The novel rare-earth scandium-based bulk metallic glasses (BMGs) are obtained by the copper mold casting method. Compared with other rare-earth BMGs reported so far, the Sc-based BMGs exhibit the highest elastic moduli (e.g., Young’s modulus, E = 85 GPa; bulk modulus, B = 77.5 GPa), glass transition temperature (Tg = 662 K), and crystallization temperature (Tx = 760 K) combined with a large region of supercooled liquid (ΔT = 98 K). A good correlation between glass transition temperature and elastic moduli is found in a variety of rare-earth-based BMGs.

Sulfide stress cracking (SSC) resistance was investigated by comparing acicular ferrite (AF) and ferrite-pearlite (FP) in a microalloyed steel and in a non-microalloyedsteel. In microalloyed steel, AF exhibited better SSC resistance than FP, while in non-microalloyed steel, AF presented far worse SSC resistance than FP. In microalloyed steel, nano-sized carbonitrides and high-density pinned dislocations in AF were analyzed to behave as innocuous hydrogen traps, offering numerous sites for hydrogen redistribution and modifying critical cracking conditions. Dislocations in AF of microalloyed steel in the final analysis are attributed to pinning by the nano-sized carbonitrides.

Mg−Cu−Y alloys with optimal glass forming ability have been found at off-eutectic compositions. The critical size for bulk metallic glass formation at the pinpointed compositions more than doubles that of the previously discovered eutectic Mg65Cu25Y10 alloy, leading to fully glassy rods with near-centimeter diameters in the ternary system upon copper mold casting. The result is a striking demonstration of the strong composition dependence of the glass forming ability, as well as of the need to scrutinize off-eutectic compositions. The implications of the discovery are discussed.

Transparent conductive In-doped Cd3TeO6 thin films were deposited on silica glass substrate by radio frequency magnetron sputtering using targets composed of CdO, TeO2, and In2O3 powders, and their electrical and optical properties were examined. The electrical resistivity of 3.2 × 10−3 Ωcm and an average transmittance above 80% in the visible region (400–800 nm) were obtained for the films deposited at the substrate temperature above 300 °C. The maximum optical band gap was 3.92 eV for the film deposited at 700 °C, demonstrating a large optical band gap comparable to indium tin oxide.

The microstructure and orientation relationships of epitaxial (111)-oriented SrTiO3 thin films grown by radio frequency magnetron sputtering on epitaxial (111)-oriented Pt/Ti electrodes on sapphire were investigated using x-ray diffraction, conventional and scanning transmission electron microscopy. We show that the epitaxial growth of (111)-oriented SrTiO3 films was promoted by thin Ti adhesion layers underneath the Pt electrode. The SrTiO3 films nucleated with two twin-related orientation variants, rotated by 180° about the 〈111〉 surface normal. The twin boundaries were oriented approximately normal to the film plane, but no strong preference for a specific boundary plane was observed. Growth mechanisms and the relationships to the dielectric properties are discussed.

One of the most common forms of cohesive failure observed in brittle thin film subjected to a tensile residual stress is channel cracking, a fracture mode in which through-film cracks propagate in the film. The crack growth rate depends on intrinsic film properties, residual stress, the presence of reactive species in the environments, and the precise film stack. In this paper, we investigate the effect of various buffer layers sandwiched between a brittle carbon-doped-silicate (CDS) film and a silicon substrate on channel cracking of the CDS film. The results show that channel cracking is enhanced if the buffer layer is more compliant than the silicon substrate. Crack velocity increases with increasing buffer layer thickness and decreasing buffer layer stiffness. This is caused by a reduction of the constraint imposed by the substrate on the film and a commensurate increase in energy release rate. The degree of constraint is characterized experimentally as a function of buffer layer thickness and stiffness, and compared to the results of a simple shear lag model that was proposed previously. The results show that the shear lag model does not accurately predict the effect of the buffer layer.

X-ray phosphors of Gd2O2S:Tb3+ and La2O2S:Eu3+ were synthesized by combustion reactions. The samples were characterized by x-ray diffraction (XRD), scanning electronic microscope (SEM), photoluminescence (PL), and x-ray excited luminescence (XEL) spectra. XRD results revealed pure oxy-sulfide phases when the sintering temperatures were no more than 500 °C, and the mean particle sizes were about 20 nm. While the sintering temperatures became higher, oxy-sulfate phases were present. SEM results illustrated a loose, porous agglomeration and a continuous three-dimensional network structure; PL spectra showed the characteristic emission of rare-earth activation ions. To our satisfaction, the PL intensities were nearly the same as some commercial x-ray phosphors. XEL spectra revealed the same characteristic emission, although their luminescence principles were different from those of the PL spectra. In addition, because absorption coefficients of these samples for x-ray and doped concentrations doped of activation ions were different, their light emission intensities and efficiencies also varied.

