In this study, the rate-dependent mechanical behavior of a Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass was studied using quasi-static and dynamic shear-punch testing at room temperature. The results demonstrate that the shear strength of this alloy is insensitive to the applied strain rate. However, the formation of shear bands and the serrated flow exhibits a significant strain rate effect. The shear banding-induced fracture patterns and the fracture-melting phenomenon were analyzed based on the free volume theory and the energy transfer model.

The adequacy of instrumented Vickers depth-sensing microindentation to determine Young's modulus of alumina-based ceramics was analyzed. Monophase alumina materials and alumina + 10 vol% aluminium titanate composites, with different microstructures, were tested to determine the effect of microcracking. The load–depth penetration of the indenter curves together with the observation of the imprints by scanning electron microscopy were used to analyze the behavior of the materials. Maximum stiffness was determined from the derivatives of the load-depth curves during unloading. The areas of the imprints measured optically were more representative of the behavior of the materials than the areas calculated from depth-penetration measurements. The formation of microcracks affected the shape of the unloading portion of the curves. Significant differences between the values of Young's modulus determined for different materials and definite relationships between the microstructural parameters of the materials and the Young's modulus were found.

Films with Fe–25 at.% Ge composition are deposited by the process of laser ablation on single crystal NaCl and Cu substrates at room temperature. Both the vapor and liquid droplets generated in this process are quenched on the substrate. The microstructures of the embedded droplets show size as well as composition dependence. The hierarchy of phase evolution from amorphous to body-centered cubic (bcc) to DO3 has been observed as a function of size. Some of the medium-sized droplets also show direct formation of ordered DO19 phase from the starting liquid. The evolution of disordered bcc structure in some of the droplets indicates disorder trapping during liquid to solid transformation. The microstructural evolution is analyzed on the basis of heat transfer mechanisms and continuous growth model in the solidifying droplets.

Lotus-type porous stainless steel (SUS304L), possessing cylindrical pores aligned in one direction, was fabricated by means of a continuous zone melting technique undera pressurized hydrogen/helium atmosphere. Compression tests were carried out on the resultant lotus stainless steel not only in the directions parallel and perpendicular tothe elongated-pore direction but also in other directions to reveal its anisotropic compressive behavior. The macroscopic deformation modes depend on porosity and the angle between the elongated-pore direction and compression direction, which is a unique characteristic resulting from its anisotropic porous structure. The yield stress in the pore direction decreases almost linearly with increasing porosity, while that in the perpendicular direction decreases more rapidly. The yield stress in the direction of θ from the elongated-pore direction decreases monotonically with increase in θ. The yield behavior of lotus stainless steel was described using micromechanical mean-field theory.

Biaxially textured magnesium oxide (MgO) templates of 10-nm thickness were successfully fabricated on glass and silicon substrates without any buffer layers using Ar+ ion beam assisted e-beam evaporation. With an additional layer of 100 nm homoepi MgO on top, the in-plane misorientation of ∼6.5° and out-of-plane misorientation of ∼2.0° have been obtained. Prior to growth, the substrates were bombarded with the same Ar+ ion beam for a certain period ranging from 5 to 35 min to provide initial substrate conditions for textured MgO formation. The ion beam induced modification of the substrate surface morphology was characterized using atomic force microscopy. Reduced surface roughness Ra from 2 to 3 nm on the original glass substrates to below 1.0 nm after 5 min ion beam bombardment was found to be an important condition for the textured MgO formation. The nearly unchanged Ra ≤ 1 nm of the silicon substrate after the ion beam bombardment, however, suggests that additional surface modification is required for the textured MgO to form.

A semi-empirical interatomic potential formalism, the modified embedded atom method (MEAM), has been applied to obtain an interatomic potential for the Fe–Pt alloy system, based on the previously developed potentials for pure Fe and Pt. The potential can describe basic physical properties of the alloys (lattice parameter, bulk modulus, stability of individual phases, and order/disorder transformations), in good agreement with experimental information. The procedure for the determination of potential parameter values and comparisons between the present calculation and experimental data or high level calculation are presented. The applicability of the potential to atomistic studies to investigate structural evolution of Fe50Pt50 alloy thin films during post-annealing is also discussed.

