EP4709043A1

EP4709043A1 - Heating diaphragm and preparation method therefor, heating pipe and heating electric appliance

Info

Publication number: EP4709043A1
Application number: EP24919563.7A
Authority: EP
Inventors: Jie RAO; Yanjun Sun; Zehui ZHANG; Wenhua Zhao; Cong Wang
Original assignee: Guangdong Midea Kitchen Appliances Manufacturing Co Ltd
Current assignee: Guangdong Midea Kitchen Appliances Manufacturing Co Ltd
Priority date: 2024-01-26
Filing date: 2024-04-23
Publication date: 2026-03-11
Also published as: WO2025156473A1

Abstract

Provided are a heating film and a preparation method therefor, a heating tube and a heating appliance. The raw materials of the heating film comprise natural graphite and/or graphene, and the weight of the heating film having a length of 1 decimeter is 0.02 g to 2 g.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit of a priority of Chinese Patent Application No. 2024101198333, filed on January 26, 2024 , the entire contents of which are incorporated herein by reference.

FIELD

The present disclosure relates to the field of electric appliance technologies, and more particularly, to a heating film and a method for preparing same, a heating tube, and a heating appliance.

BACKGROUND

Conventional electric ovens primarily heat food through heating air inside a cavity via a heating tube and directly heating a surface of the food through thermal radiation. Currently, heating appliances on the market, such as electric ovens, microwave ovens, and steam ovens, mainly employ heating elements comprising metallic heating tubes (with a maximum heating temperature ranging from 550°C to 750°C), quartz heating tubes (with a heating filament temperature ranging from 660°C to 800°C), halogen heating tubes (with a maximum heating temperature below 1,000°C), carbon fiber heating tubes (with a maximum heating temperature below 1,000°C), and the like. However, the above heating tubes suffer from drawbacks such as slow heating within their heating temperature ranges, inadequate maximum temperatures, and excessive weight, which results in prolonged cooking time and makes it difficult to obtain food that is crispy on the outside and tender on the inside during heating, causing unsatisfactory user experience. Moreover, an overall weight of a conventional heating tube is relatively high, which is unfavorable for meeting requirements for a lightweight design.

