Ferroelectric(Ba0.67Sr0.33)TixO3 (BST) thin films with x = 0.98, 1.00, 1.02, and 1.04 were prepared by the sol-gel technology, and their thermal, structural, dielectric, and gas sensing properties were systematically characterized. The amorphous (Ba0.67Sr0.33)TixO3 thin film capacitive devices were made on Si substrate to detect hydrogen gas and to study hydrogen-induced interfacial polarization potential.Experimental results showed that the Schottky I–V behavior appears in these Pd/amorphous BST thin film/metal capacitive devices and that enhanced interfacial dipole potentials as large as 4.5 V at 1000 ppm hydrogen gas in air were newly observed, which is about 7 times larger than the best value reported under similar testing conditions. It was clearly shown that the hydrogen-induced interfacial polarization potential is closely correlated with the microstructure of ferroelectric thin films and the enhancement of this interfacial polarization potential is mainly attributed to the high dielectric constant of amorphous ferroelectric thin films. A simple hydrogen interface-blocking model is also presented to explain this interesting phenomenon.

The formation of so-called Ruddlesden–Popper planar faults was studied in SrO-doped SrTiO3 for different quantities of SrO additions and sintering conditions. For small SrO additions we observed a microstructure with a uniform grain size distribution and the enrichment of SrO at the grain boundaries. Larger additions of SrO produced a microstructure of elongated grains containing random planar faults, polytypic lamellae of more or less ordered faults, and polytype loops within SrTiO3 grains. We showed that these SrTiO3 grains were elongated as a result of preferential growth of the polytypic lamellae. In addition, we discuss a correlation between the formation of planar faults embedded in the perovskite matrix at low firing temperatures and Ruddlesden–Popper phases that are stable at higher temperatures.

The isothermal oxidation of Pd-modified Ni aluminide coatings was studied as a function of Po2 and temperature (900–1200 °C). A kinetic transition was observed between 900 and 1000 °C. Grazing incident x-ray diffraction, thermogravimetric analysis, x-ray photoelectron spectroscopy, scanning electron microscopy/energy dispersive spectroscopy, and secondary ion mass spectrometry analyses are consistent with the growth of δ-alumina or α-alumina below or above this transition temperature. Moreover, because Po2 was established before specimen heating, an effect of heating rate was observed and analyzed. More importantly, no kinetic transition was observed for sand-blasted specimens oxidized at low Po2. Thus conditions for the direct growth of an α-alumina scale could be determined from the reported results.

We investigated the formation of nanowhiskers by means of air plasma dry etching using diamond films of two different kinds: as-grown diamond films and films with molybdenum (Mo) deposits. As for the as-grown diamond films, nanowhiskers were found to form preferentially at grain boundaries of diamond crystals. Auger depth profile analysis of the etched films revealed a progressive enrichment by Mo toward the whisker tip, resulting from accidental sputtering of Mo substrate holder. With dry etching of diamond films with preformed Mo deposits, well-aligned whiskers 100 nm in diameter were found to form uniformly over the entire film surface with a population density of 30/μm2. From these findings, it follows that Mo deposits serve as micromasks for the formation of the nanowhiskers. It was also confirmed that these whiskers showed excellent field-emission behavior.

PbS/ZrO2 optical films were prepared by the dip-coating method from a mixed sol containing two precursors, Zr(OC3H7)4 and Pb(CH3COO)2. The phase structure and size of PbS nanoparticles were characterized by x-ray diffraction and transmission electron microscopy, respectively. Optical absorption and fluorescence spectra were taken on the PbS/ZrO2 films. Larger blue shifts of band edge and weak fluorescence emission of PbS were observed. The third-order nonlinear properties of PbS/ZrO2 films were studied. The calculated values of nonlinear refractive indexes n2 varied between 10−8 and 10−9 cm2/W.

