Thermodynamic properties of SmFeO3(s) and Sm3Fe5O12(s)

The enthalpy increments and the standard molar Gibbs energy (G) of formation of SmFeO₃(s) and Sm₃Fe₅O₁₂(s) have been measured using a Calvet micro-calorimeter and a solid oxide galvanic cell, respectively. A λ-type transition, related to magnetic order-disorder transformation (antiferromagnetic to paramagnetic), is apparent from the heat capacity data at ∼673 K for SmFeO₃(s) and at ∼560 K for Sm₃Fe₅O₁₂(s). Enthalpy increment data for SmFeO₃(s) and Sm₃Fe₅O₁₂(s), except in the vicinity of λ-transition, can be represented by the following polynomial expressions:

Sorption of Hg2+, Nd3+, Dy3+, and Uo 22+ ions at polysiloxane xerogels functionalized with phosphonic acid derivatives

The sorption properties of silicas with mono- and bifunctional surface layers containing the complexing fragment ≡Si(CH₂)₃NHP(S)(OC₂H₅)₂ were studied. It was found that xerogels synthesized by the solgel method (like mesoporous silicas obtained by the template method) can extract mercury(II) ions from acidified solutions (SSC up to 450 mg/g). In a nonporous xerogel with a bifunctional surface layer (≡P=S/-SH), thiol groups proved to be primary sorption sites for Hg²⁺ ions; part of the ligand groups were inaccessible to metal ions. Xerogels containing the phosphonic acid residues ≡Si(CH₂)₂P(O)(OH)₂ sorbed uranyl and lanthanide ions from their nitrate solutions. The resulting surface complexes contained two (for the UO₂²⁺ ion) or three innersphere ligand groups (for the Nd³⁺ and Dy³⁺ ions). The maximum SSCs were 340 mg/g for the uranyl ion and 120 mg/g for the lanthanide ions. Original Russian Text ? O.A. Dudarko, V.P. Goncharik, V.Ya. Semenii, Yu.L. Zub, 2008, published in Zashchita Metallov, 2008, Vol. 44, No. 2, pp. 207–212.     

Bridged polysilsequioxane adsorption materials containing phosphonic acid residues

Reactions of hydrolytic polycondensation of bis(triethoxysilane) [(C₂H₅O)₃Si]₂C₂H₄ (or [(C₂H₅O)₃Si]₂C₆H₄) and functional agent (C₂H₅O)₃Si(CH₂)₂P(O)(OC₂H₅)₂ (alkoxysilanes molar ratio of 2: 1 and 4: 1, fluoride ion catalyst and ethanol solvent) yielded powder-like xerogels that contained phosphonic acid residues in the surface layer. Their treatment with boiling concentrated hydrochloric acid resulted in transformation of functional groups ≡Si(CH₂)₂P(O)(OC₂H₅)₂ into acid groups ≡Si(CH₂)₂P(O)(OH)₂. The methods of IR, ¹H MAS NMRm and ¹³C, ²⁹Si, ³¹P MAS NMR spectroscopy showed the following (1) The surface layer in the initial xerogels contains not only phosphorus functional groups, but also some non-hydrolyzed ethoxysilyl groups as well as silanol groups. (2) The hydrochloric acid treatment of the initial xerogels causes the hydrolysis of not only ethoxy groups in the phosphonic acid residues, but also most residual ethoxysilyl groups. (3) Vacuum drying of xerogels after acid treatment forms ≡Si(CH₂)₂P(O)(OH)-OSi≡ links in their surface layer (not more than 20% of phosphorus-containing groups). (4) According to ²⁹Si CP MAS NMR spectroscopic data, boiling acid treatment relatively enriches the xerogel structure T² and T³ units and accounts for the higher rigidity of the hybrid framework. These units also account for retention of the porous structure in these xerogels over time, while most initial xerogels have porous structures that collapse in 12–18 months of storage. The acid-treated xerogels were attributed to microporous adsorbents (having specific surface area of 620 to 760 m²/g). According to the AFM data, both initial and acid-treated xerogels contain almost spherical aggregates of the primary particles (globules).     

