PhD

Permanent URI for this collectionhttps://repository.cuilahore.edu.pk/handle/123456789/29

This collection archives the complete set of theses produced by students of the COMSATS University Islamabad, Lahore Campus.

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Comparative Study of Perovskite Solar Cell Encapsulation Using Two Different Rubbers As Edge Seals To Withstand Harsh External Environment
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2025) Uswa-Tuz-Zahra; FA22-R06-021; Prof. Dr. M. Zulfiqar Ali; LHR TP 9315
Photovoltaic cells for generating solar energy is therefore the richest source of renewable energy in as much as it is available and malleable for use. Among the most explored and achieved domains in solar cell technology is the development and enhancement of perovskite solar cells (PSCs). The materials selection of PSCs in the active light-harvesting layer is mainly characterized by its remarkably direct bandgap, and broadband light absorption that also withstands defects. Nonetheless, there are some issues, and the main ones are related to stability and performance. First attempts to use liquid electrolytes as HTL revealed stability issues and led to further investigations of potential solutions. Lithium salts dissolved in organic solvents became too thick to maintain a good ionic structure, making them unsuitable for applications Solid-state HTLs offered a solution by greatly enhancing stability and PCE. Further progress has been made with structural changes, new materials, and inventions in fabrication technologies that have a great impact on improving performance. Notably, recent achievements have seen PCE soar to 25.8%, surpassing established commercial PV technologies. However, stability remains a concern, with ongoing efforts focused on mitigating interface defects to enhance longevity. As the stability and efficiency of perovskite solar cells are concerned. We experimented with the solvent-engineering technology and synthesized MALI perovskite using two different approaches. In one approach we synthesized MALI using only DMF as a solvent and in another approach, ix we synthesized MALI using a mixture of solvents DMF plus DMSO. We hypothesized that changing the solvent from only DMF to DMF plus DMSO would affect the stability of the perovskite film. Films that are prepared by using a mixture of 2 solvents DMF plus DMSO show higher absorbance overall, especially in the shorter wavelength range (350 to 550 nm). From these UV visible spectra, we deduce that the addition of DMSO to the DMF as solvent improves the interaction of film with electromagnetic radiation in the visible region as compared to the films made by using only DMF as solvent. The FTIR-spectrum of perovskite material synthesized by using only DMF solvent shows the peak at the position of 1659 per cm of carbon double bond oxygen stretching also shows the peak of N-H stretching to confirm the presence of methylammonium ion. The FTIR spectrum of perovskite material synthesized by using DMF plus DMSO as solvent shows the additional peak ate 1059 per cm of S double bond O stretching. Also, the shift in the peak of MALI is shown due to the formation of the MALI-DMSO complex and this complex formation also leads to the stretching of N-H and Pb-I peaks. The addition of DMSO to the DMF solvent led to the formation of MAI-DMSO complex and PbI DMSO complex mainly due to hydrogen bonding among them which further led to the addition of peaks in FTIR spectra and stretching of already exiting peaks from their position, especially of N-H and Pb-I peaks. Films synthesized by using a mixture of solvents DMF plus DMSO show more pointed and spiky peaks which shows the presence of a higher degree of order or we can say crystallinity in these films. Those that are synthesized by using only DMF as solvent show more expended and broader peaks which shows the presence of less degree of order or less crystallinity and more defects in its structure. Heating the film at 80 degrees which is synthesized by using both DMF and DMSO solvent shows the improved film quality and phase purity as evidenced by XRD spectra.
Development of Conducting Filler Based Nanocomposites for Enhanced EMI Shielding Applications
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Taskeen Zafar; SP23-R06-024; Dr. Imran Hassan; LHR TP 9463
The increasing need for efficient, lightweight, and cost-effective electromagnetic interference (EMI) shielding materials has spurred significant research into polymer-based composites. This study presents the development of polyaniline-carbon fiber (PANI-CF) composites, enhanced with poly (3,4 ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), to achieve superior electrical conductivity and shielding performance. The composites were prepared via in-situ polymerization of aniline, incorporating varying concentrations of carbon fiber (2wt% ,5wt%), followed by PEDOT:PSS coating to improve conductivity. Characterization revealed significant improvements in structural, morphological, and functional properties of composites. Fourier transform infrared spectroscopy (FTIR) validated successful chemical interactions between the PANI matrix, CF, and PEDOT:PSS. X-ray diffraction (XRD) analysis confirmed the semi-crystalline structure of PANI and the graphitic nature of CF, with higher CF content enhancing crystallinity. Scanning electron microscopy (SEM) revealed uniform CF dispersion and the formation of smooth, continuous PEDOT:PSS coatings, mitigating filler agglomeration and enhancing electrical pathways. Thermogravimetric analysis (TGA) further highlighted the improved thermal stability, attributed to the dispersion of CF and PEDOT:PSS coating. Electrical measurements shows the shift from semiconducting to ohmic behavior in PANI CF composites, enhanced by filler content and PEDOT:PSS coating, improving charge transport and conductivity. Conductivity measurements demonstrated significant improvement, with the PANI-5%CF-PEDOT:PSS composite achieving the highest conductivity of ~0.012 S/cm. The optimized composites exhibited remarkable conducting properties making it an effective material for EMI shielding. These findings demonstrate the potential of PANI-CF-PEDOT:PSS composites as lightweight, corrosion-resistant, and thermally stable alternatives to conventional EMI shielding materials.
