Microstructure and Magnetic Properties of Highly Ordered SBA-15 Nanocomposites Modified with Fe2O3 and Co3O4 Nanoparticles

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P. F. Wang

2012-01-01

Full Text Available Owing to the unique order mesopores, mesoporous SBA-15 could be used as the carrier of the magnetic nanoparticles. The magnetic nanoparticles in the frame and the mesopores lead to the exchange-coupling interaction or other interactions, which could improve the magnetic properties of SBA-15 nanocomposites. Mesoporous Fe/SBA-15 had been prepared via in situ anchoring Fe2O3 into the frame and the micropores of SBA-15 using the sol-gel and hydrothermal processes. Co3O4 nanoparticles had been impregnated into the mesopores of Fe/SBA-15 to form mesoporous Fe/SBA-15-Co3O4 nanocomposites. XRD, HRTEM, VSM, and N2 physisorption isotherms were used to characterize the mesostructure and magnetic properties of the SBA-15 nanocomposites, and all results indicated that the Fe2O3 nanoparticles presented into the frame and micropores, while the Co3O4 nanoparticles existed inside the mesopores of Fe/SBA-15. Furthermore, the magnetic properties of SBA-15 could be conveniently adjusted by the Fe2O3 and Co3O4 magnetic nanoparticles. Fe/SBA-15 exhibited ferromagnetic properties, while the impregnation of Co3O4 nanoparticles greatly improved the coercivity with a value of 1424.6 Oe, which was much higher than that of Fe/SBA-15.

Effect of Cr2O3 on the microstructure and non-ohmic properties of (Co, Sb)-doped SnO2 varistors

International Nuclear Information System (INIS)

Aguilar M, J. A.; Pech C, M. I.; Hernandez, M. B.; Rodriguez, E.; Garcia O, L.; Glot, A. B.

2013-01-01

The effect of Cr 2 O 3 addition on the physical characteristics, microstructure, and current-voltage properties of (Co-Sb)-doped SnO 2 varistors was investigated. SnO 2 -Co 3 O 4 -Sb 2 O 5 ceramics with additions of 0.0, 0.03, 0.05 and 0.07 mol % Cr 2 O 3 were sintered at 1350 C under ambient atmosphere and characterized micro structurally and electrically. The characterization by X-ray diffraction and scanning electron microscopy show that the microstructure remains as a single phase material with multimodal size distribution of SnO 2 grains. The greatest effect of Cr 2 O 3 additions is manifested in the electric breakdown field. Additions of high levels (0.07 and 0.05 %) of this oxide promote and increase of approximately 55% in this parameter compared to the Cr 2 O 3 -free sample. Another physical property is affected: the measured density values decreases as the Cr 2 O 3 content increases. A change in the nonlinearity coefficient value is produced only at the highest Cr 2 O 3 content while at intermediate levels there is not change at all. Consequently, when seeking high nonlinearity coefficients, intermediate levels of Cr 2 O 3 are not recommended. (Author)

Microstructures and properties of TiN reinforced Co-based composite coatings modified with Y{sub 2}O{sub 3} by laser cladding on Ti–6Al–4V alloy

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Weng, Fei, E-mail: wengfeisdu@126.com [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Department of Materials Science and Engineering, Shandong University, Ji' nan 250061 (China); Shandong University, Suzhou Institute, Suzhou 215123 (China); Yu, Huijun, E-mail: yhj2001@sdu.edu.cn [Key Laboratory of High-efficiency and Clean Mechanical Manufacture (Ministry of Education), School of Mechanical Engineering, Shandong University, Ji' nan 250061 (China); Shandong University, Suzhou Institute, Suzhou 215123 (China); Chen, Chuanzhong, E-mail: czchen@sdu.edu.cn [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Department of Materials Science and Engineering, Shandong University, Ji' nan 250061 (China); Shandong University, Suzhou Institute, Suzhou 215123 (China); Liu, Jianli, E-mail: jianli21s@163.com [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Department of Materials Science and Engineering, Shandong University, Ji' nan 250061 (China); Shandong University, Suzhou Institute, Suzhou 215123 (China); Zhao, Longjie, E-mail: zhaoljsdu@sina.com [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Department of Materials Science and Engineering, Shandong University, Ji' nan 250061 (China); Shandong University, Suzhou Institute, Suzhou 215123 (China)

2015-11-25

In this study, TiN reinforced composite coatings were fabricated on Ti–6Al–4V substrate by laser cladding with Co42 self-fluxing alloy, TiN and Y{sub 2}O{sub 3} mixed powders. Microstructures and wear resistance of the cladding coatings with and without Y{sub 2}O{sub 3} addition were investigated comparatively. Results showed that the coatings were mainly comprised of γ-Co/Ni, TiN, CoTi, CoTi{sub 2}, NiTi, TiC, Cr{sub 7}C{sub 3}, TiB, Ti{sub 5}Si{sub 3} and TiC{sub 0.3}N{sub 0.7} phases. The coatings showed metallurgical bonding free of pores and cracks with the substrate. Compared with the Ti–6Al–4V substrate, the microhardness and wear resistance of the coatings was enhanced by 3–4 times and 9.5–11.9 times, respectively. With 1.0 wt.% Y{sub 2}O{sub 3} addition, the microstructure of the coating was refined significantly, and the microhardness and dry sliding wear resistance were enhanced further. The effects of Y{sub 2}O{sub 3} were attributed to the residual Y{sub 2}O{sub 3} and decomposed Y atoms. - Graphical abstract: The diagram illustration for the action mechanism of Y{sub 2}O{sub 3}: (a) dissolution of Y{sub 2}O{sub 3} and TiN, (b) re-formation of TiN and in situ formation of TiC, (c) growth of TiN, TiC and the distribution of Y atoms. - Highlights: • Coatings showing metallurgical bonding with the substrate were fabricated. • The effect of Y{sub 2}O{sub 3} on the refinement of the microstructure is notable. • A kind of Y{sub 2}O{sub 3} centered core–shell structure was picked out in the coating. • Microhardness and wear resistance of the coatings was enhanced significantly.

Nitrogen doped RGO-Co3O4 nanograin cookies: highly porous and robust catalyst for removing nitrophenol from waste water

Science.gov (United States)

Pervaiz, Erum; Syam Azhar Virk, Muhammad; Bingxue, Zhang; Yin, Conglin; Yang, Minghui

2017-09-01

The fabrication of nanograins with a uniform morphology wrapped with reduced graphene oxide (RGO) in a designed manner is critical for obtaining a large surface, high porosity and efficient catalytic ability at mild conditions. Hybrid structures of metal oxides decorated on two-dimensional (2D) RGO lacked an interface and channels between the individual grains and RGO. The present work focuses on the synthesis of RGO-wrapped Co3O4 nanograin architecture in micron-sized polyhedrons and the ability to reduce aromatic nitro compounds. Doping N in the designed microstructure polyhedrons resulted in very large surface area (1085.6 m2 g-1) and pore density (0.47 m3 g-1) microcages. Binding energies from x-ray photoelectron spectroscopy (XPS) and Raman intensities confirmed the presence of doped N and RGO-wrapped around Co3O4 nanograins. However, the morphology and microstructure was supported by FESEM and HRTEM images revealing the fabrication of high integrity RGO-Co3O4 microstructure hybrids composed of a 10 nm grain size with narrower grain size distribution. Ammonia treatment produced interconnected channels and dumbbell pores that facilitated ion exchange between the catalyst surface and the liquid medium at the grain boundary interfaces, and offered less mass transport resistance providing fast adsorption of reactants and desorption of the product causing surface renewal. Prepared N-RGO-Co3O4 shows the largest percentage reduction (96%) of p-nitrophenol (p-NP) at room temperature as compared to pure Co3O4 and RGO-Co3O4 nanograin microstructures over 10 min. Fabricated architectures can be applied effectively for fast and facile treatment of industrial waste streams with complex organic molecules.

Porous nanocubic Mn3O4-Co3O4 composites and their application as electrochemical supercapacitors.

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Pang, Huan; Deng, Jiawei; Du, Jimin; Li, Sujuan; Li, Juan; Ma, Yahui; Zhang, Jiangshan; Chen, Jing

2012-09-14

A simple approach has been developed to fabricate ideal supercapacitors based on porous Mn(3)O(4)-Co(3)O(4) nanocubic composite electrodes. We can easily obtain porous corner-truncated nanocubic Mn(3)O(4)-Co(3)O(4) composite nanomaterials without any subsequent complicated workup procedure for the removal of a hard template, seed or by using a soft template. In such a composite, the porous Mn(3)O(4)-Co(3)O(4) enables a fast and reversible redox reaction to improve the specific capacitance. The porous nanocubic Mn(3)O(4)-Co(3)O(4) composite electrode can effectively transport electrolytes and shorten the ion diffusion path, which offers excellent electrochemical performance. These results suggest that such porous Mn(3)O(4)-Co(3)O(4) composite nanocubes are very promising for next generation high-performance supercapacitors.

Evaluation of electrical, structural, thermal and optical properties of Co_3O_4 semiconductor

International Nuclear Information System (INIS)

Dias, Jeferson A.; Maestrelli, Sylma C.; Morelli, Marcio R.

2016-01-01

Among the new semiconductors, the tricobalt tetraoxide is a material of increasing interest; nevertheless, there is a limited number of studies about its properties. Thus, this work has investigated the structural, thermal, optical and electronic properties of Co_3O_4 and its correlation with structure and microstructure. For that, the commercial material was characterized by X-ray diffraction, thermal analysis, diffuse reflectance, FTIR and impedance spectroscopy. The results have shown that the assessed Co_3O_4 has non-stoichiometric spinel structure, presenting a band gap energy capable to completely absorb the visible spectra (1.75 eV). Furthermore, it can be visualized in infrared spectra the bands related to Co-O bonds. The activation energy of electric conduction was 0.35 eV related to the hopping mechanism. Therefore, the results confirm the potentiality of use of Co_3O_4 in optoelectronic devices due to its promising properties for technological utilization. (author)

Hydrothermal synthesis and electrochemical performance of Co3O4/reduced graphene oxide nanosheet composites for supercapacitors

International Nuclear Information System (INIS)

Song, Zhaoxia; Zhang, Yujuan; Liu, Wei; Zhang, Song; Liu, Guichang; Chen, Huiying; Qiu, Jieshan

2013-01-01

Highlights: • Co 3 O 4 /reduced graphene oxide sheet-on-sheet nanocomposites are synthesized. • Co 3 O 4 nanosheets consist of homogeneously assembled nanoparticles. • Co 3 O 4 /rGONS shows a specific capacitance of 402 F g −1 at 2.0 A g −1 . • Co 3 O 4 /rGONS shows enhanced capacitive performance compared with Co 3 O 4 . • The improved properties are mainly attributed to the porous composite structure. - Abstract: The composites of Co 3 O 4 /reduced graphene oxide nanosheets (Co 3 O 4 /rGONS) are prepared via a facile hydrothermal route followed by calcination, of which the morphology and microstructure are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is found that the as-obtained Co 3 O 4 nanosheets on which many fine nanoparticles are homogeneously assembled aggregate in a flower shape on the surfaces of reduced graphene oxide. Electrochemical properties are investigated using cyclic voltammetry and galvanostatic charge/discharge in 1 M KOH aqueous solution. In comparison with pure Co 3 O 4 , the specific capacity and redox performance of the as-made Co 3 O 4 /rGONS composites have been significantly improved, which are mainly attributed to the composite structure with high porosity formed due to the interaction of Co 3 O 4 and reduced graphene oxide nanosheets during the fabrication process of the Co 3 O 4 /rGONS nanocomposites. The Co 3 O 4 /rGONS-II shows good cyclic performance and coulomb efficiency with a specific capacitance over 400 F g −1 at a current density of 0.5–2.0 A g −1

Hydrogen evolution under visible light over LaCoO3 prepared by chemical route

International Nuclear Information System (INIS)

Meziani, D.; Reziga, A.; Rekhila, G.; Bellal, B.; Trari, M.

2014-01-01

Highlights: • Visible-light hydrogen evolution is achieved on the hetero-system LaCoO 3 /SnO 2 . • The crystal field splits the Co 3+ : 3d orbital by a value of 2.05 eV. • The capacitance plot shows p-type conduction with flat band potential of 0 V SCE. • The photo-electrochemistry yields a valence and conduction bands of 3d parentage. - Abstract: The semiconducting properties of the perovskite LaCoO 3 , prepared by nitrate route, are investigated for the first time by the photo-electrochemical technique. The oxide shows a direct optical transition at 1.33 eV, due to Co 3+ : 3d orbital splitting in octahedral site and possesses a chemical stability over a fair pH range (4–14). The conductivity follows an exponential type law with a hole mobility (8.3 × 10 −2 cm 2 V −1 s −1 ), thermally activated. The Mott–Schottky plot in KOH medium is characteristic of p type conduction with a flat band potential of 0 V SCE and a holes density of 1.35 × 10 17 cm −3 . The electrochemical impedance spectroscopy reveals the predominance of the bulk and grains boundaries contributions with a constant phase element and a multi-relaxation type nature. As application, the hydrogen evolution upon visible light is demonstrated on the hetero-junction LaCoO 3 /SnO 2 . The best performance occurs at pH ∼ 12.8 with an evolution rate of 0.25 cm 3 min −1 (mg LaCoO 3 ) −1 and a quantum yield of 0.11%. The improved activity is attributed to the wide depletion width of ∼10 nm and the potential of the conduction band of LaCoO 3 (−1.34 V SCE ), more negative than that of SnO 2 , the latter acts as electrons bridge for the interfacial water reduction. The relevance of 3d orbital of the performance of semi conducting photoelectrode is discussed

Microstructural evolution and stability of tetragonal precipitates in Y2O3 partially-stabilized ZrO2 single crystals

International Nuclear Information System (INIS)

Martinez-Fernandez, J.; Jimenez-Melendo, M.; Dominguez-Rodriguez, A.

1995-01-01

The microstructure and morphology of tetragonal precipitates (t-ZrO 2 ) in yttria partially-stabilized zirconia single crystals containing various amounts of Y 2 O 3 (3, 4, 4.7 and 5.8 mol%) have been studied as a function of aging time at 1,600 C in air. The precipitate size and volume fraction of t-ZrO 2 phase were determined using transmission electron microscopy. The evolution of the precipitate volume fraction with aging time indicated that the precipitation reaction was completed after 24 h of annealing, in agreement with the values of the Y 2 O 3 composition in the matrix measured by analytical electron microscopy. Further aging coarsened the precipitates which joined together forming fiber-like particles of several micrometers in length and remaining untransformed despite their large size. The stability of the t-ZrO 2 precipitates against the tetragonal to monoclinic transformation in the ZrO 2 -Y 2 O 3 system seems to be related to interactions between precipitates due to coherency stresses rather than with their morphological characteristics

Decoration of mesoporous Co3O4 nanospheres assembled by monocrystal nanodots on g-C3N4 to construct Z-scheme system for improving photocatalytic performance

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Wu, Haijun; Li, Chunmei; Che, Huinan; Hu, Hao; Hu, Wei; Liu, Chunbo; Ai, Junzhe; Dong, Hongjun

2018-05-01

The Co3O4/g-C3N4 Z-scheme system is constructed by decoration of mesoporous Co3O4 nanospheres assembled by monocrystal nanodots on the surface of g-C3N4, which dramatically improves the photocatalytic activity for degrading tetracycline hydrochloride (TC) compared with single g-C3N4. The microstructure investigations evidence the mesoporous structure and enlarged specific surface area of Co3O4/g-C3N4 Z-scheme system, which implies the increase of surface active sites and adsorption ability for reactant molecules. Moreover, by virtue of analyzing physical and photoelectrochemical properties, it evidences that the decoration effect of mesoporous Co3O4 nanospheres on the surface of g-C3N4 obviously improves the transfer and separation efficiency of charge carriers between two phase interfaces and broadens light harvest range. These important factors are beneficial to enhancing photocatalytic activity of Co3O4/g-C3N4 Z-scheme system. In addition, the photocatalityc reaction mechanism is also revealed in depth.

Co3O4 nanoneedle@electroactive nickel boride membrane core/shell arrays: A novel hybrid for enhanced capacity

International Nuclear Information System (INIS)

Li, Tingting; Zhu, Congxu; Yang, Xiaogang; Gao, Yuanhao; He, Weiwei; Yue, Hongwei; Zhao, Hongxiao

2017-01-01

Graphical abstract: Active nickel boride membrane anchored Co 3 O 4 nanoneedle arrays hybrid is synthesized via rapid interface reaction. The optimized core/shell nanostructure demonstrates greatly enhanced electrochemical properties. Display Omitted -- Highlights: •Active nickel boride membrane anchored Co 3 O 4 nanoneedle arrays core-shell hybrid architectures was fabricated via rapid interface reaction. •Specific capacity was improved by synergy between highly active components and optimized electron transfer microstructure. •The assembled asymmetric supercapacitor device exhibited excellent electrochemical performance. -- Abstract: Exploring novel hybrid materials with efficient microstructure using facile approaches is highly urgent in designing supercapacitor electrodes. Here, the Ni-B membrane was used for coating the porous Co 3 O 4 nanoneedle arrays which supported on the nickel foam (NF) frameworks through a rapid chemical reduction process (denoted as NF/Co 3 O 4 @NiB). The Ni-B membrane both provided sufficient active sites for redox reactions and inhibited the aggregation of formed hybrid architectures. Benefiting from the unique structural design and strongly coupled effects between porous Co 3 O 4 arrays and Ni-B membrane, the resulted NF/Co 3 O 4 @NiB electrode exhibited high areal capacitance of 3.47 F cm −2 (0.48 mAh cm −2 ) at a current density of 2.5 mA cm −2 , an excellent rate capability while maintaining 95.5% capacity retention after 2000 cycles. The asymmetric supercapacitor constructed with the NF/Co 3 O 4 @NiB as positive electrode and hierarchical porous carbon (HPC) as negative electrode also showed ideal capacitive behavior, and simultaneously delivered high energy and power densities. The easily decoration of Ni-B membrane on various active nanoarrays may arouse more novel design about hybrid architectures for large-scale applications.

Effect of Co2+ and Y3+ ions insertion on the microstructure development and magnetic properties of Ni0.5Zn0.5Fe2O4 powders synthesized using Co-precipitation method

Science.gov (United States)

Rashad, M. M.; Rayan, D. A.; Turky, A. O.; Hessien, M. M.

2015-01-01

Nanocrystalline Ni0.5Zn0.5-xCoxFe2-zYzO4 powders (x=0-0.3 and z from 0 to 0.3) have been synthesized via a facile co-precipitation technique. X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) are utilized in order to study the effect of variation of cobalt and yttrium substitutions and its impact on crystalline size, lattice parameter, X-ray density, microstructure and magnetic properties of the formed powders. X-ray diffraction data indicated that, after doping, all samples consisted of the main spinel phase for the formed precursors precipitated at pH 10 annealed at 1000 oC for 2 h. The lattice parameter and the unit cell were decreased linearly with increasing Co content whereas they were increased with increasing the Y incorporation. Additionally, the porosity was increased with increasing Co concentration while it was decreased with increasing the Y insertion. The mean ionic radii and hopping and bond lengths was decreased with the value of Co2+ and they were increased with the value of Y3+ ion as well as both of Y3+ and Co2+ ions. The microstructures of the produced powders were found to be cubic like structure. The addition of Y3+ ion suppressed the grain size whereas addition of Co2+ ion enhanced the grain growth availably. An examination of the magnetic properties revealed an increase in saturation magnetization with increasing Co and Y concentrations incorporation up to x=0.3. Meanwhile, the formed powders exhibited superparamagnetic characteristics. A high saturation magnetization (77.0 emu/g) was achieved for Ni0.5Zn0.2Co0.3Fe2O4 sample annealed at 1000 oC for 2 h.

Topotactic synthesis of Co3O4 nanoboxes from Co(OH)2 nanoflakes

International Nuclear Information System (INIS)

Tian Li; Huang Kelong; Liu Younian; Liu Suqin

2011-01-01

Hollow nanocubes of spinel Co 3 O 4 with the dimension of 20 nm were successfully prepared via a facile and reproducible solvothermal route. The structure and morphology of Co 3 O 4 nanoboxes were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM) techniques. And a possible growth mechanism of Co 3 O 4 nanoboxes were suggested that solid Co 3 O 4 nanocubes nucleate in-situ and grow epitaxially from hexagonal β-Co(OH) 2 precursors with the structural matching relationship of [0 0 1] β-Co(OH) 2 //[1 1 1] Co 3 O 4 , and then solid Co 3 O 4 nanocubes gradually hollow and convert to single-crystal nanoboxes owing to Ostwald ripening. - Graphical abstract: The formation mechanism of Co 3 O 4 nanoboxes can be expressed as epitaxial growth of Co 3 O 4 nanocubes from β-Co(OH) 2 nanoflakes due to a topotactic transformation and hollowing process owing to Ostwald ripening. Highlights: → Co 3 O 4 nanoboxes were prepared by a convenient, economical and controllable hydrothermal route. → Morphology and structure of Co 3 O 4 nanoboxes were characterized by XRD, SEM, and TEM techniques. → Co 3 O 4 nanoboxes grow epitaxially from Co(OH) 2 by topotactic transformation was suggested.

Microstructure and electrical properties in SnO2 ceramics with sequential addition of Co, Sb and Ca

International Nuclear Information System (INIS)

Aguilar-Martinez, J A; Hernandez, M B; Glot, A B; Pech-Canul, M I

2007-01-01

The effect of sequential additions of Co 3 O 4 , Sb 2 O 5 and CaCO 3 on the microstructure and electrical behaviour of SnO 2 -based ceramics was investigated. Although without conferring varistor properties, Co 3 O 4 additions promote densification in the material. Successive addition of Sb 2 O 5 provides the sample varistor properties but with low nonlinearity coefficient (α = 5.7) and high electric field (E 1 = 2022 V cm -1 ) at current density 10 -3 A cm -3 . Moreover, antimony oxide addition degrades the microstructure condition by inducing porosity. Subsequent addition of CaCO 3 promotes densification and grain growth. However, it does not lead to the increase in the nonlinearity coefficient. It only lowers the electric field, thus making the material suitable for lower voltage applications. Observed significant increase in the relative dielectric permittivity up to a factor of about 60 and 200 in the cases of antimony or antimony and calcium addition to SnO 2 -Co 3 O 4 (accompanied by the appearance of varistor effect) is due to the formation of barrier depletion layers at grain boundaries

Microstructure and Electrical Properties of Fe,Cu Substituted (Co,Mn)3O4 Thin Films

DEFF Research Database (Denmark)

Szymczewska, Dagmara; Molin, Sebastian; Hendriksen, Peter Vang

2017-01-01

In this work, thin films (~1000 nm) of a pure MnCo2O4 spinel together with its partially substituted derivatives (MnCo1.6Cu0.2Fe0.2O4, MnCo1.6Cu0.4O4, MnCo1.6Fe0.4O4) were prepared by spray pyrolysis and were evaluated for electrical conductivity. Doping by Cu increases the electrical conductivit...

Effects of Synthesis and Spark Plasma Sintering Conditions on the Thermoelectric Properties of Ca3Co4O9+δ

DEFF Research Database (Denmark)

Wu, NingYu; Holgate, Tim; Van Nong, Ngo

2013-01-01

Ca3Co4O9+δ samples were synthesized by solid-state (SS) and sol–gel (SG) reactions, followed by spark plasma sintering under different processing conditions. The synthesis process was optimized and the resulting materials characterized with respect to their microstructure, bulk density, and therm......Ca3Co4O9+δ samples were synthesized by solid-state (SS) and sol–gel (SG) reactions, followed by spark plasma sintering under different processing conditions. The synthesis process was optimized and the resulting materials characterized with respect to their microstructure, bulk density...

A common behaviour of thermoelectric layered cobaltites: incommensurate spin density wave states in [Ca2Co4/3Cu2/3O4]0.62[CoO2] and [Ca2CoO3]0.62[CoO2

International Nuclear Information System (INIS)

Sugiyama, J; Brewer, J H; Ansaldo, E J; Itahara, H; Dohmae, K; Xia, C; Seno, Y; Hitti, B; Tani, T

2003-01-01

Magnetism of a misfit layered cobaltite [Ca 2 Co 4/3 Cu 2/3 O 4 ] x RS [CoO 2 ] (x ∼ 0.62, RS denotes a rocksalt-type block) was investigated by a positive muon spin rotation and relaxation (μ + SR) experiment. A transition to an incommensurate (IC) spin density wave (SDW) state was found below 180 K (= T C on ); and a clear oscillation due to a static internal magnetic field was observed below 140 K(= T C ). Furthermore, an anisotropic behaviour of the zero-field μ + SR experiment indicated that the IC-SDW lies in the a-b plane, with oscillating moments directed along the c axis. These results were quite similar to those for the related compound [Ca 2 CoO 3 ] 0.62 RS [CoO 2 ], i.e., Ca 3 Co 4 O 9 . Since the IC-SDW field in [Ca 2 Co 4/3 Cu 2/3 O 4 ] 0.62 RS [CoO 2 ] was approximately the same as those in pure and doped [Ca 2 CoO 3 ] 0.62 RS [CoO 2 ], it was concluded that the IC-SDW exists in the [CoO 2 ] planes

Effect of the synthesis route on the microstructure and the reducibility of LaCoO3

International Nuclear Information System (INIS)

Ivanova, S.; Senyshyn, A.; Zhecheva, E.; Tenchev, K.; Nikolov, V.; Stoyanova, R.; Fuess, H.

2009-01-01

The effect of the synthesis route on the microstructure and reducibility of lanthanum cobaltates (LaCoO 3 ) perovskites was examined. Two synthesis methods were used: thermal decomposition of freeze-dried La-Co-citrates and the Pechini method. The crystal structure, morphology and defect structure of LaCoO 3 were characterized by XRD powder diffraction, TEM and SEM analyses and electron paramagnetic resonance spectroscopy. The reducibility was tested by thermal programmed reduction with hydrogen. The intermediate stage of reduction was determined by ex situ XRD experiments. LaCoO 3 powders obtained by the Pechini method were reduced relatively easier as LaCoO 3 obtained from freeze-dried citrates. The LaCoO 3 reduction yielded Co metal and La 2 O 3 via the formation of oxygen deficient Brownmillerite-type La 3 Co 3 O 8 and La 2 Co 2 O 5 oxides. For LaCoO 3 obtained from freeze-dried citrates and annealed at higher temperatures, Co metal, in addition to oxygen deficient perovskites, was formed at the initial stage of the reduction. The different reducibility of LaCoO 3 obtained by the Pechini method and that from the freeze-dried citrates was discussed taking into account the formation of oxygen-deficient phases from the Brownmillerite and Ruddlesden-Popper series during the reduction.

Formic Acid Modified Co3O4-CeO2 Catalysts for CO Oxidation

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Ruishu Shang

2016-03-01

Full Text Available A formic acid modified catalyst, Co3O4-CeO2, was prepared via facile urea-hydrothermal method and applied in CO oxidation. The Co3O4-CeO2-0.5 catalyst, treated by formic acid at 0.5 mol/L, performed better in CO oxidation with T50 obtained at 69.5 °C and T100 obtained at 150 °C, respectively. The characterization results indicate that after treating with formic acid, there is a more porous structure within the Co3O4-CeO2 catalyst; meanwhile, despite of the slightly decreased content of Co, there are more adsorption sites exposed by acid treatment, as suggested by CO-TPD and H2-TPD, which explains the improvement of catalytic performance.

Co3(PO4)2·4H2O

Science.gov (United States)

Lee, Young Hoon; Clegg, Jack K.; Lindoy, Leonard F.; Lu, G. Q. Max; Park, Yu-Chul; Kim, Yang

2008-01-01

Single crystals of Co3(PO4)2·4H2O, tricobalt(II) bis­[ortho­phosphate(V)] tetra­hydrate, were obtained under hydro­thermal conditions. The title compound is isotypic with its zinc analogue Zn3(PO4)2·4H2O (mineral name hopeite) and contains two independent Co2+ cations. One Co2+ cation exhibits a slightly distorted tetra­hedral coordination, while the second, located on a mirror plane, has a distorted octa­hedral coordination environment. The tetra­hedrally coordinated Co2+ is bonded to four O atoms of four PO4 3− anions, whereas the six-coordinate Co2+ is cis-bonded to two phosphate groups and to four O atoms of four water mol­ecules (two of which are located on mirror planes), forming a framework structure. In addition, hydrogen bonds of the type O—H⋯O are present throughout the crystal structure. PMID:21200978

Graphene wrapped porous Co_3O_4/NiCo_2O_4 double-shelled nanocages with enhanced electrocatalytic performance for glucose sensor

International Nuclear Information System (INIS)

Xue, Bei; Li, Kezhi; Feng, Lei; Lu, Jinhua; Zhang, Leilei

2017-01-01

Highlights: • Graphene wrapped Co_3O_4/NiCo_2O_4 DSNCs has been prepared for detection of glucose. • Sensing performance was improved by synergy between electrocatalytic activity and efficient electron transport. • The sensor has excellent sensing performance with high sensitivity and low detection limit. • The developed method was successfully applied to detect glucose in human serum. - Abstract: Graphene (G) wrapped porous Co_3O_4/NiCo_2O_4 double-shelled nanocages (Co_3O_4/NiCo_2O_4 DSNCs@G) were prepared by the formation of Co_3O_4/NiCo_2O_4 DSNCs using zeolite imidazole frameworks-67 as template with the subsequent calcination and package of G by hydrothermal method. The abundant accessible active sites provided by the porous structure of Co_3O_4/NiCo_2O_4 DSNCs and efficient electron transport pathways for electrocatalytic reaction offered by the high conductive G worked very well together in a ferocious synergy, which endowed Co_3O_4/NiCo_2O_4 DSNCs@G with excellent electrocatalytic behaviors for determining glucose. A comparison between Co_3O_4/NiCo_2O_4 DSNCs without G packing and Co_3O_4/NiCo_2O_4 DSNCs@G showed that former had linear response window concentrations of 0.01-3.52 mM (correlation coefficient = 0.999), detection limit of 0.744 μM (S/N = 3) and sensitivity of 0.196 mA mM"−"1 cm"−"2, whereas the latter exhibited linear response window concentrations of 0.01-3.52 mM (correlation coefficient = 0.999), detection limit of 0.384 μM (S/N = 3) and sensitivity of 0.304 mA mM"−"1 cm"−"2. The combination of Co_3O_4/NiCo_2O_4 DSNCs and G was a meaningful strategy to fabricate high-performance non-enzyme glucose sensors with low detection limit, good selectivity and high sensitivity.

