Method for rapidly preparing small-diameter nanoscale SiC short fibers

Abstract

The invention relates to the field of nanotechnology, and discloses a method for rapidly preparing small-diameter nanoscale SiC short fibers, which comprises the following steps: uniformly mixing silicon powder and amorphous carbon, and then putting the mixture into a carbon carrier container; then placing the carbon carrier containing the powder on a sample rack, vacuumizing and then filling protective gas; and adjusting the voltage, heating to a target temperature, keeping the temperature for a period of time, and cooling to obtain the small-diameter nanoscale SiC short fiber. Compared with the prior art, the preparation method has the advantages that the raw materials are cheap and easy to obtain, and the preparation of the small-diameter and smooth-surface SiC short fiber is realized in an extremely short time. According to the technical scheme, the preparation time is greatly shortened, and the energy consumption and the equipment cost are reduced. The obtained small-diameter nanoscale SiC short fiber is smooth in surface, has the diameter of less than 500nm, has remarkable size uniformity, and is expected to be applied to the fields of high-performance composite materials and the like.

Description

Technical Field

[0001] The invention relates to the field of nanotechnology, in particular to a method for rapidly preparing small-diameter nanoscale SiC short fibers. Background Art

[0002] Small-diameter nanoscale (1-500nm) SiC short fibers are a new type of material with excellent performance. Its high strength, high temperature resistance, corrosion resistance, high thermal conductivity, good chemical stability and oxidation resistance make it widely used in aerospace, energy, electronic devices and high-performance composite materials. In composite materials, small-diameter SiC short fibers as reinforcing phases can significantly improve the mechanical strength, toughness and thermal shock resistance of the material. Compared with SiC whiskers (diameter of about 0.5-5μm) or longer nanowires, short fibers with low diameters have unique advantages. First, short fibers with small diameters provide a larger specific surface area and increase the interface area, thereby enhancing the interfacial bonding force with the matrix material and significantly improving the mechanical properties of the composite material. Secondly, the smaller fiber diameter brings better flexibility, allowing the fibers to be more evenly dispersed in the matrix material, optimizing the stress distribution and further improving the overall strength of the composite material. For example, the application in ceramic-based composites and metal-based composites has a significant performance improvement effect, and has broad application prospects in aerospace, high-temperature structural parts, automotive industry and high-performance mechanical parts in the future.

[0003] At present, the preparation methods of small-diameter SiC short fibers include chemical vapor deposition (CVD), electrospinning, high-temperature melting and carbon thermal reduction. However, each of these methods has inherent defects. For example, although the CVD method can prepare high-purity SiC short fibers, its preparation cycle is long (usually 8-24 hours), the equipment is complex and expensive, resulting in high production costs. In addition, the CVD method has difficulties in accurately controlling the fiber diameter, especially when preparing fibers with a diameter of less than 200 nanometers, the diameter consistency is difficult to guarantee. The electrospinning method stretches a polymer solution containing a SiC precursor into slender fibers through high voltage, and removes the polymer by heat treatment to form SiC. However, this method is mainly used to prepare long fibers or nanowires, and is not effective in preparing short-cut SiC fibers because the electrospinning process tends to generate longer fibers. Although the high-temperature melting method has relatively simple process requirements and usually requires a cycle of several hours to one day, depending on the temperature and conditions of the melting process, the equipment and energy consumption costs are high, and it is difficult to control the fiber diameter and length. Impurities may be generated during the melting process, affecting the purity and performance of the final fiber. The carbon thermal reduction method is easy to operate and low in cost, but its preparation cycle is long (about 18-40 hours), and it is difficult to accurately control the fiber diameter, which usually results in a wide fiber diameter distribution and affects the consistency of the product.

[0004] Therefore, developing an efficient, low-cost and precisely controlled preparation method for small-diameter SiC short fibers is of great significance to meet the growing industrial demand and promote the development of high-performance composite materials. Summary of the invention

[0005] The present invention aims to solve the problems of long cycle, high equipment and energy consumption costs, and wide fiber diameter distribution in the existing preparation process of small-diameter nanoscale (1-500nm) SiC short fibers, and provide a method for quickly preparing small-diameter nanoscale SiC short fibers. The method utilizes the rapid heating characteristics of Joule heating and combines the nanowire growth mechanism to achieve the preparation of small-diameter, smooth-surfaced SiC short fibers in a very short time. The technical solution of the present invention not only greatly shortens the preparation time, reduces energy consumption and equipment costs, but also significantly improves the size uniformity of the fiber, making it more potential for application.

