The crystalline perfection of microwave plasma assisted chemical vapor deposited (MPACVD) diamond films grown under various conditions has been examined by TEM. Most CVD diamond films thus far reported contain a high density of defects, predominantly twins and stacking faults on {111} planes. We show that under appropriate growth conditions, these planar defects are eliminated from the center of the crystallites, and occur only at grain boundaries where the growing crystallites meet.

In this paper we report the growth of β–SiC films on Si(100) substrates by low-temperature chemical vapor deposition. Single crystals of β–SiC are grown at temperatures as low as 1150 °C. Low-temperature growth β–SiC is achieved using a SiH4–C3H8–H2–Ar gas system. The growth rate of films grown at 1150 °C is 1 μm/h. Transmission electron microscopy and x-ray diffraction results indicate that the β-SiC films grown at and above 1150 °C are single crystals. Films grown at temperatures lower than 1150 °C are polycrystalline.

We report on the magnetic-field dependent surface resistance of polycrystalline YBa2Cu3O7 (Tc ≃ 92 K), measured using a brass cylindrical cavity resonator, operating at 16.5 GHz in the TE011 mode. A de magnetic field Happ is applied parallel to the superconducting sample surface, and the temperature dependence of the surface resistance is measured for four different values of Happ (0 T, 0.22 T, 1 T, 5 T). An effective medium theory and the two-fluid model are used to fit the surface resistance versus temperature measurements both in zero field and for various applied fields. These results are applied to characterize the microwave properties of a polycrystalline ceramic superconductor.

Superconducting YBaCuO thin films have been fabricated on single-crystal MgO by the spray-pyrolysis of nitrate precursors. The effects on the superconductive behavior of processing parameters such as time and temperature of heat treatment and film thickness were investigated. The superconductive behavior was found to be strongly dependent on film thickness. Films of thickness 1 μm were found to have a Tc of 67 K while thinner films showed appreciably degraded properties. Transmission electron microscopy studies have shown that the heat treatments necessary for the formation of the superconductive phase (for example, 950 °C for 30 min) also cause a substantial degree of film-substrate interdiffusion. Diffusion distances for Cu in the MgO substrate and Mg in the film were found to be sufficient to explain the degradation of the superconductive behavior in films of thickness 0.5 μm and 0.2 μm. From the concentration profiles obtained by EDS analysis diffusion coefficients at 950 °C for Mg into the YBaCuO thin film and for Cu into the MgO substrate were evaluated as 3 × 10−19 m2/s and 1 × 10−17 m2/s, respectively.

A nonaqueous plating bath for silver deposition on the Ba2YCu3O7 superconductor has been modified with thiourea to give enhanced coverage of the metal film at low thicknesses. For both porous and high density ceramic substrates, SEM and optical microscopy show nucleation of silver deposits is increased by the additive. The resulting silver-superconductor contact resistances are comparable to those achieved without additives. Adhesion of the deposits and ease of mechanical handling are improved with thiourea. The combination of highly reactive oxidized substrate, nonaqueous solvent, and strongly surface active agent forms a novel extension for electrodeposition science.

We report the infrared reflection and absorption spectra of the high Tc superconductor Tl2Ba2CaCu2O8 in the temperature range from 10 K to 300 K. For temperatures above 100 K, the reflection spectra show only small changes with temperature. Just below 100 K, the reflectance suddenly increases for energies below 210 cm−1 with very little change as the temperature is further decreased. Several peaks corresponding to normal modes of the material are observed in both reflection and absorption spectra.

Several high Tc compounds containing Tl (thallium) were prepared starting from different initial compositions. Superconducting properties and the structure were determined for each sample. Electron diffraction and transmission electron microscopy showed the existence of polytypic high Tc compounds with the same a- and b-axes but different c-axis values. The c-axis appears to increase approximately in integral multiples of 0.15 nm with varying composition and is associated with the insertion of Cu–Ca or Cu–Tl layers in each unit cell. Several random stacking faults were also noted, which give rise to diffuse streaking in the electron diffraction pattern.

The compound Bi2Sr2(GdxCa1−x)0.8Cu2O8+δ is examined by electron diffraction for several values of x. The incommensurate modulation which has been reported for x - 0 persists for all values of x with the wave vector increasing as x increases. A secondary modulation with a wave vector equal to one-half that of the primary is observed for x  0.85. This modulation manifests itself through satellite reflections that are highly streaked normal to the (001) planes and that flank certain select positions in reciprocal space. The appearance of this secondary modulation is accompanied by a change in the average crystal structure from B-centered to F-centered orthorhombic.

