The short-range order of anodic amorphous oxide films of Ta and Nb

Алешина, Л. А.; Malinenko, V. P.; Phouphanov, A.D.; Jakovleva, N.M.

doi:10.1016/s0022-3093(86)80008-4

Cited by 37 publications

(30 citation statements)

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“…The magnetite nanoparticle sizes for both calcined and un-calcined samples, which were determined using the Scherrer formula [26], were around 8.8-9.0 nm.…”

Section: Resultsmentioning

confidence: 99%

Direct conversion of cellulose to α-hydroxy acids (AHAs) over Nb₂O₅-SiO₂-coated magnetic nanoparticles

Candu

Anita

Podolean

et al. 2017

Green Processing and Synthesis

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A series of Nb (3 wt% or 60 wt% Nb 2 O 5 )-based magnetic nanocomposites (Nb-Si@MNP) was prepared by covering the magnetic cores with Nb 2 O 5 -SiO 2 shells using either co-precipitation or sol-gel followed by precipitation methods. These materials were exhaustively characterized through XRD, Raman spectroscopy, CO 2 -and NH 3 -TPD, DRIFT spectroscopy, and TG-DTA, after which the catalytic one-pot conversion of cellulose to valuable α-hydroxy-acids (i.e. lactic and glycolic acids) was investigated. The catalytic performances, expressed in terms of lactic and glycolic acid yields, were directly correlated to the nature of the catalytic sites which, in turn, depended on the niobia content and the preparation route.

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“…The magnetite nanoparticle sizes for both calcined and un-calcined samples, which were determined using the Scherrer formula [26], were around 8.8-9.0 nm.…”

Section: Resultsmentioning

confidence: 99%

Direct conversion of cellulose to α-hydroxy acids (AHAs) over Nb₂O₅-SiO₂-coated magnetic nanoparticles

Candu

Anita

Podolean

et al. 2017

Green Processing and Synthesis

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“…The time of oxide formation was 40 min (Aleshina & Lugovskaya, 1997). Then, some ®lms were separated from the metallic substrates and used for preparing powder specimens.…”

Section: à2mentioning

confidence: 99%

“…The methods for introducing various corrections to the experimental curves and for calculating H(s) and D(r) are considered elsewhere (Aleshina et al, 1986;Aleshina & Fofanov, 1987). The coordination numbers N ij from the distribution curves of the pair functions at given values of the radii r ij of the coordination spheres and their dispersions ' ij were determined by the method of singular expansion (Forsythe et al, 1977;Lawson & Hanson, 1974).…”

Section: à2mentioning

confidence: 99%

“…The coordination numbers N ij from the distribution curves of the pair functions at given values of the radii r ij of the coordination spheres and their dispersions ' ij were determined by the method of singular expansion (Forsythe et al, 1977;Lawson & Hanson, 1974). The r ij and ' ij values were obtained using the method of successive approximations, so the discrepancy between the experimental curve and the curve obtained from the set of N ij , r ij and ' ij did not exceed 5% (Aleshina et al, 1986;Aleshina & Fofanov, 1987). The types of experimental errors and their effect on the D(r) curve were determined using the inverse Fourier transform (Aleshina et al, 1995).…”

Section: à2mentioning

confidence: 99%

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X-ray study and structure simulation of amorphous tungsten oxide

