Fuel cells have gained renewed interest for applications in portable power since the energy is stored in a separate reservoir of fuel rather than as an integral part of the power source, as is the case with batteries. While miniaturized fuel cells have been demonstrated for the low power regime (1-20 Watts), numerous issues still must be resolved prior to deployment for applications as a replacement for batteries. As traditional fuel cell designs are scaled down in both power output and physical footprint, several issues impact the operation, efficiency, and overall performance of the fuel cell system. These issues include fuel storage, fuel delivery, system startup, peak power requirements, cell stacking, and thermal management. The combination of thin-film deposition and micro-machining materials offers potential advantages with respect to stack size and weight, flow field and manifold structures, fuel storage, and thermal management. The micro-fabrication technologies that enable material and fuel flexibility through a modular fuel cell platform will be described along with experimental results from both solid oxide and proton exchange membrane, thin-film fuel cells.

Ag2S thin films of 90 nm to 300 nm in thickness were deposited at 70°C on glass substrates immersed in a bath mixture containing silver nitrate, sodium thiosulfate and dimethylthiourea. When the films are heated in nitrogen at temperatures 200°C to 400°C, crystallinity is improved and XRD pattern similar to that of acanthite is observed. These films possess electrical conductivity of 10-3 (ohm cm)-1, are photoconductive and exhibit an optical band gap of 1.36 eV. When Ag2S thin film is deposited over a thin film of Bi2S3, also obtained by chemical bath deposition from bismuth nitrate, triethanolamine and thioacetamide, and heated at 300°C to 400°C in nitrogen, a ternary compound, AgBiS2 is formed. This material has an electrical conductivity of 5x10-5 (ohm cm)-1, is photoconductive and possesses optical band gap 0.95 eV.

In this paper we describe the synthesis and characterisation of La1-xAxCoO3 (A=Ca, Sr) (0 < x < 0,5) of different morphologies using pulsed laser deposition, ceramic methods and alternative soft-chemistry techniques. Furthermore the potential use of a La1-xCaxCoO3/carbon nanotube composite material for oxygen electrodes is discussed.

A promising vanadium-based photo-catalyst (InVO4) has been proposed recently by our group. This catalyst has been shown to be active in the visible light range, up to a wavelength of about 600 nm, and is able to promote the decomposition of water. In this paper, we focus on its electronic structure, computed via first principles calculations, in order to figure out analogies and differences with similar systems (InNbO4, InTaO4 and BiVO4) that have already been reported to act as photo-catalysts. An attempt is made to address the problem of the wavelength dependency of the photo catalytic activity of the InMO4 (M = V, Nb, Ta) family and how this is related to the crystal structure. Finally, by using an ab initio molecular dynamics approach, we inspect the relaxation/reconstruction phenomena occurring at the exposed surface of the InVO4 catalyst induced by the absorption of a water molecule, that represents a crucial step in the catalysis reaction.

In this study, doped lanthanum gallate (LSGM with the composition La0.9Sr0.1Ga0.8Mg0.2O3-δ, LSGMC with the composition La0.8Sr0.2Ga0.8Mg0.15Co0.05O3-δ) films for an electrolyte of the solid oxide fuel cell (SOFC) were prepared by pulsed laser deposition (PLD) technique. In the vacuum chamber, LSGM or LSGMC targets were set on the rotating target holder. A KrF excimer laser was introduced into the chamber at an incident angle of about 45 degree. The doped LaGaO3 film was deposited onto NiO substrates without heating in argon ambient gas. The NiO substrate can be used directly as an electrode in the fabrication of the SOFC. The deposited LSGM films were characterized by X-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS) and scanning electron microscopy (SEM). As-deposited films were amorphous. After post annealing at 1273K for 6-10 hours, crystalline LaGaO3 was obtained. Films with thickness greater than several 10 μm showed an uniform and dense morphology. No gas leakage was found using thick films, which is an important characteristic for an electrolyte in fuel cells. The composition of the deposited films was slightly different to that of the target.

Pico-second pulsed laser deposition (PLD) was employed to fabricate copper indium disulfide (CIS) thin films onto pure silica and Mo coated glass substrates. By properly preparing the target materials and controlling the elemental ratio of the Cu, In and S in the deposited film followed by post-thermal annealing, good quality copper-indium-disulfide(CIS) films can be obtained. A series of characterizations were conducted including XRD, RBS, IR, UV-Vis, AFM and STM analyses.

Plasma-enhanced chemical vapor deposition (PECVD) is being developed as a flexible coating technology for a variety of oxides. In this paper we discuss the synthesis of transparent conducting oxides (TCOs), insulating oxides and electrochromic oxides. Tin oxide was synthesized using mixtures of SnCl4 and O2. By proper control of processing conditions the resistivity of this material may be varied from 10-3 < ρ < 105 Ω-cm. Films of varying resistivity were employed as buffer layers in CdS/CdTe solar cells. Preliminary device results have demonstrated that integration of a tin oxide buffer layer was very beneficial for cell performance. In addition, we demonstrate the PECVD synthesis of WO3 from WF6/O2/H2/Ar mixtures. The plasma process space that yielded adherent, transparent tungsten oxide was established. The deposited films were both amorphous and reversibly electrochromic. High temperature annealing above 400°C converted the films into a polycrystalline state.

