Effect of MgCl2·6H2O Solution on Properties of Periclase-Magnesia Alumina Spinel Refractories
Fused magnesia and fused magnesia alumina spinel were used as raw materials to prepare periclase-magnesia alumina spinel refractories,with three different concentrations of MgCl2·6H2O solution at 18 °Be′,24 °Be′ and 30 °Be′and phenolic resin as bonding agent.The effect of MgCl2·6H2O solution on cold modulus of rupture,cold crushing strength,sintering properties and thermal shock resistance of refractories was investigated by using phenolic resin as control group.The mechanisms of MgCl2·6H2O solution action on refractories were elucidated.The results show that MgCl2·6H2O solution reacts with magnesia to generate magnesium oxychloride cement(MOC)at room temperature,and the microstructure of MOC is interwoven interlocked whiskers,which makes the refractories show supervise mechanical strength after drying.The cold crushing strength of refractories reaches 79.1 MPa when the fire temperature is 1 700 ℃ and the solution concentration is 24 ° Be′,which is 58.2％higher than that of phenolic resin.The apparent porosity of refractories reduces to 16.8％when the firing temperature is 1 700 ℃ and the solution concentration is 18 °Be′,which is 13.4％lower than that of phenolic resin.The increase of MgCl2·6H2O solution concentration is beneficial to improve fracture toughness of material.MOC and Mg(OH)2 decompose to produce reactive MgO during firing process,which promotes the sintering of refractories.In addition,the quasi-spherical MgO produced by decomposition disperses and fills in the internal cracks of magnesia particles,forming a microporous structure inside refractories,which is conducive to mitigating thermal stress impact during thermal shock.
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