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In this study, photocatalytic degradation of 2,4 Dichlorophenoxyacetic acid (2,4D), one of the the most used pesticide, was investigated by TiO2 photocatalyst produced by sol-gel method. Three different parameters (Titanium isopropoxide (TIP) amount, HNO3 concentration and aging time) were investigated and modelled by applying Box Behnken Experimental Design method for optimum TiO2 synthesis. Photocatalyst production process was optimized by examining the 2,4D photocatalytic degradation rate of TiO2 photocatalysts produced under different process conditions. TiO2 samples, which were synthesized with the optimum conditions, were characterized by XRD (X-ray Diffraction), SEM (Scanning Electron Microscope), zeta potential, particle size analysis, and also compared with commercial Degussa P25 TiO2 photocatalyst. 2,4D photocatalytic degradation rate was determined as 0.0084 min-1 for the optimum condition 1 (TIP amount: 24.08 mL, HNO3 concentration: 3.53 M, aging time: 2.29 hours) and 0.0085 min-1 for the optimum condition 2 (TIP amount:10.33 mL, HNO3 concentration: 0 M and aging time: 19.51 hours). The amount of used acid was reduced to zero or the aging time was reduced to the lowest value (2.29 h) by optimizing the TiO2 production parameters via experimental design methodology, hence, a very high photocatalytic efficiency was obtained. [ABSTRACT FROM AUTHOR]

In the study, the removal performance of arsenic and antimony by drinking water treatment sludge (DWTS) was investigated. DWTS-200 was produced by thermal modification of the DWTS at three different temperatures (200, 400 and 600℃). The maximum arsenic removal was obtained at 200℃ and 1 hour contact time. The surface area and pore volume of adsorbent were analyzed by BET method; phase compositions were determined by X-ray diffraction (XRD), surface morphologies and elemental analyses were performed by scanning electron microscope (SEM) and energy disperse X-ray spectroscopy (EDS). The results showed that adsorbent had a relatively high surface area (170 m2 g-1) and was predominantly amorphous. The predominant phases were iron, calcite, oxygen, and quartz. The breakthrough volumes were obtained as 6,000 L (133,000 BV) and 640 L (14,000 BV) for 40 μg As L-1 and 80 μg Sb L-1 inlet concentrations. In order to determine the kinetic parameters and predict the breakthrough curves for column design, Thomas and Yoon-nelson models were applied. The column experimental data were fitted well to each model. The maximum adsorption capacity was calculated by Thomas model as 6.53 mg Asg-1, 5.21 mg Sbg-1. Regeneration studies were also shown that DWTS-200 could be reused after regeneration. [ABSTRACT FROM AUTHOR]

Magnesium alloys; It is widely used in metallic biomaterials with its low toxic effect and biodegradability. Although these alloys help the formation of new tissues in the body, they provide great advantages over other metallic biomaterials due to their ability to dissolve from the body after the area of use has healed. However, due to their low corrosion resistance, they cause it to dissolve in the body before the treatment process is completed. This is the major disadvantage that limits the use of magnesium alloys. Various surface modification methods are applied to magnesium alloys in order to eliminate this disadvantage. Micro Arc Oxidation (MAO) method, which can provide a coating resistant to wear and corrosion, is one of the surface modification methods applied to improve the surface properties of magnesium alloys. In this study; Composite oxide coatings with Ag nanoparticle and Hydroxyapatite were grown by MAO method. Morphological properties of the coatings were determined by Scanning electron microscope and X-Ray Diffraction instruments. The antibacterial properties of Ag nanoparticle and HA doped composite oxide layer which were grown by MAO method and the biodegradability of the coated/uncoated materials in the blood plasma were investigated. As a result of the experiments, the development of bacterial activity in the sample coated by MAO was prevented by adding Ag nanoparticle and Hydroxyapatite to the electrolite solution. In addition, the biodegradation rate has been reduced by surface treatment on AZ91 Mg Alloy. As a result of the soaking test in blood plasma, it was determined that AZ91 Mg alloy protects itself against dissolution with a rate of approximately 89%. [ABSTRACT FROM AUTHOR]

In this study, additive manufacturing technique was preferred to produce Wolfram (W), Silicon (Si), and Molybdenum (Mo) doped Co-Cr biomedical alloy. In biomedical applications, the alloy consisting of Wolfram (W), Silicon (Si), Molybdenum (Mo), Chromium (Cr), and Cobalt (Co) elements as known for its high wear and good corrosion resistance. Two group of Co-Cr-Mo alloys were produced using the Selective Laser Melting (SLM) method, one of the additive manufacturing manufacturing techniques. One of the produced samples was then subjected to a secondary heat treatment process. The microstructures of the produced alloys were investigated using X-Ray diffractometry (XRD), Energy dispersive X-Ray analysis (EDX) and scanning electron microscope (SEM). Then, the mechanical properties of the alloys were analyzed by electrochemical corrosion test, microhardness test and Archimedes principle density measurement were the final tests. The data obtained as a result of the analyzes showed that a homogeneous microstructured Co-Cr-Mo alloy was produced by the additive manufacturing production technique. In addition, heat treatment caused serious changes on the microstructure and mechanical properties of the material. The most important of these changes was the reduction of the grains forming the alloy, resulting in an increase in the microhardness value of the alloy. [ABSTRACT FROM AUTHOR]

