Characteristics of spherical particles on copper powder and changing sizes were studied in a ball mill under various experimental conditions,such as different ball diameters,high rotation speeds,and milling times,usin...Characteristics of spherical particles on copper powder and changing sizes were studied in a ball mill under various experimental conditions,such as different ball diameters,high rotation speeds,and milling times,using a discrete element method(DEM)simulation.This experiment has investigated the characteristics of spherical particle morphology evolution involved in the mechanical alloying of copper powder.The morphological evolution of the copper particle was analyzed using scanning electron microscopy(SEM).A spherical copper particle was shown with a roundness value using imageJ software.The DEM was used to simulate the ball motion in a planetary ball mill,and the impact energy and shear energy generated during the collision were analyzed to estimate the contact number between the ball and the ball wall.Therefore,as the size of the ball decreased,the number of ball-to-ball and ball-to-wall contacts increased accordingly,and the spherical shape of the copper powder changed.展开更多
We investigated the effect of the raw powder properties of carbon nanotube surface coatings on metal powder,with the goal of obtaining high-quality nanocomposites.The mechanical dry coating technique was used to fabri...We investigated the effect of the raw powder properties of carbon nanotube surface coatings on metal powder,with the goal of obtaining high-quality nanocomposites.The mechanical dry coating technique was used to fabricate CNT coatings (guest particles)on the surface of copper (Cu,host)particles using a traditional ball mill and a stirred ball mill.The coatings were produced under various experimental conditions (varying rotation speed and grinding duration,with a ball diameter of 5mm),and the effect of these conditions on the surface of the powder was determined.The coated surfaces were characterized using scanning electron microscopy and field emission scanning electron microscopy.We compared prolonged milling (48h)at a low rotation speed (50rpm),with a short milling period (12h)at high rotation speed.We found that for the TBM,successful CNT coating was achieved at 50rpm over 48h. In contrast,for the SBM,CNT coatings were obtained after a short milling period (12h)at low rotation speed (50rpm).展开更多
Luminescent solar concentrators (LSC) absorb large-area solar radiation and guide down-converted emission to solar cells for electricity production. Quantum dots (QDs) have been widely engineered at device and quantum...Luminescent solar concentrators (LSC) absorb large-area solar radiation and guide down-converted emission to solar cells for electricity production. Quantum dots (QDs) have been widely engineered at device and quantum dot levels for LSCs. Here, we demonstrate cascaded energy transfer and exciton recycling at nanoassembly level for LSCs. The graded structure composed of different sized toxic-heavy-metal-free InP/ZnS core/shell QDs incorporated on copper doped InP QDs, facilitating exciton routing toward narrow band gap QDs at a high nonradiative energy transfer efficiency of 66%. At the final stage of non-radiative energy transfer, the photogenerated holes make ultrafast electronic transitions to copper-induced mid-gap states for radiative recombination in the near-infrared. The exciton recycling facilitates a photoluminescence quantum yield increase of 34% and 61% in comparison with semi-graded and ungraded energy profiles, respectively. Thanks to the suppressed reabsorption and enhanced photoluminescence quantum yield, the graded LSC achieved an optical quantum efficiency of 22.2%. Hence, engineering at nanoassembly level combined with nonradiative energy transfer and exciton funneling offer promise for efficient solar energy harvesting.展开更多
基金convergence research financial program for instructors,graduate students and professors in 2023.
文摘Characteristics of spherical particles on copper powder and changing sizes were studied in a ball mill under various experimental conditions,such as different ball diameters,high rotation speeds,and milling times,using a discrete element method(DEM)simulation.This experiment has investigated the characteristics of spherical particle morphology evolution involved in the mechanical alloying of copper powder.The morphological evolution of the copper particle was analyzed using scanning electron microscopy(SEM).A spherical copper particle was shown with a roundness value using imageJ software.The DEM was used to simulate the ball motion in a planetary ball mill,and the impact energy and shear energy generated during the collision were analyzed to estimate the contact number between the ball and the ball wall.Therefore,as the size of the ball decreased,the number of ball-to-ball and ball-to-wall contacts increased accordingly,and the spherical shape of the copper powder changed.
文摘We investigated the effect of the raw powder properties of carbon nanotube surface coatings on metal powder,with the goal of obtaining high-quality nanocomposites.The mechanical dry coating technique was used to fabricate CNT coatings (guest particles)on the surface of copper (Cu,host)particles using a traditional ball mill and a stirred ball mill.The coatings were produced under various experimental conditions (varying rotation speed and grinding duration,with a ball diameter of 5mm),and the effect of these conditions on the surface of the powder was determined.The coated surfaces were characterized using scanning electron microscopy and field emission scanning electron microscopy.We compared prolonged milling (48h)at a low rotation speed (50rpm),with a short milling period (12h)at high rotation speed.We found that for the TBM,successful CNT coating was achieved at 50rpm over 48h. In contrast,for the SBM,CNT coatings were obtained after a short milling period (12h)at low rotation speed (50rpm).
基金This project has received funding from the European Research Council(ERC)under the European Union Horizon 2020 Research and Innovation Programme(grant agreement no.639846).
文摘Luminescent solar concentrators (LSC) absorb large-area solar radiation and guide down-converted emission to solar cells for electricity production. Quantum dots (QDs) have been widely engineered at device and quantum dot levels for LSCs. Here, we demonstrate cascaded energy transfer and exciton recycling at nanoassembly level for LSCs. The graded structure composed of different sized toxic-heavy-metal-free InP/ZnS core/shell QDs incorporated on copper doped InP QDs, facilitating exciton routing toward narrow band gap QDs at a high nonradiative energy transfer efficiency of 66%. At the final stage of non-radiative energy transfer, the photogenerated holes make ultrafast electronic transitions to copper-induced mid-gap states for radiative recombination in the near-infrared. The exciton recycling facilitates a photoluminescence quantum yield increase of 34% and 61% in comparison with semi-graded and ungraded energy profiles, respectively. Thanks to the suppressed reabsorption and enhanced photoluminescence quantum yield, the graded LSC achieved an optical quantum efficiency of 22.2%. Hence, engineering at nanoassembly level combined with nonradiative energy transfer and exciton funneling offer promise for efficient solar energy harvesting.
