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Abstract: The vertical conductivity of the p-Al0.11Ga0.89N/GaN SLs has been measured and calculated. The measured result (1.35×10−5 Scm−1) is in good agreement with the calculated result (2.26×10−5 Scm−1), indicating that the adoption of Fermi–Dirac distribution and sequential tunneling model in our calculation is very plausible. As a result, it is suggested that in p-AlGaN/GaN SLs the Fermi–Dirac distribution need to be considered in calculation related to hole distribution. [Copyright &y& Elsevier]

Abstract: The influence of various annealing temperatures on microstructure evolution of oxidized Ni(20nm)/Au(20nm) ohmic contact to p-GaN was studied by synchrotron X-ray diffraction (XRD). In association with the variation of the specific contact resistance (ρ c), it is observed that NiO and Au began to form partially epitaxial structure on p-GaN at 450°C, which played a critical role in lowering down the ρ c. At 500°C, the epitaxial structure of Au and NiO was improved further while the lowest ρ c was reached. However, at 600°C, the epitaxial structure of NiO was transformed to polycrystalline structure again with a sharp increase of ρ c. Therefore, it is suggested that the degradation of the epitaxial structure of NiO is responsible for the sharp increase of ρ c. [Copyright &y& Elsevier]

Abstracts: The microstructure evolution of oxidized Ni (20nm)/Au (20nm) contact to p-GaN with increasing annealing temperature was studied by synchrotron X-ray diffraction (XRD) and powder XRD. With the increase of annealing temperature, it was observed that the Au on the p-GaN gradually grew on the p-GaN with the orientation relationship of Au(111)//GaN(0002). NiO also had such a orientation relationship of NiO(111)//GaN(0002) at 500°C and gradually turned back to polycrystalline structure at higher temperature. The orientation relationship of Au, NiO and GaN implied that the epitaxial crystallization might occur during annealing. The specific contact resistance also reduced to the minimum 2.73×10−4 Ωcm2 at 500°C. Therefore, plausibly the epitaxial crystallization is an important mechanism for lowering the contact resistance between oxidized Ni/Au contacts and p-GaN. [Copyright &y& Elsevier]

Abstract: This work employs an anodic surfactant, sodium dodecyl sulfate (SDS), to improve the flotation performance of the electrocoagulation–flotation (ECF) process to treated fluoride containing semiconductor wastewater following calcium precipitation. The dissolved fluoride ions and CaF2 particles in the wastewater after calcium precipitation were effectively removed in the ECF process simultaneously. The dosage of SDS required for ECF was much less than those for dispersed air flotation (DiAF) or dissolved air flotation (DAF) processes because the CaF2 particles can be collected by hydro–fluoro–aluminum flocs in ECF. Thus, SDS only served as a frother to make the bubbles tiny and stable in the ECF defluoridation process. The interference of co-existing anions can be overcome by increasing the dosage of calcium ions and SDS. The optimum initial acidity for ECF is close to the initial fluoride concentration after calcium precipitation; the amount of SS removed dropped rapidly if the initial acidity exceeded the optimal value because the surface charge of the hydro–fluoro–aluminum particles increased. The initial acidity of the wastewater after calcium precipitation can be modified by changing the [Ca(OH)2]/[Ca2+]T ratio and the appropriate ratio is approximately given by the acid dissociation constant of hydrofluoric acid and the initial pH of the wastewater before calcium precipitation. [Copyright &y& Elsevier]

Batch experiments with bipolar aluminum electrodes and potentiodynamic polarization tests with monopolar systems were conducted to investigate the effects of the type and concentration of co-existing anions on defluoridation in electrocoagulation (EC) process. The results demonstrate that the type of the dominant anion directs the EC defluoridation reaction. The defluoridation efficiency was almost 100% and most of the fluoride removal reaction occurred on the surface of the anode in the solution without the co-existing anions, due to the electro-condensation effect. In the solutions with co-existing anions, most of the defluoridation took place in bulk solution. The residual fluoride concentration is a function of the total mass of Al(III) liberation from anodes and the types of the functions in the solutions with and without co-existing anions are different. The existence of sulfate ions inhibits the localized corrosion of aluminum electrodes, leading to lower defluoridation efficiency because of lower current efficiency. The presence of chloride or nitrate ions prevented the inhibition of sulfate ions, and the chloride ions were more efficient. Different corrosion types occurred in different anion-containing solutions and the form of corrosion affected the kinetic over-potential. The bypass flow causes the decrease of current efficiency and the proportion of the bypass flow of current increased due to a rise of the kinetic over potential and the conductivity of the solution. [Copyright &y& Elsevier]

