Al—Cu—Fe quasicrystalline alloys have been deformed by high-temperature creep between 680 and 740 °C. Deformations greater than 30% were achieved without cracking. Analysis of the data in the quasi-steady state regime reveals power law behavior with a stress exponent of 2.5. The activation energy for deformation was determined to be 640 ± 20 kJ/mole in the temperature region investigated. Transmission electron microscopy revealed lamellar defects which appear similar to twins.

Geometrical modeling of the B2 structure indicates that the tetrahedral interstitial site is always the largest both before and after an a/2〈111〉 translation on {110}, such as occurs during the slip of a partial dislocation in some B2 compounds. The tetrahedral site within the APB which trails a gliding a/2〈111〉 dislocation is larger than in the unslipped lattice, suggesting that interstitial atoms will segregate there. Also, some interstitial sites in a B2 lattice are larger than those in a bcc lattice of the same lattice parameter, suggesting that interstitials may have greater solubility in B2 compounds.

Strands of nanometer-sized silver particles have been grown at the glass-crystal interface of a suitable glass-ceramic system. The samples exhibit high values of dielectric constant of the order of 500 at temperatures in the range of 80 to 200 K. This is believed to arise due to the Gorkov–Eliashberg anomaly. Above 200 K, a dielectric dispersion is observed, which is explained on the basis of a diagonal-layer heterogeneous conductor model.

Ba0.75Sr0.25TiO3 thin films have been deposited on single-crystal MgO substrates by pulsed laser deposition with the objective of forming ferroelectric films with a low Curie temperature. The films have been characterized by capacitance measurements and by transmission electron microscopy, x-ray diffraction, and Rutherford backscattering spectrometry (random and channeled). Films deposited with the substrate at 500 °C are polycrystalline, while those deposited at 650 °C are highly aligned and possibly epitaxial. The films are transparent in the visible region with an optical absorption edge at about 300 nm. Capacitance measurements on the polycrystalline films reveal a Curie transition at 283 K. The lowering of Curie temperature from the corresponding bulk sample is attributed to the films being under compression, as verified by Raman spectroscopy.

Boron nitride (BN) thin films were deposited on monocrystalline Si(100) wafers using electron beam evaporation of boron with simultaneous bombardment by nitrogen and argon ions. The effect of film thickness on the resultant BN phase was investigated using Fourier transform infrared (FTIR) spectroscopy and high resolution transmission electron microscopy (HRTEM). These techniques revealed the consecutive deposition of an initial 20 Å thick layer of amorphous BN, 20–50 Å of hexagonal BN having a layered structure, and a final layer of the polycrystalline cubic phase. The growth sequence of the layers is believed to result primarily from increasing biaxial compressive stresses. Favorable surface and interface energy and crystallographic relationships may also assist in the nucleation of the cubic and the hexagonal phases, respectively. The presence of the amorphous and hexagonal regions explains why there have been no reports of the growth of 100% cubic boron nitride on Si.

An experimental study of the etching properties of defects in diamond using propane flame exposure in air is presented. Both natural diamond crystals and polycrystalline diamond films were exposed to a flame for an optimum time of 3–4 s. This process topographically delineates defects in diamond via an accelerated etch rate at defect sites. Using transmission electron microscopy (TEM) to determine the exact nature and density of defects present in the diamond, we have found a direct correlation between topographical delineation observed by scanning electron microscopy (SEM) and the defect structure observed by TEM.

Growth behavior of YBa2Cu3O7-x (YBCO) thin films from metallic Y–Ba–Cu precursors was investigated. The precursors were prepared by coevaporation of the constituent metallic sources under ultra-high vacuum conditions, and they were oxidized in a load lock chamber and a tube furnace. The grain size of YBCO and degree of crystallographic orientation of the films increased with decreasing oxygen partial pressure p(O2) during transformation of the precursor into the crystal close to the thermodynamic stability line of YBa2Cu3O6.0 in a p(O2) – 1/T phase diagram. The growth of YBCO crystal is controlled by the oxygen diffusion along the c-axis direction of the crystal. The diffusion coefficient of oxygen is determined as D = 1.94 × 1010 exp(−433 000/RT) (cm2/s).

