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世界上最轻的固体材料 – 译学馆
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世界上最轻的固体材料

World's Lightest Solid!

This is aerogel.
这就是气凝胶
The world’s lightest, that is least dense, solid.
它是世界上最轻 密度最小的固体
This piece has a mass of just 1.22 grams.
这块气凝胶的质量只有1.22克
That is only a few times
仅是同体积
the mass of the same volume of air,
空气质量的几倍而已
which kind of makes sense
这是讲的通的
because it is 99.8% air.
因为气凝胶99.8%的成分都是空气
In fact ,some aerogel is so light
事实上 有些气凝胶非常轻
that if you removed all the air from them,
轻到如果把里面所有的空气抽走
they would be less dense than air.
它们的质量会变得比空气还要小
I have long been fascinated by aerogel
长期以来 我一直被气凝胶吸引着
so I actually flew out to Aerogel Technologies in Boston
因此我来到波士顿的气凝胶科技公司
to find out why was aerogel invented.
想弄明白为什么人们要发明气凝胶
How is it made?
它是如何制成的
Why is it such a good thermal insulator
为什么它的隔热性能如此出色
and what is it used for?
以及我们能用它干什么
– Okay, we are going to try an experiment
接下来 我们要尝试做个实验
to demonstrate the insulating power of aerogel
来证实一下气凝胶的隔热能力
so over here we have two setups:
所以这里 我们放了两个铁架台
one with a glass petri dish,
一个放上玻璃培养皿
and the other one with aerogel on top
另一个放上气凝胶
both are made of silica
是二者都是由二氧化硅所制成
but with very different physical structures
但它们的物理结构却有着很大的差异
We’re gonna see how long it takes
我们想知道用本生灯加热的话
to melt these chocolate bunnies with a Bunsen burner.
需要多长时间将上面的巧克力兔子熔化
Now to have a look at this experiment,
为了便于观察
we have a FLIR T1020
我们用到了FLIR T1020
which can see temperatures up to 2,000 degrees Celsius
它的呈像温度高达2000摄氏度
Looks like it’s getting pretty hot.
它好像越来越热了
Yeah, you can see that the glass is getting really hot already.
是的 你可以看到玻璃已经很热了
And after just a minute:
仅仅一分钟过后
– It’s starting to smoke. – Okay.
-它开始冒烟了 -喔 是的
It’s definitely melting and smoking.
毫无疑问 它在不断熔化 冒烟
Oh yeah, here we go. I would say that’s phase change.
是 继续吧 我认为是发生相变了
We’ve got a liquid chocolate situation.
我们看到巧克力已经呈现液体状态了
We have some smoking bunny.
现在兔子在冒烟
Over here, the bunny is actually sort of melting over,
看这儿 这个兔子实际上已经熔化了
and look, there, it’s sort of tilting to the side.
再看那边 它有点倾斜了
Alright, I think we’re going to call that a melt.
好吧 我想我们可以说兔子已经熔化了
– What is that? – Oh!
–发生了什么 –噢
On cue, on cue.
刚好 刚好
I would say that is material fail.
我想说是材料不行
Not only did the bunny melt quickly,
兔子不仅熔化的很快
the petri dish cracked under the thermal expansion.
连培养皿都因为热膨胀碎裂了
So now let’s try the aerogel.
接下来换气凝胶试试
So how was aerogel invented?
那么气凝胶是怎么发明出来的?
Back in 1931,
早在1931年
a guy named Professor Samuel Kistler
一个名叫Samuel Kistler的教授
had a bet with his colleague Charles Learned.
和他同事Charles Learned打了个赌
Now the bet revolved around jellies,
赌约围绕凝胶类物质展开
like peanut butter and jelly jellies.
例如花生酱和果冻
Now the thing about jellies is they are actually a combination of liquids and solids.
实际上 凝胶类物质是液体和固体的混合物
I mean, they’re mostly liquid,
我是说 它们几乎由液体构成
but it’s embedded within this 3D solid structure.
但这些液体都处于3D固体结构之中
So if these jellies, like jello
