Pusat Pengajian Kejuruteraan Bahan dan Sumber Mineral - Tesis
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- PublicationProperties of epoxy composite for solder mask application: effect of inorganic fillers and hyperbranched polyester polyol(2024-08-01)William, Lim Yung LingHigh packing density of electronic components in printed circuit boards (PCBs) inevitably raised the risk of thermo-mechanical damages during PCB assembly process. As solder mask (SM) is the PCB’s outermost layer, thermal and mechanical properties of SM become increasingly vital. This study aims to improve the properties of SM by investigating the addition of inorganic fillers, hyperbranched polyester polyol (HBP-OH) toughening agent and silane coupling agents. Firstly, commercial SM was characterized and the results were used as benchmarking for comparison. In this study, different types and loadings of fillers (talc, BaSO4, SiO2 and BN at 5 and 15 wt%), HBP-OH toughening agent (10-40 wt%) and silane coupling agent (APTES and GPTMS at 3, 5 and 10 wt%) were mixed with epoxy using ultrasonication method. The samples were characterized based on tensile and thermal properties as well as pull off strength. Results unveiled that the commercial SM consists of BaSO4 filler and epoxy acrylate. Among different filler types, 15 wt% SiO2-filled epoxy showed higher tensile strength and modulus, storage modulus and glass transition temperature (Tg) with improvement of 11.6%, 16.2%, 8.8% and 1.7 ˚ C, respectively, compared to neat epoxy. Inclusion of 20 wt% HBP-OH into 15 wt% SiO2/epoxy results in enhancements of elongation at break (EB) and thermal decomposition temperature (Td). Among silane-added composites, the addition of 5 wt% APTES showed the best tensile strength and modulus, EB, and pull off strength, increasing by 5.58 MPa, 0.98 GPa, 0.235%, and 43.4%, respectively, compared to untreated sample. Overall, 5 wt% APTES/20HBP-OH/15SiO2/epoxy composite is the most recommended composition for SM application due to their superior tensile properties and pull off strength.
- PublicationDevelopment of ZnO nanorods on supporting substrates for photocatalyst applications(2024-02)Siti Nor Qurratu Aini binti Abd AzizZinc Oxide (ZnO) nanorods based photocatalyst suffers from performance deterioration over time due to loss of ZnO nanorods in the particle form. In addition, a low cost and rapid synthesis technique is needed for mass production of ZnO nanorods particularly on supporting substrate. In this work, ZnO nanorods (particle and nanorods immobilisation on substrate) were successfully synthesized by solution precipitation technique and direct heating (DH), respectively. The results were confirmed by X-ray Diffraction Spectroscopy (XRD) and X-ray Photoelectron Spectroscopy (XPS) analysis. The small IUV/IVis ratio in Room Temperature Photoluminescence (RTPL) analyses indicate that the ZnO contained crystal defects such as oxygen interstitial, zinc vacancy or oxygen vacancy. The ZnO nanorods demonstrated photodegradation of RhB dye under exposure of UV irradiation, and selectively removal on Cu2+ ions and Ag+ ions. The photodegradation of Rhodamine-B (RhB) dye complied to 1st order kinetic reaction. The scavenger study indicated that OH● free radicals and O2●- free radicals were the dominant species that actively involved in the photodegradation of RhB dye. The ZnO particles demonstrated the highest photodegradation efficiency (PE%) (72%), but deteriorated in the cyclic test. ZnO nanorods immobilised on PET fibre demonstrated decrease in PE% was attributed to reduction of surface area as the ZnO nanorods were stacked on each other. The PE% of ZnO nanorods grown on kanthal wires/meshes were the lowest. This was because of smaller catalyst loading was used in the photocatalytic test. In term of its reusability, ZnO nanorods grown on kanthal wires/meshes were the best. The selection of polymeric flexible substrate or rigid substrate depends on the usage point in the wastewater treatment. Lastly, DH technique is successfully developed to synthesise ZnO nanorods in short duration (15 min), consuming low electrical power (≤0.060 kWh). It is a potential synthesis technique that can be upscale for larger substrate size and mass production of ZnO nanorods for the fabrication of wastewater treatment module.
