Volatilization of urania under strongly oxidizing conditions

Characterization of Uranyl Coordinated by Equatorial Oxygen: Oxo in UO3 versus Oxyl in UO3+

“…1 Uranium trioxide is a vapor species under high temperature conditions, making the gas-phase reactivity of UO3 particularly relevant to nuclear material processing and mishaps. 12,13 The T-shaped structure of UO3 has been confirmed by IR spectroscopy in inert matrices, validating the description as bent UO2 2+ coordinated by equatorial O 2-. [14][15][16][17][18] The C2v structure of UO3 contrasts with typical D3h transition metal trioxides with three equivalent oxo groups.…”

“…Uranium chemistry is dominated by the hexavalent oxidation state afforded by the linear uranyl dication, which possesses highly stable axial oxo bonds, [O yl UO yl ] 2+ , that are progressively weakened by increased equatorial coordination. , Lower UO yl bond strength is indicated by longer bond length, red-shifting of the characteristic uranyl ν 2 and ν 3 stretch frequencies, and enhanced reactivity. − A particularly elementary uranyl coordination scenario is a single equatorial oxo-ligand, O 2– , which yields neutral UO 3 that can alternatively be designated as “uranyl oxide” . Uranium trioxide is a vapor species under high temperature conditions, making the gas-phase reactivity of UO 3 particularly relevant to nuclear material processing and mishaps. , The T-shaped structure of UO 3 has been confirmed by IR spectroscopy in inert matrices, validating the description as bent UO 2 2+ coordinated by equatorial O 2– . − The C 2 v structure of UO 3 contrasts with typical D 3 h transition metal trioxides with three equivalent oxo groups. , All three oxo groups in UO 3 have large bond dissociation energies ( BDEs ): , BDE [U–O] = 758 kJ/mol; BDE [OU–O] = 750 kJ/mol; and BDE [O 2 U–O] = 603 kJ/mol. The first two correspond to very strong axial UO yl , while the third is associated with the weaker equatorial UO eq , a relationship that makes UO 3 a prototypical case of the actinide inverse-trans effect .…”

Tris(2,4‐pentanedionato)scandium(III) as a Precursor for Plasma‐Assisted Liquid Injection CVD to Deposit Nanocrystalline Scandia Thin Films

“…The conventional transpiration method is still the one that is widely used for determining low vapor pressures. [34,35] There are a large number of references on determining the vapor pressures of volatile materials, include organic compounds, by using the transpiration method. Moreover, the TG-based transpiration technique has its own advantages such as mass versus time data being easily acquired through computers at any desired intervals of time and at any programmed heating mode (gradient or isothermal), and mass versus time data at various flow rates can be obtained in a quick period of time.…”

Th/U variability in Allende chondrules

“…Likewise, Th may be oxidized as ThO and ThO 2 . Under strongly oxidizing conditions, U can also be hydrated as UO 2 (OH) 2 (Olander, 1999;Alexander, 2005). The thermodynamic data for U, Th, and their oxides can be found in Green (1980), Cox et al (1989), Guillaumont and Mompean (2003), and Konings et al (2014).…”