Thermal Lens Study Research Articles

Graphene incorporated zinc oxide hybrid nanofluid for energy-efficient heat transfer application: A thermal lens study

The work focuses on the development of a hybrid nanofluid (NF) comprising zinc oxide-graphene (ZG) to address heat transfer (HT) limitations in thermal systems. The study employs a highly sensitive mode-mismatched dual-beam thermal lens (MDTL) method to analyze the lattice dislocation-induced thermal diffusivity (D) modifications of the hybrid NF. The hybrid composite (HC) is synthesized by solid-state mixing and annealing of ZG. The formation of ZG hybrid composites is revealed through X-ray diffraction (XRD), Fourier transform infrared, X-ray photoelectron, and Raman spectroscopic analyses. The structural dislocations present in the HC are understood from XRD and Raman analyses. Ultraviolet-visible and photoluminescence spectroscopic studies revealed the optical properties of the samples. The MDTL study is carried out by preparing the NFs of the synthesized samples in the base fluid, ethylene glycol (EG), and reveals the impact of crystallite defects on the thermal characteristics of the synthesized composites. Thus, the study suggests the potential capability of ZG composites in tuning the thermal behaviour of EG for HT applications.

Development of semiconducting graphitic carbon nitride nanofluid for heat transfer applications: A mode mismatched thermal lens study

The present work delineates the heat transfer potential of the semiconducting graphitic carbon nitride (g-C3N4) nanofluid. The paper also discusses the eco-friendly green synthesis of g-C3N4 nanoparticles from the natural carbon precursor portobello mushroom by the hydrothermal method. The nanoparticles synthesised are subjected to structural, morphological, thermal, and optical characterizations. The flower-like laminar structure of the sample revealed through field emission scanning electron microscope (FESEM) analysis exhibited a semiconducting nature with an optical bandgap of 2.58 eV. The formation of g-C3N4 is confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photoelectron (XPS) and Raman spectroscopic analyses. The thermogravimetric analysis (TGA) reveals good thermal stability up to 500 °C, which suggests possible applications in heat transfer fluids. The concentration-dependent thermal diffusivity variation of the g-C3N4 semiconductor nanofluid, investigated using the sensitive mode mismatched dual beam thermal lens technique, divulges its potential as an organic, metal-free additive in engine coolants for automobile applications.

Thermal lens study of hydrothermally synthesised graphitic carbon nitride nanofluids for heat transfer applications

Thermal lens study of hydrothermally synthesised graphitic carbon nitride nanofluids for heat transfer applications

Electrical, Thermal Lens and Optical Study of Fluorescein Film for Application As Organic Photovoltaic Devices.

This article is devoted to the study of various dielectric and optoelectrical parameters nonlinear optic behaviors, thermal lens and self-diffraction parameters of Fluorescein (FLs) doped polymethyl methacrylate (PMMA) films. The films were prepared with 60mM. These studies are based on the calculated values of refractive, absorption coefficient, energy gap, extinction coefficient and nonlinear Refraction index . The polymer films were prepared using the casting technique. All samples were previously investigated by UV-Vis-NIR spectrophotometric measurements and Optical microscopy SEM and ATM. Utilizing thermal lens spectrometry, an investigation of the thermo-optical characteristics as well as the nonlinear refractive index was carried out. In this method, a pump beam and a probe beam were brought into collinear alignment with one another. To determination the nonlinear Refraction index . High values of nonlinear refractive index predict a bright future for materials in optical applications. These results indicate that the new dye is a promising candidate for applications in nonlinear optical devices. Investigations were carried out on organic photovoltaic devices in addition to devices consisting of active layers with conducting polymer of PHPP:P3HT film and PHPP:P3HT/Fls. The methods of polymer and dyes synthesis are presented and their physical properties are given.

