Structure du borate d`uranium UB2O6

Gasperin, M.

doi:10.1107/s0108270187089121

Cited by 24 publications

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“…Just six compounds with the actinide cations thorium, uranium, and americium are known, namely: ThA C H T U N G T R E N N U N G (B 2 O 5 ), [12] ThB 66. 8 O 0.36 , [13] UA C H T U N G T R E N N U N G (BO 3 ) 2 , [14] (UO 2 )A C H T U N G T R E N N U N G (B 2 O 4 ), [12] AmB 9 O 18 , [11] and AmBO 3 . [15] To the best of our knowledge, no ternary actinide borates have been synthesized under high-pressure conditions so far.…”

Section: Introductionmentioning

confidence: 99%

High‐Pressure Synthesis and Characterization of New Actinide Borates, AnB₄O₈ (An=Th, U)

Hinteregger

Hofer

Heymann

et al. 2013

Chemistry A European J

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New actinide borates ThB4O8 and UB4O8 were synthesized under high‐pressure, high‐temperature conditions (5.5 GPa/1100 °C for thorium borate, 10.5 GPa/1100 °C for the isotypic uranium borate) in a Walker‐type multianvil apparatus from their corresponding actinide oxide and boron oxide. The crystal structure was determined on basis of single‐crystal X‐ray diffraction data that were collected at room temperature. Both compounds crystallized in the monoclinic space group C2/c (Z=4). Lattice parameters for ThB4O8: a=1611.3(3), b=419.86(8), c=730.6(2) pm; β=114.70(3)°; V=449.0(2) Å3; R1=0.0255, wR2=0.0653 (all data). Lattice parameters for UB4O8: a=1589.7(3), b=422.14(8), c=723.4(2) pm; β=114.13(3)°; V=443.1(2) Å3; R1=0.0227, wR2=0.0372 (all data). The new AnB4O8 (An=Th, U) structure type is constructed from corner‐sharing BO4 tetrahedra, which form layers in the bc plane. One of the four independent oxygen atoms is threefold‐coordinated. The actinide cations are located between the boron–oxygen layers. In addition to Raman spectroscopic investigations, DFT calculations were performed to support the assignment of the vibrational bands.

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Section: Introductionmentioning

confidence: 99%

High‐Pressure Synthesis and Characterization of New Actinide Borates, AnB₄O₈ (An=Th, U)

Hinteregger

Hofer

Heymann

et al. 2013

Chemistry A European J

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“…In fact, many borates that occur naturally are found in evaporated deposits in arid regions. [7] This synthetic challenge can be overcome by either removing water entirely from the system in high-temperature solid-state reactions [8][9][10][11][12][13] or slow evaporations, [14] or by reducing the dielectric constant of water using hydrothermal conditions. We were initially interested in studying high-valence actinides, either An VI or An V (An = U, Np, Pu) and therefore avoided the potentially thermally reducing conditions of hightemperature solid-state reactions, and we diminished the potential for radiolytic reduction of the neptunium or plutonium in slow evaporation crystallizations that can take months to occur.…”

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confidence: 99%

Neptunium Diverges Sharply from Uranium and Plutonium in Crystalline Borate Matrixes: Insights into the Complex Behavior of the Early Actinides Relevant to Nuclear Waste Storage

et al. 2010

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The immobilization of actinides, such as neptunium and plutonium, in solid matrixes is being used as an approach for preventing their release into the environment during longterm storage. Many waste forms have been suggested as being suitable, including zircon, garnet, pyrochlore, synroc, and monazite, [1] and there is an ongoing debate concerning the best waste form for actinides. [2][3][4] Among the earliest and most widely utilized solids for the storage and transport of actinides are borosilicate glasses. [5,6] It has been recognized that both processing techniques and high actinide content in the glasses can lead to the formation of crystalline products within these glasses. [6] These crystals possess long-range order, are generally less soluble than the glasses, and display physicochemical properties that sharply contrast with the original glasses. Despite the importance of understanding the chemical nature of these crystals, very little is known about crystalline transuranium borates. In fact, there is not a single example present in crystallographic databases. In an effort to begin the process of understanding structure-property relationships in uranium, neptunium, and plutonium borates relevant to the development of advanced waste forms for the long-term storage of these radionuclides, we have prepared a large family of U VI borates, several highly unusual intermediate-or mixed-valent neptunium compounds, and a Pu VI borate that differs in bonding from its U VI counterparts.Actinide borates are difficult to prepare by traditional methods, because water competes very successfully with borate for inner-sphere coordination sites for these metals under most conditions. In fact, many borates that occur naturally are found in evaporated deposits in arid regions. [7] This synthetic challenge can be overcome by either removing water entirely from the system in high-temperature solid-state reactions [8][9][10][11][12][13] or slow evaporations, [14] or by reducing the dielectric constant of water using hydrothermal conditions. We were initially interested in studying high-valence actinides, either An VI or An V (An = U, Np, Pu) and therefore avoided the potentially thermally reducing conditions of hightemperature solid-state reactions, and we diminished the potential for radiolytic reduction of the neptunium or plutonium in slow evaporation crystallizations that can take months to occur. Instead, we utilized a boric acid flux as the reaction medium by adding excess boric acid and various alkali-metal or alkaline-earth-metal nitrates to small droplets (ca. 5-20 mL) of 1.8 m Np V , Np VI , or Pu VI chloride or nitrate. Much larger scale (ca. 1 g) reactions were performed with uranium using a similar methodology. After three days of heating at approximately 220 8C in an autoclave and subsequent cooling, a single translucent crystalline mass was isolated. Within this mass, crystals were observed for all actinides studied. These crystals were freed from the matrix by the addition of hot water, which dissolved the exces...

