Browsing by Author "Chen, Chienchih"

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Continuous generation of TiO2 nanoparticles by an atmospheric pressure plasma-enhanced process
(2007)
Chen, Chienchih
;
Bai, Hsunling
;
Chein, HungMin
;
Chen, Tzu Ming
;
環境工程研究所
A novel method for the continuous generation of titanium dioxide (TiO2) nanoparticles by dielectric barrier discharge process is presented using titanium tetraisopropoxide (TTIP) and water as precursors. The aerosol generator employs an atmospheric pressure plasma enhanced nanoparticle synthesis (APPENS) process of alternative current (AC). The influences of applied voltage, frequency and precursor molar ratio on the generated particles were described by the SEM, XRD, and SMPS analyses. The results showed that TiO2 particles appear to be in a broad size range of bi-modal distribution when no voltage is applied. While after applying the AC plasma they become uni-modal distributed with average sizes range from around 30 to 60 nm. The applied electric frequency can be adjusted to either generate nanoparticles after the plasma reactor or develop a thin film in the reactor. An increase in the precursor molar ratio leads larger particles with a broader size distribution.
Effect of plasma processing gas composition on the nitrogen-doping status and visible light photocatalysis of TiO2
(2007-10-25)
Chen, Chienchih
;
Bai, Hsunling
;
Chang, Chungliang
;
環境工程研究所
;
Institute of Environmental Engineering
The atmospheric pressure plasma enhanced nanoparticle synthesis (APPENS) process is applied to produce nitrogen (N) doped titania (TiO2) photocatalysts. With TTIP (titanium tetraisopropoxide; Ti(OC3H7)(4)) and water vapors as precursors, the effect of plasma and annealing gas composition on the N-doping status is identified by a cross comparison of the chemical shift of N atoms with those of Ti and O atoms. The activities of various types of N-doped photocatalysts are evaluated via the conversion of isopropyl alcohol (IPA). The results show that the N-doped TiO2 particles with O-x-Ti-N-y and -(NO) dopants are produced via N-2 plasma gas followed by air or N2 annealing gases. They have better visible and UV photocatalytic activities compared to the pure TiO2 photocatalysts prepared under O-2/Ar plasma and annealing gases. On the other hand, the N-doped TiO2 photocatalyst produced under N-2/O-2/Ar plasma gas and then annealed with pure N2 gas tends to have an additional dopant of -(NO2), but its photocatalytic activity is even worse than those of the pure TiO2 photocatalysts. The results reveal that the Ox-Ti-Ny and -(NO) dopants may have positive effects on the visible light photocatalytic activity while the -(NO2) dopant tends to have a negative effect on the visible light photocatalytic activity.
Metal loaded zeolite adsorbents for phosphine removal
(2008-03-05)
Li, Wen-Chih
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Bai, Hsunling
;
Hsu, Jung-Nan
;
Li, Shou-Nan
;
Chen, Chienchih
Phosphine (PH3) is a highly toxic air pollutant commonly used in the semiconductor and optoelectronic industries, but it has received less research attention due to its handling difficulty. In this study, metal (Cu, Zn, or Mn) loaded ZSM-5 and Y zeolite adsorbents are first prepared for the adsorption of PH3 toxic gas. The physical and chemical properties of the adsorbents which influence the PH3 adsorption capacity are analyzed. The results show that >99% PH3 adsorption efficiency is achieved when zeolites are loaded with Cu. The maximal PH3 adsorption capacities are about the same for both zeolites at 1.9 mol of PH3/mol of CU, which occurs at similar Cu loaded mass of 3.0-3.5%, beyond which the decrease in specific surface area is the major factor responsible for the decrease of PH3 adsorption capacity. The maximum adsorption capacity per loaded metal mass is much higher than literature data using CuO only for adsorbing hydride gases.
