Yu. A. Khodyko

Kinetics of picoliter binary droplet evaporation on a substrate at reduced pressure

The effects of different factors on the time of evaporation of a single picoliter droplet of a water-alcohol solution on a metal substrate with a high thermal conductivity have been studied in the free molecular regime. It has been experimentally shown that the evaporation of such droplets occurs in the pinning mode. The evaporation times have been measured for droplets of water-alcohol solutions of different concentrations on the substrate at a reduced pressure. The calculations performed in terms of a one-dimensional mathematical model have shown that the rates of evaporation of pico- and femtoliter droplets of water-alcohol solutions nonlinearly depend on alcohol concentration, initial droplet height, and substrate temperature.

Coalescence and diffusion growth of nanoparticles in closed microvolume of supersaturated solution

A model is developed and numerically studied for the diffusion growth of nanoparticles in a closed microvolume of supersaturated solutions resulting from the evaporation cooling of microsized droplets of multicomponent aqueous solutions. Limits are established for the regimes that correspond to the stable growth of all nanoparticles and the onset of isothermal distillation. It is revealed that, in highly supersaturated solutions, the final nanoparticle radius is independent of the radius of primary particles. The final nanoparticle radius can be controlled by varying the concentration of primary particles. Specific calculations are performed for nickel oxide nanoparticles.

Low-temperature synthesis of metal oxide nanoparticles during evaporation of femtoliter drops of aqueous solutions

We report on experimental results on the synthesis and growth of nanoparticles formed during evaporation of micrometer droplets of concentrated solutions in a low-pressure aerosol reactor. It is shown, in particular, that macroscopic compounds of nickel oxide in the form of nanoparticles are formed at room temperature from a supersaturated solution of nickel chloride. The features of the low-pressure electrostatic precipitation of femtoliter droplets on a substrate are investigated. Theoretical and experimental morphologies of nanoparticle ensembles obtained in this way are compared.

Thermophoresis and the Brownian diffusion of nanoparticles in a flow reactor

The influence of thermophoresis and Brownian diffusion on deposition of the nanoparticles from a laminar gas flow on adsorbing walls of a flow reactor is investigated theoretically. Two similarity criteria characterizing the process of deposition of nanoparticles under nonisothermal conditions are formulated. It is shown that the influence of thermophoresis is significant only at the inlet area of the reactor, while Brownian diffusion acts over its entire length. To describe the interaction between the gas flow and the nanoparticles, the free-molecular approximation is used. The results of numerical calculations are given.