Nanotubes alumina membrane

A similar approach for the production of hydrothermal carbon nanotubes is the hydrothermal carbonization of glucose in the macrochannels of anodic alumina membranes [16]. Depending on the pore size of the membrane different hollow hydrother-... 

The Pt current collector was first used to deposit short ( 2 pm) Pt nanoposts [37,73] into the template membrane (Fig. 21A). These Pt nanoposts anchor the alumina membrane to the Pt surface and will serve to make electrical contact to the LiMu204 nanotubes. After Pt deposition, the pores in the membrane were filled with an aqueous solution that was 0.5 M in LiNOs and 1 M in Mn(N03)2 (Fig. 21B). The excess solution was wiped from the membrane surface, and the solvent (water) was removed by heating (50°C) in vacuum for 1 hour. The assembly was then heated at 500°C in air for 5 hours. This burns away the plastic tape and also causes tubules of LiMu204 to form within the pores (Figs. 21C, 22). 

Alumina nanotubes have been prepared by the anodic oxidation of aluminum [41] the resulting tubes have one-dimensional channels with uniform diameters of 5nm and lengths of 50-100 nm. An alumina membrane with a highly ordered nanohole array in 50-100 nm diameter has also been synthesized by long-period anodization thus these local alumina nanotubes have been tried as a template for metal nanowire formation. 

Imai H, Takei Y, Shimizu K, Matsuda M, Hirashima H (1999) Direct preparation of anatase Ti02 nanotubes in porous alumina membranes. J Mater Chem 9 2971-2972 Michailowski A, A1 Mawlawi D, Cheng GS, Moskovits M (2001) Highly regular anatase nanotubule arrays fabricated in porous anodic templates. Chem Phys Lett 349 1-5 Jung JH, Kobayashi H, van Bommel KJC, Shinkai S, Shimizu T (2002) Creation of novel helical ribbon and double-layered nanotube Ti02 structures using an... 

Imai H, Take Y, Shimizu K, Matsuda M, Hirashima H (1999) Direct preparation of anatase Ti02 nanotubes in porous alumina membranes. J Mater Chem 9 2971-2975... 

It should be mentioned that alternative possibilities to prepare similar membranes include the use of a porous alumina membrane as matrix, with the titania nanotubes grown in the channels. Nanoporous alumina membranes are commercial products, also synthesized by anodic oxidation. The commercial Whatman Corporation anodic membrane has holes of about 20-nm diameter at the top of the membrane and about 200-nm diameter at the bottom of membrane. Within these pores Ti02 nanotubes fabricated by template synthesis and water vapour hydrolysis could be grown, but non-uniform membrane characteristics are obtained due to the non-uniform pores of the commercial alumina... 

Yang and coworkers also used a surface imprinting approach to prepare nanotube membranes that exhibit selectivity for the molecule estrone.77 In this study, the silica nanotubes with pore diameters of 100 nm were synthesized within the cylindrical pores of nanopore alumina membranes. A covalent assembly approach was used to prepare the imprint.77 Zhang and coworkers have also recently shown how silica nanotubes can be used as an imprinting scaffold.78 In this example, trinitrotoluene (TNT)... 

Confined reactions have been used to control the size of MoS2 nanotubes. For example, MoS2 nanotubes have been grown in the voids of an anodic alumina membrane, by decomposing (NH,)2MoS4 inside the pores of the membrane.31 The membrane is dissolved by treatment with alkali to yield free tubes. This method yields large diameter MoS2 nanotubes. 

Pbres of anodic alumina have been used for the growth of coaxial nanotubes of Ti02 sheathed SiO 92 Electrochemical deposition in the pores of a polymeric alumina membrane generates arrays of Ti02 nanotubes. R>r the coaxial nanotubes, the SiOj nanotubes are first grown inside the pores of the anodic alumina membrane The Ti02 nanotubes are then grown inside the SiOj nanotubes. The existence of Ti-O-Si bonds in the amorphous sheaths is believed to play a role in the formation of these composite nanotubes... 

Mesoporous alumina membranes ( anodic aluminium oxide , or AAO) are prepared by anodic oxidation of aluminium metal [1,2]. The cylindrical pores, perpendicular to the membrane surface, form hexagonal arrays of straight non-intersecting channels with pore densities up to lO Vcm. Their diameters are controllable within the range 5 - 100 nm as a linear function of anodisation voltage. These membranes are used as molecular sieves, and have also found application as templates for metallic nanowires [3,4,5,6], metal elusters and colloids [7,8], and carbon nanotubes [9,10]. 

Aligned carbon nitride nanotubes have been fabricated in an alumina membrane using electron cyclotron resonance (EGR) plasma-assisted CVD of C2H2 [55]. The membranes have a thickness of - 50-80 pm and pore diameter of 250 nm. To promote the flow of ionic fluxes through the nanochannels of the alumina template a negative dc bias voltage was applied to the graphite substrate holder. 

Figure 1.11 (a) Stepwise production of metallic Chemical Society.) (b) Optical properties of gold nanotubules, wherethe internal surface area was nanotubes in alumina membranes at various modified with (2-cyanoethyl)triethoxysilane, sizes and lengths. (From [35] C.R. Martin, followed by electrochemical deposition and Science, 266, (1994), 1961—1966. Reprinted with removal of the alumina template. (Reprinted permission from AAAS.) with permission from Ref. [50], 1991 American... 

This section deals with a novel type of a support on which the clusters are organized into nanotubes, all oriented in the same direction - thus enabling gas-phase catalysis of a very special type. The material offering these facilities consists of nanoporous transparent alumina membranes the production of which has been described elsewhere.f " The attractiveness of the material is its ready availability and its architecture, which has 10 -10" uniform pores running in a parallel direction through the membrane, as is illustrated schematically in Fig. 7. 

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