Synthesis of Mesoporous Carbon Microwires and Nanowires
Martin Steinhart (CNMS Visiting Scholar)
Chengdu Liang, Michelle D. Pawel, and Sheng Dai (CNMS Staff)
We have reported a direct and solvent-free approach to the synthesis
of mesoporous carbon nanowires and microwires with high aspect ratios
and low defect density. Porous alumina membranes were used as hard
templates to control the 1-D morphology of the resulting mesoporous
carbon while block copolymers were employed as soft templates to
generate mesopores. The self-assembly synthesis of carbon precursors
was conducted in 1-D channels of porous alumina membranes with space
confinements. Mesoporous carbon nanowires and microwires were successfully
released from the hard templates via chemical etching of the porous
alumina membranes. Released mesoporous carbon microwires and nanowires
may be used as lightweight functional filler material that allows
tuning of the mechanical and electrical properties of nanocomposites.
The essence of our reported preparation of carbon nanowires and microwires
lies in the combination of hard-template synthesis with soft-template
synthesis. Ordered mesoporous materials combine a large specific
surface area with well-defined pore geometry and have been used in
energy storage, energy conversion, and catalysis. Their synthesis
is based on the self-assembly of block copolymers and surfactants.
Whereas the mesopore arrays thus formed may show a well-developed
local order, the control over shape and arrangement of the mesoporous
entities on a macroscopic scale remains a challenge. A strategy that
addresses these problems involves the synthesis of mesoporous silica
nanowires inside the pores of porous alumina, thus adapting an established
method for the preparation of one-dimensional nanostructures based
on the use of porous templates. It is highly desirable to apply this
concept to amorphous mesoporous carbon, which exhibits superior resistance
to acids and bases, excellent heat resistance, and high intrinsic
electrical conductivity compared to mesoporous silica. Such materials
may be promising components for miniaturized devices or nanocomposites.
C. Liang, G. W. Lynn, U. Gosele, and S. Dai, “Direct Synthesis
of Mesoporous Carbon Microwires and Nanowires,” S. Chem.
This research was
conducted in the Nanocatalyst & Building Block
Theme at the Center for Nanophase Materials Sciences, which is sponsored
at Oak Ridge National Laboratory by the Division of Scientific User
Facilities, U.S. Department of Energy.
carbon microwires with a diameter of 400 nm. (a) SEM image of the
surface of porous alumina containing microwires
(scale bar 1 µm); (b) SEM image of released microwires at low
magnification (scale bar 20 µm); (c) SE image showing a microwire
segment; (d) DFTEM image of the area shown in (c); (e) SE image of
a fractured mesoporous carbon microwire; (f) DF-TEM image of a detail
of a microwire segment at high magnification.