Highly conductive metal-oxide RuO2 thin films have been successfully grown on yttria-stabilized zirconia (YSZ) substrates by pulsed laser deposition. Epitaxial growth of RuO2 thin films on YSZ and the atomically sharp interface between the RuO2 and the YSZ substrate are clearly evident from cross-sectional transmission electron microscopy. A diagonal-type epitaxy of RuO2 on YSZ is confirmed from x-ray diffraction measurements. The crystalline RuO2 thin films, deposited at temperatures in the range of 500 °C to 700 °C, have a room-temperature resistivity of 35 ± 2 μω-cm, and the residual resistance ratio (R300 k/R4.2 k) is around 5 for the crystalline RuO2 thin films.

Stoichiometric Sr1−xBaxNb2O6 (SBN) powder and thin films were prepared by a chemical method. The starting materials were niobium ethoxide and the hydroxides of strontium and barium. Powders were obtained by evaporation of the precursor solution, and thin films were deposited by spin coating. Annealing temperature required to obtain complete conversion to the crystalline material was about 700 °C. Stoichiometric polycrystalline films of Sr1−xBaxNb2O6 were deposited on quartz and silicon substrates. Leakage current-voltage and the capacitance-voltage measurements on a metal/SBN/n-silicon structure show a diode-type characteristic.

A nanocrystalline β–Sn film of 7 nm average grain size was prepared by inert gas condensation followed by ballistic consolidation, and was investigated by x-ray diffractometry at temperatures of 77 and 293 K. Although Sn normally undergoes a βα phase transformation at 286 K, this transformation was suppressed in the nanocrystalline film. Compared with large-grained β-Sn, a larger Debye–Waller factor and a lower Debye temperature were measured for nanocrystalline β-Sn; ΘD = 133 K for nanocrystalline material while ΘD = 161 K for large-grained material. The lower Debye temperature of the nanocrystalline β-Sn indicates that its vibrational entropy is increased by 0.6 kB/atom with respect to large-grained material.

Condensed silica fume, a by-product from the production of silicon alloys, was sintered by (i) conventional heating in a dilatometric furnace, both at constant heating rate and isothermal heating, and (ii) by the microwave heating. The dense products with relative density up to 95% of theoretical can be obtained only by short runs at high heating rates, preferentially accomplished by the microwave treatment. Prolonged heating leads to the devitrification of the original glassy phase to cristobalite, accompanied by an arrest of densification.

A rapid, pressureless infiltration technique for fabricating SiC-reinforced Al-Si composites is described. The infiltration can be performed by simply dipping a ceramic preform into a molten alloy in an open air environment. This method makes it possible to produce composites that contain a high volume fraction (80%) of a variety of ceramic reinforcements, including particulates and fibers. This technique has potential for low-cost and versatile production of SiC-Al-Si composites for many industrial applications, such as automobile components and electronic packaging.

The structure of ultrafine gold particles embedded in silica glass by ion implantation has been studied by x-ray absorption fine structure spectroscopy. It is found that the Au–Au interatomic distance in the particles is very similar to that in bulk gold within 0.01 Å. Mean-square relative displacement in the particles is 1.2–1.3 times larger than that in bulk gold.

The stability fields of the NdCeCuO (NCCO) films and the Ce0.5Nd0.5O1.75 (CNO) phase grown by laser ablation from the stoichiometric targets, Nd1.85Ce0.15CuO4−8, are demonstrated, respectively. The superconducting NCCO films were grown in a specific field below and close to the CuO/Cu2O transition line, i.e., at 700–725°C in 20–50 mTorr, without vacuum annealing. On postdeposition cooling in lower oxygen pressures (<10 mTorr), the superconductivity of the NCCO films was significantly improved without vacuum annealing. The CNO phase usually appeared in the NCCO films at temperatures above 680 °C, and the higher the temperature the greater the CNO phase due to copper loss. A surplus of copper in the NCCO targets effectively suppressed the formation of the CNO phase, and thereby improved the superconductivity of the NCCO films.

Gold (Au) and silver (Ag) are known to be important contact metals on YBa2Cu3O7−x (YBCO). Both metals have been used as additives in fabricating tapes of YBCO and Bi2Sr2CaCu2O8 (BSCCO) materials, and have favorable results in improving not only the flexibility but also the weighted critical currents of the resulting composites. Previous results on superconductor/normal metal/superconductor junctions made using YBCO/Au/YBCO and YBCO/Au/Nb demonstrated that a supercurrent can be induced in the normal metal layers through the proximity effect. Our transmission electron microscopy study of the Au/YBCO interfaces shows a well-bonded interface with no extraneous phases present. Lattice fringes of the (001) plane in YBCO terminated at the interface abruptly. This observation supports previous results of contact resistance of x-ray photoelectron spectroscopy (XPS). Both (001) integral steps and multiples of 1/3 (001) steps were observed at the Au/YBCO interface. When the top gold layer was absent locally, surface degradation was observed as the (001) lattice fringes stopped short from the surface by 10 nm. Our results support that Au is a desirable contact metal and a dependable surface passivation material for YBCO.

