Search results for "Cobalt"
showing 10 items of 1098 documents
Unusual stoichiometry control in the atomic layer deposition of manganese borate films from manganese bis(tris(pyrazolyl)borate) and ozone
2016
The atomic layer deposition (ALD) of films with the approximate compositions Mn3(BO3)2 and CoB2O4 is described using MnTp2 or CoTp2 [Tp ¼ tris(pyrazolyl)borate] with ozone. The solid state decomposition temperatures of MnTp2 and CoTp2 are 370 and 340 C, respectively. Preparative-scale sublimations of MnTp2 and CoTp2 at 210 C/0.05 Torr afforded >99% recoveries with <0.1% nonvolatile residues. Self-limited ALD growth was demonstrated at 325 C for MnTp2 or CoTp2 with ozone as the coreactant. The growth rate for the manganese borate process was 0.19 A˚ /cycle within the ALD window of 300–350 C. The growth rate for the cobalt borate process was 0.39–0.42 A˚ /cycle at 325 C. X-ray diffraction of …
Interface reactivity study between La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathode material and metallic interconnect for fuel cell
2011
Abstract Interface reactivity between La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathode material and metallic interconnect (Crofer22APU) was investigated in laboratory air at 700 °C. Due to the interconnect geometry, two interfaces have been analysed: (i) interconnect rib/cathode interface (physically in contact); (ii) the interface under the channel of interconnect. In both cases, formation of a parasite phase was observed after various ageing treatments (20 h, 100 h and 200 h). However, the growth of the determined SrCrO4 parasite phase depends on interface type and on ageing time. Two different mechanisms have been established in function of interface type: (i) SrCrO4 phase was formed after solid …
Intercalation of cobalt(II)-tetraphenylporphine tetrasulfonate complex in magnetic NiFe-layered double hydroxide
2013
Abstract Hybrid magnetic multilayers have been synthesized by means of intercalation of [5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato]cobalt(II) (CoTPPS) complex in the interlayer space of a Ni II Fe III layered double hydroxide (LDH), through anion-exchange reaction. A sebacate ( − OOC–(CH 2 ) 8 –COO − ) intercalated NiFe-LDH have been used as precursor, facilitating the anion exchange reaction, thus permitting the inclusion of a paramagnetic macrocycle inside the ferrimagnetic NiFe-LDH layers. The material has been characterized by XRD, FT-IR, SEM, SQUID and ESR. The T c for the hybrid NiFe–CoTPPS, ca. 11–12 K, is very close to that shown by the precursor, despite that the intercala…
Switching of easy-axis to easy-plane anisotropy in cobalt(ii) complexes
2021
A tetranuclear cubane-type complex [Co4(ntfa)4(CH3O)4(CH3OH)4] (1) with a {Co4O4} core, and a mononuclear complex [Co(ntfa)2(CH3OH)2] (2) have been rationally obtained by adjusting the ratio of the β-diketonate and Co(II) ions, with the synthetic processes being monitored by in situ microcalorimetry. Then, following synthetic conditions to obtain 2, but using three distinct N-donor coligands - 2,2'-bipyridyl (bpy), 6,6'-dimethyl-2,2'-bipyridyl (6,6-(CH3)2-bpy) and 5,5'-dimethyl-2,2'-bipyridyl (5,5-(CH3)2-bpy) - three novel mononuclear complexes have been obtained, [Co(ntfa)2(bpy)2] (3), [Co(ntfa)2(6,6-(CH3)2- bpy)2] (4) and [Co(ntfa)2(5,5-(CH3)2-bpy)2] (5). The introduction of different cap…
La1-xSrxCo1-yFeyO3-delta perovskites: Preparation, characterization and solar photocatalytic activity
2015
Abstract LaCoO3 perovskites substituted by Sr at the A site and/or by Fe at the B site have been prepared by the citrate method. Characterizations by several techniques, such as specific surface area (BET method), XRD, TPR, SEM, UV–vis in DRS mode, XPS and TGA analyses, have been performed. The so prepared La1−xSrxCo1−yFeyO3−δ perovskites are semiconductor materials showing band gap energy values from 1.9 to 3.2 eV. They displayed solar photocatalytic activity for the 2-propanol degradation in gas–solid regime. The photocatalytic results suggest that the perovskites containing Fe are less active and the activity decreases by increasing the Fe content, however the presence of iron avoids the…
