Effect Of Ionic Impurities Research Articles

Characterization of relaxation processes over static permittivity frequency regime and compliance of the Stokes-Einstein-Nernst relation in propylene carbonate

Complex dielectric permittivity, alternating current electrical conductivity, electric modulus and impedance spectra of propylene carbonate were investigated in the frequency range from 20Hz to 1MHz and temperatures from 278K to 328K. The values of static permittivity, Kirkwood correlation factor, ionic conductivity, electric double layers and conductivity relaxation times, and the conductivity and relaxation activation energies of the propylene carbonate were determined. The effects of ionic impurities on electrical conduction and low frequency relaxation processes in propylene carbonate were explored. It was found that the conductivity behaviour of ionic contaminants in neat liquid propylene carbonate fulfilled the Stokes-Einstein-Nernst relation for the ions movement in viscous media. These results confirm great significance in interpretation of ion-conduction mechanism in liquid and solid polymer electrolytes when propylene carbonate is used as solvent and plasticizer, respectively.

Effects of ionic impurities on crystallization of cobalamin

In this paper, the influence of two typical ionic impurities (Na+ and Mg2+) is investigated with the focused beam reflectance measurement (FBRM) technique. In this system, the on-line FBRM is used as a tool for monitoring the crystallization process of cobalamin by measuring the chord length distribution of particles and the particle counts. It is noted that impurity Mg2+ has a more significant effect than Na2+ in crystal growth of the whole crystallization process. From the microscopic observation of crystals, Mg2+ has an obvious effect on the crystal habit, while Na2+ has little effect. In addition, the crystal habit changes can be monitored by particle vision measurement (PVM). Understanding these effects is helpful to aid optimization and improve process control.

Effects of ionic impurities on the crystal morphology of phosphoric acid hemihydrate

The adsorption of foreign molecules on the crystal surface is generally believed to contribute to modify crystal morphology and the different adsorption energies on different crystal faces may lead to different modifications of crystal morphologies. In order to obtain a deep understanding of the face growth intervening mechanism, phosphoric acid hemihydrate (H 3PO 4·0.5H 2O) is taken as an example to investigate the influence of several typical ionic impurities on its crystal morphology by applying a molecular simulation study using Cerius 2 software. The absolute values of the calculated binding energies for cations are larger than that for anions. Therefore, it is concluded from the simulation that cations inhibit the growth of some crystal faces, while anions has no significant inhibition to a particular crystal surface, which is in good agreement with the experimental observation. It is also noticed that significant differences of binding energies to the different crystal faces will lead to obvious modifications of crystal morphologies and higher charged cations have more obvious effects than lower charged cations on the crystal morphology modification.

Effects of Ionic Impurities (Fe2+ and SO42-) on the Crystal Growth and Morphology of Phosphoric Acid Hemihydrate during Batch Crystallization

The influence of two typical ionic impurities (Fe2+ and SO42-) and operating factors in the presence of these impurities on phosphoric acid hemihydrate (H3PO4·0.5H2O) crystallization is investigated. The crystal growth mechanism and ion−crystal face interactions are systematically studied using an in-line focused beam reflectance monitoring (FBRM) technique and molecular dynamic simulation. It is noted that the seeding supercooling and cooling rate during crystallization have a more significant effect on the crystallization process in the presence of Fe2+ than that of SO42-. From microscopic observation of crystals, it is clear that Fe2+ has a notable effect on crystal morphology, while SO42- has very little effect. In order to obtain a deep understanding of the growth mechanism, a molecular simulation study using Cerius2 software was performed. The absolute values of the calculated binding energies for Fe2+ are larger than that for SO42-. Significant differences of Fe2+ binding energies to the different crystal faces are found, while there is little difference for the case of SO42-. Therefore, it is concluded from the simulation that Fe2+ inhibits the growth of some crystal faces, but SO42- has no significant inhibition to a particular crystal surface, which is in good agreement with the experimental observation. Understanding these effects is very helpful to aid optimization and improve process control.

Effect of ionic impurities on the electric field alignment of diblock copolymer thin films

In Forschung hast Du immer zu mir gesagt, “Schaffe etwas!”. Mein Chef, ich habe immer versucht Deinen Befehlen zu folgen. Ich widme Dir diese Veroffentlichung. Mensch, mit funf und siebzig bist Du noch jung, schon Geburtstag! The effect of ionic impurities on the electric field alignment of lamellar microdomains in polystyrene-block-poly(methyl methacrylate) diblock copolymer thin films was studied using transmission electron microscopy (TEM) and atomic force microscopy (AFM). At lithium ion concentrations greater than ~210 ppm, the microdomain morphology in block copolymers could be aligned in the direction of an applied electric field, regardless of the strength of interfacial interactions. Complete alignment of the copolymer microdomains, even those adjacent to the polymer/substrate interface, occurred by a pathway where the applied electric field enhanced fluctuations at the interfaces of the microdomains with a wavelength comparable to L o, the equilibrium period of the copolymer. This enhancement in the fluctuations led to a disruption of the lamellar microdomains into smaller microdomains ~L o in size, that, in time, reconnected to form microdomains oriented in the direction of the applied field.

