Transmission electron microscopy (TEM) images, selected-area electron-diffraction patterns, high-resolution TEM images, and x-ray energy dispersive spectroscopy line scans for the ZnO/n-Si (001) heterostructures annealed at 900 °C showed that stacking faults and amorphous layers were formed in the lower region of the ZnO films. The stacking faults existing in the lower region of the ZnO columnar grains originated from the formation of zinc vacancy layers caused by the thermal treatment, resulting in the existence of a tensile strain. The formation of the amorphous layer in the ZnO film was attributed to the accumulation of zinc vacancy layers.

Magnesium hafnium tungstate [MgHf(WO4)3] was synthesized by high-energy ball milling followed by calcination. The material was characterized by variable- temperature neutron and x-ray diffraction. It crystallized in space group P21/a below 400 K and transformed to an orthorhombic structure at higher temperatures. The orthorhombic polymorph adopted space group Pnma, instead of the Pnca structure commonly observed for other A2(MO4)3 materials (A = trivalent metal, M = Mo, W). In contrast, the monoclinic polymorphs appeared to be isostructural. Negative thermal expansion was observed in the orthorhombic phase with αa = −5.2 × 10−6 K−1, αb = 4.4 × 10−6 K−1, αc = −2.9 × 10−6 K−1, αV = −3.7 × 10−6 K−1, and αl = −1.2 × 10−6 K−1. The monoclinic to orthorhombic phase transition was accompanied by a smooth change in unit-cell volume, indicative of a second-order phase transition.

A new amphiphile: octyl-β-D-glucopyranoside along with a single-source precursor, barium titanium methoxyethoxide, were used to develop a facile route for synthesis of BaTiO3, via either a hydrolytic or a nonhydrolytic method. The average particle size for the samples was on the order of 20 to 30 nm, while that for the control samples (without the amphiphile) ranged from 100 nm to several microns. The high-resolution transmission electron microscopy (HRTEM) images and selected-area electron- diffraction patterns revealed that these nanoparticles were single crystalline; the Raman active longitudinal optical modes observed in calcined (650 °C) samples at 718 and 304 cm−1 directly indicated the presence of tetragonal domains in an overall cubic lattice structure. Moreover, the one-step nonhydrolytic approach developed for the synthesis of BaTiO3 is fast, and it eliminates tedious steps such as prolonged refluxing and aging. Thermogravimetric and Fourier transform infrared (FTIR) analysis were performed to investigate the role of octyl-β-D-glucopyranoside in the evolution of the perovskite phase, grain size, and morphology. These techniques suggested that van der Waals type of interactions were present between the amphiphile and barium titanium methoxyethoxide oligomers, and in turn they led to the controlled growth of nanoparticles.

The SHS reaction in the Ni–Ti–B4C system starts with the formation of Ni–Ti and Ni–B intermetallic compounds from the solid interacted reaction among the reactants and, subsequently, the formation of Ni–Ti and Ni–B liquid at the eutectic point. Meanwhile, some C atoms from the reaction between Ni and B4C can dissolve into Ni–Ti liquid to form TiC. The heat generated from these reactions can promote the mutual diffusion of Ni–Ti–C and Ni–B liquid and simultaneously accelerate the formation of Ni–Ti–C–B liquid. Finally the precipitation of TiC and TiB2 occur when the C and B atoms in the liquid become supersaturated. The addition of Ni not only promotes the occurrence of the self-propagating high temperature synthesis (SHS) reaction by forming Ni–Ti liquid, but also accelerates the SHS reaction by forming Ni–B liquid and dissociative C. The early appearance of dissociative C from the reaction between Ni and B4C causes the formation of TiC prior to that of TiB2.

The influence of the cooling rate on the structure, microhardness, relaxation, and devitrification behavior of Cu44Ag15Zr36Ti5 glassy alloy on heating is studied in the present work. According to transmission electron microscopy investigations, the structures of Cu44Ag15Zr36Ti5 glassy ribbon and bulk samples are somewhat different. The structure of the ribbon samples is amorphous while, the nanoscale clusters of the crystalline phase (highly ordered regions) are formed in the bulk samples. It is reflected in the shift of the x-ray diffraction peak, in the magnitude of the heat of structure relaxation and crystallization, as well as in the change in the Vickers microhardness. An analysis of the cooling curve is also performed.

