Query: Cobalt crystal

title: Approaching the capacity limit of lithium cobalt oxide in lithium ion batteries via lanthanum and aluminium doping
abstract: Lithium cobalt oxides (LiCoO2) possess a high theoretical specific capacity of 274 mAh g 1. However, cycling LiCoO2 based batteries to voltages greater than 4.35 V versus Li/Li+ causes significant structural instability and severe capacity fade. Consequently, commercial LiCoO2 exhibits a maximum capacity of only ~165 mAh g 1. Here, we develop a doping technique to tackle this long standing issue of instability and thus increase the capacity of LiCoO2. La and Al are concurrently doped into Co containing precursors, followed by high temperature calcination with lithium carbonate. The dopants are found to reside in the crystal lattice of LiCoO2, where La works as a pillar to increase the c axis distance and Al as a positively charged centre, facilitating Li+ diffusion, stabilizing the structure and suppressing the phase transition during cycling, even at a high cut off voltage of 4.5 V. This doped LiCoO2 displays an exceptionally high capacity of 190 mAh g 1, cyclability with 96% capacity retention over 50 cycles and significantly enhanced rate capability.Lithium cobalt oxides are used as a cathode material in batteries for mobile devices, but their high theoretical capacity has not yet been realized. Here, the authors present a doping method to enhance diffusion of Li ions as well as to stabilize structures during cycling, leading to impressive electrochemical performance.

title: The effect of chromium and cobalt segregation at dislocations on nickel based superalloys
abstract: The segregation of solutes at dislocations in a polycrystalline and a single crystal nickel based superalloy is studied. Our observations confirm the often assumed but yet unproven diffusion along dislocations via pipe diffusion. Direct observation and quantitative, near atomic scale segregation of chromium and cobalt at dislocations within g' precipitates and at interfacial dislocations leading to the partial or complete dissolution of g' precipitates at elevated temperatures is presented. Our results allow us to elucidate the physical mechanism by which pipe diffusion initiates the undesirable dissolution of g' precipitates.

title: Cobalt ferrite nanoparticles with controlled composition peroxymonosulfate mediated degradation of 2 phenylbenzimidazole 5 sulfonic acid
abstract: Magnetic spinel cobalt ferrite nanoparticles with variable composition (CoxFe3 xO4; x 0.1, 0.5, 0.7 and 1.0) were synthesized. The nanoparticles were characterized by various surface techniques. Average sizes and surface areas of ferrites were determined in the ranges of 11 34 nm and 18.5 49.1 m2/g, respectively. Surface analysis of the nanoparticles confirmed the spinel type structures in which Co(II) incorporated into the crystal lattice. The synthesized catalysts were used to dissociate peroxomonosulphate (PMS) into reactive sulfate radicals SO 4 and further into hydroxyl radicals H O to degrade a target pollutant, 2 phenylbenzimidazole 5 sulfonic acid (PBSA) in absence of heat and light. As the molar ratio of cobalt (i.e. x) in the ferrite catalyst increased from 0.1 to 1.0, PBSA degradation enhanced from 24 to 75% in 240 min. The removal of PBSA increased significantly with the increase in PMS concentration up to 0.1 mM, followed by a decrease at PMS levels of >0.1 mM. Nitrogen content in PBSA was mineralized by the cobalt ferrite PMS system mostly into NO3 and NH4+ ions with minor formation of NO2 Only 32% TOC removal was observed over a 240 min reaction time, indicating carbon content in PBSA was not completely mineralized. A chemical probe method, based on free radical scavenging, revealed the contribution of both SO 4 and H O species in PBSA degradation. Fifteen reaction intermediates were identified using LC/Q TOF ESI MS analysis. Hydroxylation, elimination of sulfonate moiety, and ring cleavage processes were involved in the major degradation pathways. Catalyst reuse experiments demonstrated PBSA degradation efficiency either retained or increased with each subsequent reuse. The magnetic spinel Co ferrite nanoparticles can be applied effectively to activate PMS without energy aiding for degrading harmful emerging organic contaminants in water.

