Mechanism of activator and pore surface adsorption in aluminum-based flameless ration heaters: A molecular dynamics study

Abstract

The aluminum-based flameless ration heaters (FRHs) in self-heating food packaging are the heating elements, while water is the activator. Inevitable inadequate reactions can lead to reduced heating capacity and material waste. The transport behavior of activators (water and ions) in the main components of FRHs was investigated with molecular dynamics to study the mechanism of low exothermic efficiency. This paper transported a mixed solution composed of calcium ions, sodium ions, chloride ions, and water in the nanopores with three pore sizes 1.0, 1.5, and 2.5 nm. Results demonstrate that the formation of hydrogen bonds at the surface of tricalcium aluminate (C3A) with water can slow the movement of water molecules. Sodium, calcium ions, and oxygen atoms on the surface of C3A combine competitively through surface chemical bonding, forming Ca-O and Na-O bonds. In addition, as the pore size becomes smaller, the hindering effect of the nano-pore channel becomes stronger. Calcium ions and chloride ions form ion pairs through ionic bonding, which can continuously aggregate to hinder the transport of water molecules and ions. This work provides a basis for understanding the study of the transport and adsorption behavior of liquids in C3A pores and provides a viable idea for subsequent experimental studies.