Lugovskaya

Алешина

Kalibaeva

et al. 2002

Acta Crystallogr Sect B

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In this work, X-ray studies of the amorphous oxide ®lms obtained by thermal evaporation of WO 3 powder in a vacuum and by anodic oxidation were carried out. X-ray diffraction patterns were obtained in the symmetric re¯ection geometry on a DRON-4 diffractometer (Mo K radiation, LiF monochromator) in automatic mode. Molecular dynamics simulation of amorphous tungsten oxide atomic con®gurations has been carried out in the micro-canonical ensemble (NVE) for N = 208 atoms and N = 624 atoms, in a cubic cell, using pairwise Born±Mayer interaction potentials and periodic boundary conditions. One of the purposes of the present work is to analyze the in¯uence of the parameters and the cutoff of the interaction potentials on the interatomic distances. The values obtained in the molecular dynamics simulation for the pair functions D(r) are compared with the experimental data for amorphous oxides in order to choose the most convenient aforesaid values. The values of the average interatomic distances and the coordination numbers obtained by both methods are also compared. The result shows that the tungsten subsystem can be well reproduced using the potential cutoff radius of about 4 A Ê , but the oxygen subsystem can be well reproduced when the cutoff of the potential for the WÐO pairs is equal to 2.8 A Ê . The con®guration built during the molecular dynamics experiment consists of distorted octahedra. These octahedra form chains, as in the WO 3 phases of type ReO 3 , and hexagonal rings, of the same type as in the WO 3 (1/3)H 2 O phase, when we extract (1/3)O at every WO 3 unit. The pair function D(r) and scattering intensity I(s) distribution curves calculated for simulation con®gurations show a satisfactory agreement with experiment.

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“…Air-formed film and anodic oxide film on tantalum have amorphous structures with fine crystallines of β-Ta 2 O 5 [19]. Although the mechanical properties of the tantalum amorphous oxide are unknown, the recent nano-indentation test indicated that the hardness of tantalum anodic oxide was three times as much as that of the substrate metallic tantalum [20].…”

Section: Formation Mechanism Of the Protrusion Proposed To Explain Thmentioning

confidence: 99%

Nano-scratching in solution to the single-crystal Ta (100) subjected to anodic oxidation

Seo

Kawamata²

2006

J. Phys. D: Appl. Phys.

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Abstract.A single crystal-tantalum (100) surface was anodically oxidized at 5.0 V (SHE) for 1 h in pH 8.4 borate buffer solution. Nano-scratching in solution at a constant normal force of 300 µN was performed to the tantalum (100) surface kept at 5.0 V (SHE) after anodic oxidation. Nano-scratching in air was also performed to the tantalum (100) surface after anodic oxidation. A stick-slip was always observed in lateral force vs. lateral displacement curves during nano-scratching in solution. The degree of stick-slip, however, decreased with increasing scratching rate. The average friction coefficient obtained with nano-scratching in solution was significantly larger than that obtained with nano-scratching in air and increased linearly with logarithm of time required for scratching. In contrast, the friction coefficient obtained with nano-scratching in air was independent of time required for scratching. The protrusion at the scratching end of the groove produced by nano-scratching in solution was observed from the AFM image, while no protrusion was observed for nano-scratching in air. It has been proposed that the protrusion consists of anodic oxide accumulated on the moving front of the indenter tip during nano-scratching in solution and contributes to the increase in lateral force, i.e., friction coefficient.

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The short-range order of anodic amorphous oxide films of Ta and Nb

Cited by 37 publications

References 5 publications

Direct conversion of cellulose to α-hydroxy acids (AHAs) over Nb₂O₅-SiO₂-coated magnetic nanoparticles

Direct conversion of cellulose to α-hydroxy acids (AHAs) over Nb₂O₅-SiO₂-coated magnetic nanoparticles

X-ray study and structure simulation of amorphous tungsten oxide

Nano-scratching in solution to the single-crystal Ta (100) subjected to anodic oxidation

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The short-range order of anodic amorphous oxide films of Ta and Nb

Cited by 37 publications

References 5 publications

Direct conversion of cellulose to α-hydroxy acids (AHAs) over Nb2O5-SiO2-coated magnetic nanoparticles

Direct conversion of cellulose to α-hydroxy acids (AHAs) over Nb2O5-SiO2-coated magnetic nanoparticles

X-ray study and structure simulation of amorphous tungsten oxide

Nano-scratching in solution to the single-crystal Ta (100) subjected to anodic oxidation

Contact Info

Product

Resources

About

Direct conversion of cellulose to α-hydroxy acids (AHAs) over Nb₂O₅-SiO₂-coated magnetic nanoparticles

Direct conversion of cellulose to α-hydroxy acids (AHAs) over Nb₂O₅-SiO₂-coated magnetic nanoparticles