采用同步辐射小角X射线散射技术研究Al−Mg−Si合金的析出强化行为

研究Al−Mg−Si合金在等温时效过程中的析出强化行为及其对力学性能的影响。利用原位同步辐射小角X射线散射(SAXS)技术和透射电子显微镜(TEM)对纳米析出相及其结构参数(尺寸、体积分数和数密度)进行表征。结果表明,棒状β''析出相优先沿其纵向尺寸生长,但径向尺寸在时效5 h后达到峰值。如预测与测量的屈服强度和硬度结果所示,纳米析出相的尺寸和体积分数的增大与析出强化定量相关。SAXS为Ashby−Orowan模型提供了更可靠的输入参数,这有助于提高模型的预测精度和泛化能力。研究表明,随着时效时间的延长,Al−Mg−Si合金预测力学性能的演变与β''析出相的平均半径和体积分数有关。

BL19U2:Small-angle X-ray scattering beamline for biological macromolecules in solution at SSRF

The BL19U2 at the Shanghai Synchrotron Radiation Facility is a small-angle X-ray scattering beamline dedicated to structural studies pertaining to biological macromolecules in solution.The beamline has been officially opened to users in March 2015,and since then,a series of technological innovations has been developed to optimize beamline performance,thereby significantly improving the data collection efficiency and broadening the application scope of biological small-angle X-ray scattering.BL19U2 is ideal for the high-throughput screening of weakly scattered proteins,protein assemblies,nucleic acids,inorganic nanomaterials,and organic drug molecules.This paper describes the design and overview of the BL19U2 beamline.Versatile sample environments at the experimental station and some recent scientific highlights are presented.

A novel heating area design of temperature-jump microfluidic chip for synchrotron radiation solution X-ray scattering

In this paper, we present a novel design scheme of temperature-jump(T-jump) area for microfluidic device.Numerical simulation and experimental research of thermal characteristics of the solution in microchannels is completed.Numerical simulation of the temperature-jump microchannel is analyzed to study the heat transfer characteristics by comparing performance of three proposed configurations.Calculation of the power requirement is discussed in the dimensional design of microheater. Temperature-sensitive fluorescent dye is applied to investigate the temperature field of microchannel heated by a designed microheater. It is found that the T-jump microfluidic device can provide rapid heating for solutions with strong convection heat transfer ability.

FEA-based structural optimization design of a side cooling collimating mirror at SSRF

Based on finite element analysis of thermal mechanical behavior, structural optimization design was proposed for a side cooling collimating mirror subjected to high heat load for a beamline at SSRF(Shanghai Synchrotron Radiation Facility). The temperature distribution,stress concentration effect, maximum equivalent(vonMises) stress, and slope error of the mirror were analyzed.In particular, the cooling water channels of the traditional structural design were optimized, and the modified designs were further optimized. Although the traditional structural and the improved designs could meet requirements for the temperature and thermal stress, the deformation gradients were relatively large for several structural designs, and this led to larger slope error. The further improved structural designs could be of better performance.

Extraction and structural investigation of jute cellulose nanofibers

Cellulose nanofibrils(CNFs) are a type of natural nanomaterials extracted from plants and animals that have expanding applications in numerous areas benefiting from their inherent properties of renewability,biodegradability,and sustainability.For energy consumption reduction,CNFs were extracted from raw jute fibers,which were not pretreated in a hot alkali or acid solution,by TEMPOmediated oxidation.Synchrotron radiation wide-angle scattering was performed to realize the crystallization of the CNF crystallites;Fourier transform infrared spectroscopy,transmission electron microscopy,and fieldemission scanning electron microscopy were used to characterize the changes in chemical groups and visualized morphology of CNFs.The simplified preparation and shortened cycle should further help the study of the structure–function relationship of jute CNFs subjected to chemical modification.

