Polarization of deformation twinning (its propagation in a certain sense but not in the opposite one) is taken for granted. However, the same phenomenon can occur for a superdislocation glide as well, as is demonstrated in this paper. The consequences for plastic deformation of polysynthetically twinned TiAl crystals with the lamellar interfaces parallel to the loading direction are discussed. It is not the interface itself that is an obstacle for propagating deformation but also the fact that a deformation mode with the parallel Burgers vector cannot be activated in the neighboring lamella due to the directionality of superdislocation motion leading to additional stress increase.

Eu(DBM)3Phen-doped poly(methyl methacrylate) (PMMA) with different doping concentrations was prepared. Judd–Ofelt parameters Ω2 and Ω4 and the fluorescence intensity ratio R were computed from the fluorescence emission spectra and were analyzed. The radiative properties, such as transition probabilities, emission cross section (46.47 × 10−22 cm2), fluorescence branching ratios (90.34%), and radiative lifetime (1.704 ms), reveal that Eu(DBM)3 Phen-doped PMMA has potential use as a laser material.

Results are reported on the electron field emission properties of microcrystalline diamond thin films grown on molybdenum substrates by the sulfur (S)-assisted hot-filament chemical vapor deposition technique using methane (CH4), hydrogen sulfide (H2S), and hydrogen (H2) gas mixtures. Electron field-emission measurements revealed that the S-incorporated microcrystalline diamond thin films have substantially lower turn-on fields and steep rising currents as compared to those grown without sulfur. The field-emission properties for the S-incorporated films were also investigated systematically as a function of substrate temperature (TS). Lowest turn-on field achieved was observed at around 12.5 V/μm for the samples grown at TS of 700°C with 500 ppm H2S. To establish the property-structure correlation, we analyzed the films with multiple characterizations include scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy (RS), and x-ray photoelectron spectroscopy (XPS) techniques. It was found that sulfur addition causes significant microstructural changes in microcrystalline diamond thin films. S-assisted films show smoother, coarse-grained surfaces (non-faceted) than those grown without it (well-faceted) and a relatively higher content of non-diamond carbon (primarily sp2-bonded C). RS and investigations on the morphology by SEM and AFM indicated the increase of sp2 C content with increasing TS followed by a morphological transition at 700°C in the films. XPS investigations also showed the incorporation of S in the films up to a few atomic layers. It is believed that the electron-emission properties are governed by the sulfur incorporation during the chemical vapor deposition process. Although most of the S is expected to be electrically inactive, under the high doping conditions hereby used, it is shown rather indirectly through multiple characterizations that there may be some amount of S in donor states. Therefore the results are discussed in terms of the dual role of S whereby it induces the structural defects in the form of enhanced sp2 C content at the expense of diamond quality and a possibility of availability of conduction electrons. In fact the latter finding is supported through room temperature electrical conductivity measurements.

Aligned single-walled carbon nanotube (SWNT) ropes show excellent field-emission performance due to their high aspect ratio and sound alignment. In this study, the effect of geometrical parameters, such as cathode-anode distance and the height of SWNT ropes on the field-emission properties of SWNT ropes was investigated. It was found that the cathode-anode distance influences the emission properties, such as the turn-on field Fto and threshold field Fthr, of SWNT ropes, and the turn-on and threshold fields are marginally decreased at relatively larger gaps between the SWNT emitter tip and the anode plane. It was also found that the emission properties of SWNT ropes are improved by increasing the rope length, at least in the present experimental range. A possible two-step field amplification model was proposed to explain this length effect of SWNT ropes. The estimated results show that the local field at the tip of SWNT ropes, which causes a certain emission-current density, seems not to change with the cathode-anode distance, and the effective emission area of the SWNT rope is much smaller than the apparent cross-sectional area of the SWNT rope. The results obtained suggest that it is possible to optimize the performance of SWNT rope-based cold cathode by adjusting geometrical parameters of SWNT rope emitters.

The relationship between the nanohardness and the microstructures in the Fe–C martensite was studied to understand the contributions of the matrix and the grain boundary to the macroscopic strength. As-quenched martensite was examined for five kinds of Fe–C alloys with various carbon contents in the range of 0.1–0.8 mass%, while quench-tempered martensite was investigated for an Fe–0.4% C alloy. The ratio of the nanohardness to the macrohardness Hn/Hv was much smaller for the Fe–C martensite than those for the single crystals, indicating that there is a significant grain-boundary effect for the martensite. The ratio Hn/Hv of the as-quenched martensite decreased with an increase in the carbon content since the size of the block structure decreased with increasing carbon content. For the quench-tempered specimens, a significant reduction of the grain-boundary effect occured at the tempering temperature of 723 K. It is mainly due to the depression of the locking parameter caused by the disappearance of the film-like carbides on the boundaries.

