Abstract
Carbon nanofiber (CNF)-dispersed B4C nanocomposites containing 2.5 vol% Al2O3 as a sintering aid were fabricated directly from mixtures of amorphous B and C, CNF, and Al2O3 powders by pulsed electric-current pressure sintering (PECPS) at 1800°C for 10 min under 30 MPa in a vacuum. Dispersion of CNF into the B4C matrix up to ∼15 vol% introduced the enhancement of densification. A 15 vol% CNF/B4C nanocomposite revealed excellent mechanical properties: a bending strength (σb) of ∼710 MPa, a Vickers hardness (Hv) of ∼36 GPa, and a fracture toughness (KIC) of ∼7.6 MPa·m1/2, in comparison with those (σb∼530 MPa, Hv∼29 GPa, and KIC∼4.3 MPa·m1/2) of monolithic B4C.Interfaces between CNF and B4C matrix were investigated using high-resolution TEM and Eels. Thin Al-B-C-O layer with a several nm order thickness was observed along with CNF, and Eels showed that the densification and mechanical properties of CNF/B4C nanocomposites might be related to this thin binding layer.
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