Porous active carbon powder and preparation method thereof, carbon slurry and preparation method thereof, and conductive coating

Abstract

The invention provides a preparation method of porous activated carbon powder, the porous activated carbon powder, a preparation method of carbon slurry, the carbon slurry and a conductive coating, and relates to the technical field of silk-screen printing, and the preparation method comprises the following steps: calcining absorbent cotton in an inert atmosphere for carbonization treatment to obtain a carbonized sample; soaking the carbonized sample with an alkali solution for the first time, evaporating to remove moisture, and activating and calcining in an inert atmosphere to obtain an activated sample; soaking the activated sample for the second time by using an acid solution, washing to be neutral, and drying to obtain carbon aerogel; mixing the carbon aerogel with ball-milling beads according to a mass ratio, and performing ball-milling under a wetting condition to generate a ball-milled product; and drying the ball-milled product to obtain the porous active carbon powder for preparing the carbon slurry. According to the invention, the bending resistance can be improved.

Description

Technical Field

[0001] This disclosure relates to the field of screen printing technology, specifically to a method for preparing porous activated carbon powder, a method for preparing porous activated carbon powder and carbon paste, carbon paste, and a conductive coating. Background Technology

[0002] With the rapid development of flexible electronics technology, flexible electronic devices, with their significant advantages such as lightweight, bendability, and ease of integration, have shown broad application prospects in many fields such as smart wearables, flexible displays, and sensors. Screen-printed carbon paste, as a key material for preparing the conductive layer of flexible electronic devices, directly affects the reliability and lifespan of the devices.

[0003] In practical applications of flexible electronic devices, the devices need to withstand repeated bending, twisting and other mechanical stresses, which places extremely high demands on the bending resistance of the conductive layer formed by screen-printed carbon paste on the flexible substrate.

[0004] In related technologies, after screen printing carbon paste is printed on a flexible substrate, its bending resistance is poor after repeated bending, and its conductivity often decreases significantly. Specifically, the resistance value increases sharply, making it difficult to meet the requirements for long-term stable operation of flexible electronic devices. Summary of the Invention

[0005] The purpose of this disclosure is to provide a method for preparing porous activated carbon powder, a method for preparing porous activated carbon powder and carbon paste, carbon paste and conductive coating, thereby overcoming, to at least a certain extent, the problems of poor bending resistance and significant decrease in conductivity of screen-printed carbon paste on flexible substrates due to the limitations and defects of related technologies.

[0006] According to one aspect of this disclosure, a method for preparing porous activated carbon powder is provided, comprising: The defatted cotton was calcined in an inert atmosphere to obtain a carbonized sample. The carbonized sample was first soaked in an alkaline solution to remove moisture by evaporation, and then activated by calcination in an inert atmosphere to obtain an activated sample. The activated sample was soaked a second time with an acid solution, washed until neutral, and dried to obtain carbon aerogel. Carbon aerogel and milling beads are mixed in a mass ratio and milled under wetting conditions to generate the milled product. The ball-milled product is dried to obtain porous activated carbon powder for preparing carbon slurry.

[0007] In an exemplary embodiment of this disclosure, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere; the calcination heating rate is 3-7℃ / min, the calcination time is 80-100 min, and the calcination temperature is 700-900℃.

[0008] In one exemplary embodiment of this disclosure, the alkaline solution is a sodium hydroxide solution, wherein the mass of sodium hydroxide is 5-8 times the mass of the carbonized sample; the first soaking time is 12-48 hours.

[0009] In one exemplary embodiment of this disclosure, the acid solution is a 6 M hydrochloric acid solution, and the second soaking time is 12-24 hours.

[0010] In one exemplary embodiment of this disclosure, the mass ratio of carbon aerogel to grinding beads is 1:30 to 1:70; the grinding beads are zirconia grinding beads, and the grinding beads include zirconia grinding beads with a diameter of 5 mm and zirconia grinding beads with a diameter of 10 mm.

[0011] In one exemplary embodiment of this disclosure, the wetting conditions use a mixture of ethanol and water as the solvent, the ball milling speed is 400-600 rpm, and the ball milling time is 48-96 hours.

[0012] According to one aspect of this disclosure, a porous activated carbon powder is provided, which is prepared according to the above-described method for preparing porous activated carbon powder.

[0013] According to one aspect of this disclosure, a carbon slurry is provided, the components of which include: 5-15 parts porous activated carbon powder, 10-20 parts conductive carbon black, 5-10 parts epoxy resin binder, and 65-80 parts solvent.

[0014] According to one aspect of this disclosure, a method for preparing carbon slurry is provided, comprising: dissolving an epoxy resin binder in a solvent to form a homogeneous adhesive solution, adding porous activated carbon powder and conductive carbon black, mixing evenly, and then rolling to obtain carbon slurry.

[0015] According to one aspect of this disclosure, a conductive coating is provided, which is formed by screen printing carbon paste onto a flexible substrate, followed by drying and curing; the dry film thickness of the conductive coating is 10-20 μm; the carbon paste includes porous activated carbon powder, conductive carbon black, epoxy resin binder and solvent; the porous activated carbon powder is prepared according to the above-described method for preparing porous activated carbon powder.

