The interfacial intermetallic formation at 150 °C between Cu and various solders, including Sn–9Zn, Sn–8.55Zn–1Ag, and Sn–8.55Zn–1Ag–XAl was investigated. The Al contents X of the quaternary solder alloys investigated were 0.01–0.45 wt.%. The compositions and the growth kinetics of intermetallic compounds (IMCs) were investigated. The IMC consisted of three layers for Sn–9Zn/Cu, Sn–Zn–Ag/Cu, and Sn–Zn–Ag–XAl/Cu specimens after aging for 100–600 h. These three layers included the Cu3(Zn, Sn) phase adjacent to the solder, the Cu6(Sn, Zn)5 phase in the middle, and the Cu–rich phase near to Cu. For long–term aging time over 1000 h, the Cu6(Sn, Zn)5 phase grew, while the Cu3(Zn, Sn) phase diminished. Al segregation formed in the IMC for all of the Sn–Zn–Ag–XAl/Cu specimens after aging.Cracks formed, when aged for 1000 h, at the solder/IMC interface or within the IMC layer for the following solders: Sn–9Zn, Sn–8.55Zn–1Ag, Sn–8.55Zn–1Ag–0.1Al, Sn–8.55Zn–1Ag–0.25Al, and Sn–8.55Zn–1Ag–0.45Al. The crack was not detected up to 3000 h for the Sn–8.55Zn–1Ag–0.01Al/Cu couple, of which the IMC growth rate was the slowest among all solders.

Static-gap, single-spark tests were used to investigate the arc erosion behavior of newly developed silicon carbide and alumina particle reinforced silver matrix composites (SiCp/Ag, Al2O3p/Ag). Craters and hills exist on the surfaces of eroded silver matrix composites, and their depths and sizes decrease as the particle content increases and the particle size decreases. Obvious melting, flow, severe splash of molten silver, and the segregation of particles are present on the surfaces of eroded composites containing low volume percents of large particles. Easier silver flow results in smooth surfaces and reduces the total surface areas of the eroded composites containing large particles. The flow and splash of silver decreased with increasing particle content and decreasing particle size, exhibiting a better erosion resistance to single-spark tests. The static-gap, single-spark erosion behavior of silver matrix composites is dominated by the flow and splash of molten composites. A high viscosity of the liquids provides the composites a good arc erosion resistance.

A phase of new bichromatic (green, red) phosphor Ca2Al3O6F:Eu(III), was found to grow in a small fraction along with Ca5(PO4)3F:Eu(III) phase if aluminum is previously added to the reaction mixture of the latter and flourish to a sizable concentration on subsequent heat treatment. The luminescence spectrum of the as-prepared sample, where Ca5(PO4)3F:Eu(III) is the dominant phase, shows a strong band at 612 nm along with a series of less intense bands at 573, 584, 644, and 692 nm due to different 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions and indicates that the presence of aluminum in the system forces the Eu(III) ions to occupy exclusively one type of site rather than multiple types of sites. As the aluminate phase grows, a strong green emission band around 520 nm due to the 5D2 → 7F3 transition of Eu(III) occurs concomitant with a splitting of almost all the 5D0 → 7FJ bands. The excitation spectrum of the green emission (520 nm) shows a strong absorption band at 393 nm, and the electron spin resonance spectrum of this material shows existence of a fluorine-related hole center of (F2n)− type in the matrix. It is argued that the (F2n)− holes are localized in the interstitial of the Ca2Al3O6F phase near the calcium-substituted Eu(III) ions to maintain the charge balance and form a complex with the latter, which plays a vital role in the process of green emission.

Ultrafine SiC and Al2O3 particles with 30–50 nm sizes were used to codeposit with Ni in a sulfamate bath to form composite coatings. The microstructure and mechanical properties of the layers were investigated by x-ray diffractometry, scanning and transmission electron microscopy, high-resolution transmission electron microscopy, microindentation, and wear testing. The microstructural results revealed that 7 vol% of SiC or Al2O3 particles dispersed randomly in the Ni matrix. The addition of the ultrafine SiC or Al2O3powder into the Ni matrix apparently reduced the size of Ni grains during the electroplating and inhibited the grain growth during heat treatment. The microhardness and wear resistance were improved by the addition of SiC and Al2O3 particles, especially for SiC/Ni samples after heat treatment at 400 °C for 24 h. The mechanisms of hardening and wearing of Ni-based electroplated layers are discussed.

