PbxBa1−xTiO3 (0.2 ⩽ x ⩽ 1) thin films were deposited on single-crystal MgO as well as amorphous Si3N4/Si substrates using biaxially textured MgO buffer templates, grown by ion beam-assisted deposition (IBAD). The ferroelectric films were stoichiometric and highly oriented, with only (001) and (100) orientations evident in x-ray diffraction (XRD) scans. Films on biaxially textured templates had smaller grains (60 nm average) than those deposited on single-crystal MgO (300 nm average). Electron backscatter diffraction (EBSD) has been used to study the microtexture on both types of substrates and the results were consistent with x-ray pole figures and transmission electron microscopy (TEM) micrographs that indicated the presence of 90° domain boundaries, twins, in films deposited on single-crystal MgO substrates. In contrast, films on biaxially textured substrates consisted of small single-domain grains that were either c or a oriented. The surface-sensitive EBSD technique was used to measure the tetragonal tilt angle as well as in-plane and out-of-plane texture. High-temperature x-ray diffraction (HTXRD) of films with 90° domain walls indicated large changes, as much as 60%, in the c and a domain fractions with temperature, while such changes were not observed for PbxBa1−xTiO3 (PBT) films on biaxially textured MgO/Si3N4/Si substrates, which lacked 90° domain boundaries.

Nd-doped Y3ScxAl5−xO12(Nd:YSAG) powder were prepared with a chemical combustion method. The powders were nano-sized and had a pure cubic phase when calcined at 900 °C. Transparent Nd:YSAG ceramics with up to 40% scandium substitution for aluminum were successfully fabricated by sintering the powder compact at 1800 °C under H2 atmosphere. The synthesis process and optical properties were investigated in detail. It was found that the light emission intensity at 1064 nm of the Nd:YSAG with 40% scandium substitution for aluminum can be enhanced by 2–3 times over that of Nd:YAG single crystal when pumped with the same 808-nm diode laser. In addition, the material was found to have prolonged fluorescence lifetime. This highly enhanced light emission intensity is fundamentally important for obtaining higher light output together with suppressed self-heating than Nd:YAG ceramic and single crystals.

TiN/Si3N4 composite powders were obtained by a process that combines the mechanical activation of titanium and silicon powders at room temperature through high-energy milling with an isothermal annealing in a nitrogen atmosphere to complete the synthetic reaction. Mechanical activation has allowed us to complete the synthesis at 1350 °C only. The β–Si3N4 content in the final powder tends to increase as the milling time is prolonged. The microstructure of the TiN/Si3N4 composite powders has a bimodal character composed of TiN and β–Si3N4 grains and α-Si3N4 nanowires. Diameters of the nanowires range from 10 to 70 nm.

We investigated a new method of ceramic-to-metal joining, referred to as reactive air brazing, as a potential method of sealing ceramic components in high-temperature electrochemical devices. Sessile drop wetting experiments and joint strength testing were conducted using yttria stabilized zirconia (YSZ) substrates and CuO–Ag-based air brazes. Results from our studies indicate that the wettability of the braze improves substantially with increasing CuO content, over a compositional range of 1–8 mol% CuO, which is accompanied by an increase in the bend strength of the corresponding brazed YSZ joint. The addition of a small amount of TiO2 (0.5 mol%) to the CuO–Ag braze further improves wettability due to the formation of a titanium zirconate reaction product along the braze/substrate interface. However, with one notable exception, the bend strength of these ternary braze joints remained nearly identical to those measured in comparable binary braze joints. Scanning electron microscopy analysis conducted on the corresponding fracture surfaces indicated that in the binary braze joints, failure occurs primarily at the braze/YSZ interface. Similarly in the case of the ternary, TiO2-doped brazes joint failure occurs predominantly along the interface between the braze filler metal and the underlying titanium zirconate reaction layer.

