Zakiyyan Naadaa, Mathai Cherian, McFarland Jacob, Gangopadhyay Shubhra, Maschmann Matthew R
Department of Electrical Engineering and Computer Science, University of Missouri, Columbia, Missouri 65211, United States.
J. Mike Walker Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843, United States.
ACS Appl Mater Interfaces. 2022 Dec 14;14(49):55277-55284. doi: 10.1021/acsami.2c18678. Epub 2022 Nov 29.
The spallation of isolated aluminum (Al) nanoparticles (NPs) is initiated using rapid photothermal heating. The Al NPs exhibited a nominal diameter of 120 nm, with an average oxide shell thickness of 3.8 nm. Photothermal heating was achieved by coupling a focused laser (446 nm wavelength) to an optical grating substrate and to the plasmonic resonance of the Al NPs themselves. These factors enhanced the absorption cross section by a factor of 8-18 compared to no substrate and generated an Al NP heating rate on the order of 10-10 K/s. Observations indicate that molten Al is ejected from the heated NP, indicating that melting of the Al core is required for spallation. A graphene layer atop the grating substrate encouraged the formation of discrete particles of ejected Al, while irregular elongated filament products were observed without the graphene layer. Numerical simulations indicate that laser-heated Al NPs reach temperatures between approximately 1000 and 1500 K. These observations and experimental conditions are consistent with those anticipated for the melt dispersion mechanism, a thermomechanical reaction mechanism that has not previously been clearly demonstrated. Activating and controlling this mechanism is anticipated to enhance applications ranging from biological phototherapy to energetic materials.
利用快速光热加热引发孤立铝（Al）纳米颗粒（NPs）的散裂。这些铝纳米颗粒的标称直径为120纳米，平均氧化壳厚度为3.8纳米。通过将聚焦激光（波长446纳米）与光栅基板以及铝纳米颗粒自身的等离子体共振相耦合来实现光热加热。与无基板相比，这些因素使吸收截面增大了8至18倍，并产生了约10¹⁰ K/s量级的铝纳米颗粒加热速率。观察结果表明，熔融铝从受热的纳米颗粒中喷出，这表明散裂需要铝核发生熔化。光栅基板顶部的石墨烯层促使喷出的铝形成离散颗粒，而在没有石墨烯层的情况下观察到不规则的细长丝状产物。数值模拟表明，激光加热的铝纳米颗粒达到的温度约在1000至1500 K之间。这些观察结果和实验条件与熔体分散机制（一种此前尚未得到明确证实的热机械反应机制）所预期的情况一致。激活和控制这一机制有望增强从生物光疗到含能材料等一系列应用。
