Browsing by Subject "Diamond"
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Item Open Access Atomic scale study of superlow friction between hydrogenated diamond surfaces(American Physical Society, 2004) Dag, S.; Çıracı, SalimStrong attractive interaction between two clean diamond (001) slabs turns repulsive upon the hydrogenation of surfaces. This repulsive interaction serves as if a boundary lubricant and prevents the sliding surfaces from being closer to each other even under high normal forces. As a result, calculated lateral force variation generated during sliding has small magnitude under high constant loading forces. Superlow friction observed earlier between diamondlike carbon-coated surfaces can be understood by the steady repulsive interaction between sliding surfaces, as well as strong and stiff carbon-carbon and carbon-hydrogen bonds which do not favor energy dissipation. In ambient conditions, the steady repulsive interaction is, however, destroyed by oxygen atoms which chemically modify those stiff surface bonds.Item Restricted Büyük Porsuk Oteli(Bilkent University, 2020) Erdaş, Merve; Çam, Kağan; Topçu, Ayşenur; Ünlüce, Aras; Yücel, TuranEskişehir'de kurulmuş, adını Emir Porsuk'dan almış ve tarihi 1927'lere dayanan Büyük Porsuk Otel, Eskişehir'in il olması sonrasında yapılan yenilikler ve artan göçler dolayısıyla şehirdeki konaklama ihtiyacını karşılamak üzere inşa edilmiştir. Kurulduğu dönemin şartları göz önüne alınarak düşünüldüğünde diğer bina ve yapılardan üstün özelliklere sahip olan otel, önemli etkinliklere ev sahipliği yapmıştır. Otelin belediye binası olarak kullanılma kararından bir süre sonra Emekli Sandığı tarafından inşaatına başlanan diğer Porsuk Otel, 26 Mayıs 1960'da Adnan Menderes tarafından açılır. Bu çalışmada, Porsuk Otel tarihi, ilgili belge, yayın ve röportajlardan yararlanılarak anlatılmıştır. Tarihi yapılarının günümüze kadar bozulmadan gelmeleriyle ilk günkü duruşlarından ödün vermeyen oteller, yalnızca yapısal özellikleriyle büyülemeyip, verilen hizmetlerin kalitesiyle de günümüzde kendilerinden söz ettirmektedirler.Item Open Access Low-Temperature Deposition of Hexagonal Boron Nitride via Sequential Injection of Triethylboron and N2/H2 Plasma(Wiley-Blackwell Publishing, Inc., 2014) Haider A.; Ozgit Akgun, C.; Goldenberg, E.; Okyay, Ali Kemal; Bıyıklı, NecmiHexagonal boron nitride (hBN) thin films were deposited on silicon and quartz substrates using sequential exposures of triethylboron and N 2 /H 2 plasma in a hollow-cathode plasma- assisted atomic layer deposition reactor at low temperatures ( ≤ 450 ° C). A non-saturating film deposition rate was observed for substrate temperatures above 250 ° C. BN films were charac- terized for their chemical composition, crystallinity, surface morphology, and optical properties. X-ray photoelectron spec- troscopy (XPS) depicted the peaks of boron, nitrogen, carbon, and oxygen at the film surface. B 1s and N 1s high-resolution XPS spectra confirmed the presence of BN with peaks located at 190.8 and 398.3 eV, respectively. As deposited films were polycrystalline, single-phase hBN irrespective of the deposition temperature. Absorption spectra exhibited an optical band edge at ~ 5.25 eV and an optical transmittance greater than 90% in the visible region of the spectrum. Refractive index of the hBN film deposited at 450 ° C was 1.60 at 550 nm, which increased to 1.64 after postdeposition annealing at 800 ° C for 30 min. These results represent the first demonstration of hBN deposi- tion using low-temperature hollow-cathode plasma-assisted sequential deposition technique. © 2014 The American Ceramic Society.Item Open Access New equations for lattice and electronic heat capacities, enthalpies, and entropies of solids: application to diamond(Polish Academy of Sciences, 2019) Bozdoğan, A. E.; Bozdoğan, İrfan SelimNew equations for heat capacities, entropies, and enthalpies were applied to the experimental constant volume heat capacity data of diamond. The temperature ΘV corresponding to 3R/2 was found to be 468 K. The relationships between dimension, and ΘV and the Debye temperature were given. Diamond showed the dimensionality crossover from 3 to 2 at after 300 K. Temperature dependences of the Debye temperature and ΘV were given and non-monotonic behaviors were discussed. The heat capacity and entropy values predicted by the proposed models were compared with the values predicted by the Debye models. The results showed that the proposed models fit the data better than the Debye models. The enthalpy values predicted by the proposed models were compared with the values predicted by the polynomial model and good agreement was obtained.