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Öğe N-type InP Schottky diodes with organic thin layer: Electrical and interfacial properties(Journal of Vacuum Science & Technology B, 2010-03) Güllü, Ömer; Turut, AbdulmecitThe rectifying junction characteristics of methyl red (MR) organic film on n-type InP substrate have been studied. It has been observed that MR-based structure shows an excellent rectifying behavior and that the MR film increases the effective barrier height by influencing the space charge region of the n-type InP. The barrier height and ideality factor values for this structure have been obtained as 0.75 eV and 1.93 from the forward bias current-voltage characteristics, respectively. By using capacitance-voltage characteristics at 1 MHz, the barrier height and the carrier concentration values have been calculated as 0.93 eV and 5.13×1015 cm−3, respectively. The energy distributions of the interface states and their relaxation times have been determined from the forward bias capacitance-frequency and conductance-frequency characteristics. Moreover, it was seen that both the interface-state density and the relaxation time of the interface states decreased with bias voltage from experimental results.Öğe Milling Inconel 718 workpiece with cryogenically treated and untreated cutting tools(SpringerLink, 2021-07-17) Gürbüz, Hüseyin; Baday, ŞehmusAlthough Inconel 718 is an important material for modern aircraft and aerospace, it is a kind material, which is known to have low machinability. Especially, while these types of materials are machined, high cutting temperatures, BUE on cutting tool, high cutting forces, and work hardening occur. Therefore, in recent years, instead of producing new cutting tools that can withstand these difficult conditions, cryogenic process, which is a heat treatment method to increase the wear resistance and hardness of the cutting tool, has been applied. In this experimental study, feed force, surface roughness, vibration, cutting tool wear, hardness, and abrasive wear values that occurred as a result of milling of Inconel 718 material by means of cryogenically treated and untreated cutting tools were investigated. Three different cutting speeds (35-45-55 m/min) and three different feed rates (0.02- 0.03-0.04 mm/tooth) at constant depth of cut (0.2 mm) were used as cutting parameters in the experiments. As a result of the experiments, lower feed forces, surface roughness, vibration, and cutting tool wear were obtained with cryogenically treated cutting tools. As the feed rate and cutting speed were increased, it was seen that surface roughness, vibration, and feed force values increased. At the end of the experiments, it was established that there was a significant relation between vibration and surface roughness. However, there appeared an inverse proportion between abrasive wear and hardness values. While BUE did not occur during cryogenically treated cutting tools, it was observed that BUE occurred in cutting tools which were not cryogenically treated. Also, in this study, the statistical validity of the experimental values was tested with the help of secondorder equations and analyses of variance (ANOVA). R2 values obtained as 99.14%, 99.76%, and 97.98% for vibration, surface roughness, and feed force values were modeled statistically with the help of second-order equations, respectively.Öğe Electrical analysis of organic dye based MIS Schottky contacts(Microelectronic Engineering, 2010-05-25) Güllü, Ömer; Turut, AbdulmecitIn this work, we prepared metal/interlayer/semiconductor (MIS) diodes by coating of an organic film onp-Si substrate. Metal(Al)/interlayer(Orange G@OG)/semiconductor(p-Si) MIS structure had a good recti-fying behavior. By using the forward-biasI–Vcharacteristics, the values of ideality factor (n) and barrierheight (BH) for the Al/OG/p-Si MIS diode were obtained as 1.73 and 0.77 eV, respectively. It was seen thatthe BH value of 0.77 eV calculated for the Al/OG/p-Si MIS diode was significantly larger than the value of0.50 eV of conventional Al/p-Si Schottky diodes. Modification of the potential barrier of Al/p-Si diode wasachieved by using thin interlayer of the OG organic material. This was attributed to the fact that the OGorganic interlayer increased the effective barrier height by influencing the space charge region of Si. Theinterface-state density of the MIS diode was found to vary from 2.79x1013to 5.80x1012eVx1cmx2.