A bamboo-based derived carbon material for joule heating

Abstract

The application belongs to the field of new materials, and discloses a bamboo-based derived carbon material for joule heating, which is prepared by taking natural bamboo as raw material, removing lignin after cutting and polishing, and then adopting a two-step pyrolysis carbonization process for carbonization treatment, and cleaning and drying to obtain the bamboo-based derived carbon material. In the application, the bamboo-based derived carbon formed after pyrolysis carbonization has a more perfect 3D conductive network due to the rich and ordered pore structure of the bamboo, so that the free electrons are oriented under the action of an external electric field, the energy is quickly transmitted in the conductor, efficient electric heating conversion and heat management are realized, and the bamboo-based derived carbon is expected to be applied in the fields of electric heating deicing, human health care and auxiliary treatment.

Description

Technical Field

[0001] This invention belongs to the field of functional biomass materials technology, specifically relating to a bamboo-based derived carbon material for Joule heating. Background Technology

[0002] Joule heating is a technique that uses direct current to generate heat to directly heat the material being heated. Currently, the conductive materials used to prepare Joule heating materials are mainly metals, conductive polymers, and carbon materials. Metal wires have excellent conductivity but uneven heating and are easily broken. The preparation process of nanomaterials is complex, and the high conductivity of metals can limit their heating performance to a certain extent [Solar Energy Materials and Solar Cells, 2019, 201]. Conductive polymers have good conductivity and stability, but they are often used as fillers in blends with other polymers. At higher filler levels, it is difficult to avoid a decrease in the conductivity of composite materials due to poor dispersibility [Journal of Materials Chemistry C, 8(45), 16204-16215]. Carbon materials such as carbon nanotubes, carbon fibers, and MXene have good electrical conductivity, but they have disadvantages such as complex preparation process, high price, uneven heating and small heating area [Advanced Composite Materials, 2020, 283, 102226; ACS Applied Materials & Interfaces, 12(12), 14459-14467.].

[0003] Pyrolysis carbonization can convert wood into conductive wood-based carbon materials for Joule heating, but its electrothermal conversion efficiency is low, with steady-state Joule heating temperatures ranging from 28 ℃ to 83.5 ℃ at voltages of 0.5 V to 2 V [Advanced Electronic Materials, 9(7)]. CN115505375A discloses a method for preparing a graded magnetic porous carbonized wood composite phase change material. Poplar wood is impregnated with Fe(NO3)3·9H2O after lignin removal, and then pyrolyzed at 500 ℃ to obtain magnetic carbonized wood. Based on this, a multifunctional driven composite PCM is prepared using stearic acid as the heat energy guest. The optimal sample SA / MCW-4 has a temperature of around 100 ℃ at 2.5 V. However, its preparation method requires filling with the heat energy guest stearic acid, which is relatively complicated, and the saturation steady-state temperature at 2.5 V is relatively low.

[0004] Bamboo, as an important biomass resource, has attracted increasing attention due to its rapid growth, high yield, and superior mechanical properties compared to wood. Bamboo shares a similar chemical composition with wood, making it suitable for use in the preparation of Joule heating materials after pyrolysis and carbonization. However, the microstructure of bamboo differs significantly from that of wood. Compared to the porous, layered structure of wood, bamboo exhibits a gradient distribution of pores: the vascular bundles are denser and the pore size of the thin-walled cells is smaller on the side closer to the outer layer (the inner bamboo shoots), while the vascular bundles are sparser and the pore size of the thin-walled cells is larger on the side closer to the inner bamboo shoots (the outer layer). In short, bamboo has a lower porosity than wood, resulting in a more compact pore structure. This structural difference leads to significant variations in material properties. How to transform bamboo into a controllable and stable Joule heating material to efficiently convert electrical energy into heat energy for applications such as electric de-icing and human thermotherapy is a crucial issue that should be considered in improving the utilization of bamboo. Summary of the Invention

[0005] The purpose of this invention is to overcome at least one deficiency of the prior art and to provide a bamboo-based derived carbon material for Joule heating.