SUMMARY

The present disclosure aims to solve at least one of the technical problems in the related art to some extent. To this end, an objective of the present disclosure is to provide a heating film. The heating film has a relatively light mass, a relatively high heating temperature, or a relatively high temperature rise rate.
In an aspect of the present disclosure, the present disclosure provides a heating film. According to an embodiment of the present disclosure, a raw material for the heating film comprises natural graphite and/or graphene, and a weight of the heating film per decimeter length ranges from 0.02 g to 2 g. Thus, the graphite heating film prepared using the natural graphite or the graphene enables a relatively high heating temperature and a relatively high heating rate, which can help achieve higher-temperature heating and a higher heating efficiency. Moreover, the heating film of the present disclosure is made of the natural graphite, which has large reserves in the earth's minerals. In addition, during preparation of a carbon-based film material, high-temperature graphitization is not required, nor is any additional process needed, allowing for continuous production and reduced costs. Overall, the heating film of the present disclosure offers advantages such as widely available raw materials, simple preparation processes, satisfactory product stability, and ease of adjusting performance parameters as needed, providing significant benefits in reducing product costs, enhancing product reliability, and diversifying product types. If artificial graphite is used instead, an additional process for manufacturing the artificial graphite is required, which substantially increases both manufacturing costs and manufacturing duration of the heating film and reduces a production efficiency. Using the graphene as the raw material is not only beneficial for obtaining the heating film having a relatively high carbon content, but also enables a simple and mature processing process and low preparation costs. Further, the above heating film of the present disclosure has the relatively light mass, far less than a weight of a heating tube such as a metallic heating tube or a quartz tube, facilitating a lightweight design of the heating film of the present disclosure and consequently helping obtain a relatively lightweight heating tube. If the weight per unit length of the heating film is smaller than 0.02 g, manufacturability of the heating film becomes relatively unsatisfactory, affecting overall performance of the heating film. If the weight per unit length of the heating film is greater than 2 g, the manufacturability of the heating film also becomes relatively unsatisfactory.
According to an embodiment of the present disclosure, the heating film has a flake-like structure; the natural graphite and the graphene has a flake-like structure; and a flake-like extension plane of the heating film is substantially consistent with a flake-like extension plane of the natural graphite and/or flake-like extension plane of the graphene.
According to an embodiment of the present disclosure, a duration for the heating film to reach a maximum heating temperature ranges from 0.1 s to 2 s.
According to an embodiment of the present disclosure, a heat-resistant temperature of the heating film is greater than or equal to 2,500°C.
According to an embodiment of the present disclosure, the heating film has a maximum heating temperature ranging from 500°C to 1,700°C.
According to an embodiment of the present disclosure, a material of the heating film is graphite.
According to an embodiment of the present disclosure, the heating film has power ranging from 15 W to 10,000 W.
According to an embodiment of the present disclosure, the heating film comprises a plurality of heating units arranged sequentially in a length direction, adjacent heating units being arranged at an interval from each other and connected by a connection segment.
According to an embodiment of the present disclosure, each of the plurality of heating units has a hollowed-out hole.
In another aspect of the present disclosure, the present disclosure provides a method for preparing the above heating film. According to an embodiment of the present disclosure, the method comprises: providing the natural graphite, and performing an intercalation treatment on the natural graphite to obtain graphite oxide; performing an expansion treatment on the graphite oxide to obtain expanded graphite; and performing calendaring and cutting on the expanded graphite to obtain the heating film; or the method comprises: uniformly mixing and dispersing the graphene and an additive to obtain a dispersion liquid; coating the dispersion liquid to obtain a dispersion liquid film; performing a second heat treatment on the dispersion liquid film to obtain a preliminary carbon-based film; and performing calendaring and cutting on the preliminary carbon-based film to obtain the heating film. Thus, the graphite heating film prepared using the natural graphite or the graphene enables the relatively high heating temperature and the relatively high heating rate, which can help achieve the higher-temperature heating and the higher heating efficiency. Moreover, the heating film of the present disclosure is made of the natural graphite, which has large reserves in the earth's minerals. In addition, during the preparation of the carbon-based film material, the high-temperature graphitization is not required, nor is any additional process needed, allowing for the continuous production and reduced costs. Overall, the carbon-based film material offers advantages such as widely available raw materials, simple preparation processes, satisfactory product stability, and ease of adjusting performance parameters as needed, providing significant benefits in reducing product costs, enhancing product reliability, and diversifying product types. If the artificial graphite is used instead, the additional process for manufacturing the artificial graphite is required, which substantially increases both the manufacturing costs and the manufacturing duration of the heating film and reduces the production efficiency. Using the graphene as the raw material is not only beneficial for obtaining the heating film having the relatively high carbon content, but also enables the simple and mature processing process and the low preparation costs.
According to an embodiment of the present disclosure, the method comprises: mixing a graphene nanoplatelet and an additive and uniformly dispersing the graphene nanoplatelet and the additive to obtain a dispersion liquid; applying the dispersion liquid to obtain a dispersion liquid film; performing a second heat treatment on the dispersion liquid film to obtain a preliminary carbon-based film; and performing calendaring and cutting on the preliminary carbon-based film to obtain the heating film.
In yet another aspect of the present disclosure, the present disclosure provides a heating tube. According to an embodiment of the present disclosure, the heating tube comprises the above heating film. Thus, the heating tube has a relatively light mass, achieves a relatively high heating temperature, and exhibits a relatively high temperature rise rate. Those skilled in the art should understand that the heating tube possesses all the features and advantages of the above heating film, and thus details thereof will be omitted here.
In still yet another aspect of the present disclosure, the present disclosure provides a heating appliance. According to an embodiment of the present disclosure, the heating appliance comprises the above heating tube. Thus, the heating appliance exhibits a relatively high heating rate and achieves a relatively high heating temperature. Those skilled in the art should understand that the heating appliance possesses all the features and advantages of the above heating film, and thus details thereof will be omitted here.
According to an embodiment of the present disclosure, the heating appliance is an electric oven, a microwave oven, a steam oven, an electric kettle, an electric blanket, an electric heater, an electric warmer, a bath heater, an electric ceramic cooker, or a disinfection cabinet.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or additional aspects and advantages of the present disclosure will become more apparent and more understandable from the following description of embodiments taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram of thermal radiation of a heating film of the present disclosure.
