Slow crack growth in CVD diamond has been observed from indentation experiments. Diamond films of 400 μm thickness were prepared by plasma-enhanced CVD on a silicon substrate, subsequently removed from the substrate, and polished for indentation testing. A microhardness tester was used to produce Vickers indentations under low load. Crack length measurements over time revealed susceptibility to slow crack growth in ambient testing conditions. The stress-corrosion susceptibility coefficient, N, was measured as 9.3.

Single crystal films of C60 of different thickness values have been deposited on mica substrates by resistance evaporation. Electron diffraction and high resolution microscopy have been used to assess the orientational ordering and the nature of the defects present in these face-centered cubic films which exhibit a 〈111〉 direction normal to the film surface.

The structure of buried oxide layers formed by low-dose 16O+ implantation of 0.4 and 0.7 × 1018 cm−2 at 180 keV and by subsequent annealing in the temperature range of 1150 to 1350 °C has been investigated using cross-sectional transmission electron microscopy (XTEM). At a dose of 0.4 × 1018 cm−2, an 80-nm continuous uniform buried oxide layer having a breakdown voltage of approximately 40 V is formed after annealing at 1350 °C. At a dose of 0.7 × 1018 cm−2, multiple buried oxide layers having Si islands between them are formed at an anneal temperature of 1150 °C. The number of multiple layers is reduced as the annealing temperature increases, but the Si islands do not dissolve even after annealing at 1350 °C. The existence of the Si islands causes the breakdown voltage to fall to 0 V despite the higher dose.

Pb(ZrxTix)O3 (PZT) powders of 0.2–0.4 μm particle sizes could be obtained from the complex alkoxides synthesized from lead acetate, Zr(OBun)4, and Ti(OEt)4. The powders crystallized to well-crystalline perovskite phases at a temperature as low as 250 °C, independent of the compositional ratio of the B site (Zr/Ti). For the preparation of powders, the complexing of alkoxides, addition of the second solvent such as acetone, acetonitrile, or methyl acetate, and base-catalyzed hydrolysis with ammonia water were essential.

Epitaxy of cupric oxides, such as the high temperature superconductor YBa2Cu3O7, using “vacuum” techniques requires either activated forms of oxygen, such as atomic oxygen, oxygen plasma, or ozone, or a relatively high pressure of molecular oxygen. In contrast, cuprous oxides (those with formal valence of copper less than +2) can be grown epitaxially in molecular oxygen at pressures below 10−4 Torr. We have explored this regime of epitaxial growth because of the possibility of forming DyBa2Cu3O7 through low temperature ex situ oxidation of DyBa2Cu3O6. We find that the dominant phases growing epitaxially on MgO are CuDyO2, Cu2O, CuBa2O2, DyBa2Cu3O6, and the barium-rich perovskite solid solutions. Sticking coefficients of barium and dysprosium depend on substrate temperature and flux composition for substrate temperatures between 550° and 700 °C. We have obtained superconducting films by annealing Dy-rich, Cu-deficient films in oxygen at 400 °C. The nonstoichiometry (with respect to DyBa2Cu3O6) appears to stabilize “DyBa2Cu3O6,” at low oxygen pressures. We also discuss the use of copper in effusion cells.

The effect of the melt-quenching step on the refinement of Y2BaCuO5 (211) particles, and phase transformations during crystallization in the MPMG (Melt-Powder-Melt-Growth) process were investigated. The quenched powders, which mainly consisted of Y2O3 and BaCu2O2, were transformed into the 211 and liquid phases by way of the YBa2Cu3Oy (123) phase. The transformation was examined on samples quenched from various temperatures. Through crystallographic examination using several kinds of precursors, it has been demonstrated that the addition of platinum, which is a contaminant from the crucible during the first partial melting step in the MPMG method, can refine the 211 particles.

We have developed a novel pressurized partial melt growth process for producing large pieces of bulk Y–Ba–Cu–O superconductors. During long-time partial melt growth stage, an additional driving force for solidification is obtained by using pressurized oxygen gas. The microstructure and superconducting properties of the resulting samples were investigated. It was found that this new technique can eliminate porosity and inhomogeneity, promote large-scale grain-texturing, and improve interdomain coupling as well.

