A method for preparing SiC nanowires using lignite and its application

Abstract

A method and application of preparing SiC nanowires using lignite, which relates to a method and application of preparing SiC nanowires. The present invention aims to solve the problems of high cost and complicated operation of existing pure phase SiC nanowire synthesis methods. Preparation method: 1. ball milling and mixing silicon powder and quartz sand and sieving; 2. placing the mixture of silicon powder and quartz sand in a graphite crucible and covering it with a cover plate; 3. high temperature reaction. The present invention is used for preparing SiC nanowires using lignite and its application.

Description

Technical Field

[0001] The invention relates to a method for preparing SiC nanowires and application thereof. Background Art

[0002] As an important nanomaterial, silicon carbide nanowires (SiC nanowires) have attracted great attention from the scientific and industrial communities due to their excellent physical and chemical properties and broad application prospects. For example, they exhibit special properties that are different from their macroscopic morphology in terms of crystal structure, electron transport, and optical properties.

[0003] In recent years, with the continuous progress in the fields of nanotechnology and material chemistry, researchers have begun to explore various new synthesis methods, such as sol-gel method, vapor deposition method, hydrothermal synthesis method, etc., to achieve precise control and large-scale production of SiC nanowire synthesis process. However, the traditional pure phase SiC nanowire synthesis method often has problems such as high cost, complex operation, etc., which limits its application in industrial production. Summary of the invention

[0004] The present invention aims to solve the problems of high cost and complicated operation in the existing pure phase SiC nanowire synthesis method, and provides a method and application of preparing SiC nanowires by using lignite.

[0005] A method for preparing SiC nanowires using lignite is completed by the following steps:

[0006] 1. ball-milling and mixing silicon powder and quartz sand, and sieving to obtain a mixture of silicon powder and quartz sand;

[0007] The molar ratio of silicon powder to quartz sand is 1:(0.5-1.5);

[0008] 2. placing a mixture of silicon powder and quartz sand in a graphite crucible and covering it with a cover plate to obtain a graphite crucible containing the mixture;

[0009] 3. Place the graphite crucible containing the mixture in a corundum crucible, add lignite into the corundum crucible and completely cover the graphite crucible, and finally react at a temperature of 1200°C to 1600°C in an air atmosphere to obtain SiC nanowires on the lower surface of the graphite crucible cover.

[0010] The application of SiC nanowires is used in the preparation of microwave absorbing materials.

[0011] The beneficial effects of the present invention are:

[0012] 1. The present invention makes efficient use of the cheap coal resource of lignite, which not only finds a high value-added utilization direction for lignite, but also reduces the preparation requirements of SiC nanowires and reduces the cost of raw materials.

[0013] 2. The present invention mixes silicon powder and quartz sand thoroughly and evenly and puts them into a graphite crucible, then puts the graphite crucible into a corundum crucible, completely covers the graphite crucible with a sufficient amount of lignite and calcines them in a high-temperature furnace, thereby providing a method for preparing SiC nanowires with high efficiency, simplifying the traditional SiC nanowire preparation process, improving production efficiency, reducing production costs, and realizing low-cost preparation of pure phase nanowires.

[0014] 3. The SiC nanowires prepared by the present invention are pure phase, and the crystal phase of SiC is 3C-SiC. The SiC nanowires are mixed with paraffin wax in a mass ratio of 1:9, the effective wave absorption frequency band is 6GHz to 18GHz, and the minimum reflection loss is -59dB.

[0015] The invention is used for a method for preparing SiC nanowires by utilizing lignite and application thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the XRD pattern of SiC nanowires prepared in Example 1;

[0017] Figure 2 This is a scanning electron microscope image of SiC nanowires prepared in Example 1;

[0018] Figure 3 This is a diagram of the wave absorption performance of SiC nanowires prepared in Example 1. DETAILED DESCRIPTION

[0019] Specific implementation method 1: This implementation method is a method for preparing SiC nanowires using lignite, which is completed by the following steps:

[0020] 1. ball-milling and mixing silicon powder and quartz sand, and sieving to obtain a mixture of silicon powder and quartz sand;

[0021] The molar ratio of silicon powder to quartz sand is 1:(0.5-1.5);

[0022] 2. placing a mixture of silicon powder and quartz sand in a graphite crucible and covering it with a cover plate to obtain a graphite crucible containing the mixture;

[0023] 3. Place the graphite crucible containing the mixture in a corundum crucible, add lignite into the corundum crucible and completely cover the graphite crucible, and finally react at a temperature of 1200°C to 1600°C in an air atmosphere to obtain SiC nanowires on the lower surface of the graphite crucible cover.