The effect of silver (Ag) addition on the resistance to thermal shock and delayed failure of YBa2Cu3O7−δ superconducting wires has been evaluated. Resistance to thermal shock was evaluated by measuring the critical-current density (Jc) as a function of the number of thermal cycles for YBCO and its composites with 15 vol. % Ag additions. Composite YBCO-Ag wires show a slower decrease in Jc than does monolithic YBCO as the number of thermal cycles increases. The nature of delayed failure was studied by measuring strength (σf) as a function of loading rate (σ) and evaluating the value of the subcritical crack growth parameter N[σf = Aσ1/(N+1)]. The value of the N parameter was observed to increase slightly from 35 for YBCO to 41 for YBCO-Ag composites. The improved resistance to thermal shock and subcritical crack growth is believed to be due to improvements in mechanical properties (strength and fracture toughness) and thermal conductivity of YBCO as a result of Ag addition.

Copper- and yttrium-rich YBa2Cu3O7 bulk superconductors have been prepared by mixing copper oxide or yttrium oxide in nitric acid and adding the solution to premade stoichiometric YBa2Cu3O7 followed by annealing. In contrast to materials made by mixing oxide powders, both samples contain copper-rich defects spread homogeneously throughout the grains, either small platelet copper oxide precipitates or bundles of planar defects (Cu–O double planes). These materials also show large magnetic hysteresis at 77 K, comparable to the results obtained from decomposed YBa2Cu4O8. This implies that small copper oxide precipitates and bundles of planar defects are strong flux pinners, and indicates a processing route to producing large amounts of strongly intragranular pinned superconductors. However, the materials also show clean grain boundaries, so an equally valid interpretation is that there is a substantial component of intergranular superconductivity in field, enhancing the effective circuit size to a value far larger than the grain size.

The coarsening rate of Y2BaCuO5 (211) phase in liquid was investigated by observations of samples which were held at 1070 °C for different holding times. The 211 phase formed rod-like shapes, and the diameters increased with the increase in the holding time. The average diameter increased in proportion to t1/3 (t, holding time). This means that coarsening can be explained by the modified Ostwald ripening theory. Platinum-doping suppressed the coarsening rate and alumina-doping promoted it. However, both coarsening rates were also proportional to t1/3. The changes in the rate can be represented by the changes of the DLΓ value (DL, diffusivity in liquid and Γ, Gibbs—Thomson coefficient) using the Ostwald ripening theory; i.e., the value is made lower by platinum-doping and higher by alumina-doping.

Amorphous Bi2Sr2CaCu2O8 (Bi-2212) was crystallized under uniaxial loads (up to 1500 N) at temperatures up to 890 °C to induce texture. Well-textured samples (19 mm in diameter and 0.15 mm thick) were obtained for samples heated to 890 °C and quenched. Heated (10 °C/min) and quenched samples at 550, 750, 850, and 870 °C demonstrate that the crystallization path is Bi2Sr2CuO6 (Bi-2201) (550 °C) to Bi-2212 (850 °C), with texturing occurring during grain growth (T > 850 °C). Comparison of samples crystallized under load and no load demonstrates that the texturing is a result of the plane stress biasing the normal anisotropic grain growth normal to the applied stress direction.

The structural transformations occurring during the mechanical alloying of mixtures of elemental oxides in the Bi–Sr–Ca–Cu–O system have been studied. Metastable cubic structures with complete chemical disorder and amorphous phases can be synthesized by strong mechanical deformations. With proper thermal treatments, these metastable phases transform into the high Tc superconducting structures. Discussions on the mechanisms of formation and on the thermal stability of the various metastable phases are presented.

A comparison of several solution syntheses with a solid-state route to the lead-containing high Tc phase of the Bi–Sr–Ca–Cu–O system has been performed using DSC, TGA, x-ray diffraction, electron microscopy, magnetic ac susceptibility, and critical-current measurements. A novel polymer solution synthesis route is shown to yield an increased percentage of the 2223 high Tc phase when sintering is performed at the low temperature end of this phase's stability range. Under the best preparative conditions given in the literature, however, the properties of samples obtained with the different synthetic methods described in the present study are shown to be similar. Samples derived from solution syntheses have been found to contain higher amounts of carbon precipitates, while samples derived from conventional solid-state synthesis contain CuO precipitates, according to energy dispersive spectroscopy analyses.

