National Institute Of Materials Physics - Romania

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839 articles found

821. Thermal stability of amorphous Se/CdSe multilayers

Authors: Popescu, M; Sava, F; Lorinczi, A; Vateva, E; Nesheva, D; Koch, PJ; Gutberlet, T; Uebach, W; Bradaczek, H

Published: AUG 1997, SOLID STATE COMMUNICATIONS, 103, 434, DOI: 10.1016/S0038-1098(97)00207-X

The thermal stability of amorphous Se/CdSe multilayers has been investigated by X-ray diffraction. The multilayer structure is stable up to similar to 60 degrees C. After annealing at higher temperatures hexagonal selenium and hexagonal CdSe phases with nanometric crystallite size were revealed. (C) 1997 Elsevier Science Ltd.

822. Impurity-V-K centres' associations in KI crystals containing lighter halogens

Authors: Matei, L; Serban, T; Secu, M; Beica, T

Published: JUN 1997, JOURNAL OF LUMINESCENCE, 72-4, 692, DOI: 10.1016/S0022-2313(97)00039-2

An attempt has been made to put in evidence the modified V-K centres in low temperature UV irradiated Kl:Cl crystals. The interpretation of the results seems to favour a new type of V-K centre localised near an impurity halogen instead of a heteronuclear V-K centre.

823. Structure and hardness modifications induced by UV light in Ge-As-S amorphous chalcogenide films

Authors: Popescu, M; Skordeva, E; Arsova, D; Vateva, E; Sava, F; Lorinczi, A

Published: 1997, CAS '97 PROCEEDINGS - 1997 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 20TH EDITION, VOLS 1 AND 2, 470, DOI:

X-ray diffraction and transmission experiments as well as hardness measurements on virgin and ultra violet (UV)-irradiated amorphous films in the system GexAs40-xS60 have been performed. The W-light determines the plm softening for x<19 and film hardening for x>19. The structure remains amorphous but the distance characteristic to medium range order (MRO) shows variations as a function of composition and irradiation time. The main effect of the UV light is the release of a significant amount of sulphur.

824. Thermal stability of Se/CdSe multilayers

Authors: Popescu, M; Sava, F; Lorinczi, A; Koch, PJ; Gutberlet, T; Uebach, W; Bradaczek, H; Vateva, E; Nesheva, D

Published: 1996, CAS '96 PROCEEDINGS - 1996 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 19TH EDITION, VOLS 1 AND 2, 304, DOI:

825. A comparative study of zinc-polyaniline electrochemical cells having sulfate and chloride electrolytes

Authors: Sima, M; Visan, T; Buda, M

Published: AUG 1995, JOURNAL OF POWER SOURCES, 56, 136, DOI: 10.1016/0378-7753(95)80024-B

Polyaniline (PANI) films were investigated at 20 degrees C as the positive electrodes for Zn/PANI secondary cells containing either 1 M ZnCl2, 0.5 M NH4Cl or 1 M ZnSO4, 0.18 M (NH4)(2)SO4 electrolytes, respectively, at pH=4.5, Cyclic voltammograms showed similar behaviour for the thin PANI films as those in highly acid media. From the discharge curves specific capacities were calculated of 127-130 Ah kg(-1) for the Zn/PANI, Cl- cell and 82-107 Ah kg(-1) for the Zn/PANI, SO42- cell. Charging limit values of 1.48 V for the Zn/PANI, Cl- cell and 1.52 V for the Zn/PANI SO42- cell were obtained in order to prevent the electrochemical inactivation of the polymer. After 20 to 30 cycles the capacity of both cells decreases rapidly and then levels off. The self-discharge process is important only in the first approximately 80 h, after which the open-circuit voltage remains constant. Zn/PANI, Cl- cell showed better electrical characteristics for use as a secondary system.

826. INFLUENCE OF INITIAL CONDITIONS ON THE OPTICAL AND ELECTRICAL CHARACTERIZATION OF SILLENITE-TYPE CRYSTALS

Authors: HAMRI, A; SECU, M; TOPA, V; BRIAT, B

Published: JAN 1995, OPTICAL MATERIALS, 4, 201, DOI: 10.1016/0925-3467(94)00101-4

We compare a set of results concerning our measurement of the optical absorption (OA), photoconductivity (PC), thermally stimulated currents (TSC) and thermally stimulated luminescence (TSL) on the same crystal. We also investigate the effects of various preillumination treatments at room or liquid nitrogen temperature. We conclude that illumination with infrared light (rather than solely red) plays an important role which has been underestimated in the past.

