We analyzed the crystallographic c-axis tilt of (001) Y2O3 films grown on biaxially textured Ni–5%W tapes under different oxygen flux conditions. Results show that different tilting mechanisms were effective in films with different oxygen stoichiometry. Moreover, the structure of the film/substrate interface investigated by transmission electron microscopy, and the residual strain of the film investigated by x-ray diffraction were also dependent on the film oxygen content. Although the oxygen stoichiometric Y2O3 sample exhibited a coherent film/substrate interface and the sharpest out-of-plane texture, the films grown under reduced oxygen pressure exhibited a smaller overall c-axis tilt due to formation of interface dislocations and regions in which the film oxygen vacancies ordered to form a lattice superstructure.

In this work, microwave heating curves and microstructural evolution of nanocrystalline Au thin films were studied so the heating behavior of metals could be better understood. Films with different thickness were irradiated by the H and E maximums of microwave in a single-mode cavity. These samples were more efficiently heated by H field than by E field. With the increase of film thickness, the attained highest temperature increased. This phenomenon was compared with the theory of the transmission line analysis. Peaks appearing at the initial stage of the heating curves were also compared with similar heating behaviors observed in metal powder compacts, and the possible mechanisms related to the heating behavior were explored.

Calcium phosphate crystals were synthesized by diffusing calcium ions into silica hydrogels containing phosphate ions. Hydroxyapatite [HAp, Ca10(PO4)6(OH)2] and octacalcium phosphate [OCP, Ca8(HPO4)2(PO4)4.5H2O] with different types of crystal morphology were formed in the gel. The HAp had an irregular or rod shape, a few micrometers in length, while the OCP had an irregular, spherulite, rod- or ribbonlike shape, ranging in size from a few micrometers to several tens of micrometers, depending on the amount of phosphoric acid added and the reaction temperature. The morphology of the OCP changed from an irregular shape to a ribbonlike or rod shape, via a spherulite shape, depending on the amount of phosphoric acid added and the reaction temperature. The degree of supersaturation of the reaction environment and the rate-determining step in the HAp and OCP crystal growth mechanism have been ascribed to the changes in crystal morphology of the HAp and OCP.

An electrical technique was recently developed to measure the in situ contact area continuously during instrumented indentation by simultaneously monitoring electrical contact response between a conductive indenter tip and a conductive sample. This technique has the potential to overcome limitations of the Oliver-Pharr method caused by the lack of a direct contact area measurement. However, the electrical contact current-voltage (I-V) curves measured from the technique were nonlinear, posing a significant challenge to inferring accurate in situ contact areas. To overcome this challenge and extend the electrical technique to more applications, various I-V curve analysis methods were investigated for their abilities to infer in situ contact area and hardness. Annealed Cu was indented using both linear and exponential loading tests. When analyzing the resulting data, the feasibility of each method was evaluated and the optimal methods to calculate the in situ contact area and hardness were determined. It was found that a simple summation of the absolute values of area under I-V curves or the area under I-V curves at positive voltages yielded the most robust area measure, whereas error in the inferred contact area was systematic and primarily from velocity dependence of the I-V response.

Conducting nylon 6 fibers were prepared by in situ polymerization of aniline on to the fiber surface, after providing a chemical etching treatment to the fibers using chromic acid. The properties of the etched and polyaniline (PANI) coated fibers were evaluated using scanning electron microscopy, x-ray photoelectron spectroscopy, infrared spectroscopy, x-ray diffraction, thermogravimetry, and differential scanning calorimetry. Though the etching process caused a marginal decline in the mechanical properties of the fiber, it provided a reasonably rough surface for PANI adhesion and enhanced the conductivity of the fiber. The conductivity increased from 4.22 × 10−2 to 3.72 × 10−1 S/cm at an etching time of 4 h.

The effect of Ag substituting Cu on the structural features of the Cu55Zr45, Cu45Zr45Ag10, and Cu35Zr45Ag20 glassy alloys was studied using the real-space pair distribution and radial distribution functions. The experimental x-ray diffraction data obtained in a synchrotron beam were used to derive pair and radial distribution functions through Fourier transformation processing. These results suggest that a certain degree of medium-range order in this alloy is maintained up to about 2.5 nm distance. It is suggested that the addition of Ag causes formation of a more homogeneous local atomic structure compared with that of a binary Cu–Zr alloy, which could be considered as a reason for the improved glass-forming ability of this alloy.

