Department of Mechanical Engineering, Stanford University , Stanford, California 94305, United States.
Nano Lett. 2017 Oct 11;17(10):5925-5930. doi: 10.1021/acs.nanolett.7b01754. Epub 2017 Sep 11.
Silicon (Si) particles are widely utilized as high-capacity electrodes for Li-ion batteries, elements for thermoelectric devices, agents for bioimaging and therapy, and many other applications. However, Si particles can ignite and burn in air at elevated temperatures or under intense illumination. This poses potential safety hazards when handling, storing, and utilizing these particles for those applications. In order to avoid the problem of accidental ignition, it is critical to quantify the ignition properties of Si particles such as their sizes and porosities. To do so, we first used differential scanning calorimetry to experimentally determine the reaction onset temperature of Si particles under slow heating rates (∼0.33 K/s). We found that the reaction onset temperature of Si particles increased with the particle diameter from 805 °C at 20-30 nm to 935 °C at 1-5 μm. Then, we used a xenon (Xe) flash lamp to ignite Si particles under fast heating rates (∼10 to 10 K/s) and measured the minimum ignition radiant fluence (i.e., the radiant energy per unit surface area of Si particle beds required for ignition). We found that the measured minimum ignition radiant fluence decreased with decreasing Si particle size and was most sensitive to the porosity of the Si particle bed. These trends for the Xe flash ignition experiments were also confirmed by our one-dimensional unsteady simulation to model the heat transfer process. The quantitative information on Si particle ignition included in this Letter will guide the safe handling, storage, and utilization of Si particles for diverse applications and prevent unwanted fire hazards.
硅（Si）颗粒被广泛用作锂离子电池的高容量电极、热电设备元件、生物成像和治疗剂以及许多其他应用的材料。然而，在高温或强烈光照下，Si 颗粒会在空气中点燃和燃烧。在处理、储存和应用这些颗粒时，这会带来潜在的安全隐患。为了避免意外点火的问题，定量分析 Si 颗粒的点火特性（如颗粒的大小和孔隙率）至关重要。为此，我们首先使用差示扫描量热法（differential scanning calorimetry）在缓慢加热速率（约 0.33 K/s）下实验确定 Si 颗粒的反应起始温度。我们发现，Si 颗粒的反应起始温度随粒径的增加而升高，从 20-30nm 的 805°C 增加到 1-5μm 的 935°C。然后，我们使用氙（Xe）闪光灯在快速加热速率（约 10 到 10 K/s）下点燃 Si 颗粒，并测量最小点火辐射通量（即点燃 Si 颗粒床所需的单位表面面积的辐射能）。我们发现，测量的最小点火辐射通量随 Si 颗粒尺寸的减小而减小，并且对 Si 颗粒床的孔隙率最为敏感。Xe 闪光点火实验的这些趋势也通过我们的一维非稳态模拟得到了证实，该模拟用于模拟传热过程。本研究中提供的关于 Si 颗粒点火的定量信息将指导 Si 颗粒在各种应用中的安全处理、储存和使用，并防止不必要的火灾隐患。
