The equilibrium decomposition temperatures of Cu2Ln2O5 (Ln = Tb, Dy, Ho, Er, Tm, Yb, and Lu) compounds have been measured using a combined DTA-TGA apparatus under a flowing Ar + O2 gas mixture, in which the partial pressure of oxygen was controlled at 5.0 × 103 Pa. The Cu2Ln2O5 compounds yield Ln2O3 and Cu2O on decomposition. The decomposition temperature increases monotonically with the atomic number of the lanthanide element. This suggests that the stability of the Cu2Ln2O5 compounds with respect to the component binary oxides increases with decreasing radius of the Ln3+ ion.

Nanoindentation studies of sublimed fullerene films have been conducted using an atomic force microscope (AFM). Transfer of fullerene molecules from the as-deposited films to the AFM tip was observed during the indentation of AFM tip into some of the samples, whereas such a transfer was not observed for ion-bombarded films. The fullerene molecules transferred to the AFM tip were subsequently transported to a diamond surface when the diamond sample was scanned with the contaminated tip. This demonstrates the capability of material manipulation on a molecular scale using AFM. Atomic-scale friction of the fullerene films was measured to be low. Ability of fullerene films to form transfer film on the mating AFM tip surface may be partly responsible for low friction.

The partial molar entropy of solution of oxygen in YBa2Cu3Ox, δsO, has been computed using equilibrium data and the recently measured partial molar enthalpy of oxygen. While δhO is independent of oxygen content (6 < x < 7), δsO depends on x. The po2, T location of phase equilibrium between the 123 and 124 superconducting phases is calculated. The standard free energies of interactions of the superconducting phases with carbon dioxide (CO2) and water vapor (H2O) have been assessed. The free energies of carbonation of the fully oxidized 123 and 124 phases are −323 ± 22 kJ mol−1 and −291 ± 32 kJ mol−1, respectively. The free energies of hydration of the 123 and 124 are −397 ± 22 kJ mol−1 and −469 ± 32 kJ mol−1, respectively. These large exothermic values show that degradation of these superconductors at ambient conditions is thermodynamically favorable.

This article addresses issues associated with in situ growth of superconducting YBa2Cu3O7−δ thin films by ion beam sputtering. High oxygen partial pressure during ion beam deposition can cause significant beam broadening and oxidation of filaments and grids. Also, many of the targets used for processing YBCO are unstable when sputtered in a high oxygen partial pressure. It is shown that ion beam sputtering can produce YBCO films of comparable quality to those produced by laser ablation or dc magnetron sputtering. Typical film properties are Tco = 91 K and Jc (77 K) = 106 A cm−2. It appears that the oxygen gas pressure during the postdeposition cooldown has a more important influence on film properties than the oxygen partial pressure during deposition.

Rare earth additions of 3 wt. % were added to the Zn−27% Al−2% Cu−0.02% Mg alloy, known as ZA-27. The as-cast microstructure of this alloy consisted of two phases of supersaturated face-centered cubic β′s and α′s together with a hexagonal close-packed rare-earth-containing zinc-rich phase termed E phase. The phase transformations in this alloy after aging at 100 °C and 200 °C were determined. The E phase was determined to have the lattice parameters a0 = 9.0348 Å and c0 = 13.2194 Å, giving c0/a0 = 1.4632. The chemical formula of the E phase was determined to be RE1Zn10.9Cu0.8. The addition of 3% rare earths into ZA-27 delayed the phase transformations of this alloy. This was caused by an increase in the aluminum content of the supersaturated β′s phase.

