- Materials Science and Engineering, Biomaterials Engineering, Piezoelectric ceramics, Electroceramics, Biosensors, Glass, and 13 moreSol-Gel Technology, Electronic Materials, Ferroelectrics, Piezoelectric Energy Harvesting, Tellurite Glasses, Thermoelectric Materials, Nanostructured materials, Ceramic Engineering, Nano Synthesis, High Temperature Ceramics, Sintering, Semiconductor Nanostructures, and Materials and Metallurgical Engineeringedit
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Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2003Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2003Tellürit camlar, silikat ve borat camlara kıyasla düşük ergime... more
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2003Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2003Tellürit camlar, silikat ve borat camlara kıyasla düşük ergime sıcaklığı, yüksek dielektrik sabiti, yüksek kırılım indisi ve iyi kızılötesi geçirgenlik gibi kullanışlı ve ilginç fiziksel özelliklere sahiptirler. Bu nedenle, tellürit camları son yıllarda bir çok teknolojik uygulama için uygun malzemeler olmuşlardır. Bu tür camlarda meydana gelebilecek çekirdeklenme ve kristallenme olayları hakkında bilgi sahibi olmak camda çekirdeklenme ve kristallenmenin istenmediği pratik uygulamalarda (optik fiberler,lazer camları, optik dönüşüm cihazları gibi) kararlılığını belirlemek açısından önemlidir. Bu çalışmada, GeO2 miktarının (1-x) TeO2 – x GeO2 (x = 0.10, 0.20, 0.30) camlarının ısıl özellikleri, kristallenme kinetiği, mikroyapı morfolojisi ve kristal fazlarının oluşumuna olan etkisi diferansiyel termal analiz (DTA), X...
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Bu calismada, pirometalurjik yontemle metalik bakir uretiminin elektrokazanim asamasinda ortaya cikan anot camurundan bakir geri kazanimi uzerine cevre ve insan sagligina duyarli dusuk otektik noktali cozucu (DES) kullanimi... more
Bu calismada, pirometalurjik yontemle metalik bakir uretiminin elektrokazanim asamasinda ortaya cikan anot camurundan bakir geri kazanimi uzerine cevre ve insan sagligina duyarli dusuk otektik noktali cozucu (DES) kullanimi arastirilmistir. Taguchi optimizasyon yontemi kullanilarak lic sicakligi, lic suresi ve kati/sivi orani deneysel parametrelerin bakir geri kazanimi uzerine etkisi incelenmistir. Kolin klorur (ChCl) ve urenin 1:2 molar oranda karistirilmasiyla hazirlanan DES cozucusu ile yapilan lic islemleri sonunda optimum sartlar; 95 oC’lic sicakligi, 2 saat lic suresi ve 1/20 kati/sivi orani olarak belirlenmis ve bu sartlarda %98 bakir geri kazanimi elde edilmistir. Yapilan bu calisma ile ChCl-ure karisimiyla hazirlanan DES cozucusunun anot camurundan bakir geri kazanimi icin cevreci bir cozucu adayi olabilecegi ortaya konulmustur.
A study was carried out on the production of CuAlO2 by using 3 different production routes namely, hydrothermal synthesis, conventional solid state reaction and electrospinning process. For hydrothermal synthesis, commercially available... more
A study was carried out on the production of CuAlO2 by using 3 different production routes namely, hydrothermal synthesis, conventional solid state reaction and electrospinning process. For hydrothermal synthesis, commercially available metal salts, Cu2O powder and chemically precipitated CuO nanoparticles were used as precursors. Bulk CuAlO2 samples were prepared via solid state reaction route by ball milling and high temperature sintering of CuO and Al2O3 powders. CuAlO2 ceramic mats were synthesized by electrospinning process with the assistance of polyvinylpyrolidone, as a template polymer. Highly crystalline mesh structured fibers were obtained after sintering of polymer/equal moles of copper chloride and aluminum nitrate composite in air. In the current work, solid state reaction and electrospinning processes yielded phase pure CuAlO2 in hexagonal symmetry. On the other hand, products obtained from hydrothermal synthesis were CuO, Cu2O and Al(OOH), which did not yield CuAlO2 under current experimental conditions. Detailed qualitative X-ray diffraction analysis revealed the need of specific ionic species in the solution within a narrow temperature-composition-pH window to obtain phase pure CuAlO2 employing hydrothermal conditions.
