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RISS 인기검색어
- 검색키워드
- 저자 : Thanh Dong Pham (검색결과 25 건)
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Pham, Thanh-Dong,Lee, Byeong-Kyu Elsevier 2015 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.275 No.-
<P><B>Abstract</B></P> <P>We investigated a novel approach by synthesizing an integrated material, which could act as both adsorbent and photocatalytic material, for bioaerosol purification under visible light conditions. Agwas used as a dopant agent to enhance photocatalytic activity of TiO<SUB>2</SUB>, leading to high photocatalytic activity of the doped TiO<SUB>2</SUB> even under visible light. Under visible light, the doped TiO<SUB>2</SUB> photocatalyst could produce oxy radicals, oxidative agents, that participate in oxidation reactions to decompose important organic components of bacteria, leading to death or removal of bacteria from an aerosol. Adsorption property was integrated into the enhanced TiO<SUB>2</SUB> photocatalyst by using polyurethane (PU), a honeycomb structure material, as a substrate for coating process of the doped TiO<SUB>2</SUB>. Three materials including pristine PU, TiO<SUB>2</SUB> coating on PU (TiO<SUB>2</SUB>/PU), and Ag-doped TiO<SUB>2</SUB> coating on PU (Ag–TiO<SUB>2</SUB>/PU) were used to remove <I>Escherichia coli</I> in an aerosol under visible light. Under dark conditions, the removal capacities of <I>E. coli</I> in the aerosol by PU, TiO<SUB>2</SUB>/PU, and Ag–TiO<SUB>2</SUB>/PU were 1.2×10<SUP>5</SUP>, 2.7×10<SUP>5</SUP>, and 6.2×10<SUP>5</SUP> (CFU/cm<SUP>3</SUP>), respectively. Under visible light irradiation, the removal capacities of <I>E. coli</I> in an aerosol by PU, TiO<SUB>2</SUB>/PU, and Ag–TiO<SUB>2</SUB>/PU were 1.2×10<SUP>5</SUP>, 2.7×10<SUP>5</SUP>, and 1.8×10<SUP>6</SUP> (CFU/cm<SUP>3</SUP>), respectively. The improvement of the removal capacity by TiO<SUB>2</SUB>/PU and Ag–TiO<SUB>2</SUB>/PU, versus PU, is due to adsorption alone and the combination of adsorption plus photocatalytic activity, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The photocatalytic activity of TiO<SUB>2</SUB> was enhanced by Ag metal doping. </LI> <LI> TiO<SUB>2</SUB> and Ag-doped TiO<SUB>2</SUB> were coated on porous polyurethane (PU) using C–Si–O–Ti bonds. </LI> <LI> Increased adsorption ability of the photocatalyst was due to the porosity of the PU. </LI> <LI> Removal of <I>E. coli</I> from an aerosol was only by adsorption with PU and TiO<SUB>2</SUB>/PU. </LI> <LI> Under visible light, <I>E. coli</I> was removed by adsorption and photo-oxidation with Ag–TiO<SUB>2</SUB>/PU. </LI> </UL> </P>
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Pham, Thanh-Dong,Lee, Byeong-Kyu,Nguyen, Van Noi,Dao, Van-Duong Elsevier 2017 Journal of catalysis Vol.352 No.-
<P>This article has been retracted: please see Elsevier Policy on Article Withdrawal (<U>https://www.elsevier.com/about/our-business/policies/article-withdrawal</U>).</P><P>This article has been retracted at the request of the Editor, after consultation with the corresponding author Professor Byeong-Kyu Lee due to the methods described in the paper for the preparation of the catalysts being incomplete and the results not being reproduced. This was brought to the editors’ attention via a letter to the editor. Professor Lee agreed that the methods description was not complete and agreed with this course of action. <Journal of catalysis, 352 (2017) 13 – 21>, http://dx.doi.org/10.1016/j.jcat.2017.04.024.</P>
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Pham, Thanh-Dong,Lee, Byeong- Kyu Elsevier 2017 Applied Catalysis A Vol.529 No.-
