A method for preparing biochar composite conductive material

Abstract

The present application provides a method for preparing a biochar conductive composite material, which belongs to the field of conductive fiber technology. Wool fiber is used as raw material, after being cleaned and modified, it is blended with polyacrylonitrile pretreated fiber, and finally subjected to high temperature carbonization treatment and electrophoresis process to obtain a finished biochar conductive composite material.

Description

Technical Field

[0001] The present application relates to a method for preparing a biochar composite conductive material, and belongs to the technical field of conductive composite materials. Background Art

[0002] Biochar is a new type of carbon material made from biomass materials through high-temperature pyrolysis or carbonization. It has the advantages of wide sources, low price, excellent conductivity, stable physical and chemical properties, and easy morphology control. Wool fiber is a protein fiber with a wide range of sources. Its chemical structure contains a large amount of carbon elements. In an oxygen-free or inert atmosphere, non-carbon elements will volatilize and release in the form of gas after high-temperature treatment, and carbon atoms will gradually cyclize into sp2 hybridized conjugated planes at high temperatures, forming a six-membered ring structure similar to graphite, thus having excellent conductive properties. At present, there are few studies on the preparation of conductive fibers based on wool as a bio-based material. Compared with carbon cloth or carbon fiber on the market, biochar composite materials have the advantages of low cost and green environmental protection. At the same time, composite conductive materials also have the advantages of light weight, softness, and breathability. They can also be used in many fields such as medical care, wearable electronic devices, and sports monitoring. Summary of the invention

[0003] In view of this, the present application provides a biochar composite conductive material prepared using natural fiber wool as raw material, which not only gives the material good conductive properties, light weight and softness, but also has green and environmentally friendly characteristics.

[0004] Specifically, the present application is implemented through the following scheme:

[0005] A method for preparing a biochar composite conductive material, comprising the following steps:

[0006] Step 1, immersing the wool fiber in a finishing liquid, adjusting the pH of the finishing liquid to 3-7, the immersion temperature to 60-100° C., immersing for 10-30 minutes, drying, and baking at 120-150° C. to obtain a modified wool fiber, wherein the finishing liquid contains 0.5-4wt% of tannic acid and 1-2wt% of potassium aluminum sulfate dodecahydrate;

[0007] Step 2, mixing the modified wool fiber and the polyacrylonitrile fiber in a proportion of 80-20:20-80, and weaving a composite fabric;

[0008] Step 3, placing the composite fabric in a nitrogen atmosphere, treating at 600-1000°C for 20-60min, placing the obtained biochar composite material in a tubular resistance furnace, and raising the temperature from room temperature to carbonization temperature, with the heating rate being appropriately controlled at 5-10°C / min;

[0009] Step 4: using the modified copper isopropanol dispersion as the electrophoresis solution, graphite as the anode, and the biochar composite material as the cathode, first ultrasonically vibrating, then electrodepositing, to obtain the biochar conductive composite material.

[0010] In the isopropanol dispersion of modified copper, the content of modified copper is 1-5wt%.

[0011] In the above scheme, protein fiber wool from nature is used as raw material, which is first washed and modified to improve the flatness of the fiber surface, then electrospun to prepare polyacrylonitrile fiber and pretreated, and the two are blended in a certain proportion, and finally high-temperature carbonization and electrophoresis process are used to obtain biochar composite conductive material. The composite material obtained by the above method has excellent conductivity, light weight and softness.

[0012] Further, as a preference:

[0013] In step one,

[0014] Before dipping, the cleaning is performed first, and then the cleaning liquid used for cleaning contains 1-2 g / L neutral soap powder, the bath ratio is 1:30-50, the cleaning temperature is 50-60°C, and the cleaning time is 20-30 minutes. The drying temperature after cleaning and after dipping is preferably controlled at 80-90°C.

[0015] The content of tannic acid is 2-3 wt %. At this time, it is preferred to add 2 wt % of potassium aluminum sulfate dodecahydrate to form the finishing liquid.

[0016] The pH value of the finishing solution is 4-7.

