Systematic experimental work was carried out to understand the mechanism of Au diffusion to the solder interface, and a novel method was proposed to eliminate Au embrittlement by circumventing the continuous layer of (Au,Ni)Sn4 at the solder interface. Contrary to the usual expectation, it was determined that utilization of a very thin Ni metallization in the Au/Ni/Cu under bump metallization (UBM) was an effective means of maintaining mechanical integrity of the solder joint. It was found that the out-diffusion of Cu during the aging period changes the chemistry and morphology of the intermetallic compounds at the interface.

A hard magnetic Nd50Al15Fe15Co20 bulk metallic glass (BMG) was prepared in the shape of a rod up to 3 mm in diameter by suction casting. The glass transition and crystallization behaviors as well as their kinetic nature have been studied. In contrast to the previously reported hard magnetic Nd–Al–Fe–Co BMGs, Nd50Al15Fe15Co20 as-cast rod exhibits a distinct glass transition and multistep crystallization behaviors in the differential scanning calorimetry traces and lower coercivity. The BMG provides an ideal model for the investigation of glass transition and crystallization of hard magnetic Nd–Al–Fe–Co glass-forming alloys.

The formation of Au nanoclusters in MgO using ion implantation and subsequent annealing was investigated. Approximately 1200 and 1400 Au2+ ions/nm2 were implanted in MgO(100) substrates at 300 and 975 K, respectively. Subsequent annealing in air for 10 h at 1275 K promoted the formation of Au nanostructures in MgO. The sample implanted at 300 K showed severe radiation damage. In addition, two-dimensional plateletlike structures with possible composition of Au and MgO were formed during implantation in the sample that was implanted at 300 K. In contrast, Au implantation at 975 K promoted the nucleation of Au nanostructures during implantation. Subsequent annealing of both samples show three-dimensional clusters in MgO. However, the 975 K implanted sample shows clean, high-quality, single-crystal Au clusters that have an epitaxial relationship to MgO(100).

Multilayer films of pure ZrO2 and CeO2 were grown using molecular beam epitaxy on a yttria-stabilized zirconia (YSZ) substrate. Distinctive forbidden diffraction spots of (odd, odd, even) type were observed on the selected-area electron-diffraction patterns of the film. Dark-field imaging clearly revealed that these forbidden diffraction spots were solely due to the ZrO2 layers. Comparison of the electron diffraction pattern with that simulated by dynamical calculations suggest that the pure ZrO2 layers possess a cubic structure of space with the group P4 3m oxygen sublattice being displaced diagonally, rather than along the c axis as suggested for YSZ. Our results further suggest that the displacement of the oxygen from the ideal (¼, ¼, ¼) position might have been introduced during the film growth process.

Fe–Cr–Mo–(Y,Ln)–C–B bulk metallic glasses (Ln are lanthanides) with maximum diameter thicknesses reaching 12 mm have been obtained by casting. The high glass formability is attained despite a low reduced glass transition temperature of 0.58. The inclusion of Y/Ln is motivated by the idea that elements with large atomic sizes can destabilize the competing crystalline phase, enabling the amorphous phase to be formed. It is found that the role of Y/Ln as a fluxing agent is relatively small in terms of glass formability enhancement. The obtained bulk metallic glasses are non-ferromagnetic and exhibit high elastic moduli of approximately 180–200 GPa and microhardness of approximately 13 GPa.

A method to prepare samples for four point bend testing is reported in this paper. The traditional method of sample preparation involves time-consuming steps of sawing with a diamond saw followed by polishing with fine grit to remove the roughness of the sidewall. The new method uses cleaving along the 〈100〉 crystallographic direction, which renders smooth surfaces and eliminates the polishing steps. Load–displacement curves comparing polished versus cleaved samples show that the new technique provides improved results. Elimination of fracture-inducing defects is the primary benefit of this method, which also leads to data with tighter distributions.

A novel tree-like nanostructured Ag crystal, with stems, branches, and leaves, has been synthesized by pre-forming Au seeds, soaking, and annealing, based on monolithic mesoporous silica. The obtained Ag nanotrees are of single-crystal nature and statistically symmetrical in geometry. Further experiments revealed that the interconnected channels of the porous silica, heating at low temperature, and the pre-formed Au seeds are crucial to form such structure. Its formation can be attributed to the low nucleation rate and preferentially unidirectional diffusion of Ag atoms to the Au seeds along interconnected channels. This nanostructured material is of great potential to be building blocks for assembling some mini-functional devices of the next generation. The current study is also of importance in studying the diffusion mechanism of single-crystal formation, and especially in improving our understanding of the underlying physical structure of both natural and synthetic porous materials.

Chemically prepared zinc oxide powders are fabricated for the production of high aspect ratio varistor components. Colloidal processing was performed to reduce agglomerates to primary particles, form a high solids loading slurry, and prevent dopant migration. The milled and dispersed powder exhibited a viscoelastic to elastic behavioral transition at a volume loading of 43–46%. The origin of this transition was studied using acoustic spectroscopy, zeta potential measurements, and oscillatory rheology. The phenomenon occurs due to a volume fraction solids dependent reduction in the zeta potential of the solid phase. It is postulated to result from divalent ion binding within the polyelectrolyte dispersant chain and was mitigated using a polyethylene glycol plasticizing additive. This allowed for increased solids loading in the slurry and a green body fabrication study to be presented in our companion paper.

