Biomedical subjects
Publications and source records attributed to F J Rubio-Hernández.
The viscosity of dilute suspensions of several metal oxides (SiO2, Al2O3 and TiO2) was measured at different pH values. The intrinsic viscosity, [eta], was derived from the concentration dependence of the viscosity. This magnitude was pH-dependent. A correlation with the shape of the kinetic unity has been proposed.
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.
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.
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).