Synthesis And Application Of Al-C-X(X=Si,B)ternary Carbide

The ternary carbides Al-C-X?X=Si,B?have advantages of high melting point,low density,good oxidation resistance and good hydration resistance.They will be widely used in refractories and high temperature ceramics in the future.The best two ternary carbides were studied in this paper,including the synthesis of Al₄SiC₄,the effect of Al₄SiC₄ on the sintering of Si C,and the effect of Al₈B₄C₇ on phase composition,microstructure,mechanical properties,oxidation resistance and slag resistance in Al₂O₃-C refractories.?1?The effect of adding MgO on the synthesis of Al₄SiC₄ was studied.When the sintering temperatue was the same,with the increasing of MgO,the relative diffraction peak intensity of Al₄SiC₄ decreased,and the relative diffraction peak intensity of Al₄O₄C increased.MgO promoted the synthesis of Al4O4 C and reduced the amount of Al₄SiC₄.When the sintering temperatue was 1600?,the grain shape of Al₄SiC₄ was not complete.When the sintering temperatue was 1700?,without adding MgO,the grain shape of Al₄SiC₄ was the regular hexagona.And the grain surface was smooth.After adding MgO,the grain shape of Al₄SiC₄ turned to irregular.?2?The effect of Al₄SiC₄ on the sintering of SiC was studied.When the sintering temperature was lower than 2100?,in the same temperature,the density and the flexural strength of SiC increased with the increasing of Al₄SiC₄.When the sintering temperature was 2100?,the density and the flexural strength of SiC increased first and then decreased with the increasing of Al₄SiC₄.Adding the same Al₄SiC₄,the increase of temperature was beneficial to the density and the flexural strength of SiC.When the sintering temperature was 2100? the amount of adding Al₄SiC₄ was 5wt%,the flexural strength of SiC was the largest.?3?The effect of Al₈B₄C₇ on properties of Al₂O₃-C refractories was studied.When Al₈B₄C₇ replaced B4 C,the addition of Al₈B₄C₇ reacted with N₂.The reaction increased the amount of AlN whisker in the material.The staggered growth of AlN whisker and SiC whisker enhanced the mechanical properties and the flexural strength of the material.When Al₈B₄C₇ replaced Al and Si,the amount of AlN whisker was reduced,moreover,SiC whisker could not be formed in the material.As the lack of enhancement effect of whiskersthe,the flexural strength and the crushing strength decreased.On the other hand,when B4 C,Al and Si were gradually replaced by Al₈B₄C₇,the oxidation resistance of the material decreased,and the slag resistance of the material enhanced.