Sn–Zn based alloys are promising as Pb-free solders, and Cu is commonly used in electronic products. Solidification and interfacial reactions of Sn–8.8wt%Zn, Sn–8.8wt%Zn–0.05wt%Co, and Sn–8.8wt%Zn–0.5wt%Co solders on Cu substrates are investigated. Two different masses of solders are used. The degrees of undercooling increase with increasing Co additions in the Sn–8.8wt%Zn alloys. The reaction products evolve with reaction time, and the timing of different reaction stages is influenced by both the minor Co alloying and the mass of solders. In the initial reaction stage, two reaction phases, γ-Cu5Zn8 and ε-CuZn5, are observed in the Sn–8.8wt%Zn/Cu and Sn–8.8wt%Zn-0.05wt%Co/Cu couples, and only the γ-Cu5Zn8 phase is found when the Co addition is up to 0.5 wt%. The reaction layers are thinner with higher Co alloying. The addition of Co into the Sn–Zn alloys consumes Zn, and this depletion of Zn in the Sn–Zn solders is the primary reason for the changes of reaction products and the thinner reaction layers.

The synthesis of single crystalline rectangular silver bar using polyacrylamide (PAM) and silver nitrate (AgNO3) by a hydrothermal process is reported. PAM has been used to create a reducing atmosphere as well as nucleation sites to produce silver seeds along the PAM chain. Several silver nanostructures viz. nanoparticles, growth of silver nanowires, and finally a single crystalline silver nanobar with a square cross section and of several microns in length, depending upon maturity and temperature of the hydrosol, are synthesized. At relatively lower temperatures (above 380 K) and higher pressure amide group of PAM is hydrolyzed with the liberation of ammonia (NH3), which produces a reducing atmosphere. As a result, the degraded PAM chain acts as nucleation sites to produce the assembly of silver nanocrystals along the chain. As the hydrosol becomes more and more mature, a directional growth of silver nanocrystals, called a mesocrystal, is formed. This mesocrystal is converted into single crystals due to fusion of higher energy surfaces (100) of nanocrystals to minimize the total surface energy. This growth process is completed with the formation of a single crystalline rectangular silver bar with a square cross section due to the growth of silver along the [110] direction.

Activated carbon Norit R3-ex (demineralized) was annealed at various temperatures (950–2700 °C) in an argon atmosphere. The changes of the porosity of the products were characterized on the basis of N2 adsorption isotherms (at 77 K). The texture of the samples was investigated by x-ray diffraction, Raman spectroscopy, and scanning electron microscopy. The presence of surface oxygen (Fourier transform infrared) and its content in the surface layer (from energy dispersive spectroscopy) were determined. The electrical resistivity of powdered samples was measured. Cyclovoltammetry of carbon (powdered electrodes) were carried out and the electrical double-layer capacitances were estimated from the cyclic voltammetry curves. Heat treatment increased the degree of crystallization of the samples, which was correlated with changes in their conductivity. A rapid drop in porosity (at 1800–2100 °C) took place in parallel with a decrease in the electrical double layer capacity. The presence of surface oxygen as a result of oxygen chemisorption on freshly annealed carbon samples was confirmed using several methods.

SnTe is the most common compound formed at the bismuth telluride/metal soldered junction of thermoelectric modules. It affects the mechanical and electrical properties of the soldered junction. In the study we investigate the growth of SnTe compound during reaction between molten Sn–3.5Ag solder and tellurium at 250 °C. We found that the growth of SnTe is suppressed by Ag–Te bilayer compounds that block further reaction between liquid Sn and Te. With increasing reaction time, the SnTe morphology becomes rough as a result of coarsening of SnTe grains. The growth of SnTe grains follows the conservative ripening kinetics with the mean particle size proportional to one-third power of reaction time.

The initial stage of oxidation of Ti45Al7Nb0.4Y alloy (at.%) oxidized at 900 °C in air was investigated by using x-ray photoelectron spectroscopy and Auger electron spectroscopy. Experimental results revealed that YAl2 segregated along the grain boundaries preferentially oxidized to Y2O3 and Al2O3 due to strong affinity of Y to oxygen. Oxides grew faster at the grain boundaries than in lamellar colonies. As a result, Y and Al oxides pegs protruded into the substrate, which can increase the contact areas of oxide scale and substrate. Moreover, inward diffusion of oxygen more easily occurred along the grain boundaries. As a result, it promoted the external oxidation of Al within the grains due to lower inward diffusion flux of oxygen. And coarse-grained Y2O3 blocked the cationic intergranular diffusion. Therefore, Y addition can effectively enhance the Al2O3 layer and suppress the TiO2 outermost layer.

