Dissertations/Theses - Department of Materials & Metallurgical Engineering

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    Evaluating interactions of second phases with chemical conversion coating on Mg-Zn-RE (Gd, Y) alloy for surface protection
    (Department of Materials and Metallurgical Engineering (MME), BUET, 2025-05-27) Tasnuva Zahan Liza; Mamun Al Rashed, Dr. Hossain Mohammad
    Magnesium alloys are highly suitable for lightweight manufacturing and applications due to their impressive mechanical properties and high strength-to-weight ratio. However, their vulnerability to corrosion restricts their practical applications. Using a chemical conversion process, a calcium-phosphate-vanadium (Ca-P-V) composite coating was fabricated on Mg-Zn-RE (Gd, Y) alloy effectively in this research. SEM and EDX analysis of the base alloy and coated sample were carried out, and the coated surface showed different phases from different concentrations of vanadium. XRD analysis of the base alloy and coated samples were carried out, phases and crystal structure were determined. XPS analysis was performed to evaluate the interaction of coating materials on the surface of the sample and their binding energies. Ca3(PO4)2, CaCO3, and MgCO3, made up the majority of the composite coating which had a limited number of hydroxides of V(V) distributed into it. Electrochemical tests were also conducted to determine how the concentration of vanadium affected the substrate's ability to resist corrosion. Both electrochemical tests and scratch immersion tests in a 3.5 wt % NaCl solution were utilized to examine the corrosion behavior of the conversion coating. The findings demonstrated that the coated samples could self-heal in addition to having superior corrosion resistance. A unique composite layer was formed on the scratched area as a result of the Ca, P, and V ions that are liberated from the coated surface migrating in the corrosion solution. Moreover, another Mg alloy sample with different alloying percentages was coated and characterized to evaluate and compare the interaction of second phases of base alloy and coated sample.
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    Investigation of the photocatalytic performance of Nd:Gd Co-doped CuO nanoparticles via hydrothermal route
    (Department of Materials and Metallurgical Engineering (MME), BUET, 2025-03-24) Fatema-Tuz-Zahra; Muktadir Billah, Dr. Md.
    Copper oxide (CuO) is a fascinating p-type semiconductor with a narrow band gap ranging from 1.2 to 2 eV, and it crystallizes in a monoclinic structure. What makes CuO especially exciting is its non-toxic nature, stability, and the fact that it is insoluble in most organic solvents—qualities that open the door to a wide range of applications. Scientists are actively exploring its potential in energy storage, photodetectors, batteries, supercapacitors, gas sensors, biosensors, nanofluids, and photocatalysis. In recent times, enhancing the optical, electrical, magnetic, and photocatalytic properties of CuO structures by doping with rare earth metals (RE) has undergone noteworthy breakthroughs. The unique properties of rare earth elements, such as gadolinium (Gd), lanthanum (La), europium (Eu), and neodymium (Nd) render them extremely useful for many advanced applications. Considering the potential of RE elements, the specific aim of this study is to examine the impact on photocatalytic performance of undoped and Neodymium: Gadolinium (Nd:Gd) co-doped CuO nanoparticles. A set of copper oxide structures doped with different amounts of gadolinium (1, 2, and 3 mol %) and an optimal amount of neodymium (2 mol %) were synthesized using a simple hydrothermal method. The characteristics of the produced Nd:Gd co-doped CuO catalyst were investigated utilizing a range of characterization techniques. The study showed successful incorporation of Nd3+ and Gd3+ ions into the CuO structure as confirmed by the XRD and XPS analysis. The optical bandgap of the nanoparticles was determined using UV-vis spectroscopy, which demonstrates an increase in bandgap with the incorporation of Gd with 2 mol% Nd into CuO due to the presence of Gd2O3 secondary phases. To evaluate the photocatalytic efficiency, rhodamine B (RhB), an organic pollutant, was used under UV radiation. Among the various nanoparticles produced, the one with 2 mol% Nd and 3 mol% Gd demonstrated the highest photocatalytic degradation efficiency of RhB (around 85%) within just 120 minutes of exposure to UV light. The improved opto-structural and photocatalytic properties of the Nd:Gd co-doped CuO nanoparticles render them as valuable candidates for a wide range of applications, from solar cells and photocatalysts to supercapacitors, photonics, spintronics, and beyond.
