Abstract
From the mechanical perspectives, the influence of point defects is generally considered at high temperature, especially when the creep deformation dominates. Here, we show the stress-induced reversible oxygen vacancy migration in CuO nanowires at room temperature, causing the unanticipated anelastic deformation. The anelastic strain is associated with the nucleation of oxygen-deficient CuOx phase, which gradually transforms back to CuO after stress releasing, leading to the gradual recovery of the nanowire shape. Detailed analysis reveals an oxygen deficient metastable CuOx phase that has been overlooked in the literatures. Both theoretical and experimental investigations faithfully predict the oxygen vacancy diffusion pathways in CuO. Our finding facilitates a better understanding of the complicated mechanical behaviors in materials, which could also be relevant across multiple scientific disciplines, such as high-temperature superconductivity and solid-state chemistry in Cu-O compounds, etc.
Highlights
From the mechanical perspectives, the influence of point defects is generally considered at high temperature, especially when the creep deformation dominates
The bending tests were performed with a Nanofactory EP1000 transmission electron microscopy-scanning tunneling microscopy (TEM-STM) holder inside the TEM29–31
C Anelastic strain recovery as a function of time in six bending tests, d high-resolution TEM (HRTEM) image showing the nucleation of CuOx phase, which transformed back to CuO after 45 min (e)
Summary
The influence of point defects is generally considered at high temperature, especially when the creep deformation dominates. The structural stability of material subjected to intense mechanical duress is the corner stone for ensuring the robust performance in micro-electro-mechanical systems and devices, whereas there is a surging demand for the effective damping system to minimize mechanical vibration or noise[1,2] Toward this end, the anelasticity, characterized by a delay in the shape recovery after retracting the external stress and extensively utilized to dissipate the mechanical energy, has been the focus of research for decades[3,4,5]. Our findings provide the direct atomistic view regarding the point defect migration in nanosized materials at room temperature[9]
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