Sulfide capacities of lead oxide containing silicate and alumina silicate slags

Bu çalışmada PbO-SiO2 ve PbO-AlO1.5-SiO2 curuf sistemlerinin kükürt kapasiteleri gaz-curuf dengeleme yöntemi kullanılarak araştırılmıştır. Bu amaçla, 1 atm. basıncında saf SO2 gazının 1373 K sıcaklıkta oluşturduğu 2.07x10-8 atm. PO2 ve 2.94x10-5 atm. PS2 kısmi basınçları altında platin ve/veya alumina pota içerisindeki curuf numuneleri 8 saat süreyle dengelenmiştir. Her iki sistem için de bazikliğin artışıyla curuf içerisindeki kükürt miktarında artış meydana geldiği belirlenmiştir. Elde edilen kükürt kapasiteleri sonuçları (Cs), oksitlerin ve sülfürlerin kimyasal ve çözelti özelliklerini kullanarak curufların kükürt kapasitesini hesaplayan Reddy-Blander modeliyle (RB) kıyaslanmıştır. Deney ve modelleme ile belirlenen kükürt kapasitesi sonuçları birbirleriyle uyumlu bulunmuştur.Anahtar Kelimeler: Curuf, kurşun oksit, kükürt kapasitesi, Reddy-Blander modeli.  PbO-SiO2 subsystem is one of the important parts of the lead/zinc smelting slag system. PbO-AlO1.5-SiO2 subsystem is also important, since the alumina is introduced into the system as an impurity from ore feed stocks, coke ash and refractory lining of the smelting furnace. In order to understand the sulfide capacity behavior of the complex smelting slag system, first it is necessary to investigate these subsystems. In this study, the sulfide capacities of PbO-SiO2 and PbO-AlO1.5-SiO2 slags were studied using gas-slag equilibrium technique. The experiments were conducted in platinum and alumina crucibles using 1 atm. SO2 gas which created 2.07x10-8 atm. PO2 and 2.94x10-5 atm. PS2 at 1373 K for 8 hours. It was found that for both slag systems, sulfide solubility increased with an increase of basicity. The experimental sulfide capacity (Cs) results were also compared with the Reddy-Blander model based on a simple solution model and on knowledge of the chemical and solution properties of sulfides and oxides. The Reddy-Blander model (RB) for calculating Cs in the binary PbO-SiO2 and ternary PbO-AlO1.5-SiO2 slags ?a priori? is shown to be in good agreement with the experimental data. It can be concluded that the sulfide capacities of slags are directly proportional (i) to the equilibrium constant KM, and (ii) to values of aMO, which are related to the solution properties.Keywords: Slag, lead oxide, sulfide capacity, Reddy-Blander model

