Influence of particle morphology and concentration on the piezoresistivity of cement-based sensors with magneto-aligned nickel fillers

Abstract Cement-based sensors with magneto-aligned nickel fillers have the proven capability to significantly enhance piezoresistivity compared with the sensors with randomized fillers. In this paper, the influence of particle morphology and concentration of nickel particles on the piezoresistive and mechanical properties of cement-based sensors, treated with and without magnetic field intervention, are investigated experimentally. Five categories of nickel particles with different average diameters are type N50 (50 nm), N500 (0.5 μm), F(1 μm x 20 μm flake), T (5 μm) and U (25 μm). The obtained results indicate that the application of magnetic field enhances most of the piezoresistive performance and yields best piezoresistivity for the samples with type T nickel powder. Anisotropic piezoresistivity can be achieved under a very low filler content (0.1 vol.%) in N50 nano-scale nickel powder and cement composite, followed by the N500 and T nickel particles in 5 vol.% content. Small particles with lower content have similar piezoresistive performance to the samples with large particles and higher concentration. One half of the samples can achieve high giant gauge factor (GF) of over 500, two-thirds of which are aligned by magnetic field with anisotropic piezoresistive property. Samples with 5 vol.% type T nickel content has the highest GF value, followed by the sample with 5 vol.% type F nickel flakes and 10 vol.% type U nickel powder. It is also found that mechanical strength decreases with the increase of particle concentration.