Ion-beam-assisted deposition (IBAD) was used for cathode preparation in organic light-emitting diodes to fabricate dense electrode. Dark spot growth rate was decreased by employing the IBAD process due to a highly packed aluminum structure inhibiting the permeation of H2O and O2. However, undesirable leakage current was generated because energetic particles of Al assisted by Ar+ ion may damage the organic material resulting in reduction of contact resistance. The decrease of contact resistance in the IBAD device may be caused by large contact area, increase of density of states, and Li diffusion to phenyl-substituted poly-p-phenylene vinylene.

Crucial features of materials evolution due to ion beam irradiation are often revealed only through studies of process dynamics. We review some significant examples of such experiments performed over the last 25 years with the Orsay in situ facility: a transmission electron microscope setup (with temperature stages operating between 4 and 1000 K) on a medium energy (3–570 keV) ion beam line. New results on nanocavity evolution and metal silicide nanoprecipitates in Si are presented briefly.We show that CoSi2 nanoprecipitate growth is mainly due to the constant Co atom contribution from the ion beam, and CoSi2 platelet growth is the result of a three-dimensional to two-dimensional growth mode transition.

Brillouin scattering has been used to study the elastic properties of alkaline-calcium silica hydrogels synthesized from the precipitation of sodium silicate solution with calcium hydroxide. To the best of our knowledge, this is the first determination of the bulk elastic moduli for this type of alkaline-calcium silica hydrogel, also referred to as the alkali-silica reaction (ASR) gel. The measured bulk moduli for the alkaline-calcium silica hydrogels were found to be between 4 and 8 GPa for the gel containing 0.08 M Ca(OH)2 and between 10 and 25 GPa for the gel containing 0.8 M Ca(OH)2, increasing with increasing pressure. Fourier transform infrared measurements were made to correlate the moduli to the silica speciation and network formation within the gels as a function of Ca(OH)2 content. Significantly, for the concentrations considered, both the interconnection of the silica species and the bulk modulus increased with increasing Ca(OH)2 content. On this basis, Brillouin scattering was confirmed to be a useful method for distinguishing between the bulk moduli of alkaline-calcium silica hydrogels in terms of chemical composition. The potential for further characterization of ASR gels as a function of composition and water content by this technique is highly promising.

A thin film of a stiff material, patterned as a serpentine on a flat elastomeric substrate, can elongate substantially when the substrate is pulled. We showed that the film elongates by twisting out of plane, accommodated by the compliance of the substrate and the pattern of the film. Consequently, large elongations of the substrate induce small strains in the film, even when the width of the film is much larger than its thickness. Such a wide serpentine, or other compliant patterns of stiff materials, can serve as a platform on which electronic circuits can be fabricated. This architecture will make electronics elastically stretchable.

High-temperature dilatometric studies on (Pb1−xCax)TiO3 (x = 0.35, 0.35, 0.40, 0.45) ferroelectric ceramics reveal negative thermal expansion for x ≤ 0.40. The negative thermal expansion coefficient for x = 0.30, as obtained by dilatometry and powder x-ray diffraction, were found to be −8.541 × 10−6 K−1 and −11 × 10−6 K−1, respectively, which are comparable to those of other well-known negative thermal expansion materials like ZrW2O8, NaZr2(PO4)3. Results of temperature-dependent x-ray diffraction studies are also presented to show that the large negative thermal expansion behavior for x = 0.30 persists in a very wide range of temperatures, 70–570 K. Ca2+ substitution reduces the value of the negative thermal expansion coefficient of pure PbTiO3 crystal, but it enables the preparation of strong sintered ceramic bodies. The negative thermal expansion behavior is shown to disappear above the ferroelectric Curie point and is restricted to only the tetragonal compositions of (Pb1−xCax)TiO3.

