reached a constant level, the device was kept warm for 15 minutes, cooled to below 26°C, and then tested again. This process of heating to the constant temperature and keeping the temperature was repeated 10 times. The effective heating area, constant temperature, heating time after heating to the constant temperature, and state of the electric infrared heating device after repeated heating are shown in Table 7 for each electric infrared heating device, and the heating curves of each electric infrared heating device obtained by the test can be seen in Figure 3.

[0099] [Table 7]

[0100] As can be seen from the data in Table 7, the electric infrared heating film prepared according to the embodiment of the present disclosure (Examples 13, 16, and 18 are taken as examples) has a relatively high surface temperature and excellent durability, and due to the high solid content of the low-defect graphene electric heating material in the embodiment of the present disclosure, the electric infrared heating film according to the present disclosure has high durability in repeated heating tests. In the heating material, the conductive circuit is main carbon material-main carbon material, and main carbon material-amorphous carbon realizes electrical conductivity through physical contact. The electric infrared heating film prepared according to the embodiment of the present disclosure (Examples 13, 16, and 18 are taken as examples) can well meet the following characteristics that should be met in this process: (a) the change in the overall stress of the thin film during the heating and cooling process, (b) the contact stability of the conductive circuit after the main carbon material expands and contracts during repeated heating and cooling: point-point contact<line-line contact<surface-surface contact, (c) the chemical stability of the main carbon material and oxide ceramic in high temperature and electric field environment.

[0101] The commercial graphene used in Comparative Example 4 has high defects and poor thermal stability. Even under the protection of high-purity inert gas, structural rearrangement still occurs when used under high-temperature current, causing irreversible structural destruction in the redox graphene material, resulting in high resistance and impaired service life. The graphene used in Comparative Example 4 removes most of the third type of defects through the high-temperature method, but it is difficult to repair the first type of defects through the process, and therefore does not meet the above requirement (c). The carbon nanotubes in Comparative Example 5 have relatively good structural stability and have the effect of stabilizing the structure of the electric infrared heating film, but due to structural reasons, they have poor dispersion performance and are difficult to increase the solid content, making it difficult to reduce the impact of the solvent content on film formation. In addition, due to their one-dimensional electrical and thermal conductive properties, the thermal conductive ability of the carbon nanotubes along the wall diameter after film formation is relatively low. In Comparative Example 6, the carbon nanoballs of Super-P have good three-dimensional electrical and thermal conductivity effects, but they are in point contact with other materials and are susceptible to Brownian motion and thermal expansion stress during the heating process, which causes the local destruction of the constructed three-dimensional conductive network, which is disadvantageous to maintaining the overall electrical heating performance of the electric infrared heating film in use. The super-P used in Comparative Example 6 is carbon nanoballs, which makes it difficult to meet requirement (b). Therefore, after repeated heating and cooling, a short circuit occurs in the contact between the main carbon material and the main carbon material due to thermal expansion and cold contraction, which causes the local temperature to become too high, causing discharge and tearing of the thin film.

[0102] Experimental Example 3 The heating rates of Examples 13, 16, and 18 of the present disclosure and several commercially available heating tubes were compared, and the results are shown in Table 8. The commercially available heating tubes as high-temperature air heat sources (rated power ≧400W, operating temperature ≧300℃, dry burning possible) available for purchase were all assembled so that the heating wire passed through the central axis of the tube body, the rated power of the heating tube of the commercially available disinfection cabinet was 400W (the heating body was a spiral alloy heating wire), the rated power of the heating tube of the commercially available halogen oven was 400W (the heating body was a carbon fiber heating wire), the rated power of the commercially available carbon fiber heating tube was 800W (the heating body was carbon fiber), and the rated power of the commercially available metal wire shortwave infrared heating tube was 500W (the heating body was an alloy heating wire). The heating tube was heated using a constant power, the temperature sampling interval was 7.5Hz, and the time it took for the tube surface to heat up to 300℃ was measured, and the power density was calculated, and the results are shown in Table 8.