We showed, by high-resolution transmission electron microscopy and spatially resolved electron energy-loss spectroscopy, that silver atoms have been introduced into single- walled carbon nanotubes (SWCNTs) produced by the arc-discharge method with solution phase chemistry by capillary filling, and a high efficiency of filling may be realized. Both partially filled and completely filled SWCNTs were observed, and the metal inside the tube may be regarded as one-dimensional silver nanowires with high length-to-diameter ratios. The length of filling ranged from several to tens of nanometers. Under strong electron beam irradiation the filling metal condensed to a particle, while the silver-containing SWCNT shrank and disintegrated.

A shear-induced ordered structure in an exfoliated polystyrene (PS)/clay nanocomposite is reported. X-ray diffraction (XRD), transmission electron microscopy (TEM), and infrared dichroism techniques have been employed to investigate the shear-induced ordered structure in the exfoliated PS/clay nanocomposite. Compared with the broad amorphous peaks before extrusion, a series of sharp diffraction peaks were observed in XRD pattern for the extruded PS/clay nanocomposite pellet sample, showing that an ordered structure occurred under shear flow. TEM images confirmed directly that the origin of the ordered structure was mainly due to the planar orientation of the primary particles of silicate layers as well as local ordered microstructure of the primary particles, induced by shear flow. The infrared dichroism study indicated that the phenyl group of PS apparently oriented parallel to the film surface, whereas no obvious orientation of the aliphatic chain could be observed. Based on these investigations, a possible mechanism was deduced for the formation of the ordered structure induced by shear flow in the exfoliated PS/clay nanocomposite.

Mechanical milling of fullerene (soot containing C60/C70 fullerenes in a 8:2 molar ratio) was investigated through various characterization methods. It was found that mechanical milling would not destroy the molecular structure of fullerene C60 (C70), while the long-range order of the face-centered-cubic crystalline structure was easily modified and transformed into amorphous phase, a mixture of fullerene C60 (C70) polymers and monomers. Differential scanning calorimetry analysis revealed a recovery of polymers to pristine fullerene molecules at 678 K, which is much higher than the reported depolymerization temperature of fullerene polymers induced by photo irradiation and by high-pressure–temperature processes. It is suggested that the contaminated Fe acts as a catalyst in the polymerization process.

Investigations of a substitutional mechanism of Pb incorporation into the crystal structure of Ba6−3xNd8+2xTi18O54 performed by x-ray diffraction analysis, scanning electron microscopy, and energy dispersive and wavelength dispersive x-ray spectroscopy revealed that Pb2+ substitutes for Ba2+ according to the formula (Ba1−zPbz)6−3xNd8+2xTi18O54. The solid solubility limit for 0.5 = x = 0.6 compositions was determined to be at 0.35 ≤ z < 0.4 (nominal composition) which, according to measurements of PbO loss occurring during the heat treatment, gives 0.30 ≤ z < 0.35 (analyses of matrix phase). Increasing the Pb2+ concentration in (Ba1−zPbz)4.5Nd9Ti18O54, results in tf decreasing from an initial positive value (80 ppm/K) to a negative value at the solid solubility limit (−25 ppm/K at z = 0.35). In the same concentration range the Q-value decreases from an initial 2000 to 1250 (z. = 0.35), measured at 4 GHz, while permittivity remains almost constant (k = 87 ± 1.5). After exceeding the solid solubility limit of Pb2+ in (Ba1−zPbz)4.5Nd9Ti18O54 the appearance of secondary phases (Nd4Ti9O24 and Pb-rich phase at grain boundaries) changes the trends of the microwave dielectric properties; permittivity decreases, Q-value remains almost constant, and Tf increases.