The fine-grain processing of ingot metallurgy (IM) Mg–Y–Zn alloy, WZ73, was investigated. The alloy was initially produced by casting into a copper mold at a cooling rate of ∼50 K/s. The rapidly quenched bulk material was processed by means of equal channel angular extrusion (ECAE). The ECAE-processed material had equiaxed grains of 5.1 μm in size, and fine second-phase particles of Mg12YZn were dispersed in the grain boundaries. The Vickers hardness of the ECAE-processed material was 78. The dispersion of the second-phase particles, solid solution strengthening, and grain refinement contributed to the material’s hardness. The structure remained virtually unchanged, at least up to 673 K because the Mg12YZn phase served to pin the grain boundaries. The microstructure of IM WZ73 alloy, which is a suitable starting material for ECAE, was also considered.

Raw and partially infiltrated carbon–carbon composite preforms have been scanned by high-resolution synchrotron radiation x-ray computerized micro-tomography. Three dimensional high-quality images of the pore space have been produced at two distinct resolutions and have been used for the computation of geometrical quantities: porosity, internal surface area, pore sizes, and their distributions, as well as local and average fiber directions. Determination of the latter property makes use of an original algorithm. All quantities have been compared to experimental data with good results. Structural models appropriate for ideal families of cylinders are shown to represent adequately the actual pore space.

The precipitate sequence in a 6022 aluminum alloy was investigated by means of differential scanning calorimetry (DSC), transmission electron microscopy, and Vickers hardness measurements. The solution-treated samples were quenched and then immediately subjected to DSC and isothermal aging experiments. It was observed that in the early stages of aging there are some unknown small precipitates that form prior to the formation of β″ precipitates. Studies on isothermally aged and DSC heated samples suggest that some of the β″ needles transform during growth to lath-shaped precipitates. An alternative precipitation sequence for AA6022 is proposed.

The unique capability of rendering opaque specimens transparent with atomic resolution makes transmission electron microscopy (TEM) an indispensable toolfor microstructural and crystallographic analysis of materials. Conventional TEM specimens are placed on grids about 3 mm in diameter and 10–100 μm thick. Such stringent size restriction has precluded mechanical testing inside the TEM chamber.So far, in situ testing of nanoscale thin foils has been mostly qualitative. Micro-electro-mechanical systems (MEMS) offer an unprecedented level of miniaturization to realize sensors and actuators that can add TEM visualization to nano-mechanical characterization. We present a MEMS-based uniaxial tensile experiment setup that integrates nanoscale freestanding specimens with force and displacement sensors, which can be accommodated by a conventional TEM straining stage. In situ TEM testing on 100-nm-thick freestanding aluminum specimens (with simultaneous stress measurement) show limited dislocation activity in the grain interior and consequent brittle mode of fracture. Plasticity at this size scale is contributed by grain boundary dislocations and partial dislocations.

We report on photoreduction of Ag+ in aluminoborate glasses induced by irradiation of a femtosecond laser. Novel fluorescence was observed in the femtosecond laser irradiated glass when excited by a 365 nm ultraviolet lamp. Optical absorption, emission, and electron spin resonance spectra of the glass samples demonstrated that after the laser irradiation, portions of silver ions near the focused part of the laser beam inside the glass were reduced to silver atoms, which resulted in the formation of the characteristic fluorescence. The observed phenomenon may have promising applications in the fabrication of functional optical devices.

Using an all-electron, full potential first-principles method, we have investigated the topology of charge density and elastic anisotropy of Ti3SiC2 polymorphs comparatively. By analyzing the charge density topology, it was found that the Ti–Si bonds are weaker in β than in α, resulting in a destabilizing effect and lower Young’s modulus in directions between a and c axes for β. On the other hand, the Si–C bonds (absent in α) are formed in β in the c direction. The formation of the Si–C bonds not only mitigates the destabilizing effect of the weaker Ti–Si bonds, but also results in larger Young’s modulus in the c direction. In contrast to the high elastic anisotrophy, the elastic anisotropy of Ti3SiC2 is very low.

