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« Is CRN Politically Naive? | Main | C-R-Newsletter #38 »

February 28, 2006

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Rip

Don't forget this one! It's fair to include this in your post!

"Carbon Nanotubes Pass Safety Test
Functionalized carbon nanotubes are rapidly cleared from blood, excreted in urine"


http://pubs.acs.org/email/cen/html/021506181408.html

Tom Mazanec

It may sound archaic, but how would this armor fare against bladed weapons? Police are still knifed, and maybe this armor could help them as well?

Phillip Huggan

Most armour will protect to a limited degree against any impact. But the way a blade and a bullet impact armour is very different.

Kevlar vests proect against bullets that would shatter a ceramic or MNTed diamondoid vest. You're way better off with the heavy ceramic or lightweight diamondoid version if you are about to be shivved. Just a guess, but I think this new vest is simply a better version of kevlar; wouldn't offer comprehensive protection again a blade's penetration.

Tom Mazanec

How would the diamondoid work against blunt instruments? If you put a thin coat of titanium to make it nice and shiny, you would practically have Tolkein's mithril armor.

Tom Mazanec

Sigh...never post a comment when you have to leave in a few minutes.
OK, would some kind of matrix of diamondoid and buckyballs work against both kind of weapons?

Phillip Huggan

I *think* the US military has two different types of body armour. The ceramic version is too heavy for mobile activities. Would be the same problem with titanium. I doubt it, but maybe a diamond vest hit by a bullet would fracture shards inwards and tear flesh? I'm sure even if this effect occured, that the diamond layer could be encased in another material to prevent this...

http://www-materials.eng.cam.ac.uk/mpsite/interactive_charts/strength-toughness/IEChart.html
This chart is a good comparison of Toughness and Tensile Strength for different classes of materials (though they put the ceramic group's tensile strength an order of magnitude too high). Diamond is weak where polymers like kevlar are strong and vice versa. Even if weight isn't a concern and you want both Tensile Strength and Toughness in the same material, like a metal alloy, diamond still has a role to play. Diamond aerospace parts will open up the space economy and facilitate Lunar metal mining, flooring the price of metals.

Tom Mazanec

What would be the lightest metal? Aluminum? Beryllium might be good, but is poisonous, IIRC. Magnesium is also good, but hyper-flamable once it gets started (one of the biggest magnesium fires ever occurred just a few blocks from where I was working). I suppose mithril could be one of these metals coated with titanium to protect from these disadvantages and make it light and shiny as possible.

Rip

I know next to nothing about materials science. Do you know if diamondoid, or some other molecularly manufactured material, might be good at shielding astronauts from radiation in space, e.g. cosmic rays?

You mention that diamond aerospace parts would open up the space economy. I'm just curious if anyone knows any potential solutions for the radiation problems astronauts would encounter in space.

Sigma

I know that liquid, specifically water is good at blocking radiation in space. It would probably be feasable to incorporate nano or micro fluidic channels into the diamondiod structure. I am no expert so I am I also interested in hearing other responses.

S.Karl

"Ray Baughman a professor at the university of Dallas and his team created a new material. It's stronger than steel, transparent and ver,very light. A hectare-size sheet would weigh just 280 grams..."

This was taken from a Readers Digest March 24. If you want to find out more, google his name.

Brian Wang

Rip, Sigma

Info on radiation shielding concepts.

General info on radiation shielding
http://en.wikipedia.org/wiki/Radiation_shield

Shields that reduce gamma ray intensity by 50% (1/2) include (see Kearney, ref):
9 cm (3.6 inches) of packed dirt or
6 cm (2.4 inches) of concrete,
1 cm (0.4 inches) of lead,
150 m (500 ft) of air.

weight of the shield is an issue for space. So shielding with magnets are good.
Also, water can be used since the astronauts need to take water to drink. so if you put that water around the living quarters you use the water for two purposes (shielding and drinking)

Electrostatic shielding
http://www.niac.usra.edu/files/studies/final_report/921Buhler.pdf

Superconducting Magnet Technology for Astronaut Radiation Protection
http://www.niac.usra.edu/files/studies/final_report/988Hoffman.pdf

Chris Phoenix, CRN

In outer space there aren't just gamma rays, but cosmic rays which are fast-moving nuclei. Some are quite heavy (iron) and quite energetic.

As I understand it, most radiation just does a spot of damage here and there. If you can correct the mutations, and prevent radiation-induced cell death, then you may not have to worry about it too much. But some cosmic rays will drill a big hole through tissue, like a Ronco egg scrambler--no repair would be possible for cells in the way. So cosmic rays have to be shielded, lest you slowly lose irreplaceable brain cells.

I'm not an expert in this; someone please correct me if I got it wrong.