The total energies and cohesive properties of 29 Au–Sn intermetallics (stable, metastable, and virtual) are calculated from first-principles density-functional theory (DFT) employing ultrasoft pseudopotentials (USPP) and both local-density approximation (LDA) and generalized gradient approximation (GGA) for the exchange-correlation functional. Among the intermetallics considered, the ground-state structures are found to be AuSn, AuSn2, and AuSn4. Another phase Au5Sn, though present in the equilibrium diagram, lies slightly above the ground state convex hull. The formation energies of stable phases calculated using USPP–LDA and USPP–GGA are nearly the same. Except for AuSn, calorimetric data for enthalpies of formation show a good agreement with the calculated formation energies. Based on our first-principles results, it is argued that the structures of two metastable phases are cP52-type γ brass (isotypic with Al4Cu9) at Au–20.5 at.% Sn and hP1-type γ (isotypic with HgSn6–10) at Sn–8 at.% Au. For the intermetallics considered in this study, we provide optimized values of lattice parameters and Wyckoff positions. The experimental lattice parameters show a better agreement with those calculated using USPP–LDA than with USPP–GGA. The results presented here form the basis for creating a reliable thermodynamic database to facilitate calculations of stable and metastable phase diagrams of binary and multicomponent systems containing Au and Sn, relevant to electronic packaging and many other joining applications.

Grain growth in 40-nm-thick Cu films encapsulated by over- and under-layers of SiO2, Al2O3, Si3N4, and MgO was investigated. The films were magnetron sputter deposited onto cooled SiO2/Si substrates in an ultrahigh vacuum purity environment. Ex situ annealing was performed at 400 and 800 °C in 1 atm reducing gas. Films deposited at −120 °C exhibited more extensive grain growth after annealing than films deposited at −40 °C. Films annealed at room temperature had grain sizes less than 35 nm. All films exhibited some void formation after annealing at 400 and 800 °C, but the films encapsulated in Al2O3 exhibited the lowest area fraction of voids. The mean grain sizes of the Al2O3-encapsulated films, as measured by the linear intercept method, were 86 and 134 nm after annealing at 400 and 800 °C, respectively.

The temperature dependence of the thermal stability in a NiCoCrAlY coating alloy was examined by experimental observation and thermodynamic modeling in the 400–1200 °C temperature range. The results indicated that the thermal stabilities of primary β–NiAl, β–NiAl/α–Cr eutectic, and γ–Ni were slightly temperature dependent, but those of γ′–Ni3Al, σ–(Cr,Co,Ni), and α–Cr were strongly temperature dependent in the annealed NiCoCrAlY specimens. The temperature dependence of the thermal stabilities among γ′–Ni3Al, σ–(Cr,Co,Ni), and α–Cr might be ascribed to the σ → α transformation at ∼1100 °C and the γ′ → γ transformation at ∼800 °C. Further, using Thermocalc associated with TTNi7 database, thermodynamic equilibria were calculated. The modeling results were compared with the experimental results and found to be in reasonable agreement with the experimental observations of β–NiAl, σ–(Cr,Co,Ni), and γ′–Ni3Al. Some deviations observed are discussed in the light of both limited availability of thermodynamic data and experimental problems.

Silicon pack cementation has been applied to improve the oxidation resistance of Zr2Al3C4. The Si pack coating is mainly composed of an inner layer of ZrSi2 and SiC and an outer layer of Al2O3 at 1200 °C. The growth kinetics of silicide coating at 1000–1200 °C obey a parabolic law with an activation energy of 110.3 ± 16.7 kJ/mol, which is controlled by inward diffusion of Si and outward diffusion of Al. Compared with Zr2Al3C4, the oxidation resistance of siliconized Zr2Al3C4 is greatly improved due to the formation of protective oxidation products, aluminosilicate glass, mullite, and ZrSiO4.

Geometrical self-similarity is a feature of mathematically sharp indenters such as conical and Berkovich indenters. However, self-similarity is considered inappropriate for practical use because of inevitable indenter tip blunting. In this study, we analyze the load–depth curves of conical indenters with various tip radii via finite element analyses. Based on the numerical data, we propose a method of restoring the Kick’s law coefficient C of finite tip-radius indenter to that of zero tip-radius indenter, thereby retaining the self-similarity of the sharp indenter. We then regress the unloading slope for the evaluation of elastic modulus in several ways. Finally, we establish a method to evaluate elastic modulus, which successfully provides the value of the elastic modulus with a maximum error of less than 5%, regardless of tip radius and material properties of both indenter and specimen.