Three trialuminide alloys, binary Al–25Sc, ternary Al–25Zr–6Fe, and quaternary Al–23Ti–6Fe–5V, all having the cubic L12 structure, were investigated. All three alloys fracture in a brittle manner (fracture toughness, 2–3 MPa m½), predominantly by transgranular cleavage. Of nineteen cleavage facets examined in binary Al3Sc, seventeen were of the {110} type and only two were of the {100} type, consistent with our earlier work which showed that the cleavage plane occurring most frequently in quaternary Al–23Ti–6Fe–5V is also {110}. The room-temperature hardnesses and yield strengths (100–200 DPH and 100–270 MPa, respectively) of all three alloys are quite low (comparable to ductile L12 alloys like Ni3Al), indicating that there is significant dislocation activity in these materials. Consistent with this, transmission electron microscopy identified several APB-coupled dislocations with b - a/2〈110〉 gliding on the {111} planes in both binary Al–25Sc and quaternary Al–23Ti–6Fe–5V. The separations between the superpartials in Al–25Sc and Al–23Ti–6Fe–5V were measured to be 3.7 and 4 nm, respectively, giving APB energies of 313 and 274 mJ/m2, respectively. Auger analyses failed to detect any impurities on the cleavage facets themselves, or on second phase particles (or other potential cleavage crack nucleation sites). It is therefore concluded that brittle fracture in these alloys is not impurity-induced. Based on all the results obtained to date we conclude that the unusual brittleness of L12 trialuminides is related to their intrinsically low cleavage strength. Possible reasons for their low cleavage strength are discussed.

The chemical compatibility and tensile properties of a powder processed intermetallic matrix composite (IMC) were investigated in the temperature range 298–1373 K. The matrix alloy selected for this study was the ORNL developed advanced nickel-aluminide IC-221 (Ni-16Al-8Cr-1Zr-0.05B at. %). The composite contained 25 vol. % TiC particulate reinforcement. TiC/IC-221 compatibility samples were heat treated at 1373 K for up to 1000 h. A layer enriched in Zr and Ti formed at the TiC/IC-221 interface after heat treatment. In addition, Ti was observed to diffuse into the matrix. The composite exhibited higher yield strength and lower ductility than a similarly processed matrix alloy at all test temperatures. Heat treatment of the composite improved the tensile properties due to particulate/matrix interaction, resulting in improved load transfer. SEM fractography revealed that tensile failure occurred at the matrix/prticulate interface. Remnants of the matrix were observed on TiC particles on the fracture surface, suggesting good matrix/particulate bonding. The mechanical properties of the composite were very competitive with Ni-base superalloys.

The mixing of multilayers of two pure metals or alloys A and B with strong negative heat of mixing ΔHm can result in rapid heat release provided that the mixing time is short compared to the time to dissipate ΔHm in the environment, which is the case for sufficiently thin layers. The mixing reaction sets off the heat release when the composite is heated up to temperatures near or equal to the melting temperature of the metal layer with the lower melting point. Experimental results are given for the mechanisms and for the kinetics of the exothermic reaction. Possible applications of these materials are given.

The microstructure of anodic oxide films grown on Ti–6A1–4V in H2SO4 was investigated by SEM, TEM, STEM, EDX, and AES, as a complement to a recent surface spectroscopic investigation of the same oxides by XPS, AES, and SIMS. The anodic oxide films are heterogeneous and the texture reflects the duplex microstructure (α and β phases) of the underlying metal. Porous oxide regions are observed with different appearances on α-phase and mixed-phase regions. The oxide films are essentially amorphous in the investigated thickness range 60–300 nm (in contrast to as-grown anodic films on pure Ti), but crystallize to the anatase structure upon annealing. Considerable lateral variation of the V content in the oxide is observed, reflecting the corresponding variation in the underlying metal. The results are compared with a previous, similar investigation of anodic oxides on pure Ti.

Implantation of Al into nickel and co-evaporation of Ni–Al films onto nickel substrates followed by ion irradiation was conducted in order to investigate the mechanical properties of ion beam surface modifications and their relation to the composition and microstructure of the surface. Implantations were made using 400 keV Al+ to doses from 1 × 1015 to 6 × 1017 cm−2 at room temperature. Nickel films with 0–25% Al were co-evaporated onto nickel substrates and mixed using the same irradiation conditions but to a lower maximum dose. Hardness was measured using ultra-low load indentation, and residual stress was measured by the bending beam method. Results indicate that the primary contributor to the hardness increase of as-implanted surfaces is the irradiation-induced defects. The effect of Al in solution (γ phase) or Al in γ′ (Ni3Al) in either implanted or co-evaporated and mixed surfaces is evident only upon thermal treating to remove radiation damage. The high inherent hardness of the co-evaporated films is due to the small grain size of the film. The magnitude of the hardness in Al implanted nickel is very sensitive to the surface condition of the substrate. The observed hardness effects are all directly relatable to microstructure or phases present. Residual stresses change from tensile to compressive as a result of damage from low dose irradiation and heat treatment.

The microstructure and mechanical behavior of electroless deposited Ni–P on Al–Mg substrates were investigated. The microstructures of the as-deposited and annealed samples were characterized through optical and scanning electron microscopy. Hardness measurements were made both on the Al–Mg substrate and the Ni–P coating using a depth sensing hardness machine. The plastic deformation behavior of the composites was studied and the results show that the initial deformation is accompanied by the appearance of serrations on load-displacement curves. Decohesion of the hard Ni–P takes place at large strains. An estimate of the ultimate shear strength of the Al–Mg/Ni–P interface was made and the strength of the interface was determined to be −0.45 GPa. The tribological properties of the amorphous Ni–P were studied using ball-on-disk and slider-on-disk tests. In particular, the influences of humidity, surface roughness, and heat treatment on friction and durability of the coatings were investigated.

