We reported a simple and convenient method to determine the film thickness by nanoindentation tests. This method starts from the analysis of the unloading portion of the measured nanoindentation load-displacement curves according to a quadratic polynomial, P = α(h − hf)2 − P0, where P is the indentation load, P0 is the virtual load used to consider the effect of the residual contact stress, h is the indenter displacement (penetration depth), hf is the final displacement after complete unloading which should be determined by curve fitting, and α is a constant. Then the best-fit value of the parameter P0 is plotted as a function of the maximum penetration depth, hmax. Such a P0 versus hmax curve may pass through a minimum, and hmax corresponding to this minimum would be equal to the film thickness value.

Direct-write, cryogenic electron beam-induced deposition (EBID) was performed by condensing methylcyclopentadienyl-platinum-trimethyl precursor onto a substrate at −155 °C, exposing the condensate by a 15 keV electron beam, and desorbing unexposed precursor molecules by heating the substrate to room temperature. Dependencies of film thickness, microstructure, and surface morphology on electron beam flux and fluence, and Monte Carlo simulations of electron interactions with the condensate are used to construct a model of cryogenic EBID that is contrasted to existing models of conventional, room temperature EBID. It is shown that material grown from a cryogenic condensate exhibits one of three distinct surface morphologies: a nanoporous mesh with a high surface-to-volume ratio; a smooth, continuous film analogous to material typically grown by room temperature EBID; or a film with a high degree of surface roughness, analogous to that of the cryogenic condensate. The surface morphology can be controlled reproducibly by the electron fluence used for exposure.

The constituent phases, the microstructure, and the mechanical properties of a series of Fe87–xTi7Zr6Bx (x = 0, 2, 4, 6, 8, 10, and 12) alloys produced by copper mold casting were investigated. Partial substitution of iron by boron in the Fe87Ti7Zr6 ultrafine eutectic alloy induces phase/microstructural evolution and simultaneously changes the mechanical properties. In the composition range of 2 ≤ x ≤ 6, the typical lamellar structure slightly changes into a spherical cellular-type eutectic. For 8 ≤ x ≤ 12, multiphase composites containing a glassy phase form. The ultrafine eutectic composites exhibit a high compressive strength of ~2.9–3.1 GPa and a distinct plasticity of ~2–8%, whereas the glassy matrix composites show a high strength of ~3.1–3.3 GPa but no observable macroscopic plasticity before failure. These findings reveal that the plasticity of heterogeneous multiphase composites is strongly related to the length scale variables and the crystallinity of the constituent phases.

Interfacial reaction and microstructure evolution in a Zr2Al3C4 reinforced Cu composite were studied by x-ray diffraction, Raman spectroscopy, and transmission electron microscopy. Decomposition of Zr2Al3C4 was triggered by the deintercalation of Al atoms. In the initial reaction stage, depletion of Al occurred locally. ZrC and Cu platelets as well as thin twinned ZrC slices were observed inside the Zr2Al3C4 grains. In the later reaction stage, all Al atoms depleted from Zr2Al3C4 and were dissolute into the Cu matrix. The final reaction products were a Cu–Al solid solution, ZrC0.5, and highly disordered graphite, which resulted in large volume shrinkage. These experimental results provided a baseline for controlling interfacial reaction and microstructure development in Cu/Zr2Al3C4-based particle-reinforced Cu composites for optimized mechanical and electrical properties.

A procedure for predicting the in-plane and out-of-plane thermal conductivities of woven fabric composites through a combined approach of the representative volume element method and heat transfer analyses via finite element is presented. The representative volume element method was implemented using two unit cells established at different length scales with periodic boundary conditions. The procedure was exemplified on a plain weave glass fabric reinforced epoxy resin matrix composite. Sensitivity studies were conducted to quantify the influence of fiber volume fraction and thermal conductivity of the constituent phases on the effective thermal conductivities of the composite. The procedure, which can be implemented into commercial finite element codes, is an efficient tool for the design of woven fabric composites.

The interplay of large strain and large strain rate during high-rate severe plastic deformation (HR-SPD) lead to dynamic temperature rise in situ that engenders a recovered microstructure whose characteristics are not just a function of the strain, but also of the strain rate and the coupled temperature rise during the deformation. In this work, we identify three classes of microstructures characterized by multistage recovery phenomena that take place during the high strain rate SPD of Cu. It is found that the first stage of this recovery is similar to the first stage of static recovery, which is characterized mainly by annihilation of dislocations. The second stage starts around 360 K and was characterized by dislocations getting arranged in tight cell boundaries and eventually into subgrain. Recovery stages were found to be followed by a stage of grain growth and recrystallization when the temperature in the deformation zone approaches 480 K.

Effects of stacking fault energy (SFE) on the thermal stability and mechanical properties of nanostructured (NS) Cu–Al alloys during thermal annealing were investigated in this study. Compared with NS Cu–5at.%Al alloy with the higher SFE, NS Cu–8at.%Al alloy exhibits the lower critical temperatures for the initiation of recrystallization and the transition from recovery-dominated to recrystallization-dominated process, which significantly signals its low thermal stability. This may be attributed to the large microstructural heterogeneities resulting from severe plastic deformation. With increasing the annealing temperatures, both Cu–Al alloys present the similar trend of decreased strength and improved ductility. Meanwhile, the remarkable enhancement of uniform elongation is achieved when the volume fraction of Static recrystallization (SRX) grains exceeds ~80%. Moreover, the better strength–ductility combination was achieved in the Cu–8at.%Al alloy with lower SFE.

Molecular dynamic simulations of helium atoms escaping from a helium-filled nanobubble near the surface of crystalline palladium reveal unexpected behavior. Significant deformation and cracking near the helium bubble occur initially, and then a channel forms between the bubble and the surface, providing a pathway for helium atoms to propagate toward the surface. The helium atoms erupt from the bubble in an instantaneous and volcano-like process, which leads to surface deformation consisting of cavity formation on the surface, along with modification and atomic rearrangement at the periphery of the cavity. The present simulation results show that, near the palladium surface, there is a helium-bubble-free zone, or denuded zone, with a typical thickness of about 3.0 nm. Combined with experimental measurements and continuum-scale evolutionary model predictions, the present atomic simulations demonstrate that the thickness of the denuded zone, which contains a low concentration of helium atoms, is somewhat larger than the diameter of the helium bubbles in the metal tritide. Furthermore, a relationship between the tensile strength and thickness of metal film is also determined.

Shape control of nanocrystals has become an indispensable part in material research, such as developing new battery raw materials and synthesizing high activity catalysts. In this work, one-dimensional LiV3O8 nanorods have been fabricated by high temperature solid-state reaction using V2O5 nanowires as precursors obtained via a hydrothermal method. The as-prepared LiV3O8 nanorods were characterized by x-ray diffraction, transmission electron microscopy, scanning electron microscopy, and galvanostatic tests, compared with LiV3O8 samples synthesized by the traditional one-step solid-state method. The results show that LiV3O8 nanorods exhibited better electrochemical performance than those synthesized by the traditional method, indicating that a different shape will lead to huge distinctions in electrochemical properties. This work demonstrates that Li-insertion/deintercalation dynamics might be crystal morphology-sensitive.

Tin oxide (SnO2) nanotubes have been synthesized using carbon nanotubes (CNTs) as removable templates. The entire synthesis takes place on the microscale on a micromachined hotplate, without the use of photolithography, taking advantage of the device’s built-in heater. Well-aligned multiwalled CNT forests were grown directly on microhotplates at 600 °C using a bimetallic iron/alumina composite catalyst and acetylene as precursor. Thin films of anhydrous SnO2 were then deposited onto the CNT forests through chemical vapor deposition of tin nitrate at 375 °C. The CNTs were then removed through a simple anneal process in air at temperatures above 450 °C, resulting in SnO2 nanotubes. Gas sensing measurements indicated a substantial improvement in sensitivity to trace concentrations of methanol from the SnO2 nanotubes in comparison with a SnO2 thin film. The synthesis technique is generic and may be used to create any metal oxide nanotube structure directly on microscale substrates.

