The microstructure and hardness of Fe–Co-based Hiperco© alloys were investigated. Scanning electron microscopy revealed elongated grains in the as-received (cast and cold-rolled) alloys, and samples containing Nb had second phase precipitates. Annealing of alloys for 1 to 3 h at temperatures in the range 700 to 800 °C resulted in grains becoming equiaxed. In the Nb-containing alloys, the original precipitates dissolved and new precipitates appeared. The rate of grain growth decreased with increasing Nb content, suggesting that Nb or Nb-containing precipitates were responsible for a reduction in the grain boundary mobility. The hardness as a function of grain size in the annealed samples of all of the alloys could be plotted on the same Hall–Petch curve, indicating that the yield strength of these alloys is governed by the grain size, independent of the alloy composition and volume fraction of precipitates.

The local mechanical properties of silica-reinforced silicone composites were investigated using a modified atomic force microscopy technique. Elastic modulus measurements (1.5 ± 0.1 MPa) are consistent with bulk measurements (1.9 MPa), and changes in the modulus at the surface of the composite samples (E = 1.5 to 3.5 MPa) were observed as a result of α-irradiation (dose = 1.7 × 1010 to 2.0 × 1012 α/cm2). The sensitivity of the technique was demonstrated by a detectable change in modulus at even the small dose of 1.7 × 1010 α/cm2. The penetration depth of the α-particles into the material, estimated to be 22 ± 2 μm from the sample edge, was determined by cross-section depth profiling; and modeling of the ion penetration depth using transport of ions in matter codes (24.4 ± 0.4 μm) closely matched experimental observations.

Magnesium oxide (MgO) precursors were prepared by the sol-gel method using magnesium acetate. The reaction products and intermediates obtained during the sol-gel processing of magnesium acetate under various conditions were analyzed thermally and spectroscopically. No organic groups were detected by infrared spectroscopy after heat treating the reaction products at 400 °C. A large exothermic differential thermal analysis peak below 400 °C demonstrated the oxidation of organic moieties in each product. It was found that the presence of an acid catalyst was crucial during the sol-gel processing of magnesium acetate to produce sols suitable for depositing MgO films. The MgO films fabricated on Si(111) substrates using the precursor sol showed (200) orientation regardless of the presence of surface oxides on the substrates.

A novel method for synthesizing anisotropically shaped particles of materials having cubic symmetry is reported. Anisotropically shaped single-crystal particles of cubic SrTiO3 were obtained by epitaxial growth on tabular tetragonal Sr3Ti2O7. Transmission electron microscopy revealed that both the shape and the size of the single-crystal particles was regulated by selecting a precursor material that can act as a reaction site in molten KCl and has an epitaxial relation with SrTiO3. The [001] and [110] directions of tabular SrTiO3 are parallel to the [001] and [110] directions of the Sr3Ti2O7 host particle, respectively. Tabular SrTiO3 particles with rectangular faces having an edge length of 10–20 μm and a thickness of ˜2 μm were obtained by reacting TiO2 and tabular Sr3Ti2O7 particles of the same edge length in molten KCl.

The effect of microwave heating on the hydrothermal synthesis of Al-substituted tobermorite and the removal characteristics of resulting materials were examined and compared with the effect of conventional heating. The microwave heating reduced the crystallization time of Al-substituted tobermorite—i.e., Al-substituted tobermorite was synthesized within 80 min at around 140 °C—and produced smaller crystallites than the conventional heating. The minute crystallites were found to promote the removal characteristics for Cs+ ions in short reaction time.

Ten years after the discovery of high-Tc superconductivity in the system Bi–Sr–Ca–Cu–O, the superconducting compounds have been identified, and their structures, crystal chemistry, phase equilibria, and properties have been extensively investigated. In this review, the results of studies of crystal chemistry and phase equilibria are presented to give materials scientists a comprehensive insight into the phase equilibria and crystal chemistry of these challenging materials.

