On Dependence of Colloidal Stability of Magnetic Liquid on Stabilizer Dielectric Capacitivity and Dispersion Medium

Abstract

The purpose of this article is to research the possibility of using values of stabilizer dielectric capacitivity and dispersion medium to form a colloidal stability criterion of magnetic liquid. The authors researched colloidal stability of magnetic liquids with a low-polarity base, nonionogenous SAM-stabilizer (oligoester) and hydroximag nanoparticles. The received magnetic colloids were tested for stability in a gravity field to evaluate SAM stabilizing capacity. The authors propose Е-criterion that shows a relative difference between dielectric capacitivities of a dispersion medium and SAM-stabilizer. It was determined that such combination of dielectric capacitivity of solution component parts correlates with the values of SAM adsorption and colloid stability in the best way. The test results show that relative reduction of magnetization correlates well with a value of dispersion medium dielectric capacitivity due to irreversible sedimentative processes. In the next set of experiments, the authors did not change the magnetic colloid liquid content, but SAM-stabilizer. They research the dependence of colloidal stability of magnetic liquids based on a dioctyl sebacate of a stabilized SAM with various dielectric capacitivities. The test results prove regularity of increasing colloidal stability with decreasing E- criterion. The paper considers in details the physical and chemical mechanisms that help to develop the influence of dielectric capacitivity on magnetic liquid colloidal stability. The analysis of testing results showed that dielectric capacitivity of magnetic liquid components affects many physical-chemical phenomenons in the process of its synthesis. It is important that the behaviour of sorption processes on the surface of dispersed particles depends on dielectric capacitivity. The result of the empirical data research by magnetic liquid colloidal stability shows that with increasing dielectric capacitivity of dispersion medium in relation to stabilizer’s dielectric capacitivity the desorption processes of stabilizer’s molecules from a magnetic particles’ surface increses. As a result, the adsorption layer around particles becomes more incoherent and less competent. It reduces the value of a steric stabilization factor of a magnetic liquid colloidal structure. In practice it leads to deterioration or even loss of colloidal stability of magnetic liquid. The influence of dielectric capacitivity on colloidal stability using the effects of interparticle interaction is less important. To summarize, the article proves a dielectric E-criterion that can be used to provide rationale for the choice of SAM-stabilizer for magnetic liquids. According to this criterion, dielectric capacitivity of a dispersion medium should be slightly different from the similar property of SAM-stabilizer. Otherwise, molecule desorption processes of SAM from magnetic particles encourage quality degradation of covering adsorption layers, so colloidal stability worsens.Forcitation:Bolotov A.N., Novikov V.V., Novikova O.O. On dependence of colloidal stability of magnetic liquid on stabilizer dielectric capacitivity and dispersion medium. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 4. P. 75-81.

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