Official 44 Set 2

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An Application of Nanotechnology

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What is the main purpose of the lecture?
  • A. To provide an example of a practical use of nanotechnology

  • B. To show the origins of the field of nanotechnology

  • C. To give a brief outline of the main concepts of nanotechnology

  • D. To explain the growing interest in nanotechnology research

显示答案 正确答案: A

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    NARRATOR:Listen to part of a lecture in a materials science class.

    MALE PROFESSOR:OK. Last time we finished going over some of the fundamental concepts of nanotechnology—the multidisciplinary science of manipulating—or controlling—extremely small units of matter, on the scale of molecules or even atoms.

    So, I want to talk about how nanotechnology is being used today, and, just to give you an idea, we'll look at one particular application.A team of materials scientists in Massachusetts has been working on a new, ultrathin coating, a nanocoating that might be applied to objects like bathroom mirrors, car windows, and eyeglasses to prevent fogging.

    And the coating has the potential to be a permanent solution, unlike the kinds of anti-fogging, spray-on liquids that are on the market today...

    Now, fogging often occurs when a cold surface comes into contact with warm, moist air, such as when a glass shower door or mirror fogs up during a warm shower...Now, what's actually happening is, uh, what the fog is, is thousands of tiny spherical water droplets condensing on the surface of the glass.Light hits the water droplets and is scattered in random directions, causing the fogging effect.

    Now, the kind of spray-on treatments I mentioned, well, they wear off.What happens is they cause the tiny water droplets to flatten when they condense on the surface of the shower door, or bathroom mirror, or whatever object it is that it's been applied to.Because the droplets are flattened, when light hits them, the light doesn't scatter.But as I said, those kinds of treatments don't last very long.

    The new coating has two important components.One: [say “negatively charged” as a unit] negatively charged silica nanoparticles—these are basically tiny particles of glass.And two: a positively charged polymer—which, you already know, a polymer is a chemical compound.These're layered over each other... the polymer, then the silica nanoparticles, the polymer, then the silica nanoparticles, you see.They're layered in such a way that the silica nanoparticles don't pack together tightly.In other words, the structure has pores, or holes, little tiny pockets, throughout it.The coating prevents fog from developing because it loves water.It attracts the water droplets—sucking them into the tiny pores.And that alters the shape of the droplets; the droplets are forced to flatten and to join together into a single sheet of water, rather than remaining as single droplets—each of which is a sphere that scatters light in different directions.OK, so instead of being scattered, the light passes through the thin sheet of water.So there's no fogging effect.

    The ultrathin coating can be made more durable by heating it—and of course the object it's applied to—to an extremely hot temperature—500 degrees Celsius.What that does is burn the polymer away and fuse the silica nanoparticles together—while maintaining the structure of pores.But that's possible only on materials that can withstand high heat.Glass, yes.Plastics, no.But they're working on solving that problem; trying to come up with a way to coat plastics and other materials durably and effectively.

    Interestingly, it was a plant—the lotus plant—that inspired this work, I guess you could say inspired it in an indirect sort of way.The leaves of this plant are what we call "superhydrophobic."

    Lotus leaves, being superhydrophobic, don't attract water—they repel it—in a big way.When raindrops fall on lotus leaves, they remain spherical. They roll right off.So for a long time the Massachusetts scientists tried to create a coating that acted like these lotus leaves—a coating that was superhydrophobic.

    But then they began to think about the opposite extreme.Uh, could they accomplish their goal by making a coating that, instead of repelling water, actually attracted water?

    Well, they seem to have gotten quite far with this approach.It's really strong work with a range of interesting consumer applications.It's not costly to manufacture the coating.Some car makers are interested in applying it to their windshields.Looks like we'll probably see it on the markets in everyday products in the next few years.

  • 旁白:请听材料科学课上的部分内容。

    教授:上次我们讲完了关于纳米技术的一些基本概念,这是在分子或者甚至原子规模上操纵极小单位的物质的多学科科学。

    所以我想讲一讲如今我们是如何应用纳米技术的,为了让你们有个大致了解,我们来看一个具体的应用案例。一组Massachusetts的材料科学家一直在研究一种新的超薄涂层,一种也许能应用在像浴室镜子、车窗和眼镜上防止起雾的纳米涂层。

    这种涂层有永久性解决问题的潜力,不像现在市场上的那种防起雾的喷雾型液体...

    当一个冰冷的表面接触到了温暖的湿气时就会起雾,比如一个淋浴室的玻璃门或镜子会在洗热水澡时起雾。真正发生的是,恩,雾是什么,是好几千个微小的球形水滴凝结在玻璃表面。光线照到这些水滴上并且发散到了任意方向,由此导致了起雾效应。

    我之前提到的那种喷雾式的方法,它们会逐渐消失。当水滴在淋浴房的门上或浴室镜子上或者任何它们被喷上喷雾的物体表面凝结时,这种喷雾会让这些小水滴变平。因为这些水滴变平了,所以当光线照到它们时不会发散。但是我已经说过了,那种措施的有效时间不会持续很久。

    这种新涂层有两个重要的成分。一个是带阴电荷的硅纳米粒子,这些本质上是微小的玻璃微粒。第二个是带阳电荷的聚合物,你们已经都知道了,聚合物就是一种化学混合物。它们被互相叠加在一起,第一层聚合物,然后是硅纳米粒子,聚合物,再一层硅纳米粒子。你知道的。它们的这种叠加方法能防止硅纳米粒子紧紧地黏在一起。换句话说,这个结构有小孔或者小洞,整个结构中遍布微小的囊袋。这个涂层能阻止雾气形成是因为它非常爱水。能吸引水滴,把它们吸进小孔里。而那改变了水滴的形状,水滴被强行变平了,并且汇聚到一起形成了一层水,而不是保持在单个水滴,每个都是能将光线发散到不同方向的球形的状态。光线穿过了这个单薄的水片,而不是被发散出去。所以也就没有了起雾效应。

    这个超薄的涂层加热后会变得更耐用---当然也就是它所应用的物体也要被加热---要加热到一个极高的温度,500摄氏度。这个过程的作用是把聚合物烧掉,把硅纳米粒子融合到一起,同时保持住孔状结构。但是只有在物体的材料能经受住高温的情况下才可能实现。玻璃材质?可以。塑料?不行。但是他们正在努力解决这个问题,试图想出办法既耐久又有效地把塑料和其他材料涂上涂层。

    有意思的是,是一种植物---荷花---启发他们想出这个涂层的,我想你们也可以说这间接地启发了他们。我们认为这种植物的叶子超级疏水。

    超级疏水的荷叶不会吸引水,它们彻底排斥水。当雨水落到荷叶上时,它们会保持球形直接滚下来。所以很长时间以来,Massachusetts的科学家试着发明出一种像这些荷叶一样的涂层,一种超级疏水的涂层。

    但是后来他们开始思考相反的极端。他们能不能通过制造一种涂层,不是排斥水的涂层,而是吸引水的图层呢?

    他们用这种方法似乎已经取得了很大的进展。这是一个非常有力的产品,有一系列有趣的用户应用领域。生产这种涂层成本并不高。一些汽车制造商有兴趣把它应用到他们的挡风玻璃上。看上去在接下来几年里,我们可能会在市场上的日常产品中见到它的身影。

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    题型分类:主旨题

    原文定位:So, I want to talk about how nanotechnology is being used today, and, just to give you an idea, we’ll look at one particular application. 

    选项分析:教授说今天想要讲讲纳米技术如今的应用,今天主要来看一个特别的应用,对应选项A。

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