Enhancing the Flame Retardancy of Nitrile Butyl Rubber using Polyoxometalates Modified by Functionalized Halloysite Nanotubes
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2025) Faraz Noor; FA22-R06-024; Dr. Sadaf-UL-Hassan; LHR TP 9318
NBR is extensively used in various applications such as automotive, seals and gaskets, cable insulation and protective gloves etc. However, its high flammability limits its application in many fields. Nano-clays hold a significant position among the nano flame retardant filler in the domain of polymer composites due to high surface to volume ratio that required less amounts of nano-clay to obtain require properties. They possess a potential to increase the flame retardant, thermal durability as well as improve their mechanical strength of polymers. Halloysite nanotubes (HNTs) are naturally biodegradable flame retardant material. Halloysite nanotubes (HNTs) possess a nanotubular structure within the context of 1:1 clay. HNTs show inadequate dispersibility and weak interfacial interaction when integrated with polymers. To solve this problem, silane treatment was introduced which used 3 aminopropyltriethoxysilane (APTES), formed functionalized halloysites nanotubes (fHNTs) and subsequently utilized as a substrate to immobilize H4SiW12O40. The final nanofiller was prepared which confirmed by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Different rubber nanocomposites samples NBR-0 ,NBR-1, NBR-3, NBR-5, NBR -7, NBR 7HNTs, NBR-7POMs and NBR-10 were prepared by varying amount of nanofiller into NBR via melt blending in an internal mixer. The structural and morphological characteristics of these composites were analyzed by using SEM , FTIR , Raman spectroscopy and XRD. The mechanical property was characterized by using universal testing machine (UTM) and flame retardant property was evaluated by using UL-94, NBR-10 falls under the category of V-2 due char formation and gas particle which delay fire ignition phenomenon.
MXene Coated Carbon Cloth as Flexible Electrode in Supercapacitor Applications
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2025) Maryam Gull; FA22-R06-007; Dr. Sara Riaz; LHR TP 9311
Due to the rising need for energy brought on by industrialization and population increase, the globe is currently experiencing an energy crisis. Utilizing fossil fuels to meet this need results in environmental pollution and greenhouse gas emissions that fuel global warming. Though they are not reliable sources of electricity, the use of renewable energy sources including the sun, wind, and water has increased. As a result, the supercapacitor, an energy storage device, has become more well-known because of its long-life cycle, high cycling stability, and environmental safety. Compared to batteries, supercapacitors and flexible supercapacitors offer a significantly better power density. Flexible supercapacitors can be operated using the same fundamental ideas as conventional capacitors. Nonetheless, flexible supercapacitors surpass conventional capacitors in terms of capacitance due to their greater charge storage, remarkable flexibility, and reduced resistance. That’s why, an electrode material with exceptional cycle stability and enhanced power and energy density is fabricated. In present work, MXene modified with Yb-MOF. The prepared material was analyzed by XRD, FTIR, SEM, UV, and Raman spectroscopy. Electrochemical activity was investigated using GCD, EIS, and CV, covering the carbon cloth with the electrode active substance. The material that was successfully synthesized has high energy and power density, as well as outstanding cyclic stability, as demonstrated by results.
Powder Metallurgical Processing and Characterization of Biocompatible Zn-Mg-Cu Alloys for Pediatric Orthopedic Applications
(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2025) Sana Anwar; FA22-R06-022; Dr. Farasat Iqbal; LHR TP 9319
The search for resorbable metals with suitable mechanical strength for pediatric orthopedic use is still ongoing. Previous research indicates that although magnesium and iron possess favorable mechanical properties, their corrosion rate is not suitable for this particular application. Zinc alloys, on the other hand, have a suitable corrosion rate, making them a potential candidate for orthopedic applications. This study aims to develop zinc-based resorbable alloys using powder metallurgical processing and to analyze their properties using various techniques (hardness, SEM, corrosion, antibacterial assay, and cell studies). It was concluded that the addition of copper has alleviated the density and microhardness of the zinc alloys due to the small grain size. Analysis of antibacterial properties revealed that the increased release of copper and zinc ions resulted in enhanced antibacterial activity. Additionally, the biocompatibility was improved by diluting the extract from a 100% to a 10% solution.