The synthesis of efficient ZnTe powder phosphors is very difficult due to its high moisture sensitivity and chemical instability during processing. In this study, an efficient ZnTe:O powder phosphor for x-ray imaging application was successfully synthesized by vacuum firing ZnTe powder prepared from ZnTe bulk crystals ball-milled in an O2 atmosphere. The phosphors were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, photoluminescence, and cathodoluminescence (CL) measurements and found to exhibit a luminescent efficiency three times that of ZnTe:O prepared by ZnO doping. The ZnTe:O samples exhibited a deep red emission centered at 680 nm and a CL decay time of 1.1μs.

The room-temperature ductility of 95% cold-rolled and recrystallized Ni3Al(Ni–24.0 at.% Al) foils was examined as a function of heat-treatment conditions. The cold-rolled, diffused Goss texture changed to a complicated, transitional texture in the early stage of grain growth and then returned to a similar diffused Goss texture in the late stage. With the texture evolution, the total area fraction of the tough grain boundaries (GBs) such as Σ1, Σ3, and Σ9 increased from 0.23–0.38 in the early stage to 0.56–0.73 in the late stage. Tensile and bending tests revealed that the ductility was drastically improved with the grain growth. The foils in the early stage fractured without showing yielding. In contrast, the foils in the late stage were very ductile, and the tensile elongation increased to 10% with the grain growth. It was confirmed that there was no in-plane anisotropy in ductility. The ductility improvement with the grain growth was ascribed to the increase in the area fraction of the tough GBs.

Indentation analysis based on the concept of representative strain offers an effective way of obtaining mechanical properties, especially work-hardening behavior of metals, from reverse analysis of indentation load–displacement data, and does not require measuring of the projected contact area. The definition of representative strain adopted in previous studies [e.g., Dao et al., Acta Mater.49, 3899 (2001)] has a weak physical basis, and it works only for a limited range in some sense of engineering materials. A new indentation stress-state based formulation of representation is proposed in this study, which is defined as the plastic strain during equi-biaxial loading. Extensive numerical analysis based on the finite element method has shown that with the new formulation of representative strain and representative stress, the critical normalized relationship between load and material parameters is essentially independent of the work-hardening exponent for all engineering materials, and the results also hold for three distinct indenter angles. The new technique is used for four materials with mechanical properties outside the applicable regime of previous studies, and the reverse analysis has validated the present analysis. The new formulation based on indentation stress-state based definition of representative strain has the potential to quickly and effectively measure the mechanical properties of essentially all engineering materials as long as their constitutive behavior can be approximated into a power-law form.

In this study, we compare the effects of pyridine (C5H5N) and pyrimidine (C4H4N2) precursors, using ferrocene as a metal source, in the production of nitrogen containing multiwalled carbon nanotubes. Using standard chemical vapor deposition techniques, highly aligned mats of carbon-nitrogen carbon nanotube were synthesized. The maximum nitrogen concentration in these materials is between 1% and 2% when pyridine is used as the precursor and can be increased to 3.2% when pyrimidine is used as the precursor. However, the electronic structure of both materials, as determined using scanning tunneling spectroscopy, suggests that the nitrogen is incorporated into the nanotube lattice in the same way for both precursors.

Nanocomposite films consisting of gold nanoparticles embedded in an yttria stabilized zirconia (YSZ) matrix were synthesized at room temperature by radio-frequency co-sputtering from YSZ and Au targets at a 5 mTorr working pressure. The films were subsequently annealed for 2 h in 1 atm argon, with the annealing temperature varied from 600 to 1000 °C in steps of 100 °C. The composition, microstructure, and optical properties of the films were characterized as a function of annealing temperature by Rutherford backscattering spectrometry, scanning electron microscopy, Auger electron spectroscopy, x-ray diffraction, and absorption spectroscopy. An optical absorption band due to the surface plasmon resonance (SPR) of the Au nanoparticles was observed around a wavelength of 600 nm. Furthermore, the SPR band full width at half-maximum exhibited an inverse linear dependence on the radius of the Au nanoparticle, with a slope parameter A = 0.18, indicating a weak interaction between the YSZ matrix and the Au nanoparticles. The experimentally observed SPR dependence on nanoparticle size is discussed within the context of the Mie theory and its size-dependent optical constants.