Chris

Dan

In regards to safety of Fullerenes, balls have proven to kill fish. I can't remember where, but some lab dumped it in the river and there was a mass-death.

Since we're not good enough at making tubes the way we want them, we ought to be awefully careful. The byproducts of manufacture are demonstrably toxic.

~~~

Regarding radiation shielding, the problem is putting something other than ourselves in front of the particles flying at us. The key to doing that with little weight is a matter of molar mass/volume and regularity (we care about surface area, not volume)

Compressed hydrogen has been shown to be quite excellent at stopping most forms of radiation with almost no weight, but it's also quite dangerous in and of itself.

Using TiO2 IF with hydrogen soaked through it, one could probably create a very thin sheet of dense hydrogen without compression. I heard though that UV light scrubs the TiO2 sheeting... not sure if that includes hydrogen.

Just my two pennies.

Tom Craver

Wow! An urban legend in the birthing!

I don't believe there has ever been any "lab dumping" of buckyballs.

There was an experiment where fish (in tanks) were deliberately exposed to bucky balls, to test toxicity.

Phillip Huggan

I'm concerned about nanoparticle toxicity, but those fish died from salts that were a byproduct of CNT processing. That the CNTs killed them, was an erroneous conclusion. I think there is a certain length of CNTs; anything longer than this length CNTs become extreme toxic to humans. Can't remember if that was for skin exposure, ingestion or inhalation.

To answer Tom Mazenec's March question: yes if you hit diamond armor with a hammer (hard enough), it will shatter. But it will laugh in the face of any metal knife.
Generally soldiers always wear lightweight Kevlar armour that is effective against bullets (or hammers) and not too good against knives or shards of metal. They have ceramic armour for the latter (can protect against knives but not blunt trauma), but it is too heavy to wear on the field. Diamond armour would be light enough to wear for mobile activities.

John B

Also, see so-called "HESH" weaponry. The purpose isn't to break the armor, it's to induce a kinetic pulse that does bad things to whatever's inside the armor, possibly spalling off a piece of the inner surface of the armor as well to act as a projectile. These things aren't defeated by bulk armor, but rather by dissimilar laminar (layered) armors, such as is used in modern combat vehicles.

Finally, were there to be a 'perfect' armor material, there'd be optimization of weaponry to affect it. At least one possible in this battle include microwaves at the bond length frequency of this miracle material (or of some of its components, if it's something like a dissimilar lamillar form.)

Additionally, note something about radiation defense as listed above.

Magnets don't do diddly to EM, unless there's mass in there somewhere. Thus, 'hard' radiation (gamma & X) will go right through magfields without a care in the world. To block those, you need matter - specifically, nuclei - in the way. This is why denser materials tend to do better than less-dense materials.

Chris - to "prevent radiation-incurred cell death", by far the simplest solution I am aware of is to block the radiation.

-JB

M

The most important thing to remember is that toxicologists pretty much only get funded to research toxic materials. If they conduct a study, and find no toxic effects, well, that's kind of a funding dead end. That's why toxicologists like to use rats to test inhalation effects: rat lungs have much narrower channels than most other comparable mammals, and do not clear inhaled particulates nearly so rapidly.

Similarly, but different, this idea that underivatized fullerenes bind DNA on a computer is fine, and can in fact be used to selectively cleave and sequence DNA, but underivatized fullerenes are exceedingly hydrophobic, clump together in vivo, and proceed directly to the liver. They do not enter cells, much less the cell nucleus where the DNA is. SO, there is absolutely nothing to worry about from this non-experiment, except that some researcher somewhere is going to take some money from another researcher that could have done something worthwhile with it.

Now, regarding the fish. Actually no fish died in the study. Look, you can read the article free on line at Environmental Health Perspectives website (v.112, p.1058). What they toxicologist found was that oxidative stress in the brains was increased. (Meanwhile, oxidative stress in the gill was decreased.) Moreover, despite the claims of Prof. Colvin at Rice, no one really knows what the surface of the fullerene particles tested really is. Shoot, part of the preparation procedure is to use tetrahydrofuran, which is known to produce peroxides, and could well be the cause of the oxidative stress itself! From this article, which has been greatly overinterpreted (especially by the author), I can now read about how some researcher dumped fullerenes into a river and caused a massive fish kill. On the other hand, toxicologists are going to be well-funded to study nanomaterials for the forseeable future.

Clearly, the alarmists have already won the day, and any benefits from nanomaterials will be exceedingly hard to get through the smoke screen.

Oh, by the way, water-soluble fullerenes have long been known to REDUCDE neuronal oxidative stress (PNAS, v94, p9434), but I gues those author's PR team wasn't as good as the toxicologist's.

Chris Phoenix, CRN

M, please tell us who you are. Claims as specific as yours should have a source.

