RU2645536C1 - Light-absorption material - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention can be used as absolutely black body in measuring technology, heat engineering and thermal physics. Light absorbing material obtained without auxiliary substrates by CVD method contains beams of small- and multi-walled carbon nanotubes with lateral deposits in form of chaotically oriented fragments of graphene with size of up to 10 nm, has ability to mold into ribbons with thickness of at least 2 mm and density of 0.4 g/cm³ with a light absorption coefficient of about 99.9 %.

EFFECT: measuring device is proposed.

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Description

The invention relates to carbon materials, in particular to carbon nanotubes, which can be used as a completely black body in the fields of measurement technology, thermophysics and heat engineering.

Light-absorbing material as a completely black body is mainly used in the field of measurement technology, in particular when measuring photometric characteristics in thermophysics and heat engineering. So, for example, there are known (GOST 7601-78) methods for determining the thermal radiation coefficients of a measured sample from the ratio of the measured thermal radiation of a test sample to the measured thermal radiation of a light-absorbing material heated to the same temperature as the measured sample. To do this, measure the thermal radiation of a sample heated to a certain temperature. The light-absorbing material is brought to the same temperature and its thermal radiation is measured. The emissivity of the measured sample is obtained by dividing the reading of the thermal radiation heated to a certain temperature of the sample by the reading of the thermal radiation of the light-absorbing material.

The concept of “absolutely black body” is abstract, therefore models of an absolutely black body are often used. There are a number of patents related to the development and application of a model of a completely black body (MRT).

The invention of patent RU 2148801, IPC G01J 5/02 of 08.25.1998, relates to technical physics in terms of creating a blackbody model used as a reference radiation source in pyrometric, photometric and radiometric complexes at temperatures of 2500-3200 K. Such a blackbody model contains a radiating and auxiliary cavity formed by a set of pyrographite rings that have current leads. The movable current supply contains a spring-loaded movable cylinder with flexible current conductors associated with the end face of the chamber of the MChT. The other end of the chamber is the second current lead. An additional chamber is also introduced that closes the end of the cylinder. The cameras have a single gas volume. The rings in the set have increasing from ring to ring from the middle of the set of electrical resistance. The extreme values of the resistance to the middle do not exceed two. The set of rings is surrounded by a heat shield made of pyrographite on the side facing the set of rings.

The disadvantage of this method is a very complex design, including the use of an additional chamber, which is adjacent to the end of the water-cooled part of the main chamber, forms a single gas volume with the main chamber and covers the end of the movable current supply cylinder, which protrudes from the main chamber and is opposite to the rings, while the end face adjoins the additional chamber must be electrically isolated from both chambers. In addition, pyrographite rings must have different electrical resistance, where the electrical resistance of each ring relative to the neighboring increases from ring to ring as the ring moves from the middle of the set to its ends, and the ratio of the resistance values of each of the outer rings to the middle ring is not more than two, which also complicates the assembly of the blackbody model.

In the patent RU 2132549, IPC G01N 25/18 dated 01/20/1998, the invention is described for calculating thermophysical parameters, the essence of which consists in pre-heating a model of a black body formed by two identical parallel parallel plane samples together with side ones and internal partitioned screens, by passing through the samples the same electric currents, measure the strength of currents and voltage drops in the Central zone of each of the samples, the temperature of the external the surfaces of one sample and the inner surface of the second sample, produce a pulsed thermal effect on the outer surface of one of the samples, simultaneously recording the temperature of the opposite surface of the same sample and using these data, calculate parameters such as coefficients of thermal and thermal conductivity, specific heat, spectral and integral degree of blackness, electrical resistivity. The disadvantage of the proposed method is the rather complicated design of the device, requiring the use of identical thickness and density, parallel samples, constant monitoring of the temperature of the inner and outer surfaces of the samples with photopyrometer.

