Saudi Cultural Missions Theses & Dissertations
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Item Restricted NANOCARBON ORGANISATION UNDER FLOW IN THE VORTEX FLUIDIC DEVICE (VFD)(Saudi Digital Library, 2026) Alotaibi, Amjad Eid H; Colin, RastonThe development of tuneable carbon nanostructures has garnered considerable attention due to their advantageous chemical and physical properties, such as high electrical conductivity, robust mechanical strength, and favourable optical and thermal characteristics. A variety of fabrication strategies both top-down and bottom-up have been established to enable precise control over key parameters including size, shape, morphology, and surface functionality of the particles. These engineered nanomaterials have demonstrated broad applicability across numerous technological domains. Despite significant progress in their synthesis, several challenges remain. These include low production yields, reliance on chemical stabilisers, prolonged and complex processing protocols, elevated manufacturing costs, and the use of high molecular weight reagents. The challenges and constraints previously outlined may be effectively addressed through the implementation of thin film microfluidic technologies, which have recently exhibited notable progress particularly in the development of simplified, single-step methodologies for synthesising zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) nanomaterials. These innovations are pivotal in advancing sustainable and cost-effective manufacturing processes. Thin film microfluidics confer distinct advantages in chemical synthesis, including an elevated surface-to-volume ratio, reduced reaction durations, precise regulation of residence time and thermal conditions, improved operational safety, and most importantly the inherent potential to factor in scalability at the inception of the research. This dissertation aims to initiate a paradigm shift in nanoscience through the application of a thin-film microfluidic platform, the vortex fluidic device (VFD) to precisely control the fabrication of nanocarbon materials. The VFD has demonstrated versatility across a range of applications, including but not limited to: the transformation of zero-dimensional (0D) fullerenes into two-dimensional (2D) sheets; the exfoliation and v functionalisation of graphene sheets with nanodiamonds exhibit promising performance in electrochemical applications, particularly in the two-electron oxygen reduction reaction (2e-ORR); the unzipping of multiwalled carbon nanotubes under continuous flow conditions; and the controlled synthesis of composite nanocarbon structures from graphene oxide and fullerene C₇₀. Furthermore, the VFD has enabled the encapsulation and decoration of single-walled carbon nanotubes (SWCNTs) with 0D fullerenes, these fabricated nanocarbon composites are currently under investigation for their electrochemical applications. Notably, the high shear fluid dynamics within the VFD have been shown to induce chirality within flow of the liquids, contingent on the direction of tube rotation, with the process further influenced by the Earth's magnetic field. The primary advantage of the VFD lies in its capacity to fabricate nanomaterials without utilising toxic and harsh chemicals, employing straightforward one-step methods that exclude chemical stabilisers and surfactants, while also ensuring scalability of the processing.17 0Item Restricted The Interaction of Graphene/Graphene Oxide Surfaces and the Effect on Crystal Growth of Ammonium Nitrate(Saudi Digital Library, 2023) Alsalem, Yazeed; Vrcelj, RankoAmmonium Nitrate is an inorganic salt that is made from Nitric Acid and Ammonia. It is commonly used as an explosive in commercial applications such as mining, quarrying, and tunneling works. It could be used in the defence field as an oxidiser in rocket propellants. It is a cheap oxidiser and explosive, but it has many disadvantages compared to conventional alternatives; it is very hygroscopic, has low polymorphic stability, and poor ballistic performance. Graphene Oxide is one monomolecular layer of graphene that contains oxygen functional groups such as carboxyl and hydroxyl groups. It has many interesting properties such as being thermally stable and has promising electric and permeating properties due to its unique structure. It is used in water filtration membranes, biomedical applications, and