There has been controversy over the localized corrosion mechanism of super-austenitic stainless steel weld due mainly to the lack of effective evaluation technique for identification of corrosion nucleation site in weld. For this reason, an electrochemical polarization method followed by an observation of microstructure using the back-scattered electron mode in field emission-scanning electron microscopy is used. To clarify the localized corrosion mechanism, energy dispersive spectroscopy line profile analyzed by transmission electron microscopy is additionally utilized. It clearly reveals that the selective corrosion is preferentially initiated around the σ-phase precipitated in the interdendritic region in weld. The local depletion of Cr and Mo around the σ-phase can be partly replenished by the diffusion of the elements into the depleted area during the subsequent heat treatment at 1180 °C.

The combination of low areal density, high flexural rigidity, and open architecture makes metallic microsandwiching a promising candidate for structural frameworks in small-scale multifunctional devices. We demonstrate a one-step electrodeposition procedure to synthesize an aluminum–manganese (Al–Mn) microsandwich using a porous polycarbonate (PC) membrane template from room-temperature ionic liquid. Mn was added to refine the microstructure and increase the hardness of Al. A cyclic voltammogram study shows Mn codeposit with Al in an acidic chloroaluminate electrolyte. Increasing the MnCl2 concentration in the electrolyte from 0.05 to 0.25 M promoted a crystalline to amorphous phase transition of the deposited structures. Finally, mechanical properties and damage resistance of the microsandwiches were evaluated using nano- and micro-indentation tests as well as finite element methods.

Al–12Si (80 vol%)–Ti52.4Al42.2Nb4.4Mo0.9B0.06 (at.%) (TNM) composites were successfully produced by the selective laser melting (SLM). Detailed structural and microstructural analysis shows the formation of the Al6MoTi intermetallic phase due to the reaction of the TNM reinforcement with the Al–12Si matrix during SLM. Compression tests reveal that the composites exhibit significantly improved properties (∼140 and ∼160 MPa higher yield and ultimate compressive strengths, respectively) compared with the Al–12Si matrix. However, the samples break at ∼6% total strain under compression, thus showing a reduced plasticity of the composites. Sliding wear tests were carried out for both the Al–12Si matrix and the Al–12Si–TNM composites. The composites perform better under sliding wear conditions and the wear rate increases with increasing loads. At high loads, the wear takes place at three different rates and the wear rate decreases with increasing experiment duration.

A carbide cutting tool is widely used in machining process due to its availability and being cheaper than a better performance cutting tool, such as cubic boron nitride. The carbide cutting tool also has substantial hardness and toughness that is suitable to be applied in intermittent cutting. This paper presents the case study of a wear mechanism experienced on the cutting edge of the coated and uncoated carbide tools in turning and milling processes. The wear mechanisms of carbide cutting tools were investigated in machining Inconel 718, titanium alloy Ti–6Al–4V extra-low interstitial, and aluminum metal matrix composite (AlSi/AlN MMC) at their high cutting speed regime. The tools failed primarily due to wear on the flank and rake faces. The failure mode of the carbide cutting tools was similar regardless of the machining operations and coating is believed to enhance the tool life, but once removed, the tool fails similar to that with the uncoated tool.

Three classical methods (Pseudo-Avrami, Ozawa, and Mo models) were used to correlate nonisothermal melt and cold crystallization kinetics data of neat poly(3-hydroxybutyrate) (PHB) and PHB/carbon black compounds, measured by differential scanning calorimetry. The applicability of the three models was tested comparing model predictions with experimental data. Results suggest that Pseudo-Avrami model fits the experimental data well. Ozawa model does not fit data well, as verified by the large uncertainties and unphysical values of the fitting parameters. Mo model may be considered adequate if moderately deviations could be tolerated. Datasets of all compositions are included as the Supplementary Information.

