A notched bimaterial bar bend test was applied to identify weak interfaces that influence the thermomechanical performance of solid-oxide fuel cell (SOFC) stacks with planar design. The experiments were focused on the weakest interface of the multilayered cells and on the rigid glass ceramic sealants between metallic interconnects of SOFC stacks. The fracture energies of these interfaces were determined. To test interfaces within the cells, they were glued to steel strips, and the notched cell was used as a stiffener in the test. The weakest part of the cells with composite cathodes was the interface between the functional part of the cathode and the remaining current collector. Values for the interfacial fracture energies of composite cathodes both freshly prepared and after aging were determined. Taking advantage of the crack extension within the anode from the notch-tip to the interface, the fracture energy of the oxidized and reduced anodes was calculated. Sandwich specimens with glass ceramic between the interconnect steel were used to determine the fracture energies for different glass ceramic–steel interfaces. Different combinations of ferritic steel and glass ceramic were tested. The fracture path developed partly along the interface and partly in the glass ceramic, which did not influence the fracture energy. However, a significant improvement of the fracture energy with annealing time was found.

An analytical expression was derived to predict the heating profile that minimizes the cycle time for the thermal removal of binder from porous green ceramic bodies. The analytical equation was based upon the solution to a three-dimensional convective transport equation that describes flow in porous media arising from the thermal decomposition of binder. The solution to the transport problem was then combined with an algorithm derived from variational calculus. The analytical expression described the time for binder removal in terms of the body dimensions, isotropic permeability, volume fraction of binder, and threshold pressure within the green body.

Nb2O5 was added to buried resistors for low-temperature cofired ceramics, and the electrical properties of the resultant resistors were examined. Remarkable increases in electrical resistivity and attractive decreases in the temperature coefficient of resistance (TCR) were observed by the addition of Nb2O5, which was attributed to the high solubility of Nb2O5 into the PbO-SiO2-Al2O3 matrix glass. With higher dissolved contents of Nb2O5 into the glass, the resistivity of buried resistors increased by approximately six-fold magnitude, while TCR decreased substantially toward zero. It was indicated that the conductance for these buried resistors was limited by tunneling of charge carriers through the thin glass layer penetrating into the ruthenium-oxide agglomerates. A larger separation observed between RuO2 particles due to high solubility of Nb2O5 in the glass increased the charging energy (E) and lump term (Rbo), which in turn gave rise to a higher resistivity and a lower TCR value.

Metals and alloys processed by severe plastic deformation (SPD) can demonstrate superior mechanical properties, which are rendered by their unique defect structures. In this investigation, transmission electron microscopy and x-ray analysis were used to systematically study the defect structures, including grain and subgrain structures, dislocation cells, dislocation distributions, grain boundaries, and the hierarchy of these structural features, in nanostructured Ti produced by a two-step SPD procedure—warm equal channel angular pressing followed by cold rolling. The effects of these defect structures on the mechanical behaviors of nanostructured Ti are discussed.

Kaolinite mixed with calcite was sintered at low temperature (1100 °C; 5 °C/min). The successive phase transformations are metakaolinite to gehlenite and then anorthite, although the available phase diagram indicates a direct anorthite recrystallization. Transmission electron microscopy and electron diffraction studies of nanocrystallites revealed that the transformation path is favored by the structural similarities of phases. In particular, the pseudolayers of gehlenite have a major orientation relationship with the initial metakaolinite layers. The gehlenite axis, [001]G, is parallel to the metakaolinite axis, [001]A. This direct transition is favored by the existence of Si tetrahedral units and 4–fold–coordinated Al in both structures. Ca atoms, initially in the interlayer spacing of metakaolinite, remain in the interlayers of gehlenite. During the second transformation step, anorthite recrystallizes from gehlenite with axis [020]A parallel to [210]G. It is proposed that this orientation relationship is favored by the orientation and shape of Ca-atom channels through both structures, along [001]G and [100]A axes.

The past impossibility to create optical diffraction fringe image out of transparent TiO2(100) substrate was overcome by pumping light pulse of 266-nm wavelength. Thermal diffusivities (D) of TiO2(100) substrate and (Ca1–xSrx)3Co4O9 (0 ≤ x ≤ 0.125) thin films can successfully be determined with a newly proposed transient grating configuration method arising from a generic nanoscale measurement technique. The D values obtained at room temperature were 0.04 cm2/s for the former and 0.07–0.12 cm2/s for the latter, respectively.

