A new technique of surface modification by diffusion coating for AZ91D alloy was developed. A 1.0–2.0-mm alloy layer, which has hardness four to five times higher than the substrate metal, was formed after the treatment. Consequent solution treatment and aging could further improve the hardness of the alloy layer. Microstructure and chemical composition were investigated using optical microscope and electron probe.

In this paper, we report the growth of ZnO films on silicon substrates using a pulsed laser deposition technique. These films were deposited on Si(111) directly as well as by using thin buffer layers of AlN and GaN. All the films were found to have c-axis-preferred orientation aligned with normal to the substrate. Films with AlN and GaN buffer layers were epitaxial with preferred in-plane orientation, while those directly grown on Si(111) were found to have random in-plane orientation. A decrease in the frequency of the Raman mode and a red shift of the band-edge photoluminescence peak due to the presence of tensile strain in the film, was observed. Various possible sources for the observed biaxial strain are discussed.

In spite of their interesting properties, nanostructured materials have found limited uses because of the cost of preparation and the limited range of materials that can be synthesized. It has been shown that most of these limitations can be overcome by subjecting a material to large-scale deformation, as occurs during common machining operations. The chips produced during lathe machining of a variety of pure metals, steels, and other alloys are shown to be nanostructured with grain (crystal) sizes between 100 and 800 nm. The hardness of the chips is found to be significantly greater than that of the bulk material.

The crystallographic orientation plays an important role in high-temperature oxidation of the intermetallic compound CoGa. When CoGa is exposed to air at elevated temperatures, the oxide β–Ga2O3 is formed, and different scale growth rates are observed, depending on the crystallographic orientation of the CoGa grains. This dependence is a consequence of the anisotropy of the gallium diffusion rate through the β–Ga2O3 scale and of a topotaxial orientation relationship occurring between β–Ga2O3 and CoGa. The combination of ex situ techniques, such as transmission electron microscopy and electron backscatter diffraction with optical microscopy, applied in situ resulted in a thorough understanding of these relations and of the oxidation process in general.

Pulsed laser deposition of TiO2 and BaF2 layers at room temperature and subsequent annealing in flowing oxygen were used to form homogeneous epitaxial BaTiO3 films on LaAlO3. This oxide film synthesis method, known as the precursor technique, is frequently used for making combinatorial libraries. In this paper, we investigated the microstructures of the films at different stages of annealing using cross-sectional transmission electron microscopy, high-resolution imaging, and electron energy loss spectroscopy. It was shown that epitaxial BaTiO3 thin films with large grains could be formed on a LaAlO3 substrate. Their formation process consists of the following stages: At 200 °C, the BaF2 layer is partially oxidized. At 400 °C, the amorphous TiO2 layer crystallizes, further transformation of BaF2 into BaO takes place, and interdiffusion begins. At 700 °C, the formation of a polycrystalline structure with different Ba–Ti oxides occurs, epitaxial BaTiO3 grains nucleate on the film/substrate interface, and significant interdiffusion takes place. Finally, at 900 °C, the interdiffusion is completed, and the epitaxial BaTiO3 grains coalesce and grow. The presence of nonepitaxial polycrystalline regions in fully annealed films can be explained as the following: (i) stoichiometric transient regions not yet consumed by recrystallization of BaTiO3; (ii) nonstoichiometric regions resulting from inhomogeneous deposition of BaF2.

Single-wall carbon nanotube (SWNT)/poly(methyl methacrylate) (PMMA) composites were fabricated and exposed to ionizing radiation for a total dose of 5.9 Mrads. Neat nanotube paper and pure PMMA were also exposed for comparison, and nonirradiated samples served as controls. A concentration of 0.26 wt% SWNT increased the glass transition temperature (Tg), the Vickers hardness number, and modulus of the matrix. Irradiation of the composite did not significantly change the Tg, the Vickers hardness number, or the modulus; however, the real and imaginary parts of the complex permittivity increased after irradiation. The dielectric properties were found to be more labile to radiation effects than mechanical properties.