Using anodic oxidation with a time-dependent linearly varying anodization voltage, we have made films of tapered, conical-shaped titania nanotubes. The tapered, conical-shaped nanotubes were obtained by anodizing titanium foil in a 0.5% hydrofluoric acid electrolyte, with the anodization voltage linearly increased from 10-23 V at rates varying from 2.0-0.43 V/min. The linearly increasing anodization voltage results in a linearly increasing nanotube diameter, with the outcome being an array of conical-shaped nanotubes approximately 500 nm in length. Evidence provided by scanning electron-microscope images of the titanium substrate during the initial stages of the anodization process enabled us to propose a mechanism of nanotube formation.

Transformation kinetics of mullite formation in kaolin–Al2O3 ceramics was studied by x-ray diffraction, transmission electron microscopy, and energy dispersion spectrometry. The mullitization process of kaolin–Al2O3 ceramics is described by two stages; one is the primary mullite transformation at 1273 to 1573 K, and the other is the secondary mullite formation at 1573 to 1873 K. The activation energy of 1164.6 kJ mol-1 obtained for the secondary mullite formation is lower than 1356.9 kJ mol-1 for the primary mullite transformation by the general form of the Johnson–Mehl–Avrami equation. The lower value of growth morphology parameter strongly supports that in the secondary mullite formation the added alumina is dissolved into glassy phase and the mullite is then precipitated.

This study investigated the characteristics of the intermetallics that appear in Sn–Zn–Ag solder alloys, particularly their behavior in molten solder during cooling and remelting. The results indicated that the intermetallics, which deplete the Zn-rich phase, were present in the form of inhomogeneous dendrites and consisted of two intermetallic phases, ε–AgZn3 and γ–Ag5Zn8. These Ag–Zn intermetallics formed as the primary dendrites upon cooling from temperatures slightly below 300 °C. These intermetallics transformed into coarse nodules with a stable, high Ag-content phase when isothermally heated at 250 °C. These massive intermetallic particles tended to settle at the bottom of the melt due to low buoyancy. Isothermal heating at slightly above 300 °C resulted in the rapid melting of these intermetallics. Subsequent quenching caused numerous fine dendritic intermetallics to form throughout the solder.

The four-point bend test was used to measure the brittle-to-ductile transition (BDT) temperature in precracked samples of semi-insulating 4H—SiC at four different strain rates. As in other semiconductors, the BDT temperature TBDT was found to be very sharp, within ±15 °C, and to shift to higher temperatures with increasing rates of the applied load (or strain rate). The results appear to be consistent with a transition temperature Tc recently observed in the yield stress of the same material as measured by compression experiments. However, strain-rate measurements in four-point bend tests are not strictly equivalent to those in compression experiments, and therefore it is difficult to directly compare the measured BDT temperatures with the yield stress transitions. Nevertheless, it is believed that the reasonable agreement between TBDT and Tc supports the model recently proposed to explain these transition temperatures.

The growth of nickel oxide (NiO) on {100}〈001〉 cube textured, rolling-assisted biaxially textured substrates (RABiTS) of pure nickel was studied. Single-phase (100) NiO formed only in a narrow temperature range at 1250 ± 5 °C. At lower or higher temperatures, other orientations, namely (111), (311), and (220), also formed. At 1250 °C, practically single phase (100) NiO was observed for short oxidation times t of 0.2–10 min (oxide thickness < 10 μm). For 10 < t < 120 min, small quantities of (111) NiO formed in addition to (100), but near-single-phase (100) NiO formed once again after oxidation for >150 min (thickness > 35 μm). The ratio of (100) to (111) textures with oxidation time is explained in terms of epitaxial constraints, growth rates, and oxygen absorption on the (100) and (111) grains. The optimum oxidation conditions are oxidation for approximately 0.5 min at 1250 °C in flowing oxygen, yielding (100) NiO, a few microns in thickness, and root-mean-square roughness of approximately 40 nm on the length-scale of the grain size.

The parameters of the mechanically activated field-activated pressure-assisted synthesis (MAFAPAS) process, which were recently developed and patented for producing dense nanostructured materials, were studied in the case of the B2-FeAl intermetallic. Based on x-ray diffraction (XRD) experiments, residual stresses XRD analysis, relative density measurement, and secondary-electron microscopic observations, the optimal synthesis conditions (time, current intensity, and pressure) were studied. Fe + Al powders were comilled in a specially designed planetary mill to obtain a mixture of reactants at the nanoscale without the formation of any product. The milled mixtures were then subjected to a high density of alternating current (60 Hz ac, total current 1250 or 1500 A), a uniaxial pressure (70 or 106 MPa), and different times (from 2 to 5 min). This work confirms the reproducibility of the MAFAPAS process, showing the essential role of the mechanical activation step to produce a pure nanostructured material. In addition, the composition and the microstructure of MAFAPAS end-products depended on the processing parameters (time, current density, mechanical pressure). In particular, it was observed that the process of simultaneous synthesis and consolidation of the product introduced a high level of residual stresses.

