CN101636004A - Plane heat source - Google Patents

Abstract

A plane heat source comprises a heating layer and at least two electrodes which are arranged at intervals and are electrically contacted with the heating layer respectively, wherein, the heating layer comprises at least a carbon nano tube membrane which comprises a plurality of carbon nano tubes connected end to end and arrayed in the preferred orientation.

Description

surface heat source

technical field

The invention relates to a surface heat source, in particular to a surface heat source based on carbon nanotubes.

Background technique

Heat sources play an important role in people's production, life and scientific research. The surface heat source is a kind of heat source, and its characteristic is that the surface heat source has a plane structure, and the object to be heated is placed above the plane structure to heat the object. Therefore, the surface heat source can heat all parts of the object to be heated at the same time, and the heating surface Wide, uniform heating and high efficiency. Surface heat sources have been successfully used in industrial fields, scientific research fields, or living fields, such as electric heaters, infrared therapeutic devices, electric heaters, etc.

The existing surface heat source generally includes a heating layer and at least two electrodes, and the at least two electrodes are arranged on the surface of the heating layer and electrically connected with the surface of the heating layer. When the electrodes connected to the heating layer are passed through a low-voltage current, heat is released from the heating layer immediately. Now commercially available surface heat sources usually use electric heating wire made of metal as the heating layer for electrothermal conversion. However, the strength of the heating wire is not high and it is easy to break, especially when it is bent or twisted at a certain angle, so its application is limited. In addition, the heat generated by the electric heating wire made of metal radiates outward at ordinary wavelengths, and its electrothermal conversion efficiency is not high, which is not conducive to saving energy.

The invention of non-metallic carbon fiber conductive material has brought a breakthrough for the development of surface heat source. The heating layer using carbon fiber is usually coated with a waterproof insulating layer on the outside of the carbon fiber as an element for electrothermal conversion to replace the metal heating wire. Due to the good toughness of carbon fiber, this solves the shortcoming of the low strength of the heating wire and is easy to break to a certain extent. However, since the carbon fiber still dissipates heat at ordinary wavelengths, it does not solve the problem of low electrothermal conversion rate. In order to solve the above problems, the heating layer using carbon fiber generally includes a plurality of carbon fiber heat source wires laid. The carbon fiber heat source wire is a conductive core wire wrapped with chemical fiber or cotton thread. The outside of the chemical fiber or cotton thread is dip-coated with a layer of waterproof and flame-retardant insulating material. The conductive core wire is formed by winding a plurality of carbon fibers and a plurality of cotton threads coated with far-infrared paint on the surface. Cotton thread coated with far-infrared paint is added to the conductive core wire, which can enhance the strength of the core wire, and secondly, make the heat emitted by the carbon conductive fiber radiate outward at infrared wavelengths after electrification.

However, the use of carbon fiber paper as the heating layer has the following disadvantages: first, the strength of carbon fiber is not strong enough, the flexibility is not good enough, and it is easy to break. It is necessary to add cotton thread to improve the strength of carbon fiber, which limits its scope; second, the electrothermal conversion of carbon fiber itself The efficiency is low, and it is necessary to add cotton thread coated with far-infrared paint to improve the electrothermal conversion efficiency, which is not conducive to energy saving and environmental protection; third, it needs to be made into a carbon fiber heat source line before making the heating layer, which is not conducive to large-scale production and is not conducive to uniformity At the same time, it is not conducive to the fabrication of micro surface heat sources.

In view of this, it is indeed necessary to provide a surface heat source, which has high strength and high electrothermal conversion efficiency, which is beneficial to energy saving and uniform heating. The size of the surface heat source is controllable, and can be made into a large area surface heat source or a micro surface heat source.

Contents of the invention

A surface heat source, comprising a heating layer; at least two electrodes, the at least two electrodes are arranged at intervals and are respectively in electrical contact with the heating layer, wherein the heating layer includes at least one carbon nanotube film, and the carbon nanotube film It includes a plurality of carbon nanotubes connected end to end and arranged in preferred orientations.

Compared with the prior art, the surface heat source has the following advantages: first, the diameter of the carbon nanotube is smaller, so that the carbon nanotube layer has a smaller thickness, and a micro surface heat source can be prepared for heating of micro devices. Second, carbon nanotubes have a smaller density than carbon fibers, so the surface heat source using carbon nanotube layers has lighter weight and is easier to use. Third, the carbon nanotube layer includes at least one carbon nanotube film, the carbon nanotubes in the same carbon nanotube film are arranged in the same direction, have low resistance, and the electrothermal conversion efficiency of the carbon nanotubes is high, and the heat The resistivity is low, so the surface heat source has the characteristics of rapid temperature rise, small thermal hysteresis, and fast heat exchange speed.

