Films of chemically disordered fcc Ni3Al were synthesized by the vacuum evaporation of Ni3Al onto room temperature and liquid nitrogen temperature substrates. X-ray diffractometry and transmission electron microscopy showed the material to be single phase with an average grain size of about 4 nm. The formation of the equilibrium L12 ordered phase occurred simultaneously with grain growth at temperatures above 350°C. Differential scanning calorimetry provided ordering enthalpies of 7 kJ/mole and 9 kJ/mole for material evaporated onto room temperature and liquid nitrogen temperature substrates, respectively.

Thin films of barium titanate (BaTiO3) have been deposited by pulsed-laser ablation onto (001)-oriented MgO substrates. The films were epitactic with the c-axis perpendicular to the film-substrate interface, as evidenced by both transmission electron microscopy (TEM) and ion-channeling techniques. The elastic resonance of 3.045 MeV α-particles, generating the 16O(α, α)16O reaction was used to determine the oxygen stoichiometry of the film and the minimum yield based on the oxygen peaks, thereby enabling conclusions to be drawn about the crystalline perfection of the oxygen sublattice.

The grain growth and microstructure development of YBa2Cu3O7−δ have been investigated utilizing two different starting particle size distributions (normal and bimodal). The grain growth exponent, n, was found to be about 0.21 for both normal and bimodal samples. An activation energy of 125 kJ/mole was calculated. The low value of n might be attributed to the high anisotropy of grain boundary energy in this system. Samples made from the bimodal powder were found to accelerate grain growth without introducing abnormal grain growth. Although most of the samples attained fractional densities greater than 0.95, the presence of various amounts of porosity (particularly in the case of the bimodal starting powder) did not affect the growth kinetics. The measured aspect ratio of grains did not significantly change during growth. A significant difference in aspect ratio was measured between samples made from the two different starting powders. Critical currents ranged from 10 to 120 A/cm2, but no concrete relationship with grain size was established. This implies that the grains produced by this experiment were in the size range where other factors, presumably microcracking, severely limited the current carrying capacity by the weak link effect.

We introduce a novel containerless melt-spin processing technique for YBa2Cu3O7−x using prereacted oxide powders that are rapidly melted and subsequentially quenched in a controlled atmosphere. This results in flakes with typical dimensions of 3000 × 150 × 15 μm3. Powder XRD indicates that all samples contain Y2O3, but that the Ba–Cu–O phases present depend on the processing parameters. SEM and TEM studies show these phases are finely dispersed: the typical grain size for Y2O3 is 1–2 μm, and for the Ba–Cu–O phases it is <0.5 μm.

The purpose of this study was to (1) examine the spatial (within-sample) uniformity of superconducting behavior and microstructure in YBa2Cu3O7−x specimens over the pore fraction range 0.10–0.25 and (2) determine the viability of using a room-temperature, nondestructive characterization method (ultrasonic velocity imaging) to predict spatial variability. Spatial variations in a.c. susceptibility were observed for specimens containing 0.10 pore fraction. An ultrasonic velocity image constructed from measurements at 1 mm increments across one such specimen revealed microstructural variation between edge and center locations that correlated with variations in a.c. shielding and loss behavior. Optical quantitative image analysis on sample cross sections revealed pore fraction to be the varying microstructural feature.

Via in situ electrical property measurements (conductivity, Seebeck coefficient) over the temperature range 500–800 °C and oxygen partial pressure range 10−4-1 atm, the equilibrium transport properties and stability range of YBa2Cu4O8 were determined. YBa2Cu4O8 behaves like the intrinsically mixed-valent compound, magnetite (Fe3O4), with small variations in electrical properties with changes in oxygen partial pressure. The decomposition boundary to YBa2Cu3O6+y (or YBa2Cu3.5O7.5±z) and CuO occurs at log(po2, atm) = −1.24 × 104/T(K) + 11.01(773 ⋚ T(K) ⋚ 1073).

Evidence of directional structural disordering prior to complete amorphization of Cu4Ti3 during 2 MeV electron irradiation is presented. It is shown that the observed disordering is intrinsic to the irradiated material and is incommensurate with the structure of the crystalline compound. The results point to the presence of significant anisotropy in the response of the material to irradiation. A model based on local rotation of clusters of atoms within a partially chemically-disordered matrix is developed. These results are discussed in relation to recent proposed mechanisms of amorphization based on volume expansion. The questions raised by this work indicate a need for detailed studies of the atomic level structural evolution of a material during solid state amorphization.

