Spectroscopic investigations on Dy3+ ions doped zinc lead alumino borate glasses for photonic device applications

This paper presents the structural, optical absorption, photoluminescence (PL) and decay spectral properties of Dy~(3+)ions doped zinc lead alumino borate (ZPAB) glasses to elucidate their possible usage in photonic devices such as w-LEDs and lasers. A broad hump shown by the XRD spectrum recorded for an un-doped ZPAB glass confirms its non-crystalline nature. The Judd-Ofelt (J-O) intensity parameter evaluated from the measured oscillator strengths of the absorption spectral features were used to estimate various radiative parameters and also to understand the nature of bonding between Dy~(3+)ions and oxygen ligands. Under 350 nm excitation, the as-prepared glasses are exhibiting two emission bands~4F_(9/2)→~6H_(15/2)(blue),and~4F_(9/2)→~6H_(13/2)(yellow) at 483 and 575 nm,respectively. From the PL spectra,the Y/B ratio values, CIE chromaticity color coordinates and color correlated temperature (CCT) were evaluated. The experimental lifetimes measured from the decay profiles are decreasing with increase in Dy~(3+)ions concentration in these glasses which may be attributed to the cross-relaxation and nonradiative multiphonon relaxation process. Decay profiles observed for higher concentration were well fitted to Inokuti-Hirayama (I-H) model to understand the energy transfer process and subsequent decrease in experimental lifetimes. The higher values of radiative parameters, emission cross-sections,quantum efficiency, optical gain and gain band width suggest the suitability of 0.5 mol%of Dy~(3+) ions in these ZPAB glasses for the photonic device application.     

Stacked-cup-type MWCNTs as highly stable lithium-ion battery anodes

Stacked-cup type multiwall carbon nanotubes (MWCNTs) were synthesized by floating catalyst chemical vapor deposition methods. The materials were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Electrochemical measurements showed that the stacked-cup-type MWCNTs as lithium-ion battery anode materials delivered a stable capacity of ~310 mAh g^?1 at a rate of C/2 to 300 cycles. Furthermore, the materials were very stable and the coulombic efficiency exceeded 99.9 % over more than 300 cycles. Stable materials structure and the solid electrolyte interphase films were the main reasons for the durable cycling behavior, as confirmed by ex situ TEM and Raman spectroscopy, as well as electrochemical impedance spectroscopy (EIS). The results indicated that the stacked-cup-type MWCNTs produced in this work are candidate materials for lithium-ion battery anodes.     

From conventional ac flash-sintering of YSZ to hyper-flash and double flash

Flash-sintering experiments were performed on conventional 8 mol% Y₂O₃-doped ZrO₂. By varying the initial power spike, the steady state limited current density, the flash duration and furnace temperature, various microstructures corresponding to different sintering stages were observed. It is shown that operating the flash-sintering under the power dissipation regime may lead to microstructure heterogeneity. Under a quasi-adiabatic regime a better homogeneity is obtained. The major part of the shrinkage strain occurs within a short time interval of about 1 s, after the incubatory period. The remaining part appears to be a conventional shrinkage process induced by Joule heating. Hyper-flashes were performed over this short time interval, yielding relative densities up to 90%. Additional flashes can be subsequently applied up to full density. It is stressed that densification is not an absolute quality parameter in the optimization of the experimental conditions; inappropriate conditions may lead to fairly dense but brittle materials.     

Mikromechanische Eigenschaften von Weizenkörnern

The investigation of deformation and breakage behavior of wheat grains by compression test was carried out. The force‐displacement curve was obtained at stressing rate 0.02 mm s^–1. The elliptical wheat grains show quasi‐elastic and elastic‐plastic deformation behavior depending on applied force. The simple transformation procedure was applied to adapt the contact model for spherical particles to elliptic wheat grains. The breakage force, energy, strength and displacement distributions were fitted with normal distribution function.     

The EQUALANT99 experiment: in situ and satellite data for surface circulation in the tropical Atlantic

In summer 1999, an extensive survey of the tropical Atlantic ocean was operated during the EQUALANT99 cruise. Several experiments were carried out on board including, for the first time in that area, eXpendable Conductivity–Temperature–Depth (XCTD) launches. The aim of this experiment was first to evaluate XCTD temperature and salinity profiles, and secondly to check how XCTD could be used together with altimetric satellite missions in order to capture a good picture of the tropical Atlantic surface circulation.     

Kombinierte Licht‐ und Radiowellenemission während des Bruches von Partikeln

The relationship between the light and radio impulses that appear during the stressing layers of glass particles was investigated. Particles were stressed between two metallic plates under applied high voltage. The emission of light appears during the development of the first cracks within the particle. The radio wave impulses were caused by electrical breakdown of a fragment layer. It appears after the light impulse. The delay between light and radio impulse of about a few micro seconds represents the characteristic time of size reduction.     

Robust ensemble of metamodels based on the hybrid error measure

Frontiers of Mechanical Engineering - Metamodels have been widely used as an alternative for expensive physical experiments or complex, time-consuming computational simulations to provide a fast...     

Untersuchung des Prall‐ und Druckverhaltens feuchter γ‐Al2O3‐Granulate

The material behavior of dominant elastic‐plastic γ‐Al₂O₃ granules has been experimentally studied by means of quasi static compression tests and dynamic impact tests until fracture. The obtained distributions of breakage velocity and specific breakage energy are compared. Thus, velocity‐dependent influences at stressing like viscous behaviour can be derived. Additionally, the influence of particle size and moisture content are investigated.     

Synthesis of colloidal gold nanoparticles of different morphologies in the presence of triblock polymer micelles

The Au nanoparticles have been synthesized in the presence of micellar solutions of fixed concentration (i.e. 1.4 x 10(-3) mol dm(-3)) of each poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), triblock polymers (TBP), such as P103, P84, P123, and F127. The nanoparticles have also been synthesized in the presence of mixed micellar solutions of binary TBP mixtures such as P103+ P84 and P103+P123. In the previous case, "raspberry type" Au nanoparticle-TBP aggregates have been observed in which nanoparticles of 2-3 nm have been uniformly distributed throughout the TBP micelle. On the other hand, in the latter case, apart from such aggregates, prominent ordered morphologies of nanoparticles such as rod, sphere, triangle, and hexagonal have also been observed with much larger dimensions. This has been attributed to the nucleation process occurring in the mixed micelles rather than in the micelles of single TBP components.