• B M PRAVEEN

Articles written in Bulletin of Materials Science

• A conductive mechanism of PVA (Mowiol 10-98) filled with ZnO and MWCNT nanoparticles

Polyvinyl alcohol (PVA) hybrid nanocomposites are prepared via an ex situ approach with ZnO and MWCNT nanoparticle fillers and their conductive mechanisms have been investigated. The tailored hybrid nanocomposite conformation and their microstructural disparities for different filler concentrations were studied using an X-ray diffractometer. The direct current (DC) conductivity studies show an increase in the conductivity from $1.0528\times 10^{−11}$ to $2.1514\times 10^{−8}$ S cm$^{−1}$ up to a percolation threshold filler concentration of $x = 7.5$ wt%. The dielectric constant substantially indicates a decreasingtrend with increasing frequency. The exaggerated dielectric constant values of 11.8 at 5 kHz, 6.3 at 100 kHz, 5.86 at500 kHz and 2 at 1 MHz are observed for 7.5 wt% filler hybrid nanocomposites, which indicates their potential applicationas a gate material in metal-oxide-semiconductor field-effect transistors (MOSFETs). The alternating current (AC) electricalconductivity demonstrates an increasing behaviour up to $x = 7.5$ wt% filler concentration. The smaller values observedin the real part of the electric modulus ($M^{\prime}) indicates a riddance in electrode polarization. The observed higher frequencyshift in the imaginary part of the electric modulus for increasing the filler concentration up to$x = 7.5$wt%, decreases therelaxation time of the dipole orientation thereby increasing the conductivity mechanism of the hybrid nanocomposites. Apartfrom these, its small relaxation time with high electrical conductivity favours this material PVA/($x$)MWCNT($15 − x$)ZnO to have prospective application in microwave absorption appliances. The increase in the surface roughness of the film seenfrom the AFM images up to$x = 7.5$wt% concentration supports an enhancement in the crystalline nature of the filler. Differentialscanning calorimeter studies show an enhancement in glass transition temperature ($T_g$), melting temperature ($T_m$)and decomposition temperature ($T_d$) for PVA filled with MWCNTs and ZnO composites for optimum filler concentration$x = 7.5\$ wt%.

• Development of nanocrystalline multilayer Ni–Fe alloy coatings: characterization and its corrosion behaviour at elevated temperature

The present work deals with the galvanostatic fabrication of Ni–Fe nanostructured composition-modulated multilayer alloy (CMMA) coatings on steel panel from the newly optimized acid-sulphate bath solution. The recurringcathode current density combination (RCCC) and the number of layers have been optimized for enhanced performance of the coatings against corrosion. Corrosion behaviour of the nanostructured multilayered coatings was evaluated by Tafel extrapolation and electrochemical impedance spectroscopy (EIS) methods in 3.5% NaCl solution. Under optimal conditions, the CMMA coatings developed were more corrosion-resistant than the monolithic alloy coatings obtained from the same bath. Least corrosion rate (CR) was witnessed at 300 layers, above which saturation of corrosion resistance at a high temperature was found, which is attributed to a shorter relaxation time for redistribution of metal ions during multilayer deposition. Hardness and roughness of the coatings were evaluated using Vickers hardness test and atomic force microscope,respectively. Phase structure of the coatings was discussed using X-ray diffraction technique. The cross-sectional view of the coatings was characterized by scanning electron microscope. CR analysis and the surface morphology of the optimized coatings exposed to high temperature revealed the better performance of CMMA coatings at the elevated temperatures compared to the monolithic coatings.

• # Bulletin of Materials Science

Volume 43, 2020
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020