Denser nanofibre composites
A Dutch organization claims to have found a way to make dense carbon nanofibre composites. In European Patent EP 1 589 131, Utrecht-based Stichting voor den Technische Wetenschappen, says the composites have densities of at least 800 kg.[m.sup.-3].
Following decomposition of a hydrocarbon, the carbon nanofibres are formed on the surface of a supported metal catalyst based on nickel, cobalt, iron and ruthenium or combinations and/or alloys of these metals.
For instance, the Patent says that carbon nanofibres have been produced using catalytic decomposition of carbon monoxide (CO) in the presence of hydrogen on two nickel/silicon dioxide (Ni/Si[O.sub.2]) growth catalysts
(with 5 and 20% by weight of Ni). The Ni/Si[O.sub.2] catalysts were prepared via homogeneous deposition precipitation using silica (Degussa’s Aerosil 200) and nickel nitrate and urea (both from Acros). After deposition, the catalyst precursor was filtered and dried at 120[degrees]C overnight.
After drying, a sieve fraction of 425-850 [micro]m was calcined in situ in air at 600[degrees]C for 3 h (at a heating rate of 5[degrees]C.[min.sup.-1]). After this about 5 g Ni/Si[O.sub.2] was reduced in situ in 20% volume of [H.sub.2] in nitrogen ([N.sub.2]) for 2 h at 700[degrees]C.
After cooling to 550[degrees]C, a gas mixture of 20% volume CO and 7.5% volume [H.sub.2] in [N.sub.2] was passed through the catalyst. After the growth, the reactor was cooled to room temperature, flushed with nitrogen and the resulting product was collected.
For further information, see: European Patent EP 1 569 131, or contact. Stichting voor de Technische Wetenschappen (Stichting voor Fundmenteel Onderzoek der Materie),Van Vollenhovenlaan 661, 3527 JP Utrecht, The Netherlands. Tel. +31-30-6001-211. Fax. +31-30-6014-408. E-mail. email@example.com; http://www.stw.ni
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