Preparation of Single M1 Phase MoVTe(Sb)NbO Catalyst: Study of the Effect of M2 Phase Dissolution on the Structure and Catalytic Properties

The preparation of the M1 active phase of the MoVTe(Sb)NbO catalysts by chemical dissolution in an hydrogen peroxide aqueous solution, of the M2 phase concomitantly formed has been studied. The effects of the reaction temperature and of the H₂O₂ content of the aqueous solution used for the chemical dissolution have been investigated. The washed Te containing catalysts were shown in all cases to be single M1 phase from XRD diffraction but difference in chemical composition were observed depending upon the washing conditions. These differences were explained by the presence of undissolved M2 phase or amorphous phase covering the M1 phase and leading to much less active catalysts. The solids tend to loose tellurium under the most severe washing conditions, which has a direct effect on the catalytic properties of the phase with a decrease of the selectivity to acrylic acid. The M1(Sb) phase could only be obtained pure at 60 °C independently of the H₂O₂ content. No change in the metal content was observed in the washed M1(Sb) phase but a modification of the structure was detected with a distortion of the orthorhombic unit cell to a monoclinic cell with cell parameters a = 2.1143 nm, b = 2.6632 nm, c = 0.80815 nm, α = 90.83°. The pure M1(Sb) phase appears active and selective although less efficient that the M1(Te) phase. A decrease of the selectivity to acrylic with the pre-treatment temperature of the M1(Sb) phase catalysts has been observed and related to a lower Sb³⁺ content of the phase after catalytic test. Such lower Sb³⁺ content may be explained by the absence of electron transfers between antimony and the other cations and of oxygens between the hexagonal channels and the octahedral network.     

Extraction of lead with nitrobenzene solution of strontium dicarbollylcobaltate in the presence of 18-crown-6

From extraction experiments with ⁸⁵Sr as a tracer, the extraction constant corresponding to the equilibrium Pb²⁺(aq) + SrL²⁺(nb) ⇄ PbL²⁺(nb) + Sr²⁺(aq) taking place in the two-phase water – nitrobenzene system (L = 18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K_ex(Pb²⁺, SrL²⁺) = 1.5. Further, the stability constant of the PbL²⁺ complex in nitrobenzene saturated with water was calculated: log β_nb(PbL²⁺) = 12.9.     

A new Dawson-like tungstoantimonate related to [SbVW18O60(OH)2]9−

A new tungstoantimonate (NH₄)₉[Sb^VW₁₈O₆₀(OH)₂]·25H₂O (1) has been synthesized under acidic medium conditions and characterized by element analysis, IR, TG, UV, PXRD and single-crystal X-ray diffraction analysis. Compound 1 represents the first example of Sb(V)-containing polyoxometalate with unusual Dawson-like construction. The polyoxoanion incorporates an {SbO₆} unit into the center of {W₁₈O₅₄} cluster cage.     

Solubility of potassium ferrate in 12 M alkaline solutions between 20°C and 60°C

The solubility of potassium ferrate (K₂FeO₄) was measured in aqueous solutions of NaOH and KOH of total concentration 12 M containing various molar ratios of KOH:NaOH in the range 12:0 to 3:9. Several analytical methods were tested for the determination of ferrate concentration. The final method chosen consisted of potentiometric titration of the ferrate sample with an alkaline solution of As₂O₃. The assumption was made that ferrate dissociates in concentrated KOH solutions predominantly to KFeO₄⁻. The solubility constant, S, defined as the product of the molar concentration of the potassium ion, K⁺, and the ferrate anion, KFeO₄⁻, was found to be 0·044 ± 0·006 mol² dm⁻⁶ for 20°C, 0·093 ± 0·004 mol² dm⁻⁶ for 40°C and 0·15 ± 0·09 mol² dm⁻⁶ for 60°C. From these results the heat of dissolution of K₂FeO₄ was calculated as −14·3 kJ mol⁻¹. At 60°C the enhanced decomposition of the ferrate at the higher temperature led to a greater deviation in solubility values compared with data for either 20°C or 40°C.     

Effect of diantimony trioxide on direct esterification between terephthalic acid and ethylene glycol

Experiments at various Sb₂O₃ concentrations were made in a pilot plant and the effect of Sb₂O₃ on continuous esterification between terephthalic acid (TPA) and ethylene glycol (EG) was obtained. Reaction rate constants of the previously reported reaction scheme were determined to fit with the experimental data obtained. It was found that the effect of Sb₂O₃ on reaction rate constant (k_i) can be expressed as follows.

