The effects of gravity on crystallization of ZrF2–BaF2–LaF3–AlF3–NaF glasses have been studied by utilizing NASA's KC135 aircraft and a sounding rocket. Fibers were heated to the crystallization temperature in unit and reduced gravity. The fibers processed in unit gravity exhibited crystallization, while fibers processed in reduced gravity showed no signs of crystallization. An explanation based on shear thinning of liquids is presented to explain these results.

A cubic silicon nitride embedded in amorphous SiO2 compound has been characterized by means of high-resolution analytical electron microscopy. The specimen was prepared from β–Si3N4 powders at a high pressure and temperature by shock wave compression. The typical high-resolution electron microscopy image from one small crystallite together with its diffractodiagram pattern indicated that the Si3N4 crystallites had a cubic symmetry. The electron energy loss spectrum from the small crystallite is very different from those of outside amorphous SiO2 phase and raw β–Si3N4 particles, and there are more N elements that were detected in this small crystallite than those in standard Si3N4.

Most organosilicate glass (OSG), low dielectric constant (low-κ) films contain Si–R groups, where R is an organic moiety such as −CH3. The organic component is susceptible to the chemically reactive plasmas used to deposit cap layers, etch patterns, and ash photoresist. This study compares a spin-on, mesoporous OSG film with a completely connected pore structure to both its nonmesoporous counterpart and to another low-density OSG film deposited by plasma-enhanced chemical vapor deposition. The results show that the film with connected pores was much more susceptible to integration damage than were the nonmesoporous OSG films.

Hydrogenated amorphous carbon thin films were prepared by using organic hydrocarbon source, xylene (C8H10), in a plasma enhanced chemical vapor deposition-(PECVD) system. In contrast to a single broad PL peak from methane (CH4)-based hydrogenated amorphous carbon films, a new PL feature was observed from xylene-based a–C:H films in the blue-green light region. It was found that the aromatic-structures were enhanced in xylene-based a–C:H films deposited at high radio frequency power, which may result in the existence of luminescence centers in the carbon films and induce the appearance of a new PL peak.

The solidification of Al–20 wt% Mn alloy was investigated under pressures up to 6 GPa. It was found that the solidification products under pressures below 4 Gpa were about the same, composed mainly of Al and Al6Mn. A new Al–Mn phase with needle like morphology and Al nanocrystallites in size less than 20 nm were obtained in the quenched alloy at 6 GPa. Structure analysis by transmission electron microscopy and x-ray diffraction indicated that the new phase had a C-center othorhombic unit cell with lattice constants of a = 0.7565(4) nm, b = 1.2965(6) nm, and c = 0.7801(6) nm. The composition was determined to be Al77.5Mn22.5 by election probe microanalysis. The phase evolution during solidification under different pressures was discussed. Our experimental results show that the pressure, as a basic thermodynamic variable like temperature, may play an important role on the solidification of the alloy.

The effects of boron addition on the microstructure and afterglow properties of the long-phosphorescent SrAl2O4:Eu2+,Dy3+ (SAED), synthesized via a novel sol-gel route, were systematically investigated. Significant improvement on luminescence intensity and the lengthening of afterglow persistent time in boron-added SAED (BSAED) phases were observed, as compared to those without boron addition and commercial phosphors. Typical bluish-green emissions attributed to the doublet phosphorescence with wavelengths peaking at 412 and 501 nm for BSAED phase and 398 and 486 nm for the pristine SAED phase were observed. Afterglow with wavelengths peaking at 403 and 485 nm was observed for BSAED phase, whereas that with wavelengths peaking at 486.5 nm was found for the pristine SAED phase, as indicated by time-dependent afterglow decay profiles. Results from scanning electron microscopic morphological studies were used to investigate the modification of microstructure of the BSAED phases.

