Carboxylated cellulose nanofiber aerogel and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to carboxylated cellulose nanofiber aerogel and application thereof. The carboxylated cellulose nanofiber aerogel is prepared according to the following steps: sequentially carrying out lignin removal and hemicellulose removal treatment on a wood material to obtain cellulose; carrying out oxidation treatment on the cellulose to obtain carboxymethyl cellulose; carboxymethyl cellulose, a carbon-based nano material and sodium-based montmorillonite are used as raw materials and are crosslinked under the action of a crosslinking agent to obtain the carboxylated cellulose nanofiber aerogel. The aerogel prepared by the invention has high temperature sensitivity and thermal stability, and can strive for more precious time for fire early warning. The aerogel also has the characteristic of light weight, and is convenient to install and use.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and particularly relates to a carboxylated cellulose nanofiber aerogel and applications thereof. Background Art

[0002] With the continuous development and application of more and more flammable polymer materials, the frequency of fire accidents caused by them is also increasing. Timely and reliable fire warnings play a vital role in fire prevention. They can provide early warning information to people, thereby maximizing their safety and minimizing property losses. Currently, smoke and infrared fire alarms are the most widely used traditional indoor fire warning strategies. For a long time, they have provided a certain degree of fire safety assurance in many places. However, in actual application scenarios, there are some special places, such as kitchens, steam rooms, and certain industrial production workshops, where smoke and vapor often accumulate under normal circumstances. In such environments, infrared fire alarms have obvious shortcomings. Smoke strongly scatters and absorbs infrared light, resulting in poor penetration of infrared light in smoky environments, which in turn affects timely fire detection. For smoke fire alarms, on the one hand, due to the presence of a certain amount of smoke and vapor in the environment, smoke fire alarms need to distinguish these background interferences, resulting in relatively long response times. On the other hand, smoke and steam interference in the environment can easily cause smoke and steam to be misidentified as fire smoke, resulting in false alarms. Given the shortcomings of traditional fire prediction strategies, there is an urgent need to design a fire warning material with high-efficiency fire warning capabilities that can be used in places with stagnant smoke and steam.

[0003] Temperature-sensing fire warning materials mainly detect fires by sensing changes in temperature. They are less affected by these factors and can better provide fire warnings in places with large amounts of dust, smoke, and steam. The temperature-sensing fire warning materials currently in widespread use are mainly thermistors (NTCs), which are made of metal oxides such as manganese, cobalt, nickel, and copper, and are manufactured using a ceramic process. Within a certain temperature range, when the ambient temperature rises, the resistance value of the NTC will decrease. By detecting changes in the resistance value, the temperature change can be sensed, and when the preset alarm temperature is reached, the alarm device is triggered. However, NTCs have many disadvantages:

[0004] (1) NTC has a long thermal response time. NTC needs to accurately sense temperature changes and eventually trigger the alarm mechanism. Even if the ambient temperature has reached the alarm threshold, it still takes a certain amount of time to accurately sense and trigger the alarm. This period takes several minutes or even longer. The long response time results in the inability to obtain early warning information in a timely manner.

[0005] (2) NTC has poor adaptability in high-temperature industrial environments. Since high-temperature industrial environments are often accompanied by complex and harsh conditions, such as continuous high temperatures with large fluctuations, the presence of large amounts of corrosive gases and dust particles, etc., it is difficult for NTC to stably and accurately perform its temperature detection function, and it is easy to change its material properties and cause performance degradation.

[0006] (3) NTC has high requirements for overall structural design and installation. As a traditional metal or ceramic temperature sensing material, NTC is heavy and difficult to change its shape, making it inconvenient to install and use. It has high requirements for the overall structure and installation method of the alarm.

[0007] (4) NTC is not environmentally friendly. Some metal oxides and other materials used in the production of NTC have a significant impact on the environment during production and disposal. Summary of the Invention

[0008] In view of the above technical problems, the present invention provides a carboxylated cellulose nanofiber aerogel, which has high temperature sensitivity and thermal stability and can be used as a material for preparing fire alarm equipment.

