Gallium–lanthanum sulfide glasses are potential hosts for 1.3-μm optical fiber amplifiers and for fiber lasers in the near and middle infrared. In these glasses the addition of CsCl increases the thermal stability region making possible to draw optical fibers, without altering the optical properties of the glass. Ga2S3–La2S3 glasses modified by 10 to 40% CsCl have been studied by x-ray absorption spectroscopy, to investigate the structural role of CsCl. The chlorine environment is found similar to that in CsCl. The gallium-based network is composed from almost regular tetrahedra weakly connected by corners and is not altered by the addition of CsCl.

In situ synthesis of fine copper particles (>200 nm) has been carried out using borohydride reduction in preorganized gel of poly(vinyl alcohol). The copper ions were chelated by polymer matrix at room temperature thorough physical entrapment along with a weak chemical complexation. The process is akin to biomimetic route and demonstrates a high order of control over nucleation, growth, and morphologies as well as orientation of the end product. The organized arrays of copper sulfate precipitate and copper particles replicate the conformation of organic matrix and form patterned structures similar to one observed in stationary chemical waves.

High-quality ZnO thin films were grown epitaxially at 250–550 °C Al2O3(00·1) substrates using low-pressure metalorganic vapor phase epitaxy. The reactants for the growth were diethylzinc and oxygen. Growth temperature, one of the important experimental parameters for epitaxial layers, was optimized. The films grown at 500 °C exhibited good crystallinity and strong ultraviolet absorption and emission. Photoluminescence spectra of the films showed a dominant excitonic emission with a weak deep level emission. More importantly, a strong stimulated emission peak was observed even at room temperature.

An optimization study on crystallization annealing of (Ba,Sr)TiO3 (BST) thin films, grown by metalorganic chemical vapor deposition at a wafer temperature of 420 °C, was performed. The as-grown film had an amorphous structure with a dielectric constant of about 20. The annealing parameters, including temperature, atmosphere, time, and sequence, were varied considering the limitations imposed by integration processes for ultralarge-scale integrated dynamic random access memory devices. The dielectric constants of the crystallized films were largely determined by the maximum temperature that the films experienced with minor effects from the annealing atmosphere. However, the leakage current densities were quite dependent on the annealing sequence and atmosphere. It was concluded that the major factors which determine leakage characteristics were concentrations of impurities, especially carbon, oxygen vacancies, and interfacial defects caused by top electrode sputtering.

The effect of graphite particles on the damping behavior of 6061 Al–graphite composites was investigated with an aim to develop a high damping, stiffness, and hardness material. The composites were processed by mixing 6061 alloy powder with graphite particles, hot pressed as a billet and consolidated by reciprocating extrusion 10 times. The results showed that the graphite particles were greatly refined and niformly distributed in the matrix. The graphite in situ reacted with the Al matrix to orm fine dispersed Al4C3 particles during both reciprocating extrusion and subsequent olution treatment. The Al4C3 phase could result in a pronounced dispersion trengthening effect. The damping capacity of the composite increased with increasing raphite content. The composite showed a peak in damping capacity during aging reatment. The 6061 Al–20% (graphite, Al4C3) composite solution-treated for 24 h and eak-aged displayed an excellent combination of damping capacity, stiffness, and ardness. The composite retained high damping while maintaining a high modulus ecause of the coexistence of graphite and Al4C3. The operative damping mechanisms, ncluding intrinsic damping of graphite particle, interface damping, dislocation amping, and grain boundary damping, are discussed with consideration of material icrostructure.

