Faculty of Engineering and Technology

Synthesis, Characterization and Application of Graphene Based Materials

Tue, 04 Aug 2026 00:00:00 GMT

Synthesis, Characterization and Application of Graphene Based Materials Hoque, Mohammad Amirul Graphene is being exponentially utilized across diverse research fields due to its extraordinary ability to enhance material properties with its miraculous attributes. Still, the material is expensive due to difficulties in the production of high-quality graphene. In this study, a few initiatives were approached to reduce the production costs of graphene with improved properties. At first, Tour's modified Hummer’s method was adopted to synthesize improved graphene with the feed acid liquor (FAL) recycling technique. About 90% of the FAL were recycled and reused five times as feed for successive production batches. Another focus was on the oxidation reaction to achieve graphene oxides (GOs) with higher oxygen to carbon ratios. The changes in recycled FAL and synthesized GOs properties due to repeated recycling were evaluated. The synthesized GOs were utilized for the removal of arsenic (As3+) ions from water, showing a qmax of 343.14 mg/g with 98.4% removal efficiency from 300 ppm to 22 ppm. The GOs were then reduced thermally at various temperatures in water, kerosene, and kerosene followed by ascorbic acid methods and times. The major objective of the reduction was to achieve maximum reduction of GO. The synthesized reduced graphene oxides (rGO) were evaluated for the antimicrobial properties. Although the Hummer’s method produces GO and rGO with improved properties, the method is difficult to carry out, very slow, and expensive. To obtain an easy and faster method for the production of graphene in bulk, a microwave assisted rapid exfoliation process of graphene exfoliation was examined along with the effect of variation of the intercalating agent ratio. All the products of FAL, GOs, rGOs, and microwave graphene (MG) were characterized using a Karl-Fischer moisture analyzer, IC, AAS, FT-IR (ATR), FT-Raman, UV-Visible Spectroscopy, PS-Zeta potential, XPS, XRD, STA, TGA, FE-SEM, and TEM analyzer. The FAL had increased moisture content with the successive recycling, but had no significant changes in properties and composition of GO. However, GO properties greatly changed with temperature and time of reaction, and the amount of oxidizing agent. The degree of reduction of GOs in N2 atmosphere at 193.4 oC was 95% of its initial mass, even at a slow rate of heating, but at this temperature, GO explosively degraded. In water medium as well as in kerosene, the explosive degradation can be omitted, and even at 220 oC, affording 40% reduction, which was mainly due to the removal of oxygen atoms as evident from the XPS analysis. The extremely reduced rGO contained an oxygen-to-carbon ratio of only 2.49% based on its initial oxygen content. In this study, XRD data also supported the composition of rGO and showed that it contained a homogeneous amorphous or viii nanocrystalline structure, as demonstrated by the 2θ = 24.91° peak in the (002) plane, which was shifted from the GO peak at 2θ = 12.86° in the (001) plane. The SEM image measured by ImageJ software showed that the obtained grain sizes were between 100 and 200 nm for both the GO and rGO. These rGO also showed strong activities against gram-positive and gram-negative bacteria, such as B. subtilis, S. aureus, E. coli, and S. typhi. In the case of MG, the degree of exfoliation was directly proportional to the intercalating agent ratios, and this method directly produces pristine graphene. This MG was highly thermo-stable up to 700-800 oC with high crystallinity, having 2θ = 26.56° at the (002) plane. The crystalline graphene showed excellent adsorption of acid blue-25 dyes with qmax 472.8 mg/g and 94.56% removal efficiency in the case of a 300-ppm dye solution. This thesis is submitted for the degree of Doctor of Philosophy

Superiority Enhancement of Geo-Jute by Chemical Modification Through Gamma Radiation