Solid-solid interactions in Co3O4-MoO3/MgO system

International Nuclear Information System (INIS)

Radwan, Nagi R.E.; Ghozza, Ahmed M.; El-Shobaky, Gamil A.

2003-01-01

Cobalt/magnesium mixed oxide solids and cobalt-molybdenum/magnesium mixed oxide solids were prepared by thermal decomposition of basic magnesium carbonate pretreated with different proportions of cobalt nitrate and then with calculated amounts of ammonium molybdate. The proportions of cobalt expressed as Co 3 O 4 were 0.1, 0.2 and 0.3 mol while the concentrations of molybdenum expressed as mol% MoO 3 were 2.5 and 5.0. The prepared mixed solid specimens were calcined in air at 400-1000 deg. C. The solid-solid interactions in Co 3 O 4 -MoO 3 were investigated using DTA, TG and X-ray powder diffraction (XRD) techniques. The results obtained revealed that MgO dissolved cobalt oxide in its lattice forming CoO-MgO solid solution. The amount of cobalt dissolved increases by increasing the temperature in the range 800-1000 deg. C. This finding was confirmed by X-ray diffractograms in which all the diffraction lines of cobalt oxide disappeared at 1000 deg. C. MoO 3 present interacted readily with MgO and cobalt oxide by heat treatment at temperature starting from 400 deg. C producing MgMoO 4 and CoMoO 4 which remained stable by heating at 1000 deg. C. The impregnation of basic magnesium carbonate with cobalt nitrate much enhanced its thermal decomposition yielding MgO, which decomposed completely at 395.5 deg. C instead of 525 deg. C. The formation of magnesium cobaltite (MgCo 2 O 4 ) has been ruled out via XRD investigation at relatively high diffraction angles

Effect of Cr{sub 2}O{sub 3} on the microstructure and non-ohmic properties of (Co, Sb)-doped SnO{sub 2} varistors

Energy Technology Data Exchange (ETDEWEB)

Aguilar M, J. A. [Centro de Investigac ion en Materiales Avanzados, S. C., Alianza Norte No. 202, Parque de Investigacion e Innovacion Tecnologica, Nueva Carretera Aeropuerto Km. 10 Apodaca 66600, Nuevo Leon (Mexico); Pech C, M. I. [IPN, Centro de Investigacion y de Estudios Avanzados, Unidad Saltillo, Carretera Saltillo-Monterrey Km. 13, Saltillo 25900, Coahuila (Mexico); Hernandez, M. B.; Rodriguez, E.; Garcia O, L. [Universidad Autonoma de Nuevo Leon, Facultad de Ingenieria Mecanica y Electrica, San Nicolas de los Garza, Nuevo Leon (Mexico); Glot, A. B., E-mail: josue.aguilar@cimav.edu.mx [Universidad Tecnologica de la Mixteca, Division de Estudios de Posgrado, Carretera Acatlima Km. 2.5, Huajuapan de Leon 69000, Oaxaca (Mexico)

2013-10-01

The effect of Cr{sub 2}O{sub 3} addition on the physical characteristics, microstructure, and current-voltage properties of (Co-Sb)-doped SnO{sub 2} varistors was investigated. SnO{sub 2}-Co{sub 3}O{sub 4}-Sb{sub 2}O{sub 5} ceramics with additions of 0.0, 0.03, 0.05 and 0.07 mol % Cr{sub 2}O{sub 3} were sintered at 1350 C under ambient atmosphere and characterized micro structurally and electrically. The characterization by X-ray diffraction and scanning electron microscopy show that the microstructure remains as a single phase material with multimodal size distribution of SnO{sub 2} grains. The greatest effect of Cr{sub 2}O{sub 3} additions is manifested in the electric breakdown field. Additions of high levels (0.07 and 0.05 %) of this oxide promote and increase of approximately 55% in this parameter compared to the Cr{sub 2}O{sub 3}-free sample. Another physical property is affected: the measured density values decreases as the Cr{sub 2}O{sub 3} content increases. A change in the nonlinearity coefficient value is produced only at the highest Cr{sub 2}O{sub 3} content while at intermediate levels there is not change at all. Consequently, when seeking high nonlinearity coefficients, intermediate levels of Cr{sub 2}O{sub 3} are not recommended. (Author)

The evolution of interface microstructure in a ZrO2/Ag-Cu-Al-Ti system

International Nuclear Information System (INIS)

Lee, Youngmin; Yu, Jin

1993-01-01

Among ceramic/metal (C/M) joining technologies, the active filler metal method has been studied extensively due to the simple brazing process and excellent joint strength. Active metal elements, typically Ti, are intentionally added to braze alloys to enhance the formation of reaction products between the ceramic and the braze metal at the C/M interface. In the brazing of Al 2 O 3 with the Ag-Cu-Ti filler metal, reaction products such as γ-TiO, Cu 2 (Ti, Al) 4 O, Ti 3 (Cu 0.76 Al 0.18 Sn 0.06 ) 3 O were found, while products such as Ti 5 Si 3 and TiN formed in the brazing of Si 3 N 4 . The presence of reaction layers at the C/M interface influences the interface strength in a complex way. In Cu/Al 2 O 3 , Co/Al 2 O 3 , Ni/Al 2 O 3 , and Cu/diamond systems, maxima of joint strength were observed at some intermediate Ti addition, while the flexural strength decreased substantially with the thickening of the TiO layer in a ZrO 2 /Ag-Cu-Sn-Ti system. Thus, composition of the braze alloy (particularly, the content of the active metal), process conditions such as brazing temperature and time, microstructure and mechanical properties of reaction products at the C/M interfaces, interfacial chemistry, and residual stress are primary factors to be studied in order to understand the strengths of the C/M interfaces systematically. In the present and the following papers, evolutions of interfacial microstructures at various brazing conditions, and corresponding interface strengths are reported, respectively, for a ZrO 2 /Ag-Cu-Al-Ti system

Structural and morphological evolution in magnetron co-sputtered (Zn, Cr)O films

International Nuclear Information System (INIS)

Hu, Y M; Chiou, J W; Han, T C; Chen, Y T; Hsu, C W; Chen, G J; Chou, W Y; Chang, J; Hsu, J Y; Yu, Y C

2008-01-01

In this study, x-ray diffraction, scanning electron microscopy, micro-Raman spectroscopy, x-ray absorption near-edge structure and particle-induced x-ray emission are used to characterize the microstructure of (Zn, Cr)O films prepared using a co-sputtering method. We found that the Cr ions did not substitute for the Zn sites but instead formed Cr nano-particles and secondary oxide phases (SOPs) of Cr 2 O 3 and/or ZnCr 2 O 4 in co-sputtered Zn 1-x Cr x O films with Cr content x ≥ 0.1. Evidence is presented for the evolution of SOPs formed in (Zn, Cr)O films with increasing Cr sputtering power. Based on the inspection of the Cr and Zn contents in (Zn, Cr)O films, we conclude that the formation of the Cr 2 O 3 phase is driven by a substantial increase in the atomic ratio of Cr/Zn, followed by the formation of a ZnCr 2 O 4 phase promoted by a higher content of Cr than of Zn in film with increasing Cr sputtering power. It seems that a strong preference of Cr for octahedral rather than tetrahedral coordination with oxygen would trigger the formation of SOPs rather than the substitution of Cr into Zn sites and could be an obstacle for achieving a real Cr-substituted ZnO dilute magnetic oxide.

Exchange-coupled Fe3O4/CoFe2O4 nanoparticles for advanced magnetic hyperthermia

Science.gov (United States)

Glassell, M.; Robles, J.; Das, R.; Phan, M. H.; Srikanth, H.

Iron oxide nanoparticles especially Fe3O4, γ-Fe2O3 have been extensively studied for magnetic hyperthermia because of their tunable magnetic properties and stable suspension in superparamagnetic regime. However, their relatively low heating capacity hindered practical application. Recently, a large improvement in heating efficiency has been reported in exchange-coupled nanoparticles with exchange coupling between soft and hard magnetic phases. Here, we systematically studied the effect of core and shell size on the heating efficiency of the Fe3O4/CoFe2O4 core/shell nanoparticles. The nanoparticles were synthesized using thermal decomposition of organometallic precursors. Transmission electron microscopy (TEM) showed formation of spherical shaped Fe3O4 and Fe3O-/CoFe2O4 nanoparticles. Magnetic measurements showed high magnetization (≅70 emu/g) and superparamagnetic behavior for the nanoparticles at room temperature. Magnetic hyperthermia results showed a large increase in specific absorption rate (SAR) for 8nm Fe3O4/CoFe2O4 compared to Fe3O4 nanoparticles of the same size. The heating efficiency of the Fe3O4/CoFe2O4 with 1 nm CoFe2O4 (shell) increased from 207 to 220 W/g (for 800 Oe) with increase in core size from 6 to 8 nm. The heating efficiency of the Fe3O4/CoFe2O4 with 2 nm CoFe2O4 (shell) and core size of 8 nm increased from 220 to 460 W/g (for 800 Oe). These exchange-coupled Fe3O4/CoFe2O4 core/shell nanoparticles can be a good candidate for advanced hyperthermia application.

Microstructure and electrical properties in SnO{sub 2} ceramics with sequential addition of Co, Sb and Ca

Energy Technology Data Exchange (ETDEWEB)

Aguilar-Martinez, J A [Instituto de MinerIa, Universidad Tecnologica de la Mixteca, Carretera a Acatlima Km. 2.5, Huajuapan de Leon, Oaxaca 69000 (Mexico); Hernandez, M B [Instituto de Diseno, Universidad Tecnologica de la Mixteca, Carretera a Acatlima Km. 2.5, Huajuapan de Leon, Oaxaca 69000 (Mexico); Glot, A B [Division de Posgrado, Universidad Tecnologica de la Mixteca, Carretera a Acatlima Km. 2.5, Huajuapan de Leon, Oaxaca 69000 (Mexico); Pech-Canul, M I [Cinvestav Saltillo, Carr. Saltillo-Mty Km 13 Apdo., Saltillo Coahuila 25000 (Mexico)

2007-11-21

The effect of sequential additions of Co{sub 3}O{sub 4}, Sb{sub 2}O{sub 5} and CaCO{sub 3} on the microstructure and electrical behaviour of SnO{sub 2}-based ceramics was investigated. Although without conferring varistor properties, Co{sub 3}O{sub 4} additions promote densification in the material. Successive addition of Sb{sub 2}O{sub 5} provides the sample varistor properties but with low nonlinearity coefficient ({alpha} = 5.7) and high electric field (E{sub 1} = 2022 V cm{sup -1}) at current density 10{sup -3} A cm{sup -3}. Moreover, antimony oxide addition degrades the microstructure condition by inducing porosity. Subsequent addition of CaCO{sub 3} promotes densification and grain growth. However, it does not lead to the increase in the nonlinearity coefficient. It only lowers the electric field, thus making the material suitable for lower voltage applications. Observed significant increase in the relative dielectric permittivity up to a factor of about 60 and 200 in the cases of antimony or antimony and calcium addition to SnO{sub 2}-Co{sub 3}O{sub 4} (accompanied by the appearance of varistor effect) is due to the formation of barrier depletion layers at grain boundaries.

Thermogravimetric, Calorimetric, and Structural Studies of the Co3 O4 /CoO Oxidation/Reduction Reaction

Science.gov (United States)

Unruh, Karl; Cichocki, Ronald; Kelly, Brian; Poirier, Gerald

2015-03-01

To better assess the potential of cobalt oxide for thermal energy storage (TES), the Co3O4/CoO oxidation/reduction reaction has been studied by thermogravimetric (TGA), calorimetric (DSC), and x-ray diffraction (XRD) measurements in N2 and atmospheric air environments. TGA measurements showed an abrupt mass loss of about 6.6% in both N2 and air, consistent with the stoichiometric reduction of Co3O4 to CoO and structural measurements. The onset temperature of the reduction of Co3O4 in air was only weakly dependent on the sample heating rate and occurred at about 910 °C. The onset temperature for the oxidation of CoO varied between about 850 and 875 °C for cooling rates between 1 and 20 °C/min, but complete re-conversion to Co3O4 could only be achieved at the slowest cooling rates. Due to the dependence of the rate constant on the oxygen partial pressure, the oxidation of Co3O4 in a N2 environment occurred at temperatures between about 775 and 825 °C for heating rates between 1 and 20 °C/min and no subsequent re-oxidation of the reduced Co3O4 was observed on cooling to room temperature. In conjunction with a measured transition heat of about 600 J/g of Co3O4, these measurements indicate that cobalt oxide is a viable TES material.

Electrodeposited Mn3O4-NiO-Co3O4 as a composite electrode material for electrochemical capacitor

International Nuclear Information System (INIS)

Rusi; Majid, S.R.

2015-01-01

Highlights: • Composite electrodes were synthesized by in situ electrodeposition method. • The highest specific capacitance of composite electrode is 7404 F g −1 . • The power density of composite electrode is 99 kW kg −1 at current density of 20 A g −1 . • The addition of K 3 Fe(CN) 6 in KOH electrolyte has improved the electrochemical performance. - Abstract: A simple and easy galvanostatic electrodeposition method is used to synthesise a composite electrode consisting of manganese oxide (Mn 3 O 4 ), nickel oxide (NiO) and cobalt oxide (Co 3 O 4 ). The influence of Co 3 O 4 on the morphology of fixed Mn 3 O 4 -NiO particles is investigated with a field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The nature and elemental of the composite are examined by means of X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). The electrochemical performances of an Mn 3 O 4 -NiO-Co 3 O 4 nanostructure/SS composite electrode are studied by cyclic voltammetry (CV) and galvanostatic charge-discharge (CD) in various electrolytes, i.e. 0.5 M Na 2 SO 4 , 0.5 M KOH, 0.5 M Na 2 SO 4 /0.04 M K 3 Fe(CN) 6 and 0.5 M KOH/0.04 M K 3 Fe(CN) 6 electrolytes. The composite electrode prepared from 0.15 M Co deposition solution exhibits the optimum specific capacitance of 7404 F g −1 with high energy and power density of 1028 Wh kg −1 and 99 kW kg −1 at 20 A g −1 in mix KOH/0.04 M K 3 Fe(CN) 6 electrolyte, respectively. The results show that the incorporation of K 3 Fe(CN) 6 in KOH electrolyte influences the capacitance of Mn 3 O 4 -NiO-Co 3 O 4 composite electrodes

Quatenary Na//F, Cl, CO3, MoO4 system

International Nuclear Information System (INIS)

Kochkarov, Zh.A.; Lok''yaeva, S.M.; Shurdumov, G.K.; Gasanaliev, A.M.; Trunin, A.S.

1999-01-01

Perspective in applied respect quatenary system (NaF) 2 -(NaCl)-Na 2 CO 3 -Na 2 MoO 4 being element of narrowing of more complex six-membered mutual Na//F, Cl, CO 3 , MoO 4 (WO 4 ) system is investigated by differential thermal analysis with the use of projection-thermographic method for the first time. Crystallization tree of Na//F, Cl, CO 3 , MoO 4 system is established. It is shown that this system by tetrahedrating (NaF) 2 -Na 2 CO 3 -Na 3 ClMoO 4 section is triangulated on two stable system: (NaF) 2 -Na 3 ClMoO 4 -Na 2 CO 3 -(NaCl) 2 and (NaF) 2 -Na 3 ClMoO 4 -Na 2 CO 3 -Na 2 MoO 4 . Phase single units are determined too. Coordinates of desired quatenary nonvariant points are calculated on analytical models of surfaces by mutual crystallization of two phases and are refined by differential thermal analysis [ru

Magnetic field-assisted synthesis of wire-like Co3O4 nanostructures: Electrochemical and photocatalytic studies

International Nuclear Information System (INIS)

Zhao, Xiubin; Pang, Zhanwen; Wu, Mingzai; Liu, Xiansong; Zhang, Hui; Ma, Yongqing; Sun, Zhaoqi; Zhang, Lide; Chen, Xiaoshuang

2013-01-01

Graphical abstract: Schematic illustration for the magnetic field-assisted growth of wire-like Co 3 O 4 nanostructure. Display Omitted Highlights: ► Co 3 O 4 nanowires are prepared by magnetic field hydrothermal reduction and annealing. ► These Co 3 O 4 nanowires possess enhanced capacitance. ► The Co 3 O 4 nanowires have a good photocatalytic activity for methyl orange. -- Abstract: Wire-like Co 3 O 4 nanostructures were prepared by the combination of magnetic field-assisted hydrothermal reduction of cobalt ions and the subsequent ambient annealing at 500 °C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structure and morphological evolution of the products. The results show that the wire-like nanostructures possess diameters about 250 nm and lengths over 10 μm. The possible formation mechanism of the wire-like Co 3 O 4 nanostructures is also proposed based on the SEM results. Galvanostatic methods were used to characterize the electrochemical properties. The measurements indicate that the wire-like Co 3 O 4 nanostructures show larger discharge and charge capacities than that of spherical Co 3 O 4 nanoparticles prepared in the absence of magnetic field. In addition, the photocatalytic activity of the products was investigated by measuring the photodegradation of methyl orange solution under ultraviolet radiation, which shows that both the wire-like and spherical products have a good photocatalytic activity.

Magnetic behavior of biosynthesized Co_3O_4 nanoparticles

International Nuclear Information System (INIS)

Diallo, A.; Doyle, T.B.; Mothudi, B.M.; Manikandan, E.

2017-01-01

This contribution reports for the 1st time on the magnetic behavior of CO_3O_4 nanoparticles synthesized by a “green” process using an Aspalathus linearis’ leaves natural extract. More accurately magnetic behavior of CO_3O_4 nanoparticles successfully biosynthesized was investigated using vibrating sample magnetometer. The magnetization behavior for the samples manifests a combination of size dependent antiferromagnetic and paramagnetic behaviors, respectively, for the core and shell of the nanoparticles. - Highlights: • 1"s"t report on magnetic behavior of Co3O4 nanoparticles via Aspalathus linearis. • Co_3O_4 nanoparticles manifest size-dependent antiferromagnetic & paramagnetic behaviors. • Antiferromagnetic & paramagnetic behaviors were confirmed by VSM.

Profound Interfacial Effects in CoFe2O4/Fe3O4 and Fe3O4/CoFe2O4 Core/Shell Nanoparticles

Science.gov (United States)

Polishchuk, Dmytro; Nedelko, Natalia; Solopan, Sergii; Ślawska-Waniewska, Anna; Zamorskyi, Vladyslav; Tovstolytkin, Alexandr; Belous, Anatolii

2018-03-01

Two sets of core/shell magnetic nanoparticles, CoFe2O4/Fe3O4 and Fe3O4/CoFe2O4, with a fixed diameter of the core ( 4.1 and 6.3 nm for the former and latter sets, respectively) and thickness of shells up to 2.5 nm were synthesized from metal chlorides in a diethylene glycol solution. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, and magnetic measurements. The analysis of the results of magnetic measurements shows that coating of magnetic nanoparticles with the shells results in two simultaneous effects: first, it modifies the parameters of the core-shell interface, and second, it makes the particles acquire combined features of the core and the shell. The first effect becomes especially prominent when the parameters of core and shell strongly differ from each other. The results obtained are useful for optimizing and tailoring the parameters of core/shell spinel ferrite magnetic nanoparticles for their use in various technological and biomedical applications.

Microstructure evolution during annealing of TiAl/NiCoCrAl multilayer composite prepared by EB-PVD

Energy Technology Data Exchange (ETDEWEB)

Zhang, Rubing, E-mail: zrb86411680@126.com [Department of Mechanics, School of Civil Engineering, Beijing Jiaotong University, Beijing 100044 (China); Zhang, Deming [Beijing General Research Institute of Mining and Metallurgy, Beijing 100044 (China); Chen, Guiqing [Center for Composite Materials, Harbin Institute of Technology, Harbin 150001 (China); Wang, Yuesheng [Department of Mechanics, School of Civil Engineering, Beijing Jiaotong University, Beijing 100044 (China)

2014-07-01

TiAl/NiCoCrAl laminate composite sheet with a thickness of 0.4–0.6 mm as well as a dimension of 150 mm × 100 mm was fabricated successfully by using electron beam physical vapor deposition (EB-PVD) method. The annealing treatment was processed at 1123 and 1323 K for 3 h in a high vacuum atmosphere, respectively. The phase composition and microstructure of TiAl/NiCoCrAl microlaminated sheet have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Based on the sheet characterization and results of the microstructure evolution during annealing treatment process, the diffusion mechanism of interfacial reaction in TiAl/NiCoCrAl microlaminate was investigated and discussed.

Ultrathin Co3O4 Layers Realizing Optimized CO2 Electroreduction to Formate.

Science.gov (United States)

Gao, Shan; Jiao, Xingchen; Sun, Zhongti; Zhang, Wenhua; Sun, Yongfu; Wang, Chengming; Hu, Qitao; Zu, Xiaolong; Yang, Fan; Yang, Shuyang; Liang, Liang; Wu, Ju; Xie, Yi

2016-01-11

Electroreduction of CO2 into hydrocarbons could contribute to alleviating energy crisis and global warming. However, conventional electrocatalysts usually suffer from low energetic efficiency and poor durability. Herein, atomic layers for transition-metal oxides are proposed to address these problems through offering an ultralarge fraction of active sites, high electronic conductivity, and superior structural stability. As a prototype, 1.72 and 3.51 nm thick Co3O4 layers were synthesized through a fast-heating strategy. The atomic thickness endowed Co3O4 with abundant active sites, ensuring a large CO2 adsorption amount. The increased and more dispersed charge density near Fermi level allowed for enhanced electronic conductivity. The 1.72 nm thick Co3O4 layers showed over 1.5 and 20 times higher electrocatalytic activity than 3.51 nm thick Co3O4 layers and bulk counterpart, respectively. Also, 1.72 nm thick Co3O4 layers showed formate Faradaic efficiency of over 60% in 20 h. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sol-gel system study of Zr O2- Co3 O-4

International Nuclear Information System (INIS)

Cerri, J.A.; Matos, E.M.R.; Longo, E.; Varela, J.A.; Santos, C.O.P.

1992-01-01

Phases present in the system Zr O 2 + Co 3 O 4 were studied through X-Ray diffraction. The processing of the powder was developed through a modified sol-gel method, where the precursors Zr O (N O 3)2 and Co (N O 3)2 were in an ethanol solution. To verify the influence of CO 3 O 4 on the stabilization and phases formation, the crystallite size and the lattice parameter were determined considering as standard, the system without cobalt. (author)

Steam reforming of ethanol over Co3O4–Fe2O3 mixed oxides

KAUST Repository

Abdelkader, A.

2013-05-03

Co3O4, Fe2O3 and a mixture of the two oxides Co-Fe (molar ratio of Co3O4/Fe 2O3 = 0.67 and atomic ratio of Co/Fe = 1) were prepared by the calcination of cobalt oxalate and/or iron oxalate salts at 500 C for 2 h in static air using water as a solvent/dispersing agent. The catalysts were studied in the steam reforming of ethanol to investigate the effect of the partial substitution of Co3O4 with Fe2O 3 on the catalytic behaviour. The reforming activity over Fe 2O3, while initially high, underwent fast deactivation. In comparison, over the Co-Fe catalyst both the H2 yield and stability were higher than that found over the pure Co3O4 or Fe 2O3 catalysts. DRIFTS-MS studies under the reaction feed highlighted that the Co-Fe catalyst had increased amounts of adsorbed OH/water; similar to Fe2O3. Increasing the amount of reactive species (water/OH species) adsorbed on the Co-Fe catalyst surface is proposed to facilitate the steam reforming reaction rather than decomposition reactions reducing by-product formation and providing a higher H2 yield. © Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Quaternary reciprocal system Na,K//Cl,Co3,MoO4

International Nuclear Information System (INIS)

Kochkarov, Zh.A.; Gasanaliev, A.M.

2004-01-01

Quaternary reciprocal system Na,K//Cl,Co 3 ,MoO 4 has been investigated for the first time by differential thermal analysis using the methods of projective and differential geometry. A stable (KCl) 2 -Na 2 CO 3 -K 2 CO 3 -K 2 MoO 4 tetrahedron and (NaCl) 2 -(KCl) 2 -Na 2 CO 3 -K 2 MoO 4 -Na 2 MoO 4 pentatope have been revealed in the system. It has been found that four quadruple invariant points are realized in the Na,K//Cl,Co 3 ,MoO 4 system, including one eutectic and three peritectic points [ru

Effect of polymorphism of Al2O3 on the sintering and microstructure of transparent MgAl2O4 ceramics

Science.gov (United States)

Han, Dan; Zhang, Jian; Liu, Peng; Wang, Shiwei

2017-09-01

Transparent MgAl2O4 ceramics were fabricated by reactive sintering in air followed by hot isostatic press treatment using commercial Al2O3 powder (γ-Al2O3 or α-Al2O3) and MgO powder as raw materials. The densification rate, microstructure and optical properties of the ceramics were investigated. Densification temperature of the sample from γ-Al2O3/MgO was lower than that from α-Al2O3/MgO. However, in-line transmission (2 mm thick) of the sample from α-Al2O3/MgO at the wavelength of 600 nm and 1100 nm were respectively 77.7% and 84.3%, higher than those (66.7%, 81.4%) of the sample from γ-Al2O3/MgO. SEM observation revealed that the sample from α-Al2O3/MgO exhibited a homogeneous and pore-free microstructure, while, the sample from γ-Al2O3/MgO showed an apparent bimodal microstructure containing pores.

Facile synthesis and electrochemical performance of Co{sub 2}SnO{sub 4}/Co{sub 3}O{sub 4} nanocomposite for lithium-ion batteries

Energy Technology Data Exchange (ETDEWEB)

An, Bonan [School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Engineering Research Center of Materials and Technology for Electrochemical Energy Storage (Ministry of Education), Guangzhou 510006 (China); Ru, Qiang, E-mail: ruqiang@scnu.edu.cn [School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Engineering Research Center of Materials and Technology for Electrochemical Energy Storage (Ministry of Education), Guangzhou 510006 (China); Laboratory of Quantum Engineering and Quantum Materials, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Hu, Shejun; Song, Xiong; Li, Juan [School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Engineering Research Center of Materials and Technology for Electrochemical Energy Storage (Ministry of Education), Guangzhou 510006 (China)

2014-12-15

Graphical abstract: TEM of Co{sub 2}SnO{sub 4}/Co{sub 3}O{sub 4} composite and the discharge curves of pure Co{sub 3}O{sub 4}, pure Co{sub 2}SnO{sub 4} and Co{sub 2}SnO{sub 4}/Co{sub 3}O{sub 4} composite. - Highlights: • Novel Co{sub 2}SnO{sub 4}/Co{sub 3}O{sub 4} composite has been prepared by simple co-precipitation method. • Small spherical nanocrystals adhering to the surface of large polyhedral particles. • Formation mechanism is relate to solubility of Sn(OH){sub 6}{sup 2−} in high concentration OH{sup −} . • The composite shows better electrochemical performance than Co{sub 2}SnO{sub 4} and Co{sub 3}O{sub 4} - Abstract: A novel dispersed structure Co{sub 2}SnO{sub 4}/Co{sub 3}O{sub 4} composite has been successfully synthesized by a conventional co-precipitation method with certain amount of NaOH concentration. The obtained composite exhibits dispersed structure with small spherical nanocrystals adhering to the surface of large polyhedral particles, which has been studied as an anode material in lithium-ion battery. Galvanostatic charge–discharge and cyclic voltammetry has been conducted to measure the electrochemical properties of the material. The results show that Co{sub 2}SnO{sub 4}/Co{sub 3}O{sub 4} composite demonstrates good reversible capacity of 702.5 mA h g{sup −1} after 50 cycles at a current density of 100 mA h g{sup −1}, much better than that of pure Co{sub 3}O{sub 4} (375.1 mA h g{sup −1}) and pure Co{sub 2}SnO{sub 4} (194.1 mA h g{sup −1}). This material also presents improved rate performance with capacity retention of 71.1% when the current ranges from 100 mA g{sup −1} to 1000 mA g{sup −1}. The excellent electrochemical performance of the as-prepared dispersed structure Co{sub 2}SnO{sub 4}/Co{sub 3}O{sub 4} composite could be attributed to the good dispersibility of nanoparticles which can effectively alleviate the volume expansion and improve the conductivity, thus enhance the cycling stability.

Effect of Co3O4 and Co3O4/CeO2 infiltration on the catalytic and electro-catalytic activity of LSM15/CGO10 porous cells stacks for oxidation of propene

DEFF Research Database (Denmark)

Ippolito, Davide; Kammer Hansen, Kent

2015-01-01

The objective of this work was to study the effect of Co3O4 and Co3O4/CeO2 infiltration on the propene oxidation catalytic activity of a La0.85Sr0.15MnO3/Ce0.9Gd0.1O1.95 electrochemical porous cell stack (11 layers, 5 single cells in series). The effect of the infiltration of Co3O4 and Co3O4/CeO2...... on the electrochemical properties of the porous cell stack was also investigated by electrochemical impedance spectroscopy (EIS). Co3O4 and Co3O4/CeO2 exhibited high catalytic activity for propene oxidation. The increase of propene oxidation rate with +4 V (0.8 V/cell) polarization reached 10% for the Co3O4 infiltrated...... reactor and 48% of efficiency at 300 °C. The Co3O4/CeO2 co-infiltration decreased the reactor polarization resistance, while Co3O4 infiltration had negligible effect on reactor electrochemical performance. The beneficial effect of CeO2 on the electrode activity was attributed to the increased...

Electronic Structure and Thermoelectric Properties of Ca3 Co4O9

Institute of Scientific and Technical Information of China (English)

无

2006-01-01

The relation among electronic structure, chemical bond and thermoelectric property of Ca3 Co4 O9 was studied using density function and discrete variation method (DFT-DVM).The gap between the highest valence band (HVB) and the lowest conduction band (LCB) shows a semiconducting property.Ca3 Co4 O9 colsists of CoO2 and Ca2 CoO3 two layers.The HVB and LCB near Fermi level are only mainly from O(2) 2p and Co(2) 3d in Ca2 CoO3 layer. Therefore, the semiconducting or thermoelectric property of Ca3 Co4 O9 should be mainly from Ca2 CoO3 layer, but it seems to have no direct relation to the CoO2 layer,which is consistent with that binary oxides hardly have a thermoelectric property, but trinary oxide compounds have quite a good thermoelectric property.The covalent and ionic bonds of Ca2 CoO3 layer are both weaker than those of CoO2 layer.Ca plays the role of connections between CoO2 and Ca2 CoO3 layers in Ca3 Co4 O9, decrease the ionic and covalent bond strength, and improve the thermoelectric property.

