TY - GEN A1 - Grönke, Martin A1 - Schmidt, Peer A1 - Valldor, Martin A1 - Oswald, Steffen A1 - Wolf, Daniel A1 - Lubk, Axel A1 - Büchner, Bernd A1 - Hampel, Silke T1 - Chemical vapor growth and delamination of α-RuCl3 nanosheets down to the monolayer limit T2 - Nanoscale N2 - 2D layered honeycomb magnet α-ruthenium(III) chloride (α-RuCl3) is a promising candidate to realize a Kitaev spin model. As alteration of physical properties on the nanoscale is additionally intended, new synthesis approaches to obtain phase pure α-RuCl3 nanocrystals have been audited. Thermodynamic simulations of occurring gas phase equilibria were performed and optimization of synthesis conditions was achieved based on calculation results. Crystal growth succeeded via chemical vapor transport (CVT) in a temperature gradient of 973 K to 773 K on YSZ substrates. Single crystal sheets of high crystallinity with heights ≤ 30 nm were obtained via pure CVT. The crystal properties were characterized by means of optical and electron microscopy, AFM, SAED, micro-Raman and XPS proving their composition, morphology, crystallinity and phase-purity. A highlight of our study is the successful individualization of nanocrystals and the delamination of nanosheets on YSZ substrates down to the monolayer limit (≤ 1 nm) which was realized by means of substrate exfoliation and ultrasonication in a very reproducible way. KW - Crystal growth KW - Thermodynamic modeling KW - Chemical vapor transport KW - 2D layered compounds KW - Nanocrystals Y1 - 2018 UR - https://pubs.rsc.org/en/content/articlelanding/2018/nr/c8nr04667k#!divAbstract U6 - https://doi.org/10.1039/C8NR04667K SN - 2040-3372 VL - 10 IS - 40 SP - 19014 EP - 19022 ER - TY - GEN A1 - Poddig, Hagen A1 - Donath, Tom A1 - Gebauer, Paul A1 - Finzel, Kati A1 - Kohout, Miroslav A1 - Wu, Yuandong A1 - Schmidt, Peer A1 - Doert, Thomas T1 - Rare Earth Metal Polytellurides RETe1.8 (RE = Gd, Tb, Dy) – Directed Synthesis, Crystal and Electronic Structures, and Bonding Features T2 - Zeitschrift für Anorganische und Allgemeine Chemie N2 - Single crystals of the polytellurides RETe1.8 of gadolinium, terbium, and dysprosium were prepared by chemical vapor transport and alkali metal halide flux reactions. To determine proper synthesis conditions for the desired target composition, the binary phase diagram Gd-Te was evaluated by CalPhaD methods. The compounds are isostructural to SmTe1.8 and crystallize in space group P4/n (no. 85) with lattice parameters of a = 966.10(4), 960.00(3), and 957.33(2) pm and c = 1794.15(10), 1785.77(6), and 1779.38(5) pm for GdTe1.8, TbTe1.8 and DyTe1.8, respectively. The structures consist of puckered [RETe] double slabs and planar telluride layers composed of Te2 dumbbells and linear Te3 units in accordance with ELI-D based bonding analyses. The latter can be understood as a Te3(4–) anion. GdTe1.8 is a semiconductor with a bandgap of 0.19 eV/0.17 eV (experimental / calculated). Magnetization data confirm trivalent RE ions and indicate antiferromagnetic order at T(N) = 12 K for TbTe1.8 and T(N) = 9.8 K for DyTe1.8, whereas GdTe1.8 remains paramagnetic down to 2 K. KW - Phase diagrams KW - Crystal structure KW - Crystal growth KW - Chemical vapor transport KW - Thermodynamc modelling KW - Chalcogenides KW - Polytellurides KW - Bonding analysis Y1 - 2018 UR - https://onlinelibrary.wiley.com/doi/10.1002/zaac.201800382 U6 - https://doi.org/10.1002/zaac.201800382 SN - 1521-3749 SN - 0044-2313 VL - 644 IS - 24 SP - 1886 EP - 1896 ER - TY - CHAP A1 - Beckmann, Jens A1 - Günther, David A1 - Schmidt, Peer A1 - Schöneich, Michael A1 - Klepel, Olaf T1 - Template assisted synthesis of porous carbon materials using porous concrete as a template T2 - 5th International Sypmosium on “Carbon on Catalysis”, Books of abstracts, Bressanone/Brixen, 2012 Y1 - 2012 ER - TY - CHAP A1 - Beckmann, Jens A1 - Günther, David A1 - Klepel, Olaf A1 - Schmidt, Peer T1 - Porous concrete as a template for the synthesis of porous carbon materials T2 - Annual World Conference on Carbon : (Carbon 2012) Krakow, Poland 17-22 June 2012 Y1 - 2012 SN - 978-1-62993-436-5 SP - 854 PB - Curran CY - Red Hook, NY ER - TY - GEN A1 - Scholz, Tanja A1 - Schöneich, Michael A1 - Schmidt, Peer T1 - Understanding Solid-State Phase-Formation Processes by Usingthe High-Temperature Gas Balance: The Example of Zr₂PTe₂ T2 - European Journal of Inorganic Chemistry N2 - Inorganic solid-state synthesis with phosphorus and tellurium requires a careful control of the reaction parameters because of the high volatility of the components. This initial disadvantage can be used as a benefit for the investigation of phase formation mechanisms by analyzing the individual vapor pressure behavior. The high-temperature gas-balance is introduced as a device for detection of heterogeneous solid-gas equilibria in closed reaction systems. The experimentally challenging synthesis of the phosphide telluride Zr₂PTe₂ is examined as a model system: optimized synthesis runs at lower temperatures (ϑ = 650 °C) in a faster time, while the quantity as well as the crystalline powder quality is increased. A stepwise solid-solid reaction of zirconium and tellurium according to Ostwald's rule of stages and the shrinking core model is revealed while phosphorus sublimes and subsequently condenses to react to the ternary compound. Additional phenomena such as melting, expansion, and mechanical instabilities can be observed that broaden the possibilities of the gas- balance. KW - Thermal analysis KW - High-temperature Gas-balance KW - Chalcogenides KW - Phosphide telluride Y1 - 2019 UR - https://onlinelibrary.wiley.com/doi/full/10.1002/ejic.201900281 U6 - https://doi.org/10.1002/ejic.201900281 IS - 21 SP - 2577 EP - 2582 ER - TY - GEN A1 - Grönke, Martin A1 - Pohflepp, Danny A1 - Schmidt, Peer A1 - Valldor, Martin A1 - Oswald, Steffen A1 - Wolf, Daniel A1 - Hao, Qi A1 - Steiner, Udo A1 - Büchner, Bernd A1 - Hampel, Silke T1 - Simulation and synthesis of alpha-MoCl₃ nanosheets on substrates by short time chemical vapor transport T2 - Nano-Structures & Nano-Objects N2 - Alpha-molybdenum(III) chloride (MoCl₃) belongs to layered van-der-Waals materials, which are in focus to exhibit interesting properties due to their weak chemical and magnetic interactions. Especially the structure of alpha-MoCl₃ has been discussed in terms of symmetry breaking dimerization of Mo atoms at room temperature, which might led to exotic ground states. By exploiting the 2D materials characteristics, an investigation of physical properties on the nanoscale is intended. We herein demonstrate the probably first approach to synthesize phase pure, as-grown alpha-MoCl₃ few-layer nanosheets by means of a pure short time chemical vapor transport (CVT) process. Vapor growth benefits from a one-step deposition of high crystalline alpha-MoCl₃ nanosheets without stacking faults on a substrate. Thus, mostly applied subsequent delamination, associated with the introduction of structural defects, becomes redundant. According to the CVT process thermodynamic simulations of gas phase equilibria have been performed and the synthesis conditions could be optimized based on the calculation results. By CVT the as-grown nanolayers are deposited on sapphire (Al₂O₃) substrates by applying a temperature gradient of 70 K from 743 K to 673 K. Single crystalline sheets with thicknesses ≤75 nm down to five layer (3 nm) could be obtained by using a pure CVT process. According to the deposited nanostructures we approve the desired composition, morphology, phase purity and high crystallinity by using several microscopy and spectroscopy techniques. Furthermore, we show micro-RAMAN measurements which hint at a slight increase in phonon energies for nanosheets in comparison to the corresponding bulk phase. KW - Crystal growth KW - Chemical vapor transport KW - 2D layered compounds KW - Halides Y1 - 2019 UR - https://www.sciencedirect.com/science/article/pii/S2352507X18304888?via%3Dihub#! U6 - https://doi.org/10.1016/j.nanoso.2019.100324 SN - 2352-507X IS - 19 SP - 1 EP - 7 ER - TY - GEN A1 - Grönke, Martin A1 - Arrozi, Ubed S. F. A1 - Bronkalla, Nadine A1 - Schmidt, Peer A1 - Valldor, Martin A1 - Oswald, Steffen A1 - Woodcock, Thomas G. A1 - Eckert, Victoria A1 - Hao, Qi A1 - Plüschke, Laura A1 - Lederer, Albena A1 - Nielsch, Kornelius A1 - Büchner, Bernd A1 - Kaskel, Stefan A1 - Hampel, Silke T1 - Layered α-TiCl₃: Microsheets on YSZ Substrates for Ethylene Polymerization with Enhanced Activity T2 - Chemistry of Materials N2 - The transition metal halide α-titanium(III) chloride (α-TiCl₃) is a layered two-dimensional compound and a well-established Ziegler–Natta catalyst for the polymerization of ethylene. A new synthesis technique is used to obtain thin sheets of α-TiCl₃ that show exceptional physical properties in contrast to their bulk counterparts, due to an enlarged surface-to-volume ratio. Chemical vapor transport (CVT) of α-titanium(III) chloride directly on substrates results in microsheets that exhibit an improved catalytic effect. For rational planning of synthesis conditions, thermodynamic simulations of occurring gas-phase equilibria were performed. Based on these calculation results, crystal growth was achieved by adding GaCl₃via pure short term CVT in a temperature gradient of 700–600 K on yttrium-stabilized zirconia (YSZ) substrates. Phase pure, as-grown, single crystal sheets with high crystallinity and a thickness of around 4 μm were obtained. These thin sheets of α-TiCl₃ on YSZ substrates were implemented as catalysts for the ethylene polymerization reaction. A significant improvement of catalytic activity of 16% was achieved, probably due to an increased surface-to-volume ratio. As a highlight, the as-grown microsheets were exfoliated subsequently to a thickness lower than 200 nm and an even higher catalytic activity of up to 24% was confirmed experimentally due to delamination effects. This is the first time that an improved catalytic effect of α-TiCl₃ is observed as a result of downscaling from bulk to microsheets by CVT. KW - Crystal growth KW - Chemical vapor transport KW - Thermodynamic modeling KW - 2D layered compounds KW - Halides KW - Nanocrystals (1) Y1 - 2019 UR - https://pubs.acs.org/doi/10.1021/acs.chemmater.9b01818 U6 - https://doi.org/10.1021/acs.chemmater.9b01818 VL - 31 IS - 14 SP - 5305 EP - 5313 ER - TY - BOOK A1 - Schmidt, Peer T1 - Allgemeine Chemie N2 - Atombau, Konzepte der Chemischen Bindung sowie Thermodynamische Kenngrößen zu Beschreibung chemischer Gleichgewichte und zeitabhängige Einstellung des chemischen Gleichgewichts KW - Allgemeine Chemie KW - Atombau KW - Periodensystem der Elemente KW - Chemische Bindung KW - Chemisches Gleichgewicht KW - Thermodynamik KW - Kinetik Y1 - 2019 SN - 978-3-662-57846-9 PB - Springer-Spektrum CY - Heidelberg ET - 1. Auflage ER - TY - GEN A1 - Grönke, Martin A1 - Buschbeck, Benjamin A1 - Schmidt, Peer A1 - Valldor, Martin A1 - Oswald, Steffen A1 - Hao, Qi A1 - Lubk, Axel A1 - Wolf, Daniel A1 - Steiner, Udo A1 - Büchner, Bernd A1 - Hampel, Silke T1 - Chromium Trihalides CrX₃(X = Cl, Br, I): Direct Deposition of Micro‐ and Nanosheets on Substrates by Chemical Vapor Transport T2 - Advanced Materials Interfaces N2 - The experimental observation of intrinsic ferromagnetism in single layered chromium trihalides CrX₃ (X = Cl, Br, I) has gained outstanding