The depth of photocuring for a model resin system was investigated as a function of photoinitiator concentration. Direct measurements of gel thickness were made from thin films of cross-linked multifunctional methacrylate monomer. The monomer, 2,2-bis{4-[2-hydroxy-3-(methacryloxy)propoxy]phenyl}propane, was polymerized in a solution of trichloroethylene with an ultraviolet laser light source at 325 nm. The monomer solutions were photocured using varying levels of both photonic energy and photoinitiator concentration. An optimal photoinitiator concentration that maximized the gel cure depth was observed. Additionally, two regimes were shown to exist in which the shrinkage (upon solvent removal) was minimized or maximized. A model was developed to probe the physics of the system. Good agreement with experiment was obtained, and the model may be employed to predict both the existence and location of the optimal photoinitiator concentration and the corresponding cure depth. The study showed that photoinitiator plays a significant role in controlling the quality and performance of the formed gel network, with special regard to thickness of cured layers. This has potential application to fields as diverse as industrially cured coatings and dental fillings, and more generally, 3-dimensional rapid prototyping techniques.

Al–Ti multilayered films (12 at.% Ti) with bilayer period of 16 nm were deposited by magnetron sputtering. The films were annealed in vacuum at 350 or 400 °C between 2 and 24 h. During annealing, a diffusion-controlled chemical reaction between Al and Ti layers led to Al3Ti precipitation. Differential thermal analysis studies showed an exothermic reaction associated with Al3Ti formation, taking place between 320 and 390 °C, depending on the heating rate. The evolution of microstructure with annealing was examined with transmission electron microscopy and x-ray diffraction. The hardness and residual stress of the films in the as-deposited and annealed conditions were studied in relation to the microstructural changes on annealing.

Epitaxial PbZr0.5Ti0.5O3 (PZT) thin films were grown on top of a SrRuO3 epitaxial electrode layer on a (100) SrTiO3 substrate by the chemical solution deposition method at various temperatures. The microstructure of the PZT thin films was investigated by x-ray diffraction and transmission electron microscopy, and the ferroelectric properties were measured using the Ag/PZT/SRO capacitor structure. In the PZT thin film annealed at low temperature (450 °C/1h), both the perovskite PZT phase at the film/substrate interface and the fluorite PZT phase in the upper region of the film were obtained. It exhibited nonferroelectric properties. The PZT thin film annealed at temperature as low as 525 °C had only a perovskite tetragonal phase and the epitaxial orientational relationship of (001)[010]PZT∥(001)[010]SRO∥(001)[010]STOwith the substrate, and shows a ferroelectric property. The remnant (Pr) and saturation polarization (Ps) density of the sample annealed at 600 °C/1h were measured to be Pr ˜ 51.4 μC/cm2 and Ps ˜ 62.1 μC/cm2 at 5 V, respectively. The net switched polarization dropped only to 98% of its initial value after 7 × 108 fatigue cycles.

Ce1−xNdxO2−δ (x = 0.05 to 0.55) nanocrystalline solid solutions were prepared by a sol-gel route. X-ray diffraction analysis showed that Ce1−xNdxO2−δ crystallized in a cubic fluorite structure. The lattice parameter for the solid solutions increased linearly with the dopant content. The solid solubility of Nd3+ in ceria lattice was determined to be about x = 0.40 in terms of the nearly constant lattice parameters at a dopant level larger than x = 0.40. First-order Raman spectra for Ce1−xNdxO2−δ at a lower dopant content exhibited one band associated with the F2g mode. At higher dopant contents, F2g mode became broadened and asymmetric, and a new broad band appeared at the higher frequency side of the F2g mode. This new band was assigned to the oxygen vacancies. The electron paramagnetic resonance spectrum for x = 0.05 showed the presence of O2− adsorbed on sample surface at g = 2.02 and 2.00 and of Ce3+ with a lower symmetry at g = 1.97 and 1.94. Further increasing dopant content led to the disappearance of the signals for O2−. Impedance spectra showed the bulk and grain boundary conduction in the solid solutions. The bulk conduction exhibited a conductivity maximum and an activation energy minimum with increasing dopant content. Ce0.80Nd0.20O2−δ was determined to give promising conduction properties such as a relatively high conductivity of σ700 °C = 2.44 × 10−2 S cm−1 and moderate activation energy of Ea = 0.802 eV. The variations of conductivity and activation energy were explained in terms of relative content of oxygen vacancies Vö and defect associations {CeCe ′Vö}/{NdCe ′Vö}.

