Brian R. Pauw  Martin E. Vigild  Kell Mortensen  Jens W. Andreasen  Enno A. Klop 《Journal of Applied Crystallography》2010,43(4):837-849

After consideration of the applicability of classical methods, a novel analysis method for the characterization of fibre void structures is presented, capable of fitting the entire anisotropic two‐dimensional scattering pattern to a model of perfectly aligned, polydisperse ellipsoids. It is tested for validity against the computed scattering pattern for a simulated nanostructure, after which it is used to fit the scattering from the void structure of commercially available heat‐treated poly(p‐phenylene terephtalamide) fibre and its as‐spun precursor fibre. The application shows a reasonable fit and results in size distributions for both the lengths and the widths of the ellipsoidal voids. Improvements to the analysis methods are compared, consisting of the introduction of an orientation distribution for the nano‐ellipsoids, and the addition of large scatterers to account for the effect of fibrillar scattering on the scattering pattern. The fit to the scattering pattern of as‐spun aramid fibre is improved by the introduction of the large scatterers, while the fit to the scattering pattern obtained from the heat‐treated fibre improves when an orientation distribution is taken into account. It is concluded that, as a result of the heat treatment, the average width and length of the scatterers increase.  相似文献   

    

Nan Zheng  Zhiyong Yi  Zhenzhen Li  Ran Chen  Yuqing Lai  Yongfeng Men 《Journal of Applied Crystallography》2015,48(2):608-612

A grazing‐incidence sample stage was designed for realizing grazing‐incidence scattering measurements, especially in the ultra‐small‐angle regime, in a modified Xenocs Xeuss system in the laboratory. The designed sample stage, which is composed of four separate motorized positioning stages, allows the sample to be moved along four different directions to locate it in the proper position for scattering measurement. In an effort to realize grazing‐incidence ultra‐small‐angle scattering (GIUSAXS) measurements, both the separation of the collimation slit systems and the sample‐to‐detector distance have been lengthened. At a separation of the collimation slit systems of 2400 mm and a sample‐to‐detector distance of 6558 mm, the effective smallest scattering vector magnitude q_min reaches 0.01 nm⁻¹. A colloidal crystalline thin film obtained from drying a polystyrene latex dispersion on silicon substrate was measured in the setup in GIUSAXS mode at different beam sizes. The resultant GIUSAXS patterns at smaller beam sizes reveal fine crystalline structures in the film.  相似文献   

    

Norbert Stribeck  Xuke Li  Berend Eling  Elmar Pselt  Pieter J. in 't Veld 《Journal of Applied Crystallography》2015,48(2):313-317

When straining polyurethane elastomers (PUEs), it is often observed that the long‐period peak of the small‐angle X‐ray scattering (SAXS) does not shift normally. An explanation is indicated for some PUEs in the real‐space chord distribution. It exhibits a sequence of constant long‐period bands. The band positions form a Fibonacci sequence. This relates to the underlying chemical synthesis by polyaddition of hard and soft modules, indicating a nearly quasiperiodic setup in sequences of stringed hard domains. These sequences appear to be the probes provided by SAXS for the study of morphology evolution in such PUEs. Should a regular‐as‐possible arrangement of physical crosslinks optimize a property of the material, then in the synthesis the mole fraction n_H of hard modules should be chosen to be n_H = τ/(1 + τ) ≃ 0.62, where τ is the golden ratio.  相似文献   

    

Raul Garcia‐Diez  Christian Gollwitzer  Michael Krumrey 《Journal of Applied Crystallography》2015,48(1):20-28

Many low‐density nanoparticles show a radial inner structure. This work proposes a novel approach to contrast variation with small‐angle X‐ray scattering based on the constitution of a solvent density gradient in a glass capillary in order to resolve this internal morphology. Scattering curves of a polymeric core–shell colloid were recorded at different suspending medium contrasts at the four‐crystal monochromator beamline of PTB at the synchrotron radiation facility BESSY II. The mean size and size distribution of the particles as well as an insight into the colloid electron density composition were determined using the position of the isoscattering points in the Fourier region of the scattering curves and by examining the Guinier region in detail. These results were corroborated with a model fit to the experimental data, which provided complementary information about the inner electron density distribution of the suspended nanoparticles.  相似文献   

    

Andrew Senesi  Byeongdu Lee 《Journal of Applied Crystallography》2015,48(2):565-577

Herein, a general method to calculate the scattering functions of polyhedra, including both regular and semi‐regular polyhedra, is presented. These calculations may be achieved by breaking a polyhedron into sets of congruent pieces, thereby reducing computation time by taking advantage of Fourier transforms and inversion symmetry. Each piece belonging to a set or subunit can be generated by either rotation or translation. Further, general strategies to compute truncated, concave and stellated polyhedra are provided. Using this method, the asymptotic behaviors of the polyhedral scattering functions are compared with that of a sphere. It is shown that, for a regular polyhedron, the form factor oscillation at high q is correlated with the face‐to‐face distance. In addition, polydispersity affects the Porod constant. The ideas presented herein will be important for the characterization of nanomaterials using small‐angle scattering.  相似文献   

    

