No abstract

A chromium-free zirconium-based conversion coating (ZrCC) was prepared on AA5083. The ZrCC improved the corrosion resistance of AA5083 and the adhesion of epoxy resin significantly, the performance of which was much better than that of the commercial chromium-free treatment and close to that of commercial chromate conversion coating (CCC) treatment. The ZrCC displayed a three-layer structure with a thickness of approximately 1.5 μm, including an inner layer at the alloy/coating interface, a thicker middle layer with nodular particles and an outer layer on the top. Formation of the ZrCC proceeded via the stacking of nodular particles layer upon layer, the composition of which was mainly amorphous Na3AlF6, Zr(HPO4)2·H2O, ZrO2 and AlPO4. The ZrCC with the special three-layer structure provided good protection despite the absence of a “self-healing” ability.

Coordination polymers (CPs) consisting of alkali metals (Na, K, Rb, and Cs) and a powerful nitrogen- and oxygen-rich energetic ligand (4,4'-bis(dinitromethyl)-3,3'-bisnitramide-methylene-furazanate, DBMF ) were developed. Molecular structures of these CPs, confirmed by single-crystal X-ray diffraction analysis, indicated that the same ligand takes on a U-shaped state for Na and an N-shaped state for K, Rb, and Cs. Explosion tests demonstrated that both Na DBMF and K DBMF efficiently detonated the secondary explosive RDX. This indicates that they are both effective primary explosives. K DBMF exhibits better calculated detonation performance (D: 8227 m s ; P: 32.5 GPa) than the primary explosive Pb(N ) . In addition, toxicity tests and evaluation of their decomposition products reveal their low impact on the environment. Both experimental results and theoretical analyses indicate that the combination of alkali metals and a powerful energetic ligand can stimulate the development of primary explosives.

Furazan has rarely been used as a building block in the development of energetic cations. In this study, polyamino-substituted furazan-triazole was explored as an energetic cation for the synthesis of energetic salts 3−6. All new compounds were characterized by infrared and NMR spectroscopy, elemental analysis, and single crystal X-ray diffraction. The experimental results revealed that these salts have good thermal stabilities; the decomposition temperatures of these salts, except nitroformate 6, were over 200 °C. These salts (IS: 16−40 J; FS: 200−360 N) are more insensitive than RDX. The noncovalent interaction (NCI) and Hirshfeld surface analyses were performanced to comprehensively study their structure−property relationships. The good molecular stabilities of these salts can arise from (a) abundant π−π interactions on account of the planar furazan-triazole backbone and (b) an extensive hydrogen bonding network resulting from large amounts of amino groups. Simultaneously, all the salts exhibit promising detonation performances (D: 8049−8836 m s −1 ; P: 26.9−34.8 GPa), which were much higher than both those of TNT, and salt 6 was even comparable to RDX.