Neutron diffraction measurements were carried out on samples of CeO2–ZrO2 powder catalysts prepared by high-energy mechanical milling. The formation of solid solution was evidenced across the entire composition range examined. Quantitative phase evaluation by the Rietveld method indicated formation of tetragonal structure for low CeO2 content, whereas cubic solid solutions were the stable form at high CeO2 loading. In addition, a pseudocubic or tetragonal t″ cell with axial ratio of unity and with internal deformation of the oxygen sublattice was observed at intermediate composition (50 mol% CeO2). Thermal annealing up to 1000 °C showed expansion of the unit cell parameters; an increase in the degree of tetragonality at the expense of cubic and monoclinic phase was observed for composition CexZr1−xO2 (x < 0.5).

Fracture toughness and fracture mechanisms in Al2O3/Al composites are described. The unique flexibility offered by pressureless infiltration of molten Al alloys into porous alumina preforms was utilized to investigate the effect of microstructural scale and matrix properties on the fracture toughness and the shape of the crack resistance curves (R-curves). The results indicate that the observed increment in toughness is due to crack bridging by intact matrix ligaments behind the crack tip. The deformation behavior of the matrix, which is shown to be dependent on the microstructural constraints, is the key parameter that influences both the steady-state toughness and the shape of the R-curves. Previously proposed models based on crack bridging by intact ductile particles in a ceramic matrix have been modified by the inclusion of an experimentally determined plastic constraint factor (P) that determines the deformation of the ductile phase and are shown to be adequate in predicting the toughness increment in the composites. Micromechanical models to predict the crack tip profile and the bridge lengths (L) correlate well with the observed behavior and indicate that the composites can be classified as (i) short-range toughened and (ii) long-range toughened on the basis of their microstructural characteristics.

A nanocrystalline tungsten oxide photochromic thin film was prepared by colloid chemistry method. The microstructure, phase transition involved in the solution process, photochromic behavior, and mechanism of the film were investigated by means of transmission electron microscope, x-ray diffraction, ultraviolet-visible absorption spectra, and x-ray photoelectron spectra. It was found that the particle size and crystallinity of the thin film could be easily controlled by adjusting the concentration of oxalic acid in the colloid solution of tungsten oxide hydrate. With the increase of the oxalic acid concentration, the size of nanoparticles in the film decreased sharply, and meanwhile, a blue shift of the absorption peaks caused by the quantum size effect was observed accordingly. With the increase of the pH in the solution, tungsten oxide hydrate was gradually transformed into an oxided 12-tungstate with Keggin structure, which led to the change of photochromic property of the films. The photochromism of the film is believed to be due to the electron transfer between the different valence states of tungsten ions located in adjacent sites.

The thermal and mechanical properties of aluminum titanate–mullite composites prepared by a gel-coated powder processing method, namely a mullite precursor gel coating aluminum titanate particles (containing 2.5 wt% MgO), were investigated. A microstructure with both elongated and equiaxed mullite grains was observed in the composite samples. Both the mechanical strength and the thermal expansion coefficient increased with the mullite amount. The mechanical strength showed a strong dependence on the grain size of aluminum titanate with an exponent of −3. Inhibition of aluminum titanate grain growth due to the presence of the mullite phase enhanced the mechanical strength of the composites. The thermal shock resistance tended to decrease as the mullite content increased. The thermal stability of aluminum titanate was improved in the present composite system.

Cavitation was examined in an Al–Mg solid-solution alloy deformed in tension at 400 °C under conditions providing solute-drag creep, which can produce tensile ductilities from 100% to over 300%. Two nondestructive evaluation techniques were employed to measure the extent of cavitation: ultra-high-resolution x-ray computed tomography and pulse-echo ultrasonic evaluation. Subsequent to nondestructive evaluation, the sample was sectioned for examination by standard metallographic techniques. Metallographic examination confirmed that both nondestructive techniques accurately indicated the extent of cavitation. Ultrasonic testing provided a practical means of distinguishing material with cavities from that without cavities. Ultrahigh- resolution x-ray computed tomography provided an accurate three-dimensional image of internal cavitation.