Long titanate nanofibers (typically 10–500 μm in length and 20–50 nm in diameter) were successfully prepared in high yield by the direct hydrothermal processing using natural rutile as a starting material. Fourier transform infrared spectroscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, electron diffraction, and x-ray diffraction demonstrated that the as-synthesized nanofibers presumably consisted of sodium hydrogen trititanate [(Na,H)2Ti3O7, e.g., Na0.4H1.6Ti3O7] including some hexatitanate-type defects [(Na,H)2Ti6O13]. A partial topotactic condensation model explained their nanostructure well. Although the as-synthesized fibers are defective, they can be cured by a post-heat-treatment in air. The direct hydrothermal treatment for natural rutile will be a promising low-cost process for one-dimensional nanomaterials, which can act not only as a reaction step but also as a purification step.

An error occurred while printing this article in the June issue of the Journal of Materials Research. The end of the abstract was cut off, leaving it incomplete. The complete abstract is shown below:

Composites with negative stiffness constituents can exhibit material properties that exceed conventional bounds. Composites with VO2 as negative stiffness inclusions and tin as the stabilizing matrix were prepared via powder metallurgy. Specimens were tested over a range of temperature in torsion using broadband viscoelastic spectroscopy. Composites processed via powder metallurgy exhibited internal friction anomalies over a broad range of temperatures, in contrast to the single, sharp anomalies reported previously from cast specimens. The detailed material behavior encompassed a variety of responses, which were also dependent on the number of thermal cycles. Composite theory predictions assuming a distribution of negative shear moduli can account for peak broadening.

The nanostructural evolution during heat treatments of direct-current magnetron-sputtered Ag films, deposited at room temperature at different substrate bias voltages, was experimentally studied. A growth chamber equipped with a magnetron and Kapton windows for in-situ x-ray diffraction was mounted on a six-circle goniometer at a synchrotron beam line. Bragg–Brentano x-ray diffraction was used to monitor the (111) Bragg peak during thermal annealing of the Ag films. In addition, to investigate the 〈111〉 fiber texture, one-dimensional pole figures were measured ex situ. The thermal stability of the nanostructure was sensitively dependent on the substrate bias voltage. Increasing the bias voltage resulted in significantly lower rates of grain growth, which we ascribe mainly to the formation of Ar bubbles. Furthermore, the grain size in the as-deposited films decreased with increasing bias voltage while the width of the one-dimensional pole figures increased.

A series of magnetic FeCoNiAl nanocapsules was synthesized by the plasma arc discharge method; the targets of Fe, Co, Ni, and Al powders were changed with varying compositions. The compositions of the nanocapsules were found to be quite different from those of the corresponding targets; the relative amount of Al (or Ni, Co) to Fe was increased (or decreased). Structures, particles sizes, composition, surface composition, magnetic properties, and thermal stability of the nanocapsules were investigated. The saturation magnetization Ms = 106.8 emu/g and coercive force iHc = 367 Oe were achieved for the nanocapsules with the Fe62.5Co21Ni13Al2.5 target. In the FeCoNiAl nanocapsules, the binding energies of Fe, Co, and Ni were different from those of the metals Fe, Co, and Ni. The binding energies of Fe2p3/2 and Fe2p1/2 of the nanocapsules were 708.2 and 721.3 eV, respectively. The four-layer structure was proposed to give a clear statement of how the composition and phase varied radially in the nanocapsules. The major contents of the four layers—i.e., the outer shell, the inner shell, the outer core and the inner core—were amorphous alumina, crystalline alumina, transition metal oxides, and transition metal alloy, respectively. The compositions, structures, particle size, and grain size of the nanocapsules all affect their magnetic properties. In the FeCoNiAl nanocapsules, the greater th amount of the body-centered-cubic phase, the stronger the ferromagnetic magnetic properties.

Bismaleimide polymer composites were coated with adherent, uniform, crack-free, titania films. Selective deposition of either crystalline (anatase) or amorphous films was achieved as a function of deposition conditions. Films are deposited under near ambient conditions from aqueous solution and thus can be adapted to any sample geometry and still provide complete coating of the polymer composite substrate. They can be obtained crack-free in thicknesses up to 0.5 μm by using drying procedures that combine temperature and humidity control.

Slurries containing molybdenum oxide abrasives (MoO2, isoelectric point ∼pH 2) with potassium iodate (KIO3) as the oxidizing agent were used to polish copper disks and films, yielding relatively high removal rates. The relatively high copper removal rates observed were due to the in situ generation of I2 by the reaction between KIO3 and MoO2. The surface quality of the polished Cu films, however, was very poor with surface roughness values as high as 140 nm. A second polishing step using a dilute colloidal silica suspension containing H2O2, benzotriazole, and glycine at pH 4 improved the post-polish surface quality, final surface having surface roughness values as low as 0.35 nm.