Preparation method of flexible n-type nylon-based silver selenide thermoelectric film

Abstract

The application discloses a preparation method of a flexible N-type nylon-based silver selenide thermoelectric film, which comprises the following steps: synthesizing silver selenide particles by a solvent thermal method, uniformly dispersing the silver selenide particles in ethylene glycol, uniformly dropping and coating the silver selenide particles on a glass fiber filter film, and performing a spark plasma sintering (SPS) treatment to obtain a uniform and dense flexible nylon-based silver selenide film. The film prepared by the method has excellent thermoelectric performance; the spark plasma sintering (SPS) process can be used to control the micro-morphology of the film and the carrier transport characteristics, the silver content in the film is reduced, an ordered fiber structure is formed, the carrier concentration is reduced, the carrier mobility is improved, the Seebeck coefficient and the electrical conductivity are simultaneously enhanced, the method is simple in process, short in preparation period, safe and pollution-free, the film prepared by the method has excellent thermoelectric performance and good flexibility.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of new energy materials, in particular to a preparation method of a flexible N-type nylon-based silver selenide thermoelectric film. BACKGROUND

[0002] At present, with the rise of the Internet of Things era, wearable electronic devices and other products have achieved rapid development, and have broad application prospects in the fields of medical devices, environmental monitoring, intelligent clothing and the like. In recent years, the miniaturization and flexibility trend of wearable electronic devices has promoted the research process of flexible thermoelectric film devices. The flexible thermoelectric film material has the characteristics of light weight, good mechanical flexibility and low cost, and provides potential for the development and application of future wearable electronic devices.

[0003] Silver selenide has high intrinsic electrical conductivity and Seebeck coefficient at room temperature, and excellent thermoelectric performance, and is expected to meet the requirements of flexible device applications. However, due to the limitation of the preparation method, the thermoelectric performance of the flexible film prepared by cold pressing, hot pressing, printing, thermal evaporation and the like is far less than that of the silver selenide-based bulk body. Therefore, a more effective technology should be explored to prepare a silver selenide-based film with excellent performance and good flexibility. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of a flexible N-type nylon-based silver selenide thermoelectric film. The silver selenide particles are first synthesized by a solvothermal method, then uniformly dispersed in ethylene glycol, and then uniformly drop-coated on a glass fiber filter film, and then subjected to a spark plasma sintering (SPS) treatment to obtain a uniform and dense flexible nylon-based silver selenide film with excellent thermoelectric performance. This method not only reduces the silver content in the film, but also forms an ordered fiber structure, thereby reducing the carrier concentration and improving the carrier mobility, so that the Seebeck coefficient and the electrical conductivity are simultaneously enhanced. The method is simple in process, short in preparation period, safe and pollution-free, and the obtained film has excellent thermoelectric performance and good flexibility.

[0005] The present application is realized by the following technical solutions:

[0006] A preparation method of a flexible N-type nylon-based silver selenide thermoelectric film, comprising the following steps:

[0007] (1) Silver nitrate and selenium powder with a molar ratio of (2.1-2.5):1 are respectively dissolved in ethylenediamine, stirred, and then poured into a reaction kettle, and the reaction kettle is placed in a blast drying oven at 180 DEG C for 5h, and the obtained product is sequentially washed by centrifugation with deionized water and ethanol for 2-3 times, and then the washed silver selenide particles are ultrasonically dispersed into 10mL of ethylene glycol to obtain a uniform silver selenide dispersion liquid; the concentration of silver selenide is 25-35mg / mL;

[0008] (2) Under the condition of vacuum filtration assistance, the silver selenide dispersion solution obtained in step (1) is uniformly drop-coated on the glass fiber filter membrane, and the drop-coating amount of the silver selenide dispersion solution is 1-2 mL / cm 2 After the liquid is dried, the silver selenide film adhered to the glass fiber filter membrane is obtained by drying in a vacuum oven at 60℃;

[0009] (3) The silver selenide film adhered to the glass fiber filter membrane obtained in step (2) is placed between two nylon filter membranes, and is formed by spark plasma sintering (SPS), the sintering temperature is 100-200℃, the sintering time is 1-9 min, and the pressure is 30-50 MPa, then the nylon filter membrane on the back of the glass fiber filter membrane is removed, and the glass fiber filter membrane fragments on the surface of the silver selenide film are wiped off, to obtain a flexible N-type nylon-based silver selenide thermoelectric film.

