SPI-Glas™ Brand glassy carbon, some times referred to as "vitreous" carbon, can be fashioned into tubes which are universally used in electronics and other industries worldwide for carrying out chemical analyses and also for the preparation of fluorophosphate and other glassy materials. Tubes fabricated in SPI-Glas™ Brand glassy carbon are also used in the growing of single crystals and other ultra-high purity materials.
One of the wider applications for SPI-Glas™ Brand glassy carbon tubes is for the melting of precious group metals.
This glassy carbon should be thought of in perspective with regard to graphite, ordinary carbon, and diamond. Its hardness is close to that of diamond but its appearance (e.g. black) is reminescent of graphite. Quite predictably, the properties of the SPI-Glas™ Brand glassy carbon is considerably different from those of either diamond or graphite.
For example, the SPI-Glas™ Brand Glassy Carbon Tubes, relative to quartz, exhibit far higher thermal conductivity and show very little adhesion of precious group metals. Thermal cycling times are reduced, sometimes substantially. This also means that the heater coils can be operated at lower temperatures than would otherwise be mandated if ceramic or quartz tubes were being used.
As a result of the above, the cycle time is greatly reduced and the useful life of the tubes is greatly extended.
The useful lifetime of SPI-Glas™ Brand Glassy Carbon Tubes is much longer than for graphite because of the much slower oxidation rate of glassy carbon at high temperatures in air. When a reducing atmosphere over the tube is employed, the resulting virtually zero oxidation rate prevents the formation on the molten metal surface an oxide layer. The melting aids usually associated with the use of ceramic test tubes are normally not needed since the molten metal freely flows out without ever wetting the tube walls and the casting that is obtained has a uniform and featureless surface. The metal-repelling characteristics of the SPI-Glas™ Brand Glassy Carbon Tubes remain unchanged throughout the test tube's lifetime.
The SPI-Glas™ Brand Glassy Tubes will not fracture when still red hot, are placed on a cold surface.
The SPI-Glas™ Brand Glassy Carbon Tubes should never be used for the melting of chromium-cobalt-molybdenum alloys.
The SPI-Glas™ Brand Glassy Carbon Tubes are available in only one grade, SPI-Glas™ 20, which has the same identical properties as premium grade SPI-Glas™ 25, except that its maximum service temperature is 2000° C instead of 2500° C.
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