E. Rayón

Microstructure, mechanical, and thermogravimetric characterization of cellulosic by-products obtained from biomass seeds.

The microstructural, thermal, and nanomechanical characterization of biomass by-products coming from the food industry were studied. Scanning electron microscopy showed a microstructure formed by polygonal grains. The thermal behavior of seeds, evaluated by thermogravimetric analysis, revealed three main components (hemicellulose, cellulose, and lignin). Walnut shell showed the highest thermal stability and also the highest amount of lignin. The nanomechanical aspects were evaluated by nanoindentation. Samples with higher amount of cellulose presented minor modulus values. In accordance with the thermal stability, the highest modulus and hardness were observed in walnut. These by-products could be useful as reinforcement materials for biodegradable plastic industry.

Electrochemical Oscillation of Open Circuit Potential during Immersion Plating of Copper on Silicon

A new type of oscillation emerging during copper immersion plating on silicon in solutions containing HF was observed. It is the spontaneous oscillation of open-circuit potential rather than the oscillations which have been observed on silicon under high polarization. The oscillation appears at less-noble potential and in a limited HF concentration range, and the amplitude is small. The behavior is affected by the type of dopant and dopant concentration and by the surface condition. The phenomenon is likely to be explained based on reactions occurring during immersion plating in the presence of fluoride ions: the oxide formation-breakdown-repair model. However, some results cannot be simply explained by the model.

Contact Mechanics at Nanometric Scale Using Nanoindentation Technique for Brittle and Ductile Materials

In the last years, Nanoindentation or Instrumented Indentation Technique has become a powerful tool to study the mechanical properties at micro/nanometric scale (commonly known as hardness, elastic modulus and the stress-strain curve). In this review, the different contact mechanisms (elastic and elasto-plastic) are discussed, the recent patents for each mechanism (elastic and elasto-plastic) are summarized in detail, and the basic equations employed to know the mechanical behaviour for brittle and ductile materials are described.

Mechanical Properties of Double-Layer and Graded Composite Coatings of YSZ Obtained by Atmospheric Plasma Spraying

Double-layer and graded composite coatings of yttria-stabilized zirconia were sprayed on metallic substrates by atmospheric plasma spray. The coating architecture was built up by combining two different feedstocks: one micro- and one nanostructured. Microstructural features and mechanical properties (hardness and elastic modulus) of the coatings were determined by FE-SEM microscopy and nanoindentation technique, respectively. Additional adherence and scratch tests were carried out in order to assess the failure mechanisms occurring between the layers comprising the composites. Microstructural inspection of the coatings confirms the two-zone microstructure. This bimodal microstructure which is exclusive of the layer obtained from the nanostructured feedstock negatively affects the mechanical properties of the whole composite. Nanoindentation tests suitably reproduce the evolution of mechanical properties through coatings thickness on the basis of the position and/or amount of nanostructured feedstock used in the depositing layer. Adhesion and scratch tests show the negative effect on the coating adhesion of layer obtained from the nanostructured feedstock when this layer is deposited on the bond coat. Thus, the poor integrity of this layer results in lower normal stresses required to delaminate the coating in the adhesion test as well as minor critical load registered by using the scratch test.

Optical and Electrical Properties of Mg ∕ Ni Alloy Subjected to Electrochemical Hydrogenation

The work is aimed at studying properties of the Mg–Ni alloy thin film during electrochemical hydrogenation in an alkalineelectrolyte.Wehavesimultaneouslymeasuredthekineticsofthecathodicprocessesundergalvanostaticconditionsandchangesin optical transmission. We have performed in situ ac impedance measurements of gradually hydrogenated films to monitorchangesintheirelectricalproperties.Mg–Nialloysdemonstratehighopticalcontrastduringelectrochemicalhydrogenationduetoswitchingbetweenreflectiveandtransparentstates,excellentreversibilityofthehydrogenation–dehydrogenationreaction,andfairservicetime.Thevalueoftheacimpedancetechniqueforstudyingthecomplexelectricalprocessesaccompanyingtheincorpo-rationofhydrogenintoactivemetalsandalloysisdemonstrated.©2005TheElectrochemicalSociety. @DOI:10.1149/1.2083107 # Allrightsreserved.ManuscriptsubmittedMarch29,2005;revisedmanuscriptreceivedJuly21,2005.AvailableelectronicallyOctober17,2005.

Cambios en la estructura cuticular Ornithodoros erraticus hembra durante el proceso de alimentación

Los autores desean expresar su agradecimiento a D. Antonio Encinas Grandes por el suministro de Ornithodoros erraticus del area de Salamanca (Espana) y por su gran aportacion a este trabajo mediante la revision y discusion de los resultados obtenidos. Asi mismo, al servicio de microscopia de la Universidad Politecnica de Valencia. MP Arrieta ha sido becada por la Comunitat Valenciana (Grisolia/2011/007). El presente trabajo ha sido fi nanciado por el Ministerio de Educacion y Ciencia (MAT2011-28468-C02-02).