This paper presents a spin-coating layer-by-layer assembly process to prepare multilayered polyelectrolyte-clay nanocomposites. This method allows for the fast production of films with controlled layered structure. The preparation of a 100-bilayer film with a thickness of about 330 nm needs less than 1 h, which is 20 times faster than conventional dip-coating processes maintaining the same hardness and modulus values. For validation of this technique, nanocomposite films with thicknesses up to 0.5 μm have been created with the common dip self-assembly and with the spin coating layer-by-layer assembly technique from a poly(diallyldimethylammonium)chloride (PDDA) solution and a suspension of a smectite clay mineral (Laponite). Geometrical characteristics (thickness, roughness, and texture) as well as mechanical characteristics (hardness and modulus) of the clay-polyelectrolyte films have been studied. The spin-coated nanocomposite films exhibit clearly improved mechanical properties (hardness 0.4 GPa, elastic modulus 7 GPa) compared to the “pure” polymer film, namely a sixfold increase in hardness and a 17-fold increase in Young’s modulus.

Fabrication and terahertz wave properties of alumina microphotonic crystals with a diamond structure were investigated. The three-dimensional diamond structure was designed on a computer using 3D-CAD software. The designed lattice constant was 500 μm. The structure consisted of 8 × 8 × 4 unit cells. Acrylic diamond structures with an alumina dispersion of 40 vol% were formed by using microstereolithography. Fabricated precursors were dewaxed at 600 °C and sintered at 1500 °C. The linear shrinkage ratio was about 25%. The relative density reached 97.5%. The electromagnetic wave properties were measured by terahertz time-domain spectroscopy. A complete photonic band gap was observed at the frequency range from 0.40 THz to 0.47 THz, and showed good agreement with the simulation results calculated by the plane wave expansion method. Moreover, localized modes were obtained at the frequencies 0.42 THz and 0.46 THz by introducing an air defect in the diamond structure. They corresponded to the simulation by the transmission line modeling method.

Amorphous siliconlike films with hydrophobic functionalities have been deposited by plasma-enhanced chemical-vapor deposition on carbon-fiber-reinforced polymer (CFRP) unidirectional laminates used for micromechanical applications where high strength-to-weight and high stiffness-to-weight ratios are required. To improve long-term geometrical stability in ultrahigh-precision machine structures, hydrophobic CFRP materials are desirable. Three layers have been grown with different plasma-process parameters from a mixture of hexamethyldisiloxane, O2, and Ar. Chemical composition, water contact angle, surface energy, morphology, and tribological properties have been evaluated to choose the one that best fulfills hydrophobicity, wear, and scratch resistance. Wear tests have also been carried out on CFRP laminates coated with a polyurethane layer to compare the wear performance of the above specimens with that of a conventional hydrophobic coating. Scanning electron microscope images show a very good adhesion of the films to the composite substrate because the failure of the film and of the substrate (such as fiber failure) take place simultaneously.

Current stressing at densities from 2.9 to 7.3 × 104 A/cm2 has significant effects on the atomic migration of eutectic SnBi solder alloys. At lower density (2.9 × 104 A/cm2), electromigration dominates the migration of both Sn and Bi, and drives Sn and Bi atoms to migrate toward the anode side. While at higher densities (4.4 and 7.3 × 104 A/cm2), the enhanced Bi electromigration induces a back stress, which promotes a reversed migration of Sn toward the cathode side. A large number of Sn atoms accumulate at the cathode side and form lumps there.

The present study investigated the micro-impact fracture behavior of various lead-free solder joints, including Sn–1Ag–0.1Cu–0.02Ni–0.05In, Sn–1.2Ag–0.5Cu–0.05Ni, and Sn–1Ag–0.5Cu. The fracture that occurs within the solder joint corresponds to a higher impact fracture energy (1.35 mJ), while the fracture at the interface between the solder joint and intermetallic compound acquires a smaller impact energy (0.82 mJ). Two types of fracture mechanisms were proposed based on observations of the fracture morphology and the impact curve for the solder ball joints. The longer deflection distance, referring to better elongation, exists for the mechanism corresponding to the higher fracture energy.

Crystallographic ordering and defects in WSe2 thin films with ultralow thermal conductivity are characterized by electron imaging and diffraction in cross-sectional geometry. The results show that the film consists of oriented, coherent crystallites that are a few nanometers in diameter. Two films of different thickness with different thermal conductivity are compared. We show that the film with a lower thermal conductivity is characterized by less coherent crystallites with a greater degree of misorientation.

