Ratio Of Metal Cations Research Articles

Preparation and characterization of ordered mesoporous Mg–Al–Co hydrotalcite based catalyst for decarboxylation of jatropha oil

This paper reported preparation of novel order mesoporous Mg–Al–Co hydrotalcite based catalysts through sol–gel procedure using precursors such Mg(NO3)2, Al(NO3)3 and Co(NO3)2 and Na2CO3. The catalyst also contained both acidity and basicity being very convenient for decarboxylation process of vegetable oil to green hydrocarbons. The alkaline media was maintained at pH 10 during the processes. Molar ratio of metal cations and temperature of the sol–gel processes were investigated for their effect in the mesoporous structure formation. The results showed that the procedure should be established at 70 °C with the molar Mg/Al/Co ratio of 1/5/0.2. Acidity and basicity of the mesoporous hydrotalcite based catalyst were demonstrated for their co-existence. The as-synthesized material at the suitable conditions was used as catalyst for decarboxylation of jatropha oil to obtain green hydrocarbons mainly belonging to diesel fraction. The decarboxylation was carried out at 400 °C for 3 h in closed auto-pressurized reactor exhibiting a yield of diesel involving hydrocarbons of over 70% after distillation and analysis. The result also confirmed that the acidity and basicity greatly accelerated the activity of the catalyst. Some techniques were used to characterizing the catalyst including XRD, SEM, TEM, TGA, NH3-TPD, CO2-TPD and BET, and GC–MS was also used to analyze the main product composition.

The characterization of ternary Zn-Ni-Co alloy coatings electrochemically deposited on steel from sulfate solution

In this work the electrochemical deposition of ternary Zn-Ni-Co alloy coatings on steel from sulfate, additive-free electrolyte, was investigated. The ratio of metal cations [Co2+]/[Ni2+] in the plating solution was analysed, as well as the influence of deposition current densities on the chemical content and corrosion stability of ternary coatings. Coatings were deposited at 25 °C. On the basis of the results obtained it was shown that the cobalt to nickel ratio is alloy coatings is significantly higher as compared to their ratio in the plating electrolyte, indicating beneficial effect of Ni and Co codeposition. Deposition of Zn-Ni-Co alloy coatings from both plating electrolytes analysed in this work was anomalous. The optimal parameters for electrodeposition of ternary Zn-Ni-Co alloy coatings with increased corrosion stability are metal ion ratio [Co2+]:[Ni2+] = 0,46 in the plating bath and deposition at current densities of 3 i 6 A dm-2.

Citrate mediated synthesis and tuning of luminescence in Eu3+ incorporated Gd2O3 nanophosphors

Gd1.9Eu0.1O3 nanophosphors were prepared successfully by a large-scale facile solution based citrate-metal complex controlled combustion method and was systematically studied by varying the citric acid to metal cation ratio. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) measurements and radiative properties were done to evaluate the crystal structure, phase formation, phase composition, surface morphology, radiative and luminescent properties of the prepared nanophosphors. Photoluminescent emission intensity of the samples can be correlated with the amount of citric acid, improved crystallinity, uniform morphology, particle size, reduced defects, and proper diffusion of Eu3+ in to the crystal structure of Gd2O3. Higher asymmetricity results in intense red emission (612 nm) due to 5D0-7F2 forced electric dipole transition and found that photoluminescence intensity is highest for the sample prepared with citric acid to metal cation ratio of 2:1. The existence of strong red emission from Gd1.9Eu0.1O3 nanophosphor corresponding to 5D0-7F2 transition (612 nm) of Eu3+ under UV light excitation make it a promising candidate for applications in bio assays, magnetic resonance imaging, deep uv LED's, solid state lighting, fluorescent lamps and flat panel displays.

Influence of the Citric Acid and Metal Cation Ratio on the Structural and Morphological Characteristics of Aluminum Oxide Synthesized by Pechini Method

Given the opportunities that aluminas present in relation to the broad field of applications to which they refer, the literature has reported great diversity in methodology to obtain these materials in the search of generating the best properties. In this way, the aim of this work is to evaluate the use of different citric acid and metallic cation ratio on the structural and morphological characteristics of the alumina synthesized by Pechini method and calcined at 1100°C. The samples were characterized by X-ray diffraction, thermal analysis, particle size and scanning electron microscopy. The results showed a large amount of loss of mass after pyrolysis. The α-alumina phase was achieved for the two studied ratio reaching values for crystallite size of 41.4 and 52.5 nm, crystallinity of 88 and 91.2%, agglomerates size of 12.3 and 14μm, for the synthesized samples 2:1 and 3:1, respectively. According to the SEM images, the changes in the citric acid: metallic cation ratio did not significantly modify the morphology of the alumina.

