ADVANCED MATERIALS & PROCESSES | NOVEMBER/DECEMBER 2023 7 “Our process potentially would be significantly less land- and capital- intensive to build, as our separations could be done with repeated enrichment through columns full of immobilized bacteria instead of mixer-settler plants that are miles long.” While the technology is still in development, the researchers are optimistic about potential impact. The method could help develop a stable U.S. supply of rare earth elements for technology and defense applications, according to the scientists. cornell.edu. DISCOVERY OF PHOTONIC CRYSTALS ON ANCIENT ROMAN GLASS Tiny pieces of glass are being uncovered from construction sites and archaeological digs that once were glass vessels in ancient Rome. On their surface is a mosaic of iridescent colors of blue, green and orange, with some displaying shimmering gold- colored mirrors. The beautiful structures formed over time, likely as a process of corrosion and reconstruction. For Fiorenzo Omenetto and Giulia Guidetti, professors of engineering at the Tufts University Silklab, what’s fascinating is how the molecules in the glass rearranged and recombined with minerals over thousands of years to form photonic crystals—ordered arrangements of atoms that filter and reflect light in very specific ways. Photonic crystals have many applications in modern technology. They can be used to create waveguides, optical switches, and other devices for very fast optical communications in computers. They are also used in filters, lasers, mirrors, and anti-reflection devices. Through elemental analysis, Omenetto and Guidetti could see that the patina possessed a hierarchical structure made up of highly regular, micrometer-thick silica layers of alternating high and low density which resembled Bragg stacks. The vertical stacking of tens of Bragg stacks resulted in the golden mirror appearance of the patina. “The crystals grown on the surface of the glass are also a reflection of the changes in conditions that occurred in the ground as the city evolved—a record of its environmental history,” says Guidetti. tufts.edu. Microscopic view of photonic crystals on the surface of ancient Roman glass. Courtesy of Giulia Guidetti. Are you maximizing your ASM membership? Expand your knowledge and apply your ASM International member-only discounts to a variety of professional development resources: • Reference Materials • ASM Handbooks Online • Technical Journals • Continuing Education Courses Learn more about your membership benefits by visiting: asminternational.org/membership 154 Hobart Street, Hackensack, NJ 07601 USA +1.201.343.8983 • mainmasterbond.com www.masterbond.com key benefits of nanosilica filled epoxy EP30NS use a nanoreinforced EPOXY Optically clear | Refractive index: 1.56 NASA low outgassing | ASTM E595 Dimensionally stable | Hardness: 80-90 Shore D Abrasion resistant | ASTM D466-14
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