Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 3Citation - Scopus: 3Influence of Dispersing Agents on the Solubility of Perovskites in Water(Taylor and Francis Ltd., 2009) Şakar-Deliormanlı, Aylin; Çelik, Erdal; Polat, MehmetIn this study, solubility behavior of lead magnesium niobate (PMN) powders in water was investigated in the presence of pure polyacrylic acid and polyacrylic acid/polyethylene oxide comb polymers. Experiments were performed by measuring the solubility of PMN in terms of the concentration of Pb+2 and Mg+2 ions in supernatant as a function of pH and dispersing agent dosage. The concentrations of the metal ions in supernatant were found to be affected by the dispersant concentration, stirring time and the suspension pH. Results revealed that both dispersing agents enhance the cation dissolution from PMN surface at pH 9 due to weak (reversible) adsorption and complexation of Pb+2 and Mg+2 by carboxylate groups. On the other hand, under acidic conditions cation dissolution from PMN is inhibited and this was attributed to the strong adsorption of dispersing agents onto the powder surface and formation of a dense polymer layer.Article Citation - WoS: 21Citation - Scopus: 23Adsorption of Anionic Polyelectrolyte and Comb Polymers Onto Lead Magnesium Niobate(Elsevier Ltd., 2008) Şakar-Deliormanlı, Aylin; Çelik, Erdal; Polat, MehmetThis paper presents the results concerning the adsorption mechanism of polyacrylic acid (PAA) and polyacrylic acid/polyethylene oxide (PAA/PEO) comb polymer onto lead magnesium niobate (PMN) powders. In the study adsorption behavior of PAA and PAA/PEO onto PMN surface were determined in aqueous solutions and the influence of pH and ionic strength was investigated. Results showed that adsorption of PAA or PAA/PEO increased with decreasing pH of the suspensions. The increase in the ionic strength or the presence of divalent cations caused an increase in the adsorption of both polyelectrolytes. It was observed that the adsorption reaches a maximum when PAA is fully complexed in solution. On the other hand, the increase in the adsorption of PAA/PEO onto PMN in the presence of monovalent or divalent salt was attributed to the decrease in the electrostatic forces rather than complex formation with the divalent metal ions in solution. Turbidity measurements showed that there is no complex formation between the divalent metal ions and PAA/PEO comb polymers due to shielding effect of the PEO teeth.Article Citation - WoS: 3Citation - Scopus: 4Phase Formation and Microstructure of Nd +3 Doped Pb(mg 1/3nb 2/3)o 3 Prepared by Sol-Gel Method(Springer Verlag, 2008) Şakar-Deliormanlı, Aylin; Polat, Mehmet; Çelik, Erdal; Şakar Deliormanlı, Aylin Müyesser; Polat, MehmetThe aim of this study was to investigate the effects of the rare earth element neodymium on the phase formation and microstructural development of relaxor ferroelectric lead magnesium niobate, Pb(Mg 1/3 Nb 2/3)O 3 (PMN) system. Perovskite phase PMN powders were prepared using the sol - gel method and the effect of neodymium doping was investigated at different doping levels ranging from 0.1 mol% to 30 mol%. The precursors employed in the sol - gel process were lead (II) acetate, magnesium ethoxide, and niobium (V) ethoxide. All the experiments were performed at room temperature while the calcination temperatures ranged between 800 °C and 1,100 °C. Results showed that it was possible to obtain the pure perovskite phase at 950 °C using the sol - gel method. Nd +3 addition influenced the phase formation and microstructure of the multicomponent system. Pyrochlore was detected along with the perovskite phase above 10 mol% Nd. Results also demonstrated that grain size of the synthesized powders depended on the Nd +3 concentration.Article Citation - WoS: 14Citation - Scopus: 18Rheological Behavior of Pmn Gels for Solid Freeform Fabrication(Elsevier Ltd., 2008) Şakar Deliormanlı, Aylin; Çelik, Erdal; Polat, MehmetLead magnesium niobate (PMN) is a relaxor ferroelectric material and have widespread applications in the manufacture of multilayer electronic devices such as ceramic capacitors, actuators and transducers. The dielectric constant of this electrostrictive material is much higher than the well known ferroelectric barium titanate. However, aqueous processing of PMN is not investigated yet especially for the novel wet shaping fabrication. In this study, concentrated aqueous colloidal PMN gels have been designed to use in the robocasting process. Concentrated PMN suspensions were stabilized by polyacrylic acid and then gelation induced by changing the pH or ionic strength of the suspension or by addition of a cationic polyelectrolyte to the system. Through this procedure it was essential to understand the solid-liquid transition under shear to explore the feasibility of forming without excessive use of polymers. Therefore, rheological response of the samples having a gel network was investigated. Results showed that gelation induced by cationic polyethylene imine or by multivalent salts were successful methods in preparation of PMN gels. However, gelation induced by changing the pH of the suspension was challenging due to ion dissolution from PMN surface.Article Citation - WoS: 15Citation - Scopus: 15The Isoelectric Point of Lead Magnesium Niobate(John Wiley and Sons Inc., 2007) Deliormanlı, Aylin M.; Çelik, Erdal; Polat, MehmetLead magnesium niobate (PMN) is an important relaxor ferroelectric material commonly used in multilayer capacitor and actuator manufacturing owing to its high dielectric constant and superior electrostrictive properties. However, the isoelectric point of this material in water is not known and there is justification for a detailed investigation. In this work, the isoelectric point (IEP) of aqueous PMN suspensions were determined as a function of solids concentration. Results showed that IEP of the PMN suspensions strongly depended on the solids loading. The IEP was between pH 9 and 10 at particle concentrations between 10 to 20 vol%. The IEP shifted gradually to a lower pH value as the particle concentration decreased. Solubility experiments showed that Pb2+ and Mg2+ ions dissolved from the PMN surface, especially in the acidic pH range. The study provides a new insight on the aqueous stability of perovskite materials which possess more than one soluble cation in their structure.