X-ray scattering

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Cu Ka:

SAXS vs. WAXS

• Small angle x-ray scattering–

• •

• Wide angle x-ray scattering–

• •

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X-ray scattering of polymers

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HDPE

% crystallinity =

Polymeric unit cell

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Polyethylene

Crystallinity, x-tal size, unit cell

5

𝐿=

∆𝑐𝑜𝑠 𝜃

Crystal size:

(Scherrer Eq.)

Unit cell dimensions (a, b, c)

A scattering spectrum of a PE (orthorhombic ) sample, captured using Cu Ka radiation (l=1.54Å) reveals an amorphous peak at 2q=19.50, a <110> peak at 2q=21.25 and a <200> peak at 2q=23.50. The areas of each peak are 9620, 7780 and 2100 respectively. The FWHM values in radians are 3.75, 0.55, 0.85 respectively.What is the dhkl spacing of the crystallite planes? What are the values of the lattice parameters of each of the unit cells? What is the dimension, L, of the crystallites? What is the degree of crystallinity of the polymer?

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Unit cell dimension: triclinic

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Sintag XRD

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X-ray diffractometer

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