Single-walled carbon nanotubes (SWCNTs) were successfully solidified without any additives by hot-pressing and spark plasma sintering (SPS). The elastic modulus and fracture strength of the SWCNT solid prepared by the SPS method were about three and two times higher than that of the hot-pressed SWCNT solid prepared under the same processing condition. The enhancement of the mechanical properties of the SPS specimen may be due to the formation of comparatively stronger bond between SWCNTs, which is possibly brought about by the spark plasma generated in the SPS process.

Using a unique combination of template-based synthesis methods involving anodization, electroplating, and selective oxidation, we have synthesized engineered metal–oxide–metal (MOM) heterojunction nanowires in the Au–SnO2–Au and Au–NiO–Au systems for possible use in nanoelectronics. The template-based synthesis method used here is generic, and it has the potential to provide control over the structure and characteristics of the resulting MOM nanowires. By virtue of their heterojunction structure, MOM nanowires have the potential to overcome some of the drawbacks associated with all-oxide nanowire building blocks, and they present a rare opportunity to measure directly fundamental functional properties of nanoscale oxides.

Herein we report on the room-temperature spontaneous growth of Ga freestanding nanoribbons from Cr2GaC surfaces. An oxidation-based model is proposed to explain the growth of the nanostructures. The nanoribbons present a unique opportunity to study the behavior of electrons confined to two dimensions. The production of these Ga nanostructures could be the first step in the manufacture of gallium arsenide or nitride devices with enhanced characteristics for photonic, electronic, and catalytic applications.

In the search for a Pb-free compatible under-bump-metallization (UBM) barrier material, magnetron sputtering of a nonmagnetic nickel silicon alloy (NiSi) target was used to deposit a low-stress polycrystalline NiSi thin film. In the reaction with SnAg3.0Cu0.5 solder, NiSi was found to have greatly reduced reaction and intermetallics (IMC) formation rates compared with sputtered NiV. A continuous layer of IMCs in NiSi UBM-solder joint remains stable after 10 reflows and 1000 h thermal aging tests, resulting in preferred bulk solder failure mode in ball shearing/pull testing. Our results demonstrate that NiSi is a highly promising thin film barrier material suitable for Pb-free solder bumping.

Nanocrystalline Ni–Zn ferrite particles (Ni0.5Zn0.5Fe2O4) have been successfully produced by microemulsion method. The microemulsion process was first observed by transmission electron microscopy examination. The particles exhibit a blocking temperature of 95 K. They do not attain saturation magnetization even at a high field of 50 KOe. The saturation magnetization at 300 K is 29.8 emu/g, which is significantly lower than that reported for the bulk ceramic standard. Below the blocking temperature, the Ni0.5Zn0.5Fe2O4 nanocrystalline particles exhibit a hysteretic feature. The remanent magnetization and coercivity at 2K are 10.45 emu/g and 453 Oe, respectively.

The compressive properties and the Vickers hardness of Cu-, Fe-, Mg-, and Zr-based monolithic bulk metallic glasses (BMGs) as well as Ti-based nanostructure-dendrite composites were investigated and compared. The monolithic BMGs exhibit nearly the same yield strength σ y and fracture strength σf but poor plasticity. The Vickers hardness HV of the monolithic BMGs follows the empirical relationship HV/3 ≈σy ≈σf. The Ti-based composites yield at a relatively low stress level (less than 850 MPa) but fail at a very high fracture stress (∼ 2 GPa) and exhibit a large strain hardening ability. Accordingly, the Vickers hardness HV of the Ti-based nanostructure-dendrite composites obeys the relationship σy <HV/3 <σf. Based on these results, the relationship between the Vickers hardness and the compressive properties of the investigated materials will be discussed by taking the yield and fracture strength (σ y and σf), the strain hardening exponent n, and the elastic and plastic energy stored upon deformation (δΕ and δP) into account.

A new D023 metastable phase of Cu3Au was found to grow at the interfaces of Au/Cu multilayers deposited by magnetron sputtering. The extent of formation of this novel alloy phase depends upon an optimal range of interfacial width primarily governed by the deposition wattage of the direct current magnetron used. Such interfacially confined growth is utilized to grow a ∼300-nm-thick Au/Cu multilayer with thickness of each layer nearly equal to the optimal interfacial width which was obtained from secondary-ion mass spectrometry (SIMS) data. This growth technique is observed to enhance the formation of the novel alloy phase to a considerable extent. The SIMS depth profile also indicates that the mass fragment corresponding to Cu3Au occupies the whole film while x-ray diffraction (XRD) shows almost all the strong peaks belonging to the D023 structure. High-resolution cross-sectional transmission electron microscopy shows the near-perfect growth of the individual layers and also the lattice image of the alloy phase in the interfacial region. Vacuum annealing of the alloy film and XRD studies indicate stabilization of the D023 phase at ∼150 °C. The role of interfacial confinement, the interplay between interfacial strain and free energy, and the hyperthermal species generated during the sputtering process are discussed.

