Search results for "CERAMICS"
showing 10 items of 1599 documents
Numerical simulations of the mechanical characteristics of glass fibre reinforced C-profiles
2006
A mechanical characterisation analysis on pultruded glass fibre reinforced C-shaped profiles, developed as modular construction elements to assemble fastening systems, such as doors, window frames and shutters is presented. The key idea is to perform the analysis, and all the related identification procedures of the material parameters, via a coupled approach, based on a limited number of standard laboratory tests and on the numerical finite element simulations of the same tests. The proposed approach allows one to identify all those material parameters which are difficult to detect, by means of simple laboratory experiments on specimens that are extracted from commercial products. It also …
Bubble formation and motion in non-crimp fabrics with perturbed bundle geometry
2010
The behaviour of the fluid front during impregnation of non-crimp fabrics has been considered. Particular attention is paid to creation of bubbles at the fluid front and a virtual 3D model mimickin ...
Self-organization of porphyrin units induced by magnetic field during sol-gel polymerization
2007
The use of a magnetic field as a controlling factor during the hydrolysis-polycondensation of porphyrin precursors substituted by Si(OR)(3) groups, induces a self-organization of porphyrin moieties due to the stacking of these units in the hybrid material and this study also confirms the effect of the magnetic field in the nano- and micrometric organization during the kinetically controlled polycondensation process.
Excitons in SiO2: a review
1992
Abstract In this paper, excitonic properties of crystalline and glassy SiO 2 are reviewed. Experimental spectroscopic data (optical absorption and reflection spectra, as well as spectra of luminescence and its excitation), luminescence decay kinetics at different temperatures, and photoelectric properties — photoconductivity and photoelectron emission — were used to determine excitons in SiO 2 . Information on migration of excitons was obtained on the basis of energy transport to impurity luminescence centers, the latter being detectors of quasiparticles. Determination of excitonic properties in glassy SiO 2 was based on the comparison of the observed phenomena in crystalline and glassy mat…
Photo-induced magnetic bistability in a controlled assembly of anisotropic coordination nanoparticles.
2011
International audience; Anisotropic coordination nanoparticles of the photomagnetic network Cs(I)(2)Cu(II)(7)[Mo(IV)(CN)(8)](4) are obtained through a surfactant-free high-yield synthetic procedure in water. These particles are organised as Langmuir-Blodgett films with a preferential orientation of the nano-objects within the film that exhibit a magnetic bistability below 20 K with a very large coercivity due to an efficient photo-transformation.
Description of Relaxor State in Na1/2Bi1/2TiO3-SrTiO3-PbTiO3 System of Solid Solutions
2011
Vogel-Fulcher law, traditionally applied to describe dispersion of dielectric permittivity in relaxor ferroelectrics, requires introduction of two different relaxation mechanisms above and below freezing temperature correspondingly. Extending distribution function of relaxation times, previously known for low-temperature region, allows creating common description of relaxation in all range, where distribution function of relaxation times can be regarded as wide, without freezing at certain temperature.
Broadband dielectric spectroscopy of PSN ceramics
2007
Abstract The complex dielectric permittivity of ordered and disordered PSN ceramics was measured in the frequency range from 20 Hz to 3 GHz. The anomaly of dielectric permittivity is clearly seen in the region of 115 °C for ordered PSN at all measured frequencies. Disordered PSN exhibits typical relaxor behaviour with a huge frequency dispersion below 125 °C. Calculated distribution of relaxation times shows noticeable influence of polar clusters to the total dielectric spectrum of disordered PSN below 80 °C with the longest relaxation times edge diverging according to the Vogel–Fulcher law. In the case of ordered PSN, two almost not overlapping peaks in the distribution of relaxation times…
ELECTRICAL PROPERTIES OF LEAD FERROTANTALATE CERAMICS
2009
ABSTRACT Perovskite structures with high dielectric constants and magnetic properties play an important role in micro- and optoelectronics and have numerous practical applications. Relaxor type ferroelectric ceramics PbFe1/2Ta1/2O3 with perovskite structure was subject of present studies. Pyrochlore free lead ferrotantalate ceramics were produced by solid state technology from oxides. Low- and infra-low frequency studies of dielectric properties of PbFe1/2Ta1/2O3 ceramics have revealed considerable infra-low frequency dispersion at temperatures above the temperature of maximum dielectric permittivity. The observed dispersion described by lemniscates is due to a considerable Maxwell-Wagner r…
Antiferroelectric PbZrO3 thin films: structure, properties and irradiation effects
2004
Abstract Irradiation effects on highly oriented antiferroelectric PbZrO 3 and ferroelectric Pb 0.92 La 0.08 (Zr 0.65 Ti 0.35 )O 3 thin films are investigated being exposed to neutron irradiation up to fluence 2*10 22 m −2 . The higher resistance of antiferroelectric PbZrO 3 thin films as compared to ferroelectric heterostructures to large fluences of neutron irradiation is recognized and discussed. Influence of two factors (structural and charge) was taken into account analysing irradiation effects on materials of different polarization states: ferroelectric PLZT (ceramics and thin films) and antiferroelectric PbZrO 3 films.
Correlating the axial Zero Field Splitting with the slow magnetic relaxation in GdIII SIMs
2021
The field-induced out-of-phase magnetic response of a GdIII complex, selected by its good isolation in the network, has been analyzed and the behaviour of this quasi-isotropic cation has been related to its weak axial zero field splitting ∼0.1 cm-1.