Interactions of silica nanoparticles in supercritical carbon dioxide.
Interactions of silica nanoparticles in supercritical carbon dioxide.
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DOI：
10.1063/1.2994714
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发表时间：
2008-11
期刊：
影响因子：
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通讯作者：
A. Vishnyakov;Yangyang Shen;M. Tomassone
中科院分区：
文献类型：
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作者：
A. Vishnyakov;Yangyang Shen;M. Tomassone
本文报道了318 K下二氧化硅纳米粒子在超临界二氧化碳中相互作用力的分子模拟研究。我们的目标是找到一个更好的理解在超临界溶液的快速膨胀过程中的粒子间溶剂化力。流体-流体和固体-流体相互作用的原子间势的参数通过拟合我们的模拟获得（i）在给定的温度和压力下的实验体CO（2）相图和（ii）在正常沸点和临界温度下的二氧化硅上的CO（2）吸附等温线。我们的模拟表明，在p=69大气压的近临界压力下，颗粒与超临界CO（2）之间的相互作用力（即，稍低于临界条件）在颗粒外表面之间的距离为0.5- 0.8nm处达到最小值，并且在大约3 nm的距离处几乎消失。这种吸引力对于通过氢键与CO（2）强烈相互作用的致密羟基化颗粒表面最为突出。对于脱羟基颗粒，二氧化硅和CO（2）之间的有效吸引力明显较弱。我们还比较了超临界CO（2）和亚临界氮蒸气之间的流体吸附和颗粒间力，我们的结果显示了定性的相似性，这表明颗粒之间的CO（2）构型类似于液体连接。
We report molecular simulation studies on the interaction forces between silica nanoparticles in supercritical carbon dioxide at 318 K. Our goal is to find a better understanding of the interparticle solvation forces during rapid expansion of supercritical solutions. The parameters for interatomic potentials of fluid-fluid and solid-fluid interactions are obtained by fitting our simulations to (i) experimental bulk CO(2) phase diagram at a given temperature and pressure and (ii) CO(2) sorption isotherms on silica at normal boiling and critical temperatures. Our simulations show that the interaction forces between particles and supercritical CO(2) at near-critical pressure of p=69 atm (i.e., slightly below critical condition) reaches a minimum at distances of 0.5-0.8 nm between the outer surfaces of the particles and practically vanishes at distances of approximately 3 nm. The attraction is most prominent for densely hydroxylated particle surfaces that interact strongly with CO(2) via hydrogen bonds. The effective attraction between silica and CO(2) is significantly weaker for dehydroxylated particles. We also compared fluid sorption and interparticle forces between supercritical CO(2) and subcritical nitrogen vapor, and our results showed qualitative similarities, suggesting that the CO(2) configuration between the particles resembles a liquidlike junction.