Macrochannelled tetragonal zirconia polycrystals (TZP) coated with a calcium phosphate layer were fabricated using a coextrusion process to produce strong and bioactive porous bioceramics. The initial feedrod, composed of three materials [TZP (shell), calcium phosphate (intermediate layer), and carbon black (core)], was coextruded through a 750-μm orifice at 120 °C, producing a continuous and flexible filament. Each sheet, which was composed of a unidirectional array of filaments, was stacked and then warm-pressed at 140 °C with 10 MPa. After binder burnout, the green billet was sintered between 1350 and 1600 °C for 1 h in air, leaving uniform macrochannels clad on the inside with bioactive calcium phosphate on a strong TZP body. The compressive strength of the specimen was much higher than that of calcium phosphate with a similar structure.

The microstructure of the melt-spun Cu60Hf30Ti10 and Cu50Hf40Ti10 alloys was investigated. The high-resolution transmission electron microscopy (HRTEM) image in the Cu60Hf30Ti10 alloy reveals the existence of nanoscale inhomogeneity, which appears to originate from nanocrystalline particles. The compositional segregation with a diameter of approximately 5 nm was detected, and its size agrees with the scale of nanocrystalline particle. Small-angle x-ray scattering measurement of the melt-spun Cu60Hf30Ti10 alloy also indicates the development of nanoscale inhomogeneity with the same size as that of nanocrystalline particles. It is found that the Cu element is enriched in and Hf element is rejected from the nanocrystalline particles. Since the melt-spun Cu50Hf40Ti10 alloy, which has a similar alloy composition to that of the glassy region of melt-spun Cu60Hf30Ti10 alloy, has a homogeneous glassy structure without fringe contrast in the HRTEM image, it is suggested that the excess of Cu causes the nanoscale inhomogeneity with crystalline structure in the rapidly quenched Cu–Hf–Ti alloys.

We present an inexpensive, bulk-processing technique for the mass fabrication of a high-performance, nanocrystalline intermetallic with no internal flaws: the recrystallization of plastically deformed ingots through controlled heat treatments. We demonstrate that FeCo alloys with average grain sizes of 100 nm can be produced using this method. The nanocrystalline materials have tensile yield strengths as high as 2.2 GPa and have plastic tensile ductilities over 1.3%. Such superior properties at room temperature are currently unattainable when nanocrystalline materials are prepared by other methods.

A strong temperature dependence of positron annihilation with low-momentum electrons is reported for a Zr-based bulk metallic glass in the temperature range 50–300 K. The observed behavior was rationalized in terms of shallow versus deep positron traps. An interpretation of the data was presented based on the idea that there were two different types of open-volume regions: Bernal interstitial sites and thermally unstable larger holes. Bernal interstitial sites, intrinsic to the glass structure, were found to be insensitive to annealing. Alternatively, the larger holes were removed by annealing. The strong correlation between these larger holes and diffusion and viscous flow processes suggests that they may act as diffusion and flow defects.

A LiNbO3/ZnO multilayer with a preferred c-axis orientation normal to the plane of the substrate was grown on glass and SiO2/Si substrates by laser ablation. The piezoelectric activity in as-deposited films was demonstrated using a novel approach to the atomic force microscope. In the presence of an in-plane, low-frequency (0.1–5 Hz) alternating current electric field, we monitored and imaged the induced piezoelectric response normal to the film plane between two electrodes.

Zinc oxide (ZnO) films were prepared by a nearby vaporizing chemical vapor deposition method using bis(2,4-pentanedionato)zinc as a source material. The deposition rate increased exponentially from 0.58 to 147 nm min−1 with increasing substrate temperature (Ts). The highest preferred orientation to the c axis was obtained under the conditions that the distance between substrate and source surface was 5.0 mm, and the Ts was 300 °C. When we used a sapphire (0001) substrate, an epitaxial ZnO film could be deposited on this condition.