We investigated the effects of elevated temperature vacuum annealing on the morphological stability and hardness of self-supported, textured, polycrystalline Cu–Nb nanolayered films with individual layer thickness varying from 15 to 75 nm. Films with layer thickness greater than approximately 35 nm are found to resist layer pinch-off and spheroidization even after long annealing times at 700 °C, while films with layer thickness ∼15 nm exhibit layer pinch-off and evolve into an equiaxed grain microstructure. Nanoindentation measurements indicate almost no change in hardness after annealing for films that retain the layered morphology, in spite of the increase of in-plane grain dimensions. Significant decreases in hardness are noted for films that develop a coarsened equiaxed grain microstructure after annealing. The mechanism that leads to the development of a thermally stable nanolayered structure is analyzed. Also, the relative effects of in-plane grain size and layer thickness on the multilayer hardness are discussed.

An Fe-doped ZnO particle/polymer hybrid was synthesized from zinc acrylate (ZA) and iron allylacetylacetonate (IAA) using methylhydrazine. Nanocrystalline ZnO particles were formed in the organic matrix by hydrolysis and polymerization of ZA itself below 100 °C. The crystallinity of undoped ZnO particles in the hybrid was dependent upon the synthesis conditions. Similarly, the ZnO phase was observed for the product formed from ZA-IAA. Transmission electron microscopy and energy-dispersive x-ray analysis revealed that crystalline ZnO nanoparticles doped with Fe were dispersed in the organic matrix. The absorption edge of the undoped ZnO particle/polymer hybrid was blue-shifted with the decrease in size of the ZnO particles. On the other hand, the Fe-doped ZnO particle/polymer hybrid from ZA-IAA revealed a bathochromic shift of the absorption edge up to 600 nm.

The high magneto-viscous response of magnetorheological fluids (MRFs) comes from the large size (≈1 μm) of the magnetic particles dispersed in the carrier liquid. Unfortunately, in the absence of a magnetic field, this large size constitutes the origin of some problems facing the technological applications of MRFs. These problems are (i) the instability of the suspensions caused by the fast settling of the high density magnetic particles used, and (ii) the poor redispersibility due to an irreversible aggregation. In this work, we used an electromagnetic induction method to study the stability of MRFs containing micron-sized iron particles dispersed in ferrofluids composed by oleate-covered magnetite nanoparticles dispersed in kerosene. Interestingly, we demonstrated that the sedimentation rate in iron/ferrofluid suspensions can be significantly lower than in iron/kerosene MRFs.

In the current work, a novel combustion method is demonstrated for the direct synthesis of nanocomposite materials. Specifically doped tin dioxide (SnO2) powders were selected for the demonstration studies due to the key role SnO2 plays in semiconductor gas sensors and the strong sensitivity of doped SnO2 to nanocomposite properties. The synthesis approach combines solid and gas-phase precursors to stage the decomposition and particle nucleation processes. A range of synthesis conditions and four material systems were examined in the study: gold–tin dioxide, palladium–tin dioxide, copper–tin dioxide, and aluminum–tin dioxide. Several additive precursors were considered including four metal acetates and two pure metals. The nanocomposite materials produced were examined for morphology, phase, composition, and lattice spacing using transmission and scanning electron microscopy, x-ray diffractometry, and energy-dispersive spectroscopy. The results using the combustion synthesis approach indicate good control of the nanocomposite properties, such as the average SnO2 crystallite size, which ranged from 5.8 to 17 nm.

We review recent advances in the growth of Si1−xGex islands and Ge dots on (001) Si. We first discuss the evolution of the island morphology with Si1−xGex coverage and the effect of growth parameters or post-growth annealing on the shape of the islands and dots. We outline some of the structural and optical properties of Si1−xGex islands and assess progress in the determination of their composition and strain distribution. Finally, we discuss various approaches currently being investigated to engineer Si1−xGex quantum dots and in particular to control their size, density, and spatial distribution. For example, we show how C pre-deposition on Si (001) can influence the nucleation and growth of Ge islands.