We present computer simulation results for the planar faults involved in core spreading of 〈100〉 and 〈111〉 dislocations. Seven γ surfaces were computed for different crystallographic planes ({110}, {112}, {123}, {210}, {100}, {111}, and {122}). Stable APB's are observed in the {110} and {112} planes, but they are deviated from the exact 1/2a〈111〉 position. No other stable planar fault was observed. The fact that a stable minimum is observed deviated from the 1/2〈111〉 position suggests the possibility of different dissociation reactions for the 〈111〉 screw dislocation in the {110} and {112} planes. The fact that no other stable minima were observed in the γ surfaces indicates that no true core dissociation is expected for the 〈100〉 dislocations. We propose that dislocation core spreading in various planes can be understood in terms of the directions of lowest restoring forces observed for the corresponding γ surfaces.

Nanocrystalline FeTi has been prepared in two ways: by ball milling the intermetallic compound and mechanically alloying a mixture of the elemental powders. The materials obtained in each case are identical. The reaction proceeds via the formation of interfacial β–Ti(Fe) which then grows to include all of the material present. Oxygen levels above 3 at. % suppress this reaction and lead to the formation of amorphous Fe–Ti.

The results of high-temperature compressive deformation tests on a two-phase alloy consisting of Cr2Nb, a C15 Laves phase, and a soft Nb-based solid solution, are presented along with measurements of oxidation kinetics at 1273 K in air. These alloys are deformable only at temperatures above 1273 K. The measured 0.2% yield stress decreases steadily with increasing temperature and is only slightly sensitive to alloy composition. The steady state flow stress decreases steadily with increasing temperature and depends on alloy composition. A constitutive equation was fitted to the experimental data with a composition-independent stress exponent of about 2.7 and an apparent activation energy which ranges between 477 and 391 kJ/mol, also depending on alloy composition. Microstructural examination shows that cracking (cavitation) and interfacial sliding between the two constituent phases, in addition to bulk deformation of the constituent phases, are responsible for the deformation. The oxidation resistance of these alloys is very good.

The present work has examined the effect of pulsed excimer laser irradiation (λ = 308 nm, τ = 26 ns, E = 100 mJ/pulse, N = 1, 5, 10 laser pulses/spot, repetition rate 1 Hz) on the magnetic anisotropy of Fe81B13.5Si3.5C2, Fe78B13Si9, Fe40Ni38Mo4B18, and Fe40Ni40P14B6 metallic glasses. The transmission Mössbauer spectra yielded the intensity ratio R21 of the second to the first line as a function of the number of applied laser pulses. On these grounds, it was found that in the higher magnetostriction samples, controlled changes in the magnetic anisotropy could be induced without onset of bulk crystallization; in the lower magnetostriction samples, a random distribution of the magnetic moment directions was obtained. The conversion electron Mössbauer spectra were characteristic of the amorphous state but showed the same texture as the nonirradiated samples. SEM examinations of the laser-treated surfaces revealed the presence of molten zones subsequently solidified. It is suggested that the correspondingly induced stresses may account for the observed changes in the bulk magnetization orientation, and the model of closure domain structure is supported.

The interaction of molecular oxygen with thin C60 films was investigated using the 3.04 MeV resonance in the 16O(α, α)16O elastic scattering reaction to measure the concentration profile of oxygen in the fullerene films. A thin (d ≍ 20 nm) layer containing oxygen was observed on the surface of C60 films (d ≍ 200 nm) exposed to ∼1 atm of O2 for 1 h in the absence of light. In contrast, oxygen was uniformly distributed throughout the entire film when samples were irradiated for 1 h with either a 488 nm Ar ion laser or Xe lamp in the presence of ∼1 atm of O2. This O2 uptake was found to be both power dependent and reversible.

Nanophase diamond films can be grown at room temperature with a laser plasma discharge source without the use of any catalyst. This technique produces films that adhere readily to materials for which there are important applications as protective coatings. Described here is a study of the bonding and properties realized with the direct deposition of nanophase diamond on the II-VI compound of zinc sulfide. It was shown that adhesion and mechanical properties of the films can be correlated with the amounts of defects and impurities in the zinc sulfide substrates. In all cases significant interfacial layers caused by the deep penetration of carbon atoms into the substrates were observed. Resistance to wear was estimated with a modified sand blaster, and results indicated that only 1 μm coating of nanophase diamond can increase lifetimes of the zinc sulfide samples by a factor better than 5. Protection afforded by the nanophase diamond under harsh environmental conditions of rain impacts was also described.

