The Research Of Mg-TiO₂ By SHS

In this paper, the feasibility of 2Mg+TiO₂= Ti+2MgO by SHS was studied from two aspects of thermodynamics, reaction kinetics and the reaction process was studied from the processing parameter, the research could develope a new method of reducing Ti.According to the thermodynamics theories, reaction Gibbs free energy, adiabatic temperature and melting rate in Mg-TiO₂ system have been theoretically calculated and analyzed. Results of Gibbs free energy calculation showed that the reaction of 2Mg+ TiO₂= Ti+2MgO would occur below temperature 2242K because its reaction Gibbs free energy was lower than zero; might generate the low valency oxide of Ti: Ti₃O₅, Ti₂O₃, TiO et al, in the Mg-TiO₂ system and the trend of getting Ti by mean of reducing reaction would descent with temperature raised. Through calculations of the Gibbs free energy in Al-TiO₂ system, the ruler was the same in Al-TiO₂ system as in Mg-TiO₂ system. Result of adiabatic temperature calculation showed that the adiabatic temperature became lower with the increasing of x in (2+x)Mg+TiO₂=Ti+2MgO+xMg, the adiabatic temperatures were over 1800K when the x<0.5. Results of melting rate calculation of Ti showed that the adiabatic temperature plateau was the result of Ti melting endotherm. Results of Mg gasification quantity calculation showed that a great deal of Mg gasified in reaction so x should be over 0.9 in order to get the Ti.Based on Differential Thermal Analysis and kinetic theory, the reaction process was studied. The curve of DTA showed that the reaction exothermal wave was between 767K～886K which was below the melting point of Mg so the reaction was solid-solid mode; The kinetic parameters by DTA results calculation were activation energy E=248.9KJ ? mol^-1, reaction order n=0.55.Results showed that the influence of process parameters with X-ray diffraction analyse: because of the gasification of Mg, Mg would excess 0.9mol in order that the reaction of 2Mg+TiO₂= Ti+2MgO proceeded completely that was getting Ti. The higher the vacuum, the lower thevalency of Ti in generated oxides and the more complete the reaction and getting Ti more easily. The pores of combustion products became smaller and the integrity became better and the velocity of combustion wave was faster with the increase of material-pressure; the combustion temperature first rose then fell with the increase of material-pressure, the boundary material-pressure was 275MPa. The combustion temperature first rose then became stabilization but the velocity of combustion wave first rose then dropped with augment of the diameter of material.