Mechanism of anodic oxidation of molybdenum in nearly-neutral electrolytes studied by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy

Anodic oxidation of molybdenum in weakly acidic, nearly neutral and weakly alkaline electrolytes was studied by voltammetric and electrochemical impedance spectroscopic measurements in a wide potential and pH range. Current vs. potential curves were found to exhibit two pseudo-Tafel regions suggesting two parallel pathways of the dissolution process. Electrochemical impedance spectra indicated the presence of at least two reaction intermediates. X-ray photoelectron spectroscopic (XPS) results pointed to the formation of an oxide containing Mo(IV), Mo(V) and Mo(VI), the exact ratio between different valence states depending on potential and pH of the solution. A physico-chemical model of the processes is proposed and a set of kinetic equations for the steady-state current vs. potential curve and the impedance response are derived. The model is found to reproduce quantitatively the current vs. potential curves and impedance spectra at a range of potentials and pH and to agree qualitatively with the XPS results. Subject to further improvement, the model could serve as a starting point for the optimization of the electrochemical fabrication of functional molybdenum oxide coatings.     

Influence of Silicification on the Structural and Biological Properties of Buffer‐Mediated Collagen Hydrogels

A buffer‐mediated gelation route for collagen hydrogels that allows the formation of homogeneous composite and hybrid materials with various silica sources (i.e., colloidal silica and soluble silicates) at high concentration (up to 25 × 10^?3 M ) is described. Most significant improvement in rheological properties and proliferation of primary adult human dermal fibroblasts was obtained for the silicate‐based hybrid materials. A similar trend was observed in composite materials incorporating 14 nm SiO₂ nanoparticles, although to a much lesser extent, whereas larger colloids (80 and 390 nm) did not significantly impact mechanical stability and cell behavior. Modification of 80 nm particles surface with amine groups weakens the collagen‐mineral interface, resulting in the decrease of material stability and leading to particle aggregation during the course of cell proliferation experiments.     

Steerable miniature jumping robot

Jumping is used in nature by many small animals to locomote in cluttered environments or in rough terrain. It offers small systems the benefit of overcoming relatively large obstacles at a low energetic cost. In order to be able to perform repetitive jumps in a given direction, it is important to be able to upright after landing, steer and jump again. In this article, we review and evaluate the uprighting and steering principles of existing jumping robots and present a novel spherical robot with a mass of 14 g and a size of 18 cm that can jump up to 62 cm at a take-off angle of 75°, recover passively after landing, orient itself, and jump again. We describe its design details and fabrication methods, characterize its jumping performance, and demonstrate the remote controlled prototype repetitively moving over an obstacle course where it has to climb stairs and go through a window. (See videos 1–4 in the electronic supplementary material.)     

A first quantitative XPS study of the surface films formed, by exposure to water, on Mg and on the Mg-Al intermetallics: Al3Mg2 and Mg17Al12

An XPS investigation was carried out of the surface films, formed by exposure to ultrapure water, on mechanically ground Mg and the two Mg-Al intermetallic compounds: Al₃Mg₂ and Mg₁₇Al₁₂. The mechanically ground Mg surface had a film of MgO at the Mg metal surface covered by a Mg(OH)₂ layer, formed by the reaction of the MgO with water vapour in the air. Upon immersion in ultrapure water, this film converted to a duplex film with an inner MgO layer next to the Mg metal and an external porous hydroxide layer. For both intermetallics, the XPS data is consistent with (i) preferential dissolution of Mg and (ii) a 10 nm thick film on the surface after immersion in ultrapure water; the film composition on Al₃Mg₂ was AlMg_1.4O_0.2(OH)_5.4 whilst on Mg₁₇Al₁₂ the composition was AlMg_2.5(OH)₈.     