[0017] In step 2, the preparation process of the polyacrylonitrile fiber is as follows: add polyacrylonitrile to N,N-dimethylformamide solution, stir and degas to obtain a spinning solution; adopt a high-voltage electrostatic spinning process to obtain polyacrylonitrile fiber precursor, and the high-voltage electrostatic spinning parameters are: solution extrusion speed 0.5-0.8mL / h, voltage 15-25kV; pre-treat the polyacrylonitrile fiber precursor at 200-290°C for 60-120min to obtain polyacrylonitrile fiber. More preferably, the mass percentage of polyacrylonitrile in the spinning solution is 5-10%. The polyacrylonitrile fiber is placed in a tubular resistance furnace, and when the temperature rises from room temperature to the pretreatment temperature, the heating rate is appropriately controlled at 3-5°C / min.

[0018] The mixing ratio of the modified wool fiber and the polyacrylonitrile fiber is 40-50:50-60.

[0019] In step four,

[0020] The power of ultrasonic oscillation is 80 to 150 W, and the duration of ultrasonic oscillation is 30 to 60 minutes.

[0021] The electrodeposition time is 10 to 30 minutes.

[0022] In the isopropanol dispersion of modified copper, the content of modified copper is 1-2 wt %.

[0023] The preparation method of the modified copper is as follows: weigh sodium dodecyl sulfate and sodium dithionite, add deionized water and stir evenly, heat to 80°C, drip copper sulfate pentahydrate at a rate of 60 to 80 drops / min until the content of copper sulfate pentahydrate is 2 to 10% (relative to the total mass of sodium dodecyl sulfate, sodium dithionite, copper sulfate pentahydrate and deionized water), continue stirring to react after the dripping is completed, and filter to obtain modified copper particles with uniform particle size and good conductive performance.

[0024] The biochar composite conductive material prepared by the above method has excellent conductive properties and can be combined with good softness. It has been widely studied in the field of flexible and wearable conductive sensors, such as carbon materials, nanometals, and polymer-based composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 is the Raman curve of the biochar composite conductive material in this application;

[0027] Figure 2 This is the infrared spectrum curve of the biochar composite conductive material in this application;

[0028] Figure 3 The mass change of biochar composite conductive material applied at different carbonization temperatures. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application clearer, the technical solutions in the embodiments of this application will be further described in detail below in conjunction with the drawings in the embodiments of this application. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit the technical solutions of this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0030] Example 1

[0031] This embodiment provides a method for preparing a bio-based conductive composite material, the steps are as follows:

[0032] (1) Preparation of modified wool fiber:

[0033] Take 50.0g wool fiber, wash it at 60℃ for 30min in 2g / L neutral soap powder, bath ratio 1:50, and then dry it in an oven at 80℃ after being fully rinsed. Immerse the wool fiber in a finishing solution containing 2% by mass of tannic acid and 2% by mass of potassium aluminum sulfate dodecahydrate, adjust the pH value to 6 with acetic acid, immerse at 80℃, immerse for 20min, and then dry at 80℃ for 10min after immersion, and bake at 120℃ for 5min to obtain the modified wool fiber.

[0034] (2) Preparation of spinning solution:

[0035] Weigh 3.0 g of polyacrylonitrile and put it into 164 g of N,N-dimethylformamide. Heat it in a water bath at 65°C with magnetic stirring for 6 hours to fully dissolve the polyacrylonitrile. The magnetic stirring speed is fixed at 130 rpm. Dissolve it with magnetic stirring at 65°C for 10 hours. Degas the obtained spinning solution for later use.

[0036] (3) Electrospinning

[0037] The degassed spinning solution in step (1) is placed in an electrospinning device, and the electrospinning solution extrusion speed is controlled to be 0.5 mL / h and the voltage is 15 kV, and the modified polyacrylonitrile fiber is spun.

[0038] (4) Pre-oxidation:

[0039] The modified polyacrylonitrile fiber was placed in a tubular resistance furnace and pre-oxidized in an air medium. The temperature was increased from room temperature to 280°C at a rate of 3°C / min and maintained for 1 hour to obtain pre-oxidized yarn.

[0040] (5) Preparation of blended yarn:

[0041] The modified wool and the polyacrylonitrile pre-oxidized fiber were uniformly mixed in a proportion of 50:50, and the modified wool and polyacrylonitrile blended yarn was prepared by siro spinning.

