Polycrystalline TiN/VN, NbN/VN, and TiN/NbN superlattices with periods Λ between 2 and 160 nm were deposited onto steel substrates using an opposed-cathode reactive magnetron sputtering system. The nitrogen partial pressure and the substrate bias values were optimized in order to obtain dense stoichiometric films, which yielded the highest Vickers hardnesses HV. HV for TiN/VN and TiN/NbN superlattices reached maximum values of ≈5000 kgf/mm2 at Λ ≈ 5–10 nm, compared with ≈2000 kgf/mm2 for homogeneous TiN, NbN, and VN films. In contrast, HV ≈ 2000 kgf/mm2 was obtained for VN/NbN superlattices independent of Λ. Model calculations in which the hardness enhancement was proportional to the difference in layer shear moduli gave good agreement with the data. The lack of hardness enhancement in VN/NbN indicates that any other hardening mechanisms, such as coherency strains and dislocation blocking by interfacial misfit dislocations, were not important.

Plastic deformation behavior of impure nanocrystalline ceramics (NCC) was modeled using the percolative composite model in conjunction with models for plastic deformation by grain boundary sliding. The “glass transition temperature” concept was used to determine the threshold strain rate criterion below which the impure nanocrystalline ceramic would deform plastically. Threshold strain rate is stress independent. It increases with the temperature increase and with the grain size decrease. Using the dissolution-precipitation model, dependence of the strain rate on temperature, stress, and grain size in the nanometer regime for impure NCCs was calculated. As an example, the critical conditions for plasticity in impure yttria-tetragonal zirconia polycrystals (Y-TZP) were evaluated. At 600 °C, strain rates as high as 10−4 s−1 were expected in 10 nm impure Y-TZP. Comparison of the published data extrapolated into the nanometer range to the calculated threshold level showed that increase in the applied stress is associated with increase in the grain size and strain rate onsets for plastic deformation.

The reaction mechanisms observed when sintering loose Cr2O3–CaF2 powder mixtures were analyzed, and the influence of the sintering parameters on the reaction behavior is presented. Using x-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and differential thermal analysis (DTA) measurements, CaCrO4 was shown to be the reaction product when sintering in air. The reaction occurs in two steps: CaF2 transforms to CaO at the Cr2O3–CaF2 interface, followed by a CaO–Cr2O3 interaction, which creates the reaction product. Scanning electron microscopy (SEM) and x-ray fluorescence (XRF) analysis showed an increasing loss of CaF2 with increasing sintering temperature and heating rate, while an opposite evolution of the amount of reaction product was observed.

The objective of this work was to determine the mechanism of in-plane texture development in films made by ion-beam-assisted deposition (IBAD). Both in-plane texture and surface roughness were studied as functions of film thickness. A phenomenological growth model based on the preferential growth of aligned grains due to channeling was proposed, linking the surface roughness evolution and texture development. Good correlation was found between the measured roughness and the model prediction, as well as between the roughness evolution and the in-plane texture development. A critical thickness was introduced at which in-plane texture is completed. Both surface roughness and texture results gave a critical film thickness of 114–250 nm for an ion energy of 1000 eV and an R ratio of 0.4. This range of critical film thickness was far beyond the nucleation stage, providing evidence that the development of in-plane texture in IBAD Nb films was growth-controlled.

We report here a study on the electrical and magnetic properties of La1−xBaxCoO3 in the re-entrant semiconducting region (x = 0.20). We find that in this material: (i) the insulator-metal-insulator sequence is unstable and evolves toward a purely semiconducting behavior; the initial r versus T curve can be reinstated upon appropriate annealing treatments; (ii) there are relaxation effects that can be seen by changing the polarity of the electrodes; (iii) there is a negative magnetoresistance Δρ/ρ ∼ 2–3%, for a field as low as 9 kOe, especially at the metal-insulating transition temperatures; and (iv) there are important fluctuations in the electrical resistivity. Taking into account these experimental observations, we can interpret this material as an inhomogeneous system where two thermodynamic phases, one semiconducting and the other metallic and ferromagnetic, coexist, although they are crystallographically indistinguishable.

Spark plasma sintering was used to consolidate the crystallized Nd–Fe–B alloy powders. It was found that a higher sintering temperature can improve the consolidation significantly, whereas it deteriorates the magnetic properties drastically due to the appearance of a large amount of α–Fe phase and the grain growth. Sintering at lower temperature can preserve the magnetic properties better, while the powders cannot be consolidated into a fully dense compact, even under the higher pressure of 75 MPa. Finer starting powder particles show similar behavior.

