Search results for " microscopy"

Structural modulations and phase transitions in β-eucryptite: an in-situ TEM study

1999

Beta-eucryptite as grown by the flux method has been investigated by in-situ cold- and hot-stage transmission electron microscopy (TEM). Using electron diffraction and dark-field TEM imaging, we found no evidence for the merohedral twinning that accompanies structural collapse at the β-to-α-quartz transition, suggesting a true hexagonal symmetry for the aluminosilicate framework of β-eucryptite. Selected-area electron diffraction (SAED) patterns exhibited a variety of incommensurate structures along the three a axes with an average modulation period of about 6.5 a. These modulated structures arise from superperiodic stacking parallel to (100) of two structural units with different Li config…

Core-Shell Microgels with Switchable Elasticity at Constant Interfacial Interaction.

2016

Hydrogels based on poly(N-isopropylacrylamide) (pNIPAAm) exhibit a thermo-reversible volume phase transition from swollen to deswollen states. This change of the hydrogel volume is accompanied by changes of the hydrogel elastic and Young's moduli and of the hydrogel interfacial interactions. To decouple these parameters from one another, we present a class of submillimeter sized hydrogel particles that consist of a thermosensitive pNIPAAm core wrapped by a nonthermosensitive polyacrylamide (pAAm) shell, each templated by droplet-based microfluidics. When the microgel core deswells upon increase of the temperature to above 34 °C, the shell is stretched and dragged to follow this deswelling i…

Anisotropic carrier diffusion in single MAPbI(3) grains correlates to their twin domains

2020

Polycrystalline thin films and single crystals of hybrid perovskites – a material group successfully used for photovoltaic and optoelectronic applications – reportedly display heterogeneous charge carrier dynamics often attributed to grain boundaries or crystalline strain. Here, we locally resolved the carrier diffusion in large, isolated methylammonium lead iodide (MAPbI3) grains via spatial- and time-resolved photoluminescence microscopy. We found that the anisotropic carrier dynamics directly correlate with the arrangement of ferroelastic twin domains. Comparing diffusion constants parallel and perpendicular to the domains showed carriers diffuse around 50–60% faster along the parallel d…

Phase transitions and upconversion luminescence in oxyfluoride glass ceramics containing Ba4Gd3F17 nanocrystals

2017

This is the peer reviewed version of the following article: G. Krieke, A. Sarakovskis, R. Ignatans, J. Gabrusenoks "Phase transitions and upconversion luminescence in oxyfluoride glass ceramics containing Ba4Gd3F17 nanocrystals", Journal of the European Ceramic Society, 2017, 37 (4), which has been published in final form at https://www.sciencedirect.com/science/article/abs/pii/S0955221916306768 This article may be used for non-commercial purposes in accordance with Elsevier Terms and Conditions for Sharing and Self-Archiving.

Polar nanodomains and local ferroelectric phenomena in relaxor lead lanthanum zirconate titanate ceramics

2005

Transparent Pb0.9125La0.0975(Zr0.65Ti0.35)0.976O3 ceramics (conventionally abbreviated as PLZT 9.75/65/35) is a typical relaxor characterized by the absence of the ferroelectric order at the macroscopic scale. In this letter, we report on the observation of complex polar structures on the surface of this material via piezoresponse force microscopy (PFM). The irregular polarization patterns are associated with the formation of a glassy state, where random electric fields destroy the long-range ferroelectric order. The measure of the disorder, the correlation length of ∼50nm, was directly deduced from the PFM images. Local poling of relaxor ceramics resulted in the formation of a stable micro…

Nanosized shape-changing colloids from liquid crystalline elastomers.

2010

A method to prepare shape-changing nanospheres from liquid crystalline elastomers is reported. The nanosized colloids are prepared by a miniemulsion process. During this process, colloids are prepared from a liquid crystalline (LC) main-chain polyester and subsequently crosslinked into a nanometer-sized LC elastomer. The ability of these LC elastomers to change their shape at the phase transition temperature from the smectic A to the isotropic phase was detected by temperature-dependent transmission electron microscopy. The phase transition-induced shape change leads to strongly shape anisotropic nanosized elastomer particles.

Thermal Expansion of Microstructured DMPC Bilayers Quantified by Temperature-Controlled Atomic Force Microscopy

2006

Optimization of Innovative Three-Dimensionally-Structured Hybrid Vesicles to Improve the Cutaneous Delivery of Clotrimazole for the Treatment of Topi…

2019

New three-dimensionally-structured hybrid phospholipid vesicles, able to load clotrimazole in a high amount (10 mg/mL), were obtained for the first time in this work by significantly reducing the amount of water (&le

Control on the morphology and photoelectrocatalytic properties of ZnO nanostructures by simple anodization varying electrolyte composition

2021

Abstract Zinc oxide nanostructured electrodes were successfully synthesized by a simple method of anodization in different aqueous bicarbonate electrolytes. The influence of the anodization electrolyte composition (by adding ethanol or glycerol) on the morphology and the photoelectrocatalytic properties of the zinc oxide electrodes was studied, as well as the combined effect of anodizing under controlled hydrodynamic conditions. Field Emission Scanning Electron Microscope (FE-SEM) images of the ZnO electrodes showed that the addition of ethanol or glycerol to the anodization electrolyte resulted in changes in size and morphology of the nanostructures. Thus, ZnO nanowires, nanotubes, nanospo…

Structural Analysis and Photocurrent Spectroscopy of CCCs on 99.99% Aluminum

2003

A characterization of chromate conversion coatings (CCCs) formed in the presence and in the absence of accelerator (ferroferricyanide redox couple) has been performed by various techniques (transmission electron microscopy, TEM, glow discharge optical emission spectrometry, GDOES, X-ray absorption near-end structure, XANES, and photon correlation spectroscopy). The results of a detailed investigation on morphological, compositional, and solid-state properties of freshly converted aluminum samples at different immersion times (30 s-90 min) are reported. The TEM and GDOES data suggest the presence of iron-cyanide species only in the external layer of CCC of nearly constant thickness. The XANE…