Nanosheet composite materials and their preparation methods, conductive nanocomposite paper with shape memory function and its applications

Abstract

This invention belongs to the field of thermosensitive materials technology, specifically relating to a nanosheet composite material and its preparation method, a conductive nanocomposite paper with shape memory function, and its application. This invention provides a nanosheet composite material comprising M(OH)(OCH3) nanosheets and polydopamine and a conductive metal loaded on the M(OH)(OCH3) nanosheets; wherein M includes Co and Ni. The conductive nanocomposite paper prepared from the nanosheet composite material provided by this invention, based on the excellent surface conductivity and thermally triggered shape memory characteristics of nanopaper, can be used as a fire alarm paper without direct contact with flames. It can connect to the alarm circuit when abnormal heat accumulation occurs, thereby achieving sensitive early fire alarm.

Description

Technical Field

[0001] This invention belongs to the field of thermosensitive materials technology, specifically relating to a nanosheet composite material and its preparation method, a conductive nanocomposite paper with shape memory function and its application. Background Technology

[0002] Currently, the main methods for early fire alarms include smoke detectors, light detectors, and heat detectors. However, the sensitivity of smoke sensors is unreliable because the smoke emission process is greatly affected by various factors. Light detectors are ineffective in fires caused by heat accumulation, as they are only triggered when the flames are already visible. Heat-sensitive fire alarms mostly rely on external thermal sensors to monitor temperature changes, limiting their convenience and flexibility. Therefore, scientists have been working to design and manufacture functional materials capable of detecting temperature changes independently.

[0003] Against this backdrop, the development of fire alarm paper represents a significant advancement. Currently, most fire alarm nanopapers rely on the resistivity sensitivity of nanofillers that exhibit higher conductivity at high temperatures. For example, Cao et al. (CFCao, B.Yu, BFGuo, WJHu, FNSun, ZHZhang, SNLi, W.Wu, LCTang, PASong, H.Wang, Bio-inspired, sustainable and mechanically robust graphene oxide-based hybrid networks for efficient fire protection and warning, Chem. Eng. J. 439 (2022) 14) developed a novel fire-resistant and fire alarm nanopaper based on a hybrid interconnected network of graphene oxide, cellulose phosphorylation, and tannic acid, exhibiting enhanced structural stability, flame retardancy, and fire alarm response. Ma et al. (TTMa,LPLi,MZPan,CGGuo,CTMei,Multifunctional MXene-based fire alarm wallpaper with sandwich-like structure for enhanced fire safety and prevention,Chem.Eng.J.451(2023)12) prepared a flexible nano-bionic fire alarm wallpaper based on lignocellulose and MXene thermal sensors, which has ultra-sensitive fire alarm function and excellent thermal insulation performance.

[0004] However, using nanopaper as thermistors poses a significant fire hazard because they typically require very high trigger temperatures and often need to be in direct contact with flames. Summary of the Invention

[0005] The purpose of this invention is to provide a nanosheet composite material and its preparation method, a conductive nanocomposite paper with shape memory function and its application. The nanopaper prepared from the nanosheet composite material provided by this invention has shape memory function. When used as fire alarm paper, it does not need to be in direct contact with flames, has a low triggering temperature, and can realize early fire alarm.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The present invention provides a nanosheet composite material comprising M(OH)(OCH3) nanosheets and polydopamine and a conductive metal loaded on the M(OH)(OCH3) nanosheets; wherein M comprises Co and Ni.

[0008] Preferably, the polydopamine loading percentage is 10-50%.

[0009] Preferably, the conductive metal comprises silver and / or copper, and the mass percentage of the conductive metal is 30-90%.

[0010] This invention also provides a method for preparing the nanosheet composite material described in the above technical solution, comprising the following steps:

[0011] M(OH)(OCH3) nanosheets, dopamine hydrochloride, and water were mixed, and the pH of the resulting mixture was adjusted to be alkaline before polymerization was carried out to obtain nanosheet-loaded polydopamine.

[0012] The nanosheets are loaded with polydopamine, water-soluble metal salt, binder, reducing agent and water, and a reduction reaction is carried out to obtain the nanosheet composite material.

