Session: Government Agency Student Posters

Paper Number: 172927

Metal Passivation Strengthens the Interface in Metal Nanocomposites Reinforced With Boron Nitride Nanotubes 

The integration of nanofibers into metal matrices has emerged as a transformative approach to enhancing the mechanical properties of structural materials, which is vital for a broad range of engineering applications, including those in the automotive, biomedical, and aerospace sectors. As these industries increasingly demand materials that are lightweight, cost-effective, and capable of withstanding extreme service conditions, metal matrix nanocomposites (MMNCs) reinforced with nanofillers such as carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) are gaining significant attention. The key to achieving superior performance in such systems lies in the effectiveness of interfacial load transfer between nanofibers and the metal matrix.

While CNTs have been extensively studied and applied as reinforcing agents, BNNTs offer several distinct advantages, including ultrahigh Young’s modulus and tensile strength, exceptional thermal stability, high chemical resistance, and low density. These attributes make BNNTs particularly appealing for high-performance MMNC technology. However, a critical challenge that hinders their widespread adoption is the limited understanding of interfacial load transfer mechanisms at BNNT-metal interfaces. The complexity is further compounded by surface phenomena such as oxide formation during metal passivation or thermal treatment, which can profoundly affect interfacial bonding.

In this study, we investigate the interfacial mechanical behavior of individual BNNTs embedded in aluminum (Al) and titanium (Ti) matrices—both representative lightweight structural metals—using in situ nanomechanical single-nanotube pull-out tests conducted inside a high-resolution scanning electron microscope. Pull-out experiments were performed using atomic force microscopy (AFM) force sensors, allowing for the accurate measurement of force-displacement data with nanonewton and nanometer resolutions. These experimental insights were complemented by first-principles density functional theory (DFT) simulations to elucidate the atomic-scale interactions at the BNNT-metal interface.

Our results reveal that the load transfer follows a shear-lag mechanism and that the interfacial strength is significantly enhanced by metal surface oxidation. Notably, BNNTs exhibit substantially stronger interfacial bonding with metal matrices compared to CNTs, primarily due to the formation of robust covalent bonds facilitated by the oxide layers formed from passivation. This enhanced bonding persists even after extended thermal annealing at elevated temperatures, indicating thermal stability of the BNNT-metal interface. These findings suggest that metal passivation can be deliberately exploited as a self-strengthening strategy to activate and enable strong interfacial bonding interactions, thereby unlocking the full reinforcing potential of BNNTs in MMNCs.

This work provides critical insights into the role of surface chemistry and interfacial mechanics in nanocomposite design, offering a new pathway for the development of next-generation lightweight structural materials.

Presenting Author: Zihan Liu State University of New York at Binghamton

Presenting Author Biography: Zihan Liu is a PhD candidate in Mechanical Engineering at Binghamton University, specializing in nanocomposites, 2D materials, and electrospun sensors. His research focuses on interfacial mechanics, strain engineering, and material fabrication for aerospace and electronics applications.

Authors:

Zihan Liu State University of New York at Binghamton
Yingchun Jiang State University of New York at Binghamton
Changhong Ke State University of New York at Binghamton