We used the topology optimization technique to obtain two-dimensional, isotropic cellular solids with optimal effective elastic moduli and effective conductivity. The overall aim was to obtain the best (simplest) manufacturable structures for these effective properties, i.e., single-length-scale structures. Three different but simple periodic structures arose due to the imposed geometric mirror symmetries: lattices with triangular-like cells, hexagonal-like cells, or Kagomé-like cells. As a general rule, the structures with the Kagomé-like cells provided the best performance over a wide range of densities, i.e., for 0 ≰ ф <0.6, where ф is the solid volume fraction (density). At high densities (ф > 0.6), Kagome-like structures were no longer possible, and lattices with hexagonal-like or triangular-like cells provide virtually the same optimal performance. The Kagomé-like structures were found to be a new class of cellular solids with many useful features, including desirable transport and elastic properties, heat-dissipation characteristics, improved mechanical strength, and ease of fabrication.

We synthesized carbon tubule nanocoils by catalytic thermal chemical vapor deposition. The iron catalyst necessary in the growth of carbon nanocoils was prepared only by coating the iron compound solution on indium tin oxide–coated glass substrate. It was found that the iron compounds have the same catalytic function as iron thin film prepared by evaporation or electroplating. Furthermore, the density of the prepared carbon nanocoils could be easily controlled by changing the density of the solution of iron compounds. In addition, the poly(methylphenylsilane) proved to be an excellent dispersive medium for the iron compound in preparation of the carbon nanocoils in desired densities.

The ductile-to-brittle transition was observed in a superplastic silicon nitride nanoceramic. This transition depends on strain rates and deformation temperatures. Generally, the material exhibits ductility at low strain rates and high deformation temperatures. At 1600 °C, the material is brittle when the strain rates are higher than 10−3/s. At a fixed strain rate of 10−3/s, the material exhibits brittleness when the temperatures are lower than 1550 °C. Moreover, critical strain rate for the brittle to ductile transition depends on deformation temperature. The critical strain rates increase with increases in the deformation temperature. When the deformation temperature is 1700 °C, the critical strain rates reach a maximum at 10−2/s. The extent of superplastic deformation in the present material was found to be limited not by intergranular cavitation but by the initiation and growth of surface cracks.

Computational fluid dynamic techniques were used to analyze the gas flow behavior of a typical atomization configuration. The calculated results are summarized as follows. The atomization gas flow at the atomizer's exit may be either subsonic at ambient pressure or sonic at an underexpanded condition, depending on the magnitude of the inlet gas pressure. When the atomization gas separates to become a free annular gas jet, a closed recirculating vortex region is formed between the liquid delivery tube and the annular jet's inner boundary. Upon entering the atomization chamber, an underexpanded sonic gas flow is further accelerated to supersonic velocity during expansion. This pressure adjustment establishes itself in repetitive expansion and compression waves. A certain protrusion of the liquid delivery tube is crucial to obtain a stable subatmospheric pressure region at its exit. The vortex flow under the liquid delivery tube tends to transport liquid metal to the high kinetic energy gas located outside the liquid delivery tube, thereby leading to an efficient atomization.

This report studies the electromigration performance of W-plug via structures under the reservoir effect. The lifetime improvement factor M was observed to be a weak function of the stressing current and approximately equal to 2. A Simple model is included in the report to explain this observation. The model also predicts the most effective reservoir length for electromigration lifetime improvement.

Strain rate is an important factor in plastic deformation because it determines the constitutive behavior of rate sensitive materials, e.g., dislocation density and flow stress evolution, deformation heat generation, etc. In the present study, the strain rate of workpiece materials during equal-channel angular pressing (ECAP) was evaluated by a geometric approach. The results were compared to those of the finite element analyses of a model ideally plastic material with various mesh sizes. The derived equation for strain rate is in reasonably good agreement with the results of the finite element method. The effects of the die geometry (a channel angle and a corner angle) were investigated. The strain rate during ECAP increases with punch speed and decreases with die channel angle, die corner angle, and the width of the workpiece. The relation obtained can be used for analytical calculations of the deformation, thermal, and microstructural evolution behavior of materials during ECAP. In particular, the size of the deforming zone and the effect of the finite element size are discussed.

The piezoelectric and dielectric properties of Pb(Zn1/3Nb2/3)O3 (PZN)-based ceramics were investigated. The perovskite structure of PZN ceramics was stabilized by the addition of Pb(Zn0.47Ti0.53)O3 (PZT). The highest piezoelectric properties were observed for the composition of 0.5PZN–0.5PZT, which lies on the two-phase zone of morphotropic phase boundary. For further improvements in electric properties, the specimens were thermally treated in a flowing O2 atmosphere at temperatures ranging from 860 to 1030 °C. The thermal treatment eliminated the PbO-rich amorphous intergranular layer by lead evaporation. As a result of this improvement in structure, the dielectric constant (ε′), the piezoelectric coefficient (d33), and the electromechanical coupling factor (kp), were enhanced markedly after thermal annealing at 960 °C for 8 h in an O2 atmosphere.