Effect of Calcination Temperature in the Aluminum Oxide Synthesized by Pechini Method in the Citric Acid: Metal Cation Ratio of 2:1

Through the constant search by researchers to obtain materials with improved properties, literature has presented an annual increase in the number of articles that seek to optimize in the methodology used to prepare nanopowders. In this way, the aim of this work is to study how the calcined temperature (500, 600, 700, 800, 900, 1000, 1100 and 1200oC) changes the final properties of the alumina synthesized by Pechini method with citric acid: metallic cation ratio of 2:1. The alumina was characterized by thermal analysis, X-ray diffraction, particle size analysis and scanning electron microscopy. The results showed a total of mass loss of 61.6%. The alumina phase appear at 800°C of temperature, however the α-alumina only appear at 1100oC. The increase in the calcined temperature increases the crystallite size and the crystallinity of the alumina and the great value reached for the agglomerates diameter was 13μm for the alumina calcined at 1200oC. In relation to the morphology of the alumina, it was observed heterogeneous particles with different size and irregular geometry, with aspect of high density.

The effect of lead cations on the fluorescence characteristics of bovine serum albumin in aqueous solution

The effect of lead (heavy metal) cations on the fluorescence characteristics and photophysical parameters (fluorescence intensity and anisotropy, absorption cross section, excited state lifetime, and rates of singlet-triplet conversion and reversible photobleaching) of tryptophan in an aqueous solution of bovine serum albumin (two-tryptophan protein) is studied and compared with the effect in the aqueous solution of tryptophan. It is demonstrated that the effect of lead on the fluorescence characteristics of the protein is manifested at a molar concentration ratio of metal cations and protein macromolecules of greater than 10 and related to the dynamic quenching of the excited state, protein aggregation, and an increase in the rate of singlet-triplet conversion (the effect of a heavy atom) in tryptophan molecules.

Density Functional Theory Predictions of the Composition of Atomic Layer Deposition-Grown Ternary Oxides

The surface reactivity of various metal precursors with different alkoxide, amide, and alkyl ligands during the atomic layer deposition (ALD) of ternary oxides was determined using simplified theoretical models. Quantum chemical estimations of the Brønsted reactivity of a metal complex precursor at a hydroxylated surface are made using a gas-phase hydrolysis model. The geometry optimized structures and energies for a large suite of 17 metal precursors (including cations of Mg, Ca, Sr, Sc, Y, La, Ti, Zr, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, and Ga) with five different anionic ligands (conjugate bases of tert-butanol, tetramethyl heptanedione, dimethyl amine, isopropyl amidine, and methane) and the corresponding hydrolyzed complexes are calculated using density functional theory (DFT) methods. The theoretically computed energies are used to determine the energetics of the model reactions. These DFT models of hydrolysis are used to successfully explain the reactivity and resulting stoichiometry in terms of metal cation ratios seen experimentally for a variety of ALD-grown ternary oxide systems.

Optimising The Parameters For The Synthesis Of Cuin-Nanoparticles By Chemical Reduction Method For Chalcopyrite Thin Film Precursors

ABSTRACTRoll-to-roll deposition techniques for the fabrication of chalcopyrite solar cells are of major interest and are a promising alternative to state of the art vacuum processes. However, for roll-to-roll processes the preparation of precursor materials like nanoparticle inks is a crucial point. In this work a study on the preparation technique of copper-indium intermetallic nanoparticles was conducted. The preparation of the nanoparticles is based on the chemical reduction of copper and indium cations with sodium borohydride. Different parameters are discussed regarding their influence on (1) size and shape of the nanoparticles, (2) Cu/In ratio within the synthesised nanoparticles and (3) yield of the synthesis. Results show a strong dependency of the Cu/In ratio of the nanoparticles and the yield of the synthesis on the synthesis parameters. The influence of different parameters like (a) the ratio of metal cations to BH4- anions, (b) the Cu2+/In3+ cation ratio within the precursor solution and (c) the dropping rate of the copper-indium precursor solution are discussed. The Cu/In ratio within the nanoparticles can mainly be controlled by the Cu2+/In3+ cation ratio and the dropping rate of the copper-indium precursor solution. The yield of the synthesis shows saturation behaviour depending on the ratio of metal cations to BH4- anions. Shape and size of the nanoparticles are independent of the varied parameters.