[0103] [Table 8]

[0104] As can be seen from the data in Table 8, the electric infrared heating device according to the embodiment has a significantly better tube surface temperature rise rate in an open environment than the heating tube according to the comparative example at the same power or lower power / power density. The electric infrared heating device according to the present disclosure is significantly improved in terms of electric energy utilization rate, heat transfer efficiency, and heating efficiency compared to various commercially available heating tubes. Taking a commercially available metal wire short wave infrared heating tube as an example, the volume of the heating body is the smallest, the distance from the outer casing to the tube is the longest, and the temperature rise rate is the slowest, and the superiority of the temperature rise performance of the electric infrared heating device according to the present disclosure is obvious.

[0105] Experimental Example 4 Under constant power (180~185W), infrared thermography (FLIR E60, error: ±2℃) was used to measure the working state temperature of several commercially available heating tubes listed in Examples 13, 16, 18 and Experimental Example 3, and the infrared radiation conversion rate was calculated according to the Stefan-Boltzmann law. The corresponding test parameters and results are shown in Table 9.

[0106] [Table 9]

[0107] As can be seen from the data in Table 9, the electric infrared heating device according to the embodiment has an infrared conversion rate of more than 75%, and the heating element is in close contact with the outer wall of the heating device, so that it can be determined that its heat exchange mechanism is mainly radiation heat exchange, assisted by heat conduction.Compared to the heating element and tube wall of a general commercial heating tube, which are designed separately, the temperature of the outer wall of the device is the temperature from the heating film, and there is no convection heat exchange or heat transfer mechanism of heating element-internal environment-tube wall, the temperature difference between the tube surface and the heating element is relatively small, the utilization rate of electric heating energy is higher, and the advantage of infrared radiation conversion rate is obvious. In contrast to the usual electric-infrared conversion rate of 40 to 56.2% of commercially available electric heating tubes, the electric-infrared conversion rate of the electric infrared heating device according to the embodiment has an infrared radiation conversion rate of over 75% even when the power is less than half the average power (400 to 500 W) of commercially available heating tubes. This is due to the additional infrared radiation ability provided by low-defect graphene and the excellent material mechanical performance of the electric infrared heating film at high temperatures, which realizes heat transfer with no gaps with the tube wall and has excellent infrared radiation performance.

[0108] Among the above experimental examples, Examples 13, 16, and 18 are merely illustrative for comparison with the comparative examples, and do not limit the scope of the specification and claims of the present disclosure. The electric infrared heating devices prepared according to Examples 14, 15, 17, 19-20 and other embodiments of the present disclosure also have technical effects similar to those of Examples 13, 16, and 18 and all experimental effects of the above experimental examples.

[0109] The tube inner wall and the electric infrared heating film of the electric infrared heating device of the present disclosure have a small expansion coefficient during the heating process, which reduces the probability of the electric infrared heating film separating from the inner wall of the device, and therefore ensures the structural and performance stability of the electric infrared heating device. [Industrial Applicability]

[0110] In the electric infrared heating film according to the present disclosure, the low-defect graphene, inorganic filler, and amorphous carbon can reduce the volume expansion coefficient of the electric infrared heating film, reduce the difference in the volume expansion coefficient between the electric infrared heating film and substrates such as ceramic, quartz, and high-boron heat-resistant glass, prevent the electric infrared heating film from falling off from the surfaces of these materials, and extend the service life of the electric infrared heating device using the electric infrared heating film. The electric infrared heating film prepared by the method according to the present disclosure and the electric infrared heating device equipped with the same have excellent application value. [Explanation of symbols]

[0111] 1 quartz tube 2 Electric infrared heating film 3 electrodes 4 Sealing Head 5 Plate 51 First base plate 52 Second base plate 6 Concave metal electrode

Claims

1. By weight, it mainly comprises 10 to 15 parts of low defect graphene, 5 to 20 parts of inorganic filler, and 5 to 10 parts of amorphous carbon.

1. An electric infrared heating membrane comprising:

2. In the Raman spectrum of the low defect graphene, the ratio of D peak intensity to G peak intensity is 1 / 10 or less, and the molar ratio of carbon to oxygen in the low defect graphene is 20:1 or more.

