Effect Of Solution Composition Research Articles

Synthesis and coating of micro-metal-matrix composite by combined laser sol–gel processing

Of the many methods of laser treatment for improving materials surface properties that have been reported, very few have addressed laser-assisted chemical reaction. In this work laser deposition of metal-matrix composites is reported, using chromium oxide and silicon carbide powders mixed in silica sol–gel mixtures, on EN43 mild steel substrates. Very fine SiC particles ≤ 1 μm and M 7C 3 carbides were synthesised in situ and dispersed in ferrite matrix by this process. A diode laser at different powers and scanning speeds was applied to specimens coated with slurries of different chemical compositions. The effect of solution composition and bath depths were examined in order to achieve optimum experimental parameters. Surface morphology and microstructure of the deposited coatings and substrate surface layers were examined using optical microscopy, scanning electron microscopy (SEM) and field emission gun scanning electron microscope (FEG-SEM). Chemical composition was determined by energy dispersive X-ray analysis (EDX). The different phases were identified by X-ray diffraction (XRD). Results of microhardness measurements and wear properties of the coatings are also reported. Thermodynamic analysis of the reactions taking place is also given.

An iron-modified silica nanofiltration membrane: Effect of solution composition on salt rejection

Electrolyte rejection measurements with single salt solutions of NaCl, Na 2SO 4, MgCl 2, and MgSO 4 were performed to determine the effects of solution composition on the separation performance of an iron-modified silica nanofiltration ceramic membrane. The unsupported membrane material was characterized with respect to pore structure and zeta potential, whereas the supported membrane was utilized to evaluate gas diffusion properties, water flux and salt rejection. Charge exclusion mechanisms were determined to be the basic mode of salt rejection, and a qualitative relationship was constructed to relate salt rejection to the zeta potential of the membrane. The results obtained agree with the Donnan exclusion principle of electrically charged membranes. The data shows that the membrane zeta potential is not constant but depends extensively on the type of electrolyte in solution. For example, there is a dramatic drop in zeta potential when the membrane is exposed to magnesium salts as opposed to sodium salts. This drop in potential at the membrane surface leads to little rejection of magnesium salts. Results also show a charge reversal of the membrane zeta potential at high pH values due to specific adsorption of magnesium.

Membrane fouling in water treatment: effect of solution composition on resistance and compressibility of gel-forming filter cakes

Formation of highly impermeable assemblages on membranes in water treatment can result in significant problems in maintaining permeate flux and necessitate frequent cleaning of the membrane. In this study, we describe the hydraulic properties of montmorillonite clay particles and examine the link between microscopic particle–particle interactions and the bulk properties of the clay assemblage. In particular, we show that changes in the ionic composition of feed waters can have a dramatic impact on the fouling properties of montmorillonite particles with highly impermeable, voluminous filter cakes formed at low ionic concentrations and dramatically more porous assemblages formed at higher ionic strengths.

Control of wave formation pattern in self-oscillating gel by addition of hydroquinone in the Belosov-Zhabotinsky reaction solution

We have investigated the effect of solution composition on the pattern of traveling wave formation in self-oscillating gel in which a metal catalyst for the Belousov-Zhabotinsky(BZ) reaction is covalently bonded to the gel matrix. The reaction solution contains all reactants for the BZ reaction except the catalyst. The gel was synthesized by the co-polymerization of N-isopropylacrylamide(NIPAAm) and Ru(bpy)32+ catalyst monomer. To vary the composition of the environmental solution for the oscillation reaction, we added a small amount of hydroquinone to the BZ solution since hydroquinone is a good reagent inducing a characteristic wave pattern in the BZ type oscillation system. The experimental results show that the pattern of wave formation in the self-oscillating gel is influenced greatly by a change of the environmental condition of the solution composition for the oscillation reaction without other environmental change such as temperature and pH.