Vibrational spectroscopic and electrochemical characteristics of poly (propylene glycol)-silver triflate polymer electrolyte system

Fourier transform infrared spectroscopic and electrochemical complex impedance studies have been carried out on a series of complexes containing poly(propylene glycol) of molecular weight 4,000 and silver triflate (AgCF3SO3) salt corresponding to the ether oxygen to metal cation ratios (O : M) in the range 16:1 to 12:1. The formation of ion pairs and aggregates noticed in the case of specimens having high salt concentrations as well as the complete coordination of the cation with the ether oxygen at low salt concentrations within the PPG4000-AgCF3SO3 polymer electrolyte system have been confirmed. The appearance of two weak triflate bands at 1,032 and 1,272 cm−1 in the absorption spectra in respect of low salt concentrations is indicative of the fact that triflate ions are free within the polymer matrix. The room temperature (298 K) electrical conductivity is found to increase with increasing ether oxygen content while exhibiting the maximum value of 7.1 × 10−5 Scm−1 possibly due to silver ionic transport in the case of the typical composition having an O : M ratio of 16:1.

BaTiO3, SrTiO3, CaTiO3, and BaxSr1−xTiO3 Particles: A General Approach for Monodisperse Colloidal Perovskites

We describe a novel general method for synthesizing monodisperse colloidal perovskite particles at room temperature by postsynthesis addition of metal hydroxides to amorphous titania colloids. In previous work, we used titania particles to synthesize homogenously mixed silica−titania composite particles by addition of a silica precursor to the titania particles ( Chem. Mater., 2009, 21, 979). Here we show that the principle is general and can be used to prepare different titania-based composite beads. We demonstrate the synthesis of colloidal perovskites like BaTiO3, SrTiO3, CaTiO3 and Ba0.5Sr0.5TiO3, which have importance for the electronics industry for their dielectric properties. Mixed perovskites like BaxSr1−xTiO3 bring tunability in structure and properties by changing the ratio of metal cations. We also show fabrication of metal core, BaTiO3 shell particles, which could find applications in percolative capacitors, and luminescence properties of Pr3+ doped colloidal perovskites.

FT-IR spectroscopic investigation of ionic interactions in PPG 4000: AgCF 3SO 3 polymer electrolyte

The effect of salt concentration on the ubiquitous ionic interactions observed in the case of the silver ion conducting polymer electrolyte system poly(propylene glycol) (PPG)–silver triflate has been investigated using Fourier transform infrared (FT-IR) spectroscopy as a probe for the characterization of the local environment of the triflate ion in PPG-based polymer electrolytes. The maximum free anion concentrations of symmetric and asymmetric SO 3 stretching modes in the case of poly(propylene glycol) complexed with silver triflate (AgCF 3SO 3) corresponding to the ether oxygen metal cation ratios from 2:1 to 6:1 have been investigated in detail. The present Fourier transform infrared spectral studies of the C O C stretching mode have shown reduction in the intensity, due to the decrease of salt concentration. The splitting of vibrational modes has been analyzed in terms of free ions, ion pairs and aggregates. The bands of SO 3 symmetric stretching mode appearing at 1032 and 1038 cm −1 in the chosen polymer electrolyte material have been assigned to free ions and ion pairs respectively.

PARTIAL MELTING OF THE ASSEMBLAGE SPHALERITE + GALENA + PYRRHOTITE + CHALCOPYRITE + SULFUR: IMPLICATIONS FOR HIGH-GRADE METAMORPHOSED MASSIVE SULFIDE DEPOSITS

The role of Cu, added as CuFeS 2 , and S, added as FeS 2 that decomposed to FeS + S during heating, on the melting behavior of Fe-Pb-Zn massive sulfide deposits has been investigated at 2 MPa. The solidus of the assemblage CuFeS 2 -PbS-FeS-ZnS-S is located at a temperature between 700° and 730°C, at least 70°C below that of the galena-pyrrhotite-sphalerite system. The lowest temperature melt that was present in an analyzable volume in this study (at 750°C) had the average composition of 68.8 at. percent Fe, 6.5 at. percent Cu, 1.7 at. percent Zn, and 23 at. percent Pb. The experimental charges underwent gravity-driven differentiation into two density-stratified crystal-rich zones (sphalerite- and pyrrhotite-rich, respectively) floating on a melt-rich zone. Vesiculation textures developed near the top of the melt-rich portion of the quenched charges, suggesting that the melts produced in this study contained sulfur at a concentration greater than the 1:1 ratio of sulfur to metal cations that typifies the sulfides that crystallized from the melt (pyrrhotite + galena + chalcopyrite). This study demonstrates that the assemblage CuFeS 2 -PbS-FeS-ZnS-S will melt close to the second sillimanite isograd in metapelites, within the upper amphibolite facies, and will produce initial melts that crystallize approximately equal proportions (wt %) of pyrrhotite and galena, with relatively little chalcopyrite and very little sphalerite. The apparent excess sulfur in the melts, in conjunction with the relatively low copper concentrations in the melts developed close to the solidus, suggests that the depression of the solidus relative to that of the galena-pyrrhotite-sphalerite system can be attributed to the solubility of a pyrite component in the melt. These findings indicate that sulfide mobility in a melt phase should be considered in the evolution of all massive sulfide bodies metamorphosed to upper amphibolite facies conditions or higher, and that the presence of a sulfur-rich fluid phase may promote melting during high-grade metamorphism.

