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The removal of heavy metals from refinery effluents by sulfide precipitation
(BERG FAC TECHNICAL UNIV KOSICE, 2023) Kartal, Levent; Şen, Aysel; Timur, Servet
This study investigated the selective precipitation of copper (Cu2+), nickel (Ni2+) and zinc (Zn2+) ions from industrial wastewater by using sodium sulfide (Na2S). The effects of pH, time and free sulfide concentration on the selective precipitation were systematically investigated using synthetically prepared solutions and gold refinery wastewater. First, the optimum precipitation pH values of metals, the amount of Na2S and time were determined by using synthetic solutions containing Cu, Ni and Zn single metal ions. The highest precipitation efficiencies were obtained at a pH of 4, 5.3 and 5.3 for Cu, Ni and Zn, respectively. Based on these results, the effects of Na2S stoichiometry and time of precipitation were investigated with synthetically prepared solutions containing mixed metal ions (100?mg/L Cu2+, 90?mg/L Ni2+ and 100?mg/L Zn2+). Metal sulfide precipitation efficiencies increased with increasing amounts of Na2S and reached a maximum at a ratio of 1:1.75 (Metal ion: Na2S molar ratio). Lastly, the results obtained from the experiments performed with synthetic solutions were used for the metal sulfide precipitation from industrial wastewater. The precipitation from refining wastewater containing 10 g/L Cu2+, 0.3 g/L Ni2+ and 3 g/L Zn2+ ions was achieved at pH values from 2.3 to 5.3. At a pH of 2.3, Cu2+ precipitated as CuS (Cu2S) at 100% efficiency. While the Ni2+ concentration in the solution decreased by only 44% at a pH of 2.3, the Zn2+ concentration decreased by 52%. At a pH of 5.3, Cu2+ and Zn2+ precipitated together at 100%.
Single step calciothermic synthesis of nickel boride particles in molten salt
(Springer, 2023) Kartal, Levent
Abstract In this study, production of nickel boride (NixB) via calciothermic reduction in molten salt has been studied. Firstly, the electrochemical behaviors of CaO and NiO in CaCl2 melt were examined by cyclic voltammetry (CV). Then, the influences of the process parameters (temperature (1173–1273 K) and time (15–60 min)) on the powders were investigated. Based on the CV results, it was understood that NiO reduction takes place in one step at -0.25 V. Temperature investigations revealed that Ni and Ni2B phases that were present at low temperatures disappeared as the temperature increased. The Ni3B and Ni2B ratios in the particles increased as the duration went on, and almost no Ni left in the particles after 60 min. The magnetic properties of the particles were investigated and, the saturation magnetization, coercive and remanent values were determined as 25.063 emu/g, 32.694 Oe, and 0.903 emu/g, respectively. © 2023, The Author(s) under exclusive licence to Australian Ceramic Society.
Photoluminescence Investigation of Tb Doped Yb2O3 Phosphors Produced by Precipitation Method
(2021) Ünal, Fatma
In this study, un-doped and Tb doped ytterbium oxide (Yb2O3:Tb3+) particles with different dopant rates (2, 4, 6 and 8 at. %) were produced by precipitation method, followed by subsequent calcination at 1000 °C for 2 h. The crystal structure of all particles was cubic Yb2O3 structure. The presence of Tb ion in Yb2O3 host structure was proved from the XRD peak shift results. The crystal structure expanded compared to un-doped Yb2O3 particles with doping, confirming calculated lattice parameter (LP) values. The LP, crystallite size (CS) and dislocation density values were in the range of 1.0428 – 1.0596 nm, 16 – 25 nm and 0.00189 – 0.00391 nm-2 , respectively. Only one sharp emission peak was observed at 506 nm corresponding to 5D4 – 7F6 transition (green emission) from photoluminescence (PL) spectra of the phosphor particles. The PL emission intensities were found to be strongly dependent on both CS and dopant rate. There was a positive correlation between increasing CS, decreasing lattice strain/dislocation density and PL intensity. Crystal defects decreased and PL intensity increased up to 6 at. % dopant rate.
