Preparation of Photocatalytically Active Titanium Dioxide Doped with Transition Metal Oxides

2018 ◽  
Vol 88 (3) ◽  
pp. 528-531 ◽  
Author(s):  
A. V. Zdravkov ◽  
V. A. Gorbunova ◽  
A. V. Volkova ◽  
N. N. Khimich
Keyword(s):  
Titanium Dioxide ◽  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides

Titanium dioxide supported on MWCNTs as an eco-friendly catalyst in the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones accelerated under microwave irradiation

2014 ◽  
Vol 38 (8) ◽  
pp. 3514-3521 ◽  
Author(s):  
Javad Safari ◽  
Soheila Gandomi-Ravandi
Keyword(s):  
Titanium Dioxide ◽  
Transition Metal ◽  
Microwave Irradiation ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Heterogeneous Catalysts ◽  
Biginelli Compounds

Some transition metal oxides supported on MWCNTs were prepared as novel heterogeneous catalysts using the facile processes. These catalysts were used for the synthesis of Biginelli compounds under microwave irradiation.

scholarly journals Can Doping of Transition Metal Oxide Cathode Materials Increase Achievable Voltages with Multivalent Metals?

2019 ◽  
Author(s):  
Daniel Koch ◽  
Sergei Manzhos
Keyword(s):  
Titanium Dioxide ◽  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
High Performance ◽  
Molybdenum Trioxide ◽  
Type Systems ◽  
Hole Doping ◽  
Earth Abundant ◽  
Valence Bands

We investigate from first principles the use of substitutional p-doping as a means to enhance the insertion energies of multivalent metals in transition metal oxides, and therefore the resulting voltages in an electrochemical cell, due to bandstructure modulation. Multivalent and earth-abundant metals such as magnesium or aluminium are attractive candidates to replace lithium in future high-performance secondary batteries with intercalation-type electrodes. Unfortunately, the achievable voltages obtained with this kind of elements still remain uncompetitively low. We study and compare the changes in insertion energetics (voltages) of single- and multivalent metals in semiconducting and insulating transition metal oxides upon substitutional p-doping with different metals, introducing different numbers of hole states. We use a single vanadium pentoxide monolayer as model system to study the effect of p-doping on achievable voltages and deduce general trends for transition metal oxides. Our investigations reveal the formation of n-hole polarons (with n>1) in form of oxygen dimers in p-doped vanadia caused by localized <i>p</i> holes on oxide ions in agreement with previous findings. We find that the oxygen dimer formation has an adverse effect on adsorption energetics compared to the single-hole case without dimerization. We find an analogous oxygen dimerization in other TMOs with oxygen-dominated valence bands like molybdenum trioxide and titanium dioxide, while strained systems like trigonal nickel- or titanium dioxide, or Mott-type systems like monoclinic vanadium dioxide with qualitatively different valence band composition do not exhibit oxygen dimerization with multi-hole doping. Our results demonstrate the advantages and limitations of TMO electrode p-doping and show a path to possible strategies to overcome detrimental effects.

scholarly journals Can Doping of Transition Metal Oxide Cathode Materials Increase Achievable Voltages with Multivalent Metals?

2019 ◽  
Author(s):  
Daniel Koch ◽  
Sergei Manzhos
Keyword(s):  
Titanium Dioxide ◽  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
High Performance ◽  
Molybdenum Trioxide ◽  
Type Systems ◽  
Hole Doping ◽  
Earth Abundant ◽  
Valence Bands

We investigate from first principles the use of substitutional p-doping as a means to enhance the insertion energies of multivalent metals in transition metal oxides, and therefore the resulting voltages in an electrochemical cell, due to bandstructure modulation. Multivalent and earth-abundant metals such as magnesium or aluminium are attractive candidates to replace lithium in future high-performance secondary batteries with intercalation-type electrodes. Unfortunately, the achievable voltages obtained with this kind of elements still remain uncompetitively low. We study and compare the changes in insertion energetics (voltages) of single- and multivalent metals in semiconducting and insulating transition metal oxides upon substitutional p-doping with different metals, introducing different numbers of hole states. We use a single vanadium pentoxide monolayer as model system to study the effect of p-doping on achievable voltages and deduce general trends for transition metal oxides. Our investigations reveal the formation of n-hole polarons (with n>1) in form of oxygen dimers in p-doped vanadia caused by localized <i>p</i> holes on oxide ions in agreement with previous findings. We find that the oxygen dimer formation has an adverse effect on adsorption energetics compared to the single-hole case without dimerization. We find an analogous oxygen dimerization in other TMOs with oxygen-dominated valence bands like molybdenum trioxide and titanium dioxide, while strained systems like trigonal nickel- or titanium dioxide, or Mott-type systems like monoclinic vanadium dioxide with qualitatively different valence band composition do not exhibit oxygen dimerization with multi-hole doping. Our results demonstrate the advantages and limitations of TMO electrode p-doping and show a path to possible strategies to overcome detrimental effects.

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.

scholarly journals Electronic Phenomena of Transition Metal Oxides

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 256
Author(s):  
Christian Rodenbücher ◽  
Kristof Szot
Keyword(s):  
Solid State ◽  
Transition Metal ◽  
Metal Oxides ◽  
Real World ◽  
Transition Metal Oxides ◽  
Major Research ◽  
Research Fields ◽  
Real World Applications

Transition metal oxides with ABO3 or BO2 structures have become one of the major research fields in solid state science, as they exhibit an impressive variety of unusual and exotic phenomena with potential for their exploitation in real-world applications [...]

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