Sensory profiles and preference analysis in ornamental horticulture: The case of the rosebush

The context of ornamental horticulture is considered in order to extend the techniques of sensory and preference evaluation by taking the rosebush as a plant model. In a preliminary study (Boumaza, Demotes-Mainard, Huché-Thélier, & Guérin, 2009), a sensory evaluation was conducted in order to set up a list of attributes. Subsequently, this list was adapted to assess 10 rosebushes. After the control of the panel performance using a multivariate strategy of analysis, the average scores were used in product mapping. The evaluation of the preferences with regard to these rosebushes was undertaken: 253 subjects were asked to rank the products by decreasing order of liking. Thereafter, the preference data were subjected to an internal preference mapping and a cluster analysis. Six homogeneous segments of consumers were eventually retained. By way of performing an external preference mapping, the average ranks were regressed upon the sensory attributes using principal component regression: the preferences of 67% of the consumers were satisfactorily explained by the attributes.     

Assessment of biogas potential hazards

Biogas produced from anaerobic fermentation of organic substances represents an alternative renewable energy source. Its utilization would contribute to substantial reduction of the solid waste volume in land-filling and incineration. Biogas so produced could be utilized on site or it could be injected into the natural gas distribution network. Microbiological and chemical compositions of different biogas types were determined in order to conduct qualitative and quantitative risk assessments of the potential health hazards associated with biogas use for cooking. Biogas types that could be allowed for injection in the natural gas pipelines were listed with recommendations, while outlining the European biogas injection policy. Results indicated that the injection of the processed biogas in the distribution network did not present any additional chemical or microbiological risk to consumers when compared to natural gas, provided that the biogas resulted from the fermentation of non-dangerous waste. However, since this study did not examine the microbiological and chemical composition of biogas originating from wastewater sludges and/or industrial wastes, the injection of this type of biogas into the gas distribution network should not be allowed unless a similar risk evaluation study is conducted for each case.     

Lithium conducting solid electrolyte Li1.3Al0.3Ti1.7(PO4)3 obtained via solution chemistry

NaSICON-type lithium conductor Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) is synthesized with controlled grain size and composition using solution chemistry. After thermal treatment at 850 °C, sub-micronic crystallized powders with high purity are obtained. They are converted into ceramic through Spark Plasma Sintering at 850–1000 °C. By varying the processing parameters, pellet with conductivities up to 1.6 × 10^?4 S/cm with density of 97% of the theoretical density have been obtained. XRD, FEG-SEM, ac-impedance and Vickers indentation were used to characterize the products. The influence of sintering parameters on pellet composition, microstructure and conductivity is discussed in addition to the analysis of the mechanical behavior of the grains interfaces.     

Preparation of transparent PMMA/Fe(IO3)3 nanocomposite films from microemulsion polymerization

Polymethyl methacrylate (PMMA)/Fe(IO₃)₃ nanocomposite thin films are obtained by in situ particle generation in microemulsions and subsequent photopolymerization of a mixture containing methyl methacrylate, trimethylolpropane triacrylate, and crystallized iron iodate (Fe(IO₃)₃) nanorods. Hyper‐Rayleigh scattering measurements combined with X‐ray diffraction, transmission electron microscopy, and dynamic light scattering are first used to probe in situ the crystallization kinetics of iron iodate nanorods in water‐in‐oil microemulsions prepared with methyl methacrylate as the oil phase and marlophen NP12 as a surfactant. Trimethylolpropane triacrylate is then added as a crosslinker before spin‐coating. Films are deposited on glass substrates for the nonlinear optical characterizations and on silicon wafers for the piezoelectric and mechanical measurements. Nanocomposite films treated by corona discharge are finally characterized through optical microscopy, laser Doppler vibrometry, and Brillouin spectroscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1203‐1211, 2013     

Chemical stimulation techniques for geothermal wells: experiments on the three-well EGS system at Soultz-sous-Forêts,France

Rock matrix stimulation is a method of enhancing well production or injection within a broad range of challenging environments, varying from naturally fractured limestones to sandstones with complex mineralogy. A common and often successful stimulation option, matrix acidizing, utilizes acids that react and remove mineral phases restricting fluid flow. Reviewed is the technology of chemical treatments available for oil, gas and geothermal wells and the key elements and results of the chemical reservoir stimulation program at the Soultz-sous-Forêts, France, Enhanced Geothermal System Project.