attention recently due to their possible implementation in spintronic devices. However, the reproducible preparation of highly crystalline chromium(III) halide nanolayers without stacking faults is still an experimental challenge. As chromium trihalides consist of adjacent layers with weak interlayer coupling, the preparation of ultrathin CrX₃ nanosheets directly on substrates via vapor transport proves as an advantageous synthesis technique. It is demonstrated that vapor growth of ultrathin highly crystalline CrX₃ micro‐ and nanosheets succeeds directly on yttrium stabilized zirconia substrates in a one‐step process via chemical vapor transport (CVT) in temperature gradients of 100 K (600°C → 500°C for CrCl₃ and 650°C → 550°C for CrBr₃ or CrI₃) without a need for subsequent delamination. Due to simulation results, optimization of synthesis conditions is realized and phase pure CrX₃ nanosheets with thicknesses ≤25 nm are obtained via short term CVT. The nanosheets morphology, crystallinity, and phase purity are analyzed by several techniques, including microscopy, diffraction, and spectroscopy. Furthermore, a potential subsequent delamination technique is demonstrated to give fast access to CrX₃ monolayers using the example of CrCl₃ . KW - 2D layered compounds KW - Crystal growth KW - Chemical vapor transport KW - Halides KW - Nanocrystals KW - Thermodynamic modeling Y1 - 2019 UR - https://onlinelibrary.wiley.com/doi/epdf/10.1002/admi.201901410 U6 - https://doi.org/10.1002/admi.201901410 SN - 2196-7350 VL - 6 IS - 24 ER - TY - GEN A1 - Pabst, Falk A1 - Chang, Jen‐Hui A1 - Finzel, Kati A1 - Kohout, Miroslav A1 - Schmidt, Peer A1 - Ruck, Michael T1 - The Subbromide Bi5Br4 – On the Existence of a Hidden Phase T2 - Zeitschrift für Anorganische und Allgemeine Chemie N2 - Black and irregularly shaped crystals of the bismuth‐rich bromide Bi5Br4 were obtained as a by‐product of the reaction of CsBr, Bi, and BiBr3. X‐ray diffraction on a single‐crystal revealed its orthorhombic structure with the space group Pmmn (no. 59) and lattice parameters a = 1800.0(2) pm, b = 1476.1(1) pm, and c = 924.5(2) pm at 296 K. The structure is composed of Bi82+ and Bi95+ polycations and bromidobismuthate(III) anions according to the structured formula Bi5Br4 = Bi20Br16 = Bi82+Bi95+[BiBr5]2–[Bi2Br11]5–. Bi5Br4 is the bismuth‐richest among the bismuth subhalides containing isolated polycations. Extensive differential scanning calorimetry studies indicate that Bi5Br4 decomposes at 262 °C, i.e. one degree below the bismuth‐rich eutectic at 263 °C. All attempts towards a rational synthesis yielded predominantly the neighboring phases BiBr and Bi6Br7. KW - Bromine KW - Bismuth KW - Cluster KW - Phase Diagrams KW - Polycations KW - Crystal structure Y1 - 2020 UR - https://onlinelibrary.wiley.com/doi/10.1002/zaac.201800149 U6 - https://doi.org/10.1002/zaac.201800149 VL - 646 IS - 3 SP - 149 EP - 155 ER - TY - GEN A1 - Lange, Felix A1 - Ernst, Owen C. A1 - Teubner, Thomas A1 - Richter, Carsten A1 - Schmidbauer, Martin A1 - Skibitzki, Oliver A1 - Schroeder, Thomas A1 - Schmidt, Peer A1 - Boeck, Torsten T1 - In-plane growth of germanium nanowires on nanostructured Si(001)/SiO2 substrates T2 - Nano Futures N2 - Germanium (Ge) nanowires (NWs) were grown in-plane on nano-structured Si(001)/SiO2 substrates by molecular beam epitaxy using gold (Au) as the solvent. The site-selective NW growth was enabled by a rectangular array of gold droplets on silicon (Si) tips with an Au nuclei density below 0.25 μm−2 on the surrounding silicon oxide (SiO2). The initial growth of Ge NWs starting from Si–Au droplets with SixGe1−x nucleation from ternary alloy is discussed from a thermodynamic point of view. The in-plane NW elongation occurred within ⟨110⟩ directions on the substrate and NWs were mainly bounded by two 55◦ inclined 111 facets and a less pronounced planar (001) top facet. Fully relaxed crystal lattices of Ge NWs were observed from two-dimensional reciprocal space maps of x-ray diffraction measurements. KW - Crystal growth KW - Silicon KW - Germanium KW - Phase diagram Y1 - 2020 UR - https://iopscience.iop.org/article/10.1088/2399-1984/ab82a0 U6 - https://doi.org/10.1088/2399-1984/ab82a0 SN - 2399-1984 VL - 4 IS - 3 SP - 1 EP - 8 ER - TY - GEN A1 - Heinemann, Robert A1 - Schmidt, Peer T1 - Crystal Growth by Chemical Vapor Transport: Process Screening by Complementary Modeling and Experiment T2 - Crystal Growth & Design N2 - Despite chemical vapor transport (CVT) being a widely used method for crystal growth of inorganic substances, detailed mechanistic studies on the course of the crystallization process are rather few. In this study, an elaborated experimental screening run combined with sophisticated modeling of the respective heterogeneous equilibria is presented: Crystal growth of germanium by vapor transport with the addition of iodine has been chosen as a model system for validation of the applied method spectrum. In order to record the course and the interplay of heterogeneous equilibrium and non-equilibrium reactions in the system Ge–I, the experimental setup of high-temperature gas-balance (HTGB) is applied. Additionally, the observed evaporation processes are compared with saturation curves of corresponding volatile substances and, thus, can be assigned to individual species within the system. In this experimental screening, a phase sequence means to examine how the condensed phases undergo iodine depletion and how the gaseous phase undergoes a germanium enrichment when the temperature is increased. This phase screening combined with annealing experiments in the course of the phase sequence helps to analyze stepwise non-equilibrium