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The influence of annealing temperature on the gas sensing properties of multifunctional hematite (α-Fe2O3) films
(Springer, 2025) Sarf, Fatma; Er, Irmak Karaduman; Yakar, Emin; Acar, Selim
In this study, hematite (alpha-Fe2O3) were prepared using direct solution spin coating and the changes of some physical properties with annealing temperature (400, 500 and 600 degrees C) for 2 h were investigated. The sensors annealed at 400 degrees C, 500 degrees C and 600 degrees C are referred to as F400, F500 and F600 respectively. The X-ray diffraction patterns of the prepared samples confirm the polycrystalline nature of the rhombohedral crystal structure of hematite (alpha-Fe2O3). The surface roughness parameters (SA-SQ) of the alpha-Fe2O3 films decreased drastically with increasing annealing temperature from 400 to 600 degrees C (57.47-68.08/13.63-17.13). The direct optical band gap values were estimated from absorption measurements and ranged from 2.77 to 2.52 eV. The electrical resistivity measurement at room temperature of the samples decreased with increasing annealing temperature from 400 to 600 degrees C. The response of the CO sensor of F400, F500 and F600 was found at 180 degrees C. The response to 1 ppm CO gas was calculated to be 1.45%, 8% and 10% for F400, F500 and F600 respectively. The wettability test of the samples showed a water contact angle (WCA) of less than 90 degrees, demonstrating the hydrophilic surface especially for the samples annealed at 500 degrees C.
Evaluation of the use of microwave energy on green floor/wall tile drying process
(Taylor & Francis Inc, 2025) Durgut, Emrah
Drying green ceramic tiles is necessary before the decoration and sintering processes and constitutes an important input in terms of energy consumption in the production step. Nowadays, natural gas-fueled vertical dryers are used to dry green ceramic tiles. However, alternative energy-efficient and environmentally friendly technologies are being investigated and used in many drying applications, such as microwave energy. In this study, the effects of magnetron power and drying rate on moisture, surface temperature, and dried bending strength of green ceramic tiles were experimentally examined. First, floor and wall tiles with a wet-based moisture content of 6% were shaped with an industrial hydraulic press with the specific pressures of 320 kg/cm2 and 300 kg/cm2 at the sizes of 33 x 33 cm and 25 x 40 cm, respectively. The shaped green floor and wall tiles were dried separately with a horizontal pilot-based microwave dryer at 20, 35, and 50 kW magnetron powers and 0.5, 1.0, 1.5, and 2.0 m/min belt speeds, and then the changes in moisture, surface temperature, and bending strength values were measured. The minimum and maximum 51 degrees C/143 degrees C and 50 degrees C/138 degrees C surface temperature values were obtained for the floor and wall tiles, respectively, after the microwave drying. The moisture values changed in direct proportion to the magnetron power and inversely to the belt speed. The moisture values were reduced from 6% to a minimum of 0.1% under the conditions of 35, 50 kW of magnetron powers with 0.5 m/min of belt speed for floor tile and 50 kW of magnetron power with 0.5 m/min of belt speed for wall tile. In addition, the corner moisture values of microwave-dried tiles were lower than those in the center on the surface. The bending strength increased as the belt speed and magnetron power decreased within the working conditions. The maximum bending strength values for the floor and wall tiles were obtained as 29.2 kg/cm2 and 31.2 kg/cm2 at 20 kW magnetron power and 0.5 m/min belt speed, respectively. Of 52.4% and 42.6% energy savings in economic terms, 1000% and 837.5% increase in drying capacity, and 50.0% and 42.1% of environmental gain were calculated for the drying of floor and wall tiles with microwave energy compared to the natural gas, respectively. This study indicates that microwave energy can be used as a more energy efficient and capacity booster environmentally friendly process than natural gas-fueled vertical dryers in green ceramic drying. Units: m/min: meter per minute, speed; kg/cm2: kilogram-force per square centimeter, force mu m: micrometer, length; mm: millimeter, length; cm: centimeter, length; m: meter, length; kW: kilowatt, power; MHz: megahertz, frequency; GHz: gigahertz, frequency; g: gram, weight; kg: kilogram, weight; Sm3: standard cubic meter, volume; m2: square meter, area; kWh: kilowatt-hour, energy
Compact objects in f(R,Lm) theory
(World Scientific Publ Co Pte Ltd, 2025) Taşer, Doğukan; Doğru, Melis Ulu; Kirezli, Pınar; Aydın, Hüseyin; Eraslan, Erkan
