Crystallization Of Co Research Articles

Synthesis and crystallization of (Co, Cr, Fe, Mn, Ni)3O4 high entropy oxide: The role of fuel and fuel-to-oxidizer ratio

The main object of this study is to synthesize (Co, Cr, Fe, Mn, Ni)3O4 high-entropy oxide through the solution combustion synthesis (SCS) method in the presence of different fuels at various fuel-to-oxidizer (F/O) ratios. Differential thermal analysis (DTA) and in-situ high-temperature XRD (HT-XRD) results demonstrated the high degree of thermal stability of the synthesized powder up to 1100 ​°C. According to XRD results, the single-phase high-entropy oxide was crystallized at fuel-lean conditions without any heat treatment. However, the single-phase high-entropy oxide was crystallized in all samples when they were heat-treated at 600 ​°C. X-ray photoemission spectroscopy (XPS) analysis and elemental-mapping analysis results clarified the high homogeneity of the obtained powder. Statistical analysis of results revealed a direct correlation of F/O, crystallinity, crystallite size, and lattice distortion values with magnetization saturation (Ms). Besides, the data represent an indirect correlation between micro-strain and Ms. The highest amount of Ms (14.6 emu/g) was obtained for the synthesized sample with a lattice distortion of 10.28%. Moreover, a specific surface area (SBET) value of 121 ​m2/g was obtained. In summary, the results indicated the significant role of fuel type and F/O ratio in improving the physicochemical properties of SCS synthesized (Co, Cr, Fe, Mn, Ni)3O4 high-entropy oxide.

Fabrication of β-Mn type Co–Zn–Mn(001) film on MgO single crystal substrate

β-Mn type Co–Zn–Mn is a chiral magnet hosting Bloch type magnetic skyrmions and has been extensively studied because the magnetic skyrmions are observed above room temperature depending on the composition of Co, Zn, and Mn. So far, epitaxially grown film of Co–Zn–Mn on single crystal substrates has not been not realized whereas the epitaxial film is important from the fundamental and practical point of view. In this study, Co–Zn/Mn multilayered film was sputter-deposited on MgO(001) single crystal substrate and then annealed in vacuum for the crystallization of Co–Zn–Mn alloy. β-Mn type Co–Zn–Mn epitaxial film with (001) orientation was successfully fabricated although the film consisted of twinned crystal grains. We also showed that the annealing of 300–350 °C was effective to drive the crystallization, and that the possibility to enhance the crystallinity by optimizing the fabrication conditions.

Alternating [ML2(MeOH)2] and [ML2(EtOH)2] layers in low-temperature ferromagnets [ML2(MeOH)2][ML2(EtOH)2] (M = CoII, NiII or CoII0.5NiII0.5)

Crystallization of Co(ii) and Ni(ii) complexes with a 3-imidazoline nitroxide derivative from a mixture of MeOH and EtOH (1 : 10) leads to the formation of complexes with an ordered alternation of supramolecular MeOH- and EtOH-containing layers.

Solution-phase selenization engineering of zeolitic imidazolate framework (ZIF)-67-derived Co0.85Se@nitrogen-doped carbon for potassium-ion storage

Research on the synthesizing high-efficiency energy storage materials, which can the replace the harsh methods that require high temperature or high pressure, with methods that are more convenient and eco-friendly, are crucial for next-generation battery manufacturing. Herein, we introduce a facile method for the direct and short-term selenization of cobalt ions in zeolitic imidazolate framework-67 (ZIF-67) using a NaHSe solution. Co0.85Se@nitrogen-doped carbon nanostructures (sol-CoSe@NC) obtained after the subsequent Ar heat treatment for the crystallization of Co–Se bonds and the carbonization of organic matter displayed outstanding electrochemical performances in potassium-ion batteries, compared to those fabricated by the well-known gas-phase selenization process. Long cycle life, over 140 cycles (367.7 mA h g−1 at 0.1 A g−1), and excellent rate capability up to 4.0 A g−1 (202.9 mA h g−1) of the sol-CoSe@NC electrode indicated that the ultrafine distribution of Co0.85Se nanoparticles via a low-temperature and low-pressure solution-phase selenization process within the mesoporous structure derived from metal-organic framework could favorably work for the repeated insertion and desertion of potassium ions.

