Nano- and Submicrometer-Sized Spherical Particle Fabrication Using a Submicroscopic Droplet Formed Using Selective Laser Heating
Nano- and Submicrometer-Sized Spherical Particle Fabrication Using a Submicroscopic Droplet Formed Using Selective Laser Heating
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DOI：
10.1021/acs.jpcc.5b10691
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发表时间：
2016-02-01
影响因子：
3.7
通讯作者：
Shimizu, Yoshiki
中科院分区：
文献类型：
--
作者：
Ishikawa, Yoshie;Koshizaki, Naoto;Shimizu, Yoshiki
对不同激光能量密度下获得的二氧化钛颗粒进行了详细的液相脉冲激光熔融产物表征。得到的球形粒子的大小、晶体结构和内部结构取决于照射激光能量密度。利用高分辨透射电子显微镜观察了分散在乙醇中的纳米TiO 2颗粒的横截面，用纳秒脉冲激光以100 mJ cm（-2）pulse（-1）照射其表面，得到了200 nm的亚微米球形TiO 2单晶颗粒。在较高的激光能量密度（例如，225 mJ cm ~（-2）pulse ~（-1）），同时观察到直径为500 nm的具有应变和孪晶结构的大亚微米球和直径为70 nm的纳米球。根据Mie理论推导的相变通量曲线和非化学计量比TiO 2颗粒的形成引起的光吸收增加，解释了这种双峰尺寸分布的形成。因此，在适当的激光能量密度下，该激光工艺可以通过光学吸收通过选择性激光加热形成的液滴的冷却来产生单晶亚微米球形颗粒和纳米球。
Detailed characterization of products by pulsed laser melting in liquid was performed for TiO2 particles obtained at different laser fluences. The size, crystal structure, and inner structure of obtained spherical particles depended on the irradiating laser fluence. Single crystalline submicrometer spherical TiO2 particles of 200 nm were obtained using nanosecond pulsed laser irradiation at 100 mJ cm(-2) pulse(-1) onto raw particles dispersed in ethanol using cross-sectional high-resolution transmission electron microscopy observation. At higher laser fluence (e.g., 225 mJ cm(-2) pulse(-1)), large submicrometer spheres with strain and twin structures 500 nm in diameter and nanometer spheres of 70 nm were simultaneously observed. The formation of such bimodal size distribution of obtained particles was explained based on the phase transition fluence curves deduced by Mie theory and the optical absorption increase induced by the formation of nonstoichiometric TiO2 particles. Thus, with the appropriate laser fluence, this laser process can produce single crystalline submicrometer spherical particles and nanometer spheres via cooling of droplets formed by a selective laser heating by optical absorption.