Abstract: In order to prepare high-performance cordierite ceramics from fly ash,fly ash (d₅₀=4.03 μm) from a power plant,talc (≤2.6 μm),α-alumina (≤5 μm) and nano magnesia (0.1 μm) were used as raw materials to prepare fly ash-based cordierite ceramics at 1 100-1 350 ℃.The effects of the potassium fluorozirconate (K₂ZrF₆) addition (0,0.5%,1% and 1.5%,by mass) on cordierite phase transition,the physical properties and the microstructure of fly ash based cordierite ceramics were studied.The results show that with the firing temperature of 1 300 ℃,as the K₂ZrF₆ addition increases from 0 to 0.5%,the bulk density of samples increases from 1.82 g·cm^-3 to 2.02 g·cm^-3,the cold compressive strength increases from 342 MPa to 511 MPa,and the average thermal expansion coefficient from room temperature to 800 ℃ reduces to 2.48×10^-6℃^-1 from 3.12×10^-6℃^-1.K₂ZrF₆ promotes the phase transformation and improves the sintering performance for the reason that the reaction of K₂ZrF₆ to form zircon promotes the formation of magnesium aluminate spinel and the conversion to cordierite.In addition,the hydrogen fluoride gas generated in the decomposition process reacts with some solid phases,which improves the fluidity of the hot melt produced in the calcination process and promotes the liquid-phase sintering of the material.

Key words: cordierite, fly ash, phase transition, thermal expansion coefficient

摘要： 为了利用粉煤灰制备高性能的堇青石陶瓷,以电厂粉煤灰(d₅₀=4.03 μm)、滑石(≤2.6 μm)、α-氧化铝(≤5 μm)及纳米氧化镁(≤0.1 μm)为原料,经1 100~1 350 ℃热处理制备了粉煤灰基堇青石陶瓷试样。研究了分别添加质量分数0、0.5%、1%和1.5%的氟锆酸钾对粉煤灰基堇青石陶瓷的物相转变、物理性能以及显微结构的影响。结果显示,当烧成温度为1 300 ℃,氟锆酸钾的添加量(w)从0增加至0.5%时,粉煤灰基堇青石陶瓷试样的体积密度由1.82 g·cm^-3提高至2.02 g·cm^-3,耐压强度由342 MPa增加至511 MPa,室温到800 ℃ 的平均热膨胀系数由3.12×10^-6℃^-1降低至2.48×10^-6℃^-1。氟锆酸钾促进物相转变及改善烧结性能的原因在于氟锆酸钾生成锆英石的反应促进了镁铝尖晶石的生成及其向堇青石的转化;分解过程中生成的氟化氢气体与部分固相反应,提高了煅烧过程中高温熔体的流动性,促进了材料的液相烧结。

关键词: 堇青石, 粉煤灰, 物相转变, 热膨胀系数