Browsing by Subject "temperature"

Now showing 1 - 4 of 4

Open Access
Electrospinning of functional poly(methyl methacrylate) nanofibers containing cyclodextrin-menthol inclusion complexes
(Institute of Physics Publishing, 2009) Uyar, Tamer; Nur, Y.; Hacaloglu, J.; Besenbacher, F.
Electrospinning of nanofibers with cyclodextrin inclusion complexes (CD-ICs) is particularly attractive since distinct properties can be obtained by combining the nanofibers with specific functions of the CD-ICs. Here we report on the electrospinning of poly(methyl methacrylate) (PMMA) nanofibers containing cyclodextrin-menthol inclusion complexes (CD-menthol-ICs). These CD-menthol-IC functionalized nanofibers were developed with the purpose of producing functional nanofibers that contain fragrances/flavors with high temperature stability, and menthol was used as a model fragrance/flavor material. The PMMA nanofibers were electrospun with CD-menthol-ICs using three type of CD: α-CD, β-CD, and γ-CD. Direct pyrolysis mass spectrometry (DP-MS) studies showed that the thermal evaporation of menthol occurred over a very high and a broad temperature range (100-355 °C) for PMMA/CDmenthol-IC nanowebs, demonstrating the complexation of menthol with the CD cavity and its high temperature stability. Furthermore, as the size of CD cavity increased in the order α-CD<β-CD<γ-CD, the thermal evolution of menthol shifted to higher temperatures, suggesting that the strength of interaction between menthol and the CD cavity is in the order γ-CD>β-CD>α-CD. © 2009 IOP Publishing Ltd.
Open Access
Low thermal-mass LEDs: Size effect and limits
(Optical Society of American (OSA), 2014) Lu, S.; Liu W.; Zhang, Z.-H.; Tan, S.T.; Ju, Z.; Ji, Y.; Zhang X.; Zhang, Y.; Zhu, B.; Kyaw, Z.; Hasanov, N.; Sun X.W.; Demir, Hilmi Volkan
In this work, low thermal-mass LEDs (LTM-LEDs) were developed and demonstrated in flip-chip configuration, studying both experimentally and theoretically the enhanced electrical and optical characteristics and the limits. LTM-LED chips in 25 × 25 μm2, 50 × 50 μm2, 100 × 100 μm2 and 200 × 200 μm2 mesa sizes were fabricated and comparatively investigated. Here it was revealed that both the electrical and optical properties are improved by the decreasing chip size due to the reduced thermal mass. With a smaller chip size (from 200 μm to 50 μm), the device generally presents higher current density against the bias and higher power density against the current density. However, the 25 × 25 μm2 device behaves differently, limited by the fabrication margin limit of 10 μm. The underneath mechanisms of these observations are uncovered, and furthermore, based on the device model, it is proven that for a specific flip-chip fabrication process, the ideal size for LTM-LEDs with optimal power density performance can be identified. ©2014 Optical Society of America
Open Access
Model boson fluid with disorder in the self-consistent field approximation
(2001) Yurtsever, A.; Tanatar, Bilal
We study the ground-state properties of a model neutral boson fluid in the presence of disorder effects. The effective interaction between the bosons is obtained through the self-consistent field method which renormalizes the bare interaction consisting of a hard-core repulsive potential with an attractive tail at zero temperature. We introduce disorder effects within a number-conserving approximation by modifying the density - density response function. Our results for the static structure factor and the collective mode dispersion reflect the effect of disorder in qualitative agreement with other calculational approaches. © 2001 Elsevier Science B.V. All reserved.
Open Access
A radiotracer study of the adsorption behavior of aqueous Ba2+ ions on nanoparticles of zero-valent iron
(2007) Çelebi O.; Üzüm, C.; Shahwan, T.; Erten H.N.
Recently, iron nanoparticles are increasingly being tested as adsorbents for various types of organic and inorganic pollutants. In this study, nanoparticles of zero-valent iron (NZVI) synthesized under atmospheric conditions were employed for the removal of Ba2+ ions in a concentration range 10-3 to 10-6 M. Throughout the study, 133Ba was used as a tracer to study the effects of time, concentration, and temperature. The obtained data was analyzed using various kinetic models and adsorption isotherms. Pseudo-second-order kinetics and Dubinin-Radushkevich isotherm model provided the best correlation with the obtained data. Observed thermodynamic parameters showed that the process is exothermic and hence enthalpy-driven. © 2007 Elsevier B.V. All rights reserved.