• k₁ = (3.75 × 10^?4Sb + 1.0) × 1.5657 × 10⁹exp(?19,640/RT)
• k₂ = (4.75 × 10^?4Sb + 1.0) × 1.5515 × 10⁸exp(?18,140/RT)
• k₃ = (6.25 × 10^?4Sb + 1.0) × 3.5165 × 10⁹exp(?22,310/RT)
• k₄ = (4.50 × 10^?4Sb + 1.0) × 6.7640 × 10⁷exp(?18,380/RT)
• k₅ = (3.50 × 10^?4Sb + 1.0) × 7.7069 × exp(?2810/RT)
• k₆ = (1.75 × 10^?4Sb + 1.0) × 6.2595 × 10⁶exp(?14.960/RT)
• k₇ = (3.75 × 10^?4Sb + 1.0) × 2.0583 × 10¹⁵exp(?42,520/RT)

Simulation of esterification with these reaction rate constants at various Sb₂O₃ concentrations was made and the following results were obtained.

• 1 Sb₂O₃ accelerates the esterification reaction between TPA and EG.
• 2 Sb₂O₃ accelerates the main reaction and its effects on side reactions are minor. The higher the addition rate of Sb₂O₃, the lower the carboxyl end-group concentration (AV) and diethylene glycol content (DEG).
• 3 The comparison between simulation with potassium titanium oxyoxalate (PTO) in the previous report and with Sb₂O₃ in the present report shows that the acceleration of polycondensation reaction by Sb₂O₃ is higher. DEG formation rate is lower with PTO than Sb₂O₃.

     

Hard/soft effects of multivalence co-dopants in correlation with their location in PZT ceramics

Piezoelectric hard/soft effects of multivalence co-dopants (Sb and Mn) in correlation with their location in the lattice, were investigated in PZT ceramics, prepared by conventional ceramic technology, with the following compositions: Pb_0.98Sr_0.02 ((Ti_0.49Zr_0.51)_1-0.015-xMn_0.015Sb_x)O₃ with x = 0, 0.005, 0.01, 0.02, 0.03, where antimony was initially assumed to substitute for Ti/Zr ions. The antimony valence state was found to be +3 in all samples by X-ray Photoelectron Spectroscopy investigations. The Electron Paramagnetic Resonance spectra evidenced a steep enhancement of the Mn²⁺ concentration upon increasing antimony doping level, explained by a charge compensation mechanism, between the Sb³⁺ ions substituting Pb²⁺ at the A-sites and the Mn²⁺ ions, localized at the B-sites. The incorporation of Sb³⁺ at the A-site of the PZT lattice is also supported by the variation of the lattice parameters, determined by X-ray Diffraction, with the increasing Sb concentration. The investigation of the dielectric, electromechanical and ferroelectric properties evidenced a hard piezoelectric behavior, mainly attributed to the presence of large sized Mn²⁺ ions, localized at B-sites. Our results prove that the piezoelectric hard/soft response is decisively influenced by the interplay between multiple valence states and locations of the co-dopants, on one hand, and the charge compensation mechanisms, on the other hand. This provides indirect information about the location of some co-dopants which can substitute for both cationic sites in the PZT based ceramics.     

Co-doping effect of Zn and Sb in SnO2: Valence stabilization of Sb and expanded solubility limit

In this study, the co-doping effect of ZnO and Sb₂O₅ on the solubility limit in SnO₂ was investigated. When ZnO was added to SnO₂, its solubility limit was around 3 at%, while that of Sb₂O₅ could not be evaluated due to the severe evaporation of Sb₂O₅ during sintering. For the co-doping of ZnO and Sb₂O₅, the ZnSb₂O₆ phase was used for the source of Zn and Sb dopants to prevent the evaporation of Sb₂O₅. When ZnO and Sb₂O₅ were co-doped by ZnSb₂O₆, the solubility limit expanded to 60 at%. XPS analysis of the Sb revealed that Sb⁵⁺ is stable when Zn is co-doped. The extended solubility limit is explained by electrostatic and strain energy minimization in the lattice.     