Preparation of dense and phase-pure Ba2Ti9O20 is generally difficult to achieve using solid-state reaction, since there are several thermodynamically stable compounds in the vicinity of the desired composition. This study investigated the effects of B2O3 on the densification, microstructural evolution, and phase stability of Ba2Ti9O20. Samples from the host material (2BaO · 9TiO2) with and without the addition of 5 wt% B2O3 were prepared through different processing routes. For the pure host material sintered at temperatures ranging from 800 to 1100 °C, the reaction products followed the sequence of BaTi2O5 → BaTi4O9 → BaTi5O11 → Ba2Ti9O20. The phase transformation proceeded faster in the bulk compared to the free surface of the sample. BaTi5O11 and BaTi4O9 with a minor amount of Ba2Ti9O20 were found in the ground powder of ceramics sintered at 1100 °C. For the samples prepared from host material with the addition of 5 wt% B2O3, Ba2Ti9O20 started to form at temperatures as low as 800 °C. The sequence of reaction products followed Ba4Ti13O30 → BaTi4O9 → BaTi5O11 → Ba2Ti9O20. Sintering at above 1000 °C yielded pure Ba2Ti9O20 phase, suggesting the effective role of B2O3 on the phase stability of Ba2Ti9O20. It was found that precalcination of host material before the addition of B2O3 gives an additional benefit to the Ba2Ti9O20 formation. Crystallization of pure Ba2Ti9O20 phase was completed at a sintering temperature as low as 900 °C without any solid solution additive such as SnO2 or ZrO2, due to the fact that the phase transformation of the samples began with BaTi4O9 and BaTi5O11 during sintering. Also, B2O3 was found to be unstable during the high-temperature sintering at 1200 °C, and the results are discussed.

ZnO nanowires with diameters of 40–200 nm were grown with a gold catalyst in bulk quantities on alumina substrates and sapphire substrates. This synthesis procedure was achieved by heating a 1:1 mixture of ZnO and Zn powder to 500 °C with trace water vapor as an oxidizer. X-ray diffraction and transmission electron microscopy revealed that the nanowires were in the pure wurtzite phase. Photoluminescence spectroscopy showed two peaks: one was a strong ultraviolet emission at around 380 nm, which corresponds to the near-band-edge emission; the other was a weak near-infrared emission around 750 nm, which indicates a low concentration of oxygen vacancy. Moreover, we observed that the Zn/Au alloy droplets appeared on the tips of ZnO nanowires. As a consequence, we can select areas to grow ZnO nanowires by patterning the thin metal film on the substrates. These findings prove that the low-temperature growth mechanism is via vapor–liquid–solid rather than vapor transport deposition or vapor supersaturation (vapor–solid) mechanism. On the basis of the site-specific growth and the low-temperature requirement developed from this work, the synthesis of ZnO is compatible to microelectric machining system processing.

Ni-based under-bump metallization (UBM) for flip-chip application is widely used in today's electronics packaging. In this study, electroplated Ni UBM with different thickness was used to evaluate the interfacial reaction during multiple reflow between Ni/Cu UBM and eutectic Sn–Pb solders in the 63Sn–37Pb/Ni/Cu/Ti/Si3N4/Si multilayer structure. During the first cycle of reflow, Cu atoms diffused through electroplated Ni and formed the intermetallic compound (IMC) (Ni1−x, Cux)3Sn4. After more than three times of reflow, Cu atoms further diffused through the boundaries of (Ni1−x, Cux)3Sn4 IMC and reacted with Ni and Sn to form another IMC of (Cu1-y, Niy)6Sn5. After detailed quantitative analysis by electron probe microanalysis, the values of y were evaluated to remain around 0.4; however, the values of x varied from 0.02 to 0.35. The elemental distribution of IMC in the interface of the joint assembly could be correlated to the Ni–Cu–Sn ternary equilibrium. In addition, the mechanism of (Cu1−y, Niy)6Sn5 formation was also probed.

