Oscillatory extraction — New method of similar elements and isotopes separation

The new separation extraction method was created based on oscillatory extraction/stripping process in two extractors coupled by bulk liquid membrane (LM). The experimental setup to investigate the kinetics of non-stationary processes was built in Saint Petersburg State Institute of Technology in the Rare Earth Department. To induce the oscillatory extraction-stripping process the cyclic Belousov-Zhabotinsky (BZ) reaction or cyclic electrochemical oxidation-reduction was used. The possibility to use oscillatory extraction approach to separate similar elements by using the differences in their kinetic properties is demonstrated. The experimental evidences of uranium, cerium and neodymium isotopes separation were obtained. The separation of ¹⁴²Ce and ¹⁴⁰Ce isotopes between aqueous phases of two extractors coupled by bulk LM in the experiments with cyclic chemical oxidation/reduction with enrichment factor about 2.5% was observed. Under the same conditions the separation of the Nd isotopes (heavy isotopes of Nd — ¹⁴⁴Nd, ¹⁴⁵Nd, ¹⁴⁶Nd, ¹⁴⁸Nd, and ¹⁵⁰Nd from the light isotope — ¹⁴³Nd) in the same experiment with enrichment factor about 0.7–1.4% was observed.     

Выделение меченых соединений методом препаративной хроматографии

Mica Track Microfilters (MTM) are successful applied to separate two different and strongly mixed liquid phases (emulsion). The organic and the inorganic phase of the emulsion were 30% tributyl phosphate (TBP) in kerosene and 2 N HNO₃ (or H₂O), respectively. Mica filters with sharp edges (i.e. etched with H₂F₂) and having pore sizes k of 8 μm > k > 2 μm are used to get under some well defined conditions a rather complete extraction of the aqueous phase out of the emulsion. The system was calibrated with the pure phases (water as well as TBP in kerosene), and the liquid throughput is shown as a function of the pore size of the filter. The throughput depends mainly on the pore size and not that much on the kind of liquid, it is slightly larger for water as compared to that of TBP in kerosene.     

The influence of tributyl phosphate on molybdenum extraction with solutions of dibutyl phosphoric acid

Comparative investigations were carried out to study the influence of TBP on Mo extraction by HDBP solutions in xylene and TBP in xylene. The dependences of D_Mo on HNO₃ concentration for both HDBP and D2EHPA have minima at about 3 mol/L HNO₃. This shows similar extraction properties of HDBP and D2EHPA. The presence of TBP in the solvent results in the reduction of Mo extraction and in an increase in the formal slopes of the falling and rising parts of the logD_Mo — log[HNO₃] curve from −0.5 and +2 up to −2 and +4. Solvent loading curves with Mo show that in the absence of TBP a molybdenum solvate with two molecules of HDBP is formed at low acidity. Anomalous increase in the maximum solvent loading in the presence of TBP is caused by the ability of TBP to extract Mo from oversaturated low acidity solutions following the acidic mechanism. A molybdenum solvate with two HDBP molecules and one HNO₃ molecule is possibly formed at high acidity. A flowsheet for Mo recovery from HLW with HDBP-TBP solvent was tested in centrifugal contactors.     

Binding of rare earth metal complexes with an ofloxacin derivative to bovine serum albumin and its effect on the conformation of protein

The water-soluble Pr (Ⅲ) and Nd (Ⅲ) complexes with an ofloxacin derivative have been prepared and characterized. The single-crystal X-ray diffraction showed that the Pr (III) and Nd (III) complexes have the similar molecular structure. Under physiological pH condition, the effects of [PrL(NO₃)₂(CH₃OH)](NO₃) and [NdL(NO₃)₂(CH₃OH)](NO₃) on bovine serum albumin (BSA) were examined using fluorescence spectroscopy in combination with UV-vis absorbance and circular dichroism (CD) spectra. The result reveals that the quenching mechanism of fluorescence of BSA by two complexes is a static quenching process and the number of binding sites is about 1 for both. The thermodynamic parameters (ΔH=−14.52 kJ mol⁻¹, ΔS=56.54 J mol⁻¹ K⁻¹ for [PrL(NO₃)₂(CH₃OH)](NO₃) and ΔH=−24.63 kJ mol⁻¹, ΔS=22.07 J mol⁻¹ K⁻¹ for [NdL(NO₃)₂(CH₃OH)](NO₃)) indicate that hydrophobic and electrostatic interactions are the main binding force in the complexes-BSA system. The binding average distance between complexes and BSA was obtained on the basis of Förster's theory. In addition, it was proved by the CD spectra that the BSA secondary structure was changed in the presence of complexes in an aqueous solution.     