[0009] In order to achieve the above-mentioned purpose, the specific technical solutions provided by the present invention are as follows: In a first aspect, the present invention provides a carboxylated cellulose nanofiber aerogel, which is prepared according to the following steps: The wood material is sequentially subjected to delignification and hemicellulose removal treatments to obtain cellulose; oxidizing the cellulose to obtain carboxymethyl cellulose; The carboxymethyl cellulose, carbon-based nanomaterials and sodium montmorillonite are used as raw materials and cross-linked under the action of a cross-linking agent to obtain a three-dimensional cross-linked carboxylated cellulose nanofiber aerogel.

[0010] As a preferred embodiment of the present invention, the oxidation treatment is to oxidize the primary hydroxyl groups in cellulose into carboxyl groups using an oxidant.

[0011] As a preferred embodiment of the present invention, the carbon-based nanomaterial is selected from graphene oxide, carbon nanotubes or reduced graphene oxide.

[0012] Further preferably, the carbon-based nanomaterial is selected from graphene oxide. Compared with other thermosensitive materials, graphene oxide has high sensitivity and a wide temperature response range, and the resistance can be controlled by adjusting the density of oxygen-containing functional groups.

[0013] Compared to other flame retardants, sodium montmorillonite exhibits stronger synergistic flame retardancy with graphene oxide, and the aerogels produced by combining the two exhibit enhanced mechanical properties and high-temperature stability. Sodium montmorillonite can be replaced with ammonium polyphosphate and hydroxyapatite.

[0014] More preferably, the mass ratio of the carboxymethyl cellulose, graphene oxide and sodium montmorillonite is 3-5:3-5:2.

[0015] In a preferred embodiment of the present invention, the crosslinking step involves ultrasonic treatment with boric acid for 30 to 45 minutes to intercalate the carboxymethyl cellulose into the carbon-based nanomaterial. Boric acid, as a crosslinking agent, enhances the three-dimensional network stability of the solution mixture through multiple hydrogen and ionic bonds, while also imparting a flame retardant effect.

[0016] In a preferred embodiment of the present invention, the wood material is Pinus sylvestris var. mongolica. Pinus sylvestris var. mongolica has a cellulose content of 40% to 50%, and its lignin and hemicellulose structures are relatively loose, allowing for efficient separation of high-purity cellulose through chemical pretreatment. Furthermore, Pinus sylvestris var. mongolica is a fast-growing coniferous species and is readily available on a large scale.

[0017] In a second aspect, the present invention provides a use of the carboxylated cellulose nanofiber aerogel as a high-temperature resistant material.

[0018] In a third aspect, the present invention provides a use of the carboxylated cellulose nanofiber aerogel as a flame retardant material.

[0019] In a fourth aspect, the present invention provides an application of the carboxylated cellulose nanofiber aerogel in fire warning.

[0020] In a fifth aspect, the present invention provides a fire alarm comprising a component prepared from the carboxylated cellulose nanofiber aerogel.

[0021] In a sixth aspect, the present invention provides a fire alarm system, which includes the fire alarm described above.

[0022] Compared with the prior art, the beneficial effects of the present invention are: The sodium-montmorillonite added to the present invention can react better with carbon-based nanomaterials while being flame-retardant, and helps enhance the mechanical strength and stability of the aerogel, maintaining the porous structure of the aerogel to a certain extent. Furthermore, sodium-montmorillonite is an inorganic mineral with relatively stable chemical properties. It is not easy to chemically react with other substances under normal environmental conditions, and can better maintain the chemical stability of the aerogel. In addition, as a natural mineral, sodium-montmorillonite is degradable in the natural environment, has a relatively low impact on the environment, and is relatively environmentally friendly. At the same time, the addition of boric acid as a cross-linking agent in the present invention can further enhance the mechanical properties of the aerogel.

[0023] The present invention successfully prepares an intelligent carboxylated cellulose nanofiber aerogel for fire safety by adding different amounts of carboxymethyl cellulose to a carbon-based nanomaterial and sodium-montmorillonite system, and freeze-drying after cross-linking with boric acid. The aerogel exhibits high continuous current and long-term response time, and has a large specific surface area, making it extremely sensitive to temperature changes. It can quickly sense subtle changes in the ambient temperature and respond in a timely manner, buying more valuable time for fire warning. Aerogel temperature-sensing materials are thermally stable and are not prone to structural damage or performance degradation in high-temperature industrial environments. The aerogel itself is also lightweight, easy to install and use, and has lower requirements for the overall structural design and installation of the alarm. It is also derived from natural biomass and is biodegradable. This aerogel temperature-sensing material has little impact on the environment during production, use and waste disposal, which is in line with the concept of sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the aerogel preparation process. In the figure, GO is graphene oxide, BA is boric acid, and Na-MTT is sodium montmorillonite.

