We report the preparation of ordered porous carbon materials with tailored pore sizes selected between 16 and 108 nm using bottlebrush block copolymers (BBCPs) as templates. The nanoporous carbons are prepared via the cooperative assembly of polydimethylsiloxane-block-poly(ethylene oxide) (PDMS-b-PEO) BBCPs with phenol−formaldehyde resin yielding ordered precursor films, followed by carbonization. The assembly of PDMS-b-PEO BBCPs with the resin leads to films exhibiting a spherical morphology (PDMS as the minor domain) with uniform domain sizes between 18 and 150 nm in the bulk. The assembled PDMS sphere diameters scale linearly with BBCPs molecular weights, allowing precise control of domain size. Access to very large ordered domains is an enabling hallmark of BBCPs self-assembly, but reports of well-ordered spherical domains are not common. Carbonization of the ordered precursor films yields nanoporous carbon with uniform and tunable pore size. These nanoporous carbons are shown to exhibit excellent performance as supercapacitor electrodes with capacitance reaching up to 254 F g −1 at a current density of 2 A g −1 .
Carbonization
by rapid thermal annealing (RTA) of precursor films
structured by a brush block copolymer-mediated self-assembly enabled
the preparation of large-pore (40 nm) ordered mesoporous carbon (MPC)-based
micro-supercapacitors within minutes. The large pore size of the fabricated
films facilitates both rapid electrolyte diffusion for carbon-based
electric double-layer capacitors and conformal deposition of V2O5 without pore blockage for pseudocapacitors.
The pores were templated using bottlebrush block copolymers (BBCPs) via cooperative assembly of phenol-formaldehyde resin to
produce microphase-segregated carbon precursor films on a variety
of substrates. Ultrafast RTA processing (∼50 °C/s) at
elevated temperatures (up to 1000 °C) then generated stable,
conductive, turbostratic MPC films, resolving a significant bottleneck
in rapid fabrication. MPC prepared on stainless steel at 900 °C
demonstrated exceptionally high areal and volumetric capacitances
of 6.3 mF/cm2 and 126 F/cm3 (at 0.8 mA/cm2 using 6 M KOH as the electrolyte), respectively, and 91%
capacitance retention after 10,000 galvanostatic charge/discharge
cycles. Post-RTA conformal V2O5 deposition yielded
pseudocapacitors with 10-fold increase in energy density (20 μW
h cm–2 μm–1) without adversely
affecting the high power density (450 μW cm–2 μm–1). The use of RTA coupled with BBCP
templating opens avenues for scalable, rapid fabrication of high-performance
carbon-based micro-pseudocapacitors.
Silicon
carbide (SiC) and silicon oxycarbide (SiOC) ceramic/carbon
(C) nanocomposites are prepared via photothermal pyrolysis of cross-linked
polycarbosilanes and polysiloxanes using a high-intensity pulsed xenon
flash lamp in air at room temperature to yield crystalline and amorphous
phases of SiC and SiOC ceramics, graphitic, and amorphous carbon phases.
The millisecond duration of the radiation pulse is shorter than the
thermal equilibrium time of the preceramic polymers (PCPs), enabling
pyrolysis of the precursor phase and crystallization of the product
before significant energy transfer to the substrate, making this process
uniquely amenable to ceramic processing on or adjacent to thermally
sensitive materials. Rapid precursor pyrolysis and product crystallization
during flash lamp processing, even in air, limit oxidation of the
resulting ceramics. To prepare the nanocomposites, PCPs are coated
onto woven carbon fiber fabrics, thermally cross-linked, and then
flash-lamp-pyrolyzed. The resulting nanocomposites are thermally and
oxidatively stable at extremely high temperatures. The nanocomposites
exhibit excellent performance as supercapacitor electrodes with capacitance
as high as 27.2 mF/cm2 at a 10 mV/s scan rate at room temperature,
excellent stability over 1000 cycles, and Coulombic efficiency of
80%. Patterned nanocomposites are prepared via nanoimprint lithography,
followed by photothermal processing of precursor films. These nanocomposites
have potential applications in energy storage, catalysis, and separations.
We demonstrate SDN-controlled dynamic front-haul optical network pro visioning and modulation format adaptation, running on an emulation of the COSMOS testbed benchmarked against the COSMOS hardware testbed.
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