We investigate, using non-equilibrium molecular dynamics simulations and theory, the response of molecular fluids confined in slit pores under the influence of a thermal gradient and/or an applied force. The applied force which has the same functional form as a gravitational force induces an inhomogeneous density in the confined fluid, which results in a net orientation of the molecules with respect to the direction of the force. The orientation is qualitatively similar to that induced by a thermal gradient. We find that the average degree of orientation is proportional to the density gradient of the fluid in the confined region and that the orientation increases with the magnitude of the force. The concurrent application of the external force and the thermal gradient allows us to disentangle the different mechanisms leading to the thermal orientation of molecular fluids. One mechanism is connected to the density variation of the fluid, while the second mechanism can be readily observed in molecular fluids consisting of molecules with mass or size asymmetry, even in the absence of a density gradient, hence it is connected to the application of the thermal gradient only.
This study reports
a green, inexpensive, and highly versatile procedure
to synthesize well-dispersed transition-metal nanoparticles anchored
on carbon supports. The resulting metal loadings are 26 wt % or above.
Achieving both these properties simultaneously has been difficult
with established synthesis methods of carbon-supported metal catalysts,
such as impregnation and deposition-precipitation. Herein, low-molar-mass
sodium alginate with high guluronate content was ion-exchanged with
transition-metal ions, followed by a pyrolysis step at 500 °C.
The investigated transition-metal ions were Fe3+, Co2+, Ni2+, and Cu2+. The alginate’s
properties and interaction with the transition-metal ions greatly
influenced the pyrolyzed material’s characteristics, whereas
the observed metal particle size was found to negatively correlate
with the metal’s melting point. The pyrolyzed Fe-alginate was
tested as a catalyst for the Fischer–Tropsch synthesis and
exhibited an iron time yield of 885 μmolCO h–1 g–1, which is among the highest
activities reported in the literature. The activity is mainly attributed
to the iron nanoparticle size achieved by the reported synthesis procedure,
and the improved olefin selectivity is ascribed to the sodium and
sulfur that originates from the alginate and iron precursor, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.