CN112537058B - Preparation method of triboelectric thin film based on composite nanoparticle doping - Google Patents

Abstract

The invention relates to a method for preparing a friction electrification film based on composite nano particle doping, which comprises the steps of firstly weighing SiO2@ Ag composite nano particles according to the proportion that the doping mass fraction of the SiO2@ Ag composite nano particles is 0.02% -0.5%, pouring the SiO2@ Ag composite nano particles into weighed PDMS stock solution to prepare PDMS mixed solution, and stirring, defoaming, dispersing and then defoaming the mixed solution; then, dripping a curing agent into the PDMS mixed solution, and then stirring and defoaming the PDMS mixed solution; spin-coating the PDMS mixed solution on the upper surface of a clean and dry copper foil by adopting a spin-coating method to form a uniform film; finally, placing the copper foil in a culture dish, and then placing the culture dish in a vacuum drying oven for curing treatment to obtain the triboelectrification film based on the doping of the composite nano particles; the invention can improve the dielectric constant of the triboelectric film and effectively solve the problem of agglomeration of nano-particles in the triboelectric film.

Description

Preparation method of triboelectric thin film based on composite nanoparticle doping

(1) Technical field:

The invention relates to a method for preparing a triboelectric thin film, in particular to a method for preparing a triboelectric thin film based on composite nanoparticle doping.

(two), background technology:

Triboelectric nanogenerator (TENG) converts tiny mechanical energy into electrical energy based on triboelectric effect and electrostatic inductive coupling. It applies a new type of energy harvesting technology and has broad applications in micro energy and large-scale energy acquisition. prospect. However, at present, the output performance, robustness, and environmental adaptability of triboelectric nanogenerators are poor. These defects have gradually become prominent in the process of its engineering application, and have become the bottleneck of its further promotion and application. The inherent characteristics of the triboelectric material of the triboelectric nanogenerator are crucial to improving its output performance. Improving the surface charge density of the triboelectric material is the key to its high output performance, and the dielectric properties of the material are largely It affects the surface charge density of friction materials, so improving the dielectric properties of materials can effectively increase the surface triboelectric charge density of friction materials, and the incorporation of high dielectric nanoparticles into dielectric films can improve the dielectric properties of dielectric films One of the easiest and most effective methods.

From the mechanism of high-dielectric nanoparticles to increase the surface charge density of TENG, it can be known that increasing the dielectric constant of dielectric materials can effectively reduce the effective thickness of dielectric films, thereby effectively increasing the amount of transferred charges and intrinsic capacitance properties of TENG. . Theoretically, the larger the doping volume ratio of nanoparticles, the more obvious the increase in dielectric constant, but in practical applications, too much nanoparticle doping will damage the molecular structure of the dielectric material and change the dielectric material. On the other hand, excessive nanoparticle doping, especially metal nanoparticle doping, will cause percolation, which will cause a large amount of triboelectric charge leakage, thereby reducing the output performance of TENG.

One of the main problems existing in the existing nano-doping technology is the dispersion of nanoparticles. The agglomerated nanoparticles will bring more defects inside the film, which will affect the improvement of its performance. This is because the size of nanoparticles is in the nanometer Grade, with a large specific surface area and high surface energy, so it is easy to agglomerate under the action of van der Waals force, and most friction materials are easily polluted by chemicals. If the nanoparticles are dispersed by reagents and then mixed with Into the friction material, not only introduces the second variable, which brings difficulties to the analysis, but also the reagent material as a solvent may bring a certain degree of pollution to the nanoparticles and the friction material, for example, the silver nanoparticles may be oxidized during the dispersion process, thereby affecting its performance.

Doping materials are mainly divided into two types: conductive nanomaterials and insulator nanomaterials. Conductive nanomaterials have problems such as large surface potential energy of metal nanoparticles, easy agglomeration, and easy seepage, while insulator nanomaterials have limited dielectric constant and limited lifting effect. .

(3) Contents of the invention:

The technical problem to be solved by the present invention is to provide a method for preparing a triboelectric film based on composite nanoparticle doping, which can not only improve the dielectric constant of the triboelectric film under the premise of ensuring the normal operation of the triboelectric film , and can effectively solve the problem of agglomeration of nanoparticles in triboelectric thin films.

