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转：无尘室中离子风扇上污染物的成分分析及形成原因
这篇文章是我在公司时写的，不好意思是用英文写的。是分析无尘室的离子风扇上污染物的，其中有用到离子色谱。转：无尘室中离子风扇上污染物的成分分析及形成原因
Abstract –Ionizer fans are used to eliminate static electricity in clean room. After a period of use, the white unknown deposits are found on fan cover. Several analytical technologies are employed to identify the ingredient of the deposits. The cause of deposit’s formation is also discussed in this paper.
Keywords: EDX, Raman, IC, Ammonium Oxalate
I. Introduction
Ionizer fans are used to eliminate the static electricity and purify the air in clean room. After a period of use, the white unknown deposits are found on the ionizer fan cover. This kind of deposits will form on fan cover again after it’s cleaned with IPA in one month. We employ several analytical technologies to identify the ingredient of the deposit. Also we explain the cause of formation of the deposit.
II. Experiment
1) The Physics of Deposits
The deposits are white and solid, and it very easily dissolves in water.
Fig. 1. The Appearance of Deposits
2) EDX Analysis
Remove the deposits from ionizer fan cover and analyze with EDX, C, N, O and Si are found. Directly analyze the material of fan cover, C, O, Al and Si are found. So the deposit must contain N and may contain C, O and Si; it may be organic. We try to analyze it with Raman Spectrometer.
Fig. 2. EDX Spectrum of Deposits Fig. 3. EDX Spectrum of Fan Cover
3) Raman Analysis
Analyze the deposits with Raman Spectrometer. Searching in spectra library, the spectra of deposits and Ammonium Oxalate have a good match. It’s confirmed that the deposits are Ammonium Oxalate. We verify it with IC (Ion Chromatography).
Fig. 4. Raman Spectra of Deposit and Ammonium Oxalate
4) IC Analysis
a) Anion Analysis
Dissolve the deposits in DI water and test the solution with IC. Compare the chromatogram of deposits with that of Oxalate, it proves that the deposits contain Oxalate (C2O42-) (the retention time: 13.5 minute).
Fig. 5. Chromatogram of Deposits Fig. 6. Chromatogram of Oxalate
b) Cation Analysis
Dissolve the deposits in DI water and test the solution with IC. Compare the chromatogram of deposits with that of DI water (background), it proves that the deposits contain Ammonium(NH4+).
Fig. 7. Chromatogram of DI Water Fig. 8. Chromatogram of Deposits
From the results of EDX, Raman and IC Analysis, we can conclude that the ingredient of unknown deposits on ionizer fan cover are Ammonium Oxalate [(NH4)2C2O4].
III. Cause Analysis of Deposit’s Formation
Because the deposits – Ammonium Oxalate formed on ionizer fan cover in clean room, its probable source: material of ionizer fan cover and air in clean room. So we analyze the material of fan cover with Raman Spectrometer and the air in clean room with IC.
1) Raman Analysis of Material of Fan Cover
Comparing the spectrum of material of ionizer fan with that of Ammonium Oxalate, it’s confirmed that the material of ionizer fan cover is not Ammonium Oxalate.
Fig. 8. Raman Spectra of Material of Ionizer Fan Cover and Ammonium Oxalate
2) IC Analysis of Air in Clean Room
Collect the air sample with Impinger, and test it with IC. The Anion analysis of air shows that no Oxalate (C2O42-)(RT: 13.5 minute) exists in air. The Cation analysis of air shows that Ammonia(NH3) exists abundantly in air. So the Ammonium of deposits comes from the air in clean room.
Fig. 9. Anion Chromatogram of Air in Clean Room
Fig. 10. Cation Chromatogram of Air in Clean Room
3) Formation of Oxalate
GC/MS analysis of air samples shows that there’re a lot of various volatile organic compounds in air. So maybe the Oxalate is product of chemical reaction of volatile organic compounds.
(1) H.C. = total saturated and unsaturated hydrocarbons.
(2) A.B. = alkylbenzenes, benzoates, benzoic acid.
(3) Gly. = glycols (ethoxylated alcohols).
(4) NMP = N-methyl pyrrolidone / 1-methyl 2-pyrrolidinone.
(5) Phth. = phthalates (DBP, DOP, etc.), (MRL = 10 ug/m3).
(6) Phen. = phenols, naphthalene, azulene, etc.
(7) MeSi = methyl silicones (siloxanes), (MRL = 10 ug/m3).
Dicarboxylic acids are produced by the photooxidation of various volatile organic compounds. Precursors include cycloalkenes (R1), aliphatic dialkenes (R2), aldehydes, carboxylic acids, and aromatic hydrocarbons such as benzene and toluene. Photooxidation of aromatic hydrocarbon leads to ring-cleavage reactions and produces C2-C5 dicarbonyls. These can be further oxidized to form dicarboxylic acids. (1) The air in clean room has the precursors which can be transformed into Oxalic Acid. We need to explain the source of ozone.
Fig. 11. Formation of Oxalic Acid
4) Formation of Ozone
There’s a high voltage which is applied between two electrodes in ionizer fan. The electrodes are separated from each other by air. Some of the oxygen molecules in the air break down in the electric field and immediately attach themselves to free oxygen molecules, forming ozone.(2)
Fig. 11. Formation of Ozone
Above all, the Ozone(O3) is formed between two electrode with high voltage in ionizer fan. Oxalic acid is formed because volatile organic compounds in air are oxidized by ozone. Ammonium Oxalate is produced because Oxalic acid accumulates on ionizer fan and reacts with Ammonia in air of clean room.
IV. Conclusion
The deposits on ionizer fan cover are Ammonium Oxalate. The Ammonium is from the air in clean room, the Oxalate is the product of chemical reaction of volatile organic compounds in the air of clean room.
V. Acknowledges
This work is done with the guidance of Johnson Luo and is supported by Yan Peng (Raman analysis) and Yi Wu (EDX analysis).
完整版，附件下载：The Cause Analysis of Deposit’s Formation on Ionizer Fan Cover in Clean Room
[ 本帖最后由 fqdfi32 于 2010-3-22 22:44 编辑 ]
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转：无尘室中离子风扇上污染物的成分分析及形成原因
转：无尘室中离子风扇上污染物的成分分析及形成原因
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转：无尘室中离子风扇上污染物的成分分析及形成原因