Currently, researchers are paying much attention to the development of effective 3D graphene for applications in energy storage and environmental purification. Before commercialization, however, it is necessary to develop a method that allows for the large-scale production of such materials and enables good control over their structural and chemical properties. With this objective, we herein developed a simple method for the formation of large-scale (4 in. wafer) 3D graphene networks via the self-assembly of graphene sheets at a superheated liquid−vapor interface. The structural morphology of this porous network could be modified by controlling the vaporization rate, surface temperature of the target substrate, and amount of discharged colloids. The key mechanism behind this intriguing result was investigated by high-speed visualization of microdroplet behavior and extensive thermal analysis. This self-assembled 3D graphene had excellent electrical and mechanical properties. Our approach can be directly used for the mass production of graphene-based materials.
Closed-box loudspeaker
systems (CBLSSs) are compact and simple
air-suspension loudspeaker systems, and their low-frequency responses
are determined by two fundamental parameters: resonance frequency
and total damping. Recently, electronic devices have come to require
more compact designs, so the volumes of loudspeaker should be reduced.
However, a small loudspeaker cannot retain sufficient acoustic space,
resulting in poor low-frequency acoustic performance. Herein, we investigated
acoustic characterization of the CBLSS with different filling materials
such as thermally expanded graphene oxide (TEGO), activated carbon,
graphene platelets, and melamine foam (MF). Upon the powder-based
test, the resonance frequency of the loudspeaker decreased and resulted
in a volume increasing effect inside of the loudspeaker. The TEGO
shows almost double volume increase rate, compared to other particle-based
filling materials. Employing hybrid filling material that consists
of TEGO in an MF cage (TEGO@MF), the volume increase rate of the novel
loudspeaker was over 24% at 300 cc. Because of the high adsorptive
characteristics and thermal properties of TEGO, the acoustic performance
in the low-frequency domain was clearly enhanced, despite the reduced
mass loading. Furthermore, these properties were observed to be highly
effective for enhancing the low-frequency acoustic performance of
the larger loudspeaker, achieving a volume increase rate of 49.5%
in a 700 cc enclosure.
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