<P><B>Abstract</B></P> <P>In this study, Ag and Cu co-doped TiO<SUB>2</SUB> deposited on polyurethane (Ag@Cu-TiO<SUB>2</SUB>/PU) was synthesized for the conversion of CO<SUB>2</SUB> into solar fuels under visible light. The synthesized Ag@Cu-TiO<SUB>2</SUB>/PU, which synergistically inherited all the advantages of both Ag and Cu doping, exhibited very high photocatalytic activity for the reduction of gaseous CO<SUB>2</SUB> to produce CH<SUB>4</SUB> and CO fuels. The dopants defects in the TiO<SUB>2</SUB> lattice formed Ti<SUP>3+</SUP> and oxygen vacancies in the lattice. The presence of Ti<SUP>3+</SUP> and oxygen vacancies on the surface of the photocatalyst induced the formation of new adsorption sites to adsorb CO<SUB>2</SUB>. The Ag and Cu dopants also enhanced the separation of electron–hole pairs of the doped TiO<SUB>2</SUB> photocatalysts. Therefore, the Ag@Cu- TiO<SUB>2</SUB>/PU photocatalysts generated electron–hole pairs, which could react with H<SUB>2</SUB>O and CO<SUB>2</SUB> to produce the CO and CH<SUB>4</SUB>, even under visible light. 2Ag@4Cu-TiO<SUB>2</SUB>/PU, corresponding to the Ag/TiO<SUB>2</SUB> and Cu/TiO<SUB>2</SUB> ratios of 2 and 4wt%, respectively, exhibited the highest photocatalytic reduction of CO<SUB>2</SUB>. The yields of CH<SUB>4</SUB> and CO produced from the photocatalytic reduction of CO<SUB>2</SUB> by 2Ag@4Cu-TiO<SUB>2</SUB>/PU under visible light were 880 and 550 (μmol/g.cat), respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ag and Cu co-doping formed Ti<SUP>3+</SUP> and oxy-vacancies in the TiO<SUB>2</SUB> lattice. </LI> <LI> The formed Ti<SUP>3+</SUP> and oxy-vacancies enhanced both the CO<SUB>2</SUB> adsorption and conversion. </LI> <LI> Ag and Cu co-doping also enhanced the separation of electron–hole pairs of the TiO<SUB>2</SUB>. </LI> <LI> Ag@Cu-TiO<SUB>2</SUB>/PU converted CO<SUB>2</SUB> into CH<SUB>4</SUB> and CO even under visible light. </LI> <LI> The optimal doping ratios of Ag/TiO<SUB>2</SUB> and Cu/TiO<SUB>2</SUB> were 2 and 4wt%, respectively. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Pham, Thanh-Dong,Lee, Byeong-Kyu Elsevier 2017 Journal of catalysis Vol.345 No.-
<P><B>Abstract</B></P> <P>In this study, Cu and V co-doped TiO<SUB>2</SUB> deposited on polyurethane (Cu@V-TiO<SUB>2</SUB>/PU) was synthesized as a catalyst for the reduction of CO<SUB>2</SUB> with H<SUB>2</SUB>O vapor to preferentially produce CH<SUB>4</SUB> as a valuable solar fuel under visible light. The Cu and V dopants defected into the TiO<SUB>2</SUB> lattice, leading to the formation of Ti<SUP>3+</SUP> and oxygen vacancies in the lattice. The Ti<SUP>3+</SUP> formed in the doped TiO<SUB>2</SUB> lattice created an intermediate band between the valence band and the conduction band of TiO<SUB>2</SUB>, leading to an increase in the electron–hole pair separation efficiency of TiO<SUB>2</SUB>. The oxygen vacancies existing on the surface of the photocatalyst could induce new adsorption sites to adsorb CO<SUB>2</SUB>. The generated electrons and holes reacted with the adsorbed CO<SUB>2</SUB> and with H<SUB>2</SUB>O vapor to produce CO and primarily CH<SUB>4</SUB>. Therefore, the Cu@V-TiO<SUB>2</SUB>/PU photocatalysts successfully utilized visible light as the energy source and H<SUB>2</SUB>O vapor as a reductant to reduce CO<SUB>2</SUB> to CO and CH<SUB>4</SUB>. The Cu@V-TiO<SUB>2</SUB>/PU photocatalysts also supplied sufficient electrons and holes for the selective reduction of CO<SUB>2</SUB> to CH<SUB>4</SUB> rather than CO. The 2Cu@4V-TiO<SUB>2</SUB>/PU photocatalyst, with Cu/TiO<SUB>2</SUB> and V/TiO<SUB>2</SUB> ratios of 2 and 4wt.%, respectively, exhibited the highest photocatalytic activity for CO<SUB>2</SUB> conversion into solar fuels. The production rates of CH<SUB>4</SUB> and CO produced from the CO<SUB>2</SUB> reduction by the 2Cu@4V-TiO<SUB>2</SUB>/PU photocatalyst under visible light were 933 and 588μmolg<SUP>−1</SUP> cat.h<SUP>−1</SUP>, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cu and V co-doping formed Ti<SUP>3+</SUP> and oxy-vacancies in the TiO<SUB>2</SUB> lattice. </LI> <LI> The twin-metal co-doping enhanced the separation of TiO<SUB>2</SUB>’s electron–hole pairs. </LI> <LI> The formed Ti<SUP>3+</SUP> and oxy-vacancies enhanced both the adsorption and conversion of CO<SUB>2</SUB>. </LI> <LI> The Cu@V-TiO<SUB>2</SUB>/PU converted CO<SUB>2</SUB> into CH<SUB>4</SUB> and CO even under visible light. </LI> <LI> The optimal doping ratios of Cu/TiO<SUB>2</SUB> and V/TiO<SUB>2</SUB> were 2 and 4wt.%, respectively. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Pham, Thanh-Dong,Lee, Byeong-Kyu Elsevier 2015 Journal of hazardous materials Vol.300 No.-
