posted on 2023-12-05, 13:35authored byVojtech Kundrat, Kristyna Bukvisova, Libor Novak, Lukas Prucha, Lothar Houben, Jakub Zalesak, Antonio Vukusic, David Holec, Reshef Tenne, Jiri Pinkas
Tungsten suboxide
W18O49 nanowhiskers are
a material of great interest due to their potential high-end applications
in electronics, near-infrared light shielding, catalysis, and gas
sensing. The present study introduces three main approaches for the
fundamental understanding of W18O49 nanowhisker
growth and structure. First, W18O49 nanowhiskers
were grown from γ-WO3/a-SiO2 nanofibers in situ in a scanning electron
microscope (SEM) utilizing a specially designed microreactor (μReactor).
It was found that irradiation by the electron beam slows the growth
kinetics of the W18O49 nanowhisker, markedly.
Following this, an in situ TEM study led to some
new fundamental understanding of the growth mode of the crystal shear
planes in the W18O49 nanowhisker and the formation
of a domain (bundle) structure. High-resolution scanning transmission
electron microscopy analysis of a cross-sectioned W18O49 nanowhisker revealed the well-documented pentagonal Magnéli
columns and hexagonal channel characteristics for this phase. Furthermore,
a highly crystalline and oriented domain structure and previously
unreported mixed structural arrangement of tungsten oxide polyhedrons
were analyzed. The tungsten oxide phases found in the cross section
of the W18O49 nanowhisker were analyzed by nanodiffraction
and electron energy loss spectroscopy (EELS), which were discussed
and compared in light of theoretical calculations based on the density
functional theory method. Finally, the knowledge gained from the in situ SEM and TEM experiments was valorized in developing
a multigram synthesis of W18O49/a-SiO2 urchin-like nanofibers in a flow reactor.