[0016] In the technical solution provided in this disclosure, on the one hand, the prepared biomass-based porous activated carbon powder has a three-dimensional interconnected porous structure and excellent mechanical toughness. When introduced into screen-printed carbon paste, it effectively enhances electronic conductivity, the structural stability and fatigue resistance of the conductive layer, and improves bending resistance. On the other hand, when the porous activated carbon powder is used in carbon paste, it synergistically constructs a stable three-dimensional conductive network with conductive carbon black. Even if local conductive pathways break during repeated bending, the fiber network can still provide alternative conductive paths, effectively suppressing a sharp increase in resistance, improving the stability of the conductive network, and ensuring the long-term reliability of flexible electronic devices. Furthermore, using degreased cotton as a biomass carbon source to prepare porous activated carbon powder is widely available, renewable, and inexpensive, meeting the requirements of green and sustainable development. Simultaneously, the preparation process is simple and controllable, easy to scale up production, and increases application prospects. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0018] Figure 1 The flowchart illustrating a method for preparing porous activated carbon powder according to an embodiment of the present disclosure is shown.

[0019] Figure 2 The diagram illustrates a SEM image of porous activated carbon powder at a low magnification.

[0020] Figure 3 The diagram illustrates a SEM image of porous activated carbon powder at a high magnification.

[0021] Figure 4 A schematic diagram illustrating the radial size distribution of porous activated carbon powder is shown.

[0022] Figure 5 A schematic diagram illustrating the lateral size distribution of porous activated carbon powder is shown.

[0023] Figure 6 This is the XPS full spectrum of porous activated carbon powder.

[0024] Figure 7 This is the C1s spectrum of porous activated carbon powder.

[0025] Figure 8 This is the O1s spectrum of porous activated carbon powder.

[0026] Figure 9 This is the Raman spectrum of porous activated carbon powder.

[0027] Figure 10 This is the isothermal adsorption-desorption curve of porous activated carbon powder.

[0028] Figure 11 This is a pore size distribution diagram of porous activated carbon powder.

[0029] Figure 12 This is a graph showing the resistance values ​​of a screen-printed film under different bending cycles.

[0030] Figure 13 This is a graph showing the rate of change of resistance of the screen-printed film under different bending cycles. Detailed Implementation

[0031] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this disclosure more comprehensive and complete, and to fully convey the concept of the example embodiments to those skilled in the art. The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced with one or more of the specific details omitted, or other methods, components, apparatus, steps, etc., can be employed. In other instances, well-known technical solutions are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0032] The terms “a,” “an,” “the,” and “the” are used in this specification to indicate the presence of one or more elements / components, etc.; the terms “including” and “having” are used to indicate an open-ended inclusion and to mean that there may be other elements / components, etc., in addition to those listed; the terms “first” and “second” are used only as markings and are not a limitation on the number of objects.

[0033] In practical applications of flexible electronic devices, these devices must withstand repeated bending and twisting mechanical stresses. This places extremely high demands on the bending resistance of the conductive layer formed by screen-printed carbon paste on flexible substrates. Traditional screen-printed carbon paste, after being screen-printed on flexible substrates such as PET, often exhibits a significant decrease in conductivity after repeated bending. Specifically, the resistance value increases sharply, making it difficult to meet the requirements for long-term stable operation of flexible electronic devices and severely restricting the further development and application of flexible electronics technology.

[0034] Based on this, this disclosure provides a method for preparing porous activated carbon powder, used to prepare biomass-based porous activated carbon powder. Due to its unique structure and excellent performance, porous biomass-based activated carbon, when prepared into activated carbon fibers, possesses a rich porous structure, a large specific surface area, and good electrical conductivity and mechanical properties, which can improve the bending resistance of screen printing carbon paste.

[0035] refer to Figure 1 As shown, the preparation method of this porous activated carbon powder mainly includes the following steps: In step S110, the degreased cotton is calcined in an inert atmosphere to carbonize it, thereby obtaining a carbonized sample. In step S120, the carbonized sample is first soaked in an alkaline solution to evaporate and remove moisture, and then activated and calcined in an inert atmosphere to obtain an activated sample. In step S130, the activated sample is immersed a second time with an acid solution, washed until neutral and dried to obtain carbon aerogel; In step S140, carbon aerogel and milling beads are mixed in a mass ratio and milled under wetting conditions to generate the milled product. In step S150, the ball-milled product is dried to obtain porous activated carbon powder for preparing carbon slurry.

[0036] In this embodiment, the prepared biomass-based porous activated carbon powder possesses a three-dimensional interconnected porous structure and excellent mechanical toughness. When introduced into screen-printed carbon paste, it effectively enhances electronic conductivity, the structural stability and fatigue resistance of the conductive layer, and improves bending resistance. When porous activated carbon powder is used in carbon paste, it synergistically constructs a robust three-dimensional conductive network with conductive carbon black. Even if local conductive pathways break during repeated bending, the fiber network can still provide alternative conductive paths, effectively suppressing a sharp increase in resistance, improving the stability of the conductive network, and ensuring the long-term reliability of flexible electronic devices. Using degreased cotton as a biomass carbon source to prepare porous activated carbon powder is widely available, renewable, and inexpensive, meeting the requirements of green and sustainable development. Simultaneously, the preparation process is simple and controllable, facilitating large-scale production. The bend-resistant screen-printed carbon paste prepared using porous activated carbon powder is suitable for various flexible electronic devices (such as flexible sensors, wearable devices, flexible batteries, etc.), providing a material basis for their stable operation under complex mechanical stress environments and increasing application prospects.