High textured (Bi,Pb)2Sr2Ca2Cu3Ox ceramics have been fabricated by aligning deflocculated flakes of (Bi,Pb)2Sr2Ca2Cu3Ox suspended in an organic medium by means of a high de magnetic field (6 T) at room temperature followed by cold isostatic pressing. The proportion of the (Bi,Pb)2Sr2Ca2Cu3Ox phase in the precursor powder was carefully controlled, and the characteristics of the powder, such as size distribution and morphology, were determined. A high degree of grain alignment was found in the specimens after the magnetic alignment, although the bulk density of the materials was low. Cold isostatic pressing substantially increased the density of the magnetically prealigned specimens which also resulted in a slight decrease in the degree of grain alignment. This minor realignment was found to be due to the various kinds of processing defects that appeared in the specimens during compaction due to the grinding and cracking of the grains and their interlocking. The microstructural and superconducting properties of the sintered ceramic have been studied using texture goniometry, high resolution scanning electron microscopy, transmission electron microscopy, ac magnetic susceptometry, and critical current measurements.

The magnetic torque of oriented bulk specimen of Bi2Sr2CaCu2O8+δ by the shock-loading method was measured under magnetic fields up to 8 kOe in the temperature range from 4.2 to 100 K. The torque amplitude of the shocked specimen was much larger than that of the as-grown bulk specimen measured as a reference. The angular dependence of the torque was reproduced by assuming the Gauss-type distribution for the crystalline orientation. It became clear that the magnetic torque of the shocked specimen showed the high degree of crystalline orientation in which the c-axis is perpendicular to the pellet disk plane and that the flux pinning perpendicular to the pellet disk plane was enhanced by shock-loading.

Partially carbonized polyacrylonitrile fibers were observed to undergo a resistivity change of 2 to 4 orders of magnitude at a transition temperature typically in the range of 98 °C to 200 °C. The current-voltage curves exhibited an initial supercurrent-like increase, followed by a rapid drop to a high resistance state, and then a rise in current again at a later stage. These phenomena cannot be interpreted by existing theories on switching in inorganic amorphous semiconductors. They are explainable if the microstructure of the pyrolyzed fiber is viewed as comprising nanometer-scale superconducting phases interspersed with semiconducting phases, much like a large number of Josephson junctions connected in series.

We have produced and chemically analyzed a series of high purity iron-zinc alloys with iron concentrations in the range 4-27 wt. %. The technique involved slow diffusion of high purity zinc with small particle iron powder. We produced alloys within the four main iron-zinc phases, Zeta, Delta, Gamma-1, and Gamma to aid in the identification of the intermetallic phases formed in commercially produced galvanneal steel coatings. The diffusion technique produces iron-zinc alloys which are suitable as instrument calibration standards for galvanneal producers and users. A chemical titration technique which measures iron concentration to within 0.5 wt. % was also refined. In determining the bulk iron concentrations of the samples, we have compared the accuracy of the wet chemical technique with Induction Coupled Plasma spectroscopy. Homogeneity was measured using an electron microprobe and a scanning transmission electron microscope. The data show that samples are homogeneous to greater than 98% of the mean iron concentration.

The microstructure and the high-temperature deformation behavior of the C15 NbCr2 intermetallics alloyed with V, which consist of both the C15 monophase and the duplex structure with the bcc solid solution, are observed by some microscopic techniques and compression tests. The alloys consisting of the C15 monophase microstructure show moderately higher 0.2% yield stress than the unalloyed NbCr2, and the same BDTT as that in the unalloyed NbCr2, indicating a moderate improvement of the high temperature deformability. This result is attributed to the larger atomic free volumes between the atomic stacking layers along the {111} planes than those of the unalloyed NbCr2. The alloys consisting of the duplex microstructure show lower 0.2% yield stress and considerably decreased BDTT than the unalloyed NbCr2. The considerable deformation improvement in this group of alloys is attributed to the existence of the ductile bcc solid solution.

