*3.4. Characterisation*

A scanning electron microscope (SEM) was used to analyze the surface morphology of CNF particles. CNF surfaces were examined by Zeiss Environmental SEM (ESEM: model EVO HD 15 operating at controlled pressure conditions at 20 kV). Before conducting the actual SEM surface analysis, CNF specimens were gold surface-coated using Quorum-150R ES model thin film coating equipment.

A high-resolution transmission electron microscope (TEM) was used to study the dispersion of CNF particles in the epoxy polymer matrix. TEM was carried out on an ultrathin microtomed nanocomposite specimen using JEOL HR-TEM (JEM-2100 series), operating at 120 kV.

Thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) were used to examine the thermal properties of nanocomposites using TA instruments SDT Q600 model and Q800 model respectively. In TGA, thermal properties of nanocomposites such as weight loss, decomposition temperature, and degradation were evaluated. In TGA analysis, ~5 mg of the sample was placed in an alumina crucible of TA apparatus and the sample was scanned from RT to 600 ◦C at a scanning rate of 10 ◦C/min under atmospheric condition.

DMA testing on nanocomposites was carried out at a frequency of 10 Hz using a 3-point bending mode of TA instrument from 25 ◦C to 125 ◦C under atmospheric conditions. In DMA testing, specimen dimension of 5.5 cm × 1 cm × 0.3 cm was used. DMA parameters such as storage modulus, Tanδ (damping factor) and *T*g(glass transition temperature) were measured using DMA.

FTIR (Nicolet) analysis was carried out for the cured epoxy and epoxy-CNF nanocomposite series using an attenuated total reflectance (ATR) mode to study the functional group of epoxy and curing characteristics of nanocomposites. Moreover, curing characteristics of epoxy and epoxy-CNF nanocomposite were studied by directly monitoring the exothermic cure temperature at regular time intervals. The temperature of the curing reaction was recorded at regular intervals as soon as the hardener was mixed into the epoxy resin. The time–temperature graph was plotted for all the curing sample series.
