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Molten slag has different properties depending on its composition. The relationship between its composition, structure, and properties has been the focus of attention in industrial manufacturing processes. This review describes the atomistic scale mechanisms by which oxides of different compositions affect the properties and structure of slag, and depicts the current state of research in the atomic simulation of molten slag. At present, the research on the macroscopic properties of molten slag mainly focuses on viscosity, free-running temperature, melting point, and desulphurization capacity. Regulating the composition has become the most direct and effective way to control slag properties. Analysis of the microevolution mechanism is the fundamental way to grasp the macroscopic properties. The microstructural evolution mechanism, especially at the atomic and nanoscale of molten slag, is reviewed from three aspects: basic oxides, acidic oxides, and amphoteric oxides. The evolution of macroscopic properties is analyzed in depth through the evolution of the atomic structure. Resolution of the macroscopic properties of molten slag by the atomic structure plays a crucial role in the development of fundamental theories of physicochemistry. [ABSTRACT FROM AUTHOR]

Amphoteric oxides (Al 2 O 3 and B 2 O 3) represent opposite effects on the structure and properties of silicate melts in different conditions, while the understanding about the transition from acidity to basicity is far from complete. Molecular dynamics simulation was adopted in the present study to investigate the performance and acidity-basicity transformation of Al 2 O 3 and B 2 O 3 in the SiO 2 –CaO–Al 2 O 3 –B 2 O 3 system. The results showed that, different from Ca2+ ions, excessive Al3+ or B3+ ions tend to destroy the bridge oxygen structures, showing the function of basic oxide. This is similar to the behavior of Ca2+ ions and other basicity ions. It was found that, on the one hand, B3+ ions tend to form [BO 3 ]3- planar triangular structures with the increase of B3+ ions contents, on the other hand, B3+ ions could reduce the stability of Si–O bonds. Therefore, B3+ ions could make the system structure less stable, which is the reason why the B 2 O 3 is a kind of active agent. In addition, because of the significant differences in lattice energy and atomic structure between Al 2 O 3 and B 2 O 3 , the effects of Al 2 O 3 and B 2 O 3 on the thermodynamic properties of silicate melts are quite different. [ABSTRACT FROM AUTHOR]

• The Al 2 O 3 (B 2 O 3)-bearing melts structure was studied by molecular dynamics. • Amphoteric oxides Al 2 O 3 (B 2 O 3) gradually appear basic. • Basic Al 2 O 3 (B 2 O 3) will reduce the bridging oxygen content of the system. • Al 2 O 3 increases the viscosity of systems, while using B 2 O 3 the opposite occurs. Al 2 O 3 and B 2 O 3 possess properties of amphoteric oxide, so Al 2 O 3 and B 2 O 3 have many different influences on the structure and properties of silicate melts, while its influence mechanism in atomic scale has not yet been fully understood. Molecular dynamics (MD) simulation was conducted to gain a clear understanding about the influences of Al 2 O 3 and B 2 O 3 on the structure and properties of SiO 2 -CaO-Al 2 O 3 (SiO 2 -CaO-B 2 O 3) silicate melts at 1773 K. The results show that when the Al 2 O 3 content is less than 25 wt.%, the Al 2 O 3 in the system is almost acidic in the studied system, and the bridging oxygen content and polymerization degree of the system increase with the increase of Al 2 O 3 content. When the content of Al 2 O 3 exceeds 25 wt.%, part of Al 2 O 3 in the system becomes basic, which makes the bridging oxygen content of the system decrease and the growth rate of polymerization degree decrease. The effect of B 2 O 3 on the network structure of SiO 2 -CaO-B 2 O 3 (SCB) system is similar to that of Al 2 O 3 in SiO 2 -CaO-Al 2 O 3 (SCA) system, but the inflection point from acid to basic is lower (21 wt.%) and the basicity is stronger. Moreover, through two suitable viscosity calculation models, combined with experimental data, it shows that the viscosity of SCA system increases with the increase of Al 2 O 3 content, while that of SCB system is just the opposite. [ABSTRACT FROM AUTHOR]

• The B 2 O 3 -bearing slag structure was investigated with molecular dynamics. • Boron was found to form planar triangular structure with oxygen. • B 2 O 3 increase polymerization degree by increasing bridge oxygen content. • B 2 O 3 decrease slag viscosity by decreasing the stability of network structure. B 2 O 3 has the advantages of reducing the liquidus temperature and enhancing the fluidity of slag, while its influence mechanism in atomic scale has not yet been fully understood. Molecular dynamics simulation was conducted to investigate the influence of B 2 O 3 on the structure and properties of SiO 2 CaO-Al 2 O 3 -B 2 O 3 blast furnace slag system at 1773 K. Results showed that a large number of [SiO 4 ]4−-[BO 3 ]3− structures are generated in the system after B 2 O 3 added, Si4+ ions mainly exist in the form of [SiO 4 ]4- tetrahedrons and B3+ ions mainly exist in the form of [BO 3 ]3− planar triangular structures and [BO 4 ]5− tetrahedrons. With the increase of B 2 O 3 content, the proportion of [BO 3 ]3− planar triangular structures increase. In addition, the content of bridge oxygen in the microstructure of slag increases obviously, the content of non-bridge oxygen decreases, and the polymerization degree of the system increases somewhat. Through the analysis of microscopic mechanism and the modified NPL viscosity model, combined with experimental data, the truth that the slag viscosity decreases with the increase of B 2 O 3 contents were known in the simulated concentration range. [ABSTRACT FROM AUTHOR]

[Display omitted] • The influence factors of graphene oxide layer spacing on the atomic scale. • Low–temperature pyrolysis behavior of graphene oxide. • The aggregation and distribution of oxygen-containing functional. • Graphene oxide layer spacing control and membrane separation. • Application of molecular dynamics simulation in carbon materials. Due to the oxygen–containing functional groups covering the graphene oxide surface, multilayer graphene oxide has different properties. The understanding of its atomic structure and layer stacking behavior at low temperature is far from complete. This work systematically revealed how the oxygen-containing groups density, type and temperature affect the spacing of multilayer GO layers through the ReaxFF molecular dynamics simulation method. We found that the density of oxygen-containing groups is the main variable that controls the distribution of surface oxidation areas and the degree of distortion of the graphene sheets. With the increase of C/O ratio, the distribution of oxygen-containing functional groups tends to aggregate, and the deformation of graphite flakes becomes more serious. The layer spacing of multilayer GO is affected by temperature. The types of released small molecules, the degree of pyrolysis of the graphene skeleton and the interlayer spacing are all affected by OH/O ratio. With more hydroxyl groups, it is easier to release long O - H chains, and the graphene skeleton is less likely to be pyrolyzed. This in–depth investigation has helped develop a fundamental understanding of the atomic structure of graphene oxide and has laid basic foundations for an effective control of graphene layer distance and properties. [ABSTRACT FROM AUTHOR]