Method for preparing silicon carbide nanowire through pulse Joule heat

Abstract

The invention discloses a method for preparing a silicon carbide nanowire by pulse Joule heat. A silicon source precursor and a carbon source precursor are synthesized into the silicon carbide nanowire by utilizing strong pulse, large current and ultrahigh temperature generated by a capacitive Joule heat power supply. According to the method disclosed by the invention, Joule heat generated by discharging of the capacitor bank is utilized, so that a silicon source and a carbon source are subjected to a combination reaction under high-temperature thermal shock, the silicon carbide nanowire is prepared in a short time, and an expensive catalyst is not needed. The capacitive Joule thermal power supply is used for controlling the reaction temperature and the thermal shock frequency by adjusting the voltage, the discharge time, the flash evaporation times, the flash evaporation frequency and the duty ratio; the silicon source and the carbon source are respectively nano silicon, silicon dioxide powder and carbon powder such as carbon black, graphite, petroleum coke, pitch coke and biological carbon. The preparation method is simple, efficient, green and environment-friendly, and is a one-step method for rapidly synthesizing the silicon carbide nanowire with low energy consumption and low cost.

Description

Technical Field

[0001] The invention relates to the technical field of material synthesis, and in particular to a method for rapidly and efficiently synthesizing silicon carbide nanowires using a pulsed Joule heating technology. Background Art

[0002] In recent years, with the rapid growth of 5G and new energy industries' demand for high-frequency, high-power RF and power electronics, the physical limit bottleneck of silicon-based semiconductors has gradually become prominent. How to limit volume, heat generation and cost while increasing power has become a key issue in the semiconductor industry. Under this trend, the third-generation semiconductor materials represented by silicon carbide have gradually moved from scientific research to industrialization, and have the development trend of replacing some silicon-based power devices.

[0003] The traditional process of synthesizing silicon carbide nanowires is long, the growth is slow, and the preparation cost is expensive. Physical vapor deposition is currently the most commonly used preparation technology for silicon carbide nanowires. Its growth temperature range is 2200-2500℃, and the growth rate is 0.2-0.4mm / h. This method has difficulties in semi-insulating manufacturing, limited growth thickness, and no integrated equipment, which limits the large-scale production of silicon carbide. High-temperature chemical vapor deposition is another method for synthesizing silicon carbide. Its growth temperature is around 2200℃ and the growth rate is 0.3-1.0mm / h. It has the advantages of sustainable raw materials, adjustable parameters and integrated equipment, but its growth rate and defect control are still not perfect.

[0004] The existing silicon carbide nanowire synthesis technology has to go through a complex and time-consuming synthesis process, such as requiring high-temperature reactions for more than several hours, as well as strict synthesis processes and expensive synthesis costs, which increases the difficulty of large-scale production. Therefore, the development and application of efficient and low-cost synthesis methods are widely considered to be an important factor in promoting the development of the semiconductor industry, and finding more efficient, green and economical synthesis methods is one of the important research directions.

[0005] In 2020, the Tour team first used the flash Joule heating method to prepare graphene on a large scale. This method has been widely used in the field of carbon material synthesis, verifying the application prospects of the Joule heating method in the field of electrothermal synthesis based on carbon materials. With the continuous expansion of the application of third-generation semiconductors represented by silicon carbide, the efficient, green, and low-energy flash Joule heating technology provides a feasible solution for the synthesis of silicon carbide nanowires. Despite this, the application of this technology has not been reported in the field of synthesis of silicon carbide materials. The process and method for synthesizing silicon carbide nanowires using flash Joule heating technology is a vacancy in current technology. The present disclosure aims to use flash Joule heating, an electrothermal coupling technology, to explore new processes for the synthesis of silicon carbide nanowires, and to provide an effective means for the efficient, green, rapid, and low-cost synthesis of silicon carbide nanowires. Summary of the invention

[0006] Based on the above-mentioned problems of the synthesis process and cost of silicon carbide nanowires, the present invention provides a method for preparing silicon carbide nanowires at the millisecond level. The strong pulse, high current and ultra-high temperature generated by the capacitive Joule thermal power source are applied to the mixed precursor of silicon source and carbon source, so that the silicon source and the carbon source react under high temperature thermal shock, and the silicon carbide nanowires are efficiently synthesized without the assistance of a catalyst. The method is simple, efficient, green and environmentally friendly, and is a one-step method for rapidly synthesizing silicon carbide nanowires with low energy consumption and energy cost.