The main objective of this work is to examine the feasibility of depositing aluminum nitride (AlN) powders, synthesized using self-propagating high-temperature synthesis, on a mild steel substrate using the detonation spray coating technique. Thick coatings produced by utilizing the AlN powder were obtained at four different oxygen–acetylene ratios and analyzed for microstructure, microhardness, porosity, indentation fracture toughness, and phase distribution. The AlN powder particles were found to be undergoing oxidation during the deposition process. The interrelationship between the spray parameters and the extent of oxidation of AlN during the coating process was investigated. Tribological performance of the coatings was evaluated using a dry sand abrasion test and a pin-on-disc sliding wear test. The mechanical and tribological properties of the above four coatings were compared with pure alumina (Al2O3) coatings. The correlation between the structure of the coatings and their tribological performance was also established.

In continuation of our previous work [J. Ovenstone, P.J. Titler, R. Withnall and J. Silver, J. Phys. Chem. B, 105, 7170 (2001)] we report the following results. Amorphous europium-doped titania phosphors (Ti1−3xEu4xO2) were prepared with europium concentrations from x = 0.000397 to x = 0.143. From investigations using photoluminescence (PL), it was deduced that the luminescence was due to a europium/titanium compound rather than from a europium-containing precipitate dispersed within a titania precipitate. PL brightness was shown to increase linearly to a concentration of x = 0.0159 before quenching began, and the rate of increase of brightness dropped. Brightness then continued to rise (almost linearly) from x = 0.0238 to x = 0.143. Under electron beam excitation these phosphors showed weak cathodoluminescence; for the amorphous materials no quenching was observed. For the crystalline materials (prepared by annealing the amorphous materials at high temperature) no red luminescence was observed above a concentration of x = 0.00318; however, some faint red luminescence was observed below this concentration. In addition, some faint blue emission was observed in crystalline samples that had no red luminescence, indicating the presence of small amounts of Eu2+ ions. This was attributed to reduction of the Eu3+ ions in the electron beam. Europium doping was shown to increase the size of the band gap in the amorphous materials, but had little effect on the band gap of the crystalline powders.

The synthesis of lithium tantalate films by a chemical solution deposition method was studied. A precursor solution was prepared by dissolving lithium ethoxide and tantalum pentaethoxide in ethanol. The addition of formic acid to this precursor solution was very effective in the preparation of homogeneous and transparent precursor films on substrates by spin coating. Lithium tantalate films crystallized on sapphire (001) substrates with a highly preferred orientation along the c axis with heat-treating at temperatures above 450 °C. The refractive index of the film prepared at 550 °C was 2.049, which is close to the value for single crystals of lithium tantalate (2.176).

GaN films were produced by the chemical solution deposition method (CSD) using two different precursors—gallium dimethyl amide (GDA; containing gallium–nitrogen bonds) and gallium isopropoxide (GIP; containing gallium–oxygen bonds). Pyrolysis of the GDA film at 600 °C produced a continuous layer of GaN grains with a single orientational relation with the substrate [GaN (0001) ∥ Al2O3 (0001) and GaN (1010) ∥ Al2O3 (1120)], and an overlying polycrystalline film. At temperatures greater than 600 °C, the oriented grains consumed the polycrystalline layer via an evaporation–condensation mass transport. Pyrolysis of the GIP films at 600 °C produced a continuous layer of gallium oxynitride having the corundum structure [i.e., α–Ga2O(3−x)N2/3x] with an epitaxial relation to the substrate (α–Ga2O(3−x)N2/3x[0001] ∥ Al2O3 [0001] and α–Ga2O(3−x)N2/3x [1010] ∥ Al2O3 [1120]), and an overlaying polycrystalline gallium oxynitride film with a spinel structure. Increasing temperature caused growth of oriented grains in contact with the substrate and conversion of the oxynitride to wurtzite GaN at 800 °C. Room-temperature (300 K) and low-temperature(77 K) photoluminescence measurements behaved similarly to metal-organic chemical vapor deposition based GaN with additional photoluminescence most likely due to nitrogen vacancy impurities.

