Sn–0.7 wt% Cu alloy is an important Pb-free solder, and Ni–7 wt% V is the major diffusion barrier layer material of flip chip technology. Reactions at the Sn–0.7 wt% Cu/Ni–7 wt% V interface are examined at 160, 180, and 210 °C. Only the Cu6Sn5 phase is formed in the Sn–0.7 wt% Cu/Ni–7 wt% V couple reacted at 160 and 180 °C; however, in addition to the Cu6Sn5 and Ni3Sn4 phases, a quaternary Q phase is formed in the Sn–0.7 wt% Cu/Ni–7 wt% V couple reacted at 210 °C. The Q phase is a mixture of nanocrystalline Ni3Sn4 phase and an amorphous phase. With longer reaction time at 210 °C in the Ni–V/Q/Sn–Cu couple where the Q phase is in direct contact with solder, the Ni3Sn4 phase nucleates inside the preformed Q phase, and the alternating layer phenomenon Ni–V/Q/Ni3Sn4/Q/Ni3Sn4/Cu6Sn5/Sn–Cu is observed. The interesting solid state amorphization and alternating layer phenomena at 210 °C are primarily caused by the fact that Sn and Cu are fast diffusing species, while V is relatively immobile.

ZrC-based composites were produced by pressureless sintering thanks to the addition of MoSi2 as sintering aid. After preliminary tests, a baseline ZrC material and two mixed ZrC–HfC and ZrC–ZrB2 composites with 20 vol% MoSi2 were densified at 1900 to 1950 °C reaching final relative densities of 96%–98%. Mean particle size of the dense bodies ranged from 5 to 9 μm. Secondary phases were found to form during sintering, such as SiC and Zr–Mo–Si-based compounds. Room-temperature mechanical properties were in the range of the values reported in the literature for similar materials densified by pressure-assisted techniques. The flexural strength was tested at room temperature, 1200 and 1500 °C.

The combustion synthesis of Al50Ir48Ni2 (at.%) was conducted at different heating rates in both a differential scanning calorimetry (DSC) chamber and a vacuum furnace. It was found that a higher heating rate, a sufficient amount of reactant powder, and effective control of the heat loss facilitated the complete reaction and resulted in combusted single IrAl phase products. Otherwise, multiphase products containing IrAl, unreacted Ir, and Al3Ir were synthesized. The reactions involved in different processes were discussed in terms of the thermal competition between heat generation and loss during the reaction. All ignition temperatures were below 773 K, indicating that the combustion reaction occurs at the solid–solid state. With increasing heating rate, the ignition temperature increased while the product density decreased.

Dopamine covalently chelated ZnO nanoparticles were synthesized by a nonaqueous one-step chemical process at a temperature as low as 60 °C. The formation of ZnO/dopamine hybrid structure was proved by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) techniques. Detailed absorption, luminescence, and time-resolved decay studies were performed for these ZnO/dopamine hybrid nanoparticles. We observed an enhanced green emission, which could be assigned to a new band-gap emission based on the fast of nanosecond lifetime of the green emission. Our results demonstrated that the change of optical properties of ZnO nanoparticles after covalently chelated by dopamine ligands is closely associated with the formation of new band structure.

The structure evolution and oxidation behavior of ZrB2–SiC composites in air from room temperature to ultrahigh temperature were investigated using furnace testing, arc jet testing, and thermal gravimetric analysis (TGA). The oxide structure changed with the increasing temperature. SiC content has no apparent influence on the evolution of structure during the oxidation of ZrB2–SiC below 1600 °C. However, the evolution of structure for ZrB2–SiC above 1800 °C was significantly affected by the SiC content. The formation of the SiC depleted layer in the ZrB2–SiC system not only depends on the surrounding conditions of pressure and temperature but also on the structure distribution of the SiC in the ZrB2 matrix. The apparent recrystallization of the ZrO2 occurred above 1800 °C. The SiC content should be controlled at ∼16% in the ZrB2–SiC system for the ultrahigh-temperature application. The mechanisms of the structure evolution during oxidation in air were also analyzed.

A stable nano body-centered cubic (bcc) CoFe2 alloy was isolated by employing a combination of N2H4.H2O reduction and sonochemical route under basic conditions. This alloy has proved to be a potential precursor for CoFe2O4 production. X-ray diffraction and transmission electron microscopy confirms the formation of a bcc phase CoFe2 alloy with particle size <10 nm and spherical morphology. Thermogravimetric analysis confirmed the oxidation of the alloy composition showing a weight gain between 200 and 500 °C, which corresponds to fully oxidized CoFe2O4. A significant increase in the saturation magnetization (Ms = 230 emu/g) for the nano CoFe2 alloy was observed in comparison with that of the theoretical bulk value (200 emu/g) at 300 K.

