The ability of using nanoindentation raw data for characterizing the strain rate sensitivity of the flow stress of elastic–plastic materials has been assessed by finite element calculations. Correction factors for deducing the true strain rate sensitivity from the hardness sensitivity to the hardness penetration rate have been obtained for situations where the elastic contribution to the penetration is not negligible. The results of the analysis are applied to the experimental measurement by nanoindentation of the strain rate sensitivity of an ultrafine grain Sn–Bi eutectic processed by equal channel angular pressing. The flow stress of this material displays bilinear power-law strain-rate dependence. It is also shown that at very low indentation depths, discontinuities of the hardness–penetration curve of the fine-grain Sn–Bi can be correlated with local grain or interphase boundary slip events near the indentation.

Nanoindentation of the reinforcement in a particulate reinforced metal matrix composite (PR MMC) enables direct investigation of reinforcement properties within the finished material. Mismatch between the elastic moduli of the reinforcement and matrix creates a “secondary indentation” effect, whereby the stiffer reinforcement particles themselves “indent” the more compliant matrix. A finite-element investigation was undertaken to quantify the additional penetration arising under secondary indentation for spherical and cylindrical particles. Modification of Sneddon’s equation for a flat punch by a scalar particle shape factor provided an accurate estimate of the additional penetration. The modified equation was combined with the analysis of Field and Swain to extract the particle elastic modulus from results obtained using a spherical indenter under a multiple partial-unloading indentation regime. The resulting methodology was used to determine the elastic moduli of silicon carbide particles and MicralTM microspheres in two aluminum-matrix PR MMCs.

Thin films of mixed manganese (mainly 4+) and vanadium (5+) oxides deposited electrochemically on a platinum substrate have been heat-treated under vacuum at various temperatures between 25 and 400 °C. Electron spin resonance and x-ray photoelectron spectroscopy revealed that the reductive formation of Mn2+ occurs at 300 °C only in the presence of vanadium within the film. This phenomenon can be regarded as a result of electron transfer from V4+ ions generated thermally to neighboring Mn sites. Voltammetric response of the heat-treated Mn/V oxide film in borate solution was enhanced with increasing the number of potential cycles, and the steady-state current was much larger than that of pure manganese oxide. Vanadate ions were diffused from the film to maintain the charge balance during the repetition cycles. The resultant porous structure can allow easier mass transport of protons to electrically conductive Mn oxide surface, offering the improved charge–discharge performance of the electrode.

We have grown lead magnesium niobate–lead titanate (PMN–PT) single crystals, using the high-pressure vertical Bridgman (HPVB) technique, around the stoichiometric composition of 0.7 PMN–0.3PT [0.7Pb(Mg1/3Nb2/3)O3 + 0.3(PbTiO3)]. The final ingot (about 50-mm diameter, 25-mm long) was machinable using an inner diameter saw. The room-temperature x-ray diffraction on the starting powders and the final single crystal revealed a desirable perovskite structure. The natural growth direction in most of the crystals, as determined using orientation image microscopy, was (110). Examination of the final microstructures and phases/inclusions had been done using optical and infrared microscopy, energy dispersive spectroscopy, and x-ray backscatter techniques. Microstructural characterizations of the final ingots have revealed the presence of pores filled with Mg–Si–O-rich impurity phase, usually found along the cell boundary–like structures, in all the growths. We have measured some piezoelectric properties including d33 (1200 pC/N), k33 (0.85), kt (0.5), and the dielectric constant at the Curie temperature.

Monodisperse and uniform γ-Fe2O3 (maghemite) nanocrystals of variable size were prepared by thermal decomposition of iron pentacarbonyl [Fe(CO)5] in the presence of surfactants, following controlled oxidation with trimethylamine N-oxide as a mild oxidant. The influence of carboxylic acids with variable alkyl carbon chain lengths on the synthesis of γ-Fe2O3 nanocrystals was investigated. The effect of the molar ratios of surfactant to iron precursor was also studied. The nanocrystals were characterized by x-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD showed the particles were highly crystalline at the nanometer scale. The results showed that the size and shape of the nanocrystal is strongly influenced by the decomposition temperature of iron pentacarbonyl and closely related to the length of carbon chain of the capping groups and the molar ratio of surfactant to iron precursor. Following controlled evaporation from nonpolar solvents, self-assembly into two-dimensional arrays could be observed by TEM. It was also found that the distance between the nanocrystals in self-assembled structures matched the length of the capping molecules very well.