products and to identify the characteristic species. Subsequently, for the evaluation of the composition of the gaseous phase, and for the deduction of the vapor transport mechanism, thermodynamic modeling by the CalPhaD method is performed. For the reference system, it is confirmed that iodine does not act as the transport agent. Instead, GeI4 is responsible for the volatilization of germanium, forming GeI2. Nevertheless, investigations clearly illustrate how GeI4 forms naturally in the phase sequence in the system Ge–I, which makes direct addition of it unnecessary. The recommended temperature range for vapor transport of germanium spans from 460 to 800 °C. Modeling shows that migration rates for germanium reaches a maximum at a mean temperature between 540 and 550 °C. Finally, vapor transport experiments were performed from 565 to 515 °C and from 690 to 590 °C. By increasing the deposition temperature, a slight decrease of the migration rate was observed, though a positive impact on the crystal’s morphology was also found. KW - Crystal growth KW - Chemical vapor transport KW - High-temperature Gas-balance KW - Thermodynamic modeling KW - Phase barogram KW - Germanium Y1 - 2020 UR - https://pubs.acs.org/doi/abs/10.1021/acs.cgd.0c00679 U6 - https://doi.org/10.1021/acs.cgd.0c00679 SN - 1528-7505 SN - 1528-7483 VL - 20 IS - 9 SP - 5986 EP - 6000 ER - TY - GEN A1 - Hansen, Felix A1 - Wels, Martin A1 - Froeschke, Samuel A1 - Popov, Alexey A1 - Wolf, Daniel A1 - Büchner, Bernd A1 - Schmidt, Peer A1 - Hampel, Silke T1 - Thermodynamic Evaluation and Chemical Vapor Transport of Few-Layer WTe2 T2 - Crystal Growth and Design N2 - Tungsten telluride WTe2 is the sole candidate of a group of two-dimensional layered transition metal dichalcogenides (TMDCs) MX2 with a thermodynamically stable 1T′-structure at room temperature. The binary system W/Te was audited with respect to a rational approach of planning and realization of a bottom-up synthesis of WTe2 nanostructures. Thus, the parameters of the synthesis via chemical vapor transports (CVT) were derived by thermodynamic simulations of the reaction pathway according to the Calphad method. Reflecting on the peritectic melting behavior at 1020 °C, the values of ΔfHm° (298 K) = −26.5 kJ·mol−1 and Sm° (298 K) = 132 J·mol−1 ·K−1 have been obtained. According to modeling, crystal growth by short time vapor transport is reasonable under the addition of bromine or TeBr4 in the temperature range between 650 and 750 °C. Experimental implementation of crystal growth of WTe2 nanosheets succeeded in a temperature gradient from 725 to 675 °C on yttria-stabilized zirconia (YSZ) (111) substrates, observing the deposition of single crystal sheets of high crystallinity with thicknesses of 15−20 nm (∼20−30 layers). The high crystallinity, pristine morphology, and overall quality of the deposited nanosheets is shown by means of atomic resolution transmission electron microscopy, selected area electron diffraction (SAED), and atomic force microscopy as well as profound double-polarized Raman spectroscopy. KW - Crystal growth KW - Chemical vapor transport KW - Thermodynamic modeling KW - 2D layered compounds KW - Chalcogenides KW - Phase diagram Y1 - 2020 UR - https://pubs.acs.org/doi/abs/10.1021/acs.cgd.0c01004 U6 - https://doi.org/10.1021/acs.cgd.0c01004 SN - 1528-7505 VL - 20 IS - 11 SP - 7341 EP - 7349 ER - TY - GEN A1 - Knorr, Monika A1 - Icker, Maik A1 - Efimova, Anastasia A1 - Schmidt, Peer T1 - Reactivity of Ionic Liquids: Studies on Thermal Decomposition Behavior of 1-Butyl-3-methylimidazolium Tetrafluoroborate T2 - Thermochimica Acta N2 - The Ionic Liquid 1-butyl-3-methylimidazolium tetrafluoroborate [C4C1im]BF4 serves as a commonly solvent in inorganic material synthesis and analytics. Nevertheless, its application is frequently associated with trial and error approaches. Thereupon, detailed knowledge on the thermal behavior is the key information for understanding the reactivity of [C4C1im]BF4. 1-butyl-3-methylimidazolium tetrafluoroborate behaves as a glass in the cold, its glass transition temperature being ϑg = −83 °C. During heating with 10 K·min−1 [C4C1im]BF4 appears to be stable above 350 °C with onset temperatures ϑonset, DSC = 375 °C, ϑonset, DTG = 422 °C, and ϑonset, TG = 437 °C. Thereby, thermal decomposition occurs in a single step reaction forming 1-methyl-1H-imidazole (CH3C3H3N2 or C4H6N2), but-1-ene (C4H8), fluoromethane (CH3F) and boron trifluoride (BF3) as main species, as determined by thermogravimetry coupled with mass spectrometry and FTIR spectroscopy. To be more specific in thermal behavior, the temperature and time dependent stability is evaluated here on the basis of the kinetic model of maximum operation temperature − MOT. Clearly, thermal stability rises with application time, thus being 193 °C for one hour, while reaching only 141 °C for one day, and 114 °C for one week. The incipient decomposition (≤ 1 %) at the calculated time dependent maximum operation temperature finally is verified by optical analysis, infrared (IR), and nuclear magnetic resonance (NMR) spectroscopy. Y1 - 2020 UR - https://www.sciencedirect.com/science/article/pii/S0040603120307012?via%3Dihub#! U6 - https://doi.org/10.1016/j.tca.2020.178786 SN - 0040-6031 VL - Vol. 694 SP - 1 EP - 11 ER - TY - GEN A1 - Knorr, Monika A1 - Schmidt, Peer T1 - Reactivity of ionic liquids: Reductive effect of [C4C1im]BF4 to form particles of red amorphous selenium and Bi2Se3 from oxide precursors T2 - ChemistryOpen N2 - Temperature-induced change in reactivity of the frequently used ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([C4C1im]BF4) is presented as a prerequisite for the rational