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小木虫论坛-学术科研互动平台 » 材料区 » 无机非金属 » 综合其它 » 【求助】三氧化二铁的晶体结构求助
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sunxinli

[交流] 【求助】三氧化二铁的晶体结构求助

请问三氧化二铁是什么类型的晶体结构？另还有a-氧化铁、r-氧化铁和三氧化二铁的区别是什么？各自晶体结构和性质能否提供一些。谢谢
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1楼 2009-06-09 12:40:54
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queji

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sunxinli(金币+1,VIP+0):谢谢 11-17 15:17
ferric oxide has Different forms:
Alpha phase,
Beta phase,
Gamma phase,
Epsilon phase,
and
amorphous phase.

[ Last edited by queji on 2009-6-16 at 20:47 ]
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2楼2009-06-16 20:39:01
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queji

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Alpha phase
α-Fe2O3 has the rhombohedral, corundum (α-Al2O3) structure and is the most common form. It occurs naturally as the mineral hematite which is mined as the main ore of iron. It is antiferromagnetic below ~260 K (Morin transition temperature), and weak ferromagnetic between 260 K and 950 K (Neel temperature).[1] It is easy to prepare using both thermal decomposition and precipitation in the liquid phase. Its magnetic properties are dependent on many factors, e.g. pressure, particle size, and magnetic field intensity.

[ Last edited by queji on 2009-6-16 at 20:47 ]
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3楼2009-06-16 20:39:41
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queji

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Beta phase
Cubic face centered, metastable, at temperatures above 500 °C converts to alpha phase. It can be prepared by reduction of hematite by carbon, pyrolysis of iron(III) chloride solution, or thermal decomposition of iron(III) sulfate.
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4楼2009-06-16 20:40:58
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queji

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sunxinli(金币+1,VIP+0):认真 11-17 15:17
Gamma phase
Cubic, metastable, converts to the alpha phase at high temperatures. Occurs naturally as the mineral maghemite. Ferrimagnetic. Ultrafine particles smaller than 10 nanometers are superparamagnetic. Can be prepared by thermal dehydratation of gamma iron(III) oxide-hydroxide, careful oxidation of iron(II,III) oxide. The ultrafine particles can be prepared by thermal decomposition of iron(III) oxalate.
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5楼2009-06-16 20:41:29
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queji

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sunxinli(金币+1,VIP+0):认真 11-17 15:17
Epsilon phase
Rhombic, shows properties intermediate between alpha and gamma. So far has not been prepared in pure form; it is always mixed with the alpha phase or gamma phases. Material with a high proportion of epsilon phase can be prepared by thermal transformation of the gamma phase. The epsilon phase is metastable, transforming to the alpha phase at between 500 and 750 °C. Can also be prepared by oxidation of iron in an electric arc or by sol-gel precipitation from iron(III) nitrate.
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6楼2009-06-16 20:42:22
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queji

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At high pressure, it can transform to be amorphous .
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7楼2009-06-16 20:45:24
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