Micro/nano-scale deformation behavior including hardness, elastic modulus, and pop-ins, was studied in a medical austenitic stainless steel followed by post-mortem EBSD characterization. Relatively higher hardness and modulus was observed near {101} and more pop-ins occurred in this orientation at high loading rate. The activation volume (v) obtained from nanoindentation had weak dependence on grain orientation and was ~10–20 b3, indicating that neither diffusional creep processes nor conventional dislocation segments passing through dislocation forests controls plastic deformation in our study. The plastic zone radius (c) and the distance of the indent from the grain boundary (d) were used to describe the effect of grain boundary on the pop-in effect. The ratio of c/d meets amplitude version of Gaussian peak function distribution for a given orientation, whose peak value remains nearly constant for all the orientations. [ABSTRACT FROM AUTHOR]

The ingenious concept of phase reversion annealing involving cold deformation of parent austenite to strain-induced martensite, followed by annealing was used to obtain nano-grained/ultrafine-grained (NG/UFG) structure in a Cu-bearing biomedical austenitic stainless steel resulting in high strength-high ductility combination. Having employed the concept effectively, the primary objective of this study is to critically analyze the interplay between the load-controlled deformation response, strain-rate sensitivity and deformation mechanism of NG/UFG austenitic stainless steel via nanoscale deformation experiments and compare with its coarse-grained (CG) counterpart. The study demonstrated that the strain-rate sensitivity of NG/UFG was ~1.5 times that of the CG structure. Post-mortem electron microscopy of plastic zone surrounding the indents indicated that the active deformation mechanism was nanoscale twinning with typical characteristics of a network of intersecting twins in the NG/UFG structure, while strain-induced martensite transformation was the effective deformation mechanism for the CG structure. The fracture morphology was also different for the two steels, essentially ductile in nature, and was characterized by striations marking the line-up of voids in NG/UFG steel and microvoid coalescence in CG counterpart. The differences in deformation mechanisms between the NG/UFG and CG structure are attributed to the austenite stability – strain energy relationship. Furthermore, the presence of ~3 wt % Cu in austenitic stainless steel had somewhat moderate effect on strain-rate sensitivity and activation volume at similar level of grain size in its Cu-free counterpart. Specifically, in the NG/UFG structure, the nanoscale twin density was noticeably higher in Cu-bearing austenitic stainless steel as compared to Cu-free counterpart, as Cu is known to increase the stacking fault energy. [ABSTRACT FROM AUTHOR]

Abstract: Anodic coatings were prepared by using microarc oxidation (MAO) on AZ91HP in silicate containing solution (Si-solution) and phytic acid containing solution (P-solution), respectively. The influence of the electrolytes on coating structure, morphology and composition was studied by using X-ray diffraction (XRD), environmental scanning electron microscope (ESEM) and energy dispersive X-ray spectroscopy (EDX). Potentiodynamic polarization test and immersion test were employed to evaluate the corrosion resistance of anodic coatings. Different electrolytes caused the differences in the MAO process and coating properties. The breakdown voltage and the final voltage in P-solution were higher than those in Si-solution. The pore uniformity of anodic coatings obtained in Si-solution (Si-film) was worse than that in P-solution (P-film). XRD analyses indicated that Si-film was amorphous, while P-film consisted of MgO. The corrosion resistance of the sample coated with P-film was better than that with Si-film. [Copyright &y& Elsevier]

