Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Clarification of Dynamical Process of Aluminum Surface Oxidation

05.07.2013
NIMS researchers have solved a 20 year old riddle concerning the reaction mechanism of aluminium surface oxidation

Dr. Mitsunori Kurahashi, a Principal Researcher of the NIMS Nano Characterization Unit, and Dr. Yasushi Yamauchi, a Group Leader in the same unit, presented decisive evidence clarifying the dynamical process of aluminum surface oxidation by using a molecular oxygen (O2) beam with a controlled molecular alignment, which was originally developed by the researchers, and thereby settled a 20-year dispute regarding the reaction mechanism.

Dr. Mitsunori Kurahashi, a Principal Researcher of the Nano Characterization Unit (Unit Director: Daisuke Fujita), National Institute for Materials Science (President: Sukekatsu Ushioda) and Dr. Yasushi Yamauchi, a Group Leader in the same unit, presented decisive evidence clarifying the dynamical process of aluminum surface oxidation by using an aligned O2 beam, which was originally developed by the researchers, and thereby settled a dispute which had continued for 20 years regarding the reaction mechanism.

Aluminum is widely used as a corrosion-resistant lightweight material despite its high reactivity for O2 because the dense oxide film that forms on the surface prevents corrosion by oxygen, etc. in the air. In the field of fundamental surface science, O2 adsorption on aluminum surfaces had been investigated for many years as the most representative system of surface oxidation.

However, previous experimental and/or theoretical studies on the atomic-scale process of O2 adsorption/dissociation contradict with each other.

As a result, the mechanism of this simple surface reaction still remained unclear, in spite of the research extending over more than 20 years.

Using an aligned O2 beam developed by the researchers, the team headed by Dr. Kurahashi clarified that the probability of O2 adsorption on an aluminum surface depends strongly on the alignment of the O2 molecular axis.

The NIMS researchers demonstrated that low velocity O2 molecules with kinetic energies of 0.1eV or less adsorb only when their axes are nearly parallel to the surface, whereas, O2 molecules in any molecular orientations can adsorb when the kinetic energy exceeds 0.2eV. Until now, O2 molecules with its axis perpendicular to the surface had been considered to adsorb under low energy conditions, and this had long confused the discussion on the reaction mechanism.

However, the present research has concluded that this reaction mechanism is not true.

This research also explains the previous experimental results, which had appeared contradictory, and thus elucidated the whole atomic-scale dynamical process of O2 adsorption on an aluminum surface, which had been unclear for many years. Moreover, this research indicates that the slight activation energy difference of 0.1 eV among different molecular orientations needs to be considered for the future study of O2 adsorption on surfaces. O2 adsorption is important not only in the oxidation of the material itself, but also in the catalytic processes happening on the surfaces of fuel cell electrodes, etc.

Expensive rare metals such as platinum are used as catalysts that efficiently dissociate O2 molecules. The aligned O2 beam used in this research would be useful not only in reaction analysis, but also in research on substitute catalysts.

FOR MORE INFORMATION

Mitsunori Kurahashi
Principal Researcher, Spin Characterization Group,
Nano Characterization Unit, NIMS
TEL:+81-29-859-2827
FAX:+81-29-859-2801
E-Mail: kurahashi. mitsunori@nims.go.jp
Journal information
These results were published online on June 13 (local time) in "Physical Review Letters," which is a journal of the American Physical Society.

Funding information

These research results were achieved as part of the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research/Basic Research (B) “Development of a Single Spin-Rotational State-Selected O2 Beam and its Application to Surface Reaction Analysis” (Research Representative: Mitsunori Kurahashi) of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), and the NIMS 3rd Mid-Term Program Project “Development and Application of Advanced Material Characterization Technologies” (Leader: Daisuke Fujita).

Mikiko Tanifuji | Research asia research news
Further information:
http://www.nims.go.jp/eng/news/press/2013/06/p201306170.html
http://www.researchsea.com

More articles from Materials Sciences:

nachricht Scientists channel graphene to understand filtration and ion transport into cells
11.12.2017 | National Institute of Standards and Technology (NIST)

nachricht Successful Mechanical Testing of Nanowires
07.12.2017 | Helmholtz-Zentrum Geesthacht - Zentrum für Material- und Küstenforschung

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Plasmonic biosensors enable development of new easy-to-use health tests

14.12.2017 | Health and Medicine

New type of smart windows use liquid to switch from clear to reflective

14.12.2017 | Physics and Astronomy

BigH1 -- The key histone for male fertility

14.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>