Fe–N alloys with crystalline structures different from those obtained at atmospheric pressure were produced by solid-state reaction between Fe and amorphous boron nitride under high pressure. Two new paramagnetic Fe–N phases were obtained at temperatures above 800 K under pressures between 2.0 and 4.0 GPa. One is of cubic structure with lattice constant of 6.114 Å, and another is of orthorhombic structure with lattice constants of a = 4 8.443, b = 4 4.749, and c 4 3.993 Å. ε–Fe3Nx with N contents of 18.1 to 21.4 at.%, which could not be obtained at atmospheric pressure, was produced at pressures of 3.0 to 4.0 GPa and temperatures of 690 to 800 K. The mechanism of formation of ε–Fe3Nx under high pressure is discussed.

The preparation of high-permittivity perovskite materials requires high-temperature (550–750 °C) oxidizing environments, providing stringent limitations on the choice of electrode materials. To minimize interdiffusion and oxidation reactions, an electrically conductive diffusion barrier such as Ti1−xAlxN is needed below the electrode material (Pt, IrO2, RuO2…). Ti1−xAlxN films were deposited by multitarget reactive sputtering in a mixture of Ar and N2. The stability of these films has been investigated under typical conditions for crystallization of perovskite dielectrics. Sample composition was characterized using Rutherford backscattering spectroscopy and nuclear reaction analysis. In particular, the concentration depth profiles of both 18O and 27Al were measured before and after RTA treatments via the narrow resonances of 18O(p,α)15N at 151 keV (FWHM = 100 eV) and 27Al(p,γ)28Si at 992 keV (FWHM = 100 eV). The different 18O excitation curves show that the oxidation resistance increases with Al incorporation. The Al excitation curves indicate a uniform Al content for as-deposited TixAl1−xN and reveal Al diffusion to the surface during the oxidation process which indicates the formation of an Al-rich oxide layer at the TixAl1−xN surface, leaving a layer depleted in Al below it.

A systematic behavior in the crystal structure parameters of natural, synthetic, carbonate, and non-carbonate apatite is revealed from Rietveld refinements of neutron powder diffraction experiments. The results of this work on synthetic carbonate hydroxyapatites (CHAps) are consistent with the mechanism of carbonate substitution on the mirror plane of the phosphate tetrahedron, as it was introduced for the natural carbonate fluorapatite (CFAp). The present comparison shows that the tetrahedral bond lengths P–O1 and P–O2 decrease by 3–4% in all carbonate apatites. The atomic displacement parameters (ADPs) of the tetrahedral (T) and the O3 sites are greater in the carbonate than in the non-carbonate apatites. The atomic positional disorder of the T site (P/C site) is greater in the CFAp than in the CHAps, while the opposite happens at the O3 sites. Finally, the room-temperature ADPs of all of the atoms in the CFAp and CHAps show the same behavior as in the corresponding non-carbonate materials.

This paper reports on the role of boron in situ doping on enhancing crystallization of silicon germanium deposited at 400 °C and 2 torr. The dependence of growth rate on germanium content and boron concentration is investigated. The minimum boron concentration and the minimum germanium content required for crystallizing the as-grown layers is experimentally determined. The texture and grain microstructure of doped and undoped poly SiGe layers has been investigated by means of x-ray diffraction spectroscopy and transmission electron microscopy. The low deposition temperature coupled with the low tensile stress of the polycrystalline material enable postprocessing of surface micromachined microelectromechanical systems on top of standard complementry metal oxide semiconductor wafers with Al interconnects. Furthermore, the resistivity of the as-grown layers is as low as 1 mΩ cm, and hence, it can be used as a seeding layer for polycrystalline Si solar cells compatible with glass substrates.

A series of metal-matrix composites were formed by extrusion freeform fabrication of a sinterable aluminum alloy in combination with silicon carbide particles and whiskers, carbon fibers, alumina particles, and hollow flyash cenospheres. Silicon carbide particles were most successful in that the composites retained high density with up to 20 vol% of reinforcement and the strength approximately doubles over the strength of the metal matrix alone. Comparison with simple models suggests that this unexpectedly high degree of reinforcement can be attributed to the concentration of small silicon carbide particles around the larger metal powder. This fabrication method also allows composites to be formed with hollow spheres that cannot be formed by other powder or melt methods.