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

[0008] A method for preparing silicon carbide by Joule heat flash evaporation heat treatment comprises the following steps:

[0009] Step 1: weigh carbon source and silicon source raw materials according to a certain molar ratio, mix them evenly, and load the mixed raw materials into a quartz tube reaction chamber.

[0010] Step 2: Use a graphite rod plug to compress the raw materials in the quartz tube reaction chamber, and connect the graphite plug to the two electrodes of the Joule heat power source.

[0011] Step 3, adjusting the voltage, discharge time, flash times, frequency and duty cycle to control the Joule heat temperature and thermal shock frequency, turning on the Joule heat power supply, and synthesizing silicon carbide nanowires under the action of Joule heat.

[0012] Furthermore, the Joule heat power source is composed of more than two groups of capacitors, and each group of capacitors can adjust the voltage, discharge time, number of flash evaporations, frequency and duty cycle.

[0013] Furthermore, the voltage range of the capacitive Joule thermal power supply is 100V to 400V; The power-on time is 100ms to 1000ms, the number of flash evaporations is 5 to 20 times, the frequency is 100HZ to 1000HZ, and the duty cycle is 10% to 50%.

[0014] Furthermore, the capacitance of the capacitor in the capacitive Joule heat power source is 60mF to 150mF.

[0015] Furthermore, the silicon source is one of nano-silicon and silicon dioxide.

[0016] Furthermore, the carbon source is one of carbon black, graphite, petroleum coke, asphalt coke and biochar.

[0017] Furthermore, the molar ratio of the silicon source to the carbon source powder is in the range of 1:2 to 1:10.

[0018] Furthermore, the resistance of the mixed powder of the silicon source and the carbon source is 0.5Ω to 5Ω.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) the synthesis process route of silicon carbide nanowires is short, the synthesis process is green and efficient, and the synthesis time is short; (2) Joule heating is the in-situ heat generation of the sample, the peak temperature is high (2000-3000°C), and the thermal utilization rate is high; (3) the Joule heating process is an electrothermal coupling effect, the thermal shock force is large, and it is conducive to the growth of silicon carbide nanowires without the assistance of catalysts; (4) the process cost of preparing silicon carbide nanowires by Joule heating is low and easy to mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a scanning electron microscope image of the silicon carbide nanowires prepared in Example 1.

[0021] Figure 2 This is the current signal of the silicon carbide nanowire prepared in Example 1.

[0022] Figure 3 This is the XRD pattern of 6H phase silicon carbide nanowires prepared in Example 1.

[0023] Figure 4 This is a scanning electron microscope image of the silicon carbide nanowires prepared in Example 2.

[0024] Figure 5 This is the current signal of the silicon carbide nanowire prepared in Example 2.

[0025] Figure 6 This is the XRD pattern of 3C phase silicon carbide nanowires prepared in Example 2. DETAILED DESCRIPTION

[0026] Embodiment 1:

[0027] This embodiment:

[0028] Step 1, using carbon black as the carbon source and silicon dioxide as the silicon source, weighing 100 mg of silicon dioxide and 200 mg of carbon black with an analytical balance, the mass ratio of carbon source to silicon source is 2:1. Place the silicon source and carbon source in a mortar and grind for 30 minutes to ensure that the two powders are fully mixed. Place the mixed carbon source and silicon source powders in an oven for drying, the oven temperature is set to 120°C, the heating rate is 10°C / min, and the temperature is kept for 2 hours to remove moisture and increase the conductivity of the carbon source.

[0029] Step 2. Load the ground and dried mixed powder into a quartz tube reaction chamber, and compress the mixed powder in the quartz tube reaction chamber with a rod-shaped graphite plug, then install it on the reaction rack, and connect it to the Joule heat power supply electrodes at both ends of the reaction rack to form a conductive loop with the capacitive Joule heat power supply.

[0030] Step 3, adjust the reaction rack knob so that the power electrode presses the graphite plug, and ensure that the resistance of the mixed powder of silicon source and carbon source is 1 to 2 ohms, aim the infrared temperature sensor probe at the mixed powder inside the quartz reaction chamber, turn on the vacuum pump to start vacuuming. Set the charging voltage of the capacitor power supply to 150V, the discharge time to 1s, the duty cycle to 10%, repeat 20 times, and press the operation switch to perform Joule heat flash discharge. The Joule heat peak temperature of this process reaches 2500℃, and 6H phase silicon carbide nanowires are obtained within 1 minute, with an aspect ratio of 7 to 39.

