A MXene composite-based thermoelectric sensing type intelligent thermal management hydrogel and a preparation method thereof

Abstract

The application belongs to the technical field of thermal management materials, and discloses a thermal-electric sensing type intelligent thermal management hydrogel based on MXene composite and a preparation method thereof.The hydrogel is a three-dimensional polymer framework which is composed of melamine formaldehyde foam and a polymer network, and the lithium salt solution is loaded in the framework; and the MXene is also distributed in the polymer network, and the MXene is uniformly compounded in the polymer network through intermolecular hydrogen bonds.A new type of hydrogel thermal management material with efficient heat dissipation and intelligent monitoring functions is obtained, and the internal water content of the thermal-electric sensing type intelligent thermal management hydrogel based on MXene composite can be inversely calculated by monitoring the thermal-electric output signal of the thermal-electric sensing type intelligent thermal management hydrogel based on MXene composite in real time, so that the in-situ, real-time and non-destructive precise monitoring of the thermal management process is realized, and dynamic tracking and state early warning are realized.

Description

Technical Field

[0001] This invention belongs to the field of thermal management materials technology, and more specifically, relates to a thermoelectric sensing intelligent thermal management hydrogel based on MXene composite and its preparation method. Background Technology

[0002] With the rapid development of electronic information technology, electronic devices are upgrading towards higher power, miniaturization, flexibility, and integration. The informatization, intelligentization, and long-term effectiveness of thermal management systems have become core development trends. Hydrogel-based thermal management materials, with their excellent heat storage, thermal conductivity, and moisture absorption-evaporation heat dissipation properties, have become a research hotspot for novel passive heat dissipation materials. However, traditional hydrogel thermal management materials (such as the aerogel / hydrogel composite system developed by Professor Jeffrey Grossman, see: Lu Z, Strobach E, Chen N, Passive Sub-Ambient Cooling from a Transparent Evaporation-Insulation Bilayer. Joule, 2020; 4, 2693-2701, and the hydrogel heat dissipation material developed by Professor Hu Xuejiao of Wuhan University that can improve the working efficiency of semiconductors, see: S. Pu, J. Fu, Y. Liao, L.Ge, Y. Zhou, S. Zhang, S. Zhao, X. Liu, X. Hu, K. Liu, J. Chen, Promoting Energy Efficiency via a Self-Adaptive Evaporative Cooling Hydrogel. Adv. Mater. 2020, 32, 1907307.) face two major technological bottlenecks. First, with the rapid development of electronic information technology, the informatization and intelligentization of thermal management systems have become a major trend, and single thermal management materials cannot meet the needs of intelligent thermal management systems. This is also a major pain point limiting the widespread application of hydrogel thermal management materials. Furthermore, hydrogel thermal management materials possess a certain degree of self-adaptation; their thermal management capabilities change depending on their internal water content. However, this characteristic introduces significant uncertainty into the thermal management system. For example, if the hydrogel operates without water for an extended period, the heat dissipation capacity of the thermal management system may decline, leading to thermal management failure and posing a serious threat to the operational stability and safety of the equipment. Therefore, monitoring changes in the water content within the hydrogel and promptly feeding this information back to the thermal management system can effectively ensure the full utilization of the hydrogel's thermal management capabilities and prevent the collapse of the thermal management system, demonstrating significant application value.

[0003] Current methods for detecting water content within hydrogels, such as differential scanning calorimetry, suffer from limitations including complex operation, inability to perform real-time in-situ monitoring, and difficulty in synchronizing with thermal management processes. These limitations prevent the real-time correlation between dynamic changes in water content and thermal management efficiency, severely hindering the further development of hydrogels in the field of intelligent thermal management. Lu Xiang's team introduced aggregation-induced emission (AIE) molecules into hydrogels to achieve moisture absorption. Visual monitoring of the desorption process. However, this real-time visible image information can only serve as a reference for manual observation, making it difficult to collect and process information quickly and conveniently within the thermal management system, thus failing to meet the needs of an intelligent thermal management system.

[0004] Thermoelectric conversion technology enables the direct conversion of thermal energy into electrical energy, giving it unique advantages in the field of intelligent sensing. Hydrogels possess excellent ionic conductivity and structural tunability, making them ideal carriers for flexible thermoelectric materials. However, traditional hydrogels exhibit weak thermoelectric performance, low output electrical signals, and significant signal errors when exposed to fluctuations in the external environment, resulting in inaccurate feedback of moisture status and poor precision.

