41. Soot as a precursor for the low temperature synthesis of organometallic sodium carbideMohanachandran Nair Sindhu Swapna, SARITHA DEVI H V, Sankararaman S, 2019, original scientific article Abstract: The carbonaceous soot finds a wide range of applications in many fields due to the richness of various allotropes of carbon. The present work explores the possibility of least investigated sodium carbide (Na2C2) as a potential semiconducting material for photonic applications. The soot, formed by the
incomplete combustion of gingelly oil is taken as the carbon precursor for the low-temperature synthesis of the industrially significant organometallic Na2C2. The morphological modifications are analyzed using High-Resolution Transmission Electron Microscope and elemental study is carried out by Energy Dispersive Spectroscopy and x-ray dot mapping. The formation of Na2C2 is primarily identified from x-ray powder diffraction pattern and further confirmed by other structural and
thermal analysis techniques such as Fourier Transform Infrared, Raman spectroscopy, and Thermogravimetry. The region of optical absorption, bandgap, as well as its emission properties are
studied by recording the Ultraviolet-Visible and Photoluminescence spectrum. The Tauc plot analysis
suggests its semiconducting nature with direct bandgap energy of 2.08 eV. The analysis with the help of CIE, and power spectrum reveal a prominent blue emission around 440 nm irrespective of
excitation in the UV region. Thus, the major highlights of this work lie in two factors- firstly, the effective utilization of the soot and secondly, easier low-temperature and cost-effective synthesis of semiconducting Na2C2 for photonic applications.
Keywords: carbonaceous soot, sodium carbide, photonic applications
Published in RUNG: 05.07.2022; Views: 1179; Downloads: 0
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42. Generalized Theory of Thermal Conductivity for Different Media: Solids to NanofluidsMohanachandran Nair Sindhu Swapna, Sankararaman S, 2019, original scientific article Abstract: The advent of nanotechnology in the 21st
century opened a new branch of nanoscience known as
nanofluids, finding a wide range of industrial applications
especially in heat transfer. Though the theory of thermal
conductivity of solids is well established, there is no such
conclusive model to explain the thermal conductivity of
nanofluids. In the present work we propose a generalized
theory for thermal conductivity applicable to materials ranging
from heterogeneous solids, porous materials, nanofluids, and
ferrofluids. The model could explain the effective thermal
conductivity of not only the combination of solids but also
solid−fluid mixtures. The proposed theory could successfully
link the existing models for porous solid materials and
nanofluids as its special cases. The proposed model is verified against experimental data by simulating the theoretical equations
Keywords: thermal conductivity, generalised model, Sankar-Loeb model
Published in RUNG: 05.07.2022; Views: 1145; Downloads: 0
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43. Speckle interferometric investigation of argon pressure-induced surface roughness modifications in RF-sputtered MoO[sub]3 filmS. Soumya, R. Arun Kumar, S. Sreejyothi, Vimal Raj, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2021, original scientific article Abstract: Film quality analysis is of more considerable signifcance due to its diversifed applications in various felds of technology.
The present work reports the speckle interferometric analysis of the argon pressure-induced surface roughness modifcations
of RF sputtered MoO3 flms. The paper suggests a new method of surface quality analysis of thin flms through a parameter
δ, which is the diference between the initial and fnal inertia moment values in the study of the thermal-induced dynamic
speckle pattern. The limitations of root mean square surface roughness analysis of the atomic force microscopic image of the
flms is also exemplifed. The research suggests that argon pressure plays a vital role in the surface property of RF sputtered
flms and also that the dynamic speckle analysis can give precise information about the quality of flms. The contour plot of
particle displacement vector under thermal stress, suggests the degree of uniformity in the distribution of particles in the flm.
Keywords: speckle pattern interferometry, time history of speckle pattern, cross correlation, inertia moment
Published in RUNG: 04.07.2022; Views: 1155; Downloads: 0
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44. Hidden periodicity in Stripe 82 with Saraswati supercluster—a fractal analysisVimal Raj, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2021, original scientific article Abstract: The manuscript attempts to explore the periodicity in the distribution of galaxies in the recently
reported Saraswati supercluster and the Stripe 82 region containing it as an example. The report
of 120 Mpc periodicity in the Abell galaxy clusters by power spectrum analysis is the motivation
behind the study. The power spectral analysis across the central part of the Stripe 82 region
shows a periodic variation of 3.09° or 71 Mpc in fractal dimension whereas an average angular
periodicity of 3.45° or 94 Mpc is observed across the Stripe 82 region. This refers to the
periodicity of complexity or cluster density of galaxy distribution. The texture of the distribution
pattern understood through lacunarity analysis indicates a near symmetric distribution. Fractal
dimensions like box-counting dimension, information dimension and correlation dimension are
also found through multifractal analysis. While the information dimension tells about the
distribution density of galactic points, the correlation dimension details the distribution of
galaxies in the neighbourhood
Keywords: galaxy distribution, fractal analysis, multifractals, lacunarity, Saraswati supercluster, Stripe 82
Published in RUNG: 04.07.2022; Views: 1123; Downloads: 0
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45. Thermal diffusivity downscaling of molybdenum oxide thin film through annealing temperature-induced nano-lamelle formation: a photothermal beam deflection studyS. Soumya, Vimal Raj, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2021, original scientific article Abstract: The present work proposes a method of downscaling the thermal diffusivity (α)
of MoO3 thin films through annealing temperature-induced nano-lamelle formation. The
thermal diffusivity modification of the MoO3 films, prepared by the doctor blade method,
is investigated by the sensitive transverse photothermal beam deflection technique. The X-ray diffraction analysis confirms the structural phase transformation from monoclinic to
orthorhombic in the films annealed from 300 to 450 °C. The thermal induced anisotropy of
the film is evident from the variation of the morphology index and texture coefficient. The
field emission scanning electron microscopic analysis unveils the morphology modifications
from blocks to the nano-lamelle structure with layers of average thickness ~ 77 nm. The
thermal diffusivity measurement reveals a 53% reduction upon annealing the film to 450 °C.
