Search results for "Crystal"
showing 10 items of 22886 documents
Studies on the zooplankton of the deep subalpine Lake Garda
1999
The specific composition and seasonal dynamics of the zooplankton of Lake Garda have been studied through monthly surveys in two annual cycles (December 1994-November 1995 and January-December 1997). The assemblage is largely dominated by Copipo-diaptomus steueri, a typical calanoid presently identified in deep (Garda, Iseo) and shallow lakes of NE Italy and in the hinterland of the central Adriatic region (Dalmatia and Marche Region). Cladocerans and the smaller rotifers represent a significant component of the zooplankton from spring to autumn. A re-examination of the results obtained in previous studies does not seem to demonstrate substantial shifts in the composition of the dominant sp…
X-Ray characterization of 3-methyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-d]pyrimidine
2005
Abarca Gonzalez, Belen. Belen.Abarca@uv.es ; Ballesteros Campos, Rafael, Rafael.Ballesteros@uv.es ; Chadlaoui, Mimoun, michad@alumni.uv.es ; Ramirez de Arellano Sanchez, Maria del Carmen, Ramirezdearellano@uv.es
Modification of the Structure and Nano-Mechanical Properties of LiF Crystals Under Irradiation with Swift Heavy Ions
2011
The modifications of the structure and hardness of LiF crystals under high-fluence irradiation with MeV- and GeV-energy Au ions have been studied using nanoindentation and atomic force microscopy. The formation of ion-induced dislocations and bulk nanostructures consisting of grains with nanoscale dimensions (50 nm - 100 nm) has been observed. The structural modifications are accompanied by a strong ion-induced hardening which is related to dislocation impeding by assemblies of defect aggregates, dislocation loops of vacancy and interstitial types and grain boundaries. For MeV ions, the modifications are localized in a thin surface layer (few mm) where much higher density of deposited energ…
The Synthesis, Characterization and Sintering of Nickel and Cobalt Ferrite Nanopowders
2012
The NiFe2O4 and CoFe2O4 ferrites were synthesized by two methods – chemical sol-gel self-combustion method and the high frequency plasma chemical synthesis and magnetic properties, crystallite size, specific surface area of synthesized products are characterized. Nanopowders synthesized in the high frequency plasma are with specific surface area in the range of (28 – 30) m2/g (the average particle size (38 – 40) nm, crystallite size ~40 nm). The ferrite nanopowders obtained by sol-gel self-combustion method have the specific surface area of (37 – 43) m2/g (average particle size (26 – 31) nm, crystallite size (10 – 20) nm). All synthesized nanopowders were sintered via pressure-less sinterin…
Surface Morphology of Single and Multi-Layer Silicon Nitride Dielectric Nano-Coatings on Silicon Dioxide and Polycrystalline Silicon
2019
Silicon nitride (Si3N4) in a form of single and multi-layer nanofilms is proposed to be used as a dielectric layer in nanocapacitors for operation in harsh environmental conditions. Characterization of surface morphology, roughness and chemical bonds of the Si3N4 coatings has an important role in production process as the surface morphology affects the contact surface with other components of the produced device. Si3N4 was synthesized by using low pressure chemical vapour deposition method and depositing single and multi-layer (3 – 5 layers) nanofilms on SiO2 and polycrystalline silicon (PolySi). The total thickness of the synthesized nanofilms was 20 – 60 nm. Surface morphology was investi…
“SmartGlass” Obstacles for Dynamic Inducing of Light Scattering in Vision Research Experiments
2017
We describe a technique that allows control of visual stimuli quality through the use of a setup with a polymer dispersed liquid crystal (PDLC) film positioned in the optical pathway of one or both human eyes. Nowadays, PDLC films allow alteration of the resolution and contrast limits of the transmitted light due to continuous change in the light scattering that is obtained by the application of an AC electrical field. In our experimental setup, the use of a wide-aperture up to area of 20 x 15 cm2 PDLC sheet is combined with a flat-screen PC display or with a modified display emission block without its interference filter unit and with an installed individually controllable colored light-em…
New Insights into the complexation of lead(II) by 1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane (DOTAM): structural, thermodynami…
2007
The lead(II) coordination properties of the tetrapodal ligand DOTAM [1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraaza-cyclododecane] have been investigated both in the solid state and in solution in order to ascertain the stereoactivity of the lone pair and to rationalize the structural effects of a cyclen-based scaffold on the metal uptake kinetics. The crystal structure of the free base shows that the pendant acetamide groups are not equivalent: two are folded over the macrocycle and maintained by an intramolecular hydrogen bond involving an amide hydrogen atom and a neighboring tertiary amine of the cyclen ring, while the other two are extended and point away from the macrocyclic cav…
The Effect of Dopants on Sintering and Microstructure of Lead-free KNN Ceramics
2011
Lead-free potassium sodium niobate (K0.5Na0.5)NbO3 (KNN) has been prepared via conventional ceramic processing method. The influence of 0.5 wt% - 1.5 wt% MnO2 and WO3 addition on the sintering, crystallographic structure, microstructure and dielectric properties of KNN has been investigated. Optimal sintering temperatures of KNN ceramics were observed to be in the narrow interval: 1090 °C - 1110 °C for MnO2 doped KNN; 1150 °C - 1170 °C for pure KNN and doped with WO3. XRD patterns showed that all the samples have single perovskite structure with monoclinic structure. Microstructure of ceramics was changed greatly by using dopants.http://dx.doi.org/10.5755/j01.ms.17.1.251
State of the art and prospects for halide perovskite nanocrystals
2021
Financiado para publicación en acceso aberto: Universidade de Vigo/CISUG Metal-halide perovskites have rapidly emerged as one of the most promising materials of the 21st century, with many exciting properties and great potential for a broad range of applications, from photovoltaics to optoelectronics and photocatalysis. The ease with which metal-halide perovskites can be synthesized in the form of brightly luminescent colloidal nanocrystals, as well as their tunable and intriguing optical and electronic properties, has attracted researchers from different disciplines of science and technology. In the last few years, there has been a significant progress in the shape-controlled synthesis of …
Purcell Enhancement and Wavelength Shift of Emitted Light by CsPbI3 Perovskite Nanocrystals Coupled to Hyperbolic Metamaterials
2020
Manipulation of the exciton emission rate in nanocrystals of lead halide perovskites (LHPs) was demonstrated by means of coupling of excitons with a hyperbolic metamaterial (HMM) consisting of alternating thin metal (Ag) and dielectric (LiF) layers. Such a coupling is found to induce an increase of the exciton radiative recombination rate by more than a factor of three due to the Purcell effect when the distance between the quantum emitter and HMM is nominally as small as 10 nm, which coincides well with the results of our theoretical analysis. Besides, an effect of the coupling-induced long wavelength shift of the exciton emission spectrum is detected and modeled. These results can be of i…