CN101610613B - Line heat source - Google Patents

Abstract

A linear heat source, which includes a linear support structure, a heating element is arranged on the surface of the linear support structure, and at least two electrodes are arranged at intervals, and the at least two electrodes are electrically connected to the heating element, wherein the The heating element includes at least one carbon nanotube film, and the carbon nanotubes in the same carbon nanotube film are preferentially aligned along the same direction.

Description

line heat source

technical field

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

Background technique

Heat sources play an important role in people's production, life and scientific research. The wire heat source is one of the commonly used heat sources, and is widely used in electric heaters, infrared therapeutic devices, electric heaters and other fields.

Referring to Fig. 1, the prior art provides a linear heat source 10, which includes a hollow cylindrical support 102; a heating element 104 is arranged on the surface of the support 102, and an insulating protective layer 106 is arranged on the surface of the heating element 104; two The electrodes 110 are respectively disposed at two ends of the bracket 102 and are electrically connected to the heating element 104 ; Wherein, the heating element 104 is usually formed by winding or wrapping a carbon fiber paper. When a voltage is applied to the wire heat source 10 through the two electrodes 110, the heating element 104 generates Joule heat and radiates heat to the surroundings. The carbon fiber paper includes a paper substrate and pitch-based carbon fibers randomly distributed in the paper substrate. Wherein, the paper substrate includes a mixture of cellulose fiber and resin, etc., and the pitch-based carbon fiber has a diameter of 3-6 mm and a length of 5-20 microns.

However, the use of carbon fiber paper as a heating element has the following disadvantages: First, the thickness of carbon fiber paper is relatively large, generally tens of microns, which makes it difficult for the linear heat source to be made into a microstructure, and cannot be applied to the heating of micro devices. Second, because the carbon fiber paper contains the paper substrate, the carbon fiber paper has a higher density and a higher weight, which makes it inconvenient to use the linear heat source using the carbon fiber paper. Third, due to the random distribution of pitch-based carbon fibers in the carbon fiber paper, the carbon fiber paper has low strength, poor flexibility, and is easy to break, which limits its scope. Fourth, the electrothermal conversion efficiency of carbon fiber paper is low, which is not conducive to energy saving and environmental protection.

Contents of the invention

In view of this, it is indeed necessary to provide a line heat source, which has a small weight and high strength, can be made into a microstructure, and can be applied to the heating of micro devices, and has high electrothermal conversion efficiency, which is beneficial to energy saving and environmental protection.

A linear heat source, which includes a linear support structure, a heating element is arranged on the surface of the linear support structure, and at least two electrodes are arranged at intervals, and the at least two electrodes are electrically connected to the heating element, wherein the The heating element includes at least one carbon nanotube film, and the carbon nanotubes in the same carbon nanotube film are preferentially aligned along the same direction.

Compared with the prior art, the described wire heat source has the following advantages: First, the diameter of the carbon nanotube is smaller, so that the carbon nanotube structure has a smaller thickness, and a miniature wire heat source can be prepared, which can be applied to the heating of micro devices . Second, carbon nanotubes have a smaller density than carbon fibers, so the linear heat source adopting carbon nanotube structure has lighter weight and is more convenient to use. Third, the carbon nanotube structure 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 line 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 linear heat source in the prior art.

Fig. 2 is the structural representation of the linear heat source of the embodiment of the present invention

FIG. 3 is a schematic cross-sectional view of the line heat source in FIG. 2 along line III-III.

FIG. 4 is a schematic cross-sectional view of the linear heat source in FIG. 3 along line IV-IV.

Fig. 5 is a scanning electron micrograph of a carbon nanotube film in a linear heat source according to an embodiment of the present invention.

FIG. 6 is a schematic diagram of a partial structure of the carbon nanotube film in FIG. 5 .

Fig. 7 is a scanning electron micrograph of non-twisted carbon nanotube wires in the wire heat source of the embodiment of the present invention.

