Oxidation,Redox Disproportionation and Chain Termination Reactions Catalysed by the Pd‐561 Giant Cluster

Redox disproportionation of benzyl alcohol to benzaldehyde and toluene catalysed by the Pd₅₆₁phen₆₀(OAc)₁₈₀ (phen=1,10‐phenanthroline) giant cluster 1 under anaerobic conditions was found, whereas in an O₂ atmosphere cluster 1 catalyses the oxidation of benzyl alcohol to benzaldehyde and inhibits further oxidation of the latter. A study of the AIBN‐initiated and non‐initiated oxidation of benzyl alcohol, sec‐butyl alcohol and styrene in the presence of cluster 1 revealed that cluster 1 performs three functions in the oxidation reactions: 1) catalysis of polar oxidation of the substrates with O₂, 2) termination of the chains of radical oxidation, and 3) catalysis of redox disproportionation.     

Differential Activity of Plasma and Vacuolar Membrane Transporters Contributes to Genotypic Differences in Salinity Tolerance in a Halophyte Species,Chenopodium quinoa

Halophytes species can be used as a highly convenient model system to reveal key ionic and molecular mechanisms that confer salinity tolerance in plants. Earlier, we reported that quinoa (Chenopodium quinoa Willd.), a facultative C3 halophyte species, can efficiently control the activity of slow (SV) and fast (FV) tonoplast channels to match specific growth conditions by ensuring that most of accumulated Na⁺ is safely locked in the vacuole (Bonales-Alatorre et al. (2013) Plant Physiology). This work extends these finding by comparing the properties of tonoplast FV and SV channels in two quinoa genotypes contrasting in their salinity tolerance. The work is complemented by studies of the kinetics of net ion fluxes across the plasma membrane of quinoa leaf mesophyll tissue. Our results suggest that multiple mechanisms contribute towards genotypic differences in salinity tolerance in quinoa. These include: (i) a higher rate of Na⁺ exclusion from leaf mesophyll; (ii) maintenance of low cytosolic Na⁺ levels; (iii) better K⁺ retention in the leaf mesophyll; (iv) a high rate of H⁺ pumping, which increases the ability of mesophyll cells to restore their membrane potential; and (v) the ability to reduce the activity of SV and FV channels under saline conditions. These mechanisms appear to be highly orchestrated, thus enabling the remarkable overall salinity tolerance of quinoa species.     

Effect of oxide nanofillers on fabrication,structure, and properties of zirconia-based composites

We have studied the effect of NiO on the sintering of yttria-stabilized zirconia at temperatures ranging from 1300 °C to 1500 °C in air and argon environments. It was found that the addition of NiO stabilized the cubic phase of ZrO₂ independently from the sintering atmosphere. The monoclinic phase of ZrO₂ formed only during sintering within the air environment at temperatures higher than 1450 °C. The transformation of NiO to Ni by reversible decomposition depends on the sintering atmosphere, and this can lead to variations in the nature of inclusions and in changes of the structure and properties of nanocomposite materials in the system ZrO₂–NiO(Ni). NiO and Ni inclusions can increase the indentation fracture toughness of zirconia–nickel oxide composite material more than 50%, which can be compared with zirconia ceramics during sintering in a neutral atmosphere alone.     

The synthesis of single phase WC nanoparticles/C composite by solid state reaction involving nitrogen-rich carbonized polyaniline

Single phase tungsten carbide nanoparticles (WC-NPs), (mean particle diameter 5.4 nm), distributed over carbonized polyaniline (C-PANI) nanotubes/nanosheets were synthesized by a solid state reaction between WO₃ and nitrogen-rich carbonized polyaniline at 1000 °C in a reducing atmosphere. The resulting composite was characterized by X-ray diffractometry, electron microscopy, thermogravimetry in oxidizing and reduction atmospheres and elemental analysis. We suggested that the synthesis of WC as a single phase was facilitated by reactive C atoms with dangling bonds, formed upon nitrogen removal.     

