@misc{EfimovaHubrigSchmidt, author = {Efimova, Anastasia and Hubrig, Grit and Schmidt, Peer}, title = {Thermal stability and crystallization behavior of imidazolium halide ionic liquids}, series = {Thermochimica Acta}, volume = {Vol. 573}, journal = {Thermochimica Acta}, issn = {0040-6031}, doi = {10.1016/j.tca.2013.09.023}, pages = {162 -- 169}, abstract = {The 1-butyl-3-methylimidazolium halide ionic liquids are stable up to temperatures of 246(1) °C ([BMIm]Cl), 260(1) °C ([BMIm]Br), and 238(1) °C ([BMIm]I). The thermal decomposition proceeds in thermogravimetric measurements with a total mass loss of 100\%. Using evolved gas analysis (EGA) a complete degradation of [BMIm]X ionic liquids under formation of characteristic fragments CH3+, NHn+, C4Hn+, and CH3X+ (X = Cl, Br, I) has been observed. [BMIm]Cl shows enantiotropic polymorphism with a phase transition temperature at 30(1) °C, and melts at 74(1) °C (ΔHfus = 18 ± 0.5 kJ mol-1). Spontaneous e-crystallization and reversible phase transition have been found for cooling of the substance.[BMIm]Br melts at 78(1) °C (ΔHfus = 29 ± 0.5 kJ mol-1). The re-crystallization fails and thus a glassy solid is formed. The glass transition temperature is about -65 °C, the cold crystallization occurs between -30 and -20 °C. The application of both homogeneous and heterogeneous nucleation agents does not interfere the glassy state. [BMIm]I undergo solidification without crystallization. The melting effect for the amorphous substance arise at -70(5) °C with ΔHfus = 0.4 ± 0.2 kJ mol-1.}, language = {en} } @misc{EfimovaPinnauMischkeetal., author = {Efimova, Anastasia and Pinnau, Sebastian and Mischke, Matthias and Breitkopf, Cornelia and Ruck, Michael and Schmidt, Peer}, title = {Development of salt hydrate eutectics as latent heat storage for air conditioning and cooling}, series = {Thermochimica Acta}, volume = {45}, journal = {Thermochimica Acta}, number = {575}, issn = {0040-6031}, doi = {10.1016/j.tca.2013.11.011}, pages = {276 -- 278}, abstract = {Sustainable air conditioning systems require heat reservoirs that operate between 4 and 20 ◦C. A systematic search for binary and ternary eutectics of inorganic salts and salt hydrates with melting temperatures in this temperature regime and with high enthalpies of fusion has been performed by means of differential scanning calorimetry (DSC). Promising results were obtained for the pseudo-ternary system Zn(NO3)2·6H2O, Mn(NO3)2·4H2O, and KNO3 with the melting temperature range 18-21 ◦C and the enthalpy of fusion of about 110 kJ kg-1. Suitable nucleating and thickening agents have been found and tested to prevent the mixture from supercooling and phase separation.}, language = {en} } @misc{EfimovaPfuetznerSchmidt, author = {Efimova, Anastasia and Pf{\"u}tzner, Linda and Schmidt, Peer}, title = {Thermal Stability and Decomposition Mechanism of 1-Ethyl-3-Methylimidazolium Halides}, series = {Thermochimica Acta}, volume = {604}, journal = {Thermochimica Acta}, doi = {10.1016/j.tca.2015.02.001}, pages = {129 -- 136}, abstract = {The thermochemical behavior of 1-ethyl-3-methylimidazolium [EMIm] halides (Cl, Br and I) has been investigated for their crystalline and liquid states in the temperature range from -90 °C to 600 °C using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The temperatures and enthalpies of phase transitions have been determined: Tfus = 86(1) °C, ΔHfus = 14.2(0.7) kJ mol-1 ([EMIm]Cl); Tfus = 67(1) °C, ΔHfus = 19.3(0.7) kJ mol-1 ([EMIm]Br); and Tfus = 74(1) °C, ΔHfus = 16.9(0.6) kJ mol-1 ([EMIm]I). The decomposition temperatures, determined by onset of DTG at 1 K min-1 are 233(5) °C ([EMIm]Cl), 246(5) °C ([EMIm]Br), and 249(5) °C ([EMIm]I). The maximum operation temperature (MOT) has been estimated based on dynamic TGA for an operation time of 24 h: 132 °C ([EMIm]Cl), 149 °C ([EMIm]Br), 139 °C ([EMIm]I) and 8000 h: 76 °C ([EMIm]Cl), 90 °C ([EMIm]Br), 77 °C ([EMIm]I). The decomposition products of the investigated ionic liquids (ILs) after heating experiments were identified by means of TGA complemented with mass spectrometry (MS), for establishment of the mechanism of thermal decomposition of the ILs. Complete degradation of [EMIm]X ionic liquids occurs under formation of characteristic molecule fragments CH3+, NH+, and X+, CH3X+, C2H5X+ (X = Cl, Br, I).