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    Structural, optical, and photocatalytic activity of Nd-Er co-doped CuO nanoparticles via hydrothermal route
    (Department of Materials and Metallurgical Engineering (MME), BUET, 2025-04-15) Mehidi Hasan, Md.; Muktadir Billah, Dr. Md.
    Copper oxide (CuO) is a widely studied p-type semiconductor due to its narrow bandgap (1.2-1.8 eV), earth abundance, non-toxicity, and stability, making it a strong candidate for various technological applications, including photocatalysis, photovoltaics, sensors, and energy storage devices. However, despite its promising properties, the photocatalytic efficiency of CuO remains limited due to rapid charge carrier recombination. To overcome this challenge, researchers have extensively explored doping strategies, particularly with rare earth (RE) elements, to enhance the optical, electronic, and structural properties of CuO. This study examined the structural, optical, and photocatalytic properties of undoped and neodymium (Nd) and erbium (Er) co-doped CuO nanoparticles produced via a hydrothermal method. The influence of Nd and Er doping on CuO was systematically analyzed using various characterization techniques. X-ray diffraction (XRD) confirmed the successful incorporation of Nd³⁺ and Er³⁺ ions into the CuO lattice for higher co-doping percentages (2-3% Er and 2% Nd)) whereas secondary phases occur for lower co-doping percentage (1% Er and 2% Nd), leading to lattice distortions that modify its structural properties. X-ray Photoelectron Spectroscopy (XPS) verified the oxidation states of Cu2+, Nd3+, and Er3+, ensuring their proper integration into the CuO matrix. Optical studies using UV-vis spectroscopy showed that co-doping resulted in overall bandgap reduction, improving light absorption and charge separation efficiency. For the photocatalytic performance of the synthesized nanoparticles, Rhodamine B (RhB) dye degradation under UV irradiation was conducted. The results demonstrated that co-doped CuO nanoparticles exhibited significantly higher photocatalytic activity compared to both undoped and Nd-doped CuO. Among the tested samples, the one with 3 mol% Er and 2 mol% Nd achieved the highest degradation efficiency of 87% within 180 minutes. This significant improvement is due to the combined effect of Nd and Er ions, which improve charge separation, and inhibit recombination. The insights from this study will pave the way for further exploration of RE-doped CuO nanostructures in advanced applications, including solar energy conversion, wastewater treatment, and next-generation optoelectronic devices.
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    Ballistic properties enhancement of jute, kevlar and glass fiber reinforced thermoset polymer hybrid composite
    (Department of Materials and Metallurgical Engineering (MME), BUET, 2024-08) Shakhawat, Hossain; Gulshan, Dr. Fahmida
    In the last few years, natural fiber-reinforced composites have attracted the attention of materials scientists worldwide. These composites have low cost, are lightweight, are readily available, and are biodegradable. In addition, these composites have low density and high specific strength and are the most suitable candidates for low load-bearing applications. Researchers hybridize the composite with high tensile strength fiber, which can be used against high-velocity impact and in high load-bearing applications. This research used Kevlar, jute, and glass fiber with epoxy matrix for better performance, focusing on designing ballistic composite. This hybrid ballistic composite was used to defend high-impact energy projectiles. The ballistic composite is fabricated to reduce fragment penetration when dispersing bullets. This study aimed to see how epoxy matrix composites reinforced with natural jute fibers performed as a stand-alone target against high-energy munitions. To develop hybrid composites, jute fabrics must be laminated with Kevlar and plain glass cloth before being combined with epoxy. Press molding has been applied to fabricate the composite. In this research work, raw jute, scoured jute, bleached jute, jute composite, jute-glass composite, jute-Kevlar composite, and jute-glass-Kevlar composite were characterized by FTIR. The tensile, flexural, and impact properties of the four composites are found through the tensile, flexural, and impact tests. The high-velocity impact properties are found by conducting a ballistic test. The water absorption test was done for jute and different composites in normal, distilled, and saltwater for 24 hours. Fracture surface morphology and fraction nature were observed using a Field Emission Scanning Electron Microscope. The volume fraction's impact on the primary failure mechanism and tensile behavior was investigated to derive the ballistic parameter. The collected results were evaluated using statistical techniques. The depth of penetration induced by the bullet in a clay witness block representing a human body is used to assess ballistic performance according to international standards. The results have demonstrated that jute fiber and aramid fiber mixed hybrid composites absorb high-velocity impact, and jute fiber acts like brittle components like glass fiber, which helps to diminish the initial trauma of bullet impact.
