Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
Browse
3 results
Search Results
Master Thesis Exploring the Electronic and Magnetic Characteristics of Lithiated Holey Mo8s12: a Study in Inorganic Chemistry(2023) Tan, Fırat; Büyükçakır, Onur; Şahin, HasanSince graphene, the ultra-thin carbon compound, gained popularity with its remarkable electrical capabilities, various two-dimensional (2D) van der Waals-type materials have come into focus. Investigation of the electrical and optical properties of materials at atomic scale is required to understand the unique electronic behavior brought on by quantum size effects. The development of optoelectronic devices with novel features is facilitated by an increased understanding of the properties of matter within the context of theoretical techniques. This thesis includes the investigation of the lithiated holey Mo8S12 structure through calculations based on density functional theory (DFT). Motivated by the recent experimental realization of holey structure of transition metal dichalcogenides (TMDs), in this thesis, the holey structure of Mo8S12 is investigated by means of DFT-based calculations. The geometry optimization and phonon band dispersion calculations show the structural and dynamical stability of free-standing holey single-layer Mo8S12. In addition, electronic band dispersions reveal the direct band gap semiconducting nature of the structure. In order to investigate the lithiation capacity of single-layer Mo8S12, effect of Li doping on the properties of Mo8S12 is analyzed by considering both one- and double-sided lithiation. As one surface of single-layer Mo8S12 is fully saturated with Li atoms, a dynamically stable half-metallic structure is formed. The corresponding electronic band structures reveals the metallic behavior of the two-side lithiated single-layer. Overall, tunable electronic properties of single-layer holey Mo8S12 via lithiation makes it suitable candidate for various nanoelectronic applications, such as memories, capacitors, gate insulators, energy storage, high-frequency modulation in communication devices.Master Thesis Recovery of Lithium From Aqueous System Using Manganese Oxide Adsorbent With Developed Electrospun Mat Substrate(01. Izmir Institute of Technology, 2023) Akgün, Berk; Ebil, Özgenç; Demir, Mustafa MuammerLithium is used in many fields due to its high energy density and unique electrochemical properties. Recently, there has been a strong increase in demand for lithium, so the extraction of lithium from natural water resources has become a remarkable research topic. One of the most effective methods of separating lithium from natural water sources is adsorption using lithium ion-sieve adsorbents. However, the powdered nature of the adsorbents makes them challenging to process and less recyclable. Recent studies have focused on developing adsorbents using different polymeric materials as substrates or binders. In the thesis, as a new approach, flexible and free-standing polyurethane electrospun mat substrates were produced and combined with λ-MnO2 to extract lithium from aqueous systems, and their lithium removal performance was investigated. After the fabricated mats and λ-MnO2 powder were characterized, the deposition process was performed, and filtration studies were carried out in synthetic lithium solution. Optimum conditions for lithium removal were found as an adsorbent amount of 200 mg, and 200 ppm initial [Li+], and pH 12. In addition, lithium removal performances have been improved by stacking mats and multi-stage filtration processes. Lithium removal reached 76.6% when a 400 ppm lithium solution and an 8-step filtration were used. Lithium removal experiments were performed with salt-lake brine containing high concentrations of various ions and showed that these ions reduced the lithium removal. In the study, PU electrospun mats for λ-MnO2 powder were found to be a promising substrate for lithium removal from aqueous systems.Master Thesis Functionalized Cellulose-Based Adsorbent for Lithium Recoveryfrom Aqueous Solutions(01. Izmir Institute of Technology, 2021) Nampeera, Jackline; Yüksel Özşen, AslıThis study focused on generation of low-cost yet highly effective lithium selective bio-sorbent from olive pruning waste mainly olive branches. Olive branches were treated with NaOH that eliminated non-cellulosic materials and activated hydroxyl groups that inhibit the formation of active sites. Olive branches were then functionalized through homogeneous phosphorylation at 150 ⁰C. POB, NOB, and FOB samples were subjected to SEM, XRD, FTIR, BET, XPS, and TGA to observe the changes in their structure and properties. Factors affecting lithium adsorption were investigated on the synthesized FOB in a batch system and analyzed by ICP-OES. Adsorption isotherms are well fitted to the Freundlich isotherm model than the Langmuir isotherm model which exhibited a maximum adsorption capacity of 6.7 mg/g at 30 ⁰C. Kinetic studies exhibited fast kinetics and equilibrium was attained in 6 minutes while thermodynamic studies showed an exothermic, spontaneous reaction and increased randomness at the interaction interface. Regeneration studies proved the sustainability of FOB with Li+ desorption efficiency of 99.6% in 1.0 M HCl. The synthesized FOB displayed a better degree of column utilization and elution efficiency; 56.8% and 95.8% than Lewatit TP 260; 16.0% and 50.4% respectively in the adsorption column studies performed at room temperature. However, it exhibited a poor breakthrough capacity of 2.1 mg Li/ml sorbent than Lewatit TP 260 with 1.33 mg Li/ml sorbent. Based on all experimental results, the novel functionalized olive branches (FOB) proved a potential lithium selective bio-sorbent and can be applied in the recovery of lithium from its aqueous sources.