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ryxtony

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[交流] 【转帖】美国用激光造神秘黑色金属可吸收热量和辐射

http://www.optics.rochester.edu/workgroups/guo/index.htm

http://www.sciencedaily.com/releases/2009/07/090715174936.htm

Laser Technology Creates New Forms Of Metal And Enhances Aircraft Performance
ScienceDaily (July 20, 2009) — AFOSR-funded researchers at the University of Rochester are using laser light technology that will help the military create new forms of metal that may guide, attract and repel liquids and cool small electronic devices.

Dr. Chunlei Guo and his team of researchers for the project discovered a way to transform a shiny piece of metal into one that is pitch black, not by paint, but by using incredibly intense bursts of laser light. The black metal created, absorbs all radiation that shines upon it.

"With the creation of the black metal, an entirely new class of material becomes available to us, which may open up a whole new horizon for various applications," said Guo.

"To do this, we looked at the reverse process of light absorption or light radiation and transformed the incandescent lamp into a bulb that glows twice as brightly as a regular light source, while consuming the same amount of energy," he said.

The key to creating this super-filament is an ultra-brief, ultra-intense beam of light called a femtosecond laser pulse. The laser burst lasts only a few quadrillionths of a second. That intense blast forces the surface of the metal to form nano-structures and micro-structures that dramatically alter how efficiently light can radiate from the filament.

In addition to increasing the brightness of a bulb, Guo's process can be used to tune the color of the light as well. Last year, his team used a similar process to change the color of nearly any metal to blue, gold, gray, in addition to the black. They controlled the size and shape of the nano-structures -- and thus what colors of light those structures absorb and radiate -- to change the amount of each wavelength of light the filament radiates.

In addition to this research, Guo and his team have been working on creating technology that may enable the Air Force to create an additional kind of metal. They are able to do this by using the femtosecond laser once again to alter the surface of metal and create unique nano- and micro-scale structures on the metal.

"During its brief burst, the laser unleashes as much power as the entire electric grid of North America does, all focused onto a spot the size of a needle," said Guo.

The unique nano-structures which are created from the laser affect the way liquid molecules interact with metal molecules. The liquid spreads out over the metal because the nano-structures attach themselves to the liquid's molecules more readily than the liquid's molecules bond to each other. The end result is the formation of a new kind of metal that can cool the plane's electronic brain and heat pumps and allow the craft to retain dominance over any enemy that is also in flight.

Currently, the researchers need only about half an hour to change the surface of metal that is approximately the size of a quarter. Nevertheless, their next goal is to make the metal even more quickly so they can meet the ever increasing demands of warfighting.

据美国《每日科学》美国空军科学研究局资助的罗切斯特大学的研究人员们正利用激光技术来帮助军队制造一种能够吸收热量和辐射、避免液体并能够冷却小型电子设备的新型金属。

　　罗切斯特大学的郭春雷（音译）博士和他的研究小组利用令人难以置信的激光将发光的金属条制造成一种漆黑色的金属。被制造出来的黑色金属，能够吸收激光释放的所有辐射，能够吸收高热，甚至可以“驱赶”液体。

　　郭春雷博士说：“这种黑色金属作为一种新型材料，将为各种军事应用打开全新的视野。”据介绍，制造这种黑色金属的关键是一种超级简短、超级强烈的光束，叫做飞秒激光脉冲。这种激光脉冲只持续千万亿分之几秒，强烈的爆炸力量迫使金属表面形成了纳米结构和微米结构，戏剧性地改变了光从金属纤维中发出的方式，从而改变了这种金属条的结构。

　　除了增加激光发射装置的亮度，郭博士的实验也可以调节激光制造出的金属颜色。他的研究小组用相似的步骤把几乎所有金属都变成了蓝、金、灰色，但除了黑色。他们控制纳米结构的大小和形状，从而控制那些结构吸收和放射的光的颜色，来改变金属纤维放射的每种光的波长量。

　　此外，郭博士和他的团队一直致力于研究为空军创造其他种类金属的技术。他们能够再一次利用飞秒激光来改变金属表面，从而在金属上创造出独特的纳米和微米尺度的结构。郭博士说：“在短暂爆发期间，激光释放出相当于整个北美电网的电量，它们都聚焦在一个针尖大小的点上。”

　　激光创造出的独特的纳米结构影响了液态分子与金属的分子的相互作用。纳米结构将自身附着到液态分子上的速度比液态分子相互间的附着速度快地多，因此液态分子在金属表面四散开来。最终的结果是形成了一种新型金属，能够冷却飞机的电脑和热泵机组，让航空器在与任何处于飞行中的敌人对峙时始终保持优势。

　　目前，研究人员只需要大约半个小时就能改变金属表面（大约0.25英寸大小,1元人民币的大小）。然而，他们的下一个目标是用更短的时间制造出这种黑色金属，以满足日益增加的军事战斗需求。

[ Last edited by ryxtony on 2009-7-23 at 02:00 ]

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