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    Experimental study of microstructure and degradation properties of magnesium-zinc-neodymium-yttrium bioresorbable alloys
    (Department of Materials and Metallurgical Engineering (MME), BUET, 2024-09-09) Snigdha, Nusrat Jahan; Gulshan, Dr. Fahmida
    The aim of this study was development of Mg-Zn-Nd-Y alloy for biomedical applications and to identify the effect of yttrium (Y) addition on the phase development and mechanical and corrosion behavior of the alloys in as-cast, rolled, and extruded conditions. The result showed that Mg-2Zn-1Nd alloy consists of α-Mg, Mg41Nd5, and some eutectic phases. The addition of a small amount (0.5 wt.%) of Y in the alloy led to the formation of the icosahedral quasi-crystalline I (Mg3YZn6) phase, and further addition of Y (1.0wt%) led to the formation of W-phase (Mg3Y2Zn3). The Y addition significantly refined grains in the extruded state with the grain size of 17μm when Y content is 1%. The precipitates were more fragmented in extrusion than in the rolling state. The secondary dendritic arm spacing was more refined in the as-cast state as a function of Y addition. The presence of the I-phase in the alloy with 0.5wt% Y increased hardness than the alloy containing 1wt% Y due to the formation of the W phase. The maximum hardness achieved is 78.15Hv in extruded state when the Y content is 0.5%. the refined grain structures with higher volume fraction of grain boundaries, act as barriers to dislocation motion increasing the material's hardness in extruded sample than the rolled one. The weight loss corrosion was performed for the corrosion rate calculation and the alloy with the I phase had the lowest corrosion rate, whereas the W phase containing alloy showed a moderate corrosion rate, and the alloy without Y content had the most corrosion rate. The extruded state exhibited the best corrosion resistance with the corrosion rate of 0.392mm/a when Y is 0.5% than the rolled and the as-cast state due to more grain refinement, and fragmentation of the second phases. The corrosion electrochemistry also ensured the corrosion resistance behavior of the extruded alloy.
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    Structural, optical and magnetic properties of rare-earth (Nd) element doped CuO nanoparticles
    (Department of Materials and Metallurgical Engineering (MME), BUET, 2024-06-26) Mim, Samiya Rahman; Billah, Dr. Md. Muktadir
    The study mainly focused on synthesizing CuO nanoparticles (NPs) and doping these NPs with rare earth element Neodymium (Nd) dopant at various concentrations following chemical co-precipitation method. The purpose of this study was to incorporate Nd dopant into CuO lattice and tune its bandgap, affect its morphology as well as introduce ferromagnetic behavior in the lattice for sensor, solar cell, photovoltaic, magnetic storage devices, high performance motor etc. applications. In this thesis, chemical co-precipitation method was used to synthesize CuO and rare earth element Neodymium (Nd) doped CuO NPs. To investigate structural, morphological, optical and magnetic properties of CuO and doped CuO NPs, XRD analysis, FESEM, UV-Vis spectroscopy and VSM were used respectively. From XRD analysis, incorporation of Nd dopant into CuO lattice was verified. FESEM images illustrated that particle shape changed from spherical shaped particles for CuO to agglomerated particles to again homogenously distributed nanospheres by doping CuO with Nd. Indirect band gap values were calculated using Tauc plot and the values reduced from 1.36 eV for CuO to 1.29 eV for 3 mol.% Nd and then increased to 1.31 eV for 5 mol.% Nd doped CuO NPs. It was observed that magnetic hysteresis loop was introduced in Nd doped CuO NPs that demonstrated ferromagnetic properties. Nd dopant resulted in ferromagnetic properties in paramagnetic CuO NPs. Rare earth element Nd doping generates ferromagnetic property in 0.5 mol%, 1 mol%, 3 mol% and 5 mol% Nd doped CuO NPs where, from M-H diagram, extracted values of coercivity (Hc) increased from 258.35 Oe to 741.46 Oe, remanent magnetization (Mr) increased from 7.29 emu/g to 9.956 emu/g and saturation magnetization (Ms) values decreased from 0.1224 emu/g to 0.0948 emu/g.