[0037] Next, the preparation method of porous activated carbon powder in the embodiments of this disclosure will be described in detail.

[0038] In step S110, the degreased cotton is calcined in an inert atmosphere to obtain a carbonized sample.

[0039] In this embodiment, the step is a carbonization step. Degreased cotton is used as the biomass carbon source. Calcination is performed under an inert atmosphere to obtain a carbonized sample. The inert atmosphere can be a nitrogen atmosphere or an argon atmosphere. Specifically, the degreased cotton is placed in a crucible and compacted. The crucible can be placed in a tube furnace, and high-purity nitrogen gas is introduced, with a flow rate of 100 SCCM. During calcination, the temperature is increased to 700-900℃ at a rate of 3-7℃ / min, the calcination temperature is 700-900℃, and the holding time is 80-100 min. After calcination, nitrogen gas is continued to be introduced until the temperature naturally cools to room temperature. The black, blocky calcined sample is then removed; this black calcined sample is the carbonized sample.

[0040] In step S120, the carbonized sample is first soaked in an alkaline solution to remove moisture by evaporation, and then activated and calcined in an inert atmosphere to obtain an activated sample.

[0041] In this embodiment, this step is an activation step. The alkaline solution can be any suitable alkaline solution, such as sodium hydroxide solution or potassium hydroxide solution, etc. Sodium hydroxide is used as an example here. Sodium hydroxide is weighed and dissolved in deionized water to prepare the alkaline solution; the mass of sodium hydroxide is 5 to 8 times the mass of the carbonized sample.

[0042] The carbonized sample was first immersed in an alkaline solution at room temperature for 12-48 hours. After immersion, the mixture was transferred to a hot plate and rapidly stirred to evaporate moisture until no obvious liquid water remained. The remaining solid was transferred to a crucible, covered, and placed back into a tube furnace. Inert gas was introduced and the sample was activated and calcined under an inert atmosphere to obtain an activated sample. The inert gas was nitrogen, with a flow rate of 100 SCCM. During the activation and calcination process, the temperature was increased to 700-900℃ at a rate of 5-7℃ / min and held for 80-100 min. After cooling to room temperature, the black activated sample was removed.

[0043] In step S130, the activated sample is soaked a second time with an acid solution, washed until neutral and dried to obtain carbon aerogel.

[0044] This step is used to remove impurities. The acid solution can be any suitable acid solution, such as hydrochloric acid, sulfuric acid, etc. Hydrochloric acid is used as an example here. The concentration of the hydrochloric acid solution is 6 M, i.e., 6 mol / L. The activated sample is completely immersed in the acid solution for a second soaking at room temperature to remove impurities. The second soaking time can be 12-24 hours. After removing impurities, the sample is washed with deionized water by centrifugation until the supernatant is neutral. The centrifugation speed is 4000 rpm, 10 min each time. The washed activated sample is transferred to a forced-air drying oven for drying, obtaining a black, fluffy carbon aerogel. The drying temperature is 50℃.

[0045] In step S140, carbon aerogel and milling beads are mixed in a mass ratio and milled under wetting conditions to generate the milled product.

[0046] This step involves ball milling. Add the grinding beads and carbon aerogel to a ball milling jar, using zirconia grinding beads. The beads can be 5 mm or 10 mm in diameter, with a total of 10-20 beads of each size, in a 10:3 ratio, resulting in a mass ratio of activated carbon fibers to grinding beads of 1:30-1:70. Wet the sample in the ball milling jar with the mixture, seal the jar, and place it in a planetary ball mill. Ball milling is then performed under wetting conditions to generate the milled product. The milling speed is 400-600 rpm, and the milling time is 48-96 hours. The solvent used to wet the sample is a mixture of ethanol and water. The mass ratio of ethanol to water can be any suitable ratio, as long as it is sufficient to wet the sample. The milled product can be a suspension of carbon aerogel sample, ethanol, and water.

[0047] In step S150, the ball-milled product is dried to obtain porous activated carbon powder for preparing carbon slurry.

[0048] In this embodiment of the disclosure, after ball milling, the suspension (sample + ethanol + water) in the ball milling jar, i.e., the product after ball milling, is transferred to a forced-air drying oven at 50°C to dry, obtaining a black powdery porous activated carbon powder. Porous activated carbon powder refers to biomass-based porous activated carbon powder, i.e., activated carbon fiber powder. Porous activated carbon powder is used to prepare carbon slurry, which can be a screen-printed carbon slurry used to prepare conductive coatings for flexible electronic devices.

[0049] In this embodiment, degreased cotton is used as the biomass carbon source, which is widely available, renewable, and inexpensive, meeting the requirements of green and sustainable development. Simultaneously, the preparation process is simple and controllable, facilitating large-scale production. The prepared biomass-based porous activated carbon powder possesses a three-dimensional interconnected porous structure, high specific surface area, and excellent mechanical toughness. Introducing it into screen-printed carbon paste effectively enhances electronic conductivity, as well as the structural stability and fatigue resistance of the conductive layer.

