Single-crystal silicon test specimens, fabricated by lithography and deep reactive ion etching (DRIE), were used to measure microscale deformation and fracture properties. The mechanical properties of two specimen geometries, both in the form of a Greek letter Θ (theta), were measured using an instrumented indentation system. The DRIE process generated two different surface structures leading to two strength distributions that were specimen geometry independent: One distribution, centered about 2.1 GPa, was controlled by 35 nm surface roughness of scallops; the second distribution, centered about 1.4 GPa, was controlled by larger, 150 nm, pitting defects. Finite element analyses (FEA) converted measured loads into strengths; tensile elastic measurements validated the FEA. Fractographic observations verified failure locations. The theta specimen and testing protocols are shown to be extremely effective at testing statistically relevant (hundreds) numbers of samples to establish processing–structure–property relationships at ultrasmall scales and for determining design parameters for components of microelectromechanical systems.

The current work describes the simple solution process of ball-chain polycrystalline Fe nanofibers with aspect ratios (λ) and diameters (D) of over 1−65 and 30−95 nm. Static magnetic and microwave electromagnetic property studies demonstrated that such properties strongly depend on the λ and D of the Fe nanofibers. As the λ and D increase, the U-shape of the saturation magnetization (Ms) reaches a maximum of 180.0 emu·g−1, owing to the cooperative action of nanoeffects and magnetic interactions, whereas the coercivity (Hc) gradually increases due to aspect ratio variations. In contrast, the change in trends of the permittivity (ε′, ε″) and the dielectric loss (tgδE) are represented as an inverted U-shape; the permeability (μ′, μ″) and magnetic loss (tgδM) increase at low-frequency ranges and decrease at high frequency ranges. Stronger absorption and broader bandwidths of Fe nanofibers compared with Fe nanoparticles are ascribed to higher dielectric losses. The prepared Fe nanofibers have high potential in light-weight and broad bandwidth microwave absorbing applications.

We have studied the dynamic response of Fe-doped manganites with ac susceptibility measurements in La0.65Ca0.35Mn1−xFexO3 with 0.01 ≤ x ≤ 0.10 as functions of temperature and dc magnetic field. It is observed that the in-phase part of susceptibility goes through a maximum that is removed on the application of moderate dc field. DC fields suppress both the components (real and imaginary parts) with the strongest effects being at or close to TC. Conduction and ferromagnetism have been consistently suppressed by Fe substitution. Increased spin disorder and decrease in TC with increasing Fe content are evident. The effect of Fe is seen to be consistent with the disruption of the Mn–Mn exchange possibly due to the formation of magnetic clusters. There is clear correlation between the resistivity and susceptibility. Low-temperature dissipation in high-Fe-doped samples is observed; that is, increasing the Fe leads to increased spin disorder and dissipation at low temperature. The effect of the dc field is discussed in terms of the suppression of spin fluctuations close to TC.

Matusi–Akaogi force field is used in molecular dynamics simulations to generate three samples of amorphous TiO2 of 3-nm size under different heating and quenching rates. The averaged pair correlation functions, coordination numbers, bond lengths, bond angles, and dihedral angles are calculated at 315 K. It is found that overcoordinated Ti and O atoms are in the core region, 6- and 3-fold coordinated Ti and O atoms are in the central part, and undercoordinated Ti and O atoms are in the vicinity of the surface. The correlations are significant up to 10 Å and vanish at the particle size. The calculated averaged bond lengths for short-range interparticle correlations agree with the experimental data. The discrete bond angles and dihedral angles of crystalline sphere get distributed over complete range in the amorphous phase and closer strained atomic network is predicted. The relative variance in the atomic arrangements in three samples is within 4%.

The unique and highly utilized properties of TiO2 nanotubes are a direct result of nanotube architecture. To create different engineered architectures, the effects of electrolyte solution, time, and temperature on the anodization of titanium foil were studied along with the resultant anodized titanium oxide (ATO) nanotube architectures encompassing nanotube length, pore diameter, wall thickness, smoothness, and ordered array structure. Titanium foil was anodized in three different electrolyte solutions: one aqueous [consisting of NH4F and (NH4)2SO4] and two nonaqueous (glycerol or ethylene glycol, both containing NH4F) at varying temperatures and anodization times. Variation in anodization applied voltage, initial current, and effect of F− ion concentration on ATO nanotube architecture was also studied. Anodization in the aqueous electrolyte produced short, rough nanotube arrays, whereas anodization in organic electrolytes produced long, smooth nanotube arrays greater than 10 μm in length. A position effect, relative to the solution–air interface, was observed in this work. Furthermore, it was found that anodization in glycerol at elevated temperatures for several hours could possibly produce freely dispersed individual nanotubes.

The electromigration (EM) behavior of the Cu/Sn–In/Cu solder model strip was investigated under the conditions of high electrical current density (10 kA/cm2) at various temperatures. The composition of indium (In) was 0, 4, 8, and 16 in wt%. The interconnection of Sn–In solder alloys with a Cu substrate was prepared by reflow soldering at 250 °C. Microstructural analysis confirmed that primary intermetallic compound formed at the interface of the Cu/Sn–In strip was Cu6(In,Sn)5 regardless of In contents. Sn grain size became finer as In content increased. After current stressing, electrical failure was caused by the formation of voids and cracks at the cathode because of the migration of Cu atoms. Sn–16In alloy that has fine grain structure exhibits excellent EM resistance primarily due to the retardation of Cu migration.

