Super-hydrophobic film for enhancing and stabilizing thermoelectric conversion of thermoelectric device, preparation method and application

Abstract

The invention discloses a super-hydrophobic film for enhancing and stabilizing thermoelectric conversion of a thermoelectric device, a preparation method and application. The preparation method comprises the following steps: firstly, preparing a polyurethane nanofiber film by adopting electrostatic spinning; then, the PU / PDMS / SiO2 composite film is soaked in PDMS / SiO2 composite dispersion liquid for ultrasonic treatment, and after drying, the PU / PDMS / SiO2 composite film is obtained; and finally, adhering the composite film to the cold end of a thermoelectric device to obtain a PU / PDMS / SiO2 film-thermoelectric device composite system. The contact angle between the composite film prepared by the method and water drops is greater than 150 degrees; the prepared film has high reflectivity, the temperature of the cold end of the thermoelectric device can be reduced, and the thermoelectric output performance of the thermoelectric device is enhanced; the thin film adhered to the thermoelectric device can prevent the thermoelectric device from being interfered even in outdoor environments such as environmental pollution and rain wash, and stable thermoelectric conversion is maintained; a new way is provided for efficient and stable thermoelectric conversion of a thermoelectric system, and the application field of thermoelectric devices is widened.

Description

Technical Field

[0001] The present invention belongs to the technical field of super-hydrophobic materials, and in particular relates to a super-hydrophobic film for enhancing and stabilizing thermoelectric conversion of a thermoelectric device, and also relates to a preparation method and application of a super-hydrophobic film for enhancing and stabilizing thermoelectric conversion of a thermoelectric device. Background Art

[0002] Thermoelectric technology is an important way to achieve the mutual conversion of thermal energy and electrical energy. It has the characteristics of no pollution, no noise, and easy miniaturization. It has potential applications in deep space exploration, heat recovery, fire warning, flexible wearables and other fields. However, low thermoelectric output performance limits the development and practical application of thermoelectric devices and materials. The limited temperature gradient is a key factor affecting the output of thermoelectric systems. At the same time, the carrier transmission path in the thermoelectric system is easily disturbed by the liquid or outdoor environment, affecting the stability of thermoelectric conversion.

[0003] Therefore, while maintaining the device's efficient thermoelectric output, improving stability is the key to its development. Existing cooling methods that use air cooling or liquid cooling at the cold end of thermoelectric devices have achieved improved output performance of thermoelectric devices, but this method requires large equipment, consumes a lot of energy, and is costly. Attaching a film that can achieve cooling to the cold end of a thermoelectric device is also a way to improve thermoelectric conversion. However, such films are susceptible to dust accumulation or rainwater immersion during long-term outdoor use, and the cooling effect will gradually deteriorate, thereby affecting the stability of the thermoelectric device.

[0004] Superhydrophobic surfaces have attracted widespread attention in the fields of energy conversion, flexible wearables, anti-icing, and anti-fogging due to their excellent waterproof and anti-pollution properties. A superhydrophobic surface refers to a surface on which the contact angle of a water droplet is greater than 150° and the rolling angle is less than 5°. Micro-nano rough structures and low surface energy materials are two necessary conditions for constructing superhydrophobic surfaces. Researchers generally prepare superhydrophobic materials by treating the rough structure surface with low surface energy materials or constructing rough structures on the surface of low surface energy materials.

[0005] By optimizing the polymer of the super-hydrophobic material and regulating its microstructure, the optical properties can be optimized to reduce the temperature of the cold end of the thermoelectric device and increase the temperature difference between the hot and cold ends of the thermoelectric device, thereby improving the output performance of the thermoelectric device. The super-hydrophobic material on the surface of the thermoelectric device can also greatly reduce the contact area between the water droplets and the material surface and roll off the surface easily, which can not only prevent it from being wetted by liquid but also take away the dust deposited on the surface, presenting a self-cleaning function, so as to achieve efficient and stable conversion of thermoelectric devices in different environments and improve their service life in outdoor environments. Summary of the invention

[0006] The first purpose of the present invention is to provide a method for preparing a super-hydrophobic film that enhances and stabilizes the thermoelectric conversion of thermoelectric devices, thereby solving the problem that the existing cooling film used at the cold end of thermoelectric devices is affected by environmental pollution and water droplet erosion, which affects the stable thermoelectric conversion.

