Preparation method of infrared light absorber

Abstract

The present invention relates to a method for preparing an infrared spectrum absorber, which comprises the following steps: providing a substrate and growing a carbon nanotube array on the substrate; dry etching the side of the carbon nanotube array away from the substrate to shorten the carbon nanotubes so that the remaining lengths of each carbon nanotube are substantially the same.

Description

Technical Field

[0001] The invention relates to a method for preparing an infrared light absorber, and in particular to a method for preparing an infrared light absorber based on a carbon nanotube array. Background Art

[0002] Infrared light is an electromagnetic wave between microwaves and visible light. The sun's heat is mainly transmitted to the earth through infrared light. At the same time, any object in nature is a source of infrared light radiation, which is constantly radiating infrared light. At present, infrared light is mainly used in military and medical fields, such as reconnaissance of enemy situations and diagnosis of diseases. However, the widespread infrared light has not been fully and effectively utilized. Therefore, it is very necessary to study absorbers that can fully absorb infrared light and can conveniently use infrared light. Summary of the invention

[0003] In view of this, it is indeed necessary to provide a method for preparing an absorber that can fully absorb infrared light.

[0004] A method for preparing an infrared spectrum absorber includes the following steps: providing a substrate and growing a carbon nanotube array on the substrate; dry etching the side of the carbon nanotube array away from the substrate to shorten the carbon nanotubes so that the remaining lengths of each carbon nanotube are substantially the same.

[0005] Compared with the prior art, the preparation method of the infrared light absorber provided by the present invention has the following beneficial effects: by directly performing etching along the growth direction of the carbon nanotube array, the scattered lateral carbon nanotubes on the surface of the carbon nanotube array are removed, thereby obtaining a carbon nanotube array with a flat surface. The carbon nanotube array after etching has an absorption rate of more than 99.5% for the infrared wide spectrum with a wavelength of 0.4 microns to 20 microns, and can be used as an outer infrared spectrum absorber to achieve perfect absorption of infrared rays. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a flow chart of the method for preparing the infrared light absorber provided in the first embodiment of the present invention.

[0007] Figure 2 1 is a laser beam scanning path diagram provided by the first embodiment of the present invention.

[0008] Figure 3 It is a reflectivity curve diagram of the carbon nanotube array to infrared rays before and after the laser beam treatment provided by the present invention.

[0009] Figure 4 It is a scanning electron microscope image of the carbon nanotube array before and after the laser beam treatment provided by the present invention.

[0010] Figure 5It is a flow chart of the method for preparing an infrared light absorber provided in the second embodiment of the present invention.

[0011] Figure 6 It is a reflectivity curve diagram of the carbon nanotube array to infrared rays before and after etching provided by the present invention.

[0012] Figure 7 It is a scanning electron microscope image of the carbon nanotube array before and after etching provided by the present invention.

[0013] Figure 8 It is a side scanning electron microscope image of the carbon nanotube array before and after etching provided by the present invention.

[0014] Fig. 9 It is a reflectivity curve diagram of the carbon nanotube array to infrared rays after laser beam processing and etching processing provided by the present invention.

[0015] Fig.10 It is a schematic structural diagram of an infrared detector provided in the third embodiment of the present invention.

[0016] Fig.11 It is a structural schematic diagram of the infrared detector based on thermocouple provided by the invention.

[0017] Fig.12 It is a schematic structural diagram of an infrared imager provided in the fourth embodiment of the present invention.

[0018] Main component symbols

[0019] Base 101 Carbon Nanotube Array 102 Laser beam 103 Infrared light absorber 100 plasma 104 Thermoelectric elements 200 Electrical signal detector 300 Infrared detector 10 Infrared detector components 11 Infrared Receiver 12 Signal Processor 13 Infrared image display 14 Infrared imager 1

[0020] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0021] The preparation method of the infrared light absorber provided by the present invention, and the infrared detector and infrared imager prepared by the absorber obtained by the method will be further described below in conjunction with specific embodiments and drawings.

[0022] Please also read Figure 1 and Figure 2 The first embodiment of the present invention provides a method for preparing an infrared light absorber 100, which comprises the following steps in sequence:

[0023] Step S10, providing a substrate 101, and growing a carbon nanotube array 102 on the substrate 101;

[0024] In step S20, a laser beam 103 is used to perform bidirectional scanning on the end of the carbon nanotube array 102 away from the substrate 101, and the two scanning directions form a certain angle.