827. LASER-ABSORPTION IN A SPARK INDUCED BY HIGH-POWER TEA-CO2 RADIATION ON A METALLIC TARGET IN VACUUM

Authors: MOLDOVAN, M; BARBULESCU, D; DINESCU, M; APOSTOL, I; DRAGANESCU, V; MIHAILESCU, IN; MORJAN, I

Published: 1981, REVUE ROUMAINE DE PHYSIQUE, 26, 1079, DOI:

828. PLASMA-TARGET COUPLING IN THE CASE OF TEA-CO2 LASER-PRODUCED BREAKDOWN IN FRONT OF A SOLID TARGET

Authors: URSU, I; APOSTOL, I; DINESCU, M; MIHAILESCU, IN; MOLDOVAN, M; PROKHOROV, AM; AGEEV, VP; KONOV, VI; SILENOK, AV; CHAPLIEV, MI

Published: 1980, OPTICS COMMUNICATIONS, 35, 99, DOI: 10.1016/0030-4018(80)90367-3

829. Physico-chemical properties of two anhydrous azathioprine forms and their interaction with typical pharmaceutical excipients: highlighting new findings in drug formulation development

Authors: Barbatu, A; Lungan, MA; Toulbe, N; Smaranda, I; Daescu, M; Baibarac, M; Manta, CM

Published: , DRUG DEVELOPMENT AND INDUSTRIAL PHARMACY, DOI:

The physico-chemical properties of two anhydrous AZA forms and their interaction with typical pharmaceutical excipients were assessed by applying various methods (such as PXRD, HPLC, TG/DSC, IR, Raman, PL or UV-Vis) in order to highlight new directions for drug formulation. The stability assessment of AZA anhydrous forms I and II was performed in order to determine the risk of degradation of the active ingredient by accidental exposure to nonstandard conditions in the industrial environment, under different storage, transport or processing conditions. The benefits of form II include increased resistance to chemical degradation over a wide range of pH, but further control of storage and processing conditions is necessary to avoid polymorphic transformation into form I. The solubility assessment on the AZA solid forms in different environments that simulate the conditions of the gastrointestinal tract has the advantage of a significantly increased solubility of form II compared with the commercial form I due to the modification of the crystalline structure. In the case of capsules compared to AZA form I or II as powder, an improvement in their solubility was observed, promoted by the presence of one or more excipients in the formulation mixture.

830. Structural and Optical Investigations of Ce3+/Mn2+-Doped LaPO4 Phosphors

Authors: Aitmellal, O; Oufni, L; Messous, MY; Neatu, F; Florea, M; Neatu, S; Rostas, AM; Secu, M

Published: , JOURNAL OF ELECTRONIC MATERIALS, DOI: 10.1007/s11664-020-08678-7

Lanthanum orthophosphate (LaPO4) and La0.95-xCe0.05MnxPO4 (x = 0.00, 0.03, 0.10) phosphors were synthesized by a simple and cost-efficient co-precipitation method and the formation of LaPO4 nanorods with a monoclinic P21/n crystal structure was observed. X-ray diffraction pattern analysis indicated a slight distortion of the LaPO4 crystalline structure and an increase of the lattice strain as a consequence of the Mn2+ and Ce3+ dopants incorporation in the host matrix. Scanning electron microscopy revealed that the microstructure of all powders consists of agglomerations of nanorods, which are around 17 +/- 3 nm in diameter and length ranging from 100 nm to 300 nm. Electron paramagnetic resonance measurements have indicated the presence of Mn2+ in isolated species, but also as agglomerates. Ce3+ and Mn2+ doping of LaPO4 resulted also in a decrease of the band gap up to 4.70 eV compared to the un-doped sample. Because of an energy transfer effect from Ce3+ to Mn2+ ions, green emission of Mn2+ ions at around 550 nm was observed upon 275 nm excitation.