Composite material for preparing geopolymer-based triboelectric nano generator and preparation method of composite material

Abstract

The invention relates to the technical field of triboelectric nano-generators, and particularly discloses a composite material for preparing a geopolymer-based triboelectric nano-generator and a preparation method of the composite material. The composite material comprises the following components: 28%-32% of first-grade fly ash, 18%-22% of mineral powder, 4%-6% of sodium silicate, 1%-2% of graphene, 3%-4% of functionalized Ti3C2Tx nanosheets, 3%-4% of barium titanate nanoparticles, 3%-4% of polyvinylidene fluoride nanofibers, 3%-4% of polydimethylsiloxane elastic microspheres, 0.5%-1% of a polycarboxylate superplasticizer, 1%-2% of nano-hydroxyapatite and 24% of water. The geopolymer substrate disclosed by the invention is prepared from a graphene modified gelling composite material, and excellent mechanical properties can be obtained after the geopolymer substrate is completely cured for 28 days. Under the frequency of 1kHz, the dielectric constant of the graphene geopolymer substrate can reach 120.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of triboelectric nanogenerator, and particularly relates to a composite material for preparing geopolymer-based triboelectric nanogenerator and a preparation method thereof. BACKGROUND

[0002] Triboelectric nanogenerator (TENG) has attracted more and more attention due to its simple device requirements, wide material selection, avoidance of chemical reactions, high sensitivity and other advantages. It can effectively utilize the small mechanical energy from the environment, such as human movement, vehicle vibration, wind and water flow, and convert these energies into electricity. Geopolymer-based concrete, as a new type of inorganic cementitious material, uses fly ash, slag, metakaolin and other industrial solid wastes as main raw materials, and forms a three-dimensional silicon-aluminum network structure through alkali activation reaction, which has excellent mechanical properties, high temperature resistance and chemical stability. Compared with traditional cement-based materials, geopolymer materials can significantly reduce carbon dioxide emissions during the preparation process, and have good environmental friendliness and sustainable development potential. At the same time, the microstructure of geopolymer-based materials is dense, and the porosity is low. The surface can realize more abundant functional group distribution and charge transfer characteristics through component regulation, which provides a good interface basis for the enhancement of triboelectric effect. In the application of triboelectric nanogenerator, geopolymer-based composite materials not only can maintain structural stability and durability in complex environments, but also can realize efficient mechanical energy collection and conversion by using its excellent electrochemical inertness and surface polarization characteristics. Therefore, introducing geopolymer-based materials into the triboelectric nanogenerator system not only helps to improve the energy output performance and environmental adaptability, but also provides a new material approach and technical support for the self-powered and intelligent monitoring of infrastructure.

[0003] Different materials have different electron affinities. When two materials are brought into contact and separated, electrons transfer from one material to the other, which is the mechanism behind triboelectric nanogenerators. During the rubbing process, the material with lower electron affinity loses electrons and becomes positively charged, while the material with higher electron affinity gains electrons and becomes negatively charged. Polytetrafluoroethylene (PTFE) is widely used in triboelectric nanogenerators due to its highest electron affinity, followed by polyvinyl chloride (PVC), polypropylene (PP), and epoxy resin. Polymers are often used as negative triboelectric layers because of their poor electrical conductivity, which inhibits electron mobility and promotes surface charge migration. In addition, the flexibility, plasticity, and biocompatibility of polymers enable them to be used in biomedical instruments or wearable electronic devices. Metals (Au, Al, Cu, Fe, Al) exhibit slightly lower electron affinity than polymers, but due to some advantages, they are used in triboelectric nanogenerators. Most notably, metals have excellent electrical conductivity, enabling them to effectively function as electrodes in these devices. For positive triboelectric layers, materials with lower electron affinity are preferred, including paper, silk, fur, and wood. Some inorganic materials such as titanium dioxide, silicon dioxide, mica, and glass also exhibit poor electron affinity.

