National Institute Of Materials Physics - Romania

Publications

5840 articles found

5271. PROPERTIES AND HYDROGENATION ACTIVITY OF PD-DY GAMMA-AL2O3 AND DY GAMMA-AL3O2 CATALYSTS .1. PREPARATION AND CHARACTERIZATION

Authors: PARVULESCU, V; VASILIU, F; SIRBU, C; PARVULESCU, V; ANGELESCU, E

Published: JAN 1994, REVUE ROUMAINE DE CHIMIE, 39, 98, DOI:

Pd-Dy/gamma-Al2O8 and Dy/gamma-Al2O3 catalysts were prepared using the wet impregnation method. As supports was used Pd/gamma-Al2O3 and gamma-Al2O3. BFETM, TED and SAED analysis of these catallysts revelead the presence of the rare earth element as aluminate, oxide or unidentified forms. The rare earth compounds synthesis is controlled by the palladium percents on gamma-Al2O3.

5272. INFLUENCE OF THE MICROTOPOGRAPHY OF THE SIO COVERED BY PVA LAYERS ON THE TILT ANGLE OF LIQUID-CRYSTALS

Authors: MOLDOVAN, R; FRUNZA, S; BEICA, T; BARBERO, G

Published: 1994, MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 257, 130, DOI: 10.1080/10587259408033769

An evaluation of the tilt angle variation observed recently when unrubbed polyvinylic alcohol is deposited on obliquely evaporated SiO layers is presented. The method of calculation supposes that the variation of the tilt angle is due to the modification of the initial topography of SiO during the coverage process with the polymeric film. The Laplace equation was obtained by minimizing the elastic energy of the system in the uniconstant approximation and was analytically solved. The found variation of the tilt angle is in good agreement with the experimentally observed one.

5273. HIGHLY HOMOGENEOUS POLYCRYSTALLINE HGTE SYNTHESIS UNDER PRESSURE

Authors: LAZARESCU, MF; MANEA, AS

Published: 1994, CRYSTAL RESEARCH AND TECHNOLOGY, 29, 43, DOI: 10.1002/crat.2170290112

A high pressure technique for the direct synthesis of polycrystalline HgTe in quartz ampoules is presented. An excess of mercury as well as a quasi-static regime of the inert gas pressure al melt temperatures up to 750 degrees C have been used. X-ray diffraction and SEM confirmed the structural homogeneity of the synthesized material.

5274. HYPERFINE FIELDS AND MAGNETIC-ANISOTROPY IN FE100-XGDX THIN-FILMS AND FE80-XGDXB20 (0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-24) THIN-FILMS AND RIBBONS

Authors: KUNCSER, V; FILOTI, G; SERBANESCU, MD; JIANU, A; CRISTEA, L; DORMANN, JL; NOGUES, M; MAKNANI, J

Published: 1994, HYPERFINE INTERACTIONS, 94, 2326, DOI: 10.1007/BF02063782

Mossbauer measurements performed on Fe100-xGdx thin films and on Fe80-xGdxB20 both as thin films and ribbons show a dependence of the spins orientation and [H-hyp] versus temperature, Gd content and preparation conditions. Increasing the Gd content, the initial low anisotropy disappears and [H-hyp] decreases. A sharp increase of the anisotopy with temperature in ribbons with low Gd concentration is evidenced.

5275. ESR INVESTIGATIONS OF POLYPENTENAMERS DEGRADATION

Authors: DIMONIE, M; COCA, S; CHIPARA, MI; ROMERO, JR; POPESCU, L

Published: 1994, INTERNATIONAL JOURNAL OF POLYMERIC MATERIALS, 24, 279, DOI: 10.1080/00914039408028570

Electron spin resonance investigations of the thermo-oxidative degradation of trans-polypentenamer rubbers, containing various stabilizers, are reported. The dependence of the resonance line parameters on the degradation time and temperature as well as the effect of various stabilizers on the resonance line are studied in detail. The activation energies for the generation of free radicals, the reaction order for the overall generation of free radicals and the associated constant rate, are estimated.

5276. STACKING DEFECTS IN C-60 FILMS

Authors: MANCIU, M; MANAILA, R; DEVENYI, A

Published: 1994, FULLERENE SCIENCE AND TECHNOLOGY, 2, 289, DOI: 10.1080/15363839408009551

The structure of pollycrystalline C60 films prepared by sublimation from 99.9% pure C60 powder and from graphite soot was investigated by X-ray diffraction. A complex fcc (111) line was found in the former samples. Comparison of experimental and simulated (111) profiles allowed to assess quantitatively the degree of stacking disorder introduced during the growth of the film. Probabilities could be derived for continuation of already started fcc and hcp sequences, thereby characterizing the statistical microstructure of the C60 films. Also, the relative magnitudes of inter- and intra-layer disorder can be estimated. The films deposited from graphite soot show a high structural disorder.

5277. DISLOCATIONS IN SYNTHETIC QUARTZ

Authors: CHIRILA, R; ILIESCU, B

Published: 1994, CRYSTAL RESEARCH AND TECHNOLOGY, 29, 169, DOI: 10.1002/crat.2170290202

The present paper is a review of the data about the dislocations in the as-grown quartz crystal. The work presents some general considerations about dislocations, their origins and causes, methods of their observation and techniques to reduce the dislocations density. It is also shown a method to obtain a new shape crystal used in the positive X-seeds preparation.

5278. ESR INVESTIGATION OF ION-BEAM IRRADIATED POLYETHYLENE

Authors: CHIPARA, MI; IFRIM, A; GRECU, VV; TOACSAN, MI; POPESCUPOGRION, N; IONESCU, A; CHIPARA, MD; ROMERO, JR

Published: 1994, POLYMER DEGRADATION AND STABILITY, 43, 169, DOI: 10.1016/0141-3910(94)90065-5

Electron spin resonance (ESR) investigations of polyethylene, irradiated with accelerated sulphur ions, are reported- The temperature dependence of resonance line parameters in the range 20-260-degrees-C, has been studied. Additional ESR data on polyethylene irradiated with neutrons as well as on polyethylene thermally degraded in air are presented. The nature of the free radicals induced by irradiation is discussed.

5279. A supposed amorphisation phase in high-dose, medium energy he ions bombarded austenitic stainless steel

Authors: SARBU, C; CONSTANTINESCU, B

Published: 1994, ELECTRON MICROSCOPY 1994, VOLS 2A AND 2B: APPLICATIONS IN MATERIALS SCIENCES, 540, DOI:

5280. THE INFLUENCE OF THE MELT COOLING RATE ON THE PROPERTIES OF YIG SINGLE-CRYSTAL GROWN BY THE FLUX METHOD FROM SINTERED POLYCRYSTALLINE MATERIAL

Authors: LAZARESCU, MF; MANEA, AS; ELENA, E

Published: 1994, CRYSTAL RESEARCH AND TECHNOLOGY, 29, 894, DOI: 10.1002/crat.2170290621

A method for the single crystal growth of Yttrium Iron Garnet (YIG) in a PbO/PbF2/B2O3 flux mixture with a melt cooling rate of 1-2.5 degrees C/h is described. In order to keep constant the crystal stoichiometry as well as its specific structural and magnetic properties at such high rates of the cooling process, a previously sintered polycrystalline garnet has been used as raw material. The YIG single crystal quality was checked-up by metallographic analysis, X-ray diffraction, SEM, and magnetic susceptibility measurements.