[0025] Figure 2 It is a fire warning test of different CCNF-based aerogels.

[0026] Figure 3 A is the fire alarm response time of different CCNF-based aerogels, Figure 3 B is the aerogel combustion duration, Figure 3 Where C is the resistance change of aerogel, Figure 3 Where D is the peak current of the aerogel.

[0027] Figure 4 A is the morphology of aerogel on the blade, and B is the compression performance test of aerogel.

[0028] Figure 5 A is the surface microstructure of aerogel in SEM, and B is the cross-sectional microstructure of aerogel.

[0029] Figure 6 The thermal insulation performance of different CCNF-based aerogels under 200℃~240℃ and 240℃~280℃ conditions in an infrared thermal imager; A, 200℃~240℃, B, 240℃~280℃, L is CCNF, and R is CCNF-GMB-50.

[0030] Figure 7 are the thermogravimetric analysis test results of different CCNF-based aerogels. DETAILED DESCRIPTION

[0031] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0032] Temperature-sensing fire warning materials primarily detect fires by sensing temperature changes. They are less susceptible to interference from these factors and can provide better fire warnings in locations with large amounts of dust, smoke, and steam. Currently, the most widely used temperature-sensing fire warning material is the NTC thermistor, which is primarily made of metal oxides such as manganese, cobalt, nickel, and copper, and manufactured using a ceramic process. Within a certain temperature range, as the ambient temperature rises, the NTC's resistance decreases. By detecting this change in resistance, the temperature change can be sensed, and the alarm device is triggered when the preset alarm temperature is reached. However, NTC has many disadvantages: long thermal response time, poor adaptability in high-temperature industrial environments, high requirements for overall structural design and installation, and environmental impact.

[0033] Based on this, the present invention provides a carboxylated cellulose nanofiber aerogel, which is prepared according to the following steps: The wood material is sequentially subjected to delignification and hemicellulose removal treatments to obtain cellulose; The cellulose is oxidized to obtain carboxymethyl cellulose; Carboxymethyl cellulose, carbon-based nanomaterials and sodium montmorillonite are used as raw materials and cross-linked under the action of a cross-linking agent to obtain a three-dimensional cross-linked carboxylated cellulose nanofiber aerogel.

[0034] The present invention successfully prepares carboxylated cellulose nanofiber aerogel by adding carboxymethyl cellulose to a carbon-based nanomaterial and sodium-montmorillonite system, crosslinking with boric acid and then freeze-drying. The aerogel exhibits high continuous current and long-term response time, and has a large specific surface area, which makes it extremely sensitive to temperature changes, and can quickly sense subtle changes in the ambient temperature and respond in a timely manner. Aerogel temperature-sensing materials are thermally stable and are not prone to structural damage or performance degradation in high-temperature industrial environments. The aerogel itself is also lightweight, easy to install and use, and has lower requirements for the overall structural design and installation of the alarm. It is also derived from natural biomass and is biodegradable. The aerogel can be used as a high-temperature resistant material or flame-retardant material for fire warning or the preparation of fire alarms, fire alarm systems and other equipment.

[0035] The following describes the details in conjunction with specific embodiments.

[0036] Example 1 A carboxylated cellulose nanofiber aerogel is prepared according to the following steps: (1) Dry and grind the Pinus sylvestris wood, sieve out the wood powder through a 60-mesh sieve, treat 25 g of the wood powder in hot water at 75°C for 6 h, and wash it 3 to 4 times by vacuum filtration to remove impurities.

[0037] (2) The pretreated wood powder was delignified using a 2 wt% sodium chlorite solution buffered with acetic acid at 90°C for 12 h, with the solution refreshed every 4 h. Subsequently, the sample was transferred to an 8 wt% NaOH solution at 80°C for 12 h to remove the hemicellulose fraction. After completion, the sample was repeatedly washed and dried at 50°C for 12 h to obtain a white cellulose powder.