[0006] A method for rapidly preparing small-diameter nanoscale SiC short fibers comprises the following steps:

[0007] 1) Mixed powder: Mix silicon powder and amorphous carbon to obtain a uniform mixed powder;

[0008] 2) Evacuate and fill with protective gas: Place the above-mentioned mixed powder in a carbon carrier container, then place the carbon carrier containing the powder on a sample holder, evacuate to a low vacuum condition, and then fill the cavity with protective gas to a certain pressure;

[0009] 3) Heating and keeping warm: adjust the voltage to heat to the target temperature and keep warm for a period of time;

[0010] 4) Cooling and sampling: After cooling, small-diameter nano-scale SiC short fibers are obtained.

[0011] As a preferred solution, the silicon powder in step 1) is at least one of industrial silicon powder, quartz powder and silicon dioxide powder, and has an average diameter of 0.5 to 1 μm.

[0012] As a preferred embodiment, the amorphous carbon in step 1) is at least one of carbon black, activated carbon, and charcoal graphitized carbon, and has an average diameter of 0.5 to 1 μm.

[0013] As a preferred embodiment, in step 1), the molar ratio of silicon powder to amorphous carbon is (1-2):1.

[0014] As a preferred solution, the step 2) is performed under a low vacuum condition with a pressure less than 10 Pa.

[0015] As a preferred solution, the protective gas in step 2) is at least one of nitrogen and argon.

[0016] As a preferred embodiment, the pressure of the protective gas filled in step 2) is 10 2 ~10 5 Pa.

[0017] As a preferred solution, the voltage in step 3) is 110-220V.

[0018] As a preferred solution, the target temperature in step 3) is 1250-1550°C.

[0019] As a preferred solution, the insulation time in step 3) is 0.5 to 10 minutes.

[0020] The advantages of the present invention over the prior art are: utilizing the rapid temperature rise characteristics of Joule heating, combined with the nanowire growth mechanism, by applying voltage to the conductive carbon carrier, utilizing it to generate Joule heat, and realizing the preparation of small-diameter, smooth-surfaced SiC short fibers in a very short time. This method greatly shortens the preparation time, reduces energy consumption and equipment costs. The obtained small-diameter nanoscale SiC short fibers have a smooth surface, a diameter of less than 500nm, and significant size uniformity, and are expected to be used in the fields of high-performance composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a high-magnification scanning image of the small-diameter nanoscale SiC short fiber obtained in Example 1;

[0022] Figure 2 This is a low-magnification scanning image of the small-diameter nanoscale SiC short fiber obtained in Example 1;

[0023] Figure 3 This is a statistical diagram of the diameter of small-diameter nanoscale SiC short fibers obtained in Example 1;

[0024] Figure 4 This is a length statistical diagram of small-diameter nanoscale SiC short fibers obtained in Example 1;

[0025] Figure 5 This is a high-magnification scan of the small-diameter nanoscale SiC short fibers obtained in Example 2;

[0026] Figure 6 This is a low-magnification scanning image of the small-diameter nanoscale SiC short fiber obtained in Example 2;

[0027] Figure 7 This is a statistical diagram of the diameter of small-diameter nanoscale SiC short fibers obtained in Example 2;

[0028] Figure 8 This is a length statistics chart of small-diameter nanoscale SiC short fibers obtained in Example 2. DETAILED DESCRIPTION

[0029] 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.

[0030] A method for rapidly preparing small-diameter nanoscale SiC short fibers comprises the following steps:

[0031] 1) Mixed powder: Silicon powder and amorphous carbon are mixed in a molar ratio of (1-2):1 to obtain a uniform mixed powder, wherein the silicon powder is at least one of industrial silicon powder, quartz powder, and silicon dioxide powder, and the average diameter is 0.5-1 μm, and the amorphous carbon is at least one of carbon black, activated carbon, and charcoal graphitized carbon, and the average diameter is 0.5-1 μm;

[0032] 2) Vacuuming and filling with protective gas: Place the above mixed powder in a carbon carrier container, then place the carbon carrier containing the powder on the sample holder, evacuate to a low vacuum condition with a pressure less than 10Pa, and then fill the cavity with nitrogen or argon or a mixture of the two to 10 2 ~10 5 Pa, among them;

[0033] 3) Heating and keeping warm: adjust the voltage to 110-220V and heat to 1250-1550℃, keep warm for 0.5-10min;

[0034] 4) Cooling and sampling: After cooling, small-diameter nano-scale SiC short fibers are obtained.