[0025] In step S10, the carbon nanotube array 102 includes a plurality of carbon nanotubes arranged along the same growth direction, which is the long axis direction of the carbon nanotubes. It should be further explained here that the meaning of "roughly" is that since the carbon nanotubes are restricted by various factors during the growth process, such as the inconsistent flow speed of the carbon source gas flow, the uneven concentration of the carbon source gas and the unevenness of the catalyst, it is impossible and unnecessary to make each carbon nanotube in the carbon nanotube array completely parallel, and the lengths of the plurality of carbon nanotubes in the carbon nanotube array do not have to be completely equal. The growth direction of the carbon nanotube array 102 is substantially perpendicular to the surface of the substrate 101. The carbon nanotube array 102 is composed of pure carbon nanotubes. The so-called "pure carbon nanotubes" are carbon nanotubes that have not undergone any chemical modification or functionalization treatment. In this embodiment, the carbon nanotube array 102 is a super-aligned carbon nanotube array. The super-aligned carbon nanotube array is a carbon nanotube array formed by a plurality of carbon nanotubes that are roughly parallel to each other and perpendicular to the growth of the substrate. The plurality of carbon nanotubes are multi-walled carbon nanotubes. Preferably, the plurality of carbon nanotubes are metallic carbon nanotubes.

[0026] In this embodiment, the preparation method of the super-ordered carbon nanotube array adopts chemical vapor deposition, and the method for growing the super-ordered carbon nanotube array comprises the following steps:

[0027] Step S101, providing a substrate 101 with a flat surface. The material of the substrate 101 can be silicon, glass, quartz, or a silicon substrate with an oxide layer formed thereon. In this embodiment, the substrate 101 is a silicon substrate with an oxide layer formed thereon. The shape of the substrate 101 is not limited, and can be circular, square, or any irregular shape. The size of the substrate 101 is not limited and can be selected as needed.

[0028] Step S102, uniformly forming a catalyst layer on at least one flat surface of the substrate 101. The catalyst layer can be prepared by thermal deposition, electron beam deposition or sputtering. The material of the catalyst layer can be selected from iron (Fe), cobalt (Co), nickel (Ni) or any combination thereof. In this embodiment, iron is used as the catalyst.

[0029] Step S103 , annealing the substrate having the catalyst layer formed thereon in air at 700 to 900° C. for about 30 to 90 minutes.

[0030] Step S104, placing the treated substrate in a reaction furnace and heating it to 500-740°C under a protective gas environment. Then, a carbon source gas is introduced to react for about 5-30 minutes to grow a super ordered carbon nanotube array. The carbon source gas can be selected from hydrocarbons such as acetylene, ethylene, and methane. In this embodiment, the carbon source gas is acetylene, the protective gas is argon, and the resulting carbon nanotube array has a growth height of 275 microns.

[0031] By controlling the above growth conditions, the super ordered carbon nanotube array substantially does not contain impurities, such as amorphous carbon or residual catalyst metal particles, etc. The carbon nanotubes in the carbon nanotube array 102 are in close contact with each other through van der Waals forces to form an array.

[0032] In step S20, a laser beam 103 is used to scan the carbon nanotube array 102 to remove the carbon nanotubes that are arranged laterally on the surface of the carbon nanotube array, and the carbon nanotubes are shortened so that the lengths of each carbon nanotube in the carbon nanotube array 102 are substantially the same after shortening, thereby forming a flat carbon nanotube array. The term "substantially" means that the carbon nanotubes are affected by various factors during the treatment process, and it is impossible and unnecessary to make the lengths of the multiple carbon nanotubes in the carbon nanotube array 102 completely equal in a strict sense. For example, there may be a height difference in the lengths of the multiple carbon nanotubes, and the height difference is not greater than 10 nanometers. Since the carbon nanotubes have good absorption characteristics for laser, the end of the carbon nanotube array 102 away from the substrate is fully in contact with oxygen. Under the combined action of oxygen and the laser beam 103, the end of the carbon nanotube array 102 away from the substrate 101 reacts with oxygen to generate carbon oxides and is ablated and removed, and the carbon nanotube array 102 is shortened. When scanning with the laser beam 103 , the irradiation direction of the laser beam 103 is parallel to the growth direction of the carbon nanotube array 102 , that is, the irradiation direction of the laser beam 103 is substantially perpendicular to the surface of the substrate 101 .

