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Title: Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO 3 , U 2 O 7 , and UO 4

Authors:
; ; ; ;
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Materials Science of Actinides (MSA)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1387907
DOE Contract Number:
SC0001089
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Nuclear Materials; Journal Volume: 478; Journal Issue: C; Related Information: MSA partners with University of Notre Dame (lead); University of California, Davis; Florida State University; George Washington University; University of Michigan; University of Minnesota; Oak Ridge National Laboratory; Oregon state University; Rensselaer Polytechnic Institute; Savannah River National Laboratory
Country of Publication:
United States
Language:
English
Subject:
nuclear (including radiation effects), materials and chemistry by design, synthesis (novel materials), synthesis (self-assembly)

Citation Formats

Guo, Xiaofeng, Wu, Di, Xu, Hongwu, Burns, Peter C., and Navrotsky, Alexandra. Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO 3 , U 2 O 7 , and UO 4. United States: N. p., 2016. Web. doi:10.1016/j.jnucmat.2016.06.014.
Guo, Xiaofeng, Wu, Di, Xu, Hongwu, Burns, Peter C., & Navrotsky, Alexandra. Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO 3 , U 2 O 7 , and UO 4. United States. doi:10.1016/j.jnucmat.2016.06.014.
Guo, Xiaofeng, Wu, Di, Xu, Hongwu, Burns, Peter C., and Navrotsky, Alexandra. Thu . "Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO 3 , U 2 O 7 , and UO 4". United States. doi:10.1016/j.jnucmat.2016.06.014.
@article{osti_1387907,
title = {Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO 3 , U 2 O 7 , and UO 4},
author = {Guo, Xiaofeng and Wu, Di and Xu, Hongwu and Burns, Peter C. and Navrotsky, Alexandra},
abstractNote = {},
doi = {10.1016/j.jnucmat.2016.06.014},
journal = {Journal of Nuclear Materials},
number = C,
volume = 478,
place = {United States},
year = {Thu Sep 01 00:00:00 EDT 2016},
month = {Thu Sep 01 00:00:00 EDT 2016}
}
  • The thermal decomposition of studtite (UO 2)O 2(H 2O) 2¬∑2H 2O results in a series of intermediate X-ray amorphous materials with general composition UO 3+x (x = 0, 0.5, 1). As an extension of a structural study on U 2O 7, this work provides detailed calorimetric data on these amorphous oxygen-rich materials since their energetics and thermal stability are unknown. These were characterized in situ by thermogravimetry, and mass spectrometry. Ex situ X-ray diffraction and infrared spectroscopy characterized their chemical bonding and local structures. This detailed characterization formed the basis for obtaining formation enthalpies by high temperature oxide melt solutionmore » calorimetry. The thermodynamic data demonstrate the metastability of the amorphous UO 3+x materials, and explain their irreversible and spontaneous reactions to generate oxygen and form metaschoepite. Thus, formation of studtite in the nuclear fuel cycle, followed by heat treatment, can produce metastable amorphous UO 3+x materials that pose the risk of significant O 2 gas. Quantitative knowledge of the energy landscape of amorphous UO 3+x was provided for stability analysis and assessment of conditions for decomposition.« less
  • Single crystals of the new compounds Li{sub 6}[(UO{sub 2}){sub 12}(PO{sub 4}){sub 8}(P{sub 4}O{sub 13})] (1), Li{sub 5}[(UO{sub 2}){sub 13}(AsO{sub 4}){sub 9}(As{sub 2}O{sub 7})] (2), Li[(UO{sub 2}){sub 4}(AsO{sub 4}){sub 3}] (3) and Li{sub 3}[(UO{sub 2}){sub 7}(AsO{sub 4}){sub 5}O)] (4) have been prepared using high-temperature solid state reactions. The crystal structures have been solved by direct methods: 1-monoclinic, C2/m, a=26.963(3) A, b=7.063(1) A, c=19.639(1) A, beta=126.890(4){sup o}, V=2991.2(6) A{sup 3}, Z=2, R{sub 1}=0.0357 for 3248 unique reflections with |F{sub 0}|>=4sigma{sub F}; 2-triclinic, P1-bar, a=7.1410(8) A, b=13.959(1) A, c=31.925(1) A, alpha=82.850(2){sup