Aqueous Citrate Solutions Research Articles

Ba-Zr codoped sodium bismuth titanate by novel alkoxyless wet chemical route: processing and electromechanical behavior

Sodium bismuth titanate (NBT) based ceramics have been shown to be a promising lead-free alternative to commercial piezoelectrics and high capacitance materials. This article reports a novel aqueous citrate gel route for the synthesis of (Na0.5Bi0.5)xBa1-xTiyZr1-yO3 powders. Instead of alkoxides, usually used in citrate gel route, aqueous citrate solutions of titanium and bismuth were prepared from their respective inorganic salts. These solutions were used to prepare powder of (Na0.5Bi0.5)0.88Ba0.12Ti0.96Zr0.04O3. The process produced an amorphous xerogel that was readily crystallized to a pseudocubic perovskite phase when calcined at temperatures as low as 500 °C. The decomposition and oxidation of the xerogel was studied using TG-DTA, which showed complete removal of volatile components by 580 °C. The formation of crystalline phases was studied using XRD. SEM was used to evaluate the sintering behavior of the powder. The powder exhibits significant sintering at temperatures 800–900 °C. The polarization behavior of the sintered material was similar to one prepared by conventional solid state route. A maximum polarization of ∼24 μC/cm2 and peak bipolar strain ∼0.095% at 44 kV/cm was achieved in the sintered material.

III-V 화합물 반도체 InSb의 전기화학적 제조

본 연구에서는 구연산 수용액 전해질을 제조하여 전기도금 방식에 의해 III-V족 화합물 반도체 InSb를 전기화학적으로 합성하였다. 본 연구에서 제조된 InSb는 기존문헌에서 보고된 바와 달리 EPMA분석결과 In과 Sb의 조성비가 52:48로 화학양론을 정확하게 만족시키고 있고, XPS분석결과 전해질내의 구연산의 농도가 1.2M, pH가 4일 때 444.1 eV에서 InSb 화합물의 피크를 관찰하였으며 구연산의 농도가 1.2M보다 낮거나 pH가 4보다 낮을 때는 InSb화합물과 금속상태의 In이 혼재되어 있는 것을 확인하였다. 또한 XRD를 통하여 InSb(111)의 우선결정방위를 갖는다는 것을 확인하였고, I-V 특성 곡선 측정을 통해 rnSb가 고유한 반도체 특성을 보임을 확인하였다. We investigated the electrochemical formation of a stoichiometric III-V compound semiconductor of InSb from an aqueous citric solution. Under an? optimized electrochemical condition, not like other research results, the electrodeposited InSb are satisfied exactly with the stoichiometry. Furthermore it retains the inherent characteristics of III-V compound semiconductor, InSb without heat treatment. EPMA, XPS and XRD were employed for confirmation of its composition/stoichiometry, chemical state, and crystallographic orientation, respectively.

Comparison of the lipid composition of porcine buccal and esophageal permeability barriers

Pig esophageal mucosa has been shown to be a useful and practical substitute for buccal mucosa in in vitro permeability studies in that it offers a larger surface area and it is much easier to prepare. Further, the tissues demonstrate similar histological characteristics. The objectives of this work were to characterize the lipid composition of the esophageal mucosa, to compare it to that of the buccal tissue, and to correlate lipid composition with the membranes' permeability to fentanyl. The major lipid classes of buccal and esophageal epithelia were separated and analysed by automated multiple development high-performance thin-layer chromatography (AMD-HPTLC). The two epithelia presented a very similar lipid pattern. In general, there were more polar lipids than non-polar; glycosylceramides were relatively abundant whereas the amount of ceramides present was very small. The flux of fentanyl applied as the citrate in aqueous solution was comparable across the buccal and esophageal barriers. Lipid extraction provoked a significant increase in permeability. In conclusion, this research confirms the suitability of the esophageal mucosa as a model for buccal permeability studies.

Aqueous electrodeposition of iron group–vanadium binary alloys

Electrodeposition of binary iron group (IG)–vanadium (V) alloys from aqueous citrate solutions was investigated. Addition of NH 3(aq.) and increasing solution pH resulted in increased deposit V content, but non-metallic deposits were obtained at solution pH > 7. Increasing current density resulted in an almost linear decrease in V content and a sharp increase in hydrogen evolution (decreased current efficiency). In general, the amount of V deposited with the IG metal increased as follows: Ni < Fe ≪ Co. XRD spectra indicated that preferred orientations from 25 °C solutions were not displaced by elevated temperature deposits. Changes in orientation may contribute to the deposit magnetic properties; e.g., Co–V deposits with (1 0 0) planes exhibit harder magnetization than deposits with (0 0 2) planes.