那么 如果这些凝胶类物质 比如果冻
has a skeleton with nano-sized pores
拥有着一副由纳米孔构成
that gives it its rigidity,
并给它带来坚韧的骨架
and then that’s about 1% of jello.
那只占果冻的1%
So the bet was this:
所以赌约就是这样的
Could you remove the liquid from the jelly
你能在不影响立体结构的情况下
without affecting the solid structure?
去移除胶状物中的液体吗?
I mean, if you just evaporate the liquid out, well,
如果你把液体蒸发掉
then the solid structure shrinks,
固体结构就会收缩
because as you remove liquid molecules, they pull on each other,
因为当你移走液体分子时 它们会相互吸引
and they pull on the solid structure around them,
并且它们会拉着周围的固体结构
basically crumpling it from the inside.
从里面把它揉成一团
Now Samuel Kistler solved this problem in two ways.
Samuel Kistler用两种方法解决了这个问题
First, he realized
首先 他意识到
you could replace one liquid with another inside the jelly
在胶状物中一种液体可以被另一种液体替代
just by washing thoroughly.
只要将它完全洗涤即可
So you could swap out, say, water, for alcohol.
所以你可以把水换成酒精
And then, if you take the jelly and put it
然后 如果你把胶状物放进
in a high-pressure vessel called a autoclave,
一个叫做高压釜的高压容器里
By heating it to the high-temperature,high-pressure point
通过加热胶状物到一个高温高压点
called the critical point of the liquid,
这个点被称为这种液体的临界点
that liquid transformed into a semi-liquid, semi-gas
这种液体转化为半液态半气态时
called a supercritical fluid.
就被称为超临界流体
At this point,
在这个时刻上
there is no longer a distinction between liquid and gas.
液体和气体之间不再有区别了
Those molecules are no longer pulling on each other.
这些分子不再相互吸引
So once you’ve depressurized the vessel,
所以一旦你给该容器减压
that solid skeleton that 1% of the mass of the gel, is left behind intact,
凝胶质量1%的固体骨架将被完整留下
except for where there was liquid
除了孔隙里以前的液体的部分
in the pores before is now gas,
换成了现在的气体
and that solid skeleton, that nanoporous solid is what we call aerogel.
这个固体骨架 纳米孔固体就是气凝胶
Kistler published his findings in Nature in 1931.
Kistler在1931年《Nature》上发表了他的发现
It is getting pretty hot as you can see through the thermal camera.
你可以通过热摄像机看到它正变得很热
But coming up on three minutes, there’s still no sign of melted chocolate.
但是三分钟后巧克力仍然没有融化的迹象
So we’re gon na pull out a thermocouple
因此我们拿出一个热电偶
and just check the temperature underneath the bunny. Like,
来检测兔子下面的温度 同样的
underneath the aerogel, and see what,
把它放在气凝胶下面 看看
what the flame temperature is.
火焰的温度是多少
You can kind of see that,
你可以看到
of the bunny are getting hot,
部分巧克力变得很热
but it’s not the bottom of the bunny,
但是并不是在它的底部
It’s all the, around the bunny.
而是在兔子周围
Exactly. That convective heat is moving up and around the aerogel,
准确地说 是对流热在气凝胶周围上升
So you can see the thing is getting red hot.
所以你可以看到它变红了
And by four minutes, the bunny is looking a little soft.
四分钟后 兔子看着有一点软了
Still pretty good though, considering how easy it is to melt chocolate.
不过鉴于巧克力易熔 它还是相当不错的
– Can I put my finger here? – Be careful.
–我能把手指放这吗 –小心点
– It’s not that it’s hot, it’s that it’s brittle. – Right.
–不是因为太热而是因为太脆了 –是的
But yeah, totally cool to touch, right?
但是摸起来完全是凉的吗
It is, it is just warm to the touch.
摸起来只是有点温
He made aerogels out of all sorts of things.
