A route to prepare nanometer-sized Mo particulates in Al2O3 was attempted by a combination of solution reactions in molecular scale and forcing precipitation by a spray-drying technique. MoO3 was first dissolved in ammonia water and then added in the slurry with high purity, submicrometer Al2O3 powder. Mixed suspension was spray-dried, and then the dried granules were reduced by hydrogen gas and further hot-pressing to a bulky composite at various temperatures. Dissolution of Mo oxide, adsorption reactions on the alumina surface, and surface potential of alumina particles in homogeneous ammonia suspension were studied. Characterization of the granules, including compactability, flowing properties, surface morphology, grain growth of Mo and Al2O3, and mixing homogeneity, were examined. Homogeneity of the spray-dried granules was determined by the calculation of mixing index and the observation of the microstructure of the sintered body. The existence of intergranular, intragranular, and nanosized Mo particulates within Al2O3 grains was observed by transmission electron microscopy (TEM). All the evidence revealed that homogeneous composites with nanometer-sized Mo had been successfully prepared by this attempt with the proposed chemical roue and following the spray-drying process.

New molecular composite materials can be prepared based on an inorganic oxide network and an organic polymer. The polymeric component generally requires low process temperatures, due to the presence of the organic backbone or side groups. A sol-gel process therefore is suitable for synthesizing the inorganic component by dissolving soluble polymers into sol-gel precursor solutions in order to obtain ceramic and polymeric solid phases. In this work polyorganophosphazenes were used because they have many technologically interesting properties (chemical, optical, electrical, mechanical). The methods to obtain covalent bonds between polymer and inorganic network and to obtain homogeneous, transparent hybrid materials without phase separation were studied. It was possible to avoid phase separation by preparing phosphazenes containing free hydroxyl functions and by adequately choosing the experimental conditions.

The fracture strength and toughness of alumina can be increased by lamination with strategically placed nickel layers and with a modified Ni/Al2O3 interface through tape casting. In order to examine the potential of this type of laminated composite in high temperature applications, the laminates were tested at elevated temperatures. This paper describes how a modified tortuous interface, instead of a smooth interface, increases the creep resistance of the laminates. Interface modification can control high temperature laminate behavior and is critical to successful composite design.

Composed of sp3 bonded nodules of carbon, nanophase diamond films are deposited in vacuum onto almost any substrate by condensing carbon ions carrying keV energies. These multiply charged ions are obtained from the laser ablation of graphite at intensities in excess of 1011 W cm−2. The high energy of condensation provides both the chemical bonding of such films to a wide variety of substrates and low values of residual compressive stress. Coatings of 2–5 μm thickness have extended lifetimes of materials such as Si, Ti, ZnS, ZnSe, and Ge against the erosive wear from high-speed particles by factors of tens to thousands. In this research emphasis has been placed on studies of the bonding and properties realized by the direct deposition of nanophase diamond films on stainless steel substrates. Examinations of interfacial layers showed deep penetrations of carbon atoms into steel substrates. Resistances to low and high impact wear estimated by a tumbler device and a modified sand blaster, respectively, and results indicated significant increases in the lifetime of stainless steel samples. The characterization studies in this work demonstrated nanophase diamond as an attractive material for use as a protective coating in current industrial applications.

Fiber optic modulators were fabricated by coating optical fibers with electrode and piezoelectric ZnO layers. The techniques of piezoelectric fiber optic modulator (PFOM) fabrication are presented, and the microstructure and crystallographic texture of the coatings are analyzed. In order to produce thick (approximately 5 μm) ZnO coatings, it was necessary to study the reactive dc magnetron sputtering process in O2/Ar gas mixtures under conditions close to the transition between an oxidized and nonoxidized Zn target surface. In situ quartz crystal microbalance measurements of the deposition rate revealed thee distinct regions in the deposition rate (R) vs oxygen partial pressure behavior, at constant total pressure, for sputtering under conditions that provided an oxidized Zn target surface. Additionally, a transition between oxygen and argon dominated sputtering as observed by varying the sputtering pressure while maintaining a constant The transition between oxygen and argon dominated sputtering influences R to varying extents within the three R vs regions for an oxidized target surface. Correlations among the cathode current and voltage, deposition rate, and gas flow rate are presented to give a better understanding of the reactive sputtering processes occurring at the oxidized Zn target surface. Sputtering conditions optimized for a high ZnO deposition rate were used to produce 〈001〉 radially oriented ZnO fiber coatings for PFOM devices that can produce optical phase shifts as large as 0.38 rad/V.

