Catalyst-Free Synthesis of Single-Wall Boron Nitride Nanotubes via Laser Ablation
- PDF / 2,919,281 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 81 Downloads / 176 Views
Catalyst-Free Synthesis of Single-Wall Boron Nitride Nanotubes via Laser Ablation Roland S. Lee1, Julie Gavillet1, Marc Lamy de la Chapelle1, Jean-Lou Cochon2, Daniel Pigache2, Jany Thibault3, François Willaime4 and Annick Loiseau1 1 LEM, CNRS-ONERA (UMR104), Chatillon Cedex, FRANCE 2 ONERA, Palaiseau Cedex, France 3 SP2M: DRFMC, CENG, 85X, Grenoble Cedex, France 4 SRMP, CEA Saclay, Gif sur Yvette Cedex ABSTRACT Boron nitride nanotubes (BN-NTs) were synthesized in “mass” quantities (~0.6 g/h) using a continuous CO2 laser ablation reactor described in the literature [1]. High-resolution electron microscopy (HRTEM) analyses have shown the nanotubes to be organized in “ropes” comprising ~10 tubes. Analysis of HRTEM images indicate that the majority of the tubes are zig-zag. The chemical composition of the tubes was confirmed using electron energy loss spectroscopy (EELS) analysis, which also determined that nanoparticles terminating tube ends were composed of pure boron covered by BN fullerene-like “cages”. The growth mechanism of the nanotubes seems to be “root-based” with tubes growing from boron nanoparticles dispersed throughout the samples; the non-particle-terminated ends of the tubes exhibit flat “caps” characteristic of BN-NTs [2].
INTRODUCTION Boron nitride nanotubes (BN-NTs) have attracted considerable interest due to their unique physical properties which make them a possible alternative to their carbon brethren in regards to possible applications; although they share the same theoretically outstanding mechanical properties (elastic modulus ~1.2 TPa [3]), their electronic properties are very different, with all the tubes being wide gap semiconductors [4], in stark contrast to carbon nanotubes, which behave as either metals or semiconductors depending on their helicity [5]. However, careful study of BN-NTs has been stymied by the paucity of material produced by various synthesis methods, i.e. laser ablation, electric arc discharge, etc., which has prevented the realization of certain experiments [2, 6-7]. In this study, we present the results of laser ablation synthesis of BN-NTs in which we have succeeded in producing boron nitride single-wall nanotubes (BN-SWNTs) organized in long (~100 nm) “ropes”, in bulk quantities (rate of production ~0.6 g/h), without using a catalyst.
EXPERIMENTAL DETAILS Cylindrical boron nitride targets (diameter ~6.5 mm) were ablated using a CO2 laser (~7 mm diameter beam, ~1000 W) in a reaction chamber [1] under a 1 bar nitrogen atmosphere. A 100 ml/s nitrogen flow carried the ablated material from the summit of the target out of the reaction chamber where it was later recovered in a trap or a filter, located further “downstream” from the trap. The average temperature of the target during the reaction, measured via optical pyrometry, was ~3400 K. As the target was consumed, its elevation was manually adjusted in A15.3.1
order to maximize the flux of ablated material observed in a pyrex cylinder located “upstream” from the trap. After the reaction, the recovered material was so
Data Loading...
