Mechanical Properties of Silicon Nitride in Different Morphologies: In Situ Experimental Analysis of Bulk and Whisker Structures

Silicon nitride (Si N ) is widely used in structural ceramics and advanced manufacturing due to its excellent mechanical properties and high-temperature stability. These applications always involve deformation under mechanical loads, necessitating a thorough understanding of their mechanical behavior and performance under load. However, the mechanical properties of Si N , particularly at the micro- and nanoscale, are not well understood. This study systematically investigated the mechanical properties of bulk Si N and Si N whiskers using in situ SEM indentation and uniaxial tensile strategies. First, nanoindentation tests on bulk Si N at different contact depths ranging from 125 to 450 nm showed significant indentation size effect on modulus and hardness, presumably attributed to the strain gradient plasticity theory. Subsequently, in situ uniaxial tensile tests were performed on Si N whiskers synthesized with two different sintering aids, MgSiN and Y O . The results indicated that whiskers sintered with Y O exhibited higher modulus and strength compared to those sintered with MgSiN . This work provides a deeper understanding of the mechanical behavior of Si N at the micro- and nanoscale and offers guidance for the design of high-performance Si N ceramic whiskers.