| 1. |
- Islavath, Nanaji, et al.
(författare)
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Effect of hole-transporting materials on the photovoltaic performance and stability of all-ambient-processed perovskite solar cells
- 2017
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Ingår i: Journal of Energy Chemistry. - : Elsevier BV. - 2095-4956 .- 2096-885X. ; 26:3, s. 584-591
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Tidskriftsartikel (refereegranskat)abstract
- High-efficiency perovskite solar cells (PSCs) reported hitherto have been mostly prepared in a moisture and oxygen-free glove-box atmosphere, which hampers upscaling and real-time performance assessment of this exciting photovoltaic technology. In this work, we have systematically studied the feasibility of all-ambient-processing of PSCs and evaluated their photovoltaic performance. It has been shown that phase-pure crystalline tetragonal MAPbI3 perovskite films are instantly formed in ambient air at room temperature by a two-step spin coating process, undermining the need for dry atmosphere and post-annealing. All-ambient-processed PSCs with a configuration of FTO/TiO2/MAPbI3/Spiro-OMeTAD/Au achieve open-circuit voltage (990 mV) and short-circuit current density (20.31 mA/cm2) comparable to those of best reported glove-box processed devices. Nevertheless, device power conversion efficiency is still constrained at 5% by the unusually low fill-factor of 0.25. Dark current–voltage characteristics reveal poor conductivity of hole-transporting layer caused by lack of oxidized spiro-OMeTAD species, resulting in high series-resistance and decreased fill-factor. The study also establishes that the above limitations can be readily overcome by employing an inorganic p-type semiconductor, copper thiocyanate, as ambient-processable hole-transporting layer to yield a fill-factor of 0.54 and a power conversion efficiency of 7.19%. The present findings can have important implications in industrially viable fabrication of large-area PSCs.The poor conductivity of ambient-processed spiro-OMeTAD HTM layer caused by lack of oxidation is identified as a major performance limiting factor and successfully overcome by replacing with stable inorganic CuSCN.
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| 2. |
- Kumar, S., et al.
(författare)
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Microstructure and performance of cold sprayed Al-SiC composite coatings with high fraction of particulates
- 2017
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Ingår i: Surface & Coatings Technology. - 0257-8972 .- 1879-3347. ; 318, s. 62-71
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Tidskriftsartikel (refereegranskat)abstract
- Deposition of metal matrix composites (MMCs) through thermal spraying has traditionally presented problems associated with heterogeneity, porosity, and low wettability of particulates with matrix. Cold spray is a very rapid deposition process which is suitable for depositing a variety of ductile materials without any thermal degradation. Many researchers have attempted to deposit Al-SiC MMCs with 10–20% SiC using this technique. In the present study, three different powder compositions (FAl-23SiC, FAl-46SiC, FAl-71SiC) obtained by mixing Al and SiC powders were cold sprayed on aluminum substrates. The volume percentage and the average size of the SiC particulates in the cold sprayed coatings were estimated and found to be 23%, 47% and 52% for FAl-23SiC, FAl-46SiC and FAl-71SiC feedstocks, respectively. Effects of percentage and size of the SiC particulate retained in the composite coatings on the mechanical properties and the sliding wear performance were studied at different sliding conditions in the as-sprayed and heat treated conditions. The results were comprehensively analyzed and found to correlate well with the microstructure of the coatings.
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| 3. |
- Reddy, S. S., et al.
(författare)
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Evaluation of microstructural and dry sliding wear characteristics of pulsed Nd:YAG laser surface melted Al-Si alloys
- 2004
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Ingår i: Proceedings of the International Conference on Advances in Surface Treatment: Research and Applications, ASTRA. ; , s. 568-574
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Konferensbidrag (refereegranskat)abstract
- Aluminium-Silicon alloys are being increasingly considered for manufacture of wear prone components in automobile and aircraft industries owing to their light weight, superior corrosion resistance and high thermal conductivity, besides their amenability to processing methods such as casting. However, poor tribological characteristics have hampered industrial adoption of the above class of alloys. In principle, the tribological properties of these alloys can be improved by refining the microstructure by laser remelting techniques. Recently, Nd:YAG lasers have been used for processing of reflective materials such as Aluminium, as these lasers have better absorptivity compared to the CO2 lasers. The present study investigates the microstructural characteristics and improvements in sliding wear resistance that can result from surface melting of Al-Si alloys using a 400 W pursed Nd:YAG laser. Three different Al-Si alloys with varying Si content 5%, 12.5% and 20% have been investigated in the present study. The microstructures of the transverse cross sections of the treated samples were examined in detail and X-ray diffraction (XRD) studies carried out to ascertain changes in phase constitution. The surface melting and subsequent rapid solidification was found to cause considerable refinement of the microstructure, which in turn increased the hardness in the treated layer compared with that of bulk. The effect of laser beam scan speed on microhardness of the treated samples was evaluated. Dry sliding wear tests were conducted on treated and untreated samples of Al-12Si using a pin-on disc tribometer. The volume wear rates determined in case of the treated and untreated samples are discussed in the paper. The results have also been correlated with the morphological and microstructural characteristics noted in the laser treated specimens. Copyright © 2004 by Society for Advancement of Heat Treatment & Surface Engineering (SAHTSE).
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| 4. |
- Sadeghimeresht, Esmaeil, 1985-, et al.
(författare)
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Chlorine-induced high temperature corrosion of HVAF-sprayed Ni-based alumina and chromia forming coatings
- 2018
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 132:March, s. 170-184
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Tidskriftsartikel (refereegranskat)abstract
- Chlorine-induced corrosion of HVAF-sprayed Ni21Cr and Ni5Al coatings was investigated in 5 vol.% O2 + 500vppm HCl + N2 with and without KCl at 600 °C up to 168 h. Both coatings were protective in the absence of KCl. With KCl, Ni21Cr degraded through a two-stage mechanism: 1) formation of K2CrO4 followed by diffusion of Cl− through the oxide grain boundaries to yield chlorine and a non-protective oxide, and 2) inward diffusion of chlorine though defects in the non-protective oxide, leading to breakaway oxidation. Cl−/Cl2 could not diffuse through the protective alumina scale formed on Ni5Al, hence the corrosion resistance increased.
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| 5. |
- Sadeghimeresht, Esmaeil, 1985-, et al.
(författare)
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Influence of KCl and HCl on high temperature corrosion of HVAF-sprayed NiCrAlY and NiCrMo coatings
- 2018
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 148, s. 17-29
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation performance of NiCrAlY and NiCrMo coatings thermally sprayed by high velocity air-fuel (HVAF) technique has been investigated in a chloridizing-oxidizing environment, with and without a KCl deposit, at 600 °C for up to 168 h. Both coatings protected the substrate in the absence of KCl due to formation of a dense Cr-rich oxide scale. In the presence of KCl, Cl−/Cl2 diffused through a non-protective and porous NiCr2O4 scale formed on NiCrAlY, leading to formation of volatile CrCl3. On the other hand, Mo in NiCrMo stimulated the formation of a more protective Cr-rich oxide scale which increased the corrosion resistance by reducing Cl−/Cl2 diffusion.
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