Plastic instabilities were investigated by the depth-sensing microhardness test in binary high-purity Al–Mg alloys with different Mg contents. During the tests the applied load was increased from 0 to 2000 mN at constant loading rate. The instabilities appeared as characteristic steps in the load–depth curves during indentation. It was shown that the occurrence and development of the plastic instabilities depend strongly on the solute content. Furthermore, the plastic instabilities occurred only when the solute concentration was larger than a critical value, C0. From room-temperature tests on Al–Mg alloys, C0 was found to be 0.86 wt% Mg. The critical concentration, which is necessary to get plastic instabilities, was also interpreted theoretically.

An electrolytic process is described to peel off ferroelectric thin films from electroded substrates. This procedure was used to study the evolution of stress in ferroelectric calcium-modified lead titanate thin films. Stresses developed during the different steps of the preparation of the film on the substrate were calculated from curvature radii of the deposited films after each step. During the film preparation, the substrate was permanently deformed by the generated stresses. This was shown by curvature of the substrate after the electrolytic separation of the film. The laminated film liberated a large amount of stresses, as deduced from the lattice parameters of the deposited and laminated film, obtained by x-ray diffraction. The moderate residual stress that the laminated film maintained could be associated with intrinsic defects of the film.

Solidification of FeSi2 alloy by single-roller rapid solidification technology was studied, and monophase α–FeSi2 ribbons were obtained. Phase evolution of the monophase and metastable α–FeSi2 ribbons during subsequent annealing was studied with in situ electric resistance measurements. The results show that the metastable α–FeSi2 phase transforms into the β–FeSi2 phase at about 620 °C and then transforms into the α–FeSi2 phase again at a higher temperature when heated. A new relatively simple method to prepare bulk β–FeSi2 alloy, that is, formation of bulk β–FeSi2 alloy by annealing monophase α–FeSi2 alloy, is presented.

A reversible bending phenomenon of Si3N4 nanowires on the conductive carbon–formalin microgrid under an illumination of electron beam was observed using a transmission electron microscope. The nanowires exhibit high flexibility. The bending deflection is approximately proportional to the square of the current density (J) of the electron beam. The bending strength of Si3N4 nanowire is much higher than that of bulk Si3N4 materials. The force that bent the nanowires may be an electrostatic force.

Microwave plasma chemical vapor deposition was used to deposit ultrasmooth nanostructured diamond films (roughness of 14 nm) on a titanium alloy (Ti–6Al–4V) by employing a feedgas mixture containing a high methane fraction (15% by volume) in nitrogen and hydrogen. Of particular interest in this study is the exceptional adhesion of the 4-μm-thick diamond coatings to the metal substrates as observed by indentation testing up to 150 kg load with a 1/8-in.-diameter tungsten carbide ball. No film delamination was observed up to 150 kg indentation load for each of 5 samples grown under the same processing conditions. Scanning electron microscopy of the film surrounding the indentations revealed circumferential microcracking beginning at loads ranging from 60 kg to as high as 150 kg. The strain to cause film microcracking was estimated from calculations of indentation surface areas to be as high as 1.9 ± 0.2%, which represents a significant improvement in toughness over other ceramic coatings.

The influence of electropulsing on the damage of 1045 steel was studied. The results show that electropulsing can substantially increase the strength and ductility of the damaged material, with a little decrease of the Martensite hardness. After the treatment of electropulsing, the microstructure around the crack is modified, and the new structure can prevent the crack from growing. The healing effect of electropulsing on crack is discussed. It is thought that the temperature and thermal compressive stress caused by electropulsing are the main factors causing the healing effect.

The evolution in both stress and microstructure was investigated on sputtered Cu0.57Ni0.42Mn0.01 thin films of 400 nm thickness during the first temperature cycle up to 550 °C. Samples from stress–temperature measurements up to various maximum temperatures were analyzed by x-ray diffraction, scanning and transmission electron microscopy, and Auger electron spectroscopy. The columnar grains with lateral diameters of about 20 nm in the as-deposited state coarsen to about 400 nm above 300 °C. Probably due to the impurity (Mn) drag effect, the coarsening occurs by abnormal grain growth rather than by normal grain growth, starting near the film–substrate interface. The stress development results from a combination of densification due to grain growth and plastic stress relaxation.

Superconducting YBa2Cu3O7−x (YBCO) thin films grown by pulser-laser-assisted deposition were studied by micro-Raman spectroscopy. This technique was used to estimate the epitaxial quality of the films in terms of the presence of c-axis- and a-axis-oriented areas. The advantage of micro-Raman spectroscopy is its high lateral resolution, and this was used to study the homogeneity of the films at submicrometric level. Local structural changes from a large number of intergrain regions were revealed by changes of the Raman parameters. For example, the aggregation of a-axis-oriented grains formed needle-shaped macrograins. Micro-Raman measurements suggest that these grains were seeded at large-angle grain boundaries in c-axis-oriented areas.

