National Institute Of Materials Physics - Romania

Publications

5975 articles found

5491. POSSIBILITY OF COHERENT-GAMMA CERENKOV RADIATION IN RELATIVISTIC HEAVY-ION COLLISIONS

Authors: ION, DB; STOCKER, W

Published: APR 11 1991, PHYSICS LETTERS B, 258, 265, DOI: 10.1016/0370-2693(91)91081-6

Using a simple Foldy-Lax model for the refractive index of photons in a nuclear medium and actual empirical gamma-N forward Compton scattering amplitudes we show that the "coherence condition" for the emission of gamma-Cerenkov radiation is fulfilled at incident energies higher than 16 GeV/nucleon in the gamma-spectral band 140 less-than-or-equal-to omega less-than-or-equal-to 160 MeV, still well below the DELTA resonance region. The predictions for gamma-cross sections are between 62-mu-b and 248-mu-b for projectile nuclei with 16 less-than-or-equal-to A less-than-or-equal-to 32. Also the complete linear polarization of the coherent gamma-Cerenkov radiation is pointed out.

5492. STRUCTURAL INVESTIGATION OF (PB,LN)(TI,MN)O3 CERAMICS (LN = RARE-EARTH)

Authors: POPOVICI, G; NICOLAU, P

Published: APR 1 1991, JOURNAL OF MATERIALS SCIENCE LETTERS, 10, 380, DOI: 10.1007/BF00728038

5493. INFLUENCE OF HEAT-TREATMENT AND POLING ON THE MICROSTRUCTURE OF PB(ZR,TI)O3-TYPE OXIDIC CERAMICS

Authors: POPOVICI, G; RIBCO, L; CONSTANTIN, C

Published: APR 1 1991, JOURNAL OF MATERIALS SCIENCE LETTERS, 10, 393, DOI: 10.1007/BF00728042

5494. NANOCRYSTALS GROWN IN AMORPHOUS CR AND CRNI THIN-FILMS

Authors: BIRJEGA, MI; POPESCUPOGRION, N; CONSTANTIN, CA

Published: 1991, ZEITSCHRIFT FUR PHYSIK D-ATOMS MOLECULES AND CLUSTERS, 20, 371, DOI: 10.1007/BF01544013

The structure of vacuum annealed amorphous sputtered Cr and CrNi (55:45) thin films has been studied by transmission electron microscopy (TEM) and electron diffraction (TED). The thin films with thicknesses ranging from 150 to 600 angstrom were annealed while still on their alkali halide substrates under high vacuum at temperatures ranging from 200 to 370-degrees-C. The TEM and TED data permitted to establish the annealing conditions (temperature, duration), which lead to the nucleation and growth of nanosized crystals in the Cr and CrNi icosahedral glasses.

5495. THIN-FILMS OF AL2O3 AND TA2O5 OBTAINED BY MAGNETRON REACTIVE SPUTTERING

Authors: MUTIHAC, R; OPREA, A

Published: JAN-MAR 1991, REVUE ROUMAINE DE CHIMIE, 36, 54, DOI:

A magnetron with 75 cm2 effective area for reactive sputtering in pure oxygen was realised by modifying AV 500 standard equipment. Dielectric Al2O3 and Ta2O5 thin films of 30 cm2 area and thickness between 0.1-1-mu-m were obtained. Their amorphous structure and excellent visible transmission recommend them for electroluminescent devices production.1-3

5496. MOSSBAUER AND MAGNETIC STUDIES OF AMORPHOUS (FE1-XYX)84B16 ALLOYS

Authors: ZHANG, PQ; ZHAO, JG; LI, S; GABURICI, D; NISTER, CI; FILOTI, G

Published: 1991, HYPERFINE INTERACTIONS, 69, 708, DOI:

Amorphous ribbons of (Fe1-xYx)84B16 with 0 < x < 0.21 were studied using Mossbauer and magnetic measurements. The results proved a short-range order interaction in the prepared samples and nonhomogeneous regions induced by yttrium presence.

5497. CRYSTALLINE PHASES IN SUPERCONDUCTING BI-SR-CA-CU2-O-X CERAMIC

Authors: POPESCU, M; ALDICA, G; SARBU, C; PAUSESCU, P; CRUCEANU, E; VASILIU, F; APOSTOL, M

Published: DEC 16 1990, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 122, 643, DOI: 10.1002/pssa.2211220225

The crystalline phases in the superconducting ceramic Bi:Sr:Ca:Cu2:O(x) exhibiting either low superconducting transition (almost-equal-to 80 K) or both, low and high superconducting transitions (almost-equal-to 110 K) are identified by X-ray and electron diffraction. Two types of modulated structures are observed and their relation to T(c) is discussed within the frame of the oxygen-displacive mode theory.

5498. ON THE RELATIONSHIP BETWEEN THE STATIC RESPONSE AND CORRELATION-FUNCTIONS OF THE SPIN MAGNETIC-MOMENTS

Authors: MANOLESCU, A; MEZINCESCU, GA

Published: DEC 1 1990, PHYSICA A, 169, 429, DOI: 10.1016/0378-4371(90)90112-6

We consider homogeneous states of quantum multicomponent plasmas described by a spin-independent Hamiltonian. Using generalized-moment inequalities we show that the relation between the response and the correlation functions of the spin magnetic moments approaches the classical one in the infinite-wavelength limit (k-->0). For small k, the first correction is of order k2 and is bounded by the semiclassical correction.

5499. ON THE LIMITING FACTORS OF THE CRITICAL CURRENT-DENSITY IN HIGH-TC SUPERCONDUCTING CERAMICS

Authors: MIU, L; CRISAN, A; POPA, S; SANDU, V; NISTOR, L

Published: DEC 1990, JOURNAL OF SUPERCONDUCTIVITY, 3, 394, DOI: 10.1007/BF00617464

The temperature dependence of the critical current density at high temperatures and in weak applied magnetic field for YBa2Cu3O7-y ceramic samples with a pronounced granular character is analyzed. The experimental results can be explained in terms of thermally activated motion of the intergrain Josephson vortices at grain boundaries, which may be an indication that the actual limiting factor for the critical current density in ceramic samples results from a weak pinning force density for the intergrain vortices rather than from the weak-link quenching.

5500. HOPPING CONDUCTIVITY OF THE EXTENDED-HARD-CORE CUBIC LATTICE GAS

Authors: PITIS, R

Published: NOV 1 1990, PHYSICAL REVIEW B, 42, 8381, DOI: 10.1103/PhysRevB.42.8375