Browsing by Author "Erdem, İlker"

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Green Synthesis of Silver Nanoparticles Using Walnut Shell Powder and Cynara sp. and their Antibacterial Activities
(Hacettepe Üniversitesi, 2022) Erdem, İlker; Çakır, Şerife; 0000-0001-5743-0835; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Erdem, İlker
The silver (Ag) is a well-known material with interesting properties (i.e. catalytic activity, antimicrobial, etc.). The nanosized particles of silver propose enhanced properties due to having relatively higher surface areas. The green synthesis is a promising way of material preparation/production being relatively more environmentally friendly by utilization of less harmful materials. In this work, the plant extracts (Cynara & Walnut shell powder) were used as reaction media for the synthesis of silver nanoparticles (Ag NPs). The nanoparticles produced via two plant extracts were ~46 nm and ~109 nm in size, respectively. The antibacterial activities of the produced silver nanoparticles (against E. coli and S. aureus species) were determined and minimum effective concentrations (MIC) for antibacterial activity were investigated.
Influence of Calcination Temperature on Microstructure and Surface Charge of Membrane Top Layers Composed of Zirconia Nanoparticles
(SPRINGER, 2015) Erdem, İlker; Ciftcioglu, M.; 0000-0001-5743-0835; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Erdem, İlker
The purpose of the research is to investigate the changes in microstructure and physicochemical characteristics, mainly surface charge (i.e. zeta potential) of zirconia membrane top layer during calcination. Zirconia is one of the most commonly preferred materials for ceramic membrane top layers due to its superior durability. The physicochemical properties of the top layer composed of submicron / nano particles is necessary not only for Donnan exclusion but also for dynamics of membrane fouling. In the present research the possibility of preparation of zirconia top layers with varying surface charge with changing calcination temperature was shown and a correlation between phase transformation and surface charge was determined.
Influence of silica nanoparticles on the stability of paraffin wax emulsion
(YILDIZ TECHNICAL UNIV, 2023) İbrahim, Aliu Pennah; Erdem, İlker; Gönen, Mehmet; 0000-0001-5743-0835; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Erdem, İlker
Paraffin wax emulsions have been used widely in various areas. However, the basic problem faced in all areas is instability of emulsion. Different methods and emulsifiers have been proposed to overcome this problem. This study focuses on using a commercial emulsifier, (IK8000) and aqueous silica nanoparticles to formulate paraffin wax emulsions and investigate their effects on the stability and mean diameter of paraffin wax emulsions. For comparison purpose, different emulsifier, PEG-7 Glyceryl Cocoate was used to stabilize one of 20 % (wt./ wt.) paraffin wax emulsions. The PEG-7-Glyceryl Cocoate stabilized emulsion phase -separated after 3 days while the IK-8000 stabilized remained stable for more than a month. The effect of the silica nanoparticles on the emulsion's stability was studied by observing samples stored for over 2 months. It was seen that aqueous silica nanoparticles helped to increase the stability of the paraffin wax emulsions. Emulsions prepared without silica nanoparticles (only IK-8000) were stable for just a month (1 month) whereas those which were formulated with silica nanoparticles and IK-8000 remained stable for more than 2 months (> 2 months). However, the addition of aqueous silica nanoparticles did not have a significant effect on the mean particle size of the emulsion. It was observed that the addition of 0.5 mL aqueous silica nanoparticles to the paraffin wax emulsion first increased the mean particle size from 1.142 mu m to 2.680 mu m. Nonetheless, further increasing the amount of the aqueous silica nanoparticles from 1.0-5.0 mL decreased the mean particles size of the paraffin wax emulsion from 2.680 mu m to 0.942 mu m. The contact angle formed by water drop on the surfaces coated with different emulsion samples of 30%wt. PWE, 40%wt. PWE, 50%wt. PWE and 60 %wt. PWE were measured. The higher the degree of solid content in emulsion, the greater the contact angle measured thus higher hydrophobicity.