Homogenous (Bi3Pb)Sr3Ca3 (Cu4−nCrn)Ox (n 4 0 to 0.20) type glassy precursors become high-Tc superconductors by annealing at 840 °C. The suppression of Tc with increase of Cr concentration supports the pair-breaking mechanism. The feeble semiconducting behavior shown by the doped samples above their respective Tc values followed Mott's variable range hopping conduction mechanism. Like Ti- and Fe-doped samples, studied earlier, the thermoelectric power (TEP) of the present Cr-containing sample showed small positive peak above Tc, which was considered to be associated with the phonon-drag effect. The linear part of the temperature-dependent TEP (above Tc) well fitted the two-band model.

Phase-selective growth of TlBa2Ca2Cu3O9−x films is greatly enhanced by annealing chemical vapor deposition derived BaCaCuO(F) precursor films in the presence of TlF. Nucleation of superconducting phases (≥840 °C under O2) progresses in the order 2212 → 2223 → 1212 → 1223. Annealing at 855 °C results in well-defined platelet grains, a significant number of which are a-axis oriented. Residual fluoride is not detectable at any stage of the annealing process. Thin films synthesized by TlF annealing differ markedly from films processed in the presence of Tl2O3 with Tc = 103 K and Jc > 105 A/cm2 (5 K, 4.5 T).

The use of an electric field to activate the combustion synthesis of chromium silicides was investigated. Despite their relatively low adiabatic temperatures, all four silicides were synthesized by field-activated combustion synthesis. However, although self-propagating synthesis reactions were initiated, the products were not pure but contained other silicides and reactant phases. The purity of the samples increased with increasing field strength, and under the highest field, the products contained the desired silicide as the major phase with minor amounts of other stoichiometries. Observation of microstructural evolution in quenched reactions revealed the key role played by the liquid phases in the propagation of the combustion front. The phase Cr5Si3 was the first product of the interaction between the reactants when either solid–solid or solid–liquid processes were involved. These results were confirmed by isothermal solid–solid and solid–liquid diffusion couple experiments.

The microstructural development of YBa2Cu3Oy (Y-123) coated conductors based on the ion-beam-assisted deposition (IBAD) of yttria-stabilized zirconia (YSZ) to produce a biaxially textured template is presented. The architecture of the conductors was Y-123/CeO2/IBAD YSZ/Inconel 625. A continuous and passivating Cr2O3 layer forms between the YSZ layer and the Inconel substrate. CeO2 and Y-123 are closely lattice-matched, and misfit strain is accommodated at the YSZ/CeO2 interface. Localized reactions between the Y-123 film and the CeO2 buffer layer result in the formation of BaCeO3, YCuO2, and CuO. The positive volume change that occurs from the interfacial reaction may act as a kinetic barrier that limits the extent of the reaction. Excess copper and yttrium generated by the interfacial reaction appear to diffuse along grain boundaries and intercalate into Y-123 grains as single layers of the Y-247, Y-248, or Y-224 phases. The interfacial reactions do not preclude the attainment of high critical currents (Ic) and current densities (Jc) in these films nor do they affect to any appreciable extent the nucleation and alignment of the Y-123 film.

Copper-doped LiNbO3 waveguides were prepared by Cu–Li ion-exchange process. Compositional, structural, and optical analyses were performed by secondary ion mass spectrometry, x-ray diffraction, and m-line spectroscopy, respectively. The chemical state of Cu2+ ions was studied by electron paramagnetic resonance, and the results were correlated with structural modification of the LiNbO3 matrix. Copper incorporation in the crystal took place under different regimes, and it induced a lattice rearrangement with the formation of new crystalline phases. Cu2+ ions were surrounded by tetragonally compressed octahedra with rhombic distortions. Cu:LiNbO3 optical waveguides were formed supporting two optical modes.

Morphology and structure of ZnO films deposited on (0001) sapphire and glass substrates by off-axis sputtering were investigated at various temperatures and pressures. All films show highly textured structures on glass substrates and epitaxial growth on sapphire substrates. The full width at half-maximum of theta rocking curves for epitaxial films is less than 0.5°. In textured films, it rises to several degrees. The trend of surface textures in films grown at low pressures is similar to those grown at high temperatures. A morphology transition from large well-defined hexagonal grains to flat surface was observed at a pressure of 50 mtorr and temperature of 550 °C. The experiment results are explained by the transport behavior of depositing species.

Fracture toughness and fracture mechanisms in Al2O3/Al composites are described. The unique flexibility offered by pressureless infiltration of molten Al alloys into porous alumina preforms was utilized to investigate the effect of microstructural scale and matrix properties on the fracture toughness and the shape of the crack resistance curves (R-curves). The results indicate that the observed increment in toughness is due to crack bridging by intact matrix ligaments behind the crack tip. The deformation behavior of the matrix, which is shown to be dependent on the microstructural constraints, is the key parameter that influences both the steady-state toughness and the shape of the R-curves. Previously proposed models based on crack bridging by intact ductile particles in a ceramic matrix have been modified by the inclusion of an experimentally determined plastic constraint factor (P) that determines the deformation of the ductile phase and are shown to be adequate in predicting the toughness increment in the composites. Micromechanical models to predict the crack tip profile and the bridge lengths (L) correlate well with the observed behavior and indicate that the composites can be classified as (i) short-range toughened and (ii) long-range toughened on the basis of their microstructural characteristics.