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PMS [Pb(Mn1/3Sb2/3)O3] ile katkilanmis PMN-PT [Pb(Mg1/3Nb2/3)O3-PbTiO3] uclu piezoelektrik seramikleri (PMN-PT-PMS) 1100–1250 °C araliginda farkli sinterleme sicakliklarinin kullanildigi kati-hal reaksiyon yontemi ile uretilmistir.... more
PMS [Pb(Mn1/3Sb2/3)O3] ile katkilanmis PMN-PT [Pb(Mg1/3Nb2/3)O3-PbTiO3] uclu piezoelektrik seramikleri (PMN-PT-PMS) 1100–1250 °C araliginda farkli sinterleme sicakliklarinin kullanildigi kati-hal reaksiyon yontemi ile uretilmistir. Sinterleme sicakliginin kristal fazlar, mikroyapi ve elektriksel ozellikler uzerindeki etkisi sistematik olarak incelenmistir. Mikroyapi ve kompozisyon analizleri taramali elektron mikrosko u SEM ve X-isinlari kirinimi XRD ile, elektriksel karakterizasyon ise induktans-kapasitans-direnc oloer LCR metre , empedans analizoru ve Berlincourt d33-piezometre kullanilarak gerceklestirilmistir. XRD ve SEM sonuclari, saf perovskit yapinin ve homojen ir mikroyapinin elde edilmesinde sinterleme sicakliginin etkili oldugunu ortaya koymustur. 1150 °C ve altindaki sinterleme sicakliklarinda yogunlasma yetersiz olmakta ve saf perovskit yapi elde edilememekte, 1200 °C’nin ustundeki sicakliklarda ise kursun oksitin ucuculugu nedeniyle heterojen ir mikroyapi olusmaktadir. ...
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Abstract This paper describes an efficient process of recovering valuable metals from a copper anode slime sample using green chemicals such as choline chloride (ChCl) based deep eutectic solvents (DESs). The leaching agents include... more
Abstract This paper describes an efficient process of recovering valuable metals from a copper anode slime sample using green chemicals such as choline chloride (ChCl) based deep eutectic solvents (DESs). The leaching agents include ChCl-urea, ChCl-ethylene glycol, ChCl-urea-ethylene glycol and ChCl/urea-deionized water in a 1:2, 1:2, 1:0.5:1.5, and 1:1 ratio, respectively. Prior to leaching experiments, chemical and mineralogical characterization of copper anode slime was performed. Considerable amount of precious metals was detected in the copper anode slime by chemical analysis. The main phases of copper anode slime detected by XRD and SEM/EDX analysis were namely Cu2O, SnO2, and, PbSO4. After leaching experiments, 97% of copper was recovered from the copper anode slime using ChCl-urea under an optimum condition at 95 °C of reaction temperature, 4 h reaction duration and, 1/25 g/mL solid/liquid ratio. The results showed that 91% of silver was extracted from the anode slime under the optimum condition with ChCl-urea DES composition, 95 °C reaction temperature, 48 h reaction duration, and 1/10 solid/liquid ratio. Gold was not leachable in the experiment using ChCl based DES with hydrogen bonding reagents such as urea and ethylene glycol. Moreover, the results revealed that PbSO4 was very soluble in DES prepared by ChCl and urea.
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In this study, it was aimed to utilize red mud (RM, an industrial waste material) as a nanofiber adsorbent in arsenate removal from waste water. RM, obtained from Seydişehir Aluminum Plant (Konya, Turkey), was leached using nitric acid in... more
In this study, it was aimed to utilize red mud (RM, an industrial waste material) as a nanofiber adsorbent in arsenate removal from waste water. RM, obtained from Seydişehir Aluminum Plant (Konya, Turkey), was leached using nitric acid in order to recover metallic elements such as Fe, Al, and Ti. Oxides and hydroxides of these elements are known to have a high affinity toward arsenic. Metallic salt solution, obtained after leaching treatment, was used to produce nanofibers via electrospinning method to get an adsorbent material with high surface area. Compositional, phase structural, microstructural, and thermal analyses were conducted using AAS, XRF, XRD, SEM, and DT/TGA. Organic removal from nanofibers were conducted at 600 °C for 5 h, based on the DT/TGA results. After heat treatment, nanofibers with diameters ranging from 45 to 58 nm were obtained. Performance of nanofibers in As(V) (arsenate) removal from waste water was also evaluated with different amount of nanofibers (1-3 mg/L), arsenate concentration (5-100 ppm), and contact time (10-120 min). Experimental results showed that the fastest and highest removal efficiency (∼80.2%) was obtained for 3 mg/L nanofiber and 10 ppm arsenate concentration at 90 min. Kinetic studies revealed that the pseudo-second-order kinetic model was dominantly active in the adsorption process.
