Crystal homogeneity

Keywords ABC triblock copolymers Block Copolymers Crystallization Homogeneous nucleation... 

There are two approaches to nucleation kinetics that have been utilized to explain intraglobular fat crystallization—homogeneous and heterogeneous nucleation. During homogeneous nucleation, there are no impurities present to act as nucleation catalysts (6). Heterogeneous nucleation involves the presence of impu-... 

In simple liquids studied by computer simulation the problem of glass formation through structural arrest cannot be dissociated from the problem of nonequilibrium crystallization (homogeneous nucleation), since under many conditions the time scales for the two processes are comparable. A broad review emphasizing phase changes has recently been given by Frenkel and McTague, to which we refer the interested reader for a more... 

Another method, which was originally developed for the investigation of noble-gas crystals, begins at t = 0 with a molecular crystal homogeneously doped with radioactive tracer molecules. The radioactive molecules which diffuse to the crystal surface exchange at times t > 0 with non-radioactive molecules in the vapour phase... 

Figure 11.3a and b shows, respectively, the XRD spectra of a supported NaA zeolite membrane and of the resulting powder after filtering and drying the liquid phase. SEM observations allow the evaluation of membrane thicknesses, shape, orientation and size of the crystals, homogeneity and uniformity of the zeolite layer, and a morphological analysis on the existence of intercrystalline defects. SEM-energy-dispersive x-ray analysis (EDX) can be used to measure qualitatively and quantitatively the atomic composition of... 

If mechanisms one and two do not act, then under stress, a two-dimensional homogeneous nucleation would be needed. Just as with three-dimensional nucleation of phase change (e.g., condensation or crystallization) homogeneous nucleation of bare regions can be expected to be a slow, and hence rate-limiting, process. If the solid surface is rough, then stress concentrations around asperities might accelerate this nucleation process. 

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