文章来源:未知 文章作者:meng 发布时间:2010-12-20 03:34 字体: [ ]  进入论坛

A pipefitter knows how to make an exact cut on a metal rod. But it's far harder to imagine getting a precise cut on a carbon nanotube, with a diameter 1/50,000th the thickness of a human hair. In a paper published this month in the British journal Proceedings1 of the Royal Society A, researchers at Brown University and in Korea document for the first time how single-walled carbon nanotubes are cut, a finding that could lead to producing more precise, higher-quality nanotubes. Such manufacturing improvements likely would make the nanotubes more attractive for use in automotive, biomedicine, electronics, energy, optics(光学) and many other fields.

"We can now design the cutting rate and the diameters we want to cut," said Kyung-Suk Kim, professor of engineering in the School of Engineering at Brown and the corresponding author on the paper.

The basics of carbon nanotube manufacturing are known. Single-atom thin graphene sheets are immersed in(陷于,沉浸于) solution (usually water), causing them to look like a plate of tangled2(纠缠的,复杂的) spaghetti(意大利面条) . The jumbled3(乱七八糟的) bundle of nanotubes is then blasted by high-intensity sound waves that create cavities (or partial vacuums) in the solution. The bubbles that arise from these cavities expand and collapse4 so violently that the heat in each bubble's core can reach more than 5,000 degrees Kelvin, close to the temperature on the surface of the sun. Meanwhile, each bubble compresses at an acceleration5 100 billion times greater than gravity. Considering the terrific energy involved, it's hardly surprising that the tubes come out at random6 lengths. Technicians use sieves7(筛子,滤网) to get tubes of the desired length. The technique is inexact partly because no one was sure what caused the tubes to fracture.

Materials scientists initially8 thought the super-hot temperatures caused the nanotubes to tear. A group of German researchers proposed that it was the sonic boomlets(小景气,短暂的繁荣) caused by collapsing9 bubbles that pulled the tubes apart, like a rope tugged10 so violently at each end that it eventually rips.

Kim, Brown postdoctoral researcher Huck Beng Chew, and engineers at the Korea Institute of Science and Technology decided11 to investigate further. They crafted complex molecular12 dynamics13 simulations using an array of supercomputers to tease out(梳理) what caused the carbon nanotubes to break. They found that rather than being pulled apart, as the German researchers had thought, the tubes were being compressed mightily14 from both ends. This caused a buckling15 in a roughly five-nanometer section along the tubes called the compression-concentration zone. In that zone, the tube is twisted into alternating 90-degree-angle folds, so that it fairly resembles a helix(螺旋,耳轮) .

That discovery still did not explain fully16 how the tubes are cut. Through more computerized simulations, the group learned the mighty17 force exerted by the bubbles' sonic booms caused atoms to be shot off the tube's lattice-like foundation like bullets from a machine gun.

"It's almost as if an orange is being squeezed, and the liquid is shooting out sideways," Kim said. "This kind of fracture by compressive atom ejection has never been observed before in any kind of materials."

The team confirmed the computerized simulations through laboratory tests involving sonication and electron microscopy of single-walled carbon nanotubes.

The group also learned that cutting single-walled carbon nanotubes using sound waves in water creates multiple kinks, or bent18 areas, along the tubes' length. The kinks are "highly attractive intramolecular(分子内的) junctions19(连接,接头) for building molecular-scale electronics," the researchers wrote.


