Preparation method of sand field straw and carbon nanotube composite pressure sensor

Abstract

The invention relates to a preparation method of a Shatian straw and carbon nanotube composite pressure sensor, which comprises the following steps of: uniformly dispersing and distributing a metal salt catalyst solution by utilizing the unique ink absorption permeability and soft diffusivity of renewable biomass waste Shatian straw, and performing chemical vapor deposition at 750-900 DEG C to prepare the Shatian straw and carbon nanotube composite pressure sensor. The carbon nanotube is grown by using a gas carbon source to obtain a composite material film of the straw fiber and the carbon nanotube, and the composite material film can be used as a pressure sensor to obtain high-precision linear resistance-pressure sensing performance. According to the method disclosed by the invention, the infiltration and diffusion capabilities of hydroxyl groups of the sand field straws on a solution are fully utilized to realize adsorption and dispersion and firmly lock catalyst particles so as to achieve the purpose of uniform growth of the carbon nanotubes, and a formed three-dimensional structure has sensitive resistance induction. According to the invention, renewable biomass resources are fully and gradually converted into high-value utilized raw materials, agricultural waste reutilization and high-tech products are combined and innovated, and the method has high novelty and sustainable development potential.

Description

Technical Field

[0001] This invention relates to a method for preparing carbon nanotube composite materials and flexible sensor technology, specifically to a method for preparing a pressure sensor made of Shatian rice straw and carbon nanotube composite materials. Background Technology

[0002] Rice straw grown in the unique sandy soil of Jingxian County, Anhui Province. Rice straw fibers are longer, contain fewer impurities, and have a lower lignin content, making them suitable for papermaking. They increase the paper's softness, ink absorption, and whiteness. Often interwoven with the fibers of the bark of the Qingtan tree, they create a "bone and flesh" texture for writing paper. When ink falls on it, it quickly spreads outwards, creating distinct layers, varying shades, and clear outlines of ink. The rice straw fibers form a microporous network, allowing the ink to naturally diffuse and create distinct layers ("five shades of ink"). It also enhances whiteness and smoothness: after natural bleaching, it becomes pure white and delicate, suitable for calligraphy and painting, and its flexibility allows the paper to be rolled and folded without tearing. A reasonable blend improves economy while maintaining quality. This unique characteristic fills its interior with extremely tiny pores formed by interwoven plant fibers, creating a complex three-dimensional "capillary network" that generates powerful capillary force, actively and rapidly "drawing in" aqueous solutions. Its molecular structure contains a large number of hydrophilic hydroxyl groups, which can form hydrogen bonds with water molecules, thereby "capturing" water. This is very beneficial for adsorbing and diffusing the catalyst solution without allowing the salt components in the liquid to agglomerate, which in turn is beneficial for the growth of carbon nanotubes catalyzed by nanoparticles.

[0003] The growth of carbon nanotubes on other material substrates has long been a research hotspot. It requires precisely controlled high-energy environments and specific conditions to recombine the carbon source into a one-dimensional nanostructure. The catalyst is one of the most critical prerequisites, determining the growth mode, diameter, and structure of the carbon nanotubes. The carbon source gas is adsorbed and decomposed into carbon atoms on the surface of the catalyst nanoparticles. The size of the catalyst particles directly determines the diameter of the carbon nanotubes. Patent CN119764365A describes the preparation of silicon-based supported metal catalysts by controlling the reaction conditions of impregnation combined with high-temperature calcination on the surface of silicon-based materials. Based on this, single-walled carbon nanotube networks are grown by controlling the reaction parameters of chemical vapor deposition, and applied to lithium-ion battery electrode materials. This technology explores the combination of carbon nanotube growth with other materials, and its key lies in creating nanoscale metal catalyst particles on a silicon substrate. Invention patent CN114686861B selects the (100) and (111) planes of a magnesium aluminate spinel (MgAl2O4) substrate, and controls the crystallinity, atomic step height, and orientation of the substrate crystal planes through heat treatment conditions; then, an orthogonal single-walled carbon nanotube network is grown on the magnesium aluminate spinel surface using atmospheric pressure chemical vapor deposition. The development of these technologies lays the foundation for the preparation of high-performance carbon nanotube composite materials on different substrates and strongly supports the feasibility of carbon nanotube growth technology on the surface of rice straw.