With the addition of Sr into the NdO1.5–BaO–CuOz flux, series single crystals of Nd1+x (Ba1−ySry)2−x Cu3O7±δ solid solutions (Nd1113ss) were successfully grown by crystal pulling. The liquid composition control was of key importance for controlling the crystal composition, which led to a fundamental structure control. The tetragonal Nd1113ss structure was readily obtained, using a Ba-poor liquid, due to a higher Sr liquid solubility, or using a liquid with the Ba/Cu ratio around 0.33. On the other hand, a Ba-rich liquid could effectively suppress the Nd substitution at Ba sites. The higher Sr addition for achieving a stoichiometric Nd1113 compound was thermodynamically prohibited by (i) an inherently low Sr liquid solubility and (ii) the formation of BaSrCu2Oz phase in the flux at the temperature range for crystal growth. The liquid-solid-structure relation was studied.

Electrolyte electroreflectance (EER) has been used as an in situ probe for determining the distribution of energy states at the surface of naked and metal-modified TiO2 film in contact with aqueous solution. The surface modification of polycrystalline TiO2films by electrodeposition of fine (a few nanometers in size) metal particles has been shown to result in the appearance of surface states with an energy of approximately 2.15 eV for Cu, 2.40 eV for Pd, 2.50 and 2.30 eV (two peaks in the EER spectrum) for Pt, and 2.65 eV for Ag (the energy values are measured versus valence band edge of TiO2). The important role of metal-induced surface states in the enhancement of charge exchange between conduction band of semiconductor oxide and metal islets has been demonstrated using the electrocatalytic oxidation of boron hydride as a model reaction.

Silver nanoparticles (10–20 nm) embedded into silica thin films have been obtained through the use of a silver organometallic precursor compound dissolved in Spin-On-Glass and subsequently spinned onto suitable substrates. In this paper we present a study of the shape, size, and distribution of silver particles through the use of microscopes, x-ray diffraction, and optical extinction. It has been observed that the obtained films are stable for annealing up to 500 °C with a progressive degradation above this temperature. Furthermore it is possible to obtain high-density silver particles up to 15% in weight without affecting the cluster size and shape.

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.

The effect of oxygen on the reaction mechanisms in the Si/Ta/Cu metallization system was studied experimentally and by utilizing the thermodynamically assessed Ta–O binary system. It was presented that an interfacial tantalum oxide was formed between Cu and Ta and that it established an additional barrier layer for Cu diffusion. The formation of additional barrier layer was supported by the following observations: (i) No detectable amount of Cu was found from the Ta layer with the combined transmission electron microscopy and energy dispersive spectroscopy at temperatures as high as 650 °C. (ii) Secondary ion mass spectrometry measurements indicated that significant amount of oxygen was incorporated into the films already after the sputtering stage. (iii) 181Ta16O molecular ion signals were detected from the Ta/Cu interface, indicating that the additional layer was in fact some form of tantalum oxide. The diffusion of Cu through the Ta layer could not proceed until the interfacial oxide had been dissolved by the Ta matrix. Since the oxygen solubility in Ta matrix is high in the temperature range of interest, the interfacial oxide dissolution was kinetically controlled. It is to be noted that the threshold temperature range of the dissolution reaction was found to coincide with that of the β–Ta to the bcc-Ta transition, which was anticipated to enhance the kinetics of the dissolution.

