It was demonstrated that liquid phase separation by nucleation and growth (LNG) occurs in undercooled molten Pd40.5Ni40.5P19 for undercoolings ΔT ≤ 60 K (ΔT = Tl − T where Tl is the liquidus and T is the kinetic crystallization temperature), and liquid state spinodal decomposition (LSD) occurs for ΔT ≥ 100. For 60 ≤ ΔT ≤ 100 K, it is the transition regime from LNG to LSD. A ternary phase diagram is introduced to summarize the reactions occurred in undercooled molten Pd40.5Ni40.5P19. Finally, it is suggested that LSD has an important impact on glass-forming ability of metallic alloys.

Microwave dielectric properties and the relationship between the temperature coefficient of the dielectric constant (τ ɛ) and the tolerance factor were investigated in (Sr0.2Ca0.8) (Ti1–xZrx)O3 ceramics. The τɛ increased linearly as the tolerance factor decreased from 0.984 to 0.929 in the whole composition range of the (Sr0.2Ca0.8) (Ti1–xZrx)O3 solid solution. At the composition of (Sr0.2Ca0.8) (Ti0.04Zr0.96)O3, the dielectric constant was 34 and Q · f was 10,938 GHz and the temperature coefficient of the resonance frequency (τɛ) was supposed to be near zero.

Ultrafine bismuth nanowire arrays were synthesized by injecting its liquid melt into nanochannels of a porous anodic alumina template. A large area (1 cm × 1.5 cm) of parallel wires with diameters as small as 13 nm, lengths of 30–50 μm, and packing density as high as 7.1 × 1010 cm−2 has been fabricated. X-ray diffraction patterns revealed these nanowires, embedded in the insulating matrix, to be essentially single crystalline and highly oriented. The optical absorption spectra of the nanowire arrays indicate that these bismuth nanowires undergo a semimetal-to-semiconductor transition due to two-dimensional quantum confinement effects.

The evolution of surface structure, grain microstructure, and superconducting transition temperature of a-axis YBa2Cu3O7 thin films has been studied as a function of film thickness. The grain size increases and develops a bimodal distribution of grain size during film growth, concurrent with an improvement in Tc. The surface structure does not represent the grain size, but rather the development of the bimodal grain structure follows the formation of the surface structure. The results are discussed in terms of thin film growth modes.

Barium aluminum hollandite is a major phase in Synroc, a ceramic designed for the immobilization of high-level waste (HLW) from nuclear fuel reprocessing. Radioactive cesium substitutes into the channel sites, and such hollandites give 133Cs MAS nuclear magnetic resonance (NMR) spectra consisting of a single peak at 211 ppm in the absence of paramagnetic ions. However, the peak shifts to 640 ± 30 ppm and becomes extremely broad when Ti3+ replaces Al3+ in the channel walls of the hollandite structure, apparently because of Fermi contact interaction between the Cs nucleus and the unpaired electron of Ti3+. 133Cs MAS NMR of Synroc and hollandites is very sensitive to the presence of water-soluble CsAlTiO4 which would compromise the aqueous durability of Synroc. 133Cs MAS NMR spectra of Synroc-C, hot-pressed in metal bellows at temperatures as high as 1325 °C, do not indicate significant formation of CsAlTiO4. Synroc samples loaded with Cs and Sr only were shown by MAS NMR as well as electron microscopic techniques to be capable of incorporating nearly 10 wt.% Cs before CsAlTiO4 is formed.

The Na+-superionic conducting ceramics with Na5YSi4O12-type structure were synthesized using the composition formula of Na3+3x−yY1-xPySi3-yO9, in which some portions of Na+ ions are considered to replace Y3+as Na(13+8x−4y/3) [Na(4x−1)/3Y(4–4x)/3] [P4y/3Si(12–4y)/3]O12 according to Na5YSi4O12-type composition formula. The average ionic radius of the 6-coordinated Y3+ sites [= (4x − 1)/ 3 ×rNa + (4 - 4x)/3 × rY] approximately covered the range of rGd and to rSm. The ionic conduction properties were strongly dependent upon the combination of composition parameters, x and y. In this report, the dependence of conduction properties on the composition is discussed on the basis of structural considerations.

Scanning tunneling microscopy and spectroscopy have been used to characterize the atomic structure and tunneling density of states of individual single wall carbon nanotubes (SWNT's) and ropes containing many SWNT's. Analysis of atomically resolved SWNT images shows that the nanotubes consist of a wide range of diameters and helicities with no one structure clearly dominant. Tunneling spectroscopy measurements made simultaneously on atomically resolved SWNT's exhibit semiconducting and metallic behavior that depend predictably on helicity and diameter. In addition the band gaps of the semiconducting tubes were also found to depend inversely on diameter. These results are compared to theoretical predictions, and the implications of these studies as well as important future directions are discussed.

