This paper presents experimental and theoretical studies of the adhesion between the drug-eluting layer and a Parylene C primer layer in coatings present on a model drug-eluting stent. To quantify adhesion, Brazil nut sandwich specimens were prepared mimicking the layers of this coating. These samples were stressed to fracture, and the resulting initial cracks at the Parylene C/drug interface were used to measure the dependence of interfacial fracture energy of mode mixity. The mating fracture surfaces were then analyzed using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). The interfacial energy release rates were obtained over a wide variety of mode mixities. Adhesion and fracture mechanics models were then used to estimate the mode mixity dependency of interfacial fracture toughness. Fracture toughness was found to be larger under higher mode mixity than that under lower mixity and the analytical model showed close agreement with experimental results.

This paper demonstrates the production of 〈00l〉-oriented CuO-doped (K0.476Na0.524)NbO3 (KNN) piezoelectric ceramics with a polymorphic phase transition (PPT) temperature greater than 180 °C by templated grain growth (TGG) using high aspect ratio NaNbO3 template particles. A novel (to the KNN system) two-step sintering and annealing process combined with CuO doping is demonstrated to improve density and maximize texture quality (F00l = 99% and rocking curve FWHM = 6.9°) in textured KNN ceramics. The best electromechanical properties (kp ≈ 0.58, k31 ≈ 0.33, d33 ≈ 146 pC/N, To-t ≈ 183 °C, Tc ≈ 415 °C, εr = 202, and tan δ = 0.016) are achieved in 1 mol% CuO-doped KNN with F00l = 99% and a relative density of 96.3%. The values of d33, kp, and k31 are 70–90% higher than randomly oriented ceramics and are obtained without a significant reduction in the PPT temperature, resulting in stable piezoelectric performance over a wide temperature range (−50 to 180 °C). These results show that high-quality textured KNN can be obtained by TGG and that a reactive matrix is unnecessary.

A new physical method is described for the preparation of metal microspheres by ultrasonic cavitation of low-melting point metals (<380 °C) immersed in hot silicone oil. The ultrasonic radiation causes dispersion of the molten metals into spheres, which solidify rapidly on cooling. This method is illustrated for the synthesis of Pb and Au–Si eutectic alloy.

Nature produces a wide variety of exquisite mineralized tissues, fulfilling diverse functions. Organisms exercise a level of molecular control over the detailed nano- and microstructure of the biomaterials that is unparalleled in today's technology. Our understanding of the underlying design principles of biomaterials provides ample opportunities for developing new approaches to materials fabrication at the nanometer and micrometer scale. It is clear that valuable materials lessons can be taught by any organism. I will exemplify this point by describing new nano- and microfabrication strategies and devices that have been inspired by the studies of biomineralization in echinoderms. The topics will include self-assembly, control of crystallization, synthesis of adaptive optical structures, hybrid materials, and novel actuation systems at the nanoscale level.

Due to their high carrier mobilities, electromigration resistance, and tailorable optical properties, carbon nanotubes are promising candidates for high-performance electronic and optoelectronic applications. However, traditional synthetic methods have lacked control over the structure and properties of carbon nanotubes. This polydispersity problem has confounded efforts to take carbon nanotubes from the research laboratory to the marketplace, especially for electronic and optoelectronic applications, where reliable and reproducible performance is paramount. In recent years, the research community has devoted significant effort to this issue, leading to substantial advances in the preparation of monodisperse carbon nanotube materials. This article highlights the most recent and promising developments from two perspectives: post-synthetic sorting and selective growth of carbon nanotubes of predetermined physical and electronic structure. These complementary approaches have yielded improved uniformity in carbon nanotube materials, resulting in impressive advances in carbon nanotube electronic and optoelectronic technology.

Glancing-incidence x-ray diffraction (GIXRD) has been applied to the investigation of depth-dependent stress distributions within electroplated Cu films due to overlying capping layers. Cu films, 0.65 μm thick, plated on conventional barrier and seed layers received a chemical vapor deposited (CVD) SiCxNyHz cap, an electrolessly deposited CoWP layer, or a CoWP layer followed by a SiCxNyHz cap. GIXRD and conventional x-ray diffraction measurements revealed that strain gradients were created in Cu films possessing a SiCxNyHz cap, where a greater in-plane tensile stress of approximately 180 MPa was generated near the film/cap interface as a result of constraint imposed by the SiCxNyHz layer during cooling from the cap deposition temperature. Although Cu films possessing a CoWP cap without a SiCxNyHz layer did not exhibit depth-dependent stress distributions, subsequent annealing introduced stress gradients and increased the bulk Cu stress. However, a thermal excursion to liquid-nitrogen temperatures significantly reduced tensile stresses in the Cu films.