Technical scheme of the present invention:

A method for preparing a triboelectric thin film based on composite nanoparticle doping, the preparation steps are as follows:

Step 1. Take a piece of copper foil. The copper foil can be used as the electrode of the triboelectric nanogenerator. First, pretreat the copper foil. Dust and impurities are wiped off, and then the copper foil surface is blown dry with nitrogen;

Step 2. Weigh the PDMS stock solution with an electronic balance, then reset the electronic balance to zero, and then weigh the SiO ₂ @Ag composite nanoparticles at a ratio of 0.02% to 0.5% doping mass fraction of the SiO ₂ @Ag composite nanoparticles. Pour the weighed SiO ₂ @Ag composite nanoparticles into the weighed PDMS stock solution to prepare a PDMS mixed solution mixed with SiO ₂ @Ag composite nanoparticles;

Step 3, using a stirrer to stir the PDMS mixed solution prepared in step 2, and perform defoaming treatment after stirring to obtain a uniformly mixed PDMS mixed solution;

Step 4. In order to further disperse the SiO ₂ @Ag composite nanoparticles, place the uniformly mixed PDMS mixed solution obtained in Step 3 in an ultrasonic disperser for ultrasonic dispersion treatment. Since some bubbles will be introduced during the ultrasonic dispersion treatment, ultrasonic dispersion After the dispersion treatment, the PDMS mixed solution is subjected to defoaming treatment to obtain a PDMS mixed solution in which SiO ₂ @Ag composite nanoparticles are dispersed;

Step 5. Drop the curing agent into the PDMS mixed solution of dispersed SiO ₂ @Ag composite nanoparticles obtained in step 4, then use a stirrer to stir the PDMS mixed solution, and perform defoaming treatment after stirring to obtain the prepared PDMS mixed solution. solution;

Step 6, using a spin coater to spin-coat the PDMS mixed solution prepared in step 5 on the upper surface of the copper foil to form a uniform film on the upper surface of the copper foil;

Step 7, place the copper foil with a uniform film formed on the upper surface obtained in step 6 in a petri dish, in order to prevent the film on the upper surface of the copper foil from being polluted during the curing process, cover the petri dish OK, then place the petri dish in a vacuum drying oven for curing. After curing, take the copper foil out of the petri dish to obtain a triboelectric film doped with composite nanoparticles attached to the copper foil.

The stirrer is a planetary stirrer, and the planetary stirrer is a planetary stirrer of the model THINKY MIXER AR-100 produced by THINKY Company, and the ultrasonic disperser is a UH-600 ultrasonic disperser produced by Japan SMT Company.

In step 2, the PDMS stock solution is Sylgard 184 silicone rubber produced by Dow Corning Corporation of the United States.

In step 3, the rotating speed of the agitator is 1500r/min～2500r/min, the stirring time is 4 minutes～6 minutes, and the time for degassing treatment is 1.5 minutes～2.5 minutes;

In step 4, the time of ultrasonic dispersion treatment is 4 minutes to 6 minutes, and after the ultrasonic dispersion treatment, the PDMS mixed solution is subjected to degassing treatment with a stirrer, and the time of degassing treatment is 25 seconds to 35 seconds;

In step 5, the rotation speed of the agitator is 1500r/min～2500r/min, the stirring time is 4 minutes～6 minutes, and the time for degassing treatment is 1.5 minutes～2.5 minutes;

In step 6, during spin coating, the copper foil is first adsorbed on the tray of the spin coater, and then the vacuum pump of the spin coater is started to perform the spin coating operation; the spin coating operation is divided into two stages: the slow speed uniform glue stage and high-speed setting stage; in the slow glue leveling stage, the spin coater works at a speed of 250r/min to 350r/min, and the spin coating time is 115 seconds to 125 seconds; in the high speed setting stage, the spin coater works at 950r/min At the speed of min ~ 1050r/min, the spin coating time is 5 seconds to 15 seconds;

In step 7, the curing process is: first set the temperature of the vacuum drying oven to 75°C, and then preheat for half an hour. When the temperature of the vacuum drying oven is stable, place the petri dish in the vacuum drying oven, and vacuum dry The pressure in the box is pumped to about one atmospheric pressure. After drying for two hours, turn off the power of the vacuum drying box. After the temperature in the vacuum drying box drops to room temperature, take the petri dish out of the vacuum drying box.

A layer of silicone oil paper is attached to the lower surface of the copper foil. The silicone oil paper has a good anti-charge leakage effect and can protect the flatness of the copper foil on it; when cleaning the surface of the copper foil with alcohol, prevent the copper foil from contacting the silicone oil paper. into the liquid.

Further preferably, in step 2, the doping mass fraction of SiO ₂ @Ag composite nanoparticles is 0.05%-0.4%.

Further preferably, in step 2, the doping mass fraction of SiO ₂ @Ag composite nanoparticles is 0.1%-0.3%.