- PublicationIntrinsic self-healable and recyclable rubbers based on ionic crosslinked network(2023-08-01)Mohd Hafiz Bin ZainolIn modern technologies, rubbers play a significant role to serve various main manufacturing industrial products, for instance vehicles tires, damping systems, wearable electronics, safety gears and many more. In order to fabricate a component which offers high toughness, great damping properties, chemical and thermal stability, rubbers need to be chemically crosslinked through vulcanization process. However, vulcanized rubber with permanent covalent crosslinked network cannot be reprocessed, reshaped or recycled. As a result, waste rubber products have become a serious threat towards ecological and environmental systems. This problem has driven towards emerging of a self-healing rubber technology which has the ability to restore the damage and can be recycled and reprocessed at the same time. The work carried out started with investigation of the potential of self-healing non polar natural rubber (NR) based on zinc thiolate ionic network. The Zn2+ is a potential metal ion candidate for formation of reversible ionic network, thus self-healing ability, recyclability and reprocessing ability would be achievable. In the next work stage, carboxylated nitrile butadiene rubber (XNBR) was chosen to investigate self-healing ability for polar rubber. The strategy is to generate massive Zn2+ salt bonding between zinc thiolate and COOH group on XNBR in order to create electrostatic interaction that allow thermo reversible ionic network. For NR, the samples achieved 100% self-recovery within 10 minutes at room temperature. Evidence for reversible metal thiolate ionic networks was provided by Fourier Transform Infra-Red (FTIR) and swelling density. Followed by mechanical performance assessment which include tensile test, tear strength, fatigue lifespan and creep behaviour. As for the recycled and reprocessed assessment, the vulcanised rubber was recycled and reprocessed for few times and the tensile test, scanning electron microscope (SEM) and welding test were evaluated. Interestingly the rubber was able to be reprocessed for three times and recovered its initial mechanical performance up to 60%. For XNBR, the sample achieved 97.87% self-recovery within 10 minutes at 150ºC. Evidence for thermo reversible ionic network was provided by FTIR and swelling density assessment. Followed by mechanical performance assessment which include tensile test, tear strength, fatigue lifespan and creep behaviour. As for recycle and reprocessing assessment, the results showed that XNBR were able to be reprocessed for three times with significant mechanical performance recovery up to 70%. From the work carried in this research, it was found that NR self-healing rubber enables more potential for final application as the healing occur at room temperature. For potential application stage, NR self-healing rubber was chosen as candidate material for puncture proof application. The self-healing natural rubber was able to recover the puncture spot ranging from 0.8 mm to 2 mm nail diameter at 100% recovery rate throughout pressure test, temperature test, repeatability test and stability test. Evidence for healed punctured spot was provided by SEM. Both self-healing NR and XNBR had exhibit significant performance on self-healing capabilities and mechanical properties. While on puncture-proof application, self-healing NR had shown a promising performance throughout all the test that has been conducted in this research.
