The structural and electronic properties of fluorine- and bromine-intercalated graphite fibers and HOPG are summarized. In contrast to the bromine intercalate, which is purely ionic for any experimentally attainable intercalate concentration, fluorine has a dual ionic and covalent behavior in graphite. Furthermore, whereas bromine-intercalated graphite is ordered, fluorine-intercalated graphite is disordered. The stiff graphene planes are buckled and islands of various fluorine concentrations are formed. A thermodynamic model is proposed that accounts for the differences between fluorine- and bromine-intercalated graphite materials. The model describes the competition between ionically bonded and covalently bonded intercalate phases of fluorine in graphite. Covalent bonding is more favorable energetically, but an important nucleation barrier exists due to strain and to the destruction of the conjugation of the double bonds.

The growth of BaO and SrO on SrTiO3(100) substrates using mass-separated low-energy (50 eV) O+ beams has been studied using x-ray diffraction, reflection high-energy electron diffraction, and high-resolution transmission electron microscopy. It was found that the BaO and SrO films have been epitaxially grown with new structures different from those of corresponding bulk crystals: The BaO films have a cubic structure with a lattice constant of 4.0 Å, and the SrO films have a tetragonal structure with a lattice constant of a = 3.7 Å parallel to the substrate and with c = 4.0 Å normal to the substrate.

A rapid and accurate method of measuring fractal dimension of a fractured surface is described. The method uses a stereo pair of photomicrographs taken in a scanning electron microscope and digitized for computer analysis. The computer can automatically compare the offset at many places in the two images and calculate their height on the basis of the parallax angle. The sum of the area of all planes formed by an array of three-dimensional points is an approximation of the true surface area. The scale can be varied both in the microscope and in the computer; therefore, a fractal dimension can be calculated. Unlike previous methods, this one is direct and gave results intermediate between two prior indirect measurements.

Diamond crystallites and continuous films were deposited on (100) silicon with various surface treatments by microwave plasma assisted CVD at times varying from 2 min to 1600 min. In each experiment, the average diameter of the crystallites increased linearly with time, while the density of crystallites was essentially constant. Thus, nucleation of the diamond occurred within a short time interval early in the deposition process. After the nucleation event, only growth occurred. Various surface treatments were used: untreated, polished with 1 μm diamond, scratched with 350 mesh SiC, scratched with 1 μm alumina, wiped with 350 mesh graphite powder, and spin coated with polymethyl methacrylate. Only the diamond polishing affected the crystallite density, and none of the surface treatments had any effect on crystallite morphology or growth rate. Growth rates were determined by least squares fits to average diameter versus time for crystals and average thickness versus time for films. The growth rate data extrapolate to zero size at zero deposition time. Applying the Volmer–Weber model, an activation energy for nucleation of diamond on silicon was calculated to be 52 kcal/mole.

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.

Carbon aerogels are a special class of low-density microcellular foams. These materials are composed of interconnected carbon particles with diameters of approximately 10 nm. The temperature dependence of the dc electrical resistivity and magnetic susceptibility (χ) from 4 K to room temperature, magnetoresistance (MR) in a magnetic field up to 15 T, and Raman scattering were measured as a function of aerogel density. While Raman scattering measurements are not sensitive to variations in density, the χ data show that there are more free carriers in samples of higher density. Aerogel samples with different densities all show a negative temperature coefficient of resistivity and a positive MR. The less dense samples exhibit a stronger temperature dependence of resistivity and a stronger field dependence of the MR, indicating that with decreasing density and increasing porosity, charge carriers are more localized. Data analysis precludes variable-range hopping in favor of nearest-neighbor hopping and fluctuation-induced tunneling as the most likely conduction mechanisms for carbon aerogels.

A new ternary solder alloy of tin-lead-nickel was developed for solder joints. It has an optimum composition range of (60–65)% Sn, (35–40)% Pb, (0.5–1.0)% Ni by weight. The alloy exhibits a higher strength and longer fatigue life than the pure 63% Sn−37% Pb eutectic. Melting point, wettability, and fatigue life were the key properties used to determine this composition. In particular, the melting point of the alloyed eutectic solder did not change for rapidly solidified samples when up to 2 wt. % Ni was added. Instead of modifying the solution melting temperature, the majority of the Ni precipitated out as a fine dispersion of Ni3Sn4. These Ni3Sn4 particles help to strengthen the solder matrix. Reflow experiments on rapidly solidified material showed minimal coarsening and agglomeration of the Ni3Sn4 particles for up to 5 min of reflow cycles. The wettability of the solder, however, decreased significantly for contents of Ni above 1.5%. Low cycle fatigue tests show that for a solder with 0.5% Ni, the fatigue life was about twice as long as that of standard eutectic solder. Suggested processing for the alloy is rapid solidification to form the alloy powder which is incorporated into a reflowable paste.

