Capillary condensation within the pore space formed by a hexagonal arrangement of carbon nanorods is investigated using a thermodynamic model. Numerical solution of the corresponding non-linear differential equations predicts two characteristic equilibrium phase transitions corresponding to liquid-bridge formation between adjacent rods, and the subsequent filling of the entire pore space with liquid adsorbate at higher relative pressure, respectively. These separate transitions are predicted for a wide range of porosities, as demonstrated for two non-polar fluids, nitrogen and n-pentane, employing experimentally determined reference isotherms to model the fluid–solid interactions. The theoretical predictions are compared to experimental data for nitrogen and n-pentane adsorption in an ordered mesoporous CMK-3 type material, with the necessary structural parameters obtained from small-angle X-ray scattering. Although the experimental adsorption isotherms do not unambiguously show two separate transitions due to a high degree of structural disorder of the mesopore space, their general trends are consistent with the theoretical predictions for both adsorbates.

中文翻译：

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六角形有序碳纳米棒之间的毛细管桥形成

使用热力学模型研究了由碳纳米棒的六边形排列形成的孔空间内的毛细管冷凝。相应的非线性微分方程的数值解预测了两个特征性的平衡相变，分别对应于相邻棒之间的液桥形成，以及随后在整个孔隙空间中以较高的相对压力填充了液体吸附物。如两种非极性流体（氮气和正戊烷）所证明的，采用实验确定的参考等温线对流体-固体相互作用进行建模，可以预测这些单独的转变对多种孔隙度的影响。将理论预测值与有序介孔CMK-3型材料中氮和正戊烷吸附的实验数据进行了比较，具有从小角度X射线散射获得的必要结构参数。尽管由于中孔空间的高度结构紊乱，实验吸附等温线并未明确显示两个独立的跃迁，但它们的总体趋势与两种吸附物的理论预测一致。