共查询到20条相似文献,搜索用时 15 毫秒
1.
New Np(VI) and Pu(VI) dimolybdates Rb2NpO2(MoO4)2·H2O (I), Cs2NpO2(MoO4)2·H2O (II), Cs2PuO2(MoO4)2·H2O (III), and Rb2PuO2(MoO4)2·H2O (IV) were synthesized under hydrothermal conditions. The crystal structures of the compounds were determined, and their absorption spectra in the UV, visible, and IR ranges were measured. The compounds crystallize in the monoclinic system. Their crystal structure is based on [AnO2(MoO4)2]n2n– anionic layers (An = Np, Pu) formed by (AnO2)O5 pentagonal bipyramids and MoO4 tetrahedra, sharing common vertices. Each An atom in the layer is bonded to other five An atoms via MoO4 tetrahedra with the formation of a 43432 network. The effect of the ionic radius of the outer-sphere cation on the parameters of the crystal structure and features of the absorption spectra is discussed. 相似文献
2.
Previously unknown arsenates of hexavalent U, Np, and Pu, (H3O)[(UO2)(AsO4)]·3H2O (I), (H3O)· [(NpO2)(AsO4)]·3H2O (II), and (H3O)[(PuO2)(AsO4)]·3H2O (III), were synthesized under hydrothermal conditions. The crystal structure of the compounds was determined, and their absorption spectra were measured. The compounds crystallize in tetragonal space group P4/nmm. 相似文献
3.
The crystal structure of a previously unknown Np(V) sesquioxalate, Na4(NpO2)2(C2O4)3·2H2O was studied. The crystal structure consists of neptunyl(V) cations, sodium cations, oxalate anions, and water molecules of crystallization. Neptunyl(V) cations and oxalate ions form anionic chains [(NpO2)2(C2O4)3] n 4n? . The coordination polyhedron (CP) of Np (pentagonal bipyramid) contains two apical “yl” oxygen atoms and five equatorial O atoms of three oxalate ions. The CP of Na(1) and Na(2) cations are combined through the common edges into zigzag chains in the [010] direction. Two independent oxalate ions are tridentate and tetradentate ligands. 相似文献
4.
Crystalline uranyl phthalate dihydrate was prepared by hydrothermal method, and its crystal structure was determined. The crystal structure consists of infinite chains [UO2LH2O]n coupled in bands [(UO2)2L2(H2O)2]n [L = C6H4(COO)2], between which water molecules of crystallization are located. The coordination polyhedron of uranium atoms is a pentagonal bipyramid with the equatorial plane formed by oxygen atoms of three phthalate ions and coordinated water molecule. The U-O bond length in the UO
2
2+
cations is 1.766 . The coordination capacity of the ligands is 4. Anions are bidentately coordinated to uranium atoms to form seven-membered rings. Being bridging ligands, phthalate ions combine the neighboring uranium atoms into chains through one carboxy group, and the chains into bands, through the other carboxy group.Translated from Radiokhimiya, Vol. 46, No. 6, 2004, pp. 513–515.Original Russian Text Copyright © 2004 by Charushnikova, Krot, Starikova. 相似文献
5.
Mixed-anion compounds of the general composition [(CH3)4N][(AnO2)(CrO4)(NO3)], where An = U, Np, and Pu, were synthesized and structurally characterized. The structural motif of these compounds is based on anionic ribbons of the composition [AnO2(NO3)(CrO4)]nn–, consisting of seven-vertex An polyhedra linked via oppositely oriented CrO4 tetrahedra and NO3 groups acting in the An polyhedra as terminal bidentate ligands. Every four anionic ribbons form channels oriented along b-axis. Tetramethylammonium cations linked with the O atoms of the ribbons by hydrogen bonds are located in these channels. Actinide contraction is observed in the series U–Np–Pu. It is manifested in a regular decrease in the interatomic distances in the An polyhedra, in parameters b and c, and in the unit cell volume. 相似文献
6.
A new Pu(VII) compound, K3PuO4(OH)2·2H2O, was synthesized, and its structure was studied by single crystal X-ray diffraction. This compound is isostructural to the previously described K3NpO4(OH)2·2H2O. The structure of the latter compound was redetermined to obtain more precise interatomic distances in the NpO2(OH) 2 3? anion. Changes in An-O bond lengths in the tetragon-bipyramidal coordination polyhedron of the compounds K3AnO4(OH)2·2H2O in going from Np(VII) to Pu(VII) were considered. 相似文献
7.
