The reaction between shape-memory TiNi thin films and silicon has been characterized by conventional, analytical, and high-resolution transmission electron microscopy. A reaction layer is formed during the 525 °C post-deposition crystallization anneal of the sputter-deposited TiNi, and consists of several phases: Ti2Ni, a nickel silicide, and a ternary titanium nickel silicide. The mechanism for the interlayer formation is discussed.

Fine-grained kappa carbide (Fe3AlCx) materials, containing 12.5 and 14% Al, and 3.5% C, were prepared by powder processing and hipping procedures. The creep behavior of the kappa materials was shown to be identical to that observed in superplastic iron carbide, and was shown to follow a grain boundary–diffusioncontrolled grain boundary sliding relation. The tensile fracture strains in kappa, however, were shown to be considerably less than in iron carbide with a maximum elongation of 92% noted. This difference is attributed to either a low stress intensity factor or to contamination of the powder surface in the kappa material. The compression creep strength, at a given strain rate, was shown to be about two times higher than the tension creep strength.

Analysis of ball-indentation process was made by the finite element (FE) method. A series of indentation FE analyses were made on materials with different elastic modulus (E), and a simple relationship between E and the load-depth (F-h) unloading data is presented. In order to check for the influence of other material properties, thorough research has been performed, introducing a combination of response surface (RS) and FE analysis. As a result, a relationship between the indentation unloading slope, E, and the strain hardening exponent was derived. Also, the indenter compliance effect has been investigated. The indenter compliance correction was calculated and applied to the experimentally measured F-h results. Experimental testing was made on three materials with essentially different elastic moduli. Comparison of the results obtained by newly developed equations with the results from other well-known equations is also presented.

The melt of Bi–Sr–Ca–Cu–O (BSCCO) was quenched by splatting using iron plates, resulting in formation of the glassy plates (0.3–0.7 mm thickness). The plates were converted into superconductors by reheating in air. The critical temperature, Tc, depends on the thickness. The change in Tc is discussed in terms of the difference in the amount of oxygen absorption and in crystallization behavior of the glassy plate during the reheating process between the glassy phase in the interior and that around the surface. It was found that high-Tc glass-ceramic thin plates can be prepared by controlling the amount or the rate of oxygen supply.

The high energy mechanical alloying of a Ti–Ru–Fe powder mixture (atomic ratio 2 : 1: 1) has been performed by extensive ball-milling in a steel crucible. The structural evolution of the resulting materials has been studied by x-ray powder diffraction analysis. The identification of the various phases present in the materials, as well as the crystallite size and strain, has been performed by Rietveld refinement analysis. In the first stage of the material transformation, Ru or Fe atoms dissolved into Ti to yield to the formation of β–Ti. Upon further ball-milling, almost all the original constituents of the powder mixture have disappeared and a new simple cubic Ti2RuFe phase is formed, with a crystallite size as small as 8 nm. The electrochemical properties of these materials have been tested in a typical chlorate electrolyte by cold-pressing the powders into disk electrodes. At 20 h of ball-milling, where the phase concentration of Ti2RuFe reaches 96%, a reduction of the activation overpotential at 250 mA cm−2 of nearly 250 mV is observed when compared to that of a pure iron electrode.

We report on the superconducting properties of TlBa2Ca2Cu3O9−y (Tl-1223) thick films grown on smooth and rough Ag substrates. Thallium-free precursor films of the type Ba2Ca2Cu3Ag0.37O7 were deposited on Ag substrates using a spray-pyrolysis technique followed by post-thallination in a two-zone furnace. X-ray diffraction (XRD) results showed the presence of c-axis aligned Tl-1223 films and some degree of local in-plane texture (often referred to as a colony microstructure). The microstructure of the Ag surface dictates the growth behavior of Tl-1223 films. The transport critical-current densities (Jc) for Tl-1223 films grown on smooth and rough Ag substrates were ∼ 65,000 A/cm2 and ˜ 37,000 A/cm2, respectively, at 77 K and zero field. The films grown on smooth Ag substrates were strongly linked and had good in-field properties with a Jc value of ∼104 A/cm2 at 77 K and 0.5 T.