[0004] Currently, combining carbon nanotubes with other materials and using flexible substrates (such as TPU and PDMS) is an effective way to fabricate high-performance flexible sensors with high sensitivity and a wide strain range. Existing commonly used carbon nanotube sensors include gas sensors, pressure strain sensors, photoelectric sensors, and biological / chemical sensors. Future trends include integrating multiple carbon nanotube sensors into sensor arrays and combining them with artificial intelligence algorithms to develop intelligent sensing systems similar to artificial smell and taste, as well as neuromorphic sensors that integrate sensing, information storage, and processing functions into a single device. Summary of the Invention

[0005] To address the aforementioned challenges, the main objective of this invention is to provide a method for preparing a composite pressure sensor made of Shatin rice straw and carbon nanotubes. This method utilizes the hydroxyl functional groups and grooves on the surface of Shatin rice straw to achieve catalyst diffusion and nano-sizing, providing highly active catalysis for the carbon nanotubes. Simultaneously, the rice straw fiber structure provides growth sites and support for the carbon nanotubes. The resulting three-dimensional structure exhibits a strong connection between the fibers and carbon nanotubes. When used in a pressure sensor, the three-dimensional structure deforms under applied pressure, particularly the carbon nanotubes, leading to changes in the conductive network and consequently, changes in internal resistance. Upon removal of pressure, the strong structural connection and resilience allow the three-dimensional structure to return to its original state, ensuring structural stability and repeated application. This demonstrates high sensitivity, making this thin, highly sensitive, and high-strength pressure sensor suitable for applications in smart electronics, humanoid robots, and high-end medical equipment.

[0006] The present invention solves the above-mentioned technical problems through the following technical solution: A method for preparing a composite pressure sensor of rice straw and carbon nanotubes from Shatian includes the following steps: (1) High-temperature hot water and sodium hydroxide alkaline solution were used to treat the sandy rice straw in sequence to graft a large number of hydroxyl groups onto its surface.

[0007] (2) The catalyst solution is impregnated by the unique hygroscopic, permeable and diffusion capabilities of the hydroxyl groups on the surface of Shatian rice straw, so that the catalyst can be evenly diffused along the rice straw fibers and anchored to the nano-catalyst particles.

[0008] (3) By setting reaction conditions through chemical vapor deposition, carbon nanotubes are grown using a gaseous carbon source to obtain a three-dimensional composite structure of straw fiber and carbon nanotubes.

[0009] (4) The composite material of rice straw fiber and carbon nanotube was obtained and made into a thin film pressure sensor. The performance of the sensor was tested to obtain the Shatian rice straw fiber and carbon nanotube composite material pressure sensor.

[0010] Furthermore, the hot water used in step (1) is at a temperature of 90-100℃ and the concentration of sodium hydroxide is 2-5 wt.%.

[0011] Furthermore, after the steaming time in step (1) is 6-12 hours, the surface hard components are removed by a combination of solution diffusion and room temperature drying in the alkali dissolution treatment.

[0012] Furthermore, the catalyst mentioned in step (2) is one or two of ferric chloride, Fe(III)-EDTA, and ferrocene.

[0013] Furthermore, in step (1), the total mass concentration of the catalyst solution is 0.5-1 wt.%.

[0014] Furthermore, in step (3), the temperature for chemical vapor deposition is 750-900℃ and the time is 3-5h.

[0015] Furthermore, the protective atmosphere used in chemical vapor deposition is argon, and the carbon source gas is one or more of methane, ethanol, and ethylene.

[0016] Furthermore, the reaction conditions in step (3) are a temperature of 750-900℃.

[0017] Furthermore, the test load applied in step (4) is 500-2000 N / m. 2 The sensor's test dimensions are 10×10×0.1mm.

[0018] Furthermore, the sensor's resistance recovery rate with pressure changes is in the range of 80-90%.

[0019] The positive and progressive effects of this invention are as follows: This invention provides a method for preparing a composite pressure sensor made of rice straw and carbon nanotubes. The invention innovatively uses rice straw fiber as the raw material, fully utilizing the hygroscopic and diffusion capabilities of the fiber's hydroxyl groups to achieve nanoscale dispersion of the catalyst, ensuring its high activity and laying the foundation for carbon nanotube growth. Simultaneously, by growing carbon nanotubes, a stable three-dimensional conductive network can be formed between the rice straw fiber and the carbon nanotubes, achieving effective resilience under pressure deformation, thus ensuring the sensor's high sensitivity and high strength. The formed three-dimensional network can be self-supporting and can also form a thin, flexible structure, demonstrating high innovation and potential application markets in future humanoid robots, high-end medical equipment, and other fields. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0021] Figure 2This is a scanning electron microscope image of a method for preparing a composite pressure sensor of rice straw and carbon nanotubes according to Example 1 of the present invention. The image shows the structure of the fiber and the morphology of the carbon nanotubes growing vertically around the surface of the fiber, as well as the uniformly distributed catalyst particles, demonstrating the effect of the fiber's hygroscopic diffusion ability on the distribution of the catalyst and the feasibility of growing carbon nanotubes.