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In this study, Yb1.98Lu0.02Sn2O7 and Yb1.90Eu0.10Sn2O7 were produced by solid state reaction method. The characterization of the samples was achieved by thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscopy... more
In this study, Yb1.98Lu0.02Sn2O7 and Yb1.90Eu0.10Sn2O7 were produced by solid state reaction method. The characterization of the samples was achieved by thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM-EDX), photoluminescence spectrophotometer (PL), LCR-meter and d33-m. Thermal behaviours, crystal structures, surface morphology, elemental analysis, photoluminescence properties, deielectric and piezoelectric properties and Curie temperature of Yb1.98Lu0.02Sn2O7 and Yb1.90Eu0.10Sn2O7 were investigated. X-ray diffraction datas indicate that the formation of cubic crystal structures were achieved for both materials. The photoluminescence and electrical measurements showed that Yb1.98Lu0.02Sn2O7 and Yb1.90Eu0.10Sn2O7 have both luminescent and piezoelectric properties
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Abstract Effective charge separation is of importance in increasing the efficiency of photocatalysts used in removing common industrial toxic dye in wastewater. The alternative spatial electric field produced by the piezoelectric effect,... more
Abstract Effective charge separation is of importance in increasing the efficiency of photocatalysts used in removing common industrial toxic dye in wastewater. The alternative spatial electric field produced by the piezoelectric effect, when combined with the semiconductor photocatalyst, can significantly accelerate the charge separation. In this study, lead magnesium niobate-lead titanate 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) nanoparticles and tin dioxide (SnO2) nanofibers were synthesized using colloidal coating method and electrospinning synthesis methods, respectively. PMN-PT@SnO2 composites were prepared as a novel heterostructured photocatalyst for the degradation of dye molecules in wastewater. Degradation of an organic dye pollutant in the presence of SnO2 nanofibers or PMN-PT@SnO2 nanocomposite photocatalysts were investigated under magnetic stirring and/or ultrasonic wave vibration conditions. Morphologies and electrical properties of pure and composite samples were also investigated. It was observed that the photocatalytic efficiency of PMN-PT@SnO2 piezoelectric-based photocatalysts could be increased by about 29% in the magnetic stirring and 32% in the ultrasonic wave vibration, respectively.
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Abstract In this study, it is aimed to develop a hybrid bi-functional material which will enable the removal of common industrial toxic dyes in wastewater via adsorption/photocatalysis reactions. For this purpose, WO3 nanofibers and CuO... more
Abstract In this study, it is aimed to develop a hybrid bi-functional material which will enable the removal of common industrial toxic dyes in wastewater via adsorption/photocatalysis reactions. For this purpose, WO3 nanofibers and CuO particles were synthesized using electrospinning and hydrothermal synthesis methods, respectively. WO3 nanofibers were combined with different amounts of CuO particles by a simple dispersion dropping technique. Structural, morphological and optical properties of the samples were characterized by XRD, Raman, FT-IR, XPS, SEM, TEM, UV–vis, and Mott-Schottky measurements. The adsorption capacity and photocatalytic behavior of the hybrids were compared with pure WO3 nanofibers under visible light irradiations. Experimental results have shown that the hybrid samples containing only 0.75 wt.% CuO could adsorb 38.4% higher and degraded 25.7% faster the methylene blue dye compared to pure WO3 nanofibers. This improved adsorption and degradation behavior of the hybrids were discussed in detail based on the structural properties, Z-scheme heterojunction formation, and using Langmuir/Freundlich isotherm and kinetic models.
