The precipitation of cobalt carbonate nanocrystals was achieved through the reaction of a pure and rich solution of cobalt sulphate (Co<sup>2+</sup>: 16.80 g/l) with a solution of carbonate solution (200 g...The precipitation of cobalt carbonate nanocrystals was achieved through the reaction of a pure and rich solution of cobalt sulphate (Co<sup>2+</sup>: 16.80 g/l) with a solution of carbonate solution (200 g/l). A surfactant was added to the reacting mixture in order to control the shape and size of generated crystallites. Two parameters were then varied <em>i.e.</em>, the weight of surfactant agent and the precipitation time in accordance with Taguchi’s L4 full experimental procedure (2<sup>2</sup>). Chemical and structural characterizations tests of the obtained precipitates were done through X-Rays Fluorescence (XRF), Scanning Electron Microscopy (SEM) and X-Rays Diffractometer (XRD);whereas the size of crystallites was assessed according to the Laue-Scherrer formula. The results obtained from the variance analysis (ANOVA) indicated an optimal size of cobalt carbonate’s crystallites of 13 nm with a cobalt content of 44.35% (equivalent to 89.45% of CoCO<sub>3</sub>) at ambient temperature under the following conditions: pH = 7;Mixing speed: 800 tr/min;Surfactant weight: 8 g;and a mixing time: 10 minutes. SEM images revealed an agglomeration of the obtained nanocrystals due to suspected drying conditions <em>i.e.</em>, drying temperature and drying atmosphere. It is suggested that the experiment should be conducted under neutral conditions at a temperature below that of cobalt carbonate’s decomposition (181.41℃).展开更多
This study aimed to optimize cross-sectional area of the extruder and the flow rate of the material through the extruder. Extrusion process was first modelized using the continuum mechanics method before being simulat...This study aimed to optimize cross-sectional area of the extruder and the flow rate of the material through the extruder. Extrusion process was first modelized using the continuum mechanics method before being simulated with the commercial software LS-DYNA using the Johnson-Cook model based on the finite element method after optimization of the factors with simplex algorithm. The study was carried out on a connecting rod: diameter of 145 mm, cross-section of 1.65 m<sup>2</sup>, length of 0.25 m, volume of 0.41 m<sup>3</sup> and a mass of 37 kg. Optimum parameters obtained were temperature of 850℃, flow rate of 0.237 m/s, die diameter of 19.2 mm, pin diameter of 14 mm, extrusion strength of 565.6 kN and press pressure of 245 GPa. From these factors, a blank was obtained with external and internal diameters of 19.2 and 14 mm respectively over a length of 28 m with a thickness of 2.6 mm. Simulation using LS-DYNA software resulted in a difference in values of 7.4% between optimization and simulation when the difference of 2.4% was found between modelling and simulation. These values make the process optimal for industrial application to improve the extrusion requirements of copper tubes.展开更多
文摘The precipitation of cobalt carbonate nanocrystals was achieved through the reaction of a pure and rich solution of cobalt sulphate (Co<sup>2+</sup>: 16.80 g/l) with a solution of carbonate solution (200 g/l). A surfactant was added to the reacting mixture in order to control the shape and size of generated crystallites. Two parameters were then varied <em>i.e.</em>, the weight of surfactant agent and the precipitation time in accordance with Taguchi’s L4 full experimental procedure (2<sup>2</sup>). Chemical and structural characterizations tests of the obtained precipitates were done through X-Rays Fluorescence (XRF), Scanning Electron Microscopy (SEM) and X-Rays Diffractometer (XRD);whereas the size of crystallites was assessed according to the Laue-Scherrer formula. The results obtained from the variance analysis (ANOVA) indicated an optimal size of cobalt carbonate’s crystallites of 13 nm with a cobalt content of 44.35% (equivalent to 89.45% of CoCO<sub>3</sub>) at ambient temperature under the following conditions: pH = 7;Mixing speed: 800 tr/min;Surfactant weight: 8 g;and a mixing time: 10 minutes. SEM images revealed an agglomeration of the obtained nanocrystals due to suspected drying conditions <em>i.e.</em>, drying temperature and drying atmosphere. It is suggested that the experiment should be conducted under neutral conditions at a temperature below that of cobalt carbonate’s decomposition (181.41℃).
文摘This study aimed to optimize cross-sectional area of the extruder and the flow rate of the material through the extruder. Extrusion process was first modelized using the continuum mechanics method before being simulated with the commercial software LS-DYNA using the Johnson-Cook model based on the finite element method after optimization of the factors with simplex algorithm. The study was carried out on a connecting rod: diameter of 145 mm, cross-section of 1.65 m<sup>2</sup>, length of 0.25 m, volume of 0.41 m<sup>3</sup> and a mass of 37 kg. Optimum parameters obtained were temperature of 850℃, flow rate of 0.237 m/s, die diameter of 19.2 mm, pin diameter of 14 mm, extrusion strength of 565.6 kN and press pressure of 245 GPa. From these factors, a blank was obtained with external and internal diameters of 19.2 and 14 mm respectively over a length of 28 m with a thickness of 2.6 mm. Simulation using LS-DYNA software resulted in a difference in values of 7.4% between optimization and simulation when the difference of 2.4% was found between modelling and simulation. These values make the process optimal for industrial application to improve the extrusion requirements of copper tubes.
