Colloid crystal self-organization and dynamics at the air/water interface

Article Abstract:

An inorganic solution of calcium hydroxide shows spontaneous precipitation when carbon dioxide is dissolved into it. A self-organized colloid crystal of calcium carbonate microcrystals forms at the surface of the water. The microcrystals join together at the surface and take the form of a disordered gel mat. This mat possesses fractal characteristics. Aged solutions exhibit a second microcrystal population possessing 'dogtooth spar' morphology. These crystalites form a regular triangular lattice. There is stability in these structures for some 24 hours before they form part of the fractal gel.

Colloids, Crystal lattices

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Near-surface alignment of polymers in rubbed films

Article Abstract:

The X-ray scattering calculations reveal unequivocally that near surface polymer molecules become aligned when a polyimide film's surface is rubbed. The extent of the polymer chain alignment depends on the thickness of the film, with only a thin surface region of 200 nm thick film affected compared to most of a 6 nm film being within 20 degrees of the rubbing direction alignment. This property indicates different characteristics of the near surface region and the bulk polymer since bulk glass transition temperatures are not necessary for the rubbing alignment.

Polymers

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Dynamics of the silicon (111) surface phase transition

Article Abstract:

Low-energy electron microscopy has been used to investigate the real-time kinetics of a phase transformation limited to the silicon (111) surface. It was established that the transformation is controlled by the rate at which material is exchanged between the first layer of the crystal and the surface.

Oxidation reduction reactions, Silicon

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