经济学人104:一种受外力时硬度提高的新材料

 　　Science and Technology Materials science Stronger when stricken

　　科技 材料科学 越敲越结实

　　A new material that gets stiffer when it is stressed

　　一种受外力时硬度提高的新材料

　　ONE of the valuable properties of bone is that when it endures repeated stress it responds by becoming denser¹ and stronger.

　　骨头有一种很珍贵的属性，那就是当受到反复的击打时，其质地反而会变得更加紧密，坚硬度变得更高。

　　A living material can do that. A non-living one cannot.

　　只有活性材料具备这种特征，非活性材料则不具备。

　　It has no way of adding the extra matter needed to provide the extra density². But it would help engineers a lot if non-living stuff could at least stiffen³ in response to stress—and that may now be possible.

　　用添加必要物质来让材料获得更高密度的方法是不可行的，但如果非活性材料起码可以在外力作用下变得坚硬—目前达到这一点是可能的，那么这对工程师们来说有非常大的借鉴意义。

　　Brent Carey, a graduate student at Rice University in Texas, thinks he has found a way to make it happen.

　　布伦特凯利是一名德州莱斯大学的研究生，他认为他已找到了实现这一设想的办法。

　　Mr Carey made his discovery when he was testing the properties of a material made of carbon nanotubes (cylinders of carbon atoms a few billionths of a metre across) and a rubbery polymer called polydimethylsiloxane.

　　凯利在测试一种材料的属性时有所发现，该材料的成分包含碳纳米管（直径为几纳米的碳原子圆柱体）和一种名为聚二甲基硅氧烷的橡胶聚合物。

　　He created this composite by growing a forest of nanotubes using hot hydrocarbon⁴ gases and an iron catalyst⁵, and then filling the space between the tubes with the polymer.

　　材料的合成过程是这样：首先，他使高温碳氢混合气体和铁催化剂相互作用产生密集的碳纳米管群，然后再用聚合物充填碳纳米管间的空隙。

　　The surprise came when he discovered how his new material responded to repeated stress.

　　当他注意到新材料受到连续作用力而产生反应时，令他惊讶的现象出现了。

　　He found this did not cause any of the damaging fatigue⁶ that would be expected.

　　据他观察，预期中的材料损毁性疲劳并未产生。

　　Indeed, his initial inspection⁷ suggested the stuff was actually growing stiffer.

　　实际上，他的初步监测显示材料变得更加坚硬了。

　　Fascinated by this result, he took his finding to his supervisor⁸, Pulickel Ajayan, and they assembled a team to study the new material.

　　这个结果让凯利喜出望外，他马上找到了自己的导师普里克尔阿贾扬，随后他们成立了一个小组，专门研究这种新型材料。

　　They gave the composite a real workout. They compressed it five times a second for a week. That caused its stiffness to increase by 12%.

　　他们给这种合成材料做了次实验：对该材料施加5.5倍的压力，时间持续一周，结果材料硬度提高了12%，

　　Moreover, the effect showed no sign of abating⁹,

　　并且这种状态没有减弱的迹象。

　　which led them to suspect that if it were exposed to more stress it would grow stiffer still.

　　研究小组由此设想，如果对其施以更大的作用力，这种材料的硬度是否会变得更高。

　　Why this happens is still a mystery.

　　产生这种效果的原因还是个谜。

　　Mr Carey and his colleagues report in the American Chemical Society's journal Nano that heating the new material did not eliminate the response.

　　凯利和他的同事们发表在美国化工科学院的期刊杂志《Nano》的文章中说，即使对这种新型材料加热，也不能消除已产生的变化。

　　This suggests that the self-stiffening is not the result of chemical changes in the polymer, which can usually be undone¹⁰ by heat.

　　这说明材料强度提高并不是聚合物发生化学反应造成的，一般这种变化在加热状态下是可逆的。

　　The researchers do have one lead, though. Because of the regular alignment¹¹ of the nanotubes, they were able to stress the material from various directions.

　　不过研究人员已有所发现。由于碳纳米管呈规律状排列，他们能够从不同的方向对材料施加作用力。

　　They found that when the direction of stress was at right-angles to the tubes, it stiffened¹² by 5.9%.