[0042] Blending: The modified wool and polyacrylonitrile-based pretreated fibers are mixed evenly in proportion. After the fibers are opened, carded, and drawn, they are siro-spun. The fineness of the fed roving is 450tex, the feeding sliver gauge is 6mm, the yarn fineness is 37tex, and the twist is 700 twists / m.

[0043] (6) High temperature carbonization treatment:

[0044] The blended yarn was subjected to high temperature treatment in a nitrogen atmosphere, with a carbonization temperature of 900°C and a treatment time of 30 minutes.

[0045] (7) Electrophoresis process

[0046] An isopropanol dispersion of 2% modified copper by mass was used as the electrophoresis liquid, the carbonization product was used as the cathode, and graphite was used as the anode. Ultrasonic vibration was first performed for 30 minutes, and then electrodeposition was performed for 10 minutes at a DC voltage of 100 V to obtain the finished product.

[0047] Preparation method of modified copper: weigh 8.0g sodium dodecyl sulfate and 3.5g sodium dithionite in a four-necked flask, add deionized water and stir until uniform, stir at a speed of 500 rpm, and heat to 80°C, measure copper sulfate pentahydrate in a separatory funnel, add all at a speed of 60 drops per minute at 80°C, continue stirring and reacting for 2 hours, and filter to obtain modified copper particles. Among them, the mass percentage of copper sulfate pentahydrate relative to the total mass (sodium dodecyl sulfate, sodium dithionite, copper sulfate pentahydrate, deionized water) is 10%.

[0048] The performance of the finished products was tested, and the results are as follows: As can be seen from Table 1, compared with wool yarn, the biochar conductive composite material has excellent conductive properties; compared with commercially available conductive yarn, it uses natural protein fiber as the main raw material, has the advantages of environmental protection and greenness, and has better hand feel and yarn uniformity.

[0049] Table 1: Comparison of properties of bio-based conductive composites, conductive yarn and wool yarn

[0050] performance Resistivity / mΩ·cm Single yarn strength / cN / tex Strip uniformity Feel Three-dimensional carbonized conductive composites 21.4 8.23 15.56 soft Conductive yarn 25.9 6.89 18.45 Softer Wool Yarn >500 2.67 20.89 soft .

[0051] Test method:

[0052] The resistivity of the sample characterizes its conductivity. The smaller the resistivity, the better the conductivity. The sample size is 20×25cm, the probe spacing is no more than 2mm, and the average value is taken after 3 measurements.

[0053] Single yarn strength and yarn uniformity test: The yarn breaking strength and elongation are measured according to the standard GB / T3916-1997 "Determination of single yarn breaking strength and breaking elongation". The yarn uniformity is tested on the Y-135G yarn uniformity analyzer. Test conditions: temperature 20℃, relative humidity 65%.

[0054] The feel of the sample is evaluated subjectively by 2 to 3 people touching it.

[0055] The obtained product was tested and the results were as follows Figures 1-2 shown.

[0056] Depend on Figure 1 It can be seen that compared with wool fiber, the biochar conductive composite material has a conductivity of 1388 cm -1 and 1571cm -1 Obvious D peak and G peak appeared near , indicating that the degree of graphitization in the composite material was improved.

[0057] Depend on Figure 2 It can be seen that for the modified wool fiber, at 1513 cm -1 and 1126 cm -1 The characteristic absorption peaks of -NH- and -CN- groups unique to protein fibers appeared near the conductive composite material at 2237 cm -1 A weak absorption peak appears near the polyacrylonitrile structure, which is the characteristic absorption peak of the cyano group at 3434 cm -1 A larger C-OH stretching vibration absorption peak appears near 1585 cm -1 A strong characteristic absorption peak of C=C similar to graphene appears nearby, indicating that the degree of graphitization in the composite material is improved after high-temperature carbonization treatment, while the characteristic groups of wool fibers are reduced and the conductivity is improved.

[0058] Depend on Figure 3 It can be seen that with the increase of carbonization temperature, the weight of the composite material and wool gradually decreases, especially when the carbonization temperature is in the range of 600-900°C, the weight decreases significantly, indicating that high temperature treatment increases the carbonization degree of wool fibers; compared with the composite material, wool loses more weight, which is mainly due to the presence of polyacrylonitrile fibers in the composite material.