[0013] Preferably, the mass ratio of the M(OH)(OCH3) nanosheets to dopamine hydrochloride is 0.5–2:0.38;

[0014] The polymerization reaction is carried out at a temperature of 10–40°C for a duration of more than 3 hours.

[0015] The polymerization reaction is carried out under stirring conditions.

[0016] Preferably, the adhesive comprises polyvinylpyrrolidone;

[0017] The mass ratio of the nanosheet-loaded polydopamine to the binder is 1 to 2:1;

[0018] The reducing agent includes glucose or aldehyde reagents;

[0019] The mass ratio of the nanosheet-loaded polydopamine to the reducing agent is 0.02–0.1:1;

[0020] The water-soluble metal salts include water-soluble silver salts and / or water-soluble copper salts;

[0021] The mass ratio of the nanosheet-loaded polydopamine to the water-soluble metal salt is 0.5–2:1;

[0022] The reduction reaction is carried out at a temperature of 10–40°C for a time of 3 hours or more.

[0023] Preferably, when the water-soluble metal salt is a water-soluble silver salt, the reduction reaction process is as follows:

[0024] The nanosheets are loaded with polydopamine, water-soluble silver salt, binder, ammonia, reducing agent and water, and a reduction reaction is carried out.

[0025] The mass ratio of the nanosheets loaded with polydopamine and ammonia is 0.2 to 1:1;

[0026] The mixture includes:

[0027] The nanosheet-loaded polydopamine and water were first stirred and mixed to obtain a dispersion;

[0028] The dispersion, water-soluble silver salt, binder, and ammonia water are mixed by stirring to obtain a mixture.

[0029] The mixture and reducing agent are stirred and mixed for the third time.

[0030] The present invention also provides a conductive nanocomposite paper with shape memory function, which is prepared from cellulose matrix and additives;

[0031] The additive is the nanosheet composite material described in the above technical solution or the nanosheet composite material prepared by the preparation method described in the above technical solution.

[0032] Preferably, the cellulose matrix comprises hydroxypropyl methylcellulose;

[0033] The additive has a mass percentage content of 10-90%.

[0034] This invention also provides the application of the conductive nanocomposite paper described above as fire alarm paper or electromagnetic shielding paper.

[0035] This invention provides a nanosheet composite material comprising M(OH)(OCH3) nanosheets and polydopamine and a conductive metal loaded on the M(OH)(OCH3) nanosheets; wherein M includes Co and Ni. By loading polydopamine, this invention enables better pre-deposition and growth of metal ions on the M(OH)(OCH3) surface, providing sufficient oxidation sites for the reduction of metal ions and facilitating the formation of a uniform and dense metal coating layer. Furthermore, by loading a conductive metal, the conductivity of the composite material can be improved. The nanopaper prepared from the nanosheet composite material provided by this invention, based on its excellent surface conductivity and thermally triggered shape memory properties, can be used as fire alarm paper without direct contact with flames. It can connect to the alarm circuit upon abnormal heat accumulation, thereby achieving sensitive early fire alarm.

[0036] This invention also provides a nanopaper, prepared from a cellulose matrix and additives; the additives are the nanosheet composite material described in the above-described technical solution or the nanosheet composite material prepared by the preparation method described in the above-described technical solution. The nanopaper provided by this invention is an ideal, sensitive, and safe early fire alarm material, and its fire alarm strategy based on heat-triggered shape recovery has broad application prospects in fire alarm applications. Attached Figure Description

[0037] Figure 1 Characterization diagrams of the nanopapers obtained in Examples 2-4;

[0038] Figure 2 Thermogravimetric analysis (TGA) results of the nanopapers obtained in Examples 2-4 are shown.

[0039] Figure 3 The image shows a combustion test result of the nanopaper obtained in Example 1.

[0040] Figure 4 The electromagnetic shielding test results of the nanopaper obtained in Examples 2-4 are shown below.

[0041] Figure 5 The results of the test on the nanopaper shielding mobile phone signal obtained in Example 2 are shown.

[0042] Figure 6 This is a diagram illustrating the shape memory demonstration experiment of the nanopaper and hydroxypropyl methylcellulose membrane obtained in Example 1.