Synthesis of statistical poly(ethylene terephthalate‐co‐2,6‐naphthalate) (co)polymers and study on their properties: Thermal and barrier properties

AbstractIn this paper, a series of poly(ethylene terephthalate‐co‐2,6‐naphthalate) (PETN) (co)polyesters with different naphthalene ring contents were synthesized via a two‐step transesterification and polycondensation. The effects of the monomer compositions on the sequence distribution, crystallization, mechanical, thermal, and barrier properties of the (co)polymers were investigated systematically. The results showed that the introduction of naphthalene ring units (NDC) changed the sequence length of the PETN and disrupted the orderly arrangement of the PETN molecular chains, thus affecting the aggregated structure and properties of the copolymer. When the NDC content was less than 30%, the PETN copolymers displayed good ductility and higher yield strength comparable to PET, and the heat distortion temperature (HDT), thermal stability properties, and barrier properties of the copolymer were also improved. In addition, the diffusion kinetics of water and oxygen molecules in the (co)polymer were investigated by the MS program simulation software. The differences in gas barrier properties of the different PETN (co)polymers were explained at the molecular level. This study provides a systematic theoretical basis and comprehensive practical guidance for the preparation of high‐performance copolyester materials.

Partial crystallization of Co–Fe oxyhydroxides towards enhanced oxygen evolution activity

Developing high-performance noble-metal-free electrocatalysts for the oxygen evolution reaction (OER) is of great significance for the large-scale implement of electrochemical water splitting. Here, we demonstrate that cobalt-iron oxyhydroxide (CoFe0.8(OH)x) with appropriate crystallization exhibits excellent OER activity with a low overpotential of only 246 mV, which is much lower than that achieved on amorphous one. Kinetic experiments indicate that the OER active sites should be di-μ-oxo bridged Fe–Co, on which lower energy barrier is attained than that on Fe–O and Co–O sites. Partial crystallization is beneficial to the lattice contraction, the formation of Co–O–Fe sites, and the decrease of charge transfer resistance, thus accelerating OER process.

Laser induced crystallization of Co\u2013Fe\u2013B films

Local crystallization of ferromagnetic layers is crucial in the successful realization of miniaturized tunneling magnetoresistance (TMR) devices. In the case of Co–Fe–B TMR devices, used most successfully so far in applications and devices, Co–Fe–B layers are initially deposited in an amorphous state and annealed post-deposition to induce crystallization in Co–Fe, thereby increasing the device performance. In this work, first direct proof of locally triggered crystallization of 10 nm thick Co–Fe–B films by laser irradiation is provided by means of X-ray diffraction (XRD) using synchrotron radiation. A comparison with furnace annealing is performed for benchmarking purposes, covering different annealing parameters, including temperature and duration in the case of furnace annealing, as well as laser intensity and scanning speed for the laser annealing. Films of Co–Fe–B with different stoichiometry sandwiched between a Ru and a Ta or MgO layer were systematically assessed by XRD and SQUID magnetometry in order to elucidate the crystallization mechanisms. The transformation of Co–Fe–B films from amorphous to crystalline is revealed by the presence of pronounced CoFe(110) and/or CoFe(200) reflexes in the XRD θ-2θ scans, depending on the capping layer. For a certain window of parameters, comparable crystallization yields are obtained with furnace and laser annealing. Samples with an MgO capping layer required a slightly lower laser intensity to achieve equivalent Co–Fe crystallization yields, highlighting the potential of laser annealing to locally enhance the TMR ratio.