Stresses in thermally grown SiO2 films on silicon have traditionally been determined by substrate curvature measurements. This technique is useful for studying stresses in thin films, but it cannot be used to investigate stresses generated in the substrate during film growth. In the present work, we used microelectromechanical systems-based microstrain gauge devices fabricated from single-crystal and polycrystalline silicon (henceforth silicon and polysilicon, respectively) to measure oxidation-induced stresses in both dry and wet oxidizing ambients. Our microstrain gauges had thicknesses on the micrometer scale, and were themselves used as the substrates to be oxidized. Stresses could be detected in both the SiO2 scales and the silicon and polysilicon substrates. In the SiO2 scales, the stresses were compressive and exhibited viscoelastic relaxation. The as-grown compressive stresses were greater for wet oxidation than they were for dry oxidation, and greater in scales grown on polysilicon than they were in scales grown on silicon. The viscosity of thermally grown SiO2 was the same whether scales formed by wet or dry oxidation, and the same for oxide scales on silicon and polysilicon. Significant compressive stresses were also generated in polysilicon during oxidation, but not in silicon.

In this work, we analyzed the theoretical errors of reduced Young's modulus and hardness of materials provided by single sharp indenter algorithms. According to the analysis, two conclusions can be drawn. First, various methods that use only the indentation loading and unloading curves from a single sharp indenter and omit the effect of the strain hardening exponent own the same widths of the theoretical error bands defined here. They are WEb for reduced Young's modulus and WHb for hardness. Second, the upper-bounds, BUE and BUH, and lower-bounds, BLE and BLH, of theoretical errors of the measured reduced Young's modulus and hardness might be different for different methods. These conclusions, on the one hand, are relevant to the evaluation of various established single sharp indenter algorithms. On the other hand, they provide useful information (i.e., to optimize the theoretical error bounds) for correcting an established method and the development of new single sharp indenter algorithms. According to the conclusions, an energy-based method has been devised to determine reduced Young's modulus and hardness of materials from nanoindentation tests using a standard Berkovich or Vickers indenter (equivalent to a 70.3° cone). It has been shown that the present method owns the reasonable theoretical error bounds and can provide stable results in the presence of data errors.

The effectiveness of Oliver & Pharr's (O&P's) method, Cheng & Cheng's (C&C’s) method, and a new method developed by our group for estimating Young's modulus and hardness based on instrumented indentation was evaluated for the case of yield stress to reduced Young's modulus ratio (σy/Er) ≥ 4.55 × 10−4 and hardening coefficient (n) ≤ 0.45. Dimensional theorem and finite element simulations were applied to produce reference results for this purpose. Both O&P's and C&C's methods overestimated the Young's modulus under some conditions, whereas the error can be controlled within ±16% if the formulation was modified with appropriate correction functions. Similar modification was not introduced to our method for determining Young's modulus, while the maximum error of results was around ±13%. The errors of hardness values obtained from all the three methods could be even larger and were irreducible with any correction scheme. It is therefore suggested that when hardness values of different materials are concerned, relative comparison of the data obtained from a single standard measurement technique would be more practically useful. It is noted that the ranges of error derived from the analysis could be different if different ranges of material parameters σy/Er and n are considered.

The addition of Ag to Cu–Zr alloys is very effective for the increase in the stability of supercooled liquid as well as the glass-forming ability (GFA). The large supercooled liquid region (ΔTx) exceeding 60 K in Cu–Zr–Ag ternary system was obtained in a wide range of 25–55 at.% Cu, 40–65 at.% Zr, and 5–25 at.% Ag. The best GFA was obtained around Cu45Zr45Ag10, and glassy alloy rods with diameters up to 6.0 mm were formed by copper mold casting. The bulk glassy alloys exhibit good mechanical properties, i.e., compressive fracture strength of 1780–1940 MPa, Young's modulus of 106–112 GPa, compressive plastic elongation of 0.2–2.9%, and Vickers hardness of 534–599. The finding of the new Cu–Zr–Ag ternary glassy alloy system with high GFA and good mechanical properties is important for development and scientific studies of bulk glassy alloys.