Tsukasa Miyazaki  Keisuke Shimokita  Hiroki Ogawa  Katsuhiro Yamamoto 《Journal of Applied Crystallography》2015,48(4):1016-1022

A simple three‐dimensional structural evaluation system for a film during uniaxial deformation has been developed. The system is realized with an automatic film stretching machine, which allows the horizontally symmetric stretching of a film, and a synchrotron radiation X‐ray scattering apparatus. Using this system, two‐dimensional patterns of small‐angle X‐ray scattering and wide‐angle X‐ray diffraction can be obtained simultaneously during film stretching in the so‐called edge and end views, together with stress–strain data. As cylindrical symmetry of the structure can be expected for a uniaxially stretched film, the two‐dimensional patterns in the through view are identical to those in the edge view, indicating that three‐dimensional structural characterization can be performed with a combination of edge and end views during film stretching. For amorphous poly(ethylene terephthalate) and crystalline poly(vinyl alcohol) films, the preliminary results of three‐dimensional structural characterization during film stretching are shown.  相似文献   

    

Bogusz Kania  Paulina Indyka  Leszek Tarkowski  Ewa Beltowska‐Lehman 《Journal of Applied Crystallography》2015,48(1):71-78

The present work investigates the possibility of bias introduced in grazing‐incidence‐angle X‐ray diffraction techniques applied to residual stress measurements. In these studies, monotextured nanocrystalline nickel coatings obtained by electrodeposition were examined as the model reference samples. Selected Ni coatings exhibited well developed and simple gradient‐free residual stress states that were visible using conventional sin²ψ measurements with varying X‐ray penetration depths. These results were verified against the stress state picture obtained by two variants of grazing‐incidence X‐ray methods: multi‐reflection (different hkl) and constant angle of incidence (single hkl). The outcome of both grazing techniques consistently excluded stress gradients in the samples, which agreed with conventional sin²ψ measurement results. However, only the results of the constant angle of incidence technique agreed with those obtained by the sin²ψ method in terms of calculated residual stress level, suggesting this approach could be applied in further studies of graded material coatings. All analysed coatings yielded uniformly distributed tensile residual stress related to gradual structure development in electrodeposited Ni coatings studied by electron microscopy techniques.  相似文献   

    

Gerhard Fritz‐Popovski 《Journal of Applied Crystallography》2015,48(1):44-51

The new two‐dimensional indirect Fourier transformation converts small‐angle scattering patterns obtained by means of area detectors into two‐dimensional real‐space functions. These functions contain identical information to the scattering patterns, but many parameters related to the microstructure can be obtained directly from them. The size and shape of the microstructures are mainly reflected in the contours of the real‐space functions. Their height can be used to get information on the internal architecture of the microstructures. The principles are demonstrated on nanostructured silica biotemplated by spruce wood.  相似文献   

    

Oindrila Mondal  Manisha Pal  Ripandeep Singh  Debasis Sen  Subhasish Mazumder  Mrinal Pal 《Journal of Applied Crystallography》2015,48(3):836-843

The effect of dopant size (ionic radius) on the crystal growth, structure and optical properties of nanocrystalline calcium titanate, CaTiO₃ (CTO), have been studied using small‐angle neutron scattering. X‐ray diffraction, along with high‐resolution transmission electron microscopy, confirms the growth of pure nanocrystalline CTO. Rietveld analysis reveals that the difference of ionic radii between dopant and host ions induces strain within the lattice, which significantly affects the lattice parameters. The induced strain, due to the difference of ionic radii, causes the shrinkage of the optical band gap, which is manifested by the redshift of the absorbance band. Mesoscopic structural analysis using scattering techniques demonstrates that the ionic radius of the dopant influences the agglomeration behaviour and particle size. A high‐resolution transmission electron microscopy study reconfirms the formation of pure highly crystalline CTO nanoparticles.  相似文献   

    

Artem V. Feoktystov  Henrich Frielinghaus  Zhenyu Di  Sebastian Jaksch  Vitaliy Pipich  Marie‐Sousai Appavou  Earl Babcock  Romuald Hanslik  Ralf Engels  Günther Kemmerling  Harald Kleines  Alexander Ioffe  Dieter Richter  Thomas Brückel 《Journal of Applied Crystallography》2015,48(1):61-70

The KWS‐1 small‐angle neutron scattering (SANS) instrument operated by the Jülich Centre for Neutron Science (JCNS) at the research reactor FRM II of the Heinz Maier‐Leibnitz Zentrum in Garching near Munich has been recently upgraded. The KWS‐1 instrument was updated, from its active collimation apertures to the detector cabling. Most of the parts of the instrument were installed for the first time, including a broadband polarizer, a large‐cross‐section radio‐frequency spin flipper, a chopper and neutron lenses. A custom‐designed hexapod in the sample position allows heavy loads and precise sample positioning in the beam for conventional SANS experiments as well as for grazing‐incidence SANS under applied magnetic field. With the foreseen in situ polarization analysis the main scientific topic of the instrument tends towards magnetism. The performance of the polarizer and flipper was checked with a polarized ³He cell at the sample position. The results of these checks and a comparison of test measurements on a ferrofluid in a magnetic field with polarized and nonpolarized neutrons are presented.  相似文献