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5. Eco-conscious nanofluids : exploring heat transfer performance with graphitic carbon nitride nanoparticlesVijayakumar Gokul, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2023, original scientific article Abstract: Abstract
The work explores the heat transfer capabilities of semiconducting graphitic carbon nitride (g-C3N4) nanofluids. Also, it presents a sustainable and eco-friendly method for synthesizing g-C3N4 nanoparticles using commercially available rice flour as a natural carbon precursor through hydrothermal treatment. The synthesized sample subjected to various characterizations, including analysis of their structure, morphology, thermal properties, and optical properties. The optical bandgap (2.66 eV) is deduced through Tauc plot analysis and reveals the semiconducting nature of the sample. The formation of g-C3N4 is confirmed by various spectroscopic techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), and Raman spectroscopy. Thermogravimetric analysis (TGA) demonstrates the nanoparticles’ excellent thermal stability up to 550 °C, indicating potential applications in heat transfer fluids. The investigation of concentration-dependent thermal diffusivity variation using the sensitive mode mismatched dual beam thermal lens technique highlights the potential of g-C3N4 semiconductor nanofluid as an organic and metal-free additive in industry-demanding coolant applications.
Keywords: thermal lens, nanofluids
Published in RUNG: 05.01.2024; Views: 1934; Downloads: 6
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8. Reflecting the quality degradation of engine oil by the thermal diffusivity : radiative and nonradiative analysesVijayakumar Gokul, Mohanachandran Nair Sindhu Swapna, Dorota Korte, Sankaranarayana Iyer Sankararaman, 2023, original scientific article Keywords: engine oil, thermal diffusivity, thermal lens technique, oil degradation, quality monitoring
Published in RUNG: 12.01.2023; Views: 2376; Downloads: 24
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9. Concentration-dependent thermal duality of hafnium carbide nanofluid for heat transfer applications : a mode mismatched thermal lens studyVijayakumar Gokul, Mohanachandran Nair Sindhu Swapna, Vimal Raj, H. V. Saritha Devi, Sankaranarayana Iyer Sankararaman, 2021, original scientific article Abstract: he mode mismatch dual-beam thermal lens technique is a sensitive tool for studying the nanofuids’ thermal difusivity in thermal engineering. The work reports
the low-temperature green synthesis of hafnium carbide (HfC) using rice four as a natural carbon precursor and its potential in heat transfer nanofuids by studying the concentration-dependent thermal difusivity. The structure characterisations confirm the formation of HfC, whose refractory nature is revealed through the high thermal stability observed in the thermogravimetric analysis. The Tauc plot analysis shows direct bandgap energy of 2.92 eV. The fuorescence study suggests bluish-pink emission with CIE coordinates (0.271, 0.263). The existence of the critical concentration of HfC in the nanofuid decides its suitability for heat transfer or heat trap applications indicating a concentration-dependent thermal duality. Thus, the study is signifcant as it overcomes the major drawbacks of the existing methods of the synthesis of refractory HfC, using toxic chemical and costly equipment for heat transfer applications.
Keywords: hafnium carbide, hydrothermal synthesis, rice flour, thermal lens spectroscopy
Published in RUNG: 04.07.2022; Views: 2141; Downloads: 0
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10. Weathering induced morphological modification on the thermal diffusivity of natural pyrrhotite : a thermal lens studyMohanachandran Nair Sindhu Swapna, Vijayakumar Gokul, Vimal Raj, R. Manu Raj, S. N. Kumar, Sankaranarayana Iyer Sankararaman, 2021, original scientific article Abstract: Natural pyrrhotites have gained significant attention due to
their interesting electronic, antimicrobial, and chemical
properties. The present work attempts to explore the
morphology-induced modifications in the thermal
characteristics of natural pyrrhotite due to ageing. The
morphological, elemental, structure, optical, and thermal
characterisations help in understanding the effect of
ageing. The effects of five years of ageing of the sample
are (i) Field Emission Scanning Electron Microscopic
analysis reveals a morphological transformation from flakes
to agglomerated powder, (ii) elemental analyses suggest
the ageing induced compositional modification (iii) the
Tauc plot analysis shows a bandgap energy modification
from 1.46 eV to 1.92 eV, (iv) X-ray Diffraction (XRD), Fourier
Transform Infrared, and X-ray photoelectron spectroscopic
studies affirm the formation of oxy-hydroxides (v) the XRD
data indicates an increase of dislocation density, and (vi)
Photoluminescence study shows a deep violet emission
evidenced through the CIE plot. The study by the thermal
lens technique shows a lowering of thermal diffusivity
study by 23%, due to the morphological modifications,
adsorbed/chemisorbed hydroxyl groups, and the formation
of secondary compounds due to oxidation and weathering.
The phonon boundary scattering, weathering induced
smaller grain size, reduced phonon mean free path, and
point defects also account for the lowering of the thermal
diffusivity value and thereby influencing its properties.
Keywords: pyrrhotite, thermal diffusivity, thermal lens, ageing, morphology
Published in RUNG: 30.06.2022; Views: 2091; Downloads: 7
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