Reactions Of Hafnium Research Articles

HAFNIUM AND NITROGEN INTERACTION AT Hf/GaN(0001) INTERFACE

The growth and stability of hafnium films on [Formula: see text]-GaN(0001) surface with native oxide was investigated with X-ray and ultraviolet photoelectron spectroscopy (XPS, UPS). It is shown that hafnium creates a continuous and stable layer on GaN substrate. Thermal treatment at [Formula: see text]C of Hf/GaN system causes decomposition of GaN and reaction of hafnium with atomic nitrogen from the substrate. XPS spectra demonstrate the reaction by a strong shift of the N 1s and Hf 4f lines. An attempt for bringing on the same reaction with molecular nitrogen under pressure of [Formula: see text] mbar was not successful. UPS spectra show a metallic character of the hafnium adlayer in such instances.

Excitation Function of (n,α) Reactions of Hafnium and Tungsten Isotopes for Fusion Reactor Technology

Excitation Function of (n,α) Reactions of Hafnium and Tungsten Isotopes for Fusion Reactor Technology

Excitation Function of (n,α) Reactions of Hafnium and Tungsten Isotopes for Fusion Reactor Technology

The cross-section of 176Hf(n,α)173Yb, 177Hf(n,α)174Yb, 178Hf(n,α)175Yb, 179Hf(n,α)176Yb, 180Hf(n,α)177Yb, 182W(n,α)179Hf, 183W(n,α)180Hf, 184W(n,α)181Hf and 186W(n,α)183Hf reactions have been analyzed by using TALYS 1.4 in the energy range between 13 and 15 MeV. The result has been compared with several experimental values taken from EXFOR data library and evaluated data file of ENDF/B-VII.0 and ENDF/B-VII.I. It is concluded that the present results contribute significantly to enhance the knowledge of cross-sections and in optimizing the input parameters required in model based evaluation.

Solvent extraction reaction of hafnium(IV) from strong sulfuric acid solutions with D2EHPA and PC 88A

ABSTRACTHafnium can be selectively extracted over zirconium from strong sulfuric acid solutions by D2EHPA or PC 88A. Solvent extraction experiments have been performed to identify the reaction of Hf from strong sulfuric acid solutions (1 to 7 M) by these two extractants. Hafnium extraction was gradually decreased and then increased again with the increase of sulfuric acid concentration. By applying a slope method, the extracted Hf species was proposed to be HfA4·(HA)2 by D2EHPA and Hf(HSO4)2A2·(HA)2 by PC 88A, respectively. This difference in the nature of the extracted species was verified by FT-IR spectra.

Reactions of Hafnium(IV) Isopropoxide Isopropanolate with Mercapto Triazoles

Abstract The reactions of hafnium(IV) isopropoxide isopropanolate with 3-methyl-4-amino-S-triazol-5-thiol, 3-ethyl-4-amino-S-triazol-5-thiol and also with Schiff bases derived from amino triazoles with benzaldehyde, acetophenone, salicylaldehyde or o-hydroxyacetophenone have been carried out in different molar ratios 1:n (n = 1 to 4) in refluxing benzene. The products of the types [Hf(OPri)4-n(L)n] (n = 1,2 or 3), [Hf(OPri)4-n(L')n] (n = 1 or 2), [Hf(OPri)4-2n(L″)n] (n = 1 or 2), (LH = 3-methyl/ethyl-4-amino-S-triazol-5-thiol; L'H = Schiff bases derived by condensation of LH with benzaldehyde and acetophenone; L″H2 = Schiff bases derived by condensation of LH with salicylaldehyde or o-hydroxyacetophenone) have been isolated and the of elemental analysis, electrical conductance magnetic moment and spectral (electronic, infrared and 1H n.m.r.) data.

