Carbon nanotube avalanche process nearly doubles current for Semiconducting carbon nanotubes


“Single-wall carbon nanotubes are already known to carry current densities up to 100 times higher than the best metals like copper,” said Eric Pop, a professor of electrical and computer engineering at the U. of I. “We now show that semiconducting nanotubes can carry nearly twice as much current as previously thought.”

“We found that the current first plateaus near 25 microamps, and then sharply increases at higher electric fields,” said Pop, who also is affiliated with the Beckman Institute and the Micro and Nanotechnology Laboratory at the U. of I. ”We performed repeated measurements, obtaining currents of up to 40 microamps, nearly twice those of previous reports.”

As reported in the journal Physical Review Letters, the researchers found that at high electric fields (10 volts per micron), energetic electrons and holes can create additional electron-hole pairs, leading to an avalanche effect where the free carriers multiply and the current rapidly increases until the nanotube breaks down.

The sharp increase in current, Pop said, is due to the onset of avalanche impact ionization, a phenomenon observed in certain semiconductor diodes and transistors at high electric fields, but not previously seen in nanotubes.

While the maximum current carrying capacity for metallic nanotubes has been measured at about 25 microamps, the maximum current carrying capacity for semiconducting nanotubes is less established. Previous theoretical predictions suggested a similar limit for single-band conduction in semiconducting nanotubes.

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1

In general I also believe that the sovereignty of nations and regions is an over-emphasized point.

Groups can get plenty of autonomy while still being part of a larger nation. The modern world is moving more to trade blocks and structures like the European union.

that is things like Quebec talking about separating from Canada is silly. They would still be economically and socially embedded in north America.

For China, it is clear that in the current situation any internal group has to recognize the ruling party or expect a world of trouble.
But people are relatively free to do what they want economically and even in terms of beliefs if those things only try and limited changes.

I think over-reaching means that conflict should be expected. China's government makes no secret of what the responses will be.

A long term strategy of gradual political and social movement would be more constructive and productive.

2

My view is that China has a strong claim to Tibet from the Yuan Dynasty.

http://en.wikipedia.org/wiki/Tibetan_sovereignty_debate#Legal_arguments_based_on_historical_status

I don't see why any territories owned over 100 years should be disputed.

The USA itself being less than 250 years old.

Not related to this but conquered territories from a war should generally let it go unless the losing side is ready to refight and win.

3

I am unconvinced that the USA would engage in a war with China. It makes no economic sense. China and the USA are very strongly tied economically. Why would the USA jeopardize that over Taiwan? It would be absolutely devastating to the US economy.

Then there is the new president, Mr Ma, who is pro-china, which also plays a huge roll.

I know that this is unrelated to technology, but what do you think of these boycott olympics slogans that everyone and their granny has been spouting? It seems somewhat hypocritical to me.

4

Mike said:
"...so many different types of war technologies that it is difficult for any one nation to have an absolute monopoly on them...other country's armies have enough advanced and varied technology so as to make it prohibitive for the US to wage war. So I think in the future, the likelihood of any large scale war will be fairly small or nil".

Nearly all people believed the same thing in 1936. Almost no exceptions to that thinking in 1936. And then what happened 3 years later? I think the future is no less dangerous than the past.

Hopefully, the next president will not be McCain, because although he has obvious courage & patriotism, the next decade will see us playing the Great Game in the 21st Century. We know what happened in the 19th century to the British & the Russians.

If the next president is NOT McCain, then perhaps some resources can devoted to withdrawing from that self-destructive nonsense, and building up a robust & renewable energy infrastructure which can be a valuable legacy for future generations.

5

I think you might be a bit late on this...the evidence shows that Iran already has the missiles.

First, the surprising destruction of Israeli armor by Hezbollah infantry in the conflict of summer 2006. That other countries have supplied Hezbollah with weapons to accomplish this is strongly hinted at.
http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2006/08/15/wmid15.xml
http://www.hindu.com/2006/08/20/stories/2006082004721400.htm

Then the Hezbollah leader makes a speech declaring that Israel basically hasn't seen anything yet.
http://www.cnn.com/2006/WORLD/meast/09/22/lebanon.rally/index.html
"We were prepared for a long war. What we offered during that war is only a small part of our capability," he said.


8/11/06: A missile launched from Lebanon destroys an Israeli corvette. Two days later, the Israeli offensive comes to an end.


This is one of the few Western media sources that mentions this incident. Notice how they gloss over the fact that the ship was lost.
http://abcnews.go.com/International/wireStory?id=2195553

Compare the scarcity of information in that article with this one.
http://www.phayul.com/news/article.aspx?id=14009&article=China+and+the+Middle+East%3A+A+New+Patron+of+Regional+Instability&t=1&c=1
Another reason for concern is China’s weapons sales to Iran, particularly given Iran’s patronage of major regional terrorist groups. Along with Syria and Libya, Iran provides an estimated $50 million to $200 million in annual financial and material support to Hezbollah and Hamas. During the armed confrontation between Israel and Hezbollah in July–August 2006, a Chinese-made C-802 mis­sile struck an Israeli warship off Beirut. Although Hezbollah took responsibility for the attack, the missile apparently had been supplied by the Ira­nian government. [footnote erased] Iran purchased 75 C-802s from China in 1997 and allegedly has produced at least 75 more in collaboration with China.

