Method for rapidly preparing ultra-long SiC nanowire by Joule heating

Abstract

The invention relates to the technical field of nanometre, and discloses a method for rapidly preparing an ultra-long SiC nanowire, which comprises the following steps: 1, raw material pretreatment: uniformly mixing a silicon source and a carbon source, and then humidifying to obtain mixed powder with humidity; and 2, preparation of the ultra-long SiC nanowire: placing the mixed powder with the humidity in a carbon carrier container, and then performing Joule heating to obtain the ultra-long SiC nanowire. Compared with the prior art, the method has the advantages that equipment is simple, energy consumption is low, the preparation period is short, raw materials are cheap and easy to obtain, the process is simple, the sintering temperature is low, the diameter of the obtained SiC nanowire is smaller than 300 nm, and the length-diameter ratio is far higher than 100: 1. The method is beneficial to promoting the application and development of the ultra-long SiC nanowire in the multifunctional fields of composite materials, optoelectronic devices, electromagnetic shielding, high-temperature protection materials and the like.

Description

Technical Field

[0001] The invention relates to the field of nanotechnology, in particular to a method for rapidly preparing ultra-long SiC nanowires by using Joule heating. Background Art

[0002] Silicon carbide (SiC) nanowires have attracted much attention in the field of high-performance materials in recent years due to their excellent mechanical, thermal and electrical properties. Compared with traditional SiC particles or SiC whiskers, SiC nanowires exhibit extremely excellent mechanical properties, with a bending strength of up to 55-GPa and an elongation of up to 200%. These characteristics make SiC nanowires a research hotspot as a reinforcement for metal-based composites. In particular, ultra-long SiC nanowires have broad application prospects due to their high aspect ratio, excellent thermal stability, corrosion resistance and good electrical conductivity. In structural materials, ultra-long SiC nanowires can significantly enhance the strength and stiffness of composites. According to the shear lag model, nanowires with a high aspect ratio can transfer loads more effectively and further improve the mechanical properties of composites. In the field of functional materials, the aspect ratio of SiC nanowires has a significant effect on their photoluminescence, wave absorption and heat protection properties. The higher aspect ratio not only enhances the quantum confinement effect and improves the photoluminescence efficiency, but also significantly improves the wave absorption performance through multiple scattering of electromagnetic waves and the synergistic dielectric loss and conductive loss mechanisms. In addition, the higher length optimizes the heat conduction path, reduces the interface thermal resistance, and enables the material to have better heat dissipation and thermal stability in high temperature environments. Therefore, ultra-long SiC nanowires show great potential in multifunctional applications such as optoelectronic devices, electromagnetic shielding, and high-temperature protection materials.

[0003] Although ultra-long SiC nanowires have many superior properties, existing preparation technologies still face many challenges. Common preparation methods include chemical vapor deposition (CVD), laser ablation and carbon thermal reduction. These methods have some common defects: 1) Complex equipment: CVD and laser ablation require expensive and complex equipment, which increases production costs; 2) High energy consumption: Many methods need to be carried out under high temperature or high pressure conditions, resulting in high energy consumption and being unfavorable to the environment; 3) Length limitation: Existing methods are generally difficult to prepare ultra-long SiC nanowires; 4) Long preparation cycle: For example, the preparation cycle of the CVD method is usually 8 to 24 hours, and the carbon thermal reduction method requires 18 to 40 hours.

[0004] Therefore, it is crucial to develop a new method that is efficient, low-cost and capable of quickly preparing ultra-long SiC nanowires, which will not only help overcome the limitations of existing technologies, but also promote the widespread application of ultra-long SiC nanowires in composite materials and other high-performance fields. Summary of the invention

[0005] The present invention aims to solve the technical problems existing in the existing ultra-long SiC nanowire synthesis process, such as complex equipment, high energy consumption, and long preparation cycle, and provide a method for quickly and easily preparing ultra-long SiC nanowires using Joule heating technology. The present invention realizes the rapid preparation of ultra-long SiC nanowires without adding any catalyst by utilizing the advantages of Joule heating, such as uniform heating, simple operation, and low energy consumption. This method not only greatly shortens the preparation time and simplifies the process flow, but also significantly reduces energy consumption, and has broad application prospects.

[0006] A method for rapidly preparing ultra-long SiC nanowires by Joule heating comprises the following steps:

[0007] 1) Raw material pretreatment: Place the silicon source and the carbon source in a high-energy ball mill at a certain molar ratio, mix them evenly under atmospheric conditions, then add distilled water to the mixed powder, and adjust the mixture to a certain humidity to obtain a mixed powder with appropriate humidity;

[0008] 2) Vacuuming and filling with protective gas: The mixed powder with appropriate humidity is placed in a carbon carrier container, and the container is placed on the sample holder of the Joule heat device, and the reaction chamber is vacuumed until the pressure drops below 5 Pa, and then the gas is filled into the chamber to reach a certain pressure;

[0009] 3) Heating and keeping warm: quickly heating to the required temperature and keeping warm within the temperature range for a period of time;

[0010] 4) Cooling and sampling: After cooling to room temperature, the ultra-long SiC nanowires are obtained on the carbon support.

