Tailoring fracture toughness of silicon carbide ceramics film via nanoscale multi-layering with diamond

Silicon Carbide (SiC) is a superhard and strong material applied for many engineering applications including abrasives, rotating disks, bearing, high temperature coatings etc. However, like most ceramic materials, Silicon Carbide exhibits high yield strength (9 GPa) and high hardness (2800 kg/mm²) but low toughness (4.6 MPa.m⁰⁵) properties. The strong covalent (88%) bonds along with ionic bonds that form the microstructure of SiC are responsible for such mechanical responses. Unfortunately, the low-toughness characteristics of SiCs significantly limit their wide-spread structural applications. Therefore, improving toughness of ceramic material is highly desirable. In this study, we have computationally developed a nanoscale multilayer ceramic film where SiC and diamond crystals are arranged at an alternating sequence. The thickness of the nanodiamond film layers are varied between 2 nm and 10 nm. Center crack was created in the SiC layer and the corresponding fracture toughness was measured using integrated MD-FEM simulation. We have observed the fracture toughness of the multilayer film can be modulated by varying the SiC layer thickness. In particular, the mode-I fracture toughness can be increased by at least 20% when SiC layer thickness changes from 2 nm to 5 nm. The trend under mode-II fracture is opposite to mode-I. Details will be discussed in the manuscript.