The thermally induced shape instability of Fe/Au, Fe/Ag, and Nb/Cu multilayer systems during heat treatments was investigated. The disintegration temperature of these systems decreases with decreasing single-layer thickness. Up to a critical thickness, the disintegration temperature is proportional to the reciprocal layer thickness. The driving force of this process is related to the interfacial stress and the local variation of the interface curvature. After heat treatment, spherically shaped Fe and Nb nanoparticles, located in chains perpendicular to the substrate, were observed and depicted by means of transmission electron microscopy (TEM) and X-ray microscopy (XRM).

Mechanical milling has been used to synthesize ferromagnetic (FM, Co) - antiferromagnetic (AFM, NiO) composites. The coercivity, HC, and energy product, BHMax, of these composites can be enhanced at room temperature after appropriate heat treatments above the Néel temperature of the AFM, TN. Although the maximum Hc is achieved for the (NiO)1: 1 (Co) weight ratio, BHMax is further enhanced for the (NiO)2:3(Co) ratio, where higher saturation magnetization is obtained due to the larger amount of FM. Exchange coupling, responsible for these effects, decreases as the temperature is increased and vanishes close to TN. The thermal stability of the coercivity enhancement remains rather insensitive to the somewhat broad distribution of blocking temperatures of this system.

We prepared Eu-doped films of Si nanoparticles embedded in SiO2 using pellets of Eu2O3 by sputtering. We studied their photoemission, transmission and fluorescence to obtain data about their composition and particle size and the Eu interaction characteristics. We were able to incorporate Eu(III) into the Si nanoparticle / SiO2 host. We also found we obtained Eu(II) in the process. We found a lowering of photoluminescence intensity with lowering of temperature. An as yet unanswered question is the reason for the intense whitish luminescence found in some regions of the samples. Some involvement with Eu(II) is suspected. Eu(IIl) related peaks were only observed where the size distribution peak of the nanoparticles was lower than 1.3nm. Whitish luminescence was related to peak sizes ranging from 1.1nm to 1.4nm. Annealing the samples had clear effects upon their photoluminescence, but did not necessarily involve changes in particle sizes, nor were these size changes necessary to increase luminescence. The Eu doping has a tendency to halt the annealing effects on size and, when changes did occur, the particles generally became smaller.

The fabrication and testing of screen printed dye-sensitized large solar cell (15 cm × 15 cm) based on nanocrystalline TiO2 is described. It is the largest photo-electrochemical (PEC) cell that is based on the dye sensitization of thin (8-18 μm) films of TiO2 nanoparticles in contact with a non-aqueous liquid electrolyte. The cell has the potential to be a low cost, commercial, environmentally friendly, photovoltaic option. Surface as well as electrical characterization, of the nanostructured PEC cells have been performed. The efficiency of these large commercial cells are compared to the laboratory-made small PEC cells. Key words: Photoelectrochemical, solar cells, nanocrystalline, dye-sensitized

Carboxylate-alumoxanes are organic substituted alumina nano-particles synthesized from boehmite in aqueous solution which are an inexpensive and environmentally benign precursor for the fabrication of nano-, meso-, and macro-scale aluminum based ceramics. The use of carboxylate-alumoxanes as a novel high surface area alumina support for heterogeneous catalysis will be discussed. The ability to perform further chemistry on the organic ligands of the carboxylate-alumoxanes allows for attachment of catalysts. During calcination, the organic ligands are burned out, leaving behind the catalyst in a well-dispersed manner. To demonstrate this concept, the metathesis of C16 olefins using a molybdenum oxide catalyst supported on alumina will be discussed using the carboxylate-alumoxane method.

A new interatomic potential has been developed for molecular-dynamics simulations of TiO2 based on the formalism of Streitz and Mintmire [J. Adhesion Sci. Technol. 8, 853 (1994)], in which atomic charges vary dynamically according to the generalized electronegativity-equalization principle. The present potential reproduces various quantities of rutile crystal including vibrational density of states, static dielectric constants, melting temperature, elastic moduli, and surface relaxation. Calculated cohesive-energy and dielectric constants for anatase crystal agree well with experimental data. The potential is applied to TiO2 nanoclusters (size 60-80Å) for both anatase and rutile phases to analyze their equilibrium configuration and spacecharge distribution. Stable double-charge layer is found in the surface region of a spherical nanocluster for both rutile and anatase, resulting in enhanced Coulomb-repulsion between the nanoclusters at close proximity.

Evolution of atomic and electronic structures of silicon-carbide (SiC) nanocrystals during sintering is investigated by a tight-binding molecular dynamics (TBMD) method. An O(N) algorithm (the Fermi-operator expansion method) is employed for calculating electronic contributions in the energy and forces. Simulations are performed on our eight-node parallel PC cluster. In a sintering simulation of aligned (no tilt or twist) SiC nanocrystals at T = 1000K, we find that a neck is formed promptly without formation of defects. Analyses of local electronic density-of-states (DOS) and effective charges reveal that unsaturated bonds exist only in grain surfaces accompanying the gap states. In the case of tilted (<122>) nanocrystals, surface structures formed before sintering affect significantly the grainboundary formation.