[0005] Therefore, developing hydrogel thermal management materials that combine efficient heat dissipation and intelligent monitoring is of great significance for promoting the development and engineering application of intelligent thermal management technology. At present, there is no integrated technical solution that combines the thermoelectric effect of MXene composite hydrogel with real-time monitoring of the thermal management process. Summary of the Invention

[0006] In view of the above-mentioned defects or improvement needs of the existing technology, the purpose of this invention is to provide a thermoelectric sensing intelligent thermal management hydrogel based on MXene composite and its preparation method, thereby obtaining a novel hydrogel thermal management material with both efficient heat dissipation and intelligent monitoring functions.

[0007] To achieve the above objectives, according to one aspect of the present invention, a thermoelectric sensing intelligent thermal management hydrogel based on MXene composite is provided. The hydrogel is based on a three-dimensional polymer skeleton composed of melamine formaldehyde foam (MF foam) and a polymer network, and the skeleton is loaded with lithium salt solution. Furthermore, MXene is also distributed in the polymer network, and the MXene is uniformly compounded in the polymer network through intermolecular hydrogen bonds.

[0008] As a further preferred embodiment of the present invention, the mass ratio of MXene to the polymer material in the polymer network is (0.5%~2.0%):1, preferably 1.5%:1.

[0009] As a further preferred embodiment of the present invention, the lithium salt in the lithium salt solution is at least one of LiCl and LiBr, and the solvent used is at least one of water, ethylene glycol, and glycerol. The polymer network is an interpenetrating network of polyacrylamide and polyvinyl alcohol.

[0010] As a further preferred embodiment of the present invention, the upper and lower surfaces of the MXene-based thermoelectric sensing smart thermal management hydrogel are further provided with porous Ni metal mesh as electrodes, thereby forming an integrated sandwich structure.

[0011] According to another aspect of the present invention, the present invention provides a method for preparing the above-mentioned thermoelectric sensing smart thermal management hydrogel based on MXene composite, comprising the following steps: S1: Prepare MXene powder materials; S2: The polymer monomer, initiator, crosslinking agent and MXene powder are uniformly dispersed in water to obtain a uniform hydrogel precursor solution; S3: After ultrasonic cleaning, the MF foam is immersed in the hydrogel precursor solution, and after ultrasonic dispersion and vacuum impregnation cycle treatment, the MF foam with the precursor fully impregnated and penetrated is obtained. S4: The MF foam, which is fully impregnated and permeated by the precursor, is placed into a mold, and porous Ni metal mesh electrodes are attached to the upper and lower surfaces. The mixture is then photocured and polymerized, demolded and washed, and then immersed in a lithium salt solution to obtain a thermoelectric sensing intelligent thermal management hydrogel based on MXene composite.

[0012] As a further preferred embodiment of the present invention, in step S3, the vacuum pressure used for vacuum impregnation does not exceed 50 Pa, the pressure is maintained for 5 minutes at a time, and the vacuum impregnation is repeated 3 times. In step S1, the preparation method of the MXene powder material is as follows: LiF is dissolved in hydrochloric acid solution, Ti3AlC2 powder is added in batches for etching, and MXene powder is obtained by centrifugal washing, ultrasonic peeling, graded centrifugation, and freeze drying. Preferably, the mass ratio of LiF to Ti3AlC2 is 2:1, the etching temperature is 55℃, the etching time is 24 h, and the ultrasonic stripping time is 0.5 h.

[0013] As a further preferred embodiment of the present invention, step S2 involves dissolving acrylamide (AM) and polyvinyl alcohol (PVA) in deionized water, heating them in a water bath or oil bath to dissolve them, and then cooling them to room temperature to obtain an aqueous solution. Ammonium persulfate (APS), methylenebisacrylamide (MBA), and MXene powder are then added and stirred until a uniform hydrogel precursor solution is obtained. Accordingly, in step S4, the polymer network in the MXene-based thermoelectric sensing smart thermal management hydrogel is an interpenetrating network of polyacrylamide and polyvinyl alcohol. Preferably, in step S2, the mass ratio of AM to PVA is 12:8, the added mass of APS and MBA is 0.5 wt% of the mass of the aqueous solution, the temperature of the water bath or oil bath is 80℃~120℃, and the stirring time is preferably 15 min~60 min.

[0014] According to another aspect of the present invention, the present invention provides the application of the above-mentioned MXene composite thermoelectric sensing intelligent thermal management hydrogel in passive heat dissipation of electronic devices.

[0015] As a further preferred embodiment of the present invention, the internal water content of the MXene-based thermoelectric sensing intelligent thermal management hydrogel can be determined by real-time monitoring of the thermoelectric output signal of the MXene-based thermoelectric sensing intelligent thermal management hydrogel.