Commensurate BaTiO3/SrTiO3 superlattices were grown by reactive molecular-beam epitaxy on four different substrates: TiO2-terminated (001) SrTiO3, (101) DyScO3, (101) GdScO3, and (101) SmScO3. With the aid of reflection high-energy electron diffraction (RHEED), precise single-monolayer doses of BaO, SrO, and TiO2 were deposited sequentially to create commensurate BaTiO3/SrTiO3 superlattices with a variety of periodicities. X-ray diffraction (XRD) measurements exhibit clear superlattice peaks at the expected positions. The rocking curve full width half-maximum of the superlattices was as narrow as 7 arc s (0.002°). High-resolution transmission electron microscopy reveals nearly atomically abrupt interfaces. Temperature-dependent ultraviolet Raman and XRD were used to reveal the paraelectric-to-ferroelectric transition temperature (TC). Our results demonstrate the importance of finite size and strain effects on the TC of BaTiO3/SrTiO3 superlattices. In addition to probing finite size and strain effects, these heterostructures may be relevant for novel phonon devices, including mirrors, filters, and cavities for coherent phonon generation and control.

Porous magnesium with directional cylindrical pores (or “lotus-type” porous magnesium) was fabricated through the use of hydrogen decomposed from MgH2 powders during unidirectional solidification. Liquid magnesium was cast into a mold in which MgH2 powders were placed and was unidirectionally solidified, which achieved growth of pores elongated along the direction of solidification. The effect of the amount of the MgH2 powders on the pore structure (porosity, diameter, and number density of pores) and the change in the pore structure along the pore growth direction were clarified. The porosity and number density of pores increase with increasing amount of MgH2 powder, and the average diameter of pores decreases with increasing amount of MgH2 powder. The pore structure changes with the growth of pores along the solidification direction.

The dielectric anomalies and their structure dependence were evaluated and discussed in Sr4(LaxNd1-x)2Ti4Nb6O30 ceramics, together with the analysis of ultrasonic velocity shift and attenuation spectra in the low-temperature range. The room-temperature structure was confirmed as the tetragonal in space group P4bm for all compositions. One diffuse ferroelectric peak and three relaxor ferroelectric peaks corresponding to the commensurate/incommensurate modulation of oxygen octahedra, polar clusters of A-site ion ordering, and B-site ion ordering, respectively, were observed in the composition with x = 0.25. With decreasing the radius difference between A1- and A2-ions (increasing x), the dielectric relaxations, especially the one originating from the polar clusters of A-site ion ordering, tended to increase significantly and overlap the diffuse ferroelectric peak, which was completely overlapped for x ⩾ 0.75. This process just reflected the increased disordering degree of both A- and B-site ions, and the analysis of ultrasonic attenuation strongly supported the above conclusions on dielectric relaxations and their structural origins. The ultrasonic attenuation peak at approximately 100 K corresponded to the freezing process of the dielectric relaxations, and the fluctuation with composition of the ultrasonic attenuation peaks between 150 and 260 K suggested the possible structure variation.

The thermodynamic and kinetic fragilities of two near-eutectic Mg-based bulk metallic glass (BMG)-forming liquids, Mg61Cu28Gd11 and Mg59.5Cu22.9Ag6.6Gd11, were investigated using high-precision differential scanning calorimeter (DSC). The thermodynamic fragility denoted as F3/4 was determined by evaluating the temperature dependence of the excess entropy Sex. The heating rate dependence of the relaxation time at the glass transition temperature was investigated to measure the kinetic fragility. A positive correlation between the thermodynamic and kinetic fragilities could be established in Mg-based BMG-forming liquids on the basis of Adam-Gibbs equation in contrast to a number of other BMGs.

Residual stress profiles were introduced in sodium aluminosilicate glass disks using an ion-exchange process. They were fractured in two loading conditions: indentation and biaxial flexure. The fractal dimension of the macroscopic crack branching pattern called the crack branching coefficient (CBC), as well as the number of fragments (NOF) were used to quantify the crack patterns. The fracture surfaces were analyzed to determine the stresses responsible for the crack branching patterns. The total strain energy in the body was calculated. The CBC was a good measure of the NOF. They are directly related to the tensile strain energy due to the residual stress profile for fractures due to indentation loading. However, in general for materials with residual stresses, CBC (or NOF) is not related to the strength or the stress at fracture, or even to the total stored tensile strain energy. Instead, the CBC appears to be related, in a complex manner, to the distribution of stresses in the body. Therefore, in general, the characterization of the CBC of fractured materials cannot be used to ascertain the prior stress distribution.