FIG. 2 is a schematic diagram of thermal radiation of a heating tube in the related art.
FIG. 3 is a schematic structural view of a heating film according to an embodiment of the present disclosure.
FIG. 4 is a schematic structural view of a heating film according to some other embodiments of the present disclosure.
FIG. 5 is a schematic structural view of a heating film according to some other embodiments of the present disclosure.
FIG. 6 is a schematic structural view of a heating film according to some other embodiments of the present disclosure.
FIG. 7 is a schematic structural view of a heating tube according to yet some other embodiments of the present disclosure.
FIG. 8 is a schematic structural view of a heating tube according to yet some other embodiments of the present disclosure.
FIG. 9 is a schematic structural view of a heating tube according to yet some other embodiments of the present disclosure.
FIG. 10 is a temperature-resistance curve diagram of a heating film according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Solutions of the present disclosure are described below in conjunction with embodiments. Those skilled in the art should understand that the embodiments described below are only used for illustrating the present disclosure and should not be construed as limiting the scope of the present disclosure. Where specific techniques or conditions are not indicated in the embodiments, the procedures shall be carried out in accordance with the techniques or conditions described in the related literature in the field or in accordance with the product specification. The reagents or instruments used without the indication of the manufacturers are all conventional products that can be purchased commercially.
The present disclosure will now be described with reference to specific embodiments. It should be understood that these embodiments are merely illustrative and are not intended to limit the present disclosure in any way.
In an aspect of the present disclosure, the present disclosure provides a heating film. According to some embodiments of the present disclosure, a raw material of the heating film comprises natural graphite and/or graphene, and a weight of the heating film per decimeter length ranges from 0.02 g to 2 g, e.g., 0.02 g, 0.04 g, 0.05 g, 0.1 g, 0.2 g, 0.5 g, 1 g, 1.5 g, and 2 g. Thus, the graphite heating film prepared using the natural graphite or the graphene enables a relatively high heating temperature and a relatively high heating rate, which can help achieve higher-temperature heating and a higher heating efficiency. Moreover, the heating film of the present disclosure is made of the natural graphite, which has large reserves in the earth's minerals. In addition, during preparation of a carbon-based film material, high-temperature graphitization is not required, nor is any additional process needed, allowing for continuous production and reduced costs. Overall, the heating film of the present disclosure offers advantages such as widely available raw materials, simple preparation processes, satisfactory product stability, and ease of adjusting performance parameters as needed, providing significant benefits in reducing product costs, enhancing product reliability, and diversifying product types. If artificial graphite is used instead, an additional process for manufacturing the artificial graphite is required, which substantially increases both manufacturing costs and manufacturing duration of the heating film and reduces a production efficiency. Using the graphene as the raw material is not only beneficial for obtaining the heating film having a relatively high carbon content, but also enables a simple and mature processing process and low preparation costs. Further, the above heating film of the present disclosure has the relatively light mass, far less than a weight of a heating tube such as a metallic heating tube or a quartz tube, facilitating a lightweight design of the heating film of the present disclosure and consequently helping obtain a relatively lightweight heating tube. If the weight per unit length of the heating film is smaller than 0.02 g, manufacturability of the heating film becomes relatively unsatisfactory, affecting overall performance of the heating film. If the weight per unit length of the heating film is greater than 2 g, the manufacturability of the heating film also becomes relatively unsatisfactory. Further, heating power of the heating film is relatively higher, when the weight per unit length of the heating film is relatively greater. That is, the weight per unit length of the heating film is positively correlated with the heating power of the heating film. Therefore, the desired power of the heating film can be adjusted through adjusting the weight per unit length of the heating film.
According to a heat calculation formula Q=m*Cp*ΔT, where Q represents heat, m represents mass, Cp represents specific heat capacity, and ΔT represents temperature rise, it can be deduced from this formula that, under a same amount of heat, the temperature rise increases as a product of mass and specific heat capacity decreases. Since the heating film of the present disclosure has the relatively low mass and a modest specific heat capacity, a product of the mass and the specific heat capacity of the heating film of the present disclosure is small. Therefore, the carbon-based film achieves a higher temperature rise rate and a higher heating temperature under the condition where the same amount of heat is generated. In a specific embodiment of the present disclosure, the carbon-based heating film has the specific heat capacity of 0.71 kJ/(kg*K) and the mass of 0.216 g, whereas a metallic heating wire in a heating tube such as a metallic tube or a quartz tube has a specific heat capacity of 0.49 kJ/(kg*K) and a mass of 5 g. Thus, compared with the metallic heating wire, the carbon-based film of the present disclosure exhibits a higher temperature rise rate and can reach a higher heating temperature.
Moreover, according to a radiant heat transfer formula: Q=ε*σ*A*(T₁ ⁴-T₂ ⁴), where Q represents heat, ε represents emissivity, σ represents Stefan-Boltzmann constant, and T represents a surface temperature of an object, it can be obtained that the heat generated through the radiant heat transfer is proportional to a difference between fourth power of a surface temperature of one of two objects and fourth power of a surface temperature of the other object. Since a surface temperature of the carbon-based film is relatively high, the heat Q generated through the radiant heat transfer is correspondingly great, enabling the carbon-based film heating tube to have higher heating rate than the metallic tube or the quartz tube.
In some embodiments of the present disclosure, the raw material graphene may be a graphene nanoplatelet. The graphene nanoplatelet refers to an ultra-thin layered graphene stack having more than 10 carbon layers and a thickness ranging from 5 nanometers to 100 nanometers. The graphene nanoplatelet possesses satisfactory thermal conductivity and tensile strength, helping to enhance the heating temperature and mechanical strength of the prepared heating film.
According to some embodiments of the present disclosure, the heating film has a flake-like structure, each of the raw materials graphite and/or graphene used to prepare the heating film also has a flake-like structure, and a flake-like extension plane of the heating film is substantially consistent with a flake-like extension plane of each of the natural graphite and/or the graphene. Consequently, as illustrated in FIG. 1, when the flake-like structured heating film generates heat, the heat is primarily radiated in a direction perpendicular to a heating surface (i.e., a plane of the film), which results in strong directivity and more concentrated thermal radiation, better improving a heating efficiency and reducing a heat loss. In the related art, as illustrated in FIG. 2, thermal radiation from a heating tube core 1 (e.g., a metallic heating tube core or a quartz tube core) is emitted uniformly in all directions, and thus heat cannot be emitted in a concentrated manner, typically leading to a heat waste and a reduced heating efficiency. Thus, by comparison, a thermal radiation direction of the heating film of the present disclosure is more concentrated, enabling better directional heating of an object to be heated and improving the heating efficiency. It should be noted that the term "substantially consistent" as used above means that the flake-like extension plane of the heating film is generally consistent with the flake-like extension plane of each of the natural graphite and/or the graphene, and does not require the flake-like extension plane of the heating film and the flake-like extension plane of each of the natural graphite and/or the graphene to be completely identical or completely parallel.