[0006] The technical solution adopted in this invention is:

[0007] In a first aspect, the present invention provides a bamboo-based derived carbon material for Joule heating, wherein the preparation method of the bamboo-based derived carbon material includes the following steps:

[0008] 1) Cut and polish the bamboo raw material to remove the bamboo green and bamboo yellow, and obtain the bamboo base material;

[0009] 2) Remove lignin from the bamboo substrate;

[0010] 3) Immerse the bamboo substrate after removing lignin in a dilute acid solution for 0.5 h to 8 h to clean the internal pores, and then wash until neutral and dry.

[0011] 4) Carbonize the bamboo substrate treated in step 3), and after cleaning and drying, a bamboo-based derived carbon material for Joule heating can be obtained. The carbonization process includes:

[0012] First pyrolysis carbonization treatment: The bamboo substrate treated in step 3) is heated to 200 ℃ to 400 ℃ in a protective gas atmosphere at a rate of 2 ℃ / min to 10 ℃ / min to obtain the initial carbonized bamboo.

[0013] Acid washing treatment: The initially carbonized bamboo is washed in a dilute acid solution for 0.5 h to 4 h, then adjusted to neutral and dried;

[0014] Second pyrolysis carbonization treatment: The acid-washed carbonized bamboo is heated to 600℃~1500℃ at a rate of 2℃ / min~10℃ / min under a protective gas atmosphere.

[0015] In some instances, the method for removing lignin in step 2) is to remove lignin by immersing the bamboo substrate in a chlorite solution and adjusting the pH.

[0016] In some instances, the pH value is 3.8 to 6.0.

[0017] In some instances, the chlorite is NaClO2 with a mass concentration of 3% to 10%.

[0018] In some instances, the impregnation temperature for lignin removal is 60 ℃ to 90 ℃.

[0019] In some cases, the immersion time for lignin removal is 4 h to 24 h.

[0020] In some instances, the carbonization time for the first pyrolysis carbonization treatment is 0.5 h to 4 h.

[0021] In some instances, the carbonization time for the second pyrolysis carbonization treatment is 0.5 h to 4 h.

[0022] In some instances, the bamboo material is selected from any one of the following: moso bamboo, stone bamboo, longevity bamboo, green-skinned bamboo, Luohan bamboo, spotted bamboo, and Ci bamboo.

[0023] The above technical features can be combined arbitrarily as long as they do not conflict with each other.

[0024] The second aspect is the application of the bamboo-based derived carbon material of the first aspect of the present invention in the preparation of controllable Joule heating materials.

[0025] In some instances, the controllable Joule heating material can be applied to fields such as electrothermal de-icing, human health care, and adjuvant therapy.

[0026] The beneficial effects of this invention are:

[0027] The preparation method of this invention employs a low-cost pyrolysis carbonization process, using renewable and environmentally friendly bamboo as the matrix to prepare bamboo-based derived carbon materials. Benefiting from the rich and orderly pore structure of bamboo, the bamboo-based derived carbon formed after pyrolysis carbonization possesses a more complete 3D conductive network, allowing free electrons to move directionally under the influence of an applied electric field, rapidly transferring energy within the conductor and causing the conductor temperature to rise rapidly.

[0028] The bamboo-based derived carbon material for Joule heating prepared in this invention exhibits excellent electrothermal properties. By regulating the applied driving voltage, the Joule heating generated by the bamboo-based derived carbon material is controlled, achieving efficient electrothermal conversion and thermal management; the Joule heating saturation steady-state temperature can reach 28℃ to 160℃ under applied voltage conditions of 0.5 V to 2 V.

[0029] The bamboo-based derived carbon material prepared by this invention for Joule heating can be applied in fields such as electrothermal de-icing, human health care, and adjunctive therapy. Directly heating an object using the bamboo-based derived carbon material at a low driving voltage can effectively remove ice. By adjusting the appropriate voltage, it can be used for human health care and adjunctive therapy to alleviate pain caused by illness. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of a bamboo-based derived carbon material for Joule heating and its preparation method.

[0031] Figure 2 The conductivity is for Examples 1-5 and Comparative Examples 1-5.

[0032] Figure 3 The Joule heating performance of the bamboo-based derived carbon material for Joule heating prepared in Example 1 under energizing voltages of 0.5 V, 1.0 V, 1.5 V, and 2 V is shown.

[0033] Figure 4 The stability of the bamboo-based derived carbon material for Joule heating prepared in Example 1 under a 2.0 V energizing voltage condition during Joule heating cycling is measured.

