The effects of weak-localization and electron-electron interaction have to be invoked to explain anomalies in the resistivity and the magnetoresistance of quasi two-dimensional electron systems formed in acceptor graphite intercalation compounds and in prcgraphitic carbon materials. After introducing the basic concepts involved in the physics of these phenomena, a review is given of recent data for the low temperature electronic transport properties in these materials.

The fate of Fe, Co, Y, and Ce impurities is determined in the process of recrystallization of zirconium oxychloride and in its subsequent fluorination with aqueous hydrofluoric acid to ZrF4 · H2O. Techniques of gamma ray spectrometry were used to follow radioisotopes introduced at critical steps in the process. All impurities remained in the recrystallization liquor. The liquor and its associated impurities, which is retained on the crystals, can be displaced by acid washing. In fluorination, Fe and Co are rejected while Y and Ce are retained and cannot be removed by washing.

Characteristics of aqueous silicon nitride whisker suspension and the packing nature of whiskers during consolidation (sedimentation or filtration) were investigated in order to control the microstructure and density of a whisker compact. Silicon nitride whiskers (average size 0.4 μm × 3.7 μm) coated by SiO2 film were well dispersed at pH 10.5 due to the strong repulsion force among negatively charged whiskers. Low viscosity suspension of highly charged whiskers showing Newtonian behavior formed a dense whisker compact with a narrow pore size distribution of small pores. The density increase of green compact was accompanied by the orientation of whiskers where the direction in length of whiskers was perpendicular to the direction of filtration. Application of an external pressure (isostatic pressing) to porous whisker compacts consisting of network structure of randomly packed whiskers or whiskers of low orientation increased the green density.

A method is described to deposit a securely attached, self-assembled monolayer of octadecyltrichlorosilane (OTS) on the surface of freshly cleaved muscovite mica. Comparison of the infrared methylene spectra with those of closely packed Langmuir-Blodgett films implies that the surface coverage of the OTS films was a fraction 0.8–0.9 that of films formed by Langmuir-Blodgett (LB) methods. However, LB monolayers are less securely attached to the substrate. The contact angle of water on these self-assembled monolayers remained over 100° for over 24 h and it suffered no noticeable degradation after prolonged reflux in cyclohexane. The method to form an OTS monolayer on mica involves three steps; first, ion exchange of the native K+ ions of cleaved mica for H+ ions; second, control of the quantity of resulting water on the mica surface; third, adsorption and surface polymerization of octadecyltrichlorosilane (OTS) by self-assembly from dilute cyclohexane solution.

The resistance R, spectral emissivity ∊, and power consumption of W and Re filaments heated to 2500 °C in mixtures of CH4 or C2H2 in H2 have been measured in a series of experiments focusing on the state of the filament activity, i.e., its ability to dissociate the reactant gases. It has been found that these properties of the filaments, as well as the partial pressures of CH4 and C2H2 in the reaction chamber, depend critically on both the filament temperature and the reactant ratio, e.g., C2H2/H2. Specifically, both W and Re filaments show sharp jumps in power consumption at essentially the same temperature, signaling strong increases in filament activity and, hence, production of atomic hydrogen. These results are proposed to be due to the removal of nonreactive carbon from the surface of the filament via etching by atomic hydrogen and are consistent with the predictions of our thermodynamic model for the C–H system. Evidence for gas phase reactions is presented and the role of thermal diffusion is discussed. The emissivities of the W and Re filaments are observed to have significantly different temperature dependences which are attributed to differences in the phase diagrams for the W–C and Re–C systems. The implications of these results for hot-filament diamond CVD are discussed.

Titanium disulfide films were prepared by plasma CVD. Crystalline orientation of layered TiS2 was investigated in relation to deposition rate, film thickness, and kinds of substrate. The preferred orientation of TiS2 basal plane perpendicular to substrates was obtained on the films with their thickness of more than ca. 10 μm at the deposition rate of ca. 4 ⊠ 10−3 g/cm2·h on all kinds of substrate. This orientation resulted in a large discharge capacity in a lithium battery cathode application.