We predict a possible phase transition of ZnO from wurtzite to zinc blende structure using first-principles molecular-dynamics simulations. By calculating the Gibbs free energies of the two phases as a function of temperature and hydrostatic pressure, we show that their energy difference decreases continuously with increasing temperature and pressure, and the vibrational entropy plays an important role on the location of the phase transition point. At 300 K, the phase transition is expected to occur at a pressure lower than 30 GPa with an activation energy barrier of 0.386 eV/atom. The transition path was also simulated, along which the system goes through a transient face-centered orthorhombic structure to overcome the energy barrier. Our theory results may be valuable for stabilizating the zinc blende ZnO in experiment.

The correlation among apparent global plasticity, Poisson’s ratio, and fragility in monolithic bulk metallic glass (BMG) alloys has been investigated in the present study. The shear and bulk moduli in monolithic Cu-based BMG alloys have been measured by resonant ultrasound spectroscopy (RUS) and ultrasonic technique. The Cu43Zr43Al7Ag7 BMG alloy showing a large apparent global plasticity (∼8%) exhibits a high Poisson’s ratio when compared with that of Cu43Zr43Al7Be7 BMG alloy. In addition, the fragility of Cu-based BMG alloys can be obtained by differential scanning calorimetry (DSC). The fragility index m of Cu43Zr43Al7Ag7 BMG alloy is slightly larger than that of Cu43Zr43Al7Be7 BMG alloy. The correlation between Poisson’s ratio and fragility in BMG alloys can be presented by a simple relation of m − 17 = 14 (B∞/G∞ − 1). Poisson’s ratio and fragility might be regarded as an important parameter that controls global plasticity of glass-forming alloys.

The mechanical behavior [i.e., stiffness, strength, and toughness (KIC)] of SiC Al–Si–Mg metal–ceramic composites (50:50 by volume) was studied at temperatures ranging from 25 to 500 °C. The SiC phase was derived from wood precursors, which resulted in an interconnected anisotropic ceramic that constrained the pressure melt-infiltrated aluminum alloy. The composites were made using SiC derived from two woods (sapele and beech) and were studied in three orthogonal orientations. The mechanical properties and corresponding deformation micromechanisms were different in the longitudinal (LO) and transverse directions, but the influence of the precursor wood was small. The LO behavior was controlled by the rigid SiC preform and the load transfer from the metal to the ceramic. Moduli in this orientation were lower than the Halpin–Tsai predictions due to the nonlinear and nonparallel nature of the Al-filled pores. The LO KIC agreed with the Ashby model for the KIC contribution of ductile inclusions in a brittle ceramic.

This study investigated the polarity effect of electromigration (EM) on the interfacial intermetallic compounds (IMCs) (γ-Cu5Zn8, Cu6Sn5) formation at the anode and the cathode in a Cu/Sn-9Zn/Cu sandwich with a constant direct current density of 1.0 × 103 A/cm2 at 100 °C. The EM had different polarity effects on the nucleation and growth rates of the interfacial Cu5Zn8 IMC from those of Cu6Sn5 IMC. Upon current stressing, the growth rate of the Cu-Zn intermetallic compound (γ-Cu5Zn8) at the cathode interface was much faster than that at the anode. However, the nucleation and growth of the Cu6Sn5 IMC at the anode interface were enhanced, though retarded at the cathode, under the influence of electric current. The mechanism of EM-induced Cu6Sn5 IMC formation towards the anodic Cu is also discussed.

The formation of 10-nm ZnO nanopyramids using a simple synthetic route has been isolated from the reaction of Zn(OAc)2·2H2O in 1,4-butanediol followed by ripening at 90 °C. This was accomplished by establishing control over the Ostwald ripening process through the use of a carboxylic acid specific adsorbate. Using a variety of analytical methods, it is proposed that the carboxylate groups in the acetate precursor stabilize the {101} habit planes, creating septahedral shapes or nanopyramids. Particle assembly into crystallographically oriented dimers was observed with high specificity, and the association mechanism is suggested to relate to the crystal polarity and the variation in specific adsorption of the carboxylic acid to the surface facets. These materials are a candidate for biological labeling applications in living cells.