Polycrystalline SiC samples hot pressed with aluminum, boron, and carbon sintering additions (ABC-SiC) were characterized using transmission electron microscopy. The study focused on the effects of high-temperature treatment on microstructure. Three temperatures, at which considerable microstructural changes took place, were found to be critical. At a threshold temperature of approximately 1000°C, 1-nm-wide, amorphous intergranular films started to crystallize. At approximately 1300°C, lattice diffusion in SiC grains resulted in nanoprecipits, which could diffuse into grain boundaries and significantly altered composition. Quantitative microanalysis revealed doubled Al content in intergranular films after annealing at 1300°C. Except for crystallization in intergranular films and nano-precipitation in matrix grains, microstructure remained stable until 1600°C, when microstructural changes with volatile features occurred. A brief holding at 1900°C brought marked changes in microstructure, including structural change in intergranular films, dissolved nanoprecipitates, unit cell dilation, and cracking. The results indicate that ABC-SiC is highly promising in structural applications at up to 1500°C.

A fatigue damage accumulation model based on the Paris law is proposed for strain-rate-sensitive polymer composite materials. A pre-exponent factor c2/f and strain-rate-sensitive exponent n are introduced. Numerical analysis of the model was performed using experimental data obtained in the literature. Both factors were found to enhance fatigue damage accumulation. The analysis also revealed that the extent of damage increases with decreasing frequency and that the damage rate is more sensitive to the applied maximum stress than to the stiffness of the material.

We present results on the thermomechanical behavior of bare and nanocoated gold/polysilicon (Au/Si) bilayer cantilever beams for microelectromechanical system applications. The cantilever beams have comparable thicknesses of the Au and Si layers and thus experience significant out-of-plane curvature due to a temperature change. The experiments focus on the inelastic behavior of the bilayer beams due to thermal holding and thermal cycling. In uncoated Au/Si beams, thermal holding directly after release or thermal cycling both lead to a curvature decrease as a function of time or cycle number, respectively. The drop in curvature during thermal cycling or thermal holding in uncoated beams was not accompanied by a change in the slope of the thermoelastic curvature–temperature relationship. The absolute change in curvature depends on the temperature and the holding time. When holding or cycling to a temperature of 175 °C, the curvature change in uncoated beams is minimal for hold times up to 4500 min or 15,000 cycles. When holding or cycling to temperatures of 200 or 225 °C, the curvature in uncoated beams drops by a factor of three for hold times up to 4500 min or 15,000 cycles. The surface structure induced by long-term holding of uncoated beams shows grooving at the grain boundaries while the surface structure induced by cycling of uncoated beams shows consolidation of the grain boundaries. The Au/Si beams with a conformal 40-nm atomic layer deposition Al2O3 coating show a considerably different response compared to identical Au/Si bare beams subjected to the same thermal histories. The coating completely suppresses decreases in curvature when the beams are held at 225 °C for 4500 min. On the contrary, the coating does not always suppress thermal ratcheting when the beam is cycled from a low temperature to 225 °C. In the coated beams, the drop in curvature due to thermal cycling was accompanied by a change in the thermoelastic slope of the curvature–temperature relationship. Negligible microstructural changes were detected on the Al2O3-coated Au surface after holding or cycling. The results are discussed in light of potential deformation mechanisms and a simple analysis linking the mismatch strain between the layers to the curvature in the beams.

The structure of C60 and C70 whiskers with diameters between submicrometers and micrometers were analyzed by scanning electron microscopy and transmission electron microscopy. The fullerene whiskers were produced by forming liquid–liquid interfaces between toluene solutions of fullerenes and isopropyl alcohol. The growth fronts of C70 whiskers were observed to be crystalline. The C70 whiskers were assumed to be in a state of order–disorder transition. The whiskers of C60 are very flexible, and C60 whiskers bent strongly were torn into finer C60 whiskers. The C70 whiskers showed a higher crystallinity, though a high density of dislocations was observed in the C60 whiskers.

