Method for preparing SiC fiber from balsa wood and lignite

Abstract

The invention relates to a method for preparing SiC fibers, in particular to a method for preparing SiC fibers from balsa wood and lignite. The invention aims to solve the problems of high cost, complex process, strict equipment requirements and difficulty in realizing large-scale production of the existing SiC fiber. The preparation method comprises the following steps: 1, preparing wood fibers; 2, preparing superfine pulverized coal; 3, preparing a wood fiber-lignite composite material; 4, carbonizing; and 5, carbon thermal reduction reaction. The method is used for preparing the SiC fiber from the balsa wood and the lignite.

Description

Technical Field

[0001] The invention relates to a method for preparing SiC fiber. Background Art

[0002] SiC fiber has been widely used in aerospace, weapons, nuclear energy, thermal engines and other fields due to its excellent properties such as low density, high strength, high modulus, high temperature resistance, oxidation resistance and corrosion resistance. In addition, SiC fiber also has the characteristic of adjustable resistivity, which provides the possibility for its functional application in absorbing electromagnetic waves, making it show great potential as a high-performance absorbing material. And SiC fiber can also achieve toughening effect by providing a toughening mechanism to improve the toughness of composite materials. However, traditional SiC fiber is difficult to achieve large-scale production due to its high cost, complex process and strict equipment requirements. Summary of the invention

[0003] The present invention aims to solve the problems of high cost, complex process and strict equipment requirements of existing SiC fibers, and difficulty in large-scale production, and further provides a method for preparing SiC fibers using balsa wood and lignite.

[0004] A method for preparing SiC fiber by using balsa wood and lignite is completed by the following steps:

[0005] 1. Washing and soaking balsa wood in water to obtain impregnated balsa wood, subjecting the impregnated balsa wood to saturated steam steaming and twin-screw extrusion in turn to obtain coarsely ground balsa wood fiber, adding the coarsely ground balsa wood fiber to a mixed solution of NaOH and Na2SO3, uniformly heating for 3h to 6h at a temperature of 75°C to 105°C, and finally washing, dehydrating and drying to obtain wood fiber;

[0006] 2. Drying and ball-milling the lignite to obtain ultra-fine coal powder;

[0007] 3. Mixing wood fiber and ultrafine coal powder, then adding silane coupling agent and zirconate coupling agent dropwise under stirring conditions and stirring evenly, and finally drying to obtain a wood fiber-lignite composite material;

[0008] 4. Carbonizing the wood fiber-lignite composite material under an argon atmosphere and a temperature of 600° C. to 800° C. to obtain a carbonized wood fiber-lignite composite material;

[0009] 5. Using the carbonized wood fiber-lignite composite material as the carbon source and a mixture of silicon and silicon dioxide as the silicon source, the silicon source is laid on the bottom of a graphite crucible, and then the carbon source is placed on the silicon source, and a carbon thermal reduction reaction is carried out in an argon atmosphere at a temperature of 1250°C to 1600°C to grow SiC fibers on the inner surface of the crucible cover, thereby completing a method for preparing SiC fibers using balsa wood and lignite.

[0010] The beneficial effects of the present invention are:

[0011] The wood fiber of the present invention has a high carbon content, and the wood fiber carbon material obtained by high-temperature carbonization as a carbon source has good electrical conductivity. Lignite is rich in sources and has a high carbon content. The SiC fiber prepared by using wood fiber and lignite as a carbon source can extend the conduction and dissipation path of electromagnetic waves and enhance the attenuation characteristics of electromagnetic waves due to its large specific surface area. SiC fiber can easily produce an interpenetrating conductive network due to the anisotropy of its one-dimensional structure, which is conducive to the formation of microcurrents and multiple reflections and scattering of electromagnetic waves, and promotes the absorption of electromagnetic waves. In addition, the prepared SiC fiber also has a good mechanical toughening effect.

[0012] The present invention uses wood and lignite to prepare SiC nanofibers, which can significantly reduce production costs. As a cheap, renewable resource, wood meets the requirements of environmental protection and sustainable development, and its natural microstructure simplifies the process and reduces dependence on complex equipment. Furthermore, adding lignite particles to wood to prepare SiC fibers achieves high value-added utilization of lignite and solves the problems of inefficient utilization of lignite and environmental pollution. This method not only reduces costs, but also simplifies the production process, promoting the development of SiC nanomaterials in large-scale applications. That is, the present invention solves the problems of high cost, complex process and strict equipment requirements of existing SiC fibers, which are difficult to achieve large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is the XRD pattern of the SiC fiber prepared in Example 1;

