Earlier publications describe the counterflow diffusion flame burner and its unique capability to produce oxide particles having certain structures, such as spheres of one material coated with another, spheres of one composition with attached bulbs of another composition, and uniform multicomponent mixtures. Here we describe the production and properties of bulk quantities of powders produced using this burner. Measurements were made of specific surface area and, for titania, of phase composition. It was found that the controls over powder characteristics used in other forms of flame-synthesis are equally effective in the counterflow diffusion flame burner. We found that the specific surface area of both silica and titania powders decrease with increasing precursor concentrations. Transmission electron microscopy analysis of the titania powders indicates that the mean size of the particles that comprise these powders increases with increasing concentration. These trends are consistent with the collision-coalescence theory of particle growth. In addition, the crystalline phase of titania can be controlled by selecting the appropriate feed stream. For example, over the ranges TiCl4 precursor concentrations tested, feeding it only into the oxidizer stream yields mainly anatase TiO2 powders, while feeding only into the fuel stream yields mainly rutile TiO2 powders. These trends can be explained by the known atmosphere-dependent anatase-rutile transformation. The present data demonstrate that, in addition to its unique capability to produce certain particle shapes and morphologies, the counterflow diffusion flame burner can be manipulated to produce either of the major commercial titania phases, and also silica, with a wide range of specific surface areas.

Modelling, but more importantly, measurements of residual stresses are needed to guide the design and development of high integrity ceramic/metal joints. This study evaluates the influence of the metal workpiece on the residual stress state present in the ceramic part of the joint. Si3N4 was directly bonded via the active metal brazing route to several metals Cu, Mo, W, Ta, Nb, Zr, Ti, and AISI 316, selected to cover an extended range of thermomechanical properties. The residual strains in the joints were measured using an x-ray diffraction technique. The results indicate that the maximum residual stresses scale with the thermal mismatch for metals with low coefficients of thermal expansion. The experimental results are compared with analytical calculations of the residual stresses.

Polyparaphenylene (PPP)-based carbons heat-treated at temperatures (THT) from 600 °C up to 3000 °C have been characterized both structurally and in terms of their physical properties. Special attention is given to PPP heat-treated at 700 °C (denoted by PPP-700), since samples heat-treated to this temperature were observed to have exceptionally high lithium affinities when electrochemically doped with Li. At low THT below 700 °C, it is found that the local structure of PPP-based samples can be characterized mostly in terms of a disordered polymer. As a result of heat treatment to high temperature, PPP-based carbon shows graphitization behavior with regard to x-ray diffraction d002 (graphite c-axis d-spacing) development and to the increase of the Raman IG/ID intensity ratio (where IG and ID are the integrated intensities of the 1580 cm−1 and 1360 cm−1 Raman modes, respectively), as is found in so-called graphitizing carbons. However, development of the c-axis crystallite size (Lc) is restricted to very small values, in the range of so-called nongraphitizing carbons, while the a-axis crystallite size (La) attains values up to roughly 120 Å for heat treatments near 3000 °C. These structural properties of PPP-based carbons are consistent with the observed electrical characteristics and their dependence on THT. Low temperature magnetic susceptibility measurements were analyzed, along with Raman spectra, allowing for the characterization of disorder in terms of localized spin states for several heat-treated PPP samples. By interpreting the results of these various characterization techniques, we are able to present an insightful perspective on the nature of PPP-based carbons and the role of PPP-700 as an effective lithium host material for secondary battery applications.

The structure of nanocrystalline palladium and copper, made by inert gas condensation and compaction, was studied using small angle neutron scattering (SANS), optical microscopy, and scanning electron microscopy. The effects of annealing and warm compaction were also examined with these techniques. The SANS results were interpreted using a maximum entropy routine, combined with knowledge of the Archimedes density and hydrogen concentration determined by prompt gamma activation analysis (PGAA). Similar hydrogen concentrations were detected by SANS and PGAA. This hydrogen content, which was approximately 5 at. % in samples compacted at room temperature, was reduced by both annealing and warm compaction. Defects in several size classes were observed, including missing grain pores (≈1−50 nm diameter) and defects of micrometer size. Warm compaction produced a lower number density of pores in nanocrystalline palladium, which led to increased density. The observed structure was correlated with Vickers microhardness and fracture surface morphology.

The synthesis of uniform colloidal crystalline particles of Zr- and Sr-doped barium titanates at a low temperature of 85 °C by the controlled double-jet precipitation (CDJP) technique is described. The stoichiometry of the powders can be precisely controlled by adjusting the compositions of the starting reactant solutions. Barium titanate with 20% Zr substitution, sintered at 1275 °C, satisfied the requirements for the Y5V multilayer capacitors application. The grain sizes are uniform and small, ranging from 1 to 3 μm. Solids with an extremely sharp change in the dielectric constant as a function of temperature, which are suitable for thermal IR detectors application, can be obtained when both Sr and Zr are incorporated as dopants.