[0034] Figure 5 The Joule heating performance of the bamboo-based derived carbon material for Joule heating prepared in Example 2 under energizing voltages of 0.5V, 1.0V, 1.5V, and 2V is shown.

[0035] Figure 6 The stability of the bamboo-based derived carbon material for Joule heating prepared in Example 2 under a 2.0 V energizing voltage condition during Joule heating cycling is measured.

[0036] Figure 7 The Joule heating performance of the bamboo-based derived carbon material for Joule heating prepared in Example 3 under energizing voltages of 0.5 V, 1 V, 1.5 V, and 2 V is shown.

[0037] Figure 8 The stability of the bamboo-based derived carbon material for Joule heating prepared in Example 3 under a 2.0 V energizing voltage condition during Joule heating cycling is measured.

[0038] Figure 9The Joule heating performance of the bamboo-based derived carbon material for Joule heating prepared in Example 4 under energizing voltages of 0.5 V, 1.0 V, 1.5 V, and 2.0 V is shown.

[0039] Figure 10 The stability of the bamboo-based derived carbon material for Joule heating prepared in Example 4 under a 2.0 V energizing voltage condition during Joule heating cycling is measured.

[0040] Figure 11 The Joule heating performance of the bamboo-based derived carbon material for Joule heating prepared in Example 5 under energizing voltages of 0.5 V, 1.0 V, 1.5 V, and 2.0 V is shown.

[0041] Figure 12 The stability of the bamboo-based derived carbon material for Joule heating prepared in Example 5 under a 2.0 V energizing voltage condition during Joule heating cycling is measured.

[0042] Figure 13 The Joule heating performance of the bamboo-based derived carbon material prepared in Comparative Example 1 for Joule heating is shown under energizing voltages of 0.5 V, 1.0 V, 1.5 V, and 2.0 V.

[0043] Figure 14 The stability of the bamboo-based derived carbon material for Joule heating prepared in Comparative Example 1 under a 2.0 V energizing voltage condition is measured by Joule heating cycle.

[0044] Figure 15 The Joule heating performance of the bamboo-based derived carbon material for Joule heating prepared in Comparative Example 3 under energizing voltages of 0.5 V, 1.0 V, 1.5 V, and 2.0 V is shown.

[0045] Figure 16 The stability of the bamboo-based derived carbon material for Joule heating prepared in Comparative Example 3 under a 2.0 V energizing voltage condition is measured by Joule heating cycle.

[0046] Figure 17 The Joule heating performance of the bamboo-based derived carbon material prepared in Comparative Example 4 for Joule heating is shown under energizing voltages of 0.5 V, 1.0 V, 1.5 V, and 2.0 V.

[0047] Figure 18 The stability of the bamboo-based derived carbon material for Joule heating prepared in Comparative Example 4 under a 2.0 V energizing voltage condition is measured by Joule heating cycle.

[0048] Figure 19 The Joule heating performance of the bamboo-based derived carbon material for Joule heating prepared in Comparative Example 5 under energizing voltages of 0.5 V, 1.0 V, 1.5 V, and 2.0 V is shown.

[0049] Figure 20 The stability of the bamboo-based derived carbon material for Joule heating prepared in Comparative Example 5 under a 2.0 V energizing voltage condition is measured by Joule heating cycle.

[0050] Figure 21 The graph shows a comparison of the Joule heating performance of the bamboo-based derived carbon materials for Joule heating prepared in Examples 4 and 5 with other reported materials for Joule heating.

[0051] Figure 22 The image shows the application of the bamboo-based derived carbon material for Joule heating prepared in Example 5 in Joule de-icing under a 2 V energizing voltage.

[0052] Figure 23 The image shows the application of the bamboo-based derived carbon material for Joule heating prepared in Example 5 in human body assisted thermotherapy under a 1V energizing voltage. Detailed Implementation

[0053] The following disclosure provides many different implementations or examples for different ways of implementing the present invention.

[0054] Example 1

[0055] like Figure 1 As shown, a method for preparing bamboo-based derived carbon materials for Joule heating includes the following steps:

[0056] S1. Cut the green bamboo into 30 mm long pieces along the growth direction. Use a sharp knife, a sander, and sandpaper with a grit of 800 or higher to polish the surface of the bamboo to remove the green and yellow parts of the bamboo, so as to reduce the warping and deformation of the bamboo during the pyrolysis and carbonization process.