This paper examined the room-temperature thermal and mechanical properties of a mixed conducting perovskite La1−xSrxCr0.2Fe0.8O3 (x = 0.2 to 0.8). Powders were made by the combustion-synthesis technique and sintered at 1250 °C in air. Sintered density, crystal phase, and grain size were characterized. Linear thermal expansion in air was also tested. Young's and shear moduli, microhardness, indentation fracture toughness, and biaxial flexure strength were determined. It was found that the linear coefficient of thermal expansion increased with increasing Sr content, while elastic modulus appeared to decrease with increasing Sr content. Young's modulus of 128 to 192 GPa and shear modulus of 51 to 74 GPa were measured. A biaxial flexure strength of 243 MPa was measured for the lowest Sr content batches. Batches with higher Sr concentrations (x = 0.6 to 0.8) showed extensive cracking. Indentation toughness showed a decrease with increasing Sr content. In addition, fractography was used to characterize the critical flaw and the fracture mode.

Oriented GaN and LixGa(2−x)O2xN2(1−x) thin films were found to grow on LiGaO2 single-crystal (001) substrates via a reaction between ammonia (or reactive ammonia species) and substrate components at temperatures between 700 and 1000 °C. The compound LixGa(2−x)O2xN2(1−x), where x was determined to be ≈0.35, is a solid solution formed from a partial reaction of ammonia with the LiGaO2 substrate. Negligible lithium (i.e., x ≈ ≈ 0) was detected in the films formed with a constant high flow rate (164 cm3/min) of ammonia, indicating a complete reaction with the LiGaO2 single crystal. The growth of a partial surface film and surface pitting suggests a vapor reaction (via loss of LiNH2 or LiOH, and nitridation of Ga2O) similar to that observed when semiconductor grade reacts with N2 to form Si3N4. The resultant films have either a wurtzite structure or one approaching the wurtzite structure. Both films form on the substrate with the same orientation as the LiGaO2.

The characteristics of elastic waves emanating from crack initiation in 2024 and 5052 aluminum alloys subject to static and fatigue loading were investigated through laboratory experiments. The objective of the study was to determine the differences in the properties of the signals generated from static and fatigue tests and also to examine if the sources of the waves could be identified from the temporal and spectral characteristics of the acoustic emission waveforms. The signals were recorded using nonresonant, flat, broadband transducers attached to the surface of the alloy specimens. The time dependence and power spectra of the signals recorded during the tests were examined and classified according to their special features. Three distinct types of signals were observed. The waveforms and their power spectra were found to be dependent on the material and the type of fracture associated with the signals. Analysis of the waveforms indicated that some signals could be attributed to plastic deformation associated with static tests. The potential application of the approach in health monitoring of aging aircraft structures using a network of surface mounted broadband sensors is discussed.

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.

After examining ternary Al-based quasi-crystalline phase diagrams, we pointed out that the presence of e/a-constant and e/a-variant lines is a common phenomenon. Ternary quasi-crystal compositions are located at the crossing point of these lines in ternary phase diagrams. Such an empirical rule can be used to predict the ternary quasi-crystal compositions from binary ones. We applied this rule to the Al–Fe–Ni system and clarified the decagonal phase composition zone. There are two decagonal phases, D-Al72.5Fe14.5Ni13 and D′-Al705Fe12Ni17.5, that correspond respectively to Al–Fe-based and Al–Ni-based decagonal phases in the same ternary system.

