Hydrothermal synthesis and thermodynamic properties of 2CaO·3B<Subscript>2</Subscript>O<Subscript>3</Subscript>·H<Subscript>2</Subscript>O

2CaO·3B₂O₃·H₂O which has non-linear optical (NLO) property was synthesized under hydrothermal condition and identified by XRD, FTIR and TG as well as by chemical analysis. The molar enthalpy of solution of 2CaO·3B₂O₃·H₂O in HCl·54.572H₂O was determined. From a combination of this result with measured enthalpies of solution of H₃BO₃ in HCl·54.501H₂O and of CaO in (HCl+H₃BO₃) solution, together with the standard molar enthalpies of formation of CaO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpy of formation of −(5733.7±5.2) kJ mol⁻¹ of 2CaO·3B₂O₃·H₂O was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method.     

Synthesis and Electrocatalytic Properties of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanocrystallites with Various Morphologies

Co₃O₄ crystallites with particle, plate-, tube-, rod- and sheet-like morphologies were successfully prepared by the calcination of the corresponding precursors synthesized via a precipitation or hydrothermal procedure. The morphologies of the precursors and Co₃O₄ nano-tubes were detected by field emission scanning electron microscopy (FE-SEM). The as-obtained Co₃O₄ samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and special surface area measurement (BET). The electrocatalytic activity of p-nitrophenol reduction with the Co₃O₄ products decorated on a glassy carbon electrode (GCE) was tested, respectively, using cyclic voltammetry (CV) in a basic solution. The results indicated that p-nitrophenol was reduced with higher current density but almost at a constant potential on the Co₃O₄/GCE in contrast with that on a bare GCE at the same conditions. The highly catalytic activity of the as-prepared Co₃O₄ in a basic solution suggested their wide applications in environmental treatment or organic synthesis.     

One-step template-free solution route for Cu(OH)<Subscript>2</Subscript> nanowires

Cu(OH)₂ nanowires with a diameter of 8–10 nm and lengths of tens of micrometers were fabricated in the basic solution by dropping simply NaOH solution into CuCl₂ solution at ambient temperature. The formation mechanism of nanowires was discussed. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize the samples. This article was submitted by the authors in English.     

Preparation and characterization of high specific surface area Mn<Subscript>3</Subscript>O<Subscript>4</Subscript> from electrolytic manganese residue

Mn₃O₄ powders have been produced from Electrolytic Manganese Residue (EMR). After leaching of EMR in sulfuric acid, MnSO₄ solution containing various ions was obtained. Purifying the solution obtained and then adding aqueous alkali to the purified MnSO₄ solution, Mn(OH)₂ was prepared. Two methods were employed to produce Mn₃O₄. One way was oxidation of Mn(OH)₂ in aqueous phase under atmosphere pressure to obtain Mn₃O₄. The other way was roasting Mn(OH)₂ precursors in the range of 500°C to 700°C. The prepared samples were investigated by using several techniques including X-ray powder diffraction (XRD), Fourier Transformation Infra-Red (FTIR) spectra, and Brunauer-Emmett-Teller (BET) specific surface area instrument. Particle distribution and magnetic measurements were carried out on laser particle size analyzer, vibrating sample magnetometer (VSM). Through XRD, FTIR and determination of total Mn content (TMC), the products prepared were confirmed to be a single phase Mn₃O₄. BET specific surface areas can reach to 32 m² g⁻¹. The results indicated that products synthesized by aqueous solution oxidation method had higher specific surface areas and smaller particle size than those prepared by means of roasting. However the products prepared using the above two methods showed no obvious differences in magnetic property.      