}, language = {en} } @misc{GrohBreternitzAhmedetal., author = {Groh, Matthias F. and Breternitz, Joachim and Ahmed, Ejaz and Isaeva, Anna and Efimova, Anastasia and Schmidt, Peer and Ruck, Michael}, title = {Ionothermal Synthesis, Structure, and Bonding of the Catena-Heteropolycation 1∞[Sb2Se2]+}, series = {Zeitschrift f{\"u}r anorganische und allgemeine Chemie}, volume = {641}, journal = {Zeitschrift f{\"u}r anorganische und allgemeine Chemie}, number = {2}, issn = {1521-3749}, doi = {10.1002/zaac.201400543}, pages = {388 -- 393}, abstract = {The reaction of antimony and selenium in the Lewis-acidic ionic liquid 1-butyl-3-methyl-imidazolium tetrachloridoaluminate, [BMIm]Cl·4.7AlCl3, yielded dark-red crystals of [Sb2Se2]AlCl4. The formation starts above 160 °C; at about 190 °C, irreversible decomposition takes place. The compound crystallizes in the triclinic space group Pequation image with a = 919.39(2) pm, b = 1137.92(3) pm, c = 1152.30(3) pm, α = 68.047(1)°, β = 78.115(1)°, γ = 72.530(1)°, and Z = 4. The structure is similar to that of [Sb2Te2]AlCl4 but has only half the number of crystallographically independent atoms. Polycationic chains 1∞[Sb2Se2]+ form a pseudo-hexagonal arrangement along [01-1], which is interlaced by tetrahedral AlCl4- groups. The catena-heteropolycation 1∞[Sb2Se2]+ is a sequence of three different four-membered [Sb2Se2] rings. The chemical bonding scheme, established from the topological analysis of the real-space bonding indicator ELI-D, includes significantly polar covalent bonding in four-member rings within the polycation. The rings are connected into an infinite chain by homonuclear non-polar Sb-Sb bonds and highly polar Sb-Se bonds. Half of the selenium atoms are three-bonded.}, language = {en} } @misc{SchmidtEfimova, author = {Schmidt, Peer and Efimova, Anastasia}, title = {Thermal Characterization of Ionic Liquids}, series = {OnSet : News, Facts and Professional Solutions for Thermal Analysis}, volume = {15}, journal = {OnSet : News, Facts and Professional Solutions for Thermal Analysis}, pages = {14 -- 17}, abstract = {Ionic liquids (ILs) are currently of high interest due to their high performance physicochemical properties over a wide tempera¬ture range of existence of the liquid state. Among the ionic liquids investigated, 1-alkyl- 3-methylimidazolium halides were found generally preferred for their low melting points and ease of handling and preparation.}, language = {en} } @misc{PfisterSchaeferOttetal., author = {Pfister, Daniela and Sch{\"a}fer, Konrad and Ott, Claudia and Gerke, Birgit and P{\"o}ttgen, Rainer and Janka, Oliver and Baumgartner, Maximilian and Efimova, Anastasia and Hohmann, Andrea and Schmidt, Peer and Venkatachalam, Sabarinathan and W{\"u}llen, Leo van and Sch{\"u}rmann, Ulrich and Kienle, Lorenz and Duppel, Viola and Parzinger, Eric and Miller, Bastian and Becker, Jonathan and Holleitner, Alexander and Weihrich, Richard and Nilges, Tom}, title = {Inorganic double helices in semiconducting SnIP}, series = {Advanced Materials}, volume = {28}, journal = {Advanced Materials}, number = {44}, issn = {1521-4095}, doi = {10.1002/adma.201603135}, pages = {9783 -- 9791}, abstract = {SnIP is the first atomic-scale double helical semiconductor featuring a 1.86 eV bandgap, high structural and mechanical flexibility, and reasonable thermal stability up to 600 K. It is accessible on a gram scale and consists of a racemic mixture of right- and left-handed double helices composed by [SnI] and [P] helices. SnIP nanorods <20 nm in diameter can be accessed mechanically and chemically within minutes.}, language = {en} } @techreport{SchmidtEfimova, author = {Schmidt, Peer and Efimova, Anastasia}, title = {Thermal Characterization of Ionic Liquids}, publisher = {NETZSCH-Ger{\"a}tebau GmbH}, address = {Selb}, pages = {14 -- 17}, abstract = {Ionic liquids (ILs) are currently of high interest due to their high performance physicochemical properties over a wide temperature range of existence of the liquid state. Among the ionic liquids investigated, 1-alkyl-3-methylimidazolium halides were found generally preferred for their low melting points and ease of handling and preparation.