The ubiquitous nature of enthalpy-entropy compensation calls for a general model. The present model, which is formulated with compensation in ion exchange in mind, is an extension of an older general approach in that the molar fractions of the species that are exchanged in the process enter explicitly. In a different way, it is an extension to the theory of conformal solutions, which only leads to compensation under the condition of conformity. The present model allows one to decide from experiment whether interactions between exchanging species or interactions with third species (or external fields) are responsible for the compensation effect.

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The microstructure of primary carbon filaments formed on supported iron and nickel catalysts has been investigated using transmission electron microscopy, dark-held imaging, and (selectedarea) electron diffraction. It has been established that the filaments consist of cone-shaped graphite layers, stacked with their c-axes in a direction normal to the metal-carbon interface. A growth mechanism is proposed involving the excretion of cone-shaped graphite layers. To explain the constancy of the filament diameter, slippage of these layers over one another is invoked. Edge dislocations are brought about by differences in the rate of carbon excretion.

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