H2O + Fe(NO3)3 + Ni(NO3)2 ternary system isotherms at 0 °C and 30 °C

H₂O + Ni(NO₃)₂ binary system were investigated in the temperature range from −25 °C to 55 °C. The solid-liquid equilibria of the ternary system H₂O + Fe(NO₃)₃ + Ni(NO₃)₂ were studied using a synthetic method based on conductivity measurements. Tow isotherms were established at 0 °C and 30 °C, and the appearing stable solid phases are iron nitrate nonahydrate (Fe(NO₃)₃·9H₂O), iron nitrate hexahydrate (Fe(NO₃)₃·6H₂O), nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) and nickel nitrate tetrahydrate (Ni(NO₃)₂·4H₂O).     

Synthesis, crystal structure, and density of (W1−xAlx)C

A new solid solution system of Al in WC, with the stoichiometry of (W_1−xAl_x)C (x=0.10, 0.25, 0.50, 0.75, 0.86), has been synthesized by a solid-state reaction between W_1−xAl_x alloys and carbon at around 1673 K in vacuum. Environment scanning electron microscope, energy-dispersive analysis of X-ray, X-ray photoelectron spectroscopy, and inductively coupled plasma analyses are used to certify the formation of the products. The mechanism of the solid-state reaction is also discussed. (W_1−xAl_x)C is identified to crystallize in the hexagonal space group P6m2 (No. 187) and belongs to the WC structure type. The atoms of W and Al occupy the same lattice site (1a site) in the cell of (W_1−xAl_x)C. The cell parameters for each specimen in the phase of W-Al-C are quite close to that of WC, while their densities are far lower than that of WC.     

Hydrolysis of dioxouranium(VI): a calorimetric study in NaClaq and NaClO4 aq, at 25 °C

We report the results of a calorimetric study on the hydrolysis of UO₂²⁺ in different ionic media (NaClO_4 aq, NaCl_aq) at 25 °C. Experiments in NaCl were performed at different ionic strength, at I≤1 mol l⁻¹. The species considered in both ionic media were UO₂(OH)⁺, (UO₂)₂(OH)₂²⁺ and (UO₂)₃(OH)₅⁺, and in addition (UO₂)₃(OH)₄²⁺ and (UO₂)₃(OH)₇⁻ in NaCl_aq. The dependence on ionic strength of enthalpy changes in NaCl_aq was expressed by the simple linear equation ΔH_pq=ΔH°_pq+aI^1/2 (a, empirical parameter). Comparison with literature findings is given and some recommended values are reported.     

Theoretical study of the thermochemistry and the kinetics of the SFxCl (x = 0-5) series

A systematic thermodynamic and kinetic study of the entire SF_xCl (x = 0-5) series has been carried out. High-level quantum chemical composite methods have been employed to derive enthalpy of formation values from calculated atomization and isodesmic energies. The resulting values for the SCl, SFCl, SF₂Cl(C₁), SF₃Cl(C_s), SF₄Cl(C_s) and SF₅Cl molecules are 28.0, −36.0, −64.2, −134.3, −158.2 and −237.1 kcal mol⁻¹. A comparison with previous experimental and theoretical values is presented. Statistical adiabatic channel model/classical trajectory, SACM/CT, calculations of selected complex-forming and recombination reactions of F and Cl atoms with radicals of the series have been performed between 200 and 500 K. The reported rate coefficients span over the normal range of about 6 × 10⁻¹² and 5 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ expected for this type of barrierless reactions.     

Analysis of magnetic and structural phase transition behaviors of La1−xSrxCrO3 for preparation of phase diagram

The phase transition behavior of perovskite-type compounds, La_1−xSr_xCrO₃, was investigated by differential scanning calorimetry (DSC), dilatometry, dc magnetic susceptibility measurement and X-ray diffraction analysis. Both second-order magnetic phase transition from antiferromagnetic to paramagnetic and first-order structural phase transition from orthorhombic to rhombohedral were observed in the DSC or dilatometric curve of every specimen. The temperatures of both these magnetic and structural phase transitions decreased linearly with an increase in Sr content. The structural phase transition temperature of La_1−xSr_xCrO₃ with x less than 0.11 is higher than the magnetic phase transition temperature; however, a larger decrease in structural phase transition temperature than in magnetic phase transition temperature was observed with an increase in Sr content, resulting in a structural phase transition temperature lower than the magnetic phase transition temperature for La_1−xSr_xCrO₃ with x of more than 0.12. It was also observed that the heat of absorption of the structural phase transition decreased with an increase in x. In the dependence of dc magnetic susceptibility on temperature, variations by not only magnetic but also structural phase transitions were observed. It was also revealed that thermal expansion coefficient is affected not only by structural phase transition but also magnetic phase transition. Magnetic and structural phase diagram of La_1−xSr_xCrO₃, suggesting the existence of two Sr contents and temperatures at which triple phases coexist, was proposed.     