Fission fragment damage was introduced into samples of Bi2Sr2CaCu2Ox and Bi1.7Pb0.3Sr2Ca2Cu3Oy, doped with various levels of UO2, by irradiation with thermal neutrons. The critical temperatures were unchanged. Concurrent with an increase in intragranular Jc previously reported, a decrease in flux creep was observed. The apparent pinning potential for creep at 10 K and 0.8 T increased on irradiation by about two to three times for both the 2212 and 2223 compounds. This increased apparent pinning potential is attributed to the strong pinning introduced by the damage caused by the travel of the fission fragments through the crystal. Pinning potential after irradiation increased with an increase in the amount of UO2 in the sample. The increase in bulk pinning potential on irradiation was proportional to the increase in intragranular critical currents on irradiation, qualitatively as expected theoretically.

NMR study has been carried out on Ni3Al with B and C additions. The 27Al-, 11B-, and 13C-spectra have been measured as a function of temperature for determining their Knight shifts. The Curie temperature and Knight shift at low temperature in Ni3Al with B and C additions decrease in the order of atomic number of additions, but the Knight shifts around room temperature are nearly the same as that of pure Ni3Al. It is suggested that the addition of B and C affects the electronic structure of Ni, and that B atoms and possibly C atoms occupy the octahedrally symmetric sites neighboring all the Ni atoms.

Atomic force microscope measurements of elastic-plastic indentation into an Fe−3 wt. % Si single crystal showed that the volume displaced to the surface is nearly equal to the volume of the cavity. The surface displacement profiles and plastic zone size caused by a 69 nm penetration of a Vickers diamond tip are reasonably represented by an elastic-plastic continuum model. Invoking conservation of volume, estimates of the number of dislocations emanating from the free surface are reasonably consistent with the number of dislocations that have formed in the plastic zone to represent an average calculated plastic strain of 0.044.

Direct observations of dislocation arrangements about a range of microindentations into the [100] face of an Fe−3 wt. % Si single crystal have been accomplished. Dislocations of both large loop character initiated from the indenter and small loop character initiated as secondary reactions are found. Analysis of these allows the various contributions to the plastic strain gradient around the indentation to be assessed, with the experimental observations being reasonably consistent with continuum models.

An incubation time exists for the formation of MoSi2 by mechanical alloying (MA). For the particular milling conditions employed, the bulk of MoSi2 formation occurs between 3 h and 12 min and 3 h and 13 min. This abrupt formation of MoSi2 during MA suggests that the reaction occurs by a form of self-propagating high-temperature synthesis (SHS), when a critical amount of stored energy (in the form of interfacial energy and cold work) is introduced by MA, and increases the adiabatic reaction temperature sufficiently to make the reaction self-sustaining.

Mechanical attrition of intermetallic compound TiNi powder was carried out in two different ball mills and as a function of milling temperature. The microstructural changes with milling time were followed by x-ray diffraction, TEM, and DSC. The more energetic Spex shaker mill provided a higher degree of lattice strain and rapidly refined the grain size to the nanometer size regime. Amorphization was observed in the Spex mill with a linear increase in the milling time for amorphization with increasing milling temperature. No amorphization was observed in the less energetic vibratory mill, and the grain size saturated to a constant value of 15 nm after ≥60 h of milling. A critical grain size for the amorphization of 4–5 nm was estimated from the temperature dependent studies in the Spex mill. The grain boundary energy (706 mJ/m2), estimated from the vibratory mill experiments, and the above critical grain sizes (5 nm) for amorphization were used to calculate the enthalpy supplied by the nanocrystalline grain boundaries. The calculated value of 4.1 kJ/mol was comparable to the measured enthalpy of crystallization of 3.2 kJ/mol. It is concluded that the nanocrystalline grain boundary energy is responsible for driving the crystalline-to-amorphous phase transformation induced by mechanical attrition in TiNi.

Amorphous cobalt-boron alloy powders have been prepared by a high energetic ball mill at room temperature starting from different Co/B ratios. They were characterized by means of x-ray diffraction, scanning and transmission electron microscopy, and differential scanning calorimetry. Ball milling of Co–B mixtures induces solid-state amorphization which becomes faster with increasing boron content. After maximum amorphization ball milling leads to crystallization of t-Co2B in all the binary samples.