Tuesday, 24 July 2012

Thermochromic glass (III)

I'm always afraid to publish the material I found on the net, especially if it's in articles.
I found at the site http://www.hindawi.com that, in his articles it writes:
    ""Copyright © 2012 This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

You are free:
to Share — to copy, distribute and transmit the work
to Remix — to adapt the work
to make commercial use of the work

Under the following conditions: Attribution — You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work. ""
So I think I'm free to report some articles.
If someone know more about this License, please contact me.
Well, today I talk about the vanadium doping with tungsten (finally)!
To do this, I use the article http://www.hindawi.com/journals/jnm/2012/491051 [I].
Repeating the first concept already expressed before, as the basis of thermochromism:
""[..] At temperatures ranging from −147°C to 68°C VO2 materials show the fully reversible phase transition between monoclinic VO2 (M) and tetragonal rutile phase VO2 (R) fascinatingly around 68°C. [..]

Furthermore, the phase transition temperature can be adjusted to near room temperature by doping, which is realized by the incorporation of metal ions into the VO2 lattice. Tungsten, molybdenum, chromium, titanium, fluorine, and niobium, and so forth are frequently used for this purpose because they produce relatively larger TC shifts with less dopant concentrations. [..]

TC is the transition temperature.

    ""So far, as an intelligent window material, the study of W-doped VO2 mainly focused on thin films and nanoparticles. It has been prepared by a variety of methods involving excimer-laser-assisted metal organic deposition (ELAMOD) , magnetron sputtering , chemical vapor deposition (CVD) , pulsed laser deposition (PLD) , and vacuum evaporation . However, all of these methods are not suitable for putting into practice because of complex control parameters, unstable technology, and the necessity of special and expensive equipment . Chemical solution deposition seems to be an alternative solution to the above problems due to its low cost and the option of metal doping. But this method usually requires specific raw materials or pretreatments which limit their practical applications . [..] In this paper, we report a simple solution-based process to prepare pure VO2 and W-doped VO2 nanopowders with cheap and nontoxic vanadium (V) precursors and short reaction times. ""

Here it is introduced ELAMOD.
-) What is the process?On http://staff.aist.go.jp/t-nakajima/research-e.html we read:

    ""The ELAMOD is the process which applies the laser energy instead of high temperature. At first, metal-organic solution is spin-coated onto a substrate, and then the film is pre-heated to decompose organic components, if needed. Finally, the film is directly irradiated by excimer laser. This method is very useful for low-temperature fabrication. [..] So this process is enable to fabricate thin films onto the substrate which are weak against high temperature such as Si and glass. Moreover, the patterning can be also easily realized since the film is crystallized at only laser irradiated region. Thus, the ELAMOD process is quite prospective for its application potentials.""

[I] : Lihua Chen, Chunming Huang, Gang Xu, et al., “Synthesis of Thermochromic W-Doped VO2 (M/R) Nanopowders by a Simple Solution-Based Process,” Journal of Nanomaterials, vol. 2012, Article ID 491051, 8 pages, 2012. doi:10.1155/2012/491051

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