http://lib.buet.ac.bd;localhosthttp://:8080/xmlui/handle/123456789/593 Post graduate dissertations (Theses) of Materials & Metallurgical Engineering (MME) 2026-06-02T17:32:50Z http://lib.buet.ac.bd;localhosthttp://:8080/xmlui/handle/123456789/7316 Evaluating interactions of second phases with chemical conversion coating on Mg-Zn-RE (Gd, Y) alloy for surface protection Mamun Al Rashed, Dr. Hossain Mohammad; Tasnuva Zahan Liza; 0423112008; 669.34/TAS/2025 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. 2025-05-27T00:00:00Z http://lib.buet.ac.bd;localhosthttp://:8080/xmlui/handle/123456789/7221 Investigation of the photocatalytic performance of Nd:Gd Co-doped CuO nanoparticles via hydrothermal route Muktadir Billah, Dr. Md.; Fatema-Tuz-Zahra; 0422112030; 669.0283/FAT/2025 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. 2025-03-24T00:00:00Z http://lib.buet.ac.bd;localhosthttp://:8080/xmlui/handle/123456789/7200 Structural, optical, and photocatalytic activity of Nd-Er co-doped CuO nanoparticles via hydrothermal route Muktadir Billah, Dr. Md.; Mehidi Hasan, Md.; 0422112029; 669.0283/MEH/2025 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. 2025-04-15T00:00:00Z http://lib.buet.ac.bd;localhosthttp://:8080/xmlui/handle/123456789/7168 Ballistic properties enhancement of jute, kevlar and glass fiber reinforced thermoset polymer hybrid composite Gulshan, Dr. Fahmida; Shakhawat, Hossain; 0421112514; 668.422/SHA/2024 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. 2024-08-01T00:00:00Z