The previously unknown Np(VII) compound Li[C(NH2)3]2[NpO4(OH)2]·6H2O (I), containing organic cations, was synthesized and studied by single crystal X-ray diffraction. In contrast to the relatively numerous structurally characterized salts of [NpO4(OH)2]3– anions with Na+, K+, Rb+, and Cs+ cations, which were prepared only from strongly alkaline media, crystals of I were isolated from solutions with a very low concentration of OH– ions (about 0.1 M). The compound is relatively stable in storage in the dry form, but is strongly hygroscopic. In the structure of I, there are two independent Np(VII) atoms with the oxygen surrounding in the form of tetragonal bipyramids. In contrast to the other salts of the [NpO4(OH)2]3– anions with singlecharged alkali metal cations, the C(NH2) 3 + ions and hydrated Li+ ions in I interact with the oxygen surrounding of Np(VII) only via hydrogen bonds of types Ow–H···O and N–H···O with the formation of a three-dimensional H-bond network. 相似文献
8.
Banjong Boonchom 《International Journal of Thermophysics》2010,31(2):416-429
The kinetics of thermal dehydration of Mg3(PO4)2 · 8H2O was investigated using thermogravimetry at four different heating rates. The activation energies of the dehydration step
of Mg3(PO4)2 · 8H2O were calculated through the isoconversional Ozawa and Kissinger-Akahira-Sunose (KAS) methods and iterative methods, which
were found to be consistent and indicate a single mechanism. The possible conversion function of the dehydration reaction
for Mg3(PO4)2 · 8H2O has been estimated through the Coats and Redfern integral equation, and a better kinetic model such as random nucleation
of the “Avrami–Erofeev equation (A
3/2 model)” was found. The thermodynamic functions (ΔH*, ΔG*, and ΔS*) of the dehydration reaction are calculated by the activated complex theory and indicate that it is a non-spontaneous process
when the introduction of heat is not connected. 相似文献
9.
Single crystals of [UO2(OOC)2CH2(H2O)]·2H2O (I) were prepared by recrystallization of finely crystalline uranyl malonate trihydrate under hydrothermal conditions. The crystal structure of I consists of electroneutral [UO2(OOC)2CH2(H2O)]n layers and water molecules located between them. The uranium coordination number is 7. The uranium coordination polyhedron is a distorted pentagonal bipyramid with the oxygen atoms of the uranyl group in the apices. The equatorial plane is occupied by four O atoms of three malonate ligands and the water molecule. The malonate anion is coordinated in the bidentate fashion to one uranyl ion to form a six-membered ring and in the monodentate fashion to two other uranyl ions. 相似文献
10.
The structure of a double neptunium(V) lanthanum nitrate, La(NpO2)3(NO3)6·nH2O, was studied by single crystal X-ray diffraction. Each neptunyl(V) ion in the structure of the compound is bonded to four other neptunyl(V) ions, acting simultaneously as a bidentate ligand and as a coordination center for two other dioxocations. The cation-cation interaction of the neptunyl(V) ions results in formation of trigonal-hexagonal cationic networks. The surrounding of each Np atom also includes two bidentate nitrate ions. The CN of the Np atom is 8, and the coordination polyhedron is a distorted hexagonal bipyramid. The La3+ cations are surrounded only by water molecules. 相似文献
11.
D. M. Zuev E. S. Klimashina P. V. Evdokimov Ya. Yu. Filippov V. I. Putlyaev 《Inorganic Materials》2018,54(1):87-95
Highly permeable macroporous implants of various architectures for bone grafting have been fabricated by thermal extrusion 3D printing using highly filled β-Ca3(PO4)2/poly(D,L-lactide) (degree of filling up to 70 wt %) and β-Ca3(PO4)2/poly(ε-caprolactone) (degree of filling up to 70 wt %) composite filaments. To modify the surface of the composite macroporous implants with the aim of improving their wettability by saline solutions, we have proposed exposing them to a cathode discharge plasma (2.5 W, air as plasma gas) in combination with subsequent etching in a 0.5 M citric acid solution. It has been shown that the main contribution to changes in the wettability (contact angle) of the composites is made by the changes produced in their surface morphology by etching in a low-temperature plasma and citric acid. An alternative approach to surface modification of the composites is to produce a carbonate hydroxyapatite layer via precipitation from a simulated body fluid solution a factor of 5 supersaturated relative to its natural analog (5xSBF). 相似文献
12.
The effect of microwave radiation (MWR) on the decomposition of UO2(NO3)2·6H2O was studied. Determination of [UO 2 2+ ] and [NO 3 ? ], and also of the molar ratio NO 3 ? : UO 2 2+ in various fractions of the decomposition product showed that the mechanism of the UO2(NO3)2·6H2O decomposition under the action of MWR differs from the mechanism of its decomposition under common convection heating. The main precursor of UO3 as product of UO2(NO3)2·6H2O decomposition under the action of MWR is uranyl hydroxonitrate UO2(OH)NO3 formed already in the first minutes of the irradiation. In contrast to the thermolysis under convection heating, UO2(NO3)2 or its hydrates were not detected as intermediates. The mechanism of the UO2(NO3)2·6H2O decomposition under the action of MWR can be presented by the reactions UO2(NO3)2·6H2O → UO2(OH)NO3 + 5H2O + HNO3 and UO2(OH)NO3 → UO3 + HNO3. The solubility of UO2(OH)NO3 in H2O at 20°C was estimated experimentally at 6.83 × 10?2 M. 相似文献
13.
