We have developed a novel oxidant-free direct cross-coupling reaction of 2,6-lutidine and internal alkynes leading to five-membered carbocyclic compounds mediated by nonmetallocene cationic hafnium alkyl complexes. Mechanistic studies of the coupling reaction showed that the reaction begins with C(sp(3))-H bond activation via σ-bond metathesis, after which the coordinatively unsaturated hafnium...

The separation of hafnium from zirconium using tributyl phosphate offers interesting alternatives to present methods for making reactor-grade zirconium. Feed solution for the extraction step can be prepared from the reaction product of caustic and zircon sand. The purified zirconium can be converted into a variety of compounds, depending on the process chosen for reduction to the metal. It may ...

The modification of different zirconium propoxide and hafnium propoxide precursors with 2,2,6,6,-tetramethyl-3,5-heptanedione (Hthd) was investigated by characterization of the isolated modified species. The complexes [Zr(OnPr)3(thd)](2), [Zr(OnPr)(OiPr)2(thd)]2, Zr(OiPr)(thd)3, [Hf(OnPr)3(thd)]2, and Hf(OiPr)(thd)3 were isolated and characterized. The structure of the n-propoxide analogue of Z...

Despite the increasing importance of hafnium in numerous technological applications, experimental and computational data on its binary alloys is sparse. In particular, data is scant on those binary systems believed to be phase-separating. We performed a comprehensive study of hafnium binary systems with alkali metals, alkaline earths, transition metals and metals, using high-throughput first-pr...

Hafnium oxide and Hafnium oxynitrides thin films are deposited on a Si substrate using reactive sputtering. Compared with Hafnium dioxide, Hafnium oxynitrides showed excellent electrical characteristics such as low leakage current density and low capacitance equivalent oxide thickness. By X-ray photoelectron spectroscopy (XPS), we were able to confirm nitrogen incorporation in the oxide bulk an...

The paper will introduce a simple new method on the synthesis of both hafnium and zirconium nitrate precursors. The intermediate product, dinitrogen pentoxide produced from the water extraction from fume nitric acid via phosphorus pentoxide, was condensed by liquid nitrogen trap into a flask equipped with hafnium or zirconium tetrachloride. To give the high yield, the mixture of fume nitric aci...

High-density metals such as hafnium and zirconium are of interest to the propellant, explosive, and pyrotechnic industry due to their high oxidation enthalpies; however, these metal fuels suffer from electrostatic discharge (ESD) complications creating safety concerns. Previous attempts to passivate these powders have failed due to abrasion of the protective coatings. Two novel methods for dese...

Graphite is widely used in technology because of its unique properties. A drawback of graphite is its low heat resistance in oxidizing atmospheres. To increase its heat resistance, Nb-Hf protective coatings were synthesized. Electrodeposition of niobium coatings on graphite with subsequent precise surface alloying of niobium with hafnium was studied. Electrochemical synthesis of Nb-Hf coatings ...