Investigation on NTC/PTC effects of cement-based self-heating composites with varied conductive filler contents

The present study systematically investigated the influence of varied conductive filler contents on the negative/positive temperature coefficient (NTC/PTC) effects in cement-based self-heating composites. Different composite formulations containing varying proportions of carbon nanotubes (CNT) and carbon fiber (CF) were prepared and subjected to self-heating tests at different input voltages. Analysis of temperature and electrical conductivity data obtained during the tests elucidated the NTC/PTC effects. Additionally, diverse analytical techniques were employed to characterize the physicochemical properties of the samples. Results indicated a correlation between NTC and PTC effects and thermal expansion as well as variations in electrical resistivity with increasing temperature. Moreover, a specific temperature and electrical resistivity range is identified where the NTC effect transitions to the PTC effect, a transition range influenced by the conductive filler content. Enhanced heat-generation accelerated the PTC effect by inducing structural alterations in the sample's physicochemical composition.