Advances in the development of high Tc superconducting thick film components and devices for microwave, millimeterwave, and submillimeterwave applications have led to the optimization of laser patterning techniques. Plasma-sprayed superconducting thick films of YBaCuO materials on polycrystalline alumina were laser etched using an Nd: YAG laser (λ = 1.06 μm) in the Q-switched mode. Spatial uniformity of the surface elemental distribution of Y, Ba, Cu, and Al was observed in the underlying laser-etched area. An etch rate of 7.5 μm/scan was calculated at an optimized laser fluencc of 1.8 × 104 J/cm2 for a translation rate of 2.54 cm/s, having patterning widths ranging from 5–15 μm with a heat-affected zone of 3 μm. An absorption length of 18.3 μm for the Nd: YAG laser was determined to be suitable for patterning thick films (20–80 μm) for device fabrication. The results are further compared to CO2 (λ = 10.6 μm) laser etching for patterning (250 μm) thick films.

High Tc superconducting YBCO films have been prepared on Y2BaCuO5 (211) and ZrO2 substrates by screen printing and by the partial vacuum sintering method. The influence of reduced pressure and temperature in correlation with adherence, microstructure, and superconducting properties has been observed. This study was carried out under two different partial pressures, 1 and 45 mm. Films on Y2BaCuO5 substrates were found to have better superconducting properties as compared to the ZrO2 substrate.

Gd-1:2:3 films were synthesized from acetate precursors and spun-on to polycrystalline substrates of yttria-stabilized zirconia. The substrates were fired in air at 500 °C in between each applied coat. After applying 10–30 coats, they were crystallized by heating to 900 °C in Ar or O2 with or without the application of a 1 T magnetic field. The applied magnetic field was found to produce c-axis alignment for films <4 μm. Annealing in argon produced alignment, but the effect was less pronounced than annealing in oxygen. Substrates with films > 20 μm were not aligned for either environment.

In the framework of an extensive research program for the production of textured and ductile high Tc BiSrCaCuO (BiSCO) wires and tapes, the influence of processing (by melt-quenching) parameters on the crystallization behavior, the quantitative and qualitative evolution of the crystallized phases, the chemical changes in the bulk, and the superconductive properties of various initial compositions of bulk BiSCO glass ceramics, prepared by melt-quenching, have been studied. The elemental composition of the samples changes drastically during heat treatments, affecting mainly Pb, but Sr and Ca also. The identified crystallographic phases, by XRD, were the low Tc superconducting “2201” (Bi2Sr2CuO6) phase, the high Tc superconducting “2212” and “2223” phases, and the Ca2PbO4, Ca2CuO3, CuO, CaO, Bi2Sr3-xCaxOy, and (Ca, Sr)3Cu5O8 “impurities” compounds. A crystallization sequence from the amorphous state is proposed, involving a reaction at 800 °C between “2223”, CaO, Ca2CuO3, and Bi2SrCaxOy to form “2212” + Ca2PbO4 + CuO and a 2(“2212”) → “2223” + “2201” disproportionation reaction that takes place with the intake of oxygen at a higher temperature. Decomposition of Ca2PbO4, which occurs also at high temperature, causes an increase of “2212”, which favors the increase of “2223” through the disproportionation reaction. The glass transition starts around Tg = 400 °C, and the crystallization reactions from the amorphous state proceed in two steps, at Txl = 465 °C and Tx2 = 504 °C. The Bi2Sr3-xCaxOy “2212” and “2223” phases are among the first to crystallize as early as after a 1 h treatment (in air) at 488 °C. A gain in weight is observed by thermogravimetry, caused by intake of the oxygen necessary for the formation of the high Tc superconducting phases. The oxygen intake starts as early as 600 °C. The Tc onset for the “2223” phase is at 122 K, and at 85.5 °C for the “2212” phase. Coefficients of thermal expansion have been measured and shown to differ according to crystallographic direction of expansion. The resistivity is increased on cooling, indicating semiconducting behavior of the 2223 BiSCO ceramic (semiconductor-to-metal transition temperature: 210–220 K).