Fig. 8 is a scanning electron micrograph of twisted carbon nanotube wires in a wire heat source according to an embodiment of the present invention.

Fig. 9 is a graph showing the relationship between the surface temperature of the linear heat source and the heating power according to the embodiment of the present invention.

Detailed ways

The linear heat source provided by the present invention will be described in detail below with reference to the accompanying drawings.

Please refer to Fig. 2 to Fig. 4, the embodiment of the present invention provides a kind of linear heat source 20, and this linear heat source 20 comprises a linear support structure 202; A reflection layer 210 is arranged on the surface of this linear support structure 202; A heating element 204 is arranged On the surface of the reflective layer 210 ; two electrodes 206 are arranged at intervals and electrically connected to the heating element 204 ; and an insulating protection layer 208 is arranged on the surface of the heating element 204 . The length and diameter of the wire heat source 20 are not limited. Preferably, the diameter of the wire heat source 20 is 0.1 micron to 1.5 cm. The diameter of the linear heat source 20 in this embodiment is 1.1 millimeters to 1.1 centimeters.

The linear support structure 202 is used to support the heating element 204, and its material can be rigid material or flexible material. The hard material includes one or more of ceramics, glass, resin, and quartz. The flexible material includes one or more of plastic, resin and flexible fiber. The linear support structure 202 can be made of flexible materials, and at this time, the linear heat source 20 can be bent into any shape as required during use. The length, diameter and shape of the linear support structure 202 are not limited, and can be selected according to actual needs. The linear support structure 202 of this embodiment is a ceramic rod with a diameter of 1 mm-1 cm.

The reflective layer 210 is made of a white insulating material, such as one or more of metal oxides, metal salts, and ceramics. In this embodiment, the reflective layer 210 is preferably made of Al2O3, with a thickness of 100 microns to 0.5 mm. The reflective layer 210 can be prepared by methods such as physical vapor deposition or chemical vapor deposition. The physical vapor deposition method includes sputtering or evaporation. In this embodiment, aluminum oxide is deposited on the surface of the linear support structure 202 by sputtering. The reflective layer 210 is used to reflect the heat generated by the heating element 204 so that it can be effectively dissipated to the external space. It can be understood that the reflective layer 210 is an optional structure.

The heating element 204 includes a carbon nanotube structure. The carbon nanotube structure can be wrapped or wound on the surface of the reflective layer 210 . The carbon nanotube structure can be connected to the reflective layer 210 through its own viscosity, or can be connected to the reflective layer 210 through an adhesive. In this embodiment, the adhesive is silica gel. It can be understood that when the linear heat source 20 does not include the reflective layer 210 , the heating element 204 can be directly wrapped or wound on the surface of the linear support structure 202 .

The carbon nanotube structure is a self-supporting structure. The so-called "self-supporting structure" means that the carbon nanotube structure can maintain its own specific shape without being supported by a support. The carbon nanotube structure of the self-supporting structure includes a plurality of carbon nanotubes, and the plurality of carbon nanotubes attract each other through van der Waals force, so that the carbon nanotube structure has a specific shape. The carbon nanotubes in the carbon nanotube structure 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 nm to 50 nm, the double-walled carbon nanotubes have a diameter of 1.0 nm to 50 nm, and the multi-walled carbon nanotubes have a diameter of 1.5 nm to 50 nm. The length of the carbon nanotubes is not limited, preferably, the length of the carbon nanotubes is greater than 100 microns. The carbon nanotube structure may be planar or linear. Since the carbon nanotube structure is self-supporting, the carbon nanotube structure can still maintain a planar or linear structure when it is not supported by a support body. The heat capacity per unit area of the carbon nanotube structure is less than 2×10 ^-4 joules per square centimeter Kelvin. Preferably, the heat capacity per unit area of the carbon nanotube structure is less than or equal to 1.7×10 ^-6 joules per square centimeter Kelvin. Because the carbon nanotube structure in the carbon nanotube structure has good flexibility, the carbon nanotube structure has good flexibility and can be bent and folded into any shape without breaking.

