An Online Contactless Investigation of the Meniscus Velocity in a Continuous Casting Mold Using Lorentz Force Velocimetry

Metallurgical and Materials Transactions B - Monitoring the meniscus velocities of molten steel in continuous casting molds is critical for revealing the velocity field in the whole mold and...     

Laser generation at 1.3 μm in vertical microcavities containing InAs/InGaAs quantum dot arrays under optical pumping

The fundamental possibility of achieving temperature stability of laser emitters of 1.3-μm spectral range exhibiting a vertical microcavity and an active region based on InAs/InGaAs quantum dots (QDs) is investigated. It is demonstrated that using an undoped hybrid vertical optical microcavity formed by a lower undoped semiconductor and an upper distributed dielectric Bragg reflectors allows obtaining laser oscillation up to a temperature of ~100°C at nearly constant threshold optical pump power for an active region consisting of QD layers under optimal spectral mismatch between the position of maximum gain of the QD ground state and the resonance wavelength.     

ASTER and field observations of the 24 December 2006 eruption of Bezymianny Volcano, Russia

An explosive eruption occurred at Bezymianny Volcano (Kamchatka Peninsula, Russia) on 24 December 2006 at 09:17 (UTC). Seismicity increased three weeks prior to the large eruption, which produced a 12–15 km above sea level (ASL) ash column. We present field observations from 27 December 2006 and 2 March 2007, combined with satellite data collected from 8 October 2006 to 11 April 2007 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), as part of the instrument's rapid-response program to volcanic eruptions. Pixel-integrated brightness temperatures were calculated from both ASTER 90 m/pixel thermal infrared (TIR) data as well as 30 m/pixel short-wave infrared (SWIR) data. Four days prior to the eruption, the maximum TIR temperature was 45 °C above the average background temperature (− 33 °C) at the dome, which we interpret was a precursory signal, and had dropped to 8 °C above background by 18 March 2007. On 20 December 2006, there was also a clear thermal signal in the SWIR data of 128 °C using ASTER Band 7 (2.26 μm). The maximum SWIR temperature was 181 °C on the lava dome on 4 January 2007, decreasing below the detection limit of the SWIR data by 11 April 2007. On 4 January 2007 a hot linear feature was observed at the dome in the SWIR data, which produced a maximum temperature of 700 °C for the hot fraction of the pixel using the dual band technique. This suggests that magmatic temperatures were present at the dome at this time, consistent with the emplacement of a new lava lobe following the eruption. The eruption also produced a large, 6.5 km long by up to 425 m wide pyroclastic flow (PF) deposit that was channelled into a valley to the south–southeast. The PF deposit cooled over the following three months but remained elevated above the average background temperature. A second field investigation in March 2007 revealed a still-warm PF deposit that contained fumaroles. It was also observed that the upper dome morphology had changed in the past year, with a new lava lobe having in-filled the crater that formed following the 9 May 2006 eruption. These data provide further information on effusive and explosive activity at Bezymianny using quantitative remote sensing data and reinforced by field observations to assist in pre-eruption detection as well as post-eruption monitoring.     

Kinetics and Mechanism of Thermal Decomposition of Dinitramide

Kinetics of the thermal decomposition of dinitramide (HDN) in aqueous solutions and of NH₄N(NO₂)₂ (ADN) and KN(NO₂)₂ (KDN) in sulfuric acid, nitric acid and anhydrous acetic acid solutions was studied. The species N(NO₂)₋₂, HN(NO₂)₂ and H₂N(NO₂) were established to take part in the decomposition over a wide range of the medium acidity. Kinetic regularities of their thermal decomposition were determined. The role of the decomposition of dinitramide at the initial and self-acceleration stages of the decomposition of ADN was determined. The most likely mechanism of the decomposition of dinitramide, N(NO₂)₋₂ and H₂N(NO₂)₊₂ was proposed.     