Nitrogen-doped Co/Co9S8/partly-graphitized carbon as durable catalysts for oxygen reduction in microbial fuel cells

Durability of catalysts for oxygen reduction reaction (ORR) is the key factor for governing the performance of microbial fuel cells (MFCs). The cobalt (Co) chelated polyaniline (PANI) is used as the nitrogen and carbon sources to prepare the N-doped Co/Co9S8/partly-graphitized carbon (Co/Co9S8/NPGC) catalysts. Structure-activity correlations for Co/Co9S8/NPGC are explored by tuning the heating temperature (600–1000 °C) to investigate how the active components (Co/Co9S8) and N-doped functionalities (N-species) influence the ORR activity. As temperature increases, the gradual crystallization of Co originating from the reduction of Co9S8 is conducted to form the Co/Co9S8 heterojunction. MFCs with Co/Co9S8/NPGC (800 °C) cathode obtain the highest power density (1156 mW m−2) and the lowest charge transfer resistance (11.1 Ω) after 75 d running, which are better than commercial Pt/C (10 wt.%). Although the sole Co9S8 plays a limited role in ORR, the resulting Co/Co9S8 is found to be indispensable to achieve high activity and durability in MFCs cathodes. The dominant ORR pathways of Co/Co9S8/NPGC (800 and 900 °C) are the four-electron O2 reduction, which are attributed to the co-existence of pyridinic N, graphitic N and Co-Nx species. These new N-doped metal sulfide/PGC composites show promise for applications in MFCs.

Two three-dimensional supramolecular networks built from metallophenols through hydrogen bonds and coordinate bonds

Crystallization of Co(NO3)2 with 4-(imidazol-1-yl)phenol (L) gave a complex formulated as [Co(L)6](NO3)2, whose X-ray crystal structure revealed a twofold inclined interpenetrated network supported by extensive hydrogen bonding and π–π stacking interactions. Crystallization of Co(ClO4)2, L and dicyanamide (dca) in ethanol gave a complex formulated as [Co(L)4(μ-dca)] n (ClO4) n ·4n(EtOH)·nH2O. The X-ray crystal structure of this complex consisted of a three-dimensional open framework, constructed by one-dimensional coordination chains through extensive interchain quadruplicate hydrogen bonding interactions between the phenols and uncoordinated amides. The magnetic properties of [Co(L)4(μ-dca)] n (ClO4) n ·4n(EtOH)·nH2O have been studied, revealing weak antiferromagnetic exchange between cobalt atoms. Crystallization of Co(NO3)2 with 4-(imidazol-1-yl)phenol (L) gave a complex formulated as [Co(L)6](NO3)2, whose X-ray crystal structure revealed a twofold inclined interpenetrated network constructed by extensive hydrogen bonding and π–π interaction. Crystallization of Co(ClO4)2, L and sodium dicyanamide (Na(dca)) in ethanol gave a complex formulated as [Co(L)4(μ-dca)] n (ClO4) n ·4n(EtOH)·nH2O, which is a three-dimensional open framework, constructed by one-dimensional coordination chains through extensive interchain quadruplicate hydrogen bonding interactions between the phenols and uncoordinated amides.

Time-resolved synchrotron x-ray diffraction studies of the crystallization of amorphous Co(80−x)FexB20