An isothermal (30 °C) study of heterogeneous equilibria in the sucrose (C12H22O11)-calcium hydroxide (Ca(OH)2)-water system

Solid-liquid equilibria in the C₁₂H₂₂O₁₁-Ca(OH)₂-H₂O system have been determined at 30 °C. Two phases C₁₂H₂₂O₁₁·3Ca(OH)₂ and C₁₂H₂₂O₁₁·2Ca (OH)₂ have been evidenced, and solubility (liquidus) curves have been determined. It is thus shown that these ternary phases exhibit incongruent solubilities at 30 °C. These solid phases were characterized using Infrared Spectroscopy (IR), Scanning Electron Microscopy (SEM) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES).     

The Crystal Chemistry of Lithium in the Alluaudite Structure: A Study of the (Na1−xLix)CdIn2(PO4)3 Solid Solution (x=0 to 1)

Several compounds of the (Na_1−xLi_x)CdIn₂(PO₄)₃ solid solution were synthesized by a solid-state reaction in air, and pure alluaudite-like compounds were obtained for x=0.00, 0.25, and 0.50. X-ray Rietveld refinements indicate the occurrence of Cd²⁺ in the M(1) site, and of In³⁺ in the M(2) site of the alluaudite structure. This non-disordered cationic distribution is confirmed by the sharpness of the infrared absorption bands. The distribution of Na⁺ and Li⁺ on the A(1) and A(2)′ crystallographic sites cannot be accurately assessed by the Rietvled method, probably because the electronic densities involved in the Na⁺→Li⁺ substitution are very small. A comparison with the synthetic alluaudite-like compounds, (Na_1−xLi_x)MnFe₂(PO₄)₃, indicates the influence of the cations occupying the M(1) and M(2) sites on the coordination polyhedra morphologies of the A(1) and A(2)′ crystallographic sites.     

Phase relationships in the pseudo-binary 2(ZnTe)-CuInTe2 system

Subsolidus phase relationships in the 2(ZnTe)_x(CuInTe₂)_1−x system were investigated by TEM experiments combined with EDX analysis. The samples were prepared by the solid-state reaction of the elements during long annealing times, followed by either quenching in ice-cold water, or by controlled cooling at different rates. Using the chemical compositions of single and coexisting phases at various temperatures, the boundaries of the two-phase region have been determined. At room temperature, the two-phase region extends from x=0.10 to 0.31. For x<0.10 only mixed crystals with tetragonal structure exist. Between x=0.31 and 1 alloys with the cubic structure are stable.The morphology of the tetragonal domains and their orientation relationship to the cubic matrix were determined by SAD, TEM and HRTEM experiments. The tetragonal phase embedded within the cubic matrix has a flat ellipsoidal shape, whose short axis coincides with the tetragonal c-axis. The three topotaxial orientation relationships between the tetragonal domains and the surrounding cubic matrix were found to be: [001]_tetr.∥[100]_cub., [001]_tetr.∥[010]_cub. and [001]_tetr.∥[001]_cub.. There is an indication that the nucleation starts from small regions displaying cation ordering according to the CuPt-type structure. Reaching the two-phase equilibrium, the tetragonal domains as well as the surrounding cubic phase are free of this cation ordering.     

A reagentless DNA biosensor based on cathodic electrochemiluminescence at a C/CxO1−x electrode

