C60 films were deposited on a variety of substrates by thermal evaporation. The presence of C60 in the films was confirmed by Transmission Electron Microscopy and Raman spectroscopic analysis. The C60 films exhibited an average friction coefficient of 0.4–0.5. The films were irradiated with 2 MeV Ag+ and B+ ions at various doses. High energy ion bombardment created damage that resulted in partly crystalline to amorphous films, dependent on the mass and dose of ions. The amorphous films showed a friction coefficient of <0.1. Partly crystalline films showed a friction coefficient at the same level as that of unirradiated films.

In order to overcome the difficulty of nucleation of diamond particles on unscratched substrates by the chemical vapor deposition (CVD) method, carbon fibers are introduced on unscratched substrates as a nucleation site of diamond particles. With assistance of carbon fibers, diamond particles can be synthesized on unscratched silicon substrate from a gas mixture of methane and hydrogen by the hot-filament CVD method. From SEM observations, nucleation of diamond particles has been confirmed on fibers at the beginning of deposition. Fine particles have formed initially on the rugged surface of fibers, and then they grow up to be diamond particles. Detailed SEM observations reveal nucleation has occurred on irregular surfaces such as boundaries on carbon fibers. We propose that nucleation of diamond particles can be controlled by arranging carbon fibers on the substrate without applying any mechanical pretreatment.

Mo(NBut)2(NHBu1)2 is used as a single-source precursor to deposit thin films of cubic phase molybdenum carbonitride, MoCxNy (x: 0.2-0.55, y: 0.1-0.47), by chemical vapor deposition on silicon substrates. In general, the C/Mo ratios increased from 0.2 to 0.55 and the N/Mo ratios decreased from 0.47 to 0.1 with increasing the temperature of deposition from 773 to 923 K. Based on the elemental composition and the composition of the gas phase products, it is proposed that the carbon atoms were incorporated through β-methyl activation of the ligands.

The a-axis oriented YBa2Cu3Ox (YBCO) films were epitaxially grown on (100) SrTiO3 substrate by dc-100 MHz hybrid plasma sputtering. The films prepared at different temperatures with and without in situ annealing had different superconductivity, which was improved with the degradation of the crystallinity of the films. The Raman spectra for the films were very similar to each other and to that expected for YBa2Cu3O7, in spite of the different superconductivity. This indicates the importance of the symmetry of the Cu–O chains rather than the oxygen content for the superconductivity. In Rutherford backscattering measurements using a 3.05 MeV He2+ ion beam, an increase of dechanneling due to the barium atoms along the film depth was clearly observed only for the most improved superconducting film. This result suggests that the relief of the strain contained in the film is also important for improving the superconductivity in the case of a-axis oriented YBCO films.

Formation and coarsening behavior of the Y2BaCuO5 (211) phase has been examined in samples produced by peritectic decomposition of pure YBa2Cu3O7−x (123), resulting in 211 crystals and the liquid phase [BaCuO2-CuO]. Through various temperature (1020 °C-1060 °C) and time (0.25 h-10 h) studies, the fundamental coarsening behavior was determined. At 1040 °C, 211 crystals coarsen significantly over a 10 h period. The acicular crystals can be modeled by the diffusional ripening law, r–r0 = (Kt)1/3, where r=V1/3. However, the log-normal distributions of the lengths, widths, and volumes for each coarsening run are much wider than general ripening theory would predict. Results from coarsening studies at 1020 °C and 1060 °C for 3 h reveal that the 211 crystal volume increases with increasing superheat. Prior coarsening of the 123 grain size yields much larger 211 particles, suggesting that the 211 crystals must nucleate at the 123 grain boundaries during peritectic decomposition, and this nucleation governs the size of the 211 crystals for short coarsening times. Addition of properitectic 211 (15 mole %) to pure 123 before peritectic decomposition strongly influences the particle habit of the resulting 211 crystals. Without any additions, acicular or needle-like 211 crystals result from the melting of 123. However, when equiaxed properitectic 211 is added to the 123, the resulting 211 is faceted, but still equiaxed. If acicular 211 is added to the starting composition, the resulting 211 is needle shaped. These results will be discussed in terms of 123 melt-texturing and directional solidification processing.