[0010] Preferably, the molar ratio of silver nitrate and selenium powder in step (1) is 2.3:1, and the concentration of silver selenide is 28-32 mg / mL.

[0011] Preferably, the drop-coating amount of the silver selenide dispersion solution in step (2) is 1.2 mL / cm 2 .

[0012] Preferably, the sintering temperature of the spark plasma sintering (SPS) process in step (3) is 130-200℃, the sintering time is 1-7 min, and the pressure is 30 MPa.

[0013] The beneficial effects of the present application are as follows:

[0014] 1) The silver selenide particles synthesized by the solvothermal method in the present application can be uniformly dispersed in ethylene glycol, and can be uniformly drop-coated on the glass fiber filter membrane, and then subjected to spark plasma sintering (SPS) treatment, to obtain a uniform and dense flexible nylon-based silver selenide film.

[0015] 2) The flexible N-type nylon-based silver selenide thermoelectric film is prepared for the first time by using the spark plasma sintering (SPS) process, the micro-morphology and silver content of the film are controlled by optimizing the sintering process, the silver content in the film is reduced, an ordered fiber structure is formed, thereby reducing the carrier concentration and improving the carrier mobility, so that the Seebeck coefficient and electrical conductivity are simultaneously enhanced, thereby further improving the thermoelectric performance. The method is simple in process, short in preparation period, safe and pollution-free, simple and controllable, compared with the preparation methods such as cold pressing, hot pressing, printing and thermal evaporation, the thermoelectric performance of the film prepared by the present application is more excellent, and the mechanical flexibility is better. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1is a surface scanning electron microscope photograph of the silver selenide film adhered to the glass fiber filter membrane obtained in step (2) of Example 1 of the present application.

[0017] Figure 2 is a surface scanning electron microscope photograph of the flexible N-type nylon-based silver selenide thermoelectric film obtained in step (3) of Example 1 of the present application.

[0018] Figure 3 is a cross-sectional scanning electron microscope photograph of the flexible N-type nylon-based silver selenide thermoelectric film obtained in Example 1 of the present application.

[0019] Figure 4 is a relationship between the electrical conductivity and the power factor of the flexible N-type nylon-based silver selenide thermoelectric film obtained in Example 1 of the present application and the temperature.

[0020] Figure 5 is a relationship between the electrical resistance and the bending radius of the flexible N-type nylon-based silver selenide thermoelectric film obtained in Example 1 of the present application.

[0021] Figure 6 is a cross-sectional scanning electron microscope photograph of the silver selenide film adhered to the glass fiber filter membrane obtained in Comparative Example 1 of the present application.

[0022] Figure 7 is a relationship between the electrical conductivity and the power factor of the flexible N-type nylon-based silver selenide thermoelectric film obtained in Comparative Example 1 of the present application and the temperature.

[0023] Figure 8 is a relationship between the electrical conductivity and the power factor of the flexible N-type nylon-based silver selenide thermoelectric film obtained in Example 2 of the present application and the temperature. DETAILED DESCRIPTION

[0024] The following is a further description of the present application, but is not a limitation of the present application.

[0025] Example 1: A method for preparing a flexible N-type nylon-based silver selenide thermoelectric film

[0026] (1) Silver nitrate and selenium powder in a molar ratio of 2.3:1 were dissolved in 7.5 mL and 10 mL of ethylenediamine, respectively, and stirred for 30 min, and then poured into a 25 mL reaction kettle, and the reaction kettle was placed in a blast drying oven at 180°C for 5 h; the obtained product was washed by centrifugation with deionized water and ethanol alternately for 2-3 times, and then the washed silver selenide particles were ultrasonically dispersed into 10 mL of ethylene glycol to obtain a uniform silver selenide dispersion; the concentration of the silver selenide was 29 mg / mL;

[0027] (2) Under vacuum filtration assistance, the silver selenide dispersion obtained in step (1) was uniformly drop-coated onto a 20mm*5mm glass fiber filter membrane. The drop-coating amount of the silver selenide dispersion was 1.2mL / cm². 2 After the liquid is removed, it is dried in a vacuum oven at 60°C to obtain a silver selenide film adhered to the glass fiber filter membrane. A scanning electron microscope image of the film surface is shown below. Figure 1 As shown;