This paper addresses the time-dependent crystallization process occurring in “bulk” amorphous Co80−xFexB20 (x = 20, 40) metallic ribbons by means of synchrotron x-ray diffraction (SXRD) and transmission electron microscopy. Metallic ribbons, produced via melt-spinning technique, were annealed in-situ, with SXRD patterns collected every 60 s. SXRD reveals that Co40Fe40B20 alloys crystallize from an amorphous structure to a primary bcc α-(Co,Fe) phase, whereas Co60Fe20B20 initially crystallizes into the same bcc α-(Co,Fe) but exhibits cooperative growth of both stable and metastable boride phases later into the hold. Johnson-Mehl-Avrami-Kolmogorov statistics was used on post annealed samples to determine the mechanisms of growth and the activation energy (Ea) of the α-(Co,Fe) phase. Results indicate that the growth mechanisms are similar for both alloy compositions for all annealing temperatures, with the Avrami exponent of n = 1.51(1) and 2.02(6) for x = 20 and 40, respectively, suggesting one-dimensional growth, with a decreasing nucleation rate. Activation energy for α-(Co,Fe) was determined to be 2.7(1) eV and 2.4(3) eV in x = 20 and 40, respectively, suggesting that those alloys with a lower Co content have a stronger resistance to crystallization. Based on these results, fabrication of CoFeB magnetic tunnel junctions via depositing amorphous layers and subsequently annealing to induce lattice matching presents itself as a viable and efficient method, for increasing the giant magnetoresistance in magnetic tunnel junctions.

Crystallization of CO 2 ice and the absence of amorphous CO 2 ice in space

Carbon dioxide (CO2) is one of the most relevant and abundant species in astrophysical and atmospheric media. In particular, CO2 ice is present in several solar system bodies, as well as in interstellar and circumstellar ice mantles. The amount of CO2 in ice mantles and the presence of pure CO2 ice are significant indicators of the temperature history of dust in protostars. It is therefore important to know if CO2 is mixed with other molecules in the ice matrix or segregated and whether it is present in an amorphous or crystalline form. We apply a multidisciplinary approach involving IR spectroscopy in the laboratory, theoretical modeling of solid structures, and comparison with astronomical observations. We generate an unprecedented highly amorphous CO2 ice and study its crystallization both by thermal annealing and by slow accumulation of monolayers from the gas phase under an ultrahigh vacuum. Structural changes are followed by IR spectroscopy. We also devise theoretical models to reproduce different CO2 ice structures. We detect a preferential in-plane orientation of some vibrational modes of crystalline CO2. We identify the IR features of amorphous CO2 ice, and, in particular, we provide a theoretical explanation for a band at 2,328 cm(-1) that dominates the spectrum of the amorphous phase and disappears when the crystallization is complete. Our results allow us to rule out the presence of pure and amorphous CO2 ice in space based on the observations available so far, supporting our current view of the evolution of CO2 ice.

Preparation of Li2CO3 by gas‐liquid reactive crystallization of LiOH and CO2

AbstractA spinning disk reactor (SDR) was used in this research to prepare Li2CO3 by gas‐liquid reactive crystallization of LiOH and CO2. It was found that the end pH value of the above reaction should be controlled within the range of 9.0‐9.5 to obtain a high yield of Li2CO3. The effects of operational parameters (including the temperature, the concentration of LiOH solution, the rotation rate of the spinning disk, the circulation rate of LiOH slurry, the flow rate of CO2 and the ultrasound field) on the particle size and the yielding rate were investigated by an orthogonal experiment. The results show the significant factors influencing the particle size are the ultrasound field, the temperature and the flow rate of CO2. As for the yielding rate, the temperature, the concentration of LiOH solution and the flow rate of CO2 exert obvious impacts, while the effects of ultrasound field and the rotation rate of the spinning disk are limited. The SEM images show the Li2CO3products are flower‐like particles, which are composed of plate‐like primary crystals. The size analysis shows the volume mean particle size of the Li2CO3products ranges 37‐90 μm depending on the various experimental conditions. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Reduction crystallization of Ni, Cu, Fe and Co from a mixed metal effluent

Removal and recovery of heavy metals from effluent are major concerns due to diminishing fresh water resources, depletion of exploitable ores and human and environmental health concerns. The objective of this work was to efficiently recover heavy metals from effluent in their elemental form as metallic powder by reduction crystallization. This method recovers metals in a pure form and enables them to be directly used. Experiments were conducted using mixed metal solutions of Ni, Cu, Co, and Fe in a 20L Perspex batch reactor using hydrazine as a reducing agent and nickel powder as seeding material. Ni, Cu, Co and Fe were effectively reduced to their elemental states with removal efficiencies of over 99% for Ni and Co and about 98% for Cu and Fe. Residual concentrations obtained for Ni, Co and Fe were below 0.05mg/L and below 1.20mg/L for Cu. Based on the evolution of the particle size distribution (PSD) and its derived moments the dominant particulate processes identified were aggregation, growth and breakage with the possibility of nucleation in the presence of Fe. However, particle size enlargement was largely due to aggregation.

