WoS İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653

Browse

Filters

20152

Settings

Department: search.filters.department.Çankaya Üniversitesi, Mühendislik Fakültesi, Malzeme Bilimi ve Mühendisliği BölümüLanguage: search.filters.language.en

Search Results

Now showing 1 - 2 of 2
  • Article
    Kinetics and mechanisms of isothermal devitrification inamorphous cu50zr50
    (Springer, 2015) Cullinan, Tim; Kalay, İlkay; Kalay, Y. Eren; Kramer, Matt; Napolitano, Ralph
    The crystallization kinetics and microstructural dynamics associated with devitrifying a melt-spun Cu50Zr50 metallic glass were investigated using isothermal treatments, in situ high-energy synchrotron X-ray diffraction, conventional and high-resolution transmission electron microscopy, and differential scanning calorimetry. The analysis of isothermal transformations allows us to more clearly unravel the complex interplay between nucleation and growth of competing stable and metastable phases. The isothermal devitrification response was found to involve the Cu10Zr7, CuZr2, and CuZr phases, consistent with previously reported constant heating rate experiments, but here we have resolved the phase evolution and structural characteristics of the transformation, including the very early stages of crystallization. At 671 K (398 A degrees C), the isothermal transformation starts with the formation of the Cu10Zr7 phase, which grows in a generally equiaxed morphology. At a size of approximately 100 nm, the growth of the Cu10Zr7 particles is interrupted by the precipitation of a thin layer of the CuZr2 phase, upon which the metastable CuZr (B2) grows epitaxially. Crystallization kinetics are quantified here though in situ measurements (HEXRD, DSC) and ex situ microstructural analysis (TEM, HRTEM). Finally, the influences of chemical partitioning, diffusion, and crystallographic orientation on this sequence are examined.
  • Conference Object
    Temperature Dependence of the Brillouin Frequency Shift and the Linewidth of the LA Mode in the Ferroelectric Phase of PZT-x (PbZr1-xTixO3)
    (IEEE, 2015) Yurtseven, F.; Korkmaz, C. Şişman; Kiraci, A.
    The temperature dependence of the Brillouin frequency and the linewidth of the LA mode is studied for the concentration of x=0.45 in the ferroelectric phase of PbZr1-xTixO3 (PZT-x) within the temperature range of 443 to 656 K (T-C=657 K). Using the experimental data for the Brillouin frequency of the LA mode as an order parameter below T-C the temperature dependence of the linewidth (FWHM) is calculated by the pseudospin-phonon coupled model and the energy fluctuation model for the lead titanate zirconate (x=0.45). Additionally, the activation energies are compared from the damping constant (linewidth) using both models for the temperature range of 443 to 656 K in the ferroelectric phase of PbZr1-xTixO3. Our calculated values for the damping constant are in agreement with the observed data for the ferroelectric phase of PbZr1-xTixO3 single crystals. The activation energies calculated from both models are much higher in the ferroelectric phase than the value of k(B)T(C)=0.056 eV at the transition temperature for PbZr1-xTixO3 (x=0.45).