Several techniques for the sheet growth of silicon for solar cell substrates are reviewed here. These techniques usually offer an economic advantage over growth in the form of bulk crystals. At least 16 different sheet growth systems have been proposed but only five, that are actively being pursued for commercialization, are discussed here. These include dendritic web, string ribbon, edge-defined film-fed growth (EFG), ribbon growth on a substrate (RGS), and Silicon-Film. The growth systems and the characteristics of the resulting solar cells are briefly described. A discussion of their current status concludes the review.

The growth of large grain YBa2Cu3O7−δ (YBCO) by peritectic solidification in the presence of a (Sm,Y)Ba2Cu3O7−δ seed is characterized by the initial seeding process, development of a facet plane around the seed, and finally by continuous nonlocal growth away from the seed. A detailed investigation of the seeding process using electron microscopy, electron probe microanalysis, and thermal analysis techniques is reported here as the first in a series of studies of these key growth features. Results show that the seed partially melts below its nominal melting temperature due to a distribution of yttrium cations across the seed/YBCO interface. The formation of a Sm/YBa2Cu3O7−δ solid solution, which occurs via a reaction between (Sm,Y)2Ba2CuO5 and liquid state Ba3Cu5O8, has been observed across this interface at temperatures below the peritectic temperature Tp of the seed. The temperature window available for melting the YBCO phase while avoiding full peritectic decomposition of the (Sm,Y)Ba2Cu3O7−δ seed is maximized for seeds of high Sm content and thickness in excess of 0.2 mm. Finally, the dwell time at temperatures above Tp should be as short as possible if the integrity of the seed is to be maintained throughout the YBCO growth process.

The formation mechanism of aluminum borate in the combustion synthesis of Al2O3/B4C composite with Al, B2O3, and C as starting materials is proposed. Based on the formation mechanism, several approaches taken to eliminate them are discussed. The unconverted B2O3 is the major cause of the formation of 9Al2O3 · 2B2O3 when the reaction proceeds in the SHS mode. The amount of 9Al2O3 · 2B2O3 formed is very sensitive to the excess B2O3 to the stoichiometry 4Al + 2B2O3 + C and influenced by the size of B2O3 powder. The high dispersion of the reactants is helpful in prompting the thermite reaction to consume B2O3 and hence inhibiting the aluminum borate formation.

Lead-based relaxor ferroelectric multilayer ceramic capacitors (MLC's) were placed in 0.05 M NaOH solution to evolve hydrogen on their silver termination electrode by electrolysis of water. After this treatment, the MLC's failed as their insulation resistance was greatly decreased, their dielectric loss was considerably increased, and their capacitance was obviously decreased. By annealing in air at 650 °C for 30 min, the properties of the MLC's were restored. It is proposed that electrochemically generated hydrogen atoms can diffuse into the ceramic body of MLC's and undergo reduction to it, which may be one of the reasons for the negative influence of electroplating on lead-based relaxor ferroelectric MLC's.

Incinerator bottom ash samples have been characterized using analytical electron microscopy (AEM) techniques, including electron diffraction, energy dispersive spectroscopy, and electron energy loss spectroscopy. The samples were first separated by magnetic properties and density. Three resulting fractions were examined: the magnetic, high-density (MHD) fraction, the nonmagnetic/high-density (NMHD) fraction, and the nonmagnetic, low-density (NMLD) fraction. Examination of these samples revealed a variety of submicron microstructural features. For the MHD fraction, metal oxides, iron silicates, aluminum silicates, and calcium phosphate compounds were found in addition to amorphous material. The NMHD fraction contained elements similar to the MHD fraction but had more amorphous material; crystalline silicates were less common. Compounds such as MgO and chloroapatite were also found. The NMLD fraction contained SiO2 and numerous metal oxides. The results of some of these analyses were used to model leaching behavior of the ash. Based on the AEM results, three mineral phases were chosen as candidates for aqueous geochemical thermodynamic equilibrium modeling of pH-dependent leaching: chromite, chloroapatite, and zincite. In two of these three cases (chromite, chloroapatite), the selected mineral phase provided excellent agreement with the experimentally observed leaching behavior. AEM was shown to be a useful tool for elucidating mineralogy of complex environmental samples.

