@misc{HeinemannSchmidt, author = {Heinemann, Robert and Schmidt, Peer}, title = {Thermodynamic analysis of crystal growth of zinc oxide}, series = {Zeitschrift f{\"u}r Anorganische und Allgemeine Chemie}, volume = {642}, journal = {Zeitschrift f{\"u}r Anorganische und Allgemeine Chemie}, number = {18}, issn = {1521-3749}, doi = {10.1002/zaac.201690018}, pages = {1064}, abstract = {Chemical vapor transport (CVT[1]) is a suitable method for production of single-crystals of high purity. In order to find proper strategies for CVT various tools of thermodynamic calculations and analysis of solid-gas equilibria are available. Those applications are demonstrated for vapor transport of zinc oxide under addition of phosphorous and water.}, language = {en} } @misc{HeinemannSchmidt, author = {Heinemann, Robert and Schmidt, Peer}, title = {Vapor Transport Investigations using the High-temperature Gas-balance}, 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 = {2338}, abstract = {The High-temperature Gas-balance (HTGB[1]) has been established as a new method for investigations of heterogeneous phase equilibria with volatile components [1,2]. This equipment is notably well suited to analyze reversible heterogeneous equilibria which occur during chemical vapor transport reactions (CVT[3]). Experimental proof has been furnished by vapor transports of germanium and germanium(II) telluride using iodine as a transport addition. Initially the sublimation of iodine has been observed (section a - Fig. 1). The formation of GeI4(g) as the actual transport agent follows (b). Finally, the transport reaction occurs under reversible formation GeI2(g) (c).}, language = {en} } @misc{HeinemannSchmidt, author = {Heinemann, Robert and Schmidt, Peer}, title = {Crystal Growth by Chemical Vapor Transport: Process Screening by Complementary Modeling and Experiment}, series = {Crystal Growth \& Design}, volume = {20}, journal = {Crystal Growth \& Design}, number = {9}, issn = {1528-7505}, doi = {10.1021/acs.cgd.0c00679}, pages = {5986 -- 6000}, abstract = {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.}, language = {en} } @misc{BoehlerRosencrantzWolfetal., author = {B{\"o}hler, Stefan and Rosencrantz, Sophia and Wolf, Karina and Heinemann, Robert and Schmidt, Peer and Ganster, Johannes and B{\"u}sse, Thomas and Balko, Jens and Rosencrantz, Ruben R.}, title = {Active protease formulation in commodity polymers withstands melt processing into compounds and blown films}, series = {Materials Today Communications}, volume = {34}, journal = {Materials Today Communications}, issn = {2352-4928}, doi = {10.1016/j.mtcomm.2022.105018}, pages = {1 -- 9}, abstract = {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.}, language = {en} } @techreport{SchmidtGieseHeinemannetal., author = {Schmidt, Peer and Giese, Marie and Heinemann, Robert and Nawdiyal, Amruta and Knorr, Monika and Breitkopf, Cornelia and Schneegans, Marcel Felix and Pinnau, Sebastian and Lorenz, Tommy and Mickoleit, Erik and to Baben, Moritz and Keuter, Philipp and M{\"u}ller, Michael and Sergeev, Dmitry and Ewaznezhad Fard, Darya and Morsa, Amedeo and Rhys, Dominic Jacob and Yazhenskikh, Elena}, title = {PCM-Screening-2 : Evaluierung eutektischer Gemische f{\"u}r den Einsatz als PCM : thermodynamische Modellierung und experimentelle Methoden - 2}, series = {Deutsche Forschungsberichte}, journal = {Deutsche Forschungsberichte}, doi = {10.34657/28504}, pages = {182}, abstract = {Durch den Einsatz von W{\"a}rme- und K{\"a}ltespeichern in Geb{\"a}uden, Industrieanlagen und Kraftwerken k{\"o}nnen Lastschwankungen reduziert und die Anlageneffizienz verbessert werden. Latentw{\"a}rmespeicher (PCM) erm{\"o}glichen durch Ausnutzung einer fest-fl{\"u}ssig Phasenumwandlung hohe Speicherdichten bei geringen Temperaturdifferenzen. Die Verf{\"u}gbarkeit geeigneter und kosteng{\"u}nstiger PCM's ist derzeit noch eingeschr{\"a}nkt. Ein Screening geeigneter Stoffsysteme zur Bildung multin{\"a}rer Eutektika durch thermodynamische Modellierung der Phasengleichgewichte erlaubt fundierte Vorhersagen zur Zusammensetzung eutektischer Gemische, ihren Schmelztemperaturen und -enthalpien. Auf Basis der Literatur, umfangreicher experimenteller Untersuchungen und Simulationen wurde im Projekt eine im Temperaturbereich nicht eingeschr{\"a}nkte thermochemische Datenbank f{\"u}r das komplexe Stoffsystem Na+, K+, Ca2+, Mg2+ // Cl-, NO3-, SO4_2-, CO3_2- // H2O geschaffen, die eine Auswahl neuer PCM mit optimalen thermodynamischen Eigenschaften f{\"u}r spezifische Prozessanforderungen auf Basis von in Deutschland in großen Mengen verf{\"u}gbaren, preiswerten Rohstoffen erm{\"o}glicht. Weiterhin wurde ein CalPhaD-basiertes Viskosit{\"a}tsmodell, ein Screening-Verfahren inkl. Webserver und intuitive Visualisierungsm{\"o}glichkeiten hochkomponentiger Systeme entwickelt. Mittels eines Screenings erfolgte eine Vorauswahl von potentiell als PCM geeigneten Gemischen, die umfangreich charakterisiert wurden. Auf Basis der vielversprechenden Speicherdichten und der niedrigen Materialkosten wird erwartet, dass ein oder mehrere dieser identifizierten PCMs in die Anwendung als thermische Speicher gebracht werden k{\"o}nnen.}, language = {de} }