[0004] Geopolymer-based composites are a new type of inorganic cementitious material that uses fly ash, slag, metakaolin, and other silicon-aluminum-containing solid waste as the main raw material, and forms a three-dimensional Si-O-Al-O network structure through the action of an alkaline activator. Its setting and hardening process is based on the dissolution and polymerization of silicon-aluminum species, generating a dense aluminosilicate gel (N-A-S-H or C-A-S-H), with advantages such as high strength, high temperature resistance, chemical corrosion resistance, and low carbon environmental protection. To improve its mechanical and functional properties, researchers have introduced nanoscale components such as nanoscale silica, alumina, graphene, and carbon nanotubes to optimize the microstructure, enhance the compactness and interface bonding characteristics. In particular, the incorporation of carbon-based nanomaterials not only enhances the electrical conductivity and electrochemical stability, but also endows the material with electromagnetic shielding, piezoelectric, electrothermal, and energy storage functions, driving the development of structure and energy integrated materials. Despite this, there is still little research on the triboelectric properties of geopolymer-based composites. Their adjustable chemical composition and surface functional groups theoretically have excellent charge transfer potential, but the related energy conversion mechanisms and influencing factors are not yet clear, limiting their application in self-powered structures and intelligent monitoring. Therefore, there is an urgent need to conduct systematic research on the triboelectric properties and regulation mechanisms of geopolymer-based composites to provide new ideas for green energy harvesting and smart infrastructure construction.

[0005] The present application develops a new triboelectric nanogenerator based on graphene modified cementitious composite and polytetrafluoroethylene film. The cementitious material is completely cured to ensure stable electrical output and satisfactory mechanical properties. The resistivity, impedance and relative dielectric constant of these materials are optimized to improve the power output. The performance of the geopolymer-based triboelectric nanogenerator is evaluated in the contact-separation mode, and the effects of amplitude and frequency on voltage and current output are studied.

[0006] To this end, the inventors propose a composite material for preparing a geopolymer-based triboelectric nanogenerator and a method for preparing the same to solve the above problems. SUMMARY

[0007] The present application aims to provide a composite material for preparing a geopolymer-based triboelectric nanogenerator and a method for preparing the same to solve the problems raised in the background art.

[0008] To achieve the above-mentioned object, the present application provides the following technical solutions:

[0009] A composite material for preparing a geopolymer-based triboelectric nanogenerator and a method for preparing the same, comprising:

[0010] Primary fly ash 28% to 32%, mineral powder 18% to 22%, sodium silicate 4% to 6%, graphene 1% to 2%, functionalized Ti3C2T x (MXene) nanosheet 3% to 4%, barium titanate (BaTiO3) nanoparticle 3% to 4%, polyvinylidene fluoride (PVDF) nanofiber 3% to 4%, polydimethylsiloxane (PDMS) elastic microsphere 3% to 4%, polycarboxylate superplasticizer 0.5% to 1%, nano-hydroxyapatite (n-HA) 1% to 2%, and the rest is water.

[0011] A method for preparing a composite material for preparing a geopolymer-based triboelectric nanogenerator, comprising the following steps:

[0012] S1, mix 1% graphene, 4% functionalized Ti3C2T x nanosheet, 4% BaTiO3 nanoparticle with 1% superplasticizer and 14% water, and then perform ultrasonic treatment and high-pressure homogenization to obtain a composite dispersion liquid;

[0013] S2, prepare an alkali activator solution according to a fixed mixing ratio, and let the solution stand at room temperature for standby;

[0014] S3, add primary fly ash, mineral powder and nano-hydroxyapatite to the composite dispersion liquid, and stir at a low speed of 100 rpm for 2 min for primary wet mixing of the composite dispersion liquid to obtain a premixed slurry;

[0015] S4, adding PVDF nanofiber and PDMS elastic microspheres into the premixed slurry, and performing high-efficiency dispersion mixing on the premixed slurry by progressive shearing (200→300→400 rpm, 1 min each), to obtain a composite slurry;

[0016] S5, adding an alkali activator solution into the composite slurry, stirring at 200 rpm for 2 min for flow adjustment of the composite slurry, so that the slump reaches 180±10 mm, and then directly pouring into a mold (50 mm×50 mm×50 mm, 160 mm×40 mm×40 mm), and then performing tamping (60 Hz, 45 s) and constant temperature and humidity curing (25℃ / 95% RH) for 28 d and natural drying for 48 h, to obtain a solidified body;

[0017] S6, performing nanoimprinting (5 MPa, 80℃, 30 min) on the surface of the solidified body to form a microstructure functional layer, and then laminating an electrospun PVDF film and attaching a silver fiber electrode, and then pressing, to construct and obtain a final polymer-based triboelectric nanogenerator product.