[0024] Principle: This method uses lignite as a burning medium to react with air under high temperature conditions to obtain CO, which then reacts with the gas phase silicon source (SiO) formed at high temperature to obtain SiC nanowires in a low-cost manner. Specifically:

[0025] Since there is a gap between the graphite cover plate and the graphite crucible, the graphite crucible is the reaction area. CO (2C+O2=CO) generated after the lignite is oxidized enters the graphite crucible and reacts with SiO (Si+SiO2=2SiO) on the graphite cover plate.

[0026] The beneficial effects of this embodiment are:

[0027] 1. This embodiment makes efficient use of the cheap coal resource of lignite, which not only finds a high value-added utilization direction for lignite, but also reduces the preparation requirements of SiC nanowires and the cost of raw materials.

[0028] 2. In this embodiment, silicon powder and quartz sand are fully mixed and evenly placed in a graphite crucible, and then the graphite crucible is placed in a corundum crucible. The graphite crucible is completely covered with a sufficient amount of lignite and then calcined in a high-temperature furnace, providing a method for preparing SiC nanowires with high efficiency, simplifying the traditional SiC nanowire preparation process, improving production efficiency, reducing production costs, and realizing low-cost preparation of pure phase nanowires.

[0029] 3. The SiC nanowires prepared in this embodiment are pure phase, and the crystal phase of SiC is 3C-SiC. The SiC nanowires are mixed with paraffin in a mass ratio of 1:9. The effective absorption frequency band is 6 GHz to 18 GHz, and the minimum reflection loss is -59 dB.

[0030] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that the ball milling mixing described in step 1 is specifically performed at a rotation speed of 150 rpm to 500 rpm for 2 h to 10 h. The rest is the same as specific embodiment 1.

[0031] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the sieving process described in step 1 is specifically through a 60-300 mesh sieve. The rest is the same as specific implementation method 1 or 2.

[0032] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the high temperature reaction in step 3 is 0.5h to 10h. The rest is the same as specific embodiments 1 to 3.

[0033] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that a muffle furnace is used for high temperature reaction in step 3. The rest is the same as specific embodiments 1 to 4.

[0034] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that: in step 2, the mixture of silicon powder and quartz sand accounts for 5% to 30% of the volume of the graphite crucible; in step 3, the volume ratio of the graphite crucible to the corundum crucible is 1:(10 to 20). Others are the same as specific embodiments 1 to 5.

[0035] Specific embodiment 7: This embodiment is different from specific embodiments 1 to 6 in that the SiC nanowires prepared in step 3 are pure phase. The rest is the same as specific embodiments 1 to 6.

[0036] Specific embodiment 8: This embodiment is different from specific embodiments 1 to 7 in that the crystal phase of SiC in the SiC nanowires prepared in step 3 is 3C-SiC. Other aspects are the same as specific embodiments 1 to 7.

[0037] Specific implementation method 9: The application of SiC nanowires in this implementation method is used for the preparation of wave absorbing materials.

[0038] Specific embodiment 10: This embodiment differs from specific embodiment 9 in that SiC nanowires and paraffin are mixed at a mass ratio of 1:9, the effective wave absorption frequency band is 6 GHz to 18 GHz, and the minimum reflection loss is -59 dB. Other aspects are the same as specific embodiment 9.

[0039] The following examples are used to verify the beneficial effects of the present invention:

[0040] Embodiment 1:

[0041] A method for preparing SiC nanowires using lignite is completed by the following steps:

[0042] 1. Ball mill the silicon powder and quartz sand at a rotation speed of 300 rpm for 6 h, and then pass through a 60-mesh sieve to obtain a mixture of silicon powder and quartz sand;

[0043] The molar ratio of silicon powder to quartz sand is 1:1;

[0044] 2. placing a mixture of silicon powder and quartz sand in a graphite crucible and covering it with a cover plate to obtain a graphite crucible containing the mixture;

[0045] 3. Using a muffle furnace, place the graphite crucible containing the mixture in a corundum crucible, add lignite into the corundum crucible and completely cover the graphite crucible, and finally react at a high temperature of 1400°C in an air atmosphere for 2 hours to obtain SiC nanowires on the lower surface of the graphite crucible cover.