Graphene oxide nanoplatelets (GONPs) were obtained by unraveling helical-ribbon carbon nanofibers (HR-CNF) using a modified Hummers and Offeman method in conjunction with ultrasonication. In this account, we carry out a complete evaluation of the effect of different oxidative agent concentrations on the resulting platelet materials. Transmission electron microscopy, atomic force microscopy, Fourier transform infrared, x-ray diffraction, x-ray photoelectron spectroscopy, and thermogravimetric analysis were performed to carefully characterize GONPs resulting from the oxidative process. Comparative experiments using multiwall carbon nanotubes (MWCNTs) and graphite were also carried out. Our studies suggest that the oxidation treatment is more effective in HR-CNFs than in MWCNTs. Furthermore, the unraveling of HR-CNFs results in GONPs consisting of less stacked layers when compared to other starting materials such as graphite. Therefore, HR-CNFs appear to be excellent precursors to produce few-layered GONPs.

A gradient structure was synthesized on the surface of Zr55Al10Ni5Cu30 alloy with high glass-forming ability by laser surface melting (LSM). Along the laser incident direction, the surface remelted alloy exhibits gradient microstructure distributed in the sequence of amorphous structure, nanocrystal- reinforced amorphous matrix composite (transitional layer A), dendrites–amorphous phase composite (transitional layer B), and crystalline phases from the top surface to the substrate. The formation mechanism of this gradient structure is discussed based on the experimental results of the microstructure together with the finite volume simulation of the process of LSM treatment. The friction coefficient of the transitional layer A is ∼2.5 times lower than those of the other layers under the same sliding friction condition, and possible reasons for this phenomenon are discussed in connection with the rolling motion and material transfer mechanism. The transitional layer B exhibits the best wear resistance among all the structures studied here, which is related to the optimized ratio of microhardness to reduced Young’s modulus (H/Er).

We present a low-temperature, hydrothermal synthesis method for Ta-doped TiO2. Here, alkoxide-based precursors are mixed at low temperatures to suppress differential hydrolysis and phase separation. This method ensures homogeneous, molecular mixing of the Ta dopant with the native oxide up to a concentration of ∼2.5 at.%. X-ray diffraction and energy dispersive spectrometer analyses confirm a uniformly doped rutile TiO2. Scanning electron microscopy and transmission electron microscopy analyses reveal a highly branched structure. Optoelectronic properties of these structures were investigated using ultraviolet-visible spectroscopy and low-temperature photoluminescence.

Cu6Sn5 is a common intermetallic compound formed during electrical packaging. It has an allotropic transformation from the low-temperature monoclinic η’-Cu6Sn5 to high-temperature hexagonal η-Cu6Sn5 at equilibrium temperature 186 °C. In this research, the effects of this allotropic transformation and Ni addition on the thermal expansion of η’- and/or η-Cu6Sn5 were characterized using synchrotron x-ray diffraction and dilatometry. A volume expansion during the monoclinic to hexagonal transformation was found. The addition of Ni was found to decrease the undesirable thermal expansion by stabilizing the hexagonal Cu6Sn5 at temperatures below 186 °C and reducing the overall thermal expansion of Cu6Sn5.

A Mn3O4/graphene hybrid material is fabricated using a facile and simple in-situ reduction process and shown to be a promising anode for lithium rechargeable batteries. The hybrid material retains a high capacity with a good cycle life of up to 990 mAh g−1 after 30 cycles. The excellent electrochemical performance is attributable to the unique nanostructure of the hybrid material. Highly crystalline Mn3O4 particles (20–30 nm) are uniformly dispersed on graphene whose high electronic conductivity and high surface area provide a conductive percolating network throughout the electrode in the hybrid material. The conductive graphene networks enhance an electron transfer in the electrode and promote the electrochemical activity of the crystalline Mn3O4.

Although highly magnetostrictive thin films of Terfenol-D have been produced by a variety of methods, high-quality thick films have proved to be far more challenging to produce. To date, thick film processes have resulted in nanoparticulate films that contain significant porosity that reduces stiffness and results in oxidation and poor magnetostrictive performance. With the goal of understanding microstructural and compositional factors that affect performance, nanoparticulate Terfenol-D thick films were produced by laser ablation of microparticle aerosols combined with supersonic impaction. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photon spectroscopy, and magnetic measurements were performed on nanoparticles and on films as-deposited and after annealing in vacuum or in a reducing atmosphere. These measurements show that segregation occurs during oxidation of the films, prior to annealing, and results in films with poor magnetostriction. The segregation persists during annealing with no visible changes to the morphology or density of the nanoparticulate films exposed to temperatures as high as 800 °C. These results suggest that oxidation and segregation must be avoided to produce highly magnetostrictive thick films.