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Publication Metadata only Anticorrosion efficiency of ultrasonically deposited silica coatings on titanium(Elsevier Science Bv, 2013) N/A; N/A; Department of Chemistry; N/A; Ertan, Fatoş Sibel; Kaş, Recep; Miko, Annamaria; Birer, Özgür; Master Student; Master Student; Teaching Faculty; Researcher; Department of Chemistry; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/A; 163509; N/AWe utilized high intensity ultrasound to prepare coatings of silica and organically modified silica composed of multiple layers of densely packed nanoparticles. Ultrasound was used to collide nanoparticles onto an activated titanium surface with high speed. Large areas could be homogeneously coated by this method. These coatings were characterized by spectroscopy and microscopy methods and the anticorrosion efficiency in NaCl solution was evaluated by electrochemical measurements. The results indicated that the composite coatings provided good quality barrier layer on bare titanium and decreased the anodic corrosion rate. It was found that increase in the organic content of the coating shifted the passivation potential towards more positive direction. The comparison of the impedance results recorded at the corrosion potential pointed out that in each case a good quality barrier layer was formed on the titanium surface. The outstanding corrosion resistance of the composite coatings with only similar to 200 nm thickness shows that ultrasound assisted deposition can be a competitive method to obtain corrosion protective layers. (c) 2013 Elsevier B.V. All rights reserved.Publication Metadata only Investigation of microstructure, mechanical properties, and biocorrosion behavior of Ti1.5ZrTa0.5Nb0.5W0.5 refractory high-entropy alloy film doped with Ag nanoparticles(Elsevier, 2022) N/A; Department of Chemistry; N/A; Alamdari, Armin Asghari; Ünal, Uğur; Motallebzadeh, Amir; PhD Student; Faculty Member; Researcher; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; 42079; N/AEven though metallic biomaterials have long been utilized as the key materials in biomedical applications due to their exceptional mechanical properties, corrosion and bacterial infection problems place a limit on their prolonged clinical applications. In order to overcome such problems, surface modification of the implants via exerting a durable and protective coating containing antibacterial agents is crucial. In this study, undoped and Ag-doped Ti1.5ZrTa0.5Nb0.5W0.5 refractory high-entropy alloy (RHEA) films with a thickness of 1.10 mu m were deposited on Ti6Al4V alloys through RF magnetron sputtering technique. The influence of the deposited film and embedding Ag nanoparticles on microstructure, mechanical properties, and electrochemical behavior was investigated. The microstructural findings revealed an amorphous structure with cauliflower-like morphology for deposited films. Coated specimens showed a significant improvement in surface mechanical properties such as elastic modulus and hardness. Doping Ag nanoparticles in the deposited film increased the roughness and contact angle of the specimens due to the evolution of Ag nanoparticles. Furthermore, electrochemical investigations revealed that undoped and Ag-doped deposited films remarkably improved the corrosion resistance of uncoated substrate; after the films deposition process, the corrosion rate of the specimens decreased 2.3-2.8 orders of magnitude compared to the uncoated substrate. Also, embedding Ag nanoparticles notably increased the polarization resistance of deposited films.Publication Metadata only Modifying hydrogen binding strength of graphene(Elsevier Science Bv, 2019) N/A; N/A; N/A; Department of Chemistry; Panahi, Mohammad; Solati, Navid; Kaya, Sarp; PhD Student; PhD Student; Faculty Member; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; 116541The effect of the substrate on the binding strength of hydrogen on single layer graphene grown on Pt(111) surfaces has been investigated via determining its desorption activation energy. We showed that subsurface alloys on Pt(111) can dramatical modify the C-H bond strength in hydrogenated graphene. Various 3d metals, vanadium, iron, cobalt, and nickel were deposited in the subsurface layer to modify the chemical and electronical properties of the substrate. Analysis of the temperature programmed desorption data shows that subsurface alloys reduce the hydrogen desorption activation energy by weakening C-H bond energy in graphene, down to 57 kJ/mol in the case of Pt/Co/Pt(111) as compared to similar to 111 kJ/mol obtained from hydrogenated graphene grown on a bare Pt(111).Publication Metadata only Towards complete elucidation of structural factors controlling thermal stability of il/mof composites: effects of ligand functionalization on mofs(Iop Publishing Ltd, 2020) N/A; Department of Chemical and Biological Engineering; N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Durak, Özce; Kulak, Harun; Kavak, Safiyye; Polat, Hüsamettin Mert; Keskin, Seda; Uzun, Alper; Master Student; Researcher; Researcher; Researcher; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; N/A; 40548; 59917In this work, we incorporated an ionic liquid (IL), 1-n-butyl-3-methylimidazolium methyl sulfate ([BMIM][MeSO4]) into two different metal organic frameworks (MOFs), UiO-66, and its amino-functionalized counterpart, NH2-UiO-66, to investigate the effects of ligand-functionalization on the thermal stability limits of IL/MOF composites. The as-synthesized IL/MOF composites were characterized in detail by combining x-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller analysis, x-ray fluorescence, infrared spectroscopies (FTIR), and their thermal stability limits were determined by thermogravimetric analysis (TGA). Characterization data confirmed the successful incorporation of the IL into each MOF and indicated the presence of direct interactions between them. A comparison of the interactions in [BMIM][MeSO4]-incorporated UiO-66 and NH2-UiO-66 with those in their 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6])-incorporated counterparts showed that the hydrophilic IL, [BMIM][MeSO4], interacts with the 1,4-benzenedicarboxylate (BDC) ligand of the UiO-66, while the hydrophobic IL, [BMIM][PF6], is interacting with the joints where zirconium metal cluster coordinates with BDC ligand. The TGA data demonstrated that the composite with the ligand-functionalized MOF, NH2-UiO-66, exhibited a lower percentage decrease in the maximum tolerable temperature compared to those of IL/UiO-66 composites. Moreover, it is discovered that when the IL is hydrophilic, its hydrogen bonding ability can be utilized to designate an interaction site on MOF's ligand structure, leads to a lower reduction in thermal stability limits. These results provide insights for the rational design of IL/MOF composites and contribute towards the complete elucidation of structural factors controlling the thermal stability.