[0050] After obtaining porous activated carbon powder, the prepared porous activated carbon powder is mixed with conductive carbon black, epoxy resin binder, and solvent in a certain mass ratio to obtain a carbon paste. The solvent can be anhydrous ethanol. The carbon paste refers to screen printing carbon paste. Specifically, firstly, the epoxy resin binder is dissolved in anhydrous ethanol and transferred to a homogenizer until completely dissolved to form a homogeneous adhesive solution; then, porous activated carbon powder and conductive carbon black are added sequentially to the homogeneous adhesive solution, and the mixture is transferred to a homogenizer for uniform mixing to obtain a mixed paste. This paste is then rolled 3-5 times using a three-roll mill to obtain a uniformly dispersed screen printing carbon paste with suitable viscosity.

[0051] The mass ratio of porous activated carbon powder to conductive carbon black, epoxy resin binder, and anhydrous ethanol is (5-15):(10-20):(5-10):(65-80). The epoxy resin binder is dissolved in anhydrous ethanol and then transferred to a homogenizer and stirred for 30 minutes until completely dissolved. The homogenizer speed is 15000 rpm. Porous activated carbon powder and conductive carbon black are added sequentially to the homogenized slurry, and the mixture is stirred at 20000 rpm for 60 minutes until homogenized. The mixed slurry is transferred to a three-roll mill and rolled four times sequentially with roll gaps of 50 μm, 30 μm, 20 μm, and 15 μm to obtain a uniformly dispersed carbon slurry. The carbon slurry may include porous activated carbon powder, conductive carbon black, epoxy resin binder, and solvent. The components, by mass parts, include: 5-15 parts of biomass-based porous activated carbon powder, 10-20 parts of conductive carbon black, 5-10 parts of epoxy resin binder, and 65-80 parts of solvent.

[0052] After preparing the screen-printable carbon paste, it can be screen-printed onto a pretreated PET flexible substrate. After drying and curing, a conductive coating is formed. The carbon paste is screen-printed onto the pretreated PET flexible substrate, with the wet film thickness controlled at 50-100 μm. The printed substrate is then placed in a forced-air drying oven and pre-dried at 60°C for 20 min to remove solvents. The temperature is then raised to a target temperature (e.g., 100°C) for curing, and the curing time is 40 min to allow the epoxy resin binder to cross-link and form a uniform conductive coating. This conductive coating is for flexible electronic devices. The dry film thickness of the conductive coating can be 10-20 μm.

[0053] Next, a bending resistance test was conducted. The prepared conductive coating was cut to a standard size (10 mm × 50 mm), fixed on a bending tester, and subjected to a dynamic bending test. The bending radius of the dynamic bending test was 2 mm, the bending frequency was 1 time / second, and the bending angle was ±180 degrees. After each certain number of bends, the change in resistance value was measured using a resistance tester, and the rate of change in resistance was recorded.

[0054] The biomass-based porous activated carbon powder prepared in this embodiment possesses a three-dimensional interconnected porous structure and excellent mechanical toughness. When introduced into screen-printed carbon paste, it effectively enhances electronic conductivity, structural stability, and fatigue resistance of the conductive layer. In dynamic bending tests, the conductive coating with added activated carbon powder exhibits a resistance change rate (ΔR / R0) of less than 7% after 200 bends, while the conductive coating without activated carbon powder shows a resistance change rate of 16.5% after 100 bends. Therefore, the bending resistance of the conductive coating with added porous activated carbon powder is significantly improved.

[0055] Porous activated carbon powder and conductive carbon black work together to construct a robust three-dimensional conductive network. Even if local conductive pathways break during repeated bending, the fiber network can still provide alternative conductive paths, effectively suppressing the sharp rise in resistance, optimizing the stability of the conductive network, and ensuring the long-term reliability of flexible electronic devices.

[0056] The bend-resistant screen printing carbon paste prepared in this disclosure is suitable for a variety of flexible electronic devices, such as flexible sensors, wearable devices, and flexible batteries, providing a material basis for their stable operation under complex mechanical stress environments and increasing their application prospects.

[0057] Next, the preparation method of the above-mentioned porous activated carbon powder will be described in detail with reference to the embodiments.

[0058] Example 1

[0059] 1. Carbonization treatment. Take 10 g of degreased cotton and compact it in an alumina crucible. Place the crucible in a tube furnace and introduce high-purity nitrogen gas at a flow rate of 100 SCCM. Heat the temperature to 800℃ at a rate of 5℃ / min and hold for calcination for 90 min. After calcination, continue to introduce nitrogen gas until the temperature naturally cools to room temperature. Take out the black block carbonized sample, which weighs 4.2 g.

[0060] 2. Activation Treatment. Weigh 21.7 g of NaOH (6 times the mass of the calcined sample) and dissolve it in 50 mL of deionized water to prepare a NaOH solution. Completely immerse 4.2 g of the carbonized sample in this NaOH solution and allow it to stand at room temperature for the first soaking, which lasts for 24 hours. After soaking, transfer the mixture to a 120°C hot plate and rapidly stir to evaporate until no obvious liquid water remains. Transfer the remaining solid to a crucible, cover it, and place it back into a tube furnace. Purge with nitrogen at a flow rate of 100 SCCM. Further, calcine at 800°C (5°C / min) for activation. After cooling to room temperature, remove the black activated sample.