Heavy tungsten alloys with the following compositions 98W2Fe, 93W7Fe, and 95W2Fe3Ni were successfully prepared through gaseous reduction of metal oxide mixtures in the temperature range of 850–1000 °C. Reduced samples were subjected to sintering processes in reducing atmosphere (Ar/4% H2) at different temperatures (1200–1300 °C) and dwell times (30, 90 min). The prepared alloys together with the sintered samples were characterized by x-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and optical microscope. The microhardness of the sintered samples was measured and correlated to sintering temperature and dwell time. The presence of iron oxide decreases the reducibility of WO3 whereas the presence of NiO increases the reducibility of both iron oxide and tungsten oxide. With the increase of sintering temperature and dwell time, porosity of samples decreases forming dense structure which is coupled with the increase of hardness particularly for 95W2Fe3Ni alloy.

The quench sensitivity of 45vol% SiCp/2024Al composites manufactured by squeezed casting method has been investigated by employing Jominy end quench test which was designed to simulate the one dimension cooling process of the composites. It can be found that the cooling rates decreased with the increase of the distance from the quenched end. The results indicated that the as-quenched and as-aged hardness exhibited a significant decrease with increasing the distance from the quenched end. The depths corresponding to 90% of maximum as-aged hardness were 30 mm. When the quench cooling rate was 23.5 °C/s, the hardness was the maximum. The variation of as-aged hardness with cooling rate was identical with the overall enthalpy involved in the precipitation of all metastable phases (S″ + θ″ + S′ + θ′). The SiCp/2024Al composites exhibited two sensitivity regimes: at slower cooling rates the quench sensitivity had been attributed to the formation of intermediate precipitates during cooling, while it was mildly quench sensitive at higher cooling rates.

A new red-emitting phosphor, Eu3+ doped Al5BO9, was prepared for the first time by calcining the precursor of K2[Al(B5O10)]·4H2O:Eu3+ which was synthesized by a facile hydrothermal route. The obtained samples were characterized by energy dispersive x-ray spectrometer, x-ray powder diffraction, IR, scanning electron microscopy, photoluminescence, and photoluminescence excitation spectrum (PLE). Moreover, the influences of Eu3+ doping concentration, calcination temperature, and calcination time on the luminescence properties of Al5BO9:Eu3+ phosphor were also investigated. The phosphor with optimal luminescent intensity and the higher red/orange ratio was obtained by sintering the precursor at 1300 °C for 5.5 h, with 5% doping concentration, in which its luminescent decay lifetime and quantum efficiency were also measured. It is also found that the phosphor prepared by conventional solid-state reaction method exhibits the dominant transition at 591 nm (orange) with the lower color purity, while the phosphor prepared by the present precursor method exhibits the dominant transition at 615 nm (red) with the higher color purity, which indicates that this is a good method for preparing Al5BO9:Eu3+ red phosphor.

The synthesis technique that can be used to accelerate the discovery of materials for various energy conversion and storage applications is presented. Specifically, this technique allows a rapid and controlled synthesis of mixed metal oxide particles using plasma oxidation of liquid droplets containing mixed metal precursors. The conventional wet chemical methods for synthesis of multimetal oxide solid solutions often require time-consuming high pressure and temperature processes, and so the challenge is to develop rapid and scalable techniques with precise compositional control. The concept is demonstrated by synthesizing binary and ternary transition metal oxide solid solutions with control over entire composition range using metal precursor solution droplets oxidized using atmospheric oxygen plasma. The results show the selective formation of metastable spinel and the rocksalt solid solution phases with compositions over the entire range by tuning the metal precursor composition. The synthesized manganese doped nickel ferrite nanoparticles, NiMn z Fe2−z O4 (0 ≤ z ≤ 1), exhibits considerable electrocatalytic activity toward oxygen evolution reaction, achieving an overpotential of 0.39 V at a benchmarking current density of 10 mA/cm2 for a low manganese content of z = 0.20.

The removal of organics by photoelectrocatalytic oxidation offers a viable option to remove the contaminants at low concentrations. In this paper, we propose a BiVO4 thin films synthesized via spray pyrolysis for photoelectrocatalyic oxidation of phenol with solar light. We compare the properties of BiVO4 with those of the commonly used photocatalyst TiO2. In addition, BiVO4 films with W gradient doping were fabricated and tested for improving the photocatalytic performance of BiVO4. X-ray diffraction, atomic force microscopy, incident photon to current efficiency and spectrophotometry have been conducted for BiVO4 films of different thicknesses, as well as for TiO2. The electrochemical impedance spectroscopy and dark conductivity measurements were conducted. Phenol removal has been measured for both the TiO2 and BiVO4 samples. The best performance was found to be for a 300 nm undoped BiVO4 film, being able to reduce the phenol concentration up to 30.0% of the initial concentration in four hours.

Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni–40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension–tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zones underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. The onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.

A continuous process was developed to synthesize submicron boron carbide particles from boric acid and sucrose-based precursor solutions using a home-made spray pyrolysis system. A control set of samples was also prepared for comparison purposes of the microstructure and morphology of the ones synthesized via the spray pyrolysis method. Moreover, nickel nitrate was used in a precursor solution to investigate its catalyst effects on the reaction kinetics of boron carbide formation. The boron carbide phase was observed in the particles synthesized with spray pyrolysis at a reactor temperature of 1550 °C. The average particle size was approximately 0.46 μm. No effect of nickel additions was observed as a catalyst in boron carbide formation. Computational fluid dynamics software was used to model and simulate the experimental system. Simulation results provided information about the residence time and the temperature distribution along the tube reactor.

In this paper, a novel afterglow phosphor based on praseodymium ion doped Sr2Ta2O7 was synthesized successfully by solid-state reaction in the ambient atmosphere. The photoluminescence, afterglow, afterglow decay, and thermoluminescence (TL) properties were investigated in detail. The dependence of photoluminescence properties and long afterglow (LAG) performances on Pr3+ contents were investigated systematically. The optimal concentrations of Pr3+ ions for the best photoluminescence and LAG properties were experimentally to be 2 mol% and 0.5 mol%, respectively. Pr3+ exhibits prominent red emission in most reports, which derives from the 1D2 → 3H4 transition. However, the predominant blue emission locating at ∼489 and ∼507 nm coming from 3P0,1 → 3H4 transitions were observed in praseodymium ion-doped Sr2Ta2O7. Based on TL measurements, the trapping and de-trapping processes of charge carriers between shallower and deep traps were illustrated. A model was proposed on the basis of experimental results to explain the mechanisms of photoluminescence and LAG.

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.

Zinc(tris) thiourea sulphate (ZTS) is as one of the potential candidates for nonlinear optical applications due to its high nonlinearity and excellent optical properties. The synthesis of pure and titan yellow dye doped ZTS has been done and good quality rod-like single crystals of size ∼60 mm long and 2 mm diameter were grown through simplest and low cost route. The structural and vibrational analysis rules out any extra phase or change in structure of ZTS due to dye doping. Scanning electron microscope study reveals that the grown crystals are of good quality with rod-like morphology. Diffuse reflectance spectrum show a new absorption band at ∼460 nm, which may be predicted as a signature of dye. The optical band gap was calculated to be 4.6 eV for pure and 4.5 eV for doped ZTS crystals. The violet-blue emission centered at 412 nm in pure and at 414 nm in doped crystals with an additional green emission bands at 528 nm with high intensity in the photoluminescence spectra were observed. The value of ε1 is found to be enhanced from 10 (in pure) to 14 (in doped) crystals. The properties are enhanced due to dye doping and may be more useful than pure crystals in optoelectronic devices.

Monte Carlo (MC) simulations of the magnetization states of disordered self-assembled arrays of particles consisting of Co87Cu13 alloy are investigated. The assemblies of magnetic particles with ellipsoidal shapes and volumes ranging from 5 to 50 µm3 exhibit densities of about 3 × 106 particles per mm2. Magnetization was obtained in the framework of Stoner–Wohlfarth model extended to include phenomenological contributions of second-order magnetic anisotropy and coercivity mechanism with distinct configuration of easy axes of magnetization. MC simulations for assemblies containing no more than 100 particles with negligible magnetic interaction between each other and exhibiting saturation magnetization and magnetic anisotropy constant values close to those found for cobalt in bulk are in good agreement with experimental results. We evaluate and validate our computational modeling using samples having particles with different sizes and different angular distributions of the easy axis of magnetization. A simple numerical approach with minimum of parameters was used to take into account the coercive fields of the samples. Reasonable simulation results are generated based on realistic size distributions and angular distributions of easy axis of magnetization.