The electrical conduction mechanisms of approximately 8-nm-thick Ta2O5 films grown by metalorganic chemical vapor deposition were investigated by measuring the current density–voltage characteristics at various temperatures. The Ta2O5 films were grown in two steps with or without intermittent annealing at 450 °C under an O3 atmosphere with ultraviolet light radiation (UV-O3 treatment). High-resolution transmission electron microscopy of the films after post-deposition annealing at 750 °C under an O2 atmosphere showed that the intermittent UV-O3 treatment improved the crystallization of the film during post-annealing. Auger electron spectroscopy of the variously treated samples showed that the improvement in crystallization was due to the increase in the oxygen concentration of the Ta2O5 films by the UV-O3 treatment. The Ta2O5 film without the UV-O3 treatment mostly exhibited a Poole–Frenkel conduction behavior with the electron trap level of 0.62 eV from the conduction band edge. The whole layer UV-O3 treated Ta2O5 films also showed a Poole–Frenkel conduction behavior with an almost identical electron trap level and a reduced density. The partially UV-O3 treated Ta2O5 films exhibited a direct tunneling behavior in a relatively low voltage region by the tunneling through the thin (∼3.8 nm) UV-O3 treated surface layer. However, these films showed a Poole–Frenkel conduction behavior in the high-voltage region. In general, the UV-O3 treatment was an efficient method to reduce the leakage current of the high-dielectric Ta2O5 films.

A combustion synthesis method was developed for synthesis of AlN powder. Al powder and small amounts of urea were thoroughly mixed and placed in aluminum containers. A layer of AlN powder was placed on the top of the reactant powdersand in between the reactant powders and the container walls. The combustion reaction was ignited by heating the top surface of the powder stack and the aluminum container was converted completely to AlN during combustion reaction. High product yields (∼99.5%) were obtained under N2 pressures of 0.3–0.5 MPa. The product as synthesized is porous and loose and can be easily ground. A quenching technique was developed and formation of the various types of product morphology was investigated. Effects of several process parameters on the product yield were also studied. These results were reported and discussed.

Selective encapsulation of different materials or phases of a material inside a carbon nanotube leads to controlling local properties of the nanotube. We report a method of synthesizing stable γ-Fe selectively inside a carbon nanotube by transforming α-Fe through electron irradiation in situ inside a transmission electron microscope. Therefore, this method enables a single nanotube to encase both high (γ-Fe) and low (α-Fe) temperature phases of iron simultaneously. γ-Fe produced by this method may be used as a novel catalyst, and its presence inside a carbon nanotube may affect the physical properties of the nanotube, which therefore can be used to modify the nanotube.

Using cathodic arc plasma to deposit CrN on the steel has been explored and extensively studied to improve the wear and corrosion resistance of the steel structures. Metal vapor vacuum arc (MEVVA) source implantation is a novel and profitable surface-modification process coupled with the cathodic arc plasma. The effect of the MEVVA-implanted chromium on the corrosion behavior in form of Cr/steel, CrN/steel, and CrN/Cr/steel was evaluated in an aerated 0.1N HCl solution. The composition and structure of the MEVVA-implanted chromium and the cathodic arc plasma deposited CrN on steel were both examined by x-ray diffraction and transmission electron microscopy. The polarization resistance (Rp) of all samples was measured and compared with the results obtained from electrochemical impedance spectroscopy simulated by the equivalent circuit, to interpret the effect of MEVVA-implanted chromium on the corrosion mechanism of the CrN/Cr/steel. The corrosion products associated with the microstructures were analyzed by electron probe x-ray microanalyzer. The results indicated that the corrosion resistance of the CrN-coated steel was significantly enhanced by the MEVVA-implanted chromium in the CrN/Cr/steel assembly.

