Encapsulated graphite heater and process

A heater comprising

• a graphite body configured from a solid self standing body of graphite into a pattern for an electrical flow path defining at least one zone of an electrical heating circuit, said electrical circuit comprising terminal ends for terminals to be electrically connected to said electrical flow path,
• wherein a first coating layer is applied to at least one surface of said graphite body prior to being configured to form the electrical flow path pattern, said first coating layer comprising at least one of a nitride, carbide, carbonitride or oxynitride of elements selected from a group consisting of B, Al, Si, Ga, refractory hard metals, transition metals, and rare earth metals, or complexes and/or combinations thereof;
• a second coating layer disposed on said patterned graphite body, said second coating layer comprising at least one of a nitride, carbide, carbonitride or oxynitride of elements selected from a group consisting of B, Al, Si, Ga, refractory hard metals, transition metals, and rare earth metals, or complexes and/or combinations thereof, wherein the second coating layer links the graphite patterned body into one integral unit.

A method for forming a heater, said process comprising the steps of:

• a) providing a graphite body configured from a solid self standing body with at least one surface coated with a first coating layer comprising at least one of a nitride, carbide, carbonitride or oxynitride of elements selected from a group consisting of B, Al, Si, Ga, refractory hard metals, transition metals, and rare earth metals, or complexes and/or combinations thereof;
• b) configuring a pattern for an electrical flow path defining at least one zone of an electrical heating circuit in said coated graphite heater by machining through the coated graphite heater in some parts for the parts to be uncoated while still leaving the first coating layer in at least another part for the part to remain coated and for the coated part to link the uncoated graphite patterned body into one integral unit;
• c) coating said patterned graphite heater with a second coating layer comprising at least one of a nitride, carbide, carbonitride or oxynitride of elements selected from a group consisting of B, Al, Si, Ga, refractory hard metals, transition metals, and rare earth metals, or complexes and/or combinations thereof.