104 research outputs found
Ioonsetel vedelikel baseeruvad elektrilise kaksikkihi kondensaatorid
VĂ€itekirja elektrooniline versioon ei sisalda publikatsioone.Elektrilise kaksikkihi kondensaatorid ehk superkondensaatorid on uudsed energiasalvestusseadmed. VĂ”rreldes patareidega on superkondensaatoritel pikem ekspluatatsiooni aeg ning palju kiirem laadimise ja tĂŒhjenemise aeg. SeetĂ”ttu sobivad superkondensaatorid seadmetesse, kus vajatakse tihedalt korduvaid ja suurt vĂ”imsust tagavaid vooluimpulsse. NĂ€iteks kasutatakse superkondensaatoreid tĂ”stukites, bussides, prĂŒgiveoautodes, kruvikeerajates, mĂ€nguasjades jne. suure hetkevĂ”imsuse saavutamiseks.
Antud töös uuritakse toatemperatuuril vedelate soolade ehk ioonsete vedelike kasutamist superkondensaatorite elektrolĂŒĂŒdina. Hinnatakse erinevate ioonsete vedelike keemilise koostise, fĂŒĂŒsikaliste omaduste ja temperatuuri mĂ”ju superkondensaatori elektrilistele omadustele. Ioonsetel vedelikel baseeruvaid superkondensaatoreid vĂ”rreldakse teistel elektrolĂŒĂŒtidel baseeruvate superkondensaatoritega. Esitatud andmete pĂ”hjal soovitati uuritud ioonsete vedelike hulgast superkondensaatorite elektrolĂŒĂŒdiks kahte ioonset vedelikku (1-etĂŒĂŒl-3-metĂŒĂŒlimidasoolium tetrafluoroboraati ja 1-etĂŒĂŒl-3-metĂŒĂŒlimidasoolium tetratsĂŒaanoboraati) kuna need tagasid suurima vĂ”imsuse superkondensaatori tĂŒhjakslaadimisel.Electrical double-layer capacitors or supercapacitors are novel energy storage devices. Compared to batteries, supercapacitors have longer life-time and much faster charging and discharging times. For these reasons supercapacitors are suitable for applications requiring repetitious current impulses with high power density. For example, supercapacitors are used in loaders, busses, garbage trucks, screwdrivers, toys etc.
In this thesis, applicability limits of ionic liquids (salts liquid at room temperature) as electrolytes for electrical double-layer capacitors are studied. The influence of chemical composition, physical properties of ionic liquids and influence of temperature to the electrical behavior of supercapacitors is estimated. Supercapacitors based on ionic liquids are compared to supercapacitors based on other non-aqueous electrolytes. On the basis of data established two ionic liquids (1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium tetracyanoborate) from ionic liquids studied are suggested as potential electrolytes for supercapacitors as they provide highest power during the discharge of supercapacitor
\u27AbendlĂ€ndische Bildung\u27 gegen den \u27Geist der Technokratie\u27. Zur Rekonstruktion geisteswissenschaftlicher Wissensformen und humanistischer Bildungskonzepte im pĂ€dagogischen Diskurs der frĂŒhen Nachkriegszeit
Dass sich die Geisteswissenschaftliche PĂ€dagogik nach 1945 an den westdeutschen UniversitĂ€ten erneut als bestimmende wissenschaftstheoretische Richtung etablieren konnte, ist - schon aufgrund der NĂ€he einiger ihrer Vertreter zur NS-Ideologie - keineswegs selbstverstĂ€ndlich. Der Beitrag untersucht die symbolischen Praktiken, mit denen Protagonisten Geisteswissenschaftlicher PĂ€dagogik ihr Wissen wiederum als zeitgemĂ€Ăe Antwort auf aktuelle Herausforderungen prĂ€sentieren konnten. Innerhalb eines allgemeinen NS-BewĂ€ltigungsdiskurses, der den Nationalsozialismus als Folge einer destruktiven \u27nihilistischen\u27 und technikverfallenen Moderne interpretierte, konnte man wertorientierte geisteswissenschaftliche Vernunft und \u27abendlĂ€ndisch-humanistische Bildung\u27 als WiderstandskrĂ€fte gegen die moderne \u27Technokratie\u27 in Stellung bringen. (DIPF/Orig.)It was not self-evident that \u27Geisteswissenschaftliche PĂ€dagogik\u27 would be re-established in West-German universities after 1945 because of some scholars\u27 closeness to Nazi ideology. This contribution examines the symbolic practices with which the protagonists presented their form of knowledge as a contemporary response to current challenges. Within a general discourse, which interpreted National Socialism as a result of a destructive \u27nihilistic\u27 technological modernity, value-orientated spiritual sciences and \u27abendlĂ€ndisch\u27-humanistic education could be placed as resistance forces against modern \u27technocracy\u27. (DIPF/Orig.