[0018] Preferably, in step S1, 1% graphene, 4% functionalized Ti3C2T x The nanosheets, 4% BaTiO3 nanoparticles, 1% water reducing agent and 14% water are mixed, and then subjected to 40 kHz ultrasonic treatment for 45 min and 300 bar high-pressure homogenization for 3 times, to obtain a composite dispersion liquid.

[0019] Preferably, in step S2, 5% sodium silicate particles and 10% water are mixed to prepare an alkali activation solution, and the solution is cooled to room temperature for standby.

[0020] Preferably, in step S3, 32% primary fly ash, 20% mineral powder and 2% nano-hydroxyapatite are added into the composite dispersion liquid, and the composite dispersion liquid is subjected to primary wet mixing at 100 rpm for 2 min, to obtain a premixed slurry.

[0021] Preferably, in step S4, 3% PVDF nanofiber and 4% PDMS elastic microspheres are added into the premixed slurry, and the premixed slurry is subjected to high-efficiency dispersion mixing by progressive shearing, to obtain a composite slurry.

[0022] The conditions of the progressive shearing are 200→300→400 rpm, 1 min each.

[0023] Preferably, in step S5, the prepared alkali activator solution is added into the composite slurry, and the slurry is stirred at a medium speed of 200 rpm for 2 min for flowability adjustment, so that the slump reaches 180±10 mm, and then the slurry is directly poured into a mold, and the mold is vibrated and cured at constant temperature and humidity for 28 d and naturally dried for 48 h to obtain a cured body;

[0024] The size of the mold is 50 mm*50 mm*50 mm, 160 mm*40 mm*40 mm;

[0025] The vibration condition is 60 Hz, 45 s;

[0026] The curing condition is 25 DEG C, 95% RH.

[0027] Preferably, in step S6, nanoimprinting is performed on the surface of the cured body to form a microstructure functional layer, and then a silver fiber electrode is attached to the surface of the microstructure functional layer after a static spinning PVDF film is laid on the surface of the microstructure functional layer, and the silver fiber electrode is pressed, so that a final polymer-based triboelectric nanogenerator product is constructed and obtained.

[0028] The nanoimprinting condition is 5 MPa, 80 DEG C, 30 min.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] (1) The functionalized MXene nanosheet and the BaTiO3 nanoparticles are uniformly and complementarily distributed in the graphene dispersion system to form a multi-stage dielectric enhancement network. The network not only significantly improves the dielectric constant of the matrix, but also effectively promotes the storage and migration of triboelectric charges, thereby enhancing the overall charge accumulation efficiency; the PVDF nanofiber and the PDMS elastic microsphere jointly construct a flexible-tough composite skeleton, which realizes efficient deformation and rebound under external force load. The microfiber structure helps to separate the charges, and the elastic microsphere maintains the stability of the interface contact and improves the charge generation amount in each friction cycle through deformation compensation and stress buffering.

[0031] (2) The present application combines ultrasonic treatment and high-pressure homogenization and other multi-stage dispersion processes, so that each nanometer component is fully peeled and dispersed in the geopolymer matrix, thereby avoiding the agglomeration and phase separation phenomena that easily occur in traditional systems. Such high uniformity not only ensures the uniformity of the electric field distribution, but also reduces the stress concentration microcracks, thereby improving the mechanical stability and electrical performance consistency of the material; through the curing strategy of staged temperature control, the temperature gradient is used to drive the crystallization and pore self-assembly of the hydration products in different stages to form a microstructure network with interconnected channels. The network not only optimizes the internal pore distribution, but also enhances the mechanical strength, thereby effectively improving the electric-mechanical coupling conversion efficiency.

