Fine powders with high sinterability of KSbOSiO4, an isomorphous derivative of KTiOPO4, have been prepared by a sol-gel route starting from stoichiometric mixtures of KSb(OH)6 and Si(OC2H5)4 with two types of polymerization catalysts: HNO3 and aqueous ammonia. KSbOSiO4 is formed upon calcination of the gels at 1373 K, and the XRPD studies show that HNO3 improves the crystallinity. However, the crystallite size is smaller with aqueous ammonia, which should then improve the sinterability.

We have studied the electron channeling patterns (ECPs) of both pure a-axis and pure c-axis epitaxial YBa2Cu3O7−δ thin films on various substrates. ECPs from three representative a-axis films [on PrBa2Cu3O7−δ buffered LaAlO3 (001), MgO (001), and SrLaAlO4 (001)] and three c-axis films [on LaAlO3 (001), NdGaO3 (001), and SrTiO3 (001)] are presented. The differences between both sets of ECPs are discussed and recorded as references for future identifications.

The misorientations of over 200 pairs of adjacent grains separated by grain boundaries in textured YBa2Cu3O7−δ were measured using a transmission electron microscopy technique. The results indicate that there exist discrete preferred rotation angles and rotation axes. The existence of low-energy boundaries is inferred. The results are analyzed based on the Constrained Coincidence Site Lattice (CCSL) and O2-lattice theories and imply the applicability of such theories for the case of large-angle grain boundaries in a complex crystal structure such as YBa2Cu3O7−δ. The results of analysis also show that some boundaries are likely to be reduced in oxygen near the boundary to satisfy the constraint of the coincidence site lattice.

Using a highly-spatially-resolved mechanical properties microprobe, the Young's modulus and hardness of bulk YBa2Cu3O7−x (1:2:3) and YBa2Cu4O8 (1:2:4) have been determined. The Young's modulus of a superconductor is an important parameter in determining critical grain sizes above which microcracking will occur due to anisotropic thermal stresses that arise during processing. This phenomenon of microcracking has been determined to cause a decrease in the attainable critical current densities in bulk superconductors. The mechanical properties data for these two materials show that the Young's modulus of 1:2:3 is approximately 35% greater than the modulus of 1:2:4. This along with available anisotropic thermal expansion data for 1:2:3 and 1:2:4 suggests that the critical grain size for 1:2:4 is about 7 times greater than the critical grain size for microcracking in 1:2:3.

In this paper the mechanism of phase transition and structural relaxation are elucidated by means of model experiments in the differential scanning calorimeter. Materials for this study were varied in structure and oxygen content by the introduction of Ni for Cu, through co-precipitation of oxolate gels, calcination, and sintering in ambient atmosphere. Both relaxation and phase transition are revealed by scrutinizing the heating rate dependence of heat capacity, and they seem to occur contemporaneously. Two higher order transitions are observed and are characterized by activation energies of 186 kJ/mole and 550 kJ/mole at the low and high temperatures, respectively. Perhaps the first transition is of a displacive type and occurs in anticipation of a reconstructive structural change from a fourfold chain to a sixfold sheet-like configuration. It is delineated by a change in relaxation kinetics from a localized type to a cooperative type with activation energies of 36 and 10 kJ/mole, respectively. The cooperative relaxation occurs at higher temperatures and is kinetically continuous across the reconstructive transition region. The structure characteristic exponent has a value of 0.70 for both localized and cooperative relaxation and resembles the two-dimensional relaxation often observed in depolymerized glasses. With kinetic impediment the transition region seems to approach a lambda-like behavior. In the subtransitional region, impediments in relaxation are useful in delineating oxygen stoichiometric differences between samples. The above discussion is supported by the structural and chemical characteristics that were gathered by x-ray powder diffraction, Raman spectroscopy, scanning electron microscopy and microprobe, and low temperature resistance measurements on Y123 samples containing 5 and 10 at. % Ni, respectively.

