Search results for "Names"

The Electrical Properties of Ba1-ySryZrxTi1-xO3Solid Solution

2011

A lead-free solid solution Ba0.80Sr0.20Ti0.75Zr0.25O3 was prepared by a conventional technology. The structure and morphology of investgated samples were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The studies of electric conductivity were performed depending on temperature and frequency of electric measuring field. The activation energy was calculated from the Arrhenius plots.

Dependence of O2 diffusion dynamics on pressure and temperature in silica nanoparticles

2013

An experimental study of the molecular O2 diffusion process in high purity non-porous silica nanoparticles having 50 m2/g BET specific surface and 20 nm average radius was carried out in the temperature range from 127 to 177 °C at O2 pressure in the range from 0.2 to 66 bar. The study was performed by measuring the volume average interstitial O2 concentration by a Raman and photoluminescence technique using a 1,064 nm excitation laser to detect the singlet to triplet emission at 1,272 nm of the molecular oxygen in silica. A dependence of the diffusion kinetics on the O2 absolute pressure, in addition to temperature dependence, was found. The kinetics can be fit by the solution of Fick’s dif…

Photoconductivity in the columnar phases of a glassy discotic twin

1995

Energy Barrier: Focus on the Essential: Extracting the Decisive Energy Barrier of a Complex Process (Adv. Mater. Interfaces 20/2019)

2019

A theory ofnonverticaltriplet energy transfer in terms of accurate potential energy surfaces: The transfer reaction from π,π* triplet donors to 1,3,5…

2004

Triplet energy transfer (TET) from aromatic donors to 1,3,5,7-cyclooctatetraene (COT) is an extreme case of "nonvertical" behavior, where the transfer rate for low-energy donors is considerably faster than that predicted for a thermally activated (Arrhenius) process. To explain the anomalous TET of COT and other molecules, a new theoretical model based on transition state theory for nonadiabatic processes is proposed here, which makes use of the adiabatic potential energy surfaces (PES) of reactants and products, as computed from high-level quantum mechanical methods, and a nonadiabatic transfer rate constant. It is shown that the rate of transfer depends on a geometrical distortion paramet…

Broadband dielectric spectroscopy of 0.4PMN-0.3PSN-0.3PZN ceramics

2007

In this paper, results of the broadband dielectric spectroscopy of 0.4PbMg1/3Nb2/3O3-0.3PbZn1/3Nb2/3O3-0.3PbSc1/2Nb1/2O3(0.4PMN-0.3PZN-0.3PSN) are presented. Dielectric spectra of these solutions were investigated in a broad frequency range from 20 Hz to 100 GHz. Very strong and broad dielectric relaxation was analyzed in terms of distribution of relaxations times, using Tichonov regularization method. It revealed slowing down of the longest relaxation and the mean relaxation times in the agreement with the Vogel-Fulcher law and the Arrhenius law, respectively.

Current‐voltage curves of bipolar membranes

1992

Bipolar membranes consist of a layered ion‐exchange structure composed of a cation selective membrane joined to an anion selective membrane. They are analogous to semiconductor p‐n devices as both of them present current‐voltage curves exhibiting similar rectification properties. In this article, we present some current‐voltage curves obtained for different bipolar membranes at several temperatures. The results can be interpreted in terms of a simple model for ion transport and field‐enhanced water dissociation previously developed. The mechanism responsible for water splitting is assumed to be a catalytic proton transfer reaction between the charged groups and the water at the membrane int…

Domain wall energy in quasi-one-dimensional Fe/W(110) nanostripes

2003

The magnetic susceptibility in Fe/W(110) nanostripes decreases exponentially with increasing temperature according to an Arrhenius law which indicates a quasi-one-dimensional behavior. The interface energy of the Arrhenius law corresponds to the domain wall energy of a domain wall across a single stripe, separating fluctuating regions of homogeneous magnetization. The domain wall energy increases linearly with the width of the stripes, revealing a negative offset which we attribute to boundary effects. Domain wall energies have been determined for Fe/W(110) nanostripes coated with Au and Pd and are compared to values for uncoated Fe/W(110) nanostripes in ultrahigh vacuum.

Temperature dependent mechanical unfolding of calixarene nanocapsules studied by molecular dynamics simulations.

2019

Using atomistic molecular dynamics simulations, we study the temperature dependence of the mechanical unfolding of a model supramolecular complex, a dimer of interlocked calixarene capsules. This system shows reversible transitions between two conformations that are stabilized by different networks of hydrogen bonds. We study the forced dissociation and formation of these networks as a function of temperature and find a strong impact of the nonequilibrium conditions imposed by pulling the system mechanically. The kinetics of the transition between the two conformations is ideally suited to investigate the range of validity of the stochastic models employed in the analysis of force dependent…

Modeling of Point Defects in Corundum Crystals

1994

Several different approaches including Hartree-Fock ab initio cluster calculations, semiempirical INDO calculations, and atom-atom potentials were used for modeling of the spatial and electronic structure as well as migration mechanisms of both intrinsic defects (self-trapped and defect-trapped holes, O and Al vacancies) and impurities (transition-metal ions like Co, Fe, Mg, Mn, Ti). The atomic structure of all hole centers is found to be similar to V[sub K] centers in alkali halides (two-site model); their formation is energetically favorable. The energy required for 60[degree] hole reorientations inside the basic oxygen triangles is found to be similar to both the energy for hops between …