Showing papers by "Rajib Chakraborty published in 2022"
TL;DR: In this article , the authors analyzed thermal signals received from infrared pyrometer and understand the correlation between thermal signatures, phase prediction data using CALPHAD simulation, microstructure and deposition characteristics.
Abstract: In Laser Directed Energy Deposition (DED-L) process, based on the particular thermal cycle followed during the laser processing, a wide range of microstructural and dimensional outcomes are envisaged in the end product on account of the interaction of the material or the alloy with the laser. Various parameters can influence the thermal cycle and a direct correlation between the thermal characteristics with the mechanical/metallurgical properties would be helpful to control the process in a better way. Keeping in view of this, the present study is aimed at analyzing thermal signals received from infrared pyrometer and understanding the correlation between thermal signatures, phase prediction data using CALPHAD simulation, microstructure and deposition characteristics. The thermal signatures captured from infrared pyrometer revealed close interrelationship between the input process parameters and the molten pool characteristics, which have a huge influence on the solidification rate vis-à-vis microstructural properties. Total life of melt-pool showed an increase in magnitude from 137 ms to 264 ms with decrease in cooling rates from 3000 °C/s to 1750 °C/s. The grain size increased from 3.48 μm to 7.74 μm with increase in solidification shelf life from 32 ms to 110 ms. The higher solidification shelf life and lower cooling rates also resulted in the larger and the more prominent metal carbide precipitate and intermetallic formations as evident from XRD analysis . Microhardness of the deposits also increased with decrease in solidification shelf life and increase in cooling rates of molten pool. The dimensions of laser deposited tracks were also found to increase with increment in total molten pool lifetime both at increasing laser power and decreasing laser scan peed conditions. • Inconel 625 tracks were deposited at constant power, scan speed and fluence conditions by DED-L. • Shift in solidification shelf life indicated dilution of Fe from SS 304 L substrate. • Increment of solidification shelf life at constant fluence was detected. • Solidification shelf life and cooling rate influenced microstructure and microhardness. • 244 % increase in shelf life led to 122 % increase in grain size at constant scan speed. • Increase in track cross-sectional dimension at constant fluence condition was observed.
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TL;DR: In this article , the mesoporous top surfaces of methylammonium lead iodide (C H 3 N H 3 P b I 3 ) perovskite solar cells have been tuned to achieve better performance.
Abstract: Substitution of monocrystalline or polycrystalline silicon as active materials in photovoltaics with highly efficient perovskite materials is quite common. Although perovskite materials offer better flexibility, are cost-effective, and have higher conversion efficiency, they still require structural modifications for better performance. This study quantitatively investigates how mesoporous top surfaces improve the performance of methylammonium lead iodide (C H 3 N H 3 P b I 3) perovskite solar cells. In fact, both the diameter and the depth of the pores have been tuned to achieve better performance. The performance is further optimized by replacing mesoporous active material with planar active material coated with mesoporous indium tin oxide (ITO). We have demonstrated that the proposed structure achieves the maximum conversion efficiency (η) of 27.43% with an open-circuit voltage (V O C ) of 1.07 V and a short circuit current density (J S C ) of 29.09m A/c m 2, with a fill factor (FF) of 88.10%.