To study the formation mechanism and stability of the phase in the interface of tungsten carbide particles reinforced iron matrix composites, the composites were fabricated by spark plasma sintering (SPS) technique and combined with first-principles calculation. It was found that Fe3W3C compound was stable from the perspective of both thermodynamics and mechanical properties based on our calculations. Interfacial reaction product of tungsten carbide particles reinforced iron matrix composites was M6C. Experimental results indicated that the samples prepared by SPS did not appear interfacial reaction zone, while, interfacial reaction zone appeared for the remelted samples. With the increasing remelting temperature, the width of the interface reaction zone increased because the mutual diffusion occurred at the interface between tungsten carbide particles and matrix. Its formation mechanism was 3Fe + 3/2W2C → Fe3W3C + 1/2C. Our research might provide a theoretical guidance in controlling the interface of tungsten carbide particles reinforced iron matrix composites.

We investigated FeCoNiCrAl0.8 high entropy alloy and amorphous alloy powders synthesized simply via high energy ball milling for 10 and 20 h. The electromagnetic wave absorption properties of FeCoNiCrAl0.8 high entropy alloy and amorphous alloy powders were investigated. The structure and morphology of FeCoNiCrAl0.8 were analyzed by scanning electron microscopy with energy-dispersive spectrometry and x-ray diffraction, which demonstrated that FeCoNiCrAl0.8 powders were in irregular shape and monodisperse with an average size of 5–15 µm. The minimum reflection loss of FeCoNiCrAl0.8 high entropy alloy powders was −41.8 dB at 11.9 GHz with a thickness of 2.3 mm and effective bandwidth (RL ≤ −10 dB) was up to 4.7 GHz (8.7–13.4 GHz), while the minimum reflection loss of FeCoNiCrAl0.8 amorphous alloy powders was observed to be −35.5 dB at 14.6 GHz with a thickness of 1.7 mm and effective bandwidth varied from 12.7 to 16.3 GHz (3.6 GHz). Electromagnetic wave absorption properties of FeCoNiCrAl0.8 high entropy alloy powders is better than that of amorphous alloy powders, which demonstrated that phase structures of FeCoNiCrAl0.8 alloy powders affect electromagnetic wave absorption properties.

AlGaN/GaN heterostructures were grown by metal–organic chemical vapor deposition (MOCVD) on sp2-bonded BN using AlN as a nucleation layer. The best x-ray diffraction rocking curve full-width-at-half-maximums (FWHMs) are 0.13° and 0.17° for the GaN (0002) and ( $10\bar 12$ ) diffraction peaks. Hall-effect measurements show room temperature mobility near 2000 cm/V·s with sheet carrier density of ∼1 × 1013 cm−2, comparable to the best values obtained on sapphire using Fe-doped GaN buffers. The best low temperature mobility of the 2-dimensional electron gas (2DEG) is ∼33,000 cm2/V·s; indicating that the dominant scattering mechanism limiting the transport of 2DEG is interface roughness. Good quality BN grown directly onto sapphire is shown to be effective for reducing parallel conduction that exists due to residual donor impurities in the buffer. Luminescence measurements indicate good optical quality of the GaN/BN/sapphire. The residual strain in the GaN layer is found to be almost completely eliminated when it is released from the substrate.

Perovskite-based solar cells, typically CH3NH3PbI3, have reached power conversion efficiencies on par with single crystal silicon solar cells. Perovskite cells prepared with the most common perovskite solvent N,N-dimethylformamide (DMF) by different research groups exhibit disparate efficiencies and stability for nominally identical perovskite films. Although the differences can be related to processing conditions, a consistent physical cause for the differences has been lacking. Highly-sensitive time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveals significant dimethylamine (DMA) included in perovskite films. TOF-SIMS and x-ray photoelectron spectroscopy results suggest DMA levels ranging from roughly 10–50%. Only the highest levels register as perovskite peak shifts in x-ray diffraction; lower levels are invisible. We propose that methylamine (MA) can react with DMF solvent by transamidation to produce dimethylamine (DMA), which then displaces some MA in perovskite crystals, see Fig. 1. Transamidation of DMF can be catalyzed by TiO2, Al2O3, water, or acid, but in perovskite films transamidation is inhibited by water.

