Cafer Çelik

Determination of the optimum conditions for ion nitriding of AISI 5140 steel

Abstract AISI 5140 low alloy steel was ion nitrided under different process parameters including time (1, 4, 8 and 12 h), temperature (400, 450, 500 and 550 °C) and gas mixture ratio (0.05, 0.33, 1 and 3 N 2 /H 2 ). By determining the fatigue strength, surface hardness, compound layer thickness and case depth, the optimum working conditions were determined by using a Taguchi design of experiment. After ion nitriding process, it is aimed to maximize fatigue strength, surface hardness and case depth as well as to minimize compound layer thickness. While the optimum conditions were determined, due to the goals (above aims) more than one being, the trade-off among goals was considered. First of all, each goal was optimised, separately. Then, all the goals were optimised together, considering the priority of the goals, and the optimum results were obtained at 0.05 N 2 /H 2 gas mixture ratio, at the temperature of 450 °C and for 12 h process time.

Optimisation of the chlorination of gold in decopperized anode slime in aqueous medium

Abstract A study is conducted to determine optimum conditions for the chlorination of gold in decopperized anode slime with chlorine gas in aqueous medium by the Taguchi experimental design method. The effect of parameters such as reaction temperature, reaction period, stirring speed and solid–liquid ratio was sought. The optimum conditions were found to be reaction temperature 60°C, reaction period 4500 s, stirring speed 600 min−1 and solid–liquid ratio 0.1 g ml−1. The experimental results showed that, under optimal leaching conditions, the extraction of gold could be over 99%.

Determination of the optimum conditions of dissolution of copper in converter slag with chlorine gas in aqueous media

Abstract The Taguchi method has been used to determine the optimum conditions of dissolution of copper in converter slag with chlorine gas in aqueous media. After the parameters were determined to be efficient on the extraction efficiency, the experiments were begun. The chosen experimental parameters and their ranges were: (i) chlorine gas flow rate (ml min −1 ); 180–220, (ii) solid-to-liquid ratio (g ml −1 ); 0.1–0.166, (iii) stirring speed (rpm); 350–750, (vi) reaction time (min); 90–210. The optimum conditions were found to be as follows: chlorine gas flow rate (ml min −1 ); 220, solid-to-liquid ratio (g ml −1 ); 0.1, stirring speed (rpm); 550, reaction time (min); 90. Under these optimum conditions, copper, iron and zinc extraction efficiency from converter slag were 98.35, 8.97 and 25.17%, respectively.

Investigation on the Removal of COD from Colored Aqueous Solutions with O3, H2O2, HCO3−, and PAC

In this study, chemical oxygen demand (COD) was removed using different processes containing O3, H2O2, HCO3−, and powder activated carbon (PAC) from the synthetic dye solutions. The effects of the experimental parameters such as temperature, ozone dose, dye concentration, pH, and time on the removal of COD were investigated. The Taguchi method was applied to determine the optimum conditions. An orthogonal array L18 (21 * 37) experimental design plan was selected to define the optimum conditions. In addition, the mechanism of the COD removal was explained on the basis of the results of Fourier transform infrared (FTIR) spectroscopy. To gain information about COD removal mechanism at various pHs, electrophoretic mobilities of particles were measured. The chosen experimental parameters and their ranges are: (0–39 mM); temperature (18–70 °C); ozone dose (164–492 mg/min); dye concentration (200–600 ppm); PAC (0–1.5 g); H2O2 (0–0.056 mM); pH (3–12); and time (10–30 min). Under these optimum conditions, it was found that the COD removal efficiency from the synthetic dye solutions was 98%.

Taze Beton Özelliklerinin Optimizasyonu / Optimization of Fresh Concrete Properties

OZET : Bu calismada; su-cimento orani, cimento dozaji ve hava surukleyici katki maddesinden olusan parametrelerin betonun taze haldeki ozellikleri uzerindeki etkileri incelenmistir. Deney tasarimi asamasinda ve sonuclarin istatistiksel analizinde Taguchi Yontemi kullanilarak optimizasyon yapilmistir. Optimizasyon sonucunda betonun islenebilirligi icin cimento dozaji; birim agirlik ve hava icerigi icin ise hava surukleyici katki maddesi en onemli parametre olarak bulunmustur. Genellikle betonun donmacozulmeye karsi direncini artirmasi icin kullanilan hava surukleyici katki maddesi, taze betonun akiskanligini da artirmistir. Deneylerde kullanilan Taguchi Yontemi; deney sayisini azaltmis, her uc deney icin gecerli olacak sekilde parametrelerin optimum seviyelerinin belirlenmesini saglamis ve yapilmayan deneylerin sonuclarinin kestirimini mumkun kilmistir. Anahtar kelimler: Taze beton, cokme, dozaj, birim agirlik, hava icerigi, Taguchi Metodu ABSTRACT : In this study, the influence of water-cement ratio, cement dosage and air-entrainment admixture (AEA) on the properties of fresh concrete was investigated using Taguchi Method. The Method was used for both experimental design and statistical analysis of the results to optimize the parameters mentioned. The optimisation results showed that the most important parameter is cement dosage for the workability, is AEA for the unit weight and for the air content. AEA which is generally used to improve the resistance of concrete exposed to freezing and thawing increased the workability of fresh concrete. Taguchi Method decreased the number of experiments, enabled to determine the optimum levels of the parameters for all the three experiments and to estimate the results of not conducted experiments. Keywords: fresh concrete, slump, dosage, unit weight, air content, Taguchi Method