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    Investigating the Mg-Zn-RE(Y,Gd) alloys as potential biodegradable implant materials
    (Department of Materials and Metallurgical Engineering (MME), BUET, 2024-07-30) Al Amin, Syed Muhammad; Gulshan, Dr. Fahmida
    Mg alloys have recently attracted interest as biodegradable implant materials due to their biocompatibility and suitable mechanical properties. However, their rapid degradation rate re- quires further tailoring through alloying additions and thermomechanical processing. This work investigates the effects of Gd (0,1,2 wt.%) alloying and post-casting rolling and extrusion on the microstructure, mechanical performance, and corrosion of Mg-2Zn-0.5Y (wt.%) alloys. XRD and microscopy analysis revealed that the cast alloys consist of α-Mg and Mg3Zn6Y (I-phase), while Gd additions promote the formation of W Phase (Mg3Zn3Gd2) secondary phases. The presence of the W phase induces significant grain refinement down to an average grain size of 204.67 µm from 265.56 µm in Gd-free alloys. Furthermore, severe plastic deformation and dynamic recrystallization during rolling and extrusion lead to a more refined grain structure compared to the cast condition. Hardness increases with Gd content and with the rolling and extrusion process, resulting from precipitation strengthening and additional Hall-Petch strengthening enabled by extensive grain refinement. However, the corrosion rate increases in Gd-containing alloys due to an increase in surface roughness, as determined by AFM studies and galvanic coupling between W-phase particles and the Mg matrix. Weight loss testing shows that the corrosion rate increases in Gd added alloys relative to the Gd-free alloy. In contrast, rolling and extrusion disrupt galvanic effects and improve surface protection, reducing corrosion rate compared to as-cast alloys on average across compositions. These insights on synergies among composition, microstructure, and thermomechanical processing advance knowledge for designing biodegradable Mg implants with tailored degradation.
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    Thermodynamic analysis for incorporation of electric arc furnace slag in ceramic tiles and experimental validation
    (Department of Materials and Metallurgical Engineering (MME), BUET, 2024-06-24) Sadakat Sharif, Shekh; Gulshan, Dr. Fahmida
    The disposal of electric arc furnace (EAF) slag is often problematic, with most of it ending up being landfilled rather than recycled. Incorporating EAF slag into the typical clay-feldspar-quartz system to produce useful ceramic tiles offers a potential and environmentally safer option. Thermodynamics package FactSage 8.2 was employed to predict the equilibrium-products of sintering process of EAF slag mixtures at different temperatures ranging from 600-1600°C. Subsequent ceramic products were fabricated at a temperature of 1150°C following the thermodynamic analysis by considering the fraction of liquid formation and the viscosity of the system. With the addition of EAF slag to the base body, new chemical phases such as anorthite, clinopyroxene and andradite were formulated, which have a positive impact on the ceramic. These products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses and compared to the thermodynamic predictions. The physical performance of the products was also examined by evaluating the shrinkage, water absorption, apparent porosity, bulk density and modulus of rupture (MOR). When EAF slag was added to the base mixture, there was a positive trend of improvement in the physical properties and specifically, MOR peak value of 37.56 MPa was obtained when 40% EAF slag was added. However, the MOR value as well as other physical properties started to decline when the base mixture had more than 40% EAF slag. Conclusively, incorporating 40% EAF slag improved the final product and correlated with the thermodynamic studies, process parameters and experimental assessments of the ceramic tiles.
