Method for improving air stability of n-type single-walled carbon nanotube thermoelectric thin film
By forming an antioxidant and superhydrophobic layer on an n-type single-walled carbon nanotube film, the problem of poor stability of n-type single-walled carbon nanotubes in high humidity environments is solved, and their thermoelectric properties are maintained under high humidity conditions, making them suitable for flexible wearable devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INST OF ELECTRICAL ENG CHINESE ACAD OF SCI
- Filing Date
- 2023-09-11
- Publication Date
- 2026-06-26
AI Technical Summary
n-type single-walled carbon nanotubes have poor air stability, especially in high humidity environments where they are easily affected by oxygen and moisture, which affects their thermoelectric properties and the application of flexible devices.
An antioxidant slurry is formed by a mixture of polyvinylpyrrolidone, polyvinylidene fluoride and dimethylformamide, which is used to coat an n-type carbon nanotube membrane to form an antioxidant layer. A superhydrophobic layer is then coated on top of the antioxidant layer to block the contact between oxygen and water molecules and the carbon nanotubes.
The air stability of the n-type single-walled carbon nanotube film is improved, enabling it to maintain good thermoelectric performance in high humidity environments. It is expected to be combined with the p-type thermoelectric film for use in flexible wearable devices.
Smart Images
Figure CN117285732B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of thermoelectric materials technology, and in particular to a method for improving the air stability of n-type single-walled carbon nanotube thermoelectric thin films. Background Technology
[0002] Thermoelectric devices are devices that can convert heat energy into electrical energy and vice versa. They have two main applications: thermoelectric power generation and thermoelectric refrigeration. Thermoelectric materials used in thermoelectric devices are environmentally friendly new energy materials with broad application prospects.
[0003] Single-walled carbon nanotubes (SWCTs), as a typical one-dimensional material, have attracted widespread attention in the field of thermoelectric materials due to their excellent mechanical, electrical, and thermal properties. Currently, SWCTs have been successfully applied in the thermoelectric materials field. Because SWCT composite thermoelectric materials possess advantages such as light weight, high flexibility, and low cost, they are more suitable for flexible, stretchable, wearable electronic devices and complex working environments with uneven surfaces.
[0004] A complete thermoelectric device typically requires both p-type and n-type materials to operate simultaneously. However, the air stability of n-type SWCNTs has been a persistent concern, making it essential to improve the air stability of n-type doped SWCTs. Summary of the Invention
[0005] The purpose of this invention is to provide a method for improving the air stability of n-type single-walled carbon nanotube thermoelectric thin films. The n-type single-walled carbon nanotube thin films treated using this method can remain stable in high-humidity atmospheric environments and possess good flexibility, making them promising candidates for use in flexible wearable thermoelectric devices when combined with existing p-type thermoelectric thin films.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0007] This invention provides a method for improving the air stability of n-type single-walled carbon nanotube thermoelectric thin films, comprising the following steps:
[0008] Polyvinylpyrrolidone, polyvinylidene fluoride and dimethylformamide are mixed to obtain an antioxidant slurry;
[0009] The antioxidant slurry is used to coat the n-type carbon nanotube membrane to obtain an n-type carbon nanotube membrane coated with an antioxidant layer.
[0010] After connecting two wires to both ends of the n-type carbon nanotube film coated with an antioxidant layer, superhydrophobic coating is performed to obtain an n-type single-walled carbon nanotube film with superhydrophobicity and antioxidant properties.
[0011] Preferably, the concentration of polyvinylpyrrolidone in the antioxidant slurry is 0.20–0.23 g / mL;
[0012] The concentration of polyvinylidene fluoride in the antioxidant slurry is 0.001–0.005 g / mL.
[0013] Preferably, the coating method involves immersing the n-type carbon nanotube film in the antioxidant slurry and then curing it;
[0014] The soaking time is 7 to 10 minutes.
[0015] Preferably, the curing temperature is 80-100°C and the time is 7-10 minutes.
[0016] Preferably, the superhydrophobic coating uses a superhydrophobic mixture comprising polydimethylsiloxane and a curing agent;
[0017] The mass ratio of polydimethylsiloxane to curing agent is (9-11):1.
[0018] Preferably, the curing temperature of the superhydrophobic coating is 100-150°C and the curing time is 10-35 min.