Chemically prepared zinc oxide powders were processed for the production of high aspect ratio varistor components (length/diameter >5). Near-net-shape casting methods including slip casting and agarose gelcasting were evaluated for effectiveness in achieving a uniform green microstructure that densifies to near theoretical values during sintering. The structure of the green parts was examined by mercury porisimetry. Agarose gelcasting produced green parts having low solids loading values and did not achieve high fired density. Isopressing the agarose cast parts after drying raised the fired density to greater than 95%, but the parts exhibited catastrophic shorting during electrical testing. Slip casting produced high green density parts, which exhibit high fired density values. The electrical characteristics of slip-cast parts are comparable with dry-pressed powder compacts.

The two immiscible liquid phases in equilibrium with a single liquid phase have been observed during the phase diagram study of an organic analog of a metal–nonmetal system involving pentachloropyridine (PCP)–succinonitrile (SCN). The phase equilibrium shows the formation of a monotectic and a eutectic, with large miscibility gap in the system, containing 0.0456 and 0.9658 mole fractions of SCN, respectively, and the consolute temperature being 99.0 °C above the monotectic horizontal line. The heat of mixing, entropy of fusion, roughness parameter, interfacial energy, and excess thermodynamic functions were calculated based on enthalpy of fusion data determined via the differential scanning calorimetry method. The effects of solid–liquid interfacial energy on morphology of monotectic structure as well as the variation of interfacial energies with temperature have been discussed. The microstructures of monotectic and eutectic show peculiar characteristic features. The material properties of PCP and PCP doped with SCN crystals, grown by the Bridgman–Stockbarger method, have been studied via studying second harmonic generation efficiency, transparency range, and mechanical hardness.

A novel method was developed to produce Al2O3/AlN composite powders. The composite powders were synthesized by the direct nitridation of Al2O3 using various additives by plasma processed with two different types of gas (Ar/N2 and N2 plasma). The effects of these two different plasma gases and additives on the formation of the Al2O3/AlN composites were studied. The x-ray diffraction results in the composite powders showed that the cubic AlN was converted to the major phase while transient γ–Al2O3 was the minor phase when the composite powder was fully melted using nitrogen as the sole working gas. In contrast, the main phase was still α–Al2O3 when the composite powder was not well melted using the mixture of argon and nitrogen as the working gas. Carbon was found as an effective conversion additive to increase the cubic AlN of this composite powder up to 49 vol%. The reaction mechanism of forming this composite powder was also analyzed.

A Co–Ag potential in the form of TB-SMA (the second moment approximation of the tight-binding scheme) is derived based on some ab initio calculated physical properties. Applying the derived potential, molecular dynamics simulations reveal that a Co-/Ag-based solid solution retains its atomic homogeneity up to a critical ratio of9 Ag/12 Co at.%, over which the Ag/Co solute atoms begin to segregate. Correspondingly, a cage-like configuration is proposed to have 1 Ag/Co atom isotropically surrounded by 9 Co/7 Ag atoms for the homogeneous solid solution. Moreover, when the solute atoms exceed 12 Ag/18 Co at.%, the solid solution turns into an amorphous phase with inhomogeneous atomic structure.

In this paper, we reported the rapid synthesis of disklike (ZnSe)2·EN precursor via a simple and convenient polyol method. Annealing the precursor in argon stream at 500 °C resulted in the formation of ZnSe crystals with unique quasi-network structure. The obtained samples were characterized by powder x-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, infrared absorbance spectra, and thermogravimetric analysis. The influence of PEG200 on the final products in the system was also discussed.

During the manufacturing and the service life of Au–Al wire bonded electronic packages, the ball bonds experience elevated temperatures and hence accelerated interdiffusion reactions that promote the transformation of the Au–Al phases and the growth of creep cavities. In the current study, these service conditions were simulated by thermally exposing Au–Al ball bonds at 175 and 250 °C for up to 1000 h. The Au–Al phase transformations and the growth of cavities were characterized by scanning electron microscopy. The volume changes associated with the transformation of the intermetallic phases were theoretically calculated, and the effect of the phase transformations on the growth of cavities was studied. The as-bonded microstructure of a Au–Al ball bond typically consisted of an alloyed zone and a line of discontinuous voids (void line) between the Au bump and the bonded Al metallization. Thermal exposure resulted in the nucleation, growth, and the transformation of the Au–Al phases and the growth of cavities along the void line. Theoretical analysis showed that the phase transformations across and lateral to the ball bond result in significant volumetric shrinkage. The volumetric shrinkage results in tensile stresses and promotes the growth of creep cavities at the void line. Cavity growth is higher at the crack front due to stress concentration, which was initially at the edge of the void line. The crack propagation occurs laterally by the coalescence of sufficiently grown cavities at the void line resulting in the failure of the Au–Al ball bonds.