electronics. Introducing Graphene Oxide (a material already used in composite propellants to improve burn rates and moisture blockage) to Ammonium Nitrate crystals may improve AN’s polymorphic properties such as phase stability and transition thresholds. This project aims to investigate the surface interactions between Graphene Oxide substrates at varying oxygen content and Ammonium Nitrate crystals. The crystals are grown using cooling and evaporation crystallisation techniques. Different analyses are performed including X-Ray Diffraction, Atomic Force Microscopy, and Sessile Drop studies to give a detailed study of the interactions between Graphene Oxide and Ammonium Nitrate. It was found that 15% Graphene Oxide provided a Two-way stabilizing effect for AN III and IV phases. While 25-30% Graphene Oxide portrayed a behavior that is like amorphous glass.15 0Item Restricted High-Performance Cotton Hydrogel-Based Flexible Supercapacitors Consisting of graphene(Saudi Digital Library, 2023-11-18) Badawi, Nujud Mohammed M; Subramaniam, Ramesh T; Kasi, Ramesh; Bhuyan, MrutunjayaThe effectiveness of the electrochemical process for supercapacitors has been enhanced by conductive cotton hydrogel with the incorporation of graphene and other ionic contents. The inherently soft nature of cotton mixed with hydrogel provides superior flexibility of the electrolyte, which benefits the devices in gaining high flexibility. Herein, it is reported the current research progress in the field of solid-state hydrogel electrolytes based on 3D pure cotton/graphene and present an overview of the future direction of the research. The ionic conductivity of CGH2 complex hydrogel significantly increased up to 13.9 x 10-3 S/cm at 25 °C due to the presence of graphene which provides a smooth path for the transport of charge carriers and polymer. Furthermore, electrochemical studies were performed by sandwiching the composite hydrogel electrolytes between symmetric cotton-coated graphene electrodes. The electrical conductivity of cotton with different concentrations of graphene was studied. Four-probe method was employed to examine the electrical characteristics of treated cotton electrodes, the graphene coated cotton samples with 17th layers resulted in a surface resistance of 0.644 Ω/sq and retained their maximum resistance even after two months. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis are crucial tools for examining the samples' thermal stability and material degradation pattern. TGA was used to evaluate the thermal stability of the pure cotton sample and the cotton that had been treated with graphene, and the mechanical properties of the composite cotton sample were evaluated by tensile strength test. The fabricated cotton-graphene electrode/ composite hydrogel electrolyte cotton- graphene electrode based symmetric supercapacitor attained the highest specific capacitance of 327 F/g at 3 mVs-1 which was measured by cyclic voltammetry measurement and from galvanostatic charge-discharge measurement, it is obtained a maximum value of 385.4 F/g at 100 mAg-1 current density. The instruments, namely X-ray diffractometer (XRD), Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, Field emission scanning electron microscope (FESEM) have been employed to study the properties of the electrodes and electrolyte, which showed good dispersion of electrode and hydrogel electrolytes samples obtained by dimethyl sulfoxide (DMSO) doping, which reduced the ripple of the cotton. The effectiveness of symmetric supercapacitors fabricated using composite hydrogel electrolytes has been confirmed by powering up a light- emitting diode (LED). Furthermore, the electrochemical analysis demonstrated that cotton- graphene-based hydrogel electrolyte is electrically stable and could be used for the design of next-generation supercapacitors.19 0Item Restricted Interface and structural engineering of perovskite solar cells towards enhanced stability and performance(Saudi Digital Library, 2023-11-22) Almalki, Masaud; Graetzel, Michaelشهدت خلايا البيروفسكايت الشمسية تطورا سريعًا خلال العقد الأخير، حيث حققت كفاءة تنافس بالفعل أكثر تقنيات الخلايا الشمسية تأسيسًا واستخداما. تتميزهذه الخلايا بسهولة المعالجة وتتمتع بخصائص الكتروضوئية ممتازة تجعلها متاحة للعديد من التطبيقات في مجال الخلايا الشمسية والإلكترونيات البصرية. ومع ذلك، يكمن ضعف خلايا البيروفسكايت في ضعف استقرار أداها لفترة طويلة الذي يلزم