Effects of diameter and chirality on structural and dynamical behavior of [EMIM][PF6] encapsulated in carbon nanotube: A molecular dynamics study

Investigation of thermodynamics, and structural, dynamical, and electrical properties of polyoxometalate ionic liquid confined into carbon nanotubes during the melting process using molecular dynamics simulation

Understanding the properties of ionic liquids confined into nano-pores is required to use ionic liquids for many applications such as electrolytes for energy storage in capacitors and solar cells. Recently, polyoxometalate ionic liquids have attracted much attention for their potential applications in electrochemistry, catalysis, and nanotechnology. In this work, we have performed MD simulations on 1-ethyl-3-methylimidazolium Keggin ([emim]₃[PW₁₂O₄₀]) confined into armchair (20,20) CNTs to study the thermal properties and melting process. Changes in the simulated results of configurational energy of confined polyoxometallate IL indicated that the melting range of the confined polyoxometalate IL is about 650-750 K. Heat capacity at constant volume of the confined IL is about 2 (cal K^-1 mol^-1) which shows sharp changes around the melting range. The average number of hydrogen bonds (〈HB〉) of the confined IL is about 2.8 which also presents sharp changes around the melting range. The ion conductivity and self-diffusion coefficient of [emim]₃[PW₁₂O₄₀] IL also present a sharp maximum of 25 (S m^-1) and 6 × 10^-10 (m² s^-1) at the melting point. Our results did not show a significant hysteresis in the melting process and therefore, the process is reversible. Our simulation also indicated that the confinement of the polyoxometallate IL into the CNT increases its thermal stability and melting point. Our simulations also indicated that the type of CNT configuration has a small effect on the melting point of the confined polyoxometallate IL.

Investigation of the thermal properties of phase change materials encapsulated in capped carbon nanotubes using molecular dynamics simulations

Due to the high demand for clean, economic, and recyclable energy, phase change materials (PCMs) have received significant attention in recent years. To improve the performance of PCMs, they are confined in micro- and nano-capsules composed of organic or inorganic materials. In this study, encapsulated phase change material (EPCM) systems were constructed with paraffin molecules as the core material and capped carbon nanotubes (CNTs) as the shell. We investigated the effects of different parameters including CNT diameter, length, and chirality and the length of the alkane molecule chain. We also investigated metal nanocluster-enhanced PCM systems via the addition of Cu, Ag, and Al clusters to the EPCM systems. Different thermodynamic, dynamic, and structural properties including configurational energy, melting range, mean square displacement, self-diffusion coefficient, radial distribution function (RDF), and average end-to-end distance of the confined molecules were examined. We also investigated the effect of metal doping in CNT on the different properties of the confined PCM. The results indicated that a longer CNT has a lower melting point than the normal CNT system. It was also observed that the bigger (30,0) CNT, (14,14) armchair CNT, and icosane systems have higher melting ranges than the normal (25,0) system. The metal cluster systems also have a lower starting melting point than the normal system. Furthermore, it was found that the Al cluster system has the lowest starting melting point among the studied systems.

Nanocluster enhanced PCM and metal doped CNT PCM systems have lower melting points than the normal system.

Formation of methane clathrates in carbon nanotubes: a molecular dynamics study

In this study, we investigated the possible formation of methane clathrates in CNTs with different sizes.