A three-step process to produce wear-resistant, composite diamond coatings is presented. Diamonds are deposited by RF thermal plasma CVD, reinforced by an electroplated metal binder, and regrown to form a continuous film. Microscratching and pin-on-disk wear tests indicate that the three-step composite films are more adherent than plasma deposited diamonds alone.

27Al- and 63Cu-NMR measurements have been made on quasicrystalline phases of the Al65Cu20TM15 alloy (TM:Fe, Ru, and Os). There is no temperature dependence on peak shift and line width of either 27Al- or 63Cu-NMR spectra, suggesting that all the quasicrystalline phases are Pauli-paramagnetic. However, the peak shift of both spectra depends upon the constituent transition element in a different way: Al-peak shift increases from Fe through Os while the Cu-peak shift decreases.

Cracks of up to 40 μm which are either transgranular cleavage or very low energy “ductile” cracks have been introduced into large-grained fcc Ni. The mechanism for introducing this brittle fracture was dynamic indentation. Optical and scanning electron microscopy together with use of selected area channeling patterns were used to confirm that the fracture process is transgranular. The results qualitatively support the hypothesis that dynamic cracks originating in a brittle film can propagate relatively large distances into a ductile face-centered-cubic substrate by a rapid, low energy process.

We have observed a rapid amorphization reaction at ambient temperature in the Gd/Co system by employing grazing incidence x-ray scattering. We find that a 135 Å crystalline Gd film is amorphized in less than 30 min by deposition of Co. We postulate that the rapidity of the reaction is due to surface diffusion of Co atoms after deposition to fast diffusion sites such as grain boundaries in the Gd film. Once the interfacial region has been amorphized these fast diffusion paths are sealed off from the surface, rapid diffusion of Co into the Gd crystalline layer is prevented, and the amorphization reaction stops.

Nanocrystalline FexCu100−x solid solutions (x < 60) with single-phase fcc structure have been prepared by mechanical alloying. The average grain size of the powders (8–20 nm) depends on the composition of the material. Varying the composition changes the grain size reversibly. This can be explained by the underlying mechanism of plastic deformation and solution hardening during mechanical alloying coupled with the recovery behavior of the material.

The Cu, In, and Se core-level electron binding energies of the p-type Cu–In–Se–N thin film were larger than those of the n-type Cu–In–Se thin film. The positive shift of the core-electron binding energies for the Cu–In–Se–N film is consistent with that expected from the conduction types of the films. Holes were positioned in the Cu–Se antibonding orbitals of the Cu–In–Se–N film. The analysis using the Auger parameter revealed that the Cu–Se bonding interaction is stronger for the Cu–In–Se–N film than for the Cu–In–Se film.

First time experimental evidence is presented for the steady state growth of dendrites away from their normal crystallographic growth directions. The evidence is shown for transparent dendrites in the succinonitrile system, which are induced to grow along wetting surfaces. A method for the quantitative characterization of the tips of such dendrites is described and the differences in the secondary arm formation between off-axis and regular dendrites are recorded. The scientific and technological implications of this finding are examined.

A sort of composite material can be produced from a single kind of natural organic fiber. This has been observed with bovine leather. During the formation process in a die particulated leather fibers were subjected for a period of about 6 min to a pressure of over 100 bar at a processing temperature of between 60 and 200 °C. In this way a portion of these collagenous fibers was plastically deformed and converted into continuous matrix material in which unconverted fibers act as matrix reinforcement. Round, collagenous fibers assumed an angular cross section and became the building blocks of the continuous matrix. This is clearly visible on pictures made with a scanning electron microscope. At a processing temperature of 70 °C and a pressure of 650 bar, applied for 6 min, the maximum compression strength at room temperature is found to be 185 MPa. At these processing parameters Young's modulus is about 2.4 GPa and the bulk density is 1350 kg/m3. Other natural fibers, to be used as organic raw material for the production of composites, are currently under investigation.