The role of matrix microstructure on the fracture of Al-alloy composites with 60 vol% alumina particulates was studied. The matrix composition and microstructure were systematically varied by changing the infiltration temperature and heat treatment. Characterization was carried out by a combination of metallography, hardness measurements, and fracture studies conducted on compact tension specimens to study the fracture toughness and crack growth in the composites. The composites showed a rise in crack resistance with crack extension (R curves) due to bridges of intact matrix ligaments formed in the crack wake. The steady-state or plateau toughness reached upon stable crack growth was observed to be more sensitive to the process temperature rather than to the heat treatment. Fracture in the composites was predominantly by particle fracture, extensive deformation, and void nucleation in the matrix. Void nucleation occurred in the matrix in the as-solutionized and peak-aged conditions and preferentially near the interface in the underaged and overaged conditions. Micromechanical models based on crack bridging by intact ductile ligaments were modified by a plastic constraint factor from estimates of the plastic zone formed under indentations, and are shown to be adequate in predicting the steady-state toughness of the composite.

Potassium tantalate thin films (KT) were hydrothermal-electrochemically and electrochemically synthesized on tantalum substrates under galvanostatic conditions in KOH solutions at temperatures from 50 to 150 °C. The pyrochlore structures were characterized by x-ray diffraction and scanning electron microscopy for the films formed under a variety of conditions. It was found that the reaction temperature, potassium hydroxide concentration, and current density significantly affect the formation and the morphology of the KT films. When the reaction temperatures were higher than 80 °C and the KOH concentrations were greater than 2.0 M, very crystalline films with excellent film flatness and good adherence on the substrate were obtained. Based on the experimental results, it was confirmed that the formation and growth of KT films by the hydrothermal-electrochemical and electrochemical method follow a dissolution-crystallization mechanism.

The quasi binary systems LaMnO3–SrMnO3 and LaMnO3–CaMnO3 were studied. Both systems show a miscibility gap at intermediate La:Sr and La:Ca ratios below about 1400 °C in air. This phenomenon causes the decomposition of single-phase (La,Sr)MnO3−x and (La,Ca)MnO3−x solid solution into La-rich SrMnO3−x + Sr-rich LaMnO3−x and La-rich CaMnO3−x + Ca-rich LaMnO3−x at lower temperatures, respectively. At 1400 °C in the system LaMnO3–SrMnO3, a structure transformation of (La,Sr)MnO3 from orthorhombic to rhombohedral with increasing Sr content was not observed, and the structure of La0.7Sr0.3MnO3 was determined to be orthorhombic with a = 0.54927 ± 0.0009 nm, b = 0.54582 ± 0.0009 nm, and c 4 0.76772 ± 0.0034 nm.

A series of rhombohedral alkaline-earth-doped manganites, La1−x (Ca,Sr)x MnO3, were studied, with x = 0.28 to 0.375, a constant tolerance factor of 0.927 ± 0.002, a very small variation of the Mn–O bond angle (<0.3°), and constant ion size variance (ς2) of 0.0020 ± 0.0010. Compositional uniformity and crystallinity were excellent, and porosity low. The temperature of the maximum in the resistivity, Tm, for x 4 0.28 was higher (by more than 20 K) than previously reported. With increasing x (and at the same time increasing Ca for Sr substitution), the Mn–O bond length shortened, Tm decreased, and the polaron hopping activation energy increased, indicative of increased carrier localization. The behavior is opposite to the La1−xSrxMnO3 series and can be explained by a strong dependence of the electron–phonon interaction on Mn–O bond length. In order to maximize Tm, Mn–O bond length must be controlled to a precise degree.

BaxSr1−xTiO3 (x 4 0.6) (BST) thin films were successfully prepared on a Pt(111)/TiO2/SiO2/Si(100) substrate by spin coating, using the polymeric precursor method. BST films with a perovskite single phase were obtained after heat treatment at 700 °C. The multilayer BST thin films had a granular structure with a grain size of approximately 60 nm. A 480-nm-thick film was obtained by carrying out five cycles of the spin-coating/heating process. Scanning electron microscopy and atomic force microscopy analyses showed that the thin films had a smooth, dense, crack-free surface with low surface roughness (3.6 nm). At room temperature and at a frequency of 100 kHz, the dielectric constant and the dissipation factor were, respectively, 748 and 0.042. The high dielectric constant value was due to the high microstructural quality and chemical homogeneity of the thin films obtained by the polymeric precursor method.