Temel Mühendislik Ana Bilim Dalı

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Citation - WoS: 2
Citation - Scopus: 3
Analysis of the Integrated Intensity of the Central Peaks Calculated as a Function of Temperature in the Ferroelectric Phase of Lithium Tantalate
(Vinca inst Nuclear Sci, 2018) Yurtseven, Hamit; Kiraci, Ali
The integrated intensity of the central peak is calculated as a function of temperature in the ferroelectric phase (T < T-C) of nearly stoichiometric LiTaO3. This calculation is performed using the temperature dependence of the order parameter obtained from the mean field theory at temperatures lower than the transition temperature T-C (T-C = 963 K) of this crystal. The calculated values of the order parameter (squared) are fitted to the integrated intensity of the central peaks as observed from the Raman and Brillouin scattering experiments as reported in the literature in the ferroelectric phase of nearly stoichiometric LiTaO3. Our results are in good agreement with the observed behavior of LiTaO3 crystal. Because of the applications of LiTaO3 in several academic disciplines including the material science and thermal science, it is beneficial to investigate dynamic properties of this crystal such as the damping constant, inverse relaxation time and the activation energy as also we studied here.
Analysis of the Specific Heat and the Free Energy of [N(Ch 3 ) 4 ] 2 Znbr 4 Close to the Ferro-Paraelastic Phase Transition
(Taylor&Francis LTD, 2019) Kiracı, Ali
A power-law formula deduced from the Ising model was used to analyze the temperature dependence of the specific heat C p and the Gibbs free energy G of [N(CH 3 ) 4 ] 2 ZnBr 4 compound in the vicinity of the phase transition temperature of T C = 287.2 K. Obtained values of the critical exponents α from the Gibbs free energy were consistent with that predicted from 2-d potts model (α = 0.3), while obtained values of α from the specific heat in both ferroelastic and paraelastic phases were consistent with that predicted from the mean field theory (α = 0) in the vicinity of the phase transition temperature. This is an indication of that [N(CH 3 ) 4 ] 2 ZnBr 4 compound undergoes a second order type phase transition. Also, the enthalpy (H) and the entropy (S) of this crystal were calculated in terms of the extracted values of the critical exponent in both ferroelastic and paraelastic phases.
Citation - WoS: 5
Citation - Scopus: 5
Determination of Trapping Parameters of Tl2in2s3se Layered Single Crystal by Thermoluminescence
(Wiley-v C H verlag Gmbh, 2018) Gasanly, Nizami; Guler, Ipek
Thermoluminescence (TL) measurements are performed to evaluate the trap states in Tl2In2S3Se layered single crystals. TL experiments are conducted with varying temperature from 10 to 300 K and warming rates from 0.2 to 1.0 K s(-1). From the analysis of both initial rise and curve fitting methods, the activation energy of the traps is obtained as 23 meV. The Chen's method is also used to find activation energy. By means of this technique, the activation energy of the TL glow curve is calculated as 25 meV. From both Chen's method and curve fitting method, the existence of mixed order of kinetics in Tl2In2S3Se crystal is found. The cross section to capture of the trap center is found out from the results of curve fitting method. The trap distribution of the crystals is investigated with different temperatures of illumination at a constant warming rate of 0.8 K s(-1). The temperatures of illumination change from 10 to 22 K. As a result of the increase in temperatures of illumination, the peak maximum values move to higher temperatures and intensity of the TL curves decreases. This behavior shows us that quasicontinuous traps distribution is present in Tl2In2S3Se layered single crystals.
Citation - WoS: 3
Citation - Scopus: 3
N-Phosphorylation of Pyrroles: an Intramolecular Migration Reaction
(Pergamon-elsevier Science Ltd, 2018) Unaleroglu, Canan; Tasgin, Dilek Isik
A new synthetic method is reported for the N-phosphorylation of pyrroles via intramolecular migration of a phosphonate diester group. The reaction proceeds under mild conditions and produces N-phosphorylated pyrrole derivatives in moderate to good yields. (C) 2018 Elsevier Ltd. All rights reserved.
Citation - WoS: 5
Citation - Scopus: 6
Ring Annulation Versus Alkylation of Pyrrole With Α-Phosphoryl Ketones
(Pergamon-elsevier Science Ltd, 2016) Tasgin, Dilek Isik; Unaleroglu, Canan
In this study; novel aryl, heteroaryl, pyrrolyl and phosphoryl groups containing pyrrolizines were synthesized by the ring annulation reaction of aryl or heteroaryl substituted alpha-phosphoryl-alpha,beta-unsaturated ketones with pyrrole under mild reaction conditions. This domino reaction involves scandium triflate catalyzed addition of pyrrole to the double bond of alpha-phosphoryl-alpha,beta-unsaturated ketones, carbonyl group and finally ring annulation sequences. The presented work provided a convenient way for the synthesis of novel bispyrrolic compounds. (C) 2016 Elsevier Ltd. All rights reserved.

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