The microstructures of (A) near stoichiometric, (B) Y-rich, and (C) Y- and Cu-rich YBa2Cu3O7−x thin films have been studied by high-resolution transmission electron microscopy. The films were deposited on (100) LaAlO3 by plasma-enhanced metalorganic chemical vapor deposition. In near stoichiometric films, microstructural features similar to those of thin films deposited by other techniques have been observed. These features which include epitaxial growth with the c-axis perpendicular to the substrate, twin boundaries on (110) planes, and stacking faults on (100) and (001) planes were also present in the off-stoichiometric materials. In Y-rich thin films, yttria (Y2O3) precipitates with an average size of about 5 nm have been identified in the matrix. The precipitates are uniformly distributed, have a high density as large as 1024/m3, and are highly oriented with respect to the matrix. In Y- and Cu-rich thin films, CuO particles up to 1 μm in size were observed on the surfaces of the films. The observed microstructural features were similar to those of the Y-rich materials.

We investigated the in situ growth of YBa2Cu3O7−δ superconducting thin films by a sequential ion beam sputtering technique, studying the relations among deposition parameters, structural and superconducting properties. The films were deposited following the stacking sequence of YBa2Cu3O7−δ, with individual layer thicknesses nominally equal to one monolayer. O2 was supplied during deposition. Predominantly c-axis oriented films were grown on (100) SrTiO3, (100) MgO, and oxidized Si (SiO2/Si) substrates. The microstructure and film-substrate orientation relations were studied by transmission electron microscopy. X-ray studies showed the presence of homogeneous and inhomogeneous strains along the c-direction that persisted after low temperature oxygen anneals. Resistivity measurements showed correlations between the superconducting transition characteristics and the lattice distortions along the c-direction. The effect of deposition parameters on the lattice distortions was investigated, finding that the c-axis lattice parameter was larger in films grown at lower temperatures. This was interpreted in terms of the thermally activated dissociation of O2 at the film surface during growth. We assumed that the c-axis lattice expansion was due to kinetic limitations to the incorporation of oxygen into the film during growth. This led to a consistent description of the results obtained in this work and the O2 pressure dependence of the c-axis lattice expansion reported for other in situ techniques. Studies were performed on films grown by this technique as well as on films grown in situ by magnetron sputtering in an attempt to elucidate the nature of the defect structure causing the c-axis lattice distortions.

YBCO was synthesized using atomically mixed nitrate precursors. Atomic mixing was achieved using a freeze-dried process which is fully discussed here. The thermal processing behavior of these precursors is fundamentally different from that of mechanical mixtures of the Y, Ba, and Cu oxides and it is examined in detail. Ba2Cu3O5+x (normally considered a high oxygen pressure phase) and Y2O3 formed as nitrate decomposition products at ambient atmospheric conditions. Subsequent reaction of these materials (2 h at 925 °C) produced polycrystalline YBCO. Without any post-processing of the powders, product YBCO powders consisted of 30 μm agglomerates composed of crystals 1–3 μm on an edge. The powdered products exhibited a magnetic susceptibility greater than 90% – 1/4π.

Thick films of Bi–Sr–Ca–Cu–O on (100) MgO substrates have been prepared by the screen printing technique with the starting composition of 1112. The annealing process involves a two-step heat treatment. The first-step temperature is chosen between 874 °C and 898 °C for 45 min followed by slow cooling (2 °C/min) to 864 °C. In the second step, the films are kept at 864 °C for a time varying from 0 to 104 h. The Tc (R = 0) and intensity of the characteristic peaks of the high Tc and the low Tc phases in the x-ray diffraction pattern are found to be dependent on the first-step temperature and the duration of the second step. The process of crystallization and the growth of plate-like grains as a function of annealing time at the second step are studied using Scanning Electron Microscopy (SEM). Kinetics of the growth of the high Tc phase has been explained in terms of a reaction mechanism involving the first and second annealing steps.