Two types of platinum group metal particles were found in borosilicate nuclear waste glasses: needle-shaped RuO2 particles and spherical PdRhxTey alloys. They form a dense sediment of high electrical conductivity and relatively high viscosity at the bottom of the ceramic melting furnace. The sludge shows a non-Newtonian flow behavior. The viscosity and conductivity of the sludge depend not only on the platinum group metal content but also on the texture and morphology of the RuO2 particles. RuO2 forms long, needle-shaped crystals which are caused by alkalimolybdate salt melts that formed in the calcine layer. The salt melts oxidize the Ru present as small RuO2 particles after calcination to higher oxidation states. Ruthenium (VI) compounds are formed, presumably, which are not stable with respect to RuO2 under the melting conditions. RuO2 precipitates and crystallizes into long, needle-like particles.

The shear strength of materials after extensive plastic flow under a superimposed high hydrostatic stress component is most conveniently studied by means of Bridgman opposed anvils between which thin disk-shaped samples are sheared through relative rotation. A newly designed apparatus of this type permits, for the first time ever, the monitoring of sample thickness during shearing and thus the obtaining of averaged shear stress/shear strain curves. Such relations are needed for the better understanding of geological processes, behavior under shock or explosive impact, and of the surface layers during friction and wear, among others. A semiquantitative analysis shows that nonuniform pressure distribution in the samples cannot significantly falsify the results. It is concluded that distributed shearing is always accompanied by sample thinning and that, conversely, slippage between anvils and specimens is indicated whenever the sample stops thinning during rotation. Such slippage can be greatly reduced by raising the friction coefficient through etching of samples and/or anvils, but it apparently occurred undiscovered in previous studies, partly after initial distributed shearing. Further, in previous results slippage between directly contacting anvils was frequently mistaken for sample shearing. Additionally, the previously neglected sample material being extruded during shearing can falsify results, as can “turbulent flow” initiated at sample perforation. Correspondingly all prior data gained with Bridgman apparatuses are suspect. Present best results indicate (i) that in metals ordinary dislocation glide but apparently with strongly increased Peierls–Nabarro stresses continues to the highest pressures studied, (ii) that independent of thermal activation workhardening may cease at high strains, and (iii) that “turbulent flow” resulting through sample perforation or when the sample thickness decreases below a critical value, can give rise to mechanical alloying. The majority if not all of the data by Bridgman as well as Vereshchagin et al. probably involved such mechanical alloying. When plotted versus pressure in units of shear moduli, the apparent coefficients of friction of the five cubic metals examined so far follow nearly the same curve but they are lower for metals of lower symmetry.

This paper examines the stresses and displacement gradients in atomistic models of cracks based on an EAM potential devised for aluminum. Methods for computing these quantities are described. Results are presented for two models differing in terms of the orientations of the crack relative to the crystal, a [100] (010) orientation that behaves in a brittle fashion and a [111] (110) orientation that emits partial dislocations prior to extending. Both models display lattice trapping. The stresses in the brittle crack model are compared with the linear elastic prediction and found to be in remarkably good agreement to within distances of about one lattice parameter of the crack tip and at the free surface where contributions from sources other than strain energy (e.g., surface tension) influence the results. Similar results are observed for the ductile model until dislocation emission occurs. The largest stresses that develop just prior to crack extension or dislocation emission are used to estimate the ratio of theoretical tensile strength to shear strength in this material. Eshelby's conservation integrals, F and M, are also computed. F is found to be essentially contour independent and in agreement with the linear elastic prediction in both models until dislocation emission occurs, at which point a large screening contribution arises from the emitted partials. The contour size dependence of M reveals some interesting features of the crack tip including a slight wobble of the crack tip inside its potential well with changing applied K and the existence of forces acting to move the crack faces apart as blunting occurs.

The stress field, image force, and shielding effect of a screw dislocation in the vicinity of a Mode III crack were formulated for both semi-infinite and finite length cracks. The results show that there is an abnormal stress component, ŝ31, on the crack plane. This leads to a nonzero image force along the axis perpendicular to the crack plane when the dislocation is located on the crack plane. However, the abnormal stress component and image force disappear for orthotropic and isotropic media. The image force along a slip plane has the same expression as in isotropic media with an effective shear modulus. Generally the shielding effects are the same as in isotropic media. The anisotropy changes only the magnitude of the shielding effects. The case of multiple dislocations is also discussed.

