We report the formation of a novel solid form of carbon + oxygen. Exposure of C60 to high oxygen pressure [P(O2) ≍ 100 MPa] for several days at slightly above ambient temperature results in absorption of significant amounts of oxygen (up to ∼48% by weight after 3 days). X-ray diffraction measurements showed that the C60 pellets had become amorphous. Although part of the added weight is slowly lost in flowing oxygen at ambient pressure and temperature, most remains up to at least 100 °C. Heating in flowing He at 200 °C brought the weight back to near the original value. The reaction appears to be specific to C60 since the amorphous outgassed material had lost the capacity to absorb oxygen at high P(O2), and the oxygen absorption effect was absent in powdered graphite and in commercial amorphous carbon. The Raman spectrum differs from those of C60, soot, amorphous carbon, graphite, and diamond.

C60 films simultaneously exposed at T = 300 K to oxygen and visible-ultraviolet light are found to exhibit rapid diffusion of oxygen into the deep bulk of the film. The diffusion rate is found to be ∼10 times faster in the presence of light. Vibrational and optical absorption spectroscopy indicate that the photoassisted reaction of O2 with solid C60 involves two coupled reactions: (i) the photoassisted diffusion of molecular oxygen into solid C60 and (ii) oxidation of C60.

We have carried out Electron Spin Resonance (ESR) measurements on activated carbon fibers (ACF) with specific surface areas (SSA) of 3000 and 2000 m2/g. The ESR spectrum of ACF fibers in air is extremely broad (500 to 1000 Gauss), and the spin susceptibility decreases rapidly with decreasing specific surface area. Also measured was the ESR signal of the desorbed fibers in vacuum. As a result of desorption, the broad peak decreases slightly in intensity, and a narrow (≍65 Gauss at room temperature) peak appears. We report results on the temperature dependence of both peaks. The narrow peak is interpreted as due to spins associated with dangling bonds, whereas we attribute the broad peak to the conduction carrier spins which is broadened by the boundary scattering process (T1 contribution) and the dipolar broadening process (T2 contribution) associated with the dangling bond spins.

Isotherms (at 300 K and 328 K) and isobars (in the range 300 to 400 K) of n-pentane intercalation in CsC24 and CsC36 were established. With CsC24, three plateaus were identified at 0.52, 0.7, and 1.0 n-pentane/24 C, whereas only two plateaus at 0.8 and 0.97 n-pentane/36 C were found with CsC36. The progress of the reaction between n-pentane and CsC24, CsC36, and CsC56 (stage 2 to 4) was monitored by real-time neutron diffraction. The intercalation of n-pentane in CsC24 results in the simultaneous formation of a second stage ternary and a first stage binary “CsC8”, whereas, from the third stage CsC36 or the fourth stage CsC56, only pure second stage or third stage ternary compounds are formed, respectively. Owing to the formation of binary domains rich in alkali metal (CsC8) or to stage lowering produced by the ternarization, the in-plane cesium density is smaller in the ternary layer than in the starting binary. The electrostatic repulsion between the cesium ions, provoked by the sorption of n-pentane, is believed to be at the origin of the increased coverage. During the intercalation or de-intercalation processes, three-dimensional segregation occurs in each grain. A pleated layer model with canted fronts is presented. It accounts for the various phases present within each grain and for the structural transformations caused by pressure variations. At room temperature, the ternary layer seems to be disordered. The order-disorder transition appearing either by decreasing the temperature or by increasing the n-pentane pressure is correlated to a hindered motion of the intercalated molecules.

The temperature variation of the thermal conductivity, the electrical resistivity, and the thermoelectric power of a graphitized polyimide film have been measured in the temperature range 2 < T < 300 K. The effect of the electrochemical intercalation with FeCl4− ions has also been studied. The thermal conductivity measurements confirm the high degree of graphitization that may be obtained with polyimide films. They show how intercalation increases the structural disorder and how the intercalate substantially contributes to the thermal conductivity at low temperatures. The electrical-resistivity and thermoelectric-power measurements reveal that the density of free carriers is about three times lower in stage-2 FeCl4− solvated intercalation compounds obtained by an electrochemical way than in stage-2 FeCl3 compounds obtained by a classical synthesis method.

In this work, we develop a model describing the diffusion of vacancies and self-interstitials and their recombination during ion implantation. The model includes the effect of the moving surface due to regrowth and the defect generation rate as a function of depth based on Monte Carlo simulations. The results are compared to experimental measurements of the damage-to-dose ratio (DDR) after low energy, 40 eV, silicon ion implantation into silicon at 300 and 685 K. We have derived an analytic approximation which agrees with the results of the computational model, implemented on a CM-2 parallel computer. We find that the calculated effective diffusivity, the main adjustable parameter in the simulations, is much lower than predicted based on extrapolation from experiments at higher temperatures. We attribute this difference to the aggregation of self-interstitials. We also find that the effect of interstitial-vacancy recombination on DDR is negligible under the experimental conditions considered; however, the crystal surface motion has a significant impact on the results.

