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 INFORMATIONMitsunori Kurahashi
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
A new tool for discovering nanoporous materials
23.05.2017 | Ecole Polytechnique Fédérale de Lausanne
Did you know that packaging is becoming intelligent through flash systems?
23.05.2017 | Heraeus Noblelight GmbH
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...
23.05.2017 | Event News
22.05.2017 | Event News
17.05.2017 | Event News
23.05.2017 | Physics and Astronomy
23.05.2017 | Life Sciences
23.05.2017 | Medical Engineering