La0.4Sr0.6Co0.7Fe0.2Nb0.1O3-δ perovskite prepared by the sol-gel method with superior performance as a bifunctional oxygen electrocatalyst

The advancement of efficient noble-metal-free electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is crucially important for energy storage devices such as fuel cells and metal-air batteries. This paper reports the development of a novel bifunctional perovskite, La_0.4Sr_0.6Co_0.7Fe_0.2Nb_0.1O_3-δ (LSCFN). The crystal structure, morphology, adsorption, valence, and oxygen catalytic activity of LSCFN were systematically studied. In addition, an investigation of the influence of the synthetic method on the oxygen catalytic activity was performed. Sol-gel and solid-phase methods were applied for the synthesis of LSCFN, and the resulting perovskites were denoted as LSCFN-SG and LSCFN-SP, respectively. The catalyst LSCFN-SG exhibited excellent bifunctional catalytic activity, with a low overpotential (360 mV) and superior stability in the OER. Subsequently, LSCFN-SG was used as the cathode catalyst in an aluminum-air battery and exhibited a high power density. The results of this study indicate that LSCFN-SG is a promising bifunctional oxygen electrocatalyst for metal-air batteries.     

Selective photocatalytic degradation of organic pollutants by CuxS/ZnO/TiO2 heterostructures

Photoactive heterostructures containing Cu_xS/ZnO/TiO₂ have been obtained by spray pyrolysis deposition followed by post-deposition thermal treatment. The ZnO middle layer morphology was tailored by using chemical additives during the deposition. The samples have crystalline structure with average crystallite size around 80 Å for metal oxides and 90 Å for Cu_xS. The roughness varies from 27.5 nm for Cu_xS/dZnO/TiO₂ to 33.6 nm for Cu_xS/pZnO/TiO₂ samples. The wettability properties were tested based on the contact angle measurements. The highest surface energy value (106.4 mN/m) corresponding to Cu_xS/pZnO/TiO₂ with 30 min UV irradiation, with a predominant polar component of 85.3 mN/m. The photocatalytic efficiency under UV–Vis light irradiation was evaluated using methylene blue and phenol as pollutants. The highest photocatalytic values (93.4% for methylene blue and 72.3% for phenol) were obtained for Cu_xS/pZnO/TiO₂ heterostructure with successive 30 min UV irradiation at 2 h intervals. The mineralization efficiency was tested using total organic carbon analysis and the results are slightly lower compared with photocatalytic efficiency.     

The use of microplants in process development—Case study of etherification of 2-ethoxy-2-methylbutane

The successful development of a laboratory scale integrated trial plant, a microplant, was demonstrated. The operation was evaluated using the etherification of 2-ethoxy-2-methylbutane as a demonstration case. The experimental results were validated against the literature data with good correlation thus proving that the microplant can be used efficiently for the scale-up of chemical industry processes.As the hold-up of the microplant was 50 cm³ and the minimum residence time was 2 h, the effects of positive feedback could be observed very rapidly thus reducing research costs.     

Effect of nano-metal particles on the fracture toughness of metal–ceramic composite

A theoretical model is proposed to study the influence of nano-metal particles (NMPs) on the fracture toughness of metal–ceramic composites (MCC). In the framework of the model, the crack tip intersects the grain boundary of the NMPs. Stress concentration at crack tip initiates edge dislocations which makes a shielding effect on the crack and leads to fracture toughness of the MCC. The dependence of critical crack intensity factors on grain size of the NMPs was calculated. The calculation suggested that the existence of the NMPs lead to an increase of critical crack intensity factors by 14%.     

Fabrication of Pt–Cu/RGO hybrids and their electrochemical performance for the oxidation of methanol and formic acid in acid media

Pt–Cu/reduced graphene oxide (Pt–Cu/RGO) hybrids with different Pt/Cu ratios were prepared by the reduction of H₂PtCl₆ and CuSO₄ by NaBH₄ in the presence of graphene oxide (GO). The Pt–Cu nanoparticles were characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The reduction of GO was verified by ultraviolet–visible absorption spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Compared to Pt/RGO, the Pt–Cu/RGO hybrids have superior electrocatalytic activity and stability for the oxidation of methanol and formic acid. Thus they should have potential applications in direct methanol and formic acid fuel cells.     

Thermally treated wine retains antibacterial effects to food-born pathogens

Although cooking with wine and consumption of wine as a warm beverage is widespread, antibacterial effects of thermally treated wine have not been studied.We examined in vitro antibacterial activity of wine heated at 75 and 125 °C for 45 min against Salmonella enterica serovar Enteritidis and Escherichia coli. Their effects were compared with intact red wine, dealcoholized wine (DW) and dealcoholized wine reconstituted (RDW) with water to the initial volume. Samples were also analysed for their phenolics content, antioxidant capacity, resveratrol and ethanol content and pH.Total phenolics concentration and related antioxidative activity followed changes in samples volume, regardless of treatment type, while pH of all samples remained stable and ranged from 3.09 to 3.24.The order of the antibacterial activity of wine samples was: intact wine > heated at 75 °C > heated at 125 °C > DW > RDW.Antibacterial activity of the samples could not be related to their content of resveratrol as a single phenolics compound, antioxidative capacity or pH.Thermally treated wine under conditions applicable to food processing in everyday life, may be effective antibacterials in spite of significant heat-induced changes in their physical–chemical composition.     

Nanostructured manganese oxides as lithium battery cathode materials

We have designed and synthesized a novel nanocrystalline manganese oxide with a nanofibrous morphology by employing an electrodeposition process in the presence of a non-ionic surfactant. This unique nanoporous/nanocrystalline material effectively accommodates the structural transformation during lithium insertion and avoids deleterious morphological changes as observed in battery materials composed of large particles. Consequently, the material exhibits outstanding cycling stability in addition to its high discharge capacity.     

New porous silicon carbide composite reinforced by intact high-strength carbon fibres

A novel processing method to produce a carbon-fibre-reinforced silicon carbide (C/SiC) is presented and the mechanical properties are evaluated. The low-cost process yields a reaction bonded silicon carbide matrix but avoids efficiently reactive damage of the carbon fibres. Thus, the C/SiC-material shows a fibre-dominated behaviour due to high fibre strength and matrix porosity. The characteristics and mechanical properties of this C/SiC are highlighted. The discussion deals with the particular mechanical characteristics of porous-matrix materials relating to similar materials investigated hitherto.     

Immobilization of α-amylase on zirconia: A heterogeneous biocatalyst for starch hydrolysis

α-Amylase was immobilized on zirconia via adsorption. The support and the immobilized enzymes were characterized using XRD, IR spectra and N₂ adsorption studies. The efficiency of immobilized enzymes for starch hydrolysis was tested in a batch reactor. The effect of calcination temperatures on properties of the support as well as upon immobilization was studied. From XRD, IR and N₂ adsorption studies it was confirmed that the enzyme was adsorbed on the external surface of the support. pH, buffer concentration and substrate concentration had a significant influence on the activity of immobilized enzyme. Immobilization improved the pH stability of the enzyme. The Michaelis–Menten kinetic constants were calculated from Hanes–Woolf plot. K_m for immobilized systems was higher than the free enzyme indicating a decreased affinity by the enzyme for its substrate, which may be due to interparticle diffusional mass transfer restrictions.