A heating wire, its preparation method and application

Abstract

This invention belongs to the field of nanomaterials technology, specifically relating to a heating wire, its preparation method, and its application. The method for preparing the heating wire provided by this invention involves impregnating filamentous carbon nanotube fibers in a graphene-containing resin dispersion and then curing it. The resin layer containing graphene material encapsulates the filamentous carbon nanotube fibers. The filamentous carbon nanotube fibers prepared by this invention exhibit stable heating. When used in the heating system of a gas element analyzer, the heating wire exhibits low electromagnetic radiation and minimal interference with the hardware, making it more suitable for high-precision testing. The filamentous carbon nanotube fibers prepared by this invention have the advantages of stable heating and resistance to oxidation. The resin layer encapsulating the filamentous carbon nanotube fibers protects the carbon nanotubes, isolates them from air, and extends the service life of the heating element's carbon nanotubes.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a heating wire, its preparation method, and its application. Background Technology

[0002] Gas elemental analyzers, including equipment for analyzing gaseous elements such as carbon, sulfur, oxygen, nitrogen, and hydrogen, typically involve heating materials to high temperatures for a short period, releasing gas molecules instantaneously. These molecules are then converted in a conversion furnace and transported by carrier gas to an infrared or thermal conductivity detector to determine their composition. The heating temperature is generally between 1000 and 3000°C, with the furnace outlet temperature between 500 and 600°C. After release, the gas molecules travel through the pipeline with the carrier gas, and their temperature continuously decreases until they reach the detector. Without a heating system, this uneven temperature distribution can cause signal drift, and the high-temperature gases may condense in the cold pipeline, making them undetectable by the detector and affecting the accuracy and precision of the test.

[0003] The heat tracing system used in gas element analyzers has traditionally been a resistance wire or metal wire heat tracing cable. However, as the complexity of the control system of gas element analysis equipment continues to increase and the functions of the control board become more and more numerous, the traditional heat tracing system will bring electromagnetic radiation, which is not conducive to high-precision testing. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a heating wire, its preparation method, and its application. When the heating wire prepared by this invention is used in the heat tracing system of a gas elemental analyzer, it exhibits low electromagnetic radiation and minimal interference with the hardware, which is beneficial for high-precision testing.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a heating wire, comprising the following steps:

[0007] The graphene material dispersion and resin are mixed to obtain the graphene material resin dispersion.

[0008] The heating wire is obtained by impregnating filamentous carbon nanotube fibers in the graphene material resin dispersion and then curing them; the preparation method of the filamentous carbon nanotube fibers includes:

[0009] Methanol, ethanol, ferrocene and thiophene were mixed, and the resulting mixture was pyrolyzed to obtain carbon nanotube fibers.

[0010] After the carbon nanotube fibers are formed on the surface of polylactic acid yarn, the polylactic acid is removed to obtain the filamentous carbon nanotube fibers.

[0011] Preferably, the volume ratio of methanol to ethanol is 1.8–2.2:0.9–1.1.

[0012] Preferably, the ferrocene content in the mixture is 0.6–1 wt%.

[0013] Preferably, the thiophene content in the mixture is 0.3–0.5 wt%.

[0014] Preferably, the pyrolysis temperature is 1400–1600°C.

[0015] Preferably, the mass fraction of graphene material in the graphene material resin dispersion is 3-5%.

[0016] The present invention also provides a heating wire obtained by the preparation method described above, wherein the heating wire has a core-sheath structure, wherein the core-sheath structure has filamentous carbon nanotube fibers as the core and a resin layer containing graphene material as the sheath, wherein the graphene material is dispersed in the resin layer.

[0017] The present invention also provides the application of the heating wire obtained by the preparation method described above in the heat tracing system of a gas element analyzer.

[0018] Preferably, the heat tracing system of the gas element analyzer includes a converter outlet heat tracing zone, an infrared heat tracing zone, and a thermal conductivity heat tracing zone.

