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IQS Newsroom Articles on Graphite Crucibles
Graphite CrucibleGraphite crucibles are heat resistant containers that store materials and samples for various high temperature applications. Graphite is a chemically inert, temperature resistant mineral that fares well in ovens and furnaces. It resists thermal shock, oxidation and abrasions well, and won’t melt, burn or chemically change in extreme conditions. Graphite crucibles have many applications within the foundry, laboratory testing, jewelry making and fusion industries. Crucibles are made of metals like copper, platinum, quartz or porcelain, but graphite is a cost saving alternative to these more expensive materials. They are used in chemical analysis, to store materials and samples during fusion and mixing processes, in ash content determination, to melt precious metals, and in foundries to melt many different metals. Crucibles are thick, cup-like containers that come in many different shapes and sizes, with or without a removable lid and spout, which eases the pouring process. They may be barrel, cylinder or conical shaped, wide-form with a shallow, low profile, or high-form, with high, tapered walls. The graphite may be regular or high purity, and usually contains a high percentage of graphite, which is often mixed with clay. Crucibles of any size or material are measured in milliliters. To eliminate the risk of cross-contamination and a difficult cleaning process, many graphite crucibles are one-time-use disposable products. Their applications are slightly limited due to their maximum temperature, 430º C, and length of use, which much not exceed a couple hours. After graphite reaches its maximum temperature, it tends to start slowly oxidizing and if left in a furnace too long, may erode and cause contamination. Graphite crucibles are not very porous, and won’t absorb much of the material being held. Even so, recycling is not common, despite their high graphite purity. They are always portable and handled with tongs and great care, have a smooth surface and are dark grey or black in color. Many sizes are available, and they may be custom made to fit certain manufacturing requirements for a higher cost, or come in standardized sizes. The graphite is mixed with refractory clay, grog and other additives, then formed into the crucible shape by extrusion or die casting, and heat treated in an oven where carbonization takes place.
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