Tungsten oxide (WOx) films were fabricated by (i) reactive thermal evaporation (RTE) at room temperature with oxygen ambient pressure PO2 as a parameter, and (ii) reactive magnetron sputtering (RMS) with substrate temperature Ts as a parameter. The film structure revealed by x-ray photoelectron spectroscopy, x-ray diffraction, density measurements, infrared absorption, and atomic force microscopy was correlated with the nanoindentation hardness H. The RTE WOx films deposited at high Po2 were amorphous and porous, while H depended appreciably on normalized penetration depth hD (indentation depth/film thickness) due to the closing of the pores at the point of indentation. Decrease in Po2 from 10 to 2 × 10−3 mtorr led to smaller porosity, weaker hD dependence of H, and higher average H (measured at hD ≈ 0.2 to 0.3, for example). The RMS WOx film deposited at room temperature was amorphous and denser than all RTE films. The rise in substrate temperature Ts first densified the film structure (up to 110 °C) and then induced crystallization with larger grain size for Ts ≥ 300 °C. Correspondingly, the hD dependence of H became weaker. In particular, H of the RMS sample deposited at 110 °C showed a peak at hD slightly above 1 owing to pileup at the contact point of indentation. For higher Ts, pileup occurred at shallower hD and the average H (measured at hD ≈ 0.2 to 0.3, for example) rose, accompanied by the increase of grain size.

Tensile creep behavior of silicon nitride with aligned rodlike grains (anisotropic silicon nitride), fabricated by superplastic forging, was investigated at elevated temperatures. Creep rate of the anisotropic silicon nitride was about 1 order of magnitude lower than that of the isotropic one (without forging). The stress sensitivities for the isotropic and anisotropic specimens at 1200 °C were 2.1 and 2.6, respectively, and that for the anisotropic specimen at 1250 °C was 3.6. The grain alignment should cause a remarkable improvement in the creep resistance when a tensile stress is applied along the alignment direction.

The metal/ceramic interface in an in situ synthesized Ti/TiCP composite coating by laser processing was analyzed using high-resolution transmission electron microscopy. The TiC particles were distributed uniformly in the matrix and were highly faceted. The interfaces between the TiC particles and the β matrix were abrupt and free of any other reaction phases. It was the Ti-terminated TiC surface that bonded to the β matrix, resulting in the metallic bonding between the TiC particles and the matrix.

When bulk ferromagnetic Fe80P13C7 amorphous rods of approximately 2-mm diameter are compacted together in a hot press, a variety of different microstructures, depending on the experimental conditions, are produced. The most intriguing microstructure is that two different bulk amorphous rods can be fused together perfectly at a temperature of 683 K and under a pressure of 2.5 to 4 GPa for a period of 5 min.

The M-phase solid solutions Li1+x−yNb1−x−3yTix+4yO3) (0.1 ≤ x ≤ 0.3, 0 ≤ y ≤ 0.175) in the Li2O–Nb2O5–TiO2 system have promising microwave dielectric properties. However, these compounds can contain small quantities of ferroelectric impurities that affect the polarization response of the material. Due to their low concentration and their chemical similarity to the host material, the impurities cannot be detected by x-ray diffraction or local elemental analysis. Scanning surface potential microscopy and piezoresponse imaging were used to analyze phase compositions in this system. Piezoresponse imaging demonstrated the presence of thin (<200–300 nm) ferroelectric layers on the grain boundaries oriented along the c-axis of the M-phase. Differences between the surface potential and the piezoresponse of ferroelectric multicomponent systems are discussed.

Heteroepitaxial growth of the cubic skutterudite phase CoSb3 on (001) InSb substrates was achieved by pulsed laser deposition using a substrate temperature of 270 °C and a bulk CoSb3 target with 0.75 at.% excess Sb. An InSb (a0 = 4 0.6478 nm) substrate was chosen for its lattice registry with the antimonide skutterudites (e.g., CoSb3 with a = 0 4 0.9034 nm) on the basis of a presumed 45° rotated relationship with the InSb zinc blende structure. X-ray diffraction and transmission electron microscopy confirmed both the structure of the films and their epitaxial relationship: (001)CoSb3 ∥ (001)InSb; [100]CoSb3 ∥ [110]InSb.

The inability to rapidly grow thick or multilayer epitaxial films for either electronic or electrical power applications limits the utility of fluoride-based processes for YBa2Cu3O7−δ (YBCO). This problem is due to the use of water vapor in the growth process, necessary for the dissociation of metallofluorides. Flowing wet gas at low temperatures is corrosive to cuprates and responsible for destroying underlying YBCO layers in attempts to grow secondary layers. This is avoided simply by increasing the temperature where vapor is introduced into the growth ambient. Resulting two-layer films of YBCO have properties similar to those of high critical current density single-layer films.