In this embodiment, the carbon nanotube structure includes at least one carbon nanotube film. The carbon nanotube film can be wrapped or wound on the surface of the reflective layer 210 . The carbon nanotube film is a self-supporting carbon nanotube film obtained by directly pulling from the carbon nanotube array. Each carbon nanotube film includes a plurality of carbon nanotubes preferentially oriented in the same direction and arranged parallel to the surface of the carbon nanotube film. The carbon nanotubes are connected end to end by van der Waals force. Please refer to FIG. 5 and FIG. 6 , specifically, each carbon nanotube film includes a plurality of continuous and aligned carbon nanotube segments 143 . The plurality of carbon nanotube segments 143 are connected end to end by van der Waals force. Each carbon nanotube segment 143 includes a plurality of parallel carbon nanotubes 145, and the plurality of parallel carbon nanotubes 145 are closely combined by van der Waals force. The carbon nanotube segment 143 has any width, thickness, uniformity and shape. The thickness of the carbon nanotube film is 0.5 nanometers to 100 micrometers, the width is related to the size of the carbon nanotube array from which the carbon nanotube film is drawn, and the length is not limited. For the carbon nanotube film and its preparation method, please refer to the Chinese published patent application No. CN101239712A "Carbon nanotube film structure and its preparation" filed by Fan Shoushan et al. on February 9, 2007 and published on August 13, 2008. Method", Applicant: Tsinghua University, Hongfujin Precision Industry (Shenzhen) Co., Ltd. When the carbon nanotube structure is composed of a carbon nanotube film, and the thickness of the carbon nanotube structure is relatively small, such as less than 10 microns, the carbon nanotube structure has good transparency, and its light transmittance can reach 96%, which can be used For making a transparent heat source. The heat capacity per unit area of the carbon nanotube film may be less than or equal to 1.7×10 ^-6 joules per square centimeter Kelvin.

When the carbon nanotube structure includes multiple layers of carbon nanotube films that are overlapped, a cross angle α is formed between carbon nanotubes arranged in preferred orientations in two adjacent layers of carbon nanotube films, and α is greater than or equal to 0 degrees Less than or equal to 90 degrees (0°≤α≤90°). There is a certain gap between the plurality of carbon nanotube films or between adjacent carbon nanotubes in a carbon nanotube film, and when the intersection angle α is greater than 0 degrees, a plurality of micropores are formed in the carbon nanotube structure , the pore size of the micropores is less than about 10 microns. It can be understood that the thickness of the carbon nanotube structure can be controlled by controlling the number of layers of the carbon nanotube film. The thermal response speed of the carbon nanotube structure is related to its thickness. In the case of the same area, the larger the thickness of the carbon nanotube structure, the slower the thermal response speed; conversely, the smaller the thickness of the carbon nanotube structure, the faster the thermal response speed. When the thickness of the carbon nanotube structure is 1 micrometer to 1 millimeter, the carbon nanotube structure can reach the highest temperature within less than 1 second. The carbon nanotube monolayer film can reach the highest temperature within 0.1 milliseconds. Therefore, the linear heat source 20 is suitable for rapid heating of objects.

In this embodiment, the heating element 204 adopts 100 overlapping and intersecting layers of carbon nanotube films, and the crossing angle between carbon nanotubes in two adjacent layers of carbon nanotube films is 90 degrees. The length of the carbon nanotube structure is 5 cm, the width of the carbon nanotube structure is 3 cm, and the thickness of the carbon nanotube structure is 50 microns. Using the viscosity of the carbon nanotube structure itself, the carbon nanotube structure is wrapped on the surface of the reflective layer 210 .