[0032] (3) The geopolymer substrate is prepared from graphene-modified cementitious composite material, which is fully cured for 28 days to achieve satisfactory mechanical properties and waterproof performance. The dielectric constant of the graphene geopolymer substrate can reach 100 at a frequency of 1 kHz. The amplitude and frequency of the loading cycle affect the output of voltage and current. At a frequency of 8 Hz, the short-circuit current reaches 3.76 μA and the open-circuit voltage reaches 1114.5 V under a 100 N cycle. The geopolymer-based triboelectric nanogenerator shows stable voltage output after 8000 cycles. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A flow chart of a composite material preparation method for preparing a geopolymer-based triboelectric nanogenerator according to the present application;

[0034] Figure 2 Experimental and schematic diagram of the triboelectric performance of the geopolymer-based triboelectric nanogenerator;

[0035] Figure 3 Mechanical strength of the graphene-modified geopolymer-based composite material;

[0036] Figure 4 Electrical and dielectric properties of the graphene-modified geopolymer-based composite material;

[0037] Figure 5 Triboelectric performance of the geopolymer-based triboelectric nanogenerator. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0039] Example 1:

[0040] Please refer to Figures 1 to 5 The composite material for preparing a geopolymer-based triboelectric nanogenerator includes:

[0041] Primary fly ash 32%, mineral powder 20%, sodium silicate 5%, graphene 1%, functionalized Ti3C2T x (MXene) nanosheet 4%, barium titanate (BaTiO3) nanoparticle 4%, polyvinylidene fluoride (PVDF) nanofiber 3%, polydimethylsiloxane (PDMS) elastic microsphere 4%, polycarboxylate superplasticizer 1%, nano-hydroxyapatite (n-HA) 2%, water 24%.

[0042] A preparation method for preparing a composite material of a geopolymer-based triboelectric nanogenerator, characterized in that it comprises the following steps:

[0043] In step S1, 1% graphene, 4% functionalized Ti3C2T x After mixing 4% BaTi O3 nanoparticles, 1% water reducing agent and 14% water, ultrasonic treatment and high-pressure homogenization are performed to obtain a composite dispersion liquid.

[0044] In step S2, 5% sodium silicate particles and 10% water are mixed to prepare an alkali-activated solution, and the solution is cooled to room temperature for standby.

[0045] In step S3, 32% primary fly ash, 20% mineral powder and 2% nano-hydroxyapatite are added to the composite dispersion liquid, and low-speed stirring at 100 rpm is performed for 2 min for primary wet mixing of the composite dispersion liquid to obtain a premixed slurry.

[0046] In step S4, 3% PVDF nanofiber and 4% PDMS elastic microsphere are added to the premixed slurry, and progressive shear is used for efficient dispersion mixing of the premixed slurry to obtain a composite slurry.

[0047] The conditions of the progressive shear are 200→300→400 rpm, each for 1 min.

[0048] In step S5, the alkali-activated solution is added to the composite slurry, and medium-speed stirring at 200 rpm is performed for 2 min for flow adjustment of the composite slurry to make the slump reach 180±10 mm, and then it is directly poured into a mold, and after vibration and constant temperature and humidity curing and maintenance for 28 d and natural drying for 48 h, a solidified body is obtained.

[0049] The mold size is 50 mm×50 mm×50 mm, 160 mm×40 mm×40 mm.

[0050] The vibration condition is 60 Hz, 45 s.

[0051] The curing condition is 25°C, 95% RH.

[0052] In step S6, nanoimprinting is performed on the surface of the solidified body to form a microstructure functional layer, and after laying a static spinning PVDF film and attaching a silver fiber electrode, it is pressed to build and obtain a final geopolymer-based triboelectric nanogenerator product.

[0053] The nanoimprinting condition is 5 MPa, 80°C, 30 min.

[0054] The geopolymer-based triboelectric nanogenerator consists of a geopolymer substrate and a polytetrafluoroethylene film. The geopolymer substrate is prepared from a well-dispersed graphene geopolymer paste, following the steps as shown in Figure 1 x The graphene, functionalized Ti3C2T x nanosheets, and BaTiO3nanoparticles are added to a solution of weighted water and superplasticizer, and then dispersed using a combination of ultrasonication and high-pressure homogenization. Subsequently, an alkali-activator solution is prepared by mixing the remaining water with sodium silicate. The well-dispersed graphene composite suspension is then poured into a Hobart mixer, and mixed with the previously mixed fly ash, ground slag, and nano-hydroxyapatite at a low speed of 100 rpm for 2 min to obtain a premixed slurry. Polyvinylidene fluoride nanofibers and polydimethylsiloxane elastic microspheres are then added to the premixed slurry, and a progressive shear is applied to obtain a composite slurry. The PVDF nanofibers and PDMS elastic microspheres are then added to the premixed slurry, and a progressive shear (200→300→400 rpm, 1 min each) is applied for efficient dispersion mixing to obtain a composite slurry. The previously prepared alkali-activator solution is then added to the composite slurry, and a moderate speed of 200 rpm is applied for 2 min for flowability adjustment of the composite slurry, so that the slump reaches 180±10 mm. The well-mixed geopolymer slurry is then cast into a mold with dimensions of 50 mm x 50 mm x 50 mm for compression testing, and 160 mm x 40 mm x 40 mm for bending testing. All samples are cured in a curing room at a temperature of 25±2°C and a humidity of 25% for 28 days, and naturally dried for 48 h, before mechanical testing. Finally, the fully cured geopolymer-based composite material is cut into thin plates with dimensions of 40 mm x 40 mm x 4 mm, and the surface is nano-imprinted to form a microstructured functional layer. A static-spun PVDF film and a silver fiber electrode are then laid on the surface and pressed to prepare a geopolymer-based triboelectric nanogenerator product.

