Digitale Medien
Copenhagen
:
International Union of Crystallography (IUCr)
Applied crystallography online
11 (1978), S. 551-557
ISSN:
1600-5767
Quelle:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Thema:
Geologie und Paläontologie
,
Physik
Notizen:
Crystallization of a linear polyethylene from the melt was followed in situ with the ORNL 10-meter SAXS camera [Hendricks (1978). J. Appl. Cryst. 11, 15–30]. Specimens were rapidly cooled in the X-ray beam in tandem birdcage furnaces from 1̃80°C to temperatures between 115 and 126°C, and scattering patterns were recorded for 30 s in 50 s intervals. Because of this relatively high-speed data acquisition rate, it was possible to obtain data in time periods which were short compared to the rate of change of the scattering patterns. The SAXS curves showed shapes which changed continuously during crystallization. The scattering curves are the superposition of a zero-angle peak and a Bragg maximum. Guinier plots of the zero-angle peak manifest scattering by lamellae of constant thickness. The thickness value is nearly that expected for crystallites at these crystallization temperatures. A model in which skeletal spherulites form and then later fill in is consistent with these results. Decreasing SAXS intensity and changing Bragg peak intensities indicate crystal thickening during cooling to room temperature.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1107/S0021889878013862
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