Polarized neutron reflectivity studies of magnetic oxidic Fe3O4/NiO and Fe3O4/CoO multilayers

NARCIS (Netherlands)

Ball, A.R.; Fredrikze, H.; Lind, D.M.; Wolf, R.M.; Bloemen, P.J.H.; Rekveldt, M.Th.; Zaag, van der P.J.

1996-01-01

The magnetic properties of [1 0 0] oriented Fe3O4/NiO and Fe3O4/CoO multilayers, MBE-grown on MgO(0 0 1) substrates, have been studied by polarized neutron reflectometry. In both samples, the Fe3O4 layer exhibits a depth-dependent magnetic profile characterized by a reduction in the magnetization

Synthesis of Co/Co3O4 Nanocomposite Particles Relevant to Magnetic Field Processing

DEFF Research Database (Denmark)

Srivastava, A.K.; Madhavi, S.; Menon, Mohan

2010-01-01

Co/Co3O4 nanocomposite particles of various morphologies were synthesized by the reverse micelle technique. Equiaxed, rod and faceted crystals with rectangular, pentagonal and hexagonal cross sections were observed. Annealing resulted in the formation of a composite of cobalt oxide (Co3O4) and fc...... cobalt (Co). Removal of boron residues from the final product was established by surface characterization. Magnetic moment of these nanocomposite particles is relevant to magnetic field processing.......Co/Co3O4 nanocomposite particles of various morphologies were synthesized by the reverse micelle technique. Equiaxed, rod and faceted crystals with rectangular, pentagonal and hexagonal cross sections were observed. Annealing resulted in the formation of a composite of cobalt oxide (Co3O4) and fcc...

Effect of Co{sup 2+} and Y{sup 3+} ions insertion on the microstructure development and magnetic properties of Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} powders synthesized using Co-precipitation method

Energy Technology Data Exchange (ETDEWEB)

Rashad, M.M., E-mail: rashad133@yahoo.com [Central Metallurgical Research and Development Institute (CMRDI), P.O. Box 87, Helwan 11421, Cairo (Egypt); Rayan, D.A.; Turky, A.O. [Central Metallurgical Research and Development Institute (CMRDI), P.O. Box 87, Helwan 11421, Cairo (Egypt); Hessien, M.M. [Central Metallurgical Research and Development Institute (CMRDI), P.O. Box 87, Helwan 11421, Cairo (Egypt); Chemistry Department, Taif University (Saudi Arabia)

2015-01-15

Nanocrystalline Ni{sub 0.5}Zn{sub 0.5−x}Co{sub x}Fe{sub 2−z}Y{sub z}O{sub 4} powders (x=0–0.3 and z from 0 to 0.3) have been synthesized via a facile co-precipitation technique. X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) are utilized in order to study the effect of variation of cobalt and yttrium substitutions and its impact on crystalline size, lattice parameter, X-ray density, microstructure and magnetic properties of the formed powders. X-ray diffraction data indicated that, after doping, all samples consisted of the main spinel phase for the formed precursors precipitated at pH 10 annealed at 1000 {sup o}C for 2 h. The lattice parameter and the unit cell were decreased linearly with increasing Co content whereas they were increased with increasing the Y incorporation. Additionally, the porosity was increased with increasing Co concentration while it was decreased with increasing the Y insertion. The mean ionic radii and hopping and bond lengths was decreased with the value of Co{sup 2+} and they were increased with the value of Y{sup 3+} ion as well as both of Y{sup 3+} and Co{sup 2+} ions. The microstructures of the produced powders were found to be cubic like structure. The addition of Y{sup 3+} ion suppressed the grain size whereas addition of Co{sup 2+} ion enhanced the grain growth availably. An examination of the magnetic properties revealed an increase in saturation magnetization with increasing Co and Y concentrations incorporation up to x=0.3. Meanwhile, the formed powders exhibited superparamagnetic characteristics. A high saturation magnetization (77.0 emu/g) was achieved for Ni{sub 0.5}Zn{sub 0.2}Co{sub 0.3}Fe{sub 2}O{sub 4} sample annealed at 1000 {sup o}C for 2 h. - Highlights: • Ni{sub 0.5}Zn{sub 0.5−x}Co{sub x}Fe{sub 2−z}Y{sub z}O{sub 4} powders were synthesized. • The porosity decreases with Y{sup 3+} and increases with Co{sup 2+}. • The bond lengths decrease with Co{sup 2

Morphological Control of Mesoporosity and Nanoparticles within Co3O4-CuO Electrospun Nanofibers: Quantum Confinement and Visible Light Photocatalysis Performance.

Science.gov (United States)

Pradhan, Amaresh C; Uyar, Tamer

2017-10-18

The one-dimensional (1D) mesoporous and interconnected nanoparticles (NPs) enriched composite Co 3 O 4 -CuO nanofibers (NFs) in the ratio Co:Cu = 1/4 (Co 3 O 4 -CuO NFs) composite have been synthesized by electrospinning and calcination of mixed polymeric template. Not merely the mesoporous composite Co 3 O 4 -CuO NFs but also single mesoporous Co 3 O 4 NFs and CuO NFs have been produced for comparison. The choice of mixed polymer templates such as polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) for electrospinning is responsible for the formation of 1D mesoporous NFs. The HR-TEM result showed evolution of interconnected nanoparticles (NPs) and creation of mesoporosity in all electrospun NFs. The quantum confinement is due to NPs within NFs and has been proved by the surface-enhanced Raman scattering (SERS) study and the UV-vis-NRI diffuse reflectance spectra (DRS). The high intense photoluminescence (PL) spectra showing blue shift of all NFs also confirmed the quantum confinement phenomena. The lowering of PL spectrum after mixing of CuO in Co 3 O 4 nanofibers framework (Co 3 O 4 -CuO NFs) proved CuO as an efficient visible light response low cost cocatalyst/charge separator. The red shifting of the band gap in composite Co 3 O 4 -CuO NFs is due to the internal charge transfer between Co 2+ to Co 3+ and Cu 2+ , proved by UV-vis absorption spectroscopy. Creation of oxygen vacancies by mixing of CuO and Co 3 O 4 also prevents the electron-hole recombination and enhances the photocatalytic activity in composite Co 3 O 4 -CuO NFs. The photocurrent density, Mott-Schottky (MS), and electrochemical impedance spectroscopy (EIS) studies of all NFs favor the high photocatalytic performance. The mesoporous composite Co 3 O 4 -CuO NFs exhibits high photocatalytic activity toward phenolic compounds degradation as compared to the other two NFs (Co 3 O 4 NFs and CuO NFs). The kinetic study of phenolic compounds followed first order rate equation. The high photocatalytic

Microstructural and dielectric properties of Ba0.6Sr0.4Ti1-xZrxO3 based combinatorial thin film capacitors library

International Nuclear Information System (INIS)

Liu Guozhen; Wolfman, Jerome; Autret-Lambert, Cecile; Sakai, Joe; Roger, Sylvain; Gervais, Monique; Gervais, Francois

2010-01-01

Epitaxial growth of Ba 0.6 Sr 0.4 Ti 1-x Zr x O 3 (0≤x≤0.3) composition spread thin film library on SrRuO 3 /SrTiO 3 layer by combinatorial pulsed laser deposition (PLD) is reported. X-ray diffraction and energy dispersive x-ray spectroscopy studies showed an accurate control of the film phase and composition by combinatorial PLD. A complex evolution of the microstructure and morphology with composition of the library is described, resulting from the interplay between epitaxial stress, increased chemical pressure, and reduced elastic energy upon Zr doping. Statistical and temperature-related capacitive measurements across the library showed unexpected variations in the dielectric properties. Doping windows with enhanced permittivity and tunability are identified, and correlated to microstructural properties.

Enhancement of CO Evolution by Modification of Ga2O3 with Rare-Earth Elements for the Photocatalytic Conversion of CO2 by H2O.

Science.gov (United States)

Tatsumi, Hiroyuki; Teramura, Kentaro; Huang, Zeai; Wang, Zheng; Asakura, Hiroyuki; Hosokawa, Saburo; Tanaka, Tsunehiro

2017-12-12

Modification of the surface of Ga 2 O 3 with rare-earth elements enhanced the evolution of CO as a reduction product in the photocatalytic conversion of CO 2 using H 2 O as an electron donor under UV irradiation in aqueous NaHCO 3 as a pH buffer, with the rare-earth species functioning as a CO 2 capture and storage material. Isotope experiments using 13 CO 2 as a substrate clearly revealed that CO was generated from the introduced gaseous CO 2 . In the presence of the NaHCO 3 additive, the rare-earth (RE) species on the Ga 2 O 3 surface are transformed into carbonate hydrates (RE 2 (CO 3 ) 3 ·nH 2 O) and/or hydroxycarbonates (RE 2 (OH) 2(3-x) (CO 3 ) x ) which are decomposed upon photoirradiation. Consequently, Ag-loaded Yb-modified Ga 2 O 3 exhibits much higher activity (209 μmol h -1 of CO) than the pristine Ag-loaded Ga 2 O 3 . The further modification of the surface of the Yb-modified Ga 2 O 3 with Zn afforded a selectivity toward CO evolution of 80%. Thus, we successfully achieved an efficient Ag-loaded Yb- and Zn-modified Ga 2 O 3 photocatalyst with high activity and controllable selectivity, suitable for use in artificial photosynthesis.

A Pt-Co3O4-CD electrocatalyst with enhanced electrocatalytic performance and resistance to CO poisoning achieved by carbon dots and Co3O4 for direct methanol fuel cells.

Science.gov (United States)

Sun, Yue; Zhou, Yunjie; Zhu, Cheng; Hu, Lulu; Han, Mumei; Wang, Aoqi; Huang, Hui; Liu, Yang; Kang, Zhenhui

2017-05-04

Highly efficient electrocatalysts remain huge challenges in direct methanol fuel cells (DMFCs). Here, a Pt-Co 3 O 4 -CDs/C composite was fabricated as an anode electrocatalyst with low Pt content (12 wt%) by using carbon dots (CDs) and Co 3 O 4 nanoparticles as building blocks. The Pt-Co 3 O 4 -CDs/C composite catalyst shows a significantly enhanced electrocatalytic activity (1393.3 mA mg -1 Pt), durability (over 4000 s) and CO-poisoning tolerance. The superior catalytic activity should be attributed to the synergistic effect of CDs, Pt and Co 3 O 4 . Furthermore, the Pt-Co 3 O 4 -CDs/C catalyst was integrated into a single cell, which exhibits a maximum power density of 45.6 mW cm -2 , 1.7 times the cell based on the commercial 20 wt% Pt/C catalyst.

Mesoporous Co{sub 3}O{sub 4} and CoO rate at C topotactically transformed from chrysanthemum-like Co(CO{sub 3}){sub 0.5}(OH).0.11H{sub 2}O and their lithium-storage properties

Energy Technology Data Exchange (ETDEWEB)

Xiong, Shenglin; Zeng, Hua Chun [Department of Chemical and Biomolecular Engineering, KAUST-NUS GCR Program, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore (Singapore); Chen, Jun Song; Lou, Xiong Wen [School of Chemical and Biomedical Engineering, Nanyang Technological University, 70 Nanyang Drive, Singapore (Singapore)

2012-02-22

In this work, a novel hydrothermal route is developed to synthesize cobalt carbonate hydroxide, Co(CO{sub 3}){sub 0.5}(OH).0.11H{sub 2}O. In this method, sodium chloride salt is utilized to organize single-crystalline nanowires into a chrysanthemum-like hierarchical assembly. The morphological evolution process of this organized product is investigated by examining different reaction intermediates during the synthesis. The growth and thus the final assembly of the Co(CO{sub 3}){sub 0.5}(OH).0.11H{sub 2}O can be finely tuned by selecting preparative parameters, such as the molar ratio of the starting chemicals, the additives, the reaction time and the temperature. Using the flower-like Co(CO{sub 3}){sub 0.5}(OH).0.11H{sub 2}O as a solid precursor, quasi-single-crystalline mesoporous Co{sub 3}O{sub 4} nanowire arrays are prepared via thermal decomposition in air. Furthermore, carbon can be added onto the spinel oxide by a chemical-vapor-deposition method using acetylene, which leads to the generation of carbon-sheathed CoO nanowire arrays (CoO rate at C). Through comparing and analyzing the crystal structures, the resultant products and their high crystallinity can be explained by a sequential topotactic transformation of the respective precursors. The electrochemical performances of the typical cobalt oxide products are also evaluated. It is demonstrated that tuning of the surface texture and the pore size of the Co{sub 3}O{sub 4} products is very important in lithium-ion-battery applications. The carbon-decorated CoO nanowire arrays exhibit an excellent cyclic performance with nearly 100% capacity retention in a testing range of 70 cycles. Therefore, this CoO rate at C nanocomposite can be considered to be an attractive candidate as an anode material for further investigation. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Reduced graphene oxide wrapped Fe3O4-Co3O4 yolk-shell nanostructures for advanced catalytic oxidation based on sulfate radicals

Science.gov (United States)

Zhang, Lishu; Yang, Xijia; Han, Erfen; Zhao, Lijun; Lian, Jianshe

2017-02-01

In this work, we designed and synthesized a high performance catalyst of reduced graphene oxide (RGO) wrapped Fe3O4-Co3O4 (RGO/Fe3O4-Co3O4) yolk-shell nanostructures for advanced catalytic oxidation based on sulfate radicals. The synergistic catalytic action of the RGO/Fe3O4-Co3O4 yolk-shell nanostructures activate the peroxymonosulfate (PMS) to produce sulfate radicals (SO4rad -) for organic dyes degradation, and the Orange II can be almost completely degradated in 5 min. Meanwhile the RGO wrapping prevents the loss of cobalt in the catalytic process, and the RGO/Fe3O4-Co3O4 can be recycled after catalyzed reaction due to the presence of magnetic iron core. What's more, it can maintain almost the same high catalytic activity even after 10 cycles through repeated NaBH4 reduction treatment. Hence, RGO/Fe3O4-Co3O4 yolk-shell nanostructures possess a great opportunity to become a promising candidate for waste water treatment in industry.

Structural evolution of epitaxial SrCoO{sub x} films near topotactic phase transition

Energy Technology Data Exchange (ETDEWEB)

Jeen, Hyoungjeen [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Department of Physics, Pusan National University, Busan, 609735 (Korea, Republic of); Lee, Ho Nyung, E-mail: hnlee@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

2015-12-15

Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoO{sub x}) epitaxially grown by pulsed laser epitaxy (PLE) as a model system to study the oxidation-driven evolution of the structure, electronic, and magnetic properties. We grew coherently strained SrCoO{sub 2.5} thin films and performed post-annealing at various temperatures for topotactic conversion into the perovskite phase (SrCoO{sub 3-δ}). We clearly observed significant changes in electronic transport, magnetism, and microstructure near the critical temperature for the topotactic transformation from the brownmillerite to the perovskite phase. Nevertheless, the overall crystallinity was well maintained without much structural degradation, indicating that topotactic phase control can be a useful tool to control the physical properties repeatedly via redox reactions.

Cathodic electrochemical activation of Co3O4 nanoarrays: a smart strategy to significantly boost the hydrogen evolution activity.

Science.gov (United States)

Yang, Li; Zhou, Huang; Qin, Xin; Guo, Xiaodong; Cui, Guanwei; Asiri, Abdullah M; Sun, Xuping

2018-02-22

Co(hydro)oxides show unsatisfactory catalytic activity for the hydrogen evolution reaction (HER) in alkaline media, and it is thus highly desirable but still remains a challenge to design and develop Co(hydro)oxide derived materials as superb hydrogen-evolving catalysts using a facile, rapid and less energy-intensive method. Here, we propose a cathodic electrochemical activation strategy toward greatly boosted HER activity of a Co 3 O 4 nanoarray via room-temperature cathodic polarization in sodium hypophosphite solution. After activation, the overpotential significantly decreases from 260 to 73 mV to drive a geometrical catalytic current density of 10 mA cm -2 in 1.0 M KOH. Notably, this activated electrode also shows strong long-term electrochemical durability with the retention of its catalytic activity at 100 mA cm -2 for at least 40 h.

Co3(PO42·4H2O

Directory of Open Access Journals (Sweden)

Yang Kim

2008-10-01

Full Text Available Single crystals of Co3(PO42·4H2O, tricobalt(II bis[orthophosphate(V] tetrahydrate, were obtained under hydrothermal conditions. The title compound is isotypic with its zinc analogue Zn3(PO42·4H2O (mineral name hopeite and contains two independent Co2+ cations. One Co2+ cation exhibits a slightly distorted tetrahedral coordination, while the second, located on a mirror plane, has a distorted octahedral coordination environment. The tetrahedrally coordinated Co2+ is bonded to four O atoms of four PO43− anions, whereas the six-coordinate Co2+ is cis-bonded to two phosphate groups and to four O atoms of four water molecules (two of which are located on mirror planes, forming a framework structure. In addition, hydrogen bonds of the type O—H...O are present throughout the crystal structure.

Solid-state thermal decomposition of the [Co(NH3)5CO3]NO3·0.5H2O complex: A simple, rapid and low-temperature synthetic route to Co3O4 nanoparticles

International Nuclear Information System (INIS)

Farhadi, Saeid; Safabakhsh, Jalil

2012-01-01

Highlights: ► [Co(NH 3 ) 5 CO 3 ]NO 3 ·0.5H 2 O complex was used for preparing pure Co 3 O 4 nanoparticles. ► Co 3 O 4 nanoparticles were prepared at low temperature of 175 °C. ► Co 3 O 4 nanoparticles show a weak ferromagnetic behaviour at room temperature. ► The method is simple, low-cost and suitable for the production of Co 3 O 4 . - Abstract: Co 3 O 4 nanoparticles were easily prepared via the decomposition of the pentammine(carbonato)cobalt(III) nitrate precursor complex [Co(NH 3 ) 5 CO 3 ]NO 3 ·0.5H 2 O at low temperature (175 °C). The product was characterized by thermal analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV–visible spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Brunauer–Emmett–Teller (BET) specific surface area measurements and magnetic measurements. The FT-IR, XRD, Raman and EDX results indicated that the synthesized Co 3 O 4 nanoparticles are highly pure and have a single phase. The TEM analysis revealed nearly uniform and quasi-spherical Co 3 O 4 nanoparticles with an average particle size of approximately 10 nm. The optical absorption spectrum of the Co 3 O 4 nanoparticles showed two direct band gaps of 2.18 and 3.52 eV with a red shift in comparison with previous reported values. The prepared Co 3 O 4 nanoparticles showed a weak ferromagnetic behaviour that could be attributed to uncompensated surface spins and/or finite-size effects. Using the present method, Co 3 O 4 nanoparticles can be produced without expensive organic solvents and complicated equipment. This simple, rapid, safe and low-cost synthetic route can be extended to the synthesis of other transition-metal oxides.

Surface and catalytic properties of MoO3/Al2O3 system doped with Co3O4

International Nuclear Information System (INIS)

Zahran, A.A.; Shaheen, W.M.; El-Shobaky, G.A.

2005-01-01

Thermal solid-solid interactions in cobalt treated MoO 3 /Al 2 O 3 system were investigated using X-ray powder diffraction. The solids were prepared by wet impregnation method using Al(OH) 3 , ammonium molybdate and cobalt nitrate solutions, drying at 100 deg. C then calcination at 300, 500, 750 and 1000 deg. C. The amount of MoO 3 , was fixed at 16.67 mol% and those of cobalt oxide were varied between 2.04 and 14.29 mol% Co 3 O 4 . Surface and catalytic properties of various solid samples precalcined at 300 and 500 deg. C were studied using nitrogen adsorption at -196 deg. C, conversion of isopropanol at 200-500 deg. C and decomposition of H 2 O 2 at 30-50 deg. C. The results obtained revealed that pure mixed solids precalcined at 300 deg. C consisted of AlOOH and MoO 3 phases. Cobalt oxide-doped samples calcined at the same temperature consisted also of AlOOH, MoO 3 and CoMoO 4 compounds. The rise in calcination temperature to 500 deg. C resulted in complete conversion of AlOOH into very poorly crystalline γ-Al 2 O 3 . The further increase in precalcination temperature to 750 deg. C led to the formation of Al 2 (MoO 4 ) 3 , κ-Al 2 O 3 besides CoMoO 4 and un-reacted portion of Co 3 O 4 in the samples rich in cobalt oxide. Pure MoO 3 /Al 2 O 3 preheated at 1000 deg. C composed of MoO 3 -αAl 2 O 3 solid solution (acquired grey colour). The doped samples consisted of the same solid solution together with CoMoO 4 and CoAl 2 O 4 compounds. The increase in calcination temperature of pure and variously doped solids from 300 to 500 deg. C increased their specific surface areas and total pore volume which suffered a drastic decrease upon heating at 750 deg. C. Doping the investigated system with small amounts of cobalt oxide (2.04 and 4 mol%) followed by heating at 300 and 500 deg. C increased its catalytic activity in H 2 O 2 decomposition. This increase, measured at 300 deg. C, attained 25.4- and 12.9-fold for the solids precalcined at 300 and 500 deg. C, respectively

Microstructural Evolution, Thermodynamics, and Kinetics of Mo-Tm2O3 Powder Mixtures during Ball Milling

Directory of Open Access Journals (Sweden)

Yong Luo

2016-10-01

Full Text Available The microstructural evolution, thermodynamics, and kinetics of Mo (21 wt % Tm2O3 powder mixtures during ball milling were investigated using X-ray diffraction and transmission electron microscopy. Ball milling induced Tm2O3 to be decomposed and then dissolved into Mo crystal. After 96 h of ball milling, Tm2O3 was dissolved completely and the supersaturated nanocrystalline solid solution of Mo (Tm, O was obtained. The Mo lattice parameter increased with increasing ball-milling time, opposite for the Mo grain size. The size and lattice parameter of Mo grains was about 8 nm and 0.31564 nm after 96 h of ball milling, respectively. Ball milling induced the elements of Mo, Tm, and O to be distributed uniformly in the ball-milled particles. Based on the semi-experimental theory of Miedema, a thermodynamic model was developed to calculate the driving force of phase evolution. There was no chemical driving force to form a crystal solid solution of Tm atoms in Mo crystal or an amorphous phase because the Gibbs free energy for both processes was higher than zero. For Mo (21 wt % Tm2O3, it was mechanical work, not the negative heat of mixing, which provided the driving force to form a supersaturated nanocrystalline Mo (Tm, O solid solution.

Magnetic behavior of biosynthesized Co{sub 3}O{sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Diallo, A., E-mail: abdoulayediallosn@gmail.com [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation,1 Old Faure road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa); Centre for Nano Science and Nanotechnology, K.S. Rangasamy College of Technology, Tiruchengode 63721, Tamil Nadu (India); Laboratoire de Photonique et de Nano-Fabrication, Faculté des sciences et Techniques, Université Cheikh Anta Diop de Dakar (UCAD), B.P. 25114, Dakar-Fann Dakar (Senegal); Doyle, T.B. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation,1 Old Faure road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa); School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4001 (South Africa); Mothudi, B.M.; Manikandan, E. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation,1 Old Faure road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa); and others

2017-02-15

This contribution reports for the 1st time on the magnetic behavior of CO{sub 3}O{sub 4} nanoparticles synthesized by a “green” process using an Aspalathus linearis’ leaves natural extract. More accurately magnetic behavior of CO{sub 3}O{sub 4} nanoparticles successfully biosynthesized was investigated using vibrating sample magnetometer. The magnetization behavior for the samples manifests a combination of size dependent antiferromagnetic and paramagnetic behaviors, respectively, for the core and shell of the nanoparticles. - Highlights: • 1{sup st} report on magnetic behavior of Co3O4 nanoparticles via Aspalathus linearis. • Co{sub 3}O{sub 4} nanoparticles manifest size-dependent antiferromagnetic & paramagnetic behaviors. • Antiferromagnetic & paramagnetic behaviors were confirmed by VSM.

Effects of TiO2 and Co3O4 Nanoparticles on Circulating Angiogenic Cells

Science.gov (United States)

Spigoni, Valentina; Cito, Monia; Alinovi, Rossella; Pinelli, Silvana; Passeri, Giovanni; Zavaroni, Ivana; Goldoni, Matteo; Campanini, Marco; Aliatis, Irene; Mutti, Antonio

2015-01-01

Background and Aim Sparse evidence suggests a possible link between exposure to airborne nanoparticles (NPs) and cardiovascular (CV) risk, perhaps through mechanisms involving oxidative stress and inflammation. We assessed the effects of TiO2 and Co3O4 NPs in human circulating angiogenic cells (CACs), which take part in vascular endothelium repair/replacement. Methods CACs were isolated from healthy donors’ buffy coats after culturing lymphomonocytes on fibronectin-coated dishes in endothelial medium for 7 days. CACs were pre-incubated with increasing concentration of TiO2 and Co3O4 (from 1 to 100 μg/ml) to test the effects of NP – characterized by Transmission Electron Microscopy – on CAC viability, apoptosis (caspase 3/7 activation), function (fibronectin adhesion assay), oxidative stress and inflammatory cytokine gene expression. Results Neither oxidative stress nor cell death were associated with exposure to TiO2 NP (except at the highest concentration tested), which, however, induced a higher pro-inflammatory effect compared to Co3O4 NPs (p<0.01). Exposure to Co3O4 NPs significantly reduced cell viability (p<0.01) and increased caspase activity (p<0.01), lipid peroxidation end-products (p<0.05) and pro-inflammatory cytokine gene expression (p<0.05 or lower). Notably, CAC functional activity was impaired after exposure to both TiO2 (p<0.05 or lower) and Co3O4 (p<0.01) NPs. Conclusions In vitro exposure to TiO2 and Co3O4 NPs exerts detrimental effects on CAC viability and function, possibly mediated by accelerated apoptosis, increased oxidant stress (Co3O4 NPs only) and enhancement of inflammatory pathways (both TiO2 and Co3O4 NPs). Such adverse effects may be relevant for a potential role of exposure to TiO2 and Co3O4 NPs in enhancing CV risk in humans. PMID:25803285

High-pressure behavior and equations of state of the cobaltates YBaCo{sub 4}O{sub 7}, YBaCo{sub 4}O{sub 7+{delta}}, YBaCoZn{sub 3}O{sub 7} and BaCoO{sub 3-x}

Energy Technology Data Exchange (ETDEWEB)

Juarez-Arellano, Erick A., E-mail: eajuarez@unpa.edu.mx [Instituto de Quimica Aplicada, Universidad del Papaloapan, Circuito Central 200, Parque Industrial, 68301 Tuxtepec, Oaxaca (Mexico); Avdeev, Maxim; Yakovlev, Sergey [Bragg Institute, ANSTO, PMB 1, Menai, NSW 2234 (Australia); Lopez-de-la-Torre, Laura; Bayarjargal, Lkhamsuren; Winkler, Bjoern; Friedrich, Alexandra [Institut fuer Geowissenschaften, Goethe-Universitaet Frankfurt, Altenhoeferallee 1, 60438 Frankfurt a.M. (Germany); Kharton, Vladislav V. [Department of Materials and Ceramic Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal)

2012-12-15

The compressibilities of the cobaltates YBaCo{sub 4}O{sub 7}, YBaCo{sub 4}O{sub 7+{delta}}, YBaCoZn{sub 3}O{sub 7} and BaCoO{sub 3-x} were investigated by in situ powder X-ray diffraction experiments up to 30 GPa using diamond anvil cells. Pressure-induced phase transitions and amorphization were observed in all the samples. The onset of the pressure-induced phase transition and the onset of the amorphization were observed at {approx}11.7 and 12.2 GPa (YBaCo{sub 4}O{sub 7}), at {approx}14.2 and 16.1 GPa (YBaCo{sub 4}O{sub 7+{delta}}), and at {approx}16.7 and 18.7 GPa (YBaCoZn{sub 3}O{sub 7}), respectively. An attempt to laser anneal at high-pressure failed as it led to a decomposition of the YBaCo{sub 4}O{sub 7} phase into a mixture of phases. Fits of second- and third-order Birch-Murnaghan equations-of-state to the p-V data result in B{sub 0}=109(3) GPa for YBaCo{sub 4}O{sub 7}; B{sub 0}=186(4) GPa and B Prime =1.5 for YBaCo{sub 4}O{sub 7+{delta}}; and B{sub 0}=117(1) GPa for YBaCoZn{sub 3}O{sub 7}. The high-pressure behavior of the studied compounds was compared with isostructural compounds and it is shown that the oxygen-content has a very large effect on the high-pressure behavior of this class of materials. Highlights: Black-Right-Pointing-Pointer Compressibilities were investigated by in situ DAC powder X-ray diffraction experiments. Black-Right-Pointing-Pointer Pressure-induced phase transitions were observed in all the samples. Black-Right-Pointing-Pointer High-pressure phases were very sensitive to small amounts of stresses and strains. Black-Right-Pointing-Pointer Due to the metastability of the compounds, laser annealing leads to decomposition. Black-Right-Pointing-Pointer Oxygen-content has a very large effect on the high pressure behavior in these materials.

Facile formation of 2D Co2P@Co3O4 microsheets through in-situ toptactic conversion and surface corrosion: Bifunctional electrocatalysts towards overall water splitting

Science.gov (United States)

Yao, Lihua; Zhang, Nan; Wang, Yin; Ni, Yuanman; Yan, Dongpeng; Hu, Changwen

2018-01-01

Exploring efficient non-precious electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for many renewable energy conversion processes. In this work, we report that 2D Co2P@Co3O4 microsheets can be prepared through an in-situ toptactic conversion from single-crystal β-Co(OH)2 microplatelets, associated with a surface phosphatization and corrosion process. The resultant Co2P@Co3O4 2D hybrid materials can further serve as self-supported bifunctional catalytic electrodes to drive the overall water splitting for HER and OER simultaneously, with low overpotentials and high long-term stability. Furthermore, a water electrolyzer based on Co2P@Co3O4 hybrid as both anode and cathode is fabricated, which achieves 10 mA cm-2 current at only 1.57 V during water splitting process. Therefore, this work provides a facile strategy to obtain 2D Co2P-based micro/nanostructures, which act as low-cost and highly active electrocatalysts towards overall water splitting application.

