The Faculty of Engineering is located at the University's main campus and offers tuition and supervision to about 477 students at both undergraduate and postgraduate levels while conducting research in all fields covered by its departments. https://www.um.edu.mt/library/oar/handle/123456789/519 2026-04-10T21:31:37Z 2026-04-10T21:31:37Z https://www.um.edu.mt/library/oar/handle/123456789/145392 2026-04-08T06:23:33Z 2026-01-01T00:00:00Z

Title: Development of a PMMA/TiO2/LO nanocomposite for aquatic environments Abstract: Structures and vessels exposed to water are susceptible to corrosion and fouling due to multiple factors such as the complex biology present in these environments. Hence, it is important that new materials are investigated, combining durability and anti-fouling properties. To tackle this, the work in this project investigated a nanocomposite material, that consisted of a polymethyl methacrylate matrix and titanium dioxide nanoparticles encasing linseed oil as the dispersed phase. The development of the material and evaluation of its durability, anti-fouling properties and leaching of ions into the environment were the main objectives of this project. Samples were prepared using the doctor blade technique, applying a film containing 8.6, 14.8 and 28.3 wt% titanium dioxide nanoparticles on to glass substrates. To assess the durability of the material, salt-spray testing was conducted to simulate environmental conditions while leaching testing was carried out in deionised water. Prior to the salt-spray testing, the weight, wettability and surface roughness of the samples were assessed. These properties were also assessed just after the salt-spray testing and after two weeks. Optical microscopy was conducted to assess the self- healing capabilities of the material. The results showed that contact angle as well as the surface roughness of the nanocomposite increased with an increase in wt% of the nanoparticles. After salt-spray testing, the contact angle decreased while the surface roughness increased. This trend continued after the two weeks were allowed to assess any self-healing. It was noted that the nanocomposite was prone to degradation as well as showing significant adherence issues. Trends towards self-healing properties were noted within the 28.3 wt% samples that underwent both salt-spray testing as well as the leaching testing, but this was not conclusive. The liquid from leaching testing was extracted and analysed using inductively coupled plasma mass spectrometry. The leaching testing indicated that the 28.3 wt% samples leached less than 1 ng/mL of titanium ions. The anti-fouling tests conducted involved assessing the growth inhibition of the nanocomposite against both marine and freshwater algae. All the samples exhibited anti-fouling properties that were not significantly different to PMMA. They showed sufficient growth inhibition against the freshwater algae while being less effective against the marine algae, showing differing results for the latter. The material developed was not durable as would be necessary for the aquatic environment. However, the nanocomposite provided good anti-fouling properties while keeping Ti ion leaching into the environment below the threshold. Description: M.Sc.(Melit.)

2026-01-01T00:00:00Z Zakaria, Zunaida Rochman, Arif Refalo, Paul https://www.um.edu.mt/library/oar/handle/123456789/145343 2026-04-06T12:35:30Z 2026-01-01T00:00:00Z

Title: Crystallization behavior of recycled semi-crystalline polymers in 3D printing : progress, challenges, and opportunities Authors: Zakaria, Zunaida; Rochman, Arif; Refalo, Paul Abstract: In recent years, plastic recycling has emerged as a critical concern in environmental protection and waste management. Among the various techniques for repurposing plastic waste into valuable products, extrusion of filaments for 3D printing has proven to be a highly effective method. A thorough understanding of the crystallization behavior of recycled plastics used in 3D printing is essential, as it significantly influences their final performance. This review provides an in-depth analysis of the crystallization behavior and crystallinity of recycled semi-crystalline polymers, with particular emphasis on recycled commodity plastics such as recycled polyethylene terephthalate (rPET), recycled polypropylene (rPP), and recycled high-density polyethylene (rHDPE). Recent research published between 2015 and 2025 was systematically synthesized and provides information on sources of plastic waste, additives employed, and recycling processes involved, with the findings summarized in a table that highlights their effects on polymer crystallinity. Furthermore, the key factors impacting the crystallinity of 3D-printed recycled plastics were examined, including the influence of additives, multiple processing cycles, printing parameters, and thermal treatments. Research gaps and the challenges faced during the printing process were also identified and discussed. By consolidating recent findings, this review provides a comprehensive understanding of the crystallization behavior of recycled plastics in 3D printing, thereby providing guidance for future research and developing strategies to optimize the performance of these materials.