[0043] Figure 7 A schematic diagram illustrating the mechanism of thermal changes in nanopaper provided by this invention;

[0044] Figure 8 The experimental test diagram and schematic diagram of the nanopaper obtained in Example 1 as fire alarm paper are shown.

[0045] Figure 9This is a schematic diagram of the process for preparing nanosheet composite materials and conductive nanocomposite paper according to the present invention. Detailed Implementation

[0046] The present invention provides a nanosheet composite material comprising M(OH)(OCH3) nanosheets and polydopamine and a conductive metal loaded on the M(OH)(OCH3) nanosheets; wherein M comprises Co and Ni.

[0047] In this invention, the polydopamine loading percentage is preferably 10-50%, more preferably 20-40%.

[0048] In this invention, the conductive metal preferably comprises silver and / or copper. In this invention, the mass percentage of the conductive metal is preferably 30-90%, more preferably 40-80%, and even more preferably 50-60%.

[0049] This invention also provides a method for preparing the nanosheet composite material described in the above technical solution, comprising the following steps:

[0050] M(OH)(OCH3) nanosheets, dopamine hydrochloride, and water were mixed, and the pH of the resulting mixture was adjusted to be alkaline before polymerization was carried out to obtain nanosheet-loaded polydopamine.

[0051] The nanosheets are loaded with polydopamine, water-soluble metal salt, binder, reducing agent and water, and a reduction reaction is carried out to obtain the nanosheet composite material.

[0052] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0053] In this invention, M(OH)(OCH3) nanosheets, dopamine hydrochloride, and water are mixed, and the pH of the resulting mixture is adjusted to be alkaline before polymerization is carried out to obtain nanosheet-loaded polydopamine.

[0054] In this invention, the preferred mass ratio of the M(OH)(OCH3) nanosheets to dopamine hydrochloride is 0.5–2:0.38; the preferred amount ratio of the M(OH)(OCH3) nanosheets to water is 0.5 g:150 mL.

[0055] In this invention, the process of mixing M(OH)(OCH3) nanosheets, dopamine hydrochloride and water preferably includes: dispersing M(OH)(OCH3) nanosheets in water and then adding dopamine hydrochloride for mixing.

[0056] In this invention, ammonia is preferably used as the reagent to adjust the pH value of the resulting mixture.

[0057] In this invention, the polymerization reaction temperature is preferably 10–40°C, more preferably room temperature, and the reaction time is preferably greater than 3 hours, more preferably 24 hours; the polymerization reaction is preferably carried out under stirring conditions. After the polymerization reaction, this invention further preferably includes sequentially vacuum filtering and drying the obtained reaction system.

[0058] After obtaining the nanosheet-loaded polydopamine, the present invention mixes the nanosheet-loaded polydopamine, water-soluble metal salt, binder, reducing agent and water, and carries out a reduction reaction to obtain the nanosheet composite material.

[0059] In this invention, the water-soluble metal salt preferably includes a water-soluble silver salt and / or a water-soluble copper salt, wherein the water-soluble silver salt preferably includes silver nitrate, and the water-soluble copper salt preferably includes copper nitrate. In this invention, the mass ratio of the nanosheet-loaded polydopamine to the water-soluble metal salt is preferably 0.5 to 2:1.

[0060] In this invention, the adhesive preferably comprises polyvinylpyrrolidone (PVP); the mass ratio of the nanosheet-loaded polydopamine to the adhesive is preferably 1 to 2:1.

[0061] In this invention, the reducing agent preferably includes glucose or aldehyde reagent; the mass ratio of the nanosheet-loaded polydopamine to the reducing agent is preferably 0.02 to 0.1:1.

[0062] In this invention, when the water-soluble metal salt is a water-soluble silver salt, the reduction reaction process is preferably as follows: the nanosheets loaded with polydopamine, water-soluble silver salt, binder, ammonia, reducing agent and water are mixed to carry out the reduction reaction.

[0063] In this invention, the mass ratio of the nanosheet-loaded polydopamine to ammonia is preferably 0.2 to 1:1, more preferably 0.5:1.7. In this invention, the mixing preferably includes: first stirring and mixing the nanosheet-loaded polydopamine and water to obtain a dispersion; second stirring and mixing the dispersion, water-soluble silver salt, binder, and ammonia to obtain a mixture; and third stirring and mixing the mixture with a reducing agent.