In this study, it is aimed to investigate the Krori-Barua type compact stars within the scope of f(R, L-m) theory. In this context, first, the field equations are obtained by considering the f(R, L-m) = R/2 + alpha L-m(n) model. Interestingly, the model offers chance to attain all components of matter without any restrictions. In addition, data sets from LMC X-4, EXO 1785-248 and Cen X-3 are used to analyze physical stability of the solutions. It is obtained that all conditions such as causality and stability. which indicate consistency between compact objects and f(R, L-m) theory are valid for the constructed model. We obtained that small values of n in the f(R, L-m) function show significant effect on the consistency of the star models. Therefore, different n values are considered for each star data set when graphing the physical states. Finally, necessary quantities of the model are defined, compared with the considered stars and discussed in detail.
Comparative Analysis of Target Displacements in RC Buildings for 2023 Türkiye Earthquakes
(MDPI, 2025) Işık, Ercan; Avcıl, Fatih; Büyüksaraç, Aydın; Arkan, Enes
The Kahramanmaraş (Türkiye) earthquake on 6 February 2023, one of the largest earthquakes of the century, caused the collapse or severe damage of thousands of structures. This catastrophic disaster resulted in over 53,000 fatalities and rendered many structures unusable. This study addresses the observed damage in reinforced concrete (RC) structures, which constituted the majority of the existing urban building stock. In this study, firstly, information about the destructive Kahramanmaraş earthquakes was given. The predicted PGAs in the last two earthquake hazard maps used in Türkiye were compared with the measured PGAs from actual earthquakes to determine whether the earthquake hazard is adequately represented for eleven affected provinces in the earthquake region. The damages in RC structures were evaluated within the scope of civil and earthquake engineering. Structural analyses for the model created to represent mid-rise RC buildings in the region were carried out separately for each province using predicted and measured PGAs. Additionally, target displacements that were used in performance-based earthquake engineering for damage prediction, were examined comparatively for all provinces. While the predicted earthquake hazard and targeted displacements were exceeded in some provinces, there was no exceedance in the other provinces. The realistic representation of earthquake hazards will allow the predicted displacements for various performance levels of structures to be determined in a much more realistic way. Consequently, the performance levels predicted for the structures will be assessed with greater accuracy. The study highlights the importance of accurately presenting earthquake hazards to predict building performance effectively.
Impact of Local Soil Conditions on the Seismic Performance of Reinforced Concrete Structures: In the Context of the 2023 Kahramanmaraş Earthquakes
(MDPI, 2025) Işık, Ercan; Avcıl, Fatih; Büyüksaraç, Aydın; Arkan, Enes; Harirchian, Ehsan
Devastating earthquakes around the world highlight the crucial need to understand the seismic performance of structures. Local soil conditions are among the most significant factors influencing a structure's seismic behavior. Earthquake-soil-structure interactions directly affect seismic damage levels. In performance-based earthquake engineering, accurate target displacements enable a more realistic estimation of the expected performance levels for structures. This depends on obtaining realistic local soil conditions. This study conducted structural analyses on seven different variables, considering four different local soil conditions specified in Eurocode 8. The variables selected were importance class, peak ground acceleration (PGA), damping ratio, ground storey height, frame openings, number of storeys, and storey height, applied to a symmetrical and regular reinforced concrete structure. Period, base shear, stiffness, and target displacements were obtained for each variable through pushover analyses for the four various local soil conditions. All structural results were compared with one another and with other variables. This paper also aimed to reveal the effect of local soil conditions in the context of the 6 February 2023 Kahramanmara & scedil; (T & uuml;rkiye) earthquakes. The study confirms that variations in soil types, as classified in Eurocode 8, have a major impact on the seismic behavior of reinforced-concrete structures. Weaker soils amplify seismic effects, increasing target displacements and structural vulnerability.