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Y2 Zr2 O7 -doped with Eu3+ and Sm3+ phosphors were prepared for the first time as multifunctional smart materials using a solid-state reaction method at 1400o C. Thermal behaviour, crystal structure, surface morphology, and elemental... more
Y2 Zr2 O7 -doped with Eu3+ and Sm3+ phosphors were prepared for the first time as multifunctional smart materials using a solid-state reaction method at 1400o C. Thermal behaviour, crystal structure, surface morphology, and elemental analysis were characterized using thermogravimetric (TG) and differential thermal (DTA) analyses, X-ray diffraction (XRD) and scanning electron microscope equipped with energy-dispersive X-ray spectroscopy (SEM-EDX). Experimental results revealed that both phosphors have a pyrochlore structure with a cubic crystal system. Photoluminescence properties were also measured and red emission was observed from Y1.90 Eu0.10 Zr2 O7 and Y1.90 Sm0.10 Zr2 O7 phosphors. Dielectric constant, loss tangent, piezoelectric charge constant, and Curie temperature of all the samples were determined using an LCR-meter, d33 -meter, and TG/DTA. Eu doping in Y2 Zr2 O7 resulted in a high dielectric constant (9.61) and low loss tangent (1.67%) values, whereas high piezoelectric charge constant (0.68 pC/N) and high Curie temperature (820°C) could be obtained using Sm-doped Y2 Zr2 O7 .
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CuCrO2 nanoparticle decorated SnO2 nanofiber composites have been prepared as novel p-n heterostructured semiconductor photocatalysts for the degradation of organic pollutants in wastewater. The composite structure was achieved via drop... more
CuCrO2 nanoparticle decorated SnO2 nanofiber composites have been prepared as novel p-n heterostructured semiconductor photocatalysts for the degradation of organic pollutants in wastewater. The composite structure was achieved via drop casting of various amounts of hydrothermally derived CuCrO2 nanoparticles on electrospun SnO2 nanofibers. The microstructural and morphological features of each semiconductor and the formation of p-n heterojunctions between them were characterized. In addition, the photo-response and electrochemical properties of the samples were determined. The photocatalytic activity of the heterostructured photocatalysts was investigated systematically as a function of the amount of CuCrO2 nanoparticles in the samples. Experimental results showed that the optimal decoration amount was 0.6 wt% CuCrO2 on SnO2. This composite photocatalyst displayed a 41% higher rate constant value compared to pure SnO2 nanofibers in the degradation of methylene blue dye molecules an...
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On the basis of DTA analyses of 0.9TeO 2 - 0.1GeO 2 and 0.8TeO 2 - 0.2GeO 2 glasses, the Avrami parameters were determined to be 3 indicating that the mechanism for the crystallization is bulk crystallization. DTA analyses were carried... more
On the basis of DTA analyses of 0.9TeO 2 - 0.1GeO 2 and 0.8TeO 2 - 0.2GeO 2 glasses, the Avrami parameters were determined to be 3 indicating that the mechanism for the crystallization is bulk crystallization. DTA analyses were carried out at different heating rates and two crystallization peaks were observed for both of the glass compositions. The crystallization activation energies were determined by using the variation of peak temperatures with the heating rate. The absorption spectra measured between 300 - 800 nm wavelength region were used to determine the optical band-gap and Urbach energies of the glasses. It is found that they both are a function of glass composition.
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Abstract. Crystallization behaviors of 80 mol% TeO2-10 mol% GeO2-10 mol% ZnO, 85 mol% TeO2-5 mol% GeO2-10 mol% ZnO and 90 mol% TeO2-5 mol% GeO2-5 mol% ZnO glasses were investigated by using differential thermal analysis (DTA), scanning... more
Abstract. Crystallization behaviors of 80 mol% TeO2-10 mol% GeO2-10 mol% ZnO, 85 mol% TeO2-5 mol% GeO2-10 mol% ZnO and 90 mol% TeO2-5 mol% GeO2-5 mol% ZnO glasses were investigated by using differential thermal analysis (DTA), scanning electron microscopy (SEM) and X-ray diffraction (XRD). DTA curves in the temperature range from 25 °C to 750 °C with the heating rate of 10 °C/min are used to determine the thermal properties such as glass transition temperature Tg, and crystallization peak temperatures Tp. Glass samples were crystallized in the vicinity of these crystallization peak temperatures. Phase analyses were carried out by XRD and SEM techniques.