2. An electric infrared heating membrane according to claim 1.

3. The low-defect graphene has a 2D peak in its Raman spectrum, and the distance between the 2D peak and the G peak is reduced by 5 cm-1 or more compared to the distance between the 2D peak and the G peak of natural flake graphite.

3. An electric infrared heating membrane according to claim 1 or 2.

4. The inorganic filler has a thermal expansion coefficient of 5×10−7 / K or less within the working temperature range of the electric infrared heating film or within the range of 0 to 600° C.

4. An electric infrared heating film according to claim 1, wherein the heating film is a conductor.

5. The particle size D50 of the inorganic filler is smaller than the particle size D50 of the low defect graphene.

5. An electric infrared heating film according to claim 1 .

6. The inorganic filler is any one or any combination of fillers selected from the group consisting of alumina ceramic powder, zirconia ceramic powder, silicon oxide powder, mica powder, and silicon carbide powder, and the particle size D50 of the inorganic filler is 100 nm or less.

6. An electric infrared heating film according to claim 1 ,

7. The thickness of the electric infrared heating film is 100 μm or less.

7. An electric infrared heating film according to claim 1 .

8. The thickness of the electric infrared heating film is 10 to 30 μm.

7. An electric infrared heating film according to claim 1 .

9. A method for preparing the electric infrared heating film according to claim 1, comprising the steps of: The method includes a step of applying a slurry mainly containing low-defect graphene, an inorganic filler, a film-forming agent and a solvent, forming a film, volatilizing the solvent, and then performing a carbonization process to obtain the electric infrared heating film, and the film-forming agent is an organic polymer.

1. A method for preparing an electric infrared heating film, comprising:

10. The organic polymer is one or any combination of polyolefin, polystyrene, polyacrylate polymer, polyethylene oxide, polyvinylidene fluoride, polyimide, polyurethane, polyacrylonitrile, and phenolic resin. The method for preparing an electric infrared heating film according to claim 9.

11. The slurry further comprises a graphene dispersant, the graphene dispersant comprising a slurry dispersant and a thin film dispersant, the slurry dispersant being one or any combination selected from diphenyl ether, C12-C16 alkyl benzene sulfonate, ethylene oxide, polyethylene glycol, dibasic acid ester, C12-C16 alkyl diphenyl ether monosulfonate, C12-C16 alkyl diphenyl ether disulfonate, C12-C16 alkyl sulfonate, and p-C12-C16 alkyl benzene sulfonate, the thin film dispersant being one or any combination selected from C12-C16 alkyl diphenyl ether monosulfonate, C12-C16 alkyl sulfonate, alkylated derivatives of polydextrose, propylene oxide, fatty alcohol alkoxylate, hydroxypropyl methylcellulose, and polyvinylpyrrolidone. A method for preparing an electric infrared heating film according to claim 9 or 10.

12. The carbonization temperature is 600 to 1200° C., and the carbonization time is 4 hours or more. A method for preparing an electric infrared heating membrane according to any one of claims 9 to 11.

13. An electric infrared heating element and an electric infrared heating film according to any one of claims 1 to 8, The electric infrared heating film is installed on the inner wall of the electric infrared heating element and sealed inside the electric infrared heating element.

1. An electric infrared heating device comprising:

14. 1. An electric infrared heating device, comprising: A heating device comprising a tube, an electric infrared heating film according to any one of claims 1 to 8, and two electrodes, The electric infrared heating film is installed on the inner wall of the tube and sealed inside the tube; The two electrodes are both electrically connected to the electric infrared heating device and configured to heat the electric infrared heating film when electricity is applied.

1. An electric infrared heating device comprising:

15. The tube is a quartz tube, a ceramic tube, or a glass tube.

15. Electric infrared heating device according to claim 14.

16. 1. An electric infrared heating device, comprising: A plate-type electric infrared heating element; The electric infrared heating film according to any one of claims 1 to 8, The plate-type electric infrared heating element includes a plate and an electrode, the electric infrared heating film is installed on the inner wall of the plate and sealed inside the plate, and the electrode is electrically connected to the electric infrared heating device so as to heat the electric infrared heating film when electricity is applied.

1. An electric infrared heating device comprising:

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