A review and some case studies on the interatomic distances of candidate substrates in comparison to the high Tc superconductor (HTSC) phase YBa2Cu3O7−δ (YBCO) is presented, in an attempt to enhance the basis for substrate selection for YBCO film epitaxy. This preliminary study was carried out by examining a variety of interatomic distances in the structure rather than merely matching the lattice parameters. Interatomic structure matching planes of selected YBCO orientations in contact with substrates were identified. The surface termination of the substrate was found to be a crucial parameter in determining the oriented or epitaxial growth. Possible composition dependence of the orientation of the films at the nucleation stage was also anticipated depending on the comparison. Several currently most commonly used substrates are discussed in some detail.

YBa2Cu3Ox ceramic superconductors were levitated, laser-beam melted, and undercooled in pure oxygen, dry air, and pure argon atmospheres. Solidified material from this containerless melting was examined by electron microscopy and x-ray diffraction analysis. The solubility of yttrium oxide in the melt was found to depend on ambient oxygen pressure such that complete dissolution was readily achieved in argon, but not in oxygen. The material formed in argon could be deeply undercooled and resolidified to produce a fine-grained and chemically homogeneous material. Use of ambient oxygen pressure to control the product morphology is discussed.

The temperatures and pathways of crystallization for amorphous Bi–Sr–Ca–Cu–O are strongly dependent on oxygen partial pressure (Po2), the oxidation state of the glass, and the presence of Ag. Reducing the Po2 from 1 to 0 bar lowers the onset of melting 100 °C, but does not change the onset of crystallization. Decreasing Po2 does inhibit the formation of (CaSr)CuO3 (011). Although Ag appears to be immiscible in Bi–Sr–Ca–Cu–O, finely distributed Ag lowers the onset of melting by 20 to 35 °C, depending on Po2. In oxygen-deficient glass, two exotherms are observed upon heating. The first exotherm at 460 °C is independent of Po2, and Ag and corresponds with the formation of Bi2Sr2CuO6 (Bi-2201). The second exotherm occurs at 486 °C with Ag or 500 °C without Ag. The onset temperature of the second exotherm does not change with Po2, but the exotherm decreases in intensity with decreasing Po2. EXAFS indicates that in the as-quenched amorphous material, Cu is in a reduced state. Annealing the amorphous material in oxygen below the first exotherm (i.e., glass relaxation) increases the oxidation state of the Cu to that necessary for the formation of the Bi2Sr2CaCu2O8 (Bi-2212) without additional oxygen diffusion. This relaxation of the glass increases the crystallization temperature of the Bi-2201 to 500 °C. The crystallization sequence of Bi-2201 to Bi-2212 occurs at all Po2 ≥ 0.1 bar, but the composition of the secondary phases changes in the unrelaxed glass. Relaxing the glass eliminates liquid formation at low temperatures, allowing for rapid formation of the Bi-2212 phase with minimal formation of secondary phases for 0.1 ⋚ Po2 ⋚ 0.2 bar.

A method to synthesize high density Tl2Ba2Ca2Cu3O10−δ bulk superconductor with uniformity from presintered powder of the 2223 phase material was developed. With a proper annealing process, the transport critical current density and the material density of such a synthesized superconductor are much improved over those of the starting material. The critical temperature and phase purity of this material are also enhanced. In this paper, we report our systematic study on some basic parameters of this material, including the normal state resistivity, Tc, Jc, phase purity, and morphology produced under different annealing conditions. An optimum preparation technique is then derived.

A high resolution transmission electron microscopy study of multilayer films prepared by magnetron sputtering shows that the morphology of the growing interface in a-Si/Nb and a-SiN/NbN multilayers is remarkably uniform and smooth; this is in contrast to the polycrystalline AlN/NbN multilayers grown under similar conditions, which exhibit columnar grain structure with rough interfaces. For proper sputtering parameters, the amorphous layers seem to periodically restore a relatively smooth initial interface condition for the successive Nb (or NbN) layer growth, consequently interrupting the tendency toward increased roughness due to mechanisms such as columnar growth. Artificial multilayers having very flat interfaces could stimulate applications based on multilayer Josephson junctions.

