The Structure and Nanostructure of Biogenic High-Mg Calcite and Their Impact on the Mechanical Properties

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Ms. Nuphar Bianco-Stein, PhD. Candidate




Biominerals produced by living organisms have superior properties compared to their synthetic counterparts. Even though they are formed at ambient conditions and from a limited variety of building blocks, they possess remarkable structures and often combine desired qualities such as low weight and improved mechanical properties. The coralline red algae are highly prevalent around the world’s oceans and contribute to reef ecology. The structure of these algae has not been widely studied previously. In our attempt to gain a better understanding of nature’s extraordinary designs, we study the structure of a coralline red alga that resides in the shallow waters of the Mediterranean Sea. Because of its structure growing upright, this alga has to endure the great stresses applied to it by the sea waves. We discovered that its structure is highly porous, with porosity levels reaching as high as 64 vol%. We showed that its structure is intricate and is hierarchical with several orders from the nano to the macroscale, formed by crystals with nanometric diameters. Surprisingly, we revealed that its macrostructure is helical rather than cylindrical and proved that this configuration confers the alga great compliance. Furthermore, we reveal the presence of high-Mg nanoparticles dispersed within the nanocrystals of the alga that are arranged in layers with alternating Mg contents, a configuration found to hinder the propagation of cracks. The result is a sophisticated hierarchical lightweight structure allowing the alga to sustain the external stresses from its natural environment.

Advisor: Prof. Boaz Pokroy

Seminar via ZOOM