Synthesis of non-agglomerated Ba<Subscript>0.77</Subscript>Ca<Subscript>0.23</Subscript>TiO<Subscript>3</Subscript> nanopowders by a modified polymeric precursor method

In this work, we have studied the influence of the pH on the synthesis and structural properties of the Ba_0.77Ca_0.23TiO₃ nanopowders synthesized by a modified polymeric precursor method, in order to achieve non-agglomerated powders. Synthesis, morphology, thermal reactions, crystallite and average particle size of the synthesized powders were investigated through thermal analysis (DTA/TG), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and Infrared spectroscopy. In summary, Ba_0.77Ca_0.23TiO₃ nanopowders were synthesized for the first time at a relative low temperature (500 °C). It was also found that the alkalinity and acidity of the solution presented a great influence on the powder properties. The best results were obtained from solutions with pH = 8.5 and 11 whose nanopowders presented weakly agglomerate, with homogeneous particle size and a narrow size distribution (30–40 nm). This behavior could be explained based on the FT-IR results in which it was possible to see the increased of the chelation in higher pHs.     

Resonance scattering spectral detection of ultratrace IgG using immunonanogold-HAuCl<Subscript>4</Subscript>-NH<Subscript>2</Subscript>OH catalytic reaction

Nanogold particles of 10 nm were used to label goat anti-human IgG (GIgG) to obtain nanogold-labeled GIgG (AuGIgG). In a citrate-HCI buffer solution of pH 2.27, AuGIgG showed a strong catalytic effect on the reaction between HAuCl₄ and NH₂OH to form big gold particles that exhibited a resonance scattering (RS) peak at 796 nm. Under the chosen conditions, AuGIgG combined with IgG to form immunocomplex AuGIgG-IgG that can be removed by centrifuging at 16000 r/min. AuGIgG in the centrifuging solution also showed catalytic effect on the reaction. On those grounds, an immunonanogold catalytic RS assay for IgG was designed. With addition of IgG, the amount of AuGIgG in the centrifuging solution decreased; the RS intensity at 796 nm (I _{796 nm}) decreased linearly. The decreased intensity ΔI _{796 nm} was linear with respect to the IgG concentration in the range of 0.08–16.0 ng · mL⁻¹ with a detection limit of 0.02 ng · mL⁻¹. This assay was applied to analysis of IgG in sera with satisfactory sensitivity, selectivity and rapidity. Supported by the National Natural Science Foundation of China (Grant No. 20667001), Natural Science Foundation of Guangxi Province (Grant No. 0728213), and the Foundation of New Century Ten-Hundred-Thousand Talents of Guangxi Province     

Synthesis characterization and catalytic evaluation of Ni/ZrO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> aerogels catalysts

The Ni/ZrO₂/SiO₂ aerogels catalysts were synthesized via three different routes: (i) impregnation ZrO₂–SiO₂ composite aerogels with a aqueous solution of Ni(NO₃)₂, (ii) impregnation SiO₂ aerogels with a mixed aqueous solution of Ni(NO₃)₂ and ZrO(NO₃)₂ · 2H₂O, (iii) one-pot sol–gel procedure from precursors Ni(NO₃)₂/ZrO(NO₃)₂ · 2H₂O/Si(OC₂H₅)₄. These catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH₃-TPD), N₂ adsorption–desorption isotherms and Fourier transform infrared (FT-IR). The Liquid-phase hydrogenation of maleic anhydride (MA) was performed over these catalysts. The results revealed that the different preparation routes result in a difference between the obtained samples, concerning the crystal structure and composition, surface acidity, mixed level of each component, texture, and catalytic selectivity.     

Phase formation in the V<Subscript>2</Subscript>O<Subscript>5</Subscript>-Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>-MoO<Subscript>3</Subscript> system

The solid-phase interaction in the V₂O₅-Nb₂O₅-MoO₃ system has been investigated, and the formation of a solid solution bounded by the compositions MoNb₂V₄O_{18 ? δ}, Mo₂NbV₅O_{21 ? δ}, Mo₂Nb₃V₃O_{21 ? δ}, and Mo₄Nb₉V₉O_{57 ? δ} has been found (δ is nonstoichiometry). In the V₂O₅?Nb₂O₅ system, the formation of three compounds is verified, namely, VNbO₅ (tetragonal structure), VNb₉O₂₅, and V₂Nb₂₃O_62.5. The first two compounds are isostructural and form a continuous solid solution with tetragonal symmetry. A new compound of the composition Mo₃NbVO_{14 ? δ} has been synthesized. This compound is isostructural to the Mo₃Nb₂O₁₄ compound described in the literature and forms a tetragonal solid solution with it. The phase equilibria in the V₂O₅-Nb₂O₅-MoO₃ system in the subsolidus region have been determined.     

