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Chemische Transportreaktionen weisen ein gemeinsames Merkmal auf: In Gegenwart eines gasförmigen Reaktionspartners, des Transportmittels, wird eine feste oder flüssige Komponente verflüchtigt. An anderer Stelle scheidet sie sich meist in Form gut ausgebildeter Kristalle wieder ab. So ist der Chemische Transport z. B. für den Festkörperchemiker ein unentbehrliches Verfahren zur Herstellung reiner, gut kristallisierter Feststoffe. Als umfassendes Handbuch behandelt dieses Werk die vielseitigen Aspekte von chemischen Transportreaktionen: Von der Grundlagenforschung bis hin zur praktischen Bedeutung, beispielsweise für die Funktionsweise von Halogenlampen.
Since their first recognition in mineral forming processes
some 150 years ago chemical vapor transport reactions (CVTR) have attracted continuous scientific interest. Due to the pioneering work of Harald Schäfer quantitative understanding and exploitation of transport reactions for crystal growth, synthesis, investigation of high-temperature gas species, and thermodynamic studies have become possible. Renewed interest in CVT is triggered by the demand of material sciences for novel compounds with tailor-made physical properties and by the need for efficient recycling strategies for various metals from industrial waste.
Chemical Vapour Transport of Bismuth and Antimony Chalcogenides M2Q3 (M = Sb, Bi, Q = Se, Te)
(2010)
Thermodynamic modelling of the ternary systems M/Q/I (M = Sb, Bi, Q = Se, Te) indicated solid-gas equilibria suitable for chemical vapour transport of bismuth and antimony chalcogenides. The predictions of the modelling were confirmed by transport experiments on a transport balance. The optimum transport conditions using iodine as transport agent were determined for all systems to: ϑsource = 500 °C and ϑsink = 450 °C. For ΔT > 50 K the sequential transport of chalcogenide iodides MQI followed by M2Q3 occurs. Thermodynamic standard data of the gas species SbI(g) were concluded from equilibrium calculations: ΔH0f,298(SbI(g)) = 106 ± 3 kJ·mol–1; S0298(SbI(g)) = 255 ± 3 J·mol–1·K–1; Cp(SbI(g)) = 37 ± 1 J·mol–1·K–1
The term chemical vapor transport (CVT) summarizes a variety of reactions that show one common feature: a condensed phase, typically a metallic or salt like solid, is volatilized in the presence of a gaseous reactant, the so-called transport agent, and deposits elsewhere, usually in the form of crystals. The deposition will take place if the site of volatilization and the site of crystallization have different temperatures. In many cases, chemical vapor transport is associated with a purification effect. CVT-reactions of elements, oxides, sulfides, selenides, tellurides, phosphates, sulfates, halides, oxide halides, phosphides, arsenides, intermetallics, and so on, are known.
A variety of processes of crystal growth proceeds via the gas phase. If the initial solid material is volatilized in a heterogeneous reaction under presence of a gaseous reactant, the transport agent, the term Chemical Vapor Transport Reaction (CVT) is applied. Crystallization processes by CVT are known for both elements, intermetallics, binary and complex oxides, halides, chalcogenides, and pnictides. Even if the formation of volatile halides is a common feature of almost all vapor transport reactions, significant differences are there concerning the choice of a suitable transport agent depending on the nature of the initial solid phase. Actually, the appropriateness of transport agents for the respective transport reaction can be described in a thermodynamic way. Besides some basic principles for systematic evaluation more practical recommendations for suitable experimental conditions are given for CVT of different classes of inorganic materials.
Chemische Transportreaktionen weisen ein gemeinsames Merkmal auf: In Gegenwart eines gasförmigen Reaktionspartners, des Transportmittels, wird eine feste oder flüssige Komponente verflüchtigt. An anderer Stelle scheidet sie sich meist in Form gut ausgebildeter Kristalle wieder ab. So ist der Chemische Transport z. B. für den Festkörperchemiker ein unentbehrliches Verfahren zur Herstellung reiner, gut kristallisierter Feststoffe.
Als umfassendes Handbuch behandelt dieses Werk die vielseitigen Aspekte von Chemischen Transportreaktionen: Von der Grundlagenforschung bis hin zur praktischen Bedeutung, beispielsweise für die Funktionsweise von Halogenlampen.
This comprehensive handbook covers the diverse aspects of chemical vapor transport reactions from basic research to important practical applications. The book begins with an overview of models for chemical vapor transport reactions and then proceeds to treat the specific chemical transport reactions for the elements, halides, oxides, sulfides, selenides, tellurides, pnictides, among others. Aspects of transport from intermetallic phases, the stability of gas particles, thermodynamic data, modeling software and laboratory techniques are also covered. Selected experiments using chemical vapor transport reactions round out the work, making this book a useful reference for researchers and instructors in solid state and inorganic chemistry.
This comprehensive handbook covers the diverse aspects of chemical vapor transport reactions from basic research to important practical applications. The book begins with an overview of models for chemical vapor transport reactions and then proceeds to treat the specific chemical transport reactions for the elements, halides, oxides, sulfides, selenides, tellurides, pnictides, among others. Aspects of transport from intermetallic phases, the stability of gas particles, thermodynamic data, modeling software and laboratory techniques are also covered. Selected experiments using chemical vapor transport reactions round out the work, making this book a useful reference for researchers and instructors in solid state and inorganic chemistry.
