Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, Chemical EngineeringSubject: search.filters.subject.Nanoparticles

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Now showing 1 - 4 of 4
  • Master Thesis
    Influence of Ca2+ Ions on Freshly Precipitated Caco3 Particles
    (Izmir Institute of Technology, 2019) Majekodunmi, Olukayode Titus; Özdemir, Ekrem; Özdemir, Ekrem; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The objective of this study was to develop a method to synthesize CaCO3 nanoparticles from a chemical precipitation reaction under ambient and high supersaturation conditions. Equimolar CaCl2 and Na2CO3 solutions were reacted in a tubular reactor at a constant rate. The particles growth inhibition was attempted by dispersing the reaction mixture in a continuously stirred Ca(OH)2 solution. This procedure separated the nucleation phase from the growth inhibition process, and was conducted without pH and composition control. The possibility of impeding the CaCO3 particles overgrowth was explored at different precipitants and Ca(OH)2 concentrations. Their effects on the particles morphology, colloidal stability and specific surface area were studied. Although rapidlysettling particles were produced at precipitants concentration of 100 mM, colloidally stable CaCO3 nanoparticles were obtained at concentrations ≤75 mM. Additive Ca2+ ions, provided by the Ca(OH)2 solutions, inhibited the crystals growth by adsorbing irreversibly on the growth sites. The synthesized particles were as much as 95% smaller than those obtained when pure H2O was used instead. Ca2+ ions concentration and amount of precipitated particles were observed to be important factors for monodispersity and high growth inhibition. Monodisperse and stable nanoparticles were synthesized at low reactants concentration and/or precipitates volume. Vaterite phase was observed in the particles obtained when pure H2O was used as the growth-inhibiting solution. However, the presence of additive Ca2+ ions effected the crystallization of pure calcite, regardless of Ca(OH)2 or precipitants concentration, reaction mixtures retention time in the tubular reactor, volume of precipitates, and the growth-inhibiting solutions initial pH.
  • Master Thesis
    Production of Nano Caco3 in Bench Scale by Small Penetration Theory
    (Izmir Institute of Technology, 2013) Toprak, Görkem; Özdemir, Ekrem; Özdemir, Ekrem; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Calcium carbonate (CaCO3) has been used as filling material in various industries such as paint, paper, and polymeric materials. Using filling materials will enhance some of the physical properties of the composite material and decrease the product costs. Especially, the physical properties of the composite materials were enhanced significantly when the CaCO3 is used in nano sizes. CaCO3 can be produced from natural sources by crushing, grinding, and sieving processes, however, calcite obtained from the natural sources are usually in micron sizes and they are not in the desired quality and purity. Here, it was proposed that the dissolution rate of CO2 is the limiting step in CaCO3 crystallization and a small penetration method was developed for the limited dissolution of CO2 in the Ca(OH)2 solution. When Ca(OH)2 was added into the 10 mM CaCO3, zeta potential values of CaCO3 particles were increased from negative to positive value indicating that CaCO3 particles were stabilized in the presence of Ca(OH)2 solution. Rice-like CaCO3 particles were synthesized at the very early stage of crystallization. When crystallization progresses, the high energetic end sites started to dissolve, and the dissolution was progressed through the inside of the particles resulting in hollow calcite particles. BET surface area of hollow calcite particles was found to be 14.75 m2/g. Different parameters such as Ca(OH)2 flow rate, CO2 flow rate, Ca(OH)2 concentration, pipe diameter etc. were studied. Calcite particles in nano sizes, homogeneous size distribution, hollow shapes, and different morphologies were achieved to be produced.
  • Master Thesis
    Effect of Organo-Modified Clay Addition on Properties of Polyhydroxy Buttrate Homo and Copolymers Nanocomposite Films
    (Izmir Institute of Technology, 2012) Akın, Okan; Tıhmınlıoğlu, Funda; Tıhmınlıoğlu, Funda; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    As an alternative to conventional non-degradable food packaging plastics, bionanocomposites, based on bacterial biodegradable thermoplastic polyesters, poly(hydroxybuthyrate) (PHB) and poly(hydroxybutyrate-covalerate) (PHBHV) polymers incorporated with commercial organomodified monmorillonite (OMMT) were prepared by solution intercalation and melt-mixing techniques. The enhancements in barrier, mechanical, thermal, surface and optical properties of resulting nanocomposite films were evaluated as effected by OMMT concentration and preparation method. The degree of dispersion of layered silicates into polymer matrix was evaluated by X-Ray diffraction (XRD) analyses. The best level of dispersion was obtained in nanocomposites that contain 1%w/w of OMMT. However, intercalated structure was observed at higher amount of clay loaded composites. The fine delamination of OMMT in PHB and PHBHV matrix was found to be responsible for the improvements in water vapor barrier performance since more tortuous path formed for permeation of water vapor. Moreover, enhancement in mechanical and thermal properties was highly depending on the dispersion level of layered silicates which is in good accordance with structural analyses. Addition of 2%w/w of OMMT reduced the WVP of virgin films by 41.1%. Meanwhile, improvements were less significant at higher amount of clay loaded samples due to weak interaction between polymer and layered silicates. Moreover, significant improvements in mechanical properties including doubled tensile strength and 69% increase in strain at break were obtained for 2%w/w of OMMT incorporated PHB composites. In addition, significant enhancement in thermal stability, which is the major drawback of PHB films, was obtained in nanocomposites, decomposition temperature increased by 10 oC compared to pristine polymers. Moreover, addition of layered silicates into polymer matrix at low content resulted in increase in erosion rate which makes nanocomposites more eco-friendly promising alternative to conventional barrier packaging systems.
  • Master Thesis
    Synthesis of Silica Nano Particles With Custom-Made Morphology for Controlled Drug Delivery
    (Izmir Institute of Technology, 2012) Siretli, Çağrı; Polat, Mehmet; Polat, Mehmet; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The purpose was to have nanosized particles with low energy perimeters which function as non-reacting transporters for targeted delivery along with high energy sites inside the pores to achieve controlled release of specialized chemicals. Surfactants were used in combination with both base and acid catalyzed methods to achive desired structural properties and the characterization studies such as SEM, TEM, FTIR, BET surface area, pore size, size and zeta potential measurements were conducted. The effect of surfactants on mesoporous silica production changed depending on the type of methods. In the case of base catalysed method in alcohol, formation of stabilized emulsions with different sizes and their effect on the size and shape of silica particles was proposed. The effect of surfactants was attributed to their effect on a) the emulsification process and b) silica-silica and silica-surfactant interactions involved. In the case of base catalysed silica production in water, however, surfactant micelles were used as templates to produce pores. The effect of surfactant type and concentration was attributed to their effect on the CMC, micelle shape and size. Rod-like (~400 nm) at high and spherical (~200 nm) particles at low concentrations were synthesized. Here the surface area of ~1000 m2/g and average pore size of ~3 nm were obtained. Carbonization of these materials were performed to obtain nanosized silica particles with low energy perimeters successfully. Acid catalysed silica production in water was similar. Rod-like (600-800 nm) and cubic (800-1000 nm) nanoparticles were produced. These particles exhibited lower surface area of ~700 m2/g and larger pore size of ~5 nm.