Artificial barriers in Josephson junctions make it possible to change the height and width of the barrier independently. This technique can be realized in high-Tc Josephson junctions using the ramp technique. In this article the fabrication of ramp-type junctions is discussed and the importance of the morphology of the ramp is pointed out. Detailed investigations are described which address the surface roughness and the damage due to ion-beam structuring of ramps. It is shown that hard masks can significantly improve the ramp quality by reducing the ion impact angle. Furthermore, annealing of the so structured ramps leads to unit cell steps enforcing a step-flow growth mode.

Thin films of ZrO2 doped with MgO and Gd2O3, 1–1.5 μm in thickness are formed onto nickel substrates by reactive thermal evaporation using a dual-hearth electron gun. X-ray diffraction patterns of the deposits show changes in the crystallographic structure and average particle size as a function of the dopant content. A mixture of monoclinic and tetragonal phases gradually disappears to become a single cubic phase with increasing dopant molar fraction. The average crystallite size deduced from diffraction line broadening decreases as the dopant content increases. This observation is strongly confirmed by scanning electron micrographs which reveal a smooth surface topography. Fine-grained materials obtained here are interpreted in terms of high nucleation rate and kinetically limited grain growth. It appears that composition, crystallographic structure, and microstructure relations are of paramount importance in ZrO2-based films prepared by electron-beam evaporation.

A melt-textured process that involves the peritectic reaction Y2BaCuO5 + liquid → YBa2Cu3O7−x is the best method to develop bulk YBa2Cu3O7−x superconductors with improved transport and magnetic properties. Up to this point, information regarding cationic stoichiometry in textured samples is rather lacking in the literature. In this work, wavelength dispersive analysis (WDS) at a microscopic level and energy dispersive x-ray analysis (EDX) at a nanoscopic level were used to characterize the chemical composition of YBa2Cu3O7−x textured samples. The melt-textured process generally modifies the sample stoichiometry. Thus, a textured sample composition cannot be directly obtained even from an accurate knowledge of the starting composition. We have shown that WDS can be used to determine the overall composition and therefore the Y2BaCuO5 content in these samples. It is also a powerful method to control chemical homogeneity and to investigate chemical modifications occurring during processing, especially those resulting from interaction between melt and substrate. The exact nature of YBa2Cu3O7−x nucleation and crystallization still presents many unsolved questions. Nanoanalysis allowed us to study Y2BaCuO5 dissolution in the peritectic liquid, and we have confirmed that it takes place exclusively by removing yttrium from Y2BaCuO5 particles. We have also shown the existence of an yttrium-rich liquid phase, i.e., with a higher yttrium concentration that can be deduced from the equilibrium phase diagram. A liquid phase having a composition close to that of YBa2Cu3O7−x can be inferred from this work. This suggests that YBa2Cu3O7−x nucleation and crystallization take place homogeneously from this liquid.

Submicrometer-grained (SMG) microstructures are produced in an Al–Mg–Si alloy (6061) by subjecting peak-aged and overaged billets of the alloy to intense plastic strain by a process known as equal channel angular extrusion. Two types of refined structure are distinguished by optical and transmission electron microscopy. One structure is created through intense deformation (four extrusion passes through a 90° die, ε = 4.62) by dynamic rotational recrystallization and is a well-formed grain (fragmented) structure with a mean fragment or grain size of 0.2–0.4 μm. The other structure is produced by post-extrusion annealing through static migration recrystallization, resulting in a grain size of 5–15 μm. Intense deformation of peak-aged material to a true strain ε of 4.62 (four passes) produces a strong, ductile, uniform, fine, and high angle grain boundary microstructure with increased stability against static recrystallization as compared to the overaged material.

A model based on mosaic pattern analysis is shown to have the potential to describe the complex shapes and spatial distribution of phases in the microstructures of multiphase materials. Several characteristics of both micrographs of portland cement pastes and images generated using the few parameters of the model are determined and, for the most part, agreement is good. The advantage is that spatial features of the microstructures can be captured by a few parameters.

