The effect of a Cu layer on the electronic structure and magnetic properties of Ni3Fe was studied by employing the discrete-variational method in the framework of density-functional theory. Three models were established for Ni3Fe(6), Ni3Fe(3)/Cu(3)/Ni3Fe(3), and Ni3Fe(3)/Cu(3). The charge transfer, magnetic moment, and spin exchange split at the Fermi level were obtained for Fe and Ni atoms in a Ni3Fe layer. The related characterizations of Ni3Fe were estimated from those of Fe and Ni atoms. It was discovered that the magnetic properties of the Ni3Fe layer improved when adjacent to Cu layer due to the improvement of the corresponding properties of the Fe atoms in the Ni3Fe. However, the magnetic moment and the spin exchange split of the Ni atoms in the Ni3Fe decreased when the Ni3Fe was adjacent to a Cu layer.

A new D023 metastable phase of Cu3Au was found to grow at the interfaces of Au/Cu multilayers deposited by magnetron sputtering. The extent of formation of this novel alloy phase depends upon an optimal range of interfacial width primarily governed by the deposition wattage of the direct current magnetron used. Such interfacially confined growth is utilized to grow a ∼300-nm-thick Au/Cu multilayer with thickness of each layer nearly equal to the optimal interfacial width which was obtained from secondary-ion mass spectrometry (SIMS) data. This growth technique is observed to enhance the formation of the novel alloy phase to a considerable extent. The SIMS depth profile also indicates that the mass fragment corresponding to Cu3Au occupies the whole film while x-ray diffraction (XRD) shows almost all the strong peaks belonging to the D023 structure. High-resolution cross-sectional transmission electron microscopy shows the near-perfect growth of the individual layers and also the lattice image of the alloy phase in the interfacial region. Vacuum annealing of the alloy film and XRD studies indicate stabilization of the D023 phase at ∼150 °C. The role of interfacial confinement, the interplay between interfacial strain and free energy, and the hyperthermal species generated during the sputtering process are discussed.

Organic solar cells based on conjugated polymer:fullerene blends show nowadays efficiencies above 4%. After briefly presenting the science of bulk-heterojunction solar cells, we report herein a shelf lifetime study performed by encapsulating the cells in a flexible and transparent gas barrier material. This method allows lifetimes as reported for glass encapsulation. Moreover, we propose a new approach to pattern organic solar cells and design large-scale modules. This technique, based on selective Nd:yttrium aluminum garnet (YAG) laser etching, potentially enables low-cost, high-speed roll-to-roll operation.

X-ray phosphors of Gd2O2S:Tb3+ and La2O2S:Eu3+ were synthesized by combustion reactions. The samples were characterized by x-ray diffraction (XRD), scanning electronic microscope (SEM), photoluminescence (PL), and x-ray excited luminescence (XEL) spectra. XRD results revealed pure oxy-sulfide phases when the sintering temperatures were no more than 500 °C, and the mean particle sizes were about 20 nm. While the sintering temperatures became higher, oxy-sulfate phases were present. SEM results illustrated a loose, porous agglomeration and a continuous three-dimensional network structure; PL spectra showed the characteristic emission of rare-earth activation ions. To our satisfaction, the PL intensities were nearly the same as some commercial x-ray phosphors. XEL spectra revealed the same characteristic emission, although their luminescence principles were different from those of the PL spectra. In addition, because absorption coefficients of these samples for x-ray and doped concentrations doped of activation ions were different, their light emission intensities and efficiencies also varied.

From the study of alloy phase formation in nanometer-sized particles by in situ transmission electron microscopy, it is revealed that not only the surface energy but also the interface energy of an interface between two different phases (solid–solid or solid–liquid) significantly changes the phase equilibrium of nanometer-sized particles. These energies result in large suppression of the eutectic point, structural instability, and unique solid/liquid two-phase structures in isolated nanometer-sized alloy particles. A theoretical study based on thermodynamics, which is modified in such a manner that Gibbs free energies for bulk materials were modified by taking factors affecting the phase equilibrium of nanometer-sized alloy particles into consideration, was proved useful to evaluate the results obtained from experiments.

