181 research outputs found
Gençlik edebiyatının inşası: İpek Ongun
No full textThis work is a student project of the Department of History, Faculty of Economics, Administrative and Social Sciences, İhsan Doğramacı Bilkent University.The History of Turkey course (HIST200) is a requirement for all Bilkent undergraduates. It is designed to encourage students to work in groups on projects concerning any topic of their choice that relates to the history of Turkey. It is designed as an interactive course with an emphasis on research and the objective of investigating events, chronologically short historical periods, as well as historic representations. Students from all departments prepare and present final projects for examination by a committee, with 10 projects chosen to receive awards.Ankara : İhsan Doğramacı Bilkent Üniversitesi İktisadi, İdari ve Sosyal Bilimler Fakültesi, Tarih Bölümü, 2025.Includes bibliographical references (pages 19-20).16. Yüzyılda başlayan çocuk edebiyatı ürünlerini, modernleşme süreciyle ortaya çıkan gençlik yazını takip etmiştir. Hem dünya hem de türk edebiyatı bu yeniliğe tanıklık etmiş, aynı zamanda bu yeni yazın türü değişen ve dönüşen çevresel koşullar etrafında yeniden şekillenmiştir. 1980 yılı itibariyle yoğunlaşan gençlik yazını çalışmalarına, dönemin önde gelen yazarlarından İpek Ongun tarafından katkı sağlanmıştır. Bu çalışmada; geçmişten bugüne gençlik yazını örnekleri ve türün tarihsel gelişimini belirten kronolojik çalışmalardan faydalanılarak, gençlik edebiyatının gelişimi, geçmiş-bugün karşılaştırması ve İpek Ongun’un bu doğrultuda bu edebi türe sağladığı katkılar ele alınacaktır.The products of children’s literature, which started in the 16th century, had been followed by youth literature in accordance with the modernization process. Both world and Turkish literature testified this innovation, while the new literary genre reshaped around changing and transforming environmental factors. Works of youth literature that intensified as of 1980, had been contributed by İpek Ongun who is one of the leading writers of that era. This study will examine the development of youth literature, comparison of then-now and İpek Ongun’s contributions with the help of examples of youth literature from past to present and chronological researches that identify the genre’s historical evolution.by Erdinç Ofli
Pack Siliconizing of Ti6Al4V Alloy
No full textIn this study, it was aimed to produce titanium silicide layer on Ti6Al4V by a simple, cheap and efficient method of pack siliconizing. Siliconizing was performed in a pack containing a mixture composed of SiO2 powder as siliconizing source, pure Al powder as a reducer for siliconizing, NH4Cl as an activator and Al2O3 powder as filler, at 1000 degrees C for 8, 10 and 12 hours in open atmospheric furnace. Optical microscope and SEM-EDS studies indicate that the morphology of silicide layers has smooth, dense and layered nature. The presence of phases, confirmed by XRD analyses, reveals that the silicide layers formed at 1000 degrees C are composed of TiSi2, Ti3Si5, TiN, TiO2 and SiO2 compounds. Silicide layer thickness was increased with increasing process time and ranged from 7.5 to 9.0 mu m. Hardness of silicide layers, measured by Vickers indentation, is over 2100 HV
An investigation of the effect of SiC particle size on Cu-SiC composites
No full textIn this study mechanical properties of copper were enhanced by adding 1 wt.%, 2 wt.%, 3 wt.% and 5 wt.% SiC particles into the matrix. SiC particles of having 1 mu m, 5 mu m and 30 mu m sizes were used as reinforcement. Composite samples were produced by powder metallurgy method and sintering was performed in an open atmospheric furnace at 700 degrees C for 2 h. Optical and SEM studies showed that the distribution of the reinforced particle was uniform. XRD analysis indicated that the dominant components in the sintered composites were Cu and SiC. Relative density and electrical conductivity of the composites decreased with increasing the amount of SiC and increased with increasing SiC particle size. Hardness of the composites increased with both amount and the particle size of SiC particles. A maximum relative density of 98% and electrical conductivity of 96% IACS were obtained for Cu-1 wt.% SiC with 30 mu m particle size. (C) 2012 Elsevier Ltd. All rights reserved
FABRICATION AND PROPERTIES OF SiC REINFORCED COPPER-MATRIX-COMPOSITE CONTACT MATERIAL
