Browsing by Subject "Seramik"
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Item PAN-based Pd-doped activated carbon fibers for hydrogen storage: preparation, a new method for chemical activation and characterization of fibers(2008) Özgül HAKLİ; Ahu Gümrah DUMANLI; Yuda YÜRÜM; Serkan BAŞThe preparation of ACFs from PAN fibers under various conditions and the method to load Pd on ACFs were described. Chemical activation of the fibers increased the surface areas of the fibers from about 64 $m^ 2$/g to 381 $m^ 2$/g. SEM micrographs of Pd-loaded indicated the diameters of the fibers were in the range of 1.0-10.0 mm. Diameters of metallic Pd particles on the fibers changed between 80 nm and 100 nm. 4.5% (by wt) metallic palladium was deposited on the ACFs. This high percentage of palladium deposited on ACFs is useful for hydrogen storage, since Pd-H system is established under a wide range of pressure and temperature.Item Atık Kuru Pillerdeki Grafitin Seramik Plastik Çamuruna Katkısı(2009) Salih Uğur BAYÇA; kemal köseoğluBu çalışmada piyasadan toplanan atık kuru pillerdeki grafitin, seramik plastik çamurunda kullanılabilirliği araştırılmıştır. Bu amaçla kuru pilin içindeki grafit çıkarılmıştır. Elde edilen grafit az miktarda su ile karıştırılmış ve plastik çamura katılarak homojen bir şekilde yoğrulmuştur. Hazırlanan plastik çamurdan şekillendirilen parçalar, oda sıcaklığında kurutulmuş ve 900 oC'de pişirilmiştir. Elde edilen bisküvilerin kuru ve pişme küçülmesi, mukavemet ve su emme testleri yapılmıştır.Item SIMA prosesiyle üretilmiş ETİAL 180 alüminyum alaşımına eser miktarlarda magnezyum ve kalay ilavesinin etkilerinin incelenmesi(2012) Mustafa BAŞARANEL; Nurşen SAKLAKOĞLUYarı-katı halde işleme prosesleri döküm, dövme ve toz metalurjisi tekniklerinin avantajlarını bir araya toplayan bir teknik olarak tanımlanmaktadır. Bir alaşımın yarı-katı halde şekillendirilebilmesi için ince eşeksenli küresel tane yapısına sahip olması gerekmektedir. Eşeksenli mikroyapıya sahip alaşımlar tiksotropiktir yani yarı-katı halde dendritik mikroyapılı alaşımlara göre yüksek akışkanlık özelliğine sahiptir. SIMA prosesi basit ve komplike ekipmanlar gerektirmeyen bir yöntem olması dolayısıyla yarı-katı şekil verme prosesleri arasında önemli avantajlar sağlamaktadır. Alüminyum alaşımlarına eser miktarlarda ilave edilen çeşitli elementlerin alaşımın mekanik özelliklerine olumlu etkiler yaptığı bilinmektedir. Bu çalışmada basınçlı döküm alaşımı olan ETIAL 180'e eser miktarda Sn ve Mg ilave edilerek SIMA prosesi uygulanmıştır. Bu elementlerin döküm ETİAL 180'e etkileri incelenmiş, aynı zamanda SIMA prosesinin uygulanmasında bu elementlerin etkileri değerlendirilmiştir. Elde edilen numuneler metalografik olarak incelenmiş, sertlik testleri yapılmış ve XRD yöntemiyle detaylı olarak analiz edilmiştir. Sn ilavesinin sertlikte hafif düşüşe neden olduğu ancak Mg ilavesinin sertlikte artışa neden olduğu tespit edilmiştir. Sn ilavesi herhangi bir bileşik oluşuma yol açmayıp katı çözeltide bulunurken, Mg ilavesinin Mg2Si bileşiklerine yol açtığı belirlenmiştir. SIMA prosesi uygulanmış numunelerde dendiritik yapıların küresel tanelere dönüştüğü ve SIMA prosesi uygulamanın yeni bir bileşik oluşumuna yol açmadığı gözlenmiştir. Yarı-katı halde şekillendirme sırasında uygulanan kuvvetin poroziteyi azaltmak, tane inceltmek gibi nedenlerle mekanik özelliklerde iyileşme sağladığı kabul edilir. Bu çalışmada SIMA prosesi sırasında malzeme yarı-katı aralıkta iken soğutularak iç yapısı incelenmiş ancak şekillendirme yapılmamıştır. Bu nedenle beklenen mekanik iyileşmeye ulaşılamamıştır.Item Production of B4C Reinforced Composite Materials and Investigation of Their Bending Strength(2023) Halit Doğan; Yılmaz MutluIn this study, AA2024 aluminum alloy was selected as the matrix material, while B4C was selected as the reinforcement material, and particle-reinforced Al-matrix composite materials were produced using the powder metallurgy method. Examinations were made to determine the effects of different reinforcement particle ratios and sintering temperatures on