[0014] Figure 2 This is a scanning electron microscope image of the SiC fiber prepared in Example 1;

[0015] Figure 3 This is a diagram of the wave absorption performance of the SiC fiber prepared in Example 1. DETAILED DESCRIPTION

[0016] Specific implementation method 1: This implementation method is a method for preparing SiC fiber using balsa wood and lignite, which is characterized by being completed in the following steps:

[0017] 1. Washing and soaking balsa wood in water to obtain impregnated balsa wood, subjecting the impregnated balsa wood to saturated steam steaming and twin-screw extrusion in turn to obtain coarsely ground balsa wood fiber, adding the coarsely ground balsa wood fiber to a mixed solution of NaOH and Na2SO3, uniformly heating for 3h to 6h at a temperature of 75°C to 105°C, and finally washing, dehydrating and drying to obtain wood fiber;

[0018] 2. Drying and ball-milling the lignite to obtain ultra-fine coal powder;

[0019] 3. Mixing wood fiber and ultrafine coal powder, then adding silane coupling agent and zirconate coupling agent dropwise under stirring conditions and stirring evenly, and finally drying to obtain a wood fiber-lignite composite material;

[0020] 4. Carbonizing the wood fiber-lignite composite material under an argon atmosphere and a temperature of 600° C. to 800° C. to obtain a carbonized wood fiber-lignite composite material;

[0021] 5. Using the carbonized wood fiber-lignite composite material as the carbon source and a mixture of silicon and silicon dioxide as the silicon source, the silicon source is laid on the bottom of a graphite crucible, and then the carbon source is placed on the silicon source, and a carbon thermal reduction reaction is carried out in an argon atmosphere at a temperature of 1250°C to 1600°C to grow SiC fibers on the inner surface of the crucible cover, thereby completing a method for preparing SiC fibers using balsa wood and lignite.

[0022] In this specific embodiment, the wood can be decomposed into fibers by removing lignin, and lignite particles can be effectively combined with wood fibers under the action of a silane coupling agent, and the preparation of SiC fibers is achieved by regulating the reaction of carbon sources and silicon sources.

[0023] The beneficial effects of this embodiment are:

[0024] The wood fiber of this embodiment has a high carbon content, and the wood fiber carbon material obtained by high-temperature carbonization as a carbon source has good electrical conductivity. Lignite is rich in sources and has a high carbon content. The SiC fiber prepared using wood fiber and lignite as a carbon source can extend the conduction and dissipation path of electromagnetic waves and enhance the attenuation characteristics of electromagnetic waves due to its large specific surface area. SiC fiber can easily produce an interpenetrating conductive network due to the anisotropy of its one-dimensional structure, which contributes to the formation of microcurrents and multiple reflections and scattering of electromagnetic waves, thereby promoting the absorption of electromagnetic waves. In addition, the prepared SiC fiber also has a good mechanical toughening effect.

[0025] This specific embodiment uses wood and lignite to prepare SiC nanofibers, which can significantly reduce production costs. As a cheap, renewable resource, wood meets the requirements of environmental protection and sustainable development. Its natural microstructure simplifies the process and reduces dependence on complex equipment. Furthermore, adding lignite particles to wood to prepare SiC fibers achieves high value-added utilization of lignite and solves the problems of inefficient utilization of lignite and environmental pollution. This method not only reduces costs, but also simplifies the production process, promoting the development of SiC nanomaterials in large-scale applications. That is, this specific embodiment solves the problems of existing SiC fibers, such as high cost, complex process, strict equipment requirements, and difficulty in large-scale production.

[0026] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that: in step 1, the balsa wood is washed, and then immersed in water for 8h to 12h at room temperature and a pressure of -0.1MPa to -0.5MPa to obtain the impregnated balsa wood; the saturated steam steaming treatment described in step 1 is specifically carried out at a temperature of 100°C for 15min to 30min; the twin-screw extrusion treatment described in step 1 is specifically carried out at a temperature of 70°C to 85°C and a rotation speed of 1300r / min to 1500r / min. The rest is the same as specific implementation method 1.

[0027] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that: the concentration of NaOH in the mixed solution of NaOH and Na2SO3 described in step 1 is 0.4M-1M, and the concentration of Na2SO3 is 1.5M-3M; the volume ratio of the mass of the coarsely ground balsa wood fiber described in step 1 to the mixed solution of NaOH and Na2SO3 is 1g:(50-100)mL. Others are the same as specific implementation method 1 or 2.

[0028] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that the ball milling in step 2 is performed at a rotation speed of 150 rpm to 500 rpm for 2 h to 10 h. The rest is the same as specific embodiments 1 to 3.

