OSAKA, Japan -- A new waterproofing process could lengthen the lifetime and optical efficiency of silica aerogel, a material used in a variety of applications, including the cladding and protection of optical fiber.
Created by researchers at Matsushita Electric Works, the new process involves putting a waterproof coating around the silica particles in the gel. Silica aerogel is a porous inorganic material made of 10-nm-long necklaces of silica molecules and microscopic air pockets. It has a high transparency (more than 70 percent) and a low light refraction index of 1.02 to 1.06 (the refraction index of air is 1.00029, while that of quartz is 1.46). The gel also offers heat insulation three to four times better than glass wool, Styrofoam and other insulation materials.
Although it sounds like an ideal material, the gel does have some drawbacks. When exposed to air, conventional silica aerogels soon cloud and often shrink because hydroxyls (OH2) in the atmosphere readily adhere to silica molecules.
According to company tests, the upgraded material should be viable for at least 30 years. In addition, the process increases the silica aerogel's transparency by some 20 percent.
The first order of business for Matsushita is reducing production costs; the gel now costs ¥50,000 per liter. After that, the company predicts its new material will be found in skylights, where it will allow light to pass through without the heat. It could also be used to lead light from the high point on an atrium, for example, deep into the basement. Matsushita says the construction industry is working on transparent paneling reinforced with glass fibers.
Company officials expect the new silica aerogel to be used as cladding for optical fibers. The company says tests show the low refraction coefficient of silica aerogel cladding will enable the cables to carry light signals 150 percent more efficiently.
Optical fiber products should be on the market by June 1999, says Tom Kado, a spokesman for Matsushita. Transparent heat-insulating panels should be introduced in December 2000.
Kado also said the company has sent 180 liters of its silica aerogel to CERN of Switzerland (Conseil Européen pour la Recherche Nucléaire), Europe's largest research institute, for study of its elementary particles.