[0046] The lignite described in step one is selected from the lignite of Zhainoer Coal Industry, wherein the mass percentage of moisture in the lignite is 7.63%, the mass percentage of fixed carbon in the lignite is 67.86%, the mass percentage of volatile matter in the lignite is 12.63%, the mass percentage of ash in the lignite is 11.88%, the particle size is mainly concentrated in the range of 0.75 μm to 2.75 μm, and the average particle size is 1.75 μm; the silicon powder and quartz sand described in step one are commercially available silicon powder and quartz sand with a purity of 99%.

[0047] In step 2, the mixture of silicon powder and quartz sand accounts for 10% of the volume of the graphite crucible.

[0048] In step 3, the volume ratio of the graphite crucible to the corundum crucible is 1:10.

[0049] The SiC nanowires prepared in step 3 are pure phase.

[0050] Figure 1 This is the XRD spectrum of the SiC nanowire prepared in Example 1; it can be seen from the figure that the main crystalline phase of the SiC nanowire is 3C-SiC.

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

[0052] The SiC nanowires prepared in Example 1 and paraffin were mixed in a mass ratio of 1:9; Figure 3 This is a graph showing the wave absorption performance of the SiC nanowires prepared in Example 1. As can be seen from the graph, the SiC nanowires exhibit excellent wave absorption performance, almost covering 6 GHz to 18 GHz, and the minimum reflection loss can reach -59 dB.

Claims

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

1. ball-milling and mixing silicon powder and quartz sand, and sieving to obtain a mixture of silicon powder and quartz sand; The molar ratio of the silicon powder to the quartz sand is 1:(0.5-1.5); the purity of the silicon powder and the quartz sand is 99%; 2. placing a mixture of silicon powder and quartz sand in a graphite crucible and covering it with a cover plate to obtain a graphite crucible containing the mixture; The mixture of silicon powder and quartz sand accounts for 5% to 30% of the volume of the graphite crucible; 3. Placing the graphite crucible containing the mixture in a corundum crucible, adding lignite into the corundum crucible and completely covering the graphite crucible, and finally using a muffle furnace to react at a temperature of 1200°C to 1600°C in an air atmosphere to obtain SiC nanowires on the lower surface of the graphite crucible cover; The volume ratio of the graphite crucible to the corundum crucible is 1:(10-20); Lignite is used as a buried combustion medium to react with air under high temperature conditions to obtain CO. There is a gap between the graphite cover plate and the graphite crucible. The graphite crucible is the reaction area. The CO generated after the lignite is oxidized enters the graphite crucible and reacts with SiO on the graphite cover plate.

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

3. The method for preparing SiC nanowires using lignite according to claim 1, characterized in that The sieving process described in step 1 is specifically through a 60-mesh to 300-mesh sieve.

4. The method for preparing SiC nanowires using lignite according to claim 1, characterized in that In step 3, the high temperature reaction is carried out for 0.5h~10h.

5. The method for preparing SiC nanowires using lignite according to claim 1, characterized in that The SiC nanowires prepared in step 3 are pure phase.

6. The method for preparing SiC nanowires using lignite according to claim 1, characterized in that The crystal phase of SiC in the SiC nanowires prepared in step 3 is 3C-SiC.

7. The method for preparing SiC nanowires using lignite according to claim 1, characterized in that The lignite described in step 3 is lignite from Zainoer Coal Industry, in which the mass percentage of moisture in the lignite is 7.63%, the mass percentage of fixed carbon in the lignite is 67.86%, the mass percentage of volatile matter in the lignite is 12.63%, the mass percentage of ash in the lignite is 11.88%, the particle size is between 0.75 μm and 2.75 μm, and the average particle size is 1.75 μm.

8. Use of the SiC nanowires prepared as claimed in claim 1, characterized in that It is used in the preparation of microwave absorbing materials.

9. The use of SiC nanowires according to claim 8, characterized in that When SiC nanowires and paraffin are mixed in a mass ratio of 1:9, the effective absorption frequency band is 6GHz~18GHz, and the minimum reflection loss is -59dB.

Images