Fluorocarbon polymer films in the poly(tetrafluoroethylene) (PTFE)-like structure are formed by a low-pressure chemical vapor deposition technique using the hot filament excitation of the gaseous C3F6O precursor. The filament and substrate temperatures were found to influence the structure of the deposited films. Infrared absorption and electron spectroscopy studies reveal that a PTFE-like (CF2)2n linear molecular chain structure evolves by an adsorption driven nucleation and CF2 polymerization process in the films deposited with low (450 °C) filament and high (70 °C) substrate temperatures. The films formed at a low substrate temperature (–165 °C) show a higher concentration of CF and C–CF bond defects and shorter (CF2)2n chains. A high (8–10 at.%) oxygen concentration in the films deposited at 600 °C filament temperature is attributed to the reaction of the (CF2)2n chains with COF and peroxyradicals arising from the dissociation of CF3C(O)F and affects the thermal stability of the films. Such reactions are not involved in the film growth at a low (450 °C) filament temperature. These films have much lower (<2 at.%) bonded oxygen content. The films having an ordered (CF2)2n chain structure formed at 70 °C are characterized by low leakage currents ∼7 × 10−11 A cm−2 at 0.1 MV cm−1 field. In comparison, high leakage currents ∼1 × 10−8 A cm−2 are observed for the films having a higher concentration of C–F and C–CF bonds.

Solid-state wetting experiments were carried out to derive the work of adhesion (adhesion energy) of pertinent Cu/liner interfaces via the Young–Dupré equation using contact-angle measurements of the Cu equilibrium crystal shape on Ta and TaNx liners. Four types of liner surfaces were examined: untreated sputtered Ta (uSp-Ta), untreated sputtered TaNx (uSp-TaN), untreated atomic layer deposited (ALD) TaNx (uALD-TaN), and indium surfactant-treated ALD TaNx (tALD-TaN). All Cu-liner stacks were subsequently annealed at 600 °C for 48 h in a forming gas (95% Ar/5% H2) ambient. For Cu/uSp-Ta, the work of adhesion was found to be 2170 mJ/m2, corresponding to an average contact angle of 74°, while for Cu/uSp-TaN, the work of adhesion amounted to 1850 mJ/m2 for an average contact angle of 85°. Alternatively, the work of adhesion for Cu/uALD-TaN was determined to be 1850 mJ/m2, corresponding to an average contact angle of 85°, while for Cu/tALD-TaN, the work of adhesion was 2280 mJ/m2, at an average contact angle of 70°. These findings indicate that the highest degree of surface wetting occurs for the indium surfactant-treated ALD TaNx. It is thus suggested that surfactant treatment causes a reduction in the energy barrier to Cu nucleation, resulting in an enhancement in Cu wetting characteristics and a more uniform concentration of Cu nucleation sites. A critical potential outcome is the formation of atomically smooth Cu-liner interfaces with enhanced adhesion characteristics.

CeO2 thin films as insulating layers for high-temperature superconducting digital devices were studied. The dependence on substrate temperature and oxygen pressure of the surface morphology and crystallinity of CeO2 thin films prepared by pulsed laser deposition were investigated. CeO2 thin films with a flat and closely grained surface were obtained at a relatively low oxygen pressure of 3.6 Pa, whereas higher oxygen pressure led to CeO2 thin films with a rough surface and columnar grains. The recovery of oxygen content in superconducting layers was examined for multilayer structures with CeO2 thin films. Enough oxygen was supplied to the upper and lower superconducting layers when the multilayer was cooled slowly in 3 × 10−4 Pa oxygen pressure after deposition. Resistively shunted junction type I-V characteristics were confirmed for interface-engineered ramp-edge junctions in a multilayer structure including four superconducting layers with CeO2 thin films.

