Rapid preparation method of silicon carbide particles based on flash Joule heat process

Abstract

The invention provides a rapid preparation method of silicon carbide particles based on a flash Joule heat process, and belongs to the technical field of silicon carbide preparation. Under the condition that complex raw material / precursor treatment is not needed, only raw materials are subjected to simple solid-phase mixing, and on the premise that a catalyst, pretreatment and preheating are not needed, the silicon carbide particles are prepared; a sample is subjected to direct current contact heating by adopting flash Joule thermal equipment (which can be self-made) with low cost, and the silicon carbide micro-nano particles can be successfully prepared within an extremely short time within one second. The method is simple in technological process, extremely low in equipment cost and time cost and high in flexibility, raw materials can be replaced according to actual conditions, even industrial waste containing carbon and silicon can be used as raw materials for preparing silicon carbide, the method has actual application value and industrial potential, and large-scale continuous production can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of silicon carbide preparation, and in particular to a method for rapidly preparing silicon carbide particles based on a flash Joule heating process. Background Art

[0002] As one of the strategic materials of the new era, silicon carbide has a series of excellent physical and chemical properties, such as excellent mechanical properties, high thermal conductivity, small thermal expansion coefficient, stable chemical inertness, low oxidation rate, high breakdown field strength and can be used as a reinforcing material. Silicon carbide has great application prospects in fields such as structural materials, film coatings, catalysts, high-power devices, etc. There are many methods for preparing silicon carbide particles, but many methods such as carbon thermal reduction and chemical vapor deposition are often accompanied by problems such as harsh reaction conditions, complex processes, high costs or long preparation cycles, which limit their application in actual preparation and cannot meet the requirements of modern society for the preparation of silicon carbide materials. Therefore, it is necessary to use a simple method that does not require complex conditions, has a shorter cycle, and is economical and practical to prepare silicon carbide materials.

[0003] Flash Joule heating is an emerging material preparation method with the advantages of simple process, short cycle and low cost. It is currently mainly used in the field of efficient preparation of graphene. The voltage stored in the capacitor of the device can be prepared in less than one second, which is a high efficiency that all other silicon carbide preparation methods do not have. The method has a wide range of optional raw materials, low material and equipment costs, and has good flexibility and economy. Summary of the Invention

[0004] In response to the above problems, the present invention provides a method for rapidly preparing silicon carbide particles based on a flash Joule heating process. By simply solid-phase mixing the raw materials and loading them into a customized quartz tube, which is then clamped and placed on the base of the equipment, silicon carbide particles can be prepared in less than one second. This method has the characteristics of short preparation cycle, low process cost, and simple process steps, and can well make up for the shortcomings of many current silicon carbide preparation technologies.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows: This solution provides a method for preparing silicon carbide particles based on a flash Joule heating process, comprising the following steps: Step (1): After weighing the raw materials (which may be Si powder and conductive carbon black) in a mass ratio of 1:1 (with excess carbon component), the raw materials can be mixed and ground evenly in a mortar or fully mixed in a ball mill; Step (2): The mixed raw materials are loaded into a custom quartz tube (6 mm or 12 mm in diameter) and graphite electrodes / copper electrodes of the same diameter are placed at both ends to complete the loading; Step (3): Place the quartz tube containing the raw materials on the base of the equipment, adjust the sample resistance to 1-3Ω (the resistance may vary depending on the carbon source) by controlling the pressure of the electrodes on both sides of the quartz tube, place it in the reactor, connect the positive and negative electrodes, and evacuate the reactor; Step (4): Charge the flash Joule heating device to a set voltage of 150 V, set the voltage application time to 400 ms, and perform a flash discharge operation on the sample to complete the reaction; Step (5): After waiting for the discharge in step (4) to be completed and cooled, the product in the quartz tube is taken out; at this time, the main components of the product are silicon carbide and graphene, and the product is calcined at 800°C in air to remove the graphene in the product to obtain pure phase silicon carbide.

[0006] Furthermore, the silicon-containing raw materials used in step (1) of the present method include but are not limited to Si powder, SiO2 powder, SiO powder, silicon-containing industrial waste, etc.; the carbon-containing raw materials include but are not limited to carbon black, graphite, porous carbon biochar, industrial carbon-containing waste, etc.

[0007] Furthermore, the sizes of the customized reaction quartz tube in step (2) of the present method include but are not limited to 6 mm and 12 mm, which can be selected according to the volume of the raw materials.

[0008] Furthermore, in step (4) of the present method, the discharge voltage parameter can be 100-180 V, preferably 150 V, and the discharge time can be 300-1000 ms, preferably 400 ms.

[0009] Furthermore, the purification calcination parameters in step (5) of this method are 800° C. and 30 min.

[0010] In summary, the present invention has the following advantages: The present invention provides a method for rapidly preparing silicon carbide particles based on a flash Joule heating process. By using low-cost flash Joule heating equipment, silicon carbide particles can be prepared in less than one second without the need for pretreatment, catalyst, template, or cooling time, and the process steps are very simple.

[0011] The flash Joule heating process used in the present invention has strong scalability. Industrial-scale production can be achieved by modifying the sampling method or expanding the size of the quartz tube. At the same time, the choice of raw materials is diverse, and cheap industrial waste can be used for preparation, which greatly reduces costs and has environmental significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The following is a simple flow chart of a method for rapidly preparing silicon carbide particles based on a flash Joule heating process; Figure 2 This is the circuit schematic diagram of the flash heat device; Figure 3 This is the TEM image of the silicon carbide particles obtained in Example 1; Figure 4 HRTEM image of silicon carbide particles obtained in Example 1 (measured as SiC by interplanar spacing) DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, rather than all embodiments.