A uniform deposition of a Sn–Zn alloy deposit was achieved by pulse plating. Apparently, the relative composition of Sn and Zn in the deposit was affected by the bath compositions and pulse condition. A pulse-plating condition of 99.9 ms on-time and 1.0 ms off-time gave rise to a eutectic Sn–Zn deposit, with a eutectic temperature of 198.8 °C (as analyzed by differential scanning calorimetry) and a uniform composition distribution across the deposit. A mechanism for explaining the pulse-deposition behavior of the Sn–Zn eutectic deposit was proposed. A longer off-time period, 99.9 ms versus 0.1 ms, resulted in a nodular, yet thinner deposit.

The contact formed between aluminum and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT-PSS) derivatives was studied using x-ray photoelectron spectroscopy. The aluminum/PEDOT-PSS contact contains an interfacial layer formed by chemical reactions between aluminum and mainly poly(styrenesulfonic acid) (PSSH). These chemical interactions were studied with the help of model systems (PSSH, benzenesulfonic acid, and sodium benzenesulfonate). The preferred reaction site of aluminum is the SO3− and SO3−H+ groups of the PSS chains, giving rise to C-S-Al(-O) and C-O-Al species. The resulting contact formed consists of an insulating aluminum/PSS layer and a thin region of partially dedoped PEDOT-PSS. There is significant aluminum diffusion into films of the highly conducting form of PEDOT-PSS that have substantially less PSS at the surface. Hence, no (thick) aluminum/PSS layer is formed in this case, though the PEDOT chains close to the aluminum contact will still be partially dedoped as for the aluminum/PEDOT-PSS case.

We studied the thermal shock resistance of a silicon nitride containing elongated and preferentially aligned grains with different volume fractions of pores, ranging from 0 to 0.27. It was found that an increase in the volume fraction of pores decreased both the strength and the temperature through which the sample must be quenched to cause cracking. However, at intermediate values of the porosity (0.07), the temperature change required to cause cracking was much smaller than predicted. Observations of the resulting damage suggested that this had occurred because of the formation of cracks just underneath and parallel to the cooled surface of the sample that were able to change the direction of their growth. The extent of cracking was found to be only very weakly dependent on the volume fraction of pores, consistent with calculations of the variation of crack driving force within the sample.

(La, Sr)(Al, Ta)O3 (LSAT) has recently received increased attention as a substrate for the deposition of various oxide films. LSAT is usually considered as having a perovskite structure. However, the exact atomic structure of LSAT is not yet well known and has received little attention up to now. In this paper, a series of studies using x-ray diffraction, transmission electron microscopy, and energy dispersive spectrometry were conducted to determine the atomic structure of LSAT. It was found that LSAT consists of two types of domains: one with a simple cubic perovskite structure (disordered with a = 0.3868 nm) and the other with a face-centered-cubic structure (ordered with a = 0.773 nm). Computer image simulation of high-resolution lattice images suggests that the ordered structure is due to ordering of the Al and Ta ions.

This paper presents an optical mean to probe carefully the strain field generated by a microindentation on [111]-oriented GaAs sample, using micro-Raman spectroscopy and microphotoluminescence spectroscopy. Raman and photoluminescence signals recorded from the same point of the sample are directly compared. The frequency shift of the longitudinal and transverse optical phonons was analyzed in great detail, revealing unambiguously the presence of both compressive and tensile strains within the indented area. Outside the indentation fingerprint, the magnitude of strain deduced from luminescence measurements was found to be lower than the one determined by Raman scattering. The Raman spectra revealed significant variations of the optical phonons polarizability with the deformation. Finally, atomic force microscope images of the indented zone aid in the interpretation.

Fine whiskers of a C60 derivative, i.e., C60 monosubstituted by ethyl ester of malonic acid, C60[C(COOC2H5)2], were fabricated for the first time using a system of toluene with concentrated C60[C(COOC2H5)2] and isopropyl alcohol. The center-to-center distance of C60[C(COOC2H5)2] molecules along the close-packed direction of the C60[C(COOC2H5)2] whiskers was in the same range as that of the C60 nanowhiskers prepared by the same method. The C60[C(COOC2H5)2] whiskers were assumed to take body-centered tetragonal or hexagonal close-packed crystal structures. The C60[C(COOC2H5)2] whiskers showed a high density of stacking faults. The C60[C(COOC2H5)2] whiskers with the growth direction different from the C60 whiskers were observed.

