Strength by Atomic Force Microscopy (A Kelly special issue)

Kevin Kendall (1) , Aman Dhir (2) , Chin Yong (3)

1 Chemical Engineering
2 Chemical Engineering
3 Computing

Localised strength testing of materials is often carried out in the Atomic Force Microscope (AFM) as foreseen by Kelly in his book Strong Solids. It is known that contamination during AFM indentation experiments can strongly influence the observed strength, but a major problem is the theoretical interpretation of the results. Here we use molecular dynamics computer modelling to describe the contact of NaCl and MgO crystal probes onto surfaces, comparable to an AFM experiment. Clean NaCl gave elastic, brittle behaviour in contact simulations at 300K whereas MgO was more plastic, leading to increased toughness. This paper goes on to consider the strength of an oxide substrate contaminated by water molecules tested by indentation with a pyramidal probe of oxide crystal. We have studied the forces between a magnesium oxide (MgO) atomic force microscope (AFM) probe and an MgO slab. Force versus separation has been plotted as the AFM probed was moved towards and away from the substrate. Simulation results showed that the water layers could be removed in steps, giving up to four force peaks. The last monolayer of water could not be squeezed out even at pressures where MgO deformed plastically.

Mots clés: Physical Sciences

Kevin Kendall, Aman Dhir, Chin Yong. Strength by Atomic Force Microscopy (A Kelly special issue). Philosophical Magazine, 2010, pp.1. ⟨10.1080/14786430903520732⟩. ⟨hal-00586129⟩