To address the growing interest in nanoindentation for biomaterials, the following finite element study investigated the influence of indentation testing protocol and substrate geometry on quasi-static and dynamic load-displacement behavior of linear viscoelastic materials. For a standard linear solid, the conventional quasi-static indentation modulus, EQS, fell between the instantaneous and equilibrium modulus of the model. EQS approached the equilibrium modulus only for indentation unloading times 1000 times greater than the characteristic relaxation time of the model. It was nearly insensitive to other changes in the indentation testing protocol, such as tip radius and penetration depth, exhibiting variations of only 5–10%. Dynamic nanoindentation provided a quantitatively accurate assessment of the complex dynamic modulus (within ±12%) for a range material of parameters at physiologically relevant testing parameters. Both quasi-static and dynamic moduli calculated from the irregular surfaces varied with the size and shape of the irregularities but were still within 10% of the smooth surface values for penetration depths larger than the dimensions of the surface irregularities.

Fracture resistance of the interface between electroless Ni(P) and the eutectic SnBi solder alloy was examined in the as-reflowed and aged conditions, to investigate the potential role of Ni in inhibiting interfacial segregation of Bi in SnBi–Cu interconnect. In the as-reflowed condition, the fracture resistance of the SnBi/Ni(P) interface was about the same as that of the SnBi/Cu interface. Upon aging at 120 °C for 7 days the fracture resistance of the SnBi/Ni(P) interface was much higher than that of the SnBi/Cu interface. Such a difference was shown to result from the difference in fracture mechanism as the crack remained along the solder–intermetallic interface in the aged SnBi–Ni interconnect but propagated along the intermetallic–substrate interface in the aged SnBi–Cu interconnect. While fracture of the intermetallic–substrate interface in SnBi–Cu interconnect was due to Bi segregation onto that interface, no Bi was detected at the intermetallic-substrate interface in SnBi–Ni interconnects, implying that Ni(P) was effective in inhibiting the interfacial segregation of Bi.

A modified and convenient route using microemulsions (avoiding Ba-alkoxide) was evolved for the synthesis of uniform and monodisperse nanoparticles of BaTiO3 at low temperature (800 °C). X-ray line broadening and transmission electron microscopy studies show that the particle size varies in the range of 20–25 nm. Evidence for tetragonal distortion was found in these nano-sized (20–25 nm) particles of barium titanate from careful x-ray diffraction studies as well as from Raman spectroscopy. Our study showed that the critical size of the cubic to tetragonal transition in barium titanate may be much lower than suggested theoretically. The grain size showed an increase on sintering of 35 nm at 900 °C to 120 nm at 1100 °C, which was much lower than the grain size obtained at this temperature by the normal solid state route. The dielectric constant depends on sintering temperature and was found to increase from 210 (900 °C sintering) to 520 (1100 °C sintering) at 100 kHz. The dielectric constant was highly stable with temperature as well as frequency.

Fe–Pd films with Pd content varying between 26 and 30 at.% have been deposited by means of magnetron sputtering of elemental Fe and Pd targets. As-deposited films are highly supersaturated solid solutions of Pd in Fe that have a body-centered-cubic crystal structure and a very fine grain size. Substrate curvature measurements indicate that the films undergo an irreversible densification when heated above 100 °C. This densification is attributed to a structural change that is also observed in other supersaturated systems with a substantial atomic size difference between the constituents. It is possible to retain the high-temperature austenite phase at low temperature by annealing the films at 900 °C followed by rapid cooling. Depending on film composition, this metastable austenitic phase transforms to either a body-centered tetragonal (bct) or a face-centered tetragonal (fct) martensite around room temperature. Substrate curvature measurements show that formation of the fct martensite is reversible, while that of bct martensite is not. The fct transformation occurs at lower Pd content and higher temperature than reported for bulk materials. Both the fct and the fcc phase show a strong Invar effect at lower temperature and Pd content than observed in the bulk.