Electromigration at 5 × 104 A/cm2 and 100 °C was conducted to grow composite Pb/Sn whiskers from SnPb solders, in which a Pb whisker grows first and then a whisker of Sn grows. In some cases, small Sn islands are embedded in Pb whiskers. The diameter of a composite whisker is <1 μm, which is much smaller than that of spontaneous Sn whisker growth on leadframes. The growth orientation of Pb whiskers was in the [110], [1¯11], and [112] directions. This investigation proposes that compressive stress generated by electromigration at the anode provides the force driving whisker growth. Therefore, accelerated tests of whisker growth at higher temperatures using electromigration are feasible.

Crystalline samples of zinc oxide on a mesoporous amorphous silica substrate were prepared by 5 to 15 atomic layer deposition cycles with diethyl zinc and water at 150 °C. Samples were characterized by x-ray diffraction, thermogravimetry, and nitrogen adsorption–desorption isotherms. High-temperature oxide melt solution calorimetry and water adsorption calorimetry experiments were performed to measure surface enthalpy for crystalline ZnO particles supported on the substrate. The measured enthalpies 1.23 ± 0.35 and 2.07 ± 0.59 J/m2 for hydrous and anhydrous surfaces, respectively, are in agreement with previously reported measurements for unsupported ZnO nanoparticles. Feasibility of thermochemical characterization of complex system of atomic layer deposition (ALD) prepared particles on a substrate was demonstrated.

Pure CdSe and Mg-doped CdSe nanocrystal quantum dots were synthesized into the zinc-blende structure at a low temperature by the inverse micelle technique using paraffin oil and oleic acid as surface capping agents. The ripening behavior of the nanocrystals was monitored using the red shift in ultraviolet (UV)-visible light absorption peaks, and their size variation was estimated using the so-called, quantum confinement theory. The Lifshitz–Slyozov–Wagner (LSW) kinetics analyses were performed based on the variation in size according to the ripening temperature and time period. The activation energy (Q) and reaction rate constant (Ko) were determined for the ripening reaction using Arrhenius-type plots. The kinetics analyses reveal that the volume diffusion through the liquid-phase solution is the governing mechanism for the ripening of both nanocrystals. The Mg-doped CdSe nanocrystals showed enhanced ripening kinetics due to the low activation energy for the volume diffusion.

We studied the resistivity, photosensitivity, photoluminescence, and surface photovoltage of CdTe crystals doped with Ge or Sn to extend our knowledge of the influence of the deep-donor level on compensation and afterglow effects. We demonstrated a strong correlation between photosensitivity caused by photoelectrons with Fermi-level variations near the GeCd0/2+ or SnCd0/2+ energy levels. Surface photovoltage measurements confirmed that when the concentration of residual acceptors varied along the direction of growth, then trapping conditions dramatically changed as a defect was converted from a neutral state to doubly charged positive one.

This article is focused on a fractography study of cleavage cracking at triple grain boundary junctions in freestanding silicon thin films. At a triple junction, as the crystallographic orientations of the two grains ahead of the crack are different by only a few degrees, the cleavage front advance becomes quite jerky. The crack first enters the grain of smaller boundary toughness and then turns into the other grain from the lateral direction. Consequently, the overall fracture resistance cannot be analyzed in the framework of line-average theory. The nonuniform characteristic of crack behavior can be attributed to the increase in local stress intensity. A few typical crack front advance modes are identified.

The interfacial reactions and ball shear properties of an In–48wt%Sn solder joint with an electroplated Au/Ni ball grid array substrate were investigated with increasing numbers of reflows using scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectrometry, inductively coupled plasma-atomic emission spectroscopy, x-ray diffractometry, and bonding testing. After one reflow, two different intermetallic compound (IMC) layers, AuIn and AuIn2, were formed at the solder–substrate interface. The AuIn was completely transformed into the AuIn2 after three reflows. The AuIn2 IMC layer broke off, and a thin continuous Ni3(SnxIn1–x)4 IMC layer was formed between the molten solder and the exposed Ni substrate after four reflows. After 10 reflows, the AuIn2 IMC layer completely spalled off the substrate and the Ni3(SnxIn1–x)4 IMC layer was dissolved into the molten solder. These interfacial reactions greatly affected the shear properties of the solder joint.