[0028] (3) The silver selenide film adhered to the glass fiber filter membrane obtained in step (2) is placed between two nylon filter membranes and formed by spark plasma sintering (SPS) at a temperature of 200℃, a sintering time of 5 min, and a pressure of 30 MPa. Then, the nylon filter membrane on the back of the glass fiber filter membrane is removed, and the glass fiber filter membrane fragments on the surface of the silver selenide film are wiped away to obtain a flexible N-type nylon-based silver selenide thermoelectric film. The scanning electron microscope image of its surface is shown below. Figure 2 As shown, the scanning electron microscope image of its cross-section is as follows: Figure 3 As shown, its conductivity and power factor are as follows: Figure 4 As shown, the relationship between its resistance and bending radius is as follows: Figure 5 As shown. By Figure 1 , 2 It is known that, under the combined effects of temperature and pressure in the spark plasma sintering (SPS) process, silver selenide particles are compressed and stacked together, resulting in grain growth and a denser film with higher electrical conductivity. Figure 4 It can be seen that the silver selenide thermoelectric film attached to the nylon substrate has better mechanical flexibility. When the bending radius is 2.5 mm, the resistance of the film remains almost unchanged, indicating that the prepared film has good flexibility.

[0029] Comparative Example 1:

[0030] (1) Silver nitrate and selenium powder with a molar ratio of 2.3:1 were dissolved in 7.5 mL and 10 mL of ethylenediamine, respectively. After stirring for 30 min, the mixture was poured into a 25 mL reaction vessel and placed in a forced-air drying oven at 180 °C for 5 h. The resulting product was washed 2-3 times by alternating centrifugation with deionized water and ethanol. The washed silver selenide particles were then ultrasonically dispersed in 10 mL of ethylene glycol to obtain a uniform silver selenide dispersion. The concentration of silver selenide was 29 mg / mL.

[0031] (2) Under vacuum filtration assistance, the silver selenide dispersion obtained in step (1) was uniformly drop-coated onto a 20mm*5mm glass fiber filter membrane. The drop-coating amount of the silver selenide dispersion was 1.2mL / cm². 2 After the liquid is removed, it is dried in a vacuum oven at 60°C to obtain a silver selenide film adhered to the glass fiber filter membrane.

[0032] (3) The silver selenide film adhered to the glass fiber filter membrane obtained in step (2) is placed between two nylon filter membranes and cold-pressed at 30 MPa using a tablet press. Then, the nylon filter membrane on the back of the glass fiber filter membrane is removed, and the glass fiber filter membrane fragments on the surface of the silver selenide film are wiped away to obtain a flexible N-type nylon-based silver selenide thermoelectric film. A scanning electron microscope image of its cross-section is shown below. Figure 6 As shown ( Figure 6 Compared with Example 1 Figure 3 In comparison, it can be seen that the discharge plasma sintering (SPS) treatment alters the composition and morphology of the film, forming an ordered fibrous texture and changing the carrier transport characteristics of the silver selenide film. Its conductivity and power factor are as follows: Figure 7 As shown.

[0033] As can be seen from Example 1 and Comparative Example 1, the product obtained in Example 1 has significantly enhanced conductivity and power factor due to the change in carrier concentration and mobility of the thin film caused by plastic deformation, and thus has greater application prospects.

[0034] Comparative Example 2:

[0035] Silver selenide nanowires were prepared using the synthesis method described in the reference "Ultrahigh Performance of n-Type Ag2Se Films for Flexible Thermoelectric Power Generators" (Cong Jiang and Yufei Ding, DOI:10.1021 / acsami.9b21069), and then nylon-based silver selenide thermoelectric films were prepared using the sintering method of this invention.

[0036] (1) Pure selenium dioxide (0.1 g) and β-cyclodextrin (0.1 g) were added to a beaker containing 10 mL of deionized water and stirred for 10 min to obtain a clear solution. This solution was immediately poured into another beaker containing ascorbic acid solution (20 mL, 0.028 M) while continuously stirring. The mixture rapidly changed from colorless to yellow. Subsequently, a brick-red suspension was formed, indicating the formation of amorphous selenium. After reacting for 4 h, the product was collected by alternating centrifugation with deionized water and ethanol, and then redispersed in ethanol and aged for 2 h without stirring. During this process, the mixture changed from brick-red to metallic gray, yielding selenium nanowires.

