Kimyasal çözelti depozitleme yöntemi kullanılarak süperiletken filmlerin üretilmesi ve baryum zirkonat nanopartikülleri ile akı iğnelenmesi özelliklerinin geliştirilmesi

Sunulan bu tez BZO katkılı YBCO ve GdBCO süperiletken ince filmlerin yüksek manyetik alan uygulamaları için STO ve LAO tek kristal altlıklar üzerine kimyasal çözelti depozitleme yöntemi ile sentezlenmesini ve karakterizasyonunu içermektedir. Bu bağlamda, ticari olarak temin edilen YBCO tozları ve metal asetat başlangıç kimyasalları ile metanol, etanol ve propiyonik asit çözücüleri kullanılarak saydam çözeltiler hazırlanmıştır. Kayma profilinin belirlenmesi ve sıcaklığın vizkozite üzerindeki etkisinin incelenmesi için kapsamlı bir reolojik karakterizasyon çalışması yapılmıştır. Hazırlanan çözeltiler spin kaplama ile altlıklar üzerine kaplanmış ve ısıl işlem uygulanmıştır. BZO katkılı süperiletken filmlerin termal, mikroyapısal ve elektriksel özellikleri DTA/TGA, FTIR, XRD, SEM, AFM, indüktif kritik geçiş sıcaklığı, indüktif kritik akım yoğunluğu ve transport ölçümleri ile belirlenmiştir. Sonuçlar, yüzde altı mol BZO katkılı YBCO örneklerinin her iki altlık üzerinde manyetik alan altında en yüksek kritik akım yoğunluğu değerine sahip olduğunu göstermektedir. Buna ilave olarak, GdBCO süperiletken ince filmleri YBCO filmlere göre daha yüksek kritik geçiş sıcaklığı ve kritik akım yoğunluğu değerlerine sahiptir. GdBCO örneklerinde yapılan ölçüm sonuçlarına göre, yüzde oniki mol BZO katkılı örnekler, STO altlık üzerinde tüm manyetik alan değerlerinde en yüksek kritik akım yoğunluğu değerine sahiptir. Bu sonuçlar, BZO katkısının yapı içerisinde yapay iğneleme merkezleri olarak etki ettiğini ve manyetik alan altında akım taşıma kapasitesinin arttığını göstermektedir. The present thesis demonstrates synthesis and characterization of BZO doped YBCO and GdBCO superconducting thin films on STO and LAO single crystal substrates using chemical solution deposition technique for high magnetic field applications. With this respect, transparent solutions were prepared both from commercially available YBCO powder and metal acetates seperately by using different types of solvents as methanol, ethanol and propionic acid. Contact angle values of these solutions on STO and LAO substrates were determined to estimate their wettability features. A detailed rheological characterization was performed to determine shear profile and scrutinize effect of temperature on viscosity. The solutions were spin coated on the substrates and heat treated according to the profile. Thermal, microstructural and electrical properties of BZO doped superconducting thin films were determined through DTA-TG, FTIR, XRD, SEM-EDS, AFM, inductive critical transition temperature, inductive critical current density and transport measurements. The results show that six mol percentage BZO doped YBCO samples on both substrates possess the highest critical current density value for all magnetic fields. Additionally, GdBCO superconducting thin films exhibit higher critical transition temperature and self-field critical current density values in comparison to the YBCO films. According to the measurement results of GdBCO samples, the twelve mol percentage BZO doped GdBCO sample on STO substrate possess the highest critical current density value for all magnetic fields. These results indicate that the BZO dopant in the structure act as artificial pinning centers and increased the current carrying capability of films in magnetic field conditions

YBCO Yüzey Kaplanmış İletkenler İçin Sol-jel Prosesiyle Pr2O3 Buffer Katmanların Sentezlenmesi ve Karakterizasyonu

Pr2O3 films were deposited using a sol-gel process from solutions derived from praseodymium (III) isoproxide. Homogenous, crack-free, and dense films were deposited on Ni tapes between temperatures of 600o C and 850o C for YBCO surface coated conductors. These films were characterized by XRD, SEM and AFM. According to XRD pattern, Pr2O3 film is successfully grown on Ni substrate. It was found that microstructures of the films are dense, continuous, crack-free and pinhole-free. As a result, it is accepted that Pr2O3 film is suitable for YBCO surface coated conductors