Vapor-grown carbon fibers and carbon micro-beads were produced in the absence of catalysts from a natural precursor, camphor, by a thermal chemical vapor deposition process, at different temperatures in an argon medium. Scanning and transmission electron microscopy, Raman spectra, and electrical conductivity studies were used to characterize these fibers. It was observed that cylindrical fibers (diameter ∼3 μm) were obtained at 1033 K and rippled fibers (diameter ∼5 μm) were formed at 1273 K while carbon beads (diameter ∼0.5–1 μm) were formed at 1173 K. It is proposed that agglomeration of carbon beads predominate at pyrolysis temperature greater than 1173 K, resulting into rippled type fibers.

An experimental study of the inelastic deformation of bulk metallic glass Zr41.2Ti13.8Cu12.5Ni10Be22.5 under multiaxial compression using a confining sleeve technique is presented. In contrast to the catastrophic shear failure (brittle) in uniaxial compression, the metallic glass exhibited large inelastic deformation of more than 10% under confinement, demonstrating the nature of ductile deformation under constrained conditions in spite of the long-range disordered characteristic of the material. It was found that the metallic glass followed a pressure (p) dependent Tresca criterion τ = τ0 + βp, and the coefficient of the pressure dependence β was 0.17. Multiple parallel shear bands oriented at 45° to the loading direction were observed on the surfaces of the deformed specimens and were responsible for the overall inelastic deformation.

In this work, we report on the observation of Nd1Ba6Cu3O10,5 (Nd163) phase of the NdBaCuO system in melt-textured Nd123 bulk samples grown from a mixture of Nd123 and Nd210 phase powders. The observation was performed with polarized light optical microscopy and scanning electron microscopy–energy dispersive x-ray analyses. Images of the identified phase crystals show an aspect quite different from Nd422 crystals. Unexpectedly, Nd163 was individuated, even in “pure” Nd123 samples. Moreover, after long exposure to air, Nd163 disappeared completely in samples synthesized from powders containing Nd210. Thermogravimetry analyses of powders show that the stability of this phase in air is limited to temperatures higher than 900 °C, so Nd163 is unstable and highly reactive at room temperature. Moreover, an explanation of the observation of Nd163 in Nd210 free samples, based on the spontaneous formation of Nd163 phase in a Nd123 melt, is proposed.

A single LaMnO3 buffer layer was developed for the growth of superconducting thick YBa2Cu3O7−δ (YBCO) films on polycrystalline Ni-alloy substrates where a biaxially textured MgO layer, produced by ion-beam assisted deposition (IBAD), was used as a template. Using pulsed laser deposition, a 1.65-μm-thick YBCO film with a critical current density of 1.4 × 106 A/cm2 in self field at 75 K was achieved on sputtered LaMnO3-buffered IBAD MgO substrates. This corresponds to a critical current (Ic) of 231 A/cm-width. This result demonstrates the possibility of using both LaMnO3 buffer and IBAD MgO template for producing high current density YBCO-coated conductors.

This study investigated the characteristics of the intermetallics that appear in Sn–Zn–Ag solder alloys, particularly their behavior in molten solder during cooling and remelting. The results indicated that the intermetallics, which deplete the Zn-rich phase, were present in the form of inhomogeneous dendrites and consisted of two intermetallic phases, ε–AgZn3 and γ–Ag5Zn8. These Ag–Zn intermetallics formed as the primary dendrites upon cooling from temperatures slightly below 300 °C. These intermetallics transformed into coarse nodules with a stable, high Ag-content phase when isothermally heated at 250 °C. These massive intermetallic particles tended to settle at the bottom of the melt due to low buoyancy. Isothermal heating at slightly above 300 °C resulted in the rapid melting of these intermetallics. Subsequent quenching caused numerous fine dendritic intermetallics to form throughout the solder.

