Biomass-derived heat-conducting and wave-absorbing filler, preparation method and application

Abstract

The invention belongs to the technical field of microwave absorption-heat conduction multifunctional materials, and discloses a biomass derived heat conduction and wave absorption filler, a preparation method and application. The biomass-derived heat-conducting and wave-absorbing filler prepared by adopting an impregnation-low-temperature annealing process is novel in structure and formation mechanism, and the phase structure and composition of a compound can be adjusted by controlling the calcination temperature by changing the types and concentrations of a carbon source and acetate. The method disclosed by the invention is simple to operate, the product morphology is novel, the defects of harsh reaction conditions, difficult regulation and control of the reaction product morphology, poor experiment repeatability and the like in the previous preparation process are overcome, the method has low cost and excellent heat absorption and conduction performance, and meanwhile, the method is expanded to different leaves and has good industrial application potential.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave absorption-heat conduction multifunctional materials, and relates to a preparation method of a biomass-derived heat-conducting and absorbing filler and its application in the fields of microwave absorption, thermal management and energy. Background Art

[0002] Thermal conductive and wave absorbing integrated materials can not only conduct heat but also effectively absorb and attenuate the incident electromagnetic wave energy. They are an effective way to solve the current electromagnetic pollution, interference and heating problems of electronic equipment and protect their normal operation. Thermal conductive and wave absorbing multifunctional materials include three types: ceramic-based, water-based and polymer-based. Among them, the polymer-based thermal conductive and wave absorbing multifunctional materials obtained by dispersing thermal conductive and wave absorbing multifunctional fillers into polymer substrates have attracted much attention due to their good elasticity, strength, electrical insulation, stability, thermal conductivity and wave absorbing properties. However, they have a high filling ratio and the thermal conductive and wave absorbing properties are mutually restrained and difficult to achieve synergistic enhancement. Recent studies have found that multifunctional fillers with interconnected network structures can achieve the performance of "low filling ratio-lightweight-strong absorption-wideband-high thermal conductivity". The interconnected network structure has a low density, and its porous structure can produce multiple scattering and interface polarization. Filling the pores with low dielectric constant air or substrate materials can improve its impedance matching characteristics. At the same time, the interconnected network structure builds an effective conduction path for heat transfer. Therefore, designing and regulating the interconnected network structure is an effective way to improve its wave absorbing performance.

[0003] Biomass-derived carbon mainly comes from plants and animals. They can be prepared by pyrolysis carbonization, hydrothermal carbonization, laser-induced carbonization and microwave-assisted carbonization. Biomass-derived carbon materials have unique natural microstructures, high purity, diverse functions and adjustable structures. The carbonization source and carbonization method directly affect the physical and chemical properties of biomass carbon materials. Carbonized leaves have interconnected carbon fiber networks and strong adsorption capacity. The pyrolysis carbonization process is simple and can maintain the morphology of the organism itself. However, there are few reports on systematic exploration of the controllable synthesis, thermal conductivity and microwave absorption properties of biomass-derived thermally conductive and microwave-absorbing fillers.

[0004] In addition, in order to meet the actual thermal management application requirements, the filling ratio of functional fillers needs to be further reduced while maintaining high thermal conductivity. According to the impedance matching principle, carbon materials (graphene, carbon nanotubes / nanofibers, etc.) and metal materials (Al, Ni, Cu, Ag) are reflective shielding materials. Their high electrical conductivity is conducive to the reflection of electromagnetic waves, but not conducive to impedance matching. The reflected electromagnetic waves form secondary pollution; and the high electrical conductivity makes its voltage resistance poor, which limits its application in electronic devices. Therefore, reducing the filling ratio and electrical conductivity, further improving thermal conductivity, and improving impedance matching and absorption capacity are of great significance for wave-absorbing and heat-conducting multifunctional materials to meet the actual application requirements.

