TY - GEN A1 - Efimova, Anastasia A1 - Hubrig, Grit A1 - Schmidt, Peer T1 - Thermal stability and crystallization behavior of imidazolium halide ionic liquids T2 - Thermochimica Acta N2 - 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. KW - Ionic liquids (ILs); 1-butyl-3-methylimidazolium salts ([BMIm] salts); Thermal decomposition; Glass formation; Nucleation. Y1 - 2013 UR - http://www.sciencedirect.com/science/article/pii/S0040603113004875 U6 - https://doi.org/10.1016/j.tca.2013.09.023 SN - 0040-6031 VL - Vol. 573 SP - 162 EP - 169 ER - TY - GEN A1 - Efimova, Anastasia A1 - Pinnau, Sebastian A1 - Mischke, Matthias A1 - Breitkopf, Cornelia A1 - Ruck, Michael A1 - Schmidt, Peer T1 - Development of salt hydrate eutectics as latent heat storage for air conditioning and cooling T2 - Thermochimica Acta N2 - 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. KW - Phase change material (PCM); Latent heat thermal energy storage (LHTES); Cold storage; Salt hydrate eutectics Y1 - 2014 UR - http://www.sciencedirect.com/science/article/pii/S004060311300573X U6 - https://doi.org/10.1016/j.tca.2013.11.011 SN - 0040-6031 VL - 45 IS - 575 SP - 276 EP - 278 ER - TY - GEN A1 - Efimova, Anastasia A1 - Pfützner, Linda A1 - Schmidt, Peer T1 - Thermal Stability and Decomposition Mechanism of 1-Ethyl-3-Methylimidazolium Halides T2 - Thermochimica Acta N2 - 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). KW - Ionic liquids (ILs) KW - 1-Ethyl-3-methylimidazolium halides ([EMIm] halides) KW - Thermal decomposition mechanism KW - Differential scanning calorimetry (DSC) KW - Thermogravimetric analysis (TGA) KW - Mass spectrometry (MS) KW - Integral isoconversional method KW - Maximum operation temperature (MOT) Y1 - 2015 UR - http://www.sciencedirect.com/science/article/pii/S0040603115000350 U6 - https://doi.org/10.1016/j.tca.2015.02.001 VL - 604 SP - 129 EP - 136 ER - TY - GEN A1 - Groh, Matthias F. A1 - Breternitz, Joachim A1 - Ahmed, Ejaz A1 - Isaeva, Anna A1 - Efimova, Anastasia A1 - Schmidt, Peer A1 - Ruck, Michael T1 - Ionothermal Synthesis, Structure, and Bonding of the Catena-Heteropolycation 1∞[Sb2Se2]+ T2 - Zeitschrift für anorganische und allgemeine Chemie N2 - 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. KW - Chain structures KW - Antimony KW - Heteropolycations KW - Main-group elements KW - Selenium Y1 - 2015 UR - http://onlinelibrary.wiley.com/doi/10.1002/zaac.201400543/abstract U6 - https://doi.org/10.1002/zaac.201400543 SN - 1521-3749 VL - 641 IS - 2 SP - 388 EP - 393 ER - TY - GEN A1 - Schmidt, Peer A1 - Efimova, Anastasia T1 - Thermal Characterization of Ionic Liquids T2 - OnSet : News, Facts and Professional Solutions for Thermal Analysis N2 - 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. KW - Thermal Properties KW - Ionic Liquids Y1 - 2015 UR - https://dcyd0ggl1hia3.cloudfront.net/media/thermal-analysis/customer-magazine/OnSet_15_en_web.pdf?1454325612&Policy=eyJTdGF0ZW1lbnQiOlt7IlJlc291cmNlIjoiaHR0cHM6XC9cL2RjeWQwZ2dsMWhpYTMuY2xvdWRmcm9udC5uZXRcL21lZGlhXC90aGVybWFsLWFuYWx5c2lzXC9jdXN0b21lci1tYWdhemluZVwvT25TZXRfMTVfZW5fd2ViLnBkZj8xNDU0MzI1NjEyIiwiQ29uZGl0aW9uIjp7IkRhdGVMZXNzVGhhbiI6eyJBV1M6RXBvY2hUaW1lIjoxNTMzNzA4MDcwfX19XX0_&Signature=Q9l-r6mgKOmETHkMaU0IDzTKMH~FdduFunQKnxL6AmEhhrVMKNrbho6JK5pYF0NlM1GPkitI2SxlRwwdygr9m654DWkV5Ka4Qw0NA-BkcKczW4G0dX9WWiXbKk12lQGUe2Z1sMy6i9EJ2vW9wZtn8S-mCQHgrNV~hzE~I8BxV-Q_&Key-Pair-Id=APKAIBNUHYIJDHQEJVRQ VL - 15 SP - 14 EP - 17 ER - TY - GEN A1 - Pfister, Daniela A1 - Schäfer, Konrad A1 - Ott, Claudia A1 - Gerke, Birgit A1 - Pöttgen, Rainer A1 - Janka, Oliver A1 - Baumgartner, Maximilian A1 - Efimova, Anastasia A1 - Hohmann, Andrea A1 - Schmidt, Peer A1 - Venkatachalam, Sabarinathan A1 - Wüllen, Leo van A1 - Schürmann, Ulrich A1 - Kienle, Lorenz A1 - Duppel, Viola A1 - Parzinger, Eric A1 - Miller, Bastian A1 - Becker, Jonathan A1 - Holleitner, Alexander A1 - Weihrich, Richard A1 - Nilges, Tom T1 - Inorganic double helices in semiconducting SnIP T2 - Advanced Materials N2 - 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. KW - Helical semiconductor Y1 - 2016 UR - http://onlinelibrary.wiley.com/doi/10.1002/adma.201603135/full U6 - https://doi.org/10.1002/adma.201603135 SN - 1521-4095 VL - 28 IS - 44 SP - 9783 EP - 9791 ER - TY - RPRT A1 - Schmidt, Peer A1 - Efimova, Anastasia T1 - Thermal Characterization of Ionic Liquids N2 - 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. KW - Thermal analysis KW - Ionic liquid Y1 - 2015 UR - https://www.netzsch-thermal-analysis.com/en/service-support/customer-magazine-onset/ SP - 14 EP - 17 PB - NETZSCH-Gerätebau GmbH CY - Selb ER - TY - GEN A1 - Efimova, Anastasia A1 - Hubrig, Grit A1 - Pfützner, Linda A1 - Schmidt, Peer T1 - Thermal Stability of Alkyl-Imidazolium-Ionic Liquids T2 - Zeitschrift für Anorganische und Allgemeine Chemie N2 - 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. KW - Ionic liquid KW - Thermal stability Y1 - 2014 UR - http://onlinelibrary.wiley.com/doi/10.1002/zaac.201490026/full U6 - https://doi.org/10.1002/zaac.201490026 SN - 1521-3749 VL - 640 IS - 11 SP - 2391 ER - TY - RPRT A1 - Pinnau, Sebastian A1 - Efimova, Anastasia A1 - Schmidt, Peer T1 - Identifikation technischer Salze als Latentspeichermaterialien im Temperaturbereich von 4 bis 15 °C und deren Verkapselung: Abschlussbericht N2 - Der Einsatz von thermischen Speichern erlaubt eine bessere Lastanpassung von Erzeugeranlagen zur Gebäudeklimatisierung sowie eine Optimierung des Betriebsregimes unter energetischen Gesichtspunkten. Für solche Anwendungsfälle können Latentwärmespeicher zum Einsatz kommen, bei denen üblicherweise der Schmelz- und Erstarrungsvorgang sogenannter Phasenwechselmaterialien (Phase Change Materials, PCM) ausgenutzt wird. Für die Anwendungstemperaturbereiche der Klimatisierung von etwa 4 °C bis 15 °C und für die Kühlung 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 ähnlich wie Reinstoffe einen scharfen Schmelzpunkt aufweisen – kann die Bandbreite an potentiellen PCM’s für diesen Temperaturbereich vergrößert werden. Für die genannten Temperaturbereiche werden vorzugsweise anorganische Salzhydrate als potentielle Speichermedien betrachtet, da diese gegenüber organischen Substanzen häufig größere Schmelzenthalpien und geringere Kosten aufweisen. KW - Latentwärmespeicher KW - PCM Y1 - 2013 UR - https://www.tib.eu/suchen/id/TIBKAT:786966173/ U6 - https://doi.org/10.2314/GBV:786966173 CY - Dresden ER - TY - RPRT A1 - Schmidt, Peer A1 - Efimova, Anastasia T1 - Kristallisationsverhalten von Phasenwechselmaterialien als Latentwärmespeicher (KristallLaW): Abschlussbericht N2 - Phasenwechselmaterialien (PCM) sind chemische Verbindungen oder deren Mischungen, die bei einer definierten Temperatur schmelzen bzw. erstarren. Der zyklische Einsatz von Wärmespeichern ermöglicht den Ausgleich von Überlasten für den Bedarf oder den „Abfall“ von Wärme sowie die Vergleichmäßigung von Wärmeprofilen. Bestehende anorganische Materialien weisen überwiegend Einschränkungen bezüglich der Anforderungen an eine geringe Hysterese von Aufheizung und Abkühlung auf. Das Maß der Unterkühlung der Schmelze sowie ein zyklenstabiler Wärmeaustausch kann aber durch Zusätze 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, Änderung der thermochemischen Eigenschaften von PCM bei Zusatz von Keimbildnern, geeignete Konzentrationsbereiche von Keimbildnern, Homogenität/Segregation von Phasen. KW - Latentwärmespeicher KW - PCM Y1 - 2017 UR - https://www.tib.eu/suchen/id/TIBKAT:884496287/ U6 - https://doi.org/10.2314/GBV:884496287 PB - BTU Cottbus - Senftenberg, Fachgebiet Anorganische Chemie CY - Senftenberg ER -