Further preferably, in step 2, the doping mass fraction of SiO ₂ @Ag composite nanoparticles is 0.15%-0.2%.

In step 7, the petri dish is an aluminum alloy petri dish; the reason for using the aluminum alloy petri dish is that it has better heat transfer performance, a flat bottom surface, and has the advantages of not being deformed under high temperature.

It can be seen from the friction sequence table that PDMS (polydimethylsiloxane) is a material with strong triboelectric negativity. In view of its advantages such as high transparency, good thermal stability, and mature processing technology, it was selected as the negative friction material. Material.

In order to ensure a high degree of integration between the prepared triboelectrification film and the electrode, the PDMS mixed solution was directly spin-coated on the copper foil electrode by a spin-coating process, thereby preparing a device in which the triboelectrification film and the copper foil electrode were integrated.

Beneficial effects of the present invention:

1. In the present invention, SiO ₂ @Ag composite nanoparticles are doped into the PDMS stock solution according to a certain mass fraction to form a PDMS mixed solution, and then the PDMS mixed solution is stirred, ultrasonically dispersed, and then evenly coated on the copper foil electrode. Finally make it solidified on the copper foil electrode to form a triboelectric thin film; because the present invention uses SiO ₂ @Ag composite nanoparticle doping, Ag nanoparticles are attached to the surface of SiO ₂ insulating microspheres, and SiO ₂ microspheres will be in the thin film The interior constitutes a blocking layer, thereby playing the role of preventing charge leakage, which is conducive to the doping of more Ag nanoparticles and the improvement of the dielectric constant; therefore, the present invention can improve the friction under the premise of ensuring the normal operation of the triboelectric film The dielectric constant of the electrified film can effectively increase the surface charge density of TENG, increase the amount of transferred charge of TENG, improve the output performance of TENG, and make TENG excellent in robustness.

2. In the SiO ₂ @Ag composite nanoparticles of the present invention, Ag nanoparticles with a particle size of 5-10 nm are attached to the surface of SiO ₂ insulating microspheres with a particle size of 200 nm. The SiO ₂ insulating microspheres have a relatively large particle size and are dispersed The degree is better, which reduces the difficulty of dispersion in the doping process, and it is easy to obtain uniformly dispersed Ag nanoparticles, which solves the problem of agglomeration of nanoparticles in triboelectrification films, and can also ensure the original stability and activity of nanoparticles.

3. The SiO ₂ @Ag composite nanoparticle in the present invention is a composite microsphere structure, and the Ag nanoparticle with higher cost is evenly loaded on the surface of SiO ₂ , which can reduce the amount of Ag and reduce the friction of the triboelectric film. production cost.

4. In the present invention, a spin coating method is used to prepare a triboelectric film doped with SiO ₂ @Ag composite nanoparticles, so that the surface of the triboelectric film is smooth and the doping is uniform.

(4) Description of drawings:

Figure 1 is a schematic diagram of the structure model of SiO ₂ @Ag composite nanoparticles;

Figure 2 is a schematic diagram of the improvement model of traditional Ag nanoparticles doping on the performance of TENG;

Figure 3 is a schematic diagram of the performance improvement model of TENG by doping with SiO ₂ @Ag composite nanoparticles;

Figure 4 is a schematic diagram of the short-circuit current of TENG doped with SiO2@Ag composite nanoparticles with high silver content according to different mass fractions;

Figure 5 is a schematic diagram of the open circuit voltage of TENG doped with SiO2@Ag composite nanoparticles with high silver content according to different mass fractions;

Figure 6 is a schematic diagram of the short-circuit current of TENG doped with SiO2@Ag composite nanoparticles with lower silver content according to different mass fractions;

Figure 7 is a schematic diagram of the open circuit voltage of TENG doped with SiO2@Ag composite nanoparticles with lower silver content according to different mass fractions;

Figure 8 is a schematic diagram of the transfer charge of TENG after doping SiO2@Ag composite nanoparticles with high silver content;

Figure 9 is a schematic diagram of the current of an undoped TENG and its corresponding charge transfer in one cycle;

Figure 10 is a schematic diagram of the current of one cycle of TENG and the corresponding charge transfer amount when the doping mass fraction of SiO2@Ag composite nanoparticles with higher silver content is 0.3wt.%.

Figure 11 is a schematic diagram of the transfer charge of TENG after doping SiO ₂ @Ag composite nanoparticles with low silver content;

Figure 12 is a schematic diagram of the current of one cycle of TENG and the corresponding charge transfer amount when the doping mass fraction of SiO ₂ @Ag composite nanoparticles with low silver content is 0.1wt.%.

