Search results for "Static"
showing 10 items of 1528 documents
Fluoride-induced precipitates on enamel surface and subsurface areas visualised by electron microscopy and confocal laser scanning microscopy
1997
The present study examined the enamel surface after in vitro topical treatments with a neutral 2% NaF solution. For minimising the risk of artefacts, samples were inspected without pre-treatment as fresh, naturally wet specimens by complementary techniques: variable pressure electron microscopy (VP-SEM) and confocal laser scanning microscopy (CLSM). VP-SEM provided information on the surface morphology, whereas CLSM allowed non-destructive visualisation of subsurface areas. Neutral NaF solutions induced globular precipitates on the enamel surfaces. If the globules formed may be described as "calcium fluoride like material", the additional information of this experiment is that, after intera…
Cover Picture: Nanoscale Deposition of Single-Molecule Magnets onto SiO2 Patterns (Adv. Mater. 2/2007)
2007
The cover shows a schematic of scanning probe nanolithography based on the spatial confinement of an oxidation reaction within a water meniscus, and its application for fabricating ordered arrays of cationic Mn12 single-molecule magnets. Romero, Coronado, Garcia, and co-workers report on p. 291 that electrostatic interactions between the molecules and trapped charges within the nanodots drive the positioning of the molecules at the nanoscale.
Heterogeneous and homogeneous crystal nucleation in colloidal hard-sphere like microgels at low metastabilities
2011
We studied the crystallization kinetics of the homogeneous bulk as well as of the heterogeneous wall crystallization in a colloidal hard sphere model system within the fluid crystal coexistence region. Using time resolved static light scattering and Bragg microscopy we determined several parameters characterizing the crystallization process (induction times, growth coefficients, nucleation rate densities,…). By performing further analysis according to classical nucleation theory we can show that wall crystallization is favored by a vanishing nucleation barrier height leading to the conclusion that a hard sphere crystal completely wets a structureless hard wall.
Crystallization kinetics of colloidal binary mixtures with depletion attraction.
2014
In this work the crystallization kinetics of colloidal binary mixtures with attractive interaction potential (Asakura–Oosawa) has been addressed. Parameters such as fraction of crystals, linear crystal dimension and crystal packing have been quantified in order to understand how the crystal formation is driven in terms of the depth of the attractive potential and the composition of the binary mixture (described by the number ratio). It was found that inside the eutectic triangle, crystallization is mainly governed by nucleation and the crystal packing is close to the close-packing of hard spheres. Moving out from the eutectic triangle towards small component results in the crystallization o…
Solidification of a colloidal hard sphere like model system approaching and crossing the glass transition
2014
We investigated the process of vitrification and crystallization in a model system of colloidal hard spheres. The kinetics of the solidification process was measured using time resolved static light scattering, while the time evolution of the dynamic properties was determined using time resolved dynamic light scattering. By performing further analysis we confirm that solidification of hard sphere colloids is mediated by precursors. Analyzing the dynamic properties we can show that the long time dynamics and thus the shear rigidity of the metastable melt is highly correlated with the number density of solid clusters (precursors) nucleated. In crystallization these objects convert into highly…
Deformation analysis of ATHENA test filters made of plastic thin films supported by a mesh under differential static pressure
2019
Within ESA Cosmic Vision 2015-2025 Science Program, ATHENA was selected to be a Large-class high energy astrophysics space mission. The observatory will be equipped with two interchangeable focal plane detectors named X-Ray Integral Field Unit (X-IFU) and Wide Field Imager (WFI). In order to optimally exploit the detector sensitivity, X-ray transparent filters are required. Such filters need to be extremely thin to maximize the X-ray transparency, that is, no more than a few tens of nm, still they must be able to sustain the severe stresses experienced during launch. Partially representative test filters were made with a thin polypropylene film, coated with Ti, and supported by a thin highl…
Ionic Space-Charge Effects in Solid State Organic Photovoltaics
2010
The effect of mobile ions on the operation of donor-acceptor bilayer solar cells is studied. We demonstrate the large effect ions can have on the energetics of the solar cells, illustrated by (for instance) changing the output voltage of a cell in situ from 0.35 to 0.74 V. More importantly, it is shown ionic species do not obstruct the charge generating properties of the photovoltaic devices and ionic space charge can be used in situ to improve their efficiencies. The results obtained are explained by taking into account energetic changes at the donor-acceptor interface as well as built-in potentials, giving clear guidelines on how ionic species can offer many new and exciting functionaliti…
Optical emission fromSiO2-embedded silicon nanocrystals: A high-pressure Raman and photoluminescence study
2015
We investigate the optical properties of high-quality Si nanocrystals $(\mathrm{NCs})/\mathrm{Si}{\mathrm{O}}_{2}$ multilayers under high hydrostatic pressure with Raman scattering and photoluminescence (PL) measurements. The aim of our study is to shed light on the origin of the optical emission of the Si $\mathrm{NCs}/\mathrm{Si}{\mathrm{O}}_{2}$. The Si NCs were produced by chemical-vapor deposition of Si-rich oxynitride $(\mathrm{SRON})/\mathrm{Si}{\mathrm{O}}_{2}$ multilayers with 5- and 4-nm SRON layer thicknesses on fused silica substrates and subsequent annealing at 1150 \ifmmode^\circ\else\textdegree\fi{}C, which resulted in the precipitation of Si NCs with an average size of 4.1 a…
Effect of annealing treatment on the persistent luminescence of Y3Al2Ga3O12:Ce3+,Cr3+,Pr3+ ceramics
2020
Abstract The Y3Al2Ga3O12:Ce3+,Cr3+,Pr3+ (YAGG) persistent luminescent ceramics were sintered in static air (without airflow) and followed by hot isostatic pressing (HIP) treatment. The low aggregated and relatively narrow particle-size distributed starting powders, with the particle size of about 50 nm, were synthesized by using Pechini method and then annealed at 900 °C for 16 h in static air. Compared to nano-phosphors, the ceramics exhibited more intense and longer persistent luminescence (PersL). The photoluminescence and PersL spectra were found to have a similar shape, indicating that the emitting centers for photoluminescence and PersL processes were same. The intense Ce3+ and Cr3+ b…
First-principles LCAO study of the low and room temperature phases of CdPS$_3$
2020
A.K. is grateful to the Latvian Council of Science project no. lzp-2018/2-0353 for financial support. Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.