ZrO2 coating via e-beam evaporation on PE separators for lithium-ion batteries
(Springer Heidelberg, 2021) Sivlin, D.; Ünal, Fatma; Karahan, Deniz; Kazmanlı, Kürşat; Keleş, Özgür
In this paper, ZrO2 is deposited on a polyethylene-based separator via electron beam evaporation method. The analyses reveal that the application of the ceramic-based coating enhances the electrolyte uptake capability from 79 to 135% and the ionic conductivity from 7.1 x 10(-4) to 7.5 x 10(-4) S/cm. Linear sweep voltammetry tests show the superior electrochemical stability in the coated separator up to 5.5 V. This study shows that with the thin ZrO2 coating, the separator maintains its structure plus the existence of ZrO2 has an essential impact on electrolyte decomposition, SEI layer formation, and safety of the separator.
Effect of Particle Morphology on Physical, Mechanical and Wear Properties of Cobalt Metal Powders
(Springer India, 2021) Bulut, Berrak; Ünal, Fatma; Baydoğan, Murat; Kayalı, Eyup Sabri
Cobalt is used in applications that require high densities and good mechanical properties. Cobalt powder is used in batteries, cemented carbides, stainless steel, machine tools and also in manufacturing of metal matrix diamond tools designed for the cutting and drilling of hard rocks and concrete. This study aimed to investigate the structural properties and compare the mechanical and micro structural properties of two different cobalt powders, specifically the spherical grain (Co-S) and rod-like grain shapes (Co-R), to enhance the cutting performances of the diamond cutting tools. The flow properties of the powders, as a function of the shear strain rate, were determined using Freeman Technology (FT4) rheometer analysis. The microstructural characterizations were conducted using scanning electron microscopy (SEM)-energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses, and the crystallite size values were calculated using the Williamson-Hall method. The mechanical characterizations were conducted using the density measurement, hardness, compression test, and wear test. Based on the results of the FT4 rheometer analysis, the Co-S powder had higher compressibility and air permeability compared to the Co-R powder. The SEM analysis of the sintered samples revealed multiple pores in the Co-R powder. The highest mechanical properties were obtained in the sintered sample of the S series. The most suitable Co powder for the preparation of metal matrix mixtures of diamond cutting tools produced using SPS was determined to be the Co-S series.
Synthesis, characterization and radioluminescence properties of erbium-doped yttria phosphors
(Springer, 2021) Ünal, Fatma; Kaya, Faruk; Kazmanlı, Kürşat
Radioluminescence (RL) behaviour of erbium-doped yttria nanoparticles (Y2O3:Er3+ NPs) which were produced by sol-gel method was reported for future scintillator applications. NPs with dopant rates of 1at%, 5at%, 10at% and 20at% Er were produced and calcined at 800 degrees C, and effect of increased calcination temperature (1100 degrees C) on the RL behaviour was also reported. X-ray diffraction (XRD) results showed that all phosphors had the cubic Y2O3 bixbyite-type structure. The lattice parameters, crystallite sizes (CS), and lattice strain values were calculated by Cohen-Wagner (C-W) and Williamson-Hall (W-H) methods, respectively. Additionally, the optimum solubility value of the Er3+ dopant ion in the Y2O3 host lattice was calculated to be approximately 4at% according to Vegard's law, which was experimentally obtained from the 5at% Er3+ ion containing solution. Both peak shifts in XRD patterns and X-ray photoelectron spectroscopy (XPS) analyses confirmed that Er3+ dopant ions were successfully incorporated into the Y2O3 host structure. High-resolution transmission electron microscopy (HRTEM) results verified the average CS values and agglomerated NPs morphologies were revealed. Scanning electron microscopy (SEM) results showed the neck formation between the particles due to increased calcination temperature. As a result of the RL measurements under a Cu K-alpha X-ray radiation (wavelength, lambda = 0.154 nm) source with 50 kV and 10 mA beam current, it was determined that the highest RL emission belonged to 5at% Er doped sample. In the RL emission spectrum, the emission peaks were observed in the wavelength ranges of 510-575 nm (H-2(11/2), S-4(3/2)-I-4(15/2); green emission) and 645-690 nm (F-4(9/2)-I-4(15/2); red emission). The emission peaks at 581, 583, 587, 593, 601, 611 and 632 nm wavelengths were also detected. It was found that both dopant rate and calcination temperature affected the RL emission intensity. The color shifted from red to green with increasing calcination temperature which was attributed to the increased crystallinity and reduced crystal defects.
