A contact for a micromechanical switch has been fabricated using electroplated gallium (Ga) on silicon to create an electrical switch contact that can be annealed to recover its original properties after mechanical damage. The resistivity of the electroplated Ga appears to be similar to pure Ga. The resistance increased with cycling but recovered to the original value after a thermal reflow process at 120 °C for 10 min. The hardness of thermally reflowed Ga droplets was 2 MPa when the droplets were unconstrained and was up to 95 MPa for constrained droplets, suggesting that all switching in this study caused permanent deformation at room temperature and that defects formed during plastic deformation are likely candidates for the increased resistance during cycling. Up to 300 switching cycles were investigated for contacts involving up to four Ga droplets to measure contact behavior under high-current and load-switching applications. Oxidation behavior was characterized for the thermal reflow process on the Ga droplets, suggesting a passivating 30-nm oxide form at 100 °C, and electrical contact resistance nanoindentation suggests the oxide breaks during mechanical contact.

Pure Ni and Ni–W thin films with different W contents (<22 at.%) and a thickness of 500 nm have been produced by (co)sputtering. The phase composition, changes in residual stress, crystallite size, microstrain, and texture have been investigated employing in-situ x-ray diffraction measurements (25–550 °C) and ex-situ transmission electron microscopy analyses. For all compositions investigated, W dissolves substitutionally in Ni. The dissolution of W results in a highly columnar nanocrystalline microstructure with grain aspect ratios (height to width) exceeding 10. The Ni(W) solid solution exhibits a very high density of planar (twin and intrinsic stacking) faults oriented perpendicular to the growth direction. Whereas grain coarsening occurs for the nanocrystalline pure Ni thin films already upon heating to temperatures as low as about 125 °C, the microstructure of the nanocrystalline Ni–W thin films remains stable up to much higher temperatures, that is, even exceeding 350 °C. Above 350 °C, a W depletion of the Ni–W layer as a result of W segregation at planar faults occurs, which is accompanied by a change in lattice constant and in-plane stress.

Electropulsing-induced evolution of texture during recrystallization of Fe–3%Si alloy strip was studied using electron backscattered diffraction and x-ray diffraction techniques. Under electropulsing, various textures occurred during several seconds of recrystallization in the alloy. The Goss texture (G-texture) with high energy storage developed with increasing misorientation distribution of the low-angle grain boundaries. The mechanism of the electropulsing-induced G-texture evolution was discussed from the point of view of electropulsing dynamics.

Peripherally and nonperipherally tetrakisoctylthio- and tetrakisoctyloxy-substituted lead(II) phthalocyanines (PbPcs) were synthesized and characterized using elemental analysis, nuclear magnetic resonance, ultra violet–visible (UV-Vis), infrared (IR), and mass spectroscopies. The mesogenic properties of PbPcs were studied by differential scanning calorimetry, polarized optical microscopy, and x-ray diffraction. The effects of the substitution position and nature of linkage heteroatom on the liquid-crystalline properties and the orientation of the molecules were also studied. Visible absorption spectroscopy yielded an evidence of a thermally induced molecular reorganization in the films. Reflection–absorption IR spectroscopy was used to study the preferential orientation of molecules relative to the substrate surface. The intense bands in the IR spectra of the PbPcs were assigned with the aid of quantum chemical (density functional theory) computations.

Microcantilevers fabricated by microelectromechanical system processes were used to study the residual stresses in the film/substrate systems. Aluminum films were deposited on silicon nitride substrates by thermal evaporation at room and elevated temperatures, and residual stresses were characterized from the deflection profiles of the Al/SiNx microcantilevers. The Al/SiNx microcantilever beam made of room-temperature-deposited Al film was found to deflect toward the substrate side, which in turn resulted in compressive residual stress in the film. In contrary, the microcantilever of Al film deposited at 105 °C was found to deflect toward the side of Al film when the thickness ratio of film to substrate was greater than 0.31 and the residual film stresses were tensile. The axes with zero bending strain component and zero stresses, i.e., the bending and the neutral axes in the film/substrate system were also investigated. The results can be applied to the arm of the atomic force microscope to characterize its deflection and stresses.