It is shown that Cu–Ge alloys prepared by depositing sequentially Cu and Ge layers onto GaAs substrates at room temperature followed by annealing at 400 °C form a low-resistance ohmic contact to n-type GaAs over a wide range of Ge concentration that extends from 15 to 40 at. %. The contacts exhibit a specific contact resistivity of 7 × 10−7 Ω cm2 on n-type GaAs with doping concentrations of 1 × 1017 cm−3. The contact resistivity is unaffected by varying the Ge concentration in the range studied and is not influenced by the deposition sequence of the Cu and Ge layers. Cross-sectional high-resolution transmission electron microscopy results show that the addition of Ge to Cu in this concentration range causes Cu to react only with Ge forming the ξ and ε1–Cu3Ge phases which correlate with the low contact resistivity. The ξ and ε1–Cu3Ge phases have a planar and structurally abrupt interface with the GaAs substrate without any interfacial transition layer. It is suggested that Ge is incorporated into the GaAs as an n-type impurity creating a highly doped n+-GaAs surface layer which is responsible for the ohmic behavior. n-channel GaAs metal-semiconductor field-effect transistors using ohmic contacts formed with the ξ and ε1–Cu3Ge phases demonstrate a higher transconductance compared to devices with AuGeNi contacts.

The short-range order in the near surface region of the Cu3Au(001) face was investigated above the critical temperature by glancing-incidence x-ray diffraction, measuring the diffuse intensity throughout a two-dimensional region of reciprocal space. This intensity was analyzed quantitatively to obtain the two-dimensional Cowley–Warren short-range-order parameters and atomic displacements. Monte-Carlo simulation based on these values has revealed that the atomic configurations in the surface consist of ordered domains and clusters in a disordered matrix. There is a large number of {10} antiphase domain boundaries (APDB).

A technique for in situ laser light scanning (LLS) was developed to monitor surface damage on nickel-base superalloy specimens under low-cycle fatigue conditions. This technique characterizes the surface state with a parameter called the defect frequency which minimizes memory requirements and data processing time since it does not involve image processing. As a result, the present technique is capable of scanning speeds that are substantially greater than those achieved with image processing methods. Cylindrical Inconel 718 specimens were tested using an automated servo-hydraulic machine at ambient temperature under fully reversed strain control conditions for constant strain amplitudes ranging from 0.3% to 1%. The fatigue damage was monitored by scanning a laser beam along the gauge section of the specimens during periodic interruptions of the cyclic loading. Acetate replicas of the gauge section surface were also made on some of the specimens to characterize the damage using SEM and image analysis techniques. Comparisons of the results demonstrate the capabilities of the present light-scanning technique for characterizing fatigue damage on the surface of the Inconel 718 specimens. In particular, a rapid rise in the mean defect frequency is shown to correspond to an initial increase in microcrack density that saturates at approximately 20% of the fatigue life. This transient behavior is followed by a plateau in defect frequency which corresponds to crack propagation and interlinkage until failure occurs. The number of cycles to microcrack density saturation as indicated by the defect frequency is found to be linearly related to the number of cycles to failure. Accordingly, the present system provides a characterization of microcrack damage that may be used to predict the low-cycle fatigue life of Inconel 718 specimens long before failure occurs.

The morphology of Cu thin films is strongly dependent on the temperature of the substrate during and after deposition. Films grown at temperatures between 300 °C and 400 °C form clusters distributed in close packed domains and isolated clusters across the surface. Increased substrate temperatures result in cluster shape evolution indicative of mass flow and sintering. Deposition of Cu at substrate temperatures higher than 500 °C results in a completely different morphology of the film and the suppression of cluster formation. Annealing these Cu films to temperatures of 700 °C allows the system to relax into an equilibrium state characterized by large facets in the film and large areas of exposed surface. These observations are discussed in terms of basic thermodynamic data for bulk Cu oxidation and surface tensions for this system.

