（1Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201204, China) （2Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China) （3University of Chinese Academy of Sciences, Beijing 100049,China)
Small angle X-ray scattering (SAXS) is a powerful tool for the studying of the microscopic structure of materials from 1 nm to hundreds of nm and even micron scale. With the development of synchrotron radiation technology in China, synchrotron radiation SAXS has been more and more applied to the research in various fields of materials. However, since SAXS is observed in a reciprocal space, it is not as intuitive as a microscope and is not as well known as X-ray diffraction (XRD). In this paper, the basic principles of SAXS (sparse system, dense system) are introduced, and the development and progress of synchrotron radiation SAXS beamline in China are also briefly reviewed. The typical applications of in-situ SAXS techniques are introduced, for example, in-situ real-time SAXS in polymer materials processing (crystallization, orientation, periodicity, etc.), in-situ and abnormal SAXS applications in the phase precipitation of the alloy (precipitation chemical composition, clusters size, etc.), and grazing incidence X-ray scattering in the mesoporous thin films (domain size, dislocation factor, etc.) as well as organic photovoltaic film, etc. Finally, the development trends of synchrotron radiation SAXS technology and its application prospect in materials research are also discussed.