No full textThis study aims at improving mechanical properties of electrical contacts through copper and copper-matrix silicon-carbide reinforced composites produced with powder metallurgy. Copper powder was produced with the cementation method. Pure copper and mixtures of copper with 3 % of mass fraction of SiC powder were pressed with a uniaxial pressure of 280 MPa and sintered at 700 degrees C for 2 h in an atmospheric environment. After the sintering, these compacts were immediately pressed at a load of 850 MPa while the samples were hot. The characterization of the samples was made with microstructural investigations, relative-density experiments, electrical-conductivity and hardness measurements. XRD analyses revealed that there are no other phases besides Cu and SiC in the sintered samples. Electrical conductivity of pure copper was reduced from 91.7 1.8 % IACS to 66.4 +/- 0.9 % IACS but the hardness of pure copper was increased from 127 +/- 1.2 HVN to 142 +/- 6.0 HVN with the addition of 3 % of mass fraction of SiC. Contact-count experiments were made with these samples to determine the contact performance for (3000, 6000, 9000, 12.000 and 21.000) turns-on/off. The loss of the contact material increased with the increasing number of turn-ons, related with the increased copper oxide amount formed on the contact surfaces
Kinetics of borided 31CrMoV9 and 34CrAlNi7 steels
No full textIn this study, kinetics of borides formed on the surface of 31CrMoV9 and 34CrAlNi7 steels borided in solid medium consisting of Ekabor II at 850-900-950 degrees C for 2, 4, 6 and 8 h were investigated. Scanning electron microscopy and optical microscopy examinations showed that borides formed on the surface of borided steels have columnar morphology. The borides formed in the coating layer confirmed by X-ray diffraction analysis are FeB, Fe2B, CrB, and Cr2B. The hardnesses of boride layers are much higher than that of matrix. It was found that depending on process temperature and time the fracture toughness of boride layers ranged from 3.93 to 4.48 MPa m(1/2) for 31CrMoV9 and from 3.87 to 4.40 MPa m(1/2) for 34CrAlNi7 steel. Activation energy, growth rate and growth acceleration of boride layer calculated according to these kinetic studies revealed that lower activation energy results in the fast growth rate and high growth acceleration. (c) 2006 Elsevier Inc. All rights reserved
Low temperature aluminising of Inconel 718 alloy by pack cementation(ICCESEN 2017)
Get PDF244-247A novel pack-aluminizing diffusion coating has been conducted on –Inconel 718 alloy at 600 and 650°C for 2 and 4 h. The aluminising powder packs have been prepared using Al powder as a source for depositing aluminium, Al2O3 powder as an inert filler and ammonium chloride NH4Cl as an activator. The microstructures of the coatings formed on the alloy surface are characterized by means of SEM/EDS and XRD analysis. Optical microscope and SEM analysis reveal that coating layers are homogenous, compact and nonporous and there is a good bonding at the interface of the coating and matrix. Layer thickness variation is measured from the surface to the matrix and changed from 10 to 40 µm which is increased with increasing process time and temperature. The hardness of the coating layer increased to 1174 HVN with the increasing process time and the temperature while the hardness of the matrix is 300 HVN
The effect of reduction of graphene oxide on the formation of hydroxyapatite and tricalcium phosphate
No full textThis study reports on biomimetic mineralization route employing reduced graphene oxide (RGO) at different rates as a template material for biomineralization of biphasic hydroxyapatite/tricalcium phosphate (HAP/TCP). RGO-HAP/TCP hybride composites were synthesized via biomineralization in Simulated Body Fluid (SBF). GO was prepared from pristine graphite by Hummers and Offeman method. GO nanoparticles were reduced with sodium borohydride (NaBH4) before soaking in 5xSBF for 3 weeks at 37 degrees C and 7.4 pH to performing biomineralization. Surface area and average size distribution of fabricated GO were found as 813.2 m(2) g(-1) and 1.2968 mu m by using BET and DLS technique, respectively. All surfaces are overall negatively charged and zeta potentials of GO, R(1)GO, R(2)GO, R(3)GO were found to be -35.05, -30.01, 29.5, -29.01 and -28.9, respectively in the neutral pH. The contact angles of GO, R(1)GO, R(2)GO and R(3)GO are 33.5 degrees, 55.3 degrees, 57.4 degrees and 61.1 degrees, respectively. The ID/IG values determined by Raman are 1.07, 1.04, 1.02 and 1.01 for GO, R(1)GO, R(2)GO and R(3)GO, respectively. After the reduction, its maximum peak at 236 was clearly shifted to 260, 264 and 267 nm for R(1)GO, R(2)GO and R(3)GO. The precipitation of biphasic HAP/TCP on R(1)GO and R(2)GO was confirmed by XRD, FTIR and TGA analysis. (C) 2017 Elsevier Ltd. All rights reserved
The Effect of Bond Coat on Mechanical Properties of Plasma-Sprayed Al2O3 and Al2O3 – 13 wt. % TiO2 Coatings on AISI 316L Stainless Steel