Fabrication and electrical properties of Bi2-xSbxTe3 ternary nanopillars array films

Highly oriented Bi_2-xSb_xTe₃ (x?=?0, 0.7, 1.1, 1.5, 2) ternary nanocrystalline films were fabricated using vacuum thermal evaporation method. Microstructures and morphologies indicate that Bi_2-xSb_xTe₃ films have pure rhombohedral phase with well-ordered nanopillars array. Bi, Sb and Te atoms uniformly distributed throughtout films with no precipitation. Electrical conductivity of Bi_2-xSb_xTe₃ films transforms from n-type to p-type when x?>?1.1. Metal-insulator transition was observed due to the incorporation of Sb in Bi₂Te₃. Bi_2-xSb_xTe₃ film with x?=?1.5 exhibits optimized electrical properties with maximum electrical conductivity σ of 2.95?×?10⁵ S?m^?1 at T?=?300?K, which is approximately ten times higher than that of the undoped Bi₂Te₃ film, and three times higher than previous report for Bi_0.5Sb_1.5Te₃ films and bulk materials. The maximum power factor PF of Bi_0.5Sb_1.5Te₃ nanopillars array film is about 3.83?μW?cm^?1 K^?2 at T?=?475?K. Highly oriented (Bi,Sb)₂Te₃ nanocrystalline films with tuned electronic transport properties have potentials in thermoelectric devices.     

Antimony Remediation Using Ferrate(VI)

This research investigates a remediation technique for antimony involving the adsorption and co-precipitation of aqueous antimony by in-situ formed ferric hydroxide. Flocculation is initiated by the oxidation of iron(II) with potassium ferrate(VI), K₂FeO₄, along with oxidation of the more toxic Sb(III) to Sb(V). A 3/1 mole ratio of Fe(II)/Fe(VI) and a total Fe/Sb mole ratio of 300/1 was needed to achieve total antimony concentrations below the maximum contaminant levels for drinking water (6 μg/l).     

Thin films of Cu2Sb and Cu9Sb2 as anode materials in Li-ion batteries

Thin Cu₂Sb films have been prepared by heat-treating Sb films, electrodeposited on Cu substrates. The influence of the electrodeposition conditions and the heat-treatment period on composition and morphology of the films were investigated (SEM and XRD) and the obtained films were tested as anode materials for Li-ion batteries. The Cu₂Sb material showed a stable capacity of 290 mAh g⁻¹ (close to the theoretical capacity of 323 mAh g⁻¹) during more than 60 cycles. The presence of 9-11% (w/w) Sb₂O₃ in the electrodeposited films resulted in smaller particles but also slowed down formation of Cu₂Sb during the heat-treatment step. The presence of Sb₂O₃ was found to decrease the cycling stability although structural reversibility of Cu₂Sb was obtained both with and without Sb₂O₃. Longer heat-treatments of pure Sb films resulted in the formation of Cu₉Sb₂ which was shown to be reduced at a lower potential than Cu₂Sb. The Cu₉Sb₂ was converted to Cu₂Sb during repeated cycling and the capacity of the latter Cu₂Sb material was found to be 230 mAh g⁻¹. While reduction of the materials was complicated by simultaneous formation of an SEI layer, three plateaus could be identified during the oxidation of Li₃Sb, indicating the presence of three separate one-electron oxidation reactions.     

Mass Spectrometric Studies at High Temperatures: XXIX, Thermal Decomposition and Sublimation of Alkali Metal Sulfates

Mass spectrometric investigations of the high temperature equilibrium vapor species over the solids Li₂SO₄, Na₂SO₄, K₂SO₄, Rb₂SO₄, and Cs₂SO₄ have shown that the products of thermal decomposition are M(g), where M = Li, Na, K, Rb, or Cs, SO₂(g), and O₂(g). In addition, molecules like K₂SO₄(g), Rb₂SO₄(g), and Cs₂SO₄(g) were observed, and the results show that sublimation as molecules becomes increasingly important for the heavier alkali metal sulfates. The equilibrium constants at several temperatures and heats for the decomposition reaction were determined for Li₂SO₄, Na₂SO₄, and K₂SO₄. Calculated values of the heats of decomposition for Na₂SO₄ and K₂SO₄, for which thermodynamic data are available, were in agreement with the measured quantities. The heats and entropies of sublimation to monomeric molecules for K₂SO₄(s), Rb₂SO₄(s), and Cs₂SO₄(s) were ΔH⁰₂, _1154°K= 72.8 ± 2.0 kcal mole^-1 and ΔS⁰_S1554°K= 29.2 ± 1.8 eu; ΔH⁰_S, _1123°K= 69.7 ± 1.0 kcal mole^-1 and ΔS⁰_{S, 1123°K}= 27.4 ± 0.8 eu; and ΔH⁰_{S, 1081°K}= 63.9 ± 1.7 kcal mole^-1 and ΔS⁰_{S, 1081°K}= 26.2 ± 1.6 eu, respectively.     

