A single set of parameters that fit the data for unannealed acetaminophen glass does not fit the calorimetric data for annealed glass. Since acetaminophen molecules form intermolecular hydrogen-bonds in the crystal state and likely to form such bonds more easily in the disordered state, effect of such bonds on structural relaxation is likely to be significant.
Epitaxial thin films of Bi 2 FeCrO 6 have been synthesized by pulsed laser deposition on SrRuO 3 on (100)-and (111)-oriented SrTiO 3 substrates. Detailed X-ray diffraction and cross-section transmission electron microscopy analysis revealed a double perovskite crystal structure of the Bi 2 FeCrO 6 epitaxial films very similar to that of BiFeO 3 along with a particularly noteworthy Fe 3+ /Cr 3+ cation ordering along the [111] direction. The films contain no detectable magnetic iron oxide impurities and have the correct cationic average stoichiometry throughout their thickness. They however exhibit a slight modulation in the Fe and Cr compositions forming complementary stripe patterns, suggesting minor local excess or depletion of Fe and Cr. The epitaxial BFCO films exhibit good ferroelectric and piezoelectric properties, in addition to magnetic properties at room temperature, as well as an unexpected crystallographic orientation dependence of their room temperature magnetic properties. Our results qualitatively confirm the predictions made using the ab-initio calculations: the double-perovskite structure of Bi 2 FeCrO 6 films exhibit a Fe 3+ /Cr 3+ cation ordering and good multiferroic properties, along with the unpredicted existence of magnetic ordering at room temperature.
High-angle annular dark-field and annular bright-field imaging experiments were carried out on an aberration-corrected transmission electron microscope. These techniques have been demonstrated on thin films of complex oxides Ba3.25La0.75Ti3O12 and on LaB6. The results show good agreement between theory and experiments, and for the case of LaB6 they demonstrate the detection of contrast from the B atoms in the annular bright-field images. Elemental mapping with electron-energy-loss spectroscopy has been used to deduce the distribution of Cr and Fe in a thin film of the complex oxide Bi2(Fe1/2Cr3/2)O6 at the unit cell level and the changes in the near-edge structure within the inequivalent regions in the crystalline unit cell. Energy-filtered images in the low-loss region of the energy-loss spectrum show contrast and resolution consistent with the modulation of the signals from elastic scattering. High-resolution contrast, mediated by phonon scattering, is observed for interband transitions. The limitations in terms of detection and signal are discussed.
The specific heat, C p , of zinc nanoparticles (size distribution 30-180 nm and peak at 30 nm) was measured, and their melting behavior was investigated as the ZnO shell grew around the metal particles and thickened. Both structural and chemical analyses were performed by using Transmission Electron Microscopy and techniques of energy filtering and energy dispersive X-ray analyses. The C p of Zn nanoparticles is slightly higher than that of bulk metal. The melting point of Zn nanocrystals confined to the ZnO shell is only 1-2 K less than that of bulk Zn, much less than that expected from the Gibbs-Thomson equation. This is attributed to the increase in pressure on the zinc core because (i) zinc expands more on heating and on melting than ZnO, (ii) the ZnO shell thickens at the expense of the zinc core, and (iii) there is an epitaxial interaction between Zn and the ZnO shell. The enthalpy of melting decreases on thermal cycling. Nanodroplets of Zn supercooled by a few degrees before crystallizing in two steps. The high temperature step is attributed to heterogeneous nucleation at the core-shell interface, and the low temperature step to homogeneous nucleation in the particle core. The amount crystallized on homogeneous nucleation decreased on thermal cycling as the ZnO shell thickened when oxygen diffused through this layer. The enthalpy of crystallization also decreased on thermal cycling.
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