According to some embodiments of the present disclosure, as described above, the material of the heating film prepared from the raw material natural graphite or graphene is graphite, which enables the heating film of the present disclosure to have the relatively high heating temperature and the relatively high heating rate. The prepared graphite still has a flake-like structure. In addition, a planar extension direction of the flake-like structure is substantially consistent with a planar extension direction of the raw material natural graphite or graphene. That is, the flake-like extension plane of the heating film is substantially consistent with a flake-like extension plane of the material graphite for preparing the heating film.
According to some embodiments of the present disclosure, a duration for the heating film to reach a maximum heating temperature ranges from 0.1 s to 2 s, e.g., 0.1 s, 0.2 s, 0.4 s, 0.5 s, 0.6 s, 0.7 s, 0.8 s, 0.9 s, 1 s, 1.1 s, 1.2 s, 1.3 s, 1.4 s, 1.5 s, 1.6 s, 1.7 s, 1.8 s, 1.9 s, or 2.0 s. Thus, the heating film of the present disclosure has the relatively high heating rate and can reach the maximum heating temperature within a relatively short period of time, significantly improving the heating efficiency of the heating film.
According to some embodiments of the present disclosure, a heat-resistant temperature of the heating film is greater than or equal to 2,500°C, e.g., 2,500°C, 2,550°C, 2,600°C, 2,650°C, 2,700°C, 2,750°C, 2,800°C, 2,850°C, 2,900°C, 2,950°C, or 3,000°C. Thus, the heating film of the present disclosure has the relatively high heat-resistant temperature, enabling the heating film to reach the relatively high heating temperature without undergoing a degradation.
According to some embodiments of the present disclosure, the heating film has a maximum heating temperature ranging from 500°C to 1,700°C. For example, the maximum heating temperature of the heating film may be 500°C, 550°C, 600°C, 700°C, 800°C, 900°C, 1,000°C, 1,100°C, 1,200°C, 1,300°C, 1,400°C, 1,500°C, 1,600°C, or 1,700°C. Thus, the heating film of the present disclosure has the relatively high maximum heating temperature, which can even reach as high as 1,700°C. Consequently, a broad range of heating application requirements is satisfied, enabling production of heating films with various power levels, e.g., an ultra-low-power heating film or an ultra-high-power heating film.
According to some embodiments of the present disclosure, the heating film has a thickness ranging from 0.04 mm to 2 mm. For example, the thickness of the heating film may be 0.04 mm, 0.06 mm, 0.08 mm, 0.1 mm, 0.2 mm, 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm, 1.8 mm, or 2.0 mm. The heating film having the above thicknesses can meet requirements for different power levels of the heating film. In addition, the carbon-based heating film of the present disclosure has high manufacturability, i.e., a high production yield and a long service life. Additionally, the relatively thin thickness of the above heating film facilitates the lightweight design of the heating film.
According to some embodiments of the present disclosure, the heating film has a density ranging from 0.6 g/cm³ to 1.8 g/cm³. For example, the density of the heating film may be 0.6 g/cm³, 0.8 g/cm³, 1.0 g/cm³, 1.2 g/cm³, 1.4 g/cm³, 1.5 g/cm³, 1.6 g/cm³, or 1.8 g/cm³. The heating film having the above density can meet requirements for different power levels of the heating film. In addition, the carbon-based heating film of the present disclosure has the high manufacturability, i.e., the high production yield and the long service life. Further, a combination of the above density and the above thickness allows a flexible adjustment of the power of the heating film to meet usage requirements for different power levels.
According to some embodiments of the present disclosure, the heating film has power ranging from 15 W to 10,000 W, e.g., 15 W, 20 W, 40 W, 50 W, 70 W, 100 W, 150 W, 300 W, 500 W, 800 W, 1,000 W, 1,500 W, 3,000 W, 4,500 W, 5,000 W, 6,000 W, 7,000 W, 8,000 W, 9,000 W, and 10,000 W. Thus, the heating film of the present disclosure can effectively achieve a wide span of different power levels for the heating film. That is, both the ultra-low-power heating film and the ultra-high-power heating film can be achieved, satisfying various power requirements for the heating film under different application conditions.
According to some embodiments of the present disclosure, the heating film has a carbon content greater than or equal to 99%. Thus, the heating film has the relatively high carbon content, i.e., relatively high purity, which is conducive to obtaining the heating film having better performance.
According to some embodiments of the present disclosure, the heating film has thermal diffusivity ranging from 50 m²/s to 450 m²/s, e.g., 50 m²/s, 80 m²/s, 100 m²/s, 130 m²/s, 150 m²/s, 280 m²/s, 300 m²/s, 320 m²/s, 350 m²/s, 370 m²/s, and 400 m²/s. The above thermal diffusivity enables heat generated by the heating film to be transferred out of a heating cavity via thermal conduction to a lesser extent, allowing more heat to concentrate on the heating film. Consequently, the heating film attains a higher temperature. According to the Stefan-Boltzmann law, a greater temperature difference results in greater radiant energy, and thus heat is transferred into the heating cavity primarily via radiation, concentrating the heat generated by the heating film mainly onto the object to be heated. In this way, not only can an excellent heating rate be ensured, but also an excessive heat loss due to overly rapid heat transfer can be avoided, improving the heating efficiency. Further, the above thermal diffusivity also helps extend the service life of the heating film. If the thermal diffusivity is smaller than 50 m²/s, too little heat is transferred by the heating film via the thermal conduction, causing a temperature of the heating film to be too high and failing to meet a lifespan requirement. If the thermal diffusivity is greater than 450 m²/s, much heat is transferred via the thermal conduction, resulting in reduced radiant energy and a relatively low heating efficiency of the heating film. Furthermore, higher thermal diffusivity requires the heating film to have a higher density. The density corresponding to the thermal diffusivity greater than 450 m²/s is relatively large, making manufacturing difficult from a process standpoint. In addition, the raw material for the carbon-based heating film of the present disclosure is readily available and low in costs, and does not require a high-temperature graphitization treatment, making the process simpler and safer. Additionally, the above thermal diffusivity also contributes to extending the service life of the heating film and enhancing the manufacturability of the heating film.
According to some embodiments of the present disclosure, the heating film prepared from the natural graphite and/or the graphene nanoplatelet also has a self-limiting temperature characteristic. As illustrated in FIG. 10, the heating film has a critical temperature. When the temperature of the heating film is below the critical temperature, a resistance of the heating film decreases as the temperature of the heating film increases. When the temperature of the heating film exceeds the critical temperature, the resistance of the heating film increases as the temperature of the heating film increases. Thus, the heating film of the present disclosure has the self-limiting temperature characteristic. Specifically, in an initial stage of heating (i.e., when the temperature of the heating film is below the critical temperature), as the temperature of the heating film increases, the resistance of the heating film decreases, and a current increases, which causes the power of the heating film to increase as the temperature of the heating film increases. Therefore, in this stage, the heating film can heat up rapidly. When the heating temperature of the heating film reaches the critical temperature, as the temperature of the heating film increases, the resistance of the heating film increases, and the current decreases, which causes the power of the heating film to decrease as the temperature of the heating film increases. Therefore, in this stage, a temperature rise rate of the heating film begins to slow down, gradually approaching the maximum heating temperature of the heating film. On the one hand, the above self-limiting temperature characteristic of the heating film enables an acceleration of the heating rate of the heating film in a temperature range below the critical temperature, allowing the heating film to reach a target temperature as quickly as possible. On the other hand, when the temperature of the heating film exceeds the critical temperature, the above self-limiting temperature characteristic of the heating film can mitigate an issue of a fuse failure caused by the continuously rising heating temperature, enhancing reliability and stability of the heating film. It should be noted that, FIG. 10 merely illustrates a temperature-resistance curve diagram of the heating film according to embodiment, but a trend of the curve represents a schematic illustration of a temperature-resistance curve of the heating film of the present disclosure.