Forced hydrolysis preparation of zirconia sols and powders by microwave heating of zirconium tetrachloride solutions at temperatures equal to 180 °C leads in a few minutes to monodispersed nanoscale zirconia particles. Synthesis was performed in a microwave reactor called the RAMO system. This microwave reactor was designed by the authors. This flash-synthesis process combines the advantages of forced hydrolysis (homogeneous precipitation) and microwave heating (very fast heating rates). The sols and powders were characterized by x-ray diffraction,photon correlation spectroscopy (PCS), small-angle x-ray scattering, and transmission electron microscopy. Sols are colloidally stable, which means that after 6 months no sedimentation is observed and the size distribution given by PCS measurements has not changed. For all synthesis conditions (with or without HCl, zirconium salt concentration, and synthesis time), zirconia polycrystalline particles were produced. According to the different analyses, these zirconia polycrystalline particles were constituted of aggregates of small primary clusters.

The enthalpies of formation for the compounds (RE3+)PO4, (where RE = Sc, Y, La–Nd, Sm–Lu) were determined by oxide-melt solution calorimetry. Calorimetric measurements were performed in a Calvet-type twin microcalorimeter in sodium molybdate (3Na2O · 4MoO3) and lead borate (2PbO · 2B2O3) solvents at 975 K. The experiments were carried out using both powdered single crystals grown by a flux technique and powders synthesized by precipitation. Formation enthalpies were derived from the drop-solution enthalpies for (RE)PO4, RE oxides, and P2O5. Enthalpies of formation for the (RE)PO4 compounds with respect to the oxides at 298 K become more negative with increasing RE3+ ionic radius; i.e., in going from ScPO4 (−209.8 ± 1.0 kJ/mol), to LuPO4 (−263.9 ± 1.9 kJ/mol), to LaPO4 (−321.4 ± 1.6 kJ/mol). From structural considerations, a similar trend is expected for the isostructural RE vanadates and arsenates, as well as for the tetravalent actinide orthosilicates.

Nanoindentation testing of the titanium oxide/titanium system with electrochemically grown oxide films exhibits permanent deformation prior to a yield excusion, indicating that the occurrence of this suddent discontinuity is predominantly controlled by oxide film cracking rather than dislocaton nucleation and multiplication. Observations of circumferential cracking also lend support to this explanation. A model has been developed to predict the mechanical response prior to oxide fracture for the case of a hard coating on a soft substrate. During loading contact, the hard coating undergoes elastic deflection which may include both bending and membrane stretching effects, while the substrate is elastoplastically deformed. The model works well for surface films thicker than 20 nm. Additionally, the maximum radial tensile stress in anodically grown titanium oxide, which is responsible for film cracking at the critical load, is approximately 15 GPa.

According to resonant vibration fatigue tests, near-eutectic and Pb-rich hypoeutectic Pb–Sn specimens have higher crack-propagation resistance. The tensile flow stress of Pb–Sn solders that are near eutectic composition increases with decreasing Pb content. The solders were tested after either stabilizing at 373 K or natural aging for 20 days, which gave similar results. The naturally aged specimens show that the crack-propagation resistance increases with increasing aging time. A striated deformation was found to occur in Sn grain of the lower Pb specimen. This phenomenon is correlated with a deterioration of crack-propagation resistance.

After examining ternary Al-based quasi-crystalline phase diagrams, we pointed out that the presence of e/a-constant and e/a-variant lines is a common phenomenon. Ternary quasi-crystal compositions are located at the crossing point of these lines in ternary phase diagrams. Such an empirical rule can be used to predict the ternary quasi-crystal compositions from binary ones. We applied this rule to the Al–Fe–Ni system and clarified the decagonal phase composition zone. There are two decagonal phases, D-Al72.5Fe14.5Ni13 and D′-Al705Fe12Ni17.5, that correspond respectively to Al–Fe-based and Al–Ni-based decagonal phases in the same ternary system.

