Partial oxidation of methane over bimetallic nickel–lanthanide oxides

The study of partial oxidation of methane (POM) over bimetallic nickel–lanthanide oxides was undertaken. Binary intermetallic compounds of the type LnNi (Ln = Pr, Gd, Lu) were used as bimetallic nickel–lanthanide oxides precursors and the products (NiO·Pr₂NiO₄, 2NiO·Gd₂O₃ and 2NiO·Lu₂O₃) were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy, Raman and temperature programmed reduction. The catalytic activity increases when gadolinium or lutetium replaces praseodymium and the selectivity of the bimetallic nickel–lanthanide oxides is clearly different from that of single metal oxides and/or mechanical mixtures.The existence of an unusual synergism effect between the two metal oxide phases (NiO and Ln₂O₃) that lead to higher conversions of methane and higher selectivities to hydrogen and carbon monoxide correlate also the catalysts stability to deactivation. The activity and selectivity of the gadolinium and lutetium compounds is, under the same conditions, equivalent to that of a platinum commercial catalyst, 5 wt% Pt/Al₂O₃, which stresses the good catalytic performance of this new type of compounds for the production of H₂ and CO (H₂/CO = 2).     

Physical and mechanical characterization of phyllites and metagreywackes in central Portugal

This work defines the physical and mechanical characteristics of phyllites and metagreywackes belonging to a schist–greywacke complex in central Portugal. The index properties, point load strength, uniaxial compressive strength, slake durability and Schmidt rebound hardness were determined. In general, the metagreywackes gave a higher strength than phyllites with the same weathering degree. Possible correlations and estimation models were established and compared with the equations obtained by different researchers.     

TIG brazing technology for zinc-coated sheet steel for bodywork

We propose a method for the assessment of the state of welded joints in terms of arc voltage signals and feed rate appraisal. The signals were recorded during laboratory tests. For the appraisal of the signals, we applied numerical parameters such as, for instance, kurtosis. On the basis of analysis results, we developed diagnostic rules which were written in the binary diagnostic matrix. The proposed method has been implemented in the form of software, the correctness of which has been verified on experimental data.     

Iron Ore Sintering: Environment,Automatic, and Control Techniques

Sintering is a process of agglomeration of iron ore fines, fluxes, recycled products, slag-forming elements, and coke with the purpose of achieving an agglomerated product with the suitable composition, quality and granulometry to be used as burden material in the blast furnace. However, the sintering process accounts for an important percentage of the ironmaking and steelmaking emissions, so the minimization of them will promote environmental and health improvements as well as economical profitability. Automatic and control systems contribute to all these objectives.     

Polyphenolic contents in Citrus fruit juices: authenticity assessment

The contents of 49 polyphenols in sweet orange, tangerine, lemon and grapefruit juices from 18 cultivars grown in Spain were determined by reversed-phase high-performance liquid chromatography with photodiode array detection. Citrus polyphenolic profiles consist of 81–97 % of flavanones, 0.3–13.6 % of flavones, 0.1–6.0 % of flavonols, 0.6–9.6 % of hydroxycinnamic acids and 0.2–0.4 % of coumarins (only found in grapefruit juices). Several markers that allow to distinguish with practical certainty grapefruit and lemon juices between them and from the other Citrus species are reported. Each of these markers is a reliable and useful tool to detect juice adulteration. Grapefruit juice markers were naringenin-7-O-neohesperidoside, naringenin-7-O-neohesperidoside-4′-O-glucose, naringenin-O-hexosylhexoside, hesperetin-7-O-neohesperidoside, naringenin-O-rhamnosylmalonylhexoside, isosakuranetin-7-O-neohesperidoside, hesperetin-7-O-rutinoside, apigenin-6-C-hexoside-O-hexoside, apigenin-7-O-neohesperidoside and scopoletin-O-hexoside. Lemon juice markers were eriodictyol-7-O-rutinoside-4′-O-glucoside, eriodictyol-7-O-rutinoside, diosmetin-6,8-di-C-glucoside, diosmetin-8-C-glucoside, luteolin-7-O-rutinoside, diosmetin-6-C-glucoside and diosmetin-6,8-di-C-hexosideacylhexoside. The markers naringenin-O-hexosylhexoside, apigenin-6-C-hexoside-O-hexoside, scopoletin-O-hexoside, diosmetin-8-C-glucoside and diosmetin-6,8-di-C-hexosideacylhexoside were detected, characterized and quantitatively determined in grapefruit and lemon juices for the first time by our research group, as far as the authors know. Classification models provided by LDA and PLS-DA correctly identify all sweet orange and tangerine juices. Moreover, PLS regression model determines the percentage (10–70 %) of tangerine juice used to adulterate sweet orange juice with a suitable confidence interval (RMSEP = 7 %).     