Ag-sheathed tapes of Bi–Sr–Ca–Cu–O (BSCCO) and BSCCO–Ag superconducting cores were made by a powder-in-tube technique and subjected to repeated cycles of pressing and heat treatments. These thermomechanical treatments resulted in enhanced texturing and grain growth that improved the critical current density (Jc). Additions of Ag to the BSCCO core further increased texturing and brought an additional improvement in Jc. Strain tolerance of the tapes was evaluated by measuring Jc before and after application of a predetermined level of tensile strain in a uniaxial mode. The fraction of Jc retained after the strain application was higher in the BSCCO–Ag composite tapes than in the monolithic BSCCO. For a 1.2% applied strain, 90% of the initial Jc was retained in the BSCCO–Ag composite tape, compared to only 40% in the monolithic BSCCO tapes. The higher strain tolerance of the BSCCO–Ag tapes may be related to improved mechanical properties (strength, flexibility, and fracture toughness) and grain connectivity due to Ag addition.

Tracer diffusion of 85Sr in polycrystalline Bi2Sr2Can-1CunO2n+4 has been investigated for n = 1, 2, and 3 in an oxygen atmosphere between 775 and 850 °C. A radiotracer serial-sectioning technique was used to measure the concentration profiles, which were fit to a solution of the diffusion equation to calculate the diffusivities. The activation energies were 403, 553, and 519 kJ/mole, for n = 1, 2, and 3, respectively. However, the absolute values of D for the various layered superconductors did not differ by more than an order of magnitude over the measured temperature range. The diffusivity of Sr at 800 °C for n = 1 or 2 over an oxygen partial pressure range of 103 to 105 Pa increased as the pressure decreased.

Coatings of three different compositions (Al65Cu20Fe15, Al64Cu18Fe8Cr8, and Al67Cu9Fe10.5Cr10.5Si3) were realized by various thermal deposition techniques. They were studied in the as-deposited state and after annealing. In view of potential applications, these quasicrystalline coatings were examined from the point of view of tribology: friction and wear. Some basic components of friction such as roughness, plowing, and adhesion have been studied in scratch testing. The friction resistance of the coating is strongly dependent on its inherent porosity, hardness, and thickness. The damage of the coatings is essentially brittle though some ductile behavior is observed. Static indentation hardness is in the range 500–600 HV0.03 (5–6 GPa), whereas the scratch hardness varies from 1.4 to 2.4 GPa depending on the percentage of porosity. Friction coefficients (measured at constant load of 20 N) were found to be typically 0.07 and 0.20 for diamond (tip radius R = 0.79 mm) and AISI 52100 (radius R = 0.79 mm) indenters, respectively.

A methodology is presented to characterize the crystallography of individual fracture surface facets. Electron backscatter patterns (EBSP's) from a metallographic section through a facet identify grain orientation, and quantitative tilt fractography identifies facet orientation; these results are combined to establish fracture facet crystallography. For this technique, facet electropolishing is not required, the facet alignment procedure is accurate and quick, and the method can be generalized to different microstructures, test environments, or facet orientations. Method accuracy is illustrated for 25 to 50 μm fatigue crack facets in an unrecrystallized Al–Li–Cu alloy (AA2090) that has 5 μm thick subgrains in elongated grains that are 10 to 200 μm thick. The fine subgrain structure and tortuous fatigue crack profile precludes the use of other diffraction techniques for determining AA2090 facet crystallography. EBSP and tilt fractography results demonstrate that vacuum fatigue cracks in AA2090 are nearly parallel to local {111} planes.

The feasibility study of electroless plating as carbon fiber modification for aluminum matrix composites was carried out. The comparison of Cu plating and Ni plating of carbon fiber by the electroless method was investigated. The Cu- or Ni-coated carbon fiber reinforced aluminum was fabricated with a centrifugal pressure infiltration method. The mechanical property was metallographically discussed. Electroless plating is able to improve the throwing power of the precipitant into the multifilament and uniformly coat Cu or Ni onto the carbon fiber. The technique using centrifugal casting seems to be an innovative method for fabrication of composite materials. The eutectic reaction between aluminum and Cu or Ni on the fiber appears to improve the affinity of the carbon fiber and aluminum. The Cu-plated carbon fiber reinforced aluminum is two times higher in bending strength than Ni-plated carbon fiber reinforced aluminum.

Rapidly quenched Al86-xNi14Six (x = 0, 2, 6, and 10) alloys have been studied by means of transmission electron microscopy. Two-dimensional (2-D) decagonal quasicrystal with a periodicity of 1.6 nm along its tenfold axis was found in the rapidly quenched Al86Ni14 binary alloy. With the addition of some silicon, such as AlgoNi14Si6, the 2-D decagonal quasicrystal first transforms to a one-dimensional (1-D) quasicrystal that inherits the periodicity along the tenfold axis and has, in addition, translation periodicity in one of the twofold axes of the decagonal phase, and finally transforms to a new orthorhombic crystalline phase (a = 0.78, b = 1.62, and c = 1.48 nm). In the Al76Ni14Si10 ternary alloy, a 2-D decagonal quasicrystal with a periodicity of 0.4 nm and a coexisting crystalline phase with the “Al3Ni2” structure were found, and their orientational relationship has been determined.

