Search results for "boron"
showing 10 items of 352 documents
High-Pressure Synthesis of Novel Boron Oxynitride B6N4O3 with Sphalerite Type Structure
2015
A novel crystalline boron oxynitride (BON) phase has been synthesized under static pressures exceeding 15 GPa and temperatures above 1900 °C, from molar mixtures of B2O3 and h-BN. The structure and composition of the synthesized product were studied using high-resolution transmission electron microscopy, electron diffraction, automated diffraction tomography, energy dispersive X-ray spectroscopy and electron energy-loss spectroscopy (EELS). BON shows a hexagonal cell (R3m, Z = 3) with lattice parameters a = 2.55(5) A and c = 6.37(13) A, and a crystal structure closely related to the cubic sphalerite type. The EELS quantification yielded 42 at % B, 35 at % N, and 23 at % O (B:N:O ≈ 6:4:3). E…
Structure and dynamics of B2O3 melts and glasses: From ab initio to classical molecular dynamics simulations
2019
Abstract Boron oxide (B2O3) is investigated by a combination of ab initio (DFT-based) molecular dynamics (MD) simulations and classical MD simulations. From the trajectories of the ab initio MD simulation, we derive a three-body interaction potential which is used in classical MD simulations to study various structural and dynamic properties on larger time and length scales than possible in the ab initio simulations. Differences and similarities to the structure and dynamics of other network glass formers such as SiO2 and GeO2 are discussed. Moreover, various properties as obtained from the simulations are compared to those from experiments of B2O3.
A reliable procedure for the preparation of graphene-boron nitride superlattices as large area (cm x cm) films on arbitrary substrates or powders (gr…
2019
[EN] Herein, a reliable procedure for the preparation of graphene-boron nitride superlattices, either as films or powders, consisting of the pyrolysis at 900 degrees C of polystyrene embedded pre-formed boron nitride single sheets is reported. The procedure can serve to prepare large area films (cm x cm) of this superlattice on quartz, copper foil and ceramics. Selected area electron diffraction patterns at every location on the films show the occurrence of the graphene-boron nitride superlattice all over the film. The procedure can also be applied to the preparation of powdered samples on a gram scale. Comparison with other materials indicates that the superlattice appears spontaneously as…
In situ diagnostics and control of laser-induced removal of iron oxide layers
2002
The mechanism of laser-induced removal of thermally grown iron oxide layers on pure iron has been investigated by means of in situ reflectivity measurements. The experiments were carried out by irradiating the sample with λ=584 nm, τ=6 ns (FWHM) laser pulses in a buffer borate solution after a cathodic polarisation of - 1.5 V/SCE had been applied during 40 min. The removal efficiency has been studied as a function of the number of laser pulses, for several fluence values and for a few time delays after switching off the cathodic polarisation. The results demonstrate that reflectivity measurements are a suitable non-invasive in situ diagnostics tool for the assessment of the efficiency of ox…
Atomic Layer Deposition of Localized Boron- and Hydrogen-Doped Aluminum Oxide Using Trimethyl Borate as a Dopant Precursor
2020
Atomic layer deposition (ALD) of boron-containing films has been mainly studied for use in two-dimensional materials and for B doping of Si. Furthermore, lithium-containing borates show great promi...
Metallophthalocyanines as optical active dopants in borate glass
2021
Abstract B2O3 – phthalocyanine composites (B2O3@MPc) were synthesized at 410 °C by sintering boron trioxide doped with base metal-free phthalocyanine (H2Pc) and/or its complexes of Mg, Zn, Gd (Pc = C32H16N8, phthalocyanine ligand, M = metal ion). The glassy products were characterized by scanning electron microscopy (SEM, EDS) and diffuse reflectance spectroscopy (DRS) which confirmed the incorporation of the respective phthalocyanines into the amorphous borate matrix. FTIR results suggested a possible impact of the phthalocyanine dopants on the final solid structure of the glassy matrix. The UV-excited composites emitted a pronounced blue phosphorescence featured by a two-step quenching pr…
Hexagonal boron nitride luminescence dependent on vacuum level and surrounding gases
2015
Abstract Gas sensing properties of hBN powder bulk and nanosize were studied. It was demonstrated that for hBN powders with grain sizes of 70 nm, 1 μm and 5 μm the native defect-induced luminescence observed at 400 nm under 265 nm light excitation and room temperature is sensitive to oxygen gas reducing luminescence intensity. The highest value of luminescence intensity is reached when sample is in vacuum. Results obtained allow conclusion that the hBN powder is prospective for sensing of oxygen gas. Some material properties such as dependence of luminescence intensity on vacuum level and pumping time, ratio of luminescence intensity when sample is in vacuum and gas, its dependence on mater…
Influence of boron on the essential properties for new generation scintillators
2021
Abstract Cerium doped yttrium aluminum (YAG:Ce) and lutetium aluminum garnets (LuAG:Ce) are some of the most popular materials used as scintillators. While the scintillators themselves are materials that absorb and convert high-energy radiation into light. The decay time in YAG:Ce and LuAG:Ce is about 60 ns, therefore the essential task for their improvement would be to shorten it as much as possible. For this reason, in this work, the aforementioned garnets were doped with different amounts of boron. B3+ ion has a suitable neutron capture cross section and can therefore absorb gamma radiation. Because of the extremely strong absorption of thermal neutrons and the weak interaction with MeV …
Nanosensor Systems Simulations
2017
The chapter presents functionalized CNT and GNR nanostructures as the basis for the creation of physical, chemical and biochemical nanosensors. We have shown in our simulations the sensitivity of electron conductivity of FET-type nanodevices (based on CNTs and GNRs) to local doping by nitrogen and boron. This phenomenon provides the prospective of creating nanosensors.
Growth of sub-nanometric palladium clusters on boron nitride nanotubes: a DFT study.
2015
A QM/MM investigation is reported dealing with the nucleation and growth of small palladium clusters, up to Pd8, on the outer surface of a suitable model of boron nitride nanotubes (BNNTs). It is shown that BNNTs could have a template effect on the cluster growth, which is due to the interplay between Pd–N and Pd–Pd interactions as well as due to the matching of the B3N3 ring and the Pd(111) face arrangement. The values for the cluster adsorption energies reveal a relatively strong physisorption, which suggests that under particular conditions the BNNTs could be used as supports for the preparation of shape-controlled metal clusters.