We derive the dispersion relation of SiC substrate phonon-induced surface plasmon polariton (SPP) in epitaxial graphene (EG) grown on 4H–SiC, in SiC's restrahlen band (8–10 μm) by solving Maxwell equation in transverse magnetic mode. We also fabricated EG waveguide using photolithography and RIE etching for experimental study. Both theory and experimental data correlate in good agreement. Finally, we explain the viability of plasmonic device in EG both in theoretical and experimental point of view to explain electron–hole pair recombination. SPP formation finds application in nanophotonic devices for optical computing because of graphene's unique plasmonic properties. This can be applicable for high speed data switching in microprocessor and random access memory as well as optical interconnect in modern VLSI technology.

Orthorhombic SrIrO3 is a correlated metal whose electronic properties are highly susceptible to external perturbations due to the comparable interactions of spin–orbit interaction and electronic correlation. We have investigated the electronic properties of epitaxial orthorhombic SrIrO3 thin-films under compressive strain using transport measurements, optical absorption spectra, and magnetoresistance. The metastable, orthorhombic SrIrO3 thin-films are synthesized on various substrates using an epi-stabilization technique. We have observed that as in-plane lattice compression is increased, the dc-resistivity (ρ) of the thin films increases by a few orders of magnitude, and the dρ/dT changes from positive to negative values. However, optical absorption spectra show Drude-like, metallic responses without an optical gap opening for all compressively strained thin films. Transport measurements under magnetic fields show negative magnetoresistance at low temperature for compressively strained thin-films. Our results suggest that weak localization is responsible for the strain-induced metal–insulator transition for the orthorhombic SrIrO3 thin-films.

Ag–TiO2 hybrids are useful in various applications, such as photocatalysis, solar energy conversion, and biosensoring. In this study, oil-decorated TiO2 films were used to induce the formation of Ag nanoplates in AgNO3 solution via a photocatalytic method. Ag nanoplates in the products can be controlled by changing the oil-decoration time of films or changing the AgNO3 concentration of the solution. Oil decoration was found to be necessary in the formation of Ag nanoplates, and a critical concentration of AgNO3 solution was needed. The oil layer on the TiO2 films was demonstrated to play a role in the prevention of the reoxidation of the Ag atoms, and a growth model was proposed to interpret the formation of Ag nanoplates on the oil-decorated TiO2 films.

In the present research, the microstructures and mechanical properties of Al–Si–Cu alloy matrix composites reinforced with nanosized alumina (Al2O3) and zirconia (ZrO2) were investigated. For this purpose, Al2O3 particulates were replaced with different wt% of ZrO2 to improve microstructure and mechanical properties. The T6 heat treatment was also performed to investigate mechanical properties in heat-treated condition. Tensile testing, hardness measurement, optical microscopy, x-ray diffraction (XRD), energy dispersive spectroscopy, and scanning electron microscope examination were used to characterize the behavior of composite and matrix. The highest tensile strength was achieved in the specimen containing 1.25 wt% ZrO2 and 0.75 wt% Al2O3, which shows an increase to 36% in comparison with the nonreinforced base alloy. The hardness values indicated 11% increase following the heat treatment. Fracture surface examinations revealed a transition from ductile fracture mode in as-cast aluminum alloy to rather brittle in Al–Si–Cu alloy matrix hybrid composites.

In situ nano-TiB2 reinforced ultrafine-grained (UFG) Al composites were prepared via combined processes of flux-assisted synthesis (FAS) and asymmetrical rolling (ASR). The UFG Al composite with an ASR reduction ratio of 97% exhibits an average matrix grain size of 380 nm and an average TiB2 particulate size of 50 nm. Dislocation density in the composites is higher than that corresponding to the high purity (99.99 wt%) Al under identical processing conditions. The yield and ultimate tensile strength values of the UFG Al composites processed with an ASR reduction ratio of 97% are approximately 9 and 5 times higher relative to those of the initial coarse-grained Al, respectively. Moreover, the UFG Al composite with an ASR reduction ratio of 97% exhibits a higher elongation than that corresponding to the UFG pure Al under identical processing conditions, suggesting that nanoparticulates contribute to the overall plastic deformation when the matrix grains are refined to the UFG regime. Moreover, analysis of the strengthening behavior reveals no clear evidence that Orowan strengthening contributes significantly to the overall yield strength of the Al nanocomposites studied herein.

The effect of the intercritical temperature on the microstructure and mechanical properties of a newly developed quenching and partitioning steel using martensitic microstructure prior to the heat treatment process was studied. Such a quenching and partitioning process possessed a unique microstructure evolution, especially during intercritical annealing after prequenching. Excellent mechanical properties were obtained due to this unique multiphase microstructure. Significant amount of interlath-retained austenite was acquired and the relationship between the microstructure and work-hardening behaviors was proposed. The martensite/austenite islands increased at elevated annealing temperature, which deteriorated the total elongation and increased the tensile strength as hard constituents when it was excessive. The result indicated that the present full martensitic microstructure before the intercritical annealing is probably more suitable to an industrial application and is a better way to produce high strength steels with suitable ductility.

The paradox of strength and ductility is now well established and denotes the difficulty of simultaneously achieving both high strength and high ductility. This paradox was critically examined using a cast Al–7%Si alloy processed by high-pressure torsion (HPT) for up to 10 turns at a temperature of either 298 or 445 K. This processing reduces the grain size to a minimum of ∼0.4 μm and also decreases the average size of the Si particles. The results show that samples processed to high numbers of HPT turns exhibit both high strength and high ductility when tested at relatively low strain rates and the strain rate sensitivity under these conditions is ∼0.14 which suggests that flow occurs by some limited grain boundary sliding and crystallographic slip. The results are also displayed on the traditional diagram for strength and ductility and they demonstrate the potential for achieving high strength and high ductility by increasing the number of turns in HPT.

