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Let's Not Ignore the Ultrasonic Effects on the Preparation of Fuel Cell Materials

机译：让我们不要忽视超声波对燃料电池材料制备的影响

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This article is a follow-up paper recently published entitled 'The importance of ultrasonic parameters in the preparation of fuel cell catalyst inks' [1] describing the effect of low-frequency high-power ultrasound on the catalyst ink composition used for the fabrication of fuel cell electrodes. In this paper, it was shown that care should be taken when using low-frequency ultrasound whereby (i) the ultrasonic parameters such as frequency, power and duration may affect the final ink composition and rheology and therefore its electrochemical performance, (ii) the ultrasonic equipment (and make), frequencies, powers, durations and the distance between the vibrating source and the reaction vessel should be reported, (in) the catalyst ink temperature should be monitored and regulated during the course of the experiment, (iv) immersing the ultrasonic probe into the solution may lead to contamination (arising from the erosion of the titanium alloy vibrating tip) and (v) high-shear mixing of the catalyst inks using rotor-stator mixers at high rotation speed in silent conditions should be performed, analysed and compared to ultrasonicated samples for consistency and comparison purposes between studies. A careful and systematic approach should be adopted due to the fact that low-frequency ultrasound is known to be an intensification technology offering remarkable advantages: (a) an increase in fluid degasiflcation, de-agglomeration (and particle size reduction), dispersion, homogenisation, emulsification, atomisation, molecular degradation and chemical rates and yields and (b) an improvement of surfaces due to very efficient cleaning (mainly erosion). These ultrasonic effects are known to be caused by (a) an increase in mass transfer and heat transfer induced by extreme solution 'mixing' and (b) the production of cavitation bubbles undergoing very short and violent collapse within the fluid generating local 'hotspots' of high energy (temperatures of up to 5,000 K and pressures of up to 2,000 arms), leading to (i) radicals formation and (ii) jets of liquid of high velocity (up to 200 m s~(-1)) near surfaces.
机译：本文是最近发表的后续论文，标题为“超声参数在燃料电池催化剂油墨制备中的重要性” [1]，描述了低频大功率超声波对用于制造燃料电池催化剂油墨的影响。燃料电池电极。本文表明，在使用低频超声时应格外小心，因为（i）超声参数（例如频率，功率和持续时间）可能会影响最终的墨水成分和流变性，进而影响其电化学性能，（ii）应当报告超声设备（和制造商），频率，功率，持续时间以及振动源与反应容器之间的距离，在实验过程中应监测和调节催化剂墨水的温度，（iv）浸​​入超声探针进入溶液可能会导致污染（由于钛合金振动头的腐蚀而引起），并且（v）应在静默条件下使用转子-定子混合器以高转速对催化剂墨水进行高剪切混合，分析并与超声样品进行比较，以确保研究之间的一致性和比较性。由于众所周知，低频超声是一种增强技术，具有明显的优势，因此应采取谨慎而系统的方法：（a）流体脱附，解聚（和粒径减小），分散，均质化的增加，乳化，雾化，分子降解以及化学速率和产率，以及（b）由于非常有效的清洁（主要是腐蚀）而改善了表面。众所周知，这些超声波效应是由于（a）极端溶液“混合”引起的传质和传热增加，以及（b）在产生局部“热点”的流体中经历非常短而剧烈的塌陷的空化气泡的产生。高能（温度高达5,000 K，压力高达2,000臂），导致（i）自由基形成，以及（ii）在表面附近形成高速液体（高达200 ms〜（-1））。

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