National Institute Of Materials Physics - Romania

Publications

5911 articles found

5421. PEAK EFFECT IN THE MAGNETIC-FIELD DEPENDENCE OF THE TRANSPORT CRITICAL-CURRENT DENSITY IN HIGH-TC SUPERCONDUCTING CERAMICS

Authors: MIU, L; ALDICA, G; HOROBIOWSKI, M; WLOSEWICZ, D

Published: DEC 1991, JOURNAL OF SUPERCONDUCTIVITY, 4, 427, DOI: 10.1007/BF00635859

The maximum observed in the magnetic field dependence of the transport critical-current density of high-T(c) superconducting ceramics was analyzed. Transport critical current and magnetization measurements performed on Bi(Pb)-Sr-Ca-Cu-O bulk sintered samples allowed us to conclude that such a maximum may result from the influence of demagnetization effects at low applied field values and an increase of the intergrannular pinning at higher fields.

5422. EFFECT OF PEROXODISULFATE IONS ON FUNCTIONAL-BEHAVIOR OF HEMOGLOBIN

Authors: SERBANESCU, RM; FRUNZA, L

Published: DEC 1991, GENERAL PHYSIOLOGY AND BIOPHYSICS, 10, 587, DOI:

The influence of ammonium peroxodisulphate on the functional state of human hemoglobin was studied. The investigation techniques included: laser photolysis, spectrophotometry and pH measurements. Two different actions of the peroxodisulphate ions upon hemoglobin seem to occur; a) a proton consuming process and an increase of the 4th CO-binding rate constant, l'4, but not yet oxidation of the heme iron (when S2O8(2-) and heme concentrations were of the same order), and b) a marked oxidation effect (when S2O8(2-) was added in excess).

5423. NON-ARCHIMEDEAN MODEL FOR THE RELAXATION PROCESS OF THE PHOTOINDUCED DARKENING IN AMORPHOUS-CHALCOGENIDE FILMS

Authors: POPESCU, M; ANDRIESH, A; CHUMASH, V; ENACHI, N; COJOCARU, I; GROZESCU, A

Published: DEC 1991, JOURNAL OF NON-CRYSTALLINE SOLIDS, 137, 976, DOI: 10.1016/S0022-3093(05)80283-2

The relaxation of the darkening induced by nanosecond laser pulses in amorphous chalcogenide thin films (AsSe and As2Se3) was modelled on the basis of a non-archimedean (ultrametric) approach. While for AsSe only a single time scale of evolution was evidenced (tentatively related to the simple, molecular structure of the glass) in As2Se3 three time scales were evidenced and discussed in the frame of a complex hierarchical structure of the glass with layer fragments, clusters of layers (amorphites) and, possibly, bigger domains.

5424. MAGNETIC-PROPERTIES OF ZRCO5.1-XFEX ALLOYS

Authors: BURZO, E; GROSSINGER, R; HUNDEGGER, P; KIRCHMAYR, HR; KREWENKA, R; MAYERHOFER, O; LEMAIRE, R

Published: NOV 15 1991, JOURNAL OF APPLIED PHYSICS, 70, 6552, DOI: 10.1063/1.349904

The results of magnetic measurements performed on ZrCo5.1-xFex alloys in the temperature range 4.2-900 K and fields up to 7 T are reported. The presence of solid solutions is evidenced in the composition range x < 0.9. The Curie temperature and the saturation magnetization increase nearly linearly when cobalt is substituted by iron. In addition, the anisotropy field decreases and shows an unusual temperature dependence, with a maximum at T congruent-to 300 K.

5425. ASSESSING STACKING-FAULTS IN BI-SR-CA-CU-O PHASES BY X-RAY-DIFFRACTION

Authors: MANAILA, R; MIU, L; ZAHARESCU, M

Published: AUG 1 1991, JOURNAL OF MATERIALS SCIENCE, 26, 4141, DOI:

A Hendricks-Teller analysis of the X-ray diffraction line shifts in Bi-Sr-Ca-Cu-O phases allows an estimate of the stacking fault probabilities (missing or extra Cu-O layers). The probability values suggest some conclusions about the mutual relationships of the 2201, 2212 and 2223 phases and the kinetics of their formation.

5426. MAGNETIC-PROPERTIES OF GDCO4-XMXB COMPOUNDS WHERE M = FE OR NI

Authors: BURZO, E; POP, V; PLUGARU, N

Published: JUN 1991, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 97, 151, DOI: 10.1016/0304-8853(91)90174-9

The GdCo4-xNi(x)B alloys, for x less-than-or-equal-to 3 and GdCo4-xFe(x)B alloys for x less-than-or-equal-to 1.5 crystallize in a hexagonal structure of CeCo4B-type. The magnetic measurements performed in the temperature range 4.2-900 K show that GdCo4-xM(x)B compounds (M = Fe or Ni) are ferrimagnetically ordered. The mean cobalt moments increase when cobalt is substituted by iron and decrease when it is replaced by nickel. Above the Curie temperatures, the reciprocal susceptibilities for GdCo4-xNi(x)B alloys show a nonlinear temperature dependence. The exchange fields acting on cobalt atoms were evaluated. The variations of the cobalt moments are proportional to those of the exchange fields.

5427. 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.

5428. 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

5429. 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

5430. 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.