Two sol-gel derived zirconia powders were prepared at pH = 0.5 and pH = 5.5. They were investigated as a function of temperature using mainly perturbed angular correlation spectroscopy. The aim was to elucidate the relationship between the nanoscopic configurations around Zr4+ ions and the morphology and structure of the powders. The highly porous material resulting from the solution at higher pH could be described mainly by defective and disordered, very hydrolyzed tetragonal arrays. As temperature increased, the amount of these arrays decreased while they became increasingly asymmetric, thus suggesting their superficial localization. The easy removal of hydroxyls led to the early appearance of the monoclinic phase. The gel obtained from the precursor at pH = 0.5 was entirely described by configurations still involving organic residues. After their calcination, the powder underwent a well-defined two-step hydroxyl removal thermal process leading to the crystallization of the tetragonal and the monoclinic phases. The thermal stability of the metastable tetragonal phase in the investigated powders seems to be controlled by their different capability to absorb oxygen.

The effects of soft adhesive interlayers on contact-induced radial cracking in brittle coatings on supporting substrates were investigated recently. A semiempirical equation for the critical load to initiate radial cracking was derived, which used three fitting parameters obtained by comparison with the finite element results. An analytical model is derived in the present study to illustrate the effects of adhesive interlayers. This is achieved by adopting the analogy between the coating/substrate system and a plate on an elastic foundation. In the presence of an adhesive interlayer, the interlayer/substrate bilayer is treated as the effective elastic foundation. The effective modulus of foundation for the bilayer is derived, and the solution for coating/interlayer/substrate systems can be obtained from the existing solution for coating/substrate systems by replacing the modulus of foundation. Specific results are calculated for critical loads to initiate radial cracks in silicon coatings bonded by adhesive interlayers of different materials and thicknesses to glass substrates. The present analytical solution provides an alternative other than the existing semiempirical equation in predicting the effects of adhesive interlayers.

A modified high-temperature arc furnace was used to produce carbon nanotubes from carbon black by a solid-state transformation without a catalyst. The layer of carbon nanotubes thus formed was nearly pure with only a minor amount of carbon black particles. The properties of these nanotubes were found to be very similar to those produced by the conventional arc synthesis. Based on this process, a mechanism for the growth of these nanotubes is proposed. In addition, field-emission properties of these nanotubes were comparable to the properties of arc-grown carbon nanotubes.

Following the finite element simulations in our earlier work about the contact deformation regimes, mathematical formulations were derived to correlate hardness and the amount of pileup and sinking-in phenomena around sharp indenters with uniaxial mechanical properties. The formulations are applicable regardless of the deformation regime ruling the contact response of a strain-hardening solid. A methodology was devised where the use of these formulations in mechanical property assessments from indentation experiments was demonstrated. The current results make contact with existing methodologies using the II-theorem in functional analysis to extract uniaxial properties from instrumented indentation load depth of penetration curves. It is argued that since surface deformation is an essential feature of the contact response, it enters directly or indirectly in such existing methodologies. The paper considers how independent knowledge of surface deformation can be used to guide mechanical property assessments from load-depth of penetration curves. A discussion on the uniqueness of mechanical characterizations through indentation experiments is also provided.

The Pr55–xAl12+xFe33–yCuy (0 ≤ x ≤ 5, 0 ≤ y ≤ 8) bulk metallic glasses (BMGs) 5 mm in diameter and 100 mm in length were prepared by copper mold suction casting. Hysteresis loops of the Pr55–xAl12+xFe33–yCuy BMGs and the corresponding Pr55Al12Fe30Cu3 crystallized alloy were measured, and the results showed that the Pr55–xAl12+xFe33–yCuy BMGs are hard magnetic, while the completely crystallized Pr55Al12Fe30Cu3 alloy is paramagnetic at room temperature. The thermal behavior and crystallization of the Pr55Al12Fe30Cu3 BMG were studied by differential scanning calorimetry, and the results indicated that the Pr-based BMG has obvious glass transition and a wide supercooled liquid region up to 75 K. The crystallization activation energy for the Pr55Al12Fe30Cu3 BMG is much smaller than that of Zr–Ti–Cu–Ni–Be BMG.