[0033] In order to clearly explain the working process of bidirectional scanning of the carbon nanotube array 102 by using the laser beam 103, any two directions parallel to the surface of the carbon nanotube array 102 are defined as the X direction and the Y direction. The angle between the X direction and the Y direction is α, and the value of the angle α is 30° to 90°. Preferably, the value of the angle α is 60° to 90°. In this embodiment, the angle between the X direction and the Y direction is 90°. When the carbon nanotube array 102 is scanned by the laser beam 103, the laser beam 103 first moves along the X direction on the surface of the carbon nanotube array 102 and scans line by line. During the scanning process, the carbon nanotubes are ablated and shortened by the laser beam 103 until all the carbon nanotubes in the carbon nanotube array 102 are scanned. After the laser beam 103 finishes scanning the carbon nanotube array 102 along the X direction, the scanning direction of the laser beam 103 is adjusted so that the laser beam 103 moves along the Y direction on the surface of the carbon nanotube array 102 and scans row by row until all the carbon nanotubes in the carbon nanotube array 102 are scanned.

[0034] The path of the laser beam 103 scanning the surface of the carbon nanotube array 102 line by line along the X direction is formed by the laser beam 103 scanning back and forth for multiple lines along the X direction. Specifically, after the laser beam 103 scans one line along the X direction, the laser beam 103 is translated for a distance along the X' direction perpendicular to the X direction. Preferably, the translation distance is the same as the spot diameter of the laser beam 103. Then, the position of the laser beam 103 in the X' direction is kept unchanged, and the laser beam 103 continues to scan the surface of the carbon nanotube array 102 along the X direction, so that the laser beam 103 scans back and forth for multiple lines along the X direction on the surface of the carbon nanotube array 102 until all the carbon nanotubes in the carbon nanotube array 102 are scanned, thereby completing the scanning of the carbon nanotube array 102 along the X direction by the laser beam 103. After the laser beam 103 completes scanning along the X direction along the carbon nanotube array 102, the laser beam 103 is changed from the X direction to the Y direction and continues scanning. The method of scanning the carbon nanotube array 102 along the Y direction by the laser beam 103 is the same as that along the X direction, which will not be repeated here. Here, it is defined that the laser beam 103 completes scanning of the carbon nanotube array 102 only along the X direction or the Y direction as unidirectional scanning, and the laser beam 103 completes scanning of the carbon nanotube array 102 along the X direction and the Y direction at the same time as bidirectional scanning. Therefore, after the laser beam 103 completes scanning of the carbon nanotube array 102 in the X direction and the Y direction, the bidirectional scanning process of the carbon nanotube array 102 using the laser beam 103 is completed.

[0035] The laser beam 103 is generated by a laser device, which includes one of a solid laser, a liquid laser, a gas laser and a semiconductor laser. The laser device irradiates to form a laser beam spot, and the diameter of the laser beam spot is 1 micron to 5 microns. The scanning speed of the laser beam 103 is less than or equal to 100 mm / s. Preferably, the scanning speed of the laser beam 103 is greater than 80 mm / s. The translation distance of the laser beam 103 when scanning two adjacent rows is set as the scanning interval distance, and the scanning interval distance is 1 micron to 20 microns. Preferably, the scanning interval distance is the same as the diameter of the spot of the laser beam 103. The power of the laser beam 103 is 6W to 12W. In this embodiment, the power of the laser beam 103 is 6W, the diameter of the spot of the laser beam 103 is 5 microns, the scanning speed of the laser beam 103 is 100 mm / s, and the scanning interval distance of the laser beam 103 is 5 microns. After bidirectional scanning by the laser beam 103 , the height of the carbon nanotube array is greater than 3 micrometers. Preferably, the height of the carbon nanotube array 102 is 100 micrometers to 300 micrometers.

