Sn–0.7 wt% Cu alloy is an important Pb-free solder, and Ni–7 wt% V is the major diffusion barrier layer material of flip chip technology. Reactions at the Sn–0.7 wt% Cu/Ni–7 wt% V interface are examined at 160, 180, and 210 °C. Only the Cu6Sn5 phase is formed in the Sn–0.7 wt% Cu/Ni–7 wt% V couple reacted at 160 and 180 °C; however, in addition to the Cu6Sn5 and Ni3Sn4 phases, a quaternary Q phase is formed in the Sn–0.7 wt% Cu/Ni–7 wt% V couple reacted at 210 °C. The Q phase is a mixture of nanocrystalline Ni3Sn4 phase and an amorphous phase. With longer reaction time at 210 °C in the Ni–V/Q/Sn–Cu couple where the Q phase is in direct contact with solder, the Ni3Sn4 phase nucleates inside the preformed Q phase, and the alternating layer phenomenon Ni–V/Q/Ni3Sn4/Q/Ni3Sn4/Cu6Sn5/Sn–Cu is observed. The interesting solid state amorphization and alternating layer phenomena at 210 °C are primarily caused by the fact that Sn and Cu are fast diffusing species, while V is relatively immobile.

Anodized films of titanium were prepared under different controlled conditions in a water-based electrolyte containing fluorine ions, using either a constant potential or a potential gradually rising to 20 V. The films were then examined using transmission electron microscopy at different stages of growth, in particular, the very early stages of growth (30 s, 200 s, and 10 min) and when the ordered nano-tubular structure was finally established (2–4 h). The use of ramped voltage during the early stages of anodization allowed a well-interconnected porous network to develop and maintained active oxidation throughout anodization. The film, as formed, consisted mainly of amorphous oxide/hydroxides of titanium with small regions of nano-sized crystals. These were found more often in the denser regions of the amorphous network, particularly the arms of the coral-like structure that formed. As the anodized film grew in thickness, the pores tended to become aligned, leading to a surface layer of nanotubes on the electrode material. Electron optical characterization revealed that the nanotubes consist of a stack of rings where the passage of the current had been optimized.

Depth penetration per cycle and its retardation exhibited in specimens of 6061 Al were studied. By holding the maximum load reached during loading prior to cyclic oscillating, the creep could be effectively attenuated from the cyclic indentation. Constant depth penetration of sub-nanometers per cycle was found. The interrupt segments with different amplitudes (over- and underloading) or frequencies (frequency increasing and decreasing), but with same mean load, induced immediate retardations of cyclic indentation. As the interrupt segments have more than 10 cycles, the retardation is enhanced with the increase of cycle number. Accumulation of strain hardening due to stress concentration under the indenter tip is proposed to be the mechanism by which interrupt oscillation retards subsequent cyclic indentation.

Implantation of dental and orthopaedic devices is affected by delayed or weak implant-bone integration and inadequate new bone formation. Innovative approaches have been sought to enhance implant-bone interaction to achieve rapid osseointegration. The aim of this study was to develop biomimetic polypeptide nanocoatings and to evaluate cell adhesion, proliferation, morphology, and biocompatibility of polypeptide nanocoatings on implant surfaces. A recently developed nanotechnology, i.e., electrostatic self-assembly, was applied to build polypeptide nanocoatings on implant models, i.e., stainless steel discs. Our in vitro tests using human osteoblast cells revealed that substantially more (one order magnitude higher) osteoblast cells were attached to polypeptide-coated, stainless steel discs than to uncoated discs within the first few hours of contact. The developed biomimetic nanocoatings may have great potential for dental and orthopaedic applications.

Long-term effects on Nylon 6,12 crystalline fibers irradiated six years ago have been determined, including chemical structure and morphology, and their relationship with storage time. Results from x-ray diffraction, small-angle x-ray scattering, scanning electron microscopy, and atomic force microscopy are reported for those fibers and for freshly irradiated ones. Some results for non-irradiated samples are included for comparison. Changes in the shape and size of the crystals (crystallinity degree) are found; the crystallite size increases with storage time. Both surface and bulk changes are seen in the morphology. Surface damage increases with storage time. Changes observed can be attributed to irradiation causing chain scission, which, in turn, causes crystal reorganization. The present results reinforce interpretation of earlier results obtained for concretes reinforced with irradiated Nylon fibers.

Exothermic reactions in cold-rolled Ni/Al reactive multilayer foils were investigated in this study. A two-stage reaction process was observed in the self-propagating reactions in the cold-rolled foils that were ignited by a point-source flame. Foils taken out of the flame after completing the first stage of the reaction process were compared to those allowed to complete both stages. Differences in the phase-evolution sequence from the two types of foils were studied by differential scanning calorimetry (DSC), using slow and controlled heating of the samples. Several exothermic peaks could be identified from the DSC thermograms for both types of foils. Using the DSC, both the as-cold-rolled and partially reacted foils were heated to each peak temperature to identify the reaction product associated with each peak. X-ray diffraction and scanning electron microscopy analyses showed that the first two peaks corresponded to the formation of Al3Ni, while the third peak corresponded to the formation of AlNi.

