ChemInform Abstract: High-Temperature, High-Pressure Hydrothermal Synthesis, Characterization, and Structural Relationships of Mixed-Alkali Metals Uranyl Silicates.

ChemInform ◽  
2016 ◽  
Vol 47 (25) ◽  
Author(s):  
Yi-Hsin Chen ◽  
Hsin-Kuan Liu ◽  
Wen-Jung Chang ◽  
Der-Lii Tzou ◽  
Kwang-Hwa Lii
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Hydrothermal Synthesis ◽  
Alkali Metals ◽  
Mixed Alkali ◽  
Structural Relationships ◽  
Uranyl Silicates ◽  
High Temperature High Pressure

scholarly journals High-T, High-P Hydrothermal Synthesis of Uranium Silicates and Germanates

2014 ◽  
Vol 70 (a1) ◽  
pp. C759-C759
Author(s):  
Kwang-Hwa Lii
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Hydrothermal Synthesis ◽  
Alkali Metals ◽  
Spent Nuclear Fuel ◽  
Mixed Valence ◽  
Oxidation States ◽  
Uranyl Silicates ◽  
High Pressure Reaction ◽  
High Temperature High Pressure

Most uranium minerals can be classified as oxidized species in which U is fully oxidized to U(VI), and reduced species, in which U occurs primarily as U(IV). Uranyl silicates are an important group of uranium(VI) minerals in the altered zones of many uranium deposits [1]. Uranyl silicates have also received attention because they form when spent nuclear fuel interacts with water containing silicon under oxidizing conditions. One naturally occurring uranium(IV) silicate exists, namely coffinite (USiO4), which is the most important ore mineral for uranium after uraninite. Numerous synthetic uranium(VI) silicates and germanates containing organic amines or alkali metals as countercations have also been reported [2]. In contrast to the uranium(VI) compounds, the chemistry of materials containing uranium(V) is considerably less developed owing to the tendency of U(V) to either oxidize to U(VI) or disproportionate to U(IV) and U(VI). We have synthesized a pentavalent-uranium silicate and a germanate by a high-temperature, high-pressure hydrothermal method in gold ampoules contained in a high-pressure reaction vessel at ca. 600 °C and 170 MPa [3a,b]. Following the synthesis of the U(V) compounds, a number of mixed-valence uranium silicates and germanates have been synthesized, for example, a mixed-valence uranium(IV,V) silicate, Cs2K(UO)2Si4O12 [3c], a uranium(IV,VI) germanate, Cs8U(UO2)3(Ge3O9)3·3H2O [3d], uranium(V,VI) silicates and germanates, A3(U2O4)Ge2O7 (A = Rb, Cs) and [Na9F2][(UO2)3(Si2O7)2] [3e,f], and a uranium(IV,V,VI) silicate, Na7UO2(UO)2(UO2)2Si4O16 [3g] in which three oxidation states of uranium co-exist in one compound. In addition, tetravalent-uranium compounds, Cs2USi6O15 and Cs4UGe8O20 [3h,i], were also synthesized. All members in the family of uranium silicates and germanates with the oxidation states of uranium from +4 to +6 have been observed. In this presentation the high-temperature, high-pressure hydrothermal synthesis, crystal structures, and XPS spectroscopy of these interesting compounds will be reported.

High-Temperature, High-Pressure Hydrothermal Synthesis, Characterization, and Structural Relationships of Layered Uranyl Arsenates

2014 ◽  
Vol 53 (17) ◽  
pp. 9065-9072 ◽  
Author(s):  
Hsin-Kuan Liu ◽  
Eswaran Ramachandran ◽  
Yi-Hsin Chen ◽  
Wen-Jung Chang ◽  
Kwang-Hwa Lii
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Hydrothermal Synthesis ◽  
Structural Relationships ◽  
High Temperature High Pressure

High temperature—high pressure neutron scattering experiments on expanded liquid alkali metals

1990 ◽  
Vol 4 (1-6) ◽  
pp. 549-551
Author(s):  
R. Winter ◽  
W.-C. Pilgrim ◽  
F. Hensel ◽  
T. Bodensteiner ◽  
W. Gläser
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Neutron Scattering ◽  
Alkali Metals ◽  
Liquid Alkali Metals ◽  
High Temperature High Pressure

High-temperature, high-pressure hydrothermal synthesis, crystal structure, and infrared and NMR spectroscopy of a barium lead borate with a 2D layer structure: [Ba3Pb(H2O)][B11O19(OH)3]

2020 ◽  
Vol 49 (19) ◽  
pp. 6220-6226
Author(s):  
Yu-Chen Kuo ◽  
Hsin-Kuan Liu ◽  
Sue-Lein Wang ◽  
Kwang-Hwa Lii
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
Hydrothermal Synthesis ◽  
Nmr Spectroscopy ◽  
Layer Structure ◽  
Lead Borate ◽  
Fundamental Building Block ◽  
Pressure Form ◽  
High Temperature High Pressure

The structure of the hydrothermally synthesized barium lead borate contains an unusual fundamental building block, 2Δ4□:〈Δ2□〉–〈3□〉Δ, which was also found in the high-pressure form of CaB2O4 synthesized at 900 °C under a pressure of 15–25 kbar.

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