Fabrication and characterization of Yb-doped Y2O3 powders and thin films
(Carl Hanser Verlag, 2020) Kaya, Elif Emil; Ünal, Fatma; Kazmanlı, Kürşat; Gürmen, Sebahattin
Yttrium oxide (Y2O3) and ytterbium (Yb)-doped Y2O3 particles were synthesized via the sol-gel method from the aqueous solution of their nitrate salts. The synthesized powders were then deposited on Corning glass substrates using an electron beam evaporation technique to examine the growth morphology of the thin films. The effect of the Yb dopant concentration on the microstructure and morphology of the Y2O3 powders and thin films was investigated using various characterization techniques. The synthesized powders and fabricated thin films have body-centered cubic structures with space group Ia-3. Based on the X-ray peak broadening, crystallite size and lattice parameters were evaluated with the Williamsom-Hall and Cohen-Wagner methods. The lattice parameter and crystallite size decrease with increasing Yb concentration. The intensities of the Raman peaks decrease due to microstructural disorder caused by the increase in the Yb dopant concentration. The band gap values of the powders also decrease depending on the dopant concentration, similar to the lattice parameter and crystallite size. While the synthesized powders have a sponge-like morphology, they exhibit different morphological structures depending on the dopant concentration when converted into thin films.
Formation of alpha/beta-Si(3)N(4 )nanoparticles by carbothermal reduction and nitridation of geopolymers
(Wiley, 2019) Bağcı, Cengiz; Yang, Qun; Kriven, Waltraud M.
Silicon nitride (Si3N4) particles with various alpha/beta-Si(3)N(4 )ratios were fabricated from geopolymer (GP)-carbon compositions (M2O center dot Al2O3 center dot 4.5SiO(2)center dot 12H(2)O+18C), where M is an alkali ion (Na+, K+ and Cs+). They were made by carbothermal reduction and nitridation at 1400 degrees, 1500 degrees, and 1600 degrees C for 2 hours under flowing nitrogen. Characterization of carbothermally reacted GP-carbon compositions was based on XRD, SEM-EDS, HRTEM, and selected area electron diffraction analyses. Depending on the alkaline composition of GP, the carbon content and the reaction temperature, a compositionally variable alpha/beta-Si3N4 or SiAlON was achieved. Crystallization of the GPs gradually increased by heat treatment over 1400 degrees C with corresponding weight loss. It was found that NaGP, KGP, and CsGP crystallized into a major phase of alpha-Si3N4, beta-Si3N4, and SiAlON, respectively. Prolonged heating at 1600 degrees C led to an increase in the alpha/beta-Si3N4 ratio in NaGP due to the formation of aluminum nitride, while it led to a decrease in alpha/beta-Si3N4 ratio in KGP. In the case of CsGP, SiAlON replaced the pollucite which mainly formed at lower temperatures. Transmission electron microscopy revealed that the needle-like particles were of ~0.5 mu m in size and consisting of alpha/beta-Si3N4 mixtures.