複合めっき法によるＴｉＯ２分散Ｎｉ‐Ｍｏ合金皮膜の作製とその評価

Composite electrodeposition of TiO2 particles in amorphous Ni-Mo alloy matrices was carried out using aqueous citrate solutions (pH5.0) where anatase- or brookite-TiO2 particles were suspended. A white and uniform composite coating was obtained from a solution containing 200g dm−3 of TiO2. The composition of the Ni-Mo alloy matrices remained unaltered with the inclusion of TiO2. Although the uptake of TiO2 did not exceed 0.1wt.%, the resulting Ni-Mo/TiO2 layer exhibited the ability to decompose gaseous NO in the air or Methylene Blue in water. It was suggested that the anti-corrosive ability of the Ni-Mo layer is improved by the inclusion of TiO2 in the layer.

Preparation of magnesium-substituted hydroxyapatite powders by the mechanochemical–hydrothermal method

Magnesium-substituted hydroxyapatite (Mg-HAp) powders with different crystallinity levels were prepared at room temperature via a heterogeneous reaction between Mg(OH) 2/Ca(OH) 2 powders and an (NH 4) 2HPO 4 solution using the mechanochemical–hydrothermal route. The as-prepared products contained unreacted Mg(OH) 2 and therefore had to undergo purification in ammonium citrate aqueous solutions at room temperature. X-ray diffraction, infrared spectroscopy, thermogravimetric and chemical analyses were performed and it was determined that the purified powders were phase-pure Mg-HAp containing 0.24–28.4 wt% of Mg. The concentration of Mg was slightly lower near the surface than in the bulk of the HAp crystals as indicated by X-ray photoelectron spectroscopy. Dynamic light scattering revealed that the median particle size of the room temperature Mg-HAp powders was in the range of 102 nm–1.2 μm with a specific surface area between 91 and 269 m 2/g. Scanning electron microscopy confirmed that the Mg-HAp powders consisted of submicron agglomerates of nanosized crystals, less than ≈20 nm.

Electrochemical treatment of copper from aqueous citrate solutions using a cation-selective membrane

An electrolytic cell having a cation-selective membrane Neosepta CM-1 was applied to treat solutions containing equimolar amounts of CuSO 4 and citric acid. The iridium oxide and platinum coated on titanium were used as the anode and cathode, respectively. The catholyte contained the citrate-chelated Cu(II) and the anolyte consisted of NaNO 3 . All experiments were carried out at different current densities (18.5–139 A m −2 ), initial catholyte pH (1.0–9.0) and Cu(II) concentration (5–30 mM), and initial anolyte NaNO 3 concentration (1–200 mM). An economically acceptable current efficiency (>50%) and recovery of Cu(II) and citrate (>96%) could be obtained when the feed concentration the chelated Cu(II) was sufficiently high.

Barium ferrite nanoparticles prepared directly by aerosol pyrolysis

BaFe 12O 19 nanoparticles, 10 nm in diameter, have been obtained by combination of two methods, the citrate precursor and the aerosol pyrolysis technique. For the first time, well-crystallised barium ferrite particles were obtained by pyrolysis of an aerosol, produced by ultrasonic frequency spraying of a barium iron citrate aqueous solution, in a tubular furnace at 1000°C, without further heat treatment. The reason why the hexaferrite phase forms at lower temperatures than by other methods is the nature of the precursor aerosol solution. The particle size was increased up to 100 nm in diameter by heat treatment at 1000°C in an oven. The obtained particles are spherical aggregates of 400 nm, which can be easily disaggregated by grinding in a mortar. Changes in particle size and aggregation state are reflected as changes in the magnetic properties. Saturation magnetisation and coercivity values obtained for the largest particles were similar to those found for commercial pigments, 50 emu/g and 5600 Oe, respectively.

