Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bolonia study programme


1 - 10 / 14
First pagePrevious page12Next pageLast page
Morphology and mixing state of aged soot particles at a remote marine free troposphere site
Sumit Kumar, Katja Džepina, Michael P. Dziobak, Paulo Fialho, Judith A. Perlinger, Swarup China, Barbara Scarnato, Robert C. Owen, Bo Zhang, MarianT. Ampadu, 2015, original scientific article

Abstract: The radiative properties of soot particles depend on their morphology and mixing state, but their evolution during transport is still elusive. Here we report observations from an electron microscopy analysis of individual particles transported in the free troposphere over long distances to the remote Pico Mountain Observatory in the Azores in the North Atlantic. Approximately 70% of the soot particles were highly compact and of those 26% were thinly coated. Discrete dipole approximation simulations indicate that this compaction results in an increase in soot single scattering albedo by a factor of <= 2.17. The top of the atmosphere direct radiative forcing is typically smaller for highly compact than mass-equivalent lacy soot. The forcing estimated using Mie theory is within 12% of the forcing estimated using the discrete dipole approximation for a high surface albedo, implying that Mie calculations may provide a reasonable approximation for compact soot above remote marine clouds.
Found in: ključnih besedah
Keywords: atmospheric aerosol, soot, long-range transport, free troposphere, single scattering albedo
Published: 11.04.2021; Views: 1266; Downloads: 0
.pdf Fulltext (899,35 KB)

Soot effected sample entropy minimization in nanofluid for thermal system design
Sankaranarayana Iyer Sankararaman, K. Satheesh Kumar, Vimal Raj, Mohanachandran Nair Sindhu Swapna, 2020, original scientific article

Abstract: The present work suggests a method of improving the thermal system efficiency, through entropy minimisation, and unveils the mechanism involved by analysing the molecular/particle dynamics in soot nanofluids (SNFs) using the time series, power spectrum, and wavelet analyses of the thermal lens signal (TLS). The photothermal energy deposition in the SNF lowers the refractive index due to the temperature rise. It triggers the particle dynamics that are investigated by segmenting the TLS and analysing the refractive index, phase portrait, fractal dimension (D), Hurst exponent (H), and sample entropy (SampEn). The wavelet analysis gives information about the relation between the entropy and the frequency components. When the phase portrait analysis reflects the complex dynamics from region 1 to 2 for all the samples, the SampEn analysis supports it. The decreasing value of D (from 1.59 of the base fluid to 1.55 and 1.52) and the SampEn (from 1.11 of the base fluid to 0.385 and 0.699) with the incorporation of diesel and camphor soot, indicate its ability to lower the complexity, randomness, and entropy. The increase of SampEn with photothermal energy deposition suggests its relation to the thermodynamic entropy (S). The lowering of thermal diffusivity value of the base fluid from 1.4 × 10−7 m2/s to 1.1 × 10−7 and 0.5 × 10−7 m2 /s upon diesel and camphor soot incorporation suggests the heat-trapping and reduced molecular dynamics in heat dissipation.
Found in: ključnih besedah
Keywords: soot, entropy, thermal system, photothermal, time series, nanofluid, fractal
Published: 30.06.2022; Views: 359; Downloads: 0
.pdf Fulltext (2,27 MB)

Boron‑rich boron carbide from soot
Sankaranarayana Iyer Sankararaman, H. V. Saritha Devi, Mohanachandran Nair Sindhu Swapna, 2020, original scientific article

Abstract: Boron carbide is a promising super-hard semiconducting material for refractory applications ranging from the nuclear industry to spacecraft. The present work is the frst report of not only turning futile soot, containing carbon allotropes in varying composition, into boron-rich boron carbide (BC), but also developing it by a low-cost, low-temperature, and green synthesis method. The BC synthesised from gingelly oil soot is subjected to structural, morphological, and optical characterisations. The feld emission scanning electron microscope shows beautiful fower-like morphology, and the thermogravimetric analysis reveals the high-temperature stability of the sample synthesised. The Tauc plot of the sample indicates a 2.38 eV direct bandgap. The formation of BC and boron-rich carbide evidenced by X-ray difraction studies is confrmed through Raman and Fourier transform infrared spectroscopic signatures of B–C and C–B–C bonds. The fuorescence, power spectrum, and CIE analyses carried out suggest the blue light emission for excitation at 350 nm
Found in: ključnih besedah
Keywords: boron carbide, soot, carbon nanoparticle, refractory, allotropes, green synthesis
Published: 30.06.2022; Views: 364; Downloads: 0
.pdf Fulltext (1,11 MB)