The effect of micro-structure on upconversion luminescence of Nd3+/Yb3+ co-doped La2O3-TiO2-ZrO2 glass-ceramics

Science.gov (United States)

Zhang, Minghui; Wen, Haiqin; Pan, Xiuhong; Yu, Jianding; Jiang, Meng; Yu, Huimei; Tang, Meibo; Gai, Lijun; Ai, Fei

2018-03-01

Nd3+/Yb3+ co-doped La2O3-TiO2-ZrO2 glasses have been prepared by aerodynamic levitation method. The glasses show high refractive index of 2.28 and Abbe number of 18.3. Glass-ceramics heated at 880 °C for 50 min perform the strongest upconversion luminescence. X-ray diffraction patterns of glass-ceramics with different depths indicate that rare earth ions restrain crystallization. Body crystallization mechanism mixed with surface crystallization is confirmed in the heat treatment. Surface crystals achieve priority to grow, resulting in important effects on upconversion luminescence. The results of atomic force microscope and scanning electron microscope indicate that crystal particles with uniform size distribute densely and homogenously on the surface and large amount of glass matrix exists in the glass ceramics heated at 880 °C for 50 min. Crystals in the glass-ceramics present dense structure and strong boundaries, which can reduce the mutual nonradiative relaxation rate among rare earth ions and then improve upconversion luminescence effectively. Based on micro-structural study, the mechanism that upconversion luminescence can be improved by heat treatment has been revealed. The results of micro-structural analysis agree well with the spectra.

Current-voltage characteristics of SnO2-Co3O4-Cr2O3-Sb2O5 ceramics

International Nuclear Information System (INIS)

Aguilar-Martinez, J A; Glot, A B; Gaponov, A V; Hernandez, M B; Guerrero-Paz, J

2009-01-01

The effect of mechanical treatment in a planetary mill on the microstructure and electrical properties of tin dioxide based varistor ceramics in the system SnO 2 -Co 3 O 4 -Cr 2 O 3 -Sb 2 O 5 sintered in the range 1150-1450 0 C was studied. The mechanical treatment leads to an increase in shrinkage, decrease in porosity, decrease in sample diameter, change in colour of the sintered samples from grey to black and enhancement of nonlinearity. For the sample sintered at 1350 0 C the mechanical treatment enhances the nonlinearity coefficient from 11 to 31 and decreases the electric field E 1 (at 10 -3 A cm -2 ) from 3500 to 2800 V cm -1 . The observed changes in physical properties are explained in terms of an additional size reduction of oxide particles and a better mixing of oxide powder followed by the formation of potential barriers at the grain boundaries throughout the whole sample. In spite of the low porosity, the low-field electrical conductivity of mechanically treated ceramics is significantly increased with the growth of relative humidity. A higher humidity sensitivity is found for mechanically treated ceramics with higher barrier height and higher nonlinearity coefficient.

Microstructural evolution and characterisation of interfacial phases in Al2O3/Ag–Cu–Ti/Al2O3 braze joints

International Nuclear Information System (INIS)

Ali, Majed; Knowles, Kevin M.; Mallinson, Phillip M.; Fernie, John A.

2015-01-01

Alumina ceramics with different levels of purity have been joined to themselves using an active braze alloy (ABA) Ag–35.3Cu–1.8Ti wt.% and brazing cycles that peak at temperatures between 815 °C and 875 °C for 2 to 300 min. The microstructures of the joints have been studied using scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. A limited number of joints prepared with the ABA Ag–26.7Cu–4.5Ti wt.% have also been studied. In terms of characterising the interfacial phases, efforts were made to understand the interfacial reactions, and to determine the influence of various brazing parameters, such as the peak temperature (T p ) and time at T p (τ), on the microstructure. In addition, the extent to which impurities in the alumina affect the interfacial microstructure has been determined. Ti 3 Cu 3 O has been identified as the main product of the reactions at the ABA/alumina interfaces. At the shortest joining time used, this phase was observed in the form of a micron-size continuous layer in contact with the ABA, alongside a nanometre-size layer on the alumina that was mostly composed of γ-TiO grains. Occasionally, single grains of Ti 3 O 2 were observed in the thin layer on alumina. In the joints prepared with Ag–35.3Cu–1.8Ti wt.%, the interfacial structure evolved considerably with joining time, eventually leading to a high degree of inhomogeneity across the length of the joint at the highest T p . The level of purity of alumina was not found to affect the overall interfacial microstructure, which is attributed to the formation of various solid solutions. It is suggested that Ti 3 Cu 3 O forms initially on the alumina. Diffusion of Ti occurs subsequently to form titanium oxide at the Ti 3 Cu 3 O/alumina interface

Co@Carbon and Co 3 O4@Carbon nanocomposites derived from a single MOF for supercapacitors.

Science.gov (United States)

Dai, Engao; Xu, Jiao; Qiu, Junjie; Liu, Shucheng; Chen, Ping; Liu, Yi

2017-10-03

Developing a composite electrode containing both carbon and transition metal/metal oxide as the supercapacitor electrode can combine the merits and mitigate the shortcomings of both the components. Herein, we report a simple strategy to prepare the hybrid nanostructure of Co@Carbon and Co 3 O 4 @Carbon by pyrolysis a single MOFs precursor. Co-based MOFs (Co-BDC) nanosheets with morphology of regular parallelogram slice have been prepared by a bottom-up synthesis strategy. One-step pyrolysis of Co-BDC, produces a porous carbon layer incorporating well-dispersed Co and Co 3 O 4 nanoparticles. The as-prepared cobalt-carbon composites exhibit the thin layer morphology and large specific surface area with hierarchical porosity. These features significantly improve the ion-accessible surface area for charge storage and shorten the ion transport length in thin dimension, thus contributing to a high specific capacitance. Improved capacitance performance was successfully realized for the asymmetric supercapacitors (ASCs) (Co@Carbon//Co 3 O 4 @Carbon), better than those of the symmetric supercapacitors (SSCs) based on Co@Carbon and Co 3 O 4 @Carbon materials (i.e., Co@Carbon//Co@Carbon and Co 3 O 4 @Carbon//Co 3 O 4 @Carbon). The working voltage of the ASCs can be extended to 1.5 V and show a remarkable high power capability in aqueous electrolyte. This work provides a controllable strategy for nanostructured carbon-metal and carbon-metal oxide composite electrodes from a single precursor.

Single crystalline Co3O4: Synthesis and optical properties

International Nuclear Information System (INIS)

Hosny, Nasser Mohammed

2014-01-01

Crystals of Co 3 O 4 have been prepared from thermal decomposition of molecular precursors derived from salicylic acid and cobalt (II) acetate or chloride at 500 °C. A cubic phase Co 3 O 4 micro- and nanocrystals have been obtained. The as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The images of electron microscopes showed octahedral crystals of Co 3 O 4 . The volume and polarizability of the optimized structures of molecular precursors have been calculated and related to the particle size. The optical band gap of the obtained crystals has been measured. The results indicated two optical band gaps with values 2.65 and 2.95 eV for (E g1 ) (E g2 ), respectively. - Highlights: • Synthesis of Co 3 O 4 nanocrystals by decomposition of cobalt salicylic acid precursor. • Characterization of the isolated nanocrystals by using XRD, SEM and HRTEM. • The optical band gap has been measured

3D hollow sphere Co3O4/MnO2-CNTs: Its high-performance bi-functional cathode catalysis and application in rechargeable zinc-air battery

Directory of Open Access Journals (Sweden)

Xuemei Li

2017-07-01

Full Text Available There has been a continuous need for high active, excellently durable and low-cost electrocatalysts for rechargeable zinc-air batteries. Among many low-cost metal based candidates, transition metal oxides with the CNTs composite have gained increasing attention. In this paper, the 3-D hollow sphere MnO2 nanotube-supported Co3O4 nanoparticles and its carbon nanotubes hybrid material (Co3O4/MnO2-CNTs have been synthesized via a simple co-precipitation method combined with post-heat treatment. The morphology and composition of the catalysts are thoroughly analyzed through SEM, TEM, TEM-mapping, XRD, EDX and XPS. In comparison with the commercial 20% Pt/C, Co3O4/MnO2, bare MnO2 nanotubes and CNTs, the hybrid Co3O4/MnO2-CNTs-350 exhibits perfect bi-functional catalytic activity toward oxygen reduction reaction and oxygen evolution reaction under alkaline condition (0.1 M KOH. Therefore, high cell performances are achieved which result in an appropriate open circuit voltage (∼1.47 V, a high discharge peak power density (340 mW cm−2 and a large specific capacity (775 mAh g−1 at 10 mA cm−2 for the primary Zn-air battery, a small charge–discharge voltage gap and a high cycle-life (504 cycles at 10 mA cm−2 with 10 min per cycle for the rechargeable Zn-air battery. In particular, the simple synthesis method is suitable for a large-scale production of this bifunctional material due to a green, cost effective and readily available process. Keywords: Bi-functional catalyst, Oxygen reduction reaction, Oxygen evolution reaction, Activity and stability, Rechargeable zinc-air battery

Facile fabrication of Fe_3O_4 and Co_3O_4 microspheres and their influence on the thermal decomposition of ammonium perchlorate

International Nuclear Information System (INIS)

Zhang, Yifu; Meng, Changgong

2016-01-01

Fe_3O_4 and Co_3O_4 microspheres were successfully synthesized by the hydrothermal decomposition of iron oxalate and cobalt oxalate solution. The composition and morphology of synthesized powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The catalytic properties of the as-obtained Fe_3O_4 and Co_3O_4 microspheres on the thermal decomposition of ammonium perchlorate (AP) were evaluated by thermo-gravimetric analysis and differential thermal analysis (TGA/DTA) methods. The thermal decomposition temperatures of AP in the presence of 1, 2, 4 and 8 wt% of Fe_3O_4 microspheres were respectively decreased by 58, 80, 102 and 129 °C (lowered to 398, 376, 354 and 327 °C). And the thermal decomposition temperatures of AP in the presence of 1, 2, 4 and 8 wt% of Co_3O_4 microspheres were respectively decreased by 55, 74, 112 and 131 °C (lowered to 401, 382, 344 and 325 °C). The analysis of the thermal gravimetric analyzer couplet with infrared spectroscopy (TG-IR) test reveal that the additives can accelerate the thermal decomposition of AP via the high-temperature decomposition. All the results suggest the as-prepared Fe_3O_4 and Co_3O_4 microspheres have highly catalytic properties on the thermal decomposition of AP, which can be used as the promising additives in the future. - Graphical abstract: Real-time FTIR spectra to reveal the thermal decomposition process of AP. - Highlights: • Highly uniform Fe_3O_4 and Co_3O_4 microspheres were successfully synthesized. • The T_c of AP with 1, 2, 4 and 8 wt% of Fe_3O_4 microspheres was decreased by 58, 80, 102 and 129 °C. • The T_c of AP with 1, 2, 4 and 8 wt% of Co_3O_4 microspheres was decreased by 55, 74, 112 and 131 °C. • The thermal decomposition process of AP was detected by TG-IR.

Thin (111) oriented CoFe{sub 2}O{sub 4} and Co{sub 3}O{sub 4} films prepared by decomposition of layered cobaltates

Energy Technology Data Exchange (ETDEWEB)

Buršík, Josef, E-mail: bursik@iic.cas.cz [Institute of Inorganic Chemistry of the Academy of Sciences of the Czech Republic, v.v.i., 250 68 Husinec-Řež 1001 (Czech Republic); Soroka, Miroslav, E-mail: soroka@iic.cas.cz [Institute of Inorganic Chemistry of the Academy of Sciences of the Czech Republic, v.v.i., 250 68 Husinec-Řež 1001 (Czech Republic); Uhrecký, Róbert, E-mail: uhrecky@iic.cas.cz [Institute of Inorganic Chemistry of the Academy of Sciences of the Czech Republic, v.v.i., 250 68 Husinec-Řež 1001 (Czech Republic); Kužel, Radomír, E-mail: kuzel@karlov.mff.cuni.cz [Charles University in Prague, Faculty of Mathematics and Physics, Ke Karlovu 5, 121 16 Praha 2 (Czech Republic); Mika, Filip, E-mail: filip.mika@isibrno.cz [Institute of Scientific Instruments, Academy of Sciences of the Czech Republic, v.v.i., Královopolská 147, 612 64 Brno (Czech Republic); Huber, Štěpán, E-mail: stepan.huber@vscht.cz [University of Chemistry and Technology, Faculty of Chemical Technology, Technická 5, 166 28 Prague 6 (Czech Republic)

2016-07-15

Graphical abstract: Pole figures of NaCoO{sub 2} (left) and of CoFe{sub 2}O{sub 4} (right) films formed through the transformation of O3-type NaCoO{sub 2} phase in consequence of sodium deintercalation occurring at 800 °C. Films were prepared by chemical solution deposition on MgO(111) substrate. - Highlights: • Epitaxial Na(CoFe)O{sub 2} thin films by means of chemical solution deposition were prepared. • Oriented spinel films through transformation of Na(CoFe)O{sub 2} were obtained. • Orientation relation to MgO, SrTiO{sub 3} and Zr(Y)O{sub 2} substrates were determined. • Structural aspects of Na(CoFe)O{sub 2} → CoFe{sub 2}O{sub 4} transformation pathway were elucidated. - Abstract: The formation and structural characterization of highly (111)-oriented Co{sub 3}O{sub 4} and CoFe{sub 2}O{sub 4} films prepared by a novel procedure from 00l-oriented NaCoO{sub 2} and Na(CoFe)O{sub 2} is reported. The Na(CoFe)O{sub 2} films were deposited on MgO, SrTiO{sub 3}, LaAlO{sub 3}, and Zr(Y)O{sub 2} single crystals with (100) and (111) orientations by chemical solution deposition method and crystallized at 700 °C. Subsequently they were transformed into (111)-oriented spinel phase during post-growth annealing at 800–1000 °C. Morphology and structure of the films was investigated by means of scanning electron microscopy and X-ray diffraction. While all spinel films exhibit pronounced out-of-plane orientation irrespective of substrate, the rate of in-plane orientation strongly depend on lattice misfit values. Different epitaxial phenomena ranging from true one-to-one epitaxy to the existence of many-to-one epitaxy involving two or more orientations were determined by full 3D texture analysis.

Eu3+/Tb3+-doped La2O2CO3/La2O3 nano/microcrystals with multiform morphologies: facile synthesis, growth mechanism, and luminescence properties.

Science.gov (United States)

Li, Guogang; Peng, Chong; Zhang, Cuimiao; Xu, Zhenhe; Shang, Mengmeng; Yang, Dongmei; Kang, Xiaojiao; Wang, Wenxin; Li, Chunxia; Cheng, Ziyong; Lin, Jun

2010-11-15

LaCO(3)OH nano/microcrystals with a variety of morphologies/sizes including nanoflakes, microflowers, nano/microrhombuses, two-double microhexagrams sandwichlike microspindles, and peach-nucleus-shaped microcrystals have been synthesized via a facile homogeneous precipitation route under mild conditions. A series of controlled experiments indicate that the pH values in the initial reaction systems, carbon sources, and simple ions (NH(4)(+) and Na(+)) were responsible for the shape determination of the LaCO(3)OH products. A possible formation mechanism for these products with diverse architectures has been presented. After annealing at suitable temperatures, LaCO(3)OH was easily converted to La(2)O(2)CO(3) and La(2)O(3) with the initial morphologies. A systematic study on the photoluminescence and cathodoluminescence properties of Eu(3+)- or Tb(3+)-doped La(2)O(2)CO(3)/La(2)O(3) samples has been performed in detail. The excitation and site-selective emission spectra were recorded to investigate the microstructure, site symmetry, and difference in the (5)D(0) → (7)F(2) transition of Eu(3+) ions in La(2)O(2)CO(3) and La(2)O(3) host lattices. In addition, the dependence of the luminescent intensity on the morphology for the as-prepared La(2)O(2)CO(3)/La(2)O(3):Ln(3+) (Ln = Eu, Tb) samples has been investigated. The ability of generating diverse morphologies and multiemitting colors for different rare-earth activator ion (Ln = Eu, Tb) doped La(2)O(2)CO(3)/La(2)O(3) nano/microstructures provides a great opportunity for the systematic evaluation of morphology-dependent luminescence properties, as well as the full exploration of their application in many types of color display fields.

Facile synthesis of Co3O4 nanowires grown on hollow NiO microspheres with superior electrochemical performance

International Nuclear Information System (INIS)

Fan, Meiqing; Ren, Bo; Yu, Lei; Song, Dalei; Liu, Qi; Liu, Jingyuan; Wang, Jun; Jing, Xiaoyan; Liu, Lianhe

2015-01-01

Graphical abstract: Display Omitted - Highlights: • The NiO hollow spheres were decorated by Co 3 O 4 nanowires. • The NiO hollow spheres were comprised of many NiO particles. • The Co 3 O 4 nanowires were composed of nanoparticles. • The NiO/Co 3 O 4 core/shell nanocomposites have good electrochemical properties. - Abstract: The NiO/Co 3 O 4 core/shell composites as a promising supercapacitor material have been fabricated by facile hydrothermal process. The structure and morphology of the NiO/Co 3 O 4 core/shell composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicated that the NiO hollow spheres were decorated by Co 3 O 4 nanowires, and the nanowires were composed of nanoparticles. Electrochemical properties were characterized by cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy. The results suggested that the NiO/Co 3 O 4 core/shell composites had good electrochemical reversibility and displayed superior capacitive performance with large capacitance (510 F g −1 ). Moreover, NiO/Co 3 O 4 core/shell composites showed excellent cyclic performanceafter 1000 cycles

Facile synthesis of porous Co3O4 nanoplates for supercapacitor ...

Indian Academy of Sciences (India)

Administrator

Abstract. Porous tricobalt tetraoxide (Co3O4) nanoplates with large aspect ratio have been obtained by annealing Co(OH)2 precursor nanoplates synthesized by a facile reflux method without the need for any template or surfactant. After the heat treatment, the as-obtained phase-pure Co3O4 nanoplates with a well- retained ...

High power Co3O4/ZnO p–n type piezoelectric transducer

International Nuclear Information System (INIS)

Hu, Yuh-Chung; Lee, Tsung-Han; Chang, Pei-Zen; Su, Pei-Chen

2015-01-01

Enhancing the output power of piezoelectric transducer is essential in order to supply sufficient and sustainable power to wireless sensor nodes or electronic devices. In this work, a Co 3 O 4 /ZnO p–n type power piezoelectric transducer which can be operated at low frequencies has been developed by utilizing n-type semiconducting zinc oxide (ZnO) and p-type semiconducting tricobalt tetroxide (Co 3 O 4 ). We utilize ZnO to be the piezoelectric transducer and build a multi-layer (Au/Co 3 O 4 /ZnO/Ti) thin film structure. The ZnO thin film with preferred orientation along the (002) plane was deposited under optimized deposition conditions on the flexible titanium (Ti) foil with thickness of 80 μm. The Co 3 O 4 /ZnO interface forms a p–n junction and increases the difference in Fermi levels between the two electrodes, resulting in the great enhancement of output power. The measured output power of the p–n type piezoelectric transducer with optimal resistance of 100 kΩ is 10.4 μW at low operating frequency of 37 Hz, which is 10.9 times of output power of ZnO piezoelectric transducers. - Highlights: • Deposited zinc oxide performed good piezoelectric coefficient. • ZnO thin film with preferred orientation along the (002) plane was deposited. • A p–n type piezoelectric transducer with enhanced output power was fabricated. • 10.9 times increment in output power was obtained. • Increase of difference in Fermi level and p–n junction formation was explained

Synthesis and enhanced photoelectrocatalytic activity of p–n junction Co3O4/TiO2 nanotube arrays

International Nuclear Information System (INIS)

Dai Gaopeng; Liu Suqin; Liang Ying; Luo Tianxiong

2013-01-01

Highlights: ► Co 3 O 4 /TiO 2 nanotube arrays (NTs) were prepared by an impregnating–deposition–decompostion method treatment. ► Co 3 O 4 /TiO 2 NTs exhibit high photoelectrocatalytic (PEC) activity. ► The high PEC activity was attribute to the formation of p–n junction between Co 3 O 4 and TiO 2 . - Abstract: Co 3 O 4 /TiO 2 nanotube arrays (NTs) were prepared by depositing Co 3 O 4 nanoparticles (NPs) on the tube wall of the self-organized TiO 2 NTs using an impregnating–deposition–decompostion method. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–vis absorption spectroscopy. The photoelectrocatalytic (PEC) activity is evaluated by degradation of methyl orange (MO) aqueous solution. The prepared Co 3 O 4 /TiO 2 NTs exhibit much higher PEC activity than TiO 2 NTs due to the p–n junction formed between Co 3 O 4 and TiO 2 .

Structural evolution of Ba8Ti3Nb4O24 from BaTiO3 using a series of Ba(Ti1−5xNb4x)O3 solid solutions

International Nuclear Information System (INIS)

Barrientos Hernández, F.R.; Lira Hernández, I.A.; Gómez Yáñez, C.; Arenas Flores, A.; Cabrera Sierra, R.; Pérez Labra, M.

2014-01-01

Highlights: • The evolution phase Ba 8 Ti 3 Nb 4 O 24 was obtained through the mechanism Ba(Ti 1-5x Nb 4x )O 3 . • Addition of niobium can accelerate grain growth of BaTiO 3 ceramics. • Ba 8 Ti 3 Nb 4 O 24 presents a dielectric loss of 0.0035 and permittivity value of 54.6. • Electrical measurements showed that Nb 5+ content drops Curie temperature. • Samples with x ⩾ 0.0625 shows an insulating behavior. -- Abstract: In this work, the structural evolution of hexagonal phase Ba 8 Ti 3 Nb 4 O 24 by adding Nb 2 O 5 to perovskite structure of BaTiO 3 was investigated. The compositions Ba(Ti 1-5x Nb 4x )O 3 ceramics, with 0.00025 ⩽ x ⩽ 0.125 were prepared by the conventional solid state route in air atmosphere, the powders precursors, BaTiO 3 , BaCO 3 and Nb 2 O 5 , were mixed in stoichiometric proportions and ground in a ball mill using alumina balls and acetone. The mixed powders were calcined at temperatures up to 1500 °C. The phase transformation of Ba 8 Ti 3 Nb 4 O 24 from BaTiO 3 was studied by DRX, Raman spectroscopy, SEM, electrical measurements (relative permittivity and P–E hysteresis loops); Rietveld’s refinement was used to structurally characterize the samples. For the devices obtained capacitance was measured at 1 kHz; with these values we calculated the relative permittivity. The samples show typical P–E hysteresis loops at room temperature accompanied by saturation polarization (Ps) and remnant polarization (Pr). The DRX and Rietveld’s refinement results show x ⩽ 0.01 has a ferroelectric behavior. When the doped level is increased x ⩾ 0.02, a peak displacement is observed, this is due to the phase transformation of tetragonal to cubic into the unit cell. Finally, with x = 0.125 the crystal structure transforms to the characteristic hexagonal phase Ba 8 Ti 3 Nb 4 O 24 which resonates at microwave frequencies

One-step engineered self-assembly Co3O4 nanoparticles to nanocubes for supercapacitors

Science.gov (United States)

Nagajyothi, P. C.; Pandurangan, M.; Sreekanth, T. V. M.; Shim, Jaesool

2018-02-01

Tricobalt tetraoxide or cobalt oxide (Co3O4) nanocubes (NCs) were synthesized from the self-assemblies of Co3O4 nanoparticles (NPs) via a simple one-step hydrothermal method. X-ray diffraction analysis confirmed the cubic crystal structure of Co3O4 NCs. The surface properties were investigated by x-ray photoelectron spectroscopy, which suggests the co-existence of Co in +2 and +3 states. The self-assemblies of aggregation of NPs to NCs were inspected using scanning electron microscopy, which is supported by transmission electron microscopy. The electrochemical properties of Co3O4 NCs were carried out by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) curves and impedance analysis. The areal capacitance of 3.04 mF cm-2 was obtained at current density of 10 μA cm-2. The Co3O4 NCs electrode exhibits good long-cyclic stability with 92.1% capacitance retention over 3000 cycles. The CV, GCD and impedance curves of Co3O4 NCs were recorded after cyclic test, which are similar to the curves recorded before the test. Therefore, the Co3O4 NCs serves good candidate as positive electrode materials for asymmetric supercapacitors.

Photocatalytic properties of Co_3O_4/LiCoO_2 recycled from spent lithium-ion batteries using citric acid as leaching agent

International Nuclear Information System (INIS)

Santana, I.L.; Moreira, T.F.M.; Lelis, M.F.F.; Freitas, M.B.J.G.

2017-01-01

In this work, cobalt and lithium from the cathodes of spent lithium-ion batteries were recycled to synthesize a mixture of Co_3O_4 and LiCoO_2. The positive electrode was leached with citric acid in the green recycling. After being heated to 85 °C, the leaching solution formed a pink sol, and after being dried at 120 °C for 24 h, it formed a gel, which is a precursor material for Co_3O_4 and LiCoO_2 synthesis. A mixture of Co_3O_4 and LT-LiCoO_2 was obtained after the calcination of the precursor material at 450 °C for 3 h. The photocatalytic properties of the Co_3O_4 and LiCoO_2 were tested in the discoloration of methylene blue dye. The discoloration efficiency of methylene blue dye in the presence of Co_3O_4 and LiCoO_2 was 90% after 10 h and 100% after 24 h of heterogeneous catalysis. The contribution of this work is that it presents a means to produce valuable materials with photocatalytic properties from recycled batteries through a spent Li-ion battery recycling process without polluting the environment. - Highlights: • Synthesis a mixture of Co_3O_4/LiCoO_2 from spent Li-ion batteries. • Citric acid for leaching of the cathodes of the spent Li-ion batteries. • Co_3O_4/LiCoO_2 as catalysts in the photodegradation of the methylene blue dye.

Modification of Ga2O3 by an Ag-Cr core-shell cocatalyst enhances photocatalytic CO evolution for the conversion of CO2 by H2O.

Science.gov (United States)

Pang, Rui; Teramura, Kentaro; Tatsumi, Hiroyuki; Asakura, Hiroyuki; Hosokawa, Saburo; Tanaka, Tsunehiro

2018-01-25

A core-shell structure of Ag-Cr dual cocatalyst loaded-Ga 2 O 3 was found to significantly enhance the formation rate of CO and selectivity toward CO evolution for the photocatalytic conversion of CO 2 where H 2 O is used as an electron donor.

Crystal growth and magnetic properties of spinel (Co,Mn)3O4

Science.gov (United States)

Kang, Sun Hee; Kim, Ill Won; Jeong, Yoon Hee; Koo, Tae Yeong

2012-04-01

Single crystals of cubic and tetragonal spinel Co3-xMnxO4 (x=1.0 and 1.5) were successfully grown using a solvent evaporation method with PbF2 flux. Single crystals in octahedral shape with a size of about 4 mm on edge were obtained from 100 cm3 Pt crucibles. Ferrimagnetic transitions were detected at 170 K and 160 K from the measurements of temperature dependent magnetization and specific heat of Co2MnO4 and Co1.5Mn1.5O4, respectively. Low temperature field-dependent magnetization curves give a strong indication of the non-collinear spin structure, offering an insulating Co3-xMnxO4 system as a possible candidate for examining the multiferroicity.

Co3O4@CoS Core-Shell Nanosheets on Carbon Cloth for High Performance Supercapacitor Electrodes

Directory of Open Access Journals (Sweden)

Jinfeng Ning

2017-06-01

Full Text Available In this work, a two-step electrodeposition strategy is developed for the synthesis of core-shell Co3O4@CoS nanosheet arrays on carbon cloth (CC for supercapacitor applications. Porous Co3O4 nanosheet arrays are first directly grown on CC by electrodeposition, followed by the coating of a thin layer of CoS on the surface of Co3O4 nanosheets via the secondary electrodeposition. The morphology control of the ternary composites can be easily achieved by altering the number of cyclic voltammetry (CV cycles of CoS deposition. Electrochemical performance of the composite electrodes was evaluated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy techniques. The results demonstrate that the Co3O4@CoS/CC with 4 CV cycles of CoS deposition possesses the largest specific capacitance 887.5 F·g−1 at a scan rate of 10 mV·s−1 (764.2 F·g−1 at a current density of 1.0 A·g−1, and excellent cycling stability (78.1% capacitance retention at high current density of 5.0 A·g−1 after 5000 cycles. The porous nanostructures on CC not only provide large accessible surface area for fast ions diffusion, electron transport and efficient utilization of active CoS and Co3O4, but also reduce the internal resistance of electrodes, which leads to superior electrochemical performance of Co3O4@CoS/CC composite at 4 cycles of CoS deposition.

Processes of microstructural evolution during high-energy mechanical treatment of ZnO and black NiO powder mixture

Energy Technology Data Exchange (ETDEWEB)

Kakazey, M., E-mail: kakazey@hotmail.com [Centro de Investigación en Ingeniería y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos, Cuernavaca (Mexico); Vlasova, M. [Centro de Investigación en Ingeniería y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos, Cuernavaca (Mexico); Vorobiev, Y. [Unidad Querétaro del Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Querétaro (Mexico); Leon, I. [Centro de Investigaciones Quimicas, Universidad Autonoma del Estado de Morelos, Cuernavaca (Mexico); Cabecera Gonzalez, M. [Facultad de Ciencias Químicas e Ingeniería, Universidad Autonoma del Estado de Morelos, Cuernavaca (Mexico); Chávez Urbiola, Edgar Arturo [Unidad Querétaro del Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Querétaro (Mexico)

2014-11-15

Kinetics of microstructural evolution in ZnO and NiO black powder mixture during prolonged high-energy mechanical ball milling were investigated by Scanning Electron Microscopy, Laser Particle Sizer, X-ray diffraction, Electron Paramagnetic Resonance, Fourier Transform Infrared Spectroscopy and UV–vis Diffuse Reflection methods. The use of these methods allows us to control the macrostructural processes (ZnO particles and NiO granules grinding, the deagglomeration and “secondary agglomeration”), the microstructural processes (formation and annealing of different native defects in ZnO [V{sub Zn}{sup −}:Zn{sub i}{sup 0} (I), V{sub Zn}{sup −} (II), and (V{sub Zn}{sup −}){sub 2}{sup −} (III) centers] and NiO black) and the mechanothermal processes in samples. This allows to establish the relationship between microstructural evolution and the properties of the samples depending on the duration of the mechanical processing.