Formation and properties of the Fe<Subscript>8</Subscript>V<Subscript>10</Subscript>W<Subscript>16–x</Subscript>Mo<Subscript>x</Subscript>O<Subscript>85</Subscript> type solid solution

Solid solution phases of a formula Fe₈V₁₀W_16–xMo_xO₈₅ where 0≤x≤4, have been obtained, possessing a structure of the compound Fe₈V₁₀W₁₆O₈₅. It was found on the base of XRD and DTA investigations that these solution phases melted incongruently, with increasing the value of x, in the temperature range from 1108 (x=0) to 1083 K (x=4) depositing Fe₂WO₆ and WO₃. The increase of the Mo⁶⁺ ions content in the crystal lattice of Fe₈V₁₀W₁₆O₈₅ causes the lattice parameters a=b contraction with cbeing almost constant. IR spectra of the Fe₈V₁₀W_16–xMo_xO₈₅ solid solution phases have been recorded.     

Thermodynamic properties of aqueous-alcoholic solutions of sodium chloride. H<Subscript>2</Subscript>O-2-C<Subscript>3</Subscript>H<Subscript>7</Subscript>OH-NaCl

The temperature-concentration dependences of the NaCl activity coefficient in aqueous solutions of isopropanol (propanol-2) at temperatures of 298.15 and 323.15 K (solution ionic force, 0.01 to 3m; alcohol content, 10–60 wt %) were determined through the electromotive force method with an ion-selective electrode. A Pitzer model was used to mathematically describe the thermodynamic properties. The integral Gibbs energy of the solution formation of the H₂O-2-C₃H₇OH-NaCl ternary system was performed according to Darken’s method. The dissociation degree of salt in the investigated solutions was estimated using the literature data on the association constant of NaCl in aqueous-isopropanol solution.     

Electrochemical properties of spinel Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> nanoparticles prepared via a low-temperature solid route

Spinel phase Li₄Ti₅O₁₂ (s-LTO) with an average primary particle size of 150 nm was synthesised via a solid state route by calcining a precursor mixture at 600 °C. The precursor was prepared from a stoichiometric mixture of TiO₂ nanoparticles and an ethanolic solution of Li acetate and activated by ball-milling. Effects of the calcination temperature and atmosphere are examined in relation to the coexistence of impurity phases by X-ray diffraction and ⁶Li MAS NMR. The charge capacity of s-LTO, determined from cyclic voltammogram at a scan rate of 0.1 mV/s, was 142 mAh/g. The capacity of our optimised material is superior to that of commercially available spinel (a-LTO), despite the considerably smaller BET-specific surface area of the former. The superior properties of our material were also demonstrated by galvanostatic charging/discharging. From these observations, we conclude that the presented low-temperature solid state synthesis route provides LTO with improved electrochemical performance.     

Phase formation in the InPO<Subscript>4</Subscript>-Na<Subscript>3</Subscript>PO<Subscript>4</Subscript>-Li<Subscript>3</Subscript>PO<Subscript>4</Subscript> ternary system

The 950°C isothermal section of the InPO₄-Na₃PO₄-Li₃PO₄ ternary system was studied and constructed; one-, two, and three-phase fields are outlined. Five solid-solution regions exist in the system: solid solutions based on the complex phosphate LiNa₅(PO₄)₂ (olympite structure), the indium ion stabilized high-temperature Na₃PO₄ phase (Na_{3(1 − x)}In _x (PO₄); space group Fm [`3]\bar 3 m), the complex phosphate Na₃In₂(PO₄)₃, and the α and β phases of the compound Li₃In₂(PO₄)₃. A narrow region of melt was found in the vicinity of eutectic equilibria. All the phases detected in the system are derivatives of phases existing in the binary subsystems. Isovalent substitution of lithium for sodium in Na₃In₂(PO₄)₃ leads to a significant increase in the region of a NASICON-like solid solution.     

