The damage induced by oxidation and stress during the service process of Cr35Ni45Nb alloy and their influences on the microstructure evolution and creep rupture life of this alloy were studied. Continuity, compactness, and high temperature stability of the oxide layers are conductive to the performance of the alloy. A slight but complete layer of oxidation on surface improves the creep rupture life of the specimens. However, being exposed to long-term oxidation is observed to be counter-productive. Temperature stress generated during the air-cooling process creates large carbides near the surface of the specimen's cracks. Moreover, tiny carbides are precipitated from γ matrix and interfacial defects due to creep stress, but strip carbides are dissolved due to creep stress and the Gibbs–Thomson effect.

A novel core–shell particle that consists of epoxide-terminated hyperbranched polymer (HBP) and silica nanoparticles was incorporated into an epoxy/hydroxyl-terminated HBP blend to fabricate a high-performance epoxy thermoset. The effect of the core–shell particle content on the mechanical properties of the epoxy thermosets was investigated in detail. Results from tensile, flexural, and impact tests are provided. The impact fracture surface was studied by field emission-scanning electron microscopy. The incorporation of 2 wt% core–shell particles improved the tensile strength, percent elongation at break, flexural strength, and impact resistance of epoxy/hydroxyl-terminated HBP thermosets. Field emission-scanning electron micrographs showed that core–shell particle addition resulted in large-scale shear deformation and debonding from the epoxy matrix, and improved the epoxy resin toughness.

In this paper, we determine the electronic transport properties of Au–C20–Au molecular system under finite bias voltage using the non-equilibrium Green function and the density functional theory, along its localized pseudo atomic orbitals. Our aim is to peruse the various nanometer-scale transport properties and eventually predict the overall quantum transport behavior of this organic mesoscopic system. We investigate the density of states, transmission spectrum, molecular orbitals, current–voltage characteristics, rectification ratio, and differential conductance characteristics at discrete bias voltages to get the insight about various transport phenomena. The observed results elucidate that the quantum tunneling causes the electron transport in this molecular bridge and becomes prominent due to strong mechanical interactive coupling between the molecule and the electrodes having low HOMO–LUMO (highest occupied molecular orbital–lowest unoccupied molecular orbital) gap of 0.55 eV. We conclude that Au–C20–Au device exhibited metallic nature forming the current coulomb staircase with transition points at ±1 V and the quantum conductance of order 2G 0 at low bias voltages.

Pb2+-doped (Sr1−xPbx)3Ti2O7 (SPT) ceramics were fabricated by a solid state reaction. The stability and lattice structure of Sr3Ti2O7 and Sr4Ti3O10 Ruddlesden–Popper (RP) phases were studied as a function of Pb2+ content and sintering atmosphere. X-ray diffraction indicates that SrO(SrTiO3)n RP phase formation is sensitive to the Sr:Ti ratio of the raw materials and is a complex circularly iterative process. When the PbO concentration is less than x = 0.03, pure Sr3Ti2O7 can be obtained. Sr4Ti3O10 was found to be the main phase in the SPT samples for x ≥ 0.075. Pb2+ stabilizes SrO(SrTiO3)n RP phases by substitution for Sr2+ which reduces the lattice stress of the RP phase. It was observed that SrO vaporization losses at high temperature can be compensated by the decomposition of the intermediate SrPbO3 phase at lower temperature.

The effects of rare earth oxide Y2O3 additive on microstructure and mechanical properties of proeutectoid ferrite/granular bainitic coating by flux-cored arc welding were investigated. The results show that the primary austenite in the bainitic coating can be refined by Y2O3. The grain size of primary austenite is decreased from 51.2 µm to 40.1 µm with the increased Y2O3. The size of proeutectoid ferrite is decreased significantly and the fraction of the bainite is increased, which in turn facilitates the uniform distribution of the M/A island. Large number of the dislocation martensite is transformed into M/A. With the increased Y2O3 additive, the hardness and the tensile strength of the coating increases from HV 272 ± 13 to HV 312 ± 8 and from 764 ± 10 MPa to 885 ± 12 MPa, respectively. Moreover, the wear resistance of the coating with Y2O3 additive is increased simultaneously.

The oxidation behavior of three types of stainless steels, namely AISI 321, AISI 316, and AISI 409, was compared. In all stainless steels, oxide layers were formed and their masses and thicknesses increased with oxidation time. Among them, AISI 409 ferritic stainless steel demonstrated higher oxidation rate. According to the kinetical oxidation behavior of them at elevated temperatures, the oxidation mechanism was determined. Among them, the AISI 409 ferritic stainless steel showed the lowest and AISI 321 austenitic stainless steel demonstrated the highest oxidation resistance. Based on the experimental results, it was suggested that the kinetic of oxide growth in stainless steels was followed by a parabolic relationship. In all cases, a well-known Cr-rich internal oxidation zone (IOZ) was observed. The formation of IOZ was suggested by the Gibbs free energy expression and confirmed by following up the formed oxide layers at different holding times. Furthermore, the formation of thicker oxide layers in ferritic stainless steel was explained by using solid-state diffusion relations and supported by quasi-steady-state approximation of Fick's first law.

The local-density approximation (LDA)-1/2 technique has been successfully applied to surmount current limitations in density-functional theory to determine excited-states properties of solids via LDAs to the exchange-correlation functional. The main task to properly apply this technique is to choose the “cut-off” radius to truncate the long-ranged self-energy function, originated by the procedure of removing the spurious self-energy of electrons (and/or holes). The usual procedure is by choosing an extreme of the variation of the band gap as a function of this cutoff. This work examines the relationship between that cut-off parameter and the electronegativity difference between cation and anion in binary compounds calculated self-consistently with LDA-1/2.