Direct β–FeSi2 film preparation from gaseous phase was examined using a radio-frequency (rf) sputtering deposition apparatus equipped with a composite target of iron and silicon. Films composed of only β–FeSi2 phase were formed at substrate temperatures above 573 K when the chemical composition of the film was very close to stoichiometric FeSi2. The β–FeSi2 films thus formed showed rather large positive Seebeck coefficient. When the chemical composition of the films were deviated to the Fe-rich side, ∈–FeSi phase was formed along with β–FeSi2. On the other hand, α–FeSi2 phase, which is stable above 1210 K in the equilibrium phase diagram, was formed at the substrate temperature as low as 723 K when the chemical composition was deviated to the Si-rich side. The formation of α–FeSi2 phase induced drastic changes in the morphology and thermoelectric properties of the films. The α–FeSi2 phase formed in the films was easily transformed to β–FeSi2 phase by a thermal treatment.

X-ray diffraction analysis on C60 films shows that besides fcc phase, there also exists hcp phase, as well as a new crystalline phase with interplanar spacing (d-spacing) of planes parallel to the substrate 0.95 nm. The new phase may relate to the intercrystalline packed C60 molecules between fcc crystallites. The room temperature electrical conductivity of C60 films is found to be in the range of 10−5–10−8 (Ω · cm)−1. The room temperature conductivities of C60 films annealed at temperatures above 473 K are lower by one order of magnitude than those at temperatures below 463 K. This is because the interconnection between the fcc crystallites is weakened due to the disappearance of the new intercrystalline phase and the subsequent heightening of the intercrystalline potential barrier. From the measurement on the conductivity versus time when the film is maintained at a constant temperature, we identified the increase of conductivity is the result of the decrease of hcp phase, while the decrease of conductivity is due to the decrease of the new intercrystalline phase. Because the structures of the films become highly ordered, and defect states in the energy band gap decrease on annealing at high temperature, the conductivity activation energy increases.

The role of precursor stoichiometry and local firing environment on the microstructural development of sol-gel derived lead zirconate titanate (PZT) thin films was investigated. Typically, excess Pb is added to films to compensate for PbO volatilization during heat treatment. Here, it is shown that the use of stoichiometric precursors with either a PbO atmosphere powder or a PbO overcoat during the crystallization heat treatment is an attractive and viable alternative method for control of film stoichiometry. Using these approaches, we have fabricated single phase perovskite thin films with microstructures and electrical properties (Pr ∼ 36 μC/cm2 and Ec ∼ 45 kV /cm) comparable to those of films using optimized solution chemistries and excess Pb additions. The potential advantage of increasing PbO partial pressure, or activity, during firing versus excess Pb additions is discussed from the standpoint of a proposed crystallization scenario based on the kinetic competition between Pb loss and the nucleation and growth rates of the perovskite phase.

A thermal diffusion process of Ti into a LiNbO3 substrate for optical waveguides has generally been carried out under a wet gas atmosphere in order to prevent undesirable Li outdiffusion. In this work, such thermal decomposition was confirmed to be significantly suppressed for an OH-free LiNbO3 substrate, even after a dry atmosphere annealing. No extra x-ray diffraction peak for LiNb3O8 was detected from the OH-free substrate after 10 h of annealing at 1000 °C in a dry O2. Furthermore, the surface morphology of this sample, and as well an unannealed one, were smooth. In a conventional LiNbO3 substrate containing many OH ions, subjected to a similar dry annealing, the presence of the LiNb3O8 phase and a surface coarsening were observed.