The oxidation kinetics and the effects of alloying on the oxidation behaviors of copper-based bulk metallic glasses were studied. The oxidation kinetics, oxide compositions, and structures were investigated by thermogravimetric analysis (TGA), x-ray diffraction, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. Both the TGA results and the XPS depth profile measurements showed that the oxidation resistance of Cu60Zr30Ti10 bulk metallic glass was improved by adding Hf, but it deteriorated when it was alloyed with Y. The oxide phases were found to be ZrO2, Cu2O, and CuO in samples heated at 573 K while an additional metallic Cu phase was detected in the ones heated at 773 K. A porous oxide structure was observed in the (Cu0.6Zr0.3Ti0.1)98Y2 metallic glass oxidized at 673 K, and the poor oxidation resistance of the alloy is attributed to the porous structure.

Nanocrystalline GdFeO3 powder was synthesized by a combustion technique, using glycine as the fuel and the corresponding metal nitrates as oxidants. Five different molar ratios of fuel-to-oxidant were chosen to study the effect of fuel content on the phase formation and the powder properties. The powders after calcination were characterized by x-ray diffraction (XRD) and crystallite sizes calculated by x-ray line broadening. The crystallite sizes for the phase pure products after calcination at 600 °C were in the range 40–65 nm. The transmission electron microscopy observations clearly highlight the pronounced crystallinity for the propellant chemistry samples. The nature of the agglomerates was investigated by light scattering studies. The lattice thermal expansion behavior was also studied by high-temperature XRD.

When determining elastic modulus and hardness of viscoelastic-plastic materials by depth-sensing indentation, one must respect their specific response. In the monotonic load-unload testing mode, the unloading should be preceded by a dwell mitigating the influence of the delayed deforming. The continuous stiffness measurement (CSM) mode, with a small harmonic signal added to the basic monotonic load, enables continuous measurement of harmonic contact stiffness and mechanical properties as a function of depth. However, the contact depth and area in this mode actually depend on the slow (monotonic) component of the loading and should be determined not from the harmonic contact stiffness but from the unloading stiffness; otherwise, the calculated elastic modulus and mean contact pressure will be incorrect. This paper provides the formulae for these calculations, defines special characteristics—such as apparent dynamic hardness and the index of sensitivity to harmonic loading—and shows how to improve results by smoothing the harmonic stiffness curve. The proposed methods are illustrated through nanoindentation tests of polymethyl methacrylate.

In this work, the effect of Fe2O3 addition on the microstructure and piezoelectric properties of Pb(Zn1/3Nb2/3)0.2Ti0.4Zr0.4O3 (0.2PZN–0.8PZT) ceramics were investigated. The studies indicated that the solution limit of Fe2O3 in the lattice of perovskite structure was about 0.1 wt%. Phase analysis shows that small addition of doping Fe2O3 results in the phase evolution from rhombohedral to tetragonal, sharp decrease of the Curie temperature, and remarkable increase of the grain size. Meanwhile, Fe2O3 addition within the solution limit led to the increase of the εr, kp, and d33. It is believed that the variation in the dielectric and piezoelectric properties are closely related to the microstructure change, phase evolution, and tetragonal distortion as Fe2O3 added.

R2MoO6:Eu3+ (R = Gd, Y, La) phosphors were prepared by the Pechini sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), reflectance spectra, photoluminescence (PL) spectra, and lifetimes were used to characterize the resulting phosphors. The results of XRD indicate that all of the R1.96Eu0.04MoO6 (R = Gd, Y, La) phosphors crystallized completely at 800 °C. Y1.96Eu0.04MoO6 and Gd1.96Eu0.04MoO6 are of isomorphous monoclinic (α) structure, while La1.96Eu0.04MoO6 preferentially adopts the tetragonal (γ) form. FE-SEM study reveals that the samples mainly consist of aggregated particles with an average grain size ranging from 100 to 250 nm. The luminescent properties of R2MoO6:Eu3+ (R = Gd, Y, La) phosphors are largely dependent on their structure, grain size, and powder morphology. The isomorphous Y2MoO6:Eu3+ and Gd2MoO6:Eu3+ phosphors show very similar luminescence properties, which differ greatly from that of the La2MoO6:Eu3+ phosphor.

A stable mesoporous multilamellar silica vesicle (MSV) was developed with a gallery pore size of about 14.0 nm. A simulative enzyme, hemoglobin (Hb), was immobilized on this newly developed MSV and a conventional mesoporous silica material SBA-15. The structures and the immobilization of Hb on the mesoporous supports were characterized with x-ray diffraction, transmission electron microscopy, N2 adsorption-desorption isotherms, Fourier transform infrared, ultraviolet-visible spectroscopy, and so forth. MSV is a promising support for immobilizing Hb due to its large pore size and high Hb immobilization capacity (up to 522 mg/g) compared to SBA-15 (236 mg/g). Less than 5% Hb was leached from Hb/MSV at pH 6.0. The activity study indicated that the immobilized Hb retained most peroxidase activity compared to free Hb. Thermal stability of the immobilized Hb was improved by the proctetive environment of MSV and SBA-15. Such an Hb-mesoporous support with high Hb immobilization capacity, high activity, and enhanced thermal stability will be attractive for practical applications.