Diamond films were selectively nucleated and grown on single crystal (100) silicon by microwave plasma assisted chemical vapor deposition with submicron spatial resolution. A thermal silicon dioxide layer on the wafers was patterned by standard photolithography. Nucleation was performed by applying a dc bias of −250 to −350 V in a hydrogen-methane plasma. Lifting off the oxide layer by HF etching prior to growth delineated the nucleation pattern which was replicated by the diamond film after growth. The growth of polycrystalline diamond was performed in a hydrogen-carbon monoxide-methane mixture selected to facilitate (100) texturing. Individual faceted crystallites were grown on a square matrix of sites, with a pitch of 3 μm, by controlling the nucleation densities within the windows exposing the prenucleated silicon. However, the orientation of the crystallites was randomly aligned with respect to the (100) silicon lattice within the micron scale windows employed in this study.

Using a continuous microscratch technique, the adhesion strengths of Pt, Cr, Ti, and Ta2N metallizations to NiO and Al2O3 substrates have been characterized. The practical work of adhesion was determined as a function of both thickness and annealing conditions. For all except the Ta2N films, the practical work of adhesion increases nonlinearly from a few tenths of a J/m2 to several J/m2 as the thickness of the thin film is increased, indicating that a greater amount of plastic work is expended in delaminating thicker films. Further, the practical work of adhesion also increases with increasing annealing temperature, indicating stronger bonding at the interface. In the limit that the film thickness tends to zero, the plastic energy dissipation in the film tends to zero. As a result, the extrapolation to zero thickness yields the true work of adhesion for that system.

C60/C70: Ni films with 1.5 wt. % Ni concentration obtained by vacuum deposition under different thermal conditions have been investigated. The structural changes of the layers were investigated by transmission electron microscopy, electron and x-ray diffraction, and Raman spectroscopy. The polycrystalline structure was detected for the layers grown at approximately 450 K on the substrate. At elevated temperature and maintained temperature gradient on the substrate during the process, the changes of the layer's structure and the formation of Ni microcrystals were observed. The Ni microcrystals (5–10 nm in the diameter) and the elongated shapes dimensioned 10 × 150 nm were perceived.

Crystallization behavior, defects, and interface structures of sol-gel derived LiNbO3 films on three kinds of substrates were examined. The nucleation was found to occur epitaxially at the interface between the film and the substrate. The continuous film is formed by coalescence of the island-like crystallites. When sapphire substrate is used, which has large lattice mismatch with the LiNbO3, the resulting film contains a large amount of micropores, twin structures, and misfit dislocations. On the other hand, while LiTaO3 and 5% MgO-doped LiNbO3 substrates with smaller mismatch are used as substrates, the films show no evidence of the formation of dislocations and twins. The film on 5% MgO-doped LiNbO3 substrate shows better optical waveguiding property.

Carbon-carbon composites, if not suitably protected, suffer from the problem of oxidation of the surface in normal atmospheres at temperatures above 350 °C. For this reason they need to be protected from oxidizing environments by either using an impermeable coating, or using a sacrificial protective coating of a suitable material, and/or doping of an oxidation inhibitor in the carbon. In this study we have used a new family of materials with tailorable thermal expansion characteristics, namely, the [NZP] family as the materials for developing a suitable coating material for C-C composites. The candidates selected for matching thermal expansion with that of carbon are Ca0.5Sr0.5Zr4P6O24, SrZr4P6O24, and Ba1.175Zr4P5.65Si0.35O24. They can be sintered in inert atmosphere without decomposition of the phases, and can be hot-pressed in inert atmosphere with C-C composites at 1250 °C without decomposition or chemical interaction. They are stable in the presence of carbon up to 1200 °C for at least a period of 4 h. They also do not show any weight loss after exposure to various temperatures up to 1200 °C for 4 h.

In this study, porous Vycor tubes with 40 Å initial pore diameter were modified using low pressure chemical vapor deposition (LPCVD) of SiO2. Diethylsilane (DES) in conjunction with O2 or N2O were used as precursors to synthesize the SiO2 films. Both “single side” (reactants flowing on the same side of porous membrane) and “counterflow” (reactants flowing on both sides of porous membrane) reactant geometries have been investigated. The flow of H2, He, N2, Ar, and toluene (C7H8) was monitored in situ after each deposition period. Membranes modified by the “single side” reactants geometry exhibited good selectivities between small and large molecules. However, cracking in these membranes after prolonged deposition limited the maximum achievable selectivity values. Higher selectivities and better mechanical stability were achieved with membranes produced using the “counterflow” reactants geometry. Pore narrowing rate was observed to increase with oxidant flow (O2 or N2O). For membranes prepared using both oxidants, selectivities on the order of 1000: 1 were readily attained for H2 and He over N2, Ar, and C7H8. As compared to O2, the use of N2O caused improvements in both the pore narrowing rate and N2: C7H8 selectivity. Membranes prepared using the “counterflow” geometry showed no signs of degradation or cracking after thermal cycling.

We review the device and materials science behind organic electroluminescent diodes made both using discrete evaporable molecules and spin-cast organic polymers. A great deal of progress has been made in improving the efficiencies and spectral properties of organic light-emitting diodes, and these are now adequate for many applications. More work is necessary to understand the stability and degradation of emissive and charge-transporting organics, but some systems have been shown to be stable for 104 hours at display brightness. Major challenges still face the community in terms of developing satisfactory systems design and processing techniques if organic electroluminescence is to realize either performance or economic advantages over technologies and significantly penetrate the display market. We present an analysis of the suitability of organic light-emitting diodes for various applications, and consider the materials and manufacturing obstacles that must be overcome.