[0064] In this invention, the first stirring and mixing time is preferably 5 minutes. In this invention, the water-soluble silver salt is preferably in the form of an aqueous solution for the second stirring and mixing; the concentration of the aqueous solution is preferably 0.05–0.2 mol / L. In this invention, the second stirring and mixing time is preferably 30 minutes. In this invention, the third stirring and mixing process constitutes the reduction reaction.

[0065] In this invention, the temperature of the reduction reaction is preferably 10–40°C, more preferably room temperature, and the time is preferably greater than or equal to 3 hours. After the reduction reaction, this invention further preferably includes sequentially subjecting the obtained reaction system to vacuum filtration and drying.

[0066] The present invention also provides a conductive nanocomposite paper with shape memory function, which is prepared from cellulose matrix and additives;

[0067] The additive is the nanosheet composite material described in the above technical solution or the nanosheet composite material prepared by the preparation method described in the above technical solution.

[0068] In this invention, the cellulose base material preferably includes hydroxypropyl methylcellulose.

[0069] In this invention, the mass percentage of the additive is preferably 10-90%.

[0070] In this invention, the preferred method for preparing the conductive nanocomposite paper includes the following steps: dispersing additives in water, adding cellulose matrix and stirring to obtain a mixture; placing the obtained mixture in a mold to form a film, thereby obtaining the conductive nanocomposite paper. In this invention, the stirring time is preferably 3 hours. In this invention, the film formation method is preferably casting. In this invention, the film formation is preferably carried out at room temperature, and the film formation time is preferably 11 days.

[0071] In this invention, the process flow diagram for preparing nanosheet composite materials and conductive nanocomposite paper is as follows: Figure 9 As shown.

[0072] This invention also provides the application of the conductive nanocomposite paper described above as fire alarm paper or electromagnetic shielding paper.

[0073] To further illustrate the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, describes a nanosheet composite material and its preparation method, a conductive nanocomposite paper with shape memory function, and its applications, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0074] Example 1

[0075] 0.5 g of M(OH)(OCH3) (where M is Co and Ni) was dispersed in 150 mL of deionized water, and 0.38 g of dopamine hydrochloride was added to prepare a mixed solution. Ammonia water was added to the mixed solution to adjust the pH to alkaline. The polymerization reaction was carried out by stirring at room temperature for 24 h. After stirring, the solution was vacuum filtered and dried to obtain nanosheet-loaded polydopamine (M(OH)(OCH3)@PDA, hereinafter referred to as MP).

[0076] 0.5 g MP was dispersed in 46 mL of deionized water and stirred for 5 min; then 147 mL of 0.1 mol / L AgNO3 solution, 0.25 g PVP and 1.7 g ammonia were added to prepare a mixed solution; after stirring for 30 min, 11.7 g glucose was added and stirred for another 3 h at room temperature to carry out the reduction reaction; then the reaction system was vacuum filtered and dried to obtain the nanosheet composite material (M(OH)(OCH3)@PDA@Ag, hereinafter referred to as MPA).

[0077] Example 2

[0078] Nanopaper was prepared using a casting method.

[0079] First, 1.0 g of MPA obtained in Example 1 was dispersed in 50 mL of deionized water; then 0.5 g of hydroxypropyl methylcellulose (HPMC) was added to form a mixed solution; the solution was stirred evenly at room temperature for 3 h, and then poured into a round petri dish and allowed to evaporate naturally at room temperature for 11 days to obtain nanopaper (denoted as CMPA-1).

[0080] Example 3

[0081] Nanopaper was prepared according to the method in Example 2, except that the mass of MPA was 0.7g, and the resulting nanopaper was denoted as CMPA-0.7.

[0082] Example 4

[0083] Nanopaper was prepared according to the method of Example 2, except that the mass of MPA was 1.3g, and the resulting nanopaper was denoted as CMPA-1.3.

[0084] Performance testing

[0085] Test Example 1

[0086] Figure 1 These are characterization images of the nanopaper obtained in Examples 2-4, where... Figure 1 (a) is the XRD pattern of the nanopaper obtained in Examples 2-4. Figure 1 (b) to (f) are XPS images of the nanopaper obtained in Example 2, and (b) to (f) are C1s, N1s, Ag3d, Co2p and Ni2p spectra, respectively.

