Phase Evolution of Al85Co7Y8 Alloy during Mechanical Alloying

Bu çalışmada nanoyapılı Al85Co7Y8 (at.%) alaşımı, mekanik alaşımlama (MA) tekniği kullanılarak elementel tozların katı hal reaksiyonuyla sentezlenmiştir. Toz alaşımlar, argon gazı altında sertleştirilmiş paslanmaz çelik hazne ve bilyeler kullanılarak yüksek-enerjili bilyeli değirmen içerisinde 300 saatlik öğütme işlemine tabi tutulmuştur. Öğütme işlemi süresince numunelerdeki yapısal ve morfolojik değişimler X-ışını difraksiyonu (XRD) ve taramalı elektron mikroskobu (SEM) ile termal kararlılıkları ise diferansiyel termal analiz (DTA) ile incelenmiştir. MA işlemi sonucunda aşırı doymuş fcc-Al katı çözelti fazı içeren alaşımlar üretilmiştir. Al85Co7Y8 alaşımının 300 saatlik öğütme işlemi sonrasındaki kristalit boyutu yaklaşık 16 nm olarak bulunmuşturIn this study, the nanostructured AlCoY (at.%) alloy was synthesized by a solid state reaction from the constituent elemental powder mixture via mechanical alloying (MA). The powder mixture was ball milled for times up to 300 h in a planetary high energy mill using hardened steel vial and balls under argon atmosphere. Structural and morphological changes during the milling process were characterized by a combination of X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Thermal stability of the milled powders was investigated using differential thermal analysis (DTA). The results showed that supersaturated ?-Al solid solution was formed in the whole content of the milled material. The mechanically alloyed AlCoY powder for 300 h of milling indicated the formation of fine nanoparticles with a size of about 16 n

Structural and Mechanical Properties of Nanocrystalline Fe60Al30Cu10 (at.%) Powders Prepared by Mechanical Alloying

In the present study, the nanostructured Fe(Al,Cu) solid solution was synthesized by mechanical alloying (MA) process of the elemental powders. The powder mixtures were milled in a planetary ball mill for various periods of time, up to 50 h. The structural and mechanical properties of the samples were studied by using X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX) and Vickers microhardness test. Results indicated that after 10 h of milling, all Al and Cu atoms were dissolved into the Fe lattice to form bcc-Fe(Al,Cu) solid solution. The particle morphology of the alloys was followed the cold welding, fracturing and steady state stages during milling times. Both particle size and crystallite size were reduced to ~500 nm and ~6 nm, respectively after 50 h of milling. However, the microhardness values increased with the increasing milling time

Rapidly solidified Al-6.5 wt.% Ni alloy

Aluminium-nickel alloy with nominal composition 6.5 wt.% Ni has been manufactured by chill-casting and melt-spinning methods. The resulting microstructures have been examined by optical microscopy (OM) and scanning electron microscopy (SEM). These results showed that the microstructure of the rapidly solidified ribbons is clearly different from that of the chill-casting alloy. The effect of the wheel speed on rapidly solidified ribbons dimension and the relationship between ribbon thickness and wheel speed was also examined. It was found that there is good relationship between ribbon thickness and wheel speed. The ribbon thickness decreased inversely with the wheel speed. Furthermore, the microhardness of the chill-casting alloy and the rapidly solidified ribbons were measured by using a Vickers indenter. The result showed that the microhardness of the rapidly solidified ribbons is higher than that of chill-casting alloy. (C) 2003 Elsevier Science B.V. All rights reserved

NADPH oxidase P22PHOX gene expression in ulcerative colitis

Background/Aims: Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, which catalyzes the formation of reactive oxygen species (ROS) in phagocytic cells, has five subunits: p67phox ("phox"refers to "phagocyte oxidase"), p47phox, p40phox, p22phox, and gp91phox (catalytic subunit). Oxidative stress resulting from the accumulation of ROS and/or defective removal of ROS by antioxidants has detrimental effects on cellular functions and may contribute to chronic inflammation. Disruption of the colonic mucosa due to the dysregulation of antioxidants or transformation enzymes may play a role in the pathogenesis of ulcerative colitis (UC) and influence the clinical features of this disease. In this study, we examined the expression of the gene encoding NADPH oxidase subunit p22phox cytochrome b-245, alphapolypeptidein the colonic mucosa to test its possible contribution in the pathogenesis of UC.Materials and Methods: Expression levels of mRNA in the inflamed and non-inflamed colonic mucosa (determined using colonoscopy)of 22 patients with UC and in the normal mucosa of 22 healthy controls were analyzed using real-time polymerase chain reaction.Results: Expression levels of mRNA were not significantly different between patients with inflamed and non-inflamed colonic mucosa (p>0.05) and betweenpatients with inflamed colonicmucosa and healthy controls (p>0.05). Conclusion: Although our data suggest that expression of the gene encoding p22phox is not associated with chronic inflammation in patients with UC, other mechanisms can affect oxidative stress in these patients.Background/Aims: Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, which catalyzes the formation of reactive oxygen species (ROS) in phagocytic cells, has five subunits: p67phox ("phox"refers to "phagocyte oxidase"), p47phox, p40phox, p22phox, and gp91phox (catalytic subunit). Oxidative stress resulting from the accumulation of ROS and/or defective removal of ROS by antioxidants has detrimental effects on cellular functions and may contribute to chronic inflammation. Disruption of the colonic mucosa due to the dysregulation of antioxidants or transformation enzymes may play a role in the pathogenesis of ulcerative colitis (UC) and influence the clinical features of this disease. In this study, we examined the expression of the gene encoding NADPH oxidase subunit p22phox cytochrome b-245, alphapolypeptidein the colonic mucosa to test its possible contribution in the pathogenesis of UC.Materials and Methods: Expression levels of mRNA in the inflamed and non-inflamed colonic mucosa (determined using colonoscopy)of 22 patients with UC and in the normal mucosa of 22 healthy controls were analyzed using real-time polymerase chain reaction.Results: Expression levels of mRNA were not significantly different between patients with inflamed and non-inflamed colonic mucosa (p>0.05) and betweenpatients with inflamed colonicmucosa and healthy controls (p>0.05). Conclusion: Although our data suggest that expression of the gene encoding p22phox is not associated with chronic inflammation in patients with UC, other mechanisms can affect oxidative stress in these patients