[0016] According to another aspect of the present invention, the present invention provides a method for monitoring the internal water content of the above-mentioned thermoelectric sensing intelligent thermal management hydrogel based on MXene composite, which is to invert the internal water content of the thermoelectric sensing intelligent thermal management hydrogel based on MXene composite by real-time monitoring the thermoelectric output signal of the thermoelectric sensing intelligent thermal management hydrogel based on MXene composite.

[0017] Through the above technical solutions conceived in this invention, a novel hydrogel thermal management material with both high-efficiency heat dissipation and intelligent monitoring functions is obtained. MXene (e.g., MXene nanosheets) is used as a microscale thermal bridge to effectively improve the thermal conductivity of the hydrogel, while weakening the ion pair effect in high-concentration lithium salt (e.g., LiCl, LiBr) systems, significantly enhancing ion migration (i.e., σ) and thermoelectric conversion efficiency.

[0018] MXene materials possess high thermal conductivity, abundant surface functional groups, and excellent ion control capabilities. This invention utilizes MXene materials to simultaneously optimize the thermal management and thermoelectric properties of hydrogels. MXene can enhance thermal conductivity through microscale thermal bridging and synergistically increase the hygroscopic capacity of hydrogels with lithium salts (e.g., LiCl), thereby generating more water adsorption sites and lowering the diffusion barrier. Furthermore, the numerous functional groups on the MXene surface can interact with ions within the hydrogel, significantly weakening the ion-pair effect in high-concentration lithium salt solutions, enhancing the separation, diffusion, and migration of anions and cations within the hydrogel, and thus strengthening the thermoelectric effect of the hydrogel.

[0019] More importantly, based on the intrinsic relationship between the thermoelectric properties of hydrogels and their internal water content (as discussed later) Figure 7As shown in the figure, this invention is the first to construct an intelligent detection system that can monitor the water content inside the hydrogel in real time, thereby realizing the dynamic tracking and precise control of the thermal management process of the hydrogel. It breaks the isolated research mode of "thermoelectric performance enhancement" and "water content monitoring", and combines material performance optimization and functional integration.

[0020] Compared with traditional hydrogel thermal management materials, this invention addresses the problems of existing hydrogel thermal management materials, such as the inability to monitor moisture status in real time and weak thermoelectric performance. Specifically, this invention achieves the following beneficial effects: (1) Synergistic Performance Optimization: This invention adds MXene to the hydrogel matrix (which is composited with MF foam to form a corresponding three-dimensional polymer skeleton). MXene is uniformly composited in the polymer network through intermolecular hydrogen bonds, and MXene can simultaneously improve thermal conductivity, moisture absorption rate, and thermoelectric conversion efficiency. In particular, this invention can optimize the amount of MXene to 1.5 wt.% of the polymer material mass, at which point the thermal conductivity, output voltage, output current density, Seebeck coefficient, and power density are all at their highest, resulting in the best overall performance.

[0021] (2) Functional integration: It simultaneously realizes efficient passive thermal management and real-time moisture monitoring, breaks the isolated research mode of heat dissipation and sensing, and is highly compatible with intelligent thermal management systems.

[0022] (3) Precise and convenient monitoring: Based on the thermoelectric effect, in-situ non-destructive monitoring is required, no complex equipment is needed, the error is <5%, and it can be directly linked with the control system (such as the power control system of the device). Relying on the strong quantitative correlation between the thermoelectric output signal and the internal water content, this relationship is mainly expressed as the mathematical relationship between the Seebeck coefficient and the ion concentration in the solution, as shown in the following formula:

[0023] In the formula, S c and S ∞ These represent the Seebeck coefficients (Si) at different lithium salt concentrations and at the maximum lithium salt concentration. ∞ It can be considered as a constant), c is the concentration (i.e., S). c (corresponding concentration) The coefficient depends on the lithium chloride solution system. These are the fitting coefficients obtained through fitting.

[0024] Based on the above inversion formula, the change in the internal water content of the hydrogel can be inverted by testing the output voltage at both ends of the hydrogel, so as to realize in-situ, real-time, non-destructive and accurate monitoring of the thermal management process, and achieve dynamic tracking and status early warning.