UniversitĂ€ten, Humanismus und Gesellschaft im Reich um 1500. Humanistisch-lateinische Sprachbildung im Prozess der Ăffnung der UniversitĂ€ten fĂŒr gesellschaftliche QualifikationsbedĂŒrfnisse
Als im Italien des 14. Jahrhunderts entstandene kulturelle Bewegung diffundierte der Humanismus seit Mitte des 15. Jahrhunderts in zahlreiche europĂ€ische LĂ€nder nördlich der Alpen und griff in den Gebieten des Heiligen Römischen Reiches allmĂ€hlich seit den 1450er Jahren Raum. Im Gegensatz zu Italien, wo der Humanismus zunĂ€chst eine auĂeruniversitĂ€re Bewegung war, die an den italienischen UniversitĂ€ten erst in den 1420er Jahren FuĂ fasste, hatte er im Reich von Anfang an eine starke universitĂ€re PrĂ€senz. Dass der Humanismus dabei â so die im Folgenden zu entfaltende These â eine gegenĂŒber den sĂ€kularen BedĂŒrfnissen der Gesellschaft offenere Formation von Wissen reprĂ€sentierte als die scholastisch-logisch ausgerichtete universitĂ€re Lehre, soll am Beispiel der humanistischen Sprachbildung gezeigt werden: Nachdem in einem ersten Schritt die Frage nach dem Zusammenhang von humanistischer UniversitĂ€tsreform und gesellschaftlichen QualifikationsbedĂŒrfnissen bildungs- und sozialhistorisch fĂŒr das 15. Jahrhundert prĂ€zisiert und eingegrenzt worden ist (2.), sollen die programmatischen, theoretischen und praktischen NeuansĂ€tze des humanistisch-lateinischen Sprachunterrichts analysiert (3.) und die Ergebnisse schlieĂlich auf Fragen der FunktionalitĂ€t humanistischer Sprachbildung im Hinblick auf gesellschaftliche BedĂŒrfnisse nach qualifizierter Praxis in den Jahrzehnten um 1500 bezogen werden (4.). (DIPF/Orig.
Historische Bildungsforschung im (post-)digitalen Zeitalter. Das Angebot bildungsgeschichte.de
Die Autorinnen erlÀutern die Entstehung, die Zielsetzung und den Nutzen der Internetseite bildungsgeschichte.de. Dort können TextbeitrÀge veröffentlicht werden, die in Form von Data Papers digitale BestÀnde mit bildungshistorischer Relevanz erlÀutern sowie als bildungshistorische Kolumnen auf eine öffentlichkeitswirksame Platzierung von Themen und Forschungsergebnissen abzielen. (DIPF/Orig.
