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Conducting ceramics make good contacts
International Survey Polymer has powerful optical properties Photorefractivity - an optical characteristic previously found only in a few small, expensive crystals has now been reproduced by scientists from IBM in a mixture of a new type of epoxy (BiSA-NPDA)and an inorganic material (DEH) used in laser printers and copiers. In photorefractive (PR) materials, illumination by light causes electrical charges to move, altering the refractive index, the optical property that determines how light passes through a material. When two laser beams cross within a PR material, they create a pattern of electrical charge similar to a hologram that changes the optical properties of the very material they are passing through, in some cases, it would be possible to store 100 complete holograms or images - each containing 1 million bits of
information - in a tiny volume 2mm in diameter and l m m thick (slightly thicker than the head of a pin). If coated onto goggles, a PR film could disperse a laser beam so the intense light did not damage the eyes of the wearer. The resulting material exhibits only a modest diffraction efficiency of 0.01-0.1%. But more recently a PR effect 10 times stronger has been demonstrated in a mixture of DEH and another epoxy formulation (NNDN.NAN). Realistically however, a diffraction efficiency of more than 10% is n e e d e d if many PR applications are to be practical. The inventors hope that the discovery will stimulate much more research in The X where the lasers cross marks this type of material. the spot where a ne w tgpe o f Further information: IBM, PO Box p o l g m e r m a g l e a d to the 41, North Harbour, Portsmouth PO6 development o[ instant holographic 3AU, UK. Tel: +44 (0)705 321212. cameras
Mobile degassing unit for AI foundries Molten aluminium holds appreciable quantities of hydrogen in solution which originates from a variety of moisture sources, such as the furnace atmosphere, damp scrap or fluxes, or cold and damp furnace linings. The higher the melt temperature, the more dissolved hydrogen is held in solution, causing gas defects on solidification. Pinhole defects in castings are often only revealed during the machining and finishing processes and lead to poor mechanical properties and lack of pressure tightness. A mobile degassing unit (MDU) from F o s e c o for use in aluminium foundries uses an alternative m e t h o d of degassing molten aluminium. It is based on a spinning rotor system which degasses by passage of a molten gas, usually nitrogen, into the molten metal. Soluble hydrogen migrates into the nitrogen bubbles rising through the melt, thus releasing the potentially harmful gas from the melt. The MDU can be moved easily around the foundry, making it useful where there are large numbers of small treatment furnaces. All the user has to do is to simply wheel it to the furnace, swing the rotary arm across, lower the rotor into the melt
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Conducting ceramics make good contacts ....
............................................... MobL/edegassin9 unit [or aluminium [oundries and activate the system. The automatic timer, rotation speed (500-600 rpm) and gas flow can all be preset to suit any furnace capacity and enable most treatments to be completed within 3-5 minutes. Further information: Foseco International, 285 Long Acre, Nechells, Birmingham B7 5JR, UK. Tel: +44 (0)21-327 1911.
A new family of electrically active ceramics has been developed by E l m w o o d S e n s o r s through a commercial arrangement with the University of Durham; it is a direct development from the company's existing technology in ceramic thermistors, which are used as intrinsically safe heaters and temperature sensing devices. The new materials have extremely high electrical conductivity, in the region normally exhibited by metals, combined with the durability and stability of ceramics. Possible application areas include electrical contacts, rechargeable batteries and light-sensitive devices. In electrical contacts, oxides cannot form on the surface of the material, giving improved operating performance over the lifetime of the contacts. In rechargeable batteries, the new materials provide an increased power density, leading to miniaturisation, elimination of cadmium and possibly to a solid-state rechargeable battery to replace conventional nonrechargeable types. Further information: Elmwood Sensors, Elm Road, North Shields, Tyne & Wear, UK. Tel: + 4 4 (0)91-258 2821.
MATERIALS & DESIGN Vol. 12 No. 4 AUGUST 1991
information - in a tiny volume 2mm in diameter and l m m thick (slightly thicker than the head of a pin). If coated onto goggles, a PR film could disperse a laser beam so the intense light did not damage the eyes of the wearer. The resulting material exhibits only a modest diffraction efficiency of 0.01-0.1%. But more recently a PR effect 10 times stronger has been demonstrated in a mixture of DEH and another epoxy formulation (NNDN.NAN). Realistically however, a diffraction efficiency of more than 10% is n e e d e d if many PR applications are to be practical. The inventors hope that the discovery will stimulate much more research in The X where the lasers cross marks this type of material. the spot where a ne w tgpe o f Further information: IBM, PO Box p o l g m e r m a g l e a d to the 41, North Harbour, Portsmouth PO6 development o[ instant holographic 3AU, UK. Tel: +44 (0)705 321212. cameras
Mobile degassing unit for AI foundries Molten aluminium holds appreciable quantities of hydrogen in solution which originates from a variety of moisture sources, such as the furnace atmosphere, damp scrap or fluxes, or cold and damp furnace linings. The higher the melt temperature, the more dissolved hydrogen is held in solution, causing gas defects on solidification. Pinhole defects in castings are often only revealed during the machining and finishing processes and lead to poor mechanical properties and lack of pressure tightness. A mobile degassing unit (MDU) from F o s e c o for use in aluminium foundries uses an alternative m e t h o d of degassing molten aluminium. It is based on a spinning rotor system which degasses by passage of a molten gas, usually nitrogen, into the molten metal. Soluble hydrogen migrates into the nitrogen bubbles rising through the melt, thus releasing the potentially harmful gas from the melt. The MDU can be moved easily around the foundry, making it useful where there are large numbers of small treatment furnaces. All the user has to do is to simply wheel it to the furnace, swing the rotary arm across, lower the rotor into the melt
232
.................. .......
...........
Conducting ceramics make good contacts ....
............................................... MobL/edegassin9 unit [or aluminium [oundries and activate the system. The automatic timer, rotation speed (500-600 rpm) and gas flow can all be preset to suit any furnace capacity and enable most treatments to be completed within 3-5 minutes. Further information: Foseco International, 285 Long Acre, Nechells, Birmingham B7 5JR, UK. Tel: +44 (0)21-327 1911.
A new family of electrically active ceramics has been developed by E l m w o o d S e n s o r s through a commercial arrangement with the University of Durham; it is a direct development from the company's existing technology in ceramic thermistors, which are used as intrinsically safe heaters and temperature sensing devices. The new materials have extremely high electrical conductivity, in the region normally exhibited by metals, combined with the durability and stability of ceramics. Possible application areas include electrical contacts, rechargeable batteries and light-sensitive devices. In electrical contacts, oxides cannot form on the surface of the material, giving improved operating performance over the lifetime of the contacts. In rechargeable batteries, the new materials provide an increased power density, leading to miniaturisation, elimination of cadmium and possibly to a solid-state rechargeable battery to replace conventional nonrechargeable types. Further information: Elmwood Sensors, Elm Road, North Shields, Tyne & Wear, UK. Tel: + 4 4 (0)91-258 2821.
MATERIALS & DESIGN Vol. 12 No. 4 AUGUST 1991