Palladium nanoparticles supported by alumina nanofibers have been successfully synthesized by electrospinning using palladium chloride incorporated into a solution of polyvinyl pyrrolidone and aluminum acetate. Palladium agglomerate sizes and the surface morphology of the electrospun nanofibers were determined by transmission electron microscopy. Palladium nanoparticles appeared to be well dispersed within the electrospun nanofiber structure. X-ray diffraction, x-ray photoelectron spectroscopy, and Raman scattering spectroscopy techniques were used to identify the crystalline form and distinguish between oxidized and metallic palladium particles after heating and hydrogenation.

While nanowires and nanotubes have been shown to be electrically sensitive to various chemicals, not enough is known about the underlying mechanisms to control or tailor this sensitivity. By limiting the chemically sensitive region of a nanostructure to a single binding site, single molecule precision can be obtained to study the chemoresistive response. We have developed techniques using single-walled- carbon-nanotube (SWCNT) circuits that enable single-site experimentation and illuminate the dynamics of chemical interactions. Discrete changes in the circuit conductance reveal chemical processes happening in real-time and allow SWCNT sidewalls to be deterministically broken, reformed, and conjugated to target species.

Electrical conductivity of open-cell metallic foam calculated by Dharmasena and Wadley using the tetrakaidecahedral cell-based model with ligaments of constant or varying triangular cross sections along the cell edges was mistakenly concluded to strongly overestimate measured electrical conductivities of the open-cell aluminum foams (ERG Duocel). Accurate analysis shows that the model with triangular ligaments on the contrary underestimates the experimental results. A tetrakaidecahedral cell-based model that takes into account the particular ligament geometry, which is determined by constant mean curvature of ligament surfaces, is shown to explain the experimental data of electrical conductivity of the Duocel foams ranging in relative density from 4% to 12%.

The extruded Mg–Zn–Y–Zr plate was subjected to friction stir processing (FSP). FSP resulted in significant breakup and dispersion of bulky W-phase particles and remarkable grain refinement, thereby substantially enhancing superplasticity. Maximum superplasticity of 635% was achieved at 450 °C and a relatively high strain rate of 3 × 10−3 s−1. By comparison, the as-extruded sample did not exhibit superplasticity. Grain boundary sliding was identified to be the primary deformation mechanism in the FSP Mg–Zn–Y–Zr by superplastic data analyses and surfacial morphology observations. Furthermore, the superplastic deformation kinetics of the FSP Mg–Zn–Y–Zr is significantly faster than that of equal channel angular pressed (ECAP) magnesium alloys under both as-ECAP and annealing conditions.

The tailoring of cermet composition to improve tribological properties requires careful choice of the type of secondary carbide. To investigate this aspect, a number of sliding tests were carried out on baseline TiCN–20Ni cermet and TiCN–20wt%Ni–10 wt% XC cermets (X = W/Nb/Ta/Hf) at varying loads of 5N, 20N, and 50N against bearing steel. With these experiments, we attempted to answer some of the pertinent issues: (i) how does the type of secondary carbide (WC/NbC/TaC/HfC) influence friction and wear behavior, and is such influence dependent on load?; and (ii) how does the secondary carbide addition affect the stability and composition of the tribochemical layer under the selected sliding conditions? Our experimental results reveal that the added secondary carbides influence chemical interactions between different oxides and such interactions dominate the friction and wear behavior. A higher coefficient of friction (COF) range, varying from 0.75 to 0.64 was recorded at 5N; whereas the reduced COF of 0.46–0.52 was observed at 20N or 50N. The volumetric wear rate decreased with load and varied on the order of 10−6 to 10−7 mm3/Nm for the cermets investigated. The cermet containing HfC exhibited high friction and poor wear resistance. At low load (5N), the abrasion and adhesion of hard debris containing various oxides dominated the wear, and resulted in high friction and wear loss. In contrast, the more pronounced increase in friction-induced contact temperature (below 500 °C) and compaction of hard debris resulted in the formation of a distinct tribochemical layer at higher loads (20N and 50N). The formation of a dense tribolayer containing oxides of iron and/or titanium is responsible for the reduced friction and wear, irrespective of secondary carbides.

