Controlled potential studies on the Kolbe reaction and the role of coadsorbed surface oxides. II. The reaction at gold

Galvanostatic cathodic discharge and open-circuit decay transients have been obtained for the decarboxylation of formate in formic acid and interpreted quantitatively in terms of the adsorption of intermediates in the reaction. These intermediates are identified with HCOO• radicals. Extended anodic polarization at platinum and particularly at palladium leads to the formation of films of an anodic product which are considerably thicker than a monolayer. After relatively long times (> 100 seconds) of anodic polarization, the film growth obeys the inverse logarithmic rate law deduced by Mott and Cabrera. The thick films which are formed at palladium are believed to be responsible, upon autocatalytic decomposition, for the delayed gas evolution phenomenon observed at this metal.A new method for deduction of adsorption pseudocapacitance and charge associated with the ad-layer from open-circuit decay curves and Tafel parameters is used to obtain the pseudo-capacitance and charge associated with the transition region in the current–potential curves for the formate decarboxylation. It is shown that this region corresponds to filling of the surface with adsorbed intermediates formed in the reaction. These observations are shown to support the reaction mechanism proposed in Part I.

Download Full-text

On the Insignificant Role of the Oxidation Process on Ultrafast High-Spatial-Frequency LIPSS Formation on Tungsten

Nanomaterials ◽

10.3390/nano11051069 ◽

2021 ◽

Vol 11 (5) ◽

pp. 1069

Author(s):

Priya Dominic ◽

Florent Bourquard ◽

Stéphanie Reynaud ◽

Arnaud Weck ◽

Jean-Philippe Colombier ◽

...

Keyword(s):

Spatial Frequency ◽

Ambient Pressure ◽

High Spatial Frequency ◽

Native Oxide ◽

Native Oxide Layer ◽

Periodic Surface ◽

Plasma Sputtering ◽

Surface Oxides ◽

20 Nm

The presence of surface oxides on the formation of laser-induced periodic surface structures (LIPSS) is regularly advocated to favor or even trigger the formation of high-spatial-frequency LIPSS (HSFL) during ultrafast laser-induced nano-structuring. This paper reports the effect of the laser texturing environment on the resulting surface oxides and its consequence for HSFLs formation. Nanoripples are produced on tungsten samples using a Ti:sapphire femtosecond laser under atmospheres with varying oxygen contents. Specifically, ambient, 10 mbar pressure of air, nitrogen and argon, and 10−7 mbar vacuum pressure are used. In addition, removal of any native oxide layer is achieved using plasma sputtering prior to laser irradiation. The resulting HSFLs have a sub-100 nm periodicity and sub 20 nm amplitude. The experiments reveal the negligible role of oxygen during the HSFL formation and clarifies the significant role of ambient pressure in the resulting HSFLs period.

Download Full-text

Effect of Mn on Texture Evolution in Fe-Si-Mn Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.702-703.730 ◽

2011 ◽

Vol 702-703 ◽

pp. 730-733 ◽

Cited By ~ 3

Author(s):

Jin Kyung Sung ◽

Se Min Park ◽

Byoung Yul Shim ◽

Yang Mo Koo

Keyword(s):

Elastic Modulus ◽

Metal Surface ◽

Strain Energy ◽

Texture Evolution ◽

High Oxygen ◽

Annealing Atmosphere ◽

Surface Oxides ◽

Alloy Systems

The texture can be evolved through the γ to α transformation by cooling in Fe-Si alloy systems. Oxygen in the annealing atmosphere hampers the evolution of the texture. The texture evolution is associated with the fact that the {100} faces are elastically compliant so that the texture can develop in a manner consistent with minimization of strain energy. By alloying Mn to Fe-Si alloys, the texture evolves in relatively high oxygen containing annealing atmosphere. The role of Mn in the texture evolution appears to be preventing formation of surface oxides, which modify the elastic modulus of metal surface, thereby suppress the development of the correct texture.

Download Full-text