煅烧
微观结构
材料科学
鳞片岩
烧结
扫描电子显微镜
磷酸铁
化学工程
无定形固体
涂层
降水
冶金
磷酸盐
矿物学
针铁矿
复合材料
结晶学
化学
吸附
催化作用
生物化学
物理
有机化学
气象学
工程类
作者
Margita Kabátová,Eva Dudrová,Helena Bruncková
摘要
Carbonyl iron powder was coated with phosphate layer using phosphating precipitation method. The phosphated powder was dried at 60 °C for 2 h in air and heat treated by calcination at 400 and 800 °C for 3 h in air. Cylindrical specimens density of ~6.5 g.cm −3 based on iron phosphated powder calcined at 400 °C were sintered at 820, 900, 1110 °C in N 2 + 10%H 2 atmosphere and 1240 °C in vacuum for 30 min. The morphology and phase composition of the phosphate coating and sintered compacts were studied by scanning electron microscopy, atomic force microscopy (AFM) and X‐ray diffraction (XRD) analysis. Gelatinous morphology of dried phosphate coating (thickness of ~100 nm) containing nanoparticles of iron oxyhydroxides and hydrated iron phosphate was observed. From XRD, diffractogram indicated the presence of goethite α‐FeOOH, lepidocrocite γ‐FeOOH and ludlamite Fe 3 (PO 4 ) 2 .4H 2 O. The calcined phosphate coating (thickness of ~ 400 nm) contained non‐homogeneous consistency of α‐Fe 2 O 3 layer on iron particles, an inter‐layer of amorphous FePO 4 and Fe 3 O 4 top layer. The transformation to crystalline FePO 4 structure occurred during calcination at 800 °C with the presence of α‐Fe 2 O 3 forming a light top zone (rough morphology). The microstructure of compacts sintered in solid state at temperatures up to 900 °C has retained composite network character. A fundamental change in microstructure due to the liquid phase sintering occurred after sintering at temperatures of 1100 and 1240 °C. It was confirmed that the microstructure complex consists of spheroidized α‐Fe and α‐Fe 2 O 3 phases surrounded by solidified liquid phase consisting various phosphate compounds. Copyright © 2013 John Wiley & Sons, Ltd.
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