Rutile nanocrystals were directly prepared under hydrothermal conditions using TiCl4 as the starting material. The formation reactions proceeded by suppressing the crystallization of the other TiO2 polymorphs using a fixed concentration of 0.62 M [Ti4+]. With increasing reaction temperatures from 140 to 220°C, rutile nanocrystals were found to grow from 5.4 to 26.4 nm in size, and by varying the reaction time from 2 to 120 h at 200°C the particle size increased from 17 to 40 nm. The grain-growth kinetics of rutile TiO2 nanocrystals under hydrothermal conditions was found to follow the equation, Dn = k0 × t × e(-Ea/RT) with a grain-growth exponent n = 5 and an activation energy of Ea = 170.8 kJ mol-1. The nanocrystals thus obtained consist of an interior rutile lattice and a surface hydration layer. With decreasing particle size, the hydration effects at the surface increase, while the rutile structure shows a lattice expansion and covalency enhancement in the Ti-O bonding.

Concurrent synthesis of titania-carbon nanoparticles (up to 52 wt.% in C) was studied in a diffusion flame aerosol reactor by combustion of titanium tetraisopropoxide and acetylene. These graphitically layered carbon-coated titania particles were characterized by high-resolution transmission electron microscopy (HRTEM), with elemental mapping of C and Ti, x-ray diffraction (XRD), and nitrogen adsorption [Brunauer-Emmett-Teller (BET)]. The specific surface area of the powder was controlled by the acetylene flow rate from 29 to 62 m2/g as the rutile content decreased from 68 to 17 wt.%. Light blue titania suboxides formed at low acetylene flow rates. The average XRD crystal size of TiO2 decreased steadily with increasing carbon content of the composite powders, while the average BET primary particle size calculated from nitrogen adsorption decreased first and then approached a constant value. The latter is attributed to the formation of individual carbon particles next to carbon-coated titania particles as observed by HRTEM and electron spectroscopic imaging.

Powders of (1 − x) Pb(Fe1/2Nb1/2)O3-xPbTiO3 (PFN-PT) with x = 0.00, 0.10, 0.13, 0.15, 0.20, and 0.25 were prepared by the conventional solid-state route. Structure of PFN-PT was tetragonal for x [H33356] 0.10, which indicates that the morphotropic phase boundary (MPB) may be between 0 < x < 0.10. The nature of phase transition in PFN-PT changed from diffuse ferroelectric to relaxor ferroelectric to normal ferroelectric on increasing the PT content. The effect of the PT content and sintering temperature on barrier layer formation in the PFN-PT system was studied using complex impedance spectroscopy. With increasing PT content, the possibility of the barrier layer formation decreased while with increasing sintering temperature, the barrier layer formation was promoted.

We report on radiotracer diffusion measurements in metallic bulk-glass-forming Pd-Cu-Ni-P alloys. The Pd-Cu-Ni-P system, with its high stability against crystallization, allows diffusion measurements from the glassy state to the equilibrium melt for the first time. Serial sectioning was performed by grinding and ion-beam sputtering. The time and temperature as well as mass dependence, expressed in terms of the isotope effect E, of codiffusion were investigated. In the glassy state as well as in the deeply supercooled state below the critical temperature Tc, where the mode-coupling theory predicts a freezing-in of liquidlike motion, the measured very small isotope effects indicated a highly collective hopping mechanism. Below Tc, the temperature dependence showed Arrhenius-type behavior. Above Tc, the onset of liquidlike motion was evidenced by a gradual drop of the effective activation energy, resulting from the decay of hopping barriers, and by the validity of the Stokes-Einstein equation, which was found to break down below Tc. This strongly supports the mode-coupling scenario. Isotope effect measurements, which have never been carried out near Tc in any material, showed atomic transport up to the equilibrium melt to be far away from the hydrodynamic regime of uncorrelated binary collisions. The latter appears to be a prerequisite of excellent glass-forming abilities.