Monocrystalline AlN(0001) films with few defects were deposited on vicinal α(6H)–SiC(0001) wafers via plasma-assisted, gas-source molecular beam epitaxy within the temperature range of 1050–1200 °C. The Al was thermally evaporated from an effusion cell. An electron cyclotron resonance plasma source was used to produce activated nitrogen species. Growth on vicinal Si(100) at 900–1050 °C resulted in smooth, highly oriented AlN(0001) films.

Effect of surface structures upon ultrathin film interference fringes generated from extremely thin films or epitaxial layers grown on semiconductor wafers has been studied. Since dark regions of fringes correspond to the places where the thin films are destroyed or absent, the fringes are investigated to detect uneven surfaces with undesired structures. Therefore, surface microstructures can be detected and characterized effectively by the modification of the fringes.

The Li2O–B2O3–H2O system has been studied under hydrothermal conditions. Li4B7O12Cl, Li2B4O7, Li3B5O8(OH)2, Li2HBO3, and LiH2B5O9 are the phases crystallizing in this system at 250 °C and P < 100 bars. The growth of these phases has been discussed in brief. Also, the growth morphology of these phases has been studied with reference to the growth parameters.

Two coprecipitation methods were used to synthesize powder precursors of doped lanthanum chromite (La, Ca)(Cr, Co)O3. The effects of synthesis method and calcination temperature on the composition, sintered density, and microstructure of pressed compacts of (La, Ca)(Cr, Co)O3 were studied by differential thermal analysis/thermogravimetric analysis, x-ray diffraction, scanning electron microscopy, and density measurement. The cation ratios in the precipitated solids were, with few exceptions, within experimental error of the desired compositions for all four components. Powders obtained by both techniques could be sintered to densities exceeding 93% at 1400 °C. The highest densities were obtained with calcining temperatures from 450 to 700 °C. The sintered microstructures exhibited uniform grain sizes averaging 3–5 μm. The Cr(vi) compounds, CaCrO4 and La2CrO6, were observed in all of the calcined powders. The possible role of these phases on chromite densification is discussed.

Titanium (iv) oxide (amorphous, brookite, anatase, and rutile) fine particles have been synthesized by pyrolysis of an aerosol. As-received materials are constituted by hollow balloons of around 1–2 μm formed by very small crystalline nuclei, whose crystal size can be modified by annealing. By heating at 900 °C for 48 h individual crystals of around 1 μm are obtained. Intermediate sizes can be controlled as a function of the thermal treatment.

The experimental study of wave attenuation in concrete has been achieved in the case of the propagation of plane waves in concrete rods. Different mortars and concretes have been investigated. A transmitter transducer coupled to one of the ends of the concrete rod generates the propagation of a plane wave in the rod. The receiver transducer, similar to the previous one, is coupled to the other end of the rod. The experimental results lead to an analytical expression for wave attenuation as function of the concrete composition, the propagation distance, and the wave frequency.

The interaction of cobalt (Co) and low-pressure chemical-vapor-deposited silicon nitride (LPCVD Si3N4) during anneals from 200 °C−1000 °C in vacuum, Ar, and Ar–H2 ambient (95% Ar and 5% H2) has been studied. After the anneals, reduction of Si3N4 by Co to form cobalt silicide and cobalt nitride phases has been observed. Reduction of Si3N4 initially occurs at 600 °C; however, gross physical damage occurs at temperatures of ∼900 °C in Ar. The addition of hydrogen to the ambient enhances the onset of physical damage to the nitride film by as much as 200 °C. Mechanisms governing the Co/Si3N4 reaction have been proposed.

The fracture strength and toughness of alumina can be increased by lamination with strategically placed nickel layers and by controlling the geometry of the interfaces. This paper describes the interface design of a ceramic/metal bonded system produced by changing the surface topography of the interface between the metal and ceramic layers in order to vary the strength of bonding. The tortuosity of the interface is described quantitatively using fractal geometry. Experiments and models of single ductile layer laminates show that the work of fracture of ductile layers which contribute to the increment of toughness of ceramic/metal laminates is dependent on the tortuosity of the interface. The more tortuous the interface, the stronger the laminate; the smoother the interface, the tougher the laminate. The results are used to design a ceramic/metal multilayer composite. The strength and toughness of the laminates can be controlled by the tortuosity of the interface and characterized using the fractal dimension.

