National Institute Of Materials Physics - Romania

Publications

163 articles found

141. EPR and TEM characterization of electrolurninescent Alq(3)

Authors: Grecu, MN; Ghica, C; Mirea, A; Grecu, VV; Schwoerer, M

Published: 2006, ADVANCED MATERIALS FORUM III, PTS 1 AND 2, 514-516, 137, DOI: 10.4028/www.scientific.net/MSF.514-516.133

EPR and TEM investigations on sublimated solid Alq(3), [tris(8-hydroxyquinoline)aluminum(Ill)] are reported. Different paramagnetic centers in microcrystalline Alq3 fractions as synthesized and annealed are observed. Their nature, thermal treatment dependence, as well as correlation with the crystal structure are analyzed. The existence of randomly oriented triplets and quartets in annealed Alq3 fractions is evidenced from the temperature dependence of X- and Q-band EPR spectra. The spin Hamiltonian parameters are given and proposals for the model structures are made.

142. Preparation of Mo-V-Te-Nb mixed oxides using the template route

Authors: Florea, M; Gaigneaux, EM; Parvulescu, VI

Published: 2006, , DOI: 10.1016/S0167-2991(06)80979-1

143. Paramagnetic defect centres in crystalline Alq(3)

Authors: Grecu, MN; Mirea, A; Ghica, C; Colle, M; Schwoerer, M

Published: OCT 5 2005, JOURNAL OF PHYSICS-CONDENSED MATTER, 17, 6283, DOI: 10.1088/0953-8984/17/39/012

X- and Q-band electron paramagnetic resonance (EPR) investigation of different crystalline Alq(3) (tris(8-hydroxyquinoline)aluminium (III)) fractions formed by a train sublimation method are reported. Several paramagnetic defect centres corresponding to 1/2, 1, and 3/2 spin are observed at room temperature. Their intensity is dependent on the temperature, nature of the crystalline phase, and preparation conditions. Spectra simulation and analysis based on the spin Hamiltonian appropriate to a high spin system (S >=, 1) suggest the existence of randomly oriented triplets and quartets in annealed Alq(3) fractions. The crystalline Alq(3) phases responsible for the EPR powder spectra have been identified by transmission electron microscopy measurements performed on these sample fractions.

144. Supported perovskites for total oxidation of toluene

Authors: Alifanti, M; Florea, M; Somacescu, S; Parvulescu, VI

Published: SEP 1 2005, , DOI: 10.1016/j.apcatb.2005.02.018

145. Vanadium aluminium oxynitride catalysts for propane ammoxidation reaction - Effect of the V/Al ratio on the structure and catalytic behviour

Authors: Florea, M; Silvy, RP; Grange, P

Published: MAY 26 2005, , DOI: 10.1016/j.apcata.2005.02.032

146. Evidence for the participation of lattice nitrogen from vanadium aluminum oxynitrides in propane ammoxidation

Authors: Olea, M; Florea, M; Sack, I; Silvy, RP; Gaigneaux, EM; Marin, GB; Grange, P

Published: MAY 15 2005, , DOI: 10.1016/j.jcat.2005.02.020

147. Supported Co-based perovskites as catalysts for total oxidation of methane

Authors: Alifanti, M; Blangenois, N; Florea, M; Delmon, B

Published: MAR 8 2005, , DOI: 10.1016/j.apcata.2004.11.005

148. Influence of the co-precipitation pH on the physico-chemical and catalytic properties of vanadium aluminum oxide catalyst

Authors: Blangenois, N; Florea, M; Grange, P; Silvy, RP; Chenakin, SP; Bastin, JM; Kruse, N; Barbero, BP; Cadus, L

Published: JUN 10 2004, , DOI: 10.1016/j.apcata.2003.12.008

149. Epoxidation of cyclohexene on silicalite embedded BiOx clusters

Authors: Parvulescu, VI; Florea, M; Gelbard, G; Centeno, MA; Macovei, D; Lemay, G; Kaliaguine, S

Published: 2004, RECENT ADVANCES IN THE SCIENCE AND TECHNOLOGY OF ZEOLITES AND RELATED MATERIALS, PTS A - C, 154, 2654, DOI:

Silicalite embedded BiOx Clusters were prepared both with and without Na using sodium silicate and tetraethylorthosilicate as silicium precursors. Catalysts with 3 and 5 wt% Bi were obtained. The MFl structure was established from XRD, TEM, and N-2 adsorption measurements. No deterioration of the silicalite framework by bismuth was observed. Bi exists as BiOx clusters as evidenced from XPS and EXAFS characterization. These clusters are localized inside the silicalite channels. Py-FTIR measurements indicated that 5wt% Bi led to the formation of strong Lewis acid sites. Epoxidation of cyclohexene was found to depend oil both Bi and Na content. On 3%Bi-ZSM-5 it occurred with rather good conversion and selectivity to epoxide. No visible leaching was evidenced. The catalysts were reused for several runs.

150. Vanadium aluminium oxynitride catalyst for propane ammoxidation

Authors: Florea, M; Silvy, RP; Grange, P

Published: MAY-JUN 2004, , DOI: