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We propose a new method for preparing atom probe tomography specimens from nanoparticles using a fusible bismuth–indium–tin alloy as an embedding medium. Iron nanoparticles synthesized by the sodium borohydride reduction method were chosen as a model system. The as-synthesized iron nanoparticles were embedded within the fusible alloy using focused ion beam milling and ion-milled to needle-shaped atom probe specimens under cryogenic conditions. An atom probe analysis revealed boron atoms in a detected iron nanoparticle, indicating that boron from the sodium borohydride reductant was incorporated into the nanoparticle during its synthesis.
We investigated the microstructural evolution of Sn96.4Ag2.8Cu0.8 solder through in situ heating transmission electron microscopy observations. As-soldered bump consisted of seven layers, containing the nanoeutectic lamella structure of AuSn and Au5Sn phases, and the polygonal grains of AuSn2 and AuSn4, on Au-plated Cu bond pads. Here, we found that there are two nanoeutectic lamellar layers with lamella spacing of 40 and 250 nm. By in situ heating above 140°C, the nanoeutectic lamella of AuSn and Au5Sn was decomposed with structural degradation by sphering and coarsening processes of the lamellar interface. At the third layer neighboring to the lamella layer, on the other hand, Au5Sn particles with a zig-zag shape in AuSn matrix became spherical and were finally dissipated in order to minimize the interface energy between two phases. In the other layers except both lamella layers, polycrystal grains of AuSn2 and AuSn4 grew by normal grain growth during in situ heating. The high interface energy of nanoeutectic lamella and polygonal nanograins, which are formed by rapid solidification, acted as a principal driving force on the microstructural change during the in situ heating.
The in vitro corrosion mechanism of the biodegradable cast Mg–10% Ca binary alloy in Hanks' solution was evaluated through transmission electron microscopy observations. The corrosion behavior depends strongly on the microstructural peculiarity of Mg2Ca phase surrounding the island-like primary Mg phase and the fast corrosion induced by the interdiffusion of O and Ca via the Mg2Ca phase of lamellar structure. At the corrosion front, we found that a nanosized crack-like pathway was formed along the interface between the Mg2Ca phase and the primary Mg phase. Through the crack-like pathway, O and Ca are atomically exchanged each other and then the corroded Mg2Ca phase was transformed to Mg oxides. The in vitro corrosion by the exchange of Ca and O at the nanosized pathway led to the rapid bulk corrosion in the Mg–Ca alloys.
The microstructural analysis of the dehydrogenation products of the Ca(BH4)2–MgH2 composite was performed using transmission electron microscopy. It was found that nanocrystalline CaB6 crystallites formed as a dehydrogenation product throughout the areas where the signals of Ca and Mg were simultaneously detected, in addition to relatively coarse Mg crystallites. The uniform distribution of the nanocrystalline CaB6 crystallites appears to play a key role in the rehydrogenation of the dehydrogenation products, which implies that microstructure is a crucial factor determining the reversibility of reactive hydride composites.
ZnO nanowire (NW) has potential applications for transparent electrodes, gas sensors, nanoscale optoelectronic devices, piezoresponse force microscopy (PFM) and field effect transistors. In general, we have evaluated the electrical properties of nanowire device from I-V curves measured mainly from the bundle-like ensemble structure of ZnO, not individual ZnO NWs. Most applications require details on the electrical mobility of ZnO NWs. Recently, the electrical transport of single ZnO NWs has been studied only from several devices fabricated by electron-beam lithography. However their I-V curves categorized into three types of resistance, i.e., symmetrical, rectifying and linear shapes due to contact problems between ZnO NWs and electrodes, results in contradictory.
In this paper, we manufactured single NW device using an individual ZnO nanowire, of which the junctions were made by Pt deposition using a focused ion beam (FIB), and performed RTA processes. The single ZnO NW device consists of ZnO-Pt, ZnO-Au and Au-Pt junctions. The electrical transport of the single ZnO NW device was investigated by directly measuring the electrical resistance using nano manipulators from cross-sectioned devices. The device showed a typical Ohmic contact in I-V curves and the resistance was decrease with the RTA temperature. The CL (Cathodoluminescence) and EDS in TEM (Energy dispersive spectroscopy in transmission electron microscopy) measurements were also performed to evaluate the crystallinity (defect level) and chemical composition at the center and edge of the cross-sectioned ZnO NWs. From the results, we found that lots of defects were stored at the surface of ZnO NW and impurities at the junction were abruptly reduced. Therefore, the electrical transport of the single ZnO NW device depends strongly on the crystallinity of the ZnO NW and the C content at the Pt junction. From the electrical transport measured on the cross sectioned device, the ZnO-Au junction acted as the fastest transport path among ZnO-Pt, ZnO-Au and Au-Pt junctions in the single ZnO NW device.
Electron tomography and high-resolution transmission electron microscopy were used to characterize the unique 3-dimensional (3D) structures of twinned Zn3P2 (tetragonal) and InAs (zinc blende) nanowires synthesized by the vapor transport method. The Zn3P2 nanowires adopt a unique superlattice structure that consists of twinned octahedral slice segments having alternating orientations along the axial  direction of a pseudocubic unit cell. The apices of the octahedral slice segment are indexed as six equivalent <112> directions at the  zone axis. At each 30 degrees turn, the straight and zigzagged morphologies appear repeatedly at the <112> and <011> zone axes, respectively. The 3D structure of the twinned Zn3P2 nanowires is virtually the same as that of the twinned InAs nanowires. In addition, we analyzed the 3D structure of zigzagged CdO (rock salt) nanowires and found that they include hexahedral segments, whose six apices are matched to the <011> directions, linked along the  axial direction. We also analyzed the unique 3D structure of rutile TiO2 (tetragonal) nanobelts; at each 90 degree turn, the straight morphology appears repeatedly, while the in-between twisted form appears at the  zone axis. We suggest that the TiO2 nanobelts consist of twinned octahedral slices whose six apices are indexed by the <011>/<001> directions with the axial  direction.
In this study, we synthesized Cu–Zr binary alloys reinforced with an ultrafine eutectic microstructure. The alloys consisted of alternating layers of a hard superlattice phase and a ductile Cu phase with a very fine interlamellar spacing of ∼60 nm. The superlattice phase enhanced the strength of the alloys while the laminated composite structure helped improve their plasticity, making their mechanical properties comparable to those of the earlier reported high strength alloys. This paper discusses the fundamental microstructural aspects that influence the mechanical properties of these alloys.
Electron tomography and high-resolution transmission electron microscopy were used to characterize the unique three-dimensional structures of helical or zigzagged GaN, ZnGa2O4 and Zn2SnO4 nanowires. The helical GaN nanowires adopt a helical structure that consists of six equivalent <0-111> growth directions with the axial  direction. The ZnGa2O4 nanosprings have four equivalent <011> growth directions with the  axial direction. The zigzagged Zn2SnO4 nanowires consisted of linked rhombohedrons structure having the side edges matched to the <011> direction, and the  axial direction.
The phase separation behavior in a Cu–Co nanoparticle was investigated using Monte Carlo (MC) simulation. The modified embedded atom method (MEAM) was adopted to describe the interatomic potentials for the Cu–Co alloy system. Some of the cross potential parameters were fitted with experimental data such as mixing enthalpy and lattice constants of Cu–Co alloys. The present MC simulation combined with the MEAM potential describes well the phase separation between face-centered-cubic (fcc) Cu and fcc Co during the annealing of the particle.
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