Photonic, Low-Friction and Antimicrobial Applications for an Ancient Icosahedral/Quasicrystalline Nano-composite Bronze Alloy

• Published in: Transactions of the Indian Institute of Metals 2019-08, Vol.72 (8), p.2105-2119
• Main Authors: Sekhar, J. A., Mantri, A. S., Saha, Sabyasachi, Balamuralikrishnan, R., Rama Rao, P.
• Format: Article
• Language: English
• Subjects: Alloys; Antiinfectives and antibacterials; Bronzes; Chemistry and Materials Science; Corrosion and Coatings; Diffraction patterns; Ellipsometry; Flowers; Fracture surfaces; Gratings (spectra); Historical metallurgy; Icosahedral phase; Image resolution; Materials Science; Metallic Materials; Nanocomposites; Nanocrystals; Photonics; Solidification; Strain rate; Surface analysis (chemical); Surface layers; Technical Paper; Thermal transformations; Tribology; Wear rate
• ISSN: 0972-2815; 0975-1645
• DOI: 10.1007/s12666-018-1535-1

The recent discovery of an ancient mirror bronze alloy comprising of nano-quasicrystalline features is pursued further in this article. We have reported new evidence that indicates that two or more types of quasicrystalline phases may be present in the alloy along with hints of a glassy phase. The finding opens the possibilities of various new uses for this alloy. The distribution of the various phases and their morphological patterns that result from the solidification sequence of the alloy are suggestive of unique photonic applications such as optical gratings and optical cloaking. Low-friction applications at a high pair velocity are also possible with this alloy based on the modulus and the surface texture. The wear rate of many quasicrystalline phase containing alloys is low because of their minimal strain-rate softening tendencies. Based on the nano-crystal distribution and compared to known alloys, the use of the alloy is also contemplated for contact-surface antimicrobial uses. We have also reported findings of the possible evidence of an icosahedral structure even after some of the tin is “boiled” away leaving behind a copper-tin-zinc variation of the original alloy. New high-resolution electron microscope lattice imaging microstructures and diffraction patterns of the original mirror alloy have been discussed. A solidification sequence that can preserve the icosahedral features across the atomic stacking scale, the nanometer scale of the crystals and the micrometer scale of cells/dendrites has been proposed. Regardless, there is the difficulty of completely characterizing all phases in this complex mirror alloy by electron microscopy methods alone. X-ray diffraction, fracture surface analysis, thermal transformation analysis, ellipsometric and optical imaging methods are also employed for the characterization. The microstructures are compared with patterns of similar Fibonacci analogs in flowers and petals.