[0031] Embodiment 2:

[0032] This embodiment

[0033] Step 1, using graphite powder as the carbon source and metallic silicon powder (purity 98%) as the silicon source, weighing 100 mg of silicon powder and 200 mg of coke powder on an analytical balance, the mass ratio of carbon source to silicon source is 1:2. Place the silicon source and carbon source in a mortar and grind for 30 minutes to ensure that the two powders are fully mixed. Place the mixed carbon source and silicon source powders in a tubular furnace with a heating rate of 10°C / min and keep them at 200°C for 2 hours to remove moisture and increase the conductivity of the carbon source. After heating, cool naturally to room temperature, take them out and crush and grind them;

[0034] Step 2: Take 300 mg of the ground and heated mixed powder and put it into a quartz tube reaction chamber, and use a rod-shaped graphite plug to compress the mixed powder in the quartz tube reaction chamber, then install it on the reaction rack and connect it to the Joule heat power supply electrodes at both ends of the reaction rack to form a conductive loop with the capacitive Joule heat power supply.

[0035] Step 3, by adjusting the distance between the two electrodes on the reaction support, the resistance is controlled to about 1Ω. To avoid oxidation of the sample, the reaction support is placed in a vacuum box and evacuated. Then it is preheated at 60V for 5 times, and then discharged at 120V for 1s and a duty cycle of 10%. After 10 discharges, 3C phase silicon carbide nanowires with an aspect ratio of 6 to 25 are obtained.

[0036] The present invention may be summarized in other specific forms that do not violate the spirit or main features of the present invention. Therefore, the above embodiments of the present invention can only be considered as explanations of the present invention and cannot limit the present invention. The claims indicate the scope of the present invention, while the above description does not indicate the scope of the present invention. Any changes within the meaning and scope equivalent to the claims of the present invention should be considered to be included in the scope of the claims of the invention.

Claims

1. A method for preparing silicon carbide nanowires by pulsed Joule heating, characterized in that: By adjusting the voltage, discharge time, number of flash evaporations, frequency and duty cycle to control the reaction temperature and thermal shock frequency, the strong pulses, large currents and ultra-high temperatures generated by the capacitive Joule thermal power source are applied to the mixed precursor of silicon source and carbon source, so that the silicon source and carbon source react chemically under high-temperature thermal shock, and silicon carbide nanowires are efficiently synthesized without the assistance of a catalyst.

2. The method for preparing silicon carbide nanowires by pulsed Joule heating according to claim 1, characterized in that: The steps of synthesizing silicon carbide nanowires are as follows: S1 weighing carbon source and silicon source raw materials according to a certain molar ratio, mixing them evenly, and loading the mixed raw materials into a quartz tube reaction chamber; S2 pressing the raw materials in the quartz tube reaction chamber with a graphite rod plug, and connecting the graphite plug to two electrodes of a Joule heat power supply; S3 adjusting the voltage, discharge time, flash evaporation times, frequency and duty cycle to control the Joule heat temperature and thermal shock frequency, connecting the Joule heat power supply, and synthesizing silicon carbide nanowires under the action of Joule heat.

3. The method for preparing silicon carbide nanowires by pulsed Joule heating according to claim 1, characterized in that: The Joule heat power source is composed of more than two groups of capacitors, and each group of capacitors can adjust the voltage, discharge time, flash evaporation times, frequency and duty cycle.

4. The method for preparing silicon carbide nanowires by pulsed Joule heating according to claim 1, characterized in that: The voltage range of the capacitive Joule heat power supply is 100V-400V; the discharge time is 100ms-1000ms, the number of flash evaporations is 5-20 times, the frequency is 100HZ-1000HZ, and the duty cycle is 10%-50%.

5. The method for preparing silicon carbide nanowires by pulsed Joule heating according to claim 1, characterized in that: The silicon source is one of nano silicon and silicon dioxide, the carbon source is one of carbon black, graphite, petroleum coke, asphalt coke and biochar, the molar ratio of silicon source to carbon source powder is in the range of 1:2 to 1:10, and the resistance of the mixed powder of silicon source and carbon source is 0.5Ω to 5Ω.

Images