Enhanced Particle Removal in Fluorinated Liquids—An Application in Nuclear Decontamination

An experimental cleaning system has been developed to demonstrate the decontamination of model electronic circuit boards by this cleaning process. The media used in this process are a wash solution of a high molecular weight fluorocarbon surfactant in a perfluorinated carrier liquid which results in enhanced particle removal, followed by a perfluorinated carrier liquid rinse. The perfluorinated liquids of interest, which are recycled in the process, are inert, nonflammable, generally safe to use, and do not present a hazard to the atmospheric ozone layer. The cleaning experiments were performed at the MIT Nuclear Reactor Laboratory. The radioactive particles removed from the circuit boards were captured by 0.22 μm filters with a filtration efficiency of 99.5% per stage. Compatibility tests were performed on these model electronic circuit boards. The results obtained show that neither the process fluids used nor the maximum level of the ultrasonic agitation applied harmed the circuit boards or the circuit components. All the circuit boards used in these tests were still functional after the cleaning experiments. A three log reduction in contamination was obtained in 1 hour. These data indicate that this process, once implemented on a large scale, will offer users in the nuclear industry a practical and cost effective means of decontaminating and recovering a wide variety of tools and instruments.     

有机氟聚合物的应用研究进展

有机氟聚合物是一类重要的有机高分子化合物，本文主要介绍了该类聚合物的物化性质、应用以及未来的发展前景。     

Etching characteristics of thin SiON films using a liquefied perfluorocarbon precursor of C6F12O with a low global warming potential

Perfluorocarbon gas is widely used in the semiconductor industry. However, perfluorocarbon has a negative effect on the global environment owing to its high global warming potential (GWP) value. An alternative solution is essential. Therefore, we evaluated the possibility of replacing conventional perfluorocarbon etching gases such as CHF₃ with C₆F₁₂O, which has a low GWP and is in a liquid state at room temperature. In this study, silicon oxynitride (SiON) films were plasma-etched using inductively coupled CF₄ +C₆F₁₂O+O₂ mixed plasmas. Subsequently, the etching characteristics of the film, such as etching rate, etching profile, selectivity over Si, and photoresist, were investigated. A double Langmuir probe was used and optical emission spectroscopy was performed for plasma diagnostics. In addition, a contact angle goniometer and x-ray photoelectron spectroscope were used to confirm the change in the surface properties of the etched SiON film surface. Consequently, the etching characteristics of the C₆F₁₂O mixed plasma exhibited a lower etching rate, higher SiON/Si selectivity, lower plasma damage, and more vertical etched profiles than the conventional CHF₃ mixed plasma. In addition, the C₆F₁₂O gas can be recovered in the liquid state, thereby decreasing global warming. These results confirmed that the C₆F₁₂O precursor can sufficiently replace the conventional etching gas.     

Microscopic mechanism of perfluorocarbon gas formation in aluminum electrolysis process

In view of the unclear cause of perfluorocarbons (PFCs) emission in the anode effect stage of aluminum electrolysis, the microscopic formation mechanism of PFCs was studied by density functional theory calculation and X-ray photoelectron spectroscopy (XPS). It is found that the discharge of fluorine containing anions ([F]^?) on carbon anode first causes the substitution of C—H by C—F and further results in the saturation of aromatic C—C bonds, leading to the appearance of —CF₃ or —C₂F₅ group through six-carbon-ring opening. Elimination of —CF₃ and —C₂F₅ with F atom could be a likely mechanism of CF₄ and C₂F₆ formation. XPS results confirm that different types of —CF_x group can be formed on anode surface during electrolysis, and the possibility that [F]^? discharges continuously at the C edge and finally forms different C—F bonds in quantum mechanical calculation was verified.     

全氟烃分解反应催化剂的研究进展

对有效消除全氟烃的催化分解法进行了评述,重点对近年来报道的用于全氟烃催化分解的过渡金属改性γ-Al2O3、磷酸盐、磷酸盐改性γ-Al2O3催化剂进行了总结和比较。磷酸盐催化剂的初活性较高,但比表面积较小,反应稳定性欠佳;过渡金属改性γ-Al2O3催化剂表面的铝酸盐保护层在一定程度上抑制了γ-Al2O3转化为惰性物相,稳定性比纯γ-Al2O3催化剂有所提高,但经长时间反应,催化剂表面酸量不断减少,催化活性逐渐下降。相比较而言,磷酸盐改性γ-Al2O3有望成为高活性和高稳定性的全氟烃分解催化剂。     

