Search results for "Solid"
showing 10 items of 3575 documents
Performance of a thermoelectric module based on n-type (La0.12Sr0.88)0.95TiO3-δ and p-type Ca3Co4-xO9+δ
2020
Here, we present the performance of a thermoelectric (TE) module consisting of n-type (La0.12Sr0.88)0.95TiO3 and p-type Ca3Co4-xO9+δ materials. The main challenge in this investigation was operation of TE module in different atmosphere conditions, since n-type has its optimum TE-performance at reducing, while p-type at oxidizing conditions. The TE module was exposed to two different atmospheres and demonstrated higher stability in N2 atmosphere than in air. The maximum electrical power output decreased after 40 h when the hot side was exposed to N2 at 600 °C, while only 1 h at 400 °C in ambient air was enough to oxidize (La0.12Sr0.88)0.95TiO3 followed by a reduced electrical power output. T…
Order-disorder evolution in solid solutions of the NLO material KTiOPO : K Rb TiOPO and K Rb TiOPO in the temperature range 293-973 K
2000
K0.88Rb0.12TiOPO4 and K0.465Rb0.535TiOPO4 solid solutions of the potassium titanyl phosphate (KTiOPO4, space group Pna21) family, are described at 293, 473, 673, 873 and at 973 K. Their high resolution structures are obtained by using accurate single-crystal X-ray diffraction techniques at high resolution, (sin A-1. Large anharmonic motion of alkaline ions increasing with temperature allows the evolution of the rubidium and potassium ions repartition in the two alkaline sites versus temperature. To describe this motion inducing ionic conductivity phenomenon and to determine accurately the order-disorder evolution, two alkaline site refinement models are developed and discussed. A thermodyna…
<title>Holographic recording in amorphous chalcogenide semiconductor photoresists</title>
1998
The properties and mechanism of relaxation processes of holographic gratings in amorphous chalcogenide semiconductor films have been studied. The possibilities of the practical applications of these materials as the photoresists for the production of the relief holograms and holographic optical elements are discussed. It is shown that the self- enhancement phenomenon of holographic recording in amorphous chalcogenide semiconductor films by light or thermal treatment can be used to increase the diffraction efficiency of the holograms.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
<title>Investigation of As<formula><inf><roman>2</roman></inf></formula>S<formula><inf><roma…
2008
We have performed the investigation of dot matrix holographic recording in amorphous As2S3 chalcogenide films with different thickness on Al coated glass substrates. The control over the interference minimum of reflection during the evaporation process allowed obtaining As2S3-Al system with a minimum value of initial reflection in defined spectral region. The investigation of dependence of diffraction efficiency of holographic recording on both film thickness and initial conditions of reflectivity in the system was performed. The main advantage of this type of system is the possibility to increase optical sensitivity of material in predefined spectrum region for phase hologram recording.© (…
<title>Angular selectivity of thin gratings</title>
2005
The angular selectivity of thin gratings is studied both experimentally and theoretically. The concepts of thick and thin gratings are analyzed. Thin holographic gratings recorded in a-As-S-Se films have exhibited pronounced and oscillatory diffraction efficiency angular dependences. These results are explained by the obliquity factor in Fresnel-Kirchhof diffraction integral and by finite beam and grating sizes. It is also shown that oscillatory diffraction efficiency angular dependences, most probably, arise due to the interference of diffracted waves of different orders because dephasing can be significant for small grating strengths and large enough readout angles. Fabry-Perot resonator …
NUMERICAL-EXPERIMENTAL METHOD FOR THE ANALYSIS OF RESIDUAL STRESSES IN COLD-EXPANDED HOLES
2012
Hole cold expansion is a technique widely used to improve the fatigue life of components with holes, e.g. bolted or riveted joints. As it has been demonstrated in literature by analytical, numerical and experimental analyses carried out by several authors, the compressive residual stresses introduced by the hole cold expansion have a beneficial influence on both the static and the fatigue strength of the treated component, because they reduce significantly the typical stress peaks around the hole due to stress concentration. In the literature, various analyses of the residual stresses introduced by the hole cold expansion have been performed by using several methods such as X-ray diffractio…
New zeolite-like RUB-5 and its related hydrous layer silicate RUB-6 structurally characterized by electron microscopy.
2020
RUB-5 and its related hydrous layer silicate RUB-6 were synthesized in the 1990s, but so far their structures have remained unknown due to their low crystallinity and disorder. The combination of 3D electron diffraction, X-ray powder diffraction, high-resolution transmission electron microscopy, structural modelling and diffraction simulations has enabled a comprehensive description of these two nanomaterials, revealng a new framework topology and a unique silica polymorph.
Structural investigation of four-centre photopolymerisation of bis-phthalamic bis-chalcone derivative in the crystalline state
1997
By combining the results obtained from an electron diffraction tilting series with solid state NMR and powder X-ray diffraction, it was possible to determine the unit cell parameters and space group of BPABC crystals grown from DMAA solution both before and after irradiation. Subsequently semi-empirical quantum mechanical and packing energy calculations led to a model structure which agreed well with all the electron diffraction data and thus provided insight into the cross-linking mechanism. © 1997 John Wiley & Sons Ltd.
An experimental methodology to study polymer crystallization under processing conditions. The influence of high cooling rates
2002
Abstract A new experimental route for investigating polymer crystallization under very high cooling rates (up to 2000°C/s) is described. A complete and exhaustive description of the apparatus employed for preparing thin quenched samples (100– 200 μm thick) is reported, the cooling mechanism and the temperature distribution across sample thickness is also analysed, showing that the final structure is determined only by the thermal history imposed by the fast quench apparatus. Details concerning the characterization techniques used to probe the final structure are reported, including density measurements and wide angle X-ray diffraction patterns. Experimental results concerning isotactic poly…
Structural and Dielectric Properties of Na0.99Li0.01NbO3Ceramics
2006
Na0.99Li 0,01 NbO3 ceramics were prepared by solid-state reaction method. The samples were characterized by X-ray diffraction, microstructure and dielectric permittivity measurements. The X-ray diffraction analysis showed that samples have a single phase of perovskite structure with orthorhombic symmetry. Microstructure investigations revealed crystalline structures in grains. It was found that dielectric properties of Na99Li0.01NbO3 ceramic are sensitive to the applied axial pressure. This includes the shift of phase transformation, diffuseness of the ϵ (T) profile and reduction of the thermal hysteresis. These effects can be caused by change in domain structure and anisotropy of crystalli…