PACS numbers: 75.30.Gw,75.60-d,75.70-i

AlnSi12−nN12 (n = 0, 1, 2, and 4) are electron redundant systems. The calculations show that the stabilities of AlnSi12−nN12 and Al12N12 are very close. One Si atom in each Si2N2 square protrudes obviously and the cages are distorted. The excess electrons reside at the outside of the protrudent Si atoms as lone pair electrons. They occupy antibonding orbitals and form the highest occupied band. The Si–N bonds are covalent bonds with strong polarity. The overlap integral is 0.38 per Si–N bond and is 17% stronger than the overlap in Al12N12. The atoms in molecule charge on the in-plane and protrudent Si atoms are 3.13e and 1.65e, respectively. The lone pair electrons form large local dipole moments enhance the electrostatic interaction between the protrudent Si and N atoms. The energy gaps of the electron redundant cages AlnSi12−nN12 (n = 0, 1, 2, and 4) are about 1 eV smaller than the gap of Al12N12. As the lone pair electrons are loosely bond, the SiN-based cages have large hyper-polarizabilities and so have potential applications, such as nonlinear optical materials.

Growth of unexpected phases from a composite target of BiFeO3:BiMnO3 and/or BiFeO3:BiCrO3 has been explored using pulsed laser deposition. The Bi2FeMnO6 tetragonal phase can be grown directly on SrTiO3 (STO) substrate, while two phases (S1 and S2) were found to grow on LaAlO3 (LAO) substrates with narrow growth windows. However, introducing a thin CeO2 buffer layer effectively broadens the growth window for the pure S1 phase, regardless of the substrate. Moreover, we discovered two new phases (X1 and X2) when growing on STO substrates using a BiFeO3:BiCrO3 target. Pure X2 phase can be obtained on CeO2-buffered STO and LAO substrates. This work demonstrates that some unexpected phases can be stabilized in a thin film form by using composite perovskite BiRO3 (R = Cr, Mn, Fe, Co, Ni) targets. Furthermore, it also indicates that CeO2 can serve as a general template for the growth of bismuth compounds with potential room-temperature multiferroicity.

The NbCr2 Laves phase was fabricated by spark plasma sintering (SPS) using spherical Nb and Cr powders. The experimental results revealed that increasing the sintering temperature to 1773 K can result in the formation of NbCr2 Laves phase as major phase, but it always appeared with trace amounts of Nb and Cr solid solutions. Based on the theoretical calculations, the residual of Nb and Cr solid solutions was attributed to the inhomogeneous distribution of temperature increase from the particle-contacting surface to the center of particle when pulsed current passed through. Moreover, the hardness and fracture toughness of the SPS-processed NbCr2 attained 14.05 ± 0.67 GPa and 8.9 MPa·m1/2, which were 1.6 and 7.4 times of the as-cast NbCr2 Laves phase (1.2 MPa·m1/2). The formation of ductile Nb and Cr solid solutions and fine grains were considered to be the reason for the remarkable enhancements in mechanical properties.

Magnetic characteristics of nanocrystalline CoNi alloy materials embedded in silica matrix (KIT-6) have been investigated. CoNi alloys with different loading (4–12 wt%) were synthesized via a novel chemical reduction route. The materials are characterized by UV–VIS, IR, powder x-ray diffraction (XRD), transmission electron microscopy (TEM) and studied for their adsorption–desorption and magnetic properties. CoNi alloys crystallize in pure fcc phase with lattice parameters (a) and crystallite sizes in the range of 3.53(±2)–3.54(±2) Å and 13.6(±1)–16.3(±1) nm, respectively. TEM microscopy studies reveal nanocrystalline nature of the materials. Enhancement of magnetic moment with the increase in loading wt% for CoNi alloys embedded in silica matrix is observed. The values of coercivity tend to decrease after dispersion in silica matrix and thereafter increase with increasing loading wt% of various CoNi loaded samples. The observed magnetic properties have been explained on the basis of size, surface effects, and dipolar interactions.