A method for determining the stress–strain relationship of a material from hardness values H obtained from cone indentation tests with various apical angles is presented. The materials studied were assumed to exhibit power-law hardening. As a result, the properties of importance are the Young's modulus E, yield strength Y, and the work-hardening exponent n. Previous work [W.C. Oliver and G.M. Pharr, J. Mater. Res. 7, 1564 (1992)] showed that E can be determined from initial force–displacement data collected while unloading the indenter from the material. Consequently, the properties that need to be determined are Y and n. Dimensional analysis was used to generalize H/E so that it was a function of Y/E and n [Y-T. Cheng and C-M. Cheng, J. Appl. Phys. 84, 1284 (1999); Philos. Mag. Lett. 77, 39 (1998)]. A parametric study of Y/E and n was conducted using the finite element method to model material behavior. Regression analysis was used to correlate the H/E findings from the simulations to Y/E and n. With the a priori knowledge of E, this correlation was used to estimate Y and n.

Lead zirconate titanate (PZT) films between 1 and 3 μm thick were grown using solution deposition techniques to study the effects of crystal structure and orientation on the direct piezoelectric output of these films on platinized Si membranes. By varying the chemistry of the film from Zr-rich to Ti-rich, the {100}/(111) relative intensity increased for films grown on randomly oriented Pt films. The 40:60 PZT had a tetragonal crystal structure and produced greater electrical output at a given strain than the rhombohedral film (Zr:Ti concentrations less than 50:50), while having a similar e31 constant, between 4.8 and 6.3 C/m2. Orientation and voltage output at a given strain were not strongly influenced by thickness in the ranges investigated. Defects in internal PZT/PZT crystallization interfaces were identified and include porosity on the order of tens of nm, with a corresponding depletion in Pb and accumulation of O at these interfaces. The {100} texture of rhombohedral films deposited upon (111) textured Pt films is significantly greater than the {100} texture of tetragonal films, which show both a {100} and {111} orientation on the same Pt film.

Finite-element analyses for elastoplastic cone indentations were conducted in which the effect of linear strain hardening on indentation behavior was intensively examined in relation to the influences of the frictional coefficient (μ) at the indenter/material contact interface and of the inclined face angle (β) of the cone indenter. A novel procedure of “graphical superposition” was proposed to determine the representative yield stress YR. It was confirmed that the concept of YR applied to elastic-perfectlyplastic solids is sufficient enough for describing the indentation behavior of strainhardening elastoplastic solids. The representative plastic strain of εR (plastic) ≈ 0.22 tan β, at which YR is prescribed, is applicable to the strain-hardening elastoplastic solids, affording a quantitative relationship of YR = Y + ε;R (plastic) × EP in terms of the strain-hardening modulus EP. The true hardness H as a measure for plasticity is estimated from the Meyer hardness HM and then successfully related to the yield stress Y as H = C(β,μ) × Y for elastic-perfectly-plastic solids and as H = C(β,μ) × YR for strain-hardening solids, by the use of a β- and μ-dependent constraint factor C(β,μ) ranging from 2.6 to 3.2.

We report on the observation of space-selective precipitation of gold nanoparticles in Au2O-doped silicate glass by a method of irradiation with an 800-nm femtosecond laser and further heat treatment. The irradiated region of the glass first became gray in color after irradiation with the femtosecond laser and then turned red after further heat treatment at around 520 °C, indicating that gold nanoparticles have precipitated in the irradiated region of the glass. A possible mechanism has been suggested that the Au+ ions in the region irradiated are reduced to Au0 atoms by the femtosecond laser, and then the Au0 atoms accumulate to form gold nanoparticles with the glass sample heat treated. The observed phenomenon should have potential applications in the fabrication of ultrafast all-optical switches.