Phase portrait and fractal analyses in nanobiophotonics: carbon nanoparticle aided intra-pigment energy transfer in leaves

The paper delineates the potential application of nonlinear time series analysis (TSA) in Nanobiophotonics to explore the soot-assisted intra-pigment energy transport mechanism in leaves. The soot nanofluid, containing nano carbon allotropes, prepared in different concentrations, is sprayed over Lablab purpureus (L.) sweet leaves. The chlorophyll extracted from the leaves after ten days is subjected to UV-Visible absorption and single beam thermal lens (TL) studies. The variation of the absorbance of signature peaks of chlorophyll pigments with the soot concentration reveals the role of soot in the intra-pigment energy transport, divulged through the time series TL signal. The TSA of the TL signals, the plotting of phase portraits, and the computation of sample entropy (S), fractal dimension (FD), and Hurst exponent for the pigment-soot systems unwrap the particle/molecular dynamics and the flow of energy within the system. The analysis by segmenting the variations of the TSA measures with soot concentration reveals that the values of S and FD of the system are high in the low and high concentration ranges, in agreement with the randomness reflected in the phase portrait. The middle region, where S and FD decrease, seems more energy-efficient for the photosystem through heat trap and energy exchange between the pigment-soot system. The study gives information about the critical concentration range suitable for increased photosynthesis in leaves and yield enhancement.

How graph features decipher the soot assisted pigmental energy transport in leaves? A laser-assisted thermal lens study in nanobiophotonics

The paper employs the principles of graph theory in nanobiophotonics, where the soot-assisted intra-pigmental energy transport in leaves is unveiled through the laser-induced thermal lens (TL) technique. Nanofluids with different soot concentrations are sprayed over Lablab purpureus (L) sweet leaves, and the extracted pigments are analyzed. The graph features of the constructed complex network from the TL signal of the samples are analyzed to understand their variations with optical absorbance. Besides revealing the presence of optimum soot concentration that can enhance photosynthesis, the study brings out the potential application of graph features in nanobiophotonics.

Acclimatization through thermal diffusivity tuning of coconut oil – A mode mismatched dual-beam thermal lens study

BackgroundAyurvedic medicinal oils traditionally prepared by blending herbal extracts in different compositions are commonly used for treatment and improving health. The estimation of the thermal properties of medicinal oils is essential for practical applications. ObjectiveThe present work aims to expound the ability of medicinal oils for the acclimatization of body temperature by determining its thermal diffusivity and thereby providing a validation to the traditional knowledge. Materials and methodsThe medicinal oils are prepared by incorporating black pepper (Piper nigrum), aloe vera (Aloe barbadensis), hibiscus bud (Hibiscus rosa-sinensis) and Ocimum sanctum in coconut oil base. The samples are subjected to thermal diffusivity study using the mode-mismatched dual-beam thermal lens technique. ResultsThe study reveals that the incorporation of black pepper (Piper nigrum), having hot potency (Ushna veerya), to the base fluid lowers the thermal diffusivity value, suggesting its potential in heat-trapping. The addition of aloe vera (Aloe barbadensis), hibiscus bud (Hibiscus rosa-sinensis), and O. sanctum dissipates heat energy quickly, thus increases the thermal diffusivity of coconut oil revealing a cold potency (Sheeta veerya). The study provides a validation for traditional knowledge and delineates the possiblity of thermal diffusivity tuning of the base fluids. ConclusionThe thermal diffusivity tuning through incorporation of herbal extracts can effectively be used to acclimatize the human body temperature with the surroundings. A higher thermal diffusivity value induces a cooling effect and the lower value causes heating effect. This, opens up the possibility of using thermally tuned oils depending on climate and geographical location.

Development of zinc oxide-multi-walled carbon nanotube hybrid nanofluid for energy-efficient heat transfer application: A thermal lens study

This paper addresses the need for developing an energy-efficient hybrid nanofluid with zinc oxide–multi-walled carbon nanotube (ZnO-MWCNT) for overcoming the bottleneck of efficient heat transfer in thermal systems. The concentration-dependent thermal diffusivity modifications are analyzed using the highly sensitive mode mismatched thermal lens technique. The hybrid composite is prepared by the solid-state mixing and annealing of a pure multi-walled carbon nanotube (MWCNT) and zinc oxide (ZnO), synthesized by the solution combustion method. The composite formation is studied by structural, morphological, and optical characterization techniques. Among the three nanofluids ZnO, MWCNT, and ZnO-MWCNT, the composite exhibits a drastic enhancement in thermal diffusivity at a lower solid volume fraction of 0.047 mg/ml containing 0.009 mg/ml of MWCNT. All the nanofluids show an optimum concentration beyond which the thermal diffusivity decreases with the nanoparticle concentration. Thus, this study suggests the potential application of ZnO-MWCNT hybrid nanofluids in thermal system design to enhance internal combustion engines' efficiency during cold-start.