[0029] Specific embodiment 5: This embodiment is different from specific embodiments 1 to 4 in that: the silane coupling agent described in step 3 is one of KBM-403, KH550, KH560 and KH57 or a combination of several thereof; the zirconate coupling agent described in step 3 is one of NZ-38, NZ-12, NZ-44, NZ-01 and NZ-33 or a combination of several thereof. The rest is the same as specific embodiments 1 to 4.

[0030] Specific embodiment 6: This embodiment is different from specific embodiments 1 to 5 in that: the mass ratio of the silane coupling agent to the zirconate coupling agent in step 3 is 1:(1-10); the mass ratio of the silane coupling agent to the wood fiber in step 3 is 1:(1-50); the mass ratio of the silane coupling agent to the ultrafine coal powder in step 3 is 1:(1-50). Others are the same as specific embodiments 1 to 5.

[0031] Specific embodiment 7: This embodiment is different from specific embodiments 1 to 6 in that the drying described in step 1 and step 3 is freeze-dried for 8h to 12h at a temperature of -60°C to -80°C. The rest is the same as specific embodiments 1 to 6.

[0032] Specific embodiment eight: This embodiment differs from specific embodiments one to seven in that: in step four, under an argon atmosphere, the temperature is first raised to 600°C to 800°C at a heating rate of 1°C / min to 5°C / min, then carbonized for 2h to 5h under the conditions of an argon atmosphere and a temperature of 600°C to 800°C, and finally cooled to room temperature at a cooling rate of 5°C / min to 10°C / min. The rest is the same as specific embodiments one to seven.

[0033] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that the molar ratio of the carbon source to the silicon source in step 5 is 1:(4-10); the molar ratio of silicon to silicon dioxide in the mixture of silicon and silicon dioxide in step 5 is (1-10):1. The rest is the same as specific embodiments 1 to 8.

[0034] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that: in step 5, under an argon atmosphere, the temperature is first raised to 600°C to 800°C at a heating rate of 5°C / min to 10°C / min, and then raised to 1250°C to 1600°C at a heating rate of 2°C / min to 5°C / min, and carbon thermal reduction reaction is carried out under argon atmosphere and a temperature of 1250°C to 1600°C for 2h to 5h, and then the temperature is first lowered to 600°C to 800°C at a cooling rate of 2°C / min to 5°C / min, and then the temperature is lowered to room temperature at a cooling rate of 5°C / min to 10°C / min. The rest is the same as specific embodiments 1 to 9.

[0035] The following examples are used to verify the beneficial effects of the present invention:

[0036] Embodiment 1:

[0037] A method for preparing SiC fiber by using balsa wood and lignite is completed by the following steps:

[0038] 1. Wash the balsa wood, and then immerse it in water for 8 hours at room temperature and a pressure of -0.1MPa to obtain the impregnated balsa wood. Steam the impregnated balsa wood with saturated water vapor for 15 minutes at a temperature of 100°C, and then perform twin-screw extrusion at a temperature of 70°C and a rotation speed of 1500r / min to obtain coarsely ground balsa wood fiber. Add the coarsely ground balsa wood fiber into a mixed solution of NaOH and Na2SO3, and evenly heat it at a temperature of 75°C for 3 hours. Finally, wash, dehydrate and dry it to obtain wood fiber.

[0039] The concentration of NaOH in the mixed solution of NaOH and Na2SO3 is 0.4M, and the concentration of Na2SO3 is 1.5M; the mass of the coarsely ground balsa wood fiber and the volume ratio of the mixed solution of NaOH and Na2SO3 is 1g:50mL;

[0040] 2. Dry the lignite, and then grind it by ball mill at a rotation speed of 500 rpm for 10 hours to obtain ultrafine coal powder;

[0041] 3. Mixing wood fiber and ultrafine coal powder, then adding silane coupling agent and zirconate coupling agent dropwise under stirring conditions and stirring evenly, and finally drying to obtain a wood fiber-lignite composite material;

[0042] The silane coupling agent is KBM-403; the zirconate coupling agent is NZ-38;

[0043] The mass ratio of the silane coupling agent to the zirconate coupling agent is 1:1; the mass ratio of the silane coupling agent to the wood fiber is 1:10; the mass ratio of the silane coupling agent to the ultrafine coal powder is 1:10;

[0044] Fourth, in an argon atmosphere, the temperature was first raised to 600°C at a heating rate of 5°C / min, then carbonized for 2h in an argon atmosphere at 600°C, and finally cooled to room temperature at a cooling rate of 5°C / min to obtain a carbonized wood fiber-lignite composite material;

