Influence Of Dispersed Particles Research Articles

The Role of Dispersed Particles in the Physicochemical Behavior of Nanofluids

Nanodispersions can be used to solve various practical problems, such as increasing the efficiency of heating systems, cooling of electrical equipment, intensifying oil recovery, etc., because dispersing nanoparticles in liquid media provides an inexpensive and convenient way to significantly improve various functional properties of a base fluid. Although the influence of dispersed particles on surface phenomena in systems comprising nanofluids has been studied for more than 30 years, due to a number of factors, the problem of appropriate and self-consistent description of the behavior of nanofluids will apparently remain to be the focus of scientific attention in the coming decades. This paper presents a brief review of recently published results that are of general importance for understanding the behavior of the surface tension of nanofluids, as well as the processes accompanying wetting with nanofluids and their spreading over various surfaces.

Influence of dispersed particles of tungsten carbide on the microstructure of 12Kh18N10T steel obtained by centrifugal casting

The development of new technologies in various industries, such as fast neuron reactors, require a new level of operational properties from steels and raise the issues of resistance to neutron radiation, radiation swelling, embrittlement and creep, and the level of residual activation. The principal way to increase these properties is to adjust the chemical composition, and rearrange the crystal structure of the metal. The authors propose to achieve this by introducing finely dispersed particles into the melt and controlled by them to “reinforce” the crystal lattice, grinding the metal structure. During the work, using the FactSage software package, thermodynamic modeling of the interaction of dispersed particles with a 18Х18Н10T steel melt was carried out, showing that the particles will interact with the metal melt, which can lead to their complete dissociation, and at the next stage of crystallization, regardless of the degree of dissolution of tungsten carbide, the formation of carbide phases based on titanium carbide with an FSS structure, as well as a carbide phase based on chromium carbide with the formula M23C3, will become. According to the simulation parameters, experiments were conducted, experimental blanks with different contents of the introduced tungsten carbide were obtained, and heat treatment was carried out. The study of microstructures showed that the introduced particles of tungsten carbide completely dissociate when interacting with a metal melt and contribute to an increase in ferrite in the microstructure of the workpiece. Studies of microhardness confi rmed the significant effect of the introduced carbide on the properties of the material: the maximum values of microhardness are achieved at a high concentration of refractory particles in the areas of their maximum concentration (outer edge of the workpieces). Carrying out heat treatment reduces microhardness, while aligning the gradient of properties with the volume of castings. This work was financially supported by the Ministry of Science and Higher Education of the Russian Federation within the framework of the federal target program under Agreement No. 075-15-2019-1711 (internal number 05.608.21.0276) dated December 04, 2019 (unique project identifier RFMEFI60819X0276).

Modeling and Simulation of Dynamic Recrystallization of GCr15 Steel Using Cellular Automaton Method

A modified two-dimensional (2-D) cellular automaton (CA) model was constructed to simulate dynamic recrystallization (DRX) process of GCr15 steel. Particle stimulated nucleation (PSN) was incorporated into the CA model to determine the influence of dispersed particles on the nucleation of DRX. In addition, the model included the effects of particles on increasing the dislocation density and pinning the grain boundaries for accurate determination of micro-structural evolution during DRX. The model was applied to simulate the DRX process of GCr15 bearing steel. DRX grain size and volume fraction were simulated using the CA model. The simulated results indicated that the simulated stable grain size of particle-containing model is closer to measured value than particle-free model. It was observed that DRX kinetics depends on both thermo-mechanical parameters and initial grain sizes. The calculated results were compared with the experimental findings in GCr15 bearing steel, the predictions show very good agreement with the experimental results.

Simultaneous measurement of particle and fluid velocities in particle-laden flows

For the velocity measurement in a particle-laden fluid flow, the fluid velocity and the inherently dispersed particle velocity can be analyzed by using PIV and PTV, respectively. Since the PIV result statistically represents the average displacement of all the particles in a PIV image, it is inevitable that the PIV result includes the influence of the dispersed particles’ displacement if a single CCD camera is used to simultaneously measure the fluid velocity and the dispersed particle velocity. The influence of dispersed particles should be excluded before the PIV analysis in order to evaluate the fluid velocity accurately. In this study, the optimum replacement brightness of dispersed particles to minimize the false influence of dispersed particles on the PIV analysis was theoretically derived. Simulation results show that the modification of dispersed particle brightness can significantly reduce the PIV error caused by the dispersed particles. This modification method was also verified in the analysis of an actual experimental case of the particle-laden fluid flow in a triangular grooved channel.

Influence of dispersed particles on small and large deformation properties of concentrated caseinate composites

Concentrated sodium caseinate composites (30% w/w in water), which contained either dispersed palm fat or glass spheres varying in size and surface properties were prepared in a Brabender Do-Corder kneader. The influence of the dispersed phase on the structural properties of the sodium caseinate composites was investigated using both small oscillating and large tensile deformations. Both experimental results and selected models showed that all measured properties were mainly influenced by the volume fraction of the dispersed particles. The type of filler, particle size and surface properties showed no differences in the small deformation properties, whereas the matrix-filler interaction played an important role in the large deformation properties. From the latter followed that sodium caseinate exhibited amphiphilic properties. Selected theoretical relations with the maximum volume packing fraction and the matrix-filler interaction as important parameters, agreed well with the experimental results. The relatively simple models can be applied as guidelines for designing composite food products.