In the patent RU 2438103 C1, IPC G01J 5/08, G01K 15/00 dated 06/16/2010, the invention describes a device that can be used to calibrate multi-channel pyrometers. The disadvantage of this device is the design complexity: the device contains an absolute blackbody model in the form of an electric furnace with an emitter installed on the base, a program temperature controller, a thermocouple for regulating the temperature of the cavity of the electric furnace emitter, a rotary quotation mechanism, a photo signal amplifier, and a computer. The computer is electrically connected to a rotary quotation mechanism and an amplifier for photo signals. The calibrated pyrometer is fastened to the quotation mechanism and fixed on the base, which is interfaced with the outlet of the absolutely black body model.

To create models of an absolutely black body, it is most promising to use carbon materials such as graphite or carbon nanotubes (CNTs).

In the patent US 9086327, IPC G01J 5/52, G01K 15/00 dated 05/15/2013, a device and method for calibrating sensors using a thin film of CNTs are described. The disadvantage of this device is the design complexity: the voltage is applied to the first layer of CNTs to obtain the first temperature of the first layer of CNTs. The heat-conducting layer is used to ensure uniform temperature distribution associated with the temperature of the first CNT layer by smoothing the spatial variation of the first temperature. The second CNT layer provides uniform temperature distribution and emits a first blackbody radiation spectrum to calibrate the sensor. The device can be used to emit a second spectrum of blackbody radiation by changing the applied voltage. It should be noted that the thickness of the CNT films is not indicated in the patent.

Also in the patent US 9459154, IPC G01J 3/10 dated 03/19/2015, a device, a method and a thin-film structure for obtaining a spectrum of a black body are described. The disadvantage of the patent is the complexity and complexity of the method: the voltage is applied to the first layer of CNTs to obtain the first temperature of this layer of CNTs. The first layer of the device is configured to generate heat in response to an applied voltage. The second layer is configured to obtain a blackbody radiation spectrum in response to heat from the first layer. The thermal expansion layer located between the first and second layer contains a graphene sheet to reduce the spatial variation of heat in the plane of the heat layer. The patent does not indicate the thickness of the CNT films, fixing graphene sheet.

In the patent RU 2503103 C1, IPC H01Q 17/00, B32B 27/00, B32B 27/06, C09D 5/32, B82B 3/00 dated 12/27/2012, the invention is described that relates to a method for manufacturing an absorbent coating. Such a coating provides absorption in the infrared wavelength range to create black body standards in radiation simulators for Earth remote sensing equipment with stable characteristics. A method of manufacturing such a coating is very time-consuming, which is its drawback, is the formation of a sequentially adhesive layer on the carrier plate. To do this, by centrifugation or irrigation, followed by drying, a polyimide layer with CNTs is obtained from a solution of pyromilite dianhydride and oxydianiline in a polar solvent. On a dried layer, a layer is formed by centrifugation or watering from a dispersion of CNTs in a polar solvent: dimethylformamide or dimethylacetamide. After that, the polyimide layer with CNTs and with CNTs obtained from the dispersion and partially embedded in the dissolved surface layer of polyimide is dried and thermoimidized. Then, a reinforcing and absorbing layer of silicon nitride by plasma-chemical deposition is formed on a layer of CNTs embedded and protruding from a polyimide layer that has undergone thermal imidization. Thus, a reproducible and time-stable process for producing a coating with a high absorption capacity of infrared radiation operating in a wide temperature range is obtained.

In the patent US 8895997, H01L 51/50, B82Y 30/00, H01L 51/52, H01L 29/26, H01K 1/06, H01L 27/15, H01L 51/00, B82Y 20/00, H01K 3/02, H01L 31/12, H01L 33/04, B82Y 10/00, H04B 10/80, H01L 33/00, H01K 1/10 dated 04/28/2010, the device of light-emitting devices using CNTs is described. Metallic CNTs located between the electrodes generate heat when current flows to the electrodes and emit light from a black body so that the emitted light has a wide wavelength range and can be modulated at high speed. This makes it possible to realize a continuous spectrum light source that can be modulated at high speed, suitable for use in information communication, in the field of electronics. The disadvantage of this device is the need to use a substrate for CNTs, so that the radiation generated by CNTs is in the direction perpendicular to the surface of the substrate.