The drastic reduction is achieved through the annealing temperature-induced nano-lamelle
formation and the phase transformation from monoclinic to orthorhombic in the MoO3 films.
Keywords: thermal diffusivity, molybdenum oxide, thin film, nano-lamelle, photothermal beam deflection
Published in RUNG: 04.07.2022; Views: 1100; Downloads: 26
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46. 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: 1127; Downloads: 0
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47. Laser-induced thermal lens study of the role of morphology and hydroxyl group in the evolution of thermal diffusivity of copper oxideRiya Sebastian, Mohanachandran Nair Sindhu Swapna, Vimal Raj, Sankaranarayana Iyer Sankararaman, 2022, original scientific article Abstract: The paper explores the evolution of thermal behavior of the material by studying the variations in thermal diffusivity
using the single beam thermal lens (TL) technique. For this purpose, the decomposition of Cu(OH)2 into CuO is studied in a
time range up to 120 h, by subjecting the sample to morphological, structural, and spectroscopic characterizations. The time
evolution of thermal diffusivity can be divided into three regions for demonstrating the dynamics of the reaction. When the
reaction is complete, the thermal diffusivity is also found to be saturated. In addition to the morphological modifications,
from rods to flakes, the variations in the amount of hydroxyl group are attributed to be responsible for the enhancement
of base fluid’s thermal diffusivity by 165%. Thus the study unveils the role of hydroxyl groups in the thermal behavior of
CuO.
Keywords: thermal diffusivity, CuO, thermal lens, morphology, hydroxyl group
Published in RUNG: 04.07.2022; Views: 1014; Downloads: 0
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48. Tunable fluorescence from natural carbon source- PandanusMohanachandran Nair Sindhu Swapna, SARITHA DEVI H V, AMBADAS G, Sankararaman S, 2019, original scientific article Abstract: Carbon materials possessing photoluminescence properties are considered as potential candidates in a
wide range of photonic and optoelectronic applications. In this work, the cellulose derived from the natural source,
Pandanus, is autoclave-treated for the synthesis of fluorescent carbon. The natural fibres are greatly preferred
over synthetic ones due to their cost-effectiveness, easy processability, non-abrasivity, non-toxic and environment-friendly characteristics along with high mechanical strength and damage tolerance. These properties enable them
to be used as templates for synthesis, as important reinforcement materials for commercial thermoplastics and
for making value-added products. In this study, the synthesised sample is subjected to structural, morphological,
elemental and optical characterisations. These studies reveal that the sample can be used as a low-cost tunable
light-emitting source for photonic, biomedical and biosensing applications.
Keywords: Fluorescence, Pandanus, natural carbon, cellulose
Published in RUNG: 04.07.2022; Views: 1026; Downloads: 0
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49. Allotropic transformation instigated thermal diffusivity of soot nanofluid: Thermal lens studyMohanachandran Nair Sindhu Swapna, RAJ VIMAL, Sankararaman S, 2019, original scientific article Abstract: This paper employs the sensitive single-beam thermal lens technique for analyzing the thermal behavior of gasoline soot containing allotropes of carbon by preparing its nanofluid (NF). The soot, annealed at different temperatures up to 400 ○C (the samples), used for preparing the NF, is found to enhance the thermal diffusivity (α) up to 95% without changing the solid volume fraction, suggesting its possible use in
coolants. The thermal induced modifications are understood from the field emission scanning electron microscopic, X-ray diffraction (XRD),thermogravimetric, and Raman spectroscopic analyses. The variation of α of the sample is found to exhibit similar variations observed in XRD and Raman spectroscopic analyses. The study stresses the significance of the optimum temperature (300 ○C) for the soot NF above which morphological and structural modifications may lead to thermal energy trapping rather than dissipation or cooling.
Keywords: petrol soot, thermal lens, thermal diffusivity
Published in RUNG: 04.07.2022; Views: 1138; Downloads: 0
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50. Investigation of Fractality and variation of fractal dimension in germinating seedMohanachandran Nair Sindhu Swapna, SREEJYOTHI S, Sankararaman S, 2020, original scientific article Abstract: The fractal analysis has now been recognized as a potential mathematical tool in analyzing complex structures. The present work reports not only the fractal nature of Vigna radiata seed analyzed with the help of Field Emission Scanning Electron Microscopic images but also the variation of fractal dimension (FD) in a germinating seed. The variation of FD during germination in different media—water, salt, and diesel soot with carbon nanoparticles (CNPs)—is studied using the box-counting technique. The study is the first report of the fractality of seed. Irrespective of the media, the FD attains a maximum value on the day of germination and decreases after that. The time (T) for achieving maximum FD varies with the nature of stress. In the study, when the CNPs of diesel soot lower the T value, the salt raises the T value with respect to the control set. The Fourier Transform Infrared analysis of the seeds germinating in different media shows an increased rate of protein formation during the initial stage of germination and a steady state after that. In conjunction with the literature, the variation in the amino nitrogen, soluble nucleotide—RNA, and protein content of the seed during the initial days of germination gets reflected in its FD.
Keywords: fractal analysis, seed germination, Vigna radiata
Published in RUNG: 04.07.2022; Views: 1180; Downloads: 0
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