A new regime of hillock growth has been observed in patterned Al98.5 W.%Si1.0 Wt.%-Cuo0.5 wt.% films. The “surface” hillock and “side” hillock, which have been seen previously, form on patterned metal lines having linewidths greater than the larger Al alloy grain sizes (∼3 μm). None is seen on the fabricated lines having linewidths between 0.9 and 2 μm where long-range grain boundary diffusion cannot occur because of its bamboo structure. However, a new type of hillock, the “line hillock”, occurs in structures having linewidths of 0.6 μm. The presence of this last type of hillock is inconsistent with the current understanding of hillock formation and may present severe restrictions on the down-sizing of ultra–large–scale integrated devices.

We present measurements on the superconductor compound Bi–Sr–Ca–Cu–O, obtained using a scanning Auger microscope (SAM), which indicate that this material is extremely unstable under an electron beam with energy of several KeV, Using relatively high current densities for the SAM, it is possible to melt small regions of the material and to form spheres several micrometers in diameter in a few seconds. We characterize the changes in the elemental concentration of the surface of these spheres as a function of time after the beam exposure.

The microstructures of YBa2Cu3O7−x thin films deposited by laser ablation on single crystal (001) LaAlO3 substrates have been investigated. The orientation of the YBa2Cu3O7−x layer next to the interface is found to be completely c-perpendicular, with a high degree of epitaxy between the film and the substrate. Misfit dislocations, with a periodic spacing of around 13 nm, are present at the interface. Two distinct interfacial structures are seen in these films. At a film thickness of around 400 nm, nucleation of c-parallel grains occurs, leading to a switchover from a c, and, and-perpendicular to a c-parallel microstructure. Amorphous particulates, ejected from the target during processing, lead to the formation of misoriented grains, giving rise to high-angle grain boundaries in the film.

A novel process for the continuous densification of YBa2Cu3O7−δ wires by infrared zone melting is presented. Superconducting ceramic wires with moderate porosity (20–40%) were passed through a high temperature infrared zone at a speed of 1–2 cm/min, which resulted in zone melting followed by fast solidification to give near zero porosity wires. The atmospheric conditions during zone melting had a significant effect upon the resultant properties and microstructure of the wires. The best results were obtained for infrared zone melting under a vacuum that resulted in the decomposition of the superconducting phase into four phases without significant macroscopic chemical segregation across the wire. Subsequent conventional sintering and annealing treatment of such wires fully restored them to polycrystalline YBa2Cu3O7−δ wires having 96% of the theoretical density. The maximum transport critical current density obtained for such wires at 77 K in zero magnetic field was 2.65 × 103 A cm−2. Normalized critical current values as a function of magnetic field indicated that the quality of the intergrain connections for vacuum infrared zone melted wires was significantly better than that for conventionally processed wires and tapes.

Semiconducting samples of a Bi–Ca–Sr–Cu oxide, having a nominal composition 4:3:3:4, were prepared by melting high purity oxides of the various elements. Superconducting samples were obtained by annealing the semiconducting samples at a temperature close to the melting temperature. Electrical resistivity measurements indicated the presence of two superconducting phases, one with the onset temperature at about 110 K, the other with a significantly lower onset temperature. The presence of this second phase is proven by the x-ray powder diffraction patterns. The crystalline structures of both the semiconductor and superconductor samples have almost equal lattice parameters and are orthorhombic, but belong to different space groups: Fmmm and Bbmm, respectively. No significant amount of the 110 K superconducting phase was present in the diffraction pattern of the superconducting compound. XPS and XANES data on the Ca atom indicate that a different electronic state of Ca is present in the superconducting compound, which still contains an appreciable amount of the semiconducting phase.

