CN1587030A - Process for preparing boron nitride nano tube - Google Patents

Abstract

A new method for preparing boron nitride nanotubes involves inorganic nanomaterials. Boron oxide, boric acid and other boron-containing and non-toxic boron compounds are used as raw materials, first ball milled for a certain period of time, then heated to above 800°C under flowing ammonia or nitrogen, and kept for more than 0.5h. After cooling, take it out, wash the sample with dilute hydrochloric acid, distilled water and ethanol, and then dry it to obtain a white powder that is boron nitride nanotube. This method has simple process, mild conditions and easy mass production. The yield reaches more than 80%. The prepared boron nitride nanotube is a semiconductor, and can be used in nanoelectronic devices, nanostructure ceramic materials, hydrogen storage and oxidation-preventing coatings, propellant additives and composite flame retardancy, and has good application prospects.

Description

A New Method for Preparing Boron Nitride Nanotubes

technical field

The invention is a new method for preparing boron nitride nanotubes with high purity and high yield, and relates to inorganic nanometer materials.

Background technique

Boron nitride nanotubes are a very special nanotubular material. It has stable insulation, high thermal and chemical stability, and special mechanical and electrical properties. In recent years, the field of one-dimensional nanomaterials has received great attention. Electronic structure calculations show that boron nitride nanotubes are a semiconductor material with a fixed energy band width (5.5ev). Unlike carbon nanotubes, the banding does not depend on tube diameter, chirality, or nanotube wall number. Therefore, boron nitride nanotubes simplify the complexity of the energy bands of one-dimensional nanotubes, making it possible to manufacture nanoscale semiconductor elements, and provide an attractive prospect for the research and application of one-dimensional nanostructures. Boron nitride nanotubes can play their potential roles in nanoelectronic devices, nanostructured ceramic materials, hydrogen storage, and coating layers to prevent oxidation, and have good application prospects.

Preparation technology of boron nitride nanotubes. There are many reports now. The well-known preparation methods include arc discharge method, laser ablation method, arc melting method, chemical vapor deposition method and chemical method. Some of the above-mentioned methods need to be carried out under high temperature or high pressure conditions, and some are very difficult to control the reaction conditions, and usually obtain boron nitride nanotubes with dispersed structures, low yield and low purity. The application of boron nitride nanotubes is limited to a certain extent. Ball milling is a common method for preparing nanopowders, and nanocrystals, nanoparticles and nanocomposite components have been successfully prepared. During the ball milling process, due to the friction, collision and extrusion between the grinding body and the material, the structure of the material changes, such as internal stress, plastic deformation, defects and cracks. Since the structural changes of substances and chemical reactions are triggered by mechanical energy rather than thermal energy, chemical reactions can occur at room temperature and are non-equilibrium reactions. Compared with the above-mentioned arc discharge method and arc melting method, the ball milling method is carried out at room temperature, and the annealing temperature is low (<1500°C). However, it is rare to use this method to synthesize nanotubes. Ying Chen et al. ball milled B powder and boron nitride powder at room temperature, and then annealed them to obtain boron nitride nanotubes. Because the heat treatment was performed under flowing nitrogen, they obtained boron nitride nanotubes with low purity and low yield. In order to obtain high-yield boron nitride nanotubes, we adopt the ball milling method, using boron oxide, boric acid and other boron-containing and non-toxic boron compounds as raw materials, ball milling for a certain period of time, and then heat treatment under flowing ammonia gas , heating to a temperature above 800° C. and keeping it warm for a certain period of time. After cleaning, boron nitride nanotubes with high phase purity and high yield are obtained. The preparation method we adopt requires simple equipment, simple and easy process, low heat treatment temperature and high safety. Low cost, high yield, good purity, controllable growth, and mass production can be realized, so it is an ideal preparation method. Therefore, the present invention has great significance for the further extensive application of boron nitride nanotubes in the nanometer field.

Contents of the invention

The present invention is realized in the following way: first select boron-containing and non-toxic boron compounds such as boron oxide and boric acid as raw materials, first ball mill for more than 4 hours, then heat to above 800°C under flowing ammonia gas, and keep warm for more than 0.5 hours. After cooling, it is taken out, washed and dried to obtain a white powder that is boron nitride nanotube.

Description of drawings:

Accompanying drawing 1. the scanning electron microscope topography figure of prepared product, reflect the yield height of boron nitride nanotube in the product;

Accompanying drawing 2. the X-ray diffraction spectrogram of prepared product, proves that product is the boron nitride crystal of pure phase, hexagonal structure;

Accompanying drawing 3. transmission electron microscope photo of boron nitride nanotube with cylindrical shape;

Accompanying drawing 4. transmission electron microscope photograph of boron nitride nanotube of bamboo joint morphology;

Accompanying drawing 5. Selected area electron diffraction pattern photo, the boron nitride nanotube that illustrates preparation is single crystal structure;

Accompanying drawing 6. high-resolution electron microscope photo, reflect that the boron nitride nanotube has good crystallinity;

Accompanying drawing 7. Electron energy loss spectrogram, further proves that the composition of nanotube is boron nitride.