[0036] Since a plurality of tiny gaps are formed between the plurality of parallel carbon nanotubes in the carbon nanotube array 102, when the carbon nanotube array 102 is irradiated with infrared light, the plurality of tiny gaps can capture and confine photons in the carbon nanotube array, and absorb the incident infrared light through continuous scattering and absorption of the carbon nanotubes. Since the height of the carbon nanotube array 102 is very large, the incident infrared light is completely absorbed before reaching the substrate 101, so the absorptivity of the carbon nanotube array 102 can be expressed as "1-reflectivity". In addition, since the array structure of the carbon nanotube array 102 has a very low reflectivity to infrared light, it can be used as an infrared light absorber to absorb infrared light. However, the carbon nanotube array 102 has limited absorption of wide-spectrum infrared light before treatment. This is because before treatment, there may be dispersed transversely arranged carbon nanotubes on the surface of the carbon nanotube array 102 away from the substrate 101, or the different heights of multiple carbon nanotubes may cause the surface of the carbon nanotube array 102 away from the substrate 101 to be uneven, so that more infrared light is reflected on the surface, which in turn affects the improvement of the infrared light absorption rate. The surface of the carbon nanotube array 102 is scanned with a laser beam 103. The dispersed transversely arranged carbon nanotubes on the surface of the carbon nanotube array 102 can be removed by shortening the carbon nanotubes. At the same time, the shortened carbon nanotubes can also maintain approximately the same height. However, from Figure 3 It can be seen that after the carbon nanotube array 102 is unidirectionally scanned by the laser beam 103 , its reflectivity to infrared rays increases in the far infrared band compared to the case where it is not processed by the laser beam 103 , resulting in a decrease in the absorption rate in the far infrared band.

[0037] See also Figure 3, in the figure, 1# is the reflectivity curve of the carbon nanotube array to infrared light without any treatment, 2# and 3# are the reflectivity curves of the carbon nanotube array to infrared light after unidirectional scanning by the laser beam 103, and 4# is the reflectivity curve of the carbon nanotube array to infrared light after bidirectional scanning. It can be seen from the figure that the reflectivity of the carbon nanotube array 102 to infrared light after unidirectional scanning by the laser beam 103 is higher than the reflectivity of the untreated carbon nanotube array 102 to infrared light, while the reflectivity of the carbon nanotube array 102 to infrared light after bidirectional scanning by the laser beam 103 is lower than the reflectivity of the untreated carbon nanotube array 102 to infrared light. This is because after the carbon nanotube array 102 is scanned unidirectionally by the laser beam 103, although the carbon nanotubes arranged laterally on the surface of the carbon nanotube array 102 are removed after being shortened, the end of the carbon nanotube away from the substrate will bend in the direction of the movement of the laser beam 103 as the laser beam 103 scans, and the extension direction of the bent portion of the carbon nanotube is approximately parallel to the surface of the substrate 101. Therefore, the bent portion of the carbon nanotube will increase the reflectivity of infrared light. When the carbon nanotube array 102 is scanned bidirectionally by the laser beam 103, since the bidirectional scanning is composed of two unidirectional scans and the moving directions of the two scans are different, during the second unidirectional scanning of the carbon nanotube array 102, the scanning movement of the laser beam 103 will greatly improve the bending of the carbon nanotubes caused by the first unidirectional scanning. Therefore, after bidirectional scanning by the laser beam 103, the surface of the carbon nanotube array 102 is not only free of laterally dispersed carbon nanotubes but also flat, and the lengths of the carbon nanotubes in the carbon nanotube array 102 are consistent and substantially perpendicular to the surface of the substrate 101. Since the carbon nanotube array can absorb and emit infrared rays, the infrared absorption rate of the carbon nanotube array can be directly measured by measuring the absorption rate or measuring the emission rate and then calculating it. Figure 3 It can also be seen in the figure that the infrared light with a wavelength of 2 microns to 20 microns is selected to irradiate the carbon nanotube array after the bidirectional scanning of the laser beam 103, and the reflectivity of the carbon nanotube array 102 to infrared light is less than 0.5%. Therefore, the carbon nanotube array 102 can maintain a high absorption rate in the selected infrared wide spectrum range, and the absorption rate can reach more than 99.5%. Therefore, the carbon nanotube array 102 after the bidirectional scanning of the laser beam 103 can be used as an infrared light absorber to achieve perfect absorption of infrared light. Please refer to Figure 4 , (a) and (b) are scanning electron microscope images of the carbon nanotube array 102 before and after being scanned by the laser beam 103, respectively. It can be seen from the figure that before the laser beam 103 is scanned, the carbon nanotubes on the surface of the carbon nanotube array are randomly distributed laterally. After the scanning process, the number of randomly distributed carbon nanotubes in the laterally direction is reduced.

