Joyita Banerjee

V ⁵⁺ doped Fe ₂ O ₃ nanoflowers grown on nickel foam as the photo-rechargeable capacitors comprising photo energy harvesting and energy storage component materials for renewable energy storage applications.

Polypropylene (PP) and multi‐walled carbon nanotubes (MWCNTs) composites were prepared by melt‐mixing with two types of MWCNTs of varying agglomerate size. Agglomerate dominated dispersion was observed in the PP matrix, wherein N‐MWCNTs exhibit a finer dispersion as compared to D‐MWCNTs. Further, MWCNTs were encapsulated by Li‐salt of 6‐amino caproic acid in various proportions along with PP‐g‐maleic anhydride in order to achieve finer MWCNTs dispersion. Thermogravimetric analysis exhibited an increase in onset of degradation temperature and higher residual weight (%) at 500 °C of PP with increased MWCNTs concentration, which suggests the formation of a thicker “interphase.” Glass transition temperature of the PP phase was increased monotonically as a function of unmodified MWCNTs concentration, which suggests a strong interfacial interaction between PP and MWCNTs. An extensive analysis was carried out with modified MWCNTs based PP composites. Moreover, MWCNTs act as a strong hetero‐nucleating agent manifesting in smaller spherulite size of PP, wherein bulk crystallization temperature is increased to ~130 °C of the PP phase at 5 wt% MWCNTs content. The influence of unmodified and modified MWCNTs on the interaction between the PP chains and MWCNTs in the amorphous phase as well as in the crystalline domains are analyzed in PP/MWCNTs composites.

Melt‐mixing was employed to prepare multiwall carbon nanotubes (MWCNTs) based polypropylene (PP) composites, wherein MWCNTs vary in “agglomerate” size and also in terms of “agglomerate” structure. Morphological analysis revealed MWCNTs‐D type exhibits bigger “agglomerate” size with compact “agglomerate” structure with respect to MWCNTs‐N type, that show smaller “agglomerate” size with porous “agglomerate” structure in the corresponding PP/MWCNTs composites. Melt‐rheological analysis showed a rheological percolation threshold of 2 to 3 wt% in PP/MWCNTs‐N composites, whereas PP/MWCNTs‐D composites exhibited a rheological percolation of 3 to 4 wt% of MWCNTs. AC electrical conductivity measurements exhibited an electrical percolation threshold of 0.5 to 1 wt% of MWCNTs‐N, whereas MWCNTs‐D type depicts an electrical percolation threshold of 2 to 3 wt% of MWCNTs in the respective composites. Further, an unique dispersant; Li salt of 6‐aminohexanoic acid (Li‐AHA) was utilized to “deagglomerate” MWCNTs. Moreover, PP‐g‐MA was also utilized in combination with Li‐AHA encapsulated MWCNTs in the corresponding composites. An extensive morphological, rheological, and electrical conductivity measurements suggested the influence of Li‐AHA encapsulated MWCNTs and PP‐g‐MA on the transformation of MWCNTs “agglomerate” into “individualized” and smaller MWCNTs “agglomerate” in PP/MWCNTs composites.

This article reviews the recent development in performance and fabrication of carbon nanotubes (CNTs)‐based polymer nanocomposites synthesized by melt‐mixed process. CNTs have attracted enormous attention, since its presence (even in low concentration) causes drastic improvements in the mechanical and electrical properties of several polymer composites. It is suggested that the dispersion state of CNTs within polymer matrices is dictated by the cohesive strength of the CNTs “agglomerates.” Based on this suggestion, this review involves an in‐depth investigation on the origin of this CNTs “agglomerates” when present within polymer matrices. Attempts have also been done to investigate and correlate the varying extent of CNTs “agglomerates” in different polymer matrices. It is considered that the extent of dispersion of CNTs “agglomerates” depends on the interfacial interaction between the two phases, difference in their melt viscosities, and types of CNTs, compatibilizer and modifier used. A comprehensive study has been done on the effect of processing parameters used during melt‐mixing process; functionalization of CNTs, and the effect of compatibilizers and modifier on the final properties and morphology. Herein, an attempt has been done to study the correlation between the synthetic procedure, developed structure, and observed properties of nanocomposites of polymers and CNTs.