New complexes of hexavalent U, Np, and Pu of the composition [UO2(bipy)(cbc)2] (I) and [AnO2(bipy)(cbc)2]·0.5(bipy) [An = Np (II) and Pu (III)] with cyclobutanecarboxylic acid anions C4H7COO– and 2,2′-bipyridine (bipy) were synthesized, and their structures were studied. The An atoms in I–III have the coordination surrounding in the form of distorted hexagonal bipyramids with the О atoms of AnO22+ cations in the apical positions. The equatorial plane of the bipyramids is constituted by the O atoms of two C4H7COO– anions and N atoms of bipy. 相似文献
14.
Products of UO2(NO3)2·6H2O decomposition under the action of microwave radiation (MWR) were studied by thermal gravimetric analysis, X-ray phase analysis,
IR spectroscopy, and electron microscopy. The results of physicochemical studies of these decomposition products were compared
to the published data for various uranium compounds, including UO2(NO3)2·6H2O. Apart from gaseous products, the final products of decomposition of 2–10 g of UO2(NO3)2·6H2O under the action of MWR for 35 min (the maximal process temperature, 170–320°C, is attained in the first 2–5 min of irradiation)
are uranyl hydroxonitrate UO2(OH)NO3 and uranium trioxide UO3 or their hydrates. The results obtained are consistent with the mechanism suggested in our previous paper and involving the
reactions (1) UO2(NO3)2·6H2O → UO2(OH)NO3 + 5H2O + HNO3 and (2) UO2(OH)NO3 → UO3 + HNO3. The physicochemical study confirms the conclusions on the composition of products of UO2(NO3)2·6H2O decomposition under the action of MWR, made previously on the basis of chemical studies. The only precursor of UO3 in microwave treatment of UO2(NO3)2·6H2O is UO2(OH)NO3 (or its hydrates). This is the main difference between the courses of uranyl nitrate decomposition under the conditions of
microwave and convection heating. In the latter case, uranyl nitrate and its hydrates also participate in the formation of
UO3. 相似文献
15.
A. V. Logvinova B. G. Bazarov Yu. L. Tushinova J. G. Bazarova 《Inorganic Materials》2017,53(12):1286-1292
We have studied phase relations in the K2MoO4–Ln2(MoO4)3–Zr(MoO4)2 (Ln = La–Lu, Y) systems by the method of “intersecting cuts,” identified pseudobinary joins in their composition triangles, and constructed their phase compatibility diagrams. The systems have been shown to contain new ternary molybdates with the general formula K5LnZr(MoO4)6 (Ln = Dy–Lu and Y). The thermal characteristics of the synthesized compounds have been studied by differential scanning calorimetry in the temperature range 25–700°C. The new ternary molybdates crystallize in a trigonal structure (sp. gr. R\(\bar 3\)c, Z = 6). 相似文献
16.
Pickup DM Wetherall KM Knowles JC Smith ME Newport RJ 《Journal of materials science. Materials in medicine》2008,19(4):1661-1668
Glasses from the CaO–TiO2–P2O5 system have potential use in biomedical applications. Here a method for the sol–gel synthesis of the ternary glass (CaO)0.25(TiO2)0.25(P2O5)0.5 has been developed. The structures of the dried gel and heat-treated glass were studied using high-energy X-ray diffraction.
The structure of the binary (TiO2)0.5(P2O5)0.5 sol–gel was studied for comparison. The results reveal that the heat-treated (CaO)0.25(TiO2)0.25(P2O5)0.5 glass has a structure based on chains and rings of PO4 tetrahedra, held together by a combination of electrostatic interaction with Ca2+ ions and by corner-sharing oxygen atoms with TiO6 octahedra. In contrast, the (TiO2)0.5(P2O5)0.5 glass has a structure based on isolated P2O7 units linked together by corner-sharing with TiO6 groups. The results suggest that both the dried gels possess open porous structures. For the (CaO)0.25(TiO2)0.25(P2O5)0.5 sample there is a significant increase in Ca–O coordination number with heat treatment. 相似文献
17.