Carbon aerogels are synthesized via the aqueous polycondensation of resorcinol with formaldehyde, followed by supercritical drying and subsequent pyrolysis at 1050 °C. As a result of their interconnected porosity, ultrafine cell/pore size, and high surface area, carbon aerogels have many potential applications such as supercapacitors, battery electrodes, catalyst supports, and gas filters. The performance of carbon aerogels in the latter two applications depends on the permeability or gas flow conductance in these materials. By measuring the pressure differential across a thin specimen and the nitrogen gas flow rate in the viscous regime, the permeability of carbon aerogels was calculated from equations based upon Darcy's law. Our measurements show that carbon aerogels have permeabilities on the order of 10−12 to 10−10 cm2 over the density range from 0.05–0.44 g/cm3. Like many other aerogel properties, the permeability of carbon aerogels follows a power law relationship with density, reflecting differences in the average mesopore size. Comparing the results from this study with the permeability of silica aerogels reported by other workers, we found that the permeability of aerogels is governed by a simple universal flow equation. This paper discusses the relationship among permeability, pore size, and density in carbon aerogels.

Optically generated thermal waves have been used to measure the thermal diffusivity of a unidirectional carbon fiber reinforced composite plate (CFRC) both parallel and perpendicular to the fiber direction. The optically generated thermal waves have been used in combination with a noncontact optical detection technique. The diffusivity perpendicular to the fiber direction can also be determined by attaching a pyroelectric detector to the back of the sample. The value obtained this way agrees well with the results from the optical detection technique. An anisotropy factor of about 18 has been measured for a unidirectional CFRC, which agrees well with literature values obtained with completely different techniques.

The formation of ultrathin (≤20 nm) and smooth CoSi2 layers on c–Si substrates has been studied by using a one- and a two-step RTP silicidation method. Pinhole-free silicide layers with a thickness down to ∼10–12 nm were formed on n−, n+, and p+ crystalline Si substrates in the one-step RTP process by sputtering of Co films as thin as 4 nm and subsequent silicidation at 750 °C for 5 or 30 s. The two-step RTP silicidation method is based on the consumption of only a small fraction of a thick sputtered Co film to form Co2Si or CoSi during a first RTP step at 400–500 °C. A selective etch follows to remove the unreacted Co film. During a second, higher temperature, RTP step CoSi2 is formed. Pinhole-free and smooth CoSi2 films with a thickness down to 20 nm were formed in this way on both n+ and p+ monocrystalline Si substrates.

Low-temperature photoluminescence measurements have been taken to monitor the changes in the properties of strained GaAs/InGaAs/GaAs quantum wells grown by molecular beam epitaxy at different substrate (well) temperatures with and without a 90 s-growth-interruption at the heterointerfaces. Sharp exciton peaks with average linewidths as low as 1.7 meV were observed in all the spectra. The spectra from the samples grown employing interrupts were narrower than those without interrupts, indicating structurally improved interfaces. Further linewidth narrowing was also seen in samples employing an additional interrupt of the same duration at the bottom InGaAs/GaAs interface, or by increasing the interrupt time at the top GaAs/InGaAs interface to 180 s. A consistent reduction in the linewidth was also observed in wells grown at higher temperatures. This is most likely due to greater indium re-evaporation leading to a reduction in strain, well width, and interface fluctuations.