<P><B>Abstract</B></P> <P>In this study, V was used as a dopant to defect into the TiO<SUB>2</SUB> lattice, leading to formation of Ti<SUP>3+</SUP> and V<SUP>4+</SUP> in the lattice. The presence of Ti<SUP>3+</SUP> and V<SUP>4+</SUP> introduced into the TiO<SUB>2</SUB> lattice increased the electron–hole pair generation capacity and electron–hole pair separation efficiency of the TiO<SUB>2</SUB>, leading to enhancement of the photocatalytic activity of the photocatalyst. Porous polyurethane (PU) was used to immobilize the V-doped TiO<SUB>2</SUB> by creating chemical bonds. The use of porous substrate contributed to the increased adsorption ability of the enhanced photocatalyst, as well as expanded its application for the removal of toluene from aerosols. Under dark conditions, the V-TiO<SUB>2</SUB>/PU only exhibited adsorption ability for toluene treatment in aerosol. Under visible light conditions, the V-TiO<SUB>2</SUB>/PU exhibited high photocatalytic oxidation ability for the removal of toluene in aerosol. The photocatalytic oxidation ability was found to depend on the V to TiO<SUB>2</SUB> ratio. The optimal V content in V/TiO<SUB>2</SUB> for enhancing the photocatalytic activity of TiO<SUB>2</SUB> was determined to be 6wt%. Even under visible light irradiation, the 6% V-TiO<SUB>2</SUB>/PU sample could photocatalytically remove 80% of the toluene in 200-ppmV inlet gas, while 89.3% of the removed amount was mineralized into CO<SUB>2</SUB> and H<SUB>2</SUB>O.</P> <P><B>Highlights</B></P> <P> <UL> <LI> V doping was used to enhance the photocatalytic activity of TiO<SUB>2</SUB> photocatalyst. </LI> <LI> The enhanced TiO<SUB>2</SUB> was fixed on porous polyurethane (PU) by chemical bonds. </LI> <LI> The PU was used as a substrate to increase the adsorption ability of the photocatalyst. </LI> <LI> V-TiO<SUB>2</SUB>/PU adsorbed and photocatalytically oxidized toluene gas under visible light. </LI> <LI> The V/TiO<SUB>2</SUB> ratio of 6wt% was optimal for enhancing the photocatalytic activity. </LI> </UL> </P>
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Trajectory analyses of uncontrolled circular parachutes in random spatial wind fields
Thanh Dong Pham,Anh Tuan Nguyen,Vu Dan Thanh Le,Trung Kien Nguyen 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8
The present paper explores the trajectories of two uncontrolled circular parachute models which differ in size and mass in random spatial wind fields. The wind velocity components were generated through three-dimensional inverse fast Fourier transforms; and the correlations of the simulation data compared with the theoretical functions to confirm the accuracy of the wind model. The parachute systems are modelled as six-degrees-of-freedom rigid bodies, on which the aerodynamic forces and moments are applied. The dynamics model was validated before being used to study the drop trajectories of the parachute systems in spatial wind fields. Analyzing the drop trajectories and the impact point dispersion characteristics of the two parachute systems, the paper shows that the smaller one oscillates at a higher frequency and is affected more strongly by the wind. While descending at low altitude, there could be resonance between the dynamics of the larger parachute model and the wind turbulence. Moreover, it is found that the use of simplified vertical wind profiles, which include only the variation of the wind velocity against the altitude, may cause significant error in the simulation results.
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