A biomass porous aerogel, its preparation method and application

Abstract

This invention discloses a biomass porous aerogel, its preparation method, and its applications. The preparation method includes the following steps: S1: Sugarcane bagasse is soaked in an alkaline solution, washed, and its pH value is adjusted to 7; after drying, it is carbonized in an inert gas atmosphere to obtain carbonized sugarcane bagasse fiber; S2: Ti3AlC2 is weighed and etched with LiF and HCl to obtain multilayer MXene material; the multilayer MXene material is sonicated in an inert gas atmosphere, centrifuged, and the supernatant is collected and freeze-dried to obtain MXene nanosheets; S3: MXene nanosheets and carbonized sugarcane bagasse fiber are mixed, hydroxyethyl cellulose is added, and after stirring and freezing, ice crystals are removed in a vacuum to obtain biomass porous aerogel. The biomass porous aerogel prepared by this invention has low density, semiconductor properties, significant reversible compression, and excellent mechanical properties, and also features low thermal conductivity, reusability, and low cost.

Description

Technical Field

[0001] This invention relates to the field of materials preparation technology, specifically to a biomass porous aerogel, its preparation method, and its application. Background Technology

[0002] Heating and cooling account for a large portion of our society's total energy consumption. Due to the diffusion characteristics of heat energy, thermal insulation plays a crucial role in global thermal energy management and reducing total energy consumption. To reduce energy waste and improve energy efficiency, there is an urgent need for a new type of thermal insulation material with controllable shape and excellent mechanical stability.

[0003] Two-dimensional transition metal carbides and nitrides (MXenes) have attracted widespread attention in recent years due to their diverse surface chemistry, layered structures, and intriguing properties. However, the weak interactions between MXene sheets make it difficult to construct independent, mechanically flexible, and three-dimensional MXene sheet frameworks, especially in low-concentration solvents. To overcome these challenges, various strategies have been proposed to integrate MXenes or other 2D nanosheets into attractive 3D macrostructures with ultralight properties, high porosity, and large specific surface area. Aerogels have generated considerable interest in insulation, photocatalysis, and protection due to their lightweight, ultra-low thermal conductivity, and design variability. Considering the material's renewability, cost-effectiveness, and environmentally friendly resources, biomass-derived cellulose aerogels may be an attractive material compared to other traditional insulation materials. Summary of the Invention

[0004] This invention overcomes the technical problems of poor mechanical properties and poor thermal insulation effect of existing nitride thermal insulation materials, as well as the difficulty in achieving ultra-lightweight and better thermal insulation performance due to the diameter of existing chemical fiber materials being easily limited by micrometer size. It provides a biomass porous aerogel, its preparation method and application.

[0005] To solve the above problems, the present invention adopts the following technical solution:

[0006] A method for preparing biomass porous aerogels based on MXene includes the following steps:

[0007] S1: Wash sugarcane bagasse to remove impurities, soak it in a 2-10 wt% NaOH aqueous solution at 25-30℃ for 10-24 hours, wash it with deionized water and add dilute hydrochloric acid to adjust the pH value to 7; then dry it in a convection drying oven at 60-75℃ for 24-30 hours; put the dried product into a tube furnace and carbonize it at 600-800℃ for 2-6 hours in an inert gas atmosphere, and then grind it into powder to obtain carbonized sugarcane bagasse fiber;

[0008] S2: Weigh Ti3AlC2 and etch it for 24-30 hours in an aqueous solution containing 12 mol / L LiF and 9 mol / L HCl at a constant temperature of 20-35℃. Wash away the excess reactants to obtain pure, page-shaped multilayer MXene material. Disperse the multilayer MXene material in water and sonicate it in an inert gas atmosphere for 1.5-2.5 hours. Centrifuge the supernatant and freeze-dry it to obtain MXene nanosheets.

[0009] S3: Mix the MXene nanosheets and the carbonized bagasse fiber in a certain proportion, add 2.8 wt% hydroxyethyl cellulose, stir and freeze for 45-50 h, remove ice crystals in vacuum to obtain biomass porous aerogel.

[0010] Furthermore, in S1, the concentration of the dilute hydrochloric acid is 0.01 mol / L.

