Biomedical subjects

Hsunling Bai

Publications and source records attributed to Hsunling Bai.

6 recordsLinked to original sources

PubMed2005

Control of VOCs emissions by condenser pre-treatment in a semiconductor fab.

The performance of a modified design of local condensers to pre-treat a variety of volatile organic compounds (VOCs) emitted from the stripping process of a semiconductor fab was tested in this study. The reaction temperature of the condensers was controlled at around 10 degrees C, it is relatively higher than the traditional condenser reaction temperature. Both VOCs and water vapors were condensed and formed liquid films. This resulted in an enhancement of the VOCs removals, especially for VOCs of high boiling points or solubility. This can help to prevent the follow up zeolite concentrator from damage. The performance of the integrated system of condenser/zeolite concentrator could, therefore, remain highly efficient for a longer operation time. Its annualized cost would also be lower than installing the zeolite concentrator only.

Air Pollution↗

PubMed2005

Direct quantitative analysis of phthalate esters as micro-contaminants in cleanroom air and wafer surfaces by auto-thermal desorption--gas chromatography--mass spectrometry.

This study established an analytical method for the trace analyses of two phthalate esters, including diethyl phthalate (DEP) and di-n-butyl phthalate (DBP), known as the major constituents of cleanroom micro-contamination detrimental to the reliability of semiconductor devices. Using thermal desorption coupled with a GC-MS system, standard tubes were prepared by delivering liquid standards pre-vaporized by a quasi-vaporizer into Tenax GR tubes for calibration. This method was capable of achieving detection limits of 0.05 microg m(-3) for 0.1 m3 air samples and 0.03 ng cm(-2) for 150-mm wafer surface density. Actual samples collected from a semiconductor cleanroom showed that the concentration of DBP in a polypropylene wafer box (0.45 microg m(-3)) was nearly four times higher than that in the cleanroom environment (0.12 microg m(-3)). The surface contamination of DBP was 0.67 ng cm(-2) for a wafer stored in the wafer box for 24 h. Furthermore, among the three types of heat-resistant O-ring materials tested, Kalrez was found to be particularly suitable for high-temperature processes in semiconductor cleanrooms due to their low emissions of organic vapors. This analytical procedure should serve as an effective monitoring method for the organic micro-contamination in cleanroom environments.

Air Pollutants↗

PubMed2005

Applying hexagonal nanostructured zeolite particles for acetone removal.

This study examines the performance of a new adsorbent, hexagonal nanostructured zeolite particles (HNZP) for acetone adsorption and compares the results with that of commercial mobil synthetic zeolite-5 (ZSM-5) type zeolite. The HNZP is a pure siliceous adsorbent with different values of pore diameter and surface area being adjustable by the manufacturing condition. The results indicate that a slight increase in the average pore diameter (d) of HNZP from 2 to 2.5 nm leads to an increase in the acetone adsorption capacity, although its surface area is decreased, in which case (d = 2.5 nm) the adsorption capacity of fresh HNZP is better than that of ZSM-5 zeolite. Even for the fresh HNZP (d = 2 nm) of which the adsorption capacity is less than that of the ZSM-5 zeolite at relative humidity (RH) of 0%, its adsorption capacity is not deteriorated after repeated regeneration, but the adsorption capacity of regenerated ZSM-5 zeolite decays markedly. Thus, after only one regeneration, the adsorption capacity of HNZP (d = 2 nm) becomes better than that of the ZSM-5 zeolite. The decrease in the adsorption capacity of regenerated ZSM-5 zeolite might be because of its aluminum content that catalyzes the acetone into coke and, thus, blocks the adsorption sites. Furthermore, result on the moisture effect shows that because the pure siliceous HNZP was more hydrophobic than the ZSM-5 zeolite, the acetone adsorption efficiency of fresh HNZP (d = 2 nm) is better than that of ZSM-5 zeolite at RH = 50%.