Figure 13 is a schematic diagram of the output power of the undoped TENG;

Figure 14 is a schematic diagram of the output power of TENG when the doping mass fraction of SiO2@Ag composite nanoparticles with higher silver content is 0.3wt.%.

Figure 15 is a schematic diagram of the output power of TENG when the doping mass fraction of SiO2@Ag composite nanoparticles with low silver content is 0.1wt.%.

Figure 16 is a schematic diagram of the charging performance test of different TENGs on the same capacitor.

In the figure, 1 is Ag nanoparticles; 2 is a dielectric film; 3 is SiO ₂ microspheres; 4 is a blocking layer.

(5), specific implementation method:

The preparation steps of the triboelectric film preparation method based on composite nanoparticle doping are as follows:

Step 1. Take a piece of copper foil. The copper foil is cut to a size of 3.5cm×3.5cm. The copper foil can be used as the electrode of the triboelectric nanogenerator. First, pre-treat the copper foil, dip it in alcohol with a cotton swab, and clean it with alcohol On the surface of the copper foil, wipe off the dust and impurities on the surface of the copper foil, and then blow dry the surface of the copper foil with nitrogen;

Step 2. Weigh 3g of PDMS stock solution with an electronic balance, then reset the electronic balance to zero, and then weigh the SiO ₂ @Ag composite nanoparticles at a ratio of 0.15% doping mass fraction of SiO ₂ @Ag composite nanoparticles, and weigh Pour a good amount of SiO ₂ @Ag composite nanoparticles into the weighed PDMS stock solution to prepare a PDMS mixed solution mixed with SiO ₂ @Ag composite nanoparticles;

Step 3, using a stirrer to stir the PDMS mixed solution prepared in step 2, and perform defoaming treatment after stirring to obtain a uniformly mixed PDMS mixed solution;

Step 4. In order to further disperse the SiO ₂ @Ag composite nanoparticles, place the uniformly mixed PDMS mixed solution obtained in Step 3 in an ultrasonic disperser for ultrasonic dispersion treatment. Since some bubbles will be introduced during the ultrasonic dispersion treatment, ultrasonic dispersion After the dispersion treatment, the PDMS mixed solution is subjected to defoaming treatment to obtain a PDMS mixed solution in which SiO ₂ @Ag composite nanoparticles are dispersed;

Step 5. Drop 0.3 g of curing agent into the PDMS mixed solution of dispersed SiO ₂ @Ag composite nanoparticles obtained in step 4, then use a stirrer to stir the PDMS mixed solution, and perform defoaming treatment after stirring to obtain the prepared PDMS mixed solution;

Step 6, using a spin coater to spin-coat the PDMS mixed solution prepared in step 5 on the upper surface of the copper foil to form a uniform film on the upper surface of the copper foil;

Step 7, place the copper foil with a uniform film formed on the upper surface obtained in step 6 in a petri dish, in order to prevent the film on the upper surface of the copper foil from being polluted during the curing process, cover the petri dish OK, then place the petri dish in a vacuum drying oven for curing. After curing, take the copper foil out of the petri dish to obtain a triboelectric film doped with composite nanoparticles attached to the copper foil.

The stirrer is a planetary stirrer, and the planetary stirrer is a planetary stirrer of the model THINKY MIXER AR-100 produced by THINKY Company, and the ultrasonic disperser is a UH-600 ultrasonic disperser produced by Japan SMT Company.

In step 2, the PDMS stock solution is Sylgard 184 silicone rubber produced by Dow Corning Corporation of the United States.

In step 3, the rotating speed of agitator is 2000r/min, and stirring time is 5 minutes, and the time of defoaming treatment is 2 minutes;

In step 4, the time of ultrasonic dispersion treatment is 5 minutes, and after the ultrasonic dispersion treatment, the PDMS mixed solution is subjected to defoaming treatment with a stirrer, and the time of defoaming treatment is 30 seconds;

In step 5, the rotating speed of agitator is 2000r/min, and stirring time is 5 minutes, and the time of defoaming treatment is 2 minutes;

In step 6, during spin coating, the copper foil is first adsorbed on the tray of the spin coater, and then the vacuum pump of the spin coater is started to perform the spin coating operation; the spin coating operation is divided into two stages: the slow speed uniform glue stage and high-speed setting stage; during the slow glue leveling stage, the spin coater works at a speed of 300r/min, and the spin coating time is 120 seconds; during the high-speed setting stage, the spin coater works at a speed of 1000r/min, spin coating The time is 10 seconds;

In step 7, the curing process is: first set the temperature of the vacuum drying oven to 75°C, and then preheat for half an hour. When the temperature of the vacuum drying oven is stable, place the petri dish in the vacuum drying oven, and vacuum dry The pressure in the box is pumped to about one atmospheric pressure. After drying for two hours, turn off the power of the vacuum drying box. After the temperature in the vacuum drying box drops to room temperature, take the petri dish out of the vacuum drying box.

