Research Project: Sesüstü Dalgalarla Yüzeye Gömülü Korozyon Önleyici Kaplamaların Geliştirilmesi
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Contributors
Funders
ID
TB.00034
Authors
Birer, Özgür
Researcher
Publications
Shadow-casted ultrathin surface coatings of titanium and titanium/silicon oxide sol particles via ultrasound-assisted deposition
(Elsevier, 2016) Birer, Özgür; Karahan, Hüseyin Enis; Karakuş, Kerem; Yıldırım, Cansu; N/A; KUYTAM (Koç University Surface Science and Technology Center); Graduate School of Sciences and Engineering; Department of Chemistry; No; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center; College of Sciences
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.
Ultrasound assisted deposition of silica coatings on titanium
(Elsevier, 2012) Birer, Özgür; Ertaş, Fatma Sinem; Kaş, Recep; N/A; KUYTAM (Koç University Surface Science and Technology Center); Department of Chemistry; No; Research Center; College of Sciences
We present a novel ultrasound assisted method for silica coating of titanium surfaces. The coatings are formed by "smashing" silica nanoparticles onto activated titanium surface in solution using intense ultrasonic field. Homogeneous silica coatings are formed by deposition of dense multiple layers of silica nanoparticles. Since the nanoparticles also grow during the reaction, the layers of the coatings have smaller particles on the substrate and larger particles towards the surface. The thickness of the coatings can be controlled with several experimental parameters. Silica layers with thickness over 200 nm are readily obtained.
Simultaneous DLS-SLS study of titanium and titanium/silicon oxide sol growth
(Kluwer Academic Publishers, 2015) Birer, Özgür; Karahan, Hüseyin Enis; Karakuş, Kerem; N/A; KUYTAM (Koç University Surface Science and Technology Center); Department of Chemistry; No; Research Center; College of Sciences
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.
