Browsing by Author "Bhattacharyya, Debabrata"
Now showing 1 - 10 of 10
Results Per Page
Sort Options
Item Open Access A comparison of polymer film and glass collectors for concentrating solar power(Elsevier, 2014-06-02T00:00:00Z) Sansom, Christopher L.; Comley, Paul; Bhattacharyya, Debabrata; Macerol, NastjaThis paper describes work to compare the optical properties and surface texture of glass and polymer film collectors. We also present the results of experiments designed to simulate collector cleaning processes (both contact and non-contact), and the degradation of glass and polymer reflecting surfaces owing to sand and dust abrasion. Finally we present initial results on the applicability of anti-soiling and self-cleaning coatings on glass and polymer film collector surfaces. Measurements, which include specular and hemispherical reflectance, surface roughness, and electron microscopy, indicate the excellent performance of currently available polymer film in terms of its optical performance and robustness in comparison with traditional glass collectors in CSP applications.Item Open Access Effect of silver on the phase transition and wettability of titanium oxide films(Nature Publishing Group, 2016-08-30) Mosquera, Adolfo A.; Albella, Jose M.; Navarro, Violeta; Bhattacharyya, Debabrata; Endrino, José L.The effect of silver on the phase transition and microstructure of titanium oxide films grown by pulsed cathodic arc had been investigated by XRD, SEM and Raman spectroscopy. Following successive thermal annealing up to 1000 °C, microstructural analysis of annealed Ag-TiO2 films reveals that the incorporation of Ag nanoparticles strongly affects the transition temperature from the initial metastable amorphous phase to anatase and stable rutile phase. An increase of silver content into TiO2 matrix inhibits the amorphous to anatase phase transition, raising its temperature boundary and, simultaneously reduces the transition temperature to promote rutile structure at lower value of 600 °C. The results are interpreted in terms of the steric effects produced by agglomeration of Ag atoms into larger clusters following annealing which hinders diffusion of Ti and O ions for anatase formation and constrains the volume available for the anatase lattice, thus disrupting its structure to form rutile phase. The effect of silver on the optical and wetting properties of TiO2 was evaluated to demonstrate its improved photocatalytic performance.Item Open Access The effects of ejector adiabatic absorber on heat and mass transfer of binary nanofluid with heat transfer additives(Springer, 2021-08-30) Muhammad, Umar Aliyu; Bhattacharyya, Debabrata; Endrino, José L.; Fereres, SoniaThis paper presents experimental results on the study of the effects of ejector adiabatic absorber on heat and mass transfer of binary nanofluid with heat transfer additives (2-ethyl-1-hexanol and gum Arabic). In this case, H2O/lithium bromide-alumina nanofluid was suggested due to a growing interest in absorption heat transfer working fluid for solar energy application. An experimental setup — ejector test rig — was designed to study the absorption, heat, and mass transfer rate as a result of refrigerant vapour mass flow entrained by the ejector adiabatic absorber. The study was carried out at different solution mass flowrate (0.051 to 0.17 kg/s) with three prepared sample solutions, which include pure LiBr solution, LiBr-Alumina nanofluid without heat transfer additives, and LiBr-Alumina nanofluid with heat transfer additives. The absorption rate, mass transfer coefficient, heat transfer rate, and heat transfer coefficient for the three samples were reported. On the other hand, the percentage enhancements for all the parameters — at a suitable flow rate of 0.085 kg/s — due to the addition of alumina without and with heat transfer additives were recorded. The absorption rate enhancements were 25% and 96%, the enhancement rates of mass transfer coefficient recorded were 20% and 82%, the heat transfer rate enhancements were 85% and 183%, and the heat transfer coefficient enhancements obtained were 72% and 156% with addition of alumina nanoparticles only and alumina nanoparticles with heat transfer additives respectively. Material mass balance analysis suggests that mass inflow in the ejector equals to the mass outflow from the ejector, indicating a complete absorption of the entrained refrigerant vapour beyond which falling film absorption can occur due to concentration. This article also presents experimental evidence of the capability of ejector as strong adiabatic absorber, heat, and mass transfer component, which were earlier reported using numerical modelsItem Open Access Evaluation of the optical switching characteristics of erbium-doped fibres for the development of a fibre Bragg grating sensor interrogator(SPIE, 2014-06-02) Rigas, E.; Correia, Ricardo N.; Stathopoulos, N. A.; Savaidis, S. P.; James, Stephen W.; Bhattacharyya, Debabrata; Kirby, Paul B.; Tatam, Ralph P.A polling topology that employs optical switching based on the properties of erbium-doped fibres (EDFs) is used to interrogate an array of FBGs. The properties of the EDF are investigated in its pumped and un-pumped states and the EDFs’ switching properties are evaluated by comparing them with a high performance electronically controlled MEM optical switch. Potential advantages of the proposed technique are discussed. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.Item Open Access Laser transfer of sol-gel ferroelectric thin films using an ITO release layer(Elsevier Science B.V., Amsterdam., 2011-02-01T00:00:00Z) Bansal, A.; Hergert, R.; Dou, G.; Wright, Robert V.; Bhattacharyya, Debabrata; Kirby, Paul B.; Yeatman, E. M.; Holmes, A. S.A new laser transfer process is reported which allows damage-free transfer of ferroelectric thin films from a growth substrate directly to a target substrate. The thin film ferroelectric material is deposited on a fused silica growth substrate with a sacrificial release layer of ITO (indium tin oxide). Regions of the film that are to be transferred are then selectively metallised, and bonded to the target substrate. Separation from the growth substrate is achieved by laser ablation of the ITO release layer by a single pulse from a KrF excimer laser, with the laser light being incident through the growth substrate. The residual ITO on the transferred ferroelectric layer is electrically conducting, and may be suitable for incorporation into the final device, depending on the application. The new process has been demonstrated for 500 nm-thick layers of sol-gel PZT which were thermosonically bonded to a silicon target substrate prior to laser release. The transferred films show ferroelectric behaviour and have a slightly reduced permittivity compared to the as-depositItem Open Access Morphological, optical and thermal characterisation of aerogel-epoxy composites for enhanced thermal insulation(SAGE, 2018-08-15) Krishnaswamy, Suryanarayanan; Bhattacharyya, Debabrata; Abhyankar, Hrushikesh; Marchante Rodriguez, Veronica; Huang, Zhaorong; Brighton, JamesThe present work explores the possibility of introducing aerogel at different stages of the epoxy resin cure to identify the most effective method that ensures minimal destruction of the aerogel particles. The aerogel particles are added at 0.5 h, 1 h and 1.5 h after the resin and the hardener are mixed together. Additionally, the effect of a wetting agent that improves the interface between the aerogel and the resin is also investigated. The different materials are characterised using optical images and ESEM-EDX to determine the most effective processing route. Additional data are also provided by determining the different material’s optical transmittance and reflective characteristics. From the experimental results, it is observed that the addition of aerogel at the 1-h mark proves to be the most efficient route to follow. In addition, the wetting agent displays a negligible effect on the samples in the study; hence, its usage is advocated due to its influence on the interface strength. Therefore, the aerogel/epoxy/wetting agent sample with the aerogel added at the 1 h mark looks promising. A 13.3% decrease in thermal conductivity when compared with the pure resin/hardener sample along with the damage coefficient value of 0.183 demonstrates the material’s potential for thermal insulation applications.Item Open Access Morphological, optical and thermal characterisation of aerogel/epoxy composites for thermal insulation applications(Cranfield University, 2018-08-23 11:35) Krishnaswamy, Surya; Bhattacharyya, Debabrata; Abhyankar, Hrushikesh; Marchante Rodriguez, Veronica; Huang, Zhaorong; Brighton, JamesThe present work explores the possibility of introducing aerogel particles at different stages of the epoxy resin cure to find the most effective method that ensures minimal destruction of the former along with a high degree of mouldability for the composite material. The aerogel particles are added at 0.5 hours, 1 hour and 1.5 hours after the resin and the hardener are mixed together. Additionally, the effect of a wetting agent that improves the interface between the aerogel and the resin is also investigated. The different materials are characterised using optical images and electron microscope with energy dispersive X-ray spectroscopy to determine the most effective processing route. Additional data is also provided by determining the different material€™s optical transmittance and reflective characteristics. From the experimental results, it is seen that the addition of aerogel at the 1 hour mark proves to be the most efficient route to follow. In addition, the wetting agent displays a negligible effect on the samples in the study; hence its usage is advocated. Therefore, the aerogel/epoxy/wetting agent sample with the aerogel added at the 1 hour mark is the most promising material. A 13.3% decrease in thermal conductivity when compared with the pure resin/hardener sample along with the calculated aerogel damage coefficient value of 0.227 (22.7%) confirms its promise and potential for thermal insulation