[0007] The second object of the present invention is to provide a super-hydrophobic film for enhancing and stabilizing the thermoelectric conversion of a thermoelectric device, and the application of the super-hydrophobic film.

[0008] The first technical solution adopted by the present invention is a method for preparing a super-hydrophobic film for enhancing and stabilizing the thermoelectric conversion of thermoelectric devices. The specific operating steps are as follows: a polyurethane (PU) nanofiber membrane is prepared by an electrospinning method; then, the PU membrane is immersed in a polydimethylsiloxane (PDMS) / SiO2 composite dispersion for ultrasonic treatment, and then dried to obtain a PU / PDMS / SiO2 composite film.

[0009] Furthermore, the concentration of PU nanofiber membrane in the spinning solution was 13%~16%; the electrospinning voltage was set to 14~18 KV, the injection pump propulsion rate was 0.8~1.2 ml / h, and the distance from the syringe needle to the receiving roller was 8~12 cm. The morphology of the PU nanofiber membrane was controlled by adjusting the spinning parameters.

[0010] Furthermore, in the PDMS / SiO2 composite dispersion, the concentration of SiO2 is 0.5%~0.9%, and the concentration of PDMS is 3%~6%.

[0011] Furthermore, the preparation method of the PDMS / SiO2 composite dispersion is: adding SiO2 to an ethyl acetate solution of PDMS to prepare the PDMS / SiO2 composite dispersion.

[0012] Furthermore, the ultrasonic time of the PU nanofiber membrane in the PDMS / SiO2 composite dispersion is 1 to 1.5 h.

[0013] The second technical solution adopted by the present invention is to prepare a super-hydrophobic film using a super-hydrophobic film preparation method for enhancing and stabilizing thermoelectric conversion of thermoelectric devices, wherein the static contact angle between the super-hydrophobic film and water droplets is greater than 150°.

[0014] The third technical solution adopted by the present invention is to stick the PU / PDMS / SiO2 composite film to the cold end of the thermoelectric device to obtain a superhydrophobic film / thermoelectric device composite system; and utilize the optical properties and superhydrophobic properties of the PU / PDMS / SiO2 composite film to enhance and stabilize the thermoelectric conversion of the thermoelectric device.

[0015] The beneficial effects of the present invention are: The static contact angle between the prepared super-hydrophobic film and water droplets of the present invention is greater than 150°; the super-hydrophobic film has high reflectivity and emissivity, and when attached to the cold end of a thermoelectric device, it can significantly reduce its surface temperature, increase the temperature difference, and thus improve the thermoelectric output performance of the thermoelectric device. Furthermore, the super-hydrophobic film covering the surface of the thermoelectric device can enable it to maintain stable thermoelectric output when it is contaminated by soil and flushed by liquid. The present invention provides an effective way for efficient and stable thermoelectric conversion of thermoelectric materials and devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The SEM image of the surface of the super-hydrophobic film of the present invention and the change of contact angle.

[0017] Figure 2 is the reflectivity of the super-hydrophobic film of the present invention.

[0018] Figure 3 Schematic diagram showing the comparison of temperature and output voltage between the super-hydrophobic film / thermoelectric device system of the present invention and the original thermoelectric device.

[0019] Figure 4 It is a schematic diagram comparing the output voltages of the super-hydrophobic film / thermoelectric device system of the present invention and the common film / thermoelectric device system after slurry treatment.

[0020] Figure 5 Schematic diagram showing the comparison of the output voltages of the superhydrophobic film / thermoelectric device system of the present invention and the original thermoelectric device after water droplet treatment. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with examples and specific implementation modes, but the present invention is not limited thereto.