The evolution of nearly dense stoichiometric silicide compacts via powder processing is presented in this paper. For specific single-phase Mo(Si,Al)2 compacts, room-temperature environmental degradation, phenomenologically similar to the pesting behavior of binary MoSi2 was observed. This degradation occurs over a series of a few months and results in grain boundary decohesion, which leads to crumbling of polycrystalline compacts in air at room temperature. Auger electron spectroscopy, transmission electron microscopy, and energy dispersive spectroscopy of the boundaries revealed the presence of an array of lens-shaped particles each comprised of silicon carbide and aluminum. The reaction of these phases with atmospheric species was accelerated by the presence of humidity. The trace presence of carbon was unavoidable due to the use graphite pressing dies. Alloying additions were made to tie up carbon by forming more stable carbides while maintaining the desired matrix phase stoichiometry. The pest phenomenon and alloying remedy were proven applicable to other silicide systems through experimentation and ThermoCalc modeling.

The precipitate sequence in a 6022 aluminum alloy was investigated by means of differential scanning calorimetry (DSC), transmission electron microscopy, and Vickers hardness measurements. The solution-treated samples were quenched and then immediately subjected to DSC and isothermal aging experiments. It was observed that in the early stages of aging there are some unknown small precipitates that form prior to the formation of β″ precipitates. Studies on isothermally aged and DSC heated samples suggest that some of the β″ needles transform during growth to lath-shaped precipitates. An alternative precipitation sequence for AA6022 is proposed.

A technique for forming metallic nanowires by utilizing electromigration, which is the phenomenon of atomic diffusion due to high current densities, is presented. These diffused atoms can be used for creating metallic nanowires. To specify the position at which a nanowire is formed, some specific conditions need to be established. These conditions are, first, to control the atomic diffusion so the accumulation of atoms produces the desired higher compressive stress; second, to design the structure to control the areas in which diffusion takes place; third, to adjust the thickness of the passivation layer deposited on the metal; and fourth, to form a small slot in the passivation layer through which the compressive stress is released by discharging the diffused atoms. It is shown that when these factors are satisfied, an Al nanowire can be successfully generated in a passivated metal track composed of an Al line buried in a W line.

Nanoindentation tests of Pd40Cu30Ni10P20 bulk metallic glass were performed over a wide range of indentation rates (from 0.04 up to 6.4 mN s−1) under the standard load control mode. New results using the feedback displacement control mode are also presented. The dependence of the pop-in formation on the loading rate is investigated. Variations in hardness and reduced elastic modulus as a function of the indentation rate are observed. A softening effect occurs when increasing the loading rate. This is explained by the differences in plastic deformation achieved at different indentation rates. The displacement control mode was used to avoid the shear localization of the free volume, leading to the almost complete absence of pop-ins along the loading curve. The obtained results suggest that plastic flow in bulk metallic glasses is governed by the rate of creation of free volume, which depends on the strain rate and its localization into shear bands.

In situ transmission electron microscopy was used to study, in real time, the sub-surface deformation taking place in Cu–Be alloy during nanoindentation. A twinned region of the material was indented with a sharp tungsten tip in a specially developed transmission electron microscopy (TEM) holder. A flexible hinge-based force sensor was used to measure the force on the indenter, and the force–displacement curve for the tip was obtained by tracking the tip in the sequential images of a TEM video of the indentation process. Step-like structures ∼50 nm in size resulting from the tip surface roughness were observed to generate clusters of dislocations in the sample when they come in contact with the softer Cu–Be. With this setup, the forces and the mean pressure associated with such an individual deformation event in a nanostructured TEM sample were measured.

This paper describes an aspirating-dispensing ink-jet printer embedded in a combinatorial robot for high throughput studies in ceramics; LUSI, the London University Search Instrument. The process of reformatting well-plates from source inks and printing ceramic samples is described. Precautions against evaporation, sedimentation of colloidal suspensions, and segregation of mixtures during drying are taken to convert compositions specified in a spreadsheet into the form of ∼1 mm radius drops. It is concluded that when these precautions are taken, commercially available powders can be combinatorially mixed in LUSI to produce samples of2.4 mg to within 1–3 wt% accuracy.

Phase-pure Ba2Ti9O20 powders were made by doping 3 wt% of V2O5 to a Ba:Ti = 2:9 molar composition, and the effects of the dopant on the phase formation were investigated. The study shows that BaTiO3, BaTi2O5, and BaTi4O9 were the intermediate phases before the formation of Ba2Ti9O20 for samples with or without V2O5. However, with V2O5 doping, the temperature at which Ba2Ti9O20 occurred were lowered from 1150 to 1050 °C and single phase Ba2Ti9O20 powders was easily obtained at 1150 °C for 2 h. Microstructure of the powders was examined by field emission scanning electron microscopy. No evidence of V2O5–Ba2Ti9O20 solid-solution was found by x-ray diffraction and energy-dispersive spectroscopy. The benefit of V2O5 to facilitate the Ba2Ti9O20 synthesis is most probably due to a vanadium-containing eutectic liquid phase which accelerates the migration of reactant species.