title: Biimidazole containing cobalt(III) mixed ligand complexes: Crystal structure and photonuclease activity.
abstract: Two new mixed ligand complexes of cobalt(iii) containing ancillary biimidazole ligands, [Co(phen)(2)H(2)biim](ClO(4)(3).0.5(H(7)O(3)(ClO(4) (1) and [Co(bpy)(2)H(2)biim](ClO(4)(3).3H(2)O (2) have been synthesized and characterized by various spectroscopic and electrochemical techniques. Both complexes and have been characterized by the single crystal X ray diffraction method. While cobalt complex was found to crystallize in the triclinic system with the P1[combining macron] space group, complex was found to crystallize in the orthorhombic system with the Pbca space group. The unit cell packing of complex shows the presence of a water cluster, which is buttressed by oxygen atoms present in the perchlorate anions and water with an average OO bond distance of 2.41 2.86 A. Interaction of these complexes with calf thymus DNA (CT DNA) was investigated by electronic spectral titrations. The results suggest that complexes and bind to DNA through the groove via hydrogen bonding. This is due to the presence of NH in the ancillary ligand biimidazole, which favors hydrogen bonding with DNA base pairs. The intrinsic DNA binding constant values for complexes and were found to be (5.18 0.23) x 10(4) M( 1) and (1.26 0.13) x 10(4) M( 1) respectively. Groove binding of these complexes with DNA is further supported by viscosity measurements, thermal denaturation and circular dichroism studies. Among the two cobalt complexes, complex possesses greater DNA binding strength due to the presence of the conjugated aromatic structure of the phen ligand which increases the hydrophobic interactions with DNA. DNA cleavage experiments using plasmid DNA pUC 18 show that these complexes exhibit efficient photonuclease activity in the presence of molecular oxygen.

title: Engineering Catalytic Active Sites on Cobalt Oxide Surface for Enhanced Oxygen Electrocatalysis
abstract: Tuning the catalytic active sites plays a crucial role in developing low cost and highly durable oxygen electrode catalysts with precious metal competitive activity. In an attempt to engineer the active sites in Co3O4 spinel for oxygen electrocatalysis in alkaline electrolyte, herein, controllable synthesis of surface tailored Co3O4 nanocrystals including nanocube (NC) nanotruncated octahedron (NTO) and nanopolyhedron (NP) anchored on nitrogen doped reduced graphene oxide (N rGO) through a facile and template free hydrothermal strategy, is provided. The as synthesized Co3O4 NC, NTO, and NP nanostructures are predominantly enclosed by {001} {001} {111} and {112} crystal planes, which expose different surface atomic configurations of Co2+ and Co3+ active sites. Electrochemical results indicate that the unusual {112} plane enclosed Co3O4 NP on rGO with abundant Co3+ sites exhibit superior bifunctional activity for oxygen reduction and evolution reactions, as well as enhanced metal air battery performance in comparison with other counterparts. Experimental and theoretical simulation studies demonstrate that the surface atomic arrangement of Co2+/Co3+ active sites, especially the existence of octahedrally coordinated Co3+ sites, optimizes the adsorption, activation, and desorption features of oxygen species. This work paves the way to obtain highly active, durable, and cost effective electrocatalysts for practical clean energy devices through regulating the surface atomic configuration and catalytic active sites.

title: Crystal structure of cobalt substituted calcium hydroxyapatite nanopowders prepared by hydrothermal processing
abstract: A series of cobalt exchanged hydroxyapatite (CoHAp) powders with different Ca/Co ratios and nominal unit cell contents Ca10 xCox(PO4)6(OH)2, x 0, 0.5, 1.0, 1.5 and 2.0, were synthesized by hydrothermal treatment of a precipitate at 473 K for 8 h. Based on ICP (inductively coupled plasma) emission spectroscopy analysis, it was established that the maximum amount of cobalt incorporation saturated at ~12 at. under these conditions. The effects of cobalt content on the CoHAp powders were investigated using ICP emission spectroscopy, particle size analysis, transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) analyses as well as X ray powder diffraction (XRPD) including Rietveld analysis. According to XRPD, all the materials are single phase HAp and CoHAp of low crystallinity. Rietveld analysis shows that Co enrichment causes the c cell parameter to decrease at a faster rate than the a cell parameter. A microstructural analysis showed anisotropic X ray line broadening due to crystallite size reduction. In CoHAp there is significant crystal elongation in [001] and the average size decreases with increasing cobalt content. The crystallite morphology transforms from rod like for the pure HAp to lamellae at the highest degree of Co substitution. The results of Rietveld refinement (symmetry, size and morphology of the crystallites) were confirmed by TEM and HRTEM analysis.

