SPI-Glas™ Brand glassy carbon, some times referred to as "vitreous" carbon, can be fashioned into test tubes which are universally used in laboratories worldwide for carrying out chemical analyses and also for the preparation of fluorophosphate and other glassy materials. Test tubes fabricated in SPI-Glas™ Brand glassy carbon are also used in the growing of single crystals and other ultra-high purity materials. The SPI-Glas™ Brand glassy carbon also exhibits excellent biological compatibility with live tissues and therefore has high potential for applications in life science research and medicine generally.
One of the wider applications for SPI-Glas™ Brand glassy carbon test 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 reminiscent 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 Test Tubes, relative to quartz test tubes, 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 test tubes were being used.
As a result of the above, the cycle time for a casting is greatly reduced and the useful life of the test tubes is greatly extended.
The useful lifetime of SPI-Glas™ Brand Glassy Carbon Test Tubes is much longer than for graphite tubes because of the much slower oxidation rate of glassy carbon at high temperatures in air. When a reducing atmosphere over the test 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 test 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 Test Tubes remain unchanged throughout the test tube's lifetime.
The SPI-Glas™ Brand Glassy Test Tubes will not fracture when still red hot, are placed on a cold surface.
The SPI-Glas™ Brand Glassy Carbon Test Tubes are used widely in applications involving induction-heating casting centrifuges. Since glassy carbon test tubes couple in the inductive field (which is not true for ceramic or quartz test tubes), they reach the desired operating temperature far more quickly, and the metal will melt more quickly, resulting in much shorter cycle times per run.
The thickness of the wall is 2 mm.
The SPI-Glas™ Brand Glassy Carbon Test Tubes should never be used for the melting of chromium-cobalt-molybdenum alloys.
The SPI-Glas™ Brand Glassy Carbon Test 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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