Application of Small Angle X-ray Scattering in Polymer Research

Small Angle X-ray Scattering Applications in Polymer Research Li Zhihong, Wu Zhonghua, Wu Ziyu Synchrotron Radiation Laboratory, Institute of High Energy Physics, Chinese Academy of Sciences In the history of human beings, there is almost no science and technology such as polymer science making such a tremendous contribution to human society. In the early 20th century, the discovery of a reliable polymerization method, coupled with the tremendous progress in macromolecular theory, physics, and engineering, led to and promoted a material revolution. This material revolution continues today. In the 21st century, polymer science and its related technologies are facing new opportunities and challenges. With the development of production and science and technology, a variety of new requirements have been put forward for helium molecular materials: high performance, high functionality, compoundness, refinement, and intelligence. These depend on the fine resolution of the structure and function of the polymer.

For the submicroscopic structure of polymers, that is, when the structures with a size within a few tens of angstroms to several thousand angstroms are studied, small angle X-ray scattering (SAXS) method needs to be studied. This is because all scattering phenomena of electromagnetic waves follow the inverse law, that is, the structural characteristics of the irradiated object relative to a certain X-ray wavelength (the X-ray wavelength used for scattering and diffraction analysis is between 0.05 and 0.25 nm). The larger the size, the smaller the scattering angle. Therefore, when X-rays pass through a polymer having a larger structural feature size than its own wavelength, scattering effects are limited to small angles.

Small-angle X-ray scattering is the coherent scattering of electrons to X-rays over a small range of angles in the vicinity of the original beam. Since X-rays interact with electrons in the atom, SAXS is particularly sensitive to electron density inhomogeneities. Small-angle scattering occurs in all materials with nano-scale electron density inhomogeneities. Small-angle scattering pattern, intensity distribution and scatterer shape, size distribution and density of electron clouds around the medium. The shape, size, and distribution of the scattering body can be resolved by observing and analyzing scattering patterns or scattering curves (scattering intensity-scattering angles).

Morphology and size; grain shape, size and size distribution; particle size and interaction parameters measured by Zimm plots; microdomains (including disperse and continuous phases), polymeric hollows and cracks, etc. Shape, size and distribution; spatial distribution of structures; determination of wafer orientation, thickness and crystallinity, and thickness of amorphous layers in macromolecular systems by long-period measurements; molecular motion and phase transitions in helium molecular systems; Superstructure changes (such as crystalline state, liquid crystal state, amorphous state, and intermediate state) of polymer system during strain process and heat treatment; related length of molecular multiphase system (including crystalline phase system and amorphous blend system, etc.) , Interface layer thickness and total surface area; determine the presence or absence of fractal structures in polymer systems by double logarithmic plots of intensity and angle, and determine the fractal dimension-sensitivity; calculate the weight-average molecular weight of the polymer by measuring the absolute strength.

Compared with other methods, SAXS has a wide range of applications for the sample, which can be liquid, solid, crystal, non-crystalline, or a mixture thereof, and can also be a retentate and a porous material. Samples are simple to prepare, generally not destroyed in the SAXS test, and can be used repeatedly or for other measurements.

The X-ray source with synchrotron radiation intensity can make the SAXS structure study enter into dynamic (time resolution) from static, which can solve the problem that many conventional experimental devices can not solve.

Li Zhihong, male, born in 1967, Shanxi Wuyuan, postdoctoral. Mainly engaged in nano, mesoporous materials research.

Effect of copper infiltration on microstructure and properties of grain-reinforced iron-based materials Liu Fang, Zhou Kechao, Li Zhiyou State Key Laboratory of Powder Metallurgy, Central South University, Heat Treatment, Microstructure, Material Properties Preparation of Co by Sinter-infiltration and subsequent heat treatment Iron-based powder metallurgy materials reinforced with Cr-Mo-Si particles were used to study the influence of different copper infiltration on the microstructure and properties of the materials. The results show that Co-Cr-Mo-Si hard particles exist in the matrix alone, and play a role in particle strengthening. When copper is not penetrated, there are many holes, the interface between hard particles and the substrate is clearly visible, the bonding strength is low, and the material properties are poor. With the increase of the amount of copper infiltration, the degree of diffusion of alloying elements increases, and the interface strength between hard particles and the substrate is good. The porosity of the material decreases, the degree of dispersion of carbides increases, and the material properties increase significantly. At the same time, the fracture of the material mainly through the tear of the copper phase, showing a clear plastic fracture characteristics. Therefore, the amount of infiltrated copper can be used to obtain the properties of the iron-based powder metallurgy materials with uniform structure and better bonding of the phases.

Liu Fang, female, born in 1973, a doctoral student in materials science at Central South University. He has successively engaged in the research of biomedical materials and combustion synthesis to prepare coating technologies. Now mainly engaged in the development of rhodium-based iron-based powder metallurgy materials.