[0055] The linear motor (Zaber LSQ450B-T3A) is used to test the triboelectric properties of the geopolymer-based triboelectric nanogenerator, which can produce periodic contact and separation through the stroke amplitude and frequency controlled by the Zaber console software. The experimental setup and schematic diagram for evaluating the triboelectric properties of the geopolymer-based triboelectric nanogenerator are shown in Figure 2 The graphene-geopolymer plate is fixed on a metal moving bed in a u-shaped groove, and an insulating polymer plate is placed between them. The polytetrafluoroethylene film is fixed at the end of the groove and is insulated by the polymer plate. Copper strips are clamped on the back of the geopolymer substrate and the polytetrafluoroethylene film, respectively, as charge-conducting electrodes. To ensure complete contact between the geopolymer substrate and the polytetrafluoroethylene film, the surface area of the polytetrafluoroethylene is slightly larger than that of the geopolymer composite, reaching 50 mm 2 .

[0056] Example 2

[0057] Test equipment and instruments are shown in Table 1 below

[0058] Table 1

[0059]

[0060]

[0061] Test procedure

[0062] Cut the prepared composite plate into 40mm x 40mm x 4mm, paste aluminum electrodes on the back and lead out the wires.

[0063] Control group: conventional TENG sample prepared by the same size ordinary polymer + PTFE film.

[0064] Mechanical loading and electrical signal synchronous acquisition

[0065] Place the sample under the mechanical loading system, load the peak force of 10N, the sine wave loading frequency of 2Hz, and cycle 200 times.

[0066] Oscilloscope channel 1 connects the sample electrode, and channel 2 connects the force sensor.

[0067] LabVIEW program synchronously records force-voltage data at 1kHz sampling.

[0068] Charge measurement

[0069] After the loading is completed, the accumulated charge amount in a complete cycle is measured by Keithley 6514 charge amplifier.

[0070] The charge amplifier is set to integrate time of 1s.

[0071] Dielectric and capacitance test

[0072] Remove the aluminum electrode from the sample, with side length of 40mm, measure the dielectric constant εr and capacitance C, with frequency of 1kHz.

[0073] Energy efficiency calculation

[0074] According to the output voltage V(t) and the external load resistance R (10MΩ), the instantaneous power P(t) = V(t) / R is calculated, and the average power Pavg is integrated. 2

[0075] Energy conversion efficiency η = Pavg / (F·v), where F·v is the mechanical input power.

[0076] Data acquisition

[0077] ​Voltage waveform: oscilloscope export in.csv format, processed in Matlab or Excel;

[0078] Charge: Keithley 6514 meter reading;

[0079] Dielectric constant and capacitance: LCR meter automatically stored and exported;

[0080] Power calculation: 5-cycle voltage data as sample, batch calculated in Excel and averaged.

[0081] Example Three:

[0082] Mechanical strength test:

[0083] For uniaxial compression and three-point bending tests, the compression and bending strength of graphene-geopolymer composites were measured on samples of 50 mm x 50 mm x 50 mm and 160 mm x 40 mm x 40 mm, respectively. The compression equipment UH500 was used in displacement control mode, with a compression rate of 0.2 mm / min, and the bending rate of the equipment AGX50 was 0.1 mm / min. Three replicates were tested and the average value was taken.

