Development of a P‒T-Model-Based In-Situ Bending Measurement Method for Nanowires: Addressing Mechanical Challenges in High-Precision Experiments

Background

The in situ mechanical measurement of nanomaterials using microelectromechanical system accessories in electron microscopy has attracted considerable interest because of its ability to combine microstructure responses and stress conditions.

Objective

In this study, an in situ large-deflection longitudinal‒transverse bending measurement technique was developed in a double-cantilever beam system using transmission electron microscopy (TEM).

Methods

Nonlinear large-strain bending tests of raw and high-temperature-oxidized 3C-silicon carbide (3C-SiC) nanowires (NWs) were performed using TEM. After an explicit polynomial–trigonometric combined-function (P‒T model) was introduced to fit the NW contour in each image frame, a mechanical algorithm based on the fitting curve was proposed to calculate the stress and strain in batches.

Results

Contour modeling analysis using the P‒T model revealed brittle fracture in a 104-nm-diameter SiC NW with a fracture strain of 3.46% and a modulus of 590.8 GPa. Plastic deformation occurred during the bending of a 430-nm-diameter oxidized core–shell SiC-SiO₂ NW, with a fracture strain exceeding 7.07% and a modulus of 42.6 GPa.

Conclusion

Compared with results from other widely used approximation fitting models, the measurement results based on the P‒T method were more accurate and stable. The modulus reduction and brittle‒ductile transition induced by the amorphous oxide layer on the SiC core were demonstrated using the P‒T method.