Fe–Pd films with Pd content varying between 26 and 30 at.% have been deposited by means of magnetron sputtering of elemental Fe and Pd targets. As-deposited films are highly supersaturated solid solutions of Pd in Fe that have a body-centered-cubic crystal structure and a very fine grain size. Substrate curvature measurements indicate that the films undergo an irreversible densification when heated above 100 °C. This densification is attributed to a structural change that is also observed in other supersaturated systems with a substantial atomic size difference between the constituents. It is possible to retain the high-temperature austenite phase at low temperature by annealing the films at 900 °C followed by rapid cooling. Depending on film composition, this metastable austenitic phase transforms to either a body-centered tetragonal (bct) or a face-centered tetragonal (fct) martensite around room temperature. Substrate curvature measurements show that formation of the fct martensite is reversible, while that of bct martensite is not. The fct transformation occurs at lower Pd content and higher temperature than reported for bulk materials. Both the fct and the fcc phase show a strong Invar effect at lower temperature and Pd content than observed in the bulk.

Conventional plasma-sprayed hydroxyapatite coatings suffer from many difficulties that have limited their use in orthopaedic implants, including uneven resorption rates, poor fracture toughness, and poor adhesion to medical alloys. The placement of a diamondlike carbon buffer layer may overcome these obstacles by providing unique chemical inertness, hardness, and cell-interaction properties at the implant–tissue interface. Nanocrystalline hydroxyapatite and amorphous diamondlike carbon films were prepared by room-temperature pulsed-laser deposition of hydroxyapatite and graphite targets, respectively. Scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and microscratch adhesion testing were used to determine surface morphology, interfacial structure, and adhesion of the bilayer coatings. Nanocrystalline hydroxyapatite/diamondlike carbon coatings have several potential orthopaedic applications, including use in hip prostheses.

Work on nitrogen loss and structural change of nitrogen-containing SBA-15 mesoporous materials after heat treatment in air or water treatment is described herein. The nitrogen-containing SBA-15 lost nitrogen after being treated in air at high temperature or in water, the mesoporous structure of which was very well maintained and did not collapse. HRTEM, N2 sorption, powder XRD, and SEM were used to study the structural ordering and morphology of the mesoporous silicon oxynitride materials before and after treatment. FTIR and C/N/H elemental analysis confirmed that nitrogen loss occurred after the mesoporous silicon oxynitride material was treated. Nitrogen was lost via hydrolysis of ammonium groups when mesoporous silicon oxynitride material was treated in water and by being substituted by oxygen from air when it was heated in air at high temperature.

Compositional and microstructural differences from bottom to top along a water-quenched Zr41Ti14Cu12.5Ni10Be22.5 alloy rod, 90 mm in length and 22 mm in diameter, were investigated experimentally by x-ray diffraction measurement, differential scanning calorimetry, and composition analysis. The results show that the upper part of the rod contains more beryllium atoms and is amorphous. The lower part with less beryllium atoms contains crystalline phases. The composition gradient is possibly due to the gravity-driven transport of Be-rich clusters and un-melted tiny solid pieces in the alloy melt.

Interest in finding binary alloys that can form bulk metallic glasses has stimulated recent work on the Cu–Zr system, which is known to show glass formation over a wide composition range. This work focuses on copper mold casting of Cu50Zr50 (at.%), and it is shown that fully amorphous rods up to 2-mm diameter can be obtained. The primary intermetallic phase competing with glass formation on cooling is identified, and the glass-forming ability is interpreted in terms of a metastable eutectic involving this phase. Minor additions of aluminum increase the glass-forming ability: with addition of 4 at.% Al to Cu50Zr50, rods of at least 5-mm diameter can be cast fully amorphous. The improvement of glass-forming ability is related to suppression of the primary intermetallic phase.

It was found that directional coarsening was induced by phase transformation stress due to non-uniform distribution of μ phase in an experimental nickel-based superalloy. The mechanism based on the existing diffusion and coherency strain energy theory has been discussed. It was concluded that directional coarsening was the course of dissolving of γ′ portion with high free energy, diffusing and growing on the existed γ′ particles along a preferential direction.

Nd-doped Y3ScxAl5−xO12(Nd:YSAG) powder were prepared with a chemical combustion method. The powders were nano-sized and had a pure cubic phase when calcined at 900 °C. Transparent Nd:YSAG ceramics with up to 40% scandium substitution for aluminum were successfully fabricated by sintering the powder compact at 1800 °C under H2 atmosphere. The synthesis process and optical properties were investigated in detail. It was found that the light emission intensity at 1064 nm of the Nd:YSAG with 40% scandium substitution for aluminum can be enhanced by 2–3 times over that of Nd:YAG single crystal when pumped with the same 808-nm diode laser. In addition, the material was found to have prolonged fluorescence lifetime. This highly enhanced light emission intensity is fundamentally important for obtaining higher light output together with suppressed self-heating than Nd:YAG ceramic and single crystals.