No full textIn this study, Al2O3 and Al2O3-13 wt% TiO2 were plasma sprayed onto AISI 316L stainless-steel substrate with and without Ni-5 wt% Al as bond coat layer. The coated specimens were characterized by optical microscopy, metallography and X-ray diffraction (XRD). Bonding strength of coatings were evaluated in accordance with the ASTM C-633 method. It was observed that the dominant phase was Al2O3 for both coatings. It was also found that the hardness of coating with bond coat was higher than that of coating without bond coat. Metallographic studies revealed that coating with bond coating has three different regions, which are the ceramic layer (Al2O3 or Al2O3-13 wt% TiO2), the bond coating, and matrix, which is not affected by coating. The coating performed by plasma-spray process without bond coating has two zones, the gray one indicating the ceramic layer and the white one characterizing the matrix. No delamination or spalling was observed in coatings. However, there are some pinholes in coating layer, but they are very rare. The bonding strength of coatings with bond coat was higher than that of coating without bond coat. The strength of adhesion and cohesion was determined by means of a planemeter. It was seen that percentage of cohesion strength was higher than that of adhesion strength. (c) 2004 Elsevier Ltd. All rights reserved
A comparison of pretreatments on hydroxyapatite formation on Ti by biomimetic method
No full textIn this study, hydroxyapatite coating on titanium material substrate was successfully performed by using biomimetic method. Titanium plates immersed in 1.5 SBF at pH 7.4 and 37 degrees C were analyzed at the end of the first, second, and fourth weeks. At the end of the first week, the immersion process was continued with the sample exposed to the optimum selected surface pretreatment. Three different treatments have been applied to determine the optimum surface treatment: each substrate immersed into NaOH, HCl, and NaOH + HCl solutions before heat treatment at 600 degrees C for 1 h and immersed in NaOH solution was selected the optimum surface treatment. The presence of biphasic hydroxyapatite (HA, Ca-5(PO4)(3)(OH)) and tricalcium phosphate (TCP, Ca-3(PO4)(2)) on Ti surfaces were confirmed by XRD. SEM studies showed that denser HA coating which have nano-sphere-like morphology formed on Ti pretreated with NaOH solution at the end of first week than other hydroxyapatite (HA)-coated Ti pretreated with NaCl and NaOH + NaCl solutions and coating thickness increased by increasing immersion time. The HA coating thickness of the samples immersed in optimum pretreatment solution was found as 178 and 340 mu m for at the end of second and fourth weeks, respectively. The particle size analysis of the biphasic HA powders scraped from the coating layer on the substrate before and after sintering was carried out by Zetasizer and it showed that HA powders have 0.58 mu m average particle size and their particle size distribution has less dimensional dispersion after sintering. Energy-dispersive X-ray spectroscopy (EDS) analysis revealed that the Ca/P ratio in HA powders was near to 1.5. Raman and Fourier transform-infrared spectroscopy (FTIR) results combined with the X-ray diffraction (XRD) indicated the presence of biphasic hydroxyapatite after biomimetic coating process and increment in crystallinity of the powders after sintering. It was found that HA nucleation on Ti pretreated with NaOH solution was higher than Ti pretreated with other solutions which is confirmed by electrochemical impedance spectroscopy (EIS)
Effects of SiC Particle Size on Properties of Cu-SiC Metal Matrix Composites
No full textThis paper was focused on the effects of particle size and distribution on some properties of the SiC particle reinforced Cu composites. Copper powder produced by cementation method was reinforced with SiC particles having 1 and 30 mu m particle size and sintered at 700 degrees C. Scanning electron microscopy studies showed that SiC particles were dispersed in copper matrix homogeneously. The presence of Cu and SiC components in composites were verified by X-ray diffraction analysis technique. The relative densities of Cu SiC composites determined by Archimedes' principle are ranged from 96.2% to 90.9% for SiC with 1 mu m particle size, 97.0% to 95.0% for SiC with 30 mu m particle size. Measured hardness of sintered compacts varied from 130 to 155 HVN for SiC having 1 mu m particle size, 188 to 229 HVN for SiC having 30 mu m particle size. Maximum electrical conductivity of test materials was obtained as 80.0% IACS (international annealed copper standard) for SiC with 1 mu m particle size and 83.0% IACS for SiC with 30 mu m particle size
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