The reaction zone formed between niobium and silicon carbide during heating for 4 h at 1373 K was examined by transmission electron microscopy (TEM) and Auger electron spectroscopy (AES). The typical reaction layer sequence is SiC/Nb5Si4C/Nb5Si3/Nb2C/NbO/Nb. However, in one area of the specimen, the first reaction layer was NbC rather than Nb5Si4C. The high oxygen and carbon concentrations near the outer surface were shown by AES depth profiling to result from carbon and oxygen contamination from the vacuum system during annealing. In order to determine if the observed reaction layer sequence is consistent with conditions of local thermodynamic equilibrium, the quaternary Nb–Si–C–O phase diagram was calculated from available thermodynamic data. A minimum (most negative) free energy of formation for the ternary compound Nb5Si4C of −582 kJ/mole was estimated assuming that the equilibrium between NbSi2 and SiC observed experimentally at 1573 K1 also exists at 1373 K. Except for the region immediately adjacent to the substrate, the observed reaction layer sequence was in agreement with the calculated quaternary phase diagram. However, it was noted that agreement with the quaternary phase diagram would be obtained if a thin layer of either SiO2 or NbC were present at the substrate surface.

The exposure response of high resolution oxide resist materials has been examined under high intensity irradiation conditions (∼1 ⊠ 105 A/cm2) to determine the relationships among film characteristics, exposure requirements, and ultimate resolution, and to explore further the processes responsible for ablative exposure. Amorphous films of Al2O3, Y2O3, Sc2O3, 3Al2O3·2SiO2, and MgO·Al2O3 were deposited by rf sputtering onto substrates cooled to –196°C and found to require an exposure dose of approximately 5 ⊠ 103 C/cm2 to complete exposure. Amorphous film structure was found to be necessary to achieve rapid removal of material during exposure. Material properties also found to influence irradiation response and help guide the selection of new materials included ionic character, heat of formation, and melting point. Film thickness was found to influence strongly both exposure requirements and resolution, an optimum thickness occurring at approximately 90 nm in amorphous Al2O3. The dose requirement in 90 nm thick amorphous Al2O3 was determined to be 2.5 ⊠ 103 C/cm2, which is two to three orders of magnitude lower than that of oxide films produced by other techniques. Resolution of the rf sputtered oxide films allowed the production of 5.0 nm holes on 8.1 nm centers. A dedicated STEM was used for exposure studies as well as imaging, microdiffraction analysis, and monitoring of the transmitted beam current, and allowed a qualitative model of the exposure process in rf sputtered oxide resists to be developed.

The equilibrium shape of a small particle on a substrate where the particle can sink into the substrate is evaluated.

Hydrolyzed ZrCl4 and ZrO2 · nH2O have been used as starting compounds in a time-differential perturbed-angular correlation (TDPAC) investigation on the stabilization and thermal evolution of the metastable tetragonal form of ZrO2. This phase, of quadrupole parameters very similar to those reported for the high temperature tetragonal form, emerges at moderate temperatures previous to the monoclinic phase, when starting from hydrolyzed ZrCl4 and from ZrO2 · 2H2O treated previously at 673 K. Though in all cases zirconia appears initially as an amorphous compound characterized by unique hyperfine parameters, two different precursors have been observed to exist immediately previous to the occurrence of either the monoclinic or the metastable tetragonal crystal phases. Each of them exhibits a quadrupole frequency identical with and an asymmetry parameter higher than the ones characterizing the forthcoming corresponding crystal phases. A crystallization enthalpy of (33 ± 5) kJ/mol has been determined for the formation of the metastable tetragonal phase out of its precursor.

In the microwave induced plasma deposition of diamond from methane-hydrogen-oxygen mixtures, the variables available for controlling the microstructure of the resulting films are the plasma composition and density, the substrate surface properties, and the temperature. It has been demonstrated that the competition between nucleation site formation and the rate of reactive plasma etching is the critical feature in the development of the film microstructure on silicon substrates. On diamond substrates, the favorable lattice match dominates and homo-epitaxial films are formed over a wide temperature range. Raman scattering studies also demonstrate that the reactive etching of the diamond surface by oxygen-containing species is critical to the removal of non-diamond carbon species over the temperature range 450–1050 °C.

