Synthesis and crystal structure of americium(V) dichromate, Cs3AmO2(Cr2O7)2·H2O

A new Am(V) chromate complex with outer-sphere cesium cation, Cs₃AmO₂(Cr₂O₇)₂·H₂O, was prepared from aqueous solution. Its composition and structure were determined by single crystal X-ray diffraction. The Am(V) atom has coordination surrounding in the form of a distorted pentagonal bipyramid with the O atoms of the AmO ₂ ⁺ group in apical positions. The equator of the bipyramid is formed by the O atoms of four dichromate groups and of the water molecule. The mean bond lengths (Å) are as follows: Am=O 1.802(5), Am-O(Cr₂O₇) 2.443(6), and Am-O_w 2.519(6). The Am(V) pentagonal bipyramids are combined via bidentate bridging Cr₂O ₇ ^2? anions into infinite chains [AmO₂(Cr₂O₇)₂H₂O] _n ^3? arranged in layers parallel to the series of diagonal planes (111). A system of hydrogen bonds links the chains in a layer and the layers with each other. The Cs cations are arranged between the layers, forming cationic interlayers.     

Synthesis and structure of Cs3[UO2(CH3COO)3]2(NCS)·H2O

The compound Cs₃[UO₂(CH₃COO)₃]₂(NCS)·H₂O (I) was synthesized and studied by IR spectroscopy and single crystal X-ray diffraction. Compound I crystallizes in the monoclinic system with the following unit cell parameters: a = 7.8286(9), b = 19.892(2), c = 20.050(2) Å, β = 94.527(2)°, space group P2₁/c, Z = 4, R = 0.0387. The uranium-containing structural units in crystals of I are mononuclear complexes [UO₂(CH₃COO)₃]^? belonging to crystal-chemical group AB ₃ ⁰¹ (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?) of uranyl complexes.     

Crystal structure of a double Np(V) ammonium propionate, NH4[(NpO2)3(C2H5COO)4(H2O)]·3H2O

The structure of NH₄[(NpO₂)₃(C₂H₅COO)₄(H₂O)]·3H₂O was studied by single crystal X-ray diffraction. The single crystals were prepared by hydrothermal synthesis. In the structure, there are three crystallographically independent Np atoms with different equatorial surrounding. All of them have CN 7; the coordination polyhedron is a distorted pentagonal bipyramid. Each NpO ₂ ⁺ cation is bonded to four other cations, acting simultaneously as a bidentate ligand and a coordination center for two other dioxocations. The cation-cation interactions result in formation of trigonal-hexagonal cationic networks.     

Synthesis and crystal structure of a new Np(V) oxalate, Na4(NpO2)2(C2O4)3·6H2O

A new oxalate complex, Na₄(NpO₂)₂(C₂O₄)₃·6H₂O, with the Np:C₂O₄ ratio of 2:3 was synthesized and studied by single crystal X-ray diffraction. In the crystal, the NpO ₂ ⁺ cations and oxalate anions are bound in open networks [(NpO₂)₂(C₂O₄)₃] _n ^4n- parallel to the bc plane. The Na(1) cations are accommodated in large voids of the neptunyl oxalate networks with the formation of crimped mixed-cation layers of the composition [Na₂(NpO₂)₂(C₂O₄)₃] _n ^2n- . The negative charge of the layers is compensated by the Na(2) cations arranged between the layers. The Np atoms have a pentagonal bipyramidal coordination surrounding with the equatorial plane formed by the oxygen atoms of three oxalate anions. The structure contains tridentate-bridging and tetradentate-bridging oxalate anions.     

Synthesis and structure of actinide(VII) compounds Rb3NpO4(OH)2·3H2O and Rb3PuO4(OH)2·3H2O

Actinide(VII) salts Rb₃[NpO₄(OH)₂]·3H₂O (I) and Rb₃[PuO₄(OH)₂]·3H₂O (II) were prepared as single crystals and examined by X-ray diffraction. The compounds are isostructural and crystallize in the monoclinic system, space group C2/c, Z = 4; unit cell parameters: a = 12.1544(3), b = 10.9942(2), c = 7.789(2) ?, ?? = 91.0930(11)° for I and a = 12.1254(3), b = 10.9506(2), c = 7.7699(2) ?, ?? = 90.8253(12)° for II. The main structural elements of I and II are centrosymmetrical anions [AnO₄(OH)₂]^3? forming together with water molecules, owing to strong hydrogen bonding, chains oriented along [101]. In [AnO₄(OH)₂]^3? anions, the central An(VII) atom has a tetragonal-bipyramidal oxygen surrounding. The An-O(OH) interatomic distances decrease in going from I to II owing to actinide contraction by a factor of ??2 more strongly than the An-O bond lengths in the equatorial planes of the bipyramids. The previously studied structure of Cs₃[NpO₄(OH)₂]·3H₂O (III) was refined.     

