Chemistry of ancient materials of iron in India

Abstract

India is acclaimed for its rich heritage of iron making at least since the protohistoric era. The ancient artisans were able to create iron artefacts possessing outstanding characteristics, which demonstrates the level of expertise they had attained in the field of chemistry and metallurgy. Numerous iron artefacts including iron pillar in Delhi, iron pillar in Dhar, iron beams at Sun temple in Konark, bear eloquent testimony to this. Therefore, it is fascinating to study the chemistry involved in the preparation and properties of these iron-based ancient materials. Several scholars have contributed to the study of iron artefacts discovered from various sites across India which belong to different periods, regions and dynasties. Across the scholarly spectrum, special attention has been paid to study the chemistry involved in the marvelous characteristics like super corrosion resistance of iron pillars, cannons, etc.This review, therefore, presents the recent insights into iron-based materials in ancient India.Our objective is to highlight (1) a brief historical background, (2) chemical composition, (3) preparation of the material, (4) surface microstructure and (5) the mechanism behind the special features, of iron artefacts. Analysis of antiquarian remains with the help of different characterization techniques like X-ray diffraction (XRD), Proton induced X-ray emission, Energy dispersive spectroscopy (EDS), Fourier Transform Infrared spectroscopy (FTIR), Mössbauer spectroscopy, High Resolution Transmission Electron Microscopy (HRTEM), micro particles induced X-ray emission (μPIXE), etc. have been focused upon. The ancient iron making process used for producing high quality wootz steel has been discussed too. A detailed analysis of the rust-free iron pillar of Delhi has been presented. In particular, the iron pillar at Dhar, Adi-Mookambika temple, Kodachadri, and iron beams at Sun Temple, Konark, Damascus swords made of wootz steel, cannon at Thanjavur and iron specimens of Gupta period at Eran (Madhya Pradesh) are the artefacts studied to understand the characteristics of iron objects produced in India during ancient times. This study can support the future making of metallic monuments and artefacts with outstanding characteristics. This review is expected to appeal across the disciplines, including but not limited to, materials science, chemistry, physics, metallurgy, chemical engineering and archaeology.