[0038] See also Figure 5The second embodiment of the present invention provides a method for preparing an infrared light absorber, which comprises the following steps in sequence:

[0039] Step S10, providing a substrate 101, and growing a carbon nanotube array 102 on the substrate 101;

[0040] In step S20 , the plasma 104 is used to etch the side of the carbon nanotube array 102 away from the substrate 101 .

[0041] The preparation method of the infrared light absorber provided in the second embodiment of the present invention is basically the same as the preparation method of the infrared light absorber provided in the first embodiment. The difference lies in that in the second embodiment, an etching method is used to process the carbon nanotube array 102 to shorten the carbon nanotubes so that the length of each carbon nanotube in the carbon nanotube array is basically the same.

[0042] In step S20, dry etching is selected as the method for etching the carbon nanotube array 102. Dry etching refers to the process of introducing a gas to obtain a plasma under the action of an electric field, and the plasma can react with the etched substance to obtain a volatile substance. The dry etching can be reactive ion etching (RIE) or inductively coupled plasma etching (ICPE). Specifically, during the process of etching the carbon nanotube array 102, etching parameters such as etching power, etching gas pressure, and bias voltage can be adjusted according to different etching methods.

[0043] Specifically, during the etching of the carbon nanotube array 102, the etching direction is parallel to the growth direction of the carbon nanotube array 102, that is, the etching direction is along the long axis direction of the carbon nanotubes and etches the carbon nanotube array 102 toward one side of the substrate 101. The carbon nanotubes in the carbon nanotube array 102 are etched and shortened, which can remove the laterally arranged carbon nanotubes dispersed on the surface of the carbon nanotube array 102 and make the length of each carbon nanotube substantially the same.

[0044] In this embodiment, reactive ion etching is used to etch the carbon nanotube array 102, and the gas introduced is oxygen. The power of reactive ion etching is 50 watts to 150 watts, and preferably, the etching power is 100 watts to 150 watts. The oxygen introduction rate is 50 standard-state cubic centimeter per minute (sccm), and the formed gas pressure is 10Pa. The reactive plasma etching time is 30 seconds to 240 seconds, and preferably, the etching time is 30 seconds to 60 seconds. After etching, the height of the carbon nanotube array is greater than 3 microns, and preferably, the height of the carbon nanotube array is 100-300 microns. Five different samples were tested in this embodiment. Please refer to Figure 6, 1# is the infrared reflectivity curve of the carbon nanotube array without etching treatment; 2# is the infrared reflectivity curve of the carbon nanotube array with an etching time of 30 seconds; 3# is the infrared reflectivity curve of the carbon nanotube array with an etching time of 60 seconds; 4# is the infrared reflectivity curve of the carbon nanotube array with an etching time of 2 minutes; 5# is the infrared reflectivity curve of the carbon nanotube array with an etching time of 4 minutes. Similarly, infrared light with a wavelength of 2 microns to 20 microns is selected to irradiate the carbon nanotube array. The infrared reflectivity of the carbon nanotube array after etching is lower than that of the carbon nanotube array without etching treatment. Among them, the infrared reflectivity of the carbon nanotube array 102 with an etching time of 30 seconds to 60 seconds is much lower than the infrared reflectivity of the carbon nanotube array when the etching time exceeds 60 seconds. Please refer to Figure 7 , (a) and (b) are scanning electron microscope images of the carbon nanotube array before and after etching, respectively. It can be seen from the images that before etching, the carbon nanotubes on the surface of the carbon nanotube array are randomly distributed laterally, and after etching, the number of randomly distributed carbon nanotubes is reduced. Figure 8 , (a) and (b) are side scanning electron microscope images of the carbon nanotube array before and after etching, respectively. It can be seen from the figures that after etching, the length of the carbon nanotube array in the growth direction of the carbon nanotubes is shortened, and the surface of the carbon nanotube array is smooth after shortening.

