Effect of graphene orientation on microstructure and mechanical properties of silicon nitride ceramics

Abstract

Mechanical properties and microstructure of graphene platelets reinforced Si 3 N 4 composites have been investigated and compared to monolithic Si 3 N 4. The microstructure shows that graphene platelets are parallel to each other and perpendicular to the hot pressing direction. Fracture toughness and flexural strength of composite with 1 wt.% graphene measured on polished surface perpendicular to hot pressing direction are 8.7 MPa•m 1/2 and 892 MPa, respectively, which are increased about 14.5% and 20.2% compared with that parallel to hot pressing direction. The anisotropy of microstructure and mechanical properties of composites can be explained by the intrinsic anisotropy of graphene as well as the crack deflection energy release rate and the weak boundary bonding between graphene and Si 3 N 4 caused by the thermal expansion mismatch.

Research on the interface properties and strengthening–toughening mechanism of nanocarbon-toughened ceramic matrix composites

“…Bocanegra-Bernal et al also explained that extremely strong interface bonding will yield brittle ceramics [23]. Sometimes, choosing carbon nanoparticles differing from the matrix in terms of thermal expansion coefficients will cause interface mismatching, reducing the interface strength during sintering [25]. The interfacial strength of composites can be approximately calculated based on the protruding a nocarbon length.…”

“…Therefore, for the composites people just use energy dissipation (i.e., the integral of stress-strain curves) to define the toughness. The common methods used for the evaluation of the resulting composite materials have been tabulated (see Table 1) [23][24][25][26][27][28][29][30]. The foregoing are critical factors that affect the properties of nanocarbonstrengthened and-toughened ceramic matrix composites.…”

Controllable fabrication and multifunctional applications of graphene/ceramic composites

“…Powder processing typically refers to the simple process of mixing graphene sheets and ceramic powders by ball milling with a dispersion agent such as ethanol [13,47] and isopropanol [48,49]. A typical procedure is illustrated in Fig.…”

Spark Plasma Sintering of Electric Discharge Machinable 1.5Yb-1.5Sm-TZP-WC Composites

“…The anisotropic orientation of graphene depending on shaping technology has also been reported. In HP and SPS, which are axial pressing processes, graphene orients preferentially orthogonally to the pressing direction, which results in composites with anisotropic properties [25]. The type of graphene raw materials is also relevant.…”