Erik J. Brandon

California Institute of Technology, Pasadena, California, United States

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Publications (8)24.06 Total impact

  • 224th ECS Meeting; 10/2013
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    ABSTRACT: The ability to quickly store and deliver a significant amount of electrical energy at ultralow temperatures is critical for the energy-efficient operation of high altitude aircraft and spacecraft, exploration of natural resources in polar regions and extreme altitudes, and astronomical observatories exposed to ultralow temperatures. Commercial high-power electrochemical capacitors fail to operate at temperatures below –40 °C. According to conventional wisdom, mesoporous electrochemical capacitor electrodes with pores large enough to accommodate fully solvated ions are needed for sufficiently rapid ion transport at lower temperatures. It is demonstrated that strictly microporous carbon electrodes with much higher volumetric capacitance can be efficiently used at temperatures as low as –70 °C. The critical parameters, with respect to electrolyte properties and electrode porosity and microstructure, needed for achieving both rapid ion transport and efficient ion electroadsorption in porous carbons are discussed. As an example, the fabrication of an electrochemical capacitor with an outstanding performance at temperatures as low as –60 and –70 °C is demonstrated. At such low temperatures the capacitance of the synthesized electrodes is up to 123 F g−1 (≈76 F cm−3), which is 50–100% higher than that of the most common commercial electrochemical capacitor electrode at room temperature. At –60 °C selected cells based on ≈0.2 mm electrodes exhibited characteristic charge–discharge time constants of less than 9 s, which is faster than the majority of commercial devices at room temperature. The achieved combination of high energy and power densities at such ultralow temperatures is unprecedented and extremely promising for the advancement of energy storage systems.
    Advanced Functional Materials 04/2012; 22(8). DOI:10.1002/adfm.201102573 · 11.81 Impact Factor
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    ABSTRACT: Inflatable/deployable structures are under consideration as habitats for future Lunar surface science operations. The use of non-traditional structural materials combined with the need to maintain a safe working environment for extended periods in a harsh environment has led to the consideration of an integrated structural health management system for future habitats, to ensure their integrity. This article describes recent efforts to develop prototype sensing technologies and new self-healing materials that address the unique requirements of habitats comprised mainly of soft goods. A new approach to detecting impact damage is discussed, using addressable flexible capacitive sensing elements and thin film electronics in a matrixed array. Also, the use of passive wireless sensor tags for distributed sensing is discussed, wherein the need for on-board power through batteries or hardwired interconnects is eliminated. Finally, the development of a novel, microencapuslated self-healing elastomer with applications for inflatable/deployable habitats is reviewed.
    Acta Astronautica 04/2011; 68(7-8-68):883-903. DOI:10.1016/j.actaastro.2010.08.016 · 0.82 Impact Factor
  • MRS Online Proceeding Library 01/2011; 814. DOI:10.1557/PROC-814-I9.7
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    ABSTRACT: Double-layer capacitor electrolytes employing 1,3-dioxolane as a cosolvent with acetonitrile have been evaluated in coin cells using electrochemical impedance spectroscopy and dc charging and discharging tests. Addition of the lower-melting-point 1,3-dioxolane to the standard acetonitrile solvent was found to extend the low-temperature operational range of test cells beyond that of commercially available cells. By adjusting the concentration of the tetraethylammonium tetrafluoroborate salt used, the equivalent series resistance can be minimized to enable optimal power delivery at a given temperature. (C) 2008 The Electrochemical Society.
    Journal of The Electrochemical Society 01/2008; 155(10). DOI:10.1149/1.2961044 · 2.86 Impact Factor
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    ABSTRACT: This work describes the design and testing of organic electrolyte systems that extend the low temperature operational limit of double-layer capacitors (also known as supercapacitors) beyond that of typical commercially available components. Electrolytes were based on a tetraethylammonium tetrafluoroborate/acetonitrile system, modified with low melting co-solvents (such as formates, esters and cyclic ethers) to enable charging and discharging of test cells to as low as −75°C. Cell capacitance exhibited little dependence on the electrolyte salt concentration or the nature of the co-solvent used, however, both variables strongly influenced the cell equivalent series resistance (ESR). Minimizing the increase in ESR posed the greatest design challenge, which limited realistic operation of these test cells to −55°C (still improved relative to the typical rated limit of −40°C for commercially available non-aqueous cells).
    Journal of Power Sources 06/2007; 170(1):225-232. DOI:10.1016/j.jpowsour.2007.04.001 · 6.22 Impact Factor
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    ABSTRACT: We present two different kinds of semiconductor strain sensors: ungated n+ micro-crystalline silicon (n+ μC-Si), and gated hydrogenated amorphous silicon (a-Si:H). Both sensor types are fabricated on flexible polyimide substrates. The sensors were characterized with bending perpendicular, parallel, and at 45° with respect to the sensor bias direction, and for several bending diameters. Sensor size and power consumption are significantly reduced compared to metallic foil strain sensors. Small sensor size and ease of integration with a-Si:H thin-film transistors also allows arrays of strain sensors or combinations of strain sensors with varying geometric orientation to allow strain direction as well as magnitude to be unambiguously determined.
    IEEE Transactions on Electron Devices 03/2006; DOI:10.1109/TED.2005.861727 · 2.36 Impact Factor
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    ABSTRACT: We have fabricated hydrogenated amorphous silicon (a-Si:H) TFTs on Kapton<sup>(R)</sup> polyimide flexible substrates and characterized their response to deployment-like mechanical stresses and to radiation exposure. To maintain substrate flatness and provide improved thermal transfer during fabrication, we used a pressure-sensitive silicone gel adhesive layer to mount Kapton<sup>(R)</sup> substrates onto glass carriers. The test results, presented in this paper, are encouraging for space use of a-Si:H TFTs on polymeric substrates. Device function was retained even after 1 Mrad fast electron irradiation, and irradiation-induced device changes were removed by low-temperature thermal annealing. Although some TFTs were destroyed by substrate stressing, the majority survived with only small changes, suggesting that care in device design and placement may reduce or eliminate this problem.
    Device Research Conference, 2004. 62nd DRC. Conference Digest [Includes 'Late News Papers' volume]; 07/2004