A layer of silicone oil paper is attached to the lower surface of the copper foil. The silicone oil paper has a good anti-charge leakage effect and can protect the flatness of the copper foil on it; when cleaning the surface of the copper foil with alcohol, prevent the copper foil from contacting the silicone oil paper. into the liquid.

In step 7, the petri dish is an aluminum alloy petri dish; the reason for using the aluminum alloy petri dish is that it has better heat transfer performance, a flat bottom surface, and has the advantages of not being deformed under high temperature.

It can be seen from the friction sequence table that PDMS (polydimethylsiloxane) is a material with strong triboelectric negativity. In view of its advantages such as high transparency, good thermal stability, and mature processing technology, it was selected as the negative friction material. Material.

In order to ensure a high degree of integration between the prepared triboelectrification film and the electrode, the PDMS mixed solution was directly spin-coated on the copper foil electrode by a spin-coating process, thereby preparing a device in which the triboelectrification film and the copper foil electrode were integrated.

Attaching nanoparticles to the surface of a solid mechanism with a good dispersion degree, constructing a composite microsphere structure, and obtaining uniformly dispersed metal nanoparticles, not only can obtain uniformly dispersed metal nanoparticles, but also solve the problem of agglomeration of metal nanoparticles, and It can also ensure the original stability and activity of nanoparticles. SiO ₂ @Ag composite microsphere is a kind of composite microsphere structure, which uniformly loads Ag nanoparticles 1 with high cost on the surface of SiO ₂ , which reduces the amount of Ag to a certain extent and reduces the cost of materials. Silver nanoparticles with a particle size of 5-10nm are loaded on the outer surface of SiO ₂ with a particle size of 200nm to obtain uniformly dispersed SiO ₂ @Ag composite nanoparticles, and the particle size of SiO ₂ particles is relatively large, which reduces the amount of doping. The difficulty of decentralization in the complex process, its structural model is shown in Figure 1.

Figure 2 is a TENG model using traditional Ag nanoparticles 1 doping. After the doping amount of Ag nanoparticles 1 reaches a certain value, due to its conductivity, a charge leakage channel will be formed between the dielectric film 2 and the bottom electrode. , so as to reduce the output performance of TENG; Figure 3 adopts the TENG model doped with SiO ₂ @Ag composite nanoparticles, because Ag nanoparticles 1 are attached to the surface of SiO ₂ insulating microspheres, so SiO2 microspheres 3 will form barriers inside the film. Fault 4, thereby preventing charge leakage, thereby increasing the surface charge density of TENG.

After the triboelectrification film is prepared, the triboelectrification film can be used to manufacture the triboelectric nanogenerator TENG. The specific manufacturing process is as follows: first, the electrodes of the triboemission film are led out with wires, and the surrounding area is wrapped with insulating tape. The wrapping width is 0.2mm; in order to make the triboelectric film fully contact with the upper electrode during the contact process, use double-sided adhesive to paste the silicone oil paper surface of the triboelectric film on a piece of dense foam with a plane size of 3.5cm×3.5cm and a thickness of 2mm Then paste the foam on a piece of PMMA with a size of 4cm×4cm to form one side of the triboelectric nanogenerator; the other side is composed of a transparent silver wire electrode pasted on the PMMA of the same size, and the silver wire electrode and The triboelectric film has the same size (3.5cm×3.5cm), and the electrode wires are led out by wires; then positioning holes are made on the four corners of the two pieces of PMMA, and the two pieces are connected by a spring with a height of about 1cm using hot melt adhesive. The four corners of the sheet PMMA are connected to form a triboelectric nanogenerator TENG in vertical contact-separation mode.

Performance test of TENG based on SiO ₂ @Ag composite nanoparticles doping:

In order to verify the effects of SiO ₂ microspheres 3 and Ag nanoparticles 1 in SiO ₂ @Ag composite particles on the output performance of TENG respectively, two sets of control experiments were carried out.