[0005] Therefore, how to develop a biomass-derived thermally conductive and wave-absorbing filler that is simple in process, easy to industrialize, has controllable morphology and size, and has excellent performance is an urgent problem to be solved by technical personnel in this field. Summary of the invention

[0006] In view of this, in order to solve this problem, the present invention discloses a biomass-derived thermally conductive and absorbing filler and a preparation method thereof. The biomass-derived thermally conductive and absorbing filler is easy to operate and has a novel product morphology. It overcomes the defects of harsh reaction conditions, difficult to control the morphology of reaction products, poor experimental repeatability, and high cost in the previous preparation process, and has good potential for industrial application.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] The first technical purpose of the present invention is to provide a green and environmentally friendly biomass-derived thermally conductive and wave-absorbing filler suitable for industrial production. The impregnation-low-temperature annealing process is adopted, that is, the pretreated leaves are heated to 900°C at a rate of 2.5°C / min, and then naturally cooled to room temperature after being kept warm for 3 hours to obtain the biomass-derived thermally conductive and wave-absorbing filler.

[0009] Furthermore, the biomass-derived thermally conductive and wave-absorbing filler is a 2D interconnected network structure, which is composed of amorphous carbon fibers, honeycomb amorphous carbon, strip-arranged amorphous carbon, or a composite of amorphous carbon fibers / magnetic nanoparticles; and the average diameter of the carbon fibers is 0.71 to 2.79 μm, and the average length is 490 to 585 μm; the magnetic nanoparticles are Fe, Co, and Ni, and their content is 3.04 to 20.29%.

[0010] The biomass-derived thermal conductive and microwave absorbing filler prepared by the impregnation-low-temperature annealing process disclosed in the present invention not only has a novel structure and formation mechanism, but can also be used to prepare a series of carbon-magnetic composites by changing the calcination temperature and the type of leaves. The carbon-magnetic composites have a 2D interconnected network structure and excellent thermal conductivity and microwave absorption properties, and show great potential in the fields of electromagnetic protection and thermal management.

[0011] In addition, the biomass-derived thermally conductive wave-absorbing filler prepared by the present invention has excellent thermal conductivity and wave-absorbing properties, and the electrical conductivity is 1.67×10 -4 ~2.18×10 -4 S / cm; when the filling ratio is 30%, the thermal conductivity is 1.819~3.171W / (m·K); the maximum effective bandwidth of the reflectivity less than or equal to -10dB is 3.20~8.80GHz, the maximum absorption is -18.94~-55.10dB, and the sample thickness is 1.9~5.0mm.

[0012] The second technical purpose of the present invention is to provide a method for preparing the biomass-derived thermally conductive and wave-absorbing filler as described above.

[0013] In order to achieve the above object, the present invention adopts the following technical solution:

[0014] A method for preparing a biomass-derived thermally conductive wave-absorbing filler, the method specifically comprising the following steps:

[0015] (1) After washing the surface of the biomass material with distilled water, immerse it in anhydrous ethanol for 10 minutes to remove the wax layer on the surface; then place the washed biomass material in an oven at 60-80° C. for 6-10 hours;

[0016] (2) nickel acetate, cobalt acetate, iron acetate and water are mixed in a certain stoichiometric ratio to prepare a transition metal acetate solution with a concentration of 0 to 1.0 mol / L, and the pretreated biomass material is immersed in the solution for 10 to 60 minutes;

[0017] (3) After the impregnation in step (2) is completed, the sample is dried at 60-80° C. for 6-10 hours, and the biomass-derived thermally conductive and wave-absorbing fillers with different phase structures are obtained by adjusting the calcination temperature (annealing temperature is 600-900° C., and annealing time is 2-5 hours).

[0018] By adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0019] The preparation method disclosed in the present invention is simple to operate and has a novel product morphology, which overcomes the defects of harsh reaction conditions, difficult to control the morphology of reaction products, poor experimental repeatability, etc. in the previous preparation process. At the same time, it can be applied to a variety of biomass materials and has good potential for industrial application.

[0020] Furthermore, the reaction temperature is 600-800° C., and the calcination time is 3.0 h.

[0021] Furthermore, the transition metal acetate includes one or a combination of iron acetate, cobalt acetate and nickel acetate, and the thermal conductivity and wave absorption performance of the material is improved by composite magnetic metal particles Fe, Co and Ni.

