Interaction Of Rare Earth Cerium With Iron And Arsenic At High Temperature

China has a large number of rare earth resources,of which cerium is the most abundant.Arsenic is a harmful element in steel,but it can react with cerium and iron to turn into promising compounds.How to transform resource advantage into economic and technological advantage is the goal pursued.However,there is no systematic study on the interaction of rare earth cerium with iron and arsenic.First of all,in this paper,the free energies of iron-arsenic and cerium-iron-arsenic compounds are calculated by thermodynamics.Then,cerium and arsenic are sealed in H08cylinder block at atomic ratios of 1:2,1:3 and 1:4,respectively.The samples are prepared at constant temperature of 1173K,1223K and 1273K and isothermal time of1h,30h and 50h.The effects of constant temperature,isothermal time,and atomic ratio on the interaction of cerium with iron and arsenic at high temperature were studied by metalloscope,XRD,SEM and EDS.The heat of formation of Fe₂As is?H^?_Fe2As?28?37282.63J/moland the entropy of formation is?_fS^?_298,Fe2As=9.54 J/mol·K?Fe is positive 3 valence,low spin ion radius?by adopting Miedema and Crystal Ion Entropy model,whose standard free energy is?G^?_Fe2As?28?-37282.63-.954TJ/mol.When the ternary compound Ce₁₂Fe_57.5As₄₁formed by Fe₂As and CeAs meets the ideal solid solution condition,the Gibbs free energy is?G?28?-435212.63-157.21TJ/mol?Fe is positive 3 valence,low spin ion radius?.The experimental results show that there were differences in the uniformity of the microstructure distribution of the samples at different constant temperature,isothermal time,and atomic ratios.When the cerium-arsenic atom ratio is 1:3,the constant temperature is 1273K and isothermal time of 30 h,the phase structure distribution is the most uniform.The main compounds produced by the interaction of rare earth cerium with iron and arsenic at high temperature are binary compounds CeAs,Fe₂As and some ternary compounds Ce₁₂Fe_57.5As₄₁,and binary compounds CeAs and Fe₂As are the basis for the formation of ternary compounds Ce₁₂Fe_57.5As₄₁.Under different conditions,the relative content of the phase is different,and the content of Fe₂As increase when the proportion of arsenic increase.The ternary compound Ce₁₂Fe_57.5As₄₁1 is more suitable to be synthesized when the atomic ratio of cerium to arsenic is 1:3,the constant temperature is 1273K and the isothermal time is 30h.