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xbg2080

铜虫 (正式写手)

[交流] How to synthesize nanocrystal in the range of 30~100nm.

i wanna synthesize nanocrystal of Fe304 with 30~100nm.
the majority of literatures have reported the preparation of Fe304 nanocrystal with ~5% of standard deviation in size. but their size is too small, basically ~10nm, at most 20nm.   

so i desire to prepare nanocrystal in size >30nm. this size range of nanocrystal with ~5% of standard deviation is very rare in literatures reported.
who can propose new methods to do it except the seed-mediate method in literature?
Hope to discusse it.

i hv ever consulted a Korean author. He replied as follows:
___________________________________________
Actually, we don't have tried much to synthesize nanocrystals larger than 20 nm. So we have little kowledge from our experiences to anwer your question.

Theoritically, the difference between the surface free energies of a highly curved surface and a flatter surface is the driving force to redistribute the crystal monomers to result spherical shape on which the surface curvature is identical at all points. This redistribution process proceeds via intra- or inter-particle ripening. When a nanocrystal gets larger, its surface curvature decreases and so does its surface free energy. As a result, the driving force which leads to spherical shape of the particles is reduced, too. In my opinion, this might be the reason for the difficulties in synthesizing large spherical particles.

Regards,
권순구 Hyeon.
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taijun_2008

木虫 (著名写手)

Alchemist

这种由表面曲率差异导致的驱动力是不是就是Ostwald老化?
[url=http://weibo.com/1438083415?s=6uyXnP][img]http://service.t.sina.com.cn/widget/qmd/1438083415/006db0cc/5.png[/img][/url]
2楼2007-11-10 20:26:14
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xbg2080

铜虫 (正式写手)

Ostwald ripenning means larger particle will grow at the expense of consumption of smaller particle. generally the higher solubility, the smaller particle. this is general explanation.
3楼2007-11-12 16:38:08
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