[0038] (3) 0.064 g of 2,2,6,6-tetramethylpiperidin-1-oxyl radical and 0.4 g of sodium bromide were added to 200 g of cellulose solution with a concentration of 2 wt% and stirred thoroughly. 2,2,6,6-tetramethylpiperidin-1-oxyl radical and sodium bromide pretreated the primary hydroxyl groups of cellulose, paving the way for improving the efficiency of cellulose oxidation in the next step. After stirring evenly, 20 g of sodium hypochlorite was added to the cellulose solution. Under the synergistic effect of 2,2,6,6-tetramethylpiperidin-1-oxyl radical and sodium bromide, the primary hydroxyl groups of cellulose were partially oxidized to carboxyl groups. The pH of the solution was adjusted to 10 using 5 mol / L hydrochloric acid and NaOH. Repeated washing, filtration and freeze drying gave the corresponding carboxymethyl cellulose, which was labeled as CCNF.

[0039] (4) Weigh 0.5 g of CCNF and stir it evenly with deionized water to form a 1 wt% CCNF aqueous solution. Then, weigh 0.3 g of carbon nanotubes and stir it evenly with deionized water to form a 1 wt% carbon nanotube suspension, and then add 0.2 g of sodium montmorillonite and 0.05 g of boric acid to the carbon nanotube suspension and stir evenly. The evenly stirred mixed solution is then mixed with the CCNF aqueous solution and ultrasonically dispersed, and the CCNF is promoted to be inserted into the carbon nanotube nanosheets under the action of ultrasound at 30% power for 45 minutes to prepare a uniform dispersion. The mixture is transferred to a mold and pre-frozen for 6 hours, and then freeze-dried for 48 hours to produce a 3D cross-linked carboxylated cellulose nanofiber aerogel, that is, a CCNF-based aerogel with a CCNF mass fraction of 50%, as shown in FIG. Figure 1 shown.

[0040] Example 2 A carboxylated cellulose nanofiber aerogel is prepared according to the following steps: (1) The wood of Pinus sylvestris was dried and ground, and the wood powder was screened through a 60-mesh sieve. 25 g of the wood powder was treated with hot water at 75 °C for 6 h, and then washed 3 to 4 times by vacuum filtration to remove impurities.

[0041] (2) The pretreated wood powder was delignified using a 2 wt% sodium chlorite solution buffered with acetic acid at 90°C for 12 h, with the solution refreshed every 4 h. Subsequently, the sample was transferred to an 8 wt% NaOH solution at 80°C for 12 h to remove the hemicellulose fraction. After completion, the sample was repeatedly washed and dried at 50°C for 12 h to obtain a white cellulose powder.

[0042] (3) 0.064 g of 2,2,6,6-tetramethylpiperidin-1-oxide and 0.4 g of sodium bromide were added to 200 g of a 2 wt% cellulose solution and stirred thoroughly. After stirring, 20 g of sodium hypochlorite was added to the cellulose solution, and the pH of the solution was adjusted to 10 using 5 mol / L hydrochloric acid and NaOH. Repeated washing, filtration, and freeze-drying were performed to obtain the corresponding carboxymethyl cellulose, which was labeled as CCNF.

[0043] (4) Weigh 0.4 g of CCNF and stir it evenly with deionized water to form a 1 wt% CCNF aqueous solution. Then, weigh 0.4 g of graphene oxide and stir it evenly with deionized water to form a 1 wt% graphene oxide suspension. Then, add 0.2 g of sodium montmorillonite and 0.05 g of boric acid to the graphene oxide suspension and stir evenly. Then, mix the mixed solution with the CCNF aqueous solution and perform ultrasonic dispersion. Ultrasonic dispersion is performed at 30% power for 30 minutes to promote the insertion of CCNF into graphene oxide nanosheets to prepare a uniform dispersion. The mixture is transferred to a mold and pre-frozen for 6 hours, followed by freeze drying for 48 hours to produce a 3D cross-linked CCNF-based aerogel, i.e., a CCNF-based aerogel with a CCNF mass fraction of 40%.