他可以用各种各样的东西制成气凝胶
He made them out of eggs.
他用鸡蛋制成气凝胶
He made them out of rubber, out of nitrocellulose.
他还用硝基纤维素和橡胶制成气凝胶
包括硅胶也可以制成气凝胶
Actually right here on the table,
实际上就在这张桌上
I have some examples of some silica gels.
我就有一些硅胶样品
This is a, a wet silica gel
这是一种湿硅胶
It’s kind of rubbery so I can just,
有点像橡胶 所以我可以
you know, carve out a piece.
你知道 切下一块
It is 97% alcohol inside of its pores.
它的孔隙里97%都是酒精
And then the remaining 3% solid is amorphous silica. Just–
而剩下的3%是无定形二氧化硅
– Can I touch it? – Yeah, absolutely.
–我能摸吗 –当然可以
It’s kind of rubbery. Not that strong.
有点像橡胶 只是没那么结实
So was I cracking it there or was it already kinda cracked?
所以是我弄碎了还是它本来就有点碎
Yeah, you just, no — –
是啊 你只是 别
Oh whoa, it’s very easy to break. Very crumbly.
它很容易就碎开的
The next step is to replace the alcohol in the gel with liquid carbon dioxide.
接下来用二氧化碳液体代替凝胶中的酒精
We’re about to see liquid CO₂.
我们将看到二氧化碳液体
Liquid CO₂ has the advantage of being non-flammable,
二氧化碳液体的优点是不易燃烧
plus it’s got a low critical temperature.
而且它的临界温度低
Open it up, and —
打开它 然后
Yeah, I see it flooding in there.
是的 我看到它涌进去了
Yeah, it’s flooding in. There it goes. Just another solvent.
嗯 现在里面正在进行溶剂替换
[Vibration.]
[震动声]
You can clearly see that it’s so much cooler on top.
可以清楚地看到 顶部温度很低
What temperature is it on the bottom?
底下温度有多高?
We’re at 600 right now?
现在是600吗?
600 degrees Celsius.
600摄氏度
600 degrees Celsius, that’s 1250 Fahrenheit right now.
也就是说现在是1250华氏度
Notice where the bunny is melting.
注意一下兔子融化的地方
It’s melting right on that edge where the heat’s, like,
它好像就在热浪边缘融化了
the flame is kind of crawling up and over.
因为火焰会上升
– So, yeah, that’s – Oh!
– 所以它会这样熔化 –哇哦
Bunny down! [Laughs.]
兔子倒了 [笑声]
Well, not a bad result.
还好 不算太坏
Not a bad result at all.
总的来说 结果不错
I’m interested in in tasting some of this chocolate here.
我想尝尝这儿的巧克力
( – Gross.)
看着有点恶心
Is it hot?
烫吗
– It’s warm. – Warm.
–不烫 温温的 –温的
– And delicious. – Like fondue.
–而且很好吃 –像奶油一样
Mm-hmm. That was great.
嗯嗯 那很棒
once the liquid co2 has filled all the pores of the gel,
一旦二氧化碳液体充满凝胶内所有孔隙
it’s time to take it supercritical.
就是达到超临界的时候了
It was, I would say,
我会说 这像是
a kind of a spiritual experience
一种精神体验
the first time that I saw a supercritical fluid.
就像我第一次看到超临界流体那样
We’ll get to that here. [Laughs]
我们将去这里 [笑声]
– I love how much you’re into these autoclaves. – I love aerogels.
–我喜欢你对高压锅的热爱 –我喜欢气凝胶
To make a supercritical fluid, we can heat this with a hairdryer actually.
我们实际可以用吹风机加热 制成超临界流体
[Hairdryer blows.]
[吹风机吹的声音]
As we approach the critical point,
当我们接近临界点时
the surface of the liquid becomes kind of blurry.
液体的表面就会变得有点模糊
– Weird, huh? – That is like weird waves in there, yeah.
–怪了 –这里面有一些奇怪的波
I’ll speed it up so you can watch the surface disappear altogether.
我会加速 这样你能看到整个表面消失了
You’re now looking at the supercritical fluid of CO₂.
你现在看到的是二氧化碳的超临界流体
In this state, the CO₂ can be vented without affecting the solid structure,
这种状态下 二氧化碳可以排出而不影响固体结构
and what you’re left with is aerogel.
所以剩下的就是气凝胶