This paper supplies new interpretation of nanoindentation data for silicon, germanium, and gallium arsenide based on Raman microanalysis of indentations. For the first time, Raman microspectroscopy analysis of semiconductors within nanoindentations is reported. The given analysis of the load-displacement curves shows that depth-sensing indentation can be used as a tool for identification of pressure-induced phase transformations. Volume change upon reverse phase transformation of metallic phases results either in a pop-out (or a kink-back) or in a slope change (elbow) of the unloading part of the load-displacement curve. Broad and asymmetric hysteresis loops of changing width, as well as changing slope of the elastic part of the loading curve in cyclic indentation can be used for confirmation of a phase transformation during indentation. Metallization pressure can be determined as average contact pressure (Meyer's hardness) for the yield point on the loading part of the load-displacement curve. The pressure of the reverse transformation of the metallic phase can be measured from pop-out or elbow on the unloading part of the diagram. For materials with phase transformations less pronounced than in Si, replotting of the loaddisplacement curves as average contact pressure versus relative indentation depth is required to determine the transformation pressures and/or improve the accuracy of data interpretation.

We investigated the photoluminescence spectra as well as the crystal structure and optical energy gaps of the Zn1-xCdxAl2Se4 single crystals grown by the chemical transport reaction method. It was shown from the analysis of the observed x-ray diffraction patterns that these crystals have a defect chalcopyrite structure for a whole composition. The lattice constant a increases from 5.5561 A for x = 0.0 (ZnAl2Se4) to 5.6361 A for x = 1.0 (CdAl2Se4) with increasing x, whereas the lattice constant c decreases from 10.8890 A for x = 0.0 to 10.7194 A for x = 1.0. The optical energy gaps at 13 K were found to range from 3.082 eV (x = 1.0) to 3.525 eV (x = 0.0). The temperature dependence of the optical energy gaps was well fitted with the Varshni equation. We observed two emission bands consisting of a strong blue emission band and a weak broad emission band due to donor–acceptor pair recombination in the Zn1-xCdxAl2Se4 for 0.0 ⩽ x ⩽ 1.0. These emission bands showed a red shift with increasing x. The energy band scheme for the radiative mechanism of the Zn1-xCdxAl2Se4 was proposed on the basis of the photoluminescence thermal quenching analysis along with the measurements of photo-induced current transient spectroscopy. The proposed energy band model permits us to assign the observed emission bands.

The potential of the newly developed Sn–9Zn solder paste as a lead-free solder, especially focusing on the stability at high temperature, was examined. The initial interface strength between Sn–9Zn and Cu, about 50 MPa by the tensile test, is higher than other interfaces such as Sn–37Pb/Cu. While the Sn–9Zn/Cu interface maintains the high strength level after heat exposure at 125 °C, the heat exposure at 150 °C degrades strength seriously. The degradation at 150 °C is caused by dissipation and by disruption of the Cu–Zn reaction layer at the interface. Where the Cu–Zn layer is eroded to form a whole, Sn directly reacts with a Cu substrate to form a thick Sn–Cu reaction region. Such an interfacial morphology change causes the serious degradation. With the Ni/Pd/Au coating on a Cu substrate, the interface becomes much stronger than the direct interface. Even after heat exposure at 150 °C, strength degradation is not so significant. Zn segregates into the coating layer. During high-temperature exposure, Ni and Pd diffuse each other. Zn also diffuses into the coating layer to form compounds, and as a result, a depleted zone of Zn is formed in the solder close to the interface.

Phase stability and transformations of the icosahedral phase (I-phase) in a 41.5Zr41.5Ti17Ni alloy were investigated using melt-spun ribbons and arc-melted bulk samples. A perfect I-phase can be formed directly from liquid through the melt-spinning technique. The I-phase formed in the ribbon is thermodynamically stable and transforms to W-phase, a 1/1 rational approximant above 565 °C. Formation of the perfect I-phase during annealing treatment of the arc-melted sample is very sluggish. Various types of approximants exist as intermediate states for the transformation of crystalline phases to a perfect I-phase.

