Narrow Results

This computational study focuses on the dynamics of individual ferrous particles and the flow of the incompressible Newtonian fluid under the effect of an externally applied magnetic field and pressure gradient in a two-dimensional micro channel with smooth walls. The particle dynamics is simulated as a discrete phase using MATLAB code and the fluid flow is solved as a continuous phase using Computational Fluid Dynamics Software FLUENT. Interaction between the particle and fluid phases are included as hydrodynamic forces predicated by the fluid phase simulation and updated particle locations determined by the particle phase solution under non-uniform magnetic field. Non-uniform magnetic field forces the particles to move to poles of the magnet, and results in their accumulation. This causes drastic change on the continuous phase flow and pressure distribution, which in turn influences the particle motion. Predicted dynamics of the suspended ferrous particles under magnetic field and flow of the carrier fluid with pressure gradient is in reasonably well agreement with previous work. The results show that non-uniform magnetic field generated by externally placed magnets can be used to control the locations of the particles and flow of the fluid in a micro channel.

Strontium hexaferrite is a hard magnetic material and has been extensively used as a permanent magnet. In this work a novel sol-gel auto-combustion method was used to synthesize ultra fine strontium hexaferrite. The investigations show that the model of combustion changes with the change of basic agent. The XRD results show that using ammonia or trimethylamine does not change the composition of the combustion product and it also shows that the surfactant burns completely during the combustion process. The average crystallite size of hexaferrite powders was also measured by X-ray line broadening technique employing Scherrer formula. The results show that changing the basic agent makes the particle size of the final product much smaller. Basic agent also affects the formation temperature of the single phase strontium hexaferrite.

We report studies of random sequential adsorption on the pre-patterned Bethe lattice. We consider a partially covered Bethe lattice, on which monomers and dimers deposit competitively. Analytical solutions are obtained and discussed in the context of recent efforts to use pre-patterning as a tool to improve self-assembly in micro- and nano-scale surface structure engineering.

This paper describes the influence of surface roughness of steel plate on self-assembly behavior of silica particles based on SEM observations and the wettability of the suspension. The 304 stainless steel plate having two different surface roughness and spherical silica powder were used for the investigation. The silica layer was obtained by dipping the steel plate into the suspension and drawing it under various drawing speed. As a result, silica particle layers were formed on the plate surface when the stainless steel had a rough surface. In contrast, it was difficult to obtain the silica layers for the smooth surface.

Physical mechanisms of laser cleaning of solid surface from soiling particles and films are discussed. Dry laser cleaning of surface from particles is considered to be a result of inertial force, appearing due to thermal expansion of absorbing particles and/or substrate (shaking-off mechanism). Steam laser cleaning is considered for the cases of absorbing particles and absorbing substrate. In the latter case, peculiarities of bubble formation in the liquid layer under the conditions of ns laser action are analyzed. Laser cleaning of surfaces from films by shaking-off and buckling mechanisms (due to thermal tension) is considered. Conditions of the action of each of them are defined. Other physical mechanisms, blasting and evaporation, are briefly discussed.