JP2004161546A - Processes for forming boron nitride precursor and for manufacturing boron nitride nanotube using boron nitride precursor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a highly pure boron nitride nanotube in a large amount. <P>SOLUTION: Boron is reacted with magnesium oxide at 1,000-2,100°C to form boron oxide (B<SB>2</SB>O<SB>2</SB>), which is a boron nitride precursor. The precursor is reacted with ammonia at 1,000-1,500°C. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The invention of this application relates to a method for forming a boron nitride precursor and a method for producing boron nitride nanotubes using the boron nitride precursor. More specifically, the invention of this application relates to a method for forming a boron nitride precursor and a method for producing a boron nitride nanotube using the boron nitride precursor, which enable mass production of high-purity boron nitride nanotubes. .
[0002]
[Prior art]
BACKGROUND ART Nanometer-sized carbon nanotubes in which carbon atoms are arranged in a tubular shape are known. The carbon nanotube is synthesized by an arc discharge method, a laser heating method, a chemical vapor deposition method, or the like.
[0003]
In recent years, it has been known that boron nitride nanotubes are also synthesized by a method similar to the above. For example, a method of synthesizing boron nitride nanotubes using nickel boride (NiB) as a catalyst and borazine as a precursor has been proposed (for example, see Non-Patent Document 1).
[0004]
[Non-patent document 1]
O. R. Lourie, et al., Chemical Material (Chem. Material.), 2000, Vol. 12, p. 1808
[0005]
[Problems to be solved by the invention]
Boron nitride is expected to be used as a material having unprecedented properties in semiconductor materials, emitter materials, heat-resistant filling materials, high-strength materials, catalysts, and the like.
[0006]
However, with the conventional production methods, the yield of boron nitride nanotubes is poor, and only a small amount can be synthesized, and impurities such as carbon are mixed, so that physical properties such as semiconductor characteristics and strength are measured. Cannot be performed sufficiently.
[0007]
The invention of this application has been made in view of such circumstances, and a method of forming a boron nitride precursor and nitriding using the boron nitride precursor capable of producing a large amount of high-purity boron nitride nanotubes. An object of the present invention is to provide a method for producing a boron nanotube.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the invention of this application is to react boron and magnesium oxide in a temperature range of 1000 ° C. to 2100 ° C. to form boron oxide (B ₂ O ₂ ) which is a boron nitride precursor. The present invention provides a method for forming a boron nitride precursor (claim 1).
[0009]
Regarding the invention according to claim 1, the invention of this application provides, as an embodiment, that the molar ratio of boron to magnesium oxide is 1: 1 (claim 2).
[0010]
Further, the invention of this application is characterized in that, after the boron nitride precursor according to claim 1 is obtained, the boron nitride precursor is subsequently reacted with ammonia in a temperature range of 1000 ° C. to 1500 ° C. ( Claim 3) is provided.
[0011]
With respect to the invention according to claim 3, the invention of this application provides, as an embodiment, a method of heating and removing a by-product by heating a product after completion of the reaction (claim 4).
[0012]
Hereinafter, the method for forming the boron nitride precursor of the present invention and the method for manufacturing boron nitride nanotubes using the boron nitride precursor will be described in more detail with reference to examples.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
In the method for producing boron nitride nanotubes according to the invention of the present application, boron and magnesium oxide are first reacted with each other to produce boron oxide nanotubes (B ₂ O ₂ ) Is formed. Specifically, a mixture of boron and magnesium oxide is put into a crucible made of boron nitride, and the crucible is heated to a high temperature in a high-frequency induction heating furnace. The temperature at this time is suitably in a temperature range of 1000 ° C. to 2100 ° C. If the temperature is lower than 1000 ° C., the reaction is slow, and if it exceeds 2100 ° C., energy is wasted. Preferably, it is a temperature range of 1100 ° C to 1800 ° C. The reaction produces gaseous boron oxide (B ₂ O ₂ ), which is a precursor of boron nitride, and vapor of metallic magnesium.
[0014]