[0019] Preferably, the resistance of the heating wire used in the heat tracing zone of the converter outlet is 220-240Ω; the resistance of the heating wire used in the infrared heat tracing zone is 155-175Ω; and the resistance of the heating wire used in the thermal conductivity heat tracing zone is 90-110Ω.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The method for preparing the heating wire provided by this invention involves impregnating filamentous carbon nanotube fibers in a graphene-based resin dispersion and then curing them. The resin layer containing graphene material encapsulates the filamentous carbon nanotube fibers. The filamentous carbon nanotube fibers prepared by this invention have uniform diameter, uniform resistance, and stable heating. When used in the heating system of a gas elemental analyzer, the heating wire exhibits low electromagnetic radiation and minimal interference with the hardware, making it more suitable for high-precision testing. Example data shows that applying the heating wire prepared by this invention to the heating system of a gas elemental analyzer improves the stability of gas measurements and provides high discrimination for trace amounts of hydrogen, capable of detecting hydrogen concentrations as low as 0.0001 ppm (mg / kg). Furthermore, the filamentous carbon nanotube fibers prepared by this invention have the advantages of stable heating and resistance to oxidation. The resin layer encapsulating the filamentous carbon nanotube fibers protects the carbon nanotubes, isolates them from air, and extends the service life of the heating element's carbon nanotubes. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the analysis process of a gas elemental analyzer;

[0024] Figure 2 The image shows the morphology of the long carbon nanotube fibers obtained in Example 1.

[0025] Figure 3 This is a schematic diagram of the cross-section of the heating wire. Detailed Implementation

[0026] This invention provides a method for preparing a heating wire, comprising the following steps:

[0027] Graphene material, water, and resin are mixed to obtain a graphene material-resin dispersion.

[0028] The heating wire is obtained by impregnating filamentous carbon nanotube fibers in the graphene material resin dispersion and then curing them; the preparation method of the filamentous carbon nanotube fibers includes:

[0029] Methanol, ethanol, ferrocene and thiophene were mixed, and the resulting mixture was pyrolyzed to obtain carbon nanotube fibers.

[0030] After the carbon nanotube fibers are formed on the surface of polylactic acid yarn, the polylactic acid is removed to obtain the filamentous carbon nanotube fibers.

[0031] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.

[0032] This invention involves mixing a graphene material dispersion with a resin to obtain a graphene material resin dispersion.

[0033] In this invention, the graphene material preferably includes one or more of graphene, graphene oxide, and reduced graphene oxide; the graphene preferably includes single-layer graphene or multi-layer graphene, and the sheet diameter of the single-layer graphene or multi-layer graphene is preferably 20-30 μm, and the thickness is preferably 0.34-10 nm.

[0034] In this invention, the graphene material dispersion is preferably obtained by mixing graphene material and water, the concentration of the graphene material dispersion is preferably 0.5-8 wt%, and the mass ratio of the graphene material dispersion to the resin is preferably 3-15:1, more preferably 10:1.

[0035] In this invention, the resin preferably includes one or more of epoxy resin, polyethylene resin, nylon resin and polyurethane resin, and the heat resistance temperature of the resin is preferably above 120°C.

[0036] In this invention, the mixing method is preferably high-speed stirring, the speed of the high-speed stirring is preferably 3000 rpm, and the time is preferably 4 hours.

[0037] In this invention, the mass fraction of graphene material in the graphene material resin dispersion is preferably 3-5%, more preferably 4%.

[0038] After obtaining the graphene material resin dispersion, the present invention impregnates and solidifies filamentous carbon nanotube fibers in the graphene material resin dispersion to obtain the heating wire; the preparation method of the filamentous carbon nanotube fibers includes:

[0039] Methanol, ethanol, ferrocene and thiophene were mixed, and the resulting mixture was pyrolyzed to obtain carbon nanotube fibers.

[0040] After the carbon nanotube fibers are formed on the surface of polylactic acid yarn, the polylactic acid is removed to obtain the filamentous carbon nanotube fibers.

[0041] This invention involves mixing methanol, ethanol, ferrocene, and thiophene, and then pyrolyzing the resulting mixture to obtain carbon nanotube fibers.

[0042] In this invention, the volume ratio of methanol to ethanol is preferably 1.8-2.2:0.9-1.1, more preferably 2:1. The methanol and ethanol are carbon sources. The carbon nanotube fibers prepared by the methanol-ethanol volume ratio of this invention have high purity.

