Sentence:  To reduce heat transfer from the hot gas to this anode holder outside the region of the arc , a <WSD>carbon</WSD> shield was attached to the surface providing an air gap of 1/16 inch between the plate and the surface of the anode holder . 
Meaning of the word marked with <WSD> tags:  an abundant nonmetallic tetravalent element occurring in three allotropic forms: amorphous carbon and graphite and diamond; occurs in all organic compounds