The C-802 project is a fraction of China’s overall weapons stake in Iran. China has sold several hun­dred Silkworm anti-ship cruise missiles to Iran since the late 1980s and has been Iran’s major source of missile guidance equipment and technol­ogy since the early 1990s. In May 2002, Tehran reportedly purchased high-speed catamaran mis­sile patrol boats, which are equipped with up to eight C-701 anti-ship cruise missiles. [footnote erased] A group of Chinese technicians were sent to assist in training the Iranian navy and equipping the new patrol boats. Earlier in 2002, the Chinese provided Iran with shorter-range anti-ship cruise missiles for its coastal patrol boats.

So now we have a number...the C-802 (or a derivative model) anti-ship missile.

Then Israeli and U.S. intelligence both try to use the C-802 as evidence of collusion between Hezbollah and Iran...but they try to do it without calling attention to the lost ship.
http://www.iiss.org/whats-new/iiss-in-the-press/july-2006/hezbollahs-skill-more-military-than-militia
The strongest evidence of Iranian involvement with Hezbollah involves the missile used to cripple an Israeli ship off the coast of Beirut on Friday. U.S. officials also point to Hezbollah rocket attacks deep inside Israeli territory.

If the missiles that struck the ship and landed in Israeli cities were "fired by Hezbollah themselves, they would have had to have training in these missile technologies," the senior U.S. military official said, noting that such training probably would have come from Iranian military schools.

Okay, that's just standard politics. But there are still a few pieces missing.

Where did this version of the missile come from?
Type "C-802" into Wikipedia and you get the following article.
http://en.wikipedia.org/wiki/C-802
Variants: In early 2000 it was reported that North Korea and Iran were jointly developing an advanced version of the C-802 missile. The missiles initially acquired by Iran from China were rather outdated, and Iran turned to North Korea for missile system technology. The two countries are jointly developing an upgraded version with improved accuracy.

and

Flight Profile: When the missile is launched, the solid rocket propellant booster accelerates the speed of the missile from 0 to 0.9 Mach in a few seconds.

"But if the Iranians have such a beast...why didn't they ever test it?"
They did.
http://www.cbsnews.com/stories/2006/04/02/world/main1461878.shtml
Iran announced its second major new missile test in a week, saying Sunday it has successfully fired a high-speed underwater missile capable of destroying huge warships and submarines.

The Iranian-made missile has a speed of 223 miles per hour underwater, Gen. Ali Fadavi, deputy head of the Navy of the elite Revolutionary Guards, said.

Note that a Mach is typically around 760 mph, depending on the aerodynamics of the object and local sound acoustics. (Since Mach is defined as a speed ratio that breaks the sound barrier, not as a pre-set or independent speed.) Either the natural resistance of water is enough to reduce speed 66%, or this general is purposefully under-reporting the top speed of the missile.

How do we know that the Chinese had a hand in developing the C-802?
http://www.globalsecurity.org/wmd/library/congress/1997_cr/s970505b.htm
SENATE RESOLUTION 82 (5/5/97)
C-802 FACT SHEET
U.S.S. Stark: American Navy escort vessel struck by two Exocet type cruise missiles in May 1987 killing 37 sailors and disabling the ship for sixteen months.

C-802: Chinese cruise missile similar to the Exocet and marketed for use against naval escort vessels.

Iranian Revolutionary Guard Navy: Iran is believed to possess sixty C-802 missiles aboard 15 Chinese and French missile boats.

Why would the Chinese assist Iran in obtaining and developing such a weapon?
To answer that, here is a British think tank paper.
http://www.chathamhouse.org.uk/pdf/research/mep/Iran0806.pdf
China and Iran have enjoyed a cordial relationship since the 1970s and this relationship has been strengthened in the past few years. Economic ties between the two countries have developed steadily. In 1998, bilateral trade was only $1.2 billion. By the end of 2005, it had reached $10 billion. In 2004, China imported over 13 million tonnes of oil from Iran, accounting for 11% of its total oil imports. Although energy is the main component of the trade and investment between China and Iran, bilateral economic ties are not restricted to this area. More than 100 Chinese firms now operate in Iran. Chinese companies have been involved in many infrastructure projects in Iran, building motorways, airports, jetties and metro lines, and Chinese consumer goods have also found an expanding market in Iran.

The political relationship between Beijing and Tehran is also strong. The two countries issued a joint communiqué agreeing to establish a ‘friendly cooperative relationship’ during President Khatami’s visit to China in 2000. China and Iran maintain that, as developing countries, they share similar views on many regional and international issues. In 2005, Iran was granted observer status in the Shanghai Cooperation Organization, which could potentially provide an additional mechanism for Sino-Iranian cooperation. Above all, both countries believe that a good relationship with one another is in their long-term strategic interest. After 9/11, as mistrust between Iran and the US deepened, Iran attached greater importance to developing closer relations with China. Chinese companies have sold weapons and weapons technology to Iran since the 1980s and the US has accused China of assisting in the development of Iran’s missile systems. As a result, Chinese companies have faced US sanctions. Most recently six Chinese companies were sanctioned by the US in December 2005 for allegedly selling missile goods and chemical weapons materials to Iran.