[0025] As illustrated in the embodiments below, since there is a quantitative relationship between the Seebeck coefficient (S) and the output voltage, and also a quantitative relationship between the Seebeck coefficient and the ion concentration, it is only necessary to monitor the output voltage from the upper and lower electrodes, obtain the Seebeck coefficient (the Seebeck coefficient equals the output voltage divided by ΔT) by inverting the output voltage value, and then obtain the ion concentration based on the Seebeck coefficient to finally obtain the water content inside the hydrogel, thereby obtaining the mass retention rate of the hydrogel. This enables in-situ, real-time, non-destructive monitoring. Furthermore, based on the water content of the hydrogel, it can be determined whether the hydrogel needs to be decommissioned to avoid affecting the heat dissipation safety of the device.

[0026] (4) Stable and durable structure: The porous Ni electrode is firmly bonded to the hydrogel, and the water absorption and release performance is stable.

[0027] (5) Wide range of application scenarios: It is suitable for intelligent thermal management of FTTR communication equipment, flexible electronics, wearable devices, and high-power small electronic devices, especially for intelligent thermal management scenarios of flexible electronics, communication equipment, and high-power small devices that require real-time status monitoring and long-term stable operation.

[0028] Taking Example 4, which has the optimal amount of MXene in this invention, as an example, the hydrogel prepared by this invention has a thermal conductivity of up to 0.64 W / (m·K) and a Seebeck coefficient of 1.02 mV / K at the optimal amount of MXene. In the thermal management of FTTR communication devices, it can achieve a stable temperature drop of about 4.7℃, and the temperature drop decay is only 0.6℃ after 8 hours of continuous operation. The water content of the hydrogel can be monitored in real time through thermoelectric signals, and the water content calculation error is less than 5%. It has both efficient passive heat dissipation and intelligent status monitoring functions, and has broad application prospects in the field of intelligent thermal management of flexible electronics, wearable devices, communication terminals, and high-power small devices.

[0029] In summary, this invention improves the thermoelectric properties of hydrogels and, through real-time feedback of thermoelectric signals, enables in-situ, non-destructive monitoring of moisture state changes during hydrogel thermal management. This overcomes the limitations of traditional detection methods and allows for real-time correlation between dynamic changes in water content and thermal management efficiency. Furthermore, this invention simultaneously enhances thermal management performance and thermoelectric conversion efficiency through hydrogen bonding between MXene and the polymer matrix, and achieves in-situ monitoring of moisture state based on thermoelectric signals, potentially leading to the construction of an integrated intelligent thermal management system. Attached Figure Description

[0030] Figure 1 This is a conceptual diagram of the thermal management process for thermoelectric hydrogel monitoring. As shown in the figure, the temperature difference ΔT affects the output voltage U, which reflects the Seebeck coefficient S. The Seebeck coefficient S, in turn, reflects the change in ion concentration c. The change in c is due to the evaporation of water, and the change in c is equal to the change in water content.

[0031] Figure 2 This image shows the preparation method and physical sample of a hydrogel with a Ni electrode.

[0032] Figure 3 This is a SEM image of the Ni porous electrode material used in the embodiments.

[0033] Figure 4 Thermoelectric properties of hydrogels prepared for different embodiments (thermoelectric property tests were conducted under a temperature difference of 20 K).

[0034] Figure 5 Thermal conductivity of the hydrogels prepared in different embodiments.

[0035] Figure 6 The variation in moisture absorption rate of the hydrogels prepared in different embodiments.

[0036] Figure 7 The relationship between the internal ion concentration and Seebeck coefficient of the hydrogel prepared in Example 4.

[0037] Figure 8 The impedance and Warburg factor of different Mxene composite hydrogels.

[0038] Figure 9 This is a schematic diagram of a hydrogel thermal management experiment. As shown in the figure, during the experiment, the hydrogel obtained based on this invention is attached to the inner surface of the device shell (the device itself is ventilated).

[0039] Figure 10 The figure shows the thermal management temperature profiles for the hydrogel. All three samples shown are for FTTR devices. "Contrast" indicates no hydrogel was used; "With Hydrogel" indicates the pure hydrogel prepared in Example 4, but without Ni electrodes on either the upper or lower surfaces; "With Hydrogel (Ni electrode)" indicates the optimal hydrogel prepared in Example 4, with Ni electrodes on both the upper and lower surfaces.

[0040] Figure 11 The curves show the temperature difference and voltage output at both ends of the hydrogel thermal management system prepared in Example 4 as a function of time.

[0041] Figure 12 The figures show the mass testing and inversion error of the hydrogel prepared in Example 4. In the figures, the data corresponding to the "weightexperimental" legend were measured by conventional experimental methods; the data corresponding to the "weight simulated" legend were inverted according to the formula.