[0057] S2. The bamboo sheets obtained in step S1 are immersed in an 8% NaClO2 solution, and the pH of the solution is adjusted to 4.6 with CH3COOH. The solution is then placed in an oil bath at 80 ℃ for 8 h. After cooling, the solution is washed with a large amount of deionized water until neutral, and then freeze-dried for 48 h to obtain delignified bamboo sheets.

[0058] S3. The delignified bamboo sheet obtained in step S2 is immersed in a 5 mol / L dilute H2SO4 solution for 1 h to clean the internal pores of the bamboo sheet. Finally, it is washed with a large amount of deionized water until neutral and dried to obtain the pretreated delignified bamboo sheet (hereinafter referred to as bamboo sheet).

[0059] S4. The bamboo strips obtained in step S3 are heated to 400 ℃ at a heating rate of 3 ℃ / min and held for 3 h under a protective gas atmosphere for the first pyrolysis carbonization treatment to obtain initially carbonized bamboo strips. The initially carbonized bamboo strips are immersed and washed in 0.5 mol / L dilute HNO3 for 0.5 h to remove coal tar and other substances produced during the initial carbonization and to clean the internal pores of the carbonized bamboo. After completion, they are washed with a large amount of deionized water until neutral and then dried in an oven at 60 ℃ for 12 h.

[0060] S5. The initial carbonized bamboo chips obtained in step S4 are heated to 850 ℃ at a heating rate of 3 ℃ / min and held for 2 h under a protective gas atmosphere for a second pyrolysis carbonization treatment to obtain carbonized bamboo chips. Then, they are ultrasonically cleaned in a 50% ethanol solution at 100 W for 1 min and dried in an oven at 60 ℃ for 12 h to obtain a bamboo-based derived carbon material for Joule heating.

[0061] Example 2

[0062] In step S1, the bamboo material used was changed from green bamboo to moso bamboo, and the other steps and experimental parameters were the same as in Example 1.

[0063] Example 3

[0064] The bamboo used in step S1 was changed from green bamboo to moso bamboo, and the heating endpoint of the second pyrolysis carbonization treatment in step S5 was changed from 850℃ to 1050℃. Other steps and experimental parameters were the same as in Example 1.

[0065] Example 4

[0066] In step S5, the heating endpoint of the second pyrolysis carbonization treatment was changed from 850℃ to 1050℃, and the other steps and experimental parameters were the same as in Example 1.

[0067] Example 5

[0068] The bamboo used in step S1 was changed from green bamboo to stone bamboo, and the heating endpoint of the second pyrolysis carbonization treatment in step S5 was changed from 850℃ to 1050℃. Other steps and experimental parameters were the same as in Example 1.

[0069] Comparative Example 1

[0070] Comparative Example 1 was prepared according to Example 1, except that a one-step carbonization process was used. That is, step S4 was skipped, and step S5 was performed directly.

[0071] Comparative Example 2

[0072] Comparative Example 2 was prepared according to Example 1, except that the bamboo used in step S1 was changed from green bamboo to moso bamboo, and step S2 was not performed.

[0073] Comparative Example 3

[0074] Comparative Example 3 was prepared according to Example 1, except that the bamboo used in step S1 was changed from green bamboo to moso bamboo, and step S2 was not performed. The heating endpoint of the second pyrolysis carbonization treatment in step S5 was changed from 850°C to 1050°C.

[0075] Comparative Example 4

[0076] Comparative Example 4 was prepared according to Example 1, except that the heating endpoint of the second pyrolysis carbonization treatment in step S5 was changed from 850°C to 1250°C.

[0077] Comparative Example 5

[0078] Comparative Example 5 was prepared according to Example 2, except that step S3 was not performed and the internal pores of the carbonized bamboo were not cleaned after the initial carbonized bamboo was obtained in step S4.