[0035] Embodiment 1

[0036] A method for rapidly preparing small diameter nanoscale SiC short fibers is to follow the following steps:

[0037] Industrial silicon powder and carbon black are mixed uniformly in a molar ratio of 1.5:1, wherein the average diameter of the silicon powder and the carbon black is 1 μm, and the mixed powder is placed in a carbon carrier container, and then the carbon carrier containing the powder is placed on a sample rack, and a low vacuum condition of 8 Pa is drawn, and then argon protective gas is filled into the cavity to make the pressure 104 Pa; then the voltage is adjusted to 220 V and heated to 1550° C., and the temperature is kept for 5 minutes, and then it is cooled to obtain small-diameter nano-scale SiC short fibers.

[0038] The small diameter nanoscale SiC short fibers prepared in this embodiment are as follows Figure 1 and Figure 2 The statistical results of diameter and length are shown in Figure 3 and Figure 4The product has a smooth surface and uniform morphology, an average diameter of 145nm, an average length of 700nm, an aspect ratio of about 5:1, a diameter range of 60 to 260nm, and a relatively concentrated size distribution. The process is simple and low-cost, and can efficiently prepare small-diameter nanoscale SiC short fibers in a very short time.

[0039] Embodiment 2

[0040] A method for rapidly preparing small diameter nanoscale SiC short fibers is to follow the following steps:

[0041] Industrial quartz powder and activated carbon were mixed uniformly in a molar ratio of 1:1, wherein the average diameter of the silicon powder and the activated carbon was 0.5 μm, and the mixed powder was placed in a carbon carrier container, and then the carbon carrier containing the powder was placed on a sample rack, and a low vacuum condition of 5 Pa was drawn, and then argon protective gas was filled into the cavity to make the pressure 10 5 Pa; then adjust the voltage to 200V and heat to 1300℃, keep it warm for 8min, and then let it cool to obtain small-diameter nano-scale SiC short fibers.

[0042] The small diameter nanoscale SiC short fibers prepared in Example 2 are as follows Figure 5 and Figure 6 The statistical results of diameter and length are shown in Figure 7 and Figure 8 The product has a smooth surface and uniform morphology, an average diameter of 74nm, an average length of 1920nm, an aspect ratio of about 25:1, a diameter range of 20 to 180nm, and a relatively concentrated size distribution. The process is simple and low-cost, and can efficiently prepare small-diameter nanoscale SiC short fibers in a very short time.

[0043] 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 small-diameter nanoscale SiC short fibers, characterized in that: The specific steps include: 1) Mixed powder: Mix silicon powder and amorphous carbon to obtain a uniform mixed powder; 2) Evacuate and fill with protective gas: Place the above-mentioned mixed powder in a carbon carrier container, then place the carbon carrier containing the powder on a sample holder, evacuate to a low vacuum condition, and then fill the cavity with protective gas to a certain pressure; 3) Heating and keeping warm: adjust the voltage to heat to the target temperature and keep warm for a period of time; 4) Cooling and sampling: After cooling, small-diameter nano-scale SiC short fibers are obtained.

2. A method for rapidly preparing small-diameter nanoscale SiC short fibers according to claim 1, characterized in that: The silicon powder in step 1) is at least one of industrial silicon powder, quartz powder and silicon dioxide powder, and has an average diameter of 0.5 to 1 μm.

3. The method for rapidly preparing small-diameter nanoscale SiC short fibers according to claim 1, characterized in that: In the step 1), the amorphous carbon is at least one of carbon black, activated carbon, and charcoal graphitized carbon, and has an average diameter of 0.5 to 1 μm.

4. The method for rapidly preparing small-diameter nanoscale SiC short fibers according to claim 1, characterized in that: In the step 1), the molar ratio of silicon powder to amorphous carbon is (1-2):

1.

5. The method for rapidly preparing small-diameter nanoscale SiC short fibers according to claim 1, characterized in that: In the step 2), the pressure is evacuated to a low vacuum condition of less than 10 Pa.

6. The method for rapidly preparing small-diameter nanoscale SiC short fibers according to claim 1, characterized in that: In the step 2), the protective gas is at least one of nitrogen and argon.

7. The method for rapidly preparing small-diameter nanoscale SiC short fibers according to claim 1, characterized in that: The pressure of the protective gas filled in step 2) is 10 2 ~10 5 Pa.

8. The method for rapidly preparing small-diameter nanoscale SiC short fibers according to claim 1, characterized in that: In the step 3), the voltage is 110-220V.

9. The method for rapidly preparing small-diameter nanoscale SiC short fibers according to claim 1, characterized in that: The target temperature in step 3) is 1250-1550°C.

10. The method for rapidly preparing small-diameter nanoscale SiC short fibers according to claim 1, characterized in that: The insulation time in step 3) is 0.5 to 10 minutes.

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