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High Energy Densities (high + energy_density)

Distribution by Scientific Domains
Polymers and Materials Science50%

Terms modified by High Energy Densities

  • high energy density material
    		•

    Selected Abstracts

    Design and Synthesis of Hierarchical Nanowire Composites for Electrochemical Energy Storage

    ADVANCED FUNCTIONAL MATERIALS, Issue 21 2009
    Zheng Chen
    Abstract Nanocomposites of interpenetrating carbon nanotubes and vanadium pentoxide (V2O5) nanowires networks are synthesized via a simple in situ hydrothermal process. These fibrous nanocomposites are hierarchically porous with high surface area and good electric conductivity, which makes them excellent material candidates for supercapacitors with high energy density and power density. Nanocomposites with a capacitance up to 440 and 200,F g,1 are achieved at current densities of 0.25 and 10 A g,1, respectively. Asymmetric devices based on these nanocomposites and aqueous electrolyte exhibit an excellent charge/discharge capability, and high energy densities of 16,W h kg,1 at a power density of 75,W kg,1 and 5.5,W h kg,1 at a high power density of 3,750,W kg,1. This performance is a significant improvement over current electrochemical capacitors and is highly competetive with Ni,MH batteries. This work provides a new platform for high-density electrical-energy storage for electric vehicles and other applications. [source]

    Fast foods, energy density and obesity: a possible mechanistic link

    OBESITY REVIEWS, Issue 4 2003
    A. M. Prentice
    Summary Fast foods are frequently linked to the epidemic of obesity, but there has been very little scientific appraisal of a possible causal role. Here we review a series of studies demonstrating that the energy density of foods is a key determinant of energy intake. These studies show that humans have a weak innate ability to recognise foods with a high energy density and to appropriately down-regulate the bulk of food eaten in order to maintain energy balance. This induces so called ,passive over-consumption'. Composition data from leading fast food company websites are then used to illustrate that most fast foods have an extremely high energy density. At some typical outlets the average energy density of the entire menus is ,1100 kJ 100 g,1. This is 65% higher than the average British diet (,670 kJ 100 g,1) and more than twice the energy density of recommended healthy diets (,525 kJ 100 g,1). It is 145% higher than traditional African diets (,450 kJ 100 g,1) that probably represent the levels against which human weight regulatory mechanisms have evolved. We conclude that the high energy densities of many fast foods challenge human appetite control systems with conditions for which they were never designed. Among regular consumers they are likely to result in the accidental consumption of excess energy and hence to promote weight gain and obesity. [source]

    Combustion of Environmentally Altered Molybdenum Trioxide Nanocomposites

    PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 3 2006
    Kevin Moore
    Abstract Nanocomposite thermite mixtures are currently under development for many primer applications due to their high energy densities, high ignition sensitivity, and low release of toxins into the environment. However, variability and inconsistencies in combustion performance have not been sufficiently investigated. Environmental interactions with the reactants are thought to be a contributing factor to these variabilities. Combustion velocity experiments were conducted on aluminum (Al) and molybdenum trioxide (MoO3) mixtures to investigate the role of environmental interactions such as light exposure and humidity. While the Al particles were maintained in an ambient, constant environment, the MoO3 particles were exposed to UV or fluorescent light, and highly humid environments. Results show that UV and fluorescent lighting over a period of days does not significantly contribute to performance deterioration. However, a humid environment severely decreases combustion performance if the oxidizer particles are not heat-treated. Heat treatment of the MoO3 greatly increases the material's ability to resist water absorption, yielding more repeatable combustion performance. This work further quantifies the role of the environment in the decrease of combustion performance of nanocomposites over time. [source]

    Design and Synthesis of Hierarchical Nanowire Composites for Electrochemical Energy Storage

    ADVANCED FUNCTIONAL MATERIALS, Issue 21 2009
    Zheng Chen
    Abstract Nanocomposites of interpenetrating carbon nanotubes and vanadium pentoxide (V2O5) nanowires networks are synthesized via a simple in situ hydrothermal process. These fibrous nanocomposites are hierarchically porous with high surface area and good electric conductivity, which makes them excellent material candidates for supercapacitors with high energy density and power density. Nanocomposites with a capacitance up to 440 and 200,F g,1 are achieved at current densities of 0.25 and 10 A g,1, respectively. Asymmetric devices based on these nanocomposites and aqueous electrolyte exhibit an excellent charge/discharge capability, and high energy densities of 16,W h kg,1 at a power density of 75,W kg,1 and 5.5,W h kg,1 at a high power density of 3,750,W kg,1. This performance is a significant improvement over current electrochemical capacitors and is highly competetive with Ni,MH batteries. This work provides a new platform for high-density electrical-energy storage for electric vehicles and other applications. [source]

    Local electrochemical properties of laser beam-welded high-strength Al,Zn,Mg,Cu alloys

    MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 1 2008
    J. Wloka
    Butt welds of two high-strength Al,Zn,Mg,Cu alloys with different zinc contents were welded by a laser beam welding technique. Due to the high energy density of the laser beam, the microstructural changes are confined to very thin regions. Electrochemical properties of the weld heat-affected zones are investigated by local electrochemical measurement techniques and correlated with microhardness measurements, macroscopic corrosion behaviour and metallographic sections. It turned out that microelectrochemical techniques, especially the EC-pen is a versatile and easy to handle tool for the resolution of changes in the electrochemical properties across a weld bead. It unveils modifications, which cannot be resolved by hardness measurements. By microcell measurements, local corrosion kinetics can be estimated. [source]

    Fast foods, energy density and obesity: a possible mechanistic link

    OBESITY REVIEWS, Issue 4 2003
    A. M. Prentice
    Summary Fast foods are frequently linked to the epidemic of obesity, but there has been very little scientific appraisal of a possible causal role. Here we review a series of studies demonstrating that the energy density of foods is a key determinant of energy intake. These studies show that humans have a weak innate ability to recognise foods with a high energy density and to appropriately down-regulate the bulk of food eaten in order to maintain energy balance. This induces so called ,passive over-consumption'. Composition data from leading fast food company websites are then used to illustrate that most fast foods have an extremely high energy density. At some typical outlets the average energy density of the entire menus is ,1100 kJ 100 g,1. This is 65% higher than the average British diet (,670 kJ 100 g,1) and more than twice the energy density of recommended healthy diets (,525 kJ 100 g,1). It is 145% higher than traditional African diets (,450 kJ 100 g,1) that probably represent the levels against which human weight regulatory mechanisms have evolved. We conclude that the high energy densities of many fast foods challenge human appetite control systems with conditions for which they were never designed. Among regular consumers they are likely to result in the accidental consumption of excess energy and hence to promote weight gain and obesity. [source]