Photodegradation, interaction with iron oxides and bioavailability of dissolved organic matter from forested floodplain sources

Photochemical degradation of dissolved organic matter (DOM) can influence food webs by altering the availability of carbon to microbial communities, and may be particularly important following periods of high DOM input (e.g. flooding of forested floodplains). Iron oxides can facilitate these reactions, but their influence on subsequent organic products is poorly understood. Degradation experiments with billabong (= oxbow lake) water and river red gum (Eucalyptus camaldulensis) leaf leachate were conducted to assess the importance of these reactions in floodplain systems. Photochemical degradation of DOM in sunlight-irradiated quartz tubes (with and without amorphous iron oxide) was studied using gas chromatography and UV-visible spectroscopy. Photochemical reactions generated gaseous products and small organic acids. Bioavailability of billabong DOM increased following irradiation, whereas that of leaf leachate was not significantly altered. Fluorescence excitation-emission spectra suggested that the humic component of billabong organic matter was particularly susceptible to degradation, and the source of DOM influenced the changes observed. The addition of amorphous iron oxide increased rates of photochemical degradation of leachate and billabong DOM. The importance of photochemical reactions to aquatic systems will depend on the source of the DOM and its starting bioavailability, whereas inputs of freshly formed iron oxides will accelerate the processes.

Geometrical effects on residual stresses in 7050-T7451 aluminum alloy rods subject to laser shock peening

Laser shock peening (LSP) is an emerging surface treatment technology for metallic materials, which appears to produce more significant compressive residual stresses than those from the conventional shot peening (SP) for fatigue, corrosion and wear resistance, etc. The finite element method has been applied to simulate the laser shock peening treatment to provide the overall numerical assessment of the characteristic physical processes and transformations. However, the previous researchers mostly focused on metallic specimens with simple geometry, e.g. flat surface. The current work investigates geometrical effects of metallic specimens with curved surface on the residual stress fields produced by LSP process using three-dimensional finite element (3-D FEM) analysis and aluminium alloy rods with a middle scalloped section subject to two-sided laser shock peening. Specimens were numerically studied to determine dynamic and residual stress fields with varying laser parameters and geometrical parameters, e.g. laser power intensity and radius of the middle scalloped section. The results showed that the geometrical effects of the curved target surface greatly influenced residual stress fields.

The reactivity of diorganotellurium oxides towards phenol and o-nitrophenol. Hypervalent and secondary bonding of four different product classes

The reaction of the diorganotellurium oxides R2TeO (R = Ph, p-MeOC6H4, p-Me2NC6H4) with phenol and o-nitrophenol produces diorganotellurium hydroxy phenolates, R2Te(OH)OPh (1, R = Ph; 2, R = p-MeOC6H4; 3, R = p-Me2NC6H4), diorganotellurium bis(phenolates) R2Te(OPh)2 (4, R = Ph; 5, R = p-MeOC6H4; 6, R = p-Me2NC6H4), tetraorganoditelluroxane bis(o-nitrophenolates), (R′O)R2TeOTeR2(OR′) (7, R = p-MeOC6H4; 8, R = p-Me2NC6H4; R′ = o-NO2C6H4), and a hexaphenyltritelluroxane bis(o-nitrophenolate) (R′O)Ph2TeOTePh2OTePh2(OR′) (9, R′ = o-NO2C6H4), respectively. The redistribution reactions of R2Te(OPh)2 (4, R = Ph; 5, R = p-MeOC6H4; 6, R = p-Me2NC6H4) with the corresponding diorganotellurium oxides R2TeO and diorganotellurium dichlorides R2TeCl2 (R = Ph, p-MeOC6H4, p-Me2NC6H4) give rise to the formation of moisture sensitive tetraorganoditelluroxane bis(phenolates) (PhO)R2TeOTeR2(OPh) (10, R = Ph; 11, R = p-MeOC6H4; 12, R = p-Me2NC6H4) and diorganotellurium chloro phenolates, R2Te(Cl)OPh (13, R = Ph; 14, R = p-MeOC6H4; 15, R = p-Me2NC6H4), respectively. The reaction of the diorganotellurium oxides R2TeO with the corresponding diorganotellurium dichlorides R2TeCl2 (R = Ph, p-MeOC6H4, p-Me2NC6H4) affords tetraorganoditelluroxane dichlorides ClR2TeOTeR2Cl (16, R = Ph; 17, R = p-MeOC6H4; 18, R = p-Me2NC6H4) as air-stable solid materials. The reactivity of 1–18 can be rationalized by the kinetic lability of the Te–O and Te–Cl bonds. Compounds 1–18 have been characterized by solution and solid-state 125Te NMR spectroscopy and 2, 4, 6, 7, 9, 17, and 18 have also been analyzed by X-ray crystallography.

Improvement in mechanical properties of aluminum polypropylene composite fiber

Aluminum particles (Al) were added to polypropylene (PP) in the presence of poly ethylene glycol (PEG) and polypropylene-graft-maleic anhydride to produce composites. The composites were then melt-spun into a mono filament and tested for tensile properties, diameter evenness and morphology. Melt rheological properties of Al/PP composites were studied in linear viscoelastic response regions. It was observed that level of dispersion of aluminum particles within a polypropylene composite fiber could be improved by incorporating polyethylene glycol. The improvement of dispersion led to an improvement in the fibers mechanical properties through a reduction of the coefficient of variation of fiber diameter.