Effects of dopant rate and calcination parameters on photoluminescence emission of Y2O3:Eu3+ phosphors: A statistical approach
(Elsevier Sci Ltd, 2019) Ünal, Fatma; Kaya, Faruk; Kazmanli, Kursat
In this study, Y2O3:Eu3+ phosphorescent powders with different dopant rates were synthesized by sol-gel method. Statistical experimental design methods were used to investigate the effects of calcination temperature (800, 900 and 1200 degrees C), time (5 and 7 h) and dopant rate (5 and 7% at.) on the colour of the photoluminescence emission. The XRD results showed that as-prepared powders were amorphous. After calcination, the crystal structures became cubic bixbyite-type. XRD and Raman spectroscopy results confirmed the existence of Eu3+ in the Y2O3 crystal. Crystallite sizes and lattice parameters of the powders were calculated by using Williamson-Hall and Cohen-Wagner methods, respectively. Photoluminescence emission spectra of the samples were measured at room temperature by using an optical emission spectroscope with 380 nm monochromatic excitation source and the emission spectra were transformed to CIELab colour space coordinates. The emission spectra exhibited a strong characteristic peak at 611 nm and a smaller peak at 614 nm. Depending on the dopant rate and the calcination parameters, other smaller peaks appeared at 587, 592, 606, 623 and 631 nm. The CIELab colour space transformation results showed that the powders possessed orange-red emission. The dopant rate and the calcination conditions slightly changed the emission colour. According to the statistical analysis, the dopant rate had the strongest effect on a* colour space value (redness) whereas all parameters had equally significant effect on b* colour space value (yellowness). The ANOVA analysis revealed that the interaction between the temperature and the dopant rate was also statistically significant with the confidence level of 95%. This interaction was attributed to the relation between lattice strain and calcination temperature, which confirms the strong symmetry dependence of the electron-dipole (ED) transitions of the Y2O3:Eu3+ phosphors.
Production of Un-Doped and Er-Doped Y2O3 Thin Films by Electron Beam Evaporation Method
(Springer, 2019) Ünal, Fatma; Kazmanli, Kursat
In this study, un-doped and doped yttrium oxide (Y2O3) powders with different erbium concentrations were synthesized using sol-gel method. The synthesized powders were investigated by Raman analysis and the evolution of different peaks associated with Er dopant in Y2O3 structure was clearly observed. Moreover, the powders were deposited on Corning glasses using electron beam (e-beam) evaporation method. The samples were heat-treated at 300 and 400 degrees C temperatures for 6 h. The effects of the heat treatment temperatures and dopant concentrations on the optical properties were investigated. Phase constituents of the thin films were analyzed by X-ray diffraction with a thin film attachment using Cu-K-alpha radiation. Optical transmittance curves of the films were measured using optical spectrophotometer. Cross sectional morphologies of the films were examined using scanning electron microscopy (SEM). It was observed that Er dopants caused a shift in the transmittance curves to UV region.
Production and characterization of re3+:Yb2o3 nanoparticles
(Trans Tech Publications Ltd, 2021) Ünal, Fatma; Kazmanlı, Kürşat
In this study, doped ytterbium oxide (Yb2O3) nanoparticles (NPs) with different dopant type (Eu and/or Tb) and undoped were synthesized by wet chemical method using nitrate salt as a starting source. Afterwards, they were calcined at 900 °C for 4 h. The crystal structure phase, size, and morphology of undoped and doped Yb2O3 nanoparticles (NPs) were characterized by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Undoped and doped NPs were exhibited cubic bixbyite-type crystal structure (Ia-3 space group). Lattice parameter changes caused by dopant element in NPs were examined using X-ray peak profile analysis. In order to investigate the occuring changes in the crystal structure, average crystallite size (CS) and lattice parameter (LP) values were computed with Williamson–Hall (W–H) and Cohen-Wagner (C–W) methods, respectively. It was observed that the crystal structure of the doped NPs expanded compared to the undoped Yb2O3 NPs, which explains the increase in the LP and CS values. The LP values of all the NPs were ranged from 10.444 Å (R2 = 94.9) to 10.453 Å (R2 = 81.8) while the CS of them were between 19 nm (R2 = 95.9) and 24 nm (R2 = 88.8). All the NPs exhibited nearly spherical and agglomerate structure and there were also few pores between the agglomerate particles in the structure. Besides, continuous agglomerate morphology formation was observed in particles containing Tb. The average nanoparticle size values were varied between 46 and 115 nm depending on the dopant element. © 2021 Trans Tech Publications Ltd, Switzerland.