High-purity SrTiO3 bicrystal sample (the angle between two [001] directions is 24°) was used in the present experiment to develop a thermal grain boundary groove along the bicrystal grain boundary at different temperatures (1150–1400 °C) and times (15–6720 min) in air. An atomic force microscope (AFM) was used to observe the surface morphological change in the annealed bicrystal sample in order to measure the width W and depth h of the developed grain boundary groove. It was found that the log W–log t (at 1150–1400 °C) and the log h°log t (at 1400 °C) relationships are approximately linear, having slopes of approximately 1/4. Using Mullins' formulas, the surface diffusion coefficients of SrTiO3 at different temperatures were calculated. Finally, the surface diffusion coefficient determined in the present experiment appears to correspond to the titanium atom, which has the lowest diffusivity in SrTiO3.

P-type microcrystalline silicon-carbon alloy thin films have been prepared at low power by employing radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) technique; judicious choice of deposition parameters is necessary. Substrate temperature has been observed to be the most critical parameter, while high hydrogen dilution is necessary but not a sufficient condition for obtaining crystallinity in silicon-carbon alloy thin films. Best microcrystallinity at moderate power density (78 mW/cm2) has been obtained at a fairly low substrate temperature (180 °C). The highest conductivity of 5.7 Scm−1 of a boron-doped microcrystalline sample could be achieved. Incorporation of carbon in these films has been confirmed from x-ray photoelectron spectroscopic (XPS) studies. Carbon is, however, incorporated only in the amorphous phase while the crystallites are of silicon only as observed from Raman spectra.

Isothermal sections at 670, 740, and 800 °C in the Cr–Ga–N ternary system were investigated. Details of the Cr–Ga and Cr–N binary phase diagrams were confirmed, and the equilibrium diagrams were constructed. At all temperatures, Cr3GaN was in equilibrium with all the condensed phases, except GaN. In the 670–800 °C temperature range, Cr2GaN appears to be kinetically stable in contact with GaN. This led to the construction of behavior diagrams that are valid only as long as GaN is present in the initial mixture. Above ∼910 °C, Cr2GaN decomposes to form Cr3GaN, CrN, and Ga(1). At 1000 °C, Cr3GaN is in equilibrium with all the condensed phases, and CrN is in equilibrium with Ga.

Carbon nanotubes produced by the treatment of Mg1−xMxAl2O4 (M = Fe, Co, or Ni; x = 0.1, 0.2, 0.3, or 0.4) spinels with an H2–CH4 mixture at 1070 °C have been investigated systematically. The grains of the oxide-metal composite particles are uniformly covered by a weblike network of carbon nanotube bundles, several tens of micrometers long, made up of single-wall nanotubes with a diameter close to 4 nm. Only the smallest metal particles (<5 nm) are involved in the formation of the nanotubes. A macroscopic characterization method involving surface area measurements and chemical analysis has been developed in order to compare the different nanotube specimens. An increase in the transition metal content of the catalyst yields more carbon nanotubes (up to a metal content of 10.0 wt% or x = 0.3), but causes a decrease in carbon quality. The best compromise is to use 6.7 wt% of metal (x = 0.2) in the catalyst. Co gives superior results with respect to both the quantity and quality of the nanotubes. In the case of Fe, the quality is notably hampered by the formation of Fe3C particles.

Ultrathin and uniform Pt-silicide layers are prepared by electron beam evaporation on a heated silicon substrate and by magnetron sputtering at room temperature followed by rapid thermal annealing (RTP) and selective etching, respectively. In the electron-beam deposited samples, continuous Pt-silicide layers of 6–8 nm thickness are formed after thermal annealing. The interfaces between the silicide layers and the silicon substrate are not atomically flat. In the case of the sputtered Pt, continuous PtSi layers down to 3 nm thick can be produced by using two-step (low-high temperature) and modified two-step (selective etch and high-temperature anneal) RTP silicidation processes. In one-step (high-temperature) processed samples, PtSi is the dominant phase; meanwhile, a small fraction of Pt12Si5 phase is inhomogeneously distributed in the case of thicker PtSi layers. In the two-step RTP processed samples, a Pt/Pt2Si/PtSi/Si layered structure is formed after the first RTP step. The first anneal step is found to be crucial for the roughness and epitaxy of the final PtSi layer. The best Schottky barrier heights are found to be 0.249 eV for the 3 nm PtSi/p-Si(100) Schottky diodes. The e-beam and the sputtered PtSi layers follow different epitaxial growth models.

The orientation relationship and the interfaces of ZrO2(c)–CaZrO3 unidirectional solidified eutectics have been investigated by means of electron diffraction and transmission electron microscopy (TEM). In contrast to previous studies on lamellar oxide-oxide systems, neither a constant orientation relationship between contiguous lamellae nor low-index interfaces are observed in this eutectic. As for metals and plastic crystals, it displays incoherent interfaces and nonfaceted growth. This unusual behavior is discussed in terms of entropy of fusion and related to the presence of oxygen vacancies in the ZrO2(c) phase.