Mesoporous Co3O4 nanosheets-3D graphene networks hybrid materials for high-performance lithium ion batteries

International Nuclear Information System (INIS)

Sun, Hongyu; Liu, Yanguo; Yu, Yanlong; Ahmad, Mashkoor; Nan, Ding; Zhu, Jing

2014-01-01

Graphical abstract: - Highlights: • The mesoporous Co 3 O 4 nanosheets-3D graphene networks have been found to display better LIB performance as compare with Co 3 O 4 /CNT and Co 3 O 4 structures. • Electrochemical impedance spectroscopy shows that the addition of 3DGN largely enhanced the electrochemical activity of Co 3 O 4 during the cycling processes. • The large specific surface area and porous nature of the Co 3 O 4 nanosheets are very convenient and accessible for electrolyte diffusion and intercalation of Li + ions into the active phases. - Abstract: Mesoporous Co 3 O 4 nanosheets-3D graphene networks (3DGN) hybrid materials have been synthesized by combining chemical vapor deposition (CVD) and hydrothermal method and investigated as anode materials for Li-ion batteries (LIBs). Microscopic characterizations have been performed to confirm the 3DGN and mesoporous Co 3 O 4 nanostructures. The specific surface area and pore size of the hybrid structures have been found ∼ 34.5 m 2 g −1 and ∼ 3.8 nm respectively. It has been found that the Co 3 O 4 /3DGNs composite displays better LIB performance with enhanced reversible capacity, good cyclic performance and rate capability as compare with Co 3 O 4 /CNT and Co 3 O 4 structures. Electrochemical impedance spectroscopy (EIS) results show that the addition of 3DGN not only preserves high conductivity of the composite electrode, but also largely enhanced the electrochemical activity of Co 3 O 4 during the cycling processes. The improved electrochemical performance is considered due to the addition of 3DGNs which prevent the cracking of electrode. In addition, the large specific surface area and porous nature of the Co 3 O 4 nanosheets are also very convenient and accessible for electrolyte diffusion and intercalation of Li + ions into the active phases. Therefore, this combination can be considered to be an attractive candidate as an anode material for LIBs

Co3O4/MnO2/Hierarchically Porous Carbon as Superior Bifunctional Electrodes for Liquid and All-Solid-State Rechargeable Zinc-Air Batteries.

Science.gov (United States)

Li, Xuemei; Dong, Fang; Xu, Nengneng; Zhang, Tao; Li, Kaixi; Qiao, Jinli

2018-05-09

The design of efficient, durable, and affordable catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is very indispensable in liquid-type and flexible all-solid-state zinc-air batteries. Herein, we present a high-performance bifunctional catalyst with cobalt and manganese oxides supported on porous carbon (Co 3 O 4 /MnO 2 /PQ-7). The optimized Co 3 O 4 /MnO 2 /PQ-7 exhibited a comparable ORR performance with commercial Pt/C and a more superior OER performance than all of the other prepared catalysts, including commercial Pt/C. When applied to practical aqueous (6.0 M KOH) zinc-air batteries, the Co 3 O 4 /MnO 2 /porous carbon hybrid catalysts exhibited exceptional performance, such as a maximum discharge peak power density as high as 257 mW cm -2 and the most stable charge-discharge durability over 50 h with negligible deactivation to date. More importantly, a series of flexible all-solid-state zinc-air batteries can be fabricated by the Co 3 O 4 /MnO 2 /porous carbon with a layer-by-layer method. The optimal catalyst (Co 3 O 4 /MnO 2 /PQ-7) exhibited an excellent peak power density of 45 mW cm -2 . The discharge potentials almost remained unchanged for 6 h at 5 mA cm -2 and possessed a long cycle life (2.5 h@5 mA cm -2 ). These results make the optimized Co 3 O 4 /MnO 2 /PQ-7 a promising cathode candidate for both liquid-type and flexible all-solid-state zinc-air batteries.

Synthesis and photocatalytic activity of CuY{sub y}Fe{sub 2-y}O{sub 4}-CuCo{sub 2}O{sub 4} nanocomposites for H{sub 2} evolution under visible light irradiation

Energy Technology Data Exchange (ETDEWEB)

Yan, Jianhui; Yang, Haihua; Yao, Maohai; Han, Yong [Department of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Shuyuan Load, Yueyang, Hunan 414000 (China); College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan 410083 (China); Tang, Yougen; Lu, Zhouguang [College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan 410083 (China); Zheng, Shuqin [Department of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Shuyuan Load, Yueyang, Hunan 414000 (China)

2009-11-15

Spinel-type CuY{sub y}Fe{sub 2-y}O{sub 4}-CuCo{sub 2}O{sub 4} nanocomposites have been successfully synthesized via a facile citric acid (CA)-assisted sol-gel method. And the as-synthesized nanocomposites have been characterized by techniques of X-ray diffraction (XRD), nitrogen adsorption BET method, and transmission electron microscopy (TEM). The samples are composed of primary ultrafine nanoparticles with nearly spherical morphology and mean particle size of about 80 nm. Moreover, the photocatalytic H{sub 2} evolution activity of the as-obtained samples has been evaluated from aqueous oxalic acid solution under visible light irradiation. The influence of photocatalyst type, calcination temperature, Y{sup 3+} doping content, and the durability of the as-obtained photocatalyst have been investigated in detail. The best photocatalytic H{sub 2} evolution activity was obtained over the as-synthesized CuY{sub 0.08}Fe{sub 1.92}O{sub 4}-CuCo{sub 2}O{sub 4} nanocomposite. (author)

Synthesis of Co3O4 Cotton-Like Nanostructures for Cholesterol Biosensor

Directory of Open Access Journals (Sweden)

Sami Elhag

2014-12-01

Full Text Available The use of templates to assist and possess a control over the synthesis of nanomaterials has been an attractive option to achieve this goal. Here we have used sodium dodecyl sulfate (SDS to act as a template for the low temperature synthesis of cobalt oxide (Co3O4 nanostructures. The use of SDS has led to tune the morphology, and the product was in the form of “cotton-like” nanostructures instead of connected nanowires. Moreover, the variation of the amount of the SDS used was found to affect the charge transfer process in the Co3O4. Using Co3O4 synthesized using the SDS for sensing of cholesterol was investigated. The use of the Co3O4 synthesized using the SDS was found to yield an improved cholesterol biosensor compared to Co3O4 synthesized without the SDS. The improvement of the cholesterol sensing properties upon using the SDS as a template was manifested in increasing the sensitivity and the dynamic range of detection. The results achieved in this study indicate the potential of using template assisted synthesis of nanomaterials in improving some properties, e.g., cholesterol sensing.

Bimetallic-organic framework derived porous Co3O4/Fe3O4/C-loaded g-C3N4 nanocomposites as non-enzymic electrocatalysis oxidization toward ascorbic acid, dopamine acid, and uric acid

Science.gov (United States)

Hu, Bin; Liu, Yongkang; Wang, Zhuo-Wei; Song, Yingpan; Wang, Minghua; Zhang, Zhihong; Liu, Chun-Sen

2018-05-01

We report on the synthesis of Co- and Fe-based bimetallic nanocatalysts embedded in mesoporous carbon and g-C3N4 nanosheets (denoted as Co3O4/Fe3O4/mC@g-C3N4) for selectively simultaneous determination of ascorbic acid (AA), dopamine acid (DA), and uric acid (UA). These electrocatalysts consisting of bimetallic Co-Fe alloy nanoparticles encapsulated in N-doped carbon matrix were prepared via pyrolysis of Co/Fe-MOFs after grinding with high amounts of melamine. Chemical/crystal structures suggest high contents of mesoporous carbon in calcinated Co3O4/Fe3O4/mC nanocomposites, which exhibited enhanced electrocatalytic activity toward small biomolecules. The intrinsic performances of Co/Fe-MOFs with large specific surface area and regular nodes in the two-dimensional nanostructured g-C3N4 nanosheets endowed the as-prepared series of Co3O4/Fe3O4/mC@g-C3N4 nanocomposites with remarkable electrocatalytic activities and high adsorption ability toward oxidation of AA, DA, and UA. The developed biosensors also showed long-term stability and high selectivity for targeted analytes, with satisfactory results on actual samples in human urine. The results indicate that the as-synthesized Co3O4/Fe3O4/mC@g-C3N4 nanostructure exhibits good electrocatalytic activity and potential applications in clinical diagnosis and biosensing.

Effects of Synthesis and Processing on the Thermoelectric Properties of Ca3Co4O9+δ

DEFF Research Database (Denmark)

Wu, NingYu; Holgate, Tim; Van Nong, Ngo

In the present study, Ca3Co4O9+δ was synthesized by solid-state and sol-gel reactions followed by spark plasma sintering (SPS) under different conditions such as sintering temperatures, applied pressures and ramping rates. The materials were then characterized with respect to their microstructure......, phase purity and thermoelectric properties. With the identical optimal SPS process, the power factor of about 400 µW/m•K2 and 465 µW/m•K2 (at 800 °C) is measured from samples produced by solid-state and sol-gel reactions respectively, both of these values are higher than the value reported so far....... The thermoelectric performance improvement observed for the solid-state and sol-gel reactions suggests that the particle sizes may be a predominant key parameter of the Ca3Co4O9+δ thermoelectric properties. Smaller particle size (500 nm) as produced in this study by sol-gel synthesis method with optimal SPS process...

Microstructure evolution of the Si{sub 3}N{sub 4}/Si{sub 3}N{sub 4} joints brazed using Au-Ni-V filler alloys with different V content

Energy Technology Data Exchange (ETDEWEB)

Sun, Y. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Zhang, J., E-mail: hitzhangjie@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Zhang, H.W.; Fan, G.H.; He, Y.M. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2011-08-18

Highlights: > Si{sub 3}N{sub 4} ceramic was brazed using Au-Ni-V filler alloy with different V content. > The microstructure evolution of the joint was study in detail in the paper. > The polygonal Ni{sub 2}SiV{sub 3} and Ni{sub 3}V phase in the joint were investigated by TEM. > The formation of different compounds and alloys in joint was detailed discussed. - Abstract: Au-Ni-V filler alloys with different vanadium contents were designed to braze Si{sub 3}N{sub 4} ceramic at 1373 K for 30 min, and the microstructures of brazing seams were investigated by SEM and TEM. When the Au-Ni-V filler alloy contains 5 at.% V, round-like Ni[Si, V, Au] precipitates form in the Au[Ni] solid solution matrix and a VN reaction layer with 0.5 {mu}m thickness appears on Si{sub 3}N{sub 4} interface. When the V content increases to 10 at.%, a new polygonal Ni{sub 2}SiV{sub 3} phase occurs in the seam, and the Ni[Si, V, Au] precipitate coarsens and VN layer thickens. With increase of V contents to 15 and 20 at.%, laminar Ni[Au] and polygonal Ni{sub 3}V precipitates form. With 25 at.% V content in the filler alloy, the Ni{sub 2}SiV{sub 3} and Ni{sub 3}V precipitates distribute homogenously in the brazing seam. These microstructure evolutions were attributed to the reaction between Si{sub 3}N{sub 4} and vanadium, which forms VN reaction layer and releases Si into the molten alloy.

Crystal structure of alluaudite-type Na4Co(MoO4)3.

Science.gov (United States)

Nasri, Rawia; Fakhar Bourguiba, Noura; Zid, Mohamed Faouzi; Driss, Ahmed

2014-09-01

The title compound, tetra-sodium cobalt(II) tris-[molyb-date(IV)], was prepared by solid-state reactions. The structure is isotypic with Na3In2(AsO4)3 and Na3In2(PO4)3. The main structural feature is the presence of infinite chains of edge-sharing X 2O10 (X = Co/Na) dimers, which are linked by MoO4 tetra-hedra, forming a three-dimensional framework enclosing two types of hexa-gonal tunnels in which Na(+) cations reside. In this alluaudite structure, Co and Na atoms are located at the same general site with occupancies of 0.503 (5) and 0.497 (6), respectively. The other three Na and one of the two Mo atoms lie on special positions (site symmetries 2, -1, 2 and 2, respectively). The structure is compared with similar structures and other members of alluaudite family.

Controllable synthesis of Co3O4/polyethyleneimine-carbon nanotubes nanocomposites for CO and NH3 gas sensing at room temperature

International Nuclear Information System (INIS)

Lin, Yufei; Kan, Kan; Song, Wanzhen; Zhang, Guo; Dang, Lifang; Xie, Yu; Shen, Peikang; Li, Li; Shi, Keying

2015-01-01

Graphical abstract: Co 3 O 4 /polyethyleneimine-carbon nanotubes composites (CoPCNTs) have been successfully controllable synthesized via hydrothermal method at different temperature. The CoPCNTs sensors exhibited the highest response to CO and NH 3 gases with response time of 4 s and 4.3 s, low detection limit of 5 ppm and 1 ppm at room temperature, respectively. The enhanced gas sensing could be ascribed to the synergistic effect between the tiny size of Co 3 O 4 and good conductivity of carbon nanotubes functionalized by polyethyleneimine. - Highlights: • The CNTs functionalized by polyethyleneimine provided a new functional structural. • The novel 1D structure could capture and migrate electrons quickly. • The Co 3 O 4 nanoparticles liked a snake winding around CNTs. • The gas sensor could work at room temperatures, which suit to practical application. - Abstract: A novel 1D Co 3 O 4 /polyethyleneimine-carbon nanotubes composites (CoPCNTs) have been successfully synthesized via hydrothermal method at different temperature. The CNTs functionalized by polyethyleneimine (PCNTs) provided a new material with new structural and functional properties. The PCNTs was used as loading guider and electron transfer path. The Co 3 O 4 nanoparticles (NPs) loaded on the PCNTs surface liked a snake winding around CNTs, and the size was about 5–10 nm. The gas sensing characteristics of the CoPCNTs sensors to carbon monoxide (CO) and ammonia (NH 3 ) were evaluated with different gas concentration. The CoPCNTs sensors grown at 160 °C exhibited the highest response to CO and NH 3 gases with response time of 4 s and 4.3 s at room temperature (RT), respectively. Hence, the approach developed in this work would be important for the low-cost and large-scale production of the CoPCNTs materials with highly promising applications in gas sensors

Topotactic oxidation pathway of ScTiO3 and high-temperature structure evolution of ScTiO3.5 and Sc4Ti3O12-type phases.

Science.gov (United States)

Shafi, Shahid P; Hernden, Bradley C; Cranswick, Lachlan M D; Hansen, Thomas C; Bieringer, Mario

2012-02-06

The novel oxide defect fluorite phase ScTiO(3.5) is formed during the topotactic oxidation of ScTiO(3) bixbyite. We report the oxidation pathway of ScTiO(3) and structure evolution of ScTiO(3.5), Sc(4)Ti(3)O(12), and related scandium-deficient phases as well as high-temperature phase transitions between room temperature and 1300 °Cusing in-situ X-ray diffraction. We provide the first detailed powder neutron diffraction study for ScTiO(3). ScTiO(3) crystallizes in the cubic bixbyite structure in space group Ia3 (206) with a = 9.7099(4) Å. The topotactic oxidation product ScTiO(3.5) crystallizes in an oxide defect fluorite structure in space group Fm3m (225) with a = 4.89199(5) Å. Thermogravimetric and differential thermal analysis experiments combined with in-situ X-ray powder diffraction studies illustrate a complex sequence of a topotactic oxidation pathway, phase segregation, and ion ordering at high temperatures. The optimized bulk synthesis for phase pure ScTiO(3.5) is presented. In contrast to the vanadium-based defect fluorite phases AVO(3.5+x) (A = Sc, In) the novel titanium analogue ScTiO(3.5) is stable over a wide temperature range. Above 950 °C ScTiO(3.5) undergoes decomposition with the final products being Sc(4)Ti(3)O(12) and TiO(2). Simultaneous Rietveld refinements against powder X-ray and neutron diffraction data showed that Sc(4)Ti(3)O(12) also exists in the defect fluorite structure in space group Fm3m (225) with a = 4.90077(4) Å. Sc(4)Ti(3)O(12) undergoes partial reduction in CO/Ar atmosphere to form Sc(4)Ti(3)O(11.69(2)).

Oxide (CeO{sub 2}, NiO, Co{sub 3}O{sub 4} and Mn{sub 3}O{sub 4})-promoted Pd/C electrocatalysts for alcohol electrooxidation in alkaline media

Energy Technology Data Exchange (ETDEWEB)

Xu, Changwei; Tian, Zhiqun; Jiang, San Ping [School of Mechanical and Aerospace Engineering, Nanyang Technological University (Singapore); Shen, Peikang [School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

2008-01-01

This study investigated Pt/C, Pd/C and oxide (CeO{sub 2}, NiO, Co{sub 3}O{sub 4} and Mn{sub 3}O{sub 4})-promoted Pd/C for electrooxidation reactions of methanol, ethanol, ethylene glycol and glycerol in alkaline media. The results show that Pd/C electrocatalysts alone have low activity and very poor stability for the alcohol electrooxidation. However, addition of oxides like CeO{sub 2}, NiO, Co{sub 3}O{sub 4} and Mn{sub 3}O{sub 4} significantly promotes catalytic activity and stability of the Pd/C electrocatalysts for the alcohol electrooxidation. The Pd-Co{sub 3}O{sub 4} (2:1, w:w)/C shows the highest activity for the electrooxidation of methanol, EG and glycerol while the most active catalyst for the ethanol electrooxidation is Pd-NiO (6:1, w:w)/C. On the other hand, Pd-Mn{sub 3}O{sub 4}/C shows significantly better performance stability than other oxide-promoted Pd/C for the alcohol electrooxidation. The poor stability of the Pd-Co{sub 3}O{sub 4}/C electrocatalysts is most likely related to the limited solubility of cobalt oxides in alkaline solutions. (author)

Synthesis and electrochemical characterization of LiCo_1_/_3Fe_2_/_3PO_4/C composite using nano CoFe_2O_4 as precursor

International Nuclear Information System (INIS)

Wu, Kaipeng; Hu, Guorong; Du, Ke; Peng, Zhongdong; Cao, Yanbing

2015-01-01

LiCo_1_/_3Fe_2_/_3PO_4/C composite was synthesized by a solid state method with CoFe_2O_4 as the precursor and glucose as the carbon source. The composite consists of homogeneous Co–Fe distributed LiCo_1_/_3Fe_2_/_3PO_4 with its particles covered by nano-carbon layers, which could prevent the growth of the particles as well as form a fast path for electronic transmission during charging and discharging process. It shows excellent electrochemical performance as the cathode for lithium-ion batteries, which delivers discharge capacities of 154.6, 152.9, 135.4, 122.3, 105.2 and 91.3 mAh g"−"1 at 0.05, 0.1, 0.5, 1, 2 and 5 C, respectively, and retains 94.6% of its initial discharge capacity after 30 cycles at 5 C. - Highlights: • Nano CoFe_2O_4 was prepared by a co-precipitation method. • LiCo_1_/_3Fe_2_/_3PO_4/C composite was synthesized using nano CoFe_2O_4 as a precursor. • Homogeneous Co–Fe distributed LiCo_1_/_3Fe_2_/_3PO_4 is obtained. • LiCo_1_/_3Fe_2_/_3PO_4/C composite exhibits a quite good electrochemical performance.

The studies of geometrical microstructure of tetragonal Co sup 2 sup + -V sub O centers in KNbO sub 3 and KTaO sub 3 crystals from EPR data

CERN Document Server

Zheng Wen Chen

2002-01-01

From the perturbation formulas for the EPR g factors g sub p sub a sub r sub a sub l sub l sub e sub l and g sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub r sub t sub o of a 3d sup 7 ion in tetragonal octahedral crystal field based on a cluster approach, the geometrical microstructures of tetragonal Co sup 2 sup + -V sub O centers in KNbO sub 3 and KTaO sub 3 crystals are obtained by fitting the calculated g sub p sub a sub r sub a sub l sub l sub e sub l and g sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub r sub t sub o to the observed values. It is found that the Co sup 2 sup + ion in Co sup 2 sup + -V sub O centers is displaced away from the oxygen vacancy V sub O by 0.3 A in KNbO sub 3 and by 0.29 A in KTaO sub 3. These results are comparable with those of Fe sup 3 sup + -V sub O centers in ABO sub 3 perovskite-type crystals obtained from both the shell-model simulations and the embedded-cluster calculations, and from theoretical studies of EPR da...

Microstructure, Thermal, Mechanical, and Dielectric Properties of BaO-CaO-Al2O3-B2O3-SiO2 Glass-Ceramics

Science.gov (United States)

Li, Bo; Bian, Haibo; Fang, Yi

2017-12-01

BaO-CaO-Al2O3-B2O3-SiO2 (BCABS) glass-ceramics were prepared via the method of controlled crystallization. The effect of CaO modification on the microstructure, phase evolution, as well as thermal, mechanical, and dielectric properties was investigated. XRD identified that quartz is the major crystal phase; cristobalite and bazirite are the minor crystal phases. Moreover, the increase of CaO could inhibit the phase transformation from quartz to cristobalite, but excessive CaO would increase the porosity of the ceramics. Additionally, with increasing the amount of CaO, the thermal expansion curve tends to be linear, and subsequently the CTE value decreases gradually, which is attributed to the decrease of cristobalite with high CTE and the formation of CaSiO3 with low CTE. The results indicated that a moderate amount of CaO helps attaining excellent mechanical, thermal, and dielectric properties, that is, the specimen with 9 wt% CaO sintered at 950 °C has a high CTE value (11.5 × 10-6/°C), a high flexural strength (165.7 MPa), and good dielectric properties (ɛr = 6.2, tanδ = 1.8 × 10-4, ρ = 4.6 × 1011 Ω•cm).

Al2O3-Cact-(CuO, Cr2O3, Co3O4 Adsorbents-Catalysts: Preparation and Characterization

Directory of Open Access Journals (Sweden)

Gitana DABRILAITĖ-KUDŽMIENĖ

2013-03-01

Full Text Available Al2O3-Cact-(CuO, Cr2O3 Co3O4 adsorbents-catalysts were prepared using Al2O3-Cact (alumina gel–activated carbon adsorbent and different amount of CuO, Cr2O3 and Co3O4. The active components were incorporated into wet alumina gel–carbon mixture using different conditions (by sol-gel method and mixing a milled metal oxides. Equilibrium adsorptive capacity measurements of alcohol vapours were carried out in order to determine the influence of preparation conditions on the stability of prepared adsorbents–catalysts. Specific surface area of the prepared adsorbents-catalysts were measured by BET method. It was established that for adsorbent-catalyst produced by sol-gel method SBET = 244.7 m2/g. Surface area SBET = 29.32 m2/g was obtained for adsorbent-catalyst with metal oxides. On the basis of these results it was assumed that active carbon was lost in this adsorbent-catalyst during the preparation process. Sol-gel derived adsorbent–catalyst was tested for the oxidation of methanol vapours. Catalytic oxidation was carried out in fixed-bed reactor. Experimental data indicate that adsorptive capacity of the adsorbent–catalyst is (3.232 – 3.259 mg/m3 CH3OH at relative air humidity is 40 % – 50 %. During a fast heating of CH3OH – saturated adsorbent-catalyst a part of adsorbate is converted to CO2 and H2O. Methanol conversion increases with increasing of adsorbent-catalyst heating rate.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3832

High-performance lithium storage of Co3O4 achieved by constructing porous nanotube structure

International Nuclear Information System (INIS)

Cui, Zhentao; Wang, Shuguang; Zhang, Yihe; Cao, Minhua

2015-01-01

Graphical abstract: The porous Co 3 O 4 nanotubes (P-Co 3 O 4 -NTs) are prepared by coaxial electrospinning method followed by a fine annealing treatment. The resultant P-Co 3 O 4 -NTs exhibit excellent lithium storage performance in terms of specific capacity, rate capability, and cycling stability when used as an anode material for rechargeable lithium ion batteries (LIBs). - Abstract: Co 3 O 4 has been investigated intensively for its high specific capacity which makes it a promising candidate anode for high-performance lithium ion batteries (LIBs). However, rational design of Co 3 O 4 electrode that is beneficial for its electrochemical performance is still a great challenge. Herein, we designed and fabricated porous Co 3 O 4 nanotubes (P-Co 3 O 4 -NTs) by coaxial electrospinning method followed by a fine annealing treatment, which display one dimensional tubular structure with porous wall and hollow interior. The uniqueness of this strategy is that the morphologies of the P-Co 3 O 4 -NTs could be tuned by adjusting the mass ratio of reactants. The resultant P-Co 3 O 4 -NTs exhibit excellent lithium storage performance in terms of specific capacity, rate capability, and cycling stability, when used as an anode material for rechargeable LIBs. This unique structure endows a high reversible specific capacity of 1826.2 mA g −1 at a current density of 0.3 A g −1 after 100 cycles. Even at high current densities of 2 and 5 A g −1 , the P-Co 3 O 4 -NTs electrode still could deliver remarkable discharge capacities of 1506.2 and 1145.1 mAh g −1 , respectively. The excellent electrochemical performance can be attributed to the unique tubular and porous structure of P-Co 3 O 4 -NTs, which not only can accommodate the large volume change but also can provide an excellent ion diffusion and electronic conduction pathway. Therefore, the P-Co 3 O 4 -NTs have the potential for use as a high performance anode material in LIBs.

Dendrite-like Co3O4 nanostructure and its applications in sensors, supercapacitors and catalysis.

Science.gov (United States)

Pang, Huan; Gao, Feng; Chen, Qun; Liu, Rongmei; Lu, Qingyi

2012-05-21

Dendrite-like Co(3)O(4) nanostructure, made up of many nanorods with diameters of 15-20 nm and lengths of 2-3 μm, has been successfully prepared by calcining the corresponding nanostructured Co-8-hydroxyquinoline coordination precursor in air. The Co(3)O(4) nanostructure was evaluated as an electrochemical sensor for H(2)O(2) detection and the results reveal that it has good linear dependence and high sensitivity to H(2)O(2) concentration changes. As an electrode material of a supercapacitor, it was found that the nanostructured Co(3)O(4) electrode exhibits high specific capacitance and long cycle life. The Co(3)O(4) nanostructure also has good catalytic properties and is steadily active for CO oxidation, giving 100% CO conversion at low temperatures. The multifunctional Co(3)O(4) nanostructure would be a promising functional nanomaterial applied in multi industrialized fields.

Apparent molar volumes for dilute solutions of NaClO4 and [Co(en) 3](ClO4)3 in D2O and H2O at 278-318 K

International Nuclear Information System (INIS)

Bottomley, G.A.; Glossop, L.G.

1981-01-01

Apparent molar volumes for dilute solutions of NaClO 4 and [Co(en) 3 ](ClO 4 ) 3 in D 2 O and H 2 O were measured by using a dilatometry technique at 278, 298 and 318K. Comparison of limiting slopes with the Debye-Huckel predictions from the dielectric constant and compressibility of H 2 O and D 2 O is complicated by ion pairing. The apparent molar volumes for NaClO 4 were less in D 2 O than in H 2 O. The complex [Co(en) 3 ](ClO 4 ) 3 when studied in D 2 O had its amine protons exchanged by deuterium; this did not allow a direct comparison of the apparent molar volumes of the protonated complex in each solvent system, but revealed a large isotope effect. The apparent molar volumes of the [Co(en) 3 ](ClO 4 ) 3 showed a much larger temperature dependence than that of NaClO 4

Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

Science.gov (United States)

Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

2013-10-01

Here we proposed a novel architectural design of a ternary MnO2-based electrode - a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2-based nanowire arrays for constructing next-generation supercapacitors.

The effect of calcination temperature on the performance of Co3O4-Bi2O3 as a heterogeneous catalyst of peroxymonosulfate

Science.gov (United States)

Zhang, Guangshan; Hu, Limin; Wang, Peng; Yuan, Yixing

2017-11-01

In this work, a time-saving microwave-assisted method for synthesis of Co3O4-Bi2O3 was reported. The synthesized Co3O4-Bi2O3 samples were characterized with different techniques to probe their crystalline structures and morphologies. The catalytic performances of synthesized Co3O4-Bi2O3 as peroxymonosulfate activator were evaluated by the degradation of bisphenol A. The effect of calcination temperature on Co3O4-Bi2O3 products was explored and the result showed that the sample calcined at 400 °C possessing superior catalytic activity.

Steam reforming of ethanol over Co3O4–Fe2O3 mixed oxides

KAUST Repository

Abdelkader, A.; Daly, H.; Saih, Y.; Morgan, K.; Mohamed, M.A.; Halawy, S.A.; Hardacre, C.

2013-01-01

solvent/dispersing agent. The catalysts were studied in the steam reforming of ethanol to investigate the effect of the partial substitution of Co3O4 with Fe2O 3 on the catalytic behaviour. The reforming activity over Fe 2O3, while initially high

High-performance non-enzymatic catalysts based on 3D hierarchical hollow porous Co3O4 nanododecahedras in situ decorated on carbon nanotubes for glucose detection and biofuel cell application.