In conjunction with the accompanying drawings and specific implementation methods, it is explained as follows:

1. Using boron oxide, boric acid and other boron-containing and non-toxic boron compounds as raw materials, first ball mill for more than 4 hours.

2. The raw materials after ball milling are heated under flowing ammonia gas, and when the temperature reaches above 800°C, the constant temperature is kept for more than half an hour.

The invention obtains pure boron nitride nanotubes for the first time by heat-treating the ball-milled raw materials in flowing ammonia. The preparation process of the invention is simple, the reaction conditions are mild, and batch production can be realized. The key technology lies in:

1. Use suitable raw materials and ball mill for more than 4 hours.

2. The heat treatment is carried out in a flowing ammonia atmosphere, the heating temperature is above 800°C, and the holding time is above 0.5h;

The composition and structure of the prepared boron nitride nanotubes were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, selected area electron diffraction, high-resolution transmission electron microscopy, and energy loss spectroscopy. The results show that the prepared boron nitride nanotubes have good crystallinity, are single crystals with a pure phase hexagonal structure, and are in the shape of cylinders or bamboo joints. The smallest diameter is several nanometers, and the largest is about 200 nanometers. about 10 microns in length.

The invention has the advantages of simple required equipment, simple and easy process, low heat treatment temperature and high safety. Low cost, high output, good purity, and mass production can be realized, so it is an ideal preparation method. The invention provides further convenient conditions for the application of boron nitride nanotubes in related fields, and has great practical value.

Example

Embodiment 1: With the boron powder that purity is 99.8% as raw material, after ball milling for a certain period of time, feed flowing ammonia in the vacuum tube furnace for heating, the flow rate of ammonia is 100ml/min, and the speed of temperature rise is 10°C/min . When the temperature reaches 1000°C, keep at constant temperature for another 6 hours. Wash the sample several times with dilute hydrochloric acid, distilled water and ethanol, and dry it in a vacuum oven to obtain a white powder, which is the prepared boron nitride nanotubes with bamboo structure.

Embodiment 2: With the boron powder that purity is 99.8% as raw material, feed the ammonia gas of flowing in the vacuum tube furnace after ball milling for a certain period of time to heat, the flow velocity of ammonia gas is 100ml/min, the speed of heating up 10 ℃/min . When the temperature reaches 1200°C, keep at constant temperature for another 6 hours. A white powder is obtained, which is the prepared boron nitride nanotubes mainly having a cylindrical structure and a small amount of bamboo structure.

Example 3

A certain proportion of boron powder (purity 99.8%) and Fe ₂ O ₃ (analytical pure) are ball milled and then heated by flowing ammonia gas in a vacuum tube furnace. The flow rate of ammonia gas is 100ml/min, and the heating rate is 6- 10°C/min. When the temperature reaches 1300°C, keep at constant temperature for another 3 hours. Wash the sample several times with dilute hydrochloric acid, distilled water and ethanol, and dry it in a vacuum oven to obtain a white powder, which is the prepared boron nitride nanotube.

Example 4:

The mixture of a certain proportion of boric acid (purity 99.8%) and activated carbon will be heated in a vacuum tube furnace after ball milling with flowing ammonia. When the temperature reaches 1300°C, keep at constant temperature for more than 0.5h. Wash the sample with dilute hydrochloric acid, distilled water and ethanol, and dry it in a vacuum oven to obtain a white powder, which is the prepared boron nitride nanotube.

Example 5: A mixture of boron oxide and graphite in a certain proportion was ball-milled and heated in a vacuum tube furnace fed with flowing ammonia gas. The flow rate of ammonia gas was 100ml/min, and the heating rate was 7°C/min. When the temperature reaches 1200°C, keep at constant temperature for another 6 hours. Wash the sample several times with dilute hydrochloric acid, distilled water and ethanol, and dry it in a vacuum oven to obtain a white powder, which is the prepared boron nitride nanotube. The nanotube is composed of a bamboo structure with a diameter of 80-120 nanometers and small nanotubes with a diameter of several nanometers grown on and around the surface.

Example 6: A mixture of boron oxide and activated carbon in a certain proportion was ball-milled and heated in a vacuum tube furnace fed with flowing ammonia gas. The flow rate of ammonia gas was 100ml/min, and the heating rate was 7°C/min. When the temperature reaches 1200°C, keep at constant temperature for another 6 hours. Wash the sample several times with dilute hydrochloric acid, distilled water and ethanol, and dry it in a vacuum oven to obtain a white powder, which is the prepared boron nitride nanotube.

Claims (1)

1. the preparation method of a boron nitride nano-tube is characterized in that: select for use boron oxide, boric acid etc. to contain boron and avirulent boron compound is a raw material, more than the first ball milling 4h, be heated under the mobile ammonia more than 800 ℃ then, more than the insulation 0.5h.Take out the cooling back, through cleaning after drying, obtains white powder and be boron nitride nano-tube.

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