لجعلها منتجاً تجاريًا. في هذه الرسالة، كنت أعمل على تحسين الاستقرار مستهدفًا مكونات مختلفة من هيكل خلايا البيروفسكايت بما في ذلك طبقة امتصاص ضوء الشمس ونقطة إلتقاص البيروفسكايت والطبقة الحاملة للشحنات الموجبة النتجة (p-type) في طبقة البيروفسكايت. وأخيرًا، استكشاف مواد جديدة والطبقة الحاملة للشحنات الموجبة النتجة (p-type) تحمل الإمكانية لتكون أكثر استقراراً مقارنة بالمواد المستخدمة حاليًا مثل spiro-OMeTAD. في الفصل الثاني تمت دراسة نوع من البيروفيسكايت يسمى البيروفسكايت المتدرجة Layered perovskite باستخدام الفينيلين-1،4-ديميثيل أمونيوم (PDMA) وتم استكشاف تركيبها على المستوى الذري. تم فحص الاستقرار هذي المواد في بيئات ذات رطوبة عالية مظهرا استقرارية هذا النظام في هذه الظروف والحصول على فهم أعمق لهذا النظام. في الفصل الثالث تمت معالجة سطح طبقة البيروفيسكايت بإيثيل أمونيوم يوديد (DEAI) حيث تم تحسين أداء الخلية الشمسية بكفاءة بنسبة 23.3% مع تحسين استقرار الخلية تحت الظروف التشغيلية والحرارية. في الفصل الرابع تم استخدام الغرافين أكسيد المطعم بالفلزات القلوية كطبقة حامية للبيروفسكايت، مما أسفر عن تحسين كفاءة تحويل الطاقة إلى 23.4%. أظهرت الخلايا الشمسية استقرارًا ممتازًا تحت الظروف التشغيلية والحرارية. وأخيرًا، في الفصل الخامس، تمت دراسة مواد جديدة (p-type)، مما أظهر أداءًا واعدًا. تم إجراء فحص شامل لخصائصها الإلكترونية والالكتروضوئية لتحديد العوامل الرئيسية المساهمة في فقدان الكفاءة، والتي تم العثور على أنها مرتبطة بتحسين نقطة التقاء سطح البيروفيسكايت مع طبقة (p-type) بدلاً من الخصائص الجوهرية لمواد (p-type)، أنفسها. يقدم هذا الفصل استراتيجية تحسين لهذه المواد الجديدة، مبرزًا إمكانياتها كبدائل لمواد (p-type) الحالية التي تمتاز بالفعالية العالية.33 0Item Restricted Growth of Graphene and MoS2 by Chemical Vapour Deposition(Saudi Digital Library, 2023-10-12) Alsulami, Taghreed Sulaiman; Hunt, MichaelThe growth of two-dimensional materials by low-cost atmospheric pressure chemical vapour deposition (AP-CVD) is explored in this thesis, with an emphasis on understanding key features of the growth process. In particular, the growth of graphene on copper foils using a methane precursor, MoS2 on natively oxidised silicon and MoS2 on graphene, graphite and graphene ‘paper’ were studied. The resulting few-layer, monolayer and sub-monolayer films were characterised by a combination of Raman spectroscopy (RS), Scanning Electron Microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Through varying the methane flow rate it was found that there is no self-limitation to graphene growth at high methane concentrations, resulting in graphene multilayers that can delaminate from the copper substrate. The effect of a number of surface pre-treatments on graphene growth is also presented. Nitric acid etching of copper foil was found to produce a superior growth surface in comparison with those prepared with acetic acid or electropolishing, evidenced by a reduction in nucleation density and increased island size. Raman spectra showed a remarkable correlation with these observations, indicating increased hole doping with improved sample treatment. Therefore, Raman spectroscopy may be used as a probe for the effectiveness of surface preparation. Several different approaches to the growth of MoS2 on natively oxidised silicon by AP-CVD using S and MoO3 precursors are presented. It was found that the growth of MoS2 was strongly dependent on the timing with which a sufficient sulphur flux is introduced into the growth region. These results led to an investigation into the influence of sulphur partial vapour pressure on MoS2 growth. It was found that MoS2 coverage decreased with increasing sulphur vapour pressure. These results could be successfully rationalised by the Langmuir-Hinshelwood model of growth kinetics, which is usually applied to reactions on well-defined crystalline surfaces and had not previously been considered for MoS2 growth. XPS was used to study the composition of AP-CVD grown MoS2 as a function of sulphur evaporation temperature and provided clear evidence that lower sulphur vapour pressure leads to an increased concentration of sulphur vacancy defects. Attempts were made to grow MoS2 directly on highly oriented pyrolytic graphite as a model substrate. MoS2 was found to grow on graphite under similar conditions to those for natively oxidised silicon, but nucleation was observed to occur primarily at defect (step) sites. Attempts to grow MoS2 directly on graphene CVD grown on copper, commercially sourced graphene powder, and graphene paper are also reported.49 0