Effect of PES on the morphology and properties of proton conducting blends with sulfonated poly(ether ether ketone)

Development of alternate materials to Nafion, based on ionically conducting polymers and their blends is important for the wider applications of proton exchange membrane fuel cells. In this work, blends of sulfonated poly(ether ether ketone) (SPEEK) with poly(ether sulfone) (PES) are investigated. SPEEK with various ion exchange capacity (IEC) was prepared and blended with PES, which is nonionic and hydrophobic in nature. A comparative study of the water uptake, proton conductivity, and thermo‐mechanical characteristics of SPEEK and the blend membranes as a function of the IEC is presented. Addition of PES decreases the water uptake and conductivity of SPEEK. Chemical and thermal stability and mechanical properties of the membrane improve with the addition of PES. The effect of water content on the thermo‐mechanical properties of membranes was also studied. The morphology of blend membranes was studied using SEM to understand the microstructure and miscibility of the components. On the basis of the results, a plausible microstructure of the blends is presented, and is shown to be useful in understanding the variation of different properties with blending. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Role of Nanostructure in Electrochemical Corrosion and High Temperature Oxidation: A Review

The extremely fine grain size of nanocrystalline (nc) metallic alloys results in significantly different mechanical, electrochemical and oxidation properties as compared to the coarse-grained alloys of the same composition. Although the synthesis and attractive mechanical properties of nanocrystalline materials have been investigated and reviewed in great depth, the high temperature oxidation and electrochemical corrosion of these materials has received limited attention. The difference in the active dissolution and passivation behavior of nc alloys as compared to their microcrystalline counterparts varies for each alloy system. However, a unified theory explaining these phenomena still eludes us. In this context, this article reviews the progress in the electrochemical corrosion behavior of different nanocrystalline alloys, and hence, develops a better understanding of the effect of grain size, composition, interfacial phenomena and selective dissolution on corrosion of nanocrystalline alloys. This review also presents the role of nanometric grain size and the associated increase in grain boundary diffusion on the high temperature oxidation of nc alloys. The attractive possibility of enhanced oxidation resistance at lower alloying additions as compared to the coarse-grained alloys has been discussed. Although the primary focus of the article is on ferrous alloy systems, however, the lead studies on the role of ultrafine grain size in oxidation/corrosion behavior of other alloys systems have also been reviewed.     

Analyzing and Improving Network Availability in Interdomain Routing

The Internet now-a-days has become indispensable to each and everyone. It is vulnerable to node failures, link failures, and fluctuations due to many known or unknown reasons in the network connectivity. The bitter truth is even today networks’ failure, link faults are happening. A single change in a link or a node has a potential to trigger the unstable-routing-tables of many nodes. These failures may lead the network in an unstable state by increasing its convergence time significantly longer. In this paper we propose an algorithm to keep the value of the minimum route advertisement interval timer variable unlike the conventional approach of keeping it constant. The proposed approach makes the timer value varying depending on the receiver’s position with respect to the origin of the prefix advertised on the network. Simulations’ results show that the convergence time becomes significantly low and make the network converge relatively quicker.     

Plasma Etch Processes for Embedded FRAM Integration

We describe the etch processes used for integration of embedded ferroelectric random access memory (FRAM) within a standard CMOS logic flow. The ferroelectric module is inserted following front-end contact formation and prior to backend integration using only two additional mask levels: capacitor pattern and bi-level via pattern. The single-mask stack etch process employs a TiAlN hardmask to define Ir/IrO_x/PZT/IrO_x/Ir capacitors. Protective sidewalls can be formed using an etchback process. The bi-level via etch and subsequent metal fill processes complete the FRAM module formation. Functional 4 MB arrays embedded with 5 levels of Cu/FSG integration have been demonstrated.     

Thermal model of MOSFET with SELBOX structure

In this article, we present the thermal characteristics of the MOSFET with SELBOX structure. It is observed that the device shows a reduction in the self-heating effect and exhibits improved static and dynamic thermal behavior. A thermal model is developed to explain the thermal behavior of SELBOX structure. The model was evaluated using simulation implemented by Silvaco TCAD tools. Results show the effectiveness of the structure for the minimization of the self-heating effect (SHE) observed in SOI devices. Further, the results obtained from the simulation studies fit into the model showing the validity of the thermal circuit model.     