The arrangement of the two electrodes 206 is not limited, as long as they are arranged at intervals and electrically connected to the heating element 204 . Specifically, the electrodes 206 may be disposed on the same surface of the heating element 204 or may be disposed on different surfaces of the heating element 204 . The electrodes 206 can be disposed on the surface of the heating element 204 by a carbon nanotube-structured adhesive or conductive adhesive (not shown). The conductive adhesive can better fix the electrode 206 on the surface of the carbon nanotube structure while realizing the electrical contact between the electrode 206 and the carbon nanotube structure. A voltage can be applied to the heating element 204 via the two electrodes 206 . Wherein, the two electrodes 206 are arranged at intervals, so that the heating element 204 adopting the carbon nanotube structure is connected with a certain resistance value to avoid short circuit phenomenon when energized and heated. Preferably, the electrodes 206 are disposed around the surface of the heating element 204 . Since the carbon nanotube film in the heating element 204 has a lower resistivity along the direction of the carbon nanotubes, the setting of the heating element 204 is related to the setting of the electrodes 206 . Preferably, the arrangement direction of some carbon nanotubes in the heating element 204 extends along the direction from one electrode 206 to the other electrode 206 .

The electrodes 206 are conductive films, metal sheets or metal leads. The material of the conductive thin film can be metal, alloy, indium tin oxide (ITO), antimony tin oxide (ATO), conductive silver paste, conductive polymer and the like. The conductive film can be formed on the surface of the heating element 204 by physical vapor deposition, chemical vapor deposition or other methods. The metal sheet can be copper sheet or aluminum sheet or the like. The metal sheet can be fixed on the surface of the heating element 204 by a conductive adhesive.

The electrode 206 can also be a metallic carbon nanotube structure. The carbon nanotube structure is disposed on the surface of the heating element 204 . The carbon nanotube structure can be fixed to the surface of the heating element 204 by its own adhesive or conductive adhesive. The carbon nanotube structure includes a plurality of metallic carbon nanotubes aligned and evenly distributed. Specifically, the carbon nanotube structure may include at least one carbon nanotube film, at least one carbon nanotube wire structure or a combination thereof. The carbon nanotube wire structure may include at least one carbon nanotube wire, a bundle structure composed of multiple carbon nanotube wires arranged in parallel, or a strand structure composed of multiple carbon nanotube wires twisted with each other.

The carbon nanotube wire includes a plurality of carbon nanotubes aligned axially along the carbon nanotube wire. The carbon nanotube wires may be non-twisted carbon nanotube wires or twisted carbon nanotube wires. The non-twisted carbon nanotube wire is obtained by treating a drawn carbon nanotube film with an organic solvent. Please refer to FIG. 7 , the non-twisted carbon nanotube wire includes a plurality of carbon nanotubes arranged along the length direction of the carbon nanotube wire. The twisted carbon nanotube wire is obtained by using a mechanical force to twist the two ends of the carbon nanotube film in opposite directions. Please refer to FIG. 8 , the twisted carbon nanotube wire includes a plurality of carbon nanotubes arranged helically around the carbon nanotube wire axis. The length of the non-twisted carbon nanotube wire and the twisted carbon nanotube wire is not limited, and the diameter is 0.5 nanometers to 100 microns. For the carbon nanotube wire and its preparation method, please refer to the Chinese publication No. CN100411979C patent "a carbon nanotube rope and its manufacturing method" filed on September 16, 2002 by Fan Shoushan et al. ", Applicants: Tsinghua University, Hongfujin Precision Industry (Shenzhen) Co., Ltd., and the Chinese Public Patent Application No. CN1982209A filed on December 16, 2005 and published on June 20, 2007 "Carbon Nanotubes Silk and its production method", applicant: Tsinghua University, Hongfujin Precision Industry (Shenzhen) Co., Ltd.

Further, the twisted carbon nanotubes can be treated with a volatile organic solvent. Under the effect of the surface tension generated when the volatile organic solvent volatilizes, the adjacent carbon nanotubes in the treated twisted carbon nanotubes are closely combined by van der Waals force, so that the diameter and specific surface area of the twisted carbon nanotubes are reduced. Increased density and strength. Since the carbon nanotube wire is obtained by treating the above-mentioned carbon nanotube stretched film with an organic solvent or mechanical force, and the carbon nanotube stretched film is a self-supporting structure, the carbon nanotube wire is a self-supporting structure.