Crystal Structure of An(VI) Complexes with Succinate Anions, [PuO2(C4H4O4)(H2O)] and Cs2[(AnO2)2(C4H4O4)3]·H2O (An = U,Np, Pu)

Radiochemistry - Actinide(VI) complexes with succinate anions [PuO2(succ)(H2O)] and Cs2[(AnO2)2(succ)3]·H2O (An = U, Np, Pu), where succ = [C4H4O4]2 ?, were synthesized and studied by...     

Crystallization of salts M3[NpO4(OH)2]·nH2O (M = Na, K, Rb, Cs) from concentrated alkali solutions at low temperatures. Synthesis and structure of a new Np(VII) compound, Na3[NpO4(OH)2]·6H2O

Precipitation of salts M₃[NpO₄(OH)₂]·nH₂O (M = Na, K, Rb, Cs) from concentrated alkali solutions at low temperatures (about ?10°C) was studied. From solutions with [OH^?] > 9.5 M, these compounds are isolated as coarse black crystals in high yield without impurity of other phases. The K, Rb, and Cs salts crystallize in the form of the previously studied compounds K₃[NpO₄(OH)₂]·2H₂O and M₃[NpO₄(OH)₂]·3H₂O (M = Rb, Cs). In the case of Na, a new hydrate Na₃[NpO₄(OH)₂]·6H₂O was obtained, and its crystal structure was determined. Crystals of the hexahydrate consist of centrosymmetrical tetragonal-bipyramidal anions [NpO₄(OH)₂]^3?, crystallographically independent Na(1) and Na(2) cations, and water molecules. The coordination surrounding of the Np atom is characterized by noticeable difference (Δ = 0.0203 Å) in the Np-O bond lengths in the equatorial plane of the bipyramid. The [NpO₄(OH)₂]^3? anions are combined with the Na(2) cations to form infinite chains [Na(2)NpO₄(OH)₂(H₂O)₂]^2? in such a manner that the lateral edges of the anion are simultaneously the lateral edges of the Na(2) coordination polyhedron. Incorporation of one of the two crystallographically independent O atoms of the NpO₄ group into the Na(2) coordination surrounding is responsible for a noticeable difference in the Np-O bond lengths in the equator of the [NpO₄(OH)₂]^3? anion. The types of hydrogen bonding in the structures of Na3[NpO₄(OH)₂]·nH₂O (n = 0, 2, 4, 6) are compared.     

Sintering and crystallization of (SrO·SiO2)-(SrO·Al2O3·2SiO2) glass-ceramics

In the ternary SrO-Al₂O₃-SiO₂ system the pseudobinary join composition of 50 wt % SrO·SiO₂–50 wt % SrO·Al₂O₃·2SiO₂ (SS-SA2S) showed a glass melting temperature of 1500 °C and a crystallization peak temperature of 1100 °C. The (SS-SA2S) glass-ceramic pellets prepared by cold pressing and pressureless sintering, showed very low porosity. The (SS-SA2S) glass-ceramics containing B₂O₃ and those containing B₂O₃ and TiO₂ revealed crystallization peak temperatures of 1000 °C and unexpectedly high porosity. By applying Kissinger analyses to the DTA data the activation energy values for crystallization of the three glass-ceramics were determined to range from 196 to 255 kJ/mol. The Ozawa analyses on the DTA data gave the Avrami parameter values at 3.69 to 3.95. The X-ray diffraction (XRD) patterns from the three glass-ceramics revealed formation of the equilibrium crystalline phases of SrO·SiO₂ and SrO·Al₂O₃·2SiO₂ (monocelsian).     

