Biomedical subjects

E Ruiz-Reina

Publications and source records attributed to E Ruiz-Reina.

6 recordsLinked to original sources

PubMed2004

The primary electroviscous effect in colloidal suspensions.

Although a well-defined electrokinetic phenomenon, the primary electroviscous effect in dilute colloidal suspensions is still an unsolved problem. Most of the experimental tests of the different theories that we have studied have shown a lack of agreement. We have developed, during the last years, new theoretical approaches obtaining, finally, a much better agreement with the experimental results. The corrections are defined in two lines: first, it is accepted that ions present into the Stern layer, in which the fluid is stagnant, can tangentially move; second, it is accepted that the hydrodynamic interaction between colloidal particles exists although the suspensions are extremely diluted. The remarkable conclusion of our work is that the combination of both corrections should give correct theoretical results.

Aluminum Oxide↗

PubMed2003

Stern-layer parameters of alumina suspensions.

The specific adsorption of Mg(+2) and S(2)O(-2)(8) ions onto the gamma-alumina particle surface has been demonstrated. An estimation algorithm based upon the correlation between electrophoretic mobility and conductivity increment experimental data, employing a dynamic Stern-layer theory, has been developed and used to get the adsorption parameters into the Stern layer for different gamma-alumina/Mg(+2) and S(2)O(-2)(8) aqueous solutions interface.

Journal Article↗

PubMed2002

An experimental test of Booth's primary electroviscous effect theory.

The primary electroviscous effect has been investigated in dilute suspensions of titanium oxide (anatase), the viscosities of which were measured by means of a capillary viscometer with automatic timing. The linear relation between viscosity and solids volume fraction was first determined at the isoelectric point of the particles when the particles are uncharged, and the electroviscous contribution to the intrinsic viscosity was then determined at other values of pH. Booth's theory (Proc. R. Soc. London Ser. A203, 533 (1950)) agrees well with the experimental results when the particle zeta potential is small and the double layer is thin (kappa alpha approximately 7.3), but agreement is poor when the double layer is thick (kappa alpha approximately 0.6).

Journal Article↗

PubMed2000

The Primary Electroviscous Effect: Thin Double Layers (akappa>>1) and a Stern Layer.

The primary electroviscous effect due to the charge clouds surrounding spherical charged particles suspended in an electrolyte was studied by Hinch and Sherwood (J. Fluid Mech. 132, 337 (1983)) in the limit of double layers thin compared to the particle radius a. Here we introduce the effect of a dynamic Stern layer into that analysis, in order to explain the numerical results of Rubio-Hernández et al. (J. Colloid Interface Sci. 206, 334 (1998)) in terms of the ratio of the tangential ionic fluxes within the charge cloud to those within the Stern layer. The predictions of the asymptotic analysis are compared with those of numerical computations. The thickness of the charge cloud is characterized by the Debye length kappa(-1). If akappa>10 the predictions of the asymptotic analysis exhibit the same qualitative behavior as the numerical results, but akappa>1000 is required to achieve quantitative agreement to within 2.5%. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Electroviscous Effect in Dilute Suspensions of Alumina.

A study on the electroviscous effect of alumina suspensions has been made. At the low volume fraction of the particles studied here only a first-order effect was detected. Ubbelohde-type capillary viscometers have been used. A simple method to determine the hydrodynamic constant k(1) has been proposed. The experimental primary electroviscous coefficients corresponding to different electrolyte concentrations have been compared with two different theoretical approachs (I. G. Watterson, and L. R. White, J. Chem. Soc. Faraday Trans. 2 77, 1115 (1981); F. J. Rubio-Hernández, E. Ruiz-Reina, and A. I. Gómez-Merino, J. Colloid Interface Sci. 206, 334 (1998)) and the results suggest that the presence of a dynamic Stern layer plays a certain role in this effect. Copyright 2000 Academic Press.

Journal Article↗

PubMed1998

The Influence of a Dynamic Stern Layer on the Primary Electroviscous Effect.

The theory developed by Watterson and White (Watterson, I. G., and White, L. R., J. Chem. Soc., Faraday Trans. 2 77, 1115 (1981)) to calculate the primary electroviscous coefficient of a suspension of charged spherical colloidal particles has been extended, by considering the presence of a dynamic Stern layer onto the particle surface, following the method developed by Mangelsdorf and White (Mangelsdorf, C. S., and White, L. R., J. Chem. Soc. Faraday Trans. 80, 2859 (1990)) for electrophoresis. The presence of mobile ions causes the primary electroviscous coefficient to decrease compared to when the Stern layer ions are inmobile. A separate dependence of the primary electroviscous coefficient on kappa-1 (Debye length) and a (particle radius) has been found. Copyright 1998 Academic Press.

Journal Article↗