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mentioning

confidence: 99%

Neptunium Diverges Sharply from Uranium and Plutonium in Crystalline Borate Matrixes: Insights into the Complex Behavior of the Early Actinides Relevant to Nuclear Waste Storage

et al. 2010

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The immobilization of actinides, such as neptunium and plutonium, in solid matrixes is being used as an approach for preventing their release into the environment during longterm storage. Many waste forms have been suggested as being suitable, including zircon, garnet, pyrochlore, synroc, and monazite, [1] and there is an ongoing debate concerning the best waste form for actinides. [2][3][4] Among the earliest and most widely utilized solids for the storage and transport of actinides are borosilicate glasses. [5,6] It has been recognized that both processing techniques and high actinide content in the glasses can lead to the formation of crystalline products within these glasses.[6] These crystals possess long-range order, are generally less soluble than the glasses, and display physicochemical properties that sharply contrast with the original glasses. Despite the importance of understanding the chemical nature of these crystals, very little is known about crystalline transuranium borates. In fact, there is not a single example present in crystallographic databases. In an effort to begin the process of understanding structure-property relationships in uranium, neptunium, and plutonium borates relevant to the development of advanced waste forms for the long-term storage of these radionuclides, we have prepared a large family of U VI borates, several highly unusual intermediate-or mixed-valent neptunium compounds, and a Pu VI borate that differs in bonding from its U VI counterparts. Actinide borates are difficult to prepare by traditional methods, because water competes very successfully with borate for inner-sphere coordination sites for these metals under most conditions. In fact, many borates that occur naturally are found in evaporated deposits in arid regions. [7] This synthetic challenge can be overcome by either removing water entirely from the system in high-temperature solid-state reactions [8][9][10][11][12][13] or slow evaporations, [14] or by reducing the dielectric constant of water using hydrothermal conditions. We were initially interested in studying high-valence actinides, either An VI or An V (An = U, Np, Pu) and therefore avoided the potentially thermally reducing conditions of hightemperature solid-state reactions, and we diminished the potential for radiolytic reduction of the neptunium or plutonium in slow evaporation crystallizations that can take months to occur. Instead, we utilized a boric acid flux as the reaction medium by adding excess boric acid and various alkali-metal or alkaline-earth-metal nitrates to small droplets (ca. 5-20 mL) of 1.8 m Np V , Np VI , or Pu VI chloride or nitrate. Much larger scale (ca. 1 g) reactions were performed with uranium using a similar methodology. After three days of heating at approximately 220 8C in an autoclave and subsequent cooling, a single translucent crystalline mass was isolated. Within this mass, crystals were observed for all actinides studied. These crystals were freed from the matrix by the addition of hot water, which dissolved the exces...

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Structure du borate d`uranium UB2O6

Cited by 24 publications

References 0 publications

High‐Pressure Synthesis and Characterization of New Actinide Borates, AnB₄O₈ (An=Th, U)

High‐Pressure Synthesis and Characterization of New Actinide Borates, AnB₄O₈ (An=Th, U)

Neptunium Diverges Sharply from Uranium and Plutonium in Crystalline Borate Matrixes: Insights into the Complex Behavior of the Early Actinides Relevant to Nuclear Waste Storage

Neptunium Diverges Sharply from Uranium and Plutonium in Crystalline Borate Matrixes: Insights into the Complex Behavior of the Early Actinides Relevant to Nuclear Waste Storage

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Structure du borate d`uranium UB2O6

Cited by 24 publications

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High‐Pressure Synthesis and Characterization of New Actinide Borates, AnB4O8 (An=Th, U)

High‐Pressure Synthesis and Characterization of New Actinide Borates, AnB4O8 (An=Th, U)

Neptunium Diverges Sharply from Uranium and Plutonium in Crystalline Borate Matrixes: Insights into the Complex Behavior of the Early Actinides Relevant to Nuclear Waste Storage

Neptunium Diverges Sharply from Uranium and Plutonium in Crystalline Borate Matrixes: Insights into the Complex Behavior of the Early Actinides Relevant to Nuclear Waste Storage

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High‐Pressure Synthesis and Characterization of New Actinide Borates, AnB₄O₈ (An=Th, U)

High‐Pressure Synthesis and Characterization of New Actinide Borates, AnB₄O₈ (An=Th, U)