[0061] 3. Removal of impurities. Prepare 50 mL of 6 M HCl solution and immerse the activated sample a second time. Allow the sample to stand at room temperature for 12 h. Then wash with deionized water by centrifugation until the supernatant is neutral; the centrifugation speed is 4000 rpm, 10 min each time. Transfer the washed activated sample to a forced-air drying oven at 50℃ and dry to obtain a black, fluffy carbon aerogel.

[0062] 4. Ball milling treatment. The carbon aerogel and zirconia grinding beads were added together to a 50 mL agate grinding jar. The zirconia grinding beads had diameters of 5 mm and 10 mm, with 10-20 beads in total. The ratio of 5 mm to 10 mm grinding beads was 10:3, resulting in a carbon aerogel to grinding bead mass ratio of 1:50. Anhydrous ethanol and ultrapure water were added to the grinding jar to wet the sample. After sealing the jar, it was placed in a planetary ball mill. The milling speed was set to 500 rpm, and the milling time was 72 h.

[0063] 5. Dry for later use. After ball milling, transfer the suspension (sample + ethanol + water) in the ball mill jar to a forced-air drying oven and dry at 50°C to obtain black powdery porous activated carbon powder.

[0064] refer to Figure 2 SEM images and Figure 4 and Figure 5 The particle size distribution chart shows that the porous activated carbon powder has a longitudinal particle size of approximately 1-5 μm and a transverse particle size of approximately 0.5-2.5 μm.

[0065] from Figure 3 The magnified SEM image shows that the surface of the porous activated carbon powder is irregularly rough and granular.

[0066] Figure 6-8 XPS graphs and Figure 9 The Raman spectra further indicate that the surface of the porous activated carbon powder contains a variety of functional groups and defects. Figure 10 It presented 2016m 2 g -1 Large specific surface area. From Figure 11 The pore size distribution diagram shows that the porous activated carbon powder has a large number of pores, which are micropores. These characteristics are beneficial to the adhesion between the components and between the slurry and the substrate.

[0067] 6. Slurry Preparation. Weigh 10g of materials according to a mass ratio of 10:15:7:68: 1.0g activated carbon powder, 1.5g conductive carbon black, 0.7g epoxy resin, and 6.8g anhydrous ethanol. First, dissolve 0.7g epoxy resin in 6.8g anhydrous ethanol and transfer to a homogenizer at 15000 rpm, stirring for 30 minutes until completely dissolved to form a transparent and homogeneous solution. Then, add 1.0g porous activated carbon powder and 1.5g conductive carbon black sequentially, and adjust the homogenizer speed to 20000 rpm, stirring for 60 minutes to obtain a mixed slurry. Transfer the mixed slurry to a three-roll mill and roll it four times with roll gaps of 50 μm, 30 μm, 20 μm, and 15 μm to obtain a uniformly dispersed carbon slurry.

[0068] 7. Screen Printing and Curing. The carbon paste was printed onto the pretreated PET substrate using a 300-mesh screen, controlling the wet film thickness to 75 μm. After printing, the substrate was placed in a forced-air drying oven and pre-dried at 60°C for 20 min to remove the ethanol solvent. Subsequently, the temperature was raised to 100°C and cured for 40 min to crosslink the epoxy resin, resulting in a uniform conductive coating with a dry film thickness of approximately 15 μm.

[0069] 8. Bending resistance test. Cut standard samples of conductive coating into 10 mm × 50 mm shapes and fix them on a bending tester for dynamic bending tests. The bending radius for the dynamic bending test is 2 mm, the frequency is 1 time / second, and the angle is ±180 degrees. After 0 (initial), 50, 100, 150, and 200 bends, respectively, use a multimeter to measure the resistance and calculate the rate of change of resistance ΔR / R0 (ΔR = test resistance - R0, where R0 is the initial resistance).

[0070] Depend on Figure 12 As can be seen, compared with carbon paste without added carbon powder, the conductive coating prepared using porous activated carbon powder in this embodiment of the present disclosure has a significantly reduced resistance, and only changes by 6.3% after being bent 200 times. In this embodiment of the present disclosure, because the activated carbon powder is uniformly dispersed and has an intact porous structure under these conditions, it can form a "three-dimensional interconnected conductive network" with conductive carbon black. During bending, the fibrous carbon powder buffers mechanical stress, and even if local carbon black pathways break, the fibrous network can still provide alternative conductive paths, thereby suppressing a sharp increase in resistance and maintaining good stability during bending.

[0071] Example 2

[0072] 1. Carbonization treatment. Take 10 g of degreased cotton and compact it in an alumina crucible. Place the crucible in a tube furnace and introduce high-purity nitrogen gas at a flow rate of 100 SCCM. Heat the temperature to 900℃ at a rate of 6℃ / min and hold for calcination for 80 min. After calcination, continue to introduce nitrogen gas until the temperature naturally cools to room temperature. Take out the black block carbonized sample, which weighs 4.2 g.