- PublicationInvestigation of the resistive switching properties and mechanisms of polymannose based memory devices(2023-05-01)Ilias Ait TayebResistive random access memory technologies (ReRAM) are promising candidates for next-generation non-volatile memories owing to their simple device structure, low operational cost and power consumption and their compatibility with CMOS technologies. In addition, bio-organic materials are considered as prominent alternatives due to their biodegradability and benign environmental impacts. As such, the motivation behind this research is to determine the applicability of polymannose as a suitable bio-organic material for ReRAM applications utilizing a two-terminal structure. Polymannose thin-films were produced via drop casting a D-mannose powder and aqueous ethanol solution on ITO/PET substrate and dried at 160oC for different duration followed by Ag deposition as top electrode. Current–voltage (I–V) characterization was carried out and displays that resistive switching characteristics are achieved in the device when the precursor is dried between 4 - 7 h. The optimal drying time of 7 h provided optimal resistive switching characteristics, with a READ window of 2.2 V, high ON/OFF ratio of >105 at relatively low READ voltage of 0.01 V, acceptable endurance cycles of approximately 102, and a long retention time of >104 s. Further I-V analysis and HRTEM-EDS characterization reveal that high-resistance states (HRS) are governed by space charge limit current conduction resulting, while the low resistance states (LRS) are dominated by Ag metallic filaments. Furthermore, by modulating the compliance current, the polymannose successfully demonstrated twelve distinct and reliable LRS states at a READ voltage as low as -0.05 V. Moreover, the effect of fullerene (C60) on enhancing the performance of polymannose based ReRAMs has been studied. A memory device with Au-Pd/polymannose:C60/ITO/PET structure containing 5 vol% C60 has shown optimal ON/OFF ratio reaching ~105, a smaller read-memory window of 6.5 V and stable retention characteristics reaching 104 s. The electrical characteristics of the Au-Pd/polymannose:C60/ITO/PET shows a governing electronic conduction mechanism, and a model is proposed to explain the resistive switching mechanism for both device types. These results not only demonstrate the suitability of polymannose as a candidate bio-organic material for environmentally friendly high-density next generation non-volatile memories, but also show competitive performances that can potentially rival current materials used in ReRAM applications.
- PublicationThermoresponsive shape memory blend of polylactic acid/styrene-butadiene-styrene copolymer with fillers or crosslinker(2023-08-01)Fathin Hani Binti Azizul RahimShape memory polymers from biodegradable polymer blends have captured interest among researchers. However, there are some issues especially, related with responsive rate and repeatability that need to be considered. To solve the issue, a study of thermoresponsive shape memory polymer blend was prepared from the melt-blending of polylactic acid/styrene-butadiene-styrene copolymer (PLA/SBS) and morphology, thermal, shape memory, tensile, rheological and viscoelastic properties were evaluated. With the variation in the compositions, two-phase morphologies were observed due to the immiscibility of the blend. 70PLA/30SBS blend which possesses intermediate storage and loss moduli indicated optimum shape fixity ratio (Rf) and recovery ratio (Rr) with good tensile properties due to the formation of SBS droplets in the continuous PLA phase. In the second stage, 5 wt.% of erbium oxide (Er2O3), halloysite nanotube (HNT) and tungsten carbide (WC) was added separately into the binary blends of 70PLA/30SBS. 70PLA/30SBS-HNT has the highest tensile strength due to the reinforcing feature of the HNT but caused the reduction in Rf with the increasing immersion time. 70PLA/30SBS-Er2O3 showed an improvement in Rf and Rr possibly due to the spherical structure of Er2O3 and low viscosity that facilitates the chain movement during the deformation and recovery phase. The introduction of WC in 70PLA/30SBS blend led to high crystallinity and the optimum recovery time for Rr of 5 min. Meanwhile, the crosslinked 70PLA/30SBS blend was prepared by introducing different dicumyl peroxide (DCP) contents (i.e. 0.5, 1.0, 1.5 and 2.0 wt.%). The gel content and swelling density were measured to investigate the crosslinking density in the crosslinked 70PLA/30SBS blends. The presence of DCP led to high gel content value indicated the crosslinking reaction happened in the 70PLA/30SBS blends. The SBS droplet phase elongated in PLA domain as more DCP was added. The shape memory behavior was examined in three cycles. The Rf of the uncrosslinked blend increased with shape memory cycles. However, for crosslinked 70PLA/30SBS blend exhibited a reduction of Rr with test cycles. For this part, 70PLA/30SBS/1.5DCP blend is considered as the best system with optimum tensile properties, highest Rf value and intermediate Rr value. To summarize, thermoresponsive shape memory PLA/SBS blend properties were influenced significantly by the various composition, the presence of different fillers and the amount of crosslinker.