Eshelby's equivalent inclusion method is applied to the case of a single, inhomogeneous, ellipsoidal precipitate in an infinite matrix to study the morphological changes of the gamma-prime precipitates in nickel-base superalloys due to the influence of lattice constant misfit, elastic inhomogeneity and anisotropy, applied stress, and interfacial energy. The energy-minimizing inclusion shapes depend very sensitively on the degree of elastic inhomogeneity, on the sense and magnitude of the applied stress, and on the sense of the lattice constant misfit. The interfacial energy contribution can dominate that of elastic strain energy for small precipitate sizes, elastically compliant systems, nearly homogeneous alloys, and/or nearly isotropic materials. Calculations are carried out for two well-characterized nickel-base alloys: a Ni–13.5Al alloy (positive misfit, elastically hard inclusions) studied by Miyazaki et al. and CMSX-3 (negative misfit, elastically soft inclusions) studied by Pollock. The Eshelby energy calculations correctly predict the precipitate morphologies observed by Miyazaki et al. and by Pollock.

Determination of the boundary fractal dimension of planar sections through particles produced by fracturing a series of brittle intermetallic V3Au materials with increasing oxygen content provides a single parameter that describes the surface roughness. This is observed to correlate with the measured fracture toughness, K1c, as determined with an indentation cracking test. The correlation agrees quantitatively with results obtained on several brittle ceramics by other workers.

Diffusion-induced phase transformations were studied in Ni/β-Ta multilayers between 523 K and 823 K, primarily using x-ray diffraction. The multilayers had a modulation length, A, of 20.3 nm and a composition of Ni48Ta52. They were polycrystalline without coherency between the Ni and Ta sublayers. Upon annealing at relatively low temperatures (up to 723 K) Ta dissolved in crystalline Ni, concurrently with the formation of an amorphous phase. The interdiffusion reactions did not take place only at the Ni/Ta interfaces, but also along the grain boundaries in the sublayers. The chemical diffusion coefficient in the amorphous phase was determined at 673 K, using a previously developed method. The results were compared with experiments on Ni/Ti multilayers, which show similar reactions. At 723 K and higher temperatures the fcc (Ni, Ta) solid solution transformed into the stable Ni3Ta compound.

The progress of solid-state reaction in Ni–Zr composite wires with different elemental layer thicknesses has been studied in detail. Besides x-ray diffraction and differential scanning calorimetry, dilatometric measurements, magnetization and resistivity measurements, and cross–sectional transmission electron microscopy were used to monitor the reaction during constant-rate heating and to characterize the various reaction products. An amorphous phase initially forms at the interface between the elemental layers. As soon as the layer thickness exceeds a critical value, the intermetallic NiZr phase appears at the interface between the amorphous phase and pure Zr, as shown by TEM investigations. This is due to a reduced velocity of the reaction front caused by the longer diffusion path enabling the intermetallic phase to become stable. As shown in experiments at a constant heating rate, a second intermetallic phase forms at higher temperatures at the interface between Zr and crystalline NiZr. The amorphous phase remains unchanged up to crystallization at about 520 °C. To obtain fully amorphous material, the interdiffusion reaction must be completed (or especially the Zr layers must be completely reacted) before the intermetallic NiZr phase starts to form. A criterion for achieving completely amorphous bulk material is derived.

Tungsten disilicide (WSi2) was formed by annealing tungsten (W) films of 330 nm and 750 nm prepared by low pressure chemical vapor deposition (LPCVD) from tungsten hexafluoride (WF6) on Czochralski 〈100〉-Si substrates. The silicide was found to grow continuously from the WSi2/W interface. The thickness of the formed WSi2 was observed by Rutherford backscattering measurements (RBS) to increase parabolically with the annealing time, with an activation energy of 2.6 eV/atom. The crystal structure of the formed WSi2 and the unreacted W films was analyzed using x-ray diffraction (XRD) technique. The thermal history of the samples was found to play an important role for the film texture of the unreacted W and formed WSi2, indicating that the fast and inexpensive method, XRD, applied as a thickness monitor for kinetics studies of WSi2 growth will undoubtedly introduce large errors. The as-deposited W (on Si) and the unreacted W (on WSi2) were found to be under a tensile stress, as observed by means of the XRD technique.