The microstructure of Ba(Cd1/3Ta2/3)O3 ceramics with boron additive was investigated by high-resolution and analytical electron microscopy. Superlattice reflections were present at positions of (h ± 1/3, k ± 1/3, l ± 1/3) away from the fundamental reflections in the [110] zone diffraction pattern for the pseudocubic perovskite unit cell. Lattice images showed a well-ordered structure with hexagonal symmetry. No boron segregation and amorphous phase was observed along grain boundaries. An amorphous phase rich in boron-oxide was observed to form pockets partially penetrating along multiple grain junctions.

The hardness, elastic moduli, and fracture toughness of the spinel phases, γ–Ge3N4 and γ–Sn3N4, were determined using indentation data and theoretical calculations. Measurements were performed on polycrystalline specimens using the technique of nanoindentation to determine the reduced moduli and hardnesses from the unloading portion of the indent curves. Reduced moduli of γ–Ge3N4 and γ–Sn3N4 were found to be 295 and 167 GPa, respectively. The nanohardnesses of γ–Ge3N4 and γ–Sn3N4 were found to be 31 and 13 GPa, respectively. The shear moduli G0 and Poisson’s ratios ν0 were derived using theoretical bulk moduli B0 obtained from density-functional theory calculations. The calculated values were B0 = 260 GPa, G0 = 146 GPa, ν0 = 0.26 for γ–Ge3N4, and B0 = 186 GPa, G0 = 64 GPa, ν0 = 0.34 for γ–Sn3N4. Fracture toughness was estimated by direct measurement of radial cracks emanating from Vickers microindents. It was determined that for γ–Ge3N4, KIC = 2.3 MPa(m)1/2, while for γ–Sn3N4, KIC = 1.4 MPa(m).1/2

Silver nanoparticles dispersed in a silica matrix were made by the consolidation of a Ag-attached silica colloid, which was synthesized via the electrolysis of a pure Ag electrode, the reduction of Ag+ ions by H2, and the nucleation and growth of Ag particles on the silica nanoparticles in water. This simple process produced Ag/silica nanocomposites with a high concentration and narrow size distribution of nanoparticles, which was confirmed by transmission electron microscopy and x-ray diffraction. As estimated by Raman and photoluminescence measurements, the quantity of broken oxygen bonds was increased with increasing Ag concentration due to the intervention of Ag ions as structural modifiers in the silica network structure. Ag ions in the matrix are probably a residue of the Ag+ ions that could not be reduced by H2 during the electrolysis/reduction reaction. The optical-absorption spectra and the HCl-soaking test suggested that a chemical-interface damping effect, which was caused by electron transfer from the metal particles to the oxide matrix, dominates the optical-absorption properties in this system.

Cubic boron nitride (cBN) film was deposited on Co-containing WC substrates by dc jet plasma chemical vapor deposition from an Ar–N2–BF3–H2 gas system. The formation of cobalt nitrides was observed at interface, and the hindrance of Co on cBN growth was demonstrated. Growth temperature and etching treatment of the substrate before deposition influenced the cBN growth greatly. At 1050 °C, cBN films were obtained on etched substrates but not on unetched substrates. At 1090 °C, cBN films were not obtained even on etched substrates. At 960 °C, cBN films deposited even on unetched substrate but the films always peeled off after exposing to air. The film quality of cBN deposited at 960 °C is better than that deposited at 1050 °C.

A YNi2B2C thin film deposited on MgO(001) substrate by pulsed laser deposition has been investigated by transmission electron microscopy (TEM). Cross-sectional TEM analyses show that the YNi2B2C film grows in the [001] direction. Y2O3 exists not only as an interlayer at the interface of the YNi2B2C thin film and the MgO substrate but occasionally also in the YNi2B2C thin film near the substrate. The orientation relationships between the YNi2B2C thin film, Y2O3 interlayer, and MgO substrate are determined from electron-diffraction patterns to be MgO(001)[100] ‖ Y2O3(001)[100], YNi2B2C(001)[110] ‖ Y2O3(001)[100] ‖ Y2O3(001)[100, and YNi2B2C(001)[100] ‖ Y2O3(001)[100 1.5‖ Y2O3(001)[100] ‖ Y2O3(001)[100 (the numeral above the “parallel” symbol represents the misorientation (in degrees) between the [100] ‖ Y2O3(001)[100 directions).

Coarsening of the ternary eutectic in cast Sn–Ag–Cu lead-free solder alloys was investigated. The process was found to follow r3 ∝ t kinetics where r is the rod radius of the dispersed phase and t is time. The effective activation energy for the process is 69 ± 5 kJmol-1. The two types of intermetallic rods, Cu6Sn5 and Ag3Sn, in the eutectic structure coarsen at different rates, with each having a different rate-controlling mechanism. The overall coarsening kinetics for the Sn–Ag–Cu ternary eutectic is significantly slower than that found for the Pb-Sn eutectic, which has implications for long-term reliability of Sn–Ag–Cu solder joints.