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  • Küçük Resim
    Öğe
    Effects of solvent and copper-doping on polyaniline conducting polymer and its application as a counter electrode for efficient and cost-effective dye-sensitized solar cells
    (Elsevier Science Sa, 2016) Tas, Recep; Gulen, Mahir; Can, Muzaffer; Sonmezoglu, Savas
    In this study, the synthesis of Copper-doped polyaniline (NPANI-Cu-X) was performed in the following solvents: H2O, DMF, DO, THF, ACTN and ACN, and then the solvent effects on the formation of NPANI-Cu-X (X represents the dopants, I- and BF4-) were investigated. NPANI-Cu-X was characterized using scanning electron microscopy (SEM), X-ray diffractions (XRD), energy-dispersive X-ray analysis (EDAX), Fourier transform infrared spectrometry (FTIR), Atomic Absorption spectrometer (AAS), Ultraviolet-visible spectrophotometers (UV-vis), thermal analysis (TGA, DTA) and electrical conductivity measurements. The results show that the solvent is effective in the formation of NPANI-Cu-X. This effect was observed in the polymer structures, conductivities, copper contents and crystalline structures. The NPANI-Cu-X polymers synthesized with the various solvents were notably different from each other because some of the solvents create a copper-solvent complex with the copper. To understand the influence of solvent type and Cu inclusion on photoelectric performance, the obtained PANI were employed as counter electrode in a DSSC configuration. The highest double layer capacitance (24.1 mu F), low charge transfer resistance (5.13 Omega) together with series resistance (14.62 Omega), and good photovoltaic performance with conversion efficiency (6.37%) for counter electrodes are obtained the NPANI-Cu-X in ACN solvent media which is higher than that fabricated with N-PANI in same solvent media (1.36%). These results represent a promising route for developing new counter electrodes of Pt-free DSSCs by Cu doping and choosing an appropriate solvent. (C) 2015 Elsevier B.V. All rights reserved.
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    Öğe
    Evolution of residual compressive stress regions in Co-diffused Bi-2212 engineering ceramics with annealing temperature
    (Springer, 2024) Mercan, Ali; Erdem, Umit; Ulgen, Asaf Tolga; Gulen, Mahir; Turkoz, Mustafa Burak; Turgay, Tahsin; Yildirim, Gurcan
    The role of diffusion annealing temperatures intervals 600-850 degrees C on durable tetragonal phase, surface morphology, and main mechanical performance parameters of Co surface-layered Bi2.1Sr2.0Ca1.1Cu2.0Oy (Bi-2212) samples has extensively been examined by scanning electron microscopy (SEM), Electron Dispersive X-ray (EDX) technique and microindentation Vickers hardness (Hv) tests. The experimental findings have shown that every material prepared has presented different composition distributions on the specimen surface as a consequence of the successful production of materials. Besides, the mechanical characteristics and durable tetragonal phase have been noted to enhance significantly with the enhancement of annealing temperature up to 650 degrees C due to the formation of new slip systems, surface residual compressive stress regions, connections between grains, and chemical bonding between the foreign and host atoms. Further, the optimum temperature has led to the reduction in stored internal strain energy and degree of granularity in the Co-diffused Bi-2212 crystal system. In this respect, the sample with the least sensitive to the external forces has exhibited the highest elastic modulus of 0.5445 GPa, shear modulus of 17.8515 GPa, yield strength of 181.5 MPa, and resilience of 369.1 MPa under 0.295 N. Accordingly, the cracks and dislocations have preferred to propagate throughout the transcrystalline regions, and crack growth size was easily controlled. Similarly, the saturation limit region has begun at relatively higher applied test load magnitudes. Conversely, the excess annealing temperature has caused the increase in the agglomeration of cobalt ions throughout the intergranular regions. Correspondingly, the activation of stress-induced phase transformation has been triggered seriously. Bi-2212 ceramic compound exposed to the optimum diffusion annealing temperature exhibits the most uniform surface view and crystalline quality with the densest surface morphology and the largest particle distributions and orientations. Moreover, every material studied has perfectly presented the characteristic indentation size effect behavior. The examination of granularity degree depending on elasticity moduli has verified all the Hv test results and discussions. All in all, this study guides the use of engineering ceramics in more application areas due to the increase in their service life.