Some Phenomenological Aspects of Heterogeneous Combustion of Condensed Systems

The combustion process of heterogeneous condensed systems (HCS) is a complex phenomenon characterized by some peculiarities: Phase transitions in the combustion wave, time and space inhomogeneity of the temperature and burning rate, agglomeration and dispersion of the condensed phase, concentration limits, etc. The order and completeness of chemical reactions in a HCS combustion wave depend not only on the energetic parameters but on the composite structure as well (porosity, component particle size and shape, etc.). Some phenomenological aspects of the HCS combustion process are analyzed. Peculiarities of metal particle agglomeration and its influence on the metal oxide size are discussed. The high‐temperature kinetics of Al+Al₂O₃ interaction are shown. The complexity of the analyzed phenomenon calls for a non‐traditional approach and technique.     

Wettability of Halides with Molten Metals. Physico-Chemical and Practical Aspects

A study is made on the wettability of sodium chloride and oxygen-free ionic compounds fluorides of alkaline-earth elements (CaF, MgF, BaF) by molten metals. The metals Cu, Sn, Ag, Au, In, and Ga do not wet these materials ( 120-140 deg). The wettability of fluorides by aluminum is somewhat greater ( 90-100 deg), in accordance with the greater chemical affinity of aluminum for fluorine. Chemically highly active and aggressive alloys of Ti, Zr, Hf, and V (with concentrations up to 70-80%) which completely wet and destroy known refractory materials (oxide, nitride, carbide, and carbon refractories, etc.) behave anomalously in regard to fluorides they do not wet their surface and are inert when in contact with them. This is attributable to the formation of an intermediate gaseous phase (a volatile fluoride) which separates the liquid metal from the solid surface. Effective use can be made of this phenomenon to develop refractories (crucibles, containers, jackets, etc.) for use in the isothermal melting, homogenization, and casting of alloys that contain Ti, Zr, Hf, and V.     

Structuring of Multiphase Compacts in the SiC′ ― Carbon System. Part 2. Structuring during Sintering

We have studied the effect of particle sizes in the starting powders in the silicon carbide carbon system, and also effects on the structure and phase composition of self-bonded silicon carbide (SBSC) that are associated with structural interactions between the starting components.     

Liquidus Temperatures of Cryolite Melts With Low Cryolite Ratio

The effect of calcium fluoride on liquidus temperatures of the cryolite melts with a low cryolite ratio (CR) was studied. The systems KF-NaF-AlF₃ and KF-LiF-AlF₃ with CRs of 1.3, 1.5, and 1.7 have been investigated. The liquidus curves of systems containing CaF₂ are different and depend on the K/(K + Na) and K/(K + Li) ratios. In potassium cryolite with CRs of 1.3 and 1.5, the calcium fluoride solubility is low and increases with NaF (LiF) concentration.     

Surface plasmon enhanced energy transfer between donor and acceptor CdTe nanocrystal quantum dot monolayers

Surface plasmon enhanced Fo?rster resonant energy transfer (FRET) between CdTe nanocrystal quantum dots (QDs) has been observed in a multilayer acceptor QD-gold nanoparticle-donor QD sandwich structure. Compared to a donor-acceptor QD bilayer structure without gold nanoparticles, the FRET rate is enhanced by a factor of 80 and the Fo?rster radius increases by 103%. Furthermore, a strong impact of the donor QD properties on the surface plasmon mediated FRET is reported.     

Water dynamics in bulk and dispersed in silica CaCl2 hydrates studied by neutron scattering methods

Quasi-elastic and inelastic neutron scattering techniques have been used to study the dynamics of water in CaCl₂ · nH₂O (n = 1/3,2,4,6,9) hydrates dispersed in silica, in comparison with the bulk hydrates. Inelastic scattering shows that the water molecules in dispersed hydrates are in an amorphous state. Quasi-elastic scattering indicates a higher mobility of water in the hydrates dispersed in silica, compared to bulk hydrates. The self-diffusivity of water in the dispersed hydrates increases with water concentration, while remaining below the one of pure water. The neutron and pulsed-field gradient NMR diffusivities are similar, which indicates that the hydrates form a thin and continuous layer on the pore walls of silica.