O. P. Krivoruchko T. V. Larina V. F. Anufrienko I. Yu. Molina E. A. Paukshtis 《Inorganic Materials》2009,45(12):1355-1361
We have synthesized nanoparticulate cobalt(II) hydroxide containing Co2+ in tetrahedral oxygen coordination (Co Td 2+ ), atypical of such systems: nano- [Co(OH)2(H3O) δ + ]δ+. The (Co Td 2+ ) coordination in the hydroxide is inferred from its electronic diffuse reflectance spectrum, which shows a multiplet of strong absorption bands at 14500, 15000, and 16000 cm?1 (4 A 2(F)-4 T 1(P) transition). Nanoparticulate cobalt(II) hydroxide forms in a weakly acidic medium under essentially nonequilibrium conditions due to supersaturation (by three to four orders of magnitude) with the starting reagents (CoCl2 and LiOH) at the instant of the formation of the poorly soluble phase Co(OH)2. Presumably, colloidal particles of nanoparticulate cobalt(II) hydroxide in a weakly acidic aqueous medium have a positive surface charge, compensated by a counter-ion (Cl?) layer: nano-[Co(OH)2(H3O) δ + ]δ+ · δCl?. The XRD patterns of pastes (gels) containing this hydroxide show three broad-ened lines with d = 5.31 (2θ = 16.7°), 2.77 (2θ = 32.3°), and 2.32 Å (2θ = 38.8°). According to small-angle X-ray scattering data, nano-[Co(OH)2(H3O) δ + ]δ+ has a narrow particle size distribution (1.0–2.0 nm). Synthesis and storage conditions are identified which ensure stabilization of the electronic state and particle size of nano-[Co(OH)2(H3O) δ + ]δ+ for a long time. 相似文献
18.
J. Wang H. N. Dong D. F. Li J. Dong Z. C. Guo 《Journal of Superconductivity and Novel Magnetism》2010,23(6):1181-1183
Lanthanum magnesium double nitrate (LMN) crystals can be used as material for adiabatic demagnetization, magnetic thermometers
and a proton spin-polarized target in both physics and polarized neutron diffraction. In the past years, the double nitrates
doped with transition metal or rare earth ions have been studied by experimental and theoretical methods. For instance, the
electronic paramagnetic resonance (EPR) g factors of the Ce3+ ions in La2Mg3(NO3)12⋅24H2O crystal were measured decades ago. But until now, these useful experimental results have not been theoretically explained.
In this work, The EPR g factors of the trigonal Ce3+ centers in La2Mg3(NO3)12⋅24H2O are theoretically studied from the perturbation formulae of the EPR parameters for a 4f1 ion under the trigonal symmetry crystal field. The used crystal parameters are obtained from the superposition model and
the local structure of the studied crystal. The calculated results are reasonably constant to the observed values. The results
are discussed. 相似文献
19.
Two procedures for preparing the compounds M(NpO4)2·nH2O (M = Mg, Ca, Sr, Ba) using boric acid were suggested. In the first procedure, samples of freshly prepared salts M3(NpO5)2·nH2O (M = Ca, Sr, Ba) are treated with excess 0.5 M H3BO3 with vigorous stirring. In the process, the initially light green salts rapidly transform into black products of the general composition M(NpO4)2·nH2O. In the second procedure, a measured volume of a Np(VII) solution with a known LiOH concentration was added to excess 0.5 M H3BO3 solution containing a calculated amount of Mg, Ca, Sr, or Ba nitrate. The reaction yields black precipitates of the same compounds as in the previous case. After washing with water and drying in an oxygen stream, the final products contain a small impurity of Np(VI). The IR spectra suggest that the compounds obtained are structurally related to the previously studied salts MNpO4 (M = K–Cs), i.e., in their lattices there are neptunium–oxygen layers built of NpO23+ cations and bridging O atoms. New data on the properties of the compounds M3(NpO5)2·nH2O with M = Ca, Sr, and Ba were also obtained. 相似文献
20.
Nickel oxide particles were prepared by spray pyrolysis of aqueous solutions of NiSO4·6H2O and Ni(NO3)2·6H2O. In spray pyrolysis reactor hollow salt particles initially formed were collapsed by decomposition to reduce their size.
For NiSO4·6H2O less hollowness of the primitive particles and its higher decomposition temperature made the oxide particles highly spherical
with very smooth surface. On the other hand the particles prepared from Ni(NO3)2·6H2O were so hollow and fragile with rough surface since they were formed on the liquid pool of the salt melt. The particle size
decreased with the furnace set temperature while increased with the initial salt concentration. Single oxide particle was
composed of many small nuclei without sintering whose size varied with the rate of decomposition. The crystallinity of the
particles increased with both temperature and the initial salt concentration. Preliminary drying in diffusion dryer fixed
the size of the oxide particles from NiSO4·6H2O at that of the primitive particles, independent of the temperature. However, by the preliminary drying the particles from
Ni(NO3)2·6H2O became more hollow and fragile, whose sizes decreased with the temperature. 相似文献