Papers by Author: Sayan Pudwat

Abstract: Titanium dioxide (TiO₂) was prepared by Sol-Gel technique that was coated on the grade 304-stainless steel. Effect of dip coated speed, number of coated cycles and annealed temperature on films properties were investigated. The optimum condition for film preparation was at dip coated speed of 0.12 cm/s, number of coated cycles of 20 cycles and annealed temperature of 500 °C. TiO₂ film was crystal structure in anatase phase that had the main plane (101). Surface morphology of the TiO₂ films formed grain that look like knobby shape. nanograin sizes were slightly difference that showed in the range of 10-50 nm. Under optimum condition, TiO₂ film was used as photocatalyst to treat domestic wastewater. TiO₂ film was coated on the paddles of water wheel and 24 paddles were used to create water wheel. Films surface area were contact to wastewater and the light around 0.504 m² under working volume and working area of 0.0135 m³ and 0.09 m², respectively. Under irradiation of the near UV with average intensity of 0.89 mW/cm² over 24 hrs., and rotational speed of 17 rev/min. that were controlled by microcontroller box set. To compare treatment efficiency, uncoated TiO₂ - water wheel (UTWW) was run in the same condition of coated TiO₂ - water wheel (CTWW). The result showed that the CTWW had higher treatment efficiency than the UTWW. Especially for COD, TS, TDS and PO₄^3-, CTWW had greater treatment efficiency than the UTWW that percentage difference were greater than 90%.

Abstract: The borosilicate glasses doped with TiO₂ were prepared by the melt-quenching technique in compositions SiO₂B₂O₃CaO-Na₂O, and investigate their physical, optical and antibacterial properties. The result found that, after dope TiO₂, the density was decreased. The densities of glasses are not depending on TiO₂ concentration. The cutoff wavelength was shifted to longer wavelength with increasing of TiO₂ concentration from 360 nm (undoped TiO₂) to 395 nm at 7.5 % of TiO₂ concentration. The E. coli. was decreased due to TiO₂ generates reactive oxygen species from photocatalysis phenomena.

Abstract: Application of nano-structures of titanium dioxide (TiO2) films on photocatalytic activities of organic dyes was investigated. Methylene blue (MB) and cation yellow X-Gl 200% were used as organic dyes to observe decolorization. The TiO2 films were prepared on glass substrate by reactive DC magnetron sputtering. The films had thickness, grain size and root mean square surface roughness of 300 nm,  40 nm and  4 nm, respectively. Coated-TiO2 on glass and uncoated TiO2 (glass) were immerged in MB and cation yellow dyes solution. A weak ultraviolet (UV) A at peak wavelength  365 nm and intensity of 0.19 mW/cm2 was irradiated. Absorbance spectra of dyes at different UV irradiation time were observed. The efficiency of decolorization increased as UV irradiation time increased. At UV irradiation time 120 hours, coated-TiO2 showed higher percentage decolorization of MB than uncoated-TiO2 about 64%. While, at UV irradiation time 48 hours, coated-TiO2 showed higher percentage decolorization of cation yellow than uncoated-TiO2 about 84%. Under photocatalysis process of TiO2 films, at the end, MB (about 120 hours) and cation yellow dyes (about 48 hours) change to be colorless.

Abstract: Titanium dioxide (TiO2) films were prepared on glass substrates without external heating by DC magnetron reactive sputtering. Argon and oxygen were used as sputtering and reactive gases, respectively. Initially TiO2 films were produced under a constant discharge power of 300W, total operated pressure of 1.10 Pa, the Ar:O2 flow rate of 50:45 sccm and film thickness of 300 nm. After deposition, the films were annealed in air and in vacuum (8×10-1 Pa) at a temperature of 350 °C and an annealed time of 2 hours. Films structure, optical properties, photocatalytic activity (methylene blue degradation) and photo-induced hydrophilicity properties were mainly investigated to produce self-cleaning surface. Because of higher crystallinity of vacuum-annealed films lead to the highest MB degradation under UV irradiation. While, air-annealed films showed lower MB degradation than as-deposited films that could be affected of contamination on surface and defect from annealing. Vacuum-annealed films showed changes of water contact angle on the films surface higher than as-deposited films and air annealed- films.