Failures in Reinforced-Concrete Columns and Proposals for Reinforcement Solutions: Insights from the 2023 Kahramanmaraş Earthquakes
(MDPI, 2025) Işık, Ercan; Radu, Dorin; Harirchian, Ehsan; Avcıl, Fatih; Arkan, Enes; Büyüksaraç, Aydın; Hadzima-Nyarko, Marijana
Türkiye, a country that suffers significant structural damage from earthquakes, was struck by two major quakes on 6 February 2023, centered in Pazarcık (Mw = 7.7) and Elbistan (Mw = 7.6) in Kahramanmaraş. These earthquakes caused extensive damage and destruction to urban concrete structures, significantly contributing to the loss of life. Inadequate designs in columns, which are meant to maintain structural integrity and transfer forces, were a primary cause of the structural damage. This study provides information about these catastrophic earthquakes, focusing on the detailed examination of damages in reinforced-concrete (RC) columns. Structural analyses were conducted on a selected RC building, taking into account the primary causes of column damage: low-strength concrete and insufficient transverse reinforcement. Five different concrete classes and two transverse reinforcement spacing options were considered to analyze the impact of concrete strength. To address the exceeded shear forces in the columns, a fiber-reinforced polymer (FRP) wrapping method was employed for strengthening. Initially, a reinforcement analysis was performed on a single column that exceeded shear force limits, followed by strengthening applications on all columns exceeding the limit shear force. The results demonstrated that carbon fibers have a significant impact on the shear forces in columns. The conclusion of the research is that FRP increases the ductility of concrete columns, enabling them to withstand seismic forces more effectively. This is vital in ensuring the integrity of structures in earthquake-prone areas. Using FRP materials can also significantly reduce the carbon footprint associated with concrete construction by minimizing the need for maintenance and extending the lifespan of structures. FRP presents a sustainable and effective solution for addressing failures in reinforced concrete columns. Its unique properties not only enhance strength and durability but also significantly improve the resilience of structures against corrosion, seismic events, and overload conditions.
In situ Rb-Sr dating of K-bearing minerals in the Gonen granitoid from the western Sakarya Zone, NW Anatolia
(Oicc Press, 2024) Şengün, Fırat
Granitoids with ages ranging from Paleozoic to Tertiary are widely distributed in the western Sakarya Zone. The Gospacing diaeresisnen granitoid is one of these Paleozoic (Early Carboniferous) granitoids and exposed on the western part of the Sakarya Zone in NW Anatolia. The Gospacing diaeresisnen granitoid is unconformably overlain by the Jurassic Bay & imath;rkospacing diaeresisy Formation consisting of conglomerate, sandstone, siltstone, and claystone intercalation. Medium to coarse-grained, yellowish brown-colored Gospacing diaeresisnen granitoid chiefly made up of K-feldspar, plagioclase, muscovite, quartz, and biotite. In this paper, it is presented in situ Rb-Sr isochron ages for the Gospacing diaeresisnen granitoid in the western Sakarya Zone. The isochron derived from muscovite and plagiocalse minerals occurring in the granitoid yielded 299.3 +/- 3.4 Ma (Late Carboniferous), which is interpreted as the emplacement age of the Gospacing diaeresisnen granitoid. This study also testifies that radiometric in situ Rb-Sr dating can be applied to resolve absolute dating of magmatic complexes. According to the initial 87Sr/86Sr ratio, the magma producing the Gospacing diaeresisnen granitoid was derived from the enriched subcontinental lithospheric mantle forming the ancient crust. The Carboniferous magmatic event can be attributed to the northward subduction of the Palae-Tethys oceanic crust along the southern margin of Laurasia in the Early-Late Carboniferous.