We investigated adsorption and dissociation of water and HfCl4 on a Ge/Si(100) −(2 × 1) surface with a density-functional theory. The Si–Ge and Ge–Ge homodimers are used to represent the Si1−xGex surface. (i) Water first adsorbs on the bare Ge/Si(100) − (2 × 1) surface and then dissociates into OH and H. The activation energy for adsorption of water on the Ge–Ge homodimer is much higher than that on the Si–Ge heterodimer. (ii) HfCl4 dissociates upon adsorption on the Ge/Si(100) − (2 × 1) surface into HfCl3 and Cl. No net activation barrier exists during the adsorption of HfCl4 on both SiGe surface dimers. The molecular adsorption state is found to be metastable according to the calculation, which implies that the reaction tends to move toward to the product rather than trapping in HfCl4 adsorbed state. The difference in the potential energy surface between reactions on Si–Ge and Ge–Ge dimers is due to different bond strengths.

The crystallization behavior of melt-spun amorphous Al92−xNi8Lax (x = 4 to 6) alloys was investigated by means of differential scanning calorimetry, x-ray diffractometry, and transmission electron microscopy. Crystallization kinetics were analyzed by Kissinger and Johnson–Mehl–Avrami approaches. Microhardness of all the ribbons was examined at different temperatures and correlated with the corresponding structural evolution. The results show that the variation of La content from Al88Ni8La4 to Al86Ni8La6 has significant influence on the crystallization pathways from amorphous to stable crystalline phases and on the evolution of microhardness with temperature. The two stages of crystallization in Al88Ni8La4 and Al87Ni8La5 alloys correspond to formation of fcc-Al and Al11La3, Al3Ni, Al3La. In Al86Ni8La6, three stages of crystallization are observed which correspond to formation of a metastable phase, fcc-Al, Al11La3, Al3Ni, and Al11La3, Al3Ni, Al3La, and decomposition of a metastable phases to stable crystalline phases.

The solid-state reactions between Al and TiO2 that occur during heating an Al/TiO2 nanocomposite powder produced using high-energy mechanical milling have been studied using thermal analysis, x-ray diffractometry (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) in combination with compositional microanalysis. It has been found that Al and TiO2 react in the temperature range from 650 to 800 °C, forming Al3Ti, but XRD analysis, SEM examination, and detailed TEM characterization of the powder particles heated to 800 °C show that the expected Al2O3 does not form. However, α–Al2O3 particles form during heating from 800 to 1000 °C. The possible reasons for the time gap between formation of Al3Ti and Al2O3 are discussed.

A novel structural mesoporous alumina (40 mol%)/yttrium doped zirconia nanocrystalline composite has been synthesized by a solvothermal process using ethanol and ethylene glycol as a co-solvent. X-ray diffraction, thermogravimetry/differential scanning calorimetry, Fourier transform infrared, transmission electron microscopy, and nitrogen adsorption are used for the structural characterization. This novel mesoporous alumina/zirconia nanocomposite presents nanocrystalline zirconia particles with a uniform size less than 5 nm surrounded by alumina, forming a kind of core-shell structure after calcined at 800 °C. The mesostructural composite has high surface area (higher than 250 m2/g) and a narrow pore-size distribution of about 3.2 nm throughout the composite sample. The uniformly distributed nanocrystalline zirconia particles and the surrounding wormlike alumina framework act as the inorganic wall for the mesopores.

The oxidation kinetics and the effects of alloying on the oxidation behaviors of copper-based bulk metallic glasses were studied. The oxidation kinetics, oxide compositions, and structures were investigated by thermogravimetric analysis (TGA), x-ray diffraction, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. Both the TGA results and the XPS depth profile measurements showed that the oxidation resistance of Cu60Zr30Ti10 bulk metallic glass was improved by adding Hf, but it deteriorated when it was alloyed with Y. The oxide phases were found to be ZrO2, Cu2O, and CuO in samples heated at 573 K while an additional metallic Cu phase was detected in the ones heated at 773 K. A porous oxide structure was observed in the (Cu0.6Zr0.3Ti0.1)98Y2 metallic glass oxidized at 673 K, and the poor oxidation resistance of the alloy is attributed to the porous structure.