Processing and characterization of porous aluminum

Aluminum foams are now being introduced into automotive industry to reduce weight, to absorb energy in crash situations and to carry sound or heat absorbing functions. In the present study, a novel Spark Plasma Sintering (SPS) process for producing porous aluminums with controlled pore size and porosity and superior energy absorption has been developed. Experimental procedures included the mixing of starting powders, compacting, SPS sintering and leaching out of the space-holding particles. Porous aluminums with various porosities and a wide range of pore size distributions can be produced by the SPS process. Optical microscopy, scanning electron microscopy (SEM) and quantitative image analyses were used to characterize the porous aluminums. Compressive tests were carried out on the aluminum foams to evaluate the mechanical properties.

Compressive behavior and energy absorption of constructed cellular aluminum

The defoThe deformation behaviors and energy absorption characteristics of constructed cellular aluminums were investigated by compressive tests. Constructed cellular aluminum specimens with two kinds of thickness in the cold-pressed panel and various numbers of layers bonded together have been tested. The plateau stress and the energy absorption have been measured and furthermore, the deformation behaviors have been evaluated. Results indicate that superior mechanical properties with constructed cellular aluminums can be achieved when the distribution of material at cell level is properly selected. Excellent energy absorption per unit mass can be obtained by only changing the thickness of the original aluminum sheet.nnation behaviors and energy absorption characteristics of constructed cellular aluminums were investigated by compressive tests. Constructed cellular aluminum specimens with two kinds of thickness in the cold-pressed panel and various numbers of layers bonded together have been tested. The plateau stress and the energy absorption have been measured and furthennore, the defonnation behaviors have been evaluated. Results indicate that superior mechanical properties with constructed cellular aluminums can be achieved when the distribution of material at cell level is properly selected. Excellent energy absorption per unit mass can be obtained by only changing the thickness of the original aluminum sheet.

Identification and quantification of cholesterol oxides in foods

The types and levels of nine major cholesterol oxidation products was determined in a variety of foods. An estimate was made of the possible levels of cholesterol oxides in the Australian diet. These levels have been shown to cause endothelial damage in the coronary arteries of laboratory animals in previous studies. The health implications of these observations to humans is unknown.

Processing of fine-grained aluminum foam by spark plasma sintering

Porous materials are now becoming attractive to researchers interested in both scientific and industrial applications due to their unique combinations of physical, mechanical, thermal, electrical and acoustic properties in conjunction with excellent energy absorption characteristics. Metallic foams allow efficient conversion of impact energy into deformation work, which has led to increasing applications in energy absorption devices. In particular, foams made of aluminum and its alloys are of special interest because they can be used as lightweight panels, for energy absorption in crash situations and sound or heat absorbing functions in the automotive industry with the aim to reduce weight to improve crashworthiness, safety and comfort.

Correlation between shoulder flow zone quality and material flow quantity during friction stir welding of thick aluminum section using scroll shoulder tool

The so-called scroll shoulder tool is widely used particularly for thick section friction stir welding (FSW). However, the correlation between its shoulder flow zone weld quality and material flow quantity remains unclear. This information is important for tool design. In the present study, a scroll shoulder tool was used to FSW 20mm thick 6061 aluminum (Al) plates at a range of welding parameters. The pick-up material (PUM) by the scroll was quantified, and the effect of welding parameters and PUM on the shoulder flow zone formation and weld quality was studied. It was found that there is a positive linear relationship between the PUM and weld quality. In order to obtain a defect-free FSW weld produced by the scroll shoulder tool, scroll groove needs to be fully filled by PUM.

Material flow forming the shoulder flow zone using scroll shoulder tool during friction stir welding of thick section aluminum alloys

Scroll shoulder tools are widely used and they do not need to be tilted during friction stir welding (FSW). However, the detailed material flow, which is important for proper scroll shoulder tool design and subsequently for forming the defect-free shoulder flow zone, has not been fully explained. In the present study, features of material flow in shoulder flow zone, during FSW of thick 6061 aluminium (Al) plates using a scroll shoulder tool were investigated. It was observed that there is a simple layer-to-layer banded structure which appears in the bottom portion of shoulder flow zone, but disappears in the top portion of this weld zone. When the scroll shoulder tool is plunged into the workpiece to a determined depth, the workpiece material is extruded by the tool pin, and pushed up into the scroll groove beneath the shoulder forming the pick-up material. During the forward movement of the tool, the central portion of pick-up material was driven downward by the root portion of pin and then it detaches from the tip portion of pin in a layer-to-layer manner to form the weld.

Oxygen reduction reaction activity and structure of La-based perovskite oxides

1706 files in 35 folders, containing 388MB. Comprises plots, figures, and manuscripts. The data contains x-ray diffraction patterns and electrochemical data of lanthanum based perovskite oxides (e.g. 9 different perovskite compositions e.g. LaNiO₃, LaCoO₃, LaFeO₃, LaMnO₃, LaCrO₃, LaNi_0.5Co_0.5O₃ and LaNi_0.5Fe_0.5O₃, LaNi_0.5Mn_0.5O₃ and LaNi_0.5Cr_0.5O₃) characterized using rotating ring disk electrodes.

Synthesis of high surface area amorphous tin-zinc oxides by a sol-gel method

A new method to synthesize conducting oxide nanoparticles with low photocatalytic activity was investigated. Initially, the preparation of amorphous ZnO-SnO2 solid solution nanoparticles was studied using a sol-gel technique. It was found that X-ray amorphous nanopowders with low photocatalytic activity were produced when the precipitates were heat treated below 500 °C. However, FT-IR data showed that the sample may not be an oxide semiconductor. A mixture of ZnO and SnO2 crystalline nanoparticles was also produced at 800 °C and found to have much reduced photoactivity than commercial ZnO nanoparticles having a similar specific surface area.