1 proceedings Wk2zvX     
  • He was released on bail pending committal proceedings. 他交保获释正在候审。
  • to initiate legal proceedings against sb 对某人提起诉讼
2 tangled e487ee1bc1477d6c2828d91e94c01c6e     
adj. 纠缠的,紊乱的 动词tangle的过去式和过去分词
  • Your hair's so tangled that I can't comb it. 你的头发太乱了,我梳不动。
  • A movement caught his eye in the tangled undergrowth. 乱灌木丛里的晃动引起了他的注意。
3 jumbled rpSzs2     
  • Books, shoes and clothes were jumbled together on the floor. 书、鞋子和衣服胡乱堆放在地板上。
  • The details of the accident were all jumbled together in his mind. 他把事故细节记得颠三倒四。
4 collapse aWvyE     
  • The country's economy is on the verge of collapse.国家的经济已到了崩溃的边缘。
  • The engineer made a complete diagnosis of the bridge's collapse.工程师对桥的倒塌做了一次彻底的调查分析。
5 acceleration ff8ya     
  • All spacemen must be able to bear acceleration.所有太空人都应能承受加速度。
  • He has also called for an acceleration of political reforms.他同时呼吁加快政治改革的步伐。
6 random HT9xd     
  • The list is arranged in a random order.名单排列不分先后。
  • On random inspection the meat was found to be bad.经抽查,发现肉变质了。
7 sieves 4aab5e1b89aa18bd1016d4c60e9cea9d     
筛,漏勺( sieve的名词复数 )
  • This thesis emphasized on the preparation of mesoporous molecular sieves MSU. 中孔分子筛MSU是当今认为在稳定性方面很有发展前途的一种催化新材料。
  • The mesoporous silica molecular sieves Zr-MCM-41 were synthesized in ethylenediamine. 以乙二胺为碱性介质合成了Zr-MCM-41介孔分子筛。
8 initially 273xZ     
  • The ban was initially opposed by the US.这一禁令首先遭到美国的反对。
  • Feathers initially developed from insect scales.羽毛最初由昆虫的翅瓣演化而来。
9 collapsing 6becc10b3eacfd79485e188c6ac90cb2     
  • Rescuers used props to stop the roof of the tunnel collapsing. 救援人员用支柱防止隧道顶塌陷。
  • The rocks were folded by collapsing into the center of the trough. 岩石由于坍陷进入凹槽的中心而发生褶皱。
10 tugged 8a37eb349f3c6615c56706726966d38e     
v.用力拉,使劲拉,猛扯( tug的过去式和过去分词 )
  • She tugged at his sleeve to get his attention. 她拽了拽他的袖子引起他的注意。
  • A wry smile tugged at the corner of his mouth. 他的嘴角带一丝苦笑。 来自《简明英汉词典》
11 decided lvqzZd     
  • This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
  • There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。
12 molecular mE9xh     
  • The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
  • For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时,分子的碰撞就停止了。
13 dynamics NuSzQq     
  • In order to succeed,you must master complicated knowledge of dynamics.要取得胜利,你必须掌握很复杂的动力学知识。
  • Dynamics is a discipline that cannot be mastered without extensive practice.动力学是一门不做大量习题就不能掌握的学科。
14 mightily ZoXzT6     
  • He hit the peg mightily on the top with a mallet. 他用木槌猛敲木栓顶。
  • This seemed mightily to relieve him. 干完这件事后,他似乎轻松了许多。
15 buckling buckling     
  • A door slammed in the house and a man came out buckling his belt. 房子里的一扇门砰地关上,一个男子边扣腰带边走了出来。
  • The periodic buckling leaves the fibre in a waved conformation. 周期性的弯折在纤维中造成波形构成。
16 fully Gfuzd     
  • The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气,然后全部呼出。
  • They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。
17 mighty YDWxl     
  • A mighty force was about to break loose.一股巨大的力量即将迸发而出。
  • The mighty iceberg came into view.巨大的冰山出现在眼前。
18 bent QQ8yD     
  • He was fully bent upon the project.他一心扑在这项计划上。
  • We bent over backward to help them.我们尽了最大努力帮助他们。
19 junctions 8d6818d120fa2726af259fc9dc6c7c61     
联结点( junction的名词复数 ); 会合点; (公路或铁路的)交叉路口; (电缆等的)主结点
  • Metals which were mutually soluble would tend to give strong junctions. 可互溶的金属趋向于产生牢固的结合点。
  • Some adhering junctions are present as narrow bands connecting two cells. 有些粘附连接以一窄带的形式连接两个细胞。
TAG标签: energy carbon nanotube