Effect of filler size on thermophysical and electrical behavior of nanocomposites based on expanded graphite nanoparticles filled in low‐density polyethylene matrix

Various aspects of electrical and thermophysical properties of nanocomposites based on low‐density polyethylene matrix filled with nanostructuralized expanded graphite (EG) and standard, microsized graphite are presented in this article. A periodical method developed in the laboratory was used to measure simultaneously thermal conductivity, specific heat, and diffusivity of composites at room temperature. The effect of micro‐ and nanosized fillers on the final thermophysical and electrical behavior is investigated. It was found that the electrical conductivity of composites strongly depends not only on the filler content but also on the filler size. When the microsized graphite was used, the percolation concentration of the filler was found to be 15 vol%, whereas the percolation concentration of the filler in nanocomposites filled with EG of large sizes was significantly lower. Similarly, it was shown that the graphite significantly improves the thermophysical behavior of composites filled with micro‐ and nanofiller sizes. The thermal conductivity measured values were also compared with some theoretical models for the prediction of the thermal conductivity. POLYM. COMPOS., 2012. © 2013 Society of Plastics Engineers     

Case studies on process sequence design in cold forming of engine valve slider and self-locking nuts

Two cases on process sequence design are presented. One describes the procedure for manufacturing an engine valve slider, and the other for self-locking nut manufacturing. They are based on experts' experience. All operations required to produce final products, from raw material are shown, and general considerations and rules for forming sequence design are explained. For engine valve sliders several upsetting processes are used preforming operations and the final product is obtained by combined forward and backward extrusion. In manufacturing of self-locking nuts special features involved in design are shown in turning the workpiece upside down during the process sequence and producing intentionally a minor crack for the final operation of piercing. In addition, both macro structure and micro structure analysis for major deformation processes are shown.     

Structure and composition of CO2/H2 and CO2/H2/C3H8 hydrate in relation to simultaneous CO2 capture and H2 production

Gas hydrates from a (40/60 mol %) CO₂/H₂ mixture, and from a (38.2/59.2/2.6 mol %) CO₂/H₂/C₃H₈ mixture, were synthesized using ice powder. The gas uptake curves were determined from pressure drop measurements and samples were analyzed using spectroscopic techniques to identify the structure and determine the cage occupancies. Powder X‐ray diffraction (PXRD) analysis at ?110°C was used to determine the crystal structure. From the PXRD measurement it was found that the CO₂/H₂ hydrate is structure I and shows a self‐preservation behavior similar to that of CO₂ hydrate. The ternary gas mixture was found to form pure structure II hydrate at 3.8 MPa. We have applied attenuated total reflection infrared spectroscopic analysis to measure the CO₂ distribution over the large and small cavities. ¹H MAS NMR and Raman were used to follow H₂ enclathration in the small cages of structure I, as well as structure II hydrate. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

A comparative study on the electrical and mechanical behaviour of multi‐walled carbon nanotube composites prepared by diluting a masterbatch with various types of polypropylenes

Polypropylene (PP) nanocomposites with multi‐walled carbon nanotubes (CNT) were produced by a small‐scale masterbatch melt dilution technique using five PP differing in melt flow index (MFI) and degree of maleination. PP used in a masterbatch has MFI = 12 (PP₁₂), the others used PP which have MFI = 2 or MFI = 8. The state of CNT dispersion as assessed by melt rheological and morphological investigations indicated a better dispersion when using unmodified PP with MFI = 8 (PP₈) and the masterbatch's PP₁₂. Electrical conductivity results showed nanotube percolation at contents between 1.1 and 2.0 vol %, whereas lower values were obtained for the matrices with the best dispersion, i.e., PP₈ and PP₁₂. The dependencies of the relative Young's modulus on the CNT content showed that the maleinization improved the interfacial interactions between the components, especially in the case of maleated PP with MFI = 8 (PP‐MA₈), but the better dispersion was prevented by the incompatibility between polar groups of PP‐MA and the nonpolar origin masterbatch PP₁₂. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of loading‐unloading cycles on impact‐damaged jute/glass hybrid laminates

The production of glass/plant fiber hybrid laminates is a possibility for obtaining semistructural materials with sufficient impact properties, and a better life cycle analysis (LCA) profile than fiberglass. The simplest and possibly the most effective configuration for the production of these hybrids would involve the use of a plant fiber reinforced laminate as the core between two glass fiber reinforced laminates. A main limitation to the use of composites including plant fibers is that their properties may be significantly affected by the presence of damage, so that even the application of a low stress level can result in laminate failure. In particular, it is suggested that when loading is repeatedly applied and removed, residual properties may vary in an unpredictable way. In this work, E‐glass/jute hybrid reinforced laminates, impacted in a range of energies (10, 12.5, and 15 J), have been subjected to post‐impact cyclic flexural tests with a step loading procedure. This would allow evaluating the effect of damage dissipation offered by the plant fiber reinforced core. The tests have also been monitored by acoustic emission (AE), which has confirmed the existence of severe limitations to the use of this hybrid material when impacted at energies close to penetration. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers