ESR of carbons in the transition range—II

Abstract

Whereas in Part I[1] the attention was focused on ESR broadening effects caused in the transition range (900–1600°C) by impurities and/or by structural transformations, in Part II an effort is made to obtain information as to the absolute intensity of the ESR line and its composition. The contributions of surface localized, internal localized and conduction carrier spins are separated by use of air sensitivity effects and temperature dependence data, before and after reacting the carbons with spin-activating gases. Many types of carbon blacks and some chars and cokes were so investigated. It was found that new localized spin centers ( A-centers) are created by such reactions only as long as a carbon contains some other organic components attached to the surface. After all organics have departed, no A-centers are formed, but gas reactions continue to affect the width of the ESR line throughout the rest of the transition range and above. The general picture of relationships existing in the transition range and the problems of interaction between the various types of spin centers and the carbon lattice are discussed.