We investigated the influence of a chemisorbed S template with c(2 × 2) structure on the epitaxial growth of different oxide buffer layers on {100}〈100〉 Ni. The sulfur superstructure spontaneously forms on the Ni surface during the texturing anneal as a consequence of segregation. However, depending on the initial S bulk concentration and/or specific annealing conditions, the S layer can cover less than the entire substrate's surface. We show that an incomplete c(2 × 2) coverage causes degradation of the seed buffer layer texture as compared to the substrate texture. A simple step consisting of an H2S predeposition anneal can be used to control the superstructure coverage and optimize the seed layer texture.

Acrylic acid polymer thin films were deposited on the surfaces of nanoparticles of ZnO using a plasma polymerization treatment. The average size of nanoparticles was on the order of 50 nm in irregular shapes. High-resolution transmission electron microscopy (HRTEM) experiments showed that an extremely thin film of the acrylic acid layer (15 nm) was uniformly deposited on the surfaces of the nanoparticles. The HRTEM results were confirmed by time-of-flight secondary ion mass spectroscopy. The effect of plasma power on the polyacrylic thin film was studied by Fourier transform infrared experiments. The deposition mechanisms and the effects of plasma treatment parameters are discussed.

Microwave dielectric ceramics based on RETiTaO6 (RE = La, Cc, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, Al, and In) were prepared using a conventional solid-state ceramic route. The structure and microstructure of the samples were analyzed using x-ray diffraction and scanning electron microscopy techniques. The sintered samples were characterized in the microwave frequency region. The ceramics based on Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy, which crystallize in orthorhombic aeschynite structure, had a relatively high dielectric constant and positive τf while those based on Ho, Er, and Yb, with orthorhombic euxenite structure, had a low dielectric constant and negative τf. The RETiTaO6 ceramics had a high-quality factor. The dielectric constant and unit cell volume of the ceramics increased with an increase in ionic radius of the rare-earth ions, but density decreased with it. The value of τf increased with an increase in RE ionic radii, and a change in the sign of τf occurred when the ionic radius was between 0.90 and 0.92 Å. The results indicated that the boundary of the aeschynite to euxenite morphotropic phase change lay between DyTiTaO6 and HoTiTaO6. Low-loss ceramics like ErTiTaO6 (εr = 20.6, Quxf = 85,500), EuTiTaO6 (r = 41.3, Quxf = 59,500), and YtiTaO6 (εr = 22.1, Quxf = 51,400) are potential candidates for dielectric resonator applications.

The texture development during cold rolling and recrystallization of L12-type Co3Ti alloys was investigated as functions of alloy composition and rolling reduction. Two kinds of fully annealed Co3Ti alloys with different alloy compositions (Co77Ti23 and Co78Ti22), whose initial textures and grain sizes were almost identical, were used. After 70% reduction, the cold-rolling textures of both alloys were composed of strong α-fiber and weak β-fiber textures, in which the intensity of {011}〈211〉 orientation was higher than those of {112}〈111〉 and {123}〈634〉 orientations, indicating that texture transition from copper type to brass type occurred in cold-rolled Co3Ti alloys. This texture transition was more prominently recognized in the Co78Ti22 alloy, whose chemical composition was more off-stoichiometric. On the other hand, the recrystallization textures of both alloys were considerably weak, and their orientation spreads were more significant with increasing rolling reduction. Also, the recrystallization textures were basically independent of alloy composition in contrast to the rolling textures.