In patent application US 20090126783 A1, IPC G02B 5/22, H01L 31/00, B05D 5/06 of 12/12/2008, which is the prototype of this patent, describes an optical absorber device that includes a coating consisting of vertically oriented CNTs with an ultra-low reflectance of less than 0.16% and an absorption efficiency of more than 99.84%. The coating consists mainly of CNTs and also contains carbon nanowires (carbon nanowires) and nanorods (carbon nanohorn). Tubular nanostructures have a very high aspect ratio, usually greater than 10,000. This coating on a substrate is prepared by CVD (Chemical vapor deposition).

Using an electron beam evaporator, a deposit of an adhesive layer of aluminum with a thickness of 10 nm and a catalyst layer, the active component of iron particles, from 1 nm to 5 nm thick, are deposited on the surface of a silicon wafer. The substrate is placed in a CVD reactor. Ethylene is used as a carbon source, and a 15% mixture of hydrogen and argon as a reaction gas. By the time the temperature in the reactor reaches about 750-800 ° C, a gas flow is established through the CVD reactor at a rate of about 300 ml / min. After the temperature of the CVD reactor was stabilized, the gas flow rate was raised to 1300 ml / min, a second inert gas stream was bubbled through water at room temperature at a speed of 80 ml / min, while ethylene was started at a speed of 100 ml / min. Varying the synthesis time from 5 s to 30 min, a CNT coating with a thickness of 10 to about 800 μm is obtained, i.e. a coating of CNTs with a thickness of, for example, up to several millimeters can be achieved due to the longer production time. The reactor is cooled to room temperature in an inert gas atmosphere. The density of the obtained CNTs is 0.01-0.02 g / cm ³ . Transmission electron microscopy showed that it mainly consists of multi-walled CNTs, and in the case of using a catalyst-iron layer with a thickness of about 1.5 nm, mainly double-walled CNTs are formed. The refractive index and absorption constants of the obtained CNTs are independently controlled by changing the distance between the CNTs and their diameter.

The objective of the claimed technical solution is to obtain a light-absorbing material from beams of low- and multi-walled carbon nanotubes obtained by CVD with an increased light absorption coefficient, as well as expanding the technical application of this material in the field of technical physics and measuring equipment.

To solve this problem, we offer a light-absorbing material in the form of beams of low- and multi-walled carbon nanotubes obtained without the use of auxiliary substrates by CVD.

Carbon nanotubes are produced by CVD in the gas phase at atmospheric pressure using the active component ferrocene in a hydrogen atmosphere in a laboratory setup with a horizontal quartz flow CVD reactor, the scheme of which is shown in Fig. 1.

The conditions for obtaining light-absorbing material, such as the temperature of receipt, the feed rate of the reaction gases, the absence of the substrate, differ from the conditions of the prototype. Differences in the variation of such parameters (production temperature and feed rate of reaction gases) are necessary due to the excellent method of supplying the active component upon receipt. In the prototype, the active component is deposited on a substrate, in the proposed technical solution, a material with the active component in the gas phase is obtained. The high light-absorbing ability of the resulting material is associated with the non-catalytic formation of lateral carbon deposits in the form of randomly oriented graphene fragments.

The combined set of optimal parameter values, such as the composition and flow rate of the reaction mixture of gases, including hydrogen, temperature and duration of the process, allows us to achieve our goal and obtain a light-absorbing material consisting of bundles of small and multi-walled carbon nanotubes, capable of forming into ribbons .

