State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, China.
Guangdong Provincial Key Laboratory of Optomechatronics , Shenzhen 518057, China.
Langmuir. 2017 Aug 22;33(33):8225-8232. doi: 10.1021/acs.langmuir.7b01777. Epub 2017 Aug 8.
The core-shell structured PS/SiO composite nanospheres were synthesized on the basis of a modified Stöber method. The mechanical properties of monodisperse nanospheres were characterized with nanoindentation on the basis of the atomic force microscopy (AFM). The surface morphologies of PS/SiO composite nanospheres was scanned with the tapping mode of AFM, and the force-distance curves were measured with the contact mode of AFM. Different contact models were compared for the analyses of experimental data. The elastic moduli of PS/SiO composite nanosphere (4-40 GPa) and PS nanosphere (∼3.4 GPa) were obtained with the Hertz and Johnson-Kendall-Roberts (JKR) models, respectively, and the JKR model was proven to be more appropriate for calculating the elastic modulus of PS/SiO nanospheres. The elastic modulus of SiO shell gradually approached a constant value (∼46 GPa) with the increase of SiO shell thickness. A core-shell model was proposed for describing the relationship between PS/SiO composite nanosphere's elastic modulus and shell thickness. The mechanical properties of the composite nanospheres were reasonably explained on the basis of the growth mechanism of PS/SiO composite nanospheres, in particular the SiO shell's formation process. Available research data of PS/SiO composite nanospheres in this work can provide valuable guidance for their effective application in surface engineering, micro/nanomanufacturing, lubrication, and so on.
基于改进的 Stöber 法合成了核壳结构的 PS/SiO 复合纳米球。基于原子力显微镜（AFM）的纳米压痕技术对单分散纳米球的力学性能进行了表征。采用 AFM 的轻敲模式对 PS/SiO 复合纳米球的表面形貌进行了扫描，采用 AFM 的接触模式测量了力-距离曲线。对不同的接触模型进行了比较，以分析实验数据。采用 Hertz 和 Johnson-Kendall-Roberts（JKR）模型分别得到了 PS/SiO 复合纳米球（4-40 GPa）和 PS 纳米球（约 3.4 GPa）的弹性模量，证明 JKR 模型更适合计算 PS/SiO 纳米球的弹性模量。随着 SiO 壳层厚度的增加，SiO 壳层的弹性模量逐渐趋于一个常数（约 46 GPa）。提出了一个核壳模型来描述 PS/SiO 复合纳米球弹性模量与壳层厚度之间的关系。基于 PS/SiO 复合纳米球的生长机制，特别是 SiO 壳的形成过程，对复合纳米球的力学性能进行了合理的解释。本工作中 PS/SiO 复合纳米球的可用研究数据可为其在表面工程、微纳制造、润滑等领域的有效应用提供有价值的指导。