The first group of experiments: SiO ₂ @Ag composite nanoparticles with high silver content were mixed into the PDMS film according to different mass fractions, and tested. The test results are as follows:

It can be seen from Figure 4 that the short-circuit current of the TENG based on the undoped PDMS pure film is only about 25 μA. With the increase of the doping mass fraction of SiO ₂ @Ag composite nanoparticles, the short-circuit current of TENG showed a trend of first increasing and then decreasing. When the doping mass fraction of SiO ₂ @Ag composite nanoparticles was 0.3wt.% , the short-circuit current of TENG reaches a maximum value of about 57 μA, which is 2.28 times higher than that of undoped TENG. When the doping mass fraction of _SiO2 @Ag composite nanoparticles is greater than 0.3wt.%, the short-circuit current of TENG begins to decrease. When the doping mass fraction of SiO2@Ag composite nanoparticles is 0.5wt.%, the short-circuit current of TENG It has dropped to about 30μA, and the drop rate from the maximum value has reached 47%. This may be due to the fact that the thickness of the film itself is very thin, about tens of microns. The leakage current is reduced, and the dielectric loss of the film is increased at the same time, so that the output performance of the device is significantly reduced.

It can be seen from Figure 5 that the change trend of the open circuit voltage is similar to that of the short circuit. The open circuit voltage of TENG based on undoped PDMS pure film is only about 215V. With the increase of the doping mass fraction of SiO ₂ @Ag composite nanoparticles, the open circuit voltage of TENG showed a trend of first increasing and then decreasing. When the doping mass fraction of SiO ₂ @Ag composite nanoparticles was 0.3wt.% , the open circuit voltage of TENG reaches the maximum value, which is about 489V, which is 2.27 times higher than that of undoped TENG. When the doping mass fraction of SiO ₂ @Ag composite nanoparticles is greater than 0.3wt.%, the open circuit voltage of TENG begins to decrease, and when the doping mass fraction of SiO ₂ @Ag composite nanoparticles is 0.5wt.%, the open circuit voltage of TENG The voltage has dropped to about 293V, and the drop rate has reached 40% from the maximum value. The reason for the drop is similar to that of the short-circuit current drop, so I won’t repeat it here.

The second group of experiments: SiO ₂ @Ag composite nanoparticles with low silver content were mixed into PDMS films according to different mass fractions, and tested. The test results are as follows:

It can be seen from Figure 6 that the change trend is similar to that of the short-circuit current change trend of TENG after doping with SiO ₂ @Ag composite nanoparticles with high silver content. The trend decreases after increasing. The difference is that when the doping mass fraction of SiO ₂ @Ag composite nanoparticles is 0.1wt.%, the short-circuit current reaches the maximum value, which is about 60.5μA, which is lower than that of the undoped TENG. The short-circuit current increased by 2.42 times. When the doping mass fraction of SiO ₂ @Ag composite nanoparticles is greater than 0.1wt.%, the short-circuit current of TENG begins to decrease. An interesting phenomenon is that the short-circuit current of TENG does not decrease continuously like the short-circuit current of TENG doped with SiO ₂ @Ag composite nanoparticles with higher silver content, but gradually tends to be stable, and the stable value is about 30 μA. about. The reason for this phenomenon may be due to the low content of Ag, so the main effect on the output performance of the triboelectric generator in this process is the SiO ₂ microsphere 3, and the SiO ₂ microsphere 3 is an insulator material, so the inside of the film The percolation phenomenon is weak or it is difficult to form a percolation path.

It can be seen from Figure 7 that the change trend of the open circuit voltage is similar to that of the short circuit current, both of which show a trend of first increasing and then decreasing with the increase of doping mass fraction, and then tending to be stable. When the doping mass fraction of SiO ₂ @Ag composite nanoparticles is 0.1wt.%, the open circuit voltage reaches a maximum value of 514V, which is 2.39 times higher than that of undoped TENG. When the doping mass fraction of SiO ₂ @Ag composite nanoparticles is greater than 0.1wt.%, the open circuit voltage decreases and tends to be stable, and the stable value is about 389V, which is still nearly 1.81 times higher than that of undoped TENG. The reason for this phenomenon is similar to the reason for the short-circuit current, and will not be repeated here.

From the relationship between the short-circuit current (I) and the amount of transferred charge (Qsc), it can be known that:

Q _SC = ∫idt

By integrating the short-circuit current of one cycle of TENG under each doping mass fraction, the amount of transferred charge in one cycle of TENG under each doping mass fraction can be obtained.

Firstly, the short-circuit current of TENG doped with SiO ₂ @Ag composite nanoparticles with higher silver content was integrated according to different mass fractions, and the results are shown in Fig. 8 .

