DSpace Collection:http://142.54.178.187:9060/xmlui/handle/123456789/5732024-03-29T15:03:18Z2024-03-29T15:03:18ZExpanded graphite as thermal conductivity enhancer for paraffin wax being used in thermal energy storage systemsRaza, GulfamShi, YongmingDeng, Yuanhttp://142.54.178.187:9060/xmlui/handle/123456789/17882019-11-25T06:39:58Z2016-01-12T00:00:00ZTitle: Expanded graphite as thermal conductivity enhancer for paraffin wax being used in thermal energy storage systems
Authors: Raza, Gulfam; Shi, Yongming; Deng, Yuan
Abstract: Phase change material such as paraffin wax has very low thermal conductivity which leads to many defects upon its practical utilization in thermal energy storage system. In this paper, study on paraffin/expanded graphite (EG) composite has been carried out to enhance the thermal conductivity of pure paraffin (base material). EG (supporting material) with its worm-like structure has been introduced as thermal conductivity enhancer in paraffin/EG composite. A type of paraffin wax with melting temperature (Tm = 60-62 °C) has been investigated. Three samples of paraffin/EG composite have been prepared with weight percentage of EG as 5%, 10% and 15%. Self-absorption technique has been introduced by preparing the samples in a cylindrical vessel at temperature slightly more than melting temperature of paraffin for a certain period of time until maximum incorporation of paraffin wax was achieved into the porous structure of expanded graphite. Thermal characteristics have been investigated by differential scanning calorimeter which showed no change in the melting temperature of base material, however a slight change in phase transition temperature was observed, and measured latent heat of the composite was a little lower than theoretical latent heat. Thermal conductivity of each sample of paraffin/EG composite determined by laser flash method has been achieved 4 times, 6 times and 6.5 times higher than that of pure paraffin for 5%, 10% and 15% paraffin/EG composite, respectively, and as quantity of EG was increased, thermal conductivity of the composite got increased as well. Results obtained by scanning electron microscopy indicated uniform mingling of paraffin wax and expanded graphite in the composite. Form-stability has been confirmed through liquid leakage test which showed no leakage of paraffin from composite. This work is equally significant to be engaged in thermal energy storage systems, cooling of electronic devices and thermal management of batteries.2016-01-12T00:00:00ZSimplistic development and characterization of S/Se based metal chalcogenides for energy applications : Development of S/Se based metal chalcogenidesNazir, MadihaMuhyuddin, MohsinMughal, FaryalBasit, Muhammad Abdulhttp://142.54.178.187:9060/xmlui/handle/123456789/17872019-11-25T06:37:15Z2019-01-08T00:00:00ZTitle: Simplistic development and characterization of S/Se based metal chalcogenides for energy applications : Development of S/Se based metal chalcogenides
Authors: Nazir, Madiha; Muhyuddin, Mohsin; Mughal, Faryal; Basit, Muhammad Abdul
Abstract: Tellurium, sulfur and selenium elements are used to form the chalcogenide compounds by reaction of one or two of these elements with a metal. Such metal chalcogenides (e.g., PbS, CdS, SnS, SnSe and CuS etc.) are emerging as advanced energy materials owing to their efficient performance in various engineering applications including photocatalysis, solar cells, batteries and water splitting. In current study, S/Se based metal chalcogenide based compounds and composites (MCCs) were synthesized through facile fabrication techniques such as chemical bath deposition (CBD) and successive ion layer adsorption reaction (SILAR). We successfully, synthesized SnS, SnSe and CuS as well as their composites (e.g., SnSe/SnS), optimized the corresponding chemical recipes and characterized the compounds/composites using material characterization tools. Extensive field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectroscopy (EDS) was used to reveal the morphology and the elemental composition respectively, while X-ray diffraction spectrometry, thermograviometery were employed to analyze the crystalline nature and thermal behavior of synthesized MCCs. All the MCCs were additionally characterized using particle size analysis. Furthermore, synthesized MCCs were employed to degrade the toxic organic dye and their appreciable performance was divulged in the light of mechanism of photocatalysis.2019-01-08T00:00:00ZLaser Beam Rapid Solidification of Plasma Sprayed Ni-Al Coatings on SteelAkhtar, ShazeenAkhtar, NaveedTauqir, Anjumhttp://142.54.178.187:9060/xmlui/handle/123456789/17862019-11-25T06:33:52Z2019-01-08T00:00:00ZTitle: Laser Beam Rapid Solidification of Plasma Sprayed Ni-Al Coatings on Steel
Authors: Akhtar, Shazeen; Akhtar, Naveed; Tauqir, Anjum
Abstract: Hard wear-resistant surfaces of mandrill tips manufactured from hot worked steels are used for extrusion to offer smooth inside surfaces of seamless pipes. In the present study, alloyed surfaces are synthesized on steel substrates using laser surface melting. Processing parameters are optimized to achieve wear-resistant surface layers of adequate thickness. Powders of nickel and Aluminium are simultaneously deposited on steel surfaces using plasma spraying technique. Plasma coated surface layers are fragile, brittle and non-adherent. These surfaces are subjected to laser beam melting of surface, followed by rapid solidification. Beam power and spot size of focused beam are 800 watts and 3 mm, respectively. Translation speed of sample with respect to beam is varied from 100 to 300 mm.s -1 to synthesize uniform surface layers over a range of thicknesses. Melt zone is hardly visible at higher velocities while consistent and uniform depth of 0.2 to 0.6 mm is achieved at velocities from 100 to 250 mm.s -1 . Microstructural study is conducted using optical and scanning electron microscopes while micro-hardness measurements are taken as a measure of mechanical behaviour and surface pin on disk tribometer for wear testing. Rapid solidification followed by laser melting has redefined the microstructure and developed strong metallurgical bond with steel substrate. Fine microstructure, along with super-saturation in alloying elements renders hardness and strength to the material enhancing wear properties, confirmed by micro hardness test results. Hardness depth profiles clearly differentiate three distant regions i.e. laser melted zone, intermediate zone and parent substrate. The typical hardness values of these regions are found to be 540±30, 470±50 and 200±15 Hv, respectively. Refinement of microstructure as well as uniformity and reduced segregation in the laser melted zone resulted in improved resistance to wear.2019-01-08T00:00:00ZViscoelastic Properties of Rubber Material ModellingFatima, Iqra DanishShafi, NadeemAnjum, Hazeemahttp://142.54.178.187:9060/xmlui/handle/123456789/17852019-11-25T06:31:20Z2019-08-27T00:00:00ZTitle: Viscoelastic Properties of Rubber Material Modelling
Authors: Fatima, Iqra Danish; Shafi, Nadeem; Anjum, Hazeema
Abstract: Rubber has extensive application in automobiles due to its damping properties and stress relaxation behavior. Its properties largely depends on type of loading (compressive or tensile), temperature, frequency, amplitude etc. The objective of this paper is to show meaningful relation between viscoelastic properties of OGDEN type material solid like rubber under dynamic cyclic loading. Sinusoidal loading is applied to determine stress-strain behavior over time, stress relaxation, and residual stresses. Generally, viscoelastic material gives nonlinear response, but typically it gives minor linear relation initially due to elastic behavior. Material response is visualized at different amplitude of cyclic loading.2019-08-27T00:00:00Z