Chemical Engineering / Kimya Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/14

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Author: search.filters.author.Şakar Deliormanlı, AylinLanguage: search.filters.language.en

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Now showing 1 - 4 of 4
  • Article
    Citation - WoS: 14
    Citation - Scopus: 18
    Rheological Behavior of Pmn Gels for Solid Freeform Fabrication
    (Elsevier Ltd., 2008) Şakar Deliormanlı, Aylin; Çelik, Erdal; Şakar Deliormanlı, Aylin Müyesser; Polat, Mehmet; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Lead 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: 6
    Citation - Scopus: 12
    Effect of Calcium Hydroxide on Slip Casting Behaviour
    (Elsevier Ltd., 2004) Şakar Deliormanlı, Aylin; Şakar Deliormanlı, Aylin Müyesser; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The effect of calcium hydroxide addition on the casting performance of ceramic slips for sanitary ware was studied. Powder composed of feldspar (24 wt.%), quartz (24 wt.%), kaolin (35 wt.%) and ball clay (17 wt.%) was mixed with water to contain 65 wt.% of solids (specific density 1800 g/l). Either Ca(OH)2 or Na2CO3 was added at concentrations ranging between 0.060 and 0.085 wt.% and the slurries were dispersed by the optimum addition of sodium silicate. Calcium hydroxide in presence of sodium silicate improved the casting behavior of the slips, lowering the viscosity, and water absorption, increasing bending strength and cake thickness, as compared to the addition of sodium carbonate
  • Article
    Citation - WoS: 5
    Citation - Scopus: 7
    Alumina/Water Suspensions in the Presence of Peo-Ppo Triblock Copolymers
    (Elsevier Ltd., 2004) Şakar Deliormanlı, Aylin; Polat, Hürriyet; Polat, Hürriyet; Çiftçioğlu, Muhsin; Şakar Deliormanlı, Aylin Müyesser; 03.02. Department of Chemical Engineering; 04.01. Department of Chemistry; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    The aim of this study was to investigate the stability and dispersion behaviour of aqueous alumina suspensions in the presence of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) type triblock copolymers. For this purpose alumina suspensions at various solids loadings were prepared using four different methods. These are: Method I: powder and water were stirred only; Method II: powder and water were stirred and ultrasonic treatment was applied; Method III: powder and water were stirred in the presence of block copolymers; Method IV: powder and water were stirred and ultrasonic treatment was applied in the presence of block copolymers. These suspensions were characterized by means of rheological measurements. Sedimentation and turbidity measurements were also conducted to support these results and to investigate the stability of these systems for longer times. Surface tension measurements were performed to investigate the adsorption behaviour of block copolymers onto alumina surface. It was found that the use of PEO-PPO-PEO type triblock copolymers improved the dispersion behaviour of aqueous alumina suspensions in the presence of ultrasonic treatment at low solids loadings. However their effect was not significant at high solids loadings and without ultrasonic treatment.
  • Conference Object
    Citation - WoS: 2
    Citation - Scopus: 2
    Effects of Mechanical Treatment on the Formation of Α-Al 2o3 From Gibbsite
    (Trans Tech Publications, 2004) Şakar Deliormanlı, Aylin; Çiftçioğlu, Muhsin; Polat, Hürriyet; Çiftçioğlu, Muhsin; Şakar Deliormanlı, Aylin Müyesser; 03.02. Department of Chemical Engineering; 04.01. Department of Chemistry; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this study preparation of fine alpha alumina powders derived from Bayer gibbsite was studied. Preparation of the alumina powders was performed by decomposition of the gibbsite into transition alumina phase followed by controlled transformation to the alpha phase. Gibbsite was thermally treated at 350°C and 900°C to obtain a transition form of alumina. The purpose of the heat treatment at 350°C was to increase the surface area of the gibbsite particles and obtain a loosely packed structure that may reduce the size of the rather coarse precursor gibbsite during the grinding step. Mechanical treatment (by using ultrasonic forces and impact forces) was utilized to increase the transformation rate to the alpha alumina in the transition phase matrix and influence the nucleation and growth rate of the solid -solid phase transformation. These powders were calcined at 1100, 1200 and 1450°C for 1 to 8 hours. Results indicated that transformation to the alpha phase was accomplished in the powders preheated at 900°C, ultrasonically treated or ground, and then calcined at 1200°C for 2 to 8 hours or at 1450°C for 2 hours. Ultrasonic treatment accelerated the transformation rate to the alpha phase at 1100°C in 2 hours. Powders that were calcined at 1100 to 1200°C for 1 hour had a significant kappa content together with the alpha phase. Additionally the powder prepared without mechanical treatment and calcined at 1100°C was mainly in the kappa phase.