Effect of concentrated light on morphology and vibrational properties of boron and tantalum mixtures

Abstract

Heating a mixture of boron (impurities: carbon ∼ B50C2, boric acid – H3BO3) and tantalum (Ta) powders in nitrogen flow in a xenon high-flux optical furnace was performed. As-received powder composed of h-BN, H3BO3, TaB2, B9H11 and a number of other phases including β-rhombohedral boron, apparently, heavily doped with Ta. FT–IR examination of any sample of the material reveals the complicated vibration spectrum containing, in particular, an absorption band near 2260 cm−1. The shapes of these bands are different for samples because powders were synthesized at different temperatures. Known, that in β-rhombohedral boron lattice, there are nano-sized voids of different types, which allow an accommodation of single atoms or small groups of atoms. Theoretical calculations performed by the method of quasi-classical type yields the same value, 2260 cm−1, for the vibrations frequency of Ta atoms in D-type crystallographic voids in β-rhombohedral boron lattice. Since, Ta atoms are known to prefer accommodation just in D-voids the experimentally detected bands can be identified with localized vibrations of Ta atoms.

Formation of composite structure based on boron and indium components under concentrated light in flow of nitrogen

“…The initial powders of h-BN and B (particle size ∼ 0.2 μm) and metallic In at a ratio of 3:1 were chosen as an object for investigation. Detail description of origin powders and experimental were presented in a number of papers [12][13][14][15][16][17]. Heating the surface of compacted samples was carried out in a xenon high-flux optical furnace in a flow of nitrogen at the density of energy ∼0.3-0.7 × 10 4 kW/m 2 .…”

Gradient and Layered Boron Nitride Formation Under Effect of Concentrated Light in a Flow of Nitrogen

“…Detailed description of the initial powders can be found in a number of previous papers. [21][22][23] A quartz chamber was chosen for the process of heating. Surface of BN initial powder was treated in a xenon highflux optical furnace in a flow of nitrogen at the density of energy in focal zone of set-up  1.4  10 4 kW m -2 and  0.7n…”

A Tale of Two Tantalum Borides as Potential Saturable Absorbers for Q-Switched Fiber Lasers

“…The absorption mechanisms of the tantalum-based borides are explained in different articles [40], [44], [45]: the main absorption comes from the electrons in the tantalum-boride bonds which are stronger than the boron-boron bonds. The tantalum bond has an average length of 2.38Å [45]. TaB has a calculated bandgap of 0.72 eV, i.e., absorbing light at wavelengths lower than 1700 nm, while TaB 2 behaves as a metal, with no bandgap (band diagrams are calculated with Density Functional Theory).…”

“…The enormous discrepancy can be explained by the very non-uniform coating of the glass sample with tantalum boride particles, contamination of the particles by water and PVA, and the creation of small areas with no particles. Thin film calculations of borides have shown that DFT-MGGA over-estimates the material losses [45] with actual thin-film imaginary refractive indices overestimated by a factor of 2. However, the large discrepancy is mostly due to the non-uniform deposition of the micro-powder solution which strongly scatters light, as explained by Guineton and co-authors [46].…”