Search

• 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 EAM potential is suitable for characterizing the microstructure of liquid Fe-C alloy, while MEAM is not. • EAM potential could accurately predict the melting point of liquid Fe-C alloy. • Increased carbon content helps to increase the complexity of the liquid Fe-C alloy microstructure. • The transformation of Fe4C units to cementite promotes viscosity increase. The liquid Fe-C alloy is the most important system in the metallurgical process and the molecular dynamics simulation were carried out to investigate the structure and properties of liquid Fe-C alloy using EAM and MEAM potential. The local structural order, transport properties and fluidity were analyzed. By comparison, the EAM potential is better than MEAM potential to simulate the properties of liquid Fe-C system. In the liquid state, the Fe-C alloy have a short-ranged ordered structure, accompanied by the transformation of Fe 4 C units to Fe 6 C units with the carbon content increasing. And the increase in carbon content could increase the complexity of the liquid structure. In terms of transport properties and fluidity, there is an inflection point when carbon content increases to 2 wt%. When the carbon content is less than 2%, the change of Fe atom transport performance is the main factor that leads to the increase of viscosity. On the contrary, when the carbon content is more than 2%, the transportation of C atom dominates. [ABSTRACT FROM AUTHOR]

• The influence of MnO content more than or less than 4 wt% on the structure and properties of slag is different. • High bacisity and the MnO content exceeds 4 wt% enhanced depolymerization of aluminosilicate structure by MnO. • The micro complexity of slag system is positively correlated with the macro viscosity. • Low basicity and high MnO promote lower liquidus temperature of slag. In this paper, molecular dynamics (MD) is used to simulate the local structural order, oxygen bond network and transportation characteristics of the slag system under different basicity, and the influence of MnO on the properties such as viscosity, liquidus temperature and enthalpy was studied. MnO or basicity will not affect the bond length and the coordination number of Si-O, but the coordination number of Al-O is slightly reduced. The conversion rate of BO and TOs to NBO or FO is accelerated when CaO/SiO 2 ratio is 1.2 and MnO exceeds 4 wt%. It indicates that an increase in MnO content at high basicity will make the depolymerization of the slag structure more obvious. The total self-diffusion coefficient of each atoms increases with the increase of basicity and MnO, while the viscosity of slag showed an opposite trend. The enthalpy of the slag increases linearly and the conditions of low basicity and high MnO are beneficial for keeping a low liquidus temperature and realizing the stable and smooth of the blast furnace. [ABSTRACT FROM AUTHOR]

Using molecular dynamics simulations, the effects of different levels of calcium oxide and ferrous oxide on the local structural order, bonding network, transport characteristics, and other microstructures and viscosity of the aluminosilicate slag system were analyzed. It was found that CaO and FeO have almost no effect on the short-term ordering of aluminosilicates in the studied composition range. However, as the metal oxide content increases, the degree of depolymerization of CaO on the aluminosilicate network structure is greater than that of FeO. It shows that the degree of polymerization of calcium aluminosilicate system is lower than that of iron aluminosilicate, and the corresponding viscosity of this system decreases with the increase of metal oxide contents. When the mass fractions of CaO and FeO increase, the diffusion ability of each atom in the SiO 2 -Al 2 O 3 -CaO system is larger than that in the SiO 2 -Al 2 O 3 -FeO system. This indicates that the polymerization structure of SiO 2 -Al 2 O 3 -CaO slag system tends to be more simplified compared with SiO 2 -Al 2 O 3 -FeO system. • The similarities and differences between FeO-containg and CaO-containg slag. • Fe2+ and Ca2+ reduce the degree of polymerization as network modifiers. • 10 wt% is the turning point in which FeO or CaO plays a leading role. • Ca2+ is easier to destroy the slag structure than Fe2+ when FeO (or CaO) > 10 wt%. • A good relationship between viscosity and polymerization degree was found. [ABSTRACT FROM AUTHOR]