Search results for "cobalt"

Cobalt−NHC Catalyzed C(sp2)−C(sp3) and C(sp2)−C(sp2) Kumada Cross‐Coupling of Aryl Tosylates with Alkyl and Aryl Grignard Reagents

2021

The first cobalt‐catalyzed cross‐coupling of aryl tosylates with alkyl and aryl Grignard reagents is reported. The catalytic system uses CoF3 and NHCs (NHC=N‐heterocyclic carbene) as ancillary ligands. The reaction proceeds via highly selective C−O bond functionalization, leading to the corresponding products in up to 98 % yield. The employment of alkyl Grignard reagents allows to achieve a rare C(sp2)−C(sp3) cross‐coupling of C−O electrophiles, circumventing isomerization and β‐hydride elimination problems. The use of aryl Grignards leads to the formation of biaryls. The C−O cross‐coupling sets the stage for a sequential cross‐coupling by exploiting the orthogonal selectivity of the cataly…

Strain-induced magnetic anisotropies in Co films on Mo(110)

2004

Microwave signature for gas sensing: 2005 to present

2015

Abstract We present here the development and the implementation of a technique of gas detection involving a microwave transduction method. The use of low-cost sensors based on microstrip or coplanar structures, adapted to the microwaves domain, allows the sensitive materials deposition under various forms. The purpose of the study is to assess the interest of microwave transduction for gas detection. The choice of the sensitive materials concerns materials widely used in the field of gas sensing: the metal oxides (SnO2 and TiO2) as well as molecular materials like cobalt phthalocyanine (CoPc). In this article we shall apply to explain the principles of the microwave transduction before appr…

Identification of overglaze and underglaze cobalt decoration of ceramics from Valencia(Spain) by portable EDXRF spectrometry

2004

The purpose of this work is the application of non-destructive analysis to differentiate underglaze and overglaze techniques used in the decoration of glazed ceramics from Valencia (Spain). This study was carried out by portable EDXRF spectrometry using an X-ray tube and a thermoelectrically cooled semiconductor detector. From the EDXRF spectra we have identified the main elements present in the tin-opacified lead glaze and in the cobalt pigments. The identification of the underglaze and overglaze decoration is based on the different ratios between the fluorescence line of the main component of the glaze (Pb-La line) and the fluorescence lines of the main components of the pigment (Co-Ka, M…

Coordinating behaviour of a new pyridylhydrazone; tris-complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) with 2-pyridylcarb…

1991

The preparation and characterization oftris-complexes of MnII, CoII, NiII, CuII and ZnII with a new pyridylhydrazone, 2-pyridylcarbaldehyde-N,N-dimethylhydrazone (pch), are described. In all the complexes pch behaves as a bidentate ligand binding through the pyridine and azomethyne nitrogen atoms. The complexes appear to be monomeric, high spin six-coordinate, and a distorted octahedral stereochemistry around the metal is suggested. The e.p.r. results for both CuII compounds indicate a mainly dx2−y2 ground state with a static Jahn-Teller distortion, whilst for the MnII complex the e.p.r. data indicates a very low symmetry for the MnN6 polyhedron.

Ibuprofen degradation using a Co-doped carbon matrix derived from peat as a peroxymonosulphate activator

2021

The wider presence of pharmaceuticals and personal care products in nature is a major cause for concern in society. Among pharmaceuticals, the anti-inflammatory drug ibuprofen has commonly been found in aquatic and soil environments. We produced a Co-doped carbon matrix (Co-P 850) through the carbonization of Co2+ saturated peat and used it as a peroxymonosulphate activator to aid ibuprofen degradation. The properties of Co-P 850 were analysed using field emission scanning electron microscopy, energy filtered transmission electron microscopy and X-ray photoelectron spectroscopy. The characterization results showed that Co/Fe oxides were generated and tightly embedded into the carbon matrix …

Crossing the boundary between face-centred cubic and hexagonal close packed: the structure of nanosized cobalt is unraveled by a model accounting for…

2014

The properties of nanostructured cobalt in the fields of magnetic, catalytic and biomaterials depend critically on Co close packing. This paper reports a structural analysis of nanosized cobalt based on the whole X-ray diffraction (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 (h.c.p. and f.c.c.). Shape, size distribution and distance distribution between pairs of atoms are also modelled. The simulation algorithm allows straightforward fitting to experimental data and hence the quantitative …

Spin canting in an unprecedented three-dimensional pyrophosphate- and 2,2'-bipyrimidine-bridged cobalt(II) framework.

2008

The three-dimensional cobalt(ii) compound of formula {[Co(2)(P(2)O(7))(bpym)(2)].12H(2)O}(n), where the pyrophosphate and 2,2'-bipyrimidine act as bridging ligands, is a new example of a spin-canted antiferromagnet with T(c) = 19 K.

Oral intake of cadmium, cobalt, copper, iron, lead, nickel, manganese and zinc in the university student's diet.

1993

A duplicate diet meal study was carried out with a group of university students living in a hostel, in order to estimate the intake of Zn, Cd, Co, Cu, Fe, Mn, Ni and Pb. Zn, Cu, Fe, Mn and Ni were determined by flame atomic absorption spectrophotometry and Cd, Co and Pb by graphite furnace atomic absorption spectrophotometry after a nitric acid wet digestion procedure. The estimated intake values from the contents of breakfast, lunch, dinner and drinks were compared with the values of the Provisional Tolerable Daily Intake (PTDI) in the case of Cd and Pb, Recommended Dietary Allowances (RDA) of Co, Fe and Zn and Estimated Safe and Adequate Dietetic Daily Intake (ESADDI) of Cu and Mn. Neithe…

Characterization of Cobalt Catalysts on Biomass-Derived Carbon Supports

2017

Cobalt catalysts are known to have a high activity and selectivity in the Fischer–Tropsch reaction converting synthesis gas to higher hydrocarbons (C5+). These catalysts have been supported by different porous materials. Porous carbon materials like activated carbon (AC) have physical and chemical surface properties that affect the preparation of supported metal catalysts and can easily be tailored. In this study, AC was produced by carbonization and steam activation of lignin, a waste fraction from the Kraft pulping process. A series of Co/AC-catalysts was produced and characterized by several techniques. According to the results, tailored properties (high surface area, mesoporosity) were …