The crystalline disordered phase obtained by mechanical alloying of elemental 75 at. % Ni and 25 at. % Al powders has been investigated. The stability of this phase with respect to the thermal reordering process leading to the L12 structure has been analyzed by means of x-ray diffractometry, scanning electron microscopy, and differential scanning calorimetry. Atomistic simulations on an Ni3Al model, reproduced via molecular dynamics using a many-body potential, have been used to interpret experimental data. The ordering transformation takes place in an extended range of temperature (from 320 to 600 °C) and occurs simultaneously with the release of internal strain. Numerical simulations performed under different conditions show that the activation energy of the Ni-vacancy migration mechanism responsible for the ordering process depends on the local state of strain, thus suggesting an explanation for the considerable lowering of this energy in samples obtained by ball milling.

The high temperature (T = 1083–1388 K, 0.65–0.84 Tm) creep behavior of single crystalline Ni3Al(Ta, B) was investigated. A change in the creep characteristics as a function of applied stress was observed at the uppermost testing temperatures of 1288 and 1388 K. At low applied stress levels the Norton law stress exponent is equal to 4.3; for higher stresses the stress exponent is equal to 3.2. Different creep curves were observed, depending on the value of the stress exponent. The change in stress exponent and nature of the creep curve correspond to a change in the controlling deformation mechanism from dislocation climb to viscous dislocation glide for Ni3Al(Ta, B). The experimentally observed transition stress values between climb and viscous glide are in good agreement with values predicted from theory, assuming that the major force retarding viscous dislocation glide in Ni3Al(Ta, B) is the antiphase boundary interaction.

During combustion/micropyretic synthesis, conditions that give rise to rapid solidification and rapidly solidified microstructures may be encountered. In this article, many such conditions are identified for the first time in a Ni–Al system. In addition, the banded structures and aligned dendrites that are encountered in this system are also examined. The various techniques of rapid solidification that may be initiated with combustion synthesis are examined and discussed.

Precipitation of rhenium in β–NiAl was studied by analytical and high resolution electron microscopy. Extended solid solutions were created by solidification processing, and the precipitation and hardening behavior were studied. Evidence suggests that rhenium is initially precipitated as disks parallel to {100} of β-NiAl. Subsequent growth produces either a rod morphology or a pair of twin-related rods that form the shape of a butterfly. The twin plane of the butterfly is {1011} and this plane is nearly parallel to {110} of β–NiAl. A twinning transformation given by K1 = {1011}, K2 = {1013}, η1 = 〈1012 〉, and η2 = 〈3032〉 was determined for the butterfly-shaped particles. All of the precipitates exhibited an orientation relationship consisting of parallel close-packed planes and directions, i.e., (101//(0001) and [111]//[1210]. Performing the twinning transformation on a rhenium precipitate produces a variant rather than a new orientation relationship. After elevated temperature aging, a rod morphology was observed with the rod axes aligned parallel with either 〈121〉 or 〈131〉 of the β–NiAl matrix. A total of 24 different variants are possible based upon the observed orientation relationship and the two observed growth directions.

Environmental embrittlement of L12-type Ni3(Al, Ti) single crystals doped with 0.05 mass % boron was investigated at room temperature as functions of environmental media and strain rate. Environmental embrittlement occurs in air, water, and hydrogen gas, and is also very sensitive to strain rate with a decrease of elongation with decreasing strain rate. Environmental embrittlement is little influenced by boron doping, indicating no strong interaction with hydrogen in lattice. In embrittled condition, tensile elongation and fracture stress are reduced, and fracture mode is primarily {001} cracking with a river pattern. Based on these results, it is proposed that hydrogen affects lattice bonding and thereby reduces the cohesion strength on {001} atomic plane. Also, it is suggested that the major cause of environmental embrittlement of boron-doped Ni3(Al, Ti) single crystals is due to the reaction of water (i.e., H2O) in environment with the reactive element of Al (and/or Ti) and of H2 in environment with the surface reactive element of Ni.