Properties and structure of glasses in the system 10K2O·20BaO·70(SiO2, GeO2, B2O3)

Density, refractive index, glass transiton temperature and expansion coefficient of glasses in the system 10K₂O·20BaO·(70-x-y)SiO₂·xGeO₂·yB₂O₃ (mol %) have been determined. The structure of these glasses is discussed with emphasis on the shifts occurring in the boron and germanium coordination as a function of the relative concentrations of the three network-forming oxides. In GeO₂-rich glasses part of germanium is present as GeO₆ octahedra, which, upon the introduction of B₂O₃, are completely transformed into GeO₄ tetrahedra aty>10.     

Synthesis of Double Uranyl Phthalates of the M4[(UO2)4(μ3-O)2(C6H4C2O4)4] ⋅ nH2O Type with M = NH4, K, and Cs. Crystal Structure of K4[(UO2)4O2(C6H4C2O4)4] ⋅ 3H2O

Double U(VI) phthalates with NH ₄ ⁺ , K⁺, and Cs⁺ ions in the outer sphere were synthesized. The X-ray phase analysis shows that their structures are similar. Single crystals were prepared and the structure of K₄[(UO₂)₄(μ₃-O)₂(C₆H₄C₂O₄)₄] ? 3H₂O was solved. In the [(UO₂)₄O₂(C₆H₄C₂O₄)₄]^4? anions forming the main structural motif, each bridging oxygen atom μ₃-O combines one pentagonal and two hexagonal bipyramids, which, in turn, are combined in centrosymmetrical tetramers. The phthalate ions have coordination capacity equal to 3; each ligand coordinates U(1) in the bidentate fashion via one carboxy group and U(2) in the bidentate fashion to form a planar seven-membered chelate ring.     

Complexes with substituted 2,5-dihydroxy-p-benzoquinones: The inclusion compounds [Y(H2O)3]2 (C6Cl2O4)3·6.6H2O and [Y(H2O)3]2 (C6Br2O4)3·6H2O

Single crystal of [Y(H₂O)₃]₂ (C₆Br₂O₄)₃·6H₂O and [Y(H₂O)₃]₂ (C₆Cl₂O₄)₃·6.6H₂O were grown in aqueous silicagel. The compounds are in principle isostructural. In Y chloranilate one additional water site is occupied as verified by X-ray single crystal structure analysis. Y³⁺ is nine-coordinated by three water molecules and six oxygen atoms of the bischelating (C₆X₂O₄)²⁻ ions (XCl, Br). The coordination polyhedron is an only slightly distorted tri-capped trigonal prism. The connection of Y³⁺ with the dianions leads to infinite, corrugated layers. The layer stacking yields cage-like cavities in which water molecules are accomodated. Hydrogen bonds interlink adjacent layers. Further hydrogen bonds involve the entrapped water molecules. DSC measurements indicated a complicated dehydration process which caused right at the start destruction of the single crystals.     

Disordering of Pentacesium Trihydrogen Tetrasulfate in Cs5H3(SO4)4–SiO2 Composite Proton Electrolytes

(1 – x)Cs₅H₃(SO₄)₄ · yH₂O–xSiO₂ composite electrolytes were prepared in the composition range x = 0.3–0.9 and were characterized by impedance measurements, differential scanning calorimetry, and x-ray diffraction analysis. The results indicate that the introduction of fine SiO₂ particles stabilizes the high-conductivity, disordered (nearly amorphous) state of the salt, which is similar to that in pure Cs₅H₃(SO₄)₄ above the phase transition (>420 K). The conductivity of the composites is independent of SiO₂ content up to x = 0.7 and decreases at x 0.8 owing to percolation disruption. The disordering of Cs₅H₃(SO₄)₄ · yH₂O is reversible and is due to changes in the content of water of hydration.     