Effects of an excitation frequency on on-axis rf magnetron sputtering have been studied for fabrication of YBa2Cu3O7−δ thin films on MgO (100). The excitation frequencies examined are 13.56, 40.68, 67.80, and 94.92 MHz. Sputtering was performed in a pure argon gas in order to distinguish excitation frequency effects of oxygen emitted from a target from those of oxygen in a mixture atmosphere. Excitation frequencies higher than 40.68 MHz result in both a low self-bias voltage and a narrow distribution of the energy of sputtering ions, which reduce resputtering of a film surface caused by negatively charged oxygen from the target. Thin films of a-axis oriented YBa2Cu3O7−δ deposited at 94.92 MHz have shown better morphology and crystallinity than those at lower excitation frequencies under the same conditions. Furthermore, a-axis oriented superconductive YBa2Cu3O7−δ films have successfully sputtered in 200 mTorr atmosphere of argon and oxygen on SrTiO3 (100) by using an excitation frequency of 94.92 MHz, showing a full width at half maximum of 0.1° in the rocking curve through the (100) peak and a very smooth surface. The zero resistance temperature is, at most, 33 K.

YBa2Cu3O7−x superconducting films have been prepared on a YSZ ceramic substrate through the sol-gel method using metal alkoxides of Y, Ba, and Cu. A homogeneous solution containing the three metal alkoxides was prepared by dissolving the copper alkoxide, which is otherwise insoluble, in diaminoalcohol. The gel film, formed by dipping the substrate into the sol of 80 °C and withdrawing it up, was converted to a ceramic film consisting of YBa2Cu3O7−x phase by sintering at 850 °C for 30 min. The resulting film of about 10 μm in thickness showed zero resistivity (Tc end) at 54 K. Cold isostatic pressing of the film before sintering remarkably improved the Tc end to 85 K.

YBa2Cu3O7−x (1-2-3) powders and 1-2-3 powders doped with 14 wt. % Ag (AgYBa2Cu3O7−x) were produced using aerosol decomposition of nitrate solutions. Powder produced at T > 900 °C consisted of submicron particles and had Tc ≍ 92 K in magnetic susceptibility measurements. As-produced Ag-doped powder was a composite of nearly phase-pure 1-2-3 and crystalline Ag (by x-ray diffraction) for reactor temperatures between 900 °C and 950 °C, whereas powder produced at T≥ 970 °C contained significant amounts of Y2BaCuO5 which were not found in 1-2-3 synthesis in the absence of Ag. This implied that the melting of Ag (∼960 °C) or the Ag-O eutectic (∼940 °C) promoted decomposition of 1-2-3 during powder synthesis. Dilatometry showed that 1-2-3 and Ag/1-2-3 powders densified rapidly between 800 °C and 875 °C, achieving nearly 90% of theoretical density after heating to 875 °C at 5 °C/min in air. Pellets of the Ag-doped powder were also sintered for 2-60 h at 895 °C in air. Scanning electron and optical microscopy revealed that Ag grains remained fine and uniformly distributed, varying in size from ∼1 μm after 2 h to 3–7 μm after 60 h, while 1-2-3 grains became plate-shaped with thicknesses of 1–5 μm and lengths of 10–30 μm after 60 h. Thus, the use of aerosol Ag /1-2-3 powders allows the use of lower processing temperatures and shorter times to produce dense ceramics with smaller Ag and 1-2-3 grain sizes than can be obtained using solid-state reaction routes.

Modulated microwave absorption measurements at 9.3 GHz were made on the low field absorption observed in the superconducting phase of Bi–Sr–Ca–Cu–O. The line intensity observed with a low modulation amplitude of 50 mOe showed a maximum between 70 K and 80 K and dropped to zero near 95 K. With a modulation amplitude of 10 Oe, an additional broad line absorption was observed above 88 K, peaking in intensity near 95 K, and disappearing above 100 K. Hysteresis, associated with flux trapping, occurred when the maximum field Hmax in a sweep cycle exceeded a critical value H*(T), which varied from about 7 Oe at 59 K to 1 Oe at 82 K. For Hmax > H*, the hysteresis splitting at first varied linearly with (Hmax – H*), later saturating at a value δHmax(T). Above 70 K, the relationship δHmax = b(T0 – T) was obeyed with T0 = 92.3 K and b· = −0.3 Oe/K for H perpendicular and b· = −0.23 Oe/K for H parallel to the c-axis.

