Synthesis and Characterization of Bulk a''-Fe16N2.
Synthesis and Characterization of Bulk a''-Fe16N2.
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DOI：
10.1016/0925-8388(94)04901-7
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发表时间：
1995-05
期刊：
影响因子：
--
通讯作者：
K. Jack
中科院分区：
文献类型：
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作者：
K. Jack
对α″-Fe_（16）N_2薄膜磁矩的争议使得对块体材料的研究成为必要。在最初的1951年批量制备中，通过氮化α-Fe在700-750 °C下制备的N-奥氏体（γ）淬火得到N-马氏体（α′），然后在120 °C下长时间回火得到α″;最终产品含有低于50%的α″。最近在三个不同的实验室中进行的重复实验给出了不同数量的α″，同样低于50%，其评估的磁矩有相当大的变化。对α′回火的X射线衍射研究，以及对过饱和N-铁素体（α）中α″沉淀的透射电子显微镜研究表明，只有在α′和α的局部区域通过成簇过程达到Fe 8 N成分后，N原子才缓慢有序化产生α″。α′-Fe 8 N具有与α″相同的四方性ca，但不具有Fe 16 N2的N有序特性。α′-Fe_8 N →α″-Fe_（16）N_2的范围解释了磁性的变化。指出了α″-碳氮化物Fe_（16）（C，N）_2的存在，并提出了包括合金化在内的制备纯体α″的可能方法。
Controversy about the magnetic moment of α″-Fe16N2thin films makes it necessary to examine bulk material. In the original 1951 bulk preparation N-austenite (γ) prepared by nitriding α-Fe at 700–750 °C was quenched to give N-martensite (α′) which then gave α″ on long tempering at 120 °C; the final product contained less than 50% α″. Recent repetition in three different laboratories gave various amounts of α″, again less than 50%, with considerable variation in its assessed magnetic moment. X-ray diffraction studies of α′ tempering, and also transmission electron microscopy of α″ precipitation from supersaturated N-ferrite (α), showed that slow ordering of N atoms to produce α″ occurs only after localized regions of α′ and α reach the Fe8N composition by a clustering process. α′-Fe8N can be obtained with a tetragonality c a equal to that of α″, but without the N-ordering characteristic of Fe16N2. The range α′-Fe8N→α″-Fe16N2offers an explanation for the variability in magnetic properties. The existence of the α″-carbonitride Fe16(C, N)2is noted and possible methods, including alloying, for the production of pure bulk α″ are suggested.