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  • 1985-1989  (4)
  • 1840-1849
  • Polymer and Materials Science  (2)
  • drag reduction  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Flow birefringence and rheological measurements on shear induced micellar structures (1987)
    Springer
    Rheologica acta 26 (1987), S. 532-542 
    Details
    ISSN: 1435-1528
    Keywords: Surfactantsolution ; micelle ; viscoelasticity ; drag reduction ; flow birefringence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Aqueous solutions of cationic surfactant systems with strongly binding counterions show the striking phenomenon of shear induced phase transitions. At low shear rates or angular frequencies, the solutions exhibit Newtonian flow. At high rates of shear, however, the rheological properties change dramatically. Above a well defined threshold value of the velocity gradient, a supermolecular structure can be formed from micellar aggregates. This shear induced structure (SIS) behaves like a gel and exhibits strong flow birefringence. The formation of the shear induced structure is very complicated and depends on the specific conditions of the surfactant system. In this paper we discuss new results which have been obtained from rheological measurements and from flow birefringence data. We examine the stability of the shear induced state as a function of temperature, surfactant concentration and salt concentration and we analyse the effect of solubilisation of alcohols and hydrocarbons. The results are interpreted in terms of a kinetic model which accounts for the observed behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01333737
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Surfactant systems for drag reduction: Physico-chemical properties and rheological behaviour (1986)
    Springer
    Rheologica acta 25 (1986), S. 468-486 
    Details
    ISSN: 1435-1528
    Keywords: Surfactant ; solution ; micelle ; viscoelasticity ; viscosity ; drag reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The first part of the work presents an overview of the physical chemistry of surfactants which in aqueous solutions reduce the frictional loss in turbulent pipe flow. It is shown that these surfactants form rodlike micelles above a characteristic concentraionc t. The experimental evidence for rodlike micelles are reviewed and the prerequisites that the surfactant system must fulfill in order to form rodlike micelles are given. It is demonstrated by electrical conductivity measurements that the critical concentration for the formation of spherical micelles shows little temperature dependence, whereasc t increases very rapidly with temperature. The length of the rodlike micelles, as determined by electric birefringence, decreases with rising temperature and increases with rising surfactant concentration. The dynamic processes in these micellar systems at rest and the influence of additives such as electrolytes and short chain alcohols are discussed. In the second part, the rheological behaviour of these surfactant solutions under laminar and turbulent flow conditions are investigated. Viscosity measurements in laminar pipe and Couette flow show the build-up of a shear induced viscoelastic state, SIS, from normal Newtonian fluid flow. A complete alignment of the rodlike micelles in the flow direction in the SIS was verified by flow birefringence. In turbulent pipe flow, drag reduction occurs in these surfactant systems as soon as rodlike micelles are present in the solution. The extent and type of drag reduction, i.e. the shape of the friction factor versus Reynolds number curve, depends directly on the size, number and surface charge of the rodlike micelles. The friction factor curve of each surfactant investigated changes in the same characteristic way as a function of temperature. For each surfactant, independent of concentration, an upper absolute temperature limit,T L, for drag reduction exists which is caused by the micellar dynamics.T L is influenced by the hydrophobic chain length and the counter-ion of the surfactant system. A first attempt is made to explain the drag reduction of surfactants by combining the results of these rheological measurements with the physico-chemical properties of the micellar systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01774397
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Schwingungsrißkorrosion beschichteter Verdichterschaufel-Werkstoffe (1986)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 17 (1986), S. 413-418 
    Details
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Corrosion Fatigue of Coated Compressor Blade MaterialsDamage of compressor blades due to corrosion fatigue constitutes a substantial fraction of the observed stationary gas turbine failures. Dependent on environmental conditions and filtering, these blades in addition may be exposed to mechanical erosion. For corrosion fatigue protection, coatings have been used since many years. However, recently the earlier used NiCd coatings have been substituted to an increasing extent by inorganic coatings containing dispersed aluminum particles as manufactured e.g. by SermeTel. Such coatings are designed to warrant improved corrosion resistance. Within the scope of a joint research project of the German gas turbine manufacturers AEG KANIS, BBC and KWU, some of these protective coatings were tested under simulated operating conditions in different corrosive media with respect to their corrosion fatigue protection capabilities.As a result, it was shown that the aluminum dispersed coatings offer good protection against corrosion in aqueous neutral media at room temperature. One of the coatings tested guarantees in strongly acidious media only a time-limited corrosion protection. At elevated temperatures and also after erosive pre-damage, the fatigue strengths are reduced heavily. In comparison with uncoated specimens, galvanically or chemically deposited nickel-coatings, which were tested concurrently, improved the corrosion resistance only unessentially.