Carbon additive effects on the nanostructure and magnetic property of the Co–Fe–Zr–B–C films

In this study, the carbon additive Co–Fe–Zr–B alloy films were prepared by dual-gun co-sputtering. The effects of the carbon addition and heat treatment on the nanostructure and magnetic properties of the Co–Fe–Zr–B–C alloy films are reported. The experimental results show that a crystalline (Co, Fe) phase formed after heat treatment at 400 in the Co–Fe–Zr–B–C films with low carbon additive level. Carbon atoms inhibited the crystallization of the as-deposited Co–Fe–Zr–B–C films. From the TEM observation, the nanostructures, such as the atomic structure and grain sizes, showed a strong carbon content dependence. The coercivities of the Co–Fe–Zr–B–C films annealed at 400 varied from 18 to 0.3 Oe with the increasing carbon addition. However, the films annealed at higher temperature exhibited a dramatic increase in the coercivities, which correlated to the formation of the crystalline (Co, Fe) phase. The resistivities of the Co–Fe–Zr–B–C films relied on the carbon contents rather than on annealing temperatures.

The Study of the Isothermal Crystallization and Electrical Properties of Heterogeneous Metal-Ferroelectric Nano-Composites

The dc conductivity and kinetics of isothermal crystallization of amorphous nano-composites Co x [Pb0.81Sr0.04(Na0.5Bi0.5)0,15(Zr0.575Ti0.425)O3]100− x with different compositions at a presence of an alternating electric field have been studied. It is revealed that the crystallization rate increases as strength of electric field is increased because of magnification of diffusive mobility of atoms. At the same time there was not revealed any effect of frequency of an electric field on the crystallization process of studied amorphous nano-composites.

Study on Preparing and Crystallization Kinetics of Melt-Spun Co-Based Soft Magnetic Amorphous Alloy

Abstract Amorphous ribbons of Co 68.5 Fe 4 Si 10 B 17.5 were prepared by a single roller melt-spinning technique in the air atmosphere. The crystallization products were analyzed by X-ray diffraction. The crystallization kinetics of the alloys were investigated by means of differential scanning calorimetry (DSC) in the mode isothermal annealing. It is found when the isothermal kinetics was modeled by the Johnson–Mehl–Avrami equation, the Avrami exponents are calculated to be in the range of 2.11–2.58 for different isothermal temperatures. This implies that the crystallization of Co 68.5 Fe 4 Si 10 B17.5 amorphous alloy is governed by either diffusion or interface controlled three-dimensional growth, depending on the annealing temperature. On the basis of the Arrhenius relation, the activation energy E c in the isothermal process is calculated to be 113.67 kJ/mol. Finally, details of the nucleation and growth behaviors during the isothermal crystallization are discussed.

Crystallization and thermomagnetic treatment of a Co-rich Co–Fe–Ni–Zr–B–Cu based nanocomposite alloy