the mechanical properties of the AA2024 matrix composite materials that were produced. The powders were compressed in a metal mold at room temperature and a pressure of 525 MPa under a uniaxial press. The raw specimens that were obtained were sintered for 45 minutes at different temperatures. The produced composite materials were subjected to three-point bending tests and hardness measurements. Optical microscopy analysis was carried out for characterization. The results allowed us to draw a conclusion on how the reinforcement material in the produced specimens affected Al-matrix composite properties. It was determined that the B4C reinforcement added to the matrix increased the hardness values of the composites at all sintering temperatures, the highest bending strength was obtained in the composite with 10% B4C particle reinforcement, and in general, the B4C reinforcement was homogeneously dispersed in the matrix. Increased B4C reinforcement ratios resulted in higher hardness values in the composite materials.Item Structural and Dielectric Properties of RE3+, B3+ co-doped (RE3+=Sm3+, Dy3+) BaTa2O6 Tetragonal Tungsten Bronze-Type Ceramics(2024) mustafa ilhan; Mehmet İsmail KATI; Lutfiye feray GuleryuzIn this paper, the effect of boron doping on dielectric properties was investigated using BaTa2O6:xSm3+, yB3+ (x=5 mol%, y= 0, 5, 15, 30, 50, 70, 100 mol%) and BaTa2O6:xDy3+, yB3+ (x=10 mol%, y= 0, 5, 15, 30, 50, 70, 100 mol%) tungsten bronze ceramics fabricated by the conventional solid-state synthesis. XRD (X-ray diffraction) results revealed a single BaTa2O6 phase with space group P4/mbm (127) for both series. Additionally, in both series, there was an increase in crystallite sizes and cell parameters with increasing B3+ concentration. SEM (scanning electron microscopy) examinations indicated that the increase of boron promoted grain growth and grain elongation. In impedance results, in both series, increasing boron concentration up to 100 mol% increased the dielectric constant. Moreover, the presence of boron was associated with a relaxing transition in the B-site substitution of RE3+ (RE=Sm, Dy) ions and a contribution to the dielectric permittivity, while the increase in tetragonality or c/a ratio for both series was ascribed to the increase in the ferroelectric Curie temperature. In both series, a decrease in dielectric loss (tan δ) occurred, which was explained by the increasing sintering temperature effect with increasing boron, reducing the mobility of oxygen vacancies.Item Evaluation of Structural and Dielectric Properties of Eu3+, B3+ co-doped Ba2GdMO6 (M=Nb, Ta) Double Perovskite Ceramics(2024) mustafa ilhan; Lutfiye feray GuleryuzIn the study, the structural and dielectric properties of Ba2GdMO6 (M=Nb, Ta) double perovskite ceramics produced with solid-state method were examined by co-doping xEu3+ and yB3+ (x=10 mol%, y=0, 5, 15, 30, 50, 70 and 100 mol%). XRD (X-ray diffraction) results of the ceramic samples exhibited a single-phase structure with cubic symmetry Fm-3m space group, while increasing B3+ concentration led to an increase in crystallite sizes and lattice parameters up to 50 mol% in both series. SEM (scanning electron microscopy) examinations revealed the presence of boron-supported grain growth and agglomeration in the grains of both series, and also a slight angularity occurred in grain shape at high B3+ concentrations. The dielectric constant (ε') of the ceramic samples in both series increased with increasing boron concentration up to 50 mol%, and it was approximately 33.5 and 35.4 at 20 Hz for the Ba2Gd1-xNbO6:xEu3+, yB3+ and Ba2Gd1-xTaO6:xEu3+, yB3+, respectively. The decrease in the dielectric constant after 50 mol% may be attributed to the presence of increased strain in the structure, as shown by the decrease in crystallite size. The increasing B3+ concentration caused a decrease in dielectric loss (tan δ) in both series, which was attributed to the suppression of oxygen vacancies due to the increased presence of B3+ and hence to a decrease in ionic conductivity and dielectric loss.