Bora Derin

Carbothermal recovery of zinc from brass ash

Abstract Brass ash of composition (wt-%) 59·67Zn-9·22Cu-1·45Pb-2·61SiO2-0·36Cl was treated by carbothermal reduction in a temperature controlled tube furnace. The aim of the work was to collect zinc in the form of metal and/or zinc oxide in the gaseous phase. Treatment temperature (950-1200°C) and time (15-180 min) were varied. At 1200°C and 60 min, recovery of zinc was 92·5% and zinc content in the remaining residue was found to be 12·8 wt-%. Kinetic analysis of the experimental results showed that initially the reaction was under chemical control with an activation energy of 90·1 kJ mol-1. Subsequently the development of a sintering structure caused the reaction mechanism to change to diffusion control.

Production of Magnesium Metal from Turkish Calcined Dolomite Using Vacuum Silicothermic Reduction Method

In the present study, the production of magnesium metal from Turkish calcined dolomite containing 43.20 % MgO and 47.46 % CaO via Pidgeon process was studied under the pressure of 1 mbar. In the experiments, Turkish ferrosilicon containing 75 % Si and 24 % Fe was used as reducing agent. Effects of FeSi addition (90-150 % of stoichiometric requirement of silicon) and time (60-240 min.) were investigated on recovering of metallic magnesium from calcined dolomite (dolime) at the temperature of 1200 °C. Effects of fluxing additive (CaF2), calcined magnesite and different temperatures on Mg recoveries and concentrations were also studied using with 100 % of stoichiometric requirement of silicon for 180 min. It was found that magnesium recovery increases with increasing FeSi addition, temperature, time, CaF2 addition and decreases with increasing calcined magnesite additions under the pressure of 1 mbar.

Production of Al-Co-Ni Ternary Alloys by the SHS Method for Use in Nickel Based Superalloys Manufacturing

Abstract In this study, Al-Co-Ni ternary alloys were synthesized, in order to obtain low-cost starting material for Ni-based superalloy production, by a self-propagating high temperature synthesis (SHS) both under normal gravity conditions (a = 9.81 m/s2) and under high gravity conditions (up to 1000 g-force) by using a centrifugal machine. The mixture of Co3O4-NiO powder were reduced by Al powder for the production of SHS alloys with the estimated compositions of 5–10 mass% Al, 20–65 mass% Co, 25–75 mass% Ni. The effect of green mixture compositions and centrifugal overload on combustion temperature, alloy/slag separations, chemical composition and microstructure of final alloys were investigated. The chemical analysis results showed that production of SHS alloys were achieved by having up to 86.12% of Co and 92.32% of Ni recoveries. The highest metal recovery value was obtained in SHS alloy with the estimated composition of 10%Al-65%Co-25%Ni by the addition of 20% Al2O3 into the green mixture. The metal/slag separation efficiency increased by increasing the centrifugal overload.

Investigation of effect of colemanite addition on copper losses in matte smelting slag

Abstract In this study, the aim was to reduce copper losses to slag in copper production by using a boron compound, called colemanite (2CaO.3B2O3.5H2O), as flux, besides silica. In order to achieve this purpose, two different matte–slag couples were used; the flash furnace matte-slag obtained from Eti Copper Inc. (EBİ) and a master matte–slag without copper produced synthetically under laboratory conditions. Chemical analyses of flash furnace slag and synthetic master slag were 0·88%Cu–36·1%SiO2–43·9%FeO–3·7%Fe2O3 and 37·6%SiO2–60·0%FeO–2·4%Fe2O3 respectively. In each experiment, the same amounts of slag and matte were mixed with the addition of predefined amounts of colemanite and melted together at 1250°C for different durations under nitrogen atmosphere in a silica crucible. Results showed that it was possible to decrease the copper losses to about 0·3–0·4% by accelerating the settling rate of matte particles by the addition of colemanite, which was attained by the expected increase in flash furnace slag fluidity and lowering of its liquidus temperature. Dans cette étude, le but était de réduire les pertes de cuivre dans la scorie lors de la production de cuivre en utilisant un composé de bore, appelé colémanite (2CaO.3B2O3.5H2O), comme flux, en plus de la silice. Afin d’atteindre cet objectif, on a utilisé deux couples différents de matte-scorie; la matte-scorie du four éclair obtenu de Eti Copper Inc. (EBİ) et une matte-scorie modèle sans cuivre, produite synthétiquement sous conditions de laboratoire. Les analyses chimiques de la scorie du four éclair et de la scorie synthétique modèle étaient de 0·88%Cu–36·1%SiO2–43·9%FeO–3·7%Fe2O3 et de 37·6%SiO2–60·0%FeO–2·4%Fe2O3, respectivement. Dans chaque expérience, on a mélangé la même quantité de scorie et de matte, avec addition de quantités prédéfinies de colémanite, et fondu ensemble à 1250°C à différentes durées sous atmosphère d’azote dans un creuset de silice. Les résultats ont montré qu’il était possible de diminuer les pertes de cuivre à environ 0·3–0·4% en accélérant la vitesse de sédimentation des particules de matte par l’addition de colémanite, ce qui était atteint par l’augmentation attendue de la fluidité de la scorie du four éclair et par l’abaissement de sa température de liquidus.