Description of drawings

Fig. 1 is a schematic structural diagram of a surface heat source in an embodiment of the technical solution.

Fig. 2 is a schematic cross-sectional view of II-II in Fig. 1 .

Fig. 3 is a scanning electron micrograph of the carbon nanotube thin film of the embodiment of the technical solution.

Fig. 4 is a graph showing the relationship between the surface temperature of the surface heat source and the heating power in the embodiment of the technical solution.

Detailed ways

The surface heat source provided by the technical solution will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Please refer to Fig. 1 and Fig. 2, the embodiment of this technical solution provides a surface heat source 10, the surface heat source 10 includes a base 18, a reflective layer 17, a heating layer 16, a first electrode 12, a second electrode 14 and an insulating protective layer 15. The reflective layer 17 is disposed on the surface of the substrate 18 . The heating layer 16 is disposed on the surface of the reflective layer 17 . The first electrode 12 and the second electrode 14 are spaced apart from each other on the surface of the heating layer 16 , and are in electrical contact with the heating layer 16 , so as to allow current to flow through the heating layer 16 . The insulating protection layer 15 is disposed on the surface of the heating layer 16 and covers the first electrode 12 and the second electrode 14 to prevent the heating layer 16 from absorbing external impurities.

The shape of the base 18 is not limited, and it has a surface for supporting the heating layer 16 or the reflective layer 17 . Preferably, the base 18 is a plate-shaped base, and its material can be rigid materials such as ceramics, glass, resin, quartz, etc., or flexible materials such as plastics or flexible fibers. When it is a flexible material, the surface heat source 10 can be bent into any shape according to needs during use. Wherein, the size of the base 18 is not limited, and can be changed according to actual needs. The preferred substrate 18 of this embodiment is a ceramic substrate. In addition, when the heating layer 16 has a certain self-supporting property and stability, the base 18 in the surface heat source 10 is an optional structure.

The reflective layer 17 is provided to reflect the heat generated by the heating layer 16, thereby controlling the direction of heating, for single-sided heating, and further improving the heating efficiency. The reflective layer 17 is made of a white insulating material, such as metal oxide, metal salt or ceramics. In this embodiment, the reflective layer 17 is an aluminum oxide layer with a thickness of 100 microns to 0.5 mm. The reflective layer 17 can be formed on the surface of the substrate 18 by sputtering or other methods. It can be understood that the reflective layer 17 can also be arranged on the surface of the substrate 18 away from the heating layer 16, that is, the substrate 18 is arranged between the heating layer 16 and the reflective layer 17, so as to further enhance the ability of the reflective layer 17 to reflect heat. effect. When the surface heat source 10 does not include the base 18 , the heating layer 16 can be directly disposed on the surface of the reflective layer 17 . The reflective layer 17 is an optional structure. The heating layer 16 can be directly disposed on the surface of the substrate 18 , at this time, the heating direction of the surface heat source 10 is not limited, and can be used for double-sided heating.

The heating layer 16 includes a carbon nanotube layer. The carbon nanotube layer itself has a certain viscosity, and can be arranged on the surface of the substrate 18 by utilizing its own viscosity, or can be arranged on the surface of the substrate 18 through an adhesive. The adhesive is silica gel. The length, width and thickness of the carbon nanotube layer are not limited and can be selected according to actual needs. The thickness of the carbon nanotube layer provided by the technical solution is 1 micron-1 mm.

The carbon nanotube layer includes at least one carbon nanotube film. Please refer to FIG. 3 , the carbon nanotube film can be obtained by directly stretching a carbon nanotube array. The carbon nanotube film comprises a plurality of carbon nanotubes connected end to end and preferentially oriented along the stretching direction. The carbon nanotubes are uniformly distributed and parallel to the surface of the carbon nanotube film. The carbon nanotubes in the carbon nanotube film are connected by van der Waals force. On the one hand, the end-to-end connected carbon nanotubes are connected by Van der Waals force; on the other hand, the parts between parallel carbon nanotubes are also bonded by Van der Waals force. Therefore, the carbon nanotube film has certain flexibility and can be bent and folded. It can be formed into any shape without breaking, and the surface heat source 10 using the carbon nanotube film has a long service life.