[0045] In order to test whether the processed carbon nanotube array 102 has a high absorption rate for infrared light with a wide spectrum, light with a wavelength range of 0.4 microns to 2.5 microns is further selected for irradiation. Fig. 9 When the wavelength of light is between 0.4 microns and 2.5 microns, the carbon nanotube array 102 can still maintain a high absorption rate for infrared rays after being processed by the laser beam of the first embodiment of the present invention or being processed by the etching of the second embodiment of the present invention, and the absorption rate can be as high as 99.5% or more. Therefore, after being processed by the above two methods, the carbon nanotube array 102 has a good absorption effect on the infrared wide spectrum. In the wavelength range of 2.1 microns to 2.5 microns, the absorption rate of the carbon nanotube array 102 processed by plasma etching is higher than the absorption rate of the carbon nanotube array 102 processed by the laser beam 103.

[0046] The preparation method of the infrared light absorber provided by the present invention has the following advantages: by directly performing etching along the growth direction of the carbon nanotube array, the scattered lateral carbon nanotubes on the surface of the carbon nanotube array are removed, thereby obtaining a carbon nanotube array with a flat surface. The carbon nanotube array after etching has an absorption rate of more than 99.5% for the infrared wide spectrum with a wavelength of 0.4 microns to 20 microns, and can be used as an outer infrared spectrum absorber to achieve perfect absorption of infrared rays.

[0047] See also Fig.10 The third embodiment of the present invention provides an infrared detector 10, which includes an infrared light absorber 100, a thermoelectric element 200 and an electrical signal detector 300. The infrared light absorber 100 includes a plurality of carbon nanotubes of the same height, and the plurality of carbon nanotubes are parallel to each other to form a carbon nanotube array. The infrared light absorber 100 is disposed on the thermoelectric element 200 and is disposed in contact with the thermoelectric element 200. The plurality of carbon nanotubes are perpendicular to the surface of the thermoelectric element 200. The electrical signal detector 300 is electrically connected to the thermoelectric element 200 through a wire, and the electrical signal detector 300 and the thermoelectric element 200 are connected in series to form a loop for detecting changes in electrical signals of the thermoelectric element 200.

[0048] The infrared light absorber 100 is used to absorb infrared light and convert it into heat. The infrared light absorber 100 is obtained by the preparation method of the first embodiment or the second embodiment of the present application. The infrared light absorber 100 has a good absorption effect on infrared light with a wavelength of 4 microns to 25 microns. Preferably, the infrared light absorber 100 has a good absorption effect on infrared light with a wavelength of 8 microns to 15 microns. More preferably, the infrared light absorber 100 has a good absorption effect on infrared light with a wavelength of 10 microns. Specifically, the absorption of the infrared spectrum by the infrared light absorber 100 is achieved through the carbon nanotube array 102. After absorbing infrared light, the temperature of the carbon nanotube array 102 increases, and due to the high thermal conductivity of the carbon nanotubes, the carbon nanotube array 102 can effectively transfer heat to the thermoelectric element 200. The perfect absorption of the carbon nanotube array can greatly increase the responsiveness and sensitivity of the thermoelectric element 200.

[0049] The thermoelectric element 200 is arranged in contact with the infrared light absorber 100. Specifically, the carbon nanotubes in the infrared light absorber 100 are perpendicular to the surface of the thermoelectric element 200, and the heat absorbed by the infrared light absorber 100 can be directly transferred to the thermoelectric element 200. The carbon nanotube array is directly arranged on the surface of the thermoelectric element 200. Specifically, the carbon nanotube array can be directly grown on the surface of the thermoelectric element 200, and can also be directly arranged on the surface of the thermoelectric element 200 by a transfer method. Among them, the directly grown carbon nanotube array can be prepared by the method of growing a carbon nanotube array in the first embodiment of the present application, and then the carbon nanotube array is subjected to the laser scanning process of the first embodiment or the etching process of the second embodiment to obtain the infrared light absorber 100. The method of transferring the carbon nanotube array is a conventional method of transferring the carbon nanotube array, and after transferring to the surface of the thermoelectric element 200, the infrared light absorber 100 is prepared. Of course, the infrared light absorber 100 may be first prepared by using the carbon nanotube array, and then transferred to the surface of the thermoelectric element 200 by a conventional transfer method.