Further, when the temperature of the heating film is below the critical temperature, the temperature rise rate of the heating film is a first temperature rise rate; when the temperature of the heating film exceeds the critical temperature, the temperature rise rate of the heating film is a second temperature rise rate. The first temperature rise rate is greater than the second temperature rise rate. Thus, the heating film of the present disclosure has the relatively high first temperature rise rate, which can contribute to rapid heating of the heating film, in such a manner that the heating film can reach the critical temperature within a relatively short period of time. Then, the heating film continues heating at the relatively low second temperature rise rate, which can avoid the issue of the fuse failure caused by the continuously rising heating temperature, enhancing the reliability and the stability of the heating film.
According to some embodiments of the present disclosure, the heating film has the critical temperature ranging from 50°C to 500°C. For example, the critical temperature of the heating film may be 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 230°C, 250°C, 280°C, 300°C, 330°C, 350°C, 370°C, 400°C, 420°C, 450°C, 480°C, or 500°C. Thus, a specific critical temperature value of the heating film of the present disclosure can be adjusted within a relatively wide range. If the heating temperature of the heating film is relatively high, a relatively high critical temperature value can be selected. If the heating temperature of the heating film is relatively low, a relatively low critical temperature value can be selected. In this way, both the relatively high heating rate and prevention of the fuse failure of the heating film can be better ensured.
In an embodiment of the present disclosure, a specific cutting pattern of the heating film can be diversified. Those skilled in the art can flexibly design the cutting pattern of the heating film based on actual requirements for resistance, power, and the like of the heating film. Several cutting patterns of the heating film are described below according to some specific embodiments of the present disclosure.
In some embodiments of the present disclosure, as illustrated in FIG. 3, the heating film comprises a plurality of heating units 01 arranged sequentially in a length direction. Adjacent heating units 01 of the plurality of heating units 01 are spaced apart from each other and connected by a connection segments 02. Thus, the heating film of the present disclosure can be cut into structures of various patterns to meet different usage requirements. In some embodiments of the present disclosure, as illustrated in FIG. 3, an outer peripheral wall of the heating unit is formed in an oblong shape or a polygonal shape.
In some embodiments of the present disclosure, as illustrated in the portions (b), (c) and (i) of FIG. 3, each heating unit 01 has a hollowed-out hole 03. Thus, formation of the hollowed-out hole can accelerate a heat dissipation rate of the heating film, speeding up the heating rate for the object to be heated.
In some embodiments of the present disclosure, as illustrated in FIG. 4, the heating film comprises a first heating segment S1 and a second heating segment S2 adjacent to each other in the length direction. The first heating segment S1 comprises a plurality of heating units 01 connected to each other. The second heating segment S2 comprises a plurality of heating units 01 adjacent to each other. Each of the plurality of heating units 01 corresponding to the first heating segment S1 has a smaller size than each of the plurality of heating units 01 corresponding to the second heating segment S2. For example, as illustrated in the portion (a) of FIG. 4, the heating unit 01 corresponding to the first heating segment S1 has a same length as the heating unit 01 corresponding to the second heating segment S2, but a width d1 of the heating unit 01 corresponding to the first heating segment S1 is different from a width d2 of the heating unit 01 corresponding to the second heating segment S2. For example, as illustrated in the portions (b) and (c) of FIG. 4, the heating unit 01 corresponding to the first heating segment S1 has a same width as the heating unit 01 corresponding to the second heating segment S2, but a length d1 of the heating unit 01 corresponding to the first heating segment S1 is different from a length d2 of the heating unit 01 corresponding to the second heating segment S2. Thus, a structure of the heating film can be diversified.
In some embodiments of the present disclosure, as illustrated in FIG. 5, the first heating segment S1 and the second heating segment S2 are offset from each other in a width direction of the heating film. Thus, the structure of the heating film can be diversified.
In some embodiments of the present disclosure, as illustrated in the portions (d), (e), (f), (h), (i), and (j) of FIG. 3, the heating film has a plurality of openings arranged at intervals in the length direction. Thus, the structure of the heating film can be diversified. Further, in some embodiments of the present disclosure, as illustrated in the portion (i) of FIG. 3, each opening is defined through separating a part of the heating film from a remaining part of the heating film and bending the part of the heating film.
In some embodiments, as illustrated in FIG. 6, one heating film may comprise a plurality of different cutting patterns, or may comprise one cutting pattern having a non-uniform density distribution.
In another aspect of the present disclosure, the present disclosure provides a method for preparing the above heating film. According to an embodiment of the present disclosure, the method for preparing the heating film can be prepared through separately using the natural graphite and the graphene. Specific preparation steps are as follows.
In some embodiments, the method for preparing the heating film using the natural graphite comprises the following steps.
In S100, the natural graphite is provided, and an intercalation treatment is performed on the natural graphite to obtain a graphite oxide (expandable graphite).
In the present disclosure, the natural graphite is used, which does not require any additional process for preparation of the natural graphite, further reducing processes for preparing the heating film and reducing costs. If the artificial graphite is used instead, the additional process for manufacturing the artificial graphite is required, which substantially increases both the manufacturing costs and the manufacturing duration of the heating film and reduces the production efficiency. In addition, using natural flake graphite, whose single-layer structure exhibits a layered arrangement, enables the graphite within the prepared heating film to also exhibit a layered arrangement, enhancing concentrated heating performance of the heating film. Additionally, the natural flake graphite is abundant in the earth's mineral reserves. Further, during preparation of the carbon-based heating film material, the high-temperature graphitization is not required, and continuous production is achievable, which can further improve the production efficiency and lower production costs. An elimination of the high-temperature graphitization also improves production safety.
Additionally, the natural flake graphite is abundant in the earth's mineral reserves. Further, during preparation of the heating film material of the present disclosure, the high-temperature graphitization is not required, and the continuous production is achievable, which can further improve the production efficiency and lower the production costs. The elimination of the high-temperature graphitization also improves the production safety.