Effect of post-sintering annealing on microstructure and coercivity of Al85Cu15-added Nd-Fe-B sintered magnets

Effects of post-sintering annealing on the microstructure and coercivity have been investigated for the Al₈₅Cu₁₅-added (Pr, Nd)_14.8Fe_78.7B_6.5 sintered magnets. It is found that the optimum annealing temperature at which the coercivity _iH_c reaches a maximum decreases from 550 °C for the magnets added with 0.3% and 0.6% Al₈₅Cu₁₅ to 480 °C for the magnets added with 0.9% and 1.2% Al₈₅Cu₁₅. The decrease in optimum annealing temperature is related to the precipitation of Al-Cu or (Pr, Nd)−Cu liquid phase among (Pr, Nd)-rich phases during annealing. Existence of Al-Cu or (Pr, Nd)−Cu liquid phase is beneficial to dissolve the irregularities of (Pr, Nd)₂Fe₁₄B grain interface and increase the quantities of (Pr, Nd)-rich phases at the grain boundary, thus optimizing the grain boundary microstructure. The modifications of the microstructure are helpful to decouple the exchange interaction between (Pr, Nd)₂Fe₁₄B hard magnetic grains, thereby increasing the coercivity.     

The influence of dibutyl phosphoric acid on zirconium extraction with diluted tributyl phosphate and the role of uranyl nitrate

Distribution coefficients of zirconium (D_Zr) in the 30% TBP — aqueous HNO₃ solution extraction system rise 1000–2000 times with the increase of the dibutyl phosphoric acid (HDBP) concentration from 0 to 0.01–0.08 mol/L. A solvate with the molar ratio Zr: HDBP=1 was found by IR spectroscopy and analytic methods in the initial range of HDBP concentration. In the presence of U(VI) D_Zr decreases with the growing U concentration, however, the ratio of Zr distribution coefficient in the presence of HDBP (D_AZr) to D_Zr determined in its absence, R_Zr=D_AZr/D_Zr, is rather high. Function of enhancement (F) was introduced for the evaluation of simultaneous influence of U and HDBP on Zr extraction. An increase of the U concentration resulted first in the decrease in F_Zr, and then in its increase. The rising part of the F_Zr curve was more noticeable at a molar excess of Zr over HDBP. The mechanism of Zr extraction by 30% TBP solution in the presence of HDBP when Zr is in excess to HDBP indicates the formation of the solvate with the ratio Zr: HDBP=1; in the presence of U(VI) the complex with the same ratio is formed by the HDBP interaction with U in the system with a great excess of both HDBP and Zr.     

Preparation of Nd-doped BiFeO3 films and their electrical properties

The Nd-doped BiFeO₃ thin films were prepared on SnO₂(FTO) substrates spin-coated by the sol–gel method using Nd(NO₃)₃·6H₂O, Fe(NO₃)₃·9H₂O and Bi(NO₃)₃·5H₂O as raw materials. The microstructure and electric properties of the BiFeO₃ thin films were characterized and tested. The results indicate that the diffraction peak of the Nd-doped BiFeO₃ films is shifted towards right as the doping amounts are increased. The structure is transformed from the rhombohedral to pseudotetragonal phase. The crystal grain is changed from an elliptical to irregular polyhedron. Structure transition occurring in the Bi_0.85Nd_0.15FeO₃ films gives rise to the largest Pr of 64 μC/cm². The leakage conductance of the Nd doped thin films is reduced. The dielectric constant and dielectric loss of Bi_0.85Nd_0.15FeO₃ thin film at 10 kHz are 190 and 0.017 respectively.     