Phase equilibria in the system Fe-Zn-O at intermediate conditions between metallic-iron saturation and air

The phase equilibria in the FeO-Fe2O3-ZnO system have been experimentally investigated at oxygen partial pressures between metallic iron saturation and air using a specially developed quenching technique, followed by electron probe X-ray microanalysis (EPMA) and then wet chemistry for determination of ferrous and ferric iron concentrations. Gas mixtures of H2, N2, and CO2 or CO and CO2 controlled the atmosphere in the furnace. The determined metal cation ratios in phases at equilibrium were used for the construction of the 1200 °C isothermal section of the Fe-Zn-O system. The univariant equilibria between the gas phase, spinel, wustite, and zincite was found to be close to pO2=1 · 10−8 atm at 1200 °C. The ferric and ferrous iron concentrations in zincite and spinel at equilibrium were also determined at temperatures from 1200 °C to 1400 °C at pO2 = 1·10−6 atm and at 1200 °C at pO2 values ranging from 1 · 10−4 to 1 · 10−8 atm. Implications of the phase equilibria in the Fe-Zn-O system for the formation of the platelike zincite, especially important for the Imperial Smelting Process (ISP), are discussed.

Preparation of ferroelectric BaNb 2O 6 by the urea method

A precipitate was formed when an aqueous solution of BaCl 2, NbF 5 and urea in required ratio (the ratio of total metal cations to the urea is five) is heated on a water bath at 100 °C. This precipitate on decomposition at 600 °C yielded the nanocrystallites of BaNb 2O 6 (BN), as confirmed by X-ray diffraction study (XRD). This is a much lower temperature as compared to that prepared by traditional solid state method (1000° C) as reported for the formation of BaNb 2O 6. Transmission electron microscope (TEM) investigations revealed that the average particle size is 85 nm for the calcined powders. The room temperature dielectric constant at 1 kHz is found to be 900. The ferroelectric hysteresis loop parameters of these samples were also studied.

Synthesis of bismuth titanate by the urea method

A simple urea precipitation route was adopted for the preparation of bismuth titanate (Bi 4Ti 3O 12) powders. Stoichiometric quantities of BiCl 3 and TiOCl 2 were mixed with the required amount of urea (the ratio of total metal cations to urea is five), and the mixture was heated on a water bath. This leads to the formation of precipitate, which was decomposed at 973 K. The formation of bismuth titanate was observed on calcining powders at 973 K by X-ray diffraction studies. The average particle size is found to be 100 nm by microscopy. The room temperature dielectric constant is found to be 150 at 1 kHz. The hysteresis loop parameters were also obtained by home-built Sawer-Tower circuit.

Separation of heavy metals by parametric pumping with variation of pH: Part I: Application of cation exchangers in binary systems

Parametric pumping with variation of the pH is an innovative ion-exchange process which allows heavy metals from mixed waste solutions to be recovered as single components and, therefore, to be recycled. The process is based on the addition of complexing agents to a mixture, on its separation into two half volumes and a periodic contact of an ion exchanger with both liquid phases. Optimum conditions for the separation with respect to the kind of complexing agent, its amount relative to the concentration of heavy metals and to the amount of ion exchanger material have been deduced in preliminary investigations. Using citric acid as complexing agent the separation of binary mixtures of divalent/divalent and trivalent/divalent metal ions has been investigated. The kinds of metal species forming more stable complexes are concentrated in the high-pH solution, the other ones in the low-pH solution. Separation is more successful the greater the difference of the ratio of non-complexed metal cations at the two operating pH values becomes. As a consequence, systems with copper as one component can be well separated. Less effective separations were found for mixtures of other divalent metals. The separation can be emphasized by applying a second separation step to the two half volumes.