Oxygen-free precursor for chemical vapor deposition of gold films: thermal properties and decomposition mechanism

Thermal properties of oxygen-, phosphorus-, and halogen-free dimethylgold(III) diethyldithiocarbamate complex (CH₃)₂AuS₂CN(C₂H₅)₂ (gold, dimethyl(diethylcarbamodithioato -S,S′)-) having excellent storage stability and the mechanism of its decomposition to elemental gold were studied. Saturated vapor pressure was found to be ~10⁻³–10⁻¹ Torr at 50–90°C. Decomposition of the vapor on the surface starts at T = 210°C. The temperature dependence of gas phase composition was studied using the original mass spectrometric technique, it was established that the decomposition of the compound on the surface in vacuum follows three main pathways. Two of them result in the formation of elemental gold, saturated C2–C4 alkanes and (1) protonated ligand or (2) methylated ligand. The third one results in elemental gold and gaseous products: C2–C3 alkylmercaptanes and CH₃SCN(C₂H₅)₂. The formation of gold as a sole solid product within the temperature range 210–240°C was confirmed by X-ray photoelectron spectroscopy analysis. It was shown that the compound exhibits the best combination of volatility, thermal, and storage stability among volatile organogold complexes and thus it may be a promising precursor for obtaining gold films by chemical vapor deposition.     

Deriving bridged polysilsesquioxane xerogels with ≡Si(CH2)3NHP(O)(OC2H5)2 functional groups

The reaction of hydrolytic polycondensation of (C₂H₅O)₃SiC₂H₄Si(OC₂H₅)₃ [or (C₂H₅O)₃SiC₆H₄Si(OC₂H₅)₃] and (C₂H₅O)₃Si(CH₂)₃NHP(O)(OC₂H₅)₂ was used to obtain xerogels containing a phosphine oxide complexing group (0.9–1.4 mmol/g). The presence of this functional group, as well as organic bridges, polysiloxane bonds, noncondensed silanol, and ethoxysilyl groups in the synthesized bridged polysilsesquioxane xerogels, was established using IR spectroscopy and solid-state ¹H MAS NMR spectroscopy. The AFM data indicate that the structure of xerogels is similar to that of other materials of this class (conglomerates of aggregates with the size of 35–40 nm); however, all the obtained samples are practically nonporous. They extract ions of neodymium(III) and dysprosium(III) from aqueous solutions (sorption equilibrium is established in 72 h for neodymium and in 24 h for dysprosium). However, some ligand groups remain inaccessible to lanthanide ions. The whole set of the obtained results indicates that the geometrical sizes of a functional group produce a considerable effect on formation of xerogel porous structure and in the case of using bridged alkoxysilanes as structure-forming agents.     

On construction of the structures of adsorbed films of mefenamic and phenylundecanoic acids on passive iron

Successive adsorption of the components of a mixed inhibitor at oxidized iron was further studied by ellipsometry and IR spectroscopy. The mixed inhibitor was composed of salts of aromatic amino acids, viz., sodium mefenamate (SMEF) NaOOCC₆H₄NHC₆H₃(CH₃)₂ and sodium phenylundecanoate (SPU) C₆H₅(CH₂)₁₀COONa. Ultrathin adsorbed films obtained on oxidized iron by different methods were tested in a moist atmosphere to compare their protective properties. Adsorbed PU forms an iron complex on oxidized iron. Adsorption of MEF anions over a PU layer changes the IR spectral pattern, thus indicating a change in the adsorption mechanism of MEF anions in the presence of PU anions. Original Russian Text ? Yu.I. Kuznetsov, N.P. Andreeva, N.P. Sokolova, R.A. Bulgakova, A.M. Gorbunov, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 4, pp. 339–345.     

Production of SBA-15 mesoporous silica containing ammonium groups in the surface layer

The template method (surfactant: Pluronic 123) has been applied to produce mesoporous silica that contain ammonium groups [≡Si(CH₂)₃NH₃]⁺, [≡Si(CH₂)₃NH₂(CH₂)₂NH₃]²⁺, [≡Si(CH₂)₃NH₂(CH₂)₂NH₂(CH₂)₂NH₃]³⁺ and [≡Si(CH₂)₃N(CH₃)₃]⁺ in the surface layer, which has been confirmed both by data of elemental analysis for nitrogen and by IR spectroscopy. Using diffractometry and TEM, it has been demonstrated that the synthesized samples contain a hexagonal structure characteristic of SBA-15 silica. This agrees with the parameters of their porous structure calculated by isotherms of low-temperature adsorption of nitrogen: S _sp = 520–750 m²/g, V _c = 0.6–1.2 cm³/g, and d = 4.9–8.9 nm.     

