Yttria-stabilized zirconia (YSZ)-Au composite coatings have great potential as solid film lubricants for aerospace applications over a wide range of environmental conditions. They were grown on steel disks or silicon wafers by pulsed laser ablation of YSZ and simultaneous magnetron sputtering of a Au target. Such a combination of ceramics with soft metals improved the toughness of the composite coating and increased its ability to lubricate at high temperature. Information on the time-dependent response of these microstructures to changes in temperature is essential to tribological investigations of high temperature performance. In situ transmission electron microscopy was used to directly measure the dynamic change of YSZ-Au coating structure at elevated temperatures. High-resolution electron microscopy and electron diffraction showed that amorphous YSZ-5 at.% Au coatings proceeded to crystallize under the irradiation of electron beams. Time varying x-ray energy dispersive spectra measured a loss of oxygen in the sample during about 10 min of irradiation with subsequent slight oxygen recovery. This behavior was related to the activation of oxygen diffusion under electron irradiation. X-ray diffraction patterns from vacuum annealed samples verified crystallization of the coatings at 500 °C. Real-time growth of Au nanograins in the sample was observed as the temperature was increased to 500 °C in a TEM specimen holder that could be heated. The grain growth process was recorded using a charge-coupled device camera installed on the transmission electron microscope. The crystallization and growth of zirconia and Au nanograins resulted in low friction during tribological tests. The nucleation of Au islands on heated ball-on-flat specimens was responsible for lowering friction.

We demonstrated a facile route based on the use of acetone and polyvinylpyrrolidone (PVP) to prepare polystyrene (PS)/Ag/TiO2 multilayered colloids with controllable shell thickness. In this route, PVP absorbed directly onto PS colloid surface, and the Ag seed shell composed of Ag nanoparticles was synthesized directly under the PVP shell by swelling the surface layer of the PS core. Because the PVP shell increased the affinity of the Ag shell to TiO2, the hydrolyzed titania particles could deposit directly onto the core to form the outer TiO2 shell. A seed growth technique and the controllable hydrolysis reaction of tetra-n-butyl titanate were developed to grow the shell thickness of Ag and TiO2, respectively. Studies of the absorption properties indicate that the optical properties of these multilayered composite colloids can be modified by changing the coating species and shell thickness.

A preceding study of the competition between fracture modes in monolithic brittle materials in cyclic loading with curved indenters in liquid environments is here extended to brittle layers on compliant substrates. The fracture modes include outer and inner cone cracks and radial cracks that initiate from the near-contact zone and penetrate downward. Outer cone cracks are driven by stresses from superposed Hertzian and plate flexure fields; inner cone cracks also grow within these fields but are augmented by mechanical driving forces from hydraulic pumping into the crack fissures. Radial cracks are augmented by mechanical driving forces from developing quasiplasticity zones beneath the indenter. Basically, the crack-growth rates are governed by a crack velocity relation. However, the hydraulic and quasiplastic mechanical forces can cumulate in intensity with each cycle, strongly enhancing fatigue. Plate flexure generates compressive stresses at the top surface of the brittle layer, somewhat inhibiting the initiation, and tensile stresses at the lower surface, strongly enhancing the far-field propagation. The tensile stresses promote instability in the crack propagation, resulting in through-thickness penetration (failure). Experiments on a model bilayer system consisting of glass plates bonded to thick polycarbonate bases are presented as an illustrative case study. In situ observations of the crack evolution from initial growth to failure reveal that each fracture mode can dominate under certain test conditions, depending on plate thickness, maximum load, and sphere radius. Implications concerning the failure of practical layer systems, notably dental crowns, are discussed.