Formation and properties of stannate conversion coatings on AZ61 magnesium alloys

The effects of solution composition and temperature on the microstructure and corrosion resistance of stannate conversion coatings on AZ61 magnesium alloys were investigated. The conversion coating consisted of a porous layer as under layer intimately contacted with the magnesium plate and a hemispherical particle layer as major overlay formed right on top of the porous layer. During the coalescence of the hemispherical particles to form a complete coating on the magnesium alloy, some sites of discontinuity inevitably left and determined the corrosion resistance of the coating evaluated using a salt spray test. Increasing bath stannate ion concentration and lowering bath pH increased the population density of the hemispherical particles whose size was accordingly reduced. The corrosion resistance of the conversion coating was improved with finer particles, which were preferably formed at less alkaline solution with higher stannate ion contents. Furthermore, the conditions favoring the formation of finer particles also reduced the immersion time necessary for producing the conversion coating with optimal corrosion resistance.

硫ひ鉄鉱からのＡｓ溶出に及ぼす液組成の影響―酸性環境下での硫ヒ鉄鉱溶解に関する研究（第１報）―

硫ひ鉄鉱からのＡｓ溶出に及ぼす液組成の影響―酸性環境下での硫ヒ鉄鉱溶解に関する研究（第１報）―

Effect of Solution Composition of Plasmid DNA on Gene Transfection Following Liver Surface Administration in Mice

We investigated the effect of plasmid DNA (pDNA) solution composition on gene transfection following liver surface administration in mice. Gene transfection experiments in situ and in vivo were performed using the following pDNA solutions: dextrose solution, NaCl solution, phosphate buffer, phosphate-buffered saline, Tris/HCl buffer with EDTA, Tris/HCl buffer with EDTA and Triton X-100, and water. In in situ experiments, we used a glass cylindrical diffusion cell that limited the contact area between the liver surface and the naked pDNA solution. The gene transfection at the site of diffusion cell attachment increased in hypotonic solution, and decreased in hypertonic solution, compared with isotonic solution. In in vivo experiments, instillation of naked pDNA solution onto the liver surface using a micropipette caused no significant differences in gene transfection in the applied lobe. These results suggest that it is important to select the optimal pDNA solution composition to control the gene transfection.

Effect of Solution Composition and Flow Rate on Kinetics of Lead(II) Desorption from Alfisol

Slow rate of desorption combined with low amounts of the element released cause low mobility of lead(II) (Pb) in soils and make inefficient the attempts of chemical remediation of Pb contaminated lands. This study was conducted to estimate the impact of solution composition and flow rate on the kinetics of Pb desorption in Alfisol. Lead desorption rate (DR0) estimated with a thin disc flow method increased with the increase of flow rate and was proportional to Ca2+ concentration in the percolating solution. Decrease in solution pH significantly increased DR0. Small total amounts of desorbed Pb may be attributed to re-adsorption of the desorbed lead since treating the soil with the mixture of Ca(NO3)2 and Na2EDTA enabled to remove sorbed Pb almost completely due to complexing of desorbed lead by EDTA in the solution thus preventing its re-adsorption. This process followed the kinetics equation of the first-order reaction. The dependencies of lead desorption rate on Ca2+ concentration, pH, and flow rate of the leaching solution may be interpreted assuming that Pb release is a three-cation (Pb2+– Ca2+– H+) ion exchange limited both by the rate of ion exchange reaction and the rate of diffusion.

Effect of solution composition on the removal of copper ions by nanofiltration

Separation of copper ions from aqueous solution by nanofiltration was shown to be a feasible process to accomplish an effective copper removal over a broad operational range. Experimental results indicated that the rejection of copper ions increases with increasing the charge valence of co-anions present in aqueous solution. Higher degrees of copper removal were achieved for experiments conducted in acidic solutions than those conducted in alkaline solutions. The copper rejection increased with increasing operating pressure until a limiting rejection was reached, further application of higher pressure did not increase copper rejection. The surfactant presented in aqueous solution was adsorbed by the membrane to form a secondary filtration layer on the membrane surface, therefore, influenced the surface charge characteristic of the membrane. The rejection of copper chelate was markedly influenced by the solution pH and the molecular weight of chelate. The solution-diffusion model combined with film theory adequately described the behavior of copper rejection from aqueous solution by nanofiltration.