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Abstract PMN-PT ceramics with perovskite structure were prepared by powders synthesized in KCl molten salt. Dielectric and piezoelectric properties were studied and compared with those of the ceramics prepared by conventional ceramic... more
Abstract PMN-PT ceramics with perovskite structure were prepared by powders synthesized in KCl molten salt. Dielectric and piezoelectric properties were studied and compared with those of the ceramics prepared by conventional ceramic processing. The results indicate that the PMN-PT powders with perovskite structure can be synthesized at 800°C in KCl molten salt. Comparing with ceramics from conventional processing, ceramics synthesized in molten salt are denser, thus their piezoelectric properties are better. Dielectric and piezoelectric properties of PMN-PT ceramics can be improved by thermal annealing at 850°C for 4 hours. In this work, em≈ 30000, Kp = 0.66, d 33 = 540pC/N were achieved.
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PZT based piezoelectric ceramics obtained by doping with various levels of Sr2+ and La3+, designated as PSLZT, were prepared by conventional processing techniques. The effects of Sr2+ and La3+ additions, and that of the Zr/Ti ratio on... more
PZT based piezoelectric ceramics obtained by doping with various levels of Sr2+ and La3+, designated as PSLZT, were prepared by conventional processing techniques. The effects of Sr2+ and La3+ additions, and that of the Zr/Ti ratio on microstructure, on phase constitution, and on the dielectric and piezoelectric properties were investigated. XRD data revealed that all PSLZT compositions had perovskite structure in which increasing Sr and/or decreasing Zr/Ti ratio increased the tetragonality. In PSLZT ceramics the morphotropic phase boundary (MPB) appeared as regions extending from Zr/Ti ratio of 52/48 to 58/42. Among all compositions studied, the PSLZT ceramic having 5 at% Sr2+ and 1 at% La3+ with a Zr/Ti ratio of 54/46 exhibited a peak piezoelectric strain coefficient of d33 = 640 pC/N with attending dielectric and electromechanical parameters KT = 1800, kp = 0.56, Qm = 70, and tan <delta> = 1.55%.
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Abstract In this study, TiO2 nanofibers were fabricated via the electrospinning method followed by air annealing. Then, Ti-requirement in the conventional hydrothermal synthesis of BaTiO3 stoichiometry was supplied by using these... more
Abstract In this study, TiO2 nanofibers were fabricated via the electrospinning method followed by air annealing. Then, Ti-requirement in the conventional hydrothermal synthesis of BaTiO3 stoichiometry was supplied by using these nanofibers. The microstructural and compositional properties of BaTiO3 nanoparticles were studied using SEM, TEM, XRD, XPS, and Raman spectroscopy. The structural analysis showed that the cubic symmetry was the dominant one in the BaTiO3 nanoparticles, whereas Raman spectroscopy indicated the coexistence of cubic symmetry with the tetragonal polymorph. The nanoparticles displayed higher photocatalytic reactivity under UV-A light compared to visible irradiation during decomposition of methylene blue dye and reached 24.2\% and 18.8\% degradation, respectively, after 1 hour. Furthermore, the dielectric properties were investigated using sintered compacts of these nanoparticles. Among the employed temperatures for sintering, the highest relative density (90\%) and dielectric constant (2165 at 1 MHz) were obtained at 1250°C and 5 hours. This study revealed that the electrospun TiO2 nanofiber precursor can successfully be used for the production of nanoscale barium titanate particles suitable for various applications.
Motivated by the need of piezoelectric ceramics with enhanced piezoelectric properties, we investigated the effects of Sr addition on the structural, dielectric and piezoelectric properties of PMN-PT ceramics. The synthesis of... more
Motivated by the need of piezoelectric ceramics with enhanced piezoelectric properties, we investigated the effects of Sr addition on the structural, dielectric and piezoelectric properties of PMN-PT ceramics. The synthesis of (1-x)[(Pb1−ySry)(Mg1/3Nb2/3)O3]-x(Pb1−ySryTiO3) (PsMN–PsT) (y: 0 − 0.10, x: 0.35 – 0.40) ceramics was carried out by the colloidal coating method to distribute Sr uniformly in PMN and PT respectively. When x=0.35, it was found that y=0.02 gave the optimal piezoelectric properties. Furthermore, by keeping y=0.02 and varying x, it was found that x=0.37 gave even better piezoelectric properties with the optimal piezoelectric strain coefficient d33 (630 pC/N), piezoelectric coupling factor kp (0.52), dielectric constant εr (4000), and Curie temperature Tc (210 °C), exhibiting great potential for actuator and sensor applications.