[0022] Example 1 Step 1: Preparation of polyurethane (PU) nanofiber membrane: Weigh 13% PU and dissolve it in a mixed solvent of N,N-dimethylformamide (DMF) and tetrahydrofuran (THF), and stir it thoroughly. Adjust the spinning voltage of the electrospinning device to 14KV and the injection pump propulsion rate to 1 ml / h.

[0023] Step 2: Preparation of PU / PDMS / SiO2 composite film: Add SiO2 with a concentration of 0.7% to an ethyl acetate solution of PDMS with a concentration of 3% to prepare a PDMS / SiO2 composite dispersion, and immerse the PU nanofiber membrane in the PDMS / SiO2 composite dispersion and ultrasonically treat it for 1 h to obtain a PU / PDMS / SiO2 composite film.

[0024] The composite film prepared in this embodiment has a reflectivity of 91%, an emissivity of 92%, and a contact angle with a water droplet of 152°.

[0025] Step 3: Paste the PU / PDMS / SiO2 film to the cold end of the thermoelectric device to obtain a superhydrophobic film / thermoelectric device composite system.

[0026] Compared with the original thermoelectric device, the superhydrophobic film has a cold-end temperature 3°C lower than the original thermoelectric device. The output voltage of the system is increased by 8 mV, and stable conversion of thermoelectric signals can be achieved even under soil contamination and water droplet erosion.

[0027] Example 2 Step 1: Preparation of PU nanofiber membrane: Weigh 16% PU and dissolve it in a mixed solvent of DMF and THF, and stir it thoroughly. Adjust the spinning voltage of the electrospinning device to 16 KV and the injection pump propulsion rate to 0.8 ml / h.

[0028] Step 2: Preparation of PU / PDMS / SiO2 composite film: Add SiO2 with a concentration of 0.5% to an ethyl acetate solution of PDMS with a concentration of 4% to prepare a PDMS / SiO2 composite dispersion, and immerse the PU nanofiber membrane in the PDMS / SiO2 composite dispersion and ultrasonically treat it for 1 h to obtain a PU / PDMS / SiO2 composite film.

[0029] The reflectivity of the composite film prepared in this embodiment is 92%, the emissivity is 93%, and the contact angle with the water droplet is 151°.

[0030] Step 3: Paste the PU / PDMS / SiO2 film to the cold end of the thermoelectric device to obtain a superhydrophobic film / thermoelectric device composite system.

[0031] Compared with the original thermoelectric device, the cold end temperature of the superhydrophobic film is 3.2°C lower than that of the original thermoelectric device. The output voltage of the system is increased by 10 mV, and stable conversion of thermoelectric signals can be achieved under mud treatment and water droplet flushing.

[0032] Example 3 Step 1: Preparation of PU nanofiber membrane: Weigh 14% PU and dissolve it in a mixed solvent of DMF and THF, and stir it thoroughly. Adjust the spinning voltage of the electrospinning device to 18 KV and the injection pump propulsion rate to 1.2 ml / h.

[0033] Step 2: Preparation of PU / PDMS / SiO2 composite film: Add SiO2 with a concentration of 0.9% to an ethyl acetate solution of PDMS with a concentration of 6% to prepare a PDMS / SiO2 composite dispersion, and immerse the PU nanofiber membrane in the PDMS / SiO2 composite dispersion and ultrasonically treat it for 1.2 h to obtain a PU / PDMS / SiO2 composite film.

[0034] The composite film prepared in this embodiment has a reflectivity of 93%, an emissivity of 94%, and a contact angle with a water droplet of 154°.

[0035] Step 3: Paste the PU / PDMS / SiO2 film to the cold end of the thermoelectric device to obtain a superhydrophobic film / thermoelectric device composite system.

[0036] Compared with the original thermoelectric device, the cold end temperature of the superhydrophobic film is 3.5°C lower than that of the original thermoelectric device. The output voltage of the system is increased by 10 mV, and stable conversion of thermoelectric signals can be achieved under mud treatment and water droplet flushing.