[0022] The third technical purpose of the present invention is to provide the application of the above-mentioned biomass-derived thermally conductive and microwave-absorbing filler in the fields of electromagnetic protection, microwave absorption, thermal management, and energy.

[0023] It can be seen from the above technical solutions that, compared with the prior art, the present invention provides a biomass-derived thermally conductive wave-absorbing filler, a preparation method and an application thereof, which have the following excellent effects:

[0024] 1) The present invention adopts an impregnation-low-temperature annealing process, impregnates the pretreated leaves in an acetate solution, calcines them in a tubular furnace after drying, and prepares a biomass-derived thermally conductive and absorbing filler with a unique morphology. The composition and phase structure of the biomass-derived thermally conductive and absorbing filler can be controlled by changing the calcination temperature, the type and concentration of acetate, and the type of biomass material.

[0025] 2) The biomass-derived thermally conductive absorbing filler prepared by the present invention shows great potential in the field of electromagnetic protection and thermal management. By compounding amorphous carbon fibers with magnetic nanoparticles, heterogeneous interfaces and magnetic losses are introduced, which can improve the absorbing performance; and the formed interconnected network structure provides a continuous heat conduction path, which can enhance the thermal conductivity.

[0026] 3) The preparation method of the biomass-derived thermal conductive and wave-absorbing filler of the present invention is simple and unique, the raw materials are cheap and easily available, and the reaction process is simple, time-saving, energy-saving, low-risk, green and environmentally friendly, with good repeatability, low requirements for instrument precision, considerable output, low cost, and good potential for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, 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 embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0028] Figure 1 to Figure 3 The phase, composition and morphology of the product obtained in Example 1 of the present invention measured under XRD, EDX and scanning electron microscope.

[0029] Figures 4 to 6 The phase, composition and morphology of the product obtained in Example 2 of the present invention measured under XRD, EDX and scanning electron microscope.

[0030] Figure 7 to Figure 9 The phase, composition and morphology of the product obtained in Example 3 of the present invention measured under XRD, EDX and scanning electron microscope.

[0031] Figure 10 to Figure 12 The phase, composition and morphology of the product obtained in Example 4 of the present invention measured under XRD, EDX and scanning electron microscope.

[0032] Figure 13 to Figure 15 The phase, composition and morphology of the product obtained in Example 5 of the present invention measured under XRD, EDX and scanning electron microscope.

[0033] Figure 16 to Figure 18The phase, composition and morphology of the product obtained in Example 6 of the present invention measured under XRD, EDX and scanning electron microscope.

[0034] Figure 19 to Figure 21 The phase, composition and morphology of the product obtained in Example 7 of the present invention measured under XRD, EDX and scanning electron microscope.

[0035] Figure 22 to Figure 24 The phase, composition and morphology of the product obtained in Example 8 of the present invention measured under XRD, EDX and scanning electron microscope.

[0036] Figure 25 to Figure 27 The phase, composition and morphology of the product obtained in Example 9 of the present invention measured under XRD, EDX and scanning electron microscope.

[0037] Figure 28 to Figure 30 The phase, composition and morphology of the product obtained in Example 10 of the present invention measured under XRD, EDX and scanning electron microscope.

[0038] Figure 31 to Figure 33 The phase, composition and morphology of the product obtained in Example 11 of the present invention measured under XRD, EDX and scanning electron microscope.

[0039] Figure 34 to Figure 36 The phase, composition and morphology of the product obtained in Example 12 of the present invention measured under XRD, EDX and scanning electron microscope.

[0040] Figure 37 to Figure 39 The phase, composition and morphology of the product obtained in Example 13 of the present invention measured under XRD, EDX and scanning electron microscope.

[0041] Figure 40 to Figure 42 The phase, composition and morphology of the product obtained in Example 14 of the present invention measured under XRD, EDX and scanning electron microscope.

[0042] Figure 43 to Figure 45 The phase, composition and morphology of the product obtained in Example 15 of the present invention measured under XRD, EDX and scanning electron microscope. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The word "embodiment" used here as an "exemplary" does not necessarily mean that any embodiment described is superior to or better than other embodiments. Unless otherwise specified, the performance index tests in the embodiments of this application are performed using conventional test methods in the art. It should be understood that the terms described in this application are only used to describe specific implementation methods and are not used to limit the content disclosed in this application.