In some embodiments, a specific method for the intercalation treatment may involve intercalating the natural flake graphite with concentrated sulfuric acid and/or an oxidant such as a hydrogen peroxide to obtain the expandable graphite.
In S200, an expansion treatment is performed on the graphite oxide to obtain expanded graphite.
In some embodiments, after the expandable graphite enters an expansion furnace, the expandable graphite undergoes an instantaneous high temperature, rapidly expanding to form graphite worms, i.e., the expanded graphite. Through the expansion treatment, an expansion ratio of the expandable graphite can reach 30 times to 400 times. During the expansion treatment, an expansion temperature ranges from 850°C to 1,200°C, and an expansion duration ranges from 0.7 s to 1.3 s.
In S300, calendering, a first heat treatment, and cutting are performed on the expanded graphite to obtain the heating film. The heating films with different cutting patterns obtained after the cutting can be referred to in FIG. 3 to FIG. 6. Characteristics of specific cutting patterns are consistent with requirements previously described, and thus details thereof will be omitted here.
No special requirements are imposed on a specific method for the first heat treatment. Those skilled in the art can employ a specific heat treatment method known in the art for deoxidizing the graphite oxide to obtain the graphite.
Thus, by performing the calendering on the expanded graphite, parameters such as the thickness, the density, and the thermal diffusivity of the heating film can be controlled. The thickness, the density, and the thermal diffusivity of the heating film have been described above, and thus details thereof will be omitted here.
In some embodiments, the critical temperature of the above heating film prepared from the natural graphite ranges from 50°C to 200°C. Thus, the heating film having the relatively low critical temperature can be prepared using the above method.
According to the embodiments of the present disclosure, the above graphite heating film prepared using the natural graphite enables the relatively high heating temperature and the relatively high heating rate, which can help achieve the higher-temperature heating and the higher heating efficiency. Moreover, the heating film of the present disclosure is made of the natural graphite, which has large reserves in the earth's minerals. In addition, during the preparation of the carbon-based film material, the high-temperature graphitization is not required, nor is any additional process needed, allowing for the continuous production and reduced costs. Overall, the carbon-based film material offers advantages such as widely available raw materials, simple preparation processes, satisfactory product stability, and ease of adjusting performance parameters as needed, providing significant benefits in reducing product costs, enhancing product reliability, and diversifying product types. If the artificial graphite is used instead, the additional process for manufacturing the artificial graphite is required, which substantially increases both the manufacturing costs and the manufacturing duration of the heating film and reduces the production efficiency.
In some embodiments, the method for preparing the heating film using the graphene comprises the following steps.
In S400, the graphene and an additive are mixed, and the graphene and the additive are uniformly dispersed to obtain a dispersion liquid.
In some embodiments, the graphene used is the graphene nanoplatelet. The graphene nanoplatelet has a planar size ranging from 1 µm to 100 µm and a specific surface area ranging from 30 m²/g to 800 m²/g. The graphene nanoplatelet meeting the above requirements facilitates uniform dispersion.
In some embodiments, the additive comprises at least one of carboxymethyl cellulose, polyvinyl alcohol, polyethylene glycol, a polyacrylic acid, or waterborne polyurethane. The addition of the above additive can effectively enhance a film-forming ability of the graphene nanoplatelet.
Further, based on a total mass of the dispersion liquid, a mass fraction of the additive is smaller than or equal to 5% by mass percentage, e.g., a mass fraction of the additive is 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%. The relatively low usage amount of the additive does not affect satisfactory performance of the prepared heating film.
In S500, the dispersion liquid is applied to obtain a dispersion liquid film.
In some embodiments, no special requirements are imposed on a specific applying method. Those skilled in the art can flexibly select an appropriate applying method as desired, such as spin coating or spray coating.
In S600, a second heat treatment is performed on the dispersion liquid film to obtain a preliminary carbon-based film.
In this step, the graphene is deoxygenated through the second heat treatment to obtain the graphite material. The heat treatment may be performed under vacuum or in an inert atmosphere. A temperature of the second heat treatment ranges from 1,500°C to 3,000°C. With the above method, the graphite having a relatively high carbon content can be obtained. For example, the carbon content may exceed 99%.
In S700, calendering and cutting are performed on the preliminary carbon-based film to obtain the heating film. The heating films with different cutting patterns obtained after the cutting can be referred to in FIG. 3 to FIG. 6. Characteristics of specific cutting patterns are consistent with requirements previously described, and thus details thereof will be omitted here.
In some embodiments, the critical temperature of the heating film prepared from the graphene nanoplatelet ranges from 150°C to 500°C. Thus, the heating film having the relatively high critical temperature can be prepared using the above method.
According to the embodiments of the present disclosure, using the graphene as the raw material is not only beneficial for obtaining the heating film having the relatively high carbon content, but also enables the simple and mature processing process and the low preparation costs. In addition, the graphene nanoplatelet used has satisfactory thermal conductivity and tensile strength, helping to increase the heating temperature of the prepared heating film and enhance mechanical strength of the prepared heating film.
In yet another aspect of the present disclosure, the present disclosure provides a heating tube. According to an embodiment of the present disclosure, the heating tube comprises the above heating film. Thus, the heating tube has a relatively light mass, achieves a relatively high heating temperature, and exhibits a relatively high temperature rise rate. Those skilled in the art should understand that the heating tube possesses all the features and advantages of the above heating film, and thus details thereof will be omitted here.
In some embodiments, as illustrated in FIG. 7 (region S in the figure refers to a partial cross-sectional view of a sleeve), FIG. 8, and FIG. 9, the heating tube further comprises a sleeve 10. The heating film 20 is disposed inside the sleeve 10, and is provided with a terminal 21 at each of two ends of the heating film 20. The sleeve may be, for example, a quartz glass sleeve.
In still yet another aspect of the present disclosure, the present disclosure provides a heating appliance. According to an embodiment of the present disclosure, the heating appliance comprises the above heating tube. Thus, the heating appliance exhibits a relatively high heating rate and achieves a relatively high heating temperature. Those skilled in the art should understand that the heating appliance possesses all the features and advantages of the above heating film, and thus details thereof will be omitted here.
According to an embodiment of the present disclosure, the heating appliance is an electric oven, a microwave oven, a steam oven, an electric kettle, an electric blanket, an electric heater, an electric warmer, a bath heater, an electric ceramic cooker, or a disinfection cabinet.
Those skilled in the art should understand that, in addition to the above heating tube, the heating appliance further comprises structures or components essential to the heating appliance. As an example, in the electric oven, in addition to the above heating tube, essential structures or components such as a housing, a heating space, a base, and a plug are also comprised.