It can be seen from Figure 8 that the amount of charge transferred in one period of the undoped TENG is 85.56nC. Since the size of the tribofilm is 3.5cm×3.5cm, its surface charge density can be calculated to be about 69.8μC/m ² . With the increase of the doping _mass fraction of SiO ₂ @Ag composite nanoparticles with higher silver content, the amount of transferred charge first increases and then decreases. When the concentration is 0.3wt.%, the amount of transferred charge reaches the maximum, which is about 229.54nC, so it can be calculated that its surface charge density is about 187.4μC/m ² , which is about 2.68 times higher than that of undoped TENG. . Figure 9 and Figure 10 respectively show the short-circuit current signals of the two TENGs for one cycle, and the shaded area represents the amount of transferred charge in one cycle.

Secondly, the same method was used to calculate the short-circuit current of TENG doped with SiO ₂ @Ag composite nanoparticles with lower silver content according to different mass fractions, and the results are shown in Figure 11.

The change trend of the transfer charge of TENG after doping _SiO2 @Ag composite nanoparticles with low silver content is similar to that of the corresponding short-circuit current. With the increase of impurity mass fraction, the amount of transferred charge first increases and then decreases, and then tends to a stable state. When the doping mass fraction of SiO ₂ @Ag composite nanoparticles with low silver content is 0.1wt.%, the transferred charge The amount reaches the maximum, about 295.27nC, so it can be calculated that its surface charge density is about 241μC/m ² , which is about 3.45 times higher than that of undoped TENG. Figure 12 shows the short-circuit current signal of one cycle of TENG when the doping mass fraction of SiO ₂ @Ag composite nanoparticles with low silver content is 0.1wt.%. The shaded area represents the amount of transferred charge in one cycle.

From the above analysis, it can be seen that the TENG output performance is the best when the doping mass fraction of SiO ₂ @Ag composite nanoparticles with higher silver content is 0.3wt.%, while for the SiO ₂ @Ag composite nanoparticles with lower silver content The TENG output performance is optimal when the particle doping mass fraction is 0.1wt.%. Therefore, the output power of TENG and its charging performance to capacitors are further tested to analyze the effect of TENG output power improvement after doping. The test results are shown in the figure 13, Figure 14, Figure 15 and Figure 16.

By testing the output voltage of each TENG under different loads, and then using the output voltage and load resistance to calculate its instantaneous power value, the optimal output power of each TENG can be derived. Figure 13 shows the output power of the undoped TENG, which has the largest peak output power of about 1.07mW under a load of _20MΩ ; The output power of TENG at 0.3wt.%, by calculation, its peak output power is 7.69mW under a load of 5MΩ, which is about 7.18 times higher than that of undoped TENG; Figure 15 shows the silver content The output characteristics of TENG under different loads when the doping mass fraction of SiO ₂ @Ag composite nanoparticles is 0.1wt.%, the peak output power is the largest at 5MΩ load, which is 8.45mW, which is higher than that without The output power of the doped TENG is increased by about 7.9 times; the experimental results show that the output power of the TENG after doping with SiO ₂ @Ag composite nanoparticles is increased, and the impedance is significantly reduced, which is very important for the subsequent application of TENG. important. Figure 16 shows the charging characteristics of different TENGs on a 10μF capacitor under the same external excitation. It can be seen that it takes about 100s for the undoped TENG to charge a 10μF capacitor to 3V, while the SiO ₂ @ When the mass fraction of Ag composite nanoparticles is 0.3wt.%, it only takes about a dozen seconds to charge a 10 μF capacitor to 3V, while the SiO ₂ @Ag composite nanoparticles with a lower silver content doping mass fraction is 0.1wt. .% TENG can charge a 10μF capacitor to 3V for only a few seconds, and the charging efficiency has been greatly improved.

Through the above experiments, it can be found that the output of TENG doped with SiO ₂ @Ag composite nanoparticles with lower silver content is better than that of TENG doped with SiO ₂ @Ag composite nanoparticles with higher silver content, which is Because the SiO ₂ microspheres 3 in the composite nanoparticles not only play a role in improving the dispersion of the metal nanoparticles and the dielectric properties of the material, but also have a certain effect on preventing percolation current.