Study of the photon down‐conversion effect produced by thin silicon‐rich oxide films on silicon solar cells

In the present work, we studied the photon down‐conversion effect produced by thin films of silicon oxide with embedded silicon nanocrystals also called silicon‐rich oxide (SRO). These films have been used to absorb high energy light and the re‐emission of two or more low energy photons (~1.1 eV) with the goal of improving the external quantum efficiency and consequently the conversion efficiency of silicon solar cells. According to our results, the incorporation of a thin SRO film on the solar cell surface increases the short circuit current and the FF of the silicon solar cells; the enhancement of spectral response is due to the high photoluminescence intensity of the SRO in the visible region when irradiated with UV light. An improvement of 38% in the solar cell efficiency has been observed in our particular solar cell fabrication process by the use of an SRO film with high photoluminescence intensity, which replaces the conventional silicon dioxide film. Copyright © 2016 John Wiley & Sons, Ltd.     

Utilization of Ultrasonic Measurements for Determining the Variations in Microstructure of Thermally Degraded 2205 Duplex Stainless Steel

The aim of this study is to investigate the changes in attenuation of longitudinal waves and velocity of shear wave modes for assessing variations in the microstructure of thermally degraded 2205 duplex stainless steel samples that were aged isothermally at 700°C and 900°C for different time intervals. The evaluation of material microstructural changes such as phase transformation and second phase precipitation which are related to material properties is of primary importance to ensure quality of components. This paper presents evidence that indicate that the attenuation coefficient of the longitudinal mode is sensitive to gradual microstructural changes produced by the aging treatments. The gradual changes in microstructure are associated with reduction of impact properties. On the other hand, for samples aged at 700°C, the velocity of the fast mode of shear wave show changes at high aging times and does not show changes at early aging times were the materials properties are already degraded.     

On the microstructure of single wall carbon nanotubes reinforced ceramic matrix composites

A microstructural modelling of the microstructure in single wall carbon nanotubes reinforced alumina ceramics has been developed. The model accounts for the main microstructural features, being quite useful to describe the carbon nanotube distribution along the ceramic matrix. The microstructural analysis derived from this model is found to give a deeper insight into the high-temperature creep of these composites.     

Partial hydrogenation of propyne over copper-based catalysts and comparison with nickel-based analogues

The partial hydrogenation of propyne was studied over copper-based catalysts derived from Cu–Al hydrotalcite and malachite precursors and compared with supported systems (Cu/Al₂O₃ and Cu/SiO₂). The as-synthesized samples and the materials derived from calcination and reduction were characterized by XRF, XRD, TGA, TEM, N₂ adsorption, H₂-TPR, XPS, and N₂O pulse chemisorption. Catalytic tests were carried out in a continuous flow-reactor at ambient pressure and 423–523 K using H₂:C₃H₄ ratios of 1–12 and were complemented by operando DRIFTS experiments. The propyne conversion and propene selectivity correlated with the copper dispersion, which varied with the type of precursor or support and the calcination and reduction temperatures. The highest exposed copper surface was attained on hydrotalcite-derived catalysts, which displayed C₃H₆ selectivity up to 80% at full C₃H₄ conversion and stable performance in long-run tests at T ? 473 K. Both activated Cu–Al hydrotalcites (this work) and Ni–Al hydrotalcites [S. Abelló, D. Verboekend, B. Bridier, J. Pérez-Ramírez, J. Catal. 259 (2008) 85] exhibited a relatively high alkene selectivity under optimal operation conditions, but they present a markedly distinctive catalytic behavior with respect to temperature and hydrogen-to-alkyne ratio. The product distribution was assigned through Density Functional Theory (DFT) simulations to the different stability of subsurface phases (carbides, hydrides) and the energies and barriers for the competing reaction mechanisms. The behavior of Cu in partial alkyne hydrogenation resembles that of Au nanoparticles, while Ni is closer to Pd.