文章来源:未知 文章作者:enread 发布时间:2012-10-30 06:35 字体: [ ]  进入论坛
Scientific research has provided us with a fundamental understanding of how light (via photons) and electricity (via electrons) move within and between materials at the micrometer or nanometer levels, making possible a wide variety of miniature devices such as transistors1, optical sensors2 and microelectromechanical systems (MEMS). However, man's knowledge of micro- and nanoscale heat flow is rudimentary(基本的) at best. Now, a research team at the University of Illinois at Urbana-Champaign (UIUC) has developed a novel system for examining and measuring nanoscale thermal3 conductance at the interface4 between two materials. With further refinement5, the scientists believe their advance may one day provide data for applications such as harvesting electricity from waste heat, better cooling of microelectronic devices and "heat-seeking" targeting of disease cells by hyperthermal(极高热的) (above normal body temperature) therapeutics. The team's findings will be presented by Mark Losego, formerly6 a post-doctoral fellow at UIUC and now a research assistant professor in chemical and biomolecular engineering at North Carolina State University, during the AVS 59th International Symposium8 and Exhibition, held Oct. 28-Nov. 2, 2012, in Tampa, Fla.
At the nanoscale, thermal properties are the result of vibrations9 between neighboring atoms. Bonds between atoms carry these vibrations similar to an oscillating spring. The UIUC team developed a technique for studying the effects of these bonds on heat transport across an interface between two different materials. "We wanted a system where we could observe, analyze10 and quantify thermal flow across an interface with atomic-level precision," Losego says.
The system starts with a substrate base of quartz11 crystal, upon which the researchers place molecular7 chains that are 12 carbon atoms long. At the base of each chain is a chemical "cap" that covalently bonds to quartz. The attraction of these caps to the substrate(基质,底片) spontaneously aligns12 all of the carbon chains into an ordered array of molecules13 known as a self-assembled monolayer (SAM). At the opposite end of each carbon chain is a different kind of cap, either a thiol (sulfur and hydrogen) group that bonds strongly to metals or a methyl group (carbon and hydrogen) that bonds weakly.
"We then make use of a viscoelastic(粘弹性的) silicone stamp to 'transfer print' gold layers onto the SAM surface," Losego explains. "This process is similar to transferring a decal onto a T-shirt where the gold film is the 'decal' attached to the silicone stamp 'backing'. When we slowly peel away the silicone, we leave the gold layer on top of the SAM."
It is at the interface between the gold film and the SAM, Losego says, where nanoscale heat flow is characterized. "Changing the chemical groups that are in contact with the gold layer allows us to see how different bonds affect heat transfer," he adds.
Combined with an ultrafast laser technique capable of monitoring temperature decay (or heat loss) with picosecond (trillionth of a second) resolution, the UIUC researchers are able to use their experimental system to evaluate heat flow at the atomic scale. "We heat the gold layer attached to the monolayer and can monitor temperature decay with time," Losego explains. "Concurrently14, we observe oscillations in the gold film that indicate the strength of the bonds at the gold-SAM junction15. Using these measurements we are able to independently verify that strong bonds [fast-decaying oscillations] have rapid heat transfer while weak bonds [slowly decaying oscillations] have slower heat transfer."
The researchers plan to refine their nanoscale thermal measurement system and develop theoretical calculations to better interpret the data it produces.


1 transistors ff750796e6ff1fb40d6a8248a6485dc3     
晶体管( transistor的名词复数 ); 晶体管收音机,半导体收音机
  • In semiconductor receivers transistors take the place of vacuum tubes. 在半导体收音机中晶体管代替了真空管。
  • We often turn to this handbook for information on transistors. 我们常从这本手册查阅有关晶体管的资料。
2 sensors 029aee483db9ae244d7a5cb353e74602     
n.传感器,灵敏元件( sensor的名词复数 )
  • There were more than 2000 sensors here. 这里装有两千多个灵敏元件。 来自《简明英汉词典》
  • Significant changes have been noted where sensors were exposed to trichloride. 当传感器暴露在三氯化物中时,有很大变化。 来自辞典例句
3 thermal 8Guyc     
  • They will build another thermal power station.他们要另外建一座热能发电站。
  • Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。
4 interface e5Wx1     
  • My computer has a network interface,which allows me to get to other computers.我的计算机有网络接口可以与其它计算机连在一起。
  • This program has perspicuous interface and extensive application. 该程序界面明了,适用范围广。
5 refinement kinyX     
  • Sally is a woman of great refinement and beauty. 莎莉是个温文尔雅又很漂亮的女士。
  • Good manners and correct speech are marks of refinement.彬彬有礼和谈吐得体是文雅的标志。
6 formerly ni3x9     
  • We now enjoy these comforts of which formerly we had only heard.我们现在享受到了过去只是听说过的那些舒适条件。
  • This boat was formerly used on the rivers of China.这船从前航行在中国内河里。
7 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。
8 symposium 8r6wZ     
  • What have you learned from the symposium?你参加了这次科学讨论会有什么体会?
  • The specialists and scholars present at the symposium come from all corners of the country.出席研讨会的专家学者们来自全国各地。
9 vibrations d94a4ca3e6fa6302ae79121ffdf03b40     
n.摆动( vibration的名词复数 );震动;感受;(偏离平衡位置的)一次性往复振动
  • We could feel the vibrations from the trucks passing outside. 我们可以感到外面卡车经过时的颤动。
  • I am drawn to that girl; I get good vibrations from her. 我被那女孩吸引住了,她使我产生良好的感觉。 来自《简明英汉词典》
10 analyze RwUzm     
vt.分析,解析 (=analyse)
  • We should analyze the cause and effect of this event.我们应该分析这场事变的因果。
  • The teacher tried to analyze the cause of our failure.老师设法分析我们失败的原因。
11 quartz gCoye     
  • There is a great deal quartz in those mountains.那些山里蕴藏着大量石英。
  • The quartz watch keeps good time.石英表走时准。
12 aligns f51edfba3ed0b417b4851a1f2581cf7d     
使成一线( align的第三人称单数 ); 排整齐; 校准; 公开支持(某人、集体或观点)
  • HASP SRM fully aligns with the software product lifecycle. HASPSRM完全遵循软件产品的生命周期。
  • Significant employee aligns the interests of our employees and our shareholders. 员工大量持股可以使员工与股东的利益协调一致。
13 molecules 187c25e49d45ad10b2f266c1fa7a8d49     
分子( molecule的名词复数 )
  • The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
  • Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里,大分子裂变为小分子。
14 concurrently 7a0b4be5325a98c61c407bef16b74293     
  • He was given two twelve month sentences to run concurrently. 他两罪均判12个月监禁,同期执行。 来自《简明英汉词典》
  • He was given two prison sentences, to run concurrently. 他两罪均判监禁,同期执行。 来自辞典例句
15 junction N34xH     
  • There's a bridge at the junction of the two rivers.两河的汇合处有座桥。
  • You must give way when you come to this junction.你到了这个路口必须让路。
TAG标签: light materials molecules