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CuCrO2 nanoparticle decorated SnO2 nanofiber composites have been prepared as novel p–n heterostructured semiconductor photocatalysts for the degradation of organic pollutants in wastewater. The composite structure was achieved via drop... more
CuCrO2 nanoparticle decorated SnO2 nanofiber composites have been prepared as novel p–n heterostructured semiconductor photocatalysts for the degradation of organic pollutants in wastewater. The composite structure was achieved via drop casting of various amounts of hydrothermally derived CuCrO2 nanoparticles on electrospun SnO2 nanofibers. The microstructural and morphological features of each semiconductor and the formation of p–n heterojunctions between them were characterized. In addition{,} the photo-response and electrochemical properties of the samples were determined. The photocatalytic activity of the heterostructured photocatalysts was investigated systematically as a function of the amount of CuCrO2 nanoparticles in the samples. Experimental results showed that the optimal decoration amount was 0.6 wt% CuCrO2 on SnO2. This composite photocatalyst displayed a 41% higher rate constant value compared to pure SnO2 nanofibers in the degradation of methylene blue dye molecules and reached 83% degradation under UV/visible light irradiation after 1 h. The increase in the photocatalytic activity was ascribed to the incorporation of Cr3+ and Cu+ cations into the SnO2 host lattice and the more effective electron–hole pair separation in the heterostructured sample. The presented data here are highly convincing in comparison to those of UV active p–n heterostructured photocatalysts reported previously in the literature. Therefore{,} this work opens the way to develop visible light active p–n heterostructured semiconductor photocatalysts using p-type delafossites with n-type oxides.
Tetragonal BaTiO3 nanoparticles have been hydrothermally synthesized using the electrospun TiO2 nanofibers as the Ti-source. Microstructural and compositional analyses have been carried out using XRD, SEM, TEM, XPS, and Raman... more
Tetragonal BaTiO3 nanoparticles have been hydrothermally synthesized using the electrospun TiO2 nanofibers as the Ti-source. Microstructural and compositional analyses have been carried out using XRD, SEM, TEM, XPS, and Raman spectroscopy. Characterization studies confirmed that the BaTiO3 nanoparticles had a tetragonal structure with an average particle size of 100 nm. Photocatalytic activities of the nanoparticles were investigated via the decolorization of methylene blue dye aqueous solutions under visible light and UV-A irradiations. The degradation efficiency reached to 13 and 35% after exposing to light for 60 min with visible and UV-sources, respectively. Effect of sintering temperatures on the dielectric properties was also investigated. Among all the sintering temperatures employed, 1473 K was the optimum sintering temperature for these ceramics in terms of high relative density (95.3%), high dielectric constant (3162 at 1 MHz), and low loss tangent (15 × 10−3 at 1 MHz). Experimental results showed that electrospun TiO2 fibers can be used as a precursor template to produce nano-scale BaTiO3 particles which are suitable for various applications such as photocatalysis and capacitors.
Pseudo-ternary piezoelectric ceramics of PMN-PT [Pb(Mg1/3Nb2/3)O3-PbTiO3] composition modified with PMS [Pb(Mn1/3Sb2/3)O3] were produced by solid-state sintering method using different temperatures in a range of 1100-1250 °C. The effect... more
Pseudo-ternary piezoelectric ceramics of PMN-PT [Pb(Mg1/3Nb2/3)O3-PbTiO3] composition modified with PMS [Pb(Mn1/3Sb2/3)O3] were produced by solid-state sintering method using different temperatures in a range of 1100-1250 °C. The effect of sintering temperature on the crystal phases, microstructure and electrical properties were systematically investigated. Microstructural and compositional analyses have been carried out using scanning electron microscope (SEM) and X-ray diffraction (XRD). Besides, electrical characterization was performed using an inductance-capacitance-resistance (LCR) meter, impedance analyzer and a Berlincourt d33-piezometer. XRD and SEM results indicated that the sintering temperature was effective on the formation of a homogeneous microstructure and a pure perovskite structure. Densification during sintering could not be completed and pure perovskite structure was not o tained at 1150 °C and lower sintering temperatures. Furthermore, sintering at temperatures higher than 1200 °C resulted in heterogeneous microstructure. The high dielectric and piezoelectric response of PMN-PT-PMS ceramics is considered to be a result of their high densities and homogeneous microstructure obtained via proper sintering condition. The results showed that the ceramic samples sintered at 1175 °C for 2 h possessed the optimum properties (d33=265 pC/N, KT=4745, kp=0.417, tanδ=2.5%, Qm=222).