Determination of induction period and crystal growth mechanism of dexamethasone sodium phosphate in methanol–acetone system

The induction period of dexamethasone sodium phosphate at different supersaturation was experimentally determined in a methanol–acetone system. The laser monitoring observation technique was used to determine the appearance of the first nucleus in solution. The effect of solution composition on induction period was discussed. Based on classical homogeneous nucleation theory, the solid–liquid interfacial tension and surface entropy factor were calculated from the induction period data. The experimentally determined values of interfacial tension are in agreement with the theoretical values predicted by the Mersmann equation. It was found that the nucleus of dexamethasone sodium phosphate grows continuously in pure methanol and turns from continuous growth to birth and spread growth with increasing acetone content in a methanol–acetone mixture.

Formation of surfactant and polyelectrolyte gel particles in aqueous solutions

Mixing of oppositely charged surfactants and polyelectrolytes in aqueous solutions can lead to associative phase separation, where the concentrated phase assumes the form of a viscous liquid, gel, or precipitate. This phenomenon can lead to the formation of gel-like particles whose size and polydispersity can be controlled. Here we present phase behavior and structural studies of gel-like particles formed by mixing drops of N, N, N-trimethylammonium derivatized hydroxyethyl cellulose (JR-400) polyelectrolyte solution with oppositely charged anionic and catanionic surfactant solutions composed of sodium perfluorooctanoate (FC 7) and cetyltrimethylammonium bromide (CTAB). Gel formation apparently occurs due to the collapse of the polyelectrolyte chains upon the adsorption of surfactant. This process results in the release of simple ions and water, and yields dense gel-like beads. The diameter of these beads ranges approximately from 200 to 4000 μm. Both the effects of solution composition and the method of preparation are studied by optical and confocal microscopy, and are linked to the structure and stability of the bead. Our observations suggest that the structure of the resulting particles is governed by the solution composition and the method of preparation, while the particle stability is governed by phase behavior alone.

Electrodeposition of Iron Group-Rare Earth Alloys from Aqueous Media

Binary iron group (IG)-rare earth (RE) and ternary IG-RE-B alloys were codeposited from aqueous chloride and sulfamate solutions containing glycine as the complexing agent. The effects of solution composition and deposition conditions on deposit composition, coercivity, and morphology were investigated using dc and pulse current electrodeposition, resulting in nanocrystalline deposits approaching amorphism (grain size, ∼5 nm). Continuing research indicates substantially increased RE deposit contents have been achieved with modifications in solution composition and ratios of IG and RE to glycine with applied mA cm−2 and vigorous agitation; e.g., CoSm deposits containing 15-18 atom % Sm have been obtained. A mechanism for the codeposition of the alloys is proposed. It involves hetero-nuclear glycinato coordination complexes as a result of the zwitterionic characteristics of glycine. The complexes adsorbed on the cathode provide step-wise reduction of the depositing metals with surface adsorbed H atoms and/or direct electron transfer, resulting in alloy deposits. © 2004 The Electrochemical Society. All rights reserved.

Solution-Mediated Transformation of α to β l-Glutamic Acid: Rate Enhancement Due to Secondary Nucleation

The ability to control the transformation process between polymorphs of crystalline materials is critical to ensure that the correct form is produced, and hence it is essential to learn which experimental factors affect this transformation reaction. In this contribution, the kinetics of the polymorphic transformation between metastable and stable forms of l-glutamic acid was studied using a number of techniques: optical microscopy, FT-IR, Raman and UV spectroscopy. The effects of solution composition and in particular process scale were investigated. The role of secondary nucleation in which the surface of one polymorph acts as a template for the nucleation of another form is highlighted in this paper.

