Hydrothermal synthesis of transition metal oxides under mild conditions

1996 ◽  
Vol 1 (2) ◽  
pp. 227-232 ◽  
Author(s):  
M Stanley Whittingham
Keyword(s):  
Hydrothermal Synthesis ◽  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Mild Conditions

Group 5–7 transition metal oxides as efficient catalysts for oxidative functionalization of alkanes under mild conditions

2007 ◽  
Vol 248 (1) ◽  
pp. 130-136 ◽  
Author(s):  
M KIRILLOVA ◽  
A KIRILLOV ◽  
P REIS ◽  
J SILVA ◽  
J FRAUSTODASILVA ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Oxidative Functionalization ◽  
Mild Conditions ◽  
Group 5

scholarly journals Hydrothermal Synthesis of Three-Dimensional Perovskite NiMnO3 Oxide and Application in Supercapacitor Electrode

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 36 ◽  
Author(s):  
Hyo-Young Kim ◽  
Jeeyoung Shin ◽  
Il-Chan Jang ◽  
Young-Wan Ju
Keyword(s):  
Hydrothermal Synthesis ◽  
Transition Metal ◽  
Specific Surface ◽  
Metal Oxides ◽  
Surface Area ◽  
Specific Surface Area ◽  
Transition Metal Oxides ◽  
Coulombic Efficiency ◽  
Three Dimensional ◽  
Perovskite Oxide

Supercapacitors are attractive as a major energy storage device due to their high coulombic efficiency and semi-permanent life cycle. Transition metal oxides are used as electrode material in supercapacitors due to their high conductivity, capacitance, and multiple oxidation states. Nanopowder transition metal oxides exhibit low specific surface area, ion diffusion, electrical conductivity, and structural stability compared with the three-dimensional (3D) structure. Furthermore, unstable performance during long-term testing can occur via structural transition. Therefore, it is necessary to synthesize a transition metal oxide with a high specific surface area and a stable structure for supercapacitor application. Transition metal oxides with a perovskite structure control structural transition and improve conductivity. In this study, a NiMnO3 perovskite oxide with a high specific surface area and electrochemical properties was obtained via hydrothermal synthesis at low temperature. Hydrothermal synthesis was used to fabricate materials with an aqueous solution under high temperature and pressure. The shape and composition were regulated by controlling the hydrothermal synthesis reaction temperature and time. The synthesis of NiMnO3 was controlled by the reaction time to alter the specific surface area and morphology. The prepared perovskite NiMnO3 oxide with a three-dimensional structure can be used as an active electrode material for supercapacitors and electrochemical catalysts. The prepared NiMnO3 perovskite oxide showed a high specific capacitance of 99.03 F·g−1 and excellent cycle stability with a coulombic efficiency of 77% even after 7000 cycles.

Subcritical Hydrothermal Synthesis of Perovskite Manganites:  A Direct and Rapid Route to Complex Transition-Metal Oxides

2003 ◽  
Vol 15 (7) ◽  
pp. 1401-1403 ◽  
Author(s):  
Jeroen Spooren ◽  
Anja Rumplecker ◽  
Franck Millange ◽  
Richard I. Walton
Keyword(s):  
Hydrothermal Synthesis ◽  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Perovskite Manganites

HREM Study of electron-induced surface radiation damage in ReO3

1991 ◽  
Vol 49 ◽  
pp. 636-637
Author(s):  
R. Ai ◽  
H.-J. Fan ◽  
L. D. Marks
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Metal Oxides ◽  
Electron Irradiation ◽  
Transition Metal Oxides ◽  
Carbon Film ◽  
Transition Metal Ions ◽  
Surface Radiation ◽  
Valence Transition ◽  
Electron Microscopes

It has been known for a long time that electron irradiation induces damage in maximal valence transition metal oxides such as TiO2, V2O5, and WO3, of which transition metal ions have an empty d-shell. This type of damage is excited by electronic transition and can be explained by the Knoteck-Feibelman mechanism (K-F mechanism). Although the K-F mechanism predicts that no damage should occur in transition metal oxides of which the transition metal ions have a partially filled d-shell, namely submaximal valence transition metal oxides, our recent study on ReO3 shows that submaximal valence transition metal oxides undergo damage during electron irradiation.ReO3 has a nearly cubic structure and contains a single unit in its cell: a = 3.73 Å, and α = 89°34'. TEM specimens were prepared by depositing dry powders onto a holey carbon film supported on a copper grid. Specimens were examined in Hitachi H-9000 and UHV H-9000 electron microscopes both operated at 300 keV accelerating voltage. The electron beam flux was maintained at about 10 A/cm2 during the observation.

Problems with oxygen analysis in the system MgO-Al2O3-SiO2 with the electron microprobe

1992 ◽  
Vol 50 (2) ◽  
pp. 1624-1625
Author(s):  
Michel Fialin ◽  
Guy Rémond
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Electrostatic Charge ◽  
Carbon Layer ◽  
Sample Holder ◽  
Rock Matrix ◽  
Electrical Discharges ◽  
Thin Carbon ◽  
Beam Instabilities

Oxygen-bearing minerals are generally strong insulators (e.g. silicates), or if not (e.g. transition metal oxides), they are included within a rock matrix which electrically isolates them from the sample holder contacts. In this respect, a thin carbon layer (150 Å in our laboratory) is evaporated on the sections in order to restore the conductivity. For silicates, overestimated oxygen concentrations are usually noted when transition metal oxides are used as standards. These trends corroborate the results of Bastin and Heijligers on MgO, Al2O3 and SiO2. According to our experiments, these errors are independent of the accelerating voltage used (fig.l).Owing to the low density of preexisting defects within the Al2O3 single-crystal, no significant charge buildup occurs under irradiation at low accelerating voltage (< 10keV). As a consequence, neither beam instabilities, due to electrical discharges within the excited volume, nor losses of energy for beam electrons before striking the sample, due to the presence of the electrostatic charge-induced potential, are noted : measurements from both coated and uncoated samples give comparable results which demonstrates that the carbon coating is not the cause of the observed errors.

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