[0084] Measurement of impedance and dielectric constant

[0085] The resistance and impedance of graphene-geopolymer composites were measured using both direct current (DC) and alternating current (AC) methods. The direct current method included direct measurement of resistance from casting time to solidification for 28 days using a symbol SDM3045X multimeter. The impedance of the sliced geopolymer-based triboelectric layer was measured using an IM3536 LCR meter with a frequency range of 100 Hz-8 MHz. Based on equation (2), the conductivity of the geopolymer substrate can be calculated:

[0086]

[0087] where d is the thickness of the geopolymer substrate, Z is the measured impedance, and A is the cross-sectional area of the geopolymer substrate. The capacitance of the geopolymer substrate can also be measured using an LCR meter and can be used to calculate the relative dielectric constant based on equation (3):

[0088]

[0089] where C is the capacitance of the geopolymer substrate, d is the thickness, A is the cross-sectional area, and ε0 is the dielectric constant of vacuum (8.854 x 10 -12 F / m).

[0090] Triboelectric test

[0091] The triboelectric performance was evaluated by using a linear motor to periodically contact and separate the graphene-geopolymer plate and the polytetrafluoroethylene film. The force amplitude could be controlled from 2 to 200 N. Considering that civil engineering structures are usually subjected to low to medium frequency loads, the triboelectric effect of the geopolymer-based triboelectric nanogenerator was investigated with a force control of 100 N and a loading frequency ranging from 2 to 8 Hz. The short-circuit current was measured by a low-noise current preamplifier (SR570, Stanford Research Systems), and the open-circuit voltage and current of the geopolymer-based triboelectric nanogenerator were measured by connecting a 3 GΩ resistor and a resistance meter, and the potential drop was measured using a Keithley 6514 current meter.

[0092] Results and discussion

[0093] Mechanical performance test

[0094] The compressive strength and flexural strength of the graphene-geopolymer composite were about 58.2 and 3.1 MPa, respectively, as shown in Figure 3 . Its mechanical strength was higher than that of ordinary cementitious materials, indicating its feasibility for application in structural or pavement construction engineering projects. In addition, the mechanical strength of the geopolymer-based triboelectric nanogenerator significantly affected its triboelectric efficiency, mainly by improving the contact efficiency and anti-deformation performance. Cementitious composites with higher strength were less likely to deform during repeated loading and unloading, ensuring better surface contact with the polytetrafluoroethylene film. In addition, higher mechanical strength contributed to the stability of the overall structure, preventing potential damage caused by excessive external force.

[0095] Example five:

[0096] Conductivity and dielectric performance test:

[0097] The conductivity of the geopolymer-based composite was closely related to its hydration process. In the early stage of hydration, the high water content and interconnected pores resulted in a low resistivity. As the geopolymer clinker hydrated, leading to a decrease in water content, the pores were gradually filled with hydration products, and the resistivity tended to increase in the later curing stage, as shown in Figure 4 a. Previous studies have applied cementitious materials that were cured for 7 days, during which their electrical conductivity and dielectric properties can continue to change significantly with ongoing hydration. That is why the authors chose a fully cured geopolymer matrix as the triboelectric layer, aiming to improve the electrical stability of the geopolymer-based triboelectric nanogenerator. The impedance of the geopolymer-based substrate decreased rapidly and then stabilized ( Figure 4 b) with the increase of frequency. In the low frequency range, the high impedance indicated that there were significant resistive and capacitive effects inside the cementitious material. With the increase of frequency, the decrease of capacitive reactance led to the decrease of impedance. In the high frequency range, the impedance tended to be flat, indicating that conductive pathways had been established in the cementitious material, and the effect of frequency on impedance decreased.Figure 4 c shows the change in conductivity at different frequencies. In the low frequency range, the high capacitive reactance results in low conductivity. In the high frequency range, the conductivity increases significantly, indicating the enhanced mobility of charges in the geopolymer-based material. The output of the geopolymer-based triboelectric nanogenerator is closely related to the triboelectric charge density, and the open-circuit voltage can be expressed by equation (4):

[0098]

[0099] where V oc is the open-circuit voltage, p is the triboelectric charge density, x t is the distance between the two geopolymer substrates and the polytetrafluoroethylene film, and e0 is the vacuum permittivity. In the vertical contact-separation mode, the geopolymer-based triboelectric nanogenerator can be equivalent to a capacitive model, and its triboelectric charge density can be calculated by equation (5):

[0100]