A novel spin-polarized scanning electron microscope with capabilities of observing microscopic domain structures and determining in-plane magnetization directions has been used to investigate the stress-induced magnetic domains in the Fe78B13Si9 (Allied 2605-S2) metallic glass. The magnetic structure in the vicinity of shear bands that are produced near a Mode III crack has been examined. On the tensile side of bending, arrays of individual, discontinuous magnetic “islands” of similar shape and size (about 2–10 μm in length, 3 μm in width, and spaced about 2–4 μm apart) are uniformly distributed on one side of the shear bands. Their easy axis is about parallel to the shear bands. On the other hand, well-defined elliptical domains are found between shear bands on the compression side of bending. Their easy axes are approximately perpendicular to the shear bands. These results suggest the existence of isolated defects of similar stress fields located along the shear bands. The possibility that these defects are dislocations will be investigated next.

Atomic force microscope measurements of elastic-plastic indentation into an Fe−3 wt. % Si single crystal showed that the volume displaced to the surface is nearly equal to the volume of the cavity. The surface displacement profiles and plastic zone size caused by a 69 nm penetration of a Vickers diamond tip are reasonably represented by an elastic-plastic continuum model. Invoking conservation of volume, estimates of the number of dislocations emanating from the free surface are reasonably consistent with the number of dislocations that have formed in the plastic zone to represent an average calculated plastic strain of 0.044.

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.

Tracer diffusion of 57Co in amorphous Fe100−xDyx (x = 20–40), Fe75Tb25, Fe67Ce33, and Fe80Si6B14 alloys prepared by dc sputtering has been studied at temperatures of 523 and 573 K. In the Fe–Dy alloys the diffusion coefficient of 57Co shows a maximum at 33 at.% Dy. The magnitude of the diffusion coefficient of 57Co in Fe75Tb25 is nearly equal to that in Fe75Dy25, while those in Fe67Ce33 and Fe80Si6B14 are about one order of magnitude less than the values in Fe67Dy33 and Fe80Dy20. This suggests that the atomic size of the diffusant and the density of the matrix are dominant in the diffusion. Temperature dependence of the diffusion coefficient D of 57Co in the amorphous Fe75Dy25 alloy has been determined in the range from 493–673 K. It shows a linear Arrhenius relationship expressed by D = 5.7 × 10−2 exp(−199 kJ mol−1/RT) m2 s−1. The magnitudes of the pre-exponential factor and the activation energy suggest that the cobalt tracer atoms in the amorphous Fe75Dy25 alloy diffuse by an interstitial-like mechanism.

SiC thin films grown from the reaction between acetylene (C2H2) and the Si(100) substrates in a horizontal hot-wall CVD reactor by different procedures were studied using x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The growth of the SiC films was observed from the behavior of Si2p peaks and their plasmons. A SiC thin film with a thickness of 35 Å and having a smooth surface morphology was obtained in C2H2 diluted by H2 at 1050 °C for a period of 60 min. Etch pits and hillocks were observed with increasing reaction time at 1050 °C. For the conversion conducted in C2H2, but in the absence of H2, a SiC monolayer with smooth morphology was obtained at 950 °C for 7 min and defects were observed for longer reaction times at this temperature. Defects were also observed for reaction times as short as 10 s at higher reaction temperatures (e.g., 1000 °C). H2 seems to play a key role in suppressing the formation of defects and the reaction between C2H2 and Si substrate. The formation of defects was correlated to the out-diffusion of Si in the carbonization process.

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.

The kinetics of reaction between chemical vapor deposited diamond films (prepared by the hot filament method) and oxygen gas was studied by thermogravimetry. The reactions were carried out at atmospheric pressure in gas mixtures containing between 25 and 100 vol. % oxygen (balance argon), and in the temperature range of 973–1073 K. The apparent order of the reaction is close to 0.6, and the apparent activation energy is 232 kJ/mole. The kinetic data are explained by assuming no mass transfer limitations, direct reaction between CVD diamond and oxygen to form CO and CO2, and thermodynamic equilibrium between CVD diamond, CO, and CO2. The dominant chemical reaction involves the formation of CO, while the formation of CO2 is not significant. Three stage mechanistic schemes are developed involving adsorption of oxygen on CVD diamond surface, surface chemical reaction, and desorption of adsorbed species to CO or CO2. The experimental rate data conform to the reaction rate expressions developed for the mechanistic schemes leading to the formation of CO and CO2, assuming adsorption as the rate-controlling step. The adsorption rate constants for the formation of CO and CO2 are determined. The activation energy of the adsorption step leading to the formation of CO is 213 kJ/mole.