The effects of various surface pretreatments on the adhesion of electroless and sputter-deposited copper metallizations to a hybrid polymer material were investigated. Without pretreatment, the adhesion between copper and the polymer was virtually zero. The adhesion of electroless copper to the polymer was poor regardless of the pretreatment used. However, the wet-chemical pretreatment of the polymer surface markedly increased the adhesion of sputtered copper to the polymer. It preferentially removed the inorganic part of the polymer and formed micropores on the surface. The plasma and reactive ion etching pretreatments, in turn, selectively etched away the organic part of the polymer and noticeably increased the hydrophilicity. Although this resulted in even higher increase in the surface free energy than was achieved with the chemical treatment, the granular surfaces became mechanically brittle. With the help of x-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, and contact-angle measurements and with the recently developed pull test, the physicochemical changes of the wet-chemically pretreated polymer surfaces were demonstrated to have significant effects on the adhesion.

Results are reported on the electron field emission properties of microcrystalline diamond thin films grown on molybdenum substrates by the sulfur (S)-assisted hot-filament chemical vapor deposition technique using methane (CH4), hydrogen sulfide (H2S), and hydrogen (H2) gas mixtures. Electron field-emission measurements revealed that the S-incorporated microcrystalline diamond thin films have substantially lower turn-on fields and steep rising currents as compared to those grown without sulfur. The field-emission properties for the S-incorporated films were also investigated systematically as a function of substrate temperature (TS). Lowest turn-on field achieved was observed at around 12.5 V/μm for the samples grown at TS of 700°C with 500 ppm H2S. To establish the property-structure correlation, we analyzed the films with multiple characterizations include scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy (RS), and x-ray photoelectron spectroscopy (XPS) techniques. It was found that sulfur addition causes significant microstructural changes in microcrystalline diamond thin films. S-assisted films show smoother, coarse-grained surfaces (non-faceted) than those grown without it (well-faceted) and a relatively higher content of non-diamond carbon (primarily sp2-bonded C). RS and investigations on the morphology by SEM and AFM indicated the increase of sp2 C content with increasing TS followed by a morphological transition at 700°C in the films. XPS investigations also showed the incorporation of S in the films up to a few atomic layers. It is believed that the electron-emission properties are governed by the sulfur incorporation during the chemical vapor deposition process. Although most of the S is expected to be electrically inactive, under the high doping conditions hereby used, it is shown rather indirectly through multiple characterizations that there may be some amount of S in donor states. Therefore the results are discussed in terms of the dual role of S whereby it induces the structural defects in the form of enhanced sp2 C content at the expense of diamond quality and a possibility of availability of conduction electrons. In fact the latter finding is supported through room temperature electrical conductivity measurements.

An analytical expression was derived to predict the heating profile that minimizes the cycle time for the thermal removal of binder from porous green ceramic bodies. The analytical equation was based upon the solution to a three-dimensional convective transport equation that describes flow in porous media arising from the thermal decomposition of binder. The solution to the transport problem was then combined with an algorithm derived from variational calculus. The analytical expression described the time for binder removal in terms of the body dimensions, isotropic permeability, volume fraction of binder, and threshold pressure within the green body.

We studied the thermal shock resistance of a silicon nitride containing elongated and preferentially aligned grains with different volume fractions of pores, ranging from 0 to 0.27. It was found that an increase in the volume fraction of pores decreased both the strength and the temperature through which the sample must be quenched to cause cracking. However, at intermediate values of the porosity (0.07), the temperature change required to cause cracking was much smaller than predicted. Observations of the resulting damage suggested that this had occurred because of the formation of cracks just underneath and parallel to the cooled surface of the sample that were able to change the direction of their growth. The extent of cracking was found to be only very weakly dependent on the volume fraction of pores, consistent with calculations of the variation of crack driving force within the sample.

Fine whiskers of a C60 derivative, i.e., C60 monosubstituted by ethyl ester of malonic acid, C60[C(COOC2H5)2], were fabricated for the first time using a system of toluene with concentrated C60[C(COOC2H5)2] and isopropyl alcohol. The center-to-center distance of C60[C(COOC2H5)2] molecules along the close-packed direction of the C60[C(COOC2H5)2] whiskers was in the same range as that of the C60 nanowhiskers prepared by the same method. The C60[C(COOC2H5)2] whiskers were assumed to take body-centered tetragonal or hexagonal close-packed crystal structures. The C60[C(COOC2H5)2] whiskers showed a high density of stacking faults. The C60[C(COOC2H5)2] whiskers with the growth direction different from the C60 whiskers were observed.