Method for rapidly preparing nano boron carbide chopped whiskers

Abstract

The invention discloses a method for rapidly preparing nano boron carbide chopped whiskers. The method specifically comprises the following steps: 1) cleaning and drying materials; 2) preparing and spreading a sample; and 3) heating treatment and whisker preparation. Compared with the prior art, the method has the advantages that the boron powder and the graphite paper are used as raw materials to prepare the nano boron carbide chopped whiskers, the advantages of rapid temperature rise and heating, uniform sample temperature, simple and easy equipment operation and the like are realized through a Joule heating technology, and the nano boron carbide chopped whiskers are rapidly prepared. Boron powder is uniformly spread on the surface of graphite paper to increase the contact area of the two, so that the reaction is fully carried out; and the Joule heating technology has the characteristics of rapid heating and balanced heat preservation, and provides important guarantee for rapid preparation of the nano boron carbide chopped whiskers. The obtained nano boron carbide chopped whiskers are uniform in size, operation is easy and convenient, the technological process is short in time consumption and low in cost, and rapid preparation of the nano boron carbide chopped whiskers can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of nano material preparation, in particular to a method for rapidly preparing nano boron carbide chopped whiskers. Background Art

[0002] Boron carbide has a low density (2.52g / cm 3 ), high hardness (35-45GPa), high stiffness, high melting point, ultra-high wear resistance and impact resistance, etc., and has been applied to tanks, armor, anti-bullet and other fields. In addition, thanks to 10 B has a larger neutron absorption interface, which makes boron carbide widely used in the field of neutron shielding. Compared with particles, boron carbide whiskers have a higher specific surface area and stronger mechanical reinforcement effect, which can significantly improve the strength and toughness of composite materials; at the same time, whiskers can form an effective heat conduction path compared to particles, which can disperse heat more effectively, so they have better high temperature resistance than particles.

[0003] At present, the preparation methods of boron carbide chopped fibers mainly include chemical vapor deposition (CVD), sol-gel method, melt spinning method and gas phase reduction method. Among them, the chemical vapor deposition method can achieve high-quality and precise fiber preparation by using borane (such as B2H6) and hydrocarbon gas (such as CH4) or other carbon source gas, but its preparation cycle is long, usually taking several hours to several days. The sol-gel method forms a precursor by spinning or stretching, and performs high-temperature carbonization, the cycle is as long as several days to a week, and the process is difficult to accurately control. Although the melt spinning method has a shorter cycle, it has high requirements for equipment, which limits its wide application. The gas phase reduction method also faces a long preparation cycle, which usually takes several days. Although boron carbide chopped fibers have outstanding performance in enhancing the mechanical properties and high temperature resistance of composite materials, the long cycle and high cost requirements in the preparation process limit its application. In principle, the gas-liquid-solid growth method is used to prepare chopped fibers, which requires reliance on catalysts. This not only increases the preparation cycle, but also introduces impurities, reduces product purity, and increases subsequent purification processes, which also increases the preparation cycle and cost.

[0004] Therefore, there is an urgent need to develop a faster method for preparing boron carbide chopped fibers. Summary of the invention

[0005] In order to solve the problems of complicated process, long production cycle and high cost in the existing preparation of nano boron carbide, the present invention provides a method for preparing nano boron carbide chopped whiskers by rapid heating without using a catalyst through Joule heating technology. This method is different from the gas-liquid-solid reaction principle of using catalyst to synthesize materials, which not only saves time but also reduces the cost of raw materials.

[0006] The present invention adopts the following technical solutions to achieve the above-mentioned purpose:

[0007] A method for rapidly preparing nano boron carbide chopped whiskers comprises the following steps:

[0008] 1) Material cleaning and drying: After the boron powder and graphite paper are cleaned with alcohol solvent, they are placed in a drying oven for drying;

[0009] 2) Sample preparation and spreading: Spread the boron powder evenly on the surface of the dried graphite paper;

[0010] 3) Heating treatment and whisker preparation: The above samples are loaded into a carbon carrier, and the carbon carrier is placed on the sample holder of the Joule heating device. The electrodes are connected to form a loop, and then the air compressor power is turned on to evacuate the device to a low vacuum state. Then, the protective gas is filled into the sample chamber to a certain pressure, and then the device power is started. The target temperature, insulation time and number of cycles are set, and voltage is applied for heating. After the program is finished and cooled to room temperature, nano boron carbide chopped whiskers can be obtained.

[0011] As a preferred solution, the boron powder in step 1) is at least one of industrial boron powder, high-purity boron powder and amorphous boron powder, and has an average particle size of 1 μm to 5 μm.

[0012] As a preferred solution, the graphite paper in step 1) has a thickness of 0.01 mm to 0.1 mm.

[0013] As a preferred embodiment, the molar ratio of the boron powder to the graphite paper in step 2) is (2-4):1.

[0014] As a preferred embodiment, the protective gas in step 3) is at least one of nitrogen or argon.

[0015] As a preferred solution, the pressure of the protective gas filled in step 3) is 10 2 ~10 4 Pa.