[0101] where e r is the relative permittivity, d is the distance, and V is the voltage drop. Figure 4 d shows the change in the relative permittivity of the geopolymer-based substrate at different frequencies. The high permittivity at low frequencies indicates that the geopolymer-based material has a strong polarization ability. This is consistent with the high polarization characteristics of the geopolymer-based material measured in the direct current condition. As the frequency increases, the polarization within the geopolymer-based material is difficult to respond to the constantly changing electric field, resulting in a decrease in the relative permittivity. At a frequency of 1 kHz, the permittivity of the graphene-geopolymer plate can reach about 120. This is comparable to similar studies of titanium dioxide-modified cement-based triboelectric layers and carbon black-enhanced layers, where the relative permittivities were 79.3 and 82.2, respectively.

[0102] Example Six:

[0103] Output performance test of the geopolymer-based triboelectric nanogenerator:

[0104] The frequency of the external load experienced by civil infrastructure depends on the specific type of load and environmental factors, and is usually within 10 Hz. Therefore, this section investigates the effect of different loading frequencies from 2 Hz to 8 Hz on the triboelectric efficiency of the geopolymer-based triboelectric nanogenerator under the same loading condition of 100 N. As shown in Figure 5 a, the results show that the average short-circuit current of the geopolymer-based triboelectric nanogenerator at 2 and 4 Hz is 0.84 and 1.53 pA, respectively, and reaches a maximum of 3.76 pA at 8 Hz. The open-circuit voltage of the geopolymer-based sensor was measured by connecting a 1 GΩ resistor to the potential drop. As shown in Figure 5As shown in b, the output voltage at 2 Hz is 371.4 V, and the output voltage at 8 Hz is 1114.5 V. It can be inferred that higher frequency leads to faster generation and accumulation of charges, resulting in enhanced electrostatic induction and increased output current. The service life of concrete infrastructure is several decades; therefore, long-term stability ensures stable performance over a long period of time, which is crucial for the practical application of geopolymer-based triboelectric nanogenerators. Figure 5 c shows the open-circuit voltage output of the geopolymer-based triboelectric nanogenerator initially and after 1000, 2000, 4000, and 8000 loading cycles. The results show that the voltage output is consistent and unchanged after thousands of loading cycles, and maintains good repeatability and reversibility. Based on the understanding of geopolymer materials, it can be predicted that the repeatability of their electrical signals is within the elastic range. The load of the geopolymer-based triboelectric nanogenerator is 100 N (or 62.5 kPa), which is significantly less than the mechanical strength of the graphene-geopolymer composite and is within the elastic range of the geopolymer matrix. Therefore, in this application, it can be considered that the geopolymer-based triboelectric nanogenerator is elastic in the loading cycle, and the force within the elastic range has little effect on its long-term stability.

[0105] The effect of force on the triboelectric efficiency of the geopolymer-based triboelectric nanogenerator was also studied in this paper. Figure 5 d-5e represent the open-circuit voltage and short-circuit current output of the geopolymer-based triboelectric nanogenerator under the action of 2, 10, 40, and 100 N. This shows that as the force increases, the voltage output increases from about 4274-6596 V. This is because the increase in force increases the contact area between the graphene-geopolymer plate and the polytetrafluoroethylene film, thereby increasing the amount of charge accumulation and electrostatic induction, thereby increasing the output voltage. Figure 5 e shows the short-circuit current of the geopolymer-based triboelectric nanogenerator under the action of 200 N force, with an average of about 3.89 μA at 8 Hz. Compared with the corresponding counterpart loaded by 100 N force, the enhancement of current is not significant, which is why we decided to use 100 N to study the effect of frequency and power density measurements.

[0106] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are contained in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0107] In the drawings of the embodiments of the present application, only the structures related to the embodiments of the present disclosure are involved, and other structures can refer to the general design. In the case of no conflict, the same embodiment and different embodiments of the present application can be combined with each other.

[0108] Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A composite material for preparing a geopolymer-based triboelectric nanogenerator, characterized in that, include: Primary fly ash 28%–32%, mineral powder 18%–22%, sodium silicate 4%–6%, graphene 1%–2%, functionalized Ti3C2T x The composition consists of 3%–4% nanosheets, 3%–4% barium titanate nanoparticles, 3%–4% polyvinylidene fluoride nanofibers, 3%–4% polydimethylsiloxane elastic microspheres, 0.5%–1% polycarboxylic acid-based high-efficiency water-reducing agent, 1%–2% nano-hydroxyapatite, and the remainder is water.

