The interest for studying in detail the constitution of ivory material coming from the tusks of proboscidea (elephant, mammoth, … )
started in 1960 with Miles and increased since 2000 with works mainly based on microscopic observation by optical, scanning and
transmission electron microscopy (OM, SEM, TEM), structural analysis using X-ray diffraction (XRD) and elemental analysis using
X-ray photoelectron spectroscopy and Proton-induced X-ray emission (XPS, PIXE).
This research was basically performed for two reasons. On one hand, from the fundamental point of view, it was important to
understand the hierarchical structure of this biomaterial with exceptional mechanical properties and, on the other hand, it was
important to identify chemical and structural markers for the recognition of ivory by customs as this material is forbidden for trade
in order to protect animals.
Moreover, elephant ivory constitutes an important raw material for the manufacturing of works of art from prehistoric to modern times.
The studies were generally performed using one analytical technique and some chemical and structural markers could be defined.
However, a complete view of the complex organisation at different hierarchical levels of this exceptional material is still lacking.
The tusks are the upper incisors of elephants. As they are mainly used for digging, foraging and as weapons, they are subjected to
important forces and present strong macroscopic mechanical anisotropy. These macroscopic mechanical characteristics are
strongly influenced by the nature of the ivory ultrastructure from micro to nanoscale. Some mechanical tests (three points bending
tests, thermal conductivity, micro-indentation) have been performed on elephant ivory to better understand the possible correlation
between microstructure and mechanical properties. However, this work needs to be complemeted.
Therefore, additional studies using a combined and integrated analytical strategy are needed to understand the hierarchical
organisation from macro- down to nanoscale and the relationship between composition, structure and function of ivory.
The aims of this project are threefold :
1. Establishing an improved model for the ultrastructure of modern elephant ivory
The first step of this project will be to propose a more representative model of the ultrastructure of modern elephant ivory. For
these purposes, both Asian and African modern elephant ivory coming from custom seizures will be studied.
2. Studying the mechanical properties of elephant tusks
The second step of the project is to determine the key structural parameters influencing the microscopic and nanoscopic
mechanical properties of ivory to bring new insights into the previously observed correlations between composition, structure and
properties and to evaluate how the transformation of these parameters can affect the mechanical characteristics.
3. Studying the evolution over time, evaluation of the state of preservation and understanding of the underlying alteration
The third aim of the project is to study the evolution of the ivory components over time, to evaluate its state of preservation and to
better understand the alterations mechanisms occurring in specific environmental conditions (archaeological site, storage
conditions in a museum) as well as to find adequate solutions for the conservation of ancient ivories. For these purposes, archaeological elephant tusks found in a 17th century shipwreck during submarine excavation in Brittany, France will be studied.