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Öğe Effect of Milling Time on Dry Sliding Wear Behaviors of Carbon Nanotubes Reinforced Al Matrix Composites(Amer Scientific Publishers, 2020) Yildirim, Musa; Ozyurek, Dursun; Guru, MetinIn this study, the effect of mechanical milling time on microstructure, hardness and dry sliding wear behaviors of carbon nanotube reinforced aluminum matrix composites was investigated. Multi-walled carbon nanotubes (amount of 1%) were added to gas atomized AA7075 alloy as a reinforcement material and it was mechanical milled five different times. Milled Al-CNTs composite powders were added in a steel mold and pre-formed by cold pressing and hot pressing. Pre-formed composites samples were sintered. Microstructures of produced samples were examined by Scanning electron microscope. Density and hardness values were measured 1 ms(-1) sliding speed, 30 N loads and five different sliding distances were used in dry sliding wear tests on pin on disc type wear apparatus. As a result of the studies, it was found that the particle size increased as the milling time increased. Powders milled for 100 min had the largest particle size, whereas powders milled for 120 min had a smaller particle size. The results indicated that composites mechanically milled for 120 min had both the highest hardness value and the lowest weight loss.Öğe The Effects of Precipitate Size on the Hardness and Wear Behaviors of Aged 7075 Aluminum Alloys Produced by Powder Metallurgy Route(Springer Heidelberg, 2016) Yildirim, Musa; Ozyurek, Dursun; Guru, MetinIn this study, the effects of precipitate size, which occurred on the microstructure by applying T6 heat treatment at different temperatures and different time intervals, were investigated on hardness and wear behaviors of 7075 Aluminum alloys produced by powder metallurgy route. Aging heat treatments were performed at three different temperatures (110-130 A degrees C) and four different times (16-28 h). The results show that MgZn2 precipitates were formed in the microstructure by aging heat treatments and their sizes were changed depending on aging temperature and time. The precipitate size was increased by increasing aging temperature and time. The largest size of the precipitate was measured from SEM images of the samples aged at 130 A degrees C for 24 h. The highest hardness values were measured at 120 A degrees C for 24-h aged samples. The wear test results revealed that the weight loss was increased with increase in sliding distance and the minimum weight loss was observed at 120 A degrees C for 24-h aged samples.Öğe Investigation of microstructure and wear behaviors of al matrix composites reinforced by carbon nanotube(Taylor & Francis Inc, 2016) Yildirim, Musa; Ozyurek, Dursun; Guru, MetinIn this study, the effect of CNT amount in Al-CNT composites produced by adding carbon nanotube (CNT) to 7075 Al alloy in various amounts on microstructure and wear behaviors of aluminum matrix composites was investigated. CNT was added to 7075 Al alloy powder at five different amounts. The powders were mechanically milled for 2 hours. Mechanical milled powders were cold pressed and then pre-shaped by hot pressing. Pre-shaped samples were sintered for 1 hour under 10(6) millibar in 580 degrees C. Microstructure examinations, hardness measurements, and wear tests were carried out. The results show that CNT's in the microstructure were agglomerated as nanotube amount increases and there was no uniform distribution. The highest hardness value was obtained in AMC reinforced with 1% CNT while it is seen that hardness of the composite decreases and weight loss increases as CNT amount increases.Öğe PERFORMANCE IMPROVEMENT OF THE HEAT RECOVERY UNIT WITH SEQUENTIAL TYPE HEAT PIPES USING TiO2 NANOFLUID(Vinca Inst Nuclear Sci, 2019) Ozturk, Ahmet; Ozalp, Mehmet; Sozen, Adnan; Guru, MetinThis paper deals with the improvement of thermal performance of the heat recovery system in air-to-air unit by using a nanofluid of TiO2 particles and distilled water. The experimental set-up equipped with 15 copper pipes of a 1000 mm length, 10.5 mm inner diameter; and 12 mm outer diameter was used. The evaporator section consists of 450 mm of heat pipes, the condenser section is 400 mm, and the adiabatic section is 150 mm. In experimental studies, 33% of the evaporator volumes of heat pipes were filled with working fluids. Experiments were carried out at temperatures between 25 degrees C and 90 degrees C by usingfive different cooling air-flows (40, 42, 45, 61, and 84 g/s), and two different heating powers (3 kW and 6 kW) for the evaporation section, to determine heat removed from the condensation section. Trials were performed for distilled water and nanofluid respectively, and the results were compared with each other. Results revealed that a 50% recovery in the thermal performance of the heat pipe heat recovery system was achieved in the design using TiO2 nanofluid as the working liquid, at a heating power of 3 kW, air velocity of 2.03 m/s and air-flow of 84 g/s.Öğe Production and Characterization of FeB and Fe2B Compounds by Mechanochemical Method(Gazi Univ, 2023) Celik, Ulku Asli; Sunar, Talha; Ozyurek, Dursun; Guru, MetinIn this study, iron and boron powders were alloyed at different rates (according to their molar weights) in a spex-type grinding device, and FeB and Fe2B compounds were obtained by mechanochemical method (the solid phase reaction). The containment and precise measurements of iron and boron mixed in different mole ratios were carried out with the Glove-Box in an argon atmosphere. Thermogravimetric and Differential Thermal Analysis for the determination of the sintering temperature of alloys; X-ray Diffraction and Scanning Electron Microscopy analyzes were performed to examine the phase compositions and microstructures. As a result of the studies, highly amorphous Fe2B and FeB compounds were produced. Due to the stoichiometric coefficients, the peaks of the FeB composition were more pronounced. For the sample targeted as FeB, it was observed that the peaks of the FeB composition were more pronounced due to the stoichiometric coefficients. From the EDS analysis, it was understood that the iron and boron elements on the surface of the samples exhibited a homogeneous distribution in the structure. According to the hardness results, it is understood that the sample targeted as FeB is harder than the samples targeted as Fe2B. This study will contribute to the production of advanced materials with regional hardness regimes by synthesizing different compositions.Öğe Synthesis and Characterization of Zinc Fluoroborate from Zinc Fluoride and Boron by Mechanochemical Reaction(Springer Heidelberg, 2017) Aydin, Duygu Y.; Guru, Metin; Ipek, Dilek; Ozyurek, DursunThis paper deals with characterization and synthesis of zinc fluoroborate from zinc fluoride and boron by mechanochemical reaction. Zinc fluoroborate is widely used in high technological areas such as textile, chemical reaction, plating solution, and glass. In this study, zinc fluoroborate has been synthesized via high-energy ball milling method. The effect of reactant mol ratio (B/ and ball milling period was investigated on the product yield. After completion of the reaction, the product in the reaction mixture (including excess reactant and side products) was purified by the extraction with water. The samples were characterized by FT-IR and ion-selective electrode. SEM and EDX analyses were took place. Decomposition of sample was characterized by TG-DTA. The sample was sintered at 300- to compare the data with TG-DTA. The results showed that decomposition of B-F bond started at . As a result of these experiments, maximum yield was obtained at 0.8 molar ratio and 3000 min. of mechanochemical reaction duration with the use of ball milling. Eighty-three percentage pure zinc fluoroborate was produced by adding the purification step.
