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Öğe Effect of Carbon Nanotube Content on the Wear Behaviours of Cu-CNT Composites Produced by Powder Metallurgy Method(Polish Acad Sciences Inst Physics, 2019) Tasdemir, F.; Ozyurek, D.; Yildirim, M.In this study the effect of carbon nanotube content on the wear behaviours of Cu-carbon nanotube composites produced by powder metallurgy method was investigated. In the scope of the study five different amounts of carbon nanotube (0.5%, 1.0%, 1.5%, 2.0%, 2.5%) were added into pure Cu powders and mechanically milled for 360 min. The mechanically milled Cu-carbon nanotube powders were cold pressed under 600 MPa load and sintered in atmosphere-controlled furnace at 1000 degrees C for 1 h. Microstructure examinations, hardness measurements, and wear tests were carried out. In this study, the hardness values were found to have increased with increasing carbon nanotube content up to 1.5%. Then it decreased with increasing carbon nanotube content. Wear test results were compatible with hardness results. The lowest weight losses were measured with 1.5% carbon nanotube content.Öğe The effect of Ni addition on microstructure and mechanical properties of cast A356 alloy modified with Sr(Redakcia Kovove Materialy, 2021) Ozyurek, D.; Yildirim, M.; Yavuzer, B.; Simsek, I; Tuncay, T.In this study, casting A356 alloy was pre-alloyed with Ni, and the modification process with Sr was applied by the casting method. The role of Ni on the microstructural and mechanical properties of the produced A356-Ni alloys was investigated. The produced alloys were naturally aged at room temperature for 24 h and artificially aged at 170 degrees C for 10 h. Optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffractometer were used in microstructure studies of the A356-Ni alloys. Tensile tests and hardness measurements were carried out to determine mechanical properties. Statistical analysis of Weibull distribution on the tensile test results revealed that the characteristic ultimate tensile strength increased due to increasing the amount of alloying elements, while the characteristic percentage elongation is decreased. This was because Al-Si-Fe intermetallic decomposition and Al-Si-Fe-Ni intermetallics were formed, primarily, 0.5 and 1.0 % Ni addition. It was also determined that the Al-Si-Fe-Ni intermetallics with a morphology non-sharp corners formed more homogeneous in the microstructure. But in the A356 alloys with the addition of 1.5 % Ni, Al-Si-Fe-Ni intermetallics are formed in coarser morphology. In A356 alloys, aluminium dendrites, Al-Si eutectic between dendrites, Mg2Si precipitates are formed in the structure by ageing. Depending on the amount of Ni added to the A356 alloy, the tensile strength of the alloys containing 0.5 and 1.0 % Ni is increased.Öğe Effect of Sintering Time on Hardness and Wear Behaviours of Carbon Nanotubes Reinforced Aluminium Matrix Composites(Polish Acad Sciences Inst Physics, 2017) Yildirim, M.; Ozyurek, D.; Guru, M.In this study, the effects of sintering time on hardness and wear behaviour were investigated of carbon nanotubes reinforced aluminium matrix composites. 1% multi wall carbon nanotubes (90% purity with 9.5 nm in diameter, 1.5 mu m in length) and gas atomized 7075 Al alloy powders were mechanical milled for 120 min in a planetary ball mill. Mechanical milled aluminium composite powders were cold pressed under 520 MPa. Pre-shaped samples were sintered in atmosphere controlled furnace at 580 degrees C for three different sintering times (1, 2, and 3 h). As a result of study, it was observed that the hardness values of composites were decreased with increasing sintering time and the weight loss was decreased. It was determined from worn surface SEM images that adhesive wear mechanisms were dominant.Öğe The Effects of B4C Amount on Hardness and Wear Behaviours of 7075-B4C Composites Produced by Powder Metallurgy Method(Polish Acad Sciences Inst Physics, 2016) Ay, H.; Ozyurek, D.; Yildirim, M.; Bostan, B.In this study, the effects of B4C amount on hardness and wear behaviours of 7075 Al-B4C composites produced by powder metallurgy method were investigated. Within the scope of work, different amount of B4C (3, 6, 9%) added into gas atomized 7075 Al powders. The powders were mixed in Turbula with 67 rpm for 45 min. Then the composite powders were pre-shaped by cold pressing under 600 MPa pressure. Pre-shaped samples were sintered in atmosphere controlled furnace at 580 degrees C for 4 h. Scanning electron microscope, X-ray diffraction examinations and hardness measurements were carried out after standard metallographic processes. Wear tests were performed in a pin on type wear apparatus under 30 N with 1 m s(-1) sliding speed, at six different sliding distances (500-3000 m). Results show that the hardness was increased with increasing of amount of B4C. At the end of wear tests the lowest weight loss were found to 9% B4C containing composites. In addition, it is determined that the weight loss increased with increasing sliding distance.