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    Preparation and characterization of molybdenum disulfide (mos2) thin films on flexible substrates
    (Department of Materials and Metallurgical Engineering (MME), BUET, 2024-02-13) Kanon, Kamruzzaman; Sharif, Dr. Ahmed
    The production of stable thin films on flexible substrates is a fundamental prerequisite for producing flexible electronic devices. In this work, our primary objective was to synthesize stable MoS2 thin films on flexible Polyethylene Terephthalate (PET), Polyethylene (PE), Polyvinyl Chloride (PVC) substrates by the Liquid Phase Exfoliation (LPE) method. We sought to comprehend how these substrates influenced crucial film characteristics, encompassing topography, morphology, optical transmission, and film resistance. Additionally, we explored the impact of mechanical stress on the electrical behavior of these films. Our investigation uncovered significant variations in these critical aspects. The MoS2 film on the PE substrate exhibited the smoothest surface, while the MoS2 film on the PP substrate had a smaller estimated average grain area. MoS2 films on all the substrates demonstrated high film resistance, with the MoS2 film on PE displaying the lowest resistance at minimal applied current. Furthermore, the resistance of all films increased with repeated bending. These essential insights are crucial for the development of flexible electronic devices based on MoS2 thin films. These important findings has high potential to pave the way for the production of cost-effective and efficient MoS2 thin films as well as diverse applications of these films in the realm of flexible electronics.
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    EFFECT OF JUTE TYPE AND DIMENSION ON PROPERTIES OF JUTE REINFORCED HDPE COMPOSITES
    (Department of Materials and Metallurgical Engineering (MME), BUET, 2024-06-01) Jahan, Fatema Nusrat; Hasan, Dr. Mahbub
    Jute ranks as the second most significant vegetable fiber due to its adaptability. Natural fiber composites with high performance will be a key focus of the world's industrialization market. This research was undertaken to make composites from various types of jute fiber by changing their cutting length with high density polyethylene (HDPE) as the matrix to assess their suitability for agricultural and household applications. In each case, three different types of jute fiber Tossa-8 (Robi 1), Bangla Tossa (grade B) and Bangla Tossa (grade C) used to fabricate composites. For all the samples, the fiber weight percentage was fixed at 15 % and the hot press method was followed at 140°C to 160°C. The plate for making samples in the hot press machine was about 6”x6”. Jute fiber was cut into 6 inches, 2.5 inches and whisker forms to fit as the discontinuous or dispersed phase in the HDPE matrix. Mechanical characterization of raw jute fiber was conducted using the Digital Fineness Analysis system and a Stelometer. Structural analysis of fabricated composite samples was done using SEM and FTIR. Mechanical properties were identified through the hardness tester, impact strength tester and UTM machine. For analyzing the thermal stability of the samples, TGA and DSC parameters were taken into consideration. In this study, the average fiber bundle strength was good for Robi 1, at around 50.14 gm/tex. Meanwhile, by the concept of the airflow method, the fineness of Bangla Tossa grade C (BTGC) was the highest and was 49.02 µm. A composite with BTGB of 2.5 inches showed the highest hardness. However, Robi 1 resulted in relatively higher tensile strength, whereas BTGC showed highest tensile modulus. The broken surfaces of the composites were also assessed by SEM to identify better interfacial bonding as evidence. In all cases, Robi 1 and BTGB of 2.5 inches showed good flexural strength and modulus; it were 45 MPa and 6000 MPa respectively. All the longer fibers of 6 inches imparted the best thermal stability. Overall, BTGB of 2.5 inches showed the best result. From this research, characterization of the developed composite demonstrates that, the Robi 1 of 6 inch composite can be a sustainable and practical alternative for seedling trays in the agriculture and horticulture sectors. Also, BTGB fiber of 2.5 inches can be proposed for manufacturing chopping boards. This will open many new ways for promising applications in the composite industry.