[0045] 5. Using the carbonized wood fiber-lignite composite material as a carbon source and a mixture of silicon and silicon dioxide as a silicon source, the silicon source is laid on the bottom of a graphite crucible, and then the carbon source is placed on the silicon source. In an argon atmosphere, the temperature is first increased to 800°C at a heating rate of 10°C / min, and then increased to 1500°C at a heating rate of 5°C / min. Carbothermal reduction reaction is performed under argon atmosphere and a temperature of 1500°C for 2 hours, and then the temperature is first decreased to 800°C at a cooling rate of 5°C / min, and then decreased to room temperature at a cooling rate of 10°C / min, and SiC fibers are grown on the inner surface of the crucible cover to obtain SiC fibers.

[0046] The molar ratio of the carbon source to the silicon source is 1:4; the molar ratio of silicon to silicon dioxide in the mixture of silicon and silicon dioxide is 1:1;

[0047] The drying described in step 1 and step 3 is specifically freeze-drying at a temperature of -80°C for 12 hours.

[0048] The block balsa wood described in step 1 is basalt balsa wood chips.

[0049] The lignite described in step 2 is lignite from Zhalainuoer Coal Industry in Inner Mongolia, wherein the mass percentage of moisture in the lignite is 16%, the mass percentage of organic carbon in the lignite is 60%, the mass percentage of inorganic carbon in the lignite is 12%, the mass percentage of ash in the lignite is 12%, the particle size is mainly concentrated in the range of 1 μm to 2 μm, and the average particle size is 1.75 μm;

[0050] Figure 1 This is the XRD spectrum of the SiC fiber prepared in Example 1. As can be seen from the figure, the main crystalline phase of SiC in the SiC fiber is 3C-SiC.

[0051] Figure 2 This is a scanning electron microscope image of the SiC fiber prepared in Example 1; as can be seen from the image, the diameter of the SiC fiber is about tens to hundreds of nanometers, and the length is several microns to hundreds of microns.

[0052] The SiC fiber prepared in Example 1 and paraffin were mixed in a mass ratio of 3:7 to form a coaxial ring shape with a thickness of 0.3 mm, an inner diameter of 3 mm and an outer diameter of 7 mm; Figure 3 This is a diagram of the wave absorption performance of the SiC fiber prepared in Example 1. As can be seen from the figure, the SiC fiber exhibits excellent wave absorption performance, almost covering 6.8 GHz to 11.4 GHz, and the minimum reflection loss can reach -53.7025 dB.

[0053] Embodiment 2:

[0054] ① The SiC fibers and pure B4C nanoparticles prepared in Example 1 were ultrasonically dispersed in deionized water to obtain SiC slurry and B4C slurry;

[0055] The mass ratio of the SiC fiber to deionized water is 1:3; the mass ratio of the pure B4C nanoparticles to deionized water is 1:3; the particle size of the pure B4C nanoparticles is 2 μm;

[0056] ② The SiC slurry and the B4C slurry were ultrasonically mixed for 3 hours, and then dried in a rotary evaporator at a temperature of 105°C to obtain a dry powder mixture;

[0057] The mass ratio of pure B4C nanoparticles to SiC fibers in the dry powder mixture is 95:5;

[0058] ③ The dried powder mixture was ground and sieved to obtain a 120-mesh powder mixture, and then consolidated for 20 min in a FHPS device (FHP-858, Suzhou Hateng Technology Co., Ltd.) using a non-pulsed current (~4 V) under vacuum and a temperature of 1800°C to obtain a B4C-SiC composite ceramic;

[0059] Graphite paper is filled between the graphite mold and powder during the consolidation process of the FHPS equipment to prevent them from reacting.

[0060] Comparative experiment: This comparative experiment is different from Example 2 in that the addition of SiC fiber is eliminated, and the consolidation is carried out for 20 minutes in a FHPS device (FHP-858, Suzhou Hateng Technology Co., Ltd.) using a non-pulse current (~4V) under vacuum and a temperature of 1850°C. The rest is the same as Example 2.

[0061] The mechanical properties comparison between pure B4C and B4C-SiC composite ceramics is shown in Table 1. It is found that adding SiC fiber prepared in Example 1 can effectively promote the mechanical properties of B4C-SiC composite ceramics and play a toughening effect.

