Physical properties and photocatalytic performance of TiO 2 coated stainless steel plate
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Physical Properties and Photocatalytic Performance of TiO2 Coated Stainless Steel Plate Hee Dong Chun*, Jae Shin Kim, Seok-min Yoon and Chang Gyun Kim* Water Protection Research Team, Research Institute of Industrial Science and Technology, Pohang 790-330, Korea *Regional Research Center for the Coastal Environment of the Yellow Sea, Inha University, Incheon 402-751, Korea (Received 6 SeptenSer 2001 9 accepted 17 October 2001)
Absa.act-This research was conducted for the development of TiO~ thin film coated stainless steel useful in environmental and sanitary fields such as removal of indoor air pollutants and prevention of harmful microorganisms in the !dtche11 and batt~-oom. For this purpose, the research was focused on the examination of physical properties of coated surfaces as well as the photocatalytic performance of the steel plates. The coated steel's cohesiveness and anti-corrosion effect were good enough to be used even in the hard environments. To test the photocatalytic performance of the TiO, thin film coated stainless steel plate, photodegradations of m-xylene, a typical air pollutant produced by automobiles, and E. coti, under 365 ira1 UV in-adiatiol~ were conducted. The TiO~ coated stainless steel plate considerably enhanced the degradation efficiencies of m-xylene and E. coti. Key words: Photocatalysis, Dip Coating, Stainless Steel, Cohesiveness, Corrosion, E. coli
INTRODUCTION
be coated to form thin films. The composition (wt~ of stainless steel was 67.25 Fe, 18.55 Cr, 11.16 Ni, 2.01 Mo, 0.(P_6 Cu, 0.15 Si and 0.028 C. Plates (100mm l(~)mm 1 mm) were mechanically cut from large foils and then degreased ultrasonically in acetone. This material was chosen because of the heat treatment necessary for the densification of the coatings. Therefore, low carbon content steel was judged more convenient since it is less susceptible to sensitization, which in turn might promote corrosion [Uhlig et al., 1985]. In addition, stainless steel is a material widely used in chemical and structural industry environments [Seddks et al., 1979]. 2. Film Preparation TiO~ films were coated on stainless steel (ll)) ll))mm) using a s~andard dip coating process. A solution of (TiO230 mole~ o, SiO2 70 mole%) was prepared from a mixture of Ti(OC.~Hv)4and Si(OC~H,)4, absolute ethanol and glacial nitric acid as precursors, solvent and catalyst. The mL,Cure was submitted to intense ultrasonic radiation (20 kHz) until the liquid became homogeneous and clear. The subs~ates were withdrawn from the solution at a constant rate of 7 crn/ min and the gel films were dried at 100 ~ for 3 minutes. This was followed by heat treatment in a furnace at 200, 41)) and 650 ~ for 30 min. 3. Characterization of the Films The elemental composition of the film layer such as Ti, Si, O, and C was obtained by electron spectroscopy for chemical analysis (ESCA, XSAM 800 pci, Kratos Analytical). The binding energy of outer electrons was 459. 2, 1029, 531.3, and 285.2 eV for Ti, Si, O, and C, respectively. The film thickness was measured with a highresolu
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