Central small‐angle diffuse scattering from fibers is made of two components

Abstract

Small-angle X-ray and neutron scattering from materials with fibrous texture generally includes a central diffuse scattering that is either diamond-shaped or shaped like a two-bladed propeller. The central scattering from fibers of polyacrylonitrile, nylon, and poly(ethylene terephthalate) and in particular the changes seen during deformation and heating have been examined. The result is that all types of central scattering from fibers are best described as having two distinct components, where these components are an extended equatorial streak and an inner nearly isotropic scattering. They arise respectively from objects that do and do not become aligned or elongated during fiber production. Examples of objects that do not become aligned are small spherical voids and solid particles. Objects that do become aligned include internal phase boundaries, and the surfaces of the fibers themselves. The equatorial streak arises from an assembly of such elongated objects preferentially oriented along the fiber axis.

Tubular Sensor with Multi-Axial Strain Sensibility and Heating Capability Based on Bio-Mimic Helical Networks

“…With further acceleration of rotation, propeller-shaped patterns gradually degenerated into an ellipse and finally transformed into a diamond shape, accompanied with the expansion of the diffusion area. It was similar with SAXS patterns in polyacrylonitrile/carbon nanotube fibers under elevated temperature, where streaks decreased and became more circular and less elliptical . Murthy interpreted this propeller-diamond transformation by converting SAXS patterns into the overlapping of two ellipses with different semi-major and minor axes and attributed it to the decrease of the long axis representing aligned structurers.…”

“…It was similar with SAXS patterns in polyacrylonitrile/carbon nanotube fibers under elevated temperature, where streaks decreased and became more circular and less elliptical. 39 Murthy 40 interpreted this propeller-diamond transformation by converting SAXS patterns into the overlapping of two ellipses with different semimajor and minor axes and attributed it to the decrease of the long axis representing aligned structurers. Because the orientated CFs in tubes were impossible to be diminished, the diamond-shaped patterns can only be ascribed to the deviation of the ellipse, demonstrated by the two tilting semiaxes off from the meridian and equator directions.…”

Structural changes of polyacrylonitrile fibers in the process of wet spinning

“…Frankuche tangent method was used to decompose scattering curve step by step (Figure ) and the R g of pores of different size can be obtained from the tangent slope of the linear relationship of lnI( h ) vs h 2. To reduce the measured quantities, an elliptical model of pore structure was assumed (Supporting Information Figure S4). In this case, the gyration radius R g and volume fraction φ of pores of different sizes are given by where R i is the shaft radius of elliptical model and v is the volume of pore.…”

“…In this work, we investigated the structural changes of PAN fibers in the process of wet spinning, including the fibrillar network, crystallite orientation, crystallinity, and pore. Unlike previous works in which X‐ray diffraction/scattering studies were conducted to obtain the average structural parameters, the crystallite orientation, crystallinity, and pore size at different radial depths of fiber were discussed here by comparing differences of fracture morphology and compactness degree of fibrillar network. Moreover, the long‐to‐short axis ratio and volume fraction of pore with different sizes were obtained by Frankuche tangent method combined with an assumed elliptical model.…”

Modified Crystallization in PET/PPS Bicomponent Fibers Revealed by Small-Angle and Wide-Angle X-ray Scattering

“…The typical central diffuse scattering is elliptical-(Figure 5a), propeller-, or diamond-shaped (not shown). Previous literature states that the diffuse scattering is made of two components, 52 with the two independent components corresponding to scattering from aligned and randomly distributed objects. It is impossible to distinguish scattering from dense regions dispersed in a less dense medium or vice versa.…”