[0059] Example 2

[0060] The configuration of this embodiment is the same as that of embodiment 1, except that in step (1), the mass fraction of tannic acid in the finishing liquid is replaced by 0.5, 1, 1.5, and 3 respectively from 2% in embodiment 1. The influence of the mass of tannic acid in the impregnation finishing liquid on the performance of the finished composite material is shown in Table 2 below.

[0061] Table 2: Effect of tannic acid mass fraction on the properties of finished composite materials

[0062] Tannic acid mass fraction / % Resistivity / mΩ·cm Single yarn strength / cN / tex Strip uniformity Feel 0.5 21.9 7.14 17.34 soft 1 21.9 7.76 16.87 soft 1.5 21.6 7.58 16.21 soft 2 21.4 8.23 15.56 soft 3 21.9 8.21 15.58 soft .

[0063] With the increase of tannic acid concentration in the finishing solution, the single yarn strength and yarn uniformity are improved, the conductivity does not change significantly, and the resistivity decreases slightly. This is mainly because tannic acid can be wrapped in the outer layer of wool fiber, reducing the slippage of fibers during spinning, making the yarn more uniform, so the yarn strength is improved. It can be seen from Table 2 that when the potassium aluminum sulfate dodecahydrate is 2wt%, the content of tannic acid is preferably 2-3wt%.

[0064] Example 3

[0065] The configuration of this embodiment is the same as that of embodiment 1, except that in step (5), the blending ratios of the modified wool fiber and the polyacrylonitrile pretreated fiber are replaced with 70:30, 65:35, 60:40, and 40:60, respectively. The effects of different fiber blending ratios on the properties of the finished composite material are shown in Table 3.

[0066] Table 3: Effect of fiber blending ratio on the properties of finished composite materials

[0067] Blending ratio of modified wool fiber and polyacrylonitrile pretreated fiber Resistivity / mΩ·cm Single yarn strength / cN / tex Strip uniformity Feel 70:30 32.3 8.67 15.07 soft 65:35 28.5 8.54 15.18 soft 60:40 24.8 8.47 15.32 soft 50:50 21.4 8.23 15.56 soft 40:60 21.1 8.17 16.24 Softer .

[0068] As the blending ratio of polyacrylonitrile fiber increases, the resistivity of the composite material decreases, the conductivity improves, and the single yarn strength, yarn uniformity and hand feel slightly decrease, indicating that polyacrylonitrile fiber can improve the conductivity of the composite material. It can be seen from Table 3 that the mixing ratio of modified wool fiber and polyacrylonitrile fiber is preferably 40-50:50-60.

[0069] Example 4

[0070] The configuration of this embodiment is the same as that of embodiment 1, except that in step (6), the carbonization temperatures are 600, 700, 800, 900, and 1000° C., respectively. The effects of different carbonization temperatures on the properties of the finished conductive composite material are shown in Table 4.

[0071] Table 4: Effect of carbonization temperature on the properties of finished composites

[0072] Carbonization temperature / ℃ Resistivity / mΩ·cm Single yarn strength / cN / tex Strip uniformity Feel 600 30.7 7.58 15.53 soft 700 26.8 7.72 15.58 soft 800 26.6 7.95 15.54 soft 900 21.4 8.23 15.56 soft 1000 28.9 4.76 15.61 generally .

[0073] As the carbonization temperature increases, the conductivity of the composite material continues to improve, the single yarn strength and yarn uniformity are slightly improved, and the hand feel is better. This is mainly because the high temperature treatment increases the graphitization degree of wool and polyacrylonitrile fibers, so the conductivity is improved. However, when the carbonization temperature is 1000℃, the conductivity and strength of the composite material deteriorate, which is mainly caused by the destruction of the wool fiber structure at high temperature.

[0074] Example 5

[0075] The configuration of this embodiment is the same as that of embodiment 1, except that the mass fraction of modified copper in step (7) is 1%, 1.5%, 2%, and 3%. The effect of the mass fraction of modified copper on the performance of the finished three-dimensional carbonized conductive composite material is discussed, and the results are shown in Table 5.

