Two-step growth of goethite from ferrihydrite
Two-step growth of goethite from ferrihydrite
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DOI：
10.1021/la051883g
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发表时间：
2006-01-03
期刊：
影响因子：
3.9
通讯作者：
Penn, RL
中科院分区：
文献类型：
--
作者：
Burleson, DJ;Penn, RL
针铁矿（α - feooh）是一种反铁磁性的氢氧化铁，通常由均相水溶液中沉淀后时效合成。本文研究了六线水合铁纳米颗粒向针铁矿的相变以及针铁矿原生颗粒定向聚集的过程。数据跟踪针铁矿纳米晶体的生长作为一个函数的pH，温度和时间提出。一般来说，在较高的pH值和较高的温度下，定向聚集的针铁矿生长速度更快，即使随着pH值的增加，粗化的生长变得越来越重要。此外，粒径测量表明，初级纳米颗粒在奥斯特瓦尔德成熟过程中生长，即使它们正在被定向聚集消耗。最后，采用微波退火步骤制备前驱体六线水合铁纳米颗粒，大大提高了最终针铁矿产品的均匀性。最终的针铁矿纳米颗粒是未聚集的针状晶体，尺寸在几十纳米范围内。这些颗粒可能是理想的矿物液晶和磁记录介质的应用。
Goethite (alpha-FeOOH) is an antiferromagnetic iron oxyhydroxide that is often synthesized by precipitation from homogeneous, aqueous solution followed by aging. This paper addresses goethite growth by phase transformation of six-line ferrihydrite nanoparticles to goethite followed by oriented aggregation of the goethite primary particles. Data tracking goethite nanocrystal growth as a function of pH, temperature, and time is presented. In general, goethite growth by oriented aggregation is faster at higher pH and at higher temperature even as growth by coarsening becomes increasingly important as pH increases. In addition, particle size measurements demonstrate that the primary nanoparticles grow by Ostwald ripening even as they are being consumed by oriented aggregation. Finally, the use of a microwave anneal step in the preparation of the precursor six-line ferrihydrite nanoparticles substantially improves the homogeneity of the final goethite product. Final goethite nanoparticles are unaggregated, acicular crystals in the tens of nanometers size range. These particles may be ideal for mineral liquid crystal and magnetic-recording media applications.