A reagentless signal-on electrochemiluminescence (ECL) biosensor for DNA hybridization detection was developed based on the quenching effect of ferrocene (Fc) on intrinsic cathodic ECL at thin oxide covered glassy carbon (C/C_xO_1−x) electrodes. To construct the DNA biosensor, molecular beacon (MB) modified with ferrocene (3′-Fc) was attached to a C/C_xO_1−x electrode via the covalent bound between labeled amino (5′-NH₂) and surface functional groups. It was found that the immobilization of the probe on the electrode surface mainly depended on the fraction of surface carbonyl moiety. When a complementary target DNA (cDNA) was present, the stem-loop of MB on the electrode was converted into a linear double-helix configuration due to hybridization, resulting in the moving away of Fc from the electrode surface, and the restoring of the cathodic ECL signal. The restoration of the ECL intensity was linearly changed with the logarithm of cDNA concentration in the range of 1.0 × 10⁻¹¹ to 7.0 × 10⁻⁸ M, and the detection limit was ca. 5.0 pM (S/N = 3). Additionally, single-base mismatched DNA can be effectively discriminated from the cDNA. The great advantage of the biosensor lies in its simplicity and cost-effective with ECL generated from the electrode itself, and no adscititious luminophore is required.     

Crystal Structure of Pseudorhombohedral InFe1−xTixO3+x/2 (x=2/3)

The structure of pseudorhombohedral-type InFe_1−xTi_xO_3−x/2 (x=2/3) was refined by Rietveld profile fitting. The crystal is a commensurate member of a series in a solution range on InFeO₃-In₂Ti₂O₇ including incommensurate structures. The structure with the unit cell of a=5.9188(1), b=10.1112(2), and c=6.3896(1) Å, β=108.018(2)°, and a space group P2₁/a is the alternate stacking of an edge-shared InO₆ octahedral layer and an Fe/Ti-O plane along c^*. Metal sites on the Fe/Ti-O plane are surrounded by four oxygen atoms on the Fe/Ti-O plane and two axial ones. Electric conductivities of the order 10⁻⁴ S/cm were observed for the samples at 1000 K, while the oxide ion transport number is almost zero as no electromotive force was detected by an oxygen concentration cell.     

Modelling LLE and VLE of methanol + n-alkane series using GC-PC-SAFT with a group contribution kij

The fluid phase diagrams (LLE and VLE) of methanol + n-alkane mixtures series (from C₄ up to C₁₆) were modelled using GC-PC-SAFT EOS (Tamouza et al., Fluid Phase Equilibria 222–223 (2004) 67–76) combined with a recent method for computing k_ij based on the London theory (NguyenHuynh et al., Industrial & Engineering Chemistry Research 47 (2008) 8847–8858). This latter method requires pure compound adjustable parameters: pseudo-ionization energies J that may be calculated by group contribution in the case of n-alkane series. J_alkane is calculated from group parameters JCH₃$J_{\text{C}{\text{H}}_3}$ and JCH₂$J_{\text{C}{\text{H}}_2}$.     

Density-functional study for the NOx (x = 1, 2) dissociation mechanism on the Cu(1 1 1) surface

Spin-polarized density functional theory calculation is employed to study the adsorption and dissociation of NO₂ molecule on Cu(1 1 1) surface. It is shown that the most favorable adsorption structure is the NO₂ (T,T-O-,O′-nitrito) configuration which has an adsorption energy of −1.49 eV. The barriers for step-wise NO₂ dissociation reaction, NO_2(g) → N_(a) + 2O_(a), are 1.05 (for O–N–O bond activation), and 2.08 eV (for N–O bond activation), respectively, and the entire process is 0.6 eV exothermic. The energetics of single N–O dissociation with and without the presence of N atom or O atom on the surface are also calculated. The results indicate that in the presence of O atom on Cu(1 1 1) surface would raise the N–O dissociation barrier, whereas in the presence of N atom decrease it. The interaction nature between adsorbates and substrate is analyzed by the local density of states (LDOS) calculation.     

Phase relations in NaxCrxTi8−xO16 at 1350 °C and crystal structure of hollandite-like Na2Cr2Ti6O16

Phase relations of rutile, freudenbergite, and hollandite structures were examined in the pseudobinary system NaCrO₂-TiO₂ (i.e., Na_xCr_xTi_8−xO₁₆) at 1350 °C. The hollandite structure was obtained in the composition range 1.7?x?2.0. The symmetry of the samples at room temperature was tetragonal for x=1.7 and 1.75, and monoclinic for x=1.8 and above. Single crystals of monoclinic hollandite Na₂Cr₂Ti₆O₁₆ were grown and the structure refinement has been carried out using an X-ray diffraction technique. The space group was I2/m and cell parameters were a=10.2385(11), b=2.9559(9), c=9.9097(11)Å, and β=90.545(9)° with Z=1. The Na ion distribution in the tunnel was markedly deformed from that in the tetragonal form. It was suggested that Cr/Ti ratios were different between the two framework metal sites.     