Dy3+-doped GeSe2–Ga2Se3–CsI chalcohalide glasses were prepared. The thermal stabilities, optical properties, emission properties, and structure of the glasses were investigated. Upon excitation with a 808-nm diode laser, 1.32-μm near-infrared fluorescence was observed with a broad full width at half-maximum of about 90 nm. It was found the 1.32-μm fluorescence lifetime of the Dy3+-doped GeSe2–Ga2Se3–CsI glass depends on the I/Ga molar ratio and the amount of Ga2Se3 and CsI. The longest lifetime is >2.5 ms. It is noted that the value is significantly higher than those in other Dy3+-doped glasses. The enhancement of lifetime can be attributed to a decreased local phonon mode, which dominates the multiphonon relaxation. Meanwhile, it is interesting to note that the GeSe2–Ga2Se3–CsI glasses have shown good infrared transmittance. As a result, Dy3+-doped GeSe2–Ga2Se3–CsI glasses have been considered to be an attractive host for a 1.3-μm optical fiber amplifier.

There is often a tradeoff between strength and ductility, and the low ductility of ultrafine-grained (UFG) materials has been a major obstacle to their practical structural applications despite their high strength. In this study, we have achieved a ∼40% tensile ductility while increasing the yield strength of FeCrNiMn steel by an order of magnitude via grain refinement and deformation-induced martensitic phase transformation. The strain-rate effect on the inhomogeneous deformation behavior and phase transformation was studied in detail.

Bulk metallic glasses have been formed over a fairly wide composition range (54–62 at.% Ni, 32–36 at.% Nb, and 3–11 at.% Sn) in the Ni–Nb–Sn ternary system. Partial substitution of Co for Ni and Hf for Nb improves the glass-forming ability, eventually leading to 4 mm glassy rods at the Ni56Co3Nb28Hf8Sn5 composition. The positive effects of these alloying elements have been explained based on a systematic monitoring of the amount and morphology of the competing crystalline phases as a function of the Co and Hf contents.

Cubic boron nitride (cBN) composites starting with cBN–Al mixtures were sintered on WC-16 wt% Co substrates under static high pressure of 5.0 GPa and at temperatures of 800–1400 °C for 30 min. Vickers hardness of the sintered samples increased with increasing cBN content, and the highest hardness of 32.7 GPa was achieved for the cBN–5 wt% Al specimens sintered at 1400 °C. The reactions between cBN and Al started to occur at about 900 °C, and the reaction products strongly depended on the Al content, sintering temperature, and Co diffusion from the substrates according to the x-ray diffraction (XRD) observations. The high pressure and high temperature in situ resistance measurement indicated that the reactions between cBN and Al could be completed in about 90 s when the temperature was higher than ∼1200 °C at high pressure. The cBN composite sintered at 1200 °C from a cBN–15 wt% Al mixture showed the best cutting performance.

Accurate mechanical property measurement of films on substrates by instrumented indentation requires a solution describing the effective modulus of the film/substrate system. Here, a first-order elastic perturbation solution for spherical punch indentation on a film/substrate system is presented. Finite element method (FEM) simulations were conducted for comparison with the analytic solution. FEM results indicate that the new solution is valid for a practical range of modulus mismatch, especially for a stiff film on a compliant substrate. It also shows that effective modulus curves for the spherical punch deviates from those of the flat punch when the thickness is comparable to contact size.

Electrodeposited Ag film was explored as a potential interfacial barrier to Bi segregation for suppressing the interfacial embrittlement of Cu/SnBi interconnects. The presence of Ag film introduced Ag3Sn intermetallic layer at the interface, which effectively prevented Bi from reaching the Cu/intermetallic interface. When the persistent slip bands (PSBs) in the Cu single crystal were driven to impinge the Cu/Cu3Sn interface, interfacial cracking was averted and instead superceded by cracking of intermetallic compounds (IMCs) at the interface.

Microwave plasma chemical vapor deposition (CVD) was used to coat nanostructured diamond onto a copper–beryllium alloy (∼1.7 wt% Be) commonly used as a nonmagnetic gasket material in diamond anvil cell devices. The coating is expected to be useful in preventing plastic flow of Cu–Be gaskets in diamond anvil cell devices, thus allowing for increased sample volume at high pressures and leading to improved sensitivity of magnetic measurements. The coatings were characterized by Raman spectroscopy, glancing-angle x-ray diffraction, microscopy (optical, scanning electron, and atomic force), Rockwell indentation, and nanoindentation. CVD diamond deposition on pure copper substrates has historically resulted in poor coating adhesion caused by the very large thermal expansion mismatch between the substrate and coating as well as the inability of copper to form a carbide phase at the interface. While an interfacial graphite layer formed on the pure copper substrates and resulted in complete film delamination, well-adhered 12.5 μm thick nanostructured diamond coatings were produced on the copper–beryllium (Cu–Be) alloy. The nanostructured diamond coatings on Cu–Be exhibit hardness of up to 84 GPa and can withstand strains from Rockwell indentation loads up to 150 kg without delamination.