[0011] Furthermore, in S1, the mass ratio of the sugarcane bagasse to the NaOH aqueous solution is 1:10-13.

[0012] Furthermore, in S1, the inert gas is one of nitrogen, argon, and helium, or a mixture of several of them in any proportion.

[0013] Furthermore, in S2, the inert gas is one of nitrogen, argon, and helium, or a mixture of several of them in any proportion.

[0014] Furthermore, in S2, the ultrasound is performed in an ice-water bath under conditions of an ultrasound frequency of 3–30 kHz and an ultrasound power of 200–700 W.

[0015] Furthermore, the MXene nanosheets and the carbonized bagasse fiber are mixed in a mass ratio of 2:1 to 5.

[0016] Furthermore, the Ti3AlC2 is a MAX phase with a mesh size of 200.

[0017] Furthermore, in the etching reaction of S2, at least 20 ml of aqueous solution system is required to etch 1 g of Ti3AlC2.

[0018] Another object of the present invention is to protect the biomass porous aerogel prepared by the above-described method for preparing biomass porous aerogel based on MXene.

[0019] Another object of the present invention is to protect the application of the above-mentioned biomass porous aerogel in temperature sensors and as a thermal insulation material.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The biomass aerogel of the present invention has high porosity, high mechanical strength, high compressive stress and low thermal conductivity, as well as excellent thermal stability and thermal insulation performance. It can provide new opportunities for the application of agricultural waste derivatives in temperature sensors and has broad prospects in the field of thermal insulation sensing.

[0022] (2) Currently, people mainly choose fiber materials as insulation materials to protect the human body from the cold. Conventional fiber materials used for insulation can be divided into natural fiber materials and chemical fiber materials, including plant fibers (such as cotton and kapok) and animal fibers (such as down, wool, and silk). However, natural fiber materials such as cotton have poor insulation performance due to their large diameter (greater than 25μm), easy moisture absorption, and poor insulation performance. Although down has excellent insulation performance, problems such as high construction cost and inconvenience of drilling piles still exist. In contrast, chemical fibers produced in the 1930s have been widely used due to their wide variety, high cost performance, and good applicability. Due to their small diameter, low thermal conductivity, hollow characteristics, porous, crimped, and ultra-fine structures, chemical fiber materials have received widespread attention in the field of insulation. However, the diameter of chemical fiber materials is easily limited by the micron size, making it difficult to achieve ultra-lightweight and better insulation performance. Compared with commonly used plant and animal fiber materials in the prior art, the biomass carbon aerogel prepared by this invention using MXene as a substrate has a porous structure and a specific surface area of ​​up to 2.1355 m². 2 It weighs only 0.058 g / cm³ and is extremely lightweight. 3 The aerogel prepared by this invention has a controllable shape, is easy to process, has excellent mechanical properties, and has a certain degree of resilience. It can bear a weight of about 1 kg without deformation, and its thermal conductivity is lower than that of insulation filling materials such as cotton / polyester, so it has good heat insulation properties. Therefore, the aerogel prepared by this invention can replace plant fiber materials and animal fiber materials in the prior art for cold protection and warmth, and has good application prospects.

[0023] (3) The present invention synthesizes biomass porous aerogels through a simple heat treatment method. Compared with the industrial preparation method of 2000℃ or above, the reaction temperature is 600~800℃, which requires less energy, the equipment is simple and easy to operate, and the production cost is low.

[0024] (4) The carbon source of the present invention is bagasse, which is a biomass nano-carbon material. Bagasse is a common waste material in the sugar industry. Due to its low toxicity, cheap and readily available materials, low carbon and environmental protection, it shows a cost advantage compared with other types of thermal insulation fibers. Attached Figure Description

[0025] Figure 1 This is a process flow diagram of the present invention;

[0026] Figure 2 This is a SEM image of the surface of carbonized sugarcane bagasse fiber obtained in Example 1 of the present invention;

[0027] Figure 3 The images shown are SEM images of the surfaces of Ti3AlC2, multilayer MXene material, and MXene nanosheets in S2 of Example 1. In these images, a represents Ti3AlC2, b represents the multilayer MXene material, and c represents the MXene nanosheets.