[0043] In this invention, the content of ferrocene in the mixture is preferably 0.6-1 wt%, more preferably 0.7-0.8 wt%, and the ferrocene is a nucleating agent.

[0044] In this invention, the content of thiophene in the mixture is preferably 0.3 to 0.5 wt%, more preferably 0.4 wt%, and the thiophene is a promoter.

[0045] In this invention, the pyrolysis temperature is preferably 1400-1600℃, more preferably 1500℃. The pyrolysis temperature of this invention can improve the yield of carbon nanotubes. The pyrolysis time is very short and occurs instantaneously. During the pyrolysis process, alcohol is converted into carbon atoms, and ferrocene is converted into pure iron atoms after pyrolysis. Under the action of thiophene promoter, carbon begins to grow into carbon nanotubes on its surface with iron atoms as the nucleus.

[0046] In this invention, the pyrolysis is preferably carried out in a tubular furnace. In a specific embodiment of this invention, the mixture is preferably transported to the tubular furnace by a carrier gas for pyrolysis, and carbon nanotube fibers are formed at the outlet end of the tubular furnace. The carrier gas preferably includes nitrogen or argon, the nitrogen is preferably high-purity nitrogen, the argon is preferably high-purity argon, and the flow rate of the carrier gas is preferably 5 to 15 L / min, more preferably 10 L / min.

[0047] In this invention, the length of the carbon nanotube fiber is preferably 1 to 2 mm.

[0048] After obtaining carbon nanotube fibers, the present invention shapes the carbon nanotube fibers on the surface of polylactic acid yarn, removes the polylactic acid, and obtains the filamentous carbon nanotube fibers.

[0049] In this invention, the carbon nanotube fibers are preferably blown onto the surface of a rotating polylactic acid (PLA) yarn to form the fiber. The type and flow rate of the gas used for blowing are preferably the same as the carrier gas, and will not be elaborated further. The advancing speed of the PLA yarn is preferably 2–10 m / min, more preferably 4–8 m / min. During the rotation, the carbon nanotube fibers are twisted, and the twisting rate is preferably 100–500 r / min. The filamentous carbon nanotube fibers obtained by this invention through the twisting technique have uniform diameter, uniform electrical resistance, and stable heating.

[0050] In this invention, the twist is preferably 3000-8000, more preferably 4000-6000.

[0051] In this invention, the preferred method for removing polylactic acid is alkaline washing, and the reagent used for alkaline washing is preferably sodium hydroxide solution. The concentration of the sodium hydroxide solution is preferably 2-3 wt%, more preferably 2.5 wt%, and the temperature of the sodium hydroxide solution is preferably 60-95°C, more preferably 70-80°C.

[0052] In this invention, the length of the filamentous carbon nanotube fiber depends on the length of the polylactic acid fiber, the thickness is preferably tens of micrometers, and the width is preferably 1 to 5 mm.

[0053] After obtaining the filamentous carbon nanotube fibers and the graphene material resin dispersion, the present invention impregnates the filamentous carbon nanotube fibers in the graphene material resin dispersion and then cures them to obtain the heating wire.

[0054] In this invention, the process of soaking preferably includes lifting, and the total time for soaking and lifting is preferably 3 to 5 seconds.

[0055] In this invention, the curing temperature is preferably room temperature, and the curing time is preferably 1 to 2 minutes.

[0056] The present invention also provides a heating wire obtained by the preparation method described above, wherein the heating wire has a core-sheath structure, wherein the core-sheath structure has filamentous carbon nanotube fibers as the core and a resin layer containing graphene material as the sheath, wherein the graphene material is dispersed in the resin layer.

[0057] In this invention, the mass ratio of the filamentous carbon nanotube fibers to the graphene-containing resin layer is preferably 3.5 to 4.5:1, more preferably 4:1.

[0058] In this invention, the resin layer encapsulates filamentous carbon nanotube fibers, which protects the carbon nanotubes, isolates them from air, and extends the service life of the carbon nanotubes in the heating element.

[0059] In this invention, the cross-section of the heating wire is preferably circular, the diameter of the heating wire is preferably 1 to 1.5 cm, and the diameter of the filamentous carbon nanotube fibers in the heating wire is preferably 100 to 500 μm.

