Analysis of the Electroconsolidation Process of Fine-Dispersed Structures Out of Hot Pressed Al2O3–WC Nanopowders

Fabrication of alumina–tungsten carbide nanocomposite was investigated. Characteristics of the densification and sintering were analyzed considering both the nano-size particle starting powders and the processing stages. Different heating rates were generated during densification and consolidation with a maximal load was applied only after a temperature of 1000 °C was reached. Due to the varying dominance of different physical processes affecting the grains, appropriate heating rates and pressure at different stages ensured that a structure with submicron grains was obtained. With directly applied alternating current, it was found that the proportion Al2O3 (50 wt.%)–WC provided the highest fracture toughness, and a sintering temperature above 1600 °C was found to be disadvantageous. High heating rates and a short sintering time enabled the process to be completed in 12 min, saving energy and time.

Particle orbiting motion in a confined microvortex

Particle motion in viscous fluids is a common and fascinating phenomenon. The hydrodynamics of a trapped finite-size particle recirculating along a stable orbit within a microvortex is still puzzling. Herein we report experimental observations of the orbiting motion of a finite-size particle in a vortex confined in a microcavity. The orbiting particle keeps crossing the streamlines with acute changes in velocity along the orbit, which can be divided into three stages: acceleration, swerving, and following. By examining the relationship between particle orbit and vortex streamlines, we uncover a particle slingshot effect and slip motion. Particle motion and vortex structure in three dimensions are also studied, revealing many new fascinating particle motion phenomena. The results provide new insights into the physics of particle motion in vortices.

Development of Mass – Size Particle Reduction Operations Postulates Using Empirical – Analytical Approaches

Aims: This paper attempts to utilize empirical and analytical approaches to develop equations and postulates for energy and power requirement in mass – size reduction operations. Study Design: The study is based on a combination of analytical approach and empirically existing energy model obtained in a study of milling palm nut shells into fragments using static nut cracker. Place and Duration of Study: The empirical model used in this study was developed in 2014 in the University of Benin, Nigeria and the analytical approach employed for the study to obtain mass – size particle reduction models and postulates were achieved in September, 2020 in the University of Uyo, Nigeria. Methodology: In this task, the crushing efficiency, mechanical efficiency, energy and power requirements were considered based on fundamental principles coupled with the usage of the empirically developed minimum energy model for mass –size reduction operations. Results: The Equations (59), (60), (61), (62) and (63) were developed. Equations (59), (60) and (62) are in the form of bond’s energy equation but may differ in the value of the constant. This may be because the properties (density, thickness or diameter of the particle) of material and machine efficiency might easily be obtained and used to evaluate; and likely achieved an improved assessment of mass – size reduction of a given material. Conclusion: Further analysis has led to the development of postulates presented in the conclusion part of this paper which may govern the mass – size reduction operations of particle.