Moteki Ayumi, Kobayashi Motoyoshi
Graduate School of Science and Technology, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Ibaraki, Japan.
Institute of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Ibaraki, Japan.
Nanomaterials (Basel). 2024 Jul 25;14(15):1247. doi: 10.3390/nano14151247.
Oxidized carbon nanohorn (CNHox) a carbon nanomaterial that has attracted attention due to its unique material properties. It is expected to be applied in various areas like cancer treatment, gene-expression technology, fluids with high thermal conductivity, lubricants, and so on. While the rheological measurements of suspensions provide information on the effective size and interactions of suspended particles, the rheological behaviors of aqueous suspensions of CNHox have never been systematically investigated. To clarify the rheological behaviors of aqueous suspensions of CNHox, their viscosity and dynamic viscoelasticity were measured with changing particle concentration and salt concentration. The viscosity of a CNHox suspension showed yield stress at low shear rates and showed shear-thinning behavior with increasing shear rates. The viscosity of 5 weight % CNHox suspensions was comparable to that of 60 weight % silica suspensions. This high viscosity at a low CNHox concentration is probably due to the porous structure and large effective volume of the CNHox particle. The estimated effective volume of CNHox calculated by the Krieger-Dougherty equation was 18.9 times larger than the actual volume calculated by the mass concentration and density. The dependence of rheological behavior of the CNHox suspension on salt concentration was weak compared to that of the colloidal silica suspension. This weak dependence on salt concentration may be due to the roughness of the particle surface, which would weaken the effect of electric double-layer interactions and/or van der Waals interactions between particles. These rheological behaviors of the aqueous suspension of CNHox shown in this research will be useful in efforts to improve the efficiency of its utilization for the various applications.
氧化碳纳米角（CNHox）是一种因其独特材料特性而备受关注的碳纳米材料。它有望应用于癌症治疗、基因表达技术、高导热流体、润滑剂等各个领域。虽然悬浮液的流变学测量能提供有关悬浮颗粒有效尺寸和相互作用的信息，但CNHox水悬浮液的流变行为从未得到系统研究。为了阐明CNHox水悬浮液的流变行为，在改变颗粒浓度和盐浓度的情况下测量了它们的粘度和动态粘弹性。CNHox悬浮液的粘度在低剪切速率下表现出屈服应力，并随着剪切速率的增加呈现剪切变稀行为。5重量%的CNHox悬浮液的粘度与60重量%的二氧化硅悬浮液相当。在低CNHox浓度下的这种高粘度可能归因于CNHox颗粒的多孔结构和大的有效体积。通过Krieger-Dougherty方程计算得到的CNHox的估计有效体积比由质量浓度和密度计算得到的实际体积大18.9倍。与胶体二氧化硅悬浮液相比，CNHox悬浮液的流变行为对盐浓度的依赖性较弱。对盐浓度的这种弱依赖性可能是由于颗粒表面的粗糙度，这会削弱颗粒间电双层相互作用和/或范德华相互作用的影响。本研究中所示的CNHox水悬浮液的这些流变行为将有助于提高其在各种应用中的利用效率。