[0044] Example 3 A carboxylated cellulose nanofiber aerogel is prepared according to the following steps: (1) The wood of Pinus sylvestris was dried and ground, and the wood powder was screened through a 60-mesh sieve. 25 g of the wood powder was treated with hot water at 75 °C for 6 h, and then washed 3 to 4 times by vacuum filtration to remove impurities.

[0045] (2) The pretreated wood powder was delignified using a 2 wt% sodium chlorite solution buffered with acetic acid at 90°C for 12 h, with the solution refreshed every 4 h. Subsequently, the sample was transferred to an 8 wt% NaOH solution at 80°C for 12 h to remove the hemicellulose fraction. After completion, the sample was repeatedly washed and dried at 50°C for 12 h to obtain a white cellulose powder.

[0046] (3) 0.064 g of 2,2,6,6-tetramethylpiperidin-1-oxide and 0.4 g of sodium bromide were added to 200 g of a 2 wt% cellulose solution and stirred thoroughly. After stirring, 20 g of sodium hypochlorite was added to the cellulose solution, and the pH of the solution was adjusted to 10 using 5 mol / L hydrochloric acid and NaOH. Repeated washing, filtration, and freeze-drying were performed to obtain the corresponding carboxymethyl cellulose, which was labeled as CCNF.

[0047] (4) Weigh 0.3 g of CCNF and stir it evenly with deionized water to form a 1 wt% CCNF aqueous solution. Then, weigh 0.5 g of graphene oxide and stir it evenly with deionized water to form a 1 wt% graphene oxide suspension. Then, add 0.2 g of sodium montmorillonite and 0.05 g of boric acid to the graphene oxide suspension and stir evenly. Then, mix the mixed solution with the CCNF aqueous solution and perform ultrasonic dispersion. Ultrasonic dispersion is promoted to insert CCNF into graphene oxide nanosheets under the action of 30% power for 35 minutes to prepare a uniform dispersion. The mixture is transferred to a mold and pre-frozen for 6 hours, followed by freeze drying for 48 hours to produce a 3D cross-linked CCNF-based aerogel, that is, a CCNF-based aerogel with a CCNF mass fraction of 30%.

[0048] Comparative Example 1 A carboxylated cellulose nanofiber aerogel is prepared according to the following steps: (5) Dry and grind the Pinus sylvestris wood, sieve out the wood powder through a 60-mesh sieve, treat 25 g of the wood powder in hot water at 75 °C for 6 h, and wash it 3 to 4 times by vacuum filtration to remove impurities.

[0049] (6) The pretreated wood powder was delignified using a 2 wt% sodium chlorite solution buffered with acetic acid at 90°C for 12 h, with the solution refreshed every 4 h. Subsequently, the sample was transferred to an 8 wt% NaOH solution at 80°C for 12 h to remove the hemicellulose fraction. After completion, the sample was repeatedly washed and dried at 50°C for 12 h to obtain a white cellulose powder.

[0050] (7) 0.064 g of 2,2,6,6-tetramethylpiperidin-1-oxyl radical and 0.4 g of sodium bromide were added to 200 g of a 2 wt% cellulose solution and stirred thoroughly. After stirring evenly, 20 g of sodium hypochlorite was added to the cellulose solution. Under the synergistic effect of 2,2,6,6-tetramethylpiperidin-1-oxyl radical and sodium bromide, the primary hydroxyl groups of cellulose were partially oxidized to carboxyl groups. The pH of the solution was adjusted to 10 using 5 mol / L hydrochloric acid and NaOH. Repeated washing, filtration, and freeze-drying were performed to obtain the corresponding carboxymethyl cellulose, which was labeled as CCNF.

[0051] Comparative Example 2 A carboxylated cellulose nanofiber aerogel is prepared according to the following steps: (1) Dry and grind the Pinus sylvestris wood, sieve out the wood powder through a 60-mesh sieve, treat 25 g of the wood powder in hot water at 75°C for 6 h, and wash it 3 to 4 times by vacuum filtration to remove impurities.

[0052] (2) The pretreated wood powder was delignified using a 2 wt% sodium chlorite solution buffered with acetic acid at 90°C for 12 h, with the solution refreshed every 4 h. Subsequently, the sample was transferred to an 8 wt% NaOH solution at 80°C for 12 h to remove the hemicellulose fraction. After completion, the sample was repeatedly washed and dried at 50°C for 12 h to obtain a white cellulose powder.