Reactions with alumina and platinum crucibles were studied during the preparation of Bi2Sr2Ca1Cu2Oy “2212” glasses. In particular, reactions with Al2O3 are of interest since alumina is a potential substrate material in applications of this superconductor. Glasses processed using alumina crucibles were completely homogeneous and free of secondary phases although the material contained 2.26 at. % Al in solution. After heat treatments, Al was found in the form of SrCaAlOy particles located primarily along grain boundaries of the 2212 superconducting phase. Platinum contamination was minimal (<0.02 at. %) and no Pt-containing secondary phases were found in amorphous or annealed samples. Glasses made with Pt crucibles were found to contain small amounts of CaO, Sr14−xCaxCu24O41, and 2201 as second phases. Differential thermal analysis (DTA) suggested that the crystallization processes were essentially the same for all samples although the small amount of Al seemed to slow the kinetics leading to the formation of 2212. Neither Al nor Pt was detected within the 2212 phase. The measured superconducting compositions in each annealed sample were nearly the same with identical transition temperatures of 88 K. Overall differences in stoichiometry were accommodated by changes in the number and composition of the secondary phases present.

We have measured stress variations with temperature as a function of film thickness and a given grain size in pure Al and Al–0.5% Cu films on Si substrates. The variation in thickness for a given grain size is brought about by using the same film and the repeated controlled growth and dissolution of a barrier anodic oxide which can be grown uniformly on the film. Stress measurements were made as a function of temperature by measuring wafer curvature after successively removing each 0.1 μm of Al film. The components of strengthening due to the film thickness and the presence of grain boundaries were separated by assuming that the flow stress of the film is simply the sum of these two components. It is found that strengthening due to film thickness varies inversely with the thickness, which is consistent with results obtained by us using laser-reflowed films in an earlier work. The Hall–Petch coefficients calculated from the strengthening due to the grain boundaries are slightly higher than those reported for bulk Al. However, it is also recognized that the variation of the flow stress as g−1, where g is the grain size, is more plausible than that predicted by the Hall–Petch relation (i.e., as g−1/2). The variations of these two components with temperature, and under tension and compression, are discussed.

The site occupancy of ternary atoms in three L12-structured intermetallic phases, Al62.5+XTi25−Y(Fe, Ni, or Cu)12.5–Z found in three laser processed intermetallic systems was studied by the axial ALCHEMI (Atom Location by Channeling Enhanced Microanalysis). The ternary atoms in all three intermetallic phases were found preferentially to occupy the Al sublattices, although slight differences in occupancy among them were detected. A simple extrapolation method of calculating delocalization correction factors for various characteristic x-ray emissions was described, which was proved to be practically useful in ALCHEMI analyses. In order to compare the axial ALCHEMI analysis with the planar ALCHEMI in an experimental perspective, the planar ALCHEMI analysis was also carried out on the phase alloyed with Cu, which showed results in broad agreement with those of the axial ALCHEMI analysis on the same phase. Nevertheless, owing to much weaker channeling effects the planar ALCHEMI analysis gave apparently worse statistics in its results. In the end, various sources of errors in the ALCHEMI analyses at the present stage are discussed.

A review of the intermediate temperature creep properties of Ni3Al indicates that octahedral glide, the mechanism associated with the anomalous temperature dependence of yielding in this alloy, is exhausted during primary creep. Comparisons of this primary creep transient with the various models proposed to explain the anomalous yielding behavior suggest that additional transient experiments are needed to fully characterize octahedral glide in this alloy. Cottrell–Stokes type temperature change experiments, stress relaxation experiments, and deformation exhaustion/temperature drop tests have been conducted in an attempt to better characterize octahedral glide in Ni3Al. The results of these transient experiments indicate that octahedral glide is only partially a thermally reversible process and that the formation of dislocation substructure, KW locks, plays an important role in determining the flow strength of this alloy. These experiments also suggest that flow in Ni3Al should not be viewed as a viscous drag process, but can best be described as a “pure-metal-like” process involving the rapid motion of a small number of highly mobile dislocations. The stochastic nature of dislocation motion and the importance of substructure formation are emphasized and a description of octahedral glide that is consistent with the transient deformation experiments is proposed.