Crystallographic and hydriding properties of the system La1−xCexY2Ni9 (xCe=0, 0.5 and 1)

The structural properties of the system La_1−xCe_xY₂Ni₉ with x_Ce=0, 0.5 and 1 have been investigated by electron probe microanalysis, powder X-ray diffraction and absorption spectroscopy. The compound LaY₂Ni₉ adopts a rhombohedral structure of PuNi₃-type (R-3m space group, Z=3). It can be described as an intergrowth between RM₅ (Haücke phase) and RM₂ (Laves phase) type structures. Among the two available crystallographic sites for R atoms, lanthanum occupies preferentially the site 3a leading to a partially ordered ternary compound. Substitution by cerium involves anisotropic variations of the cell parameter with a decrease of a and an increase of c leading to an overall cell volume reduction. Increasing cerium content does not induce any symmetry change but leads to a statistical distribution of the rare earths over the two sites 3a and 6c involving an evolution toward a pseudo-binary compound. This behavior is related to the intermediate valence state of cerium observed by X-ray absorption spectroscopy. The hydriding properties of the two compounds LaY₂Ni₉ and CeY₂Ni₉ are described in relation with their crystallographic structure.     

The two-phase region in 2(ZnSe)x(CuInSe2)1−x alloys and structural relation between the tetragonal and cubic phases

The two-phase region in the system 2(ZnSe)_x(CuInSe₂)_1−x covers the chemical composition range 0.10<x?0.36, in which a tetragonal and a cubic phase are coexisting. The structural relation between both phases was determined by selected area diffraction (SAD) and transmission electron microscopy (TEM). Both crystal structures are very similar and the extremely small mismatch of the lattice constants of the tetragonal phase and the embedding cubic matrix phase allows for the grain boundaries to be virtually strain-free and, therefore, without notable dislocations. The tetragonal phase forms grains of flat discus-like shape in the ambient cubic matrix, with the short discus axis parallel to the tetragonal c-axis. TEM experiments proved that the discus-shaped tetragonal particles are collinear with the (100)_cub, (010)_cub and (001)_cub planes of the cubic phase. Cooling and annealing experiments revealed a near-equilibrium state only to be realized for small cooling rates less than 2 K/h and/or for a long-time annealing with subsequent rapid quenching. Only then there will be no cation ordering in both, the tetragonal domains and the parental cubic matrix phase. If, however, the samples are kept in a state far away from the equilibrium condition both phases reveal Stannite-type cation ordering. Within the composition range of 0?x?0.10 only tetragonal 2(ZnSe)_x(CuInSe₂)_1−x-alloys exist. At concentration rates above 36 mol% 2(ZnSe) only cubic structured solid solutions of ZnSe and CuInSe₂ are found to be stable. However, in the range 36 mol% to about 60 mol% 2(ZnSe) tiny precipitates with Stannite-like structure exist, too.     

LiB3O5 crystal structure at 20, 227 and 377 °C

Crystal structure of LiB₃O₅ (a framework of [B₃O₅]⁻ rings and Li atoms located in interspaces) was refined at high temperatures using single-crystal X-ray diffraction, MoKα-radiation, anharmonic approximation, orthorhombic; Pna2₁; Z=4; 20 °C (a=8.444, b=7.378, c=5.146 Å, 1411 F(hkl), R=0.022); 227 °C (a=8.616, b=7.433, c=5.063 Å, 1336 F(hkl), R=0.026), 377 °C (a=8.746, b=7.480, c=5.013 Å, 1193 F(hkl), R=0.035). A high mobility of Li atoms and their highly asymmetric vibrations are revealed. Ellipsoid of Li thermal vibrations is oviform. Li is shifted on heating to 0.26 Å mainly along a-axis causing high thermal expansion in this direction; Li temperature factors are multiplied by 4 on heating. Rigid boron-oxygen groups in LiB₃O₅ remain practically stable on heating similar to α-Na₂B₈O₁₃ and α-CsB₅O₈. At the same time these groups rotate relative to each other like hinges leading to extremely anisotropic thermal expansion (α_a=101, α_b=31, α_c=−71, α_v=60×10⁻⁶ °C⁻¹, 20-530 °C, HTXRPD data).     