In FIG. 1-9 shows a diagram and photographs explaining the claimed invention:

in FIG. 1 is a diagram of a horizontal flow type quartz CVD reactor for producing a light-absorbing material. The numbers indicate the main elements: 1 - gas supply pipe, 2 - high-temperature furnace, 3 - thermocouple in alundum case, 4 - quartz tube reactor;

in FIG. 2 shows a photograph of a light-absorbing material obtained in example 1;

in FIG. 3 shows a micrograph (magnification × 20,000) obtained using a scanning electron microscope, a light-absorbing material obtained in example 1;

figure 4 shows a photograph of a light-absorbing material obtained in example 2;

figure 5 shows a micrograph (magnification × 20,000) obtained using a scanning electron microscope, light-absorbing material obtained in example 2;

in FIG. 6 shows a photograph of a light-absorbing material obtained in example 3;

in FIG. 7 shows a micrograph (magnification × 20,000) obtained using a scanning electron microscope, a light-absorbing material obtained in example 3;

in FIG. 8 is a photograph of a light-absorbing material obtained in Example 4;

in FIG. 9 shows a micrograph (magnification × 20,000) obtained using a scanning electron microscope, a light-absorbing material obtained in example 4.

Light-absorbing material in the form of beams of small and multi-walled carbon nanotubes is obtained by CVD in the gas phase in a laboratory setup with a horizontal quartz flow CVD reactor, the scheme of which is shown in FIG. 1. Obtaining a light-absorbing material is carried out at atmospheric pressure using a volatile active component - ferrocene in a hydrogen atmosphere.

Light-absorbing material in the form of beams of small and multi-walled carbon nanotubes is obtained under the following conditions:

- The composition of the mixture of the reaction solution with the active component: 96.5 weight. % ethanol, 2.0 weight. % thiophene, 1.5 weight. % ferrocene.

- The flow rate of the reaction solution is 1 ml / min.

- The flow rate of the carrier gas of hydrogen is 500-1100 ml / min.

- The temperature of receipt of 1000-1100 ° C.

- The duration of the process of obtaining 30 minutes

Before starting production, the reactor (4) and the supply lines to it are pre-evacuated using a foreline pump, followed by purging through the gas supply pipe (1) with argon for 20 minutes at a flow rate of 500 ml / min, after which hydrogen is supplied at a flow rate of 500 ml / min and increase the temperature of the furnace (2) to 1000-1100 ° C. Constant temperature control in the central zone of the reactor is carried out using a chromel-alumel thermocouple, which is placed inside the alundum cover (3). After stabilization of the set temperature, the hydrogen flow rate is set in the range of 500-1100 ml / min, the argon supply to the system is turned off, and the reaction solution is supplied at a rate of 1 ml / min. At the end of the experiment, after 30 minutes the flow of the reaction solution and hydrogen was stopped, and the flow of argon was connected.

In accordance with the literature data [1, 2, 3] and the synthesis conditions indicated in the prototype, as well as taking into account the maximum permissible operating temperature of the quartz reactor, the production of light-absorbing material in the following examples is carried out in the temperature range from 1000 ° C to 1100 ° C, the speed of the carrier gas (hydrogen) is in the range from 500 ml / min to 1100 ml / min. Depending on the temperature and velocity of the carrier gas, the characteristics of the obtained product (the diameter of the nanotubes, the number of aligned CNTs, etc.) change.

Example 1. A light-absorbing material (Fig. 2) in the form of beams from low- and multi-walled carbon nanotubes is obtained by CVD with the active component in the gas phase in a laboratory setup with a horizontal flow quartz reactor according to the procedure described above. The production temperature in this example is 1100 ° C, the flow rate of hydrogen is 1000 ml / min. In the described manner, a product is obtained which is a bundle of carbon nanotubes about 5 cm long, the outer diameter of the nanotubes is 4-17 nm (Fig. 3). The obtained light-absorbing material is characterized by the fact that it is bundles of low- and multi-walled carbon nanotubes with lateral deposits in the form of randomly oriented graphene fragments with a size of up to 10 nm. The light-absorbing material is formed into ribbons with a thickness of at least 2 mm and a density of 0.4 g / cm ³ , the light absorption coefficient is about 99.9% in the wavelength range of 1.5-20 μm.

