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In spite of the name, pencil leads do not contain the toxic chemical element lead, but are typically made with graphite and clay, or plastic polymers. The downside of mechanical leads are that they are not as strong as traditional pencils. Wooden pencil lead is bonded to the outer wooden case, therefore providing more lead protection and strength.
Graphite blocks are also used in parts of blast furnace linings [53] where the high thermal conductivity of the graphite is critical to ensuring adequate cooling of the bottom and hearth of the furnace. [54] High-purity monolithics are often used as a continuous furnace lining instead of carbon-magnesite bricks.
Graphite pencils (traditionally known as "lead pencils") produce grey or black marks that are easily erased, but otherwise resistant to moisture, most solvents, ultraviolet radiation and natural aging. Other types of pencil cores, such as those of charcoal, are mainly used for drawing and sketching.
Nuclear graphite is any grade of graphite, usually synthetic graphite, manufactured for use as a moderator or reflector within a nuclear reactor.Graphite is an important material for the construction of both historical and modern nuclear reactors because of its extreme purity and ability to withstand extremely high temperatures.
Diamond is an excellent electrical insulator, but graphite is an excellent conductor. Diamond is an excellent thermal conductor, but some forms of graphite are used for thermal insulation (for example heat shields and firebreaks). At standard temperature and pressure, graphite is the thermodynamically stable form. Thus diamonds do not exist ...
The graphite in pencils is mixed with clay during fabrication of the "lead" to help hold its shape, and would only burn at greater than 1,000 °C (1,832 °F). [10] The quantity of graphite particles actually produced during occasional writing would be too small to constitute an electrical hazard.
The graphite lead is then honed to a sharp point with a lead pointer, which sharpens only the lead without wood. Lead pointers are also used with mechanical leadholders, with thicker diameter leads like 2 mm which have removable/refillable leads. Some sharpeners which function as a long point sharpener, have a second hole in which the blade ...
Graphite may occupy 6 to 10% of the volume of grey iron. Silicon is important for making grey iron as opposed to white cast iron , because silicon is a graphite stabilizing element in cast iron, which means it helps the alloy produce graphite instead of iron carbides ; at 3% silicon almost no carbon is held in chemical form as iron carbide.