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High quality ferrovanadium nitride was prepared successfully by carbothermal reduction nitridation process by using V2O5 and Fe as the raw materials. The effects of reaction temperature and C/O molar ratio (content of O is defined as the oxygen in V2O5) on the quality of ferrovanadium nitride were investigated in detail. It was demonstrated that C/O molar ratio had a great influence on the residue carbon, as well as the nitrogen content in the final products. It was found that the nitrogen content of the final product achieved 11.52% when the C/O molar ratio was 90% of the stoichiometric value. However, the nitrogen contents of the final products decreased with the further increase of C/O molar ratio. For the temperature higher than 1773 K, Fe became liquid phase and surrounded the solid V(C, N, O) particles tightly. The formation of liquid Fe was beneficial for the further removal of oxygen atoms left in the V(C, N, O) lattice, since it provided a liquid tunnel for carbon diffusion which greatly enhanced the reaction kinetics. From the results of X-ray diffraction (XRD) and thermodynamic calculations, phase evolution sequence of V2O5 can be obtained as: V2O5→VO2→V2O3→V(C, N, O). Moreover, the kinetic process from V2O3 to VN was studied and the results shown that the reaction rate can be described by Jander diffusion model with the extracted activation energy of 188.173 kJ/mol.

The present study is aimed to distinguish the different influences of CaO and MgO, as well as Al2O3 and SiO2 on viscosity of CaO-MgO-Al2O3-SiO2 melts. It is found that for melt without Al2O3, viscosity increases monotonously as CaO is gradually replaced by MgO. The addition of Al2O3 leads to a complex variation of viscosity. In different composition ranges, viscosity may exhibit different variation tendencies as changing the relative contents of CaO and MgO while keeping contents of other components constant. It is also found that when replacing SiO2 by equivalent mole of Al2O3, (i) in CaOAl 2O3-SiO2 system, viscosity increases when Al2O3 content is small relative to CaO content (there are enough Ca2+ ions to charge compensate Al3+ ions), but decreases when CaO content is inadequate for charge compensation; (ii) in MgO-Al2O3-SiO2 system, viscosity always decreases as substituting Al2O3 for SiO2. The reason for this difference for two systems may be resulted from the weak charge compensation ability of Mg2+ ion for Al3+ ion relative to Ca2+ ion. All the viscosity variations can be interpreted well by our new proposed viscosity model.

The structurally based viscosity model proposed in our previous study is extended to include more components, e.g. SiO2, Al2O3, FeO, MnO, MgO, CaO, Na2O and K2O. A simple method is proposed to calculate the numbers of different types of oxygen ions classified by the different cations they bonded with, which is used to characterize the influence of composition on viscosity. When dealing with the aluminosilicate melts containing several basic oxides, the priority order is established for different cations for charge compensating Al3+ ions, according to the coulombic force between cation and oxygen anion. It is indicated that basic oxides have two paradox influences on viscosity: basic oxide with a higher basicity decreases viscosity more greatly by forming weaker non-bridging oxygen bond; while it increases viscosity more greatly by forming stronger bridging oxygen bond in tetrahedron after charge compensating Al3+ ion. The present model can extrapolate its application range to the system without SiO2. Furthermore, it could also give a satisfy interpretation to the abnormal phenomenon that viscosity increases when adding K2O to CaO-Al2O3-SiO2 melt within a certain composition range.