In this investigation on the formation of multiple-layered Kirkendall voids at Cu/Sn–3.5Ag solder joints, Sn–3.5Ag solder balls were reacted with Cu under bump metallurgy (UBM), which was electroplated using bis-sodium sulfopropyl–disulfide, C6H12O6S4Na2 (SPS) additive. The sequence of multilayer Kirkendall voids and Cu–Sn IMC (intermetallic compounds) formations are explained with the aid of cross-sectional scanning electron microscopy (SEM) micrographs and schematic diagrams. During the aging treatment at 150 °C, layers of Cu6Sn5/Cu3Sn formed at the solder joints and Kirkendall voids nucleated at the Cu3Sn/Cu interface as a result of the segregation of residual S originating from SPS. However, with Kirkendall void growth, the net section area of the Cu/Cu3Sn interface decreased and the Cu flux into Cu3Sn was inhibited. As the atomic ratio of Cu against Sn in the Cu3Sn dropped, transformation of Cu3Sn into Cu6Sn5 ensued. Subsequent diffusion of Sn atoms into the remaining Cu UBM through the remaining ligament of the Cu6Sn5/Cu interface precipitated secondary Cu3Sn beneath the primary Cu3Sn/Cu interface, and the secondary Kirkendall voids formed at the new Cu3Sn/Cu interface and so on.

The electrical and physical properties of atomic-layer-deposited EryHf1-yOx thin films have been investigated with different stoichiometries of erbium oxide (Er2O3) and hafnium oxide (HfO2). The as-deposited and annealed EryHf1-yOx films exhibit much higher dielectric constants than the reported k-values of the corresponding binary oxides. The highest k-value of 37.6 ± 1 is achieved with 13 at.% of erbium in the film. The enhancement in dielectric constant is due to the formation of the cubic HfO2 phase stabilized by erbium, as revealed by x-ray diffraction experiments. The annealed mixed oxide films exhibit remarkably low oxide charges, low interface states, low leakage, and good breakdown electric fields.

In this study, we report low temperature x-ray diffraction studies combined with electrical resistance measurements on single crystals of iron-based layered superconductor FeSe to a temperature of 10 K and a pressure of 44 GPa. The low temperature high pressure x-ray diffraction studies were performed using a synchrotron source and superconductivity at high pressure was studied using designer diamond anvils. At ambient temperature, the FeSe sample shows a phase transformation from a PbO-type tetragonal phase to a NiAs-type hexagonal phase at 10 ± 2 GPa. On cooling, a structural distortion from a PbO-type tetragonal phase to an orthorhombic Cmma phase is observed below 100 K. At a low temperature of 10 K, compression of the orthorhombic Cmma phase results in a gradual transformation to an amorphous phase above 15 GPa. The transformation to the amorphous phase is completed by 40 GPa at 10 K. A loss of superconductivity is observed in the amorphous phase and a dramatic change in the temperature behavior of electrical resistance indicates formation of a semiconducting state at high pressures and low temperatures. The formation of the amorphous phase is attributed to a kinetic hindrance to the growth of a hexagonal NiAs phase under high pressures and low temperatures.

Fe1–xCx coatings were synthesized by triode magnetron sputtering of an iron target in a methane/argon atmosphere with a large range of composition (x = 0.3 to 0.6 ± 0.06). Film surfaces were characterized by grazing incidence x-ray diffraction, scanning and transmission electron microscopies, and electron energy loss spectroscopy, to study effects of the variation of the methane gas flow rate on their structural properties. The coatings were constituted of the ε-Fe3C carbide (x = 0.3 and 0.36), in which carbon atoms are in octahedral sites, and of nanocomposite structure constituted of disordered and crystalline carbide nanograins embedded in a carbon matrix made of an amorphous and poorly crystallized graphenelike material (x = 0.55 and 0.60). In situ annealing of the nanocomposite Fe0.45C0.55 coating led to the formation of carbides θ-Fe3C and Fe7C3 (with carbon atoms in prismatic sites) and C-rich cubic carbide possibly related to the τ2-Fe2C7 compound.