Asit Konsantrasyonunun Sol-jel Türevi Y2O3 Yüzey Alanına Etkisi

Yttrium oxide (Y2O3) ceramics have been investigated in detail for many technologicalpurposes and used as important material in the ceramic industry, ceramic superconductors,MOS transistors and light-emitting materials. Phosphor materials are important tools for theefficient utilization of current energy. These materials can be used in various fields such asdisplay panels, fluorescent paints, and bio-imaging. In this study, Y2O3 phosphor particles withdifferent surface areas were produced using the sol-gel method. The aim of the study is toinvestigate the effect of citric acid concentration used in the solution preparation stage on thesurface area of the final product. Luminescent materials can be more effectively used withincreasing surface area. For this purpose, starting solutions with three different acidconcentrations were prepared. The solutions were prepared to have citric acid concentrationswith respect to the total metal ions (MRCM) at 0.5, 1, and 2 molar concentrations. The organiccontents of the dried solutions were compared using Fourier transform infrared (FTIR)spectroscopy, and the phase structures of the obtained samples after heat treatment wereanalyzed using X-ray diffraction (XRD). The surface areas of the final Y2O3 particles weremeasured and characterized using Brunauer-Emmett-Teller (BET) analysis. It is observed thatthe acid concentration significantly changed the surface area of Y2O3. The surface areas of theY2O3 particles increased with increasing acid concentration. The surface areas of the sampleswith MRCM values of 0.5, 1, and 2 were measured as 19.16 m2/g, 32.76 m2/g, and 53.48 m2/g,respectively. The study showed that the surface area, which affects the luminescent propertiesof phosphor materials, can be easily modified using the sol-gel method.</p

BaIrO3 Katkılı Süperiletken YBCO İnce Filmlerin TFA-MOD Yöntemi ile Üretilmesi ve Karakterizasyonu

BaIrO3 (BIO) doped YBa2Cu3O7-δ (YBCO) superconducting thin films were prepared using yttrium, barium and copper acetate on SrTiO3 (STO) single crystal substrates by Trifluoroacetic Acid-Metal Organic Deposition (TFA-MOD) method. The effect of added BIO nanoparticles on the film structure and superconducting properties were studied. Highly textured YBCO superconducting thin films on STO substrate were deposited by spin coating technique. Surface morphologies of the films were observed by Scanning Electron Microscopy (SEM) and the morphological quality of the thin films was determined through atomic force microscopy (AFM). The phase analyses of the films were investigated by X-Ray Diffractometer (XRD). In order to determine superconducting properties critical transition temperature (Tc) values of films were measured by using standart four point method. All YBCO films with BIO nanoparticles had Tc values over 91K. Results indicate that BIO added YBCO films exhibit denser surface and higher Tc values than undoped YBCO films

Mıknatıs Teknolojisi İçin Ag Şeritler Üzerindeki Yüksek Sıcaklık Yb2O3- ZrO2 Yalıtkan Kaplamalar

In this study, synthesis and characterization of high temperature Yb2O3–ZrO2 insulation coatings on Ag substrate were investigated for magnet technologies. The produced powders and coatings were characterized by using DTA-TG, FTIR, XRD, SEM-EDS, refractometer, spectrophotometer and empendance machines. The DTA/TG result indicates three-stage decomposition for amorphous Yb2O3– ZrO2 composites. FTIR studies revealed that heat treated powders indicate several absoption bands corresponding to O-H, carboxyl and oxide groups. Though ZrO2 phase present in the structures with high intensity, Yb3O2 phase possessess low intensity peak. A regular surface morphology generally forms once Yb2O3 content increase in ZrO2 from 0 mole % to 12 mole %. The refractive indexes of Yb2O3–ZrO2 coatings were found to be in the range of 1.3539 and 1.3655. The film thicknesses of all coatings generally increased from 0.50 µm to 1.20 µm according to number of dipping. Optical band gap values of Yb2O3–ZrO2 coatings are approximately 3,014 eV. Empedance values of ZrO2 and Yb2O3- ZrO2 coatings were measured as 2.52 ohms and 2.51 ohms, respectively

Mekanik İşleme Prosesi Alev Sprey Sistemiyle SiO2 Nanosıvıların Hazırlanması ve Karakterizasyonu

Nanofluids are a relatively new class of fluids which consist of a base fluid with nano-sized particles suspended within them. Nanofluids showed a large enhancement of thermal conductivity in comparison with their base fluids. Machining experiences high temperatures due to friction between the tool and workpiece, thus influencing the workpiece dimensional accuracy and surface quality. Further, the cutting fluids also incur a major portion of the total manufacturing cost. These particles that used in nanofluid applications, generally a metal or metal oxide, increase conduction and convection coefficients, allowing for more heat transfer out of the coolant. In this study, SiO2 nanoparticles were produced by using flame spray method and they were suspended in a specified volume of the base fluid. Regarding the analysis of materials, phase analysis was determined by using Xray diffactometer (XRD) and the average particle size distribution (APS) using particle size analyzer. Besides, successful synthesis of the SiO2 nanoparticles were confirmed using Fourier transform infrared spectroscope (FT-IR). The present work shows the effect of nanofluid with SiO2 nanoparticles on the performance of the cutting tools

Parameter Adjustment in a PLD System Used for YBCO Films on STO Substrates and its Characteristic Verification