Metastable k–Al2O3 often occurs as islands in thin α–Al2O3 coatings produced by CVD. In this investigation a thick single-phased K–Al2O3 coating was produced in order to determine the mechanical properties of the K-phase. As a comparison, a CVD coating as well as a sintered bulk specimen of α–Al2O3 were studied. The mechanical behavior was probed by a depth-sensing indentation (nanoindentation) system on polished taper and cross sections at several applied loads. Hardness and elastic modulus were derived and are discussed in conjunction with the crystal structure and the microstructure of the two materials. K–Al2O3 shows a marked microstructural and structural anisotropy, which is also reflected in anisotropic mechanical properties. Parallel to the c-axis, which, in this study, closely coincided with the growth direction, both the hardness and the elastic modulus are significantly higher than in the perpendicular direction. α–Al2O3 has the same hardness and elastic modulus in the coating and in the bulk form and shows no clear anisotropy in microstructure. If the two alumina materials are compared, K–Al2O3 is significantly harder than α–Al2O3 in the growth direction (on the taper section), whereas it is significantly softer in the perpendicular direction. In either of the loading directions, the elastic modulus of K–Al2O3 is significantly lower than in α–Al2O3.

The effects of loading and unloading rate on fracture features formed during sharp indentation of polycrystalline Al2O3 have been studied. It was found that there is a transition between intergranular and transgranular fracture if the loading rate is increased by a factor of 104 during the whole indentation cycle. By varying the loading or unloading rate during indentation, and correlating the corresponding dependence of fracture features, the part of the indentation cycle can be identified in which specific segments of cracks are generated. Hence, the fracture sequence during indentation is established. The fracture sequence for polycrystalline Al2O3 is compared with those reported from direct observation in optically transparent materials such as soda-lime glass and various single crystal ceramics.

Studies of the reactive melt infiltration of silicon-niobium alloys in microporous carbon preforms prepared by the pyrolysis of a polymer precursor have been carried out using modeling, DTA, and melt infiltration. Mercury porosimetry results indicate a very narrow pore size distribution with virtually all the porosity within the carbon preforms open to infiltrants. The morphology and amount of the residual phases (niobium disilicide and silicon) in the infiltrated material can be tailored according to requirements by careful control of the properties (pore size and pore volume) of the porous carbon preforms and alloy composition. The average room temperature four-point fiexural strength of a reaction-formed silicon carbide material (made by the infiltration of medium pore size carbon preform with Si–5 at. % Nb alloy) is 290 ± 40 MPa (42 ± 6 ksi) and the fracture toughness is 3.7 ± 0.3 . The fiexural strength decreases at high temperatures due to relaxation of residual thermal stresses and the presence of free silicon in the material.

Porous α-alumina ceramics were prepared using the spray-pyrolyzed powder from aluminum nitrate solution and aluminum sulfate solution. Porosity and pore size distribution of the samples were examined with respect to the forming pressure and firing temperature. The porosity obtained changed from around 80% in the green compacts to 60–70% in the fired bodies fired at 1500 °C. The porosity of 30–40% remained even by firing at 1700 °C. Although there was no significant difference in the porosity of the fired bodies prepared from the sulfate and nitrate solutions, the fired bodies prepared from the nitrate solution showed apparently larger pore size than those from the sulfate solution. Fired bodies with an average pore radius from 0.2 to 0.8 μm can be prepared by this method. The four-point bending strength of the fired bodies, which had a porosity of 57% and an average pore radius of 0.23 μm, was 35 MPa.

27Al MAS nmr spectra from alkoxide-derived Al2O3-BaO-CaO-TiO2-ZrO2 Synroc precursors were studied after isochronal annealing in air for 1 h at temperatures between 200 and 1300 °C. At temperatures below 1000 °C, some tetrahedral and a trace of 5-coordinated Al were observed together with a majority of octahedral Al. The amount of nonoctahedral Al reached a maximum at 400–700 °C, beyond which it diminished and disappeared; essentially, complete conversion to octahedral Al took place on full crystallization at 1200–1300 °C, with the Al being contained in barium hollandite and minor α-alumina. The hollandite nmr signal was absent in Synroc which was hot-pressed at 1200 °C/20 MPa, presumably because of coincorporation of paramagnetic Ti3+ in the hollandite phase, but a signal from α-alumina was observed. Samples containing simulated waste fission products gave results similar to their waste-free counterparts when calcined at 750 °C in 3.5% H2/N2 and when hot-pressed.