Polycrystalline CuInS2 thin films are prepared by sulfuration of Cu–In–O films. The Cu–In–O films are deposited from a sintered Cu2In2O5 target by using a pulsed laser deposition (PLD) method. Then, the Cu–In–O films are converted into CuInS2 films by means of a subsequent annealing in an H2S gas atmosphere. The characteristics of the films are determined by using an x-ray diffractometer (XRD), an energy dispersive x-ray spectrometer (EDX), and a scanning electron microscope (SEM). The effects of the deposition and sulfuration temperatures of the Cu–In–O films on the structural and microstructural properties of CuInS2 films are examined experimentally. Single-phase CuInS2 films with a chalcopyrite structure are obtained when Cu–In–O films are sulfurated at a temperature higher than 400 °C. Grain size of CuInS2 is larger when a lower deposition temperature and a higher sulfuration temperature of Cu–In–O films are employed.

The crystallization process of amorphous electrodeposited samples of composition Co100–xPx (10 < x < 25) has been monitored by differential scanning calorimetry (DSC) and the resulting microstructure has been studied by scanning electron microscopy (SEM) and x-ray diffraction (XRD). Samples of composition given by x < 21 crystallize through two consecutive stages, while those with x > 21 crystallize through a single one. Depending on the composition and crystallization stage, activation energies varying from 1.76 to 2.02 eV and frequency factors of the order of 1013–1014 s–1 have been evaluated. The DSC measurements are compatible with the coexistence of two amorphous phases with different compositions in the regions that are located near the edges of the samples. The analysis of the microstructure resulting from crystallization has shown the existence of two different types of texture for samples with values of x respectively above and below 21, as well as the presence of linear structures oriented perpendicular to the plane of the samples. The development of these features can be attributed to the fundamental role that the polarization, due to magnetization, plays in the crystallization process of this system. A gradual variation of the grain size has also been observed, indicating that crystallization takes place by an inhomogeneous nucleation and growth mechanism.

Using Chemical Vapor Deposition (CVD), TiN was deposited on sharp tungsten needles. The reactant gases were TiCl4, N2, and H2. A Transmission Electron Microscopy (TEM) investigation revealed that the first nuclei of the CVD–TiN coating on tungsten did not consist of δ–TiN, but were a mixture of α–TiN and δ–TiN. These results were also verified with x-ray measurements. From these experimental results a possible mechanism for the initial growth of TiN on tungsten is suggested. It may be that the change in relative concentrations of the different titanium nitrides suggested as mechanism of the initial growth of CVD–TiN can be applied in general for all TiCl4/H2/N2/metal systems where the original substrate surface material partly or completely consists of a metal with catalytic properties.

Controlled atmosphere electron microscopy coupled with in situ electron diffraction has been used to follow the manner by which the addition of boron oxide influences the graphite-oxygen reaction. Continuous observations of the process show that at about 450 °C the boron oxide undergoes a strong interaction with both the graphite edge and the basal plane regions, and this results in a spreading of the oxide to form a uniform thin adherent film over the entire substrate. The coated graphite specimens appear to be impervious to attack by oxygen at temperatures below 815 °C. Above this temperature, however, there is a weakening of the additive-graphite interaction with the “armchair” {11$\overline 1$0} faces, and these regions then become vulnerable to attack by oxygen. At the same time very shallow pits are observed to develop in the basal plane, and this action coincides with the appearance of boron carbide species in the electron diffraction pattern. In a complementary series of experiments, it is found that boron carbide is an extremely active catalyst for the graphite-oxygen reaction even at temperatures as low as 100 °C. The impact of these low pressure studies on the behavior of carbon structures used in aerospace applications is discussed.

Stages 4–6 FeCl3–graphite intercalation compounds (GIC's) have been prepared by an ordinary two-bulb method, and the bi-intercalation processes of H2SO4 into the GIC's have been studied by x-ray diffraction. Since stages 4–6 FeCl3–GIC's have more than three vacant interlayer spaces in the c-axis repeat distance, the bi-intercalation of H2SO4 into the GIC's takes place stepwise. Consequently, various FeCl3–H2SO4–graphite bi-intercalation compounds (GBC's), from the GBC's with one H2SO4 layer to the GBC's saturated with H2SO4, are obtained in the bi-intercalation processes. Their compositions are described as C6.0nFeCl3 · c(6.0/6.5)H2SO4 from the calculation of structure factor for x-ray diffraction, where n is the stage number of the starting FeCl3-GIC's, and c is the number of H2SO4 layers. Stacking sequences of all the FeCl3–H2SO4–GBC's are also determined.

Particle size distributions derived from SEM micrographs of well-separated diamond particles, deposited on Si(100) substrates by the hot filament CVD method, have been analyzed in connection with previous measurements of particle growth rates. Rates of nucleation have been obtained from this analysis in an extended range of deposition conditions. A previously developed nucleation model has been utilized, and the kinetic parameters provide a framework for modeling the nucleation process from the gas phase.