Microstructural changes induced by electromigration were studied in eutectic SnAg solder bumps jointed to under-bump metallization (UBM) of Ti/Cr–Cu/Cu and pad metallization of Cu/Ni/Au. Intermetallic compounds (IMCs) and phase transformations were observed during a current stress of 1 × 104 A/cm2 at 150 °C. On the cathode/substrate side, some of the (Cuy,Ni1−y)6Sn5 transformed into (Nix,Cu1−x)3Sn4 due to depletion of Cu atoms caused by the electron flow. It is found that both the cathode/chip and anode/chip ends could be failure sites. On the cathode/chip side, the UBM dissolved after current stressing for 22 h, and failure may occur due to depletion of solder. On the anode/chip side, a large amount of (Cuy,Ni1−y)6Sn5 or (Nix,Cu1−x)3Sn4 IMCs grew at the low-current-density area due to the migration of Ni and Cu atoms from the substrate side, which may be responsible for the electromigration failure at this end.

The crystallization kinetics and phase developments of PbO–BaO–SrO–Nb2O5–B2O3–SiO2-based glass-ceramics was investigated. Lead strontium barium niobate, (Pb,Sr,Ba)Nb2O6, with a tetragonal tungsten-bronze structure formed as the major crystalline phase, which showed evidence of both surface and bulk crystallization. The results of the present study showed significant evidence of a change in crystallization mechanism between the as-heated surface and the interior of glass-ceramics. This effect could be attributed to a volatilization of PbO taken place readily on the surface region of sample during heating. The grain size of the bulk-nucleated (Pb,Sr,Ba)Nb2O6 crystals was substantially smaller than that of surface-nucleated crystals. This result facilitated meeting the capacitors as high energy density application due to the ultrafine grains (<60 nm) obtained. The dielectric constant increased from 27 for the as-quenched glass to 200 for a highly crystallized glass-ceramic, which was attributed to a significant volume fraction of (Pb, Sr, Ba) Nb2 O6 phase.

Enthalpies of formation from constituent oxides and elements at 298 K were determined by high-temperature oxide melt solution calorimetry for a group of technologically important perovskites LaMO3 (M = Cr, Fe, Co, and Ni). The enthalpies of formation of LaCrO3 and LaFeO3 from oxides (La2O3 and Cr2O3 or Fe2O3) are –70.06 ± 2.79 kJ/mol and –64.58 ± 2.32 kJ/mol, respectively. The enthalpies of formation of LaCoO3 and LaNiO3 from oxides (La2O3 and CoO or NiO) and O2 are −107.64 ± 1.77 kJ/mol and –57.31 ± 2.55 kJ/mol, respectively. All these data are evaluated and found to be consistent with literature values obtained using other methods. The relative stability among these four perovskites decreases in the order of Cr, Fe, Co, Ni.

The structural characteristics of silver nanoparticles embedded in glass by various routes of fabrication were studied in detail using high-resolution electron microscopy to find out if they are influenced by interaction with the surrounding glass matrix. Besides the formation conditions, the strength of the interaction between metal and glass governs the size-dependent changes of lattice spacings in such nanoparticles. However, determination of these changes is not straightforward because of complicated particle configurations and the interference nature of the lattice imaging technique. Imaging of lattice plane fringes and careful diffractogram analysis allowed the exclusion of any kind of tetragonal lattice distortion or transformation to hexagonal lattice type that may be deduced at first sight. Instead, the formation of twin faults in these nanoparticles turned out to be the essential structural feature and the main source of confusion about the lattice structure observed. The variety of particle forms is comparable to particles supported on oxide carriers. It is composed of single-crystalline particles of nearly cuboctahedron shape, particles containing single twin faults, multiple twinned particles containing parallel twin lamellae, and multiple twinned particles composed of cyclic twinned segments arranged around axes of 5-fold symmetry. The more twin planes involved in the particle composition, the more complicated is the interpretation of lattice spacings and lattice fringe patterns due to superposition of several twin segments.

Compressive properties at 573–773 K of porous aluminum produced by the spacer method were investigated and compared with those of bulk reference aluminum with the same chemical compositions. The stress exponent and activation energy for deformation at elevated temperatures in the porous aluminum were in agreement with those in the bulk reference aluminum. In addition, the plateau stress of the porous aluminum was comparable to the stress of the bulk reference aluminum upon compensation by the relative density. Therefore, it is conclusively demonstrated that the mechanism of deformation at elevated temperatures in the porous aluminum is the same as that in the bulk reference aluminum. This is likely due to the homogeneous microstructure in the porous aluminum produced by the spacer method.

