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发信人: lgzhou (沙漠之虎), 信区: HUST
标 题: [合集] 华中大校友 打破百年物理定律
发信站: 水木社区 (Thu Sep 10 11:18:56 2009), 站内
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collinjp (神奈川琥珀主) 于 (Sun Aug 2 09:30:02 2009) 提到:
華中校友陈刚 打破百年物理定律
麻省理工學院（MIT）30日宣布，該校動力工程學華裔教授陳剛與其團隊的研究，首次打破
「黑體輻射定律」公式，證實物體極接近的熱力傳導，可以高到定律所預測的千倍。研究
報告將在8月號「NanoLetter」雜誌上發表。
德國物理學家普朗克1900年創「黑體輻射定律」（blackbody radiation law），公認是物
體間熱力傳導基本法則，雖有人懷疑定律在兩物體極接近時不成立，但始終無法證明。
「黑體幅射定律」創定在不同溫度下，在絕大多數情況下都成立，但在極微小距離中穩定
控制物體以測試能量傳導，極為困難。百多年來，科學家始終無法突破。普朗克本人對此
定律在微距物體間是否仍成立，亦無把握。
陳剛出身中國華中科技大學、柏克萊加州大學，是知名奈米熱電材料和流體學者。他的團
隊採用方位較易控制的小玻璃珠對著平面物體的方式，取代在奈米（10億分之一米）距離
中根本不可能不碰觸的兩平行平面體；並採用雙金屬臂樑（bi-metallic cantilever）科
技的原子能動力顯微鏡，精準測量兩物體間溫度變化。
MIT表示，陳剛團隊證實了科學家所預言但無法實證的理論，獲國際間同領域學者喝采。不
但讓人們對基本物理有進一步了解，對改良電腦資料儲存用的硬碟的「記錄頭」（record
ing head），以及發展儲聚能源的新設計等工業應用上十分重要。
陳剛說，目前電腦使用的硬碟，記錄頭與硬碟表面約有5、6奈米距離，記錄頭容易發熱，
而研究員一直在尋找控制熱力的方法。熱力傳導和控制是磁力儲存（magnetic storage）
領域十分重要的一環，此類應用也將因陳剛的發現而迅速發展。新的發現還有助於開發新
一代能源轉換裝置，陳剛說，此研究也提供對基本物理進一步了解。
麻省理工当日首条新闻http://web.mit.edu/newsoffice/2009/heat-0729.html
MIT news
Breaking the law, at the nanoscale
Bringing notallowobjects close together can boost radiation heat transfer, acc
ording to new study that shows breakdown in Planck's law
David L. Chandler, MIT News Office
July 29, 2009
A well-established physical law describes the transfer of heat between two not
allowobjects, but some physicists have long predicted that the law should brea
k down when the notallowobjects are very close together. Scientists had never
been able to confirm, or measure, this breakdown in practice. For the first ti
me, however, MIT researchers have achieved this feat, and determined that the
heat transfer can be 1,000 times greater than the law predicts.
The new findings could lead to significant new applications, including better
design of the recording heads of the hard disks used for computer data storage
, and new kinds of devices for harvesting energy from heat that would otherwis
e be wasted.
Planck's blackbody radiation law, formulated in 1900 by German physicist Max P
lanck, describes how energy is dissipated, in the form of different wavelength
s of radiation, from an idealized non-reflective black notallowobject, called
a blackbody. The law says that the relative thermal emission of radiation at d
ifferent wavelengths follows a precise pattern that varies according to the te
mperature of the notallowobject. The emission from a blackbody is usually cons
idered as the maximum that an notallowobject can radiate.
The law works reliably in most cases, but Planck himself had suggested that wh
en notallowobjects are very close together, the predictions of his law would b
reak down. But actually controlling notallowobjects to maintain the tiny separ
ations required to demonstrate this phenomenon has proved incredibly difficult
.
"Planck was very careful, saying his theory was only valid for large systems,"
explains Gang Chen, MIT's Carl Richard Soderberg Professor of Power Engineeri
ng and director of the Pappalardo Micro and Nano Engineering Laboratories. "So
he kind of anticipated this [breakdown], but most people don't know this."
Part of the problem in measuring the way energy is radiated when notallowobjec
ts are very close is the mechanical difficulty of maintaining two notallowobje
cts in very close proximity, without letting them actually touch. Chen and his
team, graduate student Sheng Shen and Columbia University Professor Arvind Na
rayaswamy, solved this problem in two ways, as described in a paper to be publ
ished in the August issue of the journal Nano Letters (available now online).
First, instead of using two flat surfaces and trying to maintain a tiny gap be
tween them, they used a flat surface next to a small round glass bead, whose p
osition is easier to control. "If we use two parallel surfaces, it is very har
d to push to nanometer scale without some parts touching each other," Chen exp
lains, but by using a bead there is just a single point of near-contact, which
is much easier to maintain. Then, they used the technology of the bi-metallic
cantilever from an atomic-force microscope to measure the temperature changes
with great precision.