[0037] (2) Using 20 mL of ethylene glycol dispersion of selenium nanowires as a template, the mixture was reacted with silver nitrate at 40 °C for 2 h. The molar ratio of silver nitrate to selenium powder was 2.3:1. After centrifugation, the silver selenide nanostructure was obtained. The silver selenide nanowires were then dispersed in 10 mL of anhydrous ethanol.

[0038] (3) The obtained silver selenide nanowire dispersion liquid was uniformly drop-coated on a 20 mm*5 mm glass fiber filter membrane under the condition of vacuum filtration assistance, and the drop-coating amount of the silver selenide dispersion liquid was 1.2 mL / cm 2 After the liquid was dried, the product was dried in a vacuum oven at 60°C to obtain a silver selenide film adhered to the glass fiber filter membrane.

[0039] (4) The obtained silver selenide film adhered to the glass fiber filter membrane was placed between two nylon filter membranes and subjected to spark plasma sintering (SPS) molding, the sintering temperature was 200°C, the sintering time was 5 min, and the pressure was 30 MPa. Then, the nylon filter membrane on the back of the glass fiber filter membrane was removed, and the glass fiber filter membrane fragments on the surface of the silver selenide film were wiped off to obtain a flexible N-type nylon-based silver selenide thermoelectric film. The power factor of the film at 30°C was only 471.03 μW / (mK 2 ). The silver selenide dispersion liquid prepared by this method had poor dispersibility, the thickness of the finally prepared silver selenide film was uneven, the resistance was large, and thus the performance was poor.

[0040] As can be seen from Example 1 and Comparative Example 2, in Example 1, the silver selenide particles synthesized by the solvothermal method can be uniformly dispersed in ethylene glycol, and thus can be uniformly drop-coated on the glass fiber filter membrane. Then, after being subjected to spark plasma sintering (SPS) treatment, a uniform and dense nylon-based silver selenide film can be obtained, the thermoelectric performance is excellent, and the flexibility is good.

[0041] Example 2:

[0042] (1) Silver nitrate and selenium powder with a molar ratio of 2.3:1 were respectively dissolved in 7.5 mL and 10 mL of ethylenediamine, and after stirring for 30 min, they were poured into a 25 mL reaction kettle. The reaction kettle was placed in a blast drying oven and reacted at 180°C for 5 h. The obtained product was sequentially washed by centrifugation with deionized water and ethanol for 2-3 times, and then the washed silver selenide particles were ultrasonically dispersed in 10 mL of ethylene glycol to obtain a uniform silver selenide dispersion liquid. The concentration of the silver selenide was 29 mg / mL;

[0043] (2) The silver selenide dispersion liquid obtained in step (1) was uniformly drop-coated on a 20 mm*5 mm glass fiber filter membrane under the condition of vacuum filtration assistance, and the drop-coating amount of the silver selenide dispersion liquid was 1.2 mL / cm 2 . After the liquid was dried, the product was dried in a vacuum oven at 60°C to obtain a silver selenide film adhered to the glass fiber filter membrane;

[0044] (3) The silver selenide film adhered to the glass fiber filter membrane obtained in step (2) is placed between two nylon filter membranes, and is formed by spark plasma sintering (SPS), with a sintering temperature of 130°C, a sintering time of 1 min, and a pressure of 30 MPa. Then, the nylon filter membrane on the back of the glass fiber filter membrane is removed, and the glass fiber filter membrane fragments on the surface of the silver selenide film are wiped off, to obtain a flexible N-type nylon-based silver selenide thermoelectric film. The conductivity and power factor thereof are as shown in Table 1. Figure 8

[0045] Example 3

[0046] (1) Silver nitrate and selenium powder with a molar ratio of 2.3:1 are respectively dissolved in 7.5 mL and 10 mL of ethylenediamine, and after stirring for 30 min, they are poured into a 25 mL reaction kettle. The reaction kettle is placed in a blast drying oven at 180°C for 5 h. The obtained product is sequentially washed by centrifugation with deionized water and ethanol for 2-3 times. Then, the washed silver selenide particles are ultrasonically dispersed into 10 mL of ethylene glycol to obtain a uniform silver selenide dispersion liquid. The concentration of silver selenide is 29 mg / mL.