Fracture surfaces of a recently developed Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 (at.%) bulk metallic glass were investigated using a three-dimensional surface reconstruction technique. Stereoscopic scanning electron microscopy of both fatigue and overload fracture surfaces permitted the creation of digital elevation models that were used to quantify important fracture surface features. Characterization of the surfaces revealed striations of nearly constant spacing on fatigue surfaces and a vein morphology characteristic in amorphous metals on the overload fracture surfaces. Additionally, at the onset of critical failure, crack-tip openings of ˜16 μm were observed that were consistent with measured values of fracture toughness. Interestingly, at the onset of fracture, deformation was confined to one side of the fracture plane, possibly because of the asymmetric emission of shear bands from the crack tip, consistent with the highly inhomogeneous nature of deformation in this alloy.

Nanophase elemental Fe powders prepared by mechanical milling were sinter forged to full density with an average grain size in the nanophase range (below 100 nm). If Cu additions are introduced during milling to form supersaturated solid solutions (Fe85Cu15 and Fe60Cu40), grain sizes can be easily controlled to below 50 nm after consolidation. For Fe–Cu, it was observed that atomic level alloying between the two elements during milling was very helpful for obtaining a homogeneous microstructure and nanocrystalline grain/domain sizes in the consolidated product. The advantages of using sinter forging (upset die forging), as well as the role of the Cu addition, in the retention of nanocrystalline grain sizes are discussed. The consolidated Fe alloys exhibit very high strength under compression, further demonstrating that low populations of flaws and nanophase grain structures were attained in the consolidated products.

The tribological behavior of a Zr–10Al–5Ti–17.9Cu–14.6Ni (at.%) bulk amorphous alloy, in both the as-cast and annealed states, was investigated using nano-scratch tests, including ramping load scratch and multiple sliding wear techniques. The crystallization sequence of the alloy was also characterized. Mechanical properties, such as Young's modulus, hardness, friction coefficient, and tribological wear were measured. These properties were found to vary with microstructure. In general, an increase in annealing temperature results in an increase in hardness, which in turn produces a decrease in friction coefficient but an increase in wear resistance. Samples having a structure consisting of supercooled liquid matrix with dispersed nanocrystalline particles exhibit the best wear performance.

We investigated the formation of nanowhiskers by means of air plasma dry etching using diamond films of two different kinds: as-grown diamond films and films with molybdenum (Mo) deposits. As for the as-grown diamond films, nanowhiskers were found to form preferentially at grain boundaries of diamond crystals. Auger depth profile analysis of the etched films revealed a progressive enrichment by Mo toward the whisker tip, resulting from accidental sputtering of Mo substrate holder. With dry etching of diamond films with preformed Mo deposits, well-aligned whiskers 100 nm in diameter were found to form uniformly over the entire film surface with a population density of 30/μm2. From these findings, it follows that Mo deposits serve as micromasks for the formation of the nanowhiskers. It was also confirmed that these whiskers showed excellent field-emission behavior.

A nanocrystalline tungsten oxide photochromic thin film was prepared by colloid chemistry method. The microstructure, phase transition involved in the solution process, photochromic behavior, and mechanism of the film were investigated by means of transmission electron microscope, x-ray diffraction, ultraviolet-visible absorption spectra, and x-ray photoelectron spectra. It was found that the particle size and crystallinity of the thin film could be easily controlled by adjusting the concentration of oxalic acid in the colloid solution of tungsten oxide hydrate. With the increase of the oxalic acid concentration, the size of nanoparticles in the film decreased sharply, and meanwhile, a blue shift of the absorption peaks caused by the quantum size effect was observed accordingly. With the increase of the pH in the solution, tungsten oxide hydrate was gradually transformed into an oxided 12-tungstate with Keggin structure, which led to the change of photochromic property of the films. The photochromism of the film is believed to be due to the electron transfer between the different valence states of tungsten ions located in adjacent sites.

A series of copper phthalocyanine thin films were prepared on amorphous substrates using physical vapor deposition at ambient temperature. Different sample preparation conditions were used: the deposition rate was varied, and the substrates was static or rotating. The preferred orientation in the thin film was studied as a function of the deposition conditions. X-ray diffraction analysis was performed using θ/2θ and pole figure measurements. In the case of layers prepared at low deposition rates and using nonrotating substrates, a very strong fiber texture was detected with (100) crystallographic planes oriented preferably parallel to the substrate surface. At higher deposition rates, an additional second type of preferred orientation was observed with (110) planes oriented preferably parallel to the substrate surface. In the case of layers prepared with rotational substrates, the (110) type of preferred orientation was quantitatively more strongly developed. If we consider electronic band structure calculations, these results imply that the electron/hole transport through the thin films is enhanced for films prepared at high deposition rates and rotating substrates.