To prevent catastrophic failure by propagating highly localized shear bands and to overcome the limited dimension of metallic glass, centimeter-scale Ni59Zr20Ti16Si2Sn3 bulk metallic glass matrix composites were fabricated by warm extrusion of a mixture of gas-atomized fully amorphous powders and ductile brass powders. After consolidation, the composite retained the fully amorphous matrix found in the gas-atomized powder combined with the brass second phase. The glass-transition and crystallization temperatures of the extruded material were the same as those of the starting powders. The confined ductile brass phase enabled the bulk metallic glass matrix composites to deform plastically under uniaxial compression at room temperature. The combination of strength and ductility in the inherently brittle Ni-based monolithic materials could be obtained by introducing a ductile phase in the bulk metallic glass matrix. However, control of the volume fraction and distribution of the ductile brass phase was important for the proper combination of the strength and plasticity.

Interfacial reactions and intermetallic compound formation of the eutectic Sn–0.7Cu and hypereutectic Sn–3Cu on thin film metallization of Al/Ni/Cu, Al/Cu, and Al/Ni were investigated. While the Ni layer of Al/Ni/Cu was almost consumed by Sn–0.7Cu after one reflow at 240 °C, most of it was preserved with Sn–3Cu even after ten reflows. Since the Cu content in Sn–0.7Cu is below the solubility limit of Cu in Sn at 240 °C, the Cu layer of Al/Ni/Cu was dissolved completely into Sn–0.7Cu, and the Ni was exposed to the molten solder to form intermetallics. As Cu content in Sn–3Cu is more than the solubility limit, intermetallics formed between the solder and the Cu layer, but not the Ni layer, of Al/Ni/Cu. The supersaturation of Cu in Sn–3Cu was found to be beneficial in reducing the interfacial intermetallic compound formation and in improving the interfacial stability.

Glassy Fe65Co10Ga5P12C4B4 alloy powders with a large supercooled liquid region of 50 K before crystallization were synthesized in the particle size range below 125 μm by Ar gas atomization. With the aim of developing a large-size Fe-based glassy core with good soft magnetic properties, the consolidation method of spark plasma sintering was applied to the Fe65Co10Ga5P12C4B4 glassy powders. The existence of the supercooled liquid region enabled us to form a large-size glassy alloy disc 20 mm in diameter and 5 mm in thickness with a high relative density of 99.7% at the glass-transition temperature of 723 K and under the external applied pressure of 300 MPa. The resulting glassy core of 18 mm in outer diameter, 10 mm in inner diameter, and 4 mm in thickness exhibits good soft magnetic properties: 1.20 T for saturation magnetization, 6 A/m for coercive force, and 8900 for maximum permeability. The good soft magnetic properties of the Fe-based bulk glassy core are attributed to the combination of the high relative density and the maintenance of the single glassy structure.

The thermomechanical behavior of Cu thin films, 600–1125 nm thick and encapsulated between SiNx barrier and SiNx or AlNx passivation layers on silicon substrates, was studied during thermal cycling between room temperature and 400 or 500 °C using the substrate curvature method. Films were prepared with varying oxygen contents, and the distribution of oxygen through the thickness of selected films was studied before and after thermal cycling using secondary ion mass spectrometry. Large variations in the thermomechanical behavior with oxygen content were found and correlated with segregation of oxygen to the film/barrier and film/passivation interfaces. These variations are thought to be due to recovery of stored misfit dislocation energy, which is, in turn, controlled by oxygen in the film. Effects of oxygen on film deformation through variations in interfacial adhesion and diffusion-induced dislocation glide are considered.

The reduction of tungsten carbide (WC) to elemental tungsten by reaction with a Zr–Cu melt was examined. Dense WC disks were immersed in a vertical orientation in molten Zr2Cu at 1150–1400 °C for 1.5–24 h. Continuous, adherent layers of W and ZrC formed at WC/melt interfaces. The rates of thickening of the W and ZrC product layers were examined as a function of reaction time and temperature and position along the vertical WC surface. Such kinetic data, along with microstructural analyses, indicate that the incongruent reduction of tungsten carbide is likely to be controlled by carbon diffusion through one or both of the product layers.