Over the last ten years there has been substantial experimental and theoretical effort in understanding the transport properties of filled skutterudite compounds to optimize their thermoelectric properties. One such approach involves partially filling the voids in attempting to optimize the electrical properties while minimizing the thermal conductivity. We illustrate the importance of this approach by plotting and comparing the figure of merit of CoSb3 over a large range of carrier concentrations and thermal conductivity values. The thermal conductivity of partially filled skutterudites AxCo4Sb12, where A = La, Eu, and Yb, is analyzed using the Debye model to correlate the data with the type of filler atom in evaluating the role of the filler in affecting the thermal conductivity. Partial void filling has resulted in relatively high thermoelectric figures of merit at moderately high temperatures.

Wear-resistant Cu-based solid-solution-toughened Cr5Si3/CrSi metal silicide alloy with a microstructure consisting of predominantly the dual-phase primary dendrites with a Cr5Si3 core encapsulated by CrSi phase and a small amount of interdendritic Cu-based solid solution (Cuss) was designed and fabricated by the laser melting process using Cr–Si–Cu elemental powder blends as the precursor materials. The microstructure of the Cuss-toughened Cr5Si3/CrSi metal silicide alloy was characterized by optical microscopy, powder x-ray diffraction, and energy dispersive spectroscopy. The Cuss-toughened silicide alloys have excellent wear resistance and low coefficient of friction under room temperature dry sliding wear test conditions with hardened 0.45% C carbon steel as the sliding–mating counterpart.

Conventional plasma-sprayed hydroxyapatite coatings suffer from many difficulties that have limited their use in orthopaedic implants, including uneven resorption rates, poor fracture toughness, and poor adhesion to medical alloys. The placement of a diamondlike carbon buffer layer may overcome these obstacles by providing unique chemical inertness, hardness, and cell-interaction properties at the implant–tissue interface. Nanocrystalline hydroxyapatite and amorphous diamondlike carbon films were prepared by room-temperature pulsed-laser deposition of hydroxyapatite and graphite targets, respectively. Scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and microscratch adhesion testing were used to determine surface morphology, interfacial structure, and adhesion of the bilayer coatings. Nanocrystalline hydroxyapatite/diamondlike carbon coatings have several potential orthopaedic applications, including use in hip prostheses.

A new patterning technique for the deposition of sol-gels and chemical solution precursors was developed to address some of the limitations of soft lithography approaches. When using micromolding in capillaries to pattern precursors that exhibit large amounts of shrinkage during drying, topographical distortions develop. In place of patterning the elastomeric mold, the network of capillary channels was patterned directly into the substrate surface and an elastomer membrane is used to complete the channels. When the wetting properties of the substrate surfaces were carefully controlled using self-assembled monolayers (SAMs), lead zirconate titanate thin films with nearly rectangular cross-sections were successfully patterned. This technique, called microchannel molding (μCM), also provided a method for aligning multiple layers such as bottom electrodes for device fabrication.

Nanocrystalline GdFeO3 powder was synthesized by a combustion technique, using glycine as the fuel and the corresponding metal nitrates as oxidants. Five different molar ratios of fuel-to-oxidant were chosen to study the effect of fuel content on the phase formation and the powder properties. The powders after calcination were characterized by x-ray diffraction (XRD) and crystallite sizes calculated by x-ray line broadening. The crystallite sizes for the phase pure products after calcination at 600 °C were in the range 40–65 nm. The transmission electron microscopy observations clearly highlight the pronounced crystallinity for the propellant chemistry samples. The nature of the agglomerates was investigated by light scattering studies. The lattice thermal expansion behavior was also studied by high-temperature XRD.

The high-temperature indentation fracture and microstructures of dysprosium niobate (DyNbO4) were investigated by optical, scanning, and transmission electron microscopy (OM, SEM, and TEM). Polycrystalline samples were sintered at 1350 °C for 3 h and cut into 3 mm disks for TEM. The disks were indented in a Nikon QM (Tokyo, Japan) hot hardness indenter at room temperature up to 1000 °C. Many lamellar twins having different widths were observed by TEM as well as intergranular microcracks. The room temperature hardness was relatively low at 5.64 GPa and decreased with elevated temperatures. Crack lengths were short, showing a typical micro-cracking effect. In the sample indented at 1000 °C, dislocations in periodic arrays were evident, and their density increased markedly due to heavy plastic deformation.