Effect of metal ions on the thermo-optic properties of Rhodamine 6G-gold nanoparticle hybrids

The dye-plasmonic nanoparticle (NP) mixtures were reported to be an efficient probe for heavy metal detection in aqueous solution, particularly metals like Hg2+ ions. However, little is known about the variation in such dye-NP mixtures' thermal properties upon the addition of heavy metals. In this work, using the laser-based dual-beam thermal lens technique, the variation in thermal diffusivity value of Rhodamine6G (Rh6G)-gold nanoparticle (AuNP) mixture upon the addition of various concentrations of Hg2+ ions are investigated. The thermal property measurements are corroborated with optical absorption studies. The analysis reveals that the absorption peak wavelength and the shape of the spectrum are very sensitive to the addition of the Hg2+ ions. The measured thermal diffusivity values found to increase with the Hg2+ ion concentrations range from 0.1 nM to 10 µM and beyond which, the Hg2+ ions cause little variation in the thermal diffusivity value. The variation in the thermal diffusivity value originates from amalgam formation due to heavy metal-NP interaction. The investigation of dye molecules' emission spectral studies using a laser-based fluorescence setup reveal that the fluorescence behavior concurs with the data obtained from thermal lens studies. Additionally, the studies using the monovalent and divalent metal ions to dye-NP mixture elucidate that divalent metals are more efficient in tailoring the thermal and optical properties. The present study elucidates that optical sensor development based on the emission or absorption properties of the dye-plasmonic NP mixture for heavy metals have a concomitant variation in thermal properties.

Laser-induced thermal lens study of the role of morphology and hydroxyl group in the evolution of thermal diffusivity of copper oxide

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.

Soot effected sample entropy minimization in nanofluid for thermal system design: A thermal lens study

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.

Downscaling of sample entropy of nanofluids by carbon allotropes: A thermal lens study.

The work reported in this paper is the first attempt to delineate the molecular or particle dynamics from the thermal lens signal of carbon allotropic nanofluids (CANs), employing time series and fractal analyses. The nanofluids of multi-walled carbon nanotubes and graphene are prepared in base fluid, coconut oil, at low volume fraction and are subjected to thermal lens study. We have studied the thermal diffusivity and refractive index variations of the medium by analyzing the thermal lens (TL) signal. By segmenting the TL signal, the complex dynamics involved during its evolution is investigated through the phase portrait, fractal dimension, Hurst exponent, and sample entropy using time series and fractal analyses. The study also explains how the increase of the photothermal energy turns a system into stochastic and anti-persistent. The sample entropy (S) and refractive index analyses of the TL signal by segmenting into five regions reveal the evolution of S with the increase of enthalpy. The lowering of S in CAN along with its thermal diffusivity (50%-57% below) as a result of heat-trapping suggests the technique of downscaling sample entropy of the base fluid using carbon allotropes and thereby opening a novel method of improving the efficiency of thermal systems.

Thermal lens study of absolute porosity in ceria: A Sankar–Loeb model approach

The present work divulges the potential of thermal lens technique for analyzing the absolute porosity of a material in nanofluid using the recently proposed Sankar–Loeb model. The ceria nanoparticles synthesized by co-precipitation technique are subjected to morphological and structural characterizations. The study reveals that particle size and thermal diffusivity increase with annealing temperature. The nanocavities formed during the agglomeration of nanoparticles result in closed pores which give rise to absolute porosity that is probed by the thermal wave propagation (or thermal diffusivity) study. The enhancement in the particle size enhances the closed pore volume in the sample resulting in increased absolute porosity. Thus, the TL technique makes the analysis of closed pores possible through the absolute porosity study, which is not possible with the conventional BET (Brunauer–Emmett–Teller) technique.

Tuning the thermal diffusivity of the seed matter for enhanced biosynthesis: a thermal lens study

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.

Carbon nanoparticles assisted energy transport mechanism in leaves: A thermal lens study

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.