Texture and microstructure evolution during recrystallization of a heavily cold-rolled Ni9W alloy were investigated using x-ray diffraction and electron back-scattered diffraction. Brass, S and random orientations dominated the recrystallization process because the fractions of cube, Copper, and Goss orientations were low. Nearly all of the Brass and a part of the S orientation were consumed during recrystallization. Some of the S orientation was recrystallized grains, which grew during annealing and remained after the primary recrystallization. A large number of grains with other random orientations were formed as they had a significant size and fraction advantage during recrystallization. The evolution of microstructure and texture during recrystallization demonstrated that the cube grains did not have a size advantage compared with the noncube grains, which lead to the formation of a rough recrystallization cube texture in the Ni9W alloy after annealing.

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

Microstructures and austenite grain growth behavior of the alumina-forming austenitic (AFA) steel subjected to normalizing and annealing at various temperatures were investigated. A modified kinetic model of austenite grain growth was constructed based on consideration of the heating history. Abnormal growth of austenite grain occurs when the temperature is increased to 1473 K, and some special large particles of the precipitates located at grain boundaries form when the sample is normalized at the temperature of 1523 K. Both NbC and NiAl precipitates are identified using routine x-ray diffraction. The fitted data based on the kinetic model used and the consideration of the heating history is in agreement with the changes in the austenite grain growth in the AFA steel even when there is abnormal grain growth. The grain growth exponents are shown to be 2.85 and 2.42 for normalizing and annealing, respectively.

Very high cycle bending fatigue behaviors of FV520B steel under fretting wear were studied by the ultrasonic fatigue technique. The specimen system for ultrasonic bending testing was designed and the stress distribution of fatigue specimen was obtained by finite element method. The microstructure of FV520B steel was characterized by means of optical microscope, transmission electron microscope, and energy-dispersive spectroscope. The P–S–N curve was drawn based on fatigue data. The micromorphology characteristics of fretting wear surface and fracture surface for fatigue specimen were observed. The results indicate that the microstructure of FV520B steel is mainly composed of lath martensite, ferrite, and precipitation particles, with some randomly distributed internal inclusions. The P–S–N curve shows that there exists no “conventional fatigue limit” and the fatigue life decreases continuously with the increase of applied stress Smax. Most of fatigue cracks are observed on fractography and initiate from the overlap region of fretting wear zone and stress concentration zone. The fracture failure for tested specimen is ascribed to fretting wear and bending vibration fatigue.

The present work discusses about the mechanical and metallurgical properties of Incoloy 800 H friction welded joints. The process parameters namely friction pressure, friction time, upsetting pressure, upset time, and rotational speeds were varied from low level to high level to study their effects on the properties of the weldments. The tensile tests were carried out at four different temperatures namely at room temperature, 550, 650, and 750 °C. From the results, it is observed that as the testing temperature increased, there was a reduction in tensile strength of welds. The friction welds had higher hardness than the base metals. This was due to the formation of secondary phases (γ′ and M23C6) in friction welds. The tensile and impact fracture surfaces were further analyzed through SEM and finally the individual effects of the parameters with respect to the microstructures variation in the welds were studied.

In semiconductor system for solar-energy utilization by photoelectrochemical (PEC) water splitting, the effective absorption of visible light and the efficient separation and transfer of photogenerated charge carriers are still of key importance. In this manuscript, composite photoanodes of PbO sensitized ZnO nanorod arrays were prepared by a two-step hydrothermal process and used as anodes for PEC test under visible-light irradiation. The photocurrent achieved the highest value of 94 μA cm−2 at 0.8 V (versus Ag/AgCl electrode) when the amount of Pb source was optimized to form only a thin layer (a few nanometers) of PbO nanoparticles on the surfaces of ZnO nanorods. Such a nanostructure enabled the visible-light absorption, and also ensured the sufficient contact of PbO with ZnO to form junction with a type II band alignment and the sufficient contact with aqueous solution to form interfaces, thus facilitating the excitation, separation, and transfer of charge carriers to generate photocurrent and finally enhancing the PEC activity.

A novel two-stage reheating process with new alloy design has been developed to improve the microstructure morphology of semisolid Al–Si casting aluminum alloy for thixoforming. The process consists of first reheating the material to the liquidus temperature, holding for 5 min, and then lowering to the predetermined two-stage reheating temperature between 843–863 K and holding for 10 min. The experimentally-obtained grain diameter, roundness, and the amount of liquid trapped within the solid phase were characterized, along with the microstructure obtained using the traditional feedstock reheating process. The Wilcox test (with α = 0.05) was then applied to statistically analyze the measured differences in the microstructures obtained using the two different processing routes. It was found that a refined near-spherical structure with uniform globule size, higher sphericity, lower coarsening rate constant, and less entrapped liquid was obtained via the new two-stage reheating process in comparison with the microstructure obtained using the traditional feedstock reheating process.

A review of recent literature supports the notion that organisms may achieve nanoscale control over the hierarchical assembly of organic–inorganic materials by compartmentalizing reactions into small volumes containing specifically functionalized macromolecules. Such confinement may introduce a degree of determinism to the stochastic process of nucleation by greatly reducing the number of nucleation events, allowing an organism to control nucleation using “soft” organic substrates. In this way, the polymorph, orientation, shape, and size of a crystalline building block can be selected, and its assembly into a larger structure orchestrated by the organic matrix.