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Author: Dittrich, S. ×

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Now showing 1 - 4 of 4
  • Publication
    Bilayered Glass-Ceramics as Sealants for SOFCs
    ( 2019)
    Hauber, Stefanie
    ;
    Dittrich, S.
    ;
    Walter, T.
    ;
    Durschang, Bernhard
    ;
    Schell, K.G.
    ;
    Bucharsky, E.C.
    ;
    Sextl, Gerhard
    ;
    Hoffmann, M.J.
    Glass-ceramics are often used as sealants in solid oxide fuel cells (SOFC). But interfacing components, such as ferriticstainless steel and YSZ electrolyte, may vary in their requirements regarding sealing properties, especially in terms of thermalexpansion. A bilayered glass-ceramic system was developed to overcome the mismatch in coefficients of thermal expansion (CTE)between ferritic steel and YSZ. Therefore, two different glass-ceramics with slightly different CTEs were developed, one with goodbonding characteristics to the ferritic steel and the other to the YSZ electrolyte. Steel and electrolyte components were coated with alayer of their corresponding glass sealant paste and heated up to form a sandwich sample. During the heat treatment of the sealingprocess, the glasses are crystallized into glass-ceramics. The resulting interface between the two glass-ceramics is of special interest.Cross-sections of the sandwich samples were cut, polished and investigated using SEM. The glass-ceramics show continuous,gap-free layers and excellent bonding to both steel and YSZ. Energy release rates are measured for single and bilayered glass sealantsby mechanical testing. The designed bilayered glass-ceramics fulfill the special requirements of ferritic steel and YSZ. They showexcellent potential to become a new outstanding sealant for SOFCs.
  • Publication
    Ultra-high pressure and ultra-reduced minerals in ophiolites may form by lightning strikes
    ( 2017)
    Ballhaus, C.
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    Wirth, R.
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    Fonseca, R.O.C.
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    Blanchard, H.
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    Pröll, W.
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    Bragagni, A.
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    Nagel, T.
    ;
    Schreiber, A.
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    Dittrich, S.
    ;
    Thome, V.
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    Hezel, D.C.
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    Below, R.
    ;
    Cieszynski, H.
    Since ultra-high pressure (UHP) minerals have been discovered in ophiolites from Tibet and the Polar Urals, it is speculated that the mantle sections of ophiolites may originate deep within the mantle. The UHP minerals are frequently found together with ultra-reduced silicides, carbides, and nitrides. Consequently, it is argued that the deep mantle, or at least domains within it, must be highly reduced, so reduced that practically all transition elements at depth are present in the metallic state. We find it problematic to rewrite the history of ophiolite complexes based on these observations and suggest we should search for alternative and more realistic modes of origin. Electric discharge experiments at >6000 K reported here show that the UHP and highly reduced phase assemblages may precipitate from plasmas. We argue that the mineral assemblages may originate by lightning strikes. As such, they may not record the origin and emplacement history of the mantle lithologies within which they occur.
  • Publication
    On the way to a comprehensive APC library
    ( 2011)
    Hartung, U.
    ;
    Unkelbach, T.
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    Gebauer, L.
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    Dementjev, A.
    ;
    Dittrich, S.
  • Publication
    Integration of inertial MEMS sensors in active smart RFID labels for transport monitoring
    ( 2009)
    Reuter, Danny
    ;
    Nowack, M.
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    Bertz, Andreas
    ;
    Wiemer, Maik
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    Semar, R.
    ;
    Kriebel, F.
    ;
    Hopp, K.-F.
    ;
    Dittrich, S.
    ;
    Thieme, T.
    The transport monitoring of sensitive and valuable goods requires, besides the storage of logistic data, the record of climate and ambient conditions. Therefore the acquisition of physical values like temperature, humidity, pressure, acceleration and inclination is necessary. Commercially available data logger devices are expensive and sizable. A cost effective alternative are active smart radio frequency identification (RFID) label containing microelectromechanical systems (MEMS). By integration of sensors, display and autonomous energy supply in a passive RFID label, wireless smart systems are created. However, the integration of MEMS into smart labels causes special requirements concerning power consumption and packaging. The power consumption of the system is limited due to the autonomous energy supply and so energy efficiency of the sensor is a key requirement. The special demands to the packaging are caused by the assembly of smart labels. The devices are integrated by flip chip bonding on an interposer, which is laminated between the capping layers of the label. Furthermore, usual roll to roll fabrication demands flexibility of the layers. This assembly technique limits the height of the components and hence, no additional housing of the chips is applicable. Therefore, wafer level packaging of the MEMS transducer providing hermetic sealing by minimizing chip geometry is necessary. For realizing a semi-active smart RFID label monitoring temperature, mechanical shock and inclination during transport processes, a MEMS based capacitive inertial sensor has been developed. For low energy consumption of the system sensor functionalities have been integrated and a low-power mixed-signal ASIC for sensor signal processing has been developed. Hermetic sealing of the microstructures has been done by seal glass bonding and a wafer level thin film encapsulation (TFE) technology based on CF-polymer as sacrificial layer material.