Using depth-sensing indentation with sub-nanometer displacement resolution, the plastic deformation of a range of materials, including a metallic glass, amorphous selenium, Ni3Al, pure Nb, Al, Cu, and Zn metals, and an Al-Mg alloy, has been investigated at room temperature. In amorphous selenium, even the sub-nanometer displacement resolution of the nanoindentation technique cannot reveal any strain burst during deformation at room temperature. In all other metals studied, what may appear to be smooth load-displacement curves at macroscopic scale during indentation deformation in fact turn out to consist of a continuous series of random bursts of the nanometer scale. The occurrence probability of the bursts is found to decrease at increasing burst size. In all of the crystalline metals and alloys studied, the size distribution of the strain bursts seems to follow an exponential law with a characteristic length scale. The absence of the self-organized critical behavior is likely a result of the small size of the strained volume in the nanoindentation situation, which gives rise to a constraint of a characteristic strain. In the metallic glass sample, due to the limited range of the burst sizes encountered, whether the deformation bursts follow an exponential or a power-law behavior corresponding to self-organized criticality is inconclusive. From a theoretical viewpoint based on the Shannon entropy, the exponential distribution is the most likely distribution at a given mean burst size, and this is thought to be the reason for its occurrence in different materials.

A novel, low-temperature synthesis method for producing BaxSr(1−x)TiO3 (BST) thin films patterned in the form of nanotubes (“honeycomb”) on Ti substrates is reported. In this two-step method, the Ti substrate is first anodized to produce a surface layer (∼300 nm thickness) of amorphous titanium oxide nanotube (∼100 nm diameter) arrays. In the second step, the anodized substrate is subjected to hydrothermal treatment in aqueous Ba(OH)2 + Sr(OH)2 at 200 °C, where the nanotube arrays serve as templates for their topotactic (shape-preserving) hydrothermal conversion to polycrystalline BST nanotubes. A simple geometrical model is proposed to elucidate the mechanism of the hydrothermal growth of BST nanotubes. This opens the possibility of tailoring the titanium oxide nanotube arrays and of using various precursor solutions and their combinations in the hydrothermal bath to produce ordered, patterned thin-film structures of various Ti-containing ceramics. These could find use not only in a variety of electronic, optoelectronic, and sensor device applications but also in biomedical and catalysis applications, where patterned thin films are desirable.

Gold nanocrystals were formed and grown in simultaneously polymerizing hybrid organic–inorganic films. For the preparation of Au containing films, tetraethyl orthosilicate and methacryloxypropyltrimethoxysilane were separately hydrolyzed and the resulting sols were mixed, followed by the addition of a photoinitiator and a NaAuCl4 solution in methanol. The resulting solutions were spin-coated onto glass-substrates, and the so-formed films were irradiated with a solar simulator at powers ranging from 200 to 800 W. The irradiation resulted in simultaneous polymerization of the films and formation of gold nanoparticles. The irradiated films were characterized by x-ray diffraction measurements, ultraviolet–visible optical absorption spectroscopy and transmission electron microscopy studies. After irradiation at 800 W, the transmission electron microscopy experiments showed the presence of homogeneously distributed Au nanoparticles with a size distribution ranging from 2 to 12 nm. The interpretation of the results indicates that the Au particle growth depends on the matrix polymerization rate; enhancing the rate by increasing the irradiation power or the photoinitiator concentration results in smaller particle domains. This result is explained referring to influence of the polymerization rate on the diffusion of gold species through the host.

