Visualizing the Toughening Mechanism of Nanofiller with 3D X‑ray Nano-CT: Stress-Induced Phase Separation of Silica Nanofiller and Silicone Polymer Double Networks
Visualizing the Toughening Mechanism of Nanofiller with 3D X‑ray Nano-CT: Stress-Induced Phase Separation of Silica Nanofiller and Silicone Polymer Double Networks
复制标题
利用 3D X 射线纳米 CT 可视化纳米粒子的增韧机制：二氧化硅纳米粒子和有机硅聚合物双网络的应力诱导相分离
作者：
Lixian Song;Zhen Wang;Xiaoliang Tang;Liang Chen;Pinzhang Chen;Qingxi Yuan;Liangbin Li
在硅橡胶中加入二氧化硅纳米fi微粉，可使基体的断裂能提高3个数量级，远大于其他大多数纳米fi微粉−橡胶体系。为了揭示这种惊人的增韧机理，我们利用高空间分辨率(Nm)的原位同步辐射X射线纳米计算机层析成像(Nano-CT)技术研究了硅橡胶中二氧化硅纳米fi在不同ff应变下的结构演化。成像结果表明，二氧化硅纳米fi微球形成三维连通网络，与硅链网络耦合构成双网状结构。在拉伸变形过程中，二氧化硅纳米fi与有机硅聚合物链状网络之间存在应力诱导相分离现象。出乎意料的是，虽然纳米fi网络的空间位置和形态在大应变下发生了很大的变化，但纳米fi网络的连通性却表现出可以忽略不计的下降。这表明纳米fi网络同时经历了破坏和重建，其中二氧化硅纳米fi网络是可逆的高功能交联剂。二氧化硅纳米fi颗粒与硅橡胶之间或纳米fi颗粒之间的可逆键合能相互耗散机械能ff，这可能是韧性提高3个数量级的原因。
Adding silica nanofiller in silicone rubber can toughen the matrix 3 orders in terms of fracture energy, which is far larger than most other nanofiller−rubber systems. To unveil the astonishing toughening mechanism, we employ in situ synchrotron radiation X-ray nanocomputed tomography (Nano-CT) technique with high spatial resolution (64 nm) to study the structural evolution of silica nanofiller in silicone rubber matrix at different strains. The imaging results show that silica nanofiller forms threedimensional connected network, which couples with silicone chain network to construct a double-network structure. Stress-induced phase separation between silica nanofiller and silicone polymer chain networks is observed during tensile deformation. Unexpectedly, though the spatial position and morphology of nanofiller network changes greatly at large strains, the connectivity of nanofiller network shows negligible reduction. This indicates that nanofiller network undergoes destruction and reconstruction simultaneously, during which silica nanofiller serves as reversible high functionality cross-linker. The reversible bonding between silica nanofiller and silicone rubber or between nanofiller particles can dissipate mechanical energy effectively, which may account for the 3 orders enhancement of toughness..