The effect of composition on the thermal properties and the spontaneous emission probabilities of various 0.5 mol% Tm2O3 containing (1 − x)TeO2 + (x)LiCl glasses were investigated using differential thermal analysis (DTA) and ultraviolet–visible– near-infrared (UV/VIS/NIR) absorption measurements. DTA curves of the samples were obtained in the 23–600 °C temperature range with a heating rate of 10 °C/min. The value of the glass transition temperature Tg and the crystallization temperatureTc were found to vary with the glass composition. Melting was not observed for the glasses containing less than 50 mol% LiCl in this temperature range. However, a melting peak was observed at Tm = 401 °C for the glasses having higher than 50 mol% LiCl, which were also found to be moisture-sensitive. Absorption measurements in the UV/VIS/NIR region were used to determine spontaneous emission probabilities for the 4f−4f transitions of Tm3+ ions. Six absorption bands corresponding to the absorption of the 1G4, 3F2, 3F3, 3F4, 3H5, and 3H4 levels from the 3H6 ground level were observed. An integrated absorption cross section of each band, except that of 3H5 level, was found to vary with the glass composition. The role of the Judd–Ofelt parameters and therefore the effect of the glass composition on the radiative transition probabilities for the metastable levels of Tm3+ ions are discussed in detail.

To develop a highly sensitive gas sensor monitoring NOx, various kinds of n-type semiconductors made of In2O3 were prepared, and the relations between doped elements and gas sensitivities or response times were studied. Consequently, it was found that the samples doped with less than 1 at.% alkali-earth metal components have high sensitivities and responsiveness. The gas-absorbing phenomena were investigated using highly sensitive thermal analysis. From the result, it was indicated that alkali-earth component-doped In2O3 materials have higher adsorption ability of NOx than pure In2O3 has.

In this work, a finite element method was performed to simulate the spherical indentation of a ductile substrate coated by a strong thin film. Our objective was to study indentation-induced delamination of the film from the substrate. The film was assumed to be linear elastic, the substrate was elastic–perfectly plastic, and the indenter was rigid. The interface was modeled by means of a cohesive surface. The constitutive law of the cohesive surface included a coupled description of normal and tagential failure. Cracking of the coating itself was not included. During loading, it was found that delamination occurs in a tangential mode rather than a normal one and was initiated at two to three times the contact radius. Normal delamination occurred during the unloading stage, where a circular part of the coating, directly under the contact area was lifted off from the substrate. Normal delamination was imprinted on the load versus displacement curve as a hump. There was critical value of the interfacial strength above which delamination was prevented for a given material system and a given indentation depth. The energy consumption by the delamination process was calculated and separated from the part dissipated by the substrate. The effect of residual stress in the film and waviness of the interface on delamination was discussed.

The TiO2–SiO22 composite nanotubes with coaxial structure synthesized by sol-gel template method were presented. This process included 2 steps: first, grow SiO22 nanotubes in the pores of anodic alumina with a diameter of 200–250 nm; second, form TiO2 nanotubes within the SiO22 nanotubes. The TiO2 nanotubes with intact SiO22 sheaths were more uniform than those with sheaths partly removed. The existence of Ti–O–Si bonds and the amorphous sheaths is supposed to take an important role in the formation of composite nanotubes.

This work describes the entrapment of tetrakis(trimethylsilyl)silane (TK) and tetrakis(chlorodimethylsilyl)silane (TKCl) in nonhydrolytic alumina gels, and the materials' thermal behavior. During gelation and drying TK and TKCl are physically entrapped in the gel up to a limit of Si/Al = 0.33. Above this limit, sublimation and decomposition of TK and TKCl occur during heating. A larger fraction of TKCl decomposition products is retained due to their higher reactivity. Below and above Si/Al = 0.33, the gel converts to mullite + α−Al2O3or mullite + amorphous silica, respectively. Conversion to hexagonal mullite indicates atomic scale homogeneity of Si and Al during firing.