[0053] (3) 0.064 g of 2,2,6,6-tetramethylpiperidin-1-oxyl radical and 0.4 g of sodium bromide were added to 200 g of a 2 wt% cellulose solution and stirred thoroughly. After stirring evenly, 20 g of sodium hypochlorite was added to the cellulose solution. Under the synergistic effect of 2,2,6,6-tetramethylpiperidin-1-oxyl radical and sodium bromide, the primary hydroxyl groups of cellulose were partially oxidized to carboxyl groups. The pH of the solution was adjusted to 10 using 5 mol / L hydrochloric acid and NaOH. Repeated washing, filtration, and freeze-drying were performed to obtain the corresponding carboxymethyl cellulose, which was labeled as CCNF.

[0054] (4) 0.8 g of CCNF was weighed and mixed with deionized water to form a 1 wt% CCNF aqueous solution. 0.2 g of sodium montmorillonite and 0.05 g of boric acid were added to the CCNF aqueous solution and stirred evenly. Ultrasonication was then performed at 30% power for 45 minutes. The mixture was transferred to a mold and pre-frozen for 6 hours, followed by freeze drying for 48 hours. The resulting aerogel was labeled CCNF-MMT.

[0055] The aerogels prepared in Examples 1-3 with CCNF contents of 30, 40, and 50 wt% were named CCNF-GMB-30, CCNF-GMB-40, and CCNF-GMB-50, respectively. Performance tests were conducted using the CCNF aerogel samples in Comparative Example 1 and the CCNF-MMT aerogel samples in Comparative Example 2 as control groups.

[0056] In order to verify that the CCNF-based aerogel prepared in the present invention has sensitive fire response and recyclable warning functions, the prepared aerogel was subjected to a fire warning test. A 20V regulated power supply, a 2W alarm light and the aerogel were connected with wires to form a series circuit. Figure 2Initially, the circuit is not conducting and the alarm light is off. After the flame burns, the CCNF-GMB-30, CCNF-GMB-40, and CCNF-GMB-50 aerogels trigger the alarm light in 20 s, 18 s, and 16 s, respectively. The current changes with the attack and retreat of the flame, switching between conductor and insulator, thereby realizing the function of cyclic fire warning, demonstrating the sensitive fire warning response and cyclic warning capabilities of the aerogels of the present invention.

[0057] In addition, if Figure 3 As shown in Figure 2, in order to further explore the fire alarm mechanism, the resistance, current and duration changes of CCNF-based aerogels were monitored in real time when the aerogels were exposed to a fire environment. Figure 3 As can be seen, CCNF-GMB-30's structural fragility under high temperatures or fire conditions results in a fire alarm duration of only 154 seconds and a current of only 44 mA. This makes it susceptible to unpredictable external factors, making it less practical in actual fire scenarios. With an increased CCNF content, the fire alarm durations of CCNF-GMB-40 and CCNF-GMB-50 increase to 285 seconds and 300 seconds, respectively, and the corresponding current of CCNF-GMB-50 increases from 44 mA to 74 mA. Therefore, CCNF-GMB-50 achieves the optimal fire alarm duration and current.

[0058] like Figure 4 As shown in the figure, the aerogel is lightweight and the blades can easily support each aerogel. The density of CCNF-GMB-50 aerogel is 0.014g / cm 3 In addition, a weight was placed on top of the CCNF-GMB-50 aerogel to study its compression properties. The results show that the aerogel does not deform significantly under compression with a 250g weight, and can easily withstand high weights.

[0059] like Figure 5 As shown in the figure, CCNF is inserted into the graphene oxide nanosheets through hydrogen bonding. The insertion of CCNF provides ideal mechanical support for the graphene oxide nanosheets, thereby effectively reducing the shrinkage of the pore wall and the collapse of the pores in the internal structure of the aerogel. Figure 5 As shown in A, the cross-section is as follows Figure 5 As shown in B, both exhibit an ordered and continuous three-dimensional network structure, and their dense hierarchical pore wall reinforcement structure can be observed, which enhances the mechanical properties and structural stability of the aerogel.