The magnetic properties observed after various thermal-magnetic treatments for a (Co0.85Fe0.15)83.6Ni4.4Zr7B4Cu1 alloy are compared with those for a (Co0.88Fe0.12)79.4Nb2.6Si9B9 alloy of similar Co:Fe ratio which exhibited a large field induced anisotropy in previous work. The qualitative conclusions arrived at here also apply to the (Co0.85Fe0.15)88Zr7B4Cu1 alloy without Ni. For the transverse magnetic field annealed (Co0.85Fe0.15)83.6Ni4.4Zr7B4Cu1 alloy, the highest anisotropy fields HK (HK∼35–40Oe), field induced anisotropies KU (KU∼1700–2000J∕m3), and lowest coercivities HC (HC∼0.5–1.5Oe at f=3kHz) were observed for field annealed amorphous ribbons as compared to field crystallized ribbons. For the (Co0.88Fe0.12)79.4Nb2.6Si9B9 alloy, the field induced anisotropy is a maximum for field crystallized ribbons (HK∼28–45Oe, KU∼800–1800J∕m3) and the increase in dynamic coercivity (HC∼0.5–1Oe at f=3kHz) observed upon crystallization is much less dramatic. The field annealed amorphous alloy of composition (Co0.85Fe0.15)83.6Ni4.4Zr7B4Cu1 exhibited field induced anisotropies and dynamic coercivities that are competitive with the field crystallized alloys of composition (Co0.88Fe0.12)79.4Nb2.6Si9B9.

Crystallization of the (Cd,Ca)CO3 solid solution in double diffusion systems: the partitioning behaviour of Cd2+ in calcite at different supersaturation rates

AbstractConsidering an ideal solid solution, the partitioning of cadmium in calcite was studied at different levels of supersaturation (δ) using counter-diffusion experiments. The effective (non-equilibrium) distribution coefficients of Cd2+ in calcite (DCd), varied between 20 and 100 depending on the initial concentration of reactants and the evolution of supersaturation. A function that relates the DCd with the supersaturation at nucleation was derived: logDCd= —0.40logδ + 2.42. The relationship obtained suggests that in naturalwaters, Cd2+ can be incorporated to a greater degree in calcite when the solid solution-aqueous solutions system is near to equilibrium, which can occur in scenarios where the supersaturation rate and hence the supersaturation level are relatively small.

Simultaneous desorption–crystallization of CO 2–CaCO 3 in multi-stage flash (MSF) distillers

In this work, the desorption–crystallization of CO 2–CaCO 3 in MSF distillers was simulated by coupling mass transfer with chemical reaction and correlating the CaCO 3 crystallization rates to the CO 2 release rates. The model was applied to two 20-stage reference MSF once-through and recycles distillers. The CO 2 release rates decreased exponentially from the first stage to the last stage. The CO 2 release rates increased with increasing top brine temperature (TBT) and so CaCO 3 deposition rates did. The CaCO 3 deposition rates increased by 76.9, 102.5 and 123.0 g per ton distillate at 90, 100 and 110 °C, respectively. This corresponded to fouling resistance of 0.64, 0.83 and 1.00 m 2K/kW, respectively. The results were fully discussed and interpreted.

Distribution of trace amounts of M 2+ ions during Co(CH 3COO) 2·4H 2O crystallization

Distribution coefficients (Henderson–Kraček, Khlopin), D 2/1, of trace amounts of Ni 2+, Mg 2+, Cu 2+, Zn 2+, Mn 2+, Cd 2+, Ca 2+, and Sr 2+ have been determined during crystallization of Co(CH 3COO) 2·4H 2O. Their dependencies on some properties of cocrystallizing salts (acetate hydrates) as well as cocrystallizing ions (M 2+) have been analyzed. The D 2/1 values are comprised in the range of 0.004( D Sr)–3.3( D Ni) but most of them are less than 0.06. This indicates that most of investigated M 2+ ions may be effectively removed in preparation of high-purity cobalt(II) salts. M 2+ ions for which | r C o 2 + − r M 2+ | / r C o 2 + > 0.05 , cocrystallize with Co(CH 3COO) 2·4H 2O only in slight degree ( D 2/1 < 0.06). Ions having electron configuration d 1–9 cocrystallize with Co(CH 3COO) 2·4H 2O on an average in the considerable greater degree than ions of electron configuration d 0 or d 10.