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Separation of Broad Crystalline and Amorphous X-Ray Diffraction Peaks

  • O. W. Marks (a1), D. K. Smith (a2) and M. D. Chris (a1)


Separating overlapped peaks is a part of many x-ray diffraction analyses, for example, polymer crystallinity. Natta [1] defined a method for polypropylene in 1957. His method was computerized at the Hercules Research Center in 1960 with an automatic “curve follower” which punched paper tape for the computer. A later method deviated fTom Natta's method by approximating the amorphous curve with a fixed shape and a height chosen to best fit the diffraction data from 2θ = 7.5 through 10. degrees. Neither of these methods worked on “smectic” polymer samples, i.e., composed of very small crystallites. Also, a different computer program was used for each different polymer, so a general purpose computer program was developed using a peak profile method. This method has been used en polymer mixtures and copolymers of ethylene, propylene, and butene; and on cellulose, modified cellulose, and catalysts. The selection of a profile function is discussed in the next section. In later sections, the background, the fitting procedure, and computer input and output are discussed.



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[1] Natta, G., Corradini, P., Cesari, M., “Quantitative Analysis of Crystallinity of Polypropylene”, Rend. Classe sci. fix. nat. e nat., 22, 11-17 (1957).
[2] Salazar, J. M., Ortega, J. C. G., and Calleja, F. J. B., “On the Separation of Crystalline and Diffuse X-ray Scattering in Semicrystalline Polymers”, Anales de Fisca, 73, 244247 (1977)
[3] Johnson, D. J., Advances in X-ray Analyses, 24 (1981).
[4] Marouardt, D. W., “An Algorithm for Least-Sauares Estimation of Nonlinear Parameters”, J SIAM 11, 431 (1963).


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