Fine-size separation of halloysite, kaolinite, and quartz minerals as binary systems using dispersion and sedimentation methods
(Oficyna Wydawnicza Politechniki Wroclawskiej, 2025) Durgut, Emrah; Çavdar, Yunus Emre; Çınar, Mustafa; Yavuz, Osman; Özdemir, Orhan
Clay minerals are mainly composed of aluminum hydrosilicates. In some minerals, aluminum is completely or partially replaced by Fe or Mg. Alkaline minerals or alkali metals are present as major constituents of clay minerals. While some clay sources may contain a single clay mineral, they often contain different minerals such as quartz, calcite, feldspar, pyrite, etc. as impurities. They also contain organic matter and water-soluble salts. Halloysite is a clay mineral belonging to the kaolinite group and USA Environmental Protection Agency (EPA 4A) declared it as an innocuous/adaptable material to human health and the environment. Halloysite ore deposits are mainly found together with kaolinite and quartz minerals, but can also be found as a pure source. The degree of purity of halloysite ore determines the industrial area where it will be used and therefore its economic value. Since clay minerals are naturally composed of fine particles, it is necessary to disperse the clay particles in suspension to separate halloysite and kaolinite minerals. In addition, there are also fine-grained quartz minerals, and to recover pure halloysite minerals, it is necessary to determine their properties in the fine size fraction. In this study, the dispersion properties of halloysite, kaolinite, and quartz minerals in the presence of sodium silicate (SS), sodium tripolyphosphate (STPP), and sodium hexametaphosphate (SHMP) dispersants in fine-size fraction (-38 }m) were researched by particle size measurements and mineral separation properties were investigated by sedimentation experiments at different acidic, neutral, alkaline pH values. In dispersion experiments, the d90 values of halloysite, kaolinite, and quartz minerals were 74.0, 50.7, and 61.3 }m without any dispersant addition, and such values decreased to 54.7, 26.3, and 57.1 }m as SHMP increased to 10 kg/ton, respectively. d50 and d10 values showed a significant change for halloysite, while no important change was observed for kaolinite and halloysite. SHMP had the most effect on the particle size change in the dispersants especially on halloysite minerals. The least effect on particle size change was observed in the quartz sample with dispersant addition. The sedimentation experiments aimed to investigate the effects of pH on halloysite, kaolinite, and quartz recoveries in binary systems as settled products. Kaolinite settled more at acidic pH and halloysite at basic pH. There was no pH-dependent change in the settling behavior for halloysite and quartz. In the quartz-kaolinite system, quartz mineral settled more than kaolinite for all pH values. The settling experiments showed the importance of morphological differences between tubular halloysite and lamellar kaolinite minerals.
Bedrock Investigation Based on Shear Wave Velocity (Vs) on the Sites of High-Rise Buildings
(Springer Science and Business Media Deutschland GmbH, 2025) Büyüksaraç, Aydın; Ateş, Barış; Bektaş, Özcan; Pamuk, Eren; Işık, Ercan
The foundations of high-rise buildings are naturally designed with more importance than other structures. Therefore, it is necessary to know the soil conditions very well during design. High-level information production is needed, especially for designs to be made on unstable soils with high earthquake risk. In this study, which was carried out on a very weak soil, the first 30 m from the surface were used with the Multi-Channel Analysis of Surface Waves (MASW) method, while precise Vs values were obtained with the Refraction Microtremor (ReMi) method in the depth range of 30–100 m. The depth value of engineering bedrock (260 m), where Vs reached a velocity value of 760 m/s, was obtained with the Spatial Autocorrelation (SPAC) method. By combining these three data sets, Vs velocity change was modelled up to a depth of 550 m. The PS logging measurement was made in the 200 m deep well, which could be opened with difficulty, and compared with the 1-dimensional Vs velocity model, and the changes were plotted on the same graph to see their compatibility with each other. Additionally, the ground dominant vibration period was calculated using the single station microtremor method and was found as 1.4 s. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.
