Search results for "COBALT"
showing 10 items of 1098 documents
1977
Copolymers from styrene and 1-vinylimidazoles (4a–f), form low spin adducts with iron(II) porphyrins and iron(III) porphyrins, when the content of imidazolyl groups in the polymer is ten mole percent or more. With polymers having a content of imidazolyl groups of less then one mole percent, only high spin adducts are observed. With terpolymers, in which the porphyrin is covalently bound to the copolymer the same phenomenon is observed. Only the high spin Fe(II) porphyrin adducts in the solid state adsorb molecular oxygen like cobalt(II) porphyrins under the same conditions. Adsorptions and desorptions of oxygen are much slower in the cases of iron(II) porphyrins than with the cobalt(II) por…
A real-space approach to the analysis of stacking faults in close-packed metals: Modelling and Q-space feedback Longo Alessandro
2020
An R-space approach to the simulation and fitting of a structural model to the experimental pair distribution function is described, to investigate the structural disorder (distance distribution and stacking faults) in close-packed metals. This is carried out by transferring the Debye function analysis into R space and simulating the low-angle and high-angle truncation for the evaluation of the relevant Fourier transform. The strengths and weaknesses of the R-space approach with respect to the usual Q-space approach are discussed.
Macro-micro relationship in nanostructured functional composites
2012
This paper examines the results of the characterization of two functional composites: Poly(methyl methacrylate) (PMMA)-Ce:YAG (yttrium aluminium garnet doped with cerium) and PMMA-cobalt hexacyanoferrate (CoHCF). The composites were prepared as possible emitters in the fields of lighting thermal sensors. The prepared composites were char- acterized using transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) spectroscopy, thermogravi- metric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) analyses to study the correlation between micro and macro characteristics. We found that the molecular interactions of the two different fill…
(2010). Microstructure and magnetic properties of colloidal cobalt nano-clusters.
2010
The magnetic response of nanometer sized Co nanoparticles (NP) prepared using reverse micelle solutions are presented. The use of complementary structural and morphological probes (like transmission electron microscopy, high resolution electron microscopy, X-ray absorption spectroscopy) allowed to relate the magnetic properties to the size, morphology, composition and atomic structure of the nanoparticles. All data agree on the presence of a core–shell structure of NPs made of a metallic Co core surrounded by a thin Co-oxide layer. The core–shell microstructure of NPs affects its magnetic response mainly raising the anisotropy constant.
Crossing the boundary between fcc and hcp: the structure of nanosized cobalt is unraveled by a model of size distribution, shape and stacking faults …
2014
The properties of nanostructured cobalt in the fields of magnetic, catalytic and biomaterials depend critically on Co close-packing. In this paper we report a structural analysis of nanosized cobalt based on the whole XRD pattern simulation allowed by the Debye equation. The underlying structural model involves statistical sequences of cobalt layers and produces simulated XRD powder patterns bearing the concurrent signatures of hexagonal and cubic close packing. Size distribution, shape and distance distribution between pairs of atoms are also modelled. The simulation algorithm allows straightforward fitting to experimental data and hence the assessment of the model parameters. Analysis of …
Estudio de imanes moleculares de Co(ii): desde sistemas aislados hasta sistemas organizados y multifuncionales
2016
Dentro de la disciplina conocida como Magnetismo Molecular, y a raíz del descubrimiento del Mn12 en 1993, ha surgido un gran interés por las moléculas que presentan una lenta relajación de la magnetización por debajo de una temperatura de bloqueo. A estas moléculas se les conoce como Imanes Unimoleculares (Single Molecule Magnets, SMMs). En la última década, la utilización de compuestos con un único centro metálico paramagnético (Single Ion Magnets, SIMs) se ha postulado como una de las nuevas estrategias utilizadas para la obtención de compuestos que presentan lenta relajación de la magnetización con barreras efectivas más elevadas. Además, desde un punto de vista experimental y teórico, l…
Comparación de los resultados radiológicos, clínicos y analíticos de un vástago con cuello modular y su homólogo monobloque en la artroplastia total …
2022
Introducción: La artroplastia total de cadera es uno de los grandes hitos de la ortopedia moderna. Los vástagos con cuellos modulares fueron introducidos con la ventaja teórica de permitir un ajuste más exacto de la anatomía. La hipótesis de nuestro trabajo es que el vástago modular H-MAX M con cuellos intercambiables permite restaurar el offset femoral y la longitud de miembros, de forma más ajustada que con el vástago monobloque homólogo H-MAX S, obteniendo con ello mejores resultados clínico-funcionales sin añadir los riesgos de una elevación sérica de cromo ni cobalto. El objetivo de nuestro trabajo es comparar los resultados radiológicos, clínicos y analíticos de un vástago con cuell…
Estudio de propiedades magnéticas en compuestos de coordinación multifuncionales
2021
En las últimas décadas, las moléculas imán han atraído la atención de la comunidad científica, puesto que permitirían superar las limitaciones actuales de almacenamiento en dispositivos y, también, por su interés en espintrónica. El descubrimiento de las moléculas imán polinucleares (SMMs) fue impactante, pues presentan lenta relajación de la magnetización por debajo de una cierta temperatura. Por tanto, el desarrollo de moléculas imán mononucleares (SIMs) basadas en iones CoII, como único centro paramagnético responsable de ese comportamiento, son de interés por su alto espín (S = 3/2) y un inherente desdoblamiento a campo cero (zfs), que se puede modificar dependiendo de la geometría impu…
CCDC 234461: Experimental Crystal Structure Determination
2006
Related Article: R.Nunez, O.Tutusaus, F.Teixidor, C.Vinas, R.Sillanpaa, R.Kivekas|2005|Chem.-Eur.J.|11|5637|doi:10.1002/chem.200500288
Electrocatalytic properties of manganese and cobalt polyporphine films toward oxygen reduction reaction
2018
International audience; Novel member of polymetalloporphines, namely manganese polymetalloporphine of type I (pMnP-I) obtained by ion exchange from magnesium polyporphine of type I (pMgP-I) is reported for the first time and compared to its cobalt analogue (pCoP-I). Both polymer films have been obtained via two-step procedure: demetaladon of the pMgP-I electrode film via its exposure to trifluoroacetic acid solution, resulting in formation of the metal-free polyporphine of type I (pH(2)P-I) followed by electrochemically induced incorporation of Co or Mn ions from the acetonitrile solution of cobalt and manganese perchlorates. A further oxidative transformation of pCoP-I, polymer films has l…