Adaptation Planning Framework to Climate Change for the Urban Area of Ho Chi Minh City, Vietnam
(2009)
Situated in an intra-tropical and low elevation coastal zone, the developing megacity of Ho Chi Minh City is vulnerable to many of the adverse impacts of the present and future changes in climate. In consideration of climate change and urban development interrelations, the research case for adapting to climate change and the risks and opportunities of adaptation are set out. Based on the in-depth assessment of the vulnerability of Ho Chi Minh City, the categorized urban environment in form of a spatially explicit information system will act as a matrix for the formulation of appropriate adaptation strategies for future development and redevelopmentpolicies. The resulting Adaptation Planning Framework should form the future basis for spatially-explicit decision-making processes related to sustainable urban planning and development in HCMC.
Development of salt hydrate eutectics as latent heat storage for air conditioning and cooling
(2014)
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.
This paper presents an investigation of primary breakup of planar turbulent liquid jets and breakup properties at the surface of turbulent jets in still air at standard conditions. Numerical simulations are carried out for jet exit Reynolds number 23000 and Weber numbers in the range [102–107].
Due to the limitation of direct numerical simulation (DNS) to moderate Reynolds numbers, a stochastic 1D ansatz based on the one-dimensional turbulence (ODT) model is used to simulate a planar liquid jet with a high lateral resolution. ODT permits an affordable high resolution of interface and single-phase property gradients which are key for understanding the local behavior. ODT is a stochastic model simulating turbulent flow evolution along a notional 1D line of sight by applying instantaneous maps to represent the effect of individual turbulent eddies on property profiles. The most relevant mechanisms that influence the primary breakup of liquid jets are found to be represented accurately based on comparisons to experiments and correlations reported in the literature. Building on this finding, future work will focus on the statistics of droplets generated by primary breakup, both to investigate their relationship to breakup mechanisms and to provide input to models of secondary breakup and subsequent spray evolution.
The paper presents the use of indicators in a site-specific assessment method for strategic environmental assessment in regional land use planning (here: SEA-REP). It is explained with the example of the state of environment indicator ‘LUCCA 4—Urban Areas at Risk of Flooding’, how SEA as a decision-aiding instrument can contribute to the prevention of conflicts with policy for adaptation to climate change.
The method begins with the determination of impact factors for SEA. In the presented study, the physical impact factors of land consumption, land use change, and directed flooding were recognised. A core problem during the selection of indicators for land uses for the adaptation to climate change (here: LUCCA) and the derivation of assessment thresholds was a lack of region-wide policy objectives for the protection of land and resources. Therefore, in a second step, regional environmental orientation objectives were derived from national and EU environmental policy. A standard method for the selection of LUCCA indicators and the derivation of assessment thresholds for conflict analysis is described. Three classes of conflict classification for regional plan designations on the individual site are proposed. It is recommended that future adaptation measures of regional land use planning should be designations of specific land uses as priority areas for urban areas prone to flood risk.
Im Rahmen der Strategischen Unweltpruefung (SUP) ist, soweit erforderlich, eine grenzueberschreitende Beteiligung durchzufuehren. Bei dieser sind unterschiedliche administrative, rechtliche, planerische und kulturelle Rahmenbedingungen der beteiligten Staaten zu beruecksichtigen. Sie bedarf daher einer gruendlichen Vorbereitung sowie der Entwicklung geeigneter Verfahren, fuer die bisher kaum auf Beispiele und Erfahrungen zurueckgegriffen werden kann. Vor diesem Hintergrund wurde im INTERREG-Ill-A-Projekt "transSEA" am Beispiel der grenzueberschreitenden Beteiligung in der Regionalplanung zwischen Sachsen, Polen und Tschechien ein Verfahrensvorschlag entwickelt, der in diesem Beitrag vorgestellt wird.
Landschaftsverbrauch, großräumige Versiegelungen und Bodenkontaminationen haben dazu geführt, daß das Umweltmedium Boden in den letzten Jahren eine zunehmende Bedeutung als Schutzgut erfahren hat. Bodenschutz bedeutet nicht nur, die Nutzungsfunktionen der Böden in ihrer Leistungsfähigkeit zu erhalten bzw. wiederherzustellen, sondern auch, die natürlichen Bodenfunktionen vorsorgend zu schützen. Dabei hat der präventive Bodenschutz vor allem eine standortgerechte Nutzung von Flächen zum Ziel. Vor allem für planerische Zwecke werden künftig verstärkt bodenbezogene Bewertungskriterien und -abläufe erforderlich, die die Fähigkeit von Boden zur Erfüllung verschiedener Funktionen im Naturhaushalt kennzeichnen. Die Funktionsfähigkeit eines Bodens laßt sich dabei beispielsweise recht gut mit Hilfe seiner natürlichen Bodenfunktionen Produktions-, Lebensraum- und Regelungsfunktion beschreiben und bewerten.
Main development steps of the modern European legislation in the field of environmental assessment
(2007)