Synthesis, production and characterization of soda-lime photosensitive glasses

Işığa duyarlı camlar, özel bir bileşime sahip olup mor ötesi (UV-ultraviolet) ışın yardımıyla çeşitli renklerin elde edildiği camlardır. Işığa duyarlı cam, cam harmanının hazırlanması, elde edilen camın geleneksel yöntemlerle şekillendirilmesinin ardından içeriğinde bulunan elementlerin UV ışınının aktinik özellik göstererek camın mikroyapısında değişikliklere neden olmasıyla elde edilmektedir. Cam içeriğinde bulunan kolloid metal olan gümüşün, cam içerisindeki boyut ve dizilimine bağlı olarak, camın saydam ya da opak olması sağlanabilmektedir. Bu çalışmada daha önce patenti alınan ana cam kompozisyonu olarak sodyum silikat yerine, soda-kireç camı seçilmiş ve camın ticari olarak üretilme olanağı incelenmiştir. Ayrıca, ışığaduyarlı camların kompozisyonunda ana camı renklendirmeyecek miktarda Ho2O3 eklenmesinin etkileri irdelenmiştir. Mevcut ticari kompozsiyonuna gümüş, alkali oksit, florür ve klorür, bromür ve iyodür grubundan en azından birini içeren ve Ce2O3 kullanımıyla 2000 W gücünde UV ışın kaynağı kullanılarak bu ışının aktinik radyasyon etkisi gösterdiği camın üretilmesi ve farklı oranlarda holmiyum oksit eklenmesiyle cam üzerindeki ve fotokimyasal süreç sonrası spektrometrik etkisi incelenmiştir. Ho2O3 eklenmesi ile cama fotokimyasal proses uygulaması ardından numunelerde beklendiği gibi, görünür bölgede fazla değişim olmamasına karşın yapıda değişim olduğu belirlenmiştir. Bu çalışmada, cam kompozisyonunun sodyum silikat matrisinden soda-kireç-silis cam matrisine modifiye edilmesi ve fotokimyasal proses aşaması için geliştirilen UV lamba sisteminin kullanımı ile Ho2O3 içeren camlara ışığa duyarlılık özelliği verilmiştir. Anahtar Kelimeler: Işığa duyarlı cam, renklendirme, optik karakterizasyon.For centuries, as an attractive feature in glass design, colour is one of the most important factors in glass production. Coloured glasses have always taken a special place in the assortment of every glass producer and for their production different methods have been developed Photosensitive glasses, which have special compositons, can be produced in a variety of colours with the help of UV (ultraviolet) radiation After preparing the glass batch, the melting and glassification are carried out by applying conventional methods. In a second step, with the help of special materials in the recipe, the actinic radiation applied changes the microstructure of the glass. The resulting glass becomes photosensitive. Depending on the size, shape and orientation of colloidal metal particles, such as silver, the transparency of glass can be controlled and even opaque materials can be obtained. Photosensitive glasses have sodium silicate base glass composition, are known in various colors in opal or transparent form for many years ever since they were patented in 1977. These have been produced by applying conventional methods. They contain alkali halide silver (AgX), alkali oxide, fluorine, and at least one of the following substances: chlorine, bromine or iodine. Later on they are exposed to high energy or actinic radiations followed by a unique heat treatment. However, because of the instability within the end product and having a slow reaction rate, this product has never been commercially feasible, its applications have always been limited. At the beginning of the experiments, the glass batches to produce photosensitive glass were prepared by adding glass forming oxides, silver, alkali oxides, cerium oxide, antimony oxide, tin oxide, fluoride, chloride, bromide and iodide. These batches were then melted following the conventional method of glass production. The glass samples were exposed to UV (ultraviolet) radiation at room temperature. This was followed by a first heat treatment and a second UV exposure. Finally, a second heat treatment was applied after which samples were left in the furnace to cool down to room temperature. This photochemical process was carried out in a specially designed temperature-controlled box that was equipped with a UV lamp. Depending on the UVexposure time and the heat treatment temperature, a variety of colours can be produced with this photochemical process. The present study shows the effects of addition of Ho2O3, for the first time in literature. Optical characterization has been also performed before and after UV exposure. In this study, a soda lime silica glass composition was chosen instead of sodium silicate in order to produce a commercially more feasible glass. The photosensitive glasses were designed by adding the following substances: silver as sensitizer and colorant, Sb2O3 as thermal sensitizer, SnO as redox and refining agent, CeO2 as optical sensitizer, and compounds of alkali halides with Na and Ag ions to form a crystalline structure. Photosensitive glasses have been produced in laboratories for over 30 years but at very high costs and without having been able to achieve the necessary stability. The aims of this study can therefore be described as; the modification of base glass in soda lime silica glass matrix, the optical characterization of the final product, the development of a new system for the photochemical process to be used in mass production, evaluating the effect of Ho2O3, on glass in visible range. Beside these, gaining knowledge on nature of photosensitivity before and after photochemical process studied. Despite its low absorption in the UV region, the effect of Ho2O3, on the properties of photosensitive glasses was also studied. The amount of holmium oxide was chosen so as to keep base glass colourless and was determined experimentally. The effects of changing the amount of holmium oxide on the photosensitivity of glass composition were also determined. Furthermore, the relationship between the photochemical process and the time and temperature of the heat treatments were examined for all compositions that were used in this study. By modifying chemical composition and using inhouse UV lamp system, photosensivity can be reached in soda lime silica glass matrix.The results showed that modification of soda-lime-silica composition with doping minor amount of holmium oxide cause small change in resultant color. However, result of solar degredation can be minimized by the help of applied photochemical process. It is expected that with increasing amount of Ho2O3 above 0.06 % level this effect is predominant.  Keywords: Photosensitive glass, colored glass, optical characterization