Temporary alloying of Ti alloys with hydrogen is used to modify microstructure and hence enhance mechanical properties. In the present work the influence of the thermal history of the Ti–6Al–4V alloy on the final microstructure was studied. Two different kinds of microstructures were investigated: (a) as-hot isostatic pressed (HIP) having an α + β microstructure; (b) β-solution-treated and subsequently quenched (α'-microstructure). After each stage of the hydrogenation-dehydrogenation (HDH) process the material was analyzed by optical, scanning electron and transmission electron microscopy, and by x-ray diffractometry. It was found that fcc (γ) hydrides precipitate in both the α and the α' matrix. The orientation relationships were found to be the same in both cases. Hydrides precipitate from the β-phase when the hydrogen content of the alloy is sufficiently high. The minimum concentration that still led to precipitation was 1.4 wt. % H. The β/γ orientation relationship was determined. The HDH process resulted in either of two structures: (1) a fine, broken-up microstructure containing a fine mixture of α' + (α + β) when the starting microstructure was α', or (2) a modified α + β microstructure containing fine α and β precipitates and a high density of microdefects within the primary α in the as-HIP α + β microstructure specimens.

The new ternary intermetallic compound Zr3Ti2Si3, with a (Mn5Si3)16H crystal structure, was designed based on the information of the crystal structure of the related binary compounds Zr5Si3 and Ti5Si3 in order to be used in ultra-high temperature structural applications. By x-ray diffraction analysis, we demonstrate the possibility of substituting an entire layer of zirconium atoms with a layer of titanium atoms in the (Zr5Si3)16H. An analysis of atomic neighbor distances in each compound was done. It was found that the Zr–Si relative interatomic distance diminishes while the Ti–Si distance increases. This indicates that Zr–Si bond strength is maintained as in the binary Zr5Si3. The resulting ternary intermetallic compound has a 16H crystal structure and has a lower density than the original compound of zirconium silicide. This new compound, which is stronger than Ti5Si3 and lighter than Zr5Si3, is considered an excellent candidate of the next generation of intermetallic compounds for ultra-high temperature structural applications.

Stress relaxation in aluminum films of several thicknesses was characterized by using both continuous indentation and x-ray diffraction techniques. Results of the indentation and x-ray stress measurements compare closely for films of small thicknesses. Indentation data from thicker films do not compare well to the x-ray data due to the presence of a residual stress distribution.

Analytical results obtained for the transient kinetics of nucleation enable one to interpret N(gd,t), the accumulated number concentration of clusters at the instrumentally detectable size, gd. The new results enable one to extract kinetic and thermodynamic parameters of nucleation from experimentally measured cluster concentrations and to test nucleation theories experimentally. An approach to estimate the mean time to form the first nucleated cluster in a given sample is also presented.

Analytical expressions for the time-dependent crystallized volume fraction are derived from new results for the transient rate of nucleation reported in Part I. Conventional formulations that have been used in interpreting crystallization experimental data and for assessing the stability of amorphous phases are shown to be large time limits of the newly derived expressions. An approach for assessing the stability of an amorphous phase is proposed.

A simple phenomenological model is developed to explain, qualitatively, the observed temperature and ion flux dependences of either recrystallization or further amorphous growth of amorphous layers in semiconductors when exposed to ion irradiation. The model includes radiation assisted annealing processes and thermally modified amorphous zone production at the amorphous-crystal interface.

Irradiation of unsupported samples of hydrogenated amorphous silicon below 100 K with 360-MeV Xe ions results in macroscopically visible changes in sample dimensions. These changes have two different causes. Formation and growth of cavities lead to an isotropic increase of the specimen dimensions and to a drastic decrease of the mass density. Simultaneously plastic flow occurs, which produces additional but anisotropic changes of the specimen dimensions. The dimensions perpendicular to the beam grow whereas the dimension parallel to the ion beam shrinks. Neither effect saturates in the investigated fluence range (Φt < 1014 Xe/cm2) and both are absent in crystalline silicon. The effects are most likely provoked by electronic excitations and/or ionizations in the wake of the fast ions. With respect to plastic flow, a–Si:H behaves like metallic and oxide glasses. Formation of cavities and their growth, however, seem to occur only in tetrahedrally coordinated solids.

Si samples (001) oriented have been implanted with 101774Ge/cm2 (17.7 at. % maximum Ge concentration) and then pulse annealed with either ruby or excimer (XeCl) lasers in the energy density range from 0.1 to 1.5 J/cm2. Compositional and structural characterization has been performed showing that for both laser wavelengths the final product of the annealing process is a single crystal characterized by a surface layer about 150 nm thick whose composition is Si0.9Ge0.1. While after ruby laser irradiations defects are present even in the fully recrystallized samples, after XeCl irradiations good strained layers in epitaxy to the underlying silicon crystals and free from misfit dislocations are produced. Structural characterization of the regrown films indicates that the governing factor for the recovery of the crystalline quality and for the “building up of strain” is the state of the implantation “end-of-range defect” layer. When this defected layer is not melted, textured columnar grains are formed. Upon melting of the end-of-range defect layer, a single crystal epitaxial layer under compressive strain is formed.

