An improved technique is described for the accurate determination of melting points of metals in the temperature range 1500° to 2500°C. The improvements consist of gradient heating and refinements in cavity preparation to obtain true black-body conditions. The melting point of hafnium, as determined by this method, is set a t 22220-+30°C. This is over 200°C higher than one of the values reporte...

Hafnium silicate films with pure HfO2 and SiO2 samples as references were fabricated by atomic layer deposition (ALD) in this work. The optical properties of the films as a function of the film composition were measured by vacuum ultraviolet (VUV) ellipsometer in the energy range of 0.6 to 8.5 eV, and they were investigated systematically based on the Gaussian dispersion model. Experimental res...

We report the optical and dielectric properties in hafnium (Hf)-doped lithium niobate (LN) crystals. We investigated samples of congruent composition with various doping concentration varying from 0 to 8 mol%. The clamped and unclamped values of the electrooptic coefficient r22 of Hf-doped LN and the corresponding dielectric permittivity as well, have been experimentally determined and compared...

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 ...

In his paper, Chandi C. Dey reports on the measurement of the nuclear quadrupole interaction of 181Hf(β−)181Ta in α-Hf metal with a few percent zirconium heated in air by perturbed angular correlation (PAC) of γ-rays. Since he did not observe the formation of HfO2 up to 773 K and during initial heating at 873 K for one day, he concluded that no oxygen is absorbed. The time dependent hyperfine i...

 A series of seven new complexes of zirconium and hafnium with bulky ω-aryloxyalkyl substituted indenyl ligands were synthesized and characterized by NMR spectroscopy and elemental analysis. These complexes were activated with methylaluminoxane and tested for homogeneous ethylene polymerization. The zirconium catalysts showed higher activities than their hafnium an...

The international High Priority Request list notes: “In the nuclear industry hafnium is used as neutron absorbing material to regulate the fission process. Interpretation of critical experiments with UOx fuel conducted by CEA in the AZUR zero-power reactors has shown systematic underestimation of the reactivity worth that may be attributed to an overestimated natural hafnium capture cross secti...