Effect of layer thickness on the mechanical behaviour of oxidation-strengthened Zr/Nb nanoscale multilayers

Abstract

The effect of bilayer thickness (L) reduction on the oxidation-induced strengthening of Zr/Nb nanoscale metallic multilayers (NMM) is investigated. Zr/Nb NMMs with L = 10 and 75 nm were annealed at 350 ºC for a time ranging between 2 and 336 h and the changes in structure and deformation behaviour were studied by nano-scale mechanical testing and analytical electron microscopy. Annealing led to transformation of the Zr layers into ZrO 2 after a few hours, while the Nb layers oxidised progressively at a much slower rate. The sequential oxidation of Zr and Nb layers was found to be key for the oxidation to take place without rupture of the multi-layered structure and without coating spallation in all cases. However, the multilayers with the smallest bilayer thickness (L=10 nm) presented superior damage tolerance and therefore structural integrity during the oxidation process, while for L=75 nm the volumetric expansion associated with oxidation led to the formation of cracks at the interfaces and within the ZrO 2 layers. As a result, the nanoindentation hardness increase after annealing was significantly higher for the nanolaminate with L = 10 nm. Comparison between nanoindentation and micropillar compression behaviour of the oxidized NMMs demonstrate that the hardness increase upon oxidation arises from the contribution of the residual stresses associated with the volume increase due to oxidation and to the higher strength of the oxides.

Viewpoint: Atomic-Scale Design Protocols toward Energy, Electronic, Catalysis, and Sensing Applications

“…It was evident that Cu is a weak point in the interface design; substitution of Cu by Zr could indeed represent the key solution allowing for a prompt introduction of this class of materials in the future of nuclear industry. Among various systems, the Zr/Nb one has been identified ,,− as appropriate from mechanical and thermal stability point of view. Zr/Nb system outperforms mechanical properties of Cu/Nb and W/Cu above 300 °C; indeed Zr–Nb alloys are currently used in CANDU-type reactor .…”

Thermal and mechanical enhancement of styrene–butadiene rubber by filling with modified anthracite coal

“…Considering the preparation of coal‐based functional fillers, anthracite has potential advantages, including its high carbon content, moderate oxygen functional groups, and aromatic lamellar structure similar to that of graphite . In addition, the lamellar particle morphology can impede the diffusion and permeation of gases in the polymer matrix by increasing the diffusion path length of gas and solvent molecules, thus providing good gas barrier properties . The addition of superfine coal powder can increase the volume and reduce the production cost of the polymer composite; hence, if such coal can replace CB as an additive, the problems of high‐energy consumption and carbon emissions related to polymer/CB composites would be solved.…”

First-Principles Calculations and Experimental Study of H+-Irradiated Zr/Nb Nanoscale Multilayer System

“…The recombination of vacancies and interstitial atoms takes place during irradiation in the incoherent interfaces [12,13]. Some examples of such systems are Cu/Nb [10], V/Ag [9], Cu/W [8], Zr/Nb [14][15][16][17], etc. For example, Cu/Nb nanolayers show very high stability under helium ion irradiation [18].…”