[0019] This invention provides a method for improving the air stability of n-type single-walled carbon nanotube (n-walled carbon nanotube) thermoelectric thin films, comprising the following steps: mixing polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), and dimethylformamide (DMF) to obtain an antioxidant slurry; coating the n-type carbon nanotube film with the antioxidant slurry to obtain an n-type carbon nanotube film coated with an antioxidant layer; and connecting two wires to both ends of the n-type carbon nanotube film coated with the antioxidant layer, followed by superhydrophobic coating to obtain an n-type single-walled carbon nanotube film with both superhydrophobicity and antioxidant properties. This invention uses a mixture of polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), and dimethylformamide (DMF) to prepare the antioxidant layer. The dense coating formed by the mixture of PVP and PVDF can effectively coat the n-type single-walled carbon nanotube film, thereby blocking the reaction between oxygen in the air and the single-walled carbon nanotubes. Furthermore, a hydrophobic coating is prepared by coating with PDMS to further block the influence of water molecules in the air on the conductivity of carbon nanotubes, thus enabling the n-type single-walled carbon nanotube film to be used stably in high-humidity atmospheric environments. The method provided by this invention is simple and easy to implement, and can also be applied to the coating of other oxygen and water-sensitive materials and devices. The air-stable n-type single-walled carbon nanotube thermoelectric thin films prepared by the method provided by this invention have good flexibility and are expected to be used in conjunction with existing p-type thermoelectric thin films to prepare flexible thermoelectric devices that can be worn by the human body. Attached Figure Description
[0020] Figure 1This is a SEM image of the n-type single-walled carbon nanotube membrane described in Example 1;
[0021] Figure 2 This is a SEM image of the n-type carbon nanotube film coated with an antioxidant layer as described in Example 1.
[0022] Figure 3 The Seebeck coefficient of the n-type single-walled carbon nanotube membrane and the n-type carbon nanotube membrane coated with an antioxidant layer described in Example 2 changes over 30 days in an atmospheric environment with a humidity of 20%.
[0023] Figure 4 The output performance changes of the n-type single-walled carbon nanotube film with superhydrophobicity and oxidation resistance described in Example 2 over 7 days in an atmospheric environment with an air humidity of ~55%. Detailed Implementation
[0024] This invention provides a method for improving the air stability of n-type single-walled carbon nanotube thermoelectric thin films, comprising the following steps:
[0025] An antioxidant slurry is obtained by mixing polyvinylpyrrolidone (PVDF), polyvinylidene fluoride (PVP), and dimethylformamide (DMF).
[0026] The antioxidant slurry is used to coat the n-type carbon nanotube membrane to obtain an n-type carbon nanotube membrane coated with an antioxidant layer.
[0027] After connecting two wires to both ends of the n-type carbon nanotube film coated with an antioxidant layer, superhydrophobic coating is performed to obtain an n-type single-walled carbon nanotube film with superhydrophobicity and antioxidant properties.
[0028] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.
[0029] This invention mixes polyvinylpyrrolidone, polyvinylidene fluoride and dimethylformamide to obtain an antioxidant slurry.
[0030] In this invention, the concentration of polyvinylpyrrolidone in the antioxidant slurry is preferably 0.20-0.23 g / mL, more preferably 0.20-0.22 g / mL, and most preferably 0.2 g / mL; the concentration of polyvinylidene fluoride in the antioxidant slurry is preferably 0.001-0.005 g / mL, more preferably 0.0013-0.0047 g / mL, and most preferably 0.0020-0.0033 g / mL.
[0031] The present invention does not impose any special limitations on the mixing process; any process known to those skilled in the art can be used.
[0032] After mixing, the present invention preferably includes ultrasound, and the ultrasound time is preferably 40-70 min, more preferably 50-60 min, and most preferably 60 min; the present invention does not have any special limitation on the frequency of the ultrasound, and any frequency known to those skilled in the art can be used to ensure that a stable and uniform mixed slurry is formed within the above-mentioned ultrasound time.
[0033] After obtaining the antioxidant slurry, the present invention coats the n-type carbon nanotube membrane with the antioxidant slurry to obtain an n-type carbon nanotube membrane coated with an antioxidant layer.
[0034] In this invention, the coating method preferably involves immersing the n-type carbon nanotube film in the antioxidant slurry and then curing it. The immersion time is preferably 7–10 min, more preferably 7.5–9.5 min, and most preferably 8–9 min. The curing temperature is preferably 80–100°C, more preferably 85–95°C, and most preferably 88–92°C; the curing time is preferably 7–10 min, more preferably 7.5–9.5 min, and most preferably 8–9 min.
