Sameer S. Damle

High energy density titanium doped-vanadium oxide-vertically aligned CNT composite electrodes for supercapacitor applications

In this study, we provide the first report on the supercapacitance behavior of titanium doped vanadium oxide films grown on vertically aligned carbon nanotubes using a chemical vapor deposition (CVD) technique. The capacitance of CVD derived titanium doped vanadium oxide–carbon nanotube composites was measured at different scan rates to evaluate the charge storage behavior. In addition, the electrochemical characteristics of the titanium doped vanadium oxide thin films synthesized by the CVD process were compared to substantiate the propitious effect of the carbon nanotubes on the capacitance of the doped vanadium oxide. Considering the overall materials loading with good rate capability and excellent charge retention up to 400 cycles, it can be noted that attractive capacitance values as high as 310 F g−1 were reported. Ab initio theoretical studies, demonstrating the substantial improvement in the electronic conductivity of the vanadium oxide due to titanium doping and oxygen vacancies, have also been included corroborating the attractive experimental capacitance response.

Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations.

The Effect of Size and Location of Tears in the Supraspinatus Tendon on Potential Tear Propagation

Rotator cuff tears are a common problem in patients over the age of 50 yr. Tear propagation is a potential contributing factor to the failure of physical therapy for treating rotator cuff tears, thus requiring surgical intervention. However, the evolution of tears within the rotator cuff is not well understood yet. The objective of this study is to establish a computational model to quantify initiation of tear propagation in the supraspinatus tendon and examine the effect of tear size and location. A 3D finite element (FE) model of the supraspinatus tendon was constructed from images of a healthy cadaveric tendon. A tear of varying length was placed at six different locations within the tendon. A fiber-reinforced Mooney-Rivlin material model with spatial variation in material properties along the anterior-posterior (AP) axis was utilized to obtain the stress state of the computational model under uniaxial stretch. Material parameters were calibrated by comparing computational and experimental stress-strain response and used to validate the computational model. The stress state of the computational model was contrasted against the spatially varying material strength to predict the critical applied stretch at which a tear starts propagating further. It was found that maximum principal stress (as well as the strain) was localized at the tips of the tear. The computed critical stretch was significantly lower for the posterior tip of the tear than for the anterior tip suggesting a propensity to propagate posteriorly. Onset of tear propagation was strongly correlated with local material strength and stiffness in the vicinity of the tear tip. Further, presence of a stress-shielded zone along the edges of the tear was observed. This study illustrates the complex interplay between geometry and material properties of tendon up to the initiation of tear propagation. Future work will examine the evolution of tears during the propagation process as well as under more complex loading scenarios.