Effect of Nano carbon black, GO, Graphene, and ZrO2 on the mechanical properties of B4C ceramic

Abstract

The purpose of this research is to investigate the synergistic effect of ZrO2 and different additives (Nano carbon black (C.B_n), graphene oxide (GO), and graphene (Gr)) on the microstructure and mechanical properties of B4C ceramic. Four composites were fabricated using the Spark Plasma Sintering (SPS) method at 2000 °C with a 15-min holding time and a pressure of 30 MPa. Relative density, hardness, and fracture toughness were measured by Archimedes’ principle, micro Vickers hardness testing, and crack length measurement, respectively. Microstructural investigations and phase identification were also evaluated by Field Emission Scanning Electron Microscopy (FESEM) and X-ray Diffraction (XRD). The results indicated that during sintering, all ZrO2 reacts with B4C, leading to the in-situ synthesis of the new ZrB2. Thermodynamic evaluation revealed the synthesis temperature decreases by approximately 100 °C in the presence of C.B_n/GO/Gr additives. The highest relative density (99.4%) was obtained in the sample containing C.B_n. The introduction of ZrO2 and C.B_n/GO/Gr additives resulted in a decrease in the hardness of B4C decreases. The highest fracture toughness (5.7 MPa m^0.5) was obtained in the sample containing GO, while the lowest was observed in the sample without C.B_n/GO/Gr additive (3.9 MPa m^0.5). Examination of the crack path propagation showed that the activation of toughening mechanisms such as crack deviation and branching are the main reason for the enhanced fracture toughness in the sample containing GO.