Examples

Example 1

The heating film was prepared using the natural flake graphite. A schematic structural view of the heating film is illustrated in the portion (a) of FIG. 3 The heating film had a thickness of 0.04 mm, a length of 3 dm, a width of 8 mm, and a density of 1 g/cm³.

Example 2

Example 2 differs from Example 1 in that the heating film had the thickness of 0.1 mm.

Example 3

Example 3 differs from Example 1 in that the heating film had the thickness of 0.5 mm.

Example 4

Example 4 differs from Example 1 in that the heating film had the thickness of 1 mm.

Example 5

Example 5 differs from Example 1 in that the heating film had the thickness of 1.5 mm.

Example 6

Example 6 differs from Example 1 in that the heating film had the thickness of 2 mm.

Example 7

Example 7 differs from Example 1 in that the heating film had the length of 2 dm.

Example 8

Example 8 differs from Example 1 in that the heating film had the length of 6 dm.

Comparative Example 1

Comparative Example 1 differs from Example 1 in that the heating film had the thickness of 0.03 mm.

Comparative Example 2

Comparative Example 2 differs from Example 1 in that the heating film had the thickness of 2.2 mm.

Comparative Example 3

A metallic heating tube core was used and had a length of 3 dm.

Comparative Example 4

A quartz tube core was used and had a length of 3 dm.

Example 9

The heating film was prepared using the graphene nanoplatelet. A schematic structural view of the heating film is illustrated in the poriton (a) of FIG. 3. The heating film had the thickness of 0.04 mm, the length of 3 dm, the width of 8 mm, and the density of 1 g/cm³.

Example 10

Example 10 differs from Example 9 in that the heating film had the thickness of 0.1 mm.

Example 11

Example 11 differs from Example 9 in that the heating film had the thickness of 0.5 mm.

Example 12

Example 12 differs from Example 9 in that the heating film had the thickness of 1 mm.

Example 13

Example 13 differs from Example 9 in that the heating film had the thickness of 1.5 mm.

Example 14

Example 14 differs from Example 9 in that the heating film had the thickness of 2 mm.

Comparative Example 5

Comparative Example 5 differs from Example 9 in that the heating film had the thickness of 0.03 mm.

Comparative Example 6

Comparative Example 6 differs from Example 9 in that the heating film had the thickness of 2.2 mm.
A mass, a maximum heating temperature, a heating response duration, and power of each of the heating films in Example 1 to Example 8, Comparative Example 1, and Comparative Example 2 were tested. A mass, a maximum heating temperature, a heating response duration, and power of each of the heating tube cores in Comparative Example 3 and Comparative Example 4 were tested. A mass, a maximum heating temperature, a heating response duration, and power of each of the heating films in Example 9 to Example 14, Comparative Example 5, and Comparative Example 6 were tested. Test results are shown in Table 1.

In Comparative Example 1 and Comparative Example 5, the thickness of the heating film is relatively small, which results in a non-uniform overall thickness and insufficient manufacturability, making experimental testing impossible. In Comparative Example 2 and Comparative Example 6, the thickness of the heating film is relatively large, which causes the heating film to be prone to breakage, resulting in insufficient manufacturability and a production yield that fails to meet manufacturing requirements.

