Science: Heat, Lengthwise

Graphite, the substance in lead pencils, is a form of carbon that has long been one of the most useful minerals in the scientific laboratory and in industry. It is soft enough to be a good dry lubricant; its high heat resistance makes it a good material for crucibles and as a moderator in nuclear reactors. In the new age of rocketry, scientists have eyed it for use in rocket nozzles or in nose cones, which must resist the heat of reentry. But ordinary graphite has two faults: it is permeable to gases and...

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