Spark Plasma Sintering of 2D Nitride and Carbide based Ceramics

Abstract

Two-dimensional (2D) nanomaterials have stimulated significant interest among materials community due to a wide variety of application ranging from functional to structural properties. Boron nitride nanosheets (BNNS), boron-carbon-nitride (BCN), and MXene (Mn+1Xn, transition metal carbides, nitrides or carbonitrides) belongs to 2D materials family with van der Waals bonding between the layers. The research on synthesis and properties of BNNS, BCN and MXene have been predominantly explored for single- or multi-layered 2D nanosheets. In this study, the focus is to synthesize bulk layered BNNS and BCN using single or multilayered 2D nanomaterials by spark plasma sintering (SPS). The rapid processing conditions of SPS allow retention of nanoscale structure in the bulk form. Monolithic BNNS with 92% dense structure was prepared by SPS. The monolithic BNNS with h-BN structure displayed a preferred orientation of basal plane (0002) along the top-surface and this is ascribed to BNNS high aspect ratio. During high-load indentation, the total energy dissipation along top-surface was 50% higher than cross-section of BNNS pellet. Ternary BCN phase was synthesized from 2D graphene nanoplatelet (GNP) and BNNS using reactive SPS technique from temperature range of 1650 - 1750 °C. Hexagonal BCN phase with minor cubic BCN phase was formed in the reactive sintered pellets. Tribological behavior of sintered BNNS and BCN was studied at room temperature and 600°C. The coefficient of friction (COF) increased with the formation of cubic BCN at room temperature but reduced at 600°C due to graphitized transfer layer. Room temperature wear rate of BCN synthesized at 1750 °C increased as compared to BCN synthesized at 1650 °C due to higher level of densification. In this study, the other van der Waals 2D material MXenes multi-scale damping properties were explored for the first time. Multiscale damping behavior of MXene showed high loss tangent (tan δ) of 0.37 and it was 200% higher than pure MAX. It has been hypothesized the bond contraction operates within single MXene layer, compression and sliding/shearing of MXene sheets operates between MXene layers. After 50,000 long cycle test, MXene layers exhibit highly stable damping behavior suggesting its suitability as dampener.