A study was made to investigate cavity growth behavior during the superplastic deformation of submicrometer-grained titanium alloy and to compare that to cavity growth in a coarse-grained counterpart. A series of tension tests were performed at a temperature of 973 K and a strain rate of 10−4 s−1. Microstructures revealed that both the size and the volume fraction of the cavities obviously decreased as the grain size decreased. Working within the framework provided by creep models for understanding cavity growth behavior, we found the dominant growth mechanism to be superplastic diffusion, which leads to high-tensile ductility in submicrometer-grained titanium alloy.

In the present work, a previously developed neural network approach for analyzing spherical indentation experiments is applied to prestressed specimens to determine the effect of residual stresses on the identified stress–strain curves. Within this scope, a comparison to other measurement errors has been made, which are caused by surface preparation and anisotropy of the material. To validate the experimental and analysis approach, the effect of compressive and tensile prestresses was also simulated using a three-dimensional finite element model. The material investigated is a rolled 2024 T351, which is widely used for manufacturing airplanes. It is shown that the existing neural network approach is able to determine the stress–strain behavior in agreement with that obtained from tensile tests. The method is robust against most error sources, such as surface roughness, coarse grain structure, and anisotropy, if a sufficient number of experiments are available. The most important influencing factor can be the residual stress causing errors up to 20% in the identified stress–strain curves.

Single perovskite polycrystalline Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) thin films with PMN to PT ratios around the morphotropic phase boundary composition (070PMN-0.30PT, 0.65PMN-0.35PT, and 0.60PMN-0.40PT) have been prepared by chemical solution deposition (CSD). Air-stable and precipitate-free PMN and PT precursor sols were separately synthesized, and PMN-PT sols were obtained by the simple mixture in air of the former. The PMN-PT sols were deposited onto Pt-coated Si substrates and dried on a hot-plate. Crystallization of the films was carried out by rapid thermal processing (RTP) in oxygen, using different temperatures, soaking times, and heating rates. Single perovskite PMN-PT thin films were obtained at low temperatures (650 °C) with short soaking times (6s) and rapid heating rates (200 °C/s). The films show a columnar growth and a uniform thickness. Both the evolution of the perovskite distortion and the electrical properties with the PMN to PT ratio indicate the correct formation of the solid solution. The temperature and frequency dependences of the permittivity and the ferroelectric loops also indicate an increase of the relaxor characteristic of the films as compared with bulk materials. Piezoelectric coefficients were measured across the ferroelectric loop by optical interferometry, and an enhancement of piezoelectricity at the MPB composition was found. A piezoelectric d33 coefficient of ∼55 pC/N was measured in ∼300-nm-thick films of this composition with a saturation polarisation of Ps ∼25 μC/cm2.

The ignition and reaction processes of the thermal explosion reaction from the Ti–B4C system in air were studied. The thermal explosion reaction for the formation of TiC and TiB2 can be initiated at a relatively low temperature with the incorporation of air. Generally, the ignition process in air is suggested to be a chemical oven rather than gas transport, and the reaction process is proposed to be dissolution and precipitation.

Vanadium oxide thin films were deposited using pulsed direct current (dc) magnetron sputtering in an atmosphere containing argon and oxygen. The total pressure was varied from 2.5 to 15 mTorr, and the oxygen-to-argon ratio was varied from 2.5 to 30%. The resulting films were characterized using Rutherford backscattering spectroscopy (RBS), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and glancing incidence x-ray diffraction (GIXRD). Electrical resistivity was calculated from I–V curves acquired from two-point-probe measurements and thicknesses measured from bright-field TEM images of cross-sectioned samples. TEM and GIXRD were used to characterize the crystallinity of each film. A transition from nanocrystalline to amorphous growth was observed with increasing partial pressure of oxygen. In all samples, the only crystalline phase observed was cubic vanadium oxide with the sodium chloride structure. Though the cubic VOx equilibrium phase field is limited to a maximum of x = 1.3, the cubic phase was observed with a value of x up to 2 in the present work. It was apparent from electron diffraction data that increased oxygen content correlated with an increase in the film disorder. The increase in oxygen content also corresponded with an increase in the film resistivity, which varied over 7 orders of magnitude from 1.18 × 10−3 to 2.98 × 104 Ω·cm. The temperature coefficient of resistance was found to increase with increasing oxygen content from −0.1 to −3.5%/°C. A direct correlation between film disorder and temperature coefficient of resistivity (TCR) was observed and could be exploited to engineer materials with the desired TCR.

