The
work reported here aims toward the optimization of electrode
preparation methodologies for superior performance of supercapacitors
through a rigorous understanding of underlying physical parameters.
Oxygen-functionalized few-layer graphene was employed as an active
material while binders [Nafion, polyvinylidene fluoride (PVDF), and
polytetrafluoroethylene], solvents for active material dispersion
[ethylene glycol and
N
-methyl-2-pyrrolidone (NMP)],
and electrode-drying temperatures (100, 170, and 190 °C) were
varied. Maximum specific capacitances at different electrode preparation
conditions ranged from 240 to 318 F g
–1
at 1 mV
s
–1
scan rate of cyclic voltammetry for the same
active material. The study revealed that the electrodes prepared using
the PVDF binder, the NMP solvent for active material dispersion, 170
°C electrode-drying temperature (slightly below the boiling temperature
of the solvent) provided the best electrochemical performance. Electrochemical
impedance spectroscopy revealed that the resistance for electron transfer
at the electrode/electrolyte interface can be minimized while mass
transport and pseudocapacitive charging can be improved significantly
by tuning electrode preparation methodologies which resulted in smaller
time constants and hence better capacitor performances. Scanning electron
microscopy images revealed that graphene layers were properly stacked
much similar to the synthesized nanomaterial wherein better electrochemical
performances were achieved, avoiding the agglomeration of nanomaterials
on the electrode surface. Low viscosity of the solvent for active
material dispersion and better solubility of the binder in the solvent
helped to reduce the agglomeration of nanomaterials by minimizing
the strong van der Waals interaction which causes agglomeration.
In this research work, a finite element model is developed to predict the temperature field and residual stress during plasma arc welding of thin Ti-6Al-4V sheets. Dhinakaran's heat source model which is based on Parabolic Gaussian distribution is used to predict the temperature field and Anand's model is used to predict the residual stress. Numerical simulation is performed using ANSYS ®. Heat transfer analysis is carried out primarily and the temperature field is given as the input for structural analysis. The concept of APDL programming is used to implement the governing equations. Experimental work has also been conducted to validate the predicted data. Hole Drilling Method (HDM), a semi destructive method and XRD analysis is used to measure the residual stress on the welded specimen. A good agreement is found between the predicted values and measured values.
AISI 310 is a highly alloyed austenitic stainless steel used for high-temperature applications. The high chromium and nickel contents give this steel excellent oxidation resistance as well as high strength. In the present work, the material was welded using shielded metal arc welding (SMAW), Pulsed Gas Metal Arc welding (P-GMAW) and Double Pulsed Gas Metal Arc welding (DP-GMAW). A comparative study has been carried out on the basis of chemical, mechanical, metallurgical and corrosion properties of base metal and all other welded samples. SMAW process has high heat input and hence dilution effect is more prominent in this process. The mechanical properties evaluated in terms of maximum tensile strength, impact energy and hardness was obtained for DP-GMAW sample. This superior mechanical behaviour of DP-GMA welded sample was attributed to the better grain refinement occurred due to double pulsation effect. However, the DP-GMAW process showed highest corrosion rate when compared to other two welded samples.
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