CO2 adsorption enhancement over Al/C-doped h-BN: A DFT study

Dual metal synergistic modulation of boron nitride for high-temperature wave-transparent metamaterials

Electromagnetic metamaterials have demonstrated immense potential in the development of novel high-temperature wave-transparent materials, yet the requirements of their intricate structural design and strict stability pose dual challenges, particularly in high-speed radome applications. A strategy involving the synergistic modulation of boron nitride (BN) by dual metallic elements of Ca and Al (0.5Ca-0.5Al-BN) was proposed in this study, which elegantly integrates the advantages of metamaterial-like split ring resonator (SRR) features and h-BN's oxidation resistance enhancement. The highest wave transmittance at room temperature reaches 0.96 at 2-18 GHz. Notably, Al elements play a pivotal dual role in: (1) facilitating the solid solution of Ca to optimize the formation of metamaterial-like structures and (2) generating an amorphous Al2O3 protective layer to preferentially defend against surface oxidation. This further prevents the breakdown of metamaterial characteristics at high temperatures, thereby striking a dual balance between the preservation of metamaterial-like structures and the high temperature stability of BN. Notably, 0.5Ca-0.5Al-BN retains its metamaterial-like characteristics, with a low permittivity not exceeding 2 even after exposure to 1500 °C oxidation. The corresponding wave transmission rate remains above 0.7 in most frequency bands at incidence angles of 0°, 10°, and 30°, ensuring superior wave-transparent properties. Furthermore, 0.5Ca-0.5Al-BN exhibits great hydrophobicity, benefiting resistance to rain and snow erosion. By integrating the merits between fundamental materials and metamaterials, this work transcends the limitations of conventional metamaterial design and offers fresh insights and empirical support for developing high-speed aircraft radome materials.

Evaluating the CO2 capture potential of MgO sheets: a DFT study on the effects of vacancy and Ni doping for assessing environmental sustainability

Investigations on two-dimensional materials for efficient carbon dioxide (CO2) capture and storage have recently attracted much attention, especially in the global industrial sector. In this work, the CO2 uptake by three configurations of two-dimensional magnesium oxide was investigated using density functional theory. CO2 capture analysis was performed considering the geometrical, thermophysical, vibrational, electronic and optical properties. Results indicated that CO2 adsorption by magnesium oxide (MgO) sheets is a spontaneous process accompanied by a decrease in Gibbs free energy. Moreover, the CO2 molecular entropy and enthalpy of the CO2 adsorbed sheet were decreased, indicating that the entire process was enthalpy-driven. Among the pristine, vacant and nickel-doped (Ni-doped) MgO sheets, the Ni-doped system was found to have the highest values of Gibbs free energy, enthalpy and entropy in the order of -51.366 kJ mol-1-K, -65.105 kJ mol-1 and 127.606 J mol-1, respectively. It was also found to adsorb CO2 in the ultraviolet and visible (UV-Vis) regions within the range of 100-850 nm. Electronic interactions demonstrated that metallicity was significantly induced on the MgO sheet Ni impurity states, which enhanced the adsorption ability. Notably, hybrid orbitals between p y and p z revealed strong physisorption, as confirmed by the partial density of states (PDOS). The findings of this research promote CO2 capture sustainability by encouraging future experimentalists to use two-dimensional MgO as a better surface for CO2 capture.