The effect of the nickel (Ni) and aluminum (Al) reactant particle size on the micropyretic synthesis of NiAl is studied in this article. A change in the low melting component (Al particle) size is noted to have a limited influence on the micropyretic synthesis conditions. However, a change in the high melting component (Ni particle) size not only influences the combustion temperature and propagation velocity, but also affects the final porosity and grain size of the synthesized products. The combustion mode is also noted to change from stable to unstable when the Ni particle size is increased. It is noted that a diffusion-type control mechanism is dominant for the rapid reaction sequence in the NiAl system. An atomistic mechanism of the Ni-Al micropyretic reaction is also proposed in this article. Following this model, analytical expressions are developed to relatc the variation of the Ni size to the NiAl formation rate with the imposed processing conditions during the micropyretic synthesis. The mechanism of the final grain formation and the grain size changes with changes in the processing variables is also discussed.

Silicon carbide fiber-reinforced alumina bodies have been produced by ram extrusion. The Al2O3 powder and SiC fiber were milled together to give a dry dispersion of up to 30 vol % fiber which was subsequently mixed to a paste by high shear kneading using hydroxypropylmethylcellulose solutions as the binder phase. Extruded bodies with green densities ranging between 56 and 63% full theoretical density were achieved. The paste flow behavior was characterized using physically based equations which show that for any given moisture content the pressure drop and the constituent paste parameters are all systematically reduced as the fiber loading is increased. This observation can be explained almost completely by combining packing theory with the paste rheology data. Fiber interactions within the paste and the die system appear not to greatly influence the rheological character of the material. It is shown statistically that the fibers are homogeneously dispersed throughout the paste mass after extrusion. Image analysis has been used to aid in macrodefect analysis, and it is shown that the optimum concentration of fiber was 20 vol % with a quantity of binder sufficient to give an initial yield stress of 2 MPa.

SiC/AlN composites with controlled interfacial solid solution were employed in this present work to investigate the effects of interfacial chemical composition and AlN polytypes on the fatigue properties. The dynamic strength of the SiC/AlN composite was found to decrease initially as the stressing rate decreased. However, the strength increased with a decrease in stress rate at a low stress rate region of below 0.01 MPa/s. Crack arrest could have occurred before exhibiting spontaneous failure at an intermediate stress rate of 0.01 MPa/s. It was found that both the interfacial bonding strength and testing technique had essential effects on the behavior of slow crack growth.

Effects of reduction, reinforcements, and dynamic precipitation on grain refinement by hot extrusion have been investigated in a Si3N4w/Al-Mg-Si (6061) composite by tensile tests and microstructural investigation. The grain refinement was attributed to an interaction of recrystallization and dynamic precipitation, which was enhanced by reinforcements. Not only fine-grained microstructure, but also relaxing stress concentrations which are caused at matrix/reinforcement interfaces during superplastic flow are required to attain large elongations. Partial melting resulting from segregation plays an important role in relaxing the stress concentrations. DSC investigations revealed that the degree of segregation was increased by hot extrusion.

A Scanning Force Microscope (SFM) is employed to indent and image surfaces with sub-micron resolution. The SFM image shows the area and depth of each indentation as well as its location with respect to nearby topographic surface features. The image also reveals the surface roughness, which can set a lower limit on useful nanoindentation size. A cross section of a nitrided steel surface is measured to illustrate the method. The use of the SFM with separate tip-cantilever structures for indenting and imaging has significant advantages over other nanohardness methods for the study of samples with lateral inhomogeneities.

Activated carbon fibers (ACF's), already used widely as absorbent materials, are now expected to be useful as new electrical and electronic materials, for their very large specific surface areas (SSA). Chemical adsorption as well as x-ray diffraction have been mainly used for characterizing the ACF structure. While TEM observations reveal the texture of ACF's, such observations have not yet yielded quantitative information about the microstructure. To promote the quantitative interpretation of the TEM images, computer image analysis is used in this work to clarify the pore structure of ACF's. The microstructures of three samples, which are all isotropic pitch-based ACF's but with different SSA values, have been investigated. Operations such as noise reduction, low frequency cut-off filtering, and binary image formation are used to clarify the pore images of the ACF's. The distribution of the ACF porosity size is clearly shown by a frequency analysis of the two-dimensional fast Fourier transform (FFT). The results suggest that TEM images include contributions from many different pore sizes. Pores in different size ranges are extracted by the inverse FFT (IFFT) operation by selecting the specific frequency range, and by-this analysis the pore structure is shown to have fractal characteristics.

We have grown thin films of La0.84Sr0.16MnO3 on SrTiO3 (100), MgO (100), CeO2 (100)/Al2O3, and (100) oriented yttria-stabilized zirconia (YSZ) substrates by using a 90°off-axis RF magnetron sputtering deposition. X-ray diffraction analysis and ion beam channeling experiments reveal that the deposited films grow epitaxially on SrTiO3, biaxially textured on MgO, and highly textured on YSZ. Scanning tunneling microscopy reveals that the thin films possess extremely smooth surfaces.