[0028] Figure 4 The images show SEM images of the biomass porous aerogels prepared in Examples 1-5 and Control Groups 1-3 of this invention.

[0029] Figure 5 This is a SEM image of the cross-section of the biomass porous aerogel in Example 5; Figure 5 In the image, a is a cross-sectional SEM image of the aerogel at 100 μm, and b is a magnified cross-sectional SEM image of the aerogel with a pore size of approximately 20 μm.

[0030] Figure 6 SEM image of the longitudinal section of pure hydroxyethyl cellulose aerogel from control group 1;

[0031] Figure 7 SEM image of the cross-section of pure hydroxyethyl cellulose aerogel in control group 1;

[0032] Figure 8 The XRD patterns of biomass porous aerogels of Example 1, Control Groups 1 to 3, Ti2C3T3 and Ti2AlC3 are shown.

[0033] Figure 9 The ATR-FTIR spectra of biomass porous aerogels of Example 1, Control Groups 1 to 3, Ti2C3T3, and Ti2AlC3 are shown below.

[0034] Figure 10 The nitrogen adsorption-desorption isotherm of the biomass porous aerogel in Example 5 at 77 K;

[0035] Figure 11 This is a Tyndall effect diagram of the biomass porous aerogel precursor in Example 5;

[0036] Figure 12 The graph shows the change in thermal conductivity of the biomass porous aerogel of Example 5 as a function of temperature.

[0037] Figure 13 The histogram shows the thermal conductivity of the biomass porous aerogel of Example 5 compared with other insulating fibers at 20°C.

[0038] Figure 14The time it takes for the biomass porous aerogels of Examples 1-5 to turn four-leaf clovers yellow at 120°C;

[0039] Figure 15 The time it takes for the biomass porous aerogels of the blank control group and control groups 1-3 to turn four-leaf clover yellow at 120℃.

[0040] Figure 16 The figures show the compressive stress-strain curves of the biomass porous aerogels prepared in Examples 1-5 and Control Groups 1-3.

[0041] Figure 17 The graphs show the load-bearing capacity of the biomass porous aerogels prepared in Examples 1-5.

[0042] Figure 18 Thermogravimetric analysis results of the aerogels obtained in Example 1 and Control Groups 1 to 3 are shown in the figure.

[0043] In the attached figures, MC-1 is Example 1, MC-2 is Example 1, MC-3 is Example 3, MC-4 is Example 4, MC-5 is Example 5, H-Blank is Control Group 1, C-Blank is Control Group 2, and M-Blank is Control Group 3. Detailed Implementation

[0044] The present invention will be further described below with reference to embodiments and experiments.

[0045] Example 1

[0046] A method for preparing biomass porous aerogels based on MXene includes the following steps:

[0047] S1: Wash the bagasse to remove impurities. According to the mass ratio of bagasse to NaOH aqueous solution of 1:13, put the bagasse into a 10wt% NaOH aqueous solution and soak it at 30℃ for 24h. After washing with deionized water, add 0.01mol / L dilute hydrochloric acid to adjust the pH value to 7. Then dry it in a convection drying oven at 75℃ for 30h. Put the dried product into a tube furnace and carbonize it at 800℃ for 6h in a nitrogen atmosphere. Then grind it into powder to obtain carbonized bagasse fiber.

[0048] S2: Weigh Ti3AlC2 and etch it for 30 hours at a constant temperature of 35℃ using an aqueous solution containing 12 mol / L LiF and 9 mol / L HCl (at least 20 ml of aqueous solution is needed to etch 1 g of Ti3AlC2). Wash away excess reactants to obtain pure, page-shaped multilayer MXene material. Disperse the multilayer MXene material in water and sonicate it for 2.5 hours in a nitrogen atmosphere, in an ice-water bath, under ultrasonic conditions of 30 kHz and 700 W. Centrifuge, collect the supernatant, and freeze-dry to obtain MXene nanosheets.

[0049] S3: Mix the MXene nanosheets and the carbonized bagasse fiber in a mass ratio of 2:1, add 2.8 wt% hydroxyethyl cellulose, stir and freeze for 50 h, remove ice crystals in vacuum to obtain biomass porous aerogel.