Superionic conductivity of the heterovalent solid solutions R 1−x M x F 3−x (R=REE, M=Ca, Ba) with tysonite-type structure

The fluorine-ion conductivity of anion-deficient solid solutions R _1−x Ca_xF_3−x and R _1−x Ba_xF_3−x having the tysonite (LaF₃) structure was investigated by the impedance spectroscopy method. R _1−x Ca_xF_3−x (R=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho) and R _1−x Ba_xF_3−x (R=La, Pr, Nd) single crystals were grown from the melt by the Bridgman-Stockbarger method. The electrophysical measurements were performed in the frequency range 5−5×10⁵ and temperature range 300–700 K. The temperature dependences of the electrical conductivity for the crystals studied is determined by the migration of fluorine anions along various structural positions. It is shown that, from the standpoint of increasing the conductivity of tysonite matrices RF₃ (R=La, Pr, Nd), doping by CaF₂ and BaF₂ is less promising than SrF₂. Fiz. Tverd. Tela (St. Petersburg) 41, 638–640 (April 1999)     

Quantum-chemical features of Ln—O interatomic interactions in LnNbxOy (Ln=La, Ce, Pr, Nd, Pm, Sm, Eu) systems

Properties of the lanthanide—oxygen bonds in lanthanide niobates LnNb₇O₁₂(Ln=La, Ce, Pr, Nd, Pm, Sm, Eu) have been studied using the ab initio cluster X _α discrete variational method with two different basis sets of molecular orbitals. It has been found that the structural instability of lanthanides LnNb₇O₁₂ (Ln=Nd, Sm) observed in experiments is due to the combined effect of decrease in the stability of [LnO₈] cluster and increase in quantum-mechanical Ln—O repulsion when the minimum near neodymium (in the first model of the basis set of molecular orbitals) or praseodymium (in the second model of the basis set of molecular orbitals) atoms is passed.     

Enhancement of magnetocaloric effects in La0.8R0.2(Fe0.919Co0.081)11.7 Al1.3 (R=Pr, Nd) compounds

The magnetic properties and magnetocaloric effects (MCEs) in La_0.8R_0.2(Fe_0.919Co_0.081)_11.7Al_1.3 (R=Pr, Nd) compounds have been investigated. When Pr and Nd substitute for La, the Curie temperature of compounds decreases. The values of the MCEs are enhanced significantly by a partial substitution of Nd for La. Under the field change of 2 and 5 T, the maximum magnetic entropy changes for La_0.8Nd_0.2(Fe_0.919Co_0.081)_11.7Al_1.3 compound are −4.56 and −9.46 J/Kg K, respectively. It can be exploited for room temperature magnetic refrigeration material.     

Phase stability and properties of the hole doped perovskite cobaltites (La1−xRx)0.7Ba0.3CoO3−δ (0.0≤x≤1.0; R=Pr,Nd)

The structural, magnetic and electrical properties of the hole doped cobaltites, with compositions (La_1−xR_x)_0.7Ba_0.3CoO₃ (0.0≤x≤1.0; R=Pr, Nd), have been studied. Substitutions of Pr and Nd for La destabilize the stoichiometric perovskite structure at the benefit of the ordered oxygen deficient perovskite ‘112’-type structure, due to decrease in size of the rare earth ion. Our studies show that for our synthesis condition, the samples of nominal compositions, R_1−yBa_yCoO₃ (R=Pr, Nd), can form with the perovskite structure only for y<0.3. In the single-phase regions, the thermo-magnetic irreversibility and coercive field increase with the substitution of Pr and Nd for La. The low temperature resistivity minimum and negative magneto-resistance in the insulating regions of these polycrystalline compounds have been ascribed to grain boundary effects.     