　　当施力方向与碳纳米管成直角时，材料硬度提高5.9%；

　　When it was in the direction in which tubes were pointing, the increase was only 4.3%.

　　当作用力与碳纳米管所指方向一致时，材料硬度仅提高4.3%。

　　What that means is still unclear, but it may be the key to understanding the phenomenon—and thus being able to replicate¹³ it with other ingredients.

　　现在尚无法对其中的原因作出解释，但或许对于理解材料硬度变化是非常重要的—进而在其他原材料身上复制这类变化也有了可能。

1 denser   

adj. 不易看透的, 密集的, 浓厚的, 愚钝的

参考例句：

• The denser population necessitates closer consolidation both for internal and external action. 住得日益稠密的居民，对内和对外都不得不更紧密地团结起来。 来自英汉非文学 - 家庭、私有制和国家的起源
• As Tito entered the neighbourhood of San Martino, he found the throng rather denser. 蒂托走近圣马丁教堂附近一带时，发现人群相当密集。

2 density   

n.密集，密度，浓度

参考例句：

• The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
• The region has a very high population density.该地区的人口密度很高。

3 stiffen   

v.(使)硬，(使)变挺，(使)变僵硬

参考例句：

• The blood supply to the skin is reduced when muscles stiffen.当肌肉变得僵硬时，皮肤的供血量就减少了。
• I was breathing hard,and my legs were beginning to stiffen.这时我却气吁喘喘地开始感到脚有点僵硬。

4 hydrocarbon   

n.烃，碳氢化合物

参考例句：

• During incomplete combustion some of the hydrocarbon fuel is cracked.在不完全的燃烧中，一些烃燃料裂解。
• The hydrocarbon must be an alkene.这个碳氢化合物必定是烯烃。

5 catalyst   

n.催化剂，造成变化的人或事

参考例句：

• A catalyst is a substance which speeds up a chemical reaction.催化剂是一种能加速化学反应的物质。
• The workers'demand for better conditions was a catalyst for social change.工人们要求改善工作条件促进了社会变革。

6 fatigue   

n.疲劳，劳累

参考例句：

• The old lady can't bear the fatigue of a long journey.这位老妇人不能忍受长途旅行的疲劳。
• I have got over my weakness and fatigue.我已从虚弱和疲劳中恢复过来了。

7 inspection   

n.检查，审查，检阅

参考例句：

• On random inspection the meat was found to be bad.经抽查，发现肉变质了。
• The soldiers lined up for their daily inspection by their officers.士兵们列队接受军官的日常检阅。

8 supervisor   

n.监督人，管理人，检查员，督学，主管，导师

参考例句：

• Between you and me I think that new supervisor is a twit.我们私下说，我认为新来的主管人是一个傻瓜。
• He said I was too flighty to be a good supervisor.他说我太轻浮不能成为一名好的管理员。

9 abating   

减少( abate的现在分词 )； 减去； 降价； 撤消（诉讼）

参考例句：

• The storm showed no signs of abating. 暴风雨没有减弱的迹象。
• The recent public anxiety about this issue may now be abating. 近来公众对这个问题的焦虑心情现在也许正在缓和下来。

10 undone   

a.未做完的，未完成的

参考例句：

• He left nothing undone that needed attention.所有需要注意的事他都注意到了。

11 alignment   

n.队列；结盟，联合

参考例句：

• The church should have no political alignment.教会不应与政治结盟。
• Britain formed a close alignment with Egypt in the last century.英国在上个世纪与埃及结成了紧密的联盟。

12 stiffened   

加强的

参考例句：

• He leaned towards her and she stiffened at this invasion of her personal space. 他向她俯过身去，这种侵犯她个人空间的举动让她绷紧了身子。
• She stiffened with fear. 她吓呆了。

13 replicate   

v.折叠，复制，模写；n.同样的样品；adj.转折的

参考例句：

• The DNA of chromatin must replicate before cell division.染色质DNA在细胞分裂之前必须复制。
• It is also easy to replicate,as the next subsection explains.就像下一个小节详细说明的那样，它还可以被轻易的复制。