Science.gov (United States)

Wang, Shiyue; Zhang, Xiaohua; Huang, Junlin; Chen, Jinhua

2018-03-01

In this work, high-performance non-enzymatic catalysts based on 3D hierarchical hollow porous Co 3 O 4 nanododecahedras in situ decorated on carbon nanotubes (3D Co 3 O 4 -HPND/CNTs) were successfully prepared via direct carbonizing metal-organic framework-67 in situ grown on carbon nanotubes. The morphology, microstructure, and composite of 3D Co 3 O 4 -HPND/CNTs were characterized by scanning electron microscopy, transmission electron microscopy, micropore and chemisorption analyzer, and X-ray diffraction. The electrochemical characterizations indicated that 3D Co 3 O 4 -HPND/CNTs present considerably catalytic activity toward glucose oxidation and could be promising for constructing high-performance electrochemical non-enzymatic glucose sensors and glucose/O 2 biofuel cell. When used for non-enzymatic glucose detection, the 3D Co 3 O 4 -HPND/CNTs modified glassy carbon electrode (3D Co 3 O 4 -HPND/CNTs/GCE) exhibited excellent analytical performance with high sensitivity (22.21 mA mM -1  cm -2 ), low detection limit of 0.35 μM (S/N = 3), fast response (less than 5 s) and good stability. On the other hand, when the 3D Co 3 O 4 -HPND/CNTs/GCE worked as an anode of a biofuel cell, a maximum power density of 210 μW cm -2 at 0.15 V could be obtained, and the open circuit potential was 0.68 V. The attractive 3D hierarchical porous structural features, the large surface area, and the excellent conductivity based on the continuous and effective electron transport network in 3D Co 3 O 4 -HPND/CNTs endow 3D Co 3 O 4 -HPND/CNTs with the enhanced electrochemical performance and promising applications in electrochemical sensing, biofuel cell, and other energy storage and conversion devices such as supercapacitor. Graphical abstract High-performance non-enzymatic catalysts for enzymeless glucose sensing and biofuel cell based on 3D hierarchical hollow porous Co 3 O 4 nanododecahedras anchored on carbon nanotubes were successfully prepared via direct carbonizing

Hierarchical honeycomb-like Co3O4 pores coating on CoMoO4 nanosheets as bifunctional efficient electrocatalysts for overall water splitting

Science.gov (United States)

Pei, Zhihao; Xu, Li; Xu, Wei

2018-03-01

Efficient electrocatalytic water splitting is one of the most effective ways to solve the global energy crisis. In this paper, we report on a novel self-assembled hierarchical structure of Co3O4/CoMoO4 grown in situ on a bare nickel foam. The unique, three-dimensional honeycomb-like Co3O4 pores were constructed from one-dimensional nanowires and coated on two-dimensional CoMoO4 nanosheets structures grown on nickel foam. The synthesis involved a step-wise solvothermal method followed by an annealing treatment. Benefiting from the synergistic effect of the hierarchical nanostructures, the materials had more reaction active sites and a smaller electron transfer impedance, and they exhibited excellent electrocatalytic performances for the HER and OER of 143 and 244 mV, respectively, at 10 mA cm-2 in an alkaline solution. Furthermore, the materials remained stable during the long electrolysis period, over 10 h, presenting promising application prospects in the field of electrocatalytic water splitting.

Effects of Y{sub 2}O{sub 3}/CeO{sub 2} co-doping on microwave dielectric properties of Ba(Co{sub 0.6}Zn{sub 38}){sub 1/3}Nb{sub 2/3}O{sub 3} ceramics

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yuqin; Zhou, Xiaohua, E-mail: 1250590698@qq.com; Yang, Xinshi; Sun, Chengli; Yang, Fan; Chen, Hetuo

2016-09-15

The effects of CeO{sub 2}/Y{sub 2}O{sub 3} co-doping on the microstructure and microwave dielectric properties of Ba(Co{sub 0.6}Zn{sub 0.38}){sub 1/3}Nb{sub 2/3}O{sub 3}-xA-xB (x = 0,1,2,3,4,6; A = 0.1204 wt%Y{sub 2}O{sub 3}; B = 0.1 wt%CeO{sub 2}) ceramics prepared by the conventional solid-state route technique were investigated. The X-ray diffraction (XRD) results presented that all the well sintered samples exhibited the main phase BaZn{sub 0.33}Nb{sub 0.67}O{sub 3}−Ba{sub 3}CoNb{sub 2}O{sub 9}. A certain amount of Ba{sub 8}CoNb{sub 6}O{sub 24} surface secondary phase and minority phase of Ba{sub 5}Nb{sub 4}O{sub 15} were also observed in all sintered ceramics. The 1:2 B-site cation ordering degree was found to influenced by the substitution of Y{sup 3+} and Ce{sup 4+} in the crystal lattice, especially for x = 0.02. Then the scanning electron microscopy (SEM) picture of the optimally well-sintered (1350 °C for 20 h) ceramic has shown a dense microstructure. Although the ε{sub r} almost kept unchanged, appropriate doping content would greatly improve the Q × f value. Meanwhile, the τ{sub f} value first declined and then increased with increasing x. At last, the excellent microwave dielectric properties of ε{sub r} = 36.09, Q × f = 72006 GHz, τ{sub f} = 3.35 ppm/ºC were obtained for the ceramic with x = 0.02 sintered in air at 1350 °C for 20 h. - Graphical abstract: Fig. SEM images of as-sintered Ba(Co{sub 0.6}Zn{sub 0.38}){sub 1/3}Nb{sub 2/3}O{sub 3}-xA-Xb (A = 0.1204 wt%Y{sub 2}O{sub 3}; B = 0.1 wt%CeO{sub 2)}ceramics: (a) x = 0,(b) x = 0.01,(c) x = 0.02,(d) x = 0.03, (e) x = 0.04,(f) x = 0.06. The images confirmed the presences of two phases on the surface of the ceramics, plate-shaped grains (Ba{sub 8}(C{sub O},Zn){sub 1}Nb{sub 6}O{sub 24}phase) and needle-shaped grains (Ba{sub 3}(Co{sub 0.6}Zn{sub 0.38}){sub 1}Nb{sub 2}O{sub 9} phase). As a small content of CeO{sub 2}/Y{sub 2}O{sub 3} (x = 0.01–0.04) was codoped into the BCZN ceramics, the

Porous hollow Co3O4 with rhombic dodecahedral structures for high-performance supercapacitors

Science.gov (United States)

Zhang, Yi-Zhou; Wang, Yang; Xie, Ye-Lei; Cheng, Tao; Lai, Wen-Yong; Pang, Huan; Huang, Wei

2014-11-01

Porous hollow Co3O4 with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co3O4 rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g-1 and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co3O4 with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors.Porous hollow Co3O4 with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co3O4 rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g-1 and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co3O4 with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04782f

Influences of Different Preparation Conditions on Catalytic Activity of Ag2O-Co3O4/γ-Al2O3 for Hydrogenation of Coal Pyrolysis

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Lei Zhang

2014-01-01

Full Text Available A series of catalysts of Ag2O-Co3O4/γ-Al2O3 was prepared by equivalent volume impregnation method. The effects of the metal loading, calcination time, and calcination temperatures of Ag and Co, respectively, on the catalytic activity were investigated. The optimum preparing condition of Ag2O-Co3O4/γ-Al2O3 was decided, and then the influence of different preparation conditions on catalytic activity of Ag2O-Co3O4/γ-Al2O3 was analyzed. The results showed the following: (1 at the same preparation condition, when silver loading was 8%, the Ag2O-Co3O4/γ-Al2O3 showed higher catalyst activity, (2 the catalyst activity had obviously improved when the cobalt loading was 8%, while it was weaker at loadings 5% and 10%, (3 the catalyst activity was influenced by different calcination temperatures of silver, but the influences were not marked, (4 the catalyst activity can be influenced by calcination time of silver, (5 different calcination times of cobalt can also influence the catalyst activity of Ag2O-Co3O4/γ-Al2O3, and (6 the best preparation conditions of the Ag2O-Co3O4/γ-Al2O3 were silver loading of 8%, calcination temperature of silver of 450°C, and calcinations time of silver of 4 h, while at the same time the cobalt loading was 8%, the calcination temperature of cobalt was 450°C, and calcination time of cobalt was 4 h.

Pb3O4 type antimony oxides MSb2O4 (M = Co, Ni) as anode for Li-ion batteries

International Nuclear Information System (INIS)

Jibin, A.K.; Reddy, M.V.; Subba Rao, G.V.; Varadaraju, U.V.; Chowdari, B.V.R.

2012-01-01

Graphical abstract: Isostructural Pb 3 O 4 type MSb 2 O 4 (M = Co, Ni) compounds were investigated as possible anodes for lithium ion batteries. The reversible capacity is due to electrochemically active Sb and the transition metal and Li 2 O form an inactive matrix which buffers volume variations associated with alloying-de-alloying of antimony. Highlights: ► Isostructural MSb 2 O 4 (M = Co, Ni) were studied as anode for LIBs for first time. ► Li/MSb 2 O 4 (M = Co, Ni) cells displayed reversibility due to electrochemically active Sb. ► CoSb 2 O 4 showed good reversibility compared to NiSb 2 O 4 . - Abstract: Polycrystalline samples of isostructural MSb 2 O 4 (M = Co, Ni) have been prepared by solid state synthesis and lithium-storage is investigated as possible anode materials for lithium-ion batteries. The reaction mechanism of lithium with MSb 2 O 4 (M = Co, Ni) is explored by galvanostatic cycling, cyclic voltammogram and ex situ studies. Both CoSb 2 O 4 and NiSb 2 O 4 exhibit similar electrochemical behavior and show reversible capacity of 490 and 412 mAh g −1 respectively in the first cycle. Reversible alloying de-alloying of Li x Sb takes place in an amorphous matrix of M (Co, Ni) and Li 2 O during electrochemical cycling.

Carbonate mineral solubility at low temperatures in the Na-K-Mg-Ca-H-Cl-SO 4-OH-HCO 3-CO 3-CO 2-H 2O system

Science.gov (United States)

Marion, Giles M.

2001-06-01

Carbonate minerals have played an important role in the geochemical evolution of Earth, and may have also played an important role in the geochemical evolution of Mars and Europa. Several models have been published in recent years that describe chloride and sulfate mineral solubilities in concentrated brines using the Pitzer equations. Few of these models are parameterized for subzero temperatures, and those that are do not include carbonate chemistry. The objectives of this work are to estimate Pitzer-equation bicarbonate-carbonate parameters and carbonate mineral solubility products and to incorporate them into the FREZCHEM model to predict carbonate mineral solubilities in the Na-K-Mg-Ca-H-Cl-SO 4-OH-HCO 3-CO 3-CO 2-H 2O system at low temperatures (≤25°C) with a special focus on subzero temperatures. Most of the Pitzer-equation parameters and equilibrium constants are taken from the literature and extrapolated into the subzero temperature range. Solubility products for 14 sodium, potassium, magnesium, and calcium bicarbonate and carbonate minerals are included in the model. Most of the experimental data are at temperatures ≥ -8°C; only for the NaHCO 3-NaCl-H 2O and Na 2CO 3-NaCl-H 2O systems are there bicarbonate and carbonate data to temperatures as low as -21.6°C. In general, the fit of the model to the experimental data is good. For example, calculated eutectic temperatures and compositions for NaHCO 3, Na 2CO 3, and their mixtures with NaCl and Na 2SO 4 salts are in good agreement with experimental data to temperatures as low as -21.6°C. Application of the model to eight saline, alkaline carbonate waters give predicted pHs ranging from 9.2 to 10.2, in comparison with measured pHs that range from 8.7 to 10.2. The model suggests that the CaCO 3 mineral that precipitates during seawater freezing is probably calcite and not ikaite. The model demonstrates that a proposed salt assemblage for the icy surface of Europa consisting of highly hydrated MgSO 4

CuO and Co3O4 Nanoparticles: Synthesis, Characterizations, and Raman Spectroscopy

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M. Rashad

2013-01-01

Full Text Available Copper oxide and cobalt oxide (CuO, Co3O4 nanocrystals (NCs have been successfully prepared in a short time using microwave irradiation without any postannealing treatment. Both kinds of nanocrystals (NCs have been prepared using copper nitrate and cobalt nitrate as the starting materials and distilled water as the solvent. The resulted powders of nanocrystals (NCs were characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM, and atomic force microscopy (AFM measurements. The obtained results confirm the presence of the both of oxides nanopowders produced during chemical precipitation using microwave irradiation. A strong emission under UV excitation is obtained from the prepared CuO and Co3O4 nanoparticles. The results show that the nanoparticles have high dispersion and narrow size distribution. The line scans of atomic force microscopy (AFM images of the nanocrystals (NCs sprayed on GaAs substrates confirm the results of both X-ray diffraction and transmission electron microscopy. Furthermore, vibrational studies have been carried out using Raman spectroscopic technique. Specific Raman peaks have been observed in the CuO and Co3O4 nanostructures, and the full width at half maximum (FWHM of the peaks indicates a small particle size of the nanocrystals.

Co3O4 as p-Type Material for CO Sensing in Humid Air

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Svetlana Vladimirova

2017-09-01

Full Text Available Nanocrystalline cobalt oxide Co3O4 has been prepared by precipitation and subsequent thermal decomposition of a carbonate precursor, and has been characterized in detail using XRD, transmission electron microscopy, and FTIR spectroscopy. The sensory characteristics of the material towards carbon monoxide in the concentration range 6.7–20 ppm have been examined in both dry and humid air. A sensor signal is achieved in dry air at sufficiently low temperatures T = 80–120 °C, but the increase in relative humidity results in the disappearance of sensor signal in this temperature range. At temperatures above 200 °C the inversion of the sensor signal in dry air was observed. In the temperature interval 180–200 °C the sensor signal toward CO is nearly the same at 0, 20 and 60% r.h. The obtained results are discussed in relation with the specific features of the adsorption of CO, oxygen, and water molecules on the surface of Co3O4. The independence of the sensor signal from the air humidity combined with a sufficiently short response time at a moderate operating temperature makes Co3O4 a very promising material for CO detection in conditions of variable humidity.

Single crystalline Co{sub 3}O{sub 4}: Synthesis and optical properties

Energy Technology Data Exchange (ETDEWEB)

Hosny, Nasser Mohammed, E-mail: Nasserh56@yahoo.com

2014-04-01

Crystals of Co{sub 3}O{sub 4} have been prepared from thermal decomposition of molecular precursors derived from salicylic acid and cobalt (II) acetate or chloride at 500 °C. A cubic phase Co{sub 3}O{sub 4} micro- and nanocrystals have been obtained. The as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The images of electron microscopes showed octahedral crystals of Co{sub 3}O{sub 4}. The volume and polarizability of the optimized structures of molecular precursors have been calculated and related to the particle size. The optical band gap of the obtained crystals has been measured. The results indicated two optical band gaps with values 2.65 and 2.95 eV for (E{sub g1}) (E{sub g2}), respectively. - Highlights: • Synthesis of Co{sub 3}O{sub 4} nanocrystals by decomposition of cobalt salicylic acid precursor. • Characterization of the isolated nanocrystals by using XRD, SEM and HRTEM. • The optical band gap has been measured.

The co-evolution of microstructure features in self-ion irradiated HT9 at very high damage levels

Energy Technology Data Exchange (ETDEWEB)

Getto, E., E-mail: getto@usna.edu [Department of Mechanical Engineering, United States Naval Academy, Annapolis, MD, 21402 (United States); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI, 48109 (United States); Vancoevering, G.; Was, G.S. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI, 48109 (United States)

2017-02-15

Understanding the void swelling and phase evolution of reactor structural materials at very high damage levels is essential to maintaining safety and longevity of components in Gen IV fast reactors. A combination of ion irradiation and modeling was utilized to understand the microstructure evolution of ferritic-martensitic alloy HT9 at high dpa. Self-ion irradiation experiments were performed on alloy HT9 to determine the co-evolution of voids, dislocations and precipitates up to 650 dpa at 460 °C. Modeling of microstructure evolution was conducted using the modified Radiation Induced Microstructure Evolution (RIME) model, which utilizes a mean field rate theory approach with grouped cluster dynamics. Irradiations were performed with 5 MeV raster-scanned Fe{sup 2+} ions on samples pre-implanted with 10 atom parts per million He. The swelling, dislocation and precipitate evolution at very high dpa was determined using Analytical Electron Microscopy in Scanning Transmission Electron Microscopy (STEM) mode. Experimental results were then interpreted using the RIME model. A microstructure consisting only of dislocations and voids is insufficient to account for the swelling evolution observed experimentally at high damage levels in a complicated microstructure such as irradiated alloy HT9. G phase was found to have a minimal effect on either void or dislocation evolution. M{sub 2}X played two roles; a variable biased sink for defects, and as a vehicle for removal of carbon from solution, thus promoting void growth. When accounting for all microstructure interactions, swelling at high damage levels is a dynamic process that continues to respond to other changes in the microstructure as long as they occur.

High Temperature Deformation Behavior and Microstructure Evolution of Ti-4Al-4Fe-0.25Si Alloy

Energy Technology Data Exchange (ETDEWEB)

Won, Jong Woo; Lee, Yongmoon; Lee, Chong Soo [Pohang University of Science and Technology, Pohang (Korea, Republic of); Yeom, Jong-Taek [Korea Institute of Materials Science, Changwon (Korea, Republic of); Lee, Gi Yeong [KPCM Incorporated, Gyeongsan (Korea, Republic of)

2016-05-15

Hot deformation behavior of Ti-4Al-4Fe-0.25Si alloy with martensite microstructure was investigated by compression tests at temperatures of 1023 – 1173 K (α+β phase region) and strain rates of 10{sup -3} – 1 s{sup -1}. By analyzing the deformation behavior, plastic deformation instability parameters including strain rate sensitivity, deformation temperature sensitivity, efficiency of power dissipation, and Ziegler’s instability were evaluated as a function of deformation temperature and strain rate, and they were further examined by drawing deformation processing maps. The microstructure evolution was also studied to determine the deformation conditions under which equiaxed α phase was formed in the microstructure without remnants or kinked α phase platelets and shear bands, these last two of which cause severe cracks during post-forming process. Based on the combined results of the processing maps and the microstructure analysis, the optimum α+β forging conditions for Ti-4Al-4Fe-0.25Si alloy were determined.

Preparation and characterization of self-assembled percolative BaTiO3–CoFe2O4 nanocomposites via magnetron co-sputtering

Directory of Open Access Journals (Sweden)

Qian Yang

2014-04-01

Full Text Available BaTiO3–CoFe2O4 composite films were prepared on (100 SrTiO3 substrates by using a radio-frequency magnetron co-sputtering method at 750 °C. These films contained highly (001-oriented crystalline phases of perovskite BaTiO3 and spinel CoFe2O4, which can form a self-assembled nanostructure with BaTiO3 well-dispersed into CoFe2O4 under optimized sputtering conditions. A prominent dielectric percolation behavior was observed in the self-assembled nanocomposite. Compared with pure BaTiO3 films sputtered under similar conditions, the nanocomposite film showed higher dielectric constants and lower dielectric losses together with a dramatically suppressed frequency dispersion. This dielectric percolation phenomenon can be explained by the 'micro-capacitor' model, which was supported by measurement results of the electric polarization and leakage current.

Facile and green synthesis of mesoporous Co3O4 nanocubes and their applications for supercapacitors

Science.gov (United States)

Liu, Xiangmei; Long, Qing; Jiang, Chunhui; Zhan, Beibei; Li, Chen; Liu, Shujuan; Zhao, Qiang; Huang, Wei; Dong, Xiaochen

2013-06-01

Nanostructured Co3O4 materials attracted significant attention due to their exceptional electrochemical (pseudo-capacitive) properties. However, rigorous preparation conditions are needed to control the size (especially nanosize), morphology and size distribution of the products obtained by conventional methods. Herein, we describe a novel one step shape-controlled synthesis of uniform Co3O4 nanocubes with a size of 50 nm with the existence of mesoporous carbon nanorods (meso-CNRs). In this synthesis process, meso-CNRs not only act as a heat receiver to directly obtain Co3O4 eliminating the high-temperature post-calcination, but also control the morphology of the resulting Co3O4 to form nanocubes with uniform distribution. More strikingly, mesoporous Co3O4 nanocubes are obtained by further thermal treatment. The structure and morphology of the samples were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A possible formation mechanism of mesoporous Co3O4 nanocubes is proposed here. Electrochemical tests have revealed that the prepared mesoporous Co3O4 nanocubes demonstrate a remarkable performance in supercapacitor applications due to the porous structure, which endows fast ion and electron transfer.Nanostructured Co3O4 materials attracted significant attention due to their exceptional electrochemical (pseudo-capacitive) properties. However, rigorous preparation conditions are needed to control the size (especially nanosize), morphology and size distribution of the products obtained by conventional methods. Herein, we describe a novel one step shape-controlled synthesis of uniform Co3O4 nanocubes with a size of 50 nm with the existence of mesoporous carbon nanorods (meso-CNRs). In this synthesis process, meso-CNRs not only act as a heat receiver to directly obtain Co3O4 eliminating the high-temperature post-calcination, but also control the morphology of the resulting Co3O4 to form nanocubes with uniform

Characterization of soft-combustion-derived NASICON-type Li2Co2(MoO4)3 for lithium batteries

International Nuclear Information System (INIS)

Prabaharan, S.R.S.; Ramesh, S.; Michael, M.S.; Begam, K.M.

2004-01-01

This work describes the synthesis of a new polyanion material, Li 2 Co 2 (MoO 4 ) 3 , belonging to the NASICON family. A low-temperature soft-combustion method using glycine as a soft-combustion fuel was adopted to obtain single-phase powders of the new material at a temperature as low as 300 deg. C. Li 2 Co 2 (MoO 4 ) 3 was found to crystallize in an orthorhombic structure (space group Pmmm) with lattice parameters a = 17.584(7) A, b 10.464(4) A and c = 5.102(9) A. The electronic state of each element present in the new material was confirmed by X-ray photoelectron spectroscopic analysis. The powders were analyzed using inductively coupled plasma emission spectroscopy. The microstructural analysis revealed that the particles (5-10 μm) have a rather columnar shape. The electrochemistry redox behavior of the new material was studied, for the first time, and the material as positive electrode was found to exhibit topotactic Li + extraction/insertion in lithium-containing test cells

Thermodynamics of CoAl2O4-CoGa2O4 solid solutions

International Nuclear Information System (INIS)

Lilova, Kristina I.; Navrotsky, Alexandra; Melot, Brent C.; Seshadri, Ram

2010-01-01

CoAl 2 O 4 , CoGa 2 O 4 , and their solid solution Co(Ga z Al 1-z ) 2 O 4 have been studied using high temperature oxide melt solution calorimetry in molten 2PbO.B 2 O 3 at 973 K. There is an approximately linear correlation between lattice parameters, enthalpy of formation from oxides, and the Ga content. The experimental enthalpy of mixing is zero within experimental error. The cation distribution parameters are calculated using the O'Neill and Navrotsky thermodynamic model. The enthalpies of mixing calculated from these parameters are small and consistent with the calorimetric data. The entropies of mixing are calculated from site occupancies and compared to those for a random mixture of Ga and Al ions on octahedral site with all Co tetrahedral and for a completely random mixture of all cations on both sites. Despite a zero heat of mixing, the solid solution is not ideal in that activities do not obey Raoult's Law because of the more complex entropy of mixing. - Graphical abstract: Measured enthalpies of mixing of CoAl 2 O 4 -CoGa 2 O 4 solid solutions are close to zero but entropies of mixing reflect the complex cation distribution, so the system is not an ideal solution.

SYNTHESIS OF M–Nd DOPED Fe3O4 NANOPARTICLES (M = Co ...

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nanoparticles were spherical shaped with inverse spinel structure. ... To obtain nano sized spinel ferrite particles, various preparation techniques have been ... SEM images of (a) Fe3O4, (b) Fe3O4 doped with Nd3+ and Co2+, (c) Fe3O4 doped with. Nd3+ .... Nayar, S.; Mir, A.; Ashok, A.; Sharma, A. J. Bionic Eng. 2010, 7, 29.

Graphene-Embedded Co3O4 Rose-Spheres for Enhanced Performance in Lithium Ion Batteries.

Science.gov (United States)

Jing, Mingjun; Zhou, Minjie; Li, Gangyong; Chen, Zhengu; Xu, Wenyuan; Chen, Xiaobo; Hou, Zhaohui

2017-03-22

Co 3 O 4 has been widely studied as a promising candidate as an anode material for lithium ion batteries. However, the huge volume change and structural strain associated with the Li + insertion and extraction process leads to the pulverization and deterioration of the electrode, resulting in a poor performance in lithium ion batteries. In this paper, Co 3 O 4 rose-spheres obtained via hydrothermal technique are successfully embedded in graphene through an electrostatic self-assembly process. Graphene-embedded Co 3 O 4 rose-spheres (G-Co 3 O 4 ) show a high reversible capacity, a good cyclic performance, and an excellent rate capability, e.g., a stable capacity of 1110.8 mAh g -1 at 90 mA g -1 (0.1 C), and a reversible capacity of 462.3 mAh g -1 at 1800 mA g -1 (2 C), benefitted from the novel architecture of graphene-embedded Co 3 O 4 rose-spheres. This work has demonstrated a feasible strategy to improve the performance of Co 3 O 4 for lithium-ion battery application.

Co@Co3 O4 @PPD Core@bishell Nanoparticle-Based Composite as an Efficient Electrocatalyst for Oxygen Reduction Reaction.

Science.gov (United States)

Wang, Zhijuan; Li, Bing; Ge, Xiaoming; Goh, F W Thomas; Zhang, Xiao; Du, Guojun; Wuu, Delvin; Liu, Zhaolin; Andy Hor, T S; Zhang, Hua; Zong, Yun

2016-05-01

Durable electrocatalysts with high catalytic activity toward oxygen reduction reaction (ORR) are crucial to high-performance primary zinc-air batteries (ZnABs) and direct methanol fuel cells (DMFCs). An efficient composite electrocatalyst, Co@Co3 O4 core@shell nanoparticles (NPs) embedded in pyrolyzed polydopamine (PPD) is reported, i.e., in Co@Co3 O4 @PPD core@bishell structure, obtained via a three-step sequential process involving hydrothermal synthesis, high temperature calcination under nitrogen atmosphere, and gentle heating in air. With Co@Co3 O4 NPs encapsulated by ultrathin highly graphitized N-doped carbon, the catalyst exhibits excellent stability in aqueous alkaline solution over extended period and good tolerance to methanol crossover effect. The integration of N-doped graphitic carbon outer shell and ultrathin nanocrystalline Co3 O4 inner shell enable high ORR activity of the core@bishell NPs, as evidenced by ZnABs using catalyst of Co@Co3 O4 @PPD in air-cathode which delivers a stable voltage profile over 40 h at a discharge current density of as high as 20 mA cm(-2) . © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solid-state thermal decomposition of the [Co(NH{sub 3}){sub 5}CO{sub 3}]NO{sub 3}{center_dot}0.5H{sub 2}O complex: A simple, rapid and low-temperature synthetic route to Co{sub 3}O{sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Farhadi, Saeid, E-mail: sfarhad2001@yahoo.com [Department of Chemistry, Lorestan University, Khorramabad 68135-465 (Iran, Islamic Republic of); Safabakhsh, Jalil [Department of Chemistry, Lorestan University, Khorramabad 68135-465 (Iran, Islamic Republic of)

2012-02-25

Highlights: Black-Right-Pointing-Pointer [Co(NH{sub 3}){sub 5}CO{sub 3}]NO{sub 3}{center_dot}0.5H{sub 2}O complex was used for preparing pure Co{sub 3}O{sub 4} nanoparticles. Black-Right-Pointing-Pointer Co{sub 3}O{sub 4} nanoparticles were prepared at low temperature of 175 Degree-Sign C. Black-Right-Pointing-Pointer Co{sub 3}O{sub 4} nanoparticles show a weak ferromagnetic behaviour at room temperature. Black-Right-Pointing-Pointer The method is simple, low-cost and suitable for the production of Co{sub 3}O{sub 4}. - Abstract: Co{sub 3}O{sub 4} nanoparticles were easily prepared via the decomposition of the pentammine(carbonato)cobalt(III) nitrate precursor complex [Co(NH{sub 3}){sub 5}CO{sub 3}]NO{sub 3}{center_dot}0.5H{sub 2}O at low temperature (175 Degree-Sign C). The product was characterized by thermal analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV-visible spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Brunauer-Emmett-Teller (BET) specific surface area measurements and magnetic measurements. The FT-IR, XRD, Raman and EDX results indicated that the synthesized Co{sub 3}O{sub 4} nanoparticles are highly pure and have a single phase. The TEM analysis revealed nearly uniform and quasi-spherical Co{sub 3}O{sub 4} nanoparticles with an average particle size of approximately 10 nm. The optical absorption spectrum of the Co{sub 3}O{sub 4} nanoparticles showed two direct band gaps of 2.18 and 3.52 eV with a red shift in comparison with previous reported values. The prepared Co{sub 3}O{sub 4} nanoparticles showed a weak ferromagnetic behaviour that could be attributed to uncompensated surface spins and/or finite-size effects. Using the present method, Co{sub 3}O{sub 4} nanoparticles can be produced without expensive organic solvents and complicated equipment. This simple, rapid, safe and low-cost synthetic route can be extended to the synthesis of other

CO gas sensing properties of In_4Sn_3O_1_2 and TeO_2 composite nanoparticle sensors

International Nuclear Information System (INIS)

Mirzaei, Ali; Park, Sunghoon; Sun, Gun-Joo; Kheel, Hyejoon; Lee, Chongmu

2016-01-01

Highlights: • In4Sn3O12–TeO2 composite nanoparticles were synthesized via a facile hydrothermal route. • The response of the In4Sn3O12–TeO2 composite sensor to CO was stronger than the pristine In4Sn3O12 sensor. • The response of the In4Sn3O12–TeO2 composite sensor to CO was faster than the pristine In4Sn3O12 sensor. • The improved sensing performance of the In4Sn3O12–TeO2 nanocomposite sensor is discussed in detail. • The In4Sn3O12-based nanoparticle sensors showed selectivity to CO over NH3, HCHO and H2. - Abstract: A simple hydrothermal route was used to synthesize In_4Sn_3O_1_2 nanoparticles and In_4Sn_3O_1_2–TeO_2 composite nanoparticles, with In(C_2H_3O_2)_3, SnCl_4, and TeCl_4 as the starting materials. The structure and morphology of the synthesized nanoparticles were examined by X-ray diffraction and scanning electron microscopy (SEM), respectively. The gas-sensing properties of the pure and composite nanoparticles toward CO gas were examined at different concentrations (5–100 ppm) of CO gas at different temperatures (100–300 °C). SEM observation revealed that the composite nanoparticles had a uniform shape and size. The sensor based on the In_4Sn_3O_1_2–TeO_2 composite nanoparticles showed stronger response to CO than its pure In_4Sn_3O_1_2 counterpart. The response of the In_4Sn_3O_1_2–TeO_2 composite-nanoparticle sensor to 100 ppm of CO at 200 °C was 10.21, whereas the maximum response of the In_4Sn_3O_1_2 nanoparticle sensor was 2.78 under the same conditions. Furthermore, the response time of the composite sensor was 19.73 s under these conditions, which is less than one-third of that of the In_4Sn_3O_1_2 sensor. The improved sensing performance of the In_4Sn_3O_1_2–TeO_2 nanocomposite sensor is attributed to the enhanced modulation of the potential barrier height at the In_4Sn_3O_1_2–TeO_2 interface, the stronger oxygen adsorption of p-type TeO_2, and the formation of preferential adsorption sites.