Raw and partially infiltrated carbon–carbon composite preforms have been scanned by high-resolution synchrotron radiation x-ray computerized micro-tomography. Three dimensional high-quality images of the pore space have been produced at two distinct resolutions and have been used for the computation of geometrical quantities: porosity, internal surface area, pore sizes, and their distributions, as well as local and average fiber directions. Determination of the latter property makes use of an original algorithm. All quantities have been compared to experimental data with good results. Structural models appropriate for ideal families of cylinders are shown to represent adequately the actual pore space.

The pseudo NiAl binary phase was formed in a nickel-based superalloy by pack cementation. Scanning electron microscopy, transmission electron microscopy, x-ray diffraction, electron probe microanalysis, and positron annihilation technique were used to characterize the pseudo NiAl binary phase. Based on reasonable assumptions, the chemical interdiffusivities of the pseudo NiAl binary phase were then assessed by means of the modified Wagner’s method. The results showed that the chemical interdiffusivities of the pseudo NiAl binary phase were about two orders of magnitude lower than those reported by others. The analysis indicated that the change in thermodynamic properties due to the additions of the microalloying atoms originally present in a superalloy could be responsible mainly for a decrease in chemical interdiffusivities.

ZnO nanowires along with ZnO thin films were obtained on copper-metallized silicon substrates using an radio frequency-reactive sputter-deposition technique. Residual tensile stresses were found in both the copper layer and the ZnO layer. The ZnO nanowires were observed exclusively at the grain boundaries of the ZnO thin films. The average diameter of ZnO nanowires varies only slightly with the ZnO deposition time, while the average length increases linearly with the ZnO deposition time. Based on the observations a growth model involving stress-assisted diffusion of copper and reaction-controlled catalytic growth of ZnO nanowires is suggested.

Several bismuth layer-structured compounds An−3Bi4TinO3n+3 (A = Ba, Sr, Ca) with n > 4 were synthesized and investigated. The average radius of A-site cations was found to be closely related to the lattice parameters in the a–b plane and, therefore, closely related to the stability of the layer structure. For Ba2Bi4Ti5O18 ceramics, there was a diffused phase transition centered at approximately 330 °C, which should be due to the cation redistribution of A-site Ba2+ and Bi3+ in the (Bi2O2)2+ layer. For Sr2Bi4Ti5O18 ceramics, a sharp dielectric constant peak was found at 325 °C. Ceramics of five-layered Ca2Bi4Ti5O18 and six-layered Ca3Bi4Ti6O21 showed temperature-stable dielectric constants up to 800 °C, and ferroelectricity was observed. In addition, as ferroelectrics, these Ca-containing bismuth layer-structured compounds showed frequency-independent dielectric constants >150 and small tan δ on the order of 10−3–10−4 in the frequency range of 1 kHz to 1 MHz.

The plane-strain bulge test is a powerful new technique for measuring the mechanical properties of thin films. In this technique, the stress–strain curve of a thin film is determined from the pressure-deflection behavior of a long rectangular membrane made of the film of interest. For a thin membrane in a state of plane strain, film stress and stain are distributed uniformly across the membrane width, and simple analytical formulae for stress and strain can be established. This makes the plane-strain bulge test ideal for studying the mechanical behavior of thin films in both the elastic and plastic regimes. Finite element analysis confirms that the plane-strain condition holds for rectangular membranes with aspect ratios greater than 4 and that the simple formulae are highly accurate for materials with strain-hardening exponents ranging from 0 to 0.5. The residual stress in the film mainly affects the elastic deflection of the membrane and changes the initial point of yield in the plane-strain stress–strain curve, but has little or no effect on further plastic deformation. The effect of the residual stress can be eliminated by converting the plane-strain curve into the equivalent uniaxial stress–strain relationship using effective stress and strain. As an example, the technique was applied to an electroplated Cu film. Si micromachining was used to fabricate freestanding Cu membranes. Typical experimental results for the Cu film are presented. The data analysis is in good agreement with finite element calculations.

Highly oriented copper nanowires were electrochemically synthesized in a porous alumina membrane template using a new type of weak-acid electrolyte. The Cu nanowires that were deposited have (110) preferred orientation, which is different from most electrochemically deposited Cu nanowires, and they can grow homogeneously. Transmission electron microscopy was used to investigate the room-temperature oxidation behavior, and it was observed that sample treatment methods greatly influence the oxidation rate of the wires. Cu nanowires with different diameters have different resistance to oxidation. The orientation relationship between oxide layer and small-diameter Cu nanowire was determined to be (001) Cu2O // (111) Cu, (110) Cu2O // (110) Cu, and [110] Cu2O // [112] Cu. The possible oxidation process is also discussed.