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Titania Nanotubes for Hydrogen Sensors?
Roland Piquepaille writes "Everybody is talking about carbon nanotubes these days. But what about titania nanotubes? Penn State researchers think they have a great potential for sensing hydrogen . According to this news release, "titania nanotubes are 1500 times better than the next best material for sensing hydrogen and may be one of the first examples of materials properties changing dramatically when crossing the border between real world sizes and nanoscopic dimensions, according to a Penn State materials scientist." And now, the very good news: titania nanotubes are cheap. So they'll be used in industrial quality control in food plants and as weapons against terrorism. My summary contains some more details."
Yeah awful stuff found in everything from mints to plastic and coats your car with a film of white powder if its parked within 600 miles of a processing plant.
ASCII CLI question getty CLI ANSI.
You /.ed the Wikipedia.
Although I don't know what the process is, the fact that titania is a ceramic means that there is probably some creative chemical conditions in which these things practically make themselves (sol-gel process, maybe). Ceramics are generally covalent networks--each atom is connected to the next with a bond like those which hold hydrogens to oxygens in water--and so by changing the conditions under which the titanium oxidizes, you probably have fairly good control over the size/shape of the final result. Not so with carbon nanotubes, which were originally manufactured pretty much by sifting through ashes...with an electron microscope. I know there are some more creative ways to make carbon nanotubes now, but most of them are still based on chance.
Maybe someone who has actually received a BS in Materials Science wants to back me up, or correct me?
This side up.
You need to get your BS sensor checked; the research is real and legitimate.
Here's a reference to the original article, which is available online:
2003 Craig A. Grimes, Keat G. Ong, Oomman K. Varghese, Xiping Yang, G. Mor, Maggie Paulose, Chuanmin Ruan, Elizabeth C. Dickey, Michael V. Pishko, James W. Kendig and Andrew J. Mason, "A Sentinel Sensor Network for Hydrogen Sensing," Sensors, vol. 3, pp. 69-82. PDF format
Simple, hydrogen molecules in explosives give off distinct hydrogen emmision signatures, hydrogen concentration loss has a very specific profile when used in combination with nitrogen in explosives. This is very quantifiable. It is also why older explosives became unstable over time. The loss of hydrogen molecules over time caused decay separation of the explosive component and the buffer. Some explosives even give off amonia, and some are made with it, Amex for example, the stuff used by Timothy McVie. If better explosive detection devices can come from this tech great! Then there is one more hurdle for social disfunctional maniacs to overcome.
OH THE SHAME I fell off the wagon and use sigs again!
A lit match works for hydrogen detection as well as many gas hydrocarbons.
Actually, Hydrogen requires a higher fuel to air ratio than gasoline. It also disperses nearly instantly(well, except in confined/sealed areas of course)- whereas gasoline etc sink and pool(which is why your natural gas/propane water heater has that nice little picture of a gasoline can etc).
Oh, and since it's still not known enough- the Hindenburg burned because it was painted with the chemical equivalent of rocket fuel(the chemical composition of the paint etc is very close to solid rocket fuel)- not because it was full of Hydrogen, which, by itself, doesn't burn.
When it DOES burn, it burns a)instantly b)practically invisibly, c)with no smoke. Watch those films of the hindenburg, and note the a)slow b)bright yellow c)sooty fire.
It's interesting to note that hydrogen's qualities make it much safer should there be, say, an accident with a truck carrying it. It dissipates as it leaks, versus the major fire hazard/toxic waste problem created by a gasoline spill.
Please help metamoderate.
There are two things that are of help here. Firstly is the size of the tubes, when you are in the nano- or pico- regimes, there are a lot more surface features (corners, edges) per atom than there are in the bulk metal. As most reactions (catalytic or non catalytic) occur on surface features, having as many small particles as possible makes sense.
The other factor that is a help here is that the oxide is used. Introducing impurities into metal (consider the oxygen an impurity) does two things, changes the electron affinity of the metal so it can bind ligands better (or worse - also useful) and introduces point 'defects' - places where the crystal lattice is interrupted. These 'defect' sites actually provide reaction points for in this case, hydrogen.
Nice piece of chemistry!
Titanium dioxide (sometimes called "titania") is one of the most common pigments for white paint (now that lead in paint is a Bad Thing). It costs maybe a dollar per pound, bulk.
I didn't see any links to the sources yet on the blog or the article so here is the homepage for Dr. Craig A. Grimes. There are two recent pdfs about the titania nanotubes on his publications page.
(1) The press release isn't particularly well done; most aren't.
(2) The articles mentioned in the press release (which were the important part of the release) are rather better. Of course, these also assume that the reader has at least some understanding of what "titania nanotubes" are, and that the specific rules for covalent bonds applicable to carbon don't mean all that much for transition metal oxides.
(3) Combustion "doesn't result in any hydrogen"? Perhaps, but how will we know without sensors that can detect trace (sub-ppm) levels of hydrogen in the exhaust?
These sensors aren't all that novel (as the S&A-B article at least points out, several other gas sensors based on a resistance change in a metal/metal oxide semiconductor have been developed), but they're relatively easy to prepare and don't poison easily - so it's at least moderately impressive. So, yes, they do exist, and the press release is where most or all of the BS is to be found.
The price of raw titanium usually hovers around 40 cents US/pound, actually. Because it melts at 3000 degrees F, however, it's difficult to work into usable pieces, hence raising the price. Titanium shavings/scrap are much cheaper than finished bar/plate stock. It also has a reputation for being difficult to machine, which it's not; merely counterintuitive.
Titanium is expensive because it is very difficult to extract from the oxide form. The oxide form itself is very cheap. It is the main ingredient in house paint.
Curtains for windows?