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51.
52.
Şenol Durmuşoğlu İbrahim Uslu Tuncay Tunç Selda Keskin Arda Aytimur Ahmet Akdemir 《Journal of Polymer Research》2011,18(6):1999-2004
Boron doped poly(vinyl) alcohol/ bismuth - lanthanum acetate (PVA/Bi-La) nanofibers were prepared by electrospinning using
PVA as a precursor. The effect of boron doping was investigated in terms of solution properties, morphological changes and
thermal characteristics. The fibers were characterized by FT-IR, XRD, SEM and BET. The addition of boron did not only increase
the thermal stability of the fibers, but also their diameters, which yielded stronger fibers. XRD analyses showed that boron
doping increased the peak intensities and indicated that the boron doping enhanced the crystallite size. Moreover, no shifts
were noticed in diffraction angles for boron doped and undoped samples. Therefore, boron doping did not significantly alter
the lattice spacing. The SEM micrograph of the fibers showed that the addition of boron resulted in the formation of cross
linked bright surfaced fibers. Also, grain diameters of boron doped and undoped nanocrystalline sintered powders were measured
as 170 nm and 120 nm respectively. The BET results show that boron undoped and doped Bi2O3-La2O3 nanocrystalline powder ceramic structures sintered at 800 °C have surface areas of 20.44 m2/g and 12.93 m2/g, respectively. 相似文献
53.
Tuncay Tunç Şemsettin Altındal İlbilge Dökme Habibe Uslu 《Journal of Electronic Materials》2011,40(2):157-164
In this study, the temperature-dependent mean density of interface states (NSS)(N_{\rm SS}) and series resistance (RS)(R_{\rm S}) profiles of Au/PVA (Ni,Zn-doped)/n-Si(111) structures are determined using current–voltage (I−V) and admittance spectroscopy [capacitance–voltage (C–V) and conductance–voltage G/ω–V] methods. The other main electronic parameters such as zero-bias barrier height (FB0)(\Phi_{{\rm B}0}), ideality factor (n), and doping concentration (N
D) are also obtained as a function of temperature. Experimental results show that the values of FB0\Phi_{\rm{B}0}, n, R
S, and N
SS are strongly temperature dependent. The values of FB0\Phi_{\rm{B}0} and R
S increase with increasing temperature, while those of n and N
SS decrease. The C–V plots of Au/PVA (Ni,Zn-doped)/n-Si(111) structures exhibit anomalous peaks in forward bias (depletion region) at each temperature, and peak positions shift
towards negative bias with increasing temperature. The peak value of C has been found to be strongly dependent on N
SS, R
S, and temperature. The experimental data confirm that the values of N
SS, R
S, temperature, and the thickness and composition of the interfacial polymer layer are important factors that influence the
main electrical parameters of the device. 相似文献
54.
Tuncay Tunç ?emsettin Altindal ?brahim Uslu ?lbilge Dökme Habibe Uslu 《Materials Science in Semiconductor Processing》2011,14(2):139-145
Current–voltage (I–V) characteristics of Au/PVA/n-Si (1 1 1) Schottky barrier diodes (SBDs) have been investigated in the temperature range 80–400 K. Here, polyvinyl alcohol (PVA) has been used as interfacial layer between metal and semiconductor layers. The zero-bias barrier height (ΦB0) and ideality factor (n) determined from the forward bias I–V characteristics were found strongly dependent on temperature. The forward bias semi-logarithmic I–V curves for different temperatures have an almost common cross-point at a certain bias voltage. The values of ΦB0 increase with the increasing temperature whereas those of n decrease. Therefore, we have attempted to draw ΦB0 vs. q/2kT plot in order to obtain evidence of a Gaussian distribution (GD) of the barrier heights (BHs). The mean value of BH and standard deviation (σ0) were found to be 0.974 eV and 0.101 V from this plot, respectively. Thus, the slope and intercept of modified vs. q/kT plot give the values of and Richardson constant (A?) as 0.966 eV and 118.75 A/cm2K2, respectively, without using the temperature coefficient of the BH. This value of A* 118.75 A/cm2K2 is very close to the theoretical value of 120 A/cm2K2 for n-type Si. Hence, it has been concluded that the temperature dependence of the forward I–V characteristics of Au/PVA/n-Si (1 1 1) SBDs can be successfully explained on the basis of the Thermionic Emission (TE) theory with a GD of the BHs at Au/n-Si interface. 相似文献
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58.
The lap-shear technique is commonly used to evaluate the shear, creep, and thermal fatigue behavior of solder joints. We have
conducted a parametric experimental and modeling study, on the effect of testing and geometrical parameters on solder/copper
joint response in lap-shear. It was shown that the farfield applied strain is quite different from the actual solder strain
(measured optically). Subtraction of the deformation of the Cu substrate provides a reasonable approximation of the solder
strain in the elastic regime, but not in the plastic regime. Solder joint thickness has a profound effect on joint response.
The solder response moves progressively closer to “true” shear response with increasing joint thickness. Numerical modeling
using finite-element analyses were performed to rationalize the experimental findings. The same lap-shear configuration was
used in the simulation. The input response for solder was based on the experimental tensile test result on bulk specimens.
The calculated shear response, using both the commonly adopted far-field measure and the actual shear strain in solder, was
found to be consistent with the trends observed in the lap-shear experiments. The geometric features were further explored
to provide physical insight into the problem. Deformation of the substrate was found to greatly influence the shear behavior
of the solder. 相似文献
59.
Ertan Durmusoglu M. Yavuz Corapcioglu Kagan Tuncay 《Canadian Metallurgical Quarterly》2006,6(4):269-278
Municipal solid waste (MSW) landfills are not only used to dispose the refuse in most economical way but also utilized as a viable land in today’s waste management strategy. Settlement prediction is an important issue in order to guarantee the integrity of any postclosure structure on landfills. In this study, landfill settlement in saturated and unsaturated landfills is investigated by developing a one-dimensional mathematical model and performing numerical experiments. Under the saturated conditions, the landfill is considered to be completely liquid saturated by preventing gas generation at all times. On the other hand, for the unsaturated case, we assume that a gas mixture comprised of methane and carbon dioxide is generated as a result of microbial decomposition of MSW deposited. The gas generation is assumed to follow a first-order kinetic approach. The liquid phase and gas mixture are considered compressible as well as the solid matrix (landfill body). After the governing equations were discretized using the Galerkin finite-element method, the Gaussian elimination technique is employed for a solution. In saturated landfills, the settlement is mainly caused by the overburden weight of the waste deposited. Further, the mass loss due to waste decomposition contributes for an additional settlement in unsaturated landfills. The predicted settlements are within the range reported in the literature. The model developed can simulate porosity, pressures, saturations, and stress profiles in settling landfills as well as to predict the transient and ultimate settlements in saturated and unsaturated landfills. 相似文献
60.
This article presents a cross-flow plate-type heat exchanger that has been studied and manufactured in laboratory conditions because of its effective use in waste heat recovery systems. This new heat exchanger was tested with an applicable experimental setup, considering temperatures, velocity of the air, and the pressure losses occurring in the system. These variables were measured and the efficiency of the system was determined. The irreversibility of the heat exchanger was taken into consideration, while the design of the heat exchanger was such that the minimum entropy generation number was analyzed with respect to the second law of thermodynamics in the cross-flow heat exchanger. The minimum entropy generation number depends on the parameters called the optimum flow path length and dimensionless mass velocity. Variations of the entropy generation number with these parameters are analyzed. 相似文献