Growth of (Ni,Zn)Fe2O4 Thin Films by Liquid Delivery Metal-Organic Chemical Vapor Deposition

AbstractNi,Zn-ferrite (NZF) thin films are of interest for high frequency applications because of their high saturation magnetization compared to garnet films and their low eddy current losses compared to metal alloy films. Therefore there is an increasing need for methods to deposit single crystal ferrite thin films for incorporation into next generation microwave devices.Epitaxial thin films of NZF have been deposited by liquid delivery metal-organic chemical vapor deposition onto (100) oriented MgO substrates. The morphology, orientation and magnetic properties of the as-deposited films were investigated as a function of deposition temperature and pressure. X-ray diffraction (XRD) reveals highly oriented films with a film strain of 1.01% compared to bulk lattice parameters. Films with well saturated magnetic hysteresis were obtained under a number of conditions with values of saturation magnetization up to 270 emu/cc (3400 gauss) with relatively low coercive fields ~100 Oe. The influence of metal cation ratio on magnetic properties is discussed.

A Raman, ac impedance and pfg-NMR investigation of poly(ethylene oxide) dimethyl ether (400) complexed with LiCF 3SO 3

ac impedance, Raman spectroscopy and pulsed field gradient NMR measurements have been conducted on solutions of poly(ethylene oxide) dimethyl ether of molecular weight 400 complexed with LiCF 3SO 3 as a function of salt concentration; the ether oxygen to alkali metal cation ratios (O:M) ranging from 53:1 to 563:1. From an analysis of the ν S (SO 3) band envelope of the triflate anion, the relative concentrations of anions in various chemical environments have been calculated. A slight redissociation effect is observed with increasing salt concentration which correlates well with an observed increase in the molar conductivity. Pulsed field gradient NMR measurements show that the 1H, 7Li and 19F self-diffusion coefficients all decrease monotonically with increasing salt concentration. Experimental conductivity data is compared to values calculated from the diffusion coefficients using the Nernst–Einstein relation. We find that the calculated values are higher for all concentrations; the discrepancy increases with decreasing salt concentration.

Ionic Interactions and Transport Properties in Methyl Terminated Poly(propylene glycol)(4000) Complexed with LiCF3SO3

Alternating current (ac) impedance, restricted diffusion, and vibrational spectroscopic (Raman and IR) measurements have been conducted on complexes of methyl capped poly(propylene glycol) of molecular weight 4000 and LiCF{sub 3}SO{sub 3} salt. The relative concentrations of anions in different chemical environments have been calculated from an analysis of the symmetric anion SO{sub 3} stretch (Raman) over a wide concentration range. Comparisons are made to previous studies on hydroxyl capped PPG systems, and we find that polar polymer end groups play an important role in the solvation of the salt. The relative fraction of anions interacting directly with lithium cations is considerably higher over the entire concentration range in the present study, and we infer the existence of negatively charged ionic aggregates in the solutions. We also note that the fraction of spectroscopically `free` anions increases with increasing salt concentration in the ether oxygen to alkali metal cation ratio (O:M) range 502:1 to 12:1, contrary to a decrease reported for the analogue hydroxyl terminated electrolytes. The ionic conductivity has a more pronounced concentration dependency in the methyl capped system; notably, the molar conductivity ({Lambda}) increases dramatically with increasing salt concentration passing through a relatively sharp maximum at O:M = 20:1 atmore » room temperature. 71 refs., 8 figs., 1 tab.« less

The molar conductivity behavior in polymer electrolytes at low salt concentrations; A Raman study of poly(propylene glycol) complexed with LiCF 3SO 3

Raman scattering measurements have been carried out on poly(propylene glycol) complexed with LiCF 3SO 3 salt over a wide salt concentration range, the ether oxygen to alkali metal cation ratios (O:M) ranging from 4820: 1 to 12: 1. The relative concentrations of solvated anions, anion-cation pairs and ionic aggregates have been calculated from an analysis of the symmetric anion stretch. The degree of association is found to be almost constant in the O:M range 4820: 1–40: 1 whereafter it increases with increasing salt concentration. The results show that the dramatic increase reported for the molar conductivity in the O:M range 1000:1–40: 1 cannot be explained by the redissociation of contact ion pairs or the formation of conducting triplets. Instead the major contribution to the conductivity increase seems to be a concentration dependent enhancement of the ionic mobility. A percolation based ionic hopping process involving exchange between ions in pairs and dissolved ions, either free or coordinated to ether oxygen sites, is advanced as a possible microscopic mechanism.