Nanomechanical properties, nanohardness and elastic modulus, of an Antarctic sponge Rosella racovitzea were determined by using a vertical indentation system attached to an atomic force microscope. The Rosella spicules, known to have optical waveguide properties, are 10–20 cm long with a circular cross section of diameter 200–600 μm. The spicules are composed of 2–10-μm-thick layers of siliceous material that has no detectable crystallinity. Measurements through the thickness of the spicules indicated uniform properties regardless of layering. Both the elastic modulus and nanohardness values of the spicules are about half of that of either fused silica or commercial glass optical fibers. The fracture strength and fracture energy of the spicules, determined by 3-point bend tests, are several times those of silica rods of similar diameter. These sponge spicules are highly flexible and tough possibly because of their layered structure and hydrated nature of the silica. The spicules offer bioinspired lessons for potential biomimetic design of optical fibers with long-term durability that could potentially be fabricated at room temperature in aqueous solutions.

Cathodoluminescence emission spectra and photoluminescence (PL) excitation spectra were used to evaluate Eu+3 and Cr+3 as activators for red luminescence in ZnGa2O4. In the ZnGa2O4:Eu materials red emission from Eu+3 and blue intrinsic emission were observed. The blue intrinsic emission increased relative the Eu+3 emission with increasing current density and is attributed to preferential current saturation of the Eu+3 activators. In addition, PL excitation measurements revealed that the inefficient energy transfer from the ZnGa2O4 host to the Eu+3 is due to poor spectral overlap between the ZnGa2O4 emission and the Eu+3 absorption. Cr-doping resulted in a saturated red-color, and no host emission was observed over the entire current density regime investigated. The PL excitation of the ZnGa2O4:Cr revealed good overlap between the ZnGa2O4 host and the Cr+3 absorption. Efficient energy transfer to the Cr+3 activators occurs via multipolar interactions.

Recently, it was demonstrated that Ni99.45B0.55 undergoes grain refinement by either remelting or dynamic nucleation at two different undercoolings. In this work, we found that the grain refinement by remelting can be characterized by a gradual disappearance of the texture of the initially formed dendrites in the transition regime while the grain refinement by dynamic nucleation is characterized by a sudden disappearance of texture.

The effect of mechanical and field activation on the synthesis of dense nanometric MoSi2 was investigated. Powders of Mo and Si, milled separately or comilled in a planetary ball mill, were reacted in a spark plasma synthesis (SPS) apparatus under different electric current conditions. Milled powders reacted faster and required less current than unmilled powders. Mixtures of powders which were milled separately (to nanometric size) reacted in the SPS to produce micrometric α–MoSi2. Similar results were obtained for samples comilled to produce nanometric reactants which did not contain detectable amounts of the product phase. When products form during milling, they contain both the α and β modifications of MoSi2. The product after the SPS reaction was nanometric MoSi2 with a crystallite size of 140 nm.

Fiber texture in Ti/Al and Nb/Al polycrystalline multilayer thin films, with bilayer thicknesses (Λ) ranging from 20–333 nm and having a fixed stoichiometry of 1/3, has been investigated by using x-ray pole figures and transmission electron microscopy. Two sets of films were deposited; one set contained pure Al and the other Al–1.0 wt% Cu. The results indicated that texture was strengthened by the formation of a coherent superlattice for the Nb/pure-Al film with the smallest bilayer thickness. By contrast, the texture in Ti/pure-Al films with a similar period was not as strong. The texture also decreased with increasing Λ for both the Ti/pure-Al and Nb/pure-Al films. An increase in the width of the Al (111) peak and an offset of the fiber axis from the substrate normal of 5–8° was observed in the Λ = 333 nm films prepared by using Al–1.0 wt% Cu. The decrease in texture on addition of Cu to Al was attributed primarily to an increase in interlayer roughness as a consequence of reduction in the Al(Cu) grain size. These observations were interpreted in the context of structure zone and dynamic roughness models of film growth.