A Comprehensive Empirical Correlation for prediction of Supersolubility and Width of the Metastable Zone in Crystallization

Prediction of supersolubility and the width of the metastable zone has been a major concern among the workers in the field of industrial crystallization. Operation of crystallizers under the optimum supersaturation low enough to attain the desired product quality (Median Particle Size, Crystal Size Distribution (CSD), Shape, Purity) being one motif. The inherent relationship between the subject and the most fundamental concepts of crystallization being the other. Studying the conditions of primary homogenous nucleation and the crystal growth kinetics has been conducted for a wide range of inorganic materials. A simple probabilistic term called chance of having the desirable species congregation, has been introduced to account for the effect of solution composition. A semi-empirical model has been developed for occasions where primary homogenous nucleation occurs at a specified undercooling rate (0.2 oC/hr). The model has been found to satisfy the experimental results obtained for 28 inorganic systems under various conditions. Theconcept may be equally applicable in nucleation of organic materials and for cases where liquid nuclei (such as rain droplets) are formed.

Longevity of granular iron in groundwater treatment processes: solution composition effects on reduction of organohalides and nitroaromatic compounds.

Although granular iron permeable reactive barriers (PRBs) are increasingly employed to contain subsurface contaminants, information pertaining to system longevity is sparse. The present investigation redresses this situation by examining the long-term effects of carbonate, silica, chloride, and natural organic matter (NOM) on reactivity of Master Builders iron toward organohalides and nitroaromatic contaminants. Six columns were operated for 1100 days (approximately 4500 pore volumes) and five others for 407 days (approximately 1800 pore volumes). Nine were continuously exposed to mixtures of contaminant species, while the other two were only intermittently exposed in order to differentiate deactivation induced by water (and inorganic cosolutes) from that resulting from contaminant reduction. Contaminants investigated were trichloroethylene, 1,2,3-trichloropropane, 1,1-dichloroethane, 2-nitrotoluene, 4-nitroacetophenone, and 4-nitroanisole. Column reactivity declined substantially over the first 300 days and was dependent on the feed solution chemistry. High carbonate concentrations enhanced reactivity slightly within the first 90 days but produced poorer performance over the long term. Both silica and NOM adversely affected reactivity, while chloride evinced a somewhat mixed effect. Observed contrasts in relative reactivities suggest that trichloroethylene, 1,2,3-trichloropropane, and nitroaromatic compounds all react at different types of reactive sites. Our results indicate that differences in groundwater chemistry should be considered in the PRB design process.

ZnFe anomalous electrodeposition:: stationaries and local pH measurements

The kinetics of ZnFe codeposition was investigated in acid solutions. The effects of solution composition and pH were analyzed. Inhibition of H + reduction and Fe deposition occurs with increasing Zn ++ concentration in sulfate solution. An activation of Zn deposition is also observed. Increasing pH causes Zn deposition activation during ZnFe codeposition. The anomalous codeposition is also favored in chloride medium. When alloy deposition becomes the main process, the interfacial pH is governed by the individual metal deposition that controls the kinetic behavior. The interfacial pH increases during separate Fe deposition, meaning that it occurs with simultaneous consumption of H +. Individual Zn deposition brings about an H + inhibition. A correlation between the codeposition behavior of ZnFe and ZnNi in sulfate and chloride solutions suggests that the prevailing cathodic reaction governs the interfacial pH. Anomalous codeposition process does not seem to be associated with a saturation of any thermodynamic species at the electrode surface. It can only be described by kinetic arguments.