[0035] In this invention, the thickness of the antioxidant layer in the n-type carbon nanotube membrane coated with the antioxidant layer is preferably 2 to 10 μm, more preferably 3 to 5 μm, and most preferably 3 μm.
[0036] After obtaining an n-type carbon nanotube film coated with an antioxidant layer, the present invention connects two wires to both ends of the n-type carbon nanotube film coated with the antioxidant layer and then performs superhydrophobic coating to obtain an n-type single-walled carbon nanotube film with superhydrophobicity and antioxidant properties.
[0037] The present invention does not impose any special limitations on the process of connecting the wires. A process known to those skilled in the art can be used to connect the two wires to the two ends of the n-type carbon nanotube membrane covered with an antioxidant layer using silver paste.
[0038] In this invention, the superhydrophobic mixture used for the superhydrophobic coating preferably comprises polydimethylsiloxane and a curing agent; the mass ratio of the polydimethylsiloxane to the curing agent is preferably (9-11):1, more preferably (9.5-10.5):1, and most preferably 10:1. In this invention, the type of curing agent preferably includes Dow Corning DC184.
[0039] In this invention, the curing temperature of the superhydrophobic coating is preferably 100-150°C, more preferably 125-150°C, and most preferably 150°C; the curing time is preferably 10-35 min, more preferably 10-20 min, and most preferably 10 min.
[0040] In this invention, the thickness of the superhydrophobic layer obtained by superhydrophobic coating is preferably 0.5 to 2.5 mm, more preferably 1 to 2 mm, and most preferably 1 mm.
[0041] In this invention, the superhydrophobic and antioxidant n-type single-walled carbon nanotube film is preferably used as a thermoelectric material in flexible thermoelectric devices that can be worn by the human body.
[0042] The following detailed description, in conjunction with embodiments, illustrates the method for improving the air stability of n-type single-walled carbon nanotube thermoelectric thin films provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.
[0043] Example 1
[0044] 0.3g PVP, 0.003g PVDF and 1.5mL DMF were mixed to form a suspension, and the suspension was subjected to sonication (the sonication time was 1h, the power was 360W and the frequency was 40Hz) to obtain a mixed slurry (the concentration of PVP in the mixed slurry was 0.2g / mL and the concentration of PVDF was 0.002g / mL).
[0045] An n-type single-walled carbon nanotube membrane was immersed in the mixed slurry for 9 minutes to obtain a wet film with a thickness of about 20 μm. The wet film was then cured at 90°C for 9 minutes to obtain an antioxidant film with a thickness of about 3 μm, thus obtaining an n-type carbon nanotube membrane coated with an antioxidant layer.
[0046] The n-type single-walled carbon nanotube membrane and the n-type carbon nanotube membrane coated with an antioxidant layer were subjected to SEM testing, wherein... Figure 1 Here is a SEM image of the n-type single-walled carbon nanotube film. Figure 2 The image shows a SEM image of the n-type carbon nanotube film coated with an antioxidant layer. Figure 1 It can be seen that the carbon nanotubes in the n-type single-walled carbon nanotube film are distinct, uniformly dispersed, and the film surface is uniform; from Figure 2 It can be seen that after the surface of the n-type single-walled carbon nanotube film is coated with an antioxidant layer, the originally distinct carbon nanotubes are no longer visible. Instead, a uniform coating is formed on the surface, and the coating is relatively dense. This is the main reason why it can resist the reaction between external oxygen and carbon nanotubes.
[0047] Example 2
[0048] 0.3g PVP, 0.005g PVDF and 1.5mL DMF were mixed to form a suspension, and the suspension was sonicated (the sonication time was 60min, the power was 360W and the frequency was 40Hz) to obtain a mixed slurry (the concentration of PVP in the mixed slurry was 0.2g / mL and the concentration of PVDF was 0.003g / mL).
[0049] An n-type single-walled carbon nanotube membrane was immersed in the mixed slurry for 9 minutes to obtain a wet film with a thickness of about 20 μm. The wet film was then cured at 90°C for 9 minutes to obtain an antioxidant film with a thickness of about 3 μm, thus obtaining an n-type carbon nanotube membrane coated with an antioxidant layer.