The explosive reactions or self-propagating high temperature synthesis (SHS) take place during milling Ni20Ti50C30 and Ni50Ti30C20 elemental powder mixtures. The coexistence of agglomerates and powders in products indicates the occurrence of melting and solidification. TiC phase and NiTi compound were obtained during millingNi20Ti50C30, while no compound of nickel and titanium was observed when milling Ni50Ti30C20, the final product of which is TiC and Ni. It is suggested that the explosive reaction is ignited by the heat releasing from initial formation of TiC through heavy collisions of milling balls, and the reaction between Ni and Ti, as well as the existence of Ni–Ti liquid, make the following reaction self-sustained. The variation of the addition of nickel did not affect the reaction time in both compositions, but made the reaction temperature different due to the difference of composition of Ni and Ti. It is estimated that the temperature during the reaction in Ni20Ti50C30 rises above 1112 °C, while in Ni50Ti30C20, it might rise above 1349 °C. However, no phenomenon suggests the melting of pure elemental Ti; the formation of TiC is mainly controlled by the diffusion mechanism in SHS.

The constant-stress compressive creep behavior of a low-dielectric constant (low-k) glass composite, containing a low-softening-point borosilicate glass (BSG) and a high-softening-point high silica glass (HSG), has been investigated at 800–950 °C. For all stages of creep, the deformation behavior exhibits linear viscoelasticity, and is controlled by viscous flow of the low-softening-point borosilicate glass. An analytical expression is proposed to describe mathematically the creep behavior of the glass composite, and the results show a fairly good agreement with experimental observations.

Time-resolved spectroscopy of poly(ethylene) oxide (PEO) and poly(propylene) oxide (PPO) electrolytes containing different concentrations of Eu3+ and Nd3+ ions is reported. A description of the main luminescence features of the Nd3+ electrolytes is also presented. Lifetimes regarding the main transitions of the luminescence spectra (5D0 → 7F1,2 and 4D3/2 → 4I11/2 for Eu3+ and Nd3+, respectively) are determined and are presented as a function of temperature in the range of 13 to 310 K. The order of magnitude of the values obtained at room temperature (0.2–0.6 ms and ≈0.7 ms for Eu3+ and Nd3+, respectively) is a further indication of the technological potential of these new polymeric materials. For the Eu3+ ion the thermally activated quenching of the 5D0 → 7F2 luminescence is discussed in terms of the observed energy superposition between the 5D0,1 levels and the ligands-to-metal charge-transfer states.

A recently proposed method for measuring decohesion energy of ductile films on substrates is discussed. The loading mechanism that causes the decohesion of the ductile film is that of gradually depositing an additional layer, with large residual tensile stresses, on top of the film. Hence, the method involves the decohesion of a bilayer film on a substrate. The suggested method assumes that the unloading of the film is controlled entirely by elasticity. This assumption is a prerequisite for the suggested linear elastic analysis, from which the interfacial debond energy is derived in closed form. However, as is shown in the present comment, large scale yielding can occur in the wake of the crack tip and is prohibitive to the suggested linear elastic analysis. A sufficient condition for the occurrence of said large scale yielding is outlined in the present comment. Indeed it is shown that large scale plasticity must have occurred in the experiments described by Bagchi et al.1

Large scale yielding (LSY), in general, has a profound influence on the fracture toughness of metal/dielectric interfaces. For thin metal film/dielectric systems exhibiting “weak” bonding, small-scale yielding (SSY) prevails due to local plastic dissipation intrinsic to crack growth and the high yield strength of metal thin films. For systems involving low yield strength materials and strong interfaces, a more detailed LSY methodology needs to be developed.