Öğe Electronic properties of the metal organic interlayer inorganic semiconductor sandwich device(Elsevier, 2010-03) Güllü, Ömer; Turut, Abdulmecit; Kılıçoğlu, TahsinIn this study, we prepared a Metal(Al)/Organic Interlayer(Congo Red=CR)/Inorganic Semiconductor (p-Si) (MIS) Schottky device formed by coating of an organic film on p-Si semiconductor wafer. The Al/CR/p-Si MIS device had a good rectifying behavior. By using the forward bias I–V characteristics, the values of ideality factor (n) and barrier height (Φb) for the Al/CR/p-Si MIS device were obtained as 1.68 and 0.77 eV, respectively. It was seen that the Φb value of 0.77 eV calculated for the Al/CR/p-Si MIS device was significantly higher than value of 0.50 eV of the conventional Al/p-Si Schottky diodes. Modification of the interfacial potential barrier of the Al/p-Si diode was achieved by using a thin interlayer of the CR organic material. This was attributed to the fact that the CR organic interlayer increased the effective barrier height by influencing the space charge region of Si. The interface-state density of the MIS diode was found to vary from 1.24×1013 to 2.44×1012 eV−1 cm−2.Öğe Effects of natural hard shell particles on physical, chemical, mechanical and thermal properties of composites(SAGE Journals, 2021-05-31) Çelik, Yahya Hışman; Çelik, Kadir Serdar; Kılıçkap, ErolShelled herbal foods are widely consumed. The evaluation of the shells of these foods is important due to their features such as low cost, ease of recycling and environmental friendliness. In this study, hazelnut shell (HS), pistachio shell (PS), and apricot kernel shell (AKS) were brought to powder particles by grinding to dimensions of 300–425 µm. Some of the powder particles were converted into ash at 900°C. The amounts of cellulose, ash, humidity, and metal in these particles via chemical analyses were determined, while their structural properties via X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) analyses. Composite materials were produced by adding 15 wt.% to the polyester matrix material from these powder particles and ashes. Compression strength, hardness, specific weight, and thermal conductivity of these composites were analyzed. The lowest and highest humidity, ash, cellulose, hemicellulose, and lignin ratios in powders showed differences depending on the type of powders. The amount of Sn and K in the HS, PS, and AKS powders were close to each other, while the amount of Ca, Na, Mg, Fe, Mn, Cu, Zn and Si was higher in AKS powder. The reinforcement adding to the polyester increased the compression strength, hardness, specific weight and thermal conductivity properties.Öğe Effect of temperature, force, and vibration on fatigue strength of friction stir-welded AA7075 aluminum alloy joints(SpringerLink, 2021-01-04) Çelik, Yahya Hışman; Kılıçkap, Erol; Çetkin, EdipIn this study, the AA7075 alloy pairs were welded by friction stir welding method by using conical- and triangular-type stirrer pins. Welding forces and moments, vibration, and temperature values have been measured during the jointing depending on the welding parameters. Finally, microstructures were examined and mechanical tests were carried out. Results obtained from the experiments revealed that at low spindle speed and welding feed rates, the temperatures formed on the surface of the alloy pair were high, the vibrations were low, and the welding force and moments were partially high. When the microstructures of the welded areas are examined, it was determined that the conical mixing pin has a better microstructure than the triangular mixing pin. In addition, it was determined that the mechanical properties of welded joints having a good microstructure were quite good. As a result, it was observed that forces during welding, temperature of welding, and vibration values have an effect on microstructure and mechanical properties.Öğe Environmental effect on fatigue life of glass–epoxy composite pipes subjected to impact loading(Elsevier, 2013-01) Deniz, Mehmet Emin; Karakuzu, Ramazan; Özen, Mustafa; Özdemir, Okan; İçten, Bülent MuratThe main objective of this experimental study was to investigate the effects of seawater and impact loading on the fatigue life of glass–epoxy composite pipes under cyclic internal pressure. The pipes were produced by filament winding technique. Composite specimens were immersed in seawater for periods of 3, 6, and 9 months. After the impact tests are carried out at three different energy levels (5, 7.5, and 10 J), fatigue tests were conducted on the specimens. It is seen from results that fatigue life changes according to both impact energy and seawater immersion time. Fatigue life of non-impacted specimen is greater than the impacted one. Fatigue life increases in the impacted specimens up to 3 months and reaches generally maximum value. After that it decreases with increase in seawater immersion time. During the fatigue tests, fatigue damage types named perspiration, leakage, and eruption were observed.