[0079] Characterization and performance testing

[0080] The electrical properties of all embodiments and comparative examples were tested using a four-probe resistance meter, and the conductivity was obtained by σ=1 / ρ (σ is conductivity, ρ is resistivity). Based on the Joule heating principle, bamboo-based derived carbon was cut into 23 mm × 10 mm × 3 mm samples. A DC power supply was connected to both ends of the sample, and the change in sample surface temperature was monitored in real time using an infrared thermal imager. The heat generated by the sample was controlled by adjusting the voltage output of the power supply.

[0081] The electrical conductivity of the bamboo-based derived carbon materials used for Joule heating in Examples 1-5 and Comparative Examples 1-5 is shown in the figure. Figure 2 The electrothermal conversion efficiency and Joule heating performance of Joule heating are shown in Table 1 and Appendix. Figures 3-20 As shown.

[0082] The electrothermal conversion efficiency of Example 1 was 77.95% higher than that of Comparative Example 1, indicating that a bamboo-based derived carbon material with better Joule heating performance can be obtained through a two-step preparation process at the same carbonization temperature. This is because the two-step carbonization process is more conducive to the formation of a complete graphitized structure, improving the conductivity of the material and obtaining excellent Joule heating performance.

[0083] In Example 2, after lignin removal treatment, the steady-state saturation temperature of the Joule-heated surface at 2 V was 49.25 °C. Comparative Example 2 (without lignin removal) showed no detectable Joule heating performance within the voltage range of 0.5 V–2.0 V. This is because lignin removal reduces the accumulation of defective graphitic carbon, improving conductivity. Figure 2This improves the Joule heating performance of the material. However, the method used on bamboo in Comparative Example 2, which is similar to that reported in the literature (Advanced Electronic Materials, 9(7)), fails to improve the Joule heating performance of bamboo.

[0084] Compared with Comparative Example 3, Example 3 (lignin-removed) showed a higher steady-state saturation temperature at the Joule heating surface within a voltage test range of 0.5 V-2.0 V than Comparative Example 3 (lignin-free), and the electrothermal conversion efficiency of Example 3 was 52.96% higher than that of Comparative Example 3. Examples 2 and 3 fully demonstrate that the bamboo-based derived carbon material prepared by this method has excellent electrothermal conversion efficiency and Joule heating performance.

[0085] According to literature reports (Nanomaterials 2020, 10(12), 2431) and Joule's law Q=i 2 ×R×t The Joule heating performance depends on the conductivity of the material; the higher the conductivity, the better the Joule heating performance. However, Example 4 (prepared at 1050°C) exhibits higher electrothermal conversion efficiency and Joule heating performance than Comparative Example 4 (prepared at 1250°C), even though Comparative Example 4 has significantly better conductivity than Example 4. This phenomenon may be because excessively high conductivity generates more short-circuit paths during electron migration, reducing the surface temperature for Joule heating. Therefore, this preparation method can balance the conductivity and electrothermal conversion efficiency of carbon-based materials while obtaining optimal Joule heating performance.

[0086] Example 5 and Comparative Example 5 demonstrate the effects of pore structure cleaning during the preparation process on electrothermal conversion efficiency and Joule heating performance. The data in the table show that the Joule heating performance of Example 5 is better than that of Comparative Example 5, indicating that pore structure cleaning before and during preparation is beneficial for forming a more complete conductive network and improving the Joule heating performance of the material.

[0087] Table 1. Test results of Joule heating steady-state saturation temperature and electrothermal conversion efficiency in Examples 1-5 and Comparative Examples 1-5

[0088]

[0089] The controllability and stability of Joule heating are important parameters for the application of Joule heating materials. Figure 4 , Figure 6 , Figure 8 , Figure 10 , Figure 12The graphs show the Joule heating cycle stability of the bamboo-based derived carbon materials prepared in Examples 1-5 for Joule heating under a voltage of 2.0 V, indicating that the bamboo-based derived carbon materials prepared by this method have excellent controllability and stability in Joule heating.

[0090] Meanwhile, we compared the performance of a bamboo-based derived carbon material for Joule heating prepared in Examples 4 and 5 of this invention with that of Joule heating materials reported in the literature, such as... Figure 21 As shown in the figure (the source of the materials in the figure is given in references 1-13 below). It can be seen from the figure that the bamboo-based derived carbon material for Joule heating prepared by the present invention can achieve high Joule heating performance at a relatively low implementation voltage.