[0087] The XRD pattern of the CMPA sample is as follows: Figure 1As shown in (a), the results indicate that the same phase of silver (Ag, PDF: 87-0717) was detected on the surfaces of CMPA-0.7, CMPA-1.0, and CMPA-1.3. According to the standard PDF card, the three prominent peaks at 38.3°, 44.3°, and 64.5° correspond to the (111), (200), and (220) crystal planes of Ag, respectively. The detection of Ag suggests that CMPA may have high surface conductivity. The surface elemental composition of CMPA-1.0 was analyzed by XPS. Figure 1 As shown in (b), the C1s spectra show Sp2 hybrid CC bonds and Sp3 hybrid COC bonds at 284.8 eV and 286 eV, respectively, both of which are derived from polysaccharides with HPMC structures. Figure 1 The N1s spectrum in (c) shows a single peak at 40.1 eV, which is attributed to C-NH2 in the polydopamine on the nanosheet surface. The pre-deposition growth of polydopamine on the M(OH)(OCH3) surface provides ample oxidation sites for Ag+ reduction, which is beneficial for the formation of a uniform and dense Ag-coated surface. Figure 1 The Ag 3d spectra in (d) show 33d / 2 and 3d5 / 2 quantum states at 374.3 eV and 368.5 eV, respectively, indicating the presence of elemental Ag on the surface, which is consistent with the XRD results. Figure 1 The Co 2p and Ni 2p spectra in (e) and (f) show the 2p3 / 2 and 2p1 / 2 quantum states of these two elements, respectively. Co and Ni originate from the small exposed surfaces of M(OH)(OCH3). XRD and XPS results show that MPA is well bonded to HPMC, which is likely due to hydrogen bonds formed between the hydroxyl and methoxy groups of MPA and the hydroxyl, methoxy, and amide groups of HPMC.

[0088] Test Example 2

[0089] Figure 2 Thermogravimetric analysis (TGA) charts of the nanopapers obtained in Examples 2-4 are shown below. Figure 2 (a) is the thermogravimetric curve. Figure 2 (b) is the dynamic thermogravimetric curve. Figure 2 (c) is the test curve of the micro calorimeter;

[0090] The sample was heated in air from 30°C to 800°C at a rate of 20°C / min. Figure 2As shown in (a), the weight loss process of pure HPMC paper consists of three stages: removal of physically adsorbed water below 150℃, elimination of hydroxypropyl and methyl groups between 300 and 400℃, further thermal decomposition and carbonization above 400℃, and complete decomposition at 500℃. In contrast, CMPA nanopapers exhibit significantly improved thermal stability. Specifically, they lose adsorbed water below 150℃, but the second stage of weight loss due to the elimination of hydroxypropyl and methyl groups occurs in the lower temperature range of 150 to 350℃. Furthermore, the weight of the nanopapers remains almost constant from 350℃ to 800℃. At 800℃, the carbon residues of CMPA-0.7, CMPA-1.0, and CMPA-1.3 are 54.1%, 58.3%, and 69.8%, respectively, showing an increasing trend. Figure 2 As shown in (b), the maximum weight loss rate of HPMC is -2.0% / ℃, while the maximum weight loss rates of CMPA-0.7, CMPA-1.0, and CMPA-1.3 are -1.19%, -0.94%, and -0.51% / ℃, respectively. The results indicate that with increasing MPA content, the char residue of the nanopaper increases, the maximum weight loss rate decreases, and the thermal stability is enhanced. Peak heat release rate (pHRR) and total heat release rate (THR) are important indicators for evaluating the flame retardancy of materials. Figure 2 (c) shows the MCC result of the sample. From Figure 2 As shown in (c), the pHRR of CMPA-0.7, CMPA-1.0, and CMPA-1.3 were 156.6, 108.9, and 79.7 W / g, respectively, which were 45.0, 61.9, and 72.1% lower than those of HPMC (284.7 W / g). The THR of CMPA-0.7, CMPA-1.0, and CMPA-1.3 were 5.2, 3.4, and 3.0 kJ / g, respectively, all significantly lower than those of HPMC (12.6 kJ / g).