Differential scanning calorimetry (DSC) demonstrates that compounds in the pseudobinary system Ag2S–Ag2Se undergo rapid, reversible solid-state phase changes at temperatures between approximately 70 and 178 °C. These temperatures vary systematically with composition, with highs at the pure end members, Ag2S (178 °C) and Ag2Se (134 °C), and a low in the compositional range of approximately Ag2S0.4Se0.6 to Ag2S0.3Se0.7 (70 °C). These data are consistent with the presence of two solid solutions in this system at ambient conditions: the Ag2S–III-type, monoclinic, ranging to approximately Ag2S0.4Se0.6 and the Ag2Se-II-type, orthorhombic, extending from Ag2Se to Ag2S0.3Se0.7. Entropies of transition of 6 to 9 e.u. characterize compositions within the Ag2S-III-type solid solution, whereas values of 13 to 16 e.u. mark members of the Ag2Se-II-type solid solution. The high-temperature allotrope is presumably a continuous solid solution between Ag2S-II and Ag2Se-I, which have similar body-centered cubic structures.

Films of Sb : SnO2 have been formed by vacuum e-beam evaporation. The structural, electrical, and optical properties of these films have been investigated with respect to annealing time and temperature. After heat treatment in an oxygen atmosphere, thin films with a peak transmittance of 98% and 4–9 × 10−3 Ωcm resistivity have been obtained. The barrier heights and energy band diagrams of Sb : SnO2/Si n-n and p-n heterojunctions have been determined by C-V measurements.

In2O3–SnO2 films were produced by thermal decomposition of a deposit which was dip coated on borosilicate glass substrates from an acetylacetone solution of indium and tin acetoacetonate. Thermal analysis showed complete pyrolysis of the organics by 400 °C. The thermal decomposition reaction generated acetylacetone gas and was found to be first order with an activation energy of 13.6 Kcal/mole. Differences in thermal decomposition between the film and bulk materials were noted. As measured by differential scanning calorimetry using a 40 °C/min temperature ramp, the glass transition temperature of the deposited oxide film was found to be ∼462 °C, and the film crystallization temperature was found to be ∼518 °C. For film fabrication, thermal decomposition of the films was performed at 500 °C in air for 1 h followed by reduction for various times at 500 °C in a reducing atmosphere. Crystalline films resulted for these conditions. A resistivity of ∼1.01 × 10−3 Ω · cm, at 8 wt. % tin oxide with a transparency of ∼95% at 400 nm, has been achieved for a 273 nm thick film.

Cryptomelane-type manganic acid (CMA), H2Mn8O16 · 2.4H2O, with a theoretical cation exchange capacity of 2.70 meq/g, was prepared and its cation exchange properties were studied as a function of XM which is defined by the ratio of uptake in meq/g to the theoretical capacity. Plots of the corrected selectivity coefficients log KHM vs the fractional exchange M for alkali metal ions on a 2 × 2 type tunnel-structured manganic acid showed a gradual decrease in small XMM regions and a steep decrease in large XMM) were 0.92 for Li+, 0.74 for Na+ and K+, 0.67 for Rb+, and 0.44 for Cs+. These maximums have been attributed to steric limitation as well as a limit on the expansion of the crystal lattice. Some x-ray diffraction (XRD) data of alkali cation exchanged forms were in good agreement with the XRD data of synthetic alkali CMA phases as given in the cards by the Joint Committee on Powder Diffraction Standards (JCPDS). The lattice parameter a0 has been found to depend on the exchanged amounts and the nature of the cations involved, while the c0 value remained almost the same irrespective of the amount of exchange or the nature of the cations.

Thin alumina films were prepared on stainless steel and glass surfaces by dip coating from an aluminum alkoxide solution. Multiple coatings from a low-viscosity solution were necessary for high quality and sufficient thickness of the films. To determine the bonding mechanism and strength, wavelength dispersive x-ray was used. Aluminum was found to diffuse into the substrate in both cases. The possible bonding mechanism is a combination of diffusion and the formation of chemical compound between the alumina and the substrates. The surface properties of stainless steel, such as microhardness, electric resistance, and corrosion resistance, were substantially improved when coated with alumina.