[0062] Table 1

[0063]

Claims

1. A method for preparing SiC fiber using balsa wood and lignite, characterized in that It is done in the following steps:

1. Washing and soaking balsa wood in water to obtain impregnated balsa wood, subjecting the impregnated balsa wood to saturated steam steaming and twin-screw extrusion in turn to obtain coarsely ground balsa wood fiber, adding the coarsely ground balsa wood fiber to a mixed solution of NaOH and Na2SO3, uniformly heating for 3h to 6h at a temperature of 75°C to 105°C, and finally washing, dehydrating and drying to obtain wood fiber; 2. Drying and ball-milling the lignite to obtain ultra-fine coal powder; 3. Mixing wood fiber and ultrafine coal powder, then adding silane coupling agent and zirconate coupling agent dropwise under stirring conditions and stirring evenly, and finally drying to obtain a wood fiber-lignite composite material; 4. Carbonizing the wood fiber-lignite composite material under an argon atmosphere and a temperature of 600° C. to 800° C. to obtain a carbonized wood fiber-lignite composite material; 5. Using the carbonized wood fiber-lignite composite material as the carbon source and a mixture of silicon and silicon dioxide as the silicon source, the silicon source is laid on the bottom of a graphite crucible, and then the carbon source is placed on the silicon source, and a carbon thermal reduction reaction is carried out in an argon atmosphere at a temperature of 1250°C to 1600°C to grow SiC fibers on the inner surface of the crucible cover, thereby completing a method for preparing SiC fibers using balsa wood and lignite.

2. The method for preparing SiC fiber using balsa wood and lignite according to claim 1, characterized in that In step one, the balsa wood is washed and then immersed in water at room temperature and a pressure of -0.1MPa to -0.5MPa for 8h to 12h to obtain the impregnated balsa wood; the saturated steam steaming treatment described in step one is specifically carried out at a temperature of 100°C for 15min to 30min; the twin-screw extrusion treatment described in step one is specifically carried out at a temperature of 70°C to 85°C and a rotation speed of 1300r / min to 1500r / min.

3. The method for preparing SiC fiber using balsa wood and lignite according to claim 1, characterized in that The concentration of NaOH in the mixed solution of NaOH and Na2SO3 described in step one is 0.4M~1M, and the concentration of Na2SO3 is 1.5M~3M; the volume ratio of the mass of the coarsely ground balsa wood fiber described in step one to the mixed solution of NaOH and Na2SO3 is 1g:(50~100)mL.

4. The method for preparing SiC fiber using balsa wood and lignite according to claim 1, characterized in that The ball milling in step 2 is specifically performed at a rotation speed of 150 rpm to 500 rpm for 2 h to 10 h.

5. The method for preparing SiC fiber using balsa wood and lignite according to claim 1, characterized in that The silane coupling agent described in step three is one of KBM-403, KH550, KH560 and KH57 or a combination of several thereof; the zirconate coupling agent described in step three is one of NZ-38, NZ-12, NZ-44, NZ-01 and NZ-33 or a combination of several thereof.

6. The method for preparing SiC fiber using balsa wood and lignite according to claim 1, characterized in that The mass ratio of the silane coupling agent to the zirconate coupling agent in step three is 1:(1-10); the mass ratio of the silane coupling agent to the wood fiber in step three is 1:(1-50); the mass ratio of the silane coupling agent to the ultrafine coal powder in step three is 1:(1-50).

7. The method for preparing SiC fiber using balsa wood and lignite according to claim 1, characterized in that The drying described in step 1 and step 3 is specifically freeze-drying at a temperature of -60°C to -80°C for 8h to 12h.

8. The method for preparing SiC fiber using balsa wood and lignite according to claim 1, characterized in that In step 4, under an argon atmosphere, the temperature is first increased to 600°C to 800°C at a heating rate of 1°C / min to 5°C / min, then carbonized for 2h to 5h under an argon atmosphere and a temperature of 600°C to 800°C, and finally cooled to room temperature at a cooling rate of 5°C / min to 10°C / min.

9. The method for preparing SiC fiber using balsa wood and lignite according to claim 1, characterized in that The molar ratio of the carbon source to the silicon source in step 5 is 1:(4-10); the molar ratio of silicon to silicon dioxide in the mixture of silicon and silicon dioxide in step 5 is (1-10):

1.

10. The method for preparing SiC fiber using balsa wood and lignite according to claim 1, characterized in that In step 5, under an argon atmosphere, the temperature is first increased to 600°C~800°C at a heating rate of 5°C / min~10°C / min, and then increased to 1250°C~1600°C at a heating rate of 2°C / min~5°C / min. The carbon thermal reduction reaction is carried out under the conditions of an argon atmosphere and a temperature of 1250°C~1600°C for 2h~5h, and then the temperature is first decreased to 600°C~800°C at a cooling rate of 2°C / min~5°C / min, and then decreased to room temperature at a cooling rate of 5°C / min~10°C / min.

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