Synthesis and study of sodium triuranate Na<Subscript>2</Subscript>(UO<Subscript>2</Subscript>)<Subscript>3</Subscript>O<Subscript>3</Subscript>(OH)<Subscript>2</Subscript>

Sodium triuranate Na₂(UO₂)₃O₃(OH)₂ was synthesized by the reaction between aqueous uranyl acetate solution and aqueous sodium nitrate solution under hydrothermal conditions at 200°C. The composition and structure of the synthesized compound were determined, and its dehydration and thermal decomposition were studied, by chemical analysis, X-ray diffraction, IR spectroscopy, and thermal analysis.     

Coordination characteristics of trivalent lanthanides and actinides in molten hydrate salts of Ca(NO<Subscript>3</Subscript>)<Subscript>2</Subscript> and CaCl<Subscript>2</Subscript>

Distribution behavior of Ce(III), Am(III), and Cm(III) between tri-n-butyl phosphate solution and molten calcium nitrate hydrate Ca(NO₃)₂·RH₂O or molten calcium chloride hydrate CaCl₂·RH₂O was studied radiochemically. In Ca(NO₃)₂·RH₂O systems, maximum separation factors of Ce and Cm to Am were observed to be 12 (Ce/Am) and 1.7 (Cm/Am). The distribution ratios of these elements increased with the decrease of water activity in the hydrates, and the extractabilities at the water deficient region was less sensitive compared to those at the water abundant region. This trend was similar to the coordination circumstance change observed in electronic absorption spectra of Nd(III) in the hydrates.     

Oxidative dehydrogenation of propane on the VO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/CeZrO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> supported catalyst

The oxidative dehydrogenation of propane on a supported vanadium catalyst was studied (the support was a complex oxide system consisting of a ceria–zirconia solid solution deposited on γ-Al₂O₃ (CeZrO/γ-Al₂O₃)). A comparative analysis of the properties of the support and the catalyst prepared on its basis was performed. The support and catalyst were characterized by the BET method, scanning electron microscopy, X-ray diffraction analysis, and Raman spectroscopy. The catalytic properties of the catalyst and support were studied in propane oxidation at 450 and 500°C with pulse feeding of the reagent. The effect of propane on the support was found to improve the oxidative properties of the latter. This behavior of the support is related to the preparation procedure, which leads to the formation on its surface of the crystalline phase of the ceria–zirconia solid solution and amorphous ZrO₂ and Al₂O₃ phases and/or their solid solution. Similar processes occur with the catalyst support during the oxidative dehydrogenation, giving rise to additional active centers (CeVO₄).     

Improvement of the cycle life of composite xerogel V<Subscript>2</Subscript>O<Subscript>5</Subscript>/C in aqueous LiNO<Subscript>3</Subscript> solution by addition of vinylene carbonate

The xerogel V₂O₅/C composite was synthesized by a sol-gel method, using the suspension of carbon black in the solution of crystalline V₂O₅ in hydrogen peroxide as the precursor solution. The Li⁺ intercalation/deintercalation reactions of the xerogel V₂O₅/C composite, used as an anode material of a two-electrode cell with an aqueous LiNO₃ solution as the electrolyte, was studied before and after the addition of vinylene carbonate (VC). Upon addition of vinylene carbonate in an amount of only l wt %, the coulombic capacity during galvanostatic cycling, instead of commonly observed permanent fade, displayed an initial increase and then a stable plateau.     