The cavity model and the dislocation mechanics were used to analyze the plastic energy dissipated in an indentation deformation. The plastic energy dissipated in an indentation cycle was proportional to the cube of the residual indentation depth. The experimental results supported the analysis for the indentation of commercially pure titanium by a Vickers indenter. Slip bands around the indentation were observed, suggesting that the indentation deformation was controlled by dislocation motion. The indentation hardness decreased with the indentation load, showing the indentation size effect. The ratio of the total energy to the plastic energy was found to be proportional to the ratio of the maximum indentation depth to the residual indentation depth. The effects of holding time were examined on the time-dependent plastic deformation of the commercially pure titanium at ambient temperature.

A modified casting Al–Cu alloy with ultrahigh tensile strength and ductility of about 520 MPa and 13.5% was obtained by PrxOy addition. PrxOy was decomposed to form AlPrO3, which acted as the effective heterogeneous nuclei for the crystallization of the primary α–Al phase. The main reason for the simultaneous increase in the strength and ductility of the modified alloy may be attributed to the effect of a large number of regular, network, and homogeneous nanoscale θ′ phase precipitates and more crystal grain and dendrite boundaries formed by their refinement on restricting and impeding the dislocation actuation and movement.

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.

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.

A modified embedded-atom method (MEAM) interatomic potential for the Cu–Zr system has been developed based on the previously developed MEAM potentials for pure Cu and Zr. The potential describes fundamental physical properties and alloy behavior of the Cu–Zr binary system reasonably well. The applicability of the potential to atomistic investigations of mechanical and deformation behavior for the Cu–Zr binary and Cu–Zr-based multicomponent amorphous alloys is also demonstrated by showing that fully relaxed and realistic amorphous structures can be generated by molecular dynamics simulations.

The enthalpy of formation of cubic ceria–zirconia solid solutions (c-Ce(1−x)ZrxO2, 0.05 ⩽ x ⩽ 0.75) at 25 °C with respect to monoclinic zirconia (m-ZrO2) and cubic ceria (c-CeO2) has been measured by high-temperature oxide melt solution calorimetry. In contrast to fluorite solid solutions containing trivalent oxides (e.g., yttria–zirconia), mixing in c-Ce1−xZrxO2 shows moderate positive deviation from ideality. Evaluating the data within the framework of a regular solution model, the interaction parameter, Ω, is +51.0 ± 8.0 kJ/mol. The introduction of undersized Zr into CeO2 severely distorts and destabilizes the oxygen sublattice. Destabilization of c-Ce1−xZrxO2 may be relieved by reduction or clustering. A stable ordered compound in the CeO2–ZrO2 system is thermodynamically unlikely.

The standard Oliver–Pharr nanoindentation analysis tacitly assumes that the specimen is structurally rigid and that it is both semi-infinite and homogeneous. Many specimens violate these assumptions. We show that when the specimen flexes or possesses heterogeneities, such as free edges or interfaces between regions of different properties, artifacts arise in the standard analysis that affect the measurement of hardness and modulus. The origin of these artifacts is a structural compliance (Cs), which adds to the machine compliance (Cm), but unlike the latter, Cs can vary as a function of position within the specimen. We have developed an experimental approach to isolate and remove Cs. The utility of the method is demonstrated using specimens including (i) a silicon beam, which flexes because it is supported only at the ends, (ii) sites near the free edge of a fused silica calibration standard, (iii) the tracheid walls in unembedded loblolly pine (Pinus taeda), and (iv) the polypropylene matrix in a polypropylene–wood composite.

Four kinds of extruded Mg–X at.% Zn binary alloys (X = 1.9, 2.4, 3.0, and 3.4) were used to examine the effect of precipitate volume fraction on fracture toughness. All the alloys had fine grain sizes of 1–3 μm and fine sphere-shaped precipitates of 50–60 nm. The volume fraction of precipitates increased with additional zinc content. The results of mechanical property tests showed that the extruded Mg–2.4 at.% Zn alloy exhibited the best balance of strength and fracture toughness. One of the reasons was the different volume fraction of precipitates at the grain boundaries, which was the source of void formation. According to the fracture surface observations and ductile fracture model analysis, the volume fraction of precipitates of 2%–4% was shown to be enough to improve the fracture toughness for the fine-grained magnesium alloys; i.e., higher contents of zinc atoms were not needed to enhance the mechanical properties.

