| The materials loosely termed "carbons" or "charcoals," or simply "chars," have been derived by the pyrolysis of numerous organic materials for many decades and even centuries. Thus, many different types of carbons exist, their physical and chemical properties depending to significant extents on the nature of the precursors as well as on the preparation conditions. It is known that such carbons have surface functional groups, and it is generally accepted that the nature and number of these determine the carbon's chemical properties. Such knowledge is based on the results of numerous studies in which a carbon was caused to react with some chemical reagent; deductions were then made about the surface groups. However, deduced information is "indirect"; it would be better to observe functional groups directly by means of a spectroscopic technique such as infrared (IR) spectroscopy.;A number of IR spectroscopic studies of various carbons has already appeared in the literature but much of that work is unsatisfactory because it is in part fragmentary but principally because the IR techniques which were used were unsuitable and not sensitive enough, so that the spectra were of poor quality. However, despite the opacity of most carbons, it is now possible to record their IR spectra, of relatively good quality, by employing the unusual technique of photothermal beam deflection spectroscopy (PBDS), which is based on the photothermal effect.;In the present study IR FT PBDS was used with the intent of providing information about the thermal decomposition of organic precursors, the nature and stability of surface species formed on the chars, the "carbonization" of the chars, and the reaction of some of the chars with oxygen. The precursors selected were pure cellulose and a lignin, because these occur in many natural precursors; sucrose, and also coconut shell, because the literature already contains much non-IR information about chars derived from them; rice hulls, because these contain about 20 wt. % silica; and also a peat, bamboo, almond shells, and peach pits, because these are typical lignocellulosic precursors. The extensive IR data are discussed in detail. |