[0045] Unless otherwise specified, the technical and scientific terms used in this document have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0046] In order to better illustrate the content of the present application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present application.

[0047] Under the premise of no conflict, the technical features disclosed in the embodiments of the present application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of the present application.

[0048] The embodiment of the invention discloses a biomass-derived heat-conducting and microwave-absorbing filler with simple process and good microwave absorption characteristics, a preparation method and an application thereof.

[0049] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0050] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0051] Example 1

[0052] A method for preparing a biomass-derived thermally conductive wave-absorbing filler comprises the following steps:

[0053] After cleaning the surface of fresh ramie leaves with distilled water, immerse them in anhydrous ethanol and immerse them at room temperature for 10 minutes; then place the immersed ramie leaves in an oven and dry them at 60°C; then place the dried ramie leaves in a tubular furnace, calcine at 800°C, calcinate for 3 hours, and heat up at a rate of 2.5°C / min. After calcination, biomass-derived thermal conductive wave-absorbing fillers are obtained.

[0054] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 1 to 3 As shown. From the EDX image, it can be concluded that it mainly contains elements such as C, O, Ca, K and Si. The XRD spectrum shows that it is potassium silicate, calcium silicate, calcium carbonate and silicon dioxide. The product is composed of carbon nanofibers with a diameter of 1.78 to 2.34 μm.

[0055] As shown in Table 1, the obtained biomass-derived thermal conductive absorbing filler has excellent microwave absorption properties. When the thickness is 2.2 mm, the maximum effective bandwidth of the reflectivity less than or equal to -10 dB is 6.56 GHz; when the thickness is 2.6 mm, the maximum absorption is -54.39 dB; the thermal conductivity is 2.963 W / (m·K), and the electrical conductivity is 1.94×10 -4 S / cm.

[0056] Example 2

[0057] A method for preparing a biomass-derived thermally conductive wave-absorbing filler, wherein other conditions remain unchanged, and the calcination temperature is changed to 600° C. on the basis of Example 1.

[0058] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 4 to 6 As shown. From the EDX image, it can be concluded that it mainly contains elements such as C, O, Ca, K and Si. The XRD spectrum shows that it is potassium silicate, calcium silicate, calcium carbonate and silicon dioxide. The product is composed of carbon nanofibers with a diameter of 1.13 to 2.21 μm.

[0059] As shown in Table 1, the obtained biomass-derived thermal conductive absorbing filler has excellent microwave absorption properties. When the thickness is 5.0 mm, the maximum effective bandwidth of the reflectivity less than or equal to -10 dB is 8.80 GHz, the maximum absorption is -55.10 dB; the thermal conductivity is 1.819 W / (m·K), and the electrical conductivity is 1.66×10 -4 S / cm.

[0060] Example 3

[0061] A method for preparing a biomass-derived thermally conductive wave-absorbing filler, wherein other conditions remain unchanged, and the calcination temperature is changed to 900° C. on the basis of Example 1.

[0062] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 7 to 9 As shown. From the EDX image, it can be concluded that it mainly contains C, O, Ca, Si, Al and other elements. The XRD spectrum shows that it is calcium silicate, calcium carbonate, aluminum silicate and silicon dioxide. The product is composed of carbon nanofibers with a diameter of 1.43 to 2.17 μm.

[0063] As shown in Table 1, the obtained biomass-derived thermal conductive absorbing filler has excellent microwave absorption properties. When the thickness is 2.0 mm, the maximum effective bandwidth of the reflectivity less than or equal to -10 dB is 5.44 GHz; when the thickness is 1.9 mm, the maximum absorption is -39.76 dB; the thermal conductivity is 3.040 W / (m·K), and the electrical conductivity is 2.18×10 -4 S / cm.

[0064] Example 4

[0065] A method for preparing a biomass-derived thermally conductive and wave-absorbing filler is provided, with other conditions remaining unchanged, except that ramie leaves are replaced with maple leaves on the basis of Example 1.