[0016] As a preferred solution, the heating temperature in step 3) is 1200-1500°C.

[0017] As a preferred solution, the holding time in step 3) is 60 to 100 seconds.

[0018] As a preferred embodiment, the number of cycles in step 3) is 3 to 6 times.

[0019] As a preferred solution, the temperature difference between adjacent cycles in step 3) is 100-150°C.

[0020] The advantages of the present invention compared with the prior art are: the present invention uses boron powder and graphite paper as raw materials to prepare nano-boron carbide chopped whiskers, and achieves the advantages of rapid heating, uniform sample temperature, simple and easy equipment operation through Joule heating technology, thereby realizing rapid preparation of nano-boron carbide chopped whiskers. The boron powder is evenly spread on the surface of graphite paper to increase the contact area between the two, so that the reaction can proceed fully; and the rapid heating and balanced heat preservation characteristics of Joule heating technology provide important guarantees for the rapid preparation of nano-boron carbide chopped whiskers. The nano-boron carbide chopped whiskers obtained by the present invention are uniform in size, easy to operate, short in process time, and low in cost, and can realize the rapid preparation of nano-boron carbide chopped whiskers. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a low-magnification scanning image of the chopped nano boron carbide whiskers obtained in Example 1.

[0022] Figure 2 This is a scanning image of the chopped nano boron carbide whiskers obtained in Example 2.

[0023] Figure 3 This is a high-magnification scanning image of the nano-boron carbide chopped whiskers obtained in Example 2. DETAILED DESCRIPTION

[0024] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0025] A method for rapidly preparing nano boron carbide chopped whiskers of the present invention is carried out according to the following steps:

[0026] 1. Clean the boron powder and graphite paper with alcohol solvent respectively, and place them in a drying oven for drying.

[0027] The boron powder is one or any combination of industrial boron powder, high-purity boron powder and amorphous boron powder, and the average particle size is 1 μm to 5 μm.

[0028] The thickness of graphite paper is 0.01mm~0.1mm.

[0029] 2. Evenly spread the boron powder obtained in step 1 on the surface of the graphite paper obtained in step 1, and the molar ratio of the boron powder to the graphite paper is (2-4):1.

[0030] 3. Load the sample obtained in step 2 into the carbon carrier, and place the carbon carrier on the sample holder of the Joule heating device, connect the electrodes to form a loop, then turn on the air compressor power to pump the device to a low vacuum state, and then fill the sample chamber with protective gas to a certain pressure of 10 2 ~10 4Pa, then start the power supply of the equipment, set the target temperature to 1200-1500°C, the holding time to 60-100s and the number of cycles to 3-6 times, start applying voltage for heating, and wait for the program to finish running and cool to room temperature to obtain nano boron carbide chopped whiskers.

[0031] Embodiment 1:

[0032] 1. Wash the boron powder with an average particle size of 1 μm and the graphite paper with a thickness of 0.1 mm with an alcohol solvent respectively, and place them in a drying oven for drying;

[0033] 2. evenly spread the boron powder obtained in step 1 on the surface of the graphite paper obtained in step 1, and the molar ratio of the boron powder to the graphite paper is 2:1;

[0034] 3. Load the sample obtained in step 2 into the carbon carrier, and place the carbon carrier on the sample holder of the Joule heating device, connect the electrodes to form a loop, then turn on the air compressor power to pump the device to a low vacuum state, and then fill the sample chamber with nitrogen to a pressure of 10 2 Pa, then start the power of the equipment, set the target temperature to 1500℃ and the holding time to 60s, which is the first cycle; set the target temperature to 1400℃ and the holding time to 70s, which is the second cycle, the number of cycles is 4, start to apply voltage for heating, wait for the program to run and cool to room temperature, and then you can get nano boron carbide chopped whiskers.

[0035] Embodiment 2:

[0036] 1. Wash the boron powder with an average particle size of 5 μm and the graphite paper with a thickness of 0.01 mm with an alcohol solvent respectively, and place them in a drying box for drying;

[0037] 2. evenly spread the boron powder obtained in step 1 on the surface of the graphite paper obtained in step 1, and the molar ratio of the boron powder to the graphite paper is 4:1;

[0038] 3. Load the sample obtained in step 2 into the carbon carrier, and place the carbon carrier on the sample holder of the Joule heating device, connect the electrodes to form a loop, then turn on the air compressor power to pump the device to a low vacuum state, and then fill the sample chamber with nitrogen to a pressure of 10 4 Pa, then start the power of the equipment, set the target temperature to 1200℃ and the holding time to 100s, which is the first cycle; set the target temperature to 1500℃ and the holding time to 60s, which is the second cycle, the number of cycles is 2, start to apply voltage for heating, wait for the program to run and cool to room temperature, and then you can get nano boron carbide chopped whiskers.