[0042] Figure 13 The change in water mass due to the cyclic absorption and release of the hydrogel prepared in Example 4. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0044] The MXene used in the following examples is prepared by the following steps: (1) Dissolve 2.0 g LiF in 20 mL of 9 M hydrochloric acid and stir magnetically at 55 °C for 0.5 h until completely dissolved; (2) Add 1.0 g Ti3AlC2 powder in batches within 10 min and continue the reaction for 24 h to complete the etching of the Al layer; (3) Centrifuge at 3500 rpm for 5 min, wash repeatedly with deionized water and ethanol 6-7 times until the supernatant is dark green and pH > 6, and collect the lower precipitate; (4) The precipitate was redispersed in 100 mL of deionized water and ultrasonically exfoliated for 0.5 h using a cell disruptor; (5) Centrifuge at 3500 rpm for 10 min, collect the supernatant after multiple fractional centrifugations, filter, freeze-dry to obtain MXene powder, and preserve in vacuum packaging. SEM characterization confirmed that the sample was MXene nanosheets.

[0045] Furthermore, the preparation of PAM / PVA / MF-LiCl hydrogel in Example 1 and the preparation of PAM / PVA / MF@MXene-LiCl hydrogel in Examples 2-5 generally follow the following common steps (i.e., hydrogel precursor preparation, MF foam impregnation, integrated gelation and electrode composite steps): (1) Weigh 12 g AM and 8 g PVA and add them to 80 mL of deionized water. Stir at 600 rpm in a 90℃ water bath for 60 min until completely dissolved, and then cool to room temperature. (2) Add 0.5 g APS, 0.5 g MBA and a quantitative amount of MXene (0, 0.5, 1.0, 1.5, 2.0 wt.%, based on the proportion of MXene in the total mass of (AM+PVA); that is, the amounts of MXene used are 0 g, 0.1 g, 0.2 g, 0.3 g, 0.4 g respectively), stir at 600 rpm for 15 min to obtain the precursor solution; (3) After ultrasonic cleaning of MF foam, immerse it in the precursor solution, disperse it with ultrasonic assistance, maintain vacuum pressure at 45 Pa for 5 min, break the vacuum, and repeat 3 times to ensure full immersion. (4) such as Figure 2 As shown, the impregnated MF foam is placed into the mold, and porous Ni metal mesh electrodes (attached to the glass) are attached to the upper and lower surfaces; the porous Ni metal mesh used in this embodiment of the invention has a pore size of approximately 400 μm; (5) The gelation molding is achieved by repeated freeze-thaw cycles and photocuring multiple gelation polymerization. After demolding, the product is washed with deionized water to obtain the initial PAM / PVA / MF@MXene product. Then, it is added to a LiCl aqueous solution (concentration of 30wt%; the samples in each embodiment of the present invention are used in an environment of 25℃ and 50RH%; the concentration of the LiCl solution can be flexibly adjusted according to the target humidity and temperature environment) and fully immersed for 2 days. The PAM / PVA / MF-LiCl hydrogel (MXene amount is 0) or PAM / PVA / MF@MXene-LiCl hydrogel (MXene amount is not 0) can be obtained.

[0046] For hydrogels prepared with a non-zero MXene content, the hydrogel uses PAM / PVA / MF as the polymer backbone, and MXene is uniformly composited inside the backbone through hydrogen bonds. LiCl is loaded to achieve efficient moisture absorption and ionic conductivity. A porous Ni metal mesh is used as the electrode to construct an integrated "electrode-hydrogel-electrode" sandwich structure.

[0047] The intelligent thermal management hydrogel of this invention is composed of a PAM / PVA / MF polymer framework, MXene nanosheets, LiCl hygroscopic agent, and porous Ni metal mesh electrode.

[0048] In addition, the performance data involved in the following embodiments were tested using the following methods: i) Thermoelectric performance test: Under the condition of controlling the temperature difference ΔT = 20 K between the upper and lower ends of the hydrogel, the output voltage and current density were measured, and the Seebeck coefficient and power density were calculated.

[0049] ii) Moisture absorption performance test: First, the hydrogel is completely evaporated, and then placed in an environment of 25℃ and 50%RH, and its mass change is recorded.