The Mechanism of Hemolysis by Surfactants: Effect of Solution Composition

The effect of ionic strength, solute size, and osmolarity of the suspending solution on surfactant-induced erythrocyte hemolysis was studied. Two possible mechanisms of hemolysis were considered: osmotic lysis (affected by solute particle size) and solubilization (not affected by solute particle size). It was found that the ionic strength of the solution has a major effect on the hemolysis process, depending on the surfactant nature and concentration. An increase in the ionic strength lowers the rate of hemolysis induced by DTAB, and enhances SDS-induced hemolysis. Changes in ionic strength have little effect on hemolysis induced by Triton X-100. To explain these effects, it was assumed that the changes in ionic strength differently affect the adsorption of cationic and anionic surfactants to the membrane. The change in the amount of adsorbed surfactant either influences the rate of osmotic hemolysis by changing the membrane permeability or induces a transition from the osmotic mechanism to solubilization. These phenomena were observed for isotonic as well as hypertonic solutions.

Nanostructured magnetic CoNiP electrodeposits: structure–property relationships

Magnetic CoNiP thin film alloys were electrodeposited from chloride baths. The effects of solution composition, solution pH and film thickness on the magnetic properties, microstructure and phases of electrodeposited CoNiP films were investigated. Solution pH and NaH 2PO 2 concentration significantly influenced the magnetic properties of CoNiP deposits. These films when deposited from solutions of pH <2.25 exhibited soft magnetic properties, whereas from solutions of pH >2.25, hard magnetic deposits ( H C,⊥≈2000 Oe and H C,//≈1000 Oe) were obtained. X-ray diffraction revealed hcp structure consisting of nanocrystalline grains (∼50 nm) with preferred (002) planes as deposit P content and solution pH increased.

Effect of solution composition, flow and deployment time on the measurement of trace metals by the diffusive gradient in thin films technique

Diffusive gradients in thin films (DGT) is a recently developed technique capable of in situ measurement of labile metal species in water. Tests of the performance of DGT were extended in this work to cover a wide range of environmentally relevant conditions. DGT accurately measured Cd concentrations in 0.01 M NaNO 3 solutions in the pH range 5–10 and Co, Mn and Zn concentrations, between pH 3.5 and 10. Cu was measured accurately between pH 2 and 10. Above pH 11 prolonged deployments were impractical due to swelling of the diffusive gel, but even at pH 12.9 significant fractions of the total Cd and Cu concentrations were measured by DGT units deployed for a day or less. Measurements of trace metals by DGT were unaffected by the presence of Ca at concentrations found in hard water. Errors due to changes in flow velocity were less than 10% above a flow of 0.02 m s −1, where the formation of a diffusive boundary layer becomes negligible for diffusive gels of ≥0.7 mm thickness. Therefore, DGT devices prepared with this diffusive gel thickness can confidently be used in most streams and rivers. However, in quiescent solutions the DGT measurement may only be 50% of the true concentration, confirming the need in quiet waters for parallel deployments of devices with different diffusive layer thickness. Quantitative DGT measurements of Cd over a 1 month period showed that neither the diffusive nor resin gel deteriorated with time. Collectively these results show that DGT behaves predictably over a wide range of solution conditions. For Cu it can be used in very acidic solutions. The upper pH limit for DGT measurement is governed by the stability of the gel. For this gel composition the realistic limit is pH 11.

Sprayed CuInS 2 thin films for solar cells: The effect of solution composition and post-deposition treatments

CuInS 2 thin films were prepared by spray pyrolysis from solutions with different compositions. Etching in KCN solution and thermal treatments in vacuum and hydrogen were applied to as-deposited films. KCN etching removes conductive copper sulfide from the surface of Cu-rich films but has no effect on matrix composition. Vacuum annealing at 500°C and hydrogen treatment at 400–500°C purifies the films, prepared from the solutions with the Cu/In=1, from secondary phases, reduces chlorine content and improves crystallinity. Vacuum annealing results in n-type films due to the formation of In 2O 3 phase. Treatment in hydrogen reduces oxygen-containing residues and results in p-type CuInS 2 films with resistivity close to 10 Ω cm.