Effects of the alumina reinforcement ratio on the corrosion properties of iron based composite materials
(Carl Hanser Verlag, 2020) Karacif, Kubilay
Iron based composite materials reinforced with various ceramic particles are used in operating conditions requiring features such as high hardness, strength and wear resistance. The composite materials may be subject to corrosion depending on the working environment. In this study, the corrosion properties of iron based composite materials produced by powder metallurgy, containing carbon and different amounts of alumina reinforcement were investigated. In the materials production, 0.5 wt.-% carbon and 1, 3 and 5 wt.-% alumina powders were added to the iron powders as reinforcement. Followed by mixing, one–way cold pressing and sintering, respectively, both iron based carbon and alumina reinforced composite samples were obtained. The electrochemical corrosion properties of iron based composite materials containing various amounts of alumina reinforcement were investigated in a 3.5 wt.-% NaCl environment and the effects of the reinforcing material ratio on the corrosion behavior of the composite material were determined. It was determined that with an increase in the alumina reinforcement ratio, the corrosion rate of the material increases and the corrosion resistance decreases.
A New Approach for Cu and Fe/FexB Production from Chalcopyrite by Molten Salt Electrolysis
(Springer, 2020) Kartal, Levent; Daryal, Mehmet Barış; Timur, Servet
In the present study, copper (Cu) and iron boride -( FexB) were produced for the first time through molten salt electrolysis using chalcopyrite -(CuFeS2) in an oxide- based borax electrolyte. Molten salt electrolysis was carried out at 1073 K and a current density of 600 mA/cm2 for 3600 s under galvanostatic conditions. Cu and Fe/FexB were deposited on the graphite crucible surface used as the cathode. The particles obtained as a result of electrolysis were examined by X-ray diffraction (XRD) and determined to contain Cu and Fe/FexB. The location and ratio of Cu and -FexB in the particles were investigated by using EDS mapping, energy-dispersive spectroscopy (EDS), and X-ray spectroscopy (XRD); Cu and Fe/FexB were found to be present throughout the particles at different ratios. Cu and Fe/FexB were successfully separated from each other by selective leaching of copper in a 1 M -NH3-H2O solution. The time-dependent dissolution behavior of Cu was investigated at pH 8, 298 K, 600 rpm stirring rate for 900-5400 s, and it was observed that the dissolution rate increased over time and all the copper had completely dissolved after 5400 s. After leaching particles were examined by XRD and SEM, it was revealed that Fe/FexB particles did not contain any Cu.
Modelling of relation between synthesis parameters and average crystallitesize of Yb2O3 nanoparticles using Box-Behnken design
(Elsevier, 2020) Ünal, Fatma; Kaya, Faruk
A straightforward wet chemical method has been applied for the fabrication of Yb2O3nanoparticles (NPs) fromytterbium nitrate solution by using ammonium carbonate as precipitation agent. Effects of precursor molarity(0.1, 0.15 and 0.2 M), calcination temperature (800, 900 and 1000 °C) and time (2, 4 and 6 h) on averagecrystallite size (CS) of the NPs were statistically investigated by using Box-Behnken design. A simple and ef-fective quadratic model was proposed for controlling the CS. The CS values were calculated by using WilliamsonHall method (W-H) from X-Ray Diffraction (XRD) broadening data and found to be ranging between 13 and26 nm. Agglomerated NPs morphologies and particle sizes were revealed by Field Emission Gun-ScanningElectron Microscopy (FEG-SEM). Fourier Transform Infrared (FTIR) spectrophotometry confirmed that as-re-ceived Yb2(CO3)3xH2O