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.
Fifty-six-year-old Pasquale Russo has been doing metalwork for more than 30 years in a tiny southern Italy village. Many craftsmen like him brought with them fabrication skills when they came from the Old World to America.
Linear guides are one of the most important components required for the design of automated or computer-controlled equipment. Aluminum profile extrusions, used for these guides, can enable designed-in functional features.
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