Dissociation et hydratation de nitrates alcalins dans le carbonate de propylene aqueux

Dissociation of lithium, sodium, potassium and tetraethylammonium nitrates and perchlorates in propylene carbonate has been studied by conductometry. Dissociation constants of alkali nitrates are 3·14 × 10^?3 (LiNO₃), 8·35 × 10^?3 (NaNO₃ and 1·92 × 10^?2 (KNO₃) at 25°C. The perchlorates and tetraethylammonium nitrate are strong electrolytes. The solubility products are 4·1 × 10^?4 (LiNO₃), 1·2 × 10^?5 (NaNO₃ and 2·5 × 10^?5 (KNO₃). The conductivity of saturated solutions of nitrates in the aqueous solvent has been determined up to 0·6 M water. Results are used to calculate the equilibrium constants for the reaction I^± + H₂O = I^± H₂O; Li⁺ 6·5, Na⁺ 2·5, K⁺ 0·5 and NO^?₃ 2·4. Dissociation constants, solubility products and hydration constants are compared with values reported for other solvents.     

Heat capacities and thermodynamic properties of antimony substituted lanthanum orthoniobates

The results of heat capacity measurements for the lanthanum orthoniobate substituted with 10, 20 and 30 mol% of antimony (LaNb_0.9Sb_0.1O₄, LaNb_0.8Sb_0.2O₄ and LaNb_0.7Sb_0.3O₄) are presented and discussed. Temperature dependence of low temperature heat capacity was analyzed within the Debye and Einstein models. The Debye temperature decreased, whereas the Einstein temperature increased with antimony content. The decrease of the Debye temperature with increasing antimony content was correlated with decreasing scheelite–fergusonite transition temperature. The increase of the Einstein temperature of LaSb_xNb_1−xO₄ with increasing antimony content may indicate increasing frequency of optical vibrations of Nb(Sb)–O₄⁻² polyhedra relative to La³⁺ cations. Using the heat capacity data, standard entropies of the phases were calculated and combined with previously measured enthalpies of formation to obtain Gibbs energies of formation. Standard thermodynamic properties were tabulated.     

Fabrication of Sb2S3 thin films by sputtering and post-annealing for solar cells

The semiconductor antimony sulfide (Sb₂S₃) is a potential absorber materials for the top sub-cell of Si-based tandem solar cells because of its appropriate band-gap, simple binary composition, nontoxic elements, and long-term stability. In this study, polycrystalline Sb₂S₃ films were fabricated by post-annealing of radio frequency (RF) magnetron sputtered precursors using an Sb2S3 target. The effects of the post-annealing temperature and atmosphere on Sb₂S₃ film properties and device performances were investigated. A high-performance device having a 2.41% power conversion efficiency was obtained by making use of a uniform Sb2S3 absorber layer. This preliminary experimental study shows that Sb2S3 thin films could be used as top sub-cell absorber materials for third-generation high efficiency, stable, and environmentally friendly Sb₂S₃/Si tandem solar cells.     

Aqueous speciation of arsenic in sulfuric acid and cupric sulfate solutions

Physicochemical data for arsenic speciation calculations, and the development and application of an equilibrium model were determined numerically and experimentally to simulate the speciation of arsenic and copper in aqueous sulfuric acid solutions. Results show that concentrations of dissolved species depended highly on temperature, acidity, and solution concentration. A range of species can be formed, depending on pH and temperature. In acidic solutions, the principal ones are: HSO₄⁻, H⁺, Cu²⁺, CuSO_4(aq), H₃AsO_3(aq), and H₃AsO_4(aq); arsenic ions are present in low concentrations. Association degrees increase with temperature and concentration, the solutes being partially dissociated. Calculations of metal solubilities, pH, and ionic conductivity showed good agreement with experimental data. The model can be applied to study the aqueous speciation in industrial copper hydrometallurgical solutions, as well as to define and to evaluate purification strategies for the treatment of industrial effluents.     

The influence of different antimony content in Ga-As-Sb-S chalcogenide glass system: Modification of physical & spectroscopic properties and fiber forming ability

In order to improve the fiber drawing performances including the anti-crystallization in fiber drawing process and the mechanical properties, the fourth component of antimony (Sb) was introduced into Ga_0.8As_39.2S₆₀ glass, and a serial Ga_0.8As_39.2-xSb_xS₆₀ (x = 0, 1, 3,5, 7, 9 and 11) novel chalcogenide glasses doped with 3000 ppmw Dy³⁺ ions were prepared. The influences of antimony content on the physical properties, spectroscopic properties and fiber forming ability of glass were investigated. The experiment results indicate that the introduction of moderate antimony into glass effectively improves the fiber drawing performance and the spectroscopic properties of Dy³⁺ ions. The Ga_0.8As_34.2Sb₅S₆₀ composition glass possesses the best performance and it is recommended a good candidate for mid-infrared laser working medium.     