[0047] (2) Under the condition of vacuum filtration assistance, the silver selenide dispersion liquid obtained in step (1) is uniformly drop-coated on a 20 mm*5 mm glass fiber filter membrane, and the drop-coating amount of the silver selenide dispersion liquid is 1.2 mL / cm 2 . After the liquid is dried, it is dried in a vacuum oven at 60°C to obtain a silver selenide film adhered to the glass fiber filter membrane;

[0048] (3) The silver selenide film adhered to the glass fiber filter membrane obtained in step (2) is placed between two nylon filter membranes, and is formed by spark plasma sintering (SPS), with a sintering temperature of 150°C, a sintering time of 1 min, and a pressure of 30 MPa. Then, the nylon filter membrane on the back of the glass fiber filter membrane is removed, and the glass fiber filter membrane fragments on the surface of the silver selenide film are wiped off, to obtain a flexible N-type nylon-based silver selenide thermoelectric film. The power factor thereof at 30°C is 2920.01 μW / (mK 2 ).

[0049] Example 4

[0050] (1) Silver nitrate and selenium powder with a molar ratio of 2.3:1 are respectively dissolved in 7.5 mL and 10 mL of ethylenediamine, and after stirring for 30 min, they are poured into a 25 mL reaction kettle. The reaction kettle is placed in a blast drying oven at 180°C for 5 h. The obtained product is sequentially washed by centrifugation with deionized water and ethanol for 2-3 times. Then, the washed silver selenide particles are ultrasonically dispersed into 10 mL of ethylene glycol to obtain a uniform silver selenide dispersion liquid. The concentration of silver selenide is 29 mg / mL.

[0051] ​(2) The silver selenide dispersion solution obtained in step (1) is uniformly drop-coated on a 20 mm*5 mm glass fiber filter membrane under the condition of vacuum filtration assistance, and the drop-coating amount of the silver selenide dispersion solution is 1.2 mL / cm 2 After the liquid is dried, the silver selenide film adhered to the glass fiber filter membrane is obtained by drying in a vacuum oven at 60°C;

[0052] (3) The silver selenide film adhered to the glass fiber filter membrane obtained in step (2) is placed between two nylon filter membranes, and is formed by spark plasma sintering (SPS), with a sintering temperature of 200°C, a sintering time of 1 min, and a pressure of 30 MPa. Then, the nylon filter membrane on the back of the glass fiber filter membrane is removed, and the glass fiber filter membrane fragments on the surface of the silver selenide film are wiped off, to obtain a flexible N-type nylon-based silver selenide thermoelectric film. The power factor of the film at 30°C is 3038.33 μW / (mK 2 ).

[0053] Example 5:

[0054] (1) Silver nitrate and selenium powder with a molar ratio of 2.3:1 are respectively dissolved in 7.5 mL and 10 mL of ethylenediamine, and after stirring for 30 min, they are poured into a 25 mL reaction kettle. The reaction kettle is placed in a blast drying oven and reacted at 180°C for 5 h. The obtained product is sequentially washed by centrifugation with deionized water and ethanol for 2-3 times. Then, the washed silver selenide particles are ultrasonically dispersed into 10 mL of ethylene glycol to obtain a uniform silver selenide dispersion solution. The concentration of the silver selenide is 29 mg / mL;

[0055] (2) The silver selenide dispersion solution obtained in step (1) is uniformly drop-coated on a 20 mm*5 mm glass fiber filter membrane under the condition of vacuum filtration assistance, and the drop-coating amount of the silver selenide dispersion solution is 1.2 mL / cm 2 After the liquid is dried, the silver selenide film adhered to the glass fiber filter membrane is obtained by drying in a vacuum oven at 60°C;

[0056] (3) The silver selenide film adhered to the glass fiber filter membrane obtained in step (2) is placed between two nylon filter membranes, and is formed by spark plasma sintering (SPS), with a sintering temperature of 200°C, a sintering time of 3 min, and a pressure of 30 MPa. Then, the nylon filter membrane on the back of the glass fiber filter membrane is removed, and the glass fiber filter membrane fragments on the surface of the silver selenide film are wiped off, to obtain a flexible N-type nylon-based silver selenide thermoelectric film. The power factor of the film at 30°C is 3862.3 μW / (mK 2 ).