A new approach for the production of yttria-stabilized zirconia (YSZ) oxide buffer layers directly on metal rolling-assisted biaxially textured substrates (RABiTS) is described in this paper. This represents a significant advance over existing techniques and avoids the need for complicated steps to avoid substrate oxidation during direct deposition of oxides. Current densities of about 1 MA/cm2 have been achieved for YBa2Cu3O7-δ layers on the YSZ buffer, with an intermediate CeO2 layer. The process consists of reactive sputtering of a YxZr1−xN film directly on the RABiTS, which adopts its biaxial texture. This nitride film is then converted to YSZ via a thermal oxidation step. The YSZ films retain the texture of the nitride film (and of the RABiTS) through local syntaxy. In many cases, YSZ films exhibit improved biaxial texture over that of the RABiTS substrate. Nitrides can be sputter deposited at much higher rates relative to oxides, making the approach industrially scalable and economical.

The current study uses high-temperature differential scanning calorimetry to document the shift in phase-transformation temperature with particle size throughout a series of alloys in the zirconia–yttria system (0–1.5 mol% yttria). The tetragonal-to-monoclinic (T→M) phase-transformation temperature is seen to vary inversely with particle size. It is shown that a simple thermodynamic approach first proposed by Garvie predicts this inverse linear relationship. Subsequent determination of the key thermodynamic parameters therein (e.g., the surface and volume free energy, enthalpy, and entropy changes involved in the phase transformation) allows a complete predictive equation for the T→M phase transformation in the yttria–zirconia system to be developed as a function of particle size and yttria dopant level. The yttria–zirconia phase diagram is then redrawn with grain size as a third variable. It should be stressed that the current analysis is valid for particulate systems only; a parallel paper tackles the problem for fine-grained yttria–zirconia solids, where the approach is similar, but additional strain energy terms come into play.

The tensile and fatigue fracture behavior of Zr59Cu20Al10Ni8Ti3 bulk metallic glass was investigated. It was found that under tensile load the metallic glass always displays brittle shear fracture and the shear fracture plane makes an angle of θT (=54°) with respect to the stress axis, which obviously deviates from the maximum shear stress plane (45°). Under cyclic tension-tension loading, fatigue cracks first initiate along the localized shear bands on the specimen surface, then propagate along a plane basically perpendicular to the stress axis. Tensile fracture surface observations reveal that fracture first originates from some cores, then propagates in a radiate mode, leading to the formation of a veinlike structure and final failure. The fatigue fracture processes of the specimens undergo a propagation stage of fatigue cracks followed by catastrophic failure. Based on these results, a tensile fracture criterion for bulk metallic glasses is proposed by taking the effect of normal stress into account. It is suggested that both normal and shear stresses affect the fracture process of metallic glasses and cause the deviation of the fracture angle away from 45°

A new method was found to synthesize large-area (7 × 15 mm2), high-density (higher than 109 cm−2), aligned carbon nanotubes (CNTs) with uniform diameters on a silica wafer. Ferrocene/melamine mixtures were pyrolyzed through a three-step process in an Ar atmosphere in a single-stage furnace. The structure and composition of the CNTs were investigated by scanning electron microscopy, transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and electron energy-loss spectroscopy (EELS). It was found that these nanotubes have uniform outer diameters of about 22 nm and varying lengths from 10 to 40 μm. High-resolution TEM images showed that CNT is composed of graphite-like layers arranged in a stacked-cup-like structure. XPS results showed that the layer covering the tops of the aligned CNTs consists of carbon and iron. The EELS spectrum showed that these tubes are pure carbon.

The compound growth of single-walled carbon nanotube (SWCNT) and multiwalled carbon nanotube (MWCNT), which formed a nanotube cable, was achieved by the chemical vapor deposition of natural gas on an Fe catalyst supported on SiO2–Al2O3 hybrid materials at 950 °C. The microstructure of nanotubes was characterized by high-resolution transmission electron microscopy (HRTEM). The SWCNTs encapsulated inside MWCNTs can be two, three, or even more in quantity with a diameter range from 1.0 nm to 2.0 nm. The diameter of SWCNT is controlled by the size of the catalyst nanoparticles. Some bundles of SWCNT and double-walled nanotubes were also found. The possible mechanism of compound growth is briefly discussed.