The dissolution in de-ionized water (DIW) at 90 and 150 °C of Cs and Ba from mechanically polished Cs-doped Ba hollandite samples is essentially congruent. The normalized Ba and Cs release rates were <0.001 g/m2/day after 56 days in DIW at 90 °C, and the Ba normalized release rate of a Cs-free sample was 0.01 g/m2/day after 56 days in DIW at 150 °C. Varying the pH between approximately 2.5 and 12.9 affected only the Ba dissolution rates of hollandite by half an order of magnitude. The dissolution rates of all species decrease with increasing leaching time due to the formation of partly impervious surface coatings of Al- and Ti-rich species. These surface coatings were investigated by scanning electron microscopy, and in some cases by cross-sectional transmission electron microscopy and x-ray photoelectron spectroscopy.

Ion bombardment was used to produce electron-emitting microscale features on surfaces of thick films printed with carbon pastes. This technology can potentially enable the development of large-area field emission displays. Systematic investigations using microscopy and electron field emission experiments have demonstrated a close link among paste formulation, ion processing parameters, and the development of surface microstructures. These investigations were also useful in understanding the fundamentals of microstructure formation under ion bombardment and the field emission characteristics of the carbon-based emitters. Several device concepts aimed toward achieving a low-voltage switchable triode were also tested with varying degrees of success. In this paper, we discuss various technological issues related to the materials, processes, and devices.

We have investigated epitaxial superconducting SmBa2Cu3O7 (Sm123) films grown by pulsed-laser deposition on single-crystal SrTiO3 substrates. The deposition temperature plays an important role in determining the superconducting properties of Sm123 films. The superconducting transition temperature increases with the deposition temperature whereas the transition width decreases at deposition temperatures in the range of 700–875 °C. A Sm123 film deposited at 850 °C exhibits a transition temperature above 93 K with a transition width less than 0.5 K. Even though Sm123 films exhibit a higher transition temperature than Yba2Cu3O7 (Y123), the Sm123 shows lower critical current density at liquid-nitrogen temperature. The nominal critical current density of Sm123 film is less than 1 MA/cm2 at 75.4 K. Nevertheless, the Sm123 films have less anisotropy and stronger pinning characteristics compared to Y123. They are also much smoother with fewer particulates, as revealed by scanning electron microscopy.

With polypropylene as a prototype viscoelastic material at room temperature, it was found that a “nose” may appear in the unloading segment of the load–displacement curve during nanoindentation when the holding time at peak load is short and/or the unloading rate is small, and when the peak load is high enough. The load at which the nose appears was also found to decrease linearly with decreasing unloading rate. A linear viscoelasticity analysis was performed to interpret this effect. The analysis predicts a linear variation between the nose load and the unloading rate, and the slope of such a linear variation is also shown to be proportional to the viscosity parameter of the material. Thus, by measuring the slope of the nose-load versus unloading rate plot at a given temperature, the viscosity parameter of the specimen can be found. This is a new way of measuring the viscosity parameter of a material in addition to the existing method of force modulation and noting the frequency response of the displacement.

Room-temperature ductility of two Ti–Al–Nb intermetallic alloys with close chemical compositions was investigated by tensile testing. The two alloys' ductilities in the B2 single-phase state were significantly different, which indicated that the ductility of B2 phase state was sensitive to the chemical composition. The alloy with more ductile B2 phase exhibited higher ductility in O + B2 two-phase state.

The electron irradiation sensitivities of Pb(Mg1/3Nb2/3)O3 (PMN) and Pb1−xLax[Mg(1+x)/3Nb(2−x)/3]O3 (PLMN) ceramics were investigated by transmission electron microscopy. Nanoscale Pb particles formed in these materials under electron beam radiation. It was found that these fine Pb particles generally had a preferred crystallographic orientation relationship with the PMN/PLMN host and always existed at positions slightly rich in Mg2+. A preliminary mechanism involving defect chemistry reactions is proposed to interpret this unusual Pb precipitation. Possible limitations to the practical applications of these materials are discussed.