In this embodiment, two carbon nanotube films are respectively disposed on both ends of the linear support structure 202 along the length direction as the electrodes 206 . The two carbon nanotube films surround the inner surface of the heating element 204 and form electrical contact with the heating element 204 through a conductive adhesive. The conductive adhesive is preferably silver glue. Since the heating element 204 in this embodiment adopts overlapping and intersecting carbon nanotube films, the electrode 206 and the heating element 204 all adopt a carbon nanotube structure, which can reduce the ohmic contact resistance between the electrode 206 and the heating element 204, thereby The utilization rate of the electric energy of the line heat source 20 is improved.

The material of the insulating protection layer 208 is an insulating material, such as rubber, resin and the like. The thickness of the insulating protection layer 208 is not limited, and can be selected according to actual conditions. In this embodiment, the insulating protection layer 208 is made of rubber, and its thickness is 0.5-2 mm. The insulating protection layer 208 can be formed on the outer surface of the heating element 204 by coating or wrapping. The insulating protection layer 208 is used to prevent the wire heat source 20 from forming electrical contact with the outside when in use, and at the same time prevent the carbon nanotube structure in the heating element 204 from absorbing foreign impurities. It can be understood that the insulating protection layer 208 is an optional structure.

Carbon nanotubes have good electrical conductivity and thermal stability, and as an ideal black body structure, they have relatively high heat radiation efficiency. In this embodiment, the electrothermal performance measurement was carried out on the above-mentioned carbon nanotube structure composed of 100 layers of carbon nanotube intersecting films. The carbon nanotube structure is 5 cm long and 3 cm wide. The carbon nanotube structure is wrapped on a linear support structure 202 with a diameter of 1 cm and a length of 3 cm between two electrodes 206 . Current flows along the length direction of the linear support structure 202 . The measuring instruments are infrared thermometer RAYTEK RAYNER IP-M and infrared thermometer AZ-8859 respectively. Please refer to Fig. 9, when the heating power is 36 watts, the surface temperature has reached 370°C. It can be seen that the carbon nanotube structure has high electrothermal conversion efficiency.

After connecting wires of the wire heat source 20 to the power supply voltage, the wire heat source 20 can radiate electromagnetic waves with longer wavelengths by adjusting the power supply voltage between 10 volts and 30 volts. The temperature of the linear heat source 20 was found to be 50°C to 500°C by a temperature measuring instrument. For an object with a black body structure, when the corresponding temperature is 200°C to 450°C, it can emit thermal radiation (infrared rays) invisible to the human eye. At this time, the thermal radiation is the most stable and efficient, and the generated thermal radiation Heat max.

When the linear heat source 20 is in use, it can be arranged on the surface of the object to be heated or arranged at a distance from the object to be heated, and the heat radiation can be used for heating. In addition, multiple linear heat sources 20 can also be arranged in various predetermined patterns for use. The line heat source 20 can be applied to fields such as electric heaters, infrared therapeutic instruments, electric heaters and the like.

In this embodiment, since the carbon nanotubes have a nanoscale diameter, the prepared carbon nanotube structure can have a relatively small thickness. Therefore, a micro-wire heat source can be prepared by using a small-diameter linear support structure. Carbon nanotubes are highly resistant to corrosion, allowing them to work in acidic environments. Moreover, carbon nanotubes have strong stability, and will not decompose even when working in a vacuum environment with a high temperature above 3000° C., making the wire heat source 20 suitable for working in a vacuum and high temperature. In addition, the strength of carbon nanotubes is 100 times higher than that of steel with the same volume, but its weight is only 1/6. Therefore, the linear heat source 20 using carbon nanotubes has higher strength and lighter weight.

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 (20)

1. line heat source, it comprises:

One wire supporting construction;

One heating element is arranged at the surface of wire supporting construction, and;

At least two electrode gap settings, described at least two electrodes are electrically connected with this heating element;

It is characterized in that described heating element comprises at least one carbon nano-tube film, and this carbon nano-tube film comprises that a plurality of carbon nano-tube are arranged of preferred orient along same direction.