[0050] Example 2

[0051] S1: Wash the bagasse to remove impurities. According to the mass ratio of bagasse to NaOH aqueous solution of 1:10, put the bagasse into 2wt% NaOH aqueous solution and soak it at 25℃ for 10h. After washing with deionized water, add 0.01mol / L dilute hydrochloric acid to adjust the pH value to 7. Then dry it in a convection drying oven at 60℃ for 24h. Put the dried product into a tube furnace and carbonize it at 600℃ for 2h in an argon atmosphere. Then grind it into powder to obtain carbonized bagasse fiber.

[0052] S2: Weigh Ti3AlC2 and etch it for 24 hours at a constant temperature of 20℃ using an aqueous solution containing 12 mol / L LiF and 9 mol / L HCl (at least 20 ml of aqueous solution is needed to etch 1 g of Ti3AlC2). Wash away excess reactants to obtain pure, page-shaped multilayer MXene material. Disperse the multilayer MXene material in water and sonicate it for 1.5 hours in an argon atmosphere, in an ice-water bath, under ultrasonic conditions of 3 kHz and 200 W. Centrifuge, collect the supernatant, and freeze-dry to obtain MXene nanosheets.

[0053] S3: Mix the MXene nanosheets and the carbonized bagasse fiber in a mass ratio of 2:2, add 2.8 wt% hydroxyethyl cellulose, stir and freeze for 45 h, remove ice crystals in vacuum to obtain biomass porous aerogel.

[0054] Example 3

[0055] S1: Wash the bagasse to remove impurities. According to the mass ratio of bagasse to NaOH aqueous solution of 1:12, put the bagasse into 8wt% NaOH aqueous solution and soak it at 29℃ for 20h. After washing with deionized water, add 0.01mol / L dilute hydrochloric acid to adjust the pH value to 7. Then dry it in a convection drying oven at 65℃ for 32h. Put the dried product into a tube furnace and carbonize it at 700℃ for 5h in a helium atmosphere. Then grind it into powder to obtain carbonized bagasse fiber.

[0056] S2: Weigh Ti3AlC2 and etch it for 28 hours at a constant temperature of 32℃ using an aqueous solution containing 12 mol / L LiF and 9 mol / L HCl (at least 20 ml of aqueous solution is needed to etch 1 g of Ti3AlC2). Wash away excess reactants to obtain pure, page-shaped multilayer MXene material. Disperse the multilayer MXene material in water and sonicate it for 2.0 hours in an ice-water bath under a helium atmosphere and at an ultrasonic frequency of 20 kHz and an ultrasonic power of 600 W. Centrifuge, collect the supernatant, and freeze-dry to obtain MXene nanosheets.

[0057] S3: Mix the MXene nanosheets and the carbonized bagasse fiber in a mass ratio of 2:3, add 2.8 wt% hydroxyethyl cellulose, stir and freeze for 48 h, remove ice crystals in vacuum to obtain biomass porous aerogel.

[0058] Example 4

[0059] S1: Wash the bagasse to remove impurities. According to the mass ratio of bagasse to NaOH aqueous solution of 1:10, put the bagasse into 8wt% NaOH aqueous solution and soak it at 26℃ for 20h. After washing with deionized water, add 0.01mol / L dilute hydrochloric acid to adjust the pH value to 7. Then dry it in a convection drying oven at 70℃ for 26h. Put the dried product into a tube furnace and carbonize it at 700℃ for 5h in an atmosphere of nitrogen and argon with equal volume ratio. Then grind it into powder to obtain carbonized bagasse fiber.

[0060] S2: Weigh Ti3AlC2 and etch it for 25 hours at a constant temperature of 32℃ using an aqueous solution containing 12 mol / L LiF and 9 mol / L HCl (at least 20 ml of aqueous solution is needed to etch 1 g of Ti3AlC2). Wash away excess reactants to obtain pure, page-shaped multilayer MXene material. Disperse the multilayer MXene material in water and sonicate it for 2.0 hours in an ice-water bath under an equal volume ratio of nitrogen and argon atmospheres at an ultrasonic frequency of 10 kHz and an ultrasonic power of 600 W. Centrifuge, collect the supernatant, and freeze-dry to obtain MXene nanosheets.