High purity, ultrafine SiC powders have been produced from gas phase reactants (SiH4, C2H2) in a CO2 laser induced process. The flow reactor designed to operate with a medium power (10–50 W) continuous wave CO2 laser source is described. The mechanism of gas phase reactions involved has been investigated by means of on-line optical diagnostics. Powders produced have been characterized by means of conventional chemical and spectroscopic methods. The x-ray results point out a growth mechanism by coalescence; i.e., whole islands move in the flame to take part in binary collisions, analogously to that observed for particles produced by inert gas evaporation.

Low-temperature sintering (under 350°C) of hydroxyapatite was attempted by a hydrothermal hot-pressing technique. The effects of borosilicate glass addition on the characteristics of the solidified body (mechanical strength, microstructure, crystal structure, pore distribution, etc.) and on the densification process during hydrothermal reaction were investigated. The borosilicate glass increased the mechanical strength of the solidified body; compression of 50% content of apatite was 2100 kg/cm2. It is also shown that water acts as a good catalyzer during solidification under hydrothermal conditions, and micropores can increase toughness of the solidified body due to the adsorption of stress. These hydrothermal hot-pressing solidification processes are so similar to sintering with liquid phase under pressure that the initial kinetics was discussed by means of the velocity measurement of shrinkage rate. In addition, these reactions may proceed in water, and are then discussed from the point of view of a heterogeneous reaction between powder and aqueous solution. It was proposed that the solidification process was due to viscous flow with rearrangement of grains in the solidified body, and the rate-determining step followed a core model of extraction from solid to solution.

A comprehensive review and state of the art in the field of surface, interface, and thin-film magnetism is presented. New growth techniques which produce atomically engineered novel materials, special characterization techniques to measure magnetic properties of low-dimensional systems, and computational advances which allow large complex calculations have together stimulated the current activity in this field and opened new opportunities for research. The current status and issues in the area of material growth techniques and physical properties, characterization methods, and theoretical methods and ideas are reviewed. A fundamental understanding of surface, interface, and thin-film magnetism is of importance to many applications in magnetics technology, which is also surveyed. Questions of fundamental and technological interest that offer opportunities for exciting future research are identified.

The infrared transmission spectra of four silicate glasses were investigated. By using blown glass films, 1–2 μm thick, detailed infrared transmission spectra were generated over the 4000–180 cm−1 range, both before and after the films were exposed to water. The water had little effect on the spectra of the 70SiO2–20Na2O–10Al2O3 (mol %) and Pyrex compositions, but had a large effect on the spectra of the 70SiO2–30Na2O (mol %) and Corning 015 compositions. The Si–O nonbridged stretching band at ∼950 cm−1 and a largely overlooked bending band at ∼600 cm−1 were the bands most sensitive to hydration in the 70/30 and 015 compositions. Changes were also seen in the Si–O–Si bridged stretching bands at ∼1050 cm−1 and ∼770 cm−1. The water, however, had no effect on the dominant Si–O–Si bending band at 460 cm−1. It was also discovered that the 70/30 and 015 films reacted with the atmosphere to form a carbonate layer on their surface. This carbonate accounted for the 1450 cm−1 and 230 cm−1 bands seen in their infrared transmission spectra.

The role of particle and grain size on the dielectric behavior of the perovskite relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 [PMN] was investigated. Ultrafine powders of PMN were prepared using a reactive calcination process. Reactive calcination, the process by which morphological changes take place upon reaction of the component powders, produced particle agglomerates less than 0.5 μm. Through milling, these structures were readily broken down to ∼70 nanometer-sized particulates. The highly reactive powders allowed densification as low as 900 °C, but with corresponding grain growth in the micron range. Such grain growth was associated with liquid phase sintering as a result of PbO–Nb2O5 second phase(s) pyrochlore. Sintering, assisted by hot uniaxial pressing, below the temperature of liquid formation of 835 °C, allowed the fabrication of highly dense materials with a grain size less than 0.3 μm. The dielectric and related properties were determined for samples having grain sizes in the range of 0.3 μm to 6 μm. Characteristic of relaxors, frequency dependence (K and loss) and point of Tmax were found to be related to grain and/or particle size and secondarily to the processing conditions. Modeling of particle size/dielectric behavior was performed using various dielectric properties of 0–3 composites comprised of varying size powder in a polymer matrix. An intrinsic-microdomain perturbation concept was proposed to interpret observed scaling effects of the relaxor dielectric behavior in contrast to normally accepted extrinsic grain boundary models.