Preparation of N-doped TiO2 photocatalyst by atmospheric pressure plasma process for VOCs decomposition under UV and visible light sources
(2007-06-01)
Chen, Chienchih
;
Bai, Hsunling
;
Chang, Sue-min
;
Chang, Chungliang
;
Den, Walter
The nitrogen doped (N-doped) titanium dioxide (TiO2) photocatalyst was prepared by the atmospheric-pressure plasma-enhanced nanoparticles synthesis (APPENS) process operated under normal temperature, i.e. the dielectric barrier discharge plasma process. The N-2 carrier gas is dissociated in the AC powered nonthermal plasma environment and subsequently doped into the TiO2 photocatalyst that was capable of being induced by visible light sources. The APPENS process for producing N-doped TiO2 showed a higher film deposition rate in the range of 60-94 nm/min while consuming less power (< 100 W) as compared to other plasma processes reported in literatures. And the photocatalytic activity of the N-doped TiO2 photocatalyst was higher than the commercial ST01 and P25 photocatalysts in terms of toluene removals in a continuous flow reactor. The XPS measurement data indicated that the active N doping states exhibited N 1s binding energies were centered at 400 and 402 eV instead of the TiN binding at 396 eV commonly observed in the literature. The light absorption in the visible light range for N-doped TiO2 was also confirmed by a clear red shift of the UV-visible spectra.
TiO(2-x) nanoparticles synthesized using He/Ar thermal plasma and their effectiveness on low-concentration mercury vapor removal
(2011-10-01)
Tsai, Cheng-Yen
;
Hsi, Hsing-Cheng
;
Bai, Hsunling
;
Fan, Kuo-Shuh
;
Chen, Chienchih
Oxygen-vacant titanium dioxide (TiO(2-x) ) nanoparticles were synthesized using thermal plasma as a heating source at various applied plasma currents and He/Ar ratios. Samples with diverse characteristics were developed and the mercury removal effectiveness was subsequently evaluated. TiO(2) nanoparticles possessing high purity and uniform particle sizes were successfully synthesized using metal titanium and O(2) as precursors and Ar as plasma gas. TiO(2-x) in anatase phase with a particle size at 5-10 nm was formed at the He/Ar volume ratio of 25/75. Further increasing the He/Ar ratio elevated the plasma temperature, causing the tungsten to melt, vaporize from the cathode, and then dope into the formed TiO(2) nanoparticles. The doped W appeared to inhibit the growth of nanoparticles and decrease the crystallinity of formed anatase. The effectiveness of oxygen-vacant sites on Hg(0) removal under the visible light circumstance was confirmed. Hg(0) removal by the TiO(2-x) nanoparticles was enhanced by increasing the O(2) concentration. However, moisture reduced Hg(0) capture, especially when light irradiation was applied. The reduction in Hg(0) capture may be resulted from the competitive adsorption of H(2)O on the active sites of TiO(2-x) with Hg(0) and transformed Hg(2+).
TiO2-x nanoparticles synthesized using He/Ar thermal plasma and their effectiveness on low-concentration mercury vapor removal
(2011-10-01)
Tsai, Cheng-Yen
;
Hsi, Hsing-Cheng
;
Bai, Hsunling
;
Fan, Kuo-Shuh
;
Chen, Chienchih
Oxygen-vacant titanium dioxide (TiO2-x ) nanoparticles were synthesized using thermal plasma as a heating source at various applied plasma currents and He/Ar ratios. Samples with diverse characteristics were developed and the mercury removal effectiveness was subsequently evaluated. TiO2 nanoparticles possessing high purity and uniform particle sizes were successfully synthesized using metal titanium and O-2 as precursors and Ar as plasma gas. TiO2-x in anatase phase with a particle size at 5-10 nm was formed at the He/Ar volume ratio of 25/75. Further increasing the He/Ar ratio elevated the plasma temperature, causing the tungsten to melt, vaporize from the cathode, and then dope into the formed TiO2 nanoparticles. The doped W appeared to inhibit the growth of nanoparticles and decrease the crystallinity of formed anatase. The effectiveness of oxygen-vacant sites on Hg-0 removal under the visible light circumstance was confirmed. Hg-0 removal by the TiO2-x nanoparticles was enhanced by increasing the O-2 concentration. However, moisture reduced Hg-0 capture, especially when light irradiation was applied. The reduction in Hg-0 capture may be resulted from the competitive adsorption of H2O on the active sites of TiO2-x with Hg-0 and transformed Hg2+.