The efflorescent carbon allotropes: Fractality preserved blooming through alkali treatment and exfoliation
Swapna Mohanachandran Nair Sindhu, Sankararaman S, 2020, original scientific article

Abstract: The work reported in the paper elucidates morphological modification induced nanoart and surface area enhancement of graphite, graphene, and soot containing carbon allotropes through ultrasonication and alkali-treatment. The field emission scanning electron microscopic (FESEM) analysis of the samples before and after exfoliation reveals the formation of brilliant flower-like structures from spindle-like basic units due to Ostwald ripening. The x-ray diffraction analysis of the samples gives information about structural composition. The fractal analysis of the FESEM images indicates a multifractal structure with the dimensions—box-counting dimension D0 (1.72), information dimension D1 (1.66), and correlation dimension D2 (1.63)—preserved upon exfoliation. The process of ultra-sonication assisted liquid phase exfoliation resembles blooming as if the carbon allotropes are efflorescent.
Found in: ključnih besedah
Summary of found: ...surface area enhancement of graphite, graphene, and soot containing carbon allotropes through ultrasonication and alkali-treatment....
Keywords: carbon allotropes, fractal dimension, soot, fractality, alkali treatment, exfoliation
Published: 04.07.2022; Views: 321; Downloads: 0
.pdf Fulltext (8,02 MB)

Tuning the thermal diffusivity of the seed matter for enhanced biosynthesis: A thermal lens study
Sankararaman S, Swapna Mohanachandran Nair Sindhu, 2020, original scientific article

Abstract: The thermodynamics of the seed matter after imbibition is highly significant as the growth and germination involve complex biochemical exergonic process. The germination of seed and compositional variation of the seed matter has always been a fascinating field of research. The present work unveils the thermodynamics associated with the changing thermal diffusivity of the seed matter through the green technology-based single-beam thermal lens technique. Investigations are carried out in Vigna radiata seeds, germinating in media with and without carbon allotropes, through various spectroscopic techniques. The morphology of the soot and carbon allotropes is understood from the field emission scanning electron microscope images. The thermal lens study throws light into the energy trapping nature of the seed matter of the seed growing in carbon allotropic media which facilitates biosynthesis. The observed increased rate of growth of the seed is substantiated through the ultraviolet–visible–near-infrared (NIR), Fourier transform infrared, and photoluminescence (PL) spectroscopic analyses. The NIR and PL studies also reveal the formation of chlorophyll molecule during germination. Thus, the study suggests a mechanism for tuning the thermal diffusivity of the seed matter as to trap the biochemical energy to facilitate the further biosynthesis and thereby to enhance the growth rate.
Found in: ključnih besedah
Summary of found: ...various spectroscopic techniques. The morphology of the soot and carbon allotropes is understood from the...
Keywords: seed matter, thermal diffusivity, thermal lens, carbon nanoparticle, soot
Published: 04.07.2022; Views: 337; Downloads: 0
.pdf Fulltext (2,68 MB)

Allotropic transformation instigated thermal diffusivity of soot nanofluid: Thermal lens study
Sankararaman S, RAJ VIMAL, Swapna Mohanachandran Nair Sindhu, 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.
Found in: ključnih besedah
Keywords: petrol soot, thermal lens, thermal diffusivity
Published: 04.07.2022; Views: 403; Downloads: 0
.pdf Fulltext (3,08 MB)

Soot as a precursor for the low temperature synthesis of organometallic sodium carbide
Sankararaman S, SARITHA DEVI H V, Swapna Mohanachandran Nair Sindhu, 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.
Found in: ključnih besedah
Keywords: carbonaceous soot, sodium carbide, photonic applications
Published: 05.07.2022; Views: 376; Downloads: 0
.pdf Fulltext (1,33 MB)

Carbon nanoparticles assisted energy transport mechanism in leaves: A thermal lens study
Swapna Mohanachandran Nair Sindhu, 2019, original scientific article

