Effects Of Rare Earth Oxides On The Properties And Microstructure Of Magnesia Refractory

The special features of basic reractories and the status of rare earth oxides applied to high temperature structure ceramics and refractories has been introduced, and the effects of rare earth oxides on the properties of magnesia and periclase-spinel refractories has been investigated in this paper. Microstructure and phase composition of prepared samples has been observed by XRD, SEM, EDS measurements.The effects of rare earth oxides on sinterability, mechanical properties and high-temperature properties of Magnesia refractories has been investigated with fused magnesite and four rare earth oxides powder, including Y₂O₃, La₂O₃, Nd₂O₃ and CeO₂ , as raw materials. The results showed that: (1)The samples of magnesia refractories with right contents of rare earth oxides have a positive effectiveness on the sinterabilty and densification behavior. (2)The initial high temperature deformation under load of the samples without or with right content rare earth oxides are above 1600℃. (3)Compared with the samples without any rare earth oxide, the high temperature bending strength of the samples with 1Wt% Y₂O₃ contents reached to 11.01MPa at 1400℃, showed good high-temperature mechanical properties; while right La₂O₃ or Nd₂O₃ can also increase high temperature bending strength of samples, but not very greatly; CeO₂ could hardly show a positive effect on the property. (4)The fact that the residual bending strength rate of the samples with 1 Wt % Y₂O₃ contents reach to 90.1% via five times heating-cooling circle process on the condition ofΔT=1100℃indicated their thermal shock resistance improved greatly; while the other rare earth oxides were not advantageous to thermal shock resistance of samples. (5) Sintering temperature didn′t always improve some properties of the samples ; composite rare earth oxides were advantageous to improving high-temperature bending strength of magnesia refractories; (6)According to the results of phase analysis by XRD, some reactions happened to some extent between rare earth oxides and the impurities from magnesia. From the microanalysis results by SEM and EDS, some rare earth silicate phase existed between the periclase grains of sintered samples.The effects of rare earth oxides on sinterability, mechanical properties and high-temperature properties of periclase-spinel refractories has also been investigated with fused magnesite, corundum powder and four rare earth oxides, including Y₂O₃, La₂O₃, Nd₂O₃ and CeO₂ , as raw materials in this paper. In the process of sintering, MgO and Al₂O₃ reacted into spinel. Testing datas showed that rare earth oxides can improve the sintering property of the samples of periclase-spinel refractory materials; rare earth oxides were advantageous to the formation and growth of spinel and the thermal shock resistance of periclase-spinel refractory...