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  • Küçük Resim
    Öğe
    Influence of milling parameters on particle size of ulexite material
    (Elsevier Science BV, 2016) Kütük, Sezai
    Commercial raw ulexite (U) materials were milled from 0 h to 8 h by using mechanical milling technique for var-ious initial powder size (?3mm;?75?m), ball to powder ratio (5:1; 10:1), and ball size (10 mm; 5 mm). Par-ticle size, morphology, elemental, and crystal structure measurements of the milled powders were performed. Inthe particle size distribution analysis, the smallestd50andd10values were respectively found as 8.846?mand790 nm for U_5m powder (obtained from that initial powder with?3 mm in size was milled by balls with5 mm in size) at 0.5 h. In the morphology analysis, the microstructure of the U_5m powder was observed tobe more homogeneous by means of milling process. In the elemental analysis, it was deduced that the U_5mpowder is not a pure compound. In the crystal structure analysis, it was determined that the crystal structureof the U_5m powder is exponentially deteriorated with increasing the milling time, and then it has become anamorphous structure at the end of 8 h. The crystalline size of the U_5m powder is reduced to 15.5 nm after 4 hof milling. The results of this study are considered to be useful for future nano studies and industrial applicationsof ceramic ulexite compound, which is a boron mineral.
  • Küçük Resim
    Öğe
    An investigation of magnetoresistivity properties of an Y3Ba5Cu8Oy bulk superconductor
    (Elsevier Science BV, 2015) Kütük, Sezai; Bolat, Süleyman; Terzioğlu, Cabir; Altıntaş S.P.
    A bulk ceramic superconducting sample was fabricated using the standard solid state reaction (SSR) method in the stoichiometric ratio of Y:Ba:Cu:O (3:5:8). The electrical and microstructural properties of the sample were investigated by means of magnetoresistivity (R-T) and micrograph measurements, respectively. Critical temperatures (T-c) such as onset and offset, irreversibility magnetic field (H-irr), upper critical magnetic field (H-c2), and activation energy (U-0) were determined from the R-T under various values of applied magnetic field. The findings obtained were compared with a standard Y:Ba:Cu:O(1:2:3) superconducting sample fabricated by the SSR method. T-c(onset) was 95.83 K for the Y358 sample and 94.86 K for the Y123 sample without the magnetic field. T-c(offset) decreased from 92.87 to 74.08 K for the Y358 sample and from 82.83 to 32.44 K for the Y123 sample when the magnetic field ranged from 0 to 5 T. U-0 values of Y358 and Y123 samples without the magnetic field were respectively 1.1486 and 0.3166 eV. These results indicate that the Y358 sample could provide significant benefits for high temperature superconductivity applications in future.
  • Küçük Resim
    Öğe
    Öğütülmüş kolemanit içeren betonlarda sodyum klorür etkisi
    (Düzce Üniversitesi, 2020) Kara, Cuma; Kütük Sert, Tuba; Kütük, Sezai
    Bu çalışmada, %0 (Referans), %1, %2, %3, %4 ve %5 oranlarında öğütülmüş kolemanit minerali çimento ile ikame edilerek beton karışımları hazırlanmıştır. Beton karışımlar 150 x 150 x 150 mm boyutlu küp kalıplara yerleştirilmiştir. Sertleşmiş beton numuneler 28 gün suda kür edilerek, sonrasında 90. güne kadar sodyum klorür (NaCI) çözeltisine maruz bırakılmıştır. Ayrıca aynı özelliklerde üretilen kontrol beton örnekleri ise 90. güne kadar su küründe bekletilmiştir. Kontrol ve NaCI çözeltisine maruz bırakılmış beton numuneler üzerinde Schmidt çekici, ultrases geçiş hızı ve basınç dayanımı deneyleri gerçekleştirilmiştir. Gerçekleştirilen deneyler üzerinden beton numunelerin NaCI çözeltisinin etkisi ile meydana gelen kayıplar hesaplanmıştır Sonuç olarak, çimentoya ikame edilen %5 kolemanit ikameli numunenin, kolemanit içermeyen numuneye göre basınç dayanımını azalttığı, ancak %4’ kadar ikame oranlarında ise dayanımı arttırdığı tespit edilmiştir. NaCI çözeltisi kürü sonucunda, en yüksek basınç dayanımı ve en az basınç dayanımı kaybının %3 kolemanit ikameli beton karışımına ait olduğu tespit edilmiştir.