A series of samples along the composition lines Bi2+xSr2−xCuOy, and Bi2Sr2−xCuOy have been used to study the structural modulation, chemistry, and superconducting properties of pseudo-tetragonal Bi2Sr2CuO6 (2201). The 2201 phase can be formed from crystallization of thin glassy platelets. The sample displayed a strong crystallographic (00l) orientation which made it possible to determine incommensurate modulations near (00l) reflections using a conventional x-ray θ-2θ scan. From the crystallization of the 2201 phase, it was found that structural modulation was intrinsic to the phase, and ordering of the structure required a long time at high temperature. High temperature in situ x-ray diffraction of a 2201 Bi2Sr1.85CuOy platelet showed that the modulation existed at 875 °C in O2 (Tmelt ≍ 892 °C in O2). These suggest that the structural modulation cannot be caused solely by oxygen ordering and that metal-ion displacement must be involved. By removing 0.04 to 0.05 oxygen atom per formula unit from Bi2Sr2CuOy and Bi2Sr1.85CuOy, the c* components of the modulation changed from 0.31 to 0.26 and from 0.38 to 0.31, respectively, while the b* component of the modulation remained approximately 0.2. This demonstrates that oxygen, while not the sole cause, does play a role in the formation of the structural modulation. However, the invariance of bmod with respect to the change in oxygen content does not support the model that explained the modulation by inserting extra oxygen in the BiO plane. By varying metal-ion concentrations of Bi and Sr we found that both the lattice parameters and the modulation vectors depended more on the Bi/Sr ratio than on the Sr concentration alone. As the Bi/Sr ratio increased from 1.0 to 1.35, the modulation lines moved toward the (00l) reflections. The corresponding superstructural periodicities were calculated to vary from ∼1/5b* + 0.32 c* to ∼1/5 b* + 0.63 c*. Effects of oxygen content and metal-ion concentration on the 2201 phase formation and the superconducting properties will also be discussed.

Superconducting characteristics and the thermal stability of sputtered, tungsten-based, amorphous thin films are investigated. Electronic properties and crystalline structures are analyzed as a function of the metalloid content in the films. It is well known that the superconducting Tc of a bulk crystalline tungsten is 0.01 K, which is one of the lowest transition temperatures among the superconducting metals. We have found that the W film containing 5 to 70 at. % metalloids exhibits a great enhancement in Tc. In the region of 15 to 35 at. % metalloids, the Tc shows the maximum of 5.0 K, and the transition from normal to superconducting state occurs very sharply. SEM observation together with x-ray diffraction analysis indicates that these films are amorphous in structure. The electrical resistivity is about 150 μΩ-cm, and shows little temperature dependence from Tc to 300 K. In addition, the W–Si amorphous superconductor is thermally very stable after annealing at 700 °C, but the W–Ge amorphous alloy crystallizes at 600 °C.

The phase formation of elemental multilayered thin Al100−xNix films during 500 keV Xe+ irradiation has been investigated using transmission electron microscopy. The whole composition range has been covered for various substrate temperatures during the irradiation. At low temperatures, only structurally simple crystalline and amorphous phases are observed. Thermodynamic data for these simple phases were calculated using the CALPHAD method, and nonequilibrium phase diagrams were derived and discussed in the context of the experimental findings.

The intermetallic compound Al3Sc is a trialuminide with the L12 structure, which deforms easily in compression at room temperature, with yield stresses around 100 MPa. As shown by single crystal compression experiments, slip occurs on {111} planes. In tension Al3Sc fractures transgranularly in a brittle manner. The predominant cleavage plane is {011}. In a scanning electron microscope (SEM) numerous cleavage steps, which are aligned in three major crystallographic directions, are observed. The fracture surfaces almost always show microscopic waviness along the traces of intersecting slip planes. Regions that are flat within the experimental resolution of the SEM are only occasionally observed. Some of the cleavage steps consist of {111} or {001} planes, but others are not distinctly crystallographic. Plastic deformation involving dislocation motion or twinning may have occurred at these steps. Reactions among different types of steps are also observed. One type of cleavage pattern found is strikingly similar to the typical appearance of fracture surfaces of fcc or fcc related materials after stress corrosion cracking. However, this particular pattern is only rarely observed in Al3Sc and can therefore not be taken as evidence for stress corrosion cracking in this material. Our observations indicate that an interpretation of cleavage fracture in Al3Sc in terms of surface energies alone is unlikely to be successful. Similarly, any criterion that categorizes its fracture behavior into either fully brittle or fully ductile is faced with difficulties. A full understanding of the fracture morphology of Al3Sc will therefore require detailed atomistic simulations.