The carbon nanotubes in the carbon nanotube film include one or more of single-wall carbon nanotubes, double-wall carbon nanotubes and multi-wall carbon nanotubes. The single-walled carbon nanotubes have a diameter of 0.5-10 nanometers, the double-walled carbon nanotubes have a diameter of 1.0-15 nanometers, and the multi-walled carbon nanotubes have a diameter of 1.5-50 nanometers. The length of the carbon nanotube is greater than 100 microns. Preferably 200-900 microns.

The carbon nanotube film is obtained by further processing the carbon nanotube array, so its length is not limited, and its width is related to the size of the substrate on which the carbon nanotube array grows, and can be produced according to actual needs. In this embodiment, a super-aligned carbon nanotube array is grown on a 4-inch substrate by vapor deposition. The carbon nanotube film may have a width of 0.01 cm-10 cm and a thickness of 1 nm-100 microns. The thickness of the carbon nanotube film is preferably 0.1 micron to 10 micron.

When the carbon nanotube layer includes at least two overlapping carbon nanotube films, the adjacent carbon nanotube films are closely combined by van der Waals force. Further, the number of carbon nanotube films in the carbon nanotube layer is not limited, and an included angle α is formed between the arrangement directions of carbon nanotubes in two adjacent layers of carbon nanotube films, 0≤α≤90 degrees , which can be prepared according to actual needs. It can be understood that the thickness of the carbon nanotube layer can be controlled by controlling the number of layers of the carbon nanotube film. The thermal response speed of the carbon nanotube layer is related to its thickness. In the case of the same area, the thicker the carbon nanotube layer, the slower the thermal response speed; conversely, the smaller the carbon nanotube layer thickness, the faster the thermal response speed. In this embodiment, the thickness of the carbon nanotube layer is 1 μm-1 mm, and the carbon nanotube layer can reach the highest temperature within less than 1 second. In this embodiment, the single-layer carbon nanotube film can reach the highest temperature within 0.1 millisecond. Therefore, the surface heat source 10 is suitable for rapid heating of objects.

In this embodiment, the heating layer 16 adopts 100 overlapping and intersecting layers of carbon nanotube films, and the intersection angle between two adjacent layers of carbon nanotube films is 90 degrees. The length of the carbon nanotube film in the carbon nanotube layer is 5 centimeters, the width of the carbon nanotube film is 3 centimeters, and the thickness of the carbon nanotube film is 50 micrometers. The carbon nanotube layer is provided on the surface of the reflective layer 17 by utilizing the viscosity of the carbon nanotube layer itself.

The first electrode 12 and the second electrode 14 are made of conductive materials, and the shapes of the first electrode 12 and the second electrode 14 are not limited, and may be conductive films, metal sheets or metal leads. Preferably, both the first electrode 12 and the second electrode 14 are a layer of conductive film. The conductive film has a thickness of 0.5 nanometers to 100 microns. The material of the conductive thin film can be metal, alloy, indium tin oxide (ITO), antimony tin oxide (ATO), conductive silver glue, conductive polymer or conductive carbon nanotube, etc. The metal or alloy material can be aluminum, copper, tungsten, molybdenum, gold, titanium, neodymium, palladium, cesium or alloys in any combination thereof. In this embodiment, the material of the first electrode 12 and the second electrode 14 is metal palladium film with a thickness of 5 nanometers. The metal palladium and carbon nanotubes have better wetting effect, which is beneficial to form good electrical contact between the first electrode 12 and the second electrode 14 and the heating layer 16, and reduce ohmic contact resistance.

The first electrode 12 and the second electrode 14 can be arranged on the same surface of the heating layer 16 or on different surfaces of the heating layer 16 . Alternatively, when the surface heat source 10 does not include the substrate 18, the heating layer 16 can also be fixed on the surfaces of the spaced first electrode 12 and the second electrode 14, and the first electrode 12 and the second electrode 14 are used to support heating. Layer 16. Wherein, the first electrode 12 and the second electrode 14 are arranged at intervals, so that when the heating layer 16 is applied to the surface heat source 10, a certain resistance value is connected to avoid short circuit phenomenon. Since the carbon nanotube layer used as the heating layer 16 has good adhesion, the first electrode 12 and the second electrode 14 can directly form a good electrical contact with the carbon nanotube layer.

In addition, the first electrode 12 and the second electrode 14 can also be arranged on the surface of the heating layer 16 through a conductive adhesive (not shown). While the electrodes 14 are in electrical contact with the heating layer 16 , the first electrode 12 and the second electrode 14 can be better fixed on the surface of the heating layer 16 . The preferred conductive adhesive in this embodiment is silver glue.

