Appliance Design - July 2008 - (Page 21)

HEatING ElEmENtS from the forest sidewall onto adhesive tape and drawn into a continuous sheet. In order to create a denser material, researchers can place a nanotube sheet onto a substrate such as glass and immerse in an ethanol solution. The ethanol evaporates when the substrate is withdrawn from the solution and the result is a sheet with a density of roughly 0.5 g/cm3. The researchers were able to create a 5-cm, 1-meter long, 50-nm thick, transparent carbon nanotube sheets. High transparency was achieved by the densified nanotube sheets in combination with usable electrical conductive substrates, according to Baughman. This combination is needed for such applications as displays, video recorders, solar cells and solid state lighting. The research obtained a sheet resistivity of 700 ohms per square in the draw direction and 10 to 20 times higher than that in the orthogonal direction. At Fraunhofer, Ivica Kolaric, Department Manager of the Energy Efficient Mechatronic System, is overseeing the carbon nanotube AD12054Kanthal 11/8/05 12:02 PM project. There, carbon nanotubes sheets are spray coated onto the glass. Researchers in Germany have created carbon nanotube sheets with a heating power of >2,500 W per square meter. Much of their applications are in the automotive industry, but other applications might be nearing fruition. Kolaric says that the key to using carbon nanotubes is in the dispersion. If the nanotubes are not dispersed well — and nanotubes tend to clump together — then hot and cold spots can occur. Kolaric says the nanotubes come in powdered form and are then dispersed in solvent or water. The liquid material is spray coated onto the glass and as the liquid dries, the nanotubes form a conducting network inside the lacquer. By passing a current through this network, the nanotube sheet heats and passes that heat into the glass. The ability to spray coat the carbon nanotube material is one way to make the process less expensive to use, and, Kolaric feels, more attractive to manufacturers. He also says that that carbon nanotube sheets also use less voltage as compared to a metal oxide coated Page 1 pane of glass. In a de-icing application, the metal oxide glass needed about 30 to 40 volts to clear the ice, while the nanotube unit needed 3 volts. Challenges, however, still need to be overcome. The wet processes can affect transparency, creating a haze, but Kolaric feels that these issues are being overcome. While carbon nanotube technology might represent the future, electrically heated glass is being sold now. Whether using resistive wires or metal oxide coatings and films, applications for heated glass are growing. The versatility of being able to tune the coating formulation, or resistive wire grid pattern, and reach the temperature, power and size requried, are making this old material new for use in a growing array of applications. < For more information, email: Anthony International: susanw@anthonydoors.com Engineered Glass Products: info@egpglass.com Minco: Dave.Hans@minco.com Schott: tim.dye@us.schott.com Saint Gobain Glass: christian.willers@saint-gobain-glass.com LLC Introducing the SN067KX The ultimate in silicon nitride igniters Full line (120) voltage; no secondary controller required (plug-n-play). Universal HVAC kits for over 150 applications (Robertshaw, W/R, Norton, SiC). Kanthal - a Sandvik brand 1-877-456-2279 1-800-KANTHAL (526-8425) www.kanthal.com www.kanthal.com ISO 9001 ISO 9001 Registered Contact us today for special pricing: info@surfaceigniter.com www.surfaceigniter.com SPECIAL INTRODUCTION ON PAGE 25 applianceDESIGN July 2008 21 800-321-4147 www.applianceDESIGN.com http://www.surfaceigniter.com http://www.kanthal.com http://www.kanthal.com http://www.surfaceigniter.com http://www.appliancedesign.com

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Appliance Design - July 2008 Contents Editorial Shipments/Forecasts News Watch Heating Elements Gas Technology Motors & Pumps Controls & Sensors Design Marts Association Report: AHAM Advertiser's Index

Appliance Design - July 2008

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