With the ever‐increasing depletion of nonrenewable fossil fuel reserve, greater attention has been directed towards renewable energy storage devices. One of the most important of such devices is the supercapacitor, which exhibits high specific capacitance. Polyaniline (PAni) is a versatile conducting polymer, which has demonstrated excellent electrochemical properties along with good stability and ease of synthesis. Therefore, PAni has been extensively used in the fabrication of supercapacitors. In the last few decades, researchers have studied the effect of morphology, developed during the synthesis of PAni, on its electrochemical properties. It is known that the electrical conductivity and the electrochemical properties of PAni get influenced by the level and type of dopant used, the method of synthesis adopted, and the surface area and porosity possessed. However, it has been realized that supercapacitors based on PAni suffer from short cycle life. This led to development of PAni composites with carbon‐based materials and transition metal oxides. In this review, focus has been laid on the achieved performance levels of the recently developed PAni‐based supercapacitors. In addition, an attempt has been made to study the fundamental aspects of the conductivity and the electrochemical properties of PAni and their effect on the supercapacitor performance. Moreover, several new interesting applications of PAni‐based supercapacitors have also been included in this review.

The isothermal crystallization behaviour of the polypropylene (PP) phase in PP/multi‐walled carbon nanotubes (MWCNTs) composites has been investigated via differential scanning calorimetric analysis, which showed the influence of the varying dispersion level of MWCNTs in the respective PP matrix. PP/MWCNTs composites were prepared via melt‐blending technique, wherein two different grades of MWCNTs of varying average “agglomerate” size and varying entanglements (N‐MWCNTs and D‐MWCNTs) were utilized. Furthermore, the influence of melt‐viscosity of the PP phase was investigated on the crystallization kinetics of the PP/MWCNTs composites. Heterogeneous nucleation ability of MWCNTs has resulted in a decrease in half time of crystallization (t_1/2) from ∼14 min for pure PP to ∼6 min for PP/N‐MWCNTs and ∼11 min for PP/D‐MWCNTs composites at 1 wt% of MWCNTs at 132 °C. Overall rate of crystallization (k) has significantly increased to 4.9 × 10⁻² min⁻¹ for PP/N‐MWCNTs composite as compared with 6.2 × 10⁻³ min⁻¹ for PP/D‐MWCNTs composite at 0.5 wt% of MWCNTs at 132 °C. Moreover, the effect of a novel organic modifier, Li‐salt of 6‐amino hexanoic acid along with a compatibilizer (PP‐g‐MA) has also been investigated on the crystallization kinetics of the PP phase in PP/MWCNTs composites. POLYM. ENG. SCI., 57:1136–1146, 2017. © 2017 Society of Plastics Engineers

Presently, rechargeable Li-ion batteries, possessing highest energy densities among all batte-ries, are used in a major fraction of all portable electronic devices. However, for bestowing the Li-ion batteries suitable for such advanced applications, further improvements in the energy densities (Li-capacities) and in the cycle life are essential. In a broader sense, this can be achieved by replacing the presently used electrode materials by materials possessing higher Li-capacities and minimization of the degradation of such materials with electrochemical cycling. It has been realized that the major reason for degradation in battery performance in terms of capacity with cycling is the disintegration/fragmentation of the active electrode materials due to stresses generated during Li-intercalation/de-intercalation in every cycle. Such stresses arise from the reversible volume changes of the active electrode materials during Li-insertion and removal. In quest of higher energy densities, replacement of the presently used graphitic carbon by potentially higher capacity metallic anode materials (like Si, Sn, and Al) is likely to further accrue this stress related disintegration due to ∼30 times higher volume changes experienced by such materials. It has also been recently realized that passivating layer formed on the surface of the electrodes also contributes toward the stress development. After briefly introducing the mechanistic aspects of Li-ion batteries, this article focuses on the reasons and consequences associated with stress developments in different electrode materials, highlighting the various strategies, in terms of designing new electrode com-positions or reducing the microstructural scale, that are being presently adopted to address the stress-related issues. Considering that experimental determination of such stresses is essential toward further progress in Li-ion battery research, this article introduces a recently reported technique developed for real-time measurement of such stresses. It finally concludes by raising some critical issues that need to be resolved through further research in this area.