Silver-sheathed Bi–Pb–Sr–Ca–Cu–O (2223) superconducting tapes (with a starting composition of Bi1.8Pb0.4Sr2Ca1Cu2O8, calcium cuprate, and CuO) were fabricated by the powder-in-tube technique. The tapes were sintered at various temperatures to optimize the formation of Bi1.8Pb0.4Sr2Ca2Cu3O10 phase within the tape. The results show that sintering within the temperature range of 815–825 °C can produce tapes with high critical current density (Jc). The Jc of samples sintered at the higher temperature of 825 °C, where more liquid is present, depended markedly on the rate at which tapes were cooled from the sintering temperature; samples sintered at lower temperatures did not exhibit such a cooling-rate effect. The optimum combination of phase purity and microstructure that yielded an average transport Jc of ≥ 2.5 × 104 A/cm2 was obtained when the tapes were sintered at 825 °C for 150 h and cooled at a rate of 25 °C/h from the sintering temperature. Quenching studies indicate that the Bi-2223 phase becomes unstable below 700 °C during slow cooling. This result may have important implications for processing Bi–Sr–Ca–Cu–O tapes with high Jc. Addition of 15 vol.% Ag flakes to the monolithic core exerted no significant effect on Jc.

Superconducting HgBa2CaCu2O6+δ (Hg-1212) thin films have been prepared by laser ablation followed by post-annealing at high temperatures. Two synthesis methods were investigated, using (1) direct reaction of Hg–Ba–Ca–Cu–O precursor films in a Hg-controlled ambience, and (2) thermal diffusion of Hg into Ba–Ca–Cu–O precursor films in a controlled atmosphere containing both Hg- and Tl-bearing species. Effects of the annealing temperature, time, and bulk material composition on the Hg-1212 film and residual impurities are presented. Surface morphologies, growth defects, and transport properties of Hg-1212 on SrTiO3 substrates are discussed. Formation of Hg-1212 films on MgO and LaAlO3 substrates is briefly described.

We report a dendritic crystallization of ionic melt of lead molybdate (PbMoO4) under a concentric thermal field. The solidified melt is a PbMoO4 single crystal with [001] axis normal to surface. The dendrite arms propagate and branch along 〈310〉 and 〈130〉, forming a well-organized surface structure. It is evident that the interaction between a cation to its second-nearest anions determines the dendrite development and meltsolidification.

Due to its basic optical, electronic, and chemical properties, CdTe can become the base material for high-efficiency, low-cost thin film solar cells using robust, high-throughput manufacturing techniques. CdTe films suited for photovoltaic energy conversion have been produced by nine different processes. Using n-type CdS as a window-partner, solar cells of up to 16% efficiency have been made in the laboratory. Presently five industrial enterprises are striving to master low cost production processes and integrated modules have been delivered in sizes up to 60 × 120 cm2, showing efficiencies up to 9%. Stability, health, and environmental issues will not limit the commercial potential of the final product. The technology shows high promise for achieving cost levels of $0.5/Wp at 15% efficiency. In order to achieve this goal, scientists will have to develop a more detailed understanding of defect chemistry and device operation of cells, and engineers will have to develop methods for high-throughput manufacturing.

The recent application of tunneling probes in electronic structure studies of carbon nanotubes has proven both powerful and challenging. Using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS), local electronic properties in ordered aggregates of carbon nanotubes (multiwalled nanotubes and ropes of single walled nanotubes) have been probed. In this report, we present evidence for interlayer (concentric tube) interactions in multiwalled tubes and tube-tube interactions in singlewalled nanotube ropes. The spatially resolved, local electronic structure, as determined by the local density of electronic states, is shown to clearly reflect tube-tube interactions in both of these aggregate forms.

An organothermal reduction process has been successfully developed for synthesis of nanocrystalline Ni2P in benzene at 140 °C. An x-ray powder diffraction pattern (XRD) indicated that the product was pure hexagonal Ni2P phase with a cell constants a =0.5866 and c = 0.3377 nm. Transmission electron microscopy (TEM) showed that the average particle size of the powders was 40 nm with a circular-shaped flake morphology.

A successive hydrogenation system was constructed using a two-compartment cell separated by a Pd sheet. The hydrogenation rate changed greatly, depending on the kind of substrates used. For the purpose of improving the hydrogenation rate, the surface of a Pd sheet was modified with highly active catalysts such as Pd black, Pt, and Au by using active hydrogen passing through the Pd sheet as a reducing agent. As a result, the hydrogenation rate of unsaturated organic compounds such as 4-methylstyrene was markedly increased by the surface modification with these catalysts due to the increase in reaction zone and appearance of new active sites.

When molten Pd40.5Ni40.5P19 is undercooled way below its liquidus Tl, liquid state spinodal decomposition is observed. Crystallization of this system is particularly interesting because it has plenty of interfaces. The microstructure of an as-crystallized specimen can be divided into four regions, namely, A: random spinodal; B: aligned and elongated spinodal; C: coarsened spinodal and island structure; and D: rod structure and ternary eutectics. The origin of these different microstructures is discussed.