WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 21Citation - Scopus: 22Structural and Electrical Characterization of the Nickel Silicide Films Formed at 850 °c by Rapid Thermal Annealing of the Ni/Si(1 0 0) Films(Elsevier Ltd., 2010) Utlu, G.; Tarı, Süleyman; Budak, S.; Tarı, Süleyman; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyNickel di-silicide formation induced by RTA process at 850 °C for 60 s in the Ni/Si(1 0 0) systems are investigated as a function of the initial Ni film thickness of 7-89 nm using XRD, RBS, SEM, X-SEM and AFM. Based on the XRD and RBS data, in the silicide films of 400-105 nm, NiSi and NiSi2 silicide phases co-exist, indicating that Ni overlayer is completely transformed to NiSi and NiSi2 silicide phases. SEM reveals that these films consist of large grains for co-existence of NiSi2 and NiSi phases, separated from one another by holes, reflecting that NiSi2 grows as islands in NiSi matrix. These films have low sheet resistance, ranging from 1.89 to 5.44 Ω/□ and good thermal stability. For thicknesses ≤ 80 nm RBS yields more Si-rich silicide phases compared to thicker films, whereas SEM reveals that Si-enriched silicide islands with visible holes grow in Si matrix. As the film thickness decreases from 400 to 35 nm, AFM reveals a ridge-like structure showing a general trend of decreasing average diameter and mean roughness values, while sheet resistance measurements exhibit a dramatic increase ranging from 1.89 to 53.73 Ω/□. This dramatic sheet resistance increase is generated by substantial grain boundary grooving, followed by island formation, resulting in a significant phase transformation from NiSi2-rich to Si-rich silicide phases. © 2010 Elsevier B.V. All rights reserved.Article Citation - WoS: 187Citation - Scopus: 208Synergistic Effect of Natural Zeolites on Flame Retardant Additives(Elsevier Ltd., 2005) Demir, Hasan; Arkış, Esen; Ülkü, Semra; Ülkü, Semra; Demir, Hasan; Arkış, Esen; Balköse, Devrim; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe thermal degradation and flammability of intumescent fire-retardant polypropylene matrix composites consisting of ammonium polyphosphate (APP) as an acid source and blowing agent, pentaerythritol (PER) as a carbonisation agent and natural zeolite (clinoptilolite rich, Gördes II) as a synergistic agent were examined. APP and PER combinations were examined at different ratios (0.25, 0.33, 0.5, 1, 2, 3, and 4) for optimisation of the formulation for flame retardancy. The zeolite was incorporated into flame retardant formulation at four different concentrations (1, 2, 5, and 10 wt%) to investigate the synergism between the flame retardant materials. The thermal degradation and flammability of composites were characterized by thermogravimetric analysis (TGA) and by limiting oxygen index (LOI) measurement and horizontal burning (HB) tests. A synergistic effect in flame retardancy was observed when natural zeolites were used in combination with APP and PER.Article Citation - WoS: 76Citation - Scopus: 84Characterization of Pure and Silver Exchanged Natural Zeolite Filled Polypropylene Composite Films(Elsevier Ltd., 2005) Pehlivan, Hilal; Balköse, Devrim; Tıhmınlıoğlu, Funda; Tıhmınlıoğlu, Funda; Ülkü, Semra; Balköse, Devrim; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn the present study, untreated and silver exchanged natural zeolite-polypropylene (PP) composites were prepared and characterized by means of different techniques (TGA, DSC, mechanical tests, density measurements, optical microscopy and colorometer). The effects of zeolite loading and silver concentration on the composite properties were investigated. The thermal characterization studies showed that the addition of the zeolite increased the crystallinity of the composites acting as a nucleating agent in PP crystallization and retarded the degradation of PP. At low silver concentrations, the zeolite behaved as a decelerating agent in PP degradation, however at higher silver concentrations, the composites degraded at a faster rate than pure PP. The experimental densities of the composites were found to be lower than the theoretical densities. When the tensile tested samples are considered, the densities were even lower indicating porous structure of the films. From the optical micrographs of the tensile tested films, it was clearly seen that the stretching along the machine direction caused hole formation around the particles. The optimum conditions obtained in this study for the PP-silver zeolite composite film production are in the range of 2-4 wt% zeolite treated with 4.36 mg Ag+/g zeolite. At higher zeolite loadings, the film becomes brittle and at higher Ag+ concentrations, the film produced was discolored.