Browsing by Author "Baucke, Friedrich G. K."

Now showing 1 - 9 of 9
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    Accurate conductivity cell for molten glasses and salts
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1989) Baucke, Friedrich G. K.; Braun, Jutta; Röth, Gernot; Werner, Ralf-D.
    A cell for measuring absolute conductances of glass and salt melts is described. It is a further development of a conductivity cell reported earlier and is based on the principle that the actual cell volume within the bulk of the melt, which is contained in a platinum crucible, is enclosed by a partly immersed and open-ended alumina cell tube and is thus subjected to a defined, homogeneous electric field between two parallel platinum electrodes arranged perpendicular to the cell tube. The upper electrode positioned in the tube is cross-shaped for the removal of gas bubbles, the lower electrode is formed by a protrusion of the crucible base, which fits into the lower end of the tube. The arrangement is positioned within a specially designed resistance furnace guaranteeing temperature homogeneity of ± 1 Κ within the cell volume. The experimental reproducibility of the conductances is Δϰ ± 1.0 % and is demonstrated by three examples.
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    Application of oxygen sensors in industrial glass melting tanks
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1996) Baucke, Friedrich G. K.; Werner, Ralf D.; Müller-Simon, Hayo; Mergler, Kurt Wilhelm
    A comparative study of electrochemical oxygen sensors for glass melts employing zirconia solid electrolytes developed by Schott Glaswerke and by the HVG is reported. The sensors applied in a feeder Channel of a melting tank producing green glass yielded slightly different but reproducible results despite different constructions. The zirconia reference electrodes achieved more than one year active lifetime at 1200°C. Their potentials directly compared over extended periods agreed within less than 3 mV. The potential differences of the platinum measuring electrodes were traced to temperature gradients. Newly installed platinum electrodes show "induction periods" caused by convectional and diffusional equilibration of adhering surface with bulk melt. Unexpected sudden oxygen inhomogeneities of the melt were detected and explained.
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    Combined electrochemical and Mössbauer studies of the Sb3+/Sb5+ equilibrium in a silicate glass-forming melt
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1988) Stahlberg, Brigitte; Mosel, Bernd D.; Müller-Warmuth, Werner; Baucke, Friedrich G. K.
    The antimony redox equilibrium in an oxide glass-forming melt has been studied quantitatively. Oxygen fugacities at various concentrations and temperatures have been measured electrochemically, and Sb3+/Sb5+ concentration ratios were determined by Mössbauer spectroscopy. Equilibrium constants K(T) and thermodynamie standard values are given for the redox reaction in the melt at temperatures between 1000 and 1500 °C. If K{T) is known, the progress of redox fining can be followed by measuring only the oxygen fugacity.
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    Conductivity cell for molten glasses and salts
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1976) Baucke, Friedrich G. K.; Frank, Wilhelm A.
    Based on a critical analysis of cells applied to measure conductivities of molten glasses in the Aast, an immersion — or dip-type conductivity cell for glass and salt melts has been developed. A cylindrical volume within the bulk of the melt is enclosed by an open-ended alumina or silica tube partly immersed and is subjected to the uniform and homogeneous electric (a.c.) field generated between parallel platinum electrodes and defined by the tube thus permitting the cell constant to be obtained from the cell geometry. The cell is also applicable to local conductivity measurements within technical melting units. Application to molten salts demon-strated good reproducibility of literature data. The cell is described in detail; specific resistances of 15 technical glass melts (Schott) between 1000 and 1350 °C are reported. Cellule à mesurer la conductivit pour verres et sels fondus Sur la Base d'une analyse critique de cellules décrites dans la littérature pour déterminer les conductivités de verres fondus, il a été développé une cellule à mesurer la conduc-tivité par immersion pour les fontes de verres et de sels. Un volume cylindrique à l'intérieur de la fonte est entouré d'un tube en alumine ou silice, ouvert aux deux extrémités et immergé à l'une des extrémités, et soumis au champ électrique (c.a.) homogne entre des electrodes parallèles en platine, défini par le tube, et qui permet de calculer la constante de la cellule à partir de la géométrie cellulaire. La cellule est utilisable pour la mesure de conductivités locales dans des units de fonte industrielles. Son application aux sels fondus a révélé une bonne reproductibilité de données de la littérature. La cellule est décrite en detail; les résistivités des fontes de 15 verres industriels (Schott) entre 1000 et 1350 °C sont signalées. Leitfähigkeitsmeßzelle für Glas- und Salzschmelzen Auf der Grundlage einer kritischen Analyse in der Literatur beschriebener Zellen zur Ermittlung der Leitfähigkeiten von Glasschmelzen wurde eine Eintauchleitfähigkeitsmeßzelle für Glas- und Salzschmelzen entwickelt. Ein zylindrisches Volumen innerhalb der Schmelze wird von einem beidseitig offenen, einseitig eingetauchten Al₂O₃- oder SiO₂-Rohr umgeben und dem homogenen elektrischen Feld (Wechselstrom) zwischen parallelen Platinelektroden unterworfen, das durch das Rohr definiert ist und erlaubt, die Zellkonstante aus der Zellgeometrie zu berechnen. Die Zelle ist auch anwendbar zur Messung lokaler Leitfähigkeiten in technischen Schmelzeinheiten. Ihre Anwendung auf geschmolzene Salze ergab gute Reproduzierbarkeit von Literaturdaten. Die Zelle wird eingehend beschrieben ; spezifische Widerstände von Schmelzen 15 technischer Gläser (Schott) zwischen 1000 und 1350 °C werden mitgeteilt.
