Researcher:
Karakuş, Kerem

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PhD Student

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Kerem

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Karakuş

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Karakuş, Kerem

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2015 - 20173

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Researcher Of Publications: search.filters.isAuthorOfPublication.4fb54146-2125-44bb-a2af-11173d107b4c

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    Simultaneous DLS-SLS study of titanium and titanium/silicon oxide sol growth
    (Springer, 2017) N/A; N/A; N/A; N/A; Karahan, Hüseyin Enis; Karakuş, Kerem; Birer, Özgür; PhD Student; PhD Student; Researcher; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; N/A; N/A; N/A
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    Simultaneous DLS-SLS study of titanium and titanium/silicon oxide sol growth
    (Springer, 2015) N/A; N/A; N/A; N/A; Karahan, Hüseyin Enis; Karakuş, Kerem; Birer, Özgür; PhD Student; PhD Student; Researcher; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; N/A; N/A; N/A
    A commercial DLS setup was used for simultaneous DLS/SLS analysis of sol growth of titanium and titanium/silicon oxides. The scattering data were analyzed in dynamic and static modes which allowed evaluating particle size and concentration simultaneously. A binary solvent (acetone/ethanol mixture) was introduced which effectively controls monodisperse growth behavior by simply adjusting its ratio. Fixing the solvent composition to the ratio which delayed gelation the most, the effect of the amount of catalyst (acetic acid), hydrolyzing agent (water) and titanium oxide precursor (titanium tetraisopropoxide) on growth kinetics were studied. Taking the advantage of extra functionalities of the catalyst used, acetic acid, i.e., decreasing the reactivity of titanium tetraisopropoxide and increasing the reactivity of tetraethyl orthosilicate, hybrid titanium/silicon oxide growth was also studied. Here, we step-by-step showed that particle size, particle concentration and sol-to-gel transition time of titanium and titanium/silicon oxide systems can be well controlled by adjusting the composition of formulations in ambient conditions. We also showed how practical the laser light scattering is to evaluate even the early onsets of growth profiles long before visual identification of clouding. The findings reported here are particularly important for practical applications of sol-gel technology where the control of particle size/concentration and gelation time is advantageous.
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    Shadow-casted ultrathin surface coatings of titanium and titanium/silicon oxide sol particles via ultrasound-assisted deposition
    (Elsevier, 2016) N/A; N/A; N/A; N/A; N/A; Karahan, Hüseyin Enis; Birer, Özgür; Karakuş, Kerem; Yıldırım, Cansu; PhD Student; Researcher; PhD Student; Master Student; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; N/A; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; N/A; N/A; N/A
    Ultrasound-assisted deposition (USAD) of sol nanoparticles enables the formation of uniform and inherently stable thin films. However, the technique still suffers in coating hard substrates and the use of fast-reacting sol-gel precursors still remains challenging. Here, we report on the deposition of ultra thin titanium and titanium/silicon hybrid oxide coatings using hydroxylated silicon wafers as a model hard substrate. We use acetic acid as the catalyst which also suppresses the reactivity of titanium tetraisopropoxide while increasing the reactivity of tetraethyl orthosilicate through chemical modifications. Taking the advantage of this peculiar behavior, we successfully prepared titanium and titanium/silicon hybrid oxide coatings by USAD. Varying the amount of acetic acid in the reaction media, we managed to modulate thickness and surface roughness of the coatings in nanoscale. Field-emission scanning electron microscopy and atomic force microscopy studies showed the formation of conformal coatings having nanoroughness. Quantitative chemical state maps obtained by x-ray photoelectron spectroscopy (XPS) suggested the formation of ultrathin (<10 nm) coatings and thickness measurements by rotating analyzer ellipsometry supported this observation. For the first time, XPS chemical maps revealed the transport effect of ultrasonic waves since coatings were directly cast on rectangular substrates as circular shadows of the horn with clear thickness gradient from the center to the edges. In addition to the progress made in coating hard substrates, employing fast-reacting precursors and achieving hybrid coatings; this report provides the first visual evidence on previously suggested "acceleration and smashing" mechanism as the main driving force of USAD.