Jing Cheng Zhang

In aerospace and power generation, components will serve in high-temperature environments. In this work, the influence of temperature on the tribological performances of Cu/Ti₃AlC₂ composites was investigated. Cu/Ti₃AlC₂ composites were fabricated at 800°C without decomposition. The friction coefficients of the composites were in the range of 0.19 - 0.28. From 25°C to 300°C, the wear rates increased with temperature. At 300°C, the wear rate reached the highest value. Interestingly, the wear rates plummeted at 500°C and 700°C. It was found that tribofilms consisting of Ti₃AlC₂ and Cu₂O covered on the wear surfaces at 25°C and 100°C. At 300°C, material transfer and plastic flow contributed to occurrence of adhesive wear. From 500°C to 700°C, oxidation layers formed on the wear surfaces. For simplicity, a schematic of the tribological mechanisms is proposed.

Following publication of the original article [1], the authors reported an error in Schemes 1 and 2 and repeated line in subsection “Bis(ligand) nickel(II) chelate (NiL1₂)”.

Background: The general approach to the synthesis of metal complexes begins with ligand synthesis, followed by ligand reaction with metal salts to afford organometallic complexes. Our research group first reported a one-pot multicomponent synthesis of chiral oxazolinyl–zinc complexes, in the presence of a large amount of ZnCl₂ (0.4–2.6 equiv.), with the yields of some products reaching 90%. Results: Our prior strategy was extended to use copper, cobalt, nickel, manganese, palladium or platinum salts as the third component. The one-step method used 1.0 equivalent of a metal salt, such as M(OAc)₂·nH₂O or MCl₂·nH₂O (M: Cu, Co, Ni, Pd or Pt, n = 1, 2 or 4), as a reagent to generate chiral salicyloxazoline complexes 1–8 in the reaction of 2-cyanophenol with different d- and l-amino alcohols. Conclusion: Complexes 1–8 were obtained using a one-pot method with a sequential strategy. The reaction outcome was demonstrated for three-component reactions between metal salts, amino alcohols and 2-hydroxybenzonitrile to afford organometallic complexes in good yields (65–95%).

Typically, oxazolinyl metal complexes are synthesized in two steps, where the free ligand is prepared by the condensation reaction between a functionalized nitrile and an amino alcohol in the presence of a Lewis or Brønsted acid catalyst, followed by a further reaction with metal salts to obtain the corresponding metal complexes. Very often, the yield afforded by the two-step procedure is not high, and very few oxazolinyl zinc complexes have been prepared by this route. Given that metal-oxazoline complexes often contain Lewis acidic metals, it is conceivable that the two steps may be telescoped. A series of novel chiral organozinc complexes 1–15 were assembled in a single step, All crystalline compounds were fully characterized, including the report of 15 X-ray crystal structures, including a wide structural diversity. A series of novel chiral organozinc complexes were assembled in a single step, from nitriles, chiral D/L amino alcohols, and a stoichiometric amount of ZnCl2, with moderate to high yields (20–90%).

A leaf-like ZIF-L-Co is synthesized for the first time and the molar ratio of Hmim/Co plays an important role in the synthesis. ZIF-L-Co is a transient phase at the initial stage of ZIF-67 crystal growth. The crystallization process of ZIF-67 from ZIF-L-Co follows a solid transformation mechanism.