Effect of bare metal surface on the dissolution in aqueous citrate solutions of magnetite films on carbon steel

The potential–time dependence of magnetite under varying conditions of pH and Fe2 concentration and of magnetite layers on carbon steel with initially exposed small bare metal areas have been studied. The experiments simulate the case of magnetite scales partially removed from surfaces in the course of chemical cleaning when coupling conditions occur with area ratios variable with time. The interpretation is based on an equivalent electric circuit composed of internal current generators of faradaic origin and capacitors simulating the electric double layer at the metal/solution and oxide/solution interfaces.

Metallocoenzyme-Mediated Reductive Transformation of Carbon Tetrachloride in Titanium(III) Citrate Aqueous Solution

Transformation pathways for carbon tetrachloride (CCl{sub 4}) catalyzed by hematin or vitamin B{sub 12} in aqueous titanium(III) citrate solution are proposed. The reaction of CCl{sub 4} with B{sub 12} was zero order in CCl{sub 4} and first order in B{sub 12}, and the rate constant was measured from pH 7.3 to pH 10.3. The proposed rate-limiting step is the reduction of the stable trichloromethylcobalamin (CCl{sub 3}-Cbl) intermediate by titanium(III) citrate at alkaline pH and the sterically induced CCl{sub 3}-Cbl decomposition at neutral pH. The reaction kinetics can be described by a modified Michaelis-Menten model in the saturated regime. With hematin, only the pseudo-first-order rate constant was determined due to the significant deactivation of the coenzyme. The turnover number of hematin (molecules of CCl{sub 4} transformed/molecule of hematin deactivated) was 27 at pH 8.0 and 42 at pH 9.9. Vitamin B{sub 12} was a more stable and more effective catalyst (on a molar basis) than hematin with respect to CCl{sub 4}. Chloroform (CHCl{sub 3}) was the primary product in titanium(III) citrate solution, and the yield was a function of pH, Ti(III) concentration, and organic content regardless of whether a coenzyme was present or which coenzyme was used. Although B{sub 12} andmore » hematin can both enhance the CCl{sub 4} transformation rate, they have little effect on the CHCl{sub 3} yield. Titanium(III) citrate, on the other hand, controls not only the transformation rate but also CHCl{sub 3} formation. 77 refs., 10 figs.« less

Complexing ability of pesticides and related compounds. Formation and stability of the complex species of 3-amino-1, 2, 4-triazole and acetate, malonate or citrate in aqueous solution

Formation and stability of complex species deriving from interaction between 3-amino-1, 2, 4-triazole [H(ata)] with acetate, malonate and citrate, has been studied in aqueous solution, by Potentiometrie method [(H+)-glass electrode] at T=25°C. Experimental data are consistent with the formation of (ata)LHj species (j = 1…n + 1, n = number of protons in the carboxylic acid, HjL). The stability of the hypothesized species is discussed, in relation to speciation problems in natural waters.

Electrodeposition of CuInSe 2 thin films from aqueous citric solutions I. Influence of potential and mass transfer rate on composition and structure of films

It is shown that by changing, in the negative direction, the potential of citric aqueous solutions containing Cu(II) In(III) and Se(IV) under cathodic polarization, it is possible to obtain films such as CuSe, Cu 3Se 2, CuInSe 2 and In-enriched CuInSe 2. The values of the potentials under which these compounds are formed depends upon the rate of deposition, the speed of ion mass transfer in the solution, the conductivity or the electrolyte, the cathode surface area and the electrolyte temperature.

A vibrational spectroscopic study of nickel(II) citrate Ni 3(C 6H 5O 7) 2 and its aqueous solutions

A comprehensive Raman spectroscopic study of citric acid and its three anions has been made at 298 K and the four species have been characterised. From comparisons of the Raman spectra of nickel(II) citrate in the solid state and equimolar mixtures of nickel chloride and trisodium citrate in aqueous solution, it is concluded that nickel(II) citrate exists as the Ni(C 6H 5O 7) − species in aqueous solution, in confirmation of electrochemical studies on this system.

Etching of Dentin Surface with Ammonium Citrate Aqueous Solution

New dentin etchants AC (ammonium citrate) were examined. The pH of the AC solution was 7.3-7.4, and the concentration of the solutions varied from 5% to 30%. The etching of a 10% AC solution was the most effective in improving the adhesion between the composite resin and dentin among the AC solutions employed when MTYA.G.H was used as a dentin primer. The smear layer was removed and the tubules were not generally opened with AC etching. The bond strengths to dentin etched with 10% AC were comparable with those to dentin etched with neutralized 0.5 M EDTA or EDTA 3.2. The bond strengths increased with primers MTYA.H and MTYA.G.H, in that order.

