Thierry Douillard | Searcharxiv

arXiv2026

One-dimensional self-organization of water molecules in proton conducting Andersson-Wadsley titanates

Layered alkali titanates with M 2 Ti 2 O 5 chemical formula (MTO, M=K,Rb) belonging to the Andersson-Wadsley perovskite family spontaneously incorporate water to form MTO.(H 2 O) x compounds, which exhibit superionic conductivity. At very low hydration x, scanning electron microscopy evidences one-dimensional heterogeneous patterns oriented along ___ b that are arranged in an orderly manner. At higher hydration, the material is observed to spontaneously exfoliate by creating (001) surfaces. Simulations carried out using Density Functional Theory reveal an ordered arrangement of the guest water molecules in Rb 2 Ti 2 O 5 , with strong hydrogen bonds between the water molecules and the apical oxygen of the host crystal. At low hydration x, the water molecules form self-organized one dimensional (1D) double chains along ___ b. Further increase of the water content leads to the creation of hydrated (001)-surfaces that are made of densely packed water chains in agreement with the infrared spectroscopy measurements. Rb 2 Ti 2 O 5 exhibits highly anisotropic proton conductivity, with respect to the crystal orientation, with super-ionic conductivity along ___ b reaching 3 mS/cm at room temperature after hydration. The combined observations and simulations suggest that these water chains are thus at the root of fast proton conduction, which is likely powered by a Grotthuss-like mechanism.

cond-mat.mtrl-sci↗

arXiv2020

A simple approach to bulk bioinspired tough ceramics

The development of damage-resistant structural materials that can withstand harsh environments is a major issue in materials science and engineering. Bioinspired brick-and-mortar designs have recently demonstrated a range of interesting mechanical properties in proof-of-concept studies. However, reproducibility and scalability issues associated with the actual processing routes have impeded further developments and industrialization of such materials. Here we demonstrate a simple approach based on uniaxial pressing and field assisted sintering of commercially available raw materials to process bioinspired ceramic/ceramic composites of larger thickness than previous approaches, with a sample thickness up to 1 cm. The ceramic composite retains the strength typical of dense alumina ($430~\pm 30MPa$) while keeping the excellent damage resistance demonstrated previously at the millimeter scale with a crack initiation toughness of $6.6MPa.m^{1/2}$ and fracture toughness up to $17.6 MPa.m^{1/2}$. These results validate the potential of these all-ceramic composites, previously demonstrated at lab scale only, and could enable their optimization, scale-up, and industrialization.

cond-mat.mtrl-sci↗