The isotherm wetting and spreading behaviors of polycrystalline TiC by molten Zr55Cu30Al10Ni5 alloy were investigated at 1133 to 1253 K in a vacuum by using a modified sessile drop method. The system displays good wettability with the initial and final stable contact angles of 44 to 50° and 10 to 14°, respectively, mildly depending on the temperature. The spreading kinetics follows well defined exponential functions and could be described by a molecular dynamic model. On the other hand, a ZrC reaction layer was formed at the interface. The wetting was primarily promoted by the Zr adsorption at the triple junction and then by the formation of the reaction layer.

We demonstrate here in situ synthesis of bulk yield W18O49@carbon coaxial nanocables based on an easily controlled chemical vapor deposition process at relatively low temperature (760 °C) using metallic tungsten powder and ethylene (C2H4) as the raw materials. Transmission electron microscope (TEM), energy dispersive x-ray (EDX), and x-ray diffraction (XRD) analyses indicate that the resultant nanostructures are composed of single-crystalline W18O49 nanowires, coaxially covered with amorphous carbon walls. A vapor–solid (VS) mechanism is proposed to interpret the formation of the nanocables. The effect of carbon sources on the nanocable growth was investigated. The results revealed that the introduction of carbon species not only causes the production of W18O49@C nanocable structures, but also obviously modulates growth behaviors and core/shell diameter ratio of the nanocables. The obtained nanocables may find great applications in catalyst systems and optical and electronic nanodevices because of their enhanced surface properties, as well as in high chemical stability.

A significant reduction of the undercooling of Sn-based solder alloys was previously reported when they were reacted with various under bump metallurgies (UBMs). In the present study, new experiments have been designed and carried out to understand the undercooling behavior of various Cu- and Ni-doped solders on Ni UBM. Two competing mechanisms were further investigated that include the formation of intermetallic compounds (IMCs) at solder/UBM interface and the change of solder composition because of the dissolution of Ni UBM into solder. Two types of IMCs, including both Ni3Sn4 and Cu6Sn5 that were formed at the interface, were correlated with the undercooling of Sn–0.2Cu and Sn–3.8Ag–0.2Cu solders. In addition, the compositional changes of various Sn-based solders after reactions with Ni UBM were analyzed. On the basis of the experimental results, it was found that the significant reduction in undercooling is primarily caused by dissolved Ni atoms from Ni UBM and the concurrent formation of Ni3Sn4 IMC in the solder matrix. Finally, the beneficial effect of Ni dissolution is thermodynamically favorable as confirmed by the thermodynamic calculations and differential scanning calorimetry measurements with various Ni-doped solder alloys.

Microstructures of epitaxial Ca0.33CoO2 thin films, which were grown on m plane and c(0001) plane of α–Al2O3 by the reactive solid-phase epitaxy (R-SPE) method and the subsequent ion-exchange treatment, were investigated in detail by using selected-area electron diffraction, high-resolution transmission electron microcopy, spherical-aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (Cs-corrected HAADF-STEM), and electron energy-loss spectroscopy (EELS). Detailed electron diffraction analyses reveal that the orientation relationships between Ca0.33CoO2 thin film and substrate are and , having an angle of about 43° with for the film deposited on m plane, and and for the film deposited on c(0001) plane though a Ca–Al–O amorphous layer formed between them. CoO seed layer near the interface and residual Co3O4 phase inside the films were observed and identified by HAADF-STEM and EELS in both samples. Such microstructural configuration indicates that the processes of film growth during R-SPE are (i) oxidation of CoO into Co3O4 with residual CoO layer near the interface and (ii) intercalation of Na+ layer into Co3O4 to achieve the layered NaxCoO2 film while forming Na–Al–O amorphous layer at the interface.