Example 2. Light-absorbing material (Fig. 4) in the form of bundles of low- and multi-walled carbon nanotubes is obtained, as in example 1. The production temperature in this example is 1100 ° C, the hydrogen flow rate is 1100 ml / min. In the described manner, a product is obtained which is bundles of carbon nanotubes about 5 cm long, the outer diameter of the nanotubes is 7-19 nm (Fig. 5). The obtained light-absorbing material is characterized by the fact that it is bundles of low- and multi-walled carbon nanotubes with lateral deposits in the form of randomly oriented graphene fragments with a size of up to 10 nm. The light-absorbing material is formed into ribbons, as in example 1, the light absorption coefficient is about 99.9% in the wavelength range of 1.5-20 μm.

Example 3. The light-absorbing material (Fig.6) in the form of bundles of low- and multi-walled carbon nanotubes is obtained, as in example 1. The production temperature in this example is 1100 ° C, the hydrogen flow rate of 500 ml / min. The described method in the process of obtaining a product is obtained, which is a bundle of carbon nanotubes with a length of about 5 cm, the outer diameter of the nanotubes is 10-22 nm (Fig.7). The obtained light-absorbing material is characterized by the fact that it is bundles of low- and multi-walled carbon nanotubes with lateral deposits in the form of randomly oriented graphene fragments with a size of up to 10 nm. The light-absorbing material is formed into ribbons, as in example 1, the light absorption coefficient is about 99.9% in the wavelength range of 1.5-20 μm.

Example 4. Light-absorbing material (Fig. 8) in the form of bundles of low- and multi-walled carbon nanotubes is obtained, as in example 1. The production temperature in this example is 1000 ° C, the hydrogen flow rate is 500 ml / min. The described method in the process of obtaining a product that is a bundle of carbon nanotubes with a length of about 5 cm, the outer diameter of the nanotubes is 12-28 nm (Fig. 9). The obtained light-absorbing material is characterized by the fact that it is bundles of low- and multi-walled carbon nanotubes with lateral deposits in the form of randomly oriented graphene fragments with a size of up to 10 nm. The light-absorbing material is formed into ribbons, as in example 1, the light absorption coefficient is about 99.9% in the wavelength range of 1.5-20 μm.

Thus, the CVD light-absorbing material is a bundle of small and multi-walled carbon nanotubes with lateral deposits in the form of randomly oriented fragments of graphene with a size of up to 10 nm, which is formed into ribbons with a thickness of at least 2 mm and a density of 0.4 g / cm ³ , the light absorption coefficient is about 99.9% in the wavelength range of 1.5-20 microns.

Obtaining this material does not require the use of substrates, is simplified and accelerated in comparison with analogues and prototype.

EFFECT: material consisting of bundles of carbon nanotubes obtained by CVD method without the use of auxiliary substrates. This product can be molded in the form of tapes without the use of complex auxiliary equipment, the light absorption coefficient of the material is about 99.9%.

Information sources

1. Y. Sun, R. Kitaura, J. Zhang, Y. Miyata, H. Shinohara, Metal catalyst-free mist flow chemical vapor deposition growth of single-wall carbon nanotubes using C60 colloidal solutions // Carbon, v. 68, pp. 80-86 (2014).

2. M. Khavarian, S.-P. Chai, S.H. Tan, A.R. Mohamed. Floating catalyst CVD synthesis of carbon nanotubes using iron (iii) chloride: influences of the growth parameters // NANO: Brief Reports and Reviews, v. 4, No. 6, 359-366 (2009).

3. Q. Zhang. Carbon Nanotubes and Their Applications // Pan Stanford Series on Carbon-Based Nanomaterials, v. 1, p. 469 (2012).

Claims (1)

A light-absorbing material containing carbon nanotubes, characterized in that the material contains carbon nanotubes in the form of bundles of small and multi-walled carbon nanotubes with lateral deposits in the form of randomly oriented fragments of graphene with a size of up to 10 nm, capable of forming into ribbons at least 2 mm thick and a density of 0.4 g / cm ³ with a light absorption coefficient of about 99.9%.

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