Similar to the extensive interest in “graphite” and “diamond,” there is an increasing interest in metastable phases. This has various physical properties compared to those of stable phases.
However, processes to create metastable-phase materials are extremely restricted. Novel findings have been reported regarding the growth of a new metastable-phase synthesis technique. This can considerably enhance the physical properties of several materials.
A research group headed by Dr. Dong Won Chun at the Clean Energy Research Division, Korea Institute of Science and Technology (KIST; President: Yoon, Seok Jin), declared that they have been successful in developing a highly advanced metastable-phase palladium hydride (PdHx) material.
Moreover, the researchers determined its growth mechanism and reported it in the latest issue of Nature (IF 49.962). This is known to be one of the world’s most commanding journals in science and technology.
A metastable-phase material consists of high thermodynamic energy compared to that in the stable phase but needs significant energy to obtain the stable phase. This is different from the majority of the other materials. This exists in the stable phase along with low thermodynamic energy.
The research group performed a direct synthesis of a metal hydride by growing a material that has the ability to store hydrogen under an appropriate hydrogen atmosphere. This can be done without scattering hydrogen within a metal.
Remarkably, with the new crystal structure, the researchers have been successful in developing a metastable-phase metal hydride. Furthermore, they verified that the newly-developed metastable-phase material possessed twice the hydrogen storage capacity and good thermal stability of a stable-phase material.
To clarify the theoretical basis and scientific proof for these outcomes, the researchers made use of atomic electron tomography. This reconstitutes 3D images obtained from 2D electron microscope images for nanometer-sized crystals in a metal hydrate, which can be further used for analysis.
Consequently, the researchers illustrated that the metastable phase was thermodynamically stable and determined the 3D structure of metastable-phase crystals. Also, it indicates a new nanoparticle growth mechanism known as “multi-stage crystallization.”
This study holds importance as it discloses a new paradigm in metastable-phase-based material development while a majority of the research has been concentrated on developing stable-phase materials.
These study findings provide an important process to obtain source technology in the development of advanced alloy materials containing lightweight atoms. An additional study is expected to reveal a new paradigm in the development of metastable-phase-based eco-friendly energy materials that can store hydrogen and lithium.
Dr. Dong Won Chun, Clean Energy Research Division, Korea Institute of Science and Technology
“Similar to the Czochralski (CZ) method, which is used to produce single-crystal silicon, a key material in today’s semiconductor industry, it will be a source technology with great potential that will contribute to advanced material development,” concludes Dr. Chun.
Hong, J., et al. (2022) Metastable hexagonal close-packed palladium hydride in liquid cell TEM. Nature. doi.org/10.1038/s41586-021-04391-5