Kaneko Masahiro, Kawai Mika, Mitsumata Tetsu
Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
Gels. 2023 Aug 28;9(9):691. doi: 10.3390/gels9090691.
The effect of the cooling rate on magnetorheological response was investigated for magnetic hydrogels consisting of carrageenan and carbonyl iron particles with a concentration of 50 wt.%. For magnetic gels prepared via natural cooling, the storage moduli at 0 and 50 mT were 3.7 × 10 Pa and 5.6 × 10 Pa, respectively, and the change in the modulus was 1.9 × 10 Pa. For magnetic gels prepared via rapid cooling, the storage moduli at 0 and 50 mT were 1.2 × 10 Pa and 1.8 × 10 Pa, respectively, and the change in the modulus was 6.2 × 10 Pa, which was 1/3 of that for the magnetic gel prepared by natural cooling. The critical strains, where ' is equal to ″ on the strain dependence of the storage modulus, for magnetic gels prepared by natural cooling and rapid cooling, were 0.023 and 0.034, respectively, indicating that the magnetic gel prepared by rapid cooling has a hard structure compared to that prepared by natural cooling. Opposite to this, the change in the storage modulus at 500 mT for the magnetic gel prepared by rapid cooling was 1.6 × 10 Pa, which was 2.5 times higher than that prepared by natural cooling. SEM images revealed that many small aggregations of the carrageenan network were found in the magnetic gel prepared by natural cooling, and continuous phases of carrageenan network with large sizes were found in the magnetic gel prepared by rapid cooling. It was revealed that magnetic particles in the magnetic gel prepared by rapid cooling can move and form a chain structure at high magnetic fields by breaking the restriction from the continuous phases of carrageenan.
研究了冷却速率对由浓度为50 wt.%的卡拉胶和羰基铁颗粒组成的磁性水凝胶磁流变响应的影响。对于通过自然冷却制备的磁性凝胶，在0和50 mT时的储能模量分别为3.7×10 Pa和5.6×10 Pa，模量变化为1.9×10 Pa。对于通过快速冷却制备的磁性凝胶，在0和50 mT时的储能模量分别为1.2×10 Pa和1.8×10 Pa，模量变化为6.2×10 Pa，这是通过自然冷却制备的磁性凝胶的1/3。对于通过自然冷却和快速冷却制备的磁性凝胶，在储能模量的应变依赖性中'等于″时的临界应变分别为0.023和0.034，这表明通过快速冷却制备的磁性凝胶与通过自然冷却制备的相比具有更硬的结构。与此相反，通过快速冷却制备的磁性凝胶在500 mT时的储能模量变化为1.6×10 Pa，这比通过自然冷却制备的高2.5倍。扫描电子显微镜图像显示，在通过自然冷却制备的磁性凝胶中发现了许多卡拉胶网络的小聚集体，而在通过快速冷却制备的磁性凝胶中发现了大尺寸的卡拉胶网络连续相。结果表明，通过快速冷却制备并在高磁场下的磁性凝胶中的磁性颗粒能够通过打破来自卡拉胶连续相的限制而移动并形成链状结构。