It can be understood that the structures and materials of the first electrode 12 and the second electrode 14 are not limited, and the purpose of setting them is to make current flow in the heating layer 16 . Therefore, the first electrode 12 and the second electrode 14 only need to be electrically conductive, and forming electrical contact with the heating layer 16 is within the protection scope of the present invention.

The insulating protection layer 15 is an optional structure, and its material is an insulating material, such as rubber, resin and the like. The thickness of the insulating protection layer 15 is not limited, and can be selected according to actual conditions. The insulating protective layer 15 covers the first electrode 12, the second electrode 14 and the heating layer 16, so that the surface heat source 10 can be used in an insulated state, and at the same time, carbon in the heating layer 16 can be avoided. Nanotubes adsorb foreign impurities. In this embodiment, the insulation protection layer 15 is made of rubber, and its thickness is 0.5-2 mm.

When the surface heat source 10 of the embodiment of the technical solution is in use, the first electrode 12 and the second electrode 14 of the surface heat source 10 can be connected to a wire first and then connected to a power source. After the power is connected, the carbon nanotube layer in the heat source 10 can radiate electromagnetic waves in a certain wavelength range. The surface heat source 10 may be in direct contact with the surface of the object to be heated. Alternatively, since the carbon nanotubes in the carbon nanotube layer used as the heating layer 16 in this embodiment have good electrical conductivity, and the carbon nanotube layer itself already has certain self-supporting properties and stability, the surface heat source 10 It can be set at a certain distance from the object to be heated.

Carbon nanotubes have good electrical conductivity and thermal stability, as an ideal black body structure, and have relatively high heat radiation efficiency. In this embodiment, the electrothermal property measurement was carried out on the carbon nanotube layer composed of 100 carbon nanotube intersecting films. The carbon nanotube layer is 5 cm long and 3 cm wide. The carbon nanotube layer is wrapped on a substrate 18 with an outer diameter of 1 cm, and its length between the first electrode 110 and the second electrode 112 is 3 cm. Current flows along the length of the substrate 18 . The measuring instruments are infrared thermometer RAYTEK RAYNER IP-M and infrared thermometer measuring instrument, the model is AZ-8859. Please refer to Fig. 4, when the heating power is 36 watts, the surface temperature has reached 370°C. It can be seen that the carbon nanotube layer has high electrothermal conversion efficiency.

The surface heat source 10 in the embodiment of the technical solution can radiate electromagnetic waves in different wavelength ranges by adjusting the power supply voltage and the thickness of the carbon nanotube layer when the area of the carbon nanotube layer is constant. When the power supply voltage is constant, the thickness of the carbon nanotube layer is inversely proportional to the wavelength of the electromagnetic wave radiated from the surface heat source 10 . That is, when the power supply voltage is constant, the thicker the thickness of the carbon nanotube layer, the shorter the wavelength of the surface heat source 10 radiating electromagnetic waves, and the surface heat source 10 can produce a visible light heat radiation; the thinner the thickness of the carbon nanotube layer, the shorter the surface heat source 10 is. The longer the wavelength of the electromagnetic wave radiated from 10, the surface heat source 10 can generate an infrared heat radiation. When the thickness of the carbon nanotube layer is constant, the power supply voltage is inversely proportional to the wavelength of the electromagnetic wave radiated from the surface heat source 10 . That is, when the thickness of the carbon nanotube layer is constant, the greater the power supply voltage, the shorter the wavelength of the surface heat source 10 radiating electromagnetic waves, and the surface heat source 10 can produce a visible light thermal radiation; the smaller the power supply voltage, the shorter the wavelength of the surface heat source 10 radiating electromagnetic waves. The longer the wavelength, the surface heat source 10 can generate an infrared heat radiation.

Carbon nanotubes have good electrical conductivity and thermal stability, and as an ideal black body structure, they have relatively high heat radiation efficiency. The surface heat source 10 is exposed to an oxidative gas or atmospheric environment, wherein the thickness of the carbon nanotube layer is 5 millimeters, and the surface heat source 10 can radiate electromagnetic waves with longer wavelengths by adjusting the power supply voltage at 10 volts to 30 volts . The temperature of the surface heat source 10 was found to be 50°C to 500°C by a temperature measuring instrument. For an object with a blackbody structure, when the corresponding temperature is 200°C to 450°C, it can emit thermal radiation (infrared rays) invisible to the human eye, and the thermal radiation at this time is the most stable and efficient. The heating element made of the carbon nanotube layer can be applied to fields such as electric heaters, infrared therapeutic instruments, electric heaters and the like.

