  Analyzing porous (nano)materials by the atom probe tomography has been
notoriously difficult. The electrostatic pressure intensifies stress at voids
which results in premature failure of the specimen, and the electrostatic field
distribution near voids lead to aberrations that are difficult to predict. Here
we propose a new encapsulating method for a porous sample using a
low-melting-point Bi-In-Sn alloy, known as Fields metal. As a model porous
sample, we used single-crystalline wustite following direct hydrogen-reduced
into iron. The complete encapsulation is performed using in-situ heating on the
stage of the scanning-electron microscope up to approx. 70 Celsius. No visible
corrosion nor dissolution of the sample occurred. Subsequently specimens are
shaped by focused ion beam milling under cryogenic conditions at -190 Celsius.
The proposed approach is versatile, can be applied to provide good quality atom
probe datasets from microporous materials.