Thermodynamic properties and phase equilibria in the Cr-P system

A Knudsen effusion method with mass-spectrometric analysis of gaseous phase has been applied to investigate the thermodynamic properties of the chromium phosphides (1341 to 1704 K) and Cr-P liquid alloys (1664 to 1819 K). Simultaneously, DSC has been used to measure heat capacities of chromium phosphides Cr₃P and Cr₁₂P₇ in the temperature range of113 to 873 K. The entropies of formation of chromium phosphides calculated according to the second and third laws of thermodynamics agree within the limits of experimental error. The Gibbs energies of formation of the phosphides from solid Cr and P₂ gas have been approximated with the following equations (in J/mol): A_fG⁰(Cr₃P) = −(244 112 ±2800) + (70.95 ±1.80)T ΔG⁰(Cr₁₂2P₇) = −(1563 678 ±15 350) + (440.6 ±9.90)T Thermodynamic properties of liquid solutions have been described with the ideal associated-solution model assuming that CrP, Cr₂P, Cr₃P, and Cr₃P₂ complexes exist in the melt. The phase diagram computed with the help of the thermodynamic data agrees with the published information.     

Surface properties of silica gel modified by trifunctional polyfluoroalkyl silanes according to data of adsorption–structural and gas chromatography studies

Surface properties of silica gels modified by trifunctional polyfluorosilanes n-C₆F₁₃(CH₂)₂SiCl₃ and iso-C₃F₇(CH₂)₂SiCl₃ are studied using the methods of adsorption and gas chromatography with respect to nitrogen, hydrocarbon, and water molecules. It is shown that the branched structure of the grafted group and high concentration of grafted groups (2.7 nm^–2) provide better screening of both residual silanols of the support and of additional hydroxyl groups formed in the course of synthesis as a result of hydrolysis. Comparison with the properties of silica gel with grafted monofunctional silane n-C₆F₁₃(CH₂)₂Si(CH₃)₂Cl shows that, in the case of an overall decrease in the adsorption values and considerable surface lyophobization, modification by trifunctional silanes irrespective of the modifier chain length allows obtaining adsorbents containing more polar centers than those in silica gel due to the possible participation in adsorption of additional silanols and a polar fragment of the grafted chain of–CH₂–CF₂–. A considerable difference in the course of isotherms of nitrogen and hexane adsorption–desorption is found in the range of capillary condensation hysteresis related to liophobicity of polyfluoroalkyl layers, a significant decrease in the pore wetting and the corresponding increase in wetting angle θ by hexane. Adsorption of water on fluorinated silicas is negligible and capillary condensation is not observed due to nonwettability of the pore surface by liquid adsorbate (θ > 90°).     

Synthesis,X-ray structure and luminescent properties of a new 1D terbium(III) coordination polymer based on 2,4-dichlorophenoxyacetate and 4,4′-bipyridine

A new 1D terbium coordination polymer, {[Tb(2,4-dcpa)₃(H₂O)₂]·(4,4′-bpy)_1.5(H₂O)₂}_n (1) [2,4,-dcpa = 2,4-dichlorophenoxyacetate, 4,4′-bpy = 4,4′-bipyridine], was prepared by hydrothermal synthesis and characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis (TGA) and single-crystal X-ray diffraction. Complex 1 exhibits an infinite chain structure with a {Tb₂(2,4-dcpa)₆(H₂O)₄} dimeric repeat unit. Each Tb³⁺ ion is nine-coordinated to two water molecules, one monodentate carboxylate group and four bridging carboxylate groups in which the carboxylate groups are bonded to the terbium ion in one modes: the chelating–bridging tridentate. Three-dimensional fluorescence spectra of 1 were detected at room temperature under the excitation and the emission wavelengths in the range of 420–750 nm with the interval of 5 nm. The lifetime of 1 in solid-state at room temperature up to 1.132 ms. On the other hand, poor luminescence efficiency has been noted for the Tb³⁺-2,4-dcpa complex.     

Thermodynamic Calculation of HfB<Subscript>2</Subscript> Volatility Diagram

The thermodynamics of the oxidation of HfB₂ at temperatures of 1000, 1500, 2000, and 2500 K have been studied using volatility diagrams. Both the equilibrium oxygen partial pressure ( P_\textO2 P_{{{\text{O}}_{2} }} ) for the HfB₂(s) to HfO₂(s) plus B₂O₃(l) and the partial pressures of B-O vapor species formed due to B₂O₃(l) volatilization increase with increasing temperature. Vapor pressures of the predominant gaseous species also increase with P_\textO2 P_{{{\text{O}}_{2} }} . At 1000 K, the predominant vapor transition sequence is predicted be BO(g) → B₂O₂(g) → B₂O₃(g) → BO₂(g) with increasing P_\textO2 P_{{{\text{O}}_{2} }} , and the predominant gas is BO₂(g) with a pressure of 1.27 × 10⁻⁶ Pa under the condition of P_\textO2 P_{{{\text{O}}_{2} }}  = 20 kPa. At higher temperatures of 1500, 2000, and 2500 K, the system undergoes vapor transitions in the same sequence of B(g) → BO(g) → B₂O₂(g) → B₂O₃(g) → BO₂(g). Under the same condition of P_\textO2 P_{{{\text{O}}_{2} }}  = 20 kPa, the predominant vapor species is B₂O₃(g) with pressures of 2.38, 4.49 × 10³, and 3.55 × 10⁵ Pa, respectively. Volatilization of B₂O₃(l) may produce porous HfO₂ scale, which is consistent with the experimental observations of HfB₂ oxidation in air. The present volatility diagram of HfB₂ shows that HfB₂ exhibits oxidation behavior similar to ZrB₂, and factors other than volatility of gaseous species affect the oxidation rate.     