Production and development of wrought magnesium alloys

Türkiye’nin ilk magnezyum alaşımı levhası, ikiz merdaneli sürekli döküm tekniği ile üretilmiştir. Magnezyum AZ31, AZ61, AZ91, AM50 ve AM60 alaşımı levhalar 4-8 mm kalınlığında, 1500 mm eninde başarılı bir şekilde elde edilmiştir. Levhalar daha sonra homojenleştirme ısıl işlemlerine maruz bırakılmıştır. Levhaların mikroyapıları yüzey, en ve boy yönlerinde optik mikroskop ve Taramalı Elektron Mikroskobu (SEM) ile incelenmiştir. Daha detaylı mikroyapı incelemeleri Geçirimli Elektron Mikroskobu (TEM) ile yapılmıştır. Yarı nicel ve nicel elementel analizler SEM-EDS (Enerji Dağılım Spektrometresi), TEM-EDS ve EPMA (Elektron Prob Mikro Analiz Cihazı)-WDS (Dalgaboyu Dağılım Spektrometresi) sistemleri ile yapılmıştır. X-ışınları difraksiyonu (XRD) teknikleri karakterizasyon ve yönlenme incelemeleri amaçlı olarak kullanılmıştır. Malzemelerin mekanik özellikleri çekme deneyi ve sertlik deneyleri ile ölçülmüştür. Çekme deneyleri hadde yönü, hadde yönüne 45 derece açı ve 90 derece açı olmak üzere üç farklı yönde ekstensometre yardımı ile yapılmıştır. Ayrıca numune yüzeylerinde ve farklı kesitlerde mikro Vickers ve Brinell Sertlik taramaları yapılmıştır. Elde edilen levhalar üzerinde soğuk hadde, sıcak hadde ve ısıl işlem gibi termomekanik işlemler denemeleri de gerçekleştirilmiştir. Levhalar öncelikle laboratuar ölçeğinde sıcak hadde ile inceltilmişlerdir. Daha sonra elde edilen bilgiler ışığında magnezyum AZ31 alaşımı levhalar ısıtıldıktan sonra endüstriyel ölçekli hadde sistemi ile 1 mm kalınlığa kadar inceltilmiştir. Elde edilen sonuçlar ışığında otomotiv, savunma ve elektronik endüstrileri için uygun magnezyum levha alaşımlarının üretimi olası gözükmektedir. Anahtar Kelimeler: Magnezyum alaşımları, levha, ikiz merdaneli sürekli döküm.Magnesium alloy sheet has been produced by twin roll strip casting first time in Turkey. Magnesium AZ31, AZ61, AZ91, AM50 and AM60 alloy sheets of 4-8 mm thick, 1500 mm wide were successfully achieved. Afterwards, homogenization heat treatments were applied on the sheets. Microstructures of the sheets have been analysed by optical microscope and scanning electron microscope, SEM by plan, longitudinal and transverse views. More detailed microstructure investigation was analysed by transmission electron microscope, TEM. Semi-quantitative and quantitative elemental analyses has been performed by SEM-EDS (Energy Dispersive Spectrometer), TEM-EDS and EPMA (Electron Probe Micro Analyser)-WDS (Wavelength Dispersive Spectrometer) systems. XRD (X-ray Diffraction) techniques are used for both characterization and also texture purposes. Mechanical properties have been investigated by tensile tests and also hardness measurements. Tensile tests have been performed at three different directions: rolling direction, 45 degrees to rolling direction and transverse direction by using an extensometer. Micro Vickers and Brinell Hardness test measurements were done on plan view and different cross-section directions. In addition, produced sheets were investigated by cold rolling, hot rolling and annealing tests. From the results of this study production of wrought magnesium alloys suitable for automotive, military and electronics industries seems possible. Magnesium is the lightest of all structural metals with a density of 1.74 g/cm3. Aluminum is 1.5 times, titanium is 3 times and iron is 4 times of magnesium in density. Magnesium alloys have high specific strength, high specific stiffness, good castability and machinability, low heat content per unit of volume, high damping capacity, and good electro-magnetic (EMI) shielding. Magnesium is dimensionally stable, it welds easily, and it has impact and dent resistant. It is the sixth most abundant metal and eighth element on the earth's surface. Furthermore, magnesium is readily recyclable. Magnesium alloys also have effective heat dissipation. Due to these properties, there is increasing interest in using magnesium alloys especially in electronics and transportation industries. Almost 30% of the applications are structural applications (portable electronic equipment, such as laptop computers, cellular phones and video cameras; military equipment; aircraft parts; sporting goods and hand tools. Recently, using magnesium alloys that are lighter than aluminum alloys are being investigated for the automotive industry. Magnesium alloys are already used within the automotive interior as instrumental panel substrate, seat frame, seat riser, seat pan, console bracket, steering wheel, steering column parts; in the power train as valve cover, transmission cases; in the body as door and roof frames, sunroof panel, mirror bracket, tailgate; in the chassis as wheel, brake pedal brackets. High flexural/buckling stiffness and bending strength are needed for automotive body components such as doors, boot, and bonnet. VW 3L Lupo bonnet is a good prototype example for future application of magnesium sheets. Other possible wrought alloy automotive applications are extruded profiles such as window frames, seat and supporting structures. Magnesium components are usually produced by the die casting process. In spite of cost effective, the die casting process is not suitable for manufacturing large flat parts, such as hood, door, and lift-gate substrates. Also, mechanical properties of the cast parts, particularly fatigue resistance, can be substandard. Parts requiring good mechanical properties and fatigue endurance strength are best produced from wrought alloys. Replacement of conventional sheet metals with magnesium can reduce the vehicle mass, thus promote energy efficient transportation. By using wrought magnesium alloys, a decrease in vehicle weight up to 100 kg and a reduction of 5 % fuel consumption can be realized. Application of wrought magnesium alloys especially in the form of sheet is limited due to the price of conventional rolling product. However, the demand for decreasing the magnesium sheet prices is high and can be met through twin-roll casting. Keywords: Magnesium alloys, sheet, twin roll casting