Green's function for a generalized vector Hilbert problem is calculated which can be used to solve the Hilbert problem with any integrable inhomogeneity. The Green's function is obtained by using a complex transform defined by eigenfunctions of the homogeneous Hilbert problem. This method should be particularly convenient for the stress analysis of anisotropic composite materials containing cracks and free surfaces. The method is illustrated by applying it to calculate the stress field in an anisotropic bimaterial composite containing an interfacial crack. It is found that, in agreement with the earlier published work on isotropic composites, the stress field is oscillatory but, except very near the crack tip, the oscillations are negligible. Numerical results are presented for a stress field in a uniformly loaded (shear and compressive) Cu/Ni layered composite containing an interfacial crack as well as cracked homogeneous copper.

Elastic plane strain Green's function is calculated for an anisotropic bimaterial composite solid containing a free surface normal to the interface. An exact integral representation is obtained for the Green's function, which is evaluated numerically. The integral is also evaluated analytically, which gives a series representation for the Green's function. The singularities in the stress field associated with the presence of the free surface are identified and discussed. These singularities can be of the type r-δ, ln(r) as well as higher powers of ln(r), where δ is between 0 and 1 and r is the radial distance from the intersection of the free surface and the interface. The stress field may also contain an oscillatory factor of the type exp[ιg ln (r)] where g depends upon the material parameters of the two solids. For illustration, the formalism is applied to a cubic solid containing a Σ-5 grain boundary.

The elastic plane strain Green's function calculated in earlier papers is modified to account for generalized plane strain and applied to calculating the stress and the displacement field in a bimaterial composite containing a free surface normal to the interface and subjected to an out-of-plane load. The result is obtained in terms of a closed integral representation which is evaluated numerically as well as analytically. The method is applied to a cubic solid containing a Σ-5 grain boundary and to fiber-reinforced laminated composites. The singularities in the stress are identified and discussed.

The blunt tip geometry of the so-called nanoindenter is modeled by a spherical cap of various radii. The relation between area and penetration depth of the indenter is comparable with experimental results if the radius of the tip is about 1.0 μm. Simulation of indentation tests was carried out using the finite element method by incremental loading and unloading based on a continuum model. Good agreement with the experimental results for nickel is obtained also for a tip radius of 1.0 μm.

The solidification behavior of Al65Cu20Co15 and Al65Cu15Co20 alloys was studied by means of scanning electron microscopy, energy-dispersive x-ray analysis, powder x-ray diffraction, and differential thermal analysis. Slowly cooled as well as rapidly cooled ingots of both alloys contained a decagonal quasicrystalline phase as dominant phase with additions of several minor normal-crystalline phases. The decagonal phase was found to solidify in a temperature range limited by two peritectic reactions involving phases of CsCl-type structure. Formation of AlCu and Al2Cu phases was also observed.

We have carried out a detailed investigation of the Al71Pd19Mn10 alloy by using a combination of experimental techniques (neutron diffraction, electron diffraction, high resolution electron microscopy, and electron probe microanalysis). This alloy contains only the perfect icosahedral phase. This icosahedral phase is stable from room temperature up to its melting, though a transient cubic metastable phase coexists with it during the heating. It grows directly from liquid without involving any crystalline phase. Its isothermal growths at different temperatures can well be described by the Avrami equation with exponent n = 1.85. Comparisons with the Al–Cu–Fe I phase have also been made. The growth velocity of both I phases is approximately 1 μm/min with ΔT around 10 K, much slower than that of the crystalline phases growing under the same condition. After the sample was maintained at near liquidus temperature for more than 10 h, element losses and Si contamination from the crucible changed the sample composition. In consequence, crystalline phases have formed during the subsequent cooling and made the growth of the icosahedral phase a eutectic reaction.

