Experimental study on the contribution of the quantum tunneling effect to the improvement of the conductivity and piezoresistivity of a nickel powder-filled cement-based composite

The voltage?current characteristics of a nickel powder (NP)-filled cement-based composite (NPCC) and the variation of electrical resistivity of NPCC under compression are studied by using a four-pole method based on embedded loop electrodes. The generation of conductivity and piezoresistivity in NPCC is investigated by examining the morphology of NPCC by SEM and studying the variation of distance between NP particles under compression. Experimental results indicate that the electrical conductivity of NPCC is ohmic when the voltage is below 3.5?V. Although NP particles are dispersed in the cement matrix and they do not form a connected conductive network, NPCC has a low electrical resistivity of 2.29 ? 103??cm without loading. A decrease of 0.042% in the fractional change in volume of NPCC under compression causes the tunneling distance to decrease 0.60?1.42?nm and the fractional change in electrical resistivity to reach 62.61%. It is therefore concluded that the improvement of conductivity and piezoresistivity of NPCC is due to the quantum tunneling effect.