Stabilität und Instabilität in dispersen Systemen

Ohne Zusammenfassung     

An investigation into the effect of tooth profile errors on gear rattle

In previous work, experimental data have demonstrated the severity of idling gear rattle depends not only on the amplitude, but also the phase of an external sinusoidal forcing. One possible explanation for this is in small tooth profile errors. In this paper, we investigate this hypothesis, by deriving an equation of motion incorporating an error function and losses at the mesh interface, values of which are obtained from experimental data. By solving the equations of motion, theoretical gear rattle trajectories are obtained. Theoretical and experimental trajectories are then compared, by way of time domain plots as well as via contour plots linking the amplitude of backlash oscillation to the amplitude and phase of input forcing. For most profile error functions, good agreement is achieved between the model and experimental data. In the case where the profile errors are dominated by misalignment between the gear and shaft centres agreement is less good and suggestions of areas of further study required for model refinement are proposed.     

SURFACE TENSION,STICKINESS AND ENGULFMENT

The thermodynamic conditions for the engulfment of one set of particles by another has been given in terms of interfacial energies. Experimentally, it has been shown that a polymer with a high glass transition temperature can be engulfed by a particle of low glass transition temperature; also, that Inorganic particles can be engulfed by polymer particles. As a precursor to the engulfment stage heterocoagulation can be used for bringing the particles together in a ‘sticking’ mode. This appears to be a general process which is applicable to a number of scientific areas, e.g. in biology, phagocytosis, and in material science for the preparation of composite particles.     

Neutron scattering studies on micelles of dodecylhexaoxyethylene glycol monoether

Small angle neutron scattering studies have been made on solutions of dodecylhexaoxyethylene glycol in D₂O above the critical micelle concentration and as a function of temperature. It was possible to fit the experimental data at low values of scattering vector using a cylindrical model for the micelle shape.     

Studies on the mechanism of coagulation

Summary In previous work it was found that at certain concentrations of anionic surface agents the particles of positive silver iodide sols became coated with a double adsorbed layer of the surface active agent; under these conditions stable sols were formed the properties of which were found to be dependent on the nature of the head group of the surface active agent. Utilising this fact stable sols have been prepared of silver iodide particles coated with sodium tetradecyl sulphate and their stability and electrophoretic behaviour examined in the presence of a number of cations of different valency. The cations used were, Th⁺⁺⁺⁺, La⁺⁺⁺, Ba⁺⁺, Ca⁺⁺, Mg⁺⁺, Zn⁺⁺, UO₂ ⁺⁺, Mn⁺⁺, Cd⁺⁺, Na⁺, K⁺ and Li⁺. The curves of stability as a function of ionic strength and particle radius revealed marked specificity of the cations; this was attributed to cation binding with the sulphate groups of the second layer of adsorbed surface active agent. The results obtained appear to be in general agreement with those predicted in the theoretical treatment given in part 4.

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Zusammenfassung In einer der vorausgehenden Arbeiten wurde gefunden, da? bei gewissen Konzentrationen von anionischen oberfl?chenaktiven Agenzien die Teilchen von positiven Silberjodidsolen mit einer doppelten adsorbierten Schicht des Agens überzogen werden; unter diesen Bedingungen werden stabile Sole gebildet, deren Eigenschaften abh?ngig von der Kopfgruppe des Agens sind. Indem man diese Tatsache anwendet, kann man Partikel aus Silberjodid, überzogen mit Natriumtetradecylsulfat, herstellen und ihre Stabilit?t und ihr elektrophoretisches Verhalten in Gegenwart einer Reihe von Kationen von verschiedener Valenz prüfen. Verwendet wurden die Kationen Th⁺⁺⁺⁺, La⁺⁺⁺, Ba⁺⁺, Ca⁺⁺, Mg⁺⁺, Zn⁺⁺, UO₂ ⁺⁺, Mn⁺⁺, Cd⁺⁺, Na⁺, K⁺ und Li⁺. Die Stabilit?tskurven als Funktion der Ionenst?rke und des Partikelradius zeigen deutliche Spezifit?t in Abh?ngigkeit von den Kationen. Dies wird der Bindung der Kationen mit den Sulfatgruppen der zweiten Schicht des adsorbierten Agens zugeschrieben. Die Ergebnisse scheinen in allgemeiner übereinstimmung mit den Voraussagen der theoretischen überlegung, dargestellt in Teil IV, zu stehen.

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One of us (A. W.) wishes to thank the British Council for a Scholarship and the University of Cambridge for the award of theOliver Gatty Studentship.     

The measurement of forces between particles in disperse systems

Summary An experimental method is described for measuring the forces between particles in a dispersion as a function of the distance of separation of the surfaces. Experimental results have been obtained for plate-like particles, sodium montmorillonite, and spherical particles, polystyrene latices. The force measured was always repulsive. Increasing the concentration of 11 electrolyte from 10^–4 to 10^–1 M, at a constant separation distance for plates and constant volume fraction for spheres, caused a decrease in the force of repulsion between the particles. The experimental results for sodium montmorillonite were compared with theoretical calculations based on a model of two interacting flat plates at constant potential. The experimentally measured repulsion at close distances was higher than that predicted theoretically.

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Zusammenfassung Eine Methode zur Bestimmung der Kräfte zwischen Teilchen in einer Dispersion in Abhängigkeit vom gegenseitigen Abstand wurde beschrieben. Die experimentellen Resultate wurden mit plättchen-förmigen Teilchen des Natrium-Montmorillonits und kugelförmigen Latexteilchen erhalten. Die ermittelten Kräfte zeigten in allen Fällen die Abstoßung. Bei konstantem Abstand zwischen den Plättchen und bei konstantem Volumenbruch von Kugeln, eine Erhöhung in der Konzentration des 1—1 Elektrolyten von 10^–4 zu 10^–1 M verursachte eine Erniedrigung der Abstoßungskräfte zwischen den Teilchen. Die experimentellen Resultate mit Natrium-Montmorillonit wurden mit den theoretischen Berechnungen für zwei wechselwirkende Plättchen bei konstantem Potential verglichen. Die experimentell bestimmten Abstoßungen bei kleinen Abständen wurden höher als die theoretisch vorausgesagten Werte befunden.

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Plenary lecture by Professor Dr.R. H. Ottewill at the 25th Congress of the Kolloid-Gesellschaft, Munich, October 13–15, 1971.