Analysis of the Effect of Spacer Layers on Nonlinear Distortions of the Current–Voltage Characteristics of GaAlAs/InGaAs pHEMTs

Semiconductors - The paper presents the results of modeling the electrophysical parameters of AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (pHEMT) structures via...     

Mechanochemical synthesis of ternary chalcogenide chalcostibite CuSbS2 and its characterization

Journal of Materials Science: Materials in Electronics - In this work, the very rapid one-step mechanochemical synthesis of nanocrystalline ternary chalcogenide chalcostibite CuSbS2 prepared from...     

Optimization methods in inverse problems and applications to science and engineering

Optimization and Engineering -     

Monolithically-integrated BiVO4/p+-n GaAs1-xPx tandem photoanodes capable of unassisted solar water splitting

Monolithically-integrated tandem photoanodes were fabricated on substrates consisting of epitaxial n-GaAs_1-xP_x (x ? 0.32) grown on n⁺-GaAs wafers. A p⁺-n junction photovoltaic (PV) cell was first formed by zinc diffusion into the n-GaAs_0.68P_0.32 from a deposited ZnO coating. After diffusion the ZnO serves as a transparent electrical contact to the resulting p⁺-GaAs_0.68P_0.32 surface layer. Transparent, conducting SnO₂:F provides chemical and mechanical protection for the ZnO and the underlying PV cell, and it electrically connects this cell to a top BiVO₄ photocatalyst layer. In some photoanodes, a WO₃ thin film was interposed between the SnO₂:F and BiVO₄. All oxide coatings were produced by ultrasonic spray pyrolysis except WO₃, which was spin coated. Unassisted (unbiased) solar water splitting was achieved, with a solar-to-hydrogen efficiency approaching 2%, without addition of any co-catalyst to the BiVO₄ surface. This work can provide insights to other researchers regarding scalable, low cost approaches for the planar monolithic integration of oxide photoanode materials with PV cells to create new tandem devices.     

Nanotechnology‐based wastewater treatment

Water contamination is a global challenge impacting both the environment and human health with significant economic and social costs. The growing scarcity of usable water resources requires effective treatment of wastewater. In this context, developing cheaper, safer and more efficient wastewater treatment technologies are the need of the hour. One promising approach that several studies have reported success has been the usage of nanomaterials in water and waste water management. The rapid progress of research in nanomaterial sciences has shown their growing potential; however, there has not been a great amount of information available on their implementation. This review focuses on developments in nanotechnology that hold strong potential for wastewater treatment. The review covers key techniques in nanomaterial‐based water treatments including adsorption, filtration and photocatalysis with recent examples showing how to improve their properties and efficiencies according to the need.     

Using Amplitude Analysis of Acoustic Emission Signals under Cyclic and Static Loading of Steel Samples

Russian Journal of Nondestructive Testing - The results of amplitude analysis of discrete acoustic emission signals from developing sources such as fatigue cracks are presented. The studies were...     

Formation mechanism of porous reaction-bonded silicon nitride with interconnected pores in the presence of MgO

In porous reaction bonded silicon nitride, whiskers normally grow in globular clusters as the dominant morphology and deteriorate the pore interconnectivity. However, the ceramic microstructure was significantly transformed with the addition of MgO; specifically, the morphology was modified to a combination of matte and hexagonal grains. Microstructural observation along with thermodynamic studies suggest that MgO interfered with the presence and nitridation of SiO_(g). Consequently, rather than being involved in the whiskers’ formation, surface silica instead reacted with volatile MgO to form intermediate products. Through these reactions, whisker formation was blocked, and a porous interconnected structure formed which was confirmed by 3D tomography. After heat-treatment at 1700 °C, β-Si₃N₄ crystallized in a glassy matrix containing magnesium. Resulting samples had an open-pore structure with porosity of 74–84 vol. %, and density of 0.48-0.75 g.cm^?3. Combination of high porosity and pore size of <40 μm led to compressive strengths of 1.1–1.6 MPa.     

Manganese oxides treated with organic compounds as catalysts for water oxidation reaction

Manganese oxides of different crystalline structures: α-MnO₂, δ-MnO₂, α,γ-MnO₂ and Mn₂O₃; were treated with the organic compounds picolinic acid, ethylenediamine and pyridine; and were applied as catalysts in the chemical water oxidation reaction using Ce(IV) ammonium nitrate as sacrificial oxidant. The treatment led to modifications in the oxides properties, such as reduction of the particle size, increase of surface area and partial reduction of Mn⁴⁺ to Mn³⁺ for the Mn(IV) oxides, or of Mn³⁺ to Mn²⁺ for Mn₂O₃, because of favored interactions of the organic molecules with the lattice planes with higher d spacing. Oxygen evolution reaction (OER) tests showed the superior catalytic activity of the treated Mn(IV) oxides, for instance α,γ-MnO₂-en presented TOF five times higher than pure α,γ-MnO₂. The increase in surface area as well as the higher Mn³⁺ content caused by the treatment of the Mn(IV) oxides were correlated with the improvement in the OER catalytic activity.     

Real-time organic aerosol chemical speciation in the indoor environment using extractive electrospray ionization mass spectrometry

Understanding the sources and composition of organic aerosol (OA) in indoor environments requires rapid measurements, since many emissions and processes have short timescales. However, real-time molecular-level OA measurements have not been reported indoors. Here, we present quantitative measurements, at a time resolution of five seconds, of molecular ions corresponding to diverse aerosol-phase species, by applying extractive electrospray ionization mass spectrometry (EESI-MS) to indoor air analysis for the first time, as part of the highly instrumented HOMEChem field study. We demonstrate how the complex spectra of EESI-MS are screened in order to extract chemical information and investigate the possibility of interference from gas-phase semivolatile species. During experiments that simulated the Thanksgiving US holiday meal preparation, EESI-MS quantified multiple species, including fatty acids, carbohydrates, siloxanes, and phthalates. Intercomparisons with Aerosol Mass Spectrometer (AMS) and Scanning Mobility Particle Sizer suggest that EESI-MS quantified a large fraction of OA. Comparisons with FIGAERO-CIMS shows similar signal levels and good correlation, with a range of 100 for the relative sensitivities. Comparisons with SV-TAG for phthalates and with SV-TAG and AMS for total siloxanes also show strong correlation. EESI-MS observations can be used with gas-phase measurements to identify co-emitted gas- and aerosol-phase species, and this is demonstrated using complementary gas-phase PTR-MS observations.