[0061] S3: Mix the MXene nanosheets and the carbonized bagasse fiber in a mass ratio of 2:4, add 2.8wt% hydroxyethyl cellulose, stir and freeze for 48h, remove ice crystals in vacuum to obtain biomass porous aerogel.

[0062] Example 5

[0063] S1: Wash the bagasse to remove impurities. According to the mass ratio of bagasse to NaOH aqueous solution of 1:12, put the bagasse into 8wt% NaOH aqueous solution and soak it at 28℃ for 12h. After washing with deionized water, add 0.01mol / L dilute hydrochloric acid to adjust the pH value to 7. Then dry it in a convection drying oven at 70℃ for 28h. Put the dried product into a tube furnace and carbonize it at 650℃ for 3h in an atmosphere of nitrogen, argon and helium in equal volume ratio. Then grind it into powder to obtain carbonized bagasse fiber.

[0064] S2: Weigh Ti3AlC2 and etch it for 29 hours at a constant temperature of 25℃ using an aqueous solution containing 12 mol / L LiF and 9 mol / L HCl (at least 20 ml of aqueous solution is needed to etch 1 g of Ti3AlC2). Wash away excess reactants to obtain pure, page-shaped multilayer MXene material. Disperse the multilayer MXene material in water and sonicate it for 2.2 hours in an ice-water bath under an atmosphere of equal volume ratio of nitrogen, argon, and helium, with an ultrasonic frequency of 20 kHz and an ultrasonic power of 400 W. Centrifuge, collect the supernatant, and freeze-dry to obtain MXene nanosheets.

[0065] S3: Mix the MXene nanosheets and the carbonized bagasse fiber in a mass ratio of 2:5, add 2.8wt% hydroxyethyl cellulose, stir and freeze for 46h, remove ice crystals in vacuum to obtain biomass porous aerogel.

[0066] Control group 1

[0067] The aerogel of control group 1 was prepared by using 2.8 wt% hydroxyethyl cellulose to prepare the aerogel. The preparation method was as follows: 0.28 g of hydroxyethyl cellulose was dissolved in 10 ml of water, ultrasonically dispersed evenly, and then freeze-dried to obtain the aerogel.

[0068] Control group 2

[0069] The aerogel of control group 2 was prepared by using 0.1g of carbonized sugarcane bagasse fiber and 2.8wt% hydroxyethyl cellulose. Specifically, 0.1g of carbonized sugarcane bagasse fiber and 0.28g of hydroxyethyl cellulose were dissolved in 10ml of water, ultrasonically dispersed evenly, and then freeze-dried to obtain the aerogel.

[0070] Control group 3

[0071] The aerogel of control group 3 was prepared by using 0.2g MXene nanosheets and 2.8wt% hydroxyethyl cellulose. Specifically, 0.2g MXene nanosheets and 0.28g hydroxyethyl cellulose were dissolved in 10ml of water, ultrasonically dispersed, and then freeze-dried to obtain the aerogel.

[0072] See the process principle diagram of this invention. Figure 1 Among them, the biomass porous aerogel prepared in Example 5 is shown in [example description]. Figure 1 The blocky material on the rose.

[0073] The preparation process of the present invention can be explained by analyzing the SEM images of the products obtained in each step of Example 1:

