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In this work, Li/air batteries based on nonaqueous electrolytes were investigated in ambient conditions (with an oxygen partial pressure of 0.21 atm and relative humidity of ∼20%). A heat-sealable polymer membrane was used as both an oxygen-diffusion membrane and as a moisture barrier for Li/air batteries. The membrane also can minimize the evaporation of the electrolyte from the batteries. Li/air batteries with this membrane can operate in ambient conditions for more than one month with a specific energy of 362 Wh kg −1 , based on the total weight of the battery including its packaging. Among various carbon sources used in this work, Li/air batteries using Ketjenblack (KB) carbon-based air electrodes exhibited the highest specific energy. However, KB-based air electrodes expanded significantly and absorbed much more electrolyte than electrodes made from other carbon sources. The weight distribution of a typical Li/air battery using the KB-based air electrode was dominated by the electrolyte (∼70%). Lithium metal anodes and KB-carbon account for only 5.12% and 5.78% of the battery weight, respectively. We also found that only ∼20% of the mesopore volume of the air electrode was occupied by reaction products after discharge. To further improve the specific energy of the Li/air batteries, the microstructure of the carbon electrode needs to be further improved to absorb much less electrolyte while still holding significant amounts of reaction products.

The entropy changes (� S) in various cathode and anode materials, as well as in complete Li-ion batteries, were measured using an electrochemical thermodynamic measurement system (ETMS). LiCoO2 has a much larger entropy change than electrodes based on LiNixCoyMnzO2 and LiFePO4, while lithium titanate based anodes have lower entropy change compared to graphite anodes. The reversible heat generation rate was found to be a significant portion of the total heat generation rate. The appropriate combinations of cathode and anode were investigated to minimize reversible heat generation rate across the 0–100% state of charge (SOC) range. In addition to screening for battery electrode materials with low reversible heat, the techniques described in this paper can be a useful engineering tool for battery thermal management in stationary and transportation applications.

The rapid development of portable electronic devices increasingly requires much more energy to support advanced functions. However, currently available batteries do not meet the high energy requirement of these devices. Metal/air batteries, especially Li/air batteries, have a much higher specific energy than most other available batteries, but their power rate is limited by the accumulation of reaction products in the air electrode. Several approaches to improve the power rate of Li/air batteries have been analyzed in this work, including adjustment of air electrode porosity and catalyst reactivity distributions to minimize diffusion limitations and maximize air electrode material utilization. An interconnected dual pore system (one catalyzed and one non-catalyzed) is proposed to improve oxygen transport into the inner regions of the air electrode, but this approach alone cannot supply high power for long term applications. A time-release multiple catalyst approach is analyzed to provide temporal release of reactivity in the air electrode. When coupled with the dual pore configuration and catalysts with high reactivities, the time-release catalyst concept can extend the duration of higher powers to longer times, and result in maximum utilization of air electrode materials.

Intermediate-stage sintering of lanthanum strontium manganite (LSM, where Sr=0.00, 0.05, 0.10, 0.15, and 0.20) was shown in dilatometry studies to be accelerated when subjected to alternating flows of air and nitrogen. The extent of rate enhancement decreased with increased Sr content, and decreases with increased temperature, which coincides with diminished oxygen non-stoichiometry. Shrinkage rates were shown further to be sensitive to the difference in oxygen content in the alternating gas flows. Baseline air sintering rates were measured using stepwise isothermal dilatometry, from which kinetic parameters were calculated using the Makipirtti-Meng model. Activation energies for sintering in air were determined to be 255±26, 258±28, 308±32, 373±37, and 417±41 kJ/mol for Sr=0.0, 0.05, 0.10, 0.15, and 0.20, respectively. A diffusion-based model is proposed that is consistent with trends in accelerated shrinkage versus temperature. Transient cation vacancy gradients, which lead to higher cation mobility, were calculated from established oxygen diffusivities and oxygen non-stoichiometry as a function of temperature and time. A potential application of this approach is processing of LSM-based cathode-side contact pastes in solid oxide fuel cells.

The entropy changes (Δ S ) in various cathode and anode materials, as well as complete Li-ion batteries, were measured using an electrochemical thermodynamic measurement system (ETMS). A thermal model based on the fundamental properties of individual electrodes was used to obtain transient and equilibrium temperature distributions of Li-ion batteries. The results from theoretical simulations were compared with results obtained in experimental measurements. We found that the detailed shape of the entropy curves strongly depends on the manufacturer of the materials even for the same nominal compositions. LiCoO 2 has a much larger entropy change than LiNi x Co y Mn z O 2 . This means that LiNi x Co y Mn z O 2 is much more thermodynamically stable than LiCoO 2 ). The temperatures around the positive terminal of a prismatic battery are consistently higher than those at the negative terminal, due to differences in the thermal conductivities of the different terminal connectors. When all other simulation parameters are the same, simulations that use a battery-averaged entropy tend to overestimate the predicted temperatures when compared with simulations that use individual entropies for the anode and the cathode, due to computational averaging.

