APT for Materials Science Engineering

Our research focuses on utilizing the latest characterization techniques, with atom probe tomography (APT) as a key tool for analyzing complex materials. APT works by ionizing and evaporating surface atoms from a fine needle-shaped emitter under controlled conditions. The ions are then detected by a position-sensitive detector to create a 3D elemental map. APT offers high spatial resolution and chemical sensitivity, ideal for studying local phase transformations and chemical fluctuations in complex engineering alloys. While it provides structural information for pure metals and highly ordered intermetallic phases, it may not always be sufficient. To complement APT, techniques like Cr coating for active or nanosized particles, TEM, SEM, EBSD, ECCI, and focused-ion-beam (FIB) milling are used to analyze specific sample regions, such as grain and phase boundaries.

Cryo-UHV transferring system

▲ Numerical validation & simulation on in-situ experimental conditions

The cryogenic atom probe and transmission-electron microscopy findings highlight the role of advances in microscopy and microanalysis in providing new insights into the changing microstructures of active materials, which helps in the design of improved materials. Our group has recently developed cryogenic APT for advanced characterization of air- and beam-sensitive battery and energy materials. The samples are prepared in a N2/Ar glovebox and freeze-dried in liquid N2, then transferred to a SEM/FIB using a cryogenic, ultra-high-vacuum suitcase for analysis. Using cryo-APT, we are able to study the evolution of structure and composition in energy materials. For example, we have used this technique to study a bulk Na sample for use in a future sodium-ion battery electrode. By slicing the sample into a small lamella and sharpening it into a needle-like atom probe specimen, we were able to suppress the uncontrolled ion-beam milling behavior of the low-melting-point alkali metal. Our datasets allowed us to successfully investigate the bulk chemical fluctuations and adsorbed hydrogen concentration of the Na sample.