Seismic Performance of RC Structures in Pazarcık and Elbistan During the 2023 Kahramanmaraş Earthquakes
(Springer Science and Business Media Deutschland GmbH, 2025) Avcıl, Fatih; Işık, Ercan; Arkan, Enes; İzol, Rabia; Büyüksaraç, Aydın; Aydın, MCihan; Ulu, Ali Emre
On Monday, February 6th, 2023, at 04:17 and 13:24 local time, two very severe shallow earthquakes with magnitudes Mw = 7.7 and 7.6 occurred, with epicenters in Kahramanmaraş-Pazarcık and Kahramanmaraş-Elbistan. Due to the strong ground motion effect during these earthquakes, many people lost their lives and great economic losses occurred due to the destruction and damage to buildings in eleven different provinces and surrounding regions. In this study, the seismic performances of structures with various structural systems located in the Pazarcık and Elbistan districts of Kahramanmaraş city, which are the epicenters of these earthquakes, were evaluated as a result of field observations. Structural failures in the earthquake epicenters’ urban and rural building stocks directly affected the damage's extent. Structural damages occurring in both district centers and rural areas of the districts were investigated within the scope of earthquake and civil engineering. The main causes of damaged concrete structures are irregularities and insufficient reinforced concrete. The significance of earthquake-resistant structure design principles and irregularity-free structures has again become clear. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.
Einstein-Rosen universe with scalar field in f(R,T) theories
(Elsevier B.V., 2021) Taṣer, Dog̃ukan; Dog̃ru, Melis Ulu
Non-static Einstein–Rosen universe with scalar field is examined via two different selection of f(R,T) models. Firstly, we analyzed Einstein–Rosen universe with scalar field in f(R,T)=R+2f(T) model. Then, we constructed field equations for f(R,T)=f1(R)+f2(R)f3(T) model, as well. For both models, exact solutions of field equations have been attained without considering any approximation or restriction. Whether scalar field corresponds to phantom and/or quintessence scalar field are investigated for each models.
Determining the geochemical characteristics of geothermal resources and generating a geothermal information system of thermal waters in Biga Peninsula, NW Turkey
(Amer Chemical Soc, 2013) Şanlıyüksel Yücel, Deniz; Yücel, Ali Mehmet; Karaca, Zeki; Çetiner, Ziya S.; Erenoğlu, Ramazan Cüneyt; Akçay, Özgün; Kamacı, Celal; Çalışkan, Hidayet
TEK YÖNLÜ KATILAŞTIRLMIŞ OKSİT MALZEMELERİN MEKANİKSEL DAVRANIŞLARI
(Yildiz Technical Univ, 2007) Abalı, Serkan
Most conventional ceramics and ceramic composites are produced by using the powder sintering method. For this reason they contain many impurities and there are many cases of amorphous phases forming at grain boundaries. In many cases these amorphous phases and grain boundaries effectively act to increase fracture toughness and strength at room temperature but there are microstructural factors which might cause a deleterious effect on high temperature strength and creep proporties. The oxide ceramic single crystal materials eliminates these microstructural factors by controlling its stable high temperature microstructure. In this paper the microstructural and high temperature behaviours such as the flexural strength, thermal stability and creep characteristics of single crystal oxide materials are examined.