Synthesis and magnetic properties of bundled and dispersed Co3O4 nanowires

International Nuclear Information System (INIS)

Zhang, B.B.; Wang, P.F.; Xu, J.C.; Han, Y.B.; Jin, H.X.; Jin, D.F.; Peng, X.L.; Hong, B.; Li, J.; Yang, Y.T.; Gong, J.; Ge, H.L.; Wang, X.Q.

2016-01-01

Highlights: • Co 3 O 4 nanowires possessed the same diameter and the different interwires distance. • All samples possessed antiferromagnetism and superparamagnetism at high temperature. • The exchange bias effect was observed at low temperature. • The surface spin coupling restrained the surface effect of magnetic nanostructures. - Abstract: The magnetic Co 3 O 4 nanowires were synthesized using the templates of SBA-15, and then the well-dispersed nanowires (D-wires) were separated from the bundled ordered nanowires (B-wires) with the centrifugal technique. TEM images indicated that D-wires were highly dispersed Co 3 O 4 nanowires and B-wires existed in bundles. All samples possessed the antiferromagnetism and superparamagnetism at high temperature. After revealing the intrinsic magnetic properties of Co 3 O 4 nanowires with D-wires, the magnetic behavior of B-wires was discussed in detail, and then the magnetic interaction between neighboring nanowires could be deduced. The exchange bias effect from the body Co 3 O 4 antiferromagnetism and surface ferromagnetism was observed at low temperature. The magnetization of B-wires was higher than that of D-wires, which was attributed to the constraint of the surface spin coupling between the neighboring nanowires to the surface affect of nanostructures.

Structural, optical, and magnetic properties of Mn and Fe-doped Co3O4 nanoparticles

Directory of Open Access Journals (Sweden)

C. Stella

2015-08-01

Full Text Available Mn and Fe-doped Co3O4 nanoparticles were prepared by a simple precipitation method. The synthesized particles were characterized by X-ray diffraction (XRD, scanning electron microscope (SEM, transmission electron microscope (TEM, UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR, Raman spectroscopy, and vibrating sample magnetometer (VSM techniques. XRD analysis showed the cubic structure of Co3O4. SEM and TEM images confirmed the formation of interconnected nanoparticles. Mn and Fe-doped Co3O4 showed broad absorption in the visible region compared to undoped sample and the band gap values are red shifted. Five Raman active modes were observed from the Raman spectra. FTIR spectra confirmed the spinel structure of Co3O4 and the doping of Mn and Fe shifts the vibrational modes to lower wave number region. The magnetic measurements confirmed that Fe-doped Co3O4 shows a little ferromagnetic behavior compared to undoped and Mn-doped Co3O4, which could be related to the uncompensated surface spins and the finite size effects.

Na3Co2(AsO4(As2O7: a new sodium cobalt arsenate

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Abderrahmen Guesmi

2012-07-01

Full Text Available In the title compound, trisodium dicobalt arsenate diarsenate, Na3Co2AsO4As2O7, the two Co atoms, one of the two As and three of the seven O atoms lie on special positions, with site symmetries 2 and m for the Co, m for the As, and 2 and twice m for the O atoms. The two Na atoms are disordered over two general and special positions [occupancies 0.72 (3:0.28 (3 and 0.940 (6:0.060 (6, respectively]. The main structural feature is the association of the CoO6 octahedra in the ab plane, forming Co4O20 units, which are corner- and edge-connected via AsO4 and As2O7 arsenate groups, giving rise to a complex polyhedral connectivity with small tunnels, such as those running along the b- and c-axis directions, in which the Na+ ions reside. The structural model is validated by both bond-valence-sum and charge-distribution methods, and the distortion of the coordination polyhedra is analyzed by means of the effective coordination number.

Photocatalytic properties of Co{sub 3}O{sub 4}/LiCoO{sub 2} recycled from spent lithium-ion batteries using citric acid as leaching agent

Energy Technology Data Exchange (ETDEWEB)

Santana, I.L.; Moreira, T.F.M.; Lelis, M.F.F.; Freitas, M.B.J.G., E-mail: marcosbjg@gmail.com

2017-04-01

In this work, cobalt and lithium from the cathodes of spent lithium-ion batteries were recycled to synthesize a mixture of Co{sub 3}O{sub 4} and LiCoO{sub 2}. The positive electrode was leached with citric acid in the green recycling. After being heated to 85 °C, the leaching solution formed a pink sol, and after being dried at 120 °C for 24 h, it formed a gel, which is a precursor material for Co{sub 3}O{sub 4} and LiCoO{sub 2} synthesis. A mixture of Co{sub 3}O{sub 4} and LT-LiCoO{sub 2} was obtained after the calcination of the precursor material at 450 °C for 3 h. The photocatalytic properties of the Co{sub 3}O{sub 4} and LiCoO{sub 2} were tested in the discoloration of methylene blue dye. The discoloration efficiency of methylene blue dye in the presence of Co{sub 3}O{sub 4} and LiCoO{sub 2} was 90% after 10 h and 100% after 24 h of heterogeneous catalysis. The contribution of this work is that it presents a means to produce valuable materials with photocatalytic properties from recycled batteries through a spent Li-ion battery recycling process without polluting the environment. - Highlights: • Synthesis a mixture of Co{sub 3}O{sub 4}/LiCoO{sub 2} from spent Li-ion batteries. • Citric acid for leaching of the cathodes of the spent Li-ion batteries. • Co{sub 3}O{sub 4}/LiCoO{sub 2} as catalysts in the photodegradation of the methylene blue dye.

Synthesis and microstructure of La_1_−_xCa_xCoO_3 nanoparticles and their catalytic activity for CO oxidation

International Nuclear Information System (INIS)

Luu, Tien Hung; Nguyen, Xuan Dung; Phan, Thi Minh Huyen; Schulze, Steffen; Hietschold, Michael

2015-01-01

Perovskite nanoparticles of La_1_−_xCa_xCoO_3 (x = 0, 0.2, 0.3, 0.5) were synthesized by the combustion method using polyvinyl alcohol (PVA) and corresponding metal nitrates. Microstructure of samples was characterized by high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) combined with x-ray diffraction (XRD). The nanoparticles were characterized by thermogravimetric and differential thermal analysis (TG-DTA) and BET (Brunauer–Emmet–Teller). A high surface area (15–21 m"2 g"−"1) at low temperature (600 °C) of samples was obtained. The optimal preparative conditions were PVA/metals 2:1 by mole, pH = 3 and 80 °C for gel formation. Perovskites exhibit a good catalytic activity in total oxidation of CO at the low temperature (<250 °C) of reaction. (paper)

In Operando Self-Healing of Perovskite Electrocatalysts: A Case Study of SrCoO3 for the Oxygen Evolution Reaction

KAUST Repository

Tahini, Hassan A.; Tan, Xin; Schwingenschlö gl, Udo; Smith, Sean C.

2017-01-01

Perovskites are promising catalysts for oxygen evolution reactions (OER); among them, SrCoO3 is one of the best for these reactions. We study the O* intermediates and the role of surface oxygen vacancies of SrCoO3 during OER. A self-healing mechanism is proposed in which O* are incorporated into the surface to recover the redox capabilities of the material.

In Operando Self-Healing of Perovskite Electrocatalysts: A Case Study of SrCoO3 for the Oxygen Evolution Reaction

KAUST Repository

Tahini, Hassan A.

2017-01-24

Perovskites are promising catalysts for oxygen evolution reactions (OER); among them, SrCoO3 is one of the best for these reactions. We study the O* intermediates and the role of surface oxygen vacancies of SrCoO3 during OER. A self-healing mechanism is proposed in which O* are incorporated into the surface to recover the redox capabilities of the material.

Characterization and Electrocatalytic Properties of Titanium-Based Ru0.3Co0.7−xCex Mixed Oxide Electrodes for Oxygen Evolution in Alkaline Solution

Directory of Open Access Journals (Sweden)

Hongjun Wu

2011-01-01

Full Text Available Ti-supported RuO2-Co3O4-CeO2 (Ru0.3Co0.7−xCex oxide, 0≤x≤0.7 electrodes were prepared by sol-gel process. The phase structure, surface morphology, and microstructure of the oxide layer were characterized by X-ray diffraction (XRD and scanning electron microscopy (SEM. Electrocatalytic activity and oxygen evolution reaction (OER kinetics on these electrodes in 1.0 mol⋅dm−3 KOH solution were studied by recording open-circuit potential, cyclic voltammetry, and polarisation curves. The results showed that the appropriate content of CeO2 could reduce the grain size and increase active surface area. The electrocatalytic activity shows a strong dependence on the CeO2 content in the film. Catalytic performance of mixed oxide electrodes with 40 mol % CeO2 was the best, with the greatest voltammetric charge, 86.23 mC⋅cm−2, and the smallest apparent activation energy for OER at 0.60 V was 22.76 kJ⋅mol−1.

Facile fabrication of Fe{sub 3}O{sub 4} and Co{sub 3}O{sub 4} microspheres and their influence on the thermal decomposition of ammonium perchlorate

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yifu, E-mail: yfzhang@dlut.edu.cn; Meng, Changgong

2016-07-25

Fe{sub 3}O{sub 4} and Co{sub 3}O{sub 4} microspheres were successfully synthesized by the hydrothermal decomposition of iron oxalate and cobalt oxalate solution. The composition and morphology of synthesized powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The catalytic properties of the as-obtained Fe{sub 3}O{sub 4} and Co{sub 3}O{sub 4} microspheres on the thermal decomposition of ammonium perchlorate (AP) were evaluated by thermo-gravimetric analysis and differential thermal analysis (TGA/DTA) methods. The thermal decomposition temperatures of AP in the presence of 1, 2, 4 and 8 wt% of Fe{sub 3}O{sub 4} microspheres were respectively decreased by 58, 80, 102 and 129 °C (lowered to 398, 376, 354 and 327 °C). And the thermal decomposition temperatures of AP in the presence of 1, 2, 4 and 8 wt% of Co{sub 3}O{sub 4} microspheres were respectively decreased by 55, 74, 112 and 131 °C (lowered to 401, 382, 344 and 325 °C). The analysis of the thermal gravimetric analyzer couplet with infrared spectroscopy (TG-IR) test reveal that the additives can accelerate the thermal decomposition of AP via the high-temperature decomposition. All the results suggest the as-prepared Fe{sub 3}O{sub 4} and Co{sub 3}O{sub 4} microspheres have highly catalytic properties on the thermal decomposition of AP, which can be used as the promising additives in the future. - Graphical abstract: Real-time FTIR spectra to reveal the thermal decomposition process of AP. - Highlights: • Highly uniform Fe{sub 3}O{sub 4} and Co{sub 3}O{sub 4} microspheres were successfully synthesized. • The T{sub c} of AP with 1, 2, 4 and 8 wt% of Fe{sub 3}O{sub 4} microspheres was decreased by 58, 80, 102 and 129 °C. • The T{sub c} of AP with 1, 2, 4 and 8 wt% of Co{sub 3}O{sub 4} microspheres was decreased by 55, 74, 112 and 131 °C. • The thermal decomposition process of AP was detected by TG-IR.

Hierarchical Co3O4/PANI hollow nanocages: Synthesis and application for electrode materials of supercapacitors

Science.gov (United States)

Ren, Xiaohu; Fan, Huiqing; Ma, Jiangwei; Wang, Chao; Zhang, Mingchang; Zhao, Nan

2018-05-01

Hierarchically hollow Co3O4/polyaniline nanocages (Co3O4/PANI NCs) with enhanced specific capacitance and cycle performance for electrode material of supercapacitors are fabricated by combining self-sacrificing template and in situ polymerization route. Benefiting from the good conductivity of PANI improving an electron transport rate as well as high specific surface area from such a hollow structure, the electrode made of Co3O4/PANI NCs exhibits a large specific capacitance of 1301 F/g at the current density of 1 A/g, a much enhancement is obtained as compared with the pristine Co3O4 NCs electrode. The contact resistance (Re), charge-transfer (Rct) and Warburg resistance of Co3O4/PANI NCs electrode is significantly lower than that of the pristine Co3O4 NCs electrode, indicating the enhanced electrical conductivity. In addition, the Co3O4/PANI NCs electrode also displays superior cycling stability with 90 % capacitance retention after 2000 cycles. Moreover, an aqueous asymmetric supercapacitor was successfully assembled using Co3O4/PANI NCs as the positive electrode and activated carbon (AC) as the negative electrode, the assembled device exhibits a superior energy density of 41.5 Wh/kg at 0.8 kW/kg, outstanding power density of 15.9 kW/kg at 18.4 Wh/kg, which significantly transcending those of most previously reported. These results demonstrate that the hierarchically hollow Co3O4/PANI NCs composites have a potential for fabricating electrode of supercapacitors.

Growth and characterization of thin oriented Co{sub 3}O{sub 4} (111) films obtained by decomposition of layered cobaltates Na{sub x}CoO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Buršík, Josef, E-mail: bursik@iic.cas.cz [Institute of Inorganic Chemistry of the Academy of Sciences of the Czech Republic, v.v.i., 250 68, Husinec-Řež 1001 (Czech Republic); Soroka, Miroslav, E-mail: soroka@iic.cas.cz [Institute of Inorganic Chemistry of the Academy of Sciences of the Czech Republic, v.v.i., 250 68, Husinec-Řež 1001 (Czech Republic); Kužel, Radomír, E-mail: kuzel@karlov.mff.cuni.cz [Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, 121 16 Praha 2 (Czech Republic); Mika, Filip, E-mail: filip.mika@isibrno.cz [Institute of Scientific Instruments, Academy of Sciences of the Czech Republic, v.v.i., Královopolská 147, 612 64 Brno (Czech Republic)

2015-07-15

The formation and structural characterization of highly (111)-oriented Co{sub 3}O{sub 4} films prepared by a novel procedure from weakly (001)-oriented Na{sub x}CoO{sub 2} is reported. The Na{sub x}CoO{sub 2} films were deposited on both single crystal and amorphous substrates by chemical solution deposition (CSD) method and crystallized at 700 °C. Subsequently they were transformed into (111)-oriented Co{sub 3}O{sub 4} phase during post-growth annealing at 900 °C. The degree of preferred orientation in Co{sub 3}O{sub 4}, which was determined by phi-scan and pole figure measurements, depends on the content of Na in the starting Na{sub x}CoO{sub 2} phase. Surface morphology of the films was investigated using electron microscopy and atomic force microscopy. - Graphical abstract: Structure of growth twins and possible O{sup 2−} stacking sequences in (111)-oriented Co{sub 3}O{sub 4} thin films on α-Al{sub 2}O{sub 3}(001) prepared by chemical solution deposition through the transformation of (001)-oriented Na{sub x}CoO{sub 2} thin film. - Highlights: • Single phase Co{sub 3}O{sub 4} thin films was prepared by means of chemical solution deposition. • Conditions for γ-Na{sub x}CoO{sub 2} to Co{sub 3}O{sub 4} transformation were optimized. • Growth twinning of Co{sub 3}O{sub 4} films due to two possible O{sup 2−} stacking sequences. • Growth with (pseudo)epitaxial relation Co{sub 3}O{sub 4} (111)[−121]//α-Al{sub 2}O{sub 3} (001)[10−10].

Microstructural analysis of aluminum oxide boron carbide (Al2 O3-B4 C)

International Nuclear Information System (INIS)

Oliveira, E.E.M.; Bressiani, Ana H.A.; Bressiani, J.C.

1996-01-01

The densification Al 2 O 3 -B 4 C of composite was accomplished under two conditions: I- tungsten resistance furnace in commercial argon atmosphere without gas treatment system.II- graphite resistance furnace in argon atmosphere with gas treatment for humidity removal. The sintering with gas treatment showed higher density and smaller loss of mass for all composition related to the sintering in tungsten resistance furnace without gas treatment system. Microstructural characterization also showed that grain growth of alumina matrix is greatly influenced by particle size and concentration of B 4 C. Samples sintered at temperatures higher than 1750 deg C without gas treatment presented the formation of phase Al 3 B O 6 which was identified by transmission electron microscopy. (author)

Study of magnetization and magnetoelectricity in CoFe2O4/BiFeO3 core-shell composites

Science.gov (United States)

Kuila, S.; Tiwary, Sweta; Sahoo, M. R.; Barik, A.; Babu, P. D.; Siruguri, V.; Birajdar, B.; Vishwakarma, P. N.

2018-02-01

CoFe2O4 (core)/BiFeO3 (shell) nanoparticles are prepared by varying the relative molar concentration of core and shell materials (40%CoFe2O4-60%BiFeO3, 50%CoFe2O4-50%BiFeO3, and 60%CoFe2O4-40%BiFeO3). The core-shell nature is confirmed from transmission electron microscopy on these samples. A plot of ΔM (=MFC-MZFC) vs temperature suggests the presence of two types of spin dynamics: (a) particle size dependent spin blocking and (b) spin-disorder. These two spin dynamic processes are found to contribute independently to the generation of magnetoelectric voltage. Very clear first order and second order magnetoelectric voltages are recorded. The resemblance of the first order magnetoelectric coefficient vs temperature plot to that of building up of order parameters in the mean field theory suggests that spin disorder can act like one of the essential ingredients in building the magnetoelectric coupling. The best result is obtained for the 50-50 composition sample, which may be due to better coupling of magnetostrictive CoFe2O4, and piezoelectric BiFeO3, because of the optimum thickness of shell and core.

First identification and thermodynamic characterization of the ternary U(VI) species, UO2(O2)(CO3)2(4-), in UO2-H2O2-K2CO3 solutions.

Science.gov (United States)

Goff, George S; Brodnax, Lia F; Cisneros, Michael R; Peper, Shane M; Field, Stephanie E; Scott, Brian L; Runde, Wolfgang H

2008-03-17

In alkaline carbonate solutions, hydrogen peroxide can selectively replace one of the carbonate ligands in UO2(CO3)3(4-) to form the ternary mixed U(VI) peroxo-carbonato species UO2(O2)(CO3)2(4-). Orange rectangular plates of K4[UO2(CO3)2(O2)].H2O were isolated and characterized by single crystal X-ray diffraction studies. Crystallographic data: monoclinic, space group P2(1)/ n, a = 6.9670(14) A, b = 9.2158(10) A, c = 18.052(4) A, Z = 4. Spectrophotometric titrations with H 2O 2 were performed in 0.5 M K 2CO 3, with UO2(O2)(CO3)2(4-) concentrations ranging from 0.1 to 0.55 mM. The molar absorptivities (M(-1) cm(-1)) for UO2(CO3)3(4-) and UO2(O2)(CO3)2(4-) were determined to be 23.3 +/- 0.3 at 448.5 nm and 1022.7 +/- 19.0 at 347.5 nm, respectively. Stoichiometric analyses coupled with spectroscopic comparisons between solution and solid state indicate that the stable solution species is UO2(O2)(CO3)2(4-), which has an apparent formation constant of log K' = 4.70 +/- 0.02 relative to the tris-carbonato complex.

Oxygen permeation flux through 10Sc1YSZ-MnCo2O4 asymmetric membranes prepared by two-step sintering

DEFF Research Database (Denmark)

Pirou, Stéven; Gurauskis, Jonas; Gil, Vanesa

2016-01-01

Asymmetric membranes based on a dual phase composite consisting of (Y2O3)0.01(Sc2O3)0.10(ZrO2)0.89 (10Sc1YSZ) as ionic conductor and MnCo2O4 as electronic conductor were prepared and characterized with respect to sinterability, microstructure and oxygen transport properties. The composite membranes...... were prepared by tape casting, lamination and fired in a two-step sintering process. Microstructural analysis showed that a gastight thin membrane layer with the desired ratio of ionic/electronic conducting phases could be fabricated. Oxygen permeation fluxes across the 10SclYSZ/MnCo2O4 (70/30 vol......%) composite membrane were measured from 750 to 940 degrees C using air or pure oxygen as feed gases and N2 or CO2 as sweep gases. Fluxes up to 2.3 mlN min-1 cm-2 were obtained for the 7 μm thick membrane. A degradation test over 1730 h showed an initial degradation of 21% during the first 1100 h after which...

Preparation of Shape-Controlled Graphene/Co3O4 Composites for Supercapacitors

Science.gov (United States)

Chen, Jun; Chen, Ningna; Feng, Xiaomiao; Hou, Wenhua

2016-09-01

Graphene/Co3O4 nanocomposites with different morphologies were fabricated by hydrothermal method. The morphology of nanocomposites was characterized by scanning electron microscopy. These composites could be used as the electrode materials for supercapacitors. The eletrochemical behavior of the composite was tested by cyclic voltammetry and galvanostatic charge-discharge measurements in 1.0 mol/L KOH solution. The results showed that the graphene/Co3O4 nanopetal composite exhibited excellent electrochemical performance. The specific capacitance value could reach up to 714 F/g at a scan rate of 2 mV/s. Besides, the capacitance of the graphene/Co3O4 nanopetal composite was 841 F/g at a current density of 0.1 A/g. After galvanostatic charge-discharge 1000 laps at the current density of 0.4 A/g, the specific capacitance could keep 96.7% of original capacitive value, demonstrating its good cycling stability.

Co3O4 Electrode Prepared by Using Metal-Organic Framework as a Host for Supercapacitors

Directory of Open Access Journals (Sweden)

Jiaqiang Jiang

2015-01-01

Full Text Available Co3O4 nanoparticles were prepared from cobalt nitrate that was accommodated in the pores of a metal-organic framework (MOF ZIF-8 (Zn(MeIM2, MeIM = 2-methylimidazole by using a simple liquid-phase method. Analysis by scanning electron microscopy (SEM and transmission electron microscopy (TEM showed that the obtained Co3O4 was composed of separate nanoparticles with a mean size of 30 nm. The obtained Co3O4 nanoparticles exhibited superior electrochemical property. Co3O4 electrode exhibited a maximum specific capacitance of 189.1 F g−1 at the specific current of 0.2 A g−1. Meanwhile, the Co3O4 electrode possessed the high specific capacitance retention ratio at the current density ranging from 0.2 to 1.0 A g−1, thereby indicating that Co3O4 electrode suited high-rate charge/discharge.

Microstructural and compositional Evolution of Compound Layers during Gaseous Nitrocarburizing

DEFF Research Database (Denmark)

Du, Hong; Somers, Marcel A.J.; Ågren, John

2000-01-01

Compound layers developed at 848 K during gaseous nitrocarburizing of iron and iron-carbon specimens were investigated for several combinations of N and C activities imposed at the specimen surface by gas mixtures of NH3, N2, CO2 and CO. The microstructural evolution of the compound layer was stu...

Enhanced electrochemical performance of LiNi_0_._8Co_0_._1_5Al_0_._0_5O_2 by nanoscale surface modification with Co_3O_4

International Nuclear Information System (INIS)

Huang, Yaqun; Huang, Yunhui; Hu, Xianluo

2017-01-01

Highlights: • Facile coating method to prepare Co_3O_4-modified NCA. • Co_3O_4 is uniformly coated on the surface of NCA. • The nanolayer coating protects the surface of NCA during Li cycling. • Co_3O_4-modified NCA exhibits enhanced cyclability and rate capability. - Abstract: LiNi_0_._8Co_0_._1_5Al_0_._0_5O_2 (NCA) has attracted much attention because of its high capacity and low cost. Herein, we report a facile wet-chemical route to prepare a Co_3O_4-modified NCA cathode material with enhanced electrochemical performance for lithium-ion batteries. The as-prepared Co_3O_4-coated NCA cathode material delivers a specific capacity of 207.6 mAh g"−"1 with an initial Coulombic efficiency of 90.8% at 0.1 C. The capacity retention of the Co_3O_4-coated NCA cathode material is as high as 91.6% at 1 C between the potential from 2.8 to 4.3 V after 100 cycles. More importantly, the capacity retention of the resulting Co_3O_4-coated NCA is higher than 94.7% after 100 cycles at 0.2 C. In addition, the Co_3O_4-coated NCA cathode material exhibits good rate capability, especially a high discharge capacity at a high current density. The outstanding electrochemical performance of Co_3O_4-coated NCA is assigned to the surface coating of Co_3O_4 that may react with lithium-containing impurities on the surface and decrease the charge-transfer resistance.

Heterojunction-Assisted Co3 S4 @Co3 O4 Core-Shell Octahedrons for Supercapacitors and Both Oxygen and Carbon Dioxide Reduction Reactions.

Science.gov (United States)

Yan, Yibo; Li, Kaixin; Chen, Xiaoping; Yang, Yanhui; Lee, Jong-Min

2017-12-01

Expedition of electron transfer efficiency and optimization of surface reactant adsorption products desorption processes are two main challenges for developing non-noble catalysts in the oxygen reduction reaction (ORR) and CO 2 reduction reaction (CRR). A heterojunction prototype on Co 3 S 4 @Co 3 O 4 core-shell octahedron structure is established via hydrothermal lattice anion exchange protocol to implement the electroreduction of oxygen and carbon dioxide with high performance. The synergistic bifunctional catalyst consists of p-type Co 3 O 4 core and n-type Co 3 S 4 shell, which afford high surface electron density along with high capacitance without sacrificing mechanical robustness. A four electron ORR process, identical to the Pt catalyzed ORR, is validated using the core-shell octahedron catalyst. The synergistic interaction between cobalt sulfide and cobalt oxide bicatalyst reduces the activation energy to convert CO 2 into adsorbed intermediates and hereby enables CRR to run at a low overpotential, with formate as the highly selective main product at a high faraday efficiency of 85.3%. The remarkable performance can be ascribed to the synergistic coupling effect of the structured co-catalysts; heterojunction structure expedites the electron transfer efficiency and optimizes surface reactant adsorption product desorption processes, which also provide theoretical and pragmatic guideline for catalyst development and mechanism explorations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spin-Coating and Characterization of Multiferroic MFe2O4 (M=Co, Ni) / BaTiO3 Bilayers

Science.gov (United States)

Quandt, Norman; Roth, Robert; Syrowatka, Frank; Steimecke, Matthias; Ebbinghaus, Stefan G.

2016-01-01

Bilayer films of MFe2O4 (M=Co, Ni) and BaTiO3 were prepared by spin coating of N,N-dimethylformamide/acetic acid solutions on platinum coated silicon wafers. Five coating steps were applied to get the desired thickness of 150 nm for both the ferrite and perovskite layer. XRD, IR and Raman spectroscopy revealed the formation of phase-pure ferrite spinels and BaTiO3. Smooth surfaces with roughnesses in the order of 3 to 5 nm were found in AFM investigations. Saturation magnetization of 347 emu cm-3 for the CoFe2O4/BaTiO3 and 188 emu cm-3 for the NiFe2O4/BaTiO3 bilayer, respectively were found. For the CoFe2O4/BaTiO3 bilayer a strong magnetic anisotropy was observed with coercivity fields of 5.1 kOe and 3.3 kOe (applied magnetic field perpendicular and parallel to film surface), while for the NiFe2O4/BaTiO3 bilayer this effect is less pronounced. Saturated polarization hysteresis loops prove the presence of ferroelectricity in both systems.

Magneto electric effects in BaTiO3-CoFe2O4 bulk composites

Science.gov (United States)

Agarwal, Shivani; Caltun, O. F.; Sreenivas, K.

2012-11-01

Influence of a static magnetic field (HDC) on the hysteresis and remanence in the longitudinal and transverse magneto electric voltage coefficients (MEVC) observed in [BaTiO3]1-x-[CoFe2O4]x bulk composites are analyzed. Remanence in MEVC at zero bias (HDC=0) is stronger in the transverse configuration over the longitudinal case. The observed hysteretic behavior in MEVC vs. HDC is correlated with the changes observed in the magnetostriction characteristics (λ and dλ/dH) reported for [BaTiO3]1-x-[CoFe2O4]x bulk composites.

The effect of Co-Co3O4 coating on the electrochemical properties of Si as an anode material for Li ion battery

International Nuclear Information System (INIS)

Kang, Yong-Mook; Lee, Sang-Min; Sung, Min-Seok; Jeong, Goo-Jin; Kim, Joon-Sup; Kim, Sung-Soo

2006-01-01

In order to improve the electrochemical performance of Si as an anode material for Li ion secondary batteries, a biphasic layer composed of Co and Co 3 O 4 was coated on Si particles by sol-gel method. Compared to Si, Co-Co 3 O 4 coated Si showed the drastic improvement in several electrochemical properties, such as initial coulombic efficiency (55% → 88%), cyclic efficiency and cycle life. The comparison between Co-Co 3 O 4 coated Si and heat-treated Si without the coating let us know that the improvement of electrochemical properties only results from Co-Co 3 O 4 coating layer. Little changed cyclic properties (cyclic efficiency and cycle life) of Co-Co 3 O 4 coated Si even at a higher charge-discharge rate insinuated that Co-Co 3 O 4 coating layer plays a crucial role in maintaining the electronic contacts between particles and conducting parts. When trying to measure a thickness variation of the electrodes each containing Si and Co-Co 3 O 4 coated Si as active materials, it was notified that Co-Co 3 O 4 coating layer can accommodate the volume expansion of Si during Li + insertion, which has its original thickness almost recovered after Li + extraction

Porous Co3O4 nanorods anchored on graphene nanosheets as an effective electrocatalysts for aprotic Li-O2 batteries

Science.gov (United States)

Yuan, Mengwei; Yang, Yan; Nan, Caiyun; Sun, Genban; Li, Huifeng; Ma, Shulan

2018-06-01

The large over-potential during the battery operation is a great obstacle for the application of Li-O2 batteries. The porous structure and electrical conductivity of the electrocatalysts are significant for the electrocatalytic performance of Li-O2 batteries. In this work, a porous Co3O4/GN nanocomposite (Co3O4 nanorods anchored on graphene nanosheets) is prepared via a facile hydrothermal method assisted with heat treatment. The unique structure of Co3O4/GN endows efficient electrocatalystic activity for Li-O2 batteries. In comparison to the Co3O4, the Co3O4/GN demonstrates a better cycle performance showing more than 40 cycles with a 1500 mAh g-1 capacity limit strategy at a current density of 300 mA g-1, and a reduced over-potential of 110 mV at high current density (1200 mA g-1). The Co3O4/GN also displays a high initial specific capacity (7600 mAh g-1) and a good reversibility in full cycle with a coulombic efficiency of 99.8% in the first cycle. The impressed cyclability, specific capacity, rate performance, and low over-potentials indicate that the as-prepared Co3O4/GN nanocomposite is a promising catalyst candidate for reversible Li-O2 batteries.

