Whipping up a metallic frappe
(This story appeared on page 309 of the
Nov. 15, 1997, Science News.)
By Sid Perkins
Science News
Using only a kitchen blender and a laser, researchers have come up with a
faster, cheaper, and cleaner method of producing ultrafine powders, such
as the silver used in making solder, dental fillings, and high-speed
photographic film. They can produce either individual particles or clumps
of particles, such as micron-sized clusters of 10-nanometer particles of
nickel and nickel oxide.
Jogender Singh, a materials scientist at Pennsylvania State University's
Applied Research Laboratory in State College, developed the process to
produce silver and nickel powders. By firing a laser into a whirling
solution of inexpensive chemicals, Singh and his team create hot spots
where the materials react to form tiny particles of metal, they report in
an upcoming issue of the JOURNAL OF MATERIALS SCIENCE.
The researchers can control the size and to some extent the shape of the
particles by varying the concentrations of the chemicals in the blender,
the intensity of the laser, and the blender's speed.
The technique can create particles of silver metal ranging in size from 1
to 100 nanometers -- smaller than the smallest bacteria -- at rates of up
to 3 grams per minute, Singh says. This yield exceeds that from
any other technique except grinding, which cannot generate such
small particles. The silver powder is also purer and more uniform,
he adds.
Production of increasingly fine metal powders "is a growing area of
interest," says Steve Lampman of ASM International, an engineering
materials society in Materials Park, Ohio. "Everybody wants to get powder
size down for a variety of reasons -- better mixing, better reactivity,
and lower processing temperatures."
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Copyright 1997 by Science Service.
All rights reserved.
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