Thin films of La0.67Sr0.33MnO3 (LSMO) were prepared at 670 °C on LaAlO3 (LAO) and SrTiO3 (STO) substrates by liquid-delivery metalorganic chemical vapor deposition. X-ray diffraction analysis 2¸/¸ and pole figure scans showed that the films are epitaxial with (001)LSMO//(001)LAO and (001)LSMO//(001)STO. The crystal structure of LSMO/LAO was indexed as face-centered cubic with a double cell and LSMO/STO as simple cubic. Electron microscopy revealed square facets and elongated grain features. Films heat-treated between 700 and 800 °C on LAO resulted in a structural change, while those on STO showed an increase in texture.

Medium-range order in ion-implanted amorphous silicon has been observed using fluctuation electron microscopy. In fluctuation electron microscopy, variance of dark-field image intensity contains the information of high-order atomic correlations, primarily in medium-range order length scale (1–3 nm). Thermal annealing greatly reduces the order and leaves a random network. It appears that the free energy change previously observed on relaxation may therefore be associated with randomization of the network. In this paper, we discuss the origin of the medium-range order during implantation, which can be interpreted as a paracrystalline state, that is, a disordered network enclosing compacts of highly topologically ordered grains on the length scale of 1–3 nm with significant strain fields.

Crystalline hydroxyapatite (HAp) powders were prepared at room temperature from heterogeneous reaction between Ca(OH)2powders and (NH4)2HPO4 solutions via the mechanochemical-hydrothermal route. X-ray diffraction, infrared spectroscopy, thermogravimetric characterization, and chemical analysis were performed, and it was determined that the room temperature products were phase-pure, thermally stable HAp with a nearly stoichiometric composition. Dynamic light scattering revealed that the dispersed particle size distribution of the room temperature HAp powders was in the range of 0.15–3.0 μm with a specific surface area of ≈90 m2/g. Both specific surface area measurements and scanning electron microscopy confirmed that the HAp powders consisted of agglomerates containing hundreds of ≈20 nm HAp crystals.

Sol-gel technology was used to fabricate two types of near-infrared absorbing dye-doped polyceram coatings for eye protection purposes against laser radiation. Tolerance of polycarbonate visors against mechanical and chemical stresses may be enhanced by using these coatings. The visible light transmission maxima of high-quality 35 and 25 μm-thick spray-coated polyceram coatings were 70% and 90% for methacrylic and propyl functionalities, respectively. Optical densities at 1064 nm were 4 and 2.

Continuous epitaxial films of cuprous oxide (Cu2O) have been formed by the thermal oxidation of 1.5-μm-thick Cu metal films deposited on MgO(110) substrates. These films melted at 1118 °C in air, in agreement with equilibrium phase diagrams. Upon cooling from the liquid, a highly crystalline, epitaxial, 2.5-μm-thick Cu2O film was formed. X-ray diffraction spectroscopy revealed that the Cu2O film crystal structure was orthorhombically distorted from the bulk cubic crystal structure. High-resolution transmission electron microscopy showed that the film is coherent, and energy dispersive x-ray spectroscopy showed that interdiffusion is limited to the interface. These results suggest that a new epitaxially stabilized phase of Cu2O has been formed.

Thin films with thickness 100 nm of Ge10+xSe40Te50−x (x ranging from 0.0 to 16.65 at.%) were formed by vacuum deposition at 1.33 × 10−4 Pa. The change in electrical resistivity of the films has been measured using the coplanar method. The measurements have been carried out in a temperature range between 400 and 142 K. The values of the electrical activation energies lie in the range of 0.18–0.38 eV. The optical absorption behavior of these ternary thin films was studied from the reflection and transmission. The optical band gap was found to be in the range of 0.90–1.11 eV and arose from indirect transitions. On the other hand, the width of the band tail Ee was found in the range 0.19–0.32 eV and exhibits opposite behavior. This behavior is believed to be associated with a defected bond of Te–Te and a cohesive energy (CE).

Blue photoluminescent emission was observed in pure nanometer-sized γ–Al2O3 powders prepared by the sol-gel process, with aluminum alkoxide as the precursor. The photoluminescent excitation spectrum detected at »em = 422 nm showed four peaks located at 238, 255, 278.5, and 348.5 nm, respectively, the first having the strongest intensity. The photoluminescent emission spectra were made up of a broad band with four peaks located at 404.5, 422, 447, and 484.5 nm. The emission band of 422 nm had the intensity. We suggest that the defect level in the nanometer alumina powder also is the main reason for the appearance of new luminescent emission bands.