Mackinawite formation from elemental iron and sulfur

Area of Science:

• Materials Science
• Corrosion Science
• Nanotechnology

Background:

• Sulfur-assisted corrosion of iron is a well-documented phenomenon.
• Conventional mackinawite synthesis involves precipitation, often introducing unwanted ions.
• Intentional synthesis of mackinawite via elemental reaction has not been previously explored.

Purpose of the Study:

• To develop a novel method for mackinawite synthesis using sulfur-assisted corrosion.
• To investigate the influence of dissolved salts, specifically NaCl, on mackinawite formation and properties.
• To propose a new structural model for nano-mackinawite based on experimental findings.

Main Methods:

• Synthesis of mackinawite through direct reaction of iron and sulfur.
• Controlled addition of sodium chloride (NaCl) to the reaction system.
• Characterization of the synthesized mackinawite, including Fe2+ ion content and structural analysis.

Main Results:

• Mackinawite was successfully synthesized from elemental iron and sulfur without additional ions.
• NaCl addition significantly accelerated the mackinawite formation reaction.
• The presence of NaCl influenced the Fe2+ ion content within the mackinawite structure.
• A novel charged layer model was proposed to explain observed structural and particle characteristics of nano-mackinawite.

Conclusions:

• Sulfur-assisted corrosion offers a viable route for ion-free mackinawite synthesis.
• NaCl acts as a catalyst and structure-directing agent in mackinawite formation.
• The proposed charged layer model provides a new framework for understanding nano-mackinawite properties and literature discrepancies.