[0066] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 10-12 As shown. From the EDX image, it can be concluded that it mainly contains C, O, Ca, K, Si, Mg and other elements. The XRD spectrum shows that it is potassium silicate, magnesium carbonate, calcium carbonate and silicon dioxide, and the product is honeycomb amorphous carbon.

[0067] As shown in Table 1, the obtained biomass-derived thermally conductive and microwave-absorbing filler has excellent microwave absorption properties, with a thickness of 2.0 mm, a maximum effective bandwidth of 5.28 GHz with a reflectivity of less than or equal to -10 dB, a thickness of 2.9 mm, and a maximum absorption of -42.26 dB; thermal conductivity of 3.171 W / (m·K), and electrical conductivity of 1.89×10 -4 S / cm.

[0068] Example 5

[0069] A method for preparing a biomass-derived thermally conductive and wave-absorbing filler, wherein other conditions remain unchanged, and ramie leaves are replaced with leaves of Parthenocissus quinquefolius on the basis of Example 1.

[0070] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 13-15 As shown. From the EDX image, it can be concluded that it mainly contains elements such as C, O, Ca, S and Si. The XRD spectrum shows that it is calcium silicate, calcium carbonate, calcium sulfate, and the product is honeycomb amorphous carbon.

[0071] As shown in Table 1, the obtained biomass-derived thermally conductive and microwave-absorbing filler has excellent microwave absorption properties, with a thickness of 1.9 mm, a maximum effective bandwidth of 4.00 GHz with a reflectivity of less than or equal to -10 dB, a thickness of 5.0 mm, and a maximum absorption of -16.12 dB; a thermal conductivity of 3.010 W / (m·K), and an electrical conductivity of 1.95×10 -4 S / cm.

[0072] Example 6

[0073] A method for preparing a biomass-derived thermally conductive and wave-absorbing filler is provided, with other conditions remaining unchanged, except that ramie leaves are replaced with lotus leaves on the basis of Example 1.

[0074] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 16 to 18 As shown. From the EDX image, it can be concluded that it mainly contains C, O, Ca, Mg and other elements. The XRD spectrum shows that it is calcium carbonate and magnesium carbonate, and the product is honeycomb amorphous carbon.

[0075] As shown in Table 1, the obtained biomass-derived thermally conductive and microwave-absorbing filler has excellent microwave absorption properties, with a thickness of 2.4 mm, a maximum effective bandwidth of 3.20 GHz with a reflectivity of less than or equal to -10 dB, a thickness of 2.2 mm, and a maximum absorption of -41.08 dB; thermal conductivity of 2.360 W / (m·K), and electrical conductivity of 1.97×10 -4 S / cm.

[0076] Example 7

[0077] A method for preparing a biomass-derived thermally conductive and wave-absorbing filler, wherein other conditions remain unchanged, and ramie leaves are replaced with paper mulberry leaves on the basis of Example 1.

[0078] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 19 to 21 As shown. From the EDX image, it can be concluded that it mainly contains C, O, Ca, Si, K, Mg and other elements. The XRD spectrum shows that it is potassium silicate, calcium silicate, calcium carbonate, and magnesium carbonate. The product is composed of carbon nanofibers with a length of 100 to 350 μm and a diameter of 8 to 17 μm.

[0079] As shown in Table 1, the obtained biomass-derived thermal conductive absorbing filler has excellent microwave absorption properties. When the thickness is 2.3 mm, the maximum effective bandwidth of the reflectivity less than or equal to -10 dB is 6.88 GHz; when the thickness is 3.1 mm, the maximum absorption is -43.21 dB; the thermal conductivity is 2.828 W / (m·K), and the electrical conductivity is 1.96×10 -4 S / cm.

[0080] Example 8

[0081] A method for preparing a biomass-derived thermally conductive wave-absorbing filler, wherein other conditions remain unchanged, and ramie leaves are replaced with yam leaves on the basis of Example 1.

[0082] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 22-24As shown. From the EDX image, it can be concluded that it mainly contains C, O, Ca, K, S and other elements. The XRD spectrum shows that it is magnesium carbonate, calcium carbonate, potassium dithionate, and the product is honeycomb amorphous carbon.