The icosahedral (i-) phases are found over a wide composition range in melt-quenched Al–Pd–Mn alloys. The i-phase has a simple icosahedral lattice in the low Pd content region (Pd <10 at. %) and transforms to a face-centered icosahedral with increasing Pd content (Pd >10 at. %). A decagonal phase with a periodicity of 1.6 nm exists at a low Mn content region. On the basis of the change in diffraction peak intensity, it was presumed that the chemical ordering between Al and Pd exists in a face-centered icosahedral lattice in which Pd and Mn occupy one superlattice site and Al occupies the other one. A dendritic growth morphology in a mixed structure containing i- and fcc Al phases changes to a planar growth morphology in a fully single i-phase. An interpretation of dependence of morphology on composition is given in terms of the interface stability criterion using a metastable i–Al phase diagram.

The mechanical properties of nickel beryllide, NiBe, have been investigated in the temperature range 20–820 °C. The room temperature properties were studied using tension, bending, and compression tests, while the elevated temperature properties were characterized in compression only. NiBe exhibits some ductility at room temperature; the strains to failure in tension and compression are 1.3% and 13%, respectively. Fracture is controlled primarily by the cohesive strength of grain boundaries. At high temperatures, NiBe is readily deformable—strains in excess of 30% can be achieved at temperatures as low as 400 °C. Strain hardening rates are high, and the flow stress decreases monotonically with temperature. The high temperature strength of NiBe is as good or better than that of NiAl, but not quite as good as CoAl.

Phases of the nominal composition Ni3MSb (where “M” represents aluminum, gallium, or indium) were found to occur in their respective ternary systems. They were analyzed by x-ray diffraction and were found to exhibit the B81.5′ crystal structure, similar to that of Ni3GaAs. These phases were shown by differential thermal analysis (DTA) to be stable between room temperature and their melting points, which were determined to be >1150 °C, 1066 °C, and 1091 °C for Ni3AlSb, Ni3GaSb, and Ni3InSb, respectively. An analysis of their respective constituent binary systems suggested that these phases were not true ternary compounds, but rather represented specific compositions of extensive solid solutions of constituent binary phases. Speculations were made as to the solution behavior of these phases. The Ni3MSb phases were predicted to form initially in nickel/MSb diffusion couples, in an analogy to what is observed in nickel/GaAs diffusion couples.

The structure and phase relations of Te–Ge–Sn thin films are examined with application to erasable optical storage media. Free energy data from the literature predict that the region of the Te–Ge–Sn phase diagram between Ge, Sn, and the TeGe–TeSn pseudobinary consists of one two-phase field [α–Ge and Te50 (GexSn1−x)50] and one three-phase field (α–Ge, β–Sn, and TeSn). Electron diffraction from five different Te–Ge–Sn films annealed at 623 K experimentally confirms this prediction. One composition from the two-phase field is deposited as a tri-layer film with the structure 150 nm SiO2/75 nm Te36.3Ge47.4Sn16.3/150 nm SiO2 on a grooved disk substrate, and the microstructure resulting from low-power (12 mW) CW and higher-power (∽50 mW) pulsed laser exposure is studied by transmission electron microscopy and electron diffraction. Of particular significance is that laser-induced crystallization produces a single-phase structure consisting of the Te–Ge–Sn compound phase which is supersaturated with respect to the excess Ge. This supersaturation leads to a disordering of the equilibrium NaCl-type structure of this phase. Crystallization of a micron-sized amorphous spot on a ∼200 ns time scale occurs by a diffusionless process. The fast erase times required by a phase-change optical recording application can thus be achieved in off-stoichiometric compound compositions by way of a nonequilibrium crystallization process.

Melt-grown crystals of HgS and HgS : Co2+ were used to measure their optical absorption spectra. The optical energy band gaps of these crystals were 2.030 eV and 1.870 eV at room temperature, respectively. The impurity optical absorption peaks of Co2+ were observed at 4030, 5988, 12285, 12672, and 12905 cm−1. These peaks can be attributed to the electronic transitions between the split energy levels of Co2+ ion located at the Td symmetry site, where the crystal field, Racah, and spin-orbit coupling parameters were given by Dq = 403, B = 427, and Λ = −155 cm−1, respectively.