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Tutorial MenueThe World of the Platinum MetalsLearning Unit 1 of 5

Platinum as a Metallic Material

Examples of Applications in the Glass Industry

Components and equipment of ceramic refractory materials are adequate for the manufacture and processing of normal glass qualities. However, the ceramics are slowly attacked by the molten glass which can lead both to striae in the glass and to a change in the dimensions of the components. The attack of the refractories becomes more severe at high temperatures such as are encountered in the production of high strength glass qualities and in the refining of glasses for optical applications. In all areas in which the erosion of the refractory materials cannot be tolerated, the ceramic components are clad with platinum materials or the complete component is made from a platinum material, because platinum and rhodium are the only metals that are resistant both to oxidation in air and to the corrosive attack of the molten glass. Components that are subjected to high mechanical loads, such as stirrers, are made from the refractory metal molybdenum which is protected against oxidation by means of a cladding of a platinum material. The most commonly used platinum materials are alloys of platinum with 10-20 % rhodium. Components that are made completely of the precious metal have the added advantage that they can be resistively heated by directly applying an electrical current.

Crucible of chemically pure platinum for melting high quality optical glasses
© Heraeus

Melting crucible of chemically pure platinum or Pt DPH for the manufacture of optical grades of glass. In these glass qualities, an unacceptable discoloration occurs due to rhodium trioxide, Rh2O3, which forms by the oxidation of the alloying element rhodium and is taken into solution by the glass.

Stirrer of molybdenum with platinum-rhodium cladding

Feeder systems with stirrers, plungers, drain bushings etc. of platinum-rhodium alloy for the production of formed glass parts, high melting LCD glass for flat panel displays, glass-ceramics for cooker hobs and many more products.

Bushing 4,000 tips
© Heraeus

Glass fiber bushing of platinum-rhodium alloy, which are used for the manufacture of glass fibers.

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