[0050] iii) Thermal management performance testing: Prepare several FTTR communication device samples, all of which operate stably at the same power, including: a) The hydrogels obtained in all embodiments have the same size (6 cm × 6 cm × 2 mm). Figure 9As shown, the device is attached to the same position on the inner surface of the FTTR communication device housing, and the device itself is ventilated; the relationship T1(t) of the highest surface temperature of the device as a function of time is obtained by continuous monitoring. b) Prepare an FTTR communication device without hydrogel, with ventilation on the device itself; continuously monitor the relationship between the highest surface temperature of the device and time, T0(t); The temperature drop T0(t) - T1(t) was calculated at the same time t for 8 hours of continuous testing, and the maximum temperature drop was obtained from it. The temperature drop decay value was obtained based on the difference between the temperature drop at 8 hours and the maximum temperature drop. In addition, the temperature was recorded once every 10 seconds during the 8 hours of continuous testing.

[0051] The following are specific examples: Example 1 (PAM / PVA / MF-LiCl hydrogel, control sample, belonging to traditional hydrogel materials) (1) Prepare a precursor solution without MXene according to the general procedure; (2) Following the general procedure, after impregnation with MF foam and vacuum treatment, without the addition of MXene, PAM / PVA / MF-LiCl hydrogel with Ni electrodes on the upper and lower surfaces is obtained by gelation.

[0052] Performance: Thermal conductivity 0.58 W / (m·K), Seebeck coefficient 0.4 mV / K. Moisture absorption performance test results are as follows... Figure 6 As shown. The impedance test results are as follows. Figure 8 As shown.

[0053] Example 2 (MXene addition amount 0.5 wt.%) (1) Prepare MXene powder according to the steps described above; (2) Following the general procedure, add 0.5 wt.% MXene, keeping the other parameters unchanged, to prepare a hydrogel with Ni electrodes on the upper and lower surfaces.

[0054] Performance: Thermal conductivity 0.60 W / (m·K), Seebeck coefficient 0.65 mV / K. Moisture absorption performance test results are as follows... Figure 6 As shown, the moisture absorption rate increases. Impedance test results are as follows: Figure 8 As shown.

[0055] Example 3 (MXene addition amount 1.0 wt.%) (1) Prepare MXene powder according to the steps described above; (2) Following the general procedure, add 1.0 wt.% MXene, keeping the other parameters unchanged, to prepare a hydrogel with Ni electrodes on the upper and lower surfaces.

[0056] Performance: Thermal conductivity 0.62 W / (m·K), Seebeck coefficient 0.85 mV / K. Moisture absorption performance test results are as follows... Figure 6 As shown. The impedance test results are as follows. Figure 8 As shown, the ion diffusion resistance decreases, and the impedance decreases.

[0057] Example 4 (MXene addition amount 1.5 wt.%, optimal sample) (1) Prepare MXene powder according to the steps described above; (2) Following the general procedure, add 1.5 wt.% MXene, keeping the other parameters unchanged, to prepare a hydrogel with Ni electrodes on the upper and lower surfaces.

[0058] Performance: Thermal conductivity 0.64 W / (m K), Seebeck coefficient 1.02 mV / K, output voltage 20.4 mV, current density 55 mA / m², power density 0.28 mW / m²; the FTTR device's thermal management temperature drop is approximately 4.7℃, it operates stably for 8 hours, and the moisture content monitoring error is <5%. The moisture absorption performance test results are as follows: Figure 6 As shown. The impedance test results are as follows. Figure 8 As shown. Furthermore, the hydrogel with Ni electrodes on both the upper and lower surfaces was subjected to evaporation treatment. As the water evaporated, the concentration of the loaded lithium salt solution changed accordingly. The Seebeck coefficient was then measured at different lithium salt concentrations, and the results are shown below. Figure 7 As shown, the fitted line (SSimulated) satisfies the formula:

[0059] In the formula exist Figure 7 The corresponding value in the middle is 0.2071, and n is in Figure 7 The corresponding value is 1.3452. exist Figure 7 The corresponding value is 6.2618.

[0060] Furthermore, the hydrogel with Ni electrodes on both the upper and lower surfaces was subjected to a cyclic water absorption and desorption experiment, and the results were as follows: Figure 13 As shown, the porous Ni electrode is firmly bonded to the hydrogel, and its water absorption and release performance is stable.

[0061] Furthermore, to illustrate the effect of porous Ni electrodes on the thermal management performance of the hydrogel, according to Example 4, we also obtained a pure hydrogel without Ni electrodes on either the upper or lower surface. The thermal management temperature curve of this pure hydrogel is shown below. Figure 10 As shown, the thermal management performance is shown in Table 2 (the performance data for this pure hydrogel sample without upper and lower Ni electrodes are only shown in Table 2 and...). Figure 10 Other sample experimental data related to Example 4 are all for samples with Ni electrodes on the upper and lower surfaces.