screening of reaction courses in material synthesis. [C4C1im]BF4 becomes active with oxidic precursor compounds in reduction reaction at ϑ > 200°C, even without the addition of an external reducing agent. The reaction mechanism of forming red amorphous selenium from SeO2 is investigated as a model system and can be described similarly to the Riley oxidation. The reactive species but-1-ene, which is formed during the decomposition of [C4C1im]BF4, reacts with SeO2 and form but-3-en-2-one, water, and selenium. Elucidation of the mechanism was achieved by thermoanalytical investigations. The mono-tropic phase transition of selenium was analyzed by the differential scanning calorimetry. Beyond, the suitability of the single source oxide precursor Bi2Se3O9 for the synthesis of Bi2Se3 particles was confirmed. Identification, characterization of formed solids succeeded by using light microscopy, XRD, SEM, and EDX. KW - Ionic liquid KW - Thermal analysis KW - Thermal decomposition KW - Chalcogenides KW - Selenium KW - Inorganic synthesis Y1 - 2021 UR - https://chemistry-europe.onlinelibrary.wiley.com/doi/epdf/10.1002/open.202000264 U6 - https://doi.org/10.1002/open.202000264 SN - 2191-1363 VL - 10 IS - 2 SP - 125 EP - 140 ER - TY - GEN A1 - Meißner, André A1 - Efimova, Anastasia A1 - Schmidt, Peer T1 - Impacts of TGA furnace parameters for prediction of long-term thermal stability of ionic liquids T2 - Thermochimica Acta N2 - The concept of maximum operation temperature is established for the prediction of the time dependent thermal stability of ionic liquids based on kinetic evaluation of thermogravimetric analysis. The influence of the furnace control parameters on the maximum operation temperature (MOT) is shown using the example of 1-methyl-3-propylimidazolium iodide ([C3C1im]I) with respect to three different parameter sets of a programmed proportional integral derivative (PID) controller of the TGA. Kinetics of thermal decomposition of [C3C1im]I have been investigated with the implementation of an improved kinetic model. The activation energy obtained using the Kissinger-Akahira-Sunose equation showed variations apparently due to the decomposition degree. The model compound is decomposed by a one-step kinetics, which results from pseudo zero order relationship of the activation energy to the conversion rate. The activation energy, pre-exponential factor, and the activation energy are strongly dependent on the parameters of TGA furnace controller. KW - Ionic liquid KW - Thermal analysis KW - Thermal decomposition Y1 - 2021 UR - https://www.sciencedirect.com/science/article/pii/S0040603121000587#! U6 - https://doi.org/10.1016/j.tca.2021.178917 VL - 704 SP - 178917-1 EP - 178917-7 ER - TY - RPRT A1 - Schmidt, Peer A1 - Donath, Ines A1 - Wels, Martin A1 - Pinnau, Sebastian A1 - Grau Turuelo, Constantino A1 - Breitkopf, Cornelia A1 - Hack, Klaus A1 - Baben, Moritz to A1 - Reis, Bruno A1 - Müller, Michael A1 - Sergeev, Dmitry A1 - Qi, Jia T1 - PCM Screening - Evaluierung eutektischer Gemische für den Einsatz als PCM: thermodynamische Modellierung und experimentelle Methoden : Energie Speicher: PCM-Screening : Schlussbericht N2 - Ein wichtiges Ziel der Bundesregierung ist der Ausbau des Anteils erneuerbarer Energien an der gesamten Stromerzeugung. Die Entwicklung optimierter Wärme- und Kältespeicher stellt einen wichtigen Baustein bei der Erreichung dieser Zielstellung dar. Elektrisch betriebene Wärmepumpen und Kompressionskältemaschinen sowie dezentrale Klein-BHKW bieten in Verbindung mit entsprechend dimensionierten, thermischen Speichern ein großes Potential zum Lastmanagement in Smart Grids und somit zur Netzintegration von Strom aus erneuerbaren Energien. Die im Projekt entwickelte Methodik zur Suche nach neuen Latentspeichermedien kann für ein breites Anwendungsfeld von Heiz- und Kühlanwendungen in Gebäuden bis hin zur Kraftwerkstechnik eingesetzt werden. Innerhalb der Fördermaßnahme „Anwendungsorientierte Forschung und Entwicklung zur nichtnuklearen Energieforschung“ im 6. Energieforschungsprogramm der Bundesregierung wurde durch die Projektarbeiten das Schwerpunktthema Energiespeicher (3.8) adressiert, wobei der Aspekt der Entwicklung neuer Materialien mit reduzierten Kosten für einen wirtschaftlichen Betrieb im Vordergrund stand. Speziell wurden dabei die Unterpunkte 3.8.4 Thermische Speicher zur Weiterentwicklung, Optimierung und Erprobung von PCM sowie 3.8.5 Übergeordnete Themen mit Modellen und Simulationswerkzeugen für die Auswahl und Bewertung neuer Speichermaterialien adressiert. Die Projektergebnisse besitzen aber auch Berührungspunkte mit den Schwerpunkten 3.12 Energieeffizienz in Industrie, Gewerbe, Handel und Dienstleistungen sowie 3.4 Solarthermische Kraftwerke, da mit der entwickelten Screening-Methode für diese Anwendungsfälle neue Wärmespeichermaterialien auf der Basis wasserfreier Salze mit höheren Prozesstemperaturen gefunden werden können. Durch den Einsatz von Methoden zur Modellierung und Simulation von Prozessen erfolgt gleichermaßen die Umsetzung einer energie- und ressourcenschonenden Forschungstätigkeit. Das im Projekt entwickelte Vorgehen hilft dabei, einen äußerst sparsamen Einsatz von Chemikalien, eine niedrige Belastung der Umwelt durch verringerten Entsorgungsaufwand der verbrauchten Stoffe sowie einen deutlich geringeren Aufwand und Energieeinsatz für die Messtechnik zu ermöglichen. Damit wurde zugleich das Schwerpunktthema 3.8.5 Modelle und Simulationswerkzeuge für die Auswahl und Bewertung neuer Speichermaterialien angesprochen. KW - Latentwärmespeicher KW - Phase diagram KW - Thermodynamic modeling KW - Thermal analysis Y1 - 2021 UR - https://www.tib.eu/de/suchen/id/TIBKAT:177643451X/ U6 - https://doi.org/10.2314/KXP:177643451X PB - TIB – Leibniz-Informationszentrum Technik und Naturwissenschaften CY - Hannover ER - TY - GEN A1 - Ehrling, Sebastian A1 - Senkovska, Irena A1 - Efimova, Anastasia A1 - Bon, Volodymyr A1 - Abylgazina, Leila A1 - Petkov, Petko A1 - Evans, Jack D. A1 - Attallah, Ahmed Gamal A1 - Wharmby, Michael Thomas A1 - Roslova, Maria A1 - Huang, Zhehao A1 - Tanaka, Hideki A1 - Wagner, Andreas A1 - Schmidt, Peer A1 - Kaskel, Stefan T1 - Temperature Driven Transformation of the Flexible Metal-Organic Framework DUT-8(Ni) T2 - Chemistry - a European journal N2 - DUT-8(Ni) metal-organic framework belongs to the family of flexible pillared layer materials. The desolvated framework can be obtained in the open pore form (op) or in the closed pore form (cp), depending on the crystal size regime. In the present work, we report on the behaviour of desolvated DUT-8(Ni) at elevated temperatures. For both, op and cp variants, heating causes a structural transition, leading to an new, crystalline compound, containing two interpenetrated networks. The state of the framework before transition (op vs. cp) influences the transition temperature: the small particles of the op phase transform at significantly lower temperature in comparison to the macroparticles of the cp phase, transforming close to the decomposition temperature. The new compound, confined closed pore phase (ccp), was characterized by powder X-ray diffraction and spectroscopic techniques, such as IR, EXAFS, and positron annihilation lifetime spectroscopy (PALS). Thermal effects of structural cp to ccp transitions were studied using differential scanning calorimetry (DSC), showing an overall exothermic effect of the process, involving bond breaking and reformation. Theoretical calculations reveal the energetics, driving the observed temperature induced phase transition. KW - Metal organic framework (MOF) KW - Thermal analysis KW - Crystal structure KW - Phase transition Y1 - 2022 UR - https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202201281 U6 - https://doi.org/10.1002/chem.202201281 SN - 1521-3765 VL - 28 IS - 55 SP - 1 EP - 10 ER - TY - GEN A1 - Froeschke, Samuel A1 - Wolf, Daniel A1 - Hantusch, Martin A1 - Giebeler, Lars A1 - Wels, Martin A1 - Gräßler, Nico A1 - Büchner, Bernd A1 - Schmidt, Peer A1 - Hampel, Silke T1 - Synthesis of micro- and nanosheets of CrCl3–RuCl3 solid solution by chemical vapour transport T2 - Nanoscale N2 - Solid solutions of 2D transition metal trihalides are rapidly growing in interest for the search for new 2D materials with novel properties at nanoscale dimensions. In this regard, we present a synthesis method for the Cr1−xRuxCl3 solid solution and describe the behaviour of the unit cell parameters over the whole composition range, which in general follows Vegard's law in the range of a = 5.958(6)CrCl3 … 5.9731(5)RuCl3 Å, b = 10.3328(20)CrCl3 … 10.34606(21)RuCl3 Å, c = 6.110(5)CrCl3 … 6.0385(5)RuCl3 Å and β = 108.522(15)CrCl3 … 108.8314(14)RuCl3 °. The synthesized solid solution powder was subsequently used to deposit micro- and nanosheets directly on a substrate by applying chemical vapour transport in a temperature gradient of 575 °C → 525 °C for 2 h and 650 °C → 600 °C for 0.5 h as a bottom-up approach without the need for an external transport agent. The observed chromium chloride enrichment of the deposited crystals is predicted by thermodynamic simulation. The results allow for a nanostructure synthesis of this solid solution with a predictable composition down to about 30 nm in height and lateral size of several μm. When applying a quick consecutive delamination step, it is possible to obtain few- and monolayer structures, which could be used for further studies of downscaling effects for the CrCl3–RuCl3 solid solution. X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy were used to confirm the purity and quality of the synthesized crystals. KW - Crystal growth KW - Chemical vapor transport KW - Thermal analysis KW - Thermodynamic modeling KW - 2D layered compounds Y1 - 2022 UR - https://pubs.rsc.org/en/content/articlelanding/2022/NR/D2NR01366E U6 - https://doi.org/10.1039/D2NR01366E SN - 2040-3372 VL - 29 IS - 14 SP - 10483 EP - 10492 ER - TY - GEN A1 - Hansen, Felix A1 - Fucke, Rico A1 - Charvin, Titouan A1 - Froeschke, Samuel A1 - Wolf, Daniel A1 - Giraud, Romain A1 - Dufouleur, Joseph A1 - Gräßler, Nico A1 - Büchner, Bernd A1 - Schmidt, Peer A1 - Hampel, Silke T1 - Direct Deposition of (BixSb1–x)2Te3 Nanosheets on Si/SiO2 Substrates by Chemical Vapor Transport T2 - Crystal growth & design N2 - The tellurides of bismuth and antimony (Bi2Te3 and Sb2Te3) are prominent members of the V2VI3 material family that exhibit promising topological properties. We provide a method for the rational synthesis of mixed crystals of these materials ((BixSb1–x)2Te3 with x = 0.1, ..., 0.9) by means of a bottom-up chemical vapor transport (CVT) approach. Thermodynamic calculations showed the synthesis to be possible in the temperature range of 390–560 °C without significant enrichment of either component and without adding a transport agent. The starting materials were synthesized and verified by X-ray diffraction (XRD). Optimization experiments showed the ideal conditions for nanosheet synthesis to be T2 = 560 °C, T1 = 390 °C with a reaction time of t = 36 h. Crystals with heights of down to 12 nm (12 quintuple layers) were synthesized and analyzed by means of scanning electron microscopy, energy-dispersive X-ray spectrometry, and atomic force microscopy. High-resolution transmission electron microscopy confirmed the R3̅m crystal structure, high crystallinity, and overall