CN101636008A - Plane heat source - Google Patents

Abstract

A surface heat source, which includes: a base; a heating layer, the heating layer is arranged on the base; at least two electrodes are arranged at intervals and are respectively electrically connected to the heating layer; wherein, the heating layer includes a carbon nanotube layer, The carbon nanotube layer includes a plurality of carbon nanotubes that are isotropic, oriented along a fixed direction or preferentially arranged in different directions.

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. Compared with metal, carbon fiber has better toughness, which solves the shortcoming of low strength and easy breaking of heating wire 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, and it is easy to break, and cotton threads need to be added to improve the strength of carbon fiber, which limits its application range; second, the electrothermal conversion efficiency of carbon fiber itself is low, requiring Adding cotton thread coated with far-infrared paint improves 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 first and then made into a heating layer, which is not conducive to large-scale production and is not conducive to the uniformity requirements. At the same time, It is not conducive to the production 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 includes a first electrode, a second electrode and a heating layer. The first electrode and the second electrode are spaced apart on the heating layer and are in electrical contact with the heating layer. The heating layer includes a carbon nanotube layer, and the carbon nanotube layer includes a plurality of carbon nanotubes that are isotropic, oriented along a fixed direction or preferentially arranged in different directions.

Compared with the prior art, the surface heat source has the following advantages: First, carbon nanotubes can be conveniently made into carbon nanotube layers of any size, which can be applied to both macroscopic and microscopic fields. 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 has high electrothermal conversion efficiency and low thermal resistivity, so the surface heat source has the characteristics of rapid temperature rise, small thermal hysteresis, and fast heat exchange speed. Fourth, the carbon nanotube layer can be directly obtained by rolling the carbon nanotube array, which is easy to prepare and low in cost.

Description of drawings

Fig. 1 is a schematic structural diagram of a surface heat source provided by 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 a carbon nanotube layer including carbon nanotubes arranged in different directions with preferred orientations provided by the embodiment of the technical solution.

Fig. 4 is a scanning electron micrograph of a carbon nanotube layer including carbon nanotubes preferentially aligned along the same direction provided by the embodiment of the technical solution.

Detailed ways

The surface heat source of the technical solution will be described in detail below in conjunction with the accompanying drawings.

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, 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.

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. 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 carbon nanotube layer includes uniformly distributed carbon nanotubes. The carbon nanotubes in the carbon nanotube layer form an angle α with the surface of the carbon nanotube layer, wherein α is greater than or equal to zero and less than or equal to 15 degrees (0≤α≤15°). Preferably, the carbon nanotubes in the carbon nanotube layer are parallel to the surface of the carbon nanotube layer. The carbon nanotube layer can be prepared by rolling a carbon nanotube array, and the carbon nanotubes in the carbon nanotube layer have different arrangements according to different rolling methods. Specifically, the carbon nanotubes can be arranged isotropically; when rolled in different directions, the carbon nanotubes are preferentially aligned in different directions, please refer to Figure 3; when rolled in the same direction, the carbon nanotubes are arranged in a fixed direction See Figure 4 for the preferred orientation arrangement. The carbon nanotubes in the carbon nanotube layer partially overlap. The carbon nanotubes in the carbon nanotube layer are attracted to each other by van der Waals force and closely combined, so that the carbon nanotube layer has good flexibility and can be bent and folded into any shape without breaking.

The carbon nanotubes in the carbon nanotube layer include one or more of single-wall carbon nanotubes, double-wall carbon nanotubes and multi-wall carbon nanotubes. The single-wall carbon nanotubes have a diameter of 0.5 nm to 10 nm, the double-wall carbon nanotubes have a diameter of 1 nm to 15 nm, and the multi-wall carbon nanotubes have a diameter of 1.5 nm to 50 nm. The length of the carbon nanotube is greater than 50 microns. The length of the carbon nanotube is greater than 50 microns, preferably, the length of the carbon nanotube is 200-900 microns.

The area and thickness of the carbon nanotube layer are not limited and can be selected according to actual needs. The area of the carbon nanotube layer is related to the size of the substrate on which the carbon nanotube array grows. The thickness of the carbon nanotube layer is related to the height of the carbon nanotube array and the rolling pressure, and can be 1 micron to 1 mm. It can be understood that the greater the height of the carbon nanotube array and the smaller the applied pressure, the greater the thickness of the prepared carbon nanotube layer; conversely, the smaller the height of the carbon nanotube array and the greater the applied pressure, the prepared The thickness of the carbon nanotube layer is smaller. It can be understood that 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 heating layer 16 is a carbon nanotube layer with a thickness of 100 microns. The length of the carbon nanotube layer is 5 cm, and the width of the carbon nanotube layer is 3 cm. The carbon nanotube layer is disposed on the surface of the substrate 18 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 are arranged at intervals and are respectively electrically connected to the heating layer 16 , and can be arranged on the same surface of the heating layer 16 or on different surfaces of the 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.

