硅微粉对ρ-Al_2O_3结合莫来石浇注料的影响

Effect of Silica Powder on ρ-Al_2O_3 Bonded Mullite Castables

以各种粒度烧结莫来石做骨料,以棕刚玉细粉和氧化铝微粉为基质,以ρ-Al2O3微粉为结合剂,制备了莫来石浇注料,研究了不同硅微粉加入量对浇注料性能的影响,并借助XRD、SEM等对其物相和显微结构进行检测。结果表明:随着硅微粉量的增大,浇注料强度呈现先升高后降低的变化规律,高温抗折强度在硅微粉加入量为6%时达到极值。主要原因在于:硅微粉加入适量能形成液相促进烧结,并在基质中形成较多莫来石,提高了高温强度;硅微粉加入过多时,产生过烧结,在试样中产生大量液相并形成较多裂纹,又使得高温抗折强度降低。

Mullite based castables were prepared by using sintered mullite with various particle size as aggregates,brown corundum fines and alumina micropowder as matrix,and ρ-Al2O3 as a binder. The effects of different silica powder additions on room temperature physical properties and hot modulus of rupture（ HOMR） were investigated. X-ray diffraction（ XRD） and scanning electron microscopy（ SEM）were adopted to characterize the phase composition and microstructure. The results show that with silica powder increasing,the strength of the castables first increases and then decreases,and the HOMR reaches a maximum at 6% silica powder addition. The main reason is that an appropriate silica powder addition could yield liquid phase contributing to sintering and produce more mullite in the matrix enhancing the HMOR. Excess silica powder will make the material over-sintered and considerable liquid phase and more cracks formed,which in turn decreases the hot modulus of rupture.