[0011] As a preferred solution, in step 1), the silicon source is at least one of industrial silicon powder, high-purity silicon powder and micro silicon powder, and the average diameter is 0.1 to 2 μm.

[0012] As a preferred embodiment, the carbon source in step 1) is at least one of graphite, carbon black and charcoal, and has an average diameter of 0.1 to 2 μm.

[0013] As a preferred embodiment, in step 1), the molar ratio of the silicon source to the carbon source is 1:(0.2-0.5).

[0014] As a preferred solution, in step 1), the humidity of the mixture is adjusted to a moisture content of 5 to 30 wt%.

[0015] As a preferred embodiment, the carbon carrier in step 2) is at least one of graphite paper, high-purity graphite, carbon foam, and carbon sponge.

[0016] As a preferred solution, in step 2), gas is filled into the cavity to a pressure of 103 ~10 5 Pa.

[0017] As a preferred solution, the heating rate in step 3) is 1 to 5 s.

[0018] As a preferred solution, in step 3), the temperature is rapidly raised to 1100-1500°C.

[0019] As a preferred solution, the insulation time in step 3) is 5 to 60 minutes.

[0020] The advantages of the present invention over the prior art are: utilizing the advantages of the Joule heating method, including uniform heating, simple operation and low energy consumption, to achieve rapid preparation of ultra-long SiC nanowires without catalysts. By humidifying the raw materials, the reaction of water and carbon generates more CO gas, and the rapid heating makes the generation of CO and SiO gas almost synchronous, thereby providing a stable supply of CO and SiO gas for the continuous growth of SiC, and promoting the ultra-long growth of SiC nanowires. The diameter of the SiC nanowires obtained by the present invention is less than 300nm, and the aspect ratio is much higher than 100:1. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a high-magnification scanning image of the ultra-long SiC nanowire obtained in Example 1;

[0022] Figure 2 This is a low-magnification scanning image of the ultra-long SiC nanowire obtained in Example 1;

[0023] Figure 3 This is a statistical diagram of the diameters of the ultra-long SiC nanowires obtained in Example 1;

[0024] Figure 4 This is a high-magnification scanning image of the ultra-long SiC nanowire obtained in Example 2;

[0025] Figure 5 This is a low-magnification scanning image of the ultra-long SiC nanowire obtained in Example 2;

[0026] Figure 6 This is a statistical diagram of the diameters of the ultra-long SiC nanowires obtained in Example 2; DETAILED DESCRIPTION

[0027] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any reasonable combination of the specific implementation modes.

[0028] 1. Raw material pretreatment:

[0029] The silicon source and the carbon source are placed in a high-energy ball mill at a molar ratio of 1: (0.2-0.5), and mixed evenly under atmospheric conditions. Then, distilled water is added to the mixed powder, and the moisture content of the mixture is adjusted to 5-30wt.%, so as to obtain a mixed powder with appropriate humidity.

[0030] The silicon powder is one or any combination of industrial silicon powder, high-purity silicon powder or micro silicon powder, and the average diameter is 0.1-2 μm;

[0031] The carbon source is one or any combination of industrial silicon powder, graphite, carbon black or charcoal, with an average diameter of 0.1 to 2 μm;

[0032] 2. Preparation of Ultra-long SiC Nanowires

[0033] Place the mixed powder with appropriate humidity obtained in step 1 in a carbon carrier container, and place the container on the sample holder of the Joule heat device. Evacuate the reaction chamber until the pressure drops to <5 Pa. Then, fill the chamber with gas to a pressure of 10 3 ~10 5 The temperature is rapidly raised (heating rate: 1-5 s) to 1100-1500° C., and kept within the temperature range for 5-60 min. After cooling, the ultra-long SiC nanowires are obtained on the carbon support.

[0034] Embodiment 1

[0035] A method for preparing ultra-long SiC nanowires with high efficiency and low cost is to follow the following steps:

[0036] 1. Raw material pretreatment:

[0037] High-purity silicon powder and charcoal are placed in a high-energy ball mill at a molar ratio of 1:0.4 and mixed evenly under atmospheric conditions, wherein the average diameter of the high-purity silicon powder and carbon black is 0.5 μm. Distilled water is then added to the mixed powder, and the moisture content of the mixture is adjusted to 10 wt.% to obtain a mixed powder with appropriate humidity.

[0038] 2. Preparation of Ultra-long SiC Nanowires

[0039] Place the mixed powder with appropriate humidity obtained in step 1 in a graphite paper carrier container, and place the container on the sample holder of the Joule heat device. Evacuate the reaction chamber until the pressure drops to 2 Pa. Then, fill the chamber with gas to a pressure of 10 5 The temperature was raised to 1400°C for 4s and kept at this temperature for 40min. After cooling, the ultra-long SiC nanowires were obtained on the carbon support.