[0014] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the invention as claimed, but is merely intended to represent selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention. Example

[0015] This example provides a method for rapidly preparing silicon carbide particles based on a flash Joule heating process. Figure 1 As shown, the following steps are included: Step (1): weigh 20 mg of each of the raw materials (Si powder and conductive carbon black) in a mass ratio of 1:1 (with excess carbon component), and grind the raw materials in a mortar to mix them evenly and thoroughly; Step (2): The mixed raw materials were loaded into a custom quartz tube (6 mm in diameter) and copper electrodes of the same diameter were placed at both ends to complete the loading; Step (3): Place the quartz tube containing the raw materials on the base of the equipment, adjust the sample resistance to 1-3Ω by controlling the pressure of the electrodes on both sides of the quartz tube, place it in the reactor, connect the positive and negative electrodes, and evacuate the reactor; Step (4): Charge the flash Joule heating device to a set voltage of 150 V, set the voltage application time to 400 ms, and perform a flash discharge operation on the sample to complete the reaction; Step (5): After waiting for the discharge in step (4) to be completed and cooled, the product in the quartz tube is taken out; at this time, the main components of the product are silicon carbide and graphene, and the product is calcined at 800°C in air to remove the graphene in the product to obtain pure phase silicon carbide. Example

[0016] This example provides a method for rapidly preparing silicon carbide particles based on a flash Joule heating process. Figure 1 As shown, the following steps are included: Step (1): weigh 20 mg of each of the raw materials (SiO2 powder and conductive carbon black) in a mass ratio of 1:1 (with excess carbon component), and grind the raw materials in a mortar to mix them evenly and thoroughly; Step (2): The mixed raw materials were loaded into a custom quartz tube (6 mm in diameter) and copper electrodes of the same diameter were placed at both ends to complete the loading; Step (3): Place the quartz tube containing the raw materials on the base of the equipment, adjust the sample resistance to 1-3Ω by controlling the pressure of the electrodes on both sides of the quartz tube, place it in the reactor, connect the positive and negative electrodes, and evacuate the reactor; Step (4): Charge the flash Joule heating device to a set voltage of 150 V, set the voltage application time to 400 ms, and perform a flash discharge operation on the sample to complete the reaction; Step (5): After waiting for the discharge in step (4) to be completed and cooled, the product in the quartz tube is taken out; at this time, the main components of the product are silicon carbide and graphene, and the product is calcined at 800°C in air to remove the graphene in the product to obtain pure phase silicon carbide.

Claims

1. A method for rapidly preparing silicon carbide particles based on a flash Joule heating process, comprising the following steps from sample preparation before flash heating to the flash heating reaction: Step (1) Weigh a sample of a specified mass (the mass ratio of silicon source to carbon source is 1:1), put it into a mortar, mix it evenly, and grind it thoroughly or grind it using a ball mill; Step (2): The ground mixture from step (1) is placed into a quartz tube of customizable size, and copper electrodes are inserted into both sides of the quartz tube to apply a certain pressure to compact it; Step (3): Measure the resistance of the sample in the quartz tube obtained in step (2), adjust the pressure control resistance to 1-3Ω, place it in the reactor, connect the positive and negative ends of the electrodes, and evacuate the reactor; Step (4): charge the capacitor to the set voltage (150V) by controlling the switch according to the set voltage, modify the limited release time (400ms) of the set voltage through the software, release the voltage to the sample, and flash heat the sample; Step (5): After the voltage is released (if there is residual voltage, the residual voltage can be eliminated by using the discharge circuit), the resistance and length of the sample are measured after the sample cools down and the sample is removed from the quartz tube; the obtained product is then calcined at 800°C in air to remove excess crystalline carbon to obtain silicon carbide.

2. The method for preparing silicon carbide particles by flash Joule heating according to claim 1, wherein: The reference sizes of the quartz tubes used to load the raw materials are hollow quartz tubes with diameters of 6 mm and 12 mm.

3. The method for preparing silicon carbide particles by flash Joule heating according to claim 1, wherein: When the raw materials are loaded into the quartz tube and compressed and fixed, the resistance of the samples needs to be tested to the same level. The resistance before preparation varies according to different carbon sources. For example, if carbon black is used as the carbon source, the resistance is between 1 and 3 Ω.

4. The method for preparing silicon carbide particles by flash Joule heating according to claim 1, wherein: Conductive carbon sources that can be used as raw materials include: carbon black, graphite, porous carbon, and biochar.

5. The method for preparing silicon carbide particles by flash Joule heating according to claim 1, wherein: Silicon sources that can be used as raw materials include nano-silicon powder, nano-silicon dioxide powder, silicon-containing waste, and bio-silicon.

6. The method for preparing silicon carbide particles by flash Joule heating according to claim 1, wherein: The suitable voltage for preparing silicon carbide by the flash Joule heating process in step (4) varies depending on the different carbon raw materials. For example, when carbon black is used as the carbon source, the working voltage is between 120-150V. When porous carbon is used as the carbon source and silicon dioxide is used as the silicon source, the optimal working voltage is 150V.

7. The method for preparing silicon carbide particles by flash Joule heating according to claim 1, wherein: The voltage application time for preparing silicon carbide in step (4) can be modified according to different raw materials. For example, if carbon black is used as the carbon source, the voltage application time is set to 400ms.

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