Structure and magnetic order in the series BixRE1−xFe0.5Mn0.5O3 (RE=La,Nd)

The influence of Bi³⁺ on the structural and magnetic properties of the rare-earth-containing perovskites REFe_0.5Mn_0.5O₃ (RE=La,Nd) was studied, and the limit of bismuth substitution was determined to be x≤0.5 in Bi_xRE_1−xFe_0.5Mn_0.5O_3+δ (RE=La,Nd) at ambient pressure. Crystal structures in both La and Nd series were determined to be GdFeO₃-type Pnma with the exception of the Bi_0.3La_0.7Fe_0.5Mn_0.5O₃ sample, which is monoclinic I2/a in the a⁻b⁻b⁻ tilt scheme. The samples undergo a transition to G-type antiferromagnetic order along with a weak ferromagnetic component, mixed with cluster-glass type behavior. The substitution of bismuth into the lattice results in a drop in T_N relative to the lanthanide end-members. Long range ordering temperatures T_N in the range 240-255 K were observed, with a significantly lower ordered magnetic moment in the case of lanthanum (M∼1.7-1.9 μ_B) than in the case of neodymium (M∼2.1 μ_B).     

Thermoelectric properties of Ag-doped n-type (Bi2Te3)0.9-(Bi2−xAgxSe3)0.1 (x=0-0.4) alloys prepared by spark plasma sintering

Ag-doped n-type (Bi₂Te₃)_0.9-(Bi_2−xAg_xSe₃)_0.1 (x=0-0.4) alloys were prepared by spark plasma sintering and their physical properties evaluated. When at low Ag content (x=0.05), the temperature dependence of the lattice thermal conductivity follows the trend of (Bi₂Te₃)_0.9-(Bi₂Se₃)_0.1; while at higher Ag content, a relatively rapid reduction above 400 K can be observed due possibly to the enhancement of scattering of phonons by the increased defects. The Seebeck coefficient increases with Ag content, with some loss of electrical conductivity, but the maximum dimensionless figure of merit ZT can be obtained to be 0.86 for the alloy with x=0.4 at 505 K, about 0.2 higher than that of the alloy (Bi₂Te₃)_0.9-(Bi₂Se₃)_0.1 without Ag-doping.     

Structure and conductivity of strontium-doped cerium orthovanadates Ce1−xSrxVO4 (0≤x≤0.175)

A-site substituted cerium orthovanadates, Ce_1−xSr_xVO₄, were synthesised by solid-state reactions. It was found that the solid solution limit in Ce_1−xSr_xVO₄ is at x=0.175. The crystal structure was analysed by X-ray diffraction and it exhibits a tetragonal zircon structure of space group I4₁/amd (1 4 1) with a=7.3670 (3) and c=6.4894 (1) Å for Ce_0.825Sr_0.175VO₄. The UV-vis absorption spectra indicated that the compounds have band gaps at room temperature in the range 4.5-4.6 eV. Conductivity measurements were performed for the first time up to the strontium solid solution limit in air and in dry 5% H₂/Ar with conductivity values at 600 °C ranging from 0.3 to 30 mS cm⁻¹ in air to 30-45 mS cm⁻¹ in reduced atmosphere. Sample Ce_0.825Sr_0.175VO₄ is redox stable at a temperature below 600 °C although the conductivity is not high enough to be used as an electrode for solid oxide fuel cells.     

A Novel Boron-Rich Scandium Borocarbide; Sc4.5−xB57−y+zC3.5−z(x=0.27, y=1.1, z=0.2)

A novel ternary boron-rich scandium borocarbide Sc_4.5−xB_57−y+zC_3.5−z (x=0.27, y=1.1, z=0.2) was found. Single crystals were obtained by the floating zone method by adding a small amount of Si. Single-crystal structure analysis revealed that the compound has an orthorhombic structure with lattice constants of a=1.73040(6), b=1.60738(6) and c=1.44829(6) nm and space group Pbam (No. 55). The crystal composition ScB_13.3C_0.78Si_0.008 calculated from the structure analysis agreed with the measured composition of ScB_12.9C_0.72Si_0.004. The orthorhombic crystal structure is a new structure type of boron-rich borides and there are six structurally independent B₁₂ icosahedra I1—I6, one B₈/B₉ polyhedron and nine bridging sites all which interconnect each other to form a three-dimensional boron framework. The main structural feature of the boron framework structure can be understood as a layer structure where two kinds of boron icosahedron network layer L1 and L2 stack each other along the c-axis. There are seven structurally independent Sc sites in the open spaces between the boron icosahedron network layers.