[0091] Based on the excellent Joule heating performance of the above embodiments, a bamboo-based derived carbon material for Joule heating prepared in Example 5 is selected for application in electrothermal de-icing, human health care, and auxiliary heat therapy. For example... Figure 22 As shown, after applying a voltage of 2 V for 5 minutes, the ice on the original electric heater (V≈13 cm) 3 The average temperature of the ice block increased from 0.36 ℃ to 4.87 ℃, and the bottom ice partially melted. As the applied voltage time increased, the average temperature of the ice block continuously rose. After 20 minutes of voltage application, the volume of the ice block decreased by approximately one-third of its original volume; extending the voltage application time to 35 minutes resulted in almost complete melting of the ice. Experiments show that this embodiment can be applied to electric heating de-icing devices in extremely cold regions. Furthermore, the applied voltages are all below the absolute safety level for the human body (36V). This embodiment, using a bamboo-derived carbon material for Joule heating, can be applied to human health care and adjuvant thermotherapy, such as... Figure 23 As shown, the bamboo-based derived carbon material prepared in Example 5 was fixed at a human joint and a driving voltage of 1V was applied. The surface temperature of the gauze rose from 27.2℃ to 43.0℃ within 30 seconds, and finally stabilized at 52.7℃. This indicates that the bamboo-based derived carbon can be used for adjuvant thermotherapy to relieve pain caused by lesions.

[0092] The above is a further detailed description of the present invention and should not be considered as a limitation on the specific implementation of the present invention. For those skilled in the art, simple deductions or substitutions without departing from the concept of the present invention are all within the protection scope of the present invention.

[0093] References:

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Claims

1. A bamboo-based derived carbon material for Joule heating, characterized in that, The preparation method of the bamboo-based derived carbon material includes the following steps: 1) Cut and polish the bamboo raw material to remove the bamboo green and bamboo yellow, and obtain the bamboo base material; 2) Remove lignin from the bamboo substrate; 3) Immerse the bamboo substrate after removing lignin in a dilute acid solution for 0.5 h to 8 h to clean the internal pores, and then wash until neutral and dry. 4) Carbonize the bamboo substrate treated in step 3), and after cleaning and drying, a bamboo-based derived carbon material for Joule heating can be obtained. The carbonization process includes: First pyrolysis carbonization treatment: The bamboo substrate treated in step 3) is heated to 200 ℃ to 400 ℃ in a protective gas atmosphere at a rate of 2 ℃ / min to 10 ℃ / min to obtain the initial carbonized bamboo. Acid washing treatment: The initially carbonized bamboo is washed in a dilute acid solution for 0.5 h to 4 h, then adjusted to neutral and dried; Second pyrolysis carbonization treatment: The acid-washed carbonized bamboo is heated to 600 ℃ to 1500 ℃ in a protective gas atmosphere at a rate of 2 ℃ / min to 10 ℃ / min.

2. The bamboo-based derived carbon material according to claim 1, characterized in that, The method for removing lignin in step 2) is as follows: the bamboo substrate is immersed in a chlorite solution and the pH is adjusted to remove lignin.

3. The bamboo-based derived carbon material according to claim 2, characterized in that, The pH value is 3.8 to 6.

0.

4. The bamboo-based derived carbon material according to claim 2, characterized in that, The chlorite is NaClO2, with a mass concentration of 3% to 10%.

5. The bamboo-based derived carbon material according to claim 2, characterized in that, The impregnation temperature for removing lignin is 60℃~90℃.

6. The bamboo-based derived carbon material according to any one of claims 2 to 5, characterized in that, The immersion time for removing lignin is 4 h to 24 h.

7. The bamboo-based derived carbon material according to claim 1, characterized in that, The carbonization time for the first pyrolysis carbonization treatment is 0.5 h to 4 h.

8. The bamboo-based derived carbon material according to claim 1, characterized in that, The carbonization time for the second pyrolysis carbonization treatment is 0.5 h to 4 h.

9. The bamboo-based derived carbon material according to claim 1, characterized in that, The bamboo raw material is selected from any one of the following: moso bamboo, stone bamboo, longevity bamboo, green-skinned bamboo, Luohan bamboo, spotted bamboo, and Ci bamboo.

10. The application of the bamboo-based derived carbon material according to any one of claims 1 to 9 in the preparation of controllable Joule heating materials.

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