Cobalt disilicide CoSi2 of a specific resistivity of 23 μω was formed by the solid phase reaction of cobalt and silicon in the phase sequence of Co2Si, CoSi, and CoSi2 by use of rapid thermal annealing. The through-metal arsenic implantation caused the mixing of cobalt with the silicon substrate and the formation of cobalt silicides. A significant lateral growth of cobalt silicides was observed in samples subjected to one-step rapid thermal annealing process at 900 °C without through-metal ion implantation. Ion beam mixing reduced this lateral silicide growth efficiently, but resulted in a higher density of cobalt atoms remaining in the silicon oxide film than after rapid thermal annealing, as revealed by vapor phase decomposition atomic absorption spectroscopy.

A hydrogen–plasma reactive flush of the glow discharge reactor after boron–doped a–Si1−xCx : H film deposition has been used to reduce boron contamination of subsequently deposited intrinsic a–Si:H. Photoluminescence studies of p/i structures in a–Si: H show that the hydrogen–plasma process increases both the luminescence efficiency and the activation energy for the competing nonradiative recombination. The process also shifts the emission peak to higher energies by 25 meV.

Ion-channeling and transmission electron microscopy (TEM) techniques were used to examine the microstructure of single-crystal Y2O3 stabilized cubic zirconia (YSZ) after implantation with 240 keV Xe+ ions. The observed microstructure was related to Knoop indentation hardness measurements. These measurements showed an increase in hardness for low ion-doses, reaching some maximum value, then a decrease in hardness at higher doses. In the hardening regime, below 7.5 × 1015 Xe+/cm2, point defects and dislocation networks were observed by TEM. Ion-channeling showed a corresponding increase in damage as a function of ion-dose. For doses between 7.5 × 1015 and 3 × 1016 Xe+/cm2 the hardness falls, and the amount of damage, measured with ion-channeling, reaches a limiting value at less than complete damage. In this dose range the Xe concentration continues to increase beyond the dose where the amount of damage saturates. For high doses, greater than 3 × 1016 Xe+/cm2, where softening of the zirconia occurs, additional reflections appear in the electron diffraction pattern that are consistent with the lattice parameter of solid Xe. A diffuse ring is also visible; this is believed to be due to the presence of fluid Xe. Both ion-channeling and TEM show that a significant amount of monocrystalline zirconia remains even up to doses of 1 × 1017 Xe+/cm2. There is also evidence for the presence of recrystallized zirconia at the high doses. Since so much crystalline material remains, it seems that amorphization of the zirconia is not the dominant cause of the softening at high doses.

Chemical vapor deposition (CVD) of titanium oxide films has been performed for the first time under ultra-high vacuum (UHV) conditions. The films were deposited through the pyrolysis reaction of titanium isopropoxide, Ti(OPri)4, and in situ characterized by x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). A small amount of C incorporation was observed during the initial stages of deposition, through the interaction of precursor molecules with the bare Si substrate. Subsequent deposition produces pure and stoichiometric TiO2 films. Si–O bond formation was detected in the film-substrate interface. Deposition rate was found to increase with the substrate temperature. Ultra-high vacuum chemical vapor deposition (UHV-CVD) is especially useful to study the initial stages of the CVD processes, to prepare ultra-thin films, and to investigate the composition of deposited films without the interference from ambient impurities.

The problem of ice accretion and accumulation on critical structural components of fixed wing and rotary wing aircraft structures has in recent years engendered much interest. However, the mechanical properties of the accreted impact ices are at present not adequately known and, therefore, analytical modeling of this particular material is not possible. This paper proposes a technique for experimentally determining both the modulus of elasticity and tensile strength of ice. The feasibility and accuracy of the test technique were verified by determining the properties of laboratory grown ice. Results reveal a slight degradation of ice tensile strength with an increase in test temperature. The degradation in ice tensile strength is rationalized on the basis of competing mechanistic effects involving an incipient melting of the ice at the higher test temperature and a concomitant intrinsic variation in microstructural features due to variations in freezing rate. Application of the test technique to impact ices will soon be conducted inside an icing wing tunnel.