[0050] After connecting two wires to both ends of the n-type carbon nanotube film coated with an antioxidant layer using silver paste, PDMS and curing agent (Dow Corning DC184) were mixed and stirred for 5 minutes at a mass ratio of 10:1 to obtain a PDMS mixture. The mixture was then poured onto the n-type carbon nanotube film coated with an antioxidant layer connected to the two wires. The film was placed in a vacuum oven at 150°C for 10 minutes to allow the solvent to evaporate and the PDMS to gradually solidify, resulting in a superhydrophobic layer (1 mm thick). This yielded an n-type single-walled carbon nanotube film with superhydrophobicity and antioxidant properties.
[0051] The Seebeck coefficient of the n-type doped single-walled carbon nanotube thermoelectric thin film sample and the sample coated with an antioxidant layer selected in Example 2 were tested using a room-temperature thermoelectric property evaluation device (PTM) after being exposed to an atmospheric environment with 20% humidity for 30 days. Figure 3 The Seebeck coefficient changes of the n-type single-walled carbon nanotube film and the n-type carbon nanotube film coated with an antioxidant layer over 30 days in an atmospheric environment with 20% humidity are described by [the relevant data]. Figure 3 It can be seen that the Seebeck coefficients of both the freshly prepared n-type single-walled carbon nanotube film and the n-type carbon nanotube film coated with an antioxidant layer are negative, indicating n-type conductivity. However, with the increase of exposure time, the Seebeck coefficient of the uncoated n-type single-walled carbon nanotube thermoelectric film sample gradually becomes zero, indicating the sensitivity of the original n-type carbon nanotubes to oxygen and the damage caused by oxygen to their thermoelectric properties, causing their conductivity to gradually change from n-type to p-type. Under the same exposure conditions and the same exposure time, the Seebeck coefficient of the sample coated with an antioxidant layer remains basically unchanged after 30 days, indicating that the antioxidant layer protects the n-type carbon nanotubes, enabling the n-type single-walled carbon nanotube thermoelectric film to achieve air stability under low humidity conditions.
[0052] Figure 4 The change in output performance of the aforementioned superhydrophobic and antioxidant n-type single-walled carbon nanotube film over 7 days in an atmospheric environment with an air humidity of ~55% is described by... Figure 4 It can be seen that, compared with the initial performance, the output performance of the device remained basically unchanged after 7 days, indicating that the PDMS-coated film has good hydrophobicity, which prevents the damage of high concentration of water molecules in the air to the n-type carbon nanotubes, enabling the n-type single-walled carbon nanotube thermoelectric film to achieve air stability under high humidity conditions.
[0053] In summary, the method provided by this invention solves the problem of sensitivity to oxygen and moisture in the atmospheric environment during the application of n-type single-walled carbon nanotube films, and is expected to be combined with existing high-performance p-type thermoelectric thin film materials for application in flexible wearable thermoelectric devices. In addition, the oxygen-resistant and hydrophobic methods provided by this invention can also be applied to other materials and devices sensitive to oxygen or moisture.
[0054] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for improving the air stability of n-type single-walled carbon nanotube thermoelectric thin films, characterized in that, Includes the following steps: Polyvinylpyrrolidone, polyvinylidene fluoride and dimethylformamide are mixed to obtain an antioxidant slurry; The antioxidant slurry is used to coat the n-type carbon nanotube membrane to obtain an n-type carbon nanotube membrane coated with an antioxidant layer. After connecting two wires to both ends of the n-type carbon nanotube film coated with an antioxidant layer, superhydrophobic coating is performed to obtain an n-type single-walled carbon nanotube film with superhydrophobicity and antioxidant properties; The concentration of polyvinylpyrrolidone in the antioxidant slurry is 0.20~0.23 g / mL; The concentration of polyvinylidene fluoride in the antioxidant slurry is 0.001~0.005 g / mL.
2. The method as described in claim 1, characterized in that, The coating method involves immersing the n-type carbon nanotube film in the antioxidant slurry and then curing it. The soaking time is 7-10 minutes.
3. The method as described in claim 2, characterized in that, The curing temperature is 80~100℃ and the time is 7~10min.
4. The method as described in claim 1, characterized in that, The superhydrophobic coating uses a superhydrophobic mixture comprising polydimethylsiloxane and a curing agent; The mass ratio of polydimethylsiloxane to curing agent is (9~11):
1.
5. The method as described in claim 1 or 4, characterized in that, The curing temperature of the superhydrophobic coating is 100~150℃, and the curing time is 10~35min.