已有 3102 次阅读 2010-4-12 12:42 |个人分类:生活点滴|系统分类:科研笔记|关键词:磁性材料,金属钕| 磁性材料, 金属钕 |文章来源:转载

最近一种稀土元素钕引起了研究人员的广泛关注。其原因说来话长,由于Nd-Fe-B(neodymium-iron-boron )合金磁性材料的应用日趋广泛,对于钕元素的需求量大幅攀升。而中国作为这种资源的大国,完全可以控制它的价格。发达国家,尤其是美国非常担忧中国以某种借口来严格限制它的出口。最近有英文消息来源,围绕这个问题,业界正在展开一场科学竞赛试图来解决这个问题。全文如下:


Scientists Race to Engineer a New Magnet for Electronics

A magnet at the heart of high-tech products such as cell phones and hybrid cars relies upon an increasingly scarce supply of the rare earth element known as neodymium. Now one of the original inventors of that magnet hopes to create a new generation of magnetic materials that can ease or break free of that dependence.

The neodymium-iron-boron magnet represents the most powerful commercial magnet available today, and has a starring role in many technologies crucial to the U.S. economy and defense. But the U.S. overwhelmingly relies upon China for its supply of neodymium and other rare earth minerals, and China has warned that its own domestic demand may soon force it to cut off that supply.

That means the U.S. may face a shortage of neodymium and other rare earths, unless it spends the time and money to begin mining its own fairly untapped reserves. The possibility of a shortage has also led to renewed research aimed at developing magnets less dependent upon neodymium.

"It's been 27 or 28 years since the discovery of neodymium-iron-boron (Nd-Fe-B), and we have not yet found a better magnet," said George Hadjipanayis, a physicist at the University of Delaware and co-inventor of the Nd-Fe-B magnet.

Hadjipanayis leads a collaborative research effort with $4.6 million in funding from ARPA-E, the U.S. Department of Energy's agency that backs high-risk but potentially high-payoff projects.

Nd-Fe-B magnets have worked well for everything from computer hard drives to wind turbines and Toyota's Prius because of their exceptional magnetic strength - the energy product of such magnets can reach 50 million or even 60 million megagauss-oersteds (MGOe). By comparison, the energy product of the more common ferrite magnets is just 4 million to 5 million MGOe.

"The higher the strength of the magnet, the smaller the amount of magnet you need for a particular application," Hadjipanayis told TechNewsDaily. He added that Nd-Fe-B magnets play a crucial part in building ever-smaller electronic devices. (Read "The Common Elements of Innovation.")

Three routes to a better magnet

Hadjipanayis and his fellow researchers plan to pursue three different routes to possibly achieving a next-gen magnet breakthrough.

First, the U.S. Department of Energy's Ames Laboratory in Iowa plans to investigate new materials based on combinations of rare earths, transition metal elements and some elements that have not been studied before in magnets.

Many such elements require special working lab conditions under high pressures or temperatures, and create additional challenges because they have high reactivity or toxicity.

Second, an approach headed by the University of Nebraska will try to develop a rare earth-free magnet. This has proven a challenge because existing magnets without rare earths have much lower magnetic strength, but there are some theoretical ideas about changing the crystal symmetry of iron-cobalt alloys by using some non-magnetic elements as substitutes.

Third, Hadjipanayis and the University of Delaware will try to create a new magnetic material that combines the best properties of Nd-Fe-B and iron. The material would ideally end up with high magnetization, and also strongly resist demagnetization.

Simulations have predicted that a next-gen magnet built this way could have a magnetic strength of more than 100 million MGOe, and might also slash neodymium use in magnets by 30 or 40 percent.

Feeling the pressure

All efforts to create such magnetic material have faltered over the past few decades, but Hadjipanayis sees hope in a new bottom-up approach that mixes nanoparticles of Nd-Fe-B at the incredibly tiny scale of just billionths of a meter, or far smaller than the width of a human hair.

Other research participants include Northeastern University, Virginia Commonwealth University and the Electron Energy Corporation - one of the last U.S. companies making rare-earth magnets.

The group has put together an ambitious timeline that involves two years for experimenting with materials, before hopefully putting together a new magnet prototype in the third year.

"It's a fast-moving program, so I already started feeling the pressure," Hadjipanayis said. "Hopefully we'll have a breakthrough that leads to some permanent magnets."


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