Extensive experimental research work has been carried out to investigate precipitation peculiarities in Mg–Zn–Sn-based alloys during aging at different temperatures. This in-depth research was conducted on Mg–4.4wt%Zn–4.0wt%Sn–0.6wt%Y and Mg–4.4wt%Zn–4.4wt%Sn–1.1wt%Sb using x-ray diffraction (XRD), transmission electron microscopy (TEM) including high-resolution TEM, and scanning electron microscopy (SEM) equipped with an energy-dispersive x-ray spectrometer (EDS). It was found that, first, a hexagonal close-packed (hcp)-MgZn2 phase nucleates and grows in the form of needles having coherent interphase boundaries with α-Mg matrix. Then the face-centered cubic (fcc)-Mg2Sn-phase nucleates heterogeneously, mainly at the tips of MgZn2 needles. A very certain mutual orientation of crystal lattices of MgZn2, Mg2Sn, and α-Mg matrix was revealed. The orientation of Mg2Sn precipitates is perpendicular to that of MgZn2 needles. They grow in the form of plates parallel to the basal planes of α-Mg matrix. Two-phase T-like particles are very typical of alloys aged for 1 to 16 days at 175 to 225 °C. The width/length ratio of MgZn2 needles inside T-like particles differs substantially from that found in single needles. The elastic/surface energy balance of needles and its influence on the morphology and coarsening behavior has been analyzed.

Fully dense and net-shaped silicon carbide monoliths were produced by liquid silicon infiltration of carbon preforms with engineered bulk density, median pore diameter, and chemical reactivity derived from carbonization of crystalline cellulose and phenolic resin blends. The ideal carbon bulk density and minimum median pore diameter for successful formation of fully dense silicon carbide by liquid silicon infiltration are 0.964 g cm−3 and approximately 1 μm. By blending crystalline cellulose and phenolic resin in various mass ratios as carbon precursors, we were able to adjust the bulk density, median pore diameter, and overall chemical reactivity of the carbon preforms produced. The liquid silicon infiltration reactions were performed in a graphite element furnace at temperatures between 1414 and 1900 °C and under argon pressures of 1550, 760, and 0.5 Torr for periods of 10, 15, 30, 60, 120, and 300 min. Examination of the results indicated that the ideal carbon preform was produced from the crystalline cellulose and phenolic resin blend of 6:4 mass ratio. This carbon preform has a bulk density of 0.7910 g cm−3, an actual density of 2.1911 g cm−3, median pore diameter of 1.45 μm, and specific surface area of 644.75 m2 g−1. The ideal liquid silicon infiltration reaction conditions were identified as 1800 °C, 0.5 Torr, and 120 min. The optimum reaction product has a bulk density of 2.9566 g cm−3, greater than 91% of that of pure β–SiC, with a β–SiC volume fraction of approximately 82.5%.

Starting from Cu60Zr30Ti10, the compositional dependence of bulk metallic glass (BMG) formation was revisited in the Cu−Zr−Ti ternary system. It was revealed that the optimal BMG-forming composition is located at Cu60Zr33Ti7, for which a monolithic BMG rod 4 mm in diameter can be fabricated using copper mold casting. This composition is along, although slightly off, the univariant eutectic groove for the reaction (L → Cu8Zr3 + Cu10Zr7). With respect to the corresponding Cu−Zr binary alloys, Ti has a significant effect on further stabilizing the liquid, thus increasing the glass-forming ability. For the Cu60Zr40−yTiy (3 ⩽ y ⩽ 10) series BMGs, the glass transition temperature Tg decreased with increasing Ti content, at a rate of about 2.8 K/at.%. Among these BMGs, significant compositional dependence of compressive plasticity is not observed, irrespective of the Tg change. Cu60Zr33Ti7 glass exhibits maximum fracture strength around 2160 MPa.