Mixed-phase compositions in the Bi2O3–ZnO–Nb2O5 pyrochlore system have been previously identified as potential low-fire dielectric composites for high-frequency multilayer devices. However, there has been a problem with the ability to co-process this material with silver. It was found that an intermediate BiNbO4 phase that occurs during calcination can interact with silver during co-sintering, forming a deleterious phase. Processing routes to control the presence of remanent BiNbO4 were investigated, such as ZnO stoichiometric adjustment, low partial pressure of oxygen sintering atmosphere, and specific temperature-time dwells.

The sintering behavior and microwave dielectric properties of (1 − x)Cu3Nb2O8−xZn3Nb2O8 have been investigated using dilatometry, x-ray diffraction, and a network analyzer. It was found that (1 − x)Cu3Nb2O8−xZn3Nb2O8 ceramics have a much lower melting temperature than Zn3Nb2O8 ceramics without Cu3Nb2O8 additives. Samples sintered at 900 °C for 2 h exhibited densities >97% of the theoretical density. Cu3Nb2O8 acts as a sintering aid. Two phase regions were identified with increasing Zn3Nb2O8 contents. A Cu3Nb2O8−Zn3Nb2O8 solid solution exists from 0 < x < 0.5 while a mixture of Cu3Nb2O8 and Zn3Nb2O8 exists from 0.5 < x < 1. The microwave dielectric properties correlated to the crystal structure. In Cu3Nb2O8−Zn3Nb2O8 solid solution region, the variation of dielectric properties could be explained by the structure distortion of Cu3Nb2O8 due to electronic anisotropies of Cu2+ cations.

A preceding study of contact damage in a bilayer system consisting of a porcelain coating on a stiff Pd-alloy substrate is here expanded to investigate the role of substrate modulus and hardness. Bilayers are made by fusing the same dental porcelain onto Co-, Pd-, and Au-alloy metal bases. Indentations are made on the porcelain surfaces using spheres of radii 2.38 and 3.98 mm. Critical loads to initiate cone fracture at the top surface of the porcelain and yield in the substrate below the contact are measured as a function of porcelain thickness. Radial cracks form at the lower surface of the coating once the substrate yield is well developed. By virtue of its controlling role in the metal yield process, substrate hardness is revealed to be a key material parameter—substrate modulus plays a secondary role. A simple elasticitybased analysis for predetermining critical loads for a given brittle/plastic bilayer system is presented.

There is ample experimental evidence demonstrating space charge segregation in acceptor-doped BaTiO3. However there is still some controversy regarding donor-doped BaTiO3. Considering the space charge segregation theory in BaTiO3, the calculated driving force for space charge segregation is larger in acceptor-doped cases than in donor-doped cases. This result explains why acceptor segregation can be easily detected. However, a significant concentration of donors can also cause donor segregation. In donor and acceptor codoped BaTiO3, the grain sizes are very small, and donor segregation can be detected for compositions inducing a large space charge potential. In addition, in compositions that induced a small space charge potential, the grain sizes are very large, and donor segregation is not detected, although the total doping concentration is larger. This phenomenon means that donor segregation is caused by the space charge potential rather than misfit strain energy.

Nanometer-scale plowing friction and wear of a polycarbonate thin film were directly measured using an atomic force microscope (AFM) with nanoscratching capabilities. During the nanoscratch tests, lateral forces caused discrepancies between the maximum forces for the initial loading prior to the scratch and the unloading after the scratch. In the case of a nanoscratch test performed parallel to the cantilever probe axis, the plowing friction added another component to the moment acting at the cantilevered end compared to the case of nanoindentation, resulting in an increased deflection of the cantilever. Using free-body diagrams for the cases of nanoindentation and nanoscratch testing, the AFM force curves were analyzed to determine the plowing friction during nanoscratch testing. From the results of this analysis, the plowing friction was found to be proportional to the applied contact force, and the coefficient of plowing friction was measured to be 0.56 ± 0.02. Also, by the combination of nanoscratch and nanoindentation testing, the energetic wear rate of the polycarbonate thin film was measured to be 0.94 ± 0.05 mm3/(N m).