A tradeoff between high thermal conductivity
and large thermal
capacity for most organic phase change materials (PCMs) is of critical
significance for the development of many thermal energy storage applications.
Herein, unusual composite PCMs with simultaneously enhanced thermal
conductivity and thermal capacity were prepared by loading expanded
graphite (EG) after natural aging into the paraffin matrix via an
integrated blending method for the first time. Of special interest
is that the composite PCMs with an EG load as low as 4 wt % exhibited
642% thermal conductivity (4 wt % EG) and 5% (melting) or 7% (freezing)
thermal capacity (1 wt % EG), larger than those of pure paraffin.
The characterization results revealed that the short wormlike EG rods
built a flexible framework in the paraffin matrix during blending,
among which smaller exfoliated graphite flakes were cross-linked in
space; thus, a highly effective thermal conductive pathway was constructed.
Additionally, the alkylated EG surface after natural aging with high
lipophilicity contributed to the good paraffin/EG interface compatibility
because of similar chemical compositions and the same polarities of
paraffin molecules and the EG surface and thus reduced the interface
thermal resistance. Meanwhile, the least EG load in paraffin ensured
the highest thermal storage density in the whole system. Under this
premise, the increased paraffin crystallinity and the strong intermolecular
interactions between paraffin and functionalized EG finally resulted
in the enhancement of thermal capacity of the composite PCMs. This
work provides a new strategy to prepare high-performance PCMs that
are available in the real solar thermal storage applications.
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.