National Institute Of Materials Physics - Romania

Publications

5911 articles found

5201. Temperature induced surface transitions in liquid crystal tilted homogeneous cells

Authors: Moldovan, R; Frunza, S; Beica, T; Tintaru, M

Published: MAR 1996, LIQUID CRYSTALS, 20, 335, DOI: 10.1080/02678299608032042

Temperature induced surface transitions in liquid crystal tilted homogeneous cells are experimentally studied. The results are theoretically explained by an elastic theory of surface transitions and the resulting values for the effective splay-bend elastic constant (k) over bar(13) for each liquid crystal material are compared with the results from experience with other types of surface anchoring.

5202. Influence of pyrolization temperature on final characteristics of BSCCO ceramic produced by spray-frozen, freeze drying method

Authors: Badica, P; Aldica, G; Alexeev, AF; Gridasova, TY; Morozov, VV

Published: FEB 1 1996, JOURNAL OF MATERIALS SCIENCE LETTERS, 15, 188, DOI: 10.1007/BF00274446

5203. Spin probe investigation of molecular motions in polyepichlorohydrin .1.

Authors: Chipara, MI; Barb, D; Notingher, PV; Georgescu, L; Sarbu, T

Published: FEB 1996, POLYMER, 37, 712, DOI: 10.1016/0032-3861(96)83160-0

Spin probe investigations on the molecular motions in the glass transition range are reported. Within the free volume approximation, a Fox-Flory dependence of the narrowing temperature on the molecular masses is derived. The experimental results support this theoretical prediction. The glass transition temperature is estimated from the spin probe data, within various approaches, and compared to the results obtained by differential scanning calorimetry.

5204. Ag-substituted Al-Cu-Fe icosahedral phases

Authors: Manaila, R; Macovei, D; Jianu, A; Popescu, R; Nicula, R; Zavaliche, F; Devenyi, A; Xie, Y; Hu, T

Published: FEB 1996, PHYSICA STATUS SOLIDI B-BASIC RESEARCH, 193, 294, DOI: 10.1002/pssb.2221930202

The gradual substitution of Cu by Ag in the Al62Cu25.5-xAgxFe12.5 icosahedral phase (x less than or equal to 10) is investigated by X-ray diffraction from the viewpoint of the induced structural changes. The phonon and random phason disorders, estimated from diffraction linewidths, increase with x, the latter showing, however, an induction range of Ag concentrations. EXAFS results at the CuK and FeK edges show. for low Ag contents, and enhanced disorder in the first coordination sphere, partly relaxed for higher x values. The 6D hypercubic lattice parameter is found to be independent of the Ag content, despite the large diameter of monovalent Ag. The latter facts suggest a d-sp hybridization of the Ag bonds to the surrounding Al, taking place above a certain x value.

5205. The effect of Pt and Pd surface doping on the response of nanocrystalline tin dioxide gas sensors to CO

Authors: SchweizerBerberich, M; Zheng, JG; Weimar, U; Gopel, W; Barsan, N; Pentia, E; Tomescu, A

Published: FEB 1996, SENSORS AND ACTUATORS B-CHEMICAL, 31, 75, DOI: 10.1016/0925-4005(96)80018-9

SnO2 sensors were prepared by precipitating Sn(OH)(4) from an aqueous solution of SnCl4 or by evaporating SnO2 in the UHV. Subsequent X-ray and TEM measurements show grain sizes in the nanometer range after annealing at different temperatures or annealing times. The effect of Pt and Pd doping upon the response to CO is studied. Parameters, which we focused on, are sensor signal dependent on the operating temperature and dependent on the gas concentration. The results for ceramic sensors are compared with those for thin film sensors.

5206. The one-dimensional model of the off-centre potential of the fluorine ion in the NaBr lattice

Authors: Despa, F

Published: JAN 15 1996, JOURNAL OF MATERIALS SCIENCE LETTERS, 15, 173, DOI: 10.1007/BF00291458

5207. Coherent dissociation O-16->4 alpha in photoemulsion at an incident momentum of 4.5 GeV/c per nucleon

Authors: Andreeva, NP; Anzon, ZV; Bubnov, VI; Gaitinov, AS; Eligbaeva, GZ; Eremenko, LE; Kalyachkina, GS; Kanygina, EK; Seitimbetov, AM; Chasnikov, IY; Shakhova, TI; Krasnov, SA; Maksimkina, TN; Tolstov, KD; Chernov, GM; Salmanova, NA; Salomov, DA; Khushvaktova, A; Avetyan, FA; Marutyan, NA; Sarkisova, LT; Sarkisyan, VF; Vokal, S

Published: JAN 1996, PHYSICS OF ATOMIC NUCLEI, 59, 108, DOI:

First searches for the coherent dissociation of relativistic oxygen nuclei into four alpha particles are reported. It is shown that reactions of this type are characterized by a significantly lower decay temperature than the conventional multifragmentation of residual projectile nuclei. The momentum spectra and correlations of alpha particles are not reproduced by the simple statistical model of direct fragmentation. The possibility that the oxygen nucleus undergoing fragmentation acquires a nonzero angular momentum in the collision process is discussed.

5208. Corrosion behavior of some amorphous aluminium mixed-metal transition-metal alloys (Al-Mm-MT)

Authors: Ciolac, S; Calin, M; Roman, R; Jianu, A

Published: JAN 1996, REVISTA DE CHIMIE, 47, 66, DOI:

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.

5209. 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.

5210. 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.