Changes of microstructure and magnetic properties of Nd-Fe-B sintered magnets by doping Al-Cu

The microstructural and magnetic properties of Al_100−xCu_x (15at%≤x≤45 at%) doped Nd-Fe-B magnets were studied. The distribution and alloying effects of Cu or Al on the intergranular microstructure were investigated by thermodynamic analysis, differential scanning calorimetery and microscopy techniques. It was observed that when the Cu content of Al_100xCu_x exceeds to 25 at%, the (Pr, Nd)Cu and CuAl₂ phases form in these magnets. The formation of (Pr, Nd)Cu phase depends on the negative formation enthalpy of (Pr, Nd)Cu and the exclusive distribution of Cu in the intergranular regions. The eutectic reaction between (Pr, Nd)Cu phase and (Pr, Nd) occurs at 480 °C, which forms the liquid phase that dissolves the (Pr, Nd)₂Fe₁₄B surface irregularities and thus increases the quantities of (Pr, Nd)-rich phase at the grain boundaries. These changes benefit the grain boundary microstructure, especially the distribution of (Pr, Nd)-rich phase, which effectively improves the intrinsic coercivity _iH_c due to the decreases of exchange coupling between the (Pr, Nd)₂Fe₁₄B grains.     

Structural investigations of non-stoichiometric solid solutions (Bi2O3)1−x(M2O3)x (M=Y, La, Pr, Nd, Gd and Dy)

The structural investigations of the non-stoichiometric solid solutions (Bi₂O₃)_1−x(M₂O₃)_x (M=Y, La, Pr, Nd, Gd and Dy) have been carried out. Polycrystalline samples have been synthesized using ceramic technique and the synthesis parameters have been optimized for each dopant concentration. The structural phase evolution studies with dopant concentrations have been performed using X-ray powder diffraction data over a wide range of compositions 0.10≤x≤0.40. The unit cell parameters have been obtained from the analysis of the data. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Synthesis, Characterization, DNA-Binding Properties of the Ln(III) Complexes with 6-Hydroxy Chromone-3-Carbaldehyde-(4′-Hydroxy) Benzoyl Hydrazone

6-Hydroxy chromone-3-carbaldehyde-(4′-hydroxy) benzoyl hydrazone (L) and its Ln (III) complexes, [Ln = La, Nd, Eu and Tb] have been prepared and characterized on the basis of elemental analyses, molar conductivities, mass spectra, ¹H NMR, thermogravimety/differential thermal analysis (TG-DTA), UV-vis spectra, fluorescence spectra and IR spectra. The formula of the complex is [Ln L·(NO₃)₂]·NO₃. Spectrometric titration, ethidium bromide displacement experiments and viscosity measurements indicate that Eu (III) complex bind with calf-thymus DNA, presumably via an intercalation mechanism. The intrinsic binding constant of Eu (III) with DNA was 2.48 × 10⁵ M⁻¹ through fluorescence titration data.     

Synthesis, Characterization, DNA-Binding and Antiproliferative Activity of Nd(III) Complexes With N-(Nitrogen Heterocyclic) Norcantharidin Acylamide Acid

Three novel complexes [Nd(L)(NO₃)(H₂O)₂]·NO₃·2H₂O (HL¹ = N-pyrimidine norcantharidin acylamide acid, C₁₂H₁₃N₃O₄; HL² = N-pyridine norcantharidin acylamide acid, C₁₃H₁₄N₂O₄; HL³ = N-phenyl norcantharidin acylamide acid, C₁₄H₁₅NO₄) were synthesized. HL¹, HL² and HL³ are the ligand of complex(1), complex(2) and complex(3), respectively. Their structures were characterized by elemental analysis, conductivity measurement, infrared spectra and thermogravimetric analysis. The DNA-binding properties of the complexes have been investigated by fluorescence spectroscopy and viscosity measurements. The results suggest that the complexes can bind to DNA by partial intercalation. The liner Stern-Volmer quenching constant K_sq values are 3.3(±0.21)(1), 1.7(±0.19)(2) and 0.9(±0.04)(3), respectively. Complex (1) and (2) have been found to cleave pBR322 plasmid DNA at physiological pH and temperature. The test of antiproliferation activity indicates that complex(1) has strong antiproliferative ability against the SMMC7721 (IC₅₀ = 131.7 ± 23.4 μmol·L⁻¹) and A549 (IC₅₀ = 128.4 ± 19.9 μmol·L⁻¹) cell lines. The inhibition rates of complex(2) (IC₅₀ = 86.3 ± 11.3 μmol·L⁻¹) are much higher than that of NCTD (IC₅₀ = 115.5 ± 9.5 μmol·L⁻¹) and HL² (111.0 ± 5.7 μmol·L⁻¹) against SMMC7721 cell lines.     

