How to see the micro world? Before the birth of modern science, humans observed the matter through the naked eye. After the birth of the optical microscope, people saw microscopic worlds such as cells and bacteria that could not be directly observed by the naked eye, and a higher resolution electron microscope could see a smaller virus. As humans explored the microcosm, higher demands and technologies led to the development of supermicroscopes, spallation neutron sources.
SANS is China’s first pulse neutron small-angle scatterometer, and it is one of the three spectrometers built in the first phase of CSNS. It is used to detect microscopic and mesoscopic structures of material systems in the range of 1 to 100 nm. It is widely used in chemical, physics, biology, materials, geology, etc., serving many high-tech research and development of national energy, environment, biology and new materials. field.
“Small angle scatterometer is one of the most demanding spectrometers for sparse neutron source users. Foreign spallation neutron sources also include small angle scatterers at the beginning of construction.” Liang Tianjiao told reporters.
Ke Yubin, the person in charge of the SANS spectrometer, explained that there are different scales and levels of structure inside the material. For nanoscale structures, transmission electron microscopy (TEM) is usually used for observation, but the sample preparation is very difficult and may be in the preparation process. Affects or even changes the sample structure. The typical TEM sample thickness is generally around 100 nm, and the obtained micro-domain morphology is not sufficient to demonstrate the overall structure of the sample.
In fact, nanostructure observations have another common technique – small-angle scattering, such as small-angle neutron scattering. In general, neutrons are like tiny “pellets” with high penetrability. These “balls” interact with microscopic inhomogeneous structures inside the material and are ejected in different directions. A sensitive two-dimensional detector installed at a distance can capture the angle and number of these “balls” flying, and then obtain a two-dimensional distribution map of the “ball” with a small scattering angle. The map contains Measure the average size information of the nanostructures within the cm2 range of the material, such as nanoscale particles, precipitates, pores, domain structures, etc. within the material. “Nano-scale structural information is important for research in many subject areas.”
Ke Yubin further explained that in the case of shale gas and shale oil, it is necessary to evaluate the oil/natural gas enrichment by characterizing the pore structure in the shale. Among them, the characterization of nanoporosity (especially closed-cell) structures requires the use of small-angle neutron scattering techniques.
“Before the construction of SANS, other spallation neutron sources in the world have their own small-angle scatterometers. For example, the US SNS has EQ-SANS, the UK ISIS has LOQ and SANS2D, and the Japanese J-PARC has TAIKAN. But China also There is no small angle spectrometer based on pulsed neutron source,” said Ke Yubin.