Recombination luminescence in alkali metal sulfates

In this paper we present the results of investigation of the nature of intrinsic luminescence caused by photon excitation in a wide spectral range from 10.3 eV to 4 eV at a temperature of 15–300 K. It is shown that in alkali metal sulfates the main emission band formed after excitation by X-rays and photons with an energy of 9–11 eV and 4–7.5 eV at 15–300 K is located in the spectral range of 3.65–3.9 eV. When the sulfates are excited by 4–7.75 eV photons, in addition to the emission band at 3.65–3.9 eV the other effective long-wave band at 3.1–2.5 eV appears. It is assumed that the 3.65–3.9 eV radiation results from the recombination of electrons with unevenly located holes of SO₄⁻ type. The long-wave emission bands in the alkali metal sulfates may be connected with the formation of electron-hole trapping centers after irradiation by photons with energies above 4.4 eV.     

Deformation characteristics of the intermetallic alloy 60NiTi

The deformation behavior of a Ni-rich Ni₅₅Ti₄₅ (at.%) alloy, commonly known as 60NiTi (as designated in wt.%), was analyzed using neutron and synchrotron x-ray diffraction during in situ isothermal tension and compression loading, and pre and post-test electron microscopy. The alloy was shown to exhibit remarkable strength and high hardness resulting from a high density of fine Ni₄Ti₃ precipitates (size ∼67 nm), which were uniformly dispersed throughout the matrix after a solution treatment and oil quench. The precipitate volume fraction was 55 ± 3%, determined from both the neutron Rietveld refinement and conventional x-ray measurements. Non-linear stress-strain behavior was observed in tension (but not in compression) and was attributed to reversible stress-induced martensite (SIM) that forms to accommodate the stress as revealed by neutron diffraction measurements. The tensile and compressive neutron data also showed peak broadening and residual lattice strains. Transmission and scanning electron microscopy revealed stress-induced coarsening of Ni₄Ti₃ precipitates in both tension and compression tested samples, but precipitation and growth of the stable Ni₃Ti phase was observed only after tensile testing. Finally, the potential ramifications of these microstructural changes are discussed.     

Corrosion of carbon steel C1010 in the presence of iron oxidizing bacteria Acidithiobacillus ferrooxidans

In this study, corrosion behaviors of carbon steel C1010 in the presence of an acidophilic, iron-oxidizing bacterial species Acidithiobacillus ferrooxidans were examined. Results showed that A. ferrooxidans cells, with or without attaching to C1010 steel, accelerated its corrosion at a rate of 3–6× those of acidic water, at a pH of 2, without cells. A. ferrooxidans oxidized Fe²⁺ to Fe³⁺ as an energy source and the produced Fe³⁺ rapidly oxidized Fe⁰ to Fe²⁺ was proposed and verified as the reason. In addition, severe pitting corrosion was found on the C1010 steel surface in solutions containing A. ferrooxidans cells.     

Application of near infrared sensors to preconcentration of hydrothermally-formed copper ore

Near infrared sensors can be a very useful technique for the qualitative analysis of complex ores, and thus could be useful for the preconcentration of ores. In this paper, individual particles of hydrothermally-formed copper ore sampled from a mine in the Los Pozos mining district, northern Chile, were classified as product, middling and waste based on their near infrared response. The classification of copper bearing minerals (product) from gangue (waste) was considered for vibration combination bands at longer wavelengths from 2000 to 2400 nm. This region exhibits characteristic features for carbonates and hydroxyl gangue bearing minerals. The near infrared features at 1400 and 1900 nm were not considered favourable for classification and subsequent discrimination because they can be influenced by moisture and other environmental factors and are easily suppressed by iron-rich minerals.Two near infrared preconcentration strategies were applied for particle discrimination. Results indicate that targeting only the calcite (carbonate) dominated particles for discrimination as waste provided the best option for preconcentration. The near infrared discrimination analysis correlates well with mineralogical (QEMSCAN® and XRD) and elemental (XRF) data classification. The results indicate that near infrared spectroscopy is a suitable preconcentration method for supergene copper ore.     