Double SHS of W2B5 Powder from CaWO4 and B2O3

A synthesis study of W2B5 powder was carried out by double self-propagating hightemperature synthesis (D-SHS) from CaWO4, Mg and B2O3 mixture and followed by HCl leaching methods. In the first stage of SHS reaction, molar composition ratio of CaWO4:B2O3:Mg mixture was selected as 1:1:8 (SHS-1) and 1:2.5:8 (SHS-2). The both SHS products were then acid leached (HCl) at optimum conditions for 1 hour and 80 °C to eliminate MgO, Mg3B2O6 and Ca3(BO3)2 phases. The first leached products were consisted of W, WB, W2B5, and W2B phases. In the second stage of SHS process, the both leached products were reacted with the same amount of Mg and B2O3 mixture keeping previous initial ratio values (1:8 and 2.5:8). A successful SHS reaction was achieved only by using the mixture with leached SHS-2 product. After following acid leaching, the chemical composition of the leached D-SHS product was found to be 98.2 wt. % W2B5, 1.2 wt. % WB4, and 0.6 wt. % WB.

Machinability of Bulk Metallic Glass Materials on Milling and Drilling

In this study, machinability of Zr-based bulk metallic glass (Zr52.5Ti5Cu17.9Ni14.6Al10) (BMG) material was investigated by conducting a set of milling and drilling experiments. In milling, two different tool paths, spiral and slot milling, were used. To investigate the behavior of BMG in drilling by two different tools at different feed rates, two sets of drilling experiments are conducted. Crown shaped exit burr formation are observed in drilling of BMG. Best results on thrust force, exit burr formation and hole surface roughness is obtained while using micrograin WC tool on BMG drilling. No chip light emission was observed during all tests. This study concludes that BMG can be achieved machining with good surface roughness, (Ra=0.113 µm), using conventional cutting tools.

Synthesis of Mn2O3 Nanopowders with Urea and Citric Acid by Solution Combustion Route

In this study, synthesis of Mn2O3 powders by solution combustion route was carried out. Urea (CH4N2O) and citric acid (C6H8O7.H2O) was used as a fuel material in solution combustion synthesis, while manganese nitrate (Mn(NO3)2.4H2O) was used as an oxidant. Surface area of Mn2O3 synthesised by urea was calculated as 19,37 m2/g and 25,07 m2/g after the calcination at 400 °C and 500 °C, respectively. Surface area of Mn2O3 synthesised by citric acid was calculated as 63,77 m2/g when fuel/oxidizer was 1/1, ignition temperature of 250 °C and calcination temperature at 500 °C. Spherical particles of Mn2O3 having average particle size of 50–60 nm was synthesised by using urea, while foam like porous structure of Mn2O3 was obtained when citric acid was used as a fuel in solution combustion synthesis. Pore diameters between 27 and 55 nm was determined for this powders.

Field Responsive Fluids - A Review

Magnetorheological (MR), Electrorheological (ER), and Ferrofluids are considered as a class of smart materials due to their novel behavior under an external stimulus such as a magnetic and electrical field. The behavior of these synthetic fluids offer techniques for achieving efficient heat and mass transfer, damping, drag reduction, wetting, fluidization, sealing, and more. Magnetorheological fluids are suspensions of non-colloidal, multi-domain and magnetically soft particles organic and aqueous liquids. Electrorheological fluids are suspensions of electrically polarizable particles dispersed in electrically insulating oil. Ferrofluids are known as magnetic liquids that are colloidal suspensions of ultrafine, single domain magnetic particles in either aqueous or non-aqueous liquids. In this review article a history of these fluids is given, together with a description of their synthesis in terms of stability and redisperibility and how it is understood in various parts of the science and technology. Then the structural changes and rheological properties of these smart fluids under an external stimulus together with a series of applications are presented.

The Effect of Cutting Speed in Metallic Glass Grinding

In this paper, the effects of the cutting speed in metallic glass grinding were investigated in dry conditions. The results showed that grinding forces decrease as grinding energy increase with the increasing cutting speeds. The present investigations on ground surface and grinding chips morphologies ‐shows that material removal and surface formation of the BMG are mainly due to the ductile chip deformation and ploughing as well as brittle fracture of some particles from the edges of the tracks. The roughness values obtained with the Cubic Boron Nitride wheels are acceptable for the grinding operation.

Production of Zirconium Diboride Powder by Self Propagating High Temperature Synthesis

In this study, the self-propagating high-temperature synthesis (SHS) and following acid leaching techniques were carried out to produce zirconium diboride (ZrB2) powder. In the SHS experiments, technical grade ZrO2 powder, and different amounts of B2O3 and Mg powders were used. The SHS products were obtained in the form of black, spongy solid. In the leaching step, the effect of different acid concentrations on selective leaching was investigated by using optimum SHS product to eliminate the impurities such as MgO, Mg3B2O6 and Mg2B2O5. The products obtained were characterized by using XRD, ICP and SEM techniques.