| In this paper,magnesia-aluminum spinel powder was prepared by carbon-bed high-temperature solid-state sintering with light magnesium and alumina/boehmite/alumina-sol as raw materials,respectively,carbon black(CB)as additives,polyvinylpyrrolidone(PVP)solution as dispersant of CB.The phase composition of synthesized powders was characterized by X-ray diffraction,and the microstructure was depicted by field-emission scanning electron microscopy.The effects of alumina type and CB on the phase composition and morphology of synthesized powders were studied.Futhermore,the influence of synthesized spinel powder on the physical,mechanical properties and slag resistance of corundum refractory castables were studied.The results show that the type of alumina source has significant influence on the morphology of spinel powder.The average particle sizes of the product with both alumina and boehmite as alumina source are about 1.5 μm.However,the shape of the former is cobblestone while that of the latter is regular rhombic plate,and the boehmite was used as template on the surface to grow,implying that the spinel grows by “the template mechanism” when boehmite was used.But the average particle sizes of the product with alumina-sol as alumina source is about 2.1 μm,and it possesses a regular octahedral structure.The bulk density(BD),apparent porosity(AP),cold modulus of rupture(CMOR),cold crushing strength(CCS),thermal shock resistance and slag resistance properties of spinel containing castables were tested.It was found that withthe increase of the heat treatment temperature,the BD first decreases and then increases,but the change of AP is opposite.The CMOR of castables are about 3 MPa after heat treatment at 110 ℃ and 1100 ℃.However,the CMOR increases to about 33 MPa after sintering at 1500 ℃.While the CCS increases with the increase of the heat treatment temperature.By comparing the synthesized of spinel with different alumina sources,it was found that the CMOR value of castables which containing spinel synthesized with boehmite is higher than that of with alumina at 110 ℃ and 1100 ℃,but the strength of the two samples at 1500 ℃ is similar.After testing the thermal shock resistance of castables containing spinel synthesized with boehmite,it was found that with the increase of spinel content the thermal shock resistance of castables increases first and then decreases.The thermal shock resistance of castables with 3% spinel content is the best one.The slag resistance of castables is improved by adding spinel that was prepared with boehmite.CB additives have not significant effect on the shape of the product,but according to “the carbon hindrance effect” it can inhibit spinel sintering and growth at high temperature.CB was dispersed by PVP solution can more uniformly disperse in carbon black/spinel composite powder.The uniformly dispersed CB can significantly decrease the grain size of the product when alumina-sol was used as alumina source,and the grain size decreases from 2.1 μm to 0.6 μm.Compared with the castables containing pure spinel,it was found that the BD value of the castables increases when CB was added into samples and the AP decreases.The strength is higher than that of the castables without CB.However,when the content of carbon black/spinel composite powder increased to 3%,the strength of the castables decrease due to the oxidation reaction of CB and pore was generated in the castables after heat treatment. |
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