Microscopic Mechanism of Tunable Thermal Conductivity in Carbon Nanotube-Geopolymer Nanocomposites

Abstract

Geopolymer has been considered as a green and low-carbon material with great potential application due to its simple synthesis process, environmental protection, excellent mechanical properties, good chemical resistance, and durability. In this work, the molecular dynamics simulation is employed to investigate the effect of the size, content, and distribution of carbon nanotubes on the thermal conductivity of geopolymer nanocomposites, and the microscopic mechanism is analyzed by the phonon density of states, phonon participation ratio, spectral thermal conductivity, etc. The results show that there is a significant size effect in the geopolymer nanocomposites system due to the carbon nanotubes. In addition, when the content of carbon nanotubes is 16.5%, the thermal conductivity in carbon nanotubes vertical axial direction (4.85 W/(m k)) increases by 125.6% compared with the system without carbon nanotubes (2.15 W/(m k)). However, the thermal conductivity in carbon nanotubes vertical axial direction (1.25 W/(m k)) decreases by 41.9%, which is mainly due to the interfacial thermal resistance and phonon scattering at the interfaces. The above results provide theoretical guidance for the tunable thermal conductivity in carbon nanotube-geopolymer nanocomposites.

Sandwich-Structured Thermal Interface Materials with High Thermal Conductivity

“…After ten cycles, the thermal conductivity deviation of the VCF/G-6 composite was only 1.5% (25 °C) and 1.7% (100 °C), confirming the reliability and stability of heat transfer during long-term use. Figure j shows a comparison of the thermal conductivity of our work with other composites that used carbon-based fillers in previous works. ,,− …”

Tunable Thermal Conductivity of Sustainable Geopolymers by the Si/Al Ratio and Moisture Content: Insights from Atomistic Simulations

“…It is worth pointing out that we restricted our study to a sodium-based geopolymer with a Na/Al ratio of 1 to ensure the system charge balance. According to our previous research work, we found that the geopolymer system had no obvious size effect, which means that we do not need to consider the impact of the system size on the calculation results. Therefore, we set the size of simulation systems to 80 Å × 40 Å × 40 Å uniformly.…”

“…In MD simulations, the interatomic potential is crucial to accurately describe the atomistic interactions. In this work, we chose the interatomic potential that was verified earlier for geopolymer systems with a similar composition, including zeolites, metakaolin, and geopolymers. , In order to facilitate the distinction, we mark the oxygen atom in the geopolymer structure as O s , the oxygen atom in the water molecule as O w , and the hydrogen atom in the water molecule as H w . The expression for the interaction potential of M–O s (M = Si, Al, Na, O s ) is V ( r ) = C q i q j ϵ r + A 0.25em exp ( − r ρ ) − C r 6 + D r 12 r < r c where the first term is the long-range Coulomb interaction in which C is the energy conversion constant, q i and q j are the charges of atoms i and j , respectively, ϵ is the dielectric constant, which has the default value of 1.0, r is the distance between the two atoms, r c is the cutoff radius set as 12 Å.…”

“…In this work, we chose the interatomic potential that was verified earlier for geopolymer systems with a similar composition, including zeolites, 39 metakaolin, 40 and geopolymers. 31,38 In order to facilitate the distinction, we mark the oxygen atom in the geopolymer structure as O s , the oxygen atom in the water molecule as O w , and the hydrogen atom in the water molecule as H w . The expression for the interaction potential of M−O s (M = Si, Al, Na, O s ) is 31…”