Three-dimensional (3D) morphological evolution and growth mechanisms of primary I-phase particles have been investigated in directionally solidified Al–6Mn–2.5Be (wt%) alloy at a wide range of growth rates (100–1500 μm/s). At relatively low growth rates (100–600 μm/s), the I-phase particles exhibit faceted growth with strong anisotropy, forming a hierarchical flower-like aggregate with icosahedral morphological symmetry composed of several attached irregular polyhedrons or pentagonal dodecahedrons. At higher growth rates (e.g., 1000 μm/s), the interface of the I-phases becomes unstable along the edges and corners of the pentagonal dodecahedron, thereby arousing growth perturbations. Correspondingly, a transition from faceted to nonfaceted growth occurs with increasing growth rate. Further increase of the growth rate leads to the formation of I-phase columnar dendrites' preferential growth along the 3-fold axis. The configurations of the flower-like aggregates can be adequately illustrated by a geometrical model in terms of the perfect and elongated pentagonal dodecahedrons. A growth mechanism for the flower-like aggregates has been proposed based on the clear understanding of the 3D morphological evolution of the I-phase particles.

The stress relaxation and failure behavior of Ni/Sn–3.0Ag–0.5Cu/electroless nickel electroless palladium immersion gold flip-chip solder bumps undergoing electromigration (EM) at 150 °C under 1.5 × 104 A/cm2 was investigated in situ. Three modes of stress relaxation of Sn–3.0Ag–0.5Cu solder bumps were identified. At the cathode, voids and hollows with terrace morphology gradually formed to relieve the tensile stress; at the anode, especially around the current crowding corner, recrystallization of Sn grains and extrusion of hillocks occurred to relieve the compressive stress; in the solder bump, Sn grain boundary sliding that occurred to accommodate the diffusion creep was more pronounced with increasing EM time. Grain boundary sliding is considered to be an indispensable requisite for diffusion creep. The microstructural evolution of solder bumps at the last stage of lifetime was revealed, and the final EM-induced failure mode was the local fusion of a solder bump resulting from the crack formation-and-propagation at the cathode.

This study was to analyze the microstructure, microhardness, tensile and fatigue performance of the welded joints performed by a fiber laser on 22MnB5 and dual-phase steels (DP590, DP980) in similar and dissimilar combinations. The result shows that the weld zone (WZ) basically consisted of lath martensite. The HAZ in these steels can be divided into 3 parts: quenched, incomplete quenched, and tempered region. The WZ had the highest hardness, and a soft zone existed in the HAZ of all steels. Inside the WZ of the dissimilar welded joints, two hardness subregions were observed due to the difference in the alloying elements of these steels. Tensile specimens of the 22MnB5–22MnB5 and 22MnB5–DP980 welded joints were all broken in HAZ, while the 22MnB5–DP590 welded joints failed in the DP590 base metal (BM). The BM had a higher fatigue life than the welded joints, and the fatigue failure of the 22MnB5 similar and 22MnB5–DP980 dissimilar welded joints respectively occurred in the HAZ and DP980 BM. The fatigue fracture contained 3 parts: crack initiation, crack propagation, and the final fast fracture region.

First-principles shear tests were performed on pure Mg, Mg–Li, Mg–Ca, Mg–Al, Mg–Sn, Mg–Ag, and Mg–Zn models to investigate the mechanical and chemical effects of the solute elements on the generalized stacking fault energy (GSFE) of Mg. The mechanical effect increased the unstable stacking fault energy (USFE), independent of the kind of solute element tested. The intensity of the mechanical effect was explained by the average distance between a solute atom and the surrounding Mg atoms, not by a difference in atomic radius between a solute atom and a Mg atom. In contrast, the chemical effect on the USFE was complicated, and the chemical effects of Ag and Zn were lower than expected from their electronegativity. Also, the chemical effect increased the USFE for the Li addition, but it decreased the USFE for the Ca addition although the electronegativity of Li is almost the same as that of Ca.

Different parts of a casting may receive different microstructures during cooling particularly for the large scale casting, which can affect the fatigue behavior. In the present study, in consideration of the safety and reliability, the microstructures, tensile properties, and high cycle fatigue behaviors of different regions in a low-pressure sand-cast Mg–10Gd–3Y–0.5Zr (GW103K) magnesium alloy component with large scale and complicated structure were investigated. The results showed that the tensile properties particularly ultimate tensile strength (UTS) and elongation (EL) varied with regions and the fatigue strength varied in a range from 100 to 115 MPa. In addition, crack initiation, crack propagation, and fracture behavior of the studied alloys after tensile test and high cycle fatigue test were also investigated systematically.

New-type Ni-based superalloys with and without Nb were designed in this study. Their hot corrosion behaviors were investigated at 800 °C with the deposition of a mixture of Na2SO4 and NaCl. The corrosion kinetics was studied by thermogravimetry. Microstructure of the corrosion scales was studied by SEM and the phase constituent was analyzed by XRD. Results showed that the corrosion kinetics followed approximately parabolic law. The corrosion scales on the two Ni-based alloys were comprised of Cr2O3, Al2O3, TiO2, and NiCr2O4. NiO was only detected in the scale on alloy without Nb. Nb2O5 appeared with the addition of 2.0 wt% Nb. No sulfide emerged in the scales. The corrosion scales both exhibited a layered structure. With Nb addition, the hot corrosion resistance of the alloy was notably improved. The action mechanism of Nb was investigated extensively in this study.