Mapping the research landscape of bauxite by-products (red mud): An evolutionary perspective from 1995 to 2022

The global population growth has significantly impacted energy and raw material consumption, unmatched since the Industrial Revolution. Among metals, aluminium ranks second only to steel, with annual production exceeding 69 million tonnes. Due to its high demand, bauxite, the primary ore from which aluminium is extracted, is now classified as a critical material in the EU and the US, given the potential risk of supply shortages for essential applications. Geographical and production challenges surround bauxite, presenting geo-economic and environmental challenges. A critical concern in aluminium production is managing by-products, notably red mud, a bauxite residue, generating over 175 million tonnes annually worldwide. Comprehensive bibliometric research is imperative due to the high amount of bibliographical resources related to this topic, encompassing circular economy, re-valorisation, sustainability, and disposal. This study employs bibliometric methods to assess red mud valorisation, offering insights into research topics, influential authors, and key journals, shedding light on the past, present, and future of red mud research. Such bibliometric analysis not only highlights the current state of the field but also serves as a valuable tool for decision-making, enabling researchers and policymakers to identify trends, gaps, and areas for further exploration, fostering informed and sustainable advancements in the by-products of the aluminium industry

Reduction Conditions of Metallic Calcium from Magnesium Production Residues

In this paper, the theoretical and industrial definitions of metallic calcium production by the metallothermic process in a vacuum atmosphere were investigated. In the experiments, Al is the only reductant used for metallothermic calcium production. The effects of Al stoichiometry, time variances, and temperature changes were investigated. The experiments were carried out at 1200 °C, 1250 °C, and 1300 °C, and with 100% Al, 125% Al, and 150% Al stoichiometry to produce metallic calcium from the residue of metallic magnesium production. Both the raw materials and the residue phases were characterized by atomic absorption spectrometry (AAS), X-ray diffraction (XRD) spectrometry, and chemical analysis techniques. Experimental results were investigated to determine the highest efficiency of reduction conditions. From the results of the experiments, reaction kinetics and activation energy were calculated. According to the experimental results, the highest recovery rate parameters for the reduction of calcium are 150% stoichiometric Al for 480 min at 1300 °C, with 72% recovery

Deposition and Characterization of Tungsten Carbide Thin Films by DC Magnetron Sputtering for Wear-Resistant Applications

In this study, WC (tungsten carbide) thin films were deposited on high-speed steel (AISI M2) and Si (100) substrates by direct current magnetron sputtering of a tungsten carbide target having 7% cobalt as binding material. The properties of the coatings have been modified by the change in the bias voltages from grounded to 200 V. All the coatings were deposited at 250A degrees C constant temperature. The microstructure and the thickness of the films were determined from cross-sectional field-emission gun scanning electron microscope micrographs. The chemical composition of the film was determined by electron probe micro analyzer. The x-ray diffractometer has been used for the phase analyses. Nanoindentation and wear tests were used to determine the mechanical and tribological properties of the films, respectively. It is found that the increase in the bias voltages increased drastically the hardness and elastic modulus, decreased the friction coefficient values and increased the wear resistance of tungsten carbide thin films by a phase transformation from metallic W (tungsten) to a nonstoichiometric WC1-x (tungsten carbide) phase

Production of Iron Based Alloys from Mill Scale through Metallothermic Reduction

Mill scale (MS) has a potential to use as an iron source because of its high iron content. MS mainly consists of a mixture of iron oxides, metallic iron and other base metal oxides. MS is formed on the surfaces of steel ingots during continuous casting as a waste material. In this study, the use of MS as an iron source for the production of carbon-free iron containing alloys (unalloyed iron, Fe-Ni, Fe-Cr-Ni, Fe-Cr-Ni-Mo) via a metallothermic reduction process was investigated. Thermodynamic calculations and the experimental studies were performed on the basis of 100 g of MS. The effects of different stoichiometric amounts of MS and aluminum (Al) powders (as reductant) were investigated for the production of unalloyed Fe. While, different amount of metal oxide ratios and their effects on metal recoveries, compositions and microstructure of final alloys were studied during Fe-based alloys production. The highest iron recovery during unalloyed Fe production was obtained as 95.14% by using 100 g of MS and 100% stoichiometric Al (28.6 g) containing mixture. In Fe-based alloys production series, the highest metal recovery values were reached up to 95.0% for Fe, 95.1% for Ni, 68.3% for Cr and 77.2% for Mo, respectively