In situ, time-lapse images of the early stages of pitting in dilute NaCl solutions, and intergranular corrosion in dilute oxalic acid solutions, have been obtained in Type 304 SS (UNS S30400) using an electrochemical atomic force microscope (ECAFM). A pit was observed to grow from an irregular shape with ledges along the pit walls, to a round pit with an island formation, over a 6-min time span. Grain boundary chromium carbides were exposed, and then partially dissolved, over a 26-min time span. The intergranular corrosion was most prominent along the grain boundary between the carbides, rather than between the carbides and the matrix, leaving the carbides intact via ligaments of matrix material. This study demonstrated the usefulness and complexities in using the ECAFM for studying the early stages in pitting and intergranular corrosion.

Laser Raman spectroscopy was used to study the dissolution of volatile hydrocarbon molecules in thin films of poly-α-olefin oil. Above the boiling point of the hydrocarbon, or when no liquid hydrocarbon was present, the dissolution was driven by Henry's law solubilities in line with previous models. However, below the boiling point and when significant liquid hydrocarbon was present, dissolution was entropically driven. Under these conditions, where equilibrium solubilities were not achievable, the Raman spectra were used to determine dissolution rates. Over the range of conditions studied, and particularly for a given class of volatile hydrocarbons, pressure and temperature influenced the dissolution rate primarily by affecting the vapor pressure and concentration of the volatile hydrocarbon. The rate-limiting step for the dissolution involved mass transport at the vapor/film interface.

Atomistic simulations of coupled anion/cation disorder in the pyrochlore structure of Gd{sub 2}(Zr{sub x}Ti{sub 1{minus}x}){sub 2}O{sub 7} show that homoatomic cation vacancy migration energies range from 3.8 to 7.9 eV, and increase with the addition of anion defects. For ordered materials, the energies for heteroatomic Ti or Zr vacancy migrations to Gd sites are 1.4 and 1.9 eV, respectively, but the addition of neighboring oxygen defects generally reduces these energies to less than 1 eV. The heteroatomic migration of Gd vacancies to Ti or Zr sites remains rather large ({gt}2.7 eV) even with the presence of oxygen defects.

Battelle Memorial Institute as part of its U.S. Department of Energy (USDOE) Contract No. DE-AC05-76RL01830 to operate the Pacific Northwest National Laboratory (PNNL) provides technology assistance to qualifying small businesses in association with a Technology Assistance Program (TAP). Qualifying companies are eligible to receive a set quantity of labor associated with specific technical assistance. Having applied for a TAP agreement to assist with fatigue characterization of Abrasive Water Jet (AWJ) cut titanium specimens, the OMAX Corporation was awarded TAP agreement 09-02. This program was specified to cover dynamic testing and analysis of fatigue specimens cut from titanium alloy Ti-6%Al-4%V via AWJ technologies. In association with the TAP agreement, a best effort agreement was made to characterize fatigue specimens based on test conditions supplied by OMAX.

This chapter will briefly summarize the development of thin-film barrier layers in various applications, and more concisely describe the OLED vapor barrier technical requirements (Section 4.2). This is followed, in Section 4.3, by a brief summary of relevant experimental methods used to measure gas permeation in thin-films. Attempts are made to delineate the advantages and disadvantages of each measurement technique. In Section 4.4 we describe some of the historical analytical/modeling approaches that have been invoked to explain the measured analytical results, and discuss some of the more important shortcomings of those modeling concepts. This is followed in Section 4.5 by presentation of an approach suitable to describe gas diffusion in multilayer thin-film structures. Transient permeation measurements are used to extract physically reasonable values for the in-situ effective diffusivity and solubility of the various polymer and oxide layers, as well as estimates of defect size and spatial density consistent with those parameters. The implications of these results are that lag times for permeant breakthrough in multilayered barrier systems are extremely long and are likely to dominate many of the results reported to date, rather than the commonly measured steady state flux. These findings are then discussed in relation to practical OLEDmore » encapsulation in Section 4.6, along with the need for new techniques for further improving the barrier quality. Section 4.7 contains the conclusions of the paper.« less

