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Thermal Evaluation of BNNTs for Hydrogen Storage Functions


In an article lately revealed within the journal Supplies Right now Communications, researchers demonstrated the potential of carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) as hydrogen (H2) storage supplies by investigating their thermal conductivities utilizing atomistic nonequilibrium molecular dynamics (NEMD) simulations. 

Thermal Analysis of Boron Nitride CNTs for Hydrogen Storage Applications

​​​​​​​Research: Thermal conductivities of hydrogen encapsulated boron nitride and hybrid boron nitride – carbon nanotubes utilizing molecular dynamics simulations. Picture Credit score: Kateryna Kon/Shutterstock.com

BNNT, CNT, and boron nitride–carbon (BN-C) heteronanotubes had been studied in pristine and faulty states for his or her thermal conduction, with various portions of encapsulated H2. The efficiency of reactive forcefield (ReaxFF) was in contrast with non-reactive Tersoff-adaptive intermolecular reactive empirical bond order (AIREBO). Though ReaxFF constantly resulted in decrease thermal conductivity (okay) for all of the analyzed nanotubes, it supplied a greater qualitative thermal transport prediction.

Then again, the mixture of Tersoff + AIREBO + Lennard-Jones (TALJ) potentials supplied an excellent quantitative prediction of okay. Nonetheless, the explanation for the acoustic phonon remained unclear. Close to-linear mixing rule for okay in CNT-BNNT composition confirmed by each ReaxFF and TALJ potentials recommended that the interfacial warmth transport at heterojunctions was easy.

CNTs and BNNTs

CNTs and BNNTs have a structural similarity that enables their configuration into numerous geometries like hetero-nanotubular buildings, nanometric movies, nanotube arrays, and nanocomposites.

Primarily based on the dimension, chirality, and defects, CNT is both semiconducting or semi-metallic with a band hole of 1 electronvolt. Then again, BNNTs are dielectric and have an approximate bandgap of 5.5 electronvolt no matter dimensions, chirality, or defects of their electrical conduct. 

Light-weight CNTs and BNNTs have acceptable thermal stabilities and distinctive thermal conductivities that assist in the thermal administration of miniaturized digital gadgets. Chirality-pure CNTs have discovered their purposes in high-density, high-performance digital gadgets. Nonetheless, the purposes of BNNT stay unexplored because of the issue in synthesizing extremely pure BNNT. Furthermore, the synthesis of single-walled CNT-BNNT heteronanotubes with a heterojunction between CNT and BNNT layers was unsuccessful.

Molecular dynamic (MD) simulation is a sturdy software that enables molecular degree research on nanoscale supplies when it comes to their thermal transport mechanisms. Furthermore, MD simulations are sometimes utilized to check the thermal properties of BNNTs and CNTs. The computationally predicted okay worth is used as a alternative for the experimental worth because of the challenges concerned inBNNT synthesis.

C and BN nanotubular supplies include endemic lattice and impurity defects launched throughout their synthesis and different property manipulations. Though CNTs had been beforehand explored to know the affect of defects on their thermal conductivity, BNNTs and BN-C heteronanotubes stay unexplored in the identical context.

Thermal Conductivities of H2 Encapsulated BNNT and BNNT-CNT utilizing MD Simulations

Within the current research, NEMD simulations had been carried out to calculate warmth transport in pristine, faulty, and hydrogen encapsulated, capped single-walled BNNT and BNNT-CNT hybrid buildings. The entrapped weight % of H2 molecules contained in the nanotubes had been 0.00, 3.25, and 6.50.

Moreover, the ReaxFF drive discipline helped analyze the interatomic interactions of B, N, C, and H atoms, and the outcomes had been in contrast with these obtained from mixed potentials of B-C-N interplay’s Tersoff potential, H-H interplay’s AIREBO potential, and C-B-N interplay’s LJ potential. The mixture of Tersoff-AIREBO-LJ potential was termed as TALJ potential.

The research had been carried out on the impact of H2 encapsulation on the thermal conductivities of pristine BNNT, CNT, and the BN-C (50%) hybrid utilizing two totally different potentials. Evaluating TALJ and Tersoff potential for nanotubes with and with out H2 content material revealed that the thermal conductivities confirmed a lowering pattern with growing H2 content material in nanotubes.

The ReaxFF potential predicted a better impact of H2 content material in all three nanotubes. With growing H2 content material, most okay discount was noticed in CNT, adopted by BN-C hybrid and BNNT. This discount in okay was as a consequence of elevated phonon scattering that arose as a consequence of collisions between nanotube atoms and H2 molecules and H2 molecules adsorption on the nanotube partitions.

ReaxFF potential described C/B/N nanotube atom’s short-range bonded interactions and nanotube- H2 molecule’s long-range interactions which might be non-bonded. The interactions between nanotube atoms-H2 molecules led to physisorption and chemisorption of H2 molecules on the interior facet of the nanotube wall. The TALJ potentials accounted for the C-B-N atom’s short-range bonded interactions and physisorption-based, long-range non-bonded interactions with H2 molecules.

Conclusion

To summarize, NEMD simulations had been carried out together with ReaxFF forcefield and TALJ potentials to research the thermal conductivities of BNNT and BN-C heteronanotubes. The impact of a single atom (B, C, or N) and paired atom (B-N) vacancies and variable H2 content material on thermal conductivities had been explored at 300 kelvin. In comparison with TALJ potentials, The ReaxFF potential predicted decrease okay values for all three nanotubes.

ReaxFF potential might decide the impact of composition on thermal conductivities throughout BNNT-CNT hybrids and seize the reactive interactions between the nanotube and H2 molecules. Furthermore, parametrization by the inclusion of phonon dispersion quantitatively estimated okay for BNC nanotubes.

ReaxFF described each long- and short-range interactions with its set of parameters. Moreover, ReaxFF’s expandable component protection made this computational modeling helpful for numerous purposes like investigating the potential of H2 encapsulated nanotubes to retailer power and sensor exercise of molecule-encapsulated C-BN heteronanotubes.

Reference

Dethan, JFN., Yeo, J., Rhamdhani, MA ., Swamy, V. (2022) Thermal conductivities of hydrogen encapsulated boron nitride and hybrid boron nitride – carbon nanotubes utilizing molecular dynamics simulations. Supplies Right now Communications. https://www.sciencedirect.com/science/article/pii/S2352492822008017?viapercent3Dihub


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