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    Electrochemical cells for on-line measurements of oxygen fugacities in glass-forming melts
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1988) Baucke, Friedrich G. K.
    Electrochemical cells for the on-line measurement of oxygen fugacities in oxidic glass-forming melts employing yttria-doped zirconia have been developed for both laboratory and technical application. The basic electrochemistry and the different modes of construction are explained, and two applications are reported, first, the study of redox fining and second, the determination of standard Seebeck coefficients of melts by means of two ZrO2 reference electrodes.
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    Electrochemical mechanism of the oxygen bubble formation at the interface between oxidic melts and zirconium silicate refractories
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1988) Baucke, Friedrich G. K.; Röth, Gernot
    The formation of oxygen and oxygen bubbles at the interface of new, untreated, zirconium silicate (ZS) refractories and oxidic melts, which is of fundamental and economical interest, was investigated. The experiments led to a reaction mechanism which is based on an internal reduction of polyvalent ionic impurities of ZS and an oxidation of oxide ions of the melt at the ZS surface. The redox reaction proceeds via a reaction layer below the ZS surface, which forms an inherently short-circuited, internal, galvanic cell with a growing thickness. The reaction rate is controlled by solid state diffusion of charge-balancing alkali ions. The oxygen formation can be displaced to other electrodes, and the internal reduction can be accelerated and halted by an outer voltage. It was shown that the reaction mechanism is generally valid for alkali ion-containing melts whh oxidizable anions, e.g. for sodium halide melts. Oxygen fugacity measurements and bubble analyses were evaluated critically because of secondary factors, e.g. other gas bubbles often also generated at ZS, which influence the gas economy of the melts. A formal similarity with the electrochromic reaction is pointed out.
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    Entwicklung einer Sonde zur Messung des Sauerstoffpartialdrucks in Glasschmelzen
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1980) Frey, Thomas; Schaeffer, Herlmut A.; Baucke, Friedrich G. K.
    Die kontinuierliche Registrierung der Sauerstoffaktivität bzw. des Sauerstoffpartialdrucks in einer Glasschmelze stellt ein vorrangiges Problem der Glasschmelzführung zur definierten Einstellung des Oxidationszustandes der Glasschmelze dar. Es wird eine Sondenanordnung auf Festelektrolytbasis zur Bestimmung des Sauerstoffpartialdrucks in Glasschmelzen vorgestellt. Bei der Sauerstoffsonde handelt es sich um eine Verbundsonde, bestehend aus einem Pt/Rh-Rohr, das einseitig mit einer Festelektrolyt-Scheibe (stabilisiertes ZrO₂) gasdicht verschlossen ist. Die Verbundsonde zeichnet sich durch hohe Temperaturwechselbeständigkeit und mechanische Stabilität aus. An einer Boraxglasschmelze und einer Kalk-Natronsilicatglasschmelze wird die Funktionstüchtigkeit der Sonde erprobt, indem Gleichgewichtseinstellungen zwischen Glasschmelze und Ofenatmosphäre verfolgt werden. Ferner wird die Läuterwirkung von Arsenoxid als Funktion der Temperatur an Hand der Aufzeichnung des Sauerstoffpartialdrucks in der Glasschmelze demonstriert. Development of a probe for the measurement of oxygen partial pressure in glass melts The continuous recording of oxygen activity or oxygen partial pressure in a glass melt is a very important problem in defining the state of oxidation of the glass. A solid electrolyte probe for the determination of oxygen partial pressures in glass melts has been developed. The sealed probe is constructed from a Pt-Rh tube with a gas tight seal to a stabilized ZrO₂ disk at one end. The probe has good resistance to thermal shock and good mechanical stability. The effectiveness of the probe has been demonstrated in borax and soda-limesilica melts in which the approach to equilibrium between melt and furnace atmosphere was followed. The refining action of arsenic as a function of temperature was also demonstrated through measurement of the oxygen partial pressure in the melt. Mise au point d'une sonde permettant de mesurer la pression partielle d'oxygène dans les fontes de verre L'enregistrement continu de l'activité d'oxygène ou de la pression partielle d'oxygène dans les fontes de verre est un problème majeur lors de la conduite des fours quand il s'agit de maintenir l'état redoxydant de la fonte à une valeur donnée. On présente un montage utilisant une sonde à base d'électrolytes solides permettant la mesure de la pression partielle d'oxygène dans les fontes de verre. II s'agit d'une sonde composite composée d'un tube en Pt/Rh fermé d'un côté par un disque d'électrolyte solide (ZrO₂ stabilisé), ce qui le rend étanche aux gaz. Cette sonde se caractérise par une bonne résistance au choc thermique et une bonne stabilité mécanique. On a effectué des essais de fonctionnement de la sonde en contrôlant l'équilibre entre la fônte et l'atmosphère de fours de fusion d'un verre de borate de sodium et d'un verre silicosodocalcique. De plus, on met en évidence l'action d'affmage de l'anhydride arsénieux en fonction de la température en enregistrant la pression partielle d'oxygène dans la fonte.