The interfacial reaction and microstructure of Sn with an Fe-42Ni substrate soldered at 250 °C were studied primarily using transmission electron microscopy. Apparent double reaction layers formed between Fe-42Ni and Sn of the same phase of FeSn2 containing Ni from 2 to 6 at.% as a substitution impurity for Fe. The first layer, which faced an Fe-42Ni substrate, was thin and grew with a flat interface. The second layer, which adhered to Sn solder, showed needle/square pillar-shaped small crystalline structures. Between these two layers, voids were frequently observed. The morphological difference between these two layers and voids could be attributed to the slow-fast diffusion mechanism during soldering. The fast diffusion occurring along the surfaces or the grain boundary of FeSn2 in the second layer led to the growth of FeSn2 products into Sn melt. Simultaneously, the slow diffusion penetrating the Fe-42Ni and FeSn2 grain contributed to the formation of the first layer and voids. Ni from Fe-42Ni can dissolve into Sn melt at the reaction temperature. The dissolved Ni formed platelets of Ni3Sn4 intermetallic compound inside a β-Sn matrix on solidification or on cooling. In contrast, Fe formed FeSn2 crystallines directly along the interface, because its activity was higher than that of Ni in a Sn liquid at reaction temperature. The joint of Fe-42Ni/Sn/Fe-42Ni, reacted for 2 min, had a joint strength of about 65 MPa, and maintained this high strength regardless of the reaction time.

For this paper, we used radio-frequency (rf) sputter deposition to synthesize epitaxial La0.5Sr0.5CoO3−∂ (LSCO) films. We investigated the influence of sputter deposition parameters, in particular, oxygen partial pressure, plasma power, total sputter pressure, and post-deposition cooling atmosphere on film composition, microstructure, and electrical resistivity. We show that rf sputtering from a single target can produce LSCO films with La/Sr and (La + Sr)/Co ratios of unity and with low electrical resistivities of about 1 mΩ cm. Film microstructures were characterized by high-resolution transmission electron microscopy and x-ray diffraction. Formation of an ordered film superlattice, most likely due to oxygen vacancy ordering, was observed. In this paper, we discuss the relationship between the film microstructure and the electrical resistivity.

Phase formation was studied in the Fe–Ge and Cr–Ge thin-film systems by means of Rutherford backscattering spectrometry and x-ray diffraction. In the Fe–Ge system, FeGe was the first phase to form while in the Cr–Ge system, Cr11Ge8 was found to form first. The results are compared with the predictions of the effective heat of formation model. Heats of formation were calculated using the Miedema model. The effect of the transformation enthalpy term ΔHtr, used to convert a semiconducting element into a hypothetical metallic one in the Miedema model, is also discussed.

Laboratory x-ray fluorescence holography equipment was developed. A single-bent graphite monochromator with a large curvature and a high-count-rate x-ray detection system were applied in this equipment. To evaluate the performance of this equipment, a hologram pattern of a gold single crystal was measured. It took two days, which was about one-third the time required for the previous measurements using the conventional x-ray source and several times that using the synchrotron source. The quality of the hologram pattern is as good as that obtained using the synchrotrons. Clear atomic images on (002) are reconstructed.

Self-organized structures of the sodium salt of sulfonated polyaniline (prepared from the leucoemeraldine base of polyaniline) in the presence of a mixture of cationic and nonionic surfactants were studied. It was used in the latex form, which has been prepared using a conventional method with sodium dodecyl sulfate. The cationic surfactant used was didodecyl dimethyl ammonium bromide, and the nonionic surfactant used was Triton-X-100. The supramolecular organization was made in aqueous medium by varying the concentrations of the components. A three-dimensional fibrillar network and colloidal aggregate were produced due to the supramolecular organization. The thermal study indicated reversible first-order phase transition in the former cases fulfilling the criteria of thermoreversible gels. A probable explanation of the different morphology from the variation of charge density on the vesicle surface has been offered. The conductivity of fibrillar network is two orders higher than that of the colloidal aggregate.

