Magnetic properties of CNx whiskers

Carbon-nitrogen whiskers have been prepared by pyrolysis of 1,2-diaminopropane at 950 degrees C or of allylamine at 900 degrees C followed by quenching. They are scrolls of carbon film typically 250 nm thick and up to 1 mm long with about five layers in a structure like a cigare russe or brandy snap, about 50 mu m in diameter. Approximately 8 wt% of nitrogen is incorporated into the carbon films, which are practically amorphous, exhibiting a broad diffraction peak at d = 0.34 nm. The whiskers are on the border of metallic conductivity with a resistivity of about 10(-6) Omega m, and they may show either a positive or a negative temperature coefficient of resistance. The pyrolysis produces either whiskers, soot or both. Magnetization measurements of the whiskers made from 1,2-diaminopropane reveal a large diamagnetic susceptibility of x = -170 x 10(-9) m(3) kg(-1) and a small ferromagnetic component of unknown origin with as of up to 0.2 A m(2) kg(-1), whereas the soot shows a purely diamagnetic signal, with x approximate to -40 x 10(-9) m(3) kg(-1). (c) 2006 Elsevier Ltd. All rights reserved.