[0060] The present invention also provides the application of the heating wire obtained by the preparation method described above in the heat tracing system of a gas element analyzer.

[0061] In this invention, the heat tracing system of the gas element analyzer preferably includes a converter outlet heat tracing zone, an infrared heat tracing zone, and a thermal conductivity heat tracing zone. The temperature of the converter outlet heat tracing zone is preferably 110-130°C, more preferably 120°C; the temperature of the infrared heat tracing zone is preferably 72-88°C, more preferably 80°C; and the temperature of the thermal conductivity heat tracing zone is preferably 47.5-52.5°C, more preferably 50°C.

[0062] In this invention, the analytical process diagram of the gas elemental analyzer is as follows: Figure 1 As shown, the sample is heated in the heating zone at a temperature controlled by software, releasing the test gases carbon monoxide, hydrogen, and nitrogen. After passing through the conversion furnace, the carbon monoxide is converted into carbon dioxide, and the hydrogen into water vapor, which are then detected by an infrared detector and a thermal conductivity detector, respectively, and converted into AD signals for computer recognition. The temperature of the conversion furnace is 500–600°C, and the heating system ensures the temperature stability of the test gases.

[0063] In this invention, the operating voltage of the heat tracing system is preferably 24-36V, and the opening and closing of the heat tracing system is controlled by computer software.

[0064] In this invention, the resistance of the heating wire used in the heat tracing zone of the converter outlet is preferably 220-240Ω, more preferably 230Ω; the resistance of the heating wire used in the infrared heat tracing zone is preferably 155-175Ω, more preferably 165Ω; and the resistance of the heating wire used in the thermal conductivity heat tracing zone is preferably 90-110Ω, more preferably 100Ω.

[0065] In this invention, the air path length of the heat tracing system is preferably 0.5 to 1 m. When the heating wire is used in the heat tracing zone at the outlet of the converter, the twist of the filamentous carbon nanotube fibers is preferably 3000 to 5000, and the quantity is preferably 5 to 10 sets. When the heating wire is used in the infrared heat tracing zone, the twist of the filamentous carbon nanotube fibers is preferably 5000 to 7000, and the quantity is preferably 15 to 30 sets. When the heating wire is used in the thermal conductivity heat tracing zone, the twist of the filamentous carbon nanotube fibers is preferably 7000 to 8000, and the quantity is preferably 30 to 50 sets.

[0066] To further illustrate the present invention, the heating wire, its preparation method, and its application are described in detail below with reference to the accompanying drawings and embodiments, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0067] Example 1

[0068] Ferrocene and thiophene were added to a mixture of methanol and anhydrous ethanol (volume ratio 2:1), with ferrocene comprising 0.6 wt% and thiophene comprising 0.3 wt%. The mixture was transported to a tube furnace for high-temperature pyrolysis at 1500 °C using high-purity nitrogen at a flow rate of 15 L / min. Short carbon nanotube fibers were formed at the outlet of the tube furnace. A rotating polylactic acid (PLA) yarn was present at the outlet of the tube furnace. The carrier gas blew the generated short carbon nanotube fibers onto the surface of the PLA yarn, which advanced at a speed of 2 m / min. During rotation, the carbon nanotube fibers were twisted. The PLA was then removed by passing the fibers through a 2.5 wt% hot sodium hydroxide solution (60 °C), yielding long carbon nanotube fibers. The morphology is shown in the figure below. Figure 2 As shown.

[0069] By controlling the twist of the carbon nanotube long fibers and adjusting the number of carbon nanotube long fibers, carbon nanotube filaments are obtained. The carbon nanotube long fibers used to prepare the heating wire of the outlet heating zone of the converter have a twist of 3000 and a quantity of 5 sets; the carbon nanotube long fibers used to prepare the heating wire of the infrared heating zone have a twist of 5000 and a quantity of 15 sets; and the carbon nanotube long fibers used to prepare the heating wire of the thermal conductivity heating zone have a twist of 7000 and a quantity of 30 sets.