}, language = {en} } @misc{EfimovaHubrigPfuetzneretal., author = {Efimova, Anastasia and Hubrig, Grit and Pf{\"u}tzner, Linda and Schmidt, Peer}, title = {Thermal Stability of Alkyl-Imidazolium-Ionic Liquids}, series = {Zeitschrift f{\"u}r Anorganische und Allgemeine Chemie}, volume = {640}, journal = {Zeitschrift f{\"u}r Anorganische und Allgemeine Chemie}, number = {11}, issn = {1521-3749}, doi = {10.1002/zaac.201490026}, pages = {2391}, abstract = {The thermochemical behavior of two groups of ionic liquids (ILs), 1-ethyl-3-methylimidazolium [EtMeIm] and 1-butyl-3-methylimidazolium [BuMeIm] halides (Cl, Br and I) was investigated for their crystalline and liquid states in the temperature range from -100 °C to 600 °C using DSC and thermogravimetric analysis (TGA). Some investigated ILs exhibit significant subcooling effect and the glass state formation [1]. The decomposition mechanism has been identified by means of TGA with coupled mass spectrometry (MS). All investigated ILs decompose with a total mass loss of about 100 \% in the temperature range of Tonset from 230 to 290 °C (Fig. 1). By complete degradation of IL, dominant fragments CnH2n+1+, CnH2n+, CnHn+, NHn+, and the respective alkyl halides (X = Cl, Br, I) are formed.}, language = {en} } @techreport{PinnauEfimovaSchmidt, author = {Pinnau, Sebastian and Efimova, Anastasia and Schmidt, Peer}, title = {Identifikation technischer Salze als Latentspeichermaterialien im Temperaturbereich von 4 bis 15 °C und deren Verkapselung: Abschlussbericht}, address = {Dresden}, doi = {10.2314/GBV:786966173}, pages = {92}, abstract = {Der Einsatz von thermischen Speichern erlaubt eine bessere Lastanpassung von Erzeugeranlagen zur Geb{\"a}udeklimatisierung sowie eine Optimierung des Betriebsregimes unter energetischen Gesichtspunkten. F{\"u}r solche Anwendungsf{\"a}lle k{\"o}nnen Latentw{\"a}rmespeicher zum Einsatz kommen, bei denen {\"u}blicherweise der Schmelz- und Erstarrungsvorgang sogenannter Phasenwechselmaterialien (Phase Change Materials, PCM) ausgenutzt wird. F{\"u}r die Anwendungstemperaturbereiche der Klimatisierung von etwa 4 °C bis 15 °C und f{\"u}r die K{\"u}hlung bis etwa 25 °C ist die Auswahl an Reinstoffen mit einer passenden Schmelztemperatur sehr begrenzt. Durch die Bildung von eutektischen Gemischen aus zwei oder mehr Komponenten - die {\"a}hnlich wie Reinstoffe einen scharfen Schmelzpunkt aufweisen - kann die Bandbreite an potentiellen PCM's f{\"u}r diesen Temperaturbereich vergr{\"o}ßert werden. F{\"u}r die genannten Temperaturbereiche werden vorzugsweise anorganische Salzhydrate als potentielle Speichermedien betrachtet, da diese gegen{\"u}ber organischen Substanzen h{\"a}ufig gr{\"o}ßere Schmelzenthalpien und geringere Kosten aufweisen.}, language = {de} } @techreport{SchmidtEfimova, author = {Schmidt, Peer and Efimova, Anastasia}, title = {Kristallisationsverhalten von Phasenwechselmaterialien als Latentw{\"a}rmespeicher (KristallLaW): Abschlussbericht}, publisher = {BTU Cottbus - Senftenberg, Fachgebiet Anorganische Chemie}, address = {Senftenberg}, doi = {10.2314/GBV:884496287}, pages = {44}, abstract = {Phasenwechselmaterialien (PCM) sind chemische Verbindungen oder deren Mischungen, die bei einer definierten Temperatur schmelzen bzw. erstarren. Der zyklische Einsatz von W{\"a}rmespeichern erm{\"o}glicht den Ausgleich von {\"U}berlasten f{\"u}r den Bedarf oder den „Abfall" von W{\"a}rme sowie die Vergleichm{\"a}ßigung von W{\"a}rmeprofilen. Bestehende anorganische Materialien weisen {\"u}berwiegend Einschr{\"a}nkungen bez{\"u}glich der Anforderungen an eine geringe Hysterese von Aufheizung und Abk{\"u}hlung auf. Das Maß der Unterk{\"u}hlung der Schmelze sowie ein zyklenstabiler W{\"a}rmeaustausch kann aber durch Zus{\"a}tze als Kristallisationshilfen (Keimbildner) gesteuert werden. Im vorliegenden Bericht werden die Keimbildung und Kristallisation von Phasenwechselmaterialien unter folgenden Gesichtspunkten diskutiert: Methoden der Thermischen Analyse zur Untersuchung der thermochemischen Eigenschaften von PCM, thermochemische Eigenschaften anorganischer Salze und Salzhydrate als PCM, dominierende Kristallstrukturen und Strukturmotive anorganischer Salze und Salzhydrate als PCM, dominierende Kristallstrukturen und Strukturmotive anorganischer Stoffe als homogener und heterogener Keimbildner, {\"A}nderung der thermochemischen Eigenschaften von PCM bei Zusatz von Keimbildnern, geeignete Konzentrationsbereiche von Keimbildnern, Homogenit{\"a}t/Segregation von Phasen.}, language = {de} }