[0037] Example 4 Step 1: Preparation of PU nanofiber membrane: Weigh 15% PU and dissolve it in a mixed solvent of DMF and THF, and stir it thoroughly. Adjust the spinning voltage of the electrospinning device to 16 KV and the injection pump propulsion rate to 1 ml / h.

[0038] Step 2: Preparation of PU / PDMS / SiO2 composite film: SiO2 with a concentration of 0.8% was added to an ethyl acetate solution of PDMS with a concentration of 5% to prepare a PDMS / SiO2 composite dispersion, and the PU nanofiber membrane was immersed in the PDMS / SiO2 composite dispersion and ultrasonically treated for 1.5 h to obtain a PU / PDMS / SiO2 composite film; The composite film prepared in this embodiment has a reflectivity of 94%, an emissivity of 95%, and a contact angle with a water droplet of 154°.

[0039] Step 3: Paste the PU / PDMS / SiO2 film to the cold end of the thermoelectric device to obtain a superhydrophobic film / thermoelectric device composite system.

[0040] Compared with the original thermoelectric device, the superhydrophobic film has a cold-end temperature 3.7°C lower than the original thermoelectric device. The output voltage of the system is increased by 12 mV, and stable conversion of thermoelectric signals can be achieved under mud treatment and water droplet flushing.

[0041] Example 5 Step 1: Preparation of PU nanofiber membrane: Weigh 15% PU and dissolve it in a mixed solvent of DMF and THF, and stir it thoroughly. Adjust the spinning voltage of the electrospinning device to 16 KV and the injection pump propulsion rate to 1 ml / h.

[0042] Step 2: Preparation of PU / PDMS / SiO2 composite film: Add SiO2 with a concentration of 0.9% to an ethyl acetate solution of PDMS with a concentration of 3% to prepare a PDMS / SiO2 composite dispersion, and immerse the PU nanofiber membrane in the PDMS / SiO2 composite dispersion and ultrasonically treat it for 1.5 h to obtain a PU / PDMS / SiO2 composite film.

[0043] The composite film prepared in this embodiment has a reflectivity of 91%, an emissivity of 92%, and a contact angle with a water droplet of 152°.

[0044] Step 3: Paste the PU / PDMS / SiO2 film to the cold end of the thermoelectric device to obtain a superhydrophobic film / thermoelectric device composite system.

[0045] Compared with the original thermoelectric device, the superhydrophobic film has a cold-end temperature 3°C lower than the original thermoelectric device, and the output voltage of the system is increased by 8 mV. Stable conversion of thermoelectric signals can also be achieved under mud treatment and water droplet flushing.

[0046] Example 6 The key synthesis principle of the present invention: 1. This application uses ultrasonic assembly to assemble the PDMS / SiO2 dispersion on the surface of the PU film. The micro-nano rough structure formed by the agglomeration of SiO2 particles and the low surface energy provided by PDMS make the PU / PDMS / SiO2 film reach a super-hydrophobic state with a contact angle greater than 150°. The super-hydrophobic property of the film prevents the thermoelectric device from being contaminated to maintain a stable thermoelectric conversion effect.

[0047] 2. Due to the porous structure formed by the PU nanofiber membrane during the electrospinning process, it can provide efficient Mie scattering. Combined with the high emission characteristics of PDMS and SiO2, the composite film exhibits a good cooling effect, reduces the temperature of the cold end of the thermoelectric device, increases the temperature difference, and thus improves the thermoelectric output performance of the device.

[0048] like Figure 1 As shown, it can be seen that the SiO2 particles in the film prepared by the present invention are distributed on the surface and inside of the PU nanofiber membrane, forming a micro-nano rough structure combined with the low surface energy of PDMS, so that the PU / PDMS / SiO2 film reaches a superhydrophobic state with a contact angle greater than 150°.

[0049] like Figure 2 As shown, it can be seen that the PU / PDMS / SiO2 film prepared by the present invention has high reflectivity at 0.3-2.5 μm and high emissivity at 8-13 μm.