Solid oxide fuel cells (SOFCs) efficiently generate electricity, but high operating temperatures (T op > 800 °C) limit their utility. Reducing T op requires mixed ion–electron conducting (MIEC) cathode materials. Density functional theory is used here to investigate the role of potassium substitutions in the MIEC material Sr1−x Kx FeO3 (SKFO). We predict that such substitutions are endothermic. SrFeO3 and SKFO have nearly identical metallic electronic structures. Oxygen vacancy formation energies decrease by ~0.2 eV when x K increases from 0 to 0.0625. SKFO is a promising SOFC MIEC cathode material; however, further experimental investigations must assess its long-term stability at the desired operating temperatures.

Indentation method has been widely used in the measurement of material mechanical properties and residual stress for its simple, fast and nondestructive characteristics. In the indentation test, because of the plastic deformation of the material, the material accumulation and subsidence occurs around the indentation. It is found that the deformation amount of the indentation, especially the maximum pile-up around the indentation after unloading, is related to the magnitude and direction of the residual stress. In this paper, an experimental study on the pile-up morphology around an indentation for determining the direction and magnitude of residual stress is reported. Nonsymmetrical morphology of spherical indenting deformation on artificially strained steel specimen was measured with a laser scanning confocal system. A unique relationship between pile-up after unloading and biaxial residual stress was set up based on the experimental results. The direction and components of nonequibiaxial residual stress can be determined by the proposed method.

Magnetic Fe3O4–polyhedral oligomeric silsesquioxanes (POSS) particles with Si-OH were prepared by hydrosilylation reaction between the Fe3O4–SiH and POSS with hydroxyl and vinyl groups. The magnetic Fe3O4–POSS particles were characterized by using transmission electron microscopy, scanning electron microscopy, Fourier transform infrared absorption spectroscopy, thermogravimetry, and vibrating sample magnetometry. The magnetic saturation value of Fe3O4–POSS particles was 18.77 emu/g. Polyacrylonitrile (PAN)/Fe3O4–POSS nanofibers mats were subsequently fabricated by electrospinning technique. The electret properties of PAN/Fe3O4–POSS nanofibers mats and their aerosol filtration property as electrets filter media were characterized. The stability of the surface potential was remarkably improved and the surface potential retention reached 50% for PAN/Fe3O4–POSS mats with 1 wt% Fe3O4–POSS. Compared with pure PAN, the charge retention of PAN/Fe3O4–POSS was increased by 21% and reached 52.40%. Moreover, the collection efficiency increased and the filter resistance decreased when the PAN nanofibers with Fe3O4–POSS were used as electrets filter media. Our study provided an effective method to prepare novel filter materials with high efficiency and low resistance.

A bilayer film deposition process for synthesizing ultrathin amorphous carbon (a-C) films with structure and properties dominated by those of the sp3-rich bulk layer was developed in this study. This was accomplished by incorporating in conventional filtered cathodic vacuum arc (FCVA) deposition a low-ion-energy pre-deposition step (no substrate biasing) leading to the formation of an ultrathin (<1 nm) carbon layer and a post-deposition step of high-energy Ar+ ion sputtering resulting in film thinning. The thickness and cross-sectional structure of hydrogen-free a-C ultrathin films synthesized by this multistep FCVA process under optimum substrate bias conditions (−100 V pulsed bias voltage) were examined by high-resolution transmission electron microscopy and electron energy loss spectroscopy. The bilayer a-C films synthesized under these conditions exhibit slightly higher sp3 fractions and interface and bulk layers significantly thinner and thicker, respectively, compared with single-layer a-C films of similar thickness deposited under the same FCVA conditions.

In this paper, taking into account the external loading, growth strain, creep, and bending deformation during the metallic high-temperature oxidation, a residual stress evolution model is developed according to the force- and moment-equilibrium equations. In this model, oxidation kinetic relationship (the stress-dependent growth rate) is related to the stress in the oxide scale, not classical parabolic law. If and only if the stress in the scale or the activation volume is equal to zero, this relationship can reduce to the parabolic law. Then the stress-dependent oxidation kinetics is compared with the stress-independent one (the parabolic law). Finally, effects of the external loading on the stress distribution in the oxide scale, the curvature of the system and the scale thickness are discussed, and numerical results show that the tensile external loading decreases the oxidation stress and promotes the growth rate of the oxidation layer.