[0022] Figure 3 The image shows the Raman spectrum of a method for preparing a composite pressure sensor of rice straw and carbon nanotubes according to Embodiment 1 of the present invention. The image shows obvious D and G peaks, as well as the radial breathing mode (RBM) characteristic peak of carbon nanotubes, demonstrating the presence of single-walled carbon nanotubes. Detailed Implementation

[0023] The preferred embodiments of the present invention are given below with reference to the accompanying drawings to illustrate the technical solution of the present invention in detail.

[0024] Figure 1 This is a schematic diagram of the overall structure of the present invention, as shown below. Figure 1 As shown: The present invention provides a method for preparing a composite pressure sensor of rice straw and carbon nanotubes, which includes the following steps: (1) First, rice straw is treated with high-temperature hot water and sodium hydroxide solution to graft a large number of hydroxyl groups onto its surface; (2) Then, the catalyst solution is impregnated by the unique hygroscopic permeability and diffusion ability of the hydroxyl groups on the surface of rice straw, so that the catalyst is uniformly diffused along the fiber to obtain highly active nanocatalyst particles; (3) Carbon nanotubes are grown with gaseous carbon source by chemical vapor deposition at 750-900℃ to obtain a three-dimensional composite structure of rice straw fiber and carbon nanotubes; (4) The composite material of rice straw and carbon nanotubes is made into a thin film pressure sensor, and the performance of the sensor is tested to obtain a high-precision linear resistance-pressure sensor.

[0025] The specific steps of this invention include: Step 1: First, boil the Shatin rice straw fibers in hot water at 90-100℃ for 6-12 hours to remove the hard components on the surface of the straw. Then, prepare a 2-5 wt.% sodium hydroxide solution to treat the boiled fibers with alkali by a combination of solution diffusion and room temperature drying, so that a large number of hydroxyl groups are grafted onto the fiber surface.

[0026] Step 2: Next, utilizing the unique hygroscopic, permeable, and diffusion capabilities of the hydroxyl groups on the fiber surface, a catalyst solution is impregnated. The catalyst is one or two of ferric chloride, Fe(III)-EDTA, and ferrocene. The total mass concentration of the catalyst solution is 0.5-1 wt.%, allowing the catalyst to diffuse evenly along the fiber. The solution is then air-dried at room temperature to obtain highly active nanocatalyst particles.

[0027] Step 3: Then, using chemical vapor deposition, the temperature is increased at a rate of 10℃ / min in an argon atmosphere. When the temperature reaches 750-900℃, carbon nanotubes are grown using a gaseous carbon source for 3-5 hours to obtain a three-dimensional composite structure of rice straw fiber and carbon nanotubes.

[0028] Step 4: Silver electrodes are attached to both sides of the composite film of rice straw and carbon nanotubes to fabricate a pressure sensor with dimensions of 10×10×0.1mm, and a pressure of 500-2000 N / m is applied to the sensor. 2 By performing performance tests on the load, a high-precision linear resistance-pressure sensor can be obtained.

[0029] Step 5: The scanning electron microscope (SEM) of the tested material revealed a three-dimensional structure, and the Raman spectrum showed obvious characteristic peaks of carbon nanotubes. D / I G The resistance is 0.5-1, and the recovery rate of the resistance after load testing is in the range of 80-90%.

[0030] The gaseous carbon source is one or two of methane, ethanol, and ethylene.

[0031] To make the present invention more fully disclosed, more specific embodiments are described below. Specific Implementation Example 1: 1.1 First, the Shatin rice straw fiber is steamed in 100℃ hot water for 6 hours to remove the hard components on the surface of the straw. A 5wt.% sodium hydroxide solution is prepared to treat the fiber with alkali by a combination of solution diffusion and room temperature drying, so that a large number of hydroxyl groups are grafted onto its surface.