Chromium Volatilization Rates from Cr2O3 Scales into Flowing Gases Containing Water Vapor

The mass-transfer coefficient for CrO₂(OH)₂ volatilization into flowing air-10% H₂O or steam was evaluated using classical gas transport theory in the viscous-flow regime. The resulting values were applied to new thermodynamic data for the reaction: 1/2 Cr₂O₃ + 3/4 O₂(g) + H₂O(g) = CrO₂(OH)₂(g) to predict Cr-evaporation fluxes in the temperature range 650–800°C. The calculation was found to predict correctly the Cr-loss rate measured from foil specimens of Fe–20Cr–25Ni+Nb (alloy 709) exposed for up to 10,000 hr under these conditions. In 240 atm (24 MPa) high-purity steam, the calculations suggest that the Cr-evaporation rates will be much lower than in humid air.     

采用TRPO从过氧化氢溶液中萃取钼和钨的数学模型和反应机理（英文）

为了解利用三烷基氧化膦(TRPO)从过氧化氢溶液中萃取钼和钨的化学行为,采用斜率法、拉曼和红外光谱研究钼和钨的萃取反应机理。通过建立数学模型,获得钼或钨的萃取分配比(D_Mo或D_W)关于平衡pH值、TRPO浓度和温度等变量的经验公式,并进一步在H⁺-W-Mo-H₂O₂溶液中验证经验公式的可靠性。结果表明:经验公式计算的D_Mo或D_W和实验值吻合度良好。实验条件下,20℃时钼和钨的萃取平衡常数分别为K_Mo^app=8.51×10³(0.74≤pH_e≤1.70)、K_Mo^app=99.89×10³(1.7e≤4.62)和K_W^app=2.65×10³(0.92e&l...     

Gold anion catalysis of methane to methanol

The oxidation of CH₄ has been investigated in the presence and absence of the atomic Au⁻ ion catalyst. We have employed the first principles density functional theory (DFT) and dispersion-corrected DFT calculations for the transition state on the Au⁻ ion and analyzed the thermodynamics properties of the reactions as well. Our results demonstrate that atomic gold anions could be used to catalyze CH₄ into valuable industrial products without the emission of CO₂, thereby making gold extremely valuable. The fundamental mechanism involves breaking the C–H bond through the formation of the anionic Au⁻(CH₄) molecular complex permitting the oxidation of CH₄ to methanol at the temperature of 325 K which is below that of CO₂ emission. Potentially, this could significantly impact the quality of our environment.     

Surface tension and thermodynamic properties of liquid Ag-Bi solutions

With the maximum bubble pressure method, the density and surface tension were measured for five Ag-Bi liquid alloys (X _Bi=0.05, 0.15, 0.25, 0.5, and 0.75), as well as for pure silver. The experiments were performed in the temperature range 544–1443 K. Linear dependences of both density and surface tension versus temperature were observed, and therefore the experimental data were described by linear equations. The density dependence on concentration and temperature was derived using the polynomial method. A similar dependence of surface tension on temperature and concentration is presented. Next, the Gibbs energy of formation of solid Bi₂O₃, as well as activities of Bi in liquid Ag-Bi alloys, were determined by a solid-state electromotive force (emf) technique using the following galvanic cells: Ni, NiO, Pt/O ⁻²/W, Ag _X Bi _(1−X), Bi ₂ O _3(s). The Gibbs energy of formation of solid Bi₂O₃ from pure elements was derived: =−598 148 + 309.27T [J · mol⁻¹] and =−548 008 + 258.94T [J · mol⁻¹]; the temperature and the heat of the α → δ transformation for this solid oxide were calculated as 996 K and 50.14 J · mol⁻¹. Activities of Bi in the liquid alloys were determined in the temperature range from 860–1075 K, for five Ag-Bi alloys (X _Ag=0.2, 0.35, 0.5, 0.65, 0.8), and a Redlich-Kister polynomial expansion was used to describe the thermodynamic properties of the liquid phase. Using Thermo-Calc software, the Ag-Bi phase diagram was calculated. Finally, thermodynamic data were used to predict surface tension behavior in the Ag-Bi binary system.     

