Metal oxidation controlled by atomic surface steps

March 19, 2015, Brookhaven National Laboratory
(top) Schematic of the surface of a Ni-Al alloy with atomic-height surface steps, present on all crystalline materials. Aluminum oxide (Al2O3) grows by incorporating aluminum atoms released from the steps. As the oxide encounters a step, its further growth becomes inhibited. (bottom) In-situ microscopy image sequence illustrating the encounter of an Al2O3 stripe ('A') with surface steps (faint black lines).

Rust never sleeps. Whether a reference to the 1979 Neil Young album or a product designed to protect metal surfaces, the phrase invokes the idea that corrosion from oxidation—the more general chemical name for rust and other reactions of metal with oxygen—is an inevitable, persistent process. But a new study performed at the Center for Functional Nanomaterials (CFN) at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory reveals that certain features of metal surfaces can stop the process of oxidation in its tracks.

The findings, published in the Proceedings of the National Academy of Sciences, could be relevant to understanding and perhaps controlling in a wide range of materials—from catalysts to the superalloys used in jet engine turbines and the oxides in microelectronics.

The team used a low-energy electron microscope (LEEM) to capture changes in the surface structure of a nickel-aluminum alloy as "stripes" of formed and grew under a range of elevated temperatures. The metal Zhou wanted to study, nickel-aluminum, has a characteristic common to all crystal surfaces: a stepped structure composed of a series of flat terraces at different heights. The steps between terraces are only one atom high, but they can have a significant effect on material properties. Being able to see the steps and how they change is essential to understanding how the surface will behave in different environments, in this case in response to oxygen.

While the formation of thicker oxide layers has been studied extensively, the initial stages of surface oxidation remain poorly understood, particularly for complex materials such as metal alloys. The findings of this study demonstrate that atomic-height steps can play a key role in limiting the onset of oxidation. This points to new avenues for controlling oxidation in applications ranging from catalysis to corrosion protection and microelectronics.

CFN Capabilities

The unique in-situ surface microscopy capabilities in the CFN's Proximal Probes Facility were instrumental in enabling the direct observation of the interaction of oxide stripes with surface steps on NiAl(100). Microscopy with combined high spatial and temporal resolution allowed measuring in oxygen gas atmospheres how the rate of oxidation is reduced when the growing oxide encounters atomic-height steps on the .

Explore further: Microscopy reveals how atom-high steps impede oxidation of metal surfaces

More information: "Oxidation-driven surface dynamics on NiAl(100)" Proc. Nat. Acad. Sci. USA 112, E103-E109 (2015). DOI: 10.1073/pnas.1420690112

Related Stories

The finer details of rust

December 4, 2014

Scientists at the Vienna University of Technology have been studying the behavior of iron oxide surfaces. The atomic structure of iron oxide, which had been assumed to be well-established, turned out to be wrong. The behavior ...

Helping materials handle extreme stress

October 11, 2011

Important pressurized water nuclear reactor components are being made from a nickel-base alloy that contains twice the amount of chromium as the material previously used. The new alloy, called alloy 690, performs better, ...

Recommended for you

Matter waves and quantum splinters

March 25, 2019

Physicists in the United States, Austria and Brazil have shown that shaking ultracold Bose-Einstein condensates (BECs) can cause them to either divide into uniform segments or shatter into unpredictable splinters, depending ...

How tree diversity regulates invading forest pests

March 25, 2019

A national-scale study of U.S. forests found strong relationships between the diversity of native tree species and the number of nonnative pests that pose economic and ecological threats to the nation's forests.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.