Claims (8)

1. A method for preparing a triboelectric thin film based on composite nanoparticle doping, characterized in that: the preparation steps are as follows: Step 1. Take a piece of copper foil, clean the surface of the copper foil with alcohol, and then dry the surface of the copper foil with nitrogen; Step 2. Weigh the PDMS stock solution, and then weigh the SiO ₂ @Ag composite nanoparticles at a ratio of 0.02% to 0.5% doped with SiO ₂ @Ag composite nanoparticles, and then weigh the SiO ₂ @Ag composite nanoparticles Pour the particles into the weighed PDMS stock solution to prepare a PDMS mixed solution doped with SiO ₂ @Ag composite nanoparticles; Step 3, using a stirrer to stir the PDMS mixed solution prepared in step 2, and perform defoaming treatment after stirring to obtain a uniformly mixed PDMS mixed solution; Step 4. Place the uniformly mixed PDMS mixed solution obtained in step 3 in an ultrasonic disperser for ultrasonic dispersion treatment, and then perform defoaming treatment on the PDMS mixed solution after ultrasonic dispersion treatment to obtain PDMS dispersed SiO ₂ @Ag composite nanoparticles mixture; Step 5. Drop the curing agent into the PDMS mixed solution of dispersed SiO ₂ @Ag composite nanoparticles obtained in step 4, then use a stirrer to stir the PDMS mixed solution, and perform defoaming treatment after stirring to obtain the prepared PDMS mixed solution. solution; Step 6, using a spin coater to spin-coat the PDMS mixed solution prepared in step 5 on the upper surface of the copper foil to form a uniform film on the upper surface of the copper foil; Step 7, place the copper foil that forms a uniform film on the upper surface obtained in step 6 in a petri dish, cover the lid of the petri dish, and then place the petri dish in a vacuum drying oven for curing, curing After the treatment, the copper foil is taken out from the petri dish to obtain a triboelectric thin film based on composite nanoparticle doping attached to the copper foil. 2. The method for preparing a triboelectric thin film based on composite nanoparticle doping according to claim 1, characterized in that: the agitator is a planetary agitator. 3. The method for preparing a triboelectric thin film based on composite nanoparticle doping according to claim 1 or 2, characterized in that: in the step 3, the rotating speed of the stirrer is 1500r/min～2500r/min, and the stirring time 4 minutes to 6 minutes, and the time for degassing treatment is 1.5 minutes to 2.5 minutes; In step 4, the time of ultrasonic dispersion treatment is 4 minutes to 6 minutes, and after the ultrasonic dispersion treatment, the PDMS mixed solution is subjected to degassing treatment with a stirrer, and the time of degassing treatment is 25 seconds to 35 seconds; In step 5, the rotation speed of the agitator is 1500r/min～2500r/min, the stirring time is 4 minutes～6 minutes, and the time for degassing treatment is 1.5 minutes～2.5 minutes; In step 6, during spin coating, the copper foil is first adsorbed on the tray of the spin coater, and then the vacuum pump of the spin coater is started to perform the spin coating operation; the spin coating operation is divided into two stages: the slow speed uniform glue stage and high-speed setting stage; in the slow glue leveling stage, the spin coater works at a speed of 250r/min to 350r/min, and the spin coating time is 115 seconds to 125 seconds; in the high speed setting stage, the spin coater works at 950r/min At the speed of min ~ 1050r/min, the spin coating time is 5 seconds to 15 seconds; In step 7, the curing process is: first set the temperature of the vacuum drying oven to 75 ^o C, then preheat, when the temperature of the vacuum drying oven is stable, place the petri dish in the vacuum drying oven, and place the vacuum drying oven The pressure inside is pumped to an atmospheric pressure. After drying for two hours, turn off the power of the vacuum drying oven. After the temperature in the vacuum drying oven drops to room temperature, take the petri dish out of the vacuum drying oven. 4. The method for preparing a triboelectric thin film based on composite nanoparticle doping according to claim 1, wherein a layer of silicone oil paper is attached to the lower surface of the copper foil. 5. The preparation method of triboelectric thin film based on composite nanoparticle doping according to claim 1, characterized in that: in the step 2, the SiO ₂ @Ag composite nanoparticle doping mass fraction is 0.05% to 0.4% . 6. The preparation method of triboelectric thin film based on composite nanoparticle doping according to claim 5, characterized in that: in the step 2, the SiO ₂ @Ag composite nanoparticle doping mass fraction is 0.1% to 0.3% . 7. The method for preparing a triboelectric thin film based on composite nanoparticle doping according to claim 6, characterized in that: in step 2, the SiO ₂ @Ag composite nanoparticle doping mass fraction is 0.15% to 0.2% . 8. The method for preparing a triboelectric thin film based on composite nanoparticle doping according to claim 1, characterized in that: in the step 7, the culture dish is an aluminum alloy culture dish.

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