National Institute Of Materials Physics - Romania
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articles found
5271. Corrosion behavior of some amorphous aluminium mixed-metal transition-metal alloys (Al-Mm-MT)
Authors:
Ciolac, S; Calin, M; Roman, R; Jianu, A
The results of the potentiostatic polarization studies taken on some Al-Mm-MT metallic glasses in reducing acid media are presented. The rest potentials development and the electrochemical parameters evaluated from the anodic and cathodic curves were correlated with the alloys composition, and related to those of the alloying components in crystalline state. Our results indicate that: alloying with rare earths does not affect interface processes; the transition metals interfere with the hydrogen reduction kinetics determining its acceleration by increasing Ni content in the alloy composition; substitution of Ni by Fe contributes to corrosion rate reduction, to passive state extension and stabilization, so that Al-Mm-Fe alloy behaves better than Al-Mm-(Fe, Ni) and Al-Mm-Ni alloys.
5272. Anchoring energy of some nematic liquid crystals at alignment layers of different topography
Authors:
Stoenescu, DN; Frunza, S; Roques, Y; Farenc, J; Traverse, JP
Published: 1996, CRYSTAL RESEARCH AND TECHNOLOGY, 31, 1099, DOI:
Using a high electric field method, the anchoring energy was measured for tilted homogeneous cells filled with nematic liquid crystals (5CB, ZLI 1132). These cells contain aligment layers of five different types obtained either by SiO depositions at various incidence angles or by special polyvinylic alcohol (PVA) coatings. The observed differences in the anchoring energy values are due to the differences in the layer topography.
5273. STOICHIOMETRY EFFECTS ON THE Nd3+ CENTRES IN LiNbO3:Nd3+
Authors:
Loro, H; Hernandez, J; Camarillo, E; Murrieta, H; Voda, M; Jaque, F; Sole, JG
Published: 1996, FERROELECTRICS, 185, 36, DOI: 10.1080/00150199608210473
LiNbO3 crystals with three different stoicliiometries(0,88; 0,945 and 1) in the melt were grown and dcped with the same concentration of Nd3+ (0.33%). The Nd3+ centres were systematically investigated by laser spectroscopy for these three crystals. The same Nd3+ centres were obtained for all stoichiometries but its relative distribution depends on the [Li]/[Nb] ratio.
5274. Synthesis and study of the high-T-c superconductor (BiPb)(2)Sr2Ca2Cu3O10+x
Authors:
Aldica, G; Plostinaru, S; Patron, L
Published: MAR-APR 1996, REVUE ROUMAINE DE CHIMIE, 41, 210, DOI:
Three alternative routes of the oxalate method for synthesis of the high-T-c superconducting oxide Bi1.7Pb0.3Sr2Ca2Cu3O10+x have been studied. The best results were obtained using the compound III as precursor.
5276. The contribution to the non-uniform distribution of motion effects obtained for the SC-cut quartz plates
Authors:
Mateescu, I; Zelenka, J; Mateescu, I
Published: 1996, PROCEEDINGS OF THE 1996 IEEE INTERNATIONAL FREQUENCY CONTROL SYMPOSIUM (50TH ANNIVERSARY), 411, DOI: 10.1109/FREQ.1996.559888
New experimental results related to the harmonic dependence of the characteristics of SC-cut quartz resonators on various material and electrode parameters are presented. On the basis of the analysis of SC-cut trapped-energy resonators vibrating in the coupled thickness-shear and thickness-twist in the vicinity of the fundamental and odd overtone thickness-shear frequency dependencies were established of effective mass-loading, effective coupling coefficient, motional capacitance and static capacitance on electrode material and dimensions. The results put into evidence the influence of the non-uniform distribution of motion on behaviour of the SC-cut resonators. The plane-parallel polished SC-cut quartz plate of 14mm diameter with different thickness Ag and CrAu electrodes and two values of electrode diameter were used for the experimental investigations.
5277. Optical and microstructural properties of TiO2(Ni2+) thin films
Authors:
Parlog, C; Gartner, M; Osiceanu, P; Teodorescu, V; Moise, F; Ianculescu, A
Published: 1996, CERAMICS INTERNATIONAL, 22, 99, DOI: 10.1016/0272-8842(95)00062-3
Coloured TiO2(Ni2+) thin coatings doped with transitional metals (Ni) were deposited on different substrates (silicon wafers, glass, aluminum) by the sol-gel dip coating process. Complementary techniques (XPS, SE, TEM, XRD, Absorption Spectroscopy) were used to characterize the surface stoichiometry and optical properties, as well as the structure and texture of the thermally treated gels. The presence of fully oxidized film in the outer layers, crystallization in heat treatment to anatase and rutile, formation of porous and coloured films due to the influence of the dopant and the reaction with the substrate, as well as a decrease by three orders of magnitude of the resistivity of Ni-doped films, are reported.
5279. On the determination of birefringence of liquid crystals by the interference method
Authors:
Moldovan, R; Tintaru, M; Frunza, S; Beica, T; Polosan, S
Published: 1996, CRYSTAL RESEARCH AND TECHNOLOGY, 31, 955, DOI: 10.1002/crat.2170310724
A new method of processing the experimental data in the interference method for the determination of birefringence of liquid crystals which allows obtaining results in good agreement with those from prism or wedge methods, is presented.
5280. Polymer degradation within the glass transition range
Authors:
Chipara, MI; Chipara, MD; Romero, JR
Published: 1996, IEEE 1996 ANNUAL REPORT - CONFERENCE ON ELECTRICAL INSULATION AND DIELECTRIC PHENOMENA, VOLS I & II, 820, DOI:
Polymer degradation around the glass transition temperature exhibits frequently an anomalous behaviour. Starting from the hypothesis that such anomalies are related to the glass transition phenomenon, the most relevant data reported in the literature are reviewed and a theoretical description, based on the free volume approximation is suggested. The degradation process is split in three steps. It is proved that the dominant contributions come from the defect's diffusion step and from the proper chemical stage, which may be supposed to be statistically independent. It is explain, using an extended WLF equation why these anomalies are not located exactly at the glass transition temperature. The agreement between theory and experimental data reported elsewhere is good.
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