[0083] As shown in Table 1, the obtained biomass-derived thermal conductive absorbing filler has excellent microwave absorption properties, with a thickness of 2.8 mm, a maximum effective bandwidth of 4.48 GHz with a reflectivity of less than or equal to -10 dB, a thickness of 3.2 mm, a maximum absorption of -19.49 dB, a thermal conductivity of 2.362 W / (m·K), and an electrical conductivity of 1.94×10 -4 S / cm.

[0084] Example 9

[0085] A method for preparing a biomass-derived thermally conductive and wave-absorbing filler, wherein other conditions remain unchanged, and ramie leaves are replaced with Ligustrum lucidum leaves on the basis of Example 1.

[0086] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 25-27 As shown. From the EDX image, it can be concluded that it mainly contains elements such as C, O, Ca, K, Cl, etc., and the XRD spectrum shows that it is potassium chloride, calcium carbonate, potassium carbonate, and the product is honeycomb amorphous carbon.

[0087] As shown in Table 1, the obtained biomass-derived thermal conductive absorbing filler has excellent microwave absorption properties, with a thickness of 2.2 mm, a maximum effective bandwidth of 5.44 GHz with a reflectivity of less than or equal to -10 dB, a thickness of 2.1 mm, a maximum absorption of -27.44 dB, a thermal conductivity of 2.813 W / (m·K), and an electrical conductivity of 1.95×10 -4 S / cm.

[0088] Example 10

[0089] A method for preparing a biomass-derived thermally conductive wave-absorbing filler, wherein other conditions remain unchanged, and ramie leaves are replaced with phoenix tail bamboo leaves on the basis of Example 1.

[0090] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 28-30 As shown. From the EDX image, it can be concluded that it mainly contains elements such as C, O, Si, Ca, Mg, etc., and the XRD spectrum shows that it is calcium silicate, calcium carbonate, magnesium carbonate and silicon dioxide, and the product is amorphous carbon arranged in strips.

[0091] As shown in Table 1, the obtained biomass-derived thermal conductive absorbing filler has excellent microwave absorption properties, with a thickness of 2.1 mm, a maximum effective bandwidth of 3.20 GHz with a reflectivity of less than or equal to -10 dB, a thickness of 2.4 mm, a maximum absorption of -18.94 dB, a thermal conductivity of 2.478 W / (m·K), and an electrical conductivity of 2.00×10 -4 S / cm.

[0092] Implementation Case 11

[0093] A method for preparing a biomass-derived thermally conductive wave-absorbing filler comprises the following steps:

[0094] After cleaning the surface of fresh ramie leaves with distilled water, immerse them in anhydrous ethanol and immerse them at room temperature for 10 minutes; then place the immersed ramie leaves in an oven and dry them at 60°C, immerse them in 0.25 mol / L cobalt acetate solution and immerse them at room temperature for 10 minutes; then place the immersed ramie leaves in an oven and completely dry them at 60°C; then place the dried ramie leaves in a tubular furnace, calcinate them at 800°C, calcinate them for 3 hours, and heat up at a rate of 2.5°C / min, and obtain the biomass-derived thermally conductive wave-absorbing filler after calcination.

[0095] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 31-33 As shown. From the EDX image, it can be concluded that it mainly contains elements such as Co, C, O, Si, Ca, etc., and the XRD spectrum shows that it is cobalt, potassium silicate, calcium silicate, calcium carbonate and silicon dioxide. The product is a composite of amorphous carbon fiber / magnetic nanoparticles with a diameter of 0.97 to 2.44 μm.

[0096] As shown in Table 1, the obtained biomass-derived thermally conductive and microwave-absorbing filler has excellent microwave absorption properties, with a thickness of 2.5 mm, a maximum effective bandwidth of 7.52 GHz with a reflectivity of less than or equal to -10 dB, a thickness of 2.2 mm, a maximum absorption of -37.5 dB, a thermal conductivity of 3.26 W / (m·K), and an electrical conductivity of 2.95×10 -4 S / cm.

