Mechanical micro-probing as a versatile technique for the surface engineering: from mapping to patterning (Ph.D. Thesis)
In the last decades, nanoscience and nanotechnology raised their role and impact in industry due to the increasing importance of the analysis and characterization of materials at the nano-scale. In fact, at a such small (10-9 m) scale, materials exhibit properties (such as strength, stiffness, hardness but also electrical resistivity and conductivity or optical absorption) that are significantly different from the properties of the same matter at bulk scale.
For this reason, it has been necessary to realize and develop experimental and modelling tools to analyse and describe, in an accurate (resolution) and robust (repeatability) way, the behaviour of materials in this new and unexplored small sized scale.
One of the most important equipment for the mechanical characterization of materials, realized and developed about 30 years ago, is the nanoindenter, which is able to record, during an instrumented indentation test, loads and displacements with high precision and sensistivity; the strength of this equipment is strictly bound with the development of the Oliver & Pharr model, by which it is possible to calculate hardness and elastic modulus from the load and displacement data obtained as output of a single nanoindentation experiment.
The nanoindenter evolved during the last years, introducing new and more performant hardware, methods and features (high resolution head, dynamical mechanical analysis, nano-scanning and other).
In this work, a novel new high-speed nanoindentation was intensively explored and combined with statistical analysis to investigate the mechanical behaviour of highly heterogeneous materials and to study the material phases.
Several case studies such as applications to lithium rechargeable batteries, cement based materials, free standing laminates and WC-Co are presented and discussed.
The high-speed nanoindentation has been also successfully used to realize the surface patterning on both soft and hard materials (High-Speed Nanoindentation Lithography) with simple and double scale geometries of the pattern.
Statistical Nanoindentation and phase analysis
Sem Micrograph and mechanical map of a cement paste
The exploitation of the nanoindenter has been then improved towards several non-conventional use of the equipment: it has been in fact possible to modify and optimize the methods, recipes used by the equipment to realize different kinds of tests.
All the experimental tests were realized using three different nanoindenter and combining their unique features to transform the nanoindenter from a standard mechanical test equipment into a multi-functional testing and designing device.
Double scale geometry pattern on BGM
Large area pattern (10 x 5 mm) on PMMA realized with high-speed nanoindentation.
For such reasons, the present PhD thesis represent a demonstration of the potential use of nanoindentation as a high-throughput testing tool for nano-mechanical analysis of industrially relevant products.