Shape memory alloys (SMA) undergo reversible martensitic transformation in response to changes in temperature or applied stress, resulting in the properties of superelasticity and shape memory. At present, there is high scientific and technological interest to develop these properties at small scales and apply SMA as sensors and actuators in microelectromechanical system technologies. To study the thermomechanical properties of SMA at micro and nanoscales, instrumented nanoindentation is widely used to conduct nanopillar compression tests. By using this technique, superelasticity and shape memory at the nanoscale have been demonstrated in micro and nanopillars of Cu–Al–Ni SMA. However, the martensitic transformation seems to exhibit different behavior at small scales, and a size effect on superelasticity has been recently reported. In this study, we provide an overview of the thermomechanical properties of Cu–Al–Ni SMA at the nanoscale, with special emphasis on size effects. Finally, these size effects are discussed in light of the microscopic mechanisms controlling the martensitic transformation at the nanoscale.

We demonstrate the fabrication of shadow mask (SM) patterned as well as nanoimprint lithography (NIL) patterned organic transistors and integrated complementary organic inverters (ICOIs). As active layers pentacene (p-type) and either PTCDI-C13H27 or F16CuPc (n-type) were used. The SM-patterned ICOIs with a staggered bottom gate configuration, a nanocomposite dielectric and both active layer combinations (pentacene/PTCDI C13H27, pentacene/F16CuPc) exhibited high performance (3 V operation voltage; gain around 60; high level 3 V; low level 5 mV; noise margin 0.9 V). Flexible ICOIs with transistor channel lengths of 900 nm were successfully fabricated by NIL, using a benzocyclobutene derivative as dielectric. Because of the process inherent coplanar bottom gate configuration, F16CuPc was used. The ICOIs showed proper functionality (3 V operation voltage; gain around 5; high level 2.9 V; low level 25 mV). To our knowledge, this study demonstrates the first complementary submicron inverters based on fully R2R compatible imprint processes.

Tribological behavior of alumina-particle-reinforced aluminum composites made by powder metallurgy process has been investigated. The nanocomposite containing 15 vol% of Al2O3 nanoparticles exhibits excellent wear resistance by showing significantly low wear rate and abrasive wear mode. The wear rate of the nanocomposite is even lower than stainless steel. We have also demonstrated that such excellent wear resistance only occurred in the composite reinforced with the high volume fraction of nanosized reinforcing particles. The results were discussed in terms of the microstructure of the nanocomposite.

The properties of widely used Ni–Ti-based shape memory alloys (SMAs) are highly sensitive to the underlying microstructure. Hence, controlling the evolution of microstructure during high-temperature deformation becomes important. In this article, the “processing maps” approach is utilized to identify the combination of temperature and strain rate for thermomechanical processing of a Ni42Ti50Cu8 SMA. Uniaxial compression experiments were conducted in the temperature range of 800–1050 °C and at strain rate range of 10−3 and 102 s−1. Two-dimensional power dissipation efficiency and instability maps have been generated and various deformation mechanisms, which operate in different temperature and strain rate regimes, were identified with the aid of the maps and complementary microstructural analysis of the deformed specimens. Results show that the safe window for industrial processing of this alloy is in the range of 800–850 °C and at 0.1 s−1, which leads to grain refinement and strain-free grains. Regions of the instability were identified, which result in strained microstructure, which in turn can affect the performance of the SMA.

High-dielectric constant all-organic composite films consisting of polyaniline (PANI) filler and poly(butylene succinate) host were synthesized by simple blending process. The chemical structures and morphology of the composite films were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The dielectric properties of the composite films with different filler concentrations were studied in the frequency range of 100–106 Hz. A percolation phenomenon was observed in the composite films with a percolation threshold vc = 19.7% and the dielectric constant was 10 times that of the pure host material. The enhancement in the dielectric constant can be ascribed to Maxwell–Wagner–Sillars polarization and the low-dielectric loss to good dispersion of PANI filler in the host. As the host polymer is biodegradable, it may be applied as a “green” dielectric material.

High quality factor and near-zero temperature coefficient of resonant frequency (τf) are the two key issues for a certain microwave dielectric material system used in microstrip patch antennas. ZnTiO3-based ceramics is a promising candidate for microstrip patch antennas. On inhibiting the decomposition of ZnTiO3 by adding sufficient amount of MgO, high quality factor microwave dielectric material (Zn0.7Mg0.3)TiO3 was obtained. The deviations between theoretical and observed dielectric polarizabilites, the packing fraction, and bond valence were calculated to analyze correlation between structure and properties of (Zn0.7Mg0.3)TiO3. TiO2 was added to adjust τf of (Zn0.7Mg0.3)TiO3, and 0.82(Zn0.7Mg0.3)TiO3–0.18TiO2 with an εr of 28.5, a Qf of 125,050 GHz, and a near-zero τf which satisfied the requirement as a substrate material for microstrip patch antenna was obtained at 1100 °C. In addition, a dielectric microstrip antenna was designed and fabricated using the proposed dielectric materials. The microstrip patch antenna exhibited a −34.96 dB return loss and a 1.05 voltage standing wave ratio at 2.5 GHz.