Effect of duty cycle on photothermal phenomenon—A thermal lens study

Study of laser-matter interaction and the associated photothermal phenomena have led to the development of several non-destructive evaluation techniques for material characterization. Optical modulation being the unavoidable part of these techniques, modulators of different kinds was developed of which electromechanical choppers find wide range of applications. The present work explains the role of the duty cycle in the photothermal phenomenon for getting correct results. For this, chopper wheels with duty cycles 10%–90% are designed and fabricated. The low-cost optical chopper constructed is used in the single beam thermal lens setup for elucidating the impact of the duty cycle in the thermal diffusivity measurement, taking coconut oil as an example. The study reveals that for getting correct results it is advisable to keep the duty cycle less than or equal to 50%.

Thermal Lens Study of NIR Femtosecond Laser-Induced Convection in Alcohols.

We use time-resolved thermal lens (TL) experiments to examine the convective heat transfer at microscale in the first eight members of the homologous series of primary alcohols. TL measurements enable a direct study of these primary alcohols without adding any chromophore as a function of varying heat loads created via femtosecond laser pulses at 1560 nm. Convective heat transfer leads to the asymmetrical and reduced thermal gradient, which substantially weakens the TL signal. The inflection in the time profile of the TL signal of methanol at higher powers is attributed to the greater molecular convection in methanol compared to other samples. This inflection dies out with a decrease in laser power. Our results demonstrate that the convection is more prominent at higher laser powers in all samples, and it modifies the trend in the steady-state TL signal of different alcohols with pump laser power. Methanol also has the highest steady-state TL among the primary alcohol series at low laser powers. The maxima in the TL signal are shifted systematically from methanol to ethanol and then to propanol as the laser power increases. Semiempirical analysis of time-resolved TL signal by using the latest theoretical TL model enabled us to extract the coefficient of convective heat transfer in methanol at different laser powers. In addition to that, analysis of other members of alcohol series at the highest (7.3 mW) laser power shows that convection is more facile in short-chain alcohols compared to the long-chain alcohols.

Synthesis of Electrospun Titania Nanofibers for Thermal Lens Study in Heat Transport Applications

Thermal lens spectrometry (TLS) technique was used to obtain the thermal diffusivity of electrospun Titania nanofibers (TiO2), with average diameter size of 50-80 nm, in water. TiO2nanofibers have been successfully prepared by sol-gel and electrospining techniques. TLS provides reliable alternative to measure the thermal diffusivities of semitransparent materials and low thermal diffusivities. The results show that the nanofluid thermal diffusivity increases with the presence of nanofibers. Complementary techniques: scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS) were employed to characterize the nanofibers morphology, average fiber diameter and chemical composition, respectively.

Nondestructive evaluation of heat trap mechanism in coconut oil—a thermal lens study

Search for low-cost thermal energy storage (TES) materials has emerged as the recent focus of research. The present work brings out the possible use of the futile repeatedly heated coconut oil for heat trap applications through the sensitive and nondestructive thermal lens technique. Coconut oil repeatedly heated to its smoke point using a temperature controlled heating mantle are subjected to laser-induced thermal lens study to understand the variations in its thermal inertia. The thermal diffusivity of the oil is found to fall by 73.5% of its initial value on repeated heating. The spectroscopic analysis with UV Visible near infrared technique indicates the enhanced optical energy absorption with a bathochromic shift and the Fourier Transform Infrared study points to the structural stability.

Thermal diffusivity control in titanium dioxide nanofluid through phase tuning

The potential of TiO2 is greatly understood in diversified fields of science and technology. With the advent of nanotechnology, the study of nanofluids has gained significant attention. The physical properties of a fluid can considerably be varied with nanoparticle incorporation. The present work describes methods for controlling the thermal diffusivity of TiO2 nanofluid. The thermal diffusivity of the nanofluid is measured by single beam thermal lens technique. TiO2 nanoparticles synthesized by sol–gel method with different amount of oxalic acid and the sample calcined at different temperatures are analyzed by x-ray diffraction (XRD) technique. The field emission scanning electron microscopic (FESEM) image and XRD analysis confirmed the particle formed to be nano in size. The transformation of phase from anatase to rutile with temperature and the amount of oxalic acid is studied from the XRD pattern. The thermal lens study of the samples reveals that the thermal diffusivity increases with temperature and amount of oxalic acid. The study also suggests the possibility of controlling the thermal diffusivity of TiO2 nanofluid through phase tuning.