[0076] Table 5: Effect of modified copper mass fraction on the properties of finished three-dimensional carbonized conductive composites

[0077] Modified copper mass fraction / % Resistivity / mΩ·cm Single yarn strength / cN / tex Strip uniformity Feel 0 57.8 8.99 15.62 soft 1 36.9 8.87 15.67 soft 1.5 28.1 8.75 15.61 soft 2 21.4 8.23 15.56 soft 3 21.5 7.11 15.52 generally .

[0078] As the mass fraction of modified copper increases, the resistivity decreases, the conductivity increases, and the single yarn strength and yarn uniformity change slightly; when the mass fraction of modified copper is 3%, the single yarn strength and feel deteriorate. This may be caused by the deposition of more metal on the surface of the composite material after electrophoresis, which affects the sliding of the fiber. Combined with Table 5, it can be seen that the content of modified copper in the isopropanol dispersion of modified copper is appropriately controlled at 1-2wt%.

[0079] The above-mentioned embodiments only express several feasible implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention, and the embodiments are not used to limit the scope of protection in the claims of the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and all equivalent implementations or changes that do not depart from the present invention should be included in the technology of the present invention.

Claims

1. A method for preparing a biochar composite conductive material, characterized in that: Here are the steps: Step 1, immersing the wool fiber in a finishing liquid, adjusting the pH of the finishing liquid to 3-7, the immersion temperature to 60-100° C., immersing for 10-30 minutes, drying, and baking at 120-150° C. to obtain a modified wool fiber, wherein the finishing liquid contains 2-3wt% of tannic acid and 1-2wt% of potassium aluminum sulfate dodecahydrate; Step 2, mixing the modified wool fiber and the polyacrylonitrile fiber in a proportion of 80-20:20-80, and weaving a composite fabric; Step 3, placing the composite fabric in a nitrogen atmosphere, treating at 600-1000° C. for 20-60 min, to obtain a biochar composite material; Step 4: using the modified copper isopropanol dispersion as the electrophoresis liquid, graphite as the anode, and the biochar composite material as the cathode, first ultrasonically vibrating, and then electro-depositing for 10 to 30 minutes to obtain a biochar composite conductive material. In the isopropanol dispersion of modified copper, the content of modified copper is 1-2wt%, The modified copper preparation method comprises the following steps: weighing sodium dodecyl sulfate and sodium dithionite, adding deionized water and stirring evenly, heating to 80° C., dripping copper sulfate pentahydrate at a rate of 60 to 80 drops / min until the content of copper sulfate pentahydrate is 2 to 10%, and continuing to stir the reaction after the dripping is completed, and filtering to obtain modified copper particles.

2. The method for preparing a biochar composite conductive material according to claim 1, characterized in that: In step 1, the wool is first washed before dipping, then fully rinsed and dried, the washing liquid used for washing contains 1-2 g / L neutral soap powder, the bath ratio is 1:30-50, the washing temperature is 50-60°C, and the washing time is 20-30 minutes.

3. The method for preparing a biochar composite conductive material according to claim 1, characterized in that: In step 2, the preparation process of the polyacrylonitrile fiber is as follows: adding polyacrylonitrile to N,N-dimethylformamide solution, stirring and degassing to obtain a spinning solution; adopting a high-voltage electrospinning process to obtain polyacrylonitrile fiber precursor, and the high-voltage electrospinning parameters are: solution extrusion speed 0.5~0.8mL / h, voltage 15~25kV; pre-treating the polyacrylonitrile fiber precursor at 200~290℃ for 60~120min to obtain polyacrylonitrile fiber.

4. The method for preparing a biochar composite conductive material according to claim 3, characterized in that: In the spinning solution, the mass percentage of polyacrylonitrile is 5-10%.

5. The method for preparing a biochar composite conductive material according to claim 1, characterized in that: In step 2, the mixing ratio of the modified wool fiber and the polyacrylonitrile fiber is 40-50:50-60.

6. The method for preparing a biochar composite conductive material according to claim 1, characterized in that: In step 4, the power of ultrasonic oscillation is 80-150W, and the duration of ultrasonic oscillation is 30-60min.

Images