An equilibrium precipitation of Al2Ti is shown to occur within a Cu-modified Al2Ti alloy having the L12 structure. This precipitation is analyzed by conventional and high resolution electron microscopy and some insights are given concerning the mechanisms of nucleation and growth of Al2Ti within the L12 matrix. In the meantime, Vickers microhardness tests have been performed as a first approach to the mechanical behavior of this alloy and the results are compared to measurements obtained in an actual single-phased L12 compound. The Al2Ti precipitation seems to have an important hardening effect.

Relationships between embedded-atom method parameters and the energies of fcc-hcp stability and intrinsic and extrinsic fcc stacking-faults were studied for Cu, Ag, Au, Ni, Pd, and Pt. It was found that the relative magnitudes of these energies for different metals are determined primarily by the physical input data and are almost independent of the cutoff distance and the functions used in the model. These energies increase with increasing vacancy formation energy, decrease with increasing atomic volume and shear modulus, and are almost independent of variations in the cohesive energy and the bulk modulus. However, the shape of the energy versus cutoff distance curve is almost the same for all six metals and is determined primarily by the cutoff distance and the functions used in the model. The shape for a given model is almost independent of the physical input parameters used for fitting to specific metals, can yield either positive or negative values (determined primarily by the cutoff distance), and is similar for all three energies.

Nonequilibrium titanium-nitride alloy powders have been fabricated by a high energetic ball mill under nitrogen gas flow at room temperature and characterized by means of x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and differential scanning calorimetry. Initial hcp titanium is completely transformed to nonequilibrium-fcc Ti–N after 720 ks of the milling time. The fcc Ti–N phase is stable at relatively low temperature and transforms at 855 K to Ti2N and δ phases. At the final stage of milling, the particle- and grain-sizes of alloy powders are 1 mm and 5 nm, respectively, and the lattice parameter is 0.419 nm.

Using elemental powders, combustion reaction was carried out to form intermetallic-ceramic composites in the Ti–Al–N system. Ti and Al powders reacted exothermically in gaseous nitrogen and formed a mixture product which had a fine distribution of the Ti2AlN particles in the matrix TiAl with a small amount of Ti3Al. Subsequently, these reacted products were arc-melted to obtain fully dense button ingots. The resulting composites had about 30 vol. % Ti2AlN, and the Ti2AlN particles were ellipsoidal or columnar in shape with sizes of 2–10 μm and appeared to be homogeneously distributed and well bonded to the matrix TiAl. It was found that such composite materials have a high strength at both room and elevated temperatures and some intrinsic compressive ductility at room temperature. Therefore, the processing technique in the present investigation is of interest as a new combustion reaction process to make intermetallic-based composite materials.

Epitaxial TiN/NbN superlattices with wavelengths/ranging from 1.6 to 450 nm have been grown by reactive magnetron sputtering on MgO(100). Cross-sectional transmission electron microscopy (XTEM) studies showed well-defined superlattice layers. Voided low-angle boundaries, aligned perpendicular to the film plane, were also present. High-resolution images showed misfit dislocations for Λ = 9.4 nm, but not Λ = 4.6 nm. Up to ninth-order superlattice reflections were observed in diffraction, indicating that the interfaces were relatively sharp. Analysis of the first-order x-ray superlattice reflection intensities indicated that the composition modulation amplitude increased and the coherency strains decreased for Λ increased from 2 to 10 nm. Vickers microhardness H was found to increase rapidly with increasing Λ, from 1700 kg/mm2 for a TiN–NbN alloy (i.e., Λ = 0) to a maximum of 4900 kg/mm2 at Λ = 4.6 nm. H decreased gradually for further increases in Λ above 4.6 nm, to H = 2500 kg/mm2 at Λ = 450 nm. The hardness results are compared with theories for strengthening of multilayers.