A method has been developed for the study of grain boundary migration in high purity aluminum, which allows positive determination of the direction of grain boundary movements. By means of this method it was confirmed that the migration of grain boundaries resulting from surface energy takes place in the direction toward the centers of curvature of the boundaries. On the other hand, strain induced grain boundary migration, such as occurs in recrystallization, proceeds in a direction away from the centers of curvature of the moving boundaries. It was also found that certain strained grains serve as nuclei for strain-free grains of the same orientation which grow at the expense of neighboring strained grains. Most of the strain-free grains formed during the annealing of high purity aluminum cold rolled up to about 40 percent are produced by this mechanism of strain-induced boundary migration, without the formation of new nuclei.

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We report on the formation of bicelles from a mixture of dimyristoylphosphatidylcholine (DMPC) and the chelator-lipid dimyristoylphosphatidylethanolamine-diethylenetriaminepentaacetate (DMPE-DTPA) with complexed lanthanides, either thulium (Tm(3+)) or lanthanum (La(3+)). The two phospholipids used have the same acyl-chain length but differ in headgroup size and chemical structure. The total lipid concentration was 15 mM, and the molar ratio of DMPC to DMPE-DTPA was 4:1. The system was studied with small angle neutron scattering (SANS) in a magnetic field, cryo-transmission electron microscopy (cryo-TEM), and (31)P NMR spectroscopy. We found that, after appropriate preparation steps, that is, extrusion through a polycarbonate membrane followed by a cooling step, monodisperse small unilamellar disks (flat cylinders called bicelles) are formed. They have a radius of 20 nm and a bilayer thickness of about 4 nm and are stable in the investigated temperature range of 2.5-30 degrees C. Fitting of SANS data with a form factor for partly aligned flat cylinders shows that the bicelles are slightly orientable in a magnetic field of 8 T if DMPE-DTPA is complexed with Tm(3+).

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Very small recrystallized grains of a large variety of orientations were produced locally in lightly rolled high purity aluminum crystals. The rate of growth of these small grains varied greatly, depending on their relative orientation with respect to the matrix crystal. Grains with an orientation corresponding to a [111] rotation of about 40° showed by far the highest rate of growth. These results indicate that recrystallization textures developing in the spontaneous recrystallization of deformed single crystals can be accounted for by the orientation dependence of the rate of growth.

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