JP2004231442A - Boron nitride nanotube and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel boron nitride nanotube exhibiting flexibility and ductility. <P>SOLUTION: A carbon nanotube is reacted with boron nitride arranged on a titanium substrate having cobalt particles deposited thereon, at 1,500-2,500 K in a nitrogen atmosphere. The resultant product is heated at 1,700-2,500 K. Thus is obtained the boron nitride nanotube which has jointless penetration holes and a helical structure comprising connected conical shapes and exhibits flexibility and ductility. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The invention of this application relates to a boron nitride nanotube and a method for producing the same. More specifically, the invention of this application relates to a novel boron nitride nanotube exhibiting flexibility and ductility, and a method for producing the same.
[0002]
[Prior art]
Carbon and boron nitride nanotubes and nanofibers are known to have various forms such as jellyfish, spine, cedar leaf, knotty horsetail and bamboo. Above all, the bamboo-like or conical boron nitride nanotube has a structure in which the passage of the tube is closed at a node and the whole tube penetrates (for example, see Non-Patent Document 1).
[0003]
[Non-patent document 1]
Renzhi Ma et al. Am. Chem. Soc. , 2002, Vol. 124, No. 26, p. 7672
[0004]
[Problems to be solved by the invention]
Such a knotted boron nitride nanotube that does not penetrate the entire tube exhibits hard physical properties. This hard physical property is one of the properties of boron nitride nanotubes, and practical applications can be considered based on this property. However, considering a wide range of applications, other physical properties are also desired.
[0005]
The invention of this application has been made in view of such circumstances, and an object of the invention is to provide a novel boron nitride nanotube exhibiting flexibility and ductility and a method for producing the same.
[0006]
[Means for Solving the Problems]
The invention of this application solves the above-mentioned problem, and has a helical structure in which conical shapes are connected, a through hole without nodes, and exhibits flexibility and ductility. Item 1) is provided.
[0007]
In addition, the invention of this application is to react carbon nanotubes and boron oxide disposed on a titanium substrate on which cobalt particles are deposited in a nitrogen atmosphere at a temperature in the range of 1500 K to 2500 K, and then in a temperature range of 1700 K to 2500 K. The present invention provides a method for producing boron nitride nanotubes (claim 2), which comprises performing post-heating to produce the boron nitride nanotubes according to claim 1.
[0008]
Hereinafter, the boron nitride nanotubes of the present invention and the method for producing the same will be described in more detail with reference to examples.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The boron nitride nanotube of the invention of this application has a spiral structure in which conical shapes are connected and has a through-hole without nodes. Due to the absence of nodes in a single tube, the boron nitride nanotubes of the invention of this application exhibit flexibility and ductility not previously exhibited by inorganic materials. Further, since the through holes are provided, the filling of the tube with various substances is not hindered, and the entire tube can be filled with the substance.
[0010]
Such a boron nitride nanotube of the invention of this application is obtained by reacting a carbon nanotube with boron oxide disposed on a titanium substrate on which cobalt particles are deposited in a nitrogen atmosphere at a temperature range of 1500 K to 2500 K, It is obtained by performing post-heating in a temperature range of 〜2500 K.
[0011]
The weight ratio of carbon nanotubes to boron oxide is preferably in the range of 1: 5 to 1:15. This is because if the amount of boron oxide is less than 1: 5, the loss of carbon nanotubes increases, and if the amount of boron oxide is more than 1:15, the loss of boron oxide increases.
[0012]
If the reaction temperature is lower than 1500 K, the reaction rate becomes slow and the reaction does not proceed sufficiently. If the temperature exceeds 2500 K, the carbon nanotubes evaporate and escape quickly, and the yield of tubular boron nitride deteriorates. The reaction time is preferably in the range of 30 minutes to 2 hours. The reason is that if the reaction time is less than 30 minutes, it is difficult for the reaction to proceed sufficiently, and if it exceeds 2 hours, no particularly noticeable change is observed in the reaction.
[0013]
The post-heating is a step for removing carbon from the reaction product. If the temperature is lower than 1700K, the carbon remains, and even if the temperature exceeds 2500K, the effect of removing carbon is not significantly improved. The post-heating time is preferably in the range of 1 hour to 5 hours. If the time is less than 1 hour, the removal of carbon tends to be insufficient, and the removal effect is almost saturated in 5 hours.
[0014]
【Example】