Heterostructures consisting of two ferromagnetic oxides La0.7Ca0.3MnO3 (LCMO) and SrRuO3 (SRO) were epitaxially grown by pulsed laser deposition onto a silicon (Si) substrate buffered by SrTiO3 (STO)/MgO/TiN. The x-ray scans and electron-diffraction patterns reveal the epitaxial nature of all five layers. From transmission electron microscopy, the thicknesses of the LCMO and SRO layers were estimated to be ~100 and ~200 nm, respectively. The magnetic properties of individual SRO and LCMO layers are in good agreement with the previous studies reported for those individual layers deposited on lattice-matched substrates, such as STO. The LCMO/SRO heterostructures showed enhanced switching field (from 6008 to 7600 Oe), which may originate from the bulk part of the heterostructure. The ability to grow these multifunctional structures on Si provides a route for wafer scale integration with Si, in contrast to oxide substrates that are not suitable for CMOS integration for microelectronics and spintronics applications.

By solving the problems in the previous pragmatic method [Scr. Mater.90–91, 53–56 (2014)] and including the interdiffusion flux as the criteria, an augmented numerical inverse method was proposed and realized in a house-made code. The proposed augmented numerical inverse method was successfully applied to high-throughput determination of the composition-dependent interdiffusivities in different solid solution alloys ranging from binary, ternary to multicomponent systems by using a single diffusion couple. Moreover, the advance features of the augmented numerical inverse method were also demonstrated.

Direct electrical measurement of single grain boundaries is performed for ZnO-based multilayer ceramic varistors with fine grains of 2 µm, using a nano-prober. The effect of ZnO grains on non-linearity is shown to be significant. The microstructure is comprised at least two non-linear types as good- and bad-junctions. The numerical ratio of good to bad is estimated to be about one (non-linearity exponent α max ≥ 10) to two (<10), which is independent of microstructural development as grain growth. The grain control of twinning as well as crystal orientation and donor concentration is considered effective in the further improvement.

To improve the lower contrast ratio of yellow-white dual color electrophoretic display cell, dispersion polymerization, and miniemulsion polymerization method were used to obtain good performance of Pigment Yellow 110 (PY110) composite particles. Crude PY110 particles and Span80 were suspended into the ethanol by dispersion method to obtain PY110-S, which were subsequently coated with styrene (St) through a mini-emulsion polymerization procedure to acquire PS/PY110-S as an electronic ink material. The modified pigments were characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), UV–vis spectroscopy. Furthermore, the Pigment Red 146 which coated with styrene (St) through a miniemulsion polymerization procedure was doped into the PS/PY110-S. Then, the obtained mixed particles were successfully incorporated in an electrophoretic display cell. And the contrast ratio of yellow-white electrophoretic display cell was significantly improved. The contrast ratio reached 1.58.

This paper describes the direct-foaming of plaster of Paris (CaSO4·½H2O) with up to 1.7 wt% of a nonionic surface-active agent to obtain highly porous, lightweight gypsum (CaSO4·2H2O) with 65–70% total porosity and a homogeneous, bimodal pore size distribution. Based on viscosity and temperature changes in the setting plaster of Paris slurry, the nonionic surfactant is seen to retard gypsum crystallization and thus extend the working time at higher water to solid ratios. The increase in viscosity during gypsum crystallization stabilizes the macropores formed during foaming. Gypsum foams of 32% density with a submicron matrix pore size, and relatively uniform macropore size of ∼100 µm were obtained. Seeding the process with 0.5 wt% 100 µm diameter gypsum particles accelerates gypsum crystallization in the presence of the nonionic surfactant and results in a more uniform, finer (92 µm) macropore structure due to less time for bubble coalescence.

Herein is described the preparation and characterization of conductive materials for application in energy storage devices, such as fuel cells. The synthetic approach uses commercially available materials and simple experimental procedures to decorate multi-walled carbon nanotubes (MWCNTs) with plain and thiolated gold nanoparticles (Au NPs). The compositional characterization data (x-ray photoelectron spectroscopy) and the electrical conductivity data (cyclic voltammetry (CV) and oxygen reduction reaction (ORR)) for the MWCNT-Au NP composites, both pre- and post-anneal, is reported.