Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 1Citation - Scopus: 1Inhibition of Caco3 Growth and Synthesis of Submicron Particles by Preferential Adsorption of Additive Ca2+ Ions on Fresh Precipitates(Royal Society of Chemistry, 2022) Majekodunmi, Olukayode T.; Kılıç Özdemir, Sevgi; Özdemir, EkremThis study demonstrates a method to inhibit the growth of CaCO3 and synthesize submicron particles in a chemical precipitation process under ambient and high supersaturation conditions. Equimolar CaCl2 and Na2CO3 solutions were mixed in a model tubular reactor at a constant flow rate, and the precipitates were continuously dispersed in stirred 250 mL of 10 mM Ca(OH)2 solution. This approach resulted in the synthesis of colloidally stable submicron CaCO3 particles for a precipitant concentration ≤75 mM. Varying the precipitates’ retention time in the tubular reactor had no significant effects on the particle size and colloidal stability. Time-dependent changes in the mean size, crystal form, morphology and specific surface area of the synthesized particles were also studied. For a precipitant concentration of 75 mM, the particles were monodispersed and porous spindle-like scalenohedral crystals which gradually grew in all faces as more precipitates were fed into the Ca(OH)2 solution. The mean hydrodynamic size of the particles was ∼850 nm at the 8th minute. However, in the absence of additive Ca2+ ions, the particles obtained at the 8th minute were polydisperse mixtures of vaterite and rhombohedral calcite particles greater than 4 μm in size. The results show that free additive Ca2+ ions are irreversibly adsorbed onto the particles as the precipitates dissolve and recrystallize into smaller crystals upon reaching the Ca(OH)2 solution.Article Citation - WoS: 23Citation - Scopus: 31Nano-Caco3 Synthesis by Jet Flow(Elsevier Ltd., 2017) Ülkeryıldız, Eda; Kılıç, Sevgi; Özdemir, EkremA new methodology was introduced to produce hollow nano calcite particles in homogenous size distribution without aggregation. The design consisted of a jet flow system in which the crystallization region was separated from the stabilization region. The newly produced nano CaCO3 particles of about 140 nm were removed from the crystallization region as quickly as possible into the stabilization region before aggregation or crystal growth. In the stages of crystallization, the particles started to dissolve from their edges which opened-up the pores inside the particles. At the late stages of crystallization, the open pores closed. These particles were stable in Ca(OH)2 solution and no aggregation was detected. Different particles with different morphologies can be produced by adjusting the stages in the crystallization.Article Citation - WoS: 64Citation - Scopus: 70Mechanical and Morphological Properties of Recycled High-Density Polyethylene, Filled With Calcium Carbonate and Fly Ash(John Wiley and Sons Inc., 2006) Atikler, Ulaş; Başalp, Dildare; Tıhmınlıoğlu, FundaIn this study, mechanical and morphological properties of composites made up of recycled high-density polyethylene (HDPE) filled with calcium carbonate and fly ash (FA) were studied. Interfacial interactions were modified to improve the filler compatibility and mechanical properties of the composites by surface treatment of the FA filler with 3-amino propyl triethoxy silane. The composites were prepared by using a Thermo Haake Rheomixer. Effect of filler loading and treatment of FA with silane coupling agent on mechanical and morphological properties were investigated and it was found that silane treatment indicated significant improvements on the mechanical properties of the HDPE-FA composites. The improvement with silane treatment of FA was also confirmed by applying the Pukanszky model. Scanning electron microscopy on the fracture surface of composites had given direct evidence of better interfacial adhesion via silane treatment.Article Citation - WoS: 35Citation - Scopus: 45Types of the Scaling in Hyper Saline Geothermal System in Northwest Turkey(Elsevier Ltd., 2014) Demir, Mustafa Muammer; Baba, Alper; Atilla, Vedat; İnanlı, MustafaTuzla is an active geothermal area located in northwestern Turkey, 80km south of the city of Canakkale and 5km from the Aegean Coast. The geothermal brine from this area, which is dominated by NaCl, has a typical temperature of 173°C. Rapid withdrawal of fluid to ambient surface conditions during sampling causes precipitation of various compounds known as scaling. Scaling is one of the important problems in Tuzla geothermal system that reduces the efficiency of the geothermal power plant and causes economical loss. The aim of this study was to determine the type of scaling as a first step towards preventing its formation. The scales formed in the geothermal system were divided into two groups according to location: the ones that formed in downhole and the ones that accumulated along the surface pipeline. Both scales were examined in terms of their elemental composition, structure and morphology using XRF, XRD, and SEM, respectively. The former was found to be mainly composed of PbS (Galena) and CaCO3 (aragonite or calcite). In contrast, the latter was heterogeneous in nature and consisted of mainly saponite like amorphous structure along with submicrometer-sized amorphous silica particles, layered double magnesium and iron hydroxide, and NaCl.