Reaction of Cd(NO3)2·4H2O with 4,4'–bipyridine (bpy) in MeOH solvent: synthesis and characterization of T-shaped [Cd(bpy)1.5(NO3)2]·3H2O,square grid [Cd(bpy)2(H2O)2](NO3)2·4H2O and linear polymeric [Cd(bpy)(H2O)2(NO3)2]

The influence of concentration of water and metal salt in the reaction between Cd(NO₃)₂·4H₂O and 4,4′–bipyridine in MeOH has been studied and three compounds namely, T-shaped [Cd(bpy)_1.5(NO₃)₂]·3H₂O, 1 square grid [Cd(bpy)₂(H₂O)₂](NO₃)₂ 4H₂O, 2 and one dimensional linear polymer, [Cd(bpy)(H₂O)₂(NO₃)₂], 3 were isolated quantitatively in this process. Compound 1 forms in MeOH at high dilution of the metal salt (5.0 mg/mL or less) and for the metal-to-ligand ratio 1:(1.5–2.0). Compound 2 forms exclusively in the concentration range, 17–33% for water in MeOH by volume and 12–28 mg/mL for the metal salt of the solution. Outside these limits, mixtures of 2 and 3 were isolated. For 1:1 ratio of metal salt to bpy, the linear polymer, 3 was obtained in major quantity and its formation was found to be independent of concentration of water or the metal salt. Compounds 1 and 2 have been characterized by X-ray crystallography. On heating all the compounds decompose through a common intermediate [Cd(bpy)(NO₃)₂] and finally to CdO as monitored by TG.     

Influence of hydrothermal treatment on the microstructure and oxidation resistance of a Zn4B2O7·H2O (4ZnO·B2O3·H2O) coating for C/C composites

Antioxidant modification for C/C composites by in situ hydrothermal synthesise at 140 °C of a 4ZnO·B₂O₃·H₂O crystallite coating has been successfully achieved. The influence of hydrothermal time on the phase composition, microstructure of the as-prepared Zn₄B₂O₇·H₂O (4ZnO·B₂O₃·H₂O), and its antioxidant modification for C/C composites were investigated. Samples were characterised by XRD, SEM, isothermal oxidation test and TG-DSC. Results show that, 4ZnO·B₂O₃·H₂O crystalline coating is achieved on the surface of C/C composites after the hydrothermal treatment at 140 °C for time in the range of 2–12 h. A smooth and crack-free 4ZnO·B₂O₃·H₂O layer can be obtained when the hydrothermal time reaches 8 h. Isothermal oxidation test demonstrates that the oxidation resistance of C/C composites is improved. The as-modified composites exhibit only 1.52 g·cm^?2 weight loss after oxidation at 600 °C for 15 h, while the non-modified one shows a 6.57 g·cm^?2 weight loss after only 10 h oxidation. For the uncoated C/C composite the oxidation rate is approximately linear with time (non-protective oxidation), thus at 15 h exposure one can estimate the mass loss to be 6.57 g·cm^?2 after 10 h for direct comparison with the coated samples.     

Photocatalytic Properties of the MgHPO4·3H2O and MgKPO4·6H2O Phosphates

Inorganic Materials - Magnesium double phosphates, MgHPO4·3H2O and MgKPO4·6H2O, isostructural with the minerals newberyite and struvite-K have been synthesized in powder form via...     

Model of the (PuO2)2SiO4·2H2O Crystal Structure,Based on Powder X-ray Diffraction Data

Plutonyl orthosilicate dihydrate (PuO₂)₂SiO₄·2H₂O was prepared by a hydrothermal procedure at 180°C. Its powder diffraction pattern (Guinier camera, CuK ₁ radiation) was indexed in the tetragonal crystal system: a 6.912(3), c 18.563(3) Å, space group I4₁/amd. The structure of (PuO₂)₂SiO₄·2H₂O is similar to the known structures of (UO₂)₂SiO₄·2H₂O and (UO₂)₂GeO₄·2H₂O, but differs in the mutual orientation of the chains of coordination polyhedra of actinide atoms (pentagonal bipyramids) sharing common equatorial edges.     

Effects of Y2O3 and La2O3 addition on the crystallization of Li2O·Al2O3·4SiO2 glass-ceramic