Power applications of high-temperature superconducting (HTS) coated conductors will require stabilization against thermal runaway. We have developed conductive buffer layers to electrically couple the HTS layer to the underlying metal substrate. The structure comprises the layer sequence of SrRuO3 (SRO) on LaNiO3 (LNO) on biaxially textured Ni substrates. We report baseline investigations of compatibility of SRO/LNO multilayer structure with processing of Yba2Cu3O7−δ (YBCO) and demonstrate biaxially textured YBCO films on conductively buffered Ni tapes. These YBCO coatings exhibit self-field Jc values as high as 1.3 × 106 A/cm2 at 77 K, and the entire structure (HTS + conductive buffers + metal substrate) shows good electrical connectivity. These results demonstrate that SRO/LNO buffer layers may provide a basis for stabilized coated conductors.

Nanophase precipitates of CdS formed in amorphous SiO2 by ion implantation and thermal processing have recently been found to exhibit a “hollow-particle” or “shell-like” microstructure. The present investigations show that this hollow-particle microstructure can be reproduced for a variety of materials other than CdS, and these results provide new insight into the mechanisms responsible for the formation of hollow precipitates embedded in solid hosts. Various elemental metal nanocrystals were formed in (100)-oriented crystalline Si hosts by ion implantation coupled with thermal treatments in which the annealing parameters were varied to investigate the “hollow-particle” formation conditions. The results indicate that depending on the melting points and vapor pressure of the precipitates or on the initial state of the host material, several processes acting either independently or in concert can lead to hollow precipitate formation. First, the implantation of materials having a high vapor pressure, either at the implant temperature or when heated during annealing, can lead to the formation of cavities in the crystalline host. Hollow precipitates can then form by a partial filling and coating of the cavity walls by the implanted species in a diffusion-based gettering/ripening process. Internal void formation can also occur or be enhanced by volume contraction during cooling if the particle solidifies from a liquid phase.

Barium-strontium titanate (BST) thin films were prepared by a two-step deposition using radio-frequency magnetron sputtering on Pt/Ti/SiO2-buffered Si(100) substrate. The initial BST layer thickness and intermediate annealing strongly affect the resultant electric properties of the two-step BST thin films. The optimal two-step BST films, with a first-layer thickness of 30 nm intermediate annealed at 610 °C under 1 torr oxygen. The dielectric breakdown and leakage current density of the two-step film are above 625 kV/cm and 9.5 nA/cm2 at 100 kV/cm, respectively, compared with 400 kV/cm and 17 nA/cm2 for the one-step films. We conclude that the two-step deposition dramatically improves dielectric breakdown and enhances leakage current density while keeping the dielectric constant uninfluenced.

The combustion of zirconium foils in an oxygen environment was investigated for foils ranging in thickness from about 22 to 124 μm and for oxygen partial pressures ranging from about 0.3 to 0.9 atm. Temperature profile measurements showed indications of an after-burn, which became especially significant in the combustion of thicker foils. The dependence of the combustion wave temperature and velocity on the oxygen partial pressure was determined. For any partial pressure, wave velocity decreased with an increase in foil thickness. Wave propagation in this system is a complex process and is dictated by oxide formation and oxygen dissolution. The results are examined in light of a finite difference model.

Heating and annealing effects on the optical properties of slightly blue substoichiometric molybdenum trioxide thin films are reported partially. During heating and annealing, different levels of coloration seem to be generated by simultaneous reduction and proton injection into thin films, which cause the formation of hydrogen molybdenum bronzes of different concentrations. The optical band gap, Eo, of MoO3 thin film when annealed in between 313 and 473 K is decreased to 2.82 eV, and this reduction in Eo has been explained with a view to phonon and polaron species. Moreover, temperature-dependent change in the optical band gap has also been interpreted in terms of band gap slope, B, and the real part of the refractive index, n. Urbach slope, σ, also goes down to 0.67 eV−1 due to annealing treatment. Using the oscillator model, a phonon energy, hνo, of about 0.08 eV was found for the reported MoO3 thin film which is very close to the characteristic phonon energy of MoO3. Over and above, the intensity for the blue absorption band, over the photon energy range 0.4–3.0 eV, also reaches a maximum as MoO3 thin film is annealed at 473 K for 1 h and then decreases by 32% after annealing at the same temperature for 2 h. This phenomenon is due to polaronic band intensity which rises and falls during annealing. Half-width of the blue band, as found by fitting polaron model, is changed only by 3% on annealing the MoO3 thin film at 473 K as compared to its value at room temperature.