A technique of phase identification from the characteristics of electronic structures is established by Auger electron spectroscopy. GaN epilayers in wurtzite and zinc-blende polytypes are used for practical investigations. Auger spectra show phase-dependent energetic shifts and peak intensity variations. Simulation of theoretical spectra reveals the substantial correlation of the Auger line shape with the bonding electronic states. This approach demonstrates the correspondence between electronic structure and atomic structure and hence provides criteria for phase identification.

Tungsten oxide comblike nanostructures were synthesized using a two-step thermal evaporation method. The first step involving high reactor pressure and temperature was to synthesize the cores of the comb structures, upon which the teeth of the comb were grown in the second step using low operation pressures and temperatures. The teeth of the comb structure are well aligned and vertical to the side surfaces of the cores. The effects of growth parameters were examined, and the growth mechanism was investigated.

Lead loss during processing of solution-derived Pb(Zr,Ti)O3 (PZT)-based thin-films can result in the formation of a Pb-deficient, nonferroelectric fluorite phase that is detrimental to dielectric properties. It has recently been shown that this nonferroelectric fluorite phase can be converted to the desired perovskite phase by postcrystallization treatment. Here, quantitative standard-based energy-dispersive x-ray spectrometry (EDS) in a scanning transmission electron microscope (STEM) is used to study cation distribution before and after this fluorite-to-perovskite transformation. Single-phase perovskite PbZr0.53Ti0.47O3 (PZT 53/47) and Pb0.88La0.12Zr0.68Ti0.29O3 (PLZT 12/70/30) specimens that underwent this treatment were found to be chemically indistinguishable from the perovskite present in the multiphase specimens prior to the fluorite-to-perovskite transformation. Significant Zr–Ti segregation is found in PLZT 12/70/30, but not in PZT 53/47. Slight La-segregation was seen in rapidly crystallized PLZT, but not in more slowly crystallized PLZT.

Electrical conductivities of various mullite/zirconia composites, as well as monolithic mullite and zirconia, were measured using AC impedance spectroscopy from 100 Hz to 10 MHz at temperatures ranging from 150 to 1300 °C. The impedance spectra of monolithic zirconia and mullite/zirconia composites showed two semicircles because of the contributions from grains and grain boundaries, while those of monolithic mullite had one semicircle due to the predominant contribution from grains. This indicates that the conductivities of the mullite/zirconia composites increased with zirconia content. The activation energies of electrical conduction in mullite and zirconia were about 65 and 79 kJ/mol, respectively, and those of mullite/zirconia composites were between 65 and 79 kJ/mol. While the conductivities of various composites at 1 MHz were fitted by Lichtenecker’s rule, the general mixing equation could be applied to the conductivities measured at 1 kHz.

Over the past few decades, the grain refinement of Al alloys has been extensively investigated theoretically and experimentally. However, the relative importance of the parameters that contribute to grain refinement still remains unclear and is likely to be dependent on specific solidification conditions. This paper aims to investigate the mechanisms by which Ti, a common grain-refining addition in commercial-purity aluminum (CP), contributes to grain refinement using a cellular automaton—finite control volume method (CAFVM). CAFVM is used to model the grain formation and microstructure morphology under different conditions, e.g., with and without refiners, for Al alloys. In this Part I, the effect of adding solute of Ti on grain formation through its effect on growth restriction, constitutional undercooling, and the formation of extra-potential particles are taken into account in the calculations. It is shown that the calculated results are in reasonable agreement with the experimental data.

Uniaxial tensile tests were performed on Cu/Nb multilayered foils to investigate yield strength and grain boundary strengthening in the layered foils at room temperature and in fine-grained Nb at 600 °C. At room temperature, yielding in Cu/Nb multilayered foils is controlled by deformation in both layers, and grain boundary strengthening is observed with a Hall–Petch slope (kRT) of 198 ± 56 MPa·μm1/2 at a strain rate of 10−4 s−1. At 600 °C, yielding in Cu/Nb multilayered foils is controlled by deformation in just the Nb layers. Hall–Petch strengthening is observed over a range of strain rates, but the Hall–Petch slope decreases from 197 ± 71 MPa·μm1/2 for a strain rate of 10−4 s−1 to only 25 ± 40 MPa·μm1/2 for a strain rate of 10−6 s−1. The significant drop in the Hall–Petch slope for Nb with decreasing strain rate indicates a change in the controlling deformation mechanism from dislocation glide to dislocation creep.

As a liquid moves in the nanopores of a silica gel, because of the hysteresis of sorption behavior, significant energy dissipation can take place. Through a calometric measurement, the characteristics of associated heat generation are investigated. The temperature variation increases with the mass of silica gel, which consists of a reversible part and an irreversible part. The residual temperature change is about 30% to 60% of the maximum temperature increase and can be accumulated as multiple loading cycles are applied.