♫ – If you look at aerogel on a light background,
如果你在浅色背景下观察气凝胶
it’s almost impossible to see, because it is pretty transparent.
这几乎不可能看到 因为它很透明
But if you look at it on a darker background,
但如果你用暗一点的背景来看它
then you can see that it has a slight bluish color. And,
你可以看到它会轻微泛蓝
it’s bluish for the same reason
它之所以泛蓝 就像是
that the sky is blue,
天空是蓝色的 道理一样
because all those tiny little nanoscale structures,
因为所有这些微小的纳米结构
they scatter the light according to Rayleigh scattering. And,
它们会根据瑞利散射来散射光
the intensity of light scattered is proportional to 1
光的散射强度与1成正比
over wavelength to the power of 4,
和波长的4次方成反比
which means it scatters shorter wavelengths, like blue,
这意味着它散射较短的波长 比如蓝色
much more than it scatters yellow or red.
要比散射黄色或红色强度大的多
aerogel looks opaque in the ultraviolet and transparent in the infrared.
气凝胶在紫外线下不透明 在红外线下就是透明的
Now, what do you think this would look like
现在你觉得它会是什么样
if I held it up to the blue sky?
如果我把它举向蓝天
What do you think we would see?
你觉得我们会看到什么
Would it look ultra blue?
它会看起来很蓝吗
No, it looks yellow.
不 它看起来是黄的
And that’s because the aerogel is
这是因为气凝胶
actually scattering out that blue light,
实际上是它会散射蓝光
and so what passes through and makes it to our
然后穿过并让我们看到的
eyes is the longer wavelengths like the yellows and oranges.
是波长较长的黄色和橙色
It’s basically the same effect as looking at a sunset
基本上它就和看日落的效果一样
When you see the yellows and oranges of a sunset,
我们看到的日落是黄色和橙色的
it’s because the blue light has already been scattered out by the atmosphere
这是因为蓝光已经是被大气层散射出去了
the light had to pass through before it reached your eyes
所以在光到达你眼睛之前 一定先穿过大气层
So effectively looking at aerogel against blue sky is
所以 你对着天空看气凝胶的话
like looking at a portable sunset.
就像看平时的日落一样
The nanoscale pores of the aerogel are also
气凝胶的纳米孔
what makes it such a good thermal insulator.
也让它成为非常好的隔热材料
( Three.)
(三)
That’s awesome.
太棒了
– Does that look hot? – It’s definitely hot.
–那看着很热 –它确实很热
You might think that because aerogel is
你可能认为这是因为气凝胶
largely comprised of air, like 99% air,
大部分都由空气组成的 可能是99%的空气
that it has the same thermal properties as air,
所以它和空气的热特性相同
but that is not correct.
但这是不正确的
It’s actually a better insulator than air is.
它实际是一种比空气更好的绝缘体
That’s because the width of the pores is smaller
因为在撞到东西之前
than the distance air molecules travel on average
气凝胶孔隙的宽度比空气分子
before colliding with something.
平均移动的距离更小
Their so-called mean free path. Hence,
也就是所谓的平均自由路径 因此
it’s really difficult for the hot fast-moving air molecules below the aerogel
对气凝胶下面快速移动的热空气分子来说
to diffuse through it and transfer heat to the top of the aerogel.
将热量扩散到气凝胶的顶部是非常难的
This is called the Knudsen effect.
这就被称为克努森效应
It is so weird because
这很神奇
– you know, you don’t expect that’s transparent
因为一般我们觉得
to block the heat. – that well?
透明物质隔热能力不高
but this really does.
但气凝胶隔热力真的很好
And that’s why NASA used aerogel insulation
而这就是 NASA将气凝胶绝缘材料用于
on the Sojourner Rover, Spirit and Opportunity,
漫游号火星探测器 勇气号和机遇号火星探测器
the Curiosity Rover,
和好奇号探测器的原因