A one-step wet chemistry route has been explored to synthesize hollow hydroxyl titanium oxalate nanoscale spheres under mild experimental conditions. The hollow spheres were ∼200 nm in diameter, with a shell thickness of ∼30 nm. The nanospheres were formed by smaller aggregated colloidal subunits. The influence of temperature and solvent on the structure of the nanospheres was investigated. The formation of hollow interiors in the nanospheres may be rationalized by Ostwald ripening mechanism. Simple thermal treatment topotactically transformed the chemical composition into anatase TiO2. The high-order hollow porous spherical structure was preserved, with smaller crystalline anatase TiO2 nanoparticles as building units. Dense hydroxyl titanium oxalate nanospheres and their corresponding non-hollow porous anatase TiO2 nanospheres were also successfully achieved in suitable reaction conditions. The method and procedure reported herein may be extended in principle for the fabrication of other functional materials.

A novel and previously unreported, high temperature solid–liquid–solid (SLS) silica nanowire (NW) growth mode has been observed and investigated. In this mode, SLS NW nucleation and subsequent growth was uniquely promoted by—and coupled to—the formation of thermally etched pyramidal pits in the Si substrate that formed during a high temperature anneal phase before the onset of SLS NW formation. The silicon oxide-mediated thermal pit formation process enhanced Si transport to Au–Si alloy droplets directly adjacent to the pyramidal pits. Consequently, SLS NW nucleation and growth was preferentially promoted at the pit edges. The promotion of SLS NW growth by the pyramidal pits resulted in the observation of SLS NW “blooms” at the pit locations. Subsequent NW growth, occurring both at the pit sites and from Au–Si alloy droplets distributed across the planar surfaces of the Si wafer, eventually occluded the pits. This newly observed process is termed as “thermal pit-assisted growth.”

In this study, we show that the volatile monoxide species generated during the active oxidation of Ge and Si substrates can be utilized in the presence of Au catalytic nanoparticles to nucleate and grow GeOx and SiOx nanowires. A simple thermodynamic model is developed to ascertain the critical O2 partial pressure as a function of temperature required for the active oxidation of Ge and Si substrates and is experimentally verified. The ideal conditions for uniform nanowire growth across the substrate are shown to be primarily dependent on the O2 partial pressure, the annealing temperature and thicknesses of the surface oxide, and deposited Au. The role of a metastable surface oxide separating the active oxidation and NW nucleation processes is also discussed.

Mn-doped γ-Ga2O3 thin films with a defective spinel structure have been epitaxially grown on spinel (100) substrates using pulsed laser deposition. The crystal quality of the films is strongly dependent on preparation conditions, particularly substrate temperature and laser energy density, as well as Mn concentration. In the 7 cation% Mn-doped film grown under the optimized conditions, the full width at half maximum in the x-ray diffraction rocking curve for the (400) plane is 117 arcsec and the root-mean-square roughness of the surface is approximately 0.4 nm. These values are comparable to those of the spinel substrate. The film shows a uniform tetragonal distortion with a tetragonality of 1.05.

We studied nanoprecipitates (NPs) and defects in p-type filled skutterudite CeFe4Sb12 prepared by a nonequilibrium melt spinning plus spark plasma sintering method using transmission electron microscopy. NPs with mostly spherical shapes and different sizes (from several nanometers to several tens of nanometers) have been observed. Among these, two types of NPs were most commonly observed, Sb-rich superlattices and CeSb2. The Sb-rich superlattices with a periodicity of about 3.6 nm were induced by the ordering of excessive Sb atoms along the c-direction. These NPs typically share coherent interfaces with the surrounding matrix and induce anisotropic strain fields in the matrix. NPs with compositions close to CeSb2, on the other hand, have been shown to be much larger in size (∼30 nm) and have orthorhombic structures. Various defects were typically observed on the interfaces between these NPs and the matrix. The strain fields induced by these NPs are less distinct, possibly because part of the strain has been released by defect formation.

ReB2 was recently reported to exhibit high hardness and low compressibility, which both are strong functions of its stoichiometry, namely Re to B ratio. Most of the techniques used for ReB2 synthesis reported 1:2.5 Re to B ratio because of the loss of the B during high temperature synthesis. However, as a result of B excess, the amorphous boron, located along the grain boundaries of polycrystalline ReB2, would degrade the ReB2 properties. Therefore, techniques which could allow synthesizing the stoichiometric ReB2 preferably at room temperature are in high demand. Here, we report synthesis of ReB2 powders using mechanochemical route by milling elemental crystalline Re and amorphous B powders in the SPEX 8000 high-energy ball mill for 80 h. The formation of boron and perrhenic acids are also reported after ReB2 powder was exposed to the moist air environment for a 12-month period of time.