Furthermore, the surface heat source 10 in the embodiment of the technical solution is placed in a vacuum device, and the surface heat source 10 can radiate electromagnetic waves with shorter wavelengths by adjusting the power supply voltage between 80 volts and 150 volts. When the power supply voltage is greater than 150 volts, the surface heat source 10 will successively emit visible light such as red light and yellow light. It is found by the temperature measuring instrument that the temperature of the surface heat source 10 can reach above 1500° C., and a normal heat radiation will be generated at this time. With the further increase of the power supply voltage, the surface heat source 10 can also generate invisible rays (ultraviolet light) to kill bacteria, which can be applied to light sources, display devices and other fields.

The surface heat source has the following advantages: First, because carbon nanotubes have good strength and toughness, the strength of the carbon nanotube layer is relatively large, the flexibility of the carbon nanotube layer is good, and it is not easy to break, so that it has a longer service life. Second, the carbon nanotubes in the carbon nanotube layer are evenly distributed, the carbon nanotube layer has uniform thickness and resistance, and the heat generation is uniform. It has the characteristics of fast heat exchange speed and high radiation efficiency. Thirdly, the diameter of the carbon nanotube is small, so that the carbon nanotube layer has a small thickness, and a micro surface heat source can be prepared, which can be applied to the heating of micro devices. Fourth, the carbon nanotube layer can be obtained by further processing after being pulled from the carbon nanotube array. The method is simple and is conducive to the production of large-area surface heat sources.

In addition, those skilled in the art can also make other changes within the spirit of the present invention. Of course, these changes made according to the spirit of the present invention should be included within the scope of protection claimed by the present invention.

Claims (15)

1. A surface heat source comprising: a heating layer; At least two electrodes, the at least two electrodes are arranged at intervals and are respectively in electrical contact with the heating layer; It is characterized in that the heating layer includes at least one carbon nanotube film, and the carbon nanotube film includes a plurality of carbon nanotubes connected end to end and arranged in preferred orientation. 2. The surface heat source according to claim 1, characterized in that, the carbon nanotubes in the carbon nanotube film are connected by van der Waals force. 3. The surface heat source according to claim 1, characterized in that the length of the carbon nanotubes is greater than 100 microns and the diameter is less than 50 nanometers. 4. The surface heat source according to claim 1, wherein the heating layer comprises at least two overlapping carbon nanotube films, and two adjacent carbon nanotube films are closely connected by van der Waals force. 5 . The surface heat source according to claim 4 , wherein the arrangement directions of carbon nanotubes in adjacent carbon nanotube films in the heating layer form an included angle α, 0≤α≤90 degrees. 6. The surface heat source according to claim 1, characterized in that, the thickness of the carbon nanotube film is 1 nanometer-100 micrometers. 7. The surface heat source according to claim 1, characterized in that, the thickness of the heating layer is 1 micron-1 mm. 8. The surface heat source according to claim 1, wherein the materials of the at least two electrodes are metal, alloy, indium tin oxide, antimony tin oxide, conductive silver glue, conductive polymer or conductive carbon nanometer Tube. 9. The surface heat source according to claim 1, wherein the at least two electrodes are arranged on the same surface or different surfaces of the carbon nanotube layer. 10 . The surface heat source according to claim 1 , wherein the carbon nanotube layer comprises a carbon nanotube composite structure formed by overlapping at least one carbon nanotube film and at least one carbon nanotube long line. 11 . 11. The surface heat source according to claim 1, characterized in that the surface heat source further comprises a plate-shaped base, and the carbon nanotube layer is arranged on the surface of the plate-shaped base. 12. The surface heat source according to claim 11, wherein the material of the substrate is a flexible material or a hard material, and the flexible material is plastic or flexible fiber, and the hard material is ceramic, glass, resin or quartz. 13. The surface heat source according to claim 1, characterized in that, the surface heat source further comprises a reflective layer, the reflective layer is arranged on the surface of the heating layer, and the material of the reflective layer is metal oxide, metal salt or ceramics , with a thickness of 100 microns to 0.5 mm. 14. The surface heat source according to claim 13, wherein the reflective layer is arranged between the heating layer and the substrate or is arranged on the surface of the substrate away from the heating layer. 15. The surface heat source according to claim 1, characterized in that the surface heat source further comprises an insulating protection layer disposed on the surface of the heating layer, and the material of the insulating protection layer includes rubber or resin.

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