Electromagnetic response of individual boron nitride nanotubes (BNNTs) has been studied by spatially resolved electron energy loss spectroscopy (EELS). We demonstrate how dedicated EELS methods using subnanometer electron probes permit the analysis of local dielectric properties of a material on a nanometer scale. The continuum dielectric model has been used to analyze the low-loss EEL spectra recorded from these tubes. Using this model, we demonstrate the weak influence of the out-of-plane contribution to the dielectric response of BNNTs. The optical gap, which can be deduced from the measurements, is found to be equal to 5.8 ± 0.2 eV, which is close to that of the hexagonal boron nitride. This value is found to be independent of the nanotubes configuration (diameter, helicity, number of walls, and interaction between the different walls).

We report here on the catalyst features found critical in order to induce the growth of matchstick nanotubes by a sequential catalytic growth mechanism. The presence of phosphorus is required to form metal phosphide particles active for the formation of carbon nanotubes with a matchstick morphology. The metal composition does not influence the nanofilament type but strongly affect the nanotube yield. Original properties of these new periodic nanostructures are also highlighted, such as the preferential breaking at the thin nanomatch interjunctions, giving rise to individual nanomatches in suspension after ultrasonic treatment. The possibility to use this mechanism to insert carbon nanotubes with ferromagnetic nanoparticles is also reported.

Influence of oxygen on the microstructure development of a Ti-48 at. % Al alloy has been investigated by means of transmission electron microscopy and 1D atom probe. Oxygen is found to significantly increase the temperature of the α → α2 chemical ordering reaction. As a consequence, above a critical oxygen content, the α → α2 transformation is substituted to the α → γm massive transformation when the Ti-48 Al alloy is quenched from the single a-phase field. In such a case, our pervious work has shown that the alloy exhibits a fully (α2 + γ) ultrafine lamellar structure. The present work gives a complete description of the ultrafine lamellar structure formation which, in opposition to the classical lamellar structure formation, involves an intragranular nucleation and growth of the γ phase within the α2 matrix.

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].