Molecular Scale Simulations of Coating Palmitic Acid Molecules on Aluminum Surface

Abstract

In this research, molecular dynamic (MD) simulations computation is applied to generally study the coating behavior of palmitic acid molecules and aluminum (Al) nanoparticle (ANP) surface through single and multi-molecule models. Changes and comparisons of adsorption distance, energy, effectiveness and stability are generally discussed in this study. Those obtained results indicate that the adsorption configuration of palmitic acid and Al has shown the adsorption polarity clearly. For carboxyl terminal of palmitic acid and Al surface, when their critical adsorption angle is around 60∘, its distance is within 9 Å. Besides, the decisive atomic group of palmitic acid molecule is carboxyl, whose oxygen atom with double bond can adsorb the Al atom stably. This adsorption effect and formation is close to the covalent bond. During the adsorption process, van der Waals force acts on the long-distance attraction, and the Coulomb force acts more critically as the short-range adsorption force. Finally, the gas coating has proper advantages over the liquid coating, as the erosion of Al surface is much lower when it is surrounded by gas-phased palmitic acid.

Molecular Dynamics Simulation of Ignition Behavior of Low Palmitic Acid-Coated Nanoaluminum Powder

“…As shown in Figure 7, the number of Fcc structure atoms at the time of origin is an isotropic series due to the disruption of the metal structure by adsorption, with an average decrease of approximately 300 Fcc structure atoms for every 100-acid molecules, consistent with the conclusion that adsorption of one soft acid affects three Al atoms. 35 The oxidation trend in Figure 7 is roughly consistent with the adsorption trend in Figure 6. Uncoated ANP oxidizes with a relative lag but ends up oxidizing to the highest degree.…”

“…The stable oxide film on the aluminum surface is about 28 Å in the natural environment, and the oxidation reaction proceeds spontaneously upon exposure to water molecules. As shown in Figure , the number of Fcc structure atoms at the time of origin is an isotropic series due to the disruption of the metal structure by adsorption, with an average decrease of approximately 300 Fcc structure atoms for every 100-acid molecules, consistent with the conclusion that adsorption of one soft acid affects three Al atoms …”

“…More unusual is the uncoated count, where the efficiency of the uncoated aluminum powder adsorption is severely lagged at the beginning of the adsorption period, although the number of adsorbed aluminum powders without coating ultimately exceeds that of the three acid-containing coated counts. We attribute this efficiency lag to the fact that van der Waals forces are the main force for adsorption when water molecules are far away from the aluminum powder . While chondritic acid increases the van der Waals force, it also further shortens the distance to the water molecules, which is why the phenomenon of the lagging adsorption efficiency of uncoated aluminum powder is formed.…”

“…We attribute this efficiency lag to the fact that van der Waals forces are the main force for adsorption when water molecules are far away from the aluminum powder. 35 While chondritic acid increases the van der Waals force, it also further shortens the distance to the water molecules, which is why the phenomenon of the lagging adsorption efficiency of uncoated aluminum powder is formed. We compare the trends in the number of Al atoms contained in the metallic Fcc lattice at four levels of cladding over a 300 ps time period.…”

“…Among the existing coating schemes, organic coatings have highly energetic properties and have attracted much attention and research. , The properties of palmitic acids, such as melting point, relative molecular weight, and polarity (water resistance), satisfy many of the requirements of ANP coating materials , and become the simulated coating material in this paper.…”