The cubic nanocrystalline Li–Ti–O oxides were prepared by the solvothermal reaction of TiO2 and LiOH at 200 °C in water and aliphatic alcohols with different dielectric constants. The reaction in all solvents leads to the formation of white ternary compounds containing Li, Ti, and O. The actual Li content in the prepared materials increases with decreasing polarity of the used solvent. All prepared materials are crystalline, and their structure can be described using a spinel structural model. The structure of materials prepared at a relative dielectric constant (ϵr) value higher than 33 is characterized by Ti disorder when the Ti atoms are distributed between both types of the available octahedral sites with approximately the same probability. The tendency to form phases with Ti disorder decreases with decreasing ϵr of the solvent. All prepared materials are active toward electrochemical Li insertion. The observed specific capacity ranges between 60 and 150 mAh/g.

The undercooling behavior of pure Sn, Sn–0.7Cu, Sn–3.5Ag, and Sn–3.8Ag–0.7Cu solder alloys was observed in terms of various under bump metallurgies (UBMs). Four different UBMs (electroplated Cu, electroplated Ni, electroless Ni(P), and electroless Ni(P)/immersion Au) were used. The amount of the undercooling of Pb-free solder alloys was reduced when reacted with electroplated Cu UBM and Ni-based UBMs. The Ni-based UBMs were more effective than Cu UBM in reducing the undercooling of Pb-free solders. When Ni3Sn4 was formed during the interfacial reactions with Ni-based UBMs, the reduction of undercooling was significant, especially for pure Sn and Sn–3.5Ag. The effects of UBMs on the undercooing of Pb-free solder alloys are discussed by comparing intermetallic compounds formed during interfacial reactions with UBMs. In addition, the microstructural changes as well as the microhardness of four solders with or without UBMs are discussed, which could be related to their undercooling behaviors.

Nanocomposite films containing ZnO quantum dots (QDs) and SiOxNy matrix were prepared by target-attached radio frequency sputtering. Photoluminescence (PL) dominated by violet and blue emissions was observed from all ZnO QD–SiOxNy nanocomposite films with dot diameters ranging from 2.77 to 6.65 nm. X-ray photoemission spectroscopy (XPS) revealed the formation of nitrogen-correlated bonding configurations in both the SiOxNy matrix and the dot/matrix interfaces. The nitrogen-correlated configuration at the interface produced a substantial polarization effect at dot surface. The suppression of green-yellow emission observed in photoluminescence spectra of all samples was ascribed to the hole-trapping process promoted by the enhancement of the surface polarization.

Self-assembled core-shelled hierarchical structures consisting of single-crystalline pyramid Zn microtip as a core, converted ZnO coating as the shell, and the grown ZnO nanowires as branches, have been prepared. Such ZnO hierarchical structures fabricated by a simple aqueous chemical growth method on Zn foil substrate are expected to be easily integrated into nanodevices. These self-organized structures are superior to both the random nanoarchitecture arrays formed in vapor system and the precipitated nanostructures suspended in the solution. Because of the easier transportation of electrons from the metallic core to ZnO branches, the self-assembled core-shelled hierarchical structures exhibit better field-emission characteristics.

We propose a new method for the preparation of the polymer/organoclay nanocomposite, termed the solution and melt mixing (SOAM) method, where the polymer and clays are first blended in solution, and subsequently the mixture is further blended in the melt. We prepared the ternary nanocomposite systems of poly(styrene-co-acrylonitrile) (SAN), poly(vinyl chloride) (PVC) and Cloisite25A clays (C25A) by solution blending as well as by the SOAM method. The C25A content in the nanocomposite was optimized by analyzing the x-ray diffraction (XRD) data of binary mixtures (SAN/C25A and PVC/C25A nanocomposites). The values of the interaction parameter (χab) were calculated by using the molar attraction constants of the specific functional groups derived from Hoy’s table. While PVC and C25A were shown to be highly compatible, SAN and C25A were less compatible. XRD data and transmission electron microscopy observations indicated that the SAN/PVC/C25A nanocomposites had at least partially exfoliated structures. The tensile modulus and the elongation at break of the nanocomposites prepared by the SOAM method were higher than those prepared by simple solution blending.

Macroscopic cracks in bulk silicon are generally considered to be immune to fatigue. Here, evidence for pronounced fracture-related fatigue damage in cyclic contact loading of (001) monocrystalline silicon with hard spheres of millimeter-scale radius is presented. The periodic indentation field generates ring cracks around the contact, which proliferate with continued cycling. Copious debris in the form of slabs and particulates is ejected from within the crack walls onto the specimen surface. Continued ejection leads ultimately to large-scale surface removal. The fatigue damage progressively degrades the material strength, more rapidly at higher contact load. Implications concerning the function of silicon devices, including microelectro-mechanical systems, will be briefly discussed.