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Louis-Jean, James

Publications and source records attributed to Louis-Jean, James.

14 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Thermal behavior of ammonium octafluorodirhenate(III)

The thermal behavior of (NH 4 ) 2 [Re 2 F 8 ]·2H 2 O salt was studied in the temperature range 150–700 °C under flowing nitrogen gas. The decomposition products were studied by powder X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Results are consistent with the formation of (NH 4 ) 2 [Re 2 F 8 ] salt at 150 °C, amorphous rhenium metal at 300 and 400 °C, and crystalline rhenium metal at 500 and 700 °C. A mechanism of formation of rhenium metal from (NH 4 ) 2 [Re 2 F 8 ]·2H 2 O was proposed. Here, the effect of crystallite size and lattice strain was evaluated at 500 and 700 °C from powder XRD peak broadenings using both Williamson–Hall and the modified Scherrer methods.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Conversion of (NH 4 ) 2 [ReF 6 ] into ReO 2 mixed phases: A thermal analysis study

We report the thermal behavior of (NH 4 ) 2 [ReF 6 ] was evaluated in an alumina crucible using simultaneous thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) in an argon atmosphere. The TGA of (NH 4 ) 2 [ReF 6 ] is characterized by a single step decomposition while the DSC exhibits two exothermic peaks. Powder X-ray diffraction (PXRD) analyses of the decomposition products show the presence of a mixed ReO 2 phase. The formation of ReO2 is driven by the reaction of (NH 4 ) 2 [ReF 6 ] with Al 2 O 3 at the grain boundary of the alumina crucible. XRD peak broadenings due to the combined effect of crystallite size and lattice strain were evaluated using both Scherrer and Williamson-Hall methods.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

From ammonium Hexahalorhenates(IV) to nanocrystalline rhenium metal: A combined thermal, diffraction and microscopic analysis

Rhenium metal powder is a material of industrial importance. Several industrial and laboratory methods have been developed for the preparation of ultrafine Re metal powder and nanoparticles. The present study provides a better understanding of the characteristic and formation of Re metal powder from the decomposition of (NH4)2ReX6 salt (X = F, Cl, Br, I) at high temperature in inert atmosphere. Such analysis resulted in the formation of nanocrystalline Re metal as characterized by powder XRD. Williamson-Hall, Scherrer, and Williamson-Smallman methods were employed to study the effect of crystallize size, lattice strain, and dislocation density as analyzed from powder XRD peak broadening. Here, the morphology and composition of the metal were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Synthetic diversity in the preparation of metallic uranium

Uranium metal is associated with several aspects of nuclear technology; it is used as fuel for research and power reactors, targets for medical isotope productions, explosive for nuclear weapons and precursors in synthetic chemistry. The study of uranium metal at the laboratory scale presents the opportunity to evaluate metallic nuclear fuels, develop new methods for metallic spent fuel reprocessing and advance the science relevant to nuclear forensics and medical isotope production. Since its first isolation in 1841, from the reaction of uranium chloride and potassium metal, uranium metal has been prepared by solid-state reactions and in solution by electrochemical, chemical and radiochemical methods. The present review summarizes the methods outlined above and describes the chemistry associated with each preparation.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Structural and spectral studies of hydrated hexaamminecobalt(III)–hexafluororhenate(IV)

The crystal structure of the [Co(NH 3 ) 6 ] 2 [ReF 6 ] 3 ·3H 2 O (I) salt is reported. The salt crystallizes in the trigonal space group P31m with the following unit cell dimensions: a = 15.8714(4) Å, b = 15.8714(4) Å, and c = 9.8657(4) Å. Here, the structure of (I) consists of [Co(NH 3 ) 6 ] 3+ cations, [ReF 6 ] 2– anions, and co-crystallized water molecules which are linked by hydrogen bonding. In (I), independent [ReF 6 ] 2– anions and [Co(NH 3 ) 6 ] 3+ cations octahedron are slightly distorted. Characteristic vibration bands of the [Co(NH 3 ) 6 ] 3+ cation, [ReF 6 ] 2– anion as well as the co-crystallized H 2 O molecules are observed in the infrared spectra of (I). UV-Visible analyses in water showed that the absorption of the [Co(NH 3 ) 6 ] 3+ cation predominate the spectra of (I).

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2021

Coexistence of metamagnetism and slow relaxation of magnetization in ammonium hexafluoridorhenate

The (NH 4 ) 2 [ReF 6 ] (1) salt was studied by X-ray diffraction, Raman spectroscopy, theoretical calculations, and magnetic measurements. 1 crystallizes in the trigonal space group P$\overline{3}$m1 (Re–F = 1.958(5) Å). In the Raman spectrum of 1, splitting of the observed peaks was observed and correlated to the valence frequencies of vibration of the [ReF 6 ] 2– anion. The study of the magnetic properties of 1, through DC and AC magnetic susceptibility measurements, reveals the coexistence of metamagnetism and slow relaxation of magnetization at low temperature, which is unusual in the molecular systems based on the paramagnetic 5d metal ions reported so far.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

New loading method for high precision Sm isotope analysis of nuclear materials using thermal ionization mass spectrometry

This work demonstrates an analytical protocol for high precision Sm isotope analysis by thermal ionization mass spectrometry (TIMS) using a Pt activator. Here, the method permits precise measurements of small aliquots (1–20 ng) of Sm on single Re filament using a modified static-total evaporation technique. This study represents the first attempt to use such protocols for Sm isotope analyses while reducing the loading size of Sm for TIMS. The method could potentially be deployed to study geological, meteorites and lunar samples containing low Sm concentrations, to monitor neutron irradiation exposure based on 149,150 Sm, or to measure Sm isotopic composition in other types of nuclear samples.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2019

Preparation and characterization of benzotriazolium perrhenate

The title compound, [C 6 H 6 N 3 ][ReO 4 ], crystallizes in the monoclinic space group P2 1 /c (a = 12.854(2) Å; b = 4.9121(8) Å; c = 14.819(2) Å). The solid-state structure of the compound is stabilized by a series of hydrogen bonds. The solubility of [C 6 H 6 N 3 ][ReO 4 ] was measured in H 2 O, CH 3 OH (MeOH), and HCl (0.5 M and 6 M). Nuclear magnetic resonance measurements ( 1 H NMR and 13 C NMR) were performed, and results were consistent with the presence of the organic cation. The UV–visible spectrum shows a solvent dependency which DFT simulations indicate arise from which benzotriazole (BTA) species are present in solution (i. e., [C 6 H 4 N 3 ] - in H 2 O, C 6 H 5 N 3 in MeOH and [C 6 H 6 N 3 ] + in 5 M HCl).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Syntheses, Raman spectroscopy and crystal structures of alkali hexafluoridorhenates(IV) revisited

The A 2 [ReF 6 ] (A = K, Rb and Cs) salts are isotypic and crystallize in the trigonal space group type P$\bar{3}$m1, adopting the K 2 [GeF 6 ] structure type. Common to all A 2 [ReF 6 ] structures are slightly distorted octa­hedral [ReF 6 ] 2- anions with an average Re—F bond length of 1.951 (8) Å. In these salts, symmetry lowering on the local [ReF 6 ] 2- anions from O h (free anion) to D 3d (solid-state structure) occur. The distortions of the [ReF 6 ] 2- anions, as observed in their Raman spectra, are correlated to the size of the counter-cations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