Monolithic nanocarbon-based
CO2 solid sorbents offer fast mass transport, easy handling,
minor pressure
drop, and cycle operation stability because of the interconnected
three-dimensional network of pores that provides a unique porous structure.
In this work, following a one-step water-based method, graphene-based
monoliths were produced by a spontaneous reduction-induced self-assembly
of graphene oxide nanoplatelets under mild conditions (45–90
°C). By varying the reaction temperature and amount of reducing
agent (ascorbic acid, AsA), the engineering of the porous structure
of the monoliths was performed and resulted in a portfolio of different
monoliths with different capacities for CO2 adsorption.
It was found that the monolith produced at the highest temperature
and with the lowest AsA amount possessed the highest specific surface
area and porosity as well as a high level of functionalization. As
a result, this monolith presented an excellent CO2 capture
performance of 2.1 mmol/g at T = 25 °C and P = 1 atm. This value is between the highest achieved in
CO2 sorption in comparison to that of similar and nontreated
materials. The selectivity of this monolith for CO2 capture
over that for N2 at 25 °C and atmospheric pressure
is 53, presenting a high viability for practical applications. The
monolith was shown to lose capacity in cycle operations, probably
because of the collapse of the smallest pores, which was solved by
the addition of a small amount of polymer particles during the one-step
synthesis of the monolithic structures. This modification provides
for an excellent stability over five adsorption/desorption cycles.
Parts cast of metals such as iron, using expandable polystyrene foams, may have an unacceptable amount of surface defects, such as lustrous carbon. The use of foams made of styrene/methyl methacrylate copolymers can improve the quality of foam molds and metal parts made using such molds. In this work, expandable copolymers were synthesized by suspension copolymerization of styrene and methyl methacrylate in the presence of blowing agents (pentane isomers). When the surrounding temperature was high enough to vaporize the blowing agent and soften the polymer shell, the beads were expanded. The effects of monomer composition and cell structure modifying aid (polyethylene wax) on the particle size, average molecular weight and molecular weight distribution of synthesized copolymer, pentane content and expansion properties (density, residual pentane of pre-expanded particles and cell structure) were investigated. The results showed that monomer composition had a significant effect on the copolymerization kinetic and the copolymer molecular weight. In addition, cell structure, cell size and cell size distribution of the pre-expanded particles were strongly influenced by cell structure modifying aid concentration. The effects of comonomer composition and copolymer particle size on pentane content of expandable particles were also studied.
The
effect of reversible-deactivation radical polymerization on
the structure of the network formed by copolymerization of mono- and
divinyl monomers is studied. The nitroxide-mediated radical copolymerization
(NMP) of butyl methacrylate and ethylene glycol dimethacrylate, initiated
with the alkoxyamine 3-(((2-cyanopropan-2-yl)oxy)cyclohexylamino)-2,2-dimethyl-3-phenylpropanenitrile
(Dispolreg 007) in an aqueous miniemulsion was used as a case study.
Combination of asymmetric-flow field-flow fractionation and small-angle
X-ray scattering clearly showed that NMP led to a more homogeneous
network structure formed by regions of relatively open networks connected
with short polymer chain segments, whereas that of the polymer formed
by free radical polymerization consists of densely cross-linked regions
linked by long polymer chain portions.
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.