[0033] 1.2 Next, utilizing the unique hygroscopic, permeable, and diffusion capabilities of rice straw fibers, a catalyst solution was impregnated. The catalyst was ferric chloride, and the total mass concentration of the catalyst solution was 0.8 wt.%. This allowed the catalyst to diffuse evenly along the rice straw fibers, and the solution was then air-dried at room temperature to obtain highly active nano-catalyst particles.

[0034] 1.3 Then, by chemical vapor deposition, the temperature was increased in an argon atmosphere at a rate of 10℃ / min. When the temperature reached 800℃, carbon nanotubes were grown using gaseous carbon source methane for 3 hours to obtain a three-dimensional composite structure of straw fiber and carbon nanotubes.

[0035] 1.4. The composite material of fiber and carbon nanotubes was pressed into a thin-film pressure sensor with dimensions of 10×10×0.1mm. Silver electrodes were attached to both sides, and a pressure of 500-2000 N / m was applied to the sensor. 2By performing performance tests on the load, a high-precision linear resistance-pressure sensor can be obtained.

[0036] 1.5. The scanning electron microscope (SEM) of the tested material revealed a three-dimensional structure, and the Raman spectrum showed obvious characteristic peaks of carbon nanotubes. D / I G The resistance is 0.5, and the recovery rate of the change after the resistance test load is in the range of 85%. Specific Implementation Example 2: 2.1 First, the rice straw fibers were steamed in 90℃ hot water for 12 hours to remove the hard components on the surface of the straw. A 2wt.% sodium hydroxide solution was prepared to treat the rice straw fibers with alkali by a combination of solution diffusion and room temperature drying, so that a large number of hydroxyl groups were grafted onto the surface.

[0038] 2.2 Next, utilizing the unique hygroscopic, permeable, and diffusion capabilities of rice straw fibers, a catalyst solution was impregnated. The catalyst was Fe(III)-EDTA, and the total mass concentration of the catalyst solution was 1 wt.%. This allowed the catalyst to diffuse evenly along the rice straw fibers, and the solution was then air-dried at room temperature to obtain highly active nanocatalyst particles.

[0039] 2.3 Then, by chemical vapor deposition, the temperature was increased in an argon atmosphere at a rate of 10℃ / min. When the temperature reached 800℃, carbon nanotubes were grown using gaseous carbon source ethanol for 5 hours to obtain a three-dimensional composite structure of straw fiber and carbon nanotubes.

[0040] 2.4. The composite material of fiber and carbon nanotubes was pressed into a thin-film pressure sensor with dimensions of 10×10×0.1mm. Silver electrodes were attached to both sides, and a pressure of 500-2000 N / m was applied to the sensor. 2 By performing performance tests on the load, a high-precision linear resistance-pressure sensor can be obtained.

[0041] 2.5. The scanning electron microscope (SEM) of the tested material revealed a three-dimensional structure, and the Raman spectrum showed obvious characteristic peaks of carbon nanotubes. D / I G The resistance is 0.8, and the recovery rate of the change after the resistance test load is in the range of 80%. Specific Implementation Example 3: 3.1 First, the rice straw fibers were steamed in 95℃ hot water for 6 hours to remove the hard components on the surface of the straw. A 3wt.% sodium hydroxide solution was prepared to treat the rice straw fibers with alkali by a combination of solution diffusion and room temperature drying, so that a large number of hydroxyl groups were grafted onto the surface.

[0043] 3.2 Next, utilizing the unique hygroscopic, permeable, and diffusion capabilities of rice straw fibers, a catalyst solution was impregnated. The catalyst was ferrocene, and the total mass concentration of the catalyst solution was 1 wt.%. This allowed the catalyst to diffuse evenly along the rice straw fibers, and the solution was then air-dried at room temperature to obtain highly active nanocatalyst particles.

[0044] 3.3 Then, by chemical vapor deposition, the temperature was increased in an argon atmosphere at a rate of 10℃ / min. When the temperature reached 750℃, carbon nanotubes were grown using gaseous carbon source methane for 4 hours to obtain a three-dimensional composite structure of straw fiber and carbon nanotubes.

[0045] 3.4. The composite material of fiber and carbon nanotubes was pressed into a thin-film pressure sensor with dimensions of 10×10×0.1mm. Silver electrodes were attached to both sides, and a pressure of 500-2000 N / m was applied to the sensor. 2 By performing performance tests on the load, a high-precision linear resistance-pressure sensor can be obtained.