Next, in the method for producing a boron nitride nanotube of the invention of the present application, the above product is moved to a reaction chamber by flowing an inert gas such as argon, and ammonia gas is introduced into the reaction chamber, and boron oxide ( B ₂ O ₂ ) is reacted with ammonia. The reaction temperature at this time is suitably from 1000 ° C to 1500 ° C. If the temperature is lower than 1000 ° C., the reaction is slow. If the temperature exceeds 1500 ° C., plate-like crystals of boron nitride are formed, and it is difficult to maintain the tubular shape. The reaction converts boron oxide (B ₂ O ₂ ) to boron nitride. When the by-products are evaporated and removed by heating sufficiently after the reaction, white boron nitride nanotubes are obtained.
[0015]
The resulting boron nitride nanotubes exhibit a mixed phase of hexagonal and rhombohedral systems, are free from impurities based on boron oxide and other raw materials, and are very high-purity crystals. Observation with a scanning electron microscope confirms that the nanotube is several nanometers to about 70 nanometers in diameter and about 10 micrometers in length.
[0016]
As described above, in the method of forming a boron nitride precursor and the method of manufacturing a boron nitride nanotube using the boron nitride precursor of the present invention, since a compound containing carbon is not used as a raw material, carbon is mixed as an impurity. There is no. In addition, high-purity boron nitride nanotubes are produced in large quantities. Furthermore, since an expensive transition metal is not used as a catalyst, the method for forming a boron nitride precursor of the present invention and the method for producing boron nitride nanotubes using the boron nitride precursor are economically advantageous.
[0017]
【Example】
A mixture of boron and magnesium oxide was placed in a boron nitride crucible at a molar ratio of 1: 1 and the crucible was heated to 1300 ° C. in a high frequency induction heating furnace. Boron and magnesium oxide reacted, and gaseous boron oxide (B ₂ O ₂ ) and magnesium vapor were generated. This product was transferred to the reaction chamber by argon gas, and the temperature was maintained at 1100 ° C. to introduce ammonia gas. The boron oxide and ammonia reacted to form boron nitride. 1.55 g of the mixture was heated sufficiently and the by-products evaporated to give 310 mg of a white solid from the walls of the reaction chamber. The conversion to boron nitride based on boron as the starting material was 40% or more.
[0018]
The crystal structure of the obtained boron nitride was a mixed phase of hexagonal and rhombohedral based on the X-ray diffraction pattern. From the X-ray diffraction pattern, there was no peak indicating the crystalline form of the raw material or the intermediate product during the reaction, and it was confirmed that the obtained boron nitride was a high-purity product.
[0019]
Further, the obtained boron nitride was observed with a scanning electron microscope and a transmission electron microscope. FIG. 1a is a scanning electron micrograph. Boron nitride has a one-dimensional nanostructure of several nanometers to about 70 nanometers in diameter and about 10 micrometers in length. Then, they are entangled with each other and have a curved shape. FIG. 1b is a transmission electron micrograph. A linear boron nitride nanotube having a diameter of 10 nanometers is confirmed.
[0020]
Of course, the invention of this application is not limited by the above embodiments and examples. It goes without saying that various aspects are possible for details such as reaction conditions.
[0021]
【The invention's effect】
As described in detail above, the invention of this application makes it possible to mass-produce high-purity boron nitride nanotubes.
[Brief description of the drawings]
1A and 1B are a scanning electron micrograph and a transmission electron micrograph of boron nitride obtained in an example, respectively.

Claims (4)

Boron and magnesium oxide were reacted at a temperature range of 1000 ° C. to 2100 ° C., the method of forming the boron nitride precursor, characterized in that to form the boron oxide is boron nitride precursor (B 2 _{O 2).} The method for forming a boron nitride precursor according to claim 1, wherein the molar ratio of boron to magnesium oxide is 1: 1. A method for producing boron nitride nanotubes, comprising, after the boron nitride precursor according to claim 1 is obtained, subsequently reacting with ammonia in a temperature range of 1000 ° C to 1500 ° C. The method for producing a boron nitride nanotube according to claim 3, wherein the by-product is evaporated and removed by heating the product after the reaction.

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