stoichiometry. Initial characterization by XR, found both samples to be single-phase zircons. The zircons containing 8.85 wt. % 238Pu, with its 87.7 year half-life, provided a means of accelerating the a-decay rate (i.e., damage rate) by a factor of -250 when compared to the zircons containing 10 wt. % 239Pu. Self-heating in the 238Pu-substitute d zircon specimens during storage has been minimal, and specimen temperatures have been estimated to be less than 50°C. The accumulated doses in these samples are 2.8 x 1019 and 1.2 x 1017a-decays/g for the 238Puand 239Pu-substitute d zircons, respectively. Self-radiation from Pu decay in zircon results in the simultaneous accumulation of point defects and amorphous domains that eventually lead to a completely amorphous state.3 The swelling in zircon increases sigmoidally with dose and is well saturated at the highest dose. The saturation swelling increases with decreasing porosity of the synthesized zircon pellets, from 16.6% swelling for synthetic zircons with 5.5% porosity to 18.4% for natural zircons (0% porosity). In all cases, the swelling can be accurately modeled based on the contributions from crystalline and amorphous components. The XAS results at the highest doses confirmed that self-radiation damage had transformed the 238Pu-substitute d zircon into a fully amorphous state lacking long-range order.5 Surprisingly, the Pu Lm-edge XANES indicated that the Pu in both zircon samples is trivalent This was an unexpected result of originally preparing the Pu-substituted zircons under a reducing atmosphere (oxygen-purged flowing argon). Recent computer simulations using energy minimization techniques indicate that the lowest energy configuration occurs for a defect cluster composed of two near-neighbor Pu3+ substitutions on Zr4* sites and a neighboring charge-compensating oxygen vacancy.6 Detailed X-ray absorption spectroscopy and X-ray diffraction methods have characterized the short-range and long-range structures of each zircon type.7 The amorphous state of the 238Pu-substitute d zircon is consistent with the loss of longrange order and edge-sharing relationships between SiO4 and ZrO8 polyhedra. Despite this, a distorted zircon structure and stoichiometry, which consists of SiO4 and ZrO8 polyhedra that have rotated relative to each other, are retained over length scales up to 0.5 nm. The recrystallization of the amorphous ^Pu-substituted zircon could be achieved directly at temperatures as low as 1200°C if heated rapidly through the intermediate temperature regime where decomposition to oxides is preferred. The decomposition of amorphous zircon to constituent oxides observed at intermediate temperatures is probably kinetically limited by Zr diffusion, which has a lower energy barrier than the polyhedral rotation required

We report a novel, facile, and reproducible method for large-scale production of highly porous, hollow silica foams (hollow spheres) with a robust ultrathin shell of several nanometres through a simple, one-step, bubble-controlled, interfacial hydrolysis reaction. This material has exceptional properties, including ultralow density (0.028 g cm−3, approaching 99% porosity), good thermal stability up to 1000 °C, an exceptionally high capacity for oil uptake from mixed solvents (up to 25.6 cm3 g−1), and a very low thermal conductivity comparable to ultralow density silica aerogels.

The effects of carbon microstructure and carbon loading on the performance of Li/air batteries were investigated. The active carbons from various sources were compared, and a dry rolling method was optimized to prepare air electrodes with high mesopore volume. It is found that the capacities of air electrodes improve significantly when the mesopore volume of the carbon source is high. However, for carbons with low mesopore volumes, other factors such as surface activity also play an important role in determining the electrochemical performances of the Li/air batteries. A practical criterion, area-specific capacity, was used to optimize the carbon loading for air electrode. The best area-specific capacity of 13.1 mAh/cm2 was obtained at a carbon loading of 15.1 mg/cm2. Further increasing or decreasing the carbon loading led to a reduced area- specific capacity. Finally, at fixed carbon loading and discharge rates, electrolyte amount was another key factor governing cell performance. A spring mechanism is proposed to explain the formation of the tri-phase regions in air electrodes. After optimizing the parameters listed above, a high capacity of 1,756 mAh/g carbon corresponding to a specific energy of 4,614 Wh/kg carbon was obtained for Li/air batteries operated in a dry air environment.

Most current artificial lung technologies require the delivery of oxygen to the blood via permeable hollow fibers, depending on membrane diffusivity and differential partial pressure to drive gas exchange. We have identified an alternative approach in which dissolved oxygen (DO) is generated directly from the water content of blood through the indirect interaction of ultraviolet (UV) light with a semiconducting titanium dioxide thin film. This reaction is promoted by photon absorption and displacement of electrons from the photoactive film and yields a cascading displacement of electron “holes” to the aqueous interface resulting in the oxidation of water molecules to form DO. Anatase TiO2 (photocatalyst) and indium tin oxide (ITO) (electrically conductive and light transparent) coatings were deposited onto quartz flow-cell plates by direct current reactive magnetron sputtering. The crystal structure of the films was evaluated by grazing incidence x-ray diffraction, which confirmed that the primary crystal phase of the TiO2 thin film was anatase with a probable rutile secondary phase. Surface topology and roughness were determined by atomic force microscopy, demonstrating a stochastically uniform array of nanocrystallites. UV illumination of the titanium dioxide thin film through the quartz/ITO surface resulted in the rapid increase of DO and oxyhemoglobin in adjacent flowing blood on the opposite TiO2 surface at a rate of 1.0×10−5 mmol O2∕s. The rate of oxyhemoglobin generation was linearly proportional to residence time adjacent to the photoactive surface in a flow-through test cell under steady-state conditions. Preliminary biocompatibility for the proposed photocatalytic effect on whole blood demonstrated no increase in the rate of hemolysis or generation of toxic byproducts of photo-oxidation. These results demonstrate the feasibility and safety of employing optoelectronic mechanisms to promote oxygenation of hemoglobin in whole blood and provide substantiation for the use of this technology as a mechanism for artificial respiratory support.

Raman-band intensities for sputter-deposited TiO2/SiO2 multilayer coatings are found to exhibit a strong dependence on excitation wavelength of the probe laser. A model based on standing waves within the stack correctly predicts the magnitude and wavelength dependence of the observed enhancements.