[0057] Example 6:

[0058] (1) Silver nitrate and selenium powder with a molar ratio of 2.3:1 were dissolved in 7.5 mL and 10 mL of ethylenediamine respectively, and after stirring for 30 min, they were poured into a 25 mL reaction kettle, which was placed in a blast drying oven at 180℃ for 5 h; the obtained product was washed with deionized water and ethanol alternately for 2-3 times by centrifugation, and then the washed silver selenide particles were ultrasonically dispersed in 10 mL of ethylene glycol to obtain a uniform silver selenide dispersion liquid, and the concentration of silver selenide was 29 mg / mL;

[0059] (2) Under the condition of vacuum filtration assistance, the silver selenide dispersion liquid obtained in step (1) was uniformly drop-coated on a 20 mm*5 mm glass fiber filter membrane, and the drop-coating amount of the silver selenide dispersion liquid was 1.2 mL / cm 2 After the liquid was dried, it was dried in a vacuum oven at 60℃ to obtain a silver selenide film adhered to the glass fiber filter membrane;

[0060] (3) The silver selenide film adhered to the glass fiber filter membrane obtained in step (2) was placed between two nylon filter membranes, and was formed by spark plasma sintering (SPS), with a sintering temperature of 200℃, a sintering time of 7 min and a pressure of 30 MPa; then the nylon filter membrane on the back of the glass fiber filter membrane was removed, and the glass fiber filter membrane fragments on the surface of the silver selenide film were wiped off, to obtain a flexible N-type nylon-based silver selenide thermoelectric film. The power factor of the flexible N-type nylon-based silver selenide thermoelectric film at 30℃ was 2722.1 μW / (mK 2 ).

Claims

1. A method for preparing a flexible N-type nylon-based silver selenide thermoelectric film, characterized in that, The method comprises the following steps: (1) silver nitrate and selenium powder with a molar ratio of 2.3:1 are respectively dissolved in ethylenediamine, and after stirring, they are poured into a reaction kettle, the reaction kettle is placed in a blast drying oven for reaction at 180℃ for 5h, the obtained product is sequentially washed by centrifugation with deionized water and ethanol for 2-3 times, then the washed silver selenide particles are ultrasonically dispersed into 10mL ethylene glycol to obtain a uniform silver selenide dispersion liquid; the concentration of silver selenide is 25-35mg / mL; (2) Under the condition of vacuum filtration assistance, the silver selenide dispersion solution obtained in step (1) is uniformly drop-coated on a glass fiber filter membrane, and the drop-coating amount of the silver selenide dispersion solution is 1-2 mL / cm 2 After the liquid is drained, the glass fiber filter membrane is dried in a vacuum oven at 60°C to obtain a silver selenide film adhered to the glass fiber filter membrane; (3) the silver selenide film adhered to the glass fiber filter membrane obtained in step (2) is placed between two nylon filter membranes, and is sintered by a discharge plasma to form a shape, the sintering temperature is 100-200℃, the sintering time is 1-9min, and the pressure is 30-50MPa, then the nylon filter membrane on the back of the glass fiber filter membrane is removed, and then the glass fiber filter membrane fragments on the surface of the silver selenide film are wiped off, to obtain a flexible N-type nylon-based silver selenide thermoelectric film.

2. The method for preparing the flexible N-type nylon-based silver selenide thermoelectric thin film according to claim 1, characterized in that, In step (1), the concentration of silver selenide is 28-32mg / mL.

3. The preparation method of the flexible N-type nylon-based silver selenide thermoelectric film according to claim 1 or 2, characterized in that, In step (2), the drop-coating amount of the silver selenide dispersion liquid was 1.2 mL / cm 2 .

4. The method for preparing a flexible N-type nylon-based silver selenide thermoelectric thin film according to claim 1 or 2, characterized in that, In step (3), the sintering temperature of the discharge plasma sintering process is 130-200℃, the sintering time is 1-7min, and the pressure is 30MPa.

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