Mechanism Study Of Magnesium Vapor Condensation Under CO Atmosphere

Vacuum metallurgy national engineering laboratory of Kunming University of Science and Technology have done lots of carbothermic reduction for magnesia research under vacuum.In the carbothermal reduction process,the reverse reaction between magnesium vapor and CO would occur,then MgO and Mg2C3 were obtained,which would result in the purity level of magnesium lower.A lot of researches at home and abroad have been done on the inverse reaction.However,the formation mechanism of MgO and Mg2C3 has not been clearly explained.Focusing on the problems above,in this paper,the reaction mechanism of Mg with CO were studied by the first principles calculation,which can describe the formation mechanism of MgO and Mg2C3 in order to provide corresponding theoretical basis and improved scheme for inverse reaction.Firstly,under vacuum,15 reactions which may generate CO have been studied by thermodynamics calculations,the reaction of Mg and C was studied.The gaseous magnesium easily reacts with CO under 1516K,100Pa.The reaction of magnesium with C needs to occur above atmospheric pressure and 1400K.Secondly,the interaction between Mg and CO is simulated,experiments on the interaction between Mg and CO were performed.The formation mechanism of MgO was obtained.The results show that after 5ps dynamic simulation,Mg had only physical adsorption effect by single CO molecule,no chemical bond to form and break;two CO molecules interaction on Mg(100)surface,a strong C-C bond was formed between Cl and C2,C1-O1 and C2-02 were streched with different stretching levels;three CO molecules interaction on Mg(100)surface,a strong C-C-C bond was formed,the middle chemical bond was broken,O atoms get into the Mg lattice-The interaction of Mg and CO were analyzed under 973K、1023K and 1073K.The condensate surface was not smooth and the color was not uniform crystallization.Contains O and C in the condensate,condensate surface color is more deep,the higher the carbon content.The formation mechanism of MgO:three CO molecules combined to a chain of carbon under the catalysis of magnesium,C-O bonds was broken,O atoms get into the Mg lattice to form MgO.Finally,the interaction of different amounts of CO molecules with Mg and CO molecules with excess gaseous magnesium were studied,the formation of C-C-C was analyzed.The formation mechanism of Mg2C3 was obtained.By extending the computation time,it is found that two and three CO molecules do not form C-C and C-C-C on the Mg(100)surface;four CO molecules interaction on Mg(100)surface,a strong C-C-C-C bond was formed,every C-O bond was elongated,no chemical bond to break;Circular C606 molecule interaction on Mg(100)surface,every C-O bond was elongated,no chemical bond to break;gaseous Mg interaction with CO,both ends and the middle of the C-O bond will be broken,C-C-C bond was formed.The formation mechanism of Mg2C3:three CO formed C-C-C in gaseous Mg,C-C-C get into the Mg lattice to form Mg2C3 in condensation.