Combined SANS and SAXS study of the action of ultrasound on the structure of amorphous zirconia gels

In the present work, we have studied for the first time the combined effect of both sonication and precipitation pH on the structure of amorphous zirconia gels synthesized from zirconium(IV) propoxide. The techniques of small-angle neutron and X-ray scattering (SANS and SAXS) and low temperature nitrogen adsorption provided the integral data on the changes in the microstructure and mesostructure of these materials caused by ultrasonic (US) treatment. Amorphous ZrO₂·xH₂O synthesized under ultrasonic treatment was found to possess a very structured surface, characterized by the surface fractal dimension 2.9–3.0, compared to 2.3–2.5 for the non US-assisted synthesis, and it was also found to possess a higher specific surface area, while the sizes of the primary particles remain unchanged.     

Counterion condensation in ionic micelles as studied by a combined use of SANS and SAXS

We report a combined use of small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) to the study of counterion condensation in ionic micelles. Small-angle neutron and X-ray scattering measurements have been carried out on two surfactants cetyltrimethylammonium bromide (CTABr) and cetyltrimethylammonium chloride (CTACl), which are similar but having different counterions. SANS measurements show that CTABr surfactant forms much larger micelles than CTACl. This is explained in terms of higher condensation of Br⁻ counterions than Cl⁻ counterions. SAXS data on these systems suggest that the Br⁻ counterions are condensed around the micelles over smaller thickness than those of Cl⁻ counterions.     

Details of Structure Formation During the Induction Period of Spinodal-Type Polymer Crystallization

An unexpected type of primary crystal nucleation is described, involving spinodal decomposition (SD) type microphase separation due to the orientation fluctuations of rigid segments prior to crystal nucleation. This type of mechanism was found by the present authors about 10 years ago, and recently, it was theoretically revealed by Olmsted et al. to be one of three types of primary crystal nucleation: the well-known homogeneous crystal nucleation directly from the liquid–crystal coexistence domain, which occurs at higher temperatures above the binodal temperature T _b , crystal nucleation after binodal microphase separation between T _b and spinodal temperature T _s , and that after SD below T _s . The detailed experimental results for the spinodal-type crystal nucleation, especially the temperature dependence of characteristic wavelength in SD, are explained as well.     

Evidence of the hexagonal columnar liquid-crystal phase of hard colloidal platelets by high-resolution SAXS

A vast majority of compounds with bent core or banana shaped molecules exhibit the phase sequence B₆-B₁-B₂ as the chain length is increased in a homologous series. The B₆ phase has an intercalated fluid lamellar structure with a layer spacing of half the molecular length. The B₁ phase has a two dimensionally periodic rectangular columnar structure. The B₂ phase has a monolayer fluid lamellar structure with molecules tilted with respect to the layer normal. Neglecting the tilt order of the molecules in the B₂ phase, we have developed a frustrated packing model to describe this phase sequence qualitatively. The model has some analogy with that of the frustrated smectics exhibited by highly polar rod like molecules.     

Solution conformation of the response regulator proteins from Deinococcus radiodurans studied by SAXS

In this paper the solution conformation of the response regulator proteins from Deinococcus radiodurans was studied by small-angle X-ray scattering (SAXS). The SAXS curves of Dr-rrA in solutions were obtained at Beamline 1W2A of Beijing Synchrotron Radiation Facility (BSRF). Two possible conformations of the response regulator proteins, compact and incompact conformations, have been represented by the known crystallographic structures. And theoretical solution scattering curves of the two possible conformations were calculated and fitted to the experimental scattering curve of Dr-rrA, respectively. The result indicates that the solution conformation of the response regulator proteins is inclined to the compact one, which is in agreement with the result of biochemical experiments.     

Investigation of failure mechanisms in polymer composites by simultaneous measurement of ultra-small-angle scattering and acoustic emission during the deformation. I. Method

Failure mechanisms in polymer composites were investigated with the method of ultra-small-angle X-ray scattering using synchrotron radiation and acoustic emission analysis simultaneously. The composites were prepared from polystyrene filled with glass beads with different coatings. The two-dimensional scattering patterns were analyzed by means of a cylinder model, while the curves of the acoustic emission signals per stress or amplitude interval were calculated and fitted by a Weibull distribution function.     

Chain folding and the structure of nylon 6.6 spherulites

Following the assignment of the 1329 and 1224 cm^?1 infrared bands to chain-folded conformations in nylon 6.6 by Koenig et al. examination of the infrared spectra of positively birefringent and negatively birefringent spherulitic films has been made. The spectra indicate extensive regular folding in negative spherulites but fewer folds or less regular folding in the positive spherulite structure.

The assignment of the infrared fold bands to modes of vibration of the repeat unit is discussed with reference to the spectra of films with varying extents of N deuteration (normal 6.6, disordered regions deuterated, N deutero 6.6, disordered regions hydrogenated).

Electron micrographs of negative spherulites are analyzed with the infrared and previous evidence. We suggest they are built up of single-crystal lamellae of 0.2 to 0.3 μ lateral dimensions packed with a preferential orientation of the lamellae planes parallel to the radial direction but otherwise randomly oriented.     

红外光谱技术对广东博罗横岭山商周时期墓地出土古玉器上蜡工艺的揭示及其意义

广东博罗横岭山商周时期墓地是广东省目前所发现的最重要的商周时期墓葬群,该墓地出土的玉器样品通过一系列的科学鉴定研究后发现,玉器的红外光谱在2 960 cm-1(相对较弱)、2 920和2 853 cm-1附近出现了2～3个明显的特征性吸收峰,结合对纯蜡样品、现代上蜡玉器样品的测试比较,认为博罗横岭山墓地出土玉器在加工过程中曾经经过上蜡处理,首次揭示出商周时期岭南先民掌握了在加工中利用蜡来增加玉器美观技术的事实。