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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 36 (1990), S. 2531-2537 
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Unter der Annahme der Proportionalität der partiellen Drücke der während der Reaktion entstehenden Gase zur Reaktionsgeschwindigkeit wurde eine theoretische Analyse des Einflusses von Stoffübergangserscheinungen auf die Gestalt von EGA-Kurven bei der thermischen Zersetzung von Feststoffen durchgeführt. Werden gasförmige Produkte vom System weniger wirksam abgegeben, verschieben sich die EGA-Kurven zu höheren Temperaturen und die scheinbare Reaktionsordnungn nähert sich Null, während die Aktivierungsenergie annähernd konstant bleibt. Die Feststellungen wurden experimentell überprüft.
    Notes: Abstract A theoretical analysis of the influence of mass-transfer phenomena on the shape of EGA traces of the thermal decompositions of solids has been carried out by assuming that the partial pressures of the gases generated in the reactions are proportional to the reaction rate. It has been shown that the EGA curves move to higher temperatures and the apparent reaction ordern approaches zero as the efficiency of the system for removing the gas product decreases, while the activation energy remains nearly constant. These statements have been checked experimentally.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 313-319 
    ISSN: 1572-8943
    Keywords: CRTA ; synthesis of silicon nitride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Bei 1 atm Druck wurde im Stickstoffflu\ die carbothermische Reduktion von Silika mittels eines CO IR Detektors verfolgt, der am Gas-Output eines Hochtemperaturröhrenofens angeschlossen wurde. Die Reaktionstemperatur wird kontrolliert, indem das Analogsignal des IR-Detektors über ein Interface an eine Kontrolleinheit geleitet wird, welche die Verfolgung der Probentemperatur auf die Art ermöglicht, da\ die Konzentration des bei der Reaktion entstehenden CO auf einem konstanten Wert gehalten wird, den der Anwender zuvor einstellt. Die Reaktionsgeschwindigkeit kann bei einer ganz bestimmten CO-Konzentration durch entsprechende Wahl des Volumendurchsatzes des reaktiven Gases fixiert werden. Es wurde der Einflu\ von Reaktionsgeschwindigkeit und CO-Konzentration sowohl auf die Reaktionstemperatur als auch auf die Struktur der Reaktionsendprodukte untersucht.
    Notes: Abstract The carbothermal reduction of silica under flowing nitrogen at a pressure of 1 atm has been followed by means of a CO IR detector attached to the gas output of a high temperature tubular furnace. The control of the reaction temperature is carried out by interfacing the analogical output of the IR detector to a controller that allows to monitor the sample temperature in such a way that the concentration of CO generated in the reaction is maintained constant at a value previously selected by the user. The reaction rate at a particular concentration of CO can be fixed by properly selecting the flow rate of the reactive gas. The influence of the reaction rate and the CO concentration on both the reaction temperature and the structure of the final product of the reaction are analysed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-8943
    Keywords: CRTA ; material synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Some examples of the use of the CRTA method for the synthesis of materials with controlled texture and structure are given. BaTiO3 has been obtained from the thermal decomposition of Barium Titanyl Oxalate (BTO) and Barium Titanyl Citrate (BTC) by controlling the reaction temperature in such a way that the partial pressure of the gases generated in the reaction was maintained constant at a value close to 10-2 mbar. It has been shown that this method allows getting BaTiO3 with crystal sizes considerably lower than those obtained by decomposing the same precursors by conventional methods. This small crystal sizes lead to the stabilisation of the metastable cubic phase with regards to the tetragonal phase. It has been also shown that the control of the CO generated in the carbothermal reduction of silica allows tailoring the phase composition of the silicon nitride obtained as final product.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 797-802 
    ISSN: 1572-8943
    Keywords: constant rate thermal analysis ; new equipment ; Temperature Programmed Oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurde eine neue Apparatur zur Anwendung der Konstantgeschwindigkeits-Thermoanalyse (CRTA) auf temperaturprogrammierte Oxidationsprozesse (TPO) entwickelt. Die abgesaugten Gase strömen nach Verlassen des Reaktors zur Bestimmung der während der Reaktion verbrauchten Sauerstoffmenge durch einen elektrochemischen Sauerstoffsensor. Die Überwachung der Probentemperatur erfolgt, indem sowohl das Ofen-als auch das elektrische Signal des Sauerstoffsensors an einen PID-Regler weitergeleitet wird, der die Probentemperatur wiederum so regelt, daß der Sauerstoffverbrauch auf einem zuvor vom Anwender wählbaren Wert konstant gehalten wird.
    Notes: Abstract A new equipment has been developed in order to apply the constant rate thermal analysis method (CRTA) to Temperature Programmed Oxidation (TPO) processes. The exhausted gases flow through an electrochemical oxygen sensor after leaving the reactor in order to monitor the oxygen consumption in the reaction. The control of the sample temperature is carried out by interfacing both the furnace and the electrical signal of the oxygen sensor to a PID controller that allows to monitor the sample temperature in such a way that the consumption of oxygen is a constant value previously selected by the user.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of radioanalytical and nuclear chemistry 190 (1995), S. 341-346 
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Nanocomposites α-Al2O3-Fe containing 75 vol% Al2O3 have been obtained by reaction milling, in a vibratory ball mill, a stoichiometric excess of alumina with aluminum and hematite. The kinetics of synthesis of the nanocomposite has been studied for milling times between 15min. and 8h. The reduction reaction is completed in about 2h with formation of α-Al2O3, iron, hercynite (FeAl2O4) and clusters of Fe in alumina. The reaction rate appears moderated by the alumina excess.
    Type of Medium: Electronic Resource
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