Ni was surface-alloyed with Si by ion implantation. The material was examined for its redox and electrocatalytic behavior in NaOH by cyclic voltammetry. The surface was characterized by x-ray photoelectron spectroscopy, x-ray and electron diffraction, and electron and atomic force microscopy. The ion implantation enhanced activity toward the redox conversion of Ni(OH)2 ↔ NiOOH and the anodic oxidation of glucose reached about 3.5 times and about 2.8 times, respectively. The material is an amorphous mixed oxide of Ni and Si. The effect is discussed considering the true surface area and the generation of active surface sites in relation to the oxygen evolution.

An iron aluminide (Fe–40 at.% Al) was thermal oxidation (TO)-treated at 1000 °C for 30 to 150 h. The mechanical properties (e.g., hardness and elastic modulus), the scratch resistance, the deformation and damage behaviors of the TO-treated surface layers were evaluated using nanoindentation and nanoscratch techniques. It has been found that the TO treatment produced an oxide layer containing α–Al2O3 on the iron aluminide surface, which increased the surface hardness (H) and elastic modulus (Er) but reduced the ratio of Er/H. This has significantly improved the scratch resistance of the iron aluminide. Longer treatment resulted in a thicker oxide layer and led to further reduced scratch rate and an increased critical load to failure. The scratch resistance has been correlated with the scratch load, the hardness, and the Er/H ratio of the surface oxide layer.

FeCoNi ternary alloy nanowire arrays 32–106 nm in diameter were fabricated within nanoporous alumina membranes using 15 Vrms alternating current electrodeposition at frequencies of 50, 250, 500, 750, and 1000 Hz. The magnetic coercivity and hysteresis loop squareness-ratio (Mr/Ms) were studied as functions of electrolyte composition, nanowire diameter, and nanowire aspect ratio.

Several new bulk metallic glasses based on Fe–Y–Zr–(Co, Cr, Al)–Mo–B, which have a glass-forming ability superior to the best composition Fe61Zr10Co7Mo5W2B15 reported recently, have been successfully developed. The as-cast bulk amorphous alloys showed a distinctly high thermal stability with glass-transition temperatures above 900 K, supercooled liquid regions above 60 K, and high strength with Vickers hardness values larger than HV 1200. The suppression of the growth of primary phases in the molten liquids and the resultant low liquidus temperatures were found to be responsible for the superior glass-forming ability in these new alloys. It was found that the addition of 2% Y not only facilitated bulk glass formation, but the neutralizing effect of Y with oxygen in the molten liquids also improved the manufacturability of these amorphous alloys.

Bimetallic NiW sulfide nanostructures of the inorganic fullerene-like (IF-like) type were prepared by a chemical method employing ammonium thiotungstate and nickel nitrate as metal-sulfide precursors followed by sulfidation in H2S/H2 at 400 °C. The nanostructures were grown with a Ni excess, at an atomic ratio R = 0.85 (R = Ni/Ni + W). The x-ray diffraction patterns showed poorly crystalline WS2, WO2, NiS, and Ni9S8 phases. High-resolution electron microscopy micrographs revealed the formation of two fullerene-like nanostructures, nickel sulfide nanoparticles and long nanotubes filled with tungsten suboxide, both coated by several WS2 layers. The surface area of 18 m2/g measured by nitrogen adsorption (BET surface-area) revealed that these materials contained micropororosity.

The hypothetical wurtzite structure chromium chalcogenides were investigated through first-principle calculation within density-functional theory. All compounds are predicted to be true half-metallic ferromagnets with an integer Bohr magneton of 4 μB per unit. Their half-metallic gaps are 1.147, 0.885, and 0.247 eV at their equilibrium volumes for wurtzite-type CrM (M = S, Se, and Te), respectively. The half-metallicity can be maintained even when volumes are expanded by more than 20% for all compounds and compressed by more than 20%, 20%, and 5%, for CrS, CrSe, and CrTe, respectively.

The plasticity-controlled growth rate of cavities during superplastic deformationwas statistically investigated for 5083 Al alloy and AZ31 Mg alloy. When the cavity growth rate was evaluated on the basis of macroscopic strain calculated using the displacement of the specimen, the growth rate for the Al alloy was larger than thatfor the Mg alloy. However, the growth rate of the Al alloy was in agreement withthat of the Mg alloy when the cavity growth rate was evaluated on the basis of the microscopic strain due to grain boundary sliding. The results obtained lead to two conclusions: (i) the rate of cavity growth is not affected by the kind of materials,that is, the nature of the grain boundary, and (ii) the microscopic strain due to grain boundary sliding should be used to evaluate exactly the rate of cavity growth for superplastic deformation.

