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Chemical Terrorist Agents
Published in Robert A. Burke, Counter-Terrorism for Emergency Responders, 2017
The following chemicals are precursors to the production of sarin. When any of them are found in any occupancy, and their legitimate use cannot be established, law enforcement should be notified. Ammonium bifluorideDimethyl methylphosphonateDiethylphosphiteDimethylphosphiteHydrogen fluorideMethylphosphonous difluorideMethylphosphonyl dichlorideMethylphosphonyl difluoridePotassium bifluoridePotassium fluoridePhosphorus trichlorideSodium bifluorideSodium fluorideThionyl chlorideTrimethyl phosphite
Removal and repair techniques for thermal barrier coatings: a review
Published in Transactions of the IMF, 2020
X. Yang, Jian Zhang, Z. Lu, H.-Y. Park, Y.-G. Jung, H. Park, D. D. Koo, R. Sinatra, Jing Zhang
Aqueous stripping with acid fluoride salt is a method8 used to remove the ceramic layer, such as yttria-stabilised zirconia (YSZ), from a substrate without damaging the bond coat. The ceramic layer is removed by exposure to the aqueous stripping solution containing an acid fluoride salt, such as ammonium bifluoride (NH4HF2) or sodium bifluoride (NaHF2), and a corrosion inhibitor. The acid fluoride can convert zirconia to zirconium, through a process for treating a zirconia-based material which comprises reacting the zirconia-based material with ammonium bifluoride, NH4F·HF. An ammonium fluorozirconic compound is produced.9 Also, the corrosion inhibitor could protect the metal substrate. The operating temperature is about 60–75°C, and the stripping time is about 4–5 h. This process could also be combined with ultrasonic treatment. The ultrasonic treatment can be continued until the TBC is completely removed or at least sufficiently loosened so that it can be removed by brushing or pressure spray rinsing, which could shorten the process time to 2–5 h.