Four-component system LiF-K<Subscript>2</Subscript>WO<Subscript>4</Subscript>-CaF<Subscript>2</Subscript>-BaWO<Subscript>4</Subscript>

The four-component system LiF-K₂WO₄-CaF₂-BaWO₄ has been studied for the first time using physicochemical methods. The a priori prediction of the phase complex revealed the phase tree and crystallization path of the system. The prediction was verified experimentally, by construction of a topologic model of the phase diagram, and the solution of the equations of the general law of liquidus-surface formation. The density has been measured, and the heat-storage properties of eutectic mixtures have been estimated.     

Interactions in the NdF<Subscript>3</Subscript>-Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>-MF<Subscript>2</Subscript> (M = Ba,Sr) systems

Isothermal anneals (at 873 K) and powder X-ray diffraction were used to study isothermal sections of phase diagrams of the NdF₃-Nd₂O₃-MF₂ (M = Ba, Sr) systems. In studying the NdF₃-Nd₂O₃-BaF₂ system, classical solid-phase synthesis was supplemented with mechanochemical activation of feedstock mixtures or BaF₂ activated with gaseous hydrogen fluoride was used. In both systems, a solid solution with the fluorite structure based on MF₂ and NdOF phases, a solid solution with the tysonite structure based on NdF₃, and an ordered fluorite-related phase Ba₄Nd₃F₁₇ were found. The NdOF-based solid solutions were shown to have polymorphism: β_trig ai α_cub at ≈800 K; a new trigonal phase of these solid solutions has been discovered. The effect of a dimensional factor $\left( {R_{Ba^{2 + } } > R_{Sr^{2 + } } } \right)$\left( {R_{Ba^{2 + } } > R_{Sr^{2 + } } } \right) on phase formation and unit cell parameters of the solid solutions was traced.     

Synthesis,characterization and olefin hydroformylation reactions of <Emphasis Type="Italic">mer</Emphasis>-[Mo(CO)<Subscript>3</Subscript>(p-C<Subscript>5</Subscript>H<Subscript>4</Subscript>N-CN)<Subscript>3</Subscript>]

Mer-[Mo(CO)₃(p-C₅H₄N-CN)₃] was prepared by UV-irradiation of a THF solution of Mo(CO)₆ and para-cyanopyridine under heating. The complex was characterized by FT-IR, MS, ¹H and ¹³C NMR and showed catalytic activity for olefin hydroformylation (1-hexene, cyclohexene and 2,3-dimethyl-2-butene as model olefins; 600 psi synthesis gas (pCO/pH₂ = 1); 100 °C; 24 h; toluene). An examination of the complex catalyzed hydroformylation of a real naphtha cut (El Palito refinery, Venezuela), under the same conditions, also showed activity in the conversion to oxygenated products.     

Thermal oxide synthesis and characterization of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanorods and Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanowires

Fe₃O₄ nanorods and Fe₂O₃ nanowires have been synthesized through a simple thermal oxide reaction of Fe with C₂H₂O₄ solution at 200–600°C for 1 h in the air. The morphology and structure of Fe₃O₄ nanorods and Fe₂O₃ nanowires were detected with powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The influence of temperature on the morphology development was experimentally investigated. The results show that the polycrystals Fe₃O₄ nanorods with cubic structure and the average diameter of 0.5–0.8 μm grow after reaction at 200–500°C for 1 h in the air. When the temperature was 600°C, the samples completely became Fe₂O₃ nanowires with hexagonal structure. It was found that C₂H₂O₄ molecules had a significant effect on the formation of Fe₃O₄ nanorods. A possible mechanism was also proposed to account for the growth of these Fe₃O₄ nanorods. Supported by the Fund of Weinan Teacher’s University (Grant No. 08YKZ008), the National Natural Science Foundation of China (Grant No. 20573072) and the Doctoral Fund of Ministry of Education of China (Grant No. 20060718010)