A new Auger electron spectroscopical sputter depth profiling method was developed to determine the interdiffusion coefficient for the initial stage of diffusion annealing of thin films. The method is based on (i) adoption of an interdiffusion model appropriate for the specimen investigated and (ii) convolution of an accordingly calculated diffusion-induced concentration profile with the smearing effects due to atomic mixing, surface/interface roughness, escape depth of the Auger electrons, and preferential sputtering. The diffusion-induced concentration profile and the interdiffusion coefficient are determined by fitting in an iterative least-squares procedure of the calculated Auger electron spectroscopical depth profile to the measured one. The method was applied to bilayered and multilayered structures, exhibiting dominant grain-boundary diffusion and dominant volume diffusion, respectively. A very small extent of interdiffusion, characterized by diffusion distances as small as 1 nm, could be quantified.

In this paper, we report the utilization of high ionic strength (>1100 mM) calcium phosphate solutions in depositing 20–65-μm-thick, bonelike apatitic calcium phosphate on Ti6Al4V within 2–6 h, at room temperature. The super-strength solution used here multiplied the concentrations of calcium and phosphate ions in human plasma or simulated body fluid (SBF) by a factor of ten. The interesting features of the technique are given in the following. First, the solutions did not contain any buffering agents, such as Tris or Hepes. Second, during the process, homogeneous formation of calcium phosphate nano-clusters took place. However, their presence did not adversely affect the coating process. Third, other than simple surface treatments to begin with, no other additional intermediate steps were necessary. The only step needed after the preparation of the solution from reagents is the addition of proper amounts of NaHCO3 to raise the pH to 6.5 prior to the coating procedure. Fourth, there is no CO2 bubbling required, and hence, this is a robust process. Fifth, such a procedure led to a significant enhancement of coating rate enabling the formation in as little as 2–6 h. Coating proceeded with a linear rate. Sixth, the adhesion strength (12 ± 2 MPa) of the present coatings was comparable to coatings produced by soaking in 1.5× SBF solutions over a prolonged period of time, typically two to three weeks. Finally, the carbonate content (8 wt%) and Ca/P molar ratio (1.57) qualify the coating as bonelike.

The photoluminescence (PL) and PL excitation spectra of the single-crystal samples of yttria-stabilized zirconia (YSZ) were measured. We found that the PL spectra of two samples for the 280-nm excitation significantly differ from one another in intensity, although the two samples have the same macrostructure and the same chemical composition. These results indicate that PL spectroscopy is a useful method for studying the microstructure of YSZ. The result of the trace-impurity analysis suggests that the large difference in PL intensity between the two samples can be explained by considering the influence of Nb in the YSZ sample. It seems that Nb in YSZ caused an yttria-associated defect. The broad emission band around 550 nm would be attributed to this defect. These results suggest that information can be obtained from its PL measurement not only on the yttria-associated defect, but also on the trace impurity in the YSZ.

Formation of iron oxide nanoparticles within the internal cages of Na–Y zeolites was investigated. Sodium ions within the zeolites were replaced with iron(II) ions. Elemental composition studies showed a significant amount of iron in the exchanged sample. NaOH and dropwise additions of H2O2 at 60 °C triggered formation of zeolite–iron oxide systems. X-ray diffraction (XRD) patterns showed diminishing zeolite peaks along with evolution of peaks corresponding to γ-Fe2O3 and α-Fe2O3 with increasing NaOH concentration. Morphological changes from hexagonal-shaped zeolite to clusters of fine particles were observed under scanning electron microscope. Particles with about 15-nm diameter were detected by transmission electron microscopy. γ-Fe2O3 crystallites of 13.4 nm were determined from the broadening of XRD peaks. The magnetization curves of samples (precipitated using NaOH with concentrations of 2.0 M and above) showed absence of hysteresis and passed through the origin, indicating the particles are superparamagnetic. Gas adsorption–desorption measurement of the system precipitated with 2.0 M NaOH revealed a 26% increase in its specific surface area, indicating the presence of nanometer-sized particles within the zeolites.