Two-Dimensional 3d–4f Heterometallic Coordination Polymers: Syntheses, Crystal Structures, and Magnetic Properties of Six New Co(II)–Ln(III) Compounds
2014
Six new heterometallic cobalt(II)-lanthanide(III) complexes of formulas [Ln(bta)(H2O)2]2[Co(H2O) 6]·10H2O [Ln = Nd(III) (1) and Eu(III) (2)] and [Ln2Co(bta)2(H2O)8] n·6nH2O [Ln = Eu(III) (3), Sm(III) (4), Gd(III) (5), and Tb(III) (6)] (H4bta = 1,2,4,5-benzenetretracaboxylic acid) have been synthesized and characterized via single-crystal X-ray diffraction. 1 and 2 are isostructural compounds with a structure composed of anionic layers of [Ln(bta)(H2O)2]n n- sandwiching mononuclear [Co(H2O)6]2+ cations plus crystallization water molecules, which are interlinked by electrostatic forces and hydrogen bonds, leading to a supramolecular three-dimensional network. 3-6 are also isostructural compou…
Spectroscopic Signature of the Superparamagnetic Transition and Surface Spin Disorder in CoFe2O4 Nanoparticles
2012
Phonons are exquisitely sensitive to finite length scale effects in a wide variety of materials. To investigate confinement in combination with strong magnetoelastic interactions, we measured the infrared vibrational properties of CoFe(2)O(4) nanoparticles and compared our results to trends in the coercivity over the same size range and to the response of the bulk material. Remarkably, the spectroscopic response is sensitive to the size-induced crossover to the superparamagnetic state, which occurs between 7 and 10 nm. A spin-phonon coupling analysis supports the core-shell model. Moreover, it provides an estimate of the magnetically disordered shell thickness, which increases from 0.4 nm i…
Coordination of expanded terpyridine ligands to cobalt
2013
Abstract The tridentate expanded terpyridine-like ligand N,N′-dimethyl-N,N′-dipyridin-2-yl-pyridin-2,6-diamine (ddpd) and [Co(H2O)6](BF4)2 give the high-spin complex mer-[Co(ddpd)2](BF4)2 with a tetragonally compressed CoN6 coordination geometry according to X-ray diffraction and SQUID measurements. UV–Vis–NIR spectra indicate a large ligand field splitting close to the high-spin/low-spin crossover point. Oxidation of the CoII complex to CoIII is achieved with silver triflate. The self exchange between high-spin CoII and low-spin CoIII is slow on the NMR time scale.
Mono-, bi- and polynuclear complexes of diphenylmethane with Cr, Co and Ru. Synthesis and investigation by 1H, 13C and 17O NMR
1995
Abstract Complexes of diphenylmethane (Ph 2 CH 2 ): Ph 2 CH 2 Cr(CO) 3 ( 1 ), Ph 2 CH 2 [Cr(CO) 3 ] 2 ( 2 ), Ph 2 CH 2 Co 4 (CO) 9 ( 3 ), Ph 2 CH 2 [Co 4 (CO) 9 ] 2 ( 4 ), Ph 2 CH 2 Cr(CO) 3 Co 4 (CO) 9 ( 5 ) and Ph 2 CH 2 Ru 6 C(CO) 14 ( 6 ) have been prepared and characterized by 1 H and 13 C-and 17 O-NMR spectroscopy. Strong shielding effects are caused by the metal valence electrons on the 1 H- and 13 C-NMR chemical shifts of aromatic protons and carbons in π-coordinated ring(s) diphenylmethane. Generally, the order of these shielding effects on the nuclei of the aromatic rings in 1 H-NMR was Co 4 (CO) 9 6 C(CO) 14 3 and in 13 C-NMR Co 4 (CO) 9 3 6 C(CO) 14 . In addition, aromatic solve…
Alcohol oxidation by dioxygen and aldehydes catalysed by square-planar cobalt(III) complexes of disubstituted oxamides and related ligands
2001
The square-planar cobalt(III) complexes of o-phenylenebis(N′-methyloxamidate) (Me2opba) and related oxamate (Meopba) and bis(oxamate) (opba) ligands catalyse the selective oxidation, by dioxygen and pivalaldehyde, of a wide range of secondary alcohols to the corresponding ketones, in good yields and under mild conditions in acetonitrile at room temperature. Thus, the oxidation of the series of α-alkylbenzyl alcohols PhCH(OH)R (R = Me, Et, iPr, tBu) results in the exclusive formation of ketones as a product of C−H bond cleavage, and no C−C bond cleavage products are observed in any case. The modulation of catalytic activity by ligand substituents among this series of cobalt catalysts highlig…