Eighty-one years after the atomic bombing that devastated Hiroshima and killed more than 70,000 people instantly, scientists have found a previously unknown substance inside grains of sand on the beaches of Hiroshima Bay.
Nuclear explosions, meteorites and other violent events are natural laboratories for generating new materials, and that is what happened in this case.
The researchers focused on tiny spherical particles called "Hiroshimaite," which are remnants of material that melted as a result of the enormous heat exceeding 7,000 degrees Celsius within seconds of the atomic bomb explosion that was dropped on Hiroshima on August 6, 1945.
To study them, these particles were embedded in a resinous material and then polished. A team from the University of Florence used electron microscopes, chemical analysis techniques, and X-rays to study 34 particles.
Electron microscopy revealed that the intense heat vaporized metals, glass, soil, seawater, and building materials, creating a fireball that rose into the atmosphere and then cooled rapidly, forming microscopic droplets that fell to Earth. Many of these droplets remain in the sands of the Gulf to this day.
While previous studies suggested that these particles consist mainly of silicate glass at temperatures up to 1800 degrees Celsius, the new research has revealed entirely different “Hiroshimaite” materials, which form at much higher temperatures.
Interestingly, these glass spheres contained small droplets of iron- and chromium-rich alloys, with varying proportions of nickel, manganese, and molybdenum, but they constituted only 3% of the sphere's volume, and were distributed as round droplets, irregular granules, or fine aggregates.
This strange mix of elements represents a snapshot of the metals that were present at the site of the explosion when it occurred.
The biggest surprise, however, was a very fine grain containing a large amount of silicon, exceeding that found in the surrounding alloys. It was composed internally of 63% iron, 15% chromium, 9% nickel, and 7% silicon, in a homogeneous distribution, indicating that it crystallized from a single molten drop and then cooled rapidly, something that does not happen under normal conditions.
Scientists confirm that this discovery opens a new window into the behavior of materials in the harshest heat and pressure conditions that planet Earth can experience, and may pave the way for the development of new types of materials in the future.
The results were published in the journal Science Advances.