Improved performance of ionic liquid supercapacitors by using tetracyanoborate anions
Supercapacitors are energy storage devices designed to operate at higher power densities than conventional batteries, but their energy density is still too low for many applications. Efforts are made to design new electrolytes with wider electrochemical windows than aqueous or conventional organic electrolytes in order to increase energy density. Ionic liquids (ILs) with wide electrochemical stability windows are excellent candidates to be employed as supercapacitor electrolytes. ILs containing tetracyanoborate anions [B(CN) 4 ] offer wider electrochemical stability than conventional electrolytes and maintain a high ionic conductivity (6.9mScm -1 ). Herein, we report the use of ILs containing the [B(CN) 4 ] anion for such an application. They presented a high maximum operating voltage of 3.7V, and two-electrode devices demonstrate high specific capacitances even when operating at relatively high rates (ca. 20Fg -1 at 15Ag -1 ). This supercapacitor stored more energy and operated at a higher power at all rates studied when compared with cells using a commonly studied ILs
Pore wall corrugation effect on the dynamics of adsorbed H 2 studied by in situ quasi elastic neutron scattering Observation of two timescaled diffusion
The self diffusion mechanisms for adsorbed H2 in different porous structures are investigated with in situ quasi elastic neutron scattering method at a temperature range from 50 K to 100 K and at various H2 loadings. The porous structures of the carbon materials have been characterized by sorption analysis with four different gases and the results are correlated with previous in depth analysis with small angle neutron scattering method. Thus, an investigation discussing the effect of pore shape and size on the nature of adsorbed H2 self diffusion is performed. It is shown that H2 adsorbed in nanometer scale pores is self diffusing in two distinguishable timescales. The effect of the pore, pore wall shape and corrugation on the fraction of confined and more mobile H2 is determined and analyzed. The increased corrugation of the pore walls is shown to have a stronger confining effect on the H2 motions. The difference of self diffusional properties of the two H2 components are shown to be smaller when adsorbed in smoother walled pores. This is attributed to the pore wall corrugation effect on the homogeneity of formed adsorbed layer
Supercapacitors (electrochemical capacitors)
International audienceRapid development of the technologies based on electric energy in the last decades have stimulated intensive research on efficient power sources. Electrochemical energy conversion and storage systems are based on Faradaic reactions (charge transfer) and electrostatic attraction of ions at the electrode/electrolyte interface. The latter might be an interesting solution for applications requiring moderate energy density, high power rates, and long cycle life. Electrochemical capacitors (ECs) store the charge in a physical manner, hence, their energy density is moderate. At the same time, the lack of electrochemical reactions ensures very high power and long cycle life compared to batteries. Activated carbons with their versatile properties (like specific surface area, well-developed and suitable porosity, heteroatoms in the graphene matrix) are the most popular materials in EC application. This chapter provides a comprehensive overview of the carbon-based materials recently developed, with special attention devoted to those obtained by biomass carbonization and activation. Electrochemical properties demonstrated by such carbons are discussed in respect to their physicochemical characteristic
Ionic liquids at electrified interfaces
Until recently, âroom-temperatureâ (<100â150 °C) liquid-state electrochemistry was mostly electrochemistry of diluted electrolytes(1)â(4) where dissolved salt ions were surrounded by a considerable amount of solvent molecules. Highly concentrated liquid electrolytes were mostly considered in the narrow (albeit important) niche of high-temperature electrochemistry of molten inorganic salts(5-9) and in the even narrower niche of âfirst-generationâ room temperature ionic liquids, RTILs (such as chloro-aluminates and alkylammonium nitrates).(10-14) The situation has changed dramatically in the 2000s after the discovery of new moisture- and temperature-stable RTILs.(15, 16) These days, the âlater generationâ RTILs attracted wide attention within the electrochemical community.(17-31) Indeed, RTILs, as a class of compounds, possess a unique combination of properties (high charge density, electrochemical stability, low/negligible volatility, tunable polarity, etc.) that make them very attractive substances from fundamental and application points of view.(32-38) Most importantly, they can mix with each other in âcocktailsâ of oneâs choice to acquire the desired properties (e.g., wider temperature range of the liquid phase(39, 40)) and can serve as almost âuniversalâ solvents.(37, 41, 42) It is worth noting here one of the advantages of RTILs as compared to their high-temperature molten salt (HTMS)(43) âsister-systemsâ.(44) In RTILs the dissolved molecules are not imbedded in a harsh high temperature environment which could be destructive for many classes of fragile (organic) molecules
Manganositeâmicrowave exfoliated graphene oxide composites for asymmetric supercapacitor device applications
Behnisch, Michael: PĂ€dagogische Beziehung. Zur Funktion und Verwendungslogik eines Topos der Jugendhilfe. WĂŒrzburg: Ergon Verlag 2005, 274 Seiten, 34,00 EUR [Rezension]
Rezension zu: Behnisch, Michael: PĂ€dagogische Beziehung. Zur Funktion und Verwendungslogik eines Topos der Jugendhilfe. WĂŒrzburg: Ergon Verlag 2005, 274 Seiten, 34,00 EU
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