[0091] Figure 3 The image shows a combustion test result of the nanopaper obtained in Example 1; where HPMC is hydroxypropyl methylcellulose film (…). Figure 3 (d) was used as a blank control. Figure 3 As can be seen from (d), HPMC burns rapidly after ignition, leaving no residue, while CMPA-1.0 self-extinguishes quickly after ignition, basically maintaining its original shape. Figure 3 (e)).

[0092] Test Example 3

[0093] Figure 4 The electromagnetic shielding test results of the nanopaper obtained in Examples 2-4 are shown below. Figure 4Figures (a) to (c) show the electromagnetic interference shielding performance curves of CMPA-0.7, CMPA-1.0, and CMPA-1.3 in the X-band (8.2–12.4 GHz), including total electromagnetic interference shielding (SE). T ), reflection (SE) R ) and absorption (SE) A ); Figure 4 (d) represents the SE of different samples. R SE A and SE T Bar chart comparison Figure 4 (e) compares the electromagnetic shielding performance of CMPA with that of other materials. Figure 4 (f) represents the electromagnetic interference shielding mechanism;

[0094] from Figure 4 As can be seen from (a) to (c), the SE of the CMPA sample T SE R and SE A The concentration of silver increases with increasing MPA content, which is directly related to the enhanced conductivity. Furthermore, the contributions of absorption and reflection decrease slightly with increasing frequency in the X-band. Due to the skin effect, higher frequency electromagnetic waves tend to propagate near the conductor surface, which reduces energy loss caused by free electrons oscillating in the internal alternating electric field, thus reducing absorption. Normally, the skin effect enhances electromagnetic wave reflection. However, in CMPA, silver is a nanoparticle with many randomly dispersed nanoscale reflectors. This results in more diffuse electromagnetic wave reflection, which also reduces SER. Figure 4 (d) shows the maximum EMI shielding of the CMPA sample in the x-band. Figure 4 As shown in (d), the maximum EMI shielding of CMPA-1.3 is 49.0 dB, while that of CMPA-1.0 is 42.1 dB. This means that CMPA-1.3 and CMPA-1.0 can shield more than 99.99% of electromagnetic waves, meeting the high-performance shielding requirements in practical applications. It is worth noting that although the EMI shielding of metallic materials is mainly due to reflection, the SE of the CMPA samples... A Significantly higher than SE R This may be due to the large number of two-dimensional MPA layers distributed in the nanopaper, which causes electromagnetic waves to be reflected multiple times without orientation at the microscale, resulting in diffuse reflection. Figure 4 (e) compares the EMI shielding performance of CMPA-1.0 with other materials reported in the literature, and it can be seen that CMPA-1.0 nanopaper can achieve efficient EMI shielding with a relatively low thickness. Figure 4 (f) demonstrates the multiple electromagnetic interference shielding mechanisms of CMPA nanopaper.

[0095] Figure 5 The results of the test on the nanopaper shielding mobile phone signal obtained in Example 2 are shown below. Figure 5 (g) represents the experimental group containing nanopaper. Figure 5 (h) represents the blank group without nanopaper, from Figure 5 As can be seen, the phone could not be connected when the CMPA-1.0 was covered, but the phone connected after the CMPA-1.0 was removed.

[0096] Test Example 4

[0097] Figure 6 The image shows a shape memory demonstration experiment of the nanopaper and hydroxypropyl methylcellulose membrane obtained in Example 1. Figure 6 It can be seen that pure HPMC gradually unfolds within 35s, although the sample is not yet fully unfolded at this time. Further heating causes the sample to deform and lose its shape. CMPA-1.0 completely recovers its planar shape in 27s, showing a faster and more thorough shape recovery process than HPMC.

[0098] Figure 7 This is a diagram illustrating the mechanism of thermal changes in nanopaper provided by the present invention. Figure 7 It can be seen that under external force, the HPMC molecular chain transforms from its initial conformation to a new conformation adapted to the external force, that is, the polymer chain transforms from one equilibrium state to another. This transformation includes elastic deformation until the heating temperature reaches the glass transition temperature, at which point thermal relaxation occurs. With prolonged annealing time, the system's heat capacity decreases with increasing enthalpy. During this stage, chain segments move and absorb a large amount of heat, reaching the equilibrium enthalpy and recovering their shape. CMPA-1.0 exhibits a faster and more thorough shape recovery process than HPMC. This may be due to the accumulation and storage of energy at the folded positions of the rigid nanofiller MPA. When HPMC is heated and undergoes thermal relaxation, it releases mechanical potential energy, enhancing the shape recovery process of HPMC.