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    Fast and accurate analysis of silver and halides in glasses by stepwise Potentiometrie titration
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1983) Baucke, Friedrich G. K.
    An analysis of silver and halides in glasses is reported. The method requires only one decomposition of the glass, followed by the conversion of the silver chloride and/or bromide precipitates into silver iodide by a known addition of excess potassium iodide and subsequent stepwise potentiometrie titration of the halides with silver sulphate. The time required for the complete analysis of the ground glass is 2 h. Presence of silver and iodide in the glass necessitates an additional, independent, determination of one of these elements. Experimental conditions are given and discussed, the reproducibility of the method is reported. Analyse rapide et précise de l'argent et des halogénures dans les verres par titrage potentiométrique par parliers On traite d'une méthode d'analyse de l'argent et des halogénures dans les verres. Cette méthode nécessite une attaque du verre, qui est suivie d'une transformation des précipités de chlorure et/ou bromure d'argent en iodure d'argent par d'un excès connu d'iodure de potassium et d'un titrage potentiométrique par paliers des ions halogénure avec du sulfate d'argent. Deux heures sont nécessaires pour une analyse complète du verre broyé. La présence d'argent et d'iodure dans le verre nécessite la détermination supplémentaire d'une de ces éléments séparément. Les conditions expérimentales sont présentées et discutées, la reproductibilité de la méthode est examinée. Schnelle und genaue Analyse von Silber und Halogeniden in Gläsern durch stufenweise potentiometrische Titration Eine Analyse von Silber und Halogeniden in Gläsern wird beschrieben. Bei dieser Methode wird lediglich ein Aufschluß des Glases benötigt, dem die Umwandlung der Silberchlorid- und/oder -bromidniederschläge in Silberjodid durch Zugabe eines bekannten Kaliumjodidüberschusses und eine stufenweise potentiometrische Titration der Halogenidionen mit Silbersulfat folgen. Für die vollständige Analyse des gemahlenen Glases sind zwei Stunden notwendig. Die Gegenwart von Silber und Jodid im Glas erfordert die zusätzliche, unabhängige Bestimmung eines dieser Elemente. Experimentelle Bedingungen werden angegeben und diskutiert, die Reproduzierbarkeit der Methode wird mitgeteilt.
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    Mixed alkali effect of electrical conductivity in glass-forming silicate melts
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1989) Baucke, Friedrich G. K.; Werner, Ralf-D.
    Electrical conductances of nine melts of the mixed alkali glass system (1 - x) Na2O · x K2O · 0.7 CaO · 4.8 SiO2 with x = 0.0, 0.125, 0.25, to 1.0 were measured at 50 Κ intervals between 900 and 1550 °C by applying a recently published, precise conductivity cell for molten glasses and salts. The high reproducibility, the large number of measurements, and the dense sequence of experimental temperatures allowed confident extrapolation of the data up to 2000 °C. Conductance, ϰ, and activation energy, Ea, exhibit strong mixed alkali effects at an identical melt composition. While the maximum of the function Ea = f(x), however, exists up to above 2000 °C, the minimum of lg ϰ = f(x) disappears at approximately 1900 °C. This is indicated at as low a temperature as 1300 °C, above which the potassium content of the melt which is characterized by the extreme values increases with increasing temperature thus becoming unity between 1850 and 1950 °C. The existence of a mixed alkali effect also in the molten state suggests that structural entities which cause this effect in solid glasses are still present in the melts. Besides, the different upper temperature limits for ϰ and Ea raise the question whether extreme values, by which the mixed alkali effect is usually defined, are characteristic also of the underlying physico-chemical phenomenon. Deviations from "ideal" behavior, however, also exhibit different upper temperature limits.