In this study, the effect of gas pressure on the shape and size of AM60 magnesium alloy powder produced by the gas atomization method has been experimentally investigated. The experiments were carried out at a constant temperature of 820°C with a 2 mm nozzle diameter and 4 different gas pressures (5, 15, 25, 35 bar). Argon gas was used to atomize the melt. In order to determine the shape of the AM60 powder produced, scanning electron microscope (SEM), XRD, XRF and SEM-EDX analysis were used to determine the phases formed in the internal structures of the powders and the% ratios of these phases, and laser measuring device was used for the powder size analysis. Hardness tests were performed to determine the mechanical properties of the powders produced. The general appearance of the AM60 alloy powders produced was ligament, acicular, droplet, flake and spherical in shape, but due to the increase of gas pressure, the shape of the powders changed mostly towards flake and spherical. It was determined that the finest powder was formed at 820°C, 35 bar gas pressure at 2 mm nozzle diameter and the powder was generally complex. [ABSTRACT FROM AUTHOR]

In this study, one binary Al-25n alloys and eleven ternary aluminum-zinc-titanium alloys, Al-25Zn-0.01Ti, Al-25Zn-0.03Ti, Al-25Zn-0.04Ti, Al-25Zn-0.05Ti, Al-25Zn-0.075Ti, Al-25Zn-0.1Ti, Al-25Zn-0.2Ti, Al-25Zn-0.4Ti, Al-25Zn-0.6Ti, Al-25Zn-0.8Ti and Al-25Zn-1Ti, were produced by permanent mold casting method. Structural, mechanical, and corrosion properties of the tested alloys were investigated. Structural investigations were carried out with scanning electron microscope (SEM) and X-ray diffraction (XRD) studies. Mechanical properties of the alloys were determined with the Brinell hardness and tensile tests. Corrosion tests were carried out with electrochemical test setup in accordance with ASTM G5 standard. Al-25Zn and Al-25Zn-Ti alloys were composed of α and η phases as the main matrix, and it was observed that Al3Ti phase began to precipitate in the microstructure when the titanium content exceeded 0.01%. In addition, the size of dendrites or grains of the Al-25Zn-Ti alloys was found to be much smaller than that of binary alloy. The hardness, yield strength, and tensile strength values of the Al-25Zn alloy significantly increased with the 0.01%Ti addition, but when Ti content exceeded 0.01%, these values decreased with increasing titanium content. It was observed that titanium addition had a negative effect on the corrosion properties of the Al-25Zn alloy. The change on the mechanical and corrosion properties of the Al-25Zn alloy due to the titanium addition in different ratios have been explained based on the structural properties of the alloys. [ABSTRACT FROM AUTHOR]

One of the biggest problems in industrial plants is wear that directly affects equipment life. In integrated plants such as blast furnaces, many types of wear are encountered, one of which is erosive wear. Slurry erosion is one of the effective types of erosive wear. During the transfer of the slag into the liquid medium, the transport equipment is exposed to slurry erosion. The high amount of erosion seriously shortens the life of the equipment where the transportation is carried out and increases the maintenance-repair costs. In this study, blast furnace slag was used in the slurry erosive wear test system and the abrasivity of the St 37-2 reference standard pipe material, Hardox 400 and W2C-NiCrBSi coating materials was investigated. The slag was sieved to an average particle size of 505 µm and slurry containing 10%, 20% and 30% by weight of slag was prepared. The experiments were carried out at 2 m/s and 4 m/s peripheral speed values at the partical normal impact angle (90°). It has been determined by these experimental studies that the abrasivity of the slag prepared at a certain grain size is directly related to the concentration and the rotation speed (material conveyance speed) and that the wear is also increased by increasing the concentration and rotation speed. The wear values of the materials used as specimens are determined from high to low respectively as St 37-2, Hardox 400 and W2C-NiCrBSi coating material. In addition, the morphological structures of the worn surfaces were examined using SEM(Scanning Electron Microscope) in order to understand the wear mechanisms. [ABSTRACT FROM AUTHOR]

The influence of volume fraction of martensite and new ferrite on the tensile behaviour of dual-phase steel containing 0,0981% C, 1,653% Mn, 0,54% Si and 0,69% Ni has been studied. After intercritical annealing at 715, 725 and 752°C, the specimens were cooled in water, oil and furnace. The formation of carbide was not observed in the optical microscope investigation even at furnace cooling rate. The results showed that after annealing at the same intercritical temperature, the highest volume fraction of martensite was obtained by water cooling among all cooling conditions. By increasing the martensite content, both yield and tensile strengths increased while uniform elongation was decreasing. It was observed that at constant volume fraction of martensite, new ferrite content was varied by using controlled cooling from intercritical annealing temperatures. The presence of new ferrite caused a decrease in strength and increase in ductility. Scanning electron microscope investigations of fracture surface showed that the specimens with new ferrite had higher densities of microvoids in the necked region and exhibited completely ductile type of fracture. In contary, it was also observed that the specimens with no new ferrite had lower densities of microvoids and exhibited mixed type of fracture which comprises both cleavage and ductile fracture together. [ABSTRACT FROM AUTHOR]

In this work. Alumix 431 (AI7xxx) powder was pressed cold (room temperature) and warm (80°C) and its static and dynamic mechanical properties were investigated. Experiments were performed in two stages. In the first stage, cylindrical samples (Φ15 mm, h=15 mm) were pressed warm and cold under 300-500 MPa pressure with 50 MPa intervals and sintering conditions that give optimum density were determined by sintering under three different sintering medium. In the second stage, tensile and fatigue samples that give the same density with this determined sintering condition were produced and these tests were conducted. In order to obtain the same density with cold and warm pressing in tensile and fatigue samples, 230 and 180 MPa pressure, respectively, was used. Since they have the same density, tensile and fatigue test results that were pressed cold and warm were equal. In addition, microstructures and morphologies of samples were investigated with Light and Scanning Electron Microscope. [ABSTRACT FROM AUTHOR]