The electrical conductivity of discontinuous filament–reinforced unidirectional composites was investigated. The discontinuous reinforcement used was copper filament, and the matrix materials included solder and epoxy. It was found that the composite conductivity increases with filament length and eventually becomes a constant. Such behavior is described by introducing an interface impedance and the principle of rule of mixture. It was found both experimentally and theoretically that there exists a critical filament length that must be exceeded so the composites will exhibit conductivity as composites having continuous reinforcing filaments.

Oxidative hydrolysis of elemental iron nanoclusters on hydroxylated surfaces such as silica or alumina is known to be influenced by the degree of hydration of the surface. The understanding and control of this process is crucial in the synthesis of iron oxide coated silica microspheres with a desired magnetic property. The hydrolysis of iron nanoparticles followed by heat treatment in the case of a hydrated microspherical silica surface results in the formation of maghemite (γ–Fe2O3), whereas a dehydrated surface yielded hematite (α–Fe2O3) nanoparticles. The influence of adsorbed water on the formation of intermediate iron oxides/oxidehydroxides and the mechanistic aspects of their subsequent thermal dehydration iron oxide phases were investigated by thermogravimetric analysis, Fourier transform infrared, and Mössbauer spectroscopies. The reactions on both the hydrated and the dehydrated surfaces were found to proceed through the formation of an x-ray amorphous lepidocrocite [γ–FeO(OH)] intermediate and its subsequent dehydration to maghemite (γ–Fe2O3). Maghemite to hematite transformation was readily facilitated only on a dry silica surface. The retardation of the lepidocrocite →maghemite →hematite transformation in the case of a hydrated silica surface is suggested to arise from strong hydrogen-bonded interactions between the substrate silica and the adsorbed nanoparticles.

Temperature dependence of in situ fiber strength, effective interface shear stress, Young's modulus of matrix, and matrix fracture energy in a polymer-infiltrationpyrolysis (PIP)-processed two-dimensional plain-woven fabric carbon-coated Nicalon™ SiC fiber-reinforced SiC matrix composite was studied through a tensile test in air at 298 (room temperature), 800, and 1200 K. In situ fiber strength and effective interface shear stress were determined by fracture mirror size and fiber pullout length measurements, respectively. The fiber strength was insensitive to test temperature up to 800 K but dropped significantly at 1200 K. Conversely, the interface shear stress showed a strong temperature dependence, decreasing at 800 K and drastically increasing at 1200 K. The temperature dependence of both values was reasonably explained. Temperature dependence of Young's modulus of matrix was derived from Young's modulus of the composite and fiber and ranged from ≈40 to ≈38 GPa. Matrix fracture energy was also determined from the transverse matrix cracking stress and ranged from ≈16 to ≈5.5 J/m2. Both Young's modulus of matrix and the matrix fracture energy showed only slight temperature dependence up to 800 K; however, both values decreased significantly at 1200 K.

High-epsilon (HE) and ferroelectric (FE) perovskites such as (Ba, Sr)TiO3 and SrBi2Ta2O9 are attracting substantial interest for use in dynamic random-access memory and nonvolatile memory. In this paper, we describe how an easily decomposable PdO bottom electrode layer may be used as a marker for possible HE/FE damage induced by exposure to reducing environments. Oxygen loss from PdO films with and without a HE/FE overlayer was monitored by in situ x-ray diffraction during heating in an inert ambient. Additional measurements were performed on PdO films in contact with Pt underlayers. A Pt underlayer was found to reduce the temperature of oxygen release from PdO, suggesting that it may be possible to custom-design PdO-based oxygen sources with specific oxygen release characteristics to resupply the HE/FE with oxygen lost during processing.