The optical band gap, density, and hydrogen content of diamond-like carbon films have been controllably varied by rf biasing the substrate in an ECR discharge of pure methane. The optical band gap varied from 2.7 to 1.2 eV, the density from 1.4 to 2.2 g/cm3, and the atomic fraction of hydrogen from 50 to 5%. The range of measured values is in agreement with those predicted by both the random covalent network and defected graphite models.

The effects of increasing amounts of MnO additions on the microstructures, phase stability, and mechanical properties of ZrO2–12 mol % CeO2 and ZrO2–12 mol% CeO2–10 wt.% Al2O3 were studied. MnO suppressed grain growth in ZrO2–12 mol% CeO2, while enhancing the mechanical properties significantly (strength = 557 MPa, fracture toughness = 9.3 MPa at 0.2 wt.% MnO). The enhanced mechanical properties were achieved despite an increased stability of the tetragonal phase, as evidenced by a lower burst transformation temperature (Mb) and a reduced volume fraction of the monoclinic phase on the fracture surface. In ZrO2–12 mol% CeO2–10 wt.% Al2O3, the addition of MnO suppressed the grain size of ZrO2, while promoting grain growth and changing the morphology of Al2O3. More significantly, the stability of the tetragonal ZrO2 phase decreased (high Mb temperature) with a concurrent increase in fracture toughness (13.2 MPa at 2 wt.% MnO) and transformation plasticity (1.2% in four-point bending). The widths of the transformation zones observed adjacent to the fracture surfaces showed a consistent inverse relation to the transformation yield stress, as would be expected from the mechanics of stress-induced phase transformation at crack tips. The improvements in mechanical properties obtained in the base Ce–TZP and the Ce–TZP–Al2O3 composite ceramics with the addition of MnO are critically examined in the context of transformation toughening and other possible mechanisms.

Nanoindenter techniques have been used to determine the hardness. Young's modulus, and strain rate sensitivity of nanophase TiO2, which is currently available only in very small quantities and which cannot be tested by most conventional techniques. Hardness and Young's modulus both increase linearly with sintering temperature over the range 25–900°C but come to within only 50–70% of the single crystal values. Strain rate sensitivity, on the other hand, is measurably greater for this material than for single crystal rutile, and the value of strain rate sensitivity increases as the grain size and the sintering temperature are decreased. In its as-compacted form, the strain rate sensitivity of nanophase TiO2 is approximately a quarter that of lead at room temperature, indicating a potential for significant ductility in these ceramic materials. Finally, a significant scatter in hardness values has been detected within individual nanophase samples. This is interpreted as arising from microstructural inhomogeneity in these materials.

A new butt joining method for ceramics by microwave heating was developed. Ceramics were heated in a rectangular cavity, and a klystron of maximum 3 kW at 6 GHz was used as the power amplifier. The heating system can control an iris, a plunger, and the microwave power to maintain the power efficiency up to 90% and the accuracy within ±10°C at 1800 °C. This system was applied to alumina-alumina direct joining. The average strength of alumina rods (92% purity) joined for 3 min was 420 MPa, which was equal to the original strength. The joined boundary line at the interface was not observed, and there was little difference in microstructure between before and after joining. This suggests that sintering aids in the grain boundary phase were preferentially heated and melted, resulting in the sound joining of ceramics. Next, silicon nitride ceramics containing yttrium were indirectly joined with an intermediate, which was a sintered ceramic sheet having lower purity and larger dielectric loss factor than the base material. The microwave energy was concentrated on the ceramic sheet, so that only the joining area was locally heated. The strength of the joined rods was in excess of 70% of the base material, but a deficient layer of yttrium occurred in the area of the joined boundary.