powders were successfully transformed into Yb2O3NPs with calcination. High-ResolutionTransmission Electron Microscopy (HRTEM) results verified the average CS values. ANOVA analyses revealedthat linear and squared terms of the production parameters were significantly related to the CS whereas in-teraction terms were insignificant with the confidence level of 95% (R2= 92.67%, R2-adj = 87.17%). Thecalcination temperature had the highest impact on the average CS followed by the time and precursor molarity.Increasing calcination parameters resulted in bigger crystallites whereas increasing precursor molarity exhibiteda critical supersaturation value (0.15 M) from which the average CS was decreased
Geopolimerlerden mekanokimyasal aktivasyon ile silisyum karbür tip nano parçacıkların üretilebilirliğinin araştırılması
(Gazi Üniversitesi, 2017) Bağcı, Cengiz
Mekanokimyasal olarak 6, 12, 24, 48 saat süreyle aktive edilen ve M= (Na+ veya K+) olmak üzere, sodyum veya potasyum alkali metal içeren (M2OoAl2O3o4.5SiO2o12H2O+18C) geopolimer karbon kompozisyonlarının karbotermal reaksiyonu ile silisyum karbür (SiC) tip nanoparçacıklar elde edilmiştir. Aktivasyon süresi ve alkali şartlara bağlı olarak elde edilen SiC, faz analizi, parçacık boyutu ve şekli ve nanoyapı açısından XRD, rietveld arıtımı, SEM ve TEMSAD analizleri ile karakterize edilmiştir. Sonuçlar, sodyum geopolimerde mekanokimyasal aktivasyon süresinin artışı ile beraber 24 saate kadar SiC miktarının arttığını ve 48 saatte azaldığını, potasyum geopolimer durumunda ise süre artışına bağlı olarak genelde hızlı bir azalma olduğunu göstermiştir. Yüksek saflıkta SiC eldesi kritik 24 saat sodyum geopolimerde, ~% 98.4 oranında gerçekleşmiştir. Mikro yapı ise çoğunlukla kristalize olmuş, 50-200 nm çapında ve uzunlukları 2-10 µm arasında değişen nano fiber, geri kalanı ise küresel nano-parçacıklar ve çok az amorf camsı fazdan oluşmaktadır
Thermal grooving by surface diffusion: a review of classical thermo-kinetics approach
(Hitit University, 2017) Akyıldız, Öncü; Oğurtanı, Tarık Ömer
In polycrystalline materials wherever a grain boundary intersects a free surface and whenever the topographic variation associated with the atomic motion is favored by total free energy dissipation, the material surface grooves. In this review, we focused on the grain boundary grooving by surface diffusion which is an active mechanism at moderate temperatures and for grooves small in size. Starting with a description of the classical thermo-kinetics treatment of the process, we briefly reviewed Mullins' very first modeling effort with a small slope assumption at the groove root and further considerations regarding finite slopes, different grain geometries, and anisotropic surface free energies. We concluded by giving examples of experimental observations in accord with theoretical calculations.
Mechanochemical activation of sodium geopolymers containing carbon-nano powder
(Gazi Üniversitesi, 2017) Bağcı, Cengiz; Düzgün, Zehra
Mekanokimyasal aktivasyon için 9 veya 18 mol karbon nano-tozlar içeren iki farklı sodyum geopolymer iyi bilinen geopolymer yöntemi ile hazırlanmıştır. 9 mol karbon, geopolimer üretimi aşamasında geopolimer reçineye dahil edilirken, 18 mol karbon, geopolimer işleminden sonra üretilen geopolimer ile karıştırılmıştır. NaGP9C ve NaGP18C olarak adlandırılan her iki geopolimer karbon başlangıç malzemesi 24 saat mekanokimyasal olarak aktive edilmiş ve NaGP18C ayrıca 48 saat aktive edilmiştir. Aktivasyon işlemleri 250 dev/dak' da ağırlıkça bilye toz oranı 25:1 olacak şekilde bir gezegen bilyeli değirmende gerçekleştirilmiştir. Aktivasyon ve karbon içeriğine bağlı olarak, sonuç kompozisyonların oda ve yüksek sıcaklık özellikleri optik mikroskop, XRD, SEM ve DSC analizleri yapılarak değerlendirildi.
