All the thermal adhesives samples must be treated by machinery
cutting and burnishing with the size of 35 mm in diameter and
8 mm in height, before their thermal conductivities are measured
by the Hot Disk TPS-2500 thermal constants analyzer based on the
Gustafsson transient plate heat source [50], which uses a heat
source and a temperature sensor to precisely deduce the sample
thermal resistance, and the thermal conductivity of sample can be
obtained by a fitting equation. The sensor for thermal conductivity
measurements can be found in Fig. 6 and the detailed measurement
theory was reported in previous paper [51]. In order to check the credibility of the measurements, the thermal conductivities of all
thermal adhesives were measured five times. The averaged values
were adopted and the overall uncertainty in measurements was
less than 4%. To understand the improvement of the thermal conductivity
of the epoxy resin by the three different fillers intuitively,
we first measure the thermal conductivity of the pure epoxy resin.
The value is 0.17 W m1 K1 at room temperature, a little lower
than that of the previous reports [15,28], which may be due to the
sample with the additives (reactive diluent and silane coupling
agent) and little bubbles from preparation process or the possible
system error of the thermal conductivity analyzer [51].
Fig. 6 show the thermal conductivity of the samples with three
different fillings as a function of the filling load. It can be seen
obviously that the thermal conductivity of the resin filled with the
graphene sheet is improved to be 4.01Wm1 K1 at the filling load
of 10.10 wt%, which is enhanced more than 22 times than that of the
pure resin. At the maximum filling load of 16.81 wt%, the thermal
conductivity of the resin filled with the graphite nanoflake is
1.84Wm1 K1, enhanced by about 10 times that of the pure resin,