[0050] like Figure 3As shown, the PU / PDMS / SiO2 composite film prepared by the present invention can reduce the temperature of the cold end of the thermoelectric device. The thermoelectric device covered with the PU / PDMS / SiO2 film increases the thermoelectric output performance of the original device under the same environment, and can increase the output performance of the original thermoelectric device by about twice.

[0051] like Figure 4 As shown, the output performance of a thermoelectric device covered with a superhydrophobic PU / PDMS / SiO2 film and a thermoelectric device covered with a PU film before and after soil treatment was compared, indicating that the superhydrophobic property of the PU / PDMS / SiO2 composite film prepared by the present invention can protect the film from contamination to maintain the stability of the output of the thermoelectric device.

[0052] like Figure 5 As shown, the output performance of the thermoelectric device covered with the superhydrophobic PU / PDMS / SiO2 film and the original thermoelectric device before and after the water droplet fell are compared, indicating that the superhydrophobic property of the film can protect the thermoelectric device from liquid interference to maintain the stability of the thermoelectric output.

[0053] The above description is only a partial implementation scheme of the present invention, not all or the only implementation scheme. Any equivalent transformation of the technical scheme of the present invention made by ordinary technicians in this field after reading the specification of the present invention is the synthesis principle of the key steps in the present invention covered by the claims of the present invention.

Claims

1. A method for preparing a super-hydrophobic film for enhancing and stabilizing thermoelectric conversion of thermoelectric devices, characterized in that: The specific steps are as follows: The polyurethane nanofiber membrane was prepared by an electrospinning method; then, the polyurethane nanofiber membrane was immersed in a polydimethylsiloxane / SiO2 composite dispersion for ultrasonic treatment and dried to obtain a PU / PDMS / SiO2 composite film.

2. The method for preparing a super-hydrophobic film for enhancing and stabilizing thermoelectric conversion of thermoelectric devices according to claim 1, characterized in that: The concentration of the polyurethane nanofiber membrane in the spinning solution is 13%-16%; the electrospinning voltage is set to 14-18KV, and the injection pump propulsion rate is 0.8-1.2 ml / h.

3. The method for preparing a super-hydrophobic film for enhancing and stabilizing thermoelectric conversion of thermoelectric devices according to claim 1, wherein in the polydimethylsiloxane / SiO2 composite dispersion, the concentration of SiO2 is 0.5% to 0.9%, and the concentration of PDMS is 3% to 6%.

4. The method for preparing a super-hydrophobic film for enhancing and stabilizing thermoelectric conversion of a thermoelectric device according to claim 3, wherein the preparation method of the polydimethylsiloxane / SiO2 is: adding SiO2 to an ethyl acetate solution of polydimethylsiloxane to prepare a polydimethylsiloxane / SiO2 composite dispersion.

5. The method for preparing a super-hydrophobic film for enhancing and stabilizing thermoelectric conversion of thermoelectric devices according to claim 1, characterized in that: The polyurethane nanofiber membrane is ultrasonically treated in the polydimethylsiloxane / SiO2 composite dispersion for 1-1.5 hours.

6. The method for preparing a super-hydrophobic film for enhancing and stabilizing thermoelectric conversion of thermoelectric devices according to claim 1, characterized in that: The contact angle between the PU / PDMS / SiO2 composite film and a water droplet is greater than 150°.

7. A super-hydrophobic film for enhancing and stabilizing thermoelectric conversion of thermoelectric devices, characterized in that: The super-hydrophobic film is prepared by the method for preparing the super-hydrophobic film for enhancing and stabilizing the thermoelectric conversion of thermoelectric devices as described in any one of claims 1 to 6.

8. Application of super-hydrophobic film for enhancing and stabilizing thermoelectric conversion of thermoelectric devices, characterized in that: The PU / PDMS / SiO2 composite film was pasted on the cold end of the thermoelectric device to obtain a superhydrophobic film / thermoelectric device composite system.

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