Yazar "Yasin, Suleyman" seçeneğine göre listele

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    Corrosion and Wear Behaviour of Boronized high Carbon and Chromium Cast Steel
    (Iron Steel Inst Japan Keidanren Kaikan, 2013) Ahlatci, Hayrettin; Yargul, Gorkem; Cug, Harun; Cevik, Engin; Yasin, Suleyman; Sun, Yavuz
    The purpose of this study was to examine the effect of boronising heat treatment on the corrosion behaviour (in two different corrosive media) and wear properties (on two different counter sliding discs) of the DIN 1.4777 quality cast steel containing 1.7% C, 30% Cr and 1.1% Si. The steel supplied as cast was exposed to homogenisation heat treatment at 1150 degrees C for 3,5 hours and then to boronising heat treatment at 900 degrees C for 8 hours using the powder of Ekabor 2. An optical light microscope, SEM and XRD analyses were used to conduct microstructural characterisation of the steel investigated. Electrochemical potentio-dynamic polarisation measurements were taken to evaluate corrosion behaviours of the examined steels. Wear tests were conducted in a pin-on-disc type wear device by using a load between 10 N and 60 N. While the corrosion resistance of the boronising heat treated steel deteriorated by the pitting damage mechanism within corrosive media, uniform corrosion damage enhanced the corrosion resistance of the examined boronised steel. Oxidative adhesion, cracking of oxide and/or boride layer, and severe plastic deformation mechanisms were dominant during the wear tests. Severe plastic deformation and cracking of the oxide and/or boride layer caused wear mechanism to transform from mild to severe.
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    Effect of the additions of dehydrated geopolymer powders on compressive strength and integrity of the final geopolymer
    (Korean Assoc Crystal Growth, Inc, 2015) Yasin, Suleyman; Ahlatci, Hayrettin
    In this study, it is aimed to improve geopolymer compressive strength and integrity without causing any impurity. Thus, the effect of the additions of dehydrated geopolymer powders (0-40 wt.%) on compressive strength and integrity of the geopolymers cured with two different compositions was investigated. The powders were obtained by grinding of monolithic pure geopolymer which was dimensionally stabilised by thermally dehydration at 400 degrees C. Results of this study showed that when the powders were added at 10 wt.%, compactness of the microstructure and compressive strength of the samples increased. Additions of dehydrated geopolymer powder enhanced the integrity of the samples without changing the amorphous structure and typical FTIR spectrum of the pure geopolymers. Unlike the pure sample; after being thermally treated at 400 degrees C, the crack free samples, which had compressive strengths up to 51.65 Mpa could be obtained with the additions of the powders.
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    Geopolymerisation of un-calcined kaolin by the novel heat curing method
    (Korean Assoc Crystal Growth, Inc, 2022) Demir, Selin; Yasin, Suleyman
    In this study, heat curing technique (up to 320 degrees C) that allows the usage of sodium silicate solutions with un-calcined kaolins to offer a durable geopolymeric binder in a short time was investigated. Samples containing up to 40 wt.% binder have been produced to observe the binder behaviour over a wide range of additions by heat curing for one hour. The cured samples consist of kaolinite and amorphous phase and crystallinity was decreased with increasing curing temperatures. 240 degrees C was the threshold temperature for the strength development of the samples. Condensation reactions between Al-OH- units in uncalcined kaolin and silanol groups in sodium silicate solution that yield sialate (Si-O-Al-O) bridges detected by infrared analyses are the considered mechanisms of promoter effects of kaolinite. Optimum compressive strength (23.4 MPa.) was obtained with the samples produced with 20 wt.% binder addition and 300 degrees C curing temperature.