[0073] 2. Activation Treatment. Weigh 21.7 g of NaOH (6 times the mass of the calcined sample) and dissolve it in 50 mL of deionized water to prepare a NaOH solution. Completely immerse 4.2 g of the carbonized sample in this NaOH solution and allow it to stand at room temperature for the first soaking (36 h). After soaking, transfer the mixture to a 120°C hot plate and rapidly stir to evaporate until no obvious liquid water remains. Transfer the remaining solid to a crucible, cover it, and place it back into a tube furnace. Purge with nitrogen at a flow rate of 100 SCCM. Further, calcine at 900°C (6°C / min) for activation. After cooling to room temperature, remove the black activated sample.

[0074] 3. Removal of impurities. Prepare 50 mL of 6 M HCl solution and soak the activated sample a second time. Let it stand at room temperature for 18 h. Then wash with deionized water by centrifugation until the supernatant is neutral; the centrifugation speed is 4000 rpm, 10 min each time. Transfer the washed activated sample to a forced-air drying oven at 50℃ and dry to obtain a black, fluffy carbon aerogel.

[0075] 4. Ball milling treatment. The carbon aerogel and zirconia grinding beads were added together to a 50 mL agate grinding jar. The zirconia grinding beads had diameters of 5 mm and 10 mm, with 10-20 beads in total. The ratio of 5 mm to 10 mm beads was 10:5, resulting in a sample to grinding bead mass ratio of 1:60. Anhydrous ethanol and ultrapure water were added to the grinding jar to wet the sample. After sealing the jar, it was placed in a planetary ball mill. The milling speed was set to 400 rpm, and the milling time was 48 h.

[0076] 5. Dry for later use. After ball milling, transfer the suspension (sample + ethanol + water) in the ball mill jar to a forced-air drying oven and dry at 50°C to obtain black powdery porous activated carbon powder.

[0077] 6. Slurry Preparation. Weigh 10g of materials according to a mass ratio of 10:15:7:68: 1.0g activated carbon powder, 1.5g conductive carbon black, 0.7g epoxy resin, and 6.8g anhydrous ethanol. First, dissolve 0.7g epoxy resin in 6.8g anhydrous ethanol and transfer to a homogenizer at 15000 rpm, stirring for 30 minutes until completely dissolved to form a transparent and homogeneous solution. Then, add 1.0g porous activated carbon powder and 1.5g conductive carbon black sequentially, and adjust the homogenizer speed to 20000 rpm, stirring for 60 minutes to obtain a mixed slurry. Transfer the mixed slurry to a three-roll mill and roll it four times with roll gaps of 50 μm, 30 μm, 20 μm, and 15 μm to obtain a uniformly dispersed carbon slurry.

[0078] 7. Screen Printing and Curing. The carbon paste was printed onto the pretreated PET substrate using a 300-mesh screen, controlling the wet film thickness to 75 μm. After printing, the substrate was placed in a forced-air drying oven and pre-dried at 60°C for 20 min to remove the ethanol solvent. Subsequently, the temperature was raised to 100°C and cured for 40 min to crosslink the epoxy resin, resulting in a uniform conductive coating with a dry film thickness of approximately 15 μm.

[0079] 8. Bending resistance test. Cut standard samples of conductive coating into 10 mm × 50 mm shapes and fix them on a bending tester for dynamic bending tests. The bending radius for the dynamic bending test is 2 mm, the frequency is 1 time / second, and the angle is ±180 degrees. After 0 (initial), 50, 100, 150, and 200 bends, respectively, use a multimeter to measure the resistance and calculate the rate of change of resistance ΔR / R0 (ΔR = test resistance - R0, where R0 is the initial resistance).

[0080] from Figure 12 and Figure 13 It can be seen that, compared to Example 1, the initial resistance decreased slightly, while after 200 bends, the resistance change rate reached 8.0%. In Example 2, due to the short ball milling time, the fibers agglomerated, resulting in a local decrease in resistance. However, during the bending process, there were "weak points" in the conductive network, causing the resistance to rise rapidly.

[0081] Example 3

[0082] This embodiment includes the following steps: 1. Carbonization treatment. Take 10 g of degreased cotton and compact it in an alumina crucible. Place the crucible in a tube furnace and introduce high-purity nitrogen gas at a flow rate of 100 SCCM. Heat the temperature to 700℃ at a rate of 3℃ / min and hold for calcination for 100 min. After calcination, continue to introduce nitrogen gas until the temperature naturally cools to room temperature. Take out the black block carbonized sample, which weighs 4.2 g.

[0083] 2. Activation Treatment. Weigh 21.7 g of NaOH (6 times the mass of the calcined sample) and dissolve it in 50 mL of deionized water to prepare a NaOH solution. Completely immerse 4.2 g of the carbonized sample in this NaOH solution and allow it to stand at room temperature for the first soaking, which lasts for 48 h. After soaking, transfer the mixture to a 120°C hot plate and rapidly stir to evaporate until no obvious liquid water remains. Transfer the remaining solid to a crucible, cover it, and place it back into a tube furnace. Purge with nitrogen at a flow rate of 100 SCCM. Further, calcine at 700°C (3°C / min) for activation. After cooling to room temperature, remove the black activated sample.

