Browsing by Subject "Energy density"

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    Fluorescent macromolecular perylene diimides containing pyrene or indole units in bay positions
    (2010) Dinçalp H.; Kizilok S.; Içli S.
    Novel, symmetric and unsymmetric perylene diimide dyes with pyrene or indole units in the bay positions of the perylene ring were synthesized and characterized using FT-IR, 1H and 13C NMR, MS, UV-Vis spectra and cyclic voltammetry. The λmax in different solvents were in the range 526-585 nm and emission wavelengths of the dyes exhibited positive solvatochromism with increasing solvent polarity. Long wavelength emissions >750 nm of dyes with pyrene units displayed charge-separated state of perylene-pyrene system. Dyes with pyrene or indole units showed greater photostability in toluene than dyes which did not contain these bulky substituents. Incorporating electron-donating indole substituents lowered the band gap energies and, therefore, the HOMO energy levels were increased. The energy density and shape of the molecular orbitals were calculated theoretically. © 2009 Elsevier Ltd. All rights reserved.
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    Selective laser melting of Ti6Al4V alloy: Effects of process parameters at constant energy density on mechanical properties, residual stress, microstructure and relative density
    (Walter de Gruyter GmbH, 2023) Önder S.; Saklakoǧlu N.
    Selective laser melting is a production method that results in a large amount of residual stress due to high cooling rates and high thermal gradients. Although there are many studies examining the effects of process parameters on residual stress or mechanical properties in the literature, there are a few studies investigating the effects of changing laser power and scanning velocity (exposure time) at constant energy density on residual stress or mechanical properties and these studies have different results. This is a comprehensive study in this field that includes detailed comparisons with the results of similar studies in the literature. In this study, firstly specimens were produced at different process parameters and it was tried to find the process parameters that will obtain the highest relative density among the trials. Then at the constant energy density (85.0 J mm-3), which the maximum density has been obtained the effects of changing laser power and scanning velocity on residual stress, mechanical properties, microstructure and relative density were investigated. It was observed that at constant energy density, increasing or decreasing laser power and scanning velocity did not increase or decrease residual stress, tensile strength, % elongation and relative density monotonously. © 2022 Walter de Gruyter GmbH, Berlin/Boston.