In situ studies on the positive and negative effects of 1,8-diiodoctane on the device performance and morphology evolution of organic solar cells

The introduction of solvent additives is one of the most common approaches for enhancing the power conversion efficiency of organic solar cells(OSCs).However,the use of solvent additives has some negative effects,and an understanding of how solvent additives affect OSCs is currently limited.In this study,we developed an in situ grazing incidence wide-angle X-ray scattering(GIWAXS)technique in the SAXS beamline(BL16 B1)at the Shanghai Synchrotron Radiation Facility,and the additive effects of1,8-diiodoctane(DIO)on the performance and morphology evolution of the PTB7-Th/PC71 BM device was investigated in depth.The results revealed that the crystal size increased with the volume ratio of DIO,and a drastic evolution of lattice space and crystal coherence length was observed during thermal annealing for the first time,to our knowledge.The discrete PC71BM molecules dissolved by DIO have an effect similar to that of the nucleating agent for PTB7-Th,boosting the crystallization of PTB7-Th,reducing phase separation,and inducing more drastic morphological evolution during thermal annealing.Our results provide a deep perspective for the mechanism of solvent additives,while also showing the significance and feasibility of the in situ GIWAXS technique we developed at BL16 B1.

Directed Self-assembly of Vertical PS-b-PMMA Nanodomains Grown on Multilayered Polyelectrolyte Films

Layer-by-layer polyelectrolyte self-assembly, a common method for preparing high-quality ultra-thin films, was employed to direct the self-assembly behavior of polystyrene-block-poly(methyl methacrylate)(PS-b-PMMA) block copolymer for the first time. Differing from the previous neutral polymer brushes anchored to silicon substrates via chemical modification, polyelectrolyte multilayers(PEMs) were anchored by electrostatic interaction and provided a stable, smooth, and neutral interface. In the present study, PS-b-PMMA was deposited on poly(acrylamide hydrochloride)/poly(acrylic acid)(PAH/PAA) PEMs prepared by layer-by-layer self-assembly to successfully yield vertical nanodomains after thermal annealing. Seven layered PEMs revealed an excellent, smooth surface, with a low roughness of 0.6 nm. The periodic structure with interlamellar spacing of 47 nm was determined by grazing-incidence small-angle X-ray scattering(GISAXS). The morphology of the PS-b-PMMA nanodomains depended on the polyanion-to-polycation concentration ratio, which is related to the interaction between the block copolymer and the substrate. Our results demonstrate that layer-by-layer self-assembly is a helpful method for the phase separation of block polymers and the fabrication of vertical, ordered nanodomains.

Relationship between Localization of PBSU in Interlamellar/Interfibrillar Regimes and Double Peaks in DSC/SAXS in its Blend with PVDF

In this work,phase segregation and localization of PBSU have been investigated with the combination of SAXS and DSC in its blend with PVDF.After stepwise crystallization of PVDF and PBSU,there are double melting peaks of PBSU in DSC and double scattering peaks in SAXS.It has been demonstrated that double peaks can be attributed to the localization of PBSU in interlamellar/interfibrillar region in pre-formed PVDF crystal framework.In the case of low content of PBSU in blend,PBSU is trapped into the interlamellar region of PVDF crystals,resulting in the alternating lamellae crystal of them and the first peak(with low-q)in SAXS.The enhanced confinement effect produces thinner PBSU lamellae,corresponding to the lower melting temperature in DSC.Upon increasing its content in blend,some PBSU segregates in interfibrillar regions in addition to the enrichment in interlamellar regions of PVDF crystal framework.The larger space and higher concentration of PBSU in interfibrillarregions contribute to periodic lamellae structure of PBSU with higher thickness,which is the reason for the second peak(with high-q)in SAXS and DSC.Our results not only clarify the relationship between localization of PBSU in interlamellar/interfibrillar regions and double peaks in DSC/SAXS,but also provide a novel strategy to detect the interlamellar and interfibrillar segregation of low-T_(m) component in miscible crystalline/crystalline blend.