PFC emission‐reduction strategy for the LCD industry

Abstract— The perfluorocarbons (PFCs) used as etching‐process and chamber‐cleaning gases in the manufacture of LCD devices have a high global‐warming potential and a long atmospheric lifetime. Thus, to voluntarily reduce these environmentally harmful PFCs, in 2001 the Japanese LCD association established the World LCD Industry Cooperation Committee (WLICC), together with its counterpart associations in the Republic of Korea and Taiwan. Since that time involving many discussions, the WLICC reached a consensus on reducing the aggregate absolute PFC emissions to the equivalent of less than 0.82 million metric tons of carbon by 2010. Each association has been taking whatever emission reduction steps it considers best to achieve this goal. Thanks to these measures, the PFC emissions from the Japanese LCD industry have remained at the same level, or less, than those of the year 2000, in spite of the fact that PFC purchases have continually increased. In the interim, the Japanese LCD association has been obtaining experimental data for the 2006 IPCC Inventory Guidelines, which will give the emission factors needed to estimate the PFC emissions. As a result, some data are quite different from emission factors given in the current 2000 Inventory Guidelines. All the data obtained have been submitted to the IPCC to be adopted in the new 2006 Guidelines.     

Insulation characteristics of perfluorocarbon liquid/solid insulation for nonflammable large power transformer

A new type nonflammable large power transformer system is proposed in which the excellent cooling characteristics and insulation properties of nonflammable perfluorocarbon (PFC) liquid is utilized. In the system, transformer windings are put in an insulating cylinder filled with PFC liquid. The core includes cooling panel through the liquid. The space between the insulating cylinder and tank is filled with compressed SF⁶ gas. This paper describes the insulation characteristics of main insulation and inter-winding insulation models which simulate the transformer. It is found that (1) higher withstand voltage is expected by means of insulation barriers in the main insulation model; (2) partial discharge in inter-winding insulation model is beginning to behave in a constant electric field strength on the point of 0.1 mm liquid gap length.     

A Versatile Theranostic Nanoemulsion for Architecture‐Dependent Multimodal Imaging and Dually Augmented Photodynamic Therapy

To design a clinically translatable nanomedicine for photodynamic theranostics, the ingredients should be carefully considered. A high content of nanocarriers may cause extra toxicity in metabolism, and multiple theranostic agents would complicate the preparation process. These issues would be of less concern if the nanocarrier itself has most of the theranostic functions. In this work, a poly(ethylene glycol)‐boron dipyrromethene amphiphile (PEG‐F₅₄‐BODIPY) with 54 fluorine‐19 (¹⁹F) is synthesized and employed to emulsify perfluorohexane (PFH) into a theranostic nanoemulsion (PFH@PEG‐F₅₄‐BODIPY). The as‐prepared PFH@PEG‐F₅₄‐BODIPY can perform architecture‐dependent fluorescence/photoacoustic/¹⁹F magnetic resonance multimodal imaging, providing more information about the in vivo structure evolution of nanomedicine. Importantly, this nanoemulsion significantly enhances the therapeutic effect of BODIPY through both the high oxygen dissolving capability and less self‐quenching of BODIPY molecules. More interestingly, PFH@PEG‐F₅₄‐BODIPY shows high level of tumor accumulation and long tumor retention time, allowing a repeated light irradiation after a single‐dose intravenous injection. The “all‐in‐one” photodynamic theranostic nanoemulsion has simple composition, remarkable theranostic efficacy, and novel treatment pattern, and thus presents an intriguing avenue to developing clinically translatable theranostic agents.     

Propagation characteristics of impulse creepage discharge in perfluorocarbon liquid

In this paper, the propagation characteristics of a creepage discharge on the surface of a solid insulator with a back electrode in perfluorocarbon liquid under an impulse voltage application are investigated. The propagation process is observed in detail by means of a high‐speed schlieren optical technique, and simultaneously waveforms of a current and a charge are also measured. Consequently, the polarity effect of the streamer propagation and the positive streamer which propagates stepwise can be seen. The latter is concurrent with the sparse current pulse which corresponds to the charge step‐variation. These results are compared with ones obtained in transformer oil. © 2000 Scripta Technica, Electr Eng Jpn, 131(4): 19–28, 2000     

A new method for concentration analysis of bacterial endotoxins in perfluorocarbon

This communication demonstrates the feasibility of the gel-clot method for the analysis of bacterial endotoxins in water extracts of perfluorocarbon which is a water insoluble liquid medical device. Perfluorocarbon （10 mL） was shaken with 10 mL water for 15 min at 2000 r/min and the endotoxin present was extracted to the aqueous phase without interference inhibition/enhancement of the product and the recovery of endotoxin added to perfluorocarbon was determined, A validation study confirmed that endotoxins presented in perfluorocarbon pass over into the aqueous phase at concentrations of 20, 10 and 5EU/mL with recoveries from 86.8% to 96.8%. Therefore, the gel-clot test is suitable for detecting bacterial endotoxins in perfluorocarbon which is a water insoluble medical device.