The thermal stability of RuO2/Si(100) films in air was studied using ex situ synchrotron x-ray scattering. The (110) textured RuO2 film showed good thermal stability due to the low surface and strain energies. However, the RuO2 films of high strain and surface energies were transformed to three-dimensional islands during annealing up to 800 °C. We also studied, during the post annealing process, the interface roughness of BaxSr1−xTiO3 (BST)/RuO2/Si(100) and BST/Pt/Ti/SiO2/Si(100) structures comparatively, using in situ synchrotron x-ray scattering. The interfaces of the BST/RuO2/Si were thermally stable up to 500 °C, and the deterioration of the interfaces above 500 °C was attributed to the crystallization of amorphous BST film. Meanwhile, the interfaces of the BST/Pt/Ti/SiO2/Si were significantly degraded even at the low temperature of 350 °C, mainly due to the formation of the Pt–Ti alloy and the Ti oxidation.

An analysis is made of contact damage in brittle coatings on metal substrates, using a case study of a dental porcelain coating of thickness between 0.1 and 1 mm fused onto a Pd alloy base, with spherical indenter of radii 2.38 and 3.98 mm. At large coating thicknesses (>300 μm), the first damage takes the form of surface-initiated transverse cone cracks outside the contact. At small coating thicknesses (<300 μm), the first damage occurs as yield in the substrate, with attendant formation of subsurface transverse median cracks in the coating. At high loads and thin coatings, both forms of transverse cracking occur, along with subsequent delamination of the ceramic/metal interface, signalling impending failure. Conditions for avoiding such transverse cracking are considered in terms of minimum coating thicknesses and maximum sustainable contact loads. General implications concerning the design of brittle coating systems for optimum damage resistance are considered, with special reference to dental crowns.

The fatigue resistance of the interface between electroless–nickel and the eutectic tin–lead solder alloy was examined in the as-reflowed and aged conditions and compared to fatigue behavior of the copper/solder interface under the same conditions. In the as-reflowed state, the fatigue resistance of the solder/electroless-nickel interface was slightly superior to that of the solder/copper interface. However, after long-term aging, the fatigue resistance of the solder/electroless-nickel interface became far worse in the high crack growth rate regime. Examinations of interfacial microstructures and crack growth mechanisms indicated that the differences in fatigue resistance between the two interfaces were not directly related to the thickness of the intermetallic phase at the interface, as commonly believed, but were due to differences in crack growth mechanisms.

SiC nanometer powders were synthesized by the chemical vapor reaction of the SiH4–C2H4–H2 system in the temperature range between 1423 K and 1673 K. The effects of processing conditions such as reactive temperature, gas composition ratio, and total flow rate on powder characteristics were studied using transmission electron microscopy, x-ray diffraction, infrared, Brunauer–Emmett–Teller, and chemical analyses. A forming mechanism has been proposed for solid and hollow particles in different processing conditions. The experimental results concerning particle growth are discussed according to the model of G.D. Ulrich et al., which considers both collision and coalescence phenomena.

Ce3+ luminescence in Ce3+ –activated yttrium aluminium borates was studied. A substantial red shift in photoluminescence and low-voltage cathodoluminescence spectra was found to be induced by Ce concentration increase. Complicated concentration dependence of emission intensity and strong influence of cerium content on emission wavelength suggest strong activator–host interaction in rare-earth borates.

Structural evolution of undoped and boron-doped submicron vapor-grown carbon fibers (S-VGCFs) was monitored as a function of heat-treatment temperature (HTT). Based on x-ray and Raman data, over the range of HTT from 1800 to 2600 °C, it was found that boron atoms act as catalysts to promote graphitization due to boron's higher diffusivity. For the range of HTT from 2600 to 2800 °C, the process of boron out-diffusion from the host material induces defects, such as tilt boundaries; this process would be related with the improved capacity and Coulombic efficiency of boron-doped S-VGCFs. When 10 wt% S-VGCFs was used as an additive to synthetic graphite, the cyclic efficiency of the capacities was improved to almost 100%.