The effect of solid state heat treatment at 913 K on extruded XD Al/TiC metal matrix composite with 0.7 and 4.0 μm particle sizes has been investigated. The interfaces between Al and TiC after extrusion were atomically abrupt, as observed by HRTEM. On holding at 913 K, the composite with submicron particle size showed substantial changes in the phases present due to reaction between Al and TiC at 913 K. The stable reaction products are Al3Ti and Al4C3. A substantial increase in Young's modulus occurs. The room and elevated temperature strength and hardness of the composite with submicron particles also increase significantly with time of heat treatment, but at the expense of ductility. The effect of heat treatment over the time range investigated is limited to the interfaces for the 4.0 μm TiC particle size composite due to longer diffusion paths.

A detailed study was conducted of the microstructure and particle-matrix interfaces in Al/TiCp metal matrix composites prepared by the XD process and subsequent extrusion. A study of the morphology of the TiC particles showed that the surfaces are low index (111) and (200) planes, the former being more common. Direct contact on an atomic scale is established between Al and TiC, allowing chemical bonds to form. Young's modulus is in the range expected for a composite of Al and TiC with good interfacial bonding and load transfer to the particles. No third element has been detected at the interfaces, showing that they are clean. Both incoherent and semicoherent interfaces are seen. The interface character depends on the size of the particles and their orientation with respect to the neighboring Al grains. “Special” interfaces with evidence for nearly periodic dislocations were observed in both XD Al/TiC and Al/TiB2 composites, indicating the general tendency of in situ composites to lower their interfacial energy by forming such boundaries.

When an appropriate mixture of low-softening borosilicate (BSG) and high-softening high silica (HSG) glasses is sintered at temperatures ranging from 800 to 1000 °C, a crystalline phase, identified as cristobalite by XRD, is known to precipitate out of the initial amorphous binary mixture of glasses as the sintering continues. The precipitation of cristobalite is found to originate in HSG and is controlled by the transport of alkali ions (e.g., K, Na, and Li) from BSG to HSG.1 In this paper we report that when a small amount of gallium oxide is present as a dopant in the above binary mixture of BSG and HSG, the cristobalite formation is completely prevented at the sintering temperatures investigated. The above result is attributed to a strong affinity between Ga+3 from gallium oxide particle and alkali ions from BSG, which diverts the diffusion of alkali ions from HSG to gallium oxide, thus forming a K+ and Ga+3-rich reaction layer adjacent to gallium oxide particles far too rapidly compared with that of cristobalite formation.

Ca(1−x)NixO solid-solution films with varying stoichiometry have been prepared by pulsed laser deposition from sintered targets of NiO and CaO. X-ray diffraction data indicate that the films have the structure of sodium chloride. The lattice constants for different stoichiometries vary with film composition. Using the Madelung energy as the binding energy between anions and cations and assuming that nickel and calcium ions are distributed randomly in lattice sites, the lattice constants were calculated and found to compare with experimental results. This study investigated the compositional changes that occur during the target sintering process and the pulsed laser deposition of films. Using these data, a target composition can be prepared to produce Ca(1−x)NixO thin films with any desired lattice constant.

V2O5–TiO2 and V2O5–Al2O3 mixed oxide powders were synthesized in a hydrogen-oxygen flame using VOCl3, TiCl4, and Al(CH3)3 as precursors. The particle formation processes were investigated as a function of VOCl3 concentration by laser light-scattering and by collecting particles directly onto transmission electron microscopy grids. In the V2O5–TiO2 system, the oxides condense as an intimate mixture at all three VOCl3 concentrations. Spherical particles, 40 to 70 nm in diameter, are obtained. In the V2O5–Al2O3 system, chain-like particles composed of an intimate mixture of V2O5 and Al2O3 form at the lowest VOCl3 concentration. At high VOCl3 concentrations, the chain-like particles have a core-mantle structure (a core mainly of Al2O3 and a mantle mainly of V2O5). The crystalline form and the surface area of these mixed oxides were determined by x-ray diffractometry, FT-IR spectroscopy, and BET analysis by nitrogen desorption. These measurements indicate that amorphous vanadium oxide forms at low VOCl3 concentrations, and V2O5 is obtained at the higher VOCl3 concentrations. The structure of the amorphous vanadium oxide matches that published for vanadium oxide “supported” catalysts.

“(110)-oriented Bi–Sr–Ca–Cu–O superconducting thin films prepared by metalorganic chemical vapor deposition” [J. Mater. Res. 8, 978 (1993)]