First, multi-walled carbon nanotubes serving as templates used as starting materials were synthesized. A polished wafer made of stainless steel was used as a substrate, nitrogen gas (purity 99.999%) as a carrier gas, hydrogen gas (purity 99.999%) and methane gas (purity 99) as gases for generating carbon nanotubes. With the flow rate of hydrogen gas being 80 sccm and the flow rate of methane gas being 20 sccm, the reaction was carried out at a substrate temperature of 773 K by plasma CVD to deposit multi-walled carbon nanotubes on the substrate.
[0015]
Next, a boron oxide powder, which was disposed on a titanium substrate on which cobalt particles were deposited by sputtering, was reacted with the obtained multi-walled carbon nanotubes in a high-frequency induction heating furnace under a nitrogen atmosphere at 1973K for 30 minutes. At this time, the weight ratio between the carbon nanotubes and boron oxide was 1: 8.
[0016]
After completion of the reaction, post-heating was performed at 2073 K in a nitrogen atmosphere.
[0017]
As a result of observing the product using a scanning electron microscope, as shown in FIG. 1a, a helical fibrous substance having an average diameter of 100 nm and a length of 100 μm or more was obtained in high yield. From the scanning electron microscope image shown on the right side of FIG. 1a and the transmission electron microscope image shown in FIG. 1b, the product has a tubular shape with no-node through holes, and the thickness of the tube wall is reduced. It is confirmed to be 20 nm. Further, from FIG. 1b, it was confirmed that the tube wall was formed obliquely inclined with respect to the axis of the tube, and from the diffraction pattern shown on the left side of FIG. 1b, the tube was oriented in a conical shape. It is confirmed. Further, from the X-ray diffraction pattern and the result of the electron energy loss spectrum analysis shown in FIG. 2, the lattice constants are a = 0.2502 nm and c = 0.3333 nm, and the composition is composed of boron atoms and nitrogen atoms. Is confirmed.
[0018]
FIG. 3A is a transmission electron microscope image, and FIG. 3B is an enlarged image of a portion surrounded by a frame in FIG. 3A. When the portion indicated by the arrow in FIG. 3B was irradiated with an electron beam, it was observed that the portion was largely bent as shown in FIG. 3C. FIG. 3d is an enlarged image showing the cross-sectional shape, but the tube is bent 180 °. FIG. 3E is an image when the irradiation position of the electron beam is shifted. The bend is even greater, but not broken.
[0019]
FIG. 3F is a transmission electron microscope image when the intensity of the electron beam is reduced, and FIG. 3G is an enlarged image of a portion surrounded by a frame in the drawing. As can be seen from FIGS. 3f and 3g, the bending was reduced, and the bending was restored to the same degree as the images shown in FIGS. 3a and 3b.
[0020]
3B and 3G show the diffraction patterns before and after the irradiation of the electron beam, respectively. Before the irradiation of the electron beam, the tip angle of the cone is 52 °, and after the irradiation, 35 °. This indicates that the tube was elongated by the irradiation of the electron beam.
[0021]
As is clear from the above, the boron nitride nanotube of the invention of this application exhibits flexibility and ductility. The disadvantage of inorganic materials is that they are brittle, but the boron nitride nanotubes of the present invention exhibiting flexibility and ductility can be said to be extremely innovative in that sense.
[0022]
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 the details.
[0023]
【The invention's effect】
As described in detail above, the invention of this application provides a novel boron nitride nanotube exhibiting flexibility and ductility. The boron nitride nanotube of the invention of this application is expected to be applied to a wide range of applications as microelectronic components, hydrogen storage materials, optoelectronic components, reinforcing materials for composite materials, tube materials containing various substances, and the like.
[Brief description of the drawings]
FIGS. 1a and 1b are a scanning electron microscope image and a magnified image thereof, a transmission electron microscope image and a diffraction pattern of a product obtained in an example, respectively.
FIG. 2 is an electron energy loss spectrum analysis diagram of a product obtained in an example.
FIGS. 3A, 3B, 3C, 3D, 3F, and 3G are images of a transmission electron microscope, and the inset in the figure is a diffraction pattern.

Claims (2)

A boron nitride nanotube which has a spiral structure in which conical shapes are connected, has a knotless through-hole, and exhibits flexibility and ductility. The carbon nanotubes and boron oxide disposed on a titanium substrate on which cobalt particles are deposited are reacted in a nitrogen atmosphere at a temperature in the range of 1500 K to 2500 K, and then post-heated in a temperature range of 1700 K to 2500 K. 2. A method for producing a boron nitride nanotube, comprising producing the boron nitride nanotube according to 1.

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