The orientation and electrical properties of Pb(Zr,Ti)O3 thin films deposited on a Pt/Ti/SiO2/Si substrate using lanthanum nickel nitrate as a conductive buffer layer were analyzed. The lanthanum nickel nitrate buffer layer was not only electrically conductive but also effective in controlling the texture of the lead zirconate titanate (PZT) thin film. The role of the lanthanum nickel nitrate buffer layer and its effects on the orientation of the PZT thin film were analyzed by x-ray diffraction, electron beam back-scattered diffraction, and scanning electron microscopy. The annealed lanthanum nickel nitrate buffer layer was sufficiently conducting for use in longitudinal electrode configuration devices. The dielectric, ferroelectric, and piezoelectric properties of the highly (100) oriented PZT films grown with the lanthanum nickel nitrate buffer layer were measured and compared with those of (111) and (100) oriented PZT films deposited without a buffer layer.

Oxygen uptake and conductivity were measured by nuclear-reaction analysis and alternating current impedance technique at the intermediate temperature range on sol-gel grown nanocrystalline ceria films with average grain-sizes 7 nm and 38 nm synthesized at 723 and 1173 K, respectively. Higher oxygen uptake and lower ionic conductivity were observed in ceria films with ∼7-nm grain size. High permeation-assisted oxygen diffusion in nanocrystallites combined with oxygen trapping in the disordered region contributed to higher oxygen uptake. However, the lower ionic conductivity in the film resulted from the absence of long-range lattice ordering and inactive grain-boundary/surface oxygen vacancy sites due to oxygenation. The relationship between oxygen uptake and conductivity in ceria is discussed in details by considering grain-size dependent defect density, related surface area, and enhanced oxygen mobility.

Agglomerates of aligned crystals of CaxCo2O4 with a layer of CoO2 were grown using a chloride flux technique, and their thermoelectric properties in air were determined. The agglomerates take the form of a very thin flakelike cluster of crystals with a typical size of almost 3 × 2 × 0.07 mm. The values of thermoelectric power along the ab-plane are larger than 200 μV K−1 at temperatures above 873 K and reach almost 300 μV K−1 at 973 K. The temperature dependence of the electrical resistivity along the ab-plane shows bends around 450 and 825 K, and the ln ρab−T−1 curve followed an Arrhenius-type behavior below 450 K. Temperature dependence of thermal conductivity indicated that stacking faults along the c axis induce phonon scattering like that in a misfit-layered structure. The effect of the CoO2 layer on thermoelectric performance is discussed in comparison with related compounds.

Fatigue damage in 200-nm-thick Cu films was investigated and compared with the damage in thicker Cu films. The fatigued 200-nm-thick Cu films exhibited only a few, small extrusions and extensive cracking along twin and grain boundaries, whereas the thicker films showed many extrusions/intrusions and cracks lying along the extrusions rather than along the boundaries. This change in fatigue damage behavior with film thickness is attributed to the inhibition of dislocation mobility and the limited availability and activation of dislocation sources on the small length scale. It is argued that the decrease in film thickness and grain size inhibits the localized accumulation of plastic strain within grains, such as at extrusions/intrusions and in extended dislocation structures, and promotes the formation of damage such as cracks at twin and grain boundaries during fatigue. This effect is suggested as the likely cause for the increase in fatigue life with decreasing specimen dimensions.

Various shapes and sizes of colloidal Co nanoparticles were fabricated by the polyol process using Co(acac)3, 1,2-hexadecanediol, oleylamine, and oleic acid within octylether. The rice-shaped Co nanoparticles with size of 30 nm and aspect ratio of 1.8 can be fabricated into a self-assembled form without assistance of surfactants. The addition of oleylamine as surfactant decreased the particle size and aspect ratio, and the addition of oleic acid made the surface of particle faceted without decreasing particle size from that of rice shape. The mixture of oleylamine and oleic acid produce differently shaped Co nanoparticles, including nanoprism, nanowire, and nanoflower according to the ratio of components, total amount of surfactant mixture, and reaction time. The fabricated nanoparticles showed ferromagnetic properties. These results showed that the various size and shape of metallic nanoparticles can be fabricated by the polyol process into controlled forms.