title: Cobalt, chromium and nickel affect hydroxyapatite crystal growth in vitro.
abstract: Metals are widely used in orthopaedics and recent studies have reported that patients with metal implants have a significant increase of metal levels in serum and synovial fluid. Femoral neck fracture occurred in some patients with metal on metal implants for unknown reasons. Recently, bone quality has emerged as an important factor of bone strength and few studies have investigated the effects of metal ions on hydroxyapatite properties. In the present study, we investigated the effects of Co(2+ Cr(3+ and Ni(2+ on hydroxyapatite (HA) growth in vitro, using carboxymethylated poly(2 hydroxyethyl methacrylate) (pHEMA) as a biomaterial for calcification. We have demonstrated that metal ions reduced the quantity of mineral formed at the surface of the polymer and decreased the ratio Ca/P by 1.12 1.05 and 1.08 fold for Cr(2+ Cr(3+ and Ni(2+ respectively. Furthermore, the size of calcospherites was significantly increased in the metal doped HA compared to the controls, indicating a possible effect of metal ions on the crystal lattice. Indeed, the presence of metal ions increased the crystal size as well as the crystallinity of HA and reduce the lattice parameter c of the HA framework. The information obtained from this work suggests that the quality of the mineral around metallic implants could be altered. However, further investigation should be conducted to further elucidate the effects of metal incorporation on bone mineral and the functional consequences.

title: Metal dependent assembly of a tetranuclear copper(II) complex versus a 1D chain coordination polymer of cobalt(III) complex with N2O2 chelating Schiff base ligand: Synthesis, characterization and crystal structures
abstract: By changing metal ions in the presence of N2O2 chelating Schiff base ligand sal2hn [sal2hn N,N' bis(salicylidene) 1,2 diaminocyclohexane] and a large excess of NaN3 (reagent ratios (metal:L: N 3 2:1:8) tetranuclear copper(II) complex [Cu4(m sal2hn)2(m1,1 N3)2(N3)2] (1) and 1D chain coordination polymer of cobalt(III) complex {Na[Co(m sal2hn)(m1,1 N3)(N3)(H2O)(m O)}n (2) have been successfully obtained. Single crystal X ray analyses revealed that in complex 1 the copper(II) ions are bridged alternately by end on (EO) azido and phenoxo sal2hn ligands, while in complex 2 the cobalt(III) and sodium ions are bridged alternately by end on (EO) azido and phenoxo sal2hn ligands. Complex 1 crystallizes in the monoclinic system, space group P21/n, with a 11.6283(5) A, b 19.5997(8) A, c 9.1531(4) A, b 90.540(6)deg, V 2086.00(15) A3, and Z 2, while complex 2 crystallizes in the monoclinic system, space group C21/c, with a 21.1473(5) A, b 14.0604(3) A, c 15.0452(6) A, b 106.064(3)deg, V 4298.9(2) A3, and Z 8.

title: Synthesis, Crystal Structure, and Spectrum Properties of Cobalt(II) Complexes Based on Tridentate 1,3 Bis(benzimidazol 2 yl) 2 oxopropane Ligand and Derivative
abstract: Two new cobalt(II) complexes [Co(obb)2](pic)2*3(C2H3N) (1) and [Co(Etobb)2](pic)2*2DMF (2) were prepared by the reaction of cobalt(II) picrate with the ligands 1,3 bis(benzimidazol 2 yl) 2 oxopropane (obb) and 1,3 bis(1 ethylbenzimidazol 2 yl) 2 oxopropane (Etobb) respectively. Single crystal X ray diffraction revealed that [Co(obb)2]2+ and [Co(Etobb)2]2+ have a different arrangement. In complex 1 the coordination sphere around cobalt(II) is distorted tetrahedral, whereas in complex 2 the coordination sphere around cobalt(II) is distorted octahedral (where the N4 equatorial plane is formed by four benzimidazoles nitrogen atoms and the axial positions are occupied by two oxygen atoms from the two ligands) The complexes were also identified by IR and UV/Vis spectroscopy.

title: THE MAGNETIC ANISOTROPY OF A COBALT CRYSTAL