Effects of the content level and particle size of nickel powder on the piezoresistivity of cement-based composites/sensors

To explore the effects of the content level and particle size of spiky spherical nickel powder on electrical conductivity and piezoresistivity, three types of spiky spherical nickel powder with different particle sizes (3–7 µm, 2.6–3.3 µm and 2.2–2.8 µm) were dispersed into the cement–matrix to fabricate the nickel powder filled cement-based composites/sensors. Experimental results indicate that a high content level and a small practical size are beneficial for the improvement of electrically conductivity. The piezoresistive sensitivities of composites/sensors with 20, 24 and 22 vol% of nickel powder increase orderly when nickel powder particle size is in the range of 3–7 µm. The piezoresistive sensitivities of composites/sensors with different particle sizes of nickel powder decrease with an increase of nickel powder particle sizes at 24 vol% of nickel powder content level. The piezoresistive sensitivity is highly dependent on the conductive network in the composites, which is dominated by the content level and the particle size of the spiky spherical nickel powder.