Photodecarboxylation of citrate through ion pair photochemistry: the Co(Sep)3+·citraten− (n = 1,2,3) system

Abstract The Co(Sep) 3+ complex (Sep = sepulchrate = 1,3,6,8,10,13,16,19-octaazabicyclo[6.6.6]eicosane) forms ion pairs with citrate in aqueous solution at pH 4.0, 5.6 and 8.5, where the forms CIT − , CIT 2− and CIT 3− (CIT = citrate) predominate respectively. Irradiation in the ion pair charge transfer band for the three pH values leads to the decarboxylation of citrate with the production of CO 2 and Co(Sep) 2+ . In the presence of colloidal platinum, CO 2 and H 2 are evolved. The quantum yields for formation of CO 2 , Co(Sep) 2+ and H 2 were obtained and are discussed in terms of their dependence on pH.

Electrodeposition of alloys: XX electrodeposition of gold-rhenium alloys from acidic citrate solutions and their X-ray structure

Shiny, smooth and adherent deposits of gold-rhenium alloys containing 0.25 – 63.2 wt.% rhenium were electrodeposited from aqueous citrate solution. The effects of bath composition, pH, temperature, stirring, current density and pulsed current on the alloy composition, deposit appearance, current efficiency and microhardness were investigated. The X-ray structures of Au-Re alloy deposits are also reported.

Electrolytic dissolution of iron in aqueous citrate solutions

Analysis of polarization curves for electrolytic dissolution of an iron (steel) electrode in citrate solutions of various pH values and concentrations of citrate anions showed that the given medium promotes the electrolytic dissolution by shifting the corrosion potential of iron to more negative values. However, the catalytic formation of an iron(II) hydroxo complex cation in the active dissolution region according to the scheme proposed by Heusler remains the rate-determining step of the dissolution mechanism.

ChemInform Abstract: Electrochemical Behaviour of Nb(V)/Nb(IV) in Aqueous Citrate Solutions Studied at the Dropping Mercury Electrode.

AbstractSolutions of Nb(V) in NaClO4 containing citric acid in high concentration show a time‐dependence of the limiting current, indicating that the Nb(V) species is very slowly converted to an electroactive form.

The electrochemical behaviour of Nb(IV) in aqueous citrate solutions studied at the dropping mercury electrode

It is reported that, after injection of a solution of pentavalent niobium in 5 M HC10 4 into a 1.3 M citric acid+ 1 M NaC10 4 solution, only a small portion of the niobium is electrochemically active initially. This portion increases with time until after 2000 min an equilibrium is established where most of the niobium is electroactive. This transfer is shown to proceed with (pseudo) first order kinetics and its rate constant is reported together with estimates of the two equilibrium constants. In a solution in which this transfer is completed, the kinetics of the Nb(V)/Nb(IV) redox couple are studied at the DME by the impedance method. The operational transfer coefficient is found to be strongly potential dependent. This leads to the conclusion that the electron transfer is both preceded and followed by potential independent processes. The following process could be absent if the trnsfer coefficient of the electron transfer is allowed to deviate from 0.5.

Extraction of thiocyanate complexes of cobalt(II) by diphenyl-2-pyridylmethane in benzene from mineral acid solutions

Extraction of Co(II) by diphenyl-2-pyridylmethane (DPPM) in benzene form mineral acid solutions containing potassium thiocyanate has been studied at room temperature (23±2°C). Its extraction from mineral acids alone is rather poor. Optimal aqueous phase composition for the quantitative extraction of Co(II) by 0.1M DPPM is 0.1M acid+0.2M KSCN. Stoichiometric studies indicate that an ionic type complex, (DPPM·H)2·Co(SCN)4, is responsible for extraction. The metal can be back-extracted from the organic phase by aqueous acetate, citrate or oxalate solutions. Separation factors from other metals determined under optimal conditions reveal that Co(II) can be quantitatively separated from CsI), Sr(II), Cr(III), Ln(III), Zr(IV), Hf(IV), Cr(VI) and Tc(VII), Mo(VI), Zn(II), Au(III), Hg(II) and U(VI) are, however, coextracted and hence should be previously removed by other techniques or reagents.