Femtosecond photodissociation dynamics of HNO3 after exitation of the S3-state at 200 nm

The photodissociation dynamics of HNO₃ in the electronic S₃ (2 ¹ A ^′ ) state leading to the fragments OH and NO₂ was investigated in real time. HNO₃ was prepared either in a fluorescence cell at room temperature (LIF probing of OH) or rotationally cold in a molecular beam (probing of NO₂ by three-photon ionization). A 2 ¹ A ^′ lifetime of 60–80 fs could be obtained from the experimental results, indicating essentially barrierless dissociation. In addition, secondary dissociation of internally excited nascent fragments NO₂ ^* leading to products NO(X ² Π) and O(³ P) with a characteristic dissociation time of 2.3 ps was observed. This time is surprisingly long when compared with dissociation lifetimes of NO₂ from the literature, obtained after direct photoexcitation. The discrepancy is explained by differences in the preparation conditions of the dissociative state of NO₂. Received: 12 November 1999 / Published online: 13 July 2000     

High-Temperature Heat Capacity of Germanates Pr2Ge2O7 and Nd2Ge2O7 within 350–1000 K

Pr2Ge2O7 and Nd2Ge2O7 were obtained via solid-phase synthesis from Pr2O3 (Nd2O3) and GeO2 with multistage firing in air within 1273–1473 K. A temperature effect on molar heat capacity of the oxide compounds was measured with a differential scanning calorimetry. Their thermodynamic properties were calculated from the C _P = f(T) dependences.

     

Ferroelectric relaxor behaviour in Pb(Fe0.5Ta0.5)O3

The relaxor ferroelectric lead iron tantalate, Pb(Fe_0.5Ta_0.5)O₃ (PFT) is synthesized by Coulombite precursor method. The X-ray diffraction pattern of the sample at room temperature shows a cubic phase. The field dependence of dielectric response is measured in a frequency range 0.1 kHz — 1 MHz and in a temperature range from 173–373 K. The temperature dependence of permittivity (ɛ′) shows broad maxima at various frequencies. The frequency dependence of the permittivity maximum temperature (T _m ) has been modelled using Vogel-Fulcher relation.      

Low-temperature anomaly of the magnetization in alloys (Pr,Dy,<Emphasis Type="Italic">M</Emphasis>)<Subscript>2</Subscript>(Fe,Co)<Subscript>14</Subscript>B (<Emphasis Type="Italic">M</Emphasis> = Gd,Sm, Nd)

It has been found that temperature dependences of the saturation magnetization of sintered hard magnetic (Pr,Dy,M)₂(Fe,Co)₁₄B (M = Gd, Sm, Nd) alloys demonstrate an increase at a temperature lower than a critical temperature (150 K for Sm and Nd and 70 K for Gd). An additive of copper does not influence the critical temperature. It has been assumed that there is a low-temperature phase in which cobalt is replaced with boron that diffuses from the (Pr,Dy,Gd)(Fe,Co)₄B phase to the near-surface region of grains of the main magnetic (Pr,Dy,Gd)₂(Fe,Co)₁₄B phase.     

Spontaneous parametric light scattering in spatially inhomogeneous nonlinear media based on photonic crystals

The emission spectra of nonlinear media with periodical modulation of the second-order susceptibility that are based on synthetic opals infiltrated by Ba(NO₃)₂, LiIO₃, and KH₂PO₄ are studied using radiation with λ = 400 and 407 nm for excitation. The spectral angular distribution of the emission in the range of 420–650 nm is revealed, as well as the dependence of its spectrum on the photonic stop-band parameters and the exciting radiation characteristics. The emission spectrum of samples with a low dielectric contrast has the shape of a symmetric band with a maximum at 525 nm and a half-width of about 100 nm. The observed emission is interpreted as spontaneous parametric light scattering in a spatially inhomogeneous nonlinear medium.