Halloysite: Difference between revisions
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==Applications== |
==Applications== |
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A very pure halloysite is mined from an highly altered [[rhyolite]] occurrence in [[New Zealand]] uses include [[porcelain]] |
A very pure halloysite is mined from an highly altered [[rhyolite]] occurrence in [[New Zealand]] uses include [[porcelain]] and [[bone china]]. <ref>http://www.halloysite.com/index.htm</ref> Various patents exist for the use of hallosyite as nanofillers <ref>US patent #3467618, http://www.google.com/patents?id=tbh0AAAAEBAJ</ref> and in controlled release technology for a range of active agents.<ref>http://www.azonano.com/news.asp?newsID=1935</ref><ref>US patent #5651976, http://www.google.com/patents?id=KTkcAAAAEBAJM</ref> It is also used for other high-tech [[ceramic]] applications. |
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Halloysite also has been used as a petroleum cracking catalyst in the past, <ref>US Patent #3515682, http://www.google.com/patents?id=Gs8hAAAAEBAJ</ref>. Exxon has also developed a cracking catalyst based on synthetic halloysite<ref>US Patent #4150099, http://www.google.com/patents?id=ROY8AAAAEBAJ</ref>. |
Halloysite also has been used as a petroleum cracking catalyst in the past, <ref>US Patent #3515682, http://www.google.com/patents?id=Gs8hAAAAEBAJ</ref>. Exxon has also developed a cracking catalyst based on synthetic halloysite<ref>US Patent #4150099, http://www.google.com/patents?id=ROY8AAAAEBAJ</ref>. |
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Revision as of 10:54, 29 September 2007
Halloysite is a 1:1 aluminosilicate clay mineral with the empirical formula Al2Si2O5(OH)4. Its main constituents are aluminium (20.90%), silicon (21.76%), and hydrogen (1.56%). Halloysite typically forms by hydrothermal alteration of alumino-silicate minerals. [1] It can occur intermixed with dickite, kaolin, montmorillonite and other clay minerals. X-ray diffraction studies are required for positive identification. It was first described in 1826 and named for the Belgian geologist Omalius d'Halloy.
Structure
Two common forms are found, when hydrated the clay exhibits a 1 nm spacing of the layers and when dehydrated (meta-halloysite) the spacing is 0.7 nm. Halloysite naturally occurs as small cylinders which average 30 nm in diameter with lengths between 0.5 and 10 micrometres. [2]
Applications
A very pure halloysite is mined from an highly altered rhyolite occurrence in New Zealand uses include porcelain and bone china. [3] Various patents exist for the use of hallosyite as nanofillers [4] and in controlled release technology for a range of active agents.[5][6] It is also used for other high-tech ceramic applications.
Halloysite also has been used as a petroleum cracking catalyst in the past, [7]. Exxon has also developed a cracking catalyst based on synthetic halloysite[8].
Due to its structure, it can be used as filler in either natural or modified forms in nanocomposites.
Name
The halloysite is named after Baron Omalius d'Halloy (1707-1789), who was the first observer of the mineral. [9]
References
- ^ Paul F. Kerr, FORMATION AND OCCURRENCE OF CLAY MINERALS, Clays and Clay Minerals, Volume 1, page 19-32, 1952
- ^ George W. Brindley, STRUCTURAL MINERALOGY OF CLAYS, Clays and Clay Minerals, Volume 1, page 33-43, 1952
- ^ http://www.halloysite.com/index.htm
- ^ US patent #3467618, http://www.google.com/patents?id=tbh0AAAAEBAJ
- ^ http://www.azonano.com/news.asp?newsID=1935
- ^ US patent #5651976, http://www.google.com/patents?id=KTkcAAAAEBAJM
- ^ US Patent #3515682, http://www.google.com/patents?id=Gs8hAAAAEBAJ
- ^ US Patent #4150099, http://www.google.com/patents?id=ROY8AAAAEBAJ
- ^ http://webmineral.com/data/Halloysite.shtml
Links
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