Research Outputs

Permanent URI for this communityhttps://hdl.handle.net/20.500.14288/2

Browse

Filters

2008 - 200912010 - 20182

Advanced Search

Filter by

Settings

Quartile: search.filters.quartile.Q3Subject: search.filters.subject.Crystallography

Search Results

Now showing 1 - 3 of 3
  • Placeholder
    PublicationMetadata only
    Dynamics of spacing adjustment and recovery mechanisms of ABAC-type growth pattern in ternary eutectic systems
    (Elsevier, 2017) N/A; N/A; Department of Mechanical Engineering; Mohagheghi, Samira; Şerefoğlu, Melis; PhD Student; Researcher; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; 329277; 44888
    In directionally solidified 2D samples at ternary eutectic compositions, the stable three-phase pattern is established to be lamellar structure with ABAC stacking, where A, B, and C are crystalline phases. Beyond the stability limits of the ABAC pattern, the system uses various spacing adjustment mechanisms to revert to the stable regime. In this study, the dynamics of spacing adjustment and recovery mechanisms of isotropic ABAC patterns were investigated using three-phase In-Bi-Sn alloy. Unidirectional solidification experiments were performed on 23.0 and 62.7 mu m-thick samples, where solidification front was monitored in real-time from both sides of the sample using a particular microscopy system. At these thicknesses, the pattern was found to be 2D during steady-state growth, i.e. both top and bottom microstructures were the same. However, during spacing adjustment and recovery mechanisms, 3D features were observed. Dynamics of two major instabilities, lamellae branching and elimination, were quantified. After these instabilities, two key ABAC pattern recovery mechanisms, namely, phase invasion and phase exchange processes, were identified and analyzed. After elimination, ABAC pattern is recovered by either continuous eliminations of all phases or by phase exchange. After branching, the recovery mechanisms are established to be phase invasion and phase exchange.
  • Thumbnail Image
    PublicationOpen Access
    Effect of methylation of ionic liquids on the gas separation performance of ionic liquid/metal-organic framework composites
    (Royal Society of Chemistry (RSC), 2018) Department of Chemical and Biological Engineering; Nozari, Vahid; Keskin, Seda; Uzun, Alper; Zeeshan, Muhammad; Faculty Member; PhD Student; Department of Chemical and Biological Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; N/A; 40548; 59917; N/A
    1-N-Butyl-3-methylimidazolium hexafluorophosphate, [BMIM]ijPF6], and its methylated form, 1-N-butyl2,3-dimethylimidazolium hexafluorophosphate, [BMMIM]ijPF6], were incorporated into CuBTC to examine the effect of methylation of ionic liquids (ILs) on the gas separation performance of the corresponding IL/ metal–organic framework (MOF) composites. Spectroscopic analysis revealed that the interactions of the methylated ILs with CuBTC were weaker compared to those of its non-methylated counterpart. Gas uptake measurements illustrated that this difference in the interactions influences the gas separation performance of the composites. Accordingly, the CO2/N2: 15/85 and CH4/N2: 50/50 selectivities increased by 37% and 60% for [BMMIM]ijPF6]/CuBTC and 34% and 50% for [BMIM]ijPF6]/CuBTC, respectively, compared to the corresponding selectivities of pristine CuBTC at 1000 mbar. The results revealed another structural parameter controlling the performance of the IL/MOF composites, a novel type of material with rapidly expanding application areas.
  • Placeholder
    PublicationMetadata only
    FT-Raman, FT-IR, NMR structural characterization and antimicrobial activities of 1,6-bis(benzimidazol-2-yl)-3,4-dithiahexane ligand and its Hg(II) halide complexes
    (Springer/Plenum Publishers, 2008) Aghatabay, Naz Mohammed; Tülü, Metin; Mahmiani, Yaghub; Dülger, Başaran; Department of Chemistry; Somer, Mehmet Suat; Faculty Member; Department of Chemistry; College of Sciences; 178882
    1,6-Bis(benzimidaz-2-yi)-3,4-dithiahexane ligand (L) and its mercury halide complexes were prepared and characterised. The elemental analysis, molecular conductivity, FT-Raman, FT-IR (mid, far), H-1, C-13 NMR and geometry optimization in MOPAC using MNDOd parameter on CACHE, prove the existence of neutral, mononuclear and the distorted tetrahedral [Hg(L)X-2] complexes. In all the three complexes, the ligand acts as a chelating bidentate, through two of the bridging sulphur atoms and together with the monodentate coordination of the two anionic halide ligands to the metal centre forming a possible 4-coordinate compounds. The antimicrobial activities of free ligand, its hydrochlorinated salt, mercury halides and the complexes are evaluated using disk diffusion method in dimethyl sulfoxide (DMSO) as well as the minimal inhibitory concentration (MIC) dilution method, against 10 bacteria. The obtained results from disk diffusion method are assessed in side-by-side comparison with those of Penicillin-g, Ampicillin, Cefotaxime, Vancomycin, onaxacin and Tetracyclin well-known antibacterial agents. The results from dilution procedure are compared with Gentamycin as antibacterial and Nystatin as antifungal. The antifungal activities are reported on five yeast cultures namely Candida albicans, Kluyveromyces fragilis, Rhodotorula rubra, Debaryomyces hansenii and Hanseniaspora guillierinondii, and the results are referenced with Nystatin, Ketaconazole and Clotrimazole, commercial antifungal agents. In most cases, the compounds show broad-spectrum (Gram(+) & Gram(-) bacteria) activities that are comparatively, slightly less active or equipotent to the antibiotic and antifungal agents in the comparison tests.