Tungsten-carbon coatings have been deposited on stainless steel substrates by reactive magnetron sputtering from Ar–CH4 mixtures. The carbon concentration in the coatings measured by electron microprobe analyses was found to be proportional to the CH4 flow rate. Only the cubic α–W phase with a dilated lattice parameter was identified in W–C coatings having a carbon content lower than 25 at. %. Since the lattice parameter of the α–W phase in these W–C coatings increased with increasing carbon content, these coatings may be assumed to be W–C solid solutions. Only the nonstoichiometric β–WC1−x carbide (cubic phase) was detected in W–C coatings containing 30 to 70 at. % of carbon. The chemical state of the elements was investigated by x-ray photoelectron spectroscopy. The Vickers hardness of the W–C coatings was found to be considerably dependent on the carbon concentration. A maximum microhardness of 26 000 MPa was measured for W–C coatings containing either 14–15 at. % or 40–45 at. % of carbon. The correlation between crystallographic structure and microhardness is analyzed and discussed in this paper.

A model exploring the effect of the presence of a single hydrogen interstitial on the crack tip configuration of nickel is described. The model is based on a EAM-type potential developed by Daw, Baskes, Bisson, and Wolfer for describing the Ni–Ni, Ni–H, and H–H interactions, and involves the crack tip region of a semi-infinite crack in an infinite solid. Several types of interactions are observed to occur. In a model oriented such that dislocation emission is difficult, hydrogen is observed to increase the crack tip opening displacement (CTOD), exert a force on the crack tip due to interaction between the dilatancy of the defect and the hydrostatic component of the field of the crack, and increase the local tensile stresses. However, the largest contribution to extending the crack derives from the energy released when a hydrogen interstitial escapes to the crack surface. A hydrogen interstitial is also observed to assist dislocation emission in models with an easy emission orientation.

Recent alloy development efforts have shown that Fe3Al-based alloys can have room temperature tensile ductilities of 10–20% and yield strengths of 500 MPa at temperatures to 600 °C. These property improvements are important for enabling the use of iron-aluminides for structural applications that require their excellent corrosion resistance. New data are presented here from creep-rupture studies on Fe3Al and on Fe3Al-based alloys containing molybdenum or niobium plus zirconium. Binary Fe3Al alloys have low creep resistance, but the addition of 2 at. % Mo or 1% Nb plus 0.1% Zr increases the creep life and reduces the minimum creep rate, with the niobium-containing alloy being the strongest. The improvement in creep life is the result of a combination of factors which include grain boundary strengthening, resistance to dynamic recrystallization during stressing, precipitation strengthening, and changes in the formation and mobility of the dislocation network. Correlation of optical, scanning electron, and transmission electron microscopy data suggests that the intergranular creep failure found in Fe3Al after creep testing at 550–650 °C is related to weak high-angle grain boundaries and to formation of subgrain boundary arrays, which reduce the ability of dislocations to glide or multiply to produce matrix plasticity. The addition of niobium/zirconium results in solid solution strengthening effects, as well as the formation of fine MC precipitates (a small amount of carbon is present as a contaminant from the casting process) which strengthen both the matrix and grain boundaries. The result relative to the binary alloy is increased creep-rupture strength and life coupled with a change to a ductile-dimple transgranular failure mode. This suggests that the mechanisms that cause failure during creep can be controlled by macro- and microalloying effects.

Metallic iron and iron oxide particles were produced by injecting ferrocene into the afterglow region of a low pressure, low power, plasma generated using a microwave power source. This was done as part of an effort to explore the feasibility of using flow type microwave plasmas for the production of metal nanoparticles. It was found that two parameters had the largest impact on the particles: injection point and plasma composition. Analysis done using Mössbauer effect spectroscopy, transmission electron microscopy, and x-ray diffraction indicated that low yields of small particles (ca. 10 nm) resulted from injection into the afterglow region. Much higher yields of large particles (ca. 50 nm) formed if the ferrocene was injected through the coupler. In hydrogen plasmas the particles that were produced were metallic iron, whereas in oxygen and argon plasmas the particles were iron oxide. In all cases significant amounts of graphitic carbon formed around the metal particles.