A study on hot corrosion behaviour of Ni–5Al coatings on Ni- and Fe-based superalloys in an aggressive environment at 900 °C

Ni–5Al coating was deposited on Ni- and Fe-based superalloys by high velocity oxy fuel (HVOF) process to enhance their high-temperature corrosion resistance. Hot corrosion studies were conducted on bare as well as HVOF-coated superalloy specimens after exposure to a molten salt environment at 900 °C under cyclic conditions. Each cycles consisted of 1 h heating in the silicon carbide tube furnace followed by 20 min cooling in air. Thermogravimetric technique was used to approximate the kinetics of corrosion. Techniques like X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDAX) were used to characterize the corrosion products. The coatings and the oxide scale formed on the exposed surface were found to be intact with the superalloys. Superfer 800 with Ni–5Al coating has provided a good protection to the superalloys in the given molten salt environment.     

Causes and consequences of inflammation on anemia management in hemodialysis patients

Inflammation is common among hemodialysis patients, and evidence is accumulating to suggest that inflammation is a major contributor to morbidity and mortality. Several factors have been suggested as potential causes of inflammation, including infections and the atherosclerosis process, as well as etiologies directly related to kidney disease such as reduced renal function and dialysis. Among several inflammatory biomarkers investigated, serum C-reactive protein (CRP) is the most widely used. In hemodialysis patients, raised CRP levels have been shown to be predictive of cardiovascular events, hospitalization, and all-cause and cardiovascular mortality. Elevated CRP levels may correlate with comorbidities and intercurrent events, all of which may impact the response to erythropoiesis-stimulating agents (ESAs) and lead to higher ESA doses. Most dialysis facilities do not routinely measure CRP, despite recommendations by the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative. Regular measurement of CRP levels may help providers to understand change in ESA dosing and identify patients at risk for cardiovascular events. This review explores the inter-relationships between inflammation, CRP levels, and anemia management in patients receiving hemodialysis.     

Phase Reversion‐Induced Nanograined/Ultrafine‐Grained Structures in Austenitic Stainless Steel and their Significance in Modulating Cellular Response: Biochemical and Morphological Study with Fibroblasts

Materials science, engineering, and biological sciences have been combined to improve the tissue compatibility of medical devices. In this regard, nano/ultrafine structuring of austenitic stainless steel obtained using an innovative approach of “phase‐reversion” has been evaluated for modulation of cellular activity. The biochemical and morphology study with fibroblasts point toward the improvement of tissue compatibility on comparison with coarse‐grained structures, strengthening the foundation of nanostructured materials for bio‐medical applications.     

Effect of Al on the hydrogenation characteristics of nanocrystalline Mg powder

We have fabricated nanocrystalline Mg–Al powders with nominal Al compositions of 4 and 8 at% by the electrodeposition technique and have compared their hydrogenation characteristics with those for a commercially available pure Mg powder. It is elucidated that interestingly the amount of Al incorporated in MgH₂ increases with decreasing the hydrogenation temperature. This observation indicates that the magnesium hydride phase has a limited solubility for aluminum and the supersaturation of hydride with Al is attributed to the slower mobility of aluminum at low temperatures. The rejection of Al during hydride formation is shown to result in a higher fraction of the intermetallic phase, thus reducing the hydrogen capacity. It is suggested that the presence of the intermetallic phase prior to hydrogenation enhances the hydride nucleation rate, which further decreases the hydrogen capacity in comparison to pure Mg.     

Microstructure-sensitive notch root analysis for dwell fatigue in Ni-base superalloys

Macroscopic viscoplastic constitutive models for γ–γ′ Ni-base superalloys typically do not contain an explicit dependence on the underlying microstructure. Microstructure-sensitive models are of interest in many applications since microstructure can vary in components, whether intentional or not. In such cases, the use of experiments from one microstructure condition to fit macroscopic models may be too limiting. The principal microstructure attributes that can significantly affect the cyclic stress–strain response of γ–γ′ Ni-base superalloys are the grain size and γ′ precipitate volume fraction and size distributions. An artificial neural network (ANN) is used to correlate the material parameters of a macroscale internal state variable cyclic viscoplasticity model with these microstructure attributes using a combination of limited experiments augmented by polycrystal plasticity calculations performed on other (virtual) microstructures within the range characterized experimentally. The trained model is applied to an example of a component fatigue notch root analysis with dwell periods at peak load to demonstrate the methodology and explore the potential impact of microstructure-sensitive constitutive models on life prediction for notched structures subjected to realistic load histories.