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  • Küçük Resim Yok
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    Effect of etching duration on roughness and wettability of different carbon steel substrates
    (Elsevier Science Sa, 2021) Taskin, Nilhan Urkmez; Ordu, Fatih
    Surface chemistry and morphology play a significant role in affecting the wettability of engineering surfaces. To create functional surfaces that are hydrophobic or superhydrophobic, these properties must be understood and controllable. The purpose of this study is to understand the relationship between surface roughness and contact wettability. For this purpose, samples were prepared by using different steel alloys and etched at different etching durations in a mixed solution. The mixed solution for roughening process was prepared by keeping the molar ratio of nitric acid and hydrogen peroxide constant at 1:1, 1:2 respectively. The steel substrates were then immersed in another mixed solution of stearic acid and N, N'-dicyclohexylcarbodiimide in n-hexane (5 mmol/L) for 24 h to lower the surface energy of steel alloy surfaces after roughening step. The effects of the duration of chemical etching on surface roughness were evaluated by using profilometer and surface contact angles were measured using the sessile drop method. Surfaces were analyzed using scanning electron microscopy. Steel surfaces were changed from hydrophilic to hydrophobic/superhydrophobic. The obtained maximum contact angle was 168.36 degrees for CK40 samples, 161.99 degrees for CK22 samples, and 166.35 degrees for 5t37 steel samples. The results of this study showed that the surface contact angle was very sensitive to the change of surface roughness, and wettability could be controlled by changing the surface roughness. In addition, the surface roughness values of steel substrates that exhibit superhydrophobic behavior varied according to the steel type.
  • Küçük Resim Yok
    Öğe
    Metalik yüzeylerde kimyasal işleme yöntemi ile hidrofobik yüzey oluşturulması
    (Trakya Üniversitesi, 2012) Ordu, Fatih; Taşkın, Nilhan Ürkmez
    Katı bir yüzeyin sıvı ile yaptığı temas açısı 90° ile 150° arasında ise bu yüzeylere hidrofobik yüzeyler denir. Temas açısının 150° den büyük olduğu yüzeyler ise süperhidrofobik yüzeyler olarak isimlendirilir. Katı yüzeylerin süperhidrofobik özellik gösterebilmeleri için pürüzlülüklerinin arttırılması, yüzey enerjilerinin ise azaltılması gerekir. Yapılan çalışmada kimyasal aşındırma metoduyla metal yüzeylerin pürüzlülüğü arttırıldı. Bu işlem hidrojen peroksit (H2O2) ve nitrik asitten (NHO3) oluşan kimyasal aşındırıcı karışımla sağlandı. Mikro ve nano boyutta pürüzlü hale getirenden metal yüzeyler düşük yüzey enerjisine sahip stearik asit ile modifeye edildi. Aşındırma süresinin pürüzlülük ve temas açısı üzerindeki etkisinin incelenmesi amacıyla metal malzemeler farklı aşındırma sürelerinde aşındırıldı. Gerçekleştiren çalışma sonucunda elde edilen en yüksek temas açısı değerleri Ç1020 için 161,99°, Ç1040 için 168,36°, St 37 için 166,35°, 2024 Alüminyum alaşımı için ise 131,18° olarak ölçülmüştür. 303 kalite paslanmaz çelik ve 304 kalite paslanmaz çelik yüzeyler kimyasal aşındırıcı tarafından pürüzlü hale getirilemediğinden hidrofobik özellik göstermemiştir.
  • Küçük Resim Yok
    Öğe
    The Morphologies and Wetting Properties of CK40 and AA2024 Surfaces Produced by Chemical Etching and Stearic Acid Modification
    (Maik Nauka/Interperiodica/Springer, 2023) Taskin, Nilhan Urkmez; Beji, Cigdem Ovaci; Ordu, Fatih; Taskin, Vedat
    By applying surface modification after chemical etching, superhydrophobic aluminum and steel surfaces were obtained. With different etching times, from all surfaces, different surface roughness values (Ra) were obtained. The effect of Ra's on surface contact angles (CA) was determined by applying surface modification with stearic acid (STA) to all surfaces under the same conditions. With increased etching time, the surface roughness of both aluminum and steel has increased. Thus, in the current study, wettability seems to be affected only by the changes in surface roughness values. Although the etching reactive and the modification procedure are being same, higher contact angles were obtained on steel surfaces in shorter etching durations compared to aluminum surfaces. The maximum contact angles measured were 125.35 +/- 8.32 degrees on aluminum surfaces and 164.68 +/- 3.62 degrees on steel surfaces. With the current etching method, the minimum etching times required to reach the hydrophobic/superhydrophobic structure for the CK40 and the AA2024 samples were determined. Furthermore, optimum etching times under 10 min for CK40 and under 30 min for AA2024 were determined achieve the maximum contact angle.