Solution-processed n-ZnO nanorod/p-Co_3O_4 nanoplate heterojunction light-emitting diode

International Nuclear Information System (INIS)

Kim, Jong-Woo; Lee, Su Jeong; Biswas, Pranab; Lee, Tae Il; Myoung, Jae-Min

2017-01-01

Highlights: • The n-ZnO nanorods were epitaxially grown on p-Co_3O_4 nanoplates. • The heteroepitaxial p-n junction was fabricated by using hydrothermal process. • The LEDs emitted reddish-orange and violet light related to ZnO point defects. • The Co_3O_4 nanoplates function as a hole injection layer. • Junction between 1D NRs and 2D NPs provides a new approach to design nanostructures. - Abstract: A heterojunction light-emitting diode (LED) based on p-type cobalt oxide (Co_3O_4) nanoplates (NPs)/n-type zinc oxide (ZnO) nanorods (NRs) is demonstrated. Using a low-temperature aqueous solution process, the n-type ZnO NRs were epitaxially grown on Co_3O_4 NPs which were two-dimensionally assembled by a modified Langmuir-Blodgett process. The heterojunction LEDs exhibited a typical rectifying behavior with a turn-on voltage of about 2 V and emitted not only reddish-orange light at 610 nm but also violet light at about 400 nm. From the comparative analyses of electroluminescence and photoluminescence, it was determined that the reddish-orange light emission was related to the electronic transitions from zinc interstitials (Zn_i) to oxygen interstitials (O_i) or conduction-band minimum (CBM) to oxygen vacancies (V_O), and the violet light emission was attribute to the transition from CBM to valence-band maximum (VBM) or Zn_i to zinc vacancies (V_Z_n).

Nanostructural origin of semiconductivity and large magnetoresistance in epitaxial NiCo2O4/Al2O3 thin films

Science.gov (United States)

Zhen, Congmian; Zhang, XiaoZhe; Wei, Wengang; Guo, Wenzhe; Pant, Ankit; Xu, Xiaoshan; Shen, Jian; Ma, Li; Hou, Denglu

2018-04-01

Despite low resistivity (~1 mΩ cm), metallic electrical transport has not been commonly observed in inverse spinel NiCo2O4, except in certain epitaxial thin films. Previous studies have stressed the effect of valence mixing and the degree of spinel inversion on the electrical conduction of NiCo2O4 films. In this work, we studied the effect of nanostructural disorder by comparing the NiCo2O4 epitaxial films grown on MgAl2O4 (1 1 1) and on Al2O3 (0 0 1) substrates. Although the optimal growth conditions are similar for the NiCo2O4 (1 1 1)/MgAl2O4 (1 1 1) and the NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films, they show metallic and semiconducting electrical transport, respectively. Post-growth annealing decreases the resistivity of NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films, but the annealed films are still semiconducting. While the semiconductivity and the large magnetoresistance in NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films cannot be accounted for in terms of non-optimal valence mixing and spinel inversion, the presence of anti-phase boundaries between nano-sized crystallites, generated by the structural mismatch between NiCo2O4 and Al2O3, may explain all the experimental observations in this work. These results reveal nanostructural disorder as being another key factor for controlling the electrical transport of NiCo2O4, with potentially large magnetoresistance for spintronics applications.

Electrical transport and thermochromic properties of polyaniline/chitosan/Co3O4 ternary nano composite

Science.gov (United States)

V, Mini; Kamath, Archana; S, Raghu; Chapi, Sharanappa; H, Devendrappa

2015-06-01

A new Polyaniline/ chitosan/ Co3O4 (CPAESCO) ternary nanocomposite is prepared by in situ oxidation polymerization of aniline in the presence of (NH4)2S2O8, chitosan and Co3O4. The Structural, Thermal, Optical and Electrical features of Polyaniline (PANI), Polyaniline/ chitosan (CPANI) and CPAESCO were analyzed using FT-IR, TGA, UV-vis analysis and Impedance spectroscopy by varying temperature. The results show that the introduction of the Co3O4 nanoparticles into CPANI matrix enhanced its properties. Mott's parameters show 3D -VRH Type conduction in it.

Morphology Engineering of Co3O4 Nanoarrays as Free-Standing Catalysts for Lithium-Oxygen Batteries.

Science.gov (United States)

He, Mu; Zhang, Peng; Xu, Shan; Yan, Xingbin

2016-09-14

The effective shape-controlled synthesis of Co3O4 nanoarrays on nickel foam substrates has been achieved through a simple hydrothermal strategy. When they served as the binder- and conductive-agent-free porous cathodes for nonaqueous Li-O2 batteries, they sufficiently reflect the favorable catalytic characteristic of Co3O4 and alleviate the problems of serious pore blocking and surface passivation caused by insoluble and insulating discharge products. In particular, Co3O4 rectangular nanosheets exhibit superior electrocatalytic performance comparing with Co3O4 nanowires and hexagonal nanosheets, leading to higher specific capacity and better cycling stability over 54 cycles at 100 mA g(-1), which relate to their good pore structure, large specific surface area, and highly active {112} exposed plane, effectively promoting the mass transport and reversible formation and decomposition of discharge products in the cathode. These comparisons further indicate the morphology effect of nanostructured Co3O4 on their performances as free-standing catalysts for Li-O2 batteries, which also have been proved through the further analysis of discharge products on different shapes of Co3O4 nanoarrays electrodes.

Microstructure and electrical properties of (1−x)[0.8Bi_0_._5Na_0_._5TiO_3-0.2Bi_0_._5K_0_._5TiO_3]-xBiCoO_3 lead-free ceramics

International Nuclear Information System (INIS)

Wang, Ting; Chen, Xiao-ming; Qiu, Yan-zi; Lian, Han-li; Chen, Wei-ting

2017-01-01

The (1−x)[0.8Bi_0_._5Na_0_._5TiO_3-0.2Bi_0_._5K_0_._5TiO_3]-xBiCoO_3 (x = 0, 0.02, 0.05, abbreviated as BNKT, BNKT-002Co, BNKT-005Co, respectively) lead-free ferroelectric ceramics were prepared via the solid state reaction method. The phase structure, microstructure, dielectric, ferroelectric, pyroelectric, and piezoelectric properties of the ceramics were investigated comparatively by using a combination of characterization techniques. All the samples exhibit typical X-ray diffraction peaks of ABO_3 perovskite structure. The doping of BiCoO_3 causes a decrease in lattice parameters and an increase in grain size of the ceramics. The Raman spectroscopy results suggest a lattice distortion due to the doping. It is found that BNKT-002Co and BNKT-005Co have higher depolarization temperatures compared with BNKT. The Curie-Weiss law and modified Curie-Weiss law explored a diffuse phase transition character for all the samples. The results of ultraviolet–visible diffuse reflectance suggests that BiCoO_3-doped ceramics possess higher defect concentration. The impedance analysis shows a temperature dependent relaxation behavior, and the activation energy for the electrical responses varies with the change of BiCoO_3 amount. The ferroelectric and piezoelectric properties of the ceramics decrease due to the doping of BiCoO_3. Based on the results of the Rayleigh analysis, it was suggested that the differences in the electrical properties among the ceramics are closely related to the change in oxygen vacancy concentration. - Highlights: • BNKT-xCo ceramics were prepared by solid-state reaction method. • Electrical properties of BNKT ceramics are changed by the doping of BiCoO_3. • The doping causes a decrease in lattice parameters and an increase in grain size. • T_d of the ceramics increases with increasing x. • Oxygen vacancies play key role in determining electrical properties of the ceramics.

Polyaniline/Fe3O4-RGO Nanocomposites for Microwave Absorption

Science.gov (United States)

Mathew, Jithin; Sathishkumar, M.; Kothurkar, Nikhil K.; Senthilkumar, R.; Sabarish Narayanan, B.

2018-02-01

Fe3O4 nanoparticles were synthesized by co-precipitation of ferric chloride (FeCl3) and ferrous chloride (FeCl2). Reduced graphene oxide (RGO) was prepared by reducing the graphene oxide, which was synthesized by Hummer’s method, using hydrazine hydrate. Three nanocomposites based on sodium dodecyl benzene sulphonate (SDBS)-doped polyaniline were synthesized through in situ polymerization in the presence of the fillers (i) Fe3O4, (ii) reduced graphene oxide (RGO) and (iii) Fe3O4-decorated RGO respectively. The synthesized PANI and the composites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. Their microstructures, electrical conductivities, and EMI shielding effectiveness were studied. The nanocomposite containing 10 % RGO showed the maximum electrical conductivity and the one with 10 % RGO and 10 % Fe3O4 showed the maximum EMI shielding effectiveness of 7.5 dB for a 1 mm thick sample.

Orientation dependence of magnetoelectric coefficient in 1-3-type BaTiO3/CoFe2O4

Science.gov (United States)

Jian, Gang; Shao, Hui; Zhang, Cheng; Yan, Chao; Zhao, Ning; Song, Bo; Wong, C. P.

2018-03-01

Orientation dependence of magnetoelectric coefficient αE33 in 1-3-type BaTiO3/CoFe2O4 composites was calculated in arbitrary directions by three-dimensional coordinate transformation method. The space distributions of pc11‧, pc12‧, e31‧ for piezoelectric phase and mc11‧, mc12‧, q31‧ for magnetic phase were obtained independently using relative experimental data and original matrices for 4mm BaTiO3 and m3m CoFe2O4. Elastic stiffness coefficients show little orientation differences, while e31‧ and q31‧ exhibit high dependence on crystal orientation, with the MAX absolute e31‧ = 2.96 C/m2 and the MAX q31‧ = 556 × 10-12 m/A are found at θ = 0° and θ = 0°, ϕ = 45°, respectively. For space distribution of αE33‧, BaTiO3||[0 0 1]/CoFe2O4||[0 0 1] combination has the maximum value which applies to both 1-3 p/m (1.485 V/A) and 1-3 m/p composites (1.529 V/A). Volume fraction is quite independent of orientations of both piezoelectric and magnetic phases and the volume fraction for magnetic phase f around 0.5 obtains the largest αE33. The results suggest an approach to significantly enhancing magnetoelectric coefficient of composite multiferroic materials through crystal orientation controls of single crystals and textured ceramics.

Synthesis of Co3O4/TiO2 composite by pyrolyzing ZIF-67 for detection of xylene

Science.gov (United States)

Bai, Shouli; Tian, Ke; Tian, Ye; Guo, Jun; Feng, Yongjun; Luo, Ruixian; Li, Dianqing; Chen, Aifan; Liu, Chung Chiun

2018-03-01

Co3O4/TiO2 composites with p-n heterojunction have been successfully prepared by pyrolyzing sacrificial template of Ti ion loaded Co-based Zeolitic imidazolate framework (ZIF-67). The structure and morphology of composite have been characterized by means of the analysis of XRD, FESEM, HRTEM and XPS spectra. The composite with a Co/Ti molar ratio of 4:1 exhibits the maximum sensing response of 6.17-50 ppm xylene, which is 5 times higher than pristine Co3O4. Moreover, Co3O4/TiO2 composite also shows good selectivity, long-term stability and rapid response and recovery. Such excellent sensing performances are attributed to material porous structure, high specific surface and the formation of abundant p-n heterojunction that permits the gas adsorption, diffusion and surface reaction and then improve the gas sensing performance. This work develops a promising synthesized approach of metal oxide composites for broader MOFs application in gas sensor field.

Magnetic and microstructural properties of the BaFe(12-(4/3)x)SnxO19 ceramic system

International Nuclear Information System (INIS)

Marino-Castellanos, P.A.; Somarriba-Jarque, J.C.; Anglada-Rivera, J.

2005-01-01

The magnetic and microstructural properties of the M-type Sn 4+ -doped barium hexaferrite according to the stoichiometric formulation BaFe (12-(4/3)x) Sn x O 19 (x=0, 0.6, 0.8 and 1.0) have been studied. The XRD and magnetic analysis, using a rotating sample magnetometer, reveal that a correlation exists between the variation of the host lattice parameters and the decrease in the values of saturation magnetization, remnant magnetization and magnetic anisotropy with Sn 4+ content. This makes it possible to connect the microstructural properties to the magnetic behavior of doped barium hexaferrite at both microscopic and macroscopic levels

Facile synthesis of electrospun MFe2O4 (M = Co, Ni, Cu, Mn) spinel nanofibers with excellent electrocatalytic properties for oxygen evolution and hydrogen peroxide reduction

Science.gov (United States)

Li, Mian; Xiong, Yueping; Liu, Xiaotian; Bo, Xiangjie; Zhang, Yufan; Han, Ce; Guo, Liping

2015-05-01

Designing and preparing porous transition metal ferrites without using any template, shape-directing agent, and surfactant is a challenge. Herein, heterojunction MFe2O4 (M = Co, Ni, Cu, Mn) nanofiber (NF) based films with three-dimensional configurations were synthesized by electrospinning and the subsequent thermal treatment processes. Characterization results indeed show the 3D net-like textural structures of the electrospun spinel-type MFe2O4 NFs. In particular, the resulting MFe2O4 NFs have lengths up to several dozens of micrometers with an average diameter size of about 150 nm and possess abundant micro/meso/macropores on both the surface and within the films. The hierarchically porous structures and high surface areas of these MFe2O4 NFs (for example, the CoFe2O4 NFs possess a larger BET specific surface area (61.48 m2 g-1) than those of the CoFe2O4 NPs (5.93 m2 g-1)) can afford accessible transport channels for effectively decreasing the mass transport resistances, enhancing the electrical conductivity, and increasing the density and reactivity of the exposed catalytic active sites. All these advantages will be responsible for the better electrocatalytic performances of these MFe2O4 NFs compared with their structural isomers (i.e. the MFe2O4 NPs) for the oxygen evolution reaction (OER) and H2O2 reduction in alkaline solution. Meanwhile, both the OER and H2O2 reduction catalytic activities for these MFe2O4 NFs obey the order of CoFe2O4 NFs > CuFe2O4 NFs > NiFe2O4 NFs > MnFe2O4 NFs > Fe2O3 NFs. The CoFe2O4 NFs represent a new class of highly efficient non-noble-metal catalysts for both OER and H2O2 reduction/detection in alkaline media.Designing and preparing porous transition metal ferrites without using any template, shape-directing agent, and surfactant is a challenge. Herein, heterojunction MFe2O4 (M = Co, Ni, Cu, Mn) nanofiber (NF) based films with three-dimensional configurations were synthesized by electrospinning and the subsequent thermal treatment

Recycling of cobalt from spent Li-ion batteries as β-Co(OH)2 and the application of Co3O4 as a pseudocapacitor

Science.gov (United States)

Barbieri, E. M. S.; Lima, E. P. C.; Lelis, M. F. F.; Freitas, M. B. J. G.

2014-12-01

This work has investigated recycling cobalt from the cathodes of spent Li-ion batteries as β-Co(OH)2, obtaining Co3O4. β-Co(OH)2 with a hexagonal structure by using chemical precipitation (CP) or electrochemical precipitation (EP). In addition, the study has investigated whether the charge density applied directly affects the β-Co(OH)2 morphology. Co3O4 is formed by heat-treating β-Co(OH)2 at 450 °C for 3 h (h) in an air atmosphere. After calcining, the Co3O4 shows a cubic structure and satisfactory purity grade, regardless of the route used for preparation via which it was obtained. Cyclic voltammetry (CV) is then used for electrochemical characterization of the Co3O4 composite electrodes. In the cathodic process, CoO2 undergoes reduction to CoOOH, which undergoes further reduction to Co3O4. In the anodic process, Co3O4 undergoes oxidation to CoOOH, which simultaneously undergoes further oxidation to CoO2. The composite electrodes containing Co3O4, carbon black, and epoxy resin show great reversibility, charge efficiency, and a specific capacitance of 13.0 F g-1 (1.0 mV s-1). The synthesis method of Co(OH)2 influences the charge efficiency of Co3O4 composite electrodes at a scan rate of 10.0 mV s-1. Therefore, in addition to presenting an alternative use for exhausted batteries, Co3O4 composites exhibit favorable characteristics for use as pseudocapacitors.

Cauliflower-Like Co3O4/Three-Dimensional Graphene Composite for High Performance Supercapacitor Applications

Directory of Open Access Journals (Sweden)

Huili Liu

2015-01-01

Full Text Available Cauliflower-like Co3O4/three-dimensional (3D graphene nanocomposite material was synthesized by a facile two-step synthesis route (heat reduction of graphite oxide (GO and hydrothermal synthesis of Co3O4. The phase composition, morphology, and structure of the as-obtained products were characterized by scanning electron microscopy (SEM, transmission electron microscope (TEM, and X-ray diffraction (XRD. Electrochemical properties as supercapacitor electrode materials were systematically investigated by cyclic voltammetry (CV and constant current charge-discharge tests. It was found that the Co3O4/3D graphene composite showed a maximum specific capacitance of 863 F g−1, which was obtained by means of CVs at a scan rate of 1 mV s−1 in 6 M KOH aqueous solution. Moreover, the composite exhibited improved cycling stability after 1,000 cycles. The good supercapacitor performance is ascribed to the combination of 3D graphene and cauliflower-like Co3O4, which leads to a strong synergistic effect to remarkably boost the utilization ratio of Co3O4 and graphene for high capacitance.

New Method for Fabrication of Co3O4 Thin Film Sensors: Structural, Morphological and Optoelectronic Properties

Directory of Open Access Journals (Sweden)

Vikas PATIL

2011-05-01

Full Text Available Nanocrystalline Co3O4 thin films have been deposited by spin coating technique and then have been analyzed to test their application in NH3 gas-sensing technology. In particular, spectrophotometric and conductivity measurements have been performed in order to determine the optical and electrical properties of Co3O4 thin films. The structure and the morphology of such material have been investigated by X ray diffraction and Scanning electron microscopy. The X-ray diffraction studies confirmed that the films grown by this technique have good crystalline cubic spinel structure and present a random orientation. The morphology of the sol gel derived Co3O4 shows nanocrystalline grains with some overgrown clusters .The optical band gap has been determined from the absorption coefficient. We found that the optical band gap energy decreases from 2.58 eV to 2.07 eV with increasing annealing temperature between 400-700 oC. These mean that the optical quality of Co3O4 films is improved by annealing. The dc electrical conductivity of Co3O4 thin films were increased from 10-4 to 10-2(Ω cm-1 with increase in annealing temperature. The electron carrier concentration (n and mobility (μ of Co3O4 films annealed at 400-700 oC were estimated to be of the order of 2.4 to 4.5 x 1019 cm-3 and 5.2 to 7.0 x 10-5 cm2 V-1 s-1 respectively. It is observed that Co3O4 thin film annealing at 700 oC after deposition provide a smooth and flat texture suited for optoelectronic applications. Gas sensing properties showed that the Co3O4 films (at 700 oC were sensitive as well as fast in responding to NH3. A high sensitivity for ammonia indicates that the Co3O4 films are selective for this gas.

Controllable synthesis of Co{sub 3}O{sub 4}/polyethyleneimine-carbon nanotubes nanocomposites for CO and NH{sub 3} gas sensing at room temperature

Energy Technology Data Exchange (ETDEWEB)

Lin, Yufei [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China); Kan, Kan [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China); Institute of Advanced Technology, Heilongjiang Academy of Sciences, Harbin 150000 (China); Song, Wanzhen; Zhang, Guo; Dang, Lifang [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China); Xie, Yu [Department of Materials Chemistry, Nanchang Hangkong University, Nanchang 330063 (China); Shen, Peikang [Department of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Li, Li, E-mail: llwjjhlju@sina.cn [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China); Key Laboratory of Chemical Engineering Process & Technology for High-efficiency Conversion, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China); Shi, Keying, E-mail: shikeying2008@163.com [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China)

2015-08-05

Graphical abstract: Co{sub 3}O{sub 4}/polyethyleneimine-carbon nanotubes composites (CoPCNTs) have been successfully controllable synthesized via hydrothermal method at different temperature. The CoPCNTs sensors exhibited the highest response to CO and NH{sub 3} gases with response time of 4 s and 4.3 s, low detection limit of 5 ppm and 1 ppm at room temperature, respectively. The enhanced gas sensing could be ascribed to the synergistic effect between the tiny size of Co{sub 3}O{sub 4} and good conductivity of carbon nanotubes functionalized by polyethyleneimine. - Highlights: • The CNTs functionalized by polyethyleneimine provided a new functional structural. • The novel 1D structure could capture and migrate electrons quickly. • The Co{sub 3}O{sub 4} nanoparticles liked a snake winding around CNTs. • The gas sensor could work at room temperatures, which suit to practical application. - Abstract: A novel 1D Co{sub 3}O{sub 4}/polyethyleneimine-carbon nanotubes composites (CoPCNTs) have been successfully synthesized via hydrothermal method at different temperature. The CNTs functionalized by polyethyleneimine (PCNTs) provided a new material with new structural and functional properties. The PCNTs was used as loading guider and electron transfer path. The Co{sub 3}O{sub 4} nanoparticles (NPs) loaded on the PCNTs surface liked a snake winding around CNTs, and the size was about 5–10 nm. The gas sensing characteristics of the CoPCNTs sensors to carbon monoxide (CO) and ammonia (NH{sub 3}) were evaluated with different gas concentration. The CoPCNTs sensors grown at 160 °C exhibited the highest response to CO and NH{sub 3} gases with response time of 4 s and 4.3 s at room temperature (RT), respectively. Hence, the approach developed in this work would be important for the low-cost and large-scale production of the CoPCNTs materials with highly promising applications in gas sensors.

Tracking Solid Oxide Cell Microstructure Evolution by High Resolution 3D Nano-Tomography

DEFF Research Database (Denmark)

De Angelis, Salvatore

. The degradation processes are mainly attributed to morphological changes occurring within the electrodes microstructure. Therefore, precise tracking of 3D microstructural evolution during operation is considered crucial to understanding the complex relationship between microstructure and performance. In this work......, X-ray ptychographic tomography is applied to SOC materials, demonstrating unprecedented spatial resolution and data quality. The eect of a complete redox cycle on the same Ni-YSZ microstructure is visualized ex-situ in 3D, showing major rearrangement of the nickel network after reduction......, the formation of cracks in the YSZ, and void formation in nickel oxide after oxidation. Capitalizing on the high resolution of ptychography, the eect of nickel coarsening on the Ni-YSZ microstructure evolution is studied ex-situ in three dimensions, while the sample is repeatedly scanned and treated at high...

Current-voltage characteristics of SnO{sub 2}-Co{sub 3}O{sub 4}-Cr{sub 2}O{sub 3}-Sb{sub 2}O{sub 5} ceramics

Energy Technology Data Exchange (ETDEWEB)

Aguilar-Martinez, J A [Centro de Investigacion en Materiales Avanzados, S.C. (CIMAV), Alianza Norte 202, Parque de Investigacion e Innovacion Tecnologica (PIIT), Nueva Carretera Aeropuerto km. 10, Apodaca, Nuevo Leon, CP 66600 (Mexico); Glot, A B [Posgrado, Universidad Tecnologica de la Mixteca, Carretera Acatlima Km. 2.5, Huajuapan de Leon, Oaxaca, CP 69000 (Mexico); Gaponov, A V [Department of Radioelectronics, Dniepropetrovsk National University, Dniepropetrovsk 49050 (Ukraine); Hernandez, M B [Instituto de Mineria, Universidad Tecnologica de la Mixteca, Carretera Acatlima Km. 2.5, Huajuapan de Leon, Oaxaca, CP 69000 (Mexico); Guerrero-Paz, J, E-mail: josue.aguilar@cimav.edu.m [Particulate Materials Lab, Universidad Autonoma del Estado de Hidalgo, Pachuca, CP 42184 (Mexico)

2009-10-21

The effect of mechanical treatment in a planetary mill on the microstructure and electrical properties of tin dioxide based varistor ceramics in the system SnO{sub 2}-Co{sub 3}O{sub 4}-Cr{sub 2}O{sub 3}-Sb{sub 2}O{sub 5} sintered in the range 1150-1450 {sup 0}C was studied. The mechanical treatment leads to an increase in shrinkage, decrease in porosity, decrease in sample diameter, change in colour of the sintered samples from grey to black and enhancement of nonlinearity. For the sample sintered at 1350 {sup 0}C the mechanical treatment enhances the nonlinearity coefficient from 11 to 31 and decreases the electric field E{sub 1} (at 10{sup -3} A cm{sup -2}) from 3500 to 2800 V cm{sup -1}. The observed changes in physical properties are explained in terms of an additional size reduction of oxide particles and a better mixing of oxide powder followed by the formation of potential barriers at the grain boundaries throughout the whole sample. In spite of the low porosity, the low-field electrical conductivity of mechanically treated ceramics is significantly increased with the growth of relative humidity. A higher humidity sensitivity is found for mechanically treated ceramics with higher barrier height and higher nonlinearity coefficient.

The Comparative Study of Electrochemical Capacitance Performance between Sulphur-Doped Co3O4 and CoS Anodes

Directory of Open Access Journals (Sweden)

Wei Xu

2016-01-01

Full Text Available Anode materials with high capacitance performance are highly desirable for supercapacitors (SCs. In this work, nanomaterials cobalt sulfide (CoS, sulphur-doped Co3O4 (S-Co3O4, and Co3O4 were fabricated on a carbon cloth substrate by hydrothermal method. The composition and morphology of the material were characterized by X-ray diffraction (XRD patterns and Scanning Electron Microscope (SEM. The electrochemical measurements were performed in a three-electrode system. The result shows that CoS nanomaterial as anode is of the best electrochemical performance, achieving areal capacitance of 1.98 F/cm2 at 2 mA/cm2 in a 5 M LiCl solution. Moreover, the CoS anode has long-term cycling stability with more than 85.7% capacitance retention after 10000 cycles, confirming its larger capacitance, good redox activity, and electrochemical stability.

A facile route to controlled synthesis of Co3O4 nanoparticles and their environmental catalytic properties

International Nuclear Information System (INIS)

Dong Yuming; He Kun; Yin Lin; Zhang Aimin

2007-01-01

Using ammonia and Co(CH 3 COO) 2 ·4H 2 O as starting materials, a facile and surfactant-free route to controlled synthesis of Co 3 O 4 nanoparticles was proposed. Co 3 O 4 nanoparticles with average sizes of 3.5, 6, 11, 19 and 70 nm were obtained through adjusting the ethanol amount in the solvent (the ratio of ethanol to water) or the concentration of raw materials. In this process, the presence of enough O 2 was crucial for the formation of pure Co 3 O 4 phase. The environmental catalytic properties of as-obtained Co 3 O 4 nanoparticles were investigated. The results indicated their remarkable catalysis for ozonation degradation of phenol, which denoted a promising application as catalyst in waste-water treatment

Ternary mixed metal Fe-doped NiCo2O4 nanowires as efficient electrocatalysts for oxygen evolution reaction

Science.gov (United States)

Yan, Kai-Li; Shang, Xiao; Li, Zhen; Dong, Bin; Li, Xiao; Gao, Wen-Kun; Chi, Jing-Qi; Chai, Yong-Ming; Liu, Chen-Guang

2017-09-01

Designing mixed metal oxides with unique nanostructures as efficient electrocatalysts for water electrolysis has been an attractive approach for the storage of renewable energies. The ternary mixed metal spinel oxides FexNi1-xCo2O4 (x = 0, 0.1, 0.25, 0.5, 0.75, 0.9, 1) have been synthesized by a facile hydrothermal approach and calcination treatment using nickel foam as substrate. Fe/Ni ratios have been proved to affect the nanostructures of FexNi1-xCo2O, which imply different intrinsic activity for oxygen evolution reaction (OER). SEM images show that Fe0.5Ni0.5Co2O4 has the uniform nanowires morphology with about 30 nm of the diameter and 200-300 nm of the length. The OER measurements show that Fe0.5Ni0.5Co2O4 exhibits the better electrocatalytic performances with lower overpotential of 350 mV at J = 10 mA cm-2. In addition, the smaller Tafel slope of 27 mV dec-1 than other samples with different Fe/Ni ratios for Fe0.5Ni0.5Co2O4 is obtained. The improved OER activity of Fe0.5Ni0.5Co2O4 may be attributed to the synergistic effects from ternary mixed metals especially Fe-doping and the uniform nanowires supported on NF. Therefore, synthesizing Fe-doped multi-metal oxides with novel nanostructures may be a promising strategy for excellent OER electrocatalysts and it also provides a facile way for the fabrication of high-activity ternary mixed metal oxides electrocatalysts.

Hollow carbon spheres with encapsulation of Co3O4 nanoparticles as anode material for lithium ion batteries

International Nuclear Information System (INIS)

Zhan Liang; Wang Yanli; Qiao Wenming; Ling, Licheng; Yang Shubin

2012-01-01

Graphical abstract: Hollow carbon spheres with encapsulation of Co 3 O 4 nanoparticles were synthesized. As anode materials for lithium ion battery, the reversible capacity of obtained electrode is as high as 732 mAh g −1 at 74 mA g −1 and 500 mAh g −1 at 744 mA g −1 . - Abstract: Based on the high theoretical capacity of Co 3 O 4 for lithium storage, a noval type of monodisperse hollow carbon spheres with encapsulation of Co 3 O 4 nanoparticles (HCSE-Co 3 O 4 ) were designed and synthesized. The monodisperse hollow carbon spheres not only can provide enough void volume to accommodate the volume change of encapsulated Co 3 O 4 nanoparicles, but also can prevent the formation of solid electrolyte interface (SEI) films on the surface of Co 3 O 4 nanoparticles and following direct contact of Co and SEI films upon lithium extraction. The HCSE-Co 3 O 4 electrode exhibit highly reversible capacity, excellent cycle performance and rate capability attributed to the unique structure. The reversible capacity of HCSE-Co 3 O 4 electrode is as high as 500 mAh g −1 at a current density of 744 mA g −1 , while that of bare Co 3 O 4 electrode is only around 80 mAh g −1 .