Hafnium(IV) complexes with Schiff bases

Hafnium(IV) complexes have been prepared by the reactions of hafnium(IV) isopropoxide isopropanol with Schiff bases [bis(salicylaldehyde)hydrazine] (Sal-AH2), (bis(o-hydroxyacetophenone)hydrazine] (Acp-AH2), [bis(resacetophenone)hydrazine] (Res-AH2), [bis(salicylaldehyde)ethylenediimine) (SaleneH2), [bis(o-hydroxyacetophenone)ethylenediimine] (AcpeneH2) and [bis(salicylaldehyde)o-phenylenediimine] (SalpheneH2) (derived from salicylaldehyde,o-hydroxyacetophenone, resacetophenone and diamines) in appropriate molar ratios using benzene as solvent. The complexes [Hf(OPr-i)2(SB)] and [Hf(SB)2] (where SB2− represents the dianion of the Schiff base) are reported. The complexes of Sal-A, Acp-A and Res-A are 5-and 6-coordinate while those of salene, acpene and salphene are 6-and 8-coordinate. The Schiff bases draw on Sal-A, Acp-A and Res-A are tridentate and salene, acpene and salphene are tetradentate. The mode of bonding through nitrogen and oxygen and the stereochemistry of the complexes are discussed in relation to the elemental analyses and spectra (electronic, infrared and nuclear magnetic resonance).

Reactions of hafnium(IV) isopropoxide-isopropanol (1/1) with 2-aminocyclopent-1-ene-1-dithiocarboxylic acid and itsN-alkyl derivatives

A series of hafnium(IV) complexes has been synthesised by the reaction of hafnium(IV) isopropoxide-isopropanol(1/1) with 2-aminocyclopent-1-ene-1-dithiocarboxylic acids RNHC(CH2)3CC(S)SH, (where R=H, Me, Et or Bu) in 1∶1 and 1 ∶ 2 molar ratios. The compounds have been characterized by elemental analysis, i.r. and1H n.m.r. spectral studies. The complexes polymerise slowly in solution, probablyvia the sulphur atom of the >C=S group.

Ultrafine dispersion-strengthening of tungsten by chemical covapor deposition

A method of dispersion-strengthening tungsten, a refractory metal, with submicron (< 10 Å) dispersoids of hafnium nitride, a stable ceramic, is described. Simultaneous deposition of the metal and the dispersoid is achieved by a chemical vapor deposition process called covapor deposition. The tungsten and hafnium are covapor deposited by hydrogen reduction of their halides (WCl 6 and HfCl 4); the dispersoid is formed during deposition by the reaction of hafnium with NH 3 in the hydrogen gas. The microstructure of the tungsten matrix, either the large columnar grains typical of chemical vapor deposited tungsten or fine noncolumnar grains (< 1 μm), can be controlled by varying the deposition parameters. It is also possible by varying these parameters to change the number, size, and spacing of the dispersoids. The deposits were heat treated at 1700 °C for at least 1 h before hot microhardness values to 1400 °C were determined. These values were then compared with hot microhardness values determined after heat treatment for 96 and 500 h at 1700 °C. The microstructures of the deposits in these conditions were evaluated by thin film and scanning electron microscope techniques. The hot microhardness of the LRL dispersion-strengthened tungsten was superior to that of dispersion-strengthened tungstens prepared by other techniques. The possibilities of using this technique to improve the strength and creep resistance of other metals ( e.g., nickel-chromium alloys for turbine blades) is also suggested. Parameters are given for the deposition of pure tungsten and hafnium nitride from their halides.

On the physicochemical reaction of hafnium with europium

On the physicochemical reaction of hafnium with europium

Chemical detection of zirconium and hafnium

3-Hydroxyflavone, morin and quercetin are suitable for the fluorescent detection of hafnium and zirconium under proper acidity and reagent concentration conditions. 3-Hydroxyflavone is the most sensitive reagent for both metals. Substantially acid solutions are preferred for the reactions of hafnium and zirconium to increase selectivity despite decreasing reaction sensitivity. The hydroxyflavone hafnium chelates are more stable to acid than the zirconium chelates especially with morin and quercetin. The very low background fluorescence of quercetin permits the detection of hafnium in strong perchloric acid where the fluorescence of the other two reagents hinders detection.

Absorptiometric determination of hafnium with molybdophosphoric acid

A sensitive method for the absorptiometric determination of hafnium has been developed. It is based on the reaction of hafnium with molybdophosphoric acid at pH 4.0. The method follows Beer's law in the range 0–14 parts per million hafnium. Data on interfering substances are presented.