A reactive direct current magnetron sputtering system was used to prepare NbAlN coatings at different nitrogen flow rates and substrate bias voltages. Various properties of NbAlN coatings were studied using x-ray diffraction, scanning electron microscopy, atomic force microscopy, x-ray photoelectron spectroscopy, nanoindentation, the four-probe method, a solar spectrum reflectometer and emissometer, spectroscopic ellipsometry, micro-Raman spectroscopy, and potentiodynamic polarization techniques. Single-phase NbAlN with B1 NaCl structure was obtained for the coatings prepared at a nitrogen flow rate in the range of 1.5–3 sccm, a substrate bias voltage of −50 to −210 V, and a substrate temperature of 300 °C. Nanoindentation data showed that the optimized NbAlN coating exhibited a maximum hardness of 2856 kg/mm2. An approximately 100-nm-thick NbAlN–NbAlON tandem on copper substrate exhibited a high absorptance (0.93) and a low emittance (0.06), suitable for solar-selective applications. The spectroscopic ellipsometry and resistivity data established the metallic nature of NbAlN and the semitransparent behavior of NbAlON coatings. The corrosion resistance of NbAlN coatings was superior to that of the mild steel substrate. The addition of aluminum in NbN coatings increased the onset of oxidation in air from 350 to 700 °C. Vacuum-annealed NbAlN coatings were structurally stable up to 700 °C and retained their high hardness up to a temperature of 650 °C.

Mg–8Gd–2Y–Nd–0.3Zn (wt%) alloy was prepared by the high pressure die-cast technique. The microstructure, mechanical properties in the temperature range from room temperature to 573 K, and strengthening mechanism were investigated. It was confirmed that the Mg–Gd-based alloy with high Gd content exhibited outstanding die-cast character. The die-cast alloy was mainly composed of small cellular equiaxed dendrites and the matrix. The long lamellar-shaped stacking compound of Mg3X (X: Gd, Y, Nd, and Zn) and polygon-shaped precipitate of Mg5RE (RE: Gd, Y, and Nd) were mainly concentrated along the dendrite boundaries. Meanwhile, it was demonstrated that the Zn addition affects the formation of non-equilibrium precipitate Mg3X. The ultimate tensile strength, yield strength, and Young’s modulus were 302 MPa, 267 MPa, and 38 GPa at room temperature, respectively. The outstanding mechanical properties were mainly attributed to the small dendrite spacing, wide skin region, and some dispersed precipitates in the alloy formed by the high-pressure die-cast technique. Designing a novel die-cast Mg alloy with good heat resistance without Al element is a significant accomplishment.

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.

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.

Following the discussion of modeling grain refinement in Part I, [X. Yao, et al., J. Mater. Res.23(5), 1282, the effect of Al–Ti–B master alloy additions on grain formation in commercial-purity (CP) aluminum was investigated. The characteristics of the addition particles as applicable to the model are presented. The effect of adding TiB2 particles, the introduction of extra particles by reactions in the melt, and the effect of adding extra solute Ti are all modeled. The distribution of the potential particles and its effect on grain formation was also modeled to establish the relationship between the grain size and microstructure morphology and the additive characteristics. The calculated results are comparable with experimental data. Accordingly, possible mechanisms of grain refinement with Al–Ti–B refiners were proposed.

Following Part I [X. Yao, et al., J. Mater. Res.23(5), 1282 (2008)] and Part II [X. Yao, et al., J. Mater. Res.23(5), 1292 (2008)] the cellular automation–finite control volume method (CAFVM) model was used to study the grain formation and microstructure morphology resulting from solidification of a commercial Al–Si–Mg alloy with Al–Ti–B grain refiner additions. The model incorporates the effect of the introduced solute Ti and the alloying elements of Si and Mg on the growth restriction factor, constitutional undercooling, and nucleation parameters. With respect to grain refinement, it is found that the alloying elements, Si and Mg, play a role that is similar to Ti qualitatively while different quantitatively. Accordingly, a concept of “equivalent solute” determined by phase diagram parameters such as the solute partitioning coefficient and the liquidus slope is proposed to clarify the effect of each solute in the alloy on grain formation during solidification. Based on the calculations and on comparison to the experimental data, a possible mechanism of grain refinement in this alloy system is proposed.