Indentation experiments on thin films are analyzed by using a rigorous solution to model elastic substrate effects. Two cases are discussed: elastic indentations where film and substrate are anisotropic and elastoplastic indentations where significant material pileup occurs. We demonstrate that the elastic modulus of a thin film can be accurately measured in both cases, even if there is significant elastic mismatch between film and substrate.

The structure and properties of HfO2 films deposited by plasma assisted reactive pulsed laser deposition and annealed in N2 were studied upon thermal annealing as well as the evaluation of thermal stability by Fourier transform infrared spectroscopy, spectroscopic ellipsometry, and optical transmission measurements. The as-deposited HfO2 films appear predominantly monoclinic with an amorphous matrix which becomes crystallized after high-temperature annealing. No interfacial SiOx is observed for the as-deposited films on Si. The deposited HfO2 films exhibit good thermal stability and show excellent transparency in a wide spectral range with optical band gap energies of 5.65–5.73 eV depending on annealing temperature. An improvement in the optical properties by high-temperature annealing is also observed.

To fabricate graded-index optical elements by silver staining, we investigated the behavior of ion incorporation in aluminoborosilicate glasses, in which the contents of Al2O3 and Na2O were the same (in mol%). The amount of silver incorporated into the aluminoborosilicate glasses by the staining at 320 °C for 12 h was 5 to 10 times larger than that incorporated into the soda-lime silicate and borosilicate glasses. The diffusion depth of the incorporated silver ions was approximately 80 μm, which was also much deeper than that of the soda-lime silicate and borosilicate glasses. The coloration of the glasses was suppressed, particularly for the glass with the low content of Na2O. The concentration of the incorporated silver ions at the glass surface was 2 × 1021 atom/cm3 for the 37.5SiO2·25Al2O3·25Na2O·12.5B2O3 glass, corresponding to the replacement of sodium ions (20%). The refractive indices near the stained surfaces increased by 0.04 to 0.06. These values were comparable with those of the soda-lime silicate and borosilicate glasses.

In this study, the influence of T5 heat treatment on tensile and fatigue behavior of hot-extruded Mg–10Gd–3Y (wt%) magnesium alloy has been investigated. High cycle fatigue tests were carried out at a stress rate (R) of −1 and a frequency of 100 Hz using hour-glass-shaped round specimens with a gauge diameter of 5.8 mm. The results show that fatigue strength (at 107 cycles) of Mg–10Gd–3Y magnesium alloy increases from 150 to 165 MPa after T5 heat treatment, i.e., the improvement of 10% in fatigue strength has been achieved. However, the crack growth resistance is lowered by T5 heat treatment. Results of microstructure observation and scanning electron microscopy-energy dispersive x-ray (SEM-EDX) analysis suggest that the fatigue strength in the Mg–10Gd–3Y magnesium alloy is determined by the threshold stress of basal slip, which is induced by solid solution hardening and precipitation hardening.

This article reviews the materials science of graphene grown epitaxially on the hexagonal basal planes of SiC crystals and progress toward the deterministic manufacture of graphene devices. We show that the growth of epitaxial graphene on Si-terminated SiC(0001) differs from growth on the C-terminated SiC(0001) surface, resulting in, respectively, strong and weak coupling to the substrate and to successive graphene layers. Monolayer epitaxial graphene on either surface displays the expected electronic structure and transport characteristics of graphene, but the non-graphitic stacking of multilayer graphene on SiC(0001) determines an electronic structure much different from that of graphitic multilayers on SiC(0001). This materials system is rich in subtleties, and graphene grown on the two polar faces of SiC differs in important ways, but all of the salient features of ideal graphene are found in these epitaxial graphenes, and wafer-scale fabrication of multi-GHz devices already has been achieved.

Using nanoindentation, this study develops the criteria to evaluate the creep performance of the intermetallic compounds (IMCs) formed at the interface of microelectronic solder joints. Regardless of crystal structure and melting point, the creep stress exponent (X), one of the parameters determining creep resistance, is in good agreement with tendencies of the work-hardening exponent (n) and also the ratio of yield stress (Y) to Young's modulus (E), which reveals the ability against plastic deformation.

The effects of prestrain, strain rate, and temperature on the impact properties of 304L stainless steel are investigated using a compressive split-Hopkinson pressure bar. The impact tests are performed at strain rates ranging from 2000 to 6000 s−1 and temperatures of 300, 500, and 800 °C using 304L specimens with prestrains of 0.15 or 0.5. The results show that the flow stress, work-hardening rate, and strain rate sensitivity increase with increasing strain rate or decreasing temperature. As the prestrain increases, the flow stress and strain rate sensitivity increase, but the work-hardening rate decreases. The temperature sensitivity increases with an increasing strain rate, temperature, and prestrain. Overall, the effects of prestrain on the impact properties of the tested specimens dominate those of the strain rate or temperature, respectively. Finally, optical microscopy observations reveal that the specimens fracture primarily as the result of the formation of adiabatic shear bands.