The synthesis of silicides of tantalum (TaSi2, Ta5Si3, Ta2Si, and Ta3Si) by field-activated combustion synthesis was investigated. The phases TaSi2, Ta5Si3, and Ta2Si can be synthesized in relatively pure form through field activation. The first compound requires a threshold field of 6 V cm−1 to initiate a combustion wave. The second and third compounds can be synthesized with all field values (0 < E < 20 V cm−1), but require considerable ignition time when E = 0. The stoichiometry Ta3Si does not sustain a combusion front unless E ≥ 20 V cm−1. However, the product is not the desired single phase. Wave velocities in the synthesis of the Si-rich phase, TaSi2, are considerably lower than those of the other two and showed a much weaker dependence on the field. The mechanism of phase formation for TaSi2 and Ta5Si3 was investigated from frozen wave analysis. No intermediate phase forms in the TaSi2 case, while in the case of Ta5Si3, TaSi2 is present as an intermediate phase. Additional investigations on the mechanism of silicide formation included isothermal solid–solid diffusion-couple and solid–liquid experiments.

Dielectric properties and the phase compositions of (1−x)Pb(Ni1/3Nb2/3)O3−xPbTiO3 ceramics were investigated. A morphotropic phase boundary (MPB) in the system between pseudocubic and tetragonal phase regions has been identified to lie in the composition range x = 0.34–0.38 by means of x-ray diffraction and dielectric measurements. The samples of composition lying near the MPB have good dielectric properties, but at the same time, exhibit two dielectric peaks. The possible reasons for the occurrence of dielectric bipeaks are discussed. One dielectric peak is phase transition peak, and the other peak lying in 130–150 °C temperature range is suggested to result from structure defects in the ceramics.

The diffusion of oxygen in silicon was modeled to result from the diffusion of dissolved silicon monoxide. The SiO molecule dissolved in the largest space in the diamond lattice of silicon, oriented in a 〈111〉 direction, with the oxygen lightly bonded to a network silicon atom. This configuration is consistent with infrared spectra, dichroism of infrared spectral lines, and internal friction of oxygen in silicon. The anomalous rapid diffusion of oxygen below 700 °C could result from the diffusion of molecular water or oxygen in silicon, but more evidence is needed to test these possibilities. Diffusion and exchange of silicon tracer in SiO with lattice silicon can possibly explain tracer diffusion of silicon in silicon.

Tracer oxygen diffusion coefficients, D*, in polycrystalline yttria doped with Ca have been determined by a gas–solid exchange technique and secondary ion mass spectrometry. Samples containing few pores were used to avoid their influences on diffusion profiles. The resulting profiles were assigned only to volume diffusion; no grain boundary diffusion was observed. According to the effects of Ca doping on D*, the Ca contents are divided into three regions. In a Ca content region of 0–0.17 mol%, D* changed a little with Ca doping and took a minimum experimentally at 0.02 mol%. D* increased significantly within a range of 0.17–0.54 mol% and saturated at 0.54 mol% or above because of a solubility limit. The activation energies of oxygen diffusion were estimated at 249–282 kJ/mol.

Planar waveguide was fabricated in Er:Yb:phosphate glass by a single energy implantation of 2.5 MeV He+ at a dose of 1.6 × 1016 ions/cm2. The waveguide was characterized by prism coupling method, and the refractive index profile was reconstructed using the inverse Wentzel-Kramers-Brillouin method. The photoluminescence was also measured. The energy loss was simulated, and the results were compared and discussed with respect to the refractive index profile in the waveguide.

Polymer thick film (PTF) resistors were fabricated using a new laser-based transfer technique called matrix-assisted pulsed laser evaporation direct write (MAPLE-DW). MAPLE-DW is a versatile direct writing technique capable of writing a wide variety of materials on virtually any substrate in air and at room temperature. Epoxy-based PTF resistors spanning four decades of sheet resistances (10 Ω/sq. to 100 kΩ/sq.) were deposited on alumina substrates under ambient conditions. Electrical characteristics of these MAPLE-DW deposited resistors were studied at a wide frequency range (1 MHz to 1.8 GHz), and the results were explained through an equivalent circuit model and impedance spectroscopy. Temperature coefficient of resistance measurements for the PTF resistors were performed between 25 and 125 °C. The results based on the percolation theory were used to explain the temperature dependence of the resistance behavior of the PTF resistors.