http://localhost:8080/xmlui/handle/123456789/4 Repository for digital copies of Journal articles authored by NIIST Staff 2026-04-11T10:07:31Z http://localhost:8080/xmlui/handle/123456789/5138 Self-Poled PVDF Infiltrated Nylon 11 Aerogels with Oriented Crystals for High-Performance Piezoelectric Energy Harvesters and Self-Powered Acoustic Sensors Ashitha, G; Athira, B S; Chandran, A; Surendran, K P; Gowd, E B Efficient piezoelectric polymers with enhanced electromechanical conversion gain significant attention for energy harvesting and sensing applications. Among them, poly(vinylidene fluoride) (PVDF) and odd-nylons stand out due to their high piezoelectric coefficients and thermal stability. However, achieving a piezoelectric phase with a preferred crystal orientation for optimal performance remains challenging, particularly under mild processing conditions. In this study, a vacuum-assisted infiltration technique is introduced to fabricate PVDF-infiltrated nylon-11 (PVDFIPA11) aerogels with oriented polymer crystallites. Anisotropic nylon-11 aerogels, featuring aligned polymer crystals, serve as templates for PVDF infiltration under vacuum. This process facilitates the formation of highly oriented β phase PVDF crystals alongside γ phase nylon-11 crystals, yielding a fully self-poled system without the need for external poling. A piezoelectric nanogenerator (PENG) based on the PVDFIPA11 aerogel exhibits a high output voltage (peak-to-peak) of ≈45 Vpp and a peak power density of 2.2 Wm⁻3 significantly outperforming pristine PVDF and nylon-11 aerogels. Additionally, the PVDFIPA11 aerogel PENG is demonstrated as a self-powered acoustic sensor, effectively distinguishing sound signals at varying pressure levels. This work provides a scalable and practical strategy for developing self-poled piezoelectric polymer aerogels, paving the way for next-generation energy-harvesting devices and sensors. 2025-07-03T00:00:00Z http://localhost:8080/xmlui/handle/123456789/5137 Optimization of Benzodithiophene-Based Copolymer and SWCNT Composite Films for Flexible Thermoelectric Generators Navin, J; Ignatious, V; Neethi, R; Dheepika, R; Riya, M; Tanjore, P Y; Biswapriya, D; Vijayakumar, C This study investigates the thermoelectric (TE) properties of a benzodithiophene-based conjugated polymer (PBDTT-DPP) combined with single-walled carbon nanotubes (SWCNTs) for flexible, solution-processable thermoelectric generators (TEGs). Composite films are prepared with varying SWCNT content, achieving optimal performance at 50 wt.% SWCNT. Further optimization through FeCl₃ doping and thermal annealing at 200 °C significantly enhanced the electrical conductivity and overall TE performance. The doped and annealed composite film exhibited a power factor of 135 ± 8 µW mK−2 at 253 °C and a maximum ZT value of 0.17. Spectroscopic and electronic analyses revealed that doping and annealing realigned the energy bands and formed charge-transfer complexes, contributing to improved TE properties. Practical application is demonstrated through the fabrication of flexible, arc-shaped TEGs capable of harvesting energy from curved heat sources. The TEGs achieved a peak power output of 0.66 µW at ΔT = 100 K, showcasing its potential for low-grade waste heat recovery in industrial settings. This research advances the understanding of organic TE materials and offers promising solutions for sustainable energy harvesting from waste heat sources. 2025-07-08T00:00:00Z http://localhost:8080/xmlui/handle/123456789/5136 Coconut oleosomes as a sustainable ingredient for food emulsion systems Anoop, A A; Ramees, P M; Ragavan, K V Virgin coconut meal (VCM), a major by-product from the coconut milk processing stream, contains 30–40% oil, which seldom gets repurposed for food applications. In this study, we investigated the feasibility of VCM for the extraction of oleosomes and its suitability for the formulation of emulsion-based food systems such as vegan mayonnaise. Oleosome extraction parameters (pH 6.43 and feed-to-solvent ratio 1 : 1.96) were optimised using the response surface methodology. The extracted oleosomes contain 93.24 ± 1.53% of fat and 5.34 ± 0.3% of proteins, along with residual carbohydrates and moisture. Particle and morphological analyses indicated that oleosomes are monodisperse spherical particles with a mean diameter of 1.35 μm, and they are highly stable in the pH range of 6–9. The functional and thermal properties of oleosomes were interpreted through FTIR and DSC analysis. The colour profile of oleosomes is neutral with excellent whiteness, making them suitable for the formulation of food products. Rheological analysis of oleosome incorporated mayonnaise exhibited a uniform structured biphasic food matrix with soft solid-like consistency on par with commercial mayonnaise. Sensory analysis using a nine-point hedonic scale revealed that oleosome-based mayonnaise is more appealing than egg-based mayonnaise. Results from the above studies suggest that VCM is a suitable by-product for the extraction of oleosomes, and the extracted oleosomes can act as an emulsion with the potential to replace oil and emulsifiers in emulsion-based food products. The above process can be effectively applied for the extraction of oleosomes from cold-pressed meals/seed cakes. 2025-05-30T00:00:00Z http://localhost:8080/xmlui/handle/123456789/5135 CO2 Adsorption Studies of Hydrophobic Silica Sorbent Functionalized with Silicone Oil-Amine Blends under Low-Temperature Conditions Angitha, F; Ragi, T M; Mohamed, P A; Ananthakumar, S CO2 uptake using multifunctional, porous solid sorbents has gained significant attention due to their high thermochemical stability and selectivity. In this study, hydrophilic nanosilica was functionalized with blends of silicone oil and amines to develop hydrophobic silica sorbents capable of adsorbing CO2 at low temperatures in the presence of moisture. The adsorption performance of these sorbents was evaluated at 35 and 40 °C using silicone oil blends containing monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA). Among these, the sorbent prepared with MEA, a primary amine, demonstrated the highest CO2 adsorption capacity. Further enhancement was achieved by functionalizing silicone oil with aminopropyltrimethoxysilane (APTMS). The optimized silica sorbent, with a 1:1 APTMS-to-silicone oil ratio, exhibited a maximum adsorption capacity of 0.75 and 0.86 mmol/g at 35 and 40 °C, respectively, and a water contact angle of 134°, achieving an optimal balance between hydrophobicity and amine reactivity. Their enhanced adsorption capacity and structural resilience suggest applications where intermittent moisture exposure may occur, such as indoor air purification systems, industrial enclosures, and controlled environments like greenhouses or cabin spaces. The hydrophobic surface is expected to improve durability and minimize water interference in such applications. 2025-06-11T00:00:00Z