The coarsening behavior of the Pb-rich phase particles in 63Sn–37Pb (wt%) solder was investigated following isothermal annealing treatments. Samples were exposed to cooling rates of 0.1, 1.0, 10, and 100 °C/min. Annealing temperatures were 25, 55, 70, 85, and 100 °C, and times were 2–100 days. The mean particle diameter decreased from 1.8 × 10−3 to 0.8 × 10−3 mm with increased cooling rate, indicating two solidification regimes: one for cooling rates ≤1 °C/min and the other for cooling rates of ≥10 °C/min. The Pb-rich phase particles coarsened more quickly in samples made at the two fastest cooling rates. There was little Pb-rich phase particle coarsening at 25 and 55 °C for all annealing times. Coarsening rate kinetics were examined specifically for the 10 and 100 °C/min data using the expression Atnexp[−ΔH/RT]. The values of n were 0.23 ± 0.11 and 0.36 ± 0.13, respectively; n was not sensitive to annealing temperature. The corresponding 1/n values indicated that the coarsening mechanism changed from a fast diffusion to a bulk diffusion controlled process with a faster cooling rate. The apparent activation energy ΔH ranged from 16 ± 8 to 41 ± 8 kJ/mol; the values increased with cooling rate from 10 to 100 °C/min. The ΔH value was sensitive to annealing temperature only for the faster cooling rate of 100 °C/min. Together, the n and ΔH values indicated that an accelerated, fast diffusion mechanism with low activation barriers characterized the Pb-rich phase coarsening in samples exposed to a slower cooling rate, greater annealing, or a combination of the two conditions. That mechanism likely originated from the in situ development of recover/recrystallization microstructures in the Sn-rich phase. At faster cooling rates, those microstructures were not as well developed, so coarsening was controlled more by the higher activation barriers of bulk diffusion processes.

Ferroelectric and dielectric properties of niobium-doped Sr2Bi4Ti5O18 ceramics were investigated. Compared with the undoped ceramics, the niobium-doped ceramics exhibited obviously increased remnant polarization 2Pr, which is similar to the case of vanadium doping. However, the mechanisms of increasing of 2Pr by vanadium and niobium doping are quite different. In the case of Nb-doping, one relaxation peak P1 is found on the dielectric loss curves D(T) at 70 °C. The dependence of the peak on various annealing atmosphere indicates that the relaxation mechanism of the peak is related to oxygen vacancies. With niobium doping, the P1 peak declines gradually. These results suggest that the substitution of Ti4+ by a small amount of Nb5+ can result in the decreasing of the concentration of oxygen vacancies. Thus, the increase in 2Pr of Nb-doped Sr2Bi4Ti5O18 could be attributed to the significant weakening of defect pinning.

A unique straining device, fabricated using microlithographic techniques, has been developed to permit real-time investigation in the transmission electron microscope (TEM) of the deformation and failure mechanisms in ultrafine-grained aluminum. The tensile specimen is a freestanding thin film with a columnar microstructure that has a uniform cross-section (100 × 0.125 μm) and a gauge length of 300 μm. In situ TEM straining experiments show the fracture mode is intergranular with no accompanying general plasticity. Propagating cracks were halted at large grains, and crack blunting occurred through grain-boundary-mediated processes. The blunting process was accompanied by dislocation emission and deformation twinning in the grain responsible for arresting the crack. Voids or microcracks nucleated and grew on grain boundaries ahead of the arrested crack, and crack advance occurred through linkage of the microcracks and the primary crack.

The single-step synthesis and densification of the WC–6Co cemented carbide starting from elemental powders was obtained by the spark plasma sintering (SPS) technique. The operating conditions that guarantee the complete conversion of the reactants to the desired full dense material have been identified. Specifically, under the application of 800 A and a mechanical pressure of 40 MPa for about 200 s, a product with relative density higher than 99%, hardness of 14.97 ± 0.35 GPa, and 12.5 ± 1.0 MPa m0.5 fracture toughness was obtained. A kinetic investigation of the SPS process was also performed. It revealed that an intermediate phase, i.e., W2C, is the first carbide formed during the carburization process. It was observed that the synthesis and sintering stages take place simultaneously. It was also found that as the applied pulsed current intensity was augmented, the synthesis/sintering time required decreased significantly.