Table 1

	Weight of the heating film or the heating tube core per decimeter length/g	Mass/g	Maximum heating temperature/°C	Heating response duration/s	Power/W
Example 1	0.027	0.081	1,300	0.2	210
Example 2	0.064	0.192	1,300	0.2	520
Example 3	0.32	0.96	1,300	0.2	2,000
Example 4	0.64	1.92	1,300	0.2	3,000
Example 5	0.96	2.88	1,300	0.2	3,600
Example 6	1.28	3.84	1,300	0.2	3,900
Example 7	0.027	0.054	1,300	0.15	120
Example 8	0.027	0.16	1,300	0.4	450
Comparative Example 1	/	/	/	/	/
Comparative Example 2	1.4	4.2	1,300	0.2	4,000
Comparative Example 3	1.667	5	750	72	500
Comparative Example 4	1.667	5	800	23	500
Example 9	0.027	0.081	1,700	0.2	210
Example 10	0.064	0.192	1,700	0.2	520
Example 11	0.32	0.96	1,700	0.2	2,000
Example 12	0.64	1.92	1,700	0.2	3,000
Example 13	0.96	2.88	1,700	0.2	3,600
Example 14	1.28	3.84	1,700	0.2	3,900
Comparative Example 5	/	/	/	/	/
Comparative Example 6	1.4	4.2	1,700	0.2	4,000

The above data reveals that the heating response duration of the heating film is related to the length of the heating film. The heating response duration of the heating film increases as the length of the heating film increases. Further, as the weight per unit length of the heating film increases, the heating power of the heating film gradually increases. Compared with Comparative Example 3 and Comparative Example 4, the heating film of the present disclosure has an extremely short heating response duration, a relatively light weight, enabling rapid heating, a relatively high heating temperature, and a lightweight design for the heating tube.

Example 15

The heating tube from Example 4, a halogen tube, a quartz tube, and a metallic tube were respectively applied in one oven. All heating tubes were tested at same power of 600 W. Time required for each heating tube to raise a temperature at a center of the oven to 200°C was measured. Test results are shown in Table 2. Table 2

Heating film heating tube Halogen tube Quartz tube Metallic tube

Time (s) 149 218 290 279
The above Examples and Comparative Examples show that the heating film of the present disclosure has a relatively light weight, the relatively high heating temperature, the relatively high heating rate, and the relatively high temperature rise rate.
In the present disclosure, terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features associated with "first" and "second" may explicitly or implicitly comprise one or more of the features. In the description of the present disclosure, "plurality" means at least two, unless otherwise specifically defined.
Reference throughout this specification to "an embodiment", "some embodiments", "an example", "a specific example", or "some examples" means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is comprised in at least one embodiment or example of the present disclosure. The appearances of the above phrases in various places throughout this specification are not necessarily referring to the same embodiment or example. Further, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples. In addition, different embodiments or examples and features of different embodiments or examples described in the specification may be combined by those skilled in the art without mutual contradiction.
Although embodiments of the present disclosure have been shown and described above, it should be understood that the above embodiments are merely exemplary, and cannot be construed to limit the present disclosure. For those skilled in the art, changes, alternatives, and modifications can be made to the embodiments without departing from the scope of the present disclosure.

Claims

A heating film, wherein a raw material for the heating film comprises natural graphite and/or graphene, and wherein a weight of the heating film per decimeter of length ranges from 0.02 g to 2 g.
The heating film according to claim 1, wherein:
the heating film has a flake-like structure;

the natural graphite and the graphene has a flake-like structure; and

a flake-like extension plane of the heating film is substantially consistent with a flake-like extension plane of the natural graphite and/or a flake-like extension plane of the graphene.
The heating film according to claim 1 or 2, wherein a duration for the heating film to reach a maximum heating temperature ranges from 0.1 s to 2 s.
The heating film according to any one of claims 1 to 3, wherein a heat-resistant temperature of the heating film is greater than or equal to 2,500°C.
The heating film according to any one of claims 1 to 4, wherein the heating film has a maximum heating temperature ranging from 500°C to 1,700°C.
The heating film according to any one of claims 1 to 5, wherein a material of the heating film is graphite.
The heating film according to any one of claims 1 to 6, wherein the heating film has power ranging from 15 W to 10,000 W.
The heating film according to any one of claims 1 to 7, wherein the heating film comprises a plurality of heating units arranged sequentially in a length direction, adjacent heating units being arranged at an interval from each other and connected by a connection segment.
The heating film according to claim 8, wherein each of the plurality of heating units has a hollowed-out hole.
A method for preparing the heating film according to any one of claims 1 to 9, the method comprising:
providing natural graphite, and performing an intercalation treatment on the natural graphite to obtain expandable graphite;

performing an expansion treatment on the expandable graphite to obtain expanded graphite; and

performing calendering, a first heat treatment, and cutting on the expanded graphite to obtain the heating film,

or the method comprising:
uniformly mixing and dispersing graphene and an additive to obtain a dispersion liquid;

coating the dispersion liquid to obtain a dispersion liquid film;

performing a second heat treatment on the dispersion liquid film to obtain a preliminary carbon-based film;

performing calendaring and cutting on the preliminary carbon-based film to obtain the heating film.
A heating tube, comprising a heating film according to any one of claims 1 to 9.
A heating appliance, comprising a heating tube according to claim 11.
The heating appliance according to claim 12, wherein the heating appliance is an electric oven, a microwave oven, a steam oven, an electric kettle, an electric blanket, an electric heater, an electric warmer, a bath heater, an electric ceramic cooker, or a disinfection cabinet.