[0084] 3. Removal of impurities. Prepare 50 mL of 6 M HCl solution and immerse the activated sample a second time. Allow the sample to stand at room temperature for 24 h. Then wash with deionized water by centrifugation until the supernatant is neutral; the centrifugation speed is 4000 rpm, 10 min each time. Transfer the washed activated sample to a forced-air drying oven at 50℃ and dry to obtain a black, fluffy carbon aerogel.

[0085] 4. Ball milling treatment. The carbon aerogel and zirconia grinding beads were added together to a 50 mL agate grinding jar. The zirconia grinding beads had diameters of 5 mm and 10 mm, with 10-20 beads in total. The ratio of 5 mm to 10 mm grinding beads was 10:3, resulting in a carbon aerogel to grinding bead mass ratio of 1:70. Anhydrous ethanol and ultrapure water were added to the grinding jar to wet the sample. After sealing the jar, it was placed in a planetary ball mill. The milling speed was set to 500 rpm, and the milling time was 96 h.

[0086] 5. Dry for later use. After ball milling, transfer the suspension (sample + ethanol + water) in the ball mill jar to a forced-air drying oven and dry at 50°C to obtain black powdery porous activated carbon powder.

[0087] 6. Slurry Preparation. Weigh 10g of materials according to a mass ratio of 10:15:7:68: 1.0g activated carbon powder, 1.5g conductive carbon black, 0.7g epoxy resin, and 6.8g anhydrous ethanol. First, dissolve 0.7g epoxy resin in 6.8g anhydrous ethanol and transfer to a homogenizer at 15000 rpm, stirring for 30 minutes until completely dissolved to form a transparent and homogeneous solution. Then, add 1.0g porous activated carbon powder and 1.5g conductive carbon black sequentially, and adjust the homogenizer speed to 20000 rpm, stirring for 60 minutes to obtain a mixed slurry. Transfer the mixed slurry to a three-roll mill and roll it four times with roll gaps of 50 μm, 30 μm, 20 μm, and 15 μm to obtain a uniformly dispersed carbon slurry.

[0088] 7. Screen Printing and Curing. The carbon paste was printed onto the pretreated PET substrate using a 300-mesh screen, controlling the wet film thickness to 75 μm. After printing, the substrate was placed in a forced-air drying oven and pre-dried at 60°C for 20 min to remove the ethanol solvent. Subsequently, the temperature was raised to 100°C and cured for 40 min to crosslink the epoxy resin, resulting in a uniform conductive coating with a dry film thickness of approximately 15 μm.

[0089] 8. Bending resistance test. Cut standard samples of conductive coating into 10 mm × 50 mm shapes and fix them on a bending tester for dynamic bending tests. The bending radius for the dynamic bending test is 2 mm, the frequency is 1 time / second, and the angle is ±180 degrees. After 0 (initial), 50, 100, 150, and 200 bends, respectively, use a multimeter to measure the resistance and calculate the rate of change of resistance ΔR / R0 (ΔR = test resistance - R0, where R0 is the initial resistance).

[0090] from Figure 12 and Figure 13 It can be seen that, compared to Example 1, the initial resistance increased slightly, and after 200 bends, the resistance change rate was approximately 8.8%. In Example 3, the excessively long ball milling time led to fiber breakage, reduced mechanical support capacity, and inability to effectively buffer bending stress, causing the resistance increase rate to rise again.

[0091] Comparative Example

[0092] The comparative example, except for the absence of porous activated carbon powder, was identical to Example 1 under all other conditions, serving as a control group. Table 2 shows that the conductive coating prepared in the comparative example achieved a ΔR / R0 of 16.5% after 100 bends, which surged to 47.8% after 200 bends, indicating that the conductive carbon black network broke down due to bending and had no alternative pathways. The conductive coating prepared with added porous activated carbon powder showed a ΔR / R0 of less than 9% after 200 bends, verifying the reinforcing effect of the porous activated carbon powder.

[0093] The porous activated carbon powder with a three-dimensional interconnected porous structure and high specific surface area prepared in this embodiment is mixed with conductive carbon black, epoxy resin binder and solvent in a certain mass ratio, and then homogenized and rolled to form a screen printing carbon paste. This screen printing carbon paste is used to screen print a conductive coating on flexible substrates such as PET. The resulting conductive coating exhibits excellent bending resistance and conductivity stability. Under test conditions of a bending radius of 2 mm and an angle of ±180°, the resistance change rate remains below 9% after 200 bends, significantly better than traditional carbon pastes, making it suitable for flexible electronic devices such as flexible sensors and wearable devices.

[0094] In this embodiment of the disclosure, a porous activated carbon powder is also provided, which can be prepared according to the preparation method of porous activated carbon powder in steps S110 to S140. The porous activated carbon powder is an activated carbon powder with a three-dimensional interconnected porous structure and a high specific surface area.

[0095] In this embodiment, a carbon paste is also provided. This carbon paste is a flexurally resistant screen printing carbon paste, and its components include: 5-15 parts porous activated carbon powder, 10-20 parts conductive carbon black, 5-10 parts epoxy resin binder, and 65-80 parts solvent. The solvent is anhydrous ethanol. Introducing porous activated carbon powder into the screen printing carbon paste effectively enhances electronic conductivity, as well as the structural stability and fatigue resistance of the conductive layer.