"We tried for many years doing it with parallel plates," Chen says. But with t
hat method, they were unable to sustain separations of closer than about a mic
ron (one millionth of a meter). By using the glass (silica) beads, they were a
ble to get separations as small as 10 nanometers (10 billionths of a meter, or
one-hundredth the distance achieved before), and are now working on getting e
ven closer spacings.
Professor Sir John Pendry of Imperial College London, who has done extensive w
ork in this field, calls the results "very exciting," noting that theorists ha
ve long predicted such a breakdown in the formula and the activation of a more
powerful mechanism.
"Experimental confirmation has proved elusive because of the extreme difficult
y in measuring temperature differences over very small distances," Pendry says
. "Gang Chen's experiments provide a beautiful solution to this difficulty and
confirm the dominant contribution of near field effects to heat transfer."
In today's magnetic data recording systems - such as the hard disks used in co
is much easier to maintain. Then, they used the technology of the bi-metallic
cantilever from an atomic-force microscope to measure the temperature changes
with great precision.
"We tried for many years doing it with parallel plates," Chen says. But with t
hat method, they were unable to sustain separations of closer than about a mic
ron (one millionth of a meter). By using the glass (silica) beads, they were a
ble to get separations as small as 10 nanometers (10 billionths of a meter, or
one-hundredth the distance achieved before), and are now working on getting e
ven closer spacings.
Professor Sir John Pendry of Imperial College London, who has done extensive w
ork in this field, calls the results "very exciting," noting that theorists ha
ve long predicted such a breakdown in the formula and the activation of a more
powerful mechanism.
"Experimental confirmation has proved elusive because of the extreme difficult
y in measuring temperature differences over very small distances," Pendry says
. "Gang Chen's experiments provide a beautiful solution to this difficulty and
confirm the dominant contribution of near field effects to heat transfer."
In today's magnetic data recording systems - such as the hard disks used in co
mputers - the spacing between the recording head and the disk surface is typic
ally in the 5 to 6 nanometer range, Chen says. The head tends to heat up, and
researchers have been looking for ways to manage the heat or even exploit the
heating to control the gap. "It's a very important issue for magnetic storage,
" he says. Such applications could be developed quite rapidly, he says, and so
me companies have already shown a strong interest in this work
The new findings could also help in the development of new photovoltaic energy
conversion devices to harness photons emitted by a heat source, called thermo
phovoltaic, Chen says. "The high photon flux can potentially enable higher eff
iciency and energy density thermophovoltaic energy converters, and new energy
conversion devices," he says.
The new findings could have "a broad impact," says Shen. People working with d
evices using small separations will now have a clear understanding that Planck
's law "is not a fundamental limitation," as many people now think, he says. B
ut further work is needed to explore even closer spacings, Chen says, because
"we don't know exactly what the limit is yet" in terms of how much heat can be
dissipated in closely spaced systems. "Current theory will not be valid once
we push down to 1 nanometer spacing."
And in addition to practical applications, he says, such experiments "might pr
ovide a useful tool to understand some basic physics."
The work was funded by the U.S. Department of Energy and the Air Force Office
of Scientific Research.
麻省理工当日首条新闻:http://web.mit.edu/newsoffice/2009/heat-0729.html
聯合報的相关报道：http://udn.com/NEWS/WORLD/WOR4/5053297.shtml
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lgzhou (沙漠之虎) 于 (Mon Aug 3 10:16:14 2009) 提到:
华中大在线新闻：
http://news.hustonline.net/Html/2009-8-2/64483.shtml
【 在 collinjp (神奈川琥珀主) 的大作中提到: 】
: 華中校友陈刚 打破百年物理定律
: 麻省理工學院（MIT）30日宣布，該校動力工程學華裔教授陳剛與其團隊的研究，首次打
破
: 「黑體輻射定律」公式，證實物體極接近的熱力傳導，可以高到定律所預測的千倍。研究
: ...................
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xxboy (buaa) 于 (Wed Aug 5 22:55:50 2009) 提到:
这个确实很牛啊。。。
【 在 collinjp (神奈川琥珀主) 的大作中提到: 】
: 華中校友陈刚 打破百年物理定律
: 麻省理工學院（MIT）30日宣布，該校動力工程學華裔教授陳剛與其團隊的研究，首次打
破
: 「黑體輻射定律」公式，證實物體極接近的熱力傳導，可以高到定律所預測的千倍。研究
: ...................
☆─────────────────────────────────────☆
frankwanger (书生菜§秋水) 于 (Sat Aug 8 20:09:13 2009) 提到:
听过他报告
【 在 collinjp (神奈川琥珀主) 的大作中提到: 】
: 華中校友陈刚 打破百年物理定律
: 麻省理工學院（MIT）30日宣布，該校動力工程學華裔教授陳剛與其團隊的研究，首次打
破
: 「黑體輻射定律」公式，證實物體極接近的熱力傳導，可以高到定律所預測的千倍。研究
: ...................
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