Mechanism And Performance Of Oxide And Non-oxide Composite Powders Prepared By Forsterite And C

The forsterite is an excellent refractory, the most important character is that it has high refractoriness under load. The ability of resistance to iron oxide,metallic melts and slag erosion at the high temperature is strong, and forsterite has some excellent properties, such as unhydration, stable chemical and mineralogical properties, with most refractory material has good chemical compatibility, and suit for refractory, metallurgical furnace, foundry sand ceramic coating etc.In our present work, the most synthesis system of the MgO-SiC-C oxide and non-oxide composite powders were obtained by using forsterite and carbon black powders which as the starting materials in nitrogen and argon atmospheres. Because appeared a problem of magnesium loss seriously during synthesis process, in basis to join alumina or bauxite transformed into MgAl₂O₄ oxide refractory materials, so as to control the loss of magnesium, and make full use of forsterite raw materials. In addition, we have researched the sintering property and oxidation resistance of the MgO-SiC-C composite materials.By analyzing the experimental results, we got some conclusions as follows:(1) The MgO-SiC-C compound powders could be synthesized well at 1650℃under the A1and A2 formula at the argon atmosphere, in which the molar ratio of Mg₂SiO₄/C was 1:5 and 1:6. When the temperature achieves 1700℃, raw materials react exactly, and the synthetic effect of MgO-SiC-C achieved best. When the temperature achieves 1750℃, the crystal shape of SiC changed and MgO disappeared, So this sintering temperature was unfavorable for the synthesis reaction. The MgO-SiC-C compound powders could not be synthesized well at 1650℃and 1700℃under nitrogen atmosphere, but the sample of A2 appeared the phase of Si₃N₄ at 1700℃. Showed that the argon atmosphere more advantageous to reaction than the nitrogen atmosphere。(2) The MgAl₂O₄-SiC-C compound powders could be synthesized with adding the theory mole ratio of Al₂O₃, When the temperature achieves 1700℃, the synthetic effect of MgAl₂O₄-SiC-C achieved best under the A3 formula, showed that increase the content of the carbon is avorable to the reaction.when adding a spot of bauxite, showed the best crystallization in the A3 sample sintered at 1650℃. MgAl₂O₄ crystal was molten state, patches of FeSi appeared in the sample sintered at 1700℃, when the temperature increased, the shape of SiC will not be affected.(3) When research MgO-SiC-C composite materials sintering performance, could found the samples was porous, not enough compact before sintering. After sintering, the porosity of sintered samples significantly reduced, bulk density increased, compressive strength has greatly improved. It showed that effectively promoted the densification of materials and improved performance by sintering.(4) Preliminary study MgO-SiC-C composite materials properties, the A1 and A2 samples start oxidated at about 1200℃which sintered at 1650℃and 1700℃at the argon atmosphere, from TG curve,the weight increment of the A1sample were relatively smaller at different temperature, So showed that A1 sample had better the oxidation resistance.