o}, beta=88.691(2){sup o}, gamma=79.774(3){sup o}, V=3107.4(4) A{sup 3}, Z=2, R{sub 1}=0.0722 formore » 9161 unique reflections with |F{sub 0}|>=4sigma{sub F}; 3-tetragonal, I4{sub 1}/amd, a=7.160(3) A, c=33.775(9) A, V=1732(1) A{sup 3}, Z=4, R{sub 1}=0.0356 for 318 unique reflections with |F{sub 0}|>=4sigma{sub F}; 4-tetragonal, P4-bar, a=7.2160(5) A, c=14.6540(7) A, V=763.04(8) A{sup 3}, Z=1, R{sub 1}=0.0423 for 1600 unique reflections with |F{sub 0}|>=4sigma{sub F}. Structures of all the phases under consideration are based on complex 3D frameworks consisting of different types of uranium polyhedra (UO{sub 6} and UO{sub 7}) and different types of tetrahedral TO{sub 4} anions (T=P or As): PO{sub 4} and P{sub 4}O{sub 13} in 1, AsO{sub 4} and As{sub 2}O{sub 7} in 2, and single AsO{sub 4} tetrahedra in 3 and 4. In the structures of 1 and 2, UO{sub 7} pentagonal bipyramids share edges to form (UO{sub 5}){sub i}nfinity chains extended along the b axis in 1 and along the a axis in 2. The chains are linked via single TO{sub 4} tetrahedra into tubular units with external diameters of 11 A in 1 and 11.5 A in 2, and internal diameters of 4.1 A in 1 and 4.5 A in 2. The channels accommodate Li{sup +} cations. The tubular units are linked into 3D frameworks by intertubular complexes. Structures of 3 and 4 are based on 3D frameworks composed on layers united by (UO{sub 5}){sub i}nfinity infinite chains. Cation-cation interactions are observed in 2, 3, and 4. In 2, the structure contains a trimeric unit with composition [O=U(1)=O]-U(13)-[O=U(2)=O]. In the structures of 3 and 4, T-shaped dimers are observed. In all the structures, Li{sup +} cations are located in different types of cages and channels and compensate negative charges of anionic 3D frameworks. - Graphical abstract: The crystal structures of Li{sub 5}[(UO{sub 2}){sub 13}(AsO{sub 4}){sub 9}(As{sub 2}O{sub 7})] separated into tubular units and intertubular complexes.« less
  • The three new framework Rb uranyl phosphates and arsenates with anionic parts based on different type of polymeric anions have been prepared by high-temperature solid-state reactions: Rb{sub 4}[(UO{sub 2}){sub 6}(P{sub 2}O{sub 7}){sub 4}(H{sub 2}O)] (1), Rb{sub 2}[(UO{sub 2}){sub 3}(P{sub 2}O{sub 7})(P{sub 4}O{sub 12})] (2), Rb[(UO{sub 2}){sub 2}(As{sub 3}O{sub 10})] (3). The crystal structures of the synthesized compounds have been solved by direct methods: 1-monoclinic P2{sub 1}/c, a=9.672(1) A, b=12.951(1) A, c=32.231(3) A, beta=90.116(4){sup o}, V=4037.3(6) A{sup 3}, Z=4, R{sub 1}=0.0926 for 6351 unique reflections with |F{sub 0}|>=4sigma{sub F}; 2-monoclinic, P2{sub 1}/c, a=6.791(1) A, b=16.155(3) A, c=19.856(4) A, beta=97.48(5){sup o}, V=2159.8(7)more » A{sup 3}, Z=4, R{sub 1}=0.0286 for 3617 unique reflections with |F{sub 0}|>=4sigma{sub F}; 3-orthorhombic, Pbcn, a=10.558(1) A, b=11.037(1) A, c=11.464(1) A, V=1335.9(2) A{sup 3}, Z=4, R{sub 1}=0.0489 for 1384 unique reflections with |F{sub 0}|>=4sigma{sub F}. The structures of title are compounds based on 3D negatively charged frameworks with chemical compositions [(UO{sub 2}){sub 6}(P{sub 2}O{sub 7}){sub 4}(H{sub 2}O)]{sup 4-} in 1, [(UO{sub 2}){sub 3}(P{sub 2}O{sub 7})(P{sub 4}O{sub 12})]{sup 2-} in 2 and [(UO{sub 2}){sub 2}(As{sub 3}O{sub 10})]{sup -} in 3. These negative charges are compensated by rubidium cations which are in the channels of 1 and closed cages in structures of 2 and 3. The channels in 1 are directed along the a direction and have minimum dimensions approx5 Ax6 A. This is the first example of porosity generation through solid state synthesis in uranyl compounds. For the first time in uranium chemistry polymeric anionic groups P{sub 4}O{sub 12} and As{sub 3}O{sub 10} were observed in structure of 2 and 3. - Graphical abstract: The polyhedral (a) and topological (b) representation of the Rb{sub 4}[(UO{sub 2}){sub 6}(P{sub 2}O{sub 7}){sub 4}(H{sub 2}O)] crystal structure.« less