In this work, elastic properties of Mg-based bulk metallic glasses (BMGs) with different chemical compositions were investigated. By compositional tuning in the quaternary Mg–Cu–Ag–Y alloys, the Poisson’s ratio ν of 0.332 is achieved at Mg56Cu21Ag14Y9 BMG, in excess of the previously suggested critical value (ν = 0.31–0.32) for the brittle-to-tough transition in metallic glasses. With the properties of the constituent elements, the predicted values of the bulk modulus B and shear modulus μ of Mg-based BMGs are 8% and 10% greater than the measured value, respectively. Notch toughness KQ of the ten investigated Mg-based BMGs varies between 3.6 and 8.2 MPa√m. Intrinsic brittleness of Mg glass is associated with its tiny plastic zone size (in micrometer scale) and weak resistance to crack propagation. The toughness variations are lack of significant correlation with the ν or μ. Among the investigated alloys, the Mg59.5Cu22.9Ag6.6Gd11 BMG manifests a good combination of improved toughness and high glass-forming ability.

Iodine-doped CdS (I-CdS) with controllable morphologies, pure hexagonal phase, and enhanced photocatalytic activity was synthesized via a mild hydrothermal process with polyvinylpyrrolidone-iodine (PVP-I) acting as the template-directing reagent and iodine source. The morphologies of the as-prepared samples could be adjusted from irregular cone-shaped particles to uneven microspheres, further to smooth microspheres, while the crystal phases were also transformed from mixed cubic and hexagonal phases to pure hexagonal phase upon increasing the molar ratio of PVP-I to Cd2+ from 0 to 2. The iodine doping could result in red shift of the absorption edges and band gap narrowing of the I-CdS samples. Importantly, a critical point of 0.5 of molar ratio of PVP-I to Cd2+ for iodine doping was found to be necessary for obtaining a pure hexagonal phase that facilitates the improving of photocatalytic activity on the degradation of Rhodamine B in aqueous solution under visible light irradiation.

Bi1.95La1.05TiNbO9 (BLTN-1.05) thin films were prepared on fused quartz substrates by pulsed laser deposition. The x-ray diffraction (XRD) analysis and atomic force microscope (AFM) surface morphology measurements were performed on the samples. The XRD pattern demonstrated that the films are single-phase perovskite structured and well crystallized. The AFM analysis indicated that the films have less rough surface. The fundamental optical constants were obtained through optical transmittance measurements. The nonlinear optical properties of BLTN thin films were measured by a single beam Z-scan technique under 1064 nm excitation. The real and imaginary parts of the third-order nonlinear optical susceptibility χ(3) of the film were measured to be 9.56 × 10−9 and −3.67 × 10−9 esu, respectively. The Z-scan results show that BLTN thin films have potential applications in nonlinear optics.

The current study revealed the effects of reflow temperature and the reflow time on the interfacial embrittlement of SnBi/Cu joints. When the reflow temperature is below 220 °C, the joints reflowed for 150 min often fail in brittle mode because the Bi atoms from the SnBi solder easily segregated at the Cu3Sn/Cu interface. In contrast, Bi embrittlement did not occur for joints reflowed at above 260 °C for 150 min because the Bi particles were frozen in the Cu3Sn layer during the formation of intermetallic compounds (IMC) at the initial reflow stage, mainly located at the Cu3Sn grain boundary. It is interesting to note that the Bi embrittlement did occur when the joints were reflowed at above 260 °C for 250 min, which should be attributed to Bi diffusion. It is concluded that the Bi particles are frozen in the Cu3Sn layer with increasing reflow temperature, that cannot eliminate Bi embrittlement, and can only delay the occurrence of Bi embrittlement.

Three-dimensional (3D) sphere-like Eu3+-doped white light lutetium tungstate phosphors have been fabricated by the cationic surfactant cetyltrimethyl ammonium bromide (CTAB)-assisted hydrothermal method, which presents a diameter of ∼2-μm morphology assembled by nanoflakes with a length of 100 to ∼200 nm. The results demonstrate that CTAB, suitable pH values, reaction time, and reaction temperature are all essential for the formation of lutetium tungstate microspheres. Photoluminescence measurement indicates that lutetium tungstate microspheres show a broad O–W Charge transfer state (CTS) transition and the characteristic emission of Eu3+ at ∼591 and ∼611 nm.