A new conducting polymer of 2,5-bis(2-thienyl)-1H-(pyrrole) (SNS) containing carbazole subunit: Electrochemical, optical and electrochromic properties
(Elsevier Science Sa, 2009) Koyuncu, Sermet; Zafer, Ceylan; Sefer, Emre; Baycan Koyuncu, Fatma; Demiç, Şerafettin; Kaya, İsmet; Özdemir, Eyüp
We report here the synthesis of a new electroactive monomer 3,6-di-tert-butyl-[4-(2,5-di-2-thienyl-1H-pyrrol-1-yl)phenyl]-9H-carbazole in five steps and polymerization of this monomer by two different procceses: Kumada Coupling and electro-oxidative. The product obtained by chemical polymerization exhibits a high thermal stability and narrow molecular weight distribution. While, in the UV-vis absorption spectrum of monomer the absorption peaks appear at 338 nm, the chemically synthesized polymer absorbs at 428 nm with 90 nm red shift. Cyclic voltammogram of monomer shows two separate oxidation processes which reflect the first oxidation at +0.84 V and a second one at +1.43 V. When the polymeric film prepared by electrochemical process was subjected to a repeated cyclic scan between -0.2V and +1.0V, it switches among three different colors (orange, green and blue). The oxidation and reduction response times were calculated as 2.0 s for this polymer film and exhibits high redox stability. The results anticipate that this kind of polymers can be used for designing electrochromics based on the use of one molecule for the generation of three basic colors (RGB). (C) 2009 Elsevier B.V. All rights reserved.
Development of an opto-electronic measurement system for planter laboratory tests
(Elsevier Sci Ltd, 2017) Çay, Anıl; Kocabıyık, Habib; Karaaslan, Bilal; May, Şahin; Khurelbaatar, Myagmarsuren
Seed spacing uniformity is one of the important criteria in determining the planting performance of precision planters. The development of various measurement methods with different advantages has been ongoing for years to determine seed spacing. The objective of this study was to develop an opto-electronic measurement system for use in the measurement of seed spacing during the laboratory tests of precision planters and to examine the success of the system. The success of the developed system was tested by comparing the measurements on the sticky belt using 10 different seeds with different physical properties. The R-2, MAPE, e(i), beta(0) nu e beta(1) values for all seeds were determined respectively as 0.998, 3.60%, 0.484 cm, 0.022 and 1.012 as a result of the trials carried out. The system yielded very fast and correct results and there was no need for complex calibration and adjustment procedures. The opto-electronic measurement system can be used to measure seed spacing in laboratory tests for precision planters. (C) 2017 Elsevier Ltd. All rights reserved.
Electrochemical and optical properties of biphenyl bridged-dicarbazole oligomer films: Electropolymerization and electrochromism
(Pergamon-Elsevier Science Ltd, 2009) Koyuncu, Sermet; Gültekin, Burak; Zafer, Ceylan; Bilgili, Hakan; Can, Mustafa; Demic, Şerafettin; Kaya, İsmet
4,4'-Di(N-carbazoyl)biphenyl monomer (CBP) was synthesized and coated onto ITO-glass surface by electrochemical oxidative polymerization. Its CV shows two distinct one-electron and stepwise oxidation processes occurred at 1.29 and 1.61 V. By using this property, the monomer was electrochemically polymerized separately at these oxidation states and thus, two different oligomer films were obtained afterwards. Their spectro-electrochemical and electrochromic properties were also investigated. Switching ability of the oligomers was evaluated by kinetic studies upon measuring the percent transmittance (%T) at their maximum contrast point, indicating that these oligomers were found to be suitable material for electrochromic devices. (C) 2009 Elsevier Ltd. All rights reserved.
Statistical and seismotectonic analyses of the Marmara region under existing stress regime in the west of the NAFZ
(Springer Int Publ Ag, 2025) Alkan, Hamdi; Özturk, Serkan; Bektaş, Özcan; Büyüksaraç, Aydın
The Marmara Region is an active tectonic region in northwestern Türkiye, which comprises some important strike-slip active fault mechanisms and important tectonic units, located near the western part of the North Anatolian Fault Zone. In the historical and instrumental period, the Marmara Region experienced large/devastating earthquakes. Considering this continuous activity, in this study, we investigate the tectonic structure and performed future seismic hazard estimation of the region based on some seismotectonic parameters. For this evaluation, we plot the Coulomb stress change maps of 1912 Mürefte-Şarköy, 1953 Yenice-Gönen and 1999 İzmit mainshocks with the earthquakes (MW ≥ 4.5) that occurred in the study region after 2003. For the estimation of b-value, occurrence probabilities and return periods of earthquakes, we used a homogenous local seismicity catalogue consisting of 119.029 events for the period between 1912 and 2023. In the findings of this study, the lower b-values and increasing Coulomb stress changes which are trigger stress failure compatible are observed in the west and northwest of the Marmara Sea. In contrast, the higher/moderate b-values and decreasing Coulomb stress values are observed in the east and southeast of the Marmara Sea. The results of probability assessments show that an earthquake with Mw = 6.5 may occur with a probability of 98% in the west of the Marmara Sea after 2025. As a remarkable fact, a comprehensive assessment of these types of variables will supply important findings for earthquake hazard and potential in the study region.
