Hideki Kakisawa

The toughening mechanism of nacre and structural materials inspired by nacre

Abstract The structure and the toughening mechanism of nacre have been the subject of intensive research over the last 30 years. This interest originates from nacre’s excellent combination of strength, stiffness and toughness, despite its high, for a biological material, volume fraction of inorganic phase, typically 95%. Owing to the improvement of nanoscale measurement and observation techniques, significant progress has been made during the last decade in understanding the mechanical properties of nacre. The structure, microscopic deformation behavior and toughening mechanism on the order of nanometers have been investigated, and the importance of hierarchical structure in nacre has been recognized. This research has led to the fabrication of multilayer composites and films inspired by nacre with a layer thickness below 1 μm. Some of these materials reproduce the inorganic/organic interaction and hierarchical structure beyond mere morphology mimicking. In the first part of this review, we focus on the hierarchical architecture, macroscopic and microscopic deformation and fracture behavior, as well as toughening mechanisms in nacre. Then we summarize recent progress in the fabrication of materials inspired by nacre taking into consideration its mechanical properties.

Fabrication of nanocellulose-hydroxyapatite composites and their application as water-resistant transparent coatings

Nanosized composite rods ∼300 nm in length and ∼20 nm in width were produced by deposition of 22-77 wt% of a c-axis-oriented hydroxyapatite (HA) on cellulose nanocrystals (CNCs). The CNCs functionalized with sulphonic groups were covered with the HA nanocrystals through controlled nucleation and growth under a moderately supersaturated condition in a solution system based on a simulated body fluid. Water-resistant transparent coatings 2-4 μm thick were obtained via evaporation-induced assembly of CNC-HA nanocomposites by casting their suspension on a glass substrate and the subsequent growth of HA nanocrystals by vapour hydrothermal treatment. The composite coatings exhibited improved mechanical strength compared to that of crustacean exoskeletons, and potential for bone regeneration.

The 10th International Conference on EcoBalance (EcoBalance 2012) - Challenges and Solutions for Sustainable Society, November 20-23, 2012, Tokyo, Japan

The 10th International Conference on EcoBalance (EcoBalance 2012), organized by The Institute of Life Cycle Assessment, Japan, was held during November 20–23, 2012 at the Hiyoshi Campus of Keio University in Yokohama City. The conference was co-hosted by Keio University and The Ecomaterial Forum, and backed by the Cabinet Office; the Ministry of Education, Culture, Sports, Science and Technology; the Ministry of Agriculture, Forestry and Fisheries; the Ministry of Economy, Trade and Industry; the Ministry of Land, Infrastructure, Transport and Tourism; and the Ministry of Environment. It was also supported by 74 related societies and associations. The Commemorative Organization for the Japan World Exposition ‘70 and the Life Cycle Assessment Society of Japan provided monetary aid for the management of the conference. In addition, the event was co-sponsored by the following eight corporations and groups: