فایل ورد کامل اثر فلزات کاتالیزوری برای سنتز مواد نانو فولرن BN

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تعداد صفحات این فایل: ۹ صفحه

بخشی از مقاله انگلیسیعنوان انگلیسی:Effects of catalytic metals for synthesis of BN fullerene nanomaterials~~en~~

Abstract

Boron nitride (BN) fullerene nanomaterials were synthesized by an arc-melting method from Al/B, TiB2, VB2, Ga/B, YB6, YB6/Ni, NbB2 powder in N2/Ar mixture gas, and various structures were confirmed by high-resolution electron microscopy. From comparing of formation enthalpy with nitrogen and boron, tendency of catalysis metal for BN nanotube was characterized, which is a useful guideline for synthesis of BN fullerene nanomaterials.

۱ Introduction

Carbon nanocage structures, such as fullerene clusters, nanotube, nanocapsules, nanopolyhedra, cones, cubes and onions, have great potential for studying nanomaterials of low dimensions in an isolated environment w1–۶x. Recently, boron nitride (BN) nanotubes and nanocapsules have also been synthesized by an arcdischarge method using boride-based rods such as HfBand ZrB 2 2 w7,8x. The properties of BN fullerene nanomaterials would be better than those of carbon fullerene nanomaterials, from the viewpoint of wide band gap and heating resistance in air w5,9–۱۱x. However, it is difficult to produce the BN fullerene nanomaterials with the ordinary arc-discharge method because of the difficulty in the control of arc conditions.

Recently, BN nanocapsules, nanocages and nanotubes have been produced successfully by an arc-melting method from boron and metal powder compacts in a nitrogenyargon gas atmosphere w5,11–۱۴x. These nanomaterials are expected as gas storage materials, single-electron transistors and magnetic refrigeration. However, the yield for BN fullerene nanomaterials by this method is very small. Therefore, it is necessary to investigate catalytic element and to develop new process such as chemical reaction w15–۲۰x.

The purpose of the present work was to investigate effects of catalytic metals for synthesis of BN fullerene nanomaterials. It would be a useful guideline for synthesis of BN fullerene nanomaterials, such as nanocapsule, nanocage and nanotube. To investigate effects of catalytic metals, MgB, AlyB , TiB , VB , GayB , YB , 2 22 6 YB6 2 yNi, NbBpowders are used as starting materials for arc-melting in a nitrogenyargon gas atmosphere. Since these compounds and mixture powders have good conductivity, easier arc-melting is expected. Especially, boride compounds have good conductivity as well as metal, though only boron powder is difficult to start arc-discharge. Then, since niobium (Nb) and yttrium (Y) easily react to nitrogen than boron, these metals would enhance the reaction of boron and nitrogen. In addition, Y and YyNi metal had been reported to show excellent catalytic properties for producing single-walled carbon nanotubes w21x. To confirm the formation of BN fullerene nanomaterials, high-resolution electron microscopy (HREM) and electron dispersive X-ray spectroscopy were carried out. These studies will give us useful guideline for the selection of catalysis metal of BN fullerene nanomaterials.

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