quality of the synthesized (BixSb1–x)2Te3 nanosheets. Magnetotransport measurements revealed that such ternary compounds can have a significantly reduced carrier density compared to the binary parent compounds. KW - Crystal growth KW - Chemical vapor transport KW - Thermodynamic modeling KW - Chalcogenides Y1 - 2022 UR - https://pubs.acs.org/doi/abs/10.1021/acs.cgd.1c01446 U6 - https://doi.org/10.1021/acs.cgd.1c01446 SN - 1528-7505 SN - 1528-7483 VL - 22 IS - 4 SP - 2354 EP - 2363 ER - TY - GEN A1 - Böhler, Stefan A1 - Rosencrantz, Sophia A1 - Wolf, Karina A1 - Heinemann, Robert A1 - Schmidt, Peer A1 - Ganster, Johannes A1 - Büsse, Thomas A1 - Balko, Jens A1 - Rosencrantz, Ruben R. T1 - Active protease formulation in commodity polymers withstands melt processing into compounds and blown films T2 - Materials Today Communications N2 - Integrating enzymes into thermoplastic polymers is challenging due to their lack of robustness with respect to temperature and shear fields during conventional melt processing. In the present study, blown films from low-density polyethylene (LDPE) were prepared containing a technical protease from Bacillus sp. First, LDPE/protease compounds were produced followed by blown film extrusion, both processes at melt mass temperatures of 130 °C or higher. Enzyme activity was proven, both for the LDPE/protease compound and the blown film. The highest enzyme activity in the compound was determined for processing at 132 °C and a screw speed of 75 rpm. The influence of melt temperature and shear fields was studied in detail. Enzyme activities were determined for melt temperatures up to 160 °C and for screw speeds ranging from 75 to 300 rpm during compounding by twin-screw extrusion. The process was also applied for biobased and biodegradable polyesters, where similar protease activity after compounding was verified. Electron microscopy, X-ray diffraction, nuclear magnetic resonance spectroscopy and differential scanning calorimetry served to analyze components and morphology of the enzyme formulation used here. It is proposed that the porous morphology of the protease particles is beneficial for the enzyme to remain active after processing. Additionally, the polymer matrix surrounding the particles protects the protease at elevated temperatures, which can be attributed to thermal insulation. Thus, the right combination of a suited technical enzyme formulation with appropriate mild melt compounding conditions allows enzymes to be incorporated into thermoplastics and retain their activity. This opens the way to use the abundant biological functions of enzymes in thermoplastic applications. KW - Thermal analysis KW - X-ray diffraction KW - Crystal structure Y1 - 2023 UR - https://www.sciencedirect.com/science/article/pii/S2352492822018591 U6 - https://doi.org/10.1016/j.mtcomm.2022.105018 SN - 2352-4928 VL - 34 SP - 1 EP - 9 ER - TY - GEN A1 - Froeschke, Samuel A1 - Bestha, Kranthi Kumar A1 - Fucke, Rico A1 - Schiemenz, Sandra A1 - Popov, Alexey A1 - Naumann, Marco A1 - Knupfer, Martin A1 - Giebeler, Lars A1 - Wolf, Daniel A1 - Kizhake Malayil, Ranjith Kumar A1 - Sivan, Saramgi Chencheriparambil A1 - Grafe, Hans-Joachim A1 - Gräßler, Nico A1 - Corredor, Laura T. A1 - Wolter, Anja U. B. A1 - Büchner, Bernd A1 - Schmidt, Peer A1 - Hampel, Silke T1 - Structural and Magnetic Transitions Caused by Dimer Formation in the CrCl3–MoCl3 Solid Solution T2 - Chemistry of Materials N2 - In this work, we apply the concept of solid solutions to the two 2D transition metal trihalides CrCl3 and MoCl3. While CrCl3 belongs to the magnetically active CrX3 family, the magnetism in MoCl3 is intrinsically suppressed by the formation of aligned Mo–Mo dimers, which also distort the regular honeycomb lattice that is typical for the 2D transition metal trihalides. We report suitable synthesis conditions for the gapless solid solution and crystal growth by chemical vapor transport. The CrCl3–MoCl3 solid solution was initially synthesized at 650 °C for 100 h under addition of MoCl5 as mineralizer, and bulk crystals were subsequently grown by vapor transport in a temperature gradient from 600 °C → 550 °C for 60 h. The obtained solid solution exhibits multiple composition-dependent phase transitions at room temperature, as confirmed by powder X-ray diffraction measurements. The possible presence of Mo–Mo dimers in the solid solution was further investigated by infrared, Raman, electron energy loss, and nuclear quadrupole resonance spectroscopies. The combined results indicate that the Mo–Mo dimers are present over a wide range of compositions. Their orientation changes from parallel alignment for compositions from 70% ≤ c(Mo3+) ≤ 100% to random orientation for samples with c(Mo3+) < 70% content, which significantly affects the course of lattice parameters. Finally, the magnetic properties of the powder samples show a correlation between the Mo3+ content and the transition temperature into the low-temperature phase. Y1 - 2024 U6 - https://doi.org/10.1021/acs.chemmater.3c03109 SN - 0897-4756 SN - 1520-5002 VL - 36 IS - 9 SP - 4240 EP - 4253 ER - TY - GEN A1 - Froeschke, Samuel A1 - Yasmen, Nadia A1 - Popov, Alexey A1 - Schiemenz, Sandra A1 - Wolf, Daniel A1 - Giebeler, Lars A1 - Hantusch, Martin A1 - Gräßler, Nico A1 - Büchner, Bernd A1 - Schmidt, Peer A1 - Hampel, Silke T1 - Controlled Nanoplatelet Deposition of 2D Chromium Trihalide Solid Solutions T2 - Chemistry of Materials N2 - The two-dimensional (2D) chromium trihalides CrCl3, CrBr3, and CrI3 are most famous for their exotic magnetic properties when their crystals get downscaled to nanometer dimensions. One way to tune the properties of such materials and to further