Figure 7.

Representative microscopic and SEM images of the fracture surface of the VSC A sample; (A) visible compression curl on top, the direction of crack propagation and the origin on the bottom; (B) Red lines indicate the width and depth of the crack at the fracture origin. Black arrows indicate the direction of crack propagation away from the crack origin, white arrows indicate bending marks on the fracture surface; (C) microcrack spreading along the particle boundaries visible on the enlarged area of figure (B) indicated by the white arrow; (D) microcrack spreading along the particle boundaries visible on the enlarged area of figure (B) indicated by the white arrow.