[0099] Figure 8 The diagram shows the test results and schematic of the nanopaper obtained in Example 1 as fire alarm paper. Figure 8 It can be seen that during the heating process, the folded CMPA-1.0 (folded longitudinally three times with 5mm intervals) gradually regained its shape. After heating for 30 seconds, the shape of CMPA-1.0 was completely restored, and the expanded sample connected the circuit and activated the fire alarm. The experiment verified the potential of CMPA as an effective and reliable early fire alarm sensor. Furthermore, due to the low glass transition temperature of HPMC (approximately 120℃), CMPA-1.0 can recover its shape at a lower operating temperature, preventing direct flame contact and improving safety and sensitivity. Figure 8 This demonstrates the promising future of CMPA in early fire alarm systems.

[0100] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A nanosheet composite material, characterized in that, It includes M(OH)(OCH3) nanosheets and polydopamine and conductive metals loaded on the M(OH)(OCH3) nanosheets; M includes Co and Ni.

2. The nanosheet composite material according to claim 1, characterized in that, The polydopamine loading percentage is 10-50%.

3. The nanosheet composite material according to claim 1, characterized in that, The conductive metal includes silver and / or copper, and the mass percentage of the conductive metal is 30-90%.

4. The method for preparing the nanosheet composite material according to any one of claims 1 to 3, characterized in that, Includes the following steps: M(OH)(OCH3) nanosheets, dopamine hydrochloride, and water were mixed, and the pH of the resulting mixture was adjusted to be alkaline before polymerization was carried out to obtain nanosheet-loaded polydopamine. The nanosheets are loaded with polydopamine, water-soluble metal salt, binder, reducing agent and water, and a reduction reaction is carried out to obtain the nanosheet composite material.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the M(OH)(OCH3) nanosheets to dopamine hydrochloride is 0.5–2:0.38; The polymerization reaction is carried out at a temperature of 10–40°C for a duration of more than 3 hours. The polymerization reaction is carried out under stirring conditions.

6. The preparation method according to claim 4, characterized in that, The adhesive includes polyvinylpyrrolidone; The mass ratio of the nanosheet-loaded polydopamine to the binder is 1 to 2:1; The reducing agent includes glucose or aldehyde reagents; The mass ratio of the nanosheet-loaded polydopamine to the reducing agent is 0.02–0.1:1; The water-soluble metal salts include water-soluble silver salts and / or water-soluble copper salts; The mass ratio of the nanosheet-loaded polydopamine to the water-soluble metal salt is 0.5–2:1; The reduction reaction is carried out at a temperature of 10–40°C for a time of 3 hours or more.

7. The preparation method according to claim 6, characterized in that, When the water-soluble metal salt is a water-soluble silver salt, the reduction reaction process is as follows: The nanosheets are loaded with polydopamine, water-soluble silver salt, binder, ammonia, reducing agent and water, and a reduction reaction is carried out. The mass ratio of the nanosheets loaded with polydopamine and ammonia is 0.2 to 1:1; The mixture includes: The nanosheet-loaded polydopamine and water were first stirred and mixed to obtain a dispersion; The dispersion, water-soluble silver salt, binder, and ammonia water are mixed by stirring to obtain a mixture. The mixture and reducing agent are stirred and mixed for the third time.

8. A conductive nanocomposite paper with shape memory function, characterized in that, Prepared from cellulose matrix and additives; The additive is the nanosheet composite material according to any one of claims 1 to 3 or the nanosheet composite material prepared by the preparation method according to any one of claims 4 to 7.

9. The conductive nanocomposite paper according to claim 8, characterized in that, The cellulose base material includes hydroxypropyl methylcellulose; The additive has a mass percentage content of 10-90%.

10. The application of the conductive nanocomposite paper according to claim 8 or 9 as fire alarm paper or electromagnetic shielding paper.

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