Effect of Pr6O11 addition on properties of Mg2SiO4-MgO composite sand prepared from magnesite tailings
To improve the comprehensive utilization rate of magnesite tailings and solve the problem of ac-cumulation pollution,Mg2SiO4-MgO composite sand was prepared by the solid phase method with flotation magnesite tailings as the raw material and analytically pure Pr6O11 as the additive,firing at 1 600 ℃ for 3 h.The effects of the Pr6O11 addition(0,1％,2％,3％and 4％,by mass)on the phase composition,micro-structure and physical properties of the composite sand were studied.The results show that:(1)the main crystal phase of the fired samples is Mg2SiO4,and the secondary crystal phases are MgO and MgAl2O4;when the Pr6O11 addition is≥2％,Ca2Pr8(SiO4)6O2 is formed;(2)Pr6O11 can promote the growth of Mg2SiO4 crystals and replace low melting point CaMgSiO4 with high melting point Ca2Pr8(SiO4)6O2,which gradually improves the thermal shock resistance of the composite sand with the increase of the Pr6O11 ad-dition;(3)the proper Pr6O11 addition promotes the sintering and improves the cold modulus of rupture of the specimen;and the specimen with 2％Pr6O11 shows the best performance with the bulk density of 3.03 g·cm-3,apparent porosity of 5.4％,cold modulus of rupture(CMOR)of 65.2 MPa,residual MOR reten-tion ratio of 34.5％,and good thermal shock resistance.
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