[0074] This invention employs an alkaline solution to pretreat sugarcane bagasse, which breaks the α-ether bonds between hemicellulose and lignin, thus releasing the cellulose. After washing, the bagasse is carbonized to obtain high-purity carbonized sugarcane bagasse fiber. The SEM image of the surface of the carbonized sugarcane bagasse fiber obtained in step S1 is shown below. Figure 2 As shown, Figure 2 Under magnification, strip-shaped cellulose fibers can be observed. In step S2, after in-situ synthesis of HF-etched Ti3AlC2, the Al layer was removed to form a multilayered, sheet-like MXene. The structure was destroyed by ultrasonic treatment in an inert gas atmosphere, and the monolayer of MXene was successfully exfoliated. The SEM image of the MXene nanosheet surface obtained in step S2 is shown below. Figure 3 As shown in (c) of the diagram. In step S3, under the action of hydroxyethyl cellulose, due to hydrogen bonding, monolayer MXene nanosheets and CBF are composited on the aerogel framework, followed by vacuum freeze-drying to extract ice crystals, thus forming a biomass porous aerogel with an air-filled network structure. Specifically, the surface SEM images of the biomass porous aerogels prepared in Examples 1-5 and the three control groups of this invention are shown in [reference needed]. Figure 4 The cross-sectional SEM image of the biomass porous aerogel in Example 5 is shown below. Figure 5 SEM images of the longitudinal and cross-sectional sections of pure hydroxyethyl cellulose aerogel in control group 1 are shown below. Figure 6 and Figure 7 .Depend on Figures 4-7 It is known that the surface of pure hydroxyethyl cellulose is very smooth, but the surface begins to bend after the addition of CBF. In the samples with added MXene, small pieces or flakes of MXene can be observed, while fragments or blocks of MXene can be observed on the surface morphology of the aerogels of MC-1, MC-2, MC-3, MC-4 and MC-5.

[0075] The XRD patterns of biomass porous aerogels of Example 1, Control Groups 1-3, Ti2C3T3, and Ti2AlC3 are shown in [the original text]. Figure 8 ATR-FTIR spectra are shown below. Figure 9 .Depend on Figure 8 It can be seen that the (002) peak of the Ti3AlC2 phase shifts to a lower angle (2θ = 5.89°), and the most significant diffraction (104) at 38.63° disappears, which means that the MAX phase is peeled into thin MXene sheets. This trend is caused by the lattice expansion of the -OH or -F groups attached to the MXene surface. In addition, a broadened peak at (002) can be observed, indicating that the MXene is layered during ultrasonication. The spectra of all sugarcane samples represent the cellulose I structure, with peaks around 12.86° and 20.85°, respectively. The broad peak near 20.85° indicates that lignin, hemicellulose and other structural components have amorphous properties, while the higher peak intensity of delignification indicates that non-cellulose components are removed by dissolving in alkaline solution, and that the treated sample has a higher degree of orientation in its structure by rearranging the intermediate ordered regions after the removal of non-cellulose amorphous components. Figure 9 It can be seen that 3000-3650cm -1 The broad peaks within the range represent the stretching vibrations of OH groups in all samples. The peak intensity is around 2800 cm⁻¹. -1 Left and right, responsible for CH stretching. Only at 1500cm -1 The peak observed at (C=O stretching) can be attributed to the breaking of ester bonds in the carboxyl groups of lignin and / or hemicellulose. Although alkaline treatment can substantially remove different components of lignocellulose, the fibers still contain a certain level of residual lignin, remaining on the surface and between the protocellulose fibers. (900-1400 cm⁻¹) -1 The peaks in the region represent the typical structure of cellulose, with peaks at 1400, 1350, 1150, 1100, 1058, and 956 cm⁻¹. -1 The peaks at the locations are attributed to the asymmetric deformation of CH at the β-glycosidic bonds between glucose molecules, the symmetric deformation of CH, the asymmetric vibration of COC, the asymmetric stretching of the glucose ring, the stretching of CO, and the stretching of COC.

[0076] This invention further investigates the properties of the biomass aerogel of this application, wherein the nitrogen adsorption-desorption isotherm curve at 77 K in Example 5 is shown below. Figure 10 ,Depend on Figure 10 It can be seen that the specific surface area of ​​the biomass aerogel prepared in Example 5 is 2.1355 m². 2 ·g -1 .

[0077] In this invention, the biomass porous aerogels prepared in Examples 1-5 all exhibited the Tyndall effect. The Tyndall effect observed in Example 5 is shown in [the figure]. Figure 11 This indicates that the precursor in the preparation method of this invention is a colloid.