[0060] like Figure 6As shown, the present invention uses an infrared thermal imager to record and evaluate the thermal insulation performance of CCNF and CCNF-GMB-50 aerogels under different temperature conditions. The specific operation is as follows:

[0061] Select the size of 35×12×10mm 3 The CCNF and CCNF-GMB-50 aerogels were placed on a temperature-controlled hot plate instrument. When the hot plate was heated from room temperature to 280°C, the surface temperature of the aerogels was accurately recorded at different time points. When the temperature of the hot plate reached 219.5°C, the temperature of the CCNF and CCNF-GMB-50 aerogels rose to 90.9°C and 93.1°C, respectively. Figure 6 As shown in Figure A. When the temperature of the heating plate reaches 254.2 °C, the temperature of CCNF and CCNF-GMB-50 aerogels only rises to 112.3 °C and 117.1 °C, respectively. Figure 6 As shown in B.

[0062] The above thermal insulation performance tests clearly show that as the temperature of the heating plate continues to rise, the CCNF-GMB-50 aerogel demonstrates excellent thermal insulation capabilities. It can effectively block heat from penetrating into the aerogel, thereby maintaining its thermal stability in high-temperature environments and providing reliable fire alarm capabilities.

[0063] like Figure 7 As shown in the figure, a 10 mg aerogel sample was heated from 30°C to 800°C at a heating rate of 20°C / min under a nitrogen atmosphere and subjected to thermogravimetric testing. The thermogravimetric analysis results further strongly confirm the dense carbon layer structure of the CCNF-GMB-50 aerogel, with CCNF and CCNF-MMT aerogels used as controls. CCNF exhibits a distinct rapid weight loss phase between approximately 200°C and 400°C, indicating that CCNF undergoes vigorous thermal decomposition within this temperature range, breaking chemical bonds and volatilizing a large amount of organic matter. Compared to CCNF, the CCNF-MMT aerogel exhibits a slightly delayed onset temperature during the primary weight loss phase and a relatively slower weight loss rate. This suggests that the addition of Na-MMT improves the thermal stability of the aerogel to a certain extent. The layered structure of Na-MMT may act as a barrier to heat transfer and slow the decomposition of organic components within the aerogel. The starting temperature of the CCNF-GMB-50 curve in the main weight loss stage is later than that of CCNF, and the weight loss rate is also relatively slow, indicating that the composite addition of graphene oxide and Na-MMT further enhances the thermal stability of the aerogel.

[0064] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A carboxylated cellulose nanofiber aerogel, characterized in that It is prepared according to the following steps: The wood material is sequentially subjected to delignification and hemicellulose removal treatments to obtain cellulose; oxidizing the cellulose to obtain carboxymethyl cellulose; The carboxymethyl cellulose, carbon-based nanomaterials and sodium montmorillonite are used as raw materials and cross-linked under the action of a cross-linking agent to obtain a three-dimensional cross-linked carboxylated cellulose nanofiber aerogel.

2. The carboxylated cellulose nanofiber aerogel according to claim 1, characterized in that The cross-linking is carried out by ultrasonic treatment under the action of boric acid for 30 minutes to 45 minutes.

3. The carboxylated cellulose nanofiber aerogel according to claim 1, characterized in that The oxidation treatment is to oxidize the primary hydroxyl groups in cellulose into carboxyl groups using an oxidant.

4. The carboxylated cellulose nanofiber aerogel according to claim 1, characterized in that The carbon-based nanomaterial is graphene oxide, and the mass ratio of the carboxymethyl cellulose, graphene oxide and sodium montmorillonite is 3-5:3-5:

2.

5. The carboxylated cellulose nanofiber aerogel according to claim 1, characterized in that The wood material is Pinus sylvestris var. mongolica.

6. Use of the carboxylated cellulose nanofiber aerogel according to claim 1 as a high temperature resistant material.

7. Use of the carboxylated cellulose nanofiber aerogel according to claim 1 as a flame retardant material.

8. Use of the carboxylated cellulose nanofiber aerogel according to claim 1 in fire warning.

9. A fire alarm, characterized in that: The invention comprises a component prepared from the carboxylated cellulose nanofiber aerogel according to claim 1.

10. A fire alarm system, characterized in that: It includes the fire alarm according to claim 9.

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