A detailed analysis of the formation energies of transition metal hydrides is presented. The hydriding energies are computed for various crystal structures using Density Functional Theory. The process of hydride formation is broken down into three consecutive, hypothetical reactions in order to analyse the different energy contributions, and explain the observed trends. We find that the stability of the host metal is very significant in determining the formation energy, thereby providing a more fundamental justification for Miedema's “law of inverse stability” [1] (the more stable the metal, the less stable the hydride). The conversion of the host metal to the structure formed by the metal ions in the hydride (fcc in most cases) is only significant for metals with a strong bcc preference such as V and Cr - this lowers the driving force for hydride formation. The final contribution is the chemical bonding between the hydrogen and the metal. This is the only contribution that is negative, and hence favourable to hydride formation. We find that it is dominated by the position of the Fermi level in the host metal.

A grain boundary engineering approach was employed to improve the microstructure of a commercial Pb-base alloy for better performance in automobile battery application. Through a combination of cold working, recrystallization and subsequent thermomechanical-processing, it was possible to increase the fraction of the low ∑ coincidence site lattice boundaries up to 91% in addition to the substantial grain refinement. A preliminary electrochemical evaluation indicated a better corrosion resistance in the experimental material laden with the special boundaries. The high frequency of the coincidence site lattice boundaries in the specimens was interpreted in terms of the '∑3 regeneration' model proposed in previous works.

Composition spreads of La1-xSrxCoO3 (LSCO) were synthesized as thermo-electric transducer material by means of combinatorial material synthesis, and information on their thermal diffusivity throughout the specimens was obtained. Meanwhile, it is anticipated that the composition spreads of LSCO have a variety of characteristic properties of light absorption corresponding to their composition, namely their compositional variable, x. Hence, we used transient optical pump-and-probe techniques in a reflection geometry to measure thermal diffusion times on LSCO. The results of signal analysis indicate that LSCO is a peculiar synthesized substance whose apparent thermal diffusivity, 1/ι, changes abruptly at the critical point, where the compositional variable x is equal to 0.3.

The design of new materials can be made more efficient if toxicity screening is performed in early rather than in late stages of development, especially for volatile materials such as lubricants, fire retardants, fuels, and fuel additives. In our continuing efforts to develop methods for the prediction of the toxicological response to materials of interest to the U.S. Air Force, we have constructed Quantitative Structure-Activity Relationships (QSARs) for thirteen newly proposed propellant compounds. We employed two previously published in vitro toxicity endpoints in primary cultures of isolated rat hepatocytes, which measured decrease in mitochondrial function and glutathione depletion [1]. Molecular descriptors were obtained using ab initio molecular orbital theory. QSAR models were then derived for each endpoint. Correlation coefficients for 2- and 3-parameter QSARs exceed 0.9, possibly enabling toxicity predictions for similar compounds. Insight into the biophysical mechanism of toxic response can be gained from interpretation of the descriptors comprising the QSARs.

3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) layers exhibit significant photoresponse. Despite of unfavorable electronic energy level alignment at the dye/PTCDA interface, photon-to-electron conversion efficiencies as high as 1% were observed.

To explore a possibility of obtaining an ultra fine grain size in hcp materials, equal channel angular pressing (ECAP) was applied to commercially pure Zr with the initial grain size of 20 μm. To ensure the crack-free specimen during the severe deformation it was necessary to adopt different die designs at the two processing temperatures, room temperature and 350°C. Submicrometer scale grains, in the order of 200 nm, were obtained by employing the die design of 90°/20° and the deformation temperature of 350°C. With the proper choice of the processing parameters, the refined grains were surrounded by the high angle boundaries. During the severe plastic deformation, the crystal texture underwent a significant change, from a fiber texture to that of a strong (0002) component mixed with a medium {1010} components, suggesting a dual <a> slip mode of deformation on the plane of the maximum shear stress.

We describe here the interaction of poly(vinylidene fluoride) (PVDF) with graphite based on the rheological behavior of the slurries and the surface morphology of PVDF in the final composite anode. The rheological properties of slurries show the interaction between graphite and PVDF with the viscosity varying over six orders of magnitude for different graphite particles. We correlated the suspension viscosity with the final film properties. The homogeneity of the PVDF distribution in the final composite film increases as the slurry viscosity increases. The interaction between graphite and PVDF is altered through the chemical properties of polymer such as molecular weight and functionality, leading to an improved morphology of PVDF.

Direct-write technologies offer the potential for low-cost materials-efficient deposition of contact metallizations for photovoltaics. We report on the inkjet printing of metal organic decomposition (MOD) inks with and without nanoparticle additions. Near-bulk conductivity of printed and sprayed metal films has been achieved for Ag and Ag nanocomposites. Good adhesion and ohmic contacts with a measured contact resistance of 400μΩ•cm2 have been observed between the sprayed silver films and a heavily doped n-type layer of Si. Silver deposited using the MOD ink burns through the Si3N4 antireflection coating when annealed at 850°C to form an ohmic contact to the n-Si underneath. An active solar cell device was fabricated using a top contact that was spray printed using the Ag MOD ink. Inkjet printed films show adhesion differences as a function of the process temperature and solvent. Silver lines with good adhesion and conductivity have been printed on glass with 100 μm resolution.