Öğe Hepatoprotective effect of Nigella sativa L. Extract in methyl parathion exposed rats(Parlar Scientific Publications, 2019) Berkoz, M.; Kahraman, T.; Yildirim, M.; Yigit, M.F.; Allahverdiyev, O.Methyl parathion (MP) is an organophosphorus pesticide that can induce hepatotoxicity in living organisms. Although many plant extracts have been utilized againts MP induced liver injury, it has not yet known whether Nigella sativa L. extract (NSE) has protective effects or not. We aim to investigate the hepatoprotective effect of NSE through the oxidative stress and anti-inflammatory pathways. A total of 28 rats were divided into 4 groups; control, MP, NSE and MP + NSE. We measured liver MDA level and antioxidant parameters, hepatic function enzyme, plasma cytokine levels, liver MPO activity, liver iNOS and COX-2 mRNA levels and MAPK/NF-?b protein levels. Our data showed that MP increased hepatic function tests, liver MDA level and MPO activity, plasma proinflammatory cytokines, liver iNOS and COX-2 mRNA and MAPKs protein levels and decreased antioxidant parameters, antiinflammatory cytokine and liver NF-?b protein levels. NSE decreased hepatic function tests, liver MDA level and MPO activity, plasma proinflammatory cytokines, liver iNOS and COX-2 mRNA and MAPKs protein levels and increased antioxidant parameters, antiinflammatory cytokine and liver NF-?b protein levels in the MP treated rats. These results suggested the antiinflammatory and antioxidative function of NSE in MP induced liver injury. © by PSPÖğe An Investigation of the Effects of Ageing Parameters on Wear Behaviours and Electrical Conductivity of Cu-Co-Be Alloys(Polish Acad Sciences Inst Physics, 2016) Ozyurek, D.; Yildirim, M.; Tuncay, T.In this study, the effects of ageing parameters were investigated on wear behaviours and electrical conductivity of Cu-Co-Be alloy. The samples were quenched at room temperature after solution heat treated for 1 h. Then, ageing processes were applied for three different temperatures (470 degrees C, 500 degrees C, 530 degrees C) and for three different ageing times (1, 2, 3 h). Microstructure examining, electrical conductivity and hardness measurements were carried out after ageing process. On the samples, which obtained the highest hardness values from hardness test (470 degrees C), there were carried out wear tests with 1 m s(-1) sliding speed under 30 N at four sliding distance (500-2000 m). Results clearly show that the highest hardness values were measured for samples aged at 470 degrees C for 3 h and hardness values were decreased with increasing ageing temperature. The lowest weight loss values were evaluated for samples aged at 470 degrees C for 3 h. The highest electrical conductivity values were measured at 500 degrees C for 1 h aged samples.Öğe An Investigation of the Wear Behaviours of Nano Al2O3 Particle Reinforced Cu Composites(Polish Acad Sciences Inst Physics, 2019) Tasdemir, F.; Ozyurek, D.; Yildirim, M.In this study the effect of nano Al2O3 amount on the wear behaviours of Cu-nano Al2O3 composites, produced by powder metallurgy method, was investigated. In the scope of the study five different amounts of nano Al2O3 (0.5%, 1.0%, 1.5%, 2.0 %, 2.5%) were added into pure Cu powders and mechanically milled for 240 min. The mechanically milled Cu-Al2O3 powders were pre-shaped by cold press under 600 MPa load. Pre-shaped samples were sintered in atmosphere-controlled furnace at 1000 degrees C for 1 h. Microstructure examinations, hardness measurements, and wear tests were carried out. In this study the hardness values were found to have decreased with increasing Al2O3 amount. Wear test results were compatible with hardness results. The highest weight loss was measured with 2.5% Al2O3 content.Öğe The Wear Properties of In-Situ 7075 Al-Ti Composites Produced by Powder Metallurgy Route(Amer Inst Physics, 2016) Ay, H.; Ozyurek, D.; Yildirim, M.; Bostan, B.In this study, the wear properties of in-situ 7075 Al-Ti composites produced by powder metallurgy route were investigated. Different amount of Ti (2, 4, 6 %) added to gas atomized 7075 Al alloy powders and they were mixed in turbula with 47rpm for 45 minutes. Then the mixed powders were pre-shaped by press under 600 MPa pressure. The samples were cooled in the furnace after sintered at 580 degrees C for 4 hours in the atmosphere controlled furnace. Standard metallographic process such as grinding, polishing and etching were applied to sintered samples. The hardness values were measured. Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) examines were carried out. The wear tests were performed in a pin-on disc type wear apparatus with 1 ms(-1) sliding speed at six different sliding distance (500-3000 m) under 30 N loads. As a result of studies, hardness values were increased with increasing Ti content, in addition the weight losses were decreased with increasing Ti amount.