The solid-state reaction of SrNb2O6, BaNb2O6, and CeO2 to form Sr0.5Ba0.5CexNb2O6+δ at different temperatures and heating rates was investigated. A nonisothermal kinetic empirical model was used to evaluate the activation energy and rate constant of Sr0.5Ba0.5CexNb2O6+δ. The values of the activation energy evaluated from the slopes are 762, 800, and 844 kJ/mol, respectively, for S50, 1CeS50, and 2CeS50, which increase with the increase in Ce doping. The order of reaction was found to decrease with the increase of the Ce doping. A kinetic equation was developed based on the parameters evaluated from the nonisothermal reaction model, which was successfully used to predict the isothermal reaction of Ce-doped strontium barium niobate.

The use of the glass slag method in the extraction of rare earth from La–Ni alloys was studied. X-ray diffraction and electron probe microanalysis studies revealed that the La–Ni alloys produced by the glass slag method using boron trioxide consisted of Ni and Ni3B phases. No La-containing phase such as the LaNi5 phase and the La oxide phase was found in the resultant alloys. The chemical analyses confirmed that the La content in the alloys produced by the glass slag method was very limited. However, the glass slag materials contained a large amount of lanthanum. The La in the La–Ni alloys was successfully extracted by the glass slag method using boron trioxide.

We report on long-lasting phosphorescence and photostimulated long-lasting phosphorescence phenomena in femtosecond laser-irradiated Mn2+-doped alumino-phosphofluoride glasses. Long-lasting phosphorescence was observed in the glass samples after the irradiation of the focused femtosecond laser. Photostimulated long-lasting phosphorescence was observed in the femtosecond laser pre-irradiated region by excitation of an ultraviolet light of 365 nm, after the femtosecond laser-induced long-lasting phosphorescence decayed completely. The mechanisms of these phenomena have been discussed. These phenomena have potential uses in three-dimensional ultra-high-density optical recording.

Sheets of α-sialon were prepared by tape casting and pressureless sintering. Suspensions consisting of precursor α-sialon powders, dispersant, binder, plasticizer, and 60 MEK/40E as solvent were optimized for tape casting by rheological measurements. Crack-free green tapes with good flexibility and high strength were obtained from suspensions with suitable rheological properties (moderate viscosity, shear-thinning behavior, and negligible thixotropy). The obtained green tapes showed great homogeneity by means of scanning electron microscope observation and pore-size distribution, leading to homogeneous α-sialon sheets after pressureless sintering at 1750 °C for 2 h. The results showed that it was possible to fabricate homogeneous α-sialon sheets with smooth surfaces through tape casting and pressureless sintering.

The formation of barium monomolybdate (BaMoO4) in inequimolar powder mixtures of BaCO3 and MoO3 was examined under isothermal and nonisothermal conditions upon heating in air at 25–1200 °C, using thermogravimetry. Concurrence of the observed mass loss (due to the release of CO2) to the occurrence of the formation reaction was evident. Accordingly, the extent of reaction (x) was determined as a function of time (t) or temperature (T). The x-t and x-T data thus obtained were processed using a well-established mathematical apparatus and methods to characterize the nature of the reaction rate-determining step and derive isothermal and nonisothermal kinetic parameters (rate constant, frequency factor, reaction order, and activation energy). Moreover, the reaction mixture quenched at various temperatures (450–575 °C) in the reaction course was analyzed by various spectroscopic (x-ray diffractometry, infrared spectroscopy, and laser Raman spectroscopy) and microscopic (scanning electron microscopy and x-ray energy dispersive spectroscopy) techniques for material characterization. The results obtained indicated that the reaction rate may be controlled by unidirectional diffusion of MoO3 species through the product layer (BaMoO4), which was implied to form on the barium carbonate particles. The nonisothermally determined activation energy (156 kJ/mol) was found to be close to the isothermally determined one (164–166 kJ/mol)

An electroless plating and hot-pressing process was developed to fabricate silver matrix composites reinforced with uniformly distributed graphite and Saffil short fibers (Graphitesf and Saffilsf). The hardness of the composites increases as the content of short fibers increase. Static-gap, single-spark erosion and repeated-collision, multiple-arc erosion tests were used to investigate the arc erosion behavior of the composites. The composites exhibited better arc erosion resistance when the contents of short fibers were increased in a static-gap, single-spark erosion test. However, the weight loss of the composites after 10,000 times repeated-collision, multiple-arc erosion operation shows that the composites with low volume percents of short fibers have a good arc erosion resistance. The Saffilsf/Ag composites show a better arc erosion resistance than Graphitesf/Ag because of the greater strengthening effect of the finer Saffil short fibers. The erosion behavior of the composites is dominated by the viscosity of composites in single-spark tests, while it depends on the competition of viscosity and thermal properties in multiple-arc tests.