[0078] To more intuitively demonstrate the performance of the biomass porous aerogels in each experimental group, the inventors also conducted the following experiments:

[0079] 1. Thermal conductivity test:

[0080] The thermal conductivity of the biomass porous aerogel prepared in Example 5 was studied using the instruments and methods listed in Table 1 below. The results are shown in [reference needed]. Figure 12 ;

[0081] Table 1

[0082] Test Project Thermal conductivity meter (hotdisk) Instrument Model Hotdisk TPS 2500S Test methods Transient planar heat source method Reference Standard ISO 22007

[0083] Depend on Figure 12 It can be seen that the thermal conductivity of the biomass porous aerogel in Example 5 is 0.069 W·m at 20℃. -1 ·K -1 When the temperature rose from 20°C to 40°C, the biomass porous aerogel of Example 5 showed a sharp increase: from 0.069 W·m⁻¹ -1 ·K -1 Rising to 0.086 W·m -1 ·K -1 However, as the temperature continues to rise, the thermal conductivity decreases to 0.080 W·m. -1 ·K -1 The thermal conductivity remained unchanged, indicating that the biomass porous aerogel of Example 5 has a low thermal conductivity.

[0084] Based on the above experiments, the inventors also compared the thermal conductivity of the biomass porous aerogel prepared in Example 5 with that of three different fibers: cotton fiber and polyester fiber. Tests were conducted according to the instruments and methods described in Table 1 above. The thermal conductivity coefficients of the three different materials at 20℃ are shown in the table. Figure 13 The contrast histogram, by Figure 13 As can be seen, the thermal conductivity of the three materials in Example 5 is < Cotton < Polyester, indicating that the biomass porous aerogel prepared by this invention has a low thermal conductivity and good heat preservation effect.

[0085] 2. Thermal insulation performance test:

[0086] Fresh four-leaf clovers were picked and placed on the aerogels of Examples 1-5 and Control Groups 1-3, and then placed on a heating platform at a constant temperature of 120°C to observe the time required for the clover to change. The yellowing process of the clover in Examples 1-5 was as follows: Figure 14 As shown, the process of yellowing of the four-leaf clovers in the blank control group and control groups 1 to 3 is as follows: Figure 15 As shown in Table 2 below:

[0087] Table 2

[0088]

[0089] Depend on Figure 14 , Figure 15 As shown in Table 2, clover can turn completely yellow in just 1 minute and 35 seconds when placed directly on the heating platform. However, the clover in Example 5 (MC-5) of this invention takes the longest to change color, indicating that Example 5 has the best heat preservation effect.

[0090] 3. Density test:

[0091] Example 5: The density of the biomass porous aerogel, as measured and calculated, is only 0.058 g / cm³. 3 It is extremely lightweight; even a small square of it can be supported by a rose. See the photos for details. Figure 1 .

[0092] 4. Compression resistance test

[0093] 4.1 Compression Modulus Test: In this test, the aerogels prepared in Examples 1-5 and Control Groups 1-3 were all cylinders with a diameter of 30 mm and a height of 10 mm. The tests were conducted in the laboratory using a small sensor (Guangdong Pu'ao Technology Co., Ltd., TP: ZNBLS V 200 kg). Each sample was loaded onto the compression test platform and compressed until it could not be reduced further. The stress-strain curves were recorded and the compression modulus was calculated. The compression stress-strain curves are shown below. Figure 17 As shown. Figure 17 The changes in compressive modulus of different aerogel materials are shown in Table 3. When the strain of the aerogel is 90%, the corresponding stress is shown in Table 3.

[0094] Table 3

[0095]

[0096] The mechanical pressure that several composite materials with a strain of 90% reported in the prior art can withstand is shown in Table 4 below.

[0097] Table 4

[0098]

[0099] As can be seen from the comparison of Tables 3 and 4, the mechanical strength of the biomass aerogel prepared by the present invention is superior to that of other materials in the prior art.

[0100] 4.2 Load-bearing capacity test; For Examples 1 to 5, each sample was a cylinder with a diameter of 30mm and a height of 10mm. Weights were placed on each sample, and the maximum load-bearing capacity without deformation was observed visually. Figure 18 .Depend on Figure 18 It can be seen that the load-bearing capacity of MC-5, i.e. Example 5, can reach 730g.