Effect of TiO2 doping on microstructural properties of Al2O3-based single crystal ceramics
(Korean Assoc Crystal Growth, Inc, 2011) Abalı, Serkan
Powders of Al2O3-TiO2 containing, 48 and 40% TiO2 by weight were formed into single crystals with a Verneuil furnace at 2088 K. Raman spectroscopy was used to determine the phase composition of the samples solidified from the Al2O3-TiO2 powder. The resulting beta-Al2TiO5-Al6Ti2O13, beta-Al2TiO5-Al2O3 single crystals were probed with micro hardness assays, scratch test analyses, atomic force microscopy (AFM), scanning electron microscopy (SEM), thermal expansion and four-point bending tests. It was observed that the alumina-tialite single crystal retained a composition of Al2O3-TiO2 containing 60% Al2O3 by weight and displayed optimum properties.
Effect of growth rate on the microstructure and mechanical behavior of directionally solidified Y3Al5O12/MgAl2O4 eutectics
(Elsevier Science Bv, 2014) Abalı, Serkan
The mechanical properties of YAG-spinel (Y3Al5O12/MgAl2O4) eutectic rods were studied as a function of the solidification rate. Eutectic rods were grown by a laser-heated floating zone method. YAG-spinel eutectic rods measuring 2 mm in diameter and 200 mm in length were grown at rates of 0.1-10 mm/min with a temperature gradient of approximately 1 x 104 [gm. The compressive creep strength of a crystal grown at a rate of 5 mm/min and a now rate of 1.2 mm/min at 1500 degrees C under a strain rate of 1.0 x 10(-4) was only 398 MPa, which is slightly higher than that of crystals grown under different conditions. The highest flexure strength of the Y3Al5O12/MgAl2O4 material at ambient temperature was obtained at a growth rate of 5 mm/min. The maximum hardness reached 16.7 GPa, and the room fracture toughness was 3.9 MPa M-1/2. The changes in the mechanical behavior and the microstructure of the material that occurred at different growth rates are briefly discussed. (C) 2014 Elsevier B.V. All rights reserved
Polystyrene functionalized carbazole and electrochromic device application
(Elsevier Science Sa, 2009) Oral, Ayhan; Koyuncu, Sermet; Kaya, İsmet
Polystyrene (PS) functionalized carbazole macromonomer was synthesized and polymerized by electrochemical oxidative polymerization on the ITO-glass surface. The structure of the macromonomer was elucidated by (1)H NMR, FT-IR, UV-Vis and cyclic voltammetry (CV). The spectro-electrochemical and electrochromic properties of the polymer film were investigated. Also the greenish blue colored film converted to dark blue color by the applying potential. Polystyrene-carbazole/polyethylenedioxythiophene (PS-Carb/PEDOT) electrochromic device was assembled in sandwich configuration: ITO-coated glass/anodically coloring polymer (PS-Carb)//gel electrolyte//cathodically coloring polymer (PEDOT)/ITO-coated glass. According to kinetic studies of this device, the optical contrast Delta T% at 640 nm between -1.0 and +2.0V with a residence time of 10s was found to be 38% and switching time was measured as 1.1s. (C) 2009 Elsevier B.V. All rights reserved.

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