[0096] This disclosure also provides a method for preparing carbon paste, used to prepare a bend-resistant screen printing carbon paste, the preparation steps specifically including: The epoxy resin adhesive is dissolved in a solvent to form a homogeneous adhesive solution; Porous activated carbon powder and conductive carbon black are added to a homogeneous adhesive solution and mixed evenly to obtain a mixed slurry. The mixed slurry is transferred to a three-roll mill for rolling to obtain carbon slurry.

[0097] For example, 5-10 parts of epoxy resin adhesive are dissolved in 65-80 parts of solvent, and then transferred to a homogenizer and stirred until completely dissolved to form a transparent and homogeneous adhesive solution; the homogenizer speed is 15000 rpm, and the stirring time is 30 min. 5-15 parts of porous activated carbon powder and 10-20 parts of conductive carbon black are added to the transparent and homogeneous adhesive solution, and then mixed evenly using a homogenizer. After homogenization, the mixed slurry is rolled to obtain a carbon slurry. During the homogenization process, the homogenizer speed is 20000 rpm, and the stirring time is 60 min. The mixed slurry is transferred to a three-roll mill and rolled four times sequentially with roll gaps of 50 μm, 30 μm, 20 μm, and 15 μm to obtain a uniformly dispersed carbon slurry.

[0098] In this embodiment, a conductive coating is also provided. Specifically, carbon paste is screen-printed onto a flexible substrate and then dried and cured to obtain the conductive coating. The flexible substrate is a PET substrate; the curing conditions are treatment at 100°C for 40 minutes to crosslink the epoxy resin; the dry film thickness of the conductive coating is 10-20 μm. Carbon paste can be screen-printed onto the PET substrate using a 300-mesh screen, controlling the wet film thickness to 75 μm. The substrate is then placed in a forced-air drying oven for drying at 60°C for 20 minutes to remove the ethanol solvent. The porous activated carbon powder is uniformly dispersed and has a complete porous structure, which can form a "three-dimensional interconnected conductive network" with conductive carbon black. During bending, the fibrous carbon powder buffers mechanical stress. Even if local carbon black pathways break, the fibrous network can still provide alternative conductive paths, thereby suppressing a sharp increase in resistance and maintaining good stability during bending.

[0099] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of this disclosure and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0100] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

[0101] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A method for preparing porous activated carbon powder, characterized in that, include: The defatted cotton was calcined in an inert atmosphere to obtain a carbonized sample. The carbonized sample was first soaked in an alkaline solution to remove moisture by evaporation, and then activated and calcined in an inert atmosphere to obtain an activated sample. The activated sample was soaked a second time with an acid solution, washed until neutral, and dried to obtain carbon aerogel. The carbon aerogel is mixed with milling beads at a mass ratio and milled under wetting conditions to generate the milled product. The ball-milled product is dried to obtain porous activated carbon powder for preparing carbon slurry.

2. The method for preparing porous activated carbon powder according to claim 1, characterized in that, The inert atmosphere is a nitrogen atmosphere or an argon atmosphere; the calcination heating rate is 3-7℃ / min, the calcination time is 80-100 min, and the calcination temperature is 700-900℃.

3. The method for preparing porous activated carbon powder according to claim 1, characterized in that, The alkaline solution is a sodium hydroxide solution, wherein the mass of sodium hydroxide is 5-8 times the mass of the carbonized sample; the first soaking time is 12-48 hours.

4. The method for preparing porous activated carbon powder according to claim 1, characterized in that, The acid solution is a 6 M hydrochloric acid solution, and the second soaking time is 12-24 hours.

5. The method for preparing porous activated carbon powder according to claim 1, characterized in that, The mass ratio of the carbon aerogel to the grinding beads is 1:30-1:70; the grinding beads are zirconia grinding beads, and the grinding beads include zirconia grinding beads with a diameter of 5 mm and zirconia grinding beads with a diameter of 10 mm.

6. The method for preparing porous activated carbon powder according to claim 1, characterized in that, The wetting conditions used a mixture of ethanol and water as the solvent, a ball milling speed of 400-600 rpm, and a ball milling time of 48-96 hours.

7. A porous activated carbon powder, characterized in that, The porous activated carbon powder is prepared by the method for preparing porous activated carbon powder according to any one of claims 1-6.

8. A carbon slurry, characterized in that, The carbon slurry comprises: 5-15 parts porous activated carbon powder, 10-20 parts conductive carbon black, 5-10 parts epoxy resin binder, and 65-80 parts solvent.

9. A method for preparing carbon slurry, used to prepare the carbon slurry as described in claim 8, characterized in that, include: The epoxy resin adhesive is dissolved in a solvent to form a homogeneous adhesive solution; Porous activated carbon powder and conductive carbon black are added to a homogeneous adhesive solution and mixed evenly to obtain a mixed slurry. The mixed slurry is transferred to a three-roll mill for rolling to obtain carbon slurry.

10. A conductive coating, characterized in that, The conductive coating is formed by screen printing carbon paste onto a flexible substrate, followed by drying and curing; the dry film thickness of the conductive coating is 10-20 μm; the carbon paste includes porous activated carbon powder, conductive carbon black, epoxy resin binder, and solvent; the porous activated carbon powder is prepared by the method for preparing porous activated carbon powder according to any one of claims 1-6.

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