Mon, 03 Aug 2026 00:00:00 GMT

Superiority Enhancement of Geo-Jute by Chemical Modification Through Gamma Radiation Akter, Nasrin Natural fiber jute inherently possesses greater tensile strength (TS) than other natural fibers and offers numerous applications in geotechnical applications as a replacement for synthetic fibers. This research aims to enhance the physio-mechanical properties of jute fabric by improving its environmental durability. The study improves durability by chemically modifying materials using gamma radiation. Bitumen emulsion and unsaturated polyester resin were used for chemical modification. First, the jute fabric is treated with a chemical (polymer mixture), and a suitable formulation (30% BE + 10% UPR) is chosen based on durability tests. Then, the chemically treated jute fabric is irradiated with gamma radiation, selecting an appropriate dose (5 kGy) through durability testing. Finally, the pre-treated jute fabric is subjected to chemical treatment and gamma radiation, and its durability is assessed using an accelerated weathering tester. Pre-treatment was performed in two ways: (i) HEMA pre-treated, and (ii) benzoyl peroxide pre-treated. The HEMAtreated jute fabric showed better durability than the other treated sample. The tensile strength of HEMA-pre-treated samples was 50% higher than that of the raw jute fabric. At each step, samples were characterized by FT-IR, XRD, and TGA analyses, and their physico-mechanical properties were measured through tensile strength and water absorption tests. After chemical modification, the OH groups in the jute fabrics are reduced, decreasing hydrophilicity and increasing hydrophobicity, thereby enhancing the physico-mechanical properties. This research aims to strengthen these properties without making the fabric entirely plastic by breaking additional OH bonds. Pre-treatment generates free radicals from jute cellulose, and gamma radiation promotes their formation and cross-linking within the cellulose-polymer matrix. Cross-linking improves the fabric's physico-mechanical properties. Durability and physical tests show improvements in these properties. FTIR, XRD, and TGA analyses confirm the formation of free radicals and the crosslinking of jute cellulose with the polymer mixture. This research partially enhances the hydrophobicity of jute fabric. Gamma radiation not only boosts cross-linking but also reduces excess chemicals on the fabric surface, increasing porosity between yarns and making the fabric more biodegradable and eco-friendlier. An accelerated weathering test compares durability under artificial and outdoor conditions. In the lab, an accelerated weathering tester provides quicker results than outdoor exposure by controlling temperature, light, and water spray. Overall, durability testing using this method yields faster results than natural outdoor testing. Significant improvements in TS and durability testing were observed in the treated jute fabric compared to the 4 raw jute fabric. Whereas raw jute fabric deteriorates after 45 days, treated jute fabric showed enough tensile strength after 90 days. On the other hand, in the accelerated weathering durability test, after 28 days, the treated jute fabric showed significantly higher tensile strength and weight than the raw jute fabric. This thesis is submitted for the degree of Doctor of Philosophy.

Assessment of Radiological Doses and Emergency Planning Zones of the Rooppur Nuclear Power Plant

Sun, 19 Apr 2026 00:00:00 GMT

Assessment of Radiological Doses and Emergency Planning Zones of the Rooppur Nuclear Power Plant Faisal, Shafiqul Islam Bangladesh is introducing nuclear power to meet rising energy demands and reduce reliance on fossil fuels, with the Rooppur Nuclear Power Plant (NPP) commissioning two 1,200 MWe VVER- 1200 units in 2025 and 2026. While routine operations produce minimal radioactive releases, severe accidents, particularly long-term Station Blackout (LTSBO) events, can have significant radiological consequences, highlighting the need for robust emergency preparedness. Despite the use of advanced safety systems of housed VVER-1200 reactor, the adequacy of existing emergency planning zones (EPZ) and response measures at Rooppur NPP requires careful, site-specific evaluation to align with post-Fukushima IAEA safety requirements. Literature reviews point out research gaps, including limited analysis of beyond-design-basis accidents (BDBA), insufficient use of high-resolution atmospheric dispersion models, inadequate consideration of meteorological variability, lack of assessment of trans-boundary impacts, and the need for evidence-based EPZ design. This study introduces several methodological advancements in radiological dose assessment for the Rooppur NPP. It extends previous work by analyzing BDBA, particularly LTSBO scenarios initiated by external events, and by employing plant-specific source terms derived from MELCORbased SOARCA analyses. Radiological doses are evaluated across major exposure pathways while accounting for seasonal, diurnal, spatial variability using long-term (thirty-year), three-dimensional meteorological data and high-resolution atmospheric dispersion modeling. The study further applies post-Fukushima IAEA dosimetric criteria to reassess EPZs, evaluates the effectiveness of sheltering measures, and incorporates uncertainty analysis to ensure conservative and robust dose estimates. It uses modern accident consequence tools like Radiological Assessment System for Consequence Analysis (RASCAL 4.3), HotSpot 3.1.2, and Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) codes both in partial core melt (PCM) and complete core melt (CCM) under IAEA INES level 6 and 7 events. This also investigated the six LTSBO cases, both with and without passive safety systems like the Emergency Core Cooling System (ECCS), different leak rates and water uncovering times. Gaussian plume and puff models were used to simulate transport and dispersion of radioactive material for Monte Carlo randomly sampled yearly 360 possible weather scenarios considering the Rooppur region’s (Ishurdi) meteorological data. Results indicate that inhalation of I-131 dominates exposure near the plant immediately after release, while groundshine from deposited radionuclides, primarily Cs-137, becomes the main source over time. Meteorological conditions strongly affect dispersion: unstable conditions promote rapid dilution and shorter hazard distances, whereas stable conditions allow plumes to travel farther. Wet weather enhances deposition and groundshine, while dry conditions increase inhalation exposure. Deposition patterns peak close to the release point and are significantly higher during wet weather, with short-lived iodine and tellurium isotopes dominating early ground contamination. HotSpot predicts higher doses near the source but decreases faster with distance compared to RASCAL. In PCM scenarios, TEDE reached ~1,000 mSv, while CCM scenarios peaked at 11,000 mSv at 0.5 km, decreasing with smaller leaks or delayed containment failure. Simulations show that in the LTSBO event, sheltering-in-place or evacuation should be taken within 2 to 49 km of the Rooppur NPP reactor site based on criteria of TEDE 10 mSv for level 7, and within 0.7 to 14 km according to criteria of 100 mSv. Prophylactic measures to prevent radioiodine uptake by the thyroid may be necessary within a 3 to over 80 km radius for a threshold thyroid Committed Dose vii Equivalent (CDE) of 50 mSv, depending on weather and accident conditions. The sensitivity results indicate that predicted air concentrations and ground deposition can increase by approximately four to six times when using a finer concentration grid of 0.010° (≈1 km × 1 km) compared to a coarser grid of 0.050° (≈5 km × 5 km), underscoring the strong dependence of results on spatial resolution. Long-range plume dispersion analysis revealed potential trans-boundary impacts; during a dry month of January, the plume moved south and then north, reaching the Bay of Bengal, Myanmar, and beyond, with heavy fallout near Ishurdi. During a wet month of July, the fallout was confined to a zone within 10-12 km, with ground deposition reaching above 1005 Bq/m2, primarily impacting Northwestern Bangladesh and parts of Eastern India in the initial days. For 95% of the simulated weather scenarios, the maximum distance exceeding Precautionary Action Zone (PAZ) dose criteria was found to be approximately 3–4 km when sheltering in large buildings is available, increasing to 8–9 km when only residential houses are considered. Similarly, Urgent Protective Action Planning Zone (UPZ) criteria were exceeded at distances of about 20–25 km with large-building sheltering and 35–40 km with house-only sheltering. To balance public health protection with the practicality of emergency response, a PAZ radius of 5 km and a UPZ radius of 25 km are recommended for the Rooppur site. The analysis shows that taking shelter in large buildings can reduce radiation exposure much more effectively than staying in regular houses. Therefore, building large emergency shelters in nearby communities, especially in densely populated areas like Rooppur, Ishurdi, is recommended to improve public safety. Routine operation doses remain well below regulatory limits (<0.3% of the annual dose limit). Overall, the findings provide risk-informed guidance for emergency preparedness in Bangladesh, emphasizing sheltering, evacuation, iodine prophylaxis, strengthened infrastructure, and cross-border, weather-aware planning to ensure effective accident management and international safety compliance. This thesis is submitted for the degree of Doctor of Philosophy.