Diamond films have been successfully deposited by DC thermal plasma jet CVD at a rate of 40 μm/h under atmospheric and subatmospheric pressures. Transmission electron microscopy (TEM) has been used for the characterization of the diamond films and the intermediate phase. The orientation and the distribution of β-SiC at the interface between the diamond and silicon substrate have been observed using selected-area electron diffraction with the associated dark-field images. X-ray diffraction, scanning electron microscopy, and Raman spectroscopy are used for the characterization of the produced diamond films. Potential applications of selected-area channeling patterns are discussed for investigating the correlations between the growth direction and the crystalline perfection.

Chemical reaction products formed in a microwave plasma assisted chemical vapor deposition apparatus for diamond film deposition are detected using mass spectrometry. Carbon source gases CH4, C2H6, C2H4, or C2H2 produce CH4, C2H2, CO, and H2O as major stable reaction products when introduced into a H2/O2 plasma under diamond deposition conditions. The effect of oxygen addition is similar for all carbon source gases with respect to reaction product formation, indicating that a common reaction mechanism is active in all cases. On a qualitative basis, these observations are consistent with a mechanism describing the oxidation of CH4 in flames. No beneficial effects were observed using alternating growth/etch cycles to deposit films. Films grown using CH4 as the carbon source gas consistently produce higher quality diamond films compared to films grown from C2H2.

Rutherford backscattering (RBS)-ion channeling, transmission electron microscopy (TEM), and conversion electron Mössbauer spectroscopy (CEMS) have been used to determine the structure of α–Al2O3 implanted with iron at room temperature. Changes produced by post-implantation annealing in oxidizing and reducing atmospheres were followed using the same techniques. Implantation of 160 keV Fe at room temperature produces a damaged but crystalline microstructure for fluences as high as 1 × 1017 Fe/cm2. The iron resides in a variety of local environments: three Fe2+ components, one Fe0 component, and two Fe4+ components. The relative amount of each component varies with implantation fluence. Only the Fe0 component seems to be associated with second-phase formation. In this case, 2 nm diameter α-iron particles were detected by TEM studies. Recovery of implantation-induced disorder in the Al- and oxygen-sublattices occurs in two stages for annealing in oxygen and in one continuous stage for hydrogen-annealing. The end state for iron is Fe3+ for oxygen anneals and Fe0 for hydrogen anneals. The precipitated phases observed are those to be expected from the equilibrium phase diagrams.

Implantation of Fe (160 keV) into α–Al2O3 at 77 K produces an amorphous surface layer for fluences in the range of 1016 to 1017 Fe/cm2. Measurements of short-range order were made by extended energy loss fine structure analysis (EXELFS). The structure of amorphous Al2O3 produced by implantation of iron at 77 K exhibits short-range order that differs from that produced by stoichiometric (Al + O) implants. This difference is manifested by changes in the Al–O near-neighbor bond length. The local environments of implanted iron were determined from conversion electron Mössbauer spectroscopy (CEMS). The iron resides in several different local environments consistent with the electronic states of Fe2+, Fe4+, and Fe0. The relative amount of each environment depends upon the concentration (fluence) of the implanted iron ions. Regrowth of the amorphous zone during annealing occurs in the sequence amorphous → γ–Al2O3 ↠ α–Al2O3. The kinetics of regrowth and phase separation vary with implanted fluence and with annealing atmosphere. The higher the concentration of implanted iron, the slower the formation of iron-aluminum oxide precipitate phases in oxidizing atmospheres and α–Fe precipitates in reducing atmospheres.

Bulk samples of single crystalline and polycrystalline alpha alumina have been neutron-irradiated in the Experimental Breeder Reactor-II (EBR-II) to doses of 1026 n/m2 at temperatures of 925 K and 1100 K. The samples were found to swell macroscopically between 3% and 6%, depending on the temperature of irradiation and the form of the material. The damaged microstructures were investigated via transmission electron microscopy in order to understand the origin of the macroscopic swelling. In both single crystals and polycrystals the damage consists of a high density of dislocations containing predominately b = 1/3<101> dislocation loops on the (0001) planes coexistent with a high density of voids, which are aligned along the c-axis in this rhombohedral material. The established theory of void formation in metals is utilized to explain the formation of voids in alumina. The polycrystalline samples were extensively microcracked, and this is thought to be due to anisotropic swelling of the grains which in turn leads to stresses and fracturing at the grain boundaries.