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Polycrystalline (1 − x)[0.8Bi0.5Na0.5TiO3--0.2Bi0.5K0.5TiO3]--(x)[SrTiO3] (x = 0 to 0.20) lead-free piezoelectric ceramics were synthesized via a solid-state reaction route. Microstructural and compositional analyses have been carried out... more
Polycrystalline (1 − x)[0.8Bi0.5Na0.5TiO3--0.2Bi0.5K0.5TiO3]--(x)[SrTiO3] (x = 0 to 0.20) lead-free piezoelectric ceramics were synthesized via a solid-state reaction route. Microstructural and compositional analyses have been carried out using X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD patterns indicated that undoped composition (x = 0) had a tetragonal phase dominant structure, however SrTiO3 (ST) incorporations resulted in a phase shift to rhombohedral symmetry. SEM studies showed that increasing ST doping led to a decrease in grain size. Effect of ST doping on the piezoelectric and dielectric properties were also investigated. The results revealed that the dielectric constant increased gradually with the increase of ST. The ceramic having 12 mol{\%} ST possessed the optimum properties (d33 = 205 pC/N, kp = 0.36, KT = 1520, tan$\delta$ = 6.1 {\%}, Qm = 87, Tm = 285 {\textdegree}C) enabling this composition a suitable lead-free candidate for piezoelectric actuator applications.
Polycrystalline samples of (1-x)PMN-xPT [Pb(Mg1/3Nb2/3)O3-PbTiO3] (x=0.30 to 0.39) piezoelectric ceramics were synthesized via a solid-state reaction route. Based on the previous literature, 5% mol excess MgO was used in order to... more
Polycrystalline samples of (1-x)PMN-xPT [Pb(Mg1/3Nb2/3)O3-PbTiO3] (x=0.30 to 0.39) piezoelectric ceramics were synthesized via a solid-state reaction route. Based on the previous literature, 5% mol excess MgO was used in order to eliminate the formation of unwanted pyrochlore phase. Microstructural and compositional analyses have been carried out using scanning electron microscope (SEM) and X-ray diffraction (XRD). Besides, electrical characterization was performed by using impedance analyzer and Berlincourt d33-piezometer. Formation of the pyrochlore phase was eliminated significantly by using excess MgO and one-step calcination method. XRD patterns indicated a transition from rhombohedral to tetragonal phase with increasing PT content. Effect of altering PMN-PT composition on the piezoelectric and dielectric properties was also investigated. The results showed that the rhombohedral and tetragonal phases coexisted at 0.30<x<0.39 and the ceramic with x=0.33 possessed the optimum properties (d33=480 pC/N, KT=4555.5, kp=0.505, tanδ=2.9%, Qm=59.6, Tc=150 °C).
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Pb0.94Sr0.05La0.01(Zr0.54Ti0.46)0.9975O3–Pb(Mn1/3Nb2/3)O3 (PSLZT–PMnN) ceramics with pure perovskite structure were prepared by conventional mixed oxide method. The influence of PMnN on the structural, dielectric and piezoelectric... more
Pb0.94Sr0.05La0.01(Zr0.54Ti0.46)0.9975O3–Pb(Mn1/3Nb2/3)O3 (PSLZT–PMnN) ceramics with pure perovskite structure were prepared by conventional mixed oxide method. The influence of PMnN on the structural, dielectric and piezoelectric properties was investigated. The experimental results showed that the perovskite structure changed from tetragonal to rhombohedral symmetry and the Curie temperature decreased gradually with the increase of PMnN. The composition with 3 mol% PMnN exhibited favorable properties of Qm (400), d33(660 pC/N), kp (0.60), KT (1940), tan δ (0.90%) and TC (247 °C), exhibiting potential usage for piezoelectric actuator and sensor applications.