Impression creep of a flat-ended cylindrical punch pushed into a viscous layer overlaid on a rigid substrate is analyzed. The method developed here permits us to relate the impression velocity to the punching stress in terms of an auxiliary function, which represents the solution of a set of Fredholm integral equations with a continuous symmetrical kernel. By a series of numerical analysis, the influence of the boundary conditions and the effect of the thickness of the layer on the impression velocity are obtained. For infinite thickness (i.e., h/a →∞, where h is the thickness of the layer and a is the radius of the punch), the impression creep is independent of the stick or slip boundary condition at the indenter/layer interface. For finite thickness such as h/a = 20, the boundary conditions have about 5% effect on the impression velocity. For a thin film, the impressing velocity is very sensitive to the boundary conditions. In fact it suggests a possible experimental way to detect debonding at the interface between the thin film and the substrate.

parameters that govern the life of metallic materials under conditions of fretting fatigue may be divided into two broad categories. The first category concerns the material properties (e.g., yield strength, elastic modulus, and surface roughness) while the second concerns the externally imposed loading conditions and contact geometry. The two in-contact materials may either stick, slip, or stick-slip (i.e., there is a slip and a stick region on their interface) against each other. It has been shown that the fatigue life reduction is highest under partial slip. The objective of the present research effort is to develop a model that enables the prediction of the particular fretting fatigue regime (i.e., slip, stick, or mixed). The parameters that affect the fretting fatigue life of metallic components were identified and integrated into a model, which allows the prediction of the interfacial contact conditions. The model was first used to identify the sensitivity of the fretting fatigue regimes upon the materials and external, and geometrical parameters. Experimental results concerned with the fatigue life were plotted on the fretting maps; the fretting fatigue regimes indicated by the latter enabled the interpretation of the experimental data.

Nanocrystalline Inconel 625 alloy, with a uniform distribution of grains, was synthesized using cryogenic mechanical milling. Microstructures of the powder, cryomilled for different times, were investigated using transmission electron microscopy (TEM), scanning electron microscopy, and x-ray diffraction. The results indicated that both the average powder particle size and average grain size approached constant values as cryomilling time increased to 8 h. The TEM observations indicated that grains in the cryomilled powder were deformed into elongated grains with a high density of deformation faults and then fractured via cyclic impact loading in random directions. The fractured fragments from the elongated coarse grains formed nanoscale grains. The occurrence of the elongated grains, from development to disappearance during intermediate stages of milling, suggested that repeated strain fatigue and fracture, caused by the cyclic impact loading in random directions, and cold welding were responsible for the formation of a nanocrystalline structure. A high density of mechanical nanotwins on {111} planes was observed in as-cryomilled Inconel 625 powders cryomilled, as well as in Inconel 625 powder milled at room temperature, Ni20Cr powder milled at room temperature, and cryomilled pure Al.

We investigated mechanical properties of TiN as a function of microstructure varying from nanocrystalline to single crystal TiN films deposited on (100) silicon substrates. By varying the substrate temperature from 25 to 700 °C during pulsed laser deposition, the microstructure of TiN films changed from nanocrystalline (having a uniform grain size of 8 nm) to a single crystal epitaxial film on the silicon (100) substrate. The microstructure and epitaxial nature of these films were investigated using x-ray diffraction and high-resolution transmission electron microscopy. Hardness measurements were made using nanoindentation techniques. The nanocrystalline TiN contained numerous triple junctions without any presence of amorphous regions. The width of the grain boundary remained constant at less than 1 nm as a function of boundary angle. Similarly the grain boundary structure did not change with grain size. The hardness of TiN films decreased with decreasing grain size. This behavior was modeled recently involving grain boundary sliding, which is particularly relevant in the case of hard materials such as TiN.

A detailed impedance analysis using the brick-layer model is performed on a high-purity yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). Space-charge impedance is generally formulated and expressions for the respective space-charge models are therefrom derived depending on whether dopant ions are mobile or immobile. Pronounced yttrium segregation in Y-TZP is also considered in the analysis in that the dopant profile is assumed to be frozen from a high-temperature equilibrium distribution. Comparison with experimental observations shows that the electrically measured grain-boundary thickness corresponds to the Schottky-barrier width, slightly modified by the dopant segregation. The grain-boundary resistance is not consistent with any space-charge models and the strong defect interaction due to the yttrium enrichment is suggested to be mainly responsible.