Non-metal Doped TiO2 Nanocomposites for the Removal of Nuclear Waste from Water

Tue, 03 Mar 2026 00:00:00 GMT

Non-metal Doped TiO2 Nanocomposites for the Removal of Nuclear Waste from Water Hassan, Md. Mehedi This study focuses on the synthesis and evaluation of non-metal doped titanium dioxide (TiO2) nanoparticles for the potential remediation of radionuclide-contaminated water. Undoped TiO2 and doped TiO2, e.g., B-doped TiO2 (B–TiO2), C-doped TiO2 (C–TiO2), N-doped TiO2 (N–TiO2) were successfully prepared by the sol-gel method. The resultant nanoparticles were thoroughly characterized by XRD, FESEM, EDX, TEM, FTIR, UV–Vis spectroscopy, DLS, zeta potential measurement, and AAS to study their structural, morphological, optical, and adsorption properties. Furthermore, batch adsorption and photocatalytic experiments using adsorbents were conducted to assess their efficiency in radionuclide removal. While attempting to extract radioactive isotopes from water, real radionuclides were not implemented due to safety, cost, and facility constraints. Instead, the nonradioactive analogs—cobalt, iodine, manganese, and zinc (which have similar radioisotopes, such as 60Co2+, 131I-, 54Mn2+, and 65Zn2+)—were employed, due to their similarity with the radioactive elements. XRD results revealed that both the doped and undoped TiO2 were crystalline anatase, and B-doping led to the formation of a small amount of the rutile phase. Both SEM and TEM images showed that the morphology and particle dimension were influenced by doping, with the smallest average particle size being reached for C–TiO2. The adsorption capacity was evaluated using iodine adsorption and the removal of metal ions. The C–TiO2 and N–TiO2 nanocomposites were found to show excellent adsorption properties among the doped samples, which may be due to a higher surface area and improved surface chemistry. The findings indicate that non-metal doping can enhance the photocatalytic and adsorption activity of TiO2. Thus, these materials are promising candidates for treating radioactive wastewater. This thesis is submitted for the degree of Master of Philosophy.