    Notes: Schäden an den Verdichterschaufeln von stationären Gasturbinen infolge von Schwingungsrißkorrosion stellen einen großen Teil der beobachteten Ausfallursachen dar. Zusätzlich sind diese Schaufeln je nach Umgebungsbedingungen mehr oder weniger starker Erosion ausgesetzt. Zum Schutz vor diesen Beanspruchungen werden seit Jahren Beschichtungen eingesetzt, wobei in letzter Zeit die zum Teil eingesetzten NiCd-Schichten vermehrt durch anorganische Schichten aus Chromat/Phosphat-Bindemitteln mit dispergierten Aluminiumpigmenten, z.B. der Firma SermeTel, ersetzt werden, die einen verbesserten Korrosionsschutz gewährleisten sollen. Im Rahmen eines gemeinsamen Forschungsprojektes der deutschen Gasturbinenhersteller AEG KANIS, BBC und KWU wurden einige dieser Schutzschichten in unterschiedlichen, betriebsnahen Korrosionsmedien auf ihre Schutzwirkung besonders gegen Schwingungsrißkorrosion hin untersucht.Als Ergebnis kann festgehalten werden, daß die aluminiumpigmentierten Schichten in neutralem Medium bei Raumtemperatur einen guten Korrosionsschutz bieten. Eine der Schichten gewährleistet in stark saurem Medium nur einen zeitlich begrenzten Korrosionsschutz. Bei höheren Temperaturen und auch nach erosiver Vorschädigung werden die ertragbaren Wechselamplituden dagegen sehr stark herabgesetzt. Parallel dazu geprüfte galvanisch oder chemisch abgeschiedene Nickelschichten verbesserten die Korrosionsbeständigkeit nur unwesentlich gegenüber unbeschichteten Proben.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19860171107
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Struktur-Wirkungs-Prinzipien von Korrosionsinhibitoren für die Rohöl- und ErdgasförderungHerrn Prof. Dr. W. Hilger zum 60. Geburtstag gewidmet (1989)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 40 (1989), S. 629-634 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Structure efficiency relationships of corrosion inhibitors for oil and gas productionStructure efficiency relationships for quarternary ammonium compounds as corrosion inhibitors for oil and gas production were investigated in the system mild steel/aqueous NaCl solution (5 weight%, CO2 saturated) at T = 298 K and T = 343 K by Electrochemical Impedance Spectroscopy (EIS) and weight loss measurements. In-situ EIS measurements rapidly gave relatively accurate results on differential inhibitor efficiencies. Composition, thickness and inhibitor content of the inhomogeneous 3-D protecting layers formed on highly pure iron surfaces were determined by XPS measurements. The inhibition mechanism of the inhibitor used could be determined by its distribution within the 3-D protecting surface layer and is interpreted in terms of the interphase inhibition concept.
    Notes: Struktur-Wirkungs-Prinzipien von quartären Ammoniumverbindungen als Korrosionsinhibitoren für die Rohöl- und Erdgasförderung wurden anhand von Elektrochemischer Impedanz Spektroskopie (EIS) und Gewichtsverlustmessungen in Systemen C-Stahl/wäßrige NaCl-Lösung (5 Gew.%, CO2-gesättigt) bei T = 298 K und T = 343 K untersucht. Es konnte gezeigt werden, daß in-situ EIS Messungen rasch relativ genaue Resultate über differentielle Inhibitorwirksamkeiten liefern. Aus XPS Untersuchungen an Oberflächen aus Reinsteisen ließen sich Zusammensetzung, Dicke und Inhibitorgehalt der sich auf dem Substrat bildenden inhomogenen 3-D Deckschichten bestimmen. Der Wirkungsmechanismus des verwendeten Inhibitors konnte aus seiner Verteilung innerhalb der 3-D Deckschicht mit dem Konzept der Interphaseninhibition gedeutet werden.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19890401102
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    Paper (German National Licenses)
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