2. line heat source as claimed in claim 1 is characterized in that, described carbon nano-tube film comprises a plurality of carbon nano-tube fragments that join end to end and be arranged of preferred orient, and closely connects by Van der Waals force between the adjacent carbon nano-tube fragment.

3. line heat source as claimed in claim 2 is characterized in that, described carbon nano-tube fragment comprises a plurality of same length and the carbon nano-tube that is arranged parallel to each other substantially.

4. line heat source as claimed in claim 3 is characterized in that, the length of described carbon nano-tube is 200 microns～900 microns, and diameter is less than 50 nanometers.

5. line heat source as claimed in claim 1 is characterized in that described carbon nano tube structure comprises the carbon nano-tube film of at least two stacked settings, and closely connects by Van der Waals force between adjacent two carbon nano-tube films.

6. line heat source as claimed in claim 1 is characterized in that, the unit are thermal capacitance of described carbon nano-tube film is smaller or equal to 2 * 10 ^-4Every square centimeter of Kelvin of joule.

7. line heat source as claimed in claim 6 is characterized in that, the unit are thermal capacitance of described carbon nano-tube film is smaller or equal to 1.7 * 10 ^-6Every square centimeter of Kelvin of joule.

8. line heat source as claimed in claim 1 is characterized in that, the thickness of described carbon nano-tube film is 0.5 nanometer～100 micron.

9. line heat source as claimed in claim 1 is characterized in that, described carbon nano-tube film twines or wrap up the surface that is arranged at the wire supporting construction.

10. line heat source as claimed in claim 9 is characterized in that, described carbon nano-tube film is by himself viscosity or the conductive adhesive surface of being fixed in the wire supporting construction.

11. line heat source as claimed in claim 1 is characterized in that, described two electrode gap are arranged at the surface of heating element, and are positioned at the two ends of wire supporting construction.

12. line heat source as claimed in claim 11 is characterized in that, the carbon nano-tube in the described carbon nano-tube film is extended to another electrode from an electrode.

13. line heat source as claimed in claim 1 is characterized in that, described electrode is a carbon nano tube structure, and this carbon nano tube structure comprises and aligning and equally distributed a plurality of metallic carbon nanotubes that this carbon nano tube structure is arranged at the surface of heating element.

14. line heat source as claimed in claim 13 is characterized in that, described carbon nano tube structure comprises at least one carbon nano-tube film, at least one liner structure of carbon nano tube or its combination.

15. line heat source as claimed in claim 14 is characterized in that, described liner structure of carbon nano tube comprises at least one non-carbon nano tube line that reverses, at least one carbon nano tube line that reverses or its combination.

16. line heat source as claimed in claim 15, it is characterized in that, the described non-carbon nano tube line that reverses comprises that a plurality of carbon nano-tube are arranged in parallel along this non-carbon nano tube line length direction that reverses, and the described carbon nano tube line that reverses comprises that a plurality of carbon nano-tube are along the shape arrangement in the shape of a spiral of this carbon nano tube line length direction that reverses.

17. line heat source as claimed in claim 15 is characterized in that, the diameter of described non-carbon nano tube line that reverses or the carbon nano tube line that reverses is 0.5 nanometer～100 micron.

18. line heat source as claimed in claim 1, it is characterized in that, the material of described wire supporting construction is flexible material or hard material, and described flexible material comprises in plastics and the flexible fiber one or more, and described hard material comprises one or more in pottery, glass, resin and the quartz.

19. line heat source as claimed in claim 1, it is characterized in that, described line heat source comprises that further a reflector is arranged between described heating element and the wire supporting construction, and the material in described reflector comprises one or more in metal oxide, slaine and the pottery.

20. line heat source as claimed in claim 1 is characterized in that, described line heat source comprises that further an insulating protective layer is arranged at the outer surface of described heating element.

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