The interfacial properties and mechanical behavior of the SCS-6/Si3N4 composites fabricated by hot pressing from powder lay-up and tape lay-up techniques were studied. Interfacial shear strength and frictional stress were measured using an indentation test. Fracture toughness and work-of-fracture were measured using a three-point bending test on a chevron-notched specimen. The influence of interfacial shear strength on the toughening mechanisms and crack propagation behavior were investigated. The results indicate that the processing routes and fiber orientation will affect the interfacial properties, which in turn have a significant influence on mechanical properties.

Transmission electron microscopy was used to characterize microstructures of SiC densified using a transient liquid phase (resulting from the reaction of Al2O3 with Al4C3) by hot pressing at 1875 °C for 10 min in N2. High resolution electron microscopy showed that the SiC grain boundaries were free of glassy phases, suggesting that all liquid phases crystallized upon cooling. Phases that might be expected due to reactive sintering (i.e., AlN, Al2OC, Al2O3, Al4O4C, Al3O3N, or solid solutions of SiC, AlN, and Al2OC) were not observed. However, significant Al, Si, O, and C concentrations were found at all triple junctions of these rapidly densified ceramics.

Silicon carbide-based ceramics can be rapidly densified above approximately 1850 °C due to a transient liquid phase resulting from the reaction between alumina and aluminum oxycarbides. The resulting ceramics are fine-grained, dense, and exhibit high strength at room temperature. SiC hot pressed at 1875 °C for 10 min in Ar was subjected to creep deformation in bending at elevated temperatures between 1500 and 1650 °C in Ar. Creep was thermally activated with an activation energy of 743 kJ/mol. Creep rates at 1575 °C were between 10−9/s and 10−7/s at an applied stress between 38 and 200 MPa, respectively, resulting in a stress exponent of ≍1.7.

Novel apparatus and methodology have been developed for measuring the fracture toughness of ceramics using small disk-shaped samples 3 mm in diameter. The method involves the Vickers indentation of specimens ranging in thickness from 300 to 700 μm, and testing them in a ring-on-ring bending mode. Experiments on ZnS grown by chemical vapor deposition (CVD) have been used to evaluate the technique. The apparent fracture toughness of this material increases with crack length (R-curve behavior). This behavior is analyzed using established equations in conjunction with a new graphical method that obviates the need for measuring the apparent toughness of samples containing very large cracks. The fracture toughness at “infinite” crack length, 0.86 ± 0.08 MPa · m1/2, is in very good agreement with the values obtained by conventional methods. The effect of sample size on the accuracy of the results is thoroughly discussed. The thickness, t, of the sample should exceed by a factor of ten the initial crack length produced by the indentation. Also, since samples are tested at various indentation loads, P, the ratio of their thicknesses should be chosen to satisfy the condition t ∝ P2/3. The importance of several parameters in the design of the apparatus is also discussed.

Solid-state reactions between bulk samples of copper oxide and alumina have been studied using scanning electron microscopy and electron microprobe analysis. Both CuAl2O4 and CuAlO2 were found to form during reactions in air at 1100 °C between CuO powder and single-crystal alumina substrates. The relative position of the CuAl2O4 and CuAlO2 layers was observed to depend on the crystallographic orientation of the surface of the alumina substrate: CuAl2O4 formed in contact with (0001) alumina substrates while CuAlO2 formed when the alumina substrate surface was (110). Faceted Cu–aluminate/alumina phase boundaries were observed to develop when single-crystal alumina rods were reacted with CuO, although the interfaces invariably tended to be wavy.