TiO2 thin films were prepared with a spinodal phase separation structure ranging from hundreds of nanometers to micrometers in size by the sol-gel dip-coating method from a titanium tetraisopropoxide solution containing polyoxyethylene (20) nonylphenyl ether (NPE-20). It was possible to change the titania domain size of the spinodal phase separation structure by selecting alcohol as the solvent because the polycondensation and the phase separation are severely influenced by its evaporation rate from the surface of the coated film. It was also observed that the titania domains became larger in size as the film thickness increased in the bottom area of the substrate when the dip-coating method was applied, while uniformly sized titania domains were possibly formed by a spin-coating method. Furthermore, the contrast between the TiO2 phase and the air phase was not sharp when the titania domain size was smaller than several hundreds of nanometers. It was possible to prepare TiO2-air interconnective films with the spinodal phase separation structure 200–300 nm in domain size by subsequent HF etching. In addition, combining spinodal phase separation structure (SPSS) TiO2 thin film with different skeleton size has the potential to create TiO2 thin film with high photo-electron conversion efficiency due to its particular structure, higher surface area, and lack of bottleneck for electron transfer.

Bond coats play a crucial role in the performance of thermal barrier coating systems. Ru alloys have been identified as promising candidates; therefore, systematic studies were performed on the oxidation behavior of bulk RuAl (50–50 at.%). Isothermal oxidation and thermogravimetric analyses were performed at 1100 °C for different times ranging from 0.1 h to 500 h. Microstructural characterization was performed by scanning and transmission electron microscopy. The results showed the formation of an α–Al2O3 layer on top of a δ–Ru layer. Interface instability between these layers and evaporation of gaseous Ru-oxides lead to the formation of large elongated cavities and alternating α–Al2O3/δ–Ru layers.

There has been much recent interest in heat transport in nanostructures, and alsoin the structure, properties, and growth of biological materials. Here we present measurements of thermal properties of a nanostructured biomineral, ivory. The room-temperature thermal conductivity of ivory is anomalously low in comparison with its constituent components. Low-temperature (2–300 K) measurements ofthermal conductivity and heat capacity reveal a glass-like temperature dependenceof the thermal conductivity and phonon mean free path, consistent with increased phonon-boundary scattering associated with nanostructure. These results suggest that biomineral-like nanocomposite structures could be useful in the design of novel high-strength materials for low thermal conductivity applications.

In this paper, we demonstrate that films of magnetite, Fe3O4, can be deposited by the electrochemical reduction of a Fe(III)-triethanolamine complex in aqueous alkaline solution. The films were deposited with a columnar microstructure and a [100] preferred orientation on stainless steel substrates. In-plane electrical transport and magnetoresistance measurements were performed on the films after they were stripped off onto glass substrates. The resistance of the films was dependent on the oxygen partial pressure. We attribute the increase in resistance in O2 and the decrease in resistance in Ar to the oxidation and reduction of grain boundaries. The decrease in resistance in an Ar atmosphere exhibited first-order kinetics, with an activation energy of 0.2 eV. The temperature dependence of the resistance showed a linear dependence of log(R) versus T−1/2, consistent with tunneling across resistive grain boundaries. A room-temperature magnetoresistance of −6.5% was observed at a magnetic field of 9 T.

Based on a comparison of relationships between energy dissipated during indentation and the ratio of hardness to reduced elastic modulus, Malzbender has recently proposed a procedure to determine both hardness and elastic modulus from a single loading–unloading indentation curve. However, a more accurate analysis of this relationship shows that, in fact, it suffers from the same limitations as the well-known Oliver and Pharr's method; i.e., in general, the true projected imprint area has to be measured in addition to the load–penetration curve or at least two such curves obtained with different indenter geometries are to be used to unequivocally determine the hardness and the elastic modulus of a material.