2. The method for preparing a composite material for preparing a geopolymer-based triboelectric nanogenerator according to claim 1, characterized in that, Includes the following steps: S1, 1% graphene, 4% functionalized Ti3C2T x Nanosheets, 4% BaTiO3 nanoparticles, 1% water-reducing agent, and 14% water were mixed and then subjected to ultrasonic treatment and high-pressure homogenization to obtain a composite dispersion. S2. Prepare an alkaline activator solution according to a fixed mixing ratio, and let the solution cool to room temperature for later use; S3. Add primary fly ash, mineral powder and nano hydroxyapatite to the composite dispersion, and stir at a low speed of 100 rpm for 2 min to perform primary wetting and mixing of the composite dispersion to obtain a premixed slurry. S4. Polyvinylidene fluoride nanofibers and polydimethylsiloxane elastic microspheres are added to the premixed slurry, and the premixed slurry is efficiently dispersed and mixed by progressive shearing to obtain a composite slurry. S5. Add the alkali activator solution to the composite slurry and stir at 200 rpm for 2 min to adjust the fluidity of the composite slurry so that the slump reaches 180±10 mm. After pouring directly into the mold, it is compacted and cured under constant temperature and humidity for 28 days and then naturally dried for 48 h to obtain the cured body. S6. Nanoimprinting is performed on the surface of the solidified body to form a microstructure functional layer, and an electrospun PVDF film is laid on it, silver fiber electrodes are attached, and then pressed together to construct and obtain the final polymer-based triboelectric nanogenerator.

3. The method for preparing a composite material for preparing a geopolymer-based triboelectric nanogenerator according to claim 2, characterized in that, In step S1, 1% graphene, 4% functionalized Ti3C2Tx nanosheets, 4% BaTiO3 nanoparticles, 1% water-reducing agent, and 14% water are mixed and subjected to ultrasonic treatment at 40 kHz for 45 minutes, followed by homogenization at 300 bar three times to obtain a composite dispersion.

4. The method for preparing a composite material for preparing a geopolymer-based triboelectric nanogenerator according to claim 2, characterized in that, In step S2, 5% sodium silicate particles and 10% water are mixed to prepare an alkaline activation solution, and the solution is cooled to room temperature for later use.

5. The method for preparing a composite material for preparing a geopolymer-based triboelectric nanogenerator according to claim 2, characterized in that, In step S3, 32% primary fly ash, 20% mineral powder and 2% nano hydroxyapatite are added to the composite dispersion and stirred at a low speed of 100 rpm for 2 minutes to perform primary wetting and mixing of the composite dispersion, thereby obtaining a premixed slurry.

6. The method for preparing a composite material for preparing a geopolymer-based triboelectric nanogenerator according to claim 2, characterized in that, In step S4, 3% PVDF nanofibers and 4% PDMS elastic microspheres are added to the premixed slurry, and progressive shearing is used to efficiently disperse and mix the premixed slurry to obtain a composite slurry. The progressive shearing conditions are 200→300→400 rpm, 1 min each.

7. The method for preparing a composite material for preparing a geopolymer-based triboelectric nanogenerator according to claim 2, characterized in that, In step S5, the pre-prepared alkali activator solution is added to the composite slurry and stirred at a medium speed of 200 rpm for 2 minutes to adjust the fluidity of the composite slurry so that the slump reaches 180±10 mm. The slurry is then directly poured into a mold, compacted and cured under constant temperature and humidity for 28 days and then naturally dried for 48 hours to obtain the cured body. The mold dimensions are 50mm×50mm×50mm and 160mm×40mm×40mm. The conditions for vibration tapping are 60Hz and 45s; The curing conditions are 25°C and 95% RH.

8. The method for preparing a composite material for preparing a geopolymer-based triboelectric nanogenerator according to claim 2, characterized in that, In step S6, nanoimprinting is performed on the surface of the solidified body to form a microstructure functional layer, and an electrospun PVDF film is laid on it, silver fiber electrodes are attached, and then the layers are pressed together to construct and obtain the final polymer-based triboelectric nanogenerator. The conditions for the nanoimprinting are 5 MPa, 80 °C, and 30 min.

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