[0050] When the thermoelectric element 200 absorbs heat, the temperature of the thermoelectric element 200 increases, so that the electrical properties of the thermoelectric element 200 change. The thermoelectric element 200 may be a pyroelectric element, a thermistor or a thermocouple element. Specifically, the pyroelectric element is a material with a high thermoelectric coefficient, such as lead zirconate titanate ceramics, lithium tantalate, lithium niobate, triglycan titanium sulfate, etc. The thermistor may be a semiconductor thermistor, a metal thermistor, or an alloy thermistor. In the present embodiment, the thermoelectric element 200 is a lead zirconate titanate ceramic, and the size of the thermoelectric element 200 is 2*1 mm.

[0051] The electrical signal detector 300 is used to detect changes in the electrical properties of the thermoelectric element 200. In one embodiment, the thermoelectric element 200 is a pyroelectric element. The increase in the temperature of the pyroelectric element causes a voltage to appear at both ends of the pyroelectric element or generates a current. In this case, the electrical signal detector 300 may be a current-voltage converter. The electrical signal detector 300 is connected in series with the thermoelectric element 200 to form a loop. The electrical signal detector 300 can detect changes in the voltage or current of the thermoelectric element 200. In another embodiment, when the thermoelectric element 200 is a thermistor, the temperature of the thermistor increases and the resistance changes. In this case, the electrical signal detector 300 includes a power supply and a current detector. The electrical signal detector 300 is connected in series with the thermoelectric element 200 to form a loop. The electrical signal detector 300 detects changes in the resistance of the thermoelectric element 200 by measuring the current change. Please refer to Fig.11In another embodiment, when the thermoelectric element 200 is a thermocouple, the infrared light absorber 100 is set at one end of the thermocouple, and a temperature difference appears at both ends of the thermocouple, that is, a potential difference appears at both ends of the thermocouple. At this time, the electrical signal detector 300 can be a voltage detector. The electrical signal detector 300 is connected in series with the thermoelectric element 200 to form a loop, and the electrical signal detector 300 can detect the potential change of the thermoelectric element 200.

[0052] When the infrared detector 10 is working, when infrared light is radiated onto the infrared light absorber 100, due to the perfect absorption of infrared light by the carbon nanotube array, the carbon nanotube array can effectively convert the infrared light into heat and transfer it to the thermoelectric element 200; after the thermoelectric element 200 absorbs heat, the temperature rises, and the electrical properties of the thermoelectric element 200 such as resistance, current or voltage change. When the electrical signal detector 300 is electrically connected to the two ends of the thermoelectric element 200 to form a loop, the electrical signal detector 300 can detect the change of the electrical signal of the thermoelectric element 200, that is, detect the presence of infrared light in the detection area.

[0053] The infrared detector 10 provided by the present invention has the following advantages: a carbon nanotube array 102 is used as an absorber of infrared light. Since the carbon nanotube array 102 has an absorption rate of more than 99.5% for a wide infrared spectrum with a wavelength of 0.4 microns to 20 microns, the carbon nanotube array 102 can effectively convert infrared light into heat. Therefore, the infrared detector 10 can effectively detect the presence of infrared light. The infrared detector 10 is simple to prepare, low in cost, and high in sensitivity.

[0054] See also Fig.12 The fourth embodiment of the present invention provides an infrared imager 1, which includes an infrared receiver 12, an infrared detector assembly 11, a signal processor 13 and an infrared image display 14. The infrared receiver 12 is used to receive the infrared radiation spectrum and transmit the infrared light to the infrared detector assembly 11; the infrared detector assembly 11 is used to convert the infrared radiation spectrum into an electrical signal, and transmit the electrical signal to the signal processor 13; the signal processor 13 is used to process the electrical signal to calculate the thermal field distribution data; the infrared image display 14 displays the infrared thermal image according to the thermal field distribution data.

[0055] The infrared receiver 12 is used to receive the infrared radiation spectrum emitted by the object. Further, the infrared receiver 12 can also converge the infrared radiation spectrum. In this embodiment, the infrared receiver 12 is an infrared lens. Specifically, the infrared radiation spectrum emitted by the object is directly transmitted to the infrared detector assembly 11 after being received and converged by the infrared lens.