Influence of 2D rGO nanosheets on the properties of OPC paste

In this experimental study, the effects of 2D reduced graphene oxide (rGO) sheets on the properties of Portland cement paste in comparison to popularly reviewed nanomaterials like aluminium oxide nanopowder (n-Al₂O₃) and colloidal silicon dioxide nanoparticles (n-SiO₂) were investigated. The addition of 0.02% rGO sheets by weight of cement increased the 7 and 28 days flexural strength up to 70% and 23% respectively when compared to control paste. Moreover, its incorporation substantially decreased the sizes of pores/voids in the paste, even compared to the other nanomaterials, as characterized by Mercury Intrusion Porosimetry (MIP) and 3D X-ray Computed Tomography (CT) aided with image analysis technique. The assessment of Portlandite content by Thermo-gravimetric Analysis did not indicate major differences between the pastes, with the exception of the paste incorporating nano-silica. Microstructural analysis by Fourier Transform Infrared Spectroscopy, X-ray diffraction and Scanning Electron Microscopy did not reveal any major differences between the control paste and the pastes incorporating nanomaterials. The overall results suggest that the performance of rGO was better in comparison to other two nanomaterials, despite the significantly lower amounts that were used in the paste.     

A multi-stakeholder portfolio optimization framework applied to stormwater best management practice (BMP) selection

In this paper, an optimization framework for complex environmental management problems involving multiple stakeholders is developed and illustrated. In the framework, problems are represented as a series of smaller, interconnected optimization problems, reflecting individual stakeholders’ interests. The framework uses interactive visual analytics to explore and analyse optimization results, and the concept of Best Alternatives to a Negotiated Agreement (BATNAs) and an approach to reframe visualizations to encourage stakeholder negotiation. To demonstrate the utility of the framework, it is applied to a realistic case study involving multiple stakeholder groups funding different stormwater best management practices (BMPs) for a catchment management plan for a region of a large city in Australia. The problem features a total of sixteen objectives for four stakeholders. The results indicate that the proposed framework enables the identification of solutions that provide optimal trade-offs between many objectives and provides an effective and efficient means of assisting stakeholders with identifying acceptable solutions.     

Experimental investigation of hydrogen production by CH4–CO2 reforming using rotating gliding arc discharge plasma

Hydrogen produced from CH₄–CO₂ reforming by an optimized rotating gliding arc discharge plasma reactor is investigated in this study. The effect of CH₄/CO₂ ratio (mole ratio), total input flow rate, discharge gap, voltage, and discharge frequency are analyzed. The results show that H₂ yield increases with the increase of CH₄/CO₂ ratio. Arc can be stretched effectively by increasing total input flow rate, then the discharge region is enlarged. Increasing discharge gap can enlarge the discharge region, but the reaction of the gas mixture would be suppressed if the discharge region was excessively large. The discharge region decreases with the increased discharge frequency to a certain degree. Based on the experimental results, the optimal experimental condition is concluded as applied voltage 60 V, discharge frequency 20 kHz, and minimum discharge gap 3 mm. It is anticipated that the results would serve as a good guideline to the application of hydrogen production from hydrocarbon fuels by plasma reforming onboard.     

Monodisperse rutheniumcopper alloy nanoparticles decorated on reduced graphene oxide for dehydrogenation of DMAB

In this study, we report a superior dehydrogenation catalyst for dimethylamine borane, which exhibited one of the best catalytic activities. The newly formed catalyst system contains well dispersed ruthenium-copper nanomaterials on reduced graphene oxide (3.86 ± 0.47 nm), which was prepared by using the ultrasonic double reduction technique. The characterization of monodisperse ruthenium-copper alloy nanoparticles was performed using some advanced analytical methods such as TEM, HRTEM, XPS, Raman spectroscopic analysis. The experiments results revealed that the monodisperse ruthenium-copper alloy catalyst (RuCu@rGO) has one of the highest catalytic activity compared to previous studies, having a high turnover frequency value (256.70 h⁻¹). The detailed kinetic parameters such as activation energy, enthalpy, and entropy values were also calculated for the dehydrogenation of dimethylamine borane at room temperature. Also, the results showed that the monodisperse RuCu@rGO catalyst has high durability and reusability as retained its 81% initial catalytic activity even after 4th runs for the dehydrogenation of dimethylamine borane.     

Effect of N and C on stress corrosion cracking susceptibility of austenitic Fe18Cr10Mn-based stainless steels

Stress corrosion cracking (SCC) susceptibility of austenitic Fe18Cr10Mn alloys with 0.3N, 0.6N and 0.3N0.3C was investigated in aqueous chloride environment using a slow strain rate test method. The SCC susceptibility of Fe18Cr10Mn alloys in 2 M NaCl solution at 50 °C under constant anodic potential condition decreased with increase in N content from 0.3 to 0.6 wt%, and with addition of 0.3 wt% C to the Fe18Cr10Mn0.3N alloys. The present study strongly suggested that the beneficial effects of N and C on the SCC behavior of Fe18Cr10Mn alloys would be associated with the resistance to pitting corrosion initiation and the repassivation kinetics.