[0040] This embodiment has the following beneficial effects:

[0041] The SiC nanowires obtained in this embodiment are as follows Figure 1 and Figure 2 As shown, the diameter statistics are as follows Figure 3 As shown, the product has a smooth surface and a dendrite structure, and the nanowires are bent due to their smaller diameter and longer length. The average diameter is 146 nm, the diameter distribution is between 60 and 240 nm, and the aspect ratio is higher than 150:1.

[0042] Embodiment 2

[0043] A method for preparing ultra-long SiC nanowires with high efficiency and low cost is to follow the following steps:

[0044] 1. Raw material pretreatment:

[0045] Industrial silicon powder and charcoal are placed in a high-energy ball mill at a molar ratio of 1:0.3 and mixed evenly under atmospheric conditions, wherein the average diameter of the industrial silicon powder and the charcoal is 1 μm. Distilled water is then added to the mixed powder, and the moisture content of the mixture is adjusted to 30 wt.% to obtain a mixed powder with appropriate humidity.

[0046] 2. Preparation of Ultra-long SiC Nanowires

[0047] Place the mixed powder with appropriate humidity obtained in step 1 in a carbon foam carrier container, and place the container on the sample holder of the Joule heat device. Evacuate the reaction chamber until the pressure drops to 3 Pa. Then, fill the chamber with gas to a pressure of 10 4 The temperature was raised to 1300°C for 2s and kept at this temperature for 10min. After cooling, the ultra-long SiC nanowires were obtained on the carbon support.

[0048] The SiC nanowires obtained in this embodiment are as follows Figure 4 and Figure 5 As shown, the diameter statistics are as follows Figure 6 As shown, the product has a smooth surface and has many curved nanowires due to their smaller diameters and longer lengths. The average diameter is 83 nm, the diameter distribution is between 20 and 220 nm, and the aspect ratio is higher than 100:1.

[0049] The present invention and its embodiments are described above, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it and do not deviate from the purpose of the invention, they can creatively design a structure and embodiment similar to the technical solution, which should fall within the protection scope of the present invention.

Claims

1. A method for rapidly preparing ultra-long SiC nanowires using Joule heating, characterized in that: The specific steps include: 1) Raw material pretreatment: Place the silicon source and the carbon source in a high-energy ball mill at a certain molar ratio, mix them evenly under atmospheric conditions, then add distilled water to the mixed powder, and adjust the mixture to a certain humidity to obtain a mixed powder with appropriate humidity; 2) Vacuuming and filling with protective gas: The mixed powder with appropriate humidity is placed in a carbon carrier container, and the container is placed on the sample holder of the Joule heat device, and the reaction chamber is vacuumed until the pressure drops below 5 Pa, and then the gas is filled into the chamber to reach a certain pressure; 3) Heating and keeping warm: quickly heating to the required temperature and keeping warm within the temperature range for a period of time; 4) Cooling and sampling: After cooling to room temperature, the ultra-long SiC nanowires are obtained on the carbon support.

2. The method for rapidly preparing ultra-long SiC nanowires by Joule heating according to claim 1, characterized in that: In the step 1), the silicon source is at least one of industrial silicon powder, high-purity silicon powder and micro silicon powder, and the average diameter is 0.1 to 2 μm.

3. The method for rapidly preparing ultra-long SiC nanowires by Joule heating according to claim 1, characterized in that: In the step 1), the carbon source is at least one of graphite, carbon black and charcoal, and has an average diameter of 0.1 to 2 μm.

4. The method for rapidly preparing ultra-long SiC nanowires by Joule heating according to claim 1, characterized in that: In the step 1), the molar ratio of the silicon source to the carbon source is 1:(0.2-0.5).

5. The method for rapidly preparing ultra-long SiC nanowires by Joule heating according to claim 1, characterized in that: In the step 1), the humidity of the mixture is adjusted to a moisture content of 5 to 30 wt%.

6. The method for rapidly preparing ultra-long SiC nanowires by Joule heating according to claim 1, characterized in that: In the step 2), the carbon carrier is at least one of graphite paper, high-purity graphite, carbon foam, and carbon sponge.

7. The method for rapidly preparing ultra-long SiC nanowires by Joule heating according to claim 1, characterized in that: In step 2), gas is filled into the cavity to a pressure of 10 3 ~10 5 Pa.

8. The method for rapidly preparing ultra-long SiC nanowires by Joule heating according to claim 1, characterized in that: The heating rate in step 3) is 1 to 5 s.

9. The method for rapidly preparing ultra-long SiC nanowires by Joule heating according to claim 1, characterized in that: In the step 3), the temperature is rapidly raised to 1100-1500°C.

10. The method for rapidly preparing ultra-long SiC nanowires by Joule heating according to claim 1, characterized in that: The insulation time in step 3) is 5 to 60 minutes.

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