Polyacetylene shows catalytic activity in an aqueous solution for electroless deposition of amorphous alloys. The catalytic activity of polyacetylene is comparable to the activity of some highly catalytic metals, i.e., Cu, steel, and Pt. Modifications of the Shirakawa technique led to the formation of a foam-like polyacetylene, which is highly porous and has a low degree of crystallinity. This material can be used as a catalytic substrate for the preparation of amorphous metals in bulk form. The amorphous Ni–Co–B and Ni–Co–P alloys deposited on a PAc substrate were investigated by magneto-thermogravimetry and x-ray diffraction. These investigations gave a Curie temperature of about 413 K and a crystallization temperature of about 600 K for the metal-metalloid component of the system.

The intercalation reaction of NiCl2 from the mixture of CuCl2 and NiCl2 has been studied by using natural graphite and a stage 1 graphite intercalation compound with CuCl2 at different temperatures from 400 °C to 550 °C for a wide range of residence times up to 8 days. In the mixture of CuCl2 and NiCl2, CuCl2 was found to be intercalated preferentially in the beginning of the reaction. At low reaction temperatures, NiCl2 was intercalated with the increase in heating time, but its content was saturated at a rather low value, NiCl2/C = 25 wt.% after 3 days at 450 °C, for example. At temperatures as high as 550 °C, however, the content of CuCl2, which had been intercalated in the beginning of the reaction, was found to decrease and NiCl2 started to be intercalated by prolonged heating, suggesting the exchange of the former with the latter. From the reactions of a stage 1 CuCl2–GIC with the mixture of CuCl2 and NiCl2, it was clearly revealed that the intercalated CuCl2 was replaced successively by NiCl2 in keeping the stage 1 structure. The saturated content of NiCl2 in respect to graphite depended strongly on the reaction temperature, attaining NiCl2/C = 150 wt.% at 550 °C. As seen by energy dispersive x-ray spectroscopy, NiCl2 intercalation proceeds from the periphery of the host particles. To form a uniform distribution of both intercalates, CuCl2 and NiCl2, it took a long time of residence, more than 3 days at 550 °C.

The misorientation phase space for symmetrical grain boundaries is explored by means of atomistic computer simulations, and the relationship between the tilt and twist boundaries in this three-parameter phase space is clucidated. The so-called random-boundary model (in which the interactions of atoms across the interface are assumed to be entirely random) is further developed to include relaxation of the interplanar spacings away from the grain boundary. This model is shown to include fully relaxed free surfaces naturally, thus permitting a direct comparison of the physical properties of grain boundaries and free surfaces, and hence the determination of ideal cleavage-fracture energies of grain boundaries. An extensive comparison with computer-simulation results for symmetrical tilt and twist boundaries shows that the random-boundary model also provides a good description of the overall structure-energy correlation for both low- and high-angle tilt and twist boundaries. Finally, the role of the interplanar spacing parallel to the grain boundary in both the grain-boundary and cleavage-fracture energies is elucidated.

The finding of Jang and Koch that the melting enthalpy/mass, ΔHm, of a Sn matrix containing a fine dispersion of Ge particles sharply decreases with increasing Ge volume fraction, νGe, >0.5 and vanishes at νGe = ν°Ge ≍ 0.81, is accounted for by supposing that the Sn is distributed between an interfacial and bulk state. The interfacial statc is one in which the Sn is assumed to be in a disordered, possibly amorphous, structure coating the Ge particles uniformly to a constant thickness, δ. The remaining “bulk” Sn is assumed to exhibit the normal enthalpy of fusion, ΔH°m. The model accounts for the dependence of ΔHm on νGe within the experimental uncertainty. With the average width of Ge particles −10 nm, δ is estimated to be −0.23 nm; i.e., of the order of the thickness of one Sn monolayer.

An experimental silicon-containing benzocyclobutene thermosetting resin from DOW has been evaluated for use as a plasma etch stop in packaging applications. The thermal and etch properties of this particular resin (DOW UX-13005.02L) make it suitable for use as an etch stop. Further, a model for in situ laser interferometry is proposed. By applying the model to the laser interferogram, the initial etch rate and amount of material removed before etching ceases may be determined.

We present an investigation of the influence of four dopant lithium concentrations on the electrical properties of CuO. X-ray measurements have revealed a single phase formed up to 4.2 at. % of Li, and a second phase formed, Li2CuO2, in the case of 10.5 at. % of Li concentration. The log(ρ/T) vs 1/T data are better represented by two straight lines than by one and show an initial strong decrease of the conduction activation energies for small contents of Li (<1.7 at. %), which becomes weak for larger contents. The change in slope observed in the resistivity measurements as a function of temperature has also been investigated by calorimetric measurements, revealing a specific heat anomaly which can be associated with the antiferromagnetic order transition.