Scientists at Rensselaer Polytechnic Institute have found a way to grow aluminum nitride crystals large enough to slice into semiconductor substrates. The crystals can be used to make blue and ultraviolet lasers and light-emitting diodes (LEDs). "Semiconductor light sources have always been very attractive because of their ruggedness and economy," says Leo Schowalter, professor of physics at Rensselaer. "But the color of LEDs has been pretty much limited to red. Green and blue LEDs are also needed if we are to create traffic signals, automobile lighting, flat-screen TV sets, and other applications where long life and high efficiency are important." A Rensselaer researcher, Glen Slack, has demonstrated that you can grow aluminum nitride crystals in a tungsten crucible at 2,300C. However, at that temperature, the aluminum attacks the grain boundaries in the tungsten, and the crucible doesn't survive very long. Schowalter and Slack have now solved the problem and formed a company to make the aluminum nitride crystals. E-mail firstname.lastname@example.org.
Wal-Mart will hold its second Made in the USA Open Call July 7-8, at its headquarters in Bentonville, Ark. The event will be a repeat effort by the world’s biggest seller of consumer goods to increase the amount of US-made products it sells in Wal-Mart stores, in Sam’s Club members-only wholesale outlets, and on walmart.com.
This year, Design News is getting a head start on the Fourth of July celebration. In honor of our country and its legacy of engineering innovation -- in all of its forms -- we are taking you on an alphabetical tour through all 50 states to showcase interesting engineering breakthroughs and historically significant events.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.