Search results for " BORON"
showing 10 items of 33 documents
Enhancement of calcium copper titanium oxide photoelectrochemical performance using boron nitride nanosheets
2020
International audience; Photoelectrochemical water splitting under visible light has attracted attention for renewable hydrogen production. Despite prevalent investigations, many challenges still hindered an efficient energy conversion, such as enhancing the reaction efficiency in visible light. Thus controlling the photoelectrode materials is an essential step in designing new materials for water splitting. CaCu3Ti4O12 (CCTO) has received great attention as photocatalyst under solar light due to its combined band gap as result of the presence in its structure of TiO2 active in UV light and CuO active under visible light. In this work, a cubic CCTO with different amount of exfoliated hexago…
High-Mobility, Wet-Transferred Graphene Grown by Chemical Vapor Deposition
2019
We report high room-temperature mobility in single layer graphene grown by Chemical Vapor Deposition (CVD) after wet transfer on SiO$_2$ and hexagonal boron nitride (hBN) encapsulation. By removing contaminations trapped at the interfaces between single-crystal graphene and hBN, we achieve mobilities up to$\sim70000cm^2 V^{-1} s^{-1}$ at room temperature and$\sim120000cm^2 V^{-1} s^{-1}$ at 9K. These are over twice those of previous wet transferred graphene and comparable to samples prepared by dry transfer. We also investigate the combined approach of thermal annealing and encapsulation in polycrystalline graphene, achieving room temperature mobilities$\sim30000 cm^2 V^{-1} s^{-1}$. These …
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…
Optical Contrast and Raman Spectroscopy Techniques Applied to Few-Layer 2D Hexagonal Boron Nitride
2019
The successful integration of few-layer thick hexagonal boron nitride (hBN) into devices based on two-dimensional materials requires fast and non-destructive techniques to quantify their thickness. Optical contrast methods and Raman spectroscopy have been widely used to estimate the thickness of two-dimensional semiconductors and semi-metals. However, they have so far not been applied to two-dimensional insulators. In this work, we demonstrate the ability of optical contrast techniques to estimate the thickness of few-layer hBN on SiO2/Si substrates, which was also measured by atomic force microscopy. Optical contrast of hBN on SiO2/Si substrates exhibits a linear trend with the number of h…
Heteropolyacids supported on boron nitride and carbon nitride for catalytic and catalytic photo-assisted alcohol dehydration
2021
Keggin H3PW12O40 (PW12) and Wells-Dawson H6P2W18O60 (P2W18) heteropolyacids (HPAs) are photo(catalysts) for various acid-promoted and redox catalytic reactions. Their activity increases if they are deposited on certain supports as metal oxides or carbon materials. Although the surface area and acid-base interactions of the HPAs with supports are considered as key factors for the performance of the binary material, the role of the local structure changes in the HPAs upon their immobilization on solids must be also of primary importance, directly affecting both acidity and photoredox properties. Here, the (photo)catalytic performance of Keggin and Wells-Dawson heteropolytungstates supported o…
A stable path to ferromagnetic hydrogenated graphene growth
2014
In this paper, we propose a practical way to stabilize half-hydrogenated graphene (graphone). We show that the dipole moments induced by an hexagonal-boron nitride (h-BN) substrate on graphene stabilize the hydrogen atoms on one sublattice of the graphene layer and suppress the migration of the absorbed hydrogen atoms. Based upon first principle spin polarized density of states (DOS) calculations, we show that the half hydrogenated graphene (graphone) obtained in different graphene-h-BN heterostructures exhibits a half metallic state. We propose to use this new exotic material for spin valve and other spintronics devices and applications.
Clinical evaluation of neodymium-iron-boron (Ne2Fe14B) rare earth magnets in the treatment of mid line diastemas
2015
Background: To evaluate the closure of midline diastema using the Neodymium-Iron-Boron magnets and to compare the treatment duration of midline diastemas with the use of magnets compared to regular orthodontic treatment. Materials and Methods: Thirty patients with age group 12 to 30 years with the midline diastema ranging from 0.5 to 3mm were selected. These patients were divided into two groups. Diastema closure in one group was accomplished by conventional method, in other group was done with Ne 2 Fe 14 B magnets. These magnets were fitted to the labial surfaces of the maxillary central incisors such a way that the opposite poles of the magnets face each other. At each appointment, study …
R-matrix analysis of theβdecays ofN12andB12
2010
The β decays of 12N and 12B have been studied at KVI and JYFL to resolve the composition of the broad and interfering 0+ and 2+ strengths in the triple-α continuum. For the first time a complete treatment of 3α decay is presented including all major breakup channels. A multilevel, many-channel R-matrix formalism has been developed for the complete description of the breakup in combination with the recently published separate analysis of angular correlations. We find that, in addition to the Hoyle state at 7.65 MeV, more than one 0+ and 2+ state is needed to reproduce the spectra. Broad 03+ and 22+ states are found between 10.5 and 12 MeV in this work. The presence of β strength up to the 12…
Submillisecond On-Line Mass Separation of Nonvolatile Radioactive Elements: An Application of Charge Exchange and Thermalization Processes of Primary…
1985
Transportation of thermalized primary recoil ions from nuclear reactions by helium flow has been investigated as a means of injecting short-lived radioactive nuclides into an on-line isotope separator. Several short-lived radioactive isotopes of highly nonvolatile elements such as B, Sc, Nb, and W have been separated. The efficiency for heavy nuclides with half-lives above 1 ms is between 1 and 10%. The shortest-lived activity identified in an on-line separation is the 182-\ensuremath{\mu}s isomeric state in $^{207}\mathrm{Bi}$.
C12(γ,p)11B cross section from 80 to 157 MeV
1995
The $^{12}\mathrm{C}$(\ensuremath{\gamma},p${)}^{11}$B differential cross section has been measured over proton angles ranging from 58\ifmmode^\circ\else\textdegree\fi{} to 128\ifmmode^\circ\else\textdegree\fi{}, using tagged photons of energy 80--157 MeV, for low-lying regions of residual excitation energy in $^{11}\mathrm{B}$. The data have been compared with four different types of calculation. It is shown that scaling of the cross section with momentum mismatch occurs for both the ground-state and excited-state data.