A self-reinforced ultrahigh-temperature ceramic (UHTC) with elongated ZrB2 grains has been successfully densified by pressureless sintering using commercially available ZrB2, SiC, and WC powders as raw materials. Benefiting from the unique interlocking microstructure, this material had improved strength (518 ± 10 MPa) and higher fracture toughness (6.5 ± 0.2 MPa m1/2) compared to ZrB2–SiC ceramics prepared by pressureless sintering. This work provides a new route for tailoring the microstructure and mechanical properties of UHTCs.

The mechanical behavior of Ti-based metallic glass has been investigated by means of indentation experiments at different loading rates. Contrary to many crystalline materials, an increase of the loading rate causes a reduction of hardness, i.e., a mechanical softening. This effect is ascribed to deformation-induced creation of excess free volume, which is more pronounced for higher strain rates. The decrease of hardness is accompanied with an increase of the contact stiffness and a reduction of the reduced elastic modulus. Finite element simulations reveal that the mechanical response of this material can be described using the Mohr-Coulomb yield criterion. The changes in the nanoindentation curves with the increase of loading rate are well reproduced by decreasing the value of the Mohr-Coulomb cohesive stress. This result is consistent with the presumed enhancement of free volume.

The coherent fine lamellae consisting of the 2H-Mg and the 14H-type long period stacking ordered (LPSO) structure within α′-Mg matrix have been first observed in an as-cast Mg96.32Gd2.5Zn1Zr0.18 alloy. During subsequent solid solution heat treatment at 698–813 K, in addition to the lamellae within matrix, a novel lamellar X phase (Mg–8.37±1.0Zn–11.32±1.0Gd, at.%) with the 14H-type LPSO structure was transformed from the dendritical β phase, and a corresponding time–temperature–transformation (TTT) diagram was established. The 14H-type LPSO structure existing in Mg–Gd–Zn–Zr alloys derives from two variant means: the formation of LPSO structure within α′-Mg matrix and the transformation of the dendritical β phase to a lamellar X phase with the LPSO structure. The alloy solid solution treated at 773 K for 35 h exhibits higher tensile strength and better elongation than the nonheated alloy because of the lamellar X phase with the 14H-type LPSO structure and the 14H-type LPSO structure within matrix.

To study both the effect of Ag and the relative density on the elastic properties of nanoporous Au (np-Au) foams, partially as well as fully dealloyed np-Au samples with various ligament sizes were prepared. Additionally, Ag-coated np-Au samples were synthesized by immersing np-Au in a 1 M Ag nitrate solution, followed by drying and thermal decomposition of the deposited Ag nitrate salt to Ag, NO2, and O2. Cross-sectional analysis revealed that this method yields a homogeneous Ag distribution and that the Ag concentration can be adjusted within the range of 0 to 20 at.%. Mechanical testing was performed by depth-sensing nanoindentation. It was observed that the effect of the relative density on the elastic properties of np-Au seems to be much stronger than predicted by the Gibson and Ashby relationship: Even Ag contents as low as 1 at.% can significantly change the modulus values. On the other hand, the elastic modulus of np-Au seems to be independent of the ligament size.

Partial replacement of hydrating Portland cement by fly ash produces competing effects: it contributes calcium hydrate silicate (C-S-H) gel through the pozzolanic and alkali-activated reactions but dilutes the contribution of the main Portland cement reaction. To investigate this, two neutron-scattering methods were applied to density-fractionated lignite-type and bituminous-type fly ash/Portland cement pastes (20% by mass replacement). Small-angle neutron scattering (SANS) measured the effect of the fly ash on the fractal C-S-H microstructure, whereas inelastic neutron scattering (INS) measured the pozzolanic reaction in terms of calcium hydroxide (CH) consumption. The CH consumption increased with the effective density fraction, and the fractal microstructure evolved more slowly for all fly ash mixes compared with the pure cement control. However, gel volume measured by SANS showed no correlation with the CH consumption measured by INS. The implications of these results are discussed.