[0046] 3.5. The scanning electron microscope (SEM) of the tested material revealed a three-dimensional structure, and the Raman spectrum showed obvious characteristic peaks of carbon nanotubes. D / I G With a value of 1, the recovery rate of the resistance after load testing is in the range of 83%. Specific Implementation Example 4: 4.1 First, the rice straw fibers were steamed in 100℃ hot water for 10 hours to remove the hard components on the surface of the straw. Then, a 5wt.% sodium hydroxide solution was prepared to treat the rice straw fibers with alkali by a combination of solution diffusion and room temperature drying, so that a large number of hydroxyl groups were grafted onto the surface.

[0048] 4.2 Next, utilizing the unique hygroscopic, permeable, and diffusion capabilities of rice straw fibers, a catalyst solution was impregnated. The catalyst consisted of ferric chloride and Fe(III)-EDTA (mass ratio 1:1), with a total mass concentration of 0.5 wt.% (0.25 wt.% each). This allowed the catalyst to diffuse evenly along the rice straw fibers, and the solution was then air-dried at room temperature to obtain highly active nanocatalyst particles.

[0049] 4.3 Then, by chemical vapor deposition, the temperature was increased in an argon atmosphere at a rate of 10℃ / min. When the temperature reached 900℃, carbon nanotubes were grown using gaseous carbon source ethylene for 5 hours to obtain a three-dimensional composite structure of straw fiber and carbon nanotubes.

[0050] 4.4 The composite material of fiber and carbon nanotubes was pressed into a thin-film pressure sensor with dimensions of 10×10×0.1mm. Silver electrodes were attached to both sides, and a pressure of 500-2000 N / m was applied to the sensor. 2 By performing performance tests on the load, a high-precision linear resistance-pressure sensor can be obtained.

[0051] 4.5. The scanning electron microscope (SEM) of the tested material revealed a three-dimensional structure, and the Raman spectrum showed obvious characteristic peaks of carbon nanotubes. D / I G The resistance is 1, and the recovery rate after load testing is within 80%. Specific Implementation Example 5: 5.1 First, the rice straw fibers were steamed in 100℃ hot water for 6 hours to remove the hard components on the surface of the straw. A 2wt.% sodium hydroxide solution was prepared to treat the rice straw fibers with alkali by a combination of solution diffusion and room temperature drying, so that a large number of hydroxyl groups were grafted onto the surface.

[0053] 5.2 Next, utilizing the unique hygroscopic, permeable, and diffusion capabilities of rice straw fibers, a catalyst solution was impregnated. The catalyst consisted of ferric chloride and ferrocene (mass ratio 1:1), and the total mass concentration of the catalyst solution was 1 wt.% (0.5 wt.% each). This allowed the catalyst to diffuse evenly along the rice straw fibers, and the solution was then air-dried at room temperature to obtain highly active nanocatalyst particles.

[0054] 5.3 Then, by chemical vapor deposition, the temperature was increased in an argon atmosphere at a rate of 10℃ / min. When the temperature reached 800℃, carbon nanotubes were grown using gaseous carbon sources methane and ethanol for 4 hours to obtain a three-dimensional composite structure of straw fiber and carbon nanotubes.

[0055] 5.4. The composite material of fiber and carbon nanotubes was pressed into a thin-film pressure sensor with dimensions of 10×10×0.1mm. Silver electrodes were attached to both sides, and a pressure of 500-2000 N / m was applied to the sensor. 2 By performing performance tests on the load, a high-precision linear resistance-pressure sensor can be obtained.

[0056] 5.5 The scanning electron microscope (SEM) of the tested material revealed a three-dimensional structure, and the Raman spectrum showed obvious characteristic peaks of carbon nanotubes. D / I G The resistance is 0.5, and the recovery rate of the change after the resistance test load is in the range of 90%. Specific Implementation Example 6: 6.1 First, the rice straw fibers were steamed in 90℃ hot water for 8 hours to remove the hard components on the surface of the straw. A 4wt.% sodium hydroxide solution was prepared to treat the rice straw fibers with alkali by a combination of solution diffusion and room temperature drying, so that a large number of hydroxyl groups were grafted onto the surface.

[0058] 6.2 Next, utilizing the unique hygroscopic, permeable, and diffusion capabilities of rice straw fibers, a catalyst solution was impregnated. The catalyst consisted of Fe(III)-EDTA and ferrocene (mass ratio 1:1), with a total mass concentration of 0.5 wt.% (0.25 wt.% each). This allowed the catalyst to diffuse evenly along the rice straw fibers, and the solution was then air-dried at room temperature to obtain highly active nanocatalyst particles.

