Effect of graphene on the piezoelectric properties of cement-based piezoelectric composites

Two types of graphene, namely, graphene oxide (GO) and multilayer graphene nanoplatelets (GNPs), were added to a 0–3-type cement-based piezoelectric composite to investigate the piezoelectric properties of the composite. The aforementioned composite contained a cement matrix and lead zirconate titanate inclusions, each of which accounted for 50% of the composite volume. The results obtained by using ultrasonic vibrations and a hydrometer indicated that the optimal dispersion times of GO in pure water and GNPs in ethanol were 30 and 15 min, respectively. The addition of GO to the aforementioned composite decreased the composite’s relative permittivity ( ε r ) and increased dielectric loss and electrical resistance, resulting in difficulties in poling and poor polarization efficiency. GO is not conducive to improving the piezoelectric properties (piezoelectric charge coefficient d 33 , piezoelectric voltage coefficient g 33 , ε r , and electromechanical coupling coefficient k t ) of piezoelectric composites. GNP addition to cement can reduce the resistivity and increase dielectric loss of cement composites. The composites with a lower resistance can be polarized easily. The appropriate addition of GNPs can improve the polarization efficiency, thereby enhancing the piezoelectric properties of cementitious composites. In this study, the optimal addition of GNPs was 0.3%. Wet-mixing of GNP-containing cementitious composites with a superplasticizer in ethanol can further improve the piezoelectric properties of this composite ( d 33 = 123 pC/N, g 33 = 22.6 ×10 −3 V·m/N, ε r = 615, and k t = 20.2%). The GNP-containing cementitious composite mixed with a superplasticizer exhibited a high k t ; thus, this composite has potential for use as a green energy material. • The optimal GNP content for enhancing the piezoelectric properties is determined. • The addition of GO has a negative effect on the piezoelectric properties. • The k t value of PZT/cement composites containing GNPs reaches 20.2%. • The settling time of the graphene solutions is determined using a hydrometer.