TiO2 nanotube arrays were synthesized by anodic oxidation on a pure titanium substrate in solutions containing 0.175 M NH4F composed of mixtures with different volumetric ratios of DI water and glycerol. According to the results of the current curve recorded during anodization, the time of the first sharp current slope (corresponding to the initial oxide layer formation time) was found to vary from 8 to 171 s depending not only upon the water content in the electrolytes but also upon the voltage. The current curves exhibit oscillation with different amplitudes and periods. In combination with the scanning electron microscope (SEM) images, a growth mechanism, layer-by-layer model, of TiO2 nanotube arrays was presented. Based on this mechanism, many phenomena that appeared during anodization can be reasonably explained. Our results would be helpful for the design of nanoarchitectures in related material systems.

Nitrogen-doped multiwalled carbon nanotubes (N-doped MWNTs) were synthesized in a large quantity by the pyrolysis of pyridine at various temperatures in the range of 750–950 °C. The influence of temperature on the morphology, composition, thermal stability, and bonding nature of N-doped MWNTs was investigated. It is found that the yield of N-doped MWNTs increases linearly with the increase of the growth temperature. The maximum N content (4.6 at%) in MWNTs was obtained from a sample grown at 900 °C. N-doped MWNTs synthesized at 950 °C possess a unique drumlike morphology with the highest oxidizing temperature (535 °C). It is evidenced that N atoms are incorporated into the graphitic network in three different bonding forms and their relative content is affected by the growth temperature, which shows a clear influence on the morphology of N-doped MWNTs.

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.

Soldering to Cu interconnect pads with Sn-containing alloys usually leads to the formation of a layered Cu3Sn/Cu6Sn5 structure on the pad/solder interface. Frequently, microscopic voids within Cu3Sn have been observed to develop during extended thermal aging. This phenomenon, commonly referred to as Kirkendall voiding, has been the subject of a number of studies and speculations but so far the root cause has remained unidentified. In the present work, 103 different Cu samples, consisting of 101 commercially electroplated Cu and two high-purity wrought Cu samples, were surveyed for voiding propensity. A high temperature anneal of the Cu samples before soldering was seen to significantly reduce the voiding level in subsequent thermal aging. For several void-prone Cu foils, the anneal led to significant pore formation inside the Cu. In the mean time, Cu grain growth in the void-prone foils showed impeded grain boundary mobility. Such behaviors suggested that the root cause for voiding is organic impurities incorporated in the Cu during electroplating, rather than the Kirkendall effect.

Electromigration behavior and fast circuit failure with respect to crystallographic orientation of Sn grains were examined. The test vehicle was Cu/Sn–3.0 wt% Ag–0.5 wt% Cu/Cu ball joints, and the applied current density was 15 kA/cm2 at 160 °C. The experimental results indicate that most of the solder bumps show different microstructural changes with respect to the crystallographic orientation of Sn grains. Fast failure of the bump occurred due to the dissolution of the Cu circuit on the cathode side caused by the fast interstitial diffusion of Cu atoms along the c-axis of the Sn grains when the c-axis was parallel to the electron flow. Slight microstructural changes were observed when the c-axis was perpendicular to the electron flow. In addition, Cu6Sn5 intermetallic compound (IMC) was formed along the direction of the c-axis of the Sn grains instead of the direction of electron flow in all solder ball joints.

N-type Bi2Te3 alloys with different microstructural length scales were prepared by mechanical milling and spark plasma sintering (SPS). The electrical resistivity, thermal conductivity, Seebeck coefficient, carrier concentration, and Hall mobility along and perpendicular to the loading direction were determined and characterized. The SPS sintered bulk disks using nanostructured powder contain high nanoporosity and weak (00l) texture along the loading axis, in contrast to those obtained with coarse powder. The influence of nanoporosity and texture on the thermoelectric and transport properties in the n-type Bi2Te3 alloys is discussed in light of the microstructural characteristics at different length scales.