Films containing nickel and iron compounds on aluminum and titanium

The composition of films formed by plasma electrochemical oxidation-deposition on aluminum and titanium in aqueous solutions containing both Ni(II) and Fe(III) polyphosphate complexes is studied. Elementary compositions of the outer part of the layers on aluminum and titanium differ insubstantially. Concentrations of nickel and iron (up to 30 wt %) in the films vary in proportion to their molar ratio in the electrolyte. Upon annealing in air, simple and multiple metal (M) oxides and phosphates crystallize in the layers, particularly, AlPO₄, NiAl₂O₄, and Fe₂O₃ on aluminum, while Ni₂P₂O₇, Ni_0.5TiOPO₄; NaTi₂(PO₄)₃, M(II)M(III)Ti(PO₄)₃, FePO₄, and Fe₂Fe(P₂O₇)₂ on titanium. Original Russian Text ? V.S. Rudnev, V.P. Morozova, 2008, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2008, Vol. 44, No. 5, pp. 506–509.     

Effect of dysprosium and cobalt on the temperature dependence of magnetization and phase composition of a material of the Nd-Dy-Fe-Co-B system

Sintered magnetically hard materials with composition (Nd_1−x Dy_x)_13–16(Fe_1−y Co_y)_resAl_0.5−1B_7–9 (x = 0.11–0.71, y = 0.19–0.34) are investigated. The role of cobalt and dysprosium in the variation of magnetic properties of the material (residual induction, coercive force) is studied. The phase composition of the material and its effect on magnetic properties are determined. Amethod for computing the induction temperature coefficient of a material on the basis of published data on the physical characteristics (the Curie temperature, the density, the molecular mass) of the main magnetic phase (Nd, Dy)₂(Fe, Co)₁₄B is presented. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 3–10, April, 2007.     

Corrosion of bronze by acetic and formic acid vapours,sulphur dioxide and sodium chloride particles

This paper studies the corrosion of patinated and unpatinated bronze by acetic and formic acid vapours, sulphur dioxide and sodium chloride salt particles, at 100% relative humidity. Weight loss, X-ray diffraction, infrared and scanning electron microscopy were the techniques used. Acetic and formic acid vapours, sulphur dioxide and sodium chloride produce a high corrosion rate on bronze. In general, no protective effect was found by the patina on bronze. The principal compounds identified were Cu₂O, Cu₂S, Cu₅(SO₄)₂(OH)₆ · 5H₂O, Cu(CH₃CO₂)₂ · XH₂O and Cu(HCO₂)2.     

Synthesis,crystal structure and anticancer activity of 2D-coordination polymer of cerium(III) with chiral Schiff base trans-N,N′-bis-(2-hydroxy-1-naphthalidehydene)-(1R,2R)-cyclohexanediamine

The chiral Schiff base coordination polymer [Ce(H₂L)₃(NO₃)₃Ce(H₂L)₃(NO₃)₃(H₂O)]_n [H₂L: trans-N,N′-bis-(2-hydroxy-1-naphthalidehy-dene)-(1R,2R)-cyclohexanediamine] was synthesized and characterized by infrared spectroscopy, elemental analysis and single-crystal X-ray diffraction analysis. X-ray crystallography shows that the Ce(III) coordinates with three neutral Schiff base ligands and three nitrates. One Ce(III) is nine-coordinated by three oxygen atoms from three different Schiff base ligands and six oxygen atoms from three nitrates, the other Ce(III) is ten-coordinated because of the coordination of an additional water molecule. Each Schiff base ligand serves as a bridging ligand to link Ce(III) ions through oxygen atoms, leading to a coordination polymer. The Ce(III) coordination polymer displays two dimensional plane grid network structure. The antiproliferation activities of the ligand H₂L and its Ce(III) coordination polymer on MDA-MB-231 breast cancer cells were also studied by MTT (3-[4,5-dimethyltiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) method. The results indicate that H₂L and [Ce(H₂L)₃(NO₃)₃Ce(H₂L)₃(NO₃)₃(H₂O)]_n can inhibit the cellularproliferation. Moreover, the coordination polymer had higher antiproliferative activity than that of the ligand.