Abstract: This paper deals three-dimensional axisymmetric quasi-static coupled thermoelastic problems for time-dependent boundary condition. The water vapor temperature and pressure relation assumed for the inner boundary. The water vapor temperature and pressure data were obtained from a thermodynamic steam table. Laplace transform and finite difference methods are used to analyze problems. The solution is obtained by using the matrix similarity transformation and inverse Laplace transform. We obtain solutions for the temperature and thermal deformation distributions in a transient and steady state. Moreover, the computational procedures established in this thesis, can solve the generalized thermoelasticity problem for multilayered hollow cylinder with nonhomogeneous materials. [Copyright &y& Elsevier]

Concerns surrounding climate change and environmental challenge make the coal utilization network essential not only for understanding the pattern of energy provision and transfer, but also for illustrating the interaction between anthropogenic activities and ecological systems at global level. This paper fills the research gap by dint of multi-regional input output model to outline coal embodied routes from natural boundaries to economic activities, and to identify the central hubs in the global coal supply chain, based on the most recent available statistics for 2011. As the economic value and environmental influences of different kinds of coals could be remarkably diverse, the separation of coal categories in systematic analysis could provide fundamental information regarding the displacement and teleconnection of coal utilization in the world. The estimation shows that in weight 64.99% of coal direct supply is ultimately embodied in international trade, indicating the crucial roles of trade interlinks in global coal utilization. Apart from this, the findings pertinent to sectoral structure, regional supply chain and per capita characteristics of coal embodied utilization, could be valuable to identify the global energy routes driven by international trade as well as to facilitate energy and environmental policy. [ABSTRACT FROM AUTHOR]

• The fatigue life prediction model based on the surface integrity features was developed. • The eigenstrain method was used to restructure the residual stress field after milling. • Simulation of different feed rates impact on fatigue life after milling. • Mapping from microscopic characteristics to macroscopic mechanical properties was established. The surface integrity of AISI 4140 steel after milling at different feed rates (75–125 mm/min) was measured by performing laser scanning microscopy, X-ray diffraction, and electron backscatter diffraction. Subsequently, the fatigue responses under different maximum stress values (650–800 MPa) were analyzed. The results showed that the increase in the feed rate increases the residual stress and roughness, whereas the fatigue life at low stress is reduced. Moreover, the feed rate has a limited effect on the surface grain refinement layer, and fatigue life at high stress. The measured surface integrity models were used to predict the fatigue life based on the crystal plasticity theory, and these yielded results within the three times scatter bands from the corresponding experimental values. [ABSTRACT FROM AUTHOR]

Electron spin dynamics in strained In0.1Ga0.9As/Al0.4Ga0.6As quantum wells (QWs) on (1 0 0) and (1 1 0)-oriented substrates are investigated by time-resolved Faraday rotation. We find that the spin relaxation time in (1 1 0) QWs is 6 times longer than that in (1 0 0) QWs at low temperatures, which is strongly reduced by applying magnetic fields. The sign of g-factor is found positive and its magnitude decreases with increasing well width, in the well width range investigated here. [Copyright &y& Elsevier]

• A low carbon footprint Ultra-High Performance Concrete (UHPC) is developed. • The idea of full scale recycling is proposed to reuse gold tailings. • The macro properties of the developed UHPC are evaluated. • The microstructure of the developed UHPC is presented. • The environmental characteristics of the developed UHPC are assessed. This paper presents a feasible way to design a low carbon footprint Ultra-High Performance Concrete (UHPC) with gold tailings based on the idea of full scale recycling. Due to the fact that the particle size distribution of the recycled gold tailings is normally wild, from micrometer to millimeter, it could be utilized to replace powders and aggregates in UHPC simultaneously, which can get rid of sieving process and improve the recycling efficiency. Therefore, in this study, a particle dense packing model is firstly employed to design the UHPC matrix with gold tailings, based on the full scale recycling point of view. Then, the fresh and hardened properties of the newly developed UHPC are investigated, including flowability, compressive strength, hydration kinetics, durability and microstructure. The tested results indicate that the idea of full scale recycling can guarantee a relatively high long-term compressive strength, low D RCM , and low leaching toxicity for UHPC. Additionally, the environmental evaluation further proves that the developed UHPC is a green building material with advanced properties and simple preparation process. [ABSTRACT FROM AUTHOR]