applications.Item Open Access Nano- and micro-scale impact testing of zirconia, alumina and zirconia-alumina duplex optical coatings on glass(Elsevier, 2020-10-06) Beake, Ben D.; Isern, Luis; Bhattacharyya, Debabrata; Endrino, José L.; Lawson, Ken; Walker, TrevorOptimising the mechanical properties of optical coatings to improve their durability will be critical if they are to be used successfully in harsh environments where they may be subject to degradation by mechanical contact. In this study zirconia, zirconia-alumina duplex and alumina experimental coatings were deposited on soda lime and borosilicate glass and their resistance to repetitive impact under different experimental conditions evaluated in nano- and micro-scale impact tests. The influence of changing probe geometry (sharp and blunt contacts) and applied load on the deformation was studied. Spheroconical indenters were found to be more suitable to study the load sensitivity of the impact response than sharp cube corner indenters. Increased resistance to plastic deformation in the coating-substrate system (H3/E2) proved detrimental to the damage tolerance to the repetitive nano- and micro-impact tests. To compare the deformation behaviour in nano-impact and nano-scratch, tests were performed using the same spheroconical probe, revealing cracking and blistering of the glass substrate in both types of test. The change in probe depth after the first impact was found to be a very useful metric to effectively compare the evolution of surface damage on continued impact in nano- and micro-impact tests at different applied load and probe geometryItem Open Access Preparation of binary nanofluid with heat transfer additives by particle surface functionalisation(Springer, 2021-08-06) Muhammad, Umar Aliyu; Bhattacharyya, Debabrata; Endrino, José L.; Fereres, SoniaCurrent binary nanofluid synthesis methods with heat transfer additives lack an understanding of the chemistry of the nanoparticle-additive-base fluid interaction, which plays a significant role in the adsorption of the surfactant on the nanoparticle surface. Consequently, this leads to the formation of aggregates within the nanofluid after a couple of days, affecting the stability of the colloidal suspension. Here, a lithium bromide-alumina salt-based nanofluid is proposed following a newly developed synthesis method including particle surface functionalisation. The new procedure developed allows the initial preparation of the nanoparticles with the surfactant as the first step (surface functionalisation) and then the preparation of the base fluid with a dispersion stabilising agent (Gum Arabic) separately. This is then followed by the dispersion of the prepared alumina nanoparticles into the base fluid, by stirring and ultrasonication to produce the final nanofluid, lithium bromide-water (LiBr-H2O)-alumina nanofluid. Until now, proper procedures have not been reported for the nanofluid synthesis combining surfactant and dispersant and the chemistry of nanoparticles-surfactant-base fluid interaction, which was thoroughly investigated in the new approach. The fluid prepared by both the conventional and new procedures was characterised and analysed simultaneously. A thermal conductivity enhancement of 3% was achieved by using the surface functionalisation method, with greater particle concentration distribution (number of particles in suspension) of 22.7% over the conventional procedure. It also achieved a 5% decrease in dynamic viscosity. On the other hand, a Mouromtseff number value between 0.7 and 1.8 was obtained for the fluid at 293 K and 373 K temperature range, indicating a strong heat transfer capability. It was apparent from the particle size and concentration distribution analysis conducted that this procedure produced a more stable nanofluid with a high distribution of nanoparticles within the fluid. This allows high improvement of thermal properties of the fluid.Item Open Access Radioluminescence properties of the CdSe/ZnS Quantum Dot nanocrystals with analysis of long-memory trends(Elsevier, 2016-06-14) Nikolopoulos, D.; Valais, I.; Michail, C.; Bakas, A.; Fountzoula, C.; Cantzos, D.; Bhattacharyya, Debabrata; Sianoudis, I.; Fountos, G.; Yannakopoulos, P.; Panayiotakis, G.; Kandarakis, I.This paper reports radioluminescence properties of the CdSe/ZnS quantum dots. Three quantum dot samples were prepared with concentrations 14.2 × 10−5 mg/mL, 21.3 × 10−5 mg/mL and 28.5 × 10−5 mg/mL, respectively. The ultraviolet induced emission spectra of CdSe/ZnS dots exhibited a peak at 550 nm ranging between 450 nm and 650 nm. Discrepancies observed between 250 nm and 450 nm were attributed to the solvent and cuvette. The absolute efficiency calculated from random fractional-Gaussian luminescence segments varied. Long-memory fractional-Brownian segments were also found. The quantum dot solution with concentration of 21.3 × 10−5 mg/mL exhibited the maximum absolute efficiency value at 90 kVp. The CdSe/ZnS dots have demonstrated potential for detection of X-rays in the medical imaging energy range.