Unified mathematical Model of the Kinetics of Nanoparticle Phase Condensation in Magnetic Fields

In this paper, we aim to present a unified mathematical modeling and description of the kinetics of magnetic nanoparticles phase condensation (conducting to the appearance of bulk elongated aggregates) under homogeneous permanent or alternating magnetic field. For such case, the aggregate growth rate usually takes the form dV/dt = G(V)∆(t), with V and t being the aggregate's volume and time, respectively, ∆(t)—the supersaturation of the nanoparticle suspension, and with the function G(V) depending on the precise configuration of the applied field. The Liouville equation for the aggregate size distribution function is solved by the method of characteristics. The solution is obtained in parametric form for an arbitrary function G(V), providing a general framework for any type of the applied magnetic field. In the particular case of low-frequency rotating magnetic field (G(V)~V2/3), an explicit expression of the distribution function is obtained, while the dimensionless average aggregate volume 〈V〉 is found by the method of moments allowing a complete decoupling of the system of equations for the statistical moments 〈Vn〉 of the distribution function. Numerical examples are provided for the cases of permanent and low- or medium-frequency rotating fields. It is shown that in all cases, the average volume 〈V〉 only slightly depends on the relative width of the initial size distribution. Nevertheless, at any times, t > 0, the size distribution shows a significant spreading around the average value 〈V〉, which increases progressively with time and achieves a final plateau at long times. This model can be helpful for several biomedical or environmental applications of magnetic nanoparticles in which the nanoparticle suspension undergoes a field-induced phase condensation. © 2020 John Wiley & Sons, Ltd.PK acknowledges the French “Agence Nationale de la Recherche,” Project Future Investments UCA JEDI, No. ANR‐15‐IDEX‐01 (projects ImmunoMag and MagFilter) and the private company Axlepios Biomedicals for financial support. JQC acknowledges the financial support of UCA JEDI and Axlepios Biomedicals through the PhD fellowship. AZ thanks the Russian Science Foundation, project 20‐12‐00031, for the financial support

Interfacial balance equations for diffusion evaporation and exact solution for weightless drop

Introducing of additional terms into the balance equations to specify the conditions at the interface allows to study physical phenomena in the diffusion evaporation (condensation) of the liquid into the neutral gas. We have taken into account the vapour dynamic effects on evaporating liquid, as well as the waste of energy on deformation of the boundary, changing of the interfacial temperature (the interface has an internal energy and therefore heat capacity), to overcome the surface tension etc. This paper presents the balance conditions at the interface with the diffusion evaporation of the liquid into the neutral gas, for the case when the vapour is considered as an impurity in the gas phase. The analysis of the dimensionless criteria is carried out. The areas of parameters for which the effect of some physical factors take a place have been defined. The exact solution of the diffusion evaporation for a spherical drop at zero gravity conditions has been constructed. The explicit expression for the interfacial temperature and evaporation rate were derived. Solution for evaporation rate coincides with the solution obtained by Maxwell (1890). © Springer Science+Business Media B.V. 2011.SCOPUS: ar.jinfo:eu-repo/semantics/publishe