Recent advancements using carbon nanotube electrodes show the ability for multifunctionality as a lithium-ion storage material and as an electrically conductive support for other high capacity materials like silicon or germanium. Experimental data show that replacement of conventional anode designs, which use graphite composites coated on copper foil, with a freestanding silicon-single-walled carbon nanotube (SWCNT) anode, can increase the usable anode capacity by up to 20 times. In this work, a series of calculations were performed to elucidate the relative improvement in battery energy density for such anodes paired with conventional LiCoO2, LiFePO4, and LiNiCoAlO2 cathodes. Results for theoretical flat plate prismatic batteries comprising freestanding silicon-SWCNT anodes with conventional cathodes show energy densities of 275 Wh/kg and 600 Wh/L to be theoretically achievable; this is a 50% improvement over today's commercial cells.

A dual-phase (DP) Ni–66.7%Co alloy with an average grain size of 16 nm was fabricated by electrodeposition. It exhibited an ultimate tensile strength of 1800–2080 MPa, together with an elongation to failure of 10–15% at room temperature. The remarkable ductility of this DP alloy with critical scale grains was attributed to its sustained high rate of strain hardening. Its fracture surface showed an unexpected deeply dimpled structure similar to that of coarse-grained ductile materials, which also witnesses the improved ductility.

Graphite nanosheets (GNs) were introduced into polyvinylidene fluoride (PVDF) via the solution mixing technique. The nanocomposites were then subjected to compression molding for electrical measurements. Solution mixing enabled homogeneous dispersion of GN within the PVDF matrix. The electrical transport behavior of such nanocomposites was studied by means of the impedance spectroscopy in a wide frequency range from 102 to 107 Hz. The results showed that the permittivity and conductivity of the composites are frequency dependent and well obeyed with the scaling law (ε′ ∝ ωu and σ′ ∝ ω−v) in the vicinity of percolation threshold (Φc ≈ 2.5 wt%). A large dielectric constant of 173 was observed in the PVDF/GN 2.5 wt% composites at 1 kHz.

The aligned freestanding nanorods (NR) of Co3O4 and nanoporous hollow spheres (NHS) of SnO2 and Mn2O3 were investigated as the anodes for Li-ion rechargeable batteries. The Co3O4 nanorods demonstrated 1433 mAh/g of reversible capacity initially and then decreased gradually. The NHS of SnO2 and Mn2O3 delivered energy densities as 400 and 250 mAh/g, respectively, in multiple galvonastatic discharge–charge cycles. The morphologic changes of the nanostructure anodes were investigated. It was found that Co3O4 NR broke down during cycles, but SnO2 NHS still maintained their structural integrity in multiple cycles resulting in sustainable high capacity. The nanostructured metal oxides exhibit great potential as the new anode materials for Li-ion rechargeable batteries with high energy density, low cost, and inherent safety.

High energy and power density lithium iron phosphate was studied for hybrid electric vehicle applications. This work addresses the effects of porosity in a composite electrode using a four-point probe resistivity analyzer, galvanostatic cycling, and electrochemical impedance spectroscopy (EIS). The four-point probe result indicates that the porosity of composite electrode affects the electronic conductivity significantly. This effect is also observed from the cell's pulse current discharge performance. Compared to the direct current (dc) methods used, the EIS data are more sensitive to electrode porosity, especially for electrodes with low porosity values.

Self-assembly bioinspired peptide nanotubes (PNT) demonstrate diverse physical properties such as optical, piezoelectric, fluidic, etc. In this work, we present our research on environmentally clean bioinspired peptide nanostructured material, to be applied to energy storage devices-supercapacitors (SC). Such an application is based on our recently developed PNT physical vapor deposition technology. It has been found that PNT fine structure and its wettability in electrolytes are the critical factors for a strong variation of the SC capacitance. We show that PNT-coated carbon electrodes enlarge the double-layer capacitance by dozens of times; reaching 800 μF/cm2 in a sulfuric acid (normalizing to the electrode geometric surface area of carbon background electrode). The discovered effect is provided by hollow PNT possessing numerous hydrophilic nanoscale-diameter channels, elongated along the PNT axis, which dramatically increase the functional area of carbon electrodes. Another type of the observed PNT morphology is fiberlike highly hydrophobic PNT rods, which do not contribute to the SC capacitance.