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Öğe Barrier enhancement of Al/n-InP Schottky diodes by graphene oxide thin layer(Scientific Publishers, 2019) Güllü, Ömer; Çankaya, Murat; Rajagopal Reddy, VarraIn the present work, the surface morphology, structural and optical features of graphene oxide (GO) films are investigated. The Al/GO/n-InP MIS diode is formed by depositing GO layer on n-InP wafer for the barrier enhancement. Interfacial properties of the MIS diode with GO interlayer are extracted from current–voltage (I–V) measurement. The simple diode parameters such as barrier height and ideality factor are extracted from I–V plots, and the values are compared with those of conventional Al/n-InP MS contact. The value of barrier height (BH) for the Al/GO/n-InP contact is found as 0.85 eV. The BH value of 0.85 eV of the Al/GO/n-InP MIS structure is as high as around 100% compared to the value of 0.43 eV of the Al/n-InP reference contacts. We have showed that the value of 0.85 eV is one of the highest values presented for reference contacts with an interlayer.Öğe Evaluation of drilling performances of nanocomposites reinforced with graphene and graphene oxide(Springer Nature, 2018-09-16) Çelik, Yahya Hışman; Kılıçkap, Erol; Koçyiğit, NihayetThe use of graphene (G) and graphene oxide (GO) reinforced nanocomposites have a great importance since G and GO improve the interface conditions of composite materials. However, the effects of G and GO on some mechanical properties and machinability in nanocomposites are still a research topic. In this study, G was converted to GO by Hummers’ method. G and GO nanoparticles were added to epoxy at different ratios and the tensile strengths of nanocomposites were determined. By taking into account, the reinforcement ratio of nanocomposites having the highest tensile strength, epoxy with G and GO, and unreinforced epoxy were added to carbon fiber (CF) fabric by hand lay-up. Thus, fabrication of the carbon fiber-reinforced plastic (CFRP) composite, and the G/CFRP and GO/CFRP nanocomposites was carried out. The effects of the G and GO on the fabricated nanocomposites, and the effect of different drilling parameters (cutting speed and feed rate) on the cutting force, cutting torque, temperature, and delamination factor were investigated. In the drilling of these composites, drills with the different bit point angles and the diameter of 5 mm were used. As a result, it was observed that GO was successfully synthesized, and G and GO positively affected the tensile strength, and GO exhibited a more effective feature than G on the tensile strength. It was also seen that the increase of the cutting speed, feed rate, bit point angle caused the increase in the cutting forces, cutting torque, and delaminations.Öğe Evaluation of drilling performances of nanocomposites reinforced with graphene and graphene oxide(Springer Nature, 2019-02-25) Çelik, Yahya Hışman; Kılıçkap, Erol; Koçyiğit, NihayetThe use of graphene (G) and graphene oxide (GO) reinforced nanocomposites have a great importance since G and GO improve the interface conditions of composite materials. However, the effects of G and GO on some mechanical properties and machinability in nanocomposites are still a research topic. In this study, G was converted to GO by Hummers’ method. G and GO nanoparticles were added to epoxy at different ratios and the tensile strengths of nanocomposites were determined. By taking into account, the reinforcement ratio of nanocomposites having the highest tensile strength, epoxy with G and GO, and unreinforced epoxy were added to carbon fiber (CF) fabric by hand lay-up. Thus, fabrication of the carbon fiber-reinforced plastic (CFRP) composite, and the G/CFRP and GO/CFRP nanocomposites was carried out. The effects of the G and GO on the fabricated nanocomposites, and the effect of different drilling parameters (cutting speed and feed rate) on the cutting force, cutting torque, temperature, and delamination factor were investigated. In the drilling of these composites, drills with the different bit point angles and the diameter of 5 mm were used. As a result, it was observed that GO was successfully synthesized, and G and GO positively affected the tensile strength, and GO exhibited a more effective feature than G on the tensile strength. It was also seen that the increase of the cutting speed, feed rate, bit point angle caused the increase in the cutting forces, cutting torque, and delaminations.