Effects of adding Y₂O₃ and La₂O₃ on the crystallization of -quartz solid solution (ss) and the subsequent -quartz ss to -spodumene transformation of Li₂O·Al₂O₃·4SiO₂ glass-ceramic were investigated. Adding 4 mol% YO_3/2 or 8 mol % LaO_3/2 effectively improved the control of the crystallization process of the glass. Y₂O₃ did not effectively induce bulk crystallization of -quartz ss, but can reduce the rate of surface crystallization. La₂O₃ completely suppressed the surface crystallization and promoted a uniform, bulk crystallization of -quartz ss. For both the Y₂O₃- and La₂O₃-doped glasses, the kinetics for glass crystallization to -quartz ss was delayed as the doping level increased. Except for the 8 mol % LaO_3/2-doped glass in which no -spodumene was formed, the kinetics for the -quartz ss to -spodumene transformation for the doped glasses was enhanced compared with that for the undoped glass. For the 4 and 8 mol % YO_3/2-doped compositions, the relative amount of -spodumene to -quartz revealed an anomalous decrease trend with heating temperature in a particular temperature range. This can be explained by the surface crystallization characteristic, which induced an overlap of crystallization and -quartz ss to -spodumene transformation. Glass doped with 8 mol % LaO_3/2 exhibited an Avrami exponent of about 2.4 and an activation energy for crystal growth of -quartz ss of about 418 kJ mol^–1.     

A single crystal X-ray diffraction study of Na4(UO2)4(i-C4H9COO)11(NO3)·3H2O

Synthesis and the results of IR and single crystal X-ray diffraction study of Na₄(UO₂)₄(i-C₄H₉COO)₁₁·(NO₃)·3H₂O are reported. The crystals are monoclinic; the unit cell parameters at 100 K are as follows: a = 13.697(2), b = 20.285(3), c = 15.991(3) Å, β = 103.760(3)°, space group P2₁, Z = 2, R = 0.0650. The uraniumcontaining structural units are mononuclear moieties [UO₂(i-C₄H₉COO)₃]^? and [UO₂(NO₃)(i-C₄H₉COO)₂]^?, belonging to crystal-chemical group AB ₃ ⁰¹ (A = UO ₂ ²⁺ , B⁰¹ = i-C₄H₉COO^? and NO ₃ ^? ) of uranyl complexes. The IR data are consistent with the results of the single crystal X-ray diffraction study. The influence of the carboxylate ligand volume on the structure of Na[UO₂L₃]·nH₂O crystals (L = acetate, n-butyrate, isovalerate ion) is analyzed.     

Crystal Structure of Neptunium(V) Phthalate (NpO2)2(OOC)2C6H4·4H2O

The crystal structure of (NpO₂)₂(OOC)₂C₆H₄·4H₂O [rhombic cell: a = 15.937(3), b = 26.922(5), c = 8.020(2) Å, space group Pbcn, Z = 8, V = 3441.0(12) ų, d _calc = 2.988 g cm^{- 3}, CAD4, MoK , graphite monochromator, 2934 independent reflections; R ₁ = 0.0352, wR ₂ = 0.0951] was studied. The structure consists of NpO₂ ⁺ cations, H₄C₆(COO)₂ ^{2 -} anions, and molecules of coordinated and crystallization water. The crystal lattice involves neutral layers [(NpO₂)₂(OOC)₂C₆H₄(H₂O)₃] _n parallel to the {101} plane. The dioxocations in these layers are bonded to each other to form cationic networks [the Np···Np distance is 3.911(1)-4.202(1) Å]. The coordination polyhedra of Np(1) and Np(2) are pentagonal bipyramids (CN 7). The point group of the neptunyl(V) groups is close to D _h. These groups are bidentate ligands in the cation-cation interaction. The Np = O bond lengths are 1.852(6) [Np(1)-O(1)], 1.849(7) [Np(1)-O(2)], 1.845(7) [Np(2)-O(3)], and 1.841(7) Å [Np(2)-O(4)]; the O = Np = O bond angles are 178.6(3)° [O(2)-Np(1)-O(1)] and 177.4(3)° [O(3)-Np(2)-O(4)]. The equatorial plane of the Np(1) bipyramid consists of two oxygen atoms of adjacent Np(2)O₂ ⁺ dioxocations, two water molecules, and a single oxygen atom of the phthalate anion. The equatorial plane of the Np(2) bipyramid consists of two oxygen atoms of adjacent Np(1)O₂ ⁺ dioxocations, two oxygen atom of the phthalate anion, and a single water molecule. The bond lengths in the equatorial plane of the bipyramid lie in the following ranges: Np-Oyl 2.373(7)-2.437(7) Å (average 2.397 Å) , Np-Ophth 2.360(7)-2.474(7) Å (average 2.431 Å), and Np-Owater 2.534(8)-2.558(9) Å (average 2.544 Å). The phthalate anions are tridentate bridging ligands binding neptunium atoms only within a single cationic network.