Browsing by Author "Liao, Bo-Xi"

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A mass correction method for the aerosol particle mass analyzer to measure the particle mass of sub-50 nm nanoparticles
(1970-01-01)
Liao, Bo-Xi
;
Gong, Wen-Cheng
;
Li, Ziyi
;
Tsai, Chuen-Jinn
;
環境工程研究所
The particle mass measurement instrument of the aerosol particle mass analyzer (APM) tends to underestimate the particle mass of sub-50 nm nanoparticles, limiting the APM mass measurement to larger particles. In the present work, a mass correction method was developed based on a calibration reference to correct the APM mass underestimation according to a measured mass-based dimensionless parameter The correction was tested using laboratory generated silver nanoparticles and ambient nanoparticles. It was found that the measured effective density variations of silver nanoparticles due to different extent of APM mass underestimation at different operating conditions were reduced by the correction method with a significant improvement of R-squared from 0.40 to 0.87. In addition, about 20% increase in the effective density from 0.91 to 1.09 g/cm(3) was observed for 30 nm ambient wet nanoparticles using the correction method. The difference between the raw and corrected effective densities is due to the mass underestimation by the APM itself, which should be corrected in the data analysis program of the APM. Copyright (c) 2019 American Association for Aerosol Research
Exposure assessment of process by-product nanoparticles released during the preventive maintenance of semiconductor fabrication facilities
(2018-07-20)
Liao, Bo-Xi
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Tseng, Neng-Chun
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Li, Ziyi
;
Liu, Yingshu
;
Chen, Jen-Kun
This study characterized the process by product particles (mostly nanoparticles) released during the preventive maintenance of semiconductor fabrication facilities, such as chemical mechanical planarization (CMP), plasma-enhanced chemical vapor deposition (PECVD), and ion implantation. Manual sampling and real-time measurements with direct reading instruments were conducted to assess the exposure levels of nanoparticles and their physical and chemical properties. Significant amount of nanoparticles were observed in the breathing zone of the workers during the maintenance of the PECVD and ion implanters with the peak number concentrations as high as 6,470,000 and 65,444 #/cm(3), respectively, indicating that the deposited residual chemicals in the reaction chambers were released as airborne nanoparticles by the maintenance activities. In contrast, nanoparticles released during the maintenance of the local scrubber, CMP, and replacing CMP slurry drums were insignificant. Causes of the particle release were discussed and suggestions were made to mitigate the nanoparticle release and reduce the exposure levels.
The accuracy of the aerosol particle mass analyzer for nanoparticle classification
(2018-01-01)
Liao, Bo-Xi
;
Tseng, Neng-Chun
;
Tsai, Chuen-Jinn
;
環境工程研究所
;
Institute of Environmental Engineering
The aerosol mass measurement method, DMA-APM, measures a lower mass as compared to the electrical mobility diameter-based particle mass for sub-50 nm nanoparticles. The extent of underestimation increases with decreasing nanoparticle diameter and can reach as much as 20-80% for different nanoparticles between 10-20 nm. To study this issue, the DMA-APM system was tested with traceable size standards (PSL and NanoSilica) and laboratory generated silver nanoparticles. It was found that the extent of mass underestimation depended on Brownian diffusion as well as the strength of the classifying forces, and the extent was quantified by a dimensionless parameter lambda(c,P), which is suggested to be higher than 40 to eliminate the mass underestimation for size standards. Further analysis also showed that the uncertainty in the particle density of test nanoparticles should be as low as possible to minimize the error in the judgment on the accuracy of the APM. Finally, the absolute accuracy of the APM at different lambda(c,P) was determined by the size standards, which could be used to correct for the mass underestimation for sub-50 nm nanoparticles.
The Effect of Nanoparticle Convection-Diffusion Loss on the Transfer Function of an Aerosol Particle Mass Analyzer
(2014)
Lin, Guan-Yu
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Liao, Bo-Xi
;
Tzeng, Neng-Jiun
;
Chen, Chun-Wan
;
Uang, Shi-Nian
The existing theoretical response spectra of APM-3600 agree well with the experimental data for submicron particles larger than 100nm in the electrical mobility diameter but not for nanoparticles. In this study, a 2-D numerical model was developed to predict the transfer function and response spectra of APM-3600 based on the detailed simulation of flow and particle concentration fields. It was found that recirculation flows existed in the annular classifying region and APM\'s inlet and outlet regions, which led to enhanced convection-diffusion loss of nanoparticles compared to that without considering flow recirculation. As a result, the APM underestimates the mass of naonoparticles due to the shift of the peak position of the transfer function to a larger diameter than the targeted diameter. The response spectra calculated with the simulated transfer function agree well both in shapes and peak values with the experimental data present in a previous study for both nanoparticles and submicron particles larger than 100 nm. The predicted particle masses also agree well with the PSL\'s experimental data of the article.Copyright 2014 American Association for Aerosol Research