Designing a high-performance gas sensor to efficiently detect the hazardous NH₃ molecule is beneficial to air monitoring and pollution control. In this work, the first-principles calculations were employed to investigate the adsorption structures, electronic characteristics, and gas sensing properties of the pristine and B-, N-, P-, Al-, and Si-doped penta-graphene (PG) toward the NH₃, H₂S, and SO₂ molecules. The results indicate that the pristine PG is insensitive to those toxic gases due to the weak adsorption strength and long adsorption distance. Nevertheless, the doping of B, N, Al, and Si (B and Al) results in the transition of NH₃ (H₂S and SO₂) adsorption from physisorption to chemisorption, which is primarily ascribed to the large charge transfer and strong orbital hybridizations between gas molecules and doping atoms. In addition, NH₃ adsorption leads to the remarkable variation of electrical conductivity for the B-, N-, and Si-doped PG, and the adsorption strength of NH₃ on the B-, N-, and Si-doped PG is larger than that of H₂S and SO₂. Moreover, the chemically adsorbed NH₃ molecule on the N-, B-, and Si-doped PG can be effectively desorbed by injecting electrons into the systems. Those results shed light on the potential application of PG-based nanosheets as reusable gas sensors for NH₃ detection.

The viscosity of SiO 2-Al 2 O 3-CaO-MgO system and its subsystems are of fundamental importance for control and optimization of metallurgical, material, energy and geological phenomena. In this work, an accurate and simple viscosity model suitable for use in numerical simulations was established for SiO 2-Al 2 O 3-CaO-MgO system and its subsystems, based on the physically meaningful MYEGA equation. The model was calibrated by 4403 viscosity data measured in non-graphite crucibles. It was found current model calculates the viscosity with a remarkable overall accuracy of 15.8%. For each of the subsystems, current model also results in very good accuracy lower than 20%. The model could calculate the viscosity very reliably over the entire composition, temperature and viscosity value ranges studied in the work, even for viscosity value as low as 10-2 Pa•s. The composition dependences of viscosity for binary, ternary and quaternary systems were derived using established model. The effects of each component on viscosity were interpreted according to the concept of network "former" and "modifier" and the charge compensation effect of Ca 2 + on the tetrahedral-coordinated structure of Al 3 + .