High-gradient magnetic field-controlled migration of solutes and particles and their effects on solidification microstructure:A review

We present a review of the principal developments in the evolution and synergism of solute and particle migration in a liquid melt in high-gradient magnetic fields and we also describe their effects on the solidification microstructure of alloys.Diverse areas relevant to various aspects of theory and applications of high-gradient magnetic field-controlled migration of solutes and particles are surveyed.They include introduction,high-gradient magnetic field effects,migration behavior of solute and particles in high-gradient magnetic fields,microstructure evolution induced by high-gradient magnetic fieldcontrolled migrations of solute and particles,and properties of materials modified by high-gradient magnetic field-tailored microstructure.Selected examples of binary and multiphase alloy systems are presented and examined,with the main focus on the correlation between the high-gradient magnetic field-modified migration and the related solidification microstructure evolution.Particular attention is given to the mechanisms responsible for the microstructure evolution induced by highgradient magnetic fields.

Enhanced removal of ultra fi ne particles from kerosene combustion using a dielectric barrier discharge reactor packed with porous alumina balls

Ultrafine particles(UFPs)are harmful to human beings,and their effective removal from the environment is an urgent necessity.In this study,a dielectric barrier discharge(DBD)reactor packed with porous alumina(PA)balls driven by a pulse power supply was developed to remove the UFPs(ranging from 20 to 100 nm)from the exhaust gases of kerosene combustion.Five types of DBD reactors were established to evaluate the effect of plasma catalysis on the removal efficiency of UFPs.The influences of gasflow rate,peak voltage and pulse frequency of different reactors on UFPs removal were investigated.It was found that a high total UFP removal of 91.4%can be achieved in the DBD reactor entirely packed with PA balls.The results can be attributed to the enhanced charge effect of the UFPs with PA balls in the discharge space.The UFP removals by diffusion deposition and electrostatic attraction were further calculated,indicating that particle charging is vital to achieve high removal efficiency for UFPs.

Wetting behaviors of molten melt drops on polycrystalline Al2O3 substrates in high magnetic fields

We measured the contact angles of Al and Sn drops on polycrystalline Al2O3 substrates in various high magnetic fields at different temperatures.The contact angles of both Al and Sn drops on the Al2O3 substrates decreased under high magnetic fields.These decreases strongly depend on the temperature,magnetic flux density,magnetic properties of the metal drops,and the reactivity of the metal drops with Al2O3.Our results reveal that the wetting behavior of molten metal drops on ceramics can be modified by a high magnetic field.

A thermoelectric generator and water-cooling assisted high conversion efficiency polycrystalline silicon photovoltaic system

Solar energy has been increasing its share in the global energy structure. However, the thermal radiation brought by sunlight will attenuate the efficiency of solar cells. To reduce the temperature of the photovoltaic (PV) cell and improve the utilization efficiency of solar energy, a hybrid system composed of the PV cell, a thermoelectric generator (TEG), and a water-cooled plate (WCP) was manufactured. The WCP cannot only cool the PV cell, but also effectively generate additional electric energy with the TEG using the waste heat of the PV cell. The changes in the efficiency and power density of the hybrid system were obtained by real time monitoring. The thermal and electrical tests were performed at different irradiations and the same experiment temperature of 22°C. At a light intensity of 1000 W/m2, the steady-state temperature of the PV cell decreases from 86.8°C to 54.1°C, and the overall efficiency increases from 15.6% to 21.1%. At a light intensity of 800 W/m2, the steady-state temperature of the PV cell decreases from 70°C to 45.8°C, and the overall efficiency increases from 9.28% to 12.59%. At a light intensity of 400 W/m2, the steady-state temperature of the PV cell decreases from 38.5°C to 31.5°C, and the overall efficiency is approximately 3.8%, basically remain unchanged.

The accelerating nanoscale Kirkendall effect in Co films–native oxide Si(100)system induced by high magnetic fields

The morphology evolution and magnetic properties of Co films–native oxide Si(100)were investigated at 873,973,and 1073 K in a high magnetic field of 11.5 T.Formation of Kirkendall voids in the Co films was found to cause morphology evolution due to the difference in diffusion flux of Co and Si atoms through the native oxide layer.The high magnetic fields had considerable effect on the morphology evolution by accelerating nanoscale Kirkendall effect.The diffusion mechanism in the presence of high magnetic fields was given to explain the increase of diffusion coefficient.The morphology evolution of Co films on native oxide Si(100)under high magnetic fields during annealing resulted in the magnetic properties variation.