[0062] Example 5 (MXene addition amount 2.0 wt.%) (1) Prepare MXene powder according to the steps described above; (2) Following the general procedure, add 2.0 wt.% MXene, keeping the other parameters unchanged, to prepare a hydrogel with Ni electrodes on the upper and lower surfaces.

[0063] Performance: MXene showed slight agglomeration, and the thermal conductivity decreased to 0.61 W / (m²). K), Seebeck coefficient 0.90 mV / K, thermoelectric performance slightly decreased. Moisture absorption performance test results are as follows: Figure 6 As shown. The impedance test results are as follows. Figure 8 As shown.

[0064] Detailed data on the thermoelectric properties of samples from Examples 1-5 are shown in Table 1 below: Table 1: Thermoelectric properties of hydrogels with different MXene contents

[0065] The thermal management performance of the pure hydrogel sample obtained in Example 4 and the hydrogel sample with Ni electrodes on the upper and lower surfaces after 8 hours in the FTTR device is shown in Table 2: Table 2: Thermal management properties of different hydrogels

[0066] In addition, for the optimal hydrogel sample obtained in Example 4, the thermal management performance obtained in the FTTR device for 8 consecutive hours was analyzed. The Seebeck coefficient (the Seebeck coefficient equals the output voltage divided by ΔT) was obtained by inverting the output voltage value. Then, the ion concentration was obtained based on the Seebeck coefficient, and the water content inside the hydrogel was finally obtained (the "thermoelectric inversion mass retention rate" in Table 3 is positively correlated with the water content inside the hydrogel). At the same time, the mass retention rate measured by the traditional weighing method was used as a comparison (corresponding to the "measured mass retention rate" in Table 3), and the error was calculated. The results are shown in Table 3. Table 3: Error in water content retrieval from thermoelectric signals

[0067] As can be seen, the moisture monitoring accuracy of the optimal hydrogel sample obtained in Example 4 is less than 5%.

[0068] In summary, it is easy to see that Embodiments 2-5 of the present invention (especially Embodiment 4) have significant advantages over the control sample obtained in Embodiment 1 in the following aspects: (1) Excellent thermal management performance: MXene constructs a continuous thermal conduction path, increasing the thermal conductivity from 0.58 to 0.64 W / (m²). K); synergistically enhances the moisture absorption rate with LiCl, exhibiting strong stability in cyclic water absorption and desorption; the introduction of Ni electrodes provides more stable long-term heat dissipation, achieving excellent temperature reduction in the thermal management of FTTR equipment (experimental schematic diagram attached). Figure 9 The temperature change curves for a typical 1.5 wt% MXene addition are shown in the attached figure. Figure 10 As shown, the temperature drop decreases by only 0.6℃ after 8 hours.

[0069] (2) Significantly improved thermoelectric performance: MXene weakens the ion pair effect and accelerates ion separation and migration. When the optimal MXene addition amount is 1.5 wt.%, the Seebeck coefficient increases from 0.4 mV / K to 1.02 mV / K. The output signal is stable and the detection error is small. This thermoelectric performance optimization may be supported by the impedance correlation test results (see appendix). Figure 8 ).

[0070] (3) Intelligent monitoring is accurate and reliable: A quantitative correlation model between thermoelectric signals and water content is established. Water content is inverted by real-time monitoring of output voltage (i.e., thermoelectric potential). The error is less than 5%, realizing in-situ, non-destructive, and dynamic tracking of the thermal management process (see appendix). Figure 11 With appendix Figure 12 ).

[0071] The above embodiment uses PAM / PVA / MF as a three-dimensional polymer framework as an example. Besides the PAM / PVA / MF three-dimensional polymer framework, other polymer materials can also be used to form corresponding polymer networks (by combining MF foam with this polymer network to form a corresponding three-dimensional polymer framework). In other words, the composition of the hydrogel matrix can be flexibly varied, exhibiting broad applicability (the composition of the hydrogel matrix has no significant impact on the thermoelectric effect and thermal management effect monitoring of this invention). For example, the porous Ni metal mesh can also use other mesh sizes (e.g., other pore sizes from 50μm to 800μm); besides metallic Ni, porous electrodes such as Cu, Ti, Fe, and Zn can also be used, as long as they have a porous structure and can reduce the impact on water evaporation. In addition to loading LiCl aqueous solution, the hydrogel can also load other lithium salt solutions; for example, the lithium salt solute can be LiBr in addition to LiCl; the solvent can also be any one or a mixture of water, ethylene glycol, and glycerol. In addition to preparing MXene using the method described above, based on this invention, MXene materials can also be prepared using other process methods (e.g., commercially available MXene materials).

