While in the storage ring, beams of ultraviolet and x-ray light are extracted from the electron beam through the use of either bending, wiggler, or undulator magnetic devices. The ALS is an electron synchrotron that accelerates electrons to energies of 1.9 billion electron volts (GeV), focuses them into a tight beam and sends this beam around a storage ring for several hours. Pupa Gilbert, of the University of Wisconsin-Madison, is a leading authority on the dynamics of nacre formation and other aspects of biomineralization. Gilbert and her colleagues reported their findings in the Journal of the American Chemical Society, in a paper entitled: “Gradual Ordering in Red Abalone Nacre.” Co-authoring the paper with Gilbert were Rebecca Metzler, Dong Zhou and Susan Coppersmith, of the University of Wisconsin, and Andreas Scholl, Andrew Doran, Anthony Young, Martin Kunz and Nobumichi Tamura of Berkeley Lab. Now, new capabilities at the ALS, including polarized beams of x-rays, have made this possible. However, researchers in the past lacked the tools needed to study the dynamics of nacre formation at the nanoscale. The goal is to learn how nacre formation occurs in nature so that new microstructures might be engineered for ceramics and other materials that would increase their toughness. Hence nacre has been intensely studied, particularly in the ceramics and nanotechnology industries where brittleness remains a major limitation. No human-synthesized composite can outperform its component materials by such a wide margin. This unique structural arrangement was a surprise and could play a role in nacre’s remarkable resistance to fracture.”Īpproximately 95-percent of nacre’s composition is aragonite, a hard but brittle calcium carbonate mineral, yet nacre is 3,000 times tougher than aragonite. Our studies have revealed that the aragonite tablet crystals in nacre are misoriented with respect to each other. Says Pupa Gilbert, a physics professor at the University of Wisconsin-Madison who led this research, “Nacre is a biomineral composed of thin layers of crystalline aragonite tablets separated by even thinner layers of organic material. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).

Now, scientists have brought to light a new aspect of nacre’s nanostructural architecture using the polarized x-ray beams and nanoscale imaging capabilities of the Advanced Light Source (ALS), a national synchrotron facility at the U.S. In addition to its iridescent beauty, mother of pearl, or nacre, the inner lining of the shells of abalone, mussels and certain other mollusks, is also renowned for an amazing strength and toughness that has been a long-standing mystery.

Mother of pearl