Al
distributions and locations of corresponding nonframework cations
in SSZ-13 zeolites have significant impact on their catalytic and
adsorption properties. Herein, we demonstrate the feasibility of elucidating
Na+ locations and correlated Al distributions in a series
of Na-SSZ-13 zeolites with Si/Al ratios ranging from 4 to 48 by combining 23Na MQ MAS NMR spectroscopy and DFT calculations. As only
one crystallographically inequivalent T site exists in CHA cages,
the isolated Al and the Al pair (Al–O–Si–O–Si–O–Al)
and (Al–O–Si–O–Al) in 6-membered ring
(MR) distributions and the corresponding Na+ locations
are clearly discriminated. In the high-silica Na-SSZ-13 zeolite, Na+ ions are mainly located at the 6-MR SIIa0 site corresponding
to one Al substitution in the CHA cage. However, a small amount of
the Al pair in 6-MR is still observable even with an Si/Al ratio of
48, corresponding to two Na+ ions located at 6-MR SIIa1
and 8-MR SIII’a1 sites, respectively. With more Al substitutions
in the CHA cage, a portion of Na+ ions with high mobility
among different SII sites may result in the SIII’b site. In
Al-rich SSZ-13 zeolite (Si/Al = 4), the presence of Si(2Al) and Si(3Al)
may lead to Na+ being located at 6-MR SIIa2, with 23Na NMR signals exhibiting relatively large quadrupolar interactions,
and at 8-MR SIII’a2, with NMR signals overlapped with that
of the SIII’a1 site. This approach may expand its application
in discrimination of Al distributions in other zeolites to gain deeper
understanding of the relationship between the structure and the property
for their applications in catalysis and adsorption.
With the increasing number of automobiles on the road, passive safety has become a particularly important issue. In this paper, an energy-absorbing material, origami aluminum honeycomb, was manufactured by a welding process for use as an automobile energy absorbing box. The mechanical properties and deformation of welded origami aluminum honeycomb in three directions were studied through quasi-static and dynamic compression tests. The results show that the origami aluminum honeycomb had good mechanical energy absorption performance, and the optimal directions are identified. Combined with theoretical analysis, the errors between experiments and simulations are shown. The origami honeycomb structure was designed for use as an automobile energy absorbing box. Analysis shows that it could absorb at least 10% of the kinetic energy of a vehicle during a collision, and could play a role in protecting the interior of the vehicle.
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