State Key Laboratory of Fire Science, University of Science and Technology of China , 96 Jinzhai Road, Hefei, Anhui 230026, P. R. China.
ACS Appl Mater Interfaces. 2014 Jan 8;6(1):429-37. doi: 10.1021/am4044932. Epub 2013 Dec 12.
A series of sodium alginate (SA) nanocomposite films with different loading levels of graphitic-like carbon nitride (g-C3N4) were fabricated via the casting technique. The structure and morphology of nanocomposite films were investigated by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Thermogravimetric analysis results suggested that thermal stability of all the nanocomposite films was enhanced significantly, including initial thermal degradation temperature increased by 29.1 °C and half thermal degradation temperature improved by 118.2 °C. Mechanical properties characterized by tensile testing and dynamic mechanical analysis measurements were also reinforced remarkably. With addition of 6.0 wt % g-C3N4, the tensile strength of SA nanocomposite films was dramatically enhanced by 103%, while the Young's modulus remarkably increased from 60 to 3540 MPa. Moreover, the storage modulus significantly improved by 34.5% was observed at loadings as low as 2.0 wt %. These enhancements were further investigated by means of differential scanning calorimetry and real time Fourier transform infrared spectra. A new perspective of balance was proposed to explain the improvement of those properties for the first time. At lower than 1.0 wt % loading, most of the g-C3N4 nanosheets were discrete in the SA matrix, resulting in improved thermal stability and mechanical properties; above 1.0 wt % and below 6.0 wt % content, the aggregation was present in SA host coupled with insufficient hydrogen bondings limiting the barrier for heat and leading to the earlier degradation and poor dispersion; at 6.0 wt % addition, the favorable balance was established with enhanced thermal and mechanical performances. However, the balance point of 2.0 wt % from dynamic mechanical analysis was due to combination of temperature and agglomeration. The work may contribute to a potential research approach for other nanocomposites.
通过浇注技术制备了一系列具有不同石墨相氮化碳（g-C3N4）负载水平的海藻酸钠（SA）纳米复合膜。通过 X 射线粉末衍射、傅里叶变换红外光谱、扫描电子显微镜和透射电子显微镜研究了纳米复合膜的结构和形貌。热重分析结果表明，所有纳米复合膜的热稳定性都得到了显著提高，包括初始热降解温度提高了 29.1°C，半热降解温度提高了 118.2°C。通过拉伸试验和动态力学分析测量得到的力学性能也得到了显著增强。在加入 6.0wt%g-C3N4时，SA 纳米复合膜的拉伸强度显著提高了 103%，而杨氏模量从 60MPa 显著提高到 3540MPa。此外，在负载低至 2.0wt%时，观察到储能模量显著提高了 34.5%。通过差示扫描量热法和实时傅里叶变换红外光谱进一步研究了这些增强。首次提出了一种新的平衡观点来解释这些性能的提高。在低于 1.0wt%的负载下，大多数 g-C3N4 纳米片在 SA 基质中是离散的，从而提高了热稳定性和机械性能；在 1.0wt%以上和 6.0wt%以下的含量时，存在与 SA 主体的聚集，并且氢键不足，限制了热的传递，导致早期降解和较差的分散；在添加 6.0wt%时，建立了增强的热和机械性能的有利平衡。然而，动态力学分析中 2.0wt%的平衡点是由于温度和聚集的结合。这项工作可能为其他纳米复合材料的研究提供一种潜在的方法。