[0059] 6.3 Then, by chemical vapor deposition, the temperature was increased in an argon atmosphere at a rate of 10℃ / min. When the temperature reached 750℃, carbon nanotubes were grown using gaseous carbon sources methane and ethylene for 3 hours to obtain a three-dimensional composite structure of straw fiber and carbon nanotubes.

[0060] 6.4. The composite material of fiber and carbon nanotubes was pressed into a thin-film pressure sensor with dimensions of 10×10×0.1mm. Silver electrodes were attached to both sides, and a pressure of 500-2000 N / m was applied to the sensor. 2 By performing performance tests on the load, a high-precision linear resistance-pressure sensor can be obtained.

[0061] 6.5. The scanning electron microscope (SEM) of the tested material revealed a three-dimensional structure, and the Raman spectrum showed obvious characteristic peaks of carbon nanotubes. D / I G The resistance is 0.5, and the recovery rate of the change after the resistance test load is in the range of 90%.

[0062] Comparative Example 1: No alkali treatment Compared to 1.1, Shatang rice straw fibers were steamed in 100℃ hot water for 6 hours to remove the hard components on the surface of the straw. Ferric chloride was used as the catalyst, with a total catalyst solution concentration of 0.5 wt.%. Utilizing the unique hygroscopic, permeable, and diffusing capabilities of rice straw fibers, the catalyst solution was impregnated, allowing the catalyst to diffuse evenly along the straw fibers. The mixture was then air-dried at room temperature to obtain highly active nano-catalyst particles.

[0063] In contrast to 1.2, carbon nanotubes were then grown in an argon atmosphere at a heating rate of 10℃ / min using chemical vapor deposition. The temperature reached 800℃, and carbon nanotubes were grown using gaseous methane for 5 hours to obtain a three-dimensional composite structure of straw fiber and carbon nanotubes.

[0064] Compared to 1.3, the composite material of fiber and carbon nanotubes was pressed into a thin-film pressure sensor with dimensions of 10×10×0.1mm. Silver electrodes were attached to both sides, and a pressure of 500-2000 N / m was applied to the sensor. 2 By performing performance tests on the load, a high-precision linear resistance-pressure sensor can be obtained.

[0065] Compared to 1.4, the scanning electron microscope of the tested material showed no obvious carbon nanotube structure, and the Raman spectrum showed I... D / I G It has a value of 1.5, no resistance - pressure sensing response, and no deformation recovery after pressure load.

[0066] Comparative Example 2: Excess Catalyst Compared to 2.1, the rice straw fibers were first steamed in 100℃ hot water for 6 hours to remove the hard components on the surface of the straw. A 5wt.% sodium hydroxide solution was then prepared to treat the rice straw fibers with alkali by a combination of solution diffusion and room temperature drying, which resulted in the grafting of a large number of hydroxyl groups onto the surface.

[0067] In contrast to 2.2, the unique hygroscopic, permeable, and diffusion capabilities of rice straw fibers were then utilized to impregnate a catalyst solution. The catalyst consisted of ferric chloride and Fe(III)-EDTA (mass ratio 1:1), with a total mass concentration of 2 wt.% (1 wt.% each). This allowed the catalyst to diffuse evenly along the rice straw fibers, and the solution was then air-dried at room temperature to obtain highly active nanocatalyst particles.

[0068] In contrast to 2.3, carbon nanotubes were then grown in an argon atmosphere at a heating rate of 10℃ / min using chemical vapor deposition. The temperature reached 900℃, and carbon nanotubes were grown using gaseous carbon sources methane and ethanol for 3 hours, resulting in a three-dimensional composite structure of straw fiber and carbon nanotubes.

[0069] Compared to 2.4, the composite material of fiber and carbon nanotubes was pressed into a thin-film pressure sensor with dimensions of 10×10×0.1mm. Silver electrodes were attached to both sides, and a pressure of 500-2000 N / m was applied to the sensor. 2 By performing performance tests on the load, a high-precision linear resistance-pressure sensor can be obtained.

[0070] Compared to 2.5, the scanning electron microscope (SEM) of the tested material did not reveal a clear carbon nanotube structure, but rather a large number of solid particles. The Raman spectrum showed... D / I G The value is 2, and there is no change in the resistance after the load test.