and they plan to use it on future missions to Mars.
他们还计划在未来的火星任务中使用它
– Why does it need insulation? – The electronics, because
–为什么NASA需要绝缘材料 –因为电子设备
they don’t want the electronics to get cold
他们不希望电子设备在经历
during the cold nights on Mars
火星寒冷夜晚时 温度会变低
NASA has also put aerogel to more exotic uses,
NASA也将气凝胶用于其它用途
notably to catch dust from a comet as part of the Stardust mission.
特别是在星尘任务中捕捉彗星尘埃时
So the particles were traveling
粒子在以大约
about six kilometers per second relative to the aerogel
每秒6千米的速度朝气凝胶反向运动
So when they hit the aerogel,
那么 当它们撞到气凝胶时
because the aerogel’s a very low density material, very, very porous material,
由于气凝胶是一种低密度 多孔的材料
the particles actually enter the aerogel,
所以粒子实际上进入了气凝胶
and as they travel through the aerogel,
当它们穿过气凝胶时
they basically break apart the network
它们几乎完全把网络分裂开了
that makes up the aerogel and they lose energy in the process
导致 粒子在进入气凝胶的过程中损失能量
and eventually come to a stop.
并最终停下来
This is good for capturing particles,
而这有利于捕捉粒子
because if a particle like that were to hit a solid surface
因为如果粒子像这样撞击固体表面
then it just stops, you know, immediately.
它就会停止 你知道 很快的
– It just vaporizes. – And vaporizes.
–它蒸发了 –是蒸发了
So should we expect to see aerogel in our everyday lives anytime soon?
所以我们应该期待气凝胶快点用于生活中吗?
One of my running jokes is when they build skyscrapers in Antarctica,
我常听的一个笑话是在南极洲建摩天大楼
they’ll use aerogel as thermal insulation.
他们要将气凝胶作为隔热材料
[Both laugh.]
[两人的笑声]
Why do you say that?
为什么你要说这个笑话
Well, because then they’ll really care about how,
因为他们真的很关心
just how thermal efficient it is
它的热效率能有多高
because it would be so cold there.
因为那里太冷了
Right.
没错
So instead of having, you know, ten feet of fiberglass insulation, you could have
相对10英尺的玻璃纤维隔热材料
six inches or something of aerogel.
气凝胶只要6英寸左右足够了
Scientists are currently working on
科学家们目前正致力于
reducing costs and increasing durability.
降低成本和提高耐用性
– And that’s true. They do have some elasticity. – Okay.
–真的 它们确实有了一些弹性 –好的
Yeah, so there we go.
是的 我们继续
So it is not hard to break.
但它比较脆 易碎
They’ve already made a lot of progress.
他们已经取得了很大的进步
For example, original silica aerogel is hydrophilic.
比如说 原来的硅胶气凝胶是亲水的
There we go. Now this is a hydrophilic aerogel.
我们继续 现在这是一块亲水气凝胶
So once we’ve done this,
一旦我们滴上水
is that piece of aerogel ruined now?
这块气凝胶现在是坏了吗
Pretty much.
坏了很多
But there are ways to make it waterproof.
但我们也有使它防水的方法
So if you want to see
所以如果你想继续看
that and all the other next generation aerogels,
其它种类的气凝胶
then subscribe to the channel and this may be the start
可以接着订阅频道 不过这可能只是
of an aerogel trilogy.
气凝胶三部曲的开头而已

[音乐声]
[Subtitles credits: 雜碎 Chop Suey, ] [Translation credits: 雉时]
[听录: 雜碎 Chop Suey] [翻译:雉时]

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视频概述

堪比气体质量的神奇固体,并用于航空探索。气凝胶是世界上最轻、质量最小的固体,仅仅只是相同体积空气质量的几倍,其中99.8%是由空气构成的,但是绝热性比空气更好,被美国宇航局NASA 用于火星探测器及其它用途。

听录译者

收集自网络

翻译译者

Rhea

审核员

审核员SX

视频来源

https://www.youtube.com/watch?v=AeJ9q45PfD0

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