Effect of Ionic Impurities on the Crystallization of Gypsum in Wet-Process Phosphoric Acid

The dihydrate phosphoric acid production process was simulated in a bench-scale glass reactor. The influences of selected ionic contaminants (Na+, K+, Mg2+, Al3+, F-, and Fe3+) on the crystallization of the gypsum byproduct were investigated. Except for fluorine, the presence of the impurities aided gypsum precipitation, with iron and potassium showing the greatest effect. At cation impurity levels of ca. 0.1%, filter cake resistance was lowest, but filtration rates decreased at higher impurity levels. Magnesium and iron were largely retained in the acid, whereas sodium and fluorine were largely removed during the precipitation of gypsum. Sodium, magnesium, iron, and aluminum led to increased coprecipitation of phosphate, whereas fluorine and potassium had no effect

Effects of ionic impurities on EHD motion and conduction in nonpolar liquids

This paper reports the influence of an anionic surfactant, dodecyl benzenesulfonic acid on charge injection and convection assisted conduction in a naphthenic transformer oil, and three paraffinic liquids subjected to a step voltage. When impurities are present in a liquid they scavenge the surfactant and reduce its effective conduction; hence the surfactant has less influence on conduction in naphtenic oil than in the paraffinic liquids. The transient currents in test liquids containing surfactant were similar to injection currents with electrohydrodynamic (EHD) motion rather than to currents due to ionic dissociation. Injection in nonpolar liquids containing an anionic surfactant was controlled by the charge density at the interface due to adsorption of surfactant molecules and not by true charge injection. Based on the relation between the delay time t/sub d/ and field E a simple expression of the form C/sub n/=kE/sup -(2+/spl beta/)/ has been derived to describe the injection strength in nonpolar liquids with weak injection. The results show that the /spl beta/ values for nonpolar liquids with weak injection range between -0.90 and -1.32 which are significantly different from the /spl beta/=-2 value for polar liquids with strong injection. Also, the steady state current I/sub ss/ varied as I/sub ss/=k'E/sup /spl alpha// with /spl alpha/ >

Effect of Ionic Impurities on Primary Nucleation from Aqueous Solutions of Cupric Sulfate

Effect of Ionic Impurities on Primary Nucleation from Aqueous Solutions of Cupric Sulfate

Regelation and the Deformation of Wet Snow

Abstract The thermodynamics of phase equilibrium control the temperature distribution around the ice particles in wet snow. When the snow is stressed, pressure melting occurs at the inter-particle contacts and the snow densifies. Densification is described by a physical model which simulates the heat flow, meltwater flow, and particle geometry. The effects of ionic impurities, liquid saturation, and particle size are demonstrated. Typical values of the temperature difference, inter-particle film size, and density are calculated as functions of time. The calculated rates of compaction are too large, hence, at some later time, the effects of simultaneous grain growth must be added to the model.

Regelation and the Deformation of Wet Snow

AbstractThe thermodynamics of phase equilibrium control the temperature distribution around the ice particles in wet snow. When the snow is stressed, pressure melting occurs at the inter-particle contacts and the snow densifies. Densification is described by a physical model which simulates the heat flow, meltwater flow, and particle geometry. The effects of ionic impurities, liquid saturation, and particle size are demonstrated. Typical values of the temperature difference, inter-particle film size, and density are calculated as functions of time. The calculated rates of compaction are too large, hence, at some later time, the effects of simultaneous grain growth must be added to the model.

Effect of ionic impurities on the primary nucleation of potassium sulphate solutions

AbstractA technique is described for rapidly assessing the effect of impurities on primary nucleation in solutions. The influence of Ca2+, Sr2+, Ba2+, Ag+, Pb2+, Cr3+ and Ni2+ on the nucleation of potassium sulphate solutions is discussed. It is generally observed that a discontinuity in the behaviour of the impurity occurs at an impurity concentration corresponding to the solubility of the “impurity sulphate” in the solution under investigation.

Positive and negative nucleation catalysis in crystallization

The time of exposure of silver iodide to white light affects its ice nucleating abilities because the number of hydrophilic sites generated increases with time. For a not too large number of such sites the surface free energy substrate-nucleus is decreased and, as a consequence, the rate of nucleation increased. A longer time of exposure generates a large number of sites; these cause distortion in the interface, increasing the surface free energy substrate-nucleus and decreasing the rate of nucleation. Substitutional nonionic impurities with a radius larger than that of the main component (also nonionic) might have a negative effect on the rate of homogeneous nucleation. This effect is caused by the strain energy generated in the lattice of the nucleus. In the opposite case they may have a positive effect. Ionic impurities in an ionic system have similar effects if the valence of the impurity is equal to that of the main component. A discussion concerning the effect of ionic impurities with a higher valence than the main component is also included. The strain energy is calculated on the basis of a continuum model. Conditions in which nucleation is suppressed are established.