Öğe Geochemical features of the Menteşe Formation dolostones (Rhaetian) in the Karacahisar-Kasımlar area (Isparta-Turkey)(SpringerLink, 2018-08) Dinç, Salih; Özkan, Ali MüjdatThe purpose of this study is to determine the geochemical characteristics of the Menteşe dolostones (Rhaetian) in the west Taurus Mountains, Turkey. The isotope characteristics of the Menteşe dolostones show a variation in the δ18O values of the dolomites between + 1.35 and − 2.72‰ (VPDB) and a variation in the δ13C values of the dolomites between + 1.6 and + 3.33‰ (VPDB). Most of the Menteşe dolostone samples have positive oxygen isotope values; others have weak negative isotope values, which indicate early diagenetic development. In addition, oxygen, carbon, and strontium isotopes and trace element analyses suggest that these dolostones were probably resulted from insignificant recrystallizaion process than chemically similar fluids. Furthermore, Mn/Sr values of the Menteşe dolostones indicate that there is no significant diagenetic alteration. The total REE contents of the Menteşe Formation dolostones display a strong positive correlation with Si, Al, Fe, K, Ti, Ba, Rb and negative correlation with Mg, hence REE content is associated with in the first degree titanium-bearing minerals (probably sphene, rutile, anatase), second degree phosphate (apatite), and barium and rubidium-bearing minerals (probably barite). Ce anomalies versus Nd concentrations of the Menteşe dolostone samples indicate that these dolostones are formed in an anoxic environment. In addition, the K/Rb ratios of the Menteşe dolostones are not exposed to any metamorphism and indicate some diagenetic alteration. Calculated temperature values using δ18O values of the Menteşe dolostones yield precipitation temperatures of 17 to 42 °C, and suggest burial depths of 67 to 900 m. Sources of magnesium for dolomitization of the Menteşe Formation carbonates were most likely fluids from seawater and/or diagenetic brines (slightly modified seawater). The Menteşe dolostones formed as early diagenetic (Rhaetian to Cenomanian) in shallow burial areas at lower temperatures than seawater and/or diagenetic brines (slightly modified seawater).Öğe Electrical properties of organic–ınorganic semiconductor device based on rhodamine-101(SpringerLink, 2009-05) Güllü, Ömer; Turut, Abdulmecit; Yıldırım, Nezir; Çakar, MuzafferRhodamine-101 (Rh101) thin films on n-type Si substrates have been formed by means of evaporation, thus Sn/Rh101/n-Si heterojunctions have been fabricated. The Sn/Rh101/n-Si devices are rectifying. The optical energy gaps have been determined from the absorption spectra in the wavelength range of 400 nm to 700 nm. Rh101 has been characterized by direct optical absorption with an optical edge at 2.05 ± 0.05 eV and by indirect optical absorption with␣an optical edge at 1.80 ± 0.05 eV. It was demonstrated that trap-charge-limited current is the dominant transport mechanism at large forward bias. A␣mobility value of μ = 7.31 × 10−6 cm2 V−1 s−1 for Rh101 has been obtained from the forward-bias current–voltage characteristics.Öğe Effects of fuels produced from fish and cooking oils on performance and emissions of a diesel engine(Elsevier, 2014-07-15) Oktay, Hasan; Yumrutaş, Recep; Behçet, RasimIn this study, two fuels called as FOME (Fish Oil Methyl Ester) and COME (Cooking Oil Methyl Ester) were produced from waste fish and cooking oils using the transesterification method. Commercial D2 (Diesel fuel) and two fuel samples obtained by blending the FOME and COME with the D2 with a ratio of 25% on volume basis were used as fuels in a Diesel test engine. An experimental study was performed for investigating the performance and exhaust emissions of the Diesel engine using the fuels. According to the test results, it was observed that the fish oil based fuel indicated better performance and exhaust emission parameters than those of cooking oil. Results clearly showed that the engine power and torque values were lower than those of the Diesel fuel with values of 3.05% and 1.25% for FB25, and 4.07% and 2.2% for CB25, respectively. Also, brake specific fuel consumption for the produced fuels increased up to 5.69% compared to Diesel fuel. However, HC and CO emission reductions compared to the Diesel fuel were found to be around 16.24% and 19.81%, respectively. But, the amount of increase in NOx emissions for the same biodiesel fuels reached up to 17.2%.
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