Cu47Ti34Zr11Ni8 amorphous gas atomized powders were consolidated by warm extrusion. After consolidation near 723 K using an extrusion ratio of 5, the material retains between 88% and 98% of the amorphous structure found in the gas atomized powder. The onsets of the glass transition and crystallization temperatures of this extruded material are observed respectively at slightly higher and lower temperatures than those of the starting powders. These temperature shifts are attributed to a composition change in the remaining amorphous phase during partial devitrification throughout the extrusion process. Powders extruded at the same temperature, but using higher extrusion ratios of 9 and 13, exhibit substantial devitrification during the consolidation process yet still deform homogeneously.

Ultrafine BaFe12O19 powder with crystallite sizes less than 200 nm was prepared via a citric acid precursor method. Citric acid was added into an aqueous solution, containing nitrates of Ba2+ and Fe3+ in a stoichiometric ratio to form barium ferrite, to chelate metallic ions in the solution. The pH of aqueous solutions was adjusted with NH4OH. After ethylene glycol was added into the solution and the system temperature was raised, esterification and dehydratation led to the formation of solid ester precursor. The distribution and contents of metallic ions in the ester are affected by the [citric acid]/[metallic ions] molar ratio used and the pH of starting solutions. When the ester-precursor obtained at pH = 9 with [citric acid]/[metallic ions] = 1.5 was used, crystalline BaFe12O19 appeared at temperatures as low as 923 K, and pure barium ferrite was obtained at 1073 K. According to the experimental results obtained, the reaction mechanism involved in the pyrolysis of esters is proposed and discussed.

Microstructure in the SrTiO3/Si system has been studied using high-resolution transmission electron microscopy and image simulations. SrTiO3 grows heteroepitaxially on Si with the orientation relationship given by (001)STO//(001)Si and [100]STO//[110]Si. The lattice misfit between the SrTiO3 thin films and the Si substrate is accommodated by the presence of interfacial dislocations at the Si substrate side. The interface most likely consists of Si bonded to O in SrTiO3. The alternative presentation of Sr and Si atoms along the interface leads to the formation of 2× and 3× Sr configurations. Structural defects in the SrTiO3 thin film mainly consist of tilted domains and dislocations.

Polyvinylsilane (PVS), derived from vinylsilane by radical polymerization, was partially oxidized in hot carbon tetrachloride solution by flowing air. If the air flow time is adjusted, soft gel films can be formed in a Teflon dish by casting the PVS solution. After the PVS films were peeled from the substrates, they were pyrolyzed at various temperatures. Spectroscopic studies of the pyrolyzed films up to 1273 K suggested that carbosilane (Si–CH2–Si) structures are formed in the films at 473–673 K. The compositions of the amorphous films obtained at 1673 K were approximately SiC1.38O0.21 and SiC1.41O0.51, depending on the crosslinking conditions. The oxygen incorporated in the films was removed in the form of CO and SiO during further heating at 1673–1873 K. The compositions of the films were changed to approximately SiC1.25 and SiC1.26, respectively, at 2073 K. The films obtained at 1273 K did not show degradation during the oxidation at 1273–1673 K while a protective silica layer was formed on their surfaces.

The reliability of coatings that are used in industrial applications critically depends on their mechanical properties. Nanoindentation and scratch testing are well-established techniques to measure some of these properties, namely the elastic modulus and hardness of coatings. In this paper, we investigate the possibility of also assessing the coating fracture toughness and the energy of adhesion between the coating and the substrate using indentation and scratch testing. Various existing and new methods are discussed, and they are illustrated by measurements on particle-filled sol-gel coatings on glass. All methods are based on the occurrence of cracking, and they are therefore only applicable to coating systems that act like brittle materials and exhibit cracking during indentation and scratching. The methods for determining the fracture toughness give comparable results, but the values still differ to within about 50%. The values of the adhesion energy obtained from different measurements are consistent, but it remains uncertain to which extent the obtained values are quantitatively correct. The results show that the methods used are promising, but more research is needed to obtain reliable quantitative results.

We used an Ising model to determine whether boundary mobility is an intrinsic material parameter or if it depends on the nature of the driving force for boundary migration. The simulations included both capillarity and external field-driven boundary migration. The external field-driven, flat boundary simulations showed that boundary mobility depends strongly on boundary inclination at low temperature but not at high temperature. On the other hand, the boundary mobility in capillarity-driven migration shows no dependence on boundary inclination and is independent of the boundary migration geometry. An initially circular grain shrinks as a circle and a half-loop boundary retracts with profiles predicted under the assumption that the boundary mobility is isotropic during capillarity-driven migration even when the temperature is very low and the external-field-driven boundary migration is extremely anisotropic. However, when an external field is superimposed on the capillarity driven migration of the circular boundary, the circular grain exhibits well-defined corners consistent with the simulation lattice symmetry. In this case, the boundary mobility is much different than if the external field were omitted. This is a clear demonstration that the boundary mobility can depend on the nature of the driving force for boundary migration.

To improve the strength of brazed joints, a TiN-coated layer was introduced as an interlayer and reaction barrier for ceramic-ceramic joints. Al2O3, Si3N4, and ZrO2 ceramics were brazed with a Ag–Cu–In–Ti alloy after a TiN coating was applied on the ceramic substrates. The strength of as-brazed and thermally treated Al2O3 specimens with a TiN coating was found to be equivalent to that of bulk Al2O3. However, the Si3N4 and ZrO2 systems showed a significant reduction in joint strength. The difference in the strength can be explained on the basis of the bond strength of the coating, the reaction products, and residual stress developed at the joint interfaces.