Bioinspired Structural Ceramic Composite – BICuIT

In order to understand and optimize the properties of these bioinspired materials, a usual materials science approach has been used, ranging from the elaboration and shaping processes to the microstructural characterization of the materials and their mechanical properties. Numerical approaches of Brownian dynamics and discrete element modeling have been used to guide and complete the experimental studies, at different stages of the process. A fine microstructural characterization was carried out, with a particular attention given to the characterization of the texture of materials. Mechanical properties were studied at different scales, from microscopic to macroscopic. In addition, in situ mechanical tests under microscope have been developed and used to better understand the strengthening mechanisms of the materials, by combining image correlation electron microscopy and Raman microscopy, to measure the local stress state while following the crack propagation in the material. Large instruments (synchrotron) were also used to characterize the crystallography of the powders used.

The most significant advance was the development of an scalable approach for the shaping of these bioinspired composites. This new method, based on industrial tools and allowing to make larger parts, should allow the transition from the laboratory to potential applications. The characterization of the materials and their mechanical properties, coupled with new modelling approaches of the process and mechanical properties, has also provided a rational approach to understanding and improving the properties of these materials, which was lacking until now.

The advances made during the BICuIT project have highlighted the critical role of the interphase (mortar) and its mechanical properties. It is now clear that future work will focus on the control of these interfaces, which are essential to optimize the mechanical properties. However, these materials remain relatively heterogeneous, especially in terms of phase distribution, and the improvement of the material will have to take into account these constraints.

The tools developed during the project, in particular on the in situ imaging of the stress fields by Raman, the discrete element modeling of the fracture, or the application of coupled criterion in fracture mechanics, should also find further applications and developments beyond these specific materials.

The availability of industrial tools should facilitate the study and development of these bioinspired ceramic/ceramic composites for structural applications. Ceramic parts with more complex shapes than simple cylinders have already been reported using FAST, with particular attention to microstructure control in critical areas throughout the materials. Further development and possible industrial application of these materials now depends on identifying opportunities where this combination of properties would be sufficiently attractive

The articles concern the new processes of shaping of the materials developed and studied during the project but also the characterization of the microstructure and the mechanical properties at small and large scale of these new bioinspired composite materials as well as original methods of numerical simulation dedicated to these materials. New and more efficient compositions have also been studied. Several actions of scientific diffusion towards the public (press, TV) also took place.

1) Muñoz M, Cerbelaud M., Videcoq A, Saad H, Boulle A, Meille S, Deville S et Rossignol F, Nacre-like alumina composites based on heteroaggregation, J Eur Ceram Soc 40, 5773-5778 (2020) 10.1016/j.jeurceramsoc.2020.06.049
2) Doitrand A, Henry R, Saad H, Deville S, Meille S, Determination of interface fracture properties by micro- and macro-scale experiments in nacre-like alumina, J Mech. Phys. Solids 2020, vol. 145, article n°104143, 10.1016/j.jmps.2020.104143
3) Saad H, Radi K, Douillard T, Jauffres D, Martin C, Meille S, Deville S, A simple approach to bulk bioinspired tough ceramics, Materialia 2020, vol. 12, article n°100807, 10.1016/j.mtla.2020.100807
4) Radi K, Saad H, Jauffres D, Douillard T, Meille S, Deville S, Martin C, Effect of microstructure heterogeneity on the damage resistance of nacre-like alumina: insights from image-based discrete simulations, Scripta Materialia 2021, vol. 191, pp. 210-214, 10.1016/j.scriptamat.2020.09.034
5) Henry R, Saad H, Doitrand A, Deville S, Meille S, Interface failure in nacre-like alumina, J Eur Ceram Soc 2020 doi.org/10.1016/j.jeurceramsoc.2020.05.068
6) Lafond, C. et al. eCHORD orientation mapping of bio-inspired alumina down to 1 kV. Materialia 101207 (2021). doi:10.1016/j.mtla.2021.101207
7) Radi, K., Jauffres, D., Deville, S. & Martin, C. L. Strength and toughness trade-off optimization of nacre-like ceramic composites. Compos. Part B Eng. 183, (2020) 10.1016/j.compositesb.2019.107699
8) Radi, K., Jauffrès, D., Deville, S. & Martin, C. L. Elasticity and fracture of brick and mortar materials using discrete element simulations. J. Mech. Phys. Solids 126, 101–116 (2019) 10.1016/j.compositesb.2019.107699
9) Henry R, Saad H, Dankic-Cottrino S, Deville S, Meille S, Nacre-like alumina composite reinforced by zirconia particles, (en revision chez J Eur Ceram Soc). Preprint: 10.33774/chemrxiv-2021-7xpm9
10) Cerbelaud M, Muñoz M, Rossignol F et Videcoq A, Self-Organization of Large Alumina Platelets and Silica Nanoparticles by Heteroaggregation and Sedimentation : Toward an Alternative Shaping of Nacre-Like Ceramic Composites, Langmuir 36, 3315-3322 (2020) 10.1021/acs.langmuir.0c00170
11) Abando, N. et al. Anisotropy effect of bioinspired ceramic/ceramic composites: Can the platelet orientation enhance the mechanical properties at micro- and submicrometric length scale? J. Eur. Ceram. Soc. 41, 2753–2762 (2021) 10.1016/j.jeurceramsoc.2020.12.039

Although ceramics exhibit the highest stiffness and strength of all material classes they suffer from excessive brittleness that highly limits their range of application. Damage-resistant ceramics are thus in great demand. On the other hand countless damage-resistant biological materials comprise ceramics and are used for structural purposes in nature. A famous example is the nacreous part of seashells where the brick and mortar structure comprising 95 vol.% of platelets of polycrystalline aragonite (CaCO3) and 5 vol.% of a protein is extremely effective at restricting crack propagation and presents a toughness orders of magnitude greater than either of its constituents. Recently, taking this architecture as a source of inspiration, a damage-resistant fully ceramic (alumina) material has been obtained in the lab of the coordinator (Bouville, F. et al. (2014). Strong, tough and stiff bioinspired ceramics from brittle constituents. Nature Materials). The processing route is relatively simple and based on widespread techniques such as ice-templating for the platelets alignment.

The objective of the current proposal is to bring these materials to their optimum through a deliberate, rational control of the architecture and a fine understanding of the reinforcement mechanisms and process/structure/properties relationships.

The strategy proposed in BICuIT to reach these objectives is the following:

(1) Investigate new and/or improved processes to enlarge our set of strategies for reinforcement and control of the phase distribution and dimensions. In particular, the distribution of nanoparticles, creating both surface roughness and mineral bridges, if not controlled, could be greatly improved. An alternative route for platelets alignment allowing the processing of larger parts (pressing), and the introduction of residual stresses will also be studied.

(2) Develop an in-depth understanding of the reinforcement mechanisms and their relative contribution to the ultimate toughness based on modeling and in-situ mechanical testing. The interphase strength that appears to have a key role will be studied on a model bilayer system with a single, isolated interphase.