: Fly ash is an aluminosilicate and the major by‐product from coal combustion in power stations; its increasing volumes are major economic and environmental concerns, particularly since it is one of the largest mineral resources based on current estimates. Mullite (3Al₂O₃·2SiO₂) is the only stable phase in the Al₂O₃‐SiO₂ system and is used in numerous applications owing to its high‐temperature chemical and mechanical stabilities. Hence, fly ash offers a potential economical resource for mullite fabrication, which is confirmed by a review of the current literature. This review details the methodologies to utilise fly ash with different additives to fabricate what are described as porous interconnected mullite skeletons or dense mullite bodies of approximately stoichiometric compositions. However, studies of pure fly ash examined only high‐Al₂O₃ forms and none of these works reported long‐term, high‐temperature, firing shrinkage data for these mullite bodies. In the present work, high‐SiO₂ fly ashes were used to fabricate percolated mullite, which is demonstrated by the absence of firing shrinkage upon long‐term high‐temperature soaking. The major glass component of the fly ash provides viscosities suitably high for shape retention but low enough for ionic diffusion and the minor mullite component provides the nucleating agent to grow mullite needles into a direct‐bonded, single‐crystal, continuous, needle network that prevents high‐temperature deformation and isolates the residual glass in the triple points. These attributes confer outstanding long‐term dimensional stability at temperatures exceeding 1500°C, which is unprecedented for mullite‐based compositions.

中文翻译：

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粉煤灰在莫来石加工中的利用：新型渗滤莫来石的开发

：粉煤灰是一种铝硅酸盐，是发电厂燃煤的主要副产品；其增加的数量是主要的经济和环境问题，特别是因为它是目前估计的最大矿产资源之一。莫来石（3Al ₂ O ₃ ·2SiO ₂）是Al ₂ O ₃ -SiO _2中唯一稳定的相系统由于其高温化学和机械稳定性而被广泛用于各种应用中。因此，粉煤灰为莫来石制造提供了潜在的经济资源，这一点可通过对当前文献的回顾得到证实。这篇综述详细介绍了利用粉煤灰与不同添加剂来制造所谓的多孔相互连接的莫来石骨架或近似化学计量组成的致密莫来石体的方法。但是，纯粉煤灰的研究仅检查了高Al ₂ O ₃形式，而这些工作均未报道这些莫来石体的长期高温烧成收缩数据。在目前的工作中，高SiO ₂用飞灰制造渗滤的莫来石，这在长期高温浸泡后没有烧成收缩现象得到了证明。粉煤灰的主要玻璃成分提供的粘度适合形状保持，但粘度足够低，足以进行离子扩散，次要的莫来石成分则提供成核剂，使莫来石针长成直接键合，单晶，连续的针状网络，从而防止了高温变形，将残余玻璃隔离在三个点上。这些特性赋予了其在超过1500°C的温度下出色的长期尺寸稳定性，这对于莫来石基组合物而言是前所未有的。