2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/145301 2026-04-02T10:02:39Z 2026-01-01T00:00:00Z

Title: Characterisation of hydrogen engine combustion and mitigation of knock in dual-fuel operations Abstract: Over the past decades, significant efforts have been focused on reducing fossil fuel dependency by promoting sustainable energy sources. Recently, major corporations have shifted their attention to H2 as a fuel for internal combustion engines, as the development of H2 fuel cells has not progressed as rapidly as expected. H2, with its higher calorific value and carbon-free molecular composition, offers a promising clean fuel alternative. However, the limited H2 infrastructure necessitates the continued development of dual-fuel combustion. This dissertation focuses on H2 combustion characterisation and improving the performance of existing dual-fuel engines by leveraging the thermodynamic properties of fuels. H2 combustion characterisation was performed utilising in-cylinder pressure measurements obtained through experimental testing. These in-cylinder pressure measurements were processed using LabVIEW software to analyse key combustion parameters such as the rate of heat release and combustion duration. These parameters were subsequently compared to those obtained from conventional fuels. Accurate determination of the air-fuel ratio during lean operation is critical. This was achieved through simultaneous and separate measurements of fuel and airflow rates. To address the pulsating airflow, a critical flow orifice was designed and incorporated into the setup based on choked flow theory, which depends solely on upstream conditions. The major highlight of this combustion characterisation investigation is the high brake thermal efficiency of 23% achieved by H2 under λ3 mixture, compared to the 21% obtained with stoichiometric petrol testing at wide open throttle. A cryogenic setup was developed specifically for liquid natural gas injection to enhance combustion and mitigate engine knock in dual-fuel engines. However, due to safety constraints, experimentation with liquid natural gas was substituted with injections of liquid nitrogen and liquid propane. This approach aims to reduce intake air temperatures, thereby mitigating engine knock. Temperature measurements during liquid nitrogen injection revealed a reduction of approximately 45 °C at a 60% substitution ratio with vapour propane. Liquid propane injection resulted in temperature reductions of 4 °C and 7 °C at 60% and 70% substitution ratios, respectively. Across all substitution ratios and intake conditions tested, the use of liquid dual-fuel injection consistently decreased the maximum amplitude of pressure oscillations, indicating improved knock resistance. Description: M.Sc.(Melit.)

2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/145300 2026-04-02T09:59:38Z 2026-01-01T00:00:00Z

Title: Development of embedded systems for a smart and sustainable industry 5.0 Abstract: Embedded electronic systems are at the heart of enabling and emerging digital technologies in Industry 4.0 and 5.0. The emergence of Industry 5.0 as a paradigm seeks to reframe industrial systems into a broader context to emphasise human-centricity, environmental sustainability and resilience. A review of literature reveals limited guidance on how the Industry 5.0 vision and its values are to be integrated into the design of embedded systems to uphold these three pillars. This work aims to support the implementation path of Industry 5.0 by adopting and implementing a suitable design methodology for embedded systems in Industry 5.0. To address this gap, the hypothesis presented is that the Value-Sensitive Design (VSD) methodology can provide a systematic means of guiding embedded systems development for Industry 5.0. Towards this hypothesis this work identifies and adopts the Value-Sensitive Design (VSD) methodology as a structured process to elicit, translate and implement the Industry 5.0 vision into embedded hardware design. In doing so, design values for embedded systems in Industry 5.0 are presented and a stakeholder analysis is performed. Combining literature with a Delphi study involving a panel of Industry 5.0 experts, fifteen key Industry 5.0 themes and fourteen design values for Industry 5.0 are defined. These values were the basis towards fifty-one design requirements for embedded systems design in Industry 5.0. These requirements are subsequently evaluated through a mixed-methods empirical study involving embedded systems engineers while additionally examining the challenges, implications and awareness around Industry 5.0. An embedded system prototype re-design is then carried out using the outcomes of the VSD process to propose tangible technical specifications. This re-design provides examples of implementing such specifications and their resulting trade-offs, which corroborate the feedback received by the group of embedded systems engineers which participated. The outcomes of the VSD process contributed to Industry 5.0 design values and hence technical specifications according to the paradigm’s objectives. This provides evidence in support of the proposed hypothesis and are a foundation towards additional comparative studies and in-depth technical and value evaluations. These will be constructive to the development of Industry 5.0 designer tools and recommendations to better prepare current and future embedded systems designers for the requirements of Industry 5.0. Description: M.Sc.(Melit.)

2026-01-01T00:00:00Z