[0071] The composite materials in the examples and comparative examples were tested in various instruments, and the test results were calculated and compared to obtain the performance results of each example and comparative example.

[0072]

[0073] As can be seen from the above embodiments, the preparation method of the Shatian rice straw and carbon nanotube composite pressure sensor of the present invention can form a three-dimensional composite material of rice straw fiber and carbon nanotube. The carbon nanotube is arranged vertically in three dimensions along the fiber surface. Under load pressure, the structure can undergo micro-deformation to realize the conversion of resistance and has obvious pressure sensing capability. Compared with the prior art, it has the characteristics of strong bonding force, low production cost, and strong innovation. Moreover, the processing technology is simple and has a broad market.

[0074] This invention addresses the shortcomings of existing carbon nanotube sensor applications. Through in-depth research, the inventors discovered that the hygroscopic wetting and diffusion capabilities of hydroxyl groups can lead to the nano-dispersion and anchoring of catalyst particles, thereby enabling the growth of carbon nanotubes and a strong bond between carbon nanotubes and rice straw fibers. The resulting three-dimensional vertical structure exhibits high conductivity and a well-defined resistance deformation pattern. When used in flexible pressure sensors, it can accurately sense and control pressure, representing a significant breakthrough in existing carbon nanotube sensor technology. The product has broad market prospects and can be applied in fields such as humanoid robots and high-end medical testing equipment.

[0075] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. Materials with the same function derived from the raw materials of the present invention should also be included within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a composite pressure sensor of rice straw and carbon nanotubes, characterized in that, Includes the following steps: (1) The sandy rice straw was treated with hot water at high temperature and alkaline sodium hydroxide solution in turn to graft a large number of hydroxyl groups onto its surface; (2) Utilizing the unique hygroscopic, permeable, and diffusion capabilities of the hydroxyl groups on the surface of Shatian rice straw, the catalyst solution is impregnated, allowing the catalyst to diffuse evenly along the rice straw fibers and anchoring the nano-catalyst particles. (3) By setting reaction conditions through chemical vapor deposition, carbon nanotubes are grown using a gaseous carbon source to obtain a three-dimensional composite structure of straw fiber and carbon nanotubes. (4) The composite material of rice straw fiber and carbon nanotube was obtained and made into a thin film pressure sensor. The performance of the sensor was tested to obtain the Shatian rice straw fiber and carbon nanotube composite material pressure sensor.

2. The method for preparing a composite pressure sensor of rice straw and carbon nanotubes according to claim 1, characterized in that: The hot water used in step (1) is at a temperature of 90-100℃ and the concentration of sodium hydroxide is 2-5 wt.%.

3. The method for preparing a composite pressure sensor of rice straw and carbon nanotubes according to claim 1, characterized in that: In step (1), the steaming time is 6-12 hours. The surface hard components are removed by alkali dissolution treatment, which combines solution diffusion and room temperature drying.

4. The method for preparing a composite pressure sensor of rice straw and carbon nanotubes according to claim 1, characterized in that: The catalyst mentioned in step (2) is one or two of ferric chloride, Fe(III)-EDTA, and ferrocene.

5. The method for preparing a composite pressure sensor of rice straw and carbon nanotubes according to claim 4, characterized in that: The total mass concentration of the catalyst solution in step (1) is 0.5-1 wt.%.

6. The method for preparing a composite pressure sensor of rice straw and carbon nanotubes according to claim 1, characterized in that: In step (3), the temperature for chemical vapor deposition is 750-900℃ and the time is 3-5h.

7. The method for preparing a composite pressure sensor of rice straw and carbon nanotubes according to claim 6, characterized in that: The protective atmosphere used in chemical vapor deposition is argon, and the carbon source gas is one or more of methane, ethanol, and ethylene.

8. The method for preparing a composite pressure sensor of rice straw and carbon nanotubes according to claim 1, characterized in that: The reaction conditions in step (3) are a temperature of 750-900℃.

9. The method for preparing a composite pressure sensor of rice straw and carbon nanotubes according to claim 1, characterized in that: The test load applied in step (4) is 500-2000 N / m 2 The sensor's test dimensions are 10×10×0.1mm.

10. The method for preparing a composite pressure sensor of rice straw and carbon nanotubes according to claim 9, characterized in that: The sensor's resistance recovers with pressure changes at a rate of 80-90%.

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