Can you give a reference for buckyballs clumping in vivo? In vitro I have been told they do eventually dissolve/suspend, albeit exceedingly slowly.

Chris

M

Greetings Chris et al.

It's actually very hard to dose animals with underivatized fullerenes, they're so hydrophobic. Go buy $20 of fullerenes from somebody like BuckyUSA or SES, dump them in water and see for yourself. The paper I was thinking of when I wrote that is Nanolett v.5, p.2578. To be fair, a lot of their claims should also be taken with a healthy dose of salt, and (worse) their preparation method is not well documented.

Also, a very important new work in the field has been published by E. Oberdorster (the same person who did the fish study) in a historically very odd place for toxicology, the journal Carbon (v.44, p.1112). The researchers fail to obtain an LD50 for C60 in various aquatic organisms BECAUSE THEY CAN'T GET ENOUGH C60 INTO SOLUTION BY STIRRING. You will appreciate this paper because it has the kind of balance that I percieve you like to hear about. However, it's important to understand that it greatly shifts the center of balance (if you will) to a very different position than is represented by, say, the cover of this month's Mechanical Engineering (where a model of C60 is superimposed on a biohazard symbol).

The ineteresting part here is that, without sunlight (or other weak uv source), you can't even disperse 20-30 ppm in water, as Oberdoster did. (No reference available, take it or leave it - but take it. [Oh, okay I only stirred for three months and got nothing smaller than 200 nm.]) So, only in the presence of uv (which is, to be balanced, an environmentally relevent condition) is it possible to create even vastly sublethal concentrations of C60 in water. I supppose this is because the uv has modified the fullerene particle surface again, probably by polyhydroxylation.

Sorry for the slow reply.
M

Chris Phoenix, CRN

M, thanks for the reply and the references and notes.

Given the earlier response to Oberdorster's preliminary results, I wouldn't be surprised if she published in an obscure location to try to avoid a media feeding frenzy. I was very disappointed in the reaction to her pilot study--everyone piled all over each other to shoot the messenger (her), when as far as I know all she did was to discuss preliminary findings in a purely scientific meeting that happened to be open to the public (and press).

If UV can functionalize fullerenes, then not only do we have to think about a combinatorial explosion of manufactured nanoparticles with varying properties, we now have to think about all the various types of derivative particles after the manufactured versions sit in the environment for a while.

I hope I don't sound like a paranoid eco-nut when I say that the more I learn, the more I'm starting to see the point of a precautionary approach. Not the extreme, do-nothing-ever version, but the one that says count uncertainties as risk and balance them carefully against the benefit.

Chris

M

Well, I suppose it's a matter of how you want to spend your time and the government's money.

Fullerenes have a redox-active surface, and therefore innately have the potential for being active in biological systems...but only after they have been derivatized to become sufficiently water soluble to enter the biological system. Like many pharmaceuticals, one expects that they would have a dose-(desired)response curve that turns over at some point and they start causing harm instead of doing good.

The real question that I'm hoping that you're already thinking about is: How much of your time and the government's money do you want to spend investigating something that has a world wide production of ~40 tons/yr and, based on Oberdorster '06, observable but relatively mild eco/bio effects? Compare to ...well, pick your favorite chemical-eco problem: insecticide run-off, greenhouse gas emissions, heavy metal leachings from mine tailings, Hanford Site underground runoff into the Columbia River,...on and on... Current polluters have got to be estatic about the nanotoxicty flap, because it both distracts the public and channels government resources away from dealing with far more major existing problems.

Lastly, I doubt there's any reason to worrk about a "combinatorial explosion" due to UV modification of fullerenes. Thanks to thermodynamics, giant bucky particles in water in the presence of sunlight will always end up with the same product: polyhydroxylated fullernes/fullerene particles. The toxicology of such polyhydroxylated fullerenes has been studied (Nanolett 4, 1881; Toxicol Sci 91, 193; Am J Physiol Cell Physiol 290 C1495) and, because the hydroxides tie up the redox-active fullerene surface, they're even more benign than other fullerenes. Think of the uv+water as increasing bioavailibilty, but decreasing toxicity. Can't do one without the other.

I appreciate your replies to my posts, and perhaps we can have lunch someday.

Signing off,
M

Chris Phoenix, CRN

M, you make good points about relative damage.

And I'm glad to hear that buckyballs (and buckytubes?) get polyhodroxylated.

One quibble: I'm not confident that production will stay at ~40 tons per year.

I think I'd enjoy lunch. If you ever get near Savannah, drop me a note.

Chris

jim moore

Hey M,
I would be interested in how well bucky balls disperse in something like milk or lard. Things that are more lipophilic or have surfactant like properties. Are the bucky ball particles a loose agglomeration or more tightly held together like crystals?

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