针对纳米SiO_2多孔绝热材料高温收缩问题,采用纳米γ-Al_2O_3作为添加剂,研究了煅烧温度和γ-Al_2O_3添加量对绝热材料体积收缩率的影响,以及γ-Al_2O_3的引入对材料绝热性能的影响.结果表明:煅烧温度越高,纳米SiO_2多孔绝热材料体积收缩越严重.γ-Al_2O_3的引入能明显降低绝热材料的高温体积收缩率,当添加量为5%(质量分数)时,1 000℃体积收缩率从10.49%下降至3.47%,随着添加量的增加,抑制体积收缩效果越明显.在高温环境下,γ-Al_2O_3的引入对纳米SiO_2多孔绝热材料绝热性能影响较小.此外,通过固体烧结动力学理论以及XRD、FESEM等表征方法阐释了γ-Al_2O_3抑制高温收缩机理.
γ-Al_2O_3 as an additive was adopted into nano silica porous thermal insulating material to reduce the volume shrinkage at higher temperatures. The effects of sintering temperature and mass ratio on volume shrinkage were investigated, and the effect of γ- Al_2O_3 on thermal insulating properties was also analyzed. The results show that the volume shrinkage strongly increases with temperature, and the additive of γ- Al_2O_3 can significantly reduce the vol-ume shrinkage. When the mass ratio is 5%, the volume shrinkage decreases from 10.49% to 3.47% at 1 000℃. Moreover, better result can be achieved with increase of mass ratio. Meanwhile, γ- Al_2O_3 has little influence on thermal conductivity at higher temperatures. Finally, the mechanism of shrinkage restraint is illuminated by the kinet-ics of solid sintering and characteristic methods of XRD and FESEM.
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