[0097] Implementation Case 12

[0098] A method for preparing a derived thermally conductive wave-absorbing filler, wherein other conditions remain unchanged, and 0.25 mol / L cobalt acetate is replaced with 0.5 mol / L cobalt acetate based on Example 11.

[0099] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 34-36As shown. From the EDX image, it can be concluded that it mainly contains elements such as Co, C, O, Si, Ca, etc., and the XRD spectrum shows that it is cobalt, potassium silicate, calcium silicate, calcium carbonate and silicon dioxide. The product is a composite of amorphous carbon fiber / magnetic nanoparticles with a diameter of 1.34 to 2.27 μm.

[0100] As shown in Table 1, the obtained biomass-derived thermal conductive absorbing filler has excellent microwave absorption properties, with a thickness of 2.9 mm, a maximum effective bandwidth of 6.88 GHz with a reflectivity of less than or equal to -10 dB, a thickness of 1.4 mm, a maximum absorption of -35.2 dB, a thermal conductivity of 3.61 W / (m·K), and an electrical conductivity of 2.80×10 -3 S / cm.

[0101] Implementation Case 13

[0102] A method for preparing a derived thermally conductive wave-absorbing filler, wherein other conditions remain unchanged, and 0.25 mol / L cobalt acetate is replaced with 1.0 mol / L cobalt acetate based on Example 11.

[0103] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 37-39 As shown. From the EDX image, it can be concluded that it mainly contains elements such as Co, C, O, Si, Ca, K, etc., and the XRD spectrum shows that it is cobalt, potassium silicate, calcium silicate, calcium carbonate and silicon dioxide. The product is a composite of amorphous carbon fiber / magnetic nanoparticles with a diameter of 0.71 to 2.73 μm.

[0104] As shown in Table 1, the obtained biomass-derived thermal conductive absorbing filler has excellent microwave absorption properties. The thickness is 2.7 mm, the maximum effective bandwidth is 6.72 GHz with a reflectivity of less than or equal to -10 dB; the thickness is 5.0 mm, the maximum absorption is -21.5 dB; the thermal conductivity is 4.06 W / (m·K), and the electrical conductivity is 6.63×10 -3 S / cm.

[0105] Implementation Case 14

[0106] A method for preparing a derived thermally conductive wave-absorbing filler, wherein other conditions remain unchanged, and 0.25 mol / L cobalt acetate is replaced with 0.5 mol / L ferric acetate on the basis of Example 11.

[0107] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 40-42As shown. From the EDX image, it can be concluded that it mainly contains Fe, C, O, Si, Ca, Mg and other elements. The XRD spectrum shows that it is iron, ferroferric oxide, potassium silicate, calcium silicate, calcium carbonate and silicon dioxide. The product is a composite of amorphous carbon fiber / magnetic nanoparticles with a diameter of 0.98 to 2.53 μm.

[0108] As shown in Table 1, the obtained biomass-derived thermal conductive absorbing filler has excellent microwave absorption properties, with a thickness of 2.2 mm, a maximum effective bandwidth of 7.04 GHz with a reflectivity of less than or equal to -10 dB, a thickness of 3.7 mm, a maximum absorption of -37.1 dB, a thermal conductivity of 3.66 W / (m·K), and an electrical conductivity of 2.74×10 -3 S / cm.

[0109] Implementation Case 15

[0110] A method for preparing a derived thermally conductive wave-absorbing filler, wherein other conditions remain unchanged, and 0.25 mol / L cobalt acetate is replaced with 0.25 mol / L nickel acetate on the basis of Example 11.

[0111] The phase, composition and morphology of the obtained products measured by XRD, EDX and scanning electron microscope are as follows: Figures 43-45 As shown. From the EDX image, it can be concluded that it mainly contains elements such as Ni, C, O, Si, Ca, S, etc., and the XRD spectrum shows that it is nickel, potassium silicate, calcium silicate, calcium carbonate and silicon dioxide. The product is a composite of amorphous carbon fiber / magnetic nanoparticles with a diameter of 0.84 to 1.81 μm.