Synthesis of zirconium tetramethylheptanedione [Zr(thd)4] was optimized. Purity of Zr(thd)4 was confirmed by melting point determination, carbon, and hydrogen elemental analysis and proton nuclear magnetic resonance spectrometer (NMR). By using Zr(thd)4, excellent quality ZrO2 thin films were successfully deposited on single-crystal silicon wafers by metal-organic chemical vapor deposition (MOCVD) at reduced pressures. For substrate temperatures below 530 °C, the film deposition rates were very small (⋚1 nm/min). The film deposition rates were significantly affected by (i) source temperature, (ii) substrate temperature, and (iii) total pressure. As-deposited films are carbon free. Furthermore, only the tetragonal ZrO2 phase was identified in as-deposited films. The tetragonal phase transformed progressively into the monoclinic phase as the films were subjected to a high-temperature post-deposition annealing. The optical properties of the ZrO2 thin films as a function of wavelength, in the range of 200 nm to 2000 nm, were also reported. In addition, a simplified theoretical model which considers only a surface reaction was used to analyze the deposition of ZrO2 films. The model predicated the deposition rates well for various conditions in the hot wall reactor.

The pyrochlore to perovskite transition in sputtered PZT thin films has been studied using SEM and XRD. The films were annealed in the temperature range between 350 °C and 750 °C, and the transition temperature for pyrochlore to perovskite transition was found to be around 525 °C. Isothermal annealing was used to study the nucleation and growth kinetics of the perovskite phase. The results showed a linear growth rate for the perovskite phase, thereby indicating an interface controlled process. Also, the growth was found to be isotropic in two dimensions parallel to the plane of the substrate. The nucleation of the perovskite phase was found to be random. The effective activation energy of the perovskite transition was found to be 494 kJ/mol using Avrami's approach.

A novel testing technique has been developed capable of measuring the interfacial fracture resistance, Γi, of thin ductile films on substrates. In this technique, the thin film on the substrate is stressed by depositing onto the film a second superlayer of material, having a large intrinsic stress, such as Cr. Subsequent processing defines a precrack at the interface between the film and the substrate. The strain energy available for driving the debond crack is modulated by varying the thickness of the Cr superlayer. Spontaneous decohesion occurs for superlayers exceeding a critical thickness. The latter is used to obtain Γi from elasticity solutions for residually stressed thin films. The technique has been demonstrated for Cu thin films on silica substrates.

The effects of boron additions (0 to 4000 wppm B) on the room temperature deformation behavior of Ni-24Al have been examined with both quasi-static deformation and short pulse duration shock loading. Changes in compressive yield strength and hardness with the amount of boron suggest that strengthening effects are more complicated than predicted by usual interstitial solid-solution strengthening considerations. The nature of the dislocations changes from SISF-dissociated superdislocations in the Ni-24Al base alloy to APB-dissociated dislocations with the additions of small amounts of boron. Therefore, the observed variation in strength with boron additions reflects a solid-solution strengthening contribution from the interstitial boron coupled with a “softening” effect arising from the greater mobility of the APB-bounding partials relative to the SISF-bounding partials. It is suggested that this “softening” is a necessary prerequisite for enhanced ductility in Ni3Al. In addition, the grain boundary fracture strength must be increased by boron additions. While this may occur through an increased grain boundary cohesive strength due to boron segregation, it is also expected that the interaction of the dislocations with the grain boundaries will be significantly altered as the nature of the dislocations changes. The lack of a “boron effect” in Ni-25Al, the so-called stoichiometric effect, can be attributed to a diminished “softening”, combined with the rapid solid-solution strengthening observed in this alloy.

Site preference and the effects of ternary additions (Mn, V, etc.) on the twin energy in γ-TiAl were studied by means of all-electron total energy self-consistent calculations based on the local density approximation. The results show that when Mn, Ti, or V substitute on the Al-sites in γ-TiAl, the twin energy is about 20–25% lower than that of stoichiometric γ-TiAl; this may explain observations of increased twinning activity in 48% Al TiAl. By contrast, when ternary additions of V (or Al) occupy Ti-sites, the twin energy has nearly the same value as that of pure γ-TiAl, which is consistent with the observation of only a few twins for Al-rich compositions. By comparing the total energy of Ti6(XAl5) and (Ti5X)Al6 supercells, it is found that the relative stability of Ti6(XAl5) over (Ti5X)Al6 (i.e., the preference for occupying Al-sites) is increased in going from Nb, V, Cr, and Ti to Mn, in agreement with observation that excess Ti occupies Al-sites, and Nb preferentially substitutes on the Ti-sites. The results indicate that Mn preferentially substitutes on the Al-sites, and V (or Cr) may occupy both Ti- and Al-sites.