The surface heat source 10 in the embodiment of the technical solution can radiate electromagnetic waves of different wavelength ranges by adjusting the power supply voltage and the thickness of the heating layer 16 when the area of the carbon nanotube layer is constant. When the power supply voltage is constant, the thickness of the heating layer 16 and the wavelength of the electromagnetic wave radiated from the surface heat source 10 have opposite changing trends. That is, when the power supply voltage is constant, the thicker the thickness of the heating layer 16, 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 thinner the thickness of the heating layer 16, the shorter the surface heat source 10 radiates The longer the wavelength of the emitted electromagnetic wave, the surface heat source 10 can generate an infrared heat radiation. When the thickness of the heating layer 16 is constant, the magnitude of 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 heating layer 16 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. Longer, 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 oxidizing gas or atmospheric environment, wherein the thickness of the carbon nanotube layer is 1mm, and the surface heat source 10 can radiate electromagnetic waves with longer wavelengths by adjusting the power supply voltage between 10V and 30V. 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 apparatuses, and electric heaters.

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 better strength and toughness, the carbon nanotube layer is more flexible and not easy to break, so it has a longer service life. Second, the carbon nanotubes in the carbon nanotube layer are evenly distributed, so they have uniform thickness and resistance, uniform heating, and high electrothermal conversion efficiency of carbon nanotubes, so the surface heat source has rapid temperature rise, small thermal hysteresis, and heat exchange speed Fast and high radiation efficiency. Thirdly, the diameter of the carbon nanotube is small, so that the carbon nanotube layer has a small area or thickness, and a micro-surface heat source can be prepared and applied to heating of micro-devices. Fourth, the carbon nanotube layer can be directly obtained by rolling the carbon nanotube array, which is easy to prepare and low in cost.

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 (12)

1. plane heat source, it comprises:

One substrate;

One zone of heating, described zone of heating is arranged at the surface of substrate; And,

At least two electrodes, this two electrode gap settings and being electrically connected with zone of heating respectively;

It is characterized in that described zone of heating comprises a carbon nanotube layer, and this carbon nanotube layer carbon nano-tube of comprising a plurality of isotropism, being arranged of preferred orient along a fixed-direction or different directions.

2. plane heat source as claimed in claim 1 is characterized in that, the carbon nano-tube in the described carbon nanotube layer and the surface of the carbon nanotube layer α that has angle, and wherein, α is more than or equal to zero degree and smaller or equal to 15 degree (0≤α≤15 °).

3. plane heat source as claimed in claim 1 is characterized in that, the thickness of described carbon nanotube layer is 1 micron to 1 millimeter.

4. plane heat source as claimed in claim 1 is characterized in that the carbon nano-tube in the described carbon nanotube layer partly overlaps.

5. plane heat source as claimed in claim 1 is characterized in that, attracts each other, combines closely by Van der Waals force between the carbon nano-tube in the described carbon nanotube layer.

6. plane heat source as claimed in claim 1 is characterized in that, the length of described carbon nano-tube is greater than 50 microns, and diameter is less than 50 nanometers.

7. plane heat source as claimed in claim 1 is characterized in that, the material of described at least two electrodes is metal, alloy, indium tin oxide, antimony tin oxide, conductive silver glue, conducting polymer or conductive carbon nanotube.

8. plane heat source as claimed in claim 1 is characterized in that, described at least two electrodes are arranged on the same surface or the different surfaces of zone of heating.

9. plane heat source as claimed in claim 1 is characterized in that, the material of described substrate is flexible material or hard material, and described flexible material comprises plastics or flexible fiber, and described hard material comprises pottery, glass, resin or quartz.

10. plane heat source as claimed in claim 1 is characterized in that described plane heat source further comprises a reflector, and this reflector is arranged between zone of heating and the substrate or is arranged at the surface of described substrate away from zone of heating.

11. plane heat source as claimed in claim 10 is characterized in that, the material in described reflector is metal oxide, slaine or pottery, and thickness is 100 microns～0.5 millimeter.

12. plane heat source as claimed in claim 1 is characterized in that, described plane heat source comprises that further an insulating protective layer is arranged at described zone of heating surface, and the material of described insulating protective layer comprises rubber or resin.

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