[0112] As shown in Table 1, the obtained biomass-derived thermal conductive absorbing filler has excellent microwave absorption properties, with a thickness of 2.3 mm, a maximum effective bandwidth of 8.24 GHz with a reflectivity of less than or equal to -10 dB, a thickness of 1.9 mm, a maximum absorption of -32.1 dB, a thermal conductivity of 3.14 W / (m·K), and an electrical conductivity of 1.88×10 -4 S / cm.

[0113] Table 1 shows the microwave absorption and thermal conductivity of the products obtained in Examples 1 to 15 of the present invention.

[0114]

[0115] By analyzing the above data, it can be seen that the biomass-derived thermally conductive and wave-absorbing filler prepared in the present invention has good thermal conductivity and wave-absorbing properties.

[0116] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A biomass-derived thermally conductive wave-absorbing filler, characterized in that: The biomass-derived thermally conductive and wave-absorbing filler is a 2D interconnected network structure, which is composed of amorphous carbon fibers, honeycomb amorphous carbon, strip-arranged amorphous carbon, or a composite of amorphous carbon fibers and magnetic nanoparticles; the average diameter of the carbon fibers is 0.71 to 2.79 μm, and the average length is 490 to 585 μm; the magnetic nanoparticles are Fe, Co, and Ni, and their content is 3.04 to 20.29%.

2. The biomass-derived thermally conductive wave-absorbing filler according to claim 1, characterized in that: The biomass-derived thermally conductive and wave-absorbing filler has excellent thermal conductivity and wave-absorbing properties; the electrical conductivity is 1.67×10 -4 ~6.63×10 -3 S / cm; when the filling ratio is 30%, the thermal conductivity is 1.819~4.06W / (m·K); the maximum effective bandwidth of the reflectivity less than or equal to -10dB is 3.20~8.80GHz, the maximum absorption is -18.94~-55.10dB, and the sample thickness is 1.4~5.0mm.

3. A method for preparing the biomass-derived thermally conductive and wave-absorbing filler according to claim 1, characterized in that: The biomass-derived thermally conductive and wave-absorbing filler is prepared by an impregnation-low-temperature annealing process, and the specific steps are as follows: (1) After washing the surface of the biomass material with distilled water, immersing it in anhydrous ethanol to remove the wax layer on the surface; and then drying the washed biomass material; (2) immersing the biomass material pretreated in step (1) in a transition metal acetate solution of a certain concentration, and then drying; (3) placing the biomass material dried in step (2) in a tubular furnace, annealing it under the protection of an inert gas at a certain temperature, and naturally cooling it to room temperature to obtain the desired amorphous carbon fiber, honeycomb amorphous carbon or amorphous carbon fiber / magnetic nanoparticle composite, i.e., the biomass-derived thermal conductive and wave absorbing filler.

4. The method for preparing the biomass-derived thermally conductive wave-absorbing filler according to claim 3, characterized in that: The biomass material is one or a combination of ramie leaves, quinquefolia leaves, Ligustrum lucidum leaves, maple leaves, yam leaves, phoenix tail bamboo leaves, paper mulberry leaves and lotus leaves.

5. The method for preparing the biomass-derived thermally conductive wave-absorbing filler according to claim 3, characterized in that: In step (2), the immersion treatment time is 10-60 minutes, and the drying temperature is 60-80°C.

6. The method for preparing the biomass-derived thermally conductive and wave-absorbing filler according to claim 3, characterized in that: The transition metal acetate includes one or a combination of ferric acetate, cobalt acetate and nickel acetate, and the concentration of the transition metal acetate solution is 0-1.0 mol / L.

7. The method for preparing the biomass-derived thermally conductive wave-absorbing filler according to claim 3, characterized in that: In step (3), the annealing temperature is increased to 600-900° C. at a rate of 2.5-5.0° C. / min, and the annealing time is 2-5 hours.

8. Use of the biomass-derived thermally conductive and wave-absorbing filler as claimed in claim 1 or the biomass-derived thermally conductive and wave-absorbing filler prepared by the method as claimed in any one of claims 3 to 7 in the fields of electromagnetic protection, thermal management and energy.

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