Darbeli Lazer Biriktirme (PLD) sistemi üstün özellikli bir seramik film üretme cihazı olup, karmaşık teknolojili hava alma ve lazer bileşenlerinden oluşur. Şimdiye kadar yapılan çalışmalarda PLD sisteminin başarısı bilimsel yayınlarla ispatlanmıştır. Son zamanlarda, ince film kaplama amacı ile PLD’de kullanılan bileşenlerin tamamen bilgisayar kontrollü olduğu sistemler yaygınlaşmaya başlamıştır. Fakat bu tarz kontrollü ince film biriktirme sistemleri cihaz parametrelerinin hassas bir şekilde ayarlanmasını gerektirmektedir. Zira başarılı film karakteristiğini sağlamak üzere PLD sistemi bileşenlerinden olan lazer kutusu, hazne ve hatta mercek ve aynaların ayarlanması gerekir. Kullanılan sistemde, lazer ve hazne tamamen üretici Neocera Firması tarafından yazılan bilgisayar yazılımı ile kontrol edilmektedir. Sistemde yerleşik algılayıcılar vasıtası ile kontrol sağlayan bu programı kullanarak, lazer ve haznedeki gaz akış miktarını, sıcaklığı ve basıncı ayarlanmaktadır. Başarılı bir film biriktirme için etkin parametreler deney deneyimleri ile geliştirilmeye çalışılmaktadır. Bu doğrultuda, lazer aydınlatması, altlık üzerine odaklanma, altlık–hedef malzeme arası mesafe, gaz akış miktarı ve havası alınmış hazne içi basınç değeri gibi parametrelerin ayarlanmasına çalışılmıştır. Bu parametreleri kullanarak, her bir darbede biriken film kalınlığı tahmin edilebilir hale gelir ve hazne içerisinde olması gereken gaz akış hızına karar verebiliriz. Bahsedilen düzenlemeleri yaparak, biriktirme işlemini standartlaştırmak ve dolayısı ile PLD çalışma şartlarını güvenilir hale getirmek hedeflenir ki, bu özellik yeniden üretilebilirliği sağladığı için bilimsel çalışmalar açısından büyük öneme sahiptir. Bu çalışmada STO (SrTiO3) altlığa uygulanan YBCO (YBa2Cu3O7-δ) seramik süperiletken ince filmlerinin üretimi için kullanılan PLD sistemine ait çalışma parametrelerinin düzenlenmesi açıklanmıştır. Üretilen filmler üzerine edindiğimiz deneyimler açılanarak, kullanılan hazne basıncı ve altlık sıcaklığı parametreleri verilmiştir. Son olarak, ilgili parametreler ile elde edilen filmlere ait analiz ve karakterizasyon sonuçları açıklanmıştır

BaIrO3 Katkılı Süperiletken YBCO İnce Filmlerin TFA-MOD Yöntemi ile Üretilmesi ve Karakterizasyonu

BaIrO3 (BIO) doped YBa2Cu3O7-δ (YBCO) superconducting thin films were prepared using yttrium, barium and copper acetate on SrTiO3 (STO) single crystal substrates by Trifluoroacetic Acid-Metal Organic Deposition (TFA-MOD) method. The effect of added BIO nanoparticles on the film structure and superconducting properties were studied. Highly textured YBCO superconducting thin films on STO substrate were deposited by spin coating technique. Surface morphologies of the films were observed by Scanning Electron Microscopy (SEM) and the morphological quality of the thin films was determined through atomic force microscopy (AFM). The phase analyses of the films were investigated by X-Ray Diffractometer (XRD). In order to determine superconducting properties critical transition temperature (Tc) values of films were measured by using standart four point method. All YBCO films with BIO nanoparticles had Tc values over 91K. Results indicate that BIO added YBCO films exhibit denser surface and higher Tc values than undoped YBCO films

BaIrO3 Katkılı Süperiletken YBCO İnce Filmlerin TFA-MOD Yöntemi ile Üretilmesi ve Karakterizasyonu

BaIrO3 (BIO) doped YBa2Cu3O7-δ (YBCO) superconducting thin films were prepared using yttrium, barium and copper acetate on SrTiO3 (STO) single crystal substrates by Trifluoroacetic Acid-Metal Organic Deposition (TFA-MOD) method. The effect of added BIO nanoparticles on the film structure and superconducting properties were studied. Highly textured YBCO superconducting thin films on STO substrate were deposited by spin coating technique. Surface morphologies of the films were observed by Scanning Electron Microscopy (SEM) and the morphological quality of the thin films was determined through atomic force microscopy (AFM). The phase analyses of the films were investigated by X-Ray Diffractometer (XRD). In order to determine superconducting properties critical transition temperature (Tc) values of films were measured by using standart four point method. All YBCO films with BIO nanoparticles had Tc values over 91K. Results indicate that BIO added YBCO films exhibit denser surface and higher Tc values than undoped YBCO films