[0039] Embodiment 3:

[0040] 1. Wash the boron powder with an average particle size of 3 μm and the graphite paper with a thickness of 0.05 mm with alcohol solvent respectively, and place them in a drying box for drying;

[0041] 2. evenly spread the boron powder obtained in step 1 on the surface of the graphite paper obtained in step 1, and the molar ratio of the boron powder to the graphite paper is 3:1;

[0042] 3. Load the sample obtained in step 2 into the carbon carrier, and place the carbon carrier on the sample holder of the Joule heating device, connect the electrodes to form a loop, then turn on the air compressor power to pump the device to a low vacuum state, and then fill the sample chamber with nitrogen to a pressure of 10 2 Pa, then start the power of the equipment, set the target temperature to 1300℃ and the holding time to 80s, which is the first cycle; set the target temperature to 1400℃ and the holding time to 90s, which is the second cycle, and the number of cycles is 3. Start applying voltage for heating, and wait for the program to end and cool to room temperature to obtain nano boron carbide chopped whiskers.

[0043] Embodiment 4:

[0044] 1. Wash the boron powder with an average particle size of 2 μm and the graphite paper with a thickness of 0.08 mm with alcohol solvent respectively, and place them in a drying box for drying;

[0045] 2. evenly spread the boron powder obtained in step 1 on the surface of the graphite paper obtained in step 1, and the molar ratio of the boron powder to the graphite paper is 2:1;

[0046] 3. Load the sample obtained in step 2 into the carbon carrier, and place the carbon carrier on the sample holder of the Joule heating device, connect the electrodes to form a loop, then turn on the air compressor to pump the device to a low vacuum state, and then fill the sample chamber with argon gas to a pressure of 10 3 Pa, then start the power of the equipment, set the target temperature to 1300℃ and the holding time to 70s, which is the first cycle; set the target temperature to 1500℃ and the holding time to 60s, which is the second cycle, the number of cycles is 2, start to apply voltage for heating, wait for the program to finish running and cool to room temperature, then you can get nano boron carbide chopped whiskers.

[0047] The boron carbide chopped whiskers obtained in the present invention have regular shapes, smooth surfaces, and uniform diameter distribution. The morphology of the nano boron carbide chopped whiskers obtained in Example 1 is as follows: Figure 1 As shown. Figure 1 It can be seen that the particle diameter is distributed between 500 and 800 nm; the morphology of the nano boron carbide chopped whiskers obtained in Example 2 is as follows Figure 2 As shown. Figure 2 It can be seen that the particle diameter is distributed between 0.7 and 1.2 μm. Figure 3It can be seen from the high-magnification scanning electron microscope photos that the obtained boron carbide chopped whiskers have typical hexagonal crystal characteristics.

[0048] 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 steps and operating conditions are 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 structural methods and embodiments similar to the technical solution, which should all fall within the protection scope of the present invention.

Claims

1. A method for rapidly preparing chopped nano boron carbide whiskers, characterized in that: The specific steps include: 1) Material cleaning and drying: After the boron powder and graphite paper are cleaned with alcohol solvent, they are placed in a drying oven for drying; 2) Sample preparation and spreading: Spread the boron powder evenly on the surface of the dried graphite paper; 3) Heating treatment and whisker preparation: The above samples are loaded into a carbon carrier, and the carbon carrier is placed on the sample holder of the Joule heating device. The electrodes are connected to form a loop, and then the air compressor power is turned on to evacuate the device to a low vacuum state. Then, the protective gas is filled into the sample chamber to a certain pressure, and then the device power is started. The target temperature, insulation time and number of cycles are set, and voltage is applied for heating. After the program is finished and cooled to room temperature, nano boron carbide chopped whiskers can be obtained.

2. A method for rapidly preparing chopped nano boron carbide whiskers according to claim 1, characterized in that: The boron powder in step 1) is at least one of industrial boron powder, high-purity boron powder and amorphous boron powder, and has an average particle size of 1 μm to 5 μm.

3. The method for rapidly preparing chopped nano boron carbide whiskers according to claim 1, characterized in that: The thickness of the graphite paper in step 1) is 0.01 mm to 0.1 mm.

4. The method for rapidly preparing chopped nano boron carbide whiskers according to claim 1, characterized in that: The molar ratio of the boron powder to the graphite paper in step 2) is (2-4):

1.

5. The method for rapidly preparing chopped nano boron carbide whiskers according to claim 1, characterized in that: The protective gas in step 3) is at least one of nitrogen or argon.

6. The method for rapidly preparing chopped nano boron carbide whiskers according to claim 1, characterized in that: The pressure of the protective gas filled in step 3) is 10 2 ~10 4 Pa.

7. The method for rapidly preparing chopped nano boron carbide whiskers according to claim 1, characterized in that: In step 3), the heating temperature is 1200-1500°C.

8. The method for rapidly preparing chopped nano boron carbide whiskers according to claim 1, characterized in that: In step 3), the heat preservation time is 60 to 100 seconds.

9. The method for rapidly preparing chopped nano boron carbide whiskers according to claim 1, characterized in that: The number of cycles in step 3) is 3 to 6 times.

10. The method for rapidly preparing chopped nano boron carbide whiskers according to claim 1, characterized in that: The temperature difference between adjacent cycles in step 3) is 100-150°C.

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