[0070] A graphene material dispersion (manufacturer: LEVSON, model: LN-10R) was added to an epoxy polymer resin at a mass ratio of 10:1. The dispersion was carried out at high speed for 4 hours at 3000 rpm to obtain a graphene resin dispersion. Carbon nanotube filaments were then impregnated into this dispersion and cured at room temperature to form a composite filament (heating wire) with a carbon nanotube core and a graphene-polymer resin sheath. A cross-sectional diagram of the heating wire is shown below. Figure 3 As shown, the cross-section is circular. The black part in the center is a twisted carbon nanotube filament, the yellow part is a composite material of graphene and resin, which serves as the outer coating layer, and the two small blue circles are terminals. It can work when connected to a power source.

[0071] Application Example 1

[0072] The heating wire prepared in Example 1 was applied to the heat tracing system of a gas element analyzer (new heat tracing system).

[0073] Table 1 shows the electromagnetic radiation test results of the new heat tracing system. The electromagnetic radiation is only 0.248%, which is low and provides good protection for the weak current components of the instrument. In contrast, the traditional heat tracing system uses stainless steel heating wires, and the electromagnetic radiation is 6%.

[0074] Table 1 Electromagnetic radiation test results of the new heat tracing system

[0075]

[0076] Table 2. Test results of the gas element analyzer using the new heat tracing system.

[0077]

[0078] The heating wire prepared according to this invention is applied to the heating system of a gas elemental analyzer, which improves the stability of gas measurement and has a high resolution for trace amounts of hydrogen, capable of detecting hydrogen at a concentration of 0.0001 ppm. Traditional elemental analyzers currently only have a resolution of 0.1 ppm. This invention, with its novel heating system, provides stable heating, minimizes interference with control devices, reduces background noise, and improves instrument resolution by 1000 times.

[0079] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. The application of a heating wire in the heat tracing system of a gas element analyzer, characterized in that, The method for preparing the heating wire includes the following steps: The graphene material dispersion and resin are mixed to obtain the graphene material resin dispersion. The heating wire is obtained by impregnating filamentous carbon nanotube fibers in the graphene material resin dispersion and then curing them. The method for preparing the filamentous carbon nanotube fibers includes: Methanol, ethanol, ferrocene, and thiophene were mixed, and the resulting mixture was pyrolyzed to obtain carbon nanotube fibers; the volume ratio of methanol to ethanol was 2:1; the content of ferrocene in the mixture was 0.6 wt%; the content of thiophene in the mixture was 0.3 wt%; and the pyrolysis temperature was 1500℃. After the carbon nanotube fibers are formed on the surface of polylactic acid yarn, the polylactic acid is removed to obtain the filamentous carbon nanotube fibers. The formation of the carbon nanotube fibers on the surface of the polylactic acid yarn is as follows: the carbon nanotube fibers are blown onto the surface of the rotating polylactic acid yarn and formed; the speed of the polylactic acid yarn is 2~10m / min, and the carbon nanotube fibers are twisted during the rotation, and the twisting speed is 100~500r / min. The graphene material in the resin dispersion has a mass fraction of 4%. The process includes impregnation followed by lifting, with the total time for both impregnation and lifting being 3-5 seconds; the curing temperature is room temperature, and the time is 1-2 minutes. The heating system of the gas element analyzer includes a converter outlet heating zone, an infrared heating zone, and a thermal conductivity heating zone. The resistance of the heating wire used in the heat tracing zone of the converter outlet is 220~240Ω; the resistance of the heating wire used in the infrared heat tracing zone is 155~175Ω; and the resistance of the heating wire used in the thermal conductivity heat tracing zone is 90~110Ω. When the heating wire is used in the heat tracing zone at the outlet of the converter, the twist of the filamentous carbon nanotube fibers is 3000~5000; when the heating wire is used in the infrared heat tracing zone, the twist of the filamentous carbon nanotube fibers is 5000~7000; when the heating wire is used in the thermal conductivity heat tracing zone, the twist of the filamentous carbon nanotube fibers is 7000~8000.

2. The application according to claim 1, characterized in that, The heating wire has a core-sheath structure, with filamentous carbon nanotube fibers as the core and a resin layer containing graphene material as the sheath, wherein the graphene material is dispersed in the resin layer.

Images