Improvement of Medical Applicability of Hydroxyapatite/Antimonous Oxide/Graphene Oxide Mixed Systems for Biomedical Application

This study supports the binary and ternary merging tactic, this methodology is useful in the creation of new features that lacked in the parent constituents. Ra develops to reach its peak of 4.25 nm upon HAP/Sb₂O₃/GO which is shadowed by HAP/Sb₂O₃ with 3.87 nm. EDX technique offers quantitative, and qualitative elemental composition of the studied composite, where C, O, P, Ca, and Sb elements records 17.14, 66, 8.7, 7.57, and0.58%, respectively. Consequently, the composition is pure. Also, The BET technique’s resultant surface area is 39.49 for HAP/Sb₂O₃, and 50.76 m²/g for HAP/Sb₂O₃/GO. Additionally, The (HAP/GO, and HAP/Sb₂O₃/GO) ceramic composites microhardness was 3.2?±?0.2 GPa for binary composite, and 3.5?±?0.3 GPa for ternary composite. Thus, GO nano-materials enhance mechanical behavior. Applicably, the merging of the three components in one ternary nanocomposite presents the highest viability with 98.4?±?0.8%, besides the highest antibacterial performance by 15.2?±?0.4 mm for Escherichia coli and 16.1?±?0.5 mm for Staphylococcus aureus.

     

Monatomic Sb thin films alloyed with Sb2S3 enables superior thermal stability and resistance drift by spontaneous self-decomposition

Monatomic Sb thin films can eliminate the risks of compositional partitioning, but it normally crystallizes instantly and fails to maintain amorphous state at room temperature. Here, we prepared Sb_x (Sb₂S₃)_100-x thin films. The materials consist of pure Sb with low resistance drift and chalcogenide Sb₂S₃ with high thermal stability. It is found that the Sb_64·8(Sb₂S₃)_35.2 thin film possesses the advantages of these two compounds. The thin film showed good phase-change ability with an ultralow resistance drift coefficient of 0.006, much lower than conventional Ge₂Sb₂Te₅ (0.076). Moreover, it also exhibited a better amorphous thermal stability. These improvements are closely related to the hybrid nanostructure of Sb crystals and Sb–S phase by spontaneous self-decomposition in the Sb-rich Sb–S material. Our work thus demonstrates that the binary Sb-rich Sb–S thin film can become a promising alternative to replace the conventional Ge₂Sb₂Te₅ thin film with potential for neuromorphic synaptic devices.     

Thermodynamic Modeling of Solvent Extraction Systems: Successes and Problems

Abstract

Recent approaches to thermodynamic modeling of solvent extraction systems are applied to nitric acid and Am(III) extraction by dihexyl-N,N-diethylcarbamoylmethyl phosphonate in CCl₄, 1:1 and 2:1 complexes were found to form in the organic phase for nitric acid extraction with K₁ = 0.125 ± 0.00154 and K₂ = 1.41 × 10^?5 ± (2.60 × 10^?7). Extraction of nitric acid was also followed by IR spectrophotometry which verified the results obtained. Modeling of Am(III) extraction up to an initial aqueous nitric acid concentration of 4 M yielded good results. Extraction constants for species forming in the organic phase were found to be K _ex0 = 38.6 ± 30.4 for [Am(NO₃)₃-E₃]₀, K _ex1 = 7.43 ± 0.572 for [Am(NO₃)₃-E₂-(E-HNO₃)₂)]₀ and K _ex2 = 1.04 ± 0.0281 for [Am(NO₃)₃,-E-(E-HNO₃)₂)]₀. Problems encountered are highlighted and discussed, improvements to modeling approaches are suggested, and results obtained are critically discussed and compared to the literature.     

Evidence for the photochemical formation of a high-valent 2A2u antimony porphyrin π-radical cation

Irradiation of [Sb^V(tpp)(OH)₂]⁺ (tpp=dianion of 5,10,15,20-tetraphenylporphyrin) at 298 K in argon saturated dichloromethane under steady state conditions results in the formation of the highly oxidising π-radical cation [Sb^V(tpp)(OH)₂]²⁺ with spectral characteristics corresponding to a ²A_2u electronic ground state.