Kaynaklı birleştirmeli konstrüksiyonların çarpılma eğilimlerinin belirlenmesi için deneysel bir yaklaşım
(2008) Özçatalbaş, Yusuf; Fındık, Tayfun; Kurt, Adem; Karacif, Kubilay; Özer, Alpay; Vural, Halil İbrahim
Bu çalışmada, kaynaklı birleştirmeli konstrüksiyonların imalat sürecinde ve sonrasında oluşan çarpılma eğilimlerinin, çarpılma kuvvetleri vasıtasıyla belirlenmesi amaçlanmıştır. Bu amaçla, rijit bir kafes hücre sistemi ve kaynaklı konstrüksiyonlarda oluşan çarpılma kuvvetlerini ölçebilen kuvvet algılayıcı plakalar (KAP) hazırlanmıştır. Kuvvet algılayıcı plakalarda gerinim-ölçer uygulaması yapılmış ve tam Wheatstone köprüsü kurulmuştur. Hazırlanan KAP’lar, 0,36 N hassasiyette eksenel çekme ve basma kuvvetlerini algılayabilmektedir. Puntalanmış bir kafes kiriş, numune kiriş olarak, rijit kafes hücre içerisine asılmıştır. Çarpılma kuvvetlerini ölçmek için, numune kiriş ve rijit kafes arasına iki doğrultuda KAP’lar bağlanmıştır. Düğüm noktalarına uygulanan kaynak işlemlerinin numune kirişte oluşturduğu çarpılmalar, KAP’larda kuvvet değişimleri olarak algılanmıştır. Veri toplama cihazı vasıtasıyla ölçülen çarpılma kuvvetleri, ALMEMO Win Control programı vasıtasıyla kişisel bilgisayara aktarılmış ve kirişin çarpılma analizleri yapılmıştır. Bu sayede bir konstrüksiyonun, kaynaklı birleştirme anında ve soğuma sürecinde oluşan çarpılma eğilimlerinin belirlenmesi sağlanmıştır.
A comparison on physical, structural, and photocatalytical properties of TiO2 nanopowders produced using sol-gel and flame spray pyrolysis
(2013) Erol, Mustafa; Sancakoğlu, Orkut; Yurddaşkal, Murat; Yıldırım, Serdar; Çelik, Erdal
In this study, nanoscale photocatalyst TiO2 powders were synthesized via sol-gel and flame spray pyrolysis (FSP). Phase structures and ratios were analyzed by X-ray diffractometer (XRD). Size, specific surface area, and morphologies were determined using particle size analyzer, Brunauer-Emmett-Teller theory, and scanning electron microscope, respectively. Anatase phase with some rutile together was obtained in XRD analysis. The degradation rates of aqueous methylene blue (MB) by TiO2 nanopowders were calculated using UV-vis spectrophotometer. It was found that MB decomposition was successfully achieved with significantly high efficiencies for both sol-gel and FSP-derived powders with small differences. © 2013 The American Ceramic Society.
Effect of electrolytic nickel coating on fatigue life of iron based powder metal parts
(2011) Çinici, Hanifi; Karacif, Kubilay; Kafkas, Fırat; Çıtak, Ramazan
Electrolytic coating is one of the methods mainly used to provide corrosion resistance for the powder metal parts. The coatings have strong effects on mechanical properties of coated parts as well as on surface properties. The other factor that affects the mechanical properties of powder metal (P/M) parts is density ratio. In this study the effect of electrolytic coating and density ratio on fatigue life of powder metal iron parts has been investigated. Commercially pure iron powders were pressed under 150, 200 and 250 MPa pressures. Specimens were sintered at 1100? C in flowing argon atmosphere for 45 min. Some of the specimens were electrolytic nickel coated. Coated and uncoated specimens were fatigued in rotating bending under the same conditions. Also residual stress analysis was carried out on both kinds of specimens. It had been determined that electrolytic nickel coating increased fatigue life of P/M iron parts. It had also been determined that fatigue life increased with density ratio.

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