Indentation techniques are used for the measurement of mechanical properties of a wide range of materials. Typical elastic analysis for spherical indentation is applicable in the absence of time-dependent deformation, but is inappropriate for materials with time-dependent creep responses active in the experimental time frame. In the current work, a poroelastic analysis—a mechanical theory incorporating fluid motion through a porous elastic network—is used to examine spherical indentation creep responses of hydrated biological materials. Existing analytical and finite element solutions for the poroelastic Hertzian indentation problem are reviewed, and a poroelastic parameter identification scheme is developed. Experimental data from nanoindentation of hydrated bone immersed in water and polar solvents (ethanol, methanol, acetone) are examined within the poroelastic framework. Immersion of bone in polar solvents with decreasing polarity results in increased stiffness, decreased Poisson’s ratio, and decreased hydraulic permeability. Nanoindentation poroelastic analysis results are compared with existing literature for bone poroelasticity at larger length scales, and the effective pore size probed in indentation creep experiments was estimated to be 1.6 nm, consistent with the scale of fundamental collagen–apatite interactions. Results for water permeability in bone were compared with studies of water diffusion through fully dense bone.

Atomic force microscopy images showed that the size of the CdTe quantum dots (QDs) slightly increased with increasing annealing temperature up to 350 °C. Photoluminescence spectra showed that the excitonic peak corresponding to the interband transition from the ground electronic subband to the ground heavy-hole band (E1–HH1) in the CdTe/ZnTe QDs annealed at 350 °C was shifted to lower energy compared with that in as-grown CdTe/ZnTe QDs. The full width at half-maximum of the E1–HH1 transition peak in the CdTe/ZnTe QDs annealed at 350 °C decreased resulting from the improvement of the crystallinity for the annealed CdTe QDs.

A simple thermal annealing was performed to prepare tungsten oxide nanorods directly from tungsten (W) film. The W film was deposited on Si(100) substrate by chemical vapor deposition (CVD) at 450 °C using W(CO)6. A high density of tungsten oxide nanorods was produced by heating of the W film at 600–700 °C. The morphology, structure, composition, and chemical binding states of the prepared nanorods were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) analysis. XRD and TEM results showed that the grown nanorods were single-crystalline W18O49. According to XPS analysis, the W18O49 nanorods contained ∼55.69% W6+, ∼32.28% W5+, and ∼12.03% W4+. The growth mechanism based on thermodynamics is discussed for the growth of tungsten oxide nanorods from W film.

The effects of TiO2 addition on the reaction behavior, product, and mechanism in the Ti–B4C system were investigated in this study. The reaction could be self-sustaining for the TiO2 addition no more than ∼33% of the total weight of the reactants. With an increase in the TiO2 addition, the combustion temperature and wave velocity decrease progressively, the ignition delay time first decreases and then increases, while the constituents of the reaction products do not vary significantly unless the relative addition content of TiO2 exceeds ∼22 wt%. Therefore, TiO2 could be used as a favorable reaction regulator for the Ti–B4C system. The reaction mechanism, as determined by differential thermal analysis and combustion front quenching experiment in combination with subsequent x-ray diffraction examination, is changed more or less by the addition of TiO2 with the extent depending on the addition amount.

The room temperature deformation behavior of a LiNbO3 single crystal loaded along [0001] was studied by spherical nanoindentation. The threefold symmetry of the indentation marks was attributed to the formation of (10¯12) twins that reorient the basal planes to allow for basal slip, which is manifested by the formation of fully reversible, hysteretic loops upon cyclic loading. The differences in energy dissipation, threshold stresses, and loop shapes for the three different radii tips are attributed to the different sized twins that form. The results are consistent with our model for the formation of incipient kink bands within the twins.

The coexistence of high Fe content and high glass-forming ability (GFA) has been earnestly desired from academia to industry. We report a novel Fe76Si9B10P5 bulk metallic glass with an unusual combination of high magnetization of 1.51 T due to high Fe content as well as high GFA leading to a glassy rod with a diameter of 2.5 mm despite not containing any glass-forming metal elements. This alloy composed of familiar and low-priced elements, also exhibiting very excellent magnetic softness, has a great advantage for engineering and industry, and thus should make a contribution to energy saving and conservation of earth’s resources and environment.