Acetone↗

PubMed2004

Estimation of PAHs dry deposition and BaP toxic equivalency factors (TEFs) study at Urban, Industry Park and rural sampling sites in central Taiwan, Taichung.

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in gas phase and particle bound were measured simultaneously at industrial (INDUSTRY), urban (URBAN), and rural areas (RURAL) in Taichung, Taiwan. And the PAH concentrations, size distributions, estimated PAHs dry deposition fluxes and health risk study of PAHs in the ambient air of central Taiwan were discussed in this study. Total PAH concentrations at INDUSTRY, URBAN, and RURAL sampling sites were found to be 1650 +/- 1240, 1220 +/- 520, and 831 +/- 427 ng/m3, respectively. The results indicated that PAH concentrations were higher at INDUSTRY and URBAN sampling sites than the RURAL sampling sites because of the more industrial processes, traffic exhausts and human activities. The estimation dry deposition and size distribution of PAHs were also studied. The results indicated that the estimated dry deposition fluxes of total PAHs were 58.5, 48.8, and 38.6 microg/m2/day at INDUSTRY, URBAN, and RURAL, respectively. The BaP equivalency results indicated that the health risk of gas phase PAHs were higher than the particle phase at three sampling sites of central Taiwan. However, compared with the BaP equivalency results to other studies conducted in factory, this study indicated the health risk of PAHs was acceptable in the ambient air of central Taiwan.

Air Pollutants↗

PubMed2003

Adsorption and desorption characteristics of semiconductor volatile organic compounds on the thermal swing honeycomb zeolite concentrator.

The use of a honeycomb zeolite concentrator and an oxidation process is one of the most popular methods demonstrated to control volatile organic compound (VOCs) emissions from waste gases in semiconductor manufacturing plants. This study attempts to characterize the performance of a concentrator in terms of the removal efficiencies of semiconductor VOCs (isopropyl alcohol [IPA], acetone, propylene glycol methyl ether [PGME], and propylene glycol monomethyl ether acetate [PGMEA]) under several parameters that govern the actual operations. Experimental results indicated that at inlet temperatures of under 40 degrees C and a relative humidity of under 80%, the removal efficiency of a zeolite concentrator can be maintained well over 90%. The optimal rotation speed of the concentrator is between 3 and 4.5 rph in this study. The optimal rotation speed increases with the VOCs inlet concentration. Furthermore, reducing the concentration ratio helps to increase the removal efficiency, but it also increases the incineration cost. With reference to competitive adsorption, PGMEA and PGME are more easily adsorbed on a zeolite concentrator than are IPA and acetone because of their high boiling points and molecular weights.

Adsorption↗

PubMed2002

Toxic equivalency factors study of polycyclic aromatic hydrocarbons (PAHs) in Taichung City, Taiwan.

Airborne particles and polycyclic aromatic hydrocarbons (PAHs) in industrial, background and urban atmosphere environments were investigated using toxic equivalent factors (TEFs) in central Taiwan during the period of August-December 2002. Concentrations of airborne particles were 93.4, 81.3 and 102.4 microg/m3 for industrial, background and urban sites, respectively. Concentrations of 21 gaseous PAHs were 1530, 759 and 1030 ng/m3 for industrial, background and urban sites, respectively; for carcinogenic activity of gaseous PAHs, the benzo[a]pyrene (BaP) equivalent concentrations were 17.0, 7.29 and 12.6 ng/m3 for industrial, background and urban sites, respectively. Twenty-one particle-bound PAHs were only 10% of the 21 gaseous PAHs. Dibenzo(a,h)anthracene (DBA) serves as a surrogate to explain the carcinogenic activity of PAH mixtures in central Taiwan because its carcinogenicity is a high percentage of the total carcinogenic activity. During the sampling period, temperature inversion from a cold front from China occurred, leading to average daily temperatures of 16 degrees C. These cold fronts caused atmospheric particles and pollutants to accumulate in the troposphere, leading to extremely high concentrations of airborne particles and both gaseous and particle-bound PAHs in central Taiwan.

Air Pollutants↗