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TIC PROCESS MAKES CERAMIC COMPOSITES AFFORDABLE

 TIC PROCESS MAKES CERAMIC COMPOSITES AFFORDABLE
 SAN DIEGO, July 8 /PRNewswire/ -- The following is a technology


update issued by ThermoTrex Corporation (AMEX: TKN), a division of Thermo Electron Corporation (NYSE: TMO):
 Composites -- hybrid materials with desirable properties -- are among 12 "emerging" technologies that the U.S. Department of Commerce anticipates will be of major economic importance by the year 2000. Cost-effective fabrication techniques have been developed for many classes of composites, but not for one very important type, ceramic. Potential applications for these materials range from airplane engines to false teeth. With Department of Energy support, ThermTrex Corporation (TTC) has developed chemical vapor composite deposition, a rapid new single-step process for making affordable ceramic composites.
 A major portion of the fuselage of many airplanes is made of composite materials, as are the mechanical structure and heat resistant tiles of the space shuttles. The now-familiar "graphite" tennis racquets and skis are actually graphite-epoxy composites. And fiberglass, used in everything from insulation to boats, is also a composite.
 There are several classes of composites. Fiberglass, for instance, is a plastic composite made of glass fibers embedded in a plastic matrix. In its report on emerging technologies, the Commerce Department specifically mentions two other types: ceramic and metal. Both fall into the "advanced materials" category, which the department predicts will generate the largest annual sales of the 12 categories named in the report.
 Potential customers for ceramic composite technology and products include the aerospace and automotive industries. A typical ceramic composite, consisting of silicon carbide and fibers (made of silicon carbide or carbon), is less brittle and capable of withstanding more extreme changes in temperature than a pure ceramic. Ceramic composite engines for planes and automobiles would have several advantages over conventional metal engines. Lighter weight and the ability to run at higher temperature would mean improved fuel economy and reduced emissions.
 In their pure forms, ceramic materials have many desirable properties. They are heat-resistant, stable in corrosive environments, and lightweight. However, like a ceramic coffee cup, they crack and break easily. Creating a ceramic composite embedded with ceramic fibers increases the fracture-resistance without adversely affecting the beneficial qualities. But fabricating ceramic composites is complicated by several factors, not the least of which is cost.
 The most common process in use today for fabricating ceramic composites is chemical vapor infiltration. The drawback to this process is time; hundreds of hours may be required to create a component, and once the process is completed, the part still has to be extensively machined to achieve the desired shape.
 TTC's method for chemical vapor composite deposition provides an alternative to this process. A reusable mold, machined in the shape of the desired piece, is placed in a furnace and heated. Then the ceramic fibers, suspended in a silicon carbide gas stream, are blown into the furnace and deposited in the mold. The gas undergoes a reaction when it comes in contact with the hot mold and deposits a layer of silicon carbide on and around the fibers in the form. The silicon carbide bonds the fibers together, and a ceramic composite in the desired shape is produced.
 TTC's patent-pending process overcomes many of the production and cost limitations that have prevented widespread use of ceramic composites. It is fast -- as much as 100 times faster than chemical vapor infiltration -- and once the composite is completed, only light machining is necessary.
 The same characteristics that would make ceramic composite engines more energy-efficient than their metal counterparts would apply to heat exchangers used to capture waste heat in industrial stacks. Because ceramic composites can withstand higher temperatures and are more corrosion-resistant and thermal shock-resistant than metal, heat exchangers made of these materials could be placed closer to the heat source, increasing the efficiency of the process.
 Chemical vapor deposition is not limited to fabricating ceramic composites. Metal and carbon composites could also be made this way. TTC is presently developing its manufacturing capability and is working with the Holcroft division of another Thermo Electron company, Thermo Process Systems Inc. (AMEX: TPI), to develop energy-saving ceramic matrix components for Holcroft's heat-treating equipment.
 -0- 7/8/92 R
 /CONTACT: John N. Hatsopoulos of Thermo Electron Corporation, 617-622-1111/
 (TMO TPI TKN) CO: ThermoTrex; Thermo Electron Corporation; Thermo Process Systems ST: Massachusetts IN: SU:


TM -- NE008 -- 7505 07/08/92 14:45 EDT
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Date:Jul 8, 1992
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