The shapes of the interfacial delamination crack and stress states during wedge indentation in a soft-film-on-hard-substrate system were investigated systematically using the three-dimensional (3D) finite element simulation and wedge indentation experiment. In the simulation, a traction–separation law was used to characterize the failure behaviors of the interface. The effects of the wedge indenter tip length and the film thickness on the onset and growth of interfacial delamination were analyzed. It was shown that a two-dimensional (2D) to 3D transition of stress states occurred depending on the ratio of indenter length to film thickness. Furthermore, the interfacial delamination process by wedge indentation was conducted experimentally, and comparisons between the computational and experimental results yielded quantitative good agreement. Finally, a straightforward criterion based on the curvature of the delamination crack front was proposed to indicate the transition of stress states during the interfacial delamination. A guideline was therefore proposed to classify the 2D and 3D stress states for extracting the interface adhesion properties.

A novel load–displacement sensing instrument has been designed and fabricated to characterize the fracture properties of brittle thin films at low temperature (approximately −30 °C) and pressure (1.6e-4 Pa) environments. In this study, the instrument was used to investigate the effects of harsh environments on the fracture behaviors of organosilicate glass (OSG) and silicon carbonitride (SiCN) thin films under four-point bend loading. Experimental results showed that the fracture strengths of film stacks are the highest when the environment contains a very low water molecule concentration. This condition can be achieved by purging the testing chamber with pure nitrogen or reducing the chamber pressure to less than 1 Pa. In contrast, cracks propagated readily along OSG/SiCN interfaces when experiments were performed in deionized water. The effects of low temperature (approximately −30 °C) and pressure on thin film fracture were also studied, and the results demonstrated that there is no observed degradation of the OSG fracture properties. X-ray photoelectron spectroscopy (XPS) technique was used to identify the chemical composition of the fracture surfaces.

Systematic nanoindentation experiments have been carried out to study the mechanical properties of a nanocrystalline Fe–51Ni coating exhibiting anelastic and creep characteristics. An analytical method based on the correspondence principle for linear viscoelasticity was developed. The holding displacement–time data obtained in indentation creep tests at a high loading rate of 20 mN/s were analyzed, and material parameters related to the elastic, anelastic, and creep characteristics were derived using a model containing one Maxwell unit and two Kelvin units. The anelastic deformation thus contains at least two relaxation processes having relaxation times of 0.37 and 6.8 s, respectively, and the creep deformation is described by a viscosity value of 4.2 × 104 GPa·s for the alloy in an as-deposited state. The anelastic and creep characteristics descend associated with increases of the elastic modulus and hardness values after the alloy was annealed at 673 K.

We investigated microstructures, compositional distributions, and electrical properties of dielectric CaCu3Ti4O12 (CCTO) thin films deposited on Pt/TiO2/SiO2/Si substrates from 700 to 800 °C by pulsed laser deposition. With increasing the deposition temperature from 700 to 750 °C, the dielectric constants (εr) of CCTO films were greatly enhanced from ∼300 to ∼2000 at 10 kHz, respectively. However, the εr values of CCTO films were gradually decreased above 750 °C, which was surely attributable to the formation of a TiO2-rich dead layer at the interface between CCTO and Pt electrode. Compositional analyses by Auger electron spectroscopy, energy dispersive spectroscopy, and electron energy loss spectroscopy revealed that the TiO2-rich dead layer became thicker because of severe Cu diffusion from CCTO films to Pt electrode. The leakage current behaviors of CCTO films are in good agreement with Poole–Frenkel conduction mechanism, where both the TiO2-rich dead layer and rutile TiO2 nanocrystalline particles are considered to play a role of charge trapping centers.

This study investigates thermally induced structural damages to amorphous plasma-enhanced chemical vapor deposition (PECVD) SiNx thin films at elevated temperatures, including chemical structure, microstructure, and physical integrity. The films were synthesized by means of PECVD method. Heating to elevated temperatures in air was found to cause multiple forms of chemical, structural, and physical damages. Chemically the films were found to oxidize and lose their nitrogen and hydrogen contents. Structurally the amorphous SiNx matrix was found to convert partially into SiO2 as a result of oxidation and to crystallize into Si3N4 crystallites. The physical damages include pinholes, circular “penny” cracks, random “dry mud” cracks, and spalling. The types of the damages were observed in different temperature regimes. The formation of the penny cracks is attributed to excessive compressive stresses created in the film by oxidation, which is associated with a large volume expansion. The formation of the random cracks is attributed to tensile stresses caused by crystallization, which is associated with a large volume contraction. Such damages limit the suitable application conditions for devices made of these films.

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.