Ink-jet printing is an important image transfer technology. In this technology, the electronic capabilities are often constrained by shortcomings of materials functions. One of the constraints for fast reproduction of high-resolution photographic quality color images is the print dry time. This presents a challenge in the film technology where large quantities of solvent must be rapidly removed without transporting colorants outside the targeted areas. In this work, this is achieved by chemical immobilization of water by organic polymers incorporated into the film matrix. In this dense film, immobilization of large volumes of water becomes possible by a transient local swelling of the matrix—as much as 600–700%. This mechanism of water immobilization not only creates a virtually dry state instantaneously, but also leads to a tighter containment of colorants within the targeted areas, resulting in a significant improvement in edge acuity and image resolution. In addition, the film is printer and ink nonspecific and produces a high gloss on photographic paper.

Crystallographically coherent precipitates of vanadium dioxide (VO2) have been formed in the near-surface region of single crystals of sapphire (Al2O3) using a combination of ion implantation and thermal treatments. As in the case of either bulk VO2 single crystals or thin films of VO2, the thermally induced semiconductor-to-metal phase transition of the embedded VO2 precipitates is accompanied by a large hysteretic change in the infrared optical transmission. The VO2 precipitate transition temperature (Tc = 72 to 85 °C) is higher than that of bulk VO2 (Tc = 68 °C) and is sensitive to the implantation conditions. The present results show that the damage resulting from the coimplantation of vanadium and oxygen into an Al2O3 host lattice dictates the final microstructure of the VO2 precipitates and, consequently, affects the transition temperature, as well as the optical quality of the VO2/Al2O3 surface-nanocomposite precipitate system.

Y2O3 : Eu phosphor particles were directly prepared by a spray pyrolysis method. Photoluminescence, morphology, and crystallinity of the as-prepared particles were investigated. The as-prepared particles above 600 °C had good crystallinity, and the crystallinity increased with increasing reactor temperatures. The particles had spherical morphology and were nonaggregated. The mean size of the particles increased from 0.34 to 1.2 µm when the solution concentration was increased from 0.03 to 1 M. The as-prepared particles had good red emission without annealing at high temperatures when excited with uv light. The main emission peak was 612 nm. The brightness of the as-prepared particles increased with increasing temperatures because of good activation and crystallization at high temperatures.

Crystal defects in mordenite materials were observed and characterized by high-resolution electron microscopy (HREM). These defects are identified as line, planar, and 3D defects, which may result in pore blockage of the mordenite channel structure and be detrimental to their chemical properties for catalytic applications. The planar defects are the most severe ones affecting the structural properties of mordenite because of their density and scale. The main emphasis of this investigation is focused on the crystallographic aspects of these defects.

A series of gallium-lanthanum-sulfide (GLS) glasses of different oxide concentration has been made and their spectroscopic properties, thermal properties, and the crystallization behavior of the glasses have been studied. It was revealed that the formability of GLS glasses relies on the existence of a certain amount of oxide content. The thermal stability of GLS glasses changes as a function of oxide concentration. The results have also shown that increasing oxide content caused a shift of the visible absorption edge to shorter wavelengths and an increase of absorption intensity in the infrared region at the multiphonon edge. Two closely related crystalline phases have been identified in the crystallized GLS glasses. For the first time it has been revealed that thermally stable GLS glasses can be made near the eutectic point of these two crystal phases by introducing an optimized amount of oxide.

Fe K-edge x-ray absorption fine-structure (XAFS) measurements were performed on glass samples of (Fe3O4)0.3(P2O5)0.7 with various amounts of Na2O or UO2. Near-edge and extended XAFS regions are studied and comparisons are made to several reference compounds. We find that iron in the base glass is ∼25% divalent and that the Fe2+ coordination is predominantly octahedral, while Fe3+ sites are roughly split between tetrahedral and octahedral coordinations. Also, we measure roughly one Fe–O–P link per iron. Substitution of Na2O or UO2 up to 15 mol% primarily affects the first Fe–O shell. The results are compared to data from the related material Fe3(P2O7)2.

An electrochemical method used to obtain aluminum(III)-8 hydroxyquinoline (Alq3) blended into poly(N-vinylcarbazole) (PVK) matrix is described. The PVK-Alq3 blends show an intense green photoluminescence whose intensity increases by adding a small percentage of a substituted coumarin to the PVK-Alq3 solution. The material can easily be spin-coated to obtain homogeneous luminescent thin films suitable for optoelectronic applications. Spectrophotometry in the uv-vis-ir range, photoluminescence, and lifetime measurements are used to characterize the PVK-Alq3 films.

X-ray diffraction analyses of the pure components n-tricosane and n-pentacosane and of their binary mixed samples have enabled us to characterize the crystalline phases observed at “low temperature.” Contrary to what was announced in literature on the structural behavior of mixed samples in odd-odd binary systems with Δn = 2, the three domains are not all orthorhombic. This work has enabled us to show that two of the domains are, in fact, monoclinic (Aa, Z = 4), and the other one is orthorhombic (Pca21, Z = 4). The conclusions drawn in this work can easily be transposed to other binary systems of n-alkanes.