We report scanning tunneling microscope observations of fracture surfaces formed during catastrophic crack growth in three metallic glasses: Ni56Cr18Si22B4, Co69Fe4Ni1Mo2B12Si12, and Fe78B13Si9. Macroscopically, the first two glasses fail along a slip band formed during loading and display a characteristic, μm-scale pattern of vein-like ridges; in contrast, Fe78B13Si9 displays little slip prior to fracture, and its fracture surface shows a μm-scale chevron pattern of steps. STM observations of fracture surfaces of all three materials show nm-scale grooves. The grooves in Co69Fe4Ni1Mo2B12Si12 are especially prominent and display stepped edges which we attribute to the intersection of shear bands with the surface. STM observations of the vein-like features on Ni56Cr18Si22B4 also show stepped edges. We attribute the vein features to the interaction of adjacent crack fingers in which the material between adjacent fingers fails in plane stress. The origin of the grooves is uncertain, but may be due to other shear instabilities along crack fingers.

Thermodynamic and structural properties of fcc- and hcp-based Ti–Al alloys are calculated from first-principles and are used to perform an ab initio study of phase stability for the intermetallic compounds in this system. The full potential linear muffin tin orbital method is used to determine heats of formation and other zero-temperature properties of 9 fcc- and 7 hcp-based intermetallic compounds, as well as of elemental fcc and hcp Ti and Al. From the results of these calculations, sets of effective cluster interactions are derived and are used in a cluster variation method calculation of the solid-state portion of the composition-temperature phase diagram for fcc- and hcp-based alloy phases. The results of our calculations are compared with those of experimental studies of stable and metastable phases in the Ti–Al system.

6061 alloy matrix composites reinforced with β–SiC whiskers were fabricated both by squeeze casting and by hot-pressing and were heat-treated in the temperature range between 600 °C and 800 °C. The changes in interface microstructure were observed by transmission electron microscopy. In all treatment conditions, no special reaction product, e.g., Al4C3, were observed except for fine γ–Al2O3 particles adhering to the whiskers. A direct lattice connection at the whiskers/matrix interfaces was observed in all composites. β–SiC whiskers were proved to be quite stable in the 6061 matrix.

The tribological properties of polycrystalline chemically vapor deposited (CVD) diamond films grown on silicon substrates and containing varying amounts of amorphous carbon impurities were investigated. Films were characterized by secondary electron microscopy (SEM) and atomic force microscopy (AFM) for surface morphology and roughness and by spatially resolved Raman spectroscopy for amorphous carbon (a-C) content. Friction measurements were performed with a Rockwell C hemispherical diamond tip in ultrahigh vacuum (UHV) and in ambient air. In vacuum, the friction coefficient rises monotonically from 0.6 in a region with substantial a-C to 0.85 in a region with pure diamond. Under ambient conditions, the friction coefficient is substantially lower than that in vacuum and deceases slightly (from ∼0.19 to ∼0.16) with the decreasing a-C content. Under both vacuum and ambient conditions, the friction coefficient was observed to be independent of load over the range of 0.1–0.5 N. The friction values are discussed in terms of adhesion between the diamond tip and the film. Qualitative scratch hardness measurements were performed in UHV by measuring the minimum load at which plastic deformation occurs for a single traversal of the tip. Scratch hardness is found to increase with increasing diamond content of the films. The wear mechanism of the pure diamond regions was evaluated by examining wear tracks with SEM and AFM. The wear tracks showed evidence of spalling, buckling, and grain pull-out indicative of a cohesive mode of failure (failure at grain boundaries). A decrease in surface roughness in the wear tracks indicates asperity wear. Adhesive failure at the Si substrate interface or of a phase transformation of the diamond film was not observed in this load regime.

Highly oriented pyrolytic graphite has been implanted at room temperature with 165 keV C+-ions at doses from 6 × 1017 to 3 × 1019 ions/m2. Implantation-induced topographical changes of differing size scales were studied by optical, scanning electron, scanning tunneling, and atomic force microscopies. Defects with atomic resolution are seen for the lower dose implants. The formation of a vacancy line is revealed for the first time. At the higher doses a dendrite-like system of deep surface cracks is observed. This cracking develops as a result of the large basal plane contraction produced by irradiation which generates high shearing stresses between the implanted, damaged surface layer and the underlying material. Two independent systems of ridges have been characterized. One appears to follow a crystallographic direction while the other appears as a dense, intricate, generally curvilinear network with short ramifications. Additional experiments in which both the ion energy and dose rate have been varied indicate that ridge evolution progresses with increased energy and fluence, but is independent of dose rate. It is suggested that the ridge networks may form as a result of C transport by diffusion from the heavily damaged near-surface region or of a tectonic-plate-like motion or both. The geometric features of the ridge networks are related to the subsurface radiation damage as well.