Abstract: In the world of increasing population and pollution due to carbon emissions, the research for effective utilization of futile diesel soot for fruitful applications has become a necessity for a sustainable development. The contribution to pollution from vehicles and industries due to the aging of engines has caused a crisis. Carbon nanoparticles (CNPs) have been the subject of interest because of their good physical, chemical, and biological properties. The present work investigates the role of CNPs produced by internal combustion engines on the energy transport mechanism among leaf pigments using the sensitive and nondestructive single beam thermal lens technique. The studies reveal the absorption changes by various chlorophyll pigments with the concentration of CNPs sprayed on the leaves. Though for low concentrations CNPs lower the photon absorbance by chlorophyll pigments, the effect gets reversed at higher concentrations. The variation of thermal diffusivity with CNP concentration and its role in the energy transport mechanism among chlorophyll pigments are also studied. It is found that CNP concentrations of 625-2500mg/l are good for better intra-pigment energy transport leading to increased rate of photosynthesis and plant yield and thereby helping in attaining food security. The variation of CNP assisted energy transport among leaf pigments on the production of nicotinamide adenine dinucleotide phosphate (NADPH) and carbohydrates is also studied with ultraviolet (UV) and near-infrared (NIR) spectroscopy.
Found in: ključnih besedah
Summary of found: ...research for effective utilization of futile diesel soot for fruitful applications has become a necessity...
Keywords: carbon nanoparticle, soot, energy transport, thermal lens, photosynthesis
Published: 05.07.2022; Views: 383; Downloads: 0
.pdf Fulltext (1,84 MB)

Fractal and spectroscopic analysis of soot from internal combustion engines
Sankararaman S, RAJ VIMAL, SARITHA DEVI H V, Swapna Mohanachandran Nair Sindhu, 2018, original scientific article

Abstract: Today diesel engines are used worldwide for various applications and very importantly in transportation. Hydrocarbons are the most widespread precursors among carbon sources employed in the production of carbon nanotubes (CNTs). The aging of internal combustion engine is an important parameter in deciding the carbon emission and particulate matter due to incomplete combustion of fuel. In the present work, an attempt has been made for the effective utilization of the aged engines for potential applicationapplications in fuel cells and nanoelectronics. To analyze the impact of aging, the particulate matter rich in carbon content areis collected from diesel engines of different ages. The soot with CNTs is purified by the liquid phase oxidation method and analyzed by Field Emission Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, Energy Dispersive Spectroscopy, UV-Visible spectroscopy, Raman spectroscopy and Thermogravimetric analysis. The SEM image contains self-similar patterns probing fractal analysis. The fractal dimensions of the samples are determined by the box counting method. We could find a greater amount of single-walled carbon nanotubes (SWCNTs) in the particulate matter emitted by aged diesel engines and thereby giving information about the combustion efficiency of the engine. The SWCNT rich sample finds a wide range of applications in nanoelectronics and thereby pointing a potential use of these aged engines.
Found in: ključnih besedah
Keywords: Fractals, internal combustion engine, efficiency, soot, carbon nanoparticle
Published: 30.06.2022; Views: 407; Downloads: 0
.pdf Fulltext (1,05 MB)

From futile to fruitful: Diesel soot as white light emitter
Swapna Mohanachandran Nair Sindhu, Sankararaman S, 2018, original scientific article

Abstract: The present work describes a solution for the effective use of the hazardous particulate matter (diesel soot) from the internal combustion engines (ICEs) as a potential material emitting white light for white light emitting diodes (WLEDs). The washed soot samples are subjected to Field Emission Scanning Electron Microscopy (FESEM), High- Resolution Transmission Electron Microscopy (HR-TEM), Energy Dispersive Spectroscopy (EDS), UV-Visible, Photoluminescent (PL) Spectroscopy and quantum yield measurements. The CIE plot and Correlated Color Temperature (CCT) reveals the white fluorescence on photoexcitation. The sample on ultraviolet (UV) laser excitation, provides a visual confirmation of white light emission from the sample. The diesel soot collected from public transport buses of different years of manufacture invariably exhibit white fluorescence at an excitation of 350 nm. The sample show a quantum yield of 47.09%. The study is significant in the context of pollution and search for low-cost, rare-earth phosphor free material for white light emission and thereby turning the hazardous, futile material into a fruitful material that can be used for potential applications in photonics and electronics.
Found in: ključnih besedah
Keywords: White light emitter, Diesel soot, CIE plot, Quantum yield, Fluorescence
Published: 30.06.2022; Views: 388; Downloads: 0
.pdf Fulltext (1,82 MB)

Search done in 0 sec.
Back to top