Theoretical Investigation on the Adsorption of Nitroglycerin on the α-Al2O3(0001) and γ-Al2O3 (110) Surfaces

Nitroglycerin(NG) and alumina were used as the models of energetic plasticizers and the surface of fuels in propellants to investigate the microscopic mechanism of interactions between materials containing nitrate ester group and combustion agent surface. First-principles calculations based on density functional theory with the all-electron double numerical polarized basis sets were employed to study the adsorption of NC on the alpha-Al2O3(0001) and gamma-Al2O3(110) surfaces. The results indicate that strong chemical adsorption exists between NG and the alpha-Al2O3(0001) as well as gamma-Al2O3(110) surfaces, which results in significant elongation and breakage of corresponding O-NO2 bond of NG. The dissociation which produces NO2 free radical is barrierless and releases a large amount of heat. The adsorption energy is about 175. 7 kJ/mol. The interaction of NG and the fully hydroxylated surfaces comes from H-bonding interactions mainly. The adsorption energy decreases significantly and is about 50.0 kJ/mol. For partly hydroxylated surfaces, it is found that both chemical and physical adsorption would occur on the surfaces and no obvious synergy or catalysis exist for both mechanisms. The present theoretical work is useful to gain some new insights on the compatibility of materials containing nitrate ester group and the other components in propellants.