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Laboratory Tests on Mercury Emission Monitoring with Resonating Gold-coated Silicon Cantilevers

机译：共振镀金硅悬臂梁对汞排放监测的实验室测试

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摘要

To measure extremely low concentrations of mercury vapor in gases as encountered in flue gases of coal-fired power plants, accurate and reliable online and/or portable mercury detection systems are needed. As discussed in this communication, resonating silicon-based cantilevers coated with thin films of gold change their resonant frequency when exposed to mercury vapors and could serve as the basis for such sensing devices. Two different types of commercial AFM cantilevers, which differed by physical dimensions and surface finish, were coated with a 10 nm film of gold and were tested in streams of argon containing mercury. The argon flow rates ranged from 5.7 to 57.4 mL/min, carrying mercury vapors at concentrations between 37 and 700 μg/m~3. The results show that smaller cantilevers (～140 μm × 40 μm × 4 μm) with a resonant frequency of 270-275 kHz were sensitive to less than 10 picograms of mercury, whereas larger cantilevers (～245 μm × 50 μm x 7 μm) with a resonant frequency of 155-165 kHz have a sensitivity about 10 times lower. The results indicate that the kinetics of mercury capture by the gold coating follows a simple power law-correlation with the mass change (Am) being proportional to t~n, where f is the capture time and n depends strongly on the concentration of mercury in the gas. It is also demonstrated that the mercury can be stripped off the gold coating by heating to 350 ℃, which would allowthe cantilevers to be regenerated and reused.
机译：为了测量燃煤电厂烟道气中所遇到的气体中汞蒸气的极低浓度，需要准确可靠的在线和/或便携式汞检测系统。如本通讯所述，涂有金薄膜的硅基悬臂梁在暴露于汞蒸气时会改变其共振频率，并可作为此类传感设备的基础。两种不同类型的商品化AFM悬臂，其物理尺寸和表面光洁度不同，均涂有10 nm的金膜，并在含汞的氩气流中进行了测试。氩气流速为5.7至57.4 mL / min，携带的汞蒸气浓度为37至700μg/ m〜3。结果表明，共振频率为270-275 kHz的较小的悬臂（〜140μm×40μm×4μm）对小于10皮克的汞敏感，而较大的悬臂（〜245μm×50μmx 7μm）敏感谐振频率为155-165 kHz的传感器灵敏度要低约10倍。结果表明，金涂层捕获汞的动力学遵循简单的幂律相关性，质量变化（Am）与t〜n成正比，其中f为捕获时间，n强烈取决于汞在汞中的浓度。气体。还证明了加热到350℃可以从金涂层上剥离汞，这将使悬臂梁得以再生和再利用。

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