[0056] The infrared detector assembly 11 includes a plurality of infrared detectors 10, which are evenly distributed in a two-dimensional array, and each infrared detector 10 can convert the infrared radiation spectrum into an electrical signal change. It can be understood that each infrared detector 10 is equivalent to a pixel point, and each infrared detector 10 converts the infrared radiation spectrum at its location into an electrical signal, thereby realizing the infrared detector assembly 11 to detect the infrared radiation spectrum emitted by the object. The spacing between any two adjacent infrared detectors 10 can be selected according to the resolution requirements of thermal imaging. The infrared detector 10 is the infrared detector provided in the third embodiment of the present application.

[0057] The signal processor 13 is used to process and calculate the electrical signal of each infrared detector 10, so as to obtain the thermal field distribution of the object. Specifically, the signal processor 13 calculates the temperature data of the corresponding surface position of the object according to the change of the electrical signal of each infrared detector 10. That is, the signal processor 13 can calculate the thermal field distribution data of the object according to the electrical signal.

[0058] The infrared image display 14 is used to display the infrared thermal image of the object under test. The infrared thermal image of the infrared image display 14 is displayed according to the thermal field distribution data of the object, and different temperatures are displayed in different colors. Therefore, the infrared thermal image displayed by the infrared image display 14 corresponds to the temperature distribution of the object and is used to reflect the temperature conditions of various positions of the object. For example, when the infrared imager 1 is used in the medical field, the whole body thermal imaging of the human body can be performed, and professional doctors can judge the nature of the disease and the degree of the lesion in different parts of the human body based on the thermal image, providing a basis for clinical diagnosis.

[0059] When the infrared imager 1 is working, the infrared light emitted by the object is received by the infrared receiver 12; the infrared receiver 12 receives and converges the infrared light, and then transmits the infrared light to the infrared detector assembly 11; the infrared detector assembly 11 converts the infrared light into an electrical signal, and then transmits the electrical signal to the signal processor 13; the signal processor 13 processes and calculates the electrical signal to obtain temperature data of various positions of the object, that is, the thermal field distribution data of the object; the infrared image display 14 then displays the infrared thermal image of the object according to the calculated thermal field distribution data.

[0060] The infrared imager 1 provided by the present invention has the following advantages: the infrared detector assembly 11 adopts a carbon nanotube array as an infrared light absorber, and the carbon nanotube array has an absorption rate of more than 99.5% for a wide infrared spectrum with a wavelength of 0.4 microns to 20 microns, thereby making the infrared imager 1 sensitive to infrared light and being able to effectively obtain a thermal image of an object based on the infrared light emitted by the object; the infrared imager 1 is simple to prepare, low in cost, and high in sensitivity.

[0061] In addition, those skilled in the art may 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 in the scope of protection required by the present invention.

Claims

1. A method for preparing an infrared light absorber, wherein the infrared light absorber is used to absorb infrared rays. It is characterized in that The following steps are involved: Providing a substrate, and growing a carbon nanotube array on the substrate; Reactive ion etching is performed on the side of the carbon nanotube array away from the substrate. The reactive gas of the reactive ion etching is oxygen, the etching power is 50 watts to 150 watts, the etching pressure is 10 Pa, the etching time is 30 seconds to 60 seconds, and the etching direction is parallel to the growth direction of the carbon nanotube array. The laterally arranged carbon nanotubes dispersed on the surface of the carbon nanotube array are removed, and the carbon nanotubes are shortened so that the length of the remaining part of each carbon nanotube is basically the same, thereby obtaining a carbon nanotube array with a flat surface.

2. The method for preparing the infrared light absorber according to claim 1, It is characterized in that The height of the carbon nanotube array is 200 micrometers to 400 micrometers.

3. The method for preparing the infrared light absorber according to claim 1, It is characterized in that The carbon nanotubes are multi-walled carbon nanotubes.

4. The method for preparing the infrared light absorber according to claim 1, It is characterized in that The growth direction of the carbon nanotube array is perpendicular to the surface of the substrate.

5. The method for preparing the infrared light absorber according to claim 1, It is characterized in that The power of the reactive ion etching is 100 watts to 150 watts.

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