Ball-Milling Mechanochemistry at the Molecular Level-2

Ball milling mechanochemistry is receiving tremendous attention over the last years.

The applicant has pioneered the use of it for effecting catalytic reactions, culminating in catalytic ammonia synthesis from H2 and N2 at room temperature and atmospheric pressure.

In spite of the success in driving reactions mechanically, the molecular level understanding of the key processes under mechanical activation is still in its infancy. The proposed program will change this, using methods giving insight at the atomic scale.

By a multi-pronged approach, the applicant – partly in collaborations - will experimentally probe at the atomic scale hypotheses, which have been put forward to explain the special effects of mechanochemical reactions, to provide key elements for a conceptual understanding.

Three topical areas will be covered, in addition, one general purpose tool for the study of mechanochemical reactions will be developed. (1) Temperature dependent luminescence will be used to monitor temperatures during model impacts in order to probe the hot spot and magma/plasma hypotheses. (2) The role of hypothetical, short-lived, mechanically induced defects in catalysis will be analyzed locally at the atomic scale in scanning probe microscopes. (3) In order to understand mechanically induced phase transitions, mechanical forces will be applied in-situ to precursor crystals in a transmission electron microscope (TEM), and phase transitions, for instance from boehmite to corundum, will be followed at the atomic scale by TEM imaging. (4) As a general tool to study the influence of mechanical forces, a hammer/anvil system will be developed in which directly after applying mechanical force the system can be studied by various analytical methods.

Overall, the program is expected to provide deep mechanistic understanding of different aspects of mechanochemistry to advance it to a next level.