Transmission electron microscopy (TEM) was used to investigate the structural properties of sputter-deposited yttria-stabilized zirconia (YSZ) thin films. YSZ films were deposited over a range of temperatures and background oxygen levels. Additionally, a multilayered structure was produced by cyclic application of a substrate bias. Plan-view TEM showed that temperature and oxygen levels did not have a significant effect on grain size but did alter the phases present in the thin films. Cross-sectional TEM showed the development of texture in the multilayer film, both within the individual layers and in the entire film.

TiO2 ceramic coating films were deposited on silica glass substrates by the sol- gel method using aqueous solutions of Ti(SO4)2 containing polyvinylpyrrolidone (PVP) as the coating solutions. Unless PVP was added to the solution, the wettability of the substrate was poor, leading to failure in gel film formation. When PVP was added to the solution, on the other hand, homogeneous gel films could be deposited on the substrate, which could be converted to crack- free, transparent TiO2 ceramic thin films about 0.1 μm in thickness. The TiO2 films thus obtained had refractive index, porosity, and surface roughness Ra (the arithmetic average deviation of the assessed profile) of 2.68, 2.1%, and 0.94 nm, respectively. For comparison, a TiO2 film was also prepared from an alcoholic solution of Ti(OC3H7i)4, showing refractive index, porosity, and Ra of 2.65, 3.0%, and 0.98 nm, respectively. These values indicate that the TiO2 films prepared from the Ti(SO4)2 aqueous solutions containing PVP are as smooth and dense as those prepared from conventional alkoxide solutions. The solutions were found to be stable in viscosity for more than five months at room temperature in sealed containers. Thermal analysis, infrared absorption spectra measurement, and x- ray diffraction analysis indicated that the gel films are converted to ceramic films on firing via (i) vaporization of H2O; (ii) decomposition of H2SO4 and/or vaporization of H2SO4 · H2O; (iii) decomposition of SO42− coordinating Ti atoms and oxidation and decomposition of PVP, the latter of which leads to formation of residual carbons; (iv) oxidation of the carbonaceous residues; and (v) crystallization of the titania phase. During the gel- to- ceramic film conversion, the thickness decreased by 90%.

Double-layered ZnO/silicon nitride microbridges were fabricated for microbridge tests. In a test, a load was applied to the center of the microbridge specimen by using a microwedge tip, where the displacement was recorded as a function of load until the specimen broke. The silicon nitride layer in the structure served to enhance the robustness of the specimen. By fitting the data to a theory, the elastic modulus, residual stress, and tensile strength of the ZnO film were found to be 137 ± 18 GPa, −0.041 ± 0.02 GPa, and 0.412 ± 0.05 GPa, respectively. The analysis required the elastic modulus, internal stress, and tensile strength of the silicon nitride layer. They were measured separately by microbridge tests on single-layered silicon nitride microbridges. The measured tensile strength of the ZnO films represents the maximum tolerable tensile stress that the films can sustain when they are used as the functional component in devices.

A high-resolution transmission electron microscope was used to study the interfacial and twin boundary structure of nanostructured Cu–Ag filamentary composites. Copper matrix and silver filaments have the orientation relationship {111}Cu∥{111}Ag and 〈111〉Cu∥〈111〉Ag. In some regions, twin bands propagated through the silver filaments with some boundary steps at the matrix/filament interface, and the silver filament appeared to be kinked in the twin band in the same direction as the twinning shear. This suggests that twins propagated after the formation of silver filament, and twin bands were deformation twins. At the matrix/filament interface, misfit interface dislocations were introduced periodically to relieve the misfit strain. The distance between interfacial misfit dislocations along the matrix/filament interface in the longitudinal section was measured to be 1.88 nm, which is in good agreement with that (1.81 nm) calculated based on lattice misfit. In Cu–Ag nanocomposites, the spacing between Moire fringes was found to be quite close to that between interfacial misfit dislocations.

Novel photochromic nanocomposite thin films were prepared by entrapping polyoxometalate in a polyacrylamide matrix via the ultrasound technique. The ultrasound irradiation has a great effect on the microstructure and photochromic properties of the hybrid films. The polyoxometalate nanoparticles are finely dispersed in the polymer matrix after ultrasound treatment, instead of agglomeration in the unirradiated film with ultrasound. Consequently, the photochromic behaviors of the hybrid films can be controlled from irreversible heteropolybrown to reversible heteropolyblue by ultrasound. The influence of ultrasound on microstructure and photochromic properties is due to the sonochemical controlling interfacial interactions in the hybrid system.