increase their potential utility, e.g., in spintronics, is the formation of solid solutions. Here, we present a detailed theoretical and experimental study on the synthesis and nanoplatelet growth of CrBrxCl3–x and CrBrxI3–x solid solutions. Phase pure powder was obtained by tempering the respective parent compounds at 600 and 550 °C, using additional iodine in the case of CrBrxI3–x. The dominant stacking order changes at x = 1.8 for CrBrxCl3–x while remaining similar to CrI3 for the whole CrBrxI3–x series. A consecutive chemical vapor transport from 575 → 525 °C for 2 h (CrBrxCl3–x) or 600 → 550 °C for 3 h with 0.1 mmol additional iodine (CrBrxI3–x) resulted in the deposition of high-quality nanoplatelets on a substrate with only several nanometers in height. The composition can be controlled by the choice of the starting material, since only small shifts in the anion ratio occur during the transport. The deposited CrBrxCl3–x nanoplatelets can then be easily delaminated by ultrasonication in ethanol to reduce the height even further to few-layer dimensions. These nanoplatelets could potentially be used to investigate the property changes (e.g., in terms of magnetic response) for the downscaling of these solid solutions. We further demonstrate the quality of the deposited material by transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectroscopy. Raman spectroscopy of the solid solution series reveals a complex evolution of vibrational modes. Photoluminescence measurements on solid solution samples show emission peaks in the near-infrared energy range with the specific energy and intensity being composition and temperature dependent. KW - 2D layered compounds KW - Chemical vapor transport KW - Crystal growth KW - Crystal structure KW - Halides KW - Thermodynamic modeling Y1 - 2023 UR - https://pubs.acs.org/doi/full/10.1021/acs.chemmater.2c03785 U6 - https://doi.org/10.1021/acs.chemmater.2c03785 SN - 1520-5002 SN - 0897-4756 VL - 35 IS - 11 SP - 4136 EP - 4148 ER - TY - GEN A1 - Froeschke, Samuel A1 - Schroth, Karl-Georg A1 - Steiner, Udo A1 - Popov, Alexey A1 - Schiemenz, Sandra A1 - Wolf, Daniel A1 - Giebeler, Lars A1 - Gräßler, Nico A1 - Büchner, Bernd A1 - Schmidt, Peer A1 - Hampel, Silke T1 - Understanding the chemistry of 2D rhodium trihalide solid solutions: tuning of optical properties and nanocrystal deposition T2 - 2D Materials N2 - In the search for novel 2D materials with potentially valuable properties, such as a tunable band gap for optoelectronic or catalytic applications, solid solutions hold the potential to significantly expand the inventory of available 2D nanomaterials. In this study, we present for the first time the synthesis of such 2D rhodium trihalide solid solutions: RhBrxCl3−x and RhBrxI3−x. We use thermodynamic simulations and simultaneous thermal analysis to predict conditions for their rational synthesis and to investigate suitable chemical vapor transport (CVT) parameters for these solid solutions. The evolution of the lattice parameters was investigated by powder x-ray diffraction, showing an isostructural relationship of the synthesized compounds and only minor deviation from Vegard's law. The optical band gap of these materials can be tuned in an energy range from 1.5 eV (RhCl3) to 1.2 eV (RhI3) by choosing the composition of the solid solution, while the samples also exhibit photoluminescence in similar energy ranges. Ultimately, the successful deposition of bulk as well as ultrathin 2D nanocrystals of RhBrxCl3−x by CVT from 925 °C to 850 °C is shown, where the composition of the deposited crystals is precisely controlled by the choice of the starting composition and the initial amount of material. The high quality of the obtained nanocrystals is confirmed by atomic force microscopy, high resolution transmission electron microscopy and selected area electron diffraction. For RhBrxI3−x, the CVT from 900 °C to 825 °C is more difficult and has only been practically demonstrated for an exemplary case. According to the observed properties, these novel solid solutions and nanocrystals show a great potential for an application in optoelectronic devices. KW - Crystal growth KW - Chemical vapor transport KW - Crystal structure KW - Thermodynamic modeling KW - 2D layered compounds KW - Halides Y1 - 2023 UR - https://iopscience.iop.org/article/10.1088/2053-1583/acd012 U6 - https://doi.org/10.1088/2053-1583/acd012 SN - 2053-1583 VL - 10 IS - 3 SP - 1 EP - 12 ER - TY - GEN A1 - Vinokurova, Ekaterina A1 - Knorr, Monika A1 - Efimova, Anastasia A1 - Ovchinnikov, Alexander A1 - Schmidt, Peer A1 - Büchner, Bernd A1 - Isaeva, Anna A1 - Roslova, Maria T1 - Microstructural evolution of layered K-doped RuCl3 during annealing traced by thermogravimetric analysis and 3D electron diffraction T2 - Zeitschrift für Anorgische und Allgemeine Chemie N2 - Nanoscale phase separation was induced in the K-doped RuCl3 van der Waals material by annealing, and studied with the goal to find a natural design strategy for the formation of two-dimensional architectures as an alternative to the costly and time-consuming experimental artificial growth methods. Phase conversion was traced by means of thermogravimetric analysis combined with mass spectrometry. The local crystal structure of co-existing K3Ru2Cl9 domains with the sizes of about 100 nm was solved by 3D electron diffraction. KW - 2D layered compounds KW - Chemical vapor transport KW - Crystal growth KW - Crystal structure KW - Halides KW - Thermal analysis Y1 - 2023 UR - https://onlinelibrary.wiley.com/doi/full/10.1002/zaac.202300141 U6 - https://doi.org/10.1002/zaac.202300141 SN - 0044-2313 SN - 1521-3749 VL - 649 IS - 19 SP - 1 EP - 8 ER -