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PZT based piezoelectric ceramics obtained by doping with various levels of Sr2+ and La3+, designated as PSLZT, were prepared by conventional processing techniques. The effects of Sr2+ and La3+ additions, and that of the Zr/Ti ratio on... more
PZT based piezoelectric ceramics obtained by doping with various levels of Sr2+ and La3+, designated as PSLZT, were prepared by conventional processing techniques. The effects of Sr2+ and La3+ additions, and that of the Zr/Ti ratio on microstructure, on phase constitution, and on the dielectric and piezoelectric properties were investigated. XRD data revealed that all PSLZT compositions had perovskite structure in which increasing Sr and/or decreasing Zr/Ti ratio increased the tetragonality. In PSLZT ceramics the morphotropic phase boundary (MPB) appeared as regions extending from Zr/Ti ratio of 52/48 to 58/42. Among all compositions studied, the PSLZT ceramic having 5 at% Sr2+ and 1 at% La3+ with a Zr/Ti ratio of 54/46 exhibited a peak piezoelectric strain coefficient of d33 = 640 pC/N with attending dielectric and electromechanical parameters KT = 1800, kp = 0.56, Qm = 70, and tan <delta> = 1.55%.
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A study was carried out on the production of CuAlO2 by using 3 different production routes namely, hydrothermal synthesis, conventional solid state reaction and electrospinning process. For hydrothermal synthesis, commercially available... more
A study was carried out on the production of CuAlO2 by using 3 different production routes namely, hydrothermal synthesis, conventional solid state reaction and electrospinning process. For hydrothermal synthesis, commercially available metal salts, Cu2O powder and chemically precipitated CuO nanoparticles were used as precursors. Bulk CuAlO2 samples were prepared via solid state reaction route by ball milling and high temperature sintering of CuO and Al2O3 powders. CuAlO2 ceramic mats were synthesized by electrospinning process with the assistance of polyvinylpyrolidone, as a template polymer. Highly crystalline mesh structured fibers were obtained after sintering of polymer/equal moles of copper chloride and aluminum nitrate composite in air. In the current work, solid state reaction and electrospinning processes yielded phase pure CuAlO2 in hexagonal symmetry. On the other hand, products obtained from hydrothermal synthesis were CuO, Cu2O and Al(OOH), which did not yield CuAlO2 under current experimental conditions. Detailed qualitative X-ray diffraction analysis revealed the need of specific ionic species in the solution within a narrow temperature-composition-pH window to obtain phase pure CuAlO2 employing hydrothermal conditions.
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On the basis of DTA analyses of 0.9TeO2 – 0.1GeO2 and 0.8TeO2 – 0.2GeO2 glasses, the Avrami parameters were determined to be 3 indicating that the mechanism for the crystallization is bulk crystallization. DTA analyses were carried out at... more
On the basis of DTA analyses of 0.9TeO2 – 0.1GeO2 and 0.8TeO2 – 0.2GeO2 glasses, the Avrami parameters were determined to be 3 indicating that the mechanism for the crystallization is bulk crystallization. DTA analyses were carried out at different heating rates and two crystallization peaks were observed for both of the glass compositions. The crystallization activation energies were determined by using the variation of peak temperatures with the heating rate. The absorption spectra measured between 300 – 800 nm wavelength region were used to determine the optical band-gap and Urbach energies of the glasses. It is found that they both are a function of glass composition.
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On the basis of DTA analyses, crystallization mechanism and crystallization activation energy of 0.6TeO2-0.4ZnO glass were determined. Also, the effect of ZnO content on the optical band-gap and Urbach energies of (1-x) TeO2 – (x)ZnO... more
On the basis of DTA analyses, crystallization mechanism and crystallization activation energy of 0.6TeO2-0.4ZnO glass were determined. Also, the effect of ZnO content on the optical band-gap and Urbach energies of (1-x) TeO2 – (x)ZnO (where x=0.2, 0.3 and 0.4 in molar ratio) glasses have been examined by ultraviolet- visible- near infrared (UV / VIS / NIR) absorption measurements between 300 – 800 nm wavelength region. It is found that they both are functions of glass composition.