Hafnia and zirconia gels were prepared by drying hafnyl or zirconyl acetate solutions. Hafnia and zirconia gels contain both hydroxyl group and bidentate acetates which are directly bonded to the metal ions. Thermal decomposition and crystallization behavior of the gels were investigated through XRD, FT-IR, and TEM. Hafnium-containing gels crystallized directly into stable monoclinic hafnia around 500–540 °C, while zirconium-containing gels first formed metastable tetragonal zirconia around 450 °C. The dissimilar crystallization behavior of the gels into metastable, tetragonal zirconia or into stable, monoclinic hafnia can be explained through the difference in free-energy changes of the tetragonal-to-monoclinic phase transformation.

A quantitative study was made of the composition and microstructure of RuO2 films deposited on three different substrates using reactive sputtering. Most of the films had a composition within 2.5 wt.% of the correct stoichiometry; the only exceptions were films grown on Al2O3 (0001) at 150 °C, which had an oxygen-to-ruthenium ratio of 1: 2.24. The excess oxygen was attributed to a thin oxygen-rich layer that encapsulated the grains. Hydrogen concentrations for the films deposited on Al2O3 (0001) were 14, 6, 6, and < 0.5 at.% for room, 150, 300, and 450 °C growth temperatures respectively. The films deposited at room temperature were amorphous on Al2O3 (0001) and SrTiO3 (100), but weakly crystalline on Al2O3 (1102). Highly oriented RuO2 (100) films were produced on Al2O3 (0001) at deposition temperatures ≥150 °C. The in-plane alignment was and a threefold mosaic microstructure was observed. The grain boundaries in these films were discontinuous until the substrate temperature was raised to 450 °C, where coherent grain boundaries were formed. The films grown on Al2O3 (1102) at 450 °C exhibited the epitaxial relationship: RuO2(101)//Al2O3 (1102). The in-plane alignment was RuO2〈101〉//Al2O3〈1101〉, and the lattice parameters were the same as found in bulk RuO2. Transmission electron microscopy indicated a large degree of imperfection in the region between coalescing grains. The RuO2 films grown on SrTiO3 (100) at room temperature were amorphous. The film grown at 450 °C showed a preferential orientation with RuO2 (100)//SrTiO3 (100), but without in-plane orientation.

We examine quantitatively the impact of boundary nucleation on the size distribution of product grains in a computer simulation of a two-dimensional phase transformation. This is accomplished by determining the probability distribution of product grain areas under different nucleation conditions. Specifically, a comparison of the moments of normalized area distributions of product grains arising from site-biased nuclei with the corresponding moments of the area distribution of Voronoi grains reveals those spatial features of the collection of catalytic sites which most affect product microstructure. The impact of other relevant length scales, including the square root of the inverse nucleation site density, the lattice parameter, and the system size, on microstructure is also discussed.

Ion implantation into amorphous carbon has been initiated to investigate the possibility of superhard carbon-nitride formation. Studies of implantation-temperature effects by 100 keV N+ or 80 keV C+ ions at 50 μA show a narrow temperature window at approximately −100 °C for the optimum surface hardness and elastic modulus (measured by nanoindentation), both values much higher than those for the unimplanted amorphous carbon. No distinguishable properties are found between nitrogen and self (carbon) implantations. At a dose rate of 5 μA, however, the optimum hardness and modulus are found at a lower implantation temperature, with a broader temperature window. The enhanced strengths are well correlated with the asymmetric diffuse peak at around 1500 cm−1 in Raman spectroscopy, and the increased ratio of sp3- over sp2-bonded carbon sites observed by electron energy loss spectroscopy.

A liquid phase serves to relax stress concentrations caused by sliding at interfaces and grain boundaries in high-strain-rate superplasticity for aluminum matrix composites. However, the presence of a liquid phase does not always lead to high-strain-rate superplasticity because too much liquid causes decohesion at a liquid phase. The critical conditions of the optimum distribution, thickness, and volume in a liquid phase are discussed based on the observation results by differential scanning calorimetry and transmission electron microscopy. As a result, a very thin and discontinuous liquid phase is required both to assist relaxation of the stress concentrations and to limit decohesion at a liquid phase.