[0072] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A thermoelectric sensing smart thermal management hydrogel based on MXene composite, characterized in that, The hydrogel is based on a three-dimensional polymer framework composed of melamine-formaldehyde foam (MF foam) and a polymer network, with lithium salt solution loaded in the framework. Furthermore, MXene is also distributed in the polymer network, and the MXene is uniformly compounded in the polymer network through intermolecular hydrogen bonds.

2. The thermoelectric sensing intelligent thermal management hydrogel based on MXene composite as described in claim 1, characterized in that, The mass ratio of MXene to the polymer material in the polymer network is (0.5%~2.0%):1, preferably 1.5%:

1.

3. The thermoelectric sensing intelligent thermal management hydrogel based on MXene composite as described in claim 1, characterized in that, The lithium salt in the lithium salt solution is at least one of LiCl and LiBr, and the solvent used is at least one of water, ethylene glycol, and glycerol. The polymer network is an interpenetrating network of polyacrylamide and polyvinyl alcohol.

4. The thermoelectric sensing intelligent thermal management hydrogel based on MXene composite as described in claim 1, characterized in that, The upper and lower surfaces of the MXene-based thermoelectric sensing smart thermal management hydrogel are also provided with porous Ni metal mesh as electrodes, thereby forming an integrated sandwich structure.

5. The preparation method of the thermoelectric sensing intelligent thermal management hydrogel based on MXene composite as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: Prepare MXene powder materials; S2: The polymer monomer, initiator, crosslinking agent and MXene powder are uniformly dispersed in water to obtain a uniform hydrogel precursor solution; S3: After ultrasonic cleaning, the MF foam is immersed in the hydrogel precursor solution, and after ultrasonic dispersion and vacuum impregnation cycle treatment, the MF foam with the precursor fully impregnated and penetrated is obtained. S4: The MF foam, which is fully impregnated and permeated by the precursor, is placed into a mold, and porous Ni metal mesh electrodes are attached to the upper and lower surfaces. The mixture is then photocured and polymerized, demolded and washed, and then immersed in a lithium salt solution to obtain a thermoelectric sensing intelligent thermal management hydrogel based on MXene composite.

6. The preparation method according to claim 5, characterized in that, In step S3, the vacuum pressure used for vacuum impregnation does not exceed 50 Pa, the pressure is maintained for 5 minutes at a time, and the vacuum impregnation is repeated 3 times. In step S1, the preparation method of the MXene powder material is as follows: LiF is dissolved in hydrochloric acid solution, Ti3AlC2 powder is added in batches for etching, and MXene powder is obtained by centrifugal washing, ultrasonic peeling, graded centrifugation, and freeze drying. Preferably, the mass ratio of LiF to Ti3AlC2 is 2:1, the etching temperature is 55℃, the etching time is 24 h, and the ultrasonic stripping time is 0.5 h.

7. The preparation method according to claim 5, characterized in that, Step S2 involves dissolving acrylamide (AM) and polyvinyl alcohol (PVA) in deionized water, heating them in a water bath or oil bath, and then cooling them to room temperature to obtain an aqueous solution. Ammonium persulfate (APS), methylenebisacrylamide (MBA), and MXene powder are then added and stirred until a homogeneous hydrogel precursor solution is obtained. Accordingly, in step S4, the polymer network in the MXene-based thermoelectric sensing smart thermal management hydrogel is an interpenetrating network of polyacrylamide and polyvinyl alcohol. Preferably, in step S2, the mass ratio of AM to PVA is 12:8, the added mass of APS and MBA is 0.5 wt% of the mass of the aqueous solution, the temperature of the water bath or oil bath is 80℃~120℃, and the stirring time is preferably 15 min~60 min.

8. The application of the MXene composite thermoelectric sensing intelligent thermal management hydrogel as described in any one of claims 1-4 in passive heat dissipation of electronic devices.

9. The application as described in claim 8, characterized in that, By monitoring the thermoelectric output signal of the MXene composite-based thermoelectric sensing intelligent thermal management hydrogel in real time, the internal water content of the MXene composite-based thermoelectric sensing intelligent thermal management hydrogel can be determined.

10. The method for monitoring the internal water content of a thermoelectric sensing intelligent thermal management hydrogel based on MXene composite as described in any one of claims 1-4, characterized in that, The internal water content of the MXene-based thermoelectric sensing intelligent thermal management hydrogel is determined by real-time monitoring of its thermoelectric output signal.

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