[0101] 5. Thermal stability test

[0102] This test examined the thermal stability of the aerogels prepared in Example 1 and Control Groups 1 to 3. The thermogravimetric analysis results are shown in the figure below. Figure 18 .Depend on Figure 18 It is known that the slight weight loss between 80 and 100°C is due to the loss of moisture in the nanocomposite material. The maximum weight loss is observed between 200 and 400°C due to the decomposition of cellulose. According to TGA analysis, the MC-1 of this invention is thermally stable at temperatures up to 200°C, exhibiting high thermal stability and promising potential for use as a building insulation material.

[0103] In summary, the biomass aerogel prepared by this invention exhibits excellent elasticity and flexibility. Hydroxyethyl cellulose and MXene / carbonized bagasse fiber have a synergistic effect, giving the biomass aerogel ideal electrical and mechanical properties, as well as excellent thermal insulation performance. Based on this invention, the biomass aerogel possesses porosity, high mechanical strength, high compressive stress, low thermal conductivity, and excellent thermal stability and insulation performance. It can provide new opportunities for the application of agricultural waste derivatives in temperature sensors, showing broad prospects in the field of thermal insulation sensing. It can also be applied to building insulation materials; due to its light weight and good thermal insulation performance, it can replace existing plant and animal fiber materials for cold protection and warmth preservation, demonstrating promising application prospects.

[0104] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for preparing biomass porous aerogels based on MXene, characterized in that, Includes the following steps: S1: Wash sugarcane bagasse to remove impurities, soak it in 2-10wt% NaOH aqueous solution at 25-30℃ for 10-24h, wash it with deionized water and add dilute hydrochloric acid to adjust the pH value to 7; then dry it in a convection drying oven at 60-75℃ for 24-30h; put the dried product into a tube furnace and carbonize it at 600-800℃ for 2-6h in an inert gas atmosphere, and then grind it into powder to obtain carbonized sugarcane bagasse fiber; S2: Weigh Ti3AlC2 and etch it for 24-30 hours in an aqueous solution containing 12 mol / L LiF and 9 mol / L HCl at a constant temperature of 20-35℃. Wash away the excess reactants to obtain pure, page-shaped multilayer MXene material. Disperse the multilayer MXene material in water and sonicate it in an inert gas atmosphere for 1.5-2.5 hours. Centrifuge the supernatant and freeze-dry it to obtain MXene nanosheets. S3: Mix the MXene nanosheets and the carbonized bagasse fiber in a certain proportion, add 2.8wt% hydroxyethyl cellulose, stir and freeze for 45~50h, remove ice crystals in vacuum to obtain biomass porous aerogel.

2. The method for preparing biomass porous aerogels based on MXene according to claim 1, characterized in that, In S1, the concentration of the dilute hydrochloric acid is 0.01 mol / L.

3. The method for preparing biomass porous aerogels based on MXene according to claim 2, characterized in that, In S1, the mass ratio of sugarcane bagasse to the NaOH aqueous solution is 1:10~13.

4. The method for preparing biomass porous aerogels based on MXene according to claim 1, characterized in that, In S1 and S2, the inert gas is one or more of nitrogen, argon, and helium.

5. The method for preparing biomass porous aerogels based on MXene as described in claim 1, characterized in that, In S2, the ultrasound is performed in an ice-water bath under conditions of an ultrasound frequency of 3~30KHz and an ultrasound power of 200~700W.

6. The method for preparing biomass porous aerogels based on MXene as described in claim 1, characterized in that, In S3, the MXene nanosheets and the carbonized bagasse fiber are mixed in a mass ratio of 2:1 to 5.

7. The method for preparing biomass porous aerogels based on MXene as described in claim 1, characterized in that, The S2 